• 한국주조공학회지
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• 제3권4호
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• pp.239-247
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• 1983

CV graphite cast iron has been studied and generally known to have properties close to the average values of those between flake and spheroidal graphite cast iron. However, the thermal diffusivity of CV graphite cast iron is much larger than that of the average value of those between flake and spheroidal graphite cast iron. In this study, an easy production method of CV graphite cast iron with small additions of a Al-Cu which is known as the element of the graphitization was investigated. The effects of hold time and of Al-Cu additions after the treatments with spheroidizer (Fe-Si-Mg alloy) were also investigated. Increasing the additions of a Al-Cu alloy, the holding time to form a CV graphite cast iron was decreasing. Tensile strength and thermal diffusivity (flash method) were measured in order to find the changes of the mechanical properties and the physical properties. Spheroidal, CV, and flake graphite cast iron have tensile strengths 46.44, 38.29, and $27.29\;kg/mm^2$ and thermal diffusivities $3.95{\times}10^{-6,}$ $8.41{\times}10^{-6}$, $8.81{\times}10^{-6}m^2/sec$, respectively at room temperature.

• 한국주조공학회지
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• 제24권4호
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• pp.202-208
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• 2004

Effects of Co addition on sliding wear properties of multi-component white cast iron were investigated. The microstructures of multi-component white cast iron containing from 0%Co to 10%Co exhibited little difference. However, the hardness increased with an increase of the Co content. Increasing the Co content, wear properties were improved and the iron oxide on worn surface was increased in the low sliding speed range of the steady-state wear region. Hence, Co addition was effective to improve the wear properties of multi-component white cast iron by accelerating the corrosive wear as well as the enhancement effect of hardness.

• 열처리공학회지
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• 제12권1호
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• pp.40-46
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• 1999

Rotary bending fatigue tests were carried out to investigate the improvement of fatigue limit in annealed and austempered spheroidal graphite cast iron. Main results obtained are as follows. (1) The tensile strength(hardness) of Series C is higher than that of Series B, and fatigue limits are 245MPa in Series C, 230MPa in Series B and 195MPa in Series A, respectively. (2) The fatigue limits of Series B and Series A are mainly governed by the resistance to fatigue crack initiation. Whereas, the fatigue limit of Series C is governed by the resistance to fatigue crack initiation and growth. The defect size and the resistance to crack initiation and growth should be considered to clarify the fatigue properties in spheroidal graphite cast iron. (3) Improvement of fatigue limit by half-austempering is more reasonable than that of full-austempering treatment in multi defective materials as spheroidal graphite cast iron.

• Journal of Welding and Joining
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• 제15권4호
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• pp.154-165
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• 1997

Abrasive wear characteristics of high Cr white cast iron-based hardfacing were investigated using the rubber wheel abrasion wear test method according with the ASTM G65-85. Mild steel was also tested for comparison with high Cr cast iron hardfacing. Wear experiments, where the applied force, wheel revolution rate and abrasive powder feed rate were selected as test valuables, were planned and analyzed by response surface method to evaluate wear statistically and quantitatively. Weight loss of high Cr cast iron hardfacing was mostly affected by the applied force and wheel revolution rate, and little by the powder feed rate. Weight loss of mild steel was greatly affected by the wheel revolution rate and powder feed rate, and slowly and steadily increased with the applied force. Abrasive wear mechanism of high Cr cast iron and mild steel was discussed in the light of the wear test results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.139-142
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• 2003

In this study, casting/forging process was used to produce an aluminum lower control arm for automobiles. Firstly, casting experiments were carried out to get an enhanced preform for forging the lower control arm. In the casting experiment, the effect of an additive, Sr, on the mechanical properties such as tensile strength and elongation and the microstructure of a cast preform were investigated. And a finite element analysis was peformed to determine an optimal configuration of the cast preform. Lastly, a forging experiment was carried out to make the final product of aluminum lower control arm by using the above cast preform. In the casting experiments, when 0.025% Sr was added into molten A356, the maximum values of tensile strength and elongation of the cast preform were obtained. In the forging experiment, It was confirmed that the optimal configuration of a cast preform predicted by FE analysis was very useful. The cast/forged product using designed preform was made without any defects.

• The Journal of Advanced Prosthodontics
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• 제3권1호
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• pp.33-36
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• 2011

In process of fabrication of a fixed partial denture, dies are trimmed to expose margins of the preparations. The need for the soft tissue cast is quite evident as the soft tissue emergence profile that surrounds the prepared tooth is destroyed in the process of fabrication. This article describes a modified technique to fabricate the soft tissue cast for the conventional fixed partial denture. The impression made with the polyvinylsiloxane was first poured to prepare the die cast. After retrieval of the cast, the same impression was poured second time with the resin based resilient material to cover the facial and proximal gingival areas. The remaining portion of the impression was poured with the gypsum material. This technique does not require additional clinical appointment, second impression procedure, technique sensitive manipulations with impression, or cumbersome laboratory procedures. The simplicity of this technique facilitates and justifies its routine use in fabrication of the fixed partial denture.

• 대한간호학회지
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• 제24권4호
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• pp.517-528
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• 1994

The purpose of this study was to compare the circumference, skinfold thickness and strength of the normal and casted lower limb prior to casting and following removal of the cast. The subjects for the study were nine orthopedic patients who had had long and short leg casts due to a tibial, fibula, or calcaneus fracture, or to a lateral collateral ligament rupture. Circumference, skinfold thickness, and strength of the normal and casted lower limb following removal of the cast were compared with those prior to the application of the cast. Measurements were made before cast application and after removal of the cast. Skinfold thickness was measured by fat caliper, circumference was measured by tape and strength was determined by measuring the length of time the leg was held elevated at 45$^{\circ}$. The results can be summarized as follows 1. There was no change in the normal limb in the circumference of the midthigh and midcalf after casting as compared to before cast application. 2. In the casted limb the circumference of the midthigh decreased by 3.23% and that of the midcalf decreased significantly by 7.49% during the period of casting. 3. In the normal limb skinfold thickness of the quadriceps decreased and that of gastrocnemius increased by 20.63% during the period of cast application. 4. In the casted limb skinfold thickness of the quadriceps decreased significantly by 12.37% and that of gastrocnemius decreased by 10% during the period of cast application. 5. Strength of the normal lower extremity decreased significantly by 48.37% and that of casted lower extremity decreased remarkably by 73.07% during the period of cast application. 6. Circumference of the midthigh and the midcalf decreased significantly by 7.6% and 9.4% respectively on the casted side as compared to the normal side. Skinfold thickness of the quadriceps and the gastrocnemius on the casted side decreased by 6.12% and 18.55% respectively as compared to the normal side and strength in the lower extremity on the casted side decreased significantly by 44.32% as compared to the nor-mal side. From these results, it may be concluded that muscle atrophy occurs in the casted lower limb and muscle strength of the normal lower limb are also reduced during the period of application of a leg cast.

• 열처리공학회지
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• 제33권5호
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• pp.219-225
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• 2020

The objective of this study was to investigate the tensile properties and thermal conductivities of Mg9.3%Al alloy in as-cast state and heat-treated state consisting of fully discontinuous precipitates (DPs), respectively. The fully DPs microstructure was obtained by solution treatment at 405℃ for 24 h, followed by furnace cooling to RT. The as-cast alloy showed a partially divorced eutectic β(Mg₁₇Al₁₂) phase particles formed along the α-(Mg) cell boundaries. The DPs had various apparent (α+β) interlamellar spacings, which is related to different transformation temperatures during the furnace cooling. The DPs microstructure exhibited better tensile strength than the as-cast one, resulting from the higher value of elongation in response to its more homogeneous microstructure. It is noticeable that the DPs microstructure had 12.4% higher thermal conductivity in average than the as-cast one between RT and 200℃. The XRD analyses revealed that the lower Al concentration in the α-(Mg) matrix may well be responsible for the better thermal conductivity of the DPs microstructure.

• 한국재료학회지
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• 제12권5호
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• pp.414-422
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• 2002

Three different multi-component white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their as-cast and solidification structures. Three combinations of the alloying elements were selected so as to obtain the different types of carbides and matrix structures : 3%C-10%Cr-5%Mo-5%W(alloy No.1), 3%C-10%V-5% Mo-5%W(alloy No. 2) and 3%C-17%Cr-3% V(alloy No.3). The as-cast microstructures were investigated with optical and scanning electron microscopes. There existed two different types of carbides, $M_7C_3$ carbide with rod-like morphology and $M_6C$ carbide with fishbone-like one, and matrix in the alloy No. 1. The alloy No. 2 consisted of MC carbide with chunky and flaky type and needle-like $M_2C$ carbide, and matrix. The chunky type referred to primary MC carbide and the flaky one to eutectic MC carbide. The morphology of the alloy No. 3 represented a typical hypo-eutectic high chromium white cast iron composed of rod-like $M_7C_3$ carbide which is very sensitive to heat flow direction and matrix. To clarify the solidification sequence, each iron(50g) was remelted at 1723K in an alumina crucible using a silicon carbide resistance furnace under argon atmosphere. The molten iron was cooled at the rate of 10K/min and quenched into water at several temperatures during thermal analysis. The solidification structures of the specimen were found to consist of austenite dendrite(${\gamma}$), $ ({\gamma}+ M_7C_3)$ eutectic and $({\gamma}+ M_6C)$ eutectic in the alloy No. 1, proeutectic MC, austenite dendrite(${\gamma}$), (${\gamma}$+MC) eutectic and $({\gamma}+ M_2C)$ eutectic in the alloy No. 2, and proeutectic $M_7C_3$ and $ ({\gamma}+ M_7C_3)$ eutectic in the alloy No 3. respectively.

• 한국재료학회지
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• 제10권11호
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• pp.760-769
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• 2000

Nb, Ti 및 V를 0.15%씩 각각 첨가한 3종의 HSLA 주강을 오스테나이징 온도 및 템퍼링 시간을 변화시킨후 기계적 특성등을 관찰한 결과 다음과 같은 결론을 얻었다. 오스테나이징 온도를 $1150^{\circ}C$로 하여 2시간 가열시킨 경우 첨가원소의 종류에 관계없이 경도가 가장 증가하였으며 $1100^{\circ}C$이하의 온도에서는 서서히 경도가 감소하는 경향을 나타내었다. 오스테나이징 온도를 $1150^{\circ}C$로 하여 2시간 가열시킨 경우 Nb, Ti, V 첨가원소중에서 경도가 가장 높게 나타난 것은 Ti 첨가 HSLA 주강이며 오스테나이트 온도변화에 따라 경도차가 나는 주된 이유는 베나이트 조직의 상대적인 양과 고용강화에 주로 기인하였다. $1150^{\circ}C$에서 오스테나이징한 Ti 첨가 HSLA 주강의 경우를 제외하고는 대부분의 경우에 있어 C-Mn 주강을 대체 하기위한 최소 충격값이 2kg-m/$\textrm{cm}^2$이상의 충격치를 나타내었다. $1150^{\circ}C$에서 2시간 오스테나이징한 경우 첨가원소의 종류에 관계없이 10분정도 템퍼링에서 경도가 증가하여 V 첨가 HSLA 주강을 제외하고는 그이후는 템퍼링 시간이 증가함에 따라 일정하게 유지되는 경향을 나타내었다.