制管工艺及应变时效对X70抗大变形钢管性能的影响

结合中缅天然气管线工程用X70级准1016mm×17.5mm抗大变形直缝埋弧焊管的试制,研究了直缝埋弧焊管制管前后、应变时效前后力学性能变化的一般规律。成型、扩径工艺导致母材发生加工硬化,产生较强的形变强化,使其屈服强度、抗拉强度、屈强比同时增大,使均匀延伸率、应力比降低,且屈服强度、屈强比的增加幅度要大于抗拉强度的增加幅度。应变时效使材料均匀延伸率进一步降低。但是制管和时效后钢管管体各项性能均在X70抗大变形钢管标准要求的范围内,管体纵向应力-应变曲线仍呈圆屋顶形,试制的X70抗大变形钢管具有优异的变形能力。

Effect of Pipe Manufacturing Process and Strain Aging on Properties of X70 Steel Pipe with High Deformation Resistance

Based on trial production of X70 Ф 1 016 mm×17.5 mm SAWL pipe for the Myanmar-China Gas Pipeline Project, the general changing rules of mechanical properties of SAWL pipe before and after pipe manufacturing, before and after the strain aging were studied. The pipe forming and expansion process not only cause work hardening of base metal and the greater deformation strengthening, but also increase the yield strength, the tensile strength and the yield ratio; decrease the uniform elongation rate（UEL） and the stress ratio, moreover, the increasing degree of yieht strength and yield ratio is higher than that of tensile strength. The strain aging reduces the UEL of the material further. However, various properties of pipe body after pipe manufacturing and ageing are all within the range required by the X70 steel pipe with high deformation resistance, and the longitudinal stress-strain curve of pipe body is still vaulting shape, thus the trial manufactured X70 pipe with high deformation resistance has excellent deformability.