GALA PULSE SYNERGIC DR ADVANCED. Instructions Manual
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8.4.12. GALVANISED STEELS AND DISSIMILAR MATERIALS WELDING.
In joint welding processes with copper alloys, the same or similar. Welding is heterogeneous, as it is carried out with
different filler materials to the base material.
In this type of joints, the preparation of the parts to be welded becomes especially important, as to permit gases,
produced during the welding, to escape, and for no pores or defects to appear in the welding bead, a slight
separation must be maintained between the parts to be joined together.
The application of galvanised materials, used to increase the corrosion protection of the base metal, is especially
recommended to manufacture and repair bodywork, exhaust pipes, coffee-maker water tanks, joints in galvanised
installations.
Apart from the protection against corrosion, this type of welding reduces the heat input in the joint and reduces
cleaning work carried out after welding galvanised materials.
The galvanised layer is a film of zinc that coats the entire plate and that is applied via electrolysis. Then the primers
are applied and finally the colour layers and varnishes. This is basically the protection of a galvanised plate against
corrosions.
In conditions that favour oxidation (daily life), the zinc film is the first to oxidise, as this covers the entire plate and the
actual zinc oxide forms a new film around the plate which also acts as a protective layer. Thus, whilst zinc oxidises,
steel does not.
This type of welding is called MIG Brazing. This type of welding is carried out in inert gas atmosphere (around 10
l/minutes), such as Argon and it is called strong welding.
Bearing in mind that zinc melts at 419°C and evaporates at 908°C, whilst steel melts at 1550°C and
evaporated 2500°C. When we weld with steel wire or electrode, we need it to heat above 1550°C for it
to melt with the plates and form the joint when it hardens, but with these temperatures, apart from
melting the zinc we evaporate it, so when we weld we have eliminated the protection from the plate at
that point. We have always been able to observe that the first place where oxide appears is in a welding
that we have carried out.
8.4.13. WELDING WITH CuSi3 FILLER METAL.
Welding with filler wires with copper-silicon, increases the resistance to corrosion of the joints and is easy to apply. It
offers high resistance to frictional wear and its 3% silicon content provides it with excellent fluidity.
It has a melting point of 950°C, reducing the input heat and reducing the deformation of the pieces to be welded. It
provides high resistance to corrosion as it prevents the zinc from evaporating.
The copper and silicon alloy at 3% (CuSi3) melts at around 950°C and evaporates at 2300°C. This
means that to melt and weld, we only need to reach a temperature of 950°C, with which we evaporate
much more zinc, still maintaining part of the material protection.
If we look at the temperatures at which the different materials melt, we will see that steel melts at
1550ºC and CuSi3 at 950ºC. The fusion of both occurs because the filler material (CuSi3) when melted,
penetrates the sheet by capillarity. Thus, low temperature resistant welding is achieved, avoiding the total
loss of the galvanised layer.
Tensile strength MIG-Brazing with CuSi3% - 309,5 N/mm / MAG with carbon steel 320,9 N/mm.
Applications:
NAVAL REPAIRS
AUTOMOTIVE INDUSTRY
ADVERTISING SYSTEMS
AUXILIARY TRANSPORT
RENEWABLE ENERGIES
