• 열처리공학회지
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• 제7권1호
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• pp.25-34
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• 1994

To investigate the effect of austenitizing tempratures on the mechanical properties and corrosion resistance of 0.19%C-13.6%Cr martensitic stainless steel, the changes in martensitic trasformation temperatures, mechanical properties and anodic polarization curve were examined after changing the austenitizing temperatures and tempering temperatures. On increasing heating rate at the same austenitizing temperatures, $A_s$, $A_r$ and $M_s$ increased. And the $M_s$ temperature showed to be decreased with increasing austenitizing temperature. With increasing tempering temperature up to $500^{\circ}C$, strength, hardness and impact value were not changed remarkably, on the other hand the tensile strength and hardness decreased and impact value increased after tempering above $550^{\circ}C$ owing to the $M_{23}C_6$ carbide precipitation. The abrupt decrease in elongation at the tempering temperture of $500^{\circ}C$ proved to the precipitation of $M_7C_3$ carbide. The effect of austenitizing temperature on the mechanical properties of the tempered specimen showed to be decreased in impact value and elongation at the austenitizing temperature of $1150^{\circ}C$. At low tempering temperatures the corrosion resistance of the tempered specimen was not changed obviously with increasing tempering temperature. On the other hand, the resistance decreased above the tempering temperature of $600^{\circ}C$ due to the precipitation of $M_{23}C_6$ carbides. The corrosion resistance showed to be improved with increasing the austenitizing temperature owing to the dissolution of carbides.

• 열처리공학회지
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• 제17권1호
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• pp.29-35
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• 2004

The effect of low tempering in a temperature range of $150{\sim}400^{\circ}C$ on corrosion resistance in 420J2 stainless steel austenitized at $1000^{\circ}C$ was investigated by the application of salt spray test, electrochemical pitting test in 3.5% NaCl solution and DL-EPR test for intergranular corrosion in 0.5M $H_2SO_4$+0.01M KSCN solution. In salt spray test, good corrosion resistance was obtained in a tempering temperature range of $150{\sim}250^{\circ}C$. Pitting potential was increased to the tempering temperature of $250^{\circ}C$, but decreased with the increase of temperature up to $400^{\circ}C$ And it was thought that the degradation of pitting corrosion resistance showed at the tempering temperature of around $400^{\circ}C$ was due to the precipitation of $Cr_7C_3$ of $M_7C_3$ type. The degree of sensitization showed increasing tendency with the increase of tempering temperature, and also Cr depletion phenomena were observed in the vicinity of grain boundary.

• 한국식품과학회지
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• 제7권2호
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• pp.96-99
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• 1975

쌀보리의 합리적인 제분 방법을 규명하고저 tempering 최적조건 부분 도정후의 제분성, 밀과의 혼합 제분성 등을 test mill 을 이용, stock stream 별로 검토해 본 결과 다음과 같은 결과를 얻었다. 1. 쌀보리의 최적 tempering 조건으로서는 수분 13. 5%에서 48시간 일차 tempering 을 한 후 이어 제분 30분전 0. 5% 가수 처리하는 것이 가장 유리하였다. 2. tempering 전후 부분 도정을 실시하므로써, 회분 함량은 저하시킬 수 있었으나 수율이 크게 저하되고, 부분도정 후 제분이란 두 단계의 가공 과정이 필요하므로 비효율적이었다. 3. 쌀보리를 밀과 혼합하여 제분할 때, 쌀보리의 혼합비율은 $10{\sim}20%$가 합리적이며, 이때 사용되는 원료 밀은 연질보다 경질의 밀이 더욱 유리하였다.

• 한국식품과학회지
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• 제6권3호
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• pp.133-137
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• 1974

밀 제분공정(製粉工程)을 이용(利用)한 보리류(類)의 제분성(製粉性)을 구명(究明)코자 하는 의도 하에 국산(國産) 보리류(類) 4종(種)과 미주산(美洲産) 수입(輸入)밀(혼합(混合)) 1종(種)에 대하여 Tempering 최적조건(最適條件), 제분수율(製粉收率), 제분공정(製粉工程)에서의 Stock의 흐름 등을 조사(調査)하여 다음과 같은 결과(結果)를 얻었다. 1) 보리류(類)의 최적(最適) tempering 조건(條件)은 겉보리가 수분(水分) 15%에서 24시간(時間), 쌀보리가 수분(水分) 14%에서 48시간(時間), 겉보리쌀과 쌀보리쌀은 수분(水分) 13%에서 48시간(時間)이다. 2) 보리류(類)의 가루는 밀 제분공정(製粉工程)에서 뒤로 밀리기 때문에 밀 제분공정(製粉工程)을 이용(利用)하려면 공정(工程)의 부분적(部分的) 재조정(再調整)이 필요(必要)하다. 3) 보리류(類)의 제분성(製粉性)은 겉보리쌀, 쌀보리쌀, 쌀보리, 겉보리의 순(順)으로 좋으나, 겉보리쌀과 쌀보리쌀은 정곡(精穀)인 까닭에 1차 도정(搗精, 2차 제분(製粉)의 두 단계(段階) 가공과정(加工過程)을 거쳐야 하므로 가공비용(加工費用)이 과중(過重)하게 되고 수율(收率)에 있어서도 조맥(粗麥) 대(對) 분(粉)의 비율(比率)이 조맥제분(粗麥製粉)에 비(比)하여 겉보리쌀은 13.6%, 쌀보리쌀은 12.5%가 떨어지므로 경제성(經濟性)이 불리(不利)하다. 4) 밀과 보리류(類)를 9 : 1로 혼합제분(混合製粉)한다면 밀 제분공정(製粉工程)을 그대로 이용(利用)할 수 있다. 5) 겉보리는 쌀보리에 비(比)하여 수율(收率)이 6% 떨어지고 제분공정(製粉工程)에서 거칠은 외과피(外果皮)가 부에 혼입(混入)되어 사료적(飼料的) 이용가치(利用價値)를 결정적(決定的)으로 떨어뜨린다. 6) 밀과의 혼합제분용(混合製粉用)으로는 쌀보리가 가장 좋다.

• 한국식품과학회지
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• 제23권1호
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• pp.19-24
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• 1991

고형 유지의 상승 융점 변화에 영향을 주는 여러 가지 조건들 중 처리 온도와 시간이 미치는 영향에 대하여 연구하였다. 실험결과 처리 온도가 $4^{\circ}C$ 이하인 경우는 시간에 의한 영향을 크게 받지는 않았다. 그러나 $10^{\circ}C$에서 처리한 경우는 저융점 트리글리세리드들이 미처 결정을 형성하지 못하였으므로 돈지 및 팜유에서는 비교적 낮은 온도에서 융점이 측정되었다. 그러므로 고형 유지의 융점을 측정하기위해서는 유지 내의 자유 에너지도를 낮춘 상태에서 충분한 결정을 형성 시킨 후 측정해야하므로 바람직한 전처리 조건은 $4^{\circ}C$에서 방치하여 고형화한 후 융점을 측정하는 것이다.

• 한국주조공학회지
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• 제35권4호
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• pp.88-98
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• 2015

The effects of quenching and tempering temperatures on the tensile, impact and corrosion properties of A487 alloy cast with different C contents of 0.16, 0.19 to 0.23 wt.% were examined. The impact tests were conducted at $25^{\circ}C$ and $-60^{\circ}C$ and the immersion test was performed using 3.5% NaCl solution for 14 days. The quenching temperature affected the mechanical properties of A487 alloy cast, while the magnitude of change varied depending on the C content. The increase in tempering temperature showed the typical trend of decreasing tensile strength and increasing impact properties. The change in quenching and tempering temperature in this study did not affect the corrosion properties of A487 alloy significantly. The change in mechanical and corrosion properties of A487 with different C contents was discussed based on the microstructural and fractographic observation.

• Nuclear Engineering and Technology
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• 제46권3호
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• pp.413-422
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• 2014

Presented in this study are the variations of microstructures and mechanical properties with tempering and Post-Weld Heat Treatment (PWHT) conditions for SA508 Gr.4N steel used as Reactor Pressure Vessel (RPV) material. The blocks of model alloy were austenitized at the conventional temperature of $880^{\circ}C$ then tempered and post-weld heat treated at four different conditions. The hardness and yield strength decrease with increased tempering and PWHT temperatures, but impact toughness is significantly improved, especially in the specimens tempered at $630^{\circ}C$. The sample tempered at $630^{\circ}C$ with PWHT at $610^{\circ}C$ shows optimum mechanical properties in hardness, strength, and toughness, excluding only the transition property in the low temperature region. The microstructural observation and quantitative analysis of carbide size distribution show that the variations of mechanical properties are caused by the under-tempering and carbide coarsening which occurred during the heat treatment process. The introduction of PWHT results in the deterioration of the ductile-brittle transition property by an increase of coarse carbides controlling cleavage initiation, especially in the tempered state at $630^{\circ}C$.

• 열처리공학회지
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• 제23권6호
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• pp.338-343
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• 2010

Mechanical properties and microstructures of medium carbon high manganese steels were investigated in terms of alloying elements such as Mn, C contents, and heat treatment condition. Austenite volume fraction was increased with increasing Mn content, leading to hardness decrease in the range of Mn content of above 10% after quenching and tempering. Such results are also supported by microstructural analysis and X-ray diffraction in that the increase in mangaese content results in the increase in austenite fraction. Studies on tempering condition indicated that not only hardness and tensile strength but also charpy impact values were reduced as tempering temperature were raised in the range of $250^{\circ}C$ to $600^{\circ}C$. It was also observed that fracture mode was changed from dimple to intergranular fracture. Such results are thought to be due to very fine carbide precipitation or impurity segreagation at grain boundaries as tempering temperature goes up. Heat treatment of Fe-5Mn-2Si-1Al-0.4C can be optimized by austenitizing at $850^{\circ}C$, air cooling and tempering at $250^{\circ}C$, resulting in 1950 MPa in Tensile strength, 17% in elongation and 23.3 $J/cm^2$ in charpy impact energy with high work hardening characteristics.

• 열처리공학회지
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• 제4권3호
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• pp.54-62
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• 1991

The effect of tempering temperature on the ultrasonic propagation velocity at SCM 440 steel quenched from $870^{\circ}C$ and $1000^{\circ}C$ has been studied by metallurgical and crystallographical observation. The measurements of ultrasonic velocity were made on the specimen by appling an immersion ultrasonic pulse-echo technique with a constant frequency of 10 MHz. The quenched microstructure of this steel was a lath martensite. As the tempering temperature was increased, the martensite was transformed into the tempered martensite composed of cementite and carbide. The ultrasonic velocity increased with increasing the tempering temperature. It was thought that these were resulted from the microstructural transformation. The change of ultrasonic propagation velocity with quenching and tempering heat treatment was resulted from microstrain due to the change of internal stress. Considering these results concerning to the change of ultrasonic propagation velocity. the phenomena of microstructural transformation were estimated. Consequently, it was thought that the degree of quenching and tempered heat treatment of steel could be nondestructively evaluated with the change of ultrasonic propagation velocity.

• 열처리공학회지
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• 제25권1호
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• pp.14-21
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• 2012

The effects of cutting condition and tempering temperature for the shape of cutting chip were investigated. For this purpose, a lead-free brass containing 1wt.% of Bi extruded at $750^{\circ}C$ in straight turning was used in this study. The cutting chip preferred was mainly found to be loose form of arc chips with curling discontinuity, and these were formed by shear fracture. However, some of fragmental element chip were found to be mixed when tempering temperature was as high as $500^{\circ}C$. The form and size of chip was more affected by feed rate than by tempering temperature and cutting rate. In addition, the cutting surface was observed to be formed more rough in the case of high feed rate and low cutting rate compared to low feed rate and high cutting rate.