LESSON VII ©
COPYRIGHT 2000 THE ESAB GROUP, INC. of
filler metal per foot of weld. Figure 5B shows a sketch of a typical fillet
weld made with the
flux cored CO2 shielded process. The
leg length of this weld measures only 3/8". The deep
penetration of the process results in a throat dimension equal to that in Figure
5A, 0.35". The
cross-sectional area of this fillet weld is 0.070 square inches and requires 0.239
pounds of weld metal per foot of weld.
This results in a savings of 0.186 pounds per foot of
weld, or a savings of 44% in weld metal
volume. It should be remembered that not only is the
cost of the weld metal saved, but also the cost of the labor and overhead that
would be spent
in depositing the extra metal. The chart in Figure 6 shows the increase
in volume of weld
metal required as the fillet size increases. It shows that if a 5/16" fillet
weld is made where
a 1/4" fillet would suffice, more than half (58%) of the amount of weld metal
is wasted.
7.4.2
Shielding
Gas -
Gas shielded flux cored electrodes require that an adequate
gas shield be present at all times.
Gusty or high velocity winds cannot be tolerated and in
such instances, it may be necessary
to place a curtain or other wind screen around the operator.
Light breezes will not affect the gas shield. Inadequate gas shielding
will be evidenced
by porosity on the surface of the weld metal. 7.4.2.1
CO2
is the most common shielding gas used; however, Argon-CO2
mixtures may be
recommended for some types. The gas shield effectively protects the arc
from atmo- spheric
oxygen and nitrogen but some oxygen will be present from the dissociation of the
shielding gas. The deoxidizers
in the core materials allow the electrodes to tolerate these
small amounts of oxygen. The
need to denitrify the weld metal is of less importance be-
WELD METAL FILLET
SIZE CU. IN/IN
% INCREASE 1/4
.031 58%
5/16 .049
43% 3/8
.070 78.5%
1/2 .125
COST OF OVERWELDING
FIGURE 6
