Industrial induction heating expert EFD Induction and inductive charging and power supply innovator IPT Technology will combine to form ENRX. On March 27, 2023, the new brand will officially launch. Under the new name, ENRX will provide induction technology for inductive heating, charging, and power supply with low or no carbon footprint.
Bjørn Eldar Petersen CEO of ENRX Source: ENRX
Magnus Vold CCO of ENRX Source: LinkedIn
“We are a new company with more than 70 years of experience in induction heating,” says Bjørn Eldar Petersen, CEO of ENRX. “We now have a new brand, ENRX, and many products in the pipeline.”
ENRX, with locations in North America and headquarters in Skien, Norway, has 1,100 employees. The new brand bringing EFD Induction and IPT Technology together will hold over 1,200 patents for induction technology.
“Inductive wireless charging and contactless power supply are technologies for the future,” says Magnus Vold, CCO of ENRX. “In the new world that is emerging, everything is based on automation, digitalization and electrification."
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
We've assembled some of Heat TreatToday's resources on forging and metalcasting. Read or listen to what the experts have to say on these important topics in the heat treat industry.
This Technical Tuesday original content piece will help you wade into an introduction of these heat treatment processes. Follow the links to dive deeper into the studies.
The span of articles, radio episodes, and TV clips below are compiled to learn more about forging and casting. Heat treating is developing and changing through the years, and it's wise to keep swimming with the current of information.
Simulating Induction Heating for Forging
What can simulation software do for you? Manufacturers are able to run the software to act upon the steel billet prior to forging. Read more about the process here. The simulation shows results in the metal to help the user best plan for desired results. One of the decisions that can be helped is, "the selection of right forging temperatures for plain carbon and alloy steels to avoid possible damage by incipient melting or overheating."
A Look at Steel and Iron
Dan Herring "The Heat Treat Doctor" The HERRING GROUP, Inc.
Read or listen to this episode of Heat TreatRadio with expert Dan Herring who discusses metals such as stainless steel, tool steel, cast iron, high and low carbon steels, and more. He looks at their production and their uses.
"I wanted to set the stage for it to say that it’s the end-use application by the customer that fuels the type of steel being produced and fuels the form in which the steel is produced," says Herring.
Investment Casting in Turbine Blades
Take a look at how an alumina and silica (quartz) mix are improving metal casting for support rods used in aerospace manufacturing. "LEMA™, a range of proprietary alumina-based materials that provide double the mechanical strength of quartz while providing significantly improved leaching times, compared with typical high purity alumina," provides many benefits for metal casting. Jump into this piece to find out more about this metal casting example.
Direct From the Forge Intensive Quenching
President Akron Steel Treating Co & Integrated Heat Treating Solutions, LLC
In this discussion, expert Joe Powell says, "My thing is to develop a robust process that can be applied and implemented using automation and new equipment with the proper pumps and material handling that is all integrated into a seamless process." He plunges in to talking about immediate quenching pieces in water after heat treating and what they are learning at the forge shop.
Heat TreatTV
Here are a few episodes to keep you afloat while moving into deeper waters.
Click on these two illustrations to watch the full episodes.
What is the most common cause of induction tooling failures? What is essential for the longevity of induction tooling? What is a vital component for induction tooling’s successful performance? This informative article shares the answers to these questions and provides valuable guidance for your induction needs.
This Technical Tuesday is provided by David Lynch, vice president of Engineering at Induction Tooling, Inc. and was featured in the Heat Treat Today’s2021 May Induction print edition. Check out more original content articles in this digital edition or other editions here.
David Lynch Vice President, Engineering Induction Tooling, Inc.
Most induction heat treating applications are challenged with a harsh environment often dealing with high frequencies, high power, heat, smoke, steam, dirt, oil, quench fluid, quench additives, and contaminates. How induction tooling components are maintained in these harsh environments greatly impacts their performance and longevity.
The induction power supply, workstation, and material handling system should all be properly grounded. The work holding system should be level, square, and have proper alignment between the inductor coil and the workpiece for it to be heat treated. Part-holding fixtures should be held to a dimensional tolerance to ensure proper positioning and repeatability with minimal runout. The heat-treating process should include documentation of parameters including positioning (the air gap of the inductor coil relative to the workpiece), scan rates (in/sec), power (kw), frequency (kHz), heat time (sec), dwell time (sec), and quench time (sec). If auxiliary quench lines or nozzles are used, recording positioning data with pictures will guarantee repeatability of the process. Keeping track of quench water temperature, pressure, and flow along with percentage of polymer (aka viscosity) will help ensure consistent results. Keeping track of cooling water temperature, pressure, and flow is important in troubleshooting water cooling issues. The power supply should be routinely serviced and calibrated along with having an active preventative maintenance schedule.
Ball Race Inductors
Inductor coils should be properly designed to not only produce a heat treat specification, but also be of high quality, manufactured from quality materials with maximized water cooling and robust construction. Flux intensifiers should be properly matched to the operating frequency and attached to the inductor coil securely. Teflon insulators should be virgin grade and replaced if damaged or worn. Fasteners, fittings, and hose clamps should be non-ferrous such as brass or 300 series stainless steel. Hoses should be specified non-conductive and rated to meet or exceed supplied water pressure. Epoxies used should be rated for high temperatures and allow for expansion and contraction. Electrical contacts should be silver plated to provide superior contact and prevent oxidation.
Gear Tooth Scan Inductor
Manufacturing inductor coils is a skill that takes years to develop and several more to master. These tools can be made from copper tubing utilizing fabrication techniques with the use of bending fixtures and forming dies. Most tools today are machined from solid, raw materials often with complex geometries. To ensure quality and consistency, 5-axis CNC machining is often used. Thirty to forty percent silver braze should be used for joining the inductor coil components and sealing water-cooling passages. Designs should avoid sharp corners and provide smooth transitions for optimal current flow and minimal stress risers. Computer-solid models, engineering drawings, and process forms following ISO 9001:2015 certified standards guarantee a quality manufactured induction coil.
Ring Bearing Inductor
Inductor coils are precision handmade tools and should be treated as such. Inductor coils should be supplied in a heavy-duty case with packing materials to provide the proper support and protection during shipping and storage. Identification should be clearly marked on the case. Many cases are lockable as theft may be a concern. When inductor coils are removed from service, they should be cleaned with soap and water using a Scotch-BriteTM cleaning pad. Steel wool and steel bristle brushes should be avoided as the steel can imbed into the copper and may cause more harm than good. Once the inductor is cleaned, it should be closely evaluated for signs of wear or damage. If there are any signs of wear or damage, it should be sent out for maintenance or repair so it will be ready for the next use. After tools are cleaned and evaluated, cooling passages should be blown out with air and the inductor should be dry before sealed in the case and put into inventory. Notes and pertinent data related to the inductor can also be stored with it such as the number of parts processed, any modifications made to the inductor coil, and recorded setup data.
All of what was stated above about design and manufacture of inductor coils also applies to bus bars and quick-change adapters. These devices are used between the workstation and the inductor coil to bridge the gap closer to the workpiece. Originally developed for the automotive industry, quick-change adapters can drastically reduce changeover time, often without the use of hand tools. Since these devices are typically kept on the machine for long periods of time, it is important to check the condition and perform maintenance when needed. Scheduled maintenance of removal and cleaning of these devices will exceedingly increase their life. As with inductor coils, soap, water and a Scotch-BriteTM cleaning pad is all that is needed for these items; steel wool and steel bristle brushes should be avoided.
Multi-Turn O.D. Scan & Quench
When installing bus bars, adapters, and inductor coils with a bolted contact, it is extremely important to make sure that each of the mating surfaces are clean and free from debris. When dirt accumulates or ferrous debris is contained between the contacts, severe arcing and melting can occur.
It is also very important to use proper fasteners. For correctly fastening contact surfaces, 300 series stainless steel bolts with heavy brass washers are preferred. The heavy brass washers help distribute the load evenly and help prevent damaging the copper. The bolt threads should be inspected for wear and replaced new if there is any sign of wear or damage. It is also very important to verify that the length of the bolts will properly clamp without bottoming out before tightened. The recommended torque procedure for 3/8-16 stainless steel bolts is to tighten each bolt twice at 35 to 40-foot pounds. Special "break-away" bolts are available that are designed to fail beneath the washer if they are over tightened. This prevents damage to the threaded insert inside the copper contact. The remainder of the bolt can then be removed with pliers. This is much easier and less expensive than having to repair a bus bar contact or workstation transformer.
O.D. Scan with Quench
The workstation contacts, bus bars, adapters, and inductor coils are all electrical components that when energized are a live circuit, often with high power. The inductor coil produces a strong magnetic field used to heat the workpiece. There are also stray magnetic fields in the surrounding area. It is very important that everything in the surrounding area of these components be non-ferrous to prevent them from heating up. Something as simple as a steel hose clamp in close proximity to the magnetic field could heat up, causing a hose to melt, or a hose to come off, preventing water cooling and severely damaging the induction tooling or the induction machine. Steel fittings can rust and contaminate a water system very rapidly, choking the water flow internally and causing premature failure from low water flow. Any support structure to the induction tooling components should be a quality non-porous insulating material. Non-porous materials prevent liquid and contaminates from being absorbed and ultimately may cause a short circuit.
Proper water cooling is essential to the performance and longevity of tooling components. Both the induction power supply components and induction tooling components need to be properly cooled. Most power supply manufactures have a closed loop cooling system requiring deionized or distilled water. Most power supply manufacturers require that the cooling water temperature be maintained from 80 to 90 degrees Fahrenheit to prevent condensation inside the cabinet and on the circuitry. For cooling the inductor coil, bus bars, and adapters, deionized or distilled water is not necessary. Cooling water for these induction tooling components is best to be kept below 70 degrees Fahrenheit. 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, short cycle applications.
The internal water-cooling passages of the inductor coil can play a significant factor in performance and longevity. Each inductor design should focus on maximizing water flow while minimizing sharp transitions.
The cooling water supply should come from a clean water source with a filtration unit of 25 microns placed just before it enters the induction tooling components. This guarantees that contaminates are filtered out, which may otherwise cause a low-flow or no-flow condition.
Quality non-ferrous fittings should be properly sized and configured to ensure the hoses are attached correctly to the induction tooling. It is very common to see 3/8" quick-change fittings used for cooling lines and 1/2" or 3/4" quick-change fittings used for quench lines. Using quick-change sockets for supply lines and quick-change plugs for return lines ensures the proper connections are made every time. Color-coding the hoses also helps in identifying water lines. It is very common to see blue hose for supply lines, red hose for return lines, and black hose for quench lines.
Single Shot Stem Inductor
Some inductor coils can be very small, having very limited water-cooling passages due to physical space. With these small inductors, it is even more important to have proper water cooling. In these situations, the use of a high-pressure booster pump may become necessary. These pumps can ensure cooling water continues to flow through these tight passages. Positive displacement pumps can also overcome steam pockets and help prevent vapor locks.
Problems with a cooling system can be detrimental to the performance and longevity of induction tooling components. Contamination in the cooling system can lead to low water flow. Problems with the water pump can also cause a low water flow condition. Then, low water flow can cause a steam vapor lock in the inductor coil leading to a rupture at a braze joint, a rupture through the tubing in a fabricated inductor coil, or a breach in the copper exposing the cooling chamber. Low water flow can also cause laminar flow internally which leads to thermal failure, resulting in exposed surface cracks through to the cooling chamber. Low water flow is sometimes identified by darkening of copper with purple color tones on the cooling return side of the inductor coil.
Wheel Bearing Single Shot Hardening
Induction tooling components cannot survive without water cooling. Symptoms include darkening of copper with purple color tones, melted copper, and catastrophic failure. Catastrophic failures caused by a no-water condition cannot be patched and require a major rebuild or replacement. It is a wise investment to have a flow indicator on the machine that prevents operation if there is no water flow or a low water flow condition.
All of what is stated earlier about the design and manufacture of inductor coils, bus bars, and adapters can also apply to quenches. These devices are used to evenly cool the part after heating to transform the structure consistently. Let’s discuss some of the important details in a quench system such as their design, fitting and hose requirements as well as pumps, filtration, and maintenance.
Quenches should be designed to provide a sufficient amount of quench to fully transform the metallurgical structure as specified. The quench pattern should be a uniform array of holes to quench the part at a proper impingement angle. The volume of water required should be matched with a supply having an inlet to outlet ratio not to exceed 1 in: 2 out. Hoses should be specified non-conductive and rated to meet or exceed supplied water pressure. Fittings should be high quality, non-ferrous without auto shutoffs, which can hinder quenching action and tend to clog more often.
Quenches can be a component that is kept on the machine for long periods of time. It is important to check the condition of these devices and perform routine maintenance. Scheduled maintenance of removal and cleaning these devices will exceedingly increase their life. Soap, water and a Scotch-BriteTM cleaning pad works well, and again, steel wool and steel bristle brushes should be avoided. Having a quench designed with bolted removable quench plates allows easy clean out.
Quench water needs to be filtered and contaminates kept at a minimum to improve performance and increase longevity of induction tooling components. A typical quench filter consists of a stainless-steel filter housing and a 100-microns bag filter. It is also very important to have a system for magnetic particle removal. Magnetic rod filters are available in many configurations, some that install inside the filter housing with the bag filter. Automatic separators are also often used. A low-cost alternative is to install a rubber coated magnet in the quench tank. In a non-ferrous tank, it can simply be dropped to the bottom. In a ferrous tank, it must be suspended to prevent the tank itself from becoming magnetized. All these methods can work, but only if they are properly maintained. A solid preventative maintenance schedule for these filters is essential.
Low Water Flow Failure
When filters are not used or maintained, tooling repairs are required more frequently. Common contaminates found inside quenches include oil dry, metal chips, and chewing tabaco. We see inductor coils come in for rebuild with a heavy patina of dirty, crusty contaminates. These contaminates are commonly a buildup of magnetic particles attracted by the magnetic field generated by the inductor coil. This patina accumulates and can create a short circuit, damaging the inductor coil.
To summarize, contamination is by far the most common cause of induction tooling failures. Water cooling is essential for longevity of induction tooling. Maintenance is essential for the performance of induction tooling. High quality, well-designed, robust induction tooling should be used for best results and consistency. Analyze induction tooling failures when they occur. Troubleshoot induction tooling rebuilds for possible machine issues. Look for methods of improvement with each opportunity. In closing, the best way to improve the performance and longevity of induction tooling components is to have open and frequent lines of communication with your tooling vendor.
About the Author: David Lynch is vice president of engineering at Induction Tooling, Inc. with 36 years of experience and is also 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.
For more information, Contact David at dlynch@inductiontooling.com.
In preparation for Heat TreatToday's May Induction magazine, here is a best of the web to end your week on.
How do they do it? What happens to metals when they are being induction heated? If you've had experience with heat treating using induction, how does it compare to other forms of heat treatment? This helpful article runs down the basics of induction and includes a video with different phases of the process. Check it out!
"As current flows through a medium, there will be some resistance to the movement of the electrons. This resistance shows up as heat (The Joule Heating Effect). Materials that are more resistant to the flow of electrons will give off more heat as current flows through them, but it is certainly possible to heat highly conductive materials (for example, copper) using an induced current."
Maciej Korecki Vice President of the Vacuum Furnace Segment SECO/WARWICK (source: SECO/WARWICK)
An international arms and military equipment manufacturer in Brazil needed to quickly expand and was recently able to receive a new vacuum furnace to meet their manufacturing demands.
The solution was provided by the parent company to North American SECO/VACUUM, SECO/WARWICK. Their furnace, the VECTOR®, is a single-chamber vacuum furnace that uses gas quenching and can be used for multiple metal heat treatment applications and processes. In this configuration, equipped with a round graphite heating chamber, it may be used for most standard processes including hardening, tempering, annealing, solutionizing, brazing and sintering.
"A situation where we have a product almost ready to be collected is rare. This time, the customer was indeed looking for a standard solution," said Maciej Korecki, vice president of the Vacuum Furnace Segment at the SECO/WARWICK Group.
This article continues the ongoing discussion on Equipment Selection for Induction Hardening by Dr. Valery Rudnev, FASM, IFHTSE Fellow. Six previous installments in Dr. Rudnev’s series on equipment selection addressed selected aspects of scan hardening and continuous/progressive hardening systems. This post is the third in a discussion on equipment selection for one of four popular induction hardening techniques focusing on single-shot hardening systems.
Previous articles in the series on equipment selection for single-shot hardening are here (part 1) and here (part 2). To see the earlier articles in the Induction Hardening series at Heat TreatToday as well as other news about Dr. Rudnev, click here.
Single-Shot Inductors for Non-Cylinder Parts
Single-shot inductors can be successfully used for hardening not only components of classical cylinder geometries but other geometries as well. This includes workpieces of general conical shapes, such as elliptic, parabolic, hyperbolic geometries—and the list can grow. As an example, Figure 1 shows induction surface-hardened ball joints (ball studs) and the single-shot inductors used to harden them. Ball studs are used in automotive, off-road, and agricultural machinery and can be different in shape and size (Compare images on the left in Figure 1 with images on the right.), requiring noticeably different hardness patterns.
Figure 1. Surface-hardened ball joints (ball studs) and single-shot inductors used for its hardening. (Courtesy of Inductoheat Inc., an Inductotherm Group company.)
In any attempt to scan harden workpieces with appreciable diameter changes, the scan coil must have a sufficient gap to clear the largest diameter. When scanning the section(s) of the workpiece with smaller diameters, an inductor-to-shaft air gap might be very large, resulting in low electrical efficiency and potentially exhibiting difficulties in load matching as well as in controlling the austenitizing pattern along the length of the part producing "cold" and "hot" spots. Additional difficulties may appear in controlling the hardness pattern in regions (e.g., near geometrical irregularities) where good control is most needed.
Thus, the substantially different workpiece-to-inductor electromagnetic coupling variations might not permit using classical multiturn solenoid coils or scan inductors. In contrast, single-shot inductors allow not only better electromagnetic coupling along the entire length of heat treated components (Figure 2) but also better address the geometrical irregularities of heat treated workpieces, producing the required hardness patterns at minimum process times with superior metallurgical quality.
Figure 2. Single-shot inductors allow better electromagnetic coupling along the length of heat treated components properly addressing the geometrical complexity of the workpiece. (Courtesy of Inductoheat Inc., an Inductotherm Group company.)
As stated in Part 1 of this series, in contrast to scan hardening, a single-shot inductor can be contoured along the length of the part properly addressing the geometrical complexity of the workpiece. Furthermore, the use of flux concentrators helps drive the current into the desired areas and allows producing a well-defined hardness profile with minimum distortion. The trade-off here is that more finesse is required in the design stage to produce the properly profiled single-shot inductor at the lowest possible cost.¹ Errors are costly since these inductors are each custom made for a given part or application and modifications can be quite costly. Thus, computer modeling is a helpful assistant as an attempt to keep the development cost down and shorten the "learning curve".
Proper hardening of such components as output shafts, flanged shafts, planet carriers, yoke shafts, sun shafts, intermediate shafts, driveshafts, turbine shafts, and some others may require extensive copper profiling, making a single-shot hardening inductor a complex electromagnetic device.
Certain geometrical features such as flanges, diameter changes, bearing shoulders, grooves, undercuts, splines, etc., may distort the magnetic field generated by an inductor, which, in turn, can cause temperature deviations, making it challenging to achieve certain hardness patterns.
For components containing fillets, it is often necessary to increase the heat intensity in the fillet region owing to the geometrical specifics. Also, the larger mass of metal in the proximity of the heated fillet and behind the region to be hardened produces a substantial thermal “cold sink” effect.¹ This draws heat from the fillet due to thermal conduction, which must be compensated for by generating additional heating energy in the fillet area.
Needed energy surplus can be achieved by narrowing the current-carrying face of the crossover segment of the single-shot inductor (Figure 3). Here is a simplified illustration of an impact of a copper profiling of the inductor’s heating face: if the current-carrying portion of the inductor heating face is reduced by 50 percent, there is a corresponding increase in current density. This will be accompanied by an increase of the eddy current density induced within the respective region. According to the Joule effect, doubling the induced eddy current density increases the induced power density roughly by a factor of four. Also, attaching a magnetic flux concentrator to certain areas of the hardening inductor further enhances the localized heat intensity.
Figure 3. Longitudinal leg sections of single-shot indicators and their crossover segments can be profiled by relieving selected regions of the copper to accommodate workpiece geometrical features. Attaching a magnetic flux concentrator to certain areas of the inductor further enhances localized heat intensity. (From V. Rudnev, A. Goodwin, S. Fillip, W. West, J. Schwab, S. St. Pierre, Keys to long-lasting hardening inductors: Experience, materials, and precision, Adv. Mater. Processes, October 2015, pp. 48–52.)
When using a single-shot inductor, it is particularly important that the workpiece is properly located in the heating position because seemingly minor dislocations may noticeably affect the heat treat pattern and metallurgical quality of hardened parts.
Traditionally designed single-shot inductors may exhibit high process sensitivity that is associated with the electromagnetic proximity effect.¹ A change in positioning of the workpiece inside the single-shot inductor attributed to excessive bearing wear of the centers, improper machining of the centers and fixtures, incorrect part loading, and other factors may produce a correspondent appreciable variation in the hardness pattern (particularly within the fillet region, undercut areas, and the part’s end zone). A reduced hardness case depth and the formation of unwanted microstructural products associated with incomplete phase transformation may be the result of that. Magnitude and distribution of transient and residual stresses might also be altered. Thus, attention should be paid to part’s reliable positioning during heating and quenching cycles.
As can be concluded, there are good reasons for using single-shot hardening, scan hardening, or continuous/progressing hardening approaches in induction hardening applications. The decision must be well thought out based on many factors such as geometry specifics, product quality, production rate, design proficiency, limitations of available equipment, reliability requirements, cost considerations, and some other factors.
The next installment of this series, “Dr. Valery Rudnev on . . . ”, will continue the discussion on design features of induction single-shot hardening systems.
This article was written by Dr. Vadims Geza, chief scientist at CENOS. More information on CENOS Platform can be found here.
Induction is becoming an increasingly popular choice for heating steel billets prior to forging due to its ability to create high heat intensity quickly and within a billet, which leads to low process-cycle time (high productivity) with repeatable high quality, occupying minimal space on the shop floor. It is more energy-efficient and inherently more environmentally friendly than most other heat sources for steel billets.
In this article, the author demonstrates a simulation example on how to optimize a progressive induction heating system for a steel billet. The method used is CENOS Platform, a 3D simulation software which focuses specifically on induction heating and uses open source components and algorithms.
CENOS platform is capable of simulating various types of induction heating for forging. It is possible to simulate both static heating and progressive heating where the billet is moved through the coil with constant velocity. In accomplishing this simulation, coil design is not a limitation: both single coil and multi-coil are possible to simulate. Besides the coil, it is also possible to simulate any material and frequency.
The functional performance of the software
CENOS is a finite element method-based, computer-aided engineering desktop software for 2D and 3D physical process simulation and computational modeling of induction heating, induction hardening, brazing, annealing and tempering of steel, aluminum, copper, and other materials.
The simulation process consists of three steps:
Choose the workpiece geometry (from built-in templates or create your own CAD file).
Define induction heating parameters (frequency, voltage, time, etc.).
Run 2D or 3D simulation of your choice.
At the conclusion, results like temperature and magnetic field are displayed in 3D renderings, plots, and more. Apparent power, induced heat, and inductance are logged into an Excel file.
3D Simulation example—comparison of two heating systems
In the simulation, two systems under consideration—two-stage and three-stage systems—in the progressive heating of the billet. The target for the simulation was to reach 2192°F (1200°C) ± 122°F (50°C). To check both systems, the user has to create set up for both of them, set physical parameters (material properties, frequency, current, etc.), and start the simulation.
After the simulation is done, the user will have access to different output variables, including:
Temperature distribution
Current density and Joule heat distribution
Magnetic field lines
Total, reactive and apparent power
Inductance of the coil
Coil current, voltage
In our example of billet heating, it is possible to compare both cases and the output.
It is observable how a three-stage system can decrease power consumption and increase the production rate for this specific case. It is also possible to plot the distribution of temperature, Joule heat, magnetic field, etc. Resulting temperature distribution in the billet across the radius is shown in Figure 1. As can be seen, better temperature homogeneity is obtained in the three-stage system.
Figure 1. Temperature distribution along the billet radius at the outlet of the heating system
Figure 2. Temperature distribution in the long billet during scanning (progressive) induction heating.
Figure 2 shows how different systems lead to different temperature distribution. In the two-stage system, the temperature required for forging is reached with shorter coils, thus also with smaller scanning speed. This leads to worsened temperature uniformity and smaller production rates. On the other hand, the three-stage system heater gradually increases the temperature of the billet and the resulting temperature difference between core and surface is smaller.
Platform users are free to change all the input parameters and assemble the system of any number of stages required for their process.
Should the same system need to be used for scanning of shorter billets where end effects play a more significant role, it is possible to set up a simulation with a moving billet. An example of temperature dynamics in such simulation are shown in GIF images below:
A simulation with a moving billet in a two-stage system.
A simulation with a moving billet in a three-stage system.
Simulation helps make better decisions for production set-up and planning
As demonstrated in the simulation example, it is possible to compare two different systems and get results. The scope and variety of different simulations are unlimited; it all depends on what problem the user wants to solve:
Dr. Vadims Geza
Heating system design—to optimize induction heating performance, improve product quality, and avoid unpleasant surprises related to subsurface overheating
The selection of power, frequency, and coil length in induction billet heating applications
The selection of right forging temperatures for plain carbon and alloy steels to avoid possible damage by incipient melting or overheating.
Main Photo Image via CENOS, courtesy of efd-induction.com
This article continues the ongoing discussion on Equipment Selection for Induction Hardening by Dr. Valery Rudnev, FASM, IFHTSE Fellow. Six previous installments in Dr. Rudnev’s series on equipment selection addressed selected aspects of scan hardening and continuous/progressive hardening systems. This post is the second in a discussion on equipment selection for one of four popular induction hardening techniques focusing on single-shot hardening systems.
The first part on equipment selection for single-shot hardening is here; the third part is here. To see the earlier articles in the Induction Hardening series at Heat TreatToday as well as other news about Dr. Rudnev, click here.
Traditional Designs of Single-Shot Inductors
Figure 1 shows a typical shaft-like component (Figure 1,top-left) suitable for a single-shot hardening inductor, as well as a variety of traditionally designed single-shot inductors for surface hardening shaft-like workpieces. Sometimes, these inductors are also referred to as channel inductors.
A conventional single-shot inductor consists of two legs and two crossover segments, also known as bridges, “horseshoes,” or half-loops [1]. The induced eddy currents under the legs primarily flow along the length of the part (longitudinally/axially) with the exception of the regions of the workpiece located under the crossover segments where the flow of the eddy current is half circumferential. Unlike scanning inductors, traditional designs of single-shot inductors can be quite complicated.
Figure 1. A typical shaft-like component (top-left image) suitable for a single-shot hardening and a variety of traditionally designed single-shot inductors for surface hardening shaft-like workpieces (Courtesy of Inductoheat Inc., an Inductotherm Group company)
With a predominantly longitudinal eddy current flow, the heat uniformity in the diameter change areas of the stepped shafts is dramatically improved and the tendency of corners and shoulders to be overheated is reduced significantly compared to applying a single-turn or multi-turn solenoid coils commonly used in scan hardening and continuous/progressive hardening.
Because the copper of single-shot inductors does not completely encircle the entire region required to be heated, rotation must be used to create a sufficiently uniform austenitized surface layer along the workpiece perimeter. Upon quenching, a sufficiently uniform hardness case depth along the circumference of the part will be produced. For single-shot inductors, the rotation speed usually ranges from 120 to 500 rpm.
Different types of magnetic flux concentrators (also called flux intensifiers, flux controllers, flux diverters, magnetic shunts, etc.) complement the copper profiling of an inductor, helping to achieve the required hardness pattern. Flux concentrators may provide several considerable benefits when applied in single-shot inductors. This includes an increase of coil electrical efficiency, a noticeable reduction of coil current, and a significant reduction of the external magnetic field exposure.
As an example, Figure 2 shows a transverse cross-section of a single-shot inductor and a straight shaft. Computer-modeled electromagnetic field distribution of a bare inductor (Figure 2, left) compared to an inductor with a U-shaped flux concentrator (Figure 2, right) is shown. Note that the magnitude of magnetic field intensity on both images is different. The use of U-shaped magnetic flux concentrators in single-shot hardening applications typically results in a 16% to 27% coil current reduction compared to using a bare inductor while having a similar heating effect. A reduction of the external magnetic field exposure while applying flux concentrator is even more dramatic (Figure 2, right).
Figure 2. Computer-modeled EMF distribution in the transverse cross-section of a bare inductor (left) compared to an inductor with U-shaped flux concentrator (right). Note: the scale of magnetic field intensity on both images is different [1].Different applications may call for various materials used to fabricate magnetic flux concentrators including stacks of silicon-steel laminations, pure ferrites, and various proprietary multiphase composites. The selection of a particular material depends on a number of factors, including the following [1]:
applied frequency, power density, and duty cycle;
operating temperature and ability to be cooled;
geometries of workpiece and inductor;
machinability, formability, structural homogeneity, and integrity;
an ability to withstand an aggressive working environment resisting chemical attack by quenchants and corrosion;
brittleness, density, and ability to withstand occasional impact force;
ease of installation and removal, available space for installation, and so on.
It should be noted that, though in most single-shot hardening applications flux concentrators will improve efficiency, there are other cases where no improvement will be recorded, or efficiency may even drop. A detailed discussion regarding the subtleties of using magnetic flux concentrators is provided in [See References 1, 2.].
Sufficient rotation is critical when using any single-shot inductor design. As an example, Figure 3 shows the sketch of a single-shot induction hardening system.
Figure 3. Sketch of single-shot induction hardening of an axle shaft. Note: The right half of this induction system is computer-modeled in Fig. 4 [3].Taking advantage of symmetry, only the right side of such a system was modeled using finite-element analysis. Figure 4 shows the result of computer simulation of initial, interim, and final heating stages, taking into consideration the shaft rotation. Insufficient part rotation resulted in a non-uniform temperature distribution along the shaft perimeter (Figure 4, left). Proper shaft rotation results in a sufficiently uniform temperature pattern (Figure 4, right).
Figure 4. Results of numerical simulation of heating an axle shaft by using a single-shot inductor [3].There should be at least eight full rotations per heat cycle (preferably more than 12 rotations), depending on the size of the workpiece and the design specifics of the inductor, though, as always in life, there are some exceptions. Shorter heating times and narrower coil copper heating faces require faster rotation during the austenitization cycle.
An appropriate inductor design with a closely controlled and monitored rotation speed will produce a hardness pattern with minimum circumferential and longitudinal temperature deviations, which will result in sufficiently uniform hardness patterns (Figure 5, left four images). Failure to ensure proper rotation as well as the use of worn centers (lacking grabbing force resulting in slippage and excessive part wobbling) could lead to an unacceptable heat non-uniformity, severe local overheating, and even melting (Figure 5, right). Manufacturers of induction equipment such as Inductoheat have developed various proprietary tools, holders, fixtures, and monitoring devices to ensure proper rotation and high quality of single-shot hardened parts.
Figure 5. Inductor design with closely controlled rotation speed will produce a hardness pattern with minimum circumferential temperature deviations (left four images). Failure to ensure proper rotation speed as well as the use of worn centers (lacking grabbing force resulting in slippage) could lead to unacceptable heat non-uniformity and can even cause a localized melting (right image).
The next installment of this column, "Dr. Valery Rudnev on . . . ", will continue the discussion of design features of induction single-shot hardening systems.
Induction heat treaters know that proper coil design is crucial to increasing longevity, improving production quality, and cutting costs. Among the topics addressed in this paper about induction heat treat coil design and fabrication (presented by R. Goldstein, W. Stuehr, and M. Blackby at ASM International) are these:
The design and fabrication of induction heating coils over the years
The Variable of Flow and the Influence of Frequency
Control and Presentation
Structure, Quenching, and Cooling
The paper closes out with a case study using computer simulation to show typical temperature distributions in a single-shot induction hardening coil.
A good place to start whenever preparing parts for induction heat treating is the consideration of inductor design. The authors provide this list (an excerpt):
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Considerations for Inductor Design
Induction heat treating coils are available in many shapes and sizes and must perform a variety of tasks in a given induction heat treating application. Depending on the application, the induction coil design requirements include:
Meet heat treatment specifications in desired production rates
Be robust enough to tolerate manufacturing variations
Mount into the induction machine
Have electrical parameters that match the induction power supply
Deliver quench
Have a satisfactory lifetime
Have satisfactory efficiency
Be repeatable from inductor to inductor
In developing a new induction heat treating coil and process, the first question is whether the component will be produced on an existing system or if a new machine must be built. In many cases, the part producer’s desire is to develop new tooling for an existing machine with spare capacity. This reduces the degree of freedom and can make the induction coil design procedure more complicated because a less-than-optimal frequency or coil style will be necessitated to fit the existing machine (Ref 16).
To determine the ability to use existing equipment, it is necessary to make an analysis of the part to be heat treated. Part material, prior processing, geometry, production rate, and heat treatment specifications all play roles. The part material and prior processing determine what the minimum heat treatment temperature should be, along with how much time is allowed for cooling. The part geometry and heat treatment specifications indicate how much energy is required, what the preferred frequency ranges are, and what type of induction method (i.e., single shot, scanning) is best suited for the application. Finally, the production rate determines how much power and/or how many spindles or stations are required.
Dr. Mihails Scepanskis is the CEO and co-founder of CENOS LLC.
Induction heating is an efficient way to quickly heat electrically conductive metals with pinpoint accuracy. It starts very simply, with a coil of conductive material, however initial design and optimization of the process are very complicated—it's hard to predict power, frequency, and heating time to get necessary results.
Computer simulation for induction heating is a powerful tool that enables engineers to investigate or design a physical system and process using a virtual mathematical model, thus saving time and money on numerous physical design iterations.
Dr. Vadims Geza is the chief scientist at CENOS.
Induction heating computer simulation offers the most efficient means of developing customized and optimized solutions and is, therefore, a necessity—not a luxury—in the modern induction heating industry. In this article, Dr. Mihails Scepanskis and Dr. Vadims Geza, both of CENOS LLC, based in Riga, Latvia, list features and benefits, obstacles and solutions of induction heating; advantages and disadvantages of computer simulation vs physical testing; what should be taken into account when choosing the right simulation software.
How simulation software can help companies save time and money on induction coil and process design
About Induction Heating
Today induction heating is used in many industrial processes, such as heat treatment in metallurgy, crystal growth and zone refining used in the semiconductor industry, and to melt metals which require very high temperatures.
Where Is Induction Heating Used?
Automotive
Construction
Aerospace
Metallurgical Plants
Oil & Gas Component Manufacturing
Special Applications
NASA's experimental NTP fuel elements heated with induction (Photo: CENOS)
Features:
Heat generation occurs inside the part.
Heating is contactless—as a result, product warpage, distortion and reject rates are minimized.
This method can provide very high power densities.
Heating may be highly selective in the depth and along the surface.
Any processing atmosphere (air, protective gas, vacuum) can be applied.
Very high temperatures may be reached.
The general benefits of induction surface heat treatment are
Short heating times—production rates can be maximized.
Optimized consistency—induction heating eliminates the inconsistencies and quality issues associated with open flame, torch heating, and other methods.
Extended fixture life—induction heating delivers heat to very small areas of your part without heating any surrounding parts. This extends the life of the fixturing and mechanical setup.
Environmentally sound without burning fossil fuels—induction is a clean, non-polluting process. Improves working conditions for employees by eliminating smoke, waste heat, noxious emissions, and loud noise.
Effective energy consumption—this uniquely energy-efficient process converts up to 90% of the energy expended energy into useful heat; batch furnaces are generally only 45% energy-efficient. Requires no warm-up or cool-down cycle.
Flexible adaptation to the hardening tasks
Closed loop computerized process control and compatibility with overall process automation
Large gear heat treatment (Photo: CENOS)
Obstacles:
Initial design and optimization of the process is very complicated.
It is hard to predict power, frequency and heating time to get necessary results.
Unlike other heating methods, induction heating requires specific coil design for each workpiece, so it's not very economic unless you need to process multiple similar workpieces.
To design and calculate the induction heating process you can:
Do a rough analytical estimation, then proceed with countless design iterations in the lab.
Find a professional company that can do induction coil and process design for you, but keep in mind that you most likely will be charged for design hours spent in the lab.
Buy a sophisticated multi-physics simulation software and hire a trained simulation engineer/analyst or pay for engineer's training (usually takes 3 months).
Start using a simple, affordable, and induction heating-focused simulation software like CENOS Platform, which features online training and templates for a quick and easy start.
Induction Heating and Computer Simulation
What Is a Computer Simulation?
Nowadays, in various industries, manufacturers prefer using software simulations over physical testing. Computer simulation is a powerful tool that enables engineers and scientists to investigate or design a physical system and/or process using a virtual mathematical model, thus saving time and money on numerous physical design iterations.
The vast majority of modern computer simulation software packages utilize numerical methods (e.g. finite element method or “FEM”) to evaluate extremely complex physical systems—systems that are otherwise impossible to precisely analyze. By leveraging the power of modern computer hardware, simulation software can provide substantial improvements in the efficiency, reliability, and cost-effectiveness in design and development processes.
Computer Simulation in Induction Industry
First works on computer simulation of induction coils were made in the 1960s. Due to limited access to computers, their low memory, speed, and poor programming methods, the computer simulation did not receive significant industrial application until the 1980s.
Now computer simulation has become a practical tool for everyday use in the induction industry. It allows the user to design optimal systems, improve equipment performance, dramatically reduce development time and costs, and better understand the process dynamics, etc.
Though there are still difficulties in an accurate simulation of non-linear and different mutually coupled tasks, computer simulation is effectively used for the design of induction heating coils and problem solution.
The 10 cm gear hardening with one concentric inductor at 170 kHz and 1.9 kA over 120 ms
Benefits and Value of Induction Heating Computer Simulation
The use of induction heating computer simulation software can promote substantial improvements in the performance and cost-effectiveness of induction heating equipment, in addition to large reductions in the cost and time required to design and develop induction heating processes.
From a design perspective, computer simulation is valuable for a number of reasons, two of the most notable being:
The physics involved in utilizing electromagnetic induction as a deliberate and controlled source of heat generation is extensive and multi-faceted. Computer simulation provides a quantitative approach to designing and developing induction heating processes, allowing complex physical phenomena that cannot be physically observed and/or measured to be clearly visualized and quantified.
Because electromagnetic induction offers an extremely effective, economical, and versatile means of heating conductive materials, the scope of induction heating applications is very broad. This includes (but is not limited to):
Furthermore, each of these general applications includes countless different workpiece types, geometries, materials, and heating requirements. As a result, no “universal solution” exists in the design of induction heating equipment. Induction heating computer simulation offers the most efficient means of developing customized and optimized solutions and is, therefore, a necessity—not a luxury—in the modern induction heating industry.
Combining Simulation With Real World Tests for the Best Results
Example of simulation results (Photo: CENOS)
Inductor design is one of the most important aspects of the overall induction heating system. A well-designed inductor provides the proper heating pattern for your part and maximizes the efficiency of the power supply, while still allowing easy insertion and removal of the part. With the right design, it's possible to heat conductive materials of any size and form, or only the portion of material required.
Computer Simulation vs Experimental Method
Computer Simulation
Advantages
Can work for any geometry and operating conditions
Demonstrates the entire dynamics of the process
Leaves records for future
Limitless accuracy of calculations
Does not require special equipment
Less expensive and less time-consuming
Future improvements expected
Provides 3D process visualization for customers (pictures, video)
Limits and Disadvantages
Requires special software and databases
Not all the processes may be simulated (as of today)
Does not provide physical samples
Experimental Method
Advantages
May provide the most reliable results
Can show the performance of the whole system including unexpected effects and troubles
Does not require a material property database
Provides physical samples for properties validation
Limits and Disadvantages
May require expensive equipment
Does not provide a good understanding of the process
Difficult to transfer knowledge (to scale a company)
Case dependent accuracy
Limited access to production equipment (expensive)
Time-consuming—may cause production delay due to multiple design iterations.
Challenges in coil design
The induction coil, also known as an "inductor", is essential to induction heating. Single-turn, flexible, multi-turn cylindrical, left-turn, right-turn, rod-shaped, hair-pin, parallel, ear-shaped, tiny, big—whatever the coil shape and size—the right design maximizes the lifetime of the coil and ensures lowest energy consumption and best effects on work process and materials.
Many factors contribute to a coil’s effectiveness: the care taken to make it, the quality of the materials used, its shape, its maintenance, its correct matching with the power source, etc.
Here are just three of the many hurdles to be overcome in order to make safe and efficient coils:
Impedance matching
It is necessary to achieve the correct impedance matching between the coil and the power source in order to use the latter’s full power. The coil designer must also consider that coils need five to ten times as much reactive as active power.
Magnetic flux concentrators
Concentrators focus the current in the coil area facing the workpiece. Without concentrators, much of the magnetic flux may propagate around the coil. This flux could engulf adjacent conductive components. But when concentrated, the flux is restricted to precise areas of the workpiece.
Water flow and speed
It is generally important to achieve an adequate flow of cooling water through the coil. When high power density is expected in the inductor, the coil designer must consider the flow rate and the water’s velocity. This is because velocity significantly influences the heat transfer between inductor and coolant and therefore has a major impact on the longevity of the coil. A booster pump is sometimes needed to maintain the desired flow and velocity. Professional designers will also specify a purity level for the water in order to minimize coil corrosion.
Tools and Processes Necessary To Ensure Coil Longevity and Performance
Advanced induction coil design includes:
Detailed analysis of specifications, available equipment, and environment
Coil style and heating process selection (scanning, single-shot, static, etc.)
3D design programs and computer simulation for coil head optimization
Analysis of benefits of magnetic flux controllers application
Advanced manufacturing techniques, mandrels to achieve tight tolerances
Testing in a laboratory or industrial plant for performance and final dimensional check
Final corrections if required
Designing and making induction coils is technically challenging. Computer simulation helps tackle some of the challenges, limiting costs and maximizing effectiveness.
CENOS Platform's mission is to help companies switch from old and cumbersome experimental methods to a powerful computer simulation that is simple, affordable, and induction heating-focused. CENOS, combined with real-world trials, will yield the best results in a fast and cost-effective way.
How To Choose the Right Simulation Software
The induction heating market is small compared to other industrial sectors, and there are only a few specialized simulation packages on the market that can be used for induction process and coil design. Induction heating simulation involves a set of mutually coupled non-linear phenomena. Many induction applications are unique and may require different program modules. In addition to computer simulation software, an extensive material database is necessary for accurate results.
1D, 2D or 3D?
Majority of practical simulations now are being made in 1D or 2D approaches. But with 1D and 2D, the structure and geometry of real induction systems are often very simplified. In reality, a majority of induction systems are 3D. In addition, interference of induction device and source of power must be considered in many cases. That's why 3D will ensure less space for errors and a more thorough analysis.
Cloud vs Desktop
Working with cloud-based software requires uploading your data to the third party. Frequently induction heating equipment manufacturers are not allowed to share their customer CAD files with a third party due to NDA. Furthermore, while cloud computing may provide increased calculation speed, one should consider the time it takes for uploading the design files and downloading the result files.
Importance of training & support (time, costs)
There is a common opinion that simulation software requires a specially educated (and well paid) simulation engineer/analyst, usually hired only for one kind of task—simulation. This is definitely true for sophisticated multi-physics simulation packages, which might require 3 to 4 months of intense training because of a plethora of numerical aspects which should be taken into account in order to get reliable results in a simulation. However, CENOS 3D desktop software keeps focus solely on induction heating and tries to avoid any unnecessary functionality which might confuse an inexperienced user. By using CENOS-dedicated templates, a beginner can run his first induction simulation in just under 30 minutes and become a pro user with any 3D geometry after 2 weeks of training, guided by CENOS engineers.
Cost
Licensing software can cost $20,000 to $80,000 up front plus additional annual payments in 20% value of purchase price just for support and updates. And that's only for an induction heating module, whereas CENOS's annual license is $7,200 and requires no upfront investment. Alternatively, one could consider a “pay as you go” purchase model, paid by hours, but one must keep in mind that 3D calculations take time, which might make this particular subscription model cost inefficient.
Open Source software—a free alternative with some drawbacks
Open source is very cost efficient—open source tools like Elmer or GetDP are free to use. However, these tools might require a long training period (6 to 10 months); plus extra steps and routines required for everyday simulation will take up to 1,000 additional hours a year. Overall, open source tools are a solid choice because they are validated by the community but not focused on user experience.
Benefits:
Community. Open source solutions often have thriving communities around them, bound by a common drive to support and improve a solution and introduce new concepts and capabilities faster, better, and more effectively than internal teams working on proprietary solutions.
The power of the crowd. The collective power of a community of talented individuals working in concert delivers not only more ideas but quicker development and troubleshooting when issues arise.
Transparency. Open source code means just that—you get full visibility into the code base, as well as all discussions about how the community develops features and addresses bugs.
Reliability. Because there are more eyes on it, the reliability of open source code tends to be superior as well. Code is developed on online forums and guided by experts. The output tends to be extremely robust, tried, and tested. In fact, open source code now powers about 90% of the internet and is being rapidly adopted across major enterprises for this reason.
Better security. As with reliability, open source software's code is often more secure because it is much more thoroughly reviewed and vetted by the community.
Drawbacks:
Because there is no requirement to create a commercial product that will sell and generate money, open source software can tend to evolve more in line with developers’ wishes than the needs of the end user. For the same reason, they can be less “user-friendly” and not as easy to use because less attention is paid to developing the user interface.
There may also be less support available for when things go wrong – open source software tends to rely on its community of users to respond to and fix problems.
Because of the way it has been developed, open source software can require more technical know-how than commercial proprietary systems, so you may need to put twice as much time and effort into training employees to the level required to use it.
Many different open source solutions are not compatible with each other. Take for example GetDP - an open source finite element solver, its core algorithm library uses its native pre-processing and post-processing tool Gmsh, which frankly, compared to other solutions, is not the best in its class.
CENOS Makes Open Source User-Friendly and Easy To Use
CENOS Platform uses GetDP solver and offers integration with far more superior open source tools like SALOME for pre-processing and Paraview for post-processing, which by default are not compatible with GetDP.
“CENOS” stands for “Connecting ENgineering Open Source”, highlighting its new software approach: connecting the best of open source tools in one seamless user experience. CENOS platform technology enables affordable simulation available for small to midsize companies by connecting third-party open source algorithms GetDP, Salome, and Paraview, developed by strong academic communities involving world top research centers and universities like Sandia National Lab, Imperial College, KU Leuven, and others. The academic world has already built plenty of smart algorithms; there is no need to charge money for the scientific heritage. Use of free open source algorithms makes it possible for CENOS to be affordable for everyone.
The company has built a user-friendly interaction layer and interconnection between previously incompatible separate open source software algorithms. CENOS Platform consists of a user interface, special data optimization procedures including necessary data reformatting for inter-operational compliance ensuring data flow and control between different open source tools. This way CENOS lets engineers save up to 80% of design time by replacing physical prototyping with powerful simulation software which is affordable and easy to use.
About the Authors: Dr. Mihails Scepanskis is the CEO and co-founder of CENOS LLC, based in Riga, Latvia. Dr. Vadims Geza is the chief scientist at CENOS.
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![Figure 2. Computer-modeled EMF distribution in the transverse cross-section of a bare inductor (left) compared to an inductor with U-shaped flux concentrator (right). Note: the scale of magnetic field intensity on both images is different [1].](https://www.heattreattoday.com/wp-content/uploads/2019/08/Rudnev-Part-2-Fig-2.jpg)
![Figure 3. Sketch of single-shot induction hardening of an axle shaft. Note: The right half of this induction system is computer-modeled in Fig. 4 [3].](https://www.heattreattoday.com/wp-content/uploads/2019/08/Rudnev-Part-2-Fig-3.jpg)
![Figure 4. Results of numerical simulation of heating an axle shaft by using a single-shot inductor [3].](https://www.heattreattoday.com/wp-content/uploads/2019/08/Rudnev-Part-2-Fig-4.jpg)
