Laser heat treating, a form of case hardening, offers substantial advantages when distortion is a critical concern in manufacturing operations. Traditional heat treating processes often lead to metal distortion, necessitating additional post-finishing operations like hard milling or grinding to meet dimensional tolerances.
This Technical Tuesday article was originally published in first published in Heat Treat Today’sJanuary/February 2024 Air & Atmosphereprint edition.
In laser heat treating, a laser (typically with a spot size ranging from 0.5″ x 0.5″ to 2″ x 2″) is employed to illuminate the metal part’s surface. This results in a precise and rapid delivery of high-energy heat, elevating the metal’s surface to the desired transition temperature swiftly. The metal’s thermal mass facilitates rapid quenching of the heated region resulting in high hardness.
Key Benefits of Laser Heat Treating
Consistent Hardness Depth
Laser heat treatment achieves consistent hardness and hardness depth by precisely delivering high energy to the metal. Multiparameter, millisecond-speed feedback control of temperature ensures exacting specifications are met.
Minimal to Zero Distortion
Due to high-energy density, laser heat treatment inherently minimizes distortion. This feature is particularly advantageous for a variety of components ranging from large automotive dies to gears, bearings, and shafts resulting in minimal to zero distortion.
Precise Application of Beam Energy
Figure 1. Laser heat treating of automotive stamping die constructed from D6510 cast iron material (Source: Synergy Additive Manufacturing LLC)
Unlike conventional processes, the laser spot delivers heat precisely to the intended area, minimizing or eliminating heating of adjoining areas. This is specifically beneficial in surface wear applications, allowing the material to be hardened on the surface while leaving the rest in a medium-hard or soft state, giving the component both hardness and ductility.
The low-to-zero-dimensional distortion of laser heat treatment reduces or eliminates the need for hard milling or grinding operations. Post heat treatment material removal is limited to small amounts removable by polishing. Eliminating hard milling or grinding operations saves substantial costs in the overall manufacturing process of the component. Our typical tool and die customers have seen over 20% cost savings by switching over to laser heat treating.
Applicable for a Large Variety of Materials
Any metal with 0.2% or more carbon content is laser heat treatable. Hardness on laser heat treated materials typically reaches the theoretical maximum limit of the material. Many commonly used steels and cast irons in automotive industry such as A2, S7, D2, H13, 4140, P20, D6510, G2500, etc. are routinely laser heat treated. A more exhaustive list of materials is available at synergyadditive.com/laser-heat-treating.
Conclusions
Laser heat treatment is poised to witness increased adoption in the automotive and other metal part manufacturing sectors. The adoption of this process faces no significant barriers, aside from the typical challenges encountered by emerging technologies, such as lack of familiarity, limited hard data, and a shortage of existing suppliers. The substantial savings, measured in terms of cost, schedule, quality, and energy reduction, provide robust support for the continued embrace of laser heat treatment in manufacturing processes.
Needing to learn more about the fundamentals and latest developments of stop off coatings? Mark Ratliff, president of AVION Manufacturing Company, Inc., applies his background in chemical engineering to understand and create what makes the best stop-off coatings/paints for carburizing and other heat treat processes. In this episode, Mark and Heat Treat Radio host, Doug Glenn, uncover the varieties of coatings, their uses, and the future of coating solutions.
Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.
The following transcript has been edited for your reading enjoyment.
Chemistry in Coatings: Mark Ratliff’s Start in the Industry (00:22)
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Doug Glenn: I have the really great honor today of talking with Mark Ratliff from AVION Manufacturing. We’re going to do a “painting class” . . . kind of, but not really. Industrial paint — we’re going to talk about stop-off paints and things of that sort.
Mark has been working at AVION, currently located in Medina, Ohio, since 1994. He graduated with a Bachelor of Science degree in chemical engineering from the University of Cincinnati. Prior to that — I did not know this about you, Mark — he worked at Shore Metal Treating with your father, huh?
Mark Ratliff: That’s correct, yes.
Doug Glenn: How long was he there?
Mark Ratliff: Well, he started the company. I went working there and was loading baskets of parts since I was about 8 years old. He would pay me $5.00 for a basket, “under the table,” and that was a lot of money back then. I was really rich, at the time!
Mark Ratliff, President, Avion Manufacturing (Source: AVION Manufacturing)
Doug Glenn: That’s pretty cool. It is very interesting to see people’s backgrounds and how they got involved in the industry. A lot of people start young, you know? You may win the record though — 8 years old! The labor board may be calling about your childhood.
Why Use Stop-Off Paints? (01:54)
Let’s talk today. Technically, we want to talk about something that not everybody may know about, and I think you and your company are kind of experts on these things, and that’s stop-off paints. Just from a 30,000-foot view — and you don’t have to go into a lot of detail here, Mark — what are stop-off paints and why do we use them?
Mark Ratliff: Stop-off paints are protective barrier-type coatings. What they do is prevent either carburization or the nitriding process from entering into the steel. They were created probably well over 50 years ago as a replacement for copperplating these parts. In the past, a long time ago, they would copperplate the part that they did not want carburized or nitrided. That’s a time-consuming process as well as being very expensive. The stop-off coatings were developed as an economical alternative to copperplating.
AVION Line of Stop-Offs (Source: AVION Manufacturing)
DougGlenn: When you say “copperplating,” does that mean it was actual thin sheets of copper metal?
MarkRatliff: That’s correct, yes.
Doug Glenn: And you actually had to wrap whatever you did not want nitrided or carburized in this copper and that would keep it from nitriding?
Mark Ratliff: That’s correct, yes.
Doug Glenn: Just in case people don’t know — but I would imagine that most people that are listening to this do know — nitriding and carburizing are both surface hardening technologies in which either nitrogen (in the case of nitriding) or carbon (in the case of carburizing) are infused into the surface. That, of course, gives improved wear properties, typically corrosion properties to those areas that receive the infusion of the metal.
Why do people not want the nitrogen or carbon to be infused to certain areas of the part?
MarkRatliff: When you harden a part, as with carburization or nitriding, a lot of times hardness equates to brittleness. So you may induce certain stress in various parts, in various areas.
Also, if you want to do a post-heat treatment machining on the part, it would be virtually impossible if that part were carburized or nitrided because the surface is so hard that the tool can’t cut through it to do further machining on the part.
“If you want to do a post-heat treatment machining on the part, it would
be virtually impossible if that part were carburized or nitrided because the surface is so hard that the tool can’t cut through it to do further machining on the part.”
— Mark Ratliff, AVION Manufacturing
Doug Glenn: Gotcha.
Can you give a couple examples of parts, and if you can do a description of where on those parts you might apply a stop-off coating?
Mark Ratliff: Well, a lot of times the end user (the customer) is painting an end of a shaft where he’ll heat treat the shaft and make the shaft harder, but he wants to spin a thread on the end of that shaft. That’s a prime example of why you would use a stop-off coating.
A lot of times, the parts are made with the threads already on, but you don’t want those threads to be hardened because, again, hardness equals brittleness, and those threads would crack off after heat treatment. That would be an area where you would apply a stop-off coating.
Doug Glenn: Tell us a little bit about the actual physical “properties" of these stop-off coatings. We also call them “stop-off paints.” I’m assuming a lot of times these are just painted on — it’s a liquid format.
Mark Ratliff: They are all supplied in liquid form with the viscosity ranging right around 3500–8500 centipoise (cP). For the carburizing stop-off, we have two different kinds. (This is not new in the industry; most people know the formulations of the stop-offs.)
We have boric acid-based stop-offs; we have two different kinds of that — a waterborne and a solvent borne. The idea behind the boric acid-based stop-offs is that as the boric acid thermally decomposes, it creates a boron oxide glass. This glass is actually the diffusion barrier of the carbon. What’s nice about the boric acid-based stop-offs is that they’re water washable after the heat treatment process; the coating and the residue can get washed off.
Another type of stop-off coating that we have is based on silicate chemistry. A silicate chemistry is basically like putting a glass on the part. It’s more of a ceramic-based coating. It works very, very well, but the drawback of the silicate-based stop-offs is that you have to bead-blast the parts after heat treatment; it does not wash off in water.
Doug Glenn and Mark Ratliff
Doug Glenn: So, you’ve got to brush it off.
Mark Ratliff: You’ve got to brush it off, mechanically, correct.
Doug Glenn: That’s interesting.
When I think of painting something on and then putting it into a furnace, the first thing I think of is that paint is going to get completely obliterated in the furnace. But you just kind of answered that question. Those things will either transform into a glass or a ceramic of some sort after they’ve been in high heat for a while, and that’s what creates the barrier.
Mark Ratliff: That’s correct.
You have the active ingredient in the stop-offs — you either have the silicate or you have the boric acid. Those are the active ingredients. The vehicle that the paint itself — be it the water-based latex or the solvent-borne bead — those do, indeed, get charred off. They get burned off, leaving the active ingredient behind.
Doug Glenn: Are you able to use either of those — the water-based or the solvent-based — in vacuum furnaces? Do you have any trouble with off-gassing and things of that sort?
Mark Ratliff: Yes, a little bit. We’ve got to be careful in the vacuum furnace market because you do have the off-gassing. The combination of the vacuum and the heat at once can cause the coating to boil and blister. We do recommend pre-heat treatments when doing a vacuum operation.
Doug Glenn: And the pre-heat just kind of helps it adhere to the part without the blistering, I guess?
Mark Ratliff: That’s correct. And it drives off a lot of the residual water or solvent that might be left in the coating.
Different Chemistry, Different Technology: Plasma Nitriding Stop-Off Coatings (08:32)
Doug Glenn: Okay, good.
Now I understand that there is a new product coming out on the nitriding end of things. Can you tell us a little bit about that and why you’re developing it?
Mark Ratliff: We’ve been making a nitriding stop-off coating since 1989 when we came out with our water-based version. We actually had it patented. We were the first on the market with a water-based nitriding stop-off. This particular stop-off has been used in the industry for 45 years now.
We got called by a current customer asking, “Hey, do you have a plasma or an ion-nitriding stop-off?” At the time, we did not. So, we developed a new plasma — aka, ion-nitriding — stop-off, and that’s a different chemistry, different technology. It is going to be available in the market very soon.
Doug Glenn: Interesting.
I’m curious about this: Are stop-off paints used more in carburizing or nitriding?
Mark Ratliff: By far, carburizing — it’s probably 10 to 1 carburizing to nitriding, for sure.
Doug Glenn: Okay, gotcha.
This episode of Heat TreatRadio is sponsored by AVION.
So, you’ve been doing this for 30 or some years, right?
Mark Ratliff: It will be my 30th anniversary in the month of April.
Doug Glenn: Very nice! Well, congratulations.
Mark Ratliff: I did work for my father prior to that, when he ran AVION for many years before that.
Doug Glenn: Well, congratulations, first off — that’s good. It shows longevity, which is good.
Memorable Moment of Innovation (11:11)
Doug Glenn: Has there been a memorable challenge that you had to deal with, with these stop-off paints?
Mark Ratliff: One thing I’m particularly proud of, Doug, is we always had the water-based carburizing stop-off coating — both varieties — the boric acid-based and the silicate-based. I had a few customers reach out to me and say, “Hey, we’re doing heat treatment for the aerospace industry or for the automotive industry, and they don’t like water-based coatings on their parts,” because you run into corrosion, you run into rust, and so forth and so on. So, these customers asked me to create the solvent-borne, which we did about seven or eight years ago.
One thing I’m particularly proud of is, I got called by the Fiat Chrysler plant in Michigan (they’re going by Stellantis, now), and unbeknownst to them, their current stop-off provider, at the time, changed the formulation. (That was due to the REACH regulations in Europe.) Since they changed the formulation, Stellantis started seeing all these problems. So, they reached out to me and asked, “Do you have an equivalent? We’d like a solvent-borne stop-off.” I was quick to respond, “Oh, by the way, yes, we do. And yes, our product is better,” because even though it’s solvent-borne, we created a nonflammable stop-off coating. In addition to being nonflammable, the solvent that we used in the coating is VOC exempt — VOC meaning volatile organic compounds — which are basically air pollutants that people want to avoid when using these stop-off coatings.
AVION Green Label pail (Source: AVION Manufacturing)
Doug Glenn: Okay, very interesting. I was going to ask you — because I saw on your website — about your green label, which you kind of hit on with the VOC part, but can you tell us a little bit about the green label products that you have and why you’re calling them “green label”?
Mark Ratliff: We called it “green label” a long time ago — that was our original stop-off which kicked off our business 50+ years ago. But I think you’re referring to our eco green label which we created about two years ago.
We’ve been getting a lot of pressure to remove VOCs from our coatings. Clients like John Deere and Caterpillar said, “Hey, we love your coating, but if you could do anything to get the VOCs out of it, we’d really appreciate it.” So, that was one of the biggest goals and one of the biggest accomplishments — to create a coating that didn’t have any of these VOC or HAP (hazardous air pollutants)-type solvents in the coating, and we have successfully done that.
Doug Glenn: That’s good. Especially in the ‘green movement’ that’s going on today, that’s obviously very important.
What coating solution should heat treaters be looking at, in the near future? Is it just VOC stuff, the lack of VOC, or what?
Mark Ratliff: Well, yes, of course. I mean, we’re proud to say that all of our coatings are virtually VOC-free. We are still making the original green label because some customers are not happy to change, so we still offer that. But every single one of our coatings right now have a less than 10 gram/liter VOC threshold, and we’re really quite proud of that.
But, you know, as you’re talking about new coatings coming to the market, we’re coming out with the plasma nitriding stop-off. But we’re also looking into a stop-off for salt bath carburizing. We’ve had a couple people reach out to us, just recently, asking, “Do you have a coating that we can use to paint on the parts that go into a salt bath carburizing operation?”
Doug Glenn: That would be interesting because there is a bit of abrasion going on there, yes?
Mark Ratliff: There is, correct.
Final Questions: Supply Chain, Technical Assistance, and Target Markets (14:51)
Doug Glenn: Now, that’s interesting.
I have two additional questions for you. One has to deal with supply chain issues. Have you guys had any issues with being able to deliver quickly or anything of that sort, ala Covid?
Mark Ratliff: Sure. Right after Covid, we had trouble getting the main ingredient for the carburizing stop-off coating which is boric acid. Currently, I have three suppliers that supply that to me, and there was a point in time where none of them could get the material because the manufacturer of this product was not delivering east of the Mississippi. So, I had to do several days of researching and scrounging around, and I found a distributor in California that said, “Yes, we can get it to you, but you have to buy a whole truckload, which we were very happy to do.”
Doug Glenn: Yes, you take what you can get, at that point.
But no issues now?
Mark Ratliff: No, everything is pretty much back to normal. I mean, gone are the days where you could pick up the phone and get material delivered to you in three days, but most of our raw materials get delivered in under two weeks, and we keep a pretty adequate inventory of all of our raw materials so that we don’t run out of anything.
Doug Glenn: So, you get the raw materials. Do you do your own formulations there? I mean, do you actually do the mixing and all that stuff?
Mark Ratliff: We do. Everything is all done here, in-house, correct.
Doug Glenn: Finally, technical assistance and competency on your guys’ part: Do you have people on your staff — yourself or others — that if a customer calls in with an issue, you can help talk them through it?
“[Look] at the copperplating method: It’s, number one, very expensive, and number two, from what I’ve been told, it’s not very environmentally friendly — you’re working with a lot of hazardous ingredients, hazardous waste."
— Mark Ratliff, AVION Manufacturing
Mark Ratliff: Absolutely. So, I’m the “go to guy” here at AVION. If anyone has any technical questions, I’m the one that’s going to be answering them. And if it’s something where I need to come out to the plant, I’ll get in my car or get on a plane and visit that customer, if the quantity of it dictates that.
Doug Glenn: Yes, sure; it’s got to be a good business opportunity, obviously. But I’m sure you can use the phone to answer questions too.
Mark Ratliff: Yes, most of the time it’s by phone.
Doug Glenn: So, Mark, in the marketplace, is there an ideal client, someone who maybe should be considering stop-off paints that isn’t currently using it? Is there someone out there that you would say, “Hey, you know, if you’re doing this, maybe you ought to think about stop-off paints, if you’re not already doing them.”
Mark Ratliff: Well, I would certainly still target those that are copperplating. Look at the copperplating method: It’s, number one, very expensive, and number two, from what I’ve been told, it’s not very environmentally friendly — you’re working with a lot of hazardous ingredients, hazardous waste. So, those are the types of people that I will continue to target for stop-off coatings.
Doug Glenn: Well, Mark, listen, that’s great. Hopefully, this has been a good primer for people who didn’t know what stop-off paints/coatings were, and hopefully they can get ahold of you if they need something. I appreciate you being with us.
Mark Ratliff: Okay, thank you very much, Doug. I appreciate it myself.
About the Expert
Mark Ratliff started at Avion Manufacturing in 1994 after earning his bachelor’s of science degree in Chemical Engineering at the University of Cincinnati. Prior to getting his degree, Mark spent many of his summer breaks working for his father at Shore Metal Treating where he gained a good deal of knowledge about the heat treating industry.
Case hardening is an essential process for many heat treating operations, but knowing the different types and functions of each is far from intuitive.
In this best of the web article, discover the differences between carburization, carbonitriding, nitriding, and nitrocarburizing, as well as what questions you should ask before considering case hardening. You will encounter technical descriptions and expert advice to guide your selection of which case hardening process will be most beneficial for your specific heat treat needs.
An excerpt:
Case hardening heat treatments, which includes nitriding, nitrocarburizing, carburizing, and carbonitriding, alter a part’s chemical composition and focus on its surface properties. These processes create hardened surface layers ranging from 0.01 to 0.25 in. deep, depending on processing times and temperatures. Making the hardened layer thicker incurs higher costs due to additional processing times, but the part’s extended wear life can quickly justify additional processing costs. Material experts can apply these processes to provide the most cost-effective parts for specific applications.
Thinking about travel plans for the upcoming holiday season? You may know what means of transportation you will be using, but perhaps you haven't considered the heat treating processes which have gone into creating that transportation.
Today’s Technical Tuesday original content round-up features several articles from Heat TreatToday on the processes, requirements, and tools to keep planes in the air and vehicles on the road, and to get you from one place to the next.
Standards for Aerospace Heat Treating Furnaces
Without standards for how furnaces should operate in the aerospace, there could be no guarantee for quality aerospace components. And without quality aerospace components, there is no guarantee that the plane you're in will be able to get you off the ground, stay in the air, and then land you safely at your destination.
In this article, written by Douglas Shuler, the owner and lead auditor at Pyro Consulting LLC, explore AMS2750, the specification that covers pyrometric requirements for equipment used for the thermal processing of metallic materials, and more specifically, AMEC (Aerospace Metals Engineering Committee).
This article reviews the furnace classes and instrument accuracy requirements behind the furnaces, as well as information necessary for the aerospace heat treater.
Dissecting an Aircraft: Easy To Take Apart, Harder To Put Back Together
Curious to know how the components of an aircraft are assessed and reproduced? Such knowledge will give you assurance that you can keep flying safely and know that you're in good hands. The process of dissecting an aircraft, known as reverse engineering, can provide insights into the reproduction of an aerospace component, as well as a detailed look into the just what goes into each specific aircraft part.
This article, written by JonathanMcKay, heat treat manager at Thomas Instrument, examines the process, essential steps, and considerations when conducting the reverse engineering process.
If you are one of the growing group of North Americans driving an electric vehicle, you may be wondering how - and how well - the components of your vehicle are produced. Electric vehicles (EVs) are on the rise, and the automotive heat treating world is on the lookout for ways to meet the demand efficiently and cost effectively. One potential solution is laser heat treating.
Explore this innovative technology in this article composed by Aravind Jonnalagadda (AJ), CTO and co-founder of Synergy Additive Manufacturing LLC. This article offers helpful information on the acceleration of EV dies, possible heat treatable materials, and the process of laser heat treating itself. Read more to assess the current state of laser heat treating, as well as the future potential of this innovative technology.
When the Rubber Meets the Road, How Confident Are You?
Reliable and repeatable heat treatment of automotive parts. Without these two principles, it’s hard to guarantee that a minivan’s heat treated engine components will carry the family to grandma’s house this Thanksgiving as usual. Steve Offley rightly asserts that regardless of heat treat method, "the product material [must achieve] the required temperature, time, and processing atmosphere to achieve the desired metallurgical transitions (internal microstructure) to give the product the material properties to perform it’s intended function."
TUS surveys and CQI-9 regulations guide this process, though this is particularly tricky in cases like continuous furnace operations or in carburizing operations. But perhaps, by leveraging automation and thru-process product temperature profiling, data collection and processing can become more seamless, allowing you better control of your auto parts. Explore case studies that apply these two new methods for heat treaters in this article.
Cuáles son las características más deseables de un probador de dureza Brinell? Esta reseña del equipo le permitirá evaluar si debe o no incorporarlo a su departamento de tratamiento térmico.
Read the Spanish translation of this article in the version below or read the English translation when you click the flag to the right. Both the Spanish and the English versions were originally published in Heat Treat Today's August 2023 Automotive Heat Treat print edition.
Toda empresa dedicada al tratamiento térmico deberá practicar ensayos de dureza, algunos de ellos utilizando la medición Brinell que data desde el año 1900, lo que lleva a que se amerite el análisis de tan perdurable técnica. La prueba en mención requiere de un penetrador de bola de carburo de tungsteno que impacte de manera vertical sobre la superficie del material a ser ensayado, previamente ubicado éste sobre un yunque fijo. Paso seguido, se mide el diámetro de la “huella” generada por la bola, mínimo por los ejes “x” y “y,” y se toma el promedio de estas mediciones como cifra operativa de la que se pueda valer el técnico para establecer la dureza, bien sea alimentando una ecuación o mediante la lectura de una tabla de valores en la que se relacione diámetro frente a dureza.
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Para el ensayo Brinell se dispone de una amplia gama de cargas de fuerza, al igual que de diámetros de penetradores, reflejando la gran variedad de metales a ser probados; no obstante, en la mayoría de ensayos se implementa una bola de 10mm bajo una carga de 3.000 kg. En las grandes máquinas de apoyo a suelo por lo general el penetrador es motorizado, aunque otras operan a partir de palancas y pesas, mientras que también las hay hidráulicas o neumáticas.
Existen tres razones principales por las que la prueba Brinell no deja de ser el método más opcionado para la medición de la dureza en muchas industrias de tratamiento térmico.
1. Preparación de la superficie
La preparación de la superficie de una muestra para las pruebas Brinell toma solo unos segundos con una amoladora. Siempre que la muestra esté firmemente asentada sobre el yunque presentando la cara superior en dirección perpendicular a la dirección de la fuerza del penetrador, de acuerdo a lo exigido por las normas, no es necesario lograr una superficie demasiado lisa.
Figura 1. Robusto probador Brinell in situ
2. Contaminación de la superficie
Es poco probable que los contaminantes diminutos en una superficie generen una “prueba errónea” bajo un penetrador Brinell, a diferencia de la prueba de dureza Rockwell (el método más común en la industria). En esta prueba un pequeño indentador de diamante penetra menos de una centésima de pulgada, arrojando como resultado el que cualquier contaminante o anomalía en la superficie que pueda impedir o favorecer el progreso del penetrador (incluído el paralelismo) represente un problema, y obligando a que las muestras para la prueba Rockwell se deban preparar cuidadosamente antes de realizar la misma.
3. Portabilidad
Quizás el factor más significativo es que los robustos equipos portátiles de mano Brinell, con cabezales de prueba hidráulicos, permiten probar, in situ, piezas grandes, pesadas, de superficies rugosas o formas irregulares. Esta característica es de tal utilidad en la industria que ha motivado a que los órganos de normalización internacional otorguen una dispensación especial, una excepción si se quiere, a las máquinas portátiles, pese a que la ejecución de las mismas no sea susceptible de verificación directa como sí lo es la de sus equivalentes, las máquinas fijas.
Con fuerzas que van desde los 3000 kg hasta 1 kg, y bolas penetradoras tan pequeñas como 1 mm, las pruebas Brinell se pueden usar en una amplia gama de metales, pero los lugares en los que existiría la mayor probabilidad de encontrar un equipo de 10mm/3000kg son las forjas, las fundiciones, las plantas de tratamiento térmico, los laboratorios y las áreas de control de calidad. Previamente mencionamos que no se requiere que la superficie de las muestras de prueba sea absolutamente lisa; de hecho, es posible medir con un grado importante de precisión las superficies irregulares en materiales de configuración gruesa ya que el diámetro de la hendidura es tan grande en relación con cualquier irregularidad en la superficie.
Figura 2. Probador de Brinell, grado calibrador, en primer plano
En la Figura 2 se puede apreciar cómo un probador Brinell de grado calibrador introduce la bola de carburo de tungsteno en la muestra de prueba. Se mantiene la bola en posición para estabilizar la deformación plástica.
Las normas que rigen de manera detallada las pruebas Brinell son la ASTM E-10 y la ISO 6506, pero el procedimiento práctico para los técnicos es muy sencillo, tanto que el entrenamiento no debería tardar más de una hora. Para ensayar piezas forjadas, palanquillas y otras muestras, una hendidura debería bastar aunque, desde luego, en ciertas aplicaciones de extrema importancia se podrá utilizar más de una para mayor seguridad.
Saber si analizar o no cada muestra en un lote determinado deberá decidirse con base en la inconsistencia de las muestras mismas, más no responde a problemática alguna con las pruebas de Brinell en sí. En ciertas industrias se prueba cada pieza que se produce debido a que el riesgo de error es demasiado alto. Un buen ejemplo lo encontramos en la producción de los componentes de los eslabones para las orugas utilizadas en tanques y maquinaria pesada (retroexcavadoras y demás). Cada eslabón de cada oruga de un tanque en uso en el ejército británico ha sido probado por Brinell en una máquina totalmente automática, de alta velocidad, que cuenta con una poderosa abrazadera integral para mantener el componente absolutamente rígido durante la prueba. Por cierto, esa máquina es la de la primera foto. Con un cuidado adecuado y razonable, un probador Brinell robusto podrá generar cientos de miles de pruebas; de hecho, el probador de la Figura 1 ha realizado varios millones.
Las pruebas duran aproximadamente quince segundos ya que el penetrador se debe dirigir hacia el material de manera uniforme sin permitir la posibilidad de un “rebote” y evitando por completo llegar a golpear el material. Por otro lado, el metal debe recibir la presión por un período de tiempo suficiente que garantice que la hendidura se deforme de la manera más plástica posible, es decir, minimizando al máximo el riesgo de la más ligera contracción de la hendidura una vez retirado el penetrador.
Figura 3. Medición de una hendidura de prueba de dureza Brinell
Sin embargo, es en este punto que se presentan las complicaciones. Después de generar cuidadosamente la hendidura y retirar la muestra de prueba de la “boca” de la máquina probadora, es necesario medir la hendidura en al menos dos diámetros. Dado que las hendiduras de Brinell tienen como máximo 6 mm de ancho y que una diferencia de 0,2 mm en el diámetro podría equivaler a 20 puntos de dureza, obtener la medición correcta es esencial y de alta complejidad. La mayoría de los técnicos usan un microscopio iluminado para lograrlo, pero aún así puede ser un desafío. Considere la Figura 3.
Los microscopios de medición manual han mejorado a lo largo de los años, y cuando se obtiene una hendidura relativamente “limpia” con una retícula nítidamente iluminada, se le puede facilitar al técnico experimentado realizar una medición precisa. La Figura 4 presenta un escenario menos complejo que el anterior pero, aun así, ¿cómo podemos saber si realmente se ha juzgado con precisión la posición del borde?
Figura 4. Medición con microscopio mejorado y retícula bien iluminada.
Al crearse la hendidura se genera un cordoncillo en el perímetro de la misma debido a que el metal no solo presiona hacia abajo, sino también hacia los lados. Este cordoncillo puede difi cultar la ubicación del punto en el que comienza realmente la hendidura, y tres técnicos diferentes pueden hacer fácilmente tres estimaciones diferentes de su lugar de inicio. Es esta variación en la interpretación de los resultados por parte de los operadores la que ha llevado a que, durante más de 80 años, la prueba Brinell se haya considerado un poco “ordinaria”, apta tal vez para el maquinista en el taller, pero de dudoso valor para el científi co en el laboratorio.
En 1982 llegó a los mercados el primer lector automático, siendo éste la culminación de años de investigación, y valiéndose de software privado que llevó a las computadoras de la época a sus límites. El equipo podía hacer cientos de mediciones de un lado a otro de la hendidura y calcular el diámetro medio en una fracción de segundo. Poco después llegó a ser parte integral de una máquina de prueba Brinell. La noticia de la aparición de este equipo pronto llegó a algunos usuarios importantes en la industria de las herramientas petroleras quienes exigieron a sus proveedores valerse de él; quince años más tarde se había diseminado ampliamente el uso de esta tecnología generando la transformación de la percepción que se tenía de la prueba Brinell. Podríamos decir que la prueba Brinell había llegado a la mayoría de edad.
Figura 5. La última versión de ese microscopio automático en acción
Desde luego, como con cualquier equipo de medición importante, la calibración y el mantenimiento regulares son aconsejables, si no obligatorios. Los fabricantes mismos suelen estipular un cronograma de mantenimiento que se debe tener en cuenta junto con las reglas de calibración establecidas por las agencias internacionales.
Al considerar las opciones para la prueba de dureza en muestras con tratamiento térmico, en última
instancia existen tres métodos: Brinell, Rockwell y Microdureza (Vickers o Knoop).
Pese a que no es adecuada para muestras muy pequeñas o demasiado delgadas, la prueba Brinell es relativamente “inmune” a los contaminantes pequeños, los penetradores no son costosos, y, gracias al ancho de la hendidura, las pruebas de superficies con acabado áspero e irregular no presentan dificultades. Con el desarrollo, hace 40 años, de la medición automática de la hendidura, se superó la única deficiencia grave de la prueba Brinell, proporcionando las garantías que tan vital importancia revestían para los proveedores de piezas esenciales en industrias de toda índole, incluídas las de petróleo y gas, aeroespaciales y de defensa y transporte.
Sobre el autor: Alex Austin se viene desempeñando desde 2002 como gerente de Foundrax Engineering Products Ltd. Foundrax es proveedor de equipos de prueba de dureza Brinell desde1948, siendo en realidad la única compañía en el mundo especializada en el campo.
Alex funge en el Comité de Prueba de Dureza por Hendidura ISE/101/05 del British Standards Institution. En su calidad de miembro de la delegación británica de la Organización Internacional de Normalización, ha aportado como consultor para el desarrollo de la norma ISO 6506 “Materiales metálicos–prueba de dureza Brinell” y preside en la actualidad la revisión ISO de dicha norma.
Exothermic gas undergoes a few metamorphoses from the time it is produced to the time it is cooled down after use. Explore the transformations that occur within the combustion chamber to discover the impact these phases can have on the heat treatment atmosphere of your workpieces.
This Technical Tuesday article was composed by Harb Nayar, president and founder, TAT Technologies LLC. It appears in Heat Treat Today'sAugust 2023 Automotive Heat Treating print edition.
Background
Harb Nayar
President and Founder
TAT Technologies LLC
Source: LinkedIn
Exothermic gas, more commonly referred to as Exo gas, is produced by partial combustion of hydrocarbon fuels with air in a well-insulated reaction or combustion chamber at temperatures well above 2000°F. Immediately after they exit the combustion chamber, the reaction products are cooled down using water to a temperature below ambient temperature to avoid condensation. The typical dew point of the cooled down Exo gas is about 10°F above the temperature of the water used to cool down. The cooled down Exo is then delivered to the heat treat furnaces where it gets reheated to the operating temperatures between 300°F and 2100°F.
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A simplified schematic flow diagram of Exo gas production followed by its cool down below ambient temperature and its final use in heat treat furnaces is shown in Figure 1.
The following aspects of the Exo gas production are clear from Figure 1:
There is lot of energy lost out of the reaction chamber.
There is additional heat lost during cooling using water.
A good deal of water is used for cooling.
The cooled down Exo gas is re-heated to the process temperature in heat treat furnaces.
Exo gas has been predominantly used and is still being used as a source of nitrogen rich atmosphere for purging, blanketing, and mildly oxide reducing applications in the heat treat and metal working industries.
Figure 1. Schematic flow diagram showing Exo production, cool down, and its use.
Source: Morris, “Exothermic Reactions,” 2023
Examples of applications:
Brazing
Annealing
Hardening
Normalizing
Sintering
Tempering, etc.
Examples of materials:
Irons
Steels
Electrical steels
Copper
Copper-base alloys
Aluminum
Jewelry alloys
Examples of product sizes and shapes:
Tubes
Rods
Coils
Sheets
Plates
Components
Small parts, etc.
Exo is the lowest cost gas used in furnaces operating at temperatures above about 700°F to keep air out and provide a protective atmosphere with some oxide reducing potential to the materials being thermally processed.
There are two types of Exo gases: lean Exo gas, with mostly nitrogen and carbon dioxide and very little hydrogen, and rich Exo gas, with a little less nitrogen and carbon dioxide and substantially more hydrogen and some carbon monoxide. Typical compositions are given below:
Figure 2. Exo gas operating range
Source: SECO/WARWICK
Figure 2 shows graphs of Exo gas composition at various air to natural gas ratios. H2, CO, and residual CH4 decreases with increasing air to natural gas ratio whereas CO2 goes in the opposite direction. H20 content not shown in the graphs is typically in the 2–4% range depending upon the temperature and cooling efficiency of the cooling system. N2 is the balance which increases with increasing air to natural gas ratio.
The generator designs to produce lean and rich Exo gases are slightly different as shown in the schematic flow diagrams below in Figures 3 and 4.
Objective
This paper will demonstrate a simplified software program (harb-9US) developed recently by TAT Technologies LLC that can easily calculate the reaction products composition, temperature, exothermic energy released, various ratios, and final dew point for various combinations of air and fuel flows entering the reaction chamber at a predetermined temperature and pressure.
The data presented in this paper is under thermodynamically equilibrium conditions only, captured when the reaction is fully completed. It does not tell how long it will take for the reaction to reach completion. However, it can be safely said that reactions are completed relatively fast at temperatures above about 1500°F and very slow at temperatures below about 1000°F. The current software program uses U.S. units: flow in SCFH, pressure in PSIG, temperature in degrees Fahrenheit, and heat as enthalpy in BTU.
The composition of the Exo gas for a fixed incoming air to hydrocarbon fuel ratio changes from production in the combustion chamber to the cool down equipment to bring the Exo gas to below the ambient temperature and finally into the furnace where the material is being heat treated.
Understanding the changes in gas composition from Step 1 (Production in the Combustion Chamber) to Step 2 (Cool Down to Ambient Temperature) to Step 3 (At Temperature of Heat Treated Part) can help to improve the composition, quality, and control of Exo gas that will surround the metallic products being heat treated in the furnace.
Step 1: Composition of Exo Gas as Produced in the Combustion Chamber
Table A shows the Exo gas compositions as generated within the combustion chamber at various air to natural gas ratios supplied at 100°F and 0.1 PSIG. In these calculations natural gas composition is assumed as 100% CH4 and air is assumed as 20.95% oxygen and balance nitrogen. CH4 is fixed at 100 SCFH and air flow is varied to give air to natural gas ratios between 9 and 6. Typically a ratio of 9 is used for lean Exo and 7 is used for rich Exo applications. Other ratios are used in some special applications.
Table A: Exo gas compositions in reaction chamber based on 100 SCFH of CH4 with air 900, 850, 800, 750, 700, 650, and 600 SCFH to give air to natural gas (CH4) ratios of 9, 8.5, 8, 7.5, 7, 6.5 and 6 respectively. Air and natural gas (CH4) are at 100°F before entering the combustion chamber.
Source: TAT Technologies LLC
The following key conclusions can be made from Table A as one moves from air to natural gas (CH4) ratio of 9 down to 6:
The peak temperature in the reaction chambers goes from a high of 3721°F down to low of 2865°F. Because of high temperatures, good insulation around the combustion chamber is a must. A significant portion of the exothermally generated energy within the reaction chamber is lost to the surroundings.
There is no residual CH4 in the Exo gas composition at these high temperatures. There is no soot (carbon residue) under equilibrium conditions.
H20 content in the natural gas (CH4) gas in the reaction chamber is very high — from high of 19.11% to low of 15.87%. These correspond to dew point 139°F to 132°F — well above the ambient temperature. Because of the very high dew point, the Exo gas coming out of the reaction chamber must be cooled down below the ambient temperature to remove most of the H20 in the Exo gas to avoid any condensation in the pipes carrying the Exo gas toward the furnace and into the
furnace.
H2% changes significantly from 0.67% to 9.96%.
The oxide reducing potential (ORP) as measured by H2/H20 ratio changes from a very low of 0.035 to 0.628. ORP in the reaction chamber is overall quite low because of high percentage of H20.
Nitrogen content varies from 70.34% to 61.26% of the total Exo gas in the reaction chamber.
Exothermic heat generated varies from 95.3 MBTU to 54.34 MBTU — it gradually becomes a less exothermic reaction. Gross heating value of CH4 (at full combustion) is 101.1 MBTU/100 cubic foot of CH4.
Question: What happens to the composition of Exo gas as it cools from peak temperature in the combustion chamber to different lower temperatures after it exits from the combustion chamber?
Answer: It changes a LOT, assuming enough time is provided to reach its equilibrium values during cooling down to any specific temperature. Whenever there is a mixture of gases, such as CH4, H2, H20, CO, CO2,O2, N2, there are a variety of reactions going on between the constituents in the reactant gases to produce different combinations of gas products and heats (absorbed or liberated) at different temperatures. The most popular and well-known reactions are:
Partial Oxidation Reaction: CH4+ 1/2O2 → CO + 2H2 — exothermic. The reaction becomes more exothermic as O2 increases from 0.5 to 2.
Water Gas Shift Reaction: CO + H20 → CO2 + H2 — slightly exothermic. It usually takes place at higher temperatures faster. A catalyst in the reaction chamber can help to lower the high temperature requirement. There are many catalysts. Commonly used are either Ni or precious metals.
CO2 Reforming Reaction: CH4 + CO2 → 2CO + 2H2 — endothermic.
All of these reactions have different degrees of influences from changes in temperature. One could say that the final equilibrium composition of the Exo gas is a continuously moving target as temperature changes. Only the N2 portion stays constant. One can make the following generalized statements covering a broad range of Exo gases (lean and rich) in the reaction chamber:
a) N2 content does not change. It remains neutral at all temperatures.
b) H2 content decreases with increasing temperature.
c) H20 (vapor) content increases with increasing temperature.
d) CO content increases with increasing temperature.
e) CO2 content decreases with increasing temperature.
f) Residual CH4 decreases with increasing temperature.
g) Soot decreases with increasing temperature.
h) Catalysts facilitate the speed of reactions at any temperature.
Conclusion
Exo gas composition changes during its time in the combustion chamber. Reaction products composition, temperature, exothermic energy released, various ratios, and final dew point are all items that need to be taken into consideration to protect the metallic pieces that will be heat treated in the resulting atmosphere. Part 2 will demonstrate this principle and discuss Step 2 (Cool Down to Ambient Temperature) and Step 3 (At Temperature of Heat Treated Part).
About the author:
Harb Nayar is the founder and president of TAT Technologies LLC. Harb is both an inquisitive learner and dynamic entrepreneur who will share his current interests in the powder metal industry, and what he anticipates for the future of the industry, especially where it bisects with heat treating
Nikola Tesla afirmó: <<Si quieres descubrir los secretos del universo, concéntrate en la energía, la frecuencia y la vibración.>>
Al revisar los mecanismos internos de un sistema de inducción es posible evidenciar cada uno de estos tres elementos. Los 10 pasos de esta guía servirán para apoyar a los operadores de departamentos internos de tratamiento térmico en entender los secretos de la inducción para así identificar posibles escollos en tales sistemas y dar solución a problemas comunes que se puedan presentar.
This original content article was first written by Alberto Ramirez, engineer of Power Supply and Automation at Contour Hardening, Inc. and an honoree from Heat TreatToday’s40 Under 40 Class of 2021, for Heat TreatToday’sMay 2023 Sustainable Heat Treat Technologies print edition. Read the Spanish version below, or click the flag above right for the English version.
Alberto Ramirez
Power Supply and Automation Engineer
Contour Hardening, Inc.Contact us with your Reader Feedback!
Los metales pueden calentarse mediante el proceso de inducción electromagnética, mediante el cual un campo magnético alternativo cerca de la superficie de una pieza de trabajo metálica (o conductora de electricidad) induce corrientes de Eddy (y, por lo tanto, calentamiento) dentro de la pieza de trabajo.
Los sistemas de inducción pueden llegar a ser sistemas complejos que tienen como objetivo endurecer piezas o secciones específicas de un componente mecánico, dependiendo del grado de complejidad de la pieza a tratar; para el profesional, el desafío será el diagnóstico de los problemas que se lleguen a presentar.
1. Familiarízate con el proceso
Figura 1. Proceso de endurecimiento por inducción
Source: Contour Hardening, Inc.
El proceso de inducción envuelve muchas características tales como: posición de la pieza dentro de la bobina de inducción, posiciones de carga, posiciones de enfriamiento, tiempos de ciclo, potencia eléctrica aplicada, entre otras. Es importante que el profesional sea capaz de identificar la falla y la situación particular en el momento en el que se está presentando.
En algunas ocasiones las fallas no son evidentes y, por ende, es indispensable analizar la pieza que ha sido tratada; este análisis puede ser clave para entender situaciones tales como: falta de profundidad de capa por potencia eléctrica o disminución en la frecuencia de salida, entre otros posibles escenarios.
Adicional al análisis de la pieza, es vital inspeccionar la “escena del crimen” ya que muchos de los sistemas de inducción, dada la naturaleza del proceso y el peligro que implica manejar altos potenciales eléctricos, suelen ser en extremo automatizados y las estaciones de trabajo de difícil acceso para el personal, así que una buena estrategia de trabajo consiste en observar detenidamente las condiciones generales del equipo para determinar el punto de inicio para la resolución del problema.
2. Identifica los componentes principales de tu sistema de inducción, así como los mecanismos de seguridad para ciertas zonas en particular
Entender la interrelación del sistema es importante para comprender qué elemento realiza cierta acción, así como los canales de comunicación entre ellos. Una vez que se genere este conocimiento, se puede asociar una falla a un componente en particular. Usualmente los sistemas de inducción se componen de los siguientes elementos:
Figura 2. Componentes de un sistema de inducción
Source: Contour Hardening, Inc.
Como mencionamos con anterioridad el proceso implica altos potenciales eléctricos, y para eso la naturaleza de las fuentes de alimentación involucra dispositivos electrónicos de potencia, como capacitores eléctricos, los cuales almacenan energía y, por ende, es importante descargar eléctricamente el sistema antes de comenzar a inspeccionar un equipo.
3. Ten preparadas las herramientas necesarias para realizar un buen análisis del problema
Figura. Capacitores
Source: Contour Hardening, Inc.
Al igual que cualquier problem técnico, el uso de la herramienta mecánica es indispensable al realizar algún tipo de proyecto, pero para el diagnóstico de una falla en un equipo de inducción es importante contar con:
Osciloscopio
Generador de funciones
Amperímetro
Multímetro digital y analógico.
Sondas de alto voltaje
Sin estos elementos es muy difícil llegar a un diagnóstico fiable, y la posibilidad de encontrar la falla es mínima. Por ende, tener estos medidores en buen estado y, sobre todo, calibrados nos da una perspectiva más clara del problema.
4. Verifica que los sensores del proceso, los monitores de energía y las bobinas de inducción funcionen correctamente
Existen distintos medidores que recogen información acerca del proceso; esta información en su mayoría puede ser visualizada a través del HMI (Human Machine Interface), y, en muchas ocasiones, una buena manera de comenzar a entender el problema es recopilar la información del proceso. Si los medidores no funcionan correctamente, te pueden llevar a conclusiones erróneas.
Verifica que los medidores de energía estén funcionando correctamente, así como tus señales de entrada y de salida.
Las bobinas de inducción son un elemento clave en el proceso de inducción ya que acorde a su geometría generan los campos magnéticos adecuados para lograr los resultados metalúrgicos esperados. Si existen fugas de agua o los elementos de transmisión eléctrica se encuentran sueltos o sucios, seguramente podrán ser la raíz del problema. Es importante comenzar a realizar el diagnóstico de la falla una vez se haya descartado este circuito en particular.
Figura 4. Ejemplo de parámetros de energía
Source: Contour Hardening, Inc.
5. Realiza estudios de energía constante en tu subestación para identificar posibles problemas en tu suministro de energía, así como tiempos críticos
La energía eléctrica es la fuente principal en un proceso de inducción; las fuentes de alimentación transforman y potencializan este recurso para crear campos electrónicos lo suficientemente fuertes para generar el calor en la pieza.
Por ende, es importante descartar con evidencia que el problema en cual nos encontramos no se debe a una falla del sistema eléctrico del cual nuestro sistema de inducción forma parte. De igual manera entender cómo se comporta nuestro sistema eléctrico nos puede ayudar a generar patrones de comportamiento que puedan determinar la solución en momentos específicos en los que se lleguen a presentar.
6. Trabaja de forma metódica documentando tus movimientos y realiza un paso a la vez
Los sistemas de inducción pueden ser muy intimidantes si no has tenido experiencia previa, y, al igual que con cualquier elemento o situación, es importante abordar de manera lógica el problema analizando el modo de la falla, identificando las partes principales que interactúan en ese preciso momento, y, a partir de este análisis, documentar y realizar pequeños pasos, uno a la vez, ya que, de no ser así, es muy probable que pierdas todo el trabajo realizado y la situación empeore.
Figura 5. Antes y durante un arco eléctrico dentro de la línea de transmisión
Source: Contour Hardening, Inc.
Si los movimientos no son exitosos, siempre puedes regresar a tu punto de partida e intentar otro acercamiento. La idea consiste en que el modo de la falla se mantenga estable sin importar los movimientos realizados hasta que se resuelva el problema. De esta manera lograrás contener la falla; de otra manera podrías estar dañando otros elementos sin darte cuenta.
Es muy importante entender que los procesos son secuencias que anteceden y preceden a nuevos eventos; si entiendes el proceso y, una vez resuelto el problema, ahora tienes una nueva falla, es importante analizar si esta falla es la continuación del proceso ya que, de ser así, es posible que te encuentres frente al caso de un evento que está desencadenado una serie de fallas y se haga necesario practicar un análisis más profundo. La idea general es llegar a la raíz del problema y mitigar el riesgo.
7. Intenta cualquier posibilidad relacionada con el proceso sin importar que la relación entre ésta y el problema no sea directa
Un pensamiento lógico puede resolver la mayoría de las fallas técnicas de un sistema, pero, para fallas excepcionales, es necesario utilizar la imaginación y agotar todos los recursos posibles ya que el área de interés más insignificante o el lugar menos pensado puede ser la clave para resolver un problema.
8. Conoce tus fuentes de alimentación
Uno de los factores claves en cualquier equipo de inducción son sus fuentes de alimentación. Las fuentes de alimentación son equipos que no requieren un mantenimiento tan arduo en comparación con otros sistemas en la industria, pero, de no presentarse las condiciones mínimas de mantenimiento, pueden generar altas pérdidas para la organización.
Figura 6. Diagrama de flujo del proceso eléctrico en una fuente de alimentación
Source: Contour Hardening, Inc.
En los casos en los que el problema se encuentra en las fuentes de alimentación, es vital que se siga el mismo proceso metódico previamente descrito. Entender cómo funciona el proceso de transformación de la energía te dará una ventaja, al igual que conocer los componentes empleados o el tipo de tecnología utilizado en el proceso de rectificación, en la inversión (estado sólido o tubos de electrones) y en el circuito resonante. Generalmente las fuentes de alimentación siguen el siguiente patrón de transformación (Figura 6).
9. Identifica las partes críticas de tu equipo de inducción y prepara un inventario de éstas
Figura 7. Daño en una bobina de inducción
Contour Hardening, Inc.
Usualmente los componentes que forman parte de las fuentes de alimentación son difíciles de conseguir dependiendo de la antigüedad de tu equipo, y con la reciente crisis de microchips en el mercado, existen tiempos de entrega muy largos para los elementos de control y automatización; de igual manera, los precios de los mismos se han disparado. Por ende, es vital que exista una lista de partes críticas y un inventario de éstas.
Adicionalmente a los elementos descritos, las bobinas de inducción suelen ser elementos muy característicos e importantes en el proceso de inducción. Éstas bobinas son elementos complejos que han sido diseñados exclusivamente para la pieza, por lo que su fabricación puede tomar varias semanas, y es importante tomar las precauciones necesarias para mantener un movimiento de mantenimiento constante.
10. Realiza mediciones preventivas al sistema para generar un patrón de comportamiento
Figura 8. Ejemplo de posibles mediciones
Contour Hardening, Inc.
Cuando el sistema se encuentre trabajando en óptimas condiciones, genera un plan de medición el cual te permita recopilar información de puntos específi cos dentro del sistema. Una vez que se vuelva a presentar una nueva falla puedes comparar las mediciones de falla contra las del buen funcionamiento. Algunos ejemplos de mediciones pueden ser:
Temperatura
Voltaje
Corriente eléctrica
Resistencia y capacitancia
Formas de onda
En resumen
Una metodología de trabajo ordenada y documentada, un buen catálogo de piezas de recambio, junto con las herramientas de trabajo necesarias, pueden ser elementos clave para entender un problema y, lo que es más importante, resolverlo de forma eficaz.
Es vital que los profesionales se capaciten de manera constante para mejorar los tiempos de paro debido a fallas en los sistemas de inducción. La capacitación relacionada con procesos metalúrgicos sería una buena forma de complementar tus habilidades de resolución de problemas permitiéndote interpretar las características de los sistemas de inducción, al igual que de los elementos que los componen.
Bibliografía
Valery Rudnev and George Totten, ed., ASM Handbook Volume 4C: Induction Heating and Heat Treatment, (Materials Park, OH: ASM International Heat Treating Society, 2014), 581- 583
Sobre el autor: Alberto C. Ramirez es ingeniero en Mecatrónica egresado del Instituto Tecnológico Nacional de México Campus León con una maestría en Administración de Tecnologías de la Información por el Instituto Tecnológico de Monterrey. Cuenta con más de 8 años de experiencia en fuentes de alimentación, gestión de proyectos, mantenimiento y automatización. Actualmente se desempeña como ingeniero de fuentes de alimentación y automatización en Contour Indianapolis. Alberto inició su carrera en la fi lial de Contour en México y debido a su dedicación forma parte del staff en los Estados Unidos.
He is also an honoree from Heat TreatToday’s 40 Under 40 Class of 2021.
Nikola Tesla afirmó: <<Si quieres descubrir los secretos del universo, concéntrate en la energía, la frecuencia y la vibración.>>
Al revisar los mecanismos internos de un sistema de inducción es posible evidenciar cada uno de estos tres elementos. Los 10 pasos de esta guía servirán para apoyar a los operadores de departamentos internos de tratamiento térmico en entender los secretos de la inducción para así identificar posibles escollos en tales sistemas y dar solución a problemas comunes que se puedan presentar.
This original content article was first written by Alberto Ramirez, engineer of Power Supply and Automation at Contour Hardening, Inc. and an honoree from Heat Treat Today’s 40 Under 40 Class of 2021, for Heat Treat Today's May 2023 Sustainable Heat Treat Technologiesprint edition. Read the Spanish version below, or click the flag above right for the English version.
Alberto Ramirez Power Supply and Automation Engineer Contour Hardening, Inc.
Contact us with your Reader Feedback!
Los metales pueden calentarse mediante el proceso de inducción electromagnética, mediante el cual un campo magnético alternativo cerca de la superficie de una pieza de trabajo metálica (o conductora de electricidad) induce corrientes de Eddy (y, por lo tanto, calentamiento) dentro de la pieza de trabajo.
Los sistemas de inducción pueden llegar a ser sistemas complejos que tienen como objetivo endurecer piezas o secciones específicas de un componente mecánico, dependiendo del grado de complejidad de la pieza a tratar; para el profesional, el desafío será el diagnóstico de los problemas que se lleguen a presentar.
1. Familiarízate con el proceso
Figura 1. Proceso de endurecimiento por inducción Source: Contour Hardening, Inc.
El proceso de inducción envuelve muchas características tales como: posición de la pieza dentro de la bobina de inducción, posiciones de carga, posiciones de enfriamiento, tiempos de ciclo, potencia eléctrica aplicada, entre otras. Es importante que el profesional sea capaz de identificar la falla y la situación particular en el momento en el que se está presentando.
En algunas ocasiones las fallas no son evidentes y, por ende, es indispensable analizar la pieza que ha sido tratada; este análisis puede ser clave para entender situaciones tales como: falta de profundidad de capa por potencia eléctrica o disminución en la frecuencia de salida, entre otros posibles escenarios.
Adicional al análisis de la pieza, es vital inspeccionar la “escena del crimen” ya que muchos de los sistemas de inducción, dada la naturaleza del proceso y el peligro que implica manejar altos potenciales eléctricos, suelen ser en extremo automatizados y las estaciones de trabajo de difícil acceso para el personal, así que una buena estrategia de trabajo consiste en observar detenidamente las condiciones generales del equipo para determinar el punto de inicio para la resolución del problema.
2. Identifica los componentes principales de tu sistema de inducción, así como los mecanismos de seguridad para ciertas zonas en particular
Entender la interrelación del sistema es importante para comprender qué elemento realiza cierta acción, así como los canales de comunicación entre ellos. Una vez que se genere este conocimiento, se puede asociar una falla a un componente en particular. Usualmente los sistemas de inducción se componen de los siguientes elementos:
Figura 2. Componentes de un sistema de inducción Source: Contour Hardening, Inc.
Como mencionamos con anterioridad el proceso implica altos potenciales eléctricos, y para eso la naturaleza de las fuentes de alimentación involucra dispositivos electrónicos de potencia, como capacitores eléctricos, los cuales almacenan energía y, por ende, es importante descargar eléctricamente el sistema antes de comenzar a inspeccionar un equipo.
3. Ten preparadas las herramientas necesarias para realizar un buen análisis del problema
Figura. Capacitores Source: Contour Hardening, Inc.
Al igual que cualquier problem técnico, el uso de la herramienta mecánica es indispensable al realizar algún tipo de proyecto, pero para el diagnóstico de una falla en un equipo de inducción es importante contar con:
Osciloscopio
Generador de funciones
Amperímetro
Multímetro digital y analógico.
Sondas de alto voltaje
Sin estos elementos es muy difícil llegar a un diagnóstico fiable, y la posibilidad de encontrar la falla es mínima. Por ende, tener estos medidores en buen estado y, sobre todo, calibrados nos da una perspectiva más clara del problema.
4. Verifica que los sensores del proceso, los monitores de energía y las bobinas de inducción funcionen correctamente
Existen distintos medidores que recogen información acerca del proceso; esta información en su mayoría puede ser visualizada a través del HMI (Human Machine Interface), y, en muchas ocasiones, una buena manera de comenzar a entender el problema es recopilar la información del proceso. Si los medidores no funcionan correctamente, te pueden llevar a conclusiones erróneas.
Verifica que los medidores de energía estén funcionando correctamente, así como tus señales de entrada y de salida.
Las bobinas de inducción son un elemento clave en el proceso de inducción ya que acorde a su geometría generan los campos magnéticos adecuados para lograr los resultados metalúrgicos esperados. Si existen fugas de agua o los elementos de transmisión eléctrica se encuentran sueltos o sucios, seguramente podrán ser la raíz del problema. Es importante comenzar a realizar el diagnóstico de la falla una vez se haya descartado este circuito en particular.
Figura 4. Ejemplo de parámetros de energía Source: Contour Hardening, Inc.
5. Realiza estudios de energía constante en tu subestación para identificar posibles problemas en tu suministro de energía, así como tiempos críticos
La energía eléctrica es la fuente principal en un proceso de inducción; las fuentes de alimentación transforman y potencializan este recurso para crear campos electrónicos lo suficientemente fuertes para generar el calor en la pieza.
Por ende, es importante descartar con evidencia que el problema en cual nos encontramos no se debe a una falla del sistema eléctrico del cual nuestro sistema de inducción forma parte. De igual manera entender cómo se comporta nuestro sistema eléctrico nos puede ayudar a generar patrones de comportamiento que puedan determinar la solución en momentos específicos en los que se lleguen a presentar.
6. Trabaja de forma metódica documentando tus movimientos y realiza un paso a la vez
Los sistemas de inducción pueden ser muy intimidantes si no has tenido experiencia previa, y, al igual que con cualquier elemento o situación, es importante abordar de manera lógica el problema analizando el modo de la falla, identificando las partes principales que interactúan en ese preciso momento, y, a partir de este análisis, documentar y realizar pequeños pasos, uno a la vez, ya que, de no ser así, es muy probable que pierdas todo el trabajo realizado y la situación empeore.
Figura 5. Antes y durante un arco eléctrico dentro de la línea de transmisión Source: Contour Hardening, Inc.
Si los movimientos no son exitosos, siempre puedes regresar a tu punto de partida e intentar otro acercamiento. La idea consiste en que el modo de la falla se mantenga estable sin importar los movimientos realizados hasta que se resuelva el problema. De esta manera lograrás contener la falla; de otra manera podrías estar dañando otros elementos sin darte cuenta.
Es muy importante entender que los procesos son secuencias que anteceden y preceden a nuevos eventos; si entiendes el proceso y, una vez resuelto el problema, ahora tienes una nueva falla, es importante analizar si esta falla es la continuación del proceso ya que, de ser así, es posible que te encuentres frente al caso de un evento que está desencadenado una serie de fallas y se haga necesario practicar un análisis más profundo. La idea general es llegar a la raíz del problema y mitigar el riesgo.
7. Intenta cualquier posibilidad relacionada con el proceso sin importar que la relación entre ésta y el problema no sea directa
Un pensamiento lógico puede resolver la mayoría de las fallas técnicas de un sistema, pero, para fallas excepcionales, es necesario utilizar la imaginación y agotar todos los recursos posibles ya que el área de interés más insignificante o el lugar menos pensado puede ser la clave para resolver un problema.
8. Conoce tus fuentes de alimentación
Uno de los factores claves en cualquier equipo de inducción son sus fuentes de alimentación. Las fuentes de alimentación son equipos que no requieren un mantenimiento tan arduo en comparación con otros sistemas en la industria, pero, de no presentarse las condiciones mínimas de mantenimiento, pueden generar altas pérdidas para la organización.
Figura 6. Diagrama de flujo del proceso eléctrico en una fuente de alimentación Source: Contour Hardening, Inc.
En los casos en los que el problema se encuentra en las fuentes de alimentación, es vital que se siga el mismo proceso metódico previamente descrito. Entender cómo funciona el proceso de transformación de la energía te dará una ventaja, al igual que conocer los componentes empleados o el tipo de tecnología utilizado en el proceso de rectificación, en la inversión (estado sólido o tubos de electrones) y en el circuito resonante. Generalmente las fuentes de alimentación siguen el siguiente patrón de transformación (Figura 6).
9. Identifica las partes críticas de tu equipo de inducción y prepara un inventario de éstas
Figura 7. Daño en una bobina de inducción Contour Hardening, Inc.
Usualmente los componentes que forman parte de las fuentes de alimentación son difíciles de conseguir dependiendo de la antigüedad de tu equipo, y con la reciente crisis de microchips en el mercado, existen tiempos de entrega muy largos para los elementos de control y automatización; de igual manera, los precios de los mismos se han disparado. Por ende, es vital que exista una lista de partes críticas y un inventario de éstas.
Adicionalmente a los elementos descritos, las bobinas de inducción suelen ser elementos muy característicos e importantes en el proceso de inducción. Éstas bobinas son elementos complejos que han sido diseñados exclusivamente para la pieza, por lo que su fabricación puede tomar varias semanas, y es importante tomar las precauciones necesarias para mantener un movimiento de mantenimiento constante.
10. Realiza mediciones preventivas al sistema para generar un patrón de comportamiento
Figura 8. Ejemplo de posibles mediciones Contour Hardening, Inc.
Cuando el sistema se encuentre trabajando en óptimas condiciones, genera un plan de medición el cual te permita recopilar información de puntos específi cos dentro del sistema. Una vez que se vuelva a presentar una nueva falla puedes comparar las mediciones de falla contra las del buen funcionamiento. Algunos ejemplos de mediciones pueden ser:
Temperatura
Voltaje
Corriente eléctrica
Resistencia y capacitancia
Formas de onda
En resumen
Una metodología de trabajo ordenada y documentada, un buen catálogo de piezas de recambio, junto con las herramientas de trabajo necesarias, pueden ser elementos clave para entender un problema y, lo que es más importante, resolverlo de forma eficaz.
Es vital que los profesionales se capaciten de manera constante para mejorar los tiempos de paro debido a fallas en los sistemas de inducción. La capacitación relacionada con procesos metalúrgicos sería una buena forma de complementar tus habilidades de resolución de problemas permitiéndote interpretar las características de los sistemas de inducción, al igual que de los elementos que los componen.
Bibliografía
Valery Rudnev and George Totten, ed., ASM Handbook Volume 4C: Induction Heating and Heat Treatment, (Materials Park, OH: ASM International Heat Treating Society, 2014), 581- 583
Sobre el autor: Alberto C. Ramirez es ingeniero en Mecatrónica egresado del Instituto Tecnológico Nacional de México Campus León con una maestría en Administración de Tecnologías de la Información por el Instituto Tecnológico de Monterrey. Cuenta con más de 8 años de experiencia en fuentes de alimentación, gestión de proyectos, mantenimiento y automatización. Actualmente se desempeña como ingeniero de fuentes de alimentación y automatización en Contour Indianapolis. Alberto inició su carrera en la fi lial de Contour en México y debido a su dedicación forma parte del staff en los Estados Unidos.
He is also an honoree from Heat TreatToday's 40 Under 40 Class of 2021.
Nikola Tesla said, “If you want to find the secrets of the universe, think in terms of energy, frequency, and vibration.” These three components are evident in getting to know the inner workings of an induction system. When it comes to troubleshooting such a system at in-house heat treat departments, this 10 step guide will help heat treat operators understand the secrets of induction and solve common problems that may arise.
This original content article was first written by Alberto Ramirez, engineer of Power Supply and Automation at Contour Hardening, Inc. and an honoree from Heat Treat Today’s 40 Under 40 Class of 2021, for Heat Treat Today's May 2023 Sustainable Heat Treat Technologiesprint edition.
Alberto Ramirez Power Supply and Automation Engineer Contour Hardening, Inc.
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Metals can be heated by the process of electromagnetic induction, whereby an alternative magnetic field near the surface of a metallic (or electrically conductive) workpiece induces eddy current (and thus heat) within the workpiece. Induction systems can be complex systems that aim to heat treat specific parts or sections of a mechanical component; depending on the degree of complexity of the part to be treated, it will be the challenge of a professional to detect any problem.
1. Familiarize Yourself with the Process
Figure 1. Induction hardening process Source: Contour Hardening, Inc.
The induction process involves many characteristics such as: position of the piece within the induction coil, load positions, cooling positions, cycle times, applied electric power, and others. It is important that the professional can identify the failure and the particular situation at the moment in which it is occurring.
On some occasions, the failures are not evident and therefore it is essential to analyze the part that has been treated. This analysis can be key to understanding situations such as poor depth due to electrical power or decrease in output frequency, among other possible scenarios.
In addition to the analysis of the piece, it is vital to inspect the “crime scene,” since many of the induction systems — given the nature of the process and the danger involved in handling high electrical potentials — are usually highly automated and the work stations are difficult for staff to access. A good work strategy consists of carefully observing the general conditions of the equipment to determine where the problem will begin to be solved.
2. Identify Main Components and Certain Security Mechanisms of Your Induction System
Understanding the interrelationship of the system is important to comprehend which element performs a certain action, as well as the communication channels between them. Once this knowledge is generated, a failure can be associated with a particular component. Induction systems are usually made up of the elements in Figure 2.
Figure 2. Induction system components Source: Contour Hardening, Inc.
As we mentioned before, the process involves high electrical potentials, and for this reason, the nature of the power supplies involves power electronic devices such as electrical capacitors, which store energy. Therefore, it is important to electrically discharge the system before beginning to inspect a piece of equipment.
3. Have the Necessary Tools Ready To Carry Out a Good Analysis of the Problem
Figure 3. Capacitors Source: Contour Hardening, Inc.
Like any technical problem, the use of a mechanical tool is essential when carrying out some type of project, but for the diagnosis of failure in induction equipment it is important to have:
Oscilloscope
Function generator
Ammeter
Digital and analog multimeter
High voltage probes
Without these elements it is exceedingly difficult to reach a reliable diagnosis, and the possibility of finding the fault is minimal. Therefore, having these meters in good condition and above all, calibrated, gives a clearer perspective of the problem.
4. Verify that the Process Sensors, Power Monitors, and Induction Coils Are Working Properly
There are different meters that collect information about the process. This information can mostly be viewed through the HMI (human machine interface). On many occasions, a good way to begin to understand the problem is by collecting the information on the process. If these meters do not work correctly, they can lead you to wrong conclusions.
Verify the energy meters are working correctly, as well as your input and output signals.
Induction coils are a key element in the induction process since, according to their geometry, they generate the appropriate magnetic fields to achieve the expected metallurgical results. If there are water leaks or the electrical transmission elements are loose or dirty, it could be the root cause of the problem. It is important to start troubleshooting once this circuit is ruled out.
Figure 4. Energy parameters example Source: Contour Hardening, Inc.
5. Carry Out Studies of Constant Energy in Your Substation To Identify Possible Problems in Your Energy Supply, Including Critical Times
Electrical energy is the main source in an induction process, power supplies transform and potentiate this resource to create electronic fields strong enough to generate heat in the piece.
Therefore, it is important to find evidence that rules out failures of the electrical system that the induction system is a part of. In the same way, understanding how our electrical system behaves can help us generate behavior patterns that can determine the solution at specific times when it may arise.
6. Document Your Work Methodically and Take One Step at a Time
Induction systems can be very intimidating if you have not had previous experience, and, like any element or situation, it is important to logically approach the problem by analyzing the failure mode, identifying the main parts that interact at that specific moment. From there, document and take small steps, one at a time. If you don’t, it is very likely you will lose all the work you have done, and the situation will get worse.
Figure 5. Before and after of an arc at the transmission line Source: Contour Hardening, Inc.
If the moves are unsuccessful, you can always return to your starting point and try another approach. The idea is that the failure mode remains the same no matter what moves you make until the problem is resolved. In this way you will have the failure contained, otherwise you could be damaging other elements without realizing it.
It is very important to understand that the processes are sequences that precede and proceed new events. If you understand the process and solve a problem, but now have a new failure, it is important to analyze if this failure is the continuation of the process. If so, it is possible that you find yourself in a case where an event is triggering a series of failures. Therefore, a more in-depth analysis must be carried out. The idea to generate is to get to the root cause and mitigate the risk.
7. Try Any Possibility Related to the Process Regardless of Whether the Relationship Between It and the Problem Is Not Direct
Logical thinking can solve most of the technical failures of a system. For exceptional failures, however, it is necessary to use your imagination and exhaust all possible resources, since the smallest area of interest or the least thoughtful place can be the key to solving a problem.
8. Get To Know Your Power Supplies
One of the key factors in any induction equipment is its power supplies. Power supplies are equipment that do not require such arduous maintenance compared to other systems in the industry, but if the minimum maintenance conditions are not present, they can generate high losses for the organization.
Figure 6. Flow diagram of the energy process at the power supply Source: Contour Hardening, Inc.
In cases where the problem is the power supplies, it is vital that the same methodical process previously described is followed. Understanding how the energy transformation process works will give you an advantage, as will knowing the elements that compose them or the type of technology used in the rectification process, in the inversion (solid state or electron tubes) and in the resonant circuit. Generally, power supplies follow the transformation in Figure 6.
9. Identify the Critical Parts of Your Induction Equipment and Prepare an Inventory
Figure 7. Coil damage Contour Hardening, Inc.
Usually, the elements that belong to the power supplies are difficult to obtain depending on the age of your equipment. With the recent microchip crisis in the market, control and automation elements have very long delivery times or the prices are very high. Therefore, it is vital that there is a list of critical parts and an inventory of these.
In addition to the elements described, induction coils are usually very characteristic and important elements in the induction process. These coils are complex elements that have been designed exclusively for the piece, so their manufacture can take several weeks, and the necessary precautions must be taken to maintain a constant maintenance movement.
10. Perform Preventative Measurements to the System To Generate a Pattern of Behavior
Figure 8. Possible examples of measurements Contour Hardening, Inc.
When the system is working in optimal conditions, generate a measurement plan which allows you to generate information on specific points within the system. Once a new failure occurs again you can compare the measurements of failure against those of good performance. Some examples of measurements can be:
Temperature
Voltage
Current
Resistance and capacitance
Waveforms
Summary
An orderly and documented work methodology, a good spare parts catalog, and the necessary work tools can be key elements to understand a problem and, more importantly, to solve it effectively.
It is vital that professionals are in continuous training in order to decrease downtime due to failures in induction systems. Training related to metallurgical processes would be a good way to complement your resolution skills by being able to interpret the characteristics of induction systems with the elements that compose it.
References
Valery Rudnev and George Totten, ed., ASM Handbook Volume 4C: Induction Heating and Heat Treatment, (Materials Park, OH: ASM International Heat Treating Society, 2014), 581- 583.
About the Author: Alberto C. Ramirez graduated from the National Technical Institute of Mexico as a mechatronics engineer. He earned his master’s degree in information technology administration from Monterrey Institute of Technology. With more than eight years of experience in power supplies, project management, maintenance, and automation, he currently works as a Power Supply and Automation Engineer at Contour Indianapolis. Alberto began his career at the Contour subsidiary in Mexico and due to his dedication, he is part of the staff in the United States. He is also an honoree from Heat TreatToday's 40 Under 40 Class of 2021.
Induction heat treating: no harsh chemicals, gases, or even CO2 emissions. But to get there, heat treaters should first understand how to plan for an induction design and fabrication project upfront. Consider these five important factors before you dive into induction.
This Technical Tuesday article was composed by John Chesna, general manager at Induction Tooling, Inc. and honoree in Heat Treat Today's 40 Under 40Class of 2022. It appears in Heat Treat Today's May 2023 Sustainable Heat Treat Technologiesprint edition.
Introduction
John Chesna General Manager at Induction Tooling Source: Induction Tooling, Inc.
There are many less than obvious factors to consider when preparing and planning for induction. So where to start? There are five important factors that manufacturers with in-house heat treat operations should understand in order to successfully prepare an induction heating project and design.
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But first, what is induction heating? Induction heat treating is the process in which a high frequency conductor (induction tool) induces currents (eddy currents) into an electrically conductive workpiece. Without ever touching the work-piece, the current generated and the resistance causes heating. Ever since its proven usefulness around the time of World War II, induction has been chosen as the go-to heat treatment for a variety of applications across many industries including agricultural, medical, and transportation. Now, it seems that most industries have taken advantage of induction heat treating, and its popularity will likely only continue to increase with the push for the use of “clean” and “green” energy.
#1 Plan for Inductor Wear
One of the most important factors to an induction project is realizing the inductor/ coil is a wear item. It can be highly engineered, hand fabricated, machined, or even 3D printed. Yet, in the overall process, it is still a wear item: an item that will eventually require replacement or repair. The inductor is exposed to the worst of the elements during the induction process and can fail from standard use, accidents, or unforeseen circumstances. Inductor designers are constantly being challenged to create tools that will last longer, require less maintenance, or run more cycles. All of those can be achieved, but the inductor will eventually require replacing and that is not a bad thing!
A properly serviced and maintained inductor will ensure quality parts are being produced. As the inductor wears, the efficacy degrades, leading to undesirable results. Repair of the inductor will correct this issue and ensure the parameters required for the desired heat treat pattern are restored. Depending on production needs, a good principle is to have more than one inductor on hand so that while one is being repaired the spare inductor can remain on the machine to keep up with manufacturing demand. Planning for this is important for the project’s timing and budget.
#2 Types of Inductor Designs
Determining a specific inductor design will be necessary to properly heat parts. The inductor creates the magnetic field in the workpiece, and typically the inductor is shaped to couple closely where heat treatment of the part is desired. Additionally, if quenching is required for the heating application, this function will be considered in the inductor’s design. The inductor’s design must deliver the electrical energy and quench medium to the workpiece while allowing accessibility for material handling purposes. For this reason, inductors take on many different designs.
Six turn multi-turn inductor Photo Source: Induction Tooling, Inc.
Pancake inductor with strap supports Photo Source: Induction Tooling, Inc.
MIQ (Machined Integral Quench) scanning inductor with removable quench plate Photo Source: Induction Tooling, Inc.
Common inductor designs include:
Pancake: used for heating flat surfaces
Single turn or multi-turn: commonly shown as copper tubing wrapped around cylindrically around the workpiece
Hairpin: typically, a simple back and forth loop used to heat long lengths internally or externally on the workpiece
Split return: used to focus the energy in particular areas of the workpiece
MIQ (machined integral quench) paddle: the most commonly used design for scanning applications
#3 Power and Frequency
Know the power supply and/or work-head power and frequency. Depending on the composition of the part that requires processing, the power and frequency of the equipment will help estimate the depth of the pattern that can be achieved, as well as help determine how successful the part will be for induction heating. Irregularly shaped geometries with points, holes, or sharp edges sometimes cause difficulty establishing eddy currents where the induction pattern is desired. Some parts, after review, are good candidates for induction heat treatment but cannot be processed with the existing power supply and/or work-head setup.
If an inductor is being built to mount to existing induction equipment, it is important to know the scope of parts that are currently being processed or expected to be processed on the machine. The electrical circuit of the power supply, work-head, and inductor must load match to the part. If a variety of parts are being run then multiple styles of inductors may exist or will be required to be used. Different designs of inductors, e.g., single-turn, multi-turn, or split return used on the machine will change the transformer effect and capacitor requirements of the system. Availability to tune the system capacitance and inductance becomes vitally important for operation. Please note that adjusting capacitance can be dangerous and should only be done by a trained technician. Newer power supplies function differently than older models, yet load tuning needs to be considered.
#4 Part Details
A detailed pre-induction print is needed. The print should list the material as well as the desired heat treatment pattern to determine the inductor design. As the print specifies the pattern, it should also provide limits. Inductors are then typically designed to the shape of the part. The inductor may require an integrated quench, electrically insulating protective coating, locators, or additional assembly fixturing depending on the part’s size. An inductor built for one part may be used or tried on a similar part. However, the same results cannot be expected to render on the part for which it was not designed. If the manufacturer knows that a family of parts will be run, the full scope should be presented to inductor designers for consideration before the build.
#5 Material Handler
Ideally an inductor supplier would be contacted to develop the induction heating process for a part; then, that information should be shared with the material handling designer. That would be the ideal, but that’s not the way it usually happens. Sometimes, a machine is built to process a part that no longer is in use, so the machine is now being retrofitted to process different parts. The design of a new inductor is needed to accommodate this existing machine which may create size constraints to the inductor’s design.
The contact style, how the inductor mounts to the work-head, will need to be determined. There are a variety of commonly used power supplies and work-heads available from OEMs in the market. As each OEM keeps their contacts standard to their equipment, there is no singular standard footprint in the market. Once the contact style has been determined, the inductor can be designed for maximum power delivery efficiency. How the part and inductor are presented to each other is important. The centerline distance, a measurement from where the inductor mounts to where the part will be processed, needs to be known. The centerline determines the required length of the inductor and indirectly how much room is available for the inductor’s design.
Conclusion
Due to the variety of factors, no two projects are ever the same. Induction heating is an exciting technology, and I encourage everyone to learn more about it.
About the Author: John Chesna is the general manager of Induction Tooling, Inc. and has been involved with the induction heat treating industry for over 8 years. He is a graduate of the University of Akron with a Bachelor of Science in Mechanical Engineering Technology. His responsibilities include overseeing day-to-day operations including the design, manufacturing, and testing of induction heat treating inductors. Additionally, John was a recipient of Heat Treat Today's 40 Under 40 award in 2022.
