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In metalworking and jewelry making, casting is a process in which a liquid metal is delivered into a mold that contains a negative impression of the intended shape. The metal is poured into the mold through a hollow channel called a sprue. The metal and mold are then cooled, and the metal part is extracted. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods.
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer or a die. Forging is often classified according to the temperature at which it is performed: cold forging, warm forging, or hot forging. For the latter two, the metal is heated, usually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Forging has been done by smiths for millennia; the traditional products were kitchenware, hardware, hand tools, edged weapons, cymbals, and jewellery. Since the Industrial Revolution, forged parts are widely used in mechanisms and machines wherever a component requires high strength; such forgings usually require further processing to achieve a finished part. Today, forging is a major worldwide industry.
Aluminium–silicon alloys or Silumin is a general name for a group of lightweight, high-strength aluminium alloys based on an aluminum–silicon system, i.e., Aluminium-silicon alloys (AlSi) that consist predominantly of aluminum - with silicon as the quantitatively most important alloying element. Pure AlSi alloys cannot be hardened, the commonly used alloys AlSiCu and AlSiMg can be hardened. The hardening mechanism corresponds to that of AlCu and AlMgSi. The rarely used wrought alloys in the 4000 series and the predominantly used cast alloys are standardized in the 40000 series. AlSi alloys are by far the most important of all aluminum cast materials. They are suitable for all casting processes and have excellent casting properties. Important areas of application are in car parts, including engine blocks and pistons. In addition, their use as a functional material for high-energy heat storage in electric vehicles is currently being focused on.
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter, and tin-based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.
Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick or viscous under static conditions will flow over time when shaken, agitated, shear-stressed, or otherwise stressed. They then take a fixed time to return to a more viscous state. Some non-Newtonian pseudoplastic fluids show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower its viscosity. A thixotropic fluid is a fluid which takes a finite time to attain equilibrium viscosity when introduced to a steep change in shear rate. Some thixotropic fluids return to a gel state almost instantly, such as ketchup, and are called pseudoplastic fluids. Others such as yogurt take much longer and can become nearly solid. Many gels and colloids are thixotropic materials, exhibiting a stable form at rest but becoming fluid when agitated. Thixotropy arises because particles or structured solutes require time to organize. An overview of thixotropy has been provided by Mewis and Wagner.
Spin casting, also known as centrifugal rubber mold casting (CRMC), is a method of utilizing inertia to produce castings from a rubber mold. Typically, a disc-shaped mold is spun along its central axis at a set speed. The casting material, usually molten metal or liquid thermoset plastic, is then poured in through an opening at the top-center of the mold. The filled mold then continues to spin as the metal solidifies.
Metal injection molding (MIM) is a metalworking process in which finely-powdered metal is mixed with binder material to create a "feedstock" that is then shaped and solidified using injection molding. The molding process allows high volume, complex parts to be shaped in a single step. After molding, the part undergoes conditioning operations to remove the binder (debinding) and densify the powders. Finished products are small components used in many industries and applications.
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal into a mold, and removing the mold material after the metal has solidified as it cools. The most common metals processed are aluminum and cast iron. However, other metals, such as bronze, brass, steel, magnesium, and zinc, are also used to produce castings in foundries. In this process, parts of desired shapes and sizes can be formed.
Magnesium alloys are mixtures of magnesium with other metals, often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminium, copper and steel; therefore, magnesium alloys are typically used as cast alloys, but research of wrought alloys has been more extensive since 2003. Cast magnesium alloys are used for many components of modern automobiles and have been used in some high-performance vehicles; die-cast magnesium is also used for camera bodies and components in lenses.
An aluminium alloy is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin, nickel and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al–Si, where the high levels of silicon (4–13%) contribute to give good casting characteristics. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.
A release agent is a chemical used to prevent other materials from bonding to surfaces. It can provide a solution in processes involving mold release, die-cast release, plastic release, adhesive release, and tire and web release.
Fusible core injection molding, also known as lost core injection molding, is a specialized plastic injection molding process used to mold internal cavities or undercuts that are not possible to mold with demoldable cores. Strictly speaking the term "fusible core injection molding" refers to the use of a fusible alloy as the core material; when the core material is made from a soluble plastic the process is known as soluble core injection molding. This process is often used for automotive parts, such as intake manifolds and brake housings, however it is also used for aerospace parts, plumbing parts, bicycle wheels, and footwear.
Ceramic foam is a tough foam made from ceramics. Manufacturing techniques include impregnating open-cell polymer foams internally with ceramic slurry and then firing in a kiln, leaving only ceramic material. The foams may consist of several ceramic materials such as aluminium oxide, a common high-temperature ceramic, and gets insulating properties from the many tiny air-filled voids within the material.
In the automotive industry, alloy wheels are wheels that are made from an alloy of aluminium or magnesium. Alloys are mixtures of a metal and other elements. They generally provide greater strength over pure metals, which are usually much softer and more ductile. Alloys of aluminium or magnesium are typically lighter for the same strength, provide better heat conduction, and often produce improved cosmetic appearance over steel wheels. Although steel, the most common material used in wheel production, is an alloy of iron and carbon, the term "alloy wheel" is usually reserved for wheels made from nonferrous alloys.
Ceramic mold casting, also known ambiguously as ceramic molding, is a group of metal casting processes that use ceramics as the mold material. It is a combination of plaster mold casting and investment casting. There are two types of ceramic mold casting: the Shaw process and the Unicast process.
Shell molding, also known as shell-mold casting, is an expendable mold casting process that uses resin covered sand to form the mold. As compared to sand casting, this process has better dimensional accuracy, a higher productivity rate, and lower labour requirements. It is used for small to medium parts that require high precision. Shell molding was developed as a manufacturing process during the mid-20th century in Germany. It was invented by German engineer Johannes Croning. Shell mold casting is a metal casting process similar to sand casting, in that molten metal is poured into an expendable mold. However, in shell mold casting, the mold is a thin-walled shell created from applying a sand-resin mixture around a pattern. The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds. A reusable pattern allows for higher production rates, while the disposable molds enable complex geometries to be cast. Shell mold casting requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal.
AJ alloys are die castable alloys of magnesium that have good creep resistance at high temperature. They contain magnesium, aluminium, and strontium.
Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. This deformation is produced by forcibly inserting a non-consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The precursor of this technique, friction stir welding, is used to join multiple pieces of metal without creating the heat affected zone typical of fusion welding.
In continuum mechanics, time-dependent viscosity is a property of fluids whose viscosity changes as a function of time. The most common type of this is thixotropy, in which the viscosity of fluids under continuous shear decreases with time; the opposite is rheopecty, in which viscosity increases with time.
Friction extrusion is a thermo-mechanical process that can be used to form fully consolidated wire, rods, tubes, or other non-circular metal shapes directly from a variety of precursor charges including metal powder, flake, machining waste or solid billet. The process imparts unique, and potentially, highly desirable microstructures to the resulting products. Friction extrusion was invented at The Welding Institute in the UK and patented in 1991. It was originally intended primarily as a method for production of homogeneous microstructures and particle distributions in metal matrix composite materials.
References
Notes
- ↑ "Welcome to MyNADCA!". diecasting.org. Retrieved 2015-08-20.
- 1 2 Young, p. 1.
- 1 2 3 Lowe, Anthony; Ridgway, Keith; Atkinson, Helen (September 1999), "Thixoforming", Materials World, 7 (9): 541–543.
- ↑ Vinarcik, Edward J. (2003), High integrity die casting processes, vol. 1, Wiley-IEEE, pp. 91–101, ISBN 978-0-471-20131-1.
- ↑ P. Kapranos, Proc. 10th Inter. Conf. Semi-Solid Processing of Alloys and Composites, Aachen, Germany & Liege, Belgium, 2008
- ↑ S. LeBeau & R Decker, "Microstructural Design of Thixomolded Magnesium Alloys", Proc. 5th Inter. Conf. Semi-Solid Processing of Alloys and Composites, Golden, Colorado, 1998
- 1 2 Stephen P. Midson, Semi-Solid Casting of Aluminum Alloys: An Update, Die Casting Engineer, Sept. 2008
- 1 2 John L., Jorstad (September 2006), "Aluminum Future Technology in Die Casting" (PDF), Die Casting Engineering: 18–25, archived (PDF) from the original on 2011-06-14.
- ↑ Stephen P. Midson, Robert K. Kilbert, Stephen E. Le Beau & Raymond Decker, "Guidelines for Producing Magnesium Thixomolded Semi-Solid Components used in Structural Applications", Proc. 8th Inter. Conf. Semi-Solid Processing of Alloys and Composites, Limasol, Cyprus, 2004
- ↑ Young, p. 2.
- ↑ Stephen P. Midson, NADCA Semi-Solid & Squeeze Casting Conference, Rosemont, Illinois, 1996
Bibliography
- Young, Kenneth P., Semi-Solid Metal Casting: Reducing the Cost of Copper Alloy Parts (PDF), Massachusetts Office of Technical Assistance, archived from the original (PDF) on 2006-10-07.
