Casting (Intro, Advantages, Disadvantages & Classification)

What is metal casting

What is Casting?
Casting is a manufacturing process by which a liquid material is usually poured into a mold cavity of desired shape, and then it is allowed to solidify.
The solidified part is ejected out of the mold cavity and this solid part is also known as casting.

There are various types of casting materials like metals, cold setting materials and their mixtures (epoxy, concrete, plaster), etc.

In metal casting, the molten metal flows into a mold cavity of desired shape and it solidifies to form a solid casting.

Generally the casting process is used for manufacturing the complex shapes that are difficult to manufacture by other methods.

So, this was a short and simple introduction to the casting process. Now let’s proceed to the advantages and disadvantages of casting.

Advantages of Casting

The advantages and uses of casting are mentioned below.

  1. By using a casting process, the components having difficult shapes can be manufactured, which ultimately minimize the machining process as well as forging and welding process.
  2. Heavy components like large pump housing, valves, parts of hydroelectric plants, etc can be manufactured by using a casting process. The components weighing upto 200 tons can also be manufactured by casting process.
  3. Some metals can not be hot worked into bars or rods. So for such metals, the casting process is preferred.
  4. By using a casting process, the entire casting can be made in one piece which avoids the assembly and joining of different parts.
  5. Casting process is also applicable for mass-production of the components. In other words, more components can be manufactured in less time by using a casting process. For example, in the automobile industry thousands of engine blocks and transmission cases are made using a single casting pattern.
  6. Casting process has many metallurgical advantages, physical advantages as well as economical advantages as compared to other manufacturing methods.
  7. Casting process is considered the cheapest method for manufacturing different shapes of metals.
  8. The strength of the casted metal is equal all over the component, in all the directions.
  9. Practically all metals can be casted.

Disadvantages of Casting

The disadvantages of casting are mentioned below.

  1. Some mechanical properties cannot be achieved by using a casting process.
  2. Porosity can be seen in the casted component, if the hot gases remain trapped in the casting.
  3. Smooth surface finish cannot be obtained by the casting process. Hence, machining is required on a casted component.
  4. Safety is required while performing a casting practice because of the high temperature of molten metal.

Classification of Casting process

Nowadays, there are various types of casting processes used  for manufacturing different components.

As discussed above, the casting process is also beneficial for manufacturing the components with complicated shapes. And casting processes are also used for mass production in industry.

The classification of the casting process is mentioned below.

The metal casting process is basically divided into two categories.

  1. Expendable mold casting
  2. Permanent mold casting

These two categories are again divided into other subcategories as mentioned below.

  • Expendable mold casting
    • Sand casting
    • Shell mold casting
    • Vacuum casting
    • Expanded polystyrene
    • Investment casting
    • Plaster mold casting
    • Ceramic mold casting
  • Permanent mold casting
    • Permanent mold casting
    • Variations of permanent mold casting
    • Die casting
    • Centrifugal casting

Differences between Expendable mold casting and Permanent mold casting

The difference between Expendable mold casting and Permanent mold casting are mentioned below.

Expendable mold castingPermanent mold casting
1). By using expendable mold casting, only one casting can be produced.1). Many castings can be made by using permanent mold casting.
2). Expendable molds are usually made up of moulding sand. For better adhesiveness of the molding sand, the binders are also used.2). Permanent molds are usually made up of metal or refractory ceramic materials.
3). The sand mold is destroyed to remove the solidified casting.3). The metal molds can be opened to remove the casting.

External links:
Automobile casting part: Image by Honhi Linhai, CC BY-SA 4.0, via Wikimedia Commons

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