• 한국주조공학회지
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• 제25권4호
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• pp.156-160
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• 2005

There are many factors that influence solidification behavior during continuous casting, e.g. include superheat, casting speed, cooling rate and holding time. However, when melt is stirred by electromagnetic force, there would be some changes in its solidification behavior compared to that of the ordinary casting process. In this study, the billets of A356 alloy with a diameter of 3 inch were fabricated with electromagnetic stirring under various conditions of superheat, casting speed and input voltage of electro magnetic stirring (EMS) device. The microstructure was also investigated under the various casting conditions and electromagnetic input voltages. When increase in input voltage, the microstructure was changed from dendritic to rosette type and finally to spheroidal. With pouring temperature, casting speed and electromagnetic input voltage were $650^{\circ}C$, 100 mm/min and 140 V, respectively, the billet with a diameter of 3 inch, which has a uniform dispersed spheroidal particles in the whole area of billet except for the surface area, was manufactured.

• 대한기계학회논문집A
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• 제23권11호
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• pp.2087-2095
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• 1999

One of the main causes of unwanted dimensional changes in precision metal mold casting parts is excessive and irregular residual stresses induced by temperature gradients and plastic deformation in the solidifying shell. Residual stresses can also cause stress cracking, and lower the fatigue life and fracture strength of the casting parts. In the present study, aluminum alloy casting system with metal mold equipped with electrical heating elements and water cooling units was designed and the casting specimens were produced to quantify the effects of different cooling conditions on the development of residual stresses. The layer removal method was used to measure the biaxial residual stresses in casting specimens produced from the experiments. The experimental results agreed with Tien-Richmond's theoretical model for thermal stress development for the solidifying metal plate.

• 한국주조공학회지
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• 제31권3호
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• pp.101-105
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• 2011

• 소성∙가공
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• 제15권8호
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• pp.586-590
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• 2006

42Ni-Fe Invar alloy strips were fabricated using conventional ingot casting and melt drag casting followed by rolling. Mechanical properties such as tensile strength, elongation and blanking deformability of the strips were evaluated. The properties were strongly depended on fabrication methods. Tensile strength and elongation of all strips were in the range of $40-60kg/mm^{2}$ and 26-35%, respectively, which are enough values for the manufacture of the final products. In some of the strips, however, burrs occurred at deformed surface. The properties of strips were explained in terms of microstructure such as grain size and texture formation during rolling. Additionally, strips by melt drag casting method were compared to those by conventional ingot casting.

• 한국주조공학회지
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• 제21권2호
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• pp.127-134
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• 2001

Misch metal (rare earth element, Ce, La, Nd, Pr) which has large influence on high-temperature stability and toughness was added to the Al-5%Ni-5%Mg alloy, and squeeze casting was used for Al-5%Ni-5%Mg-(Mm) alloys. The effect of applied pressure and misch metal additions on mechanical properties in Al-5%Ni-5%Mg alloy by direct squeeze casting has been investigated. The applied pressure were 0 MPa(gravity casting), 25, 50 and 75 MPa. Squeeze-cast Al-5%Ni-5%Mg-(Mm) alloys had better mechanical properties than those of non-pressurized cast alloys because of the increased cooling rate by the application of pressure during solidification. By the addition of misch metal in Al-5%Ni-5%Mg alloy, better combination of strength and elongation was obtained. The addition of 0.3%Mm in Al-5%Ni-5%Mg alloy improved the heat resistant property due to the formation of fine eutectic phases.

• 한국산업융합학회 논문집
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• 제23권4_1호
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• pp.541-547
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• 2020

This paper relates a rheo die casting using electromagnetic force, which is one of the representative semi-solid methods for aluminum. The most important factors in electromagnetic stirring would be the melt temperature, sleeve temperature, electromagnetic force, and input time. The effect of the temperature of molten alloy on the direct rheo-casting is assessed in this study. The temperature of the molten alloy is set to 590 ℃ with a solidification of 40%, 600 ℃ with 30%, and 610℃ with less than 20%. Under the condition of 590 ℃ with a solidification of 40%, the whole molten alloy is solidified, causing non-forming during forming process. Meanwhile, under the condition of 600 ℃, where the solidification was 30%, appropriate amount of molten alloy is solidified, filled well into the mold, resulting in good forming, while at 610 ℃ with the solidification of 20%, the molten alloy is not sufficiently solidified and scattered away. The investigation of the defects inside the product with the help of the X-ray equipment shows that the electromagnetic stirring at 590 ℃ with a solidification of 30% produces many air-pores inside the product.

• 대한치과기공학회지
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• 제31권3호
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• pp.27-34
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• 2009

This study compared and analyzed changes to the mechanical characteristics to nonprecious metal alloy for porcelain fused to metal crowns when it's repetitively used without the addition of new alloy. Metal samples were made with the Verabond V nonprecious metal alloy. Those samples to measure tensile and yield strength were made in the standardized design(ISO 22674), those to measure bond strength in the $25mm{\times}3mm{\times}0.5mm$ format, and those to measure hardness in the $10mm{\times}10mm{\times}1mm$ format. A ceramic to measure bond strength was made at the center of the metal sample in the length of $8{\ss}{\AE}$ by using Noritaker Super Porcelain EX-3. Ten samples were prepared for one, three and five repetitions of casting each. The test results were as follows: 1. The more casting was repeated, the more significantly tensile strength dropped. 2. The more casting was repeated, the more significantly yield strength dropped. 3. Repetitive casting didn't cause significant changes to bond strength. 4. The Vickers hardness significantly fell with increasing repetitions of casting. There were no changes to bond strength observed with the increasing number of repeating casting. But tensile strength, yield strength, and Vickers hardness decreased. Those results indicate that repeated casting can affect durability and that careful attention should be paid by avoiding repetitive use or excessive increase of uses when no new alloy is added.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.3-7
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• 2002

The die casting process was used to manufacture a alternator housing for automobile. Specially automobile parts were required light and hight strength. Therefore simulation have been carried out die casting process of the alternator housing. In this paper, we investigated about characteristics of the die casted alternator housing the HPDC(High Pressure Die Casting) process. Also we designed the die casting die with the simulation results of the alternator housing. The MAGMAsoft and Auto-CAD was used as computer simulation and design code and used material was ADC12(Aluminum Die Casting Alloy). We present the results of filling behavior and design of die process of the alternator housing cast. The result obtained about filling behavior and design of die of the cast showed good agreement with test result.

• 한국정밀공학회지
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• 제15권12호
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• pp.62-67
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• 1998

An experimental study has been carried out to investigate casting process parameters which influence on the microstructures of cast preforms in casting/forging process of aluminum alloy. In the casting process, pouring temperature, pouring time, mold temperature, mold material, and, cooling method are selected as process parameters. With the cast preform, a forging test has been performed to compare mechanical properties of final products between casting/forging process and forging process. From the experimental results, low mold temperature and water cooling method are favorable for obtaining minute microstructures of cast preforms. Casting defects included in cast preforms. such as pores and shrinkage cavity, are eliminated by the forging process. And comparing cast/forged products with conventionally forged products, the former are almost as same as the latter in mechanical characteristics.

• 소성∙가공
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• 제8권5호
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• pp.491-497
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• 1999

The effect of partial squeeze on the quality of casting products in the vacuum die casting was investigated to make defect free casting products with excellent mechanical properties. The partial squeeze and vacuum die casting process was industrially implemented in making reaction shaft support which was made of a hypereutectic Al-15%Si alloy. To combine squeezing and vacuum effects, the plunger injection system was designed and attached on the chill vent type vacuum machinery system. The combination of vacuum effect before injection and partial squeezing effect after injection resulted in defect free die casting products. The uniform distribution of fine eutectic and proeutectic Si obtained from trial process also provided excellent mechanical properties.