Centrifugal casting

CENTRIFUGAL CASTINGa metallurgical manufacturing process by casting.

INTRODUCTION

Centrifugal casting

Has two types:

Industrial – that refers on an industrial scale.

Silversmithing – for smaller scale.

INDUSTRIALA type of centrifugal casting.

Centrifugal Casting (Industrial)

Centrifugal casting also known as 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.


Centrifugal casting Centrifugal casting was the invention of Alfred

Krupp, who used it to manufacture cast steel tyres for railway wheels in 1852.

PROCESSHow is centrifugal casting done?


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.


Process 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.


Process Casting machines may be either horizontal

or vertical-axis. Horizontal axis machines are preferred for long, thin cylinders, vertical machines for rings.


Process 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.

FEATURESWhat are the prominent part of centrifugal casting?


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.


Features of centrifugal casting: Eliminates the need for cores.

Resistant to atmospheric corrosion, a typical situation with pipes.


Features of centrifugal casting: Mechanical properties of centrifugal

castings are excellent.

Only cylindrical shapes can be produced with this process.


Features of centrifugal casting: 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).


Features of centrifugal casting: 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.

BENEFITSWhat are the helpful results of centrifugal casting?


Benefits: Cylinders and shapes with rotational

symmetry are most commonly cast by this technique.


Benefits: 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.


Benefits: 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.


Benefits: Providing that the shape is relatively

constant in radius, noncircular shapes may also be cast.

MATERIALSWhat types of materials can be casted by centrifugal casting?


Typical materials that can be cast with this process are: Iron Steel stainless steels Glass alloys of aluminum, copper and nickel.

(Note: Two materials can be cast together by introducing a second material during the process.)

APPLICATIONWhere can we apply centrifugal casting?


Typical parts made by this process are: Pipes Boilers pressure vessels Flywheels cylinder liners other parts that are axi-symmetric sleeve valves for piston engines

SILVERSMITHINGA type of centrifugal casting.

Centrifugal Casting (Silversmithing)

Centrifugal casting in silversmithing is a casting technique where a small mould is poured, then spun on the end of an arm. The centrifugal force thus generated encourages a successful pour.

PROCESSHow is centrifugal casting done?


Process: Centrifugal casting, or centrifuging, is used as a

means of casting small, detailed parts or jewelry.

An articulated arm is free to spin around a vertical axle, which is driven by an electric motor or a spring.


Process: The entire mechanism is enclosed in a tub or

drum to contain hot metal should the mold break or an excess of metal be used.

Single use molds are prepared using the lost wax method.


Process: A small amount of metal in a crucible (a sort of

ceramic pan) next to the mold is heated with a torch.

When the metal is molten the arm is released, forcing (by centrifugal force) the metal into the mold.


Process: The high forces imposed on the metal

overcome the viscosity, resulting in a finely detailed workpiece. For casting of small parts using poured hot metal, a disk shaped mold is contained within a rotating drum, and molten metal is poured into the center.

PROCESS (GLASS)Specialized for glass.


Process (Glass): The technique is known in the glass industry as

"spinning".

The centrifugal force pushes the molten glass against the mold wall, where it solidifies.


Process (Glass): This cooling process takes anywhere between

16 to 72 hours depending on the impurities or volume of material.

Typical products made using this process are television picture tubes and missile nose cones.

APPLICATIONWhere can we apply centrifugal casting?


Application: Centrifugal casting is commonly used to

shape glass into spherical objects such as marbles.

MACHINERYMachines involved in centrifugal casting.


Machinery: Many machines are available which can

perform centrifugal casting, and they are relatively simple to construct. All that is required is an arm which rotates with an adequate amount of centrifugal force, a container on the end of said arm to hold both a mold and the material to be cast into the mold.

VIDEO PRESENTATIONA summary of our report

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Centrifugal casting

Engineering

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