80QL钢的CCT曲线及相变行为

doi:10.13251/j.issn.0254-6051.2025.05.015

摘要/Abstract

摘要： 采用Gleeble-3500热模拟试验机对80QL钢进行变形温度为950 ℃、变形速率为10 s^-1、变形量为40%,冷却速度为0.5~80 ℃/s的连续冷却转变试验。采用膨胀法测得相变点温度并绘制了CCT曲线。利用SEM和EBSD研究了不同冷速下的组织演变行为,并测量了其洛氏硬度。结果表明,80QL钢Ac₁为729 ℃,Ac₃为886 ℃。当冷速在0.5~5 ℃/s区间内,只发生珠光体相变,随着冷速的增大珠光体片层间距由138 nm减小到127 nm,晶粒尺寸由9.15 μm减小到6.64 μm。当冷速在10~20 ℃/s区间内,同时发生珠光体和贝氏体相变,且随着冷速的增大,贝氏体含量增加;当冷速达到30 ℃/s时,发生马氏体相变,且随着冷速的继续增大,马氏体含量逐渐增大;当冷速为80 ℃/s时,则全部为马氏体,硬度达到64 HRC。由EBSD试验结果可知,随冷速增大,晶粒尺寸减小,位错密度增加,这也是导致硬度增大的原因。

关键词: 80QL钢, 连续冷却转变, 相变行为, 晶粒尺寸, 位错密度

Abstract: Continuous cooling transformation test of 80QL steel at deformation temperature of 950 ℃, deformation rate of 10 s^-1, deformation amount of 40%, and cooling rate ranging from 0.5 ℃/s to 80 ℃/s was carried out by using Gleeble-3500 thermal simulation machine. The transformation point temperature was measured by dilatometry method and the CCT curve was plotted. The microstructure evolution under different cooling rates was investigated by using SEM and EBSD, and Rockwell hardness was measured. The results show that the Ac₁ temperature of the 80QL steel is 729 ℃, and the Ac₃ temperature is 886 ℃. When the cooling rate is in the range of 0.5-5 ℃/s, only pearlite transformation occurs. With the increase of cooling rate, the lamellar spacing of pearlite decreases from 138 nm to 127 nm, and the grain size decreases from 9.15 μm to 6.64 μm. When the cooling rate is within the range of 10-20 ℃/s, both pearlite and bainite phase transformations occur simultaneously, and with the increase of cooling rate, the bainite content increases. When the cooling rate reaches 30 ℃/s, martensitic transformation occurs, and the martensite content gradually increases with the further increase of cooling rate. When the cooling rate is 80 ℃/s, it is all martensite and the hardness reaches 64 HRC. According to the EBSD test results, as the cooling rate increases, the grain size decreases and the dislocation density increases, which is also the reason for the increase in hardness.

Key words: 80QL steel, continuous cooling transformation, phase transformation behavior, grain size, dislocation density

中图分类号:

TG142.1

王洪锋, 韩书栋, 王庆娟, 王钦仁, 许荣, 张伟, 胡楠. 80QL钢的CCT曲线及相变行为[J]. 金属热处理, 2025, 50(5): 94-100.

Wang Hongfeng, Han Shudong, Wang Qingjuan, Wang Qingren, Xu Rong, Zhang Wei, Hu Nan. CCT curve and phase transformation behavior of 80QL steel[J]. Heat Treatment of Metals, 2025, 50(5): 94-100.

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