| 摘要 |
PURPOSE:To obtain a high tensile steel plate having excellent weldability and low temp. toughness without normalizing by rolling a steel specified in the contents of C, Si, Mn, Al, S, and Ti in a specific temp. range and subjecting such steel to controlled cooling, then to light draft rolling. CONSTITUTION:The steel contg., by weight, 0.01-0.15% C, 0.05-0.5% Si, 0.5-2.5% Mn, 0.005-0.08% Al, <=0.008% S, and 0.05-0.20% Ti is cast. Such steel is rolled at least at 50% draft in the temp. range from the Ar3 transformation point+100 deg.C down to Ar3-60 deg.C. The steel is immediately thereafter cooled down to 700-500 deg.C at 2-30 deg.C/sec cooling rate. The steel is lightly rolled down at 3-15% draft in a 650-450 deg.C range and is then cooled with air or slowly cooled. The dispersion in the distortion and material quality of the steel plate is decreased by the above-mentioned method, by which the high tensile steel plate having the excellent weldability and low temp. toughness is stably produced without normalizing.
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