This set of Foundry Multiple Choice Questions & Answers (MCQs) focuses on “Gravity Die Casting”.
1. Blowing of air is required in water passages is gravity die casting.
Explanation: Water is sometimes used as a cooling agent in the gravity die casting process. Water passages in the mould or cooling fins made on the outside of the mould surface are blown by air otherwise water mist is created in the chilling effect.
2. Cores in permanent moulds used in gravity die casting are made up of ___________
b) Metal and Non-metals
c) Metals and sand
d) Only sand
Explanation: Metal cores are used when they can be easily extracted from the casting whereas a dry sand core or a shell core is preferred when the cavity is to core is such that a metal core cannot be possibly withdrawn from casting. Hence, metal and sand are employed.
3. A chill is used to promote directional solidification in gravity die casting.
Explanation: Chills are pieces of copper, brass or aluminum and are inserted into the mould’s inner surface. The chill is a component used to promote solidification in a specific portion of a metal casting mould.
4. The mold halves are clamped by ________ in gravity die casting.
d) Lathes, Pneumatic and Toggles
Explanation: In a gravity die casting, the two mould halves present are securely clamped before the pouring operation takes place. Simple mechanical clamps (latches, toggle clamps etc.) are adequate for small moulds where as larger permanent moulds need pneumatics or power clamping methods.
5. For faster cooling, fins are provided __________ the permanent mould.
c) At the surface
d) Near the end
Explanation: The pouring cup, sprue, gates and the risers are built inside the mold halves itself. The fins and other projections are provided on the outside of the permanent mould as they ensure faster cooling of the casting.
6. In gravity die casting, __________ the thickness of the mold walls, greater the amount of heat removal.
Explanation: The greater thickness of the mold walls can remove greater amounts of heat from the casting, they that is the mould walls are made thicker opposite thicker sections of the castings. This provides a desirable chilling effect.
7. The thickness of the permanent mould is _______
Explanation: The permanent moulds are made of dense, fine grained, heat resistant cast iron, steel, bronze, anodized aluminum, graphite or other suitable refractories. The thickness is moderate to around 15-50 mm are higher dimensions are avoided.
8. A permanent mould is made up of two halves.
Explanation: The permanent mould is made in two halves in order to facilitate the removal of the casting from the mould. It may be designed with a vertical parting line or with a horizontal parting line.
9. Molten metal is poured into the mould due to the effect of gravity with _______ external pressure in gravity die casting.
Explanation: Molten metal is poured into the mould under gravity only; no external pressure is applied to the force the liquid metal into the mold cavity. However, the liquid metal solidifies under pressure of metal in risers.
10. Gravity die casting makes use of a permanent mould.
Explanation: A gravity die or a permanent mould casting makes use of a mould which is permanent that is the mould can be reused many times before it is reused or rebuilt.
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