PURPOSE: To produce a hot rolled high strength steel plate having superior surface characteristics and excellent in fatigue characteristics.
CONSTITUTION: A steel which has a composition containing 0.01-0.20% C, ≤2.5% Si, 0.5-2.5% Mn, 0.03-0.20% P, and 0.10-0.5% Cu, further containing 0.01-0.05%, in total, of Nb and/or Ti, and satisfying the relation in Cu(%)+2P(%)<0.6% is held at ≥1150°C, and then, hot rolling is started while regulating the temp. of the steel surface to ≤1050°C. Even if plating, etc., are applied to the steel sheet, no change in material is brought about. This plate is particularly suitable for steel plates for automobile under carriage parts and reinforcing parts. Further, because of its high fatigue characteristics and corrosion resistance, this steel plate can also be used for civil engineering and construction.
ANAMI GORO
YOKOI TOSHIO
IWAI TAKAFUSA
