Microstructural characterization and in-process traverse force during friction stir welding of austenitic stainless steel

Abstract

Welding AISI 304 stainless steel is challenging, especially as fusion-based welding processes (such as arc welding) severely undermine the material's corrosion resistance due to sensitization. Solid-state friction stir welding is one of the most suitable alternatives. Friction stir welding of high-strength high-softening materials such as AISI 304 is difficult mainly because of the non-availability of affordable tools and tool life. In this study, AISI 304 stainless steel was successfully butt-welded by friction stir welding. The experiments were performed using Taguchi's L27 orthogonal array. Shoulder diameter, tool r/min, and traverse speed were selected as the most influential welding parameters. A Tungsten Carbide (WC) tool was employed with a tapered pin profile. Defect-free joints were fabricated successfully for all the welding conditions. Microstructural examinations using optical microscopy and scanning electron microscopy revealed significant grain refinement in the stir zone and the presence of distinct structural features such as stepped, dual, and ditch in various characteristics zones. The presence of precipitates was also observed in samples and was confirmed via energy-dispersive X-ray spectroscopy analysis. The in-process traverse force was measured by a special arrangement of force measuring units attached to the work fixture. The traverse force data were analyzed and optimized. The results of an analysis of variance reveal that the traverse speed was the most important parameter, followed by tool r/min, interaction between the tool shoulder diameter and traverse speed, interaction between the tool shoulder diameter and tool r/min, and, finally, the tool r/min.

An analytical and experimental investigation considering the effect of material flow velocity on tensile strength of a steel alloy joint produced by friction stir welding process

“…Therefore, it can be noted that by adjusting the vertical force at lower values, low linear speeds increase the fluidity of the workpiece material and provide a better welding quality. Also, low linear speeds result in reducing applied traverse force to the tool, 22 which can increase the tool life.…”

Predicting the weld zones size in FSSW of 304L stainless steel plates by mathematical model based on RSM

“…However, by developing new technology and tool materials, this process can be even applied to weld the stainless steel now (Aota and Ikeuchi, 2009;Lakshminarayanan et al, 2015;Ahmed et al, 2016). Hence the application of the FSW/FSSW on the stainless steels is the subject of recent studies, which provides important knowledge about the properties and microstructure of welded stainless steel parts by investigating various parameters (Reynolds et al, 2003;Kokawa et al, 2005;Park et al, 2003;Siddiquee et al, 2015;Ragab et al, 2021;Siddiquee et al, 2020). For example, Reynolds et al (2003) have examined an initial assessment of the tensile properties, optical microstructure, and residual stress state of two friction stir welds in 304L SS.…”

Investigate the Process Parameter on the Friction Stir Welding of Dissimilar Aluminium Alloys

“…Plastic deformation occurs up to a lower level in the region next to SZ (TMAZ), which leads to partial dynamic recrystallization. e HAZ is exclusively subjected to a temperature influence [9].…”