Production manner null of the steel sheet for welding structure which is superior in cruciform welded joint

摘要

PURPOSE: To provide a method for producing a steel sheet for welding structures causing no cracks in a cross welding joint of a steel structure. ;CONSTITUTION: The slab subjected to slight rolling reduction continuous casting of a steel having a compsn. contg., by weight, 0.06 to 0.09% C, ≤0.5% Si, 1.0 to 1.7% Mn, ≤0.02% P, ≤0.002% S, Ca: 0.5 to 2.0% as Ca/S, ≤0.0002% B, 0.005 to 0.060% sol.Al, respectively 0 to 0.5% Cu, Ni and Cr (including the case of no addition) and 0 to 0.3% Mo (including the case of no addition), furthermore contg. one or more kinds among 0.005 to 0.04% Nb, 0.02 to 0.1% V and 0.005 to 0.10% Ti, moreover satisfying 0.20% PCM, and the balance substantially Fe is prepd. This slab is heated to ≥1050°C and is subjected to hot rolling. In this hot rolling, it is subjected to rolling reduction at the Ar₃ or below at 30 to 70% cumulative draft, and the hot rolling is finished at ≥650°C. After the heating of the slab, the rolling is completed at the Ar₃ or above, and immediately after that, it is water-cooled at ≥3°C/S cooling rate. The water cooling is stopped in the temp. range of 400 to 600°C, and after that, it is air-cooled. Moreover, the PCM can be expressed by the formula.;COPYRIGHT: (C)1996,JPO