Paper on Cold-Rolling of Steels in Pil
[pic] INTRODUCTION ABOUT PENNAR INDUSTRIES LIMITED Pennar industries limited are a multi-product, multi-location enterprise.The company manufactures six different products.• Cold rolled steel strips • Cold rolled form sections • Engineering components • Road safety systems • Precision tubes • Fabrication Pennar industries has received the ISO 9001,2000 quality certification from RWTUV of Germany and committed to achieving excellence in the quality of product.
The CRSS division, with its units at Patancheru, Isnapur and Chennai has combined annual cold rolling capacity of 1,20,000 Metric Tons.
Pennar manufactures Steel Strips from 600mm to 750mm width and thickness range of 0. 25 to 5. 00mm both in coil and sheet form. Pennar caters to a wide range of customers from various sectors like: • Automobiles • Wide goods • Domestic appliances • Bearings • General engineering industries FACILITIES: • Quality control measures at every stage of the manyfacturing process, right from the selection of raw material to chemical analysis using spectrometer. • Semi-continuous push-pell type pickling lines feed the rolling mill with scale free,iled and bright HR coils. • PLC-Controlled MECON WEAN UNITED 4-HI Rolling Mill. Bell type annealing furnaces for heat treating of cold rolled steel strip • Skin pass mills. CR Slitting lines and Cut to length lines. • Every process is closely monitored and end products are subjected to a battery of tests to determine Hardness, Tensile strength, Yield strength,% of Elongation, cupping test and Bend test in order to meet stringent customer specification. • Finished products are carefully packed, using polythene and gunny for coils and poly craft and wooden/steel pallets for sheets to provide total protection to the products during transit and handling.
Pennar Industries group is well known for fulfilling their commitments. Many times they have been awarded and rewarded. [pic] PROCESS FLOW CHART (COLD ROLLED CLOSE ANNEALED STEEL STRIP) [pic][pic] RAW MATERIAL AND SOURCES The raw material for production of CRSS is ‘Hot Rolled Steel coils’ and these HR coils are produced by using “primary roughing mills” which is a 2-HI reversing mill with a 0. 6 to 1. 4 mm diameter rolls. The main purpose of the mill is to reduce casting ingots into blooms. The work piece has to be pass 10-20 times between the rolls, to have a desired width, the work piece is made to pass through “edge grooves”.
HR colis are also produced in ‘Universal Mills’ without edge grooves. These coils are mainly low carbon steels which are either ‘Si’ or ‘Al’ killed. Specifications: Range 1. width 1350-1800 mm 2. Thickness 5-6 mm Ultimate Tensile strength 80 kg /mm2 Yield strength 40 kg/mm These Hot rolled coils are exported from many places like JINDAL STEEL WORKS (Karnataka), LLOYD STEELS LTD (Maharashtra), ESSAR STEELS LTD (Gujarat), ISPAT INDUSTRIES LTD (Maharashtra), SAIL etc..
There will be a sticker present on every HR coil and it will be as follows… ISPAT INDUSTRIES LTD DIST-RAIGAD, MAHARASHTRA, INDIA Heat Number : 08201137 Coil Number : 0820113706/0 Grade/Specification : WG29AC Batch Number : 0001063785 Invoice Number : 2180040447 Invoice Date : 07. 05. 08 Net Weight : 23. 700MT / 52258. 501lbs Size : 1250. 00mm x 4. 00mm x mm Customer :Pennar Industries Limited Purchase Order No : 0021047514
A sample of these HR coils is taken and it is sent to spectroscopy lab for chemical analysis. SPECTROSCOPY Chemical analysis: Chemical composition of steels is checked by means of SPECTRO. Generally C, Si, Mn, P, S, Cr, Mo, Ni, Al, Cu, Nb, Ti, V, Sn, B, and N are analyzed. Test procedure for spector is as below. Preparation of sample: ? The sample must be free from slag inclusions, rust, grease, oil, fracture, voids. ? The sample must be handy for polishing. ? The dimension of the sample must be fit on the spark stand. ? The sample must be flat (to get completely seated on the spark stand). The sample is prepared on the abrasive disc grinder by using suitable abrasives having 60 grade coarseness. Method of Testing: The spectro lab is switched on half-n-hour before sparking for warming up. The spark stand is flushed with grade-I argon for few seconds before sparking. Before sparking the unknown, the primary standard/internal standards are sparked and results are compared. If the results found to be ok sparking of the unknown sample is carried out by keeping the prepared unknown samples on spark stand in inverted position and is clamped and sparking is carried out.
If the results are found not ok, the spectro lab is standardized with setting up samples (RE12, RE13, RE14, 5 SUS 5) supplied along with spectro lab. |[pic] | Each sample is sparked for minimum 2 times and the average results are recorded and print is taken out and the composition is known. These HR coils are sent to HR slitters.. HR SLITTERS Hot rolled coils are slitted as desired to provide material for cold-rolling. For slitting of HRSI in 1350 mm whereas HRSII is 1800 mm. he different parameters the coils,two slitters HRSI and HRSII are in use. The maximum slitting width are: Coil parameter input coil output coil Coil I. D500mm (or) 880mm 500 mm Coil O. D 1800 mm 1370(max) Coil weight 30 Tons(max) 10 tons(max) Strip thickness 5 mm – 8 mm 5 mm – 8 mm Width 1500 mm(max) 1500 mm(max) Line speed:250m/min. | |HOT ROLLED SLITTER | |[pic] | | | PICKLING Immersion of a metal component in a solution which is preferentially remove oxides and mill scales, with little effect upon the underlying metal. Solutions are usually acids or alkalies, often with addition of an inhibitors to minimize attack on the underlying metal. Typical solutions for plain carbon steels are: 5% HCl + 0. 05% Galvene at 15-500 C PROCESS: The aim of pickling is to remove the oxidation scales & rust formed during hot rolling. Initially the HR slitted coil strip is passed through three tanks called the ACID TANKS or PROCESS TANKS (Tanks 1, 2 & 3) in which the commercial HCL (Hydro Chloric Acid) acid is present with maximum concentration of 20%. In this pickling all the rust and scales on the sheet are removed. Once the sheet is passed through acid tanks it is then passed through rinse water tanks 1, 2 and 3. This is done so because after the coil is passed through the acid tanks the acid will be present on the coil/sheet.
When we clean with soft water then it becomes safe for the operator. Once the coil/sheet is rinsed there are chances of getting corroded again that are why water is drained away from the coil/sheet by hot air drier and finally applied emulsion (Castrol) oil on the coil to prevent corrosion. The specifications of acid tanks 1, 2 and 3 are listed below: Acid Tank -1 Acid concentration : 2-7% % Iron content : 22max Temperature : 55-70oC Acid Tank-2 Acid concentration : 6-12% % Iron content : 22max Temperature : 50-65oC Acid Tank-3 Acid concentration : 9-16% Iron content : 20max Temperature : 45-60oC Types of pickling equipment: • Cage picklers • Push pull picklers • Semi-continuous pickle lines • Shallow picklers • Turbulent pickling • Spiral pickling. In pennar industries, we use semi-continuous pickling . [pic] The main reactions which take place during pickling are: Fe0+2HCl ( FeCl2+H2O Fe+2HCl ( FeCl2+H2 Care should be taken during pickling to prevent the pitting, small holes and formation of spots on the coil due to over pickling will reduce the thickness of the sheet. When the pickling process is going on, by titration process we have to check he percentage of acid and iron in the tanks. TITRATION PROCESS: Titration process is carried out to know the percentage of iron and acid content in the tanks. This is because if the iron content exceeds the permissible level(20% Fe Content) in acid tank, then acid is to be taken off and new acid is added in the tanks to carry out pickling. Take 20ml of distilled water in a conical flask. Add 0. 2ml of Hydrochloric acid (HCl) to it. Then add few drops of acid indicator named Bromophenol blue AR with chemical formula C19H10O5SBr4 to obtain yellow coloured solution. Take Sodium Hydroxide (NaOH) in a burette and note down the initial reading.
Start titrating with NaOH solution till brown coloured solution (i. e. end-point) is obtained. Note down the final reading. The difference of the final and the initial reading is determined. From the table, the corresponding percentage of acid is noted down. Then add few drops of Orthophosphoric acid to neutralize the solution. Add few drops of iron indicator named Barium Diphenylamine Sulphonate GR with chemical formula C24H20BaN2O6S2 to obtain yellow colured solution. Take Potassium Dichromate (K2Cr2O7) in a burette and note the initial reading. Start titrating with K2Cr2O7 solution till brown coloured solution (i. . end-point) is reached. Note down the final reading. The difference of the final and the initial readings is determined. From the table, the corresponding percentage of iron is noted down. OBSERVATIONS: 1. Titration with NaOH: Initial Reading : 25. 2 Final Reading : 26. 9 Difference : 1. 7 From the table, 3. 06% of acid. 2. Titration with K2Cr2O7: Initial Reading : 22. 9 Final Reading : 29. 0 Difference : 6. 1 From the table, 17. 08% of iron content. NOTE: After pickling recoilng is carried out with tension and apply the emulsion oil to prevent corrosion.
These pickled coils are processed to next stage i. e. , cold rolling. COLD ROLLING COLD ROLLING is the process where the material is deformed plastically by passing it between rolls below recrystallisation temperature. In pennar industries cold rolling is done by 4HI Reversible Cold Rolling Mill. The name itself indicates that it is a reversible mill i. e. the rollers can rotate in forward as well as in reverse directions. In 4 HI Rolling mill, there are four rollers, of which two are back-up rolls and another two are work rolls. The load is fed to the back-up rolls and the sheet is passed through the work rolls.
The back-up rolls act as the driving rolls and the work rolls as driven rolls. The direction of driving and driven rolls is opposite to each other. [pic] 4 HI-COLD REVERSING MILL PROCESS: Pickled coils are reduced to final gauge at the 4HI mill by forward and reverse rolling with load applied on the work rolls through the SCREWDOWN MECHANISM. The coils are placed on the coil car by an EOT crane. The coil car is moved towards the mandrel to load it. After loading on the mandrel the coil is fed into the work roils through the pay off reel to the delivery tension mandrel (DTR).
From DTR the coil is passed through rolls to Entry Tension Reel (ETR). The coil is reduced in each pass according to the required thickness. Most care is taken during rolling to maintain required tension and speed such that the possibilities of rolling defects are minimum. The pass from the pay-off to DTR is known as the first pass and for the second pass the coil is sent from DTR to ETR. The number of passes depends on gauge reduction / final requirement. The diameters of the back-up rolls are 610mm and the work rolls are of 225mm. The barrel lengths of the rolls are 700mm and 768mm. There is a gear box present for the screw down load.
There are primary and secondary motors. The ratio of primary motor is of 1:16 and that of secondary motor is 1:32. The pitch of the screw down screw is 8mm and diameter is 180mm. At the weld portion the mill is slow down and the number wraps at which weld passed the roll bite is noted down the direction of rolling reversed. The tail end is clamped to the entry tension reel . tension and load are applied and level is checked. Guage is checked by the help of non contact guage and the mill is operated at higher speeds. The operation is repeated till the doil is finished to the final guage.
Final pass reduction is maintained low i. e. , 8%-16%. To maintain shape coil is wounded on low tension. Final pass thickness is checked at operating and drive sides and it is maintained throughout the strip by adjusting load and tension after the rolling operation is over the coil end lap is wound,and bonded and transferred to the skid. TECHNICAL DATA ON ROLLING: MILL MANUFACTURES: Latest computer controlled MECON WEAN UNITED 4 HI cold reversing Mill GRADES : Mild steel[DDDEDDEDDSMEDIUM] SPECIFICATIONS : IS 513, IS 4397,IS 4030
STRIPSHEET WIDTH : 25 mm to 630 mm THICKNESS : 0. 25 mm to 6. 00 mm SURFACE FINSH : Bright, Fine Matt, Matt, Rough. BACK UP ROLL DIA : 610 mm to 567 mm WORK ROLLS DIA : 225 mm WORK ROLL LENGTH : 700 mm After cold rolling process, the grains are enlarged the coil becomes very hard due to work hardening and internal stresses that are developed in the material. In order to restore ductility and relieve internal stresses of the material ANNEALING has to be done. ANNEALING Annealing is the process of heat treatment by which the metal very ductile.
It is also used to homogenize the material, composition by diffusion and it relieves the residual stresses which are arising from cold working. It also results in grain refinement by recrystallisation process. The temperature to which the metal is subjected and the time for which the temperature is maintained depends upon the parent metal and the particular properties that are desired on the final stage. In pennar industries annealing is generally carried out for following reasons:- ? To obtain softness. ? To increase or restore ductility. ? To relieve internal stresses. ? To refine grain structure. To homogenize the mechanical properties. In Pennar Industries SUB CRITICAL ANNEALING is carried out (below recrystallisation temperature). SUB CRITICAL ANNEALING Is a method of annealing while include heating of metal to the metal below the lower critical temperature. I. e. below 737C. Soaking for some time and cooling at a very slow rate in the furnace it self. ANNEALING PROCEDURE: Generally, Annealing is carried out in bell type furnaces or Electric arc furnaces which uses diesel and LPG as a fuel and temperature will be regulated by the fuel supply to undergo annealing process. BELL TYPE FURNACE [pic]
TECHNICAL DATA: FURNACE : Apex and allied COIL DETAILS : OD 1200 -1700 ID 400 OR 500 CHARGE WEIGHTS : 30000 TO 40000 CHARGE HEIGHT : 2650 MM (MAX) FURNACE TEMP : 960 (MAX) FLOW METER FOR NITROGEN GAS: TEMPERATURE :86 0 C(MAX) PRESSURE : 1 PSI (MAX) The different stages in annealing process are as follows: Charging: The coils are stacked on the base in such a way that coils with decreasing diameter will be arranged from bottom to top.
The coil should be stacked with centers of the coils and axis. If furnace stacking should be absolutely concentric so that uniform gap is obtained between the coils and inner cover. The intermediate concentricity should be provided between all the coils to ensure good circulation. Purging: The inner hood shall be brought on to the charge and fixed to the base. The protective gas flow starts at a rate of 15 Nm3/ hour and maintained for about 45 min, so that the initial air in the hood is fully replaced by the protective gas. This process is called as purging process. Heating:
After the charging space has been filled with HYDROGEN and NITROGEN and flow rate of around 15m/hr, the heating can be commenced. All the settings and attachments needed to start the furnace are finished. The rate of heating depends upon the charge weight, % of reduction and carbon equalent. Generally heating rate is 40c/hour upto 520c and 30c/hour from above 520c. In PENNAR INDUSTRIES fired furnaces are used for heating. When the temperature at the thermocouple reaches the set point the fuel supply will be regulated periodically. Soaking: Maintaining the specific temperature of charge for required hours , is known as soaking.
In the process the charge coil are soaked for some hours depending upon the different qualities of coils, under the required temperature. When the soaking is over, an audio alarm is given and the furnace is automatically disconnected by the central controls. The annealing cycle comes on end. Cooling: The furnace is removed from the base and cooling hood is brought on the base to expand the cooling process. The cooling hood is removed when the charge temperature reaches about 90c. At 90c the charge is ready for loading. After cooling, the coils are discharged from the base and are placed for air cooling.
The coils are cooled completely for room temperature in 2 to 3 hrs, after which they are processed further. PSL consists of 33 bases, 14 furnaces and 16 cooling hoods in annealing yard. The loading capabilities of different bases are given. Bases capacity(tons) 22. 15-20 33. 25-30 Technical characteristics: Charge materials : MS,D,DD,EDD Stack height :2650 mm(max) Estimated coil dia : 1600(max) Charge temperature :300 C Annealing temp : 7300 C
Bell furnace temp : 9000 C Flow of protective gases: During purging ;14 Nm3/hr During heating :8-10 Nm3/hr During cooling :2 Nm3/hr PROTECTIVE GAS PLANT Protective Gas plant is operated for producing Nitrogen in pennar steels ltd. Equipment:- In Pennar steels the Nitrogen gas produces from air by absorption with pure drier and ammonia cracker unit. PLANT CAPACITY :60 N. M3 HR TYPE :PSA 60. 7. 10 + DEOXO/NLPD 60. 7+CU 60. 7+NH3 -10E
ANALYSIS :HYDROGEN APPROX 4% BY VOLUME OXYGEN MAX 10 PPM AMMONIA MAX 10-20PPM NITROGEN+RARE GASSES-BALANCE DEW POINT :APPROX 40 C WITH DELIVERY PRESSURE CONSUMPTION : GAS AMMONIA APPROX 1. 8 KG/HR AT MAX VALUES PRESSSURE OF 18 KG/CM2 POWER APPROX :49. 87 KWH/HR COOLING WATER :12. 5 M3/HR TEMP INLET : 300C
TEMP OUTLET :400C PRESSURE :2-3 KG/CM2 SKIN PASS The annealed cold rolled strip is very limited in its usage because of the yield point phenomenon. When annealed strip is processed in the dead soft condition, it tends to yield unequally manifesting luder lines or stretcher strains. This is the process manifestation of the break in the stress strain curves. If luder lines are to be avoided, this thing has to be smoothened as shown in the adjacent curve. This is achieved by the process of skin pass where the strip is given a very minor reduction of the order of 1. % max elongation. This makes the strip surface tough but the interior of the strip retains the softness so that when further drawing operations are carried out, the strip forms smoothly without any evidence of luder lines. The other advantages of temper rolling are as follows: ? Providing desired finishes such as matt or bright on the strip surface ? Imparting flatness to the strip ? Breaking up spangles from galvanized strip Skin pass process:- |[pic] |
Skin pass is a process of applying a regulated and very low load on the material in the mill it self. The reduction of thickness in skin pass is just below 5% reduction. The skin pass operation is a single pass operation unlike reduction in the rolling mill. The operation is similar to rolling but only one pass from pay off reel to delivery reel is giving with minimum load and with required surface finish work rolls and with proper tension. Anticrimping rolls are used in the skin pass for good shape control and to go flat surface. Surface roughness of the material is measured with the help of surface roughness checking unit i. . ,SURTRONIC-10. After the skin pass a sample is taken from the strip and it is sent to quality assurance department to find out the different properties like UTS,YS,elongation,hardness,drawability and bending. QUALITY ASSURANCE DEPARTMENT Various mechanical test has to be done on the sample taken from the product(coil) to prove its quality. The various machinery in use,in QAD are • Vacuum spectroscopy • Rockwell Hardness Machine • Vickers hardness machine • Universal testing machine • Ericsson testing machine • Optical microscope. HARDNESS TEST:
Hardness is defines as “Resistance of metal to plastic deformation, usually by indentation. However, the term may also refer to stiffness or temper, or to resistance to scratching, abrasion, or cutting. It is the property of a metal, which gives it the ability to resist being permanently, deformed (bent, broken, or have its shape changed), when a load is applied. The greater the hardness of the metal, the greater resistance it has to deformation. There are three types of tests used with accuracy by the metals industry; they are the Brinell hardness test, the Rockwell hardness test, and the Vickers hardness test.
ROCKWELL HARDNESS TEST: The Rockwell Hardness test is a hardness measurement based on the net increase in depth of impression as a load is applied In the Rockwell method of hardness testing, The indenter may either be a steel ball of some specified diameter or a spherical diamond-tipped cone of 120? angle and 0. 2 mm tip radius, called Brale. The type of indenter and the test load determine the hardness scale(A, B, C, etc) A minor load of 10 kg is first applied, which causes an initial penetration and holds the indenter in place. Then, the dial is set to zero and the major load is applied.
Upon removal of the major load, the depth reading is taken while the minor load is still on. The hardness number may then be read directly from the scale. SCALES AND VALUES: The different scale used for different materials are tabulated as follows: |Various Rockwell scales | |Scale | VICKERS HARDNESS TEST: Vickers hardness is a measure of the hardness of a material, calculated from the size of an impression produced under load by a pyramid-shaped diamond indenter.
Devised in the 1920s by engineers at Vickers, Ltd. , in the United Kingdom, the diamond pyramid hardness test, as it also became known, permitted the establishment of a continuous scale of comparable numbers that accurately reflected the wide range of hardnesses found in steels. The indenter employed in the Vickers test is a square-based pyramid whose opposite sides meet at the apex at an angle of 136?. The diamond is pressed into the surface of the material at loads ranging up to approximately 120 kilograms-force, and the size of the impression (usually no more than 0. 5 mm) is measured with the aid of a calibrated microscope.
The Vickers number (HV) is calculated using the following formula: HV = 1. 854(LD2) [pic] with L being the applied load (measured in kilograms-force) and D2 the area of the indentation (measured in square millimetres). The applied load is usually specified when HV is cited. As a result of the latitude in applied loads, Vickers testers is applicable to measuring the hardness of very thin sheets as well as heavy sections. The specimen is taken from the strip and indentation is done by using both vicker and Rockwell and then the values of Vickers and Rockwell is tabulated .
TENSILE TEST:- Tensile test is done to know the tensile strength, yield strength and percentage elongation of the material whether they are in specified limits of the customer tolerances are not. Tensile test values apply to transverse specimen in case of sheets/strips. Strips having a width of 250mm and below shall be tested longitudinally. UNIVERSAL TESTING MACHINE [pic] PROCEDURE:- Tensile test is widely used to determine strength, ductility, toughness, resilience and several other material properties.
A test specimen of rectangular crossection of 20mm width of suitable length is prepared from the material to be tested. During the preparation of the sample to avoid sharp sides by deburring the sample with the help of file, this reduces the chances of failures of specimen at low stress values. After this the specimen is held by suitable means between the two heads of a testing machine and subjected to a progressively increasing tensile load till the specimen fractures. A record of the load acting on the specimen with progressive extension of the specimen is obtained.
YIELD STRENGTH:- Most non ferrous materials and high strength steels do not possess a well defined yield point. For these materials the maximum useful strength is the yield strength. The yield strength is the stress at which the material exhibits a specifies limiting deviation from the proportionality of stress to strain. This value is usually determined by the “off-set method”. The value of off-set method is generally between 0. 1 and 0. 2 % of the gauge length. The value of yield strength can be calculate by YS = ((DIVISIONS * LOAD) / (WIDTH * GAUGE)) = ………..
N/sq. mm Here, the divisions are obtained from the graph between stress and strain given by the UTS machine. The experimental values are tabulated. DUCTILITY: The ductility of material is indicated by the amount of deformation i. e. , possible until fracture. This is determined in tension test by two measurements ELONGATION: This is determined by fitting together, after fracture, the parts of the specimen and measuring the distance between the original gauge marks Elongation=(Lf-Lo)/ LoX100
Where Lf-Final gauge length Lo- Original gauge length In reporting percentage elongation, the Original gauge length must be specified since the percentage elongation will vary with gauge length Elongation is carried out in UTS machine and the values are obtaines in either 50 GL 80 GL. The experimental values are tabulated: ULTIMATE TENSILE STRENGTH: The value of ultimate tensile strength gives the maximum stress that the strip can with stand before fracture and this value can be calculated by the graph obtained from the universal testing machine.
The graph plotted in between the load applies and strain. UTS = (LOAD/(WIDTH * GAUGE)) = ………. N/sq. mm EXPERIMENTAL DATA Mechanical Properties: | |S/P ID |MIDDLE |S/P OD | |COIL NO |83215-A |83215-A |83215-A | |SIZE |492 X 1. 8 |492 X 1. |492 X 1. 8 | |QUALITY |D |D |D | |SPECIFICATION |S/P (ID) |CTL (M) |S/P (OD) | |GAUGE |2. 0 |1. 8 |1. 78 | |WIDTH |20. |20. 2 |20. 3 | |LOAD |14000N |10206N |12370N | |UTS |348. 25N/sq. mm |320. 72N/sq. mm |342. 37N/sq. mm | |HRB |59 |57 |57 | |YS |250. 7N/sq. mm | |271. 25N/sq. mm | |ELONGATION | | | | |80GL |41 |40 |38 | |50GL |47 |46 |44 | |S/P ID |MIDDLE |S/P OD | |COIL NO |83312-A |83312-A |83312-A | |SIZE |408 X 1. 2 |408 X 1. 2 |408 X 1. | |QUALITY |EDD |EDD |EDD | |SPECIFICATION |S/P (ID) |CTL (M) |S/P (OD) | |GAUGE |2. 4 |1. 22 |1. 29 | |WIDTH |20. 2 |20. 3 |20. | |LOAD |14000N |6870N |7470N | |UTS |288. 77N/sq. mm |277. 39N/sq. mm |285. 25N/sq. mm | |VPN/RHN |75 |42/43 |44/45 | |YS |235. 14N/sq. mm |214. 81N/sq. mm |265. 14N/sq. m | |ELONGATION | | | | |80GL |40 |41 |41 | |50GL |46 |47 |47 | COLD ROLLED SLITTING The width of the coil at the time of HR Slitting is planned such that the width at which the material is rolled will be generally in multiples of the requirements.
Also at the time of rolling the edges of the sheet will be damaged. So in order to remove the spoiled edges the cold roll slitting is done. The slitting of the coil is done according to work order. The main purpose of slitting is to ensure that:- 1. width is always as per the W. O requirements and the properties are also ensured 2. sufrace of the strips on both sides is to be ensured as free from defects such as rust, pits, holes,scales,dents,unslit edges, laminations,patches,scratches,scoring and other defects which disturbs the end products 3. hape,cambers and other requirements has given in the W. O are totally ensured. 4. Rust preventive oil is applied uniformly on all sheets or wraps. PROCESS: The coils are placed on the coil car by EOT cranes. The coil mandrel is expanded to grip the coil and binding strap is cut. The uncoiler is inched by the inched drive and the load end is separated from the coil. The load end is taken to the entry pinch roll, hold down roll is lifted and further threading is done by jogging pinch roll drive. [pic] | Side guide is adjusted to the correct width. The slitter drive is jogged and load end is passed ahead of the slitter. The loop pit table is transverse over the pit by jogging slitter. The slit stands are taken to drag wise over the loop pit table which is separated and threaded to recoiler. The slit stands are passed properly in the rewind mandrel. The drag vice is closed and few wraps are taken by jogging and the recoiled is under low tension.
The scrap is threaded to scrap winder and initially winding is done by jogging the drive. The machine can be run at a required speed The CRS machine is chosen as per the specifications of the machine for which the gauge of the sheet forms the important criteria. The specifications of different CRS machines are as follows: CRS I: MAKE : M/S DAS NAGAR, KOLKATTA SPECIFICATIONS : I/P COIL THICKNESS : 0. 25 to 6mm max ID : 500mm OD : 1800mm MAX COIL WT : 10MT
O/P COIL WIDTH : 20mm to 710mm NO OF SLITS : 7 max TOL : +/- 0. 15 ID : 400/500mm OD : 1800mm CRS II: MAKE : M/S BOMBAY CRANES PVT. LTD, MUMBAI SPECIFICATIONS : I/P COIL THICKNESS : 100mm to 7. 2mm max ID : 500mm OD : 1800mm MAX COIL WT : 10MT O/P COIL
WIDTH : 20mm to 710mm max NO OF SLITS : 7 max TOL : +/- 0. 15 ID : 500mm OD : 1800mm CRS III: MAKE : LYKA INDUSTRIES, KOLKATTA SPECIFICATIONS : I/P COIL THICKNESS : 0. 3 to 1. 2mm ID : 400(500mm) OD : 1600mm MAX COIL WT : 2MT O/P COIL
WIDTH : 6mm to 250mm ID : 400(500mm) OD : 1500mm NO OF SLITS : 7 max TOL : + / – 0. 15 CUT TO LENGTH After slitting of CR coils in slitters into required sheet form, it will taken into the C. T. L Units. The coil is fed through leveler and copped to the length required by the customer. The length, width, thickness, quality and the visible defects are checked by the quality department persons.
The finished sheets and strips shall be free from harmful defects, such as scale, rust, blisters, laminations, pitting, porosity, cracks or torn edges or any other defects which are harmful to the intended use. The degree or amount of surfaces defects in a coil may be expected to be more than in cut length because of the impossibility of rejecting portions of the coil. This shall be taken into account by the purchaser in his assessment of the material. An excessive amount of defects may lead to the rejection of lot. The sheets shall be reasonably flat and edges cleanly sheared and squared to the specified dimensions.
The CTL machine is selected according to the work order i. e. the gauge and size required. The specifications of the machines are: CTL I: MAKE : TATA DAVY LTD. , KOLKATTA MIN WIDTH : 30mm THICKNESS : 0. 4mm LENGTH : 340mm I/P COIL ID : 400/500mm COIL WEIGHT : 7. 5MT max MAX WIDTH : 685mm THICKNESS : 3. 1mm LENGTH : 3000mm I/L COIL OD : 1800mm CTL II: MIN WIDTH : 30mm THICKNESS : 2. 0mm LENGTH : 400mm I/P COIL ID : 400/500mm COIL WEIGHT : 7. 5MT max
MAX WIDTH : 720mm THICKNESS : 6. 5mm LENGTH : 3500mm I/L COIL OD : 1800mm CTL III: MAKE : M/S GODREJ, MUMBAI MIN WIDTH : 70mm THICKNESS : 0. 2mm LENGTH : 450mm I/P COIL ID : 500mm COIL WEIGHT : 7. 5MT max MAX WIDTH : 720mm THICKNESS : 1. 6mm LENGTH : 4500mm I/L COIL OD : 1800mm DESPATCH Sheets and strips shall be supplied in coils or bundles of cut length or in packages each weighing not more than three tones as may be agreed the purchaser and the supplier.
Sheets and strips shall be packed in water proof paper or polythene lined Hessian and securely tied around with hoop iron. A number of coils may be bundled with wooden patterns in between or may be packed in wooden boxes. Strips may also be packed with separate thin metallic sheets wrapped around and with bands of hoop iron. ———————– PICKLING HR SLITTING INSPECTION RAW MATERIAL ROLLING ANNEALING SKIN PASS MATERIAL TESTING CR SLITTING CUT TO LENGTH PACKING & DESPATCH