What Is Centrifugal Casting - Its Introduction, Production Process, Types

Introduction :-

A family of casting processes in which the molten metal is pouring into mold which is rotated at high speed, so centrifugal force distributes molten metal to outer regions of the die cavity. This method was first suggested in the early 1800s. There are three types of centrifugal casting: true centrifugal casting, semicentrifugal casting, and centrifuging.

Types of Centrifugal Casting :-

True Centrifugal Casting :-

In true centrifugal casting, molten metal is poured into a rotating mold to produce a tubular part. Orientation of the axis of mold rotation can be either horizontal or vertical, the former being more common. Molds are made of steel, iron, or graphite and may be coated with a refractory lining to increase mold life. The high-speed rotation results in centrifugal forces that cause the metal to take the shape of the mold cavity. Thus, the outside shape of the casting can be round, octagonal, hexagonal, and so on. But inner surface of the casting remains cylindrical, because the molten metal is distributed uniformly by the centrifugal forces. Castings with good quality, dimensional accuracy, and external surface detail are produced by this process.

Cylindrical parts ranging from 13 mm to 3 m in diameter and 16 m long can be cast centrifugally with wall thicknesses ranging from 6 to 125 mm. True Centrifugal Casting. In true centrifugal casting, hollow cylindrical parts such as pipes, gun barrels, bushings, engine-cylinder liners, bearing rings with or without flanges, and street lampposts are produced by the technique. The pressure generated by the centrifugal force is high; such high pressure is necessary for casting thick-walled parts.

The basic process is :-

1. The mold is set up and rotated along a vertical (rpm is reasonable), or horizontal axis.
2. The mold is coated with a refractory coating.
3. While rotating molten metal is poured in.
4. The metal that is poured in will then distribute itself over the rotating wall.
5. During cooling lower density impurities will tend to rise towards the center of rotation.
6. After the part has solidified, it is removed and finished.

Semicentrifugal Casting :-

It is similar to Centrifugal casting except that in this type the Centrifugal force is used to produce solid castings rather than tubular parts. The rotation speed in semicentrifugal casting is usually set so that G-factors of around 15 are obtained and In this type, molds are designed with risers at center to supply feed metal. Density of metal in the final casting is greater in the outer sections than at the center of rotation. Wheels and pulleys are examples of castings that can be made by this process. Expendable molds are often used in semicentrifugal casting, as suggested by the illustration of the process.

Centrifuge Casting :-

In centrifuging (also called centrifuge casting), mold cavities of any shape are placed at a certain distance from the axis of rotation. so that the molten metal poured into the mold is distributed to these cavities by centrifugal force. The process is used for smaller parts, and radial symmetry of the part is not a requirement as it is for the other two centrifugal casting methods. The properties of the castings can vary by distance from the axis of rotation, as in true centrifugal casting.