JNTU B Tech ii Semester Examinations,Foundry Technology, Apr/May 2008

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JNTU B.Tech II Semester Examinations, Foundry Technology, Apr/May 2008

(Metallurgy & Material Technology)

Time: 3 hours Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

SET-IV

1. (a) A cast iron jobbing foundry need to make 50 pieces of axisymmetric shell

castings (dimensions 2000mm internal diameter and height 601 mm). The average shell thickness is 35 mm. What should be the pattern material?

Justify your choice. If the external profile of this casting require usage of a concentric outer core, what should be the core material?

(b) What general factors decide the parting line (plane) in the production of the pattern of a cored casting?

(c) Usage of a vertical core is necessary to produce the internal detail in a hollow

surface of a steel casting. What measures do you take against flotation of core under high metallostatic pressure. [6+5+5]

 

2. (a) Explain the advantages of foamed plaster molding over conventional plaster molding process.

(b) Explain the steps involved,in producing molds and pouring them with liquid metal, in the foamed plaster molding process. [8+8]

 

3. (a) Draw a schematic sketch of vertical centrifugal casting process and explain the process.

(b) Explain how it is possible to feed molten metal into thinner and lighter sections with ease in centrifugal casting.

(c) Comment on the centrifugal cast parts in terms of casting yield, uniformity of properties, rigidity and axiality of sand molds used, of permanent molds used. [5+4+7]

 

4. What are various methods of risering a casting? Under what conditions, a riserless

gating system works satisfactorily? [16]

 

5. (a) How do you control the rate of flow of metals in moulds? Explain.

(b) What is centerline feeding resistance of the castings? Discuss its importance. [8+8]

 

6. Draw a neat sketch of a coke fired pit furnace. Explain the procedure for melting aluminium alloys in it. [16]

 

7. (a) Describe the various steps involved in Full-mould process. How its alliance with V-process is helpful? Enumerate the advantages of this process.

(b) What are the criteria for the selection of a particular moulding process for a given casting? Discuss your views in detail. [10+6]

 

8. State the reasons for the occurrence of the following casting defects and suggest the remedies for their control.

(a) Mismatch

(b) Variation in wall thickness of castings

(c) Scab

(d) Core shift. [16]

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