关键词: NM400耐磨钢, CCT曲线, 热膨胀法, 相变点, 组织

Abstract: By Gleeble3500 thermomechanical simulator to determine the dilation curves at continuous cooling conditions, the critical transformation points of steel NM400 are Ac₁=719. 4 ℃ and Ac₃ =847. 8 ℃，and combined with the metallographic method, the continuous cooling transformation (CCT) curves of super cooling austenite of tested steel are plotted using Origin software. The results show that with the increase of cooling rate, the microhardness of steel increases gradually, and the phase transformation gradually changes from ferrite and pearlite to bainite and martensite, and the ferrite content decreases gradually ； when the cooling rate is less than 1 ℃/s, the pearlite content increases gradually, and the grain size gradually decreases; when the cooling rate is greater than 5 ℃/s, the ferrite and pearlite phase transition disappears ,and with the increase of the cooling rate the bainite phase decreases and martensitic phase is gradually increasing.