Microstructure and mechanical properties of Nb-B bearing low carbon steel plate: Ultrafast cooling versus accelerated cooling |
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Authors: | Bingxing Wang Fuzhi Dong Zhaodong Wang Misra Rdk Guodong Wang |
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Affiliation: | 1.State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang,China;2.Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials Research and Innovation and Department of Metallurgical and Materials Engineering,University of Texas at El Paso,El Paso,USA |
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Abstract: | The microstructure and mechanical properties of low carbon bainite high strength steel plate were studied via different cooling paths at the pilot scale. There was a significant increase in mechanical properties, and notably, the yield strength, tensile strength, and toughness at -40 °C for the tested steel processed by ultra-fast cooling were 126 MPa, 98 MPa and 69 J, respectively, in relation to steel processed by accelerated cooling. The ultra-fast cooling rate not only refined the microstructure, precipitates, and martensiteaustenite (M/A) islands, but also contributed to the refinement of microstructure in thick plates. The large size M/A constituents formed at lower cooling rate experienced stress concentration and were potential sites for crack initiation, which led to deterioration of low-temperature impact toughness. In contrast, the acicular ferrite and lath bainite with high fraction of high-angle grain boundaries were formed in steel processed by ultra-fast cooling, which retarded cleavage crack propagation. |
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