Effect of cooling rate on microstructure and properties of microalloyed medium carbon non-quenched and tempered steel

doi:10.13251/j.issn.0254-6051.2022.07.005

Abstract

Abstract: Heat treatment was adopted to simulate the coarse microstructure of microalloyed medium carbon non-quenched and tempered steel for crankshaft after closed-die forging with small deformation amount, the corresponding mechanical properties were tested, and the effects of cooling rate and microalloying elements Ti, Nb on microstructure and mechanical properties of the tested steels was studied. The results show that the comprehensive mechanical properties of V-Ti-Nb steel after furnace cooling are the best: the tensile strength, yield strength, elongation and impact absorbed energy are 960.6 MPa, 672.1 MPa, 17.5% and 22.9 J, respectively. With the increase of cooling rate, the tensile strength and yield strength are increased by nearly 120 MPa, the plasticity is decreased due to the existence of bainite, but the impact property is nearly unchanged due to the refinement of prior austenite grain size. With the addition of Ti and Nb, the yield strength is increased by 76.5 MPa due to the precipitation strengthening of (V, Ti, Nb)(C, N) and the refinement of pearlite interlamellar spacing, and in addition, the impact property of the V-Ti-Nb steel is improved mainly due to the refinement of both the pearlite interlamellar spacing and the prior austenite grain size.

Key words: non-quenched and tempered steel, microalloying, cooling rate, small deformation amount, mechanical properties

CLC Number:

TG142.1

Tian Ziwei, Yao Yanxin, Liu Jiaxing, Wang Zhiyi, Hu Zhangquan, Jiang Bo. Effect of cooling rate on microstructure and properties of microalloyed medium carbon non-quenched and tempered steel[J]. Heat Treatment of Metals, 2022, 47(7): 27-33.

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