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针对2mm厚SUS301L奥氏体不锈钢薄板进行CO2激光-熔化极惰性气体保护电弧(MIG)复合对接焊试验,深入分析了焊接接头不同区域的显微组织及相组成,研究了装配间隙对焊接接头微观组织和力学性能的影响。结果表明,SUS301L奥氏体不锈钢复合焊接接头中心区域呈一定方向性的细小枝晶组织,未出现等轴晶区域,偏离焊缝中心区为垂直于熔合线向焊缝中心生长的柱状晶组织,距焊缝中心距离越远,晶粒越粗大;焊接接头主要由γ奥氏体相和少量δ铁素体相组成,焊缝凝固模式为铁素体-奥氏体结晶(FA)模式,凝固过程中发生的δ-γ转变由块状转变和相界面处的短程自由扩散作用共同完成;随着装配间隙的增大,焊缝残余δ铁素体含量逐渐降低,抗拉强度随之下降,断裂发生在焊缝靠近熔合线区域的粗大柱状晶区。
Aiming at the microstructure and phase composition of 2 mm thick SUS301L austenitic stainless steel sheet by CO2 laser-melting inert gas arc welding (MIG) composite welding, the microstructure and phase composition of different regions of welded joint were analyzed. Effects of tissue and mechanical properties. The results show that the microstructure of SUS301L austenitic stainless steel composite welded joint shows a small dendritic structure in the central area with no equiaxed grains. The center deviating from the welding seam is a columnar grain growing perpendicular to the fusion line toward the weld center. The farther away from the weld center, the coarser the grain size. The welded joints mainly consist of γ-austenite phase and a few δ-ferrite phases. The weld solidification mode is ferrite-austenite crystal (FA) The δ-γ transformation occurred during the process is mainly accomplished by the massive transition and the short-range free diffusion at the phase interface. As the assembly clearance increases, the residual δ-ferrite content gradually decreases and the tensile strength decreases. Fractures occur in the coarse columnar zone near the weld line in the weld.