December 2025 MTI’s Commercial Heat Treating Supplement
December 2025 MTI’s Commercial Heat Treating Supplement Read More »
Answers in the Atmosphere: Successful Thermal Processing of Metals Requires Atmosphere Savvy
Heat Treat Today is 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 in Heat Treat Today’s October 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 Treat Today readers become better buyers and users of atmospheres, so that you can run a smoother, more reliable, and more profitable operation.
About The Author:
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.
For more information: Contact Dave Wolff at Wolff-eng@icloud.com.
Kaiser Completes $25M Heat Treat Expansion at Trentwood
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 Treat Today 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.
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.
Kaiser Completes $25M Heat Treat Expansion at Trentwood Read More »
Flame and Fire: History of the Industrial Gas Industry
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 in Heat Treat Today’s November 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!
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:
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.
Flame and Fire: History of the Industrial Gas Industry Read More »
The Ultra-Clean Revolution: Why All-Metal Hot Zones Are Becoming the New Standard
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 Treat Today 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.
See the full articles here: Solar Atmospheres Expands for Medical Industry and All-Metal Hot Zone Furnace for Solar Atmospheres
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.
See the full article here: Stack Metallurgical Group Increases Operations with Horizontal Vacuum Furnace
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.
See the full article here: Arconic $57.5 Million High Purity Aluminum Production Expansion for Aerospace & Defense
Toward a New Standard for Mission-Critical Work
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.
The Ultra-Clean Revolution: Why All-Metal Hot Zones Are Becoming the New Standard Read More »
Newton Heat Treating Upgrades Enhance Aerospace Processing Capabilities
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.
SOURCE: Newton Heat Treating
SOURCE: Heat Treating
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 Treat Radio 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.
Newton Heat Treating Upgrades Enhance Aerospace Processing Capabilities Read More »
Ask The Heat Treat Doctor®: What Masks the Steel’s Surface in Case Hardening?
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’s November 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
“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.
For more information: Contact Dan at dherring@heat-treat-doctor.com.
For more information about Dan’s books: see his page at the Heat Treat Store.
Ask The Heat Treat Doctor®: What Masks the Steel’s Surface in Case Hardening? Read More »
Bhuj Polymers Advances Production Capabilities with New Vacuum Furnace
Bhuj Polymers, an established precision components manufacturer, is expanding its manufacturing capabilities through the acquisition of a state-of-the-art vacuum furnace. This investment will enable the company to meet growing demands while providing advanced vacuum hardening services that comply with global quality standards.
Vice President of Vacuum Business Segment
SECO/WARWICK
SECO/WARWICK, a heat treat solutions provider with locations in North America, supplied the vacuum furnace that will be used to process tool steels with high thermal requirements, such as H13, H11 and D2. Prior to this acquisition, production capabilities were constrained by existing equipment limitations. The company’s locally manufactured furnace operated with a cooling pressure of up to 4 bar. This specification prevented effective processing of components requiring high-pressure gas hardening. Increasing production loads and customer requirements prompted Bhuj Polymers to invest in next-generation vacuum technology.
“The furnace delivered combines 15-bar high-pressure gas cooling with perfect temperature uniformity and precise control of thermal processes. This solution meets NADCA (tool & die global standard) requirements and is ready for Nadcap (aerospace global standard) certification, enabling Bhuj Polymers to expand their manufacturing services to the most demanding customers from industries such as automotive and aerospace,” says Maciej Korecki, vice president of the Vacuum Segment of the SECO/WARWICK Group.
This installation represents a significant advancement in local manufacturing capabilities. As part of SECO/WARWICK’s strategy to strengthen local production competencies, the furnace was manufactured entirely in India, reducing logistical costs, increasing competitiveness, and eliminating challenges associated with global customs policy.
Managing Director of SECO/WARWICK India
“Bhuj Polymers is a partner who trusted that our vacuum project, carried out entirely in India, was the correct solution for their manufacturing needs. This trust is of great value to us, as it opened a new chapter in the history of SECO/WARWICK India. This installation is an important step towards building a strong and independent technological infrastructure in India. We are pleased to be part of the growth of companies like Bhuj Polymers, who choose world-class technology produced locally,” said Arvind Agarwal, managing director of SECO/WARWICK India.
This event may serve as a significant impetus for other companies, not only in the state of Gujarat. This expansion demonstrates the importance of local production and support for manufacturers of aluminum die-casting molds, plastic processing tools, or precision components.
Press release is available in its original form here.
Bhuj Polymers Advances Production Capabilities with New Vacuum Furnace Read More »
A Thanksgiving Note
Over the past year, Heat Treat Today has experienced many transitions: sending off several amazing editors into the next, family-focused stage of life and integrating the gifts of several outstanding editors and operations individuals. As we’ve dedicated time to focus on making what we do more compelling and helpful to you, we come to the last month of the year grateful for the opportunities we’ve had to take a call from an industry colleague, receive an editorial email from a reader, and bump shoulders at your heat treat operations and various industry events.
This Thanksgiving, we are thankful for how our team and the industry transforms. This is a particularly acute blessing as we see the final leaves descend this fall. God bless you and keep you and yours through all the changes of life.
For housekeeping purposes: our offices will be closed on November 27 and 28. Happy Thanksgiving!
A Thanksgiving Note Read More »