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采用Gleeble-3800热模拟机研究了多相抗变形x100高Nb含量管线钢的焊接性能,利用金相显微技术(OM)、扫描电镜(SEM)、电子背散射衍射(EBSD)对模拟焊接热影响区的组织进行了表征,结合示波冲击及微观硬度实验结果分析了影响模拟焊接热影响粗晶区(CGHAZ)的低温韧性及热影响区硬度与组织之间的关系.研究表明,高Nb抗变形X100管线钢单道次焊接热输入小于20 kJ/cm时的CGHAZ具有较高韧性,形成大角晶界密度较高的板条贝氏体或针状铁素体;焊接热输入大于等于25 kJ/cm会导致CGHAZ晶粒均匀性的恶化,使M/A组元粗化,并形成取向单一的粗大粒状贝氏体;示波冲击实验及SEM断口分析显示,粗大的M/A组元处极容易启裂,高的大角晶界密度可显著提高裂纹扩展功,使材料韧化.同时,为保证焊接热影响区不过度软化,以及高硬度产生抗氢致延迟破坏,单道次的焊接热输入以15—20 kJ/cm为宜.
The welding performance of multi-phase anti-deformation x100 high Nb content pipeline steel was studied by using Gleeble-3800 thermal simulator. The effects of welding heat-affected zone The relationship between the low temperature toughness and the hardness of the heat-affected zone (CGHAZ) and the microstructure was analyzed based on the experimental results of the oscillometric impact and microscopic hardness.The results show that high Nb anti-deformation X100 pipeline steel single pass welding heat input of less than 20 kJ / cm when the CGHAZ high toughness, the formation of high-angle grain boundary lath bainite or acicular ferrite; welding heat input greater than or equal to 25 kJ / cm will lead to the deterioration of the grain homogeneity of CGHAZ, roughen the M / A component and form a coarse granular bainite with a single orientation. Oscillographic impact test and SEM fracture analysis show that the coarse M / A component pole Easy to crack, the high density of large-angle grain boundaries can significantly improve the crack extension work, make the material toughening.At the same time, in order to ensure that the HAZ soft zone does not over-soften, and the high hardness produces hydrogen-induced delayed damage, single pass welding heat Enter 15-20 kJ / cm is appropriate.