Welding Inspection & Metallurgy API ICP Self Study Notes

One of the main differences between nickel alloy and carbon steels, and
austenitic stainless steels, is there tendency to be sluggish during welding.
This means for nickel alloys that the molten weld pool will not move as easily
as it does for other metals.
This sluggish tendency means the welder should move the weld pool with a
weave or oscillation pattern to ensure good sidewall fusion. If some oscillation
is not used, a high convex weld contour will result which cause sidewall lack
of fusion, weld undercut or slag inclusions. The formation of a slightly
concave weld bead profile will be more resistant to centerline cracking. It is
also important that the bevel angle for nickel alloys be wide enough to allow
for this necessary oscillation of the welding torch. The wider weld bevel will
also be beneficial with respect to weld penetration. Nickel alloys also suffer
from shallower weld penetration as compared to carbon steels and austenitic
stainless steel. To overcome this, the weld joint is modified by having a wider
bevel and thinner root face.