| 摘要 |
PURPOSE:To manufacture a thick tough steel at a low cost by hot working a steel contg. specified percentages of C, Si, Mn, Ni, Cr, Mo and Al to a prescribed thickness, reheating the resulting plate to a specified temp., and rapidly cooling it. CONSTITUTION:A steel consisting of, by weight, 0.08-0.25% C, <=1.0% Si, 0.4- 2,0% Mn, 2.0-4.5% Ni, 0.3-2.5% Cr (Mn/Cr>=0.3), 0.2-1.0% Mo and <=0.002% Al as essential components and the balance Fe with inevitable impurities is hot worked to a prescribed thickness. The steel may further contain one or more among <=2.0% Cu, <=0.1% V, <=0.1% Nb, <=0.01% B and <=0.1% Ca. The resulting plate is cooled once, reheated to a temp. above the Ac3 point, and rapidly cooled from the temp. above the Ac3 point to room temp. to carry out hardening. A steel having >= about 40mm. plate thickness, >= about 100kg/mm.<2> tensile strength and superior toughness at low temp. is obtd. at a low cost. |
