• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.268-271
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• 2001

The die design of the liquid and semi-solid forming process is performed by CAE technology, The die design by the computer simulation has some advantages compared with the conventional method which has been performed by the designer's experiences in trials and emu. The defect zones such as porosity and shrinkage has been predicted by simulation results. The result of the numerical analysis for the proposed casting condition shows the characteristics of thixotropic flow, and was used to determine the geometry of the gating system and die cavity. The optimized production conditions were also proposed by result of computer aided engineering.

• 한국정밀공학회지
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• 제19권2호
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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.

• 한국주조공학회지
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• 제27권1호
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• pp.31-35
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• 2007

본 연구에서는 Mg합금의 반응고성형 공정기술을 개발하기 위하여 여러 가지 전단속도와 냉각속도에 따른 Mg합금의 점도와 딕소트러픽 거동을 분석하였으며, 이를 전산모사연구와 비교 검토하였다. 전산모사연구에서는 미세조직과 공정변수를 고려한 반응고 슬러리의 유변학적 거동을 분석하였다. 반응고 온도영역에서의 Mg합금(AZ91D) 슬러리의 점도는 고상율에 따라 지수함수적으로 증가하였으며, 전단속도가 증가하면 감소하는 경향을 나타났다. Mg합금 슬러리의 유변학적 거동을 정확하게 분석하기 위하여 Carreau 모델을 사용하여 ANYCAST 프로그램에서 고압다이캐스팅용 금형으로의 Mg합금 반응고 슬러리의 충진거동을 모사하였다. 전산모사된 결과는 동일한 조건에서의 실제 실험결과와 잘 일치하였다.

• 한국주조공학회지
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• 제40권3호
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• pp.61-65
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• 2020

Rheo-diecasting with stirring has been used in many material industries. As the 4th Industrial Revolution approaches the world, eco-friendly high-strength and light-weight materials become more important. Casting methods have been studied and used for aluminum-alloy automobile parts. This study carried out the effect analysis of the micro-structure and mechanical properties, such as yield/ultimate tensile strength, elongation, and hardness, of A356 using the 6-pole EMS (electro-magnetic stirring) casting process with a high electromagnetic force. As a result, the hardness and elongation of the A356 after T6 heat-treatment show a significant improvement, respectively, by 20% and 50%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.808-811
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• 2002

In thixoforming process, the size of Si particles is changed by many parameters of forming. Especially, reheating and heat treatment are very important parameters. It was found that the mechanical properties was significantly improved by the thixoforming process. In this study, to investigate the relation between the mechanical properties and Si particles, the experiment of semi-solid die casting has been performed. Large suspension part with A356 alloy was fabricated with controlled ram speed. The effect of the size and shape of silicon particles on microstructure of tensile test has been investigated.

• 한국주조공학회지
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• 제19권1호
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• pp.47-53
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• 1999

Squeeze casting process has been used in the field of a commercial manufacturing method, in which metal is enforcedly solidified under pressure enough to prevent the cast defects such as either gas porosity or shrinkage defect. In this paper, to clarify the relationship between applied pressures and macro ${\cdot}$ microstructural behaviors in gravity and direct squeeze casts, specimens were cast by various squeezing pressures during solidification of 7000 series Al wrought alloy in the metal die designed specially. The applied pressures used in this study were 0, 25, 50, and 75 MPa. The microstructural morphologies of squeeze cast were more fine and dense with increasing the applied pressures, because of the greater solidification rate of billet resulting from the applied pressure. A normal segregation phenomenon of an increasing in amount of eutectics towards the center of the billet was observed for squeeze casts, whereas gravity cast showed an inverse segregation phenomenon of an increasing in amount of eutectics towards the edge in the billet. This change in segregation pattern which is normal or inverse is due to a higher radial temperature gradient and reduced time in the semi solid state for squeeze casting.