This set of Foundry Multiple Choice Questions & Answers (MCQs) focuses on “Green Sand Moulding”.
1. In green sand molding, the sand id claimed to be green because it has _______
Explanation: In foundry processes, the sands are called green due to the moisture content in them. The moisture content makes the sand wet which is suitable for the molding. The moisture content varies according to the type of casting to be made.
2. The sand has to undergo ____________ process before it is called green and is ready for molding.
Explanation: The green sand, before being called green has to undergo a process called mulling process in which the clay, binders and various additives are blended together to make it suitable for its usage.
3. Which of the following is not used in the green sand?
Explanation: In the making of the green sand, clay is present in the form of bentonite. Water percentage is varied as required for a particular casting. Oil is not the kind of binder used in the green sand. Bentonite is the only binder used.
4. Green sand molding cannot be used for _________ moulds.
Explanation: In green sand molding, the metal is poured in them in wet condition. It is easy to mould the wet sand with hand only for small to medium sized moulds which make it difficult to use the green sand molding for the production of the complex castings.
5. Green sand is widely used for hand molding purposes.
Explanation: The green sand is a mixture of silica sand with 15-25 percent clay and 6-8 percent water. Being damp the sand can be easily worked with hand to give it only desired shape due to its easy mold ability.
6. Green sand molding methods can be used for ________ molding machines.
c) Fully automatic
d) All of the mentioned
Explanation: The green sand molding method involves highly moldable sand which ensures flexibility of the castings that could be prepared using this method. It is flexible to be used in all the (manual, semi-automatic and fully automatic) machines.
7. Which of the following characteristic is not expected in the green sand in the green sand molding process?
a) Flowable nature
b) Plastic Nature
Explanation: If the green sand develops the quality of reactivity in it, it will have significant defects in it which will result in discarding of the entire casting. Hence all the qualities except reactivity are desired in the sand.
8. Green sand molding is replacing the costlier molding processes as the sand control methods are being applied.
Explanation: In green sand molding, proper attention can be given on the content of sand, range of the moisture, additives and binder content etc. Sand control methods are established and so it has an edge over the other molding methods.
9. Green sand must exhibit high refractoriness in the green sand molding.
Explanation: Green sand must guarantee good refractoriness to withstand the high temperature which is generated due to the molten metal and it should not be involved in any kind of melting or fusing with the metal.
10. Green sand does not require dry strength.
Explanation: Dry strength refers to the strength of the sand when the surface dries out. Green sand is also required to have adequate dry strength when it is to be used in the green sand molding in order to prevent the erosion of the liquid metal during pouring as the mould surface dries out.
Sanfoundry Global Education & Learning Series – Foundry and Forging.
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