OP-ED

When the Pressure Gets Too Much — And It Helps

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, OP-ED

Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about the double-edged sword of heat recovery technology — explaining how efforts to reduce fuel consumption inadvertently drove up NOx emissions, and how flue gas recirculation (FGR) emerged as the design solution capable of cutting both fuel use and emissions by up to 50%.

This editorial was first released inHeat Treat Today’s February 2026 Annual Air & Atmosphere Heat Treating print edition.

A furnace guy walks into the heat treating plant and says to the operators standing nearby, “This exhaust system and these burners all have a negative attitude.” The other furnace guys say, “They better be negative, or they would not work well!” As if we don’t have enough negativity swirling around in our world as it is, now we are happy about it?

In the Annual People of Heat Treat (September 2025) we talked about the types of burners that were developed as heat treating and furnace sciences and combustion designs evolved. We also chatted about how the advent of new fuels and government regulations was going to take a chunk of our attention in the coming years — for example, pollution laws coming to the forefront of our industry in the late ‘70s and onwards. Interesting new burner designs sprung up, primarily, as you recall, to address the usage of gas. In other words, how can we reduce fuel usage?

But First, NOx

The cost of gas skyrocketed for a stretch and it led us first to energy reduction plans. But with heat recovery sciences came the phenomenon of higher flame temperatures. When you get higher flame temperatures, you can sometimes (okay… all the time) generate NOx. One of the primary constituents of atmospheric pollution is NOx, and it became a prime target for reduction by the EPA and other governing air quality folks. As it should be.

Just a quick step back to the “remind me again, Jim” world. What do we breathe? Air, right? We have to have oxygen. But what we tend to forget is that air is roughly 79% nitrogen. So, what we breathe is actually nitrogen spiked with oxygen, and the fuel that we generally burn, natural gas, has some nitrogen in it too.

Natural gas can have as much as 5% nitrogen in it, although membrane filtering usually controls pipeline gas content at around 1%. The point is that nitrogen is the dominant gas in our combustible portfolio, and when we make it really hot, it makes NOx. And that is considered bad for all of us. So, NOx from fuel-borne nitrogen can be released at temperatures as low as 1400°F. Sometimes that is referred to as “sudden NOx” because it releases quickly. All of us Furnace Guys know that 1400°F ain’t nothing in our world.

The second form of NOx is referred to as “thermal NOx” and that is the major source of NOx in our world. That is when we heat the air we are combusting in a burner, burning off most of the 21% oxygen. Then, flame temperature climbs, and continues to now superheat and try to burn that remaining 79% of nitrogen. As temperatures approach 2300°F, the magic happens.

Thermal NOx forms significantly at high combustion temperatures, typically starting above 1300°C (2372°F), with formation increasing exponentially as temperatures rise, especially above 2800°F (1538°C), due to atmospheric nitrogen and oxygen reacting at peak flame temperatures. Does anybody remember what happens to flame temperatures when we preheat the combustion air (recuperation, recirculation, etc.)? Flame temp and heat transfer increase and we go up to theoretical flame temperatures of 3200°F without even working at it.

Solving Energy Efficiency Through Design

So, let’s return to the original question: What happened when we tried to only save gas with heat recovery? Answer: We installed energy efficient burners but increased the emissions footprint in doing so. We cut down on energy expenditure but made exhaust an issue with the higher temps.

For most industrial and commercial applications, the optimal range for flue gas recirculation (FGR) is between 10% and 25% as this range offers significant NOx reduction without compromising combustion stability or efficiency. By adjusting the pressures coming into the burner and then balancing the exhaust outlet pressures over the heat exchanger body, normally with an extraction device called an “eductor,” we can dial in the percentage of recirculation the burners are operating under.

Figure 1. Flow diagrams depicting the basic design for both direct fired and radiant tube style burners | Image Credit: Honeywell

With this design, I have seen fuel and emission reductions of 50% when compared to the existing conventional combustion systems. It really is a testament to what design and research can produce for us (Figure 1).

We’ll look more closely at these designs next time.

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.

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Ask The Heat Treat Doctor®: Hot Topic for a Cold Day — Why Is Hot Gaseous Corrosion So Devastating?

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, CARBURIZING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, OP-ED

Ask The Heat Treat Doctor® has returned to bring sage advice to Heat Treat Today readers, answer questions about heat treating, brazing, sintering, and other types of thermal treatments, as well as metallurgy, equipment, and process-related issues. In this installment, Dan Herring examines the devastating effects of hot gaseous corrosion on furnace alloys: exploring the mechanisms behind metal dusting, the gas-solid reactions that drive catastrophic carburization, and the mitigation strategies to extend the life of heat treaters’ most valuable furnace components.

This informative piece was first released in Heat Treat Today’s January 2026 Annual Technologies To Watch print edition.

Have questions or feedback? We’d love to hear from you — reach out to our editorial team at editor@heattreattoday.com.

Corrosion is a concern experienced by everyone involved in manufacturing industrial products. While there is a plethora of data and information on the effects of corrosion on engineered materials available (sources provided in the references section of this column), most corrosion engineers are focused on aqueous corrosion. By contrast, heat treaters must understand the effects of hot gaseous corrosion, especially on our furnace alloys. Let’s learn more.

Corrosion Basics

It is important to understand that all materials are chemically unstable in some environments and corrosive attack will always occur. In the scientific world, it can often be modeled and its effects predicted by studying thermodynamic data and knowing which of the many corrosion-related chemical states are active. In our world, however, it is equally important to understand the various forms of corrosion, namely:

  • Dezincification (aka selective leaching)
  • Electrolytic
  • Erosion
  • Galvanic (or two metal) action
  • General (aka uniform) attack
  • Intergranular attack
  • Pitting
  • Stress corrosion

The greater the metal’s solubility, the greater the degree and severity of the corrosive attack. There are many important variations of these forms of corrosion; two of the most important are 1) localized corrosive attack (e.g. pits, intergranular attack, crevices) and 2) interaction with mechanical influences (e.g., stress, fatigue, fretting). These actions are frequently rapid and have catastrophic effects.

The number of ways to combat corrosion have been well-documented, including alloying to produce better corrosion resistance materials; cathodic protection (via sacrificial anodes); coatings (metallic or inorganic); organic coatings (e.g. paints); metal purification; alteration of the environment; and nonmetallic or design (i.e., physical) changes.

Heat Resistant Alloys

Furnace interiors contain numerous examples of heat-resistant nickel-chromium-iron (Ni-Cr-Fe) alloys, including radiant tubes, fans, heating elements, roller rails and rollers, thermocouple protection tubes, chain guides, and atmosphere inlet tubes, to name a few. Baskets, grids, and fixtures are other examples. These alloys are normally selected based on their strength (at temperature) rather than resistance to corrosive attack.

Since these heat-resistant alloy parts are often the most expensive furnace components, heat treaters must understand how they can be attacked and what can be done to extend their life by minimizing or preventing corrosion.

Gas-Solid Reactions

A chemical reaction involving a (non-equilibrium) gas or gas mixture and a solid is classified as a gas-solid reaction. Examples of intermediate and high temperature reactions of this type include oxidation, sulfidation, carburization, and nitriding. Effects of gases containing vapors of chlorine, fluorine, and effluents from deposits of various alkaline chemicals (from cleaning compounds) and even phosphates are also problematic. The principles are the same for all types — only the details differ. As heat treaters, our interest is in controlling, retarding, or suppressing these reactions to prevent unwanted corrosion, gasification, or embrittlement of the furnace alloy or materials being processed.

Examples of Catastrophic Carburization (a.k.a. Metal Dusting)

Figure 1. Pusher furnace alloy fan and shaft assembly | Image Credit: The Heat Treat Doctor®

Metal dusting (Figure 1) is a hot gaseous corrosion phenomenon in which a metallic component disintegrates into a dust of fine metal and metal oxide particles mixed with carbon.

Generally, metal dusting occurs in a localized area, and how rapidly the disintegration progresses is a function of temperature, the composition of the atmosphere and its carbon potential, and the material. Other significant factors include the geometry of the system, reaction kinetics, diffusivities of alloy components, the specific-volume ratio of new and old phases, and the ultimate plastic strain.

Metal dusting usually manifests itself as pits or grooves on the surface, or as an overall surface attack in which the metal can literally be eaten away in a matter of days, weeks, or months. As an example, this writer has seen a 330-alloy plate mounted underneath a refractory-lined inner door of an integral quench furnace (where atmosphere passes underneath the door and into the quench vestibule) reduced in thickness from 12.5 mm (0.50 in) to less than 0.75 mm (0.03 in) in a little over two months.

Figure 2. 330 alloy radiant tube removed after six months of use (rotary retort furnace) | Image Credit: The Heat Treat Doctor®
Figure 3. Microstructural view: catastrophic carburization | Image Credit: The Heat Treat Doctor®

In another example, a metallographic investigation performed by this writer on a failed wrought 330 alloy radiant tube (Figure 2) was conducted. Optical microscopy of the inside (Figure 3) and outside diameter surfaces in the attacked area revealed evidence of massive carbides. These carbides are formed by the reaction of carbon with chromium, depleting the matrix of chromium in regions adjacent to the carbides. Grain detachment and subsequent failure by erosion then occurred.

How Does It Occur?

In general, catastrophic carburization of ferrous alloys proceeds via the formation and subsequent disintegration of metastable carbide. The first step in the process is absorption of the gaseous phase on the surface of the metal; the more reactive this phase, the easier it decomposes or is catalytically decomposed (in the case of iron) on the surface. This step is followed by diffusion of carbon atoms from the surface into the bulk metal.

As a result, there is a continuous buildup of carbon within the surface layer. As this layer becomes saturated with carbon, a stable carbide, metastable carbide, or an active carbide complex forms, which then grows until it reaches a state of thermodynamic instability, at which point it rapidly breaks down into the metal plus free carbon.

It’s at this stage that the metal disintegrates to a powder as the result of plastic deformation and subsequent fracture in the near-surface layer. The process is controlled by internal stresses due to phase transformation; in other words, competition between stress generation and relaxation exceeds the ultimate strength in this near-surface layer and causes fracture to occur.

In Ni-Cr-Fe alloys, the phenomenon occurs slower (but does not stop) since the disintegration leads to larger metal particles, which are less active catalysts for carbon deposition than the fine iron particles that form with ferrous metals. Therefore, the mass gain from carbon depositing onto high-nickel alloys is much lower. Also, the decomposition of high-nickel alloys occurs by graphitization and not via unstable carbides.

Pourbaix-Ellingham Diagrams

Thermodynamics can be applied to solid-gas reactions to obtain equilibrium dissociation pressures below which no reactions occur. Data and diagrams are available for the free energies of formation versus temperature for most metallic compounds. An interesting use of Pourbaix diagrams (generally reserved for mapping out possible stable equilibrium phases of an aqueous electrochemical system) as a predictor of stable alloy systems is found by superimposing the various elemental constituents. These diagrams are read much like a standard phase diagram (with a different set of axes).

In Summary

Hot gaseous corrosion should be an area of focus for every heat treater to extend the life of alloy components, reduce downtime, and save money. Mitigation in the form of alloy selection, equipment design, type of atmosphere, process/cycle selection, and idling temperatures will play a huge role in extending the life of our furnace alloys, baskets, and fixtures.

References

ASM International. 1971. Oxidation of Metals and Alloys.

ASM International. 2003. ASM Handbook. Vols. 13A–C.

Fontana, Mars G., and Norbert D. Greene. 2008. Corrosion Engineering. New York: McGraw-Hill.

Herring, D. H. 2003. “What to Do About Metal Dusting.” Heat Treating Progress, August.

Herring, Daniel H. 2015. Atmosphere Heat Treatment. Vol. 2. Troy, MI: BNP Media Group.

Javaheradashti, Raza. 2008. Microbiologically Induced Corrosion. Berlin: Springer-Verlag.

NACE International. www.nace.org.

Nateson, K. 1980. Corrosion–Erosion Behavior in Metals. Warrendale, PA: Metallurgical Society of AIME.

National Bureau of Standards. 1978. Gas Corrosion of Metals.

Pourbaix, Marcel. 1974. Atlas of Chemical and Electrochemical Equilibria in Aqueous Solutions. Houston, TX: NACE International.

Pourbaix, Marcel. 1998. Atlas of Chemical and Electrochemical Equilibria in the Presence of a Gaseous Phase. Houston, TX: NACE International.

Schweitzer, Philip A. 1996. Corrosion Engineering Handbook. New York: Marcel Dekker.

Staehle, R. W. 1995. “Engineering with Advanced and New Materials.” Materials Science and Engineering A 198 (1–2): 245–56.

Stempco, Michael J. 2011. “The Ellingham Diagram: How to Use It in Heat-Treat-Process Atmosphere Troubleshooting.” Industrial Heating, April.

Uhlig, Hubert H. 2008. Corrosion and Corrosion Control. Hoboken, NJ: Wiley-Interscience.

Fabian, R., ed. 1993. Vacuum Technology: Practical Heat Treating and Brazing. Materials Park, OH: ASM International.

The Boeing Company. n.d. “Practical Vacuum Systems Design Course.”

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.

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.

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Answers in the Atmosphere: Nitrogen — Flow Rate, Sourcing, & Costs

/ BULK GASES & SYSTEMS TECHNICAL CONTENT, OP-ED

In this installment of Answers in the Atmosphere, David (Dave) Wolff, an independent expert focusing on industrial atmospheres for heat treat applications, explores the versatile role of nitrogen gas in thermal processing.

This informative piece on nitrogen’s flow rate considerations, sourcing strategies, and cost factors — drawing on insights from Air Products engineers to help heat treaters make informed, cost-effective supply decisions — was first released in Heat Treat Today’s December 2025 Annual Medical & Energy Heat Treat print edition.

We’re picking up the topic of nitrogen this month with a continued discussion of several key aspects of flow rate, expert assistance, and atmosphere costs that I had the pleasure of hearing about from several key industry experts. My thanks to these Air Products individuals: John Dwyer, principal engineer; Bryan Hernandez, commercial technology sales engineer; and Emily Phipps, strategic marketing manager.

First, the experts shared that in a typical thermal processing operation, the required instantaneous nitrogen flow rate may vary significantly depending on several factors including number of furnaces in operation, flowrate required per furnace, and materials being processed. The nitrogen supply system must be capable of meeting these varying flowrate requirements, from minimum to maximum, on demand.

Although non-cryogenically generated nitrogen may be acceptable for some processes and materials, they emphasized that varying flowrate demands may make sizing a nitrogen operation system challenging.

Additionally, because nitrogen purity from non-cryogenic generation may vary depending on required flowrate (with purity decreasing as flowrate demand increases), it is important to prevent changes in nitrogen purity, which can cause quality issues with the material being heat treated.

Dwyer and his colleagues advise securing expert assistance when evaluating nitrogen needs prior to choosing a new or modified supply approach. This might involve going to your industrial gas provider or to an independent consultant. If you are working with an industrial gas provider, make sure that you are getting the technical assistance needed to determine the most cost-effective nitrogen supply system to meet your requirements.

There are upfront costs involved with both delivered and generated nitrogen supplies. According to the Air Products team, users may prefer a lower initial cost approach of dealing with a full-service industrial gas provider to provide a nitrogen system with higher operating costs (for delivered gas), versus a more complex generated nitrogen gas system with higher upfront costs that may offer significant long term savings through lower nitrogen costs. An industrial gas provider may also offer you a lease option for an on-site generation system that could offer you reliability at lower cost.

Besides the costs and investment timing, there are other considerations the experts shared:

  • NFPA 86 (and your insurance provider) may require sufficient nitrogen to be available for purging and inerting regardless of whether your electricity is operating.
  • Because delivered nitrogen production and delivery costs are a significant fraction of the nitrogen price, depending on where the nitrogen producing plant is, some suppliers may offer better prices than others.
  • Electricity costs are a significant fraction of the cost of both delivered and on-site generated nitrogen. If your local electric costs are high but the nitrogen comes from an area with lower electric costs, that may affect potential nitrogen costs and supply decisions.
  • Nitrogen tanks may require meaningful site investments in foundations and piping. If you are leasing your building, consider if a delivered or generated nitrogen supply solution minimizes your site investment.
  • An onsite nitrogen generation system requires large volumes of clean, dry air. In addition to buying a nitrogen generator, you may need to invest in additional air compression capacity. You also need to maintain your compressed air system, because oily air will destroy the expensive air separation media in a PSA nitrogen generation system. Consider your staff’s capabilities carefully.

It is important to take the time to think about a reliable supply that will avoid sending workers home due to lack of available nitrogen. Onsite nitrogen generation allows nitrogen users to make their own nitrogen, without the need for a tank and deliveries. At the same time, nitrogen generation requires large amounts of clean, dry compressed air. For companies that can commit to maintaining their air compression and nitrogen generation equipment, nitrogen generation can be a powerful approach to cost savings. But be realistic. If you can’t commit to 100% uptime for your air supply system, you need to plan for nitrogen downtime and production interruptions.

As a final note, the ideal nitrogen supply approach for your operations may be different from others in your industry. Dwyer, Hernandez, and Phipps say it is important to consider your process needs, ability to invest, interest in ownership vs. delivered utility, staff’s ability to manage a generation system, and the specific costs. Take the time to evaluate and understand that you can choose a different solution at a later time if your needs change.

About The Author:

David (Dave) Wolff
Industrial Gas Professional
Wolff Engineering

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.

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Cost of Fuel Drives Change

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, OP-ED

Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about how rising fuel costs have driven dramatic improvements in furnace efficiency and combustion technology over the past 60 years, transforming heat treat processes from 20% to 70% fuel efficiency.

This editorial was first released in Heat Treat Today’s January 2026 Annual Technologies to Watch print edition.

A furnace guy walks into the shop and sees the cost of gasoline. “This keeps going up, what gives?”

My first car got about 10 MPG — we will not even go near to discussing when that was. Gasoline costs have since driven cars to become more efficient with 30+ MPG vehicles.

Last month’s article highlighted how there are five qualities in our heat treat processes: Quality and Accuracy, the necessary attributes; Efficiency and Performance, the variables; and Profit, which comes whenever we improve the two variables. We have discussed government regulation on emissions and technological breakthroughs that improved combustion technology in earlier articles, but now we turn to the connection of combustion and cost: how gasoline costs drove improvement of the two variable qualities of heat treat processing for combustion, Efficiency and Performance.

Gasoline Costs: A Timeline

Up until about 1960, the world of heat processing was pretty much a level playing field with Efficiency and Performance. We had tons of fuel at our disposal. Pollution was known but not yet a criterion to manage processes. So, burner efficiency and design were very low end. Nobody cared. Fuel was almost free. In doing research for this story, I found records of natural gas being less than $0.50 per million BTUs. Electricity was on par with delivered BTU costs. But then the cost of fuel started to fluctuate. The furnace guys started to notice; if nothing else changed, our friend Profit would weaken.

From 1930 to 1980, electricity pricing went up 500%. Natural gas started to bounce around in price. It was less than a $1.00/thm in the ’60s and ’70s, peaking during times of fuel shortage at $16.00/thm. Ten years later, in 2016, it hit $2.30/thm again. Some pretty wild fluctuations. In fact, it should be noted that the industry overseas had already begun to shift technologies — several years ahead of the U.S. — because they had been suffering with high fuel costs in Great Britain, Germany, Western Europe, and in Asian markets.

Furnace guy and the suppliers had to improve the efficiency and performance.

Troubleshooting and Combustion Design Changes

At first, you look at easy fixes to improve Efficiency and Performance. An example would be that insulation and refractory science really improved. If you can keep the heat in the furnace, you need less fuel to hold it at these high temperatures, right? So, improve the insulation.

Next, let’s get the burners from just being the opening in the furnace that you pour gas into, and make the burner more like a carburetor on an engine. Let’s get control of the air and gas ratios.

Next, let’s recover some of the flue gases and pre-heat the air coming into the burner. When you do that, the flame temp goes up, sometimes by as much as 400-500°F. That means higher heat transfer rates to the parts inside a now well-insulated furnace. Huge efficiency gains started happening.

Efficiency and Performance got a huge boost when the burners started to have high velocity discharge rates. In other words, we now had flames that were hotter and going into the furnace at several hundred miles an hour more than before. With that comes circulation improvement inside the furnace. And much like pudding in a blender, the faster the beaters, the smoother the mix. To give you an idea of the scope of these improvements, form 1960 to 1990, a matter of only 30 years, furnace and burner technology improvements went from 20% fuel utilization to estimated 60-70% fuel efficiencies, even higher in some instances. And there it was, super efficiency driven to occur by fuel cost and flucturation of supply.

To really hit home what that meant, let’s look at a 1,000-lb load of steel. Our process temp is 1750°F. Our furnace and combustion efficiency used to be 20%. That would require 1,370,000 BTU to heat up in an hour. Now, with 75% furnace and burner efficiency, that’s 352,000 BTU. You just saved approximately 1,000 ft3 of gas per hour! If we use the average industrial gas price today at $3.80/1,000 ft3, the difference of all this is $24,000/year, and that’s just a 1,000-lb load. Real world, the numbers are significantly higher, as all you furnace guys know. Imagine the dollar savings when fuel was at $16.00/thm?

And so, there it is. The well-known realization that in most markets, the dollar cost of the energy triggers improvement of technology.

Until next time…

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.

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Answers in the Atmosphere: Nitrogen — The Swiss Army Knife for Thermal Processors

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, BULK GASES & SYSTEMS TECHNICAL CONTENT, OP-ED

In this installment of Answers in the Atmosphere, David (Dave) Wolff, an independent expert focusing on industrial atmospheres for heat treat applications, explores the versatile role of nitrogen gas in thermal processing.

This informative piece on nitrogen’s critical functions in safety, as a diluent, and as an atmosphere component — including production methods and purity requirements — was first released in Heat Treat Today’s November 2025 Annual Vacuum Heat Treating print edition.

As discussed in the introduction for this series of gas-focused columns, nitrogen gas is ubiquitous in thermal processing — by far the most-used delivered or generated gas in secondary metallurgy. This column covers many important considerations for the use and availability of nitrogen gas, featuring the insights from my recent interview with Air Products experts: John Dwyer, principal engineer; Bryan Hernandez, commercial technology sales engineer; and Emily Phipps, strategic marketing manager. Because of its key role in thermal processing, we expect to have additional columns on nitrogen gas in this series.

Nitrogen serves three important purposes in secondary metallurgy:

  1. Safety
  2. Diluent
  3. Atmosphere

Regarding safety, the Air Products experts shared important attributes of nitrogen and several applications it is most often used in. According to them, nitrogen:

  • will not react with most metals used in fabrication applications until reaching extremely high temperatures
  • will not support combustion or oxidation
  • has about the same density as air (which is 78% nitrogen)
  • is the least expensive industrial gas on a volumetric basis.

For those reasons, nitrogen is used as a purging and inerting gas in metallurgical applications, such as inerting the furnace in preparation for a flammable atmosphere to be introduced, as well as expelling flammable atmosphere at the end of a furnace cycle. They further noted that the National Fire Protection Association (NFPA) Standard 86 for Ovens and Furnaces mandates that nitrogen be always available for furnace inerting except for very specific exceptions where alternative approaches are used (burn in and burn out). Beyond the strict safety considerations, nitrogen protects furnace linings and components from high temperature oxidation.

Dwyer, Hernandez, and Phipps emphasized that when used as a diluent, nitrogen makes it possible to use relatively small volumes of a more expensive reactive gas or gas blend and ensure that the diluted active gas can provide benefits for an entire furnace load of parts. Examples include nitrogen/hydrogen atmospheres where nitrogen gas can enable a relatively small volume of very powerful reducing gas hydrogen to be mixed with a higher volume of nitrogen to fill the furnace interior. I would add that a blended atmosphere of nitrogen/hydrogen will have a higher density than hydrogen alone, and hence may distribute more widely in the furnace rather than just pooling at the ceiling level.

They further discussed how nitrogen can be used as a sole constituent in a furnace atmosphere in many cases, especially at lower temperature ranges, such as tempering and stress relief. In situations where surface finish is a secondary consideration, or where additional operations are going to be performed, they note that the part lower finish quality provided under inert nitrogen alone might be acceptable.

The team then reported that nitrogen forms the bulk of the atmosphere and cryogenic air separation is now available virtually worldwide; because of this, liquified or gaseous compressed nitrogen can also be delivered to clients virtually worldwide. Cryogenically separated nitrogen is, by the nature of the process, extremely pure, and can be assumed to be 99.999% or purer as delivered into the client’s storage vessel. Nitrogen can also be made at the client’s site, using non-cryogenic or cryogenic air separation techniques. For secondary metallurgy, non-cryogenic techniques are the most common because the volumes of nitrogen required are too low for a dedicated cryogenic air separation unit.

Continuing along this line, they explained that while both pressure swing adsorption (PSA) and hollow fiber membrane techniques can be employed to generate nitrogen for a single customer site, the PSA technology is the one primarily used to supply generated nitrogen for thermal processes. This is because the membrane technique for non-cryogenic nitrogen generation makes relatively impure nitrogen, with too much oxygen to achieve the desired surface properties sought by heat treaters. As such, membrane generated nitrogen is primarily used for chemical blanketing and similar low temperature air displacement applications.

The final discussion point I will share from the interview today is about the variability in accepted purity based on the planned usage of nitrogen. The three Air Products experts pointed out that NFPA86 mandates that the atmosphere in a furnace must be below 1.0% oxygen before any flammable gas species can be introduced. So, they continued, nitrogen used solely for safety purging can be relatively impure and still achieve the 1.0% maximum oxygen allowed. When used as the sole atmosphere component (i.e., 100% N₂), or as a carrier gas blended with an active gas like hydrogen, they explained that nitrogen purity must be much higher in order to achieve acceptable surface quality. In general, for atmosphere uses, it should be assumed as a general rule that the purer the nitrogen is, the easier it is to achieve satisfactory heat treat results. The three concluded this thought noting that in blended atmospheres it may be possible to use slightly higher levels of active gases (like hydrogen) to react with excess oxygen in the nitrogen supply, but that approach is unlikely to make sense economically since nitrogen is typically far less expensive than an active gas.

In the December 2025 installment of Answers in the Atmosphere, I’ll share further insights that my interview uncovered. Until then, consider your unique nitrogen needs and therefore whether having direct access to this gas for the benefit of your heat treat operations is essential.

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.

For more information: Contact Dave Wolff at Wolff-eng@icloud.com.

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Refine Your Process, Get Profits

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, OP-ED

Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about how focusing on the right priorities in the right order naturally leads to profitability in heat treating.

This editorial was first released in Heat Treat Today’s December 2025 Annual Medical & Energy Heat Treat print edition.

It’s a crisp winter day, and a furnace guy walks into the heat treat plant and says, “Something has changed here, it feels…more modern.” The rest of the furnace guys shrug and continue with the tasks at hand. But the furnace guy is right — something has been changing all along and will continue to do so in the foreseeable future, I’ll wager.

We’ve talked about how certain trends and needs have driven the growth in the industry. My ramblings have included bed posts and pipelines and the flavors of different fuels, and what it all boils down to is change. These changes are attempts to get the following qualities into our processes in the heat treating world:

  1. Quality
  2. Accuracy
  3. Efficiency
  4. Performance
  5. Profit

“But Jim, you listed profit as the last measuring stick! What is wrong with you?” It would be pretty easy to invert this list; turn these guideposts upside down and the world you are in would still work. But if we add longevity in business as an additional goal, then it will not be too long before you begin to realize that the order is listed correctly here. For the most part, in my experience, the heat treating industry has kept the order intact. It is an honorable path, I think.

Quality and Accuracy are the new givens. We do not have to spend time on this. As long as we have been wielding control over metal, those properties are the constant. From hammering out the very first horseshoes, if they did not fit the horse or cracked and broke after a couple of steps, you were not in the horseshoe business very long. These days, standards clearly map out the goal: a client tells us what is demanded, maps it out for us in a specification, and we meet it.

Items 3 and 4 are where we focus today. If we can improve Efficiency and Performance after meeting the Quality and Accuracy targets, then good old item 5 happens — Profit. It just happens. What a concept! Now you may think this is a re-run of every BUS-101 class or seminar you have seen. Maybe you are right, but this is where I veer off as a furnace guy and get back to the business of combustion as it applies to our industry.

We talked earlier about how the natural gas industry expanded and built this fantastic infrastructure to provide fuel to all of us. Electric providers did and are still doing the same thing.

At the end of the transmission line, whether gas pipe or electrical cable, sit the furnaces and ovens that heat treating needs. The buck stops here. Speaking of bucks, in order to get to profit, what must we do? If we really only have Efficiency and Performance in our control (Quality and Accuracy are presumed to be met), then let’s look at how that changed, in furnace guy world…next year [in 2026].

All the best to everyone in the Holiday seasons. May you be blessed with good health and happiness.

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.

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Endings… People We Lost

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Beginnings and endings often come together. As we begin the new year, we want to pause to remember a few lives that came to an end in 2025. Although the following individuals are by no means the only important endings, Heat Treat Today would like to honor the memory of these individuals who left their mark in the heat treating world.

This tribute was first released in Heat Treat Today’s December 2025 Annual Medical & Energy Heat Treat print edition.

Waldron “Wally” L. Bamford (1932-2025)

Source: CAN-ENG Furnaces International

Wally Bamford, co-founder of CAN-ENG Furnaces International, passed away in Ottawa, Ontario, at 93. After serving as a Royal Canadian Navy officer, Wally entered the heat treating and furnace-building industry and helped establish CAN-ENG in 1964. Under his leadership, the company became a global name in industrial furnace design and manufacturing. He also served as the first Canadian president of the Metal Treating Institute (MTI) and was a generous supporter of its scholarship program. Wally is remembered for his integrity, optimism, and lifelong commitment to advancing the heat treating profession.

Michael “Mike” A. Shay, Hauck Manufacturing (1953-2024)

Kevin Walters
Research & Development Manager
OMG Inc.

Mike Shay of Lebanon, Pennsylvania, passed away at 71. Mike dedicated much of his career to Hauck Manufacturing working in field services and sales; his last position held was president of Hauck. Known for his strong leadership and community involvement, he served on local boards and was active in his church and the Boy Scouts. Mike is remembered for his dedication to both his work and his community, as well as his warmth and generosity toward colleagues and friends. Surviving in addition to his wife are his children, Daniel Shay (Julia) of Wilmington, DE, Erin Koch (Dan) of Lebanon, grandchildren, Lydia and Bennett Shay, and a brother, Patrick Shay.

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Navigating Heat Treaters’ Most Defining Moments

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We like to celebrate the wins for good reason: they inspire us when times get tough. Regardless of where you find yourself in the North American heat treat community, you will face challenges that may redirect your life and prompt you to question your goals or values. Given this universal experience, we asked respected individuals from across the industry to share the hardest decisions of their professional lives. Just as successes inspire resilience, these challenges offer lessons in navigating the toughest moments of your career.

This inspiring piece was first released in Heat Treat Today’s September 2025 Annual People of Heat Treat print edition.

“No Jerks” Rule, with Sarah Jordan

Sarah Jordan
Founder & CEO
Skuld, LLC

For Sarah Jordan, president and CEO of the cutting-edge casting startup Skuld LLC, hard decisions have paved the path of her career. An earnest visionary — and as down-to-earth as they come — Sarah has made a habit of launching startups for the metal processing industry. Today, she leads a team that has developed a toolless, net-shape casting process and the equipment to perform it, advancing the way parts are formed while minimizing post-processing needs.

It comes to no surprise that her hardest decision came while forging this path. In 2009, Sarah’s first startup, Aesir Metals, faced fall-out from the 2008 economic recession. The impact was most acute when their largest customer informed them that they were unable to pay.

Faced with this reality, Sarah had to make the painful choice to close the company. Just after Christmas that year, every employee was let go. “And that’s awful when everybody’s…you know, they’re counting on you, their families are counting on you.” It was her first time navigating such a challenge, and while it was difficult, it became a formative experience.

Leading her current company, Sarah operates with a “‘no jerks’ rule.” She says culture and people are critical, and the postmortem of Aesir Metals revealed other opportunities for improvement. While mistakes are inevitable — learning requires that — she moves forward, determined not to repeat the same ones.

Upgrade Your Skillset, with Kevin Walters

Kevin Walters
Research & Development Manager
OMG Inc.

Kevin Walters‘s official title is R&D manager at OMG Inc. out in Massachusetts — however, his nickname “Father of Interns” is extremely fitting. With decades of engineering experience, Kevin has dedicated 25 of them (and counting) to mentoring interns, first at Spalding Sports Worldwide and now at OMG. Using his own career for reference, he tells them this story.

Approaching his forties with four boys near or in their teenage years, Kevin began thinking seriously about his career trajectory. He knew that to stay relevant in engineering, he needed to expand his skillset. In this field, the rule is simple: upgrade your abilities or risk becoming obsolete. The question was how.

“I’m a guy who likes to fix stuff — work with my hands,” Kevin told me. The typical career-advancement routes didn’t seem like the right fit: waiting for an opportunity to open up in the company could take too long, a doctorate might pigeonhole him into academia, and an MBA didn’t align with his engineering focus. It took five years of consideration, conversation, and research to find the right path.

That opportunity appeared when he learned about a management degree specifically tailored for engineers. With Spalding’s full “blessing” and tuition reimbursement program, Kevin enrolled at Western New England University, taking two courses per year while balancing his job and his sons’ baseball games. In five years, he had earned his Master’s of Science in Engineering Management.

These kinds of programs have become more widely available, and Kevin encourages his interns to pursue them. “Engineers, if they don’t upgrade their skillset, become obsolete,” he says. “I see too many engineers who graduated with their four-year degree — did great things at the beginning of their career — but because technology is advancing and they’re not learning with it, they are not as useful as they used to be.”

Each summer, Kevin continues mentoring one or two interns, urging them to think strategically about building their résumés and preparing for an industry that never stops moving.

It’s the People, with Dan Bender

Dan Bender
Director of Sales
Control Concepts

As Dan Bender reflects on his 47 years in industry, many as director of sales at Control Concepts, one priority has guided him: bring in business so the people in manufacturing have a job, can feed their families, and keep a roof over their heads.

In the late ’80s and early ’90s, there were a lot of mergers and acquisitions of companies by holding firms. A general attitude that “work is work” within industry started to emerge. He observed that people were being treated as just another factor of direct manufacturing costs.

This inhumane approach was augmented by a larger lack of pride in the business by the leadership. He also perceived that businesses were treated as financial investments; leadership seemed to be just concerned with flipping the company for a profit. Eventually, these factors reached Dan’s workplace.

Desiring more from his employer and wanting to be useful and productive in a place where people mattered, he parted ways. He reflects, “I left a pretty good job and went out to try some other things, realizing I still had a family to support.”

Over the next few years, he explored different roles, leaning on the counsel of friends and mentors from outside the heat treat industry, many of them from his church. Then, in 2008, the recession hit. Dan was working for a European company when it eliminated nearly all North American positions, and for the first time in his career, he was out of a job.

“That was tough,” he commented. “That was a hard, a hard thing…I did some interviews, I had some possibilities, I had some decent things, but I wanted to find somewhere where…people are important.”

His faith was central to that search, and in time, he found the right fit at Control Concepts. While it was not the best offer at the time, it was “what made me feel good, and it [did turn] out to be very financially rewarding for me.”

Choosing to stick with his principles also meant staying in an industry where he had built decades-long relationships. Dan says he looks forward to seeing those connections at tradeshows like Heat Treat 2025 this fall and Furnaces North America next year. “It’s to me, you know…that’s a blessing that I can have conversations with those people and feel a real sense of knowing they are very interested in what you’re doing as well as you being interested in what they’re doing at this stage in their career and your life.” Serving the heat treat industry, and the people in it, is why Dan has no plans to retire anytime soon.

Never Stand Still, with Bill Stuehr

William (Bill) Stuehr
President & CEO
Induction Tooling Inc.

What do you do when an unforeseen market collapse changes the fabric of your business? William (Bill) Stuehr, engineer, founder, and CEO of Induction Tooling Inc., has a clear answer: make a plan and move forward. “I’m a pragmatist,” he says. “I look at things the way they are, then I make decisions and proceed with what has to be done. That’s all.”

In 2005, Bill built a brand-new facility to expand his operations from 14,000 to 30,000 square feet. Business had been picking up for induction heating since the 1980s and ’90s, and manufacturers of driveline components were interested in induction. Induction was becoming more accepted on two fronts: first, as a green energy source; second, as an integrated manufacturing step in cell production, allowing automotive components such as wheel bearings and axle shafts to come out finished at the end of the line. With the expectation to expand to 50 employees by 2015, the city even granted Induction Tooling a tax abatement to encourage expansion and boost the local economy.

The critical moment happened in 2009, beginning on the heels of the 2008 financial crisis. With the housing collapse, people stopped purchasing automobiles, and the automotive industry went reeling. In April and June, General Motors and Chrysler appeared before U.S. Congress after filing for bankruptcy. Bill’s tier 1 automotive manufacturing customers began shutting down operations. “I had never seen it in my career, ever.”

Work was running out. Bill made the hardest decision of his career: “I had to lay off half of my workforce. I went from 28 people to 14 in less than a year.” Some of them had been with him since he started in the late 1970s. “It was out of my control. I tried to keep them on as long as possible without suffering the financial hardship of my own.” Even in hard times, the company covered all employee medical insurance, a practice Bill maintains to this day.

By 2012, the market showed signs of recovery. Bill pivoted the business to focus almost exclusively on CNC automation for rebuilding tooling — a move that met the needs of their tier 1 customers with high production rates and sidestepped the challenges of rehiring or retraining a large workforce.

Commenting on today’s market, Bill revealed it had never truly recovered. “The buyers of the automotive companies had the time to seek outsourcing worldwide.” He continued, explaining that over the course of the four years that followed the crash, there was enough offshoring of driveline components to an enthusiastic, energetic workforce with new facilities and abilities. Reshoring to the U.S. has not gained back the momentum that it had, though perhaps that will change with the priorities of the current U.S. administration.

From those years came a few lasting lessons. First, embrace automation to keep the business profitable, especially when attracting young talent is a struggle. Second, when hard times come, make a plan and commit — but remember that you can’t control time, the weather, or other people. Bill sums it up with gritty simplicity: “You never stand still; you just keep going. ‘What do I have to do and how can I get it done?’ That’s it.”

Bethany Leone
Managing Editor
Heat Treat Today
Contact: Bethany Leone at bethany@heattreattoday.com

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Merry Christmas from Heat Treat Today

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As we wrap up 2025, our hearts are full. This year brought meaningful growth across the heat treat community — from stronger in-house innovation to new digital tools, expanded training resources, and stories that reminded us why this industry matters. We’re grateful for every reader, partner, and friend who walked with us through another year of learning and connection.

During this season of hope, we celebrate the joy and peace that Christ brings. May that light fill your homes, your work, and your days ahead.

Our offices will be closed for the Christmas holiday, but we look forward to returning in the new year with more news, insights, and encouragement for heat treaters everywhere.

Wishing you a blessed and Merry Christmas,
The Heat Treat Today Team

For housekeeping purposes: our offices will be closed from December 22, 2025 to January 2, 2026. Happy holidays!

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Answers in the Atmosphere: Successful Thermal Processing of Metals Requires Atmosphere Savvy

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, ATMOSPHERE GENERATORS TECHNICAL CONTENT, BULK GASES & SYSTEMS TECHNICAL CONTENT, OP-ED

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:

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.

For more information: Contact Dave Wolff at Wolff-eng@icloud.com.

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