Forging is a method of producing metal parts by melting and pouring molten metal into a mold cavity. Parts are produced in one piece, not by pressing or drawing. The method was invented by Abraham Lincoln, who used it to produce a large tumbler, or drinking vessel, for the White House. The term was later applied to large castings such as the cylinder of an internal-combustion engine. It can be used to cast castings as large as several hundred pounds (70–270 kg) but is most commonly used to produce castings of less than 100 lb (45 kg).
There are two main casting processes: permanent mold (mold) casting and sand casting.
Mold casting
Mold casting involves pouring molten metal into a heated, hollowed out mold cavity made from sand or ceramic. The process can be used to produce a wide variety of castings including cast iron, aluminum, copper, bronze, brass, nickel, stainless steel, etc. Mold casting can be performed in one of two ways: either molding molten metal into the sand of the mold cavity before the sand hardens or by adding molten metal into the sand cavity of the mold after it has hardened. The latter is commonly referred to as lost-wax casting. When molding, the metal is heated to the melting point and poured into the mold cavity, which is typically hotter than the melting point of the metal. The molten metal will then harden into a casting. The hot metal enters the mold at a very high rate of speed, causing it to splash out of the mold.
Castings may be gas shielded or vacuum sealed. Castings can be made in three forms: bar (or ribbon), button, or slug.
Bar casting
Bar casting is the simplest form of casting. It is done by pouring molten metal into a small open cavity within a mold with a cooling agent. In all, the cavity contains either a single slab or a series of slabs of metal. The metal is heated to a temperature where it is liquid and the mold is heated to a temperature slightly above its melting point. When the mold has been heated to a temperature where it is just below the melting point of the metal, the molten metal is poured into the cavity. The metal cools and hardens and is removed from the mold. The casting will have one, several, or many connecting surfaces that can be cut or removed ac619d1d87
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