Mixing an alloy

[Mike W1]

Some while back I'd run some BHN tests on an alloy and had gotten some results that had me wondering if I was getting things mixed thoroughly enough as there were some pretty wide spread results. For the latest batch I sent some samples to have a XrF test run on them and and got the results back. The batch yielded 94 lbs so it's a fairly good sized one.

My question would be whether the results on Ingot #2 are significantlly different or do you suppose it's a fluke? The actual samples submitted are about the size of a BB.

Or perhaps I need to spend a lot more time stirring?

INGOT 1
Pb = 95.4%
Sb = 3.8%
Sn = 0.8%

INGOT 1 1st 3 samples virtually identical
Pb = 95.6%
Sb = 3.9%
Sn = 0.5%

INGOT 3
Pb = 95.6%
Sb = 3.7%
Sn = 0.7%

INGOT 2
Pb = 92.7% Significantly different????
Sb = 5.6%
Sn = 1.7%

 

[Brad]

Doesn't take much to mix the alloy in a uniform manner. Look at how fast two liquids mix when dumped together. Now add the convection currents due to hearing and some stirring and they mix fast.

I have my doubts on the precision of the XRF guns at most places. I would use the results as a strong approximation, maybe accurate to 1/4 percent at best.

I wonder if there wasn't an inclusion of an SbSn intermettalic where the reading took place they skewed the results.

Go with the trend. If all were poured from same pot then I would use the results that seem common, not the outlyers.

 

[freebullet]

The guns can be manipulated via input parameters. I doubt you have much to worry about with those #'s.

 

[Rick]

I'd be willing to bet if you re-tested the sample that tested out of the norm it would show different results. Those hand held units as expensive as they might be are a long way from infallible. First thing to remember with them is that they don't automatically show what's in an alloy. You need to tell it what to look for and it'll give an approximation if it's in the alloy. In other words, if you tell to look for Pb/Sb/Sn and there is 5% Au in the alloy the Au won't show in the results. They are a handy tool but don't bet the farm on 100% accuracy. They can give an idea of what your working with but not much more. As Brad said, go with the average and feel confident that it's a reasonable approximation.
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[Brad]

Want precise results? Find a wet lab and talk to them. Better have a large stack of Benjamins in your hand.