Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
COLD ROLLED GALVANIZED STEEL STRIP WITH SPECIFIC SURFACE COATING THICKNESS REQUIREMENT FOR GALVANIZED WIRE APPLICATION.



2 APPLICANT (S)

Name : JSW STEEL COATED PRODUCTS LIMITED.

Nationality : An Indian Company incorporated under the Companies Act, 1956.

Address : JSW CENTRE,
BANDRA KURLA COMPLEX,
BANDRA(EAST),
MUMBAI-400051,
MAHARASHTRA,INDIA.



3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION

The present invention relates to a cold rolled Galvanized Steel strip and more specifically to Galvanized, Non skin pass, Stretch leveled, 0.5 mm thick, Zinc Coating 420 GSM, AS PER IS 277 Galvanized Plain (GP)_250 Grade for the application galvanized wire.

BACKGROUND OF THE INVENTION

Galvanizing is a technique of providing a protective Zinc coating on Steel or iron, to prevent it from rusting.Hot-dip galvanizing is one of the most common forms of galvanizing. There is requirement of high zinc coating weight in lower base metal thickness with specific Top: Bottom zinc coating weight ratio. This current invention is about overcoming the challenges to achieve the end requirement with Z420 GSM coating in 0.44mm cold rolled thickness, as per IS 277 Galvanized Plain (GP)_250 Grade.

CN110257747B(2021-04-30) disclosed an ultrathin coating hot-dip galvanized steel plate and a manufacturing process thereof. The manufacturing process of the ultrathin coating hot-dip galvanized steel plate comprises the following steps: s1, adopting an assistant plating solution with the temperature of 60-70 ? to carry out assistant plating treatment on the steel plate which is sequentially degreased, washed and pickled for 2-2.5 min; s2, carrying out hot air drying and annealing treatment on the steel plate; s3, placing the steel plate into a zinc pot, wherein the temperature of zinc liquid in the zinc pot is 435-440 ?, the hot dipping time of the steel plate is 3-6S, and then performing air knife blowing, cooling and hot air drying on the steel plate in sequence; and S4, soaking the steel plate in a passivation solution with the pH value of 2-5 for 15-30S, drying at 80-100 ? after passivation, and cutting, curling, uncoiling and packaging to obtain the ultrathin coating hot-dip galvanized steel plate. The preparation process has the advantages of good zinc liquid fluidity, strong adhesive force, thin thickness of the prepared galvanized layer, and difficult shedding and stripping. This document does not target Z420 GSM coating in 0.44mm cold rolled thickness, with specific Top: Bottom zinc coating weight ratio as per IS 277 Galvanized Plain (GP)_250 Grade.

CN105437653B(2017-09-15) discloses a kind of super thick galvanizing wire drawing clad steel sheet, including steel substrate, and wire-drawing surface is followed successively by passivating film, hot dip galvanizing coating, steel substrate from outside to inside;Non- wire-drawing surface is followed successively by passivating film, hot dip galvanizing coating, steel substrate from outside to inside, and hot dip galvanizing coating composition is Al0.7wt%~1.5wt%, and Si0.4wt%~1.2wt%, Fe0.1wt%~wt0.5%, surplus are Zn;Wire-drawing surface thickness of coating >=25 µm, not 10 µm~20 µm of wire-drawing surface thickness of coating, hot dip galvanizing coating case hardness is HV110~HV160, wire-drawing surface transverse direction Ra=0.6 µm, Rz=6,180 >=Rpc >=120 (/cm). This document is having different hot dip galvanizing coating composition and does not target Z420 GSM coating in 0.44mm cold rolled thickness, with specific Top: Bottom zinc coating weight ratio.

CN114959441 A (2022-08-30) disclosed Hot stamped steel plate, manufacturing method of hot stamped component comprising the same, and application thereof in automobile parts wherein steel plate comprises a substrate and a coating (pure Zn coating, Zn-Fe alloy coating with the Fe content of 10-20 wt%, etc.) on the substrate. The substrate comprises (by mass percentage) C 0.01-0.1, Si 0.01-1.0, Mn 0.30-1.6, P 0-0.1, S 0-0.05, Al 0.01-0.05, N 0-0.01 and Fe in balance. This patent does not deal with thin sheet for wire application more specifically with Z420 GSM coating in 0.44mm cold rolled thickness, as per IS 277 Galvanized Plain (GP)_250 Grade.

CN113215485 A (2021-08-06) disclosed hot-dip coated dual-phase steel for automobile application which is 780 MPa grade hot-based coated dual-phase steel comprises (by wt%) C 0.04-0.08, Si 0.5-0.8, Mn 1.4-2.1, Al 0.02-0.50, Nb 0.04-0.07, Ti 0.05-0.14, Cr 0-0.25, Cu 0-0.01, Ni 0-0.01, B 0-0.001, P 0-0.015, S 0-0.001, Fe bal. The preparation method includes (1) heating plate blank at 1,230-1,270°C for 120-180 min, and hot rolling at rough rolling start rolling temperature of 1,130-1,190°C, rough rolling final rolling temperature of 1,080-1,140°C, finish rolling start rolling temperature of 1,030-1,060°C and finish rolling final rolling temperature of 890-930°C. (2) Water cooling to 620-670°C, air cooling for 6-10 s, water cooling to 460-500°C, coiling at 460-500°C, slowly cooling, uncoiling, and pickling. (3) Preheating to 220-240°C, heating to 600-660°C, soaking for 35-200 s, cooling to 430-470°C, and hot-dip coating zinc/zinc-magnesium-aluminum at 430-470°C to obtain the final steel. The steel has high strength grade, good formability and excellent corrosion resistance, and is particularly suitable for production of automobile components. This patent is also not intended for galvanized thin sheet for wire application more specifically with Z420 GSM coating in 0.44mm cold rolled thickness, as per IS 277 Galvanized Plain (GP)_250 Grade.

IN201811036417 A (2020-04-03) disclosed thin, uniform, dense ad adherent ceramic Cr-C coating with thickness of 10µm -200µm on the stainless steel of grade 316L material electrodeposited from environmentally acceptable trivalent chromium (Ill) electrolyte bath with optimized conditions within less than 10 min and high c.d. Very thin micro-electrodeposited ceramic Cr-C coating exhibited excellent liquid corrosion resistance in molten metal Zn or Zn alloy due to its non-reactive and non-wettability characteristics, high contact angle (145-155°), good thermal shock resistance, high hardness, good fracture toughness, anti- delamination or spalling tendency, less number of crack d., high adhesive strength and thermal stability in hot dip galvanizing baths like Zn (Pure zinc, at 460°C), Zn-0.2wt.%Al (Galvanize, at 460°C), Zn-5wt.%Al (Galfan, at 480°C) and Zn-55wt.%Al-I.5wt.%Si (Galvalume, at 600°C). This invention deals with thin Cr-C coating with thickness of 10µm -200µm on the stainless steel of grade 316L material electrodeposited with high adhesive strength and thermal stability in hot dip galvanizing baths. This is not intended for wire application.

Thus none of the prior art documents meet the requirement of high zinc coating weight in lower base metal thickness with specific Top: Bottom zinc coating weight ratio. This current invention is about overcoming the challenges to achieve the end requirement with Z420 GSM coating in 0.44mm cold rolled thickness, as per IS 277 Galvanized Plain (GP)_250 Grade, as targeted by present invention.

OBJECTS OF THE INVENTION

The basic object of the present invention is to provide galvanized, Non-Skin-pass, Stretch-level, steel strip of thickness 0.50mm, coating 420 GSM material as per IS 277 Galvanized Plain (GP)_250 and a process to produce the same.

A further object of the invention is to provide the above specific steel strip material adapted for application of galvanized wire.

A still further objective of the present invention is to achieve the Z420 GSM Coating with the specified top: Bottom ratio, avoiding edge built up and wavy issue.

A still further objective of the current invention is to overcome the possible challenges going to be faced during the trials and making the process smooth.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a cold Rolled Galvanized steel strip having steel composition comprising

C – 0.032 to 0.062 % by wt. preferably 0.036 % by wt;
Mn- 0.27to 0.4 % by wt. preferably 0.3 % by wt;
P-0.0 % to 0.025% by wt. preferably 0.012 % by wt;
S- 0.0 to 0.02 % by wt. preferably 0.015 % by wt;
Si-0.0 to 0.03 % by wt. preferably 0.008 % by wt;
Al- 0.025 to 0.05% by wt. preferably 0.04 % by wt;
optionally upto 0.001% Nb; and rest is iron;
which is Zinc coated with thickness in the range of 0.48 mm to 0.52 mm preferably 0.5 mm and is non-skin pass having Yield Strength – 250 MPa to 350 MPa preferably about 320 MPa Tensile Strength – 360 MPa to 480 MPa preferably about 390 MPa; and Elongation 20 % to 30% preferably minimum 20% in 50mm gauge length having matching specifications of IS 277Galvanized Plain (GP) 250.

A further aspect of the present invention is directed to said cold rolled galvanized steel strip which is non-skin pass and stretch levelled having thickness of 0.48 mm to 0.52 mm preferably 0.5 mm and zinc coating 430 GSM to 440 GSM preferably more than 420GSM and having top: Bottom coating ratio of 55:45, suitable for wire application..

A still further aspect of the present invention is directed to said cold rolled galvanized steel striphaving finish size of 0.48 to 0.52 x 1170 to 1175 preferably 0.5 X 1175..

A still further aspect of the present invention is directed to a process for manufacture of cold rolled galvanized structural steel strip as described above including:
i)providing HR coil of steel sheet having steel composition comprising
C – 0.032 to 0.062 % by wt. preferably 0.036 % by wt;
Mn- 0.27to 0.4 % by wt. preferably 0.3 % by wt;
P-0.0 % to 0.025% by wt. preferably 0.012 % by wt;
S- 0.0 to 0.02 % by wt. preferably 0.015 % by wt;
Si-0.0 to 0.03 % by wt. preferably 0.008 % by wt;
Al- 0.025 to 0.05% by wt. preferably 0.04 % by wt;
Optionally upto 0.001% Nb and rest is iron;
ii) carrying out HR coil slitting;
iii) subjecting to pickling for removal of the oxide layer;
iv)subjecting to cold rolling including mechanical working of mild steel material to below its recrystallization temperature such as to reduce the thickness at cold rolling mills;
v) subjecting to galvanizing involving (a) annealing (b) coating of cold rolled steel strip to increase corrosion resistance strip (c ) stretch levelling to impart antifluting property of galvanized steel strip and desired shape involving tensile stress and bending stress of thickness in the range of 0.48 mm to 0.52 mm preferably 0.5 mm and having Yield Strength – 250 MPa to 320 MPa preferably about 320 MPa Tensile Strength – 360 MPa to 480 MPa preferably about 390 MPa; and Elongation 20% to 30% preferably 20%min in 50mm gauge length.

A further aspect of the present invention is directed to said process wherein said step of cold rolling is carried out to obtain coils of sizes 0.44 x 1175 to 0.46 X 1180 preferably about 0.45 X 1175, weight 24.5 Mt to 30.5 Mt preferably about 24.965 Mt. , wherein input HR thickness is 2.46 mm to 2.54 mm preferably about 2.5 mm , output thickness 0.44 mm to 0.46 mm preferably about 0.45mm and achieve a reduction in the range of 80 % to 83 % preferably about 82 %.

A still further aspect of the present invention is directed to said process wherein said step of galvanizing is carried out involving a zinc bath comprising of Al % 0.14 % to 0.2 % preferably about 0.165 %, Pb % 0.02 % to 0.04 % preferably about 0.025 % and Fe % 0.024 % to 0.0265 % preferably about 0.025 % and rest is Zn.

Another aspect of the present invention is directed to said process wherein said step of galvanizing is carried out involving select temperature control in various furnace sections including select exit temperatures comprising in Non-ox Furnace (NOF) 600 0C to 700 0C preferably 6500C ,Radiant Tube Furnace (RTF) 725 0C to 780 0C preferably 7600C, soaking furnace 740 0C to 770 0C preferably 7600C and Jet Cooling Furnace (JCF) 470 0C to 490 0C preferably 4800C.

Yet another aspect of the present invention is directed to said process wherein said step of galvanizing involve furnace operative parameters including subjecting cold rolled coil of size of 0.44 x1175 mm to 0.46 x 1175mm preferably 0.45x1175 mm to line speed of 140 mpm to 150 mpm preferably about 145 meters per minute, 34 TPH to 38 TPH preferably about 36 Mt./Hrs, Furnace tension 880 Kgf to 1200 Kgf preferably about 1000 Kgf , Pot tension 1000 Kgf to 1500 Kgf preferably about 1200 Kgf, Air Knife RPM 1650 to 2500 RPM preferably about 2000 RPM, Air Knife Pressure 60 to 80 Mbar preferably about 75 Mbar and air knife gap 10~15mm preferably about 12mm.

The above stated and other aspects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting drawings and examples:

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: process flow chart for producing the galvanized steel according to present invention.
Figure 2: shows the graphical plot of Coil No VG3A2I0533 to VG3A2I0540, Showing Strip Temperature at Exit in Deg. Centigrade at different Furnace Sections – Non-ox Furnace (NOF), Radiant Tube Furnace (RTF), Soaking Furnace (SF) and Jet Cooling Furnace(JCF).

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS AND EXAMPLES

The present invention is directed to a cold Rolled Galvanized steel strip having steel composition comprising

C – 0.032 to 0.062 % by wt. preferably 0.036 % by wt;
Mn- 0.27to 0.4 % by wt. preferably 0.3 % by wt;
P-0.0 % to 0.025% by wt. preferably 0.012 % by wt;
S- 0.0 to 0.02 % by wt. preferably 0.015 % by wt;
Si-0.0 to 0.03 % by wt. preferably 0.008 % by wt;
Al- 0.025 to 0.05% by wt. preferably 0.04 % by wt;
optionally upto 0.001% Nb; and rest is iron;
The cold rolled steel strip is Zinc coated with thickness in the range of 0.48 mm to 0.52 mm preferably 0.5 mm and is non-skin pass having Yield Strength – 250 MPa to 350 MPa preferably about 320 MPa Tensile Strength – 360 MPa to 480 MPa preferably about 390 MPa; and Elongation 20 % to 30% preferably minimum 20% in 50mm gauge length having matching specifications of IS 277Galvanized Plain (GP)_250.

Also said cold rolled galvanized steel strip which is non-skin pass and stretch levelled having thickness of 0.48 mm to 0.52 mm preferably 0.5 mm and zinc coating 430 GSM to 440 GSM preferably more than 420GSM and having top: Bottom coating ratio of 55:45, suitable for wire application.

The present invention is described in details with reference to drawings Figure 1 & 2 and experimental data as per following tables 1 to 6

EXPERIMENTAL PROCEDURE
Experimental trials under present invention were conducted at Galvanizing Line(CGL3)at Vasind Plant of Applicants through the following activities:

• Selection of suitable raw material
• Coldrolling
• Galvanizing in CGL3
• Mechanical Testing
• Data compilation and analysis

The inventive steel grade is produced through following Process Path:
Hot Rolled Coil (HR coil) ------> HR Coil Slitting ------> Pickling ------> Cold Rolling ------> Galvanizing ------> Packing.

Accompanying Figure 1 shows the flow process chart for producing the galvanized structural steel according to present invention showing detailed process steps.

Detail of HR Coils
Sourced from JSW Steel Dolvi plant:Table 1
HR No. Size (mm) Grade
VDNB2H2051 2.50 X 1230 93B ( JDHST29BCN )
VDNB2H2332 2.50 X 1170 91 (JDHCG04ACN )
VDNB2H1932 2.50 X 1190 91 ( JDHCG04ACN )
VDNB2H0799 2.50 X 1230 93B ( JDHST29BCN )

Chemistry:Table 2
HR No. Heat No. %C %Mn %P %S %Si %Al %N
VDNB2H2051 B006213 0.0610 0.335 0.012 0.0160 0.005 0.042 0.0044
VDNB2H2332 A004198 0.0360 0.272 0.020 0.0150 0.008 0.053 0.0045
VDNB2H1932 B004237 0.0320 0.258 0.008 0.0150 0.007 0.041 0.0042
VDNB2H0799 B004458 0.0620 0.300 0.020 0.0160 0.014 0.047 0.0040

Detail of CR Coils: Table 3
HR No. CR No. Size (mm) Reduction %
VDNB2H2051 VL1A2H2533 0.44 X 1179 82.4
VDNB2H2332 VL1A2H2534 0.44 X 1200 82.4
VDNB2H1932 VL1A2H2769 0.44 X 1177 82.4
VDNB2H0799 VL1A2H2757 0.44 X 1178 82.4

Furnace Parameters:Table 4

Parameters Units Reading
Avg. Line Speed m / min 145
Avg. ton per hour (TPH) Mt / Hrs. 36
Avg. Direct Fired Furnace (DFF) Deg. Centigrade 650
Avg. Radiant Tube Furnace (RTF) Deg. Centigrade 760
Avg. Soaking temperature Deg. Centigrade 750
Avg. Exit temperature Deg. Centigrade 480
Skin Pass Mill (SPM) load Ton Nil
Skin Pass Mill (SPM) Elongation % Nil
Tensile leveller (TL) Elongation % 0.7
Spencer Blower Air % Top: 57, Bottom: 57
Air Knife Pressure RPM 2000
Air knife Gap mm 12~15

Accompanying Figure 2 shows the graphical plot of Coil No VG3A2I0533 to VG3A2I0540, Showing Strip Temperature at Exit in Deg. Centigrade at different Furnace Sections – Non-ox Furnace (NOF), Radiant Tube Furnace (RTF), Soaking Furnace (SF) and Jet Cooling Furnace(JCF).

The process of hot dip Galvanizing coating on Cold Rolled Strip with a layer of zinc to increase the corrosion resistance of Strip included
1. Annealing: Heating of CR strip up to desired temperature, soaking the strip.
2. Zn Pot: Coating of Cold Rolled Steel strip with a layer of Zinc & alloy to increase corrosion resistance of the strip.
3. Stretch Levelling: To achieve antifluting property of the Galvanized steel strip & to get desired shape by applying tensile stress & bending stress.
4. Passivation: Chemical treatment of the Galvanized or Galvalume surface with a superficial layer of Cr, chromic acid or any other passivation chemical to improve corrosion resistance.

The GI product obtained has to comply as follows:
FinishSize–0.5X1175mm

Mechanical Properties Required for IS 277 Grade Galvanized Plain (GP)250
Yield Strength - 250 MPa (Min)
Tensile Strength - 360MPa (Min)
Elongation -20 % (Min) In 50 mm Gauge Length.

Zinc Coating Mass 420 GSM: Specific coating requirements as below,
Coating Class designation Minimum Coating Mass Gram per Square Meter TOP: Bottom Coating Ratio
Total Both Surfaces One Surface
55:45
Triple Spot Single Spot Single Spot
Z420 420 355 142

Testing & Conclusion of Galvanized Plain (GP) coils:
A) Mechanical Properties : Table 5
Requirement Galvanized Plain (GP) coils
VL1A2H2184 VL1A2H3032 VLIA2H2769 VL1A2H2757
VG3A2I0533 VG3A2I0534 VG3A2I0535 VG3A2I0536 VG3A2I0537 VG3A2I0538 VG3A2I0539 VG3A2I0540
Size (mm) 0.50 X 1175 0.50 X1175 0.50 X 1175 0.50 X 1175 0.50 X 1175 0.50 X 1175 0.50 X 1175 0.50 X 1175
YS (Mpa) 250 Min. 311 311 300 300 317 317 333 333
TS (Mpa) 360 Min. 391 391 379 379 391 391 405 405
%EL 20 Min. 28 28 26 26 30 30 30 30

B) Tested Coating: Table 6
Batch No. Minimum Coating Mass Gram per Square Meter Top :Bottom Coating results
Total Both Surfaces One Surface Top Surface Bottom Surface
Triple Spot Single Spot Single Spot
VG3A2I0533 441 377 148 245 195
VG3A2I0535 435 373 149 240 193
VG3A2I0537 435 371 147 242 192
VG3A2I0539 429 362 142 236 193

Conclusion:
Coating top & bottom configuration and Mechanical Properties Yield strength, Tensile strength are achieved as per IS 277 Galvanized Plain (GP)_250.

Benefit:
Galvanized, Non-skinpass, Stretch leveled material, as per IS 277 Galvanized Plain (GP)250 can be used for the wire Application.
, Claims:We Claim:

1. A cold Rolled Galvanized steel strip having steel composition comprising
C – 0.032 to 0.062 % by wt. preferably 0.036 % by wt;
Mn- 0.27to 0.4 % by wt. preferably 0.3 % by wt;
P-0.0 % to 0.025% by wt. preferably 0.012 % by wt;
S- 0.0 to 0.02 % by wt. preferably 0.015 % by wt;
Si-0.0 to 0.03 % by wt. preferably 0.008 % by wt;
Al- 0.025 to 0.05% by wt. preferably 0.04 % by wt;
Optionally upto 0.001% Nb ; and rest is iron;
which is Zinc coated with thickness in the range of 0.48 mm to 0.52 mm preferably 0.5 mm and is non-skin pass having Yield Strength – 250 MPa to 350 MPa preferably about 320 MPa Tensile Strength – 360 MPa to 480 MPa preferably about 390 MPa; and Elongation 20 % to 30% preferably minimum 20% in 50mm gauge length having matching specifications of IS 277Galvanized Plain (GP) 250.
2. The cold rolled galvanized steel strip as claimed in claim 1 which is non-skin pass and stretch levelled having thickness of 0.48 mm to 0.52 mm preferably 0.5 mm and zinc coating 430 GSM to 440 GSM preferably more than 420GSM and having top: Bottom coating ratio of 55:45, suitable for wire application..
3. The cold rolled galvanized steel stripas claimed in anyone of claims 1 or 2 having finish size of 0.48 to 0.52 x 1170 to 1175 preferably 0.5 X 1175..
4. A process for manufacture of cold rolled galvanized structural steel strip as claimed in anyone of claims 1 to 3 including:
i)providing HR coil of steel sheet having steel composition comprising
C – 0.032 to 0.062 % by wt. preferably 0.036 % by wt;
Mn- 0.27to 0.4 % by wt. preferably 0.3 % by wt;
P-0.0 % to 0.025% by wt. preferably 0.012 % by wt;
S- 0.0 to 0.02 % by wt. preferably 0.015 % by wt;
Si-0.0 to 0.03 % by wt. preferably 0.008 % by wt;
Al- 0.025 to 0.05% by wt. preferably 0.04 % by wt;
Optionally upto 0.001% Nb and rest is iron;
ii) carrying out HR coil slitting;
iii) subjecting to pickling for removal of the oxide layer;
iv)subjecting to cold rolling including mechanical working of mild steel material to below its recrystallization temperature such as to reduce the thickness at cold rolling mills;
v) subjecting to galvanizing involving (a) annealing (b) coating of cold rolled steel strip to increase corrosion resistance strip (c ) stretch levelling to impart antifluting property of galvanized steel strip and desired shape involving tensile stress and bending stress of thickness in the range of 0.48 mm to 0.52 mm preferably 0.5 mm and having Yield Strength – 250 MPa to 320 MPa preferably about 320 MPa Tensile Strength – 360 MPa to 480 MPa preferably about 390 MPa; and Elongation 20% to 30% preferably 20%min in 50mm gauge length.
5. The process as claimed in claim 4 is wherein said step of cold rolling is carried out to obtain coils of sizes 0.44 x 1175 to 0.46 X 1180 preferably about 0.45 X 1175, weight 24.5 Mt to 30.5 Mt preferably about 24.965 Mt. , wherein input HR thickness is 2.46 mm to 2.54 mm preferably about 2.5 mm , output thickness 0.44 mm to 0.46 mm preferably about 0.45mm and achieve a reduction in the range of 80 % to 83 % preferably about 82 %.
6. The process as claimed in anyone of claims 4 or 5 wherein said step of galvanizing is carried out involving a zinc bath comprising of Al % 0.14 % to 0.2 % preferably about 0.165 %, Pb % 0.02 % to 0.04 % preferably about 0.025 % and Fe % 0.024 % to 0.0265 % preferably about 0.025 % and rest is Zn.
7. The process as claimed in anyone of claims 4 to 6 wherein said step of galvanizing is carried out involving select temperature control in various furnace sections including select exit temperatures comprising in Non-ox Furnace (NOF) 600 0C to 700 0C preferably 6500C ,Radiant Tube Furnace (RTF) 725 0C to 780 0C preferably 7600C, soaking furnace 740 0C to 770 0C preferably 7600C and Jet Cooling Furnace (JCF) 470 0C to 490 0C preferably 4800C.
8. The process as claimed in anyone of claims 4 to 7 wherein said step of galvanizing involve furnace operative parameters including subjecting cold rolled coil of size of 0.44 x1175 mm to 0.46 x 1175mm preferably 0.45x1175 mm to line speed of 140 mpm to 150 mpm preferably about 145 meters per minute, 34 TPH to 38 TPH preferably about 36 Mt./Hrs, Furnace tension 880 Kgf to 1200 Kgf preferably about 1000 Kgf , Pot tension 1000 Kgf to 1500 Kgf preferably about 1200 Kgf, Air Knife RPM 1650 to 2500 RPM preferably about 2000 RPM, Air Knife Pressure 60 to 80 Mbar preferably about 75 Mbar and air knife gap 10~15mm preferably about 12mm.

Dated this the 8th day of September, 2023
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199