| 摘要 |
A sheet steel with a structure wherein at least either intragranularly grown acicular ferrite or bainite with a packet size of 30-300 mu m accounts for at least 95 % of the whole is produced by casting continuously a steel into a thin cast strip with a thickness of 0.5-5 mm, said steel containing 0.01-0.20 % (by weight, the same will apply hereinbelow) of carbon, 0.005-1.5 % of silicon, 0.05-1,5 % of manganese, at most 0.03 % of sulfur, and if necessary 0.0005-0.0100 % of calcium or 0.005-0.050 % of rare earth element (REM), and the balance consisting of iron and inevitable impurities, cooling the cast strip at an average cooling rate of at least V ( DEG C/sec) as defined by the following formula (1): log V >/= 0.5-0.8 log Ceq ( DEG C/sec) (wherein Ceq = C + 2.0 Mn), from the temperature range of the casting temperature to 900 DEG C to the temperature range of 650 DEG C to 400 DEG C, and winding the cooled strip at 650 DEG C or below. <IMAGE> |
