低碳微合金钢连续管低周疲劳性能研究  

Study on Low Cycle Fatigue Property of Low Carbon Microalloyed Steel Coiled Tubing

作　　者：毕宗岳 张锦刚[1,2,3] 余晗 鲜林云[1,2,3] BI Zongyue;ZHANG Jingang;YU Han;XIAN Linyun(Chinese National Engineering Research Center for Petroleum and Natural Gas Tubular Goods Co.,Ltd.,Xi'an 710018,China;CNPC Baoji Petroleum Steel Pipe Co.,Ltd.,Baoji 721008,Shaanxi,China;Shaanxi Province Key Laboratory of High Performance Coiled Tubing,Baoji 721008,Shaanxi,China)

机构地区：[1]中油国家石油天然气管材工程技术研究中心有限公司,西安710018 [2]中国石油宝鸡石油钢管有限责任公司,陕西宝鸡721008 [3]陕西省高性能连续管重点实验室,陕西宝鸡721008

出　　处：《焊管》2023年第7期38-44,共7页Welded Pipe and Tube

基　　金：中国石油科学研究与技术开发项目“连续管井下电动马达钻井系统研究”(项目编号2021DJ4305)。

摘　　要：通过控制应变和控制应力方法,对12CrMnMoNi低碳微合金钢连续管管材进行了室温下的低周疲劳试验和循环应变硬化测试,分析了影响疲劳寿命的因素。结果显示,在0.4%~1.2%不同应变幅条件下,管材总体呈现循环软化现象,在1.2%大应变幅下疲劳寿命只有54次,是0.6%~0.8%应变幅的20%左右;在循环初始阶段,低应变表现为循环软化,高应变表现为循环硬化,临界应变(εc)介于0.8%~1.0%。在控制应力高于屈服强度5%时,平均疲劳寿命为318次,表明管材在承受较高载荷下仍具有良好的疲劳性能;同时,硬化指数对疲劳寿命有直接影响,在总循环次数的50%以内,随着循环次数的增加,硬化指数增加,表明该管材在循环过程中依靠硬化实现均匀变形的能力增强;细小的铁素体+M/A组元是实现良好疲劳性能的组织保障;断口SEM观察表明,疲劳裂纹起源于外表面,且伴有二次裂纹产生。The low cycle fatigue test and cyclic strain hardening test were carried out on 12CrMnMoNi low carbon micro alloyed steel coiled tubing at room temperature by controlling strain and stress,and then the factors affecting fatigue life were analyzed.The results show that under the condition of different strain amplitudes of 0.4%~1.2%,the whole tube exhibits cyclic softening and the fatigue life is only 54 times under the large strain amplitude of 1.2%,which is about 20%of the strain amplitude of 0.6%~0.8%.At the initial stage of the cycle,low strain shows cyclic softening and high strain shows cyclic hardening,and the critical strain(εc)is between 0.8%and 1.0%.When the control stress is higher than the 5%yield strength,the average fatigue life is 318 times,indicating that the material still has good fatigue performance under high loads.At the same time,the hardening index has a direct effect on the fatigue life.Within 50%of the total cycle number,the hardening exponent increases with the increase of the cycle number,indicating that the ability of the tubing to achieve uniform deformation by hardening during the cycle process is enhanced.The fine ferrite and M/A component are the microstructure guarantee to achieve good fatigue performance.The fracture SEM observation results show that the fatigue crack originate from the outer surface,accompanied by secondary cracks.

关 键 词：连续管 低碳微合金钢 低周疲劳 硬化指数 

分 类 号：TG113.255[金属学及工艺—物理冶金] TE931.2[金属学及工艺—金属学]