冷却速度对X80管线钢焊接热影响区组织性能的影响
Effect of Cooling Rate on Microstructure and Properties of Welding Heat Affected Zone in X80 Pipeline
张 蕾1,2， 石 凯1， 胡美娟2， 李金凤2
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作者单位：（1.西安石油大学,陕西 西安 710065；2.中国石油集团石油管工程技术研究院,陕西 西安 710065）
中文关键字：冷却速度；组织性能；X80管线钢；热影响区；热模拟
英文关键字：cooling rate; microstructure and properties; X80 pipeline steel; heat affected zone; thermal simulation
中文摘要： 利用Gleeble 3500热模拟试验机,建立了X80管线钢焊接热影响区的连续冷却转变曲线(SH-CCT曲线),采用金相分析、显微硬度测试和夏比冲击试验,分析了X80管线钢焊接粗晶区在不同冷却速度下的组织转变和性能变化规律。结果表明：当冷却速度低于0.3℃/s时,粗晶区组织为多边形铁素体和少量珠光体或粒状贝氏体的混合物,具有较好的冲击性能,但硬度较低；当冷却速度为0.3～2℃/s时,粗晶区中的粒状贝氏体和MA岛状组织增多,且晶界模糊,其冲击性能较差；当冷却速度在2～30℃/s时,热影响区组织以粒状贝氏体为主,MA岛状组织的形状和分布均匀,具有优良的冲击性能；当冷却速度大于30℃/s时,随着冷却速度的增加,粒状贝氏体的含量逐渐减小,而贝氏体铁素体的含量逐渐增多,硬度升高,冲击性能下降。
英文摘要：The simulated heat-affected zone continuous cooling transformation curve (SH-CCT curve) of X80 pipeline weld heat affected zone was made by Gleeble 3500. By the metallographic analysis, microhardness measurement and charpy impact test, the rules of phase transformation and properties change of X80 pipeline weld coarse-grain region at different cooling rate were investigated. The results show that when cooling rate is lower than 0.3℃/s, the microstructure of coarse-grain region is the combination of coarse polygonal ferrite and a small amount of pearlite or granular bainite, and the impact toughness is good but the hardness is low. When cooling rate is between 0.3℃/s and 2℃/s, the granular bainite and MA island structure increase, the grain boundary is dim and the impact toughness is bad. When cooling rates is between 2℃/s and 30℃/s, the main microstructure of the X80 pipeline weld heat affected zone is granular bainite, the shape and distribution of MA island structure were uniform, and the impact toughness is excellent. When cooling rates is faster than 30℃/s, the content of the granular bainite decreases with the increase of cooling rate, while the content of bainite ferrite increases gradually, the hardness increases and the impact toughness decreases.