WELDING OF THIN SHEET OF Al ALLOYS BY USING DIFFERENT GMA WELDING PROCESSES

Abstract

Recently, environmental protection has become a matter of great importance. Weight reduction in vehicles is constantly being reviewed as one of the most effective means of improving fuel efficiency and reducing exhaust gas emissions. So new types of car and motorcycles produced from thin sheets are under rapid development. Because aluminum alloys are light and strong and can be recycled, aluminum alloys sheets are greatly used in automobile industry. This is not only the field of automobile engineering in which use of thin sheets has been explored, but also in medical, food, instruments, electronic & other industries. Welding is one of the key technologies in the mass production of cars and motorcycles, and a new welding system is therefore urgently required to improve the welding quality and productivity in sheet metal joining. When welding joints in sheet metal, specially aluminum, the main problems are burn through, gap bridging, and distortion. Lot of research is going on to develop new welding processes or techniques to join thin sheets of aluminum alloys. So this dissertation was also aimed towards the same research goal. In this dissertation three advanced GMA welding process variations { DC P-GMAW (using vario wire), AC P-GMAW and Cold Metal Transfer (CMT) } were tested for butt & overlap welding of thin sheets (1 mm and 0.8 mm) of aluminum alloys (6082 Al alloy and 5754 Al alloy). In addition tailor welded blanks were also tested. Along with proper monitoring of all the parameters, high speed photography was carried out to study the metal transfer behavior. The soundness of weld joints was examined by macro & micro testing. Also tensile strength tests & hardness tests were carried out to compare the mechanical properties. Finally an effort was made to suggest some suitable techniques, along with suitable welding parameters to weld thin sheets of Al alloys. Also the comparison was made between the three different advanced GMA welding processes variation with regards to their utility for thin sheet welding -applications