FIELD OF INVENTION
The present invention relates to a new developed rubber clad wringer rolls for tension leveling system used at the entry and exit side of the pickling line in pickling and tandem cold mill (PLTCM) plant of a cold rolling complex. More particularly, the invention relates to improvement of rubber roll to enhance the service life of wringer rolls to 150 days from 15-20 days.
BACKGROUND OF THE INVENTION AND PRIOR ART
Tension leveler rubber clad rolls constitute an essentially important part of the tension leveling system which is used in wet type pickling line (Ref: Fig.l for schematic lay out of the pickling section with tension leveling unit). The system utilizes the combined effect of stretching and bending of the hot rolled low carbon steel having typical thickness of 2.0 to 6.5 mm and width of 800 to 1500 mm. The purpose of such stretching and bending is to break the scales on steel strip surface and also to improve the strip surface profile. The operating line speed is approx. 150 to 180 m/min. with line tension at entry and exit side is around 10,000 kgf/T and 5500 kgf/T respectively. The leveling tension is around 40,000 kgf/T.

In the pickling section, oxide scale at the hot rolled steel strip surface is removed before cold rolling. Wet type pickling line is where HCI acid solution is used for pickling the material. There could be mechanical de-scaler to remove the surface oxide scale but the current invention is related to wet type pickling line where the rubber clad wringer rolls mainly performs the squeezing action to remove the left over solution after treatment from the strip surface to avoid liquid carry over. The tension leveling system as shown in Fig.2 consists of:
1. Entry wringer rolls
2. Leveling unit
3. Tensiometer roll (Deflector roll)
4. Anti-cambering unit
5. Exit wringer rolls
Position of the tension leveller unit is shown in Fig.l. Specification of tension leveler
1. Handling Material: Low carbon hot rolled steel
Thickness : 2.0 to 6.5 mm
Width : 800 to 1,580 mm
Yield Point : 35 Kgf/mm2 (Design base)
2. Line speed : Max. 180m/min.
3. Threading speed : Max. 50m/min.
4. Acceleration rate : 30 m/min.
5. Drive side : Right hand to strip running direction
6. Elongation : Max. 2.0% (Equipment 2.5%)

7. Leveling Tension : Max. 40,000 Kgf/T
8. Line Tension : Entry side of Entry B/R " shaped i.e. cut is initiated from middle portion of roll surface and propagates outwards. This is genuinely related to maintenance of uniformity in line tension as any wavy edged metal sheet moving under high line speed between two rubber rolls under pressure will effectively act as a sharp blade.
(d)Axial & circumferential corrugation on rubber surface (Ref: Fig 7): In order to function as wringer roll, the rubber covered roll must be able not only to deflect under working pressure but also to recover to its original form. Deformation taking place in a rubber covered roll under equilibrium loading conditions is shown in Fig.8 wherein F = Force, D = Overall roll diameter, T = rubber covering thickness, x =

deflection height of the rubber cover under compressive load and b = width of deflection/length up to which the rubber cover is deflected due to the compressive load. Due to the incompressible nature of rubber, the area under deflection is equal to the bulged area.
The deformation of rubber covering during each pass through nip area between two rolls must be recoverable before entire rotation is completed. Cyclic stress of high frequency results from high revolution per minute (RPM) which is equivalent to high line speed, demands rubber covering to recover under less relaxation time available. Any sluggishness in recovery from deformation imposes additional stress on un-recovered/partially un-recovered rubber leading to stress accumulation and continuous repetition of such results in the development of axial corrugations which on further running is converted to circumferential corrugation as also severe surface cracks. The matter is further elaborated in Fig.9. A point (a) approaching the nip region gets stretched due to deformation under pressure which can be termed as "entry bulge". The surface appears to be stretched and because of an increased radius the surface speed is reduced. As the point (a) heads towards the centre of the nip region, it experiences acceleration in surface speed, due to a decrease in various and at the centre of the nip it achieves its greatest speed (c). As the point passes out of the nip, it again experience deceleration while it enters the "exit bulge'. Out of the exit bulge the rubber covering now has to recover to its normal diameter (e) before reentry at nip. The above process demands high elastic characteristics from rubber covering along with low relaxation time, high resilience and low permanent set. In the developed rubber

covering composition these features have been uniquely incorporated through proper choice of rubber, reinforcing agent and high cross-linking density.
(e) De-lamination between rubber-to-metal and rubber-to-rubber (Ref: Fig.lO and 11):
Working condition of tension leveler rubber wringer rolls is severe as discussed earlier imposing not only high compressive forces but also severe shear stress under a high shear rate thereby demanding extremely good bonding between the rigid metal cores to highly deformable rubber covering as well as between the layers of rubber covering. All these have been properly taken care of in currently developed rubber covering composition by using vulcanizing system which results in both ionic and covalent bonds and also by using suitable re-enforcing fillers to modify the elastic modular.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a new developed rubber clad wringer rolls for tension leveling system used at the entry and exit side of the pickling line in PLTCM plant of a cold rolling complex which is capable of eliminating the disadvantages of prior art.
Another object of the invention is to propose a new developed rubber formulation for tension leveling system used at the entry and exit side of the pickling line in PLTCM plant of a cold rolling complex which is able to enhance the service life of the rubber rolls.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l - shows a schematic line diagram of the PLTCM and the position of the Tension
Leveller Unit
Fig.2 - shows schematically the different sub-units within Tension Leveller Unit
Fig.3 - Photograph showing rubber abrasion from surface
Fig.4 - Photograph showing Groove mark at edges
Fig.5 - Photograph showing edge cut
Fig.6 - Photograph showing "V" shaped cut mark
Fig.7 - Photograph showing circumferential corrugation defect in rubber layer
Fig.8 - Deformation under equilibrium loading condition
Fig.9 - Mechanism of axial corrugation defect in rubber layers
Fig. 10 - Photograph of delamination from rubber to metal interface
Fig. 11 - Photograph of delamination from rubber to rubber interface
As shown in Fig.2,
Tensiometer roll
The Tensiometer roll or the deflector roll is Polyurethane roll where Polyurethane is
cladded over the steel barrel. The function of the roll is to maintain the strip pass-line
by moving (deflection) within limit.
Anti-camberina unit
A tension leveler has two sets of staggered work rolls (anti-cambering unit). It causes the strip to pass through the leveller along a sinusoidal path and flexed under tension in

opposite directions alternately. It is of course important that no bending of any of the leveller work rolls should occur, since if bending occurs the flatness of the product suffers. Therefore, where circumstances allow, either very large work rolls are used which are stiff enough to support the applied loads without deflection, or, if small work rolls have to be used, these require to be supported by back-up rolls.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The present invention relates to the manufacturing of rubber clad wringer rolls with new rubber formulation for the application in tension leveller system especially in wet type pickling line. Rubber rolls are manufactured to eliminate the various defects of the roll in prior art and to enhance the service life of the rubber rolls on the basis of rubber formulation. In the present invention, the rubber rolls are manufactured with the
following materials with amount in grams as shown.


The unique features incorporated in the rubber rolls manufactured by using the above materials with specified weight are,
1. Excellent bonding with the metal core
2. Excellent consolidation between rubber layers
3. Very high abrasion resistant characteristics
4. High swelling resistance under the operating chemical environment
5. Low permanent set property
6. Good resilience
7. High elastic modulus
The hardness maintained in the rubber roll is 70-75° A shore. This rubber formulation
developed for the tension leveller wringer rolls had given an established service life of 150 days against 15-20 days of service life of prior art. Laboratory test results of the formulation applied for patent
RHEOGRAFH DATA
Description of work : XNBR Temperature: 150°C Chart motor: 30 min Range scale: 100 blue X-Xs Arc ± : 3°


The laboratory test shows that the rubber formulation can be used for higher scale
application like tension leveller system with wet type pickling line. This test is actually
stimulating the vulcanization cycle and the rubber flowability which is required for
rubber roll manufacturing.
Physical Properties of the rubber formulation
Original Properties
Hardness: 66 Shore W
Tensile Strength: 140 Kg/cm2
Elongation at break: 600%
DIN Standard abrasion resistance: 52 mm3
Properties after accelerated ageing in hot air at 100°C for 7 days
Hardness: 72 Shore W
Tensile Strength: 140 Kg/cm2
Elongation at break: 450%
DIN Standard abrasion resistance: 80 mm3
Properties after accelerated ageing in hot 12% hydrochloric acid at 60°C for 7 days
(working medium of the rubber rolls):
Hardness: 64 Shore W
DIN Standard abrasion resistance: 66 mm3
Change in weight after test: +0.97%
Change in volume after test: +0.87%

The properties of the rubber formulation tested with accelerated ageing in hot air as well as in hot hydrochloric acid to understand the stability of the composition under simulated operating conditions and the results revealed high resistance to swelling (low weight and volume change after test) of the new developed formulation as compared to the formulations used in prior art (weight and volume change approximately +/- 10-15%). The most important properties of the rubber formulation after accelerated ageing in hot hydrochloric acid is considered to be the change in weight and volume after the test. The test with the present invention shows a change in weight after test being +0.97% and change in volume after test being -0.87% compared to change in weight/volume +15% to -15% of prior art.
Rubber rolls manufactured from the formulation were tested in the actual production line. Around 20 numbers of rolls made from the same formulation were tested for a year in actual service condition and the service life of the roll was established.

WE CLAIM
1. A new developed rubber clad wringer rolls for tension levelling system used at the entry and exit side of the pickling line in PLTCM plant of a cold rolling complex comprising:
90.00 grams of Carboxylated (7.5%) Nitrile Rubber (XNBR); 10.00 gms of Poly Butadiene Rubber-Grade 1220; 1.00 gm of Anti Crystalline Polyethylene; 2.00 gm of Anti oxidant-Polymerized Tri-hydro Quinoline; 1.00 gm of Poly Ethylene Glycol-Grade 4000; 5.00 gm of Cumarone Indane Resin (M.P. < 80°C); 2.5 gm of Stearic acid; 1.10 gm of Sulfur;
15.00 gm of Intermediate Super Abrasion Furnace Black; 4.00 gm of Di-octyl Phtnalate;
1.40 gm of Accrlarator-Cyclo hexyal Benzo Thiazol Sulphur Amide; 7.00 gm of Zinc peroxide;
characterized in that, this rubber composition achieves during vulcanization both ionic and covalent bonding between the rigid metal core to highly deformable rubber covering and between the layers of rubber covering and re-enforced fillers are adapted to provide high elastic modular wherein the rubber roll acquires a hardness of 66 Shore 'A', a tensile strength of 140 Kg/cm2, an elongation at break of 600% and DIN standard abrasion resistance of 52 mm3.

2. The new formulated rubber clad wringer rolls as claimed in claim 1 wherein, the said rubber rolls are applied in the wet type pickling line of the tension leveling system.
3. The new formulated rubber clad wringer rolls as claimed in claim 1 wherein, each wringer roll has a diameter of 300 mm with rubber covering thickness of 25 mm and barrel length 1950 mm.

A new developed rubber clad comprising 90.00 grams of Carboxylated (7.5%) Nitrile Rubber (XNBR), 10.00 gms of Poly Butadiene Rubber-Grade 1220, 1.00 gm of Anti Crystalline Polyethylene, 2.00 gm of Anti oxidant-Polymerized Tri-hydro Quinoline, 1.00 gm of Poly Ethylene Glycol-Grade 4000, 5.00 gm of Cumarone Indane Resin (M.P. < 80°C), 2.5 gm of Stearic acid, 1.10 gm of Sulfur, 15.00 gm of Intermediate Super Abrasion Furnace Black, 4.00 gm of Di-octyl Phtnalate, 1.40 gm of Accrlarator-Cyclo hexyal Benzo Thiazol Sulphur Amide, 7.00 gm of Zinc peroxide when this above composition achieves during vulcanization both ionic and covalent bonding between the rigid metal core to highly deformable rubber covering and between the layers of rubber covering and re-enforced fillers are adapted to provide high elastic modular wherein the rubber roll acquires a hardness of 66 Shore W, a tensile strength of 140 Kg/cm2, an elongation at break of 600% and DIN standard abrasion resistance of 52 mm3.