• Title, Summary, Keyword: reheating

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Induction Heating of Aluminum Alloys for Thixoforging (Thixoforging 공정을 위한 알루미늄 재료의 유도 가열)

  • 정홍규;강충길
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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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.

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Effect of Microwave Reheating on the Quality of Cooked Rice (마이크로파 재가열이 쌀밥의 품질에 미치는 영향)

  • Kum, Jun-Seok;Han, Ouk;Kim, Yong-Hwan
    • 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.

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Optimal Reheating Condition of Semi-solid Material in Semi-solid Forging by Neural Network

  • Park, Jae-Chan;Kim, Young-Ho;Park, Joon-Hong
    • 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.

Environmental Conditions in the Reheating Furnace for High Quality Advanced High Strength Steels for Automobiles

  • Sohn, Il-Ryoung;Chin, Kwang-Geun
    • Corrosion Science and Technology
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    • v.6 no.4
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    • pp.193-197
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    • 2007
  • It is well known that the development of Advanced High Strength Steels (AHSS) is very important for the automotive industry in order to improve fuel efficiency and the reduction of material costs. However, it is particularly difficult to improve the surface quality of AHSS because the high amount of Si, Al, Mn and Ti etc. in AHSS promote selective oxidation, resulting in surface defects. The reheating process in the hot strip mill would cause severe oxidation because it is carried out at elevated temperatures under aggressive environments. In this study a reheating furnace simulator was developed to investigate oxidation phenomena in the reheating process. The environmental gas for the reheating furnace was made by burning coke oven gas with air in the simulator. The air/fuel ratio is precisely controlled by MFC. Ti oxides are easily formed on grain boundaries and Mn and Si oxides are usually formed in inner grains near the steel surface with a small round shape.

Effect of Cooking, Reheating Methods and Storage Conditions on the Quality Characteristics of ′Nuhbiani′ (조리, 재가열 방법 및 저장 조건이 너비아니 품질 특성에 미치는 영향)

  • 김정원;김희섭
    • 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.

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The Effect of globule size on the Mechanical Properties in Reheating Process of Aluminium Alloys (알루미늄소재의 재가열 공정에서 구상화의 크기가 기계적 성질에 미치는 영향)

  • 박상문;강충길
    • 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.

Reheating of Semi-Solid Aluminum Alloys and Mechanical Properties of Thixoforged Product (반용융 알루미늄 합금의 재가열 및 Thixoforging 부품의 기계적 성질)

  • 정홍규;강충길
    • Transactions of Materials Processing
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    • v.8 no.5
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    • pp.437-448
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    • 1999
  • The reheating of the billet in the semi-solid state as quickly and homogeneously as possible is one of the most imposrtant parts. To obtain a fine globular microstructure in cross section of billet, the optimal design of the induction coil for variation of alloys and specimen sizes is necessary. For the thixo-forging process the construction of the reheating data base is very important, because the reheating conditions are different for variation of SSM and billet sizes. So in this study, the optimal coil design of A356 (ALTHIX) and Aι2024 with d×ι=60×90 (mm) to obtain the globular microstructure is theoretically proposed. The suitability of an optimal coil design will be demonstrated by reheating experiments. Finally, the thixoformability of an arbitrarily shaped product is evaluated by its forming variables. The defects and mechanical properties are also investigated.

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A Study on the Optimum Reheating Profess of A356 Alloy in Semi-Solid Forming (반용융 성형에서 A356합금의 최적 재가열 과정에 대한 연구)

  • Yoon, Jae-Min;Park, Joon-Hong;Kim, Young-Ho;Choi, Jae-Chan
    • 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.

A Study on the Performance of Cooling/Reheating System Using Polymer Heat Exchanger (폴리머 열교환기를 사용한 냉각/재가열 시스템의 성능에 관한 연구)

  • Kim, Jin-Hyuck;Yoo, Seong-Yeon;Han, Kyu-Hyun
    • Proceedings of the KSME Conference
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    • pp.2154-2159
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    • 2008
  • In conventional air-conditioning systems, when the circulated air from the air-conditioned space pass through the cooling coil in the air-conditioning system, the air is over-cooled to eliminate the moisture as well as to decrease the temperature. The purpose of this study is to test and evaluate performance of the cooling/reheating system which can save both cooling energy and reheating energy by exchanging heat between the cooled air and reheated air. Experimental apparatus consists of fan, ducts, polymer exchangers, cooling coil, electronic auxiliary heater and data acquisition system. Two types of polymer exchanger, plate type and dimple type, made of polypropylene for cooling/reheating system are designed. Heat transfer and dehumidification characteristics of system are tested. The results show that the energy saving is up to 40% in the range of present experimented conditions, and it decreases with increasing velocity, inlet temperature and specific humidity.

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A study on measurement of oxygen in a reheating furnace using TDLAS (가열로에서 TDLAS를 이용한 각대산소농도측정에 관한 연구)

  • Kim, Young-Il;Kim, Ki-Hong;Lee, In-Bum
    • 한국연소학회:학술대회논문집
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    • pp.160-167
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    • 2006
  • In this project, we studied more accurate and reliable sensing method for oxygen in reheating furnace, made the empirical model for NOx concentration based on oxygen and evaluate the stability of the Tuneable Diode Laser (Absorption) Spectroscopy(TDL(A)S). The tested oxygen monitoring system is installed at work-field reheating furnace on hot roll at POSCO and compared with the Zr sensor system which shows too sensitive because it measures oxygen concentration on a spot unlike TDLS sensor which is successfully applied at 13m-width reheating furnace to measures the line average along the Optical Path Line(OPL).

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