【作者】 隋永莉；

【导师】 杜则裕；

【作者基本信息】 天津大学 ， 材料加工工程， 2008， 博士

【摘要】 国内外输气管线的发展都趋向于高强度钢级、大口径管道的方向。已经开工建设的西气东输二线工程、以及筹建的中缅、中俄输气管线等都将采用X80管线钢管。而现场焊接是管道施工的关键环节之一。本课题是以X80级钢管为研究对象,进行了X80管线钢抗裂性研究,以及X80管线钢管自保护药芯焊丝半自动焊焊接接头的性能试验及分析。该项研究成果提出了系统的、全面的X80管线钢管自保护药芯焊丝半自动焊技术的焊接工艺方案。考虑到焊接材料含氢量、预热温度和焊接工艺方法等诸因素对管道环焊缝根部焊接质量的影响,采用斜Y型坡口焊接裂纹试验及插销冷裂纹试验的方法,针对长输管道根焊施工的具体情况进行X80管线钢的抗裂性研究。研究结果表明,扩散氢含量较高的纤维素型焊条的抗裂性较差,在预热温度不足的情况下会产生焊接冷裂纹。因此,本研究首次提出了在X80长输管线的环焊接头根部焊接施工中,不准使用纤维素型焊条电弧焊工艺。扩散氢含量较低的低氢型焊条和实心焊丝具有良好的抗裂性。由于STT焊接方法的热输入量较小,应当采用设计合理的坡口钝边尺寸来避免根部焊接时的焊趾未熔合。环焊缝焊接接头的性能试验、研究及分析结果表明:焊缝金属和HAZ的组织为先共析铁素体、针状铁素体和粒状贝氏体,其焊缝金属中可以清晰地观察到柱状晶和晶内交错分布的针状铁素体;由于焊接过程为多层多道焊,根焊层的组织细小,盖面层组织粗大,填充层为粗大的晶粒与细小的晶粒层叠交替的组织;环焊接头实现了与母材的等强匹配,焊接接头的硬度、韧性、CTOD和抗HIC等性能均满足X80管线的安全要求。根据X80管线的技术要求和焊接接头的CTOD值还对可接受的最大平面型缺欠尺寸提出了相应的焊接施工与验收的技术规定。该项研究成果已被编入到西气东输二线工程的相关企业标准中。研究结果表明,采用本文提出的“低氢型焊条根焊与自保护药芯焊丝填充盖面”的组合焊接工艺方案所完成的X80管线钢管对接环焊接头,其各项性能指标均满足工程相关技术标准及设计文件的要求和规定,焊接施工质量优良。该项成果正在举世瞩目的国家重点工程“西气东输二线”管道工程的焊接施工中应用。更多还原

【Abstract】 The development of domestic and foreign gas pipeline tend to pipe with high-strength grade and large diameter. Many projects will use line pipe steel of X80 grade, for example Second West-East Gas Pipeline being build, China-Burma Pipeline being planed and China-Russian Gas Pipeline. The field welding is a key factor in pipeline construction. Taking X80 grade pipe as the object of study, this dissertation researches the crack-resistance of X80 grade line pipe steel, executes the performance test and analysis of semi-automatic weld joint of X80 line pipe welded with self-shield flux cored wire. The research result provides comprehensive and systematic welding procedure schedule of semi-automatic welding technique using self-shield flux cored wire on X80 line pipe.Take in consideration that the influence of hydrogen content of filling material, pre-heating temperature, welding process and other various factors on root bead quality of girth seam of pipeline, this dissertation analyzes the crack-resistance of X80 line pipe according to actual construction condition of root weld in long-distance transportation pipeline by the slit type cracking test and implant cold crack test. The research result indicates the higher hydrogen content in cellulose electrode will gain lower crack-resistance, in case of insufficiency pre-heating temperature, the cold crack will occur. Therefore, this dissertation think for the first time that the cellulose electrode can not be permitted for welding root bead in welding construction of long-distance transportation pipeline with X80 grade line pipe. The low-hydrogen electrode and solid cored wire of low hydrogen content are of good crack-resistance. Due to the heat input of STT welding is low, the root face should be designed properly to avoid incomplete fusion on root toe.The performance test, research and analysis result of weld joint indicate, the structure of weld metal and HAZ is PF pro-eutectoid ferrite, acicular ferrite, granular bainite. The acicular ferrite interlaced in columnar zone and lattice will be found clearly in weld metal. Due to multi-pass and multi layer technique during welding, the structure on root bead is tiny, structure on cap bead is gross, and on filling bead, the tiny and gross grain will be interlaced. The strength of weld joint is matched to its of base metal. The hardness, toughness, CTOD and HIC resistance etc. can meet the safety requirement of X80 grade pipeline. Meanwhile, according to the technique requirement of X80 grade pipeline and the CTOD of weld joint, the acceptable maximum imperfect size of plane type is specified for corresponding welding construction and acceptance technical specification. This research result has been incorporated to relevant enterprise standard of Second West-East Gas Project.The research result indicates regarding this weld joint of X80 pipe, which uses welding process of low-hydrogen electrode for root bead and self-shield flux cored wire for filling & cap bead mentioned in this dissertation, each performance index can satisfy all requirements specified in relevant technical standard and design document. This welding procedure also can make sure well welding construction quality. This research achievement is being applied to the national key project“Second West-East Gas Pipeline”which is focused in the world.更多还原