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Thread: Gearing up for sand casting

  1. #181
    Senior Member Tobho Mott's Avatar
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    I believe so, yes. Although the "real" alloys all seem to have a little iron in them too. From what I've read you should not go much more than 10% Aluminum or you can get a very brittle alloy.

    Good luck and let us know how it went if you try it!

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  2. #182
    Senior Member Tobho Mott's Avatar
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    Quote Originally Posted by Tobho Mott View Post
    ...Also I don't think I sharpened it right, I will probably work on it a little more...
    Well that was a mistake. Not to want it to be sharper, I still think that was needed. But I let it get too hot re-grinding the edge I think, after more hammering. One corner of the sharp edge even changed colours. First to a darker gold colour, then to a sort of purple. Oops! Dammit!

    It got much sharper, but I totally mangled it within only a minute or so of chopping on the tree I took down in the last video.

    Screenshot_20170911-121430.jpg

    Back to the bench to try and fix it I guess... Gonna do a bit more grinding (going much easier this time) and more hammering to see if I can bring it back with more work hardening, followed by sharpening with files/stones so it won't get too hot again. If that doesn't work and I can't figure out how I can try the heat treatment, I'll probably have to melt it down and try again.

    Been reading C. W. Ammen's 'Casting Brass' book a little more. He suggests the heat treatment of aluminum bronzes is only necessary if you leave the casting in the mold too long; you're supposed to shake it out while it's still red hot and brush off all the sand and let it cool that way. To me this hints that if you demold at the right time, it kind of heat treats itself. Could be I am reading too much into that. But if not, maybe that is why the axe stood up so well to my testing before I decided to redo the grinding? I did not shake it out that early but maybe I got lucky? Or else it was the work hardening, which I must have undone by overheating it with the grinder.

    Anyone have any thoughts or suggestions on fixing this? I am getting beyond my depth here with all this heat effects stuff, which is weirder than it usually would be since it is being applied to a copper alloy instead of steel, and few who have commented seem to have much personal experience with that. And I'm not sure how far to trust Ammen's info in the first place since some of it disagrees with some other things I have read...

    Jeff
    Last edited by Tobho Mott; 09-11-2017 at 04:26 PM.
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  3. #183
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    There are alloys which act like steel, and since yours softened with low temperature grinding I'll bet it will harden upon quenching. Try heating it to a good red (1,200F) and quench in water, then see if it is harder to a file.

  4. #184
    Senior Member Tobho Mott's Avatar
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    A bit of grinding to straighten the edge back.out followed by more cold hammering seems to have restored its hardness - I made it through the tree trunk in the previous pic easily and with no further damage. It's actually sharper than when I tested it in the video above now. Thanks to those who have commented for the advice. I should probably try something like what oldironfarmer suggests with a piece of the gating or something, so I will know what to expect if there is a next time...

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  5. #185
    Senior Member Tobho Mott's Avatar
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    Already 'spoiled' by the previous post, but here is more video showing the edge getting ruined, then re-tested after successful repairs were done. Work hardening in action!



    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

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