Continuous cooling transformation behavior of a novel low-alloy ferritic low-temperature steel

doi:10.13251/j.issn.0254-6051.2025.04.014

Abstract

Abstract: Influence of cooling rate on the microstructure, hardness, and phase transformation behavior of low-alloy ferritic low-temperature steel was investigated by means of Gleeble-3800 thermal simulator, OM and Vickers hardness tester through thermal expansion method and metallographic-hardness method, and the continuous cooling transformation curve of the low-temperature steel was drawn. The results show that when the cooling rate is 0.1-1 ℃/s, the microstructure of the low-temperature steel is ferrite, pearlite and bainite, and the content of bainite increases continuously with the increase of cooling rate, and the hardness of the low-temperature steel increases from 166 HV0.5 to 217 HV0.5. When the cooling rate is 3-15 ℃/s, the increase of undercooling inhibits the transformation of proeutectoid ferrite, the content of ferrite decreases, and the microstructure of the low-temperature steel is ferrite and bainite, and the microstructure is fine and uniform. The hardness of the low-temperature steel increases continuously and reaches 224-243 HV0.5. When the cooling rate is 20-40 ℃/s, the larger undercooling causes the undercooled austenite to transform into martensite. At this time, the microstructure of the low-temperature steel is ferrite, bainite and a small amount of martensite, and the microhardness continues to increase, reaching the maximum value of 290 HV0.5 at cooling rate of 40 ℃/s. Considering the plasticity, toughness and hardness comprehensively, the optimal controlled cooling range of the novel low-alloy ferritic low-temperature steel is 3-15 ℃/s.

Key words: low-alloy ferritic low-temperature steel, cooling rate, microstructure, hardness, CCT curve

CLC Number:

TG142.1

Chen Li, Gao Jianwen, Zhang Ke, Wei Hongyu, Zhang Mingya. Continuous cooling transformation behavior of a novel low-alloy ferritic low-temperature steel[J]. Heat Treatment of Metals, 2025, 50(4): 95-100.

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