Sanicro25 / G115 异种钢焊接接头的微观组织及力学性能

Select ERNiCrCoMo-1 as the welding wire and use tungsten argon arc welding (GTAW) to weld Sanicro25/ G115 dissimilar steel. Microstructure and mechanical properties of the welded joint were studied by means of optical microscope, scanning electron microscopy, transmission electron microscopy and tensile testing. The results show that the microstructure of the weld, Sanicro25 steel and its heat affected zone(HAZ) is austenite+precipitated phase. The microstructure of the G115 steel and its heat affected zone is tempered martensite, and the base metal of the G115 steel still maintains regular martensitic lath with width of about 466 nm. The martensitic lath characteristics in fine grained heat affected zone (FGHAZ) of the G115 steel side disappear, forming subgrains with lower dislocation density, and M₂₃C₆ and MX phases are distributed along subgrain boundaries and within grains respectively. There is no δ-ferrite observed near the weld and fusion line of the G115 steel side. The microhardness of the weld is 246 HV0. 1, and the hardness of the coarse grain heat affected zone (CGHAZ) adjacent to the G115 steel side of the weld is the highest, while the hardness of FGHAZ is the lowest. The hardness of the Sanicro25 steel increases from 230 HV0. 1 to 246 HV0. 1, while the hardness of the G115 steel decreases from 263 HV0. 1 to 250 HV0. 1 after welding thermal cycle and post-weld heat treatment. The welded joint exhibits ductile fracture, and the strength at room temperature and yield strength at 650 ℃ are higher than the standard lower limit of the base metal. The fracture location is located at the FGHAZ of the G115 steel side.