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Cross Coating Weight Control by Electromagnetic Strip Stabilization at the Continuous Galvanizing Line of ArcelorMittal Florange

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Abstract

In hot dip galvanizing lines, strip bending around the sink roll generates a flatness defect called crossbow. This defect affects the cross coating weight distribution by changing the knife-to-strip distance along the strip width and requires a significant increase in coating target to prevent any risk of undercoating. The already-existing coating weight control system succeeds in eliminating both average and skew coating errors but cannot do anything against crossbow coating errors. It has therefore been upgraded with a flatness correction function which takes advantage of the possibility of controlling the electromagnetic stabilizer. The basic principle is to split, for every gage scan, the coating weight cross profile of the top and bottom sides into two, respectively, linear and non-linear components. The linear component is used to correct the skew error by realigning the knives with the strip, while the non-linear component is used to distort the strip in the stabilizer in such a way that the strip is kept flat between the knives. Industrial evaluation is currently in progress but the first results have already shown that the strip can be significantly flattened between the knives and the production tolerances subsequently tightened without compromising quality.

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Abbreviations

b :

Bottom side

c :

Channel number (from 1 to 60)

d :

Drive side

e :

End of scan

i :

Top or bottom side

j :

Operator or drive side

k :

Scan or channel number

lin:

Linear component of coating weight

n :

Scan or channel number

nl:

Non-linear component of coating weight

o :

Operator side

p :

Number of the pair of magnets (from 1 to 8)

q :

Scan or channel number

raw:

Raw coating weight

s :

Start of scan

t :

Top side

a :

Slope of linear regression

b :

Intercept of linear regression

C :

Control (knife pressure, knife skew, or stabilization offset)

c :

Channel number (from 1 to 60)

D :

Knife-to-strip distance (10−2 mm)

d :

Knife-to-strip distance correction factor (10−2 mm)

E :

Strip position error (10−2 mm) or coating weight error (g/m2)

K :

Proportional gain

k :

Portion of channel overlapping two magnets (mm)

N :

Total number of channels (≤60)

P :

Blowing pressure (mbar)

p :

Number of the pair of magnets (from 1 to 8)

S :

Line speed (m/min)

s :

Skew (10−2 mm)

s m :

Spacing between magnets (220 mm)

to s :

Strip track-off (mm)

W :

Coating weight (g/m2)

w c :

Channel width (33 mm)

w m :

Magnet width (150 mm)

w s :

Strip width (mm)

x :

Longitudinal direction of the strip (m)

y :

Cross direction of the strip (mm)

y 0 :

Edge strip offset (mm)

z :

Normal direction to the strip (mm)

α :

Line speed exponent of the feed-forward pressure model

β :

Knife-to-strip distance exponent of the feed-forward pressure model

γ :

Coating weight exponent of the feed-forward pressure model

Δ:

Magnet-to-strip distance (10−2 mm)

δ:

Strip position between magnets (10−2 mm)

κ:

Constant of the feed-forward pressure model

λ :

Constant of the Smith predictor

BS:

Bottom side

CGL:

Continuous galvanizing line

CWC:

Coating weight controller

FFC:

Feed-forward controller

FBC:

Feed-back controller

OS:

Operator side

PW:

Pulse-and-wait controller

DS:

Drive side

FC:

Flatness controller

SMTH:

Smith controller

TS:

Top side

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Acknowledgments

The authors are very grateful to the line operators and shift leaders for their commitment in this project. They would like to thank also ArcelorMittal Global R&D for its technical support.

Author information

Authors and Affiliations

  1. Process Automation, ArcelorMittal, 17, Avenue des Tilleuls, 57190, Florange, France

    Nicolas Guelton (Process Engineer)

  2. Galvanizing, ArcelorMittal, 17, Avenue des Tilleuls, 57190, Florange, France

    Catherine Lopès (Process Engineer) & Henri Sordini (Process Engineer)

Authors
  1. Nicolas Guelton
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  2. Catherine Lopès
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  3. Henri Sordini
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Corresponding author

Correspondence to Nicolas Guelton.

Additional information

Manuscript submitted December 30, 2015.

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Guelton, N., Lopès, C. & Sordini, H. Cross Coating Weight Control by Electromagnetic Strip Stabilization at the Continuous Galvanizing Line of ArcelorMittal Florange. Metall Mater Trans B 47, 2666–2680 (2016). https://doi.org/10.1007/s11663-016-0672-3

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  • DOI: https://doi.org/10.1007/s11663-016-0672-3

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