The Catagories of steel series can be divided as bellows:
1) Austenitic: Chromium nickel alloy, heat treated and not hardenable. The representative types are 303, 304, and 316.
2) Ferrite: Pure chromium, non hardening after heat treatment. The representative types are 405 and 430.
3) Martensite: Pure chromium, which can be hardened through heat treatment. The representative types are 410, 420, 431, and 440C.
4) Precipitation hardening
• The martensitic chromium type can be hardened by heat treatment and is only produced from bars and wires, except for Type 410. They harden by heating to a critical temperature or above the transition temperature, and then rapidly cool in oil or air. By selecting the correct grade and conducting analysis, various "quenching hardness" can be obtained, mainly depending on the carbon and chromium content. These grades can achieve maximum corrosion resistance in a hardened state. They can be annealed to achieve optimal cold working and processing characteristics. All martensite types are. Always magnetic.
• Ferritic chromium type cannot be hardened by heat treatment. Moreover, they cannot harden to any significant extent through high-temperature quenching. They are usually used in an annealed or softened state. They are referred to as "pure" chromium grades and do not contain nickel, but are sufficient to meet many applications.
• Austenitic chromium nickel steel has the highest corrosion resistance among all stainless steels, as well as excellent mechanical properties. They cannot be hardened through heat treatment, but they can generate significant tensile strength and hardness through cold working. Although these alloys are usually non magnetic, they become slightly magnetic during cold working. They are widely used in strip and plate, as well as bar and wire products, regardless of whether alloy elements are added. In the annealed state, the tensile strength of austenitic steel ranges from 75000 to 100000 psi, significantly higher than that of low-carbon steel. Brands with a high chromium nickel ratio (such as Type 301) can achieve extremely high tensile strength through cold work hardening while still maintaining good ductility.
• The precipitation hardening group contains the martensitic or austenitic steel used, but they
By utilizing precipitation hardening reaction instead of phase transformation used in heat treated steel, the strength during the heat treatment process is improved. At present, these types do not have AISI model numbers, as each type is a proprietary product of Armco Steel Corporation and holds patents.