COLD ROLLING OILS. Introduction Mechanism of Roll Lubrication Requirements of a Rolling Oil Trends...

COLD ROLLING OILS

• Introduction• Mechanism of Roll

Lubrication• Requirements of a

Rolling Oil• Trends

(Past/Present/Future)

• Evaluations of Rolling Oil

• Our Lab Mill Trials at RDCIS

• Emulsion Management

• Popular Brands of Rolling Oils in India

• Rolling Mills in India

• Rolling Oil Potential

Contents

Cold Rolling Oil

An Oil / Emulsion introduced at the Roll-bite in the process of Cold Rolling to control Friction at the interface of Work Rolls and Strip

Various Processes in Steel Rolling

Type of Cold Rolling Mills

Why Cold Rolling?• Limitation of HSM to

produce thinner gauge with– Superior surface finish – desired mechanical &

metallurgical properties

• Potential application of the product in consumer goods industry

• Newer cold rolled products are being continuously developed both in bare & coated variety

Type of Cold Rolling Mills

2 Hi Mill • Suitable for hot or cold rolling of ferrous and nonferrous metals.

• Ideal for breakdown, run down, tempering and skin pass operations. 

Type of Cold Rolling Mills

4 Hi Mill

Undesirable contact area results in a bending force which causes edge drop.

Type of Cold Rolling Mills

4 Hi Mill • Used both as Non-reversing Mills for intermediate rolling and as Reversing Mills for finish rolling

• Smaller rolls reduce thickness of metal being rolled more easily and with much less pressure than large rolls of a 2-High Mill 

• This decreased pressure reduces roll bending and separating forces and permits rolling of wider and thinner materials with a more uniform gauge

• 4-hi mills are a cost-effective means for industry to product a wide range of sheet products . 90% of Mills are of this type.

Type of Cold Rolling Mills

Reversing Mills

Advantages

1. Less Capital Cost

2. Occupy less space

3. Any required gauge can be obtained

Disadvantages

1. Low output

2. High Roll Consumption

Continuous Mills

Advantages

1. Suitable for large outputs

2. Higher gauge accuracy

Disadvantages

1. High capital cost

2. Large production of one size product

Type of Cold Rolling Mills

4 Hi Tandem Mill

Type of Cold Rolling Mills

• Provide improved flatness due to their workroll bending mechanism and intermediate roll adjustment in an axial direction.

• Main advantages are improved shape of rolled strip, increased reductions and greater rolling efficiency.

6 Hi Mill

Drawbacks :• Complicated and hard to maintain roll cluster

unit• Cooling problems resulting from the smaller

circumferential area of their working rolls.

• Undesirable contact area is virtually eliminated by shifting the intermediate rolls axially.

• This can be done quickly and easily, making the HC-MILL the ideal solution for the real world.

• Use of the HC-MILL not only significantly improves quality, but has significant ramifications for the system.

Type of Cold Rolling Mills

6 HI Mill

Type of Cold Rolling Mills

20 Hi Mill

Type of Cold Rolling Mills

20 Hi Mill

Tandem Mill – Continuous Mill

• Modern Tandem Cold Mill consists upto 6 sets of independently driven pairs of Work rolls, each pair being supported by a large no. of back-up rolls

• Cumulative Mill reduction could be in the range of 50% - 90%

• Ensures high gauge accuracy and proper flatness

• Roll separating force involved in rolling 1250 mm wide strip may be as high as 1000T

Mechanism of Roll Lubrication

• Friction is a necessity as a transmitter of Deformation Energy

• Optimization of friction – Adequately high to

Ensure traction in the Roll bite

– Low enough to optimize Mill Motor Power requirement

Mechanism of Roll Lubrication

Oil Pooling at the Bite• Positive Pressure gradient

at the inlet zone• Viscous component of the

oil diffuse more in the roll bite

• Higher Strip temperature (120 -200 oC) evaporates water in emulsion

• Fatty substance affinity to the strip/roll surface

Mechanism of Roll Lubrication

• Vo>Vp>Vi• At neutral Point

Vx=Vp• Contact angle is

about 3-4 Degrees only

• Pressure on the rolls buildup from entry to the neutral point and then declines till exit.

Mechanism of Roll Lubrication

• Lubrication Regimes in– Pre-deformation

Zone•Elasto

Hydrodynamic

– Deformation Zone•Plasto

Hydrodynamic•Boundary•EP Lubrication

Some Important Formulae

dd{(2K p)y} ( )Rp0

y tf2

R2

2 ti tf

R

p2K

Cy2Re

where

2 Rtftan

1 Rtf

p2K

Cy2Re

where

2 Rtftan

1 Rtf

Some Important Formulae

(p2K)before

2yti(1

x

2K)e

( i )

and

(p2K)after

2ytf(1

x

2K)e

(p2K)before

2yti(1

x

2K)e

( i )

and

(p2K)after

2ytf(1

x

2K)e

Pressure Distribution

hfilm 6Vyieldtan

(1 2r3)

Functions of a Cold Rolling Oil

• Lubrication:– Control friction,

wear and surface damage of rolls and strip

• Scavenging:– Heat– Dirt– Wear Debris

Requirements of a Rolling Oil Optimum lubricity,

high film strength, shear stability, high plate-out characteristics

High heat transfer co-efficient

Optimum Emulsion stability/Good chemical stabilityLong emulsion

lifeEasy maintenance

High cleanliness properties Good Burn off

characteristicsGood emulsion

detergencyMinimum soap

formation Easy disposal

Environment friendliness

Bio-degradable

Additional Requirements of a Rolling Oil

Good rust/corrosion protection capacity Good resistance to tramp oil

contamination Easy removability after rolling Complete System Compatibility

Rolling Mill & Strip ComponentsPickling Oil/acid traces carry over

from pickling line Economical

Constituents of Cold Rolling Oils

• Lubricant Base (80% - 90%)– Natural Oils– Fats & their Derivatives– Mineral Oils– Synthetic Esters

• Boundary Additives– Molecules with permanent

dipole moment like Derivatives of Fatty Oils (acids, alcohols, amines)

– Long chain acids are preferred

– Neutral soaps of Esters

Constituents of Cold Rolling Oils

• EP & AW Additives– Chlorinated Paraffins– Sulfurized Mineral

Oils/Fats– Chloro-sulphides– Sulfur-phosphorus

compounds– Nitrogen-phosphorus

compounds

• EmulsifiersHLB ValueEmulsion stabilityOil Particle SizePlate OutShear Stability

• Dispersant / Surfactants

Properties of Rolling Oils• Viscosity

– Higher Film thickness Viscosity• Saponification Value

– Indicates amount of Esters present– Higher SAP value means better lubricity– Higher SAP may impair Cleanliness

behavior of oil• Free Fatty Acid (FFA)

– Help decreasing friction due to adsorption on strip & roll surface thus provide good boundary lubrication

– Prone to oxidation, polymerization and formation of sticky deposits on storage.

– Affects Cleanliness behavior of oil

• Iodine No.– Indicates degree of un-saturation of fatty

materials/esters• Pour Point

– Lower value is desired– May help cooling efficiency– Too low pour oils using short chain compounds

may possess poor lubricity & load bearing ability• pH Value

– Vital for emulsifier’s effectiveness– Affected by

• Carryovers from pickling lines• Water Quality• Tramp Oils• Degeneration/Oxidation of the Rolling Oil

itself

Properties of Rolling Oils

Properties of Rolling Oils• Ash Content

– Low ash formulations are preferred

• Oil Particle Size– Greatly affects Lubricity, Plate-out,

Iron Content of emulsion– Indication of shear stability of the oil

ParametersSheet Rolling

Tin Plate Rolling

Mean Particle Size, µ 2 - 5 3.5 - 10

ESI,% 80 - 90 50 - 95

Oil Plate-out, mg/m2 350 - 600 500 - 1100

Iron Content, ppm 0 - 300 100 - 700

Trends

Palm Oil

Natural Oil/ Fats/

Derivatives

Fatty Oils & Mineral Oils

Synthetic Esters

High

Mol

. Wt.

Polym

ers

Evaluations of Rolling Oils

• Laboratory Tests– Physico-chemical Tests– Functional Tests

• Tribological Tests• Lab. Mill Trial• Industrial Trials

Laboratory Tests of Rolling Oils Physico-chemical Tests

1. Ash Content, % Wt

2. Carbon Residue, CCR, % Wt3. Flash Point, COC, oC4. Free Fatty Acid, Oleic %5. Iodine Number 6. Kinematic Viscosity, @ 40

oC, cSt7. pH of 2% Emulsion in

Distilled Water 8. Pour Point, oC9. Saponification Value, mg of

KOH/gm

Laboratory Tests of Rolling Oils Functional Tests

1. Burn-Off Characteristics

2. Emulsion Stability Index

3. Mean Particle Size, µm

4. Plate-out Characteristics

5. Cleanability6. Iron Corrosion7. HLB Value8. Staining Tendency

Tribological Test Rigs

Test Contact Configuration

Type of Contact

Soda Pendulum

Pin on Two Pairs of Balls

Point Contact

Amsler Wear Test

4 Pairs of Crowned Discs

Line Contact

SRV Test Rig Ball or Roller on Disc Point/Line Contact

LFW1 Rig Ring on Block Line Contact

Ring Compression Test

Ring on Platen Surface Contact

Plint Tribometer

Pin on Sheet Line Contact

Tribological Test Rigs LFW 1 Oscillating Test

Test Description

A steel block pressed against a lubricated oscillating ring.

Test Result Static and dynamic friction coefficient µ, wear in mm, life time of lubricant

Standards ASTM D 2714, ASTM D 2981, ASTM D 3704

Tribological Test Rigs LFW 1 Rotating Test

Test Description

A steel block pressed against a lubricated rotating ring.

Test Result Static and dynamic friction coefficient µ, wear in mm, life time of lubricant

Standards ASTM D 2714, ASTM D 2981, ASTM D 3705

Tribological Test Rigs Falex Pin & Vee Block Tester

Test Description

A lubricated, rotating steel shaft between two V-shaped steel blocks under specified load.

Test Result Friction coefficient µ, wear in mm, endurance life in h, load carrying capacity N

Standards ASTM D 2670, ASTM D 2625, ASTM D 3233, ASTM D 3704

Tribological Test Rigs Falex Pin & Vee Block Tester

Tribological Test Rigs Falex Pin & Vee Block Tester

Tribological Test Rigs SRV Tester

Tribological Test Rigs SRV Tester

Test Description

Measure friction and wear under oscillatory or rotational motion.

Test Result Coefficient of friction µ, wear rate in mm  

Standards DIN 51834, ASTM D 5706-7, DIN 50324

Tribological Test RigsFour Ball Machine

Test Description

Wear properties and weld load of consistent lubricants in a four ball system (rotating ball on three fixed balls).

Test Result Welding load in N, wear scare in mm

Standards DIN 51350

Tribological Test Rigs Amsler Wear Test

Tribological Test Rigs Amsler Wear Test

PIN ON DISC TRIBO TESTER

Plint Tribometer

Emulsion Management

Good emulsion management provides

– Consistent performance of oil

– Longer emulsion life

Emulsion Management

What all to manage of an emulsion?1. Concentration2. Temperature3. pH4. Conductivity5. Oil Particle Size (OPS)6. Tramp Oil7. Iron fines8. Bacterial Count

Emulsion Concentration

Variations in actual production line may be high owing to:

– Disproportionate Oil addition– Evaporation of Water– Change in emulsion characteristics of oil– Skimming of tramp oil

•Online oil concentration measurement helps – The oil content directly relates to the velocity

of sound in the fluid. A change of 1% oil content brings about an change of approx. 2 m/s.

Emulsion Temperature

Higher emulsion temperature than desired

– Brings down oil film thickness by decreasing viscosity

– Declines Cooling Efficiency– Emulsifier’s behavior may get affected

Normally kept within 45 – 55oC

Emulsion pH

Emulsifier system is pH sensitiveCauses of pH disturbances

– Acid carry over from pickling line– Inferior feed water for emulsion– Tramp Oil mixing

• Preferred pH range: 5.0 – 7.0

pH < 5.0Increase Particle sizeCorrosion ProblemErratic Rolling

pH > 7.0Reduce Particle sizeMore metallic soaps Affects cleanliness

Emulsion Conductivity

Major contributors: H+, OH-, Cl-, SO42-

Minor Contributors: Ca2+, Mg2+, Na+, K+

Conductivity of Emulsion < 200 µS/cm

Should never exceed 500 µS/cm

Conductivity of – De-mineralized Water < 10 µS/cm– Industrial Hard Water < 500 µS/cm

Tramp Oil

Oil in emulsion that doesn't derive from the emulsion concentration itself is uncontrollable and therefore undesirable.

•Sources of tramp oil – oil leaks from transmissions,

hydraulic systems and other lubrication points

Negative effects of Tramp Oil

• Loss of cooling & wetting properties • Deplete emulsifiers• Nullifying rust-inhibitors • Cuts off air and thereby provides an

excellent base for growth of anaerobic bacteria• Reduce amount of sulfur additives • Drop in pH • Create bad smell• Low pH increases ionization of heavy

metal in coolant and this in turn may create unhealthy working atmosphere.

Desired Values of Some Important Emulsion Parameters

Parameters Desired Value1 Chloride in Pickling Rinse

Water< 60 ppm

2 Chloride on Pickled Strips < 0.03 mg/ft2

3 Emulsion Conductivity < 500 mS/cm2

4 Hardness of Water < 250 ppm

5 Bacteria < 5 x 106 counts/ml

6 Yeast < 200 counts/ml

7 Tramp Oil < 20 - 30 %

8 Iron in Emulsion < 200 ppm

9 pH Variation + 0.5 - 1.0

10

Iron on CR Strip < 100 mg/m2

11

Oil on CR Strip < 100 mg/m2

12

Carbon on Annealed Strip < 7 mg/m2

Emulsion Management

FFA Usually lower than Fresh

Oil as some FFA are lost due to soap formation with Iron & hard water salts

Lowered due to Mineral Oil Contamination

May increase due to excessive bacterial activity

Analysis of Used Extracted Oil

Emulsion Management

SAP Value Lowered with

contamination of Tramp Oils

% drop Indicates reduction of the active oil in emulsion

Should not fall below 70%

IR Spectroscopy– Predicts Ester content &

Fatty acid concentration– Identify contamination

Analysis of Used Extracted Oil

Cold Rolling Mills in India

No. of unit

s

Unit Capacity

(TPA)

Width Range (mm)

Total capacity

20 up to 30,000 upto 450 240,000

16 up to 72,000 450-700 570,000

15 up to 300,000

700-1250 1,420,000

5 up to 300,000

1250-1560 1,310,000

2 > 1,000,000 > 1560 2,690,000

    Total 6,230,000

Rolling Oil Potential in India

Specific Rolling Oil consumption in Cold Rolling:

1.2 kg/T of Rolled Sheet for Mineral Oils

0.6 kg/T of Rolled Sheet for Semi-synthetic/Synthetic Oils

Considering the above, Cold Rolling Oil potential would be about 3500 – 5000 KL per Annum

Popular Cold Rolling Oils

Manufacturer

Brand Name

D A Stuart Rolkleen 1000, 2000, 3000

Quaker Chemicals

Quakerol CA 29

B&L Balmerol Aquaroll 431, 432

Indian Oil Servo Steerol C4, C6

HPCL HP Cold Rolling Oil

Houghton Houghto-Roll