• Journal of Korea Foundry Society
• /
• v.26 no.5
• /
• pp.222-226
• /
• 2006

Steel making slag has gained a considerable attraction as one candidate of eco-materials in research fields for recycling resources. Thus, many researches have been performed but were limited to development of substitute for cement being used in the construction field. A little research work also has been done on development of higher value-added materials, including heat resistant and sound absorbing materials. For this reason, the present study were focused on macrostructure characterization of fabricated slag fibers which are applicable to heat resistant materials. The slag fibers were fabricated through a modified melt extraction method. The processing variables employed were the wheel speed and molten slag temperature. The synthesized fibers were characterized by optical microscope and scanning electron microscopy. It was found that the wheel speed of 1400 rpm generated better quality of mineral fibers in terms of the relative amount of shot, diameter and length. This was attributed to the relative extent of contact width between the flowing melt and the rotating wheel. The thickness of the slag fibers also were decreased with increasing the slag melt temperature due mainly to significant decrease in the viscosity of the slag melt. In addition, the lower melt temperature caused an increase in number of shots plus the mineral fibers.

• Journal of Korea Foundry Society
• /
• v.18 no.4
• /
• pp.383-388
• /
• 1998

Effects of $CaCN_2$ addition on the grain refinement in the AM60 magnesium ingots were investigated. The effects of the $CaCN_2$ are estimated with different inoculation temperatures, inoculation contents, and holding time to find out the optimum condition. AM60 alloy was melted in the low carbon steel crucible by cylindrical electric furnace under an argon atmosphere. The melting and casting apparatus is specially designed for magnesium alloys. The grain size of AM60 magnesium alloy decreased significantly with an increase in $CaCN_2$ content and, at 0.8 wt% $CaCN_2$ or more, grain size becomes constant at about $85 {\mu}m$. The optimum condition was obtained in the 0.8 wt% $CaCN_2$ for holding molten metal of 30 min. at the temperature of $710^{\circ}C$. The tensile properties of AM60 magnesium alloys were improved due to grain refinement by addition of $CaCN_2$. In the optimum condition, the yield strength, tensile strength and elongation were ${\sigma}_{0.2}=107 MPa$, ${\sigma}_{T.S}=234 MPa$ and e=14.2%. The variation of stress with strain obeyed the relationship of the ${\sigma}=K{\varepsilon}^n$. The strain-hardening exponent, n and strength coefficient, K obtained in the 0.8 wt% $CaCN_2$ added AM 60 magnesium alloy were n=0.21 and K=390 MPa.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.55-55
• /
• 2009

FGB(Flexible Glasswool Backing) Submerged Arc Welding has been one of the main welding processes for one side butt welding in shipbuilding industries, which can efficiently improve the welding productivity by the addition of a supplementary filler metal into the molten weld pool. As recent ships have become larger in size, the application of high tensile and higher grade of steels has been continuously increased. Single pass FGB SA welding process accompanies such a high heat input when welding thick plates that the mechanical properties of weld metal can be dramatically degraded. This study has been performed in order to obtain high toughness and tensile properties of high heat input FGB SA welds, and to evaluate the effect of alloy elements on their mechanical properties. To complete welding 25mm-thick EH36 grade steel plate by single pass, 1.2mm diameter and 1.0mm long cut wires has been distributed in the groove before welding, and three different test coupons have been made using C-1.5%Mn, C-1.8%Mn-0.5%Mo, and C-1.4%Mn-1.7%Ni cut wires to investigate the influence of nickel(Ni) and molybdenum(Mo) on the mechanical properties of welds. Test results showed that the addition of Ni and Mo effectively promotes the formation of Acicular Ferrite(AF), while significantly reducing the amount of Grain Boundary Ferrite(GBF) in weld metal microstructures, which resulted in a beneficial effect on low temperature impact toughness and strength.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.571-576
• /
• 1998

This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.1
• /
• pp.18-25
• /
• 2000

In this paper, we have designed a microwave level meter based on the FM-CW radar theory using a YIG-tuned oscillator (YTO). YTO has an excellent frequency linearity, so a linearizer circuit is not necessary for the level meter. It is shown that interference signals reflected from nearby obstacles can be removed by using a digital band-pass filter. An FIR band-pass filter is designed using the Kaiser window. The distance measurement has been performed in the outdoor test field. The measurement data have been obtained for the range of 1~40m with 1m step, and the results show that the standard deviation of the measured data is 2.33 cm. The level meter manufactured in this study can be applied usefully in the industrial facilities which are not accessible easily, for example, to measure the level of molten metal in the iron and steel company.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.10
• /
• pp.5919-5924
• /
• 2014

Accumulated dross adhered to the cutting support degrades the cutting accuracy and aggravates the working environment by reducing the efficiency of the dust collector. Furthermore, the cutting machine and product can be damaged by the scattering of molten metal. In this study, an attempt was made to increase the productivity of steel cutting process and improve the working environment by dross control. The dross adhesion characteristics were invested by a cutting experiment and the design concept for a dross removal machine was devised. Finally, a cutting support cleaning system and its operating algorithm were developed. The applicability of the developed system was examined and verified by a long-term field test after installation of the plasma arc cutting system of a shipyard.

• Korean Journal of Materials Research
• /
• v.20 no.3
• /
• pp.111-116
• /
• 2010

Chloride-based fluxes such as NaCl-KCl are used in the refining of Al melt. The vapor pressure of the chloride is one of the fundamental pieces of information required for such processes, and is generally high at elevated temperatures. In order to measure the vapor pressure for chlorides, the apparatus for the transpiration method was assembled in the present study. The vapor pressure of $ZnCl_2$ and $FeCl_2$, which is related with the process of aluminum refining and the recovery of useful elements from iron and steel industry by-products, was also measured. In the measurement of vapor pressure by the transpiration method, the powder of $ZnCl_2$ or $FeCl_2$ in a alumina boat was loaded in the uniform zone of the furnace with a stream of Ar. The weight loss of $ZnCl_2$ and $FeCl_2$ after holding was measured by changing the flow rate of Ar gas (10 sccm -230 sccm), and the partial pressures of $ZnCl_2$ and $FeCl_2$ were calculated. The partial pressures within a certain range were found to be independent of the flow rate of Ar at different temperatures. The vapor pressures were measured in the temperature range of 758-901K for $ZnCl_2$ and 963-983K for $FeCl_2$. The measured results agreed well with those in the literature.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.3
• /
• pp.161-168
• /
• 2023

Converter slag is a by-product generated by refining the pig iron produced into molten steel in the blast furnace, occupying about 15 % of the weight of steel production. It has a high free-CaO content that can generate expansion cracks when used for concrete aggregate. This is the main reason to make it difficult to recycle. To solve this problem, government guideline requires that converter slag has to be aged in an open yard for 90 days. However, aging can not be perfectly performed because it entails time and cost. In this study, we tried to investigate the applicability of converter slag as a cementitious material rather than an aggregate by mixing converter slag with mortar formulations. According to the EDS results of the converter slag in the experiment, we found that screening in the aggregate phase was more effective than that in the powder phase. When the particles separated by a magnet in the aggregate state were pulverized and used for concrete up to a 15 % replacement ratio, various engineering characteristics, such as flow, length change, and compressive strength, showed engineering characteristics similar to those of the control mix.

• Nuclear Engineering and Technology
• /
• v.49 no.7
• /
• pp.1547-1554
• /
• 2017

VESTA (Verification of Ex-vessel corium STAbilization) and VESTA-S (-small) test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging $ZrO_2$ melt jet on a sacrificial material were performed to investigate the ablation characteristics. $ZrO_2$ melt in an amount of 65-70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40), and the other is a stainless steel (SUS304) melt. Metallic melt in an amount of 1.5-2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. $ZrO_2$ melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is $UO_2$ 60%, Zr 10%, $ZrO_2$ 15%, SUS304 14%, and $B_4C$ 1%, was melted in a cold crucible using an induction heating technique.

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10b
• /
• pp.1639-1645
• /
• 1991

Because of the important role LD converters play in the production of high quality steel, various dynamic models have been attempted in the past by many researchers not only to understand the complex chemical reactions that take place in the converter process but also to assist the converter operation itself using computers. And yet no single dynamic model was found to be completely satisfactory because of the complexity involved with the process. The process indeed involves dynamic energy and mass balances at high temperatures accompanied by complex chemical reactions and transport phenomena in the molten state. In the present study, a mathematical model describing the dynamic behavior of LD converter process has been developed. The dynamic model describes the time behavior of the temperature and the concentrations of chemical species in the hot metal bath and slag. The analysis was greatly facilitated by dividing the entire process into three zones according to the physical boundaries and reaction mechanisms. These three zones were hot metal (zone 1), slag (zone 2) and emulsion (zone 3) zones. The removal rate of Si, C, Mn and P and the rate of Fe oxidation in the hot metal bath, and the change of composition in the slag were obtained as functions of time, operating conditions and kinetic parameters. The temperature behavior in the metal bath and the slag was also obtained by considering the heat transfer between the mixing and the slag zones and the heat generated from chemical reactions involving oxygen blowing. To identify the unknown parameters in the equations and simulate the dynamic model, Hooke and Jeeves parttern search and Runge-Kutta integration algorithm were used. By testing and fitting the model with the data obtained from the operation of POSCO #2 steelmaking plant, the dynamic model was able to predict the characteristics of the main components in the LD converter. It was possible to predict the optimum CO gas recovery by computer simulation