薄壁无缝钢管顶管过程拉凹缺陷研究

为了解决CPE顶管机组轧制薄壁无缝管实际生产中出现的管壁拉凹问题,基于某钢管公司?114 mm CPE顶管机组的装备和工艺条件,借助于有限元分析软件Simufact,对42CrMo4钢管典型规格?111 mm×4.35 mm顶管过程的辊模力、各机架轧件出口壁厚、应力应变及相对滑动速度进行了分析。结果表明,顶管过程中,减壁量较大的机架之间存在张力作用,机架减壁量越大,轧件在辊缝处壁厚减薄量越大;轧件在辊缝处所受到的轴向应力均为拉应力,在靠近轧件头部一段距离内轧件所受到的轴向拉应力较大,发生壁厚拉凹的倾向性增大。机架过大的减壁量和减壁率引起的轧件沿孔型宽度方向的严重不均匀变形、机架间大的张力及芯棒与轧件间过大的速度差引起的芯棒拽入力是顶管过程管壁拉凹缺陷产生的主要原因。

Study on defect of pulled concave in push bench process of thin walled seamless steel tubes

In order to solve tube wall pulled concave problem in the actual production of thin walled seamless steel tube rolled by CPE push bench mill, the push bench process of 42CrMo4 steel tubes with typical specification of 111mm×4,35mm was numerically simulated by using 3D finite element analysis software Simufact, based on the equipment and technological conditions of the 114mm CPE push bench mill of a steel tube company. The rolling force, the outlet wall thickness of rolled tube at each stand, stress/strain and relative sliding velocity between the inner surface of the workpiece and the mandrel in the push bench process were analyzed. The results show that there has a tension between stands with larger wall reduction, and the greater the wall reduction of the stand, the greater the reduction of the wall thickness of rolled tube at the roll gap. The axial stress of the rolled tube at the roll gap is tensile stress, and the axial tensile stress on the rolled tube is larger within a distance close to the head of the rolled piece; the tendency of wall thickness pulled concave increases. The main causes of the tube wall pulled concave are the serious inhomogeneous deformation of the workpiece along the width of the pass caused by the excessive wall reduction and the reduction rate, the larger tension between the stands and the mandrel pulling force produced by the excessive velocity difference between the mandrel and the workpiece.