ssc-367 - Ship Structure Committee

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Controlled Erosion
An alternate weld toe modification technique uses a highcontaining
grit. Under carefully
pressure water jet
controlled conditions the weld toe area can be eroded as
though itwere beingground. Work carried outon filletwelds
with abrasive water jetting (AWJ) by Maddox and Padilla
(Reference9.4) andKing (Reference9.5) indicatethat fatigue
life improvement due to AWJ erosion and toe grinding are
comparable. The S-N curve improvements obtained due to weld
toe abrasivewater jet erosion are illustratedon Figure 9-3.
This approach does not require heat input and can be carried
out quickly, offering an advantage over alternative methods.
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Remeltinq Techniques
Remeltingweld material to a shallow depth along the weld toe
results in removal of inclusions and helps achieve a smooth
transitionbetweentheweld and the platematerial. Tungsteninert-gas
(TIG) and plasma welding are not practical
techniquesfor routine use, but TIGandplasma dressing can be
used to improve the fatigue strength of selective areas.
TIG welding is based on astringer bead process
is performed on welds made by other processes
region is melted to a shallow depth without
TIG dressing
where the toe
the use of a
filler material. Slag particles in the remelted zone are
brought to the surface, 1caving the weld toe area practical1y
defect free. Ahigh heat inputshould be maintainedto obtain
a good profile and a low hardness. A low hardness in the
heat-affectedzone (HAZ)may be also achieved by a second TIG
pass.
Plasma dressing requires remelting the weld toe using the
plasma arc welding technique. It is very similar to TIG
dressing, but plasma dressing uses a wider weld pool and
higher heat input. This technique is relatively insensitive
9-1o