ArcelorMittal is advancing a major expansion in electrical steel production that includes a preparation line, a continuous annealing and varnishing line, and a slitting line — developments that reflect ongoing job growth and investment in industrial heat treating processes worldwide. The project has already mobilized more than 300 external contractors, with 175 employees now dedicated to the new lines and staffing expected to reach approximately 200 as the next phase of work progresses. Phase 2, currently underway, includes construction of an annealing-pickling line and a reversible rolling mill, with all five planned production lines scheduled to be operational by 2027.
Entry zone of the continuous annealing and varnishing line Source: ArcelorMittal FranceBruno Ribo Managing Director ArcelorMittal France
ArcelorMittal France announced that the first three lines of its new electrical steel production unit at the Mardyck industrial site will enter into operation by the end of 2025. The project, representing a €500 million investment and described as the largest undertaken by the Group in Europe over the past decade, marks a significant expansion in the production of electrical steels, complementing the company’s existing output at Saint-Chély-d’Apcher and bringing the company’s total European output to approximately 295,000 metric tons annually.
Bruno Ribo, managing director of ArcelorMittal France, emphasized the significance of the development for both the site’s workforce and the broader market. “Creating new production lines is an exceptional experience in the life of an industrial site. It is just as exceptional for our employees who have been involved in the development of the lines, from the project phase to the operational phase. I, like them, will be very moved to see the first of the 155,000 tons of electrical steel that we will eventually deliver annually roll off the lines,” he said.
Annealing and varnishing line control cabin Source: ArcelorMittal France
The electrical steels produced at Mardyck — ultra-thin rolled steels engineered for specific magnetic and mechanical properties — are used in all types of electric motors. ArcelorMittal notes that the new unit will support the electrification of applications in both industrial and automotive sectors. As global demand grows for these specialty steels, capacity developments of this scale create benchmarks for manufacturers across regions, including North America, as companies assess long-term sourcing strategies and material availability for high-efficiency motor components and transformer systems.
The project is supported in part by a €25 million contribution from the French State under the France 2030 program.
Press release is available in its original form here.
Heat Treat Today has gathered the four heat treat industry-specific economic indicators for December 2025. The December results suggest more limited growth than what was predicted in November of 2025.
December’s indices showed modest expansion with mixed momentum across different indicators. The Inquiries stayed moderately positive at 51.3 (from 56.5 in November). Bookings are encouraging at 56.3 (up from 55 in November). The Backlog index is in contraction territory at 46.3 (from 55 in November). Finally, the Health of the Manufacturing Economy index showed moderate growth at 53.8 (from 56.5 in November).
The data suggests cautious optimism but warrants close monitoring of inquiry trends and backlog levels in coming months.
The results from this month’s survey (December) are as follows: numbers above 50 indicate growth, numbers below 50 indicate contraction, and the number 50 indicates no change:
Anticipated change in Number of Inquiries from November to December:51.3
Anticipated change in Value of Bookings from November to December: 56.3
Anticipated change in Size of Backlog from November to December: 46.3
Anticipated change in Health of the Manufacturing Economy from November to December: 53.8
Data for December 2025
The four index numbers are reported monthly by Heat Treat Today and made available on the website.
Heat TreatToday’sEconomic Indicatorsmeasure and report on four heat treat industry indices. Each month, approximately 800 individuals who classify themselves as suppliers to the North American heat treat industry receive the survey. Above are the results. Data started being collected in June 2023. If you would like to participate in the monthly survey, please click here to subscribe.
Producing durable, wear-resistant gears for the wind turbine industry requires exacting control of carbon diffusion. Modern low pressure carburizing (LPC) is pushing the boundaries of control and consistency. This technology fine tunes carbon diffusion into the surface of components, and applied in a new pit-style vacuum furnace, it also delivers temperature uniformity, stronger gears, and shorter cycle times for large, complex components, all while eliminating oxidation and direct CO₂ emissions. In this Technical Tuesday installment, Tom Hart, director of sales for North America at SECO/WARWICK Corporation, examines how modern LPC technology in a pit-style vacuum furnace is reshaping high-volume carburizing for today’s in-house heat treaters.
This informative piece was first released inHeat Treat Today’sNovember 2025 Annual Vacuum Heat Treating print edition.
The Need To Carburize
Carburizing is a thermochemical treatment that finds applications across the automotive, aviation, and energy industries, particularly in power transmission systems. The widespread use of this process across many industries stems from its ability to improve mechanical properties by enriching the surface of steel with carbon.
Consider the wind turbine industry, growing with a CAGR (compound annual growth rate) of 6.2% from 2024 to 2033 (GlobeNewswire 2024). Carburizing plays a key role in the production of gears and pinions. These components, often made of alloy steels, such as 18CrNiMo7-6, 4320, 4820, and 9310 (GearSolutions 2009, Jantara 2019), must meet high strength and quality requirements. Carburized layers, often over 4 mm thick, provide resistance to wear and dynamic loads, which is important given the turbine’s expected service life of at least twenty years.
In practice, however, gears often require servicing after five to seven years (Jantara 2019), with their failures generating long downtimes and high costs (Perumal and Rajamani 2014).
Figure 1a: Pit-LPC in a hardening cell (model)Figure 1b: The view from the operator platform
The carburizing process, combined with hardening (usually in oil) and tempering, increases:
Surface hardness: improving abrasian resistance
Core ductility: protecting against cracks
Fatigue strength: extending the life of the part, which translates into lower operating costs
Alternative technologies, such as nitriding or surface hardening, offer other benefits (e.g., reduced deformation), but have limitations, such as thinner hardened layers, relatively long nitriding process times, or difficulties with complex geometry for surface hardening.
Pit Meets Vacuum LPC
Traditional atmospheric carburizing, despite its established position, has reached its limits in process performance expectations. In response to market needs, LPC (low pressure carburizing) technology is being increasingly implemented to enable precise process control, reduced emissions, and improved energy efficiency. More specifically, a pit furnace with vacuum heat treatment capabilities, aka the Pit-LPC, has been designed and developed to carburize thick layers on very large and/or long parts. This furnace combines the advantages of LPC technology with the ability to integrate existing hardening cells, facilitating the modernization of older installations.
While a vacuum furnace opening to an air atmosphere is a feature previously reserved for atmospheric furnaces, this innovative pit furnace has ceramic insulation and a dedicated heating system to leverage this capability. The chamber door can therefore be opened at process temperature in an air atmosphere for the direct transfer of the charge to the hardening tank. Additionally, the furnace is equipped with a closed circuit forced cooling system, which significantly shortens the charge cooling time from the carburizing temperature to the hardening temperature, increasing efficiency and shortening the production cycle.
Furthermore, the furnace allows for the process to be carried out at temperatures of 1925°F (1050°C) and higher, significantly shortening carburizing time and reducing production costs, even while maintaining a safe level of grain growth (e.g., 1800°F (980°C)).
Benefits of LPC technology designed in a pit furnace include:
Reduced process time due to higher operating temperatures
Elimination of internal oxidation (IGO) in the carburizing process
Highly uniform carburized layer
Low process gas consumption
No direct CO₂ emissions and fire risk
Ready for operation without lengthy conditioning
Computer-aided process support
Additionally, the furnace design increases work safety and comfort in its elimination of open flames, risks of explosion, and the need for constant atmospheric monitoring.
Figure 2. SimVac program window with an example LPC process simulation
This new pit furnace is compatible with SimVac software, developed by Lodz University of Technology and SECO/WARWICK, which enables the simulation and optimization of LPC parameters, reducing the need for process tests. SimVac Plus is a simulation software that includes a vacuum carburizing module (Figure 2). The program can be used either as a standalone tool for designing processes based on the desired carburized layer requirements or to visualize the effect of a given boost/diffusion sequence in the form of a carbon profile.
Testing the Furnace Characteristics and Technical Parameters
The furnace was designed to meet the highest requirements for heat treatment equipment. The basic technical parameters are as follows:
Working space / charge weight: 71″ diameter x 118″ deep / 17,600 lb (1,800 mm x 3,000mm deep / 8,000 kg)
Operating temperature: up to 2010°F (1100°C)
Heating power: 360 kW, three independent zones
Vacuum level: 10⁻² torr
Carburizing gas: acetylene
Temperature Uniformity
Temperature distribution tests were conducted in the furnace, with 12 load thermocouples arranged according to the diagram shown in Figure 2. Measurements were taken at several temperatures under vacuum conditions. The purpose of the tests was to confirm compliance with the Class 1 ±5°F (3°C) requirements of the AMS2750 standard.
Figures 3a-d. Location of the TUS load thermocouples and the results in vacuum at temperatures of 1550°F (840°C), 1800 °F (980°C), and 1925°F (1050°C)
The results presented in Figure 3 indicate that the furnace provides above-average temperature uniformity, which is particularly important for a large workspace with 71″ diameter x 118″ deep (1,800 mm diameter × 3,000 mm deep) and the processing of large-sized components with thick layers. The temperature difference (ΔT) between the extreme thermocouples, measured at 1550°F (840°C), 1800 °F (980°C), and 1925°F (1050°C), did not exceed 3.5°F (2°C). This means that the furnace meets the Class 1 requirements of the AMS2750 standard by a wide margin.
Operational Dynamics
Additionally, to evaluate the furnace’s operational dynamics, heating and cooling tests were performed on an empty device with samples. Figure 4a shows the heating curve; the furnace reaches a temperature of 1800°F (980°C) in 60 minutes. The furnace’s high energy efficiency has a heat loss of just 32 kW under these circumstances.
Figure 4a. Heating RateFigure 4b. Cooling Rate
Figure 4b shows teh curve of cooling forced by nitrogen at atmospheric pressure, measured in three zones and on samples with diameters of 1″ (25 mm) and 4″ (100 mm). The temperature drops from 1800°F (980°C) to 575°F (300°C) in 60 minutes; reaching 210°F (100°C) takes only two hours, whereas natural cooling would take several days.
Vacuum tests show that the furnace reaches operating vacuum of 10⁻¹ hPa in under 30 minutes and has a leakage rate of 10⁻³ mbar·l/s, which meets the industry standard for vacuum furnaces.
Test of Atmosphere vs. Vacuum Carburizing Processes
To obtain a carburized layer 0.145–0.160″ (3.7–4.0 mm) thick for 52.3 HRC (550HV1), two tests were compared: one in the PEGAT atmosphere furnace (Figure 5a) and another in the Pit-LPC vacuum furnace (Figure 5b). In both cases, the charge consisted of seven gears made of 18CrNiMo7-6 material, with a total weight of approximately 6.5 tons and a surface area of 280 ft² (26 m²). The process consisted of three stages:
Stage I: heating to the carburizing temperature and soaking
Stage II: actual carburizing with cooling to the hardening temperature and holding
Stage III: hardening in an external quenching tank — identical in both processes
Table A. Atmosphere vs. Vacuum Carburizing Process ComparisonFigure 5a. Essential process data and schematic flow of the carburizing process in a PEGAT atmosphere furnaceFigure 5b. Essential process data and schematic flow of the carburizing process in the Pit-LPC vacuum furnace
The LPC process, which consists of saturation and diffusion segments (Figure 6) allows for the precise control of carbon distribution. As the process progresses, the duration of the diffusion segments is extended, ensuring uniform saturation of the material.
Figure 6. Vacuum carburizing process trends in the Pit-LPC
After carburizing and hardening, all components were tempered at 355°F (180°C) for three hours.
Table B. Chemical Composition of 18CrNiMo7-6 (according to EN10084)
Gears and samples made of 18CrNiMo7-6 steel were used for destructive testing, in accordance with the EN 10084 standard. Six cylindrical samples were placed throughout the workspace — inside and outside the part — to assess carburization uniformity.
Tests conducted:
Vickers microhardness (HV1): performed on a Struers Durascan 70 device, allowing for the determination of hardness profiles and carburized layer depth (ECD) — a load of 9.81 N (HV1).
Surface and core hardness (Rockwell): measurements were performed on a Wilson Wolpert TESTOR tester with a load of 1470.1 N. At least five measurements were taken for each sample.
Microstructure: assessed on a Nikon LV150 optical microscope after nital etching.
Internal oxidation (IGO): analyzed on the unetched surface of the microsection.
Figures 7a-f. Microhardness profiles after the full process (carburizing, hardening, and tempering)
Figure 7 shows the microhardness profiles for the tested samples. For each sample, microhardness paths were inspected in three cross-sections. Based on this, the effective ECD layer thickness obtained on each sample was determined, as presented in Table C.
Table C. Thickness of the Carburized Layer Read from the Microhardness Charts (effective case depth average is 0.145–0.160″ (3.7–4.0 mm) at 52.3 HRC (550 HV1))
Average ECD values obtained for the samples ranged from 0.148 to 0.154″ (3.77 to 3.91 mm).
Surface and core hardness values for all samples were consistent and typical of carburized layers (Table D). Surface hardness ranged from 61.0 to 63.2 HRC and core hardness from 39.9 to 40.7 HRC. Interestingly, samples located on the inner side of the wheel achieved slightly higher surface hardness values (caused by retained austenite and cooling intensity).
Table D. Measured values of surface hardness and core hardness
Microstructure images of low-tempered martensite, along with retained austenite, were identified, ranging from 17 to 20% (Figure 8). The amount of retained austenite was determined using NIS-Elements software. No variation in structure was observed depending on sample location.
Figure 8a. Exemplary post-processing microstructure pictures of sample 1 surface. Magnifications x100 (left) and x500 (right). Nital etching 2%. Martensite with residual austenite (approx. 18%).Figure 8b. Exemplary post-processing microstructure pictures of sample 4 surface. Magnifications x100 (left) and x500 (right). Nital etching 2%. Martensite with residual austenite (approx. 20%).
The presence of intergranular oxidation (IGO) was also inspected, averaging 5.5 μm throughout the tested samples. For comparison, intergranular oxidation in the atmospheric process averages above 15 μm. In the new LPC pit furnace, internal oxidation only occurs during unloading and transfer of the charge to the hardening tank, whereas in the atmospheric furnace, the presence of oxygen in the carburizing atmosphere is also significant, significantly increasing the IGO value.
The level of hardening deformation after the process conducted in the new LPC pit furnace and the atmosphere furnace is comparable due to the use of the same hardening tank in both devices and the absence of the carburizing process.
Comparison of Process Economics
Economic aspects play a key role in modern heat and thermochemical processing. Therefore, the consumption of basic utilities was compared for the reference processes (described in Chapter 5), resulting in a 0.152″ (3.8 mm) thick hardened layer. The analysis included a Pit-LPC and a PEGAT-type atmospheric furnace, both with identical workspace and the same charge. In addition, the LPC process was simulated at 1900°F (1040°C). The results are summarized in Table E.
Table E. Comparison of utility consumption and costs
The results show that the new LPC furnace model consumes significantly less electricity by approximately 57%, which translates into a lower carbon footprint, especially when energy is derived from fossil fuels. Nitrogen consumption is comparable, with a slight advantage for the Pit-LPC (savings of up to 10%).
The largest differences are found in carburizing gases. The atmospheric furnace consumes 9,900 ft³ (280 m³) of methane — approximately 440 lb (200 kg) and an additional 4.4–13.2 lb (2–6 kg) of propane per process. In the LPC furnace, acetylene consumption is reduced to 39.2 lb (17.8 kg) because carburizing gas only flows during the boost phase.
Importantly, the LPC process does not generate direct CO₂ emissions, unlike an atmospheric furnace, which emits approximately 1325 lb (600 kg) of CO₂ per cycle. Cooling water consumption in the new LPC furnace is also reduced by over 45%.
The presented comparison of utility consumption in the two types of furnaces directly translates into the economic aspects of using these devices and conducting production processes. For cost comparison purposes, the following unit utility costs were assumed, as presented in Table F:
Table F. Unit costs of energy factors and technological gases according to European averages
In summary, the total utility costs for the process conducted in the Pit-LPC at 1800°F (980°C) are 53% lower compared to an atmospheric furnace conducted at 1700°F (925°C). At a temperature of 1925°F (1040°C), savings reach 60%. These savings are primarily due to lower energy and process gas consumption. Furthermore, the lack of CO₂ emissions eliminates the need to pay emission fees.
The efficiency of this furnace is almost twice as much at 1795°F (980°C) and three times as much at 1925°F (1040°C) compared to an atmospheric furnace.
Summary
The new Pit-LPC vacuum furnace combines the design features of a top-loaded pit and performs carburizing using vacuum technology instead of atmospheric technology. Bringing higher processing temperatures than traditional atmospheric furnaces to the market, as well as the ability to open hot in an air atmosphere, this technology proves that direct transfer of the charge to the hardening tank is possible in vacuum furnaces.
Another key development, this design significantly shortens carburizing time compared to atmosphere furnaces since the furnace can operate under vacuum, inert gas (nitrogen, argon), air, and carburizing gases, at temperatures up to 2010°F (1100°C).
Since this new pit furnace design does not require the use a retort or atmosphere mixer, which are the most vulnerable components inside a traditional atmospheric furnace, the furnace operates with greater reliability and lower costs. Furthermore, an efficient and robust vacuum pumping system provides the vacuum environment and operational readiness in less than 30 minutes. Time is also saved by the integrated closed-loop gas cooling system that shortens cooling time: dropping temperatures from 1800°F (980°C) to 1545°F (840°C) in 30 minutes for a full charge and to 210°F (100°C) in two hours for an empty furnace, operations which would take several hours and days respectively in atmosphere furnaces.
The advanced thermal insulation and a uniform heating element layout ensure high energy efficiency and precise temperature uniformity in the working space, yielding additional cost and energy savings.
This carburizing process is based on FineCarb LPC technology and supported by the SimVac simulator, enabling precise carbon profile shaping and achieving layers 0.148–0.154″ (3.77–3.91 mm) thick with high repeatability.
With the ability to operate at temperatures up to 1925°F (1050°C), the new LPC pit-styled furnace significantly shortens process time, reduces utility consumption, and lowers operating costs by up to 50%, while increasing productivity by a factor of x2 to x3. One of these furnaces can replace two to three atmosphere furnaces of the same size.
Finally, the furnace operates in a safe and non-flammable atmosphere, emits no direct CO₂, and reduces energy consumption, making it an environmentally friendly solution.
Conclusions
The Pit-LPC furnace is a modern alternative to the traditional atmosphere furnace and offers a number of advantages in terms of quality, efficiency, safety, economy, and ecology. Providing an innovative solution for vacuum carburizing and meeting stringent carburization layer thickness guidelines, this design is a viable option to fully replace traditional atmospheric pit furnaces operating in a carburizing atmosphere.
Jantara, Valter Luiz Jr. 2019. “Wind Turbine Gearboxes: Failures, Surface Treatments and Condition Monitoring.” In Non-Destructive Testing and Condition Monitoring Techniques for Renewable Energy Industrial Assets, edited by Mayorkinos Papaelias, Fausto Pedro García Márquez, and Alexander Karyotakis. Amsterdam: Elsevier.
Perumal, S., and G. P. Rajamani. 2014. “Improving the Hardness of a Wind Turbine Gear Surface by Nitriding Process.” Applied Mechanics and Materials 591: 19–22.
Tom Hart Director of Sales for North America SECO/WARWICK Corporation
Tom Hart joined SECO/WARWICK in 2011 as a sales engineer and has been in the precision manufacturing industry for over 16 years. His responsibilities have him caring for SECO/WARWICK’s clients and their various process and heat treatment equipment needs. Tom received his manufacturing engineering degree from Edinboro University of Pennsylvania, has authored numerous white papers, and is recognized throughout the heat treatment industry as a go-to-guy for thermal processing.
Heat Treat Todayis pleased to welcome this regular column spot, Answers in the Atmosphere, to David (Dave) Wolff, an independent expert focusing on industrial atmospheres for heat treat applications. This column explores various atmospheres with Dave and different industry specialists.
This informative piece on the critical role of atmosphere control in metal thermal processing was first released inHeat Treat Today’sOctober 2025 Ferrous & NonFerrous Heat Treatments/Mill Processing print edition.
Thermal processing of metals is critical to successful production of fabricated metal parts and assembled systems. Characteristics of parts and devices, including blades, springs, wire and cable, medical implants, and electric motors, all depend on successful thermal processing to produce metallic components with specific properties to meet the requirements of the part, assembly, or device. What is sometimes overlooked, however, is that atmosphere is as critical as the heat itself. The wrong furnace atmosphere can undo the best processing recipe, while the right one ensures that parts achieve their intended properties consistently.
Tune into the news, and you will find stories about metal parts incorrectly handled during thermal processing: gears that degrade to powder, camshafts that were too soft, electric switches that fail, materials with the wrong magnetic properties, knives that cannot hold an edge, and so on. These are all problems that occur too frequently and are expensive to resolve, because metal parts are often components in a more complex and expensive assembly. (Imagine the responsibility of parts-making for military jet engines or body-implanted parts. You do not want to be the shop supplying inadequate parts!) It is imperative that heat treating and sintering processes are completed correctly the first time.
Metals thermal processing requires more than just heat. As indicated above, atmosphere is essential to the heat treating process, coming alongside temperature, time, and a specific sequence of operations in a recipe that will ensure the material yields the desired performance. Much like baking bread, thermal processing of metals requires equipment, materials, conditions, and recipes. The furnace is the main equipment (other operations may be performed in a less expensive thermal processing oven). Then there are the materials — the parts being heat treated — which may be bulk metals, alloys, or compacted powder parts with unique blends and surface morphology. The conditions of time, temperature, atmospheres, and perhaps a quenching step come together in a specified recipe. Properly done, heat treating and sintering operations will yield parts that meet the hardness, toughness, appearance, surface finish, shape, dimensions, and other specialized and specified properties.
Since cost is an important driver, metals thermal processors strive to produce compliant parts in as few steps as possible. Innovations can assist in making it possible to consolidate steps, too. But mistakes in thermal processing may result in defective parts or require expensive rework or even additional (secondary) operations to correct deficiencies.
Each issue, this column will focus on the atmospheres component of heat treating. You’ll read interviews with industry experts focused on the atmospheres used in thermal processing — from relatively inert atmospheres, such as vacuum, nitrogen, and argon, to chemically active atmospheres used for annealing, hardening, and sintering. We will assist thermal processors by explaining how various atmospheres work, what the key properties are that determine successful results, how to buy and utilize the atmospheres, and precautions and alternatives for that atmosphere.
My hope is that this column will help Heat TreatToday readers become better buyers and users of atmospheres, so that you can run a smoother, more reliable, and more profitable operation.
About The Author:
David (Dave) Wolff Independent expert focusing on industrial atmospheres for heat treat applications
Dave Wolff has over 40 years of project engineering, industrial gas generation and application engineering, marketing, and sales experience. Dave holds a degree in engineering science from Dartmouth College. Currently, he consults in the areas of industrial gas and chemical new product development and commercial introduction, as well as market development and selling practices.
Kaiser Aluminum Corp., a producer of heat treated, flat-rolled aluminum products, has completed a $25 million expansion of its Trentwood rolling mill in Spokane Valley. This marks the latest phase of the company’s long-term strategy to increase heat treatment throughput for aerospace, automotive, and general engineering markets.
The original source was published in Spokane Journal of Business, and the following content has been adapted for our Heat TreatToday audience.
The project, which is part of more than $415 million invested in the facility over the past 20 years, extends one of the mill’s major heat treat furnaces, increasing plate-processing output by approximately 5 percent. For in-house heat treaters, the upgrade reflects a continued industrywide push toward higher-capacity, efficiency-driven thermal operations as demand for tight chemistry and reliable mechanical properties climbs.
Kaiser Aluminum has completed a $25 million project at its Spokane Valley plant that includes an expansion of its horizontal heat treat furnace. Source: Kaiser Aluminum Corp.
According to Kevin Barron, vice president of manufacturing, the expansion enhances the mill’s ability to heat treat and stretch large-format aluminum plate products without altering staffing levels at the 1,000-employee site. The project was completed within the plant’s existing footprint with support from regional contractors and furnace supplier Otto Junker USA.
The Trentwood mill, one of only three U.S. sites capable of producing heat treated aerospace-grade plate, has undergone seven phases of reinvestment since 2005. Recent work builds on earlier additions to the facility’s furnace lineup, along with upgrades to hot rolling, homogenizing, and casting capacity — areas closely linked to the performance and consistency of downstream heat treating.
Kaiser paused expansion activities during the pandemic, storing some equipment purchased pre-COVID. With the current project complete, the company has reestablished its pattern of continuous, phased improvements intended to keep pace with global aerospace and defense demand.
For manufacturers with in-house heat treat operations, Kaiser’s latest phase underscores a broader trend: large producers are expanding thermal processing capability not only to increase volume but to ensure uniformity, cleanliness, and repeatability at scale. As aerospace OEMs tighten specifications, upstream suppliers are reinforcing their heat treatment infrastructure to meet rising expectations for precision and throughput.
Kaiser Aluminum, headquartered in Franklin, Tennessee, operates 13 facilities across the U.S. and Canada. The Trentwood site remains a key supplier to Boeing and other aerospace manufacturers, continuing a relationship that dates back to World War II.
Press release is available in its original form here.
Jim Roberts of U.S. Ignition entertains readers in a Combustion Corner editorial about how the industrial gas industry evolved from its humble beginnings in the early 1900s into a precision-driven force that transformed combustion technology and modern manufacturing.
This editorial was first released inHeat Treat Today’sNovember 2025 Annual Vacuum Heat Treating print edition.
Let’s think about how young the industrial gas industry really is.
A Short Pipeline in Time
The first real industrial usage was way back in the 1800s somewhere. But there was no infrastructure, no supply other than bottled gas for industrial applications. The gas industry, as far as we recognize it, did not really take off until somewhere around the early 1920s when the first welded pipeline was installed. Then, as usage increased, it became apparent that safety was going to be a concern. The addition of mercaptan (rotten egg smell) was not until the late 1930s.
With the growth of commercial and residential usage, the demand for gaseous fuels grew by 50 times the original market size anticipated between 1910 and 1970! What does that demand look like? Today there are over 3 million miles of gas distribution lines connected to 300,000 miles of big transmission pipelines in the U.S. alone. All that growth in a span of 100 years, essentially. That means the transmission pipeline system in the U.S. could stretch around the planet 12 times!
USS coke gas pipeline in the foreground with the Conrail Port Perry Bridge spanning the Monongahela River, Port Perry, Allegheny County, PA (Lowe, 1994) Source: Library of Congress Prints and Photographs Division
Most of that construction occurred during the post-war 1940s to 1960s timeline. That’s one busy industry! And it dragged all the thermally based markets and industries along with it. Now, we have come to accept the availability of natural gas as so commonplace that we cannot imagine life without it.
Responding with Precision
So, now you ask yourselves, “Why this history lesson, Jim?” Well, because we are supposed to be learning about combustion and the era of major combustion advancements — and if I would quit veering off into side topics we might actually get there. But it is all interconnected.
If you recall the story of the heat treater with the bedpost burners (October 2025 edition), he had no inspiration to improve efficiency or performance because those darn bedposts would burn gas just fine. So, what changed? Firstly, the world had been through a couple of military conflicts during this rise of the gas industry. And sadly, sometimes the best technological advances occur in times of conflict; engineering becomes more precise. All of a sudden, instead of hammering out horseshoes for the cavalry, we were heat treating gun barrels and crankshafts for airplanes. We needed to be more than precise — actually, we had to be perfect. So, we stepped away from the old heat treatment ways and developed systems that we could control to within a couple of degrees.
As a result, burners became specialized. Each process became unique and precise. Instead of pack carburizing components, a company called Surface Combustion developed a piece of equipment called an Endothermic generator. This device made carbon-based atmosphere out of natural gas or propane- and nickel-based catalysts. All of a sudden, we could do very precise non-scale covered heat treating. And the burners from companies like North American Combustion, Eclipse Combustion, Maxon, Hauck, Pyronics, Selas, W.B. Combustion, and on and on, all scrambled to develop the specific types of burners that the heat treaters and iron and steel makers needed.
Another important milestone hit around 1963: the Government got involved (gasp!). The Clean Air Act of 1963 essentially said we needed to burn our fuels cleanly and not spit smoke into the air. Those laws got reviewed again in 1970, 1977, and again in the updated Clean Air Act of 1990 with some of the biggest revisions.
With all of these changes, we had several drivers for innovation in the combustion world. Again, precision became a must. Heat treating became a very standards-driven industry. Metallurgists roamed the planet inventing both new materials and the processes to achieve them. Gas companies themselves became huge drivers of innovation and developed think tanks, like the GRI (Gas Research Institute), where people learned and laboratories hummed with development projects investigated in conjunction with burner and furnace companies. Academia became involved with industry in the form of organizations like The Center for Heat Treating Excellence (CHTE) and the Metal Treating Institute (MTI). Suddenly, the industry was more than just blacksmiths.
We’ll talk about how burner companies became design specialists and system efficiency experts and what that meant to various burner styles in next month’s offering.
References
Lowe, Jet. 1994. Panorama of Industry (Conrail Port Perry Bridge, Spanning Monongahela River, Port Perry, Allegheny County, PA). Historic American Engineering Record, HAER PA,2-POPER,1-2. Library of Congress Prints and Photographs Division.
About The Author:
Jim Roberts President US Ignition
Jim Roberts president at U.S. Ignition, began his 45-year career in the burner and heat recovery industry focused on heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.
For more information: Contact Jim Roberts at jim@usignition.com.
As aerospace, defense, and medical applications demand tighter chemistry and flawless surfaces, heat treaters are accelerating their move toward all-metal hot zones and ultra-high-vacuum systems. The push for cleaner processing is quickly reshaping expectations not only for commercial heat treaters, but also for in-house heat treat operations supporting mission-critical production.
Today’s original content brings together recent Heat TreatToday reporting on all-metal hot zones, next-generation vacuum systems, and supply-chain investments redefining clean processing for aerospace, defense, and medical work.
All-Metal Hot Zones Drive Cleaner, More Predictable Processing
Heat treaters serving medical, aerospace, and turbine production continue to adopt all-metal hot zones to reduce contamination risk, stabilize vacuum performance, and deliver more consistent surface conditions.
Solar Atmospheres has expanded its all-metal vacuum furnace capacity across multiple locations in 2025, most recently at its Western Pennsylvania facility dedicated to critical medical work. The system features an all-molybdenum hot zone, finely polished stainless-steel cold wall, and dual isolation valves to maintain vacuum integrity, accompanied by a major clean-room expansion to support downstream handling.
Earlier this year, the company added a similar all-metal furnace at its Hermitage campus. Designed for precipitation-hardened stainless steels, nickel-and cobalt-based superalloys, titanium, and niobium, the system reflects the rising expectations placed on heat treat environments supporting high-performance material systems.
Michael Johnson, sales director at Solar Atmospheres of Western Pennsylvania, underscored the significance of the shift, noting that the all-metal design delivers “the purest possible processing environment” and produces “pristine end products that meet the most demanding industry standards.”
With vacuum levels reaching below 5 × 10⁻⁶ Torr through a diffusion pump, oversized main valve, and polished stainless chamber, these furnaces support bright, contamination-free results — conditions increasingly relevant to in-house heat treaters tasked with eliminating process variation.
High-Performance Vacuum Systems Support Tighter Internal Specifications
Across the industry, new vacuum systems are being introduced that emphasize uniform quenching, reduced gas consumption, and shorter cycle times — benefits that resonate strongly with in-house heat treat teams striving for throughput without sacrificing metallurgical integrity.
A recent example is the addition of a 6-bar Ipsen TurboTreater horizontal vacuum furnace at Stack Metallurgical Group‘s Portland, Oregon facility. It’s designed for 360-degree uniform quenching and engineered to reduce cycle times by up to 20 percent. Its versatility — supporting hardening, tempering, brazing, sintering, annealing, and more — illustrates the broader trend toward equipment that supports multiple metallurgical pathways while maintaining low-contamination processing.
While not an all-metal hot zone, SMG’s investment signals the same market direction: vacuum systems are increasingly becoming the backbone for operators who prioritize clean surfaces, repeatable thermal cycles, and consistent downstream machining performance.
High Purity Feedstock Becomes a Process-Control Advantage
Arconic Corporation has recently invested $57.5 million in an effort to boost high purity aluminum (HPA) capacity for aerospace and defense applications at its Davenport Works plant, a major in-house heat treating operation. The expansion strengthens both its full thermal processing line and the broader aerospace and defense supply chain.
By the same token, this manufacturer is upstream in product development. For aerospace manufacturers of aluminum products with in-house heat treaters, access to cleaner feedstock translates into more predictable microstructures, fewer surprises at the furnace, and reduced process deviations, which is a meaningful advantage as specifications tighten.
Diana Perreiah, Arconic’s EVP of Rolled Products North America, positioned the investment as a deliberate step toward enhancing U.S. industrial capability, emphasizing that the expansion supports the advanced manufacturing base required for next-generation platforms. Her comments highlight a growing recognition that material purity upstream directly influences thermal processing reliability downstream.
The project includes two new furnaces, automation upgrades, and modernized controls, ensuring consistent supply of the high purity aluminum essential for complex structures ranging from aircraft wing skins to high-strength defense components.
Across furnaces, feedstock, and facility upgrades, the direction is unmistakable: the industry is moving rapidly toward ultra-clean, tightly controlled thermal environments.
For in-house heat treat departments, the message is clear. These technologies are not simply expanding commercial heat treat capacity — they are redefining expectations for internal operations where scrap reduction, audit readiness, and end-to-end process reliability are central.
All-metal hot zones, advanced vacuum systems, and high purity input materials are quickly becoming a baseline for meeting stringent performance requirements for many in today’s aerospace, defense, and medical applications.
Newton Heat Treating has completed a major equipment upgrade, replacing steam accumulators that had been in service for 20 years in its uphill quenching/cold stabilization operation. The upgrade directly impacts the company’s aerospace processing capabilities, with many parts destined for optical components in space applications undergoing this critical heat treatment process.
Saying goodbye to the old steam accumulators SOURCE: Newton Heat TreatingNew steam accumulators fully installed SOURCE: Heat TreatingJohn Avalos Quality Engineer Newton Heat Treating
According to the company, the new steam accumulators have delivered immediate operational improvements. The heat treat transfer time from the steam accumulators to the steam chambers (where parts are inserted) is faster, providing better tensile stress reduction. Energy efficiency has also improved, with steam blasting time cut by about 10%.
John Avalos, quality engineer at Newton Heat Treating, reported, “primary operator who runs this process, Alfred Ojeda, said that the new steam accumulators don’t take as long to pressurize.” This will cut down on processing time, he explains.
Newton Heat Treating partnered with McKenna Boiler Works, Inc. for the installation project, which was completed on time and to specifications.
The uphill quenching/cold stabilization process is essential for aerospace components, particularly those requiring precise dimensional stability and stress relief for mission-critical optical systems used in space.
Want to learn more about uphill quenching? Check out the Heat TreatRadio episode where Newton Heat Treating CEO Greg Newton and John Avalos discuss this little-known but highly effective process for controlling residual stress in aluminum alloys.
Press release is available in its original form here. Additional details provided by the company.
Ask The Heat Treat Doctor® has returned to bring sage advice to Heat Treat Today readers and to answer your questions about heat treating, brazing, sintering, and other types of thermal treatments as well as questions on metallurgy, equipment, and process-related issues.
This informative piece was first released in Heat Treat Today’sNovember 2025 Annual Vacuum Heat Treating print edition.
Case depth, case uniformity, and final mechanical (as well as other) properties rely not only on controlling both equipment and process variability during heat treatment, but on having clean, properly prepared part surfaces prior to and during heat treating. Expert Dan Herring encourages to learn more below.
Case hardening is a thermochemical surface treatment process designed to add a particular element or combination of elements to a material such as steel. Familiar examples include carbon (carburizing); carbon and nitrogen (carbonitriding); boron (boriding); nitrogen (nitriding); and nitrogen and carbon (nitrocarburizing — ferritic or austenitic). These processes are typically designed to increase the near surface hardness of steel after quenching.
However, various problems can arise due to either the materials or the manufacturing methods employed prior to or during heat treating that will retard or prevent absorption and/or diffusion of the desired element(s) during heat treating. Some of the metallurgical consequences can include:
Shallow or uneven case depths
Surface oxidation
Intergranular oxidation or decarburization
High levels of retained austenite
Soft spots due to incomplete hardening
Machine-Induced Surface Conditions
Improper machining prior to case hardening can compromise surface integrity. Tooling choices, improperly maintained equipment, inadequate operator training, and even environmental factors can contribute to a variety of issues.
While machining problems occur frequently, they are mostly preventable. Attention to part surface condition, cleanliness, and mechanical integrity is essential before heat treating. Training, standardizing machining protocols, planned preventative maintenance programs, and part inspection prior to heat treating will help avoid these issues. Consult Table A for further details on how the causes and effects of undesirable machine-induced surface conditions can be solved.
Splatter of Stop-off Paints on Unintended Areas
A material that masks the surface of steel and delays or prevents case hardening is called a stop-off or maskant. These materials are applied to specific areas of a steel part to prevent the diffusion of hardening elements (like carbon or nitrogen) into the surface during case hardening processes, such as carburizing, nitriding, or carbonitriding. (See Table B.)
Enriching Gas Additions (Sooting)
During the carburizing or carbonitriding process, it is not uncommon to develop a layer of soot on the surface of the parts, especially if the enriching gas additions begin before the entire load is uniformly up to temperature. In some instances, the amount of soot formation is such that the case depth or uniformity is affected. This is often difficult to diagnose, as the soot layer “washes off” during quenching in a liquid, and the part surfaces come out of the furnace looking reasonably clean.
Material-Related Issues
The use of scrap in steelmaking, especially for low alloy case hardening steels can lead to a relatively high level of impurities and tramp elements. At high temperatures these impurities tend to segregate at grain boundaries and migrate toward the surface. This type of segregation can retard case hardening by impeding element (e.g., carbon) transfer. For example, the effects of tin (Sn) and antimony (Sb) on the kinetics of carburization are particularly problematic (Figure 1).
The effect of tramp elements on retardation of carburization can be expressed in the following order (Andreas, et al. 1996), namely Sb > Sn > P > Cu > Pb. To see the effect of one such element, the carbon transfer coefficient (ß) for typical commercial steels is shown as a function of antimony (Sb) content (Figure 2).
In Summary
These are a few of the many causes delaying or preventing case hardening from being effective. There are many others, including alkaline cleaning compounds (in too high a concentration) and even phosphate and other drawing lubricants used in the manufacture of fasteners. Inspection and cleaning of the part surface prior to case hardening will avoid many of these issues. Reviewing material certification sheets for elements known to interfere with case hardening is also an effective way to anticipate problems with case hardening.
References
Herring, Daniel H. 2014. Atmosphere Heat Treatment, Volume 1. Troy, MI: BNP Media.
Herring, Daniel H. 2015. Atmosphere Heat Treatment, Volume 2. Troy, MI: BNP Media.
Ruck, Andreas, Monceau, Daniel, and Grabke, Hans Jürgen. 1996. “Effects of Tramp Elements Cu, P, Pb, Sb, and Sn on the Kinetics of Carburization of Case Hardened Steels.” Steel Research 67 (6): 242–48.
About the Author
Dan Herring “The Heat Treat Doctor” The HERRING GROUP, Inc.
Dan Herring has been in the industry for over 50 years and has gained vast experience in fields that include materials science, engineering, metallurgy, new product research, and many other areas. He is the author of six books and over 700 technical articles.
