4. A picture of the rolling mill:
Adjusting Screw
Rolls Rolls Housing/
Stand
5. Rolling
Rolling is a bulk
deformation process in
which the thickness of
the
work is reduced by
compressive forces
exerted by two opposing
rolls. The rolls rotate to
pull and simultaneously
squeeze the work
between them.
6. Types Of Rolling
Flat Rolling
The final shape of
the product is
either classed as
sheet or plate .
7. Draft
In flat rolling, the work is squeezed between two
rolls so that its
thickness is reduced by an amount called the draft:
8. Calculation Of Draft
D = to - tf
where
d: draft
to: starting thickness
tf : final thickness
As a fraction of the starting thickness:
% reduction = % r = (d/ to) * 100%
9. Structural Defects In Flat Or Sheet Rolling:
Wavy Edges Center cracking Edge cracking Alligatoring
10. Shapes Rolling
The final product may be a round rod or
other shaped bar, such as a structural
section (beam, channeletc)
11. CLASSIFICATION OF ROLLING
AS ANY OTHER METAL FORMING
PROCESS, ROLLING CAN BE PERFORMED
HOT (HOT ROLLING) OR COLD (COLD
ROLLING).
MOST ROLLING IS CARRIED OUT BY HOT
ROLLING, OWING TO THE LARGE
AMOUNT OF DEFORMATION REQUIRED.
12. Hot Rolling
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 termed as hot
rolling
13. RECRYSTALLIZATION
The lowest temperature at which the
distorted grain structure of a cold-
worked metal is replaced by a
new, strain-free grain structure during
prolonged annealing. Time, purity of
metal, and prior deformation are
important factors.
15. After casting we achieve three intermediate
shapes called blooms, billets, and slabs:
Blooms have square cross section 6” x 6” or
larger. They are rolled into structural shapes.
16. Billets have square cross section 1.5” x 1.5”
or larger. they are rolled into bars and rods.
Slabs have rectangular cross section 10” x
1.5” or larger. They are rolled into plates,
sheets.
17. Advantages Of Hot Rolling
The possibility of producing a very dramatic
shape change in a single working
step, without causing large amounts of
internal stress, cracks or cold working;
Sometimes hot working can be combined
with a casting process so that metal is cast
and then immediately hot worked. This saves
money because we don't have to pay for the
energy to reheat the metal.
18. Disadvantages Of Hot Rolling
If the recrystallisation temperature of the worked
metal is high e.g. if we are talking about steel,
specialised methods are needed to protect the
machines that work the metal. The working processes
are also dangerous to human operators and very
unpleasant to work near.
19. Cold Rolling
If the temperature
of the metal is
below its
recrystallization
temperature, the
process is termed
as cold rolling
20. Advantages Of Cold Rolling
A better surface finish may be achieved
Dimensional accuracy can be excellent because the
work is not hot so it doesn't shrink on cooling; also the
low temperatures mean the tools such as dies and
rollers can last a long time without wearing out.
21. Disadvantages Of Cold Rolling
Higher forces are required to produce a
given deformation, which means we
need heavily built, strong forming
machines .
22. Rolling Mills
Two-high rolling mill: consists of two
opposing rolls. These rolls may rotate only
in one direction (non reversing) or in two
directions (reversing).
Three-high rolling mill: allows a series of
reductions without the need to change the
rotational direction of the rolls.
23. Rolling Mills
Four-high rolling mill: Using small rolls
reduces power consumption but increases
the roll deflection. In this
configuration, two small rolls, called
working rolls, are used to reduce the
power and another two, called backing
rolls, are used to provide support to the
working rolls.
Cluster rolling mill: another configuration
that allows smaller working rolls to be
used.
25. What is difference b/w a tube &
a pipe
The difference between a pipe and a tube
is how they are measured, and ultimately
what they are used for.
A pipe is a vessel - a tube is structural.
A pipe is measured ID - a tube is
measured OD.
26. Production Of Seamless Piping &
Tubing
Seamless Pipes:-
. Seamless (SMLS) Steel Pipe is made from a solid round
steel ‘billet’ which is heated and pushed or pulled over a
form until the steel is shaped into a hollow tube. The
seamless pipe is then finished to dimensional and wall
thickness specifications in sizes from 1/8 inch to 26 inch
O
27.
28. Seamless Tubes:-
The process involves the progressive bending
of metal strip as it passes through a series
of rollers at speed up to 80m/sec. Only
bending take place, all bends are parallel.
Seam welding process carried out to form a
proper tube.and wed flashes are removed
by scarfing blades.
29. Comparison Of Seamless Pipe &
Tube
Seamless Pipe Seamless Tube
Seamless pipe Welded pipe often
provides the most has tighter
reliable pressure dimensional
retaining tolerances.
characteristics. cheaper if
easily available than manufactured in the
welded pipe. same quantities.
More Expensive. Size is greater than
Size is less than 3 3 inch dia.
inch dia.
