Experimental investigation on mechanical properties of SS316 stainless steel welded joints using robotic gas metal arc welding process

Abstract

newline Welding techniques are widely used by the industries namely Tungsten Inert Gas (TIG) welding, Gas Metal Arc Welding (GMAW), friction welding, plasma welding, resistance spot welding, friction stir welding and electron beam welding were used depending upon the materials being welded and end applications. Out of these welding process, MIG welding process is widely used in the industries because of its ease of operation, low cost and ability to weld different metals. However controlling the weld speed and wire feed are difficult by manual welding method. To overcome this, Robotic welding is used in this research work. The results shows that increase in current and gas flow rate increases the hardness, ultimate tensile strength and impact strength of Stainless Steel SS316 welded joints. Higher the current supports the sufficient heat generation and higher the gas flow rate supports the ionization process to increase the arc efficiency. In addition, increase in travel speed and wire feed rate increases the strength of welded joints to certain values. Further increase in travel speed and wire feed rate decreases the strength of Stainless Steel SS316 welded joints. The travel speed is crucial since it contribute significantly on the heat input. At lower values, excessive heat supplied create wider weld bead, excessive penetration and wider heat affected zones. On the other hand, at the higher travel speed, insufficient heat supplied and the bonding will be poor due to lack of penetration. The optimum process parameters for obtaining higher hardness, tensile strength and impact strength were reported. Gas flow rate of 15 l/min, current of 140 A, travel speed of 35 cm/min and wire feed rate of 4 m/min offered higher tensile strength of 627 MPa. Gas flow rate of 15 l/min, current of 140 A, travel speed of 35 cm/min and wire feed rate of 4 m/min offered higher hardness of 237BHN. Gas flow rate of 15 l/min, current of 140 A, travel speed of 25 cm/min and wire feed rate of 4 m/min resulted in higher impact stren