Adding Copper Using speaker wire.

[jsizemore]

Normally the wire is tinned to prevent oxidation of the copper which occurs rapidly when heated.

Thanks for that info. I fluxed with pine rosin after adding the wire. Between stirring and flame I cut down on the oxidation and increased the surface temp of the melt. I make my own flux for soldering electrical parts from pine rosin.

[WebMonkey]

also tinning is not alloying.

so tinning won't bring the melt temp of copper down to solder melt temp.

i'm not saying anything about speaker wire in casting lead, i'm just saying tinning isn't alloying. just helps solder stuff together.

[Hamish]

The short answer is, copper can not be melted into lead alloy in a casting pot by the home casting hobbiest.

I am amazed, literally daily, at the speed at which knowledge under general discussion on this board disappears, and later, sometimes within months, is said to be impossible or never happened.

(Not directed at you Hannibal, it runs all through this thread and many others, notably the 7383 thread currently up.)

[jmort]

This is from the thread that was linked, and makes sense:

"I found out what the eutectic for lead-copper is at our temperatures - it's 0.06%. That's the solubiity of copper into lead."

[sqlbullet]

Hamish and jmort bring some great context to this dialog. I hope I can add a few items as well.

First some chemical precedence. Table salt melts at 1,474°F. However it will dissolve in plain old water at room temperature of 72° F, to a point. That point is the solubility point to which jmort refers. Generally, the higher the temperature, the higher the solubility. Likewise, sugar melts at 320° F, but will dissolve into water at room temperature. And, anyone that has made sweet tea knows that it is easier to dissolve the sugar in hot tea than in cold tea. And anyone who has made sugar rock crystals as a kid knows that you can over-saturate the water with sugar and then see it come back out of solution as the temperature drops.

So, independent of melting we have a couple of principles here:

1. A solute will dissolve in a solvent at temperatures less than the melting point of the solute.
2. Solubility is the maximum concentration of the solute in the solvent at a given temperature.
3. Full concentration of the solute can be achieved more rapidly by raising the temperature of the reaction.
4. If the solution is over-saturated for the current temperature, the solute will crystalize back out of the solution.

The melting point of copper is very high (1,984° F) and not achievable in our bullet casting pots, though it is well below the boiling point of lead (3,180° F). And partial pressure vaporization of lead would become a hazard for the operator of a lead pot at a temperature high enough to melt copper.

This leaves us with the question of solution. Can solid copper dissolve in lead. jmort has provided the needed data already. Yes, and it's solubility is 0.06%.

But, we don't actually deal with lead. We use lead/tin/antimony alloys. And it turns out that copper is more soluble in tin than it is in lead. Close to 10% copper will dissolve in tin at 700° F.

It also turns out that "tinning" a copper wire with pure tin solder will result in an intermetallic boundary composition where right at the boundary between the two the copper dissolves into the tin. It is a significant problem in modern integrated circuits that the technology world is trying to solve. But for us, this is a win as this intermetallic alloy does have a lower melting point than copper. I could not easily find any information about the constituent percentages of the intermetallic tin/copper compound, and so I cannot estimate the melting point of the compound. I would guess it is still higher than our pot temp, and the percentage of copper involved in the intermetallic layer is very, very small, so this is a small win that doesn't really buy us much.

So, now we know the following items as well:

1. Copper will dissolve in lead, but not at a high enough solubility to get us much result.
2. Copper will dissolve in tin at a much higher rate.
3. Tinning copper with pure tin solder results in a fully saturated boundary.
4. The boundary is so thin as to not net us enough solubility boost to matter much.

So, with this information, on to practical usage of this knowledge.

I started out with copper filings in the pot of lead. Just as granulated sugar or salt will dissolve more quickly than a large crystal due to surface area, copper filings offer far more surface area. I had several problems with this method: I am not a patient man. I am an irrational cheapskate who couldn't just walk away from a burning propane. I had to stay anyway to regulate the melt temp so as not to oxidize off more than I was gaining.

So, copper filings were a bust for me.

I didn't try copper sulfate. I didn't have any and I did have lots of copper wire around from a remodel.

I tried tinning wire and putting it in the pot. I carefully cleaned the wire with steel wool and immediately tinned it with pure tin solder. This went into the pot but the same basic challenges I had with copper filings came up.

So, I checked a binary phase chart for copper-tin and gained hope. Pure tin melts at a reasonably achievable temperature. And pure tin should dissolve a fair bit of copper pretty easily. And, I really didn't need that much, as I just wanted to get to about .25-.5% copper in my final lead/antimony/tin/copper alloy. That is 4-8 ounces of copper in a 100 lb dutch oven of lead alloy.

Well, copper may have a much higher solubility in tin than in lead, but it is not enough higher to offset my impatience. On to plan four.

I set up my 4 lb steel ladle and grabbed my MAP torch and set about melting 5 oz of copper. That worked. Then I started adding tin bar solder. Luckily I have a fair bit from some trading I did seven or eight years back. The goal here was to dilute the copper down to a solution in the tin, then add that mixure to a pot of lead I already had melted. But, that was going to require over 3 lbs of tin, which was a higher tin level than I really wanted in my final alloy. I finally decided to just do it. I had tin laying around.

So, 50 ounces of tin were added to my 5 ounces of copper, for a final solution of 9% copper, 91% tin. This remained liquid down to about 650° and so could be added to a 700° pot. 1 lb ingots were cast, and I still have those floating around. I ended up with 87 lbs of ingots from that pot, which works out to 0.35% copper, 2.88% antimony, 4.55% tin and 92.22% lead. My plan was to use these about 3:1 with my standard isotope lead.

But, since I created this alloy several years back, I have been busy with a home remodel, wedding and garage build, and shooting has taken a back-seat to these other priorities.

To the OP...Speaker wire would have an advantage of more surface area to volume and so would dissolve more quickly relative to a 12 or 14 gauge solid wire. Also, if frayed and tinned individually, a greater percentage of intermetallic compound would form. Though I don't think it will melt at pot temp, it should dissolve more quickly in your melt than pure copper. Tinning the wire without fraying would probably offset the surface area to volume benefit of a solid wire. Stranded wire would still be better than solid, but not as good as frayed strands.

I have largely ignored oxidation in this post, but it is very relevant. Copper oxide will prevent the copper from dissolving, and I bypassed this by melting the copper in my method.

Hamish, I don't know if I have added any knowledge to this thread or not. But I hope I have.

Edit: Citations!

https://www.ncbi.nlm.nih.gov/books/NBK431100/
https://www.researchgate.net/profile...st-of-this.png
https://en.wikipedia.org/wiki/Copper
https://en.wikipedia.org/wiki/Intermetallic
https://www.tandfonline.com/doi/abs/...nalCode=ytim20 (paywall, but the abstract is here.)
https://www.sciencedirect.com/scienc...5964540100146X (paywall, but the abstract is here.)

[Hossfly]

Very good experiment, and explains the total experience. Thanks for that. Been following this since it started. I’m relatively new at casting and find all aspects of it very interesting.

[Mr_Sheesh]

Hamish, lots of peoples' brains are Swiss Cheese-y - My excuse is that it's my "Old-Timers" LOL - All of us can remember some things and not others. We're not computers, and that is a GOOD thing

[Hamish]

sqlbullet,

Bravo sir, outstanding post!

0.25-0.5% Cu equals "sweet spot". More is not better.

[Hamish]

Hamish, lots of peoples' brains are Swiss Cheese-y - My excuse is that it's my "Old-Timers" LOL - All of us can remember some things and not others. We're not computers, and that is a GOOD thing

Too many state an opinion without talking a minute to do a search.......

[BNE]

Hamish and jmort bring some great context to this dialog. I hope I can add a few items as well.

First some chemical precedence. Table salt melts at 1,474°F. However it will dissolve in plain old water at room temperature of 72° F, to a point. That point is the solubility point to which jmort refers. Generally, the higher the temperature, the higher the solubility. Likewise, sugar melts at 320° F, but will dissolve into water at room temperature. And, anyone that has made sweet tea knows that it is easier to dissolve the sugar in hot tea than in cold tea. And anyone who has made sugar rock crystals as a kid knows that you can over-saturate the water with sugar and then see it come back out of solution as the temperature drops.

So, independent of melting we have a couple of principles here:

1. A solute will dissolve in a solvent at temperatures less than the melting point of the solute.
2. Solubility is the maximum concentration of the solute in the solvent at a given temperature.
3. Full concentration of the solute can be achieved more rapidly by raising the temperature of the reaction.
4. If the solution is over-saturated for the current temperature, the solute will crystalize back out of the solution.

The melting point of copper is very high (1,984° F) and not achievable in our bullet casting pots, though it is well below the boiling point of lead (3,180° F). And partial pressure vaporization of lead would become a hazard for the operator of a lead pot at a temperature high enough to melt copper.

This leaves us with the question of solution. Can solid copper dissolve in lead. jmort has provided the needed data already. Yes, and it's solubility is 0.06%.

But, we don't actually deal with lead. We use lead/tin/antimony alloys. And it turns out that copper is more soluble in tin than it is in lead. Close to 10% copper will dissolve in tin at 700° F.

It also turns out that "tinning" a copper wire with pure tin solder will result in an intermetallic boundary composition where right at the boundary between the two the copper dissolves into the tin. It is a significant problem in modern integrated circuits that the technology world is trying to solve. But for us, this is a win as this intermetallic alloy does have a lower melting point than copper. I could not easily find any information about the constituent percentages of the intermetallic tin/copper compound, and so I cannot estimate the melting point of the compound. I would guess it is still higher than our pot temp, and the percentage of copper involved in the intermetallic layer is very, very small, so this is a small win that doesn't really buy us much.

So, now we know the following items as well:

1. Copper will dissolve in lead, but not at a high enough solubility to get us much result.
2. Copper will dissolve in tin at a much higher rate.
3. Tinning copper with pure tin solder results in a fully saturated boundary.
4. The boundary is so thin as to not net us enough solubility boost to matter much.

So, with this information, on to practical usage of this knowledge.

I started out with copper filings in the pot of lead. Just as granulated sugar or salt will dissolve more quickly than a large crystal due to surface area, copper filings offer far more surface area. I had several problems with this method: I am not a patient man. I am an irrational cheapskate who couldn't just walk away from a burning propane. I had to stay anyway to regulate the melt temp so as not to oxidize off more than I was gaining.

So, copper filings were a bust for me.

I didn't try copper sulfate. I didn't have any and I did have lots of copper wire around from a remodel.

I tried tinning wire and putting it in the pot. I carefully cleaned the wire with steel wool and immediately tinned it with pure tin solder. This went into the pot but the same basic challenges I had with copper filings came up.

So, I checked a binary phase chart for copper-tin and gained hope. Pure tin melts at a reasonably achievable temperature. And pure tin should dissolve a fair bit of copper pretty easily. And, I really didn't need that much, as I just wanted to get to about .25-.5% copper in my final lead/antimony/tin/copper alloy. That is 4-8 ounces of copper in a 100 lb dutch oven of lead alloy.

Well, copper may have a much higher solubility in tin than in lead, but it is not enough higher to offset my impatience. On to plan four.

I set up my 4 lb steel ladle and grabbed my MAP torch and set about melting 5 oz of copper. That worked. Then I started adding tin bar solder. Luckily I have a fair bit from some trading I did seven or eight years back. The goal here was to dilute the copper down to a solution in the tin, then add that mixure to a pot of lead I already had melted. But, that was going to require over 3 lbs of tin, which was a higher tin level than I really wanted in my final alloy. I finally decided to just do it. I had tin laying around.

So, 50 ounces of tin were added to my 5 ounces of copper, for a final solution of 9% copper, 91% tin. This remained liquid down to about 650° and so could be added to a 700° pot. 1 lb ingots were cast, and I still have those floating around. I ended up with 87 lbs of ingots from that pot, which works out to 0.35% copper, 2.88% antimony, 4.55% tin and 92.22% lead. My plan was to use these about 3:1 with my standard isotope lead.

But, since I created this alloy several years back, I have been busy with a home remodel, wedding and garage build, and shooting has taken a back-seat to these other priorities.

To the OP...Speaker wire would have an advantage of more surface area to volume and so would dissolve more quickly relative to a 12 or 14 gauge solid wire. Also, if frayed and tinned individually, a greater percentage of intermetallic compound would form. Though I don't think it will melt at pot temp, it should dissolve more quickly in your melt than pure copper. Tinning the wire without fraying would probably offset the surface area to volume benefit of a solid wire. Stranded wire would still be better than solid, but not as good as frayed strands.

I have largely ignored oxidation in this post, but it is very relevant. Copper oxide will prevent the copper from dissolving, and I bypassed this by melting the copper in my method.

Hamish, I don't know if I have added any knowledge to this thread or not. But I hope I have.

Edit: Citations!

https://www.ncbi.nlm.nih.gov/books/NBK431100/
https://www.researchgate.net/profile...st-of-this.png
https://en.wikipedia.org/wiki/Copper
https://en.wikipedia.org/wiki/Intermetallic
https://www.tandfonline.com/doi/abs/...nalCode=ytim20 (paywall, but the abstract is here.)
https://www.sciencedirect.com/scienc...5964540100146X (paywall, but the abstract is here.)

BRAVO Sir. Best answer and explanation. There is a huge difference between melting and alloying. You described it well. Thank you. I hope some of the original nay sayers come back and read your post.
BNE.

[dimaprok]

If a 6,000+ degree flame won't melt a torch tip made out of copper, what makes you think a 700 degree lead pot will melt or dissolve it tinned or not?

I've done it, I melted about 2.85oz of copper wire (80 grams) in to tin making it about 10% copper alloy per my calculations based on weight.

When I read original post the author used the acid flux for soldering pipes but I didn't have any so I decided to use rosin puck I had for 20 years that my friend gave me, I knew I would never use it my lifetime so might as well put it to good use and it worked!

So I discovered as others wrote is multi stranded wire by itself dipped in to tin would not melt but when dipped it in tin to heat it up and dipped in to rosin it would melt pretty quick, I also used candle wax to keep tin oxidation down. I also melted couple copper pennies but it was very hard to do and took long time. I was using propane coleman camping stove and it was messy as rosin splatters and smokes. In the end when I made little puddles of tin it had bronze color to it compare to normal tin. Bronze IS tin and copper after all just in opposite ratio with high percentage of copper.

[jmort]

I predict you have a hot mess on a molecular/alloy level. Would love to see a few XRF results to see. Even then, only an electron microscope would reveal the alloy matrix. I hope you found what you are looking for.

[10 ga]

after reading all this my old head hurts. I'm thinking my 1 - 1 - 1 + 2% is pretty good. That's range scrap - COWW - soft + 2%tin !!! 10

[popper]

Solubility of Cu in Pb is 0.03% at room temp. Cu fills empty crystal lattice spaces in the Pb and does increase 'hardness' an malleability. The Sb/Cu molecules fill the lattice void. I have gone to 2% Cu in a Sb/Pb mix, hard as superhard. Cu alloys with Sb, so Sb MUST be 2x the Cu%. 12%Sb/6%Cu works (limit of strengthening) but hey who needs that? Adding Cu to high Sb alloy prevents the boolit from being brittle. Rosin & acid flux is used to remove oxidation from copper wire and reduce surface tension of tin further so the tinning 'bonds' and yes it is a thin layer. Semiconductor industry has some really exotic 'solders' to eliminate tin, copper, gold migration problems. NASA invented 'non-weldium alloys that would not 'weld' at 0 deg. Kelvin in a vacuum. Couldn't disconnect the wiring in returning space craft.

[Lloyd Smale]

when smelters alloy metals they use fluxes especially formulated to mix them and temps high enough to do it. If you take some copper wire and got it hot enough to melt over your pot the second it hits the 700 degree lead its going to act just like you dropped it in water. I doubt you will get anything more then blobs of copper in your lead. You need to find babbit that has already had copper added.

[jmort]

@sqlbullet
Very interesting. You have to consider the alloy.
Interesting thread.

[Tom W.]

When I could get Ni Babbitt It had no lead but did have some copper in it. It was mostly tin, and made some hard boolits if used by itself. I had some scraps of Silver solder left over from putting carbide teeth onto saws so I saved a few pieces and took them home to add to my lead pot to see what would happen.

Nothing.
They just floated around.

Maybe if I had added them to my dutch oven and tried melting them with COWW they may have blended, but I'll never know.....

[dimaprok]

when smelters alloy metals they use fluxes especially formulated to mix them and temps high enough to do it. If you take some copper wire and got it hot enough to melt over your pot the second it hits the 700 degree lead its going to act just like you dropped it in water. I doubt you will get anything more then blobs of copper in your lead. You need to find babbit that has already had copper added.

Didn't you read anything that was written in this thread??? A) People have done it including me and no copper didn't float like blob it got dissolved like a salt dissolves in the water even though salt has something like 1300 melting point. If you're not going to read the whole thread than at least read what SQLbullet wrote.

[beagle]

Probably the easiest way to add copper to your alloy is to find some copper rich Babbitt alloy. This will melt into the mix. Felix and I did some tinkering with this way back and it works. Normally one Babbitt bar to a pot does the trick. The problem is the alloy content is very hard to repeat and it's a hit or miss thing. We were messing with .223s so once a pot of alloy was established, we made a whole pot of .22 bullets./beagle