Thermal effect section tenacity of full house thermal welding is superior the steel and its production manner

摘要

PROBLEM TO BE SOLVED: To obtain a steel material improved in toughness in HAZ to a greater extent by specifying the composition of a steel and incorporating a compound oxide which contains Ca, Ti, and Al and in which grain size and the number of grains are respectively specified. ;SOLUTION: A molten steel, having a composition consisting of, by weight, 0.03-0.18% C, ≤0.50% Si, 0.40-2.0% Mn, ≤0.02% P, 0.0010-0.010 S, 0.005-0.020% Al, 0.005-0.020% Ti, 0.0005-0.0030% Ca, 0.0020-0.0060% N, and the balance Fe, is cast and then rolled, by which a steel containing a compound oxide which contains Ca and Ti and/or Al and in which grain size and the number of grains are regulated, respectively, to 0.01-1.0μm and (5×10³ to 1×10⁵) pieces/mm² is obtained. After Ti of 0.005-0.20%, by weight, of final content is added to the molten steel in which Si concentration and dissolved oxygen concentration are regulated, respectively, to 0.05-0.20% and 20-80ppm, Al of 0.005-0.020% final content is added and further Ca of 0.0005-0.0030% final content is added, and then, Si in an amount compensating the shortage base on the final composition and other alloys are added, by which the steel material can be produced.;COPYRIGHT: (C)1998,JPO