Aluminum extrusion

Materials with high formabUity are suitable for bar extrusion aluminum and its alloys, copper, etc. The common materials and their extmsion temperatures are listed in Table 1 (Bauser et al. 2001). 

Integral (or extruded). An aluminum outer tube from which fins have been formed by extrusion, mechanically bonded to an inner tube or liner. 

Scientists from Politecnico di Milano and Ineos Vinyls UK developed a tubular fixed-bed reactor comprising a metallic monolith [30]. The walls were coated with catalytically active material and the monolith pieces were loaded lengthwise. Corning, the world leader in ceramic structured supports, developed metallic supports with straight channels, zig-zag channels, and wall-flow channels. They were produced by extrusion of metal powders, for example, copper, fin, zinc, aluminum, iron, silver, nickel, and mixtures and alloys [31]. An alternative method is extrusion of softened bulk metal feed, for example, aluminum, copper, and their alloys. The metal surface can be covered with carbon, carbides, and alumina, using a CVD technique [32]. For metal monoliths, it is to be expected that the main resistance lies at the interface between reactor wall and monolith. Corning... 

Seams can be soldered, welded, cemented, treated with solutions, compound lined, dry, etc. Seams can be one piece drawn, stamped, or pressed. They may be drawn and wall ironed (DWI) or drawn and redrawn (DRD). Seams may be treated by impact extrusion (rigid and flexible, e.g., collapsible aluminum tubes are annealed). 

Before aluminum alloys can be used for rolling or extrusion and subsequently for other aluminum forming operations, they are usually cast into ingots of suitable size and shape. 

In the extrusion process, high pressures are applied to a cast billet of aluminum, forcing the metal to flow through a die orifice. The resulting product is an elongated shape or tube of uniform cross-sectional area. 

Although aluminum can be extruded cold, it is usually first heated to a temperature ranging from 375 to 525°C, so that little work hardening will be imposed on the product. Heat treatment is frequently used after extrusion to achieve the desired mechanical properties. 

The extrusion process requires the use of a lubricant to prevent adhesion of the aluminum to the die and ingot container walls. In hot extrusion, limited amounts of lubricant are applied to the ram and die face or to the billet ends. For cold extrusion, the container walls, billet surfaces, and die orifice must be lubricated with a thin film of viscous or solid lubricant. The lubricant most commonly used in extrusion is graphite in an oil or water base. A less common technique, spraying liquid nitrogen on the billet prior to extrusion, is also used. The nitrogen vaporizes during the extrusion process and acts as a lubricant. 

We use extrusion coating to apply thin layers of polymer to the surface of non-polymeric substrates such as cardboard or aluminum foil. Extrusion coated materials are extensively used in food packaging. Products include the coated cardboard used to make milk cartons and the coated aluminum foil used to seal dairy product tubs. The process of extrusion coating has much in common with film casting. 

Copolymers of ethylene with up to 15-20% acrylic or methacrylic acid offer improved adhesion, abrasion resistance, toughness, and low-temperature flexibility compared to EVA. Applications include extrusion coatings on aluminum foil for pouches, wire and cable, packaging film, laminations with metal and glass fibers (building and automotive products) and polyurethane (carpet backing). 

In contrast to most extmsion processes, extrusion coating involves a hot melt, ca 340°C. The thin web cools rapidly between the die and nip even at high linear rates. Both mechanical and chemical bonding to substrates are involved. Mechanical locking of resin around fibers contributes to the resin s adhesion to paper. Some oxidation of the melt takes place in the air gap, thereby providing sites for chemical bonding to aluminum foil. Excessive oxidation causes poor heat-sealing characteristics. 

Aluminum is unique among the metals because it responds to nearly all of the known finishing processes. It can be finished in the softest, most delicate textures as exemplified by tableware and jewelry. Aluminum can be anodized and dyed to appear like gold. It can be made as specular as a silver mirror and jet black. The metal also can be anodized to an extremely hard, wear- and abrasion-resistant surface that approaches the hardness of a diamond. Aluminum is available in many convenient forms-shapes, sheet, plate, ingot, wire, rod and bar, foil, castings, forgings, powdered metals, and extrusions. 

Extrusion Coating. In extrusion coating, a thin film of molten polymer is pressed onto or into the substrate. Coating thickness may range from 6.5 ua or less to more than 100 xm. In polymer lamination, a related operation, two or more substrates, such as paper or aluminum foil, are combined by using the polymer film as adhesive and moisture barrier. In order to coat a substrate, the polymer must be extruded through a narrow slit in the extrusion coating die by an extruder screw. 

ETFE resins have a good thermal stability however, for high-temperature applications thermal stabilizers are often added67 A wide variety of compounds, mostly metal salts, such as copper oxides and halides, aluminum oxide, and calcium salts, will act as sacrificial sites for oxidation. Addition of certain salts can alter the decomposition from oligomer formation to dehydrofluorination. Iron and other transition metal salts accelerate the dehydrofluorination. Hydrofluoric acid itself destabilizes ETFE at elevated temperatures and the degradation becomes self-accelerating. For that reason, extrusion temperatures higher than 380°C (716°F) should be avoided.68... 

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