Mystery bronze

Home enthusiasts discuss their Foundry & Casting work.

Moderator: Harold_V

jscarmozza
Posts: 345
Joined: Mon Mar 03, 2014 5:09 pm

Mystery bronze

Post by jscarmozza » Thu Apr 16, 2020 5:57 pm

I wanted to make some bronze bushings but was out of suitable sized rods, so I figured I would cast a few cylinders in the diameter that I needed. I had part of an old water meter casting laying out in the back yard for about 20 years. It was there because it was next to impossible to break up with a sledge hammer or saw with any saw in my shop. That being said, I spent about 2 hours on the vertical band saw and cut enough to make the pours I wanted. I melted about 10 pounds, it took about an hour and a half to get to the melt temperature from a cold start, and I was surprised to see a very heavy layer light weight granular dross that when skimmed off contained almost no liquid metal. The metal below the dross was bright and liquid and poured well when a large in gate was used, in the mold with the small gate, the metal froze before filling the mold completely. Within about 5 minutes of returning the crucible to the furnace after the last pour, while I was getting my ingot mold in place to pour off the remaining melt, the metal turned into the granular dross previously described! Does anyone have an idea what alloy this may be, and what melting technique should be used to avoid the deterioration of the metal into dross? Thanks.
John

FKreider
Posts: 133
Joined: Fri Feb 02, 2018 8:44 pm
Location: Sturbridge, MA

Re: Mystery bronze

Post by FKreider » Thu Apr 16, 2020 8:45 pm

Are you getting a very bright flame with a lot of yellow/white smoke? If you are that is the zinc boiling off due to the temp being too high, this is a common problem when melting yellow brass. Not sure that is what you have going on but once you have this happen to you its easy to tell (and should be avoided due to how toxic the fumes are.)
-Frank K.

jscarmozza
Posts: 345
Joined: Mon Mar 03, 2014 5:09 pm

Re: Mystery bronze

Post by jscarmozza » Fri Apr 17, 2020 7:19 am

Frank, I believe this is bronze, but what type of bronze? Silicon bronze, aluminum bronze or something else; not too long ago the EPA mandated unleaded bronze for the water industry, this meter body predates that. I have been trying to research what it could be, but there was no name on the piece I have so I can't look up the manufacturers specs. The longer the melt soaked, the more of it turned into the light,dry, ash like dross. I wonder if this stuff has to be melted under some type of cover?

I'm going to machine the cylinders I cast, if they machine nicely, I'm going to want to figure out what this is and how to properly melt it. If it doesn't machine well, then it's off to the junk yard.

jkimberln
Posts: 103
Joined: Sat Dec 05, 2009 10:32 am
Location: Richmond, California

Re: Mystery bronze

Post by jkimberln » Fri Apr 17, 2020 5:35 pm

Might be manganese bronze which is about 20% manganese and 20% zinc, 56% copper and a little of this and that. If so, I'd guess the pouring temperature to be about 1600 F. So you could try reducing the temperature if you are melting at a higher temp. Machinability about 80. Not too good.

jscarmozza
Posts: 345
Joined: Mon Mar 03, 2014 5:09 pm

Re: Mystery bronze

Post by jscarmozza » Sat Apr 18, 2020 7:55 am

Once I got through the outer scale the material machined very nicely. It's very difficult to saw, but machines like butter...I wouldn't have thought that. I'm going to call one of the larger scrap yards and ask, they will probably know.

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Mystery bronze

Post by Harold_V » Sat Apr 18, 2020 3:29 pm

That it is difficult to saw is because it's a copper alloy, and you are most likely using a blade that has seen service in cutting steel. The keen edge is gone from the teeth of the blade, so it tends to float in the cut instead of make chips. That's very common with alloys that are good bearing material. With a new blade, you most likely will discover it saws just as nicely as it machines.

That it machines nicely tends to make me think it isn't manganese bronze, which can be extremely difficult to machine. Makes me wonder if, maybe, the alloy contains bismuth. If you are fortunate enough to find a yard willing to give it a test, I'd enjoy hearing what the alloy contains.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

jscarmozza
Posts: 345
Joined: Mon Mar 03, 2014 5:09 pm

Re: Mystery bronze

Post by jscarmozza » Mon Apr 20, 2020 7:10 pm

Harold, I've never been told that I have a dull saw in a nicer way:)
So far I'm not having much luck finding out what this is.

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Mystery bronze

Post by Harold_V » Mon Apr 20, 2020 11:33 pm

jscarmozza wrote:
Mon Apr 20, 2020 7:10 pm
Harold, I've never been told that I have a dull saw in a nicer way:)
Chuckle! Well, that's the voice of experience speaking---and, trust me, I have a lot of experience with dull blades! :wink: Been there, done that, and have several T shirts. :D

I think I said it might be bithsmus, but what I really wanted to say was antimony. Bit of a brain cramp, which I'll blame on old age.

H

Edit: I should have mentioned that a blade that has seen service cutting steel but won't deal with copper alloys will often still perform perfectly well for more steel cutting. It just doesn't respond well to copper alloys once that very keen edge is damaged by use with steel.
Wise people talk because they have something to say. Fools talk because they have to say something.

jscarmozza
Posts: 345
Joined: Mon Mar 03, 2014 5:09 pm

Re: Mystery bronze

Post by jscarmozza » Tue Apr 21, 2020 1:36 pm

H. You hit the nail on the head with your edit, last week I was cutting angle iron on the saw and was zipping right through it, that's why I didn't think it was dull.

I did a small experiment today melting about 1lb of bronze under a borax cover. It melted with no dross formation. I poured it into a preheated cast iron muffin mold which wasn't the best idea, the borax glass formed on the surface of the ingot and around the contact surface between the mold and ingot, making the ingot difficult to remove from the mold. I let the melt soak for 5 minutes after the last charge completely melted, this would have resulted in a lot of dross formation if it had not been under the borax cover, the crucible was full of nice bright metal under a layer of liquid glass. So melting under a cover appears to be the way to melt this stuff, whatever it may be. When this corona lock down ends I'll take a piece to the scrap yard to see if the can ID it for me.

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Mystery bronze

Post by Harold_V » Tue Apr 21, 2020 11:40 pm

I've mentioned before that I spent more than 20 years refining precious metals. I started out doing so as a hobby, then it became overwhelming and I couldn't keep up, so I closed the doors on my machine shop, processing precious metals until I retired in 1994.

I make mention because fluxing was all important when melting, especially silver. Pure gold, which does not oxidize, does not rely on flux to be melted. The addition of traces to the melting vessel assures that it will pour completely, however. It acts more like a lubricant than anything.

What I learned.

Flux is extremely hard on crucibles. I used to melt silver in #8 bilge type. When melting recovered silver, which is a fine powder contaminated with traces of copper and other elements, I could expect, at best, about eight heats, with the crucible developing a full perforation at the flux line. The crucible, below the molten metal line, was still pristine. Without flux, the silver had a tendency to not become a common mass. With flux, it readily flowed in to a homogenous alloy, primarily of silver, with traces of precious metals from the platinum family, as well as traces of copper and gold. When the platinum metals were present, silver became the vehicle by which they were recovered. Hard to understand if you don't understand refining.

Flux creates a barrier for oxygen, plus has the ability to absorb oxidized metals. Your experience, to me, makes perfect sense. The flux you used prevented oxygen from oxidizing one of the alloying elements. It should be noted that it is difficult to oxidize silver. That was never a problem, but the oxidized traces of base metals was, thus the need for fluxing silver.

If you choose to pour to a mold along with flux, a cone mold makes cleanup easy. Also, blackening the mold prior to pouring prevents the slag from sticking to the mold. That was my routine when melting silver. The mold can be blackened with a sooty acetylene torch, or there's a prepared blackening agent available from foundry supplies. It's painted on with a brush.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

DavidF
Posts: 270
Joined: Wed May 14, 2014 12:28 pm
Location: Delaware

Re: Mystery bronze

Post by DavidF » Fri May 22, 2020 7:24 pm

Not bronze or anything fancy. Just red brass.
Sounds like you were just not hot enough to me...

jscarmozza
Posts: 345
Joined: Mon Mar 03, 2014 5:09 pm

Re: Mystery bronze

Post by jscarmozza » Sun May 24, 2020 7:43 am

David, why do you think it's red brass, in the first response to my question Frank also thought it may be brass? I'm curious, I've been using the items that I cast on an engine project where bronze, not brass, is the appropriate material,I always thought all water meter bodies were bronze. Also, what's your reason to suspect the temperature wasn't high enough? I melt in a natural gas furnace and I do keep the flame a bit on the reducing side. However, by the end of the pour that I originally referred to, the furnace and crucible were white hot and that's when a few pounds of the metal remaining in the crucible turned into the dry ashy dross that I described.
John

Post Reply