DEFINITION OF CASTING:
It is generally means pouring molten metal into a refractory mould with a cavity of the shape to be made and allowing it to solidify. when solidified, the desired metal object is taken out from the refractory mould by taking mould apart.
it is clear from the definition of the process that a successful casting operation needs a knowledge in the following areas:
- Preparation of moulds and patterns (used to make the mould).
- Melting and pouring of the liquefied metal.
- Solidification and further cooling to room temperature.
- Defects and inspection.
- Parting line
- Bottom board
- Facing sand
- Moulding sand
- Pouring basin
- Pattern and pattern allowance
A moulding flask is one which holds the sand mould intact. depending upon the position of the flask in the mould structure it is referred to by various mames such as:
DRAG-lower moulding flask
COPE-upper moulding flask
CHECK-intermediate moulding flask used in three piece moulding.
it is made up of wood for temporary application and more generally of metal for long term use.
Pattern is a replica of the object to be made with some modification.the mould cavity is made with the help of the pattern.
This is the dividing line between the two moulding flasks that makes up the sand mould. in split pattern it is also the dividing line between the halves of the pattern.
This is a board normally made of wood which is used at the start of the mould making.the pattern is first kept on the bottom board,sand is sprinkled on it and then the ramming is done in the drag.
The small amount of carbonaceous material sprinkled on the inner surface of moulding cavity to give a better surface finish to the casting.
It is the freshly prepared refractory material used to making the mould cavity.it is a mixture of silica,clay and moisture in appropriate proportion to get the desired results and it surrounds the pattern while making the mould.
It is used for making hollow cavities in castings.
A small funnel shaped cavity at the top of the mould into which the molten metal is poured.
The passage through which the molten metal from the pouring basin reaches the mould cavity. in many cases it controls the flow of the metal into the mould.
The passageways in the parting plan through which molten metal flow is regulated before it reaches the mould cavity.
The actual entry point through which molten metal enters mould cavity.
Chaplets are used to support inside the mould cavity to take care of its own weight and overcome the metallostatic forces.
Chills are metallic objects which are placed in the mould to increases the cooling rate of casting to provide uniform or desired cooling rate.
It is a reservoir of molten metal provided in the casting so that hot metal can flow back into the mould cavity when there is a reduction in volume of metal due to solidification.