What is casting (die casting) and their application

A casting can be defined the process of producing metal parts of desired shape and size by pouring the molten metal into a prepared refractory mould cavity and then allowing the molten metal to cool and solidify. The solidified metal is known as casting.
Advantage of Casting:-Intricate part can be produced by casting. Therefore I other shaping processes like machining, rolling, welding, forging, extruding, etc. Can be minimised or eliminated.Those metals which can be hot worked can be hot worked can be cast easily. Objects can be cast in a single piece which otherwise would require assembly of several pieces . Large number of castings can be produced very rapidly. Large and heavy parts can be cast when they will be difficult or impossible to be produced otherwise parts produced by casting have better vibration damping capacity.


Applications of Casting:-

  • Sanitary fittings
  • Construction industries
  • Transportation vehicles
  • Turbine vanes,Blades, etc
  • Tractor parts
  • Power generators
  • Irrigation equipments
  • Aircraft engine blades
  • Agricultural parts, etc.
Dies casting:-In die casting,the molten metal is forced into moulds by applying pressure and held under pressure during solidification. Since it involves a combination of metal moulds and high pressure during solidification. Since it involves a combination of metal moulds and high pressure, fine section and excellent details can be obtained along with prolonged moulds life. Dies are generally made of hardened tool steels.The life of die depends on working temperature of molten metal . Because of cyclic heating and cooling, surface cracks appear on the dies surfaces . Following are two types of die casting:


  1. Hot chamber(or Goose-neck) die casting:-In this set up, the melting unit is in the machine itself that is the reason it is called(Hot chamber) die casting machine. Hot chamber die casting machine offers a fast cycling rate upto around 15cycles per minute. Molton metal is injected from the same chamber in which it is melted . This system involves no handing or transfer of molten metal. 
The goose neck container is always immersed in the molten metal pot.The molten metal from the container is forced into the die by means of a plunger,the molten metal due to pressure comes up and fills the cylinder. When the plunger moves down, the metal forced into dies
Hot chamber die casting is not a application for higher melting points metals.There is a tendency for molten aluminium to pick up some iron as a result of extended time in contact with the casting equipment. Hot chamber is used for Tin, Lead and zinc.

2 . Cold chamber die-casting:-In this set up, metal separately in a furnace and transported to die casting machine by means of small hand ladle.After the closure of die, the molten metal is forced into the die cavity and pressure is maintained during solidification. Since molten metal has to be transferred to die chamber for each cycle, the cold chamber casting process has a longer process cycle as compared to that of hot chamber machine, Aluminium, Manganese and copper base alloys are preferred for cold chamber. 
Advantage of die casting:-

  • Less floor space is required. 
  • Thin sections of complex shapes can be produced at economic rate.
  • Production rate achieved is high.
  • Greater surface finish can be obtained. 
  • Casting defects are less than that in sand casting. 
  • Longer life than other castings methods. 
  • Non-ferrous alloys can be cast easily
Limitations of die casting :-

  • Die and equipment cost is higher than that of sand casting.
  • Ferrous alloys can't be cast .
  • Casting size is limited.
  • In some cases, dies may create undesirable chilling effect on the die casting.
  • Air in the die cavity is entrapped in the casting and porosity. 
Applications of die casting:-

  • Automobile
  • Marine parts
  • Domestic products
  • Parts used in refrigerator,  washing machine,  TV, projector, etc.
  • Zinc, Lead,  tin base alloys. 

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