基本信息
项目批准号：51774085
申请代码：E0414
项目名称：搅拌摩擦焊高强管线钢环缝的复相组织演化与增韧机制研究
项目负责人：
谢广明
依托单位：
东北大学
研究期限：2018-01-01 至 2021-12-31
资助经费：60.0（万元）
项目摘要
中文摘要：
目前油气管线的连接主要采用熔焊，但熔焊的高热输入易引起热影响区（HAZ）组织的粗化和脆化，降低接头韧性。搅拌摩擦焊（FSW）属固相焊，其较低的热输入可显著改善HAZ韧性。现有FSW管线钢研究普遍采用峰值温度>>A3的高热输入参数，因而导致焊缝组织粗化，韧性降低。本申请拟采用中等热输入进行FSW高强管线钢，即峰值温度被控制在奥氏体的未再结晶区，奥氏体在强变形和焊后冷却作用下转变成细小的贝氏体/铁素体复相组织，可显著改善焊缝韧性。研究中拟采用热扭转模拟FSW变形过程，揭示FSW过程中的奥氏体高温变形行为、形变诱导铁素体相变和连续冷却相变机制，并建立FSW过程的应变场和温度场。通过研究焊缝组织和韧性，揭示复相组织中的相组成、有效晶粒尺寸、晶界和相界特征、M-A组元和碳氮化物的尺寸和分布对裂纹萌生和扩散的作用机制，阐明FSW焊缝的增韧机理，为FSW在油气管线连接中的应用提供理论和技术参考。
英文摘要：
Presently, fusion welding was widely used to join girth welds for oil and gas transportation pipelines. However, fusion welding easily resulted in coarsening and embrittling of the heat affected zone (HAZ), reducing toughness of the HAZ. Friction stir welding (FSW), as a solid state welding technology, can improve toughness of the HAZ due to lower heat input. In recent some studies, relatively high heat input conditions with higher peak temperatures of >> A3 were exerted to join the pipeline steels, causing a reduction in toughness of the welds due to coarsened microstructure. In this proposal, by means of using medium heat input, the peak temperatures were controlled within the austenitic non-recrystallized range, and austenite was transformed to fine bainite/ferrite multi-phase structure due to the action of severe deformation and cooling, increasing toughness. In this study, the thermal torsion was used to simulate the FSW process to build temperature and strain fields and uncover the effect of FSW on austenitic deformation at elevated temperature, deformation induced ferrite transformation and following continuous cooling transformation. Through studying microstructure and toughness of welds, the influence of phase composition, effective grain size, grain and phase boundaries, size and distribution of M-A constituent and carbonitride on both initiation and propagation of crack was revealed for fine multi-phase structure. Finally, the mechanism responsible for enhancement in toughness was elaborated, providing important reference in theory and technology for joining oil gas transportation pipelines.
——来自https://kd.nsfc.gov.cn/
