발간논문

Home > KJMM 논문 > 발간논문

Numerical analysis is made to see how to control the defects caused by fluid flow and solidification in the casting process. With SIMPLER algorithm the Marker Method that is induced in the MAC or SMAC method has been adopted to analyse the behavior of the free surface in the mold. The normal and the tangential stress condition have been used as free surface boundary conditions. The flow field and thermal behavior is investigated from the start of the filling process to the final solidification. The flow is assumed to be 2-D, incompressible, and laminar, and the material is pure aluminium. Calculation domain was organized on the basis of the staggered mesh generation. For one model, different inlet condition has been applied to estimate the flow, solidification, the free surface position, and the phase change surface motion. This result is helpful to find the most desirable mold design.

keyword :

For the purpose of establishing basic data to purify silver, the adsorption behavior of Cu(II) ion on AgCl in aqueous solution was studied in the presence of chloride ion. The results obtained were as follows : 1. The adsorption of Cu(II) ion on AgCl increases with increasing the concentration of NaCl, and it is reasonable to assume that CuCl- is supposed to be adsorbed. And Langmuir adsorption isotherm, when applied to the isotherm data, was obeyed. 2. The adsorption of Cu(II) ion on AgCl with HCI is about half as much as that with NaCl. 3. In the presence of Ag- ion of higher concentration, the adsorption of Cu(II) ion on AgCl is similar to that which has been shown to be adsorbed with HCl. 4. The adsorption of Cu(II) ion on AgCl decreases with increasing the temperature, and the enthalpy of adsorption is -8.0kJ/mol.

keyword :

The manganese reaction between the CaO-MgO-Fe1O-SiO2-MnO-ΣMxOy, slags saturated with MgO and molten iron was investigated by changing the MnO content from 2 to 30wt% in the temperature range of 1823K to 1973K. The activity coefficient of MnO and the manganese distribution were quantified in terms of the slag composition and temperature. The results obtained are as follows; 1) The activity coefficient of MnO is revealed to be dominated by the contents of Fe1O and MnO, and hardly affected by basicity and temperature. It can be written as follows; log γ MnO = -1.079(NMnO + 0.9NFeto) + 0.6394. 2) The equilibrium quotient kMn is controlled by basicity, and shows less correlation with contents of Fe1O and MnO. The following equation is obtained. logkMn = 0.00l[-1.651(%CaO) + 39.13(%MgO) + 4.64(%Fe1O) + 5.133(%MnO) + 11.86(%SiO2) - 99.7(%P2O5)] + 8086/T - 4.262

keyword :

X-ray fluoroscopy was applied to directly observe the smelting reduction phenomena of iron are at high temperatures ranging from 1400℃ to 1550℃. Two types of reductants, graphite crucible and carbon-saturated molten iron, were used to study the difference of physical behavior. In the smelting reduction by carbon in the graphite crucible, it was shown from the observation results that the smelting reduction proceeded by the following two stages; initial quiet reduction without foaming(stage 1), and next highly active reduction with severe foaming(stage 2). The foaming phenomenon was found to be caused by the inside reaction between carbon in the carburized iron layer and the molten iron oxide(FexO). In the smelting reduction by carbon in the molten iron, it was also observed that carbon should be fully saturated in the molten iron to prevent the foaming phenomena. Prereduction to 30% enhanced the melting rate of iron ore and reduced the total reaction time. Therefore, using iron are in the form of wustite, in the real smelting reduction process, is thought to be most economical.

keyword :

Kinetics of the smelting reduction of iron ore by the graphite crucible and the carbon-saturated molten iron was investigated between 1400℃ and 1550℃. At 1500℃. by the graphite crucible, the reduction rate of iron ore was found to be 8.88 × 10-5mol/cm2·sec, and by the molten iron, 8.25 × 10-5mol/cm2·sec. The activation energies for the reduction by the graphite crucible and the molten iron were 24.1kcal/mol and 22.9kcal/mol, respectively. For the smelting reduction by the graphite crucible, it was found from the comparison of each elementary reaction rate that the overall reaction was controlled by the chemical reaction(C+CO2=2CO) between carbon in the carburized iron and CO2 gas. Based on the results of present research and X-ray fluoroscopic observation, it could be concluded that these two reduction reactions of iron ore by the graphite crucible and the molten iron are essentially the same.

keyword :

The present study is concerned with TiN/carbon steel functionally gradient materials (FGM) processed by an irradiation of high-energy electron beam. The mixtures of TiN powders and flux were deposited on a plain carbon steel plate, and were irradiated using an electron accelerator. The microstructures of the irradiated surface layers were examined by optical and scanning electron microscopy. Residual pores, TiN powder agglomerates, and interior quench cracks were found in the sample processed without flux, whereas these defects were hardly observed in the samples processed with a considerable amount of flux. As a result of irradiation, the Ti content decreased along the depth from the irradiated surface, thereby yielding the characteristics of FGM. The hardness of the irradiated surface layer was greatly improved, which is associated with the microstructural modification including the formation of fine cuboidal Ti (C,N) particles.

keyword :

A dual halogen lamp heating system of ZMR process was applied to control the temperature gradient on an Si film deposited on an SiO2 layer. Temperature gradient on the Si film was closely related to the character of crystalline defects such as subboundaries found in the Si film. Computer simulation was also performed to verify the experimental results. The effect of the second lamp was very similar with that of the lower pre-heating lamp. As the intensity of light emitted from the second lamp increased, the morphology of the defects was changed from even sub-grainboundary into feather-like pattern and this result could be identified by the computer simulation. While unfocused side lamp just over the film made only a little effects on the defects spacing, the controlling the defects spacing needed another lamp which should be focused.

keyword :

A new method of low temperature(≤500℃) crystallization of a-Si films was developed and crystallization mechanism was proposed. A few tens of micron long area from Patterned Pd films area could be crystallized in a short time at 500℃ by Metal-Induced Lateral Crystallization without any metal incorporations. The mechanism of the enhanced crystallization of a-Si film was studied by the microstructure analysis at the initial stage of the crystallization, by which the mechanism of MILC can be explained. In the case of Pd, crystallization of a-Si was initiated at the preformed Pd2Si in an a-Si matrix. The Pd2Si precipitates were separated into fine particles, and propagated into the a-Si matrix transforming a-Si into c-Si behind themselves. The growing direction of crystallized Si was <111>, which coincided with the epitaxial direction of Si with Pd2Si.

keyword :