This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Casting Processes”.
1. Phenolic resin and fine dry silica are mixed with ________ for shell mold casting.
a) Warm water
b) Cold water
c) Mercury
d) Alcohol
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Explanation: The mold material of shell mold casting contains 5-10% phenolic resin mixed with fine dry silica. These are mixed with either dry oil or in the presence of alcohol. This pattern is heated to about 230-600oC.
2. In shell molding, the pattern and sand are inverted after _________
a) 20-30 seconds
b) 1-2 minutes
c) 45-50 minutes
d) 3-4 hours
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Explanation: The pattern made in shell mold casting is heated to about 230-600oC. Then the sand-resin mixture is blown over its surface. The heated pattern melts and gardens the resins. After a specified time of 20-30 seconds, the pattern and sand are inverted, which gives a normal shell thickness of 6 mm.
3. The molten wax in investment casting is at a pressure of _______
a) 1 bar
b) 4 bar
c) 12 bar
d) 26 bar
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Explanation: In investment casting, wax or plastic is injected under pressure into the die as the pattern is used to make a die out of soft material. The molten wax is slightly above its melting point and injection pressure is above 4 bar. If it is a plastic material like polystyrene, the injection pressure may be of the order of 35 bar with higher temperature.
4. Which of these is a refractory powder used in ceramic mold casting?
a) Magnesia
b) Helium
c) Zircon
d) Argon
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Explanation: In ceramic mold casting, the ceramic slurry is prepared by mixing fine-grained refractory powders. These powders are Zircon, alumina, fused silica, and patented bending agents. The slurry is applied to the pattern surfaces and baked in a less expensive fireclay.
5. Lost wax process is used for making items of ___________
a) Brass and bronze
b) Tin
c) Cadmium
d) Bismuth
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Explanation: Investment casting method is also known as the lost wax method. This method is used to make brass and bronze statues of religious images, jewelry, and dentistry. The molten metal is poured into an already made mold cavity by melting the mold pattern in the mold itself.
6. Permanent mold casting is otherwise known as _____________
a) Pressure die casting
b) Gravity die casting
c) Centrifugal casting
d) Continuous casting
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Explanation: In gravity die casting, the mold is generally made of two halves hinged at one end. This method is useful for making simple components with uniform wall thickness. This process is otherwise also known as permanent mold casting.
7. Centrifugal casting is used for making _________
a) Solid casting
b) U-tubes
c) Washing machine parts
d) Hollow casting
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Explanation: Centrifugal casting is used for making hollow castings like a pipe without using core. The end of the mold is closed by end cores to prevent the flow of metal. The metal is poured through a long spout and rotated by an electric motor or by mechanical means.
8. How can cracks in casting be avoided?
a) Soft ramming
b) Correct pouring temperature
c) Tapered edges
d) Correct gating system
View Answer
Explanation: Cracks in castings occur due to the presence of sharp edges. When these edges are tapered, cracks can be minimized. Ramming, pouring temperature, and gating systems are checked for other kinds of defects.
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