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?