Title of Invention

IMPROVED RUBBER CLAD ROLLS FOR THE MANUFACTURE OF CONTINUOUS GALVANIZED STEEL SHEETS

Abstract An improved rubber clad roll for continuous galvanizing lines (CGL) and planetary tandem continuous mill (PLTCM) comprising an optimum rubber covering composition suitable for the physical and chemical characteristics demanded by the service conditions of said rubber clad rolls while said rubber covering for alkali section rolls has a composition of: Sulphur 1.0 Zno 15 Stearic acid 1.5 2,2,4-trimethyl-l ,2,-dihydroquinoline 1.5 polymerized (HS/TQ) 2-mercapto benz (MB) 1.5 coumarone indene resin (C I Resin) 4.0 PF resin 10 high abrasion furnace black (HAF) 30 semi-reinforcing furnace black(SRF) 15 polyester resin (T 90) 3.0 di-n-octyl phthalate (DOP) 4.0 N-(cyclohexylthio) phthalimide (PVI) 0.5 N-cyclohexyl-2-benzothiazolesulphenamide 1.5 (CBS)
Full Text FIELD OF APPLICATION
The present invention relates to improved rubber clad rolls for the manufacture
of continuous galvanized steel sheets. In particular, it relates to cladding rolls of
cold rolling mill with improved rubber compound.
BACKGROUND OF THE INVENTION
During the production of galvanized sheets in a continuous galvanizing line the
steel sheets are passed through acid (HCL) for pickling. In order to remove the
carry over acid from the sheets, the rolls are passed through an alkali medium
followed by passing through the squeeze rolls for absorbing the left over alkali.
The steel sheet is then passed through chromate section followed by squeeze
rolling.
In the case of planetary tandem continuous mill (PLTCM) after pickling to
eliminate the carry over acid the sheet is passed through a cleaning section
followed by rolling with wringer rolls.
Rubberized rolls are used extensively as squeeze rolls, wringer rolls for the
production of galvanized steel sheet. These rolls have very short life and fail
within a maximum period of 10 - 12 days under the production condition. This
causes frequent shut down of the plant, to replace rolls and this hampers
production of steel sheet.
Apart from short service life, rubber covering used in Alkaline / chromate
cleaning section used to fail due to (a) change in surface hardening, (b) surface
cracks formation, (c) layer separation within rubber covering, (d) groove
formation, (e) slippage and (f) cut. The objective should be to minimize and
eliminate these failures.
There was therefore, a need to develop better rubber compounds and
manufacturing techniques to increase life of these rolls.
SUMMARY OF THE INVENTION
The main object of the present invention is to improve the quality of the
rubberized rolls used in continuous galvanizing lines and planetary tandem
continuous mills which will lead to increase in life of the rolls.
This and other objectives of the present invention can be achieved by providing
an optimum rubber covering composition suitable for the physical and chemical
characteristics required for the rubber cladding.
Understanding the service requirements wherein the rubber covered rolls are to
perform is very important. This needed several measures to be taken like
studying the exact working conditions through visits to the plant, going through
the line working drawings and collecting informations / report from plant
maintenance personnel.
Based on the above, an outline was drawn as to the requirements of the rubber
covering composition with respect to its various physical and chemical
characteristics.
The type and nature of failure that has taken place to various rolls supplied by
existing sources were studied thoroughly. The study involved (a) visual
observations (b) photographic study of surface characteristics (c) measurement
of various physical and chemical characteristics such as dimensions, hardness,
surface topography and acetone extraction comparisons of samples of rubber
coverings between working portions and non-working portions.
The study also involved examining the characteristics of failed portions to
ascertain mode of failure as to whether the same is due to chemical attack, or
due to heat build-up, or fatigue failure or abrasive or cutting type of failure or is
due to construction or manufacturing faults like de-laminations or interfacial
failure. As in many instances the nature of failure revealed that the same is due
to the combined effect of various facts. Further analysis had to be done to find
out the predominant one involved.
Based on the above mentioned study a refinement on the requirements of the
properties to be attained in the rubber covering compositions has been proposed
for the present invention. On this a series of rubber covering compositions were
made and their various properties have been studied.
After screening of the results of such compositions, several rubber formulations
have been selected which were then subjected to simulated environments and
based on the comparative evaluation results selections were made.
A fine-tuning of the selected formulations have been carried out so that those
laboratory developed formulations are transferred to usable and process-able
ones to real plant conditions. Such fine tuned compositions again have
undergone simulated service tests and finally have been used in actual roll
manufacturing.
The key point of the present invention lies in attaining a unique balance between
the various physico-chemical properties demanded by the service conditions of
the rubber rolls. Accordingly two approaches have been taken; one to improve
the original properties of the rubber coverings and the other to maintain the
attained properties with minimum change with time at the working conditions
prevailing which may involve reaction with chemicals, higher temperatures,
dynamic stress-strain cycle and cutting and abrasive conditions.
For the planetary tandem continuous mill both NBR based and chloroprene based
rubber coverings have been found to increase the life of the rolls.
In Alkali sections of continuous galvanizing line, the blending of polymers with PF resins
provided excellent resistance against chemical attack maintaining other physical properties
such as cut and abrasion resistance etc.
While in chromate section of continuous galvanizing line, the inclusion of epoxy resins
provided not only increased cross - linking of the polymer but also improved the acid
resistance property along with maintenance of physical properties which are so crucial in the
cruel working conditions involved.
Thus the present invention provides an improved rubber clad roll for continuous galvanizing
lines (CGL) and planetary tandem continuous mill (PLTCM) comprising an optimum rubber
covering composition suitable for the physical and chemical characteristics demanded by the
service conditions of said rubber clad rolls.
BREIF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be described in detail with the help of the figures of the
accompanying drawing in which
Figure 1 shows separation of layers in the existing rubber cladding.
Figure 2 shows formation of edge cuts and groove marks
on the existing rubber rolls.
Figure 3 shows groove formation and shallow surface
cracks in rolls at chromating section.
Figure 4 shows groove formation at edges in chromating
section squeeze rolls.
Figure 5 shows in line diagram form the continuous galvanizing
line (CGL) where the present invention is applied.
Figure 6 is a line diagram for planetary tandem continuous mill (PLTCM)
where the present invention is applied.
DESCRIPTION OF THE INVENTION
Figures 1 and 2 respectively show the failure in existing rubber rolls by layer separation
probably due to liquid penetration in pin hole and edge cuts with groove formation.
In the chromating section the defects develop due to groove formation resulting in carry
over with no edge cut problem. Shallow surface cracks develop which disappear after
grinding. Hardness after service is 65-85 shore A. (Figure 3).
Figure 4 shows the defects in chromating section squeeze rolls with problem of groove
formation at edge resulting in carry over.
A continuous galvanizing line shown in Figure 5 produces galvanized sheets for commercial
market. Cold rolled strips in the thickness range of 0.80 mm to 9.18 mm are processed in
this line for galvanizing. In the degreasing section the strip is first washed with 4 % NaOH
solution and followed by hot water at 60 - 900° C to clean the strip surface for zinc coating.
In degreasing section four pairs of rubber clad rolls are used to squeeze the degreasing
medium from strip surface and prevent solution carry over inside the furnace.
After degreasing the strip is baked inside a furnace and subsequently galvanized by hot dip
galvanizing method. After galvanizing, the coated strip is quenched in water. Two pairs of
rubber clad rolls are used to squeeze the water from the strip surface. After galvanizing the
strip is passed through chromating section. Here the strip is treated with 2.5 - 3.5 %
chromic acid at 60 - 900° C. In chromating section another four pairs of rubber clad rolls
are used to squeeze the chromic acid solution before the strip goes to recoiler.
Figure 6 shows the planetary tandem continuous mill (PLTCM). Input material for the PLTCM
line is hot rolled coils of 2 to 6 mm thickness and 900 to 1580 mm width. Hot rolled coils are
pickled in HCL and cold reduced to required thickness in this line. Area 1 as marked in
Figure 6 contains the first critical set of rubber covered rolls in the line. These rolls are
termed as wringer rolls. Number of rubber covered rolls are used in the pickling area
marked as Area 2 in Figure 6. There are four numbers of pickling tanks and HCL
concentration gradually increases from tank 1 to tank 4. After acid pickling and before water
rinsing section, two pairs of rubber covered rolls are used for squeezing which are
termed as steering wringer rolls. There are four tanks for water rinsing and six pairs of
rubber covered rolls are used in the water rinsing section. Out of the six pairs, first four
pairs are called squeeze rolls and the end two pairs of rolls are called as wringer rolls. After
water rinsing the coil is hot air dried and goes for cold reduction in 5 strand tandem mill.
The formulations for improved rubber flats provided by the present invention are shown in
Tables 1 to 4.
Table 1 shows the rubber formulation used in the present invention for the alkali section of
the continuous galvanizing line.
Table 2 shows the formulations used in the chromate section. The formulations used for the
planetary tandem continuous mill (PLTCM) are shown in Tables 3 and 4. The formulation of
Table 3 uses acrylo nitrile butadiene rubber (NBR) based compound. The formulation given
in Table 4 uses a chloroprene based compound.
Tables 5 and 6 show comparative evaluation of physico-chemical properties of existing
rubber covering vis-a-vis those of the rubber coverings of present invention. The tables
show wide variation in change in properties of existing rolls before and after use.
At the same time the rubber rolls of the present invention reveal uniform change in
properties before and after use of the rolls.
The rolls developed by the present invention do not show any signs of major failure like
surface crack, groove formation, edge cut, layer separation, slippage etc. Also there is no
change in properties after continuous running. Moreover, extension of service life yields
benefits in terms of (a) less breakdown time (b) reduction in frequency of shutdown, (c)
uninterrupted production, (d) cost effectiveness due to less consumption of rubber rolls, (e)
reduction of maintenance cost and (0 reduced rejection of rolls on the basis of quality.
In the present invention the life of the rolls has been increased from 2 to 12 days to 35 days
upto first grinding and 105 days after first grinding for alkali section of continuous
galvanizing lines (CGL 1), 50 days upto first grinding and 120 days after first grinding for
chromate section of continuous galvanizing line (CGL 1), and 90 days without any grinding
for the wringer rolls of planetary tandem continuous mill (PLTCM).
WE CLAIM ;
1. An improved rubber clad roll for continuous galvanizing lines (CGL) and
planetary tandem continuous mill (PLTCM) comprising an optimum rubber
covering composition suitable for the physical and chemical characteristics
demanded by the service conditions of said rubber clad rolls wherein said
rubber covering for alkali section rolls has a composition of:
Sulphur 1.0
Zno 15
Stearic acid 1.5
2,2,4-trimethyl-1,2,-dihydroquinoline 1.5
polymerized (HS/TQ)
2-mercapto benz (MB) 1.5
coumarone indene resin (C I Resin) 4.0
PF resin 10
high abrasion furnace black (HAF) 30
semi-reinforcing furnace black(SRF) 15
polyester resin (T 90) 3.0
di-n-octyl phthalate (DOP) 4.0
N-(cyclohexylthio) phthalimide (PVI) 0.5
N-cyclohexyl-2-benzothiazolesulphenamide 1.5
(CBS)
2. The improved rubber clad roll as claimed in claim 1, wherein the rubber
covering for said rolls for the alkali section of the CGL is acrylo nitrile
butadiene (NBR) with polymers blended with PF resin.
3. The improved rubber clad rolls as claimed in claim 1, wherein the covering
for rolls used in chromate section of the CGL are provided with epoxy
resins.
4. The improved rubber clad rolls as claimed in claim 3, wherein said roll
covering has the following composition:
epoxy 10
nickel di-n-butyldithiocarbamate (NBC) 1
Semi-reinforcing furnace black (SRF) 30
coumarone indene resin (CI Resin) 3
dihydroquinoline polymerized (TQ) 2
poly ethylene glycol (PEG) 1
di-n-octyl phthalate (DOP) 8
spindle oil 6
Epoxidized vegetable oil (Ivamol) 4
dibenzthyiazyl disulphide (MBTS) 0.5
dipentamethylenethiuramhexasulphide 0.75
(Tetron A)
N,N'-di-o-tolylguanidine (DOTG) 0.5
Sulphur 1
5. The improved rubber clad rolls as claimed in claim 1, wherein the covering
for rolls used in PLTCM is based on acrylo nitrile butadiene rubber (NBR)
having the following composition:
Sulphur 1.0
ZnO 15
Stearic acid 1.5
2,2,4-trimethyl-l,2,-dihydroquinoline 1.5
polymerized (HS/TQ)
2-mercapto benz (MB) 1.5
coumarone indene resin (CI Resin) 4.0
high abrasion furnace black (HAF) 30
semi-reinforcing furnace black (SRF) 27
polyester resin (T 90) 3.0
di-n-octyl phthalate (DOP) 4.0
N-(cyclohexylthio) phthalimide (PVI) 0.5
N-cyclohexyl-2-benzothiazole 1.5
sulphenamide (CBS)
6. The improved rubber clad rolls as claimed in claim 1, wherein the covering
for rolls used in PLTCM is based on chloroprene rubber (neoprene W)
having the following composition :
MgO 4
Stearic Acid 1.5
coumarone indene resin (CI Resin) 4
octylated diphenylamine (OCD) 1
intermediate super abrasion furnace black 40
ISAF (N220)
N-(l,3 dimethyl butyl)'-N'-phenyl-p- 1
phenylene diamine (4020)
Veg Oil 3
dibenzthyiazyl disulphide(MBTS) 1.3
ZnO 5
ethylene thiourea (NA-22) 0.7
7. An improved rubber clad roll for continuous galvanizing lines (CGL) and
planetary tandem continuous mill (PLTCM), substantiall as substantially as
herein described and illustrated in the accompanying drawings.


An improved rubber clad roll for continuous galvanizing lines (CGL) and
planetary tandem continuous mill (PLTCM) comprising an optimum rubber
covering composition suitable for the physical and chemical characteristics
demanded by the service conditions of said rubber clad rolls while said
rubber covering for alkali section rolls has a composition of:
Sulphur 1.0
Zno 15
Stearic acid 1.5
2,2,4-trimethyl-l ,2,-dihydroquinoline 1.5
polymerized (HS/TQ)
2-mercapto benz (MB) 1.5
coumarone indene resin (C I Resin) 4.0
PF resin 10
high abrasion furnace black (HAF) 30
semi-reinforcing furnace black(SRF) 15
polyester resin (T 90) 3.0
di-n-octyl phthalate (DOP) 4.0
N-(cyclohexylthio) phthalimide (PVI) 0.5
N-cyclohexyl-2-benzothiazolesulphenamide 1.5
(CBS)

Documents:

00485-kol-2006-abstract-1.1.pdf

00485-kol-2006-abstract.pdf

00485-kol-2006-claims.pdf

00485-kol-2006-correspondence others-1.1.pdf

00485-kol-2006-correspondence others.pdf

00485-kol-2006-correspondence-1.2.pdf

00485-kol-2006-description(complete).pdf

00485-kol-2006-description(provisional).pdf

00485-kol-2006-drawings-1.1.pdf

00485-kol-2006-drawings.pdf

00485-kol-2006-form-1-1.1.pdf

00485-kol-2006-form-1.pdf

00485-kol-2006-form-2-1.1.pdf

00485-kol-2006-form-2.pdf

00485-kol-2006-form-3.pdf

00485-kol-2006-form-5.pdf

00485-kol-2006-g.p.a.pdf

485-KOL-2006-ABSTRACT 1.1.pdf

485-KOL-2006-AMANDED CLAIMS.pdf

485-KOL-2006-CORRESPONDENCE 1.1.pdf

485-KOL-2006-CORRESPONDENCE.pdf

485-KOL-2006-DESCRIPTION (COMPLETE) 1.1.pdf

485-KOL-2006-DRAWINGS 1.1.pdf

485-KOL-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

485-KOL-2006-EXAMINATION REPORT.pdf

485-KOL-2006-FORM 1-1.2.pdf

485-KOL-2006-FORM 18 1.1.pdf

485-kol-2006-form 18.pdf

485-KOL-2006-FORM 2-1.1.pdf

485-KOL-2006-FORM 3.pdf

485-KOL-2006-FORM 5.pdf

485-KOL-2006-GPA.pdf

485-KOL-2006-GRANTED-ABSTRACT.pdf

485-KOL-2006-GRANTED-CLAIMS.pdf

485-KOL-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

485-KOL-2006-GRANTED-DRAWINGS.pdf

485-KOL-2006-GRANTED-FORM 1.pdf

485-KOL-2006-GRANTED-FORM 2.pdf

485-KOL-2006-GRANTED-SPECIFICATION.pdf

485-KOL-2006-OTHERS.pdf

485-KOL-2006-REPLY TO EXAMINATION REPORT 1.1.pdf

abstract-00485-kol-2006.jpg


Patent Number 251615
Indian Patent Application Number 485/KOL/2006
PG Journal Number 13/2012
Publication Date 30-Mar-2012
Grant Date 26-Mar-2012
Date of Filing 23-May-2006
Name of Patentee TATA STEEL LIMITED
Applicant Address RESEARCH AND DEVELOPMENT DIVISION JAMSHEDPUR-831001
Inventors:
# Inventor's Name Inventor's Address
1 BHATTACHARYYA, SANDIP KR. TATA STEEL LIMITED, RESEARCH AND DEVELOPMENT DIVISION JAMSHEDPUR 831001
2 BANERJEE, ATANU TATA STEEL LIMITED, RESEARCH AND DEVELOPMENT DIVISION JAMSHEDPUR - 831001
3 CHAKRABARTI, INDRANIL TATA STEEL LIMITED, RESEARCH AND DEVELOPMENT DIVISION JAMSHEDPUR-831001
PCT International Classification Number C08L 17/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA