During welding, the base metal, HAZ, and
underlying weld passes experience stresses due
to thermal expansion and contraction. On solidification,
high levels of residual stress, often close
to the material yield stress, remain as a result of
weld shrinkage. Stress-concentration effects as
a result of geometrical discontinuities, such as
weld reinforcement (excess weld metal) and lack
of full weld penetration (dangerous because of
the likelihood of crevice corrosion and the possibility
of fatigue cracking), are also important
because of the possibility of stress-corrosion
cracking (SCC) in some environments