| 摘要 |
PURPOSE:To obtain a high tension steel having superior cold workability and requiring no heat treatment by prescribing the amount of alloying elements in a steel, hot rolling the steel under prescribed conditions, and cooling and bundling it under prescribed conditions. CONSTITUTION:The composition of a steel is composed of, by weight, 0.05- 0.2% C, 0.1-0.9% Si, 1.35-2% Mn, 0.001-0.005% B, 0.02-0.15% Ti, 0.5-1.2% Cr and the balance Fe with inevitable impurities. The steel is hot rolled at the Ar3 point or above and >=70% draft, and it is rapidly cooled, coiled at <=900 deg.C, cooled at 1-15 deg.C/sec average cooling rate, and bundled. Bainite having >=75kg/ mm.<2> tensile strength and >=50% reduction of area is formed as the principal structure. |
