TiN/NbC Compound Particle Formation during Thin Slab Direct Rolling of HSLA Steel
SCIE
SCOPUS
- Title
- TiN/NbC Compound Particle Formation during Thin Slab Direct Rolling of HSLA Steel
- Authors
- Lee, Y; De Cooman, BC
- Date Issued
- 2014-07
- Publisher
- WILEY-V C H VERLAG GMBH
- Abstract
- Compound two-phase particles were found in thin slab direct rolled Ti-added Nb high strength low alloy (HSLA) steel after the rough rolling stage of an in-line strip processing line. The compound two-phase particles are composed of a cuboid Ti-rich (TixNb1-x) N (0.73 >= x>0.60) core and an Nb-rich cap-shaped epitaxial deposit of (TixNb1-x)C (0.35 >= x> 0.06) or NbC formed on the {100}-type faces of the cuboid (TixNb1-x)N (0.73 >= x>0.60) core. At the interface between the cuboid core and the cap-shaped deposit, the Ti/(Nb + Ti) atomic ratio was found to increase gradually from a low value of Ti/(Nb + Ti) approximate to 0, on the cap-side of the particles, to a high value of Ti/(Nb + Ti) approximate to 0.7, on the cuboid core side of the precipitate. The fact that compound TiN/NbC two-phase particles are present in the matrix indicates that NbC has a greater thermodynamic stability, i.e. a lower solubility, in the presence of TiN precipitates. A kinetic precipitation model is proposed to explain this effect. The model is based on the formation of geometrically necessary dislocation (GND) around TiN precipitates. A high TiN volume fraction leads to a high density of GND and a high density of heterogeneous nucleation sites for NbC. Consequently, the solute Nb content is lowered and the strain accumulation due to the suppression of the inter-pass recrystallization is limited. This results in the high softening ratio observed in multi-hit compression test.
- Keywords
- thin slab direct rolling; hot deformation; microalloying; softening ratio; COMPLEX HETEROGENEOUS PRECIPITATION; DYNAMIC RECRYSTALLIZATION; GAMMA-IRON; GRAIN-REFINEMENT; AUSTENITE; SOLUBILITY; NITRIDE; CARBON; TEMPERATURE; CARBIDES
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/14326
- DOI
- 10.1002/SRIN.201300280
- ISSN
- 1611-3683
- Article Type
- Article
- Citation
- STEEL RESEARCH INTERNATIONAL, vol. 85, no. 7, page. 1158 - 1172, 2014-07
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