Hi Chuck,

I have seen this problem many times with. I have even had this accur on someof the recievers I have welded. I have found that making shorter beads sometimes helped to stop the hardening. I could not explain why it is only the edges of the bead and not the center. Could be that the filler material at the edges has has more material migration from the parent material which is a higher carbon content causing the hardness at the edges.

Bill G.