Whether you need insight on enhancing your energy utilization, managing induction systems (troubleshooting), or prolonging equipment longevity, today’s Technical Tuesday original content feature will keep you well-informed.
Heat TreatToday has coalesced technical information across articles from key experts, including tips to improve your energy efficiency, a walk-through guide for troubleshooting your induction system, and ten practical tips for improving your equipment longevity.
Induction and Sustainability Tips Part 2: Efficient Power
As energy efficiency becomes a driving force in modern heat treating, manufacturers are turning to smarter induction technologies to cut waste and lower costs. In this second installment of Heat Treat Today’s sustainability series, explore how AC-to-DC conversion, intelligent power feedback systems, and advanced diagnostics can transform your induction heating setup into a cleaner, more consistent, and cost-effective process.
“Furthermore, transformers operate at optimal efficiency when under a reduced load – i.e., less than 70% output in steady-state heating – rather than ramping up to the full operating temperature. Another advantage of the DC-type transformer is that its operating power factor is very close to 1.0, which lowers the utility company’s calculation of peak demand surcharges.”
Facing erratic heating, poor consistency, or unexpected shutdowns in your induction system? This comprehensive guide walks heat‑treat operators through a ten‑step diagnostic framework for identifying and resolving common induction issues.
Figure 2. Induction
system components Source: Contour Hardening, Inc.
“The induction process involves many characteristics such as: position of the piece within the induction coil, load positions, cooling positions, cycle times, applied electric power, and others. It is important that the professional can identify the failure and the particular situation at the moment in which it is occurring.
On some occasions, the failures are not evident and therefore it is essential to analyze the part that has been treated. This analysis can be key to understanding situations such as poor depth due to electrical power or decrease in output frequency, among other possible scenarios.”
New and Improved Tips for Induction Equipment Longevity
Heat treaters are always looking for ways to extend the life of their induction tools, but what methods are proven maintenance strategies? Focusing on the durability of coils, bus bars, inductors, and quench components, this technical article will give you practical and reliable tips to promote longevity in your equipment.
Figure 2. Break-Away bolts designed to fail beneath the washer if over tightened
“More than coils — When working to optimize the life of induction equipment, don’t focus solely on the coils. Bus bars, inductors, and quenching equipment are also key to success.
Austenitic stainless steel — Use austenitic stainless steel for fasteners, fittings, and hose clamps, and remember, non-ferrous is the way to go.
CNC machining — Manufacturing with a 5-axis CNC machine ensures quality and consistency.
“Break-Away” bolts — For fasteners, use “Break-Away” bolts on contact surfaces. These bolts are designed to fail beneath the washer if they are overtightened, a design that prevents damage to the threaded insert inside the copper contact.”
By Jose Miguel Equihua Toral, Head of the New Projects and Development, BOINSA Mexico and Manager,InTech NDT, USA.
Nondestructive testing (NDT) techniques have been used exclusively to detect defects in structures and components after they have been manufactured. To protect public safety and security, it is imperative to test parts efficiently and ensure their quality. Nondestructive evaluation, like ultrasonic backscattering, serves an important role in this area.
This informative piece was first released inHeat TreatToday’sApril 2025 Annual Induction Heating & Melting print edition.
Induction hardening is a critical process in manufacturing automotive, agricultural, and aeronautical components, such as crankshafts, camshafts, constant velocity joints, and axle shafts (Figure 1a). The procedure for the evaluation of metallurgical characteristics is carried out in the laboratory and is destructive testing (Bernard, “Methods of Measuring Case Depth in Steels”). This means the component will be unusable. Additionally, this procedure is time-consuming, expensive, and cannot be integrated into the production line. Over time, the industry has sought faster and more efficient methods to evaluate metallurgical characteristics, such as eddy current testing, magnetic methods, and ultrasound. Having the capability of monitoring material properties after each key process can help minimize the cost of processing out-of-specification material. A combination of nondestructive testing methods can help to guarantee the quality of induction heat treatment operations (ASM Handbook, vol 4c).
Ultrasonic methods, for example, can be used to determine microstructural differences in metals. For this, contact testing with pulse-echo technique is used. For inductive-hardened parts, the ultrasonic backscattering method works because the hardened layer (martensite) is almost transparent to ultrasonic waves (in range of 20 MHz), while bulk material (ferrite-pearlite) scatters ultrasonic waves very strongly.
In this article, we will address the use of industrial ultrasound applying the backscattering technique, which offers a direct determination of the depth. This method is simple and does not require prior calibration to evaluate the components (Figure 1b).
Iron crystals exhibit notable acoustic anisotropy, meaning the acoustic velocity (c) varies depending on the direction of travel within the crystal. Grain boundaries represent transitions between crystal structures with varying orientations. The resulting variation in impedance causes the ultrasonic pulse to scatter at the grain boundaries. The ultrasonic technique for measuring hardness depths (SHD) utilizes this grain boundary scattering effect. This technique is known as the ultrasonic backscattering method (Kruger et al., “Broadband Ultrasonic Backscattering”).
The ultrasonic backscattering method for hardness depth testing relies on finding the ultrasound frequency that does not scatter at the fine-grained hardened microstructure of the outer layer but at the coarse-grained core material (Figure 2a). The different scattering properties from the varied grain sizes of the hardened surface layer and the core material are seen in the backscattering measurement. The connection between scattering and the material’s grain size is utilized to produce a detectable backscattering echo when the ultrasound penetrates the core material.
The depth (SHDUS) of the interface can be determined using the time (t) it takes for the sound pulse to reach the scattering interface, the angle of the shear wave (βT), and the velocity (c) of the shear wave in steel. Therefore, the following equation is relevant for a flat shape:
SHDUS=1/2∙c∙t∙cos∙βT
Based on this equation, the acoustically measured surface hardness depth (SHDUS) is always found before the sound exit point of the probe wedge. To guarantee an accurate measurement of this location during destructive testing, this distance (A) must be calculated. The next equation is used for a plane geometry:
A=1/2∙c∙t∙sin∙βT
The backscattered ultrasonic amplitude depends on the actual gradient of the microstructure. In the transition zone, grain boundaries, grain size, and second phases change the acoustic impedance value discontinuously, depending on the ultrasonic frequency. Different backscattering signals in the hardened and bulk material occur (Yanming Guo, “Effects of material”). Th ese amplitude characteristics can be used to evaluate the case depth by using simple time-of-flight measurements (Figure 2b). Contact testing is generally done by using portable equipment, using a contact wedge where the transducer is mounted to be inclined at a certain angle, and shear waves are emitted into the component. Ultrasonic backscatter takes place at the surface of the component due to surface roughness and results in the return of the energy to the transducer (first echo). Ultrasonic energy enters the hardened surface layer made of fine martensitic structure, and thus, no scatter of ultrasonic waves takes place in this region. However, when the shear waves reach the transition zone where martensitic structure is gradually converted into ferrite-pearlite structure, which has a larger grain size, once again energy is scattered at the grain boundaries, and the transition zone backscatter forms the second echo. The difference in time-of-flight of these two echoes is proportional to the case depth of the component.
Technical Requirements
Technical requirements for testing hardness depth using the ultrasonic backscattering method will produce optimal results in the following conditions:
The test parts should be induction-hardened.
The test parts must be forged, not cast.
There is minimal or no microstructure present between the hardened martensitic microstructure and the core material.
The grain size of the core material is significantly larger than the grain size of the hardened microstructure, leading to considerable backscattering of shear waves at a frequency of 20 MHz.
The minimum hardness depth that can be measured is 1.2 mm. Smaller hardness depths need special considerations, such as adjustments to the wedge design.
Practical Correlation Between NDT and DT
Destructive hardness depth testing is a method to determine the thickness of the case depth of hardened parts. In the process, the parts are destroyed, or their surface is altered rendering each tested part unusable. Hardness depth profiles are usually determined by using the Vickers test to measure the hardness of a reference sample at different points in a line from the surface to the core.
If you compare the acoustically measured surface hardness depth SHDUS with the surface hardness depth measured with destructive methods SHDDT, you will see a basic difference: Independent of the hardness limit and the minimum hardness, the acoustic testing always determines the depth of the core material that has not been affected by the hardening process. As a consequence, this value tends to be slightly higher than the surface hardness depth measured with destructive methods SHDDT. This difference can be compensated by means of a correction term ΔT (“Off set”):
SHDUS = SHDDT – ΔT
In the case of hardness curves with rapidly decreasing hardness values just above the interface, the transit time is measured at 20% of the height of the backscattering signal’s amplitude, and the results of the acoustic and the destructive hardness depth tests will match. The reason for this is the slightly shorter sound path in the marginal ray of the divergent sound field, which induces the backscattering echo.
If cases occur regularly in which the hardness curve deviates significantly from the characteristics, reference tests must be conducted to determine the correction factor ΔT. Reasons for this could be material and/or process related. The calculated correction factor can then be integrated in the respective test task as a test parameter.
Technical Description and Measurement Highlights
The manual device includes a four-channel ultrasonic board managed by a software package for program settings, signal processing, reporting, and overall quality assurance requirements. The parts are put together in an industrial notebook meant for tough industrial settings. The probe systems allow testing of components with complex shapes. The wedge of the probe system is adjusted to fit the geometry of the specific test location. Testing can be done before or after machining.
The primary cause of measurement error is the evaluation of surface position; the shape of the surface signal relies on proper coupling and the operator’s skill. Another source of error is the placement of the marker that indicates the time-of-flight when the pulse hits the interface. The sharper the signal rises, the less the error. Therefore, a shear wave angle as low as reasonable is employed, and scanning in the direction of decreasing SHD is advised. Achievable accuracy of better than ±0.1 mm is possible for standard parts with high-quality surfaces. Nevertheless, the operator must monitor the “good” shape of the A-scan during data collection. Accuracy based on microindentation hardness profiles compared to the backscatter method is slightly lower, estimated at ±0.2 mm on average, based on the material microstructure (Bogaerts et al., “Surface Hardness Depth Measurement”). We are able to test different geometries like crankshafts (Figure 3), camshaft s (Figure 4), tulips (Figure 5), and barshafts (Figure 6), to mention some components.
Situation: During induction hardening, an unanticipated variation on the case depth was detected on the shaft of an axle bar (Figure 7). We were requested to examine the case depth in this important area using a P3123 Hardness Depth Tester to find out if the case depth met specifications.
Figure 7. Induction case-depth variationFigure 8. Axle bar inspection
Results: During the testing, we noted the case depth was insufficient compared to the minimum required case depth of 5.5 mm. This meant all induction hardened parts made before the discovery had to be paused while a complete check of the case depth was performed. All axle bars hardened after the discovery were analyzed (Figure 8), starting with the most recently hardened parts. Case depth was also evaluated by making a microindentation hardness profile in the hardened area, showing a case depth consistent between ultrasound readings with the P3123 and the destructive testing measurements. In Figure 9, we can observe the measurement of the out of specification case depth, and in Figure 10, we have the measurement within specification case depth.
Hardness depth testers are used for optimizing production parameters, reducing downtimes after inductor changes, fast production control, and quality management. The techniques discussed in this article offer the technical advantages to ensure quality assurance for both steel and induction hardened components. Feasibility testing is required, which can be performed with prompt review of the ultrasound behavior in components.
Figure 10. Case depth within specificationFigure 9. Case depth out of specification
Bernard, William J. “Methods of Measuring Case Depth in Steels.” Steel Heat Treating Fundamentals and Processes (2013): 405-416. https://doi.org/10.31399/asm.hb.v04a.a0005795.
Bogaerts, Mike, Michael Kroening, Paul Kroening, and Tobias Mueller. “Surface Hardness Depth Measurement Using Ultrasound Backscattering.” AM&P Technical Articles 177, no. 8 (2019): 58-62. https://doi.org/10.31399/asm.amp.2019-08.p058.
Guo, Yanming. “Eff ects of material microstructure and surface geometry on ultrasonic scattering and fl aw detection.” Dissertation, Iowa State University, 2003.
Kruger, S.E., J.M.A. Rebello, and J. Charlier. “Broadband Ultrasonic Backscattering Applied to Nondestructive Characterization of Materials.” IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 51, no. 7 (2004): 832-838. https://doi.org/10.1109/tu c.2004.1320742.
About The Author:
Jose Miguel Equihua Toral Head of New Projects and Development BOINSA Mexico Manager, InTech NDT, USA
Jose Miguel Equihua Toral graduated as a mining engineer from Guanajuato University and obtained his Master’s Degree in Engineering from the National Technology Institute of Mexico. He currently works as head of the new projects and development department of BOINSA de Mexico, involved in technological and operational advances in the design, manufacture, and repair of induction coils, as well as advances in the application of non-destructive testing methods for the quality assurance of components for the automotive, agricultural, and energy industries. This experience has led to the formation of InTech NDT, to serve the U.S. market.
For more information: Contact Jose Miguel Equihua Toral at miguel.equihua@intech-ndt.com.
What is missing from induction heat-treating maintenance? Learn seven methods for improving your induction tooling component performance in today’s article by David Lynch, Vice President of Engineering at Induction Tooling, Inc.
This informative piece was first released inHeat Treat Today’sApril 2025 Annual Induction Heating & Melting print edition.
The heat-treating industry is constantly evolving, whether it is due to the influx of AI or the introduction of new materials. The field of induction is not exempt from this constant change. Yet there remains a constant — induction tooling components need to be tough to resist harsh environments comprised of high frequencies, high power, heat, smoke, steam, dirt, oil, quench fluid and additives, and contaminants. It’s been almost four years since we visited the topic of induction tooling equipment longevity and maintenance (see the May 2021 print edition). Amidst the constant change, how do we protect against the same old toxic environment?
Let’s explore some new methods of improving the performance and longevity of induction tooling components:
Figure 2. Break-Away bolts designed to fail beneath the washer if over tightened
More than coils — When working to optimize the life of induction equipment, don’t focus solely on the coils. Bus bars, inductors, and quenching equipment are also key to success.
Austenitic stainless steel — Use austenitic stainless steel for fasteners, fittings, and hose clamps, and remember, non-ferrous is the way to go.
CNC machining — Manufacturing with a 5-axis CNC machine ensures quality and consistency.
“Break-Away” bolts — For fasteners, use “Break-Away” bolts on contact surfaces. These bolts are designed to fail beneath the washer if they are overtightened, a design that prevents damage to the threaded insert inside the copper contact.
Cooling water — For cooling the inductor coil, bus bars, and adapters, reverse osmosis and distilled and deionized water are overkill. Stick with keeping the water below 70°F. This may require a separate cooling supply. Through laboratory experimentation and real-world production trials, it has been proven that lower cooling water temperatures can drastically increase the life of these components, especially in high-volume, high-power, and short cycle applications. In some hard water areas, this may not be possible. Typical cooling-conductivity for the inductor and bus bar is 200–800 microsiemens per centimeter (μS/cm).
Non-ferrous fittings — Use non-ferrous fittings on cooling and quenching water connections, as well as color-coded hoses.
Cleaning — Design with cleaning in mind. Designing a quench with bolted removable quench plates ensures easy clean out. As the heat-treating industry continues to evolve, our practices and technologies for optimizing the performance and longevity of induction tooling equipment evolve with it. Whether it’s using a new method or revamping a tried-and-true practice, we can continue to produce strong induction tooling components to sustain these harsh environments.
Figure 3. 5-axis CNC machining of water-cooling passages to maximize water flow and minimize sharp transitionsFigure 4. CVJ inductor with non-ferrous fittings and color-coded hoses on cooling and quench water connectionsFigure 5. Barrel style OD quench ring with bolted removable quench plates to allow easy clean outFigure 6. Multi-turn OD scanning inductor with integrated quench featuring removable quench plate for easy clean outFigure 7. Heavily used inductor
About The Author
David Lynch Vice President of
Engineering Induction
Tooling, Inc.
David Lynch is Vice President of Engineering at Induction Tooling, Inc. He has over 36 years of experience and is the deputy of the ISO quality system. He has created and developed the system and templates being used today for creating and tracking engineering drawings, job history, rate tracking, and job performance. David holds several design patents, has authored several published articles, and has often presented at technical sessions. He enjoys working closely with customers to develop valued solutions across a wide range of induction heating applications from initial design concepts to implementation, customer support, and troubleshooting.
In this Technical Tuesday installment,Josh Tucker, manager of Induction Heating, Tucker Induction Systems, Inc., relates new research conducted on the strength of coils which have been produced through 3D printing.
This informative piece was first released inHeat Treat Today’sApril 2025 Induction Heating & Melting print edition.
Research on 3D printing induction coils finds that coils are stronger and have a longer life when compared to traditionally manufactured coils. Read about how additive manufacturing removes steps like brazing the joints and provides new design capabilities.
Tucker Induction Systems began exploring the possibility of using 3D printing technology to manufacture coils and found that, in many cases, 3D printed coils were stronger and longer lasting than traditionally manufactured counterparts.
The quest to develop 3D printed coils began in 2020. When COVID-19 hit, Macomb County, Michigan, started an initiative called Project DIAMOnD, which stands for Distributed, Independent, Agile Manufacturing on Demand. It provided small-to-medium-sized area manufacturers with Markforged Fused Deposition Modeling-style 3D printers as both a way to quickly manufacture much needed personal protective equipment for the pandemic and to help small-to-mid-sized manufacturers overcome the supply chain issues that plagued industry during the crisis.
We were eager to gain hands-on additive manufacturing experience through the DIAMOnD initiative and, in doing so, found that it sparked our curiosity about the possibility of 3D printing our coils and new ways to design them that go beyond the capabilities of traditional machining.
In 2021, we began a two-year research and development process of printing coils and discovered that by 3D printing induction coils we were able to drastically increase the strength of the coils and potentially lengthen the useful life of the coil. The experience has opened new realms in designing our coils, as well as giving us the ability to design coils using methods that go beyond the capabilities of traditional machining.
It is common industry knowledge that the weakest parts of a coil are the braze joints, but through the R&D process, we have learned that by 3D printing the coils, it is possible to eliminate most, if not all, braze joints in the head of a coil. This increases the strength and, potentially, the life of a coil. After years of testing and evolving, the end results were better than we expected, proving that the coils can be printed and will last in the field.
Figure 1. 3D printed single-shot hardening induction coil heads
However, there were some challenges in adapting to using 3D printing technology. For example, the type of copper printing we required was not being done in the United States, which was an obstacle in trying to form a process that resulted in a successfully printed coil. But one of the biggest challenges after we locked down the process and material was in designing the internal cooling passages for the coils. The passages needed to be designed in a way that was self-supporting and non-restricting. We had to produce the same flow rate as traditionally made coils and ensure we were driving the cooling into the right areas. Figuring that out took many failed attempts — learning opportunities — before achieving success.
Once that goal was achieved, we installed a metal 3D printer at Tucker Induction in January 2024 and have been successfully printing all different types of coils. Some examples include two turn ID, spindle, single-shot, and scanning coils.
The Benefits of Using 3D Printed Coils
While traditional coils (such as our interchangeable, quick-change coil for two-turn induction systems and single-shot designs with accurate clamping pressure) have changed the industry, the additional capability of 3D printing allows us to print dimensionally accurate, durable parts that are capable of performing in the field and that can go beyond the barriers of traditional machining.
Figure 2. 3D printed single-shot induction coil with keepers
3D printed coils bring several worthwhile benefits to the table including time savings, longevity, and faster coil repair. Time savings is one of the biggest advantages. Because the 3D printer can run “lights out,” the processing time from the printer to the client is far shorter when compared to traditionally fabricated coils. We refer to the processing time as the additional time needed to complete the coil assembly after printing. In some situations, it is possible to print a completed coil assembly with the coil immediately ready to be sent to the client. Other times, additional brazing or supplemental details may be required to complete the assembly.
Since all coils are different, the processing time varies from coil to coil. However, by printing as much of the assembly as we can, we are able to limit the amount of additional work needed to complete the job.
Strength and potential longevity of 3D printed coils are additional advantages. The weakest parts of the coil are the braze joints, but the process we use to print the coils drastically reduces the amount of braze joints, thus making the workforce of the coil a solid construction. This results in a product that will be stronger in the induction environment and has the potential to outlast its traditionally manufactured counterpart.
When it comes to the lifetime of the 3D printed coils, our baseline is that the printed coils need to last at least as long as traditionally manufactured coils. However, in our research, we have seen, on average, that our 3D printed coils can last two to three times longer than traditionally manufactured coils. While the longevity of each coil is case dependent, as there are many factors that go into the lifespan of a coil, one of our original test coils is still running in the field with over one million heat cycles.
While continuing to improve processes and designs, we are also pushing to decrease the time for repairs. Getting our clients’ coils repaired and returned in an effort to limit their downtime has always been something we strive for with our traditional coils, but we have found that 3D printed coils are easier to repair. Since multiple braze joints are not an issue in printed coils, it reduces the chance of causing additional problems as you work on the original repair. If the repair consists of replacing the head of the coil, we are able to recall the original print and run it again, as opposed to having to re-machine and re-assemble and braze the entire coil, significantly reducing the repair time of many 3D printed coils.
Limitations of 3D Printing Coils
Despite the advantages of 3D printing induction coils and the fact that the capability to print coils gets you into the mindset that every coil needs to be printed, there are some instances when it is still more effective to use traditional manufacturing.
Figure 3. 3D printed sample structures
For example, coils that are larger than the machine is capable of printing — our print bed size is roughly 12 x 12 x 13 inches — can be a limiting factor. Other times, the coil may be manufactured faster using traditional methods. The printer does have limitations, and it is not the best option for certain coils. For example, coils that are less intricate and made from tubing is one type that would be a better candidate for traditional manufacturing; these coils simply require wrapping copper tubing around a mandrel.
The Future of 3D Printed Coils
We are continuing to research and fine tune the processes of 3D printing our coils and strive to provide our clients with the best possible product. In order to do that, we must stay vigilant and be willing to continuously learn and improve our designs and processes.
As we learn more and perfect our 3D printing coil processes, I believe 3D printed coils will play a vital role in the future of the industry. We have proven that 3D printing coils is not just possible, but that in some cases 3D printed coils can outperform their traditionally manufactured counterparts.
About The Author:
Josh Tucker Manager of Induction Heating Tucker Induction Systems, Inc.
Josh Tucker graduated with a bachelor’s degree from Grand Valley State University and was then hired as the head of Purchasing at Tucker Induction Systems. Since starting eight years ago, Josh’s role and capabilities have expanded to machining, wire EDM, 3D printing, and laser engraving. He also organizes the day-today operations and flow of the shop floor. Josh was recognized in Heat Treat Today’s 40 Under 40 Class of 2024.
As we get further into the heart of fall, it’s time to turn up the heat (treat)! – but how can this be done in an optimized and sustainable way?
Today’s Technical Tuesday original content round-up features tips and tricks from our summer print editions on how to optimize and sustain your heat treat operations, even during the chilly months. So, bundle up, grab a hot drink, and review these insightful pieces!
Sustainability Insights Corner
In May, Heat TreatToday began publishing "Sustainability Insights" from the IHEA editorial team. Here's a brief overview of the recent insights all in one place:
June: NEW Sustainability and Carbonization Webinar Series. Although this year's IHEA Webinar series may have come and gone, it's not too late to establish a foundational understanding of carbon and sustainability here!
August: Reducing the Carbon Footprint of Your Heat Treating Operations. Brian Kelly of Rockford Combustion is back with yet another suitability insight, here exploring ways to assess your heat treating operation's carbon footprint, tune your combustion systems, explore renewable fuels, and much more.
September: Process Heating and the Energy-Carbon Connection. Explore the issue of greenhouse gases and how recent conversations are affecting the heat treating industry with Michael Stowe of Advanced Energy.
In Case You Missed the May Issue: Induction and Sustainability Tips
Looking for sustainability tips for your heat treating operation, but lacking in time? Heat TreatToday's May Issue has you covered with a quick read: "13 Induction and Sustainability Tips." We'll highlight a few below which made it into a recent Technical Tuesday feature:
Sustainable Energy for Furnaces? What does the Future Hold?
What will the future run on? With growing discontent around current energy sources like natural gas and other fossil fuels, power sources for furnace equipment are due for a makeover.
Explore the question of sustainable energy for furnaces in the future with industry experts John Clarke of Helios Electric, Philippe Kerbois of Glass, various authors from Watlow, and Stuart Hakes of F.I.C. (UK) Limited.
How much electrical power is being used in the typical heat treatment plant? And how can power (and money) be saved in these operations? If these questions peak your interest, explore further with Roger A. Jones and William Jones of Solar Atmospheres.
Learn about savings in electricity and money in areas of electric motors, high vacuum diffusion pumps, gas blowers, building lighting, AC/heating, and more in this article.
Discover expert tips, tricks, and resources for sustainable heat treating methods Heat TreatToday’srecent series. Part 4, today’s tips, covers induction heating, quench, and insulation tips. We’ve added resources towards the end of today’s post for further enrichment.
This Technical Tuesday article is compiled from tips in Heat TreatToday’sMay Focus on Sustainable Heat Treat Technologiesprint edition. If you have any tips of your own about induction and sustainability, our editors would be interested in sharing them online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own ideas!
1. Tips for Induction Hardening
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What are the benefits of induction hardening? Here are a few:
Saves space: Induction hardening requires minimum space required in comparison with furnaces
Saves energy: Induction heating equipment does not need to be kept running when not in use
Clean: Induction heating equipment requires no combustion gases
Energy-efficient: Only a small proportion of the material needs to be heated
Minimize deformation: Induction hardening requires no applied force
Save maintenance costs: Inductor coils have a long life, reducing the need for maintenance
Source: Humberto Torres Sánchez, Chief Metallurgist, ZF Group
2. Insulation = Key for Energy Savings in Vacuum Furnaces
Look for insulation quality in your next vacuum furnace.
Source: NITREX
Improvements in insulation materials are also contributing to greater energy efficiency of vacuum furnaces. Most furnaces on the market today have a 1” (25.4 mm) graphite board with bonded Grafoil and two layers of graphite felt. However, the insulation performance of a 1” (25.4 mm) graphite board is about 25% less efficient than a 1” (25.4 mm) graphite felt. For processes that require high operating temperatures, typically over 2,200°F (1,204°C), an all graphite felt that is 2” or 2.5” thick (50.8 mm or 63.5 mm) minimizes heat loss inside the hot zone. Efficiency gains of up to 25% are possible over the standard 1” (25.4 mm) board and 1” (25.4 mm) graphite felt insulation and an even greater gains at higher operating temperatures. To safeguard the graphite felt from mechanical harm and localized compression, these thicker all-graphite felt insulation configurations are usually covered with a carbon fiber composite (CFC) sheet about 0.050” (1.27 mm) thick.
Fuel efficiency (and the stringent requirement for passenger safety) has raised the bar for the automotive industry to procure steel with high strength, hardness, and ability to fabricate. Reduction of weight requires lighter cars with thinner body material which can absorb impact. These dual contradictory properties of high hardness material which can be easily shaped can normally be achieved either by heat treat or through addition of alloys. These two processes are described below.
Normal heat treatment to produce small grains in the material will increase the hardness in steel but also create a propensity to fracture. Thus, a process known as quench and partition — where carbon diffusion from martensite to retained austenite to stabilize the latter — has been introduced. Further verification and prediction of the phases has been conducted using thermodynamics modeling for phase characteristics by Behera & Olsen at Northwestern University, Materials Science and Engineering.
The process starts with full automatization (or in some cases intercritical annealing) followed by fast quench to a defined quench temperature (QT) between the martensite start, Ms, and martensite finish, Mf, temperature. The steel is then reheated to the partition temperature (PT) and held there for a certain partition time followed by a quenching step again to room temperature, as shown in the image.
Quench and partition process
Source: Speer et al. The Minerals, Metals, & Materials Society 2003
The quenching step establishes the largely martensite matrix while the partition step helps stabilize the retained austenite by carbon partitioning. During the holding step, carbon diffuses from martensite to retained austenite and thus improves its stability against subsequent cooling or mechanical deformation. The final microstructure consists predominantly of tempered martensite and stabilized retained austenite with possibly a small amount of bainite formation and carbide precipitation during the partition step and fresh martensite formation during final quenching.
The other process to achieve high hardness and high ductility is by alloy addition in carbon steel. Over, 2,000 different types of steel exist. A new type of steel that is extremely strong, but simultaneously ductile is used in the automotive industry. Small quantities of elements like vanadium or chrome in steel promotes ductility. They are not brittle; however, up until now they have not been strong enough to enable the construction of car bodies with thinner sheets.
In the crystals of steels, the atoms are more or less regularly arranged. Steels become particularly ductile though if they can switch from one structure to another. This is because this process allows energy absorption, which can then no longer initiate any damage in the material. In a car body or other steel components, tiny areas then alternate with the two different atom arrangements.
Ductile steels have two coexisting crystal structures. The search produced an alloy made from 50% iron, 30% manganese and 10% respectively of cobalt and chrome (Max Planck Institutes).
What makes the geometry of a part “complex”? With the increasing use of AM and 3D printing for parts along with typically complex parts, heat treaters in many industries must acquire the equipment and technical know-how for precise applications.
This Technical Tuesday article is compiled from Heat TreatTodayarticles and industry news releases. Email Bethany Leone at bethany@heattreattoday.com or click the Reader Feedback button below to chime in on the topic.
What Are Complex Geometries?
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Complex geometries in industrial parts are often defined by their intricate patterns and structures, which entail specialized heat treat processing. As Inductoheat describes in a case study with Stellantis, “Many times, complex geometries of components are linked to intricate hardness patterns and specific requirements for magnitude and distribution of residual stresses.”
Heat Treat Equipment for Processing Parts with Complex Geometries
Be it for highly customized medical implants or for engine components in the burgeoning electric vehicle industry, complex geometries need to heat treated carefully. Fasteners in the medical device industry can be quite intricate and susceptible to creep or other dimensional changes; one method heat treating these parts — particularly titanium alloy parts — would be in a vacuum furnace. In vacuum and in hot isostatic presses, the environment allows for complex geometries that are 3D printed to be made into a unified whole piece. “Heat conduction can be carefully monitored [in induction heating coils] to confirm that an overheat condition does not occur at the target temper areas,” making induction a key candidate for heat treating your parts with complex geometries (“Tempering: 4 Perspectives — Which makes sense for you?“). To accommodate the complexities of certain parts, designing an induction coil for the desired case hardening may entail simulation to “[predict] coil heating, which altogether results in a longer coil lifetime,” (“Simulation Software and 3D Printers Improve Copper Coils”). For more on induction coils, check out this article by Dr. Valery Rudnev.
Suffice it to say, there is a great diversity of heat treatment options to explore when it comes to identifying the appropriate equipment for your application.
What Processes Are Used in Heat Treating Complex Geometries?
Perhaps you have all of your equipment needs necessary for heat treating your parts with complex geometries. Are you completing your heat treat processing in the most technically sound manner? Check out the following excerpts that speak to processing complex geometries.
“[Forging] at elevated temperatures enables reaching high strains and forming complex geometries in a single stroke. Additionally, thermal and mechanical influence during the forging can lead to improving local mechanical properties and the quality of the resulting joining zone.” (“Thermomechanical Processing for Creating Bi-Metal Bearing Bushings“)
“In some cases, such attempts result in a component’s geometries that might be prone to cracking during heat treating or might be associated with excessive distortion . . . . The subject of induction hardening of complex geometry parts (including but not limited to gears, gear-like and shaft-like parts, raceways, camshafts, and other critical components) is also thoroughly discussed, describing inventions and innovations that have occurred in the last three to five years.” (“Heat Treat Training Benefits Stellantis“)
“LPC [low pressure carburizing] with gas quenching can be an attractive option for distortion prone complex geometries as the cooling rates are slower than oil quenching; however, given the slower cooling rate, it becomes very important to choose a higher alloyed steel that will achieve the desired hardness.” (“Elevate Your Knowledge: 5 Need-to-Know Case Hardening Processes“)
Complex Geometries In the News
See how your peers are solving complex geometries needs in these real-life partnerships with industry suppliers. From additive manufacturing (AM) and precision manufacturing parts to heat treat technology, maybe your company is next to leverage manufacturing equipment to “wow” the industry.
Discover expert tips, tricks, and resources for sustainable heat treating methods Heat TreatToday’srecent series. And, if you’re looking for tips on combustion, controls systems, or induction in general, you’ll find that too! Part 2, today’s tips, digs into energy and electricity. We’ve added another resource towards the end of today’s post to further enrich your knowledge of induction heating.
This Technical Tuesday article is compiled from tips in Heat TreatToday’sMay Focus on Sustainable Heat Treat Technologiesprint edition. If you have any tips of your own about induction and sustainability, our editors would be interested in sharing them online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own ideas!
1. Maximizing Energy Efficiency of Vacuum Furnaces
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The use of AC to DC transformers is an energy-efficient innovation that can significantly lower energy consumption of the heating system. Typically, a system uses alternating current as the primary source, which fluctuates output during each half cycle. Using AC to DC transformers limits these fluctuations, reducing the amount of energy used. Furthermore, transformers operate at optimal efficiency when under a reduced load – i.e., less than 70% output in steady-state heating – rather than ramping up to the full operating temperature. Another advantage of the DC-type transformer is that its operating power factor is very close to 1.0, which lowers the utility company’s calculation of peak demand surcharges
Try power feedback for your electric heating elements. Power feedback is ideal for variable resistance heating elements. Kilowatts are used as the unit of control, rather than just current or voltage.
Conserving energy is not only good for the environment, but it can mean more money in your pocket and less downtime. Here are three tips to improve furnace efficiency with diagnostic technology:
Do you have tight and secure terminal connections? Poorly connected power cables waste electricity and can cause fires. An SCR power controller monitors terminal temperature changes and will alert you before failures happen. It also monitors heat sink temperatures and ensures the control’s cooling fan is working properly.
Do you have a heater-break alarm? Heating zones typically have multiple heating elements, wired in parallel. A broken element is difficult to detect and will impact the heater’s circuit, reducing the power of the process. This can waste energy and affect product quality. A heater-break alarm will alert you to a failing heater circuit.
Do you pay high electricity bills? You could benefit from a factory load management system. It’s now possible to limit peak current loads and power usage across your factory and multiple furnaces. These systems communicate by sharing important power-demand information and providing more effective power distribution.
A connected and automated factory network saves electricity and improves operational efficiency by establishing powerful furnace management systems.
After absorbing today’s tips, you may want to take one step farther to read up on induction heating. Take a look at “Why Induction Heating is a Green Technology” to help broaden the horizon.
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
Discover expert tips, tricks, and resources for sustainable heat treating methods Heat Treat Today's recent series. And, if you're looking for tips on combustion, controls systems, or induction in general, you'll find that too! Part 1, today's tips, digs into cleaning and maintenance
This Technical Tuesday article is compiled from tips in Heat Treat Today's May Focus on Sustainable Heat Treat Technologiesprint edition. If you have any tips of your own about induction and sustainability, our editors would be interested in sharing them online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own ideas!
1. Maintenance of Induction Coils Used in Hardening Applications
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Soap and hot water will remove sticky quench and debris. Source: Induction Tooling, Inc.
How should you maintain induction coils used in hardening applications? Elbow grease — a little goes a long way. After each use, a simple solution of soap and hot water will remove sticky quench and debris. Scrub hardened dirt with a Scotch-Brite pad. Check for pitting, arcing, and insulator damage. If all is good, use a hot water rinse, and it’s ready for use. If the inductor is to remain on the machine for an extended period, it is advised to wash it and the associated bus daily. Check for damage. Following this simple procedure will reduce business waste.
As industry tries to become more “green,” a number of companies are switching from lubricants that are petroleum or mineral oil-based to water-based (“aqueous”) lubricants instead. However, some of these companies then make the mistake of not changing their degreasing fluids that they use to remove these lubricants prior to their next processing operations, and stay with their standard degreasing fluids, such as acetone or alcohol, which are not effective at fully removing water-based lubricants. Instead, they need to run tests to find an appropriate alkaline-based degreasing fluid for such water-based lubricants, since alkaline-based degreasers will be effective at removing such lubricants. Commonly available dish-detergents (alkaline-based) have been shown to be highly effective for such use.
Nikola Tesla afirmó: <<Si quieres descubrir los secretos del universo, concéntrate en la energía, la frecuencia y la vibración.>>
Al revisar los mecanismos internos de un sistema de inducción es posible evidenciar cada uno de estos tres elementos. Los 10 pasos de esta guía servirán para apoyar a los operadores de departamentos internos de tratamiento térmico en entender los secretos de la inducción para así identificar posibles escollos en tales sistemas y dar solución a problemas comunes que se puedan presentar.
This original content article was first written by Alberto Ramirez, engineer of Power Supply and Automation at Contour Hardening, Inc. and an honoree from Heat Treat Today’s 40 Under 40 Class of 2021, for Heat Treat Today's May 2023 Sustainable Heat Treat Technologiesprint edition. Read the Spanish version below, or click the flag above right for the English version.
Alberto Ramirez Power Supply and Automation Engineer Contour Hardening, Inc.
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Los metales pueden calentarse mediante el proceso de inducción electromagnética, mediante el cual un campo magnético alternativo cerca de la superficie de una pieza de trabajo metálica (o conductora de electricidad) induce corrientes de Eddy (y, por lo tanto, calentamiento) dentro de la pieza de trabajo.
Los sistemas de inducción pueden llegar a ser sistemas complejos que tienen como objetivo endurecer piezas o secciones específicas de un componente mecánico, dependiendo del grado de complejidad de la pieza a tratar; para el profesional, el desafío será el diagnóstico de los problemas que se lleguen a presentar.
1. Familiarízate con el proceso
Figura 1. Proceso de endurecimiento por inducción Source: Contour Hardening, Inc.
El proceso de inducción envuelve muchas características tales como: posición de la pieza dentro de la bobina de inducción, posiciones de carga, posiciones de enfriamiento, tiempos de ciclo, potencia eléctrica aplicada, entre otras. Es importante que el profesional sea capaz de identificar la falla y la situación particular en el momento en el que se está presentando.
En algunas ocasiones las fallas no son evidentes y, por ende, es indispensable analizar la pieza que ha sido tratada; este análisis puede ser clave para entender situaciones tales como: falta de profundidad de capa por potencia eléctrica o disminución en la frecuencia de salida, entre otros posibles escenarios.
Adicional al análisis de la pieza, es vital inspeccionar la “escena del crimen” ya que muchos de los sistemas de inducción, dada la naturaleza del proceso y el peligro que implica manejar altos potenciales eléctricos, suelen ser en extremo automatizados y las estaciones de trabajo de difícil acceso para el personal, así que una buena estrategia de trabajo consiste en observar detenidamente las condiciones generales del equipo para determinar el punto de inicio para la resolución del problema.
2. Identifica los componentes principales de tu sistema de inducción, así como los mecanismos de seguridad para ciertas zonas en particular
Entender la interrelación del sistema es importante para comprender qué elemento realiza cierta acción, así como los canales de comunicación entre ellos. Una vez que se genere este conocimiento, se puede asociar una falla a un componente en particular. Usualmente los sistemas de inducción se componen de los siguientes elementos:
Figura 2. Componentes de un sistema de inducción Source: Contour Hardening, Inc.
Como mencionamos con anterioridad el proceso implica altos potenciales eléctricos, y para eso la naturaleza de las fuentes de alimentación involucra dispositivos electrónicos de potencia, como capacitores eléctricos, los cuales almacenan energía y, por ende, es importante descargar eléctricamente el sistema antes de comenzar a inspeccionar un equipo.
3. Ten preparadas las herramientas necesarias para realizar un buen análisis del problema
Figura. Capacitores Source: Contour Hardening, Inc.
Al igual que cualquier problem técnico, el uso de la herramienta mecánica es indispensable al realizar algún tipo de proyecto, pero para el diagnóstico de una falla en un equipo de inducción es importante contar con:
Osciloscopio
Generador de funciones
Amperímetro
Multímetro digital y analógico.
Sondas de alto voltaje
Sin estos elementos es muy difícil llegar a un diagnóstico fiable, y la posibilidad de encontrar la falla es mínima. Por ende, tener estos medidores en buen estado y, sobre todo, calibrados nos da una perspectiva más clara del problema.
4. Verifica que los sensores del proceso, los monitores de energía y las bobinas de inducción funcionen correctamente
Existen distintos medidores que recogen información acerca del proceso; esta información en su mayoría puede ser visualizada a través del HMI (Human Machine Interface), y, en muchas ocasiones, una buena manera de comenzar a entender el problema es recopilar la información del proceso. Si los medidores no funcionan correctamente, te pueden llevar a conclusiones erróneas.
Verifica que los medidores de energía estén funcionando correctamente, así como tus señales de entrada y de salida.
Las bobinas de inducción son un elemento clave en el proceso de inducción ya que acorde a su geometría generan los campos magnéticos adecuados para lograr los resultados metalúrgicos esperados. Si existen fugas de agua o los elementos de transmisión eléctrica se encuentran sueltos o sucios, seguramente podrán ser la raíz del problema. Es importante comenzar a realizar el diagnóstico de la falla una vez se haya descartado este circuito en particular.
Figura 4. Ejemplo de parámetros de energía Source: Contour Hardening, Inc.
5. Realiza estudios de energía constante en tu subestación para identificar posibles problemas en tu suministro de energía, así como tiempos críticos
La energía eléctrica es la fuente principal en un proceso de inducción; las fuentes de alimentación transforman y potencializan este recurso para crear campos electrónicos lo suficientemente fuertes para generar el calor en la pieza.
Por ende, es importante descartar con evidencia que el problema en cual nos encontramos no se debe a una falla del sistema eléctrico del cual nuestro sistema de inducción forma parte. De igual manera entender cómo se comporta nuestro sistema eléctrico nos puede ayudar a generar patrones de comportamiento que puedan determinar la solución en momentos específicos en los que se lleguen a presentar.
6. Trabaja de forma metódica documentando tus movimientos y realiza un paso a la vez
Los sistemas de inducción pueden ser muy intimidantes si no has tenido experiencia previa, y, al igual que con cualquier elemento o situación, es importante abordar de manera lógica el problema analizando el modo de la falla, identificando las partes principales que interactúan en ese preciso momento, y, a partir de este análisis, documentar y realizar pequeños pasos, uno a la vez, ya que, de no ser así, es muy probable que pierdas todo el trabajo realizado y la situación empeore.
Figura 5. Antes y durante un arco eléctrico dentro de la línea de transmisión Source: Contour Hardening, Inc.
Si los movimientos no son exitosos, siempre puedes regresar a tu punto de partida e intentar otro acercamiento. La idea consiste en que el modo de la falla se mantenga estable sin importar los movimientos realizados hasta que se resuelva el problema. De esta manera lograrás contener la falla; de otra manera podrías estar dañando otros elementos sin darte cuenta.
Es muy importante entender que los procesos son secuencias que anteceden y preceden a nuevos eventos; si entiendes el proceso y, una vez resuelto el problema, ahora tienes una nueva falla, es importante analizar si esta falla es la continuación del proceso ya que, de ser así, es posible que te encuentres frente al caso de un evento que está desencadenado una serie de fallas y se haga necesario practicar un análisis más profundo. La idea general es llegar a la raíz del problema y mitigar el riesgo.
7. Intenta cualquier posibilidad relacionada con el proceso sin importar que la relación entre ésta y el problema no sea directa
Un pensamiento lógico puede resolver la mayoría de las fallas técnicas de un sistema, pero, para fallas excepcionales, es necesario utilizar la imaginación y agotar todos los recursos posibles ya que el área de interés más insignificante o el lugar menos pensado puede ser la clave para resolver un problema.
8. Conoce tus fuentes de alimentación
Uno de los factores claves en cualquier equipo de inducción son sus fuentes de alimentación. Las fuentes de alimentación son equipos que no requieren un mantenimiento tan arduo en comparación con otros sistemas en la industria, pero, de no presentarse las condiciones mínimas de mantenimiento, pueden generar altas pérdidas para la organización.
Figura 6. Diagrama de flujo del proceso eléctrico en una fuente de alimentación Source: Contour Hardening, Inc.
En los casos en los que el problema se encuentra en las fuentes de alimentación, es vital que se siga el mismo proceso metódico previamente descrito. Entender cómo funciona el proceso de transformación de la energía te dará una ventaja, al igual que conocer los componentes empleados o el tipo de tecnología utilizado en el proceso de rectificación, en la inversión (estado sólido o tubos de electrones) y en el circuito resonante. Generalmente las fuentes de alimentación siguen el siguiente patrón de transformación (Figura 6).
9. Identifica las partes críticas de tu equipo de inducción y prepara un inventario de éstas
Figura 7. Daño en una bobina de inducción Contour Hardening, Inc.
Usualmente los componentes que forman parte de las fuentes de alimentación son difíciles de conseguir dependiendo de la antigüedad de tu equipo, y con la reciente crisis de microchips en el mercado, existen tiempos de entrega muy largos para los elementos de control y automatización; de igual manera, los precios de los mismos se han disparado. Por ende, es vital que exista una lista de partes críticas y un inventario de éstas.
Adicionalmente a los elementos descritos, las bobinas de inducción suelen ser elementos muy característicos e importantes en el proceso de inducción. Éstas bobinas son elementos complejos que han sido diseñados exclusivamente para la pieza, por lo que su fabricación puede tomar varias semanas, y es importante tomar las precauciones necesarias para mantener un movimiento de mantenimiento constante.
10. Realiza mediciones preventivas al sistema para generar un patrón de comportamiento
Figura 8. Ejemplo de posibles mediciones Contour Hardening, Inc.
Cuando el sistema se encuentre trabajando en óptimas condiciones, genera un plan de medición el cual te permita recopilar información de puntos específi cos dentro del sistema. Una vez que se vuelva a presentar una nueva falla puedes comparar las mediciones de falla contra las del buen funcionamiento. Algunos ejemplos de mediciones pueden ser:
Temperatura
Voltaje
Corriente eléctrica
Resistencia y capacitancia
Formas de onda
En resumen
Una metodología de trabajo ordenada y documentada, un buen catálogo de piezas de recambio, junto con las herramientas de trabajo necesarias, pueden ser elementos clave para entender un problema y, lo que es más importante, resolverlo de forma eficaz.
Es vital que los profesionales se capaciten de manera constante para mejorar los tiempos de paro debido a fallas en los sistemas de inducción. La capacitación relacionada con procesos metalúrgicos sería una buena forma de complementar tus habilidades de resolución de problemas permitiéndote interpretar las características de los sistemas de inducción, al igual que de los elementos que los componen.
Bibliografía
Valery Rudnev and George Totten, ed., ASM Handbook Volume 4C: Induction Heating and Heat Treatment, (Materials Park, OH: ASM International Heat Treating Society, 2014), 581- 583
Sobre el autor: Alberto C. Ramirez es ingeniero en Mecatrónica egresado del Instituto Tecnológico Nacional de México Campus León con una maestría en Administración de Tecnologías de la Información por el Instituto Tecnológico de Monterrey. Cuenta con más de 8 años de experiencia en fuentes de alimentación, gestión de proyectos, mantenimiento y automatización. Actualmente se desempeña como ingeniero de fuentes de alimentación y automatización en Contour Indianapolis. Alberto inició su carrera en la fi lial de Contour en México y debido a su dedicación forma parte del staff en los Estados Unidos.
He is also an honoree from Heat TreatToday's 40 Under 40 Class of 2021.
