• Title/Summary/Keyword: Optimum heat-treatment temperature

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Study for Heat Treatment Optimization of Titanium Hollow Casted Billet (타이타늄 중공마더빌렛 주조재의 열처리공정 최적화 연구)

  • Youn, Chang-Suk;Park, Yang-Kyun;Lee, Hyung-Wook;Lee, Dong-Geun
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.2
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    • pp.68-73
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    • 2019
  • ${\alpha}$-titanium alloy has a relatively low heat treatment characteristic and it is mainly subjected to heat treatment for residual stress, recovery or dynamic recrystallization. In this study, commercially pure titanium hollow castings was fabricated by gravity casting. Heat treatments were carried out at $750^{\circ}C$, $850^{\circ}C$ and $950^{\circ}C$ to investigate the effect of post-heat treatment on microstructure and mechanical properties. Beta-transus temperature ($T_{\beta}$) was about $913^{\circ}C$, and equiaxed microstructure was shown at temperature below $T_{\beta}$ and lath-type microstructure at temperature above $T_{\beta}$. Microstructure and mechanical properties did not show any significant difference in the direction of solidification for titanium hollow billet, so it can be seen that it was a well-made material for extrusion process. The optimum heat treatment condition of hollow billet castings for the seamless tube production was $850^{\circ}C$, 4 hr, FC, indicating a combination of equiaxed microstructure and appropriate mechanical properties.

Kinetic study for the optimization of ginsenoside Rg3 production by heat treatment of ginsenoside Rb1

  • Vo, Hoang Tung;Cho, Jae Youl;Choi, Yong-Eui;Choi, Yong-Soon;Jeong, Yeon-Ho
    • Journal of Ginseng Research
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    • v.39 no.4
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    • pp.304-313
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    • 2015
  • Background: Ginsenoside Rg3 is a promising anticancer agent. It is usually produced by heat treatment of ginseng, in which ginsenoside Rb1 is the major ginsenoside. A kinetic study was conducted to optimize ginsenoside Rg3 production by the heat treatment of ginsenoside Rb1. Methods: Ginsenoside Rb1 was heated using an isothermal machine at $80^{\circ}C$ and $100^{\circ}C$ and analyzed using HPLC. The kinetic parameters were calculated from the experimental results. The activation energy was estimated and used to simulate the process. The optimized parameters of ginsenoside Rg3 production are suggested based on the simulation. Results: The rate constants were $0.013h^{-1}$ and $0.073h^{-1}$ for the degradation of ginsenosides Rb1 and Rg3 at $80^{\circ}C$, respectively. The corresponding rate constants at $100^{\circ}C$ were $0.045h^{-1}$ and $0.155h^{-1}$. The estimated activation energies of degradation of ginsenosides Rb1 and Rg3 were 69.2 kJ/mol and 40.9 kJ/mol, respectively. The rate constants at different temperatures were evaluated using the estimated activation energies, and the kinetic profiles of ginsenosides Rb1 and Rg3 at each temperature were simulated based on the proposed kinetic model of consecutive reaction. The optimum strategies for producing ginsenoside Rg3 from ginsenoside Rb1 are suggested based on the simulation. With increased temperature, a high concentration of ginsenoside Rg3 is formed rapidly. However, the concentration decreases quickly after the reaching the maximal concentration value. Conclusion: The optimum temperature for producing ginsenoside Rg3 should be the highest temperature technically feasible below $180^{\circ}C$, in consideration of the cooling time. The optimum reaction time for heat treatment is 30 min.

Aging Treatment Optimization of Ti-3Al-8V-6Cr-4Mo-4Zr Alloy for Spring Application (스프링용 Ti-3Al-8V-6Cr-4Mo-4Zr 타이타늄 합금의 시효열처리 최적화)

  • Youn, Chang-Suk;Park, Yang-Kyun;Kim, Jong-Hyung;Lee, Soo-Chang;Lee, Dong-Geun
    • Journal of the Korean Society for Heat Treatment
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    • v.30 no.6
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    • pp.279-284
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    • 2017
  • Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

Analysis of the Aluminum Extrusion Process Equipped with the Continuous Heat Treatment System

  • Lee, Bong-Sang;Cho, Young-Hee;Lee, Jeong-Min;Lim, Hak-Jin;Koo, Jar-Myung;Yoon, Bo-Hee;Lee, Tae-Hyuk;Lee, Jong-Hyeon
    • Korean Journal of Materials Research
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    • v.21 no.1
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    • pp.39-45
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    • 2011
  • In this study, the heat flow of the plant scale aluminum extrusion process was investigated to establish optimum continuous heat treatment conditions. During the extrusion of 6061 aluminum alloy, processing parameters such as the extrusion pressure, speed and temperature histories of billets were logged as a function of time. The surface temperature of the billets increased at constant ram speed, while it decreased with decreases of the ram speed. In order to maintain the billet temperature within a solutionizing temperature range prior to the succeeding water quenching step, the ram speed or the temperature of the blower should be controlled. The temperature histories of the billets during the extrusion and hot air blowing processes were successfully simulated by using the velocity boundary model in ANSYS CFX. The methodology to design an optimum process by using a commercial simulation program is described in this study on the basis of the metallurgical validation results of the microstructural observation of the extrudates. The developed model allowed the advantages of taking into account the motion of the extrudate coupled with the temperature change based on empirical data. Calculations were made for the extrudate passing through the isothermal chamber maintained at appropriate temperature. It was confirmed that the continuous heat treatment system is beneficial to the productivity enhancement of the commercial aluminum extrusion industry.

Surface Modification by Heat-treatment of Propellant Waste Impregnated ACF

  • Yoon, Keun-Sig;Pyo, Dae-Ung;Lee, Young-Seak;Ryu, Seung-Kon;Yang, Xiao Ping
    • Carbon letters
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    • v.11 no.2
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    • pp.131-136
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    • 2010
  • Propellant waste was impregnated on the surface of activated carbon fiber and heat-treated at different temperature to introduce newly developed functional groups on the ACF surface. Functional groups of nitrogen and oxygen such as pyridine, pyridone, pyrrol, lacton and carboxyl were newly introduced on the surface of modified activated carbon fiber. The porosity, specific surface area, and morphology of those modified ACFs were changed as increasing the heat-treated temperature from 200 to $500^{\circ}C$. The optimum heat-treatment temperature was suggested to $500^{\circ}C$, because lower temperature given rise to the decrease of specific surface area and higher temperature resulted in the decrease of weight loss. Propellant waste can be used as an useful surface modifier to porous carbons.

A Study of Tensile Strength in 18% Ni Maraging Steel Sheet Welded with Electron Beam (E.B 용접된 18% Ni 마르에이징강 박판의 인장이음강도에 관한 연구)

  • 정병호;김무길;김원녕
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.2
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    • pp.157-165
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    • 1997
  • The strength level of welded joint in room temperature and elevated temperature up to $600^{\circ}C$ was investigated in 250 and 300 grade 18% Ni maraging steel sheet welded with electron beam. The results obtained in this study are as follows; 1. Optimum welding heat input was 600J/cm in 1.0mm thickness and the room temperature tensile strength, joint efficiency of welded joint treated with optimum aging condition were found to be about 166kg/$mm^2$, 95% in 250 grade, 189kg/$mm^2$, 92% in 300 grade maraging steel sheet, respectively. 2. Tensile strength of welded joint in room temperature increased slightly by aging after repeated solution heat treatment, but the fracture mode showed a shear. 3. Joint efficiency at a temperature between $540^{\circ}C$and $600^{\circ}C$ found to be about 72% to 55%, but the joint efficiency exceeded about 90% below $300^{\circ}C$. 4. The fracture occurred in most weld metal, and the fracture surface showed a shallow dimple.

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Effect of the grain size of temperature dependence on the creep behavior of SUS 316 (SUS 316 강의 온도의존성 결정입경이 크리이프 거동에 미치는 영향)

  • Oh, Sae-Wook;Kang, Oug
    • Journal of Welding and Joining
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    • v.1 no.2
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    • pp.61-68
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    • 1983
  • Austenitic stainless steel has been investigated widely for creep strength of heat resistant material and effects of grain sizes due to various solution treatment time under constant temperature. It was studied that effects of grain sizes subject to solution treatment temperature 1100.deg. C, 1125.deg. C, 1175.deg. C, 1250.deg C, and 1300.deg. C respectively on the creep strength, fracture behaviour and fractography of SUS 316 stainless steel. The experimental results obtained were as follows. 1. The optimum grain size for the maximum creep strength did not vary with creep testing temperatures and stress levels. 2. Among various grain sizes due to different solution treatment temperature, the optimum grain size for the creep strength was found 0.044mm. Also the size showed the minimum initial strain regardless creep temperature. 3. Garofalo's equation of creep rupture life was applied well to SUS 316 stainless steel. 4. The fractography of optimum size was ductile intergranular fracture of dimple type and showed along with the increase of grain size intergranular fracture of w type.

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Thermal diffusion behaviors of electrogalvanized steel sheets (전기아연도금강판의 열확산 거동)

  • 김영근
    • Journal of Surface Science and Engineering
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    • v.28 no.5
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    • pp.320-328
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    • 1995
  • The electroplated steel sheets were heated during the short periods(10~60 seconds) at high temperature ($360^{\circ}C$$500^{\circ}C$) in order to investigate thermal diffusion behaviors. When the steel sheets were heated for 10 seconds, all the coated layers were alloyed at $420^{\circ}C$ but at temperature lower than $400^{\circ}C$ the $\eta$ phase partially remained on the coated surface. At higher temperature, the longer the time for heat treatment the iron contents were increased in coated layer but the glossiness and whiteness of the coated surface were decreased. While the alloying phases of $\eta$, $\zeta$, $\delta_1$ and $\Gamma$ were appeared in the coated layer at the heat treatment temperature of $360^{\circ}C$, the phase was disappeared at $420^{\circ}C$ but the rests grew in size at the temperature of $440^{\circ}C$. When the heat treatment temperature and heating time were increased, the thickness of $\Gamma$ phase was rapidly increased to 0.8 $\mu\textrm{m}$. The optimum conditions for the heat treatment to prevent powdering of coated layer were obtained to heat it for 30 seconds at $400^{\circ}C$ and 10 seconds at $440^{\circ}C$, and the iron content in coated layer was suited to be 10 percents.

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A Study on Electromagnetic Wave Absorbing Properties of $Ni_{0.5}$$-A_{0.1}$-$Zn_{0.4}$.${Fe_2}{O_4}$Ferrite-Rubber Composite by Heat-Treatment Temperature of ferrite (전파흡수체용 $Ni_{0.5}$$-A_{0.1}$-$Zn_{0.4}$.${Fe_2}{O_4}$의 열처리 온도에 따른 Ferrite-Rubber Composite의 전파흡수특성에 관한 연구)

  • 박연준;김동일;이창우
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2000.05a
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    • pp.109-114
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    • 2000
  • In this paper, we studied the relation between heat-treatment temperature of ferrite and electromagnetic wave absorbing properties of ferrite-rubber composite. The heat-treatment temperatures of ferrite are 1200 and 1300 $^{\circ}C$, 2 hr. As s result, it has been shown that the optimum heat-treatment temperature of ferrite for electromagnetic wave absorber are related to the chemical composition. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the control of heat-treatment temperature of ferrite.

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The Effect of Solution Heat Treatments on the Microstructure and Corrosion Behaviour for a Duplex Stainless Steel

  • Kim, Ki-Joon;Lee, Joon-Goo;Oh, Jae-Whan;Lee, Myung-Hoon;Moon, Kyung-Man
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.2
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    • pp.217-227
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    • 2004
  • The bowl in a ship purifier suffers from high stress and high temperature in a detrimental heavy fuel oil environment. Duplex stainless steel(DSS) is a primary material to withstand this harsh condition. Newly-manufactured STS 329 grade DSS has been evaluated by various mechanical and electrochemical test methods. Eight heat treatment(HT) conditions with different temperature and time were applied to the DSS samples to improve corrosion resistance. Microstructure and polarization test results concluded the optimum HT condition was $1.090^{\circ}C$-60 minutes. Confirmation experiments for applying to a real bowl including stress corrosion cracking test exhibited the reproducibility of the optimum HT condition.