Research On Temperature Field Simulation And Resistance Brazing Process Of Titaniun Steel Dissimilar Metals

In order to respond to the national call for energy saving and emission reduction,to achieve lighter structure,more and more structural parts in the aerospace and automotive fields are connected by two or more materials.As two widely used metal materials,it will be of great significance to achieve their reliable connection of titanium alloy and steel.Resistance brazing is widely used because of its high welding efficiency and low energy consumption,and the change of temperature field directly affects the structure and mechanical properties of the welded joint,mastering the change law of temperature field in the process of resistance brazing has a guiding significance for achieving reliable connection of materials.Therefore,this paper uses simulation software to simulate the temperature field in the welding process,and obtains the change law of the temperature field under different welding methods,and explores the effect of different metal interlayers(Cu,Ni,Ni/Cu)on the joint structure and performance in the best way of welding methods.Provide new ideas for the realization of the safety,reliability and convenience of titanium steel dissimilar metals welding.MSC.Marc software was used to simulate the temperature field of titanium steel resistance brazing under three welding methods:graphite thermal compensation,electrodes with the same diameter(10mm)and electrodes with different diameters(upper 10mm and lower 8mm).The results show that although the thermal compensation method maintains the heat and raises the maximum temperature,the peak temperature zone is always located at the contact part of the lower electrode and graphite,and the high temperature region shifts.The electrode melts while the block is crushed.When simulating electrodes with the same diameter,the peak temperature zone is always offset to one side of the titanium base material,and the temperature difference between the two sides of the base material is always large.When using electrodes with different diameters for simulation,it can be ensured that the welding heat is mainly concentrated in the center of the weld seam,and the temperature distribution is more reasonable,so that the temperature of the weld seam area is raised,and the heat offset problem on the titanium side during the welding process is improved.According to the simulation results,the resistance brazing process test of dissimilar metals of titanium steel was carried out under the best electrode configuration,and the effects of no interlayer,nickel,copper and nickel-copper alloy interlayer on weld formation,microstructure and mechanical properties were analyzed.The results show that when welding with no interlayer,nickel and copper as interlayer,the weld joints all form a nugget,and there are a lot of cracks and void defects inside the nugget,and the mechanical properties are low.However,when the nickel-copper alloy is used as the intermediate layer for welding,the joint does not form a nugget but is divided into obvious three layers of layered transition distribution.The interface junction is mainly connected by element diffusion without obvious defects,the presence of the nickel-copper alloy interlayer suppresses the interdiffusion of Fe and Ti elements and the formation of Ti-Fe intermetallic compounds.The joint area is mainly composed of Cu₄Ti₃,Ni₄Ti₃,Fe Ti,Ti₂Ni?Fe₂Ti,and Ni₃Fe phases.The mechanical properties of the welded joint are greatly improved.The shear load is 12726N,which is twice that without the interlayer.