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组织转变的模拟研究,对准确预测硬化处理后组织与残余应力的分布有重要意义。本研究建立了电子束扫描45钢表面相变硬化过程中温度场与组织转变的数学模型;模型中考虑了热源分布、热物性参数、热辐射等因素对温度场的影响,基于Scheil叠加法则考虑了快速加热对奥氏体开始转变温度的影响;计算了相变硬化过程中各相组织含量和空间分布;分析了快速加热对奥氏体转变的影响;并进行了相应试验验证。结果表明,完全相变硬化区马氏体体积分数高达92.5%;硬化层横截面马氏体分布呈月牙状,且组织过渡明显;相变硬化奥氏体开始转变温度可高达1246 K,完成转变时间可短至0.1 s;硬化区冷却过程只发生马氏体相变;模拟结果与实验结果吻合较好。
The simulation study of tissue transformation is of great significance to accurately predict the distribution of tissue and residual stress after hardening treatment. In this study, a mathematical model of temperature field and microstructure transformation during the electron beam scanning of 45 steel was established. The influence of heat source distribution, thermophysical parameters and heat radiation on the temperature field was considered in the model. Considering the Scheil superposition law The effect of rapid heating on the initial transformation temperature of austenite was calculated. The content and spatial distribution of each phase in the phase transformation hardening process were calculated. The effect of rapid heating on the transformation of austenite was analyzed. The corresponding experimental results were also given. The results show that the volume fraction of martensite in the complete transformation hardening zone reaches as high as 92.5%. The martensite distribution of the hardened layer is crescent-shaped and the microstructure transition is obvious. The transformation temperature of transformation hardening austenite can reach as high as 1246 K, The time can be as short as 0.1 s; only the martensite transformation occurs in the cooling zone of the hardening zone; the simulation results are in good agreement with the experimental results.