Page 484 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

464 Chapter 17 Powder-Metal Processing and Equipment

QUANTITATIVE PROBLEMS

|]l7.25. Estimate the maximum tonnage required to (and the percentage of volume) occupied by this layer if the
compact a brass slug 75 mm in diameter. Would the height copper particle itself is 60 ,um in diameter?
of the slug make any difference in your answer? Explain ll l7.30. A coarse co PP er owder is com acted in a mechan-
P
P
your reasoning. ical press at a pressure of 275 MPa. During sintering, the green
D I7.26. Refer to Fig. 17.10a. What should be the volume part shrinks an additional 7%. What is the final density?
of loose, fine iron powder in order to make a solid cylindrical ll l7.3 I. A gear is to be manufactured from iron powders.
compact 25 mm in diameter and 20 mm high? It is desired that it have a final density 90% that of cast iron,
17.27. Determine the shape factors for (a) a cylinder with a and it is known that the shrinkage in sintering will be approx-
dimensional ratio of 1:1:1 and (b) a flake with a ratio of imately 5%. For a gear that is 90 mm in diameter and has a
1:10:10. 15-mm hub, what is the required press force?
I 7.28. Estimate the number of particles in a 5 00-g sample of l7.32. Assume that you are an instructor covering the topics
iron powder if the particle size is 75 um. described in this chapter and you are giving a quiz on the nu-
merical aspects to test the understanding of the students.
I7.29. Assume that the surface of a copper particle is covered
by an oxide layer 0.1 mm in thickness. What is the volume Prepare two quantitative problems and supply the answers.

SYNTHESIS, DESIGN, AND PROIECTS

|7.33. Make sketches of PM products in which density vari- l7.39. It was stated that powder-injection molding com-
ations (see Fig. 17.11) would be desirable. Explain why in petes well with investment casting and small forgings for var-
terms of the functions of these parts. ious materials, but not with zinc and aluminum die castings.
l7.34. Compare the design considerations for PM products Explain why.
with those for (a) casting and (b) forging. Describe your l7.40. Describe how the information given in Fig. 17.14
observations. would be helpful to you in designing PM parts.
|7.35. Are there applications in which you, as a manufactur- l7.4I. It was stated that, in the process shown in Fig. 17.19,
ing engineer, would not recommend a PM product? Explain. shapes produced are limited to axisymmetric parts. Do you
I7.36. Describe in detail other methods of manufacturing think it would be possible to produce other shapes as well?
the parts shown in Fig. 17.1. Describe how you would modify the design of the setup to
produce other shapes, and explain the difficulties that may be
l7.37. Using the Internet, locate suppliers of metal powders encountered.
and compare the cost of the powder with the cost of ingots
for five different materials.
l7.38. Explain why powder-metal parts are commonly used
for machine elements requiring good frictional and wear
characteristics and for mass-produced parts.