The alloying constituents are generally divided unto carbide, austenite and ferrite forming elements. Furthermore, the purpose for which they are added to steel must be taken into consideration. According to its content, each alloying element imparts specific properties to steel. When several elements are present the effect may be increased, a fact which is fully utilized in modern alloying technology. There are, however, alloy compositions for which the individual elements do not exert their influence regarding a certain properties in the same direction, but rather counteract one another.

The presence of alloying elements merely creates a prerequisite for desired properties, but it is the processing and heat treatment operations which permit us to achieve them. The principal effects of alloying constituents and trace elements upon steels will be outlined below.