摘要
介绍了P91钢焊缝金属中马氏体组织的形态及形成条件,分析了焊缝金属中马氏体组织的影响因素,探讨了马氏体组织对焊缝金属韧性的影响,提出了马氏体形态控制机理。结果表明,P91钢焊后状态的焊缝组织为板条马氏体+δ铁素体,焊后热处理状态的组织为回火马氏体+δ铁素体+碳化物,回火马氏体的板条碎化且板条间的位向消失,位错密度变小,焊缝中马氏体形态的变化在很大程度上受焊接热输入控制。在马氏体组织的影响因素中,合金元素及其优化含量对形成细小板条马氏体有重要影响,合理的焊接工艺参数(如小的焊接热输入、较低的预热温度和较低的层间温度)和焊后回火温度,对获得细小板条马氏体有益,焊接方法中,以钨极氩弧焊形成的马氏体形态最细小,埋弧焊缝马氏体最粗大,焊条电弧焊缝马氏体也较粗大。马氏体形态与焊缝韧性之间存在对应关系,即粗大板条马氏体的焊缝韧性很差,而细小板条马氏体的焊缝韧性优良。优化的合金系统和化学成分是控制板条马氏体形成的必要条件,而合理的焊接条件和工艺参数则是控制细小回火马氏体形态的充分条件,二者缺一不可。推荐了一项有效改善P91钢焊缝韧性的创新工艺,该工艺使得焊接工艺变得较为宽松,具有推广价值和应用前景。
The morphology of martensite structure and its formation conditions in the weld metal of P91 steel were introduced firstly. The influencing factors on martensite structure were analyzed. The effect of martensite morphology on weld metal toughness was discussed, and then the mechanism to control martensite morphology was proposed. The experimental results show that the as-deposited microstrueture of P91 weld metal is consisted of lath martensite and δ ferrite. After post-weld heat treatment, it is tempered martensite + δ ferrite + carbides. Lath of tempered martensite is broken up and the orientation of lath disappears, the dislocation density become small. It is suggested that the change of martensite morphology is controlled by welding heat input to a large extent. In the influencing factors of martensite structure, alloying elements, the optimum content of alloying elements, the proper welding parameters (such as a low welding heat input, lower preheat temperatures and interpass temperature) and post weld heat treatment have an important influence on the formation of fine lath martensite. The martensite made by tungsten inert arc welding is the finest grain than that by the other welding method, such as submerged arc welding and shielded metal arc welding. There is a corresponding relationship between martensite morphology and weld metal toughness, that is to say, the toughness of weld metal with coarse lath martensite is lower that that with fine martensite. The optimization of 'alloy composition is the necessary conditions, while the reasonable welding conditions are the sufficient conditions for controlling the fine tempered martensite morphology, and neither is dispensable. A new technology to effectively improve toughness of P91 welded deposition is recommended. This technology is expected to result in the wider welding conditions and has application and prospect and spreading value.
出处
《焊接》
北大核心
2010年第4期7-12,共6页
Welding & Joining
