开冷温度对420MPa级海洋工程用钢延伸性能的影响  

Effects of initial cooling temperature on elongation performance of 420 MPa grade marine engineering steels

作　　者：李家安 赵坦 李文斌[1,2] 李俊博 金耀辉[1,2] 朱隆浩 LI Jiaan;ZHAO Tan;LI Wenbin;LI Junbo;JIN Yaohui;ZHU Longhao(State Key Laboratory of Metal Material for Marine Equipment and Application,Anshan 114009,China;Angang Steel Company Limited,Anshan 114009,China)

机构地区：[1]海洋装备用金属材料及其应用国家重点实验室,辽宁鞍山114009 [2]鞍钢股份有限公司,辽宁鞍山114009

出　　处：《轧钢》2024年第3期21-28,共8页Steel Rolling

基　　金：辽宁省重大科技专项项目(2020 JH1/10100001);辽宁省自然科学基金项目(2022-BS-359)。

摘　　要：针对工业生产的420 MPa级海洋工程用钢进行了研究。采用轧后弛豫相变技术对实验钢板微观组织进行控制,得到3种不同铁素体与贝氏体(F/B)比例的双相组织钢板。借助改进的C-J分析方法和应变硬化曲线,分析了硬质相贝氏体比例和软质相铁素体晶粒尺寸对钢板变形过程中加工硬化行为的影响,并通过EBSD技术验证了双相组织在不同变形阶段的协调变形行为。同时,还分析了两相区弛豫过程中碳扩散对双相组织形貌的影响。结果表明:对于EH420实验钢板,控轧后弛豫开冷温度在650~750℃范围内,贝氏体比例随开冷温度的降低而增加且贝氏体弥散分布程度降低;铁素体平均晶粒尺寸随开冷温度的降低而增大且铁素体出现局部混晶现象,其原因是开冷温度越低则钢板在Ar1到Ar3温度区间停留时间越长,先共析铁素体中碳原子向奥氏体的扩散进行得越充分,导致奥氏体碳富集区域面积增加,快速冷却后转变的贝氏体比例增加、弥散分布程度降低,同时铁素体局部晶粒粗化。钢板拉伸过程的塑性变形主要贡献自铁素体,铁素体比例越高、铁素体平均晶粒尺寸越小,钢板的应力指数mⅡ越低,且mⅡ阶段持续过程更长,出现颈缩时的应变值越大,钢板的延伸性能也越好。因此,提高铁素体比例、铁素体晶粒尺寸均匀性和贝氏体的弥散分布程度是提高EH420钢板延伸性能的主要途径。This investigation focused on the development of 42o MPa grade steel for marine engineering applications,conducted within an industrial production framework.Three high strength marine engineering plates of 420 MPa with ferite/bainite(F/B)dual-phase and varying volume fractions of fetriten and bainite were produced through controlled rolling,relaxing and accelerated cooling control processing.The effects of hard phase(bainite)content and soft phase(ferrite)grain size on the work-hardening behavior of the plate during deformation were studied using the modified Crussard-Jaoul(CJ)analysis and work-hardening rate curves,and the cooperatire deformation behavior of dualphase microstructwe at different deformation stageswhich were validated by electron backscattered diffraction(EBSD)technique.At the same time,the effect of carbon diffusion during relaxation in two phase region on the dual-phase microstructure were also analyzed.The results illustrated that for the EH420 experimental plates,managing the controlled rolling followed by relaxation cooling temperatures within the range of 650-750 C leads to an increase in the proportion of bainite as the cooling temperature decreases,along with a decrease in bainite dispersion.Simultaneously,a decline in cooling temperature leads to an increase in the average grain size of ferrite,with instances of partial mixed crystal phenomena emerging within the ferrite This phenomenon is attributed to the lower cooling temperatures extending the duration of the plates within the Ari to Ars temperature intervals,thereby facilitating a more comprehensive diffusion of carbon atoms from the proeutectoid ferrite to the austenite Consequently,this process enlarges the area of austenite regions enriched with carbon,which,upon rapid cooling,increases the proportion of transformed bainite,decreases its dispersion,and induces localized grain coarsening in ferrite The study delineates that the plastic deformation of the plates is predominantly influenced by ferrite during the tensile deformation p

关 键 词：海洋工程用钢 延伸性能 驰豫控制相变技术 铁素体/贝氏体双相钢 改进C-J分析方法 协调变形 

分 类 号：TG142.1[一般工业技术—材料科学与工程]