| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To produce a high-tension steel plate having≥570 MPa tensile strength and excellent in toughness on the surface layer part. <P>SOLUTION: The steel mainly contained of 0.06-0.18% C, 0.05-0.6% Si, 0.5-1.6% Mn, 0.005-0.1% Al, 0.0005-0.008% N as the main components, and≤0.30% Pcm value which is defined by a prescribed expression, is heated in the temperature range of 1,000-1,300°C, and after hot-rolling, successively, direct-quenching is performed from not lower than A3 transformation point, and after stopping the cooling in the temperature range of≤400°C, rapid-heating is performed so that the maximum reaching temperature on the steel plate surface becomes 500-720°C and the temperature-rising speed on the steel plate surface becomes 25°C/sec, and then, a tempering treatment is applied. <P>COPYRIGHT: (C)2004,JPO&NCIPI</p> |
