COLD ROLLING MILL

TO LEARN ABOUT COLD ROLLING MILLOVERALL PROCESS LAYOUT

COLD ROLLING MILL-PROCESSCold roiling mill carried out under recrystallization temperature.The starting material of cold-rolled is steel sheet is pickled hot-rolled breakdown coil from the continues hot strip mill.The total reduction achieved by cold-rolling generally will vary from about 50-90%.Generally the lowest percentage reduction is taken place in the last pass to permit better control of flatness, gage, and surface finish.Cold rolling provide product with superior surafce finish (due to low temperature-no oxide scale)Better dimensional tollarance compared with hot rolled products due to less thermal expansion.

COLD ROLLED METALS ARE RATED AS TEMPERSkin rolled: metal undergoes the least rolling ~0.5-1% harden, still more workable.Quarter hard: Higher amount of deformation. Can be bent normal to rolling direction without fracturingHalf hard: Can be bent up to 90Full hard: Metal is compressed by 50% with no cracking. Can be bent up to 45.PICKLING LINE

WHAT IS PICKLING?Pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contamination, rust or scale from ferrous metals, copper, and aluminum alloys.A solution called pickle liquor, which contains strong acids, is used to remove the surface impurities. It is commonly used to descale or clean steel in various steelmaking process. HOT ROLL SCALE FORMATIONMany hot working process and other process that occur at high temperatures leave a discoloring oxide layer or scale on the surface.In order to remove the scale the work piece is dipped into a vat of pickle liquor.

PICKLING AGENTSThe primary acid used is hydrochloric acid, although sulfuric acid was previously more common, hydrochloric acid is more expensive than sulfuric acid, but it pickles much faster while minimize base metal loss.The speed is requirement for integration in automatic steel mills that run production at high speed; speed as high as 243 mpm have been reportedPICKLING LINE #1

SPECIFICATIONSSemi Continuous lineLine speed 170 MPM maximumEntry looper capacity 20 MTRSExit looper capacity 10 MTRS4 Acid tanks6 Rinsing tanks1 Hot air drierCapacity of line 6,00,000 MTPAManual arc welder

10PICKLING LINE #2

SPECIFICATIONSContinuous lineLine speed 150 MPM maximumEntry looper capacity 400 MTRSExit looper capacity 200 MTRS5 Acid tanks4 Rinsing tanks2 Hot air drierCapacity of line 8,00,000 MTPAManual arc welderOnline trimmingCoil preparation before picklingPARAMETERSHCL Concentration % of Scale formation (Fe2O3,Fe3O4,FeO)Flow rate of HCLTemperatureLine speedPREPARATION FOR PROCESSPerfect HEAD end of rollRemove Edge WavyRemove telescopic errorDo notching before Welding Align HEAD end to TAIL end

PRECAUTIONS DURING PROCESSKeep Tension in line for reduce waviness Reduce sleeping of sheet using pinch rollMaintain speed above optimum value to reduce high contamination of HCLMaintain Looper for some undesired time delayMaintain HCL concentration, temperature and flow rate Maintain RINSING water flow and Air drier flow.RECOILER PRECAUTIONMaintain Shearing time and AlignmentKeep mandrel perfectly positioned to reduce telescopic errorMaintain Coil CAR Speed and Alignment to reduce telescopic error and time delay

MODIFICATION ACCORDING TO ESSAR PICKLING LINEHCL FLOW RATENOZZEl CONSENTRATIONPUMPING PRESSURE LOOPER ARRENGEMENTVERTICAL LOOPER INSTEAD OF LOOP PIT

COLD ROLLING MILLSTANDEM MILLS Rolling mills may be classified according to the number and arrangement of the rolls.(a): Two high rolling mills(b): Three high rolling mills (c): Four high rolling mills (d): Tandem rolling mills (e): Cluster rolling millsFour high rolling mill:It has a roll stand with four parallel rolls one above the other. The top and the bottom rolls rotate in opposite direction as do the two middle rolls. The two middle are smaller in size than the top and bottom rolls which are called backup rolls for providing the necessary rigidity to the smaller rolls.

A four high rolling mill is used for the hot rolling of armor and other plates as well as cold rolling of plates, sheets and strips.Tandem rolling mills:It is a set of two or three stands of roll set in parallel alignment. So that a continuous pass may be made through each one successively with change the direction of material.

5-STAND 4-HI SPEED CONTINUES TANDEM MILL (CTCM)

5-STAND 4-HI SPEED CONTINUES TANDEM MILL SPECIFICATIONSSupper-SVAICCapacity-1.2 MTPAWork roll Diameter-480 to 560Backup Diameter-1350 mm to 1500 mmRolling force-3000T by standMILL SPECIFICATIONMill type4-HI-5-Stand continuous cold rolling millmill speed maximum 1000 mpmentry product thickness 1.55 to 5.00 mmexit product thickness 0.2 to 3.00 mmcoil max width 650 (min) to 1625 mm(max)Special Features Flush butt welder90 turning pit6-Stand-600 meters entry looperL-2 automationMill clean systemAutomatic flatness controlAutomatic thickness controlCoil maximum weight -28MTDSRI In Std#5 for better shape controlFlying shear to cut the sheet at 200 mpmProduct controlShape less than 10IUThickness +- 1% and 98TOG

6-HI-1-STAND REVERSING COMBINATION COLD MILL

LINE SPECIFICATIONMATERIALHot rolled and pickled low carbon steelTHICKNESS1.20 mm to 4.80 mmWIDTH 700 mm to 1270 mmFINISH PRODUCT THICKNESS0.15 mm to 1.60 mmMAXIMUM TENSION12.2 MTContinues Galvanizing Line

GALVANIZINGHot-dip galvanization is a form of galvanization. It is the process of coating iron, steel or aluminum with a thin zinc layer, by passing the metal through a molten bath of zinc at a temperature of around 860 F (460 C). When exposed to the atmosphere, the pure zinc (Zn) reacts with oxygen (O2) to form zinc oxide (ZnO), which further reacts with carbon dioxide (CO2) to form zinc carbonate (ZnCO3), a usually dull grey, fairly strong material that stops further corrosion in many circumstances, protecting the steel below from the elements. Galvanized steel is widely used in applications where rust resistance is needed, and can be identified by the crystallization patterning on the surface (often called a spangle).Galvanized steel can be welded; however, one must exercise caution around the resulting zinc fumes. Galvanized steel is suitable for high-temperature applications of up to 392F (200C). The use of galvanized steel at temperatures above this will result in peeling of the zinc at the intermetallic layer. Electro galvanized sheet steel is often used in automotive manufacturing to enhance the corrosion performance of exterior body panels; this is, however, a completely different process.

CONTINUES GALVANIZATION LINE #1

SPECIFICATIONIn put material: Cold rolled / hot rolled low carbon, including structural steelStrip thickness: 0.30mm (min) to3.25mm (max)Strip width: 800mm(min) to 1370mmCoil weight: 25 T (max) / 5 T (min)Coil inner Dia(): 508 / 610 mmOuter Dia: 1800 Max Line speed : 160 mpm THREAD SPEED : 20 mpmProcess : 160mpmEntry and recoiling : 200mpmFurnace : 56 tph

CONTINUES GALVANIZATION LINE #2

SPECIFICATIONIn put material : Cold rolled, including structural steelStrip thickness : 0.12mm (min) to 0.60mm (max)Strip width : 700 mm (min) to 1250 mmCoil weight : 22 T (max) / 5 T (min)Coil inner Dia () : 508/610 mmOuter Dia : 1800 MaxLine speed : 150 mpmTHREAD SPEED: 20 mpmProcess : 150 mpmEntry and recoiling : 180 mpmLine Capacity : 25 TPHCold Rolled Close Annealed(CRCA)

PROCESSESECLBatch Annealing FurnaceCold Skin Pass MillLIRFIMIICTLDMSELECTROLYTE CLEANINGElectrolyte - A substance, in solution with water or another liquid, which is chemically changed by passage of electric current through it.The electrolyte we use and refer to is the substance you mix with water in a bucket into which you place an electrode and the part you wish to clean.Ion - An atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.

. REQUIREMENT OF ELECTROLYTIC CLEANINGCold rolled coils processed in cold rolling mills have a thin film of residual rolling oil on the surface after rolling. The alkaline cleaning of cold rolled coils by the use of high current density (HCD) ensures totally clean surface of the strip before annealing. This electro-chemical cleaning process is called Electrolytic Cleaning and the processing line the Electrolytic Cleaning Line. These techniques are more effective in cleaning cold rolled steel than conventional cleaning processes used on high speed electro tinning and alkaline-cleaning lines. A cleaning of 92% was achieved by Essar Indonesia using Dassnagar's high-current-density Electrolytic Cleaning linesThey are categorized into two types :High Current Density (HCD) Electrolytic cleaning linesLow Current Density (LCD) Electrolytic cleaning linesFact sheet Following figures have been achieved :

Cleanliness : 95% Cleaning solution used : Na4SiO4

Contaminants Incoming Strip Outgoing Clean Strip

Oil and Dirt 800 mg / sq. meter 20 mg / sq. meter Iron Fines 200 mg / sq. meter ELECTROLYTE CLEANING LINE(ECL)

SPECIFICATIONTHICKNESS0.25 to 3.0WIDTH600 to 1650 mmLINE SPEED270 mpmSTRIP TENSION12 N/mmOIL AND DIRT INPUT400 mg/m/faceIRON FINES INPUT200 mg/m/faceSTRIP FLATNESS50 IUPARAMETERSHot alkaline tank temp 70-79CHot alkaline concentration 30-70 mg/litResidual oil load in hot alkaline tank-5 mg/litIron load in hot alkaline tank 1.5 mg/litElectrolytic cleaning tank temp 70-90CElectrolyte cleaning concentration 40-90 mg/litResidual oil load in electrolyte cleaning tank 3 mg/litDissolved iron in electrolytic cleaning tank1.5 mg/litDryer temperature >80 CIron level on the strip at output (max 25 mg/m per surafce OR reflectivity >70%)Reflectivity of the strip at output min 70%Oil level on the strip at output max 50 mg/m per surface OR reflectivity >70%Alkaline/water carry overNo carry over allowedScratchiness latentNot allowed

ANNEALINGIn A Cold Rolling Mill, Hot Rolled Steel Strips Are Rolled At LowTemperature To Achieve Improved Surface Quality And MechanicalProperties To Decrease Thickness Of Steel Sheets.Extensive Deformation During The Cold Rolling Operation And Low temperatures Reduces The Formability And Ductility Of Cold Rolled Sheets Significantly. Therefore Cold Rolled Sheets Must Be Annealed. During The Annealing Operation, Deformed Microstructures Of The Cold Rolled Sheets Are Recovered And Recrystallization Takes Place. There Are TwoTypes Of Annealing Process: The Continuous Annealing Line (CAL)And Batch Annealing Furnace (BAF)BATCH ANNEALING FURNACE

PROCESSESCharge preparation-At first, on the base unit, several cold rolled steel coils are place done above the other. These cylindrical shaped coils are called charge.Loading-After loading the base with the coils, a protective cover is put in place and hydrogen gas is circulated with in this enclosure.Clamping-Then a furnace is placed over this cover.Tightness testInitial nitrogen purgingHeating and soaking-The protective cover is heated through burners of furnace, and it heats circulating hydrogen gas, then inner and outer surfaces of the coils get heated by convection from circulating hydrogen gas and by radiation between the cover and the coil. The inner portions of the coil are heated by conduction.RadiatingCooling-Cooling hood is placed on protective cover.Final nitrogen purgingUnclamping-Remove protective cover from charges.Unloading and coil identificationLIR

Specifications:Slitting line 2 LIR LINEMake M/S DMS FranceCapacity 18000 MTPAStrip thickness 0.4-2.5 mmStrip width 600-1500 mmSlit minimum width 300mmSlit maximum width 3 piecesYield strength 45 kg/mm^2(maximum up to 3 mm THK)FIMI

Specifications:Shearing line -FIMI LINE(cut out length line)Make M/S FIMI ItalyCapacity 140000 MTPAStrip thickness 0.3-3.0 mmStrip width 400-1600 mmShear length 500-3500 mm Yield strength 42 N/50mm

DMS

Specifications:Slitting line 1 DMS LINEMake M/S DMS FranceCapacity 69900 MTPAStrip thickness 0.3-3.0 mmStrip width 500-1300 mmSlit minimum width 250mmSlit maximum width 5 piece Yield strength 42 kg/mm^2(maximum up to 3 mm THK)

ICTL

Specifications:Slitting line 3 ICTL LINEMake M/S DONG BANG, koreaCapacity 300000 MTPAStrip thickness 0.3-3.0 mmStrip width 600-1650 mmSlit minimum width 1000mmSlit maximum width 1 pieces Yield strength 45 kg/mm^2(maximum up 3 mm THK)

COLD SKIN PASS MILL Against the background of a global market, rolling-mill owners are under constant pressure to cut their production costs and to open up new market segments with the help of innovative products. At the same time, requirements in terms of strip quality, such as thickness and flatness tolerances, surface structure and mechanical properties, are becoming increasingly strict. SMS Siemag, as a provider of complete solutions for rolling mill equipment, is faced with the challenge of taking appropriate measures to help achieve these targets. Therefore, conducting continuous and wide-ranging development activities is indispensable to SMS Siemag. Long-standing solutions need to be questioned and new technologies examined for their usability and benefits in rolling mills. With regard to skin pass rolling, our main areas of development are: Improving flatness and surface quality Increasing flexibility to handle high-strength material such as DP1000 as well as very soft material like interstitial-free (IF) grades Improving the automation by process models and control systems based on innovative online measurement devices REQUIREMENT

Besides the feed-forward module the structure of the controller consists of a tension control component as well as an adaptive force control component for feedback control. The feed-forward module calculates, based on the implemented model, the actual set-up as well as the actual speed, the force and tension values, which are added to the output of the feedback controller. Thus, the elongation control achieves the desired elongation faster in transient situations and so reduces the length out of tolerance. The difference in the adjusted force by the feedback control and the predicted force by the feed-forward module is shown in Figure . It is apparent that the feed-forward controller would raise the force faster and thus reduce the off-tolerance length. SKIN PASS MILL

APPLICATIONS OF COLD ROLLED STEEL SHEET

GENERAL PURPOSE COLD ROLLED STEEL SHEET AND COIL(JIS:G 4131)

THANK YOUCREATED BY:HARSH A. KALSARIYA