铝合金/镀锌钢板脉冲MIG电弧熔-钎焊接头组织与性能

MICROSTRUCTURES AND PROPERTIES OF PULSED MIG ARC BRAZED-FUSION WELDED JOINT OF Al ALLOY AND GALVANIZED STEEL

采用数字化脉冲MIG焊机,以ER4043焊丝为填充材料.实现了6013-T4铝合金薄板与镀锌钢板的熔-钎焊接,研究了焊接热输入对接头组织和性能的影响,结果表明,在熔-钎焊接头熔化焊缝焊趾处存在主要由Zn-Al共晶体、富A1的α固溶体和Fe3Al组成的富Zn区:钎焊界面上的Fe-Al金属间化合物层厚度在1.05-4.50μm之间.且随焊接热输入的增加而增大.Fe-Al金属间化合物呈'锯齿'或'舌'状向焊缝内生长,主要为FeAl_2,Fe_2Al_5和Fe_4Al_(13).随着焊接热输入的增大,熔-钎焊接头的抗拉强度先增大而后减小.在850 J/cm的热输入下达到229 MPa,拉伸后在铝合金焊接热影响区发生断裂,为塑韧性断裂;当焊接热输入较小时接头在钎焊界面断裂,属于脆性断裂.

Because there are great differences in physicochemical properties and mechanical properties between A1 alloy and steel, their joining with high quality and high efficiency is one of difficult problems in study of welding technology. According to their difference in melting point, the brazing-fusion welding technology of A1 alloy to steel was developed based on MIG welding. In pulsed MIG arc brazing-fusion welding process, the molten filler metal and A1 alloy base metal will form the fusion welded joint, and will form the brazed joint together with unmelted steel plate, which can efficiently prevent the intermetallic compounds （IFICs） from the formation. With the digital pulsed MIG arc welding machine, the brazing-fusion welding of 6013-T4 A1 alloy plate to galvanized steel plate was realized with the filler metal of ER4043, and the effect of welding heat input on microstructures and properties of the joint was studied. The results showed that there is a zinc-rich zone in the weld toe of fusion weld in the brazed-fusion welded joint, which is composed of Zn-A1 eutectic, Al-rich a solid solutions and Fe3A1. Fe-A1 IMCs layer on the brazed interface is 1.05-4.50 μm in thickness and become thicker with the welding heat input being increased. Fe-A1 IMCs with sawtooth or tongue shape grow towards the weld, which mainly includes FeA12, Fe2A15 and Fe4A113. With the welding heat inputbeing increased, the tensile strength of the brazed-fusion welded joint firstly increases and then decreases. At the welding heat input of 850 J/cm, the tensile strength of the brazed-fusion welded joint can be up to 229 MPa and the ductile fracture appears in the HAZ of A1 alloy. At the lower welding heat input, the brittle fracture easily occurs.being increased, the tensile strength of the brazed-fusion welded joint firstly increases and then de- creases. At the welding heat input of 850 J/cm, the tensile strength of the brazed-fusion welded joint can be up to 229 MPa and the ductile fracture appears in the HAZ of A1 alloy. At the lower welding heat input, the brittle fracture easily occurs.