This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Die Casting”.
1. Which of the following considerations distinguish die casting from the permanent mould casting?
a) Moulding material
b) Way of pouring molten metal
c) Coating on mould
d) Size of castings
View Answer
Explanation: Die casting is almost the same as permanent mould casting, in that both the processes use reusable metallic dies. Die casting involves the preparation of components by injecting molten metal at high pressure into a metallic die; this way of pouring of molten metal distinguishes die casting from the permanent mould casting.
2. It is easy to produce any complex shapes and narrow sections in the die casting.
a) True
b) False
View Answer
Explanation: In die casting, as the metal is forced in under pressure compared to the permanent mould casting, it is also known as pressure die casting. Because of involvement of high pressure in die casting, any type of complex shapes, narrow sections and fine surface details can easily be produced.
3. Due to the presence of ejector die, there is no need of lubricant for the removal of casting from the dies.
a) True
b) False
View Answer
Explanation: For the easy removal of casting from the dies, lubricant is required. The lubricant is sprayed on the die cavity manually or by the auto lubrication system so that the casting will not stick to the die. Ejector die only moves out itself for the extraction of the castings, but the lubricant is essential for the easy removal of the castings.
4. A single piece or unitary part of the metallic die is used for making castings in die casting.
a) True
b) False
View Answer
Explanation: Die casting mainly has two parts. One part is the stationary half or cover die, which is fixed to the die casting machine. The second part is the moving part or ejector die that is moved out for the extraction of the casting. The casting cycle basically starts when the two parts of the die are apart.
5. Which of the following ways of cooling is used for the maintaining of die temperature?
a) Natural air cooling
b) Forced air cooling
c) Water channels cooling
d) Liquid nitrogen cooling
View Answer
Explanation: As the metallic die is used in the die casting as a mould, so the extraction of heat from the molten metal will not be easy. So for maintaining proper die temperature, water cooling channels are used near the castings through the cover and ejector die. This makes the proper solidification of the castings.
6. In cold chamber die casting, rapid cooling of the castings is done as compared to the hot chamber die casting.
a) True
b) False
View Answer
Explanation: In hot chamber die casting, the holding furnace for the liquid metal is integral with the die casting machine, whereas in cold chamber die casting, the metal is melted in separate furnace and then poured into the die casting machine with the help of a ladle for each casting cycle which is also called shot.
7. In the hot chamber die casting process, which of the following parts is used for the pumping of liquid metal into the cavity?
a) Accumulator
b) Slug
c) Guide pin
d) Gooseneck
View Answer
Explanation: A gooseneck is used for the pumping of liquid metal into the die cavity. It is made of ductile iron or of cast steel. The gooseneck is submerged in the holding furnace containing the molten metal. Then a plunger which is hydraulically operated moves up in the gooseneck to open the entry port for the entry of liquid metal into the gooseneck.
8. In hot chamber die casting processes, downward motion of plunger in the gooseneck leads to injection of molten metal into the cavity with high pressure.
a) True
b) False
View Answer
Explanation: In the gooseneck, the highest position of the plunger facilitates the filling of the gooseneck by the liquid metal. Then the plunger starts moving down to force the metal in the gooseneck to be injected into the die cavity. The metal is then held at the same temperature till it is solidified.
9. In hot chamber die casting, the plunger is also used for taking back of unused molten metal to the gooseneck after the fulfilling of the cavity.
a) True
b) False
View Answer
Explanation: After the filling of molten metal into the cavity, somewhat of melt still remains in the nozzle or sprue part. To avoid the wastage of melt, plunger is used, which by moving back returns the unused liquid metal to the gooseneck. This process saves a lot of molten metal and hence economizes the production.
10. Which of the following materials is not suitable to be cast by a hot chamber die casting process?
a) Lead
b) Tin
c) Aluminium
d) Zinc
View Answer
Explanation: The hot chamber die casting process is basically used for the low melting temperature alloys. But, for material such as aluminum, its high melting temperature makes it difficult to cast by hot chamber die casting process, because continuous contact of gooseneck with the molten metal can destroy the gooseneck material.
11. Using of the ladle in the cold chamber die casting has no affects on contact time between the molten metal and the shot chamber.
a) True
b) False
View Answer
Explanation: When the molten metal is ladled into the shot chamber of the machine either manually by a hand ladle or by an auto ladle, which is a form of a robotic device. This process reduces the contact time between the molten metal and the shot chamber, so the high melting temperature materials can be cast easily.
12. The chances of defects in the castings by cold chamber die casting are more than the castings produced by hot chamber die casting.
a) True
b) False
View Answer
Explanation: Since the metal is ladled into the machine from the furnace, so it may lose the superheat and may cause defects in the castings such as cold shuts. Also, there is a main disadvantage in the cold chamber die casting process is the longer cycle time needed as compared to the hot chamber die casting process.
Sanfoundry Global Education & Learning Series – Casting, Forming and Welding.
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