PURPOSE: To improve the season cracking resistance at the time of production in low austenite stability as a steel sheet by subjecting a steel whose chemical compsn. and Ni equivalent are specified to hot rolling, thereafter holding it under heating to a specified temp. and next controlling the cooling conditions.
CONSTITUTION: The compsn, of steel is incorporated with, by weight, 0.09 to 0.30% C, ≤2.0% Si, ≤2.0% Mn, 10.0 to 20.0% Cr, 5.0 to 10.0% Ni and ≤0.10% N and is furthermore incorporated with one or two kinds among 0.1 to 3.0% Mo, ≤1.0% Nb, ≤1.0% Ti and ≤1.0% V. Furthermore, the Ni equivalent shown by the formula is regulated to the range of 19.0 to 24.0%. This steel slab is subjected to hot rolling, is thereafter held under soaking to 1000 to 1300°C and is next subjected to controlled cooling in the temp. range of 950 to 550°C at 1 to 10°C/min cooling rate. In this way, the metastable austenitic steel excellent in the season cracking resistance can be produced by simple means.
IKEGAMI YUJI
HIRATA SHIGERU
