The Influence of Welding Parameters on the Nugget Formation of Resistance Spot Welding of Inconel 625 Sheets
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NTRODUCTION
RESISTANCE spot welding (RSW) is one of the most important methods for sheet metal welding being used in many industries such as the automobile, aerospace, electronics, etc. Compared with other welding processes such as arc welding processes, RSW is fast, easily maintained, and automated. This welding process includes coupled interactions of electrical, thermal, metallurgical, and mechanical phenomena and even surface behaviors. Because of this complexity, it is difficult to obtain insightful information on the welding process through experiments alone. In recent years, numerical method provides a powerful and reliable technique for studying these interactions and prediction in the welding processing industry, and, at the same time, costly experimental process can be avoided. Strength and quality of the welds of RSW are defined by size and shape of weld nuggets. In general, there is a direct correlation between heat generation and nugget size in RSW process. The contact resistances at the faying surface between workpieces, welding time, current density, and sheet thickness principally determine the heat generation during welding and the subsequent nugget shape and size.[1] Nickel-based superalloy Inconel 625 was developed as a solid solution-strengthened alloy containing relatively HAMID REZA REZAEI ASHTIANI, Assistant Professor and ROOZBEH ZARANDOOZ, Student of Master Degree, are with the School of Mechanical Engineering, Arak University of Technology, Arak, Iran. Contact e-mails: [email protected]; [email protected] Manuscript submitted August 5, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
high levels of chromium, molybdenum, carbon, and niobium. It is widely employed in aerospace, marine, chemical, and petrochemical applications, due to its excellent mechanical properties, fatigue strength, oxidation resistance, weldability, and resistance to hightemperature corrosion on prolonged exposure to aggressive environments.[2,3] To obtain a superior performance, a better understanding of spot welding processes of Inconel 625 has become necessary and the control of weld quality is much more essential. Also, in experimental methods, it is not possible to obtain a perfect model of temperature distribution, stresses, and deformation in whole welding zone, so the numerical modeling has proven to be an effective method in understanding the RSW process, and more research is needed to better understanding the thermal and mechanical behaviors of materials. Spot welding was recognized in the late nineteenth century and it was used for joining plates since 1920.[4] Nied[5] introduced an FE model for RSW process in ANSYS commercial software, then investigated the effect of the electrode geometry on the workpiece deformation and stresses as a function of temperature, and verified its results with experimental results of welding AISI 316 materials. A three-dimensional transient heat transfer model has been developed to predict temperature distribution during RSW by Wei and Ho.[6] In a similar research, Tsai et al.
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