NS blade / Advanced Air Knife for Hot Dip Continuous ... · Generation of edge splash and top dross loss in High Speed Operation Zinc pot Air knife ↑Strip Strip Coating target Over

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“NS blade” / Advanced Air Knife for Hot

Dip Continuous Galvanizing Line

NS means Nippon steel & Sumikin engineering.

Hatsuki KAKUNO

Makoto KATSUBE

Muneshige OGAWA

NIPPON STEEL & SUMIKIN ENGINEERING CO., LTD., JAPAN

2

Hatsuki KAKUNO, Makoto KATSUBE, Muneshige OGAWA


18 JUNE.2015

1. Difficulty of High Speed CGL Operation

As Line Speed increases, zinc-takeout pulled by strip increases.

②Difficulty in thin coating

③Edge over coat

■Generation of edge splash leads to the loss of zinc consumption.

■ Generation of edge splash and top dross loss in High Speed Operation

Zinc pot

Air knife

↑Strip

Strip

Coating target

Over Coat

① Top dross loss

3


■ Generation of edge splash in High Speed Operation



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Jet collision

4

Wiping gas flow

Wiping width(> Strip width)

Nozzle

Impinging jet

Strip



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・Splash ・edge over coating

■ Ordinary nozzle Jet collision issue


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■ Baffle plate issue


Less than 5mm

Ineffective condition

Strip

Edge baffle plate

Wiping gas flow

Wiping width(> Strip width)

Nozzle

6

Wiping nozzle

Cross section of nozzle

NS blade

Strip

Tracking

Wiping gas flow



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NS blade

2. Features of NS blade

■ Configuration of NS blade Air knife

8



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1. Non contact baffle setting Safety for high speed operation

2. According to the jet effect,

EOC and splash shall be avoided even at high speed operation *EOC: Edge over coating

BLADE

Nozzle

Wiping width ( Strip width)

Wiping gas flow

Position variable

2. Features of NS blade

■ NS blade advantage

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Air pressure

Nozzle Sound meter

Camera

3. High speed coating test using NS blade

■ Schematic of experiment apparatus

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Wiping nozzle

Front view Side view

Edge splash

Front view Side view

Reduce Edge

Splash

(a) Ordinary nozzle

(b) NS blade


■ Test results 1 / Edge splash (Front view and side view)

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Without NS blade With NS blade


■ Test results 1 / Edge splash (Front view and side view)

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Flow velocity vector

X

Z

Y Y

Z

X


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■ Test results 2/ Coating thickness distribution

5 10 15 20

Coat

ing

weig

ht

Distance from strip edge (mm)

Coating weight distribution (near the strip edge)

F w/o EB

B w/o EB

F With EB

B with EB

without BLADE (F)

without BLADE (B)

with BLADE (F)

with BLADE (B)

-20%

+60%

+40%

+20%

Target

Edge over coat

Very little variation

in the coating weight

⇒ NS blade is effective in prevent of Edge over coat and allow thin coating

Strip


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Improve Noise level ■ Test results 3/ Noise level


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Galvanizing Line 55%Aluminum+Zinc coating lineCoil spec. 0.23mm thick X 914mm width 0.35mm thick X 1200mm width

Line 160mpm 150mpm speed

Coating Z08(40g/m2 per side) AZ40(20g/m2 per side)thicknessSplash None None

Overcoat None None

Noise 105dB 100dB

■ Operation condition

4. Commercial line test

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■ Coating weight distribution

4. Commercial line test

60

80

100

120

140

160

180

0 5 10 15 20 25Re

late

ive

Co

atin

g th

ickn

ess

[%]

60

80

100

120

140

160

180

0510152025

NS blade

Ordinary nozzle

Distance from strip edge [mm] Left side Right side

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5. Conclusion

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Without NS blade With NS blade

■ Coating test at test line ⇒ Reduce EOC, noise level and zinc splash

■ Commercial line operation (GI and 55% Al+Zinc bath)

⇒ Achieve maximum line speed and minimum coating weight operation

Thank you for your attention.

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18 JUNE.2015

Documents

NS blade / Advanced Air Knife for Hot Dip Continuous ... · Generation of edge splash and top dross loss in High Speed Operation Zinc pot Air knife ↑Strip Strip Coating target Over