rolling

03/05/2023 rolling and the ring 1

Metal process Technology (MEng 5233)

Rolling and ring rollingDesign of roll passes in shape rolling

03/05/2023rolling and the ring

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Material and Geometry of cutting tool

Flat- and Shape-Rolling Processes

Schematic outline of various flat- and shape-rolling processes.

Rolled Products Made of Steel

Shape Rolling

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.

Flowchart of Rolling Operations

Figure 1 Flow chart for the production of various finished and semi-finished steel shapes. Note the abundance of rolling operations.

Rolling Process

Flat-Rolling

(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,

Four-High Rolling Mill

Schematic illustration of a four-high rolling-mill stand, showing its various features. The stiffness of the housing, the rolls, and the roll bearings are all important in controlling and maintaining the thickness of the rolled strip.

Backing Roll Arrangements

Schematic illustration of various roll arrangements (a) two-high; (b) three- high; (c) four-high; (d) cluster (Sendzimir) mill.


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Grain Structure During Hot Rolling

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.


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Tandem Rolling

A tandem rolling operation.


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ADVANTAGES…

Cold Working

No heating is required Better surface finish is obtained

Superior dimensional control is achieved, so little, if any, secondary machining is required

Products possess better reproducibility and interchangeability

Strength, fatigue and wear properties are improved through strain hardening

Directional properties can be imparted

Contamination problems are minimized

DISADVANTAGES…

Cold Working

Higher forces are required to initiate and complete the deformation

Heavier and more powerful equipment is required

Intermediate annealing may be required to compensate for the loss of ductility that accompanies strain hardening

Metal surfaces must be clean and scale-free Less ductility is

available imparted directional

properties may be detrimental

Undesirable residual stresses may be produced


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Diagram of Flat Rolling

Draft = thickness reduction:

Conservation of Volume:

fo ttd

fffooo LwtLwt

fffooo vwtvwt

Diagram of Flat Rolling

There is a point on the roll where the work velocity equals the roll velocity, this is the no-slip point. Friction is in opposite directions on either side of this point. Forward slip:

where, Maximum draft:Roll force: Rd 2

max

r

rf

vvv

s

)( foffcontactf ttRwYwLYF

min/revNDNvr

frictionoftcoefficien


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Ring-Rolling

(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.

Ring Rolling One roll is placed through

the hole of a thick-walled ring and a second roll presses on the outside

Produces seamless rings Circumferential grain

orientation and is used in rockets, turbines, airplanes, pressure vessels, and pipelines

Figure 6 Schematic of horizontal ring rolling operation. As the thickness of the ring is reduced, its diameter will increase.

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