Stepping-quenching-partitioning treatment of 20SiMn2MoVA steel and effects of carbon and carbide forming elements
Tóm tắt
A novel heat treatment process, stepping quenching and partitioning (S-Q-P), has been developed to manipulate microstructure and mechanical properties of steels. Based on incomplete partitioning of carbon from martensite to austenite, volume fraction and distribution of the retained austenite resulting from the following quenching of the steels could be effectively controlled, and then the synthesized mechanical properties of the steels would be improved. In this paper, 20SiMn2MoVA steel was treated with conventional quenching-tempering (Q-T), currently prevailing quenching-partitioning (Q-P) and S-Q-P processes, respectively. The results indicated that the volume fraction of the retained austenite of the steel treated by Q-P and S-Q-P processes increased significantly that resulted in the increase of ductility and decrease of strength. The product of strength and ductility of the steel treated by S-Q-P process reached 23.7GPa%, that was increased by about 13% and 7% compared with that after Q-T and Q-P processes, respectively. Compared with the great improvement of the synthesized mechanical property obtained by S-Q-P process with another steel 35SiMn, there would be some factors that deteriorated the effect of S-Q-P process on 20SiMn2MoVA steel. It was found by microstructural testing that the carbide forming elements V and Mo in the steel led to precipitation of carbides during partitioning period and lack of carbon in austenite. As a result, less austenite would remain after final quenching and mechanical properties of the steel would be influenced. The results would be beneficial for understanding the principle of S-Q-P process and improving the design of the S-Q-P steel compositions.
Tài liệu tham khảo
Sarikaya M, Jhingan A K, Thomas G. Retained austenite and tempered martensite embrittlement in medium carbon steels. Metall Mater Trans A, 1983, 14: 1121–1133
Ziaebrahimi F, Krauss G. The evaluation of tempered martensite embrittlement in 4130 steel by instrumented charpy V-notch testing. Metall Mater Trans A, 1983, 14: 1109–1119
Ziaebrahimi F, Krauss G. Mechanisms of tempered martensite embrottlement in medium-carbon steels. Acta Metallurg, 1984, 32: 1767–1778
Matlock D K, Krauss G, Speer J G. Microstructures and properties of direct-cooled microalloy forging steels. J Mater Process Tech, 2001, 117: 324–328
Speer J G, Matlock D K, De Cooman B C, et al. Carbon partitioning into austenite after martensite transformation. Acta Mater, 2003, 51: 2611–2622
Speer J G, Streicher A M, Matlock D K, et al. Quenching and partitioning: A fundamentally new process to create high strength trip sheet microstructures. In: Damm E B, Merwin M J, eds. Austenite Formation and Decomposition. Chicago: Iron & Steel Soc, Prod Phys Met Comm; ASM MSCTS, Phase Transformat Comm; Minerals, Met & Mat Soc, MPMD, 2003. 505–522
Matlock D K, Briutigam V E, Speer J G. Application of the quenching and partitioning (Q&P) process to a medium-carbon high Si microalloyed bar steel. Mater Sci Forum, 2003, 426–432: 1089–1094
Hillert M, Agren J. On the definitions of paraequilibrium and orthoequilibrium. Scripta Mater, 2004, 50: 697–699
Hillert M, Agren J. Reply to comments on “On the definitions of paraequilibrium and orthoequilibrium“. Scripta Mater, 2005, 52: 87–88
Barbacki A, Mikolajski E. Optimization of heat treatment conditions for maximum toughness of high strength silicon steel. J Mater Process Tech, 1998, 78(1–3): 18–23
De Moor E, Lacroix S, Clarke A J, et al. Effect of retained austenite stabilized via quench and partitioning on the strain hardening of martensitic steels. Metall Mater Trans A, 2008, 39: 2586–2595
Li H Y, Lu X W, Li W J, et al. Microstructure and mechanical properties of an ultrahigh-strength 40SiMnNiCr steel during the one-step quenching and partitioning process. Metall Mater Trans A, 2010, 41: 1284–1300
Santofimia M J, Speer J G, Clarke A J, et al. Influence of interface mobility on the evolution of austenite-martensite grain assemblies during annealing. Acta Mater, 2009, 57: 4548–4557
Santofimia M J, Zhao L, Sietsma J. Model for the interaction between interface migration and carbon diffusion during annealing of martensite-austenite microstructures in steels. Scripta Mater, 2008, 59: 159–162
Clarke A J, Speer J G, Matlock D K, et al. Influence of carbon partitioning kinetics on final austenite fraction during quenching and partitioning. Scripta Mater, 2009, 61: 149–152
Kim D H, Speer J G, Kim H S, et al. Observation of an isothermal transformation during quenching and partitioning processing. Metall Mater Trans A, 2009, 40: 2048–2060
Moor E D, Speer J G, Matlock D K, et al. Effect of carbon and manganese on the quenching and partitioning response of CMnSi steels. ISIJ Int, 2011, 51: 137–144
Moor E D, Matlock D K, Speera J G, et al. Austenite stabilization through manganese enrichment. Scripta Mater, 2011, 64: 185–188
Wang F Y, Zhu Y F, Zhou H H. Stepped quenching and partitioning heat treatment process of steels containing carbide formation inhibiting elements. China Patent, 201010569862.8, 2010
Zhu Y F, Zhou H H, Zhong X Y, et al. Incomplete partitioning of carbon and manipulation of microstructure and mechanical properties of steels. Metaphase Research Report for National Basic Research Program of China (“973” Program) with Grant No. 2010CB630805, 2010
Kehoe M, Kelly P M. The role of carbon in the strength of ferrous martensite. Scripta Metallurg, 1970, 4: 473–476