• Journal of Powder Materials
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• v.8 no.4
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• pp.223-230
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• 2001

Ti-37.5at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ti and Si) were observed for the 5 min mechanically alloyed (MA 5 min) powder, but only $Ti_5Si_3$phase was observed for the 30 min mechanically alloyed (MA 30 min) powder. $Ti_5Si_3$phase was observed for the HIPed compact of MA 5 min and 30 min powders at 150 and 190 MPa for 3 hr at $1000^{\circ}C$. For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at $1350^{\circ}C$ at 190MPa for 3hr. The hardness values of the HIPed $Ti_5Si_3$compacts at $1350^{\circ}C$ at 150/190 MPa for 3hr were higher than HRC 76. The densification and mechanical property of HIPed $Ti_5Si_3$compacts was found to depend on more HIP temperature than HIP pressure.

• Design & Manufacturing
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• v.10 no.2
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• pp.44-49
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• 2016

The roll forming produces mass products using the continuous production process. Also we need the process that continuous long material or goods cutting into a desired length. Our study uses 3-D driving cutter and roll forming material as SPCC to investigate this. When we cut the material using the process of roll forming, the shear resistance is raised at the cutting punch's edge. The result is remained the trouble about burr and progressive deformation on the material. This study shows the method minimizing the above trouble. The material of punch was considering heat generated on the continuous production process. So we used the type of STD 61 for the material of punch and had the vacuum heat treatment for the surface hardness of HRC 53. The structure of the mold is designed with forming a double cam die at the upper punch and the both sides of central core. We conducted the experiment three times. In the result when had to make V-groove within the angle between 105 and 110 on the punch front end, we could get the minimum shear resistance on the punch front end. Also with the same condition we minimizes the material jams in the continuous production process.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.67-74
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• 2012

Although high productivity is possible, cold forged helical gears have not been widely used due to difficulty in achieving mechanical properties as well as dimensional accuracy of the product. Confidence in the gear characteristics also is very important in heavy-duty gear applications. Therefore, the properties of forged gears must be compared to the properties of conventional machined gears. The properties might be different due to the different fabrication processes. In this study, machined and forged products both before and after heat-treated have been compared by measuring the residual stress and involute curve of the tooth. Characteristics of hardness and microstructure were also compared. Additionally, tooth fracture strength was compared for the heat-treated products. Moreover, the tooth strength and the fracture pattern were compared between the machined and forged gears. The forged gear showed decreased changes in residual stress and decreased changes in dimensions when compared to the machined gear before and after heat treatment. The forged gear was over 10% better than the machined gear in tooth strength.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.8
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• pp.87-93
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• 2000

Powder Forging technology is being developed rapidly because of its economic merits and the possibility of lightening parts by replacing steel parts with aluminum ones especially in automotive parts manufacturing. Recently Powder Forging process is widely used for manufacturing primary mechanical parts as a combined technology of P/M and precision hot forging. This paper describes the process conditions for the powder forging of Aluminium alloy piston. For example powder alloy design preform design by FEM simulation cold of compaction of specimens and preform sintering of preform powder forging process. The characteristics of sintered compaction of specimens and preform sintering of preform powder forging process. The characteristics of sintered products and final forged piston ones are investigated with tensile strength hardness ductility and so on. Eventually its results prove the improve mechanical properties of the piston produced by powder forging.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.5
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• pp.224-229
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• 2019

PVD coating is a technology that can be applied to various industries, and is widely used for processing molds and machinery, improving performance of core parts, and extending the life. Therefore, there is a need for a research on a device and a process technology that can adjust the performance to suit each application. In this study, a PVD coating device with ion density control was used to deposit a coating layer on SKD 11, a cold die steel, with magnetron currents of 1 A, 2 A, 3 A at arc currents of 80 A, 100 A, 130 A. It examined the mechanical properties for each condition. Increasing the arc current and magnetron current could improve the thickness, adhesion, and hardness of the coating layer. Especially, When the magnetron current was high, it suppressed the droplets that could be generated by the high arc current, showing excellent surface uniformity and adhesion of the coating layer.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.186-193
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• 2022

The application of UHSS sheet is being expanded up to 50% to reduce the weight of automobiles and improve safety. However, due to the high strength and low elongation of the ultra-high tensile strength steel sheet, product defects such as spring back and mold defects such as cracks and chippings also occur. In this study, Pin/Ring on Disc and Spiral wear tests were conducted to evaluate the durability of Ti/Cr-coated molds for forming 1.2GPa grade UHSS sheets. Component analysis and thickness were measured for each coating layer, and hardness and adhesion were investigated to determine mechanical properties. Combining the results of various wear tests, it was found that the TiAlN coating had the best wear and sticking resistance.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.1-8
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• 2024

Phase stability of tetragonal crystals in yttria-stabilized zirconia ceramics is dependent on the content of yttria and the heat-treatment condition, related with mechanical properties. In this study, we fabricated the 1.5 mol% yttria-stabilized zirconia (1.5Y-YSZ) ceramics by cold isostatic pressing (CIP) and post-sintering at temperature range of 1200 to 1350℃ for 2 hours and investigated the sintered properties and microstructural evolution. Sintered and microstructural parameters, i.e, apparent density, grain size and phase composition of 1.5Y-YSZ ceramics were mainly dependent on the sintering temperature. Maximum sintered density of 99.4 % and average grain size of 200-300 nm could be obtained from the heat-treatment condition above sintering temperature at 1300℃ for 2 hours, possessing the superior mechanical hardness with 1200 Hv. However, phase stability of tetragonal grains in 1.5 YSZ ceramics is very low, inducing the phase transformation to monoclinic crystals on specimen surface during cooling after heat-treatment.

• The Korea Journal of Herbology
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• v.39 no.4
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• pp.11-17
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• 2024

Objective : The purpose of this dissertation is to make a list of the Rhodophyta growing naturally in the Korean coastal waters, and to carry out a survey on the current distribution status to investigate the Bangiaceae which can be used as medicinal herbs. Methods : References and research papers about herbology published at home and abroad were examined. Results : A list was made about Bangiaceae plant which were cultivated or grew naturally in Korea, after investigated the data on domestic and foreign Bangiaceae plants. Out of those lists, serviceable plants were selected , their distributions were analysed. 1. A total of 2 genera and 18 species of Bangiaceae were found in the Korean coastal waters among which 1 genera and 4 species(approximately 22%) were medicinal plants. 2. Out of the 18 species of Bangiaceae 16 species belonged to Porphyra, and out of the 4 species of medicinal plants 4 species belonged to Porphyra. 3. Among the medicinal parts 4 species belonged to algae species had cold property, and had salty and sweet flavors. 4. 4 species had the efficacy of Lung, Spleen and bladder meridian had the potency of soften hardness, which helps to remove hard clots generated, cure phlegm in human body. 5. No toxic drugs were detected. Conclusion : There were totaled to 18 genera and 2 species in Bangiaceae in Korea and among them medicinal plants are 1 genera, 4 species, some 22% in total.

• Journal of Applied Biological Chemistry
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• v.62 no.1
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• pp.25-30
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• 2019

This study investigated the quality changes in whole super sweet corn during thermal processing to extend its shelf-life. To minimize the reduction of unique texture of whole sweet corn after the sterilization, the alcohol sanitation applied and the cold point of a whole corn ear was determined using a computer simulation. The cold point was located between the corn kernel and the cob. The microorganisms on the surface of sweet corn were reduced by more than 1 log CFU/g after alcohol sanitation, then the whole corn was treated to satisfy the degree of sterilization ($F_{121.1}=4$). The quality of sterilized sweet corn was compared with the control that was treated with steaming. The quality changes of sterilized sweet corn during storage were monitored for 9 months at $25^{\circ}C$. The hardness was maintained within 30% of its initial value. The minimum of hardness was $464.50{\pm}103.35g$ and maximum of hardness was $514.50{\pm}81.83g$. The differences in the sugar content among the samples were found, but the sugar content of corn kernel remained within 30% of the control, ranging from $28.83{\pm}1.05$ to $34.36{\pm}0.42%$. The yellowness was higher than that of control by 5%. The maximum value of yellowness was $34.36{\pm}0.42$. The general bacteria and molds and yeasts in corn kernel stored at $25^{\circ}C$ were not detected after 9 months of storage at $25^{\circ}C$. Therefore, in this study, we have demonstrated that the thermal sterilized method extends the shelf-life of whole sweet corn with minimizing its quality changes over 6 months in room temperature.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.4
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• pp.277-282
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• 2016

The consumption of waxy corn is steadily increasing in Korea. Waxy corn is harvested before it reaches full maturity and consumed immediately or follwing cold storage. Glutinous and sweet kernels are preferred due to their high palatability. The kernel properties can change rapidly following harvest, and, therefore, optimal conditions to maintain the kernel quality of corn should be identified. In addition, the timing of harvest of waxy corn ear should be also determined for optimal marketable corn production. From 10 days after silking (DAS) to25 DAS. fresh ear weight and single kernel weight rapidly increased from 78.3 g and 1.13 g, respectively, to 224.9 and 3.61 g, respectively. However, by 30 DAS both fresh and single kernel weight decreased by 10.6% and 6.1%, respectively. Kernel hardness significantly increased up to 25 DAS, and a further slight increase in kernel hardness was observed at 30 DAS. Total sugar content in kernel decreased from 12.5% at 10 DAS to 3.5% at 35 DAS, which was the result of the conversion of sugars to starch during ear development. Crude protein content in kernel did not vary significantly in comparison to kernel hardness. During storage of ear, kernel hardness increased from $726g\;cm^{-2}$ at harvest to $1894g\;cm^{-2}$ following 28 days of storage at a low temperature ($0^{\circ}C$). Kernel hardness increased 2.5 fold from 15 DAS to 30 DAS. Soluble protein level in kernel increased until 10 DAS, following which a slight decrease was observed. The soluble protein content decreased from 1.85% at 5 DAS to 1.45% at 35 DAS. Total sugar content in kernel decreased regardless of storage temperature; however, the rate of reduction was lower at $0^{\circ}C$ than that observed following storage at $4^{\circ}C$ and $10^{\circ}C$. The rate of reduction in kernel moisture content was also lower at $0^{\circ}C$ than that observed at $4^{\circ}C$ and $10^{\circ}C$.