Schmelztauchveredeltes Feinblech.Hot-dip coated sheet.

Production of hot-dip coated sheet
The process for the production of hot-dip
coated sheet follows directly on from the
cold-rolling. This process combines in
one line the cleaning, annealing, galvanizing
and temper-rolling which in the
production of electrogalvanized sheet
are each carried out on separate lines.
The work-hardened strip is cleaned of
emulsion residue and of iron abrasion
from the cold-rolling process first roughly
in a mechanical cleaning section, then
finely in an electrolytic cleaning section.
Following this, the strip, still work-hardened,
passes into a continuous annealing
furnace where it is recrystallized in a
controlled atmosphere between 700 and
850° C depending on the steel grade.
Thus the sheet obtains the desired
mechanical properties.
Also in a controlled atmosphere the strip
is cooled down in the subsequent
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annealing section of the furnace to a
temperature of about 20° C above the
bath temperature of the molten zinc of
450° C in which it is dipped while still
in a controlled protective atmosphere.
The zinc bath is temperature-controlled.
Thanks to the intensive cleaning
described above, an intermetallic interlayer
is produced from an iron-aluminium
compound as adhesion composite.
In the case of hot-dip aluminium as with
the GALVALUME ® coating a ternary ironaluminium-silicon
compound produces
the adhesion composite. The coating
thickness, i.e. the coating ordered by
the customer, is attained by air knives,
on each the top and the bottom side of
the strip, blowing pressure-controlled air
or nitrogen on the strip and wiping off
the excess zinc. A closed control system
guarantees a uniform coating across the
strip width and strip length. A different
Hot-dip coating line
1 Decoiler
2 Shears
3 Quality assurance (s. p. 17)
4 Welding machine
5 Strip cleaning
6 Quality assurance (s. p. 17)
7 Entry section
8 Furnace
9 Quality assurance (s. p. 17)
10 Zinc pot (changing pot)
11 Air knives
12 Quality assurance (s. p. 17)
13 Galvannealing furnace
14 Quality assurance (s. p. 17)
15 Cooling
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coating for each side, the so-called differential
coating, can also be produced.
The temperature and the chemical composition
of all baths are continuously
checked. The whole process, subdivided
into part processes, is computer-controlled.
The now finished hot-dip coated sheet
can be temper-rolled continuously in the
exit section of every plant and tension
levelled. This way qualities with high
surface requirements and flatness can
be produced. Hot-dip aluminized sheet
is only supplied in tempered form.
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Quality assurance (s. p. 17)
Water cooling
Quality assurance (s. p. 17)
Temper-roll stand
Tension-leveller
Quality assurance (s. p. 17)
Surface post-treatment
Quality assurance (s. p. 17)
Delivery strip accumulator
Side-trimming shears
Quality assurance/strip inspection (s. p. 17)
Oiling
Quality assurance (s. p. 17)
Shears
Coiler
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