大口径厚壁无缝钢管孔隙性缺陷的焊合问题

Research on the inner crack healing of large-sized seamless steel tube

大口径厚壁无缝钢管是关系我国能源安全的重要产品。在斜轧穿孔过程中,由于轧辊和顶头的挤压及摩擦作用,其金属内部的变形程度和速度都极为复杂。在复合变形的条件下,孔隙性缺陷的焊合极为困难。文章通过圆柱形试样压缩实验,深入研究金属材料的孔隙性缺陷在复杂应力应变情况下的变化与发展规律,确定了复杂应力应变条件下孔隙性缺陷的消除判据;通过理论分析和数值模拟,研究大口径厚壁无缝钢管斜轧穿孔过程中的变形机理,得到影响无缝钢管中孔隙性缺陷焊合的因素及规律;建立了以消除大口径厚壁无缝钢管的孔隙性缺陷为目标的斜轧穿孔参数的制定原则和方法。

The large-sized thick-walled tube is an important product which is related the energy security of our country . In the process of molten steel solidifying ,a lot of voids appear in the steel ingot . With the metal flow ,the voids become the crack defect in the tube .In the roll-piercing of the tube ,the metal is deformed under squeeze and friction effects by the rollers and plug .The deformation in the materiel is very complicated . In the complex deformation conditions ,the bonding of the inner crack defect becomes very difficult . This paper carried out the upsetting experiment of cylindrical specimen . It focuses on the development of metal porosity defect in complex stress and strain conditions . The bonding criterion of the crack defects in the complicated stress state has been gained . Via the theoretical analysis and the simulation ,the deformation mechanism in the tube roll-piercing process has been studied . This research finds the principle and the method to design the roll-piercing process parameters for eliminating the inner crack defects .