PRODUCTION OF WIDE FLANGE SHAPE EXCELLENT IN REFRACTORINESS AND REDUCED IN YIELD RATIO

摘要

PURPOSE:To inexpensively produce a wide flange shape excellent in refractoriness and reduced in yield ratio by subjecting a bloom of a steel having a specific composition consisting of C, Si, Mn, Mo, Nb, Al, N, Ni, Cu, Cr, V, Ti, and Fe to specific reheating and then to hot rolling. CONSTITUTION:A bloom of a steel having a composition which consists of, by weight, 0.03-0.15% C, =0.6% Si, 0.2-1.0% Mn, 0.7-1.5% Mo, 0.005-0.04% Nb, =0.1 % Al, 0.001-0.0060% N, one or more kinds among 0. 05-0.50% Ni, 0.05-0.50% Cu, 0.05-0.50% Cr, 0.005-0.04% V, and 0.005-0.03% Ti, and the balance Fe with inevitable impurities and in which the value of DI represented by an equation DI=0.316C0.5(1+0.7Si) (4.1Mn+0.35) (1+3Mo) (1+0.36Ni) (1+2.2Cr) (1+0.365Cu) is regulated to 0.8 is reheated at 1200-1350 deg.C. Then, hot rolling is finished at 750-1050 deg.C. By the above procedure, the microstructure of the bloom is formed into a structure composed essentially of ferrite. By this method, the amount of expensive additive elements can be reduced, and the wide flange shape excellent in refractoriness and reduced in yield ratio can be obtained.