A Study of the Action of Various Energizers in the Carburization of Steel

The object of casehardening is to produce articles of steel having a tough or ductile interior and a hard sur­face. Quenching produces a surface somewhat harder than the interior, but in order to obtain a high surface hard­ness, the percentage of alloying elements in the steel must be raised to such an extent that the core or central por­tion becomes hard and brittle also.

The Isothermal Transformation Curve for S.A.E. 6150

More than 3000 years ago, men began quenching and tem­pering tools to improve their physical properties. The an­cient people found that iron was easier to shape and form in a heated condition. Charcoal was used as the fuel, and when the shaping process was completed, the smiths cooled the piece in the most obvious way, quenching in water. Quite un­intentionally, these people stumbled on the process for im­proving the properties of iron, and the art of blacksmithing began.