On Friday, July 22, 2016 at 12:48:09 PM UTC-4, wrote:

I

Complex alloys, including most grades of stainless, can produce oxide colors all over the map, so that is not a guide. As for the likely materials for those grates, that depends entirely on the oven's range of operating temperatures.

Melting temperatures of 302 SS, 310 SS, and Incoloy 800 are within 50 deg. C of each other. Stiffness and yield strength show some wider gaps, but they're still close enough that you won't find your answer just in physical properties.

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Ed Huntress

The selection of which stainless would not be on melting temperature. It would be on resisting corrosion at elevated temperatures.

Dan