X80管线钢焊接接头的微观组织及耐蚀性研究

发布时间：2017-12-31 13:16

  本文关键词：X80管线钢焊接接头的微观组织及耐蚀性研究　出处：《长安大学》2016年硕士论文　论文类型：学位论文

  更多相关文章： X80管线钢 焊接热输入 峰值温度 显微组织 耐蚀性

【摘要】：长距离管道运输过程中需经过各种各样的地质环境,运输管线钢面临着腐蚀造成的一系列安全问题。在实际服役过程中,管线钢的焊接接头由于组织差异以及杂质等因素的影响,最容易腐蚀而产生裂纹,而焊接应力诱发裂纹扩展容易造成腐蚀断裂,从而导致严重后果。因此,本研究针对目前我国管道运输采用的X80管线钢,对其焊接接头的微观组织、力学性能和腐蚀性能等进行系统研究,从而为X80管线钢焊接管线大规模长期应用提供依据。本研究采用金相显微镜和扫描电镜观察焊缝、热影响区和母材的微观组织,分析焊接热循环参数对热影响区组织的影响。结果表明,峰值温度为1350℃时,随着热输入的增大,贝氏体、铁素体逐渐减少,粒状贝氏体增多;随着峰值温度降低,组织逐渐由贝氏体、铁素体及粒状贝氏体转变为块状铁素体。采用Gleeble-3500型热模拟试验机研究了在不同焊接热输循环条件下X80管线钢及其焊接热影响区的硬度特征。研究结果表明,X80管线钢的热影响区粗晶区(CGHAZ)显微硬度随焊接热输入增大呈下降趋势;热影响区显微硬度随峰值温度增大呈升高趋势。采用了Autolab电化学工作站分别研究了在0.5 mol/L Na2CO3+1 mol/L NaHCO3腐蚀溶液中和5%NaCl+0.5%醋酸溶液中X80管线钢母材、焊缝和热影响区的耐蚀性。结果表明,热输入对CGHAZ的耐蚀性影响比较明显,随着热输入增加腐蚀速率减小,CGHAZ的耐腐蚀性能变好;在峰值温度为较高的1350℃或者是较低的800℃时,对应的腐蚀速率较高;焊缝和热影响区的腐蚀倾向远大于母材,耐蚀性均较差;X80管线钢焊接接头在酸性腐蚀液中的耐蚀性比在碱腐蚀液中差,但都会产生钝化膜,在酸性腐蚀液中钝化膜不稳定。
[Abstract]:During the long distance pipeline transportation, the transportation pipeline steel is faced with a series of safety problems caused by corrosion. In the actual service process, the transportation pipeline steel faces a series of safety problems. The welded joints of pipeline steel are most likely to corrode due to the influence of different structure and impurity, while the welding stress induced crack propagation is easy to cause corrosion and fracture, which leads to serious consequences. In this study, the microstructure, mechanical properties and corrosion properties of welded joints of X80 pipeline steel used in pipeline transportation in China were studied systematically. In this study, the microstructure of weld, heat-affected zone and base metal was observed by metallographic microscope and scanning electron microscope. The effect of welding thermal cycle parameters on the microstructure of HAZ is analyzed. The results show that the bainite, ferrite and granular bainite decrease with the increase of heat input at the peak temperature of 1350 鈩，

本文编号：1359931