Foil sticking

T

Tom Lambert

Member
Hi folks. Interesting problem today, I was heat treating four 440 C blades. Heating two at a time in separate double wrap high temp foil. I went to plate quench and found that the foil had welded to the blades in spots. Temp was 1880 for 15 minutes. Have not had this problem before. Your help is appreciated
 
Craig, How much chalk do you use? Do you cover the whole blade?

Tom, what type of foil are you using? 309 or 321? So far (knock on wood), I've had pretty good luck with the lower temperature 321, but 309 is what's generally recommended for heat treating. Do you put a small bit of brown paper inside the foil packet to burn up the Oxygen?

Ken H>
 
Reaching for straws here, because it does happen and it seems this is your normal, problem free process. I have found a tendency for foil to weld to blades when the oven is opened and closed during the heat treat. Cooling the air in the well sealed envelope can have a shrink wrap like effect - and seems to sometimes lead to the sticking.

We use a bit of paper or powder in the envelope as well, but I can't prove that makes any difference. Pretty sure it does no harm.
 
Thanks Knifemaker. I was thinking back to other blades I've done and the conclusion I came to is that I stacked two blades in foil on my quench plates. Before I have always quenched individual blades. Good advice on the powder. I never thought of that
Thanks to all the Pack Members who answered my question.
 
I think it was Darrin Sanders that gave me this tip.

Make sure the blade is "CLEAN', then dust both sides with talcum powder before sealing in the envelope.

I have not had any sticking problems since I started doing this.

Robert
 
If I have any problems with foil sticking I'll try that powder. I tried two blades in one foil packet and it just didn't "seem" to work as well..... I think I'll also be staying with one blade per packet.

Ken H>
 
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