Investigation of the Weld Properties of Dissimilar S32205 Duplex Stainless Steel with AISI 304 Steel Joints Produced by Arc Stud Welding
UNS S32205 duplex stainless steel plates with a thickness of 3 mm are arc stud welded by M8 × 40 mm AISI 304 austenitic stainless steel studs with constant stud lifts in order to investigate the effects of welding arc voltages on mechanical and microstructural behaviors of the joints. As the welding arc voltage increases starting from 140 V, the tensile strength of the weldment also increases but the higher arc values results in more spatters around the weld seam up to 180 V. Conversely, the
... er arc voltages causes poor tensile strength values to weldments. Tensile tests proved that all of the samples are split from each other in the welding zone but deformation occurs in duplex plates during the tensile testing of weldments so that the elongation values are not practically notable. The satisfactory tensile strength and bending values are determined by applying 180 volts of welding arc voltage according to ISO 14555 standard. Peak values of micro hardness occurred in weld metal most probably as a consequence of increasing heat input decreasing the delta ferrite ratios. As the arc voltage increases, the width of the heat affected zone increases. Coarsening of delta-ferrite and austenite grains was observed in the weld metal peak temperature zone but it especially becomes visible closer to the duplex side in all samples. The large voids and unwelded zones up to approximately 1 mm by length are observed by macro-structure inspections. Besides visual tests and micro-structural surveys; bending and microhardness tests with radiographic inspection were applied to samples for maintaining the correct welding parameters in obtaining well-qualified weldments of these two distinct groups of stainless steel materials. Metals 2017, 7, 77 2 of 11 Duplex stainless steels form various kinds of detrimental precipitates due to the temperatures that they experience. Hence, some precautions should be taken into account while they are welded or heat treated. Besides, as the cooling rate of weldment or heat-treated duplex alloy increases, the delta-ferrite ratio increases and the amount of austenitic phase structure also decreases [1-3,6-8]. The delta-ferrite content of these alloys also depends on temperatures that encountered in their thermal treatments [1, 2, 9] . As austenitic stainless steels are cheaper than duplex stainless steels, they can be substituted for duplex alloys mainly for economic considerations. Thus in this work; austenitic AISI 304 stainless steel is displaced for S32205 duplex stainless alloy due to economic viewpoints. In many industrial applications, these two distinct alloy groups are joined by each other with numerous kinds of well-known arc welding techniques such as TIG, MIG, and covered electrode welding. However, in this practice, owing to fast and practical way of application, arc stud welding process is preferred. The arc stud welding process has been used as an alternative metal-fastening method since the 1940s . Arc stud welding technique is widely used in basic applications such as bolts, nuts, pins, furniture chassis, household appliances, automobiles, structural applications, and heat insulation parts. Stud arc welding, also known as arc stud welding, is a commonly used method for joining a metal stud, or fastener, to a metal work piece as schematically shown in Figure 1 .