Question about heat treating lead/antimony/tin alloys

[John in WI]

I have a very nice casting alloy. I'm not sure of it's precise composition, but it was mixed from clip ons, with probably 10% antimony added, and 1% tin added to that mix. The antimony content should be right around 5%, with maybe 3% tin. (sorry for the rough guesses--this was my first every alloy, and I took 0 notes--just threw things into a pot...)

I was doing some reading on water dropping and oven treating and there is something I don't get about tin containing alloys.

Am I right that you CAN harden tin bearing alloys. The issue is that it just retards the RATE at which the boolit achieves maximum hardness?

Or is it that tin, in general, retards hardening?

Thanks for any clarifications. I'm not hoping to do any really critical heat treating. I have been using this alloy for casting buckshot (air cooled) and was curious about hardening some up and seeing what effect on the pattern it might have.

[cbrick]

Tin will harden the alloy but only a bit and yes, it can inhibit HT in a high percentage. High tin alloys will age soften more quickly. It is antimony that enables hardening by heat treating or quenching. Look at a trace of arsenic (WW) as a great catalyst to the antimony in HTing.

If you added antimony at 10% by weight how did you end up with 5% antimony? If you have a 10% antimony alloy, that's really high and could be brittle. If you added 1% tin and your only other source of tin was the WW you have about 1.5% tin, possibly up to 2%.

Rick

[John in WI]

Ah--my mistake Rick--what I meant to say was 10% linotype, not 10% antimony. All I meant was that I basically hopped up WW with some lino and a bit of solder.