Effect of Superheat on Integral Morphology Characteristics of Solidification Structure and Permeability in Bearing Steel Billet

被引:2
作者
Cao Jianghai [1 ,2 ]
Hou Zibing [1 ,2 ]
Guo Zhongao [1 ,2 ]
Guo Dongwei [1 ,2 ]
Tang Ping [1 ,2 ]
机构
[1] Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400044, Peoples R China
[2] Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China
关键词
superheat; solidification structure; fractal dimension; specific surface area; permeability; bearing steel; SEGREGATION; DENDRITE;
D O I
10.11900/0412.1961.2020.00274
中图分类号
TF [冶金工业];
学科分类号
0806 ;
摘要
As a typical bearing steel, GCr15 steel tends to solidify over a wide temperature range during casting because of its high carbon content. The size of the mushy zone is relatively large, causing macrosegregation and porosity defects in bearing steel. The morphology of the solidification structure plays an important role in governing macrosegregation severity. Solidification structures have conventionally been characterized by measuring the primary or secondary dendrite arm spacing in a dendritic network, but these measures do not adequately describe the branched appearance of secondary and tertiary arms. In this work, fractal dimension and specific surface area have been introduced, and the solidifica-tion structure integral morphology characteristics of different locations in the continuous casting billet of GCr15 bearing steel have been quantitatively investigated. Then, the permeability of the interdendritic channels were calculated based on fractal dimension and specific surface area. The size of the billets was 220 mm x 220 mm, and the sampling location was in the cross section of the billet. Two superheats (20 and 35 degrees C) were considered for studying the integral characteristics of the solidification structure. First, fractal dimension can describe the self-similar complexity of the solidification structure, and specific surface area can describe dendritic coarsening. Second, it was determined that the fractal dimension was larger and the specific surface area was smaller at 35 degrees C superheat compared with 20 degrees C superheat. This indicates that the self-similar complexity of dendrites is larger, and the dendrite coarsening is more significant at high superheating. Finally, the permeability in the equiaxed grain zone calculated using fractal dimension and specific surface area is lower at 20 degrees C superheat. The smaller the permeability, the greater the flow resistance of the liquid, which is more conducive to the control of the macrosegregation defects. In addition, to effectively restrain the formation of macrosegregation defects at high superheat, the cooling rate in the equiaxed grains zone should increase by adjusting the process parameters under isothermal solidification conditions.
引用
收藏
页码:586 / 594
页数:9
相关论文
共 32 条
[1]   Mechanism for Complex Morphology Due to Mechanical Vibration [J].
Aritaka, Eiichi ;
Esaka, Hisao ;
Shinozuka, Kei .
ISIJ INTERNATIONAL, 2016, 56 (08) :1413-1419
[2]   The fractal dimension of xenon dendrites [J].
Bisang, U ;
Bilgram, JH .
JOURNAL OF CRYSTAL GROWTH, 1996, 166 (1-4) :207-211
[3]   Morphology characteristics of solidification structure in high-carbon steel billet based on fractal theory [J].
Cao, Jianghai ;
Hou, Zibing ;
Guo, Dongwei ;
Guo, Zhongao ;
Tang, Ping .
JOURNAL OF MATERIALS SCIENCE, 2019, 54 (19) :12851-12862
[4]  
[曹江海 Cao Jianghai], 2019, [钢铁研究学报, Journal of Iron and Steel Research], V31, P286
[5]  
CARMAN PC, 1956, FLOW GASES POROUS ME, P10
[6]   Three-dimensional fractal analysis of fracture surfaces in titanium-iron particulate reinforced hydroxyapatite composites: relationship between fracture toughness and fractal dimension [J].
Chang, Q. ;
Chen, D. L. ;
Ru, H. Q. ;
Yue, X. Y. ;
Yu, L. ;
Zhang, C. P. .
JOURNAL OF MATERIALS SCIENCE, 2011, 46 (18) :6118-6123
[7]   Morphology and segregation in continuously cast high carbon steel billets [J].
Choudhary, S. K. ;
Ganguly, Suvankar .
ISIJ INTERNATIONAL, 2007, 47 (12) :1759-1766
[8]   EVALUATING THE FRACTAL DIMENSION OF PROFILES [J].
DUBUC, B ;
QUINIOU, JF ;
ROQUESCARMES, C ;
TRICOT, C ;
ZUCKER, SW .
PHYSICAL REVIEW A, 1989, 39 (03) :1500-1512
[9]   Our understanding of macrosegregation: Past and present [J].
Flemings, MC .
ISIJ INTERNATIONAL, 2000, 40 (09) :833-841
[10]   Effect of solidification conditions on fractal dimension of dendrites [J].
Genau, Amber L. ;
Freedman, Alex C. ;
Ratke, Lorenz .
JOURNAL OF CRYSTAL GROWTH, 2013, 363 :49-54