SS envelope fell apart

[olymon]

OK, simple problem with many complex answers. I heat treated a D2 blade I was working on. Foil wrapped it in .004" ss that I had m I was worried about cracks in the stainless from bending it so I wrapped the whole blade in paper before I put it in the pack. I put it in our oven at work 24" ×24" ×12" that was already up to temp. I let it in the for 40 minutes.
I went to pulp out the pack and noticed it was bulged out pretty good m grabbed the knife wroth my tongs and the ss foil just fell apart. So I just moved the blade to my 2" thick quench plates and clamped it down. Without the foil on there I noticed that the portions of the knife touching the plates cooled very quick but the thin section was still hot. Almost the opposite of an oil wish where the thin section coils quicker.
I'll have to see what my scale looks like when I get some time to work on it. I need more time for my hobby!

 

[JTknives]

Did you use low or high temp foil. That is WAY to much paper to put in the foil packet. Most people don’t even use paper any more. For that matter I don’t even use foil any more, I use nitrogen gas shealding.

 

[Stacy E. Apelt - Bladesmith]

I give the blade a spray of WD-40. That provides plenty of carbon to combine with the oxygen in the packet. The foil has to be 2200F type.
Don't work about the edge staying hotter than the spine in the plates. D2 is air hardening steel, and the pearlite nose is at ten minutes, not a few seconds. It will cool completely to hand temp in less than a minute. You could just hang it in the air and go to lunch and it would fully harden ... but would likely warp more than in aluminum quench plates.

 

[jdm61]

I have use the "low" temp foil and a dab of kerosene for forge welding Ferry flip billets. I did two welding passes and the foil came apart during the second pass, which worked perfectly for my needs.

 

[olymon]

OK, well big lesson learned. I didn't even know that there was a high temp stainless foil. I guess I should have researched that more. We'll see what it looks like when I start sanding the blade. I hope it doesn't have a lot of scale. I should have just sent it out to be heart treated, I'm not in a time crunch.