低温下N80钢油套管冲击韧性和断口特征研究  

Study on Impact Toughness and Fracture Characteristics of N80 Steel Oil Casing at Low Temperature

作　　者：邢希金 刘婉颖[2] 武广瑷 周定照 张智[3] XING Xijin;LIU Wanying;WU Guangai;ZHOU Dingzhao;ZHANG Zhi(CNOOC Research Institute Ltd.,Beijing 100028,China;School of New Energy and Materials,Southwest Petroleum University,Chengdu 610500,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China)

机构地区：[1]中海油研究总院有限责任公司,北京100028 [2]西南石油大学新能源与材料学院,四川成都610500 [3]西南石油大学油气藏地质及开发工程国家重点实验室,四川成都610500

出　　处：《材料保护》2023年第11期53-62,共10页Materials Protection

基　　金：国家自然科学基金联合基金项目(U22A20164);油气藏地质及开发工程全国重点实验室(西南石油大学)项目(PLN2022-44);四川省重点实验室开放课题项目(2022CL05);中海石油(中国)有限公司北京研究中心项目(CCL2021RCPS0349PSN)资助。

摘　　要：为了明确低温条件下油套管N80钢的韧性变化规律,利用示波冲击仪对N80钢油套管材料进行不同温度(25、0、-20、-40℃)条件下的示波冲击试验,采用SEM观察N80钢冲击试样断口形貌,研究了不同温度条件下N80钢的韧脆特性及断口裂纹扩展特征。结果表明:N80钢的冲击功随温度降低而减小,裂纹扩展功与冲击功的比值随温度升高先减小后增大再减小,起裂功与冲击功的比值随温度升高先增大后减小再增大。断口形貌分析表明,裂纹萌生及扩展的断口特性与力-位移示波冲击曲线反映出的断裂特性一致。25℃时,断口面可见裂纹稳态扩展阶段,起裂区断口为韧窝状韧性断裂;0℃时稳态扩展过程短,温度降至-20℃和-40℃时显示出解理脆性断裂特征。-20℃时为韧性和脆性断裂特征,-40℃时完全脆性化,N80钢组织中所含贝氏体和块状铁素体加剧其低温脆性断裂。For clarifying the toughness change rules of N80 steel for oil casing under low temperature conditions,the oscillometric shock performance tests were conducted on N80 steel oil casing materials at different temperatures(25,0,-20,and-40℃)using an oscilloscope impact meter.The fracture morphology of N80 steel impact specimens was observed using SEM,and the ductile brittle properties and fracture crack propagation characteristics of N80 steel under different temperature conditions were studied.Results showed that the impact energy of N80 steel decreased with the decrease of temperature.The ratio of crack propagation energy to impact energy decreased firstly,then increased and then decreased with increasing temperature.The ratio of initiation energy to impact energy first increased,then decreased,and then increased with increasing temperature.The morphology analysis of the fracture surface indicated that the fracture characteristics of crack initiation and propagation were consistent with the fracture characteristics reflected by the force-displacement oscillometric impact curve.At 25℃,the steady expansion stage of crack could be seen on the fracture surface,and the fracture surface in the crack initiation zone was a dimple-like ductile fracture.Besides,only a short steady-state expansion stage existed as the temperature decreased to 0℃.When the temperature decreased to-20℃and-40℃,cleavage brittle fracture characteristics appeared.Specifically,ductile and brittle fracture characteristics were observed at-20℃,and completely brittle occurred at the temperature of-40℃.Moreover,the bainite and lumpy ferrite contained in the N80 steel structure aggravated its low temperature brittle fracture.

关 键 词：温度 N80钢 示波冲击 断裂韧性 脆性断裂 

分 类 号：TE921.2[石油与天然气工程—石油机械设备]