02-16-2018, 09:11 AM
Thank you for the kind words and interest, Mr. Grepper.
Yes, differentially heat treated blades are hard on the edge, but softer on the spine. There are basically two ways to do this, but I usually do both.
First I harden the edge by heating it to austenization temp with an O/A torch, and quench in oil. This leaves a hardened edge of martensite, but the steel that wasn't *quite* at austenization temp is left as soft pearlite. There is a surprisingly clear distinction, which is brought out as a "hardening line" by etching the blade in mild acid. This just leaves a unique, organic line, which mostly just looks very groovy.
Next, I heat the blades in my kiln to an even temperature of 1465°F, and hold for 20 minutes, after which, I full quench the entire blade, which results in complete martensite, the strongest phase of steel. After cryo in liquid nitrogen, I temper the blades in the kiln.
The last step is what makes the blades flexible, but still strong. I draw the spine back to about HRC 46-48, with two atmospheric propane burners, while protecting the edge from the heat with very fine clay and grape seed oil. This turns the hard but brittle martensite to very resilient spring steel, while leaving the edge about HRC 62, with very fine grain throughout the entire blade.
The result is just what you've seen in the video. Basically indestructible blades with extraordinary cutting capacity, and every blade is uniquely beautiful.
Yes, differentially heat treated blades are hard on the edge, but softer on the spine. There are basically two ways to do this, but I usually do both.
First I harden the edge by heating it to austenization temp with an O/A torch, and quench in oil. This leaves a hardened edge of martensite, but the steel that wasn't *quite* at austenization temp is left as soft pearlite. There is a surprisingly clear distinction, which is brought out as a "hardening line" by etching the blade in mild acid. This just leaves a unique, organic line, which mostly just looks very groovy.
Next, I heat the blades in my kiln to an even temperature of 1465°F, and hold for 20 minutes, after which, I full quench the entire blade, which results in complete martensite, the strongest phase of steel. After cryo in liquid nitrogen, I temper the blades in the kiln.
The last step is what makes the blades flexible, but still strong. I draw the spine back to about HRC 46-48, with two atmospheric propane burners, while protecting the edge from the heat with very fine clay and grape seed oil. This turns the hard but brittle martensite to very resilient spring steel, while leaving the edge about HRC 62, with very fine grain throughout the entire blade.
The result is just what you've seen in the video. Basically indestructible blades with extraordinary cutting capacity, and every blade is uniquely beautiful.