Civil Engineering Reference
In-Depth Information
If the weld is to be finished by an unspecified mechanical means the
letter U is used in the AWS system, as shown in
Fig. 8.4
.
U
U
8.4
Unspecified fin-
ishing (AWS).
Convex contour
The symbol for a convex weld is rather mysterious because it
is difficult to imagine a case where a convex profile would be spe-
cified for either a butt/groove weld or a fillet weld. All welds are
normally deposited with a slightly convex profile to provide the
minimum required throat thickness without excess weld metal. This
symbol, without further instructions, could cause confusion in a
welding shop because it would encourage a welder to deposit excess
weld metal, which would create potential problems and additional
costs.
The location of the convex weld symbol is shown in
Fig. 8.5
.
8.5
Location of the
convex weld symbol.
It is worth noting that AWS D1.1-2000 Structural Welding Code
specifies limits to convexity of welds depending on the width of the
weld face as follows:
Width of weld face
Maximum convexity
W £ 8mm
2mm
W > 8 to < 25 mm
3 mm
W ≥ 25 mm
5 mm
Excess weld metal refers to the metal that lies outside the surface
of a mitre fillet or outside a straight line between the toes of the
butt/groove weld. This excess metal is sometimes wrongly called
reinforcement. This is incorrect because in only very rare cases
would it increase the static strength of a joint and in many cases it
would reduce the fatigue strength.
