Strange smelting session

[whisler]

Friday, I decided to clean up some odds and ends of lead that I had, part bucket of wheel weights, some lead pipe and roofing lead, some purchased scrap lead,etc.

Everything went fine except for the wheel weights. I thought that this bucket had been separated so I just dumped the bucket in the plumbers furnace and fired it up. When I checked it again part way through the melt I saw that the melted part had gone way high in temperature & I noticed some stick-ons and a steel weight that wouldn't have been there if they were sorted. I thought " boy I hope there are no zincers in there but what is the chance of that". Poured the ingots and they all looked galvanized. Nuts!!!

Today I thought I would check the ingots by melting a small batch at 600 deg. and see if I see oatmeal.The strange part is that the ingots melted at 500 deg. (by my Lyman thermometer) with no oatmeal at all. The thing I find most strange is the melt point of the ingots. Isn't 500 deg. low for wheel weights?

Any ideas?

[zxcvbob]

500 sounds low, but I wouldn't worry about that. The "galvanized" look on the ingots is normal for lead alloys. So is a sparkly finish. I bet they don't tarnish much either. Pure lead ingots have a smooth finish that eventually turns blue-gray.

[runfiverun]

linotype melts at 515-550 ish.
so the lower melt temp indicates tin to me.
ww's have a lower melt temp than pure [630] lead [in the 600- 615 range]

[I'll Make Mine]

I'll agree, 500º F seems low for wheel weights (I'd have expected close to 600º), but it's clearly too low for zinc to be present. Maybe you got something in there that added enough tin to lower the melting point? Got any way to check the hardness of the ingots after re-pouring the melt?

[ipijohn]

I might think of thermometer calibration? Or check with another measuring device.

[whisler]

Checked the thermometer with boiling water (best I could do) and it checks 20-25 deg. low at that temperature, but since that is the low end I expected it to be off some. I do have some pure lead that I can use to check it against with a ball bearing (also best I can do). At least it doesn't seem to have zinc in it. Sure can't figure where tin would come from with just wheel weights.
At least I dodged the zinc boolit (pun intended).

[warf73]

My money is on very high tin content in the mix.

[I'll Make Mine]

Wheel weights are the "pot metal" of the lead world -- there's no reason for the manufacturer to be concerned about the alloy, other than cost. They need some antimony to harden the lead, but beyond that they'll use whatever they have in the pot; if the maker bought a load of scrap that had a bunch of linotype or bar solder in it, there might well be enough tin to lower the melting point to what you're seeing.