Alloy Steels

Abstract

Carbon steels, as made commercially, always contain certain amounts of other elements which are present in the ore and complete removal of which would be extremely difficult and expensive. Sulphur and phosphorus, when more than 0.05% of either is present, tend to make steel brittle, so that during steel making the amounts present are reduced at least to this value. Silicon has little effect on strength and ductility if less than 0.2% is present. As the content is raised to 0.4%, the strength is increased without impairing the ductility, but above 0.4% it causes a decrease in ductility. Silicon is frequently used as a deoxidizer in steel making, and the fraction that does not form silicon dioxide, which passes into the slag, will remain in solution in the steel. The quantity of silicon used has to be controlled so that, except in special cases, there is not more than a total of 0.4% left in the steel finally.