S34MnV钢的连续冷却转变行为及相变动力学研究  

Continuous Cooling Transformation Behavior and Transformation Kineticsof S34MnV Steel

作　　者：阎勇 李萌蘖 卜恒勇 郑善举 YAN Yong;LI Mengnie Victor;BU Hengyong;ZHENG Shanju(Faculty of Materials Science and Engineering,Kunming University of Science and Technology,Kunming 650093,China)

机构地区：[1]昆明理工大学材料科学与工程学院,昆明650093

出　　处：《材料导报》2021年第20期20129-20136,共8页Materials Reports

基　　金：科技部材料基因工程关键技术与支撑平台重点研发计划(2017YFB0701804)。

摘　　要：本工作利用DIL-805ADT动态热膨胀相变仪测定了S34MnV钢不同冷却速率下的相变膨胀量,通过光学显微组织观察、SEM组织观察、能谱成分扫描、XRD物相检测等手段对S34MnV钢在连续冷却过程中的组织转变规律进行了深入分析,运用切线法对相变拐点前后的膨胀曲线进行线性拟合,得到了S34MnV钢在加热和不同速度冷却下的相变点,根据所得到的相变点和对应的相变时间结合微观组织分析绘制了S34MnV钢的连续冷却转变(CCT)曲线。同时为更好地描述S34MnV钢在连续冷却过程中的扩散型相变,本工作采用了针对低合金钢更加准确实用的Li模型,根据绘制出的CCT曲线修正了描述铁素体、珠光体、贝氏体相变的Li模型参数,使其可以用于热处理冷却过程中复杂的奥氏体分解,并拟合出马氏体相变Koistinen-Marburger(K-M)方程的参数,较为完整地建立了S34MnV钢连续冷却转变过程中的铁素体、珠光体、贝氏体和马氏体相变的动力学模型。结果表明,本研究所述模型计算所得的转变量与实验所得结果一致,说明该模型可用于预测S34MnV钢热处理冷却过程中的相变,也为后续大型船用曲轴的数值模拟提供了准确的数学模型。Dilations of S34MnV steel during continuous cooling at different cooling rates were measured utilizing DIL-805ADT dynamic dilatometer.The transformation points of S34MnV steel,which are the austenitizing critical points Ac 1 and Ac 3,bainite transformation points B s and B f,martensitic transformation points M s and M f,were obtained under different heating and cooling speeds by the tangent method that fits the expansion curves before and after the transformation inflection point.The microstructure and phase of continuous cooling transformation of S34MnV steel were observed and analyzed by optical microscope(OM),scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and X-ray diffraction(XRD).The CCT curve of S34MnV steel was drawn according to the transformation time corresponding to these transformation points and the microstructure analysis.Meanwhile,a more accurate and practical Li model for low alloy steel is adopted in this paper to describe the diffusion transformation in the continuous cooling process.The ferrite,pearlite and bainite transformation described by the Li model,which was used to calculate the complex austenite decomposition reaction in the cooling process of heat treatment was modified by the CCT curve and the Koistinen-Marburger(K-M)equation of the martensitic transformation was fitted.The dynamic models of ferrite transformation,pearlite transformation,bainite transformation and martensite transformation in the continuous cooling transformation process of S34MnV steel were established comprehensively.The results of the experimental observation are consistent with the transformation calculated by the model,which could provide an accurate mathematical model for the numerical simulation of large marine crankshaft,and could be used to predict the phase transformation of S34MNV steel during the cooling process of heat treatment.

关 键 词：S34MnV 船用曲轴钢 膨胀曲线 相变点 CCT曲线 相变动力学 

分 类 号：TG142.33[一般工业技术—材料科学与工程]