Carbon. Most of the microalloyed steels developed for forging have carbon contents ranging from 0.30 to 0.50%, which is high enough to form a large amount of pearlite. The pearlite is responsible for substantial strengthening. This level of carbon also decreases the solubility of the microalloying constituents in austenite.

Niobium, Vanadium, and Titanium. Formation of carbonitride precipitates is the other major strengthening mechanism of microalloyed forging steels. Vanadium, in amounts ranging from 0.05 to 0.2%, is the most common microalloying addition used in forging steels. Niobium and titanium enhance strength and toughness by providing control of austenite grain size. Often niobium is used in combination with vanadium to obtain the benefits of austenite grain size control (from niobium) and carbonitride precipitation (from vanadium).

Manganese is used in relatively large amounts (1.4 to 1.5%) in many microalloyed forging steels. It tends to reduce the cementite plate thickness while maintaining the interlamellar spacing of pearlite developed; thus high manganese levels require lower carbon contents to retain the large amounts of pearlite required for high hardness. Manganese also provides substantial solid solution strengthening, enhances the solubility of vanadium carbonitrides, and lowers the solvus temperature for these phases.

The silicon content of most commercial microalloyed forging steels is about 0.30%; some grades contain up to 0.70%. Higher silicon contents are associated with significantly higher toughness, apparently because of an increased amount of ferrite relative to that formed in ferrite-pearlite steels with lower silicon contents.

Sulfur. Many microalloyed forging steels, particularly those destined for use in automotive forgings in which machinability is critical, have relatively high sulfur contents. The higher sulfur contents contribute to their machinability, which is comparable to that of quenched-and-tempered steels.

Aluminum and Nitrogen. As in hardenable fine-grain steels, aluminum is important for austenite grain size control in microalloyed steels. The mechanism of aluminum grain size control is the formation of aluminum nitride particles. It has been shown that nitrogen is the major interstitial component of vanadium carbonitride. For this reason, moderate to high nitrogen contents are required in vanadium-containing microalloyed steels to promote effective precipitate strengthening.