Determination and analysis of continuous cooling transformation curves of SWRCH35K steel

doi:10.13251/j.issn.0254-6051.2023.04.004

Abstract

Abstract: Thermal dilatometric curves of SWRCH35K steel were measured by DIL805A thermal dilatometer. The continuous cooling transformation (CCT) curves of the tested steel were drawn by the tangent method combined with the microstructure and hardness. The influence of the cooling rate on microstructure evolution of the tested steel during the continuous cooling process was analyzed. The results show that when the cooling rate is in the range of 0.1-1 ℃/s, the microstructure is polygonal proeutectoid ferrite and pearlite. With the increase of the cooling rate, the microstructure is refined, the content of pearlite increases, and the hardness is 148-165 HV. When the cooling rate is 3 ℃/s, a small amount of Widmanstátten structure and bainite begin to appear, and the hardness increases to 189 HV. When the cooling rate is in the range of 5-50 ℃/s, the ferrite appears as network along the grain boundary, and the acicular Widmanstátten structure increases, the microstructure is composed of ferrite at grain boundary, pearlite, Widmanstátten structure and bainite. When the cooling rate is 30-50 ℃/s, the ferrite content and size are greatly reduced, and the hardness is 225-237 HV. The morphology of pearlite changes differently under different cooling rates. When the cooling rate is small, the morphology of pearlite is mainly lamellar and short rod-shaped, and with a small amount of spherical. With the increase of cooling rate, the proportion of short rod-shaped pearlite increases, and the proportion of the lamellar and spherical pearlite decreases.

Key words: SWRCH35K steel, CCT curve, microstructure, pearlite, hardness

CLC Number:

TG142.1

Wang Zibo, Jiang Chang, Lu Hengchang, Man Tinghui, Zuo Jinzhong, Dong Han. Determination and analysis of continuous cooling transformation curves of SWRCH35K steel[J]. Heat Treatment of Metals, 2023, 48(4): 23-27.

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