On Thu, 21 Jun 2012 22:55:00 -0500, Ignoramus17625
wrote:

On 2012-06-22, wrote:
I believe we are talking about an almost new compressor unit with a
crack close to where the foot was welded on - considered to likely be
due to vibration (metal fatigue) which would lead me to believe the
initial welding of the foot was not stress relieved - resulting in a
crack at the edge of the heat affected zone. Welding is more likely to
make that worse, while brazing, if done correctly, is more likely to
anneal the area around the crack - and the brass will strengthen the
area, where a bead of weld is likely to make the problem worse. Of
course it IS possible to lay a few beads over the area to build it up
with a stick welder to get the same effect, more or less - but brazing
is simpler and a lot less likely to CAUSE a problem down the road.
Could even "sweat braze" a patch over the crack, depending where it
is (not applicable as I understand the failure in this case).

How do you anneal a braze?
Brazing helps anneal the steel (heat to dull cherry red and cool
slowly) while welding is more likely to harden the steel (high heat,
and cool quichly)

Don't quench either a welded or brazed patch.