How Do You Harden Aluminum Bronze?

#1

Hello Everyone!
I am relatively new to blacksmithing and metal working. Recently, I cast a knife from aluminum bronze that was about 10% aluminum and 90% copper. While filing it to remove excess material, I noticed that the knife was quite soft. What would be the best way to make the aluminum bronze harder?

Thanks, OneFromTheShadows_

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#2

Hey @OneFromTheShadows,

Those are both soft alloys, you will find it very hard to get either of them hard enough to put them up against anything. Usually thise alloys, being soft, are used for guards and pommels. Steel is the primary knife steel.

Welcome to Blacksmith Forums!

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#3

Thank you very much for your reply.
Is there a specific type of steel that you would recommend for making a dagger?

Thanks, OneFromTheShadows

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#4

@OneFromTheShadows,

If you’re just starting out, I would go with a lower carbon steel - in fact, I would practice the shape and design of a dagger on some mild steel first. Mild steel is the cheapest and most widely available.

Mild steel can harden a little, but it won’t serve a real great purpose if you’re putting the tool to work.

For that, in your situation I would probably find some leaf spring or coil spring from a car - this steel can be hardened and hold a good edge and is typically cheap and easy to find. I’ve gone to a junk yard and grabbed some coil/leaf springs.

You can also purchase steel online at places like http://newjerseysteelbaron.com/ which will allow you to get the steel closer to the shape you need, means less forging to shape. W-1 and W-2 are both good choices, if you go the 10 series of carbon steel I would go 1084 or lower as it’s more forgiving in heat treatment than 1095.

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#5

Thanks for all of your help!

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#6

Of course! Have any pictures of that casting you did? I’m pretty interested in seeing it.

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#7

I don’t have the knife with me currently, and this is the only photo that I have of it.05508AE8-2FFD-4E9D-AA12-2D93D04E8AC8 Since I took the photo, I have polished it and removed excess metal from it. I plan to hammer it down to make it more thin but haven’t yet had a chance to do that.

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#8

Hey that looks pretty cool! If I were you I’d almost leave it as is since its a softer alloy, thinning it may make it more prone to bending.

A good wall hanger :slight_smile: You can take a finer file to it and that will smooth it out and shine it up pretty nice. You might need to thin the tang a little if that’s going to be a hidden tang, otherwise the handle will need to be pretty large.

Post another photo when you finish it up, I’d be interested to see it!

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#9

Thanks, I’ll be sure to post a photo when its finished. :slight_smile:

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#10

I just wanted to point out that aluminum bronze is one of the hardest bronzes that you can make, it is up in the realm of phosphor bronze.
Tin bronze will get you about 60-80 Brinell
Aluminum bronze gets you from 80-240 Brinell depending on alloy and heat treat
I’m still really interested in knowing how to properly harden the stuff myself, been reading that it is supposed to be quench hardened, but haven’t found a procedure yet.

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#11

Oooh, shiny! With it finished that would be a sexy blade, can’t wait to see.

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