Effects of Heat Input and Interpass Temperature on the Microstructure, Intergranular Corrosion, and Mechanical Properties of Flux-Cored Arc Welded Type 316L Stainless Steel

Type 316L austenitic stainless steel is widely used in chemical, petrochemical, and nuclear industries because of its excellent corrosion resistance and mechanical properties. However, the thermal cycles generated during welding can alter the weld microstructure, thereby affecting corrosion resistance and mechanical integrity. In this study, the effects of heat input and interpass temperature on the microstructure, intergranular corrosion behavior, and mechanical properties of flux-cored arc welded (FCAW) 316L stainless steel were systematically investigated. Welding was performed under three heat input conditions of 14, 25, and 41 kJ/cm while maintaining the interpass temperature below 100 °C. In addition, specimens were fabricated at a constant heat input of 25 kJ/cm with interpass temperatures controlled within the ranges of 150-200 °C and 251-350 °C. Non-destructive testing confirmed that all welds were free from welding defects. Microstructural analysis revealed that increasing heat input and interpass temperature reduced the cooling rate, resulting in a decrease in the δ-ferrite fraction and an increase in the secondary dendrite arm spacing (SDAS) in the weld metal. Intergranular corrosion tests showed crack formation in all specimens except those welded under the lowest heat input condition, indicating that sensitization was promoted under higher heat input conditions. Furthermore, as the SDAS increased, the yield and tensile strength decreased, whereas the elongation increased. These findings clarify the relationships among welding thermal parameters, microstructural evolution, and property degradation, and provide useful guidance for optimizing FCAW conditions to improve the long-term reliability of Type 316L stainless steel weldments used in corrosive environments.