| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a refractory steel product for structural having excellent fire resisting strength even if fireproofing coating is omitted and usable as a hot-dip galvanized steel product. SOLUTION: A steel bloom having a steel composition which consists of 0.06-0.15% C, 0.10-0.25% Si, 0.50-1.40% Mn, 0.20-0.60% Mo, 0.02-0.06% V, 0.0010-0.0060% N, 0.01-0.08% Al and the balance Fe with inevitable impurities and in which the value of G stipulated by an equation mentioned below is 0.7-1.2, is heated at 1,050 to 1,200 deg.C and then, hot rolled at 760 to 880 deg.C of a rolling finishing temperature. After the completion of hot rolling, hot-dip galvanizing is performed as secondary working.
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