API X70和X80管线钢管屈服强度的双循环模拟试验分析和估算

为了准确估算API X70和X80管线钢管的屈服强度,分别对API X70和X80管线钢板和钢管进行了制管和压平过程的双循环模拟试验,并将包申格应力参数和Swift方程相结合来估算钢管的屈服强度。试验和估算结果表明,包申格应力参数和Swift方程相结合的估算方法中已经包含了显微组织和制管过程的影响因子,因而能较为准确地估算钢管的屈服强度。因拉压强度差效应较小且和反向流动曲线可用一条曲线表示,因此利用展平钢板的拉伸/压缩性能可有效估算制管前后屈服强度的变化,该估算方法对控制显微组织和制造工艺参数进而控制管线钢板的屈服强度有着重要的作用。

Analysis and Estimation of the Yield Strength of API X70 and X80 Linepipe Steels by Double-cycle Simulation Tests

In order to accurately estimate the yield strengths of API X70 and X80 linepipe steel pipes,a double-cycle simulation test for the piping and flattening processes was respectively conducted to estimate the yield strength.The simulation test results indicated that the yield strengths of the outer or inner wall of the pipe could be estimated by combination of Swift's equation and the Bauschinger stress parameter,and that these estimated yield strengths were well matched within a small error range with the measured yield strengths.Thus,the variations in yield strength before and after the piping could be effectively estimated using the tension/compression properties of the leveled sheets because the strength differential effect was small and the reverse flow curves were expressed by a single curve.These findings suggested that the present estimation method played an important role in controlling microstructural and manufacturing process parameters to minimize the reduction in yield strength of the linepipe steel sheets.