Microstructural and Mechanical Properties of Heat-Treated Low Carbon Steel Welded with Varied Joint Designs

This study examined the effects of joint design and post-weld heat treatment (PWHT) on the microstructural features and mechanical properties of low-carbon steel welded using the shielded metal arc welding (SMAW) process. Three joint configurations—bevel, butt, and half-lap—were welded under consistent parameters, with a subset of samples subjected to PWHT involving quenching in either used or unused oil baths. Mechanical testing, including tensile, hardness, and impact toughness tests, was conducted on both as-welded (AW) and PWHT-treated samples. Results showed that bevel joints exhibited the highest tensile, yield, and impact strengths, while butt joints demonstrated superior hardness. PWHT, particularly quenching in unused oil, significantly enhanced tensile strength, yield strength, and hardness, whereas quenching in used oil achieved the highest impact strength. Microstructural analysis of the bevel joints after quenching in unused oil, along with mechanical testing for tensile strength, yield strength, hardness, and impact toughness, revealed that PWHT notably improved mechanical performance compared to AW conditions. The bevel joints exhibited significantly higher tensile and yield strengths, as well as enhanced hardness, indicating the formation of a refined martensitic structure due to the quenching process. The study concluded that the choice of joint design and quenching medium can optimize welded joint properties for specific industrial applications. Bevel joints were recommended for high tensile and yield strength, whereas butt joints were preferable when hardness and toughness were essential.

کلیدواژه ها:

low carbon steel ، weld joints ، oil bath ، post-weld treatment ، shielded metal arc welding