Welding Hastelloy C-22 in many ways is similar to
traditional 316L material. There are no special welding
requirements or concerns, given that proper techniques
and procedures are followed. The GTAW process is the
most common method and can be done manually or
automatically with orbital welding equipment.
Orbital welding parameters for Hastelloy C-22 are also
similar to those for welding 316L. Weld schedules for
a given size are comparable in weld current inputs,
pulsing, travel speeds (IPM), and gas shielding of weld
pool for both cover and backing.
Any modern welding power supply with adequate
output and controls can be used for common fusion
welding. Generally, weld heat input is controlled in the
low to moderate range.
Nickel-based alloys generally exhibit sluggish welding
and shallow penetration characteristics; therefore, the
possibility of incomplete fusion increases. Care must
be used to ensure a sound weld. If orbital or automatic
welding equipment is used, programs should utilize a
pulsed current. Pulsed current inputs can help control
weld penetration without exclusive heat input. Pulsing
also helps control the weld pool, improving the uniformity
of weld bead appearance.
Cleanliness is critical when welding nickel-based alloys.
Contamination by grease, oil, lead, sulfur, or other low-
melting-point elements can lead to severe cracking
problems. The welding surface and adjacent areas
should be cleaned thoroughly with an appropriate
solvent, such as 99.9% isopropanol (IPA). Prior to
welding, all foreign matter such as lubricates, cutting
chips, burrs, and crayon markings should be removed.
In the majority of corrosive environments, C-22 products
are used in as-welded condition. Post-weld heat
treatment such as full solution annealing or stress relief
annealing is usually not required.
Orbital welding C-22 to other alloys such as AL-6XN or
316L can be done autogenously; however, performance
expectations in corrosive environments should be kept
low. Welding procedure development and mechanical
testing should follow the requirements set by the
applicable code or standard. Additional test methods
should also be considered when evaluating corrosion.
It is advisable to consult a metallurgist with corrosion
experience to assess the service requirements for the
specified application.
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