Scale after heat treat - O1 - 3/32"

W

WhiteOwl

Joined
Nov 10, 2011
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29
I'm using 3/32" O1 for stock removal. I asked a local knifemaker if I could pay him to heat treat my blades. He said there is going to be quite a bit of scale after heat treating and that my knife might be too thin once it's removed. Is that the case? How do people heat treat thinner O1 and avoid this?
 
I'll second that. Anti scale is a must when running heat cycles. Scale on the surface indicates loss of iron.

Good luck with the heat treat, Fred
 
I do this all the time, without the descaling compound, 30 seconds or less with a 60 grit belt will remove the thin layer of oxidation(its not really scale) Its about .001" thick.
Del
 
I use an oven that ha a pretty tight door and I only get a real thin layer of oxidation also. I think a lot of how much scale occurs is in the heat source for HT.
 
The "scale" was very very mild and easy to clean off. My first batch of blades came out great! I made one knife for the purpose of testing and it's holding up fine.
 
If you are using a steel that requires more than just a few minutes of soak for thorough austenitization, you need some kind of protection. Anti-scale also protects against decarb. I like the ATP anti-scale. It is water based and is painted on, or you can dip the blade in it. This coating comes off in the quench, and leaves the surface as smooth as you prepped it, with no noticable de-carb.
 
with the steel only being 3/32, couldn't you heat treat and do all of your grinding after? That way you won't need to worry about scale at all
Jason
 
I have used a thin wash of refractory clay slip with good results. It won't work for cycling though... once the steel comes down from a high temperature the clay flakes off.
 
I have used a parts washing solvent (the same stuff used for welding Damascus) prior to heat treat with very good results. The steel comes out nice.
 
Rick Marchand said:
I have used a thin wash of refractory clay slip with good results. It won't work for cycling though... once the steel comes down from a high temperature the clay flakes off.
Click to expand...

Rick,
Would there be an issue if you put the thin wash on say, 2 or 3 days ahead of the time that the blades will be heat treated?
 
Nope waiting days/weeks would be okay... it is the contracting and expanding of thermal cycling that breaks the clay free (like decarb during the quench). In other words, don't use it for normalizing cycles... It's a one-time-use application.
 
I use, like rick a thin wash of satanite. Keeps the scale down and pops right off in the quench leaving a pretty pristine blade from my experience.
 
also, if I understand correctly using a proper sealed HT oven will eliminate / reduce scaling?
 
The key for me was figuring out that I didn't have to water it down as much I was. Applying thin layer doesn't necessarily mean using thinly mixed clay. I get it to the consistancy of toothpaste. The important part is mixing it up thoroughly, so there are no clumps.

Tai uses a chunk of hardwood or charcoal to eat up the oxygen in his mufflepipe set up. I would imagine that kilns with controlled atmospheres are mucho $. A tight door just wouldn't cut it.
 
one more question on the topic of oven treating O1, do you bring the blades up to heat along with the oven or do you preheat the oven and then put the blades in.

Something tells me you should put the blades in first and then set it to 1475 and go but again, I've read both...
 
does this look okay? I got the clay to "toothpaste" consistency. The small grains are part of the clay. Also I'm not sure what (if any) effect the lines will have. I painted it on with a small brush.
2011-12-16170236.jpg
 
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