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09-19-2018, 03:58 PM
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Accidental Hamon?
I’m working on a series of five knives from the same pattern, and applying the same heat treat with each knife. The blades are 1095, and were brought up to 1475 degrees in the kiln and quenched horizontally in an electric turkey fryer and peanut oil that had been preheated to 120 degrees.The attached photo shows the two blades after etching in a 70/30 mix of ferric chloride and apple vinegar and handles fitted. The edge retention and hardening on both blades is very good. My theory is that the horizontal quench caused the blade to harden differently, with the thicker part showing the Hamon line. Any other ideas? Thanks.
Last edited by Johnnyjump; 09-19-2018 at 04:02 PM.
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09-20-2018, 08:15 AM
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Assuming the area above the hamon line was not submerged in the oil the that is exactly why the line is there......
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09-20-2018, 10:06 AM
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I have made a Hamon by simply putting a piece of steel in the oil that only allowed me to quench half of the blade, thus giving me a differential heat treat plus a hamon after bluing. I was just playing around.
Last edited by jimmontg; 09-20-2018 at 10:17 AM.
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09-20-2018, 12:06 PM
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Actually, I did submerge the blade completely, but it's possible I lifted it out while moving the blade in the quenching to prevent vapor seal.
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09-20-2018, 12:10 PM
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I think that what you are looking at was caused by using a shallow hardening steel, the 1095. There's a thing called film heat-transfer control (pg 88 Verhoeven, Steel Metallurgy for the Non-Metallurgist). What is boils down to is that steel under around 1/4"won't quench harden with a jacket of martensite around a pearlite core. It will only harden to a depth of about 1/16". So with the blade hardening from both sides it will harden to around 1/8" and thicker than that it will be pearlite. Now there is one other thing that will effect hardenability and that's grain size. The larger the grain size the more hardenable the steel will be but this will be at the expense of the strength of the blade. That may be why the auto-hamon didn't show up on the other blades or maybe those blades ended up a little thinner at the ricasso.
From the shape of the hamon I doubt that edge quenching was the culprit in this case. I think that if you follow the line of the hamon that it will follow the thickness of the grind.
Oh, by the way, those are real nice looking knives.
Doug
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Last edited by Doug Lester; 09-20-2018 at 12:13 PM.
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09-20-2018, 12:15 PM
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Join Date: Nov 2010
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I think you are absolutely correct. The type of steel, 1095, and the thickness seems to make the most sense to me. Thanks for the explanation!
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Tags
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1095, a, auto, bee, blade, blades, degrees, edge, etching, hamon, handles, heat, heat treat, knife, knives, made, make, pattern, photo, quenched, retention, steel, thickness |
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