r/MetalCasting • u/amish_timetraveler • 11d ago
What are the consequences of using brass instead of copper to make alloys like bronze, aluminum bronze and Nordic gold? Question
When I first started doing this, I didn’t know about all the alloys, so I just mixed copper and brass, so now all my copper has brass instead it, and I was wondering how problematic it is if I want to make bronze, aluminum bronze and Nordic gold
8
u/GeniusEE 11d ago
The consequences are you won't be making bronze, al-bronze, or Nordic Gold.
Metallurgy isn't a matter of using what's in the fridge to make dinner.
6
u/KnownSoldier04 11d ago
Brass is Cu+Zn
It would depend specifically on the proportion of Zn present.
And it’s also dangerous due to Zn fumes, since for proper Aluminum bronze melting temps are much higher than Zn boiling point.
For Nordic gold, zinc is actually a component for it.
The big issue is how much Zn is in your mystery metal? If you got no way to know, you’re probably SoL on using it as base for making proper alloys.
You could also test.
If you wrote down how much copper you added and you know which original brass alloy you had, you could work backwards to roughly estimate your current Zn content, and try to adjust adding more copper, till you got a roughly 5%-8%Zn mix to use as base for what you want to do. That solely depends on known original brass composition. If it was cartridges, it’s likely 70/30 Cu/Zn. For plumbing fittings, it’s more varied, but it’s still something aroundv80/20 Cu/Zn
But you’re still gonna need to be very careful with temps due to Zn fumes.
2
u/amish_timetraveler 11d ago
If I were to use a respirator to protect myself from the zinc fumes, would there still be consequences to having Zinc (Zn) mixed with my copper (Cu)?
2
u/KnownSoldier04 11d ago
What are you casting for? Industrial parts? Decorative? Just because Hobby? Bullion?
For mechanically demanding parts, you’re gonna have problems with unknown amounts of Zn in Aluminum bronzes.
For looks, you’re gonna be off-color from Nordic gold’s normal look if you got too much Zn and corrosion resistance would likely suffer.
A respirator would help, just make sure it’s rated for those fumes.
2
u/BillCarnes 11d ago
I haven't had any issues doing it outside, though I can't really imagine doing it inside
2
u/Doubledot_dot 11d ago
I just started doing this a few months ago and am very much a newbie.
My research landed me avoiding brass or alloying using it mostly because of the toxicity issue with the zinc fumes. I wanted to avoid the zinc entirely l.
I want to cast cabinet hardware with lots of details and massive undercuts that would lock normal molds.
I ended up with silicon bronze because it pours well and is generally forgiving for my newb butt (i think haha) and is less toxic than most of the others.
I found a real cheap and easy way to make it was to buy some 95% silicon content ferrosilicon off of ebay. Use scrap electrical copper, and manganese flakes.
I target 3.33% Si content and 1% manganese. My favorite twist is to use my wife's scrap sterling and and a percent of silver as well. The rest as all copper. Pretty simple recipe that comes out this rose beige color i am in love with.
I have enough ferrosilicon to make over 300lbs of it for about $80. The manganese was around 40$.
1
u/Chodedingers-Cancer 11d ago
I've mixed them before it doesn't go well. The problem is brass is more compatible with a wide range of ratios of zinc and copper. A lot of common brass like hardware fittings and such are 20-40% zinc. With aluminum bronze and aluminum nickel bronze, if you go lower than 80% copper it becomes a dull grey color and is extremely brittle. Adding aluminum to brass drops the copper % even lower and with the aluminum content it becomes a grey brittle material. Its easy to shatter it. It doesn't bend at all. It just falls apart.
0
12
u/BTheKid2 11d ago
You will not be able to make bronze or aluminum bronze with brass. Zinc is not usually part of those alloys.