船用高强球扁钢的连续冷却转变与奥氏体相变动力学分析

doi:10.13251/j.issn.0254-6051.2025.08.001

摘要/Abstract

摘要： 使用Formaster-FⅡ热膨胀仪,结合光学显微镜(OM)、扫描电镜(SEM)和维氏硬度测试,绘制了某船用高强球扁钢的连续冷却转变(CCT)曲线,并对其升温过程中的奥氏体转变进行动力学分析。结果表明,试验钢的Ac₁=672 ℃、Ac₃=793 ℃。在0.06~38.2 ℃/s冷速范围内,不发生珠光体转变。冷速为0.06~0.3 ℃/s时,发生贝氏体转变,且随冷速提高,贝氏体含量减少;冷却速度为0.8~3.8 ℃/s时,发生马氏体-贝氏体混合相变,随着冷速提高,马氏体含量增加;冷却速度为7.6~38.2 ℃/s时,发生马氏体相变。随着冷却速度的升高,试验钢硬度先快速升高,冷速达到7.6 ℃/s后硬度增加减缓,冷速为38.2 ℃/s时,硬度达最大值359 HV5。利用热膨胀曲线和杠杆定律得到升温过程试验钢的奥氏体转变动力学方程,表明其奥氏体转变为三维方式生长。

关键词: 球扁钢, CCT曲线, 组织转变, 相变动力学

Abstract: Continuous cooling transformation (CCT) curve of a high strength bulb flat ship steel was plotted by using Formaster-FⅡ thermal dilatometer combined with optical microscope (OM), scanning electron microscope (SEM), and Vickers hardness test, and austenite transformation kinetic analysis during the heating process was conducted. The results show that the Ac₁ and Ac₃ of the tested steel are 672 ℃ and 793 ℃, respectively. Within the cooling rate range of 0.06-38.2 ℃/s, no pearlite transformation is observed. When the cooling rate is 0.06-0.3 ℃/s, bainite transformation occurs, and the bainite volume fraction decreases with the increase of cooling rate. When the cooling rate ranges from 0.8 ℃/s to 3.8 ℃/s, mixed martensite-bainite phase transformation occurs, and the volume fraction of martensite increases with the increase of cooling rate. Martensitic transformation occurs within the cooling rate range of 7.6 ℃/s to 38.2 ℃/s. With the increase of the cooling rate, the hardness of the tested steel first increases rapidly. After the cooling rate reaches 7.6 ℃/s, the hardness increases slowly, and reaches the maximum value of 359 HV5 at the cooling rate of 38.2 ℃/s. The kinetics equation of austenite transformation is derived from the thermal dilatometric curve combined with the lever rule, revealing that the austenite transformation during the heating process follows a three-dimensional growth mechanism.

Key words: bulb flat steel, CCT curve, microstructure transformation, phase transformation kinetics

中图分类号:

TG142.7

祁震, 梁丰瑞, 罗小兵, 柴锋, 葛启录, 展之德, 宋成民, 罗坤杰. 船用高强球扁钢的连续冷却转变与奥氏体相变动力学分析[J]. 金属热处理, 2025, 50(8): 1-7.

Qi Zhen, Liang Fengrui, Luo Xiaobing, Chai Feng, Ge Qilu, Zhan Zhide, Song Chengmin, Luo Kunjie. Continuous cooling transformation and kinetic analysis of austenite transformation of high strength bulb flat ship steel[J]. Heat Treatment of Metals, 2025, 50(8): 1-7.

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