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
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) Dry sand molds are not used as often as green sand molds? State the reason.
(b) If under-baked cores are used, what kind of defects they can introduce in the castings?
(c) How do green sand cores when baked attain their strength? Which additive provides the core with green strength to with stand ejection, handling until they are baked?
(d) What is composite molding process? Explain its advantages. [4+4+4+4]
3. Write short notes on:
(a) Pressure die casting
(b) Permanent mold casting. [8+8]
4. (a) What is the role of gating system design on the metal yield of a foundry?
(b) Compare the design and performance of a gating system with choke at sprue runner junction to that where the choke is situated at the in-gates connecting mold cavity with the runner. [8+8]
5. Write short notes on :
(a) Ingot defects
(b) Coring and segregation. [8+8]
6. (a) Mention the various types of copper & aluminium casting alloys and illustrate
their properties and applications.
(b) What do you under stand by slag, metal reaction and how can it be prevented? [10+6]
7. Mention the self setting processes and explain the bonding mechanism achieved in
these processes. 
8. (a) What are the causes of external hot tears, cold cracks and warpage? How would you prevent their formation?
(b) Discuss internal hot tear formation. How would you prevent hot tear formation in a flat, rectangular plate casting? [10+6]