STEEL PLATE HAVING LOW WELDING STRAIN AND GOOD BENDING WORKABILITY BY LINEAR HEATING AND METHOD FOR PRODUCING THE SAME, AND WELDING MATERIAL AND METHOD FOR PRODUCING THE SAME

摘要

Steel material is specified to contain, by weight percentage, C (0.02-0.25 %), Si (0.01-2.0 %), Mn (0.30-1.5 %), Al (0.003-0.10 %), Nb (0.005-0.10 %), Mo (0.05-1.00 %), and the remaining portion constituting Fe and inevitable impurities to produce a steel plate, 3 to 100 mm thick (in particular, in a case where the plate thickness ranges from 3 to 25 mm, the upper limit of Nb and Mo should be 0.025 %, respectively), and, as its yield stress, a ratio of the yield stress σyT of the steel plate at a temperature T to the yield stress σy of the same as a room temperature is specified to fall within the range of the following formula over the room temperature to 600°C: 1.00-1.083x10-3T(σyT/σy)1.16-5.101x10-4T. Furthermore, the constituents of welding material are specified, and a transformation temperature γ3 is set to less than 620 °C and as the yield stress of its deposited metal a ratio of the yield stress σy0T0 of the deposited metal at a temperature T0 to the yield stress σy0 of the same at a room temperature is specified to fall within the range of the following formula over the room temperature to 600°C: 1.00-1.083x10-3T0(σ¿y0T0/σy0)1.16-5.101x10-4T0. The above steel plate is welded by the above welding material so as to provide a welded steel plate having small welding strain.