METHOD OF HARDENING OF ARTICLES FROM STEELS AND ALLOYS Russian patent published in 2002 - IPC

FIELD: heat treatment of machine parts from steels and alloys; applicable in aircraft, airspace and other industries. SUBSTANCE: method includes heating of articles in furnace to temperature of 260-280 C, holding at this temperature for 3 h and cooling in the air. Articles are heated to hardening temperature corresponding to given steel grade. Articles from steels with final hardening temperature not exceeding 900-1100 C, for instance, grades 30CrMnSiNiMoN-Wcu, WniSi-2, WniSi-5 are heated to hardening temperature and held at this temperature. Articles from steels with final hardening temperature exceeding 900-1100 C, for instance, grade B18, are heated in molten salt bath, first, to temperature not exceeding 900- 1100 C and held at this temperature up to full worming up. Then, these articles are transferred to melt of barium-chloride salt bath, heated in this bath up to final hardening temperature corresponding to given steel grade and held at this temperature. Isothermal hardening of articles from steels and alloys is conducted at temperature corresponding to upper interval of bainite preconversion. Treatment of parts with cold is carried out in fluidize bed of loose materials cooled with nonfreezing medium (for instance, liquid nitrogen) to temperature corresponding to maximum conversion of austenite into martensite. Further on, articles ore subjected to tempering (ageing). EFFECT: higher quality of finished articles. 4 cl, 4 ex