Bonding Strength of 12Cr-0.4C/Low Carbon Steel (LCS) Weld Joint After Solid Solution Heat Treatment

The metal inert gas (MIG) technique plays a vital role in enhancing the durability and lifespan of 20 steel under harsh operating conditions across various industries. A strong bond is crucial for preventing joint separation. Fe-based materials with appropriate Cr/C exhibit high compatibility with carbon steel bonding. Solid solutions can improve the situation faced by MIG-treated joints. In this work, weld joints were manufactured by MIG, and half of them were treated with a solid solution, and. after the analysis of microstructure and properties, it was found that the untreated fused zone (FZ) showed good forming quality with martensite, retained austenite, and had a carbide microstructure. The solid solution eliminated the retained austenite and exhibited an even hardness. The untreated heat-affected zone had a complex microstructure, dominating upper bainite, and discrepancy-shape ferrite. The untreated group's base material (BM) consisted of grain boundary martensite, ferrite, and pearlite in a matrix, while the solid-solution group's hardness was similar. Tensile tests revealed that the untreated group had a yield strength of 639 MPa, while the solid solution group gained 339 MPa. The untreated group in BM fractures was caused by grain boundary martensite, while the solid-solution group in FZ fractures was caused by α′ and carbides.