工程科学学报.第44卷.第2期：228-234.2022年2月 Chinese Journal of Engineering,Vol.44,No.2:228-234,February 2022 https://doi.org/10.13374/j.issn2095-9389.2021.01.10.004;http://cje.ustb.edu.cn 石墨化钢石墨化过程的金相分析及其动力学方程 张永军四，李新鹏，王九花，刘靖，韩静涛 北京科技大学材料科学与工程学院，北京100083 ☒通信作者，E-mail:zhangyi@mater..ustb.edu.cn 摘要在650、680和710℃不同温度条件下对碳质量分数为0.66%的淬火高碳钢进行了石墨化处理，并利用场发射扫描 电子显微镜、电子探针、X射线衍射仪和透射电子显微镜对其石墨化过程的组织进行金相分析，以及利用组织转变动力学理 论，绘制了其石墨化过程的动力学曲线，并建立了相应的动力学方程.研究结果显示：在石墨化过程中，淬火马氏体首先向析 出碳化物的稳定状态转变，且在碳化物为渗碳体F©3C时，石墨粒子析出速度开始明显增加；基体组织中针叶状a-Fε发生再结 晶，由等轴状铁素体逐步代替针叶状的@-F:铁素体中的碳含量随着石墨化时间的延长而逐步降低，即由过饱和状态转变为 稳定态.碳含量在石墨粒子中突变增为峰值，而铁含量则突变降为谷值，由此表明，渗碳体分解的碳向石墨核心扩散，铁自石 墨核心处扩散出来，而形成石墨粒子：石墨粒子面积分数随时间变化的曲线呈S形状，即该动力学过程符合动力学模型 JMAK(Johnson-Mehl-Avrami-Kolmogorov)方程，且该方程中的n值为1.5-1.7. 关键词石墨化钢；石墨粒子；铁素体；金相分析；JMAK(Johnson--Mehl-Avrami--Kolmogorov)方程 分类号TG113.26 Metallographic analysis and kinetic equation of the graphitization process of graphitized steel ZHANG Yong-jun,LI Xin-peng,WANG Jiu-hua,LIU Jing,HAN Jing-Tao School of Materials Science and Engineering.University of Science and Technology Beijing,Beijing 100083,China Corresponding author,E-mail:zhangyj@mater.ustb.edu.cn ABSTRACT Graphitized steel can have good machinability and formability,or high strength through controlling microstructure.The graphitization process is formation of graphite particles in graphitized steel,which is key to control the microstructure and properties of the steel.In this paper,the quenched high carbon steel with 0.66%carbon(mass fraction)was graphitized at 650,680,and 710C, respectively.The microstructure formed during the graphitization process was analyzed by a field emission scanning electron microscope,electron probe microanalysis,X-ray diffraction,and a transmission electron microscope.According to the dynamic theory of phase transformation,the kinetic curve of the graphitization process was drawn,and the corresponding kinetic equation was established. The results show that in the graphitization process,the quenched martensite is first transformed to the stable state of precipitation carbide.When the carbide is cementite FeC,the precipitation rate of graphite particles increases significantly.The acicular a-Fe in the matrix recrystallizes,and is gradually replaced by equiaxed ferrite.With prolonged graphitization time,the carbon content in ferrite decreases gradually:that is,it changes from a supersaturated state to a stable state.The carbon content increases to the peak value in graphite particles,whereas that of Fe decreases to the valley value.These changes show that the decomposed carbon of cementite,FeC. diffuses into the graphite core,whereas Fe diffuses from the graphite core,and then graphite particles are formed.Additionally,when steel is graphitized,the curve of graphite particle area fraction with time is an S shape;that is,the dynamic process of the tested steel is in accordance with the JMAK (Johnson-Mehl-Avrami-Kolmogorov)equation,and the value of n in the equation is between 1.5 and 1.7. 收稿日期：2021-01-10 基金项目：北京市自然科学基金资助项目(2172035)石墨化钢石墨化过程的金相分析及其动力学方程 张永军苣，李新鹏，王九花，刘    靖，韩静涛 北京科技大学材料科学与工程学院，北京 100083 苣通信作者， E-mail: zhangyj@mater.ustb.edu.cn 摘    要    在 650、680 和 710 ℃ 不同温度条件下对碳质量分数为 0.66% 的淬火高碳钢进行了石墨化处理，并利用场发射扫描 电子显微镜、电子探针、X-射线衍射仪和透射电子显微镜对其石墨化过程的组织进行金相分析，以及利用组织转变动力学理 论，绘制了其石墨化过程的动力学曲线，并建立了相应的动力学方程. 研究结果显示：在石墨化过程中，淬火马氏体首先向析 出碳化物的稳定状态转变，且在碳化物为渗碳体 Fe3C 时，石墨粒子析出速度开始明显增加；基体组织中针叶状 α-Fe 发生再结 晶，由等轴状铁素体逐步代替针叶状的 α-Fe；铁素体中的碳含量随着石墨化时间的延长而逐步降低，即由过饱和状态转变为 稳定态，碳含量在石墨粒子中突变增为峰值，而铁含量则突变降为谷值，由此表明，渗碳体分解的碳向石墨核心扩散，铁自石 墨核心处扩散出来，而形成石墨粒子；石墨粒子面积分数随时间变化的曲线呈 S 形状，即该动力学过程符合动力学模型 JMAK（Johnson-Mehl-Avrami-Kolmogorov）方程，且该方程中的 n 值为 1.5～1.7. 关键词    石墨化钢；石墨粒子；铁素体；金相分析；JMAK(Johnson-Mehl-Avrami-Kolmogorov) 方程 分类号    TG113.26 Metallographic  analysis  and  kinetic  equation  of  the  graphitization  process  of graphitized steel ZHANG Yong-jun苣 ，LI Xin-peng，WANG Jiu-hua，LIU Jing，HAN Jing-Tao School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 苣 Corresponding author, E-mail: zhangyj@mater.ustb.edu.cn ABSTRACT    Graphitized steel can have good machinability and formability, or high strength through controlling microstructure. The graphitization process is formation of graphite particles in graphitized steel, which is key to control the microstructure and properties of the  steel.  In  this  paper,  the  quenched  high  carbon  steel  with  0.66% carbon  (mass  fraction)  was  graphitized  at  650,  680,  and  710℃, respectively.  The  microstructure  formed  during  the  graphitization  process  was  analyzed  by  a  field  emission  scanning  electron microscope, electron probe microanalysis, X-ray diffraction, and a transmission electron microscope. According to the dynamic theory of phase transformation, the kinetic curve of the graphitization process was drawn, and the corresponding kinetic equation was established. The  results  show  that  in  the  graphitization  process,  the  quenched  martensite  is  first  transformed  to  the  stable  state  of  precipitation carbide. When the carbide is cementite Fe3C, the precipitation rate of graphite particles increases significantly. The acicular α-Fe in the matrix  recrystallizes,  and  is  gradually  replaced  by  equiaxed  ferrite.  With  prolonged  graphitization  time,  the  carbon  content  in  ferrite decreases gradually; that is, it changes from a supersaturated state to a stable state. The carbon content increases to the peak value in graphite particles, whereas that of Fe decreases to the valley value. These changes show that the decomposed carbon of cementite, Fe3C, diffuses into the graphite core, whereas Fe diffuses from the graphite core, and then graphite particles are formed. Additionally, when steel is graphitized, the curve of graphite particle area fraction with time is an S shape; that is, the dynamic process of the tested steel is in accordance with the JMAK (Johnson-Mehl-Avrami-Kolmogorov) equation, and the value of n in the equation is between 1.5 and 1.7. 收稿日期: 2021−01−10 基金项目: 北京市自然科学基金资助项目（2172035） 工程科学学报，第 44 卷，第 2 期：228−234，2022 年 2 月 Chinese Journal of Engineering, Vol. 44, No. 2: 228−234, February 2022 https://doi.org/10.13374/j.issn2095-9389.2021.01.10.004; http://cje.ustb.edu.cn