(1) steel for construction and Engineering: plain carbon structural steel A.; B. low alloy structural steel; C. steel. (2) structure steel A. mechanical manufacturing steel: (a) quenched and tempered steel; (b) surface hardening of steel structure: including carburizing steel, infiltration of surface quenching ammonia steel, steel; (c) free-cutting steel; (d) cold forming steel: including cold stamping, cold heading steel steel. B. spring steel bearing steel C. (3): A. tool steel carbon tool steel; B. alloy tool steel; high-speed tool steel c.. (4) special steel performance: A. stainless steel heat resistant steel B. including antioxidant steel, heat resistant steel, valve steel C. electrothermal alloy steel; D. steel; e. steel for low temperature service; F. electrical steel (5) professional steel -- such as bridge steel, ship steel, boiler steel, pressure vessel steel, machinery steel.