• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.08a
• /
• pp.216-222
• /
• 2004

The caster roll shells have the good thermal conductivity and the low thermal expansion and have to exhibit high enough strength and good ductility at temperature up to $600^{\circ}C$. Thermal stress in particular is very high due to the contact with the liquid aluminium. The main stresses are of thermal origin, which bring a plastic fatigue on surface. This paper will represent one survey about the investigation of the failure of roll shells for continuous casters and an analysis using the simulation of the temperature distribution and the state of stress during hot rolling. Moreover, there will be a discussion on the roll shell of Mod. HAR 5 which is developed by heat treatment process. Mod. HAR 5 has advantages of high strength, high toughness and increased thermal stress resistance while maintaining the same productivity as the conventional roll.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.461-464
• /
• 2004

In this paper, the elastic epoxy added elastomer having viscoelasticity to existing epoxy was measured thermal, structural properties through TGA(Thermogravimetric Analysis) and FESEM(Field Emission Scanning Electron Microscope). Specimens were made of dumbbell forms by the ratio of 5[phr], 10[phr], 15[phr], and 20[phr] by regulation with elastomer contents. The measurement temperature dimensions of TGA were $0[^{\circ}C]\;to\;800[^{\circ}C]$, and rising temperature was $5[^{\circ}C/min]$. And we observed structure through FESEM at the magnification of 1000times with the voltage of 15[kV] after breaking by quenching specimens. As thermal analysis results, we could know that thermal and structural properties was improved quantity according to decrease of elastomer contents. In general, thermal, structural properties of 15[phr] was excellent among the specimens.

• Journal of the Korean Ceramic Society
• /
• v.22 no.5
• /
• pp.66-70
• /
• 1985

This study was to investigate physical properties of the system $Ca(Mg_{1-x}Al_x) (Si_{2-x}Al_x)O_6$ by quenching method. This system $\chi$=0.1 to 0.3 had same crystal phase microstructure and similar properties. Bulk density microhardness thermal expansion coefficient and modulus of rupture of these solid solutions were 2.87~2.95g/cm3 850~900kg/$mm^2$, $7.5~7.8{\times}10^{-6}$/$^{\circ}C$ and 1950~1980kg/$cm^2$ respectively.

• Journal of the korean Society of Automotive Engineers
• /
• v.6 no.4
• /
• pp.46-53
• /
• 1984

The analysis of temperature distribution and change of metallic structures during water quench were presented by finite element method. In temperature calculation the equation of unsteady state hear conduction problem considering latent heat due to phase transformation was applied to finite solid cylinder, SM 45C of 40mm diameter and 40mm height. In metallic structure analysis iso-thermal transformation curve and the equations of evolution in pearlite-martensite transformation were applied. The calculated results upon temperature and metallic structures were agreed with those of experimental observations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.4
• /
• pp.204-209
• /
• 2017

Thermal and structural stability in the glass transition region of chalcogenide glasses has been investigated in terms of thermodynamics for application to various optoelectronic devices. In this study, the compositions of $Ge_xSb_{20}Se_{80-x}$ (x = 10, 15, 20, 25, and 30) were selected to investigate the glass stability according to germanium ratios. The chalcogenide bulks were fabricated by using a traditional melt-quenching method. Thin films were deposited by a thermal evaporation system, maintaining the deposition ratio of $3{\sim}5{\AA}$ in order to have uniformity. The thermal and structural properties were measured by a differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The DSC analysis provided thermal parameters and theoretical glass region stabilities. The XRD analysis supported the theoretical stabilities because of where the crystallization peak data occurred.

• Journal of the Korean Society for Heat Treatment
• /
• v.34 no.5
• /
• pp.226-232
• /
• 2021

The relationship between precipitation and coefficient of thermal expansion of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments were studied by the thermodynamic analyzer (TMA) and differential scanning calorimetry (DSC). Solution heat treatment of the alloy was carried out at 535℃ for 6 h followed by water quenching, and the samples were artificially aged in the air at 180℃ and 220℃ for 5 h. The coefficient of thermal expansion (CTE) curve showed some residual strain and decreased with increasing aging temperature. The CTE curves changed sharply in the temperature range of 200℃ to 400℃, and the corresponding peak shifted for the aged samples due to the change in the precipitation behavior of the secondary phase. These transformation peaks in the aged sample are related to the volume of the precipitation of the Si phase as determined by DSC analysis. The change in CTE is mainly caused by the precipitation of the Si phase in the Al-Si alloy, and the size of the change occurs simultaneously with the size of the precipitate.

• Journal of Welding and Joining
• /
• v.35 no.1
• /
• pp.89-94
• /
• 2017

The microstructure and dilatation for 0.15C steels were investigated to define the phase transformation during the quenching and partitioning (Q&P) process. For the one step Q&P dilatation, the isothermal martensite/bainite transformation occurred because the holding temperature was between $M_s$ and $M_f$. The isothermally transformed martensite/bainite and the athermally transformed martensite were produced by a loss of retained austenite. As the holding time increased, new martensite-start ($M_s$) temperature produced from the final quenching process decreased due to the carbon partitioning from the martensite to the retained austenite. This was the direct evidence of increment for the retained austenite stability. For the two step Q&P dilatation, the isothermal bainitic transformation occurred because the partitioning temperature was larger than the $M_s$ and new $M_s$. The partitioning at $400^{\circ}C$ indicated the short incubation period for the bainite transformation than the $350^{\circ}C$ partitioning because the partitioning at $400^{\circ}C$ should acquire the larger thermal driving force for carbon partitioning than the $350^{\circ}C$ partitioning. A quick drop of $M_s$ and short period of bainite incubation for the $400^{\circ}C$ partitioning steel were also the direct evidence of significant effects of carbon partitioning on the stability of retained austenite.

• Journal of the Korean Society for Heat Treatment
• /
• v.28 no.6
• /
• pp.300-309
• /
• 2015

The aim of the present study was to predict the variations in microstructure and deformation occurring during gas carburizing and quenching processes of a SCM420H planetary gear in a real production environment using the finite element method (FEM). The motivation for the present study came from the fact that previous FEM simulations have a limitation of the application to the real heat treatment process because they were performed with material properties provided by commercial programs and heat transfer coefficients (HTC) measured from laboratory conditions. Therefore, for the present simulation, many experimentally measured material properties were employed; phase transformation kinetics, thermal expansion coefficients, heat capacity, heat conductivity and HTC. Particularly, the HTCs were obtained by converting the cooling curves measured with a STS304 gear without phase transformations using an oil bath with an agitator in a real heat treatment factory. The FEM simulation was successfully conducted using the aforementioned material properties and HTC, and then the predicted results were well verified with experimental data, such as the cooling rate, microstructure, hardness profile and distortion.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.2 no.1
• /
• pp.31-40
• /
• 1998

To predict residual stresses of aluminum ring rolls after quenching and element removal, 2-D and 3-D thermal elasto-plastic analyses were performed. Strains measured by three step sectioning method were directly compared to those analysed using ABAQUS's element removal. Numerical residual stresses after quenching had similar tendency to measured ones after 2 step aging, but the difference between numerical and measured ones was large. The difference is the reason why there are nonuniform residual stress distributions to ring height direction due to small height of ring, It is judged that the increase of ring height will improve the accuracy of measured ones and decrease the difference. By direct comparison between 3-D numerical strains to simulate three step sectioning method and measured ones, the accuracy of measurement and analysis can be improved. It is concluded that there can be predicted the deformation behavior on machining complex shaped large structures with residual stresses.

• Journal of Energy Engineering
• /
• v.10 no.4
• /
• pp.349-356
• /
• 2001

Phenomenon of direct contact condensation (DCC) heat transfer between steam and water is characterized by the transport of heat and mass through a moving steam/water interface. Since the DCC heat transfer provides some advantageous features in the viewpoint of enhanced heat transfer, it is widely applied to the diversified industries. This study proposes a simple condensation model on the stable steam jets discharging into a quenching tank with subcooled water from a single horizontal pipe for the prediction of the steam jet shapes. The model was derived from the mass, momentum and energy equations as well as thermal balance equation with condensing characteristics at the steam/water interface for the axi-symmetric coordinates. The extremely large heat transfer rate at the steam/water interface was reflected in the effective thermal conductivity estimated from the previous experimental results. The results were compared with the experimental ones. The predicted steam jet shape(i. e. radius and length) by the model was increasing as the steam mass flux and the pool temperature were increasing, which was similar to the trend observed in the experiment.