Optimization of the Welding Properties of Friction Stir Weld Butt Joints Using the Response Surface Method Based on Taguchi’s Design

The present study aims to optimize friction stir welding (FSW) using statistical tools, thereby improving the mechanical properties of butt welds and achieving the desired butt welds for practical applications, such as arts of traditional handicraft and metal sculpture products. The influence of friction stir welding parameters on butt welds was determined by the orthogonal array test and variance analysis. The pin length, dwell time, tool rotational speed, and traverse speed were found to be highly significant factors of the butt welds. In addition, the response surface method (RSM) was used to construct the model from the data of the orthogonal array experiment run using the significant factor application via Taguchi’s design. The experimental results showed that the mechanical properties of butt welds were enhanced by FSW, and the strength of butt welds reached 91%. Furthermore, the fractured properties showed a fine recrystallized grain with fewer defects or imperfections, thereby improving the workability. This was of great significance to the structural safety of large-scale metal sculptures and the pursuit of precision of handicraft products. Based on the tensile strength regression models of friction welding, the linear, interactive, and quadratic models were established, and the quadratic model with 3D contours of the tensile behavior was further developed. The results showed that the predicted values of RSM for butt weld tensile properties were very close to the experimental data, which proved the advisability and availability of RSM based on Taguchi’s design in improving the mechanical properties of friction stir welds.