| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a laser welding method for a high strength hyperfine-grained thin steel sheet by which the softening caused in the weld heat affected zone is suppressed and the strength of a welded joint is improved. <P>SOLUTION: In the laser welding method for the high strength hyperfine-grained thin steel sheet having a ferrite structure in which the average crystal grain size is≤4μm over the full thickness, directly before welding, cooling is performed in such a manner that the temperature of the surface and back faces in the steel sheet at least in the vicinity of a laser irradiation point is controlled to≤-100°C using a cooling medium, preferably, liquid nitrogen or liquid helium. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
