Ultra-high strength steel according to its degree of alloying and microstructure is divided into low-alloy medium carbon martensitic steel, medium alloy medium carbon secondary precipitation hardening type steel, high alloy medium carbon Ni-Co type steel, ultra-low carbon martensitic age-hardening type steel, semi-austenitic precipitation hardening stainless steel, etc.

Low-alloy medium carbon martensite-reinforced ultra-high strength steel (MART) is developed on the basis of low-alloy tempered steel, with total alloying elements generally not exceeding 6%.The main grades include the traditional 40CrNiMo, 45 CrNiMoV, 30CrMnSiNi2A, 43CrNiSiMoV developed on the basis of 4340 steel by adding silicon and vanadium, etc.

Typical grades of medium alloy medium carbon secondary precipitation hardening steel are H11 and H13, etc. It has high strength and toughness in high temperature tempered condition, good heat resistance, mostly used in aircraft landing gear, rocket shells, etc.

High alloy medium carbon steel is developed on the basis of 9% Ni low temperature steel, the main grades are HP-4-25,AF1410 and so on. These steels have good stress and corrosion resistance and are widely used in aerospace, aviation, submarines and other products.

In addition, there are TM210 17-7PH, PH15-7Mo, S32205, etc., which are also common ultra-high strength steels in the industry.