ch13 rolling

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Chapter 13Rolling of Metals


Flat-Rolling andShape-Rolling

Processes

Figure 13.1 Schematicoutline of various flat-rolling and shape-rollingprocesses. Source:After the American Ironand Steel Institute.


Flat-Rolling Process

Figure 13.2 (a) Schematic illustration of the flat-rolling process. (b) Friction forces acting onstrip surfaces. (c) Roll force, F, and the torque, T, acting on the rolls. The width of the strip,w, usually increases during rolling, as shown later in Fig. 13.5.


Roll Arrangements

Figure 13.3 Schematic illustration of various roll arrangements: (a) four-highrolling mill showing various features. The stiffness of the housing, the rolls, and theroll bearings are all important in controlling and maintaining the thickness of therolled strip; (b) two-hill mill; (c) three-high mill; and (d) cluster (or Sendzimir) mill.


Bending of Rolls

Figure 13.4 (a) Bending ofstraight cylindrical rolls caused byroll forces. (b) Bending of rollsground with camber, producing astrip with uniform thicknessthrough the strip width.Deflections have beenexaggerated for clarity.


Spreading in Flat Rolling

Figure 13.5 Increase in strip width (spreading) in flat rolling. Note thatsimilar spreading can be observed when dough is rolled with a rolling pin.


Effects of Hot Rolling

Figure 13.6 Changes in the grain structure of cast or of large-grain wroughtmetals during hot rolling. Hot rolling is an effective way to reduce grain sizein metals for improved strength and ductility. Cast structures of ingots orcontinuous castings are converted to a wrought structure by hot working.


Roller Leveling

Figure 13.7 (a) A method of roller leveling to flatten rolled sheets.(b) Roller leveling to straighten drawn bars.


Defects in Flat Rolling

Figure 13.8 Schematicillustration of typicaldefects in flat rolling: (a)wavy edges; (b) zippercracks in the center of thestrip; (c) edge cracks; and(d) alligatoring.


Residual Stresses Developed in Rolling

Figure 13.9 (a) Residual stresses developed in rolling with small-diameter rolls or at smallreductions in thickness per pass. (b) Residual stresses developed in rolling with large-diameter rolls or at high reductions per pass. Note the reversal of the residual stress patterns.


Rolling Mill

Figure 13.10 A general view of a rolling mill. Source: Courtesy of Ispat Inland.


Tandem-Rolling

Figure 13.11 An example of a tandem-rolling operation.


Shape Rolling of an H-section part

Figure 13.12 Steps in theshape rolling of an H-section part. Various otherstructural sections, such aschannels and I-beams, alsoare rolled by this kind ofprocess.


Roll-Forging

Figure 13.13 Two examples of the roll-forging operation, also known as cross-rolling.Tapered leaf springs and knives can be made by this process. Source: After J. Holub.


Production of Steel Balls

Figure 13.14 (a) Production of steel balls by the skew-rolling process. (b) Production ofsteel balls by upsetting a cylindrical blank. Note the formation of flash. The balls made bythese processes subsequently are ground and polished for use in ball bearings.


Ring-Rolling

Figure 13.15 (a) Schematic illustration of a ring-rolling operation. Thickness reductionresults in an increase in the part diameter. (b-d) Examples of cross-sections that can beformed by ring-rolling.


Thread-Rolling Processes

Figure 13.16 Thread-rolling processes: (a) and (c) reciprocating flat dies; (b) two-roller dies.(d) Threaded fasteners, such as bolts, are made economically by these processes at highrates of production. Source: Courtesy of Central Rolled Thread Die Co.


Machined and Rolled Threads

Figure 13.17 (a) Features of a machined or rolled thread. Grain flow in (b) machined and(c) rolled threads. Unlike machining, which cuts through the grains of the metal, the rollingof threads imparts improved strength because of cold working and favorable grain flow.


Cavity Formation in Bar

Figure 13.18 Cavity formation in a solid, round bar and its utilization in the rotary tube-piercing process for making seamless pipe and tubing. (see also Fig. 2.9.)


Various Tube-Rolling Processes

Figure 13.19 Schematic illustration of various tube-rolling processes: (a) with afixed mandrel; (b) with a floating mandrel; (c) without a mandrel; and (d) pilgerrolling over a mandrel and a pair of shaped rolls. Tube diameters and thicknessesalso can be changed by other processes, such as drawing, extrusion, and spinning.


Forming of Solid Rocket Casings

Figure 13.20 The Space Shuttle U.S.S.Atlantis is launched by two strapped-on solid-rocket boosters. Source: Courtesy of NASA.

Figure 13.21 The formingprocesses involved in themanufacture of solid rocketcasings for the SpaceShuttles.

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