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The initial growing dendrite is influenced significantly by the complicated solidification conditions in continuously oscillating mold. The uneven growth of dendrite causes some defects seen commonly such as internal crack, subsurface porosity, subsurface inclusion and other defects of continuous casting billet. The induced initial defects in mold can be expanded and propagated in the following process such as secondary cooling, straightening, rolling and other subsequent handling procedure and then evolve into serious defects that can restrict the development and the quality refinement of final steel products. The mechanical stress caused by mold oscillation and the melt flowing is a crucial factor that leads to the uneven microstructure growth of initial solidifying shell in continuous casting mold. In this work, we simulate the growth and the morphology evolution of primary dendrites in mold area by using the cellular automaton (CA) method in combination with the actual conditions for continuously cast low carbon billet (Fe-0.6 wt.%C). Further, the mechanical state of initial dendrite is analyzed by regarding primary dendrite as a cantilever beam and its mechanical stress is calculated by combining thermo-physical properties and flow rate of steel based on the principle of materials mechanics to shed light on the formation of initial defects formation in mold area of continuous casting process. The results show that the solute concentration of initial dendrite tip gradually increases with undercooling from 2 to 10 K, and the maximum concentration rises by 0.07% when the increment of undercooling is 2 K. The length of dendrite arm increases significantly with undercooling from 2 to 6 K. However, the length of dendrite arm remains steady in a stable growth rate of 0.08 mms-1 when the undercooling is enhanced from 6 to 10 K. The increase of undercooling reduces the bending stress at dendrite root when the flow rate of molten steel is improved from 0.13 to 0.33 ms-1, while the mechanical stress continuously increases with the growth of primary dendrite at a constant undercooling. The bending stress of dendrite root has a high possibility to exceed its critical fracture strength under the condition of undercooling below 6 K or dendrite grow up more than 1 s. The primary dendrite is likely to be fractured and form initial defects of billet.
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Keywords:
- continuously cast low carbon steel /
- primary dendrites /
- growth and stress /
- cellular automaton method
[1] Chen R, Xu Q Y, Liu B C 2014 Acta Phys. Sin. 63 449 (in Chinese) [陈瑞, 许庆彦, 柳百成 2014 物理学报 63 449]
[2] Dou K, Qing J S, Wang L, Zhang X F, Wang B, Liu Q, Dong H B 2014 Acta Metall. Sin. 50 1505 (in Chinese) [窦坤, 卿家胜, 王雷, 张晓峰, 王宝, 刘青, 董洪标 2014 金属学报 50 1505]
[3] Li R, Shen H D, Feng C M, Pan H, Feng C N 2013 Acta Phys. Sin. 62 188106 (in Chinese) [李日, 沈焕弟, 冯长海, 潘红, 冯传宁 2013 物理学报 62 188106]
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[7] Han R H, Dong W C, Lu S P, Li D Z, Li Y Y 2014 Acta Phys. Sin. 63 228103 (in Chinese) [韩日宏, 董文超, 陆善平, 李殿中, 李依依 2014 物理学报 63 228103]
[8] Hesselbarth H W, Göbel I R 1991 Acta Metall. Mater. 39 2135
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[14] Zhu M F, Hong C P 2001 ISIJ Int. 41 436
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[16] Kundu S, Dutta M, Ganguly S, Chandra S 2004 Scr. Mater. 50 891
[17] Lan Y J, Li D Z, Li Y Y 2004 Acta Mater. 52 1721
[18] Qian M, Guo Z X 2004 Mater. Sci. Eng. A 365 180
[19] Zheng Y X, Niu L S 2009 Comput. Mater. Sci. 46 443
[20] Dahle A K, Arnberg L 1997 Acta Mater. 45 547
[21] Dahle A K, Thevik H J, Arnberg L 1999 Metall. Mater. Trans. B 30 287
[22] Pilling J, Hellawell A 1996 Metall. Mater. Trans. A 27 229
[23] Meng X N, Lin R G, Yang J, Zuo X J, Zhu M Y 2015 J. Iron. Steel Res. Int. 22 1085
[24] Zuo X J, Lin R G, Wang N, Yang J, Meng X N, Zhu M Y 2016 Steel Res. Int. 87 413
[25] Lazaro B S, Doru M S 2003 Metall. Mater. Trans. A 34 367
[26] Nastac L 1999 Acta Mater. 47 4253
[27] Gaskell D R 1992 An Introduction to Transport Phenomena in Materials Engineering (New York: MacMillan Publishing Company) p125
[28] Lipton J, Glicksman M E, Kurz W 1984 Mater. Sci. Eng. 65 57
[29] Alizadeh M, Jahromi A J, Abouali O 2008 ISIJ Int. 48 161
[30] Flemings M C 1991 Metall. Mater. Trans. B 22 269
[31] Meng Y, Thomas B G 2003 Metall. Mater. Trans. B 34 685
[32] Kubota J 1990 Sixth International Iron and Steel Congress Proceeding Nagoya, Japan, October 21-26, 1990 p356
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[1] Chen R, Xu Q Y, Liu B C 2014 Acta Phys. Sin. 63 449 (in Chinese) [陈瑞, 许庆彦, 柳百成 2014 物理学报 63 449]
[2] Dou K, Qing J S, Wang L, Zhang X F, Wang B, Liu Q, Dong H B 2014 Acta Metall. Sin. 50 1505 (in Chinese) [窦坤, 卿家胜, 王雷, 张晓峰, 王宝, 刘青, 董洪标 2014 金属学报 50 1505]
[3] Li R, Shen H D, Feng C M, Pan H, Feng C N 2013 Acta Phys. Sin. 62 188106 (in Chinese) [李日, 沈焕弟, 冯长海, 潘红, 冯传宁 2013 物理学报 62 188106]
[4] Chopra M A, Glicksman M E, Singh N B 1988 Metall. Mater. Trans. A 19 3087
[5] Koss M B, Lacombe J C, Tennenhouse L A 1999 Metall. Mater. Trans. A 30 3177
[6] Nastac L, Stefanescu D M 1996 Trans. Am. Found. Soc. 104 425
[7] Han R H, Dong W C, Lu S P, Li D Z, Li Y Y 2014 Acta Phys. Sin. 63 228103 (in Chinese) [韩日宏, 董文超, 陆善平, 李殿中, 李依依 2014 物理学报 63 228103]
[8] Hesselbarth H W, Göbel I R 1991 Acta Metall. Mater. 39 2135
[9] Gandin C A, Desbiolies J L, Rappaz M 1999 Metall. Mater. Trans. A 30 3153
[10] Gandin C A, Rappaz M 1994 Acta Metall. Mater. 42 2233
[11] Rappaz M, Gandin C A 1993 Acta Metall. Mater. 41 345
[12] Kermanpur A, Evans D G, Siddall R J 2004 J. Mater. Sci. 39 7175
[13] Yamazaki M, Natsume Y, Harada H 2006 ISIJ Int. 46 903
[14] Zhu M F, Hong C P 2001 ISIJ Int. 41 436
[15] Nastac L 2012 Mater. Sci. Technol. 28 1006
[16] Kundu S, Dutta M, Ganguly S, Chandra S 2004 Scr. Mater. 50 891
[17] Lan Y J, Li D Z, Li Y Y 2004 Acta Mater. 52 1721
[18] Qian M, Guo Z X 2004 Mater. Sci. Eng. A 365 180
[19] Zheng Y X, Niu L S 2009 Comput. Mater. Sci. 46 443
[20] Dahle A K, Arnberg L 1997 Acta Mater. 45 547
[21] Dahle A K, Thevik H J, Arnberg L 1999 Metall. Mater. Trans. B 30 287
[22] Pilling J, Hellawell A 1996 Metall. Mater. Trans. A 27 229
[23] Meng X N, Lin R G, Yang J, Zuo X J, Zhu M Y 2015 J. Iron. Steel Res. Int. 22 1085
[24] Zuo X J, Lin R G, Wang N, Yang J, Meng X N, Zhu M Y 2016 Steel Res. Int. 87 413
[25] Lazaro B S, Doru M S 2003 Metall. Mater. Trans. A 34 367
[26] Nastac L 1999 Acta Mater. 47 4253
[27] Gaskell D R 1992 An Introduction to Transport Phenomena in Materials Engineering (New York: MacMillan Publishing Company) p125
[28] Lipton J, Glicksman M E, Kurz W 1984 Mater. Sci. Eng. 65 57
[29] Alizadeh M, Jahromi A J, Abouali O 2008 ISIJ Int. 48 161
[30] Flemings M C 1991 Metall. Mater. Trans. B 22 269
[31] Meng Y, Thomas B G 2003 Metall. Mater. Trans. B 34 685
[32] Kubota J 1990 Sixth International Iron and Steel Congress Proceeding Nagoya, Japan, October 21-26, 1990 p356
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