Laser weld "cracking"

Hello again everyone! I am a newbie with my laser welder, about 2
months. It is a Crafford, about 8 years old, that I bought from a
jeweler that was upgrading. My question is “Why do my welds
sometimes have a distinct crack down the center?” I usually come
back over them by filling with wire, but I’m wondering if this is
correct. I notice the cracking usually when soldering 2 rings
together, yellow or white. I am using argon with the white. I
tried to research in the archives, but didn’t see anything specific.
Any help appreciated.

Chad Dupuis, Baton Rouge

    Hello again everyone!  I am a newbie with my laser welder,
about 2 months.  It is a Crafford, about 8 years old, that I bought
from a jeweler that was upgrading.  My question is "Why do my welds
sometimes have a distinct crack down the center?" 

Hello Chad, Working with laserwelding for a couple of years, I
noticed also small cracks over the centre of the weldspot sometimes.
The only reason I can figure out is the rapid cooling of the weldspot
so the stress on that spot gives a crack from shrinkage of the metal.
Sometimes when welding titanium without gasprotection (not advicable)
the crack can be strong enough to destroy the connection.

Jan Matthesius