组织及残余应力对新能源汽车铜杆扭转性能的影响

Effect of Microstructure and Residual Stress on Torsional Properties of Copper Rods for New Energy Vehicles

采用上引铸造法、连铸连轧法(SCR)、上引连铸+连续挤压法制备了三种Ф8.0mm新能源汽车用铜杆,并对其显微组织、拉伸性能与扭转性能进行了研究。以上三种工艺制备的铜杆平均晶粒尺寸分别为198.1μm、11.3μm、13.4μm,抗拉强度分别为182.3 MPa、236.8 MPa、259.5 MPa,伸长率分别为41.5%、37.3%、41.1%。扭转实验结果表明,正转25转后,上引连铸+连续挤压法制备的铜杆具有最高的反转次数,达到了70.5转;SCR铜杆为30.1转;上引连铸最低,为22.9转。粗大的柱状晶+等轴晶是导致上引连铸铜杆扭转性能较差的主要原因。相比于连续挤压制备的铜杆,SCR杆尽管具有相当的抗拉强度和更好的伸长率,但是由于其沿轴向分布着更不均匀的残余应力,使其在扭转过程中更易受到损伤。

Three types of oxygen-free copper rods were prepared by upward continuous casting,SCR continuous casting and conform continuous extrusion,respectively.The microstructure,tensile properties and torsional properties of the oxygen free copper rods were studied.The results of torsion test show that after 25 turns around its own axis in one direction,the copper rod prepared by conform continuous extrusion has the highest number of turns in the opposite direction among all samples,up to 70.5 turns.Coarse columnar crystal+equiaxed crystal is the main reason for the poor torsional performance of upward continuous casting copper rod.Compared with the copper rod prepared by continuous extrusion,although SCR rod has considerable tensile strength and better elongation performance,it is more vulnerable to damage in the process of torsion because of its more uneven residual stress along the radial direction.