Rolling

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Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-1
CHAPTER 13
Rolling of Metals
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-2
Flat- and Shape-Rolling Processes
Figure 13.1 Schematic
outline of various flat- and
shape-rolling processes.
Source: American Iron and
Steel Institute.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-3
Flat-Rolling
Figure 13.2 (a) Schematic illustration of the flat-rolling process. (b) Friction forces acting on strip surfaces.
(c) The roll force, F, and the torque acting on the rolls. The width w of the strip usually increases during
rolling, as is shown in Fig. 13.5.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-4
Four-High Rolling Mill
Figure 13.3 Schematic
illustration of a four-high
rolling-mill stand, showing its
various features. The
stiffnesses of the housing, the
rolls, and the roll bearings are
all important in controlling
and maintaining the thickness
of the rolled strip.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-5
Roll Bending
Figure 13.4 (a) Bending of
straight cylindrical rolls, caused
by the roll force. (b) Bending
of rolls ground with camber,
producing a strip with uniform
thickness.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-6
Spreading of a Strip
Figure 13.5 Increase in the width
(spreading) of a strip in flat rolling
(see also Fig. 13.2a). Similarly,
spreading can be observed when
dough is rolled with a rolling pin.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-7
Grain Structure During Hot Rolling
Figure 13.6 Changes in the grain structure of cast or of large-grain wrought metals during hot rolling. Hot
rolling is an effective way to reduce grain size in metals, for improved strength and ductility. Cast structures
of ingots or continuous casting are converted to a wrought structure by hot working.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-8
Roller Leveling and Defects in Flat Rolling
Figure 13.7 A method of roller leveling to
flatten rolled sheets. See also Fig 15.22.
Figure 13.8 Schematic
illustration of typical defects in
flat rolling: (a) wavy edges; (b)
zipper cracks in the center of the
strip; (c) edge cracks; and (d)
alligatoring.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-9
Residual Stresses in Rolling
Figure 13.9 (a) Residual stresses developed in rolling with small rolls or at small
reductions in thickness per pass. (b) Residual stresses developed in rolling with
large rolls or at high reductions per pass. Note the reversal of the residual stress
patterns.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-10
Rolling Mill
Figure 13.10 A general
view of a rolling mill.
Source: Inland Steel.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-11
Backing Roll Arrangements
Figure 13.11 Schematic illustration of various roll arrangements: (a) two-high; (b) three- high; (c) four-
high; (d) cluster (Sendzimir) mill.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-12
Tandem Rolling
Figure 13.12 A tandem rolling operation.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-13
Shape Rolling
Figure 13.13 Stages in the
shape rolling of an H-section
part. Various other structural
sections, such as channels and
I-beams, are also rolled by this
kind of process.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-14
Ring-Rolling
Figure 13.14 (a) Schematic illustration of a
ring-rolling operation. Thickness reduction
results in an increase in the part diameter. (b)
Examples of cross-sections that can be formed
by ring rolling.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-15
Figure 13.15
Thread-rolling
processes: (a)
and (c)
reciprocating flat
dies; (b) two-
roller dies.
Threaded
fasteners, such as
bolts, are made
economically by
these processes,
at high rates of
production.
Thread-
Rolling
Figure 13.16 (a) Features of a
machined or rolled thread. (b)
Grain flow in machined and
rolled threads. Unlike
machining, which cuts through
the grains of the metal, the
rolling of threads causes
improved strength, because of
cold working and favorable grain
flow.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-16
Mannesmann Process
Figure 13.17 Cavity formation in a solid round bar and its utilization in the rotary tube piercing process
for making seamless pipe and tubing. (The Mannesmann mill was developed in the 1880s.)
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-17
Tube-Rolling
Figure 13.18
Schematic illustration
of various tube-rolling
processes: (a) with
fixed mandrel; (b)
with moving mandrel;
(c) without mandrel;
and (d) pilger rolling
over a mandrel and a
pair of shaped rolls.
Tube diameters and
thicknesses can also
be changed by other
processes, such as
drawing, extrusion,
and spinning.
Kalpakjian • Schmid
Manufacturing Engineering and
Technology
©2001 Prentice-Hall Page 13-18
Spray Casting (Osprey Process)
Figure 13.19 Spray casting
(Osprey process), in which
molten metal is sprayed over
a rotating mandrel to produce
seamless tubing and pipe.
Source: J . Szekely, Scientific
American, J uly 1987.

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