formula for alloy?

[Nora]

Is any one familiar with a math formula that will give an accurate and repeatable percentage for alloy content? I'm only looking for the tin percentage in batch sizes and solder types that will vary. Assuming that WW's have a .5% tin content, and my target is 1%. Today I may be looking at 10lbs of WW's and have 60/40 solder, wile tomorrow it may be 50lbs of WW's and 90/10 solder.

Thanks in advance

Nora

[leftiye]

Add one ounce (or pound)of tin per every 100 ounces (or pounds) of lead or alloy as the case may be. If your alloy already has 1/2% tin, add only 1/2 % more. Solders are by weight. To get one ounce of tin from 50/50 solder add 2 ozs of solder. In this case you would add 1 oz if you only wanted 1/2% more tin. Same kind of calculation with 63/37 - 63 in to 100 (inverse) = approx 1 2/3 oz solder yeilds 1 oz tin. If you want 1/2 % tin multiply this by .5 (1.67X.5).

[ANeat]

The cast bullet association has a good downloadable alloy calculator

http://www.castbulletassoc.org/downloads.shtml

[garandsrus]

Hi,

If you do a search here, you will find several alloy calculators. Most are written to work with Excel.

John

[GLL]

Use a little caution using the Cast Bullet Association Excel calculator ! The BHN for tin (Sn) is VERY wrong !

Jerry

[southpaw]

I got it!! I got it!! Get your pencil

Let D%SN represent your desired % of tin in the alloy

Let TW represent the total weight of your alloy

Let %SNA represent the % of tin in your alloy

Let %TB represent the % of tin in you tin bar. ie 63, 50,40....

Here is the formula:

[(D%SN - %SNA) x tw] / %TB

Lets try it with 20lbs of ww (.5%sn) and try to achieve 1% sn with 63% solder

[(1% - .5%) x 20lbs] / 63%
(.5% x 20) / 63%
10%/63%
=.158lbs of solder. Lets call it .16. Since it is a small number multiple it by 16 (ounces in a pound). .16 x 16 = 2.56 ounces

Hope this helps.

Jerry Jr.

[John Boy]

You can denote a tin lead alloy in 2 different ways.
A 1 part tin and 19 part lead alloy can be referred to as 1 in 20 and written as 1 / 20 or 1:19 which would contain 5% of tin in the alloy.

A 1 part tin and 20 part lead alloy can be referred to as 1 and 20 and written as 1:20 or 1 / 21 which would contain 4.762% tin in the alloy.


To calculate the amount of the Add Alloy to mix in with the Old Alloy in order to arrive at a certain percentage of Tin in the New Alloy:

Let X = the Weight of the Add Alloy which will be a 50% tin and 50% lead alloy.

Let the New Alloy be a 1 in 20 or 1 / 20 Alloy which will contain 5% Tin.

Let The Old Alloy be pure lead which will contain 0% Tin.

OldAlloyWt * ( 1 - %Tin in OldAlloy / 100) + X * ( 1 - % Tin in AddAloy / 100 ) = ( OldAlloyWt + X ) * ( 1 - %Tin in NewAlloy / 100 )

%Tin in OldAlloy = 0
%Tin in AddAlloy = 50
%Tin in NewAlloy = 5

10 pounds of Old Alloy

10 * ( 1 - 0 / 100 ) + X * ( 1 - 50 / 100 ) = (10 + X ) * ( 1 - 5 / 100 )

10 * ( 1- 0 ) + X * ( 1 - 0.5 ) = ( 10 + X ) * ( 1 - 0.05)

10 * 1 + X * 0.5 = ( 10 + X ) * 0.95

10 + X - 0.5*X = 9.5 + 0.95*X

10 - 9.5 = 0.95*X - .5*X

0.5 = 0.45*X

X = 0.5 / 0.45

X = 1.1111 pounds of Add Alloy to add to the 10 pounds of Old Alloy

This adds up to 11.111 lbs of alloy of which 0.55555 lbs is tin

0.55555 / 11.1111 = 0.05 or 5% Tin or a 1 in 20 Tin Lead Alloy

If you have wheelweights and want to add enough 60:40 Tin Lead Solder to arrive at a 5% tin alloy, it goes like this

Wheelweights = 95% Lead, 4.5% Antimony and 0.5% Tin

10 lb Wheelweights = 0.5% Tin
New Alloy = 5% Tin
Solder = 60% Tin

10 * ( 1 - 0.5 / 100 ) + X * ( 1 - 60 / 100 ) = (10 + X ) * ( 1 - 5 / 100 )
10 * 0.995 + X - X * 0.6 = ( 10 + X ) * 0.95
9.95 + 0.4*X = 9.5 + 0.95*X
9.95 - 9.5 = 0.95*X - 0.4*X
0.45 = 0.55*X
X = 0.45 / 0.55
X = 0.818181 = lbs of 60:40 solder to add to 10 lbs of wheel weights to have a 5%tin alloy
This New Alloy contains 4.15% Antimony 5% Tin and 90.85% Lead


Hope this helps
Tom Myers
Precision Ballistics and Records

[John Boy]

Use a little caution using the Cast Bullet Association Excel calculator ! The BHN for tin (Sn) is VERY wrong !

Jerry, the creator of the CBA Calculator's response to me why Sn is not in the table as Bhn 7. I use it and find the results to be good

From: James Hitchman [j hitchman at comcast.net]
Sent: 12/01/2008 11:11 AM
To: xxxxxxxxxxxxxxx
Subject: Question about Sn Data Table Value
Attachments: AlloyExtra2.xls

John,

You are perfectly correct in that the hardness of Tin is about BHN 7. The
problem is that in a lead tin alloy at the molecular level the organization of
the atoms leads to an overall greater bond strength (simplification) and a
greater BHN. Using Lead BHN ~5 and Tin BHN ~7 and looking at just the initial
hardness of pure substances gives no indication of final product hardness. The
results must be all empirically determined. Different configurations in the
microstructure are possible for different concentrations in the alloy and
different cooling rates - also affecting BHN. For the alloy this is not in a
linear relationship but the easiest quick and dirty method is to give the tin
a BHN of 30 and not 7 in calculations. Low value BHN alloys are the hardest to
calculate and stock alloy recipes are the best to use - see Lyman website
perhaps. Now if other trace elements that cause hardening are present such as
Zinc, Silver or Arsenic, it becomes quite difficult to predict the eventual
hardness of the alloy with any finesse.

I'm not sure which excel version of alloy03.xls spreadsheet you have...? ( Yes
more than one with the same name - sorry)

Attached is perhaps a different form of the Excel Alloy spreadsheet for you to
use.
Most of the spreadsheet cells are locked - unlock with the password "alloy".
Fairly pedantic I know so to unlock use: > Tools > Protection > Unprotect Sheet > alloy

I would stress that the best worksheet to refer to is the one labeled as "BHN
Chart". The two moving points, one red - additions as weights and one green -
additions as percentages, are generated from the tin and antimony percentages
from the previous pages. This chart is an adaptation (slightly simplified
curves around the 23 - 24 BHN equipotential lines) from a 1950's publication
and is much more dependable than the BHN calculations on the excel sheet. Try
various combinations and you will see that some give quite different results
than expected. The tabulated hardness of the pure tin and pure antimony are of
course incorrect ( should be lower as mentioned above) but are used this way
in an attempt to calculate simply the hardening effects seen in the final
alloy. Obviously the BHN chart page has limited functionality in the low < 16
BHN area - where most of my shooting interests lie.

The chart is the best graphical BHN estimation chart I know of for "Pure"
Lead/ Tin/ Antimony alloys.

On the "Print page", (no laughing please) the data (for example set in
original attachment):

Not Accurate:
Overall Brinnel Hardness 13.78
Chamber pressure maximum psi. 19600
Working Pressure (x0.9) 17600


are not regarded as accurate by the CBA. I tend to agree with them but have
left it in.

If you shoot a hole in your foot with any of this information please call me
so I can skip town before the marshals get here.

Have a great day and please let me know what should be done to improve the
spreadsheet.

cheers
Jim