镀锌钢光纤激光搭接焊添加铜粉的试验研究

采用4kW光纤激光器对2片1.2mm厚H220YD镀锌钢板间添加不同质量分数铜粉进行了激光搭接焊.对工艺参数优化后所得到的焊接接头进行了焊缝表面成形、力学性能、断口形貌、成分分布和主要物相等分析.结果表明:添加铜粉质量分数为2.82%时,焊接接头的平均抗拉强度和延伸率分别为382.5MPa和32.5%;添加铜粉质量分数不大于3.46%时,拉伸断裂于母材,属于韧性断裂,而添加铜粉质量分数大于3.46%时,拉伸断裂于焊缝区,属于韧性断裂为主脆性断裂为辅的混合断裂;夹层铜粉的加入,改变了镀锌钢界面的元素分布及物相组成,焊接接头焊缝区域C,Al,Mn,Fe,Zn,Cu元素的混合区宽度较大;当添加铜粉质量分数为2.82%时,Cu元素变化比较稳定,因铜能固溶于锌中形成锌铜固溶体,起到很好的固溶强化作用,故增强了焊缝的强度;当添加铜粉质量分数为8.06%时,Cu元素会向热影响区扩散,易形成Cu5Zn8脆性金属间化合物,使得拉伸易断裂于焊缝区.

Experimental Study of the Fiber Laser Lap Welding of Galvanized Steels with the Cu Powder

Experiments of laser lap welding of two 1.2 mm thick galvanized steel planks with different Cu powder concentrations were performed by using a 4 kW fiber laser. The transverse weld topography, the mechanical properties, fracture morphology, component distribution and the main phase of the welded joint regional were studied under the optimal welding process parameters acquired through process optimization. It is shown that, when Cu powder concentration is 2.82%, the average tensile strength and elongation of the welding joints is 382.5 MPa and 32.5% respectively. When Cu powder concentration is not more than 3.46%, the tensile specimens are broken in the base material due to ductile fracture. On the contrary, the tensile specimens are broken in weld area due to the mixture of predominant ductile fracture and subordinate brittle fracture. Element distribution and phase in the galvanized steel interface are changed with the addtion of Cu powder added. In the weld area, the width of mixing zone of C, Al, Mn, Fe, Zn, Cu elements is larger. When Cu powder concentration is 2.82%, Cu element changes stably and Cu element in the weld area plays an important role in solid fusion reinforcement with the formation of Cu-Zn solid solution, and therefore, the strength of the weld area is improved. When Cu powder concentration is 8.06%, Cu element may spread from weld area to heat affected zone and is therefore prone to form brittle intermetallic compound Cu5Zn8, making specimens easily fractured in the weld area.