大坡度山区管道焊接接头应力数值模拟研究

Numerical Simulation of Stress of Pipeline in Mountain Areas with Large Slopes

长输管道经过的地势多山区丘陵,管道敷设及焊接过程有时需在5°~45°坡度情况下进行。大坡度山区管道常出现因过大的拉应力导致失效的现象,因此其应力分布成为必要的研究课题。文中就坡度为25°的X70钢全自动焊外根焊工艺下山区管道焊接接头应力分布规律进行研究。基于TMM理论,根据实际焊接接头建立大坡度山区管道焊接接头有限元模型,将实际热源模型及施工环境作为边界条件,独特将焊接接头分为上下坡口,最终得到其应力分布规律,填补了大坡度山区管道焊接接头应力分布研究的空白。通过盲孔法及矫顽力法对管道内外表面应力水平进行测量,验证应力模拟结果准确性。通过模拟与实际测量得到结论,由于重力及支持力的作用,焊接接头受到沿管道轴向的应力,导致大坡度山区管道焊接接头应力分布与无坡度管道不同。其根焊层上坡口粗晶区平均宽度较下坡口宽27μm,热焊层上坡口粗晶区平均宽度较下坡口宽21μm。根焊层上坡口拉应力较下坡口高135 MPa,高拉应力区较下坡口宽1.6 mm。

The long-distance pipeline passes through mountains and hills,and the laying and welding process sometimes needs to be carried out at a 5°~45°slope.The pipeline in mountain areas with large slopes often fails due to excessive tensile stress,so its stress distribution becomes a necessary research topic.In this paper,the stress distribution of welded joints of X70 steel with a slope of 25°using automatic welding is studied.Based on the Thermal-Metallurgic-Mechanical theory,the finite element model of the welded joints of pipelines in mountainous areas with high slopes is established,and the actual heat source model and construction environment are taken as the boundary conditions.The welded joints are uniquely di-vided into higher and lower sides,and finally,the stress distribution is obtained,which fills the gap in the study of the stress distribution of welded joints in mountainous areas with large slopes.The hole-drilling method and the coercive method are used to measure the stress level of the inner and outer surfaces of the pipeline to verify the accuracy of the stress simulation.The welded joints are subjected to axial stress along the pipe due to gravity and supporting force.So the stress distribution of welded joints of pipelines in mountain areas with large slopes is different from that of pipelines without slope.The average width of the coarse-grained zone of the root welding layer of the higher side is 27μm wider than that of the lower side.The average width of the coarse-grained zone of the hot welding layer of the higher side is 21μm wider than that of the lower side.The tensile stress of the root welding layer of the higher side is 135 MPa higher than that of the lower side,and the high tensile stress zone of the root welding layer of the higher side is 1.6 mm wider than that of the lower side.