Temp to alloy superhard questions

[Jaybeez]

Hi everyone, I have just a few questions about adding superhard to my alloy.

Rotometals says I need about 745 degrees to alloy it to my lead. I didnt realize that and was running my pot at 700 degrees, just trying to get things setup for casting later this week.. When it cooled it looks like the SH floated to the top.

I used the excel calculator here, and was adding about a half pound of SH to some lead/tin in hopes to get a 12bhn.

Will it mix back in at 750, or did I ruin this little batch?

And finally, once its been melted and mixed in, do I have to keep my melt at 750, or can I back off to a more reasonable 700?

Thanks in advance.

[popper]

I cast @ 725 (PID), never had a problem with SH nuggets, goes right in. If it need hotter, let pot cool some before casting. Let it soak for a while, stir often. 700 is probably too low for bottom pour anyway, spot cools too fast.

[kevin c]

I don't monitor temp when adding SuperHard to make casting alloy, but given that other the metals I use have melting temps up to that of pure lead, and that I use a high BTU burner, it's probably around 800°. I'm also sure that any unmelted lumps in your pot will blend into the mix on remelting, once it all liquifies.

Like popper, I run my PID controlled bottom pours at 720° to 730°, with the higher temps used in cool or breezy conditions (outdoors caster here).

[Conditor22]

I've found that the harder the common boolit casting alloy, the lower the melting temp.

I also do most of my casting between 700 -720 with a PID controlled pot

[Lloyd Smale]

if its already alloyed with lead it should mix in at the temp it melts. Only trouble ive seen is getting unalloyed antimony to mix in. If it had to be at a set temp to alloy then why does something like linotype that is rich in antimony melt and mix in at a lower temp then pure lead takes. now that said ive never fooled with superhard. If its is just antimony then i could see it. But i have mixed pure antimony in with lead to make an alloy and after that it took no different procedure to add to another batch of lead to make a different alloy.

[cwlongshot]

When mixing if too cold you will see that "cottage cheese" looking metallic mixture on top.

Just "cook it longer" allowing temp to come up so things can mix properly. DONT SKIM IT OFF!!

I do this REGULARLY!! I have a good supply of soft but need hard. So as a final back stop if I dont have lino or Mono I keep a doz bars of SH in reserve. It mixes just fin just needs higher temp.

CW