Lincoln Electric Welder - Manual (Page 16)

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stainless steel is selected, it is the
welding engineer’s responsibility to
design the joints, select the weld filler
metal, welding process and welding
procedure.
7.0
DESIGN FOR
STAINLESS
STEELS
Since the coefficient of thermal
expansion for austenitic stainless
steels is relatively high, the control of
distortion must be considered in
designing weldments of these alloys.
The volume of weld metal in joints
must be limited to the smallest size
which will provide the necessary
properties. In thick plate, a “U”
groove, Figure 3(c), which gives a
smaller volume than a “V” groove,
should be used. If it is possible to
weld from both sides of a joint, a
double “U” or “V” groove joint
preparation should be used. This not
only reduces the volume of weld
metal required but also helps to
balance the shrinkage stresses.
Accurate joint fitup and careful joint
preparation which are necessary for
high quality welds also help minimize
distortion.
Joint location and weld sequence
should be considered to minimize
distortion.
Strong tooling and fixturing should be
employed to hold parts in place and
resist tendencies for components to
move during welding. When any of
the gas shielded processes are used,
the tooling should also provide an
inert gas backup to the root of the
weld to prevent oxidation when the
root pass is being made. This is
particularly important when GTA
welding pipe with insert rings to allow
the weld metal to wet and flow
together at the root of the joint.
In welding pipe, insert rings, Figure 4,
of the same composition as the filler
metal should be used for the root
pass and be welded by the GTAW
process. If copper chills are to be
used near a weld area, they should
be nickel plated to prevent copper
pickup. If copper is in contact with
the high temperature region of the
heat affected zone, it can melt and
penetrate the grain boundaries of
austenitic stainless steel causing
cracking.
8.0
SELECTION OF
FILLER METALS
Filler metals for welding stainless
steels are produced as coated
electrodes (AWS A5.4), solid and
metal core wire (AWS A5.9) and flux
core wire (AWS A5.22). The various
electrodes, solid wires, metal cored
wires and flux cored wires are
contained in AWS “Filler Metal
Comparison Charts”, latest edition.
According to these charts, matching
filler metal should be available for
almost every type of austenitic
stainless steel available, although
many types may be produced in
small quantities by only a few
companies and may not be readily
From AWS D10.4
FIGURE 3 — Typical joint designs for welding austenitic stainless steel pipe.
A = 37-1/2°± 2-1/2° D = 2 times amount of offset
B = 10° ± 1° E = 30° max
C = 1/16 in. ± 1/32 in. (1.6 mm ± 0.8 mm) R = 1/4 in. (6.4 mm)