• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.107-112
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• 1998

The semi-solid materials(SSMs) fabricated under electric-magnetic stirring condition are necessary to be applicated in the thixoforging process. The optimal reheating conditions to thixoforging process were investigated with changing the reheating time, holding time, reheating temperatures, capacity, and adiabatic material size. In the case of solid fraction fs=50%, the microstructure of SSM (specimen size:d76X 190) at the condition of the first reheating time 4min, holding time lrnin and reheating temperature 350%, the second reheating time 3min, holding time 3min and reheating temperature 575C, the thlrd reheating time lmin, holding time 2min and reheating temperature 584'C, capacity Q=8.398KW, and adiabatic material size 53mm is obtained with globular microstructure and finest.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.3
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• pp.504-512
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• 1996

Changes in quality of cooked rice after microwave reheating were evaluated. Ceramic coated microwave oven reduced a reheating time(1 min). Storage temperature, storage time and microwave reheating did not affect the color value of cooked rice after microwave reheating. Hardness of cooked rice after microwave reheating decreased in frozen storage treatment. Photomicrographs of cross-section of cooked rice after microwave reheating showed restoration of starch. Effect of storage temperature and time were not significant in appearance, aroma, taste and texture of cooked rice after microwave reheating for sensory evaluation test.

• Transactions of Materials Processing
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• v.11 no.2
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• pp.155-164
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• 2002

One of the important steps on semi-solid forming Is the reheating process of raw materials to the semi-solid state. This Process is not only necessary to achieve the required SSM billet state, but also to contro1 the microstructure of the billet. In reheating process, the globule size is determined by the holding time of last heating stage. Therefore, some experiments to investigate the relationship between the mechanical properties and the holding time in the last heating stage was performed. The alloys used in this experiment were 357, 319 and A390 alloys. The experiments of reheating were performed by using an Induction heating system with the capacity of 50kw. This paper shows the evolution of the microstructure according to the holding time of last reheating stage. Furthermore, to evaluate the effect of globule size controlled by holding time in last heating stage uniaxial tension test was performed. The strain-stress curves were plotted according to the holding time.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.2
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• pp.49-56
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• 2003

As semi-solid forging (SSF) is compared with conventional casting such as gravity die-casting and squeeze casting, the product without inner defects can be obtained from semi-solid forming and globular microstructure as well. Generally, SSF consists of reheating, forging, and ejecting processes. In the reheating process, the materials are heated up to the temperature between the solidus and liquidus line at which the materials exists in the form of liquid-solid mixture. The process variables such as reheating time, reheating temperature, reheating holding time, and induction heating power has large effect on the quality of the reheated billets. It is difficult to consider all the variables at the same time for predicting the quality. In this paper, Taguchi method, regression analysis and neural network were applied to analyze the relationship between processing conditions and solid fraction. A356 alloy was used for the present study, and the learning data were extracted from the reheating experiments. Results by neural network were in good agreement with those by experiment. Polynominal regression analysis was formulated using the test data from neural network. Optimum processing condition was calculated to minimize the grain size and solid fraction standard deviation or to maximize the specimen temperature average. Discussion is given about reheating process of row material and results are presented with regard to accurate process variables fur proper solid fraction, specimen temperature and grain size.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.114-125
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• 2002

As semi-solid forging (SSF) is compared with conventional easting such as gravity die-easting and squeeze casting, the product without inner defects can be obtained from semi-solid forming and globular microstructure as well. Generally speaking. SSF consists of reheating, forging, ejecting precesses. In the reheating process, the materials are heated up to the temperature between the solidus and liquidus line at which the materials exists in the form of liquid-solid mixture. The process variables such as reheating time, reheating temperature, reheating holding time, and induction heating power have much effect on the quality of the reheated billets. It is difficult to consider all the variables at the same time when predicting the quality. In this paper, Taguchi method, regression analysis and neural network were applied to analyze the relationship between processing conditions and solid fraction. A356 alloy was used for the present study, and the learning data were extracted by the reheating experiments. Results by neural network were on good agreement with those by experiment. Polynominal regression analysis was formulated by using the test data from neural network. Optimum processing condition was calculated to minimize the grain size, solid fraction standard deviation, otherwise, to maximize the specimen temperature average. In this time, discussion is liven about reheating process of row material and results are presented with regard to accurate process variables for proper solid fraction, specimen temperature and grain size.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.06a
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• pp.16-27
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• 1997

A semi-solid forming has a lot of advantages compared to the die casting, squeeze costing and convenctional forging, therefore, semi-solid forming process are now becoming of industial interest for the production of metal components and metal matrix composites. However, the material behaviour in the semi-solid temperature range is not sufficiently known although it controls the whole process through forces and geometry evolutions bcause the behaviour of metal slurries is complex. The semi-solid materials(SSM) fabricated under electric-magnetic stirring condition is necessary to be applicate in forming process. A reheating conditions were studied with the reheating time, holing time and reheating temperatures. The microstructure of SSM (which specimen size:d 40${\times}$i60) on condition of heating time 10min and heating temperature 590$^{\circ}C$ is most globular and finest one. The microstructure of SSM(specimen size:d75${\times}$i60) reheated under the three step reheating conditions is most globular and finest.

• Transactions of Materials Processing
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• v.7 no.3
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• pp.215-224
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• 1998

A semi-solid forming has a lot of advantages compared to the die casting. squeeze casting and conventional forging. therefore, semi-solid forming process is now becoming industrial interest for the production of metal components and metal matrix composites. However the material behaviour in the semi-solid temperature range is not sufficiently known although it controls the whole process through forces and geometry evolutions because the behaviour of metal slurries is complex. The semi-solid materials(SSMs) fabricated under electric-magnetic stirring condition is necessary to be applicated in forming process. A reheating conditions were studied with the reheating time holding time and reheating temperatures. The microstructure of SSM(specimen size : d39${\times}$h85) at the condition of heating time 10min and heating temperature 590${\circ}C$ is the most globular and finest one. The microstructure of SSM(specimen size : d76${\times}$h60) reheated under the three step reheating conditions is most globular and finest.

• Journal of Korea Foundry Society
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• v.28 no.3
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• pp.129-135
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• 2008

The reheating stage of electromagnetically stirred Al billet is a critical factor in the thixoforming process. When reheated to the solid-liquid state, the microstructure evolves to a more globular and more homogeneous structure by a coarsening mechanism, the kinetics depending on the initial microstructure. Microstructural evolution has been characterized by conventional parameters (mean size of particle and shape factor) as a function of holding time in the solid-liquid state. The aim of this study is to report experimental results concerning microstructural evolution in the solid-liquid state of electromagnetically stirred Al billet. The material was elaborated in the form of continuously cast bars solidified with electromagnetic stirring to degenerate the dendritic structure. The choice of the reheating conditions is determined by a dendritic ripening and coalescence mechanism, involving variations of both the shape and size of the particles. The reheating time has to be long enough to allow a minimum degree of spheroidizing, but has to be limited as much as possible in order to avoid excessive ripening. The optimum microstructure was obtained at the reheating temperature of near $584^{\circ}C$ and the holding time of 5 min. The only means of combining high productivity with good casting quality was to use feedstock billets whose microstructure showed rapid transformation characteristics.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.236-239
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• 2001

In thixoforming, the globule size is determined by the hoding time of last reheating stage. In this study, some experiments to investigate the relationship between the mechanical properties and the holding time were performed A357, A390 and A3l9 alloys are used in this study. This paper shows the evolution of the microstructure according to the holding time of last reheating stage. Tensile test was performed for each reheating condition to examine the effect of globule size.

• Korean journal of food and cookery science
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• v.11 no.5
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• pp.494-502
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• 1995

The study was conducted to evaluate the characteristics of Nuhbiani qualities with the different cooking, reheating methods and storage conditions. Cooking and reheating methods were used with pan, microwave and their combinations. Precooked samples were stored for 0, 1, 4, 7, 15 days in the refrigerator and for 15, 30 days in the freezer. TBA value, shear value by rheometer and sensory attributes in rancidity, hardness, juiciness and overall acceptability were measured. There was no significant difference between cooking, reheating methods in TBA values. Lower values in TBA were noted in the Nuhbiani of frozen storage as compared with that of refrigerated storage. There is a tendency that TBA values were increased as the storage time extended during the refrigeration. Shear values were more increased by microwave cooking and microwave reheating than other methods showing harder texture. Results from sensory evaluation of rancidity, hardness, juiciness and overall acceptability show that there were no significant differences between storage methods, among storage periods and cooking, reheating methods.