How long have you been heat treating automotive gears? Which thermal processing techniques do your operations gravitate towards? In this best of the web article, uncover some of the common heat treatment functions and the properties they create in gears. Let us know what you think of this general overview of the world of heat treating gears in our Reader Feedback form!
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Additionally, when you read to the end of the article, future trends that we can anticipate for heat treaters in the automotive industry are offered; as one might guess, they include digital and energy-saving technologies.
An excerpt: “Automotive gear heat treatment (process) includes two aspects: firstly, conventional heat treatment such as annealing, normalizing, quenching, tempering, and quenching and tempering; secondly, surface heat treatment, which encompasses methods like surface quenching (e.g., induction quenching, laser quenching) and chemical heat treatment (e.g., carburizing, carbonitriding, nitriding, nitrocarburizing).”
Oil quenching can be a dirty phrase around the heat treat shop. But with vacuum, does it have to be?
This Technical Tuesday article was written by Don Marteeny, vice president of engineering at SECO/VACUUM Technologies,forHeat Treat Today’sNovember 2023 Vacuum Heat Treating print edition.
There are metallurgical advantages to oil quenching for which there are no gas quench substitutes, but for a time, those advantages only came bundled with some disadvantages that proved incompatible with a growing preference for vacuum processes. This drove vacuum oil quenching (VOQ) to evolve and improve, often faster than its reputation. VOQ has since matured into a convenient, safe, and economical choice, offering today’s vacuum heat treaters all the metallurgical advantages of oil quench without any of the compromises.
A Familiar Scene . . .
Don Marteeny
Vice President of Engineering
SECO/VACUUM TechnologiesContact us with your Reader Feedback!
When oil quenching is mentioned in the break room of any heat treat department, it’s a sure bet that those listening have very similar thoughts. With just the mere mention of oil, their thoughts carry them, not to memories of the first time they helped their dad change the oil in their car in the family garage, but instead to a row of furnaces belching flames from their doors. Next, they are sure to see one of the doors open, and the familiar sensation of hot air moves through their mind. They may – for a moment – expect the smell of salt air, the sand between their toes, and the sun from above.
For many heat treaters, this is but a momentary escape. Soon, the taste and smell of hot oil and metal return them to the moment, and they know they are standing next to a row of batch integral quench (aka, batch IQ or BIQ) furnaces.
It’s about then they will feel the heat of those flames at the end of this furnace line or by the transfer car, wiping the sweat from their brow with a sooty hand and anticipating a return to the break room for a cool drink of water.
Sound familiar? If so, you’re one of the hundreds of heat treaters who has had the pleasure of operating a tried-and-true atmosphere integral quench line; it faithfully does its job, hardening and case hardening steels where oil is the only heavy lifter that can do the job.
While heat treaters have been diligently pumping out oil hardened steels, furnace builders and OEMs alike have been trying to find ways to move away from oil to quenchants that, primarily, reduce distortion, but also that are cleaner, require less processing, and present a safer working environment. Despite their efforts working with modified quenchants – including high pressure gas quenching (HPGQ) in vacuum furnaces – oil quenching has proven robust, maybe even stubborn.
Does that mean we are stuck with the integral quench furnace and its fire-breathing ways? Not necessarily. . . .
Figure 2. D-Type double chamber for batch work processing with conventional loading over the oil quench
Source: SECO/VACUUM Technologies
An Invention Waiting on Improvement
The concept of a vacuum oil quenching furnace is nothing new. When first developed, it was unique because it combined the advantages of vacuum heat treating with the ability to oil quench. But at the time, they were an unlikely couple that never really got along as well as the atmosphere furnace with an oil quench tank.
Vacuum oil quench furnaces were expensive, had large footprints, and were not particularly reliable. Plus, if case hardening was required, low pressure carburizing was not particularly attractive as it was still in its infancy, at least compared to gas carburizing. So, VOQ stayed in the shadows, fulfilling limited roles where the application warranted the extra complication of vacuum. In the meantime, the integral quench furnace became the workhorse of choice, churning out oil and case hardened parts for industries worldwide.
HPGQ Drives Improvement in Vacuum Furnace Technology
Despite the success of the integral quench furnace, VOQ remained present, stirring in the shadows. In the meantime, vacuum furnace technology advanced through the development of high pressure gas quenching. The design and construction of a vacuum furnace lent itself to this application well and introduced a host of advantages, such as found in Maciej Korecki’s “Case Study of CMe-T6810-25 High Volume Production”:
• Decreased distortion
• Elimination of intergranular oxidation (IGO)
• No decarburization
Vacuum Furnaces Move from Niche to Standard Issue
In addition, these design developments supported the opportunity to case harden parts through the use of low pressure carburizing (LPC). Coupled with quenching pressures up to 25 bar, the HPGQ-equipped vacuum furnace became a real option for the heat treater interested in through hardening that did not require:
• Special atmosphere generation equipment (atmosphere generator)
• Lengthy furnace-conditioning cycles to assure the correct gas carburizing conditions as is typically necessary in the batch IQ furnace
• Post-heat treating surface cleaning in the form of washing or oxidation removal
VOQ Begins to Follow Suit
Still, vacuum and HPGQ were limited in their ability to serve in the role of hardening some steels when considering common geometries. This meant that, for those steels, oil remained the go-to quenching solution. As a result, the VOQ furnace became the furnace of choice.
It still required:
• Post-quench wash
• Aggressive oil circulation to minimize distortion
• Selection of the appropriate oil
• Careful fixture design
However, the advantages were too many to ignore. The fact that one could through harden steels like 8620 in a clean environment without the safety and cleanliness concerns inherent to integral quench furnaces was a huge advantage. And although furnace footprint remained a concern until the early 2000s, advancements in areas such as mixer design, vacuum pumps, and low vapor pressure quenching oils all contributed to decreasing the footprint and increasing the reliability of VOQ, making it an even more viable option. In more recent times, environmental concerns have also renewed attention to the VOQ furnace because of its vacuum capability.
Advantages include:
• Electric heating – no natural gas consumption
• Inert gas atmosphere or vacuum environment – no atmosphere generator needed • Zero CO2 emissions, even when case hardening using LPC
Figure 3. T-Type triple chamber for continuous batch work – oil quench or gas cooling/quenching with a separate chamber for preheating and semicontinuous operation
Source: SECO/VACUUM Technologies
Which Brings Us to Today
Vacuum oil quenching technology has progressed to overcome the challenges of yesteryear, and technological improvements have made it a flexible and configurable option for a heat treater’s current – and future – needs.
The VOQ is now available in configurations that provide both batch and semicontinuous options. This provides the opportunity to harden or case harden components with increased productivity and efficiency.
A common configuration offered is the two-chamber VOQ furnace as pictured in Figure 2. In this batch type configuration, common working zone sizes – such as 24″ x 24″ x 36″ or 36″ x 36″ x 48″ – are available with load capacities up to 2,650 lbs. A graphite-insulated hot zone provides the capability to achieve working temperatures up to 2400°F while providing the platform to case harden using LPC. This configuration also has the ability to conduct partial pressure heating using nitrogen. When quenching, the use of high-flow oil mixers promotes good oil mixing during quench to minimize distortion. This configuration can also cool in nitrogen above the oil in the quench tank, providing additional process flexibility.
In applications requiring higher productivity, a third preheating chamber can be added to the furnace system to provide the opportunity to preheat the furnace charge. The addition of the preheating chamber provides a semicontinuous operation as opposed to the batch operation provided by the two-chamber furnace. The result is a two times increase in throughput of the furnace system. Depending on the process requirements, production rates of up to 440 lb/hr are possible. The modern vacuum oil quench offers a versatile platform with a compact design capable of multiple processes and high production rates. The traditional two-chamber VOQ offers a batch platform capable of neutral and case hardening through the use of LPC. The three-chamber model provides similar options with the opportunity for high-capacity production through the addition of a preheating chamber with semicontinuous processing. Both demonstrate the advancements and the potential of this modern furnace as flexible, safe, and environmentally-friendly option in oil quenching.
Figure 4. An LPC process that yielded a net 1,322 lb (600 kg) load of gears with an effective case depth of 0.039 in (1 mm). This resulted in a throughput of 294 lb/hr (133 kg/hr). Slight adjustments to this process have rendered production of up to 440 lb/hr. (Source: Maciej Korecki, “Case Study of CMe-T6810-25”)
Source: SECO/VACUUM Technologies
About the Author: Don Marteeny has been vice president of Engineering for SECO/VACUUM Technologies for over five years. He is a licensed professional engineer and has been a leader at the company over the last several years filling project management and engineering leadership responsibilities. Don is a member of Heat Treat Today’s 40 Under 40 Class of 2021.
For more information: Contact Don at Don.Marteeny@secowarwick.com
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
Thirsting for knowledge about quenching, but not sure where to start? Heat TreatToday has coalesced technical information across articles and podcast episodes from key experts, including significant quenching methods, innovative developments with quenching, and how to control temperature during the process.
Discover more about these three topics in today’s Technical Tuesday original content feature.
Monitor Quench Temperatures with Unique Thermal Barrier Designs
Automotive heat treating operations require repeatable operations to ensure that the composite parts within an automobile perform reliably. Steve Offley, also known as “Dr. O," the product marketing manager at PhoenixTM, outlines case studies of several temperature-critical operations to demonstrate how unique thermal barrier design for thru-process monitoring systems can solve temperature measuring problems. These processes include sealed gas carburizing into an integrated oil quench as well as LPC followed by transfer to a sealed high-pressure gas quench chamber.
Offley comments on the quenching process following LPC, saying, "During the gas quench, the [thermal] barrier [for temperature monitoring] needs to be protected from Nitrogen N2(g) or Helium He(g) gas pressures up to 20 bar." If you are facing heat treat processing with integrated quench, learn more about this temperature monitoring solution.
Intensive Quenching: An Answer for a "Greener" Heat Treat?
Gas furnaces have the potential to be a significant source of carbon emissions in many essential heat treat processes. However, an innovative approach combining induction through heating with intensive quenching could be one answer for greener heat treating, particularly for steel production.
In this article, Chris Pedder,Edward Rylicki, and Michael Aronov share that an “ITH + IQ” technique "eliminates, in many cases, the need for a gas-fired furnace when conducting through hardening and carburizing processes." A lot of this comes down to shortening the time it takes to perform this process, but there is so much more that the authors illuminate in their tests and graphs.
Drinking from a Firehose: Answering Your Quench Questions with a Thorough Radio Review
Stay afloat in a sea of quenching tips with this Heat TreatRadio review, summarizing three recent podcast episodes centered around quenching tips, techniques, and training — especially applying to the auto industry.
Explore the "green" process of salt quenching with Bill Disler of AFC-Holcroft, the topic of water in your quench tank with Greg Steiger of Idemitsu Lubricants America, and a broad review of auto industry quenching with Scott MacKenzie of Quaker Houghton, Inc.
In addressing the challenges of modern automated production flow, thru-process temperature monitoring and process validation strategies provide viable options in the automotive heat treat industry. Could they help your operations?
This Technical Tuesday article was composed by Steve Offley, “Dr. O,” product marketing manager, PhoenixTM.It appears in Heat Treat Today’s August 2023 Automotive Heat Treatingprint edition.
The Heat Treat Monitoring Goal
Dr. Steve Offley, “Dr. O”
Product Marketing Manager
PhoenixTM
Source: LinkedIn
In any automotive heat treatment process, it is essential that the heat treat application is performed in a controlled and repeatable fashion to achieve the physical material properties of the product. This means the product material experiences the required temperature, time, and processing atmosphere to achieve the desired metallurgical transitions (internal microstructure) to give the product the material properties to perform it’s intended function.
When tackling the need to understand how the heat treat process is performing, it is useful to split the task up into two parts: focusing on the furnace technology first, and then introducing the product into the mix.
If we consider the furnace performance, we need to validate that the heat treat technology is capable of providing the desired accurate uniformity of heating over the working volume of the furnace for the desired soak time where the products are placed. This is best achieved by performing a temperature uniformity survey (TUS). The TUS is a key pyrometry requirement of the CQI-9 Heat Treat System Assessment (AIAG) standard applied by many automotive OEMs and suppliers.
Traditionally temperature uniformity surveys are performed using a field test instrument (chart recorder or static data logger) external to the furnace with thermocouples trailing into the furnace heating chamber. Although possible, this technique has many limitations, especially when applying to the increasingly automated semi or continuous operations discussed later in this article.
Thru-process Temperature Profiling — Discover the Heat Treat DNA
When it comes to heat treatment, the TUS operation gives a level of confidence that the furnace technology is in specification. However, it is important to understand the need to focus on what is happening at the real core of the product from a temperature and time perspective. Product temperature profiling, as its name suggests, is the perfect technique. Thermocouples attached to the part, or even embedded within the part, give an accurate record of the product temperature at all points in the process, referred to as a product temperature profile. Such information is helpful to determine process variations from critical factors such as part size, thermal mass, location within the product basket, furnace loading, transfer rate, and changes to heat treat recipe. Product temperature profiling by trailing thermocouples with an external data logger (Figure 1) is possible for a simple batch furnace, but it is not a realistic option for some modern heat treat operations.
Figure 1. Typical TUS survey set-up for a static batch furnace. PhoenixTM PTM4220 External data logger connected directly to a 9 point TUS frame used to measure the temperature uniformity over the volumetric working volume of the furnace.
Source: PhoenixTM
With the industry driving toward fully automated manufacturing, furnace manufacturers are now offering the complete package with full robotic product loading — shuttle transfer systems and modular heat treat phases to either process complete product baskets or one-piece operations.
The thru-process monitoring principle overcomes the problems of trailing thermocouples as the multi-channel data logger (field test instrument) travels into and through the heat treat process protected by a thermal barrier (Figure 2).
Figure 2. PhoenixTM thru-process monitoring system. (1) The thermal barrier protects internal multi-channel data logger, (2) the field test instrument, (3) the product thermal profile view, (4) the temperature uniformity survey (TUS), and (5) short nonexpendable mineral insulated thermocouples.
Source: PhoenixTM
The short thermocouples are fixed to either the product or TUS frame. Temperature data is then transmitted either live to a monitoring PC running profile or the TUS analysis software via a two-way RF (radio frequency) telemetry link or downloaded post run.
Although thru-process temperature monitoring in principle can be applied to most heat treat furnace operations, obviously no one solution will suit all processes, as we know from the phrase, “One size doesn’t fit all.”
For this very reason, unique thermal barrier designs are required to be tailored to the specific demands of the application whether temperature, pressure, atmosphere, or geometry as described in the following section.
Product Profiling and TUS in Continuous Heat Treat Furnaces
Thru-process product temperature profiling and/or surveying of continuous furnace operations, unlike trailing thermocouples, can be performed accurately and safely as part of the conventional production flow allowing true heat treat conditions to be assessed. As shown in Figure 3, surveying of the furnace working zone can be achieved using the plane method. A frame attached to the thermal barrier positions the TUS thermocouples at designated positions relative to the two dimensional working zone (furnace height and width) as defined in the pyrometry standard (CQI-9) during safe passage through the furnace (soak time).
Figures 3. Temperature uniformity survey of a continuous furnace using the plane method applying the PhoenixTM thru-process monitoring system. The data logger travels protected in a thermal barrier mounted on the TUS frame performing a safe TUS at four points across the width, which is impossible with trailing thermocouples.
Source: : Raba Axle, Györ, Hungary
Sealed Gas Carburizing and Oil Quench Monitoring
For traditional sealed gas carburizing where product cooling is performed in an integral oil quench, the historic limitation of thru-process temperature profiling has been the need to bypass the oil quench and wash stations.
In such carburizing processes, the oil quench rate is critical to both the metallurgical composition of the metal and to the elimination of product distortion and quench cracks, and so the need for a monitoring solution has been significant. Regular monitoring of the quench is important as aging of the oil results in decomposition, oxidation, and contamination of the oil, all of which degrade the heat transfer characteristics and quench efficiency.
To address the process challenges, a unique barrier design has been developed that both protects the data logger in the furnace (typically 3 hours at 1700°F/925°C) and during transfer through the oil quench (typically 15 minutes) and final wash station.
Figures 4. PhoenixTM thru-process temperature profiling system monitoring the core temperature of automotive parts in a traditional sealed gas carburizing furnace with integral oil quench. (left) System entering carburizing furnace in product basket. (right) Thermal barrier showing outer structural frame and sacrificial insulation blocks protecting inner sealed thermal barrier housing the data logger.
Source: PhoenixTM
The key to the barrier design is the encasement of a sealed inner barrier (Figure 4) with its own thermal protection with blocks of high-grade sacrificial insulation contained in a robust outer structural frame. The innovative barrier offers complete protection to the data logger allowing product core temperature monitoring for the complete heat treat process under production conditions.
Low Pressure Carburizing with High Pressure Gas Quench
In the current business environment, an attractive alternative to the traditional sealed gas carburizing application for both energy and environmental reasons is low pressure carburizing (LPC). Following the vacuum carburizing process, the product is transferred to a sealed high-pressure gas quench chamber where the product is rapidly gas cooled using typically N2 or Helium at up to 20 bars.
Such technology lends itself to automation with product baskets being transferred by shuttle drives and robot loading mechanisms from chamber to chamber in a semi-continuous fashion. The sequential processing (with stages often being performed in self-contained sealed chambers) can only be monitored by the thru-process approach where the system (thermal barrier protected data logger) is self-contained within the product basket or TUS frame.
In such processes the technical challenge is twofold. The thermal barrier must be capable of protecting against not only heat during the carburizing phase, but also very rapid pressure and temperature changes inflicted by the gas quench. To protect the thermal barrier in the LPC process with gas quench, the barrier construction needs to be able to withstand constant temperature cycling and high gas pressures. The design and construction features include:
Metal work: 310 stainless steel to reduce distortion at high temperature combined with internal structural reinforcement
Insulation: ultra-high temperature microporous insulation to minimize shrinkage problems
Rivets: close pitched copper rivets reduce carbon pick up and maintain strength
Lid expansion plate: reduces distortion during rapid temperature changes
Catches: heavy duty catches eliminating thread seizure issues
Heat sink: internal heat sink to provide additional thermal protection to data logger
During the gas quench, the barrier needs to be protected from Nitrogen N2 (g) or Helium He(g) gas pressures up to 20 bar. Such pressures on the flat top of the barrier would create excessive stress to the metal work and internal insulation or the data logger. Therefore, a separate gas quench deflector is used to protect the barrier. The tapered top plate deflects the gas away from the barrier. The unique design means the plate is supported on either four or six support legs. As it is not in contact with the barrier, no force is applied directly to the barrier and the force is shared between the support legs.
In LPC technology further monitoring challenges are faced by the development of one piece flow furnace designs.
Figures 5. (left) Thermal barrier being loaded into LPC batch furnace with TUS frame as part of temperature uniformity survey. (right) Thermal barrier shown with independent quench deflector providing protection during the high pressure gas quench.
Source: PhoenixTM
New designs incorporate single piece or single product layer tray loading into multiple vertical heat treat chambers followed by auto loading into mobile high pressure quench chamber. Miniturization of each separate heat treat chamber limits the space available to the monitoring system. The TS02-128-1 thermal barrier has been designed specifically for such processes utilizing the compact 6 channel “Sigma” data logger allowing reduction of the footprint of the system to fit the product tray and reduce thermal mass. With a height of only 128 mm/5 inch and customized independent low height quench deflector, the system is suitable for challenging low height furnace chambers and offers 1 hour protection at 1472°F/800°C in a vacuum.
Figure 6. (left) Low profile TUS system (TS02-128-1 thermal barrier six channel Sigma data logger) designed with TUS surveying individual one-piece flow heat treatment LPC furnace chambers (right) Thermal barrier shown with optional low profile gas quench deflector.
Source: PhoenixTM
In modern rotary hearth furnaces (Figure 7), temperature profiling using trailing thermocouples is impossible as the cables would wind up in the furnace transfer mechanism. Due to the central robot loading and unloading and elimination of charging racks/baskets, the use of a conventional thru-process system would also be a challenge.
Figure 7. A modern rotary hearth furnace.
Source: PhoenixTM
To eliminate the loading restrictions, a unique thermal barrier small enough to fit inside the cavity of the engine block and allow automated loading of the complete combined monitoring system and product has been developed. To optimize the thermal performance of the thermal barrier with such tight size constraints, a phased evaporation technology is employed. Thermal protection of the high temperature data logger is provided by an insulated water tank barrier design keeping the operating temperature of the data logger at a safe 212°F/100°C or less. The system allowed BSN Thermoprozesstechnik GmbH in Germany to commission the furnace accurately and efficiently and thereby optimize settings to not only achieve product quality but also ensure energy efficient, cost effective production.
Summary
Thru-process product temperature profiling and surveying provide a versatile, accurate, and safe solution for monitoring increasingly automated, intelligent furnace lines and the means to understand, control, optimize, and certify your heat treat process.
About the author:
Dr. Steve Offley, “Dr. O,” has been the product marketing manager at PhoenixTM for the last five years after a career of over 25 years in temperature monitoring focusing on the heat treatment, paint, and general manufacturing industries. A key aspect of his role is the product management of the innovative PhoenixTM range of thru-process temperature and optical profiling and TUS monitoring system solutions.
On site at heat treat operations, gas-fired furnaces can be a significant source of carbon emissions. But depending on the desired heat treatment, an alternative approach that combines induction through heating and intensive quenching could be the “green ticket.” Learn about the ITH + IQ technique and discover how certain steels may benefit from this approach.
This Technical Tuesday article was composed by Edward Rylicki, Vice President Technology, and Chris Pedder, Technical Manager Heat Treat Products and Services, at Ajax TOCCO Magnethermic Corp., and Michael Aronov, CEO, IQ Technologies, Inc.It appears in Heat Treat Today's May 2023 Sustainable Heat Treat Technologiesprint edition.
Introduction
Chris Pedder, Technical Manager Heat Treat Products and Services, Ajax TOCCO Magnethermic Corp. Source: Ajax TOCCO Magnethermic Corp.
Induction heating is a green, environmentally friendly technology providing energy savings and much greater heating rates compared to other furnace heating methods. Other advantages of induction heating include improved automation and control, reduced floor space, and cleaner working conditions. Induction heating is widely used in the forging industry for heating billets prior to plastic deformation. Induction heating is also used for different heat treatment operations such as surface and through hardening, tempering, stress relieving, normalizing, and annealing. However, the amount of steel products subjected to induction heating in the heat treating industry is much less compared to that processed in gas-fired furnaces.
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Gas-fired heat treating equipment is a major source of carbon emissions in the industry. As shown in Reference 1, induction through heating (ITH) followed by intensive quenching (IQ) (an “ITH + IQ” technique) eliminates, in many cases, the need for a gas-fired furnace when conducting through hardening and carburizing processes — the two most widely used heat treating operations for certain steel parts. Eliminating gas-fired furnaces will result in significant reduction of carbon emissions at on-site heat treat operations.
Dr. Michael Aronov, CEO, IQ Technologies, Inc. Source: Ajax TOCCO Magnethermic Corp.
The goal of this article is twofold: 1) to evaluate carbon emissions generated during through hardening of steel parts and carburizing processes when conducted in gas-fired furnaces, and 2) to discuss how these emissions can be reduced to zero using the ITH + IQ process.
Evaluation of Carbon Emissions for Through Hardening and Carburizing Processes
Ed Rylicki, Vice President Technology, Ajax TOCCO Detroit Development & Support Center Source: Ajax TOCCO Magnethermic Corp.
Most through hardening and carburizing operations for steel parts are conducted in batch and continuous integral quench gas-fired furnaces. Assumptions made for evaluating CO2 emissions produced by a typical integral quench furnace are presented in Table 1. Note: The values of carbon emissions presented Table 1 are conservative since they don’t consider the amount of CO2 produced by furnace flame screens and endothermic gas generators used to provide a controlled carburizing atmosphere in the furnace. Also, it’s assumed that the furnace walls are already heated through when loading the parts, so there are no heat losses associated with the thermal energy accumulated by the furnace walls.
Table 1. Assumptions for calculating of carbon emissions by integral quench furnace Source: Ajax TOCCO Magnethermic Corp.
Emissions Generated During the Through Hardening Process
A furnace time/temperature diagram for the through hardening process considered is presented in Figure 1. Carbon emissions Ehard produced by the furnace considered during heating of the load to the austenitizing temperature prior to quenching are calculated by using the following equation,
(Equation 1) Ehard = k • Qhard
where:
■ k = the emission coefficient (equal to 0.050 • 10-3 kg per 1 kJ of released energy when burning natural gas (see Reference 2) ■ Qhard = thermal energy required for heating up the above load from ambient to the austenitizing temperature
A value of Qhard is calculated by the equation below,
■ M = load weight, kg ■ C = steel specific heat capacity (kJ/kg°C) ■ Ta = part austenitizing temperature (°C) ■ To = part initial temperature (°C) ■ Eff = furnace thermal efficiency (a ratio of the furnace thermal losses to the gross heat input)
From equations (1) and (2), the amount of carbon emissions produced by the above furnace during one hardening operation is 40.2 kg. To determine an annual amount of carbon emissions, calculate the number of hardening cycles per year (Nhard) run in the furnace. From Figure 1, a duration of one hardening cycle is 4 hours (3 hours for austenitizing of the parts plus 1 hour for quenching the parts in oil and unloading/loading the furnace). Thus, Nhard is equal to:
Nhard = 360 day • 24 hour • 0.85 / 4 hour = 1826
Figure 1 Source: Ajax TOCCO Magnethermic Corp.
Annual CO2 emissions from one integral quench batch gas-fired furnace are 40.2 • 1836 = 73,807 kg, or more than 73 t
Emissions Generated During Carburizing Process
A simplified furnace time/temperature diagram for the carburizing process considered is presented in Figure 2. Carbon emissions (Ecarb) produced by the above furnace during the carburizing process are calculated by the following equation,
(Equation 3)
Ecarb = k • Qcarb
where:
■ Qcarb = a thermal energy expended by the furnace during the carburizing process. A value of Qcarb amounts to two components:
(Equation 4)
Qcarb = Qcarb1 + Qcarb2
Qcarb in the following equation is:
■ Qcarb1 = energy required for heating up the load to the carburizing temperature
■ Qcarb2 = energy needed for maintaining the furnace temperature during the remaining duration of the carburization process (for compensation of the furnace thermal losses since the parts are already heated up to the carburizing temperature)
A value of Qcarb1 is calculated using equation (2) where the part carburizing temperature Tc is used instead of part austenitizing temperature Ta (see Table 1):
A value of Qcarb2 is a sum of the flue gas losses and losses of the thermal energy through the furnace walls by heat conduction. Qcarb2 is evaluated from the following considerations. Since the assumed furnace thermal efficiency is 65%, the furnace heat losses are equal to 35% of the gross heat input to the furnace. Hence, the furnace heat losses Qloss1 during the load heat up period (the first 3 hours of the carburizing cycle, see Figure 2) are the following:
Thus, the total amount of the thermal energy expended by the furnace during the carburizing cycle is Qcarb = 0.887 • 106 + 0.827 • 106 = 1.71 • 106 kJ. The total amount of the CO2 emissions from carburizing of the load in the furnace considered according to equation (3) is: Ecarb = 0.050 • 10-3 • 1.71 • 106 = 85.7 kg. To determine an annual amount of carbon emissions from one carburizing furnace, calculate the number of carburizing cycles run in the furnace per year. Per Figure 2, a duration of one carburizing cycle is 12 hour (1 hour for the furnace recovery plus 10 hour for carburizing of parts at 927°C plus 1 hour for quenching parts in oil and for unloading and loading the furnace). Thus, the number of carburizing cycles per year Ncarb is:
Ncarb = 360 day • 24 hr • 0.85 / 12 hr = 612
Figure 2 Source: Ajax TOCCO Magnethermic Corp.
Annual CO2 emissions from one integral quench batch carburizing furnace is about 85.7 • 612 = 52,448 kg, or more than 52 t.
Reducing Carbon Emissions Using the ITH + IQ Process
Reference 1 presents results of two case studies of the ITH + IQ process on automotive input shafts and drive pinions. The study was conducted with a major U.S. automotive part supplier. A two-step heat treating process was used for the input shafts, consisting of batch quenching parts in oil or polymer using an integral quench gas-fired furnace for core hardening followed by induction hardening. This two-step method of heat treatment is widely used in the industry for many steel products. It provides parts with a hard case and tough, ductile core.
Substituting the “ITH + IQ” method for the two-step heat treating process not only eliminates the batch hardening process, but also requires less alloy steel for the shafts that don’t require annealing after forging. Thus, in this case, applying the ITH + IQ technique eliminates two furnace heating processes for the input shafts, resulting in the reduction of the CO2 emissions to zero for the shafts’ heat treatment. Per client evaluation, as mentioned in Reference 1, the hardness profile in the intensively quenched input shafts was similar to that of the standard shafts. Residual surface compressive stresses in the intensively quenched shafts were greater in most cases compared to that of the standard input shafts, resulting in a longer part fatigue life of up to 300%.
Per Reference 1, the environmentally unfriendly carburizing process can be fully eliminated in most cases for automotive pinions when applying the ITH + IQ method and using limited hardenability (LH) steels that have a very low amount of alloy elements. A case study conducted for drive pinions with one of the major U.S. automotive parts suppliers demonstrates the intensively quenched drive pinions met all client’s metallurgical specifications and passed both the ultimate strength test and the fatigue test. It was shown that the part’s fatigue resistance improved by about 150% compared to that of standard carburized and quenched in oil drive pinions. In addition, distortion of the intensively quenched drive pinions is so low that no part straitening operations were required.
Conclusion
Coupling Ajax TOCCO’s induction through heating method with the intensive quenching process creates a significant reduction of CO2 emissions produced during heat treatment operations for steel parts. For the through hardening process, eliminating just one batch integral quench gas-fi red furnace will reduce carbon emissions by more than 73 ton per year. For the carburizing process, eliminating just one batch carburizing furnace will reduce carbon emissions by more than 52 ton per year. Note that for continuous gas-fired furnaces, the carbon emission reduction will be much greater due to higher continuous furnaces production rates (hence a much higher fuel consumption).
Per our experience, the ITH + IQ process can be applied to at least 20% of the currently through-hardened and carburized steel parts. Per two major heat treating furnace manufacturers in the U.S., there are thousands of atmosphere integral quench batch and continuous furnaces in operation in the U.S. That means hundreds of gas-fired heat treating furnaces can be potentially eliminated, drastically reducing carbon emissions in the U.S., supporting a lean and green economy.
Ed Rylicki has been in the induction heating industry for over 50 years. He is currently Vice President Technology at Ajax TOCCO Detroit Development & Support Center in Madison Heights, Michigan.
Mr. Chris Pedder has over 34 years of experience at Ajax Tocco Magnethermic involving the development of induction processes in the heat treating industry from tooling concept and process development to production implementation.
Dr. Michael Aronov has over 50 years’ experience in design and development of heating and cooling equipment and processes for heat treating applications. He is CEO of IQ Technologies, Inc. and a consultant to the parent company Ajax TOCCO Magnethermic.
Fundamentals of furnace maintenance sometimes fall between that tricky area of realizing their importance and getting pushed to the end of the to-do list. This original content piece shares tips to bring the fundamentals back to where they belong: at the top of the to-do list.
Ben Gasbarre President, Industrial Furnace Systems Gasbarre Thermal Processing Systems
Safety First | Whether the furnace is in operation, or it is having down time, proper safety measures must be in place. Personal protective equipment, proper shut down of power sources, and even the buddy system are topics taken in to consideration.
Asset Management System | Have up-to-date maintenance records available to any and all employees. "Ensuring important information, such as alloy replacements, burner tuning, or control calibration information, can help operations and maintenance personnel as they plan and assess future equipment needs," comments Ben Gasbarre, president industrial furnace systems at Gasbarre Thermal Processing Systems.
Cleaning | Reminders include: change filters on combustion blowers, clean things like burners and flame curtains, clean out endothermic gas lines, burn off manual probes at least once a week, etc.
Daniel Hill, PE Sales Engineer AFC-Holcroft Source: AFC-Holcroft
Rules and Regulations | The military and energy industries are sectors that have strict standards to follow. Different heat treating shops are using a software module to maintain furnace data, looking at data reports to make sure the furnace systems are running properly.
Timely Maintenance | Making a maintenance plan and then following it means that no tasks are overlooked or forgotten.
After Repairs and Adjustment | Make sure that after trouble shooting and performing repairs, the software generated reports are examined and that furnaces continue to be maintained. Daniel Hill, PE, sales engineer at AFC-Holcroft says, "This saves valuable time and resources, improves availability, and likely increases profitability."
Greg Steiger Senior Key Account Manager Idemitsu Lubricants America
Proper Levels of Sludge and Water Quench | Failing to keep the quench oil clean results in problems on surface finish. Maintain the quench from the start by filtering, cleaning, and replenishing to keep end product surfaces more acceptable.
Frequency of Sampling | "[The] more often a quench oil is analyzed, the easier it is to use the quench oil analysis as a tool in the proper care of a quench oil," explains Greg Steiger, senior key account manager at Idemitsu Lubricants America.
Regular Addition of Fresh Oil | Proper maintenance of quench oil will result in some loss through filtration. Be sure to replenish.
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
Twice a month, Heat TreatToday publishes an episode of Heat TreatRadio, an industry-specific podcast that covers topics in the aerospace, automotive, medical, energy, and general manufacturing realms. Each episode provides industry knowledge straight from the experts.
Stay abreast of quenching tips, techniques, and training --- especially in the auto industry --- with this original content piece that draws from three video/audio episodes.
Heat Treat Radio: The Greenness and Goodness of Salt Quenching with Bill Disler
Bill Disler President, CEO AFC-Holcroft Source: AFC-Holcroft
Sure, salt quenching has been around for quite some time, but this method is coming more to the forefront when we consider some of the concerns and costs of oil quenching. In this Heat TreatRadioepisode, listen in to Bill Disler of AFC-Holcroft discuss the pros and cons of salt quenching. His brief overview and then salt versus other quench options will leave you ready to embrace quenching at your heat treat shop.
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"I’d say, in general, the most common thoughts with salt are to use it for bainitic quenching. If you’re quenching into a bainitic structure, salt has always been the only way to do this," comments Bill. "But what we’re seeing the growth into, and much more activity, is martensitic quench." As you listen, key into the point of salt quenching offering a "green-minded" solution due to recyclability.
Heat Treat Radio: Water in Your Quench with Greg Steiger, Idemitsu
Greg Steiger Senior Key Account Manager Idemitsu Lubricants America
Water in the quench tank? How much is too much? What do you do to get rid of it? Is it possible to prevent water from getting into the tank? Greg Steiger of Idemitsu answers these questions and more in this essential episode.
"Our research has shown that basically about 200-250 ppm water, you start to get uneven cooling," Greg Steiger cautions. "When you start getting up to large amounts of water, somewhere around 750 ppm to over 1000 ppm, it becomes a safety issue."
The entire episode gives answers to how to identify, prevent, and remove water in the quench.
Heat Treat Radio: All Things Auto Industry Quenching with Scott MacKenzie
D. Scott MacKenzie, Ph.D Senior Research -- Metallurgy Quaker Houghton, Inc.
This interview gets to some nitty gritty details regarding quenching and the shift to electric vehicles. What does the future of heat treating look like for electric vehicles (EVs)? Where is aluminum heat treat fitting in? Listen in to get industry insight on these answers. Scott MacKenzie of Quaker Houghton also explores simulation and modeling, the need for trained metallurgists in our industry, and more broad heat treat considerations.
"The next thing you have to understand is the quenchant itself," Scott MacKenzie advises. "You have to understand the physical properties."
Heat Treat Radio host andHeat Treat Today publisher, Doug Glenn, sits down with Dr. D. Scott MacKenzie, the senior research scientist and metallurgist at Quaker Houghton, for a deep dive into quenching in the automotive heat treat industry. We’re talking the implications of electric vehicles (EV), aluminum and automotive manufacturing, simulation, and training in quench and heat treat.
This automotive industry-focused episode about quenching comes on the heels ofHeat Treat Today's August 2022 Automotiveprint edition.
Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.
The following transcript has been edited for your reading enjoyment.
Doug Glenn (DG): We’re here today with Dr. D. Scott MacKenzie from Quaker Houghton. We’re going to talk a little bit about quenching. Scott, first off, welcome to Heat Treat Radio.
Scott Mackenzie: Thank you. And I just go by “Scott.”
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DG: Very good. You and I have known each other long enough, I can probably do that and get away with it, so that’s okay.
SM: Everybody calls me Scott. I don’t like being called doctor.
DG: Let me give the folks a bit of an intro and then I’m going kind of highlight some of the stuff we’re going to be covering today. We’re going to be talking quenching because Scott is obviously the “quench king” here. We’re going to talk about EV (electric vehicles) a little bit. We’re going to talk about aluminum in the automotive industry, modeling and simulation and, briefly, we’re going to talk about a product that Quaker Houghton came out with not too terribly long ago called GREENLIGHT. We’re also going to talk about training for captive and/or commercial heat treaters in regard to quenching. So, that’s stuff to look forward to.
First, let me just mention that Scott is presently the senior research scientist and metallurgist for Quaker Houghton (formerly Houghton International) in Conshohocken, PA. He joined Houghton International in 2001 as a technical specialist heat treating marketing and moved into the heat treat laboratory, to the supervisor position, in 2007. Prior to joining Houghton, he worked as an associate technical Fellow in failure analysis, at the company actually, for six years and manufacturing engineer for the steel and aluminum heat treating departments for twelve years. He was past president of IFHTSE (International Federation for Heat Treatment and Surface Engineering) from 2018 to 2020. He is an active member of ASM and served on a lot of committees at ASM as well as member or chairman. You’ve authored, Scott, several books and over one hundred peer-reviewed papers.
So, I expect to see an increase in induction hardening or, at least, stay the same, but more atmosphere, traditional atmosphere, endothermic atmosphere and quenching and quenching in a quenchant — that’s going to be drastically hit in the next five to ten years.
Scott got his BS in metallurgical engineering from Ohio State University and got his MS and PhD from the University of Missouri Rolla. Bottom line, Scott is well qualified to talk about quenching and that’s what we want to do.
Scott, before we jump in and ask the first question, is there anything else you’d like to share with us about your background: where you’ve been, some of your more interesting experiences, or things that would be of interest?
SM: One, I got my PhD late in life. I started on my PhD when I was 45. So, I already had practically 15 years of experience on the shop floor, mostly doing heat treat with doing all the landing gear for the F/A-18, the F15, the AV-8B Harrier, wing skins for aircrafts like MD-80, DC-9, DC-10, MD-11 and then later when I was at Boeing, some of the 737 wing skins and all that sort of stuff. A lot of manufacturing on the shop floor.
DG: It’s a real advantage going to school late in life, too, because you come there with a real different perspective. You’re not green, you know the questions to ask, you know what’s BS and what’s not BS.
SM: Well, the trouble with that is twofold: One, you’re not willing to take any BS from the professors, right? And also, you are more willing to challenge them. In that, from a teacher’s perspective, you’re a much more difficult student because you question more. But, by the same token, you’re also easier to teach because you’re more motivated — you’re not just there because mommy is paying the bill.
"Well, there’s a big thing about EV that is going to drastically impact heat treating and the heat treating industry, as well as quenchants." -- Scott MacKenzie
DG: Yes, absolutely. I taught school a little bit, not college level, but I’d much rather have students that are engaged.
Let’s talk about electric vehicles. It’s a transition that seems to be coming on. Let’s talk about it in terms of heat treating, in general, and quenching, in particular. What do you think about this EV thing? How is it going to impact heat treat?
SM: Well, there’s a big thing about EV that is going to drastically impact heat treating and the heat treating industry, as well as quenchants. Presently, approximately 50% of the heat treaters, (at least in the U.S. and probably globally), are related to heat treating of gears. . . transmission gears, etc. Then we have doing other suspension components, like the tulips with the drive shaft, etc. But should the complete EV — and I’m not talking hybrids, I’m talking about a complete EV . . . EV’s drive by, you put your foot on the accelerator, it goes through, like, a potentiometer computer and that will control the four motors at each wheel, or just two. There’s no transmission involved. So, since there’s no transmission involved, there is no requirement for gears and since there is no requirement for the gears, there is no requirement for heat treat. And so, if we get a full implementation of electric vehicles, we’ll have roughly 50% excess capacity in the heat treat industry, which means the grid people won’t be selling as many grids and the quenchant people won’t be selling as much quenchant.
Even in the racing world — why, even Formula 1 is going to electric, they have Formula E which is all electric. You look at even the super cars. Aston Martin just announced a fully electric vehicle. Pagami just came out with a [indiscernible] last night. (I’m a big fan of Aston Martin.) You have the Lamborghini, Ferrari – they’re all coming out with electric vehicles, either hybrid or fully electric. Volvo is committed to 100% electric by 2025. So, we need to pay attention to where the industry is going.
Now, you will still the suspension components, for instance the tulips, the drive shaft where the motor attaches to the wheel, and back shafting. But that will be predominantly not by traditional atmospheric quench, it’s going to be done by induction hardening. So, I expect to see an increase in induction hardening or, at least, stay the same, but more atmosphere, traditional atmosphere, endothermic atmosphere and quenching and quenching in a quenchant — that’s going to be drastically hit in the next five to ten years.
DG: So, gears, I assume, cam shafts — we’re not going to see that? Drive shafts to a certain extent, not the same type of drive shafts that you’ve got now, but they’ll be a different type — there will be four independent ones, I suppose. Does the move to EV add anything? Are we doing heat treating of armatures or anything in the motors, motor laminations or anything of that sort? Does it add to the heat treat load?
SM: Certainly, the motor laminations- that requires a special thermal process. It’s not quite heat treating because the thermal lamination is going to require different materials (right, silicon steels). You are also going to see much more, leading into your other question about aluminum heat treating, because the structures are going to be moving in either much higher strength steels or bodies to meet crash tests. You’re either going into aluminum because of lighter weight or for very high performance, you’re going to go into carbon fiber. Carbon fiber will require the resins and the pre-peg will require thermal processing. But that’s more like in an autoclave, like airframers do.
Aluminum will require a different mindset. This will require, and it’s already starting to happen where automotive manufacturers are starting to do aluminum heat treating, and a lot of them are adopting a lot of the aerospace specifications, for good or bad, by AMS 2770 or heat treating recipes. It eliminates a lot of research and development on their part.
DG: Right, you’ve got to stick the AMS 2770.
SM: Or, you can do like the Japanese have done, in many cases. They’re not going to aluminum. What they’re doing is higher strength steel and just making it thinner and they’re going to add using special design steels, much more highly refined grain, you’ve got other stuff in there, you’ve got other stuff, to get the high hardness. Then, what they’re doing is, for instance, they’re forging it at a high temperature, and the Germans are also doing this, too, as part of Audi and Mercedes, is they forge the sheet, they take the forge sheet, they put into a pour compress, they heat it up to the forging temperature, then what they do is then they stamp it into the sheet, into the form, the very complicated form, and then what they do is they quench it while it’s in plaque. In other words, they have all kinds of pulls in the dye and so it’s actually acting like the quench press, in this case, by quench press. So, then they have a fully heat-treated part as it exits the forging press.
DG: And that was steel or aluminum?
SM: Steel.
DG: Steel, ok. High strength steel, specially designed, let’s say, “designer steels,” or whatever. Okay.
SM: So, all it does is once it gets out of the forge press, it’s stamped and goes out. It goes directly into the tempering process. Sometimes it goes directly out without tempering, it gets painted and then puts into a [indiscernable] and that does the tempering operation.
DG: As far as the quenching part, obviously you’re quenching through the dye, as you mentioned, so that’s changing. Is any impact the same type of polymer quenching, I assume?
SM: No, it’s just the mass of the dye. They may use air and the mass of the dye. You know, when you think of it, a dye has to buried large compared to my sheet metal; it’s a thermal mass. So, they’re using the thermal mass of the dye to quench the part.
DG: Which they’re obviously cooling that dye because it’s going to be warming up. Okay, very interesting.
SM: One of the problems is cooling the dye and cooling the dye quick enough, so they have to use all kinds of very special panels, high velocities of water, etc.
DG: Just a quick editorial comment about this: There is a debate out there — maybe you can comment on this if you’d like, Scott — in the “green” world regarding the use of aluminum panels versus steel in the automotive industry with body and white type of panels for cars. Those who are “green” seem to say, “We need to push for aluminum.” But the fact of the matter is aluminum takes a lot more energy and actually has a higher carbon footprint to produce than most steels do when the steels are created. So, it’s an interesting thing that the Japanese and the Germans are moving towards custom design, high strength steels as opposed to potentially aluminum. What do you think?
SM: Well, if you look at aluminum, and it depends on at what point in the process you look at it. If you look at just the overall of aluminum, because of the high degree of recycling of aluminum, we’re not mining anything, we’re not mining bauxite, so all of it goes in and then it’s all ready. All you have to do is melt it and alloy it but grade the alloy.
So, instead of making it with the high energy cost of the bauxite process — which is interesting, some of the cheapest is up in Iceland. It’s just tremendous because of the cost of electricity. It’s really interesting seeing those in Iceland. Anyway, that’s neither here nor there. If you look at the whole process from a cradle to grave aspect, aluminum is very attractive. Steel, on the other hand, while we’re doing a lot more recycling and we’re putting it in instead of the old process where you take the taconite and you make a series of blast furnaces and then you put it into a mixer and then you put it into the open hearth or BOF cast and ingot, etc., now we’re running scrap nearly 100% scrap in an electric arc furnace, put into a caster and out.
So, from electricity required to melt it, it obviously doesn’t take as much electricity to melt the aluminum as it does steel just because the temperature is different. You’re looking at 2700 versus 1200 for aluminum. So, in terms of an environmental impact, you have to look at all the numbers. Aluminum would come out the winner because you don’t have to mine it.
DG: Our next topic I want to talk about with you is simulation and modeling. We’ve talked a bit about that offline, and the developments there. As far as quenching goes, what can you tell us in the quenching world, as far as simulation and modeling? What is happening?
SM: It can be done, and it can be done accurately. But part of that is dependent upon the quality of your materials data. That’s the part. We need to know how that will respond as a function of the constituent of equations within the part. For instance, if I put a stress on it or put a strain on it, what’s the plasticity of the part? How will it perform?
The next thing you have to understand is the quenchant itself. You have to understand the physical properties. Let me share something if I may. Can you see the screen?
DG: Yes, I can actually.
SM: We have to look at the heat transfer. We have to look at the temperature, we have to look at the thermal conductivity, thermal detectivity as well as the position and space (X, Y, Z), as well as time, because you know, obviously it’s a time function. So, we have to understand that within the part.
Now, we also have to do the same sort of thing on the quenchant, but now it’s a function of space on the surface of the part. Now we have to look at velocity, we have to look at surface temperature, velocity, thermal conductivity as well as X, Y, Z, and time.
That’s why there’s been so much modeling and good effect with, for instance, high pressure gas quenching. Because the properties of the gases used are well known, well documented. You just look them up in a table someplace. Quenchants, on the other hand, the quenchant suppliers have done a lousy job of documenting the thermal properties. That’s starting to change. So, that’s one of the problems that you see is that the thermal properties of the quenchant are not well established.
The second thing is, is looking at the boundary conditions of the part is that changes as a function of position and agitation — the agitation rates can change around a part. If I look a part, the quench rates change as a function of velocity. Well, the suppliers have not done a real good job of characterizing their quenchants as a function of velocity. That’s a problem, which is getting worked on.
In terms of the simulation, it can be done if you’ve got good boundary conditions. The boundary conditions being the stuff on the outside of the part and the stuff inside the part. Once you do that, and you can do this with either using something like computational flow dynamics and then applying that as whatever velocity heat transfer coefficient that you get out of that and apply to the boundary of the part, then you can use a variety of different software programs, such as Dante or SIMHEAT — both of those are good, just a difference in their material databases. Each will give similar results but it’s a function — garbage in, garbage out. You have to have good material properties and good boundary conditions. If you have those, then you can get a reasonable result. But, if you don’t, you’ll just get garbage results.
DG: As far as simulation goes, obviously it’s something that can be done. Do you see the use of it growing significantly over the next 5-10 years and, if so, any particular areas do you see it growing? I’m assuming it’s going to be in high value parts, right? You’re probably going to see it more there than in your nuts and bolts.
SM: I see it more in the higher value parts. And also, induction hardening. Let me explain: One, in the high value parts because they want to be able to characterize the parts. Either as, “Oops, I sent this part out and it cracked, what happened” as an analysis tool to prevent or to explain why something broke. I see this occurring more in the automotive world at the OEM level. You see some of it in the second-tier aerospace where they’re trying to understand to reduce residual stresses, reduce distortion. At the commercial heat treat? No. They just get paid to quench the part and shove it out the door.
DG: Is it genuinely accessible today? You mentioned Dante and things of that sort. I know Quaker Houghton probably is, but are most of the quench companies working with modeling or is it not that commonplace?
SM: It’s not that common. Part of it is because, you know, the quenchant business is a very competitive business. It just is. A lot of people look at it as strictly a commodity. Quite frankly, we’ve lost sales, I’ve lost sales, over a penny a gallon. And so, one of the things that’s very difficult, and it’s more difficult for the salespeople is to look at the value ad and that value ad can either be we’re not the cheapest quenchant out there. We’re the Cadillac, we’re not the Chevy. So, to justify that higher price (and my salary), we have to sell the value ad, and that value ad can be help with making sure that when I quench my parts in it, I’m going to make properties.
For instance, most quenchant suppliers do not have a metallurgist. One, metallurgists are hard to find anyway, so they’ll get a materials science person which may or may not be exposed to heat treating. So, they have to help them understand whether or not they’re going to make parts. In other words, to mitigate the risk in changing to another quenchant. The value ad is the back-up support from the metallurgical point of view. That’s help understanding, not only just the chemistry of the quenchant and what it does, but what happens to the part. Why is my part stained? Why did my part crack? Or why did my part work this way as opposed to that way? How can I approve the residual stress state in that part? How can I reduce distortion? How can I achieve better properties? Those are the things that we can help with.
Some of the other suppliers can also do it, but they’re not doing using modeling or using computational flow dynamics or using the modeling program, they’re doing it based on their experience. It’s something I do too, but I can do that with the modeling and my experience to get it even closer.
Did that answer your question?
DG: Yes. Basically, I was just trying to get a sense from our listeners, many of them are going to be manufacturers with heat treat in-house, “captive heat treaters,” as we call them. I’m just curious how accessible it is. Is it something they can call today and say, “Can you help me with this, and can we model it?” It sounds like, “yes” but not with all quench suppliers, but it is possible.
SM: There are also consultants out there that can do it.
DG: Speaking of green, speaking of money, Quaker Houghton, several years ago, probably three or four years ago. . .
SM: Three years, next month.
GREENLIGHTTM
DG: . . . came out with this product called Greenlight Unit and I’ve been wanting to talk to somebody over there about that. From a 30,000-foot view, what is it, why does it work, why should people care about it?
SM: What the GREENLIGHT unit is, at it’s very simplest — you’re measuring something and that measuring something could be, for instance, polymer concentration using [indiscernible]. You’d be measuring ph. You could be measuring some other physical property. You tell the unit — these are the ranges that I want to use. You can use it to computer interface or PLC interface, and I set this box on, for instance, my induction hardener which is very common. I have a concentration range for the polymer quenchant. If I go below that it puts a big red flag. If everything is good, it waves a green flag. If it’s either too high or too low, it waves a red flag and says, “pay attention.” Now, that red flag can be either I could add water or add polymer and I could tell either a person to do that, you know, “Operator, come and do this for me” or it can tell a PLC to actuate a pump — either add water or to add polymer. All automated, don’t have to pay attention to it.
DG: And that works, not just on induction equipment, just to be clear. You can do this on quench coolant tank or whatever.
SM: Yes, absolutely, anywhere. I can put it on polymer quenchant, for example. Most commonly, it is being used on induction. In fact, it’s standard on some of the induction hardening equipment.
DG: So basically, just a simple human-machine interface or human-quench fluid interface is going to tell you whether it’s within spec or not and if it’s not in spec, the green light goes out and the red light comes on.
SM: And some alarm comes on and some enunciation, whether it’s visual or audible or both.
DG: And you either fix it manually or you’ve got it programed so that a PLC can make whatever adjustments.
SM: You can contact those so that you can tell a PLC to do some action.
Training for quench and heat treat knowledge is available, and the next generation of metallurgists and engineers need it: "As far as training goes, the fact of the matter is, if you don’t have in-house resources to help you understand heat treating and/or the quenching aspect of it, I think, point being, there are consultants out there that can do it, there are quench companies like Quaker Houghton, for example." - Doug Glenn
DG: Let’s hit one other main topic before we wrap up today. You’ve already kind of hinted at it, but I think that it’s something that’s important. We’ve talked a lot about “brain drain” in the industry and the fact that, and you and I actually spoke off-line not too long ago about, metallurgy programs versus material science programs and the fact that sometimes material science graduates don’t necessarily have a full grasp on what metallurgy is and how it works. . . .
When companies that are manufacturers with their own in-house heat treat are needing help, how are they going to get training? Where can, in fact, they go to get questions answered and things of that sort. And how bad is that problem?
SM: One, it’s a global issue. Metallurgy is kind of like a forgotten science. I was one of the last at Ohio State to actually graduate with a metallurgy degree, metallurgical engineering. After that they changed to material science.
The reason is because one of our illustrious funding [parameters] for grant-funding says: We already know everything there is to know about heat treatment metallurgy; we need to be focusing our energies on nano-this or green-this or additive manufacturing or whateverkind of buzz word. In other words, I’ll send something in, toss in those buzz words and you can get a grant. In other words, it’s because the universities are chasing the government cheese when, really, what the industry needs is people who have a strong grasp of the metallurgy of something. For instance, when I went to school, back in the dark ages (about 1980), back when we still used slide rules (I still have mine), we actually had whole courses, multiple semesters on heat treating. How does a steel react when I change the quench rate? We have the different microstructures you get. Looking at the microstructure, what do we get?
Now, with a material science degree, what we were exposed to in multiple semesters, they may get mentioned in a single lecture.
DG: And spend the rest of the time talking about plastics, polymers, composites and high-faulting new stuff, which is important, but. . . .
SM: Just to give you an idea: I had a customer, and they were having, roughly, 95% cracking. They asked me to help. They’re using our quenchant. What they were doing is that they were taking the parts and they were putting them into the high temperature in the austenizing furnace. They would then quench them into our polymer quenchant, and these were parts like 4340, big parts. They only had one furnace. So, what they would do is after they quenched it, they’d take up the parts then they would put them outside in the snow so they could let the furnace cool down so they could then temper them. Usually, it would take overnight. But when they would come around the next morning, all these big, expensive, large — and we’re talking several hundred-pound parts — were sitting there in multiple pieces because of quench cracking. They wanted to understand why this was happening. So, I go in there and I meet and talk to their metallurgist, and I said, “Ok, the problem you’re having is an issue with quench cracking which is due to transformation martensite, and you need to get rid of the residual stresses by putting in to temper immediately. The metallurgist looked at me and asked me, “What’s martensite?” I had to control my . . . yeah. And I asked her, “Where did you go to school?” She went to Carnegie Mellon.
DG: Not that it’s not a good school; your point being they’re not covering the metallurgy that they need.
SM: I looked at her and I said, “I know a lot of the professors there. In fact, I flunked out of Carnegie Mellon.” You know, I got lousy grades, I flunked out of Carnegie Mello. I was accepted and then flunked out, so I know! I mean, Metallurgical and Materials Transactions A is by Dave Laughlin who is at Carnegie Mellon. He is a wonderful person; I think he may have retired now. He was a wonderful professor, and he gave me my first metallurgy program. He was also very supportive of me throughout my career. But I looked at him and said, “As I recall, we were taught these courses, I had. . . I mean we were taught these courses.” I mean we had Massalski, Laughlin, I had a whole bunch of people that were well up in the [field]. She looked at me and said, “Well, it was a material science degree, and I took the ceramic option.” So, anyway, we had to go through and do all the training, what’s required and all that stuff. We got it and so we understood what was going on, we understood the ramifications of different quench rates and got that all resolved.
Then I talked to this When I was working on my. . . . Afterwards, I talked to one of my professors who has since passed away at University of Missouri Rolla (or now known as Missouri Institute of Science & Technology), and he said that’s unfortunately truth. If you want somebody that’s knowledgeable in heat treatment, don’t hire a material science person, hire a mechanical engineer because at least they will be exposed to it.
DG: That’s a good point. It’s possible that the mechanical engineers are going to have more exposure to, at least, the effects of heat treat and understand heat treat more than maybe materials engineers do who may have one course. You mentioned before, Scott, that there are only a couple of schools in the U.S. now that still maintain an actual metallurgy degree. Do you recall who they are?
SM: Yes. I believe the University of Missouri Rolla (Missouri Institute of Science & Technology) in beautiful and scenic Rolla, Missouri. There is the University of Arizona, but I believe they are focused strictly on, mostly, mining. . .
DG: Yes, because there’s a heavy metallurgy emphasis in mining, as well.
SM: . . . There is the University of South Dakota and maybe the University of Idaho, but I’m not sure on that one.
DG: The Colorado School of Mines? I think they, at least, used to.
SM: Yes, they still do. But that’s four colleges.
DG: I guess an application here is for companies who are looking to hire people to help them with metallurgy because what we’re talking about here is training and getting the brain-drain, is to be very careful who you’re hiring and where they came from. Not to say that all materials engineers are not worth their salt, because that is not the case, but you need to ask the question: “How much exposure, what has been your experience in metallurgy, specifically?” I think that’s the point.
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SM: And I’ll tell you what. The industry right now is a bunch of old guys. We’re retiring. I’m going to be retiring probably in the next up to three years. But if you look at other people in the world, we’re all getting up there, and the young people to replace us will have to be knowledgeable, otherwise we’re going to repeat all the same mistakes all over again.
DG: Well, I want you know, there are a lot of young people coming up in the industry, right there, 40 Under 40. There are some good, good people. It’s amazing. But your point is very well taken.
SM: And one of those 40 Under 40 has been brought along. Sergio.
DG: Sergio, wonderful, wonderful.
SM: That said, somebody that is very knowledgeable in heat treatment, is still going to be needed —whether you’re doing for production of gears, not necessarily for transmissions, but gears or wind turbines. Heat treatment of turbine blades, heat treatment of . . . whatever. Somebody who’s knowledgeable in heat treatment, a young person, will be able to write their own ticket.
DG: I agree with you!
SM: One of the beauties of heat treatment that I’ve had is I’ve never had to worry about losing my job, I’ve never had to be worried about being laid off, and I’ve been through some ugly layoffs. When I was at McDonnell Douglas, we had 64,000 people at one time; the next morning we had 30,000. In one day, they laid off 35,000 in one location. So, I’ve never had to worry about being laid off. I’ve never had to worry about — if something happens, will I be able to find a job? I’ve never had that issue.
DG: It’s never been an issue for you. That’s great.
SM: And I think that that will be true of any young person in heat treating. You’ll always be able to find a position.
DG: That’s great, Scott. I appreciate it. Just to wrap this one little segment up as far as training goes, the fact of the matter is, if you don’t have in-house resources to help you understand heat treating and/or the quenching aspect of it, I think, point being, there are consultants out there that can do it, there are quench companies like Quaker Houghton, for example.
SM: And there are heat treating societies, for instance, ASM heat treat society. Since this is global, all of the heat treating societies, whether it is the Chinese heat treating association, the Chinese heat-treating society (there are two of them), ASMET which is the Austrian, IWT which is the German, the Italian heat treat society, the Czechoslovakian, Indian heat treat society (which is actually part of ASM) — all those societies have their own training programs and they’re good. I taught some of them and other people have taught. Take advantage of your local heat treating society. And do the training of your own people. Or you can use consultants.
DG: Right. And I was going to say to anybody listening, if they need help finding those resources, you can feel free to call us. I’m sure that Bethany will put some information in this podcast about how you can get ahold of us to help. If nothing else, we can put people in touch with you, Scott, which leads me to the final question: How much information are you willing to give away as far as people contacting you. And don’t worry, you’re probably not really allowed to retire, so even if you do, these people will find you. How can they contact you?
SM: Well, you have my email address — scott.mackenzie@quakerhouton.com. Right now, I’m not taking any consulting positions. I get asked routinely. Part of that is because it’s a conflict of interest with my existing job. If you’re using our quenchants, I can help you. Or, if you’re looking to use our quenchants, I can help you. And that isn’t just choosing a quenchant. Obviously, I can help you select a quenchant if you’re unhappy with your existing product. But I can also help you minimize distortion, better reproduce better properties, whether that’s now we do do a company can come to us and ask for CFP modeling of a quench tank — we can do that. Or we can do that as part of the modeling of the part, we can do that. And we can do it and tie them together, as best we can, depending on the position of the quench tank, and we can do that on as-needed basis. So, I can help you in that fashion. But there are also other people out there — Andy Banka at Airflow Sciences, which can do CFP work; Dante Technologies; TRANSVALOR in Europe and in the U.S. can also do stuff. We happen to work with TRANSCALOR. They can all do that, and they can do it for a consulting fee.
So, it can be done. When I figure out when I’m going to retire, then I’m going to try and figure out what I’m going to do after that.
DG: We’ll find you, don’t worry; you won’t be able to hide.
SM: That’s what I’m afraid of.
DG: Exactly. Very good, Scott. I appreciate it. Are there any closing comments you’d like to make? Is there anything we missed that you’d want to include? I think we’ve hit on most of the major stuff we were thinking about.
SM: I think probably the biggest thing is encourage your young people to go to conferences, and I’m not just talking about where they’re laying out a whole bunch of equipment. Not just an exhibition so you can look at equipment. They need to go to the events so one, they can meet other experts, so they can be educated, and I’m not just talking about taking an ASM course; I’m talking about going to the conference, being able to ask questions of other experts as well as talk to their peers. What are the problems their peers are having? The point is, it’s likely the same sort of problem. And be able to expand the horizon by seeing the conference, the conference proceedings, etc. Encourage them to go to those sorts of things. And also submit papers, etc. because that’s the only way they’ll grow. And that’s what you want, you want the people to grow within the organization, and encourage them to grow within the organization so they become more of a value to that organization.
DG: Yes. There’s no better way to learn than to teach. Once you decide you’ve got to teach, you’ve got to learn the stuff.
Well, you’ve done a great job of that over the years, Scott. I know there’s many, many people in the industry who have appreciated your expertise and we certainly appreciate you being with us here today. Thank you very much for your time and we’ll look forward to talking with you again. Don’t retire too soon — we’ll need you here, so stick around!
Heat treaters often target gas nitriding and carburizing as key additions to their facility, but sometimes they miss a low-cost opportunity for big wear improvement called Deep Cryogenic Treatment. What is it and could it be a game changer for your business?
This Technical Tuesday feature was written by Jack Cahn, president of Deep Cryogenics International and was first published in Heat TreatToday's May 2022 Induction Heating print edition.
Jack Cahn President Deep Cryogenics International Source: Deep Cryogenics International
Benefits
Deep Cryogenic Treatment (DCT) is a thermal process which provides 20–70% increased wear life, 10–20% increased ultimate tensile strength (UTS )/yield strength, and up to a 30% reduction in corrosion effect (Figures 1 & 2). Unlike case hardening or surface coating there is no part distortion, and cryogenically treated items are not prone to fatigue cracking. Whereas nitriding leaves a recast or white layer, DCT does not. Unlike all three processes, dissimilar materials (such as ferrous and non-ferrous) with varying geometric thicknesses can be treated together to increase mechanical and chemical properties. DCT can also be combined with gas nitriding to yield fine precipitates of carbo-nitrides and thru-core eta carbides — combining the best of diffusion and quenching with a diffusion-less thermo-kinetic process (Figure 3). DCT offers permanent, non-reversible wear improvement with no degradation over time.
(Left) Figure 1. Yield strength improvement; (Right) Figure 2. Corrosion reduction Source: Deep Cryogenics International
Many knife and tool steel manufacturers recommend the use of DCT after austenitizing and quenching but before tempering. It is standard industry practice to employ DCT to increase the wear life of D2, H13, S7, 440C, and several mold steels used in the plastic injection, stamping, and forging die industries.
DCT is also one of the lowest cost thermal processes available to heat treaters who already support exothermic and endothermic processes using onsite liquid nitrogen. Environmentally, DCT is neutral: it improves metallic wear life but leaves behind no chemicals, waste, or cleanup and requires no flammable, hazardous, or explosive gases. Fifteen of the 20 largest commercial heat treaters in North America promote their own DCT services and hundreds more have small DCT equipment.
Figure 3. Wear resistant carbides Source: Deep Cryogenics International
How It Works
The DCT process usually follows austenitizing and quenching and is, effectively, a continuation of the quench process below martensite start and finish temperature. Items are placed in a specially designed chamber and slowly cooled from ambient to approximately -320°F (-195.5°C) over six to eight hours and then maintained in a dry, nitrogen gas environment for 8–30 hours before slowly returning to ambient — followed by 1–3 tempering steps. Round, vacuum-insulated processors use less liquid nitrogen (LN2 ) than rectangular chambers and can temper heavy items in-situ (Figure 4).
Figures 5a. MnS inclusions in G2 cast iron; baseline Source: Deep Cryogenics International
Figures 5b. MnS inclusions in G2 cast iron; DCT Source: Deep Cryogenics International
Figure 6. 14,000 lbs of Mn crusher cone mantles in the 36K Source: Deep Cryogenics International
DCT is a diffusion-less thermal process that causes the transformation of retained austenite into martensite without embrittlement and the precipitation of primary and secondary eta carbides. With a low enough temperature and soak time there is a phase change from face-centered cubic (FCC) into body-centered cubic (BCC) or hexagonal close packed (HCP) slip systems. DCT relieves both cyclic and imposed stresses in metals caused by heat treating or manufacturing, further reducing the migration of crystalline defects such as stacking faults, dislocations, inclusions, and vacancies (Figures 5a & 5b). With the reduction in defect migration comes a reduction in interatomic spacing — directly lowering fatigue crack nucleation and propagation.
The process is effective on castings, forgings, additive manufactured, and fully machined items because DCT is a through-material process — maintaining wear protection long after surface coatings and case hardening have eroded. With the recent availability of industrial DCT equipment capable of treating parts 8’ x 8’ x 20’ and up to 30,000 lbs., the process now can be used on large turbine, oil and gas, and mining components previously cast too large for DCT (Figure 6).
So, with all these benefits, why has this process been so overlooked and underused?
Early Adoption and Stall
In the 1980s, heat treaters accepted cold treatment (-80°F) to reduce retained austenite and, later, shallow cryogenic treatment (-140°F to -240°F) to reduce residual stress. However, a lack of DCT test labs that could scientifically demonstrate DCT wear benefits, no large capacity DCT equipment available, and no DCT-specific ASTM test methods were key barriers hampering market growth. Unfortunately, DCT doesn’t show increased wear improvement using the universally adopted Rockwell hardness test ASTM E18-20. Without a specific ASTM test to validate process improvement and no suppliers of large size DCT chambers to complement the existing car bottom industrial furnaces, few heat treaters readily adopted DCT. The DCT chamber frequently sat unused in a corner of the shop.
The Current Opportunity
The key breakthrough for the DCT technology has been the evolution of industrial size equipment. Built and prototyped by Deep Cryogenics International in late 2021, the 36K offers heat treaters a new means to expand their service offerings and new capacity to DCT large parts. Since the 36K cryogenically treats at -320°F but also tempers to 350°F, the entire process (including post-DCT tempering) can be performed in one chamber. No longer will capacity be a technology limiter.
A new business model has also changed the DCT industry: low-cost leasing. By removing the high cost of capital purchase, Deep Cryogenics International’s captive leasing program offers heat treaters access to industrial scale DCT, coupled to an on-site liquid nitrogen generator and a 3,000-gallon storage dewar. Now LN2 can be generated on site at less than bulk supplied gas — dropping the “all in” cost of DCT to less than $0.20 per pound.
Figure 7. DCI VP Linda Williams next to the 36K Source: Deep Cryogenics International
Lloyd’s Register is currently qualifying both the 36K and the DCT technology using a new approach to a recognized test standard — ASTM E2860 Residual Stress testing using X-ray diffraction. This non-destructive test method will positively identify DC-treated parts and correlate a level of improvement based on the drop in residual stress.
2022 will be a big year for DCT with a lot of firsts: large capacity equipment, a captive leasing program, and industry test and certification.
About the Author: Jack Cahn is president of Deep Cryogenics International — a manufacturer of DCT equipment with an in house DCT research lab. His 25-year background in DCT includes design and development of DCT procedures used in scientific, military, energy, and mining applications. He is the author of several patents, certification marks, and research papers. DCI will be opening a DCT demonstration facility in southern Alberta in June 2022.
Heat TreatRadiohost, Doug Glenn, talks with Greg Steiger of Idemitsu Lubricants America Corp. about the causes and dangers of water in your quench tank, how to know if you have too much, and what to do about it if you do. This highly-informative episode is a must watch/listen for those who oil quench.
Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.
The following transcript has been edited for your reading enjoyment.
Doug Glenn (DG): Greg, welcome to Heat TreatRadio. This is the first time you’ve been on, and I know we’ve talked about doing this for quite a while, so, welcome!
Greg Steiger (GS): Thank you, it’s my pleasure.
DG: I asked the question, before we hit the record button, but I think we need to ask the question again: The big white flag in the background with the W, you need to tell us about that.
GS: That’s the flag that they fly outside of Wrigley Field every time the Cubs win. They’ve been doing this for almost a century so that way when they were only playing day baseball and you could come home on the L, you could see if the Cubs won or lost without looking at a box score.
DG: That’s great! Now, you are not in the Chicago area, are you?
GS: No, I’m in the Columbia, SC area, but I was born and raised in the Chicago area.
DG: So, you’re a Cubby fan.
GS: I am.
DG: Being from Pittsburgh, I forgive you for that.
So, Greg, first thing, can you give our listeners and viewers a brief background about yourself and then we’ll jump into the water topic, so to speak?
GS: Sure. I got into this industry when I graduated from college in 1984 as a formulating chemist. I eventually worked my way into, what we call, customer service or tech service, where I’d go out and visit customers, run product trials if customers had problems. I worked my way into laboratory management and eventually sales and marketing. I’ve been at Idemitsu for the past 9 years. Since I’ve been at Idemitsu, I’ve earned a master’s degree in materials engineering, and I’ve learned a lot about heat treat and it’s really become my passion. I am currently the market segment leader for heat treat products for Idemitsu.
DG: I should congratulate you on that degree, by the way. I know a year or so ago, you were still working on that, so that’s great!
GS: May 6th I graduate.
DG: Tell us, just briefly, for those who might not know about Idemitsu. We can see it on your shirt but tell us about them a little bit, so people have a sense.
GS: Idemitsu is a very well-kept secret here in the U.S. They are actually the 8th largest oil company in the world. We are a Japanese owned company. There is about an 85-90% chance that no matter what vehicle you drive, you’ve got some of our fluids in it. The largest market share is the automotive air conditioning compressor market, but basically, if you drive a Honda, Mazda, Subaru, or Toyota, it left the plant with our engine oils, our transmission fluids in it at the factory.
When it comes to quench oils on the industrial side, Idemitsu is actually the 2nd largest quench oil provider in the world. Even though we’re Japanese, all of our heat products, in general, are made and blended here in the U.S.; we don’t import anything from Japan for our heat treat products.
DG: Very interesting. So, a big company — somebody worth paying attention to, I think is the point. You’re right — it’s the best kept secret. We’re trying to work to not make it so secret.
GS: We’re doing what we can, Doug.
DG: This next question I’m going to ask you is very, very basic and most people listening I’m sure will know this but there may be some who don’t: Why is water in quench oil a problem?
GS: A little bit of water is not a problem because it will happen naturally through condensation, but when you start to get too much water in there, a couple of things happen. Our research has shown that basically about 200-250 ppm water, you start to get uneven cooling.
A quench oil is not a completely homogenous fluid; it’s possible to have water in one area of the tank and no water in the other so you can get different cooling speeds in different areas of the tank. When you start getting up to large amounts of water, somewhere around 750 ppm to over 1000 ppm, it becomes a safety issue. What happens is — when water turns into steam, it actually expands. Most things when they get warmer, they contract, but water is the opposite — it expands. It expands 1600 times at boiling and the hotter the steam gets, the more it expands.
"A little bit of water is not a problem because it will happen naturally through condensation, but when you start to get too much water in there, a couple of things happen. Our research has shown that basically about 200-250 ppm water, you start to get uneven cooling."
Think of it: If you have a gallon of water in a 3,000-gallon quench tank, when you boil that water, it turns into 1600 gallons of steam, and it’s got nowhere to go but up and out of the quench oil and it’s going to carry the quench oil with it onto flame curtains, other hotspots on the furnace, and that’s why it becomes so dangerous.
DG: It’s really the risk of explosion, in a sense. That’s basically what we’re talking about. I could be wrong, but my gut feeling is that a vast majority of quench fires are started because of water that happened or simply the product not getting down into the quench fast enough. But a lot of it is caused by carrying water in with the part.
GS: Not necessarily on the part but being in the oil itself through various means. As I said, it happens naturally every time you heat an oil up and you cool it down, you get condensation, but that’s usually only a few parts per million, and every time you drop a load in, you’re driving that water off.
DG: Right. Raising up the temperature and therefore boiling off the water.
GS: Right.
DG: This is a follow-up question into what we were just talking about, and maybe we’ve answered it: Where does the water come from? Is it typically just condensation or what are the top ways water gets into the tank?
GS: Condensation is something we can’t prevent because we live in a hot, humid environment. But what we can prevent is human error, and that’s where most of the water comes from. For instance, if a heat treater has their quench oil stored outside, perhaps in totes — it’s particularly important to make sure that the caps and lids on these totes or drums are very tight and secure because otherwise they’ll get condensation in there and rainwater in there.
We’ve seen instances where people are working on a furnace, and they will hit the sprinkles and the sprinklers will set off and put water into the quench oil. Heat treat furnace doors and, not so much anymore but, heat exchanges where water cooled. Anything that is under pressure is eventually going to leak and that’s why you see companies going to air-cooled heat exchangers. It’s still more difficult to get that air-cooled door and there is still some water in those doors. Like I say, anything under pressure is eventually going to leak and that’s where you see some of the water infiltration, as well.
DG: Typically speaking, how warm or how cool is the oil in a quench tank? You mentioned about condensation being caused by when it cools down, you’re going to have some condensation in there. Where do we run those tanks?
GS: It depends on if you’re using a hot oil or a cold oil. A cold oil is basically an oil that you add some heat to get it around 130-160 F, then you use your heat exchangers to keep taking the heat away when you quench the load in there. A hot oil you add heat to constantly because you want to keep that typically 250-300 F. In a hot oil, you really don’t have a lot of issues with water, unless the furnace goes down and then you get a lot more condensation than anything else. Now, cold oil, you have issues with water because you’re not above the evaporation point of the water.
DG: The bottom line is: If you’ve got too much water in the quench tank, it’s an issue.
Tell us about the measurement. How do we know if we’ve got water in there, and how do we know how much we have?
GS: Well, there are some portable test kits out there. The ones I’m familiar with are made by the Hach Company. You can purchase these from industrial supply houses like McMaster-Carr or places like that. They will give you ppm’s of water.
You heard a lot of old-timers always talk about crackle tests. That is not an effective way to determine how much water is in there. Our studies have shown that you can get as much as 1000-1500 ppm of water before that oil starts to crackle. The way you run a crackle test is — you take a hot panel, (that’s hotter than the boiling point of water), put a couple of drops of oil on it and if it crackles, there is water in there. Sometimes, the oil is so thick, it doesn’t really crackle, and you can’t see it until you get too much water in there.
The way all quench oil providers do it in their lab is something called a Karl Fischer titration. This is not something that the typical heat treater would have in their lab — it’s a relatively expensive piece of equipment. We use automated ones because we do so many at a time, but you can buy manual ones, if you’d like, and those are a little bit less expensive, but again, you’re talking about laboratory equipment and you’re talking about thousands of dollars instead of hundreds of dollars.
Another way to determine if you have water in your quench oil, especially on lighter colored quench oils, is to take a flashlight, put it in a clear beaker, and take a flashlight and put that flashlight at the bottom of the beaker. If nothing in that beaker is hazy and everything is very clear and amber and you can see through it, chances are there is no water in it. But if it’s a dark quench oil, like a lot of cold oils are where it’s almost jet black, the flashlight won’t do you any good.
One of our customers has talked about using a paste. Unfortunately, I don’t know the manufacturer of it, but what he did is he took a paste and put it on a wooden stick and stirred it all throughout its tank. The paste didn’t turn colors, so he knew there was no water in it. To prove that the paste was still good, he actually licked a finger and put it onto the paste and the past turned pink.
DG: This paste that you put on the stick, it doesn’t dissolve into the liquid — it’s just testing whether there is water there. And if it changes color, then you’ve got water. We’ll have to find out what that is and maybe we can put a note about that on the screen.
DG: Probably the best, most reasonable method that doesn’t cost so much, is maybe getting one of those testing kits. Do you have suggestions, Greg, on how frequently a heat treater ought to be checking his or her tank for water?
GS: I would say weekly. I don’t think it needs to be tested any more unless you think there’s a problem. If there’s a problem, obviously, test as often as you need to. But weekly is good enough.
Again, when you’re dropping a load into quench oil, you’re anywhere from 1300-1800 F, so when you drop that load in, you’re driving almost all of the water off that would be in the quench oil from condensation. It’s just if you’re worried about some sort of a human error, that’s when you want to take more frequent testing.
DG: So, it’s going to be somewhat dependent on your process.
How about the material that you are quenching? Are some materials more sensitive to water than others, or is not really an issue?
GS: Not really. It’s more of an issue of part geometry. And that goes really for distortion and cracking along with the water. A little bit of water can crack a very thin part, but on a very thick part, it may not have much effect at all.
DG: How about cosmetics? I know that some people are very concerned with cosmetics. Is water in the quench oil going to cause any issue with cosmetics, such as spotting?
GS: Short-term no, long-term yes. What causes a lot of stains is oxidation. Water, when it heats up, will actually dissociate into hydrogen and oxygen. The hydrogen won’t oxidize the oil, but the oxygen does. That’s one of the reasons why heat treaters use flame curtains — not to allow the oxygen from the atmosphere into the furnace. At the temperatures that you heat treat at, it doesn’t take much oxygen presence to oxidize not only the parts, but also the oil.
DG: We talked briefly about why water is a problem. We talked about measuring it and trying to determine if you have an issue. Let’s move on to this: Ok, we’ve got water in the quench and it’s at an unacceptable level. What do we do?
GS: There are a few ways to do it. It really depends on what level of water you’re at, how safe you feel, and how soon do you need that furnace. Many furnaces have a bottom drain. If you turn the agitation off in the quench oil, the water is going to be heavier and denser than the oil and it will sink to the bottom. This is going to take a couple of days, at least. If you’re looking at 1000 ppm or so, this is probably the best way to do it, because then you can drain from the bottom of the tank until you no longer see water coming off and you see oil.
Let’s say you’ve got 500 ppm or 400. We recommend an upper limit of 200. For that you can run some scrap through your furnace. Again, you have to be incredibly careful because you’re not really at what would be an explosive level, but you don’t want to run good parts through there because you may get some strange hardness results — they may be higher in hardness than what you’re expecting.
Another way, (again, this will take some time), is to actually bring the temperature of your oil above the boiling point of water. If you brought it up to about 220 degrees or so, as the oil starts to evaporate, you will see bubbles and a froth (almost like a head you would see on a beer) come to the top of the oil tank. Once that’s gone, chances are your water is gone.
The last thing you can do is do a complete dump, drain, and recharge. But I would caution anybody who suspects that they have water in their quench oil, and you want to do any of this testing — before you run any loads through that furnace (with good parts), make sure you send a sample overnight to your quench oil provider and they can test it for you. That’s the biggest issue.
DG: I want to back up because you said something that I didn’t catch the fullness of, I don’t think. You said one of the solutions was to simply run scrap parts through your furnace?
GS: Yes.
DG: Now, how does that help you eliminate the water?
GS: Again, you’re taking these scrap parts and they come through your furnace and the furnace may be 1800-2200 degrees. When you dump that load into the quench, if you’ve got just a small amount of excess water, it will evaporate off.
DG: Gotcha. You’re basically bringing up the temperature of the oil so that the water evaporates.
GS: Exactly. You’re almost flashing it off.
DG: We talked about the draining and the replacing. I know of some companies recycle their oil. Any thoughts or comments about that that heat treaters ought to be aware?
GS: Yes, because that’s also a potential source of contamination for water because they skim the oil off of their cleaner tanks. I’ve been at a lot of heat treaters where they have these reclamation systems — they heat the oil up, theoretically they drive all the water off, but not always. Again, this is part of that human error. As a quench oil company, we understand that our customers are doing this, especially with oil continuing to go up. But, again, working with your quench oil supplier here is key because we’ll analyze the samples for our customers and tell them if they’re getting all that water off. Obviously, it’s in the quench oil supplier’s best interest, and the customer’s best interest, to make sure everybody is safe. If a plant burns down, nobody wins.
DG: We’ve discussed why water is a problem, how we measure it to make sure we know it, and then what to do with it. Being a quench expert, do you have any other resources, if someone was interested in learning more, whether it be specifically about water in quench oil or just other quench resources — is there anything that you can recommend for further reading?
GS: I wrote a series of articles on quench oil and how to get water out of the quench oil for your publication Heat Treat Today. Also, how to use your analysis from your quench oil supplier to operate your furnace. You should always let the data tell you how to operate a furnace and not do something just because we’ve always done it this way.
Others, such as Scott Mackenzie, have presented papers. I know back in 2018, there was a conference Thermal Processing in Motion by ASM, and he presented a paper there on how to get rid of water out of quench oil.
DG: Any other resources you’d like to recommend to people?
GS: Use your quench oil supplier. They are the experts. They’re the ones that have all of the testing equipment you need and use them as a resource. Quite frankly, if you don’t get the service from your current quench oil supplier, there are a bunch of us out there, and that’s how we distinguish ourselves — through our service — so find somebody with better service.
DG: There are a number of quench oil suppliers out there. I know some of them are not specifically targeting the heat treat market, but people still use them because they’re a local distributor or something like that.
I want to recommend to people that if you’re having trouble with the processing of parts, whether it be the mechanical properties and things of that sort, and you have a hint that it might be quench-related, it’s probably best to get ahold of people like Greg, who are actually focused in more on the heat treat market. They may have some good recommendations. This is just an encouragement to people that if you’re not using a heat treat specific quench company, there are a couple of them out there and, obviously, Greg at Idemitsu, we appreciate you giving us a little bit of expertise today.
Thanks very much, Greg. Appreciate it very much and appreciate you being with us.
GS: Thanks for your time, Doug. I appreciate the opportunity.
On site at heat treat operations, gas-fired furnaces can be a significant source of carbon emissions. But depending on the desired heat treatment, an alternative approach that combines induction through heating and intensive quenching could be the “green ticket.” Learn about the ITH + IQ technique and discover how certain steels may benefit from this approach.
DG: Our next topic I want to talk about with you is simulation and modeling. We’ve talked a bit about that offline, and the developments there. As far as quenching goes, what can you tell us in the quenching world, as far as simulation and modeling? What is happening?
In terms of the simulation, it can be done if you’ve got good boundary conditions. The boundary conditions being the stuff on the outside of the part and the stuff inside the part. Once you do that, and you can do this with either using something like computational flow dynamics and then applying that as whatever velocity heat transfer coefficient that you get out of that and apply to the boundary of the part, then you can use a variety of different software programs, such as Dante or SIMHEAT — both of those are good, just a difference in their material databases. Each will give similar results but it’s a function — garbage in, garbage out. You have to have good material properties and good boundary conditions. If you have those, then you can get a reasonable result. But, if you don’t, you’ll just get garbage results.
Heat treaters often target gas nitriding and carburizing as key additions to their facility, but sometimes they miss a low-cost opportunity for big wear improvement called Deep Cryogenic Treatment. What is it and could it be a game changer for your business?
DG: I should congratulate you on that degree, by the way. I know a year or so ago, you were still working on that, so that’s great!
