EN welding technology

MIG soldering – for new areas of application, new materials
and new regulations especially in automotive applications.
Grinding
Galvanised sheet steel is very much in demand.
It is used, e.g., in car making, ventilation and
air conditioning technology, facility engineering
and the furniture industry.
Why galvanised?
When zinc is applied to steel (by electrolytic
treatment or hot-dip galvanising), it creates a
barrier layer that provides protection against
corrosion. Additionally, zinc provides cathodic
protection. If the layer of zinc is damaged, the
material in the surrounding area of 1-2 mm
of the damage remains protected against
corrosion. This remote protection effect that zinc
provides means that non-coated cut edges and
micro-cracks are also protected.
1. Werkstück
2. Lötnaht
3. Drahtvorschub
4. Drahtspule
5. Gasdüse
6. Kontaktrohr
7. Schutzgas 7
8. Lichtbogen
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8
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F
What is MIG soldering?
MIG soldering is a hard soldering process for
galvanised and coated thin sheets as well as
higher strength steel sheet.
In contrast to legacy shield gas welding (approx.
1600 °C), the basic material is not melted in
MIG soldering; instead a hard soldier joint is
created between the workpieces using soldering
wire (typically a copper-based additive) with a
low melting point of around 1000 °C.
Zinc already starts to vaporise at 480 °C. This
means that in legacy welding, the layer of
sync would burn off large areas of the surface.
Evaporating zinc and oxides then lead to
porosity, cracks and a lack of fusion.
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5
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The base material
does not
melt
Using copper-based additives (bronze) means
that less heat can be applied. Because less
heat is applied, very little zinc vaporises and
component distortion is reduced.
The strength values are relatively high and the
soldiers seem is corrosion resistance due to
alloy components because the additive is made
of bronze.
The micro-section shows that the base material
does not melt in MIG soldering.
Surface coating and pre-treating
Sheet metal with zinc coating of up to 15 µm
can typically be joined without any trouble using
arc soldering processes.
Solders containing aluminium are recommended
for aluminised base materials. Additionally,
galvanised sheet can be organically coated,
which requires some adjustment of the
processing parameters.
To ensure metallurgical interaction between the
base material and the wetting liquid solder, the
boundary surface to the solder should be bare
metal for the most part; otherwise problems
with porosity, a lack of fusion, etc., can occur.
Additives and auxiliary materials
Wire electrodes and welding rods made of
ML CuSi3 and ML CuAl8 are typically used in
arc soldering. In Germany, ML CuSi3 is more
widespread, while other countries often use an
ML CuAl8 alloy for similar tasks. ML CuAl8 is
used for MIG soldering of stainless steel as well
as the joints in which the visual appearance of
the weld surface is important. This can be of
great importance in the furniture industry, for
example.
Inert gases
Argon, I1 or Ar compounds including CO 2 or O 2
a typically used in arc soldering. In the case of
soldering materials with an Si or Sn component,
smaller active CO 2 or O 2 components are
beneficial. They stabilise the arc and reduce
the risk of porosity, while at the same time
enhancing heat input to the base material.
In the case of soldering materials with an Al
component, Ar-He compounds without an active
component are a good choice.
N 2 Additives may stabilise the arc and cause
a wide seam, however, they can lead to
considerable porosity problems.
H 2 As a shield gas component is suitable for
accelerating the soldering feed speed, however,
it can also lead to porosity. To perfectly match
the shield gas with the soldering task in hand,
it is important to draw on the experience of the
shield gas supplier.
Typical MIG soldering seam due to the CuSi wire
melting
Our recommendation:
PRO-MAG 200-2 AM
PRO-MIG 230-4 AM
TRI-MIG 240
SYN-MIG 200 i
The benefits of the MIG soldering method
At a Glance:
XXNo corrosion on the soldering seam
XXMinimum weld spatter
XXEasy reworking of the soldering seam
XXLower working temperature
XXLess distortion
XXLess impact on the structure in the case of
higher strength steels
XXCapillary effect of the solder causes 1/3
higher strength in round hole and slot
soldering
XXLess melting material loss of the coating
XXCathodic protection of the base material in
the immediate vicinity of the weld (zinc)
XXCorrosion protection without reworking
XXOptimum controls for keeping the sheet
thickness
Electrochemical processing Plasma cutting equipment Electrode inverters
TIG inverters
Multifunctional inverters MIG/MAG
7
Welding accessories