Schmelztauchveredeltes Feinblech.Hot-dip coated sheet.

Joining techniques
Welding is the most commonly used
joining technique. Both hot-dip galvanized
sheet and GALFAN ® can be easily
resistance-spot welded. However, a
higher welding current and greater electrode
force have to be used compared
with cold-rolled sheet because the coating
has less transitional resistance. As a
result of this, the normal copper electrodes
become alloyed and the electrode
life, i.e. the number of spot welds
is less than with cold-rolled sheet. This
can be counteracted by using suitable
electrode material, e.g. CuCrZr and
adapted electrode geometry as well as
sufficient cooling. A staggered control,
for example, raises the welding current
in stages and thereby increases the
electrode life significantly.
Hot-dip galvanized sheet Galvannealed
can be welded more economically, as
the copper electrode alloys up to a lesser
degree because of the zinc-iron layer.
The figure on page 24 compares the
welding current range of hot-dip coated
materials with cold-rolled sheet and its
electrolytically coated variants. It shows
that the welding-current range of the
galvannealed variant is almost identical
to that of cold-rolled sheet.
Roller seam welding can also be used.
The rollers have to be continuously
cleaned using scrapers or brushes or
with a knurled roller, which serves
simultaneously as the drive and
smoothes the contact area of the rollers.
In the cases of GALVALUME ® and fal,
roller seam welding with wire electrodes
(Soudronic process) has more than
proven itself.
Projection welding and stud welding can
also be used, even if, compared to cold-
rolled sheet, the welding current and
electrode force are increased or the stud
is pressed with somewhat greater force
into the melt.
The familiar, conventional methods,
such as GMA and TIG welding are also
suitable for joining hot-dip galvanized
sheet. Other possibilities are soldering
and brazing, whereby the inert gas technique
is advantageous for the latter.
Because the coating metal burns in the
melt of the welding seam, a welding
method should be chosen which introduces
little heat into the welding area in
order to reduce the corrosion protection
as little as possible. A welding speed,
less than that used for cold-rolled sheet,
allows the melt to degas and prevents
pore formation. The welding fumes
must be drawn off.
Plasma welding and laser welding are
recommended welding methods. The
heat-affected area is comparatively
small, the seam is free of pores and
only slightly overfilled.
Our specialists from the research and
application technology department area
are pleased to help solve special problems.
Durch Laserstrahlschweißen können „maßgeschneiderte
Bleche“, auch in unterschiedlichen Dicken und
Oberflächenbeschichtungen mit einer blechebenen
Schweißnaht hergestellt werden.
Laser welding makes it possible to produce “tailored
blanks” with a weld that is flush with the sheet, also
when joining sheets of dissimilar thickness and coating.
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