• Journal of the korean Society of Automotive Engineers
• /
• v.4 no.3
• /
• pp.24-39
• /
• 1982

It has already been known that quenching effect is influenced greatly by stirring and changing coolant's temperature on quenching. But according to the past investigations its effect has not been taken into consideration quantitatively in the cooling process. The purpose of this study is that the influence of flow rate and temperature on the quenching effect of cooling water as quenching medium is quantitatively examined by using the open channel. The stream of water in this study is turbulent flow. The temperature of the specimen made of pure copper is measured by CA thermocouple in the vicinity of the surface and recorded by an automatic recorder during the quenching process in city water. The results obtained are as follows; 1. The quenching effect of cooling water generally increases with Reynolds Number(characteristic length; specimen diameter)as shown in the experimental formula; but at the realm of Reynolds Number from 1.2 * 10$^{4}$ to 9.2 * 10$^{4}$, the increasing rate of quenching effect shows little increase. 2. The increasing rate of quenching effect was increased under the flow rate of 221 cm/sec. On the other hand, it was decreased below this flow rate. 3. The quenching effect was influenced by the water temperature and the flow rate. But it was rather dependent upon the former than the latter. 4. Although the quenching effect appeared loosely in the water temperature of 50.deg. C, it was shown that the quenching effect increased in the low flow rate of 31 cm/sec. comparing with the still water. 5. It is desirable to design the quenching system to be over 1.2 * 10$^{4}$ in Reynolds Number or over, 3000$cm^{-1}$ / in V/v in order to increase the quenching effect of the system using open channel.annel.

• Journal of the Korean Society for Heat Treatment
• /
• v.37 no.4
• /
• pp.182-187
• /
• 2024

To improve and control the mechanical properties of low alloy steel, the influence of quenching and tempering process conditions was investigated. In the case of quenching heat treatment, a comparison was made between the conventional method of heating to the austenite region followed by single quenching and a method involving double quenching, followed by high-temperature tempering. It was observed that specimens subjected to double quenching exhibited significantly finer tempered microstructures compared to those subjected to conventional quenching, resulting in noticeably higher hardness. Additionally, a study was conducted to investigate the variation in hardness with changes in tempering temperature and time after the same conventional quenching treatment. As expected, an increase in tempering temperature or time led to a decrease in hardness, and the correlation between hardness and the Hollomon-Jeffe Parameter was confirmed. It was also observed that during high-temperature tempering, the size of carbides significantly increased.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.3
• /
• pp.79-84
• /
• 1998

It is very difficult to analyze the transient temperature distribution during quenching of the steel because of coupled effects among temperature, structures and stresses. In this paper, using Inoue's equation of evolution and mixture rule, transient temperature distribution is calculated by the finite element method considering latent heat of transformation structure and temperature dependence of physical and mechanical prperties for the 0.45% carbon cylindrical steel bar with 40mm diameter and 20mm height during end-quenching.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.7
• /
• pp.469-473
• /
• 2003

The effect of photoquenching on infrared image of the EL2 center in semi-insulating(S.I.) GaAs has been studied using near infrared transmission techniques. Particular interest is devoted to as-grown and annealed samples of undoped S.I. GaAs. It is found that the quenching mechanism is different in each sample and also the quenching rate is dependent on the materials and the quenching temperature which is somewhat inconsistent with other existing publications.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.431-434
• /
• 2008

In the present study, direct quenching of alloyed steel after hot forging was simulated using commercial finite element program, $FORGE^{TM}$. A typical heat treatment of alloyed steels consists of quenching for hard martensite and subsequent tempering for toughness. In the practice, forgings which cool down to room temperature are heated to temperature of austenite regime. As investigated in the present study, direct quenching of hot forged stock would be beneficial in terms of energy saving. This process has already been propose and termed as ausforging or forged hardening. However, it is well known that quenching temperature would be the most critical factor to control heat treated forging properties. And it is very difficult to control quenching temperature when forged stock gets directly quenched after forging. In this study, we have calculated final forging temperature of stock. Also, quenching simulation was conducted using a series of material parameter which were also calculated using JMATpro, a commercial program for physical properties of materials.

• Transactions of Materials Processing
• /
• v.19 no.1
• /
• pp.25-31
• /
• 2010

To achieve desired microstructure and mechanical property of a manufacturing product, heat treatment process is applied as a secondary process after forging. Especially, quenching process is used for improving strength, hardness, and wear resistance since phase transformation occurs owing to rapid heat transfer from the surface of the specimen. In the present paper, a study on surface temperature measurement for water quenching of eutectoid steel was investigated. In order to determine the temperature history in experiments, three different measuring schemes were used by varying installation techniques of K-type thermocouples. Depending on the measured temperature distribution at the surface of the specimen, convective heat transfer coefficients were numerically determined as a function of temperature by the inverse finite element analysis considering the latent heat generation due to phase transformation. Based on the inversely determined convective heat transfer coefficient, temperature, phase, and hardness distributions in the specimen after water quenching were numerically predicted. By comparing the experimental and computational hardness distribution at three different locations in the specimen, the best temperature measuring scheme was determined. This work clearly demonstrates the effect of temperature measurement on the final mechanical property in terms of hardness distribution.

• Journal of the Korean Society of Combustion
• /
• v.10 no.2
• /
• pp.1-8
• /
• 2005

Incomplete combustion due to quenching in a narrow confinement has been a major problem for realization of a reliable micro combustion device. In most micro combustors, effects of flows are absent in the quenching because the flow is laminar and no severe stretch is present. In such circumstance, quenching is caused either by heat loss or by removal of active radicals to the wall surface of the confinement. An experimental investigation was carried out to investigate the relative significance of these two causes of quenching of a premixed flame. A premixed jet burner with a rectangular cross section at the exit was built. At the burner exit, the flame stands between two walls with adjustable distance. The gap between the two walls at which quenching occurs was measured at different wall surface conditions. The results were analyzed to estimate the relative significance of heat loss to the wall and the removal of radicals at the surface. The measurements indicated that the quenching distance was independent of the wall surface characteristics such as oxygen vacancy, grain boundary, or impurities at low temperature. At high temperature, however, the surface characteristics strongly affect the quenching distance, implying that radical removal at the wall plays a significant role in the quenching process.

• Journal of the Korean Society for Heat Treatment
• /
• v.8 no.3
• /
• pp.213-221
• /
• 1995

Temperature distribution, transformation and residual stresses generated during the quenching process of carbon steel. It follows many difficulties in the analytical considerations on those quenching process because of the coupling effects on temperature and metallic structures. In this paper one of the basic study on the quenching stresses was carried out for the case of the round steel bar specimen(SM45C) with 40mm both in its diameter and length. The temperature distributions considering strain hysteresis were numerically calculated by finite element technique. In calculating the transient temperature field, the heat flux between water and rod surface was determined from the heat transfer coefficient. The gradient of temperature is almost same to geometric of specimen. At early stage of the quenching process, the abrupt temperature gradient has been shown in the surface of the specimen.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.5
• /
• pp.697-701
• /
• 2012

Numerical modeling for a coke dry quenching process was developed and evaluated. The cokes had similar characteristics to a porous material, therefore, its quenching analysis was simplified as a cooling process of porous blocks. A uniform inlet temperature and constant properties of materials in the oven were also assumed. With given operating conditions, temperature profiles in the cokes were calculated and compared to the actual values. The calculated temperature gradient was high at the upper part of the coke flow and the cooling rate decreased as cokes came down to the exit port. The exit port temperature of cokes was similar to the measured value, however, temperature-dependent material properties and operating conditions must be considered to predict the temperature precisely. The calculated results could be applied to design a coke oven to produce high quality cokes.

• 연구논문집
• /
• s.34
• /
• pp.11-19
• /
• 2004

An Experimental study on the characteristics of high pressure gas quenching system was carried out in the present study. The characteristics of gas quenching system have been studied with high pressure gas chamber and specimen for various gas pressure and velocity which are the design parameter of quenching system. The quenching gas was used compressed air which properties are very similar with Nitrogen gas usually used in industrial gas quenching system. The result shows that the quenching rate of mid surface of specimen is lower than each ends of them which are close to low temperature quenching surface. And to increases the quenching intensity, the increment of quenching gas pressure is more efficient than the increment of quenching gas velocity at the point of reducing the circulation fan power.