304/304L不锈钢TIG焊两种搭接接头的组织及力学性能
Microstructure and Properties of Different TIG Lap Joint of 304/304L

搭接接头焊缝在实际工况中存在受拉力和剪切力两种受力状态，其力学性能的差异对工程应用中选取焊缝形式有重要意义。对不锈钢304及304L进行钨极惰性气体保护焊（TIG焊），研究了两种样件焊接接头的显微组织、硬度、拉伸性能和疲劳特性。结果表明：两种搭接形式下的焊接接头从母材到焊核，可根据晶粒类型和大小分为7个区域。焊缝受拉力样件的断裂延伸率为19.3%，在接头区域两种组织过渡处断裂；受剪切力样件的断裂延伸率为12.7%，在材料尺寸变化、应力集中处断裂。焊缝受拉力样件断裂韧性、抗拉强度和疲劳性能更强，结构尺寸变化和应力集中对受剪切力样件力学性能的影响较大。
There exists two stress state by the tensile force and shear force of lap joint weld, the differences of mechanical performance make sense for choosing weld form in engineering application. Tungsten inert gas (TIG) is used to weld 304 and 304L stainless steel. With metallographic, hardness, quasi static tensile and fatigue experiments, the structure microstructure, hardness distribution and mechanical properties of two different laps are obtained. The results show that the lap weld joint from the parent metal to the welding is divided into seven areas for the difference of microstructure. Besides, the tensile sample's elongation rate is of 19.3% and fructures at differences in the organization, while the shear sample's elongation rate is of 12.7% and fructures for size changing and stress concentration. The tensile sample has higher fracture toughness, tensile strength and fatigue damage properties, while joint strength of shear sample is significantly affected by the change in structure size and the stress concentration