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Kiln heat treat problem


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I tried using a kiln for heat treat for the first time, and I'm pretty sure I ruined my blade.  Here is what I did.  My blade is PW 15n20 and 1084(1/8" at it's thickest), and I applied a thin layer of satanite between heats to try to prevent scale.

3x normalize @ 1700f, 1600f, and 1500f

heat for quench with 10min hold @1550f quenched into ambient temp canola oil (attempted 2 quenches)

The blade did harden a little that a file will bite just the slightest bit.  All together the steel was in the kiln for about 4 total hours.  As far as I can tell 1 of 2 things happened.  1 I decarbed my blade to the point where it's junk.  2 my oil being on the cold side is the culprit.  I'd like to save this blade if possible, but I already got into polishing and the edge thinned before I concluded my HT was unacceptable.  So I'd like to avoid putting more time into this if it's useless efforts anyway.  I read up a little on kiln heat treat(after I tried it of course><) so I suspect #1 is what happened.  Now the question at this point, is my blade salavable as is?

Tonight I'm going to try HT with my forge into warm canola just to be certain.  I figure it couldn't hurt to see if others share my assumptions or if I'm completely wrong.

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Well, it's much harder to carburize than to decarburize ( but technically possible ), so I'd just live with the lower hardness and buy some actual anti-scale compound.

Hot oil might not hurt, but 1084 has enough manganese ambient should have done it.

Finally, why in the world would you go to 1700 (or even 1600) to normalize?  And why would you soak?  I suspect massive decarb along with massive grain growth.  For 1084 and 15n20 both all you need to do to normalize is get it to just kick over the top of critical, say 1475- 1500.  Do Not Soak.  Immediately remove from the kiln and let cool to black in still air, i.e. don't lay it down for a while.  Once it shows no color at all in the dark you can quench if you want. Repeat, lowering upper temperature by 25-50 degrees each time if that floats your boat or if you started at 1550.

Any time you feel tempted to soak simple steels remember this blade.  Soaking is only for high alloy steels and controlled atmospheres.  Incidentally, anti-scale compound will start pitting the blade if taken higher than 1650 or so, which should tell you something about ideal heat treating temperatures.  Yeah, stainless and many air-hardening alloys and especially HSS require higher heat and long-ish soaks, but they are typically wrapped in HT foil with a bit of paper first to create a neutral to reducing atmosphere.

Wish I had better news for you.  :(

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Thanks Alan.  It seems I misremembered the thread back from 2013 on kiln heat treating 1084 in my haste.  The silver lining is that the blade being just barely usable means I cant let anyone but me use it.  So I get to keep my frankensteinish jelly roll:/ and at the very least I want to see what the full pattern ended up as.  I'll have to follow your advice on the next one.  Man I read kilns(especially the low V ones) take a while to come up to heat, but I really underestimated that time until I saw it for myself.

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