基于多次热循环的高级别管线钢焊接粗晶区的组织演变规律及增韧机理

For the safety of oil and gas transmission pipelines, it is very important to ensure high toughness and prevent embrittlement in the welding seam and heat affected zone (HAZ) of high grade pipeline steel after heating and cooling quickly at high temperature. This project is intended to use X80 and X90 high grade pipeline steel as the research objects. The fine and miniature pipeline steel samples were prepared carefully, and lots of real welding process parameters from engineering practice were collected. Then, a kind of high temperature phase transformation instrument (DIL805A/D, TA-Instruments, USA) with high precision was adopted to carry out the welding thermal simulation experiments for pipeline steel samples after multiple thermal cycles. By optical microstructure analysis technology (OM) , electron microscopy analysis technology (SEM and TEM), micro-hardness testing, instrumented impact testing and fracture toughness testing, we finally got the laws of evolution of microstructure in coarse grain HAZ (CGHAZ) of high grade pipeline steel after multiple thermal cycles, and obtained continuous cooling transformation diagram of simulated welding heat affected zone (i.e., SHCCT curves) with high accuracy and more abundant information. Also, we built a quantitative relationship between welding microstructure and toughness of coarse grain heat-affected zone, and then revealed the toughening mechanism of CGHAZ. Our research will provide some good scientific guidance and references for the optimization and further application of X80 pipeline steel welding process, and also for the research and development of X90, X100 and X120 higher level pipeline steel in oil and gas transmission pipelines.

如何保证高级别管线钢在高温快速加热和冷却后焊缝和热影响区（HAZ）的高韧性，防止脆化是保证油气输送管线安全的关键因素之一。本项目以X80、X90高级别管线钢作为研究对象，加工制备出精细微缩管线钢试样，采用高精度高温相变仪（DIL805A/D），采集四川油建公司工程现场焊接工艺参数作为依据，通过焊接热模拟技术、光学显微分析技术、电子显微分析技术（SEM、TEM）以及显微硬度测试、示波冲击试验、断裂韧度试验等研究方法与实验手段，获得多次焊接热循环作用后的管线钢焊接粗晶区显微组织演变的相关规律，测定更精确和信息更丰富的模拟焊接热影响区连续冷却转变图（SHCCT曲线），建立焊接粗晶区显微组织与韧性之间的定量相关性，并揭示基于M-A组元控制的焊接HAZ粗晶区的增韧机理。项目研究可为X80管线钢的焊接工艺优化与进一步推广应用，以及X90、X100和X120等更高级别管线钢的研制提供科学指导与参考依据。

如何保证高级别管线钢在高温快速加热和冷却后焊缝和热影响区（HAZ）的高韧性，防止脆化是保证油气输送管线安全的关键因素之一。本项目以X80、X90、X100等高级别管线钢作为研究对象，加工制备了精细微缩管线钢试样，采集四川石油天然气建设工程有限责任公司工程现场焊接工艺参数作为基本依据，采用高精度高温相变仪（DIL805A/D）实施了高级别管线钢焊接热模拟技术，随后采用光学显微分析技术、电子显微分析技术（SEM、TEM）以及显微硬度测试、示波冲击试验、断裂韧度试验等研究方法与实验手段，获得多次焊接热循环作用后的管线钢焊接粗晶区显微组织演变的相关规律，测定了X80、X90、X100更精确和信息更丰富的模拟焊接热影响区连续冷却转变图（SHCCT曲线），建立了焊接粗晶区显微组织与韧性之间的定量相关性，同时揭示了基于M-A组元控制的焊接HAZ粗晶区的增韧机理。项目研究结果可为X80、X90、X100等管线钢的焊接工艺优化与进一步推广应用，以及X120甚至更高级别管线钢的研制提供科学指导与参考依据。