"Ignoramus15937" wrote in message
...

You see the weld with slag removed, from both sides. I then used a
chop saw to cut the joined pieces to see what's happening in the
weld. To my surprise, the weld looked like it was original metal, no
sign of any dissimilarity or boundary.

It's very difficult to see dissimilarity and slight imperfections in metal
that has been rough cut. You should try grinding the cross-section smooth
and flat (a disc sander is ideal for this) and then polishing it. Then
you'll really see what's going on.

- Michael