MESSER SolidWELD MIG 250GS Guide D'utilisation page 20

020 MIG 250GS Operating manual
Convex Fillet Weld
Actual Throat Actual Throat
Convexity
Effective Throat Effective Throat
The following terms and definitions are important in specifying and
describing fillet welds.
Leg Length
A fusion face of a fillet weld, as shown above. All specifications for
fillet weld sizes are based on leg length.
Throat Thickness
A measurement taken through the centre of a weld from the root
to the face, along the line that bisects the angle formed by the
members to be joined.
Effective throat thickness is a measurement on which the strength
of a weld is calculated. The effective throat thickness is based on a
mitre fillet (concave Fillet Weld), which has a throat thickness equal
to 70% of the leg length. For example, in the case of a 20 mm fillet,
the effective throat thickness will be 14 mm.
Convex Fillet Weld
A fillet weld in which the contour of the weld metal lies outside
a straight line joining the toes of the weld. A convex fillet weld of
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
Actual Throat
& Effective Throat
Convexity
Leg
Lengh
Theoretical Throat Theoretical Throat
Concave Fillet Weld
Actual Throat
& Effective Throat
Concavity
Leg
Size
Leg
Lengh
Theoretical Throat
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)
5.0
6.3
8.0
10.0
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. The angle of the electrode for various runs in a downhand
fillet weld is shown on the next page.
Concavity
Leg
Size
Size Leg Size Leg
Theoretical Throat
Minimum Throat Plate Thickness
Thickness (mm) (mm)
3.5 5.0–6.3
4.5 6.3–12
5.5 8.0–12 & over
7.0 10 & over
Electrode Size
(mm)
3.2
4.0
4.0
4.0