• 제목/요약/키워드: Hot bending

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The fabrication and characterization of hard rock cutting diamond saw (석재가공용 다이아몬드 톱의 제조 및 특성)

  • Lee Hyun-Woo;Jeon Woo-yong;Lee Oh-yeon;Seol Kyeong-won
    • Journal of Powder Materials
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    • 제11권5호
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    • pp.412-420
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    • 2004
  • The purpose of the present study is to determine an optimum composition using cheaper powders keeping with high performance of hard rock cutting diamond saw blade. With 50Fe-20(Cu . Sn)-30Co specimen, a part of Co was replaced by Ni(5%, 10%, and 15%, respectively). These specimens were hot pressed and sintered for predetermined time at various temperature. Sintering is performed by two different methods of temperature controlled method and specimen dimension controlled method. In order to determine the property of the sintered diamond saw blade, 3 point bending tester, X-ray diffractometer, and SEM were used. As the Co in the bond alloy was replaced by Ni, the hardness of the specimen increased. Thus the 50Fe-20(CuㆍSn)-15Co-15Ni specimen showed the maximum hardness of 104(HRB). The results of 3 point bending test showed that flexure strength decreased along with increase in Ni content. This is attributed to the formation of intermetallic compound(Ni$_{x}$Sn) determined by X-ray diffraction. The fracture surface after 3 point bending test showed that diamond was fractured in the specimen containing 0%, 5%, and 10%Ni, and the fracture occurred at the interface between diamond and matrix in the specimen containing 15%Ni. The cutting ability test showed that the abrasive property was not changed in the specimen containing 0%, 5%, and 10%Ni. The optimum composition determined in this study is 50Fe-20(CuㆍSn)-20Co-10Ni.

Modified Densification Process for Increasing Strength Properties of Pine and Gmelina Wood from Community Forests

  • Yunianti, Andi Detti;Tirtayasa P., Kidung;Suhasman, Suhasman;Taskirawati, Ira;Agussalim, Agussalim;Muin, Musrizal
    • Journal of the Korean Wood Science and Technology
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    • 제47권4호
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    • pp.418-424
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    • 2019
  • Densification is a process for improving the strength properties of wood from the felling of young trees, which is a common harvest practice in community forests. A series of experiments was conducted to refine the process with particular regard to the determination of suitable pretreatment and treatment conditions. Samples of pine and gmelina measuring $23cm(L){\times}20cm(W){\times}2cm(T)$ underwent pretreatment through immersion in a 1:1 $CH_3COOH-H_2O_2$ solution at concentrations of 15%, 20%, and 30%. Samples pretreated with the 20% solution showed the greatest improvement in strength; further experiments were conducted to determine the optimum treatment conditions in terms of temperature and duration following immersion. Test samples with the same dimensions as those in the pretreatment experiment were soaked in a 1:1 20% $CH_3COOH-H_2O_2$ solution and warmed in a water bath. The test samples were then individually hot pressed to the target thickness, which was 30% less than the original thickness and held at $150^{\circ}C$ or $170^{\circ}C$ for 15 or 30 minutes. The treated samples were cut for an analysis of their density, recovery of set, and bending strength. Pine and gmelina exhibited the best characteristics after treatment at $150^{\circ}C$ for 30 and 15 minutes, respectively. The results suggest that the modified densification process had increased the bending strength of the wood, but the temperature and duration of treatment must be carefully considered for different wood species.

Hot Pressing Technology for Improvement of Density Profile and Sound Absorption Capability of Particleboard (파티클보드의 밀도경사와 흡음성 개선을 위한 열압기술)

  • Park, Hee Jun;Kim, Hyun-Joong
    • Journal of the Korean Wood Science and Technology
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    • 제30권1호
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    • pp.25-33
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    • 2002
  • Improvement of density profile and sound absorption capability of particleboard was attempted. Three types of hot pressing methods examined ; flat-platen pressing method (A-type pressing), hot pressing in forming box (B-type pressing), and hot pressing set up jagged caul in forming box (C-type pressing). The raw materials were larch(Larix leptolepis (S, et. Z.) Gorden) shavings, phenol formaldehyde resin, and the particleboard perforated with stair type. The physical and mechanical properties such as specific gravity, bending strength (MOR), internal bonding strength (IB) and sound absorption coefficients were examined. The results are summarized as follows : 1) The MOR and internal bonding strength of the board pressed in forming box were higher than those of flat-platen pressed board. 2) The minimum density to average density ratio in thickness direction which pressed in forming box showed about 923%, in the case of 35 mm commercial particleboard and 50 mm flat-platen pressed board, its values showed about 66.4% and 865% respectively. 3) Sound absorption coefficients of the particleboard perforated with stair type were higher than those of flat-plated pressed board and commercial particleboard.

Bending Strength Properties of SiC Ceramics at Different Roughness Values of Polishing Plates (연마판의 거칠기에 따르는 SiC 세라믹스의 굽힘강도 특성)

  • Nam, Ki-Woo;Kim, Eun-Sun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제35권7호
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    • pp.779-784
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    • 2011
  • This study was carried out on the crack healing of three types of SiC ceramics based on a $SiO_2$ additive, taking into account the roughness of the polishing plate used for polishing the specimens. The mixtures were subsequently hot-pressed in $N_2$ gas for one hour under 35 MPa at 2053 K. In these specimens, the optimized crack-healing condition was 1373 K for one hour in air. The crack-healing material of the cracked part was the glassy phase of $SiO_2$ that was formed by the oxidation of SiC. In the optimum healing condition, the bending strength of non-polished SiC ceramics was not completely recovered. However, the bending strength of the SAY specimen was excellent, considering the economic aspects of SAY, SAYS-1, and SAYS-2. The SAY specimen is definitely superior to the others after an hour of heat treatment. There was a decrease in the number and size of defects in the specimen polished by using a $125-{\mu}m$ polishing plate; however, the micro-surface defects were not completely repaired. The specimen polished by using a 40-${\mu}m$ polishing plate showed little voids or surface defects after an hour of heat treatment. The bending strength of the specimen mirror-polished by using a 6-${\mu}m$ polishing plate was completely recovered.

An Applicability Estimation of Plastic Vertical Pipes using Electric Fusion Fittings through Measurement (실측을 통한 융착식 플라스틱 입상배관 성능 평가)

  • Park, Yool;Ahn, Young-Chull;Kim, Hyun-Dae;Kim, Jeong-Su;Goark, You-Shik;Kim, Young-Kyoung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • 제25권11호
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    • pp.595-599
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    • 2013
  • The pipes used in buildings are generally categorized into metallic or plastic materials. Metal pipes, such as copper and stainless steel pipes, are mainly used for water and hot water supply, and for the heating system. However, plastic pipes made of polyethylene and cross-linked polyethylene are used for floor heating, water drainage, and air vent systems. Usually, plastic pipes have thermal demerits, such as high linear expansion coefficients and bending phenomenon by hot water, although the pipes have several merits of light weight, low price, low thermal conductivity, and the comparatively high workability of metal pipes. Therefore, if those kind of demerits are overcome, plastic pipes can be easily accepted for hot water systems. This research is aimed to evaluate the applicability for vertical heating pipes of a plastic pipe system consisting of electric fusion fitting of a conductive carbon compound and propylene random glass fiber pipe, through measurement of the expansion rate and leakage in summer and winter seasons, in the apartment construction field.

Effects of Hot Isostatic Pressing on the Microstructure and High-Temperature Fatigue Life of the Ni-base Superalloy IN738LC (IN738LC 초내열합금에서 미세조직과 고온 피로수명에 미치는 고온등압압축(HIP) 공정의 영향)

  • Choi, Cheol;Kim, Doo-Soo;Lee, Young-Chan;Park, Young-Kyu;Kim, Gil-Moo;Kim, Jae-Cheol
    • Korean Journal of Materials Research
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    • 제10권2호
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    • pp.128-137
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    • 2000
  • A study has been made to investigate the effects of hot isostatic pressing(HIPing) on the microstructure and high temperature fatigue lives of the IN738LC, Ni-base superalloy used in turbine blades, with emphasis on the elimination of casting microporosity and fatigue damage through HIP treatments. Microstructure was observed using OM, SEM and the fatigue life was investigated with rotate bending fatigue tester. The results show that the fatigue lives of properly HIP-processed specimens could be extended be extended by a factor of about sixty. In contrast, no comparable life improvement was achieved with heat treatment only. The repetitive HIP treatment was shown to be very effective as a means of rejuvenating the fatigue life of intentionally fatigue-damaged IN738LC by restoration of the initial alloy microstructure and additional removal of fine casting defects which remained in the HIP-processed material.

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Effect of Moulding Conditions on Properties of Table Top for Student Desk Manufactured by Wood Waste Materials (폐기 목질 재료로 제조한 학생용 책상 천판의 성능에 미치는 성형조건의 영향)

  • Roh, Jeang-Kwan;Kim, Jae-Kyung;Kim, Sa-Ick;Jo, Jong-Soo;Yoon, Seung-Lak;Ra, Jong-Bum;Do, Jeong-Lak
    • Journal of the Korean Wood Science and Technology
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    • 제30권4호
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    • pp.106-113
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    • 2002
  • This research was performed to investigate the effect of moulding conditions on properties of the table top for student desk manufactured by wood waste materials. The table top manufactured using the mat mixed properly with fine particles and coarse particles generally showed better physical properties than those manufactured using either fine particles or coarse particles did/ Especially, highest performance for overlaying was observed when fine particles were used for face layer and coarse particles were used for core layer. The internal bond (IB) strength, the bending strength and thickness swelling increased with the increase of density. Most of physical properties were improved with the increase of hot pressing temperature. The best physical properties were found at 190℃ when the first hot pressing and the second hot pressing times were two minutes. However, the effect of the second hot pressing time of two minutes on the physical properties was not markedly different from that of one minute. This result suggests that the second hot pressing time of one minute is enough to increase the productivity in manufacturing the table top with the least decrease of the physical properties.

Effect of Temperature on the Deposition Rate and Bending Strength Characteristics of Chemical Vapor Deposited Silicon Carbide Using Methyltrichlorosilane (메틸트리클로로실란을 이용한 화학증착 탄화규소의 증착율 및 굽힘강도 특성에 미치는 온도의 영향)

  • Song, Jun-Baek;Im, Hangjoon;Kim, Young-Ju;Jung, Youn-Woong;Ryu, Hee-Beom;Lee, Ju-Ho
    • Composites Research
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    • 제31권2호
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    • pp.43-50
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    • 2018
  • The effects of deposition temperature on chemical vapor deposited silicon carbide (CVD-SiC) were studied to obtain high deposition rates and excellent bending strength characteristics. Silicon carbide prepared at $1250{\sim}1400^{\circ}C$ using methyltrichlorosilane(MTS : $CH_3SiCl_3$) by hot-wall CVD showed deposition rates of $95.7{\sim}117.2{\mu}m/hr$. The rate-limiting reaction showed the surface reaction at less than $1300^{\circ}C$, and the mass transfer dominant region at higher temperature. The activation energies calculated by Arrhenius plot were 11.26 kcal/mole and 4.47 kcal/mole, respectively. The surface morphology by the deposition temperature changed from $1250^{\circ}C$ pebble to $1300^{\circ}C$ facet structure and multi-facet structure at above $1350^{\circ}C$. The cross sectional microstructures were columnar at below $1300^{\circ}C$ and isometric at above $1350^{\circ}C$. The crystal phases were all identified as ${\beta}$-SiC, but (220) peak was observed from $1300^{\circ}C$ or higher at $1250^{\circ}C$ (111) and completely changed to (220) at $1400^{\circ}C$. The bending strength showed the maximum value at $1350^{\circ}C$ as densification increased at high temperatures and the microstructure changed from columnar to isometric. On the other hand, at $1400^{\circ}C$, the increasing of grain size and the direction of crystal growth were completely changed from (111) to (220), which is the closest packing face, so the bending strength value seems to have decreased.

The Relaion between Cold Rolling Factors and the Edge Drop (냉연 작업인자와 edge drop의 상관관계)

  • Yeo W. K.;Hwang S. M.;Chung J. S.;Kim J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 한국소성가공학회 2001년도 추계학술대회 논문집
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    • pp.142-146
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    • 2001
  • In this study, it was investigated the influence of cold rolling factors on the edge drop. Edge drop was highly affected by the shape of work roll, the amount of work roll shift and the crown of hot strip, but the effect of bending force at the front stand was relatively small. The used numerical model was examined by comparing to the result of measured field data, and it showed a qualitative agreement with each other.

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Effect of Ni Addition Interfacial Reaction and Corrosion Resistance in Hot Dip Galvanizing (용융안연 도금욕의 Ni첨가가 도금강판의 게면반응 및 내식성에 미치는 영향)

  • 이경구;시희봉;이도재
    • Journal of Surface Science and Engineering
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    • 제31권6호
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    • pp.379-388
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    • 1998
  • The iron-zinc interfacial reaction and corrosin properties in galvanizing bath containning Ni have been intestigated. The substrate steel plates were galvanized in Zn or Zn-0.018Al baths with various Ni contents. The corrosion resistance of galvanized specimens was also evaluated by $60^{\circ}$bending test for galvannealing speaaimens. The corrosion resistance was improved with Ni addition in pure Zn bath, while deteriorated with Ni addition in Zn-0.18Al bath. The anti-powdering property, on thhe otherhand, was improved with Ni addition in Zn-0.18Al bath, while deteriorated with Ni addition in pure Zn. It was found that the anti-powdering property was improved with increasing $\xi$ phase ratio in reaction layer.

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