中文摘要：

采用4 kW光纤激光器进行了1.6 mm厚的双相高强度钢B340/590DP的激光对接焊。进行了不同对接间隙的焊接接头的表面、截面形貌分析,接头力学性能、金相组织和显微硬度测试。选择某车身零部件,在优化的工艺参数下进行三维对接焊,焊后进行了碰撞试验。激光焊接结果表明,在合适的焊接工艺参数下,当对接间隙小于板厚的18%（约为光斑直径的57.6%）时,可以得到焊缝成形好、热影响区（HAZ）窄的焊缝;当对接间隙小于板厚的16%（约为光斑直径的51.2%）时,焊缝的拉伸强度优于母材;对接间隙变化对焊缝显微硬度以及金相组织无明显影响。碰撞试验表明,激光焊缝碰撞试验强度符合设计标准,某车身三维零部件光纤激光对接焊优于电弧对接焊。

英文摘要：

Laser butt welding of 1.6-mm thick dual-phase high-strength steel B340/590DP is performed by using a 4-kW fiber laser.Weld topography and cross secsion of different butt joint gaps are analyzed.And mechanical properties,microstructure and microhardness of weld are tested.Laser butt joint welding of a three-dimensional body part under optimized process is carried out.Crash tests are performed after welding experiments.The results of laser welding experiments prove that weld with good appearance and narrow heat affected zone（HAZ） can be obtained when butt joint gap is narrower than 18%（about 57.6% of focused spot diameter） of sheet thickness under the proper welding condition.When butt joint gap is narrower than 16%（about 51.2% of focused spot diameter） of sheet thickness,the tensile strength of weld is better than the base metal.Different butt joint gaps have no significant effect on the micro-hardness and microstructure of the weld.The crash tests prove that crash strength of laser welds is in accordance with the design standards.Fiber laser butt welding is better than arc butt welding for a three-dimensional body part.