• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1529-1540
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• 1993

The quenching of steels by water is one of the imprtant problems in the applications of heat treatment, but the fundamental researches by way of theoretical approaches have not been satisfactorily improbed yet. This study aimed at measuring the exact subcooled transient boiling curve for cylindrical specimens and at conducting the analytical researches into the prediction of cooling curves, including the latent heat of phase transformation of steel. Experiments of quenching were made with cylindrical specimens of carbon steel S45C of diameters from 12 to 30 mm and with Cu specimens of 12 mm diameter respectively. The internal temperature of specimens during the quenching process was measured by C-A sheathed thermocouple. The heat fluxes were numerically calculated by the numerical method of inverse heat conduction problem, using the measured inner temperature of specimen as a boundary condition. In case of ${\Delta}T_{sub}=80K$, $q_{s}$ is as follows $q_{s}=2.02{\times}10^{5}{\Delta}T_{set}^{0.05}:{\Delta}T_{set}\le500K.$ And the numerical analysis of unsteady heat conduction during the quenching process was made and the cooling curves were calculated by TDMA method.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1633-1637
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• 2010

The UV-vis absorption spectrum of protoporphyrin IX shows a very sharp and strong absorption maximum peak at 398 nm in acetonitrile-water mixture solution (1:1 v/v). When divalent metal ions such as $Cu^{2+}$, $Zn^{2+}$, and $Ca^{2+}$ ion were added to protoporphyrin IX, metal protoporphyrin IX complexes were thereby produced. Cu-protoporphyrin IX complexes have the largest formation constant ($K_f$) among them. The fluorescence intensity of protoporphyrin IX was diminished by the presence of $Cu^{2+}$, $Zn^{2+}$, $Ca^{2+}$, $Mn^{2+}$, and $Ni^{2+}$ ions as quenchers. However, $Mg^{2+}$, $Mn^{2+}$, and $Ni^{2+}$ ions are hardly combined with protoporphyrin IX. $Mg^{2+}$ ion does not take part in the fluorescence quenching process of protoporphyrin IX in acetonitrile-water mixture solution. According to the Stern-Volmer plots, fluorescence quenching by $Cu^{2+}$, $Zn^{2+}$, and $Ca^{2+}$ ions involves static quenching, which is due to complex formation. On the contrary, dynamic quenching has a large influence on the overall quenching process, when $Mn^{2+}$ and $Ni^{2+}$ ions were added to protoporphyrin IX in acetonitrile-water mixture solution.

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

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.58-68
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• 1997

The residual stresses in injection-molded plastic parts can be divided into two, i.e., the flow-induced residual stress produced in flowing stage and the thermally-induced residual stress produced in cooling stage. Especially, the main source for the defect in the final parts, such as warpage, is known to be the thermally-induced stresses. For the freely quenched samples the structures of residual stresses and bire-fringence have been investigated by many researchers extensively. However, the boundary condition for free quenching was found to be improper to study actual injection molding process. In the present study a datailed structure of the residual stresses and birefringence produced under constrained quenching has been investigated experimentally. In constrained quenched samples a similar pattern but much less stress values than that for the freely quenched samples has been found in the case of the thickness of 1.0 mm. Howvere, in the case of the thickness of 4.0mm, totally different stress profile has been found experimentally. Suprisingly uniform birefringence throughout whole thickness has been found for all the cases of constrained quenching. Finally, to explain the mechanism to produce the final residual stresses and bire-fringence some preliminary numerical results including free volume theory have been introduced briefly.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.1
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• pp.26-31
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• 2003

Decarburized zone of metal tongue which is used in seat belt for automobiles was carbon-restoration quenched and tempered using nitrogen-methanol gaseous atmosphere. The effects of microstructure and mechanical properties of metal tongue on the effectiveness of carbon-restoration during tempering was studied. Metal tongue showed $20{\sim}30{\mu}m$ decarburized zone. However, after carbon-restoration, it has uniform microstructure and thus hardness without decarburized zone. Carbon-restoration quenching and tempering process resulted in better wear and corrosion resistances than quenching and tempering process.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1677-1681
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• 2002

A computational approach of the arc quenching process in GCB was developed. it is capable to calculates the thermodynamic quantities of the gas as a function of time taking into account of all spaces concerned with the arc quenching. Basically using so-called FLIC method, this program adoptes 'Simplified Enthalpy Arc Model', which is somewhat modified. And, to examine whether our works were done properly, it was simulated the whole process of the arc quenching that is based on self-flow generation phenomena/current interruption in a thermal expansion type circuit breaker. This program was verified by experiments, both showed fairly good agreement.

• Bulletin of the Korean Chemical Society
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• v.20 no.7
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• pp.796-800
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• 1999

Three anthrylazacrown ethers in which the anthracene fluorophore π system is separated from the electron donor atoms by one methylene group were synthesized, and their photophysical study was accomplished. These fluorescent compounds showed a maximum fluorescence intensity at pH=5 in aqueous solutions and a decrease in fluorescence intensity upon binding of paramagnetic metal cations (Mn 2+ (d 5 ), Co 2+ (d 7 ), Cu 2+ (d 9 )). The decrease in fluorescence intensity may be attributed to the paramagnetic effect of metal cations to deactivate the excited state by the nonradiative quenching process. The benzylic nitrogen was found to play an important role in changing fluorescence intensity. From the observed linear Stern-Volmer plot and the fluorescence lifetime independence of the presence of metal ions, it was inferred that the chelation enhanced fluorescence quenching (CHEQ) mechanism in the system is a ground state static quenching process. Enhanced fluorescence was also observed when an excess Na + ion was added to the quenched aqueous solution, and it was attributed to cation displacement of a complexed fluorescence quencher.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.2
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• pp.147-158
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• 1996

Generally, analytical consideration on the behaviour of metallic structures during quenching process, and analysis on the thermal stress and deformation after heat treatment are very important in presumption of crack and distorsion of quenched material. In this study a set of constitute equations relevant to the analysis of thermo elasto-viscoplastic materials with strain hysteresis during quenching process way presented on the basis of contimuum thermo-dynamics mechanics. The thermal stresses were numerically calculated by finite element technique of weighted residual method and the principle of virtual work. In the calculation process, the temperature depandency of physical and mechaniclal properties of the material in consideration. On the distribution of elasto-viscoplastic thermal stresses according to radial direction, axial and tangential stress are tensile stress(50MPa, 1.5GPa and 300MPa) in surface and compressive stress(-1.2GPa, -1.14GPa and -750MPa) in the inner part on the other hand, radial stress is tensile stress(900MPa) in area of analysis. According to axial direction, tangential stress gradients are average 60MPa/mm on the whole. The reversion of stress takes place at 11.5 to 16.8mm from the center in area of analysing.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.106-107
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• 2006

A series of vinyl monomers and their saturated model compounds containing different chromophores were synthesized. These monomers display strong intra-molecular fluorescence quenching, their fluorescence quantum yields and lifetimes are generally lower than those of their model compounds. It was found that the C=C bonds in these monomers played a key role in the intra-molecular quenching, which was confirmed by intermolecular fluorescence quenching and time-resolved fluorescence studies. On the basis of the intra-molecular quenching, a new fluorescence approach can be developed to monitor the process of the polymerization and curing of bismaleimides, which can directly reflect the C=C bond consumption during polymerization and curing.

• Korean Journal of Dental Materials
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• v.44 no.3
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• pp.197-206
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• 2017

The hardening effect by ice-quenching after oxidation of a Pd-Ag-Sn-Au metal-ceramic alloy during porcelain firing simulation was investigated by means of hardness test, field emission scanning electron microscopic observations, and X-ray diffraction analysis. The hardness decreased by ice-quenching after oxidation, which was induced by the homogenization of the ice-quenched specimen. The decreased hardness by ice-quenching after oxidation was recovered from the wash stage which was the first stage of the remaining firing process for bonding porcelain. After wash stage, the hardness of the ice-quenched specimens decreased during the subsequent porcelain firing process. But the final hardness of the ice-quenched specimens after oxidation was higher than that of the specimens cooled at stage 0 after oxidation. The increase in hardness of the specimens during the first firing process was caused by the lattice strains generated at the interface between the face-centered cubic Pd-Ag-rich matrix and the face-centered tetragonal Pd3(Sn, Ga, In) precipitate. The decrease in hardness of the specimens during the remaining firing process was caused by the microstructural coarsening.