高级别管线钢焊接显微组织、力学性能与CCT曲线研究

发布时间：2018-03-10 03:13

  本文选题：管线钢　切入点：焊接热循环　出处：《重庆科技学院》2017年硕士论文　论文类型：学位论文

【摘要】：石油与天然气是国民经济发展的主要能源和重要战略资源,采用管道输送石油与天然气目前是国内外首选的技术方案。无论在制管成型、管道现场铺设安装,还是在管道维修过程中,管道用管线钢均需依赖焊接来实现。然而,经历焊接这一快速的不均匀加热和冷却的复杂热循环过程后,往往会发生管线钢焊接接头尤其是焊接热影响区(HAZ)的性能与管材本身性能严重不匹配的现象,引发服役安全可靠性问题。因此,如何获得显微组织和力学性能优异的管线钢焊接接头,长期以来是油气输送中备受关注的热点与焦点问题。管线钢SHCCT曲线是一种把焊接工艺条件与焊接后获得的组织性能联系起来的关系图,能够有效指导管线钢焊接生产和施工。本论文以X80、X90和X100三种高级别管线钢为研究对象,加工制备出精细的实心和空心管线钢试样,采用高精度DIL805A/D淬火膨胀仪,采集四川石油天然气建设工程有限责任公司(简称四川油建公司)工程现场熔化极气体保护焊(GMAW)焊接工艺参数作为依据,制定三种不同焊接热循环工艺(热循环工艺一:以10℃/s加热至950℃,保温10min后以3~600s的不同t_(8/5)冷却到室温;热循环工艺二:以150℃/s和200℃/s加热至1100℃,保温10s后以100℃/s冷却到900℃保温1min,再以1.5~600s的不同t_(8/5)冷却到室温;热循环工艺三:以200℃/s加热至900℃(1100℃或1350℃)保温10s后以1.5~600s的不同t_(8/5)冷却到室温),通过光学显微分析技术、电子显微分析技术(SEM)以及显微硬度测试等研究方法与实验手段,获得不同焊接热循环下管线钢的焊接显微组织、力学性能和CCT曲线(SHCCT曲线),并进一步对三种管线钢进行了对比分析,得到的主要研究结论如下:(1)在热循环工艺一条件下,X80、X90、X100三种管线钢显微组织变化相似,均是多边形铁素体(PF)+珠光体(P)→多边形铁素体(PF)+准多边形铁素体(QF)→细小粒状贝氏体(GB)+贝氏体铁素体(BF),晶粒尺寸随t_(8/5)增大而变小,显微硬度随t_(8/5)减小而增大。(2)在热循环工艺二条件下,加热速度不同,三种管线钢出现贝氏体铁素体(BF)的t_(8/5)也不同,加热速度越大,X80管线钢出现贝氏体铁素体的t_(8/5)越大,X90与X100管线钢的t_(8/5)越小,且三者显微组织演变规律相似。(3)在热循环工艺三条件下,当t_(8/5)=300~600s时,X80、X90、X100三种管线钢模拟焊接临界晶区与细晶区的室温显微组织组成不同;当t_(8/5)=1.5~120s时,X80、X90、X100管线钢在模拟焊接临界晶区、细晶区和粗晶区时的显微组织演变规律相同,但显微组织大小和显微组织的临界t_(8/5)不同,三种管线钢的显微硬度在该三种热循环工艺中均随t_(8/5)的减小而增加。此外,本论文获得的三种热循环工艺条件下的X80、X90、X100三种管线钢的CCT曲线与SHCCT曲线,它们不仅为热处理工艺和焊接工艺的制定提供参考依据,同时也为X80、X90、X100管线钢的实际应用提供有效的实验数据。
[Abstract]:Oil and natural gas are the main energy and important strategic resources in the development of national economy. Pipeline transportation of oil and natural gas is currently the preferred technical scheme at home and abroad. Also in the process of pipeline maintenance, pipeline steel for pipeline depends on welding. However, after welding, which is a complicated thermal cycle of rapid uneven heating and cooling, The serious mismatch between the properties of welded joints of pipeline steel, especially the HAZ) and the properties of the pipe itself will often occur, which will lead to the problem of safety and reliability in service. How to obtain welded joints of pipeline steel with excellent microstructure and mechanical properties, The SHCCT curve of pipeline steel is a kind of relation diagram which relates welding process conditions with microstructure and properties obtained after welding. In this paper, three kinds of high grade pipeline steel X80, X90 and X100 are taken as the research object, the fine solid and hollow pipeline steel samples are prepared, and the high precision DIL805A/D quenching expander is used. The welding process parameters of GMAW in Sichuan Petroleum and Natural Gas Construction Engineering Co., Ltd (Sichuan Oil Construction Company) are collected as the basis. Develop three different welding thermal cycling processes (heat cycling process I: heating to 950 鈩，

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