Effects Of Process Conditions On The Microstructure And Mechanical Properties Of Product During Continuous Extrusion Of Copper Strip

Copper strip is mainly used in transformers, motors, generators and windings of electrical equipment. Compared with the traditional process, the use of advanced continuous extrusion could produce quality copper strip. Continuous extrusion process can realize the continuous production, reducing energy consumption, improving material utilization ratio and labor productivity. This process has achieved obvious economic benefit.With the development of electric manufacturing, the comprehensive performance of copper strip has been put forward higher requirements. It was found that copper strip has high hardness in actual production and is easy to appear rebound during the winding process, resulting in labor-intensive and low-quality windings. Therefore it is significant that the effects of process conditions on microstructure and mechanical properties of copper strip during the continuous extrusion were researched.This paper makes continuous extrusion forming technology used in the production of TLJ250and TLJ300produced by Dalian Jiaotong University. Through the engineering test and numerical simulation, the effects of extrusion wheel rotation speed, die-chamber channel length, extrusion ratio, heat treatment process and billet preheating temperature on microstructure and mechanical properties of copper strip during the continuous extrusion were studied, which provides the basis for making continuous extrusion process parameters of copper strip and better guide the practical production.The temperature of the die opening and the microstructure and mechanical properties of product at different process parameters are investigated by analysis of the engineering test samples. The results show that effection of extrusion ratio on the temperature of the die opening had the greatest influence, especially between1and2. When the extrusion ratio is3, grain becomes coarse. So the amount of the extrusion ratio is crucial for the actual production process. Along with the extrusion wheel rotation speed increased from4rpm to lOrpm, the percentage of crystal recrystallization tends to increase and microstructure tends to be uniform. Compared with the method of water cooled, the tensile strength of the product is reduced by27.4%, the yield strength is reduced by46.1%and the hardness is decreased by12.0%using the method of air cooled. But the change of billet preheating temperature has no effect.Application DEFORM software with copper strip continuous extrusion process, the temperature, equivalent stress and so on were studied by numerical simulation. The results showed that the highest temperature appeared in the right bending deformation and the maximum equivalent stress is in the die opening and above abutment during continuous extrusion. With the die-chamber channel length, extrusion wheel rotation speed and extrusion ratio increases, the temperature in the chamber tend to increase. But billet preheating temperature has no effect.