SS foil and heat treat question

L

Lo/Rez

Joined
Feb 10, 2013
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I heat treated these Murray Carter design knives in AEB-L today. Every once in a while I will have one knife that I have to peel the foil off of after heat treat. The second one from the bottom turned out that way today, just like it was vacuum sealed on. Any idea as to why this happens? On one knife I think I had a pin hole in the foil. It's the top knife of the four. Will it be usable?

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There are two grades of heat treat foil. One is for temps up to 1900 the other up to 2200. Maybe your foil is the lower temp and the every once in awhile is a hot spot in your HT furnace close to a coil? Just guessing the experts will be along shortly.
 
I have the high temp foil stick sometimes where it takes a bit of effort to peal it all off. It welds to itself too sometimes.

There is stuff in the foil, titanium I think, that helps it consume oxygen and seal shut. I think sometimes these extras might not be perfectly distributed which makes a spot here and there act weird?
 
Could be. If memory serves it's almost like the surface gets hardened. I couldn't bead blast (glass) the areas that it happened before until I reground the flats.
 
Holes happen at the tip, ricasso, or anywhere there is a sharp point. The top two have points at the bottom of the heel. These can puncture and allow oxygen in. The black oxide that developes is very hard. It also creates a decarb layer that is only one or maybe two thousandths thick which should be ground away.

There is no need to fill the envelope with anything that will burn out the O2.

I like the 321 alloy for most stainless and high alloy steels.

Hoss
 
When your Heat treat program calls for two segments do you use the same foil or re wrap for the second segment?
Thanks Jay
 
I wasn't clear. They said plate quench after each segment. Is it one continuous process still?
Thanks for your answer.
 
Plate quench is done at the end of the process. In this case after soaking at 1995F for 5 minutes.
 
I use the same foil both times. I plate quench both times leaving the blade in the foil.

Hoss
 
Hoss, please explain the process and the rational behind it. I'm always interested in doing something better.
 
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