回火次数对P91焊管接头力学性能的影响  

Influence of tempering times on the mechanical properties of P91 weld joints

作　　者：王超[1,2] 党文静 鲁路[1,2] 王瑜 崔征[1] 王伟博[1] 

机构地区：[1]西安建筑科技大学冶金工程学院,西安710055 [2]陕西省冶金工程技术研究中心,西安710055 [3]陕西省锅炉压力容器检验所,西安710048

出　　处：《工程科学学报》2017年第4期529-534,共6页Chinese Journal of Engineering

基　　金：国家质检总局科技计划资助项目(SNQTS_2013QK148)

摘　　要：采用光学显微镜、X射线衍射分析、透射电镜、选区电子衍射及常温与高温拉伸试验等检测手段,基于不同回火次数下P91焊接接头显微组织的演化过程研究其对力学性能的影响.结果表明,随着回火次数的增多,接头显微组织主要保留了板条马氏体位向的回火索氏体,主要相为α-Fe相和Fe-Cr相,热影响区的室温及高温强度先增大后减小.在回火一次时,弥散析出的MX(M=V/Nb,X=C/N)型碳氮化物、位错缠结及亚稳态的位错网对接头有一定的析出强化及位错强化作用,其力学性能较佳,高温抗拉强度达最大值232.66 MPa;随着回火次数进一步增多,离散分布的碳化物Cr23C6逐渐偏聚并在晶界处演化为串链状分布,使晶界脆化,强度降低,但韧性有所改善.The P91 weld joint used in the experiment is re-tempered according to the heat treatment process. The effect of tempering times on its mechanical properties,including that at room temperature and high temperature,was then investigated in relation to the evolution of its microstructure using optical microscopy（ OM）,X-ray diffraction（ XRD）,transmission electron microscopy（ TEM）,selected area electron diffraction（ SAED）,and tensile tests. Results indicate that the strength at room and high temperature of the heat affected zone increases first and then decreases with an increase in tempering times. In addition,the microstructure is still tempered sorbite that reserves the orientation of lath martensite,and the main phases are the α-Fe phase and Fe-Cr phase. After being tempered once,its high-temperature tensile strength reaches a maximum of 232. 66 MPa. These improved mechanical properties relate to the dispersed distribution of niobium and vanadium carbonitride precipitate particles,dislocation tangles,and dense metastable dislocation networks. With the increase of tempering times,the distribution of Cr23C6 precipitates gradually undergoes a change from being isolated to displaying a continuous manner in the grain boundaries; this can embrittle the grain boundary and reduce the strength while improving toughness.

关 键 词：无缝管 焊接接头 回火 微观组织 高温力学性能 

分 类 号：TG156.5[金属学及工艺—热处理]