Martempering is applied to oil ( or air) hardening steels to give the same hardness of oil quenching but with less distortion and less danger or cracking. In Martempering, the parts are heated to the normal temperature and then quenched in a molten bath of FRANK 150.

The Parts are held there until the bath temperature is reached and finally air cooled. It is usual to keep the FRANK 150 bath temperature to 200-250°C. It has been found that the addition of 1% of water to FRANK150 Baths used at 200-250°C for tempering improves the cooling power of the FRANK 150 bath. The water is usually added to the surface of the bath by means of a small jet.