Study On The Electrical Contact Properties Of Cu-graphite Contact Materials

In this paper,according to low-voltage electrical appliances and household wall switch in the performance requirements of electrical contacts,to have a certain antioxidant capacity of copper alloy as the matrix,graphite for the ablative material,add a small amount of extinguishing role of tin dioxide,Preparation of silver-free contact material Contact material.The copper-graphite electrical contact materials were successfully prepared by powder casting and vacuum sintering.The effects of pressing pressure,sintering temperature and holding time on the sintered body were systematically investigated.The effects of graphite content and graphite plating on the mechanical properties and electrical properties of copper-graphite composites were studied.In this process,the relationship between the compactness of the sintered body and the pressing pressure,the relationship between the hardness and the conductivity of the sintered body and the sintering temperature and the holding time are studied.The effect of the pressure on the microstructure and properties of the sintered body is investigated.The final optimum process is as follows: pressing pressure was 1470 MPa,sintering temperature is 850 ?,holding time is 150 min,annealing temperature is 450 ?,annealing time is 120 min.The Pressure relief is1600 MPa.Annealing at 450 ? for 2h,,the density,hardness and electrical conductivity of the composites were increased by 12.72%,24.01% and 50.98%.Through the research on the microstructure and properties of different graphite content of copper graphite composite materials,it is found that with the increase of graphite content,the continuity of copper matrix is damaged;contact material density,hardness and electrical conductivity and tensile strength were decreased.The observation of fracture shows that the fracture mode of the material changes from ductile fracture to brittle fracture with the increase of graphite content.XRD analysis shows that the lattice of copper has no obvious change with the increase of graphite.Cu-1C,Cu-1.5C and Cu-2C electrical contact materials into electrical contacts,the temperature rise test and on-off test and electrical life detection.The results show that the temperature rise of the material changes obviously with the increase of the graphite content.After 200 closed-break tests,the surfaces of the moving and static contacts are relatively flat,and the surface of the contact surface produces a small amount of splash,and the surface element distribution shows,The distribution of elements is relatively uniform;by observing Cu-1.5C electricalcontact material after 40,000 times the electrical life test shows that the moving contact surface is relatively flat,the surface of a large number of spatter,microstructure mainly by the crack,quenching tissue and spatter Constitute;static contact deformation is serious,the arc appeared selective erosion,from the element surface distribution shows that the static contact appears in the element segregation.The Cu-1C electrical contact due to less graphite content,after 18,000 times the life of the experiment,due to copper alloy matrix melting,resulting in matrix adhesion,electrical life test stopped.Cu-2C electrical contact due to the current exothermic,after the electrical life of 20000 times,making the dynamic and static contact phenomenon,the electrical life test to stop.Cu-1.5C electrical contact material performance to meet national standards,indicating that graphite has played a very good resistance to ablation.