STUDY OF VARIATION IN PARAMETERS AND ITS EFFECTS ON SPOT WELDING OF ADVANCED HIGH STRENGTH STEEL

Abstract

Abstract Resistance Spot welding process have been focus of research in the fields of sheet metal manufacturing form last many years. In this process, an electrical current flows through resistive circuit to generate enough heat between two pieces of sheet metal so that the metal reaches molten stage. The resistance to the flow of current is provided by the work piece. The maximum heat is generated at the point of maximum resistance. In the present work, macro structural characteristics of resistance spot welding joints of the two dissimilar thickness dual phase steel having dissimilar thickness and dissimilar phase were described in terms of melting rate, indentation rate, nugget diameter and indentation diameter. The results revealed that the melting rate of the DP600 side was higher than that of the DP780 side and the indentation rate of the DP600 side was lower than that of the DP780 side of the welded joints. The base metal lap order had the important effect on nugget diameter, and the DP780/DP600 spot welded joints tended to get the larger nugget diameter than DP600/DP780 spot welded joints with the same process parameters. The indentation diameters of DP600 and DP780 sides depended on the electrode geometry and force. The reason for most spot weld capability method is to insure that, for given material, a weld piece of satisfactory size can be achieved. There are three recognized parameters of resistance spot welding – weld current, cycle duration and forging pressure which impacts the material size. Because of variety of these parameters, there is additionally impact on the mechanical properties spot weld joint. The experimental work is done to study the effects of variation of parameters on nugget diameter and properties in resistance spot welding process for a particular isotropic material. The tests are led on isotropic material and its different physical and warm properties were know Experiments alone neither can easily study the separate effects of various factors involved in the resistance spot welding process, nor can they accurately predict the complex behavior of coupled electrical, mechanical and thermal processes during the spot welding procedure. Moreover, they are often limited in scope because of the restricted operational capabilities with regard to the available hardware. Also, the scope is reduced due to excessive time and cost associated with experimental procedures, which involve many influential 2 parameters. FEM is numerical based approach and considered to be efficient tool for solving field problems. In comparison to the analytical analysis, one important merit of this model is that it can be easily applied to a model, which includes the non-uniform material properties and/or complex boundaries. Keywords: Advanced High Strength Steel (AHSS), DP780, DP600, Spot Welding, Parameters, FEM, ANSYS