• Journal of Korea Foundry Society
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• v.30 no.4
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• pp.130-136
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• 2010

Sulfide segregation behavior, characteristics of solidification microstructure and compositional distribution in the riser/castings junction of heavy-section main bearing support (MBS) steel castings were investigated; Sulfide streaks of A segregation were formed in the transitional region from columnar grain to coarse equiaxed grain and floated with aggregation of the dendritic free crystal. Solute segregation behaviors of elements Si, P and S were V shape negative segregation from the bottom of the castings to upper part of the riser with the reference of vertical center-line of the specimen block. Those of elements C and Mn were V shape negative segregation in the main body and A shape positive segregation in the riser of the casting. Just beneath the pipe shrinkage in the riser segregation ratio of each element was the highest, and that of S was 3.6 times higher, C 3.3 times, P 2.1 times, Si 1.6 times and Mn 1.0 times respectively. [Mn/S] ratio of the specimen block was distributed in the wide range of 20~275.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.731-732
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• 2006

Recently warm compaction techniques are focused on and commercialization of one high-density compaction process in the P/M industry. Another development is a new SEGLESS using a developed lubricant that reduces ejection force at room temperature compaction. It is possible to achieve high-density by reducing lubricant amount. In this paper we confirmed that green density was $7.35g/cm^3$ at 686MPa of compaction pressure when the new SEGLESS was applied to relatively lower temperature warm compaction process, such as $80^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1015-1020
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• 1997

In the Nd;YAG crystal growth by Czochralski method, the relationship between the core formation and the solid-liquid interface was observed by controlling the temperature gradient in the furnace. When the crystal was grown along<111> direction, defects and core area were reduced as the temperature gradient increased. The optimum temperature gradient was found to be higher than 4$0^{\circ}C$/cm. The Nd3+ concentration analysis by ICP-Mass showed that the segregation coefficient was about 20% higher in the core region than core-free region, where the segregation coefficients of core region and core-free region were 0.22 and 0.18, respectively.

• Journal of Korea Foundry Society
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• v.13 no.1
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• pp.71-80
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• 1993

Squeeze casting has advantages to improve mechanical properties of nonferrous castings without losing high productivity. Sound pore free structure makes it possible to be subjected to heat treatment and welding. This process became popular to produce lighter automobile parts alternating cast iron parts. It has, however, two disadvantages of segregation and scattered structure due to the solidified layers in sleeve. In this study segregation behavior of squeeze cast Al-7%Si-0.3%Mg alloy bars was investigated using HVSC machine under various injection conditions. Degree of segregation decreased with injection pressure and effect of injection velocity on it was small. Segregation mode of solute was strongly governed by solidification mode and flow pattern.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.917-920
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• 2001

Effects of addition of manganese and final reduction on segregation behavior of sulfur and final mangetic induction during final annealing have been investigated in the 300 ppm sulfur-contained 3% silicon-iron alloy strips with or without manganese. At the same concentration of sulfur, lower final reduction is favorable for final Goss texture. This is because the probability that the initial Goss grains survive under the highly segregated sulfur atmosphere and grow selectively within the segregated sulfur-free time range becomes higher. In the case of 3% silicon-iron with manganese, much lower magnetic induction was obtained, although the weak final reduction of 30% is given to the alloy, comparative to the 40%. This is because MnS particles acted as an reducer in the primary grain size.

• Proceedings of the Korean Magnestics Society Conference
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• 2010.06a
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• pp.165-166
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• 2010

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.737-737
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• 2006

• Journal of Preventive Medicine and Public Health
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• v.22 no.4 s.28
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• pp.474-479
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• 1989

This research was conducted to evaluate the effect of improvement in work environment and of segregation in a fluorescent lamp manufacturing factory. Among the total of 80 workers, 8 workers whose mercury concentration in urine reached a hazardous level ($200-299{\mu}g/l$) were moved to mercury free workplace. The follow-up examination for their mercury concentration in urine was done three times ; on May 3, 1988, September 1, 1988 and April 3, 1989. The results were as follows : 1. Mercury concentration in the air was reduced from 0.140 to 0.107 $mg/m^3$ in 4 months, and to $0.087mg/m^3$ in one year after environmental improvement in workplace. However the level still exceeded the Threshold Limit Value. 2. The geometric mean of urinary mercury concentration among 80 workers was $173.0{\mu}g/l\;(5.1{\sim}458.6{\mu}g/l$). The distribution of workers according to urinary mercury concentration showed that 9 workers (11.2%) were above the mercury poisoning level ($300{\mu}g/l$), 24 workers (30.0%) were $200-299{\mu}g/l$, 35 workers (43.8%) were $50-199{\mu}g/l$, and 12 workers (15.0%) were below 50 ${\mu}g/l$. 3. Among the 24 workers whose urinary mercury concentration was 200-299 $50-199{\mu}g/l$, 8 were able to be followed up. Their mean urinary mercury concentration before segregation was $244.9{\mu}g/l$, but decreased to $151.4{\mu}g/l$ in four months, $128.8{\mu}g/l$ in six months, and $46.8{\mu}g/l$ in one year after segregation.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.33-37
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• 2008

A noticeable amount of Kirkendall voids formed at the Sn-3.5Ag solder joint with electroplated Cu, and that became even more significant when an additive was added to Cu electroplating bath. With SPS, a large amount of voids formed at the $Cu/Cu_3Sn$ interface of the solder joint during thermal aging at $150^{\circ}C$. The in-situ AES analysis of fractured joints revealed S segregation on the void surface. Only Cu, Sn, and S peaks were detected at the fractured $Cu/Cu_3Sn$ interfaces, and the S peak decreased rapidly with AES depth profiling. The segregation of S at the $Cu/Cu_3Sn$ interface lowered interface energy and thereby reduced the free energy barrier for the Kirkendall void nucleation. The drop impact test revealed that the electrodeposited Cu film with SPS degraded drastically with aging time. Fracture occurred at the $Cu/Cu_3Sn$ interface where a lot of voids existed. Therefore, voids occupied at the $Cu/Cu_3Sn$ interface are shown to seriously degrade drop reliability of solder joints.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.395-401
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• 2006

It is reported that semi-solid forming process takes many advantages over the conventional forming process, such as a long die life, good mechanical properties and energy saves. It is important to predict the deformation behavior for optimization of the forging process with semi-solid materials and to control liquid segregation for mechanical properties of materials. But rheology material has thixotropic, pseudo-plastic and shear-thinning characteristics. So, it is difficult for a numerical simulation of the rheology process to be performed because complicated processes such as the filling to include the state of the free surface and solidification in the phase transformation must be considered. General plastic or fluid dynamic analysis is not suitable for the analysis of the rheology material behavior. Recently, molecular dynamics is used for the behavior analysis of the rheology material and turned out to be suitable among several methods. In this study, molecular dynamics simulation was performed for the control of liquid segregation, forming velocity, and viscosity in compression experiment as a part of study on the analysis of rheology forming process.