• Journal of Korea Foundry Society
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• v.41 no.1
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• pp.11-15
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• 2021

Scrap steel used as a charge material in melting process of cast iron foundry is mostly press scrap. The press scrap usually causes several problems including energy loss, workability, safety, and so on. By charging the shredded scrap instead of the press scrap, it is expected that the above-mentioned problems can be solved. In this study, the power basic units to produce cast iron by using the press and shredded scrap are compared in 3t/h medium-frequency induction melting furnace. Charging the shredded scrap instead of the press scrap was confirmed that the power basic unit is improved by about 15%. The characteristics and restrictions of the usage according to the shape and size of scrap steel were considered.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.3017-3029
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• 2023

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m². The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.6
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• pp.31-37
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• 1993

InSb thin films were fabricated by zone melting recrystallization of In/Sb multilayered thin films prepared by sequential evaporation. Unreacted metal phase or dispersed metal precipitates lowered the electron mobility and the electron mobility increased with development of (111) prefered orientation. Properties of the film could be controlled by changing mzximum temperature and scanning speed, and the electron mobility as high as 12, 000 cm $^2$/Vsec could be obtained under the optimized conditions.

• Journal of environmental and Sanitary engineering
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• v.22 no.1 s.63
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• pp.1-16
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• 2007

The incineration process has commonly used for wastes amount reduction and thermal treatments of pollutants as the technologies accumulated. However, the process is getting negative public images owing to matter of hazardous pollutants emission. Specially dioxins became a main issue and is mostly emitted from municipal solid wastes incineration. In this reason, pyrolysis/gasfication/melting process is presented as a alternative of incineration process. The pyrolysis/gasfication/melting process, a novel technology, is middle of verification of commercial plant and development of technologies in Korea. But the survey about the pollutant emission from the process, and background data in these facilities is necessary. So in this survey, it Is investigated that the behavior of dioxins in three pyrolysis/gasfication/melting plant (S, T, P) of pilot scale. In case of S plant, concentration of dioxins shows high at latter part of cogenerated boiler and stack which are operate on low temperature conditions than a latter parts of pyrolysis and melting furnace which are operate on high temperature condition. Concentration of gas phage dioxins had increased after combusted gas passed cogenerated boiler and this is attributed to react of precursor materials such as chlorobenzene and chlorophenol. Concentration of dioxins in T plant showed lower levels at latter part of cooling equipment which are operate with water spray type on low temperature conditions than a latter parts of gasfied melting furnace which are operate on high temperature condition. Removal efficiency of dioxins at gas treatment equipment was 78.8 %. Concentration of dioxins in P plant was low at latter part of SDA/BF which is operate at low temperature conditions than a latter parts of pyrolysis gasfied chamber which are operate at high temperature condition. Removal efficiency of dioxins of SDA/BF was 85.9 % and therefore, it showed high efficiency at those of stoker type incineration facility. However, concentration of dioxins which emitted at high temperature condition were low in three facilities and satisfied present standard emission level of dioxins. To consider the distribution ratio of dioxins, Particulate phase dioxins at S and P plants showed similar ratio with which shows in current stoker type for middle scale domestic waste incineration facility. It is necessary to continuos monitoring the ratio of distribution of dioxins in T plant in because ratio of gas phage dioxins showed high.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.175-181
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• 2005

Ingots of rutile single crystals were grown by the skull melting method, and their characteristics were compared in terms of melt-dwelling time for each melt. The method is based on direct inductive heating of an electrically conducted melt by an alternating RF field, and the heating is performed by absorption of RF energy. $TiO_2$ is an insulator at room temperature but its electric conductivity increases elevated temperature. Therefore, titanium metal ring(outside diameter : 6cm, inside diameter : 4cm, thickness 0.2cm) was embedded into $TiO_2$, powder (anatase phase, CERAC, 3N) for initial RF induction heating. Important factors of the skull melting method are electric resistivity of materials at their melting point, working frequency of RF generator and cold crucible size. In this study, electric resitivity of $TiO_2$, $(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$ at its melting point was estimated by compairing the electric resitivities of alumina and zirconia. Inner diameter and height of the cold crucible was 11 and 14cm, respectively, which were determined by considering of the Penetration depth $(0.36\~1.13cm)$ and the frequency of RF generator.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.68-74
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• 2016

Adoption of narrow gap welding shall be increased for the butt joint of thick plate, because the deformation and welding cost is reduced by decrease of cross-sectional area. However, sometimes narrow gap causes defects such as lack of fusion since it has small groove angle and narrow groove width. Therefore, GMAW, GTAW and SAW process shall be adopted to narrow gap welding with small bead hight and low deposition rate. In this study, Super-TIG welding using C-type strip was applied to semi-narrow gap butt joint in order to increase the welding productivity. High deposition rate 10kg/hr was obtained by high current 600A without undercut, humping bead and other welding defects. Measuring the mean and standard deviation of the melting depth to evaluate the developed processes, the fusion line type was determined by measuring the difference between maximum and minium melting depth. Furthermore, a model on arch fusion line and linear fusion line was suggested in order to prevent LF on groove wall in narrow gap butt welding.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.245-254
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• 1995

The purpose of this study was to examine the effects of low melting point phase(LMPP) on mechanical properties in the Al-Cu-Li-X(In, Be) alloys. This study was performed by the differential scanning calorimetry(DSC), the transmission electron microscope(TEM), hardness test, tensile test and notch tensile test. The shape of LMPP in the specimens homogenized at $570^{\circ}C$ was film type due to remelting at grain boundary during homogenization. Low melting point phases had no effects on mechanical properties in the aging treated materials, because the density of LMPPs was low. Mechanical properties of the aging treated materials were affected by the density of matrix precipitation phases and grain sizes. For the In or In, Be added Al-Cu-Li alloys, the optimum solution treatment temperature was $550^{\circ}C$. The strength of Al-Cu-Li-In-Be $T_6$ treated alloy was higher than that of 2090-$T_8$ alloy.

• Korean Journal of Human Ecology
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• v.22 no.6
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• pp.673-686
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• 2013

The purpose of this study is to identify consumer needs and sensory evaluation of jacquard fabrics for blind using low melting polyester. Ten kinds of jacquard fabric used for this study were developed. Developed jacquard fabrics were assessed subjectively by 164 consumers using 7-point scale of 22 consumer needs and 43 sensory descriptors. The results were briefly summarized as follows: the most important parameter to choose fabric for blind was 'Easy-use' and the other parameters are 'Lightproof', 'UV-protect', 'Design', 'Price', 'Color', 'Insulation', 'Easy-care'. The image sensibility of jacquard fabrics was explained by six factors: feminine, active, modern, traditional, pure, cozy. Higher preference was found in jacquard fabrics of clear, natural, luxurious, simple, feminine, young, cozy, graceful image. The preference was predicted 38.2% with feminine, modern, pure, cozy, traditional factors. Correlation coefficient between image sensibility factor 1 and preference was 0.437. The 3 factors (feminine, modern, pure)were selected as significant image sensibility affecting preference.

• The Journal of Advanced Prosthodontics
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• v.9 no.1
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• pp.52-56
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• 2017

PURPOSE. Considering the importance of metal-ceramic bond, the present study aimed to compare the bond strength of ceramics to cobalt-chrome (Co-Cr) alloys made by casting and selective laser melting (SLM). MATERIALS AND METHODS. In this in-vitro experimental study, two sample groups were prepared, with one group comprising of 10 Co-Cr metal frameworks fabricated by SLM method and the other of 10 Co-Cr metal frameworks fabricated by lost wax cast method with the dimensions of $0.5{\times}3{\times}25\;mm$ (following ISO standard 9693). Porcelain with the thickness of 1.1 mm was applied on a $3{\times}8-mm$ central rectangular area of each sample. Afterwards, bond strengths of the samples were assessed with a Universal Testing Machine. Statistical analysis was performed with Kolmogorov-Smirnov test and T-test. RESULTS. Bond strength in the conventionally cast group equaled $74.94{\times}16.06\;MPa$, while in SLM group, it equaled $69.02{\times}5.77\;MPa$. The difference was not statistically significant ($P{\leq}.05$). CONCLUSION. The results indicated that the bond strengths between ceramic and Co-Cr alloys made by casting and SLM methods were not statistically different.