| 摘要 |
PURPOSE:To assure a high yield strength without increasing the ratios of alloy elements by subjecting steel material contg. a specific ratio each of Mn, Ni, Cr, Mo, etc., to hardening at a regulated temp. then to two stages of tempering treatments. CONSTITUTION:The steel contg., by weight, 0.06-0.18% C, <=0.10% Si, <=1.00% Mn, 3.00-12.00% Ni, 0.40-3.00% Cr, 0.20%n2.00% Mo, <=0.010% P, 0.03-0.20% V, 0.005-0.040% Al and 0.0010-0.0150% N is produced. Such steel material is hardened at the temp. above the Ac3 transformation temp. After the hardened steel is subjected to the primary tempering treatment in a 550-680 deg.C range, the steel is subjected to the secondary tempering treatment. The extra-thick tempered steel plate having the high yield strength is obtd. without deteriorating the toughness by the above-mentioned method. The steel plate is free from low temp. temper embrittlement and the toughness value thereof at the wall thickness section is made homogenous. |
