• 소성∙가공
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• 제16권3호
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• pp.178-186
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• 2007

Rheo-forging process of aluminum alloy is suitable for large parts of net shape without defects and excellent mechanical properties in comparison with conventional die casting and forging process. To control the microstructure of the product with high mechanical properties in rheo-forming, solid fraction is required to prevent porosity and liquid segregation. Therefore, in rheo-forging process, die shape, pressure type and solid fraction are very important parameters. The defects such as porosity, liquid segregation and unfitting phenomena occur during rheo-forging process. To prevent these defects, mechanical properties and microstructure analysis of samples versus the change of pressure are carried out and the problem and its solutions are proposed. Also, the mechanical properties versus various pressures were compared with and without heat treatment. The alloys used for rheo-forming are A356 and 2024 aluminum alloy. The rheology material is fabricated by electromagnetic process with controlling current and stirring time.

• 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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.99-102
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• 2004

In rheo forming process, slurry making is very important factor because the microstructure of slurry affects the quality of final products. To control the microstructure of slurry, slurry making by new rheo die casting was studied. In new rheocasting method, processes parameters are degree of overheat in molten metal, cooling condition, high frequency induction heating condition and cup temperature. Microstructures according to these parameters were observed. By image analysis, equivalent diameter and roundness of grain were investigated and discussed. To find out mechanical properties of grain controlled aluminum part by rheo die casting, tensile tests were carried out to the T6 heat treatment.

• 소성∙가공
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• 제15권3호
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• pp.195-205
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• 2006

This paper focuses on a rheo-forming of am part fabricated by electromagnetic stirring system (EMS). This forming process take place under high pressure of high pressure die casting and thin walled casting is possible. Furthermore, the productivity is better than low pressure die casting because of shorter cycle time. The advantages of rheo-forming are performed in the semi solid state with laminar flow and the gas content is low, which makes welding possible. Therefore this research applies for arm part with EMS and has investigated the mechanical properties after T6 and T5 heat-treatment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.124-128
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum ahoy has been studied Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The unposed mathematical model is applied to the die shape of the two type. To calculate the velocities and temperature fields during rheology forming process, the each governing equation correspondent to the liquid and solid region are adapted. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.340-343
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• 2005

This paper focuses on an rheo-forming of arm part fabricated by electromagnetic stirring system (EMS). This forming process take place under high pressure of high pressure die casting and thin walled casting is possible. Also the productivity is better than low pressure die casting because of shorter cycle time. The advantages of rheo-forming are performed in the semi solid state with laminar flow and the gas content is low, which makes welding possible. Therefore this research applies for arm part with EMS and has investigated the mechanical propriety after T6 and T5 heat-treatment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.371-374
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• 2009

Die casting process has been used widely for complex automotive products such as the knuckle, arm and etc. Generally, a part fabricated by casting has limited strength due to manufacturing defects by origin such as the dendrite structure and segregation. As an attempt to offer a solution to these problems, forging has been used as an alternative process. However, the forging process provides limited formability for complex shape products. Rheo-forging of metal offers not only superior mechanical strength but also requires significantly lower machine loads than solid forming processes. This paper presents the results of an A356 aluminum alloy sample, which were obtained by experiment and by simulation using DEFORM 3D. Samples of metal parts were subsequently fabricated by using hydraulic press machinery.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.103-106
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• 2004

The new rheology fabrication process has been developed to rheo die casting and rheo forming process. Thixoforming process has disadvantages in terms of induction reheating process, scrap recycling, loss of raw material and cycle time. Therefore, to reduce the number of process, new rheology fabrication process with specially designed the rotational barrel type equipment has been proposed to apply in various part productions. The barrel type equipment, which could continuously fabricate the rheology materil, was specially designed to have a function to control cooling rate, shear rate and temperature. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed. The barrel surface has both the induction heating system and the cooling system to control the temperature of molten metal. By using this system, the effect of the rotation speed and the rotation time on the microstructure was widely examined. The possibility for the rheoforming process was investigated with microstructural characteristic.

• 한국공작기계학회논문집
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• 제15권1호
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• pp.82-87
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• 2006

The cutting tests of aluminum alloy with heat treatmented various hardnesses after rheo-fonning were carried out using CNC milling machine. The surface roughness(Ra, Rmax) of cut surface and cutting forces are measured at various cutting conditions such as low spindle speed, feed speed and hardness. In the CNC end-milling, the surface roughness increases as feed speed increases and decreases as spindle speed increases. However, the bulit-up edge has occurred on in case of low hardness and low feed speed. In experimental conditions, as the hardness of aluminum alloy increases, the surface roughness(Ra, Rmax) decreases

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.135-138
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• 2007

A semi-solid forming processing has been developed for manufacturing near net-shape components. The semi-solid forming has two methods. One is thixo-forming with reheating prepared billet, the other is rheo- forming with cooled melt until semi-solid state. In indirect forging processing, this experiment used aluminum rheology materials by electromagnetic stirring system. Rheology material is made by A16061. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. Forged samples are found microstructures and mechanical properties. Forged samples are accomplished heat treatment T6 for high mechanical properties.