Journal of Welding Science

The friction stir spot welding (FSSW) process is a solid-state welding technique recognized as one of the most significant advancements in metal joining over the past decade. In this study, the effects of rotational speed and tool contact time, with a unique design different from previous research, on the microstructure and mechanical properties of 5754 series aluminum alloy were investigated. The workpiece was clamped using a specialized fixture on a radial drilling machine, and welding operations were performed using a FSSW machine at different rotational speeds and various tool contact times. Subsequently, the microstructure, microhardness, and tensile-shear strength of the welded spot region were evaluated. The results showed that increasing the tool rotational speed and prolonging the tool contact time led to an improvement of approximately 105% in the tensile-shear strength. According to statistical analyses, the factors of rotational speed and tool contact time significantly affected the shear strength with a confidence level greater than 95%; however, statistical analyses revealed different results regarding the relationship between rotational speed, contact time, and hardness.

This study presents a comparative evaluation of SMAW and GMAW welding processes for blade-to-shaft joints in St37 steel industrial mixers operating in lead-processing environments. The effects of welding process selection and joint geometry modification on the microstructural and mechanical properties of the welded joints were investigated. The results showed that the use of the GMAW process reduced the average heat-affected zone (HAZ) width from 1532 μm to 871 μm, corresponding to a 43.1% reduction compared to SMAW. In addition, the ultimate tensile strength increased from 376 MPa for SMAW joints to 400 MPa for GMAW joints, representing a 6.4% improvement. Microhardness measurements revealed an increase in the average HAZ hardness from 145 HV to 160 HV, corresponding to a 10.3% increase. Microstructural examinations also revealed noticeable differences in the characteristics of the weld metal and HAZ produced by the two welding processes. The findings indicate that the combination of GMAW and optimized joint geometry can improve the mechanical performance and reliability of blade-to-shaft joints in industrial mixers.