Release agent question

Home enthusiasts discuss their Foundry & Casting work.

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Harold_V
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Re: Release agent question

Post by Harold_V » Mon Feb 22, 2021 3:29 pm

Thanks. I appreciate your report and hope to be able to put that information to good use in the near future.

Brass wheels. Everything I've read indicates that the copper alloys are more difficult to pour than aluminum or iron. I'd really enjoy reading about your process and eventual success, so please post accordingly if you're so inclined.

I have saved scrap copper and alloys for years, and have a few hundred pounds of the stuff on hand. I'm curious if you will use such materials, or are you paying for ingots? The cost of copper has gone through the ceiling, so that would be a rather expensive route.

One question in regards to sodium silicate and silicone spray. Is it safe to conclude that the sodium silicate was not ruined by the silicone spray, that, maybe, it has a shelf life and had expired? I really need to get a firm understanding of what works well. Your reports are helping.

I miss our old friend Big Dave. He and I communicated for years. I feel like I lost an old buddy.

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

FKreider
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Re: Release agent question

Post by FKreider » Tue Feb 23, 2021 9:23 pm

Harold_V wrote:
Mon Feb 22, 2021 3:29 pm
Brass wheels. Everything I've read indicates that the copper alloys are more difficult to pour than aluminum or iron. I'd really enjoy reading about your process and eventual success, so please post accordingly if you're so inclined.

I have saved scrap copper and alloys for years, and have a few hundred pounds of the stuff on hand. I'm curious if you will use such materials, or are you paying for ingots? The cost of copper has gone through the ceiling, so that would be a rather expensive route.
I find brass to be extremely annoying to cast - the melting point of copper is higher than the boiling point of zinc so its easy with a home foundry setup to end up boiling zinc off and that is not fun or safe. Best bet is to melt the copper first and then add the zinc (and other alloys for other copper based alloys) after the copper is molten.

I use scrap for most of my casting but I did buy zinc ingots off ebay to alloy with my copper scrap in order to produce yellow brass.

Aluminum is EASY in comparison. I've never melted Iron and at this point in time I have no intentions of doing so with my home foundry setup - I will use a real iron foundry if/when necessary.
-Frank K.

Harold_V
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Re: Release agent question

Post by Harold_V » Wed Feb 24, 2021 1:38 am

Thanks for your comments, Frank.
I've melted and poured a fair amount of copper, as I used it for recovering silver from a nitrate solution, all a part of refining silver. I melted a lot of small bits of copper buss and small wire, so I'd have large pieces that are easily retrieved from the resulting cement silver (that's what it's properly called). I can honestly say melting copper was not enjoyable. It melts at approximately the same temperature as pure gold, roughly 1,950°F.

Have you experienced any particular problems in using scrap? I suspect that so long as one is careful to segregate to ensure that no aluminum gets combined with the heat, you should be good to go. Aluminum bronze has a different appearance, and can be identified if one is astute. I was told by an old sand crab that getting even a trace of aluminum mixed in brass (or most bronzes) results in poor flow. I also understand that the copper alloys are more difficult to cast than either aluminum or iron, with iron being the best in that regard. Its higher temperature requirements make it a lot less desirable for the home shop, plus melting with a crucible furnace can be difficult.

H
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jscarmozza
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Re: Release agent question

Post by jscarmozza » Wed Feb 24, 2021 2:45 pm

I was just talking to my casting buddy about zinc loss last night, I have a tendency to use my sprues and runners over and over. That's not a problem for aluminum but the quality of red alloys degrade after each pour. We add Zinc from time to time but the whole process is kind of random since we start with scrap of unknown type and then add the old sprues and runners. I've turned out some pretty crappy brass castings, very porous, but I think that was more of a gas problem than a metal quality problem. Since I started to de-gas the castings pour better and are much less porous. I also found that red metals need bigger in-gates and a higher sprue head. I always extend the sprue with an old tin can to get the extra head to help the mold fill, just make sure you clamp the flasks together so you don't get a runout. The quality of the metal comes into play when you machine it and put it into use, soft difficult to machine brass isn't very useful...so you you throw those castings back in the scrap pile, and melt them again😀

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ChipsAhoy
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Re: Release agent question

Post by ChipsAhoy » Wed Feb 24, 2021 4:05 pm

Jscarmozza
We pick up some porosity in the brass now and again. What are you using to degas the bronze?
And, when you degas, are you dealing with a glass zinc seal cover?
Scotty

Harold_V
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Re: Release agent question

Post by Harold_V » Wed Feb 24, 2021 4:30 pm

I recently made mention of casting copper. I simply cast ingots, which were then used to recover silver from solution. Because they had no need to be of quality, I did nothing to prevent porosity in the ingots, and recall only one coming out without. I cast no fewer than a dozen.

Gassing with the copper alloys can be a serious problem from what I learned, made worse when working with pure copper.

Foundry supply sources sell pellets of phosphor copper, to be used to degas brass/bronze alloys. Has anyone here used them? If so, would you please comment accordingly?

H
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jscarmozza
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Re: Release agent question

Post by jscarmozza » Wed Feb 24, 2021 5:32 pm

Scotty and Harold, we de-gas red brass with phosphor copper shot, and yellow brass with aluminum. I cut up an aluminum sprue or runner into nickel sized pieces and use one piece to de-gas a #8 crucible about 3/4 full of yellow brass. After the final skim and about two minutes before pouring, we'll drop in the de-gassing metal. You'll immediately see the melt appearance change, the surface gets as shiny as a mirror.
Scotty I have some old red brass water meter bodies that I melt under a borax cover, if I don't cover the melt the entire crucible will turn to dross (found this out the hard way) With that, I skim the cover, add the de-gas, let it soak for about a minute and pour; throw in some more borax and recharge the crucible. This is what works for us after a lot of trial and error.
John

FKreider
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Re: Release agent question

Post by FKreider » Wed Feb 24, 2021 9:13 pm

jscarmozza wrote:
Wed Feb 24, 2021 5:32 pm

Scotty I have some old red brass water meter bodies that I melt under a borax cover, if I don't cover the melt the entire crucible will turn to dross (found this out the hard way)
I've also had entire melts turn to dross when attempting to cast yellow brass from clean copper scrap (stripped electrical wire) and zinc ingots. I also learned the hard way that a borax cover may be required to prevent this.
-Frank K.

Harold_V
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Re: Release agent question

Post by Harold_V » Thu Feb 25, 2021 5:54 am

The problem with borax is the destruction of the crucible. When I'd melt cement silver, borax was a necessity. The recovered silver was melted under a borax cover, then poured to a cone mold. While I melted about 200 ounces per heat, it was killer expensive, as I'd get about 8 heats from a #8 silicon carbide crucible before it perforated at the slag line.

Cement silver very much resembles Portland Cement (thus the name). The fine particles are generally not clean, in spite of being well washed in a Buchner funnel, so flux (borax) was mandatory.

That said, when melting brass, have any of you used a glass covering instead of borax? I would think it would be less destructive. A layer of charcoal might serve well, too. Anything to isolate the charge from atmosphere that doesn't combine with the charge should work adequately.

Comments?

H
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FKreider
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Re: Release agent question

Post by FKreider » Thu Feb 25, 2021 6:40 am

I have heard of people successfully using the glass cover but I have not tried it myself.
-Frank K.

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ChipsAhoy
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Re: Release agent question

Post by ChipsAhoy » Thu Feb 25, 2021 7:23 am

We use glass to cover our melts to seal the surface and help prevent zinc fire. For that it works but what a mess. It does nothing as far as I can tell towards degassing. A problem we are having, and perhaps we use too much glass, it that it seems to condense outside of the crucible. After the pour the crucible has a "bubbled up" texture of what appears to be glass, and frequently we have the plinth stuck to the bottom of the crucible. In this case a carbon layer did nothing.
Have not tried borax, but I will hoping it is less messy.
For degassing I will try your "phosphor copper shot".
Thx Scotty

Harold_V
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Re: Release agent question

Post by Harold_V » Thu Feb 25, 2021 3:51 pm

ChipsAhoy wrote:
Thu Feb 25, 2021 7:23 am
Have not tried borax, but I will hoping it is less messy.
Here I can help, as I used borax extensively when I refined. Depending on our choice of borax, you may find common glass far better. Anhydrous or borax glass are quite nice to use, as they contains no water and melt tranquilly. Of the two, my first choice was always borax glass, in spite of the higher cost. It is dead stable and is heavy, so it remains where put and melts without theatrics. Borax glass has been melted, and is perfectly stable, assuming it has not been allowed to rehydrate. It is hygroscopic, thus it can and will, albeit not quickly. Anhydrous has not been melted, but does not contain water. The rest of the borax grades are miserable to work with, as they contain a percentage of water and expand when heated and are easily blown away by the furnace atmosphere. Until they become molten, they are horrible. They ruin the furnace quickly (the sticking plinth of which you made mention, to say nothing of the degradation of the furnace lining). Any flux will be hard on the crucible and furnace. That's part of what they're supposed to do---clean up "dirt".
For degassing I will try your "phosphor copper shot".
While I have not used it, I understand it works, and that it takes very little per heat. Assuming you give it a go, please report on your results.

Thanks!

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

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