Hey everybody!
I've been working on a Japanese-y short sword with hamon, but I'm quenching in oil, so I have to put in extra curve since it straightens in the quench.
Why do differentially heat treated blades gain curvature when quenched in water, but lose curvature when quenched in oil?
Here's a neat video of a water quench, showing how the blade curves down, then up, when quenched in water:
My guess is that it curves down because the iron matrix is shrinking back around the carbon to form martensite, coupled with thermal expansion, then curves up as it settles into a body-centered tetragonal structure. The oil, being more efficient, freezes the spine before that can happen.
Does anyone have any other thoughts?
-Ethan
Hello Ethan,
This is a very complex and long considered subject. I can provide some answers but it can't be done in a few short lines, and a lot of it will require your mind to bend around new concepts for most, or at least recognizable concepts in new ways. There is a lot going on in such a quench and even more going on when you add other quenchants to the mix. I will need to set aside a block of time to type if people are actually interested in the technical details.
"One test is worth 1000 'expert' opinions" Riehle Testing Machines Co.
Im sure it has to do with the rates of expansion and contraction of the steel in various states during it's cooling. All affected by the zones of carbon levels and locations of the zone lines, blade length, and geometry. Many others as well.
However, I would like to hear your thoughts and finding Kevin. This would be a great thing to have on record for posterity as well as to help us to use our old noggins.
I'd be interested in hearing about it too <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />
Want to see more of my work follow me on Instagram:JasonVolkertKnives
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After taking the time to type it up I thought this explanation would be a better fit in the more advanced ABS University Heat Treating and Metallurgy forum. ABS members can find where I have posted it there under the same thread title.
"One test is worth 1000 'expert' opinions" Riehle Testing Machines Co.
