矩形管成品拉拔的芯头工作带设计与变形平滑化

Design in the mandrel land and smoothing the deformation of rectangular tube drawing

分析矩形管带芯头拉拔工艺实质和变形平滑化机理,提出'以小变形量控制矩形截面管坯均匀的从模具工作带挤压出来'的拉拔平滑化方法。建立了带芯头拉拔工艺简化的三维运动模型及弹塑性有限元模拟模型,采集矩形长边中点、短边中点、圆角中点三个研究的关键点,分析获得直线型与带台阶型两种方案关键点的等效塑性应变和接触应力变化规律。在表面质量最难以保证的长边中点,带台阶方案的等效塑性应变较直线型芯头提高45.5%,其接触应力由0提高到13MPa。采用带台阶型的芯头工作带拉拔,获得'一拉二压'的应力状态,以少量挤压变形调控壁厚偏差、提高矩形管材内外表面质量。

With-mandrel drawing process and the mechanisms of smoothing deformation have been analyzed. A method of smoothing deformation is brought forward that rectangular tube should be extruded uniformity out of die land with little amount of deformation. The dynamics model simplified and FE model of with-mandrel drawing process are established based on FEM software,then simulations are performed. Three points including the center of long side,the center of short side,and the center of corner are positioned for further analysis. As for linear-type and step-type mandrel lands,the effective plastic strain and contact stress of three key points are evaluated. As for the plastic strain at the center of long side,a most difficult place to ensure surface quality,step-type mandrel land can improve 45.5%. As for the contact stress,step-type mandrel land can increase to 13MPa from 0. Drawing with step-type mandrel land achieves the stress status tensile stress in one orientation and compressive stress in other two orientations,which purposes of little amount of deformation to correct thickness tolerance and improve inner and outer surface quality of rectangular tube.