不锈钢表面镀铜对铝/钢YAG激光焊接的影响

Effects of stainless steel copper plating on YAG laser welding of aluminum / steel

对0.3 mm厚的316L不锈钢/6061铝合金进行了脉冲激光(YAG)封边焊接试验。为了改善铝钢的冶金结合,对不锈钢表面进行了镀Cu处理,对比了镀铜前后的焊接情况;利用光学显微镜、扫描电镜及能谱分析等方法研究了接头界面区显微组织特征、熔合情况、元素分布和断口形貌。结果表明:对于铝/钢直接焊接,焊接电流I=130 A,激光脉宽D=4 ms,激光频率f=13 Hz,焊接速度V=150 mm/min,气体流量25 L/min,零离焦时,焊缝平整、成型美观。镀铜层形成了铝钢焊接的过渡层,减缓了界面处液态金属传递,抑制了铁铝之间的熔合,铝钢熔合线向钢一侧偏移。不锈钢未镀铜情况下,焊接接头组织主要由靠近铝一侧的针状或粗大板条状Fe2Al5及靠近钢一侧的FeAl组成;镀铜后Cu主要固溶到Fe中,接头界面组织主要由(Fe,Cu)_2Al_5、(Fe,Cu)_3Al组成。镀铜前后接头拉伸断口形貌未发生明显变化,然而,接头强度明显提高,提高约40.32%,达到15.63 N/mm。

316L stainless steel and 6061 aluminum alloy with the thickness of 0. 3 mm were jointed by using YAG laserwelding method. In order to improve the metallurgical bonding characteristics of aluminum and steel, stainless steelwas plated with a Cu coating. Welding effects of aluminum/steel were compared before and after copperplating. Microstructure, fusion effect, element distribution and fracture morphology of welding joints were studied byoptical microscope, scanning electron microscope, energy dispersive spectrometer. The results show that when the weldingconditions were welding current of 130 A ,laser pulse width of 4 m s,laser frequency of 13 Hz,welding speed of 150m m /m in, the gas flow rate of 25 L/m in and defocusing amount of 0m m , the appearance and quality of the welding jointwere good. The Cu-coating layer as transition layer of aluminum and steel welding can slow down liquid metal transferof the interface and suppress the fusion between iron and aluminum, thus the fusion line between aluminum and steelshifts to the steel side. Microstructure analysis shows that, before copper plating, the welding joint is composed ofFe2Al5 near the aluminum side and the FeAl near steel side. However,after copper plating,the welding joint is composedof （F e ,C u ）2Al5 and （F e ,C u ）3Al due to the dissolution of Cu. Tensile fracture morphology of the welding jointsare similar before and after copper plating,but the strength of the welding joint increases about 40. 32% ,and reaches15. 63 N/mm