At room temperature, the carbon atoms inside a piece of steel are trapped inside a crystal structure called . But when we heat the steel past about 730°C (1346°F)—a critical point known as the eutectoid temperature—a revolution occurs.
To produce a uniform, fine-grained structure. How it works: Similar to annealing, but after soaking, the metal is cooled in still air . Result: Stronger and harder than annealed steel, but not brittle. Application: Structural steel beams, railroad car frames. heat treatment of metals by vijendra singhpdf