PURPOSE: To develop martensitic stainless steel excellent in ductility-toughness, workability, weldability and the softening resistance in the weld heat affected zone by subjecting low C and low N- contg. Ni-Cr stainless steel to hot working and heat treatment under specified conditions. ;CONSTITUTION: The ingot of low C and low N-contg. Ni-Cr stainless steel having a compsn. contg., by weight, 0.03% C, 1.0% Si, 1.0% Mn, 0.05 to 1.0% Cu, 5.0 to 7.0% Ni, 13.0 to 17.0% Cr, 2.0% Mo and 0.02% N, and the balance Fe and satisfying the inequalities 1, 2 and 3 is heated to a temp. T satisfying the formula 4 or below and is thereafter subjected to hot working capable of being finished in the temp. range of ≥700°C. Immediately after that, it is cooled to the temp. range of the Mf point or below at ≥3°C/min colling rate, is furthermore heated to the temp. range of 450°C to the Ac1 point and is subsequently cooled. The martensitic stainless steel having 0.2% proof stress at ≥800MPa and furthermore excellent in corrosion resistance can be produced.;COPYRIGHT: (C)1994,JPO&Japio
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