MIG Welding Optimization of Muffler Manufacture by Microstructural Change and Thermal Deformation Analysis

Abstract

Metal inert gas (MIG) welding is commonly used for automotive muffler assembly. However, the thermal deformation caused by high temperature leads to dimensional problems of the muffler fabrication. Therefore, the welding deformation has to be predicted prior to the actual welding process to improve the quality of welded structures. In this study, the prediction for the thermal deformation of the automotive muffler was modeled by using SYSWELD software. A heat source fitting method was applied for MIG welding modeling to obtain accurate simulation results, which iteratively adjusts the heat source conditions until the morphology of fusion zone agrees with that of the test specimen. The simulation results were verified with experimental results. Microstructural changes, the phase of the MIG welded part were observed by analysis instruments such as optical microscope and electron back-scatter diffraction. The observations show a good agreement with the simulation results. Besides, we have observed the weld zone to measure its hardness using hardness tester. Using the relation of hardness, we have performed the welding analysis to investigate the residual stress and the deformation shape of the weld zone. As a results, an optimized MIG welding process of the muffler for automotive exhaust system was proposed by the theoretical and experimental results. Key words: MIG welding, Thermal deformation, Finite element method, Optical microscope (OM), Electron back scatter diffraction (EBSD), Microstructure, Hardness