Arc Behavior And Welding Quality In Joining Aluminum Alloy To Stainless Steel By Pulse MIG Welding-Brazing

With the rapid development of modern manufacturing industry, the demand for energy increased sharply, the situation of energy-saving and emission-reduction is becoming more and more serious, hybrid structure of aluminum alloy and stainless steel attracts more and more attention and has a high potential of application in the fields of automobile and aerospace vehicle with its unique advantage of light weight and high strength. However, joining aluminum alloy and stainless steel has great difficulty since the their physical and chemical properties are greatly different and brittle intermetallic compounds can easily form in the joint. Pulsed MIG welding-brazing is favored because of its controllable heat input and high efficiency.The key issues to control the thickness of brittle intermetallic compounds and obtain beautiful weld and high-strength joint is how to control the distribution of heat input on both sides of aluminum alloy and stainless steel.In this paper, arc behavior in the process of pulse MIG welding-brazing of aluminum alloy and stainless steel lap joint was first studied and two action modes of arc were designed. When the position of the wire end differs, the law of the arc shape and the heating position varied was explored and the machanism was revealed by arc physics theory. This paper focused on the effect of the distribution of heat input aroused by the position of arc on weld formation, the thickness of brittle intermetallic compounds and shear strength of the joint. Further, An evaluation system of the stability of arc was established, using statistics parameters as the main body and the waveform of current and voltage, the graph of arc shape and the graph of U-I as supplements. Then the relationship between the stability of arc and welding quality was studied tentatively.The study of arc shape in the welding process of aluminum alloy and stainless steel lap joint found that, the different characteristics of the two material and the specialty of the lap joint led to special characteristics of the arc behavior variation.Particle distribution of the arc space, arc stiffness and principle of minimum voltage together influenced the arc shape. Different position of the arc led to different shear strength of the joint. Analysis showed that, the shear strength of the joint is affectedby the three factors as follows, the area of the brazing interface and the thickness of the intermetallic compounds.An evaluation system of the stability of arc was established based on statistics theory and the results showed that the position of arc and dip angle had great influence on the stability of arc. The arc showed high stability when the heeling angle is 20°. The analysis showed the relationship between the stability of arc and shear strength is small because of the specialty of arc behavior in the process of pulse MIG welding-brazing of aluminum alloy and stainless steel lap joint.