Hot Deformation Behavior And Hot Extrusion Process Of ZnSnO₃/Cu/Cuelectrical Contact Materials

Nowadays,copper based electric contact materials are widely used in low voltage switch and breaker. This paper studied a new copper based electric contact material, it added ZnSnO3 and rare metal La in copper. The density of electrical contact materials prepared by traditional powder metallurgy method is low, and the density has great influence on materials’ comprehensive performance. In order to meet the application requirement of circuit switch, we need to do densification processing. by far, the most commonly used densification process is hot extrusion. High temperature deformation behavior of metal can reflect the internal organization evolution regularity and hot forming performance, so researching hot deformation behavior of ZnSnO3/Cu electrical contact materials not only can significantly increase the density and performance, but also can guide to choose the hot extrusion process parameters.In this paper, I prepared the experiment sample by powder metallurgy method, and then study the high temperature deformation behavior of ZnSnO3/Cu by means of the high temperature compression. After that, we established the flow stress constitutive equation and drew the hot working map of this material. Then,we optimized hot extrusion process parameters by DEFORM finite element simulation analysis. Finally, we analyzed ZnSnO3/Cu electrical contact materials’ microstructure organization evolution regularity, dynamic recrystallization mechanism and some properties by means of actual hot extrusion. We got the best hot extrusion process parameters and it can guide the actual hot extrusion deformation process.The result shows that, if the other deformation conditions are the same, increasing deformation temperature and reducing strain rate will reduce material’s flow resistance. Combined with thermal processing map, we can found high temperature and low strain rate can improve this material’s hot forming properties. We got the optimal scope of hot working process parameters: deformation temperature of 790~850 ℃, strain rate of 0.01~0.56s-1. Finite element simulation results show that, extrusion nozzle position will happen stress, strain, temperature, strain rate and flow speed’s rising. Improving the deformation temperature, extrusion ratio and hot extrusion rate will raise the temperature of blank, and increasing the hot extrusion rate is the most effective method among them. So in the actual hot extrusion, we can change the hot extrusion rate to control the actual hot extrusion temperature and improve material’s performance. We choose the optimized hot extrusion process parameters are: hot extrusion temperature of 810-830 ℃, hot extrusion rate of 16 mm/s, extrusion ratio21:1. The actual hot extrusion results indicate, when the deformation of the material, ZnSnO3 happened decomposition. It decomposed into Zn2SnO4 and SnO2. In the same time, copper matrix oxided and produced Cu2+1O phase. Zr segregated and oxidized to ZrO2 phase. So, we can change the hot extrusion temperature, hot extrusion rate and extrusion ratio to influence the properties of this material, these methods mainly through changing the size of dynamic recrystallization and the second phase dispersed degree to influence material’s properties. Finally, we comprehensive analyzed the results of finite element simulation,hot working map, and the actual hot extrusion process parameters’ influence on the microstructure and mechanical properties. We got the resulting hot extrusion process parameters are: deformation temperature of 810 ~ 830℃, extrusion ratio of 21:1, extrusion rate 16 mm/s.