摘要
采用DIL 805A/D/T多功能淬火膨胀仪,结合显微组织表征和硬度测试,研究了25Cr2Ni4MoV钢在短时奥氏体化条件下的连续冷却转变(CCT)动力学和组织演变规律。结果表明:在850℃短时奥氏体化条件下,连续冷却相变发生在450~150℃区间;当冷速大于2℃/s时得到的室温组织为马氏体,随着冷速降低,试样中出现贝氏体;当冷速小于0.5℃/s时其显微组织主要为贝氏体组织;随着冷速的进一步降低,当冷速为0.02℃/s时,除了贝氏体以外还有少量的马氏体/奥氏体岛和残留奥氏体。冷速从2℃/s降低至0.5℃/s时硬度变化较明显,这与组织中形成的马氏体与贝氏体的比例有关。由于短时奥氏体化条件下存在未溶解的碳化物,基体碳浓度较低,其Ms温度较高;贝氏体转变速率也较快,这可能与奥氏体的晶粒尺寸小和存在未溶碳化物有关。
Based on the dilatometric curves measured by DIL 805A/D/T multifunctional quenching dilatometer,microstructure characterization and hardness test,the continuous-cooling-transformation(CCT)curves of 25Cr2Ni4MoV steel was investigated.The results show that the continuous cooling transformations mainly take place between 450℃and 150℃after short-time austenitizing at 850℃;when the cooling rate is higher than 2℃/s,the room temperature microstructure is martensite,while bainite forms along with the decrease of the cooling rate;when the cooling rate is lower than 0.5℃/s,the microstructure is mainly bainite;when the cooling rate is 0.02℃/s,the microstructure after transformation is composed of bainite with a few complex martensite/austenite islands and isolated retained austenite dispersed.The hardness decreases significantly when the cooling rate decreases from 2℃/s to 0.5℃/s,which is related to the changes in the relative fraction ratio of martensite and bainite.Due to the existence of undissolved carbides after short-time austenitizing,the carbon content of austenite is low,resulting in higher Ms temperature;the bainite transformation rate is also higher,which may be related to the finer austenite grains as well as the undissolved carbides.
作者
宋逸思
李传维
陈益华
郑奇峰
郭正洪
顾剑锋
Song Yisi;Li Chuanwei;Chen Yihua;Zheng Qifeng;Guo Zhenghong;Gu Jianfeng(School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Guilin Fuda Heavy Forging Co.,Ltd.,Guilin Guangxi 541199,China)
出处
《金属热处理》
CAS
CSCD
北大核心
2019年第11期52-57,共6页
Heat Treatment of Metals
