| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength steel sheet having excellent warm rolling workability and a method for producing the same. <P>SOLUTION: A steel material having a chemical composition comprising, in mass%, 0.01 to 0.2% of C, 0.5% or less of Si, 2% or less of Mn, 0.03% or less of P, 0.01% or less of S, 0.07% or less of Al, and 0.01% or less of N and additionally containing at least one component selected from Ti, Nb, V, Mo, W and B is subjected to a hot rolling step and a heat treatment step sequentially, wherein the hot rolling step comprises carrying out the hot rolling in which the steel material is heated at a temperature falling within an austenite single phase temperature range and is finished at the finish rolling temperature of 860°C or higher and winding the steel sheet at a winding temperature of not lower than 400°C and lower than 600°C, and the heat treatment step comprises carrying out a heat treatment at a temperature of 650 to 750°C. In this manner, it becomes possible to produce the steel sheet having excellent warm rolling workability, which has both such an elongation property that the local elongation is larger than the uniform elongation at a test temperature of 400°C or higher and such an elongation property that the ratio of the uniform elongation to the entire elongation is 40% or more at a test temperature of lower than 400°C, and which has a structure that is composed of a matrix comprising substantially only a ferrite single phase and an alloy carbide having a size of less than 10 nm and dispersed and precipitated in the matrix without requiring the choice of any variant. <P>COPYRIGHT: (C)2012,JPO&INPIT |
