Originally Posted by duanedr

Thanks.

The clamp cracked almost immediately upon cooling. I had heard of someone having a hard time with KVA or 953 or some other stainless tubing and had the same problem - cracked when it cooled.

I had a few things working against me:

• I used pretty thick material for the extension since stainless is a bit weaker than 4130
  • It took more heat than stainless likes apparently to get filler to really soak into the joint
  • the flux didn't burn and it flowed fine and I got a nice inner fillet
  • there is a suggestion that even heating of the whole part might have prevented it.
• nickel silver melts a bit higher temp even than brass
  • After it happened, I read up a little and it mentions copper/zinc fillers don't get along with stainless. I assumed it was something about the filler getting into the grain structure of the stainless or something.
  • The more I read, I think they just take higher temps to melt and stainless doesn't like that; there are suggestions to anneal the tube before brazing but then strength goes way down so, I'm not sure if that's the solution.
• thermal expansion/contraction rates are different for the filler and stainless steel which adds stress
• The clamp had already been through one heat cycle to attach the bosses with 56%.

I think the combination caused the clamp part to crack. <snip> I think if I had just used Fillet Pro, It would have been fine.