Tin and temperature

[melloairman]

I have been told that if you get your lead to hot you can singe your tin and throw the bhn off .
1 Is this true ?
2 If so at what temperature does this take place ?
3 And does it make the bhn higher or lower .? Marvin

[sqlbullet]

Tin will not singe, or scorch. However, the higher the temperature the faster your alloy will oxidize. Tin likes to oxidize, and so it dissapears from your alloy faster than the lead, depleting the tin. This will lower the BHN. It occurs at any temperature, but occurs faster the hotter the melt. Keep your temp as low as you can and still get good fill out.

[lwknight]

1. Maybe but not likely or easily done.
2. over 2000 degrees
3. Only a little bit.

[melloairman]

Thats what I thought but I wanted some other opinions .Thanks to both of you Marvin

[cbrick]

Lead oxidizes when in contact with air or impurities and antimony oxidizes even more rapidly, the Sn in your melt helps inhibit this oxidation in melts up to about 750 degrees. With higher temps than this tin itself oxidizes much more rapidly and looses much of it's ability to inhibit Sb and Pb oxidation. It's not only the surface of the top of the melt in your pot that's in contact with air but also the stream of alloy from a bottom pour pot or even from a ladle that Sb will also oxidize, the hotter the alloy the faster the oxidation. This stream of alloy into your mold is where tin will play it's most effective roll under 750 degrees in reducing the oxidation (surface tension) of antimony (Sb) or lead (Pb).

Rick