So I Baked My Brass at 425 For a Bit...

RLinNH

Sergeant of the Hide
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Minuteman
Mar 23, 2019
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I like to dry my wet tumbled brass in the oven at 225 for 30 minutes, then let it cool in the oven overnight to to insure that it's dry. Long story short, I left the brass in the oven for a few days. Wife pre heated the oven to 425 for some nom nom nom onion rings, and lo and behold. When she went to place the onion rings into the oven, there sat my brass. The brass was in that environment for about 25 minutes. It now has a nice rainbow hue to it in the right light. What type of damage did I do to that brass?
It's no real loss as it's only range .223/5.56 brass. Only 100 pieces that I was part of a lot that I will be turning into .300 BO Brass. But I would like to know what damage I did to the brass? Why is it now a rainbow hue? Obviously due to the high heat at a prolonged time, but metallurgically speaking, what happened to the brass? Should I throw it away now as it may be unsafe to use?
 
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It’s not going to heat soak the brass before ambient temps kick the preheat off. It’s been discussed here before. Smash as many pieces as you need to be confident, but the brass is fine.
 
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It’s not going to heat soak the brass before ambient temps kick the preheat off. It’s been discussed here before. Smash as many pieces as you need to be confident, but the brass is fine.
The brass will exchange heat with the heating element through a process called radiation heat transfer. It will get hotter than the air temperature while the radiant heating element is on. The brass may be fine but your assumption is wrong.
 
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The brass will exchange heat with the heating element through a process called radiation heat transfer. It will get hotter than the air temperature while the radiant heating element is on. The brass may be fine but your assumption is wrong.
No, I’m not assuming wrong. Radiation heat transfer requires a clear path, which you won’t have with brass on a tray from the bottom element. Unless the broil setting is used, the upper element won’t matter much, as they are barely used or not at all in the preheat or baking setting. Even with a convection oven, given the fact that the brass has to be viewed in a certain light to see the rainbow hue, you can pretty much rule out annealed brass.

I get what you’re saying, I agree that it could be the case in different instances. In this particular case, that brass is fine.
 
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Thanks to all for the great information. I'll crush a few pieces to see how it holds up.
At 425 F for 25 mins, there's zero chance of the cases being annealed.
At low temps of around 220 C which is 425 F, 70-30 brass has been measured to increase slightly in hardness during lab testing of the annealing process.
As long as you're confident that the brass didn't get substantially hotter, don't worry about crushing any of them, tells you nothing as you probably couldn't feel any reliable difference with pliers anyhow.
Even at 525 F, 25 mins is too short a time frame.
Load it & go.