Welcome toHeat Treat Today’sThis Week in Heat TreatSocial Media. From mind-bending materials to mesmerizing shop-floor videos — and even a few LEGO bricks — heat treat social media had a little bit of everything! We scrolled, watched, learned, and smiled our way through posts that remind us why this industry is equal parts science, craft, and creativity.
As you know, there is so much content available on the web that it’s next to impossible to sift through all of the articles and posts that flood our inboxes and notifications on a daily basis. So, Heat Treat Today is here to bring you the latest in compelling, inspiring, and entertaining heat treat news from the different social media venues that you’ve just got to see and read!If you have content that everyone has to see, please send the link to editor@heattreattoday.com.
1. Looped and Loaded
Warning: this reel of glowing steel coiling in real time may cause viewings…on loop. Mastars Industries brings the shop floor to your screen, showing molten-hot metal bending and twisting with hypnotic precision.
2. Foamed Metals Head to Space
In honor of National Bubble Wrap Day, Ipsen took a nostalgic (and futuristic) look back at its work with NASA in the 1960s. The post revisits how foamed metals — often likened to bubble wrap — were explored for lightweight, heat-resistant applications in space.
3. Forging + Metallurgy + Heat Treat = 🔥
The Forging Industry Association was right: watching a glowing billet get squeezed into shape never gets old. Impression die forging gets a clear, engaging showcase that reminds us why classic manufacturing techniques still matter.
4. Metallurgy Brain Teaser
This post from Metallurgical Engineering serves up a quick #metallurgyquiz to test your materials instincts. Are you smarter than your microstructure?
5. LEGO Meets Heat Treatment
SECO/WARWICK brings a playful twist to serious tech on LEGO Day, showing heat treat principles with a LEGO build that earns a smile.
6. Underwater Forging? What Wizardry Is This?
This post is sure to induce some head-scratching among our metallurgists. Is it AI or some genius innovation?
7. Fun Friday Goes Mini-Metal
Heat TreatToday’s own Fun Friday post brightens up the day with curious kids and heat treat fun — proof that inspiration starts young…and queens = 🔥!
8. When Slag Comes Alive
This mesmerizing reel captures molten slag as it cools from 1100°C to 920°C, revealing crystals forming in real time under a high-temperature confocal laser scanning microscope. Swoon-worthy, especially with Olivia Dean singing in the background!
Heat TreatRadio connects energy policy to the realities of manufacturing. Informative, timely, and worth adding to your listening queue.
10. Celebrating the People Behind the Process
February is Black History Month, and MetalTek International reflects on a century of honoring the achievements, resilience, and lasting impact of Black leaders and innovators — including those who have shaped American manufacturing. A thoughtful reminder that the strength of our industry is built by people from all backgrounds, past and present.
From serious engineering insights to lighthearted LEGO builds, this week’s round-up of heat treat social media posts proves there’s no single way to tell the industry’s story. Whether you’re here to learn, be inspired, or just enjoy watching metal move, we’ll keep bringing you the posts worth a pause in your feed. Have a great weekend!
Heat Treat Today publishes twelve print magazines annually and included in each is a letter from the publisher, Doug Glenn. This letter is from theDecember 2025 Annual Medical & Energy Heat Treat print edition.
I believe the accurate saying is, “Don’t despise the day of small beginnings,” but I would like to modify it a bit and talk business.
The Origin of That Saying
First off, the origin of that saying is from a rather obscure Bible verse in the book of Zechariah 4, verse 10, which says, “For who has despised the day of small things? But these seven will be glad when they see the plumb line in the hand of Zerubbabel — these are the eyes of the LORD which range to and fro throughout the earth” (NASB 1995). This verse and another like it in Luke 16, verse 10, which says, “He who is faithful in a very little thing is faithful also in much; and he who is unrighteous in a very little thing is unrighteous also in much,” remind me of the importance of small beginnings.
Sharpening the Saw
In his famous book, 7 Habits of Highly Effective People, Stephen R. Covey lists “sharpening your saw” as one of the seven habits. To put it simply, this means taking regular time to rest from the day-to-day grind and make sure your systems, tools, and being are sharp and ready to perform.
To sharpen my publishing skills, I recently spent two days with a publishing industry colleague and consultant to talk about Heat TreatToday and how I, as the publisher, could be a better leader. It was a very refreshing and enjoyable time that will hopefully bear fruit in the future in the form of better content for our readers and better services for our advertisers.
Did you know…?
I learned a lot during those two days, but there were several statistics that my publisher friend mentioned which captured my attention. Did you know:
Roughly 90% of all businesses in the United States have fewer than 20 employees.
Roughly 75% of all businesses in the United States have fewer than 10 employees.
Talk about small things! I was quite surprised by these numbers. And if you go to the source (Small Business & Entrepreneurship Council 2025), you’ll see that these percentages jump even higher if you include non-employer businesses, meaning companies with only ONE person:
Only 9% of small businesses in the United States have revenues exceeding $1 million (Entrepreneurs HQ 2025).
Only about 2% of all the individuals that start a business, the founders, even make it to the point where their revenues exceed $10 million (Vetter 2019).
Start Small
If you’re one of those individuals who has entertained the idea of starting your own company but have not yet pulled the trigger, let me encourage you to get started. The publication you are reading was started in the evening hours during the fall/winter of 2015 and launched publicly in the beginning of June 2016. To say the least, it was a SMALL business. I remember being so excited when I brought the mail home and showed my wife that my good friends at Dry Coolers (and others) had sent me a $500 check for an ad that they had placed on our newly launched website. It was a thrill and very satisfying.
Get out there and start. Don’t despise the day of small beginnings. Start small and work hard.
References
Covey, Stephen R. 1989. The 7 Habits of Highly Effective People: Powerful Lessons in Personal Change. New York: Free Press.
A manufacturer specializing in advanced thermal management solutions has expanded its production capabilities with the delivery of a new continuous controlled atmosphere brazing (CAB) line. The system will support increased output of high-performance cooling components such as heat dissipation plates for data centers and cold plates for electric vehicles, while also serving demand across aviation, photovoltaics, and rail transport.
The company, a Chinese manufacturer focused on temperature control platforms and cooling systems, is investing in the continuous CAB line to strengthen production capacity and support growing demand for compact, high-efficiency thermal management technologies.
The CAB line, supplied by SECO/WARICK — a global thermal processing equipment manufacturer with operations in North America — features a 1,000mm (39.2 in) belt width and is designed to process multiple product types, including 3D vapor chambers and cold plates. The system includes a dry-off oven for part preparation, a radiation brazing furnace operating in a controlled atmosphere, a clean-out chamber to stabilize internal conditions, an air-jacketed cooling chamber, and a final cooling chamber. An integrated control system enables centralized operation and process management across all stages.
Piotr Skarbiński Vice President of Aluminum and CAB Products Segment SECO/WARWICK
“What makes this project unique is the ability to braze two distinct product groups — 3D-VC (3d vapor chambers) and cold plates — on a single line,” said Piotr Skarbiński, vice president of the Aluminum and CAB Products Segment at SECO/WARWICK. Through tailored throughput calculations and a customized cooling configuration, the system is engineered to deliver temperature uniformity and repeatable process control — factors essential to producing high-quality components for modern electronics and power systems, he adds.
As AI servers, EV systems, and advanced electronics generate increasing heat on compact surfaces, reliable aluminum brazing technologies remain essential to delivering performance, durability, and efficiency in next-generation thermal management systems.
Press release is available in its original form here.
Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about how rising fuel costs have driven dramatic improvements in furnace efficiency and combustion technology over the past 60 years, transforming heat treat processes from 20% to 70% fuel efficiency.
This editorial was first released inHeat Treat Today’sJanuary 2026 Annual Technologies to Watch print edition.
A furnace guy walks into the shop and sees the cost of gasoline. “This keeps going up, what gives?”
My first car got about 10 MPG — we will not even go near to discussing when that was. Gasoline costs have since driven cars to become more efficient with 30+ MPG vehicles.
Last month’s article highlighted how there are five qualities in our heat treat processes: Quality and Accuracy, the necessary attributes; Efficiency and Performance, the variables; and Profit, which comes whenever we improve the two variables. We have discussed government regulation on emissions and technological breakthroughs that improved combustion technology in earlier articles, but now we turn to the connection of combustion and cost: how gasoline costs drove improvement of the two variable qualities of heat treat processing for combustion, Efficiency and Performance.
Gasoline Costs: A Timeline
Up until about 1960, the world of heat processing was pretty much a level playing field with Efficiency and Performance. We had tons of fuel at our disposal. Pollution was known but not yet a criterion to manage processes. So, burner efficiency and design were very low end. Nobody cared. Fuel was almost free. In doing research for this story, I found records of natural gas being less than $0.50 per million BTUs. Electricity was on par with delivered BTU costs. But then the cost of fuel started to fluctuate. The furnace guys started to notice; if nothing else changed, our friend Profit would weaken.
From 1930 to 1980, electricity pricing went up 500%. Natural gas started to bounce around in price. It was less than a $1.00/thm in the ’60s and ’70s, peaking during times of fuel shortage at $16.00/thm. Ten years later, in 2016, it hit $2.30/thm again. Some pretty wild fluctuations. In fact, it should be noted that the industry overseas had already begun to shift technologies — several years ahead of the U.S. — because they had been suffering with high fuel costs in Great Britain, Germany, Western Europe, and in Asian markets.
Furnace guy and the suppliers had to improve the efficiency and performance.
Troubleshooting and Combustion Design Changes
At first, you look at easy fixes to improve Efficiency and Performance. An example would be that insulation and refractory science really improved. If you can keep the heat in the furnace, you need less fuel to hold it at these high temperatures, right? So, improve the insulation.
Next, let’s get the burners from just being the opening in the furnace that you pour gas into, and make the burner more like a carburetor on an engine. Let’s get control of the air and gas ratios.
Next, let’s recover some of the flue gases and pre-heat the air coming into the burner. When you do that, the flame temp goes up, sometimes by as much as 400-500°F. That means higher heat transfer rates to the parts inside a now well-insulated furnace. Huge efficiency gains started happening.
Efficiency and Performance got a huge boost when the burners started to have high velocity discharge rates. In other words, we now had flames that were hotter and going into the furnace at several hundred miles an hour more than before. With that comes circulation improvement inside the furnace. And much like pudding in a blender, the faster the beaters, the smoother the mix. To give you an idea of the scope of these improvements, form 1960 to 1990, a matter of only 30 years, furnace and burner technology improvements went from 20% fuel utilization to estimated 60-70% fuel efficiencies, even higher in some instances. And there it was, super efficiency driven to occur by fuel cost and flucturation of supply.
To really hit home what that meant, let’s look at a 1,000-lb load of steel. Our process temp is 1750°F. Our furnace and combustion efficiency used to be 20%. That would require 1,370,000 BTU to heat up in an hour. Now, with 75% furnace and burner efficiency, that’s 352,000 BTU. You just saved approximately 1,000 ft3 of gas per hour! If we use the average industrial gas price today at $3.80/1,000 ft3, the difference of all this is $24,000/year, and that’s just a 1,000-lb load. Real world, the numbers are significantly higher, as all you furnace guys know. Imagine the dollar savings when fuel was at $16.00/thm?
And so, there it is. The well-known realization that in most markets, the dollar cost of the energy triggers improvement of technology.
Until next time…
About The Author:
Jim Roberts President US Ignition
Jim Roberts president at U.S. Ignition, began his 45-year career in the burner and heat recovery industry focused on heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.
TFL Incorporated, a Houston-based provider of refractory materials and precast shapes, has been acquired in a move that strengthens resources and technical support for high-temperature industries. The acquisition enhances service capacity and product availability for clients operating in demanding thermal-processing environments, including sectors that rely on consistent refractory performance to maintain uptime and efficiency.
Click the image above to read more about a related refractory acquisition.
TFL has long specialized in the distribution and manufacturing of refractory materials and precast refractory shapes for industrial applications requiring durable, heat-resistant solutions. Its expertise supports operations across energy, petrochemical, and other high-heat industries throughout the Gulf Coast region.
Plibrico Company, a manufacturer of monolithic refractories and engineered refractory solutions, completed the acquisition as part of its continued growth strategy. The addition of TFL expands Plibrico’s geographic footprint, particularly in Texas and the Southern U.S., and strengthens its ability to deliver comprehensive refractory products and technical services to customers facing increasingly complex thermal processing demands.
John Paul Surdo President and CEO Plibrico Company
“This combination enhances the technical and operational strengths that matter most in the field,” said John Paul Surdo, president and CEO of Plibrico. He noted that TFL’s established customer relationships, combined with Plibrico’s engineering depth and precast abilities, provide broader solution options and strengthened technical collaboration for clients across key industrial markets it serves.
Press release is available in its original form here.
Heat Treat Today has gathered the four heat treat industry-specific economic indicators for February 2026. The February results show building momentum compared to the January 2026 predictions.
February’s data points to a steady manufacturing environment, as all four indices remain above the growth threshold, driven by a notable jump in expectations for growth in the Number of Inquiries at 67.5 (up from 56.9 in January). Bookings stayed firmly in growth territory, reflecting stable demand at 58.2 (from 59.5 in January). The Backlog index showed modest softening but remained neutral, indicating balance rather than decline at 52.5 (from 57.8 in January). Finally, the Health of the Manufacturing Economy index continued its upward trend at 57.9 (up from 56.1 in January).
February’s indicators reinforce a theme of stability with underlying momentum. While month-to-month fluctuations remain, the overall picture points to resilience and selective strengthening as the industry moves deeper into the first quarter.
The results from this month’s survey (February) are as follows: numbers above 50 indicate growth, numbers below 50 indicate contraction, and the number 50 indicates no change:
Anticipated change in Number of Inquiries from January to February:67.5
Anticipated change in Value of Bookings from January to February: 58.2
Anticipated change in Size of Backlog from January to February: 52.5
Anticipated change in Health of the Manufacturing Economy from January to February: 57.9
Data for February 2026
The four index numbers are reported monthly by Heat Treat Today and made available on the website.
Heat TreatToday’sEconomic Indicatorsmeasure and report on four heat treat industry indices. Each month, approximately 800 individuals who classify themselves as suppliers to the North American heat treat industry receive the survey. Above are the results. Data collection began in June 2023. If you would like to participate in the monthly survey, please click here to subscribe.
Global pipe manufacturer Tenaris has reactivated quenching and tempering operations at its Koppel, Pennsylvania facility, restoring a critical stage of in-house heat treating capacity that supports domestic oil country tubular goods (OCTG) production for the U.S. energy sector. The restart reinforces supply chain reliability for clients requiring high-performance steel pipe.
Guillermo Moreno President Tenaris U.S.
The reactivation follows Tenaris’s broader investment in its Pennsylvania operations and coincides with the reopening of the adjacent steel mill. “Reopening the heat treatment and finishing lines in Koppel reinforces the strength of our domestic production capabilities for our clients across the U.S.,” says Guillermo Moreno, Tenaris U.S. President. “Koppel remains a cornerstone of our U.S. operations, allowing us to deliver high-quality steel products that support U.S. energy and industrial needs.”
Tenaris operates an integrated steel pipe manufacturing system across Pennsylvania and Ohio. At the Koppel facility, steel billets are produced in an electric arc furnace and shipped to Ambridge, Pennsylvania, where they are rolled into seamless OCTG to client specifications. The pipes are then returned to Koppel for quenching and tempering, followed by finishing, nondestructive testing, and inspection.
In the final stage of production, the pipes are sent to Tenaris’s Brookfield, Ohio, facility for threading and final inspection before shipment to oil and gas clients across the United States. With the Koppel heat treatment lines back online, Tenaris strengthens its U.S. production capabilities and continues delivering high-performance steel products for energy and industrial applications.
Press release is available in its original form here.
Insufficient austenitizing affects far more than final hardness. It disrupts phase transformation, weakens mechanical performance, and increases the risk of distortion or failure in demanding service conditions. In this Technical Tuesday installment, Ana Laura Hernández Sustaita, founder of Consultoría Carnegie, explains the metallurgical origins of incomplete austenite formation, how furnace uniformity, heating rate, steel chemistry, and part geometry contribute to the problem, and modern process-control and simulation strategies that ensure full transformation and repeatable, high-quality results.
This informative piece was first released inHeat Treat Today’sJanuary 2026 Annual Technologies To Watch print edition.
When a steel part is insufficiently austenitized, it is commonly referred to as underhardening, the resulting loss of hardness after quenching. However, in this article, we will extend the discussion beyond hardness alone, exploring the phenomenon of insufficient austenitizing, analyzing its causes and direct influence on microstructure and mechanical properties, and discussing modern strategies to prevent it.
The Role of Austenitizing in Heat Treatment
The main purpose of heat treatment is to produce a homogeneous or a desired mixed microstructure that ensures the required mechanical properties for the intended service conditions: tensile strength, impact resistance, yield strength, etc. Austenitizing is the first critical step for many processes. It involves heating the steel above the A3 temperature (typically 30–50°C or 85–120°F higher) to transform its microstructure into a face-centered cubic (FCC) lattice for a certain period of time. This step resets the steel’s structural history, particularly after casting, forging, or rolling, and defines the baseline for subsequent quenching and tempering operations.
What Is Insufficient Austenitizing?
Figure 1. Time-temperature-austenitization diagram for Ck 45 (SAE/AISI 1045) steel. | Image Credit: Figure 7, ASM International 2013
Austenite formation involves structural and compositional changes influenced by the initial microstructure and the steel’s chemical composition. When austenitizing parameters are not properly established, such as insufficient temperature, inadequate soaking time, or poor furnace performance (e.g., lack of thermal uniformity), the transformation remains incomplete. The result is a microstructure containing undesired residual phases that compromise hardness, dimensional stability, and mechanical strength. Therefore, any microstructure that fails to fully transform to austenite due to these factors can be directly associated with insufficient austenitizing.
Common causes of insufficient austentizing include:
Inadequate austenitizing temperature: Ferrite and carbides do not fully dissolve if the temperature is too low.
Insufficient holding time: A short soak time prevents uniform carbon diffusion throughout the austenite.
Thermal non-uniformity in the furnace (cold zones): This leads to regions with different degrees of transformations.
Chemical composition of the steel: Alloying elements modify diffusion kinetics and impact the critical transformation temperatures.
Geometry and dimensions of the part: Larger cross-sections require longer soak times for full heat diffusivity.
Rapid heating rates: Excessive heating, especially during induction hardening, can result in structural inhomogeneity and incomplete transformation.
Effects of Insufficient Austentizing
Heterogeneous Microstructure
As illustrated in the ASM Handbook, Volume 4A: Steel Heat Treating Fundamentals and Processes (2013), the kinetics of austenite formation depend strongly on the heating rate. At lower heating rates, diffusion-driven homogenization occurs at relatively lower temperatures, whereas rapid heating produces microstructural heterogeneity, an effect that is especially critical in induction or direct-flame heating. In other words, insufficient austenitizing is more likely to occur when high heating rates are used.
Consequently, a microstructure with heterogeneous composition leads to variations in the martensite transformation temperatures (Ms and Mf) throughout the part. During quenching, regions with lower carbon content transform earlier, producing softer martensite, while areas with higher carbon content transform at lower temperatures, resulting in internal stresses and an overall inconsistent microstructure.
Risk of Distortion and Premature Failure
The transformation from BCC or BCT to FCC (Defined: BCC: body-centered cubic; BCT: body-centered tetragonal; FCC: face-centered cubic) lattice during austenitizing involves a specific volume change. If this transformation occurs unevenly, differential expansion generates internal stresses, distortion, and in severe cases, microcracks. Rapid heating or poor furnace convection exacerbates these effects by producing steep temperature gradients across the part.
Reduced Hardness and Mechanical Strength
Incomplete transformation leaves undissolved carbides and residual ferrite, reducing hardenability and the amount of carbon in solid solution. This limits the formation of martensite during quenching and lowers final hardness and strength.
Increased Brittleness and Lower Toughness
A mixed structure of ferrite, pearlite, partial martensite, and retained austenite results in mechanical anisotropy and reduced energy absorption under impact loading. This condition increases the risk of brittle fracture, particularly in high-stress or cyclic applications.
How to Prevent Insufficient Austenitizing
Accurate Furnace Control
Figure 2. Example of loading analysis | Image Credit: Consultoría Carnegie
To ensure proper process control during the soaking stage, it is essential to use calibrated thermocouples strategically positioned inside the furnace to obtain accurate temperature measurements. Regular calibration prevents temperature reading errors and directly contributes to heat treatment quality. It is also important to get advice from an expert to determine the recommended service life of the thermocouples. Maintaining proper traceability and replacing them at the appropriate intervals ensures optimal system performance.
Additionally, the use of internal circulation fans in convection furnaces helps maintain thermal uniformity, preventing the formation of hot or cold zones.
Another method to monitor and control process temperature is using temperature data loggers. These devices, which are connected to contact thermocouples and placed directly on the parts, are especially recommended for components with complex geometries or large cross-sections. They record real-time temperature data throughout the process, allowing verification that no transient fluctuations occur during the soaking period.
Accurate Loading Distribution
For loads where heat treatment must be applied to a significant number of parts, it is recommended that a study be conducted to determine the maximum stacking height that will ensure proper heat flow and uniform heating. A preliminary assessment can be performed by strategically placing thermocouples in different locations and on different parts, for example, on the first part in the load, one in the middle section, and another at the bottom of the stacking tower.
Once the parts enter the process, their heating behavior can be monitored to verify that the soaking time is sufficient for all pieces in the stack to complete their transformation upon reaching the target temperature or to determine whether adjustments to the loading configuration are necessary.
Use of Thermodynamic Simulation to Optimize Process Parameters
Each steel grade has an optimum austenitizing temperature in function of its chemical composition. For carbon steels (10XX series), these temperatures can be estimated using the Fe–C diagram; however, once alloying elements are added, this diagram is no longer sufficient. In such cases, it becomes necessary to rely on critical temperature calculations or on more advanced tools such as thermodynamic simulations using specialized software, like Thermo-Calc®.
Although the ideal scenario would be to heat treat each material at its specific optimum temperature, this approach is impractical in industrial production; the required processing of each part individually would slow the manufacturing line and increasing resource consumption, including time and fuel.
Thermodynamic tools such as Thermo-Calc allow engineers to evaluate how variations in chemical composition (arising from casting tolerances or adjustments in alloying elements) affect transformation temperatures. This enables the selection of an optimum processing temperature that ensures complete austenitization for all possible compositional variations within the specification. As a result, the heat treatment operation becomes more robust, more reproducible, and more energy efficient.
For example, in Figure 3, if a 4140 steel is heated only to 750°C (1380°F) instead of 850°C (1560°F), the ferrite will not fully dissolve. As a result, the microstructure will consist of soft martensite and residual ferrite after quenching, rather than a fully homogeneous and hard martensitic structure. This significantly reduces the material’s hardness and mechanical strength.
Figure 3. Equilibrium diagram, AISI 4140 0.38C, 0.78Mn, 0.85Cr, 0.22Mo (%wt.) | Image Credit: Consultoría CarnegieFigure 4. Histogram of Ac3 transformation temperature for AISI 4140 steel within the specification range. | Image Credit: Consultoría Carnegie
We can observe in the histogram (Figure 4) that even within the same steel grade, the A3 temperature can vary from approximately 760−776°C (1400−1429°F) solely due to the composition tolerances specified for the alloy. If we also consider the presence of residual or microalloying elements, it becomes clear that we cannot expect identical behavior during heat treatment or identical mechanical properties across all heats.
In such cases, thermodynamic tools allow us to evaluate a batch of possible chemistries and determine an optimal austenitizing temperature that is suitable for all compositional variations.
Heating Curve Design
To ensure that transformation temperatures are reached uniformly (whether in processes involving large loads or parts with variable geometries), it is advisable to implement controlled heating rates. Although this approach may increase processing time, the benefits include reduced distortion risk and assurance of complete austenitic transformation.
The key is to design an appropriate time–temperature profile, which depends on factors such as part dimensions and material properties, including thermal diffusivity, heat capacity, density, and thermal conductivity.
Conclusion
Insufficient austenitizing, also known as underhardening, represents far more than a loss of hardness. It is a metallurgical deficiency that affects microstructural homogeneity, dimensional stability, and mechanical performance. Through rigorous control of temperature, time, and furnace uniformity combined with modern simulation tools, engineers can ensure reliable transformations, minimize distortion, and achieve consistent high-quality results in steel heat treatment.
Callister, W. D. 2019. Materials Science and Engineering: An Introduction. Hoboken, NJ: Wiley.
Herring, Dan. Metallurgical Fundamentals of Heat Treatment. Industrial Heating.
Krauss, G. 1980. Principles of Heat Treatment of Steel. ASM International.
Nuñez González, G. 1990. Fallas en los Tratamientos Térmicos para Aceros Herramienta.
Thomas, L. 2018. “Austenitizing Part 2: Effects on Properties.” Knife Steel Nerds. https://knifesteelnerds.com/2018/03/01/austenitizing-part-2-effects-on-properties/.
Totten, G. E. 2007. Steel Heat Treatment: Metallurgy and Technologies. Boca Raton, FL: CRC Press.
About The Author:
Ana Laura Hernández Sustaita Founder Consultoría Carnegie
Ana Laura Hernández Sustaita holds a Master’s degree in Materials Science and engineering. She is the founder of Consultoría Carnegie, a technical consulting and training firm specializing in steel heat treatment in Mexico. Additionally, she works as a technical support engineer at Thermo-Calc Software, providing assistance to clients across México, Canada, and United States of America. Ana actively promotes metallurgical education throughout Latin America and advocates for the integration of computational tools into industrial heat treatment practice.
Un austenizado insuficiente afecta mucho más que la dureza final. Interrumpe la transformación de fase, debilita el rendimiento mecánico y aumenta el riesgo de deformación o fallo en condiciones de servicio exigentes. En esta entrega de Technical Tuesday, Ana Laura Hernández Sustaita, fundadora de Consultoría Carnegie, explica los orígenes metalúrgicos de la formación incompleta de la austenita; como la uniformidad del horno, la velocidad calentamiento, la composición química del acero y la geometría de la pieza, contribuyen a ese problema; y las estrategias modernas de control de procesos y simulación que garantizan una transformación completa y resultados repetibles de alta calidad.
Este artículo informativo se publicó por primera vez enHeat Treat Today’sJanuary 2026 Annual Technologies To Watch print edition.
En inglés, el término underhardening se utiliza para describir aceros que no alcanzan una austenización completa, lo que se traduce en una pérdida de dureza después del temple. Sin embargo, en este artículo ampliaremos el análisis más allá de la dureza, centrándonos en el fenómeno de la austenización insuficiente, analizando sus causas, su influencia directa en la microestructura y en las propiedades mecánicas, así como las acciones que podemos implementar en el proceso para prevenirla.
El rol del proceso de austenización
El objetivo principal del tratamiento térmico es obtener una microestructura homogénea o mixta que garantice las propiedades mecánicas requeridas para las condiciones de servicio establecidas: resistencia a la tracción, resistencia al impacto, límite elástico, entre otras.
El proceso de austenización es el primer paso crítico para muchos procesos. Consiste en calentar el acero por encima de la temperatura A3 (normalmente entre 30 y 50°C/85 y 120°F adicionales) para obtener una microestructura con red cúbica centrada en las caras (FCC) durante un tiempo determinado. Este paso es fundamental después de procesos como solidificación, forja o laminado, ya que “reinicia” la historia microestructural del acero.
¿Qué es la austenización insuficiente?
Figura 1. Diagrama tiempo-temperatura de austenización para acero Ck 45 (SAE/AISI 1045). | Image Credit: Figure 7, ASM International 2013
La formación de austenita implica cambios estructurales y composicionales influenciados tanto por la microestructura inicial como por la composición química del acero. Cuando los parámetros de austenización no se establecen adecuadamente: temperatura insuficiente, tiempo de permanencia corto o problemas de desempeño del equipo, como la falta de uniformidad térmica del horno, la transformación no se completa. El resultado es una microestructura que conserva fases no deseadas, lo que afecta la dureza, la estabilidad dimensional y la resistencia mecánica. Por lo tanto, cualquier microestructura que no logre transformarse completamente a austenita debido a los factores mencionados puede considerarse un caso de austenización insuficiente.
Causas de la Austenización Insuficiente:
Temperatura de austenización inadecuada: si la temperatura es demasiado baja, no se logra la disolución completa de ferrita o carburos.
Tiempo de empape insuficiente: un tiempo de empape (permanencia) demasiado corto impide la difusión homogénea del carbono en la austenita.
Distribución térmica no uniforme en el horno: produce zonas con distintos grados de transformación.
Composición química del acero: los elementos de aleación modifican la cinética de difusión y desplazan las temperaturas críticas de transformación.
Geometría y dimensiones de la pieza: las secciones más grandes demandan mayor tiempo de empape, para alcanzar el calentamiento completo.
Velocidades de calentamiento rápidas: pueden impedir la homogeneización de la microestructura y generar una transformación incompleta, especialmente en procesos por inducción.
Efectos de una austenización insuficiente
Microestructura heterogénea
Tal como se ilustra en el ASM Handbook, Volume 4A: Steel Heat Treating Fundamentals and Processes, la cinética de formación de la austenita depende fuertemente de la velocidad de calentamiento. A bajas velocidades, la homogeneización por difusión ocurre a temperaturas relativamente menores; en contraste, los calentamientos rápidos generan heterogeneidad microestructural, un efecto especialmente crítico en procesos como el endurecimiento por inducción o el calentamiento directo por flama. En otras palabras, la austenización insuficiente se presenta con mayor frecuencia cuando se emplean altas velocidades de calentamiento.
En consecuencia, una microestructura con composición heterogénea provoca variaciones en las temperaturas de transformación martensítica (Ms y Mf) a lo largo de la pieza. Durante el temple, las regiones con menor contenido de carbono transforman primero, originando una martensita más suave, mientras que las zonas más ricas en carbono transforman a menores temperaturas, generando tensiones internas y una microestructura inconsistente.
Mayor riesgo de deformaciones y fallas prematuras en servicio
Anteriormente se mencionó que el proceso de austenización implica un cambio en la estructura cristalina del material. Si este cambio no es homogéneo a lo largo de la pieza, se presentarán diferentes fases, resultando en un arreglo cristalográfico variado y, por ende, un cambio volumétrico. Por otra parte, calentar una pieza muy rápidamente provoca que el calor no se distribuya ni penetre de manera uniforme, causando transformaciones heterogéneas y, por lo tanto, tensiones debido a los cambios volumétricos en la estructura cristalina.
Reducción en la dureza y resistencia mecánica
Una austenización incompleta deja restos de ferrita o carburos no disueltos en la microestructura, que impide la transformación completa a martensita durante el temple, reduciendo la dureza final. Además, una menor cantidad de carbono en solución afecta negativamente la resistencia mecánica.
Aumento de la fragilidad y menor tenacidad
Una microestructura heterogénea (ferrita y perlita con martensita parcial y austenita retenida) disminuye la resistencia mecánica. Esto se traduce en menor capacidad para soportar cargas sin fracturarse.
Como prevenir la austenización ineficiente
Control preciso de temperatura y tiempo del horno
Figura 2. Ejemplo de un análisis de carga | Image Credit: Consultoría Carnegie
Para garantizar un control adecuado durante el mantenimiento, es fundamental utilizar termopares calibrados y ubicarlos estratégicamente dentro del horno para asegurar mediciones precisas. La calibración periódica previene errores en la lectura de temperatura, lo que contribuye directamente a la calidad del proceso. Además, es indispensable contar con la asesoría de un experto para determinar la vida útil recomendada de los termopares. Mantener una trazabilidad adecuada y realizar los reemplazos en tiempo y forma asegurará un funcionamiento óptimo del sistema.
Por otra parte, el uso de ventiladores internos en hornos de convecciones nos ayudara a mantener una uniformidad térmica dentro del horno, evitando zonas frías o calientes.
Otra forma de poder controlar la temperatura del proceso es el uso de registradores de temperatura o graficadores de temperatura. Estos dispositivos, conectados a termopares de contacto instalados directamente en las piezas, son especialmente recomendables para componentes con geometrías complejas con grandes espesores. Su función es registrar la temperatura en tiempo real y verificar que no existan fluctuaciones durante el tiempo de mantenimiento.
Distribución adecuada de la carga
En cargas donde es necesario realizar el tratamiento térmico de una cantidad considerable de piezas, es recomendable llevar a cabo un estudio para determinar la altura máxima de apilamiento que permita un flujo de calor adecuado y un calentamiento homogéneo. Un análisis preliminar puede realizarse colocando termopares estratégicamente en diferentes ubicaciones y en distintas piezas: por ejemplo, en la primera pieza de la carga, otra en la parte media y una más en la parte inferior de la torre de apilamiento.
Una vez que las piezas ingresan al proceso, es posible monitorear el comportamiento térmico de cada una de ellas, verificando que el tiempo de empape sea suficiente para que todas alcancen la transformación requerida al llegar a la temperatura objetivo, o bien, determinar si es necesario realizar ajustes en la configuración de la carga.
Uso simulación termodinámica para optimizar los parámetros del proceso
Cada grado de acero tiene una temperatura óptima de austenización determinada por su composición química. En los aceros al carbono (serie 10xx), estas temperaturas pueden estimarse mediante el diagrama Fe–C; sin embargo, cuando se incorporan elementos de aleación, dicho diagrama deja de ser suficiente. En esos casos, es necesario recurrir al cálculo de temperaturas críticas o al uso de herramientas más precisas, como simulaciones termodinámicas mediante software especializado, por ejemplo, Thermo-Calc®.
Aunque lo ideal sería tratar cada material a su temperatura específica, en la producción industrial esto no es eficiente, ya que implicaría procesar cada pieza de manera individual, lo cual ralentizaría la línea de fabricación y aumentaría el consumo de recursos, como tiempo y gas.
El uso de herramientas termodinámicas como ThermoCalc software ® permite evaluar cómo las variaciones en la composición química (debidas a tolerancias de colada o ajustes en elementos de aleación) afectan las temperaturas de transformación. Esto facilita la selección de una temperatura óptima de proceso que garantice que, para cada composición posible dentro de las especificaciones, las temperaturas de austenización sean las adecuadas. Con ello se optimiza el rendimiento del tratamiento térmico y se mejora la reproducibilidad del proceso.
Por ejemplo, en la figura 3, si un acero 4140 se calienta únicamente a 750°C (1380°F) en lugar de 850°C (1560°F), la ferrita no se disolverá por completo. Como resultado, después del temple se obtendrá una microestructura compuesta por martensita blanda y ferrita residual, en lugar de una martensita homogénea y dura. Esto reduce significativamente la dureza y la resistencia mecánica del material.
Figura 3. Diagrama de un eje para un acero 4140, (Fe, 0.4C, 0.8Mn, 0.2Si, 0.8Cr, 0.2Mo, 0.02Ni) | Image Credit: Consultoría Carnegie Figura 4. Histograma de la temperatura de transformación Ac3 para un acero AISI 4140 dentro del rango de especificación. | Image Credit: Consultoría Carnegie
En el histograma (figura 4) podemos observar que, incluso tratándose del mismo grado de acero, la temperatura A₃ puede variar aproximadamente 760−776°C (1400−1429°F) únicamente debido a las tolerancias químicas establecidas en la especificación. Si además consideramos la presencia de elementos residuales o microaleantes, es evidente que no podemos esperar el mismo comportamiento durante el tratamiento térmico ni las mismas propiedades mecánicas en todas las coladas.
En estos casos, herramientas termodinámicas como ThermoCalc software® permiten evaluar un conjunto amplio de posibles composiciones químicas y determinar una temperatura de austenización óptima que sea adecuada para todas las variaciones permitidas dentro de la especificación.
Diseño de curvas/rampas de calentamiento
Para asegurar que las temperaturas de transformación se alcancen de manera homogénea (tanto en procesos con cargas de alto volumen, como en piezas con geometrías variables) es recomendable implementar un calentamiento controlado. Aunque esto puede aumentar el tiempo de procesamiento, los beneficios incluyen una menor probabilidad de distorsión y la garantía de lograr una transformación austenítica completa.
La clave radica en diseñar un perfil adecuado de tiempo–temperatura, el cual dependerá de factores como las dimensiones de la pieza y las propiedades del material, entre ellas: difusividad térmica, capacidad calorífica, densidad y conductividad térmica.
Conclusión
La austenización insuficiente, conocida como underhardening, representa mucho más que una simple pérdida de dureza. Es una deficiencia metalúrgica que afecta la homogeneidad microestructural, la estabilidad dimensional y el desempeño mecánico.
Mediante un control riguroso de la temperatura, el tiempo y la uniformidad del horno, combinado con herramientas modernas de simulación, los ingenieros pueden asegurar transformaciones confiables, minimizar la distorsión y lograr resultados constantes y de alta calidad en el tratamiento térmico de los aceros.
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Nuñez González, G. 1990. Fallas en los Tratamientos Térmicos para Aceros Herramienta.
Thomas, L. 2018. “Austenitizing Part 2: Effects on Properties.” Knife Steel Nerds. https://knifesteelnerds.com/2018/03/01/austenitizing-part-2-effects-on-properties/.
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Acerca de la autora:
Ana Laura Hernández Sustaita Fundadora Consultoría Carnegie
Ana Laura Hernández Sustaita cuenta con Maestría en Ciencia e Ingeniería de los Materiales, Es fundadora de Consultoría Carnegie, una firma de consultoría y capacitación técnica especializada en el tratamiento térmico de aceros en México. Asimismo, se desempeña como Ingeniera de Soporte Técnico en Thermo-Calc Software, brindando asistencia a clientes en México, Canada y Estados Unidos de América. Ana promueve activamente la educación metalúrgica en Latinoamérica y fomenta la integración de herramientas computacionales en la práctica industrial del tratamiento térmico.
In today’s News from Abroad installment, we highlight several major global developments — from furnace upgrades and smarter heating technologies to expanded structural steel capacity and induction heating acquisitions — reflecting continued investment in efficient, modern metal processing worldwide.
Heat TreatTodaypartners with two international publications to deliver the latest news, tech tips, and cutting-edge articles that will serve our audience — manufacturers with in-house heat treat. Furnaces International, a Quartz Business Media publication, primarily serves the English-speaking globe, and heat processing, a Vulkan-Verlag GmbH publication, serves mostly the European and Asian heat treat markets.
Tonggang optimizes ladle furnace performance with Primetals Technologies revamp.
“Primetals Technologies has completed a ladle furnace upgrade at Tonghua Iron and Steel (Tonggang) in Jilin Province, China. The project included the manufacture and installation of three-phase electrode arms and commissioning services. Primetals highlighted that the copper-clad electrode arms help increase power output, improve clamping precision, and maximize service life. Furthermore, they outlined that they also reduce energy consumption.”
High-Efficiency Burner Technology Improves Furnace Performance in Aluminum Manufacturing
The plant specializes in high-quality aluminum wire for the energy and automotive industries.
“TRIMET has upgraded its foundry’s energy efficiency with regenerative burner technology. The facility, located in Saint-Jean-de-Maurienne, France, has equipped its two furnaces of the plate casting machine with this new system.”
“Regenerative burners work on the principle of heat recovery: instead of venting hot exhaust gases unused, their thermal energy is stored in a heat exchanger and then used to preheat the comnustion air. This reduces the energy requirements of the gas burners and substantially lowers natural gas consumption as well as the foundry’s CO2 emissions.”
Structural Steel Capacity Set to Double at Major Indian Facility
Jindal aims to boost structural steel capacity to support infrastructure and industrial demand. | Source: Adobe Stock / industrieblick
“Jindal Steel announced a significant expansion of its structural steel manufacturing capabilities at its Raigarh facility, under which the company will double its existing structural steel capacity from 1.2 million tons per annum (MTPA) to 2.4 MTPA by mid 2028.”
“As part of the expansion roadmap, Jindal Steel will commission a new, dedicated structural steel mill, alongside advanced upstream and downstream technology upgrades. This will enable the manufacture of larger, heavier, and more complex parallel flange sections required for next-generation infrastructure and energy projects.”
Metal Processing Sees Boost from Induction Heating Acquisition
Teams of ANDRITZ and Sanzheng come together at final closing. | Source: ANDRITZ
“International technology group ANDRITZ has acquired a 51% stake in Baoding Sanzheng Electrical Equipment Co., Ltd., a China-based provide of advanced industrial induction heating systems. This further acquisition strengthens ANDRITZ’s position as a comprehensive solutions provider for steel processing, in particular electric steel.”
“The expanded offering strengthens the group’s ability to deliver full-line solutions for electrical steel processing, galvanizing, annealing, and forging.”
