The Research Of CMT Brazing Of Magnesium Aluminum Alloy And Galvanized Steel

Aluminum is a light metal which shows the good machinability and low cost. However,in industrial production, the strength of aluminum often can not attain the demand, so the composite structural of aluminum and steel is widely used in automotive, construction,aviation and other fields. However, joining of aluminum alloy and steel has great difficulty since brittle intermetallic compounds(IMCs) are formed in the joint. Therefore, using CMT arc welding-brazing technique and optimizing the process parameters have became effective means to enhance the strength of joints.In this paper, three different kind of aluminum have weld to galvanized steel by CMT welding method. Using SEM, EDS and other testing method to compare the macro-morphology, microstructure, elemental composition to analysis the differences of welding effect between 1060, 5052, 5A05 aluminum alloy. Analyzing the growth mechanism of interfacial layer compounds and the growth mode of alloying elements on the interface layer. To Study the effect of welding heat input on 5A05 aluminum and galvanized steel joints when use AlSi5 and AlSi12 welding wire, and to determine the optimum welding heat input. Using different filler metal to study the affect of macro morphology and microstructure of the joint to prove which filler metal will improve the joint property. Then to study the effects of the wire feed speed and the welding speed on the joint forming and microstructure of 5052 aluminum alloy and Q235 galvanized steel sheet to obtain optimum welding parameters.Filling AlSi5 wire, the 5052 and 5A05 aluminum joints were fractured in brazed interface with brittle characteristics significantly. The thickness of 5A05 joint interface layer is 2.5?m, and the interface was smooth. The thickness of intermetallic compounds on 5052 aluminum alloy's interface layer was 2 ~ 4?m and a small amount of whiskers from compound layer was grown into the weld to strengthen the combination between the two materials.Mg could reduces the formation of Fe-Al intermetallic compound to make the interface layer became thinner, and weaken the binding force between the base material.When filling with AlSi12 wire, the 5052 and 5A05 aluminum joint was fractured in the melting area, and the grain of 5052 aluminum was uniformly, and the grain of 5A05 aluminum was dendritic. Combining Mg to Al elements can generate a brittle compound to make the composition uneven and the mechanical properties deteriorate. Filling AlSi12 wire,the optimum strength of 5A05 aluminum and galvanized steel joint was obtained as106.1MPa; when the filling material is AlSi5 wire, the optimum strength was 96.7MPa. Si could refine the grain to enhance the strength of the joint, and to control the growth of the intermetallic compound. The optimum tensile of 5052 aluminum to galvanized steel welded joints was 117.9MPa. Process parameters and weld filler have had a marked impact on morphology, grain structure, joint property. Improper parameters could reduce the solder wettability and increase the generation of weld defects like porosity.