Editor’s note: The following is an edited (for length) transcription of an interview between SECO/WARWICK’s Tom Hart and Dan Herring, The Heat Treat Doctor. It was part of the company’s E-Seminar held in September 2020. Click here if you'd like to hear Dan discuss this article in greater detail with Industrial Heating's Reed Miller.


Tom Hart: What’s going on in the world with heat treatment and COVID-19?

Dan Herring: Just as the world was going along smoothly, all of a sudden the COVID-19 happened, and depending on what country you are in, the virus has affected us differently. At least here in the U.S., the virus has had little effect on most of heat treating. However, manufacturing demand is down. As a result, the industry has slowed down, but certainly the demand for heat-treating services and equipment has not stopped. The time has extended between people being interested in a piece equipment, for example, and the time they purchase. But they are purchasing, so it still remains a very vibrant industry.


Tom: That’s good news to report and great to hear. I have the same sentiments about what I’m seeing in heat treating, especially as of late. What do you think about discussing equipment? What about integral quench? What are your thoughts about the process and its future?

Dan: Integral quench (IQ) is very near and dear to my heart. I’m old enough to remember not quite the dawn of the IQ furnace but darn near close. When the atmosphere IQ furnace was introduced into the marketplace, there was a lot of excitement because it offered a way to heat treat parts in an inert atmosphere that could remain neutral to the surface of the steel.

Also, hydrocarbon gas additions could be used for carburizing or for carbon restoration. Almost from the dawn of time, most furnaces were gas-fired because natural gas, at least in the U.S., was an inexpensive fuel source.

If we go back maybe 80 years and look at the 1940s, IQ furnaces were introduced to the marketplace. Manufacturing seized upon them because they gave us a vehicle to become better and better. But IQ furnaces were not perfect. There were many issues with them, such as controlling the atmosphere, making sure the combustion and heating systems were working properly, and load transfer was always risky at best. If we got eight out of 10 loads to transfer to the quench, we had a great day! In spite of the technology having problems, it did work. IQ made heat treating and the steels being heat treated better.

In the early 1970s, there was certainly a need for an alternate technology, which led to the birth of the vacuum carburizing industry. I’m a great advocate of vacuum carburizing, and I wish it had been a robust technology when it was introduced. If it had been, there wouldn’t be any atmosphere quench furnaces today. Unfortunately, vacuum carburizing had both equipment and process problems. The old joke was “vacuum carburize today, change your heating elements tomorrow.”

Something I always call the savior of the atmosphere quench furnace was the invention and widespread use of the oxygen probe in the early 1970s. Before that time, we were using dew cups, dew pointers and sometimes infrared analyzers. With the introduction of the oxygen probe, we saw a rebirth of the technology in the 1970s and 1980s, and it continued out into 1990s and beyond. It’s a dinosaur, in my professional opinion, but it’s the technology that we know and that we trust will work. We have always struggled to find a replacement technology.

I am happy to report and proud to say that low-pressure “vacuum” carburizing, which came to be in the mid-1990s, solved most if not all of the process-related problems. With equipment improvements, we are ready to see a transition (in my professional opinion) from atmosphere not only to vacuum but also to hybrid. I don’t think the IQ furnace is disappearing from the market anytime soon, but I see that within the next 10-20 years there will be a transition into hybrid technologies or more vacuum carburizing.


Tom: I appreciate that insight about where you think we are going in the coming years. Can you speak to the U.S. market and where it stands?

Dan: We can analyze the health of the U.S. economy by looking at gross domestic product (GDP) growth. After World War II, the GDP was almost 40% of the U.S. economy. This has steadily dropped over the years until today it is in the 11.5-12.5% range. The U.S. must once again reinvest in manufacturing as we are coming out of this COVID world. When we are able to put the virus behind us, I think you’re going to see a boom in the U.S. manufacturing economy.

You are going to see every country – U.S., Canada, Mexico, Europe and even Asia – becoming more self-sufficient with what they manufacture. This will result in GDP growth of the manufacturing segment. There is a desire to do this because of what we experienced with COVID, which was a breakdown in the global supply chain. For instance, we want to be able to rely on the supply of aerospace bearings from purchase anywhere in the world, but we can’t when the global supply chain breaks down. More of that manufacturing will need to be done in the U.S., which will improve GDP growth. There will be a reinvestment in manufacturing.


Tom: Maybe we can shift gears a bit and talk about quenching. Can you speak about the various quenching applications and how they relate?

Dan: There are two aspects to quenching that are important. People are always trying to find a better and better quenchant, but the real secret to success in quenching is to use the quench media that gives you the best management of distortion. Notice I didn’t use “controlling” distortion, but I talked instead about managing it.

In a related topic, one of the biggest changes that I see occurring today is in our steel mills. The steel industry is divesting itself of its talent similar to what the furnace industry did some 30 years ago. So, the mills are becoming much more specific in what they manufacture and much more limited in their technical support. What does this have to do with distortion? The mills are not going to want to invest heavily in the development of new and better steels (for distortion control).

You would think that the mills in North America would want to develop a super 8620 that would be easily gas quenchable, yet that technology escapes us. For this reason, you are going to see the use of oil quenching for quite some time to come. That said, from a person who loves high-pressure gas quenching (HPGQ), there are technologies such as quenching one part at a time that are poised to become a dominant part of the industry as an alternative. This technology will be able to eliminate press quenching to produce a part with a predictable and controlled distortion rate. I still foresee that oil and HPGQ technologies will compete for the next 10-20 years.


Tom: You touched on distortion as well, which is a big factor in the manufacturing process. How can users limit their distortion?

Dan: It starts with looking at the hardenability of the material. It really starts with the end-use application of the component that is being manufactured. Why is it that we seem to carburize a great many components today? There are other technologies (nitriding, for example) that result in far less distortion. We have to have the right steels and the right engineering designs, but we can replace a higher-temperature, more distortion-prone technology with a lower-temperature, less distortion-prone technology.

As a result of that, I see changes in processing being a major part of what is going to help distortion control. I also think modeling and modeling software, which has come on very strong in the last 20 years, is going to allow us to do things on our computers today that as design engineers we have never had the tools to do in the past. These tools are being brought into the world of heat treatment. So, computer modeling and predictive computer software will be a huge step toward controlling distortion, changing our processes, getting us better steels and impacting the way we heat treat them.


Tom: Can you speak to how electric cars are impacting the market and the fact that the automotive industry has historically been so reliant upon heat treatment? How do you see that the dynamic playing out?

Dan: First of all, I am extremely excited about it, whether it’s an electric car or a flying car. I think what is important for everyone to understand is that it is not the last 80 years that are important. It’s the next 20 years and where we are going in the near future that is going to have a profound impact on this industry.

Everyone is predicting that we will put men and women on Mars by the 2040s. The fact is that, in the next 20 years, furnace manufacturers and the thermal-processing industry will undergo a tremendous transition from where we are today to where we need to be tomorrow. This is a natural process, but it’s going to be accelerated not only by the use of computers but by the use of things like artificial intelligence (AI).

What we are comfortable doing in heat treatment today, we will have to step out of our comfort zone in the next 20 years to satisfy the demands of a much more highly sophisticated manufacturing community. For example, vacuum furnaces and vacuum-furnace technology will be critical to that advancement. Why? Because it is quicker to adapt or change than many of the atmosphere technologies.

If you make an investment in an atmosphere furnace today (and there are many good atmosphere furnaces out there), you fix your technology in time and space. With vacuum equipment, however, you have the opportunity to grow or change or be more flexible and to be ready for change that occurs in the near future. So I think there is a tremendous opportunity for all of the furnace manufacturers – all of manufacturing as a matter of fact – to look at how we are going to get from where we are today to future advances.

One of the things I like to ponder is when we are going to develop the room-temperature transformation to martensite. I actually wonder about that quite a bit these days. We have to think outside the box. Just when we get comfortable with one technology, it is replaced with another.

An example of this is when I was in college. Everyone on campus knew we were engineers because we carried our slide rules around with us. By the way, we went to the moon using slide rules, but who in their right mind would use a slide rule today when you have a calculator or a computer available to you? Is there anything wrong with slide-rule technology? No, it works well, but why would you ever use one?

Better technological solutions come up, and that’s exactly what we are saying. You have the evolution of the IQ furnace and the evolution of the gas nitrider into different designs. You have additive manufacturing (AM) taking the place of conventional manufacturing. AM is going to have a significant impact on the future of heat treating and the future of how we make products. You have electric cars, you have AM components and you have new technologies that are replacing perfectly fine technology.

I always call this the slide-rule principal. Who in their right mind would use the technology of the 1960s in the 2020s and 2030s? It boggles my mind.


Tom: But like you said, we went to the moon on slide rule, right?

Dan: Yes, but we did have a “little” computer there to help us as well.


Tom: You have commented on the future, but maybe you can summarize. Where is heat treat going to be in the next 20-30 years?

Dan: I see growth in two industry segments, in particular. Vacuum technology will become the dominant heat-treating technology. I also see applied energy and, in particular, induction heating as a technology that is moving forward at a very rapid pace. The other thing I see is a transition from heat treating batches to heat treating parts one at a time. Furnace manufacturers have gone from large-batch heat treating to small-batch, but it is still batch heat treatment.

In the next 20 years, my vision is that you will see parts heat treated individually for a variety of reasons. One is that the quantities being ordered are going to change. The materials that are developed will require new heat treatments, flexibility and change. As a result, the vacuum and induction fields will be growth industries.

I also believe that processes are going to move to lower temperatures whenever possible. The reason for this is that if you look at the amount of money spent to control distortion, the ultimate goal would be to eliminate the heat-treat process. This isn’t practical, but can you have a heat-treatment process that gives you consistently minimum, if any, distortion? The future is moving in that direction.

The other thing, and perhaps a final comment on my part, is that I think change is going to happen exponentially. It’s not going to be linear, straight-line growth. It is going to be an exponential growth upward. I think you’re going to see as much change for heat treating in the next 20 years as you have in the past 80. I truly believe that, so I think this industry is headed toward those technologies that are flexible and adaptable to change.