Kinetics and formation mechanisms of intragranular ferrite in V-N microalloyed 600 MPa high strength rebar steel |
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| Authors: | Jing Zhang Fu-ming Wang Chang-rong Li |
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| Affiliation: | 1. School of Metal urgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China;2. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China |
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| Abstract: | To systematically investigate the kinetics and formation mechanisms of intragranular ferrite (IGF), isothermal heat treatment in the temperature range of 450°C to 600°C with holding for 30 s to 300 s, analysis of the corresponding microstructures, and observation of the precipitated particles were conducted in V-N microalloyed 600 MPa high strength rebar steel. The potency of V(C,N) for IGF nucleation was also analyzed statistically. The results show that the dominant microstructure transforms from bainite (B) and acicular ferrite (AF) to grain boundary ferrite (GBF), intragranular polygonal ferrite (IPF), and pearlite (P) as the isothermal temperature increases from 450°C to 600°C. When the holding time at 600°C is extended from 30 s to 60 s, 120 s, and 300 s, the GBF content ranges from 6.0vol%to 6.5vol%and the IPF content increases from 0.5vol%to 2.8vol%, 13.1vol%, and 13.5vol%, respectively, because the ferrite transformation preferen-tially occurs at the grain boundaries and then occurs at the austenite grains. Notably, V(C,N) particles are the most effective nucleation site for the formation of IPF, accounting for 51%of the said formation. |
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| Keywords: | high strength steel ferrite kinetics formation mechanisms nucleation microalloying |
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