query: At what temperature does steel melt?
passage: Red-short carbon steel
Iron or steel, when heated to above 900 °F (460 °C), glows with a red color. The color of any heated object changes predictably (due to black body radiation) from dull red through orange and yellow to white, and can be a useful indicator of its temperature. Good quality iron or steel at and above this temperature becomes increasingly malleable and plastic. Iron or steel having too much sulfur, on the other hand, becomes crumbly and brittle. This is due to the sulfur forming iron sulfide/iron mixtures in the grain boundaries of the metal which have a lower melting point than the steel.[1]
passage: Autoclave (industrial)
The pressure vessel specification will include both the highest and the lowest temperatures to which the vessel shell is exposed. Since steel properties change as the metal becomes colder, the vessel will be stamped for an MDMT of -20 °F unless the user requires lower. Customarily, the metal thickness is driven by the code requirements relating to visual inspection. Thinner metal can be used, providing the welds are radiographed. This saves cost when the metal is not SA516 but stainless steel or a refractory alloy.