FIELD OF INVENTION
The present invention relates to a method of and an apparatus for enhanced cooling
hot-rolled strips in hot strip mill using nanofluid. More particularly the invention relates
to an online method of and apparatus for enhanced cooling in the cooling section of an
industrial Hot Rolling Mill using water containing nano-particles injected at high
pressures.
BACKGROUND OF THE INVENTION AND PRIOR ART
Laminar cooling is one of the most important stages of the entire hot rolling process. It
plays a key role in the development of grain structure and mechanical properties of the
final product. The aim of laminar cooling is to use water sprays to cool the red-hot steel
strip in order to achieve a desired temperature profile throughout the strip length and
to attain a specified target cooling temperature, within a tolerance as strict as possible.
Nevertheless, new steel products, such as dual-phase steel, transformation-induced-
plasticity steel, and ferrite-bainite steel, are developed and applied as advanced
materials in the automobile industry; all of them need controlled fast cooling in the
laminar cooling section. The major obstacle in achieving faster cooling in the laminar
cooling section is the limited pressure, flow rate and thermo-physical properties of
cooling water.

The promise to develop new steels comes with the challenge of controlled and faster
cooling in the rolling process. A summary of the patents is given below:
• The patents "A Method for Faster Cooling Rate by a New Medium for Run out
Table of Hot Strip Mill" (Application No. 430/KOL/07) and "Development of a
new cooling medium for run out table of hot strip mill" (740/KOL/08) target the
laboratory scale usage of nanofluids for cooling hot plates. The patent covers
the usage of nanofluids as free flowing fluids falling directly onto hot plates in
a diluted form. The mechanism of feeding the nanofluids into existing cooling
system at large volumes is not covered.
• The patent "A process of producing multi-phase steels using nano-coolants"
(329/KOL/10) describes the process of achieving high strength steels enabled
by faster cooling, again in the laboratory scale.
• The patent "A Process and Apparatus for application of Coolants to achieve
Higher Cooling Rates In the Water Boxes of a Wire Rod Mill (291/KOL/2009)
pertain to the development of a system in which nanofluids replace the
existing cooling system and achieve a higher rate of cooling in a wire rod mill.
A separate standalone cooling system is proposed in this patent for the
nanofluid usage.
• The patent "A Method and Apparatus for achieving higher cooling rates of a
gas during bypass cooling in a batch annealing furnace of a cold rolling mills"

(292/KOL/2009) describe the development of a cooling system using
nanofluids replacing the existing system.
• The patent "A Process and an apparatus for Large-scale synthesis of nano-
fluids" (293/KOL/2009) describes a process and an apparatus for large scale
synthesis of nano-fluids using a rotor-stator assembly.
The above prior arts do not cover the following:
(a) The invention proposed in Patent Application No. 293/KOL/2009 does not cover
the preparation of highly concentrated nanofluids as a transition fluid for future
use by injecting inside a flowing water stream.
(b) Injection of nanofluids at high pressure and high concentration into water
pipelines
(c) Modifications of water pipelines and use of constant flow-rate peristaltic pumps
to achieve (a).
(d) Modifications in the headers in the Run-Out Table to achieve higher cooling rate.
SUMMARY OF THE INVENTION
The present invention describes an online method and apparatus for enhanced cooling
in the cooling section of a rolling mill water containing nano-particles injected at high
pressures.

Using the invention mentioned in Patent Application No. 293/KOL/2009, nano-particles
were closed into water and a concentrate was prepared. This concentrate was injected
at desired concentration levels into the existing pipelines carrying the cooling water of
the cooling section. For the delivery at high pressure, fixed speed close coupled,
constant flow rate peristaltic pumps were used. To achieve proper dispersion into the
existing flow stream, modifications were done at appropriate delivery angles to the
existing pipelines. This enables localized turbulences inside the flowing water stream.
Finally the nanofluid of desired concentration is poured continuously on the hot strip so
as to achieve enhanced cooling rate.
It is therefore required of the present invention to design an online method and
apparatus for industrial application of nanofluids for the cooling section of a rolling mill
capable of handling red-hot strips.
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose a method of and an apparatus for
cooling hot-rolled strips in Hot Strip Mill using nanofluid which is capable of injecting
nanofuids at high pressure and high concentration into water pipelines.
Another object of the invention is to propose a method of and an apparatus for cooling
hot-rolled strips in Hot Strip Mill using nanofluid which can achieve higher cooling rate.
A further object of the invention is to propose a method of and an apparatus for cooling
hot-rolled strips in Hot Strip Mill using nanofluid which is capable of keeping the flow
rate of nanofluid constant.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure (1) describes the schematic of the invented process
Figure (2) describes the modification to the pipelines.
Figure (3) shows a table indicating the comparison of temperature drops of hot rolled
coils cooled by water and nanofluid.
Figure (4) describes the schematic of the peristaltic pump used in this process.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The present invention describes an online method (Fig.l) and apparatus (6) for
enhanced cooling in the cooling section of a rolling mill, water containing nano-particle
injected at high pressures. The online method describes a method of preparation of the
composite of nano-particles and water, injecting the composite into the existing water
line and achieving enhanced cooling by spraying the composite in the cooling section of
an industrial rolling mill.

The process has three steps: Preparation of concentrate nanofluid using high shear
mixer (7), pumping of prepared nanofuid using peristaltic pumps (6) and finally
injection of nanofluid inside the flowing water stream.
In first step, using the invention mentioned in Patent application no. 293/KOL/2009,
nano-particles were dosed into water and a concentrate is prepared (7). The nano-
crystalline particles in powder form are directly injected in the high shear mixer
comprised of a rotor-stator assembly. The output is a uniformly dispersed, concentrated
nanofluid of concentration 0.001% to 100% weight/volume.
In a second step, sets of peristaltic pumps (6) draw this concentrated nanofluid from a
common suction header connected with the mixer outlet. These peristaltic pumps (6)
have polypropylene hoses (3) inside their cavities. These hoses (3) are squeezed by a
cam (1) with preset geometrical configuration. This squeezing action results into the
release of the concentrated nanofuid to the delivery end of the pump. The flow rate of
nanofluid is kept constant by fixing the RPM of the cam using an automotive drive
control system connected with the pump.
In third step, nanofluid is delivered at a higher pressure than the laminar cooling water
in steel pipes connected to individual top and bottom laminar cooling headers (4,5). In
a steel plant, hot-rolled red-hot steel plates/strips are cooled by water from top and
bottom to get the desired metallurgical properties of the finished saleable steel product.
This cooling is done by water headers placed at top and bottom. In present innovation,
the nanofiuid setup is retrofitted in the existing top and bottom headers to get faster
cooling of red-hot steel without dismantling the present infrastructure. The directions
of flow of water and nanofiuid should have an angle of 10° to 80° (8) for proper mixing
of the two. These flows intermingle (Fig. 2) within a mixing length purposefully created
between the injection point and the nozzle delivery point of individual water header.
Nozzle banks release the nanofiuid on the red hot steel strip coming from the last
rolling stand of hot strip mill. Online pyrometers installed near the red-hot strip capture
the temperature profile along the strip length. The same temperature profile is recorded
in the mill automation system for future reference and feedback control. This
temperature drop is a major contributor to the thermal treatment done on the hot-
rolled strip to achieve desired microstructure, mechanical and metallurgical properties of
the finished saleable steel product.
Enhanced cooling describes a method and apparatus capable of cooling at a rate up to
50% more efficiently than water at ambient temperatures. Enhanced cooling is
achieved with water kept at ambient temperature and also the entire cooling circuit.
The cooling section is the run out table of an industrial rolling mill comprising of
headers (4,5) capable of spraying water or any other cooling medium onto the product.
The nanofiuid is drawn in desired flow rate by sets of fixed-speed, close-coupled
peristaltic pumps (6), which release the fluid at a constant volume set by automotive
drive control system connected with the pump-motor assembly. The flow rate of such
pump can vary between 1 liter per minute and 1000 liters per minute and the delivery
pressure of such pump can vary between 2 Bars and 20 Bars. The delivery lines of the
pumps are connected with the water carrying pipes in laminar cooling section of hot
strip mill. The nanofluid flows are injected at an angle between 10° and 80° (8) to the
water flow. This cross-flow is purposefully created for creating a turbulent mixing length
inside the water pipe. This mixing length provides a homogenous uniformly dispersed
nanofluid of desired concentration that can be disposed on the red-hot surface of the
hot rolled strip. The nanofluid of such desired concentration (between 0.0001% and
100% weight by volume) travels through the laminar cooling nozzles and finally falls on
the red-hot steel strip coming from the last rolling stand of hot strip mill.
Table-1 shows the chemical composition of steel strip, parameters of hot rolling and
actual final temperature after cooling in °C. The table shows that the final temperature
(660) after cooling with nanofluid as cooling medium is much less than that with water
as cooling medium (740).

WE CLAIM
1. A method of enhanced cooling hot rolled strips in hot strip mill using nanofluid
comprising the steps of:
injecting the nano-crystalline particles in powder form in the high shear mixture
to prepare a uniformly dispersed concentrated nanofluid (7);
pumping and injecting the prepared concentrated nanofluid from a common
suction header connected with the mixer outlet to the cooling water;
squeezing the hoses (3) by a cam (1) with preset geometrical configuration to
release the concentrated nanofluid to the delivery end of the pump;
fixing the RPM of the cam (1) to keep the flow rate of nanofluid constant;
characterized in that;
the nanofluid is delivered at a higher pressure than the laminar cooling water in
steel pipes connected to individual top and bottom laminar cooling headers (4,5)
when the direction of flow of water and nanofluid have an angle of 10° to 80°
(8) to mix the two properly, the said flows intermingle within a mixing length
purposefully created between the injection point and the nozzle delivery point of
individual water header when nozzle banks release the nanofluid on the red hot
steel strip coming from the last rolling stand of hot strip mill while online
pyrometers installed near the red hot strip capture the temperature profile along
the strip length.

2. The method as claimed in claim 1, wherein the RPM of the cam is controlled by
an automotive drive control system.
3. The method as claimed in claim 1, wherein the temperature profile is also
recorded in the mill automation system to have future reference and feedback
control.
4. The method as claimed in claim 1, wherein the nano-crystalline particles are
directly injected in powder form in the high shear mixer.
5. The method as claimed in claim 1 and 4, wherein concentration of nanofluid is
0.001% to 100% weight/volume.
6. The method as claimed in claim 1, 4 and 5, wherein the nanofluid is drawn in
desired flow rate by sets of fixed speed, close-coupled peristaltic pumps, which
release the fluid at a constant volume set by automotive drive control system
connected with the pump motor assembly.
7. The method as claimed in claim 1, wherein the flow rate of the said pump can
vary between 1 litre per minute and 1000 litres per minute when the delivery
pressure of the pump can vary between 2 Bars and 20 Bars.

8. The method as claimed in claim 1, wherein the cross flow of nanofluid and water
flow is created to produce a turbulent mixing length inside the water pipe so that
the mixing length provides a homogenous, uniformly dispersed nanofluid of
desired concentration that is disposed on the red-hot surface of the hot rolled
strip.
9. An apparatus for enhanced cooling hot rolled strip in hot strip mill using
nanofluid comprising:
a peristaltic pump assembly, the said pump is motor and cam driven fixed speed
close coupled pump.
10. An apparatus as claimed in claim 9, wherein the flow rates of the pump varies
from 0.92 litres/min to 15.3 litres/min and pressure is upto 2 bar (30 psi).

A method of enhanced cooling hot rolled strips in hot strip mill using nanofluid
comprising of injecting the nano-crystalline particles in powder form in the high shear
mixture to prepare a uniformly dispersed concentrated nanofluid and then pumping the
same to the cooling water. For the delivery at high pressure, fixed speed close coupled,
constant flow rate, peristaltic pumps (6) are used. To achieve proper dispersion into the
existing flow stream, the delivery angles are modifies to 10° and 80° for proper mixing
of the two. Nozzle banks release the nanofluid on the red hot steel strip coming from
the last rolling stand of hot strip mill.