Method of manufacturing high productive and high strength rolled H-shaped

A method of manufacturing a rolled H-shape comprising:

• reheating a molded raw steel material to a temperature of from 1150° C. to 1320° C.;
• then subjecting the molded raw steel material to a break down rolling comprising performing a reverse multi-pass rolling to obtain rough raw material for steel strip, a rough universal rolling comprising performing reverse multi-pass rolling to obtain a rolled steel material, and a finishing rolling comprising adjusting the final shape of the H-shape, the raw steel material comprising:
• C:
• 0.014 to 0.05wt. %,
• Si:
• 0.1 to 1.0 wt. %,
• Mn:
• 1.0 to 1.8 wt. %,
• P:
• 0.030 or less,
• S:
• 0.020 wt. % or less,
• Al:
• 0.1 wt. % or less,
• B:
• 0.0003 to 0.0040 wt. %,
• N:
• 0.006 wt. % or less,
• Nb:
• 0.03 to 0.1 wt. %,
• Ti:
• 0.005 to 0.04 wt. %,
• and the balance of Fe and unavoidable impurities;
• wherein, in the rough universal rolling, an accumulated reduction at a rolling temperature of 950° C. or lower is 5% or more, and the rolled steel material is reversed fast;
• wherein, in the finishing universal rolling, the rolling temperature is at least 750° C.;
• and
• wherein the H-shape comprises flange portions which each have a thickness of 40 mm or less.