陕京输气管道弯管力学性能

Mechanical Properties of the Bend for Shannxi--Beijing Gas Transmission Pipeline

具有90年代国际先进水平的陕京输气管道工程,由于国内弯管标准对力学性能等没有要求或要求不明确,国外弯管标准不完全适用,因此参照国外普遍采用的先进标准及国内外制造弯管的经验,制定了该工程的弯管技术条件、力学性能等指标,这些指标均达到美国弯管标准。对实际制造的弯管检测数据表明,弯管力学性能等指标达到了技术条件的要求,与原材料钢管相比,σ_s、σ_b均降低,σ_s降幅更大,故屈强比降低,延伸率提高,表明弯管在热弯后塑性提高。对制定我国油气输送管道用弯管技术标准提出了建议。

DN650 bend,with the curvature radius of 5D and five times of the outer diameter,were fabricated by using X60 and the hot-bending with medium frequency induction heating. Because there was no clear requirements to the mechanical properties of bends in domestic standards, and foreign standards were not completely appropriated to the pipeline,so,the technical specification and indexes of mechanical properties for large bends were worked out based on some international standards or codes. Some specified indexes, such as σs≥415 MPa,σb≥51 MPa,yield strength ratio≤0.88,elongation to API-5L,crystal-size to 9 or more without heating treatment,conformed to MSS SP75-1993. The measuring results showed that the mechanical properties for fabricated bends completely conformed to the technical specification. Comparing with the raw material of steel pipe,the bends had lower σb and much lower σs. Therefore,the yield strength ratio reduced,but the elongation (%) increased,which showed that the plasticity of bends increased while bending. Some suggestions on working out the technical standards of bend in gas transmission pipeline were set forth.