An analysis to optimize the process parameters of friction stir welded low alloy steel plates

Abstract

The friction stir welding (FSW) of steel is a challenging task. Experiments are conducted here, with a tool having a conical pin of 0.4mm clearance. The process parameters are optimized by using the Taguchi technique based on Taguchi’s L₉ orthogonal array. Experiments have been conducted based on three process parameters, namely, the tool rotational speed, tool tilt angle and travel speed. Tensile strength has been predicted for the Optimum welding parameters and their percentage of contribution in producing a better joint is calculated, by applying the effect of the signal-to-noise ratio and analysis of variance. Based on the study, the tool tilt angle is found to be the most significant variable over the other process parameters, and it enhances the quality of the weld on steel rather by the tool axis which is perpendicular to the work plate. The optimum tensile strength predicted through the ANOVA is 472 MPa. Confirmation tests have been performed for the resulting optimum parameter and the average tensile strength was found to be 474 MPa. A metallurgical analysis for the optimum parameter was performed on the specimens and typically two distinct Heat affected zones (HAZ) were observed with variation in the micro structure.

Keywords: Low alloy steel, Taguchi, Tensile strength, conical pin, tool tilt angle