This set of Metal Casting Multiple Choice Questions & Answers (MCQs) focuses on “Crucible Furnaces”.
1. Which of the following furnaces is not the type of crucible furnace?
a) Pit furnace
b) Pot furnace
c) Oil fired tilting furnace
d) Stack furnace
View Answer
Explanation: Pit furnace, pot furnace and oil fired tilting furnace are the types of crucible furnace, but stack furnace is different furnace which is a modified reverberatory furnace where its efficiency is improved by better sealing of the furnace and flue gases are mainly used for preheating the charge materials.
2. A crucible is basically a metal plate used for directional solidification in the casting process.
a) True
b) False
View Answer
Explanation: A crucible is basically a type of container which carries molten metal to transport it to the mould cavity. It is capable of withstanding very high temperatures necessary for melting the materials like glass, metal, pigments etc. Crucibles are mainly made of graphite or silicon, which are inexpensive and economical to use in the casting process.
3. Square crucible furnaces are more efficient than the round crucible furnaces.
a) True
b) False
View Answer
Explanation: Round crucible furnaces are generally more efficient than the square crucible furnaces because there is uniformity of thermal load in the round furnaces. These furnaces are sized according to the number of crucible used in the furnace. And the burner port is normally placed below the bottom of the crucible which basically depends on the type of metal melting.
4. Silicon carbide can be used as a liner for the crucible furnaces.
a) True
b) False
View Answer
Explanation: The liners used in the crucible furnaces mainly are casted bricks which are mostly made by using the silicon carbide. Alumina ceramic can also be used as a liner, or sometimes high temperature refractory materials like clay or cement are used as liners which are rammed on the crucible furnaces.
5. Cracks may be generated due to the firing of liners used in the crucible furnaces.
a) True
b) False
View Answer
Explanation: When the ramming of liners is done, they usually wrapped in plastic tightly and then after some time, they are fired gradually. It is very important to maintain the dryness of the refractory material used for liners because it may trap moisture inside it. When this liner is fired, there are chances of generating cracks in the liners.
6. Crucible furnace is a very expensive method of melting the metal for small scale production.
a) True
b) False
View Answer
Explanation: Crucible furnace is not an expensive melting method, it is a very cheap method of melting the metal and it is mainly preferred for melting small volumes of non-ferrous materials. It is very popular in jobbing and die casting foundry shops because tapping and charging process is very easy with another type of alloy.
7. Crucible furnaces are economical for melting metal, but heat loss is the major problem in the crucible furnaces.
a) True
b) False
View Answer
Explanation: In crucible furnaces, there is no direct collision of flame on the material. And the heat loss to the outside surrounding is restricted by the refractory walls. However, the energy efficiency of the crucible furnace is low with approximately 60% of the heat loss affected by the radiation and the temperature control is also very difficult in the crucible furnaces.
8. Radiant energy transmission can be minimized by implementing a radiant panel lining in the crucible furnaces.
a) True
b) False
View Answer
Explanation: Radiant energy transmission is generally minimized by having a radiant panel lining in the crucible furnaces, which basically merges high-alumina radiant panel with the low thermal mass insulating material. This produces a surface area that raises radiant energy transfer to the outer surface area of the crucible.
9. Heat loss through the sides of the crucible furnace does not affect the efficiency of the furnace.
a) True
b) False
View Answer
Explanation: Reduction in heat loss through the sides of the crucible furnace can increase the efficiency of the furnace. It is generally estimated that the technology used like pre-fired radiant panels can improve the efficiency of crucible furnace by 30 % and also improves the melting rates of material used in the furnace.
10. Crucible furnace is a type of stationary furnace used for melting and holding the molten metal.
a) True
b) False
View Answer
Explanation: Crucible furnace is a compact furnace which is widely used for melting and holding molten metal with the help of crucible. It is a type of stationary furnace which cannot move and remains fixed to a position. It has major advantages like energy saving, higher melt yield and better quality of molten metal.
Sanfoundry Global Education & Learning Series – Metal Casting, Forming and Welding.
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