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Post by Deleted on Sept 26, 2007 19:44:59 GMT
Question from the noob here.
At what point will a sword lose it's tempered edge? The reason that I ask is that I have had a few ideas with regards to sword customization and want to avoid any obvious pitfalls.
I have an idea, forgive me that I don't share it yet (but I will on a future thread) regarding customizing a katana. The idea happens to require heating the blade to about 400 degrees F.
Will this ruin the temper of the sword?
Secondly, if one does ruin the temper can it be regained by cryo teatment turning the austenite into martensite ?
Thanks in advance for the information.
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Post by Dan Davis on Sept 26, 2007 23:26:30 GMT
there is no specific point where steel loses it's temper; rather, it is a decreasing curve of temperature over time. A draw at 600F for 2 hours results in a spring temper, but a draw at 400F for 8-10 hours does the same.
Most through-hardened swords are tempered at 400-450F for approximately 2 hours; most katana are not tempered at all or are tempered the same although it is not strictly necessary.
Cryogenic treatment will degrade retained austenite, but there is no guarantee that it will form martensite and statisticly speaking it will most likely form ferrite. Also, a properly heat-treated blade should not have any retained austenite in the first place.
Most of the time retained austenite it is the result of imprecise heat treatment of poor-quality stainless alloys and the bulk cutlery and knife manufacturers utilise "deep cryogenic tempering" on their cheapo crapo because it is faster (and cheaper) to fix their screwed-up cheap metals than to properly heat treat a decent alloy, thus more cost-effective. Plus, it has become a buzz-word that misleads the partially-informed into thinking they are buying something decent; helping to boost sales.
In no case will cryo treatment restore hardness to a blade; this only occurs when the blade is heated enough above allotropic phase transformation A1to cause complete conversion to austenite, followed by rapid cooling below A2
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Deleted
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Post by Deleted on Sept 27, 2007 4:31:21 GMT
Thanks for the information again. Looks like I be able to skip the cryo-treatment then. I just noticed your location; we're practically neighbors. EDIT: Actually just checked out your shop. I've been in it at Scarborough Faire ... small world
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Post by Dan Davis on Sept 27, 2007 13:09:38 GMT
I thought you looked familiar. I'm the cranky-looking guy that sits out front under the tree.
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