PURPOSE: To obtain the titled steel even in severe corrosive environment of H2S existence, by hot working, water cooling and tempering steel having a prescribed component compsn. under respectively prescribed temp. ranges.

CONSTITUTION: Steel contg. by weight, 0.10W0.40% C, 0.05W0.50% Si, 0.30W1.5% Mn, 0.1W2.0% Cr, 0.2W7.5% Mo and restricted quantities of ≤0.005% S, ≤0.005% P is treated as follows: Namely, the steel is heated to Ac3 transforma tion point + ≥50°CW≤1,150°C, to obtain uniform bainite structure, then hot worked at ≥Ar3 transformation point by ≥30% draft. The steel after working is immediately water cooled to 600°CW room temp. by 5W60°C/sec rate for preventing coarsening of austenite grain due to recrystallization and growth, then tempered at temp. of 400°CWAc1 transformation point to obtain the aimed titled steel.