WELDING GALVANIZED STEEL
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Tests at The Welding Institute sponsored by the International Lead Zinc
Research Organisation (ILZRO) have established that satisfactory high
quality welds can be made on hot dip galvanized steel and that the
tensile, bend and fatigue properties of such welds can be virtually
identical to those of similar welds made on uncoated steel. Welding
speeds are slower and there is more spatter, particularly when CO<sub>2</sub>= welding.
All the fusion welding processes can readily be used on galvanized
steel but minor variations in technique may be required depending on
the welding process used, the type of joint and the welding position.
For example, with manual metal arc welding:
- A slight 'whipping' action moving the electrode forward and backward
along the line of the joint encourages volatization of the zinc in front of the weld pool.
- Slightly wider gaps are recommended in butt joints to give complete penetration.
- A short arc length gives better control of the weld pool and helps to
prevent either intermittent excess penetration or undercut.
- Both basic and rutile coated electrodes can be used but, simple
procedural tests should be made before undertaking production welding.
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Detailed recommendations for this and other fusion welding processes are available from Galvanizers Association.
While zinc is a necessary trace element in the human diet and it does
not accumulate in the human body, the inhalation of freshly formed zinc
oxide fumes can cause a transient 'metal fume fever' with symptoms
similar to influenza. To maintain fume levels within acceptable levels,
extraction should be provided when welding galvanized steel in confined
areas, as indeed it should when welding uncoated steel. Wherever
welding takes place, due note must be taken of the relevant COSHH
regulations.
RUST PREVENTION AT WELDS
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All welds made in galvanized articles should be protected against rust
as soon as welding is finished, as the top surface is then free from
rust and easy to treat.
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