The principle of heat treating is fairly straight forward, heat treating takes place when steel is rolled at a certain temperature and then cooled after at a specific rate, the cooling rate is what makes up the particular microstructures within the metal. The most common and simplest of heat-treating methods is that of normalizing, this principle consists of holding the steel product at the temperature between 20 and 40 degrees Celsius and then cooling it afterward in completely still air. This then transform the as-rolled or as-cast steel to contain the austenite microstructures, which dissolves carbides. Thus, during cooling a very uniform grain is formed, consisting of either pearlite and ferrite or pearlite and cementite, depending on carbon content. In all heat treatment of metals, the temperatures, holding times, and heating and cooling rates depends vastly on the chemical composition, size, and shape of the steel. In alloy steels, which possess a lower heat conductivity than carbon steels, they are then heated more slowly to avoid internal stressing. Electric arc furnace billets are used through a heating process using electricity to avoid creating potential stress fractures in the metal.