ATMOSPHERE AIR FURNACES TECHNICAL CONTENT

Mesh Belt Atmosphere Heat Treatment Systems: Meeting Demands for Performance, Quality, and Innovation

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT

OCMesh belt furnaces are the workhorse of the heat treating industry. With constant pressure to enhance performance and develop quality products, mesh belt furnaces are keeping up with the demand. In this article written by Tim Donofrio, vice president of Sales at CAN-ENG Furnaces International Limited, discover the ways mesh belt furnaces are addressing demands for innovation and quality.

This Technical Tuesday article appeared in Heat Treat Today’s February 2022 Air & Atmosphere Furnace Systems print edition.

Tim Donofrio
Vice President of Sales
Can-Eng Furnaces International
Source: Can-Eng Furnaces International Ltd.

Introduction

Manufacturers of high volume, high strength metal components constantly face increasing pressures to improve and develop enhanced performance and quality products while simultaneously addressing cost pressures placed upon them. The quality products include cold-formed automotive fasteners and clips, construction nails and screws, cutting and timing chain products, drive system gears, and bearing components, to mention a few. These reference components all require different types of heat treatment processes that impart a unique thermal profile which results in making the component stronger, tougher, more flexible, resistant to wear and corrosion, and improves the overall life of the component.

Mesh Belt Furnaces — Background

Mesh belt furnaces are synonymous with high volume heat treatment of formed, forged, and machined metal components that require soft handling methods to prevent part damage during processing. Furthermore, these systems are well equipped with features that reduce the opportunity for part mixing and contamination within the system. Modern mesh belt furnaces have been put into production around the world to achieve capacities from 100 lb/hr to 7000 lb/hr. Manufacturers today often favor higher capacity heat treatment systems as they offer more efficient returns on investment over lower capacity systems. The heat treatment processes ideally suited for mesh belt furnace systems include neutral hardening, marquenching, austempering, light case carburizing, carbonitriding, carbon restoration, normalizing, and tempering. In most cases, these processes include a multi-step process which involves heating the product to austenitizing temperatures under a reducing or carbon rich atmosphere, followed by an automatic transfer for drop from the furnace belt conveyor into a liquid quench conveyor system where the material transformation takes place. Quench systems vary in size and capacities and are custom designed around the product being heat treated. Design features may include agitation, fluid flow, and conveyor design which can greatly influence the quench speed and material transformation that results in the final physical properties achieved through quenching. Mesh belt heat treatment systems can implement various quench medias that include oil, polymer, water, and molten salts.

Mesh Belt Furnaces — Benefits

Mesh belt furnace benefits have grown significantly from their earlier developments that targeted reduced part damage and part mixing potential. Today, users are exploiting the benefits associated with increased part size range processing flexibility and capability. In the early days, part processing size range was limited to parts that weighed less than 1lb and were less than 4” in length. Today, with design enhancements, users can now process a product range that includes part sections ranging from 3/16” to 1-3/8”, part lengths up to 12” long, and part weights exceeding 2.5lbs each. This increased processing flexibility is made possible through the integration of modernized automated loading and transfer systems that minimize part drop heights and inertia, ensure precise loading, convey, and distribute products that protect against part damage while also ensuring dimensional stability is maintained to acceptable levels.

Additional advancements in the application and use of molten salt quenching have been recently exploited in response to the demand for low distortion and low residual stress level part processing. These demands are largely a result of customers’ needs to engineer products that outlive and outperform previous designs. This is largely a result of recent advancements made to support the shift in transportation technology; most noticeably, vehicle electrification and increased demands of vehicle propulsion systems. This has resulted in improved austemper and martemper technologies, paving the way for new molten salt handling designs that increase the overall safety and use of the systems. Specifically, new techniques for molten salt quench agitation, distribution, and quench drop chute fluid control have greatly improved the controllability of these systems and have also greatly improved the maintainability which has traditionally been difficult for users of previous designs.

Conclusion

It is well understood that the mesh belt furnace design provides significant benefits over other continuous and batch type processing systems for processing high volume and high-quality components that require exact metallurgical properties. The benefits of this system are immense, and system customization allows for further benefits to be integrated. The benefits discussed earlier represent recent advancements made to the mesh belt atmosphere furnace system that users are enjoying today. It should be recognized that several other design benefits also include:

  • Electrical heating systems, natural gas, and atmosphere reduction systems as a means of reducing users’ carbon footprint
  • Improved temperature uniformity of systems to support the expectations of the Automotive Industry Action Group (AIAG) CQI-9 guidelines
  • Hybrid quenching systems that allow for greater processing flexibility and sophisticated Industry 4.0 diagnostics, reporting and data archiving of equipment conditions, and process and product processing attributes

In closing, there are many options available to manufacturers requiring heat treating processes; therefore, the benefits of the mesh belt atmosphere heat treatment system should be strongly considered when seeking out the lowest cost of ownership for manufacturing processes.

About the Author:

Tim Donofrio, vice president of Sales at CAN-ENG Furnaces International Limited, has more than 30 years of thermal processing equipment experience. Throughout his career, he has held various positions within the custom engineered forging, commercial heat treating services, and custom engineered heat treating equipment industries.

Contact Tim at tdonofrio@CAN-ENG.com or (905) 380-6526.

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Ovako’s Transformational Heat Treat Benefits with Electric Retrofit

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HTD Size-PR LogoFor Ovako, a centuries old manufacturer of engineering steel, innovative approaches to producing their product has taken the form of electrifying their roller hearth furnaces over the course of the past decade.

The process of converting to electric heating began in 2014, each furnace installed with up to 86 Tubothal® metallic heating elements from Kanthal. Now, 14 roller hearth furnaces are electrified. The estimated CO2 savings is around 1,400 to 2,000 tons per year per furnace.

“[In] our heat treatment shop in Hofors,” shares Anders Lugnet, a furnace technology specialist at Ovako (pictured above), “we originally had around 450 gas burners, and there was always a problem somewhere in one of them. Since replacing them with 300-odd Tubothal® elements, the daily maintenance is simply not there. Occasionally, an element needs to be replaced, but it is nothing compared to the way it was.”

He continues that, previously, NOx and CO2 emissions were problematic. But with green electricity, emissions are zero, and with no flue-gas losses, total efficiency has improved significantly.

You can read more about this gas burner to electrification retrofit piece of news here: “Clean and Simple: How Electric Heating Transformed Ovako’s Heat Treatment Furnaces”

 

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“Shaped” Wire Belt Withstands Rigors of Heat Treating

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OCEngineered geometry increases strength, decreases stretch, and withstands thermal cycling.

For today’s Technical Tuesday, we are sharing an original content article on how innovative design of wire for mesh belts in heat treat can reduce costs to heat treaters. Technical writer Del Williams writes, that though it seems that manufacturers regard the “periodic replacement of wire belting simply a cost of doing business, innovative alternatives have been developed that can significantly prolong its life and drive down operational cost.” Read on to learn more!

Engineered geometry increases strength, decreases stretch, and withstands thermal cycling.

Whether for automotive, aerospace, or heavy equipment, manufacturers using heat treatment – which can reach temperatures up to 2400°F and vary from a few seconds to 60+ hours – need conveyor belting that can withstand the rigors of the process. However, traditional round balance weave wire belting has changed little in 100 years and often requires annual replacement, causing costly production downtime.

Heat treating is essential to improve the properties, performance and durability of metals such as steel, iron, aluminum alloys, copper, nickel, magnesium, and titanium. This can involve conveying to hardening, brazing, and soldering, as well as to sintering furnaces, carburizing furnaces, atmosphere tempering furnaces, and heat processing in annealing and quenching furnaces. Parts treated can range from bearings, gears, axles, fasteners, camshafts and crankshafts to saws, axes, and cutting tools.

Heat treat-grade balance weave belts – made of temperature-resistant stainless steel or other heat resistant alloys, suitable to be run on a conveyor with friction drive – can cost thousands of dollars, depending on the dimensions and quality. So, even though wear and premature replacement seems inevitable, such wire belting should not be considered a low-cost consumable. While many manufacturers using heat treating consider periodic replacement of wire belting simply a cost of doing business, innovative alternatives have been developed that can significantly prolong its life and drive down operational cost.

Conveyor belting for heat treating process
Source: Del Williams

Although heat resistant wire belting is available, repeated thermal cycling between heating, soaking, and cooling while carrying substantial loads can continually weaken its structure until it fails. The greater and more frequent the temperature fluctuations in heat treatment steps, the shorter the wire belt’s usable life becomes.

In addition, on conveyor belts, belt stretch accelerated by heat and dynamic loading forces on the belt, is typically the main cause of breakage and failure.

Fortunately, industry innovation in the form of engineered, “shaped” wire belting has minimized these challenges. The design vastly prolongs usable life with increased strength and decreased stretch, which dramatically curtails replacement costs and production downtime.

This approach can also help to extend the longevity of wire belting used with increasingly popular powder metal parts, particularly sintered parts that may be heat treated to enhance strength, hardness, and other properties. In such cases, powder metal serves as a feed stock that can be processed into a net-shape without machining.

Resolving the Core Issues

Although conventional round wire belt has been the industry standard for generations, the geometry of the wire itself contributes to the problem.

Traditional round wire belt and even top-flattened wire belting is prone to belt stretch and premature replacement, particularly under high heat treatment temperatures. In testing, typical round and top flattened conveyor wire belt have been observed to stretch approximately 7%.

Even though many producers of conveyor wire belting simply import semi-finished product and finish it domestically, at least one U.S.-based manufacturer has gone to the root of the problem.

“Shaped” wire is designed to provide more strength in the wire belt of a given diameter so it can better withstand high heat processing conditions. This significantly prolongs its usable life.

As an example, one engineered wire belt, called Sidewinder, by Lancaster, PA based Lumsden Belting, compresses and expands wire so it is taller than it is wide with flat sides.

To begin with, the patented side flattened wire’s “I-beam” design provides 3 times greater structural support for heat treated parts compared to standard round wire. The added height of the wire also provides a longer wear life without needing heavier wire. Together, the design limits belt stretch to only 1-2%. This minimizes the potential for damaged belt. Minimal belt stretch also helps the conveyor belt to track straighter, improving production throughput with less required maintenance.

The design significantly extends the usable life of wire belt conveyors used in a variety of heat treat processes. This ranges from hardening, brazing, and soldering to sintering, carburizing, and atmosphere tempering furnaces.

It is also prolonging wire belt conveyor life in secondary powder metal processes used to improve hardness and other mechanical properties. In this vein, it could be utilized in a mesh belt sintering furnace, where compacted parts are placed in a controlled atmosphere and heated. It could also be used in processes such as quench and temper, case carburizing and induction hardening.

When heat treatment is used for hardening, followed by rapid cooling submerged in a medium like oil, brine or water, the shaped wire belt also enhances the open area for the same gauge wire. This reduces residue build up and eases cleaning, while minimizing drag.

Although the cost of the shaped wire belt is slightly more than traditional round wire, for manufacturers relying on heat treatment the gains in lifespan and production uptime can provide a speedy ROI.

About the Author: Del Williams is a technical writer based in Torrance, California. Images provided by the author.

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Mesh Belt Heat Treatment System Advancements for Automotive Fastener Production

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, AUTOMOTIVE HEAT TREAT, FEATURED NEWS, TEMPERING TECHNICAL CONTENT

OC

Tim Donofrio
Vice President of Sales
CAN-ENG Furnaces International Limited
Source: Can-Eng Furnaces International

Manufacturers of high volume, high strength precision automotive fasteners have constantly faced increased product quality standards, delivery and price pressures over the last decade. These pressures force manufacturers to seek new developments and creative methods for improving their long-term competitive positions.

This Technical Tuesday article by Tim Donofrio, vice president of sales at CAN-ENG Furnaces International Limited, will discuss two developments of mesh belt heat treatment systems – innovative tempering and dephosphating systems – that have been successfully integrated and exploited by manufacturers to maintain their competitive position.

Heat Treat Today first published this Original Content article in the Air and Atmosphere 2021 print magazine. Access the digital version of the magazine here. Contact Karen Gantzer for more information on how to contribute to future editions.

Introduction

Methods for heat treating threaded fasteners have evolved significantly over the last 20 years. Earlier versions of low-capacity shaker hearth, rotary hearth, and plate belt systems have now become extinct in favor of modern, highly efficient, continuous soft handling mesh belt heat treatment systems.

Figure 1. Mesh belt fastener heat treatment system
Source: Can-Eng Furnaces International

Today’s mesh belt fastener heat treatment systems (Figure 1) integrate soft handling techniques that use bulk dunnage unloading and sophisticated metering systems. These metering systems uniformly distribute fasteners across the conveyor width, avoiding any inconsistent loading that could vary the heat-up and soak times which can impact the fasteners’ mechanical properties distribution. Fasteners are conveyed through various washing, austenitizing, quenching, tempering, and post-treatment soluble oil processes, while carefully controlling critical processing parameters that ensure compliance to DIN EN ISO-898 fastener manufacturing standard and, more recently, Automotive Industry Action Group (AIAG) CQI-9 heat treatment system assessments.

With the integration of soft handling conveyors and low inertia part transfers, modern mesh belt furnaces can significantly reduce the opportunity for part damage and the likelihood of part mixing. Further system efficiencies are realized through external furnace load preparation, allowing for precise presentation of fasteners to the conveyor belt, resulting in minimal empty belt gaps between lots for part traceability integrity.

Figure 2. Comparison of automotive fastener temper furnace thermal
profiles following integration of technology advancements
Source: Can-Eng Furnaces International

Temper Furnace Uniformity Improvements

With increased quality objectives placed upon fastener manufacturers, furnace systems must be more and more precise. One of the most critical steps in the fastener heat treatment process is tempering, which is performed after austenitizing and quenching. Tempering is performed to increase iron-based alloy toughness, resulting in the reduction of excess hardness that occurs after subjecting the fastener to temperatures below the critical temperature for a defined period of time required for transformation. As quality restriction limits are imposed, so is the need to reduce the product temperature variation to meet the desired metallurgical and mechanical properties distribution.

With advancements in tempering furnace design, modern high capacity (+6000 lbs/hr) mesh belt temper furnaces can achieve product temperature uniformities of ±10°F or better, which is half of the allowable temperature uniformity survey (TUS) limits set out in AIAG CQI-9 assessment at ±20°F for continuous tempering furnaces (Figure 2).

These improvements in performance are made possible through the use of modern computational fluid dynamic (CFD) modeling tools. CFD modeling gives engineers the ability to conduct higher level analysis and optimization of the furnace’s forced recirculation and heating systems, internal furnace geometry, and product-to-airflow relationship.

Today, users of modern temper furnaces enjoy design improvements that increase the overall process reliability, while also exceeding the quality expectations of their customers.

Integration of Dephosphate Removal Systems

For a long time, washers integrated into continuous heat treatment systems have been considered to have companion equipment status, with not much attention paid to their product quality and total cost of ownership. The importance of washer design is currently changing, mainly due to a desire to protect furnace internal components, increase uptime, and improve the quality of the final product.

Washer design configurations include rotary drum, belt, and batch bin systems. For the purpose of this discussion, we will focus on the continuous rotary drum and belt washers for integration with high-capacity mesh belt fastener heat treatment systems (Figure 3). Both systems, if properly designed, can provide suitable performance, with each system providing enhanced features depending upon the fastener size and performance expectations. Careful consideration should be taken during the application review process to identify the configuration that best suits the range of products that will be processed.

Most modern manufactured fasteners are mechanically formed from carbon and alloy steel coils and are normally coated with a phosphate lubricant which is applied to reduce cold forming friction and increase tooling life and part quality. It is widely understood that DIN EN ISO 898 Part 1, Class 12.9 requirements for fasteners specifies that phosphate lubricants be removed prior to heat treatment as phosphate elements can diffuse into the austenite during the heat treatment process and form delta ferrite, which can lead to fastener brittleness and crack propagation failures.

Figure 3. High-capacity in-line rotary dephosphating system
Source: Can-Eng Furnaces International

A recent trend in the industry is the increase in demand for integrated inline pre-heat treatment dephosphating systems. Although not a new requirement to the North American fastener market, more demand has recently been recognized largely due to increased demand for 12.9 strength class fasteners and increased localization of European automotive fasteners (Volkswagen/Audi), who specify strength class 10.9 and greater be dephosphated before heat treatment.

To satisfy these demands, modern heat treatment manufacturers are often integrating inline continuous dephosphating capability as part of their pretreatment strategies. The aqueous chemical removal of phosphate can be by acid or alkaline, however due to the risk of hydrogen-induced brittle fracture, the alkaline processes are preferred. Pretreatment wash systems implement a multi-stage process that includes:

  1. Oil removal & rinse
  2. Dephosphate
  3. Rinse 1
  4. Rinse 2
  5. Drying

Careful consideration must be taken to guarantee wash solutions are completely removed and fasteners are properly rinsed prior to entry into the high temperature furnace to ensure protection of the furnace internals and product quality concerns.

The fasteners are conveyed either by independent conveyors or continuous rotary drums that transport fasteners through each stage of the washing and dephosphating process. Careful consideration and control of wash solution concentration, solution circulation, product dwell time, solution temperatures, and avoidance of contamination is integrated into the equipment design as it is paramount to successful dephosphating integration and final product quality.

The effectiveness of the removal of phosphate is determined by colorimetric analysis, also known as the “blue test.” In this test, a defined quantity of product with a known surface area is immersed into a chemical solution, which will react with any residual phosphate present to form a blue color. The intensity of the color is proportional to the amount of phosphate present.

The effective removal of the phosphate layer prior to the heat treatment is critical to the final fastener quality. Modern dephosphating systems, when properly integrated with the pretreatment and heat treating system, can provide the manufacturer with improved processing flexibility and product quality performance at the lowest cost per pound to process.

 

About the Author: Tim Donofrio, vice president of sales at CAN-ENG Furnaces International Limited, has more than 30 years of thermal processing equipment experience. Throughout his career, he has held various positions within the custom engineered forging, commercial heat-treating services, and custom engineered heat treating equipment industries.

 

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Effective Integral Quench Furnace Maintenance

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OC

Considerable investment is made when purchasing a batch integral quench (BIQ) furnace. These popular furnaces need specific care and maintenance to keep them in prime operating condition. In this informative article by Ben Gasbarre, president of Industrial Furnace Systems at Gasbarre Thermal Processing Systems, learn how you can protect your BIQ from avoidable downtime. 

This original content article appears in Heat Treat Today’s Air and Atmosphere’s February 2021 magazine. When the print edition is distributed, the full magazine will be accessible here.

Ben Gasbarre
President, Industrial Furnace Systems
Gasbarre Thermal Processing Systems

The batch integral quench furnace, or sealed quench furnace, is one of the most popular pieces of equipment in the heat treating industry. The core benefit is its versatility as it can easily adjust to changes in load weight, configurations, and heat treating processes. This makes
it a highly efficient and profitable piece of equipment for both captive and commercial heat treaters.

With all the good that is done in these furnaces, the downside comes in the maintenance of the equipment. By nature, these furnaces are hot, dirty, and have many moving parts, including multiple doors, load handlers, elevators, fans, quench agitators, and pumping systems; this furnace has it all! Although there are many areas of an integral quench furnace, understanding the subassemblies and having a good maintenance program can ensure the equipment operates safely and maintains its highest level of performance year after year.

Maintenance Safety

The discussion on maintenance of any piece of equipment begins and ends with safety. Prior to any work being done on the equipment, safety measures need to be considered based on the work being performed. Certain maintenance activities must be completed while the equipment is in operation; in these cases, proper personal protective equipment must be considered for work being done around hot surfaces, high voltages, elevated work, and potentially hazardous gases. If work is necessary while the equipment is offline, additional safety procedures must be followed, including lockout/tagout of all major power sources, special atmospheres, and natural gas supplies to the furnace.

Integral quench furnaces are considered confined spaces. Prior to entry into the quench vestibule, furnace chamber, and even quench pit, confined space procedures must be followed; hard stops must be in place for doors and elevators. Technicians need to ensure proper oxygen levels and air circulation prior to entry. The buddy system is always recommended when someone is entering the furnace. Prior to returning the furnace to operation, it is important to ensure all necessary safety and maintenance equipment has been removed, all supply lines are receiving designed gas pressures, and proper startup procedures are followed.

For furnace safety during shut down periods, it is wise to review furnace interlock systems and safeties to ensure proper operation. This includes items such as high-limit controllers, solenoid valves, burn off pilots, and other components critical to emergency situations. Additionally, per NFPA 86 requirements, valves and piping should be leak-checked periodically.

Reporting and Metrics for Optimum Performance

Image Source: Gasbarre Thermal Processing Systems

While Industry 4.0 is a popular concept in today’s manufacturing environment, the basic concepts behind the technology are what is important to any good maintenance plan. First, having an asset management system that enables engineers, operations, and maintenance personnel to access maintenance records is critical to ensure they can troubleshoot issues and perform maintenance activities more efficiently. Asset management tools are readily available and can range from well-established cloud-based software systems to simple Excel spreadsheet records. 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.

The second concept is preventive or predictive maintenance plans. While these are not interchangeable concepts, the goal of implementing either is to reduce the likelihood of significant unplanned downtime, which can be costly to an organization. Preventive maintenance is a schedule of planned maintenance activities on a piece of equipment using best practices that give the best chance to catch a problem before it arises.

Predictive maintenance uses data and analytics from equipment operations that can be used to predict when problems are likely to occur. There are considerations for either approach, and the evaluation criteria for preventive versus predictive maintenance plans could be an article in and of itself.

Integral Quench Furnace Maintenance

As stated previously, breaking the furnace down into a series of subassemblies is the easiest way to develop an overall maintenance plan for equipment that has many sections and components. Discussed items will include mechanical assemblies, the heating system, the filtration system, atmosphere controls, temperature controls, and furnace seals. Each has its own importance to ensuring reliable equipment performance.

Mechanical Assemblies

Typical load transfer system alignment.

The mechanical system includes the load transfer system, recirculation fans, quench agitators, door assemblies, and elevator system. There are many exterior items that can cause abnormal equipment operation, including position sensors, rotary cam switches or encoders, and proximity switches, that if not operating properly can interrupt or cause failure within the furnace. Position settings should be logged for future reference, and sensors should be inspected regularly. Belts that may be used on recirculation fans and quench agitators should be inspected regularly for damage and excessive wear. Vibration of these items should be monitored as excess vibration can be an indication of damage or wear to the fan or agitator bearings, shaft, or blades.

The largest item of concern in this system is the alignment of the load transfer system. Unsuccessful load transfer due to misalignment or obstruction can cause significant furnace damage and create unsafe conditions within the furnace. Internal alloy components should be evaluated for integrity and alignment every six to twelve months. Elevator alignment should be reviewed to ensure smooth operation during the same period. Frequent visual inspection through sight glasses, quench time monitoring, and motor load data can give valuable information of future potential transfer issues within the furnace.

Heating Systems

Whether your furnace is gas or electrically heated, well-maintained systems can have significant impact on the operating efficiency of a furnace. For gas-heated systems, proper burner tuning and combustion blower filter cleaning can ensure optimum gas usage and can also improve radiant tube life. Burners, pilots, and flame curtains should be cleaned at least once or twice a year to ensure proper performance.

Electrically heated systems typically require less general maintenance and have fewer components that are susceptible to failure. Regular checks of heating element connections and electrical current resistance can help to identify upcoming element failure.

The largest and most critical components of reliable process performance are the radiant tubes. A crack or leak in a radiant tube can cause part quality issues. Changes in your furnace atmosphere gas consumption or troubles from controlling carbon potential can be signs of tube leaks. If the radiant tube failure is unexpected, it can also cause significant downtime if replacement tubes are not available. Cycle logs and run hour timers are the best metrics for preventive or predictive maintenance on radiant tubes.

Filtration Systems

Filtration systems are recommended for most integral quench applications. They help to eliminate build up and contamination in the oil recirculation system that flows through the heat exchanger and top/atmosphere cooler on the furnace quench vestibule. Filtration systems typically are comprised of a pump, dual filters, and an alarm system to alert users when it is time to change filters. Maintenance on your quench oil can vary by composition. Quarterly analysis of the quench oil performance is common. However, it is recommended to consult with your quench oil supplier to ensure safe and effective performance.

Atmosphere Controls

Integral quench furnace atmosphere systems can vary both by manufacturer and in overall gas composition. The most common being endothermic gas, nitrogen/methanol, along with options for ammonia or other process gases. Although these items may vary, maintenance remains consistent. Users need to ensure the integrity of the piping system including regulators, solenoid valves, and safety switches.

Endothermic gas lines should be cleaned out at least once or twice a year. Many furnace atmosphere problems can be traced back to endothermic gas generator issues, so it is important to have a well-maintained atmosphere generator to ensure peak performance in your integral quench furnace.

Typical integral quench furnace atmosphere system.

Recent technology allows for automatic burn-off of carbon probes and automated atmosphere sampling. However, probes should be burned off once per week if they are manual. Probes will require calibration and periodic replacement, and they can be rebuilt to like-new specifications. Controllers or gas analyzers that support carbon potential control should be calibrated quarterly, biannually, or annually depending on heat treat specification requirements.

Updates in the automotive CQI-9 specification will require calibration of all atmosphere flowmeters on a periodic basis. Users will need to be aware of this requirement and understand how their gas flowmeters should be calibrated. In some cases, control upgrades may be required.

Temperature Controls

Temperature control maintenance typically follows AMS2750 or CQI-9 specifications. This would relate to thermocouple replacement, system accuracy test procedures, and controller calibrations. Depending on the age of the equipment and specification requirement, these items may need to be done as frequently as once per quarter or annually.

Temperature uniformity surveys (TUS) follow similar specifications for frequency. However, a TUS can diagnose areas of the furnace that may need maintenance attention. Having a baseline TUS to reference will help identify changes in furnace performance. Changes to a TUS can indicate burner or element tuning requirements, an inner door leak, refractory damage, fan wear, or radiant tube failure.

Furnace Seals

Integral quench furnace seals can be a source of heartache for any maintenance technicians working to troubleshoot a furnace. Typical seal areas include the inner door cylinder rod, elevator cylinder rods, inner door seal against furnace refractory, outer door seal against quench vestibule, fan shaft(s), and an elevator seal if there is a top atmosphere cooler.

Typical sealing of cylinder shafts are glands comprised of refractory rope and grease. Greasing of these areas should be completed weekly. Outer door and elevator seals are typically fiber rope and may have adjustment built in as they wear, but ultimately will need to be replaced. Frequent inspection of these areas will help identify early issues. Using a flame wand or gas sniffer can help find leaks in unwanted locations. Small furnace leaks can cause part quality issues, and larger leaks can also create safety concerns within the furnace.

Additional Maintenance Items

Other key maintenance items include a bi-monthly or monthly burn out of the furnace heating chamber. This requires the furnace to have air safely injected into the chamber at or slightly above process temperature to allow the carbon to burn out of the furnace. Doing this process on a regular basis will help improve refractory and alloy component life as well as helping to maintain good process control.

Example thermal camera image

Another helpful snapshot of furnace health is using a thermal camera to take images of the equipment. It is recommended to do this on a monthly or quarterly basis. Thermal camera images can identify hot spots on the furnace outer steel shell that may indicate refractory deterioration or a furnace atmosphere leak. Thermal images can also identify potential issues with motors or bearings on fans and agitator assemblies.

Conclusion

In the end, all furnaces have different nuances that require different maintenance approaches. This could be based on the manufacturer, types of processes being run, or utilization of the equipment. By consulting with your original equipment manufacturer or other furnace service providers, a strong maintenance plan can be developed and implemented. This can include support and training from experienced professionals on that style of furnace. Broader cost benefit analysis should be done as it relates to spare part inventories, resource allocations, frequency of preventive maintenance activities, or investments into predictive maintenance and asset management technologies and how those activities can maximize utilization of each piece of equipment.

 

 

About the Author: Ben Gasbarre is president of Gasbarre’s Industrial Furnace Systems division. Ben has been involved in the sales, engineering, and manufacturing of thermal processing equipment for 13 years. Gasbarre provides thermal processing equipment solutions for both atmosphere and vacuum furnace applications, as well as associated auxiliary equipment, and aftermarket parts and service.

 

 

 

 

 

 

All images provided by Gasbarre Thermal Processing Systems.

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High-Temperature Bearing Failures- Engineering a Solution

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Eric Ford, Vice President of Sales and Marketing, Graphite Metallizing Corp.

In this Technical Tuesday original article, read how an automotive manufacturing plant is able to solve high-temperature bearing failures by upgrading to bearings that use a self-lubricating material that can operate in extreme temperatures. Author, Eric Ford, Vice President of Sales and Marketing at Graphite Metallizing Corp., shares how these bearings decreased the need for unplanned and costly maintenance of parts in the case study that follows.

 

An automotive engine manufacturing plant in the Midwest upgraded the bearings in their gas nitriding ovens after encountering numerous failures with rolling element bearings.

An example of a flame curtain in an industrial setting (Photo source: Graphite Metallizing Corp)

This large manufacturing plant runs automated gas nitriding furnaces for treating their various engine components. A flame curtain, at the entrance to the furnace, produces a vertical stream of combustion products to minimize both the infiltration of room air into the furnace chamber and the disruption of the furnace atmosphere inside. The bearings for the conveyor rollers, closest to the flame curtain, are subjected to intense heat for a short period of time, about 30 seconds, which is enough to cook the grease in the bearings and degrade their performance.

In many automotive plants, these machines are running 24/7 for up to six months at a time. Any breakdown of this equipment has serious consequences in terms of profitability and delivery schedules.

Excessive Downtime

The plant was having trouble with the repeated failure of the rolling element bearings, located just prior to the furnace’s flame curtain. These bearings were failing within six months, causing unscheduled maintenance and downtime. Though there was an automatic grease system, temperatures of approximately 300°F resulted in the grease being cooked away rapidly, resulting in conveyor roller seizure.

When the bearings seized, production on the line stopped. The furnaces then needed time to cool sufficiently for maintenance personnel to be able to access and replace the bearings. Starting the system up again wasted yet more production time.

The conveyor transporting the parts has bearings to support the load and convey the product through the furnace. (photo source: Graphite Metallizing Corp)

It was taking three people about four to six hours to replace the bearings and start the furnace again each time the bearings failed. These unscheduled shutdowns cost tens of thousands of dollars in production loss, labor, and materials. In addition to the expense of the downtime, there was also the added safety risk of handling parts when unloading the furnace and performing maintenance on the equipment, which was still hot.

Successful Trials

At a heat trade show during this time, the production manager of the plant learned about Graphalloy bushing materials; Graphalloy is the name for a specific family of proprietary graphite/metal alloys developed by Graphite Metallizing Corp of Yonkers, NY. Its featured qualities include non-galling, corrosion resistant, dimensionally stable, and can operate at temperatures from cryogenic to higher than 1000°F (538°C). These materials work very well in severe environments and services due to their self-lubricating properties – no grease or oil is required. There are more than 100 grades of these high-temperature bushings which are designed for specific conditions.

Flange Bush 845 (photo source: Graphite Metallizing Corp)

Soon after the show, company representatives went to the plant and proposed a simple drop-in replacement for the current greased bearing flange block assemblies. The production manager agreed to test a few of the company's 4-bolt flange blocks with copper bushings, and they were installed a few weeks later.

The target was a difficult one: The production supervisor said that a doubling of the lifespan of the roller element bearings would enable the plant to stick to its twice-annual scheduled maintenance intervals. By achieving this goal, unscheduled maintenance shutdowns would be avoided.

During the one-year trial period, the high-temperature bushings were a success. Based on the positive result, the production manager installed additional bushing assemblies of this brand type during subsequent scheduled maintenance dates, until all furnaces had been converted to new self-lubricating bushings.

Update: Saving Time and Money

Graphalloy 4-bolt flange block in service. (photo source: Graphite Metallizing Corp)

The original bearing assemblies, installed over six years ago, have been operating  without a single failure or showing any appreciable wear.

By replacing the metal bearings with newer graphite bushings, the automotive company eliminated at least two unscheduled shutdowns and dozens of hours of maintenance work per year. According to the production manager, using this has saved this automotive giant hundreds of thousands of dollars to date.

For more information, Graphite Metallizing Corp

High-Temperature Bearing Failures- Engineering a Solution Read More »

Bill Disler on Carburizing Trends in the Automotive Heat Treating World

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, AUTOMOTIVE HEAT TREAT, CARBURIZING TECHNICAL CONTENT, FEATURED NEWS, OP-ED

Bill Disler President & CEO AFC-Holcroft

Automotive part designs and heat treating processes have undergone many changes over the years, especially the powertrain. By looking back at the progress of these changes, we can learn more about emerging trends in automotive heat treating today.

In this Heat Treat Today Technical Tuesday feature, Bill Disler, president and CEO of AFC-Holcroft, brings his familiarity with big atmosphere carburizing systems and LPC automotive cell carburizing systems and looks at how the evolution of equipment and process requests says a lot about the trends we see today in automotive heat treating.

This article originally appeared in Heat Treat Today’s June 2019 Automotive print edition.

Although many components undergo heat treatment processes, the powertrain—specifically, gears— typically requires more carburizing time than other automotive parts. Not surprisingly, the powertrain has also seen many changes in heat treatment trends.

Not only have powertrain designs gone through tremendous transformations but so has the equipment being used to process those evolved components. Having spent years on the supplier side of atmosphere furnaces, vacuum carburizing, and gas quench as well as induction systems, I find it interesting to look back at some of the drivers that have helped morph this industry’s heat treat needs.

Traditional Continuous Atmosphere Furnace

Large atmosphere pusher furnaces produced nearly all of the powertrain gears 20+ years ago. Today, cellular low-pressure carburizing (LPC) and gas quench systems carry the load, although the results have not been cost saving. Moving from high volume gas heated carburizing equipment to small batch carburizing in electrically heated furnaces did not reduce utility costs per part; instead, other areas adjusted to compensate. Eliminating the expense of hard grinding transmission gears was an acceptable rationale for this increase in both capital expense and operating costs. Eventually, streamlining the overall gear manufacturing process, combined with locating heat treat within machining lines, produced positive measurable results. Plant traffic decreased, minimizing safety risks. Cooler and cleaner furnace systems were designed. And installations were made easier. Many agreed the changes were justified.

Integrated Vacuum Heat Treat Cells

As we look back, many of these drivers for change proved valid. Others, not so much. In most cases, consumer preference for quiet powertrains necessitates hard grinding of gears. Green is in and talk of the absolute need for zero intergranular oxidation (IGO) in carburized gears has slowed. LPC/Gas post quenched parts are perceived as cleaner and leaner; however, it is often difficult to differentiate green parts from processed parts, so it has become a best practice to add part marking after carburizing and hardening to avoid even the remote risk of sending soft parts down the line to the next stage of manufacturing. Shot peening is still common for strength reasons. The ability to nest large cellular LPC systems within machining has been a success, but rarely are the installations as quick and easy as promised.

Hybrid Furnace Concepts

Conventional atmosphere furnace technology has advanced as well, although at a slower pace, in step with a renewed interest in energy efficiency, particularly in the U.S. where gas is cheap and electric is not. Combustion systems operate cleaner and at much higher efficiency than in the past. Having said that, it is curious how little interest end users have in trading cost-saving gas-heated systems for the easier to install, neater looking electric heating options. In addition, it is no longer common to use water for cooling conventional atmosphere furnace systems as end users do not want to deal with the cost and complications that accompany this option. The market is polarized over this. LPC systems rely on large water volumes for cooling, and they are small batch, electrically heated systems. At the same time, gas quench systems consume huge quantities of water and require giant 300 HP plus motors that are tough to manage in plant power systems.

Flexible and Re-deployable Heat Treat Systems

It is my observation that the automotive market is anticipating the next iteration of heat treat equipment. One type of process or equipment style will not fit all needs, yet all hope for the perfect single part flow solution—an elusive dream due to physics. The cost/time equation still does not balance, and carburizing offers the benefits many manufacturers are looking for, despite the desire to design the process out of practice. Many automotive transmission parts that were originally processed in LPC and gas quenched now use gas nitriding instead, even though gas nitriding is another long process, and nitriding introduces ammonia back into the process—something most automotive plants are not enthusiastic to have in their plants. Two steps forward and one step back.

Repackaging Continuous Furnace Systems

With the widening range of processes and solutions under exploration, as well as ever changing powertrain systems designed to accommodate supplemental electric motors, lighter weights, smaller cars, and larger SUVs, all we can be certain of is ongoing change. I believe that we have witnessed major adjustments in automotive heat treat processing as the pendulum has swung from big, multi-row atmosphere pushers with salt or oil quench to electric-heated cellular LPC and gas quench units. One surprising result has been the resurgence of salt quenching, which controls distortion of high-pressure gas at a much lower cost with less complexity. Salt, like gas, is a single-phase quench media: It does not boil in these processes like oil does, and it can be used at temperatures that support martensitic quench with far less thermal shock and much higher heat transfer than the options. Older processes carry the baggage of tarnished past reputations, but I no longer count them out. Today’s automation, process control technology, and innovation can provide the foundation for brand new concepts, repackaging of older ideas, and hybrids of multiple technologies. Together, these create building blocks that heat treat equipment suppliers will use to meet changing trends in automotive carburizing and heat treatment. It will be interesting to be involved in the journey as these changes take place.

About the Author: Bill Disler is president and CEO of AFC-Holcroft, part of the Aichelin Group located in Vienna, Austria. He is a member of the Board of Trustees -Metal Treating Institute (MTI), and a member of the Board of Advisors at Lawrence Technical University, College of Engineering in Southfield, Michigan. This article originally appeared in Heat Treat Today’s June 2019 Automotive print edition.

Bill Disler on Carburizing Trends in the Automotive Heat Treating World Read More »

Furnace Gas Composition Controlled with CO and CO2

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, BULK GASES & SYSTEMS TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT, MANUFACTURING HEAT TREAT TECH

 

Source: AZO Sensors

 

 

Many heat treat processes require protective or process gases. These gases often require careful monitoring. One of the protective and/or process gases used in many heat treat applications is an endothermic atmosphere which is made up largely of CO, CO2, H2, and N2. This article is about the creation and proper monitoring of endothermic atmospheres.

In an atmosphere furnace, the proper mix of these gases can help facilitate changes in the metal such as proper hardness and strength, resistance to temperature, or improved tensile strength to mention a few. Without careful control of temperature, time and atmosphere, metals can experience unwanted changes in properties such as hydrogen embrittlement, surface bluing, soot formation, oxidation, and decarburization. With such critical outcomes in the balance, it is necessary to control the endothermic gas.

An excerpt:

“In order for the required metal treatment to be a success, you must control and monitor the gas composition with extreme care. The concentrations of gases, CO₂, H₂O, CH₄, N₂, H₂ and CO, that make up the endothermic gas atmosphere should be measured in order to aid the prevention of unwanted reactions and ensure that the endogas generator and the furnace are operating normally.”

 

Read more: “CO and CO2 Control of Endothermic Gas in Heat Treatment Furnaces”

Furnace Gas Composition Controlled with CO and CO2 Read More »

Heat Treat Tips: Atmosphere Control

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, CONTROLS, FEATURED NEWS, HEAT TREATING ACCESSORIES, MANUFACTURING HEAT TREAT, MANUFACTURING HEAT TREAT TECH

During the day-to-day operation of heat treat departments, many habits are formed and procedures followed that sometimes are done simply because that’s the way they’ve always been done. One of the great benefits of having a community of heat treaters is to challenge those habits and look at new ways of doing things. Heat Treat Today‘s 101 Heat Treat Tips, tips and tricks that come from some of the industry’s foremost experts, were initially published in the FNA 2018 Special Print Edition, as a way to make the benefits of that community available to as many people as possible. This special edition is available in a digital format here.

Today, we begin an intermittent series of Technical Tuesday posts of the 101 tips by category, starting with Atmosphere Control. 

Atmosphere Control

Heat Treat Tip 5

Out of Control Carburizing? Try This 11-Step Test

When your carburizing atmosphere cannot be controlled, perform this test:

  1. Empty the furnace of all work.
  2. Heat to 1700°F (926°C).
  3. Allow endo gas to continue.
  4. Disable the CP setpoint control loop.
  5. Set generator DP to +35°F (1.7°C).
  6. Run a shim test.
  7. The CP should settle out near 0.4% CP.
  8. If CP settles out substantially lower and the CO2 and DP higher, there’s an oxidation leak, either air, water or CO2 from a leaking radiant tube.
  9. If the leak is small the CP loop will compensate, resulting in more enriching gas usage than normal.
  10. Sometimes but not always a leaking radiant tube can be found by isolating each tube.
  11. To try and find a leaking radiant tube, not only the gas must be shut off but combustion air as well.

Submitted by AFC-Holcroft

Heat Treat Tip 13

Finding the Cause for Bad Parts

So you just ran a batch and the parts are bad. Now what? According to Jim Oakes at Super Systems Inc., here is a good checklist to use to start isolating the problem. While not exhaustive, this list can at least take you through a progression of steps to help start identifying the culprit.

Step 1:  Review the process data for abnormalities. Did the setpoint for temperature and atmosphere get set properly? Does the process chart show good control of the temperature and atmosphere? Was the time at heat correct? Was the quench and temper processes run properly?

Step 2:  Check the generator to make sure it was pumping out the right atmosphere.

Step 3:  Check the furnace atmosphere. Even if the generator is working, there may be leaks in the furnace.

Step 4:  Check carbon controller to make sure it matches furnace atmosphere reading. Verify probe accuracy and adjust carbon controller.

Step 5:  Do probe troubleshooting. And if all else fails . . .

Step 6:  Replace the probe or call Super Systems for help.

Submitted by Super Systems Inc.

Heat Treat Tip 49

What to Do When Parts Are Light on Carbon

Many factors can contribute to why parts are not meeting the correct hardness readings. According to Super Systems Inc., here is a quick checklist of how to start narrowing down the culprit:

  1. Review process data for abnormalities: The first thing to do is make sure the parts were exposed to the right recipe. Check the recorders to make sure the temperature profile and atmosphere composition were correct. Make sure all fans and baffles were working correctly. Determine if any zones were out of scope and that quench times were acceptable. If any red flags appear, hunt down the culprit to see if it may have contributed to soft parts.
  2. Check the generator. Next, check the generator to make sure it is producing the gas composition desired for the process. If available, check the recorders to make sure the gas composition was on target. If not, check the generator inputs and then the internal workings of the generator.
  3. Check the furnace atmosphere. If the generator appears to be working correctly, the next step would be to check the furnace itself for atmosphere leaks. Depending on what type of furnace you have, common leak points will vary; for continuous furnaces, common leak points are a door, fan, T/C, or atmosphere inlet seals. Other sources of atmosphere contamination may be leaking water cooling lines in water-cooled jackets or water-cooled bearings. More than likely, if the generator is providing the correct atmosphere but parts are still soft, there is a leak into the furnace. This will often be accompanied by discolored parts.
  4. Check carbon controller to make sure it matches furnace atmosphere reading (verify probe accuracy and adjust carbon controller). This can be done using a number of different methods: dew point, shim stock, carbon bar, 3 gas analysis, coil (resistance), etc. Each of these methods provides a verification of the furnace atmosphere which can be compared to the reading on the carbon controller. If the atmosphere on the carbon controller is higher than the reading on the alternate atmosphere check, that would indicate the amount of carbon available to the parts is not as perceived. The COF/PF on the carbon controller should be modified to adjust the carbon controller reading to the appropriate carbon atmosphere. If the reading is way off, it may require the probe to be replaced.
  5. Check the carbon probe.
  6. Replace the probe – CALL SSI.

Submitted by Super Systems Inc.

Heat Treat Tip 62

Double Check Carbon Potential Control

Configuring your atmosphere controller to ensure the correct carbon potential readings can sometimes be tricky. We suggest you double check your atmosphere control settings to make sure they are set up correctly. Before making a change to the carbon controller, make sure the atmosphere that the carbon probe and carbon controller are reading is matching up to an alternate method of atmosphere. This can be done using a number of different methods: dew point, shim stock, carbon bar, 3 gas analysis, coil (resistance), etc. Each of these methods provides a verification of the furnace atmosphere which can be compared to the reading on the carbon controller. The COF/PF on the carbon controller should be modified to adjust the carbon controller reading to the appropriate carbon atmosphere.

It is important to make sure that the alternate method of verifying atmosphere is done properly (sampling ports, time for atmosphere exposure, sample prep, etc).

The calculation of carbon in the atmosphere using a carbon/oxygen probe is based on the output millivolts — created based on the partial pressure of oxygen in the reference air versus partial pressure of oxygen in the furnace, the temperature of the furnace, and a calculation factor referred to as COF (CO Factor), PF (Process Factor), or Gas Factor.

The carbon controller can be modified so the COF/PF value can be changed to match up with the alternate reading. A furnace calculator on the SSI website or mobile app can help determine what these settings should be. It is important to note that you should not change these values to the point where you are masking another issue such as a bad probe or a furnace/generator issue.

Again, if the reading is way off (a setting of a COF below 130, for example), it may require the probe to be replaced.

Submitted by Super Systems Inc.

Heat Treat Tip 75

Carbon Probe Trouble Shooting

If you’re having atmosphere problems with a furnace that has been operating normally for some time, avoid the temptation to remove the carbon probe. There are several tests you can run on nearly all carbon probes while the probe is still in the furnace, at temperature, in a reducing atmosphere. Super Systems Inc. provides an 11-step diagnostic procedure in a white paper on their website, in a paper titled, “Carbon Sensor Troubleshooting” by Stephen Thompson.

Submitted by Super Systems Inc.

 

Heat Treat Tip 88

Slight Positive Pressures Are Best

Atmosphere furnace pressure should be only slightly above ambient. The range should be between 0.25 – 0.35 inches water column. Higher pressures in multiple zone pusher furnaces will cause carbon control issues. High pressures in batch furnaces will cause high swings when doors and elevators move.

Submitted by AFC-Holcroft

Heat Treat Tip 94

Confirm Composition of Endothermic Atmosphere

Wisdom dictates a trust-but-verify approach to your endothermic generator. Although your generator is supposed to crank out a consistent endo atmosphere, we suggest periodically verifying the integrity of that atmosphere with a dewpoint analyzer or a 3-gas analyzer. Generator control systems provide control of air gas ratio and possibly a trim system, used to maintain a dew point that could be rich (too much gas) or lean (too much air). The dew point range could typically be between 30°F and 50°F. Flowmeters are provided to maintain a base ratio (2.7 : 1) for the air/gas mixture supplied to a retort filled with nickel-coated catalyst. The gas is then passed through an air cooler (some older systems used water) to freeze the reaction so the gas can be transported through a header system to furnaces. The ratio at which the gas is generated offers a dew point that can be measured. The makeup of the endothermic gas provided by a generator is typically 40% hydrogen, 40% nitrogen, and 20% carbon monoxide. Maintaining these percentages will result in a carburizing atmosphere that is conducive to best carburizing practices.

Non-dispersive infrared analyzer (NDIR) systems are invaluable when trying to troubleshoot generator issues. The analyzer will typically measure CO, CO2, and CH4. As mentioned earlier, if we know that 20% CO is being generated, we can cross check the air/gas ratio and sticking flow meters, or determine that an adjustment of the air and/or gas ratio is required. The measurement for indication of sooted or nickel depleted catalyst can also be achieved by using an analyzer. If the indicated measurement of CH4 is higher than .5%, a burnout of the catalyst is required, using the manufacturer’s required procedures. If after a burnout the CH4 level is still high, the catalyst may need to be replaced altogether.

Submitted by Super Systems Inc.  

If you have any questions, feel free to contact the expert who submitted the Tip or contact Heat Treat Today directly. If you have a heat treat tip that you’d like to share, please send to the editor, and we’ll put it in the queue for our next Heat Treat Tips issue. 

Heat Treat Tips: Atmosphere Control Read More »

Effective Furnace Scheduling

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT

 By John Young, Young Metallurgical Consulting

Effective furnace scheduling requires the inclusion of several key elements.

“Customer” Demands:  Manufacturers with in-house heat treat departments have internal customers who, like customers the world over have one thing in common, they want to provide parts to you tomorrow and have them processed and ready yesterday.  These internal customers cause frustration and angst but their work is what pays the bills.

Product & Process Variables:  There are numerous product and furnace process variables all of which must be considered when scheduling.  Common variables include:

  • Material grade and chemistry
  • Atmosphere carbon potential
  • Hardening and tempering furnace temperatures
  • Ammonia addition for carbonitriding and the purge time required when finished
  • Belt speeds
  • Cycle times
  • Variable quench programs

Process changes are necessary but minimizing the degree of variation between consecutive product runs is the goal.  The more significant the change, the longer the gap time required to allow the furnace to stabilize with the new furnace parameters.  Gap time is an unrecoverable cost – wasted time and money.

Sample Furnace Scheduling Sheet

 

 

Sample Furnace Scheduling Sheet

Quality issues can also be caused by not allowing sufficient time between significant process parameter changes.  If the proper gap time is not provided, the end of one lot or the beginning of the next may experience quality issues.

Each heat treat department must determine the balance of efficiency and customer service that works best for their operation.

Developing a close working partnership with your internal customers is beneficial for both parties.  Heat treating is typically at or near the end of the manufacturing cycle and all the lead time has been utilized by the previous steps.  Teach them the basics of your operation and explain the ways they can help you provide better service and delivery. By providing as much information as possible about their delivery requirements, you can schedule to meet their demands.

Rush jobs are the nature of the business and will always be with us. They are inevitable but they can be reduced. I know of one customer who provided parts at 3:00 PM and asked for impossible results for the next morning.  After numerous conversations with the heat treat department, the part supplier finally understood the heat treat process and now allows one, two, or even 3 days for results. Encourage part suppliers to give you next week’s Hot List at the end of the current week.

Heat treat scheduling is never easy but it can be improved to help your operation.

About Young Metallurgical Consulting

Young Metallurgical Consulting works with in-house heat treat departments to teach the day-to-day processes necessary to manage and improve their area of operation. In-house heat treaters will learn the aspects of heat treating that are not taught in a classroom and can only be gained through direct, hands-on experience. Contact John Young at john@youngmetallurgicalconsulting.com.

John Young
John Young, Young Metallurgical Consulting

 

Effective Furnace Scheduling Read More »