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AL-6XN alloy is easy to weld using similar parameters
as Type 316L stainless steel, including travel speed (IPM)
and weld current. It is common to use a weld insert ring
for additional alloying when orbital or manual welding in
the field.
USE WELD INSERT RINGS
When using weld insert rings for orbital or manual
welding, never use filler wire in place of weld insert rings
for sanitary tubing. Welding techniques that apply filler
wire to the weld face risk the possibility of insucient
alloying in the weld root.
The alloy of the insert ring must have a higher
molybdenum content than the AL-6XN to compensate
for alloy dilution on cooling. Typically, Alloy C-22 (13%
Mo) is used. If Alloy C-22 is not available, Alloy 625 (9%
Mo) or Alloy C-276 (15% Mo) may be substituted. CSI
stocks C-22 weld insert rings.
PLACE THE WELD INSERT RING
AND FUSION WELD
The weld insert ring should be placed between the two
sections and fusion-welded as usual. The weld current
must be increased slightly to compensate for increased
thickness due to the insert ring.
USE INERT GAS FOR WELD COVER
AND BACKING
Inert gases such as helium may be used, although argon
is more common. In some applications, the addition of
3-5% nitrogen to shielding gas can help compensate for
the loss of nitrogen during welding.
REMOVE HEAT TINTS
The weld heat-aected zone (HAZ) should be no darker
than a light straw color. A color-free silver weld and heat-
aected zone are best. Any darker weld heat tints must
be removed before placing in service. Dark blue and
black heat tints are the most susceptible to corrosion.
Remove these tints by using abrasives followed by acid
cleaning or passivation. A poorly cleaned surface may
be just as susceptible to corrosion attacks as the original
heat tint.
NOTE: When the temperature of the metal is below the
dew point, allow it to warm above the condensation
temperature to prevent moisture condensate on the
surface, which can cause heat tint.
WELD INSERT RINGS
RING WELDED
BETWEEN SECTIONS HEAT TINTS REMOVEDORBITAL WELD
AL-6XN® GENERAL WELDING
RECOMMENDATIONS
