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Thread: formula for alloy?

  1. #1
    Boolit Master Nora's Avatar
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    formula for alloy?

    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
    If you don't have the time to do it right, when are you going to find the time to fix it?

  2. #2
    Boolit Master leftiye's Avatar
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    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).
    Last edited by leftiye; 05-25-2009 at 04:02 PM.
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  3. #3
    Boolit Master
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    The cast bullet association has a good downloadable alloy calculator

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

  4. #4
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    Hi,

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

    John

  5. #5
    Boolit Master
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    Use a little caution using the Cast Bullet Association Excel calculator ! The BHN for tin (Sn) is VERY wrong !

    Jerry
    S&W .38/44 Outdoorsman Accumulator

  6. #6
    Boolit Master southpaw's Avatar
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    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.
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  7. #7
    Boolit Master
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    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
    Regards
    John

  8. #8
    Boolit Master
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    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
    Regards
    John

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