DISTORTION
-
If steel fabrications distort during galvanizing, this is usually due
to "built-in" stresses being released, as the steel is heated to
the galvanizing temperature. Stresses may be inherent in the steel, but they
can also be introduced by welding, cold forming, and hole punching.
Efforts can be made at the design stage and elsewhere to minimise residual stresses, for example:
1. Controlling welding procedures during fabrication.
|
 |
2. Arranging weld seams symmetrically. The size of weld seams should be kept to a minimum.
3. Avoiding large changes in structural cross-section, which may increase distortion and thermal stress in the galvanizing bath.
Where there is an inherent tendency to distort, e.g. in asymmetrically
shaped fabrications, the effect can be minimised or possibly eliminated
by restricting the fabrication to such a size and design that it can be
rapidly immersed in a single dip. The galvanizer should be consulted
for advice at an early stage if this is being considered. The size and
position of filling and drainage holes in fabricated vessels can have a
major effect on distortion, as can the size and position of lifting
holes or lugs, particularly on hollow fabrications.
|
