CENTRIFUGAL CASTING PROCESS | MANUFACTURING PROCESS | MECHANICAL (2017)

CENTRIFUGAL CASTING PROCESS

In Centrifugal Casting , A Permanent Metal Mold is rotated continuously on its own axis at high speed 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 rained casting.
Vertical Centrifugal Casting Machine is ideal for Gearblanks.

Centrifugal casting or rotocasting is a casting technique that is typically used to cast thin-walled cylinders. It is used to cast such materials as metal, glass, and concrete.

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.

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

   Steps Involved in Centrifugal Casting

1. Starting with a rotating die, liquid metal is introduced into the die.
2. Because the die is rotating, the g-forces drive the liquid metal against the die walls, which simultaneously begin to freeze the castings from the outside in.
3. Shrinkage voids are filled under high pressure from centrifugal force. Slag, dirt and dross, being of lower densities than the metals, spin to the core or center.
4. The tubes are machined to remove these non-metallic impurities that have spun to the center.

    Types of Centrifugal Casting

Centrifugal casting can be divided into three categories namely 

1. True centrifugal casting,
2. Semi centrifugal casting
3. Centrifuging.

(clear explanation of all above types will be in next blog)

    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 6 m (20 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.

Advantages of Centrifugal casting

Centrifugal casting has certain advantages such as 

1. High wear resistance
2. High metal density.
3. No blisters.
4. Centrifugal castings have no non metallic inclusions and slag.
5. This method is cost effective.
6. Both ferrous and non-ferrous metals can be used.
7. The equipment can be used for multiple types of metals without sacrificing quality.
8. Impurities are pulled toward the inside surface and can be easily machined.
9. Castings with good dimensional accuracy and quality are produced.
10. Can produce castings with up to 10 feet in diameter and 50 feet in length.
11. High rate of productivity.

   Disadvantages of Centrifugal Casting

Centrifugal casting has certain disadvantages such as 

1. Cannot produce complex geometric shapes.
2. Segregation and Banding: “zones of segregated low melting point constituents such as eutectic phases and sulphide and oxide inclusions.
3. The mold rotating too slowly or the pouring rate too fast can result in the metal falling down from the top of the rotation onto the bottom.
4. Vibration defects due to improper mounting and faulty equipment.