FIELD OF INVENTION:
This invention relates to an aqueous lubricant for rolling of high strength steel,
said product being formulated with nano particles and some additives.
BACKGROUND OF THE INVENTION
Of late steel hot rolling mills have been predominantly using water as a coolant as
well as lubricant. However, there is an emerging trend to employ full or partial roll
lubrication to reduce rolling load, at the same time, to reduce the rate of wear of
the work roll. Over the years several materials such as oils, graphite, grass frits,
solid thin film etc have been employed for lubricating purposes, however, with
substantial limitations. In this regard an aqueous lubricant have been developed
with serpentine nano particles which are having layered plate like structures, in
combination with other additives which will help in saving lots of energy by cooling
the roll and stronger steel can be rolled down.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an aqueous lubricant for
rolling of high strength steel which eliminates the disadvantages of prior art.
Another object of the invention is to propose an aqueous lubricant for rolling of
high strength steel which reduces the cost of energy for rolling by reducing the
rolling force and wearing of the work roll.

A still another object of the invention is to propose an aqueous lubricant for rolling
of high strength steel which improves the surface texture of steel.
A further object of the invention is to propose an aqueous lubricant for rolling of
high strength steel, which reduces the formation of oxide scales during rolling.
BRIEF DESCRIPTION OF THE ACCOMPAYING DRAWING
Fig. 1 - electrical conductivity vs time plot for the aqueous lubricant
DESCRIPTION OF THE INVENTION
The invention relates to an aqueous lubricant for rolling of high strength steel
which has superior properties compared to conventional lubricant. The present
aqueous lubricant comprises of serpentine nano particles giving due
consideration of nano particles for particle size, thermal stability and structure.
Serpentine mineral is grinded in different grinding mill to make the nano
particles.These particles along with the deflocculant agent and additives are
mixed with plant DM water to make dispersed solution and stirred with
mechanical stirrer to get a homogenous solution. After extensive study on the
effect of lubricant in-hot rolling of steel, optimised formulation to design the
new aqueous lubricant is achieved.
The pH of the solutions measured is nearly 6 and to get the alkaline solution pH
adjusted between 9 and 11, alkali solution is added.
Immediately after preparation of the samples viscosity and density are measured.

All the solutions were exposed in 100 ml measuring cylinder to study the
stability of the dispersed particle and with the other set of experimentation
electrical conductivity of the solution is measured at different time interval.
Thermal stability of the nano fluid is tested by heating the steel samples at
900°C in the Muffle Furnace and the fluid is poured on it followed by the EDX
analysis of steel samples to see the surface condition of the steel.
Results: Serpentine mineral is having the chemical formula Mg3(OH)4 (Si305) has
been used as the solid for this new formulation. The Particle size distribution for
the formulation was measured by Direct Light Scattering.
Dynamic Light Scattering is also known as Photon Correlation Spectroscopy. This
technique is one of the most popular methods used to determine the size of
particles. Shining a monochromatic light beam, such as a laser, onto a solution
with spherical particles in Brownian motion causes a Doppler Shift when the light
hits the moving particle, changing the wavelength of the incoming light. This
change is related to the size of the particle. It is possible to compute the sphere
size distribution and give a description of the particle's motion in the medium,
measuring the diffusion coefficient of the particle and using the autocorrelation
function.
The average particle size is given below:


It is known that for particle size >300nm, gravity and viscosity both acts on
the dispersed solution and hence the setting time is lesser than the particle
size <300nm where only viscosity of the solution acts.
The zeta potential of dispersed solution was measured in DLS system. The zeta
potential of a particle is the overall charge that the particle acquires in a particular
medium. The magnitude of the measured zeta potential can be used to predict the
long-term stability of the product. If the particles in a suspension have a large
negative or positive zeta potential then they will tend to repel each other and
resist the formation of aggregates. However, if the particles have low zeta
potential values, i.e. close to zero, then there will be nothing to prevent the
particles approaching each other and aggregating.

Table 2 indicates that higher the zeta potential value more will be the dispersed
state of nano fluids. From Table 1 it is seen that the formulation is giving the zeta
potential between -41 and -60 mv which reveals the good stable condition of
dispersed nano fluid.
In the experiment plant DM water is being used as base fluid which is very low
viscous fluid and the viscosity of the formulations in the range of 1 and 1.5 which

is causing the rapid settling of prepared nano fluid. But on the other hand the
zeta potential (Table-1) of the formulations comes under a good range of stability.
This effect comes from the additives what has been added to the lubricant.
As shown in Fig. 1 the electrical conductivity of the solution is measured by
plotting against time. It is evident from the graph that the electrical conductivity is
increasing with time period. This is because increasing of negative charge on the
micelles serpentine being adsorbed as an anion, giving complexes with the
flocculant cations and substituting the cations in the double layer of clay or
serpentine with Na+ ions. In this case we are getting 400 hours under increasing
electrical conductivity which again shows the good stable condition of the fluid.
For the study of characteristics of lubricant, co-efficient of friction is measured
and compared with conventional lubricant and the coefficient of friction of the
present lubricant is to be lower than the conventional one.