WHATZIT??? ID help, please

[geargnasher]

Got some ingots, likely high tin content, dross inclusions look like radiator shop drippings, density 7.95 g/mL, BHN 9.8 (aged, I'm sure, not that it matters if it's binary Pb/Sn).

I know it could be about 80/20 Sn/Pb, but I don't know if that jives with the BHN.

The alloy has a slight, light grey oxide and small, wrinkly dross formations from the ladle tails which is reminiscent of WW alloy, meaning to me some antimony content, but they don't ring, just kind of a dull tinkle.

I have some known, tested 63/37 ingots that are shiny and check 9.2 with the same tester. Pure tin ingot is off the chart to the soft end with the Lee tester, guessing it's about 6.8 or so by the .086" indent.

Any ideas on this without doing multivariable calculus on it? My main problem is I have little experience testing hardness of high-tin alloys, so I don't know what numbers to expect. The density is correct for 80/20 Sn/Pb, and if the hardness of 9.8 matches, then that's close enough for me.

Thanks in advance for any input,

Gear

[sagacious]

My math shows that your SG of 7.95 indicates approx 78% Sn content.

[geargnasher]

Thanks, Sagacious, figured you'd be one of the few to weigh in. Thing is, 25% Pb/25%Sb/50%Sn has an SG of 8.1 g/mL (didn't do the math to make it exactly mimic 7.95) so that still doesn't help me much. I was hoping to narrow it down by the BHN, do you know if a hardness chart exists for Pb/Sn binarys in different proportions? Maybe solder companies?

Gear

[sagacious]

Gear,
Yeah, I was just chiming-in with a SG/composition math confirmation. You are of course correct about the SD alone not being diagnostic. The rub is that the BHN may be equally non-specific for that SG. Wouldn't hurt to know, tho.

I don't think I have any Sn/Pb binary solder BHN tables. I figured someone would by now have posted the results of a spreadsheet that calculated given-alloy BHN to an approximate value. Isn't there a proprietary spreadsheet available for this?

[geargnasher]

Beats me. The one at CBA that everyone loves to hate has been put up and taken down a few times. Seems that nobody agrees on the BHN of pure tin, depends way to much on how it was cast/formed etc.

I was hoping that with the SG and the bhn together I could eliminate some variables, or at least what the percentages couldn't be. I think if it has any antimony in it it isn't much. For my purposes I think I'll just call it 80/20 and use it as such. My boolit alloying isn't rocket science, I use a postage scale and alloy in large batches so it isn't really that precise anyway. I don't think it has much more than trace of anything else in it, either, maybe some copper or aluminum and sundry such that doesn't concern me.

Your metallurgical expertise is, as always, much appreciated.

BTW, Mrs Geargnasher wants to know if the citric acid solution we use for cleaning brass is safe for solid sterling silver or silver plated untensils?

Gear

[sagacious]

You are welcome. I found something on solder that may be helpful. Sn80/Pb20 solder, melt point 388.4*F, BHN 15.2. That BHN sounds about right, and compares reasonably with the BHN of your known 63/37 ingots. So, it may be that what you have is not quite 78% Sn, and a closer estimate might require stricter testing. Like you, I'd probably call it 80/20 or 75/25 and be OK with that.

Re: Mrs Geargnasher's question: I tested citric acid on silverplate and a bunch of other metals, and posted the results a few months back. I found that a room-temp citric solution showed no effect on tarnished silverplate after 10 minutes soak time However, if you add some tablesalt to a warm/hot citric solution, it will remove silver tarnish. Here's a link if you're interested:
http://castboolits.gunloads.com/showthread.php?t=83978

Both citric and citric+salt are safe to use on eating utensils. Just rinse with fresh water, and you're set to go. Hope this helps, good luck.

[geargnasher]

Thanks again!

As far as "safe" with the silver I meant would the acid eat the surface off or something. Sorry I missed the thread, but I gots it now!

I got the approximate melting point from a phase chart in the Lyman CBM#3, figured it at 375* but your numbers are much closer. I'll check melt point when I resmelt this to clean it. That BHN sounds awful hard to me, but properties of alloys can be very strange sometimes.

Gear

[sagacious]

Yes, that BHN seemed unexpected at first, but doesn't look too crazy. The industry-reported BHN of Sn/Pb solders is not set in stone, and BHN numbers vary by several whole digits due to differences in testing method, actual alloy content (vs nominal alloy content), and alloy processing, etc. It is for this reason that BHN may be non-specific for a given SG. Keep us posted.

[geargnasher]

I just can't leave it alone. Remelted the stuff tonight to clean and flux it some more, checked temps: It begins to turn slushy at 365*, and stays slushy and thick until 380* where it can be stirred but is still very thick and grainy, still grainy until about 410 where it starts getting smooth, and about 425* it pours like 700* WW metal. Same in reverse, it gets very "crystally" as it's trying to freeze, at about 360* I dug a screwdriver into it and it acted just like compacted wed sand, tearing up grainy chunks. By the Pb/Sn chart I have, that puts it somewhere between 80-85% Sn if my judgement and thermometer are anywhere close to accurate. The slush point of Pb/Sn goes from the eutectic phase change temperature of 361* all the way up to the melt point of Sn at 449* with concentrations ranging from 62% to 100% Sn. My slush point lasted until about 425*, or around 85%, so that makes me think the percentage is a little higher than I thought before.

I'll average the temperature data, the SG data, and my seat-of-the-pants opinion just from working with and observing the behaviour and appearance of the metal and stick with 80% Sn. I think this is pretty much a binary, doesn't act like there is any antimony or much of anything else except trace.

Gear

[sagacious]

With that wide pasty range, it does sound like Sn/Pb binary. High-Sn/Pb binary alloys also do give those 'ladle-tails'.