Today we will learn about centrifugal casting its working principle, types, application, advantages and disadvantages. Centrifugal casting is one of the most important type of casting process in which mould is rotated rapidly about its central axis during casting is solidified or metal is poured. This process was patent in 20 century to make higher standards hollow castings. The first centrifugal casting machine was invented by a British, A.G. Eckhardt in 1807. This process is widely used for casting hollow pipes, tubes and other symmetrical parts.
It works on basic principle of centrifugal force on a rotating Component. In this process, a mould is rotated about its central axis when the molten metal is poured into it. A centrifugal force acts on molten metal due to this rotation, which forces the metal at outer wall of mould. The mould rotates until the whole casting solidifies. The slag oxide and other inclusion being lighter, gets separated from metal and segregate towards the center.
True Centrifugal Casting:
True centrifugal casting is sometime known as centrifugal casting is a process of making symmetrical round hollow sections. This process uses no cores and the symmetrical hollow section is created by pure centrifugal action. In this process, the mould rotates about horizontal or vertical axis. Mostly the mould is rotated about horizontal axis and the molten metal introduce from an external source. The centrifugal force acts on the molten metal which forces it at the outer wall of mould. The mould rotates until the whole casting solidifies. The slag particles are lighter than metal thus separated at the central part of the casting and removed by machining or other suitable process. This process used to make hollow pipes, tubes, hollow bushes etc. which are axi-symmetrical with a concentric hole.
Semi Centrifugal Casting:
This process is used to cast large size axi symmetrical object. In this process mould is placed horizontally and rotated along the vertical axis. A core is inserted at the center which is used to cast hollow section. When the mould rotates, the outer portion of the mould fill by purely centrifugal action and as the liquid metal approaches toward the center, the centrifugal component decreases and gravity component increase. Thus a core is inserted at center to make hollow cavity at the center without centrifugal force. In this process centrifugal force is used for uniform filling of axi symmetrical parts. Gear blanks, flywheel etc. are made by this process.
In this process there are several mould cavities connected with a central sprue with radial gates. This process uses higher metal pressure during solidification. It is used to cast shapes which are not axi symmetrical. This is only suitable for small objects.
- It is widely used in aircraft industries to cast rings, flanges and compressor casting.
- It is used for cast Steam turbine bearing shell.
- Roller for steel rolling mill is another example of centrifugal casting.
- It is used in automobile industries to cast gear blank, cylindrical liners, piston rings etc.
- It is used to cast bearings.
- This process used to cast switch gear components used in electronic industries.
Advantages and Disadvantages:
- It provides dense metal and high mechanical properties.
- Unidirectional solidification can obtain up to a certain thickness.
- It can use for mass production.
- No cores are required for cast hollow shapes like tubes etc.
- Gating system and runner are totally eliminated.
- All the impurity like oxide or other slag particles, segregated at center from where it can easily remove.
- It required lower pouring temperature thus save energy.
- Lower casting defects due to uniform solidification.
- Limited design can be cast. It can cast only symmetrical shapes.
- High equipment or setup cost.
- It is not suitable for every metal.
- Higher maintenance required.
- High skill operator required.
- In this casting process, solidification time and temperature distribution is difficult to determine.
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