This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Continuous Casting”.
1. Which of the following methods of casting is the fastest method for the production of constant cross-section shapes of casting?
a) Permanent mould casting
b) Centrifugal casting
c) Continuous casting
d) Die casting
Explanation: Basically, the starting point of any structural steel product is the ingot which is rolled through a number of mills before a final product such as a slab or a bloom. Continuous casting allows for the fast production of constant cross-sectional shapes of the casting in large volume.
2. The rolling process is an essential part of the continuous casting for the production of castings.
Explanation: Wide adopting of continuous casting has changed that scenario by directly casting of slabs, billets and blooms without going through the rolling process. So in continuous casting, there is no requirement of any rolling operation, this makes the process very fast and economical too.
3. Which of the following methods of casting is best suitable for the casting of long length slabs and billets?
a) Investment casting
b) Permanent mould casting
c) Die casting
d) Continuous casting
Explanation: To produce continuously long length metallic objects in mass production directly from the liquid metal this technique can be used. Liquid metal is allowed through the die opening and the output of the die is a solid crust on which water will be sprayed to cool the material at a faster rate.
4. Which of the following is the approximate thickness (in mm) of the skin of casting formed at the initial of continuous casting process?
a) 1 to 5
b) 10 to 25
c) 25 to 75
d) 75 to 150
Explanation: In continuous casting process, the liquid steel is poured into a double-walled, bottomless water-cooled mould where a solid skin is formed quickly and a semi-finished skin emerges from the open mould bottom. The skin formed in the mould is approximately 10 to 25 mm in thickness.
5. In continuous casting, different cooling rates provide different properties to the castings.
Explanation: In continuous casting, depending on properties required by object, different cooling rates are provided. For example, intense cooling by water sprays makes the casting of fine structure and with good hardness, and if the air cooling is done then the casting of a coarse structure is made with good ductility in it.
6. Which of the following terms is used for the intermediate pouring vessel in continuous casting?
Explanation: In continuous casting process, the molten steel is collected in a ladle and kept over a refractory lined intermediate pouring vessel which is termed as tundish. The steel is then poured into water cooled vertical copper moulds which are approximately 450 to 750 mm in length.
7. Before starting of casting process, a dummy starter bar is used in the continuous casting method.
Explanation: At initial, a dummy starter bar is kept in the mould bottom. After starting of a process, as the metal level rises to a desirable height then the starter bar is withdrawn from the system. The initial metal freezes onto the starter bar as well as the periphery of the mould, and then this solidified shell supports the liquid metal as it moves downwards.
8. Which of the following parts is used for the support of steel shell in continuous casting?
a) Steel balls
b) Conveyor belt
c) Steel rollers
d) Steel frame
Explanation: In continuous casting, steel shell is mechanically supported by steel rollers as it moves down through the secondary cooling zone for the complete solidification then the water is sprayed onto the shell surface to solidify the casting, after that it is cut to the desired length of the billet or slab.
9. Higher extent of automation can be possible in a continuous casting method.
Explanation: The operations in the continuous casting cannot be done manually, so a higher extent of automation is introduced in this technique to perform the operations easily. For example, torch cutters, water sprayers, tundish, metallic rollers etc. are the automatic devices which are used to make the process fast and easy.
10. Continuously cast products in the continuous casting show very less segregation.
Explanation: In continuous casting, the dense metal is accumulated in a unitary form which is properly supported by the mould. This technique makes the better quality of casting products and the continuously cast products in the continuous casting show very less segregation.
11. Which of the following is used for the reduction of friction between the mould’s surface and metal strand?
b) Casting powder
Explanation: In continuous casting, at the beginning of solidification of molten metal in the mould, the casting powder is added onto the top side of molten metal in the mould. This casting powder melts and penetrates between the surfaces of the mould and solidified strand to minimize the friction, which leads to completion of the operation in less time.
12. Defects like diagonal cracks and blow holes can be induced in the casting by the oscillation of mould.
Explanation: Mould oscillation leads to a generation of shape defects of the casting. But the internal defects like blow holes, diagonal cracks or any kind of cracks are originated in the cast product due to the mechanical and thermal stresses which are caused by the non-uniform cooling of casting in the secondary zone.
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