| 摘要 |
A thin steel sheet having a structure comprising at least one member selected from a transgranular acicular ferrite and a bainite having a packet size of 30 to 300 .mu.m, in a proportion of not less than 95% of the structure, is produced by subjecting a steel comprising, in terms of % by weight, 0.01 to 0.20% of C, 0.005 to 1.5% of Si, 0.05 to 1.5% of Mn and not more than 0.03% of S and optionally 0.0005 to 0.0100% of Ca or 0.005 to 0.050% of REM with the balance consisting of Fe and unavoidable impurities to continuous casting into a thin cast strip having a casting thickness in the range of from 0.5 to 5 mm, cooling the thin cast strip from the temperature range of from the casting temperature to 900.degree.C to the temperature range of from 650 to 400.degree.C at an average cooling rate of not less than V (.degree.C/sec) represented by the following formula (1); and coiling the cooled strip at a temperature of not more than 650.degree.C: log V ~ 0.5 - 0.8 log Ceq (.degree.C/sec) ..... (1) wherein Ceq = C + 0.2Mn. |
