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오경식,박중길 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.10
The solidification behavior of steel in continuous casting billet mold was examined by plant test, i. e. tracer(FeS) test in mold and solidification modelling. From the above test, it has been found that solid shell grows linearly with time regardless of steel grades in billet mold. Solidification constant k was found to be 32-37㎜/min for low carbon (C%=0.07-0.19) steel, 41-44㎜/min for high carbon(C%=0.40-0.73) steel, respectively. Unevenness of solid shell along the transversal and longitudinal direction for the low carbon steel grade which solidifies as δ ferrite initially was greater than that of high carbon steel grade. When applied an in-mold electro-magnetic stirring(MEMS), solid shell formed uniformly in thickness direction. Finally, measured solid shell profiles in mold were found to agree well with the calculated results from the solidification modelling.
이상목,홍준표,박중길,이성윤 한국주조공학회 2000 한국주조공학회지 Vol.20 No.5
A three-dimensional model was developed in order to simulate heat and fluid flow of a continuous casting billet. The model was coded with the general-purpose CFD program FIDAP, using the finite element method. The present model consists of 2 individual calculation schemes, named model 1 and model 2. Mold region only was calculated to check the pouring stream through submerged nozzle with model 1. Entire region, which consists of mold, secondary cooling, radiation cooling was calculated to predict crater end position, temperature profile and solid shell profile(model 2). Standard k-A^ turbulence model has been applied to simulate the turbulent flow induced by submerged nozzle. Enthalpy method was adopted for the latent heat of solidification. Fluid flow in mushy zone was treated using variable viscosity approach. The more casting speed and superheat increased, the more metallurgical length increased. The shell thickness at the mold exit is proved to be mainly controlled by superheat by the present simulation. It may be concluded that the present model can be successfully applied far the prediction of heat and fluid flow behavior in the continuous casting process.
연주 빌렛 주편의 표층부결함및 편석 저감에 미치는 주형내 전자교반의 영향
장영원,오경식,박중길 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.9
The effect of an in-mold electro-magnetic stirring(MEMS) on the subsurface defects and macrosegregation in the CC billets has been examined by a plant test and a new evaluation method. The reduction behavior of macrosegregation by a combination stirring has also been discussed through analyzing the thicknesswise cast structures at the centre region and mushy zone depending on the various EMS conditions. It is found that the subsurface defects and macrosegregation can effectively be reduced under an optimum stirring condition. The reduction of macrosegregation in CC billets by (M+S+F) EMS appears to be caused by 1) increasing the flow resistance of solute enriched interdendritic liquid in the mushy zone due to highly close-packed fine equiaxed crystals, 2) decreasing the flow distance of solute enriched interdendritic liquid in the mushy zone due to increased solidification rate at the centre region, and 3) decreasing ferrostatic pressure at the time of macrosegregation formation caused by the shortened distance of crater end.
이상헌,오규환,임창희,박중길,한흥남,최주,이동녕 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.1
Thermal deformation of slab mold during continuous casting was analysed by the coupled finite element method with heat and thermo-elasto-plastic deformation. In order to consider the effect of air gap on the heat transfer coefficient between strand and mold, thermal deformation of strand and temperature distributions in strand and mold were calculated. The effects of mold thickness, temperature of cooling water, velocity of cooling water and mold taper on deformation of mold was investigated. The deformation of mold was due to the difference of thermal expansion between mold and supporting plate of mold. During heating in continuous casting process, mold was deformed toward the strand, while mold was deformed toward the supporting plate of mold during cooling. The amount of deformation increased with increasing the hot face temperature in mold.
이상목,김성빈,홍준표,박중길,이성윤 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.5
A coupled numerical model was developed to predict macrosegregation in continuously cast steel billets. Continuum formulation was adopted to investigate macroscopic transport behavior of momentum, heat and species in the continuous casting process. In order to model fluid flow damping in the mushy zone solidification was considered to occur in two successive stages. In the first stage with the solid fraction below a certain critical value, the relative viscosity concept was employed to treat fluid flow in the dilute mushy zone. In the second stage with the solid fraction above critical value, the permeability concept was used to treat the concentrated mushy zone as a porous medium. Turbulent fluid flow during continuous casting was treated by the standard k-ε model. Thermal and solutal convections were also considered in the simulation of solute redistribution in the mushy zone. The effect of interdendritic flow on surface temperature, metallurgical length and centerline segregation were investigated. It is suggested that the present model can be successfully applied to simulate the macrosegregation in continuous casting of steel billets.