After 15 years of collaboration, a new CAB furnace designed for production of heat exchangers for delivery vehicles, trucks, and cars is set to begin operating in Monterrey Mexico.
This 15-year collaboration between SECO/WARWICK and their Asian partner began in 2010 when the two began working together on solutions for heat exchanger production for trucks, passenger cars, and new energy technologies. The new CAB line that will operate in Mexico is equipped with a thermal degreasing furnace, preheating chambers, a radiation furnace, a deicing furnace, a final cooling chamber, and an advanced control system. These features are designed to meet the requirements of the automotive industry, as well as ensure long-term and reliable operation.
Liu Yedong Managing Director SECO/WARWICK China.Piotr Skarbiński Vice President of Aluminum and CAB Products Segment SECO/WARWICK
“We can say that this is the jubilee 15th order, exactly on the 15th anniversary of our cooperation beginning,” said Piotr Skarbiński, vice president of the Aluminum and CAB Products Segment at SECO/WARWICK Group.
“The CAB line with a 1,400 mm wide belt ensures excellent temperature uniformity across the entire width, which translate into the final product quality,”Liu Yedong, managing director of SECO/WARWICK China added.
Press release is available in its original form here.
In this Technical Tuesday by Paulo Duarte, project manager, Metalsolvus, explores how digital tools lead the way in vacuum hardening operations to ensure energy efficiency and processing repeatability.
This piece was originally published inHeat Treat Today’sMarch 2025 Aerospace print edition.
Vacuum hardening has been the chosen process for hardening tools used in plastic injection, die casting, and metal sheet stamping over the past few decades. Although widely used and accepted, there is still room for improvement in tool performance through quality-driven procedures. By employing easy methods of measurement, study, and testing, it is possible to enhance part integrity and mechanical properties, while simultaneously reducing heat treatment time and energy consumption. Advanced metallurgical analyses of heat treatment cycles and equipment can introduce better tools on the market, as well as provide time and cost saving heat treatments.
Basics of Vacuum Hardening
In vacuum hardening furnaces, temperature and time are carefully controlled at specific load locations to ensure optimal hardening. Optimal practices focus on heating and soaking the metal parts during heat treatment. The controlled introduction of vacuum and inert gases during the process ensures the right protective atmosphere for treatment, resulting in steel that is mainly free from oxidation and decarburization. This preserves the surface integrity of the tools.
Cooling is achieved through the injection of an inert gas into the heating chamber, with controlled pressure and adequate recirculation between the heat exchanger and the hot zone (Figure 1). Different gas injection directions are utilized depending on the load being treated, ensuring optimal cooling.
Figure 1. Cooling parts in vacuum hardening furnaces — inert gas injection on the hot chamber during cooling
Hardening of Large Tools
Heating and quenching large tools is one of the most challenging situations for vacuum hardening, as temperature control and part microstructure integrity are more difficult to obtain, which affects part quality. Large tools, typically made of hot work tool steels, are hardened in large furnaces. To minimize deformation, parts are preferably positioned vertically inside the furnace (Figure 2).
Figure 2. Large molds positioned inside the vacuum hardening furnace, two parallel cavities
Surface soaking times for big tools can significantly exceed standard austenitization and tempering times due to thermal gradients existing within the parts. Mold cores usually achieve the right soaking and tempering recommendation through accurate temperature control, monitored by well-positioned core thermocouples. A tool’s microstructure and performance will depend heavily on geometry, size, and temperature uniformity achieved during treatment. See Figure 3 for the core and surface typical hardening cycles for large tools.
Figure 3. Heating and soaking cycle for the hardening of large tools (“Heat Treatment of a AISI H11 Premium Hot-Work Tool Steel”)
The cooling phase is crucial in determining the final properties of both the surface and core of the tool. Higher gas injection pressures result in faster cooling and increased toughness, but this also introduces greater deformation risks, when directly cooled from austenitization temperature, so martempering done at low pressures is usually required.
Balancing cooling pressure is one of the most secret topics in vacuum hardening. With a variety of parameters and procedures used among heat treaters, measuring and testing is essential for achieving consistent quality for better controlling the hardening process and attaining the best part quality.
Figure 4. Microstructure and toughness obtained after the use of different hardening cooling rates (image from Transactions of the 15th NADCA Congress, 1989)
The use of higher or lower inert gas pressures directly affects the cooling rate, making it faster or slower, respectively. Regulating the gas injection pressure during the cooling phase significantly impacts the material’s toughness, even when cooling occurs within the bainitic-martensitic domain commonly observed in vacuum hardening practices. Faster cooling leads to finer microstructures, which in turn results in tougher materials. However, fully martensitic microstructures are rarely achieved in industrial vacuum hardening furnaces and are typically limited to smaller loads composed of small parts. In larger parts, the risk of pearlite formation increases, especially when cooling rates fall around 3°C/min (5°F/min) at the core, as illustrated in Figures 4 and 5.
Figure 5. Microstructure of Uddeholm Orvar Supreme steel after quenching using different cooling rates
In industrial heat treatments of large tools, accurately monitoring core temperature is challenging, as it is difficult to position a thermocouple hole exactly at the innermost location or a nearby region. This makes it harder to control the hardening process and prevent pearlite formation. Therefore, studying the process to establish effective control measures is essential for achieving the highest possible quality.
Heat treatment simulation simplifies this task by allowing the hardening process to be predicted, with thermal gradients estimated and compensated through furnace control parameter adjustments. Figure 6 presents a real case study, where the temperature distribution inside a large mold was fully characterized during the entire heat treatment cycle using FEM (Finite element method) simulation and validated through actual thermocouple measurements. FEM simulation, as a proven and highly effective technique for predicting heat treatment cycles, enables heat treaters to implement optimized, computer-supported heat treatment practices.
Figure 6. Mold temperature gradients during vacuum hardening: a) FEM mesh, b) gradients during heating at lower temperatures, c) gradients at the last pre-heating steps, and d) gradients during austenitization from Maia et al. “Study of Heating Stage of Big Dimension Steel Parts Hardening”; e) gradients during mold cooling from Pinho et al. “Modelling and Simulation of Vacuum Hardening of Tool Steels”
Vacuum Hardening Standard Block Size and Cycle Forecast
When working with loads composed of small to medium-sized parts, the core temperature of the load can be monitored using dummy standard blocks. These blocks have a central hole to accommodate the thermocouple used to control the heat treatment cycle. The dummy block should be selected to closely match the size of the largest part in the load. However, in commercial heat treatment settings, part sizes can vary widely, making it di cult to maintain a comprehensive set of dummy blocks that represents all possible heat treatment scenarios.
Once again, simulation proves valuable in helping heat treaters gather useful data to anticipate the heat treatment cycle and determine the appropriate range of dummy blocks to have available on the shop floor. The procedure for selecting the dummy block range and forecasting the corresponding heat treatment times is outlined in the following equations. Ideally, the standard block should be made from the same material as the largest part in the load. If the materials differ, the characteristic length of the block can be calculated using the first of the following equations.
Table 1. Proposed dimensional distribution range for cubic and cylindrical
standard blocks and expected cycle times in a typical 600 x 600 x 900 mm
hardening furnace (data from Figueiredo et al., “Study of a Methodology for
Selecting Standard Blocks for Hardening Heat Treatments”)
Table 1 lists a range of proposed dummy block sizes to be used for monitoring the load temperature during heat treatment. The time to end of soaking at higher temperature is also given by Table 1 for a typical 600 x 600 x 900 mm hardening furnace. Times were obtained by FEM simulation and can be used to forecast the end of austenitization in a hardening process of each dummy block.
The simulated times were validated by using real parts temperature measurement by thermocouples. These were the calculated errors based on simulation and heat treat validation trial:
Plate Example: 20 x 300 x 200 mm
Ideal standard block: diameter or edge: 51 mm
Maximum Error — same material block:
Cylindrical: -0.2% (-0.7 min)
Cubic: -0.1% (-0.4 min)
Maximum Error — block — Stainless steel 304:
Cylindrical: +2.2% (+9.2 min)
Cubic: +1.65% (+6.9 min)
EDM Block Example: 200 x 200 x200 mm
Ideal standard block: diameter or edge: 200 mm
Maximum Error — same material block:
Cylindrical: -3.9% (-22.6 min)
Cubic: 0% (0 min)
Maximum Error — block — stainless steel 304:
Cylindrical: +17.3% (+100.3 min)
Cubic: +12.2% (+70.8 min)
Optimizing the Vacuum Hardening of Tools
Figure 7. Effect of selecting different temperature ( T)
range for starting to control the isothermal stage time. a)
T criteria and respective cycle time reduction; b) surface
mechanical properties obtained by using different T;
and c) core properties after tempering at different T
range (Miranda et al., “Heat Treatment of a AISI H11
Premium Hot-Work Tool Steel,” MSC)
FEM simulation can also be used to optimize the heat treatment process, but metallurgical testing remains crucial for providing reliable insights into safely reducing cycle time and energy consumption. Typically, for setting the isothermal stage time, a tolerance of -5°C relative to the temperature setpoint is used, leading to savings in both heat treatment duration and power consumption, as shown in Figure 7a. However, Figure 7b demonstrates that higher tolerance values (ΔT) can be considered. Tolerances of up to -10°C or even -20°C can be applied for controlling the soaking time without significantly affecting the hardness and toughness of the parts. Naturally, these results depend on the desired setpoints for the isothermal stages, but Figure 7c reflects the worst-case scenario for ΔT, referring to the use of lower austenitizing and tempering temperatures commonly applied in the hardening of hot-work tool steels.
Future Trends of Vacuum Hardening
Innovations like digitalization, automation, and resource reduction, as part of Industry 5.0 initiatives, are expected to drive advancements in heat treatment processes. Long martempering, a heat treatment under development for hardening hot-work tool steels, shows promise as an alternative to traditional quenching and tempering. This process offers a balance of high hardness and toughness in significantly less time, providing energy savings and faster turnaround.
Figure 8. New long martempering heat treatment cycle: AISI H13 premium toughness for two different long martempering temperatures (“Study of The Bainitic Transformation of H13 Premium Steel”)
New Vacuum Hardening Process — Long Martempering
Long martempering is a heat treatment under development that can be used to harden hot-work tool steels. Long martempering is a process somewhat similar to austempering but is applied to steels rather than cast irons. Performed at temperatures within the martempering range, long martempering corresponds to an interrupted bainitic heat treatment with a specific process window (Figure 8) where high toughness is achieved at hardness levels exceeding those obtained through traditional quenching and tempering. Table 2 lists the mechanical properties attained for 5Cr hot-work premium tool steels.
The transformation during long martempering is not yet fully characterized in terms of microstructure, however, curved needles of bainitic ferrite are observed without carbide precipitation. This phenomenon is generally not associated with steel but rather with ausferrite in cast irons. Nonetheless, it is evident in at least H11 and H13 premium steel grades. This one day martempering treatment could potentially replace the traditional two- to three-day heat treatment cycle for large tools, offering significantly faster lead times and reduced energy consumption. Moreover, the mechanical properties achieved through long martempering are notable, as high levels of both hardness and toughness are obtained simultaneously, as demonstrated in Table 2.
Table 2. Mechanical properties of the new hardening process — long martempering
Industry 5.0
The integration of heat treatment equipment with management software enhances furnace utilization, quality control systems, and maintenance practices. Industry 5.0 can be implemented in heat treatment plants through the connection of databases that collect inputs from furnaces (e.g., temperature, time, pressure, heating elements, and auxiliary equipment performance) and production data (e.g., batch numbers, order details, operator information, cycle setup, and load weight). This data is analyzed by software to generate valuable insights for plant management, process optimization, predictive maintenance, and quality control.
A supervision interface for a 5.0 solution can monitor furnaces and control them remotely in real time (Figure 9). Operators receive updates on tasks, alerts, and production schedules. Additionally, plant productivity, efficiency, and maintenance can be tracked through the same supervision software, whether on site or remote. Automatic reporting is also possible, enabling the approval or rejection of cycles based on criteria that are not typically used in heat treatment plants. This not only improves quality but also facilitates process optimization and cost reduction.
Conclusion
Figure 10. Heat treatment quality automatic report including automatic approval
Acquiring a full understanding of furnaces in operation through data measurement and analysis allows full control over the heat treatment process. This facilitates process development, enabling cycle optimization and improvement in part quality. Additionally, testing and simulation practices can lead to cost reduction and shorter lead times.
The introduction of long martempering and Industry 5.0 will significantly enhance heat treatment processes, leading to improved delivery times and reduced operational risks. Automation and digitalization bring more data to the shop floor, improving plant management and resulting in greater efficiency, higher quality parts, and simplified task execution.
Finally, current personnel are busy with routine operations that are based on longestablished practices and may be limiting opportunities for innovation. Therefore, new teams or external consultants can be leveraged to focus on designing, studying, testing, and implementing each new heat treatment solution.
References
Fernandes, José, Laura Ribeiro, and Paulo Duarte. “Study of the Bainitic Transformation of H13 Premium Steel.” MSC thesis, Faculty of Engineering of Oporto University, 2021.
Figueiredo, Ana, Paulo Coelho, José Marafona, and Paulo Duarte. “Study of a Methodology for Selecting Standard Blocks for Hardening Heat Treatments.” MSC thesis, Faculty of Engineering of Oporto University, 2022.
Kind & Co. “Vacuum Hardening with Highest Levels of Precision.” Accessed January 30, 2025. https://www.kind-co.de/en/company/technologies/vacuum-hardening.html.
Maia, Pedro, Paulo Coelho, José Marafona, and Paulo Duarte. “Study of Heating Stage of Big Dimensions Steel Parts Hardening.” MSC thesis, Faculty of Engineering of Oporto University, 2013.
Metaltec Solutions. “Brochure Presentation.” Accessed January 30, 2025. https://www.metalsolvus.pt/en/wp-content/uploads/2019/01/plant-supervisionbrochure-V3.pdf.
Miranda, Isabel, Laura Ribeiro, and Paulo Duarte. “Heat Treatment of AISI H11 Premium Hot-Work Tool Steel.” MSC thesis, Faculty of Engineering of Oporto University, 2024.
Pinho, José Eduardo, Gil Andrade Campos, and Paulo Duarte. “Modelling and Simulation of Vacuum Hardening of Tool Steels.” MSC thesis, Aveiro University, 2017.
Ramada. “New Hardening Furnace up to 4 Tons.” Accessed January 30, 2025. https://www.ramada.pt/pt/media/noticias/novoforno-de-tempera-vacuo—ate-4-tons-.html.
Schmetz. “Schmetz Heat Treatment Furnaces.” Accessed January 30, 2025. https://edelmetal.com.tr/en/heat-treatmentfurnaces.
Schmetz. Sketch of the Cooling Process in the Vacuum Hardening Furnace: Schmetz Commercial Proposals Drawing – Metalsolvus Training Courses Documentation.
Seco/Warwick. Vector 3D Hardening Furnace Commercial Brochure.
Solar Manufacturing. “Solar Vacuum Hardening Furnace.” Accessed January 30, 2025. https://solarmfg.com/vacuum-furnaces/horizontal-iq-vacuumfurnaces.
Wallace, J.F., W. Roberts, and E. Hakulinen. “Influence of Cooling Rate on the Microstructure and Toughness of Premium Grade H13 Die Steels.” Transactions of the 15th NADCA Congress (1989).
About the Author:
Paulo Duarte is a researcher and consultant on heat treat technologies. His education and expertise in metallurgy has culminated in several articles and patents. He was a former technical manager within bohleruddeholm group for the Portuguese market and heat treatment manager with the same group. Currently, Paulo efforts focus on helping heat treaters by providing innovative, more efficient, and profitable heat treatment services to companies.
For more information: Contact Paulo Duarte at paulo.duarte@metalsolvus.pt.
A major automaker announced a $20 billion investment in United States-based manufacturing.
Hyundai‘s investment, which the automaker described as a pledge to increase localized production in the United States, will create over 1,000 jobs. As part of the pledge, the company will open a $5.8 billion steel plant in Louisiana.
This near-shoring move by Hyundai is one among many automakers who are currently planning major U.S. investments, including Stellantis, which promised $5 billion to U.S manufacturing and Honda, which is expected to produce new Civic hybrids in Indiana.
Press release is available in its original from here.
Heat TreatToday publishes twelve print magazines a year and included in each is a letter from the editor, Bethany Leone. In this installment, which first appeared in the March 2025 Aerospace Heat Treatingprint edition, Bethany gives a preview of important events ahead in 2025 for the heat treating industry.
Feel free to contact Bethany at bethany@heattreattoday.com if you have a question or comment.
Just about now, the demands of one big event — welcoming a newborn into our family — will be monopolizing my time for the next few months. While I am more than happy to set aside work to get to know this little person, let’s not deny that I’m missing out on quite a few amazing industry events!
The late spring period of the year sees more people willing to travel, and so events abound for our industry. This editor’s page highlights just a few things that you can enjoy (and that I will be missing) between now and June.
March Highlights
The end of March kicks off the trade show season in Las Vegas, NV. At TMS 2025, metallurgists gather from March 23 to 27 to discuss industrial innovations. With more than 100 symposia on the docket, the sessions are divided into 11 tracks. These categories include additive manufacturing, advanced characterization methods, and light metals. The exhibition includes a poster presentation space. Suffice it to say, this event is intended for heat treat researchers and implementers who are looking to hear about practical innovations in the materials space.
April Highlights
Four years ago, I attended the International Conference on Hot Isostatic Pressing (HIP) in Ohio. This April 6 to 10, the city of Aachen, Germany, will be hosting the conference. Attend sessions and tour plants in the area over the course of several days. Additive manufacturing coupled with HIP as well as heat treating with HIP vessels will be part of the discussion. The event page says, “Improvements in HIP technology … have the potential to strengthen the competitiveness of many companies which are active in emerging industrial areas.”
During that same week, heat treaters will be gathering in Detroit, MI, for RAPID + TCT from April 8 to 10. For those interested in staying at the top of industrial innovation in additive manufacturing and industrial 3D printing, this is the event to watch. Browse real-world solutions at the show and dig into the details at technical sessions. Being that this is the largest AM show in North America, it is worth a visit if this is a technology your operations are curious about or interested in understanding better.
The following week, CastExpo will be attracting suppliers, peers, and customers to the casting market. Happening in Atlanta, GA, from April 12 to 15, this is primarily a time once every three years to network and advance strategy. Among the different topics addressed through exhibits, presentations, and featured events, two are particularly noteworthy for the U.S. manufacturing industry in 2025: reshoring and supply chain & logistics. Of ever-growing importance are topics such as artificial intelligence & machine learning and simulation.
If you are interested in any part of the ceramics supply chain — be it sourcing material or implementing new technologies, the Ceramics Expo USA in Novi, MI, will be the event to attend from April 28 to 30. is annual event, like many, offers space to collaborate and new partners to create solutions.
May Highlights
Launch your May with AISTech 2025 returning to Nashville, TN. The annual iron and steel conference offers opportunities to connect and hear advances happening in the industry. There are so many opportunities to connect with suppliers in the industry and advance one’s understanding of what is happening. From May 5 to 8, you can take the pulse of what direction this segment of American manufacturing is headed and how to prepare.
Bonus Event
While nominations are always open, Heat TreatToday’s40 Under 40 launch will be happening in May 2025. Jayna McGowan led the charge last year, and the team already is excited to see what in-house heat treat professionals in North American manufacturing will be nominated and recognized this year. Visit www.heattreattoday.com/40under40 for more information about how to nominate.
I’m looking forward to reconnecting with the industry folks later this summer. In the meantime, there are a few Heat Treat Kids onesies I’m needing to sort …
A German industrial plant will be the first to receive locally generated wind power through a direct connection.
With the green energy from the four new wind turbines installed by project partner SL NaturEnergie, thyssenkrupp Hohenlimburg, a subsidiary of thyssenkrupp Steel, can now cover 40% of its average annual electricity requirements.
The four wind turbines, each up to 160 meters in height and with a rotor diameter of 138 meters, are connected to the thyssenkrupp Hohenlimburg plant network via a direct line a good 3 kilometers in length. The wind farm generates over 55 million kilowatt hours annually, allowing the majority of this energy to be used directly without relying on the public grid. Surplus quantities are only supplied to other Group sites via the public grid in the event of high wind speeds or lower demand at the plant.
Nadcap certifications are integral to aerospace heat treating. Maintaining compliance, however, can be a headache. Learn how a new technology is streamlining Nadcap certifications.
This article by Chantel Soumis was originally published inHeat Treat Today’s March 2024 Aerospace Heat Treatprint edition.
Challenges to Capture Nadcap Certifications
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The Nadcap certification (National Aerospace and Defense Contractors Accreditation Program) plays a critical role in maintaining the integrity of heat treating processes, especially in the aerospace and defense industries. Recognized globally, the certification sets rigorous standards for heat treatment facilities, ensuring that heat treating processes produce parts and materials with the necessary strength, durability, and reliability.
The certification addresses the data that needs to be documented concerning all aspects of the heat treat processing, such as temperature control, process documentation, and quality management. A survey from the Performance Review Institute (PRI) indicates that 80% of aerospace and defense companies consider Nadcap accreditation as a requirement when selecting suppliers, and 90% of aerospace and defense prime contractors would disqualify a supplier without Nadcap accreditation. And when such a strict standard is implemented and then subject to regular audits, a 40% reduction in nonconformance costs are likely, as was reported by companies in the aerospace and defense sector in a study by the National Center for Manufacturing Sciences (NCMS).
While compliance with Nadcap and other heat treat certifications demonstrates a commitment to quality and opens doors to lucrative contracts with aerospace, defense, and other precision industries, actually capturing the data can be tedious. The effort and cost of employing disconnected systems — capturing measured data from system A, making the certification documents in system B, and then emailing the certification results to clients from system C — can be cut by synthesizing these actions into one system.
Digitizing Certification Management for Complete Compliance Control
Many organizations facilitate the certification process via digital means. This may be through the use of digital quality management systems (QMS) or enterprise resource planning (ERP) software that includes modules designed for certification management. These tools help automate record keeping, provide alerts for upcoming certification renewals, and streamline the overall certification tracking process, ensuring that heat treating operations remain compliant and efficient.
Nadcap Scanner tracking a process via QR code
But more should be done.
Veterans Metal, a metal finishing plant in Clearwater, Florida, was driving manual processes: everything was written down and data was being entered into spreadsheets for tracking purposes. Like many heat treaters, each step the company took to process a part required manual intervention to write down 20+ line items of information and then incorporate the associated data entry into spreadsheets.
The company was looking to modernize their plant.
After careful evaluation of Veterans Metal’s processes and needs, Steelhead Technologies developed and deployed the Steelhead Certification Scanner (or Nadcap Scanner) line that includes a handheld scanner and a system of QR codes to facilitate an easier user experience, including an interface that allows for swift operator proficiency, typically within minutes. This digital interface allows users to measure data, create certifications, and email this from the one system.
Smart Scanning in Action
The metal processing company received a 15-minute walk-through of the Nadcap Scanner, how to process parts, and where to find the data within the system. Using the handheld device, operators scanned QR codes (specifically created by Steelhead Technologies) that were placed on processing stations. As parts were moved from one process station to the next manually, a user would scan the accompanying QR code on the next current station, locking in data from the previous process and automatically reflecting that the next step was in process.
When operators scanned a process station, the device showed the remaining time in the process and displayed all parts being processed, custom instructions, and key data collection, such as oven temperature. This timer automatically starts when a process station QR code is scanned, gives a one minute warning when the process is nearing completion, and stops automatically when the next process station QR code is scanned.
Chet Halonen, a plant optimization expert for Steelhead Technologies, presented the “Powered by Steelhead” certification to the Veterans Metal team.
With the intuitive layout and guided steps, operators were easily able to navigate the accreditation process, significantly reducing time spent on extensive training. More importantly, the Nadcap Scanner line eliminated handwritten data entry, margin of error, and additional time needed to develop certifications since the scanner automatically generates them from the data and sends them to clients. The scanner has since been adopted by many other Nadcap-compliant operations across the United States.
Take Nadcap Digital
Achieving Nadcap accreditation is crucial for showcasing a commitment to quality, aligning with industry benchmarks, and accessing lucrative business opportunities. With the advent of digitized solutions like the Nadcap Scanner implemented within a comprehensive manufacturing ERP, companies will streamline the accreditation process, enhance operational efficiency, and bolster compliance with a system that’s “literally just button clicking,” as one manufacturer observed.
Embracing innovative tools not only saves time and resources, but also strengthens market positioning and client relationships. By merging the prestige of Nadcap accreditation with digital advancements, heat treaters can elevate their operations to reach new heights of excellence.
About the Author
Chantel Soumis, Head of Marketing, Steelhead Technologies
Chantel Soumis is serving as the head of Marketing at Steelhead Technologies. With a robust background in manufacturing technology and strategic partnerships, she leverages over 15 years of experience to shape the company’s marketing landscape.
For more information: Contact Chantel at chantel@gosteelhead.com.
Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com
For gun barrels, tempering is essential to bring steel to the necessary hardness. But what equipment is needed, and how is this done under a nitrogen cover gas? Explore how low-oxygen temper furnaces — often electrically heated — accomplish this feat.
This article by Mike Grande was originally published inHeat Treat Today’sMay 2024 Sustainable Heat Treat Technologies 2024print edition.
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Steel tempering is a heat treatment process that involves heating the steel to a specific temperature and holding it at temperature for a specific time to improve its mechanical properties. Tempering is most commonly performed on steel that has been hardened by quenching. Quenched steel is too brittle for most uses, and so it must be tempered to bring the hardness down to the desired level, giving the steel the desired balance between strength, toughness, and ductility.
Steel is tempered in an oven (often referred to as a “temper furnace”) at temperatures of roughly 350°F to 1300°F, with the exact temperature dependent on the alloy and the desired hardness and toughness. This heating process creates a layer of oxide scale on the surface of the tempered steel, which is unsightly, can weaken it, and can lead to failure or damage. Further, the scale can directly interfere with the intended use of the steel parts. Although in many applications this surface oxidation is not a detriment (it may be removed in a subsequent operation for example), it is not acceptable for certain steel parts.
In order to prevent surface oxidation during tempering, the oxygen can be removed from the oven using nitrogen injected into the heating chamber. More specifically, the nitrogen acts as a protective “cover gas” by displacing the oxygen, reducing the percentage of oxygen in the heating chamber. Essentially, the nitrogen dilutes the oxygen in the oven until it is brought down to a low concentration, such that very little oxidation can occur, preserving the surface quality of the tempered steel.
Gun barrels, for example, are tempered to remove the residual stresses from rifling and other prior processes and bring the steel down to the required hardness.
The tempering process involves heating the barrel to a specific temperature in a nitrogen atmosphere which is very low in oxygen. This helps prevent oxidation and other unacceptable surface contamination that would weaken the steel and make it unsuitable for the rigors of shooting. The internal barrel pressure during the firing of an AR15 rifle, for example, can reach 60,000 PSIG, which generates the 2,200 pounds of force required to produce the typical 3,000 feet per second (2,000 miles per hour) muzzle velocity. Considering these operating conditions and the temperature cycling experienced by the barrels, the tempering process must be performed precisely, and it must be very repeatable. This requires a carefully designed furnace engineered specifically for low-oxygen tempering under a nitrogen cover gas.
Design of the Low-Oxygen Temper Furnace
The key features of a properly designed temper furnace are a tightly sealed shell, a robust heating and recirculation system, a nitrogen delivery and control system, and an atmosphere-controlled cooling arrangement.
The shell of the controlled-atmosphere temper furnace must be tightly sealed so that the factory air, which contains oxygen, is prohibited from mixing with the heated environment inside the furnace. Air contains about 21% oxygen, and if it gets into the interior of the furnace during heating, this oxygen will quickly cause oxidation of the steel. This requires the heating chamber itself to be designed and manufactured with tight tolerances to prevent uncontrolled entrainment of air into the furnace and leaking of the nitrogen cover gas out of the furnace.
Low-oxygen temper furnaces are most commonly electrically heated, and the wall penetrations for the heaters are designed with special seals to preserve the low-oxygen furnace atmosphere. The same is true for the penetrations to accommodate the thermocouples and other sensors, the cooling system, and the door. Special attention must be given to the door opening, and the door itself. As the interface between the hot furnace interior and the room temperature factory environment, it is especially prone to warping, which will allow leaks. There are different technologies used to combat this, including double door seals, water cooled seals, and clamps to squeeze the door against the furnace opening.
Figure 1. Nitrogen temper furnace with a load/unload table
As with a conventional non-atmosphere temper furnace, the heating and recirculation system must be designed with a high recirculation rate and a sufficiently robust heating system to aggressively and evenly transfer the heat to the load of steel. The furnace manufacturer will do calculations to ensure the heaters are sufficiently sized to heat the loaded oven within the desired time, and this is an important part of the technical specification for anyone purchasing a temper furnace. Otherwise, the equipment may not be able to maintain the required production rate.
One of the most critical parts of the atmosphere temper furnace is the nitrogen control system. The idea is to inject sufficient nitrogen into the heating chamber to maintain the reduced oxygen level, and no more than that. Th e most effective design uses a sensor to continuously measure the oxygen level in the furnace, and a closed-loop control system to regulate the flow of nitrogen into it. It is important the nitrogen is high purity (that it contains a sufficiently low oxygen level), and that it is sufficiently dry, as moisture in the heating chamber can greatly increase the likelihood of oxidation.
The process starts by purging the furnace with nitrogen to establish the required low-oxygen environment. Sufficient nitrogen is introduced to the furnace to bring the oxygen level down to the percentage required to heat the parts without undo oxidation. Each time a quantity of nitrogen equal to the interior furnace volume is injected into it, it is considered one “air change.” The number of air changes employed is determined by the desired oxygen concentration in the furnace, with five air changes being a common rule of thumb.
Figure 2. Purging the furnace with nitrogen to reduce the oxygen concentration
Purging is complete when sufficient nitrogen has been injected into the furnace to reduce the oxygen purity to the desired level. The nitrogen flow is then reduced to the minimum required to replace any nitrogen leaking out of the furnace. Some furnace designs simply flood the furnace with a high volume of nitrogen in an uncontrolled manner. Although effective at reducing the oxygen concentration, these systems can waste a profuse amount of nitrogen since it is used at an unregulated rate. A nitrogen control system, therefore, is advisable.
After the load is heated up and soaked at temperature for the required time, the furnace must be cooled down. In an ordinary non-nitrogen furnace, the door is simply opened, or a damper system is actuated, allowing cool factory air into the furnace, while exhausting the heated air. A nitrogen atmosphere temper furnace, however, must remain tightly sealed with the door closed, until the temperature is reduced to below the oxidation temperature, commonly 300°F to 400°F, aft er which the door can be opened. Since the equipment utilizes a well-insulated, tightly sealed design, it would take many hours, or even days, to cool sufficiently without a forced cooling system. For this reason, nitrogen temper furnaces must employ a sealed cooling system that cools the furnace without introducing factory air. This is done with a heat exchanger used to separate the reduced-oxygen furnace atmosphere from the cooling media, which is air or water.
Figure 3. Rear-mounted cooling system
The most effective style of cooling system uses cooling water passing through one side of the heat exchanger and the furnace atmosphere passing through the other. The heat exchanger is mounted to the rear exterior of the furnace, and the furnace atmosphere is conveyed through the exchanger, with dampers included to start and stop the atmosphere flow, thereby starting and stopping the cooling action. There are also systems available that pass cooling air through the exchanger, rather than water. Although less expensive, they provide a much slower cooling rate, which greatly increases the cooling time and reduces the production rate of the equipment, as fewer loads can be processed on an annual basis.
Nitrogen Tempering for Materials Other Than Steel
Some metals other than steel are heat processed in a low-oxygen nitrogen environment, while others do not benefit from this process.
Pure copper can be processed under a nitrogen cover gas to reduce oxidation during heating. If the oxygen concentration is not low enough, spotting of the material can occur, where black, sooty spots appear on the surface. Copper is much less sensitive than steel to moisture in the heating chamber. Copper alloys, such as brass or bronze, are not suitable for processing in a nitrogen atmosphere due to a phenomenon known as dezincification, which removes zinc from the alloy, weakening the material and turning it a yellow color. Titanium is not processed with nitrogen, as “nitrogen pickup” (a nitrogen contamination of the titanium) will occur. Aluminum can be processed under a low-oxygen nitrogen atmosphere to some benefit, which slows down the growth of surface oxidation during heating, but not to the degree experienced with steel.
About the Author
Mike Grande,
Vice President
of Sales,
Wisconsin Oven
Corporation
Mike Grande has a 30+ year background in the heat processing industry, including ovens, furnaces, and infrared equipment. He has a BS in mechanical engineering from University of Wisconsin-Milwaukee and received his certification as an Energy Manager (CEM) from the Association of Energy Engineers in 2009. Mike is the vice president of Sales at Wisconsin Oven Corporation.
For more information: Contact sales@wisoven.com.
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A group of graduates from MIT and Duke University identified manufacturing as an industry overburdened by rapidly growing energy costs and proposed a technology to provide electric bill savings of up to 30%. They will be piloting this technology with a U.S. heat treater, ThermoFusion, a Californian heat treater and brazer.
EQORE, a startup tackling energy issues for manufacturers, is developing smart energy storage systems. They aim to cut industrial energy bills by a third while offering a payback period of 1–3 years. Connected behind the meter, an EQORE system serves as an optimizing filter for electric equipment without changing its operation in any way. The system consists of a wall-mounted computing unit and a compact floor-mounted battery pack. It can be installed inside or outside of a facility and only needs a connection to the electric panel and internet.
The founding team features backgrounds in energy storage engineering from Tesla and Apple, as well as software and business development, and is supported by an innovation fund at MIT. The technology specifically targets reducing demand charges, which can account for 60–70% of industrial electricity costs. Demand charges penalize high variability in electric usage, a characteristic of heat treating facilities like ThermoFusion. For these facilities, a single peak in power usage can drastically increase the entire bill. Remarkably, in some locations in the U.S., demand rates have doubled since 2022.
After talking to over 200 businesses, utility representatives, and energy experts, the team concluded that the solutions to the demand issue remain limited. Available power optimizations disrupt customer operations, while independent power generation like solar is often out of reach due to its decade-long repayment periods. EQORE’s solution empowers clients to reduce energy costs while maintaining existing production levels.
Their team is actively looking to engage with more pilot customers and is open to collaborations.
The original press release is available upon request.
A blacksmith sweating over an open flame is not the image most heat treaters immediately identify with in 2024. In the present, heat treating tends to look more like a trained metallurgist supervising a complex brazing operation. Yet we should not throw out the blacksmith and his hammer, even though bridging the gap between past and present is a tough job. Bennett Heat Treating & Brazing Co., Inc. is known for doing just that.
This New Jersey heat treater was originally founded by Wilbur Bennett (a one-armed blacksmith turned heat treater) and was purchased by Anthony Quaglia in 1954. They make it their job to bridge the knowledge gap between the experienced and the novice heat treaters within their own team. After the sudden death of David Quaglia in 2017, John Quaglia leveraged his father’s foundational expertise to build a highly skilled team of seasoned veterans and emerging talent, which will one day include his children Anthony and Abby Quaglia. Today, Bennett Heat Treating has over 100 years of knowledge and over three generations of expertise to draw from in order to create an innovative future.
The original Bennett Heat Treating inspection department circa 1950s (Source: Bennett Heat Treating & Brazing Co., Inc.)
Technology and equipment are the keys to an innovative future, but new technology would be useless without inherited expertise. Bennett has been able to combine their modern equipment with veteran experience to create heat treating processes that are reliable. For example, their neutral salt bath with marquenching enables clients to control dimensions of parts with tight tolerances at high hardness requirements. The marquenching process is so repeatable that a few clients intentionally machine their intricate helical gears out of tolerance because they are sure Bennett’s process will return the parts to tolerance.
A solid team of knowledgeable experts who will bridge the heat treat industry’s generational gap also seamlessly meets the needs of clients. For Bennett’s major private, aerospace prime, and U.S. military clients, the metallurgical consultant team within Bennett bases its success on carefully listening to clients, identifying major lessons learned in the past, and collaborating with clients to methodize production processes that avoid past mistakes.
John Quaglia with wife Kerri and children Abby and Anthony at Bennett’s 100th year celebration (Source: Bennett Heat Treating & Brazing Co., Inc.)
John Quaglia recalls an example of how his team leads with expertise to collaborate with clients: a curved, thin part requiring nitriding on one area and optional nitriding all over it. After years of nitriding these parts, the team noted that when both sides of the part were nitrided, the edges chipped and the part would bow. Collaborating with the client, Bennett confirmed that only one side of the part needed to be nitrided. The team then developed tooling that was able to mask the part while maintaining the part’s dimensions.
In the future, Bennett Heat Treating & Brazing Co. intends to focus on gaining new equipment and building a cohesive team of employees to continue the high level of precision and quality work. No doubt, they will continue to seek to bridge the gap between seasoned heat treaters and new members on the scene through close communication — both amongst themselves and with clients. While the team will not be found in a blacksmith’s forge of the past, they will be collaborating with veteran experts and learning to apply that wisdom to meet the needs of present and future clients.
Poor energy efficiency in industrial furnaces usually impacts companies’ production costs since more energy consumption is required to achieve the desired temperature. This, in turn, has a tangible impact on their carbon emission footprint. In this Technical Tuesday by Alberto Cantú, VP of Sales at NUTEC Bickley, learn energy-saving solutions for industrial furnaces.
This article was originally published inHeat Treat Today’sMay 2024 Sustainable Heat Treat Technologies 2024print edition.
According to the International Energy Agency, the industrial sector is one of the main culprits when it comes to global energy consumption. In many situations, industrial furnaces tend to be the pieces of equipment that consume the most energy.
In this article, we will share a series of solutions you can implement to improve energy efficiency, reduce production costs, and be socially and environmentally responsible.
Factors that May Be Affecting Your Energy Efficiency
There are a couple of obvious factors that may be harming your energy efficiency ratings.
Heat Losses in the Furnace Process
These may be due to structural damage to the insulation or incorrect gas flow distribution inside the furnace.
Inefficient Combustion Processes
Contact us with your Reader Feedback!Industrial furnace flow check
Inefficiencies here are probably due to inadequate or excessive air/fuel ratios or poor mixture caused by internal damage to the burner.
Some tips we can pass on to help you improve furnace energy savings are:
Monitor the temperature on the cold side of the furnace, carefully checking that there are no hot spots.
Periodically analyze the composition of the furnace combustion gases, ensuring you are maintaining the expected levels of oxygen and CO.
Periodically check that the combustion air and fuel flows are in a stoichiometric ratio.
Check at least twice a year that the burners are in good condition and show no damage.
Avoid infiltration of cold air into the furnace that could affect the efficiency of the process.
Keep the temperature control loops tuned. If there is no temperature control loop, we recommend integrating one.
Periodically monitor consumption, either manually or automatically.
Ensure there is a program of predictive maintenance on the combustion system.
How Does Predictive Maintenance Work?
Attention to detail during predictive maintenance
This type of maintenance is based on the storage, monitoring, and analysis of data and quantifiable equipment variables in real time, such as temperature, vibration, and frequency.
It is necessary at the outset to understand the processes thoroughly and identify which aspects need to be analyzed, to make this approach work. These aspects include:
Temperature — monitoring the temperature may reveal abnormal changes, indicating possible overheating or component failure.
Vibration — unusual vibration may indicate machinery wear or imbalance, resulting in more severe damage if not addressed in time.
Frequency — analyzing particular patterns and behaviors during heat treat processing can provide insight into what may evolve into future potential problems.
Th ese actions will depend on appropriate measurement and detection control systems, the primary variable for these being sensors and algorithms. Firstly, sensors play a fundamental role in predictive maintenance, as they can detect subtle changes in the equipment’s performance, making it possible to identify potential failures before they occur. It is advisable to have access to an inventory of recognized sensor and spare parts brands, allowing you to measure your equipment’s variables.
Secondly, algorithms identify patterns and trends indicative of possible issues by processing large data amounts, allowing timely and planned interventions.
Factors Influencing Measurement Time
The time it can take to measure variables during a predictive maintenance process depends on many internal and external factors. Below we address some of them.
External Factors
Data analysis is a key component for effective preventative maintenance
The process — each industrial procedure has its own characteristics and requirements. For example, constant and real-time monitoring might be required in a continuous process, while a specified intervals approach might be best in other situations.
The product — some products may require frequent or strict monitoring due to their nature and characteristics.
Customer philosophy — some customers may have stricter standards or request more frequent monitoring to ensure the quality and reliability of their products.
Internal Factors
Capacity — strategic planning and scheduling measurements may be necessary if the equipment is limited or employed for other processes.
Availability of qualified personnel — ensuring that qualified staff are available at the right time to interpret the data obtained is crucial.
Energy-saving solutions for industrial furnaces — this is where you need to be able to rely on your combustion expert partner to advise on the most up-to-date energy-efficiency solutions you can implement in order to improve furnace performance and to help you reduce production costs.
Systems To Improve Furnace Energy Efficiency
Today, some systems that can significantly assist in reducing energy consumption can be implemented in your furnaces, thus preventing losses and/or eliminating inefficient processes. Here are some systems that can be implemented:
Energy Recovery Systems
These can be added to your furnaces to recover the heat from the flue gases so that they can be used again, heating the combustion air. Some options for these systems are self-recuperative burners and regenerative burners.
Flue Gas Measurement Systems
These guarantee that your furnaces always have the correct proportion of air and gas in their system. With them, you can continuously monitor the status and thus make decisions based on these data to adjust any out-of-proportion levels.
Preventive Maintenance Services
Besides the tips and systems for energy saving already mentioned, there are other actions that save energy, reduce costs, prevent failures in your industrial furnaces, improve their operation, and more.
Two of these are:
Audit and diagnosis service: The furnace input and output variables are measured in order to indicate current efficiency levels and to identify possible areas for improvement.
Burner calibration service: The air/fuel ratio is checked to ensure burners operate in the correct range.
Conclusion
In summary, if you consider implementing any of the tips and systems presented here, you can improve energy efficiency in your industrial furnaces and significantly reduce your operating costs. Be sure to check out the International Energy Agency if you are looking for further information on this topic.
About the Author
Alberto Cantú, Vice President of Sales, NUTEC Bickley
Alberto Cantú is the vice president of Sales at NUTEC Bickley. Cantú has more than twenty years of professional experience and has written prolifically for a variety of journals. Cantú is an honoree from Heat Treat Today’s40 Under 40 Class of 2020.
For more information: Contact Alberto at albertocantu@nutec.com.
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