Continuous Annealing Line and Electrolytic Tinning

Line

JSW STEEL COATED PRODUCTS Ltd. Tarapur

Total Capacity : 0.75 MTPA. Source coils : Vijaynagar and Dolvi.

India’s largest producer and exporter of Coated Products

The plant has 5 cold rolling mills and five coated strips division (two dual pots galvanizing cum galvalume lines, two colour coated lines and a 30 MW captive power plant)

Specialized in Galvanizing , Galvalume and colour coated steels.

H.R. SLITTING

PICKLING

H.R. COILS

COLD ROLLING

GALVANIZE

GALVALUME

DISPATCH

COLOUR COATING

PROFILING

CORRUGATED SHEET

WHY CAL?

Uniformity of products

Large production volumes

Less labor requirement

LINE SPECIFICATION:Type : Continuous annealing line

Furnace Capacity: Grade Ref size(mm)

Speed (mpm)

Capacity(TPH)

T3 1000*0.2059

374.4 38.8

T2.5 1000*0.1991

398.3 37.5

T2 1000*0.1926

385.2 36.3

T1 1000*0.1801

400 33.9

T4/T5 1000*0.2317

370.7 43.7

DR08/DR10

1000*0.2253

391.8 42.4

Fuel : RLNGLCV : 8500Kcal/Nm^3

MATERIAL SPECIFICATION:Weight 5000 – 25000 kg

Inner diameter 508 mm

Outer diameter 900 – 2000 mm

Strip thickness 0.14 – 0.6 mm

Strip width 650 – 1250 mm

Tensile Strength 700 – 800 MPa

ANNEALING FURNACE Preheating section

Radiant tube section

Soaking Furnace(SF)

Rapid Cooling Section(RCS)

Overaging sections(OA)

Final cooling section(FC)

Water quenching section(WQ)

Typical annealing cycle in a CAL

STEEL GRADE

Heating exit

SF RCS OA FC WQ

Temp( C)

Temp( C)

Time(s) ExitTemp(C)

Enter Temp(C)

Exit Temp(C)

Time(s)

Temp(C)

Temp(C)

T3 710 710 20 400 400 380 60 <=140 45

T2.5 720 720 20 400 400 380 60 <=140 45

T2 730 730 20 400 400 380 60 <=140 45

T1 750 750 20 400 400 380 60 <=140 45

T4-T5 670 670 20 - - 360 - <=140 45

DR8-DR10 680 680 20 - - 360 - <=140 45

Thermal cycle

0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.650

50

100

150

200

250

300

350

400

450

PRODUCTION CURVE

T3T2.5T2T1T4/T5DR08/DR10

strip thickness(mm)

Lin

e sp

eed(

mpm

)

Effect of annealing(at different temperatures) on Hardness

ELECTROLYTIC TINNING LINE

ELECTROLYTIC TINNING LINE

PROCESS DESCRIPTION:

• Entry Section : (Entry coil car, Welder, Accumulator, Bridle units, Deflector rolls, Pinch rolls, Steering system, CPC)

• Process Section : (Cleaning section, Pickling Section, Tin Plating section, Reflow of tin, Chemical Treatment Section, TFS section)

• Delivery Section (exit) : (Vertical Inspection System ,Exit accumulator, Exit thickness gauge, Exit snip shear, automatic edge position control, Tension reel, Exit coil cars)

Processes incurred in an ETL :

• Cleaning and Pickling : removing loose particles and rolling oils

Cleaning/Pickling Process : Electrolytic Cleaning/Pickling Current : 18000 A – 32 V

• Tin Plating :

12 vertical tanks, 9 for electroplating and 3 (for drag and rinse) Plating Process : Phenol Sulfonic acid Plate(PSA & Future provision for MSA) Plating Current : 153000 A – 32 V with 16 % plating efficiency

Electrolyte : Phenol Sulphonic Acid (PSA)

• Reflow :

Reflowing involves reheating the tin above its Melting Point(231C/450F) reduces the internal stresses improves the bond between the tin plating and the base material. provides good thickness uniformity and a glossy surface finish. Parts treated with reflowed tin exhibit excellent corrosion resistance. increase its solderability.

• Quench Tank : for lowering strip temperature to 45oC

Temp in/out (oC) 50/275

Power in strip (kW) 1000

• Chemical Treatment :

to stabilize the tin oxide layer (formed during induction reflow in the presence of air) by electrolytic treatment with sodium dichromate.

Temperature : 44-58 oC

• Oiling :

The clean, dried strip passes through an electrostatic oiler in which the required amount of lubricant is deposited.

• TIN FREE STEEL (TFS) Section : apply coatings of metallic chrome and chrome hydroxide on

the steel strip surface.

• Tin Free Steel :

Tin free steel (TFS) is composed of four layers, including steel base, metallic chromium layer, chromium oxide layer and oil film

INCOMING Coil Characteristics :

Material Medium and low carbon steel , cold rolled and tempered (EN 10202:2001)

Steel Grades • SR: T1 – T5 DR: DR480, DR8, DR9, DR10

Yield Strength • SR: 230 – 550 N/mm2

DR: 350 – 700 N/mm2

Coil weight 25 ton (max)I.D 508mmO.D 914-1950 mmSurface iron and oil 75-150 mg/m2 per side

OUTGOING Material Characteristics :

Material Tin Plate and TFSCoil weight 25 ton(max.)I.D 420/508mmO.D 914 - 1950 mmCoating Type Tin Plate(PSA & Future provision for

MSA) and TFS(2 steps)Coating weight Tinplate

0.56 to 16.8 g/m2 per sideTFS 50 to 140 mg/m2 per side(Chromium) 7 to 35mg/m2 per side (Chromium in Oxide)

Chemical Treatment • Sodium Dichromate 2 – 10 mg/m2 ,Cr each side (for 311 type) 1 – 3 mg/m2 ,Cr each side (for 300 type)

Entry section speed 500 m/min

Process section speed 400 m/min.

Exit section speed 500 m/min

Acceleration/Deceleration rate 45 m/min/s

Technical Data :

An alternative approach :

MSA as an electrolyte (instead of PSA) :

The MSA bath is a plating bath which is composed mainly of methane sulfonic acid (CH3SO3H) and Sn2, and has the following features:

• . Sludge generation is small

• Because the main components of the sludge are Sn(OH)4 and SnO2, recycling is easy.

• The proper electrolysis current density (10– 55A/dm2) is wide

Pitfalls of using an MSA bath :

• The MSA bath is strongly corrosive (pH 1).

• The unit cost of the electrolyte is extremely high in comparison with the halogen bath.

Thank You

Himanshu Sankhe