This set of Foundry Assessment Questions and Answers focuses on “Pressure Die Casting”.
1. The pressure is obtained by which of the following methods in pressure die castings?
Explanation: In the pressure die casting process, the molten metal is forced into the permanent mold or dies cavity under pressure. The requirement for pressure is high. The pressure is generally obtained by compressed air or by hydraulic methods.
2. Gooseneck injection type mechanism is ___________ chamber mechanism.
c) Temperature Independent
d) Room temperature
Explanation: The Gooseneck or the air injection type process utilizes air at relatively high pressures. The pressure if the air is around 30 to 40 kg/cm². As the molten metal is also present beneath the surface it is a hot chamber process.
3. The pressure is maintained in the mould till the casting is solidified.
Explanation: The entire pressure die casting process when required to produce castings of certain types, requires the same pressure to be retained till the end of the solidification process. This pressure has to be maintained to obtained good quality castings.
4. The Gooseneck mechanism is more efficient than the plunger mechanism.
Explanation: The compressed air is used in gooseneck mechanism and this compressed air does not produce pressure on molten metal as effectively as the plunger does. Hence the plunger is more effective.
5. In hot chamber machine, the melting unit constitutes and integral part.
Explanation: Depending on the size, hot chamber die-casting machine produces the components. The molten metal possess normal amount of superheat and, therefore, less pressure is needed to force the liquid metal into the die. This is easier because the melting unit is an integral part.
6. Air injection processes can be used for __________
Explanation: The air injection type of hot chamber die casting machine can produce castings of low melting point metals such as zinc, tin and lead etc.
7. __________ are useful in cold chamber machines.
Explanation: The melting unit is not an integral part of the cold chamber die casting machine. Molten metal is brought and poured into the die-casting machine with the help of the ladles that carry this molten metal.
8. ______________ pressure is recommended in the cold chamber process.
d) Room temperature
Explanation: The pressure required to force metal into the die of the cold chamber die casting process is of the order of 200 to 2000 kg/cm² and hence high squeezing action is exerted on the metal while it solidifies.
9. Low melting point alloys can be cast in the cold chamber pressure die casting.
Explanation: Cold chamber die casting machines are chiefly used for making castings in aluminum, brass and magnesium. Though the low melting point alloys also can be cast, but they are more economically done so in fast operating hot-chamber machines.
10. Pressure die casting is used for high volume production because ____________
a) High maintenance
b) Costly machinery
c) Complex dies
d) All of the mentioned
Explanation: The pressure die casting process is used only for the processes which require tight tolerances and detailed geometry. For making such dies, the economical aspect is very high and the maintenance of these machines is equally large. Hence they are used only for high-end production.
Sanfoundry Global Education & Learning Series – Foundry and Forging.
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