• 열처리공학회지
• /
• 제33권3호
• /
• pp.117-123
• /
• 2020

Due to high corrosion resistance, Zinc has been widely used in the automobile, shipping or construction industries as a galvanizing material. Zinc is popular as a coating element, but its low mechanical strength impede the expansion of applications as a load-bearing structure. The mechanical strength of Zinc can be increased through zinc based alloy process, but the ductility is significantly reduced. In this study, the mechanical strength and ductility of Zinc-Magnesium alloys with respect to heat treatment hold time was investigated. In order to enhance the mechanical strength of Zinc, a Zinc-Magnesium alloy was fabricated by a melting process. The heat treatment process was performed to improve the ductility of Zinc-Magnesium alloy. The microstructure of the heat-treated alloy specimen was analyzed using SEM. The hardness and compressive strength of the specimen were measured by a micro-hardness tester and a nano-indenter, respectively.

• 플랜트 저널
• /
• 제6권4호
• /
• pp.56-62
• /
• 2010

This study investigated characteristics of the post-weld heat treatment of SA213-T23, which was developed for water wall of the ultra super critical power boiler. The temperature of post weld heat treatment should be $730^{\circ}C$ or higher to reduce hardness of the deposit metal and heat affected zone. Coincidently, the temperature should remain $760^{\circ}C$ or lower to prevent hardness of the base metal from dropping. Hardness decline of deposit metal was trivial according to time when the holding time of heat treatment at $740^{\circ}C$ of post-weld heat treatment gradually increased from initial 15 minutes.

• Restorative Dentistry and Endodontics
• /
• 제19권1호
• /
• pp.194-204
• /
• 1994

The purpose of this study was to evaluate the surface hardness of composite resins according to heat treatment. storage condition and storage time. In this study. two kinds of composite resin inlays and one kind of conventional posterior composite resin were used as experimental materials. One hundred eighty composite resin specimens were constructed from composite resin inlays and conventional posterior composite resin. The conditions of this study were heat treatment. storage condition and storage time. Hardness readings were taken from the top surface of each samples using the Vickers microhardness tester(MHT-l. Matsuzawa. Japan}. The following results from this study were obtained: 1. Regardless of storage condition. both composite resin inlay and conventional posterior composite resin have a higher surface hardness under heat treatment than not. 2. Composite resins with heat treatment have a higher surface hardness under dry storage than under water immersion. 3. In case of Clearfil Photo Posterior and Brilliant Enamel with heat treatment. there was no significant difference with time. but Clearfil CR Inlay with heat treatment. there was statistical difference after 24 hours. 4. Surface hardness of composite resins with coarse hybrid type was higher than that of composite resin with fine hybrid type.

• 한국세라믹학회지
• /
• 제26권3호
• /
• pp.297-304
• /
• 1989

The dielectric properties of SrTiO3 GBL Capacitor have been investigaetd as a function of the second heat treatment time and the amount of Ta. The grain size of semiconductive SrTiO3 after sintering at 1,46$0^{\circ}C$ for 4 hours in N2/H2 atmosphere increased as the amount of Ta increased, and then decreased as the amount of Ta exceed 0.01 mole. Also, the dielectric constant after the second heat treatment showed the same tendency. When the semiconductive SrTiO2 was second heat treated at 1,10$0^{\circ}C$ in air with varying time, the dielectric constant increased as the second heat treatment time increased up to 60 minutes, and then decreased as the time became longer than 60 minutes.

• 열처리공학회지
• /
• 제18권6호
• /
• pp.375-382
• /
• 2005

This paper presents the results of experimental investigation for the effect of heat conduction on the evaporation cooling of water droplet in the process of heat treatment. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter at aluminum. The range of surface temperature is from $80^{\circ}C$ to $140^{\circ}C$, surface roughness is from $R_a=0.18{\mu}m$ to $R_a=1.36{\mu}m$ and droplet diameter is from 2.4 mm to 3.0 mm. The results show that the total evaporation time is shorter for the larger surface roughness, the time averaged heat flux has maximum value for the larger surface roughness and exist the critical heat flux. The total evaporation time has a big influence on the evaporation region for the smaller droplet size, but the total evaporation time has not influence on the nuclear boiling region.

• 한국정보전자통신기술학회논문지
• /
• 제14권5호
• /
• pp.438-443
• /
• 2021

본 논문은 multiplex deposition sputter system을 사용하였고 ITO 유리기판 위에 CdS 박막을 증착하여 투과율을 향상시키고 제작비용을 절감하는데 목적을 두었다. CdS 박막을 제작할 때 열처리시간을 변화시켜 태양전지를 제작할 때 우수한 조건을 찾고자 하였다. 열처리 시간 변화에 따른 두께와 면 저항은 큰 차이가 없는 것으로 관찰되었다. 비저항은 최소값 6.68에서 최대값 6.98로 측정되었다. 열처리 시간이 20분 이상하였을 때 투과율은 75% 이상으로 측정되었다. 열처리시간이 10분일 때 밴드갭은 3.665 eV이고 20분 이상은 3.713 eV로 똑같은 결과로 측정되었다. XRD를 분석한 결과 CdS의 구조는 hexagonal로 나왔으며 다른 불순물이 없이 CdS 박막 만 증착되었다. 반치폭 (FWHM)을 계산한 결과는 열처리시간을 20분으로 하였을 때 0.142로 최대값으로 측정되었고 40분일 때 0.133으로 최소값으로 측정되어 열처리 시간을 변화 주었을 때 반치폭은 큰 차이가 없었다. 입자 크기를 측정한 것으로는 열처리시간을 40분으로 하였을 때 11.65 Å으로 최대값이고 20분일 때 10.93 Å으로 최소값으로 측정되었다.

• 열처리공학회지
• /
• 제30권3호
• /
• pp.99-105
• /
• 2017

This study was carried out to investigate the effect of heat treatment on the microstructure and mechanical properties in 90% hot forged Incoloy 825 alloy. With increasing solution treatment temperature, the grain size increased and the volume fraction of total precipitates decreased, and the precipitates disappeared at $1,000^{\circ}C$. With increasing aging time at $700^{\circ}C$, the volume fraction of precipitate increased and the precipitates size increased. Most of the precipitates consist $Cr_{23}C_6$ carbide, and a small amount of TiC carbide was also observed. With decreasing solution treatment temperature and increasing aging time, tensile strength and hardness increased, and the elongation and impact value decreased. With increasing aging time, the impact value decreased sharply by the increased of the precipitate size.

• 한국세라믹학회지
• /
• 제28권11호
• /
• pp.908-916
• /
• 1991

The characteristics of the carbonized and calcined products made from coal tar pitch coke and coal tar pitch, were investigated in the aspect of the manufacture of isotropic graphite with high density. The mesophase from the pitch was rapidly formed at higher heat-treatment temperature between 410$^{\circ}C$ and 450$^{\circ}C$, where the insolubes in the pitch accelerated the rate of nucleation and growth of the mesophase. The benzene insolubles and the quinoline insolubes were increased as the heat treatment temperature and the heat-treatment time increased. The ratio of benzene insolubles and quinoline solubles (BI/QS) was decreased as the heat-treatment temperature was higher and maintained to be nearly constant regardless of heat-treatment time at fixed heat treatment temperature. The bulk density of the calcined carbon was linearly proportional to the ratio of quinoline solubes to volatile matter in the green coke. Anisotropic ratio of electrical resistance was measured to be between 0.98 and 1.10.

• 열처리공학회지
• /
• 제9권1호
• /
• pp.62-68
• /
• 1996

In order to establish making process of water atomized iron powder for powder metallurgy, effect of heat treatment condition on change of powder properties and impurities was investigated at each tempeature of $850{\sim}950^{\circ}C$. The results are as follows. Particle morphology of iron powder changed slightly from sphercial type to irregular type and the amount of fine particle decreased more and more with increasing of heat treatment time at each temperature. The flow rate and apparent desity of iron powder also decreased due to particle coalescence in order of $850^{\circ}C$, $950^{\circ}C$, $900^{\circ}C$. Those powder Properties became to decrease particularly at $900^{\circ}C$ in alpha iron region. On the other hand, residual carbon and oxygen contents in iron powder decreased extremely with increasing of heat treatment temperature and time.

• 열처리공학회지
• /
• 제32권3호
• /
• pp.118-123
• /
• 2019

The aim of this study investigates the feasibility of scanning acoustic microscope (SAM) with high frequency transducer for material degradation. The test specimen was prepared by artificial heat treatment of Co-base superalloy. The high frequency 200 MHz acoustic lens was used to generate the leaky surface acoustic wave (LSAW) on the test specimens. The matrix precipitates coarsened with thermal aging time, and then grow up to several tens of micrometers. The velocity of LSAW decreased with increasing aging time. Also, it has a good correlation between LSAW and hardness. Consequently, V(z) curve methods of SAM using high frequency transducer is useful tool to evaluate the heat treatment effects on microstructure.