Centrifugal casting (industrial)

Centrifugal casting (industrial)
Centrifugal casting

Centrifugal casting or rotocasting is a casting technique that is typically used to cast thin-walled cylinders. It is noted for the high quality of the results attainable, particularly for precise control of their metallurgy and crystal structure. Unlike most other casting techniques, centrifugal casting is chiefly used to manufacture stock materials in standard sizes for further machining, rather than shaped parts tailored to a particular end-use.

Contents

Process

In centrifugal casting, a permanent mold is rotated continuously about its axis at high speeds (300 to 3000 rpm) as the molten metal is poured. The molten metal is centrifugally thrown towards the inside mold wall, where it solidifies after cooling. The casting is usually a fine-grained casting with a very fine-grained outer diameter, owing to chilling against the mould surface. Impurities and inclusions are thrown to the surface of the inside diameter, which can be machined away.

Casting machines may be either horizontal or vertical-axis.[1] Horizontal axis machines are preferred for long, thin cylinders, vertical machines for rings.

Most castings are solidified from the outside first. This may be used to encourage directional solidification of the casting, and thus give useful metallurgical properties to it. Often the inner and outer layers are discarded and only the intermediary columnar zone is used.[2]

Features of Centrifugal Casting

  • Castings can be made in almost any length, thickness and diameter.
  • Different wall thicknesses can be produced from the same size mold.
  • Eliminates the need for cores.
  • Resistant to atmospheric corrosion, a typical situation with pipes.
  • Mechanical properties of centrifugal castings are excellent.
  • Only cylindrical shapes can be produced with this process.
  • Size limits are up to 3 m (10 feet) diameter and 15 m (50 feet) length.
  • Wall thickness range from 2.5 mm to 125 mm (0.1 - 5.0 in).
  • Tolerance limit: on the OD can be 2.5 mm (0.1 in) on the ID can be 3.8 mm (0.15 in).
  • Surface finish ranges from 2.5 mm to 12.5 mm (0.1 - 0.5 in) rms.

Benefits

Cylinders and shapes with rotational symmetry are most commonly cast by this technique. "Tall" castings (in the direction of the settling force acting, usually gravity) are always more difficult than short castings. In the centrifugal casting technique the radius of the rotation, along which the centrifugal force acts, replaces the vertical axis. The casting machine may be rotated to place this in any convenient orientation, relative to gravity's vertical. Horizontal and vertical axis machines are both used, simply to place the casting's longest dimension conveniently horizontal.

Thin-walled cylinders are difficult to cast by other means, but centrifugal casting is particularly suited to them. To the rotation radius, these are effectively shallow flat castings and are thus simple.

Centrifugal casting is also applied to the casting of disk and cylindrical shaped objects such as railway carriage wheels or machine fittings where the grain, flow, and balance are important to the durability and utility of the finished product.

Providing that the shape is relatively constant in radius, non circular shapes may also be cast.

Materials

Typical materials that can be cast with this process are iron, steel, stainless steels, glass, and alloys of aluminum, copper and nickel.

Two materials can be cast together by introducing a second material during the process.

Applications

Typical parts made by this process are pipes, boilers, pressure vessels (see autofrettage), flywheels, cylinder liners and other parts that are axi-symmetric. It is notably used to cast cylinder liners and sleeve valves for piston engines, parts which could not be reliably manufactured otherwise.

See also

References

Further reading

  • Kalpakjian, Serope; Schmid, Steven R.. Manufacturing Engineering and Technology (5th ed.). pp. 525. 

External links


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Centrifugal casting — is a metallurgical manufacturing process by casting that may refer to either: Centrifugal casting (industrial), on an industrial scale Centrifugal casting (silversmithing), for a smaller scale A related process is spin casting This disambiguation …   Wikipedia

  • Centrifugal casting (silversmithing) — This article is about Silversmithing. For the industrial process, see Centrifugal casting (industrial). Centrifugal casting in silversmithing is a casting technique where a small mould is poured, then spun on the end of an arm. The centrifugal… …   Wikipedia

  • Casting (metalworking) — Casting iron in a sand mold In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which… …   Wikipedia

  • industrial glass — Introduction       solid material that is normally lustrous and transparent in appearance and that shows great durability under exposure to the natural elements. These three properties lustre, transparency, and durability make glass a favoured… …   Universalium

  • Casting defect — A casting defect is an irregularity in the metal casting process that is undesired. 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,… …   Wikipedia

  • Lost-wax casting — A model of an apple in wax …   Wikipedia

  • Investment casting — For investment casting in art, see lost wax casting. Investment casting, also called lost wax casting, is one of the oldest known metal forming techniques. From 5,000 years ago, when beeswax formed the pattern, to today’s high technology waxes,… …   Wikipedia

  • Spin casting — or Centrifugal Rubber Mold Casting (CRMC) is a method of utilizing centrifugal force 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… …   Wikipedia

  • Sand casting — Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. It is relatively cheap and sufficiently refractory even for steel foundry use. A suitable bonding agent (usually clay)… …   Wikipedia

  • Riser (casting) — Underfeeder redirects here. For the health problem, see Underfeeding. A bronze casting showing the sprue and risers A riser, also known as a feeder,[1] is a reservoir built into a metal casting …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”