Effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of high-strength boron steel
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- Title
- Effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of high-strength boron steel
- Authors
- Dong Jun Mun; Eun Joo Shin; Young Won Choi; Jae Sang Lee; Koo, YM
- Date Issued
- 2012-05-30
- Publisher
- Elsevier
- Abstract
- The phase transformation behavior of high-strength boron steel was studied considering the segregation and precipitation behavior of boron (B). The effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of B-bearing steel as compared with B-free steel were investigated by using dilatometry, microstructural observations and analysis of B distribution. The effects of these variables on hardenability were discussed in terms of non-equilibrium segregation mechanism and precipitation behavior of B. The retardation of austenite-to-ferrite transformation by B addition depends strongly on cooling rate (CR); this is mainly due to the phenomenon of non-equilibrium grain boundary segregation of B. The hardenability effect of B-bearing steel decreased at higher austenitizing temperature due to the precipitation of borocarbide along austenite grain boundaries. Analysis of B distribution by second ion mass spectroscopy confirmed that the grain boundary segregation of B occurred at low austenitizing temperature of 900 degrees C, whereas B precipitates were observed along austenite grain boundaries at high austenitizing temperature of 1200 degrees C. The significant increase in B concentration at austenite grain boundaries due to grain coarsening and a non-equilibrium segregation mechanism may lead to the B precipitation. In contrast, solute B segregated to austenite grain boundaries during cooling after heavy deformation became more stable because the increase in boundary area by grain refinement does not cause B concentration at grain boundaries to exceed the critical point; thus the effect of B on hardenability could be maximized under controlled cooling after hot deformation. Therefore, the austenite grain size and non-equilibrium segregation behavior of B are important variables that determine the magnitude of the hardenability effect of B in steel. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.
- Keywords
- Boron; Non-equilibrium segregation; Austenite-to-ferrite transformation; High-strength steel; Hardenability; GRAIN-BOUNDARY SEGREGATION; LOW-CARBON STEELS; PRECIPITATION BEHAVIOR; HARDENABILITY; DECOMPOSITION; MO
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/15599
- DOI
- 10.1016/J.MSEA.2012.03.047
- ISSN
- 0921-5093
- Article Type
- Article
- Citation
- Materials Science and Engineering: A, vol. 545, page. 214 - 224, 2012-05-30
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- There are no files associated with this item.
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