فرزام سليمي عليشاهي

Stainless steels, as one of the best options for use in corrosive environments, and welding as one of the best methods of connection, have always been popular among craftsmen. Resistance Spot Welding, due to features like a clean appearance and high speed, is one of the best welding methods in the automotive and oil and gas industries. 304L austenitic stainless steel and 2304 duplex stainless steel which are among the most weldable groups of these steels, were selected for this research. Resistance Spot welding of two dissimilar alloys, due to having different properties, creates an asymmetric weld joint which makes its study and analysis challenging. In this research, the effects of two important welding parameters, namely current and welding force, on the macrostructure, microstructure, and mechanical properties are investigated and eva‎luated. In macroscopic studies, the dimensions of different weld zones were measured. In microscopic studies, microstructural developments, welding metallurgy, and solidification behavior are described. Also, by performing a tensile-shear test, the tensile-shear load and fracture energy were measured. Generally, increasing the welding current played an increasing role in the diameter of the weld nugget, its area, tensile-shear strength, and fracture energy. The width of the heat-affected zone on the 2304 side was larger than on the 304L side, and this difference decreased with increasing current. The nugget diameter in the maximum condition in the welded sample at 11 kA current under 4 kN force reached 8.23 mm. The type of solidification was ferritic, and the final microstructure included 40% ferrite. The austenite phase was observed as Widmanstatten plates at the ferrite grain boundaries. The hardness of the heat-affected zone on the 2304 side was higher than other weld areas. The hardness of this area reached about 340 Vickers due to the precipitation of chromium nitride. The maximum tensile-shear force was 18.7 kN, related to the sample welded at 10 kA current and under 4 kN force, and the maximum fracture energy, related to the sample welded at 10 kA current and under 3 kN force, was 68.6 joules. Simulation was performed at 11 kA and 9 kA currents, and the simulation error for these currents was calculated as 11.5% and 14%, respectively.

فولادهاي زنگ‌نزن , پارامترهاي جوشكاري مقاومتي نقطه‌اي , ارتباط ريزساختار و خواص مكانيكي , جوش پذيري , مسير انجمادي , شبيه‌سازي

Stainless Steels , Resistance Spot Welding parameters , Correlation of microstructure and mechanical properties , Weldability , Solidification path , Simulation

farzam salimi alishahi

hossein arabi-bagher mohammad sadeghi