Linde BOC RAPTOR 250R MIG Operating Manual page 43

Convex Fillet Weld
Actual Throat Actual Throat
Convexity
Effective Throat Effective Throat
specified leg length has a throat thickness in excess of the effective
measurement.
Concave Fillet Weld
A fillet in which the contour of the weld is below a straight line
joining the toes of the weld. It should be noted that a concave fillet
weld of a specified leg length has a throat thickness less than the
effective throat thickness for that size fillet. This means that when
a concave fillet weld is used, the throat thickness must not be less
than the effective measurement. This entails an increase in leg
length beyond the specified measurement.
The size of a fillet weld is affected by the electrode size, welding
speed or run length, welding current and electrode angle. Welding
speed and run length have an important effect on the size and
shape of the fillet, and on the tendency to undercut.
Insufficient speed causes the molten metal to pile up behind the
arc and eventually to collapse. Conversely, excessive speed will
produce a narrow irregular run having poor penetration, and where
larger electrodes and high currents are used, undercut is likely
to occur.
Fillet Weld Data
Nominal Fillet Minimum Throat
Size (mm) Thickness (mm)
5.0 3.5
6.3 4.5
8.0 5.5
10.0 7.0
Actual Throat
& Effective Throat
Convexity
Leg
Lengh
Theoretical Throat Theoretical Throat
Plate Thickness Electrode Size
(mm) (mm)
5.0–6.3 3.2
6.3–12 4.0
8.0–12 & over 4.0
10 & over 4.0
Concave Fillet Weld
Actual Throat
& Effective Throat
Concavity
Leg
Size
Leg
Lengh
Theoretical Throat
Selection of welding current is important. If it is too high the weld
surface will be flattened, and undercut accompanied by excessive
spatter is likely to occur. Alternatively, a current which is too low
will produce a rounded narrow bead with poor penetration at the
root. The first run in the corner of a joint requires a suitably high
current to achieve maximum penetration at the root. A short arc
length is recommended for fillet welding. The maximum size fillet
which should be attempted with one pass of a large electrode is 8.0
mm. Efforts to obtain larger leg lengths usually result in collapse of
the metal at the vertical plate and serious undercutting. For large
leg lengths multiple run fillets are necessary. These are built up as
shown above.
Recommended Electrode Angles for Fillet
Welds
Multi-run horizontal fillets have each run made using the same run
lengths (run length per electrode table). Each run is made in the
same direction, and care should be taken with the shape of each,
so that it has equal leg lengths and the contour of the completed
fillet weld is slightly convex with no hollows in the face.
Vertical fillet welds can be carried out using the upwards or
downwards technique. The characteristics of each are: upwards –
current used is low, penetration is good, surface is slightly convex
and irregular. For multiple run fillets large single pass weaving runs
can be used. Downwards – current used is medium, penetration is
poor, each run is small, concave and smooth (only BOC Smootharc
13 is suitable for this position).
The downwards method should be used for making welds on thin
material only. Electrodes larger than 4.0 mm are not recommended
BOC RAPTOR 200C & 250R MIG Operating manual
Concavity
Leg
Size
Size Leg Size Leg
Theoretical Throat
43