Search

Condenser tubes are mainly produced by precision extrusion with a porthole die and are used to allow flow in refrigerant cooling systems in automobiles. To produce condenser tubes, the recent goal has been to develop a tube that has high strength to allow for multi-cellizing and flattening, and to minimize the wall thickness, and to increase the heat transfer area and heat efficiency. This study was designed to produce Al3003 condenser tube for industrial production, including extrusion die design, inspection of die design through the results of FE simulation and performance of trial extrusion. Chamber shape dimension and initial temperatures of tool and die were variables and the possibility of extrusion was estimated from the forming load, welding pressure, and stress analysis of die in this paper. The validity of the simulated results was verified by extrusion experiments on the condenser tubes.

The objective of this study is to develop an optimal drawing process for clad wire. Steel wires with copper clad are widely used, e.g. in telecommunication, power engineering, electronics as a replacement of traditional applied copper wire. The reason is that the properties of these bimetal wires combine the good strength of steel with the good conductivity and corrosion resistance of copper. The main aspect of producing clad wires is to ensure the uniform thickness of the sleeves, i.e. the coating ratio. This study investigates the effect of the process variables such as semi-die angle and reduction in area on the maximum damage value and the coating ratio through FE-analysis. FE-analysis and an experiment verified that the final coating ratio depends on the initial coating ratio. To produce a clad wire with a single or variety of coating ratios, the wire with the required coating ratio should be produced in a continuous casting process.

In accordance with environmental regulations on refrigeration technology, the commercial A1100 alloy condenser tube that has widely been used in CFC and HCFC refrigerant systems and operated at a low working pressure (10–30 bar) was inappropriate to the eco-friendly CO 2 refrigerant systems which possess a high working pressure (60–80 bar) due to the low mechanical properties. As a result, the stiffness of the conventional 1000 series alloys might not be appropriate in this requirement. The present study is mainly aimed at developing condenser tube material such as A3003 alloy for the application of eco-friendly refrigerants with higher working pressure rather than for conventional CFC and HCFC refrigerants. The mechanical properties and pressurized strength of condenser tube are greatly affected by the coarse grains, which grow during the brazing process. According to the pressurized testing, A3003 alloy is more suitable than A1100 alloy when the condenser tube is applied to eco-friendly refrigerants usage because A3003 alloy can be durable in a heat exchanger which requires high working pressure.

Magnesium alloys are attractive for structural components in transportation industries. At present, magnesium components for structural applications are mainly produced by die casting process. It is, however, commonly acknowledged that structural components made from wrought alloys through metal forming processes have great advantage in terms of obtainable strength and toughness. In addition, most of wrought magnesium alloys are heat treatable and thus allow their strengths to be further improved or their mechanical performance to be tailored by adjusting the parameters of heat treatment. However, wrought process route of melting, ingot casting/continuous casting, forming and heat treatment for magnesium alloys should be carried out under protective cover gas to prevent oxidation and ignition. The purpose of this study was to eliminate cover gas during whole wrought process route. This paper discussed effect of CaO on ignition and oxidation behaviors of AZ31 Mg alloy as well as on surface roughness and mechanical properties AZ31 Mg alloy extruded parts.

The aim of this study is to develop novel thixoextrusion process for hard-to-form Al wrought alloys. Thixoextrusion for 7003 Al alloy of Al–Zn–Mg system and 7075 Al alloy of Al–Zn–Mg–Cu system were investigated as functions of isothermal holding temperature and time in the partially remelted semisolid state. The interesting point of the results was that the thixotropic structures of 7003 and 7075 Al alloys could be obtained without additional pretreatment only through simple partial remelting. More than that, the thixoextrusion pressure of 7075 Al alloy was lower than the thixoextrusion pressure of 7003 Al alloy at the same liquid fraction of 10%, despite the big difference of extrudability index between 7075 and 7003 Al alloys. The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures.

Porthole die extrusion has a great advantage in the forming of hollow sections of Al alloy tubes that are difficult to produce by conventional extrusion with a mandrel fixed at the stem. In general, the porthole die extrusion process consists of three stages (dividing, welding, and forming stage) through the complex die structure composed of container, porthole, mandrel, welding chamber and bearing part. Thus, in order to obtain the detailed mechanics, to assist in the design of proper die shapes and sizes, and to improve the quality of products with high welding strength, porthole die extrusion should be analyzed in as non-steady state as possible. This paper analyzed porthole die extrusion processes through 3D FE simulation in the non-steady state during the entire process for following process variables: initial billet temperature, bearing length, tube thickness, and extrusion ratio. The extrusion load for each stage, the welding pressure, and the dead metal zone in the welding chamber were examined through a numerical analysis. Extrusion loads found by FE simulation were compared with experimental results. The surface state of extruded products was also examined. Whole investigations were made for Al7003.

Porthole die extrusion has a great advantage in the forming of hollow section tubes that are difficult to produce by conventional extrusion with a mandrel on the stem. Because of the complicated structure of the die assembly, the extrusion of hollow section tubes has been investigated experimentally. Analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded. In porthole die extrusion the welding strength promises the possibility of producing sound hollow section tubes. Welding strength is affected by many parameters, such as extrusion ratio, extrusion speed, die shape, porthole number, bearing length, billet temperature and mandrel shape. In this paper, parameters such as billet temperature, bearing length and product thickness, are examined. The welding pressures are examined through 3D simulation of the non-steady state and compared with experimental results. The objective of this study is to analyze the metal flow and to predict the welding pressure of product by FE simulations and experiments. These results will be applied to porthole die design in the future.

In a view point of mechanical property of medium strength alloy such as A7003 aluminum alloy, it is necessary to increase Mg content in the alloy however an increment in Mg content has an adverse effect on the extrudability. Furthermore, it has been generally practiced to reduce the Mg content for enhanced recovery efficiency during Al scrap recycling in the aluminum industry. Therefore, it is important to select the amounts of alloy elements for mechanical property and extrudability in medium strength A7003 alloy. To examine the effect of Mg content on extrudability in A7003, hot extrusion experiments and then microstructure examination by XRD, SEM and EPMA have been performed. The quantitative analysis of energy consumption and CO2 emission for production of A7003 extruded bar are estimated with different process variables such as Mg content, extrusion process (direct or indirect extrusion) and billet pre-heating process (heating by light oil or LPG). The estimation of energy consumption is performed in a stage except mining and extraction (from shipping to gate) to investigate an influence of the parameters on energy consumption and CO2 emission in detail. As Mg content is increased, the flow stress and the extrusion pressure for A7003 alloy are increased. It has been thought that an increment in extrusion pressure with increasing Mg content is caused by the solid solution hardening of Mg atoms in the matrix and an increment in volume fraction of intermetallic compound, Mg2Si. The energy consumptions can be reduced when lower content of Mg in A7003 alloy and indirect extrusion process are used. It has been found that CO2 emission in billet heating process can be reduced when induction heating process is introduced.

The presence of an inclusion in wire makes wire breaks easy to occur even with a high reduction ratio. The investigation presented here is mainly aimed at determining the reduction ratio when size of an inclusion, application of back tension and distance between inclusions are considered. In order to investigate the effect of back tension on wire breaks, the applied back tension in a slip type continuous drawing machine is calculated quantitatively using some parameters such as diameter and peripheral speed of capstan and coiling number. The effect of an inclusion size and reduction ratio on wire breaks is investigated when quantitatively calculated back tension being 28% of drawing force is applied. The size of an inclusion varies 5, 7 and 10 μm, the reduction ratio varies 10, 13 and 16%, the distance between inclusions is set to be 0.25 and 0.5 mm, respectively. Conical dies with a half angle α of 7°, which is the value generally used in commercial production. As the FEM code, the commercially available software DEFORM-2D is used. Copper is used for fine wire drawing process that initial diameter is 1 mm and final diameter is up to 50 μm. Accumulated strain and mean stress are simultaneously calculated to obtain damage value in the multistage wiredrawing. The defects of central burst type are generated at a smaller total reduction ratio with decreasing unit reduction ratio and with increasing inclusion size. Furthermore, damage value rises because the tensile stress in deformation zone increases by applied back tension. The distance between inclusions would not affect wire breaks because the distance is expanded excessively through multistage wiredrawing.

The optimization technique is applied widely in metal forming processes for various objectives, fold-over and excessive die forces, etc. The aim of this study is to design the optimal tool shape in metal forming processes for the improvement of the mechanical properties of the product by a uniform microstructure. Thus, this study presents a method for designing a tool shape based on uniform microstructure distribution with an optimization technique and the finite element method. The tool shape is controlled using a Bezier curve to define the boundary of the tool. The method proposed in this study is demonstrated with an extrusion die design and preform shape design for uniform microstructure distribution. Finally, to show the validity and effectiveness of the result of this study, an experiment in hot extrusion was performed, and the result of the experiment compared with that of the simulation.