Time testing hardness

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  • Last Post 17 July 2016
JPnewhampshire posted this 14 July 2016

 

Hi All: Last week I received my new Lee bullet metal hardness tester”€on sale at Amazon// I have been smelting wheel wgts this last few weeks (500 lbs+) at about a 60% lead yeald//. I have been testing the hardness as I went along with considerable varying results so I decided to set up a test. Every 12+- lbs I make a small test pc in a Mini cupcake tin See pics. Using one test pc I have started testing as follows: test # time   reading     Bn

1   1 hr     . 072        9.8

2   4hr       .071        10.1

3   10hr     .070        10.4

4   21hr     .068        11.0

5   42hr      .065       12.0

My plan is to try and continue to test and post till the changing stops ?/ Any thoughts?? Perry

http://s1293.photobucket.com/user/jpteele2/media/CIMG6334_zpskv2ncnvk.jpg.html>http://s1293.photobucket.com/user/jpteele2/media/CIMG6333_zpstyb7h7x9.jpg.html>

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onondaga posted this 14 July 2016

http://www.castbulletassoc.org/view_user.php?id=9530>JPnewhampshire

 There is a factor to consider that has escaped your test method.

Small ingot molds with freshly poured alloy cool faster and harder than large ingot molds do and the small ingots skew test results toward higher BHN numbers.

The 5 pound ingots like Rotometals uses, or even better their large pigs of lead are much truer to the truth of BHN than small cupcake ingots like yours. Large ingots allowed to cool of their own accord give the most consistent and accurate test results for BHN.

Just by looking at the pictures of your ingots, I can see surface crystalline patterns of Antimony. That is from rapid cooling or quenching. Test results on those ingots will present a false high BHN. Large ingots that are cooled naturally and are shiny on the surface with no crystalline or frost patterns give the most accurate and consistent test results.

I'd really expect the test results from the ingots you picture to run all over the place and not be fair to evaluate any hardness testing tool. The appearance of ingots doesn't lie. If they don't look consistent, they aren't.

Also, age hardening becomes pretty constant at 5 days. After that the changes are minuscule by time. That is just metallurgical science. if you aren't verifying that in your tests, you are doing something wrong.

Gary

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onondaga posted this 15 July 2016

If you are looking for a suggestion to get better test consistency with ingots like yours, cut into them about 1/16” or more with a fine file to prepare a flat test area for indentation. This will remove the layer of disturbed cooling that is higher in Antimony and gives false high BHN readings. Technical tips from Lee mention this.

I have done BHN testing for a number of members here with my Lee Hardness Test Kit and always prepare test areas with a file whether it is on bullets, ingots or pieces of scrap.

Gary

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Duane Mellenbruch posted this 15 July 2016

If you read the last line, it is pretty clear to me that the true hardness of the alloy is not the goal.

"My plan is to try and continue to test and post till the changing stops ?/ Any thoughts?? Perry"

He is only looking for a period of change. Perhaps the ingot size may influence this rate, perhaps not. If he was looking for actual hardness the more accurate sample would be the actual bullet.

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JPnewhampshire posted this 15 July 2016

OK: I don't see whats wrong with my ingots ?? I ran a test on one --fileing a flat on one part and testing and testing on the other part--2 tests each with about 1 line (.002) diff.--close as I cant read any better than +- 1/2 line
Todays test (day 3 was .065 -same as last reading // Perry

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onondaga posted this 15 July 2016

Perry, your ingots don't appear uniform . Some cooled shiny, some cooled frosty, some cooled pitted. When that happens with like alloy ingots, they weren't poured or cooled uniformly and they will give false inaccurate and inconsistent BHN readings.

Gary

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JPnewhampshire posted this 15 July 2016

My procedure is : I scoop in WWs ,melt them, skim, repeat till I have about 25 lbs in the pot. flux and skim again. then using my 1 1/2 lb laddle I poor 12 ingots in a corn bread pan. then go back and fill the pot dump out the pan and repeat// I'll make about 100 lbs at a time I think the process is quite constant and I see the ingots as very uniform--note: the rt hand box in the photo is pure lead not WW. Perry

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Larry Gibson posted this 15 July 2016

JP

I see nothing wrong with your ingots.  You're results are consistent with those most of us have gotten with similar tests.  Appears your  batch of WWs is a good batch. The BHN will vary slightly when measured on actual cast bullets but that is to be expected. Adding  2% tin to your WW alloy should result in BHNs of 13 - 16 on actual cast bullets.  It would be an excellent alloy for most cast bullet uses producing very good cast bullets.Well done test btw.  I frequently run a very similar test on new batches of alloy.  As long as your testing methods are consistent  the results correlate for your use.LMG

Concealment is not cover.........

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JPnewhampshire posted this 15 July 2016

Thanks LMG// I was planning on selling most of this BUT seeing the quality of WWs getting less and less lead-I think I'll sell about 150 lbs to recover costs and keep the rest//Perry

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JPnewhampshire posted this 17 July 2016

I have re written the test results report to offer a little more Data //

test #day    time         reading Bn     day temp= 90f, nite 65+- cast 11 am 7/12 Tue #1 7/12    12 am Tue .072     9.8 still warm #2 7/12     3 pm Tue .071      10.14 cool #3 7/13     9 am Wed .070     10.4 #4 7/13     6 pm Wed .068     11.0 #5 7/14     11am Thu .065     12.0 #6 7/15     11am Fri .065       12.0 #7 7/16     11am Sat .0655 ? 12.+ hard to read +-1/2 #8 7/17     11 am Sun .064    12.5    air  temp= 60f It looks like the hardness has settled down so I'll only test every few days for a while.   From the above I would say one must wait at least 3 days to get a good  Bn reading  Perry

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