The Study On Welding Process Of Zinc-based Alloy

Zinc-based alloy is an environmental protection material, with high strength, good plasticity, excellent wear resistance and non- magnetic, which has been widely used in machinery industry, light industry, instrument industry and electrical industry, etc. But because Zn has low melting point and boiling point, moreover easily oxidation, its weldability is poor, so that the study on welding process of znic-based alloy is little. In this article, zinc-based alloy specimen are welded by TIG, laser welding and induction soldering respectively. The feasibility of process and the characteristics of joint were analyzed by means of metallographic microscope, SEM and EDS, which is provide some theoretical basis and process technology about the selection of zinc-based alloy welding process for engineering practice.Serious evaporation of Zn, poor quality of formation of weld and the coarse crystal zone often appear in the fusion welding znic-based alloy, which have bad effect to the welded joint. TIG of Zinc-based alloy, the weld microstructure is dense, and the fusion zone and heat affected zone without coarse crystal. But the fusion zone generate unstable ZnAl, which don’t decompose absolutely under the rapid cooling so that it decompose at room temperature with the expansion of the volume, large internal stress, so the mechanical property of the joint reduced. The hardness value of different zone of joint is: weld bead > heat affected zone > base metal > fusion zone. Laser weld of Zinc-based alloy, there is an pit at the central zone of the joint surface, which reduces the strength of welded joint and may cause the crack, so that it’s a weakness zone. The depth to width ratio is bigger than TIG, and the microstructure of weld bead is more denser. Fusion zone and heat affected zone, which is very narrow, did not produce overheating coarse crystal area, and because of the recrystallization, the welding joint will have good mechanics performance. The hardness value of different zone of joint is: weld bead > fusion zone and heat affected zone > base metal.Induction soldering can effectively avoid the evaporation of Zn and decrease the welding deformation. But if the process is not suitable, the interface is prone to produce defects such as brittle microstructure. In this article, through wetting experiment to choose the suitable solder(Sn-3.5Ag), induction soldering weld zinc-based alloy under the protective atmosphere. The analysis shows that the diffusion of soldering filler metal and the dissolution of parent metal exist in the process of induction soldering, and the solder ing area produces interaction crystallization and forms uniform equiaxed crystal, so that the joint of induction soldering are excellent. In the process of induction soldering, more holding time is contribute to the spread of the elements, and if the holding time is long enough, the soldering seam will disappear.