Induction hardening
Hardening with induction
In induction hardening, heat is generated by eddy currents in the surface layer of the workpiece. The eddy currents are caused by the field of an induction coil in which a high-frequency alternating current flows. The penetration depth can be adjusted by the alternating frequency of the current. Rotationally symmetrical components are particularly suitable for induction hardening.
Induction surface hardening
Hardening the surface layer of a workpiece is used when the workpiece requires a hard and wear-resistant surface layer but a high-strength and tough core. This is necessary for workpieces whose surfaces are subject to wear and which have to bear impact-like and alternating loads, such as shafts, bolts, gear wheels or slideways.
In induction surface hardening, a thin outer layer of the workpiece made of hardenable steel is rapidly heated by a strong heat input and hardened by immediate quenching. This results in martensite. The deeper areas of the workpiece are not yet sufficiently heated during the short heating time and remain unhardened.
Hardening of carburized workpieces
Steels with a carbon content of 0.1% to 0.2%, which are not actually hardenable, are used for carburizing. The workpieces are annealed for several hours at 880°C to 980°C in carbon-emitting feedstocks. Carbon diffuses into the surface layer, making it hardenable. Solid substances (coke charcoal granulate), liquid substances (highly toxic cyanide salt melts) or gases (mixture of CO and H2) are used as feedstocks
Subsequent induction hardening and tempering gives the carburized workpieces the desired performance properties. Only the surface layer is hardened, the workpiece core remains unhardened and tough.
What makes induction hardening so interesting?
Induction hardening offers a number of positive advantages in the series production of components:
- A hardening machine can be easily integrated into fully automated series production, which has a positive effect on unit costs
- The hardness results are reproducible
- Process data is recorded and monitored
- The energy costs are relatively low, as induction only partially heats the component
Basics of induction heating
Further information on induction heating can be found in the following brochure: