MANUFACTURE OF LOW ALLOY HIGH TENSION STEEL FOR OIL WELL SUPERIOR IN SULFIDE STRESS CRACKING RESISTANCE

摘要

PURPOSE:To obtain steel for oil well superior in sulfide stress cracking resistance, by austenitizing low alloy steel having a specified compsn. contg. reduced Mn and valid P quantities under a specified temp. condition, then quenching to convert it to martensite, further tempering the steel. CONSTITUTION:Steel composed of, by weight 0.10-0.35% C, =0.25% Si, 0.1-0.7% Mn, =0.005% S, 0.01-0.10% Nb, =0.008% N, =0.028% Ti, further -0.005%=Ti-3.4N=0.01%, 0.0007-0.0020% B, =0.020% P further P-0.018Mo=1X10-3%, further if necessary =1.5% Cr and the balance Fe is refined. The steel is austenitized at (Ac3 point + 20 deg.C)-1,020 deg.C, then quenched to convert =90% thereof to martensite structure, next, temperature at 560 deg.C-=Ac1 point. By this method, the titled steel is obtd.