工程机械用Q550高强钢气保焊接头的微观组织和力学性能研究

Research on Microstructure and Mechanical Properties of GMAW Welded Joints of Q550 High Strength Steel for Engineering Machinery

采用富氩气体保护焊方法,分别匹配ER50-6和MK·G60-1实芯焊丝对50°、60°、70°三种不同坡口角度的Q550钢板进行对接焊,并对其焊接接头的金相组织进行了观察分析,对接头拉伸、冲击等力学性能进行了检验。结果表明,ER50-6焊缝组织为AF+PF+FSP;MK·G60-1焊缝组织为AF+PF,其中铁素体含量明显少于ER50-6焊缝,针状铁素体也明显细化且含量明显增多。ER50-6焊丝所得接头拉伸试验全部断裂于焊缝,随着坡口角度的加大,焊缝强度先增加,后大幅降低,断后伸长率逐渐降低,接头三区的冲击功均是先升高后降低。随着坡口角度的增加,MK·G60-1焊丝所得焊接接头拉伸强度逐渐下降,断后伸长率呈逐渐增加的趋势,焊缝及HAZ冲击功均是先降低后升高,熔合区的冲击功则是逐渐升高,接头拉伸、冲击等力学性能明显优于使用ER50-6焊丝。

By rich-argon gas shielded arc welding method, Q550 welding test plates with 50°, 60°, 70° in three different groove angles were welded matching with ER50-6 and MK ·G60-1 solid wire, respectively. The microstructure of welded joints was observed and the joint tensile and impact properties were tested. The results show that the weld mierostructure for ER50-6 wire is AF＋PF＋FSP, and the weld microstructure for MK. G60-1 wire is AF＋PF, in which the ferrite content reduces, the acicular ferrite is refined and its content increases obviously compared with the weld for ER50-6 wire. The tensile test totally fractures in weld for welded joint matching with ER50-6 wire; and with the increase of groove angle degree, the weld strength first increases and then decreases substantially, and the elongation decreases, the impact energy for three zone of the welded joint increases first and then decreases. With the increase of the groove angle, for welded joint matching with MK- G60-1, the tensile strength gradually decreases, the elongation increases, the impact energy of weld and HAZ increase firstly and then decrease, the impact energy of fusion zone gradually increases, the tensile strength and impact properties of the welded joint are much better than those of matching with ER50-6 wire.