• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.158-161
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• 2003

Extrusion of forward-gear and backward-rod by combined extrusion with controlling the extrusion velocity using a counter tool is studied. In the combined forward-backward extrusion with controlling extrusion velocity, only parts with short gear can be formed. To obtain longer gear parts, extrusion with reverse ram motion is carried out after the combined forward-backward extrusion process. In this method, combined forward-backward extrusion is carried out until excessive extrusion length is attained and then, the motion of the punch is stopped and the counter tool is moved in the inverse direction and returned to the position for obtaining the desired extrusion length. The experiment is carried out by using lead for billets as a model material. With reverse ram motion, longer gear teeth without under-filling defect can be formed than that by only combined extrusion with controlling extrusion velocity.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.66-72
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• 2003

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. Original metal flow of condenser tube by porthole die extrusion is similar to hollow cylinder extrusion but the estimation of metal flow for extrusion parameters is different. For example, variation of chamber length in hollow extrusion only affects the welding pressure, however, the welding chamber length in condenser tube extrusion influences to the welding pressure as well as the deflection of mandrel. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to angular variation in the bottom of chamber in porthole die. Estimation was carried out using finite element method in as non-steady state. Analytical results can provide useful information the optimal design of porthole die.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.311-318
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• 2001

Porthole die extrusion has a great advantage in the forming of long hollow section tubes. It is difficult to produce long hollow section tubes with complicated section by the conventional extrusion process with a mandrel on the stem Because of the limit of the length of mandrel and the complexity of cross section. Porthole die extrusion is affected by many parameters, such as extrusion ratio, extrusion speed, die geometry, porthole number, bearing length etc. Up to now, most of studies about porthole die extrusion have been investigated by experiments or steady state FE-analysis. However, in this paper, porthole die extrusion is analysed by the unsteady state 3D FE-simulation. And the result of unsteady state analysis is compared with the experimental result. Also, the surface state of extruded tubes are examined for the various process conditions.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.73-81
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• 2003

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. Original metal flow of condenser tube by porthole die extrusion is similar to hollow cylinder extrusion but the estimation of metal flow for extrusion parameters is different. For example, variation of chamber length in hollow extrusion only affects the welding pressure, however, the welding chamber length in condenser tube extrusion influences to the welding pressure as well as the deflection of mandrel. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to angular variation in the bottom of chamber in porthole die. Estimation was carried out using finite element method in as non-steady state. Analytical results can provide useful information the optimal design of porthole die.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.59-69
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• 1995

A simple kinematically admissible velocity field is proposed to determine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of regular polygonal-shaped bars from circular billets. From the proposed velocity field, the upper-bound extrusion load and the average extruded length are determined by minimizing the total power consumption with respect to four parameters. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reason able agreement in average extruded length between theory and experiment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.74-77
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• 2000

Porthole die extrusion has a great advantage in the forming of hollow section tubes difficult to produce by conventional extrusion with a mandrel on the stem. Because of the complicated structure of die assembly, extrusion process as a forming of hollow section tubes has been investigated experimentally Therefore, analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded Welding strength is affected by many parameters, which are such as extrusion ratio, extrusion speed, die shape, porthole number, bearing length, billet temperature and mandrel shape. In this paper, the parameters, which are such as billet temperature, bearing length and tube thickness, are examined. The welding pressures are examined through 3D simulation of non steady state and compared with experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.11a
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• pp.33-41
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• 2002

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to variation of chamber length. in porthole die. Estimation was carried out using finite element method. Porthole die is analyzed in as non-steady state. Analytical results provide useful information the optimal design of porthole die.

• Progress in Superconductivity
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• v.3 no.2
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• pp.193-197
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• 2002

There are many problems in wire fabrication of long length Bi-2223 superconductor by using conventional extrusion method. They are mainly due to high surface resistance and inhomogeneous distribution of inner stress. Hydrostatic extrusion process will not only decrease the extrusion pressure but also enhance homogeneous deformation of material by reducing friction force between billet and container Hydrostatic extrusion method is considered to be useful fur fabrication of the homogeneous wire with high density. In this paper, hydrostatic extrusion process is introduced to fabricate Bi-2223 superconducting tape, and also discussed are the interface homogeneity and microstructural aspects of extruded BSCCO/Ag billet.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.302-310
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• 2001

The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted inclined die surface connecting the die enterance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the twisting of die surface and the shear work is calculated by the consumption of shear energy. The increase rate of angular velocity is determined by the minimization of plastic work. The angular velocity of die exit can be controlled by the land length and the length of inclined die. The alular velocity assums to be increased linearly by the axial distance from the die enterance to the die exit. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction constant.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.143-149
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• 1995

A simple kinematically admissible velocity field is proposed to drtermine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of non-axisymmetric bars from circular billets. The proposed velocity field is applied to the square-die extrusion of trochoidal gear-shaped bars and rectangular-shaped bars, the profile function of a rectangular being approximated by using a Fourier series. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreements in average extruded length between theory and experiment.