Hardening of the surface (s. Hardness) of casting products (cast iron and steel) that are heated up to the required hardening temperature using a torch.
Heat-up by means of a torch involves relatively long heating times and in general only achieves hardnesspenetration depths of less than one millimeter. Therefore, flame hardening is preferably used for small series production. As soon as the hardening temperature is reached, the surface is quenched by means of a water sprinkler. This may cause hardness cracks, particularly with hardnesspenetration depths of more than 2 mm. However, this defect can be avoided by using oil or water emulsion mixtures for quenching.