• 동력기계공학회지
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• 제5권2호
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• pp.63-70
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• 2001

To obtain the optimal condition of heat treatment of wear-resistant alloy, hardness and Charpy V-notch test have been performed with Co-based Stellite No.4, No.6 and Tribaloy 800 alloys, following by heat treatment at the various conditions. Heat treatment at $1250^{\circ}C$ for 1 hours caused the as-casted Tribaloy 800 with FCC crystal structure to transform to HCP structure and lamellar eutectic structure was disappeared, which did not influence on the hardness. Aging at $800^{\circ}C$ for 20 hours, following by $1250^{\circ}C$ for 2 hours heat treatment has enhanced hardness significantly, which is due to the precipitation of large amounts of Laves-phase. The hardness of Stellite alloys was increased by the aging at $800^{\circ}C$ to 5 hours, and was nearly constant by the aging over 5 hours. The toughness of Stellite alloys was a few influenced by the aging treatment.

• 열처리공학회지
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• 제7권3호
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• pp.184-189
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• 1994

The heat treatment charaterristic of SCM 440 and B 16 steels has been investigated in various condition(A, B and C) to the effect of heat treatment on mechanical properties, and the following results were obtained. 1. We are obtained a good nitriding characteristic in bainitic structure than other heat treatment cycle in our experiment. 2. Fatigue characteristic has shown in order of B)C)A condition as heat treatment cycle. 3. The effective hardening depth and fatigue characteristic has been excellented in B 16 than SCM 440 after the nitriding and Q. T for Band C condition. 4. Nitriding depth has been increased in addition of Cr, V and the nitriding efficiency is increased as easiness of banite formation to wide range of cooling rate by addition of Mo. 5. The depth of compound layer in parallel surface, notched slop plane and notched bottom has been varied to the nitriding depth of 5, 4 and 3 ${\mu}$ in relatively uniform pattern after 10h nitriding treatment for SCM 440 into A condition.

• 동력기계공학회지
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• 제15권2호
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• pp.49-54
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• 2011

Effect of tempering treatment on the mechanical properties of 12Cr heat resistant steel with ferrite phase was investigate in this study. As time and temperature of tempering treatment were increase, C and Cr contents in matrix structure were decreased. Due to increase of the amount of Cr26C6 type carbides. It was confirmed in mechanical properties experimental that tensile strength and hardness were decreased, while elongation and impact value were, increased with increasing the time and temperature.

• 동력기계공학회지
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• 제7권4호
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• pp.55-60
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• 2003

This paper is to investigate the fatigue crack growth of plasma-sprayed coating steels according to heat treatments. The experimental materials are carbon steels(substrate: S45C) with plasma-sprayed coating layers of Ni-4.5%Al and $TiO_2$. The fatigue test is conducted on compact tension specimen by a servo-hydraulic fatigue testing machine. The specimens are heat-treated at $400^{\circ}C\;and\;800^{\circ}C$, respectively. Loading condition is a constant amplitude sinusoidal wave with a frequency of 10Hz and a load ratio of 0.1. The fatigue crack growth length is automatically measured by a compliance method. In the case of non-heat treated specimens, the fatigue crack growth rates of both substrate and coating specimen are almost same. The crack growth rates of substrates and coating steels by heat treatment are larger than those of the non-heat treated one, because the ductile property increase by heat treatment. In ${\Delta}K<18MPa{\cdot}m^{1/2}$, the crack growth rates of the heat-treated specimens are slightly taster than non-heat treated one. But the both heated and non-heated one are almost same in ${\Delta}K>18MPa{\cdot}m^{1/2}$.

• 한국정밀공학회지
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• 제31권1호
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• pp.29-33
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• 2014

Recently, Difficult-to-cut materials are used in many manufacturing industry. But the difficult-to-cut materials are difficult-to-cutting process. So difficult to cut material cutting process was used after heat treatment through preheating for easy cutting process. In this study, Inconel 625 was preheating using laser heat source in computer simulation. Laser heat source temperature applied $1290^{\circ}C$ that suitable preheating temperature for Inconel 625. And temperature effects such as temperature distribution for moving heat source studied apply to similar actual process condition. Simulation results for heat treatment effects through temperature distribution verified.

• 한국농공학회논문집
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• 제48권5호
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• pp.51-60
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• 2006

In order to examine the heat transfer characteristic of a soil warming system and effects of soil warming on the greenhouse heating load, control experiments were performed in two greenhouses covered with double polyethylene film. One treated the soil warming with an electric heat wire and the other treated a control. Inside and outside air temperature, soil temperature and heat flux, and heating energy consumption were measured under the set point of heating temperature of $5,\;10,\;15,\;and\;20^{\circ}C$, respectively. Soil temperatures in a soil warming treatment were observed $4.1\;to\;4.9^{\circ}C$ higher than a control. Heating energy consumptions decreased by 14.6 to 30.8% in a soil warming treatment. As the set point of heating temperature became lower, the rate of decrease in the heating energy consumptions increased. The percentage of soil heat flux in total heating load was -49.4 to 24.4% and as the set point of heating temperature became higher, the percentage increased. When the set point of heating temperature was low in a soil warming treatment, the soil heat flux load was minus value and it had an effect on reducing the heating load. Soil heat flux loads showed in proportion to the air temperature difference between the inside and outside of greenhouse but they showed big difference according to the soil warming treatment. So new model for estimation of the soil heat flux load should be introduced. Convective heat transfer coefficients were in proportion to the 1/3 power of temperature difference between the soil surface and the inside air. They were $3.41\;to\;12.42\;W/m^{2}^{\circ}C$ in their temperature difference of $0\;to\;10^{\circ}C$. Radiative heat loss from soil surface in greenhouse was about 66 to 130% of total heating load. To cut the radiation loss by the use of thermal curtains must be able to contribute for the energy saving in greenhouse.

• 한국식품저장유통학회:학술대회논문집
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• 한국식품저장유통학회 2003년도 제23차 추계총회 및 국제학술심포지움
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• pp.167.1-167
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• 2003

To maintain high quality and to extend the shelf life of intact and minimally processed apple cubes, the effect of heat shock on the texture and color of apple cubes (Fuji) was evaluated in this study. After peeled and cored, the apples were cut into cubes of 1.5 cm. The heat shock was immersion in heated water from 25$^{\circ}C$ to 95$^{\circ}C$ in 10$^{\circ}C$ increments for 2 min and cooling to storage temperature as soon as possible after heat treatment. The effect of heat treatment in terms of color and texture measurements with respect to time was investigated, respectively during 7 days storage at in LDPE film bags without sealing at 4$^{\circ}C$, and 95% relative humidity air. Results suggest that heat shock (55$^{\circ}C$, 2 min) may have effectively delayed browning, and there were significant changes in color of apple cube when the temperature of heat shock is above 75$^{\circ}C$. And hardness, stiffness and firmness, which were used to describe texture, behaved similarly in the textural qualities. It was shown that the texture of the apple cubes was decreased with temperature increase. The value of them were most decreased to 70% of the initial ones after treated with 85$^{\circ}C$ and 95$^{\circ}C$ on the lust day.

• 한국식품영양학회지
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• 제14권5호
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• pp.385-390
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• 2001

1. 비가열 시료인 a와 b가 PE의 활성은 저장 둘째 주에 급격히 증가하다가 감소하였고, 가열 시료인 c 는 저장 넷째 주에 증가하다가 감소하였고, 병행 열처리와 trehalose 처리 시료는 저장 끝까지도 증가하였다. 2. PG의 활성은 비가열 시료인 a와 b는 저장 둘째 주부터 감소하다 저장 끝에는 증가하였고, 가열 시료인 c와 d는 저장 기간 동안 변화가 거의 없었다. 3. POD의 활성은 비가열 시료인 a와 b는 저장 둘째 주에 증가하다 감소하였고, 가열 시료인 c는 둘째 주에 약간씩 감소하였고, 병용 열처리하고 trehalose 처리군은 감소하였다. 4. 관능검사 결과 시료 a. b, d는 아작함과 기호도가 전 저장 기간동안 높았고, 시료 c는 갈색과 신맛의 증가로 기호도가 낮았다 저장기간에 따라서는 2주차에는 아작함과 형태가 좋았으나 4주 6주로 가면서 아작함과 기호도의 값이 감소하였다. 그리고 각 시료별 기호도에 가장 영향을 주는 항목은 아작함이었고 시료 c는 갈색, 맛, 조직감 등에서 음의 관계를 나타냈다.

• Corrosion Science and Technology
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• 제13권1호
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• pp.28-35
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• 2014

Recently, the fuel oil of diesel engines of marine ships has been increasingly changed to heavy oil of low quality as the oil price is getting higher and higher. Therefore, the spiral gear attached at the motor of the oil purifier which plays an important role to purify the heavy oil is also easy to expose at severe environmental condition due to the purification of the heavy oil in higher temperature. Thus, the material of the spiral gear requires a better mechanical strength, wear and corrosion resistance. In this study, the heat treatment(tempering) with various holding time at temperature of $500^{\circ}C$ was carried out to the alloy of Cu-7Al-2.5Si as centrifugal casting, and the properties of both hardness and corrosion resistance with and without heat treatment were investigated with observation of the microstructure and with electrochemical methods, such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and a.c. impedance. in natural seawater solution. The ${\alpha}$, ${\beta}^{\prime}$ and ${\gamma}_2$ phases were observed in the material in spite of no heat treatment due to quenching effect of a spin mold. However, their phases, that is, ${\beta}^{\prime}$ and ${\gamma}_2$ phases decreased gradually with increasing the holding time at a constant temperature of $500^{\circ}C$. The hardness more or less decreased with heat treatment, however its corrosion resistance was improved with the heat treatment. Furthermore, the longer holding time, the better corrosion resistance. In addition, when the holding time was 48hrs, its corrosion current density showed the lowest value. The pattern of corroded surface was nearly similar to that of the pitting corrosion, and this morphology was greatly observed in the case of no heat treatment. It is considered that ${\gamma}_2$ phase at the grain boundary was corroded preferentially as an anode. However, the pattern of general corrosion exhibited increasingly due to decreasing the ${\gamma}_2$ phase with heat treatment. Consequently, it is suggested that the corrosion resistance of Cu-7Al-2.5Si alloy can be improved with the heat treatment as a holding time for 48 hrs at $500^{\circ}C$.

• 한국기계연구소 소보
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• 통권16호
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• pp.3-16
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• 1986

The first specimens were sampled across the depth of roll products processed by rapid heating and cooling of the roll, namely, differential heat treatment. The second samples were taken from the non-heat treated roll at different depths. The samples were heat treated following the same temperature history as that at each corresponding location in the roll where the samples were taken. Consequently, both specimens showed the similar microstructure and mechanical properties (tensile, impact and fatigue strength etc.)