MANUFACTURING HEAT TREAT TECH

Ask the Heat Treat Doctor®: Guidelines for a Successful Heat Treatment Outcome — Part Two

/ HARDENING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Ask The Heat Treat Doctor® has returned to bring sage advice to Heat Treat Today readers and to answer your questions about heat treating, brazing, sintering, and other types of thermal treatments as well as questions on metallurgy, equipment, and process-related issues. In this installment, Dan Herring explores how to set realistic expectations for heat treatment outcomes, continuing his guidelines for design engineers and their clients. He explains how Jominy curves and H-band steels help predict and narrow hardness variation, why the lowest-hardenability steel that meets requirements best limits distortion, and how chemistry, including manganese sulfide in resulfurized steels and boron additions, affects hardenability and case consistency.

This informative piece was first released in Heat Treat Today’s October 2026 Ferrous & Nonferrous Heat Treatments/Mill Processing print edition.

If you have any comments or queries, on this article, let us know at editor@heattreattoday.com.

Para leer el artículo en español, haga clic aquí.

We continue our series of heat treatment articles offering guidelines focused on getting the job done right, the first time, and every time in the real world. Let’s learn more.

How We Achieve Our Goals (Continued)

As discussed in Part One (People of Heat Treat, September 2026), experienced heat treaters often point to the most common mistakes made by design engineers and/or their clients, that is, selecting materials, defining and understanding the limitations of the requested heat treatment processes, and specifying realistic outcomes from heat treating. These include the desired hardness, case depth, and dimensional tolerances. These issues generally result from a failure to recognize the differences in the material’s chemical composition and form (e.g., wrought or powder metallurgy, castings, forgings). The design engineer should also understand the mill processing methods used to produce the material. Often, the tolerances for the specified heat treatment properties are either too aggressive, ambiguous, or too restrictive from a real-world standpoint. Here are additional basic metallurgical guidelines that can, from a practical standpoint, help avoid these problems (Herring 2014, 2015; SAE International 1989).

Hardenability

Figure 1. Jominy equivalent cooling rate by bar size and quench severity (Dosset 2007, TimkenSteel 2014)

We often need to determine the expected core hardness range, and this can be accomplished by using the Jominy equivalent cooling rate (JEC) chart (Figure 1) and the hardenability band for the steel being used (Figure 2). These curves for 4140H show that using a strong oil quench results in a surface hardness for a 50.8 mm (2 inch) round would be at J4 and the core would at J8.5. The hardenability curves show that the corresponding surface hardness would be 51-59 HRC with a core hardness of 46-57 HRC. The actual hardness for a given heat of steel depends strictly on the specific hardenability (in Jominy or ideal diameter, DI values) for the specific heat from which the component parts were manufactured.

Figure 2. Jominy hardenability data for SAE/AISI 8620 steel (Dosset 2007, SAE International, 1989)

To reduce the variation in hardening response and thus narrow the surface and core hardness values that result after heat treatment, the hardenability of the steel chosen can be narrowed by using an “H-band” steel or using a restricted hardenability “RH-band” steel. For example, there is an effect on hardenability of an 8620 versus 8620H steel (Figure 3). The effect of changing to 8620H for carburized parts having a cross-section less than 25.4 mm (1 inch) is a reduction of up to 30% in the variation in core hardness after heat treatment along with greater dimensional stability.

Figure 3. Comparison of Jominy hardenability curves for SAE/AISI 8620H and 8620 steels. Chemical composition at maximum and minimum of the compositional range (Dossett, Jon L., “Make Sure Your Specified Heat Treatment is Achievable”, Heat Treating Progress, March/April 2007.)

Generally, the most economical steel that will achieve the desired properties when heat treated should be selected (e.g., surface and/or core hardness, tensile and/or yield strength). It is important to remember that a steel with the lowest hardenability that will still transform to the desired results should be selected to manage part distortion. First, check the maximum attainable hardness chart (Table 1 in Part One) using the carbon range that will give the required surface hardness, from the 95% or 99.9% martensite column, to select the proper steel. Following these guidelines will also result in greater dimensional stability and uniformity after heat treatment.

Influence of Chemistry on Hardenability

Resulfurized Steel-Hardenability Problems

An often-overlooked factor is the type of steel being specified. For example, specifying resulfurized steels for case hardening processes is highly dependent on the interrelationship and reaction of sulfur and manganese, and the design engineer must be aware that this can have a significant effect on both case and core hardenability and microstructure (Herring 2014, 2015; Dosset 2007).

All steels contain a certain percentage of sulfur, but certain high sulfur grades of steels have much larger amounts. Sulfur preferentially combines with some of the manganese to sulfide (MnS) often in the form of stringers. These manganese sulfides serve as a chip breaker and lubricity agent that cause these steel grades to be more machinable than other standard lower sulfur grades. However, the formation of MnS present in the form of inclusions has several negative effects including:

Table A. Manganese Available for Hardenability for Several Common Case Hardening and Induction Hardened Steels
  • Reduction of the fatigue limit compared with low sulfur steels and the tendency of “banding” in the steel in the as-rolled condition.
  • Diminished hardness as a function of the amount of sulfur present since manganese sulfide lowers the hardenability of the steel. The interaction of manganese and sulfur in forming manganese sulfide is determined by the ratio of atomic weights of Mn (56) and S (32) in the ratio 56/32, that is, 0.0175 wt.% of the manganese combines with each 0.01 wt.% of sulfur present (Table A).

Manganese (and other alloying elements) and grain size influence case and core hardenability. For the steels shown, manganese is the principle alloying element.

In addition, during carburizing or carbonitriding, control of the furnace parameters (time, temperature, and carbon potential) establishes the surface carbon content and carbon profile for a given steel chemistry. However, the effective case depth (to 50 HRC) depends on case hardenability and core hardness, which are dependent on hardenability. Thus, for the same total case carbon profile, the higher the case hardenability, the higher the effective case. For this reason, effective case depth variations for resulfurized materials are significantly greater than those for nonresulfurized steels.

The final negative effect of case hardening resulfurized steels is the large variation in case microstructure (principally with regard to retained austenite) for the same heat treatment. The problem can be attributed to the variation in manganese levels due to varying amounts of sulfur present.

Boron Steels

Boron steels improve hardenability by adding a minute quantity of boron. It is generally accepted that a hardenability peak is reached when the amount of boron ranges between 3 and 15 parts per million (ppm). If an excessive amount of boron (>30 ppm) is present, the boron constituents become segregated in the austenite grain boundaries, which not only lowers hardenability but may also decrease toughness, cause embrittlement, and produce hot shortness. The effect of boron on hardenability also depends on the amount of carbon in the steel being inversely proportion to the percentage of carbon present (Herring 2007).

Boron must be in its atomic state to improve hardenability, which means that care must be taken during steel production for the boron to be effective. Boron may also become ineffective if its state is changed by incorrect heat treatment. For example, high austenitizing temperatures must be avoided, as well as temperature ranges where certain boron precipitates occur.

Hardenability is highly dependent on the behavior of oxygen, carbon, and nitrogen present in the steel. Boron reacts with oxygen to form boron oxide (B₂O₃); with carbon to form iron borocementite (Fe₃(CB)) and iron borocarbide (Fe₂₃(C,B)₆); and with nitrogen to form boron nitride (BN). Loss of boron due to combination with oxygen is prevented by making the boron addition to silicon- or aluminum-killed steels and by using good ladle and mold practices.

Strong nitride formers (titanium, aluminum, zirconium) protect the boron from reaction with nitrogen. For example, if nitrogen is fixed by using titanium, satisfactory hardenability is obtained in the temperature range up to 1830°F (1000°C) provided that the steel contains about 5-20 ppm of boron. When specifying boron steels, many companies report that a minimum 3:1 and even 4:1 ratio is desirable to avoid the problem of “ineffective” boron. The hardenability of boron steel is also closely related to austenitizing conditions and is generally said to decrease by heating above 1830°F (1000°C). Boron steel must also be tempered at a lower temperature than other alloy element steels of the same hardenability.

Next month, we will discuss total and effective case depth and set reasonable expectations for hardness values and achievable part tolerances.

References

Dossett, Jon. 2007. “Make Sure Your Specified Heat Treatment Is Achievable.” Heat Treating Progress (March/April).

Dossett, Jon. 2025. Private conversation.

Herring, Daniel H. 2007. “Boron in Steel.” Industrial Heating, May 2007.

Herring, Daniel H. 2014. Atmosphere Heat Treatment. Vol. 1. Troy, MI: BNP Media Group II.

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

SAE International. 1989. SAE Handbook. Vol. 1, Materials, 1.72.

TimkenSteel Corporation. 2014. Practical Data for Metallurgists. 17th ed., 64.

About the Author

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP, Inc.

Dan Herring has been in the industry for over 50 years and has gained vast experience in fields that include materials science, engineering, metallurgy, new product research, and many other areas. He is the author of six books and over 700 technical articles.

For more information: Contact Dan at dherring@heat-treat-doctor.com.

For more information about Dan’s books: see his page at the Heat Treat Store.

Ask the Heat Treat Doctor®: Guidelines for a Successful Heat Treatment Outcome — Part Two Read More »

Ask the Heat Treat Doctor®: Lineamientos para Obtener Exitosos Resultados de Tratamiento Térmico — Parte Dos

/ HARDENING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Ask The Heat Treat Doctor® ha regresado para ofrecer consejos sabios a los lectores de Heat Treat Today y responder sus preguntas sobre tratamiento térmico, soldadura fuerte (brazing), sinterizado y otros tipos de tratamientos térmicos, así como preguntas sobre metalurgia, equipos y problemas relacionados con los procesos. En esta entrega, Dan Herring explora cómo establecer expectativas realistas para los resultados del tratamiento térmico, como continuación de sus lineamientos para ingenieros de diseño y sus clientes. Explica cómo las curvas de templabilidad Jominy y los aceros de “banda H” ayudan a predecir y acotar la variación de dureza, por qué el acero con la menor templabilidad que cumpla los requisitos es la mejor opción para limitar la distorsión, y cómo la composición química, incluidos el sulfuro de manganeso en los aceros resulfurados y las adiciones de boro, afecta la templabilidad y la consistencia de la capa.

Este artículo informativo se publicó por primera vez en Heat Treat Today’s October 2026 Ferrous & Nonferrous Heat Treatments/Mill Processing print edition.

Si tiene comentarios o preguntas sobre este artículo, háganoslo saber en: editor@heattreattoday.com.

To read this article in English, click here.

Seguimos con nuestra serie de artículos sobre tratamiento térmico, ofreciendo lineamientos enfocados en “Hacer las cosas bien, la primera vez y cada vez” en el mundo real. Aprendamos más.

Cómo Alcanzamos Nuestros Objetivos (Continuación)

Como se comentó en la Parte Uno (People of Heat Treat, septiembre de 2026), los especialistas en tratamiento térmico con experiencia suelen señalar los errores más comunes cometidos por los ingenieros de diseño y/o sus clientes, es decir, la selección de materiales, la definición y comprensión de las limitaciones de los procesos de tratamiento térmico solicitados, y la especificación de resultados realistas a partir del tratamiento térmico. Estos incluyen la dureza deseada, la profundidad de capa y las tolerancias dimensionales. Estos problemas generalmente resultan de no reconocer las diferencias en la composición química del material y su forma (por ejemplo, mecanizado o pulvimetalurgia, fundiciones, forjas). El ingeniero de diseño también debe comprender los métodos de procesamiento en planta utilizados para producir el material. A menudo, las tolerancias de las propiedades de tratamiento térmico especificadas son demasiado agresivas, ambiguas o restrictivas desde un punto de vista práctico. A continuación, se presentan lineamientos metalúrgicos básicos adicionales que, desde un punto de vista práctico, pueden ayudar a evitar estos problemas (Herring 2014, 2015; SAE International, 1989).

Templabilidad

Figura 1. Velocidad de enfriamiento equivalente Jominy según el tamaño de barra y la severidad de temple (Dossett 2007, TimkenSteel 2014)

A menudo necesitamos determinar el rango de dureza del núcleo esperado, lo cual puede lograrse mediante el uso de la gráfica de velocidad de enfriamiento equivalente Jominy (JEC, por sus siglas en inglés) (Figura 1) y la banda de templabilidad del acero utilizado (Figura 2). Estas curvas para el acero 4140H muestran que, al utilizar un temple en aceite con alta severidad de enfriamiento, la dureza superficial para una barra redonda de 50.8 mm (2 pulgadas) estaría en J4 y el núcleo en J8.5. Las curvas de templabilidad muestran que la dureza superficial correspondiente sería de 51-59 HRC, con una dureza del núcleo de 46-57 HRC. La dureza real de una colada determinada de acero depende estrictamente de la templabilidad específica (en valores Jominy o de diámetro ideal, DI) de la colada específica a partir de la cual se fabricaron las piezas.

Figura 2. Datos de templabilidad Jominy para acero SAE/AISI 8620 (Dossett 2007, SAE International, 1989)

Para reducir la variación en la respuesta al temple y así estrechar los valores de dureza superficial y del núcleo que resultan después del tratamiento térmico, la templabilidad del acero elegido puede acotarse utilizando un acero de “banda H” o un acero de templabilidad restringida de “banda RH”. Por ejemplo, existe un efecto sobre la templabilidad de un acero 8620 frente a uno 8620H (Figura 3). El efecto de cambiar a 8620H en piezas cementadas con una sección transversal menor a 25.4 mm (1 pulgada) es una reducción de hasta el 30% en la variación de la dureza del núcleo después del tratamiento térmico, junto con una mayor estabilidad dimensional.

Figura 3. Comparación de las curvas de templabilidad Jominy para los aceros SAE/AISI 8620H y 8620. Rango de composición química en el máximo y el mínimo (Dossett, Jon L., “Make Sure Your Specified Heat Treatment is Achievable”, Heat Treating Progress, marzo/abril de 2007).

Generalmente se busca seleccionar el acero más económico que, al ser tratado térmicamente, logre las propiedades deseadas (por ejemplo, dureza superficial y/o del núcleo, resistencia a la tracción y/o al límite elástico, etc.). Es importante recordar que, para controlar la distorsión de la pieza, a menudo conviene seleccionar un acero con la menor templabilidad que aún se transforme para lograr los resultados deseados. Primero se debe revisar la gráfica de dureza máxima alcanzable (cf. Tabla 1 en la Parte Uno) utilizando el rango de carbono que proporcione la dureza superficial requerida, a partir de la columna del 95% o del 99.9% de martensita, para seleccionar el acero correcto. Seguir estos lineamientos también dará como resultado una mayor estabilidad dimensional y uniformidad después del tratamiento térmico.

Influencia de la Composición Química en la Templabilidad

Problemas de Templabilidad en Aceros Resulfurados

Un factor que suele pasarse por alto es el tipo de acero especificado. Por ejemplo, la especificación de aceros resulfurados para procesos de cementación depende en gran medida de la interrelación y la reacción entre el azufre y el manganeso, y el ingeniero de diseño debe tener en cuenta que esto puede tener un efecto significativo tanto en la templabilidad de la capa y el núcleo como en la microestructura (Herring 2014, 2015; Dossett 2007).

Todos los aceros contienen un cierto porcentaje de azufre, pero ciertos grados de acero con alto contenido de azufre tienen cantidades mucho mayores. El azufre se combina preferentemente con parte del manganeso para formar sulfuros (MnS), a menudo en forma de filamentos (stringers). Estos sulfuros de manganeso actúan como rompevirutas y agentes lubricantes, lo que hace que estos grados de acero sean más maquinables que otros grados estándar con menor contenido de azufre. Sin embargo, la formación de MnS en forma de inclusiones tiene varios efectos negativos, entre ellos:

Tabla A. Manganeso Disponible para la Templabilidad en Varios Aceros Comunes de Cementación y Endurecimiento por Inducción
  • Reducción del límite de fatiga en comparación con los aceros de bajo contenido de azufre, y la tendencia al “bandeado” en el acero en condición de laminado.
  • Disminución de la dureza en función de la cantidad de azufre presente, ya que el sulfuro de manganeso reduce la templabilidad del acero. La interacción entre el manganeso y el azufre en la formación de sulfuro de manganeso está determinada por la relación de los pesos atómicos del Mn (56) y el S (32), es decir, en una proporción de 56/32; esto es, un 0.0175% en peso de manganeso se combina con cada 0.01% en peso de azufre presente (Tabla A).

El manganeso (junto con otros elementos de aleación) y el tamaño de grano influyen en la templabilidad de la capa y el núcleo. Para los aceros mostrados, el manganeso es el principal elemento de aleación.

Además, durante la cementación o la carbonitruración, el control de los parámetros del horno (tiempo, temperatura y potencial de carbono) establece el contenido de carbono superficial y el perfil de carbono para una composición de acero determinada. Sin embargo, la profundidad de capa efectiva (hasta 50 HRC) depende de la templabilidad de la capa y de la dureza del núcleo, las cuales dependen a su vez de la templabilidad. Por lo tanto, para el mismo perfil total de carbono de la capa, cuanto mayor sea la templabilidad de la capa, mayor será la capa efectiva. Por esta razón, las variaciones en la profundidad de capa efectiva de los materiales resulfurados son considerablemente mayores que las de los aceros no resulfurados.

El último efecto negativo de la cementación de aceros resulfurados es la gran variación en la microestructura de la capa (principalmente en lo que respecta a la austenita retenida) para un mismo tratamiento térmico. Este problema puede atribuirse a la variación en los niveles de manganeso debido a las diferentes cantidades de azufre presentes.

Aceros al Boro

Los aceros al boro mejoran su templabilidad mediante la adición de una cantidad mínima de boro. Por lo general, se acepta que el pico de templabilidad se alcanza cuando la cantidad de boro se encuentra entre 3 y 15 partes por millón (ppm). Si hay una cantidad excesiva de boro (>30 ppm), los constituyentes de boro se segregan en los límites de grano de la austenita, lo cual no solo reduce la templabilidad, sino que también puede disminuir la tenacidad, provocar fragilización y producir fragilidad en caliente. El efecto del boro sobre la templabilidad también depende de la cantidad de carbono en el acero, siendo inversamente proporcional al porcentaje de carbono presente (Herring 2007).

El boro debe encontrarse en estado atómico para mejorar la templabilidad, lo que significa que debe tenerse cuidado durante la producción del acero para que el boro sea efectivo. El boro también puede volverse ineficaz si su estado se modifica debido a un tratamiento térmico incorrecto. Por ejemplo, deben evitarse las temperaturas de austenización elevadas, así como los rangos de temperatura en los que se producen ciertos precipitados de boro.

La templabilidad depende en gran medida del comportamiento del oxígeno, el carbono y el nitrógeno presentes en el acero. El boro reacciona con el oxígeno para formar óxido de boro (B₂O₃); con el carbono para formar borocementita de hierro (Fe₃(CB)) y borocarburo de hierro (Fe₂₃(C,B)₆); y con el nitrógeno para formar nitruro de boro (BN). La pérdida de boro por combinación con el oxígeno se evita realizando la adición de boro en acero desoxidado con silicio o aluminio, y mediante buenas prácticas de cuchara y molde.

Los fuertes formadores de nitruros (titanio, aluminio, circonio) protegen al boro de la reacción con el nitrógeno. Por ejemplo, si el nitrógeno se fija mediante el uso de titanio, se obtiene una templabilidad satisfactoria en el rango de temperatura de hasta 1830 °F (1000 °C), siempre que el acero contenga entre 5 y 20 ppm de boro. Al especificar aceros al boro, muchas empresas informan que una relación mínima de 3:1, e incluso de 4:1, es deseable para evitar el problema del boro “inefectivo”. La templabilidad del acero al boro también está estrechamente relacionada con las condiciones de austenización, y en general se dice que disminuye al calentar por encima de 1830°F (1000°C). El acero al boro también debe revenirse a una temperatura más baja que otros aceros con elementos de aleación de la misma templabilidad.

El próximo mes, analizaremos la profundidad de capa total y efectiva, y estableceremos expectativas razonables para los valores de dureza y las tolerancias alcanzables en las piezas.

Referencias

Dossett, Jon. 2007. “Make Sure Your Specified Heat Treatment Is Achievable.” Heat Treating Progress (March/April).

Dossett, Jon. 2025. Private conversation.

Herring, Daniel H. 2007. “Boron in Steel.” Industrial Heating, May 2007.

Herring, Daniel H. 2014. Atmosphere Heat Treatment. Vol. 1. Troy, MI: BNP Media Group II.

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

SAE International. 1989. SAE Handbook. Vol. 1, Materials, 1.72.

TimkenSteel Corporation. 2014. Practical Data for Metallurgists. 17th ed., 64.

Acerca del Autor

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP, Inc.

Dan Herring lleva más de 50 años en la industria y ha adquirido una vasta experiencia en áreas que incluyen ciencia de materiales, ingeniería, metalurgia, investigación de nuevos productos y muchas otras. Es autor de seis libros y de más de 700 artículos técnicos.

Para más información: Contacte a Dan en dherring@heat-treat-doctor.com.

Para más información sobre los libros de Dan: consulte su página en el Heat Treat Store.

Ask the Heat Treat Doctor®: Lineamientos para Obtener Exitosos Resultados de Tratamiento Térmico — Parte Dos Read More »

Ask the Heat Treat Doctor®: Guidelines for a Successful Heat Treatment Outcome — Part Three

/ CARBURIZING TECHNICAL CONTENT, HARDNESS TESTERS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Ask The Heat Treat Doctor® has returned to bring sage advice to Heat Treat Today readers and to answer your questions about heat treating, brazing, sintering, and other types of thermal treatments as well as questions on metallurgy, equipment, and process-related issues. In this installment, Dan Herring explores the third part of his series on heat treatment guidelines, covering how to define and specify case depth, hardness values, and testing locations on prints, and how to choose the right hardness test method to get accurate repeatable results.

This informative piece was first released in Heat Treat Today’s November 2026 Annual Vacuum Heat Treating print edition.

If you have any comments or queries, on this article, let us know at editor@heattreattoday.com.

Para leer el artículo en español, haga clic aquí.

We continue our heat treatment series offering guidelines focused on “getting the job done right, the first time and every time” in the real world. Let’s learn more.

How We Achieve Our Goals

Here are a few more basic metallurgical and heat treatment guidelines that can, from a practical standpoint, help to avoid heat treatment issues (Herring 2014a, 2014b, 2014c).

Defining Terminology

Figure 1. Total case-depth determination by the visual method | Image Credit: The HERRING GROUP, Inc.

It is important to understand what we mean when we specify a heat treat requirement. For example, consider atmosphere gas carburizing. The technical definition for a carburized case depth is expressed in terms of carbon content:

  • Total case depth: The depth at which the carbon content of the steel is 0.04% above the core carbon content of the steel. In other words, total case depth is the point at which differences in the chemical or physical properties of the case and core can no longer be distinguished (Figure 1). Many metallurgists determine the total case depth by (Nital) etching a steel sample and measuring the zone affected by the etchant.
  • Effective case depth: The depth at which the carbon content of low-alloy steel is 0.40% and approximately 0.30% for medium alloy and high-alloy steels.

Since it is often time consuming and expensive to measure carbon concentration as a function of depth in a carburized component to determine case depth, other techniques are commonly used, such as microhardness. In certain situations involving very deep case depths, hardness can be measured on a test sample directly on the Rockwell “A” or “C” scales. The following definitions are used:

Figure 2. Example of effective case-depth determination by microhardness testing | Image Credit: The HERRING GROUP, Inc.
  • Effective case depth (U.S.): The distance from the surface (in inches) to a point within the case where the hardness is 50 HRC (542 Knoop or 513 HV). This measurement is done on a cross-section by microhardness techniques with a Knoop or Vickers indenter (Figure 2). These values are then converted to Rockwell C hardness when a 500-gram-force load is used per ASTM E384 (latest revision). Interpolation is required to arrive at the proper case-depth value. The effective case depth depends on the carbon gradient and the case hardenability, but 50 HRC is typically equated to a carbon content of 0.40% in low-alloy steels and 0.30% in medium- and high-alloy steels.
  • Effective case depth (international): The distance from the surface (in millimeters) to a point within the case where the hardness is 550 HV (approximately 52.5 HRC). This measurement is done by a Vickers microhardness method with a predefined load of 1 kilogram and is not converted to Rockwell C. The effective case depth still depends on the carbon gradient and the case hardenability. For highly alloyed case-hardening steels, the carbon content for 550 HV is typically in the range of 0.25- 0.30%. For medium-alloy grades, it is approximately 0.30-0.35% C, and for low-alloy steels, it is approximately 0.35-0.40% C.

Case-Depth Callouts on Prints

Case depth on engineering drawings should be stated as total case depth, effective case depth, or finished effective case depth after a defined amount of material is removed from the surface. It is important to note that if neither total nor effective case depth is specified, it should not be assumed that total case depth is intended (although at one time many years ago this was a commonly held belief).

A “rule of thumb” is often used to approximate the total case depth from the effective case depth. Given the effective case depth, the total case depth can be estimated by multiplying the effective case depth by 3/2. To determine the effective case depth from the total case depth, multiply the total case depth ⅔. The steel grade, chemistry, material hardenability, and case depth influence this rule.

Other important considerations include:

  • Specify the condition of the part at the time of testing (as-quenched, as-tempered, after final grind).
  • Specify the test procedure at each location and for each characteristic.
  • State the maximum and minimum specification tolerance.
  • Show the part print and specification to your test lab and part producer and check their interpretations of the specification against your requirements.

When specifying the required case-hardening heat treatment, it is important to define the process, the desired case depth range, and the hardness testing scale to evaluate the parts.

This is best illustrated in a case study where hardened light-duty bearings made of 1117 steel failed after being heat treated to a specification requiring a hardness of 58 HRC and a case depth of 0.015–0.020 inches. There are several technical concerns with the specification regarding process definition, case depth definition, and the unspecified hardness scale to measure case depth.

Hardness Values

When specifying the hardness range or tolerance for expected surface hardness values or core hardness, it is necessary to recognize the full range of hardenability of the specified steel at the point of interest on, or in, the part. The expected variation in surface hardness after induction or flame hardening can be determined by checking the high and low values of the carbon for the specific grade of steel versus the hardness values shown in the 99.9% martensite column in Table 1 (Part One). For example, SAE 1045 steel, with a carbon range of 0.43–0.50%, can achieve a fully martensitic as-quenched hardness of 57–60 HRC, while SAE 4140 steel, with a carbon range of 0.38–0.43%, can achieve only 55-57 HRC.

For through-hardening heat treatments, curves (c.f., Figure 1, Part Two) can be used with the Jominy hardenability data for the specific steel grade to predict the actual variation in surface or core hardness for a given steel and quenching situation. To predict the expected variation in core hardness at the center of a 13-mm (0.5-inch) section of 8620H, the center of the section when quenched in oil with good agitation (H = 0.35) will yield hardnesses equivalent to about the J3 position. From the Jominy hardenability data (c.f., Figure 2, Part Two), the hardness values at the J3 position are 32-44 HRC, or a 12 HRC point spread. This range of core hardness values would be the appropriate print specification given this specific situation.

Part Geometry

Total case depth and effective case depth can vary on a part that is uniformly heat treated due to section size, steel hardenability, and part geometry. Therefore, it is good practice to identify the critical area(s) where case depth or core hardness values are to be determined. This identification is still critical for gears where it is generally understood that the tests are to be at the pitch line or root diameter. For other parts, such as tubes, shafts, and parts having convex or concave spherical sections, it is very important to define the testing location. The effective case depth on a part having both a flat surface and concave surface can vary as much as 30% on a properly carburized part.

Hardness Testing

Table A. Minimum Effective Case Depth Required for Accurate Hardness Test Results

When specifying the surface hardness requirements for case hardened parts, care must be taken to specify the proper hardness scale to ensure that the case will support the test and that accurate hardness values can be obtained. There is a relationship between the hardness test method that can be used and the required minimum specified effective case depth (Table A).

Next time we will look at how to best determine process cycles, focusing on two of the more common case hardening methods, carburizing and carbonitriding.

References

Dossett, Jon. 2007. “Make Sure Your Specified Heat Treatment Is Achievable.” Heat Treating Progress (March/April).

Dossett, Jon. 2025. Private conversation.

Herring, Daniel H. 2014a. Atmosphere Heat Treatment. Vol. 1. Troy, MI: BNP Media Group II.

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

Herring, Daniel H. 2014c. “Interpreting Carburized Case Depths, Part 1: Hardness Testing Methods.” Industrial Heating, July, 2014.

Herring, Daniel H. 2014d. “Interpreting Carburized Case Depths, Part 2: Methods for Measuring Case Depth.” Industrial Heating, August, 2014.

About the Author

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP, Inc.

Dan Herring has been in the industry for over 50 years and has gained vast experience in fields that include materials science, engineering, metallurgy, new product research, and many other areas. He is the author of six books and over 700 technical articles.

For more information: Contact Dan at dherring@heat-treat-doctor.com.

For more information about Dan’s books: see his page at the Heat Treat Store.

Ask the Heat Treat Doctor®: Guidelines for a Successful Heat Treatment Outcome — Part Three Read More »

Ask the Heat Treat Doctor®: Lineamientos para Obtener Exitosos Resultados de Tratamiento Térmico — Parte Tres

/ CARBURIZING TECHNICAL CONTENT, HARDNESS TESTERS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Ask The Heat Treat Doctor® ha regresado para ofrecer consejos sabios a los lectores de Heat Treat Today y responder sus preguntas sobre tratamiento térmico, soldadura fuerte (brazing), sinterizado y otros tipos de tratamientos térmicos, así como preguntas sobre metalurgia, equipos y problemas relacionados con los procesos. En esta entrega, Dan Herring explora la tercera parte de su serie de pautas sobre tratamiento térmico, en la que explica cómo definir y especificar la profundidad de capa, los valores de dureza y las ubicaciones de ensayo en los planos, y cómo elegir el método de ensayo de dureza adecuado para obtener resultados precisos y repetibles.

Si tiene comentarios o preguntas sobre este artículo, háganoslo saber en: editor@heattreattoday.com.

To read this article in English, click here.

Continuamos nuestra serie sobre tratamientos térmicos ofreciendo directrices enfocadas en “hacer el trabajo correctamente, la primera vez y siempre” en el mundo real. Conozcamos más.

Cómo alcanzamos nuestros objetivos

A continuación, se presentan algunas directrices básicas adicionales sobre metalurgia y tratamientos térmicos que, desde un punto de vista práctico, pueden ayudar a evitar problemas en el tratamiento térmico (Herring 2014a, 2014b, 2014c).

Definición de la terminología

Figura 1. Determinación de la profundidad total de capa mediante el método visual | Crédito de la imagen: The HERRING GROUP, Inc.

Es importante comprender a qué nos referimos cuando especificamos un requisito de tratamiento térmico. Por ejemplo, consideremos la carburización gaseosa en atmósfera. La definición técnica de la profundidad de capa carburizada se expresa en términos del contenido de carbono:

  • Profundidad total de capa: La profundidad a la cual el contenido de carbono del acero es un 0.04% superior al contenido de carbono del núcleo del acero. En otras palabras, la profundidad total de capa es el punto en el cual ya no pueden distinguirse las diferencias en las propiedades químicas o físicas de la capa y el núcleo (Figura 1). Muchos metalurgistas determinan la profundidad total de capa mediante el ataque químico de una muestra de acero con Nital y la medición de la zona afectada por el reactivo.
  • Profundidad efectiva de capa: La profundidad a la cual el contenido de carbono del acero de baja aleación es del 0.40% y aproximadamente del 0.30% para los aceros de media y alta aleación.

Dado que medir la concentración de carbono en función de la profundidad en un componente carburizado para determinar la profundidad de capa suele requerir mucho tiempo y resultar costoso, comúnmente se utilizan otras técnicas, como la microdureza. En determinadas situaciones que involucran profundidades de capa muy grandes, la dureza puede medirse directamente en una muestra de ensayo mediante las escalas Rockwell “A” o “C”. Se utilizan las siguientes definiciones:

Figura 2. Ejemplo de determinación de la profundidad efectiva de capa mediante ensayo de microdureza | Crédito de la imagen: The HERRING GROUP, Inc.
  • Profundidad efectiva de capa (U.S.): La distancia desde la superficie (en pulgadas) hasta un punto dentro de la capa donde la dureza es de 50 HRC (542 Knoop o 513 HV). Esta medición se realiza en una sección transversal mediante técnicas de microdureza con un indentador Knoop o Vickers (Figura 2). Estos valores se convierten posteriormente a dureza Rockwell C cuando se utiliza una carga de 500 gramos-fuerza, de acuerdo con ASTM E384 (última revisión). Se requiere interpolación para obtener el valor correcto de profundidad de capa. La profundidad efectiva de capa depende del gradiente de carbono y de la templabilidad de la capa, pero 50 HRC normalmente se equipara a un contenido de carbono del 0.40% en aceros de baja aleación y del 0.30% en aceros de media y alta aleación.
  • Profundidad efectiva de capa (internacional): La distancia desde la superficie (en milímetros) hasta un punto dentro de la capa donde la dureza es de 550 HV (aproximadamente 52.5 HRC). Esta medición se realiza mediante un método de microdureza Vickers con una carga predefinida de 1 kilogramo y no se convierte a Rockwell C. La profundidad efectiva de capa sigue dependiendo del gradiente de carbono y de la templabilidad de la capa. Para aceros de cementación altamente aleados, el contenido de carbono correspondiente a 550 HV normalmente se encuentra en el intervalo de 0.25–0.30%. Para los grados de aleación media, es aproximadamente 0.30–0.35% C, y para los aceros de baja aleación, es aproximadamente 0.35–0.40% C.

Indicaciones de profundidad de capa en los planos

La profundidad de capa en los planos de ingeniería debe indicarse como profundidad total de capa, profundidad efectiva de capa o profundidad efectiva de capa final después de retirar una cantidad definida de material de la superficie. Es importante señalar que, si no se especifica ni la profundidad total ni la efectiva de capa, no debe suponerse que se pretende la profundidad total de capa (aunque hace muchos años esta era una creencia comúnmente aceptada).

A menudo se utiliza una “regla práctica” para aproximar la profundidad total de capa a partir de la profundidad efectiva de capa. Dada la profundidad efectiva de capa, la profundidad total de capa puede estimarse multiplicando la profundidad efectiva de capa por 3/2. Para determinar la profundidad efectiva de capa a partir de la profundidad total de capa, multiplique la profundidad total de capa por ⅔. El grado del acero, su composición química, la templabilidad del material y la profundidad de capa influyen en esta regla.

Otras consideraciones importantes incluyen:

  • Especificar la condición de la pieza en el momento del ensayo (condición temple, revenida, después del rectificado final).
  • Especificar el procedimiento de ensayo en cada ubicación y para cada característica.
  • Indicar la tolerancia máxima y mínima de la especificación.
  • Mostrar el plano de la pieza y la especificación al laboratorio de ensayos y al fabricante de la pieza, y comprobar sus interpretaciones de la especificación frente a sus requisitos.

Al especificar el tratamiento térmico requerido para el endurecimiento superficial, es importante definir el proceso, el intervalo deseado de profundidad de capa y la escala de ensayo de dureza para evaluar las piezas.

Esto se ilustra mejor mediante un estudio de caso en el que unos rodamientos endurecidos de servicio ligero fabricados con acero 1117, los cuales fallaron después de ser tratados térmicamente conforme a una especificación que exigía una dureza de 58 HRC y una profundidad de capa de 0.015–0.020 pulgadas. Existen varias inquietudes técnicas con respecto a la especificación relacionadas con la definición del proceso, la definición de la profundidad de capa y la escala de dureza no especificada para medir la profundidad de capa.

Valores de dureza

Al especificar el intervalo o la tolerancia de dureza para los valores esperados de dureza superficial o dureza del núcleo, es necesario reconocer todo el intervalo de templabilidad del acero especificado en el punto de interés sobre la pieza o dentro de ella. La variación esperada en la dureza superficial después del endurecimiento por inducción o por llama puede determinarse comprobando los valores máximo y mínimo de carbono para el grado específico de acero frente a los valores de dureza mostrados en la columna de 99.9% de martensita de la Tabla 1 (Parte uno). Por ejemplo, el acero SAE 1045, con un intervalo de carbono de 0.43–0.50%, puede alcanzar una dureza de 57–60 HRC en estado recién templado y totalmente martensítico, mientras que el acero SAE 4140, con un intervalo de carbono de 0.38–0.43%, solo puede alcanzar 55–57 HRC.

Para tratamientos térmicos de endurecimiento en toda la sección, pueden utilizarse curvas (véase la Figura 1, Parte dos) junto con los datos de templabilidad Jominy del grado específico de acero para predecir la variación real de la dureza superficial o del núcleo para un acero y una condición de temple determinados. Para predecir la variación esperada de la dureza del núcleo en el centro de una sección de 13 mm (0.5 pulgadas) de 8620H, el centro de la sección, cuando se templa en aceite con buena agitación (H = 0.35), producirá durezas equivalentes aproximadamente a la posición J3. A partir de los datos de templabilidad Jominy (véase la Figura 2, Parte dos), los valores de dureza en la posición J3 son de 32–44 HRC, o una diferencia de 12 puntos HRC. Este intervalo de valores de dureza del núcleo sería la especificación adecuada en el plano para esta situación específica.

Geometría de la pieza

La profundidad total de capa y la profundidad efectiva de capa pueden variar en una pieza tratada térmicamente de manera uniforme debido al tamaño de la sección, la templabilidad del acero y la geometría de la pieza. Por lo tanto, es una buena práctica identificar las áreas críticas donde deben determinarse los valores de profundidad de capa o dureza del núcleo. Esta identificación sigue siendo fundamental para los engranajes, en los que generalmente se entiende que los ensayos deben realizarse en la línea de paso o en el diámetro de raíz. Para otras piezas, como tubos, ejes y piezas que presentan secciones esféricas convexas o cóncavas, es muy importante definir la ubicación del ensayo. La profundidad efectiva de capa en una pieza que tiene tanto una superficie plana como una superficie cóncava puede variar hasta un 30% en una pieza correctamente carburizada.

Ensayos de dureza

Tabla A. Profundidad efectiva mínima de capa requerida para obtener resultados precisos en los ensayos de dureza

Al especificar los requisitos de dureza superficial para piezas con endurecimiento superficial, se debe tener cuidado de especificar la escala de dureza adecuada para garantizar que la capa soporte el ensayo y que puedan obtenerse valores de dureza precisos. Existe una relación entre el método de ensayo de dureza que puede utilizarse y la profundidad efectiva de capa mínima requerida especificada (Tabla A).

La próxima edición examinaremos cómo determinar mejor los ciclos de proceso, centrándonos en dos de los métodos más comunes de endurecimiento superficial, la carburización y la carbonitruración.

Referencias

Dossett, Jon. 2007. “Make Sure Your Specified Heat Treatment Is Achievable.” Heat Treating Progress (March/April).

Dossett, Jon. 2025. Private conversation.

Herring, Daniel H. 2014a. Atmosphere Heat Treatment. Vol. 1. Troy, MI: BNP Media Group II.

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

Herring, Daniel H. 2014c. “Interpreting Carburized Case Depths, Part 1: Hardness Testing Methods.” Industrial Heating, July, 2014.

Herring, Daniel H. 2014d. “Interpreting Carburized Case Depths, Part 2: Methods for Measuring Case Depth.” Industrial Heating, August, 2014.

Acerca del Autor

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP, Inc.

Dan Herring lleva más de 50 años en la industria y ha adquirido una vasta experiencia en áreas que incluyen ciencia de materiales, ingeniería, metalurgia, investigación de nuevos productos y muchas otras. Es autor de seis libros y de más de 700 artículos técnicos.

Para más información: Contacte a Dan en dherring@heat-treat-doctor.com.

Para más información sobre los libros de Dan: consulte su página en el Heat Treat Store.

Ask the Heat Treat Doctor®: Lineamientos para Obtener Exitosos Resultados de Tratamiento Térmico — Parte Tres Read More »

Improving Thermocouple Accuracy with Innovative Cold Junction Compensation

/ MANUFACTURING HEAT TREAT TECH, THERMOCOUPLES TECHNICAL CONTENT

Accurate thermocouple readings depend on more than the sensing element itself. In this Technical Tuesday installment, Mark Betts, principal hardware design engineer at Watlow, examines how an innovative approach to cold junction compensation can reduce measurement uncertainty caused by airflow, thermal gradients, and changing ambient conditions, supporting greater accuracy, process stability, and repeatability in heat treat operations.

This informative piece was first released in Heat Treat Today’s October 2026 Ferrous & Nonferrous Heat Treatments/Mill Processing print edition.

Accurate temperature measurement has always been fundamental to industrial process control. Whether manufacturers are operating heat treatment furnaces, life sciences processes, power generation facilities, water and wastewater treatment plants, or food production systems, reliable temperature data is essential to safe, efficient, and repeatable operation. As manufacturing tolerances continue to tighten, achieving higher levels of measurement accuracy is becoming increasingly challenging. In regulated applications, measurement systems may need to satisfy demanding standards, such as AMS2750 and CQI-9, making every source of uncertainty within the measurement chain important.

The challenge is particularly important in heat treatment, where measurement systems must meet demanding accuracy
requirements. Client experience also highlighted the need for improvement, with reports that forced airflow within control cabinets could affect thermocouple readings. Addressing these effects required reconsidering how the cold junction temperature itself was determined.

Patented Precision Analog Input Module (AI3) | Image Credit: Watlow

Recognizing this challenge, Watlow has developed an innovative approach to cold junction compensation (CJC) as part of its new Edge Process Management™ (EPM™) platform. Designed to bring together high-precision measurement, process control, data management, and automation within a scalable architecture, the EPM platform is being developed to provide an integrated approach to process management. The EPM data solution is designed to support the creation of trusted process records for regulated industries.

The Hidden Challenge of Accurate Thermocouple Measurement

Unlike resistance temperature detectors (RTDs), thermocouples do not measure absolute temperature directly. Instead, they generate a small voltage proportional to the temperature difference between two junctions formed by dissimilar metals. One junction is located at the point being measured, while the second exists where the thermocouple wires connect to the measurement instrument. To calculate the correct process temperature, the instrument must know the temperature at this reference point, making accurate CJC an essential part of every thermocouple measurement.

Although the principle is well understood, accurately determining the cold junction temperature is more difficult than it first appears. Most modern measurement systems estimate the terminal temperature using a sensor mounted on the printed circuit board (PCB). This has proven to be an effective and economical solution for many years, but it relies on the assumption that the PCB temperature accurately represents the temperature at the field terminals. In practice, these two locations rarely remain at exactly the same temperature, and even small differences can introduce measurable errors into the final process reading.

As industrial control systems have become smaller, more powerful, and more densely populated with electronics, maintaining thermal uniformity has become more difficult. Ambient temperature changes, forced airflow from cabinet cooling systems, heat generated by neighboring components, and thermal conduction through field wiring all contribute to temperature gradients between the PCB and the field terminals. As these gradients increase, the PCB sensor no longer accurately represents the true temperature at the thermocouple termination, meaning the compensation itself becomes a source of measurement uncertainty.

These limitations become even more significant in systems that use removable terminal blocks. Removable terminals simplify installation, commissioning, and maintenance, but they also introduce another thermal interface between the field wiring and the measurement electronics. During startup or changing operating conditions, different parts of the assembly warm and cool at different rates, meaning conventional compensation methods require time to stabilize before optimum accuracy can be achieved.

These effects are typical of conventional CJC measurements where the temperature is measured some distance from the actual thermocouple termination. The resulting thermal gradients can make the measurement more susceptible to internal
self-heating, position within the equipment, changing ambient temperature, and airflow. As expectations for measurement accuracy increase, reducing the influence of these external factors becomes more significant.

Rethinking Cold Junction Compensation

Rather than accepting these limitations, Watlow engineers investigated whether the temperature measurement could be moved closer to the point where CJC takes place. The result is an innovative design that integrates an additional thermocouple junction within the removable terminal assembly itself.

Instead of relying solely on a PCB-mounted temperature sensor, the design incorporates two dissimilar conductive materials within the terminal assembly to create an internal T-type thermal sensor. Rather than directly measuring the absolute temperature of the terminal, this internal sensor measures the temperature difference between the PCB and the field termination. Combined with the PCB temperature measurement, this enables the system to calculate a more representative cold junction temperature while significantly reducing errors caused by thermal gradients between the electronics and the field wiring.

CJC measurement error | Image Credit: Watlow

This seemingly simple change fundamentally alters how CJC is performed. Conventional systems infer the terminal temperature from a nearby location on the PCB. The new approach measures the thermal relationship between the PCB and the terminal directly, allowing the cold junction calculation to compensate more effectively for changing operating conditions.

The benefits extend beyond improved measurement accuracy. Positioning the sensing function within the removable terminal improves thermal coupling with the field wiring while reducing susceptibility to convective airflow, module self-heating, and thermal conduction effects. Because the design is integrated within a standard removable terminal block, it also avoids the need for specialist thermocouple connectors or external isothermal reference blocks in many applications, while retaining the convenience and serviceability engineers expect from removable field wiring.

The difference becomes particularly important when airflow changes. In conventional CJC arrangements, relatively large thermal gradients can exist between the point where the CJC temperature is measured and the thermocouple terminal. Forced airflow can change these gradients rapidly, causing the indicated thermocouple temperature to change even though the process temperature has not. With the new CJC approach, the measurement is in very close thermal contact with the terminated thermocouple junction, so these gradients are much smaller. Airflow can still have an effect, but its magnitude is significantly reduced.

Testing also examined performance as ambient temperature was varied between 0°C and 55°C. The results demonstrated that changes in ambient conditions had substantially less influence on the thermocouple reading with the new CJC approach. This has practical implications in an industrial control cabinet. Opening a cabinet door can allow accumulated warm air to escape rapidly, while heat generated by the process or surrounding equipment can progressively increase cabinet temperature. Reducing the influence of these changes helps maintain a more stable process measurement.

Achieving the required performance was only part of the engineering challenge. The solution also had to be robust, resistant to damage, and economical to manufacture, without placing electronics inside the removable terminal block. Watlow therefore developed an approach using a commonly available alloy for the additional measurement while working with terminal block manufacturers to identify suitable contact materials and manufacturing methods. All of this had to be accommodated within the dimensions of a standard terminal block.

Performance Under Real Operating Conditions

Industrial environments rarely remain thermally stable. Cabinets warm throughout the day, cooling systems cycle on and off, process loads fluctuate, and equipment experiences repeated thermal cycling during normal operation. Under these conditions, maintaining a stable and representative cold junction temperature becomes just as important as the accuracy of the thermocouple itself.

Where the thermocouple measurement is also used as the process control input, improved measurement stability has consequences beyond the indicated temperature. A measurement that is less influenced by changing ambient conditions provides the control system with a more stable process variable, supporting more repeatable control closer to the required set point.

Faster stabilization is another practical advantage. Conventional CJC arrangements can require significant warm-up time before the measurement fully stabilizes, whereas the new CJC approach provides an accurate thermocouple process reading with very little warm-up time. This can reduce the time required when checking system calibration and, in heat treatment applications, help reduce the risk of failing a system accuracy test because the measurement system itself has not reached thermal stability.

Supporting High-Integrity Process Measurements

The innovative CJC technology reflects a broader engineering philosophy in which improvements are achieved by strengthening every part of the measurement chain rather than focusing solely on the sensing element itself. More representative cold junction measurements support higher-quality process data, providing greater confidence in the information used for process control, quality assurance, and regulatory compliance. Heat treatment was a particular consideration during development, with the need to meet demanding accuracy requirements providing one of the drivers for efforts to improve CJC performance.

The approach demonstrates that meaningful innovation can still be achieved within mature measurement technologies. Thermocouples have been used successfully for decades, and the principles of CJC are well established. However, by challenging the assumption that the printed circuit board is always the best place to determine the cold junction temperature, Watlow has identified an opportunity to reduce one of the most significant sources of uncertainty within the thermocouple measurement chain.

Conclusion

The significance of improved CJC extends beyond a better accuracy specification. A thermocouple measurement that is less
susceptible to internal self-heating, airflow, and changing ambient conditions provides a more dependable representation of the actual process. Where that measurement is used for control, greater stability can support more repeatable operation closer to the required set point. In heat treatment applications, reduced CJC uncertainty and very little warm-up time can also simplify calibration checking and help reduce the risk associated with system accuracy testing.

By moving the CJC measurement into close thermal contact with the terminated thermocouple junction, Watlow has
developed an approach that reduces the influence of thermal gradients on thermocouple measurement. The result is an innovative solution that can support greater measurement accuracy, control stability and process repeatability within the EPM platform.

About The Author:

Mark Betts
Principal Hardware Design Engineer
Watlow

Mark Betts is a hardware engineer with more than 30 years of product development experience at Watlow, where he has played a key role in developing Eurotherm-branded products. His experience spans the complete product development lifecycle, from initial concepts and design through testing, validation, and final release, with a focus on quality, reliability, and performance.

For more information: Contact Mark Betts at mark.betts@watlow.com.

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Emerging Technologies: Modernizing Heat Treat Controls with PLCs and HMIs: Part 1

/ CONTROLS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Heat Treat Today’s contributing experts series on emerging technologies examines how modern automation and manufacturing tools are reshaping heat treat operations. In this Emerging Technologies installment, Alex Marcy, CEO of Corso Systems, discusses why programmable logic controllers (PLCs) and human machine interfaces (HMIs) must be current, sercure, and performing as designed before heat treaters add layers like analytics, data collection, or advanced integration. Marcy outlines what that readiness looks like, from updated firmware and cybersecurity alignment to reliable long-term operation, and explains how the benefits include reduced downtime risk, greater repeatability, and better data quality.

This informative piece was first released in Heat Treat Today’s September 2026 People of Heat Treat print edition.

Editor’s Note: Alex Marcy’s contributing columns to this series will cover his ten steps of progressive heat treat automation adoption. This column is just step one but yields fully actualized benefits even if you stop here. Look out for his future installments.

Programmable Logic Controllers (PLCs) and Human Machine Interfaces (HMIs) are the foundation of every automation system. PLCs run your equipment using logic to perform repeatable operations and HMIs give your staff control over and display the status of your equipment and production lines. Outdated, unsupported, or misconfigured PLCs and HMIs limit visibility, increase risk, and create roadblocks for future growth.

Ensuring these core systems are up to date is critical before adding technology layers like analytics, data collection, or advanced control and integration.

The first step towards a fully integrated manufacturing process focuses on validating that your control systems are current, secure, and performing as designed. This includes:

  • Ensuring up-to-date and functional process control logic for automated equipment
  • Updating firmware and software to supported versions
  • Aligning your system with current cybersecurity best practices
  • Verifying proper configuration and operation of your equipment, PLCs, and HMIs
  • Ensuring reliability and maintainability for long-term, repeatable operation of your system

Benefits of using PLCs and HMIs for heat treat operations include:

  • Reduced risk of downtime or system failure
  • Increased repeatability across production runs
  • Improved data quality and visibility

Taking the time to address PLC and HMI readiness now prevents costly delays later. If you are using relay logic or manual controls to operate your equipment, upgrading to a PLC and HMI is a great first step. Outdated PLC equipment puts you at risk of downtime if the hardware fails and should be considered for replacement every 10 years.

Using PLCs and HMIs to run your equipment sets you up for larger benefits gained from using manufacturing technology across your business.

About the Author

Alex Marcy
CEO
Corso Systems

Alex Marcy is the CEO of Corso Systems, helping heat treat companies improve operations since 2011.

For more information: Contact Alex Marcy at alex@corsosystems.com.

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How Logistics Considerations Affect Industrial Gas Users

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

Industrial gas costs involve far more than the gas itself. In this Technical Tuesday installment, Dave Wolff, an independent expert focusing on industrial atmospheres for heat treat applications, draws on an interview with Josh Weinmann, president of DeLille Oxygen Co., to explore how delivery logistics, storage, tank sizing, supply contracts, and supplier selection can affect both costs and supply reliability.

This informative piece was first released in Heat Treat Today’s October 2026 Ferrous & Nonferrous Heat Treatments/Mill Processing print edition.

DeLille Oxygen is a regional multilocation industrial gas manufacturer and distributor serving Ohio and adjoining areas with industrial and specialty gases. The company recently celebrated its 100th year in operation, an enviable record of success. Josh Weinmann has worn many hats at DeLille, from cylinder filler and bulk driver to operations management and now is president of the organization. We discussed the importance and cost implications of gases logistics in serving industrial gases clients.

The Real Cost of Gas Delivery

Josh Weinmann
President
DeLille Oxygen Co.

Because industrial gases are gaseous products, shipped either as highly compressed gases or as liquefied cryogenic liquids, they are hazardous materials requiring special handling. For that reason, when a client plans to purchase bulk industrial gases from a supplier, that arrangement includes delivery of those gases to the client. While some gases may be manufactured at the client’s location (so-called on-site gas production), in most cases, the gas is manufactured at large process plants far from the client and shipped by truck to the client. The embedded shipping costs are a large fraction of the pricing that clients pay for delivered industrial gases.

Industrial gas transportation requires special trailers, drivers with specialized training and licenses, and very precise procedures. The cryogenic trailer itself may cost several hundred thousand dollars. Backhauls are uncommon, so the trailers are returned empty to the plants, further increasing costs. In Josh’s experience, delivery costs are often higher than the “spigot” price of the gas at the plant before delivery. But the gases must be delivered to be used, so clients pay for both product and delivery.

Different suppliers handle shipping costs differently. Some suppliers provide a single price for their gases, including delivery. In that case, the client may be asked to pay say 90 cents per 100 scf for their nitrogen, including delivery costs, assuming normal delivery arrangements.

Other suppliers, like DeLille, quote gas prices at the spigot (source location), plus a delivery charge. They might quote 45 cents per 100 scf at the spigot, plus a fixed freight charge per delivery, for example. The two line items, gas plus delivery, will appear separately on each invoice, providing an additional degree of transparency. This approach is clearer about the cost structure and provides the client with visibility over costs and incentive to reduce the number of delivery events by maximizing the amount delivered at each delivery event.

Understanding Your Industrial Gas Contract

Industrial gas contracts detail the financial, legal, and procedural requirements of the supplier and the client. Most bulk supply contracts span 3 to 7 years. These contracts include provisions for cost recovery by the suppliers as their costs change over time. Typically, contracts include cost recovery on electricity and/or natural gas for production of the gas product and cost recovery for changes in cost of diesel fuels and labor for delivery. There also may be factors built in for changes in overall costs such as inflation recovery. All modern contracts will also include provisions for uncommon/impactful events, such as those experienced during Covid when supply and delivery mechanisms were dramatically challenged.

Most industrial gas contracts are negotiated with a certain amount of monthly use in mind. It is important to be realistic and relatively transparent when negotiating quantities because the final contract will specify the range of product deliveries that the supplier is committed to supply and the client is required to buy. While the client may wish to get a cheaper price by specifying a larger amount of monthly use to get a cheaper price, if the client regularly uses less gas than committed to, the supplier may adjust the pricing accordingly. Possibly even more important, the contract will specify a certain increment of additional product that the supplier commits to making available to a client above and beyond their expected monthly use. You don’t want to be in the position of begging for additional gas supply to meet your needs if your business is highly successful. Commitments between clients and suppliers for industrial gases apply in both directions.

Telemonitoring and Delivery Schedule

In the past, industrial gas clients would have an employee who was responsible for monitoring the tank levels of their industrial gases and calling their supplier(s) to schedule deliveries when levels got low. That operational model has been largely abandoned, and most clients and suppliers today use telemonitoring to monitor tank levels for each cryogenic and compressed gas product in use. For cryogenic liquid tanks, telemonitoring generally monitors liquid level or uses a load cell to measure tank filled weight; for gaseous products such as compressed hydrogen, telemonitoring measures and reports on tank pressure, which corresponds to inventory. The suppliers continuously monitor tank levels and can schedule deliveries to achieve continuous supply at the lowest cost of deliveries. In theory, telemonitoring should eliminate the risk of runouts. Because telemonitoring data provides real-time data and powerful analytics regarding client gas use, DeLille makes that data available to their clients through a client portal. It is worthwhile for clients to request access to their data from tank telemonitoring.

Image Credit: DeLille Oxygen Co.

Industrial gas providers work 24×7 to produce and deliver industrial gases. DeLille, like many industrial gas providers, prefers to deliver to clients at night, when client operations are at low ebb, and traffic delays affecting expensive delivery assets are less likely. The standard contract assumes that the supplier will be able to deliver around the clock. Clients that require restricted deliveries, either fewer than 24 hours/day or only certain days of the week, will most likely be required to pay additional costs for delivery. Clients should make every attempt to provide unrestricted delivery to keep their costs down.

Making Every Delivery Count

Because liquid and gas bulk trailers are filled to capacity before they start the day, they may end the day with some residual gas that has not been delivered to clients. It is to the supplier’s benefit to deliver that remaining cargo to one of their clients before returning to refill, because it does not make sense to pay to transport the gas back and then haul it out again. As such, suppliers sometimes dump the remaining product, often just a few thousand cubic feet of gas, at a client willing to accept it.

Clients should be aware of two things regarding these unscheduled deliveries. First, every delivery requires a certain amount of gas to be wasted to depressurize tanks, fill pipes, and cool down hoses. The wasted product amount is the same regardless of small delivery or large one. The client pays for that vented product. For a large delivery, the wasted product is a small percentage, but for a small delivery of residual product, the wasted amount can be a meaningful percent of the total amount of gas to be paid for. It is fair to come to an agreement with your supplier about some equitable way for the supplier to drop off residual product without the client paying extra for gas that is wasted on a small delivery.

Because the supplier did not plan the route to fill your tank, it seems clear that the client should not pay full delivery charges for product delivered for supplier convenience. Regardless of whether your agreement splits out delivery cost or bundles it into the product price, clients should ensure they pay a full delivery fee only for product associated with a trip made specifically to meet your needs.

It is worth understanding how quantities delivered are computed for compressed and cryogenic gas deliveries. Previously, trucks with cryogenic gases would weigh before and after each delivery at a commercial truck scale, charging the client for the weight difference associated with that delivery. Now, most cryogenic trailers are equipped with calibrated volume meters, similar to the meter in a gasoline pump, that measures the exact amount of liquid cryogenic fluids dispensed. For gaseous deliveries like compressed bulk hydrogen, the delivery ticket will show the starting pressure of the receiving tank or tubes, the ending pressure, and the temperatures at the beginning and end of the delivery. The exact amount of gas dispensed can thus be determined for billing purposes.

Storage Tanks: Renting, Maintaining, and Sizing

Gas storage tanks and tubes are normally rented from your industrial gas supplier. That system works well for both supplier and client, but it does create limitations in flexibility. For example, no other supplier will deliver into a different supplier’s tank, unless written permission from the tank owner (not the renter) is received. If your supplier runs into delivery problems, you need to seek temporary written permission to have another supplier deliver.

Tank owners are responsible for having tanks inspected according to schedules established by OSHA and referring to codes from ASME and NFPA. Required inspections include insulation, piping, regulators, and safety relief valves. Industrial gas suppliers have staff to perform these inspections while clients may find it difficult or expensive to have these required inspections done. It is rarely attractive for clients to buy their own cryogenic and compressed gas storage equipment.

Cryogenic liquefied gas storage tanks are like giant thermos bottles and use a vacuum insulation system to keep the precious cryogenic liquefied gas from evaporating. The normal loss rate for a cryogenic tank evaporation rate during periods of non-use is under 1% of the tank volume per day of non-use. Over time, the vacuum may gradually leak down, creating a loss of insulation and the possible loss of gas to evaporation. Tank renters should be aware that tank evaporation rate may increase over time and should alert their supplier if they feel that evaporation has increased. It is the supplier’s job to maintain proper insulation.

Image Credit: DeLille Oxygen Co.

Most suppliers want to deliver to their clients once per month, unless the client’s usage rate is high enough to require more frequent delivery. It is important for both the client and the supplier for deliveries to be efficiently managed or there will be extra costs incurred which will eventually impact the client. Once-per-month delivery means sizing the volume of cryogenic liquid or gaseous storage to hold enough volume to enable the client to be delivered once per month without risk of runout. Because bigger tanks have a higher rental rate than smaller tanks, tank sizing can sometimes provoke a lively discussion between client looking to minimize rental rates and suppliers looking for additional storage. Experience has shown that sizing storage representing about 1.5 to 2 months use is generally the most efficient size.

While too small a tank forces extra deliveries and increases likelihood of runouts, too large a cryogenic tank can also be problematic because cryogenic evaporation rate increases with tank wall surface area; therefore, a larger tank will lose more gas during periods of non-use. One possible exception to the tank-sizing conventions may be for argon, which is subject to frequent swings in supply availability. It may be wise to moderately oversize argon storage to ensure continuous supply and eliminate risk of runouts. The extra tank capacity makes it possible to run through temporary supply shortfalls. Argon users who are willing to step up slightly in tank size may wish to try to negotiate a slightly lower gas price by improving their attractiveness as delivery locations (because the larger tank can improve delivery efficiency).

Choosing the Right Gas Supplier

When choosing a gas supplier, logistics are a huge component of the delivered gas cost to the client, even though logistics are only indirectly visible to the average industrial gas user. Just as Amazon stocks warehouses close to clients with many common items to achieve unprecedented short client delivery times, local gas distributors and industrial gas companies may have local depots where they have inventory of gases ready to be loaded and delivered to nearby clients. Talk to several potential suppliers about your use of gases to find a supplier that can meet your needs. If you use more than one bulk gas (say nitrogen plus hydrogen, for example), consider having just one supplier to vastly simplify dealing with your supplier. Be aware that the standard language of most bulk industrial gas contracts claims that the gas supplier has a right of first refusal to supply all the bulk industrial gases used at the location served (not just the gas listed on the accompanying rider document).

Industrial gases are a true commodity meaning nobody’s nitrogen is any “better” than any other supplier. As such, feel free to negotiate hard to achieve your economic and supply assurance goals when negotiating a contract. DeLille suggests that local distributors may be able to offer unique security of supply to clients while eliminating the need for clients to seek permission from their supplier for alternative supply during a supply shortfall or interruption of supply. Distributors may be able to pivot to an alternative supplier without the need for their clients to be involved.

It may not be obvious what industrial gas suppliers serve a particular area, so potential gas users can use a general-purpose search engine to find one, or consult with the member headquarters of one of the two major industry organizations: GAWDA (Gases and Welding Distributors Association) or IWDC (Independent Welding Distributors Cooperative). For highest satisfaction, choose a supplier that has a significant commitment to serving your geographic area and the gases you plan to use.

The delivery vehicles used for industrial gases can be as large as a tractor trailer, and they are transporting a dangerous cargo. As such, there is tremendous focus by suppliers on the safety of clients’ delivery environment. If a client cannot or will not provide a safe environment for a gas delivery, many suppliers will not deliver to the site or will have to use specialized equipment that will cost extra. Of particular interest to suppliers is the ability to pull through a client’s site because backing up bulk trailers is the most risky part of a delivery. If backing up can be avoided, the attractiveness of the supply contract will increase.

Negotiating a Contract that Works for Both Sides

When negotiating an industrial gas supply contract, most clients make operations the primary participant in the discussions, with procurement and legal as advisory. It seems wise to narrow the field of potential suppliers with the active participation of operations, and then use procurement and legal to avoid liability and issues with terms and conditions. The number of industrial gas suppliers is finite, and your process requires industrial gases, so be realistic about negotiations. Your objective should be to achieve a contract which serves the needs of both parties.

About The Author:

David (Dave) Wolff
Industrial Gas Professional
Wolff Engineering

David Wolff has over 45 years of project engineering, industrial gas generation and application engineering, marketing and sales experience. Dave holds a degree in engineering science from Dartmouth College. Currently, he consults in the areas of industrial gas and chemical new product development and commercial introduction, as well as market development and selling practices.

For more information: Contact David Wolff at Wolff_eng@icloud.com.

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Why is it Getting Warm in Here? Part 2

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Jim Roberts of U.S. Ignition engages readers in a Combustion Corner column about the three methods of heat transfer found in heat treating shops — examining how advection, convection, and radiation each move thermal energy, from forced hot-gas circulation by fans and burners, to the natural buoyancy-driven stirring of fluids, to the electromagnetic waves emitted by glowing radiant tubes that deliver the temperature uniformity so critical to heat treating.

This informative piece was first released in Heat Treat Today’s September 2026 People of Heat Treat print edition.

A furnace guy walks into a heat treat facility and says, “Hey, I think I’m warming up to this place.” The operators say, “It’s about time… and temperature.” This might be a lame joke on the most common requirement in heat treating, but time at temperature is the secret, right? How we get that combination of properties is the question.

Last month, we discussed that one of the Laws of Thermodynamics was advection. It’s not a term we use regularly, but it’s a better description of what we experience in our lives. Advection is when hot gases or hot atmosphere is circulated by force. In other words, it is not a natural transfer of heat to the product. It is when that heat is forced around the work piece, and it is in a state of unnatural agitation. We are moving the heat around by a fan or the velocity of the hot gases from the burner, some method of creating a “stirring effect” by using another energy source. A great example would be a heated fan. You can feel the heat from the coils, but most of that is because the air movement of the fan is scrubbing off the heat from the heat source and blowing it at you. Both the heat transfer of the heat source to the air and then that air transferring heat to you are examples of advection.

Now we turn to convection. Convection is sometimes described as a form of thermal transfer wherein the motion of a fluid is driven by the buoyancy of the fluid and is caused by temperature differences in the fluid. In engineering circles, a fluid can be liquid, air, a gaseous atmosphere, etc. Convection is all natural, and advection is using outside energy. A mug of hot water will lose its heat through the change in temperature caused by thermal lift in the liquid. Then, it will continue to transfer and lose heat as the steam or temp continues to rise away from the mug and into the air, all by natural stirring or lift. That mug will eventually release its thermal energy and equalize with the area around it.

This leads us to radiation. Ansys Engineering describes radiation as the mechanism that transfers heat energy as electromagnetic waves or photons. That’s right, Capt. Kirk, that phaser technology might just be real! In other words, thermal energy can cause the atoms in any matter to move. The movement of those charged particles (protons and electrons at an atomic level) will result in the release of electromagnetic radiation. In its purest form, radiation heat transfer will only occur in a vacuum or through a medium that is transparent to the radiation. Furnace atmospheres come to mind.

Also, re-radiation is possible from an object, such as a heat treating load, so the radiant source is also absorbing radiation some of the time. Radiation transfer is very efficient and is used effectively in radiant tube furnaces. The tubes are heated electrically or by gas burners, and when they begin to glow (somewhere around 1250°F), they begin in earnest to try and bring the furnace or the load up to temperature.

Image Credit: Ashikul / AdobeStock

When radiation is at work, these types of heating devices provide good temperature uniformity. This is because once the furnace has determined that the chamber temp has been achieved, the radiation will continue to try to bring the chamber up to temperature, and these electromagnetic pulses try for equilibrium in the chamber.

Radiation is very efficient in most cases. Radiation is like a living thing — it wants everything to be the same temperature. So it normally has sight line between the glowing heat source and the load. Thermal radiation transfers heat via infrared rays and visible light waves. Hot furnace walls and heating elements emit these electromagnetic waves, which then heat the metal parts without needing direct contact or air movement.

That covers the styles and methods of heat transfer we can see in our heat treating shops. We’ll pick up a new topic next month.

About The Author:

Jim Roberts
President
US Ignition

Jim Roberts president at U.S. Ignition, began his 45-year career in the burner and heat recovery industry focused on heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.

For more information: Contact Jim Roberts at jim@usignition.com.

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How 3D-Printed Copper Inductors Improve Heat Treat Performance

/ INDUCTION HEATING EQUIPMENT TECHNICAL CONTENT, INDUCTION HEATING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Inductor design plays a critical role in heating efficiency, temperature uniformity, and process stability, but conventional manufacturing methods can limit what coil geometries are possible. In this Technical Tuesday installment, Max Wissing, technology manager at PROTIQ, explores how 3D-printed copper inductors expand design freedom, allowing heat treaters to more closely tailor electromagnetic fields, cooling, and overall coil performance to demanding applications.

This informative piece was first released in Heat Treat Today’s October 2026 Ferrous & Nonferrous Heat Treatments/Mill Processing print edition.

Why Inductor Design Matters More Than Ever

Induction heating remains one of the most established and widely used technologies in modern heat treating. It enables precise, contactless energy transfer and offers a high degree of repeatability, making it particularly suitable for demanding applications, such as surface hardening, partial hardening, and localized treatment of highly stressed components.

At the same time, requirements in industrial heat treatment continue to increase. Manufacturers are expected to improve energy efficiency, reduce cycle times, and maintain consistent process quality. These demands are further intensified by the growing complexity of component geometries, which require more precise control of electromagnetic fields and temperature distribution than ever before.

Within this context, the inductor itself becomes a decisive factor, as its design directly influences heating behavior, efficiency, and process stability. However, many conventional inductors are still constrained by the limitations of their manufacturing methods. These constraints often force compromises between manufacturability and functional performance, meaning that coil geometries are not always ideally adapted to the component or the specific heat treat application. In more complex cases, this can lead to reduced energy efficiency or non-uniform temperature distributions, ultimately affecting process consistency.

In response, recent developments have increasingly focused on application-driven coil design and improved engineering approaches. Industrial 3D printing introduces a fundamentally different paradigm by enabling inductors to be designed according to functional requirements rather than production constraints. This shift opens up new possibilities for optimizing electromagnetic field distribution, improving energy transfer, and enhancing overall process performance in induction heat treating.

Where Conventional Coil Design Reaches Its Limits

Traditional induction coils are typically manufactured by bending and assembling copper tubes or machined elements. These methods are well established and widely used, but they impose inherent restrictions that can limit further optimization.

Geometric flexibility, for example, is constrained by bending radii and available tube profiles. As a result, the coil design often represents a compromise between what is theoretically optimal and what can be manufactured. In more complex applications, this can lead to non-uniform heating or less efficient energy coupling.

In addition, conventional manufacturing involves a considerable degree of manual work, which can introduce variability. Small deviations in geometry may affect electromagnetic behavior and, consequently, process consistency. The presence of joints — created through soldering or welding — further introduces potential weak points that can impact durability under thermal and mechanical stress.

Taken together, these factors not only influence manufacturing efficiency but also define the performance limits of the entire induction heating process.

3D Printing as a Design Enabler

Industrial metal 3D printer | Image Credit: PROTIQ

Additive manufacturing, often referred to as industrial 3D printing, is a production technology that creates metal components directly from digital design data. In processes like laser powder bed fusion (LPBF, often called SLM), a high-power laser selectively melts thin layers of metal powder. By repeating this process layer by layer, complex metal parts can be produced without the need for molds, tooling, or many of the manufacturing steps associated with conventional production methods.

This manufacturing approach offers a fundamentally different level of design freedom. Traditional manufacturing processes often require designers to adapt component geometries to machining, forming, or joining constraints. With additive manufacturing, many of these restrictions can be reduced or eliminated, allowing engineers to focus more directly on the functional requirements of the heat treatment application.

For induction heating, this means that the geometry of the inductor can be tailored more closely to the desired electromagnetic field distribution and heating characteristics. As a result, component design, process requirements, and performance objectives can be aligned more effectively.

Another important advantage is the ability to manufacture inductors as monolithic components. Instead of assembling multiple individual parts, the inductor can be produced in a single piece. This eliminates joints that may act as potential mechanical weak points while also enabling the integration of internal features, such as cooling channels. These channels can follow complex three-dimensional paths that would be difficult or impossible to realize with conventional manufacturing methods, enabling more targeted and efficient thermal management.

Impact on Induction Heating Performance

The increased design freedom enabled by additive manufacturing translates directly into improved process performance. When the geometry of the inductor is closely matched to the component, the electromagnetic field can be shaped more precisely. This allows for a more uniform temperature distribution, which is essential for achieving consistent material properties in heat treated parts.

Inductor with spray cooling | Image Credit: PROTIQ

Optimized geometries also improve the coupling of energy into the workpiece. In practical terms, this means that the required heating energy can be delivered more efficiently, often resulting in shorter cycle times. At the same time, improved cooling concepts help stabilize the process by keeping the inductor within its operating limits, even under demanding conditions.

Because additive manufacturing allows components to be reproduced with high accuracy, it also supports consistent process results. Compared to manually fabricated coils, this reproducibility reduces variability and contributes to overall process stability. The absence of soldered or welded joints can further increase service life, as common failure mechanisms are eliminated by design.

Copper in Additive Manufacturing: From Challenge to Application

Copper is the preferred material for induction coils due to its high electrical conductivity. However, its processing in laser-based additive manufacturing systems has long been considered challenging. The high reflectivity of copper and its thermal conductivity make it difficult to achieve stable and efficient melting during the build process.

In recent years, these challenges have been addressed through advances in machine technology, laser systems, and material development. Today, it is possible to manufacture copper components with properties suitable for demanding industrial applications, including conductivity levels comparable to conventional materials.

Despite this progress, successful implementation still requires a detailed understanding of both material behavior and process conditions. The interaction between geometry, material properties, and manufacturing parameters must be carefully considered to ensure that the final component meets both functional and mechanical requirements.

Companies such as PROTIQ have developed extensive experience in processing pure copper by additive manufacturing. This knowledge helps ensure stable production processes and application-oriented solutions for demanding industrial components like inductors.

Bridging Design and Reality Through Simulation and Experience

Simulation tools are an important element in the development of modern inductors. They provide insights into electromagnetic field distribution and thermal behavior, allowing engineers to evaluate and optimize designs before manufacturing.

Inductor simulation optimization | Image Credit: PROTIQ

However, simulation alone cannot fully predict how a component will perform under real operating conditions. Factors, such as material characteristics, surface quality, and manufacturing tolerances, can influence actual results. For this reason, experience in both additive manufacturing and induction applications remains essential.

In practice, effective inductor development is based on a combination of simulation, engineering expertise, and manufacturing know-how. This integrated approach helps ensure that theoretical designs can be translated into reliable solutions for industrial use.

Typical Applications in Heat Treating

The advantages of additively manufactured inductors become particularly evident in applications where conventional designs reach their limits. This is often the case in the heat treatment of components with complex geometries or varying cross-sections, where uniform heating is difficult to achieve.

In surface hardening processes, for example, tailored coil geometries can improve the consistency of hardness profiles across critical areas. Similarly, localized hardening applications benefit from the ability to precisely confine the electromagnetic field to specific regions of the component.

Custom 3D-printed inductors | Image Credit: PROTIQ

Another important field of application involves components with limited accessibility or intricate features. Here, additive manufacturing allows the realization of coil designs that can be adapted closely to the part geometry, enabling effective heating in areas that are difficult to reach with conventional inductors.

These application scenarios illustrate how additive manufacturing expands the solution space in induction heating, particularly for tasks that require a high degree of customization.

From Technology to Industrial Practice

While additive manufacturing offers significant opportunities, its successful use in induction heating depends on several factors. Material selection, manufacturability, and process stability must all be considered from the outset. Not every theoretically optimal design can be produced reliably, and design decisions must account for the specifics of the additive process.

Equally important is a deep understanding of the application itself. The requirements of the heat treat process, the properties of the component, and the desired outcomes must all be reflected in the inductor design.

In practice, additive manufacturing is not always the only or best solution. Depending on the application, a combination of conventionally manufactured and additively produced features can provide the most effective balance between performance, manufacturability, and cost.

This is where manufacturing expertise becomes critical. Companies like PROTIQ support clients in evaluating which parts of an inductor benefit from additive manufacturing and which may be better suited to conventional production methods. By combining process knowledge, material expertise, and industrial manufacturing capabilities, innovative designs can be translated into reliable and economically viable components.

Application-Driven Inductor Design

Additive manufacturing represents a shift in how induction coils are conceived and realized. By removing many of the constraints associated with conventional manufacturing, it enables a more direct alignment between design and function.

For heat treat operations, this opens up new possibilities for improving efficiency, quality, and reliability. Instead of adapting processes to the limitations of available coil geometries, inductors can be tailored to the specific requirements of the application.

As the technology continues to mature, additively manufactured inductors are likely to become an increasingly important element in advanced heat treat processes. Their successful application, however, depends not only on access to manufacturing technology but also on a comprehensive understanding of materials, processes, and application context.

About The Author:

Max Wissing
Technology Manager
PROTIQ

Max Wissing is the technology manager for 3D printing at PROTIQ with nearly a decade of industry experience. He holds a degree in mechanical engineering, specializing in the optimization of 3D-printed induction coils.

For more information: Contact Max Wissing at mwissing@protiq.com.

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Ask the Heat Treat Doctor®: Guidelines for a Successful Heat Treatment Outcome — Part One

/ HARDENING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH

Ask The Heat Treat Doctor® has returned to bring sage advice to Heat Treat Today readers and to answer your questions about heat treating, brazing, sintering, and other types of thermal treatments as well as questions on metallurgy, equipment, and process-related issues. In this Technical Tuesday installment, Dan Herring explores practical guidelines for getting heat treatment right the first time, every time, in the first part of a series inspired by the work of Jon L. Dossett. He outlines seven keys to success in heat treating and the two questions design engineers must answer about what a component must endure in service and how it will be made. He then examines the most common specification mistakes, including unrealistic hardness, case depth, and tolerance requirements, and shows how carbon content, section size, mass effect, and commercially achievable tolerances determine whether a steel can be hardened to specification.

This informative piece was first released in Heat Treat Today’s September 2026 People of Heat Treat print edition.

If you have any comments or queries, on this article, let us know at editor@heattreattoday.com.

Para leer el artículo en español, haga clic aquí.

In our day-to-day work, most of us face the challenge of meeting production demands while navigating tight manufacturing deadlines in an ever-changing materials and manufacturing landscape. Heat treatment can be defined as the controlled application of time, temperature, and atmosphere to produce a predictable change in the internal structure (i.e., microstructure) of a material, resulting in the desired metallurgical, mechanical, physical, and other properties we desire. There is, however, an alternate and equally important definition of heat treating: getting the job done right the first time — every time.

In this short series, we will examine practical guidelines to help make that objective a reality. Let’s learn more.

7 Keys to Success in Heat Treating

To accomplish this goal, we must be able to meet the seven key considerations in heat treating to ensure both our success and survival (Herring 2014a, 2014b, 2015):

  1. To know, metallurgically, what you want to accomplish.
  2. To be able to predict the outcome of a heat treatment operation.
  3. To have repeatability built into the process.
  4. To get the most out of the equipment you have and to use state-of-the-art heat treating equipment whenever possible.
  5. To be aware of how changes to our manufacturing operations influence the outcome of a given heat treatment process or series of processes.
  6. To not compromise on quality.
  7. To know our costs and understand our profitability.

Challenges Faced by Today’s Engineers

In the design of any engineered component, it is necessary to fully understand and address two key questions that design engineers working with metallurgists are often best qualified to answer (Herring 2014a, 2015, 2017):

  1. What must the component endure during service (i.e., what are the product requirements)? To answer this question, consider the following: What are the rigors of the application, and what is the design life? Must the component part provide premier service, or is there an adequate design life involved (i.e., will other factors end its service long before its useful life is expended)? What loading, lubricants, temperature, and contaminants are involved? What other service and performance aspects specific to the product must also be factored into the selection process?
  2. How will the component part be made (i.e., what are the process requirements)? Consider the following: How will its basic form be generated, and how will it be heat treated — if at all? Will it be important to introduce particular mechanical properties? If so, how (i.e., by heat treatment or by mechanical means)? Is geometry or surface finishes important? Will special coatings be used? Is dimensional control (including stability at temperature) an issue? What other processing aspects specific to the product must be considered?

How We Achieve Our Goals

Experienced heat treaters often point to the most common mistakes made by design engineers and/or their clients, that is, selecting materials, defining and understanding the limitations of the requested heat treatment processes, and specifying realistic outcomes from heat treating.

These include, for example, the desired hardness, case depth, and dimensional tolerances. These issues generally result from a failure to recognize the differences in the material’s chemical composition and form (e.g., wrought or powder metallurgy, castings, forgings). The design engineer should also understand the mill processing methods used to produce the material.

Often, the tolerances for the specified heat treatment properties are either too aggressive, too ambiguous, or too restrictive from a real-world standpoint. Here are a few basic metallurgical guidelines that can, from a practical standpoint, help avoid these problems (Herring 2014a, 2015; Dossett 2007, 2026).

Steel Selection

Table A. Carbon Content vs. Hardness for Different Martensite Levels (Dossett 2007)

Problems in specifying the proper steel grade for a particular application generally involve choosing a steel grade that cannot be hardened to the specification and/or specifying a surface or core hardness range that is too restrictive. For example, Table A provides a guideline for the maximum surface hardness achievable using induction or flame hardening treatments. The maximum obtainable hardness is a function of the carbon content of the steel being used.

If the material selected is 4140H with a carbon range of 0.37–0.44%, we would expect the surface to be approximately 99.9% martensite after quenching. Thus, the expected as-quenched hardness would fall in the range of 54–58 HRC for all the heats of this steel. However, the ability to achieve this hardness depends on the severity of quenching, the quenchant used, the quench tank design, and the adequate removal of surface decarburization that might be present on the wrought steel itself.

Table B. Maximum Surface Hardness as a Function of Section Size (Chandlar 1995)
Table C. Mass Effect on Maximum Surface Hardness: (Oil) Quenched 4140 Steel (0.40%C) (Bethlehem Steel Company 1949)

By contrast, in the case of furnace heat treatment, the maximum attainable surface hardness depends both on steel’s carbon content and its hardenability. The maximum section size (Table B) and effect of mass (Table C) are shown for several steel grades based on oil quenching. The commercially accepted range for surface hardness after tempering is ± 2.5 HRC points or ± 20 BHN points (Table D).

Table D. Commercially Desired Print Specification Tolerances for Properly Specified Materials

Next month we will review steel hardenability and how to determine the expected core hardness range.

This series was motivated by and contains insightful content from Jon L. Dossett who has granted permission. Jon’s distinguished career includes commercial heat treating involvement, extensive teaching career at ASM, and his work as editor of several volumes of the ASM Handbook series.

References

Bethlehem Steel Company. 1949. Modern Steels and Their Properties. Handbook 268. Bethlehem, PA: Bethlehem Steel Company.

Chandlar, Harry, ed. 1995. Heat Treater’s Guide: Practices and Procedures for Irons and Steels. Materials Park, OH: ASM International.

Dossett, Jon. 2007. “Make Sure Your Specified Heat Treatment Is Achievable.” Heat Treating Progress (March/April).

Dossett, Jon. 2025. Private conversation.

Herring, Daniel H. 2014a. Atmosphere Heat Treatment. Vol. 1. Troy, MI: BNP Media Group II.

Herring, Daniel H. 2014b. “Industry 4.0 and the 7 Key Considerations in Heat Treating.” Industrial Heating (September).

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

Herring, Daniel H. 2017. “The Relevance of Metallurgy in Engineering and Manufacturing.” Industrial Heating (November).

About the Author

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP, Inc.

Dan Herring has been in the industry for over 50 years and has gained vast experience in fields that include materials science, engineering, metallurgy, new product research, and many other areas. He is the author of six books and over 700 technical articles.

For more information: Contact Dan at dherring@heat-treat-doctor.com.

For more information about Dan’s books: see his page at the Heat Treat Store.

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