popper
02-03-2017, 01:28 PM
I have found that copper can be added to your alloy to give more malleability and/or zinc for hardness to low antimony alloys. Approximately 0.3% Cu and 0.2% Zn can be added to pure Pb, still casts easily (~730F) yet is still a 'soft' alloy. Increasing the Cu to 0.5-2% increases BHN (~38 BHN for 2%) with good malleability, they don't shatter. Heat treating will increase BHN further. The trick is to have equal or more antimony in the alloy. 1% Cu works for 50k psi.
Ok, the HOW-TO.
Use a simple paper painter's mask when doing this. No toxic fumes are released but the powder from the process is bad to inhale. Use the normal protective gear for handling Pb.
This process will replace ALL tin or zinc in your alloy on a 1:1 % basis. The atomic weights of Pb/Sn/Zn are 207/119/65. You can calculate the weights needed but 1/4 US zinc penny/pound of Pb is correct (break them to aid in melting). Tin takes twice as much. I don't use any WW, just use any supposed tin content in them. I cast ~720F so take your alloy up to 750F or so, add Zn (much cheaper) or tin and let it melt. Sprinkle in one tablespoon of CuSO4, Zep root killer is what I use - $12 bottle lasted me 3 years. It is blue and will turn white when the water is cooked off. I lightly push the stuff under the melt to speed the process but watch for the tinsel sprite - you will get some bubbles. You probably will get a blob of crusty 'stuff' on top. Just grind/stir it into your melt. Repeat until the Zep stays white. You're done. Spoon off the powder 'dross' from the top, stir and scrape to get all the powder out and dispose of it. Flux as needed. If you use tin, powder will be grey, zinc makes brownish powder. Both are nasty. I have an old sauce pan for dross, when it cools I add water to keep the dust down, makes dumping easier.
If you want zinc in your alloy, add it after adding Copper. So far, > 0.2% Zn gets tough to cast.
Performance? So far, 'soft' takes the pressure of max 40SW loads (~30k psi), hard works PB to 50k psi (300 BO), GC ~60k psi (308W) with accuracy. I'm testing with BLL so the alloy gets tested. So far I've tested in 9, 40, 30/30 & 300BO, all PB. I'm frugal (cheap) so only use GC for the 308 AR. No complaints. This stuff just plain works. Actually I did try the 'soft' in 30/30 @ 1400 fps GC, results weren't bad so a mushrooming hunting alloy? Still tinkering.
Thanks to R5R for suggesting Cu enhanced when I was having trouble with the 40sw. I sold my welder years ago and don't want to play with tinning speaker wire. Zep just works and is easy/fast/cheap.
EDIQT: my intent here was just instructional as the other threads get a little long.
Ok, the HOW-TO.
Use a simple paper painter's mask when doing this. No toxic fumes are released but the powder from the process is bad to inhale. Use the normal protective gear for handling Pb.
This process will replace ALL tin or zinc in your alloy on a 1:1 % basis. The atomic weights of Pb/Sn/Zn are 207/119/65. You can calculate the weights needed but 1/4 US zinc penny/pound of Pb is correct (break them to aid in melting). Tin takes twice as much. I don't use any WW, just use any supposed tin content in them. I cast ~720F so take your alloy up to 750F or so, add Zn (much cheaper) or tin and let it melt. Sprinkle in one tablespoon of CuSO4, Zep root killer is what I use - $12 bottle lasted me 3 years. It is blue and will turn white when the water is cooked off. I lightly push the stuff under the melt to speed the process but watch for the tinsel sprite - you will get some bubbles. You probably will get a blob of crusty 'stuff' on top. Just grind/stir it into your melt. Repeat until the Zep stays white. You're done. Spoon off the powder 'dross' from the top, stir and scrape to get all the powder out and dispose of it. Flux as needed. If you use tin, powder will be grey, zinc makes brownish powder. Both are nasty. I have an old sauce pan for dross, when it cools I add water to keep the dust down, makes dumping easier.
If you want zinc in your alloy, add it after adding Copper. So far, > 0.2% Zn gets tough to cast.
Performance? So far, 'soft' takes the pressure of max 40SW loads (~30k psi), hard works PB to 50k psi (300 BO), GC ~60k psi (308W) with accuracy. I'm testing with BLL so the alloy gets tested. So far I've tested in 9, 40, 30/30 & 300BO, all PB. I'm frugal (cheap) so only use GC for the 308 AR. No complaints. This stuff just plain works. Actually I did try the 'soft' in 30/30 @ 1400 fps GC, results weren't bad so a mushrooming hunting alloy? Still tinkering.
Thanks to R5R for suggesting Cu enhanced when I was having trouble with the 40sw. I sold my welder years ago and don't want to play with tinning speaker wire. Zep just works and is easy/fast/cheap.
EDIQT: my intent here was just instructional as the other threads get a little long.