1. Structural Mill Operation
โข The aim is to show the different individual
working area that integrate as functional units in
a specific sequence to form a Hot Rolling Mill.
โข The functions of each working area will be stated
in brief to understand its role as a sub unit of the
Mill.
โข Any functional area will be the assimilation of the
functions executed by their Local Control Stations
which cater to the basic needs and Main Control
Desk located inside a Control Pulpit
2. A.) Billet Yard
1. Billets are unloaded on selected Roller Table.
2. Billets are transferred on Roller Table in front
of the Elevator.
3. Billet is transferred by elevator to Roller Table
with pushers.
4. Billet length is measured with laser.
5. Billet is then passed to Roller Table with
weighing system and the following happens:
4. B.) Furnace (200 T/H Walking Beam)
โข Charging cycle:
1. Once the stopper disappears the Furnace
Door opens and Charging RT receives the
billet.
2. The position of the billet is checked w.r.t.
loading diagram.
3. Charging door closes.
4. Aligning machine starts Fwd & Rev cycle.
5. โข Discharging cycle:
1. Kick Off cycle starts.
2. Kick off moves the billet to discharging Roller
table.
3. Discharge side door opens which is followed
by the motion of discharging Roller tables.
4. When the tail of the billet leaves the
discharging door closes.
6. C.) Reheating Furnace Exit Area
1. This area is entered once Furnace is ready to
discharge and the disappearing stopper is down.
2. The entry of billet head at the descaler is
followed by a high pressure water delivery to
remove the scales and stops when the tail has
left the descaler.
3. The Pinch Roll (PR) and Roller Table (RT) first
slows down to bite speed and then is adjusted
with the speed of the 1st working Stand.
4. The cycle restarts by synchronizing the PR and
RT with RHF RT
7. D.) Mill Area
The Mill Area is classified into 3 zones:
1. Roughing Mill consisting of 7 stands and
Pendulum Shear and 1 Crop Shear.
2. Intermediate Mill consisting of 5 stands and 1
Shear
3. Finishing Mill consisting of 5 Stands and 1
Shear
4. Then comes the diverter that bifurcates the
Rolling Mill into 2 lines, Line-1 & 2.
8. Mill Area Operation Features
1. Speed Reference system to generate required
speed.
2. Single mode speed variation that controls the
speed of a single motor.
3. Cascade mode that controls the speed of a
particular motor and also the speed of all the
motors preceding that particular motor inorder
to bring the system to a synchronization.
4. Master control generates the reference for
speed reference system
9. Mill Area Operation Features
5. Lead Speed designed to improve the speed of
introduction of the material to a particular
Stand.
6. Material Tracking that is aimed to track the shift
in head or the tail of a material so that
subsequent functions like continuity control,
tension control and loop control can be
executed efficiently.
7. Continuity Control supervises the arising of
cobble and controls the cropping action of the
shears
10. Mill Area Operation Features
8. Tension Control applicable for large profiles only
that eliminates the tension between 2 stands.
9. Loop Control comes into play inorder to reduce
the tension between 2 stands especially when
the material is thin & deforming.
10. Excluded Stand Control which excludes some
specific stands from the process depending upon
the required material profile.
11. Mill Area Operation Features
11. Ready to Roll that performs the
management of all alrms and interlocks that
combine in specific sequence prior to giving
consent for rolling.
12. Ghost Rolling which simulates the process of
billet rolling inorder to identify the error in
any field sensors.
12. E.) Cooling Bed Area
1. Cooling Bed cycle sets up the movement of
the bars by initiating the Lining up RT.
2. Layer forming is started as Cleaning cycle
sends the bars proceed towards Cooling Bed
Exit RT.
3. The layer is moved to aligning bar so that an
uniform layer can be fed to the Straightener.
4. Straightener is not a mandatory component
and can be bypassed using a bypass RT.
13. F.) Straightener Area
1. The Multi strand Straightening machine rolls
and Pinch roll positioning is verified.
2. Straightening Line Control ensures that bars
are towards Straightener.
3. Bar Straightening takes place.
4. Straightening Line control ensures that the
bar travels from Straightener to downstream.
14. Details of Straightener
โข Its main components are:
1. Main Motor Drive
2. Upper Roll Axial adjustment system
3. Lower Roll Vertical adjustment system
4. Roller changing tool.
5. Machine Lubrication system
6. Cobble detection system.
15. G.) Layer Preparation Area
1. It is the area between Cold Saw and Straightener
and includes the Tail Recovery System.
2. Bars are charged from Straightener exit RT by
Liftable Chain Transfer.
3. Layer formation takes place with the help of
entry and exit chain transfer & must be
compacted by pushers.
4. Once the layer is completed it is discharged
towards Saw Entry RT for Cold Cut.
16. Tail Recovery System
โข This consists of the RT that carry the bars from
layer preparation area to the cold saw
โข When the last cut to length has been
performed and the tail has been detected the
bar tails are discharged by a discharging table.
โข These tails are collected at the pockets by a
set of discharging levers.
17. H.) Cut to Length Area
โข During normal cutting cycle SAW-1 cuts the layer
at a length 3 times the final length. SAW-2 & 3
make the cutting together to obtain the final
length. Here SAW-2 is movable and SAW-3 is
fixed.
โข There are 2 locking devices at the entry and exit
of the disc SAWS that allows the material to be
cut without movement.
โข Booster pumps are provided to provide water at
correct pressure to provide accurate cutting.
18. Cut to Length Operation
1. Layer ready at Saw Entry RT โLine Startโ is
initiated.
2. Layer aligning is checked first at disappearing
stopper and then at Wheeled stopper-1.
3. SAW-1 makes the cut & is followed by layer
aligning on Wheeled Stopper2.
4. SAW-2 & 3 makes the cut and layer is
transported to discharging are upto the stopper
where aligning is again checked.
5. Layer is the ready for extraction and discharging.
19. I.) Stacker & Forming Area
โข This area has the following sub-divisions:
1. Entry area
2. Liftable chain transfer
3. Layer forming transfer
4. Turning and Deposit magnet heads
5. Forming pockets
6. Liftable chain transfer
20. Stacker and Forming Area Operation
1. The Entry area layer loading & discharging takes
place via Liftable chain transfer.
2. Then the layer moves to the Forming area 7
towards the magnets.
3. The magnet pick up the layer and discharge
them to the pockets.
4. Pockets are lowered and the process continues
till step by step stack formation gets completed.
5. When the stack is โReadyโ pockets lower and
discharge them to RT. Pockets are the ready to
accept new stack.
21. J.) Tying & Collecting Area
The following functions are performed:
1. Weighing the product
2. Tying and strapping the product
3. Dispatch from Liftable transfer table by
Magnet cranes.
