• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.836-837
• /
• 2006

A CCT diagram for Cr-Mo prealloyed sintered steels suitable for sinter hardening was established by combining dilatometry data, microstructural studies and microhardness measurements of the material. CCT diagrams deepen the understanding of material properties after sinter hardening and support the design of materials on an industrial scale by providing information about required cooling rates for successful sinter hardening of these materials.

• Journal of Welding and Joining
• /
• v.8 no.1
• /
• pp.54-61
• /
• 1990

A pilot production is made to the high carbon Cr-Ti alloy rail steels with slight quantity of Cr & Ti added to the eutectoid carbon steel. As a part of weldability of these alloy steels, SH-CCT diagram for welding is first applied to the high carbon Cr-ti alloy rail steel with 0.1wt% Ti. The microstructure, which will be appeared at the HAZ of Enclosed-arc welding of this alloy rail seel, is a single phase of pearlite. As a result of this, it shows that the welding condition of Enclosed-arc welding applied to this alloy rail steel is a good condition.

• Journal of Welding and Joining
• /
• v.17 no.1
• /
• pp.133-144
• /
• 1999

To fine seam annealer capacity of through thickness seam annealing in terms of through thickness microstructure change with increased toughness and elongation leaving heat trace on it, high strength steel pipes of ERW with different thickness were tested in different seam annealing temperature measured on the outer surface of pipes. Annealing temperature and microstructure of the weld seam were changed through applied seam annealing condition. Toughness and tensile test with hardness and microstructure analysis were done on the annealed weld seam to fine its characteristics as a primary step and annealing characteristics according to different seam annealing condition. Through a study of annealed ERW weld seam characteristics and seam annealing technology, amount of electric power should apply in decreased manner to arranged inductors of annealer in the order of 1st, 2nd, 3rd, so on for proper seam annealing. For example of 15.4mm thick and 610mm outside diameter pipe, applied power for proper seam annealing is 600 -650kw at 1st inductor, 450 - 500kw at 2nd inductor, 200-250 kw at 3rd inductor of annealer during 10 - 12M/minute moving speed of pipe. Also, the penetration depth of heat trace along the thickness direction of weld during seam annealing can be estimated through the equation 17mm/kv$\times$voltage(kv) with the microstructure and hardness analysis of thick weld seam as well as study of seam annealing and comparison of cooling condition to CCT diagram of low carbon high strength steel. From this result, the difference between the technological applicability of full annealing condition based on phase diagram and full penetration of heat trace based on CCT diagram along the thickness of weld seam is discussed.

• Journal of Korea Foundry Society
• /
• v.23 no.5
• /
• pp.276-285
• /
• 2003

In the undercooled melt of $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy, the solidification behavior including nucleation and growth of crystals at the micrometer level has been observed in-situ by use of a confocal scanning laser microscope combined with an infrared image furnace. The $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy specimens were cooled from the liquid state to glass transition temperature. 575 K, at various cooling late under a helium gas flow. According to the cooling rate, the morphologies of the solidification front are changed among various types, irregular jog like front, columnar dendritic front, cellular grain, star like shape jog and fine grain, etc. The velocities of the solid-liquid interface are measured to be $10^{-5}{\sim}10^{-8}$ m/s which are at least two orders higher than the theoretical crystal growth rates. Combining the morphologies observed in terms of cooling rates and their solidification behaviors, we conclude that phase separation takes place in the undercooled molten $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy. The continuous cooling transformation (CCT) diagram was constructed from solidification onset time at various linear cooling conditions with different rate. The CCT diagram suggests that the critical cooling rate for glassy solidification is about 1.5 K/s, which is in agreement with the previous calorimetric findings.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.961-965
• /
• 2006

White organic LED spectrum for lighting and displaying should be designed for high luminous efficiency as well as good chromaticity coordinate, pleasant correlated color temperature and color rendering. A program based on Matlab was made to make these calculations convenient. The chromaticity coordinate and luminous efficiency was calculated according to the CIE 1931 colorimetric system, while the correlated color temperature(CCT) was calculated based on CIE 1960 UCS diagram. The color rendering characteristics were evaluated according to the CIE Color Rendering Index (CRI), using Ra, Ri and ${\bigtriangleup}E$ from the 14 color samples defined in CIE13.3.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.59-62
• /
• 2003

This study investigated the phase transformation of the $REBa_2Cu_3O_{7-x}$ (RE=Nd, Gd, By) superconductor, and CCT (Continuous-Cooling-Transformation) along with the TTT (Time-Temperature-Transformation) diagrams are suggested according to the isothermal and continuous cooling heat-treatments. According to result of fabricated single crystal of RE-123 superconductor through TSMG method based on phase transformation neted among heat treatment process, when the ionic radius elements was decreased, RE-211 phase was well-distributed. According to result that examine about seed of pretreatment effect of TSMG method, magnetic hysteresis improved when preprocess among oxygen atmosphere in same seed. and used after. Effect of miscut expressed good superconducting special quality in case miscut uses big seed.

• Journal of Welding and Joining
• /
• v.16 no.3
• /
• pp.74-84
• /
• 1998

The microstructures of the HAZ (Heat Affected Zone) are generally different from the base metal due to rapid thermal cycle during welding process. Particuraly, CGHAZ (Coarsened Grain Heat Affected Zone) near the fusion line is the most concerned region in which many metallurgical and mechanical discontinuities have been normally generated. A computer program by the numerical formularization of phase transformation during cooling with different rates was developed to generate the CCT diagram, and to predict microstructural (phase) changes in the CGHAZ. In order to verify simulated results, isothermal and continuous cooling transformation experiments were conducted. The simulated and experimental results showed that the developed computer model could successfully predict the room temperature microstructural changes (changes in volume fraction of phases) under various welding conditions (heat input & cooling rate $(Δt_{8/5})$).

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.5
• /
• pp.67-73
• /
• 2012

Failure mechanisms for a solid propellant were discussed, and the stip-yield and the inherent flaw models were applied to them. Then, failure assessment diagram methods were investigated by means of modified two models. Fracture toughness tests using CCT(center-cracked tension) specimens made of a solid propellant were conducted to generate the failure assessment diagrams. The failure assessment diagram of the inherent flaw model was normalized in order to compare with that of the modified strip-yield model. From the comparison of two failure assessment diagrams, it was found that the failure assessment diagram of the modified inherent flaw model more conservatively assesses the failure than that of the modified strip-yield model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.532-538
• /
• 2012

Failure mechanisms for a highly filled elastomer were discussed, and the stip-yield and the inherent flaw models were applied to them. Then, failure assessment diagram methods were investigated by means of modified two models. Fracture toughness tests using CCT(center-cracked tension) specimens made of a highly filled elastomer were conducted to generate the failure assessment diagrams. The failure assessment diagram of the inherent flaw model was normalized in order to compare with that of the modified strip-yield model. From the comparison of two failure assessment diagrams, it was found that the failure assessment diagram of the modified inherent flaw model more conservatively assesses the failure than that of the modified strip-yield model.

• Journal of Welding and Joining
• /
• v.25 no.5
• /
• pp.36-44
• /
• 2007

This paper is the first part of the study on the accuracy improvement of numerical analysis of steel welds. The aim of this paper is to raise the accuracy of thermal analysis results, such as the shape and size of the weld cross section and the hardness distribution in HAZ(Heat-Affected Zone). It is known that the factors affecting on the accuracy are thermal properties, metallurgical properties and welding heat source model. It was found that the arbitrary distributed heat source model should be used to predict practical weld cross section shape and size. Also, in order to improve the prediction accuracy of HAZ hardness distribution, it was essential to consider 2 CCT(Continuous Cooling Transformation) diagrams in calculating volume fraction of transformed phases. One is the peak temperature being around melting temperature. The other is the peak temperature being around metallurgical transformation temperature.