CMT Welding Between Aluminum Alloy And Steel And Corrosion Behavior Of Joint

In this paper, 5083 aluminum alloy and EH36 steel were used for the base materials with thickness of 4mm, ER4043 and ER5183 were employed for the filler metal. The CMT welding process was employed to achieve sound joint between aluminum alloy and galvanized steel and joint between aluminum alloy and precoating steel. The microstructures and properties of the joints were observed by SEM which is coupled with energy dispersive spectrometer(EDS).The CMT welding parameters which were suitable for welding aluminium alloy and steel were gained by technology experiment, as follows: wire feed speed of 3.2m/min, welding speed of 250mm/min, welding current of 65 A, welding voltage of 14.5V, collaborative pulse correction of 2, pulse frequency of 5HZ.Firstly, using CMT machine to do the wetting and spreading test. The influnce of brazing filler metal, surface condition of steel and welding parameters on wetting and spreading ability of filler metal on the steel surface was analyzed. The results show that, increasing arcing time or wire feed speed can not promote the wetting and spreading ability of brazing filler metal on the surface of steel without zinc coating or brazing flux coating; increasing arcing time or wire feed speed can promote the wetting and spreading ability of brazing filler metal on the surface of steel with zinc coating; when the steel is with brazing flux coating, increasing arcing time or wire feed speed can promote the wetting and spreading ability of AlSi5 brazing filler metal on the surface of steel, increasing wire feed speed is more than arcing time can promote the wetting and spreading ability of AlMg5 brazing filler metal on the surface of steel.The appearance of joints of aluminium and galvanized steel welded by CMT with AlSi5 and AlMg5 filler metal are both very good. The strength of joint welded with AlSi5 is 159 MPa, the thickness of interface is 2.8μm~7.1μm; The strength of joint welded with AlMg5 is 40 MPa, the thickness of interface is 38.6μm~48.6μm. The appearance of joint of aluminium and precoating steel welded by CMT with AlSi5 is good, while the appearance of joint welded with AlMg5 is terrible. Because of technological factor, there is non-fusion in the joint welded with AlSi5,its strength is 82MPa; the strength of joint welded with AlMg5 is only 10 MPa, because the density of weld pool is small, brazing flux can not come up from weld pool, it will stop the interfacial reaction.Electrochemical experiment results show that the corrosion resistance of Al/steel welding-brazing joint is between the corrosion resistance of steel and aluminium alloy, the corrosion resistance of joint using AlMg5 filler metal is better than that using AlSi5 filler metal. The influence of condition of steel surface on the corrosion behavior of joint is small.