• 소성∙가공
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• 제27권6호
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• pp.379-385
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• 2018

This study investigated the effect of extrusion conditions on microstructures and mechanical properties of AM80 magnesium alloys. The billets of magnesium alloy used for hot extrusion were prepared by permanent mold casting method, and its extrusion was hot direct extrusion with different extrusion conditions. The results of microstructural analysis showed that the main phases in the as-casted alloys were ${\alpha}-Mg$, ${\beta}-Mg_{17}Al_{12}$, and lamella $Mg_{17}Al_{12}$. Hot extrusion results, The tensile strength of the most soundly manufactured extruded bars (extrusion temp: $350^{\circ}C$, extrusion ratio: 27:1, ram speed: 2mm/s) was approximately 327MPa at room temperature. The increase in the mechanical properties of hot-extruded alloys was as a result of grain refinement by dynamical recrystallization during hot extrusion.

• 한국주조공학회지
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• 제13권3호
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• pp.248-258
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• 1993

A semi-solid alloy in which solid and liquid phase are co-existing is obtained by stirring of A17075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semisolid alloy. The fabrication possibility of fiber-reinforced aluminum alloy containing $Al_2O_3$ short fibers with vigorous agitation of short fibers were obtained by control of stirring time, solid fraction and impeller speed in extrusion billet fabrication processes. The microstructure to extrusion billet fabricated by low pressure casting was investigated for fiber dispersion state. The relationship between the extrustion force and velocity at hot extrustion, the flow strain and extrusion ratio were theoretically described. The surface defects with lubricants and without lubricant after hot extrusion were investigated. The composites materials after hot extrusion were measured by vickers hardness with extrusion ratio. It has become clear that the secondary working such as hot extrusion was very useful to obtained improved the mechanical properties of metal matrix composites.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.433-436
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• 2009

This study is concerned with an effect of frictional condition in a forward/backward combined extrusion process. Generally, the material flow of the billet is influenced by the corners of the die cavity, the ratio in reduction in area, and thickness ratio of backward can thickness to forward can thickness. In addition, the frictional condition in contact area between the billet and the punch/die also affect the material flow. This paper investigated the effect of frictional condition for variable friction factors. The FEM simulation has been carried out in order to examine the effect of frictional condition. Deformation patterns and flow characteristics were examined in terms of design parameters such as extruded length ratio etc. Die pressure exerted on the die-workpiece interface is calculated by the simulation results and analyzed for safe tooling. Therefore the numerical simulation works provide a combined extrusion process of stable cold forging process planning to avoid the severe damage on the tool.

• 소성∙가공
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• 제10권4호
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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.

• 한국정밀공학회지
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• 제18권6호
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• pp.166-173
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• 2001

Composite materials consists of two or more different material layers. The usefulness of clad metal rods forms the possibilities of combination of properties of different metals. Copper clad aluminum composite materials are being used for economic and structural purpose. In this study, composite billet consists of commercially pure copper and aluminum(A6061) and experimental conditions consist of the combinations of clad thickness, extrusion ratio, and semi-cone angle of die. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios, semi-cone angles of die, and composition rate of Cu:Al.

• 한국환경과학회지
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• 제16권10호
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• pp.1169-1177
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• 2007

The main objective of this research was to evaluate the effects of process variables which were forming ability, flow displacement, effective stress, effective strain, fluid vector and products defects on manufactured artificial lightweight aggregate made of both incinerated sewage sludge ash and clay by means of the numerical analysis of a rigid-plastic finite element method. CATIA (3D CAD program) was used for an extrusion metal mold design that was widely used in designing aircraft, automobile and metallic molds. A metal forming analysis program (ATES Co.) had a function of a rigid-plastic finite element method was used to analyze the program. The result of extrusion forming analysis indicated clearly that a shape retention of the manufactured artificial light-weight aggregate could be maintained by increasing the extrusion ratio (increasing compressive strength inside of extrusion die) and decreasing the die angle. The stress concentration of metal mold was increased by increasing an extrusion ratio, and it was higher in a junction of punch and materials, friction parts between a bottom of the punch and inside of a container, a place of die angle and a place of die of metal mold. Therefore, a heat treatment as well as a rounding treatment for stress distribution in the higher stress concentration regions were necessary to extend a lifetime of the metallic mold. A deformity of the products could have made from several factors which were a surface crack, a lack of the shape retention and a crack of inside of the products. Specially, the surface crack in the products was the most notably affected by the extrusion ratio.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.931-932
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• 2012

• 대한기계학회논문집
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• 제17권7호
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• pp.1740-1750
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• 1993

The aluminar short fiber reinforced composite materials for hot extrusion were fabricated by semi-solid stirring method, and extruded at extrusion temperature $400^{\circ}C$ with various extrusion ratio. The hot extrusion load of volume fraction 15% metal matrix composites and base alloy Al7075 has been compared. The fiber length distribution, fiber breakage and fiber orientation are investiged to know the fiber behaviour in before and after hot extrusion. The tensile strength of the hot extruded billet are experimentally determined for different of extrusion ratios, and compared with theorically calculated strength.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.225-230
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• 2002

As in most metal forming processes, die and lubrication are of vital importance in hydrostatic extrusion. An efficient die design and lubrication system selection reduce the pressure required for a given reduction ratio by lowering friction at the billet-die interface. In contrast to the conventional macroscopic extrusion, fine-wire fabrication requires higher extrusion pressure and effect of friction is much more significant. Forming fine Au, Ag, and Cu wire with hydrostatic extrusion process in cold condition, the effect of extrusion die angle, lubrication and billet's initial diameter was studied.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.660-665
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• 2014

다량의 무기물이 첨가된 고분자제품을 초박막의 두께로 고속생산 할 경우 가장 중요한 요소는 적절한 원재료의 선정도 중요하지만 대개의 경우 한정된 범위의 수지를 사용할 수밖에 없기 때문에, 가장 중요한 요소는 압출기내에서 흘러나온 용융수지의 흐름을 균일하게 유지할 수 있도록 고분자의 용융 유동에 적합한 최적의 다이스 설계와 압출기의 공정 파라미터의 제어를 통해 균일한 두께 유지와 연신이 필요하다. 이와 관련하여 고분자 압출필름의 적절한 연신을 위하여 압출조건이 연신에 미치는 영향에 대한 연구가 필요하지만 관련된 연구는 아직 충분히 이루어지지 않고 있다. 따라서 본 연구는 통기성 필름의 압출필름에 주로 사용되는 LLDPE(Linear Low Density Polyethylene)에 대하여 압출기의 실린더 온도, 압출속도, 압출기의 다이스온도, 냉각롤의 온도, 연신비, 그리고 연신롤 온도 등의 압출 조건의 변화가 압출필름의 연신에 미치는 영향에 대하여 압출실험을 통하여 연구하였다. 연구결과에서 연신비가 2.0:1일 때 고분자압출필름의 연신에 가장 큰 영향을 미침을 알 수 있었다.