Flame hardening

As an alternative to induction hardening this process is also used for surface hardening similar materials. The surface to be hardened is traversed by an oxy-gas flame ‘head’ followed closely by the quench spray. Either oil mixtures or polymer quenchants may be used. Although it is not capable of quite the same degree of control or automation as the induction method, it has the advantage of being applicable to a wider range of geometrical shapes and sizes. Early flame hardening equipment was developed from standard oxy-gas metal cutting torches. Modern sets incorporate gas volume control, temperature and time controls.

Heating times are longer than by induction , and there is more likelihood of variations in hardening response across the surface traversed. In many instances both induction and flame hardening are applied to previously hardened and tempered parts. This combination provides optimum results in terms of wear resistance and fatigue life improvement.