Effect of cooling process on microstructure and properties of 40CrMoNbVTi steel

doi:10.13251/j.issn.0254-6051.2022.12.012

Abstract

Abstract: Effect of cooling process on microstructure and properties of 40CrMoNbVTi steel was studied. The results show that the specimens quenched at 780 ℃, oil cooled and tempered at 550 ℃ have higher tensile strength and impact absorbed energy, which are 1250 MPa and 78.63 J, respectively. After cooling by 20% polyethylene glycol quenching solution, the tensile strength is 1140 MPa, and the impact absorbed energy is 80.7 J. The microstructure is sorbite and a small amount of ferrite after oil cooling and 20% polyethylene glycol quenching solution cooling. The tensile strength of the specimens quenched at 860 ℃, fog cooled/air cooled, and tempered at 550 ℃ is 1010 MPa and 945 MPa respectively, the impact absorbed energy is 35.7 J and 38.4 J, respectively, and the microstructure is tempered sorbite or granular bainite. Quenching at 780 ℃, oil cooling/commercial quenching solution cooling are more suitable quenching cooling processes. The impact fracture mechanism of quenching at 780 ℃, oil cooling/20% polyethylene glycol quenching cooling, tempering at 550 ℃ is ductile fracture, while the impact fracture mechanism of quenching at 860 ℃, fog cooling/air cooling, tempering at 550 ℃ is brittle fracture. Increasing the quenching cooling rate can improve impact fracture morphology.

Key words: 40CrMoNbVTi steel, cooling process, microstructure, properties

CLC Number:

TG142.1

Sun Yongzhen, Cheng Juqiang, Li Meixuan. Effect of cooling process on microstructure and properties of 40CrMoNbVTi steel[J]. Heat Treatment of Metals, 2022, 47(12): 74-77.

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