Effect of welding electrode variation on microstructure and mechanical properties of AISI 204 stainless steel plates joined using shielded metal arc welding

Abstract

The current study investigates the effect of some welding electrodes and post-weld heat treatment on the micro-structure, tensile strength, and hardness of austenitic stainless steel (AISI 204) weldments using the shielded metal arc welding (SMAW) technique. Four different electrode specifications were used in this study, these include stainless steel electrodes (E308L and E308L-16) and mild steel electrodes (E6013 and E7018). Samples of the austenitic stainless steel plate of 5 mm thickness were first sectioned and welded across the width using the four electrodes. Following the welding operations, a post-weld heat treatment was carried out at 1100 oC, soaked for 60 minutes, and then allowed to cool naturally in the open air. Both the heat-treated and the as-welded samples were then subjected to tensile and hardness tests. The hardness and ultimate tensile strength of the weldments with mild steel electrodes are higher than those of stainless-steel electrodes. However, heat treatment after the welding results in even higher hardness and ultimate tensile strength values for all the weldments except for the E6013 electrode. It is, therefore, not advisable to use inappropriate electrodes to weld austenitic stainless steel. Also, the high difference in mechanical properties between the weldments and the base metal will introduce stresses to the material, resulting in solidification cracking. The microstructures of the weldments show distinct dark and bright features, which indicates the depletion of elements like Cr in the steel.