Abstract: The continuous cooling transformation ( CCT) curves of high carbon alloy steel 75Crl (/% : 0. 75C, 0. 27Si, 0. 85Mn, 0. 010P, 0.003S, 0.60Cr) and the effect of cooling rate on phases and structure of steel are obtained by Gleeble-3800 thermal simulation testing machine to carry out first reduction 25% deformation with deformation rate 15 s"1 at 1 090 °C then with 20 °C/s cooling to 880 °C and second reduction 25% with deformation rate 20 s^-1 then with 0. 05 〜 45 ℃ /s cooling to ambient temperature. Results show that the critical points of phase transformation Ac ₁and Ac₃ are respectively 730 °C and 773 °C ; with cooling rate being lower than 1°C /s the main structure of steel is proeutectoid ferrite and fine pearlite, with cooling rate being 1 〜10 °C/s, the structure of steel is pearlite and bainite; with cooling rate being larger than 10 °C/s the martensite occurs in structure and with increasing cooling rate the amount of martensite increases, and with cooling rate being larger than 18 °C/s the main structure of steel is martensite and has minor bainite.

摘要： 通过Gleeble-3800热模拟机将高碳合金钢75Cr1(/%:0.75C,0.27Si,0.85Mn,0.010P,0.003S,0.60Cr)在1090℃以15 s^-1进行第1道次25%压缩变形,以20℃/s冷却至880℃,20 s^-1进行第2道次25%压缩变形,再分别以0.05~45℃/s不同冷速冷却至室温,得出连续冷却转变(CCT)曲线和冷却速率对该钢相和组织的影响。结果表明,相变临界Ac₁和Ac₃分别为730℃和773℃;冷速低于1℃/s时钢的组织主要为先共析铁素体和细小珠光体,冷速在1~10℃/s时钢的组织为珠光体和贝氏体,冷速高于10℃/s时组织中会出现马氏体,马氏体会随着冷速的增加逐渐增多,当冷速大于18℃/s时,钢的组织以马氏体为主,含有极少量的贝氏体。