Red-short carbon steel

Red-short, hot-short refers to brittleness of steels at red-hot temperatures. It is often caused by high sulfur levels, in which case it is also known as sulfur embrittlement.

Iron or steel, when heated to above 460 °C (900 °F), glows with a red color. The color of heated iron 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. Red-short iron or steel, on the other hand, becomes crumbly and brittle.