Heat Treatment Properties of 42CrMo Steel for Bearing Ring of Varisized Shield Tunneling Machine

doi:10.1007/s40195-014-0062-2

Abstract

Abstract:

The heat treatment properties of 42CrMo steel for bearing ring of varisized shield tunneling machine were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and impact tests. The addition of 0.03 wt% C into 42CrMo steel can increase the hardness. But it reduces the impact energy by 46 J because of the appearance of coarser carbides in the matrix and the carbides along the austenite grain boundary. The addition of 0.40 wt% Mn into 42CrMo steel can improve hardenability. However, the toughness of steel is also reduced by 26 J mainly because of the coarsening of carbides and the strengthening of matrix. Both hardenability and toughness of 42CrMo steel can be improved by adding 1.49 wt% Ni and reducing 0.32 wt% Cr. The depth of hardening layer can be raised to 45 mm, and the impact energy at -20 °C is 120 J. Thus, it is concluded that a good combination of hardness, hardenability, and toughness of 42CrMo steel can be achieved by alloying with adding some content of C and Ni. Detailed content of C and Ni should be on the requirements of heat treatment properties of steel for bearing ring of varisized shield tunneling machine.

Key words: Shield tunneling machine, Bearing ring, 42CrMo steel, Hardenability, Toughness

Bo Jiang, Leyu Zhou, Xinli Wen, Chaolei Zhang, Yazheng Liu. Heat Treatment Properties of 42CrMo Steel for Bearing Ring of Varisized Shield Tunneling Machine[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(3): 383-388.

Figures/Tables 8

Table 1 Chemical compositions of 42CrMo steels (in wt%)

Steel	C	Si	Mn	Cr	Mo	Ni	Fe
No. 1	0.39	0.23	0.60	1.08	0.22	0.02	Bal
No. 2	0.39	0.26	1.02	1.02	0.23	0.02	Bal
No. 3	0.39	0.26	0.64	0.76	0.19	1.49	Bal

Fig. 1 Optical microstructures at different distances from surface of different steels a 15 mm, No. 2; b 50 mm, No. 2; c 65 mm, No. 2; d 15 mm, No. 3; e 45 mm, No. 3; f 65 mm, No. 3; g 7 mm, No. 1; h 11 mm, No. 1; i 30 mm, No. 1

Fig. 2 Hardness at different distances from surface of different steels

Fig. 3 SEM images showing the fractographs of the samples after Charpy impact tested: a No. 1; b No. 2; c No. 3; d No. 4

Fig. 4 SEM images showing the microstructures of the tempered steels: a No. 1; b No. 2; c No. 3; d No. 4

Fig. 5 TEM images showing the microstructures of the tempered steel No. 2: a short rod-like carbide; b large spherical carbide

Table 2 Compositions of carbides in different steels (at%)

Steel	Carbide	Cr	Mn	Mo	Ni	Fe
No. 4	A	3.74	4.80	0.87	–	90.58
No. 4	B	15.14	5.99	1.47	–	77.40
No. 4	C	2.97	3.24	0.39	–	93.40
No. 2		7.33	3.52	0.53	–	88.62
No. 3		4.35	3.60	0.58	0.97	90.50

Fig. 6 TEM images showing the microstructures of the tempered steels No. 4 a and No. 3 b

References 17

[1]	S.L. Hu, S.S. Qiao, Const. Mach. 11, 16(1999). (in Chinese)
[2]	Y. Koyama, Tunnelling underground space. Technol. 18, 145(2003). (in Chinese)
[3]	A. Salemi, A. Abdollah-Zadeh, Mater. Charact. 59, 484(2008)10.1016/j.matchar.2007.02.012
[4]	A. Matsuzaki, T. Hoshino, H. Hagihara, Kawasaki. Steel Giho. 34, 104(2002). (in Japanese)
[5]	G.W. Shen, K.Y. Chen, X.S. Xiang, H.G. Fu,Wind Power Bearing Steel, Chinese Patent, No. 201010549735, 2010. (in Chinese)
[6]	B.H.Yu, Computer Design of Steel(Metallurgical Industry Press, Beijing, 1996), pp. 12–21. in Chinese
[7]	P.K. Sokolowski, B.A. Lindsley, Int. J. Powder. Metall. 46, 43(2010)
[8]	X. Xu, L.Q. Zhang, J.C. Wu, Heat Treat. Met. 32, 7(2007). (in Chinese)
[9]	P.A. Manohar, T. Chandra, ISIJ Int. 38, 766(1998)10.2355/isijinternational.38.766
[10]	Y.H. Yang, H.B. Wu, Q.W. Cai, L. Chen, Trans. Mater. Heat Treat. 31, 73(2010). (in Chinese)
[11]	R. Ma, Y.F. Yang, Q.Z. Yan, Y. Yang, X.G. Li, C.C. Ge, Acta Metall. Sin. (Engl. Lett.) 23, 451(2010)
[12]	M. Gojic, L. Kosec, P. Matkovic, J. Mater. Sci. 33, 395(1998)10.1023/A%3A1004375914591
[13]	J.D. Chen, W.L. Mo, P. Wang, S.P. Lu, Acta Metall. Sin. 48, 1186(2012). (in Chinese)
[14]	H.Y. Song, S.H. Zhang, L.Y. Lan, C.M. Li, H.T. Liu, D.W. Zhao, G.D. Wang, Acta Metall. Sin. (Engl. Lett.) 26, 390(2013)10.1007/s40195-012-0183-4
[15]	D.H. Huang, G. Thomas, Metall. Trans. 2, 1587(1971)
[16]	C. Bellot, P. Lamesle, D. Delagnes, Acta Metall. Sin. (Engl. Lett.) 26, 553(2013)10.1007/s40195-013-0078-z
[17]	E.C.BainH.W.Paxton, Alloying Elements in Steel(American Society For Metals, Metals Park, 1966), p. 291