摘要
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.
A single welding thermal-cycles with different heat inputs （8, 16, 20, 25, 30 and 50 kJ/cm） were simulated by Gleeble 3800 to study the correlation of toughness, hardness and microstructure in heat affect zone （HAZ） of the X100 pipeline steel with multi-phases and 0.10%Nb （mass fraction）. The microstructures of the CGHAZ in HAZ were characterized by means of OM, SEM and EBSD, and mechanical properties were tested. The results show that for a low heat input of less than 20 kJ/cm, the microstructure is lath bainite or acicular ferrite structure with high-density of large angle boundaries （≥15°）, which exhibits good Charpy impact toughness. However, for a large heat input over 25 kJ/cm, the uniformity of prior austenite grains becomes worse, the M/A constituents and the granular bainite （GB） are coarsening, and the amount of large-angle boundaries decreases with the increase of heat input. The results of the instrumented Charpy impact test and the observation of fracture surfaces on the specimens indicate that the cracks are induced near the coarse M/A constituents and the large-angle boundaries can remarkably restrict crack prop-agations. Therefore, in order to ensure a strong match between the HAZ and the base metal, and the resistance to hydrogen induced delayed damage because of high hardness of HAZ, the heat input energy should be about between 15 and 20 kJ/cm.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第7期797-806,共10页
Acta Metallurgica Sinica
基金
国家重点基础研究发展计划资助项目2010CB630801~~
关键词
X100管线钢
热影响区
热输入
韧性
抗变形
显微组织
pipeline steel, heat affect zone（HAZ）, heat input, toughness, deformationresistance, microstructure
