成形内应力对油气管屈服强度的影响

根据美国石油学会API标准规定,采用管体取样压平试样的屈服强度表征输油管体屈服强度.通过对UOE管与外控成形螺旋焊管弹复应力进行测试表明,由于UOE管弹复应力低,包申格效应使压平试样的屈服强度低于经强力扩径强化的管体屈服强度,因此这种表征是偏于安全的;而对于螺旋焊管(外控成形)管体内有较高的弹复应力存在,管体取样,弹复应力释放,虽然压平的包申格效应使试样屈服强度降低,但弹复应力使管体屈服强度降低更严重,因此这种表征是偏于不安全的.

The Influence of Forming Internal Stress on Yield Strength of Oil and Gas Pipeline

API regulates that the yield strength of flatten specimen from pipe body is used to characterized the yield strength of oil pipeline body. A test on the elasticity restoring stress of UOE pipe and spiral weld pipe is made and the influence of forming internal stress of oil and gas pipeline on yield strength of specimen from pipe body and the yield strength of pipe body is analyzed. The test results show that for the UOE pipe,Bauschinger Effect makes the yield strength of flatten specimen lower than that of the yield strength of pipe body duo to the low elasticity restoring stress of UOE pipe,therefore,this characterization is safer. As to the spiral weld pipe,there is a high elasticity restoring stress in the pipe body. When the body specimen is taken, the elasticity restoring stress is reliving. Although Bauschinger Effect of flatten specimen lowers the yield strength of specimen, the elasticity restoring stress lowers greatly the yield strength of pipe body,so,this characterization trends towards unsafe.