Specifications

8
313AU : IPRM 2007 : SECTION 8 : CONSUMABLES
WARNING Welding can give rise to electric shock, excessive noise, eye and skin burns due to the arc rays, and a potential health hazard if you breathe in the emitted fumes and gases.
Read all the manufacturer’s instructions to achieve the correct welding conditions and ask your employer for the Materials Safety Data Sheets. Refer to www.boc.com.au or www.boc.co.nz
Fundamentals of Manual Metal Arc (MMA) Welding
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
Size (mm)
Min.Throat
Thickness (mm)
Plate Thickness
(mm)
Electrode
Size (mm)
5.0 3.5 5.0–6.3 3.2
6.3 4.5 6.3–12 4.0
8.0 5.5 8.0–12 and over 5.0
10.0 7.0 10 and over 4.0
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. 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 below. The angle of the electrode for various runs in a
downhand fillet weld is also shown.
Recommended Electrode Angles For Fillet Welds
1st Run 2nd Run
3rd Run Multi-run Fillet
Multi-run (multi-pass) 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.
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 3.2 mm or 4.0 mm diameter
electrode. Subsequent runs for large fillets may be either numerous
straight runs or several wide weaving runs.
Correct selection of electrodes is important for vertical welding.
In overhead fillet welds, careful attention to technique is necessary
to obtain a sound weld of good profile. Medium current is required
for best results. High current will cause undercutting and bad
shape of the weld, while low current will cause slag inclusions. To
produce a weld having good penetration and of good profile, a short
arc length is necessary. Angles of electrode for overhead fillets is
illustrated below.
Recommended Electrode Angles for Overhead Fillet Welds
30˚
15˚
45˚
Fundamentals of Manual Metal Arc (MMA) Welding