中低温热处理对SUS304不锈钢TIG焊接接头组织及力学性能的影响

轨道交通车辆在冲击振动试验后,部分设备SUS304不锈钢焊接件出现断裂失效现象.为了提升SUS304不锈钢焊后机械性能,采用金相显微镜、扫描电镜、硬度测试及拉伸试验等方法,研究了中低温热处理工艺对2 mm厚SUS304不锈钢板TIG焊接接头的组织及力学性能的影响.研究发现,经400℃热处理30 min及焊接后未处理态焊...

Effect of Heat Treatment on Microstructure and Properties of SUS304 Stainless Steel TIG Welded Joint

After the impact and vibration test of rail transit vehicles, some equipment 304 stainless steel welded parts appeared fracture failure. In order to improve the mechanical properties of 304 stainless steel after welding, in this paper, by means of metallographic microscope, scanning electron microscope, hardness and tensile test, the effects of medium and low temperature heat treatment process on the microstructure and mechanical properties of 2 mm thick 304 stainless steel plate TIG welded joints were studied. It is found that the microstructure of the untreated weld is composed of γ-austenite and δ-ferrite after heat treatment at 400 ℃ for 30 min, and δ-ferrite mainly distributes in the Cr-rich zone and appears as a worm,and the content of δ-ferrite decreases to some extent after heat treatment. After heat treatment, the hardness of welded joints is lower than that of untreated ones. The yield strength of welded joints after welding is 189.5 MPa, and the strain is 64.5%.After heat treatment, the yield strength is 221 MPa, the strain is 72.7%, and the yield strength is increased by 16.6%, reaching the yield strength of base metal. The fracture surface shows ductile fracture characteristics and no significant welding defects, mainly showing deep dimples, and the dimples are distributed with second phase particles, which hinder the slip and cause stress concentration and produce micro-pits, which become one of the main craters of cracks.