If you're not afraid of using chemicals, you might try a product called "Sokoff." I buy it through "Home Improvements" catalog. I use it specifically for cleaning the glass on the inside of the oven door, but it claims that it will not harm any metal. It is specifically made to remove baked on carbon and grease. Brush on a thin coat and leave as long as possible - of course, read the instructions carefully!
Question: Is your oven self-cleaning? If not, you should get excellent results from the original Easy Off - you know, the really caustic formula. (Assuming it's still being made) That stuff always made my crusty oven look like new! But you cannot use it on a self-cleaning oven.