Research Of Titanium/Steel Resistance Welding Process And Joint Forming Mechanism Of Copper Matrix Composite Transition Layer

The composite components of titanium alloy and stainless steel can give full play to their advantages in performance and economy,and are widely used in the fields of aerospace,manned deep-sea diving and seawater desalination.However,due to the difference in physical properties between titanium alloy and stainless steel,it is easy to produce ti-fe brittle intermetallic compounds in the joint,which makes the joint easy to crack and seriously affects the welding quality.The transition layer in the middle of the intervention in reducing the joint brittle Ti-the number of Fe series compounds,to improve the mechanical properties of joint and tissue composition,but with a single metal as the transitional layer,transition layer structure,the components of a single,difficult to meet the demand of parent metal on both sides of metallurgy at the same time,using solder as matrix of composite metal,insufficient solder itself strength become weak ring joint performance.In view of these problems,two aspects of research work are carried out in this paper: first,copper foil is used as the transition layer to explore the titanium/steel resistance welding technology and joint forming mechanism of copper foil transition layer;Second is on both sides of copper foil as matrix material and in its preparation composite transition layer in a certain way,explore the copper matrix composite transition layer of titanium/steel resistance welding process implementation method and joint formation mechanism,determine the applicable to the preparation of compound transition layer of copper foil type and preparation methods,established the composite evaluation index in the transitional layer,explores the different components,ratio of composite transition layer on the joint microstructure and mechanical properties,the influence of the atomic diffusion behavior mechanism.The research work and conclusions are as follows:(1)Copper foil as a transition layer of titanium/steel resistance welding process and joint formation mechanism were explored.With the joint design of assembly and anti-oxidation protection measures,the process parameters to explore the methods to realize the titanium/steel,welding joint shear strength as the joint mechanical performance evaluation index,9 copper foils with different thickness of T1,T2,T4,TU0,TU1,TU2,H62,HSn62-1 and QSn1.5-0.2 were used as transition layers to conduct resistance welding test of titanium/steel lap joints.to probe the different thickness of transition layer joint microstructure,mechanical properties and phase composition,by atomic concentration curve drawing,establish joint metallurgy reaction model and method to study the formation mechanism of joint.The experimental results show that it is feasible to use copper foil as the transitionlayer.Compared with other copper foil,T4 copper foil transition layer joint can obtain better mechanical properties.The intervention of copper foil transition layer inhibited the formation of ti-fe series compounds and formed phase and structure in the joint which was beneficial to improve the performance of the joint.(2)The preparation method and technology of copper foil as matrix composite transition layer were explored.According to the demand of the welding joint and reliable connection,the transition layer structure,component design,respectively to study the powder compacting,powder coating,the preparation of compound transition layer in titanium/steel,welding joint microstructure and mechanical properties,phase composition,preparation methods of composite transition layer was determined by the comparison of measurement is compound the ply of the transition layer,and through the thickness of transition layer and powder adding quantity to calculate the density of composite transition layer,set up the evaluation indexes of compound transition layer,try a more effective compound preparation technology transition layer.The analysis shows that the composite transition layer has a three-layer structure,which is composed of a side adsorption layer near titanium alloy,a base copper foil layer and a side adsorption layer near stainless steel.The powder pressing method is an ideal method to prepare the composite transition layer.Taking the thickness and density as the quality evaluation indexes of the composite transition layer,the copper matrix composite transition layer with a certain thickness and density can be prepared by controlling the powder dosage and pressing pressure.(3)A method for realizing resistance welding process of titanium/steel in copper matrix composite transition layer was explored.Copper matrix composite transition layer in the titanium/steel welding,sub assembling and more complex,anti-oxidation protection measures by adjusting the compound is placed in the transitional layer,the reserved clearance of sealant when daub and welding technology parameters such as measures to implement the titanium/steel connections,studied the welding current,welding time,electrode pressure regularity of influence on the mechanical properties of joint by joint shear strength as index,through the contrast test to determine the composition and ratio of copper matrix composite transition layer.The results show that the copper matrix composite transition layer can be used as titanium/steel transition layer.The relationship curves between welding process parameters and joint mechanical properties are normally distributed.The composition and ratio of copper matrix composite transition layer are: the adsorption layer group of titanium alloy is divided into Nb and V mixed powder layer,the ratio is Nb: V= 3:1,the adsorption layer group of stainless steel is divided into Cr powder layer,and the substrate layer is0.4mm T4 copper foil.(4)The forming mechanism of titanium/steel resistance welding joint in copper matrix composite transition layer was investigated.According to the intervention of copper matrix composite transition layer adsorption layer location design four types of connectors,to probe the adsorption layer in position of joint microstructure and mechanical properties,mechanism and the influence of the atomic concentration of joint shear strength as the evaluation index,the research can obtain high-quality titanium/steel joint adsorption layer thickness,density,by probing the adsorption layer thickness and density effect on joint mechanical properties and microstructure of the mechanism and methods of metallurgical reaction model is established to reveal the copper matrix composite formation mechanism of transition layer of titanium/steel joint.The results show that the location of adsorption layer has a great influence on the performance and structure of the joint.After the copper matrix composite transition layer is involved,the mechanical properties of the joint are significantly higher.The change of the thickness and density of the adsorption layer leads to the change of the mechanical properties and microstructure of the joint,which seriously affects the formation mechanism of the joint.