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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 square mesh method was used to measure the length of the mesh on the outer surface of the pipe before and after cold bending of X70 large deformation pipe. The relative plastic deformation of different regions of cold pipe was calculated by the change of edge length, and the plastic strain was taken as the cold bend. The characteristics and causes of strain distribution are analyzed, and the plastic formability of the steel pipe is discussed. The results show that the longitudinal strain of the cold pipe is in good agreement with the theoretical strain calculation. The strain increases with the increase of the forming angle per unit step length. The vertical strain changes the forming angle per unit step length more reasonable, while the lateral strain changes Which fluctuated mainly in the range of -0.9% -0.5%. The maximum compressive strain was -3.12% in the range of 120 ° -150 ° and 5-7 m in the horizontal direction, which was 1.23% higher than the theoretical strain of 1.89% In the cold bending process of 0.5 ° / 300 mm, the strain distribution is more uniform and the pipe exhibits good plastic forming properties. The analysis shows that forming angle in unit step is the main factor affecting the strain distribution. By designing a reasonable cold-bending process, the quality of cold-formed pipe can be ensured to meet the requirements of the standard specifications.