CCT and TTT curves of a carbide-free bainitic steel

doi:10.13251/j.issn.0254-6051.2025.02.011

Abstract

Abstract: Continuous cooling transformation and isothermal transformation tests of undercooled austenite were carried out on a carbide-free bainitic tested steel by using the DIL-805A phase transformation tester. The CCT and TTT curves of the tested steel were obtained. The results show that the starting and ending transformation temperatures of austenite of the tested steel are 760 ℃ and 860 ℃, respectively, and the starting transformation temperature of martensite is approximately 300 ℃. When the cooling rate is between 0.1-15 ℃/s, the undercooled austenite mainly transforms to bainite+martensite complex structure. When the cooling rate is between 15-50 ℃/s, the undercooled austenite transforms into martensite. The microhardness of the tested steel increases with the increase of cooling rate, up to 742 HV0.5. When the tested steel undergoes isothermal transformation, the bainite transformation temperature range is 300-400 ℃, and the "nose tip" temperature is about 360 ℃.

Key words: carbide-free bainitic steel, CCT curve, TTT curve

CLC Number:

TG151.3

Yang Siyuan, Li Aiguo, Luo Ping, Zhang Wenliang, Li Xianjun, Zhang Minghao, An Weicheng, Wang Kaize. CCT and TTT curves of a carbide-free bainitic steel[J]. Heat Treatment of Metals, 2025, 50(2): 74-80.

References

[1] Peter J, Peaslee K D, Robertson D G. Review of progress in developing continuous steelmaking[J]. Iron and Steel Technology, 2005, 2(2): 53-60.
[2] 李缘, 栾道成, 胡志华, 等. 城际及高铁轨道用辙叉贝氏体钢的组织与性能[J]. 金属热处理, 2021, 46(8): 70-72.
Li Yuan, Luan Daocheng, Hu Zhihua, et al. Microstructure and properties of bainitic steel for frog used in intercity and high-speed railway track[J]. Heat Treatment of Metals, 2021, 46(8): 70-72.
[3] 齐祥羽, 严玲, 李广龙, 等. 逆转变奥氏体稳定性对中锰钢强韧性的影响[J]. 金属热处理, 2021, 46(9): 205-210.
Qi Xiangyu, Yan Ling, Li Guanglong, et al. Effect of reversed austenite stability on strength and toughness of medium-Mn steel[J]. Heat Treatment of Metals, 2021, 46(9): 205-210.
[4] 郑红红, 赵爱民, 曹佳丽, 等. 水韧处理对高锰钢铸件组织与性能的影响[[J]. 金属热处理, 2014, 39(2): 112-115.
Zheng Honghong, Zhao Aimin, Cao Jiali, et al. Effect of water toughening on microstructure and mechanical properties of high manganese steel casting[J]. Heat Treatment of Metals, 2014, 39(2): 112-115.
[5] Long Xiaoyan, Liu Wei, Zhu Ranran, et al. Effect of the cooling rate in the medium temperature zone on the phase transformation and microstructure of carbide-free bainitic steel[J]. Journal of Materials Research and Technology, 2024, 29: 50-66.
[6] 田亚强, 田耕, 郑小平, 等. 低碳高强贝氏体钢的研究现状[J]. 钢铁研究学报, 2018, 30(7): 505-514.
Tian Yaqiang, Tian Geng, Zheng Xiaoping, et al. Research status of low carbon high strength bainitic steel[J]. Journal of Iron and Steel Research, 2018, 30(7): 505-514.
[7] 罗平. 基于组织调控改善贝氏体钢轨钢的抗磨损和抗接触疲劳性能[D]. 北京: 北京交通大学, 2016.
Luo Ping. Modification the resistance to wear and RCF for bainitic railway by tailoring microstructure[D]. Beijing: Beijing Jiaotong University, 2016.
[8] 张家涛, 王洪纲, 钟毅. 加热奥氏体化过程的数学模拟[J]. 昆明理工大学学报, 1997, 22(1): 135-138.
Zhang Jiatao, Wang Honggang, Zhong Yi. Mathsmatical anology on process of austenizing during heating[J]. Journal of Kunming University of Science and Technology, 1997, 22(1): 135-138.

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