| 摘要 |
PURPOSE:To obtain a unnormalized high tensile and high toughness steel plate having surface characteristics by casting high Nb steel of specific compsn. limited particulrly in the contents of T.N and Ti continuously and hot rolling the cast steel, then air cooling the same at a rate lower than air cooling. CONSTITUTION:The steel contg. 0.005-0.06% C, 0.02-0.50% Si, 1.5-2.5% Mn, <=0.005% S, 0.06-0.20% Nb, 0.005-0.10% SolAl, contg. <=0.006% T.N, and 0.005-0.030% Ti, and further contg. V, Cr, Cu, Mo, Ni, B, Ca, etc. according to need is cast continuously. After the slab is hot rolled, the slab is cooled at a cooling rate lower than air cooling. By such method, the degradation in the suitability to hot rolling, and the generation of surface flaws of the continuous casting ingot by the hot rolling are prevented, and the intended high Nb type unnormalized high tensile and high toughness steel plate is obtained easily. |
