Dave Answers in Atmospheres

Answers in the Atmosphere: Hydrogen Part 1 — Powerful Reducing Properties, High Thermal Conductivity

/ ATMOSPHERE GENERATORS TECHNICAL CONTENT, BULK GASES & SYSTEMS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, OP-ED, SINTERING POWDER/METAL TECHNICAL CONTENT

In this installment of Answers in the Atmosphere, David (Dave) Wolff, an independent expert focusing on industrial atmospheres for heat treat applications, examines the powerful reducing properties and high thermal conductivity that make hydrogen a critical atmosphere in metal thermal processing.

This informative piece on hydrogen’s role in sintering, annealing, and surface protection — including how it is sourced, how it behaves inside the furnace, and how operations can safely manage this flammable atmosphere under NFPA 86 — was first released in Heat Treat Today’s April 2026 Annual Induction Heating & Melting print edition.

Hydrogen is widely used in metal thermal processing for sintering of powdered metal fabrication technologies and for heat treatment (e.g., annealing, brazing) of bulk metal manufactured components. This column draws heavily from an interview the author had with Stephen Feldbauer Ph.D., director of Research & Development at Abbott Furnace. Abbott Furnace is a leading furnace manufacturer for continuous furnaces and furnace controls. As R&D Director, Steve leads Abbott’s work in pioneering furnace advances with a special focus on debinding and sintering.

Why Hydrogen?

Stephen Feldbauer, PhD
Director of Research & Development
Abbott Furnace

Hydrogen provides two desirable characteristics to heat treaters: very high chemical reducing potential and the highest thermal conductivity of any gas. The high reducing potential enables hydrogen to convert heated metal oxide coatings to pure metals. This is extremely helpful for successful sintering of powder metallurgical parts. Superior thermal conductivity enables rapid part heat up and cool down. Compared with either vacuum or inert gas atmospheres, hydrogen enables much faster throughput and achieves shorter furnace cycles.

Hydrogen-containing atmospheres are required to successfully sinter most iron-based metal parts, whether manufactured by powder metallurgy (PM), metal injection molding (MIM), or binder-jet metal additive manufacturing techniques. As-received, the iron-containing metal powders used for these advanced fabrication techniques are covered with an iron-oxide coating, making it virtually impossible to successfully sinter the particles together under reasonable temperature conditions. Reducing the oxide coating enables successful sintering.

Hydrogen-based atmospheres used with a tube or strand furnace are the primary surface protective technology used for drawn components (e.g., wire, tubing, and profiles). Hydrogen simultaneously protects the part surface from oxidation and allows metal to anneal, which softens it and restores toughness after it has been hardened by the drawing process.

Sourcing Hydrogen

Because of its high reactivity, hydrogen is almost never found in nature as a pure gas (H2). Instead, it is generally found as a component in a compound like water (H2O) or a hydrocarbon gas or liquid, such as methane (CH4), propane (C3H8), or longer hydrocarbon. In order to be used as a thermal processing atmosphere, hydrogen is liberated from these hydrogen-containing compounds to exist as a pure gas while in use in the hot furnace.

The liberation of elemental hydrogen from its compound carrier can happen at a remote plant operated by an industrial gas company provider, in which case the hydrogen would be compressed or liquified for delivery to the thermal treatment client, or may be conducted at the site of the thermal processor themselves through use of on-site generation equipment. User choices of approaches to pure hydrogen supply will be covered in future columns.

Inside the Furnace

Inside the hot furnace, hydrogen changes metal oxide coatings to pure metals by preferentially reacting with the metal oxides to produce pure metal and water vapor. Thus, the furnace atmosphere dewpoint (a measure of gaseous water content) will increase as the hydrogen simultaneously creates pure metal surfaces and produces water vapor as a byproduct. The water vapor is swept out of the furnace and replaced by the clean furnace atmosphere that flows counter current to the heated metal product. Furnace atmosphere controls for hydrogen-based atmospheres use dewpoint as a key operating parameter.

Hydrogen’s ability to protect the part surface from oxidation is critical in the annealing process. | Image Credit: Abbott Furnace

Since furnaces must open to admit parts for thermal processing, the furnace, the atmosphere system, and the procedures must all be designed to prevent unsafe conditions caused by hydrogen leaking out of the furnace, or air leaking in. Furnaces intended for a flammable gas atmosphere use doors, curtains, and pilot lights (i.e., flame curtains) to prevent hydrogen or other flammable gas from leaving the furnace without being combusted. These precautions avoid explosions inside or outside the furnace.

Furnaces for hydrogen-containing atmospheres utilize unique design and construction approaches to safely use this flammable atmosphere. In the U.S., furnace design and operation is guided by NFPA 86, the furnace code. NFPA 86 defines certain furnace design features and also defines standard operating techniques for safe operation with a combustible atmosphere, such as a hydrogen-containing atmosphere. Similar codes and standards are used in other countries.

Next month, this column will pick up the question of cost by looking at options for generation of hydrogen atmosphere blends. Generation of pure hydrogen will be a future topic.

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.

Answers in the Atmosphere: Hydrogen Part 1 — Powerful Reducing Properties, High Thermal Conductivity Read More »

Answers in the Atmosphere: Argon Part 2 — Market Perspectives

/ BULK GASES & SYSTEMS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, OP-ED

In this installment of Answers in the Atmosphere, David (Dave) Wolff, an independent expert focusing on industrial atmospheres for heat treat applications, examines the market realities shaping argon supply and demand.

This informative piece on argon’s sourcing and distribution landscape, safety considerations, and emerging growth drivers — from U.S. titanium refining and powder metallurgy to the reshoring of domestic steel production — was first released in Heat Treat Today’s March 2026 Annual Aerospace Heat Treating print edition.

Akin Malas
Business Development Manager / Metallurgist
Linde

If you are just beginning to read this column, welcome. I encourage you to read the February 2026 installment to have a better understanding of the attributes of argon as an industrial gas for the thermal processing industry. Akin Malas, business development manager and metallurgist at Linde, joins me in this foray into argon, and we’re exploring market realities in this installment.

Though many companies compete for market share in the supply of gases such as nitrogen, oxygen, and hydrogen because they are relatively less expensive to source and process, the number of companies that have sufficient scale and expertise to produce and market argon is generally considered to be limited to the top tier of industrial gas companies like Linde, Air Liquide/Airgas, Air Products, Matheson, and Messer. Many other companies operate ASUs; however, very few of the plants are large enough to separate and purify argon. In the case of some ASUs owned and operated by very large steel mills, they generally sell their crude argon to industrial gas suppliers for purification and subsequent marketing and sales.

Linde gas delivery truck | Image Credit: Linde

Argon is delivered as a liquid cryogenic product (LAR), like liquid nitrogen (LIN), or liquid oxygen (LOX), but there may be differences in the storage and dispensing equipment installed at a client’s site due to the variety of uses for argon. Certain high-volume applications, such as ladle stirring and metals atomization, may require substantially higher pressure than normal cryogenic tanks are set up to store, making the use of boosters or cryogenic pumps necessary. If your application requires argon pressure to be above 100 psig, make sure that you are talking to a supplier that is experienced in providing and maintaining the equipment needed for your process.

From an NFPA codes standpoint, argon storage is comparable to nitrogen storage, and the clearances in NFPA 55 are the same for argon and nitrogen. But there are some key points to consider as far as safety in use:

  • While all cryogenic gases will create a vapor cloud that hugs the ground if there is a release, the clouds from nitrogen and oxygen will disperse and rise relatively rapidly as the gas warms. But because argon has much higher density than oxygen and nitrogen, a release will tend to hug the ground and can create a serious oxygen deficient atmosphere issue in low spots. Users of pit furnaces with argon need to be particularly aware of the unique characteristics of argon.
  • Because argon is generally shipped much longer distances than oxygen or nitrogen, tanks tend to be larger sized so that more can be delivered in a single visit. Since the transportation element of the price is considerable, keep in mind that your tank size (and NFPA clearance calculations) may be different than is typical for nitrogen.

While argon cannot be cost-effectively produced from air by non-cryogenic generation techniques (like membrane and PSA techniques used for nitrogen and oxygen), argon recovery/recycling is possible from argon-based industrial streams. A few of the larger industrial gas providers can provide recycling equipment that uses cryogenic separation technology to re-create very high purity argon from argon-rich offgas streams. Note that these installations are relatively expensive and specialized and are generally only of interest to the largest argon consumers.

After many years of relatively modest growth in the consumption of argon, several market segments are driving potentially important growth in argon use:

  • Several companies are developing U.S.-based titanium refining capabilities. Argon is required for processing and refining titanium metal, and the U.S. titanium production may become an important consumption driver.
  • Virtually all atomization of the special metals for powder metallurgical applications currently is done with argon used as the atomization gas. Though cheaper water-based atomization is being developed, it is not yet suitable for high quality powders. The metals powder industry has experienced strong growth and continues to grow.
  • The U.S. is reshoring iron and steel production, meaning that argon use for ladle stirring will rise. This means that overall argon use will rise, and that some new argon-capable ASU capacity will be built to serve the needs of new and refurbished steel plants.

Akin and I hope that these last two column installments have helped readers understand the factors in the market for argon that make it different in several ways from the more familiar nitrogen/oxygen marketplace.

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.

Answers in the Atmosphere: Argon Part 2 — Market Perspectives Read More »

Answers in the Atmosphere: Argon Part 1 — An Inert Alternative

/ BULK GASES & SYSTEMS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, 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 practical role of argon as a truly inert alternative to nitrogen in thermal processing.

This informative piece on argon’s unique properties, production challenges, and applications — from vacuum heat treating of titanium to powder metallurgy and additive manufacturing — was first released in Heat Treat Today’s February 2026 Annual Air & Atmosphere Heat Treating print edition.

Akin Malas
Business Development Manager / Metallurgist
Linde

In this column, I’ve invited Akin Malas, business development manager and metallurgist at Linde, to bring his deep expertise in the subject of argon gas. What follows is the fruit of our discussion and continued conversations about this specialized yet indispensable industrial gas in thermal processing applications.

Compared to nitrogen (the industrial gas this column last covered), argon exhibits actual inertness, enabling its use in high-temperature environments and for processing metals that cannot tolerate nitrogen atmospheres, such as titanium and certain high-performance stainless steels. While argon is significantly higher cost than nitrogen, it remains far more economical than helium, another highly inert alternative.

Argon plays a vital role across multiple stages of metal processing, including:

  • Primary metallurgy: ladle stirring
  • Powder metallurgy: atomization of metal powders
  • Additive manufacturing: laser and electron-beam processes requiring inert chamber atmospheres
  • Vacuum heat treating: backfill gas for titanium and specialty alloys

Argon is used differently than nitrogen in most cases. Inexpensive nitrogen is often used as a utility pressurization gas, for scavenging, and blended with other gases (such as hydrogen); however, argon is most often used in pure form. Nitrogen is considered inert for heat treatment applications except in extraordinarily high temperatures or heat treatment of reactive metals, such as titanium and stainless steels. In this case, using an actual inert gas like argon or helium is necessary. Also, while nitrogen is virtually the same density as air and thus will diffuse throughout a vessel, argon is much denser than air and can be used to form a stratified inert layer.

Linde gas storage tanks | Image Credit: Linde

Both argon and nitrogen are separated from air in a cryogenic air separation unit (ASU), but there are three main factors that make argon much harder to make than nitrogen and thus much more expensive:

  • Argon is only 1% of air while nitrogen is 78% of air. Argon boils at nearly the same temperature as oxygen, making a separate purification process necessary. Those two factors mean that only the largest ASUs make enough argon to make it worth purifying.
  • Argon cannot economically be separated from air non-cryogenically (primarily because the percentage in air is so low), so there is no low-cost competition to cryogenic argon. Also, because argon is prized for its inertness, there is much less interest in argon that might be lower purity.
  • Because argon is made in only the largest ASUs (typically those serving very large steel mills) and because those plants tend to be geographically grouped, shipping distances for argon tend to be much farther than for nitrogen and oxygen, further driving up the costs.

Processors of titanium parts and parts made of some stainless steels, such as the 300 series stainless alloys (SS), cannot be processed in nitrogen-containing atmospheres, because the metals will nitride at heat treating temperatures. Hence these metals may be processed in a pure argon (for Ti) or hydrogen (for SS) atmosphere blends.

We’ll pick up this discussion next month to see what market options are available, particularly in the U.S.

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.

Answers in the Atmosphere: Argon Part 1 — An Inert Alternative Read More »

Answers in the Atmosphere: The Tremendous Value of Industrial Gas Smartphone Apps

/ BULK GASES & SYSTEMS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, OP-ED

In this installment of Answers in the Atmosphere, David (Dave) Wolff, an independent expert focusing on industrial atmospheres for heat treat applications, highlights the practical value of smartphone apps designed for industrial gas calculations and conversions.

This informative piece on mobile tools that simplify gas property calculations, unit conversions, and storage or flow-rate estimations — drawing attention to apps developed by major gas suppliers and equipment providers that help heat treaters access critical data in the field — was first released in Heat Treat Today’s January 2026 Annual Technologies to Watch print edition.

The field of industrial gases is complicated by the fact that the physical characteristics of gases depend on the temperature and pressure at the time of measurement. Industrial gases may be delivered and stored as cryogenic liquids and highly pressurized gases, though they are generally used in relatively low-pressure gaseous form. Additionally, gases may be used for different purposes; for example, hydrogen may be used as a metallurgical atmosphere or as a burner fuel. As such, users need a ready source of data on various industrial gases to make necessary calculations.

Image Credit: Open Library/Internet Archive

Years ago, industrial gas users had to rely on data tables in publications like the CRC Handbook of Chemistry and Physics — the nearly 8 lb, $195 hardbound handbook that has been published continuously since 1914 and is currently on its 106th edition.

Today, there are many more mobile solutions in the form of smartphone applications. Several of the major gas providers have developed handy apps available for both Apple and Android operating systems to simplify gas conversions and calculations. Equipment providers have also developed apps to help understand the specifics of their equipment. All of these can be helpful to metals thermal processors, including heat treaters at in-house processing operations.

Some examples follow:

  • Air Products and Linde both provide powerful conversion engines that enable users to convert from imperial to metric units, from mass to volume measurements, and from liquid to gaseous volumes for common industrial gases. For example, users can calculate how many hours of atmosphere coverage 6,000 gallons of liquid hydrogen stored in a tank will provide.
  • Cyl-Tec, Inc. has developed an app that focuses on calculations primarily specific to cryogenic and pressurized gas storage. In addition to unit of measure conversions for each common industrial gas, the app provides detailed information on each of the storage vessels that the company makes.
  • WITT-Gasetechnik of Germany has developed an app to support their gas safety and controls business. Their products include gas mixers, gas analyzers, regulators, and other controls. The app provides a variety of gas blending and measurement information, including welding gas blend suggestions, unit conversion, and flow rate calculators.
  • Gasmet of Finland has developed an app that simplifies calculation of dewpoint and combustion products depending on the fuel being combusted.

While these suppliers hope that you will buy their products, be assured that the measurements and conversions performed with their tools, and the recommendations generated, will be equally applicable to products and systems supplied by others.

I suggest you create a folder called “calculations and conversions” on your smartphone and load it up with several of these apps while you are connected to your home or office internet, so that you will have the apps handy when you are away from your standard technical resources.

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.

Answers in the Atmosphere: The Tremendous Value of Industrial Gas Smartphone Apps Read More »

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.

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

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.

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

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.

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