How to Calculate BHN for a Mix of Alloys??

[STAR4ever]

Hi Guys:

I am interested in the math associated with the theoretical calculation of BHN for a resultant bach of alloy composed of 2 or more donor alloys, each with a different BHN rating.

An example:

10 Pounds of wheel weight alloy with a BHN of 12
and
10 Pounds of pure lead with a BHN of 5

The math I would use would be as follows.....

Pounds of Alloy 1 X BHN of Alloy 1

Plus

Pounds of Alloy 2 X BHN of Alloy 2

divided by the total pounds of both alloys....

or

(10 X 12) + (10 X 5) / 20 = 8.5 BHN

Is my conceptual grasp of this calculation correct?

I know there is a freeware spreadsheet out there called Alloy03.xls

However the copy of this which I have does not calculate an estimated BHN of the batch.

Oddly, the spreadsheet appears to have been once designed to do this calculation but the calculation is not present in the version I have.

I am all ears to any who may help me better understand the math I posit above.

Thanks In Advance

Art

[lwknight]

I always thought that you had to subtract the 5 on everything before averaging the value. It didn't dawn on me that it comes out the same either way.

[DrBill33]

RE: WWW BHN... I see 12 stated often; however, when I test what i find, I actually find them to be 9. So, it is best to check them prior to calculating your alloy mix. DrBill33

[montana_charlie]

RE: WWW BHN... I see 12 stated often; however, when I test what i find, I actually find them to be 9. So, it is best to check them prior to calculating your alloy mix. DrBill33
Okay, Bill, let's say those ten pounds of wheelweights turn out to be 9 BHN.

Will the resulting alloy actually be 7 BHN?

The adequacy of the formula is the question being explored, here.
CM

[JSnover]

Hi Guys:

I am interested in the math associated with the theoretical calculation of BHN for a resultant bach of alloy composed of 2 or more donor alloys, each with a different BHN rating.

An example:

10 Pounds of wheel weight alloy with a BHN of 12
and
10 Pounds of pure lead with a BHN of 5

The math I would use would be as follows.....

Pounds of Alloy 1 X BHN of Alloy 1

Plus

Pounds of Alloy 2 X BHN of Alloy 2

divided by the total pounds of both alloys....

or

(10 X 12) + (10 X 5) / 20 = 8.5 BHN

Is my conceptual grasp of this calculation correct?

Art

That will get you in the ballpark but there are a lot of variables. My WW test anywhere from 9-12 a week or two after casting. I do it pretty much the same way you do but I keep enough pure lead and tin babbit on hand to tweak the melt if it needs it. Get a tester and experiment with small amounts.

[STAR4ever]

The adequacy of the formula is the question being explored, here.
CM

Well Said... I gave the example in the original post as just that... an example...

I feel my logic is correct based upon weight contribution of the alloy components.

One thing I fear is that somehow that adding a certain alloy REALLY bias's the overall mix well beyond its weight contribution to the total sum of the parts. I hope that is not the case.

I have emailed the guys that wrote Aloy03.xls but have not yet gotten a response from them. I have gone ahead and added my calculations to the spreadsheet and I find it pretty handy.

I was also perhaps going to modify the spreadsheet to work in ounces vs pounds as my ingots are never exactly 1 pound in weight.

Well... I hope someone out there can say YAY or NAY regarding the calcuation

thanks amigos... Art

[kelbro]

Here's the formula that I use for the alloy.xls file:

=SUM(8.6+(0.29*C32)+(0.92*F32))

I read this formula somewhere. Not sure how accurate it is but it is very close to my results from measuring ball bearing indents.

[STAR4ever]

Gents:
In this morning's email was a nice email and a new updated Excel spreadsheet that James Hitchman sent to me. He apparently has been adding to and tweaking his Alloy spreadsheet.
It now does "estimate" BHN and also it graphs the BHN on a chart page with all the other BHN lines known. He explains that any antimony or tin even as a trace can effect BHN so that the result is NOT linear or therefore easily estimateable.

Like JSnover says above you have to test all alloys with a good tester. I have both the Cabin Tree and SAECO testers.

How long after casting an ingot or a bullet should one WAIT before testing for BHN???

I have been testing 24 hours later... is this too long or short a period of time?

[LAH]

RE: WWW BHN... I see 12 stated often; however, when I test what i find, I actually find them to be 9.

Been awhile since I checked but this is my findings.............Creeker

[badgeredd]

Like JSnover says above you have to test all alloys with a good tester. I have both the Cabin Tree and SAECO testers.

How long after casting an ingot or a bullet should one WAIT before testing for BHN???

I have been testing 24 hours later... is this too long or short a period of time?

My understanding is that air cooled alloy will takes weeks to reach full hardnes while water dropped alloy takes less time but still requires a signicant aging time. Just for my own information, I have been checking one batch every week for the last month. It is getting harder with age. A friend here told me that full hardness can be expected after 6 months if the boolits are a/c.

Edd

[STAR4ever]

My understanding is that air cooled alloy will takes weeks to reach full hardnes while water dropped alloy takes less time but still requires a signicant aging time. Just for my own information, I have been checking one batch every week for the last month. It is getting harder with age. A friend here told me that full hardness can be expected after 6 months if the boolits are a/c.

Edd

Badgeredd:
Boy that is REALLY discouraging.... How much harder have the alloys been getting over the period of time....

In other words, have you gone from 30:1 to 20:1? or just find subtle changes so that a batch of 30:1 is STILL 30:1 but just a wee bit harder in that range?

[Barnowl]

Attached is an Excel spreadsheet called "Cast Bullet Alloy Mix.xls" by John T. Larson that is very flexible for tweaking the mix to achieve the desired ratio of Sn:Sb:Pb. I made a couple of edits in the text at the top of the sheet but more importantly I added the formula for BHN (8.6+(.29x%Sn)+(.92x%Sb)=projected BHN) as found in another post on CastBoolits. It is nicely done and provides a lot of information.

Kevin

(The file in attached as a .zip file)

[Edubya]

Kevin, Thanks for your time and effort. That's one of the great things about the board and its members; willingness to share.
EW

[largom]

I have been testing alloy hardness all summer in an attempt to find a composition that gave the boolit expansion I wanted and still penetrated well. Some of the things I found were: 1: Boolits water dropped still required at least 2 weeks to reach full hardness.

2: Boolits air cooled required 4 to 5 weeks to reach full hardness.
I tested my samples on a weekly basis using a Lee tester and a LBT tester. A total of 4 different compositions were tested and the required ageing time was the same for each, before the hardening cycle stabilized.

Larry

[Edubya]

I have been testing alloy hardness all summer in an attempt to find a composition that gave the boolit expansion I wanted and still penetrated well. Some of the things I found were: 1: Boolits water dropped still required at least 2 weeks to reach full hardness.

2: Boolits air cooled required 4 to 5 weeks to reach full hardness.
I tested my samples on a weekly basis using a Lee tester and a LBT tester. A total of 4 different compositions were tested and the required ageing time was the same for each, before the hardening cycle stabilized.

Larry
I'm beginning to wonder if the antimony migrates to the outside of the boolits to give us false indications of hardness. I've tried similar experiments and have had conflicting results. I've read that antimony tends to collect around the tin in our alloy; could there be other characteristics that we are not aware of taking place?:?
What is the composition of your boolit mold? What caliber of mold are you testing? Is it something that I could duplicate to verify your results?
EW

[largom]

I'm beginning to wonder if the antimony migrates to the outside of the boolits to give us false indications of hardness. I've tried similar experiments and have had conflicting results. I've read that antimony tends to collect around the tin in our alloy; could there be other characteristics that we are not aware of taking place?:?
What is the composition of your boolit mold? What caliber of mold are you testing? Is it something that I could duplicate to verify your results?
EW

I tested 50/50 Pb & WW, 55%Pb & 45% WW, and 60%Pb & 40%WW. I tested water dropped and air cooled. I cast 8mm, 30 Cal., and 35 Cal. boolits. However, I also cast several 45-70 boolits which I used for hardness testing. The 45-70 boolits were placed in my mill and a flat milled on one side to give me a large enough area for several tests on each boolit. I have also taken boolits AFTER they had aged and milled a flat on them to test if the hardness was on the surface or throughout. These boolits tested same as ones milled right after casting.

Larry

[405]

I found early on that the final BHN of the combination of alloy mixes containing lead, tin and antimony cannot be calculated based on the percentages of the various parts' BHNs. The statement posted about, "the relationship is NOT linear" seems to be correct at least with my "alchemy of alloys".

I don't have any "certified alloy" other than known 60/40 solder. I have a very large supply of pure lead. For my smokeless type loads I start with about 20# of pure lead in the big pot. Then add my lead/tin/antimony alloy ingots in 1# increments until I get the BHN desired.

For my BPCR type loads I start with about 20# pure lead then add the correct % amount of 60/40 tin solder to get to my desired alloy... usually about 30:1 lead/tin.

I tried the BHN prediction math a long time ago and found something like:
Start with 20# pure lead then add 1# lead/tin/antimony ingots. As the BHN goes up with each added 1# of the lead/tin/antimony all seemed linear until a certain point is reached then the formula usually goes to pot! :)

Example: Start with 20# pure lead. Add 1# of 22 BHN alloy and the final BHN goes to 6. Add another 1# of 22 BHN and the final BHN goes to 6.5. Add another 1# of 22 BHN and the final BHN goes to 7. Add another 1# of 22 BHN and the final BHN jumps to 15 or something wild!!! Most assuredly not linear.

Now I just add the "hardener" in small amounts until the measured BHN reaches the objective. Yes, an alloy will take some time to reach equilibrium... yet another variable and unkown rate that I quit trying to predict and quit worrying about.

[Barnowl]

Found some errors in my edits to the attached Excel file in post #12 which I have corrected.
Should have looked it over better.

Kevin

[smallshot13]

Found some errors in my edits to the attached Excel file in post #12 which I have corrected.
Should have looked it over better.

Kevin

If you test your spread sheet by entering 100% pure lead, the hardness calculates to BHN 9. :killingpc

[Barnowl]

If you test your spread sheet by entering 100% pure lead, the hardness calculates to BHN 9.
smallshot13,

It is accurate for creating lead alloys. Create an alloy that duplicates a known alloy (hardball, Lyman #2) and see if the expected hardness agrees. The formula for Expected BHN is not designed to calculate pure lead alone.

See post #10 in the following discussion for info on the BHN Formula:

http://castboolits.gunloads.com/showthread.php?t=67128&highlight=formula+bhn

Kevin

[garandsrus]

Kevin,

Thanks for improving the spreadsheet I created. I didn't know the formula to predict the BHN.

John

[Barnowl]

Kevin,

Thanks for improving the spreadsheet I created. I didn't know the formula to predict the BHN.

John

Howdy John,
That is a very nicely done spreadsheet! Hope you don't mind that I messed with it a bit. I don't think of it as improving your work. The original intent of my edits was just to customize it for my own use but then I ended up posting it here when the alloy discussion started.

I found a formula for "Estimated minimum peak pressure required for bullet obturation" on the LASC site at http://www.lasc.us/FryxellCBAlloyObturation.htm and included it in this version. See attached, ver 1.1.

I am repeating the credit for the spreadsheet again here:

Attached is an Excel spreadsheet called "Cast Bullet Alloy Mix.xls" by John T. Larson that is very flexible for tweaking the mix to achieve the desired ratio of Sn:Sb:Pb. For my own use I made a couple of edits in the text at the top of the sheet and also added the formulas for BHN (8.6+(.29x%Sn)+(.92x%Sb)=projected BHN) as found in another post on CastBoolits and "Estimated minimum peak pressure required for bullet obturation" as found on LACS. It is nicely done and provides a lot of information.

Kevin

[LouisianaMan]

Thanks for this work, guys! I've got WW, but no pure lead yet, and had been wondering what options I had to effectively alloy it to give obturation and/or possible expansion in low-velocity revolver loads, such as various weights of .32SWL/HRM/.327, .38SPL, and .45LC.

This spreadsheet gives me some ideas to work from, and should improve both accuracy & leading issues. Excellent!

[leadman]

Thanks for all your work on this.
I have litterally a ton of pure lead and, some lino, and some reclaimed shot. This should allow me to mix up a good alloy for my purposes.