BOC Smootharc MMA 170, Руководство по эксплуатации, Страница: 13 / 36

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‘T’ Joints
A fillet weld may be placed either
on one or both sides, depending
on the requirements of the work.
The weld metal should fuse into
or penetrate the corner formed
between the two members.
Where possible the joint should
be placed in such a position as to
form a “Natural ‘V’ fillet” since
this is the easiest and fastest
method of fillet welding.
Lap Joints
In this case, a fillet weld may be
placed either on one or both
sides of the joint, depending on
accessibility and the requirements
of the joint. However, lap joints,
where only one weld is accessible,
should be avoided where possible
and must never constitute
the joints of tanks or other
fabrications where corrosion is
likely to occur behind the lapped
plates. In applying fillet welds to
lapped joints it is important that
the amount of overlap of the
plates be not less than five times
the thickness of the thinner part.
Where it is required to preserve
the outside face or contour
of a structure, one plate may
be joggled.
Corner Joints
The members are fitted as
shown, leaving a ‘V’-shaped
groove in which a fillet weld
is deposited. Fusion should be
complete for the full thickness
of the metal. In practice it is
generally necessary to have a
gap or a slight overlap on the
corner. The use of a 1.0–2.5 mm
gap has the advantage of assisting
penetration at the root, although
setting up is a problem. The
provision of an overlap largely
overcomes the problem of
setting up, but prevents complete
penetration at the root and
should therefore be kept to a
minimum, i.e. 1.0–2.5 mm.
The following terms and definitions are
important in specifying and describing
fillet welds.
Leg Length
A fusion face of a fillet weld, as shown below.
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.
Convex Fillet Weld
ACTUAL THROAT
EFFECTIVE THROAT
CONVEXITY
LEG
LENGH
THEORETICAL THROAT
CONCAVITY
ACTUAL THROAT
AND EFFECTIVE
THROAT
LEG
SIZE
SIZE LEG
THEORETICAL THROAT