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对新开发大截面贝氏体塑料模具钢SDP2在极低冷速下的过冷奥氏体连续冷却转变过程和相变动力学进行了研究。采用DIL805A高精度差分热膨胀仪测量SDP2钢线膨胀行为,利用SEM分析冷却转变产物;根据JMA公式计算SDP2钢贝氏体相变激活能和Avrami指数。结果表明,SDP2钢过冷奥氏体连续冷却过程包含珠光体、贝氏体和马氏体转变,而无铁素体转变;当冷速大于0.02℃/s时,转变产物以下贝氏体或马氏体为主;小于0.02℃/s时,以上贝氏体或粒状贝氏体为主,并出现珠光体。SDP2钢贝氏体转变的激活能为117 k J/mol,SDP2钢在不同冷速下贝氏体转变动力学指数Avrami指数n≈2~3,经分析计算所得的Avrami指数值所对应的显微组织形态和实验所观察到的显微组织相符合。
The newly developed large-section bainitic plastic die steel SDP2 under extremely low cooling rate under subcooling austenite continuous cooling transformation process and phase transformation dynamics were studied. The DIL805A high-precision differential thermal expansion instrument was used to measure the expansion behavior of SDP2 steel. SEM analysis was used to cool the transformation products. The bainite activation energy and Avrami index of SDP2 steel were calculated according to JMA formula. The results show that the continuous cooling of SDP2 steel involves the transformation of pearlite, bainite and martensite without ferrite transformation. When the cooling rate is higher than 0.02 ℃ / s, the transformation products below bainite or Martensite; less than 0.02 ℃ / s, the above bainite or granular bainite and pearlite. The activation energy of the bainite transformation of SDP2 steel is 117 kJ / mol. The Avrami index of the bainite transformation kinetics of SDP2 steel at different cooling rates is n ~ 2 ~ 3, and the Avrami index value calculated by the analysis shows significant The morphology of the microstructure coincided with the microstructure observed in the experiment.