JNTU B.Tech II Semester Examinations,
, 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) Explain the methods of CO2 gassing of sodium silicate molds. Explain how this step is critical in attaining a mold with uniform strength.
(b) What do you understand by multiflask molding?
(c) What is a two high or three high molding sand? [8+4+4]
3. (a) What are limitations of permanent mold casting process?
(b) What are the metals that can be die cast? Why it is not possible to die cast certain metals and alloys? [7+9]
4. (a) With a neat sketch explain the nomenclature associated with a gating system
(b) Explain how microshrinkage and microsegregation are developed in solidified parts?
(c) Compare vertical gating sytem with a horizontal gating system. [5+6+5]
5. (a) How do you distinguish between center-line shrinkage, micro shrinkage and gross shrinkage. What is their importance in casting production?
(b) What is a “mushy zone” and its influence on its solidification characterization? [8+8]
6. (a) What happens to melting point of pure iron if carbon is added?
(b) What is the maximum percentage of carbon, which dissolves, in superheated liquid iron?
(c) What happens to carbon in liquid iron if iron is made to solidify? [5+5+6]
7. (a) Discuss the applications of various cold setting and self setting processes in
respect of the component parts of metals & alloys.
(b) Does the self setting processes involve any heating? If so, mention the details of the temperature and time of heating. Otherwise, also do the temperature have any effect on rate of setting. Discuss. [8+8]
8. (a) Describe the various defects which are likely to be caused in sand castings because of higher pouring temperatures.
(b) What are the causes for dimensional errors in castings and suggest methods to eliminate them? [8+8]