Alloy hardness vs. ambient temp.

[Slinger]

I've made up alloy and cast bullets out of it in a Cold workshop. By cold, I'm talking below freezing down to say 29 degrees. The bullets were air cooled in the workshop, cooling down quickly. Question is could that make the bullets harder than they should be at normal room temp., whatever that is? I made up a batch of alloy that should be 11 Bhn, but is reading more like 18 on the LBT tester. The weight of the bullets is correct for 11 Bhn.....420 grains. Wheelweights that were smelted back in the summer that should be around 11-12 Bhn are reading 15 or a bit more. Pure lead I melted down is still at 5 Bhn or below. Anyone else run into this or am I the only dummy to cast bullets in a cold workshop??!!?!? This is the first time I've experienced this as I cast in much warmer temps.

[sqlbullet]

Yes. They will be harder than if air-cooled at room temperature.

[Slinger]

Huh.......Guess I'll either have to turn on the heat in the shop or wait till late spring when it warms up.

[lwknight]

Cold or hot is a matter of perception.
Lead alloys that melt at 550 or more won't think that ambient of 29 vs 79 is a big difference.
Could you tell the difference between 600 degrees and 650 degrees by feel? Of course not. Its just plain hot.
A fan would make more difference than temperature alone in the ambient.
I would expect a slight difference in hardness on a cold day but would take a longer look at possible alloy differences or actual mold temp at the test cast.

That'sa just my thought and I can't prove any of it.

[runfiverun]

water dropping hardens boolits by making them cool off faster.
that's the whole magical secret...

[Slinger]

water dropping hardens boolits by making them cool off faster.
that's the whole magical secret...

So then, are you thinking that because they're cooling off so quickly in the cold air that they are becoming harder?????

[Dusty Bannister]

What is the actual alloy you are making up that "should be" the same as what you had before? Perhaps a better test would be to take your old alloy ingots and remelt and pour, and then the new alloy and remelt and pour and then follow the test proceedures specific to the LBT tester, and keep in mind that ingots and bullets might not measure the same hardness. Then measure again in a few weeks to see if there is any change. Maybe something happened to your tester. Any pure samples to verify the readings? Dusty

[Slinger]

I've got some Lino & pure lead. Both are reading at 22 & 5 or less on the LBT respectively. That's the first thing I thought (my LBT is out of calibration). But the tester is fine.

[runfiverun]

yeah that's what I'm saying.
it's called precipitation [not like rain] airc.

[Slinger]

yeah that's what I'm saying.
it's called precipitation [not like rain] airc.

That would make things a lot easier for me..........just introduce heat.