The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Minseok Kim - One of the best experts on this subject based on the ideXlab platform.
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deformation induced center segregation in twin Roll cast high mg al mg strips
Scripta Materialia, 2018Co-Authors: Minseok Kim, Suhyeon Kim, Hyoungwook KimAbstract:Abstract The formation mechanism of center segregation in twin-Roll cast (TRC) Al–Mg strips was studied. The center segregation was found to gradually change from channel segregation to a segregation band with increasing casting speed. Deformation induced by the Roll Separating Force (RSF) was the main mechanism of center segregation in the TRC strips. The dilatant behavior of dendrite cells under the RSF appears to be the main mechanism for the formation of segregation band. At relatively low casting speeds, a low compression rate can cause the liquid to squeeze toward the transverse and melt pool directions to form channel segregation.
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Solidification Structure and Casting Defects in High-Speed Twin-Roll Cast Al-2 mass% Si Alloy Strip
MATERIALS TRANSACTIONS, 2013Co-Authors: Minseok Kim, Shinji KumaiAbstract:Al2mass% Si alloy, which has wide freezing temperature range, was cast using a laboratory-scale vertical-type high-speed twin-Roll caster. The solidification structure and several kinds of casting defects were examined using OM, SEM and SEM-EDS. The results showed that the unstable melt pool condition could cause the surface defects such as the ripple mark, “un-shiny” zone and the inverse segregation. In the present nozzle type, constructing a stable high melt pool level was seemed to be essential to obtain a sound strip with no defect on the strip surface. A large-scale internal cracking along the casting direction was also observed in the high-speed twin-Roll casting of aluminum alloy. The present results revealed that the cracking was related to distribution of the residual liquid in the central band region, which could be contRolled by the Roll Separating Force near the Roll nip. It is considered that the Roll Separating Force caused the shear localization in the central band region and promoted a formation of continuous liquid film in the shear localized region. The liquid film was a cause of the internal cracking when the strip passed through the Roll nip. [doi:10.2320/matertrans.L-M2013824]
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formation of internal crack in high speed twin Roll cast 6022 aluminum alloy strip
Materials Transactions, 2010Co-Authors: Minseok Kim, Yoshiyuki Arai, Yasuharu Hori, Shinji KumaiAbstract:An Al-Mg-Si based 6022 aluminum alloy, which represents a wide freezing temperature range in solidification, was cast through high-speed twin-Roll casting (HSTRC). Under a Roll rotation speed of 60 m/min and an initial Roll Separating Force of 14.1 kN, the cast strip showed a large central crack, which deteriorated a quality of the cast strip. The strip exhibited an equiaxed grain structure at the near-surface region and a band of fine globular grains at the mid-central region. The large central crack was mostly observed at a boundary between the central band and dendritic solidified shell. It was considered that decrease of cooling rate near the minimum Roll gap caused the cracking due to residual liquid. In order to find the condition for defect-free strip casting, HSTRC was carried out under various casting conditions. Large-scale central cracking was prevented when a sufficient Roll Separating Force was applied by increasing a solidification time, or increasing an initial Roll Separating Force. From a direct temperature measurement during the HSTRC using a sensitive thermocouple, it was confirmed that a cooling rate increased with increasing the Roll Separating Force.
Zhengyi Jiang - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of slab edging process by the reproducing kernel particle method considering friction effect
International Journal of Surface Science and Engineering, 2009Co-Authors: Shangwu Xiong, Zhengyi JiangAbstract:A mesh-free approach is used for analysing the effect of the friction factor on three-dimensional steady state slab edging, which is based on the Reproducing Kernel Particle Method (RKPM, Liu et al., 1995) and the material flow formulation for slightly compressible materials (Osakada et al., 1982). In order to cope with the singularity at the corner of the Roll entry, a simple technique with a very thin array of cells at the inlet region adjacent to the plastic deformation zone (Xiong et al., 2003) is used. The results show that the dog-bone shape becomes smaller with the increment of friction factor. The Roll Separating Force and total Rolling torque increase with the friction factor.
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a 3 d finite element method analysis of cold Rolling of thin strip with friction variation
Tribology International, 2004Co-Authors: Zhengyi JiangAbstract:In this paper, a three-dimensional rigid-plastic finite element method (FEM) model to simulate the cold Rolling of thin strip with different friction models is described. The effects of Rolling parameters, such as work Roll diameters and reductions, are analysed in this study. The simulation and experimental values of Rolling pressure and spread (the difference of strip width before and after Rolling) show a good agreement when friction variation in the Roll bite is considered. The Roll Separating Force, spread and forward slip for constant friction and friction variation models are also compared. The friction variation in the Roll bite has a significant effect on the simulation results.
Shinji Kumai - One of the best experts on this subject based on the ideXlab platform.
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Solidification Structure and Casting Defects in High-Speed Twin-Roll Cast Al-2 mass% Si Alloy Strip
MATERIALS TRANSACTIONS, 2013Co-Authors: Minseok Kim, Shinji KumaiAbstract:Al2mass% Si alloy, which has wide freezing temperature range, was cast using a laboratory-scale vertical-type high-speed twin-Roll caster. The solidification structure and several kinds of casting defects were examined using OM, SEM and SEM-EDS. The results showed that the unstable melt pool condition could cause the surface defects such as the ripple mark, “un-shiny” zone and the inverse segregation. In the present nozzle type, constructing a stable high melt pool level was seemed to be essential to obtain a sound strip with no defect on the strip surface. A large-scale internal cracking along the casting direction was also observed in the high-speed twin-Roll casting of aluminum alloy. The present results revealed that the cracking was related to distribution of the residual liquid in the central band region, which could be contRolled by the Roll Separating Force near the Roll nip. It is considered that the Roll Separating Force caused the shear localization in the central band region and promoted a formation of continuous liquid film in the shear localized region. The liquid film was a cause of the internal cracking when the strip passed through the Roll nip. [doi:10.2320/matertrans.L-M2013824]
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formation of internal crack in high speed twin Roll cast 6022 aluminum alloy strip
Materials Transactions, 2010Co-Authors: Minseok Kim, Yoshiyuki Arai, Yasuharu Hori, Shinji KumaiAbstract:An Al-Mg-Si based 6022 aluminum alloy, which represents a wide freezing temperature range in solidification, was cast through high-speed twin-Roll casting (HSTRC). Under a Roll rotation speed of 60 m/min and an initial Roll Separating Force of 14.1 kN, the cast strip showed a large central crack, which deteriorated a quality of the cast strip. The strip exhibited an equiaxed grain structure at the near-surface region and a band of fine globular grains at the mid-central region. The large central crack was mostly observed at a boundary between the central band and dendritic solidified shell. It was considered that decrease of cooling rate near the minimum Roll gap caused the cracking due to residual liquid. In order to find the condition for defect-free strip casting, HSTRC was carried out under various casting conditions. Large-scale central cracking was prevented when a sufficient Roll Separating Force was applied by increasing a solidification time, or increasing an initial Roll Separating Force. From a direct temperature measurement during the HSTRC using a sensitive thermocouple, it was confirmed that a cooling rate increased with increasing the Roll Separating Force.
De-wen Zhao - One of the best experts on this subject based on the ideXlab platform.
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the calculation of Roll torque and Roll Separating Force for broadside Rolling by stream function method
International Journal of Mechanical Sciences, 2012Co-Authors: Shun-hu Zhang, De-wen ZhaoAbstract:Abstract A two-dimensional velocity field for broadside Rolling is proposed by reducing the dual-stream function velocity field. By using the field and the strain vector inner product, an analytical solution of Roll torque and Separating Force for broadside Rolling is first obtained. The theoretical predictions of Roll torque and Separating Force are compared with actual measured data. The result reveals that the proposed solution is appropriate for solving broadside Rolling, and the Roll torque and Separating Force are in good agreement with the actual measured ones since the maximum errors are less than 15%. Moreover, the effects of various Rolling conditions such as thickness reduction, friction factor and shape factor, upon Separating Force, location of neutral angle, and stress state coefficient are discussed systematically.
Hyoungwook Kim - One of the best experts on this subject based on the ideXlab platform.
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deformation induced center segregation in twin Roll cast high mg al mg strips
Scripta Materialia, 2018Co-Authors: Minseok Kim, Suhyeon Kim, Hyoungwook KimAbstract:Abstract The formation mechanism of center segregation in twin-Roll cast (TRC) Al–Mg strips was studied. The center segregation was found to gradually change from channel segregation to a segregation band with increasing casting speed. Deformation induced by the Roll Separating Force (RSF) was the main mechanism of center segregation in the TRC strips. The dilatant behavior of dendrite cells under the RSF appears to be the main mechanism for the formation of segregation band. At relatively low casting speeds, a low compression rate can cause the liquid to squeeze toward the transverse and melt pool directions to form channel segregation.
