Son of BHN and Tensile Strength

[joeb33050]

Some data on BHN and Tensile Strength
Here's a NIST site showing a collection of data from various sources.
www.boulder.nist.gov/div853/lead%20free/solders.html
Database for Solder Properties with Emphasis on New Lead-free Solders
Release 4.0

1. Table 1.18 gives the BHN of the eutectic alloy, 63% Tin, 37% Lead, as 17.
Table 1.2 gives the tensile strength of this alloy as 4442 psi, 30.6 MPa
To check the MPa number: The Pascal, Pa = 1.45 * 10^-4 psi.
The MPa is then 1.45 * 10^-4 * 10^6 = 1.45 * 10^2 psi.
The Table 1.2 figure of 30.6 MPa = 1.45* 10^2 * 30.6 = 4437 psi which looks close enough to 4442 psi for all the rounding going on.
Some estimate tensile strength at 1422 * BHN. Then 17*1422 = 27174 psi, which is a lot higher than the Table 2 4442 psi.

2. www.lasc.us/CastBulletNotes.htm
This site, among others, shows the hardness of 1:10 tin:lead alloy as BHN 11, and the hardness of 1:20 tin:lead alloy as BHN 10.
Using the 1422 factor:
1:20 BHN = 10 * 1422 = 14220 psi.
1:10 BHN = 11 * 1422 = 15642 psi.

Table 1.14 on the NIST site shows Tensile strength of 5% Tin 95% Lead alloy as 4190 psi. Compare with 14220 psi just above.
That table shows Tensile strength of 10% Tin, 90 % Lead alloy as 4400 psi. Compare with 15642 psi just above.
(I understand that 95:5 lead:tin isn't exactly 20:1 lead tin.)
Note that Table 1.14 gives the Tensile strength of the eutectic alloy as 6700 psi, and Table 1.2 gives the Tensile strength of the eutectic alloy as 4442 psi. Certainly these numbers do not agree, but the disparity between these numbers and the "1422" estimates is much greater.

3. This site is about engineering fundamentals.
http://www.efunda.com/materials/solders/tin_lead.cfm

The table shows the Tensile Strength of:
5% Tin:95% Lead at 28 MPa = 4060 psi.
If BHN is 10(LASC above), 10 * 1442 = 14420 psi. The 1442 factor.

10% Tin and 90% Lead at 30 MPa = 4350 psi.
If BHN is 11(LASC above), 11 * 1442 = 15862

63% Tin and 30% Lead at 37 MPa = 5365 psi. Note that this is between the Table 1.2 4442 and Table 1.14 6700 psi.
If BHN is 17 (Table 1.18, NIST site), 17 * 1442 = 24514

4. Here is the Mountain Molds site.
www.mountainmolds.com/bhn_psi.htm

Tensile strength is estimated at psi = 375 * BHN + 500
Then a 10 BHN alloy would have a Tensile strength of 10*375+500 = 4250, "1442" factor is 14420 psi.
An 11 BHN alloy....11*375+500 = 4625 psi
A 17 BHN alloy.....17*375+500 = 6875 psi.

Summary all in psi, 1,2,3,4 refer to par. above.)
"1422" 1 2 3 4
Eutectic BHN 17 24174 psi 4442 6700 5365 6875
95:5, 20:1 BHN 10 14420 psi 4190 4060 4250
90:10, 10:1 BHN 11 15862 psi 4400 4350 4625

Unless I'm making a big mistake here somewhere, estimating Tensile strength by multiplying BHN by 1422 is completely wrong.
Please tell me if I've gone wrong here.
joe b.

[45 2.1]

Unless I'm making a big mistake here somewhere, estimating Tensile strength by multiplying BHN by 1422 is completely wrong.
Please tell me if I've gone wrong here.
joe b.

joe b-
As an engineer, I understand what these guys are talking about. The only problem is that tensile strength has absolutely nothing to do with cast bullets as we use them. Surprised?? Compressive strength yes, but exactly what do we do to pull on both ends of the bullet in this (which is what tensile strength is). BTW, tensile strength is usually about 1/10 the compressive strength of materials. We haven't seen to much about yield strength either, but that one is the one you want to look at in this.

[felix]

Yes, yeild strength becomes important on figuring how fast we have to accelerate the boolit to make the nose collapse down into the grooves. This has to do with the overall "toughness" of the alloy. However, most important to most us shooting 2200 fps or less, the toughness comes into play for holding on to the lands. Ideally, we want the boolit to compress easily here, giving absolutely zero hint of any pushing any lead down the length of the boolit as the boolit moves forward. We want the lead to be pushed by the lands INTO the boolit, and never squirted away. An obvious impossibility because no matter what we do, we always can find fins on the end of a boolit even when using checks. ... felix

[45 2.1]

Fins are a matter of friction, not alloy strength. There are no fins on moly coated lead bullets, proved by Merril Martin. Tensile strength, that is lead in tension, has no actual place here.

[felix]

Correct you are, Bob! Tearing the boolit by any reason is not desired, and anyway that can be stopped is desirable. I have not seen a lead boolit that did not have fins, however. I have not tried moly dusting the boolits, mainly because I don't think enough pressure exists up front to make the moly work without the lead frictioning off underneith first. ... felix

[sundog]

Don't know about sheer, tensil, etc., but I know that when I shot a 35-200-FN from a 35 Rem at 2000 mv today into an over 10-pound WW ingot at 50 yards the hole was a might bigger than 35 caliber! It yielded, for sure. In fact, it was at least an inch and all the through. Quite interesting, to say the least. Looked for bullet remains or at least the GC, but found none - maybe embedded to far in the berm. Maybe I can get a pic or two and get it posted. Sure made an audible WHACK when it hit....

We were plinking [Silver Bullet] cans and the light was just right and we could see the boolits in flight! Really neat. Clear, blue, and twenty-two, with a one knot variable (yea, NO WIND). And it was 75dF! Really freaky for this time of year, but who's complaining. Still getting outside chores done wearing shorts and t-shirt. Go figger. sundog

edit: btw, that 35 Rem is a Marlin MG and it's consistently deadly accurate. At least this MG bbl is cast boolit friendly.

[joeb33050]

joe b-
As an engineer, I understand what these guys are talking about. The only problem is that tensile strength has absolutely nothing to do with cast bullets as we use them. Surprised?? Compressive strength yes, but exactly what do we do to pull on both ends of the bullet in this (which is what tensile strength is). BTW, tensile strength is usually about 1/10 the compressive strength of materials. We haven't seen to much about yield strength either, but that one is the one you want to look at in this.

That's what I thought-I was wrong. You need to google "tensile strength", and read about how it is a measure of deformation in compression also.
joe b.

[45 2.1]

That's what I thought-I was wrong. You need to google "tensile strength", and read about how it is a measure of deformation in compression also.
joe b.

Funny they didn't call it that in Theoretical and Applied Material Courses.

[sundog]

See my above post. sundog

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