脉冲功率对冷轧双相钢焊接接头组织及性能的影响

Effect of Pulsed Laser Power on Microstructure and Properties of Cold Rolled Dual Phase Steel Welded Joint

利用脉冲固体激光器对厚度1mm车用冷轧退火态双相钢DP590进行了激光焊接实验，研究了脉冲激光功率（45～130W）对焊接接头的宏观形貌（横截面形貌、熔深、熔宽）、微观组织、力学性能及成形性能的影响，同时分析了冲压成形方向对焊接接头成形性能的影响。结果表明，随着脉冲功率的提高，焊缝区凹陷量、焊缝熔深及熔宽均逐渐增大，脉冲功率为75W及以上可获得全熔透焊缝，焊缝横截面形貌变化规律为“Y”型→“V”型→“X”型；不同的脉冲功率条件下，焊缝区组织以板条马氏体为主，但随脉冲功率的增加，焊缝中逐渐出现贝氏体和铁素体，导致焊缝区硬度逐渐降低；对于全熔透焊缝而言，拉伸实验失效位置均出现在母材区，断裂方式为韧性断裂。“Y”型焊接接头成形性能最差，且对冲压方向最为敏感，“V”型焊接接头成形性能居中，“X”型焊接接头成形性能最佳，脉冲功率为90～100W时，焊接接头的杯突值可达到母材的80％左右。

In this paper, laser pulsed welding was implemented on DP590 dual-phase cold rolled steel sheet with lmm thickness. The effect of pulsed laser power（45 - 130 W）on macroscopic morphology（cross section morphology, weld depth and width）, microstructure, mechanical properties and formability was studied. In the same time, the effect of punch direction on the formability of welded joints was analyzed. The results show that the deboss, welded seam（WS） of weld depth and width are increasing with the pulsed laser power increaseing, and the full penetration WS can be obtained when it is more than 75 W. The variation of WS cross-section morphology is： ＂Y＂ shape→＂V＂ shape→＂X＂shape. The microstructure of WS is mainly lath martensite on different pulsed laser powers, while the bainite and ferrite can be observed in WS with the pulsed laser power increasing which will lead to the hardness decrease. For the full penetration WS samples, the tensile fractures are presented on based metal and the fracture mode is ductile fracture. The formability of ＂Y＂ shape welded joint is worst and most sensitive to stamping direction, the formability of ＂X＂ shape welded joints is best and ＂V＂ shape is better. When the pulsed laser is 90- 100 W, the erishen value of welded joints can reach to 80% of base metal.