4Cr5Mo2V热作模具钢TTT曲线测定及球化退火工艺探索

Explore of TTT curve tested and spheroidizing annealing process of 4Cr5Mo2V hot-working die steel

采用热膨胀法测定4Cr5Mo2V热作模具钢奥氏体化后在不同等温温度下的相变膨胀曲线,结合组织观察和相转变后材料硬度的测定,绘制了4Cr5Mo2V钢奥氏体等温转变曲线(TTT曲线),并对曲线进行了分析和讨论,为制订合理的球化退火工艺建立了依据。结果表明,4Cr5Mo2V钢的相变临界点Ac1为835℃、Accm为938℃、Ms为321℃,其最佳固溶温度为1 060~1 080℃,最佳保温时间为1 h,最佳球化退火工艺为870℃×2 h+750℃×8 h。

The phase transition expansion curves of austenitized 4 Cr5 Mo2 V hot-working die steel at different isothermal temperatures were tested by thermal expansion method. Combined with the observation of the microstructure and hardness of the material after phase transition, the austenite isothermal transformation curve(TTT curve) of 4 Cr5 Mo2 V steel were drawn and analyzed, which could establish a basis for the development of a reasonable spheroidizing annealing process. The results showed that the phase transition critical point of 4 Cr5 Mo2 V steel is Ac1: 835 ℃, Accm: 938 ℃, Ms: 321 ℃, the optimum solution temperature is 1060 ℃ ~1080 ℃ holding for 1 h;the best spheroidizing annealing process is870 ℃×2 h+750 ℃×8 h.