Linde BOC Smootharc Advance MIG 425R Operating Manual page 49

Recommended Electrode Angles for Fillet Welds
1st Run
40° 40°
40°
40°
3rd Run
20–30° 20–30°
20–30°
20–30°
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
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.
2nd Run
55–60° 55–60°
55–60°
55–60°
Multi-run Fillet
6 6
6
6
5
3 5
3
5
3 5
3
1 2
1 2 4 4
1 2
1 2 4
4
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
BOC Smootharc Advance III MIG 425R & 555R Operating manual
Recommended Angles for Overhead Fillet Welds
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 for vertical down
welding. All strength joints in vertical plates 10.0 mm thick or more should
be welded using the upward technique. This method is used because of
its good penetration and weld metal quality. The first run of a vertical up
fillet weld should be a straight sealing run made with 3.15 mm or 4.0 mm
diameter electrode. Subsequent runs for large fillets may be either numerous
straight runs or several wide weaving runs.
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