• Title, Summary, Keyword: hardness

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Characteristics of Hardness and Wear-Resistance of Plasma-Nitrided and Nitrocarburized Carbon Steels (플라즈마질화 및 침질탄화처리한 탄소강의 경도와 내마모특성)

  • Kim, M.K.;Jung, B.H.;Park, H.S.;Lee, B.C.;Shin, S.H.;Lee, J.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.12 no.2
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    • pp.166-173
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    • 1999
  • Commercial carbon steels containing 0.2~0.55 wt.----C were plasma-nitrided or plasma nitrocarburized at $550^{\circ}C$ for 21.6Ks using $H_2-N_2$ or $H_2-N_2$-CO mixed gas respectively. The characteristics of hardening and wear-resistance of each treatment were studied and compared. And also microstructure of nitrided layer and nitrides formed in compound layer near surface were studied. All plasma-nitrided steels investigated showed remarkable increase of surface hardness with the increase of carbon content. But nitrocarburized steels resulted in higher surface-hardness than plasma-nitrided steels, which means that nitrocarburized has higher surface-hardening effect. Plasma-nitrided steels showed hardness increase in through-thickness direction near surface. And also nitrocarburized steels showed similar hardness distribution in through-thickness direction to that of plasma-nitrided steel. However, nitrocarburized steels had higher cross-sectional maximum-hardness than plasma-nitrided steels as much as 100Hv. Wear test showed that the amount of specific wear was reduced by both plasma-nitriding and nitrocarburized, showing that the amount of specific wear was not related to the hardness. But non-treated specimen showed that the amount of specific wear was related to the hardness.

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Changes in free amino acids and hardness in round of Okinawan delivered cow beef during dry- and wet-aging processes

  • Hanagasaki, Takashi;Asato, Naokazu
    • Journal of Animal Science and Technology
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    • v.60 no.9
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    • pp.23.1-23.9
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    • 2018
  • Background: Aging trials are conducted to determine characteristics associated with dry- and wet-aging processes of beef from delivered cows grown in Okinawa, i.e., dams that have finished giving birth (Okinawan delivered cow beef). Changes in free amino acids, hardness, and other factors were analyzed in round of Okinawan delivered cow beef during dry- and wet-aging processes along with a comparison with characteristics of beef imported from Australia. Results: Functional amino acids did not increase during both dry- and wet-aging processes. However, proteinogenic amino acids increased significantly (P < 0.05) and hardness tended to decrease during both dry- and wet-aging processes. On comparison between dry- and wet-aging processes by analysis of variance, drip and cooking losses were significantly lower during the dry-aging process than during the wet-aging process. However, there was no significant difference in free amino acids or hardness in this comparison. Conclusion: There was no significant difference between dry- and wet-aging methods for all studied variables related to free amino acids or hardness in this study.

Evaluation of Heat Treatment of an Al-Si Alloy forging by Using Its Relationship between Electrical Conductivity and Hardness (경도-전기전도도 상관관계를 이용한 A1-Si 알루미늄합금 열간 단조품의 열처리상태 평가)

  • 이석원;전만수;이준현
    • Transactions of Materials Processing
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    • v.10 no.5
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    • pp.418-424
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    • 2001
  • In this study, a relationship between hardness and electrical conductivity for an Al-Si aluminum alloy, forged after extruded, is investigated. Microvickers hardness is measured and compared with its corresponding electrical conductivity obtained by the eddy current test. It is found that a distinct relationship between the hardness and the electrical conductivity exists for the material. Using the relationship, the hardness of forging is predicted from the electrical conductivity obtained by eddy current test and the result is used to evaluate the condition of heat treatment.

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Effects of Long-term Artificial-Aging on the Hardness Variation of Dissimilar Metal Weldments (이종금속 용접부의 경도변화에 대한 장시간 인공열화의 영향)

  • Kim, Chung-Seok
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.1
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    • pp.31-37
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    • 2019
  • This study investigates the effects of long-term artificial-aging on hardness variation in the dissimilar metal weldments for nuclear power plant facilities. These dissimilar welds are inevitably required to join the components in nozzle parts of pressurized vessels, such as austenitic stainless steels and ferritic steels. A artificial thermal aging was conducted in an electrical furnace to simulate material degradation at high temperatures. The test materials were held at the temperature of $600^{\circ}C$ for 10000 hours and interrupted at various levels of degraded specimens. The degradation of hardness is a well-known phenomenon resulting from long-term aging or high-temperature degradation of structural materials. In this study, the variation of hardness at each position was different, and complicated in relation to microstructures such as twins, grains, precipitates, phase transformations, and residual stresses in dissimilar weldments. We discussed the variation of hardness in terms of microstructural changes during long-term aging.

Research on the Electric device for the Noncontacting Hardness Tester (비접촉식 경도 측정용 전기 설비에 관한 연구)

  • 이진락;백기남
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.45-47
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    • 1991
  • In this research, we verify the relations between the mechanical hardness of a strip and the output of Residual Magnetic Flux Detector, which is installed in the end side of #2 CAL. First, we install the strip speed detector and get a hardness signal and a speed signal 2 seconds, and then do signal processing and send an output to a printer every 30 seconds. The system that performs above functions is Magnetic Hardness Data Acquisition & Processing System. We got the relation between output current and hardness for the strip of T3 BP through on-line tests. Seconds, we made a hardness Measurement Simulator and observed the speed characteristics of residual magnetic flux, with using it.

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The Effects of Solution Heat Treatment and Aging Treatment on the Electrical Conductivity and Hardness of Cu-Cr Alloys (크롬동합금의 도전율과 경도에 미치는 용체화처리와 시효처리의 영향)

  • Kim, Shin Woo
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.1
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    • pp.21-24
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    • 2002
  • The electrode materials for welding machine in automobile industry such as Cu-Cr, Cu-Zr and Cu-$Al_2O_3$ require the high electrical conductivity and the proper hardness. Therefore the effects of solution heat treatment and aging treatment on the electrical conductivity and hardness of Cu-0.8wt%Cr and Cu-1.2wt%Cr alloys have been investigated. Cu-0.8wt%Cr alloy showed the higher electrical conductivity and hardness than Cu-1.2wt%Cr alloy and both alloys showed the better electrical conductivity at $930^{\circ}C$ among 930, 980 and $1030^{\circ}C$ solution heat treatment temperatures. The electrical conductivity and hardness in both alloys were not affected by aging treatment but remarkably affected by solution heat treatment temperature. The final drawing process reduced electrical conductivity and increased hardness more in Cu-1.2wt%Cr alloy.

Effect of Heat Treatments on the Final Hardness of STS 420J2 Martensitic Stainless Steel (420J2마르텐사이트 스테인레스강의 최종경도에 미치는 열처리조건의 영향)

  • Kim, K.D.;Sung, J.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.3
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    • pp.175-183
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    • 1994
  • The effect of batch annealing conditions and austenitizing temperatures on the hardness and microstructural factors were examined by using 420J2 martensitic stainless steel. In spite of the similler hardness after batch annealing, the difference in hardness at the same austenitizing temperature was caused by changes in dissolved carbon during batch annealing. The highest hardness of the specimen was obtained at the batch annealing temperature of $820^{\circ}C$ and austenitizing temperature of $1050^{\circ}C$. The main factor affecting the final hardness of the cold annealed 420J2 specimen was proved to the austenitizing temperature rather than batch annealing temperature.

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Studies on the cigarette hardness(II) The Influence of relative humidity, temperature and net weight on cigarette hardness (담배 경도에 관한 연구(II) 상대습도, 온도 및 진충량이 담배의 경도에 미치는 영향)

  • 정한주;민영근;김병구;김기환
    • Journal of the Korean Society of Tobacco Science
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    • v.13 no.1
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    • pp.13-18
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    • 1991
  • This experiment carried out to review influence of relative humidity, temperature and net weight on cigarette hardness for the uniformal control of cigarette quality. Obtained results are as follows: 1. The difference in the cigarette physical properties of constant hardness control is considerably lower than that of constant net weight control. 2. Contribution rate for cigarette hardness is relative humidity > net weight > temperature. 3. The multiple regression equation of cigarette hardness related with relative humidity, temperature and net weight is calculated as follows.

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Effects of Zn, Zr Addition on Microstructures and Hardness of Mg/SiCp Composites Fabricated by Rheo-Compocasting (Rheo-Compocasting법으로 제조한 Mg/SiCp 복합재료의 조직 및 경도 특성에 미치는 Zn, Zr 첨가의 영향)

  • Hong, Sung-Kil;Choe, Jung-Chul
    • Journal of Korea Foundry Society
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    • v.15 no.6
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    • pp.588-595
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    • 1995
  • SiC particles reinforced Mg-Zr, Mg-Zn and Mg-Zn-Zr composites were manufactured by Rheocompocasting method. Effects of Zn, Zr addition on microstructures and hardness were investigated by using the micro Vickers hardness tester, the optical and scanning electron microscopy. By the Zr addition to the pureMg/SiCp composites, SiC particles become more homogeneously dispersed and grain refined so that the micro hardness of the composite increased. In case of Zn addition, although grain refinement and homogeneous dispersion effects of SiC particles were not obtained, hardness was more increased than the only Zr added composite by the formation of many Mg-Zn intermetallic compounds at grain boundary. In the Mg-Zn-Zr/SiCp composite, the highest value of hardness was obtained by triple effects such as grain refining, dispersion hardening of SiC particles and Mg-Zn compounds.

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Effect of Composition on the Hardness and Toughness in PZT-PYW Ceramics (PZT-PYW 세라믹스의 조성변화가 경도 및 인성에 미치는 영향)

  • 류소연;임대순;윤석진;김현재
    • Journal of the Korean Ceramic Society
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    • v.31 no.3
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    • pp.305-311
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    • 1994
  • In this paper, a change of fracture toughness and hardness in PZT-PYW ceramics system before and after poling treatment was measured to investigate the effect of composition on the mechanical properties in PZT-PYW ceramics. The hardness of the PZT-PYW ceramics increased with increasing mole fraction of PYW. The fracture toughness achieved maximum values for x=0.03. Both of the hardness and the fracture toughness also increased with poling treatment. The variation of both hardness and fracture toughness with increasing PYW mole fracture was explained by the change in microstructures such as grain size and second phase. The difference in hardness and fracture toughness in the electrically poled and unpoled specimens was also explained on the bases of internal stress.

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