Title of Invention

A METHOD FOR FORMING EASY TO REMOVE OXIDE SCALES FOR HIGH CARBON RODS

Abstract A method to form an 'easy to remove oxide scale' during mechanical descaling of high carbon rods consists of simulating oxide scale formation of wire rod samples maintaining different thermal profile at Gleeble- 1500 and measuring the oxide composition of the wire rod samples by means of semi quantitative reitveld method by GAXRD. The samples are heated by GAXRD. The samples are heated to 1200°C and held for austenitising and cooling them to 1000°C in 20 secs. These are further cooled to 860°C at cooling rate 140°C/ sec. Different samples are cooled at different cooling rate maintaining stelmor cooling to cool them to 600°C- 550°C and finally cooling them in air. The observations at different cooling rates LHT are plotted to find a relationship between % Fe2O3 with LHT for high cooling rate and a relationship between % Fe2O3 with LHT for various cooling rates to record the best inference.
Full Text

FIELD OF THE INVENTION:
This invention relates to a method to form an 'easy to remove oxide
scale' during mechanical descaling of high carbon rods. More
particularly, the invention relates to a method which results formation
of hematite very less during the process of wire rod rolling.
BACKGROUND OF THE INVENTION:
During the process of wire rod rolling, oxide scale are formed on the
surface of steel wire rods. This scale should be removed before any
further processing like wire drawing. Initially the descaling process was
done by pickling using hydrochloric acid. Nowadays, because of
stringent laws for environmental protection use of HCl is being
discouraged. So, a lot of emphasis is being laid for alternate methods of
descaling like mechanical descaling. Reverse bending procedure is being
used today as a method of mechanical descaling in wire rod mills.
Oxide layers in high carbon wire rods are not completely removed by
mechanical descaling process. Formation of hematite causes poor

mechanical descaling whereas magnetite and wustite are found to be
non-adherent oxides.
Accordingly there exists a need to find a method which enables
formation of hematite very less during the process of wire rod rolling
that results formation of easily removable oxide scale during
mechanical descaling of high carbon rods.
SUMMARY OF THE INVENTION:
Oxide formation at high temperature has been thoroughly studied using
Gleeble simulation and it is found that high laying head temperature
(LHT) followed by faster cooling reduces the formation of hematite layer
which is adherent in nature so that during mechanical descaling oxide
scales are easily removed.
OBJECTS OF THE INVENTION:
It is therefore an object of the invention to propose a method to form an
'easy to remove oxide scale' during mechanical descaling of high carbon
rods which enables the formation of adherent oxides like hematite very
less.


Another object of the invention is to propose a method to form an 'easy
to remove oxide scale' during mechanical descaling of high carbon rods
which restricts the formation of Fe2O3 to maximum around 10%.
BRIEF DESCCRIPTION OF THE ACCOMPANYING DRAWINGS:
Table 1: It shows the chemical composition (% wt.) of the wire rod used
for the experiments.
Table 2: It shows the details of thermal profiles maintained in Gleeble -
1500
Fig 1- It shows the quantitative analysis obtained from semi reitveld
method to record,
(a) a relationship between % Fe2O3 with LHT for high cooling rate.
(b) a relationship between % FC3O4 with LHT for various cooling
rates.


DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FOR
THE INVENTION
The chemical composition of wire rod is given in Table 1. The oxide
scale formation was simulated using the Gleeble-1500. Gleeble-1500 is
thermo-mechanical simulator where heat treatment or thermo-
mechanical treatment can be applied to material of interest. This
simulator is used in order to study the oxide formation at high
temperature on wire rods.
The different thermal profile maintained at Gleeble-1500 is given in
Table-2. Initially the samples are heated to 1200°C and held for
austenitising (rate not important) and then cool to 1000°C in 20 sec
(rate not important). After that cooling from 1000° to 860° (precise
cooling rate 140° C/sec) is done. Finally, different cooling rates are
maintained during the rest and it is limited up to the end of stelmor
cooling i.e. up to 600-550°C, then conventional forced air cooling is
done. After the wire rods are rolled at high temperature (Hot rolling) the
wire rods are layed and cooled to desired temperature to achieve desired
microstructure and properties. This cooling is known as Stelmor cooling
where air is blown from the bottom by putting some fans.

After the Gleeble simulation the oxide composition of the wire rods is
measured by semi quantitative reitveld method using GAXRD and the
result is shown in Fig. 1 a and b.
Semi quantitative reitveld method is done in X-ray diffraction machine.
After getting the XRD plot for different phases present at a particular
sample the relative amounts of each phase is determined by using this
technique. This is done using "ExpertPro" software attached with X-ray
machine.
GAXRD is known as Grazing angle XRD. This is mainly used to
determine the coating/thin layer/oxide layer composition. The incident
beam is kept at an angle 0.5-5 degree.
In Fig 1 the result of fast cooling rate is plotted. From Fig la it is
evident that at lower LHT, the amount of hematite has increased
significantly. The wire rods after getting rolled to desired size are layed.
The temperature at which the laying process starts is known as Laying
Head Temperature.
At high temperature as per the oxide stability diagram only magnetite
and wustite are stable. But during the cooling process, equilibrium


diagram is not maintained properly and so hematite formation takes
place. But at higher LHT the formation of hematite is low. From
literature it is known that the formation of magnetite and wustite is
favourable for mechanical descaling purpose. The variation of magnetite
at different cooling rate at different LHT is shown in Fig 1 b. In Fig 1 b
each data point corresponds to particular LHT followed by particular
cooling rate as described in Table 2. From Fig 1 b it can be seen that at
faster cooling rate the amount of magnetite is always higher compared
with two other cooling rates. At high temperature as wustite and
magnetite scales are dominant and as the cooling process starts the
tendency to decompose of these oxides to form hematite starts. If
cooling rate is maintained high then the time for formation of hematite
is very less and therefore higher amount of magnetite is observed.
Whereas, for slower cooling rate chance of hematite formation is high
and as a result less amount to magnetite is observed. Phase
transformation in oxide scale depends on various factors like
availability of oxygen, cooling rate. As the complete process takes place
in normal air condition so that availability of oxygen is not the critical
factor. In this type of condition, only cooling rate plays important role in
determining the oxide scale composition.



WE CLAIM
1. A method for forming easy to remove oxide scales for high carbon rods
comprising:
- heating the rods to 1200°C for austenitising;
- cooling them to 1000°C;
- cooling them again from 1000°C to 860°C at a cooling rate of 140°C/sec; and then
- further cooling to normal temperature.



ABSTRACT


A METHOD FOR FORMING EASY TO REMOVE OXIDES SCALES FOR HIGH
CARBON RODS

A method to form an 'easy to remove oxide scale' during mechanical descaling of
high carbon rods consists of simulating oxide scale formation of wire rod samples
maintaining different thermal profile at Gleeble- 1500 and measuring the oxide
composition of the wire rod samples by means of semi quantitative reitveld
method by GAXRD. The samples are heated by GAXRD. The samples are heated
to 1200°C and held for austenitising and cooling them to 1000°C in 20 secs.
These are further cooled to 860°C at cooling rate 140°C/ sec. Different samples
are cooled at different cooling rate maintaining stelmor cooling to cool them to
600°C- 550°C and finally cooling them in air. The observations at different
cooling rates LHT are plotted to find a relationship between % Fe2O3 with LHT
for high cooling rate and a relationship between % Fe2O3 with LHT for various
cooling rates to record the best inference.

Documents:

440-KOL-2009-(08-02-2013)-ABSTRACT.pdf

440-KOL-2009-(08-02-2013)-CLAIMS.pdf

440-KOL-2009-(08-02-2013)-CORRESPONDENCE.pdf

440-KOL-2009-(08-02-2013)-DESCRIPTION (COMPLETE).pdf

440-KOL-2009-(08-02-2013)-DRAWINGS.pdf

440-KOL-2009-(08-02-2013)-FORM-1.pdf

440-KOL-2009-(08-02-2013)-FORM-2.pdf

440-KOL-2009-(08-02-2013)-OTHERS.pdf

440-kol-2009-abstract.pdf

440-KOL-2009-CANCELLED PAGES.pdf

440-kol-2009-claims.pdf

440-KOL-2009-CORRESPONDENCE-1.1.pdf

440-kol-2009-correspondence.pdf

440-kol-2009-description (complete).pdf

440-kol-2009-drawings.pdf

440-KOL-2009-EXAMINATION REPORT.pdf

440-KOL-2009-FORM 1-1.1.pdf

440-kol-2009-form 1.pdf

440-kol-2009-form 18.pdf

440-kol-2009-form 2.pdf

440-kol-2009-form 3.pdf

440-kol-2009-gpa.pdf

440-KOL-2009-GRANTED-ABSTRACT.pdf

440-KOL-2009-GRANTED-CLAIMS.pdf

440-KOL-2009-GRANTED-DESCRIPTION (COMPLETE).pdf

440-KOL-2009-GRANTED-DRAWINGS.pdf

440-KOL-2009-GRANTED-FORM 1.pdf

440-KOL-2009-GRANTED-FORM 2.pdf

440-KOL-2009-GRANTED-FORM 3.pdf

440-KOL-2009-GRANTED-SPECIFICATION-COMPLETE.pdf

440-KOL-2009-REPLY TO EXAMINATION REPORT.pdf

440-kol-2009-specification.pdf

abstract-440-kol-2009.jpg


Patent Number 256531
Indian Patent Application Number 440/KOL/2009
PG Journal Number 27/2013
Publication Date 05-Jul-2013
Grant Date 28-Jun-2013
Date of Filing 12-Mar-2009
Name of Patentee TATA STEEL LIMITED
Applicant Address RESEARCH AND DEVELOPMENT AND SCIENTIFIC SERVICES DIVISION, JAMSHEDPUR
Inventors:
# Inventor's Name Inventor's Address
1 PINDER SINGH MANDLEY TATA STEEL LIMITED, RESEARCH AND DEVELOPMENT AND SCIENTIFIC SERVICES DIVISION, JAMSHEDPUR-831001
2 ARNAB CHATTOPADHYAY TATA STEEL LIMITED, RESEARCH AND DEVELOPMENT AND SCIENTIFIC SERVICES DIVISION, JAMSHEDPUR-831001
PCT International Classification Number B24B27/033; C21D9/46
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA