| 摘要 |
PURPOSE:To manufacture a steel plate for high heat input welding having superior tensile strength and forming a weld heat-affected zone which is not embrittled by added B by regulating the carbon equiv. of a steel plate contg. a rare earth element or Ti and the B content in the steel plate to a specified value each. CONSTITUTION:A steel slab having a composition contg. 0.03-0.15% C, 0.01-0.50% Si, 0.50-1.80% Mn, 0.005-0.08% Al, 0.0003-0.0050% B, <0.01% N and <=0.03% in total of at least one among <0.03% each of Ti, Ca and REM and having 0.28-0.42% carbon equiv. (Ceq) represented by formula 1 is heated to 900-1,050 deg.C and rolled at <=30% draft per one pass to manufacture a steel plate for high heat input welding having superior tensile strength and forming a weld heat-affected zone which is not embrittled. In the composition, B contains <=0.0005% soluble B and the quantitative relation among Ti, B and N satisfies formulae 2, 3.
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