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Permanent Mold Casting
Permanent mold casting is a metal casting process that employs reusable Molding (process), molds ("permanent molds"), usually made from metal. The most common process uses gravity to fill the mold, however gas pressure or a vacuum are also used. A variation on the typical gravity casting process, called slush casting, produces hollow castings. Common casting metals are aluminium, magnesium, and copper alloys. Other materials include tin, zinc, and lead alloys and iron and steel are also cast in graphite molds.. Typical products are components such as gears, spline (mechanical), splines, wheels, gear housings, Piping and plumbing fitting, pipe fittings, fuel injector, fuel injection housings, and automotive engine pistons. Process There are four main types of permanent mold casting: gravity, slush, low-pressure, and vacuum. Gravity process The gravity process begins by preheating the mold to . to ease the flow and reduce thermal damage to the casting. The mold cavity is then coat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuel Injector
Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All compression-ignition engines (e.g. diesel engines), and many spark-ignition engines (i.e. petrol (gasoline) engines, such as Otto or Wankel), use fuel injection of one kind or another. Mass-produced diesel engines for passenger cars (such as the Mercedes-Benz OM 138) became available in the late 1930s and early 1940s, being the first fuel-injected engines for passenger car use. In passenger car petrol engines, fuel injection was introduced in the early 1950s and gradually gained prevalence until it had largely replaced carburetors by the early 1990s. The primary difference between carburetion and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while carburetion relies on suction created ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hollowcast
Permanent mold casting is a metal casting process that employs reusable molds ("permanent molds"), usually made from metal. The most common process uses gravity to fill the mold, however gas pressure or a vacuum are also used. A variation on the typical gravity casting process, called slush casting, produces hollow castings. Common casting metals are aluminium, magnesium, and copper alloys. Other materials include tin, zinc, and lead alloys and iron and steel are also cast in graphite molds.. Typical products are components such as gears, splines, wheels, gear housings, pipe fittings, fuel injection housings, and automotive engine pistons. Process There are four main types of permanent mold casting: gravity, slush, low-pressure, and vacuum. Gravity process The gravity process begins by preheating the mold to . to ease the flow and reduce thermal damage to the casting. The mold cavity is then coated with a refractory material or a mold wash, which prevents the casting from s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riser (casting)
A riser, also known as a feeder, is a reservoir built into a metal casting mold to prevent cavities due to shrinkage. Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify. Risers prevent this by providing molten metal to the casting as it solidifies, so that the cavity forms in the riser and not the casting.. Risers are not effective on materials that have a large freezing range, because directional solidification is not possible. They are also not needed for casting processes that utilized pressure to fill the mold cavity. Theory Risers are only effective if three conditions are met: the riser cools after the casting, the riser has enough material to compensate for the casting shrinkage, and the casting directionally solidifies towards the riser. For the riser to cool after the casting, the riser must cool more slowly than the casting. Chvorinov's rule briefly states that the slowest cool ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molding Sand
Molding sand, also known as foundry sand, is a sand that when moistened and compressed or oiled or heated tends to pack well and hold its shape. It is used in the process of sand casting for preparing the mold cavity. Green sand Green sand is an aggregate of sand, bentonite clay, pulverized coal and water. Its principal use is in making molds for metal casting. The largest portion of the aggregate is a sand, usually silica or sometimes olivine. There are many recipes for the proportion of clay, but they all strike different balances between moldability, surface finish, and ability of the hot molten metal to degas. The coal, typically referred to in as sea-coal, which is present at a ratio of less than 5%, partially combusts in the surface of the molten metal, leading to the offgassing of organic vapors. Sand casting is one of the earliest forms of casting practiced due to the simplicity of materials involved. It still remains one of the cheapest ways to cast metal because ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Fatigue
A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. Thermals on Earth The Sun warms the ground, which in turn warms the air directly above. The warm air near the surface expands, becoming less density, dense than the surrounding air. The lighter air rises and cools due to its expansion in the lower pressure at higher altitudes. It stops rising when it has cooled to the same temperature, thus density, as the surrounding air. Associated with a thermal is a downward flow surrounding the thermal column. The downward-moving exterior is caused by colder air being displaced at the top of the thermal. The size and Power (physics), strength of thermals are influenced by the properties of the lower atmosphere (the ''troposphere''). When the air ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Tear
A casting defect is an undesired irregularity in a metal casting process. Some defects can be tolerated while others can be repaired, otherwise they must be eliminated. They are broken down into five main categories: ''gas porosity'', ''shrinkage defects'', ''mould material defects'', ''pouring metal defects'', and ''metallurgical defects''. Terminology The terms "defect" and "" refer to two specific and separate things in castings. Defects are defined as conditions in a casting that must be corrected or removed, or the casting must be rejected. Discontinuities, also known as "imperfections", are defined as "interruptions in the physical continuity of the casting". Therefore, if the casting is less than perfect, but still useful and in tolerance, the imperfections should be deemed "discontinuities". Types There are many types of defects which result from many different causes. Some of the solutions to certain defects can be the cause for another type of defect. The following def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molten Metal
Melting, or Enthalpy of fusion, fusion, is a physical process that results in the phase transition of a chemical substance, substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or Divorce, pressure, which increases the substance's temperature to the melting point. At the melting point, the ordering of ions or molecules in the solid breaks down to a less ordered state, and the solid melts to become a liquid. Substances in the molten state generally have reduced viscosity as the temperature increases. An exception to this principle is Allotropes of sulfur, elemental sulfur, whose viscosity increases in the range of 130 °C to 190 °C due to polymerization. Some organic compounds melt through mesophases, states of partial order between solid and liquid. First order phase transition From a thermodynamics point of view, at the melting point the change in Gibbs free energy ''∆G'' of the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core (casting)
A core is a device used in casting and moulding processes to produce internal cavities and reentrant angles (an interior angle that is greater than 180°). The core is normally a disposable item that is destroyed to get it out of the piece.. They are most commonly used in sand casting, but are also used in die casting and injection moulding. For example, cores define multiple passages inside cast engine blocks. One model of GM V-8 engine requires 5 dry-sand cores for every casting. Materials required to make cores *Core sand *Bentonite clay *Pulverized coal *Resin oil Advantages and disadvantages Cores are useful for features that cannot tolerate draft or to provide detail that cannot otherwise be integrated into a core-less casting or mold. The main disadvantage is the additional cost to incorporate cores. Requirements There are seven requirements for cores: #Green strength: In the green condition, there must be adequate strength for handling #In the hardened state, it must ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
