Alloy Identification help

[MtGun44]

I have an unknown alloy that is perported to be "solder".

It shows 14 BHN on my LBT hardness tester, repeatable in multiple
ingots.

I melted two ingots and put a lead thermometer in and recorded temp
vs time as it cooled. The long flat portion had my thermometer reading
319F. I had read about this method of checking 'melting point' - actually
phase change point, in this direction of temp change, it would be
the solidification point. It got slushy and semi-solid at about 400F indicated
temp, and by about 370F on the thermometer it appeared to be
solid. Note that the absolutely flat portion of the graph is well below
the temp where the alloy seemed to be visually solid, and with wiggling
the thermometer indicated near solid. There was an eleven minute
period where the needle didn't move even a hair. I knew that this should
happen but still, I tapped the thermometer to be sure it wasn't stuck. It
wasn't.

19914

Since eutectic tin-lead (the lowest possible melting temp for tin-lead
alloys) melting point is 361F, I must have either a 42F temp error in my
thermometer (seems likely to me) or maybe a tertiary or more complex
alloy with a lower melting temp.

I have read that eutectic tin-lead alloy should have a hardness of 17 BHN.

So, too low melting temp and too low hardness for 63-37 eutectic solder,
assuming that the flat portion of the graph represents the true 'melting point'
or phase change temperature for this alloy.

Any ideas?

Bill

[lwknight]

You might try a specific gravity test.

[ANeat]

If it got slushy then it wont be the eutetic mix. If youre indicating the melting temp is approx 400 that would lead me to believe that its closer to 50/50 solder.

I wouldnt say for sure without comparing to a known sample.

I dont know if 50/50 solder is 14 bhn or if there may be something else in there.

Comparing bullet weight between a say known 50/50 and the unknown alloy may give a couple clues

[7of7]

By melt temp it appears it could be 60/40 tin/lead.. cast a couple bullets.. one from this alloy, and one from known pure lead... post your results... I want to check out a spreadsheet I created...

[montana_charlie]

I'm not sure you could tell the difference between 63/37 and 60/40, but...
There is also such a thing as 40/60 solder. It should be measurably softer than 63/37.

CM

[MtGun44]

Well I have the BHN at 14, doesn't that provide the hardness info by itself?

I was also thinking that the eutectic alloy is supposed to NOT have a slushy phase and this
stuff was definitely slushy from about 400 down to 319 or so. I believe that I read that
the flat line temp was the freezing temp - can anybody verify this??

Any idea on how to set up to weigh it in water for sp grav test?? I suppose hang it from
a thread on my old beam scale (have to dig it out) the dip into water. Compare the
wt in and out of water.

Bill

[deltaenterprizes]

eutectic alloy has no plastic state, it goes form liquid to solid

[lwknight]

Since you say " dig the old beam scale out" I'm guessing that you use a digital scale.
The beam scale would be harder to use than an electronic scale because of the beam end in your way and because you would have to hold the sample suspended while you adjust the scale to balance.

You have to work with what you have. I use a refrigerant scale and measure 10 pound or so ingots in a 1 gallon water jug with the scale set up in metric mode. I suspend the ingot with a 1/2" SS band and I know that it will affect the reading slightly but with that size sample , its minimal.

For a SG chart Right Click here and save target as: (http://castboolits.gunloads.com/attachment.php?attachmentid=18225&d=1261865841)

[7of7]

I'm not sure you could tell the difference between 63/37 and 60/40, but...
There is also such a thing as 40/60 solder. It should be measurably softer than 63/37.

CM

60/40 would be fairly hard... and not a 14 bhn...

[MtGun44]

I'm not sure I can see how I could use my digital pan scale? How to suspend the sample
from the pan in the water?

Hmm, I guess I could make a wire frame that sits on the scale, tare out the frame and then
attach an ingot hanging from the frame. Weight the ingot with the frame tared out, then
put a bowl of water under the frame with the ingot immersed but with me holding the
bowl.

May work.

PS, I measured the hardness of a bar of 50-50 solder and it was about 11, same as wwts usually
show for me.

Bill

[sagacious]

I believe that I read that the flat line temp was the freezing temp - can anybody verify this??
Yes, the beginning of the flat portion of the cooling curve indicates the beginning of solidification/freezing. While 319*F is possible, a variance in your thermometer is also possible. Verify it's accuracy in boiling water and report back.

[Glen]

While I can't offer any authoritative answers here, I can offer this --

1. This alloy shows a "slushy" phase, therefore it is not a simple binary lead/tin alloy, and must have a third component.

2. In an air-cooled state (I assume?) it shows a BHN of 14, which is pretty darned hard for a binary lead/tin alloy (it can be reached, but given #1 I bet it's got something else in there).

Now for something labelled "solder" the "mystery meat" components can be pretty far-reaching -- anything from antimony to silver to ???. Personally, I would mix it in with some of my "standard lead alloy" to achieve the desired hardness and see how it shot...

[sagacious]

...
This alloy shows a "slushy" phase, therefore it is not a simple binary lead/tin alloy, and must have a third component.
...
Please forgive this clarification, but only the binary 63/37 solder alloy has no pasty range. However, all other common binary lead/tin solder alloys have a pasty range. For example, 50/50 solder has a pasty range of 60*F. So, the nominal 30*F pasty range would not itself be a discriminator for a third alloying component.

Just tryin ta help. :drinks:

[lwknight]

MtGun, I was imagining that the scale had a flat platform that you could just sit a small pill botle with about 2" or so water in it then cast a small ingot in the shape of a boolit to susspend into the water with a thread. However I have no idea what your weight capacity is so that may be a limiting factor.

[Linstrum]

Besides helping mould fill-out, another purpose for having antimony in bullet alloy is to reduce leading problems since antimony and its other family members prevent lead/tin alloys from soldering to ferrous metals. You can still get leading but it comes out more easily, so if your mystery alloy doesn't appear to have any antimony in it, add some linotype. Antimony expands on freezing, which helps identify its presence WHEN there is enough to overcome the shrinkage of the other constituents. Arsenic and bismuth also expand on cooling and they also help reduce leading problems.

You don't need to take specific gravity measurements in Metric units to get the correct answer since it is the ratio of the dry/wet weights that determine specific gravity. Specific gravity is the density of an object in relation to the same volume of water, and since the Metric System is partly based on water's properties, your answer will automatically be in a correct Metric System unit of measurement, such as grams per cubic centimeter. Pure lead weighs 11.34 grams per cubic centimeter so it has a specific gravity of 11.34 since a cubic centimeter of water weighs one gram.

Any time you have a liquid that is in the process of freezing, its temperature will remain constant even though it is giving off heat. It will stay constant until all of the liquid has frozen, this giving up heat while still staying at the same temperature is called "heat of fusion". The same thing happens when a gas condenses to a liquid, except for helium because it lacks valence electrons. It works the other way, too, that's why water is always 100 C/212 F when boiling at sea level. Turn up the stove burner higher but the water won't get any hotter as long as steam is coming off. The lower the atmospheric pressure, the lower the boiling point, which royally messes up trying to bake a cake or cook rice at 12,000 feet (been there, done that and I had to eat crunchy rice up near the top of Engineer Mountain at Silverton in Colorado). From what you've said you already know this stuff, but other readers may not and wonder what's going on. When you've got more than two materials in a mixture it really messes up trying to figure out what all is in it and sometimes you just have to do a qualitative analysis, which is a lot of bother without a good "wet lab" set-up. I hope you can use this stuff okay.


rl735

[MtGun44]

Well the problem is whether I want to trade for some of this metal at a pretty high
wwt to "solder" ratio or not?

I'm thinking that it is looking like it is not actually just eutectic solder, and therefore
not worth as much as a trading metal. If it had no slush phase and seemed to melt
closer to 360F, I'd be happy to trade for it, but I'm not sure now and am more and
more thinking it has something else in it. Not sure what would lower the melting
point to about 320F.

I agree with Glen that trying it would be the real proof, but at this point, I don't really
own it, and am not sure that I want to own it.

The only other relatively easy test is the specific gravity test.

Bill

[joeb33050]

For a good guess, see
"CAST BULLETS FOR BEGINNER AND EXPERT" at http://sports.groups.yahoo.com/group/CB-BOOK/
in FILES.

3.2 BULLET CASTING METALS
pgs. 61-64
where specific gravity testing is shown and explained,. and a chart of s.g. vs. alloys is available.
joe b.

[lwknight]

The only reason that I had mentioned taking the measurements in metric was in regard to my refrigerant scale where it requires only to press a button so I don't have to fool with converting pounds/oz to decimal pounds. A grain or gram scale is decimal anyway so its irrelevant to what graduation that is used if the sample weight is in the same scale both suspended and dry weight.

[MtGun44]

Joe,

Thanks for the reference. Great info, only the max tin percent they list is 12% and my
alloy is likely 50% or more. Also, if it is solder, there is no antimony, of course the slushy
phase has me thinking it is not 63-37 alloy, altho I tested 50-50 solder and it is a lot
softer than this alloy.

[lwknight]

I forgot to add that you can change the percent number and the chart will recalculate.
I suggest saving a copy before you go changing things in case you accidently change a formula cell. You can trial and error it till the cross cells match your exact SG.