• Transactions of Materials Processing
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• v.13 no.5
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• pp.422-428
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• 2004

At present, the design of extrusion dies and operation in extrusion companies are primarily based on trial and error. The experience of the die designer, the press operator and the die corrector determine the performance of the extrusion die and the efficiency of the process. In order to produce defect-free products of desirable quality in terms of strength, surface quality and geometrical dimensions, it is important to obtain more knowledge of the processes that occur during extrusion. Recently, to reduce the costs of designing and manufacturing of extrusion dies, and to ensure the quality of the extruded products, numerical simulation for extrusion processes such as FEM (finite element method) is applied increasingly and becomes a very important tool for the design and development of new products. However, most of the studies about FE simulation have been accomplished for simple geometry and low extrusion ratio in the filed of steady metal flow conditions. The extruded products of AI alloy in industrial practice involve complicated sectional geometry. This study was designed to reduce the time of die design and manufacturing in the extrusion process using FEM simulation. FEM simulations of extrusion process were performed in non-steady states conditions by changing weld plate included in extrusion die set. Product which was employed in this study is heat sink that has been used in the parts of heat exchanger of electric circuits. It is generally applied for aluminum or its alloys due to heat efficiency and easy production of complicated shapes, and manufactured by extrusion process. The simulated results showed that weld plate shape in extrusion dies influences meta] flow and dimensional accuracy of products.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.5
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• pp.232-238
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• 2020

Heating experiments using the 7075 aluminum alloy in the state of billet and extrudate have been performed to investigate the pertinent ranges of working temperatures and holding times for the application to the various automobile parts. The 7075 specimens from raw billet of 152 mm in diameter and 400 mm in length prior to extrusion were used for heating with a holding time of 10 minutes at temperatures between 380℃ and 550℃. Then, an extrusion process using the billet has been fulfilled at 380℃ with extrusion speed of 0.8 mm/min to get an plate-type extrudate of 75 mm in width and 4.2 mm in thickness. The samples from the extrudate were subjected to heating experiments at temperatures between 380℃ and 440℃ with holding times such as 10 min, 30 min, 60 min and 120 min at each heating temperature. The microstructures were investigated on the optical and EBSD micrographs. The hardness measurement and the tensile test have been performed to investigate the effect of the heat treatment on the mechanical property. The results showed for the 7075 extrusion process that the safe heating of billet can be performed below 450℃ and the extrusion can be done safely up to 400℃.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.30-39
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• 1993

The study is concerned with the thermo-viscoplastic finite element analysis of nonisothermal hot container extrusion through conical dies. The problem is treated as a non-steady state incorporating the nonisothermal heat transfer analysis. The analysis of temperature distribution includes heat transfer though the boundary surface including conduction, convection and radiation. The analysis of heat transfer is decoupled with the analysis of deformation and the material interaction is considered through iteration procedure. The effect of important process parameters including die angle and extrusion ratio in the process is investigated. Due to the geometric feature for the container extrusion through conical dies, automatic remeshing is mandatory. Automatic remeshing is achieved by introducing the modular remeshing technique.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.313-317
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• 2003

Porthole die extrusion is the method which put the billet in the container and push it between die hole by ram. This method make it possible that product manufacture which have complex shape of area with excellent induction of area, in addition that this is economical. So this method is used as the basic manufacturing method of many industrial materials. The subject of this research is the forming technology development of heat sink which is being produced by extrusion process in my country. Flow condition of extrusion for heat sink, and metal flow of billet in the die are estimated by the means of rigid-plasticity finite element method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.2
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• pp.56-64
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• 2006

Rapid progress in many branches of technology has led to a demand on new materials such as high strength light weight alloys, powdered alloys and composite materials. The hydrostatic extrusion is essentially a method of extruding a clad rod through a die. In order to investigate the effect of the process conditions such as friction heat, deformation and clad thickness on the clad extrusion process, viscoplastic finite element simulations were conducted. A specific model for theoretical analysis used in this study is The single scalar variable version of Hart's model. An experiment also has been carried out using 1.5MN hydrostatic extruder with variable speed ram, LVDT and load cell for comparison. It is found that the hydrostatic extrusion pressure considering the effect of heat dissipation in this theoretical work was closer to the experimental pressure than the isothermal hydrostatic extrusion pressure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.207-225
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• 1992

The study is concerned with the thermo-viscoplastic finite element analysis of axisymmetric forward hot extrusion through square dies. The problem is treated as a nonsteady state problem because the distribution of temperature and material properties are continuously changing with the punch travel. In square die extrusion, difficulties arise from the severe distortion and die interference of elements at the aperture rim of the die even with a small punch travel. And finite element computation is impossible without intermittent remeshing. Accordingly, an automatic remeshing technique is proposed by employing specially designed mesh structure near the aperture rim. The analysis of temperature distribution includes heat conduction through material interfaces, heat convection and radiation to the atmosphere and is carried out by decoupling the heat analysis from the analysis of the deformation. The extrusion load and the distributions of strain rate and temperature are computed for the given cases rendering reasonable results. Computed grid distortions are found to be in good agreement with the experimental results. It has been thus shown that the proposed method of analysis can be effectively applied to the axisymmetric hot extrusion through square dies.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.281-284
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• 2003

The microstructural changes of Al-Zn-Mg-Cu alloy containing Sc during hot extrusion and post heat treatment is investigated. Two kinds of Al-Sc alloys with different alloying elements (B1, B2) are hot extruded to make I-shape bars at 380$^{\circ}C$, then the bars are solution treated at 480$^{\circ}C$ for 2hrs followed by artificial aging at 120$^{\circ}C$ for 24hrs. The interior microstructure of as extruded bar consists of elongated grains, however, fine equiaxed grains are mainly observed around surface. The microstructural gradient suggests that different restoration process can proceed during the hot extrusion. For B1 and B2, different grain growth behaviors are found around the surface during the post heat treatment. Rapid grain growth behavior around the surface is discussed related with the crystallographic orientation of the grain.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.39-45
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• 2011

In this study, the heat flow of the plant scale aluminum extrusion process was investigated to establish optimum continuous heat treatment conditions. During the extrusion of 6061 aluminum alloy, processing parameters such as the extrusion pressure, speed and temperature histories of billets were logged as a function of time. The surface temperature of the billets increased at constant ram speed, while it decreased with decreases of the ram speed. In order to maintain the billet temperature within a solutionizing temperature range prior to the succeeding water quenching step, the ram speed or the temperature of the blower should be controlled. The temperature histories of the billets during the extrusion and hot air blowing processes were successfully simulated by using the velocity boundary model in ANSYS CFX. The methodology to design an optimum process by using a commercial simulation program is described in this study on the basis of the metallurgical validation results of the microstructural observation of the extrudates. The developed model allowed the advantages of taking into account the motion of the extrudate coupled with the temperature change based on empirical data. Calculations were made for the extrudate passing through the isothermal chamber maintained at appropriate temperature. It was confirmed that the continuous heat treatment system is beneficial to the productivity enhancement of the commercial aluminum extrusion industry.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.231-234
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• 1998

This study presents steady-state finite element analysis of three-dimensional hot extrusion of sections through square dies. The objective of this study is to develop a steady-state finite element method for hot extrusion through square dies, and to provide theoretical basis for the optimal die design and process control in the extrusion technology. In the present work, steady-state assumption is applied to both analyses of deformation and temperature. The analysis of temperature distribution includes heat transfer. Convection like element is adopted for the heat transfer analysis between billet and container, and also billet and die. Distributions of temperature, effective strain rate, velocity and mean stress are discussed to design extrusion die effectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.1010-1015
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• 2008

In this study, the characteristics of aluminum tube hydroformed products at different extrusion type and heat treatment conditions were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, free bulge test was performed at room temperature to $300^{\circ}C$. Also mechanical properties of hydroformed products at various pre- and post-heat treatments were estimated by hexagonal prototype hydroforming test at $250^{\circ}C$. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube. As a results, hydroformability of full annealed tube is $5{\sim}8%$ higher than that of extruded and T6-treated tube. The tensile strength and elongation of T6-post heat treated indirect extrusion tube were more than 330MPa and 12%, respectively. However, T6 pre treated hydroformed product represents high strength, 330MPa and low elongation, 8%. Therefore, Hydroformability of Al6061 tube showed similar value for both extrusion types. However flow stress of direct tube showed $20{\sim}50MPa$ lower value than indirect tube.