Is There a Formula??

[VTDW]

Is there a formula/group of formulas that will tell you:

X % of Lead + Y % of Tin + Z % of Antimony = ? Brinnell Hardness

There has to be.

Thanks,

Dave:cool:

[fourarmed]

There might be, but it would also involve temperature data, because there are different crystalline states that alloys can assume, and they have different hardnesses. More likely, you would have a three dimensional graph that would differ for different cooling rates. Might even depend on the solunar tables.

[wills]

Sounds like an engineer.

[VTDW]

:drinks: Naaah. Just an old welder wanting to get to the heart of the matter.:mrgreen:

[Tom Myers]

I don't know of a simple formula to arrive at a BHN for Lead/Tin/Antimony alloys but I do use a simple "Rule of Thumb" to estimate the BHN of a Lead-Tin-Antimony alloy.

As we know, the BHN of pure lead is 5.
If I add 5% tin to pure lead I add 5 and 5 and get a BHN of 10

If I have wheel weights with 0.5% tin and 4% Antimony I add 5 + 0.5 + 4 and get a BHN of 9.5.

Lyman #2 Alloy has 5% Tin and 5% Antimony so 5 + 5 + 5 = 15 (right on)

Linotype has 3% tin and 11% Antimony so I add 5 + 3 + 11 for a BHN of 19 (it isn't right but it is close to 22)

I did make up a rational equation that returns a fairly accurate BHN for Tin/Lead alloys using the ratio of the tin/lead alloy. It is a little involved but it
does work.

Divide the weight of tin in an alloy by the total weight of the alloy to arrive at the ratio "R" then use this formula to get the BHN

BHN = ( 222.5 x R - 7.82 x R x R ) / ( 1 + 23.12 x R ) + 5


Let "R" equal a Ratio which is the weight of the Tin in the alloy divided by the total weight of the alloy...Then:

1 part tin plus 19 parts lead (by weight) equals a 1 in 20 alloy


Then 1 / 20 = 0.05..... So then R = 0.05..... Therefore:
BHN = ( 222.5 x 0.05 - 7.82 x 0.05 x 0.05 ) / ( 1 + 23.12 x 0.05 ) + 5
The Brinell Hardness Number of a 1 in 20 Tin-Lead alloy = 10.15

This will only work up to a 1/10 ratio as the alloy doesn't get much harder after that point is reached.

You can view an expanded Saeco Hardness Number to Brinell Hardness Number chart that I made up and posted on my website at this link.

Saeco to BHN chart (http://www.uslink.net/~tom1/bhchart.htm)

Hope this helps.

Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)

[wills]

Nice pictures on photobucket, appears you like to hunt hogs with leverguns.

[cherok9878]

some of the time, old welders can fix a problem before engineers. Not putting down engineers by any means. We need them and they have their place. I have a family menber, by marriage, that is an aeronautical engineer. He can explain anything and everything about combat aircraft, intellegent beyong belief. Ask him what time it is and he will tell you how to build a watch. I hate him and love him at the same time.

[Harry O]

Is there a formula/group of formulas that will tell you:

X % of Lead + Y % of Tin + Z % of Antimony = ? Brinnell Hardness

There has to be.

Thanks,

Dave:cool:

If there is, I have not been able to find it -- and I have looked (and more than on the Internet). I found a graph of lead/antimony. I also found a graph of lead/tin. The problem is that they are NOT linear. The lead/antimony changes a LOT and is far from a straight line. The lead/tin does not change nearly as much, but is still not a straight line. For the percentages usually used by casters, though, it is close enough to straight.

For rough numbers, you can add the percent tin and percent antimony to 5 and get a rough hardness. It is far from exact. I did a bunch of experiments myself and worked up an empirical formula for what you want. You figure the percent antimony and percent tin of your melt. Find the percent antimony on my chart and then add the percent tin directly to it. It works out pretty close for predictions. It is halfway down in this article:

http://www.sixshootercommunity.com/articles/cast_bullet_hardness.html

However, even that is not the whole story. I once figured out a melt that should have had an 18 Bhn. I cast with the same melt with three different moulds. One was tested at about 17, one about 18, and one about 19. The smaller the bullet (by weight), the higher the Bhn. It cools faster and that also affects the Bhn. So everything is approximate. However, it works for me.

[georgeld]

The way I've got it figured out where it works quite well for me
is:

IF I can't mark it with my thumb nail, it won't lead the barrel.

That's good enough for my needs.

I'm an old welder too.

[Mugs]

Check www.lasc.us. You should be able to find info. there.
Mugs

[VTDW]

Thank you ALL so very much. You are quite a tolerant group that is eager to share your vast knowledge. My thanks to Ranch Dog for leading me to this excellent site.

Wills - You are soooo right!:castmine:

Harry O. Your website is awesome. Thanks for sharing!!!!

Dave:cool: