posco korea - galvanized sheet

Hot-Dip Galvanized Steel 1

POSCO 2001


Hot-dip galvanized steel products have versatile usage. It is used in civil engineering and construction as well as in automobile and electrical parts. POSCO produces superb quality galvanized steel sheets with excellent corrosion resistance, formability, weldability, and paintability. POSCO will spare no effort to continuously develop world -class steel products to fill the needs of our customers.


Annealing Process AnAny trace of lubrication on cold-rolled coil is removed. The coil is then heated in the annealing furnace to achieve a clean surface and optimal metal properties.

Hot-Dip Galvanizing Process The steel sheet is immersed into the molten zinc pot for coating and the air knife sprays high pressure air to achieve the appropriate coating weight.

Galvannealing Process he galvanized steel sheet is reheated in the galvannealing furnace, the pure zinc coated layer becomes an iron-zinc alloy producing a galvannealed sheet with excellent weldability and paintability.

Shape Formation and Chemical Treatment Process Galvanized sheets pass through the skin pass mill to give them a flat and bright surface. To prevent white rust from forming and to enhance corrosion resistance, the steel sheet is treated with chromate.


1. Hot-Dip Galvanizing Steel Sheet Line

Classification Kwangyang 1CGL Kwangyang 2CGL Kwangyang 3CGL Kwangyang 4CGL

Days of Full Operation 88.12 91.6 95.6 00.6

Capacity 367,000ton/year 367,000ton/year 300,000ton/year 450,000ton/year

Thickness 0.2~2.3mm 0.2~2.3mm 0.2~1.6mm 0.4~2.3mm

Width 720~1,860mm 720~1,570mm 600~1,270mm 900~1,860mm Product

Dimensions Weight 5~40ton 5~35ton 5~33ton 5~35ton

Coating Weight Both sides:60~720g/m² Both sides:60~380g/m² Both sides:60~720g/m² Both sides:60~720g/m²

Surface Finish zero spangled galvannealed zero spangled galvannealed zero spangled zero spangled galvannealed

Product Type Commercial, (light) drawing, deep drawing, extra deep drawing, structural quality, high strength steel

Chemical Treatment Chromate, Oiling

Furnace Type Vertical

Diameter 508/610mm

2. Hot-Rolled Galvanized Steel Sheet Line

Classification Kwangyang PGS

Capacity 500,000ton/year

Thickness 1.4~4.5mm

Width 740~1,570mm Product

Dimensions Weight Maximum 1.35ton

Coating Weight Both sides : 60~600 g/m²

Surface Treatment Zero Spangled

Product Type Commercial, Structural Quality

Chemical Treatment Chromate, Oiling

Furnace Type Horizontal

Diameter 610mm


1. Hot-Dip Galvanized Steel Product Characteristics

Product Coating Layer

Structure Characteristics Major Usage

Zero Spangled (Minimized Spangle)

While molten zinc solidifies on the surface of the steel sheet, normal zinc crystalization is suppressed creating fine crystals. The surface is flat and has a fine appearance after painting. Paintability is superior to regular spangle products.

Furniture, office appliances, inner &outer panels of home appliances, substrates for painting, automobile inner plates, pipes, construction materials

Galvannealed

By a thermal diffusion process, steel sheet and zinc react to produce Zn-Fe alloy coating layer. Weldability and paintability is superior to galvanized steel sheets. Iron in the alloy layer enhances corrosion resistance after painting.

Inner&outer panels of home appliances and automobiles


1. Products

Zero Spangled Galvannealed

?? Metal furniture ?? Inner & outer panels of home appliances ?? Substrates for painting ?? Inner panel of automobiles ?? Construction materials ?? Pipes

?? Inner& outer panels of automobiles ?? Fuel tanks

2. Applications


1. Hot-Dip Galvanized Steel Product Standard

Cold-Rolled Coil

ASTM Classification / Standards POSCO

KS D3506

JIS G3302 89 95

EN10142

Commercial CGCC SGCC SGCC A526 A 653-CQ DX51D

Lock forming CGCF SGCD 1 SGCD1 A527 A 653-LFQ -

Drawing CGCD SGCD 2 SGCD 2 A528 A 653-DQ DX52D

Deep drawing CGCP SGCD 3 SGCD 3 - - DX53D

Non-Aging Deep Drawing CGCN SGCD 3N SGCD 3N A642 A 653-DQSK DX54D

Non-Aging Extra Deep Drawing CGCE - - - - -

Structural Quality

CGL35 -

CGC41 CGC45 CGC50 CGC58

SGC35 -

SGC 41 SGC 45 SGC 50 SGC 58

SGC 340 -

SGC 400 SGC 440 SGC 490 SGC 570

A446 Gr A Gr B Gr C Gr D Gr F Gr E

A 653-SQ230 A 653-SQ255 A 653-SQ275 A 653-SQ340

- A 653-SQ550

S220 GD S250 GD S280 GD S320 GD S350 GD S550 GD

High- strength Steel

CGCHS 35 CGCHS 40 CGCHS 45 CGCHS 50 CGCHS 60

- - - - -

*1)Standard for En structural quality is En10147 *2)Tensile strength of A446 Grade A is 32kg/m²

Hot-Rolled Coil

Classification / Standards POSCO KS D 3506 JIS G 3302

Commercial CGHC SGHC SGHC

Structural Quality

CGH41 CGH45 CGH50 CGH55

SGH41 SGH45 SGH50 SGH55

SGH400 SGH440 SGH490 SGH540


2. POSCO Standards

Cold-Rolled Coil

Elongation? min. %

Thickness mm Classification

Thickness mm

Yield Point min.

Kg/m²

Tensile Strength

min. Kg/m²

0.2525and over, under

0.40


0.60


1.0


1.6


2.3

Test Piece

CGCC - - - - - - -

CGCF - 28 - 34 36 37 38

CGCD - 28 - 36 38 39 40

CGCP - 28 - 38 40 41 42

CGCN - 28 - 38 40 41 42

CGCE - 28 - 40 42 43 44

CGC35 25 35 20 20 20 20 20

CGC41 30 41 18 18 18 18 18

CGC45 34 45 18 18 18 18 18

CGC50 37 50 16 16 16 16 16

CGC58 57 58 - - - - -

CGCHS35 20 35 28 30 32 34 36

CGCHS40 23 40 25 27 29 31 33

CGCHS45 32 45 23 25 27 28 29

CGCHS50 34 50 21 22 23 24 25

CGCHS60

0.2~2.3

40 60 16 17 18 18 18

No.5, rolling direction

Remark: 1. Non-aging of CGCN and CGCE is guaranteed for 6 months after shipping.


Hot-rolled Sheet

Classification Thickness (mm) Yield Point min.Kg/m²(N/m²) Tensile Strength min.Kg/m²(N/m²)

Elongation min.%

Test Piece

CGCH - - -

CGC 35 25(245) 35(340) 20

CGC 41 30(295) 41(400) 18

CGC 45 34(335) 45(440) 18

CGC 50 37(365) 50(490) 16

CGC 55

1.4~4.5

41(400) 55(540) 16



3. Coating Weight

Minimum Coating Weight (Both-sided coating)

Corresponding Standards (Marking Symbol) Coat Weight Type

Average Value of Both-Sided, Triple Spots Method

Minimum Value of Both-Sided, Single Spot Method KS D3506 JIS G3302

060 60 51 Z06, F06 Z06, F06

080 80 68 Z08, F08 Z08, F08

090 90 77 - -

100 100 85 Z10, F10 Z10, F10

120 120 102 Z12, F12 Z12, F12

150 150 128 - -

180 180 153 Z18, F18 Z18, F18

200 200 170 Z20 Z20

220 220 187 Z22 Z22

250 250 213 Z25 Z25

275 275 234 Z27 Z27

300 300 255 - -

350 350 298 Z35 Z35

450 450 383 Z45 Z45

500 500 426 - -

600 600 510 Z60 Z60

Remark: 1. "K" is marked for non- alloy products and "S" is added in front of the alloy product code. However, in case of alloy products, coat weight should not exceed

200. 2. For drawing (CGCF,CGCD,CGCP,CGCN,CGCE), marking codes exceeding K350 and S100 are not applied. 3. For both-side, triple spots coating weight, the average value of the measurement of 3 test pieces is applied. 4. For one-side, single spot coating weight, the minimum value of the measurement of 3 test pieces is applied. 5. Separate consultation is necessary for the maximum coating weight on both sides.


Minimum Coat Weight

Type Coating

Non- Alloy Zero Spangle J Both side

Alloy G

Remark: ?Otherwise specified, both-side zero spangle is used in principal.

Chemical Treatment

Type Mark

General chromate treated CL

Special chromate treated CH

Non-treated M

Oiling

Type mark

Oiled O

Non-oiled X

4. Thickness tolerance

Cold-Rolled Coil

Thickness / Width Under 630 630 and over, under1,000 1,000 and over, under

1,250 1,250 and over, under

1,600 1,600 and over

under 0.25 ±0.04 ±0.04 ±0.04 - -

0.25 and over, under0.40 ±0.05 ±0.05 ±0.05 ±0.06 -

0.40 and over, under 0.60 ±0.06 ±0.06 ±0.06 ±0.07 ±0.08

0.60 and over, under 0.80 ±0.07 ±0.07 ±0.07 ±0.08 ±0.09

0.80 and over, under1.00 ±0.08 ±0.08 ±0.09 ±0.10 ±0.11

1.00 and over, under 1.25 ±0.09 ±0.09 ±0.10 ±0.11 ±0.13

1.25 and over, under 1.60 ±0.10 ±0.11 ±0.12 ±0.13 ±0.16

1.60 and over, under 2.00 ±0.11 ±0.12 ±0.13 ±0.15 ±0.17

2.00 and over, under 2.30 ±0.13 ±0.14 ±0.15 ±0.17 ±0.19


Hot-Rolled Coil

Thickness / Width 1,000šE¸ ̧1,000 and over, under

1,250 1,250 and over, under

1,600 1,600 and over

1.60 and over, under 2.30 ±0.17 ±0.18 ±0.20 ±0.22

2.30 and over, under 3.20 ±0.21 ±0.22 ±0.27 ±0.30

3.20 and over, under 4.50 ±0.30 ±0.32 ±0.35 -

Equal Coating Thickness

Coating Weight Marking Code (Zinc)

K060 K080 K100 K120 K180 K200 K220 K250 K275 K350 K450 K600

Coating Thickness 0.013 0.017 0.021 0.026 0.034 0.040 0.043 0.049 0.054 0.064 0.080 0.102

Coating Weight Mark (Alloy) SO40 SO60 SO80 S100 S120

Coating Thickness 0.008 0.013 0.017 0.021 0.021

5.Width Tolerance

Tolerance

Hot-Rolled Coil Width

A B Cold-Rolled Coil

1,500 and under +7 0

1,500 Over

+25 0

+10 0 +10

0 Remark: Unless otherwise specified, A is applied.


6. Length Tolerance

Cold-Rolled Coil Hot-Rolled Coil

+10 0

+10 0


7. Shape

(Camber)

Cold-Rolled Steel Sheet

Sheet Width / Length

Under 2,000 2,000 and over Coil

Under 630 4 4 to 2,000 to any given length

630 and over 2 2 to 2,000 to any given length

Hot-Rolled Steel Sheet

Sheet Width/ Length

Under 2,500 2,500 and over under4,000 4,000 and over Coil

Under 630 5 8 12

630 and over, under 1,000 4 6 10

1,000 and over 3 5 8

5 to 2,000 to any given length

((off-squaredness) off-squaredness: A/WX100(%), it shall not exceed 1%


8. Flatness

Cold-Rolled Steel Sheet

Width / Type Wave (Bow) Center Wave Edge Wave

Under 1,000 128 and under 8 8 and under 8 and under

1,000 and over, under1,250 15 8 and under 9 8 and under 9 and under

1,250 and over, under1,600 15 8 and under 11 8 and under 11 and under

1,600 and over 20 8 and under 13 8 and under 13 and under

Hot-Rolled Sheet

Width / Type Wave (Bow) Center Wave Edge Wave

Under1,000 16 and under 16 and under 16 and under

1,000 and over, under1,600 18 and under 18 and under 18 and under

1,600 and over 20 and under 20 and under 20 and under

Remark: Flatness is measured on top of a flat table. The value is calculated by subtracting the thickness of the steel from the maximum deformation value. It is applied to the upper side of the sheet.


9. KS standard(KS D 3506 Hot-Dip Galvanized Steel Sheet and Coil)

Cold-Rolled Steel Sheet (unit::3 )

Elongation (min.%)

Thickness Classification Thickness

Yield Point min.

N/mm²

Tensile Strength

min. N/mm²

0.25 and over

0.40 and over,

under0.06

0.06 and over,

under1.0

1.0 and over,

under1.6

1.6 and over, under

2.3

1.6 and over

Test Piece

SGCC 0.25?3.2 205 270 - - - - - -

SGCD 1 - 270 - 34 36 37 38 -

SGCD 2 0.40?2.3

- 270 - 36 38 39 40 -

SGCD 3 0.60?2.3 - 270 - (38) 40 41 42 -

SGC 35 245 340 20 20 20 20 20 20

SGC 41 295 400 18 18 18 18 18 18

SGC 45 335 440 18 18 18 18 18 18

SGC 50

0.25?2.3

365 490 16 16 16 16 16 16

SGC 58 0.25?2.0 560 570 - - - - - -


Remark: Prior consultation is required for the values in ( ).

Hot-Rolled Sheet

Classification Thickness

(3 ) Yield Point min. N/mm²

Tensile Strength min. N/mm²

Elongation min.%

Test Piece

SGHC 205 270 -

SGH 35 245 340 20

SGH 41 295 400 18

SGH 45 335 440 18

SGH 50 365 490 16

SGH 55

1.6?4.5

400 540 -


Remark:The yield point and tensile strength of SGHC are 206N/mm² and 275N/mm² or over, respectively


10. Thickness Tolerance

Cold-Rolled Steel Sheet (unit::3 )

Thickness/Width 630 and under 630 and over,

under1,000 1,000 and over,

under1,250 1,250 and over,

under1,600 1,600 and over

Under 0.25 ?l0.04 ?l0.04 ?l0.04 - -

0.25 and over, under 0.40 ?l0.05 ?l0.05 ?l0.05 ?l0.06 -

0.40 and over, under 0.60 ?l0.06 ?l0.06 ?l0.06 ?l0.07 -

0.60 and over, under 0.80 ?l0.07 ?l0.07 ?l0.07 ?l0.07 ?l0.08







3.15 and over ?l0.17 ?l0.18 ?l0.20 ?l0.21 -


Hot-Rolled Sheet (unit:3 )

General Use Structural Quality


11. Width Tolerance (unit:3 )

Tolerance

Hot-Rolled Sheet Width

A B Cold-Rolled Sheet

1,500 and under ? 7 0

Over1,500

? 25 0

? 10 0 ? 10

0

12.Length Tolerance

Cold-Rolled Sheet Hot-Rolled Sheet

? 15 0

? 15 0


1. Galvanized Steel Corrosion Resistance General Properties

Electrochemical Protection

Hot-dip galvanized steel has strong corrosion resistance. Galvanized steel consists of a zinc coating on a steel substrate. Since zinc is anodic to iron, a break in the coating does not lead to corrosion of the substrate. This sacrificial anode of zinc is a form of galvanic protection.

Physical Protection

Zinc itself is an "active" metal, thus when exposed to the atmosphere it initially reacts with oxygen in the air to oxidize while contact with carbon gas creates zinc carbonate. These thin films protect the steel from more serious environmental attack. It is tenacious and serves as a barrier between the steel and environment to prevent further corrosion.

Corrosion Resistance to atmospheric assault

Corrosion of galvanized steel sheets depends on the protective surface film. The thin film can provide better protection when air is less polluted. If the air contains harmful gases such as sulfur dioxide, a porous film forms on the surface and accelerates corrosion. The lifespan of steel sheets is proportionate to the amount of zinc coating, but in the case of identical amount of zinc coating, environment is the most important factor of corrosion. In cities and industrial areas, steel sheets deteriorate faster than out in the country where the air is cleaner. The corrosion resistance rate of steel sheet in industrialized areas stand at only 25~40% of that in rural regions. In addition, the lifespan of steel sheets are 5-10 times longer indoors than in an outdoor environment.

Galvannealed Steel Sheet

To improve weldability and paintabilty of pure zinc galvanized steel, it is reheated (500~550 °C) in a galvanneal furnace to give it a gray Fe-Zn alloy layer. Iron consists of about 10% of the alloy layer, making it a more noble appearing metal and less susceptible to ionization. Galvannealed steel sheet is optimal for preventing local corrosion.


2. Formability

Hot-dip galvanized steel sheet manufactured at continuous galvanizing line has excellent zinc tenacity and the Fe-Zn alloy layer is very thin so coating does not exfoliate during drawing. Galvanized steel sheet produced from vertical furnace has excellent formability compared to that of cold-rolled steel sheet.

Mechanical Properties

3.Paintability

Galvanized sheets are usually painted before use. Paint adhesiveness and corrosion resistance after painting is heavily influenced by the type of treatment before painting. Generally, oiling is preferred to chromate treatment. It is important to clean the surface before painting to have strong adhesion. Galvannealed steel sheets have a phosphate layer due to the Fe-Zn alloy coating giving steel sheets improved adhesiveness and corrosion resistance.

Result of Paintability Test

Erichsen test after cross-cutting (adhesive tape flaking test)

DURGRIP(Galvanized) DURGRIP(Galvanized) Cold-rolled steel sheet Corrosion resistance after painting

DURGRIP(Galvanized) DURGRIP(Galvanized) Cold-rolled steel sheet

Paintabilty Testing Procedure


4. Weldability

Characteristics - zinc coating has better conductivity than iron, thus reducing electrical resistance on the contact area .This leads to lower heat generation. -Since the melting point of zinc is lower than that of iron, continuous welding is impaired by attachment of zinc at the electrode. -Zinc is more ductile than iron so electrical density is reduced as pressure from the electrode is applied onto large contact area of steel sheets.

Property of Repeated Welding

The graph shows optimum welding conditions of galvanized steel sheets. Optimum range of galvanized steel sheet is higher than that of the cold-rolled sheet. thickness: 0.8mm electrode:0.5mm (cylinder type with cut edge) time:10seconds When continuously spot welding galvanized steel sheet, zinc attaches onto the electrode, impairing the welding process. This intensifies with increased zinc coating weight. Galvanized steel sheet with thin zinc coating can be continuously welded more than 5000 times. In case of painted sheets, appropriate electrode conditions must be met. Galvannealed steel sheets can be continuously welded more than 5000 times.


Methods for Improving Weldability

Spot Welding Seam Welding

Raise welding current by 10~30% Increase the current flow time by 10% Increase electrode pressure Use conical shaped Cr-Cu alloy electrode Take extra care of electrode and cool sufficiently with water

Set welding current higher Deter internal defects and air bubbles by increasing pressure Adopt alternating current; greater on/off time ratio will produce better welding Cool electrode sufficiently with water

Shield Metal Arc-Welding

When shield arc welding, it advisable to use an electrode with high basicity to obtain good fludity and metal properties. For example, KSD 7004 E 4303 (lime titanium type), E 4313 (high titanium oxide), E 4316 (low hydrogen type) are good covers

Solderability

Galvanized steel sheet can be soldered without exfoliating the surface film. Any simple solvent will remove the film. Chromate-treated steel sheet has excellent solderability. Non-corrosive solvent or mixture of zinc chloride (15~20%) and ammonium chloride(3.3~5%) are favored solvents. It is necessary to thoroughly clean and dry the steel sheet after applying solvent.

5. Galvannealed Steel Sheet

Resistance Welding Welding galvanized steel is more difficult than welding cold-rolled steel because it has lower electric resistance, a lower melting point, and wider contact area under electrode pressure. Galvannealed steel sheet, coated with a Fe-Zn alloy, has a higher melting point and greater hardness than pure zinc coated steel; thus weldability is enhanced.

Shield Metal Arc Welding Has similar weldability as cold-rolled sheets.

Change of welded part strength and nugget diameter in

accordance to welding current


Commercial (SJ) Galvannealed (CQ,DQ)

Galvannealed (DDQ,EDDQ) High-strength Steel (TS 35,40,50kg)


Structural Quality (TS41-49kg) Structural Quality (58kg)


1. Coil

2. Sheet


3.Marking

Label

Marking Sheet

posco korea - galvanized sheet

Documents

galvannealed sheet

hotdip galvanizing process

world class steel products

ton coating weight

gm surface treatment

cgl kwangyang

appropriate coating

gm surface finish