Lubricants are of two types:

1)process lubricant (e.g rolling oil)

2)maintenance lubricant(grease, hydraulic oil etc.)

The coolant that is use for rolling purpose is known as roll coolant.

Function of roll coolant-

1)lubrication2)reduce heat from roll bite zone.

Emulsion-

Two immiscible liquids are mixed in presence of a compound(emulsifier)to form emulsion or coolant.

e.g Milk is an example of natural emulsion where casein(already present in milk) acts as an emulsifier.

Emulsifier also known as surfactant because it activates both the surface of two immiscible liquids.

In emulsion of oil and water(used for rolling purpose)a)Water acts as coolant(reduce heat from roll bite)b)Oil acts as lubricant(Reduce friction i.e reduce roll force)

EMULSIFIER:

Is a chemical compound which mixed two immiscible liquid to form to form emulsion. (e.g Sodium oleiate).Emulsifier has two parts: a)Head Part b)Tail PartIf in preparation of emulsion head part of the emulsifier containsa)Positive Charge-Emulsion is known as cationic.b)Negative Charge-Emulsion is known as anionic.c)Neutral-Emulsion is known as non ionic.

Tail part of the emulsifier contains long hydrocarbon chains.

Head part binds water.

Emulsifier decreases surface tension between two immiscible phases(oil and water) and make them soluble.

Emulsifier are two type: a) Monomeric b)Polymeric

WHY WE USE DM WATER FOR PREPARATION OF EMULSION?

Since raw water contains huge amount of magnesium, calcium, iron, sodium, potassium etc ions, when water got evaporated during application of emulsion in mills concentration of these ions build up in emulsion. So formationof patch, black spot, rust on the strip.Since DM water does not contains these ions probability of the formation of rust, black spot, patch is less.

COMPONENTS OF ROLLING OIL:

1)ESTER:NATURAL ESTER(E.G VEGETABLE OIL,TALLOW FAT)(RESPONSIBLE FOR LUBRICATION)

2)FREE FATTY ACID: IT IS REPONSIBLE FOR LUBRICATION.

3)EMULSIFIER(E.G SODIUM OLEATE)

4)FILM FORMER: a)FATTY ACID. b)SOME POLYMERIC MATERIAL

5)ANTIOXIDANT: PREVENT OXIDATION OF OIL.

6)ANTI CORROSIVE AGENT

7)ANNEALING AIDS

8)ANTI STAINING AGENT.

EMULSION MAINTENANCE:

We maintain the following emulsion parameters:

1)Temperature(50 –58 degree Celsius):

Temperature is critical from three aspects.a)Strip shape.b)Microbiological control(at lower temperature there is a tendency of bacterial attack)c)Emulsifier Behaviour(at higher temperature emulsifier package broken)

2)pH(5.0-5.5):

pH=Log(1/Hydrogen ion concentration in solution)Represent acidity and alkalinity of an aqueous solution.PH controls the followings:a)Controls partical size distribution.b)Control Bacterial growth in certain rolling oil technology.

3)Conductivity(200 micro S/cm Max):

Effect when above the range:

a)Stability of the coolant decreases.b)Residual Oil increases.c)If due to chloride ion and sulphate ion pin point rust on strip may appear.

Action:

a)Check the conductivity of Rinse waterb)Check the conductivity of DM water.

4)IRON(200 ppm Max):

Reasons of iron generation:

a)Lack of lubrication.b)No floatation of tramp oil with iron fines.c)No sedimentation of iron fines.d)Carry over of iron salts from pickling lines.e)Bad pickling.f)Bad hot bandg)Little emulsion flow

Effect when above the range:

a)residual iron increases.b)Plate out increasesc)Lubricity increases.

Action:Check magnetic seperator action.

5)CHLORIDE(50ppm Max):

Effect when above the range:

1)Pin point rust2)Conductivity increases.3)ESI decreases

Action:

a)Check the rinse water chlorideb)Volume decrease by patial dumping and fresh DM water addition after that.

6)ESI(EMULSION STABILITY INDEX)(O.5-0.6):

a)Unstable emulsion(ESI:0.1-0.3)b)Stable emulsion(ESI:0.85-1.0)c)Meta Stable emulsion(ESI greater than unstable emulsion but less than stable emulsion).

So our emulsion is meta stable type.

Effect when above the range:

a)Lubricity reduces.b)More iron on the strip.

Effect when below the range:

a)More residual oil on the strip.b)Low reflectivity after annealing.

Action:a)Check Rinse water chloride.b)Check iron content of the running tank.

7)SAPONIFICATION NO:(213 mg KOH/gm Max):

The no of milligram of KOH required to saponify 1gm of oil is known as saponification no of the oil.It represents the amount of fatty matter in oil.

8)ACID NO:(22 mg KOH/gm Max):

Represents amount of free fatty acid present in the oil.

Effect when above the range:

a)Staining increases.b)Microbiological infestation tendency increases.

9)TRAMP OIL(10% Max):

Tramp oil(%)=(Saponification no of supplied oil-Saponification no of oil extracted from emulsion)/Saponification no of supplied oil*100

Effect when above the range:

a)Lubricity can be effected.b)Carbon shoot formation after annealing

Action:

a)Check Saponification no.b)Check any leakage.

LIQUID APPLIED IN SKIN PASS MILL: WET TEMPER FLUID:

Why Wet Temper?

1)Prevent pick up dirt from strip by work roll.

2)Roughness of the tempered material is reduced by reduction of work roll due to less pick up of dirt.

3)Provides strip with imperceptible film.

WET TEMPER FLUID FUNCTION:

1)Lubrication

2)Detergency

3)Rust Protection

WET TEMPER FLUID COMPONENTS:

1)Alkaloamines.

2)Soap

3)Water

4)Special additives

APPLICATION:

5% solution of the liquid in DM .

PARAMETER CHECKING OF THE WTF SOLUTION:

1)PH(at ambient temperature)

2)Conductivity(Micro S/cm)

3)Concentration(%)

WHY SKIN PASSING?

1)To achieve optimum mechanical properties(YS, Hardness etc)

2)To prevent occurance of stretcher stains in annealed steel.

3)To impart desire surface finish-“Matte” on the strip surface.

4)To improve strip shape.