TEMPERING METHOD FOR HARDENED ARTICLES OF STRUCTURAL AND TOOL STEEL Russian patent published in 2005 - IPC

FIELD: steel hardening, particularly for heat treatment of articles made of structural or tool steel.

SUBSTANCE: method involves heating article at least in two stages and isothermic tempering thereof after each heating stage; cooling the article in coolant up to coolant boiling stopping. The first heating stage is performed under 180°-260°C, the last one is carried out under temperature of not more than A_cl-20°C. Water under temperature of not less than 80ºC or aqueous ambient medium having maximal heat-transfer coefficient corresponding to temperature of not less 250°C are used as the coolant. Aqueous ambient medium may be 3-26% aqueous solution of NaCl, 10-50% aqueous solution of NaOH or bischofite with 1.1-1.32 kg/m³ density.

EFFECT: optimization of process parameters.

3 cl, 2 tbl