Modelling of Inclusion Effects on Macrosegregation in Solidifying Steel Ingot with a Multi-phase Approach
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steel ingots are high demand in many industrial applications, such as, for use in nuclear power plants, in aerospace equipment, and for heavy industrial machinery. During the long-term solidification process, inevitable casting defects such as macrosegregation and inclusions are formed. These defects pass through the downstream hot working processing procedure, leading to a severe heterogeneous structure to eventually cause fatal failures. In the 1970s, Flemings[1] first suggested that macrosegregation is derived from the density difference between liquid and solid during solidification. Up to DUANXING CAI and FENGLI REN are with the School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. HONGHAO GE is with the Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou 310014, China. HEE-SOO KIM is with the Department of Materials Science & Engineering, Chosun University, Gwangju 501759, Korea. JUN LI is with the School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, China and also with the Department of Engineering, University of Leicester, Leicester LE1 7RH, UK. JIANGUO LI is with the School of Materials Science and Engineering, Shanghai Jiao Tong University and also with the Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, China. Contact e-mail: [email protected] Manuscript submitted April 4, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
now, it’s believed that macrosegregation is generated by many mechanisms: thermal-solutal buoyancy,[2] fluid flow induced by sedimentation/floatation of solid grains (equiaxed crystals[3] and inclusions[4]), and the shrinkage force of solidification contraction. Apart from theoretical[5] and experimental analyses,[1,6] verified solidification models are of great necessity to predict the formation of macrosegregation in large ingots from the perspective of practicality and economy. Considerable improvements to the numerical simulation of segregation has been made since the pioneering studies of Flemings and co-workers[7] in the mid-1960s and Fujii et al.[8] developed the first mushy zone model at the end of the 1970s. In the 1990s, Wang et al.[9] coupled solid phase transport and melt convection together as two of the most important and fundamental processes of solidification. Researchers have improved the aforementioned two-phase model in the last twenty years by studying the effect of morphology, the motion of equiaxed grains[10] and developing new formulations, such as a mixed three-phase (i.e. melt, stationary columnar trunks and moving equiaxed grains) approach created by Wu.[11] Li et al.[12] elucidated a model combining the consideration of these three phases. The model successively predicted the quasi A-segregation and the negative base segregation and was in good agreement with experimental results. Additionally, the effects of ingot size on the formation of macrosegregation was also investigated by their
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