Is this scale or something I should worry about?

Was your oil heated? 1095 needs a fast quench so to get that with canola oil it needs to be heated.Edge quenching could of slowed down the quench as the oil is trying to quench the edge but the spine keeps pumping heat into it. Have you file checked the edge for hardness? Hardened carbon steel will normally have a nice ash gray color. It’s not uncommon to see things that look like circles or possibly blisters. Usually if thy look like blisters or a ton of circles you can almost bet that the steel was overheated. Over heated steel will still harden but the grain size will be larger which affects toughness and things get brittle.
 
JTknives said:
Was your oil heated? 1095 needs a fast quench so to get that with canola oil it needs to be heated.Edge quenching could of slowed down the quench as the oil is trying to quench the edge but the spine keeps pumping heat into it. Have you file checked the edge for hardness? Hardened carbon steel will normally have a nice ash gray color. It’s not uncommon to see things that look like circles or possibly blisters. Usually if thy look like blisters or a ton of circles you can almost bet that the steel was overheated. Over heated steel will still harden but the grain size will be larger which affects toughness and things get brittle.
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Yes, I heated up a small piece of 1095 and put it in the oil a few minutes before quenching the blade. Also, I file checked it and it was for sure hard. Did you see the photo in the link? It has what looks like the circles you described. However when I magnet tested the steel the color looked like a very dull orange and the magnet was still just barley sticking but not quite. I got nervous and quenched it thinking I would rather quench on the cooler side vs it being way to hot.
 
You’re most likely fine then. The surface condition is probably from using coal.
 
AustinS1234 said:
I hope so. Is the link viewable?
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It worked for me.
Just in case the link is not working for some folks.
48700006626_ddfc057eea_k.jpg
 
That looks like surface oxides and decarb. It is normal for any blade worked in a forge. (Unless the blade was severely overheated for a long time)

Did you do any thermo-cycling or grain reduction after forging and before HT?
 
Stacy E. Apelt - Bladesmith said:
That looks like surface oxides and decarb. It is normal for any blade worked in a forge. (Unless the blade was severely overheated for a long time)

Did you do any thermo-cycling or grain reduction after forging and before HT?
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No, I didn’t forge the blade I just hack sawed the shape I wanted and then went at it on the belt grinder. Would that method require thermo cycling?
 
There is no need to do thermal cycling on a stock removal blade if the 1095 steel was from a regular knife supplier.
 
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