OPTIMIZATION OF MARTENSITE STAINLESS STEEL MACHINABILITY FEATURE Russian patent published in 2016 - IPC C21D6/02 C21D1/18 C22C38/24 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy. To improve machinability of martensite stainless steel blank the heat treatment method includes the steps of: 1) heating the blank to a temperature exceeding the steel austenitizing temperature T_AUS, cooling till the hottest part of the blank reaches the temperature less or equal to the maximum temperature T_max and more or equal to the minimum temperature T_min with the cooling rate preventing the austenite conversion into a ferrite-pearlite structure, 2) first annealing with cooling till the hottest part of the blank reaches the temperature less or equal to T_max and more or equal to T_min, 3) second annealing with further cooling to the ambient temperature T_A. Maximum temperature T_max is less or equal to the M_F' temperature of martensitic transformation finish at cooling interdendritic volumes in the steel. At the end of each of the steps 1) and 2) stage ω) is performed when the hottest part of the blank reaches the maximum temperature T_max, the blank is repeatedly heated to the temperature not below T_max.

EFFECT: improved machinability of martensite stainless steel.

10 cl, 3 dwg