| 摘要 |
PURPOSE:To obtan a tough steel material with superior delayed rupture resistance by hot rolling a low alloy steel having a specified composition, and directly hardening it by rapid cooling from a specified finishing temp. CONSTITUTION:A steel consisting of, by weight, 0.18-0.28% C, <=0.5% Si, <=0.5% Mn, 0.5-4.0% Cr, <=0.01% P and the balance Fe with inevitable impurities is hot rolled. The steel may further contain >=1 kind among <=0.1% Nb, <=0.3% V, <=0.003% B and <=0.05% Ti. The finishing temp. of the hot rolling is regulated to >=900 deg.C, and the hot rolled steel is directly hardened by rapid cooling from the temp. The steel is then tempered at <= about 450 deg.C as required. By this method a machine structural steel with high strength, toughness and superior delayed rupture resistance is obtd. |
