Rolling Final

Introduction
Roll milling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more
pairs of rolls to reduce the thickness and to make the thickness uniform. The concept is similar to the
rolling of dough. Rolling is classified according to the temperature of the metal rolled. If the temperature
of the metal is above its recrystallization temperature, then the process is known as hot rolling. If the
temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In
roll milling deformation process in which Metal(s) in its semi-finished or finished form is passed between
the two opposing rollers, which reduces the metal’s thickness through the compression process. The
rollers rolls around the metal as it squeezes in between them.
Most rolling mills feature two or more rolls arranged in a symmetrical pattern, with half above the work
and half below the work to be rolled. Typically, the rolls are mounted one above the other and rotate at
the same speed in opposite directions. The metal is passed through the machine multiple times with the
spaces between the cylinders decreasing each time so the metal becomes increasingly thinner.
Cold Rolling
Cold rolling mills pass metals though the rollers at a temperature below its recrystallization temperature.
This process is typically used to decrease the thickness of plate and sheet metal by increasing the metal’s
yield strength and hardness through the introduction of defects to its crystal structure. The defects
produced by cold rolling mills prevent slip and reduce the grain size of the metal, which results in Hall-
Petch hardening.
The deformation mechanism in cold roll-forming is quite complex and the inherent complexity of the
process has often resulted in the adoption of a trial and error approach towards solving many problems
encountered in practice. Despite the appearance of both theoretical and experimental studies in the
literature the approach has remained very empirical.
Principle of Rolling
The Rolling Process consists of two opposing rollers and a metal squeezing in between them. The basic
consideration is that the thickness between the rollers should be less than the Metal’s (Ingot) Initial
Thickness. This consideration will help metal’s forward motion as it passes through the gap between the
Rollers. Rolling Process decreases the Thickness of Metal and Increases its Length and Breadth, Keeping
Overall Volume Constant.
Theory and Working of Cold Rolling
Rolling mills work by using multiple rollers to manipulate the physical properties of sheet metal. In
steelmaking, they offer a uniform thickness and consistency for the steel sheet metal with which they are
used. Rolling mills contain rollers that squeeze and compress sheet metal as it passes through them.
Therefore, the sheet metal may have an inconsistent size or shape beforehand. After passing through the
rollers in a rolling mill, however, the sheet metal will develop a uniform size and shape.
It’s important to note that rolling mills support both cold rolling and hot rolling processes. Cold rolling
means the sheet metal is pressed between the rollers at or near room temperature. Hot rolling, on the
other, means the sheet metal is pressed between the rollers at a temperature above the metal’s
recrystallization point. Cold rolling allows for the production of stronger and more durable steel products,
whereas hot rolling is a faster and easier rolling process that allows for streamlined production activities.
Rolling mills can be used for both cold rolling and hot rolling.
Cold roll-forming is a process of forming metal from sheet, strip or coiled stock into shapes of essentially
uniform cross-section by feeding the strips through successive pairs of rolls arranged in tandem. The
deformation in cold roll-forming is quite complex and due to this inherent complexity of the process, the
roll design and other decision-makings often involve a good deal of trial and error. The "forming angle"
method, which is regarded as reasonably dependable for assisting in determination of the number of roll
stations to form a bend, takes account of it the intermittent deformation under each roll station only in a
crude way. The deformation length under each roll station a priori by minimizing the deformation energy
and assuming the material to be rigid--plastic.
The theoretical results have been verified by roll forming channel sections from mild steel and aluminum
strips and the agreement between the theory and the experiment has been found to be extremely good.
The results also suggest that the deformation length depends on the physical parameters of the produced
channel section but is practically independent of the mechanical properties of the work material for the
situations considered in the present investigation.
Rolled products, i.e. sheet, plate and foil constitute almost 50% of all aluminum alloys used. Sheet is also
used extensively in building for roofing and siding, in transport for airframes, road and rail vehicles, in
marine applications, including offshore platforms, and superstructures and hulls of boats.
Characteristics of Cold Rolling:
 Glossy like an oily and smooth surface.

 The surface is more finished and better with closer tolerances.
 Tubes have straightness and the concentric uniformity is better.
 The edges or the corners of the bars are well defined and the shape of the bars are more perfect
than hot rolled products.
Defects in Rolling Products:

Several defects are arises in the rolling process. These defects are as follows:
(i) Edge Cracking:
This Occurs due to limited ductility of the material, or uneven deformation, mainly at the edges. This type
of deformation Occurs mostly in Ingots, plates, or slabs.
(ii) Alligatoring:
In this type of defect, the Metal tears down into 2 Pieces in the Horizontal Plane. It mainly occurred with
slabs and Occurs when slab thickness to the length of Contact falls between 1.4 to 1.65.
iii) Folds:
This type of defect occurs when the reduction per pass is minimal. Folds are very frequent in plate rolling.
(iv) Scale Formation:
In this type of defect, an Oxide layer is formed above the metal layer. Scale formation Occurs during the
Hot Rolling Process.
Specifications and Applications
When choosing rolling mills, roll diameter and the type of metal to roll are important specifications to
consider. For each series, model, and type of machine, three diameters may be listed: work rolls, back-up
rolls, and roll journal. Other parameters include maximum separation force at 1000 feet per minute
(fpm), total column area, and estimated floor space. Rolling mills include both small, manually-operated
bench top systems and large, powered machines. They are used in the production of bars, rods, wire rods,
bands, hoops, metal shapes, plates, and jewelry.
Rolling Process is one of the most widely used processes in Industries. It is used to manufacture things
ranging from balls of bearing to turbines. Apart from this, the rolling process is also used for mass
manufacturing of sheets, strips, wires, bars, slabs, etc. which are the secondary products in the rolling
process.
It must always be remembered that the rolling process is primarily used to change the shape of metal,
which led to different applications in various fields.
ADVANTAGES:
 Aluminium being anti-corrosive
 maintenance-free
 non-inflammable finds application in Fan Blade
 Bus Body
 Utensils
 Sliver Can
 Insulation and many more
Rolling of Aluminium
Rolling is a mechanical process involved in many metals processing operations. Rolled aluminum
products are essential materials for our daily life. Thick products are used as structural members for rail
cars and aircraft, and thin products are used as packaging materials such as aluminum cans and aluminum
foils.
Rolled products, i.e. sheet, plate and foil constitute almost 50% of all aluminum alloys used. In North
America the packaging industry consumes the majority of the sheet and foil for making beverage cans,
foil containers and foil wrapping. Sheet is also used extensively in building for roofing and siding, in
transport for airframes, road and rail vehicles, in marine applications, including offshore platforms, and
superstructures and hulls of boats.
The selection of aluminum for a specific use is normally in reaction to an ever increasing demand for an
improved strength to weight ratio along with a number of other key property advantages.
Rolled aluminum can be presented in several forms including sheets, plates and foils, and is used in many
industries adding to the flexibility and its position as a critical material for modern applications.
Recent technological advancement in aerospace, automotive, marine, construction and leisure industries
has made the demand for materials having high strength to weight ratio, high specific modulus, good
corrosion resistance and good thermal conductivity to be on the increase. Aluminum and its alloys offer
such combination of tremendous properties.
Aluminum 1000 series
The 1000 series grades of aluminium are the purest of all of the commercial aluminium grades. Each and
every grade in the 1000 series contains a minimum of 99% pure aluminium. This high aluminium content
gives the 1000 series grades exceptional resistance to corrosion caused by both chemicals and the
atmosphere.
Tensile Strength range= 10-25 Ksi
Von Mises Theory
According to it, yielding occurs when the distortion energy reaches a critical value. This critical value,
which is specific for each material, can easily be obtained by performing a simple tension test. When a
body, in an initial state of equilibrium or unreformed state, is subjected to a body force or a surface force,
the body deforms correspondingly until it reaches a new state of mechanical equilibrium or deformed
state.
The inner body forces are the result of a force field such as gravity, while the surface forces are forces
applied on the body through contact with other bodies.
Equation
(σv) = √(σx2 - (σx x σy) + σy2 + (3 ×τxy2))
Where,
σv = Von Mises Stress
σx, σy = Normal Stress
τxy = Shear Stress
Von Misses Stress
The concept of Von mises stress is derived from distortion energy failure theory. It applies to test the
isotropic and ductile materials such as metals, and determine whether it will yield when directed towards
complex loading condition.
Irritatingly, the ‘representative’ stress, σRep, for meeting the yield criteria that we’ve derived above
doesn’t add up to the uniaxial stress, σ, that we have in pure tension, σ. It is actually √2/3 times that as we
can see above. In order to overcome this potentially confusing issue, we simply scale the reference stress
by √3/2 in order to get a representative scalar stress value that is equivalent to the uniaxial tensile stress
from the test. We’re allowed to do that in this case because the resulting σVM is still proportional to the
deviatoric strain energy:
Conducting full cooling and increasing reduction greatly increases von Mises effective stress at the bite
region, stress inside the roll is not much affected
Numerical Calculations:
There are five rollers which are used in cold roll milling of Aluminium alloy whose core functions are
mentioned below:
 2 x Flat Sheet Rollers (75 x 41mm Ø)
 2 x Textured Rollers to create interesting effects
 1 x Half round and V shaped wire roller to enable you to create your own wire
To Find Thickness
In passing through the roll gap a strip of constant width w, undergoes a thickness change from ho to hl, or
Ah, and because the deformation has been assumed to be one of plane strain on an incompressible
material the following relationship holds:
W×ho×Vo = whv =wh1 v1
Thus the velocity of the strip increases steadily from entry to exit and the velocity of the rolls must have a
value somewhere vo and v1.
To find Length
Length: The length of the deformation zone (ld) for absolutely solid rolls is calculated using the
following equation:
ld =√ R △ h−¿ ¿
Where
ld= Length of deformation
R= Radius
H= Thickness
To find Position
Position: The position of aluminium sample can be describe by the parameter S which can be define by
the equation
S=△t/t0
Where
△t= distance from the center,
t0= the sheet thickness
Rolling to Desired Thickness

When the aluminum slabs are ready, they go through several stages of roller mills with decreasing
separation between them. The roller mills apply force to the top and bottom of the slab. They continue to
do so until the slab reaches the desired thickness. Each pass remove the 0.25mm part of material to get the
final length 2400mm.
The strip is passed several times between a series of rollers until it is gradually reduced to the desired
gauge and wound into a coil. Cold Rolling occurs with the metal is treated below its re-crystallization
temperature, which increases the strength (via Strain Hardening) by up to 20%, and enables tighter
tolerances. The process also renders dimensional accuracy and surface finish to products, making them
optimal for a vast variety of applications.
Depending on the final thickness of the aluminum, the resulting product will be classified in one of three
ways, as defined by the Aluminum Association.
Each of the three types of rolled aluminum is suited to different purposes.
No. 1 – Aluminum Plate
Aluminum rolled to a thickness of 0.25 inches (6.3 mm) or more is called aluminum plate, which
aerospace companies often use in aircraft wings and structures.
No. 2 – Aluminum Sheet
Aluminum rolled to between 0.008 inches (0.2 mm) and 0.25 inches (6.3 mm) is called aluminum sheet,
and many consider it to be the most versatile rolled aluminum form. Manufacturers use aluminum sheet to
produce beverage and food cans, highway signs, license plates, automobile structures and exteriors, and
many other products.
No. 3 – Aluminum Foil
Aluminum rolled into anything thinner than 0.008 inches (0.2 mm) is considered foil. Food packaging,
insulation-backing in buildings, and laminated vapor barriers are examples of applications for aluminum
foil.
Conclusion
Rolling is one of the most versatile methods of aluminum forming, and its applications are endless.
Demand for flat-rolled products is expected to continue to increase in the coming years, so it’s no wonder
that aluminum product producers often consider rolling for their first processing step.
Aluminum alloys are economical in many applications. They are used in the automotive industry,
aerospace industry, in construction of machines, appliances, and structures, as cooking utensils, as covers
for housings for electronic equipment, as pressure vessels for cryogenic applications, and in innumerable
other areas.
References
1. D. Bhattacharyya, P. S. (1983). The prediction of deformation of length in cold roll forming.

Mechanical Working Technology, 11.
2. Davis, J. (2001). Aluminum and Aluminum Alloys. Alloying: Understanding the Basics, 66.
3. Woodward, R. (1994). The Rolling of Aluminium: the process and the Product. European
Aluminium Association , 24.

Rolling Final

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Introduction

 Glossy like an oily and smooth surface.

Defects in Rolling Products:

Rolling to Desired Thickness

1. D. Bhattacharyya, P. S. (1983). The prediction of deformation of length in cold roll forming.

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