Classification of Stainless Steel
Stainless steel can be divided into austenitic stainless steel, ferritic stainless steel, martensitic stainless steel and duplex stainless steel according to its metallographic structure.
(1) Austenitic stainless steel
The room temperature structure of austenitic stainless steel is austenite, which is formed by adding appropriate nickel to high chromium stainless steel.
Austenitic stainless steel has stable austenite structure only when Cr contains about 18%, Ni 8% to 25%, and C about 0.1%. Austenitic stainless steel is based on Cr18Ni9 iron-based alloy. With different uses, six series of austenitic stainless steels have been developed.
Common grades of austenitic stainless steel: (1) 1Cr17Mn6Ni15N; (2) 1Cr18Mn8Ni5N; (3) 1Cr18Ni9; (4) 1Cr18Ni9Si3; (5) 06Cr19Ni10; (6) 00Cr19Ni10; (7) 0Cr19Ni9N; (8) 0Cr19Ni10NbN; (9) 00Cr18Ni10N; (10) 1Cr18Ni12; (11) 0Cr23Ni13; (12) 0Cr25Ni20; (13) 0Cr17Ni12Mo2; (14) 00Cr17Ni14Mo2; (15) 0Cr17Ni12Mo2N; (16) 00Cr17Ni13Mo2N; (17) 1Cr18Ni12Mo2Ti; (18) 0Cr; 1Cr18Ni12Mo3Ti; (20) 0Cr18Ni12Mo3Ti; (21) 0Cr18Ni12Mo2Cu2; (22) 00Cr18Ni14Mo2Cu2; (23) 0Cr19Ni13Mo3; (24) 00Cr19Ni13Mo3; (25) 0Cr18Ni16Mo5; (26) 1Cr18Ni9Ti; (27) (29) 0Cr18Ni; 0Cr18Ni13Si4;
Austenitic stainless steel contains a large amount of Ni and Cr, making the steel austenite at room temperature. It has good plasticity, toughness, weldability, corrosion resistance and non-magnetic or weak magnetic properties. It has good corrosion resistance in oxidizing and reducing media. It is used to make acid-resistant equipment, such as corrosion-resistant containers and equipment lining and transportation. Pipes, nitric acid-resistant equipment parts, etc., can also be used as the main material of ornaments. Austenitic stainless steel generally adopts solution treatment, that is, the steel is heated to 1050 to 1150°C, and then water-cooled or air-cooled to obtain a single-phase austenite structure.
(2) ferritic stainless steel
Commonly used grades of ferritic stainless steel: (1) 1Cr17; (2) 00Cr30Mo2; (3) 00Cr17; (4) 00Cr17; (5) 1Cr17Mo; (6) 00Cr27Mo;
Ferritic stainless steel is stainless steel whose structure is mainly ferrite at room temperature. Chromium content is 11%-30%, its corrosion resistance, toughness and weldability increase with the increase of chromium content, chloride stress corrosion resistance is better than other types of stainless steel, this type of steel generally does not contain nickel, sometimes It also contains a small amount of Mo, Ti, Nb and other elements. This type of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance, and excellent stress corrosion resistance. It is mostly used to produce atmospheric resistance, water vapor, water and oxidizing acids. Corroded parts. However, the mechanical properties and process performance are poor, and they are mostly used in acid-resistant structures with little stress and as anti-oxidation steels. It can also produce parts that work at high temperatures, such as gas turbine parts.