Study On Static Fusion Welding Performance Of Cu-W Composite Electric Contact Based On Micro Directional Skeleton Structure

When the contact of DC relay is stably pulled in,the contact will melt and adhere under the action of short-time withstand current,resulting in relay contact failure.On the premise of meeting the requirements of conductivity and mechanical properties,improving the thermal conductivity of electrical contact materials can effectively inhibit the fusion welding erosion of electrical contact.Selecting electrical contact materials with low and stable contact resistance is one of the effective ways to inhibit static fusion welding erosion.The three-dimensional interconnected microstructure of electrical contact materials is directly related to its thermal conductivity and fusion welding resistance.In this thesis,the influence of the microstructure of the electrical contact of high-power DC relay on its static fusion welding performance is deeply studied.Three kinds of Cu-W composite electric contacts with micro directional skeleton structure,quadrilateral,hexagonal and rhombic dodecahedron are designed here,based on the structural bionic theory and combined with the characteristics of dragonfly’s wing vein.The influence of the microstructure of the composite electrical contact on its thermal conductivity is studied and compared with the Cu-W composite electrical contact with disordered skeleton structure.The temperature,conduction heat flux and thermal conductivity of several electrical contacts with different microstructure at the same time are simulated and calculated by finite element method.The results show that the thermal conductivity of electrical contacts with rhombic dodecahedral skeleton structure is the best,followed by electrical contacts with quadrilateral,hexagonal and disorderly distributed skeleton structure respectively.The micro oriented W skeleton structure can effectively improve the thermal conductivity of Cu-W composite electrical contacts.Based on the theory of hydrodynamics and considering the role of Marangoni effect,the molten pool characteristics of Cu-W composite electrical contacts with different microstructures are analyzed.Due to the regular arrangement and distribution of Cu and W two-phase materials,the erosion range of static fusion welding of electrical contacts with micro oriented W skeleton structure is significantly reduced,and the volume and melting area of metal liquid are rhombic dodecahedron < quadrilateral < hexagon < disorderly distributed skeleton structure electrical contacts from small to large.The micro oriented W skeleton structure can significantly reduce the static fusion welding erosion of Cu-W composite electrical contact,and the static fusion welding resistance of diamond dodecahedral skeleton composite electrical contact is the best,followed by quadrilateral and hexagonal skeleton electrical contact.The voltage and current parameters are extracted through the contact breaking experiment,and the contact resistance of electrical contacts with different microstructure is calculated.Compared with the electrical contacts with rhombic dodecahedral skeleton structure,the contact resistance of electrical contacts with disordered distribution structure is greater,and the electrical contacts with micro directional skeleton structure have lower and stable contact resistance.The correctness of the simulation results is verified,and the influence of contact closing speed on the contact resistance is explored.The test results show that the contact resistance decreases with the increase of closing speed.