Induction Hardening

Induction hardening offers excellent hardness distribution with minimal defects

Induction hardening offers significant advantages over traditional methods for heat-treating steel, alloy, and other metal parts. This process is perfect for metal with a carbon content of more than 0.3%, particularly hardened steel with a low alloy content (C34, C35, C60, etc.), as described in the DIN EN 100083 industry norm. Shafts, gears, armatures, sprockets and other components can all be hardened using this induction process.

The process is very demanding on the equipment and the inductor used. Ideal hardening results can only be achieved by perfectly matching a precisely controlled energy source with an optimum inductor design. eldec's experienced engineers custom design the induction coils to meet customer unique specifications, including single turn, two-turn, face-heating, clamshell, and clamp inductors. Every machine is completely inspected and tested to ensure optimum power and heat settings.

Heating directly with induction hardening

Induction hardening is a process in which the heat is generated directly in the workpiece. The principal advantage of this type of heat treatment is that the material quickly reaches the desired temperature to produce hardened metal parts. With traditional heat treatments such as flames, ovens, or by convection, heat is applied to the part by heating up the surface layer. These methods take considerably longer and require significantly more energy to produce the desired hardness. Induction hardening, by contrast, offers extremely short heating times. It is a very effective and attractive method in the manufacturing of steel shafts, components, and other metal parts across a range of industries. Additionally, induction heating can be very precisely controlled via the power, frequency, and inductor geometry. This minimizes deformities in the workpiece and ensures the efficiency of the process.

How induction hardening works

The primary application of this induction method is the hardening of steel. One or many induction coils are used to generate and target an alternating magnetic field. This magnetic field produces eddy currents in the metal, which heat the workpiece up to the desired temperature. Immediately after heating, the component then goes through a quenching process using water, oil, or an emulsion. This cools the metal until martensitic transformation occurs, producing a hardened surface that is tougher than the base metal.

After quenching, the steel undergoes tempering, a low-temperature heat treatment process, to reach the desired hardness / toughness ratio. The maximum hardness of a steel grade obtained through the hardening process gives the material a low toughness. Treating the steel through tempering reduces the hardness in the material and increases its toughness.

The hardening depth in the workpiece is controlled, very precisely, by adjusting the electrical power output of the induction machine and the frequency of the inductor / coil current. The thickness of the heated layer from the surface of the metal to some point below the surface is inversely proportional to the frequency of the applied alternating current. Higher frequencies produce thinner skins. Case hardening the surface of steel increases the wear resistance of the component without reducing the ductility of the bulk of the material. eldec offers energy sources with the latest converter technology in three frequency ranges:

  • Low: 1 – 7 kHz
  • Medium: 8 – 40 kHz
  • High: 60 – 500 kHz

Induction hardening with SDF

With Simultaneous Dual Frequency, also known as SDF, eldec offers an additional  method that is used especially for workpieces with complex shapes. A medium frequency is overlaid with a high one so that both act upon the material simultaneously at a uniform depth. This guarantees the component is heated at a consistent temperature across the entire part to ensure even surface hardness. This application is perfect for the process of manufacturing cogs and gears. Even though the top and bottom of the gear teeth are at different distances from the inductor, a smooth and precise hardness layer can be achieved.

Induction Hardening

What are the advantages of induction hardening?

Induction hardening offers users outstanding control over of the hardening process. This safe heating method enjoys a multitude of applications, including the manufacture of steel shafts and axels, and can be used across a range of industries. Induction heating machines have minimal space requirements and can be easily integrated into manufacturing processes and production lines. Furthermore, they do not have to be kept running when not in use, unlike surface hardening furnaces.

The use of induction is very energy efficient since only a small portion of the material is heated. Typically, less than 5% of the mass needs be targeted to accomplish the required properties. The results are outstanding, achieving accurate hardening results even on complex pieces with contours. The number of rejected or deformed parts is also minimized with this process.

Why eldec?
eldec offers a wide range of compact generators for induction hardening that provide customers with the highest-quality in terms of performance. With the precision frequency adjustment, even the most demanding jobs can be completed with ease. To ensure that the perfect solution is discovered for any application, the MIND range of machines have been specially designed and manufactured to meet customer requirements. Not only does eldec offer hardening systems, but they also offer a wide range of generators, tools and brazing and heating systems.


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