Abstract
Ferritic stainless steels are iron-chromium alloys having chromium content usually in the range of 10.5–27%. In these steels the predominant metallurgical phase present is ferrite. These steels are Fe-Cr-C alloys with sufficient chromium or chromium plus other ferrite stabilizer, such as aluminium, niobium, molybdenum, titanium, used to inhibit the formation of austenite phase on heating. Ferritic stainless steel (FSS) is generally considered to have poor weldability when compared to austenitic stainless steel (ASS) but has recently drawn greater attention owing to their lower costs and better resistance to stress corrosion resistance than austenitic stainless steel. Ferritic stainless steels have been widely used in vessels, vehicles, household appliances, kitchen equipments and building decoration because of its excellent stress corrosion and spot corrosion resistance addition to good strength. Because it does not contain nickel, it is a cheaper alternative of austenitic stainless steel. In this work weldments of FSS welded by pulse MIG welding using argon as a shielding gas were investigated. The austenitic stainless steel (ER309L) and ferritic stainless steel (ER430) electrode wires were used to prepare the weldments. To obtain a good welded joint the welding process parameters were experimentally optimised. The microstructures and mechanical properties of the prepared weldments were investigated. In the weldment welded by austenitic stainless steel electrode wire dendritic austenitic phase was observed in the weld metal zone. In heat affected zone intragranular carbide precipitation and grain boundary martensite were observed. In case of weldments welded by ferritic stainless steel electrode wire coarse grains were formed in weld metal zone and heat affected zone. Grain boundary martensite, ferrite and intragranular carbide precipitation were found in weld metal zone and heat affected zone. Impact strength of the weldments welded by austenitic stainless steel electrode wire was found higher due to formation of austenite phase in the weld metal zone. Impact strength of the weldments welded by ferritic stainless steel electrode wire was found very low due to formation of coarse grain and martensite in the weld metal zone. The ultimate tensile strength and percentage elongation of the weldments welded by austenitic stainless steel electrode wire were found higher than the weldments welded by ferritic stainless steel electrode wire. Hence weldments of ferritic stainless steel having superior mechanical properties will be obtained by using austenitic stainless steel electrode wire. During the tensile test the specimens were broken outside the welded joint (in base metal) which confirms the good quality of the joints
Published Version
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