Comparative analysis of welding quality in Q235/20# dissimilar steel: Intermittent vs. full TIG welding

Abstract

This study investigates the microstructural evolution, mechanical properties, and fracture morphology of Q235/20# dissimilar steel welded joints subjected to both intermittent and fully tungsten inert gas (TIG) welding processes. The specimens, sized 200 mm × 200 mm × 12 mm, were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), microhardness testing, and tensile testing to compare the effects of the two welding techniques. The results reveal that both welding processes produced well-formed joints with minimal metal spatter at the start, and no significant defects. Microstructural analysis showed that the intermittent welding process resulted in finer and more uniformly distributed grains compared to the fully welded joints. The welded metal predominantly consisted of lath martensite, which grew significantly larger during the second welding pass. The microstructure of the welds and their mechanical properties were found to be well-correlated. A higher lath martensite content was associated with increased microhardness and tensile strength. Under the intermittent welding process, the welded joints exhibited finer and more uniform grain structures, enhancing toughness. The microhardness distributions of both welding processes followed similar trends. In tensile tests, specimens welded using the intermittent process achieved up to 90% of the base metal's performance. The fracture morphology of these specimens was characterized by numerous dimples, indicating ductile fracture behavior. In conclusion, the intermittent TIG welding process yielded a more uniform microstructure and superior performance in Q235/20# dissimilar steel joints compared to the full welding process.

Keywords

• Dissimilar metals
• TIG
• Process optimization
• Microstructure
• Mechanical properties
• Intermittent welding