Manganese used in small quantities (.30% to 1.50%) will produce certain desired effects. Under these conditions it acts as a purifier. And when added in the form of Ferro Manganese to a heat of steel it unites with the oxygen and transforms it to slag as oxide of manganese. There is also good reason for believing that manganese prevents the coarse crystallization, which impurities such as Phosphorus and Sulphur would otherwise produce. Five per cent to 14% manganese renders the steel non-magnetic as well as a poor conductor of electricity.
SILICON.
The dividing line between silicon-treated steels and silicon-alloy steels is not clearly defined, but the latter are used for several important purposes.
Such steel has been used in springs of the leaf type for automobiles and other vehicles, the silicon being considered to add slightly to the toughness of the springs. However, the most important use of steels of this type is probably in the manufacture of electrical machinery. It is possible to produce a silicon-alloy steel which has not only a greater magnetic permeability than the purest iron, but also, a high electrical resistance. Its hysteresis is, of course, low, this property always accompanying a high permeability. It therefore is a very valuable material for use in electro-magnets, and in electric generating machinery, is the most efficient material known.
In silicon-treated steels, the silicon is used somewhat as a scavenger, although it also produces results somewhat similar to manganese.
PHOSPHORUS.
Phosphorus has little effect upon the hot properties, but in the cold state makes the steel brittle and is of course highly undesirable although some writers have claimed that it adds to the tensile strength in about the same degree as carbon.
SULPHUR.
Sulphur has just the opposite effect of Phosphorus, and makes the steel crack while it is being hot worked, although after the metal is cold it seems to have no particular effect upon the physical properties.