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The World of precious Metals

Basic Information on MIG Soldering of zinc-coated steel sheets

Welding of zinc-coated steel sheets:


Zinc begins to vaporise as soon as the arc is ignited. During welding this zinc vaporisation results in pore formation, binding faults and an unstable burning arc. In this thin-sheet range deformation or warping should also be taken into account.
An alternative to the welding of galvanised steel sheet is MIG soldering using Silox R 1 S bronze wire and Silox R 4 A. aluminium bronze. The melting range of the solder additives is between 965°C and 1040°C. As a result of the low working temperature, around 500 °C below the melting point of the base material, there is only a minimal amount of burning off of the zinc layer. The soldered seam is corrosion-resistant as a result of the alloy components. The minimal zinc burn-off in the immediate vicinity of the soldered seam is protected from corrosion by the cathodic protective action of the base material. When the iron/zinc pair is used (galvanised steel sheet), damage to the surface (zinc burn-off) causes the formation of cathodic and anodic regions. As a result of the different material potentials, the baser metal (zinc) continuously releases zinc ions to the more noble metal, iron (cathode), However, this protective effect is only feasible over a width of 1-2 mm.

MaterialMelting Point or RangeBoiling Point
Zinc419 °C915 ° C
Steel1500 °C
Silox R 1 S965 - 1035 °C
Silox R 4 A1030 - 1040 °C

Advantages:

  • Working temperature is around 500 °C below the melting point of the base material
  • Minimal burn-off of the zinc layer - cathodic protective effect of the base material in the immediate vicinity of the soldered seam.
    This protective effect takes place over a distance of 1-2 mm of the uncoated surface.
  • No corrosion of the soldered seam
  • Low influx of heat, little warping or deformation of the sheet metal because the stretching energy is 20% lower
  • Almost spatter-free welded seam
  • No after-Treatment of the welded seam because there is very little spattering

The back of the galvanised steel sheet is not damaged by the TIG or MIG soldering.
At most there is some melting of the zinc layer but no vaporisation of the zinc layer.