In the surface hardening process the metallic structure in the outer layer of a component is changed by heating and quenching to improve properties in only a selected area of the component. For instance, the bearing track only in a bearing element; the gear tooth only on a gear; the slideway surface only on a guideway; or the cam track area only of a cam. It is neither a coating process nor a finishing process, so it does not add any further elements to the material or lay on different materials.

The process is highly energy efficient, since heat is applied only to those areas requiring better properties and not to the whole bulk of the component. The necessary heating of components is obtained by either electro-magnetic induction techniques or directly applied high intensity flames, the technique being to heat the required area as quickly as possible. Among the many advantages of the process are that it is highly energy efficient and that it can produce considerably less distortion than conventional heat treatment processes using readily available steels.

It is often the case that one thing leads to another, and as well as the press tools a trend has been identified towards using surface hardening to improving the fatigue life and wear resistance of parts in the actual press mechanisms. Higher production rates of automotive body parts calls for greater use of steel strip, and this in turn requires the use of levelling rollers, back-up rollers, and table rollers, all of which can be surface hardened.