【作者】 王跟浩；

【导师】 运新兵；

【作者基本信息】 大连交通大学 ， 材料科学与工程， 2018， 硕士

【摘要】 用来加工高压、超高压真空开关内的动、静导杆,高压、超高压电器控制器的接触器以及大流量导体器件的铜棒材尤其是高精度铜棒材的需求日益旺盛。铜棒材的传统加工工艺有9～12道工序,生产周期长、能耗高、污染环境以及不连续生产效率低。而连续挤压技术可实现坯料到产品的一次成形和连续生产,因此开展铜棒材连续挤压成形规律研究,有助于解决铜棒在实际生产中成形、成性问题,为生产出组织致密,性能良好的铜棒产品提供指导依据。本文以纯铜为研究对象,基于TLJ250连续挤压机通过Deform-3D软件对铜棒材连续挤压过程进行模拟分析,分析不同工艺参数对铜棒连续挤压成形的影响,并通过连续挤压工艺实验,研究夹杂分层缺陷分布规律以及工艺参数对铜棒产品组织的影响。铜棒材连续挤压成形数值模拟及实验结果表明:在铜棒的连续挤压全过程中,坯料的等效应力峰值有2处,一处在初始压入阶段等效应力值达到175MPa,另一处在镦粗变形阶段等效应力值达到200MPa。坯料温度从轮槽变形区到直角弯曲区逐渐升高,在直角弯曲区最高温度达到418℃,进入扩展挤压区,坯料温度增至550℃。面积扩展比(ζ=2.25、4、6.25):扩展区的金属在对称面上的纵向流动呈现上下对称层流分布状态;当面积扩展比是ζ=4时,金属纵向流动速度曲线最平稳,模具出口速度最均匀、组织致密,圆周近表层只存在少量夹杂分层,夹杂分层主要集中在产品横截面底侧附近,沿着铜棒长度方向连续分布。挤压轮转速(n=10rpm、7rpm、4rpm):金属的流动速度、变形速率、变形温度随着挤压轮转速的降低而降低;当挤压轮转速n=4rpm时,其纵向流动速度曲线最平稳,模具出口速度最均匀,模具出口温度分布最均匀,铜棒产品组织致密性较好、夹杂分层缺陷较少;随着挤压轮转速的减小,产品的晶粒尺寸减小、夹杂分层缺陷减少。模腔结构:增加扩展通道长度、减小模具收缩角度可提高产品出口速度均匀性;在面积扩展比ζ=4、挤压轮转速n=4rpm优化工艺条件下,模腔结构的变化对改善铜棒夹杂分层缺陷影响不明显。研究结果表明,采用挤压轮转速n=4rpm、扩展通道长度L=10mm、面积扩展比ζ=4的工艺条件连续挤压挤压出来的铜棒产品的夹杂分层缺陷最少,分层厚度仅为0.2mm、长度为3mm。更多还原

【Abstract】 The market demand of copper bar especially high precision copper bar,which is used for processing dynamic or static guide rod in high or ultra-high pressure vacuum switch,contactors for high voltage or ultra high voltage appliance controllers and heavy traffic conductor devices,is becoming more and more vigorous.The traditional processing technology of copper bar has 9～12 processes,longer production cycle,higher energy consumption,lower discontinuous production efficiency and pollutes environment.While the continuous extrusion technology can realize the forming and continuous production from billets to products through only one process,so studying the forming law of copper bar by continuous extrusion technology is helpful to solve the problem of forming copper bar in actual production,and provides guidance for producing compact and well-behaved copper bars.In this paper,pure copper is used as the studying object,the continuous extrusion process of copper bar is simulated and analyzed by Deform-3D software based on TLJ250 continuous extrusion machine,and analyzes the effect of different process parameters on the forming of copper bar by continuous extrusion technology.And also studies the law of delamination defect distribution and the effect of process parameters on the copper bar products through the continuous extrusion process experiment.The numerical simulation results and experimental results show that:During the whole continuous extrusion forming of copper bar,there are 2 effective-stress peaks of billets,one is appear in clamping zone which reaches 175MPa,the other is appear in upsetting deformation zone which reaches 200MPa.The temperature of billets is becoming higher from groove deformation zone to right-angle bending zone,the maximum temperature reaches 418℃ in right-angle bending zone and reaches 550℃ in extending extrusion zone.Area expansion ratio(ζ=2.25、4、6.25):In extending extrusion zone,stratified flow with symmetry axis in longitudinal symmetry.When the area expansion ratio is 4,the longitudinal velocity curve is the smoothest and the velocity at calibrating strap is the most uniform,the compactness of copper products is better,there are only a few delamination defect in the near surface of copper bar.delamination defect mainly appear near the bottom side of the product’s cross-section and distribute continuously along the length of the copper bar.Extrusion wheel angular velocity(n=10rpm、7rpm、4rpm):The flow velocity,deformation rate and deformation temperature of the metal decrease with the decrease of extrusion wheel angular velocity.When the wheel angular velocity is 4rpm,the longitudinal velocity curve is the smoothest,both the velocity and temperature at calibrating strap is the most uniform,the compactness of copper products is better and the delamination defect appearing near the bottom side of product’s cross-section is less.Average grain size and stratified defect quantity decrease with the decrease of extrusion wheel angular velocity.Structures of tooling mould:Increasing the extended channel length or decreasing the die angle can improve the uniformity of flow velocity at calibrating strap.The change of tooling mould structure has no obvious effect on improving the stratified defect in optimized process conditions(when the area expansion ratio is 4,the wheel angular velocity is 4rpm).The results of research show that:The copper bar product,which is extruded under this process condition the wheel angular velocity is 4rpm,the extended channel length is 10mm,the area expansion ratio is 4(n=4rpm,L=10mm,ζ=4),has the least delamination defect.The thickness of the least delamination defect is only 0.2mm,the length of the least delamination defect is 3mm.更多还原