Alloy Mixing Question

[h8dirt]

Let's assume I have two alloys that are mixtures of lead, tin and antimony and I don't know the mix but I can measure the hardness. Can I calculate a mixture (based on the known hardnesses of the two alloys) to create a desired hardness that lies somewhere between the two samples? To simplify, can I mix 1# of 10 BHN and 1# OF 20 BHN to get 2# of 15 BHN?

[DRNurse1]

I think BHN is a logarithmic value so that direct proportion thing may not work. I am not the most knowledgeable person on this topic so there may be a better post later.

The hard way to do what you are trying to do is to melt a known amount of the harder alloy then add a known amount of the softer alloy, then check the hardness, and repeat until you have the hardness you desire.

One thing to consider is that alloy's can age harden, and water dropping changes the hardness as well. It would helo to know the application you are considering as well.

Happy Casting!

[JonB_in_Glencoe]

Let's assume I have two alloys that are mixtures of lead, tin and antimony and I don't know the mix but I can measure the hardness. Can I calculate a mixture (based on the known hardnesses of the two alloys) to create a desired hardness that lies somewhere between the two samples? To simplify, can I mix 1# of 10 BHN and 1# OF 20 BHN to get 2# of 15 BHN?
NOPE.
also, if your "mixtures of lead, tin and antimony" are large enough, larger than you can melt in one big batch, your attempt at blending can vary in alloy composition and alloy hardness. Now does it matter for your casting ? If it does, I'd order some certified alloy to suit your need.

[sqlbullet]

Having read all your posts, I am left wondering about your alloys. It appears you started about a month ago with linotype and pure lead. I am inferring from reading through your posts that you have made some alloys...Specifically 4 lbs of 96/3/1 and another batch of about 40 lbs of about the same alloy (96.72/2.46/0.82). All alloys listed are lead/antimony/tin. Both of these were made using linotype and pure lead at about a 1:4 ratio.

So, have you come up with some new mystery lead, or are you just considering a change to the alloy you have been using so far...the afformentioned 96/3/1?

[bangerjim]

Just get it in the 12 range and powder coat it. That solves all your problems. I make all my sub-sonic pistol and rifle soup at ~12. Faster rifles are 14-15.

We assume you have a GOOD hardness tester (cabine or saeco) and not just finger-nailing it!

Powder coating minimizes the problems with hardness and eliminate the need for greasy lubes and does not lead the barrel! If you are not familiar with it check the stickies on electrostatic gun coating on here.

banger

[h8dirt]

Having read all your posts, I am left wondering about your alloys. It appears you started about a month ago with linotype and pure lead. I am inferring from reading through your posts that you have made some alloys...Specifically 4 lbs of 96/3/1 and another batch of about 40 lbs of about the same alloy.

So, have you come up with some new mystery lead, or are you just considering a change to the alloy you have been using so far...the afformentioned 96/3/1?

That's for taking the interest and trying to help, sql'. What I have is a mix of linotype, monotype and factory-type -- as I smelt these in ~40 pound batches, I suspect they will be somewhat different due to the specific mix of the 3 ingredients. I also have some ingots that were made from type-spacers of various and unknown alloys (some of which were very soft and some hard) and I have a good supply of pure lead ingots. I am using the Lee hardness tester. I want to end up with around BHN 12 bullets. So ... I was simply wondering if there is a rule of thumb mixing formula based on hardness alone. Again, thanks for trying to help.

[Lloyd Smale]

simple answer to your question is yes. Mix one lb of 10bhn and one lb of 20 and you might not be spot on 15bhn but you will be close enough to call it good.

[sqlbullet]

I would treat them as if all those lino/mono/foundry ingots were monotype, and make up a 10 lb pot of 4:1 pure lead (or stick on WW) to those alloy.

You will almost certainly end up with something in the 11-13 range. Mixing lino with foundry in a 50/50 ratio, ±10% gives you basically monotype. Add in the fact that they were roughly thirds, with the third being mono which tends to attenuate deviations away from monotype ratios you can pretty much bet those ingots are about 70% lead, 20% antimony and 10% tin.

Good luck.

[Saltner]

If this can be useful there Xls file to download
http://castboolits.gunloads.com/attachment.php?attachmentid=45784&d=1341560870

[Larry Gibson]

Let's assume I have two alloys that are mixtures of lead, tin and antimony and I don't know the mix but I can measure the hardness. Can I calculate a mixture (based on the known hardnesses of the two alloys) to create a desired hardness that lies somewhere between the two samples? To simplify, can I mix 1# of 10 BHN and 1# OF 20 BHN to get 2# of 15 BHN?

Sometimes that works but sometimes it doesn't. Depends a lot on the Sn & Sb %s in each alloy. Many times with ternary alloys the sum of the total divided by 2 does not equal the median, at least as far as BHN goes.

Why not simply start 10 lbs of the 10 BHN and add the 20 BHN in 10% increments testing each increment until you had 15 BHN? Might take a while but at least you'll have the exact %s for what you want to mix the rest up. You might even have some of one left over for something else.

Larry Gibson

[h8dirt]

Thanks to everyone that has replied and helped me think through this. My question has been answered and a variety of good perspectives and ideas have been presented. Along the way, I've done some of my own "what if" thinking using the available hardness formulas that factor in Sn, Sb and Pb ratios. Got it. I'm off to do some mixing. Again, thanks! Done.