Alloy structural steel (structural alloy steel), used for mechanical parts and a variety of engineering components and contains one or more of a certain amount of alloy elements in steel.

   Role:

There are three aspects: ① increase the hardenability of steel. Hardenability of steel is quenched, quenched to martensite from the surface layer from the depth, is to achieve good overall performance of the main parameters. In addition to Co, almost all alloying elements such as Mn, Mo, Cr, Ni, Si and C, N, B, etc. can improve the hardenability of steel, including Mn, Mo, Cr, B the strongest effect, followed by Ni , Si, Cu. The strong carbide forming elements such as V, Ti, Nb, etc., can only increase when dissolved in austenite hardenability of steel. ② affect the process of tempering steel. As the alloying elements in tempering steel can hinder the diffusion of atoms, which at the same temperature and the carbon steel compared to generally play a delay of martensite decomposition and the role of carbide grew up together, thereby enhancing the steel tempering stability, namely, to increase anti-temper softening steel, V, W, Ti, Cr, Mo, Si more significant role, Al, Mn, Ni is not obvious. Contains a high content of carbide forming elements such as V, W, Mo and other steel, tempering at 500 ~ 600 ℃, the precipitation of fine carbide particles dispersed as a special V4C3, Mo2C, W2C, etc., instead of part of the coarser alloy cementite, so that the strength of steel is no longer decreased but increased, that is a secondary hardening (see tempering). Mo on the temper brittleness of steel have to block or weaken the effect. ③ affect the strengthening and toughening steel. Ways to strengthen the Ni solid solution strengthening of ferrite; Mo, V, Nb and other carbide-forming elements, both in the solid solution strengthening dispersion hardening way Youyi way to improve the yield strength of steel; carbon reinforcement the most significant. In addition, adding these alloying elements, are generally austenite grain refinement, increased grain boundary strengthening effect. Factors that affect the toughness of the steel complex, Ni improve the toughness of the steel; Mn austenite grain coarsening easy to make, sensitive to the temper brittleness; lower P, S content, improve the purity of steel, to improve the toughness of steel is important role (see the strengthening of metal).