• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.66-71
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• 1998

It is required the superior materials for the parts of machines or structures, which could be endurable in severe load and environment. According to advancement of casting technology, nodular graphite cast iron is used as suitable for such condition. But nodular graphite cast iron is scattering of fatigue strength and low reliability. Therefore in this study, the effect of matrix structure and number of nodular graphite on the initiation of fatigue crack and fatigue strength. It was found that the material which has relatively high ferrite volume fraction was more easily cracked than other materials and fatigue limit was low. The material which has not found pinhole on the surface, the crack was initiated in graphite went through ferrite and propagated into through graphite, but separated graphite and ferrite grain boundary and combined with other cracks to fro large one.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.193-197
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• 2002

In this study, the casting/forging process was applied to the Shift-Fork, a manual transmission part of automobiles. In the casting experiments, the effects of additives, Sr, Ti＋B and Mg, on the mechanical properties and the microstructure of a cast preform were investigated. When 0.03% Sr were added into the molten aluminum alloy, the finest silicon-structure was observed in the cast preform and the highest tensile strength and elongation accomplished. And when 0.2% Ti＋B were added into the molten Al-Si alloy, the highest values of tensile strength were obtained. The maximum hardness was in case of 0.2% Mg. In the forging experiment, it was confirmed that the optimal configuration of the cast preform could be predicted by FE analysis. To minimize the cost as the press size, the compact shape of preform was proposed to reduce the volume of flash. The modification of shape in designing preform was performed to attain a satisfactory performance in the areas where the mechanical strength were more required. By using FVM(Finite Volume Method) software, it was verified that a proposed casting design was available. To identify the relationship between effective strain and mechanical properties of the final forged product, the compression test was performed. As the result, the tensile strength and elongation of a cast preform were much higher than before forging. The minimum forging temperature was found 40$0^{\circ}C$ to save heating time.

• Korean Journal of Organic Agriculture
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• v.11 no.4
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• pp.93-102
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• 2003

This research was made to determine the optimum mixing ratio cattle manure and food waste investigating the effect that gets the growth and reproductive efficiency of earthworm and productivity of earthworm casts at processing process when handled cattle manure and food waste by vermicomposting, in order to establish the treatment system of organic wastes by vermicomposting. Survival ratio of earthworm was highest in the mixing ratio 80~100% : 20~0% of cattle manure and food Waste, and the increasing ratio was highest in cattle manure 100%, and the number of young worms, the weight of young worms and the productivity of earthworm casts in plots more than the mixing ratio 60% of cattle manure were significantly higher than in the other treatment plots(p<0.05). Total nitrogen and carbon contents in earthworm cast were decreased when rearing time of earthworm was increased. Carbon and nitrogen rate(C/N) of earthworm cast in plots more than the mixing ratio 80% of cattle manure was significantly higher than in the other treatment plots(p<0.05). pH in earthworm cast was higher than that in residual matter. The contents of electrolytic conductivity in the higher mixing ratio of food waste were significantly higher than those in the other treatment plots(p<0.05).

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.248-253
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• 2002

Effect of Sn addition on the fatigue properties of Al-Cu-Mn cast alloy was investigated by low and high cycle fatigue tests. Fatigue life showed the maximum value of 5450cycles in the Al-Cu-Mn alloy containing 0.10%Sn, but decreased rapidly beyond 0.20% of Sn additions. It was found that the fatigue strength was 132MPa and fatigue ratio was 0.31 in the alloy containing 0.10%Sn. Metallographic observation revealed that the fatigue crack initiated at the surface and propagated along the grain boundary. This propagation path was attributed to the presence of PFZ along the grain boundary. The tensile strength increased from 330MPa in 7he Sn-free Al-Cu-Mn cast alloy to 429MPa in the alloy containing 0.10%Sn. But above 0.20%Sn additions, tensile strength was decreased by the segregation of Sn.

• Applied Microscopy
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• v.48 no.3
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• pp.73-80
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• 2018

Ductile cast iron is widely used for many automotive components due to its high wear resistance and fatigue resistance in addition to the low cost of fabrication. The improvement of wear resistance and fatigue properties is key to the life time extension and performance increase of the automobile parts. Surface nanocrystallization is a very efficient way of improving the performance of materials including the wear- and fatigue-resistance. Shot peening treatment, as one of the popular and economic surface modification methods, has been widely applied to various materials. In this study, ductile cast iron specimens were ultrasonic shot peening (USP) treated for 5 to 30 min using different ball size. The microstructures were then microscopically analyzed for determination of the microstructural evolution. After the USP treatment, the hardness of pearlite and ferrite increased, in which ball size is more effective than treatment time. With USP treatment, the graphite nodule count near the surface was decreased with grain refinement. The lager balls resulted in an increased deformation, whereas the smaller balls induced more homogenously refined grains in the deformation layer. In addition, formation of nanoparticles was formed in the surface layer upon USP.

• Journal of Korea Foundry Society
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• v.19 no.1
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• pp.77-83
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• 1999

Strip casting process, a new casting technology which makes thin strip of $0.5{\sim}5\;mm$ thickness directly from molten metal, has been dramatically developed for past 10 years and faced commercialization in the case of STS304 strip. In this study, ductile cast iron strip which is 1.1 mm thick and 100 mm wide is manufactured by the twin roll strip caster. Graphite and matrix structure of the strip can be controlled through heat treatments and the mechanical properties are examined. The microstructure of the as-cast strip consists of cementite and pearlite. Especially the equiaxed crystal zone of pearlite exists in the center region of the thickness due to the characteristics of the strip casting process. Matrix structure can be transformed into fully ferrite or ferrite/pearlite mixed structures by the different graphitization heat treatments. The heat-treated strip with ferrite/pearlite matrix structure showed higher hardness and tensile strength than that with full ferrite matrix structure.

• Journal of Korea Foundry Society
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• v.13 no.4
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• pp.333-341
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• 1993

The effects of alloying elements on the structure and mechanical properties of compacted/vermicular graphite cast irons containing copper, tin and molubdenum for producing pearlite matrix, and also containing phosphorus and boron for increasing wear resistance, were investigated. The Brinell hardness and ultimate tensile strength of the specimens with the range of compositions, [1.5% Cu-0.05% Sn-(0.2-0.4)% Mo-(0.2-0.6)% P-(0.035-0.070)% B], was found to fall within in the following range, depending on their composition; Brinell hardness of BHN 250-315, ultimate tensile strength of $28.1-40.3kg/mm^2$. It was also found within this experiment that CV graphite cast irons possessing higher amount of phosphide eutectic exhibit better wear resistance, but the wear resistance became deteriorate when the area fraction of phosphide eutectics exceed more than 10%. From these experimental results, it could be concluded that the CV graphite cast iron containing 1.5% Cu, 0.05% Sn, 0.4% Mo, 0.2% P and 0.035% B showed good mechanical and wear resistance properties.

• Journal of Korea Foundry Society
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• v.17 no.3
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• pp.252-257
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• 1997

The 8 mm dia: Sn-38%Pb eutectic alloy rods were produced by use of the horizontal continuous casting process with the heated mold and chill cast process. The cast rods were rolled into 2.0${\sim}$0.5 mm thick plates and structural and mechanical properties were examined. The results revealed that the plates produced by the continuous casting process with the heated mold show much higher superplasticity at ambient temperature (1550% elongation at 0.5mm thick plate and 0.5mm/min strain rate) than the plates procuced by chill cast process (630% elongation). Such a high superplasticity of the continuous cast plates is due to the high-quality plates free from any inside and surface defects with fine and uniform distribution of eutectic phases.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.1
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• pp.45-52
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• 2014

Diagnosis and treatment planning is initial step to fabricate removable partial denture, and one of most important factor influencing the prognosis. Partial edentulous patients have various condition of remaining teeth and oral mucosa. Therefore, for the proper diagnosis and treatment planning for each patient, getting many informations from patients during initial examination and fabricating accurate diagnostic cast are required. Especially, because the use of various diagnostic tools and surveying of diagnostic cast will be a guide for the abutment teeth selection, oral preparation and design of partial denture, dentist should understand and be able to apply this procedure during diagnosis.

• Corrosion Science and Technology
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• v.15 no.4
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• pp.171-181
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• 2016

In this work, synergistic corrosion inhibition effect of nitrite and 3 kinds of ethanolamines on ductile cast iron using chemical and electrochemical methods was evaluated. This work attempts to clarify the synergistic effect of nitrite and ethanolamines. The effects of single addition of TEA, DEA, and MEA, and mixed addition of nitrite plus TEA, DEA or MEA on the corrosion inhibition of ductile cast iron in a tap water were evaluated. A huge amount of single addition of ethanolamine was needed. However, the synergistic effect by mixed addition was observed regardless of the combination of nitrite and triethanolamines, but their effects increased in a series of MEA + nitrite > DEA + nitrite > TEA + nitrite. This tendency of synergistic effect was attributed to the film properties and polar effect; TEA addition couldn't form the film showing high film resistance and semiconductive properties, but DEA or MEA could build the film having relatively high film resistance and n-type semiconductive properties. Moreover, it can be explained that this behaviour was closely related to electron attractive group within the ethanolamines, and thus corrosion inhibition power depends upon the number of the electron attractive group of MEA, DEA, and TEA.