High-frequency Induction Brazing Technology Study Of Al/Steel

This thesis summarizes the development history of the aluminum/steel metal welding.First of all,one of the best welding solder formulations of aluminum/steel is developed in this article based on aluminum/steel heterogeneous metal welding characteristics;Then,under the protection of argon gas the aluminum steel brazing is realized using the high frequency induction method.The conductive performance, weld structure and hardness distribution of aluminum/ steel brazing metals are studied by means of SEM,electron probe microanalysis(EPMA),X-ray diffraction(XRD), micro-hardness test and so on.The high frequency induction brazing process on the conductive properties and the weld interface reaction mechanism has been researched. The results indicate that high-frequency induction brazing process of aluminum/steel can replaced explosion welding to reach the purpose of saving energy and reducing consumption.Are as follows:1.First,choose the best solder and flux of aluminum/steel welding through research.Then,choose the welding solder formulation with a different proportion of solder,flux and different solder binders.Under the same conditions,respectively,the wettability and dissolution of steel-based and aluminum-based are both studied.The performance of solder binders with different components and different proportion is analyzed too.The results show that the solder binder which is made of 60 percent of Si-Al powder(-150-+300),40 percent of flux(KF,NaF):AlF₃=1:10 and 1-2 percent of potassium tartrate displays the best performance under all conditions.2.The aluminum/steel brazing is realized under the different high frequency induction brazing technological conditions.We research the resistance value changes of brazing metals along with the technological parameter changes by bridge arms method.The results indicate that the resistance value of aluminum/steel brazing metals is the lowest at voltage 4.5KV,when heating-up time 30s.And the resistance value is 2.7 percent lower compared to the explosion welding metals,reaching the purpose of saving energy and reducing consumption.3.The microstructure performances of argon protect high-frequency induction brazing interface of Al/steel were studied by SEM and XRD.The results indicated that the wetting effect of the bonding interface was excellent and there was no porosity and cracking near the interface,and the microstructure of the brazing metal was mainly composed of equiax crystal.The fracture mode of the brazing metal was coarse and gray fiber-shape,the brazing metal zone mainly consisted of Al_0.7Fe₃Si_0.3,Al_76.84Fe₂₄, Al,Fe,and there was no obvious brittleness phase of high hardness.