Lincoln Electric Welder - Manual (Page 22)

20
problems. Welding is generally done
using direct current, electrode
positive. Alternating current is some -
times used for moderate penetration
and good arc stability.
Since deposit composition depends
upon the filler wire composition, any
alloy additions to the flux and
chromium oxidation and loss to the
slag, flux selection and welding
conditions must be rigorously
controlled. Voltage, current and
travel speed variations will influence
the amount of flux melted and the
resulting weld deposit composition
and ferrite content.
Conventional austenitic stainless steel
electrodes such as ER308, ER309
and ER316 can be used with
conventional stainless steel fluxes for
welding most of the austenitic
stainless steels except applications
where Ferrite Number must be less
than 4.
If base metal strength must be
attained in martensitic or precipitation
hardening stainless steels, special
procedures and fluxes must be used
with the correct filler metal to provide
a weld deposit which will respond to
postweld heat treatment. If special
fluxes are not used, the weld metal
probably will not respond to heat
treatment. This is particularly true for
aluminum-bearing electrodes where
aluminum is lost through metal-slag
reactions. The stainless flux
manufacturers should be consulted
for recommendation on fluxes and
welding procedures.
9.3
GAS METAL
ARC WELDING
If the production application involves
long joints in relatively thick material
or a large number of parts, the
GMAW process with solid or metal
cored wire may be the best choice.
Solid or metal cored wire will provide
WELDING TECHNIQUES FOR SHIELDED METAL ARC WELDING
Use a short arc without touching the puddle. This minimizes alloy loss in the arc and reduces porosity
and spatter. Red Baron and Blue Max electrodes can be dragged.
Weld with a low current consistent with good fusion to minimize heat input for distortion control. The
low current also reduces penetration when minimum admixture is needed for corrosion resistance and
cracking or porosity resistance.
Stringer beads minimize heat input to control distortion. If weave beads must be used, limit the weave
to 2 1 /
2
times the electrode diameter.
Flat beads with good wash-in are needed for easy slag removal, particularly in deep groove welds.
Fill craters by holding a short arc and moving back over the finished bead before breaking the arc. This
avoids crater cracks.
Cl ean each bead thoroughly before welding over it. Because the slag from lime coated Stainweld
XXX-15 electrodes crumbles, particular care is needed to remove all particles.
For vertical and overhead positions, weld with 5 /
32
” (4.0mm) or smaller electrodes. The easiest to use
vertical-up are Stainweld XXX-15 electrodes. Blue Max electrodes require the widest weave for
vertical-up. Vertical-down welding is best accomplished with Red Baron -V electrodes.
For vertical-down welding with Red Baron-V electrodes, use a dragging technique and current towards
the high end of the recommended range. For vertical-up, Stainweld XXX-15 can be run without weave.
All others require a weave – a triangle weave or inverted Vee weave works well.
In the overhead position, Red Baron and Blue Max electrodes work best by a dragging technique.
Stainweld electrodes work best with a short arc and slight circular motion during steady forward motion.
Penetration should be only enough to seal openings in root passes and bond to the base plates. Deep
penetration can cause cracking and loss of corrosion resistance and provides no advantages.