Too hot?
 

I cleaned my chain today and put it in the oven to dry it @ <200 degrees F and shut the oven off. A while later I went to retrieve the chain and found the oven ON @ 450 F! My son had put something in, saw the chain on the tin foil and put the stuff he was cooking on top of it.....don't ask. Anyway I'm wondering if the temper of the steel has been affected?

Yes, 450 F is enough heat to draw the temper of the steel. I know this from my own experience. Not with a chain, but rather from heat treating steel for tool/knife making purposes.

You may not have a problem -

The main wear factor for chains is not the strength of the steel but how long the brass bushings, between the pins and the rollers, will last "chain stretch" is really caused by bushing wear!!!

Ride good bushings
pat

You aren't serious are you?:rolleyes:

Gee, Pat-you buy brass chains? No wonder they keep wearing out!!!
FWIW, I doubt anybody has used brass bushings since maybe the victorian era in the way you describe. Brass is very soft and wears quickly. Yes, chain stretch is caused by bearing wear, but I can assure you that those bearings are steel, either annodized or hardened (in any chain worth buying, that is..) not brass. They may be even harder materials. You may find a brass or similar material used in a washer next to a roller, but not on a heavily stressed bearing surface like that.
As far as the chain in question is concerned, yes, it probably became re-tempered. How this has affected the metallurgy depends on the amount of time it was held at what temperature, and how quickly it cooled. Was the chain annodized? If so, then it probably didn't depend on anything like surface hardening for wear reduction. It might be compromised, then again, it might not. Best bet is to get yourself a new chain, and keep this one as a spare, or put it on a beater bike. I'd bet that there's a 50/50 chance it's fine, but odds like that are still hardly encouraging.

:D :D :D :D reminds me of the story of the guy who washed his stinky cycling shoes in the dishwasher & didnt think to delete the drying cycle & the soles melted all thru the plate racks, hard one to explain to the wife !!:beer: