CRAP LINE

Presented By…..

Chandan kr. Singh

KEY SECTIONS OF LINE

TECHNICAL SPECIFICATIONS OF CRAP LINE

BASIC TECHNICAL DATAType: Continuous Annealing Pickling Line.Line Direction: Right to Left Line speed: 10 – 60/80 m/min – Uncoiler section 10 - 60 m/min – Process section 10– 60/80 m/min - Recoiler sectionMaterial: Cold rolled Stainless Steel Strip, (AISI 200, 300 and 400).Strip width: 850 mm - 1,280 mm Strip thickness: 0.4 - 4.0 mmCoil weight: 20,000 kg max. Exclusive. sleeve and interleaving paper Coil ID: 610 mm (nominal) ,660 mm (With Adapter)Coil OD : 1829 mm max / 850 mm min.Length of C-APL approx. 400 m 

ENTRY SECTION

Entry Coil Storage Saddle :

Capacity :20,000 kg.

Coil OD : 1829 mm max / 850 mm min.Entry Coil Car : Lift capacity 20,000 kg.Uncoiler 1 :

Coil ID :585mm , Coil OD : 1829mm

Expand diameter:785 mm, Collapse diameter 585 mm. Uncoiler 2 :

Coil ID : 590 mm , Coil OD: 1300 mm

Expand diameter: 650 mm, Collapse diameter 585 mm.

BRITISH FEDERAL LAP SEAM WELDING MACHINE

Specification:

- Application - For Welding Strip ends on continuous AP line.

- Material to be welded - Cold rolled stainless steel (uncoated)

- Strip Width - 600 mm (min) - 1600 mm (max)

- Strip Thickness - 0.20 mm to 1.6 mm

- Max. Capacity of welder - 1600 mm wide x 1.6 mm thick- Max. strip clearance - 1700 mm x 150 mm.

- Type and quality of Weld - Overlap seam weld.

- Direction of Weld - Right to left

- Overlap adjustment range- 0.5 mm to 6.0 mm

- Rating - 250 KVA

DEGREASING SECTION Alkali Cleaning Tank Hot Water Rinse Tank Hot Air Dryer

THICKNESS OF THINNER SHEET FORCE

HYD PRESSURE IN BAR

WELD ON TIME (CYCLE) HEAT(%) TAP NO

0.4 150 7.5 8 65% 2

0.5 185 9.25 8 65% 2

0.7 275 13.75 8 65% 2

0.9 340 17 8 65% 2

1.2 550 27.5 8 65% 2

1.6 685 34.25 9 70% 2

2 865 43.25 12 70% 2

2.4 1000 50 14 70% 2

PARAMETERS OF WELDING MACHINE

ENTRY ACCUMULATOR SECTIONThis is an arrangement used for accumulating the strip for uninterrupted operations of the process while joining the two coil ends together in order to make the strip continuous.

The storage capacity is 330 meters.

FURNACE TECHNICAL SPECIFICATIONOVERALL DIMENSION.

Total length from entry -seal to exit seal roll 72.510 metersLength of furnace no 1. 14.600 metersLength of furnace no 2 14.600 meters Length of furnace no 3. 18.760 meters Length of furnace no 4. 18.760 metersWidth inside furnace No 1 & 2. 3.438 metersWidth inside furnace No 3 & 4. 2.638 meters

NO OF FURNACE

NO OF HEATING ZONES

NO OF BURNERS EACH ZONES

TYPE OF BURNERS

TOTAL NO OF PILOT BURNERS

NO OF REGENRATIVE BOX

F#1

F#2 3 4,4,4 10 No's- 60/80 Therm / 2 No's –EJ18

12 NOS 12 NOS

F#3 3 4,4,4 12 NOS 60/80 THERM

12 NOS 12 NOS

F#4 3 4,4,5 4 NOS-60/80NA,9 NOS -20 THERM

12 NOS 4 NOS

Thickness (mm)

Zone 4 in °C

Zone 5 in °C

Zone 6 in °C

Zone 7 in °C

Zone 8 in °C

Zone 9 in °C

Zone 10 in °C

Zone 11 in °C

Zone 12 in °C

0.38 - 0.55 1000 1000 1000 1170 1190 1170 1160 1180 1160

0.56 - 0.65 1130 1150 1130 1190 1210 1190 1160 1180 1160

0.66 -0.83 1150 1170 1150 1210 1220 1210 1180 1200 1180

0.84 - 4.10 1170 1190 1170 1210 1220 1210 1180 1200 1180

FURNACE TEMPERTURE FOR 300 SERIES

Thickness (mm)

Zone 4 in °C

Zone 5 in °C

Zone 6 in °C

Zone 7 in °C

Zone 8 in °C

Zone 9 in °C

Zone 10 in °C

Zone 11 in °C

Zone 12 in °C

0.38 - 0.55 920 940 940 960 960 960 950 950 950

0.56 - 0.65 950 960 960 980 980 980 980 980 980

0.66 -0.83 980 980 980 1000 1000 1000 1000 980 980

0.84 - 4.10 1020 1020 1020 1050 1050 1050 1080 1050 1050

FURNACE TEMPERTURE FOR 200 SERIES

QUENCHING SECTION

Air flow to air quench Water and air flow to caster jets Water flow to water quench

Total length of quenching section 48.000 mtrs

Length of Air Quenching section. 22.900 mtrs

Length of 12 Pair caster jet 14.500 mtrs

Length of Water quench. 5.300 mtrs

Length of Dryer 1.750 mtrs

Length of Dryer (Future Scope) 3.550 mtrs

Max working pressure 3.5 bar

PICKLING SECTION

This process section of the pickling line consists mainly of the following treatment stages:Neutral electrolytic pickling with Na2SO4

Mixed acid picklingScrub brush machine with PP brushesFinal rinse with scrub brush machineEdge Blow-Off Device and Strip drier

OVERALL DIMENSION OF PICKLING SECTION 

Total length of pickling section 88.290

mtrs

Length of Electrolytic section. 42.660

mtrs

Length of Mixed acid section. 27.917

mtrs

Length of Squeeze & Brush Section 10.255

mtrs Length of Dryer 1.750

mtrs

ELECTROLYTIC PICKLING SECTION

Specification details:No of Tanks : 03 Tank Capacity :13 m³Anode type : flat mild steel covered with lead Set of Anodes : 24 set (8 set in each tank each set consists of a separate electrode for upper & a separate electrode for lower side).Cathode type : Stainless steel (AISI 316)Set of Cathodes :48 set (16 set in each tank each set consists of a separate electrode for upper & a separate electrode for lower side) Electrolyte circulation system, consisting of:

No of Circulation tanks : 03 Tank capacity : 35 m³ each

No of circulation pump : 09

No of sump pump : 02

No of Heat exchanger : 02

Electrolytic pickling section with Sodium sulphateNeutral electrolyte : 150- 220 Na2SO4 g/l Operating Temperature : 70 – 85 Deg CHeating and Cooling : In direct by heat exchangerRectifier : 1 Sets - 8,000 A Current Density : 8 to 10 Amp /dm²

• GOAL: Convert the stable Cr3+ to the soluble valence Cr6+

Anode reactions: Cr3+ => Cr6+ + 3e-

2H2O => O2 + 4H+ + 4e-

Cathode reactions : 2H2O + 2e- => H2 + 2 OH- + 2e-

NEOLYTE SECTION /THEORY

LAYERS OF STAINLESS STEEL (ANNEALED )

Oxide layer (iron-, chroium oxides etc.)

Cracks and pores

Annealed stainless steel surface

Chromium depleted zone approx. 1/100 mm

Normal chrom. content > 18% Cr

Oxide 50-60% Cr2O3

20-25% Fe2O3 + Fe3O4

5-10% MnO2

5-10% SiO2

3-5% NiO

Chromium depleted zone < 10% Cr

PICKLING OF STAINLESS STEEL

Stainless steel surface

Annealed

Electrolytic pickling

Mixed acid pickling

Final product

NEOLYTE PARAMETERS

Neolyte Bath Parameter Aim Range

Specific Gravity 1150 1120 - 1180

pH 7 6 - 8

Temperature (0C) 65 60 - 70

Bath Current (kA) 4.5 -

Brush Current (A) 20 16 - 20

Re-circulation Flow (m3/hr) 2 x 100 -

Re-circulation Pressure (bar) 3 -

MIXED ACID SECTION

Specification details:

No of Tanks : 02 Tank Capacity : 12 m³ Mixed acid circulation system, consisting of:

No of Circulation tanks : 02

Tank capacity : 26 m³ each

No of circulation pump : 06

No of sump pump : 02

No of Heat exchanger : 02

20 | 15 April 2023 | Avesta Research Centre, Process Chemistry

Pickling

Only nitric acid (HNO3) is ”operating”

+

+

+

+

+

+

+ + + + + + + + + + + + + + + +

+ + + + + +

+++

+ + + +++

+

HNO3 penetrates the cracks/pores in the oxide

The chemical dissolution of the chromium depleted zone ceases when the concentration of Fe3+ is high enough

2 Fe + 3 NO3- + 6 H+ 2 Fe3+ + 3 NO2

- + 3 H2O

Pickling

+ + + + + + + + + + + + + + + + + + + + + + +

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# # ## # #

#

#

#

#

#

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# #

#

Both HNO3 and HF are operating!!!

The positive iron ions (+) reacts with hydro fluoric acid forming complex ions (#) allowing HNO3 to continue dissolving the chromium depleted zone. The nitrous fume contributes to the scale breaking.

Clean surface Fe3+ + 2 HF FeF2

+ + 2H+

Fe3+ + 3HF FeF3 + 3H+

2 NO2- + 2H+ NO + NO2 + H2O

ACID BATH PARAMETERSAcid Bath Parameter Aim Range

HNO3 Concentration 135g/l (13.5%) 120-145g/l (12-14.5%)

HF Concentration 36g/l (3.6%) 32-40 (3.2-4%)

Temperature (0C) 60 55-65

Metals (g/l) 25 25-30

Re-circulation Flow (m3/hr) 2 x 200 -

Re-circulation Pressure (bar) 2  

Tank Turbulence 100% 100%

• One pump on duty, one pump on standby• Flow rate – 270 l/min • 4 spray bars on duty (2 top, 2 bottom) and 4 spray bars on standby • Water pressure – 95-110 bar• Water temperature – ambient• Contamination – non-recirculating system

LOW PRESSURE RINSE• Flow rate – 25m3/hr• Water pressure – 2 bar

• Contamination – HNO3 25g/l (2.5%) max; HF 5 g/l (0.5%) max; Metals 5g/l max.

• Brushes – 16 to 20 amps

Dryer • To remove water content from the sheet.

HIGH PRESSURE RINSE

EXIT ACCUMULATOR SECTION

This is an arrangement used for accumulating the strip for uninterrupted operations of the process when the exit section is stopped for removing the welded joint, unloading the coil from recoiler mandrel, loading the sleeve on the mandrel and wrapping the lead end of new coil on the recoiler mandrel.

The storage capacity is for 180 mtrs.

EXIT SECTION

Recoiler:

Coil ID : 660 mm

Maximum coil OD : 1850 mm

Minimum Coil OD : 850 mm

Maximum coil weight : 22000 kg.

Exit Coil Car :

Exit Coil Storage Saddle

Tension Unit Factors:- Uncoiler - 0.3 -0.5 kg/Cm² Entry Accumulator- 0.8 -1.0 kg/Cm² Furnace - 0.5 -0.8 kg/Cm² Shot Blast - 0.8 -1.0 kg/Cm² Pickling - 1.2 – 1.6 kg/Cm² Exit Accumulator - 1.5 – 1.8 kg/Cm² Recoiler - 2.5 - 3.0 kg/Cm²

Formula For Calculating Tension:-

Width × thickness × unit factor = Tension

TENSION PARAMETERS

Thickness (mm) Speed (m/min)

0.4 60

0.5 60

0.6 60

0.7 60

0.8 60

0.9 60

1 54.5

1.2 45.8

1.5 37.9

LINE SPEED

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