X70大变形钢冷弯管应变分布研究

Study on strain distribution of cold bending pipe for high deformability steel X70

采用方形网格法测量X70大变形管线钢管冷弯加工前后外表面网格边长,以边长变化值来计算冷弯管不同区域的相对塑性变形大小,并作为冷弯管的塑性应变。分析了应变分布特点及其原因,并讨论了钢管的塑性成形性能。结果表明：冷弯管纵向应变与理论计算应变结果较为一致,应变随着单位步长内成形角度的增大而增大,选用纵向应变设计单位步长内成形角度较为合理,而横向应变变化较小,主要在-0.9%0.5%范围内波动,仅在横向120°－150°、5－7 m的区域出现最大压应变-3.12%,高于理论应变（1.89%）约1.23%;在0.5°/300 mm的冷弯工艺下,应变分布较为均匀,管材表现出良好的塑性成形性能。分析认为单位步长内成形角度是影响应变分布的主要因素,通过设计合理的冷弯工艺,可保证冷弯管质量符合标准规范要求。

The grid side lengths of outer surface of high deformability line pipe X70 before and after cold bending processing were measured by the square grid method. The relative plastic deformation in different regions was calculated by length variations,and was regarded as the plastic strain of cold bending pipe. The strain distribution and its reasons were analyzed and the plastic deformation properties of pipe were discussed. The results indicate that the longitudinal strain of cold bending pipe is in agreement with theoretical calculation value,which increases with the increase of forming angle within unit step. It is more reasonable to design the forming angle within unit step by selecting the longitudinal strain. But the change of the transverse strain is smaller from-0. 9% to 0. 5%,and the maximum compressive strain-3. 12% only occurs in the transverse regions 120°-150°,5-7 m,which is 1. 23% higher than the theoretical calculation strain（ 1. 89%）. The pipe is of excellent plastic deformation property and uniform distribution of strain under the technology of 0. 5 ° /300 mm. The analysis shows that the forming angle within unit step is the main factor influencing the strain distribution. The quality of cold bending pipe can meet standard code and specification when cold bending process is designed reasonably.