Induction Heating Equipment for Annealing

Induction annealing systems and processes

Process reliability and reproducibility – two good reasons to use induction annealing for stress relief and impurity removal from metal components. The induction annealing process allows precise and reliable control of metal material properties within workpieces, including hardness, toughness and internal stress. Although mainly used for soft and stress-relieving annealing, induction also offers enormous advantages over conventional methods because it can be used to thermally remove impurities during a process called bright annealing.

Unlike conventional methods, induction annealing generates heat directly in the workpiece by using an alternating electromagnetic field. The entire heating process is carried out without contact and in a very short time. Often, the cooling process for the part creates less distortion as well because the temperature of the workpiece can be reduced slowly without coolant rather than quickly through abrupt immersion in water or coolants. eldec’s power supplies can fine-tune the frequency, power and annealing time, and eldec experienced technicians can help you find the perfect recipe of settings for your production environment.

Common applications for induction annealing

Induction annealing can be used to control material properties of metals in various manufacturing scenarios. It is often used to stress-relieve parts, increase material toughness and to remove residues from recycled metals. The ability to precisely control where heat is applied as well to control the temperature in that exact location ensures the process can be accurately reproduced, which is especially important in mass production environments.

Although annealing can be adapted to many processes, here are three examples that may help spark your imagination and lead to possibilities within your own plant:

Soft annealing - is used to reduce the hardness of a metal in order to increase its toughness. The process makes the metal less brittle and prone to fracture. Pelton, a turbine manufacturer, used eldec’s MF (Medium Frequency) power supplies to stress relieve the welds of turbine blades destined for a hydro-electric power plant.

 

 

Induction tempering - eliminates or minimizes stresses created during machining or forming. The process is similar to soft annealing, but much lower temperatures are used. It is especially helpful for heat treating workpieces with high internal stresses.

 

 

Induction de-coating - can be used to remove residues from recycled metals quickly and efficiently. The precision of the process using eldec’s MF power supplies ensures the metal is not damaged.

Induction heating benefits for annealing

Manufacturers in industries ranging from automotive to aerospace, oil and gas production and distribution to power generation among others rely on induction annealing to strengthen critical metal parts. Advantages of induction annealing over furnace tempering include:

• Anneal workpieces only where needed
• Reduce workpiece distortion
• Thermal elimination of surface impurities
• Control temperatures precisely
• Shorter cycle times
• Create reliable, reproducible processes
• Better energy efficiency
• The ability to manufacture a part as an in-line process rather than requiring to "batch" parts through an oven

Continue reading to see how induction heating equipment for annealing has been used in various manufacturing situations and environments.

Soft annealing to prevent part fatigue fractures in your operation

Soft annealing is used to reduce the hardness of a metal in order to increase its toughness. The process makes the metal less brittle and prone to fracture. There are few mechanical parts that have to withstand loads as great as those imposed on turbines in hydroelectric power plants. Water gushes out under high pressure from specially designed nozzles before hitting the individual blades at a high speed. The blade that is hit first drives the wheel a short distance, but is then idle again for a revolution, resulting in high alternating forces in the root area of the blade.

To prevent fatigue fractures in the root area, turbine makers anneal the weld between the turbine wheel and blade. This relatively gentle, heating process improves the durability of the part significantly. However, the heating must be reproducible and carried out with high precision to ensure turbine quality requirements are met.

Annealing water turbine blade welds is just one example of how the process can be used to stress-relieve parts. eldec’s experienced technicians have a thorough understanding of induction annealing. They’ll begin with a design review of your parts as well as a review of your manufacturing processes. Request a consultation by giving eldec a call or request a consultation and we’ll contact you to see how eldec can help you prevent part fatigue fractures in your operation.

Induction tempering to obtain optimal properties for shafts, bars and joints

Induction tempering eliminates or minimizes stresses created during machining or forming and will make metal less brittle. The process is similar to soft annealing, but much lower temperatures are used. It is especially helpful for heat treating workpieces with high internal stresses. Since induction tempering can be precisely controlled using a generator’s power, frequency and the inductor’s geometry, deformities in the workpiece can be avoided and the process is more efficient.

Induction tempering can be broken down into two categories:

• Surface hardening and tempering of automotive and aviation parts such as valve seats, gears, transmission and axle shafts
• Thorough hardening and tempering of workpieces such as chain links, structural metal used in construction and seamless, electrical-resistant tubing and pipe necessary for safe oil and gas production and distribution

This process can be used across a wide range of industries, and in some cases, like hardening and tempering a shaft, tempering can be performed right after the hardening process -- sometimes using the same coil. Our experienced application engineers can help you select the right power supply and design specialized inductors for your specific workpiece and manufacturing environment.  They will also work with you to optimize your production process for optimum speed and efficiency.

Induction de-coating to efficiently refurbish steel barrels

Refurbishing steel barrels used for industrial packaging is a good example of how to use the induction annealing process to de-coat metal.  Removing chemical residues and damaged coating from the surfaces of steel barrels prior to recycling can be a challenge – especially since the residues and coatings must be completely removed and common chemicals can form deep deposits in the surface of the steel. However, it is possible to use induction heating equipment for de-coating the barrels to ensure the metal will not be damaged.  Best of all, the induction de-coating process is incredibly fast and thorough.

Two types of inductors are required for de-coating steel barrels. eldec’s experienced technicians first design a custom-fit, ring inductor, which encloses the outside diameter of the steel barrel, ensuring even heating of the steel surfaces. The ring inductor, often part of an automated process, travels along the length of the barrel. Simultaneously, a flat inductor is used to heat up the base.  Once the metal reaches approximately 500° C (932° F), any coating or chemical residue will evaporate from the barrel.

Generators and inductors for induction annealing

eldec manufactures a wide array of generators that are appropriate for induction annealing. They range from power supplies to complete heating systems.  Units are available in low, medium, high frequencies and dual or simultaneously dual frequencies.

Typically, a true annealing process requires more than lowering the hardness value of the surface by a few points.  In this case, a lower frequency power supply, a medium frequency or even low frequency model, depending on the thickness of the material, would work best.  When tempering, a high frequency generator would be appropriate because you would only need to lower the hardness value by a couple of points.  De-coating, on the other hand, requires only the surface of the workpiece to get hot in order to strip the coating.  In this case, either a medium frequency or high frequency generator would work well.  For barrel de-coating, eldec recommends using a medium frequency power supply with an outside heating coil.

The following models of eldec induction power supplies work well for annealing, tempering and de-coating:

• eldec’s PICO-S is available in medium frequency ranges of 8-20 kHz or 16-40 kHz or high frequency ranges of 70-175 kHz or 140-350 kHz. Continuous, tap and timer mode, power, current and temperature control as well as program memory storage are standard. The PICO-S’s Plug & Play commissioning means you can unpack it, plug it in and start heating. Accurate power control and current flow provide optimal heating results as well as outstanding workpiece quality. Models start as low as $17,500, making the PICO-S affordable as well as flexible and easy to use.
• Reliable, highly efficient and virtually maintenance free, eldec’s ECO LINE is available in medium frequency ranges of 8-20 kHz, 10-25 kHz or 16-40 kHz or high frequency ranges anywhere from 60 up to 400 kHz. They include single or multiple outputs and flexible options for control.
• eldec’s CUSTOM SDF® models are simultaneous dual frequency generators that are capable of running two different frequencies at the same time. This patented generator has one high frequency and one medium frequency converter sharing a common power output.  The higher frequency’s occillation is superimposed on the medium frequency occillation during the heating process.  This model of induction power supply is often used for complex workpiece components such as gear wheels. CUSTOM SDF®models are available in10 kHz to 25 kHz and 150 kHz to 350 kHz.
• eldec’s CUSTOM DF models are dual frequency generators that are capable of switching between medium or high frequency settings. They are similar in the quality you expect from eldec’s CUSTOM SDF® power supplies, but at a much lower price. They are available in medium frequency ranges of 8-20 kHz , 10-25 kHz or 16-40 kHz or high frequency ranges of 140-350 kHz or 160-400 kHz.

If you are unsure which model to choose, we can help select the best induction annealing system for your workpiece components and operating environment.

Schedule a consultation

Want to learn how induction annealing can help your operation? Schedule a consultation with our induction heating experts. eldec LLC’s team will help you choose the induction power supply and design induction coils for your specific parts and production environment. If induction heating is new to you and your staff, operator and maintenance training is available in our plant in Auburn Hills, Michigan or at your site. Give us a call or send a request for a consultation and we’ll contact you. We look forward to talking with you.