Research Of Process On CMT Welding-brazing Of Dissimilar Metal Aluminum/steel

For the advantages such as high strength,corrosion resistance,light quality,aluminum/steel dissimilar metal welding structure widely used in aerospace,automobile manufacturing,shipbuilding and other fields.However,the physical and chemical properties of these two materials vary greatly,which produce joint brittle intermetallic compounds,so the traditional electric arc connection seriously affect the mechanical properties of material.It has become a difficult problem in the field of welding materials.In recent years,arc welding brazing method has become a hot research direction of aluminum/steel dissimilar metal welding because of its convenient and the efficiency characteristics.First,this paper summarized the basic principle,introduced the characteristics of the aluminum/steel dissimilar metal welding,and the history and current situation of development.According to the actual requirements of welding,the importance of impr oving the welding process was put forward.Then,in this paper,5052 aluminum alloy with the thickness of 1.5mm and Q235 galvanized steel have been selected,and the welding experiment was carried out by the CMT melting-brazing process.Studied on different welding parameters,such as the welding speed and the influence of welding current on weld formation,porosity and heat affected zone,the mechanical properties of the joints and the mechanical properti es of the joints were tested.On this basis,the effects of different filling materials and zinc coating to the properties of the joint were studied.To study the welding parameters and the mechanical properties of the joint,it wa s found that welding current was 75 A,welding speed was 0.75m/min,welding voltage was 12.1V,the wire feeding speed was 4.2m/min.On the situation,the weld shape was good,the stoma was relatively few and small,and the joint performance was best.Under the optimal process parameters,the influence of AlSi5 and AlSi12 welding wire on the microstructure and mechanical properties of joints was studied.It was fou nd that the tensile strength and micro hardness of joints obtained by using AlSi12 wel ding wire were higher than those obtained by AlSi5 welding wire.To studying the effect of zinc coating on the microstructure and properties of the joint,it was found that the existence of zinc coating can improve the wetting and spreading properties of liquid metal on the steel plate.It could improve the quality of the weld further.According to the results of the experimental research and the actual production ex perience of the welding work,a general summary and prospect of the research were made finally.