Page 354 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

334 Chapter 13 Metal-Rolling Processes and Equipment

(c) a decreasing ratio of the roll radius to the strip thickness. |3.25. Describe the importance of controlling roll speeds,
Explain why. roll gaps, temperature, and other process variables in a
tandem-rolling operation, as shown in Fig. 13.11. Explain
l3.22. As stated in this chapter, flat rolling can be carried
out by front tension only, using idling rolls (Steckel rolling). how you would go about determining the distance between
Since the torque on the rolls is now zero, where, then, is the the stands.
energy coming from to supply the work of deformation in |3.26. In Fig. 13.9a, if you remove the top compressive
rolling? layer by, say, grinding, will the strip remain flat? If not, which
13.23. Explain the consequence of applying too high a back way will it curve and why?
tension in rolling. l3.27. Name several products that can be made by each of
I 3.24. Note in Fig. 13.3d that the driven rolls (powered rolls) the operations shown in Fig. 13.1.
are the third set from the work roll. Why isn’t power supplied l3.28. List the possible consequences of rolling at (a) too
through the work roll itself? Is it even possible? Explain. high of a speed and (b) too low of a speed.

QUANTITATIVE PROBLEMS

ll l3.29. In Example 13.1, calculate the roll force and the thick, and rolled to a thickness of 7 mm. The roll radius is
power for the case in which the workpiece material is 1 100-O 200 mm, and it rotates at 200 rpm.
aluminum and the roll radius, R, is 200 mm. |3.32. Assume that you are an instructor covering the
|]l3.30. Calculate the individual drafts in each of the topics described in this chapter and you are giving a quiz
stands in the tandem-rolling operation shown in Fig. 13.11. on the numerical aspects to test the understanding of the
students. Prepare two quantitative problems and supply the
ll |3.3l. Estimate the roll force, F, and the torque for an
AISI 1020 carbon-steel strip that is 200 mm wide, 10 mm answers.

SYNTHESIS, DESIGN, AND PROIECTS

I3.33. A simple sketch of a four-high mill stand is shown in 13.35. If you repeat the experiment in Problem 13.34 with a
Fig. 13.3a. Make a survey of the technical literature and pres- harder eraser, such as that used for erasing ink, you will note
ent a more detailed sketch for such a stand, showing the that the whole eraser will begin to crack and crumble.
major components. Explain Why.
|3.34. Obtain a piece of soft, round rubber eraser, such as l3.36. Design a set of rolls to produce cross sections other
that at the end of a pencil, and duplicate the process shown in than those shown in Fig. 13.12.
Fig. 13.18b. Note how the central portion of the eraser will
begin to erode, producing a hole.