• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.61-64
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• 2003

In the field of automobile industry, suspension parts have been fabricated by the light metal part to substitute the steel part. For application light metal of suspension parts, mechanical property of high strength was performed. For anting semi-solid die casting of suspension part, die filling and solidification simulation have been carried out with Ostwald-de Waele rheological model. We designed the optimal die and secured injection condition as possible as laminar flow based on the result of computer simulation. Mechanical properties of knuckle part and heat treatment condition were investigated.

• 한국주조공학회지
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• 제25권6호
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• pp.240-248
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• 2005

The rheocasting characteristics are strongly influenced by the microstructural morphology such as particle size, form factor and contiguity. In this study, the effect of structural morphology on fluid flow characteristics of A356 semi-solid alloy was investigated with a vacuum suction fluidity test. Semi-solid metal slurry was made by the mechanical stirring, the liquidus casting, and H-NCM to be analysed. H-NCM could obtain uniform and fine globular microstructures of 0.9 form factor and 55 ${\mu}m$ particle size. Inoculation was found to be effective for reducing particle size, however, for H-NCM it should be avoided due to the cause of increasing contiguity. The fluidity test indicated that the non-stirring method had higher fluidity and smaller liquid segregation in the same solid faction of 0.4 than the stirring method, for smaller particle size and higher form factor. It was observed that liquid segregation decreased as the particle size is smaller and form factor is higher. The results of die-casting experiment were a good agreement with those of fluidity test.

• International Journal of Precision Engineering and Manufacturing
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• 제4권2호
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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.

• 한국산업융합학회 논문집
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• 제23권4_1호
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• pp.541-547
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• 2020

This paper relates a rheo die casting using electromagnetic force, which is one of the representative semi-solid methods for aluminum. The most important factors in electromagnetic stirring would be the melt temperature, sleeve temperature, electromagnetic force, and input time. The effect of the temperature of molten alloy on the direct rheo-casting is assessed in this study. The temperature of the molten alloy is set to 590 ℃ with a solidification of 40%, 600 ℃ with 30%, and 610℃ with less than 20%. Under the condition of 590 ℃ with a solidification of 40%, the whole molten alloy is solidified, causing non-forming during forming process. Meanwhile, under the condition of 600 ℃, where the solidification was 30%, appropriate amount of molten alloy is solidified, filled well into the mold, resulting in good forming, while at 610 ℃ with the solidification of 20%, the molten alloy is not sufficiently solidified and scattered away. The investigation of the defects inside the product with the help of the X-ray equipment shows that the electromagnetic stirring at 590 ℃ with a solidification of 30% produces many air-pores inside the product.

• 한국공작기계학회논문집
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• 제17권6호
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• pp.28-34
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• 2008

Mg alloy is widely used for the IT, auto and consumer electronics industries. Semi-solid casting(SSC) of magnesium alloys is used to produce high quality components. SSC process is analogous with the injection molding of plastics. The high strength and low weight characteristics of magnesium alloys render the high-precision fabrication of thin-walled components with large surface areas. To produce thin-walled magnesium alloy parts, SSC process parameters on the quality of the finished product should be clearly studied. In this paper, to select optimal process parameters, Taguchi method is applied to the optimal design of the process parameters in the SSC process. The die temperature, injection velocity and barrel temperature of the SSC process are selected for the process parameters. The effectiveness of the optimal design is verified through the CAE software.

• 한국주조공학회지
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• 제22권5호
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• pp.245-251
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• 2002

Cast AZ91 and extruded AM50 alloys were isothermally heated as solid/liquid coexistent temperatures, and semi-solid formed into sheets. Mold filling ability of semi-solid slurry with different liquid fractions was investigated in relation to process variables such as injection speed and mold temperature. Relatively uniform distribution of solid particle size and liquid fraction were observed throughout the semi-solid formed sheet. AZ91 alloy sheets were also manufactured by conventional die casting and compared with the semi-solid formed. It was found that the surface was more smooth and the dimensional accuracy was higher in case of the semi-solid formed.

• 소성∙가공
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• 제6권3호
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• pp.239-249
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• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for filling phenomena in forging process of arbitrarily shaped dies. To produce a automotive part which has good mechanical property, the filling pattern according to die velocity and solid fraction distribution has to be estimated for arbitrarily shaped dies. Therefore, the estimation of filling characteristic in the forging simulation with arbitrarily shaped dies of semi-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for arbitrarily shaped dies is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process with arbitrarily shaped dies is performed to the isothermal conditions of two dimensional problems. To analysis of forging process by using semi-solid materials, a new stress-strain relationship is described, and forging analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for forging force and filling limitations will be compared to experimental data. The filling simulation of simple products performed with the uniform billet temperature(584$^{\circ}C$) from the induction heating by the commercial package MAGMAsoft. The initial step of computation is the touching of semi-solid material with the end of die gate and the initial concept of proposed system just fit with the capability of MAGMAsoft.

• 소성∙가공
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• 제7권3호
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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.

• 소성∙가공
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• 제14권4호
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• pp.338-350
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• 2005

Recently, in the field of automobile industry, to solve the problem of reducing the weight of automobile for the improvement of fuel efficiency and the protection of environment, the aluminum alloy parts have been substituted for the steel parts. However, the aluminum alloy does not have as good mechanical property as the steel part. To improve the mechanical property, the semi-solid die casting process is performed to make automobile parts. In the fabrication of semisolid material the control of the liquid segregation is very important to improve the material properties of aluminum alloy. In the present paper we examine the influence of the liquid segregation by the injection conditions in the semi-solid die casting has been investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.848-851
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• 2002

In the field of automobile industry, lightweight problems are very important in terms of reducing fuel and protecting environment. To satisfy these demands, the attempt to substitute aluminum automobile components for cast steel part has been actively carried out. To fabricate the aluminum automobile suspension part that has the same mechanical properties with cast steel part, design conditions such as shape and dimension of part shall be established. Therefore in this study, shape and dimension conditions of suspension part were proposed. Aluminum automobile suspension part was fabricated by semi-solid die-casting process under the obtained design conditions. Moreover to evaluate the possibility of application to the automobile component, stress and fatigue analysis were performed by using ABAQUS S/W and compared with those of conventional automobile suspension part.