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| Microstructure and mechanical properties of nanobainitic steel subjected to multiple isothermal heat treatments |
| Ning Liu1? Xin Zhang1 ? Jing Ding1 ? Jun He1 ? Fu-xing Yin1 |
| 1 School of Material Science and Engineering and Research Institute for Energy Equipment Materials, Hebei University of Technology, Tianjin 300130, China |
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Abstract Nanostructured bainite in 62MnSiCr steel was prepared by two-stage transformation process at different temperatures for less than 2 h. Microstructures, phase distribution and mechanical properties of the obtained steel were investigated. The results showed that the thickness of bainite plate and the amount of retained austenite decreased obviously after the twostage transformation, while the carbon concentration in the retained austenite showed a small change. With increase in the second holding temperature within the bainite transformation range, all of them increased slightly. The additional formation of bainite at the second transformation stage is beneficial to refining the austenite and further enriching it with carbon, resulting in the enhancement of the mechanical stability. Bainite transformed in two-stage process showed a better comprehensive performance. Absorbed impact energy of 88 J and an ultimate tensile strength of 1818 MPa have been achieved by isothermal heat treatment at 300 C followed by 260 C. Meanwhile, there was a slight change in mechanical properties when the second transformation temperature varied from 260 to 220 C.
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Received: 11 September 2017
Published: 14 November 2018
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2018, Vol. 25 
