• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.905-909
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• 2001

The significance of casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from $420^{\circ}C$ to $450^{\circ}C$. The suitable strain rate was 1.5 $sec^{-1}$. The deformation amount of a preform in a forging process is key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of cast preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for the low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeds 0.7. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1438-1443
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• 2001

The significance of the casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to reduce press capacity and material cost. Firstly, a hot compression test was performed with cast cylindrical billets in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from 420$\^{C}$ to 450$\^{C}$. The suitable strain rate was 1.5 sec(sup)-1. The deformation amount of a preform of a preform in a forging process is a key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of case preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeded 0.7. From the result of FE analysis, optimal configurations of the cast preform and the die were designed for a large flange. The filling and solidification analysis for a sound cast-preform was carried out with MAGMA soft. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.414-419
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• 2009

Good control of thermal energy helps to increase characteristics and eliminate defects of large cast-forged part, such as large sized forged shell. Thermal energy control is a important factor. We have studied about forging process and after heat treatment process by FEM simulation. There are three ways of process. Changes of temperature and microstructure for forged shell were predicted according to temperature declination in large cast-forged product. So we will be able to choose the proper time from heat treatment conditions by FEM simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.50-52
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• 2007

Large size forged parts usually were made by hot open die forging because of the die cost, high applied load and small manufacturing quantities. Cast ingots were used in open die forging and the ingots almost included the cavities in its inside. Therefore, one of the aims for forging processes is to close and remove the cavities. However, its criteria were well not defined since the studies have many difficulties to investigate the cavity behaviors because of its large size. In this study, the cavity closure behavior was investigated by experimental and FE analysis. The FEM analysis is performed to investigate the overlap defect of cast ingots during free forging stage. The measured flow stress data were used to simulate the forging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}$-3D. The calculated results of cavity closure behavior are compared with the measured results before and after forging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

• Transactions of Materials Processing
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• v.18 no.6
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• pp.458-464
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• 2009

Thermal energy control is a important factor to control properties of large sized product in ingot-forging. Good control of thermal energy helps to increase characteristics and eliminate defects of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment process by FEM simulation. Changes of temperature and microstructure for forged shell were predicted according to different heat treatment conditions. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.329-336
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• 2010

Ring forging process is more appropriate for high-length and thin walled ring, because it utilizes the forging press and hence does not require heavy-duty ring rolling mill. Although ring forging process is very simple and economic for facilities, the process is not efficient because of multi-forging-step and low material utilization. An effective ring forging process is developed using a hollow ingot. When a hollow ingot is used with a workpiece, the ingot can be forged into a final ring without multi-stage pre-forging process, such as, cogging, upsetting, and piercing, etc.. Finally it has advantages of the material utilization and process improvement because a few reheating and forging process are not necessary to make workpiece for ring forging. The important design variables are the applied plastic deformation energy to eliminate cast structure and make uniform properties. In this study, the mechanical properties after forging of hollow cast ingot were investigated from the experiment using circumferential sectional model. Also, the effects of process variables were studied by FEM simulation on the basis of thermo-visco-plastic constitutive equation. Applied strain is different at each position in length direction because diameter of hollow ingot is different in length direction. The different strain distribution become into a narrow gap by additional plastic deformation during diameter extension process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.102-106
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• 2009

Thermal energy control is a important factor in a large size casting and forging. Good control of thermal energy makes characteristics and defect of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment by FEM simulation. Also, changes of temperature and microstructure for forged shell were predicted. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.293-298
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• 2007

Recently, there is a need to produce a large forged part for the flight, shipping, some energies, and military industries, etc. Therefore, an open die forging technique of cast ingots is required to obtain higher quality of large size forged parts. Cogging process is one of the primary stages in many open die forging processes. In the cogging process prior to some open die forging processes, internal cavities have to be eliminated for defect-free. The present work is concerned with the elimination of the internal cavities in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis is performed to investigate the overlap defect of cast ingots during cogging stage. The measured flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}-3D$. The calculated results of cavity closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.416-420
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• 1995

An attempt has been made to investigate the mechanism of magnetic alignment in the magnets produced by upset forging the $Pr_{20}Fe_{74}B_{4}Cu_{2}$ cast bulk alloy. Upset forging of the cast alloy was carried out for 20 sec to an 80 % thickness reduction (strain rate : $4{$\times}10^{-2}s^{-1}$) in an open die configuration at varying temperatures in the range $600^{\circ}-900^{\circ}C$. It has been found that the upset forging process at temperatures above $800^{\circ}C$ can achieve a magnetic alignment to a great extent from copper-containing Pr-Fe- B-type cast ingot. The growth manner of the ferromagnetic $Pr_{2}Fe_{14}B$ matrix grain in Pr-Fe-B-type alloys was studied by examining the morphology change of the matrix grain in sintered body, and it was found that the matrix grains grew in anisotropic manner such that the grain grew more rapidly along the a- or b-axis than along the c-axis. This anisotropic grain growth led to the plate-like shape of the matrix grain. The magnetic alignment during the upset forging was attributed to grain boundary gliding of the plate-like grains, and the geometry of the grains in the cast ingot and the presence of a large amount of the praseodymium-rich grain boundary phase were thought to play a key role in the achievement of magnetic alignment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.160-164
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• 2007

In the steel industry, there is a need to produce large forged parts for the automobile industries, the flight and shipping industries ad military industries. In the steel-industry application, a cogging technique for cast ingots is required, because the major parts are needed as one large body in order to obtain higher quality. Therefore, cogging process is the primary step in manufacturing of practically large open-die forging. In the cogging process, internal voids have to be eliminated as defects, The present work is concerned with the elimination of the internal voids in large ingots so as obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis are performed to investigate the overlap defect of cast ingots during cogging stage. The measure flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of void closure are performed by using the $DEFORM^{TM}$-3D. The calculated results of void closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the void closure can be investigated by the comparison of practical experiment and numerical analysis.