中文摘要：

扩径矫圆工艺是大型直缝焊管生产过程中的重要工序之一,研究管件扩径矫圆弹复规律是合理确定扩径矫圆工艺参数的理论基础。将扩径矫圆过程按时序分为整圆、扩径、弹复三个阶段,根据其工艺特点认为整圆阶段为弹性纯弯曲过程,扩径阶段根据管壁所处的弹塑性应变状态又分为完全弹性变形、部分塑性变形和完全塑性变形三种情况,其分界点为弹性临界扩径率λ1和塑性临界扩径率λ2,借助扩径矫圆几何约束方程和弹复方程给出了不同扩径情况下弹复后管坯壁厚中心线任意一点曲率半径的表达式。通过扩径矫圆的物理模拟试验和大型直缝焊管的扩径矫圆试验,验证了理论解析结果的正确性,并从理论上揭示扩径矫圆的工艺原理和主要影响因素对弹复后形状参数的影响规律,具有重要的实际应用价值。

英文摘要：

Expanding and setting round is one of the most important processes for large diameter longitudinal submerged arc welded（LSAW） pipes production.The research of springback rules for pipe＇s expanding and setting round is the theoretical foundation for reasonably determining the process parameters.Expanding and setting round process is divided into three steps,namely,setting round,expanding and unloading in sequence.Based on the process characteristics,the step of setting round is considered as elastic pure bending.The step of expanding is divided into three conditions due to the strain of pipe by elastic critical expanding rate and plastic critical expanding rate,which are pure elastic deformation,partial plastic deformation and pure plastic deformation.The curvature radius of any point on cross-section＇s center line is given by geometric constraint equations and springback equation.Excellent agreement is found between theoretical and experimental results,which are obtained by physical simulation experiments and large diameter LSAW pipes.The results indicate the process principles of pipe＇s expanding and setting round,as well as the effect law of main influencing factors on the roundness after springback,and which has important practical application value.