Generally, it can be divided into five categories according to its metallographic structure:
1. Austen stainless steel
The 304 stainless steel commonly seen is of this type. Its standard composition is 18% chromium plus 8% nickel, commonly known as 18-8 stainless steel. This type of stainless steel is non-magnetic, can not change its metallographic structure by heat treatment, and has good workability. Because it contains the alloy element nickel, its corrosion resistance is superior to the other two types of stainless steel containing only chromium (without nickel). 300 series stainless steel is mainly used for general people's livelihood, such as kitchen tableware, building materials, medical and health equipment, food processing materials, transportation tools, chemical equipment and pipe fittings, mechanical equipment and parts. In the eyes of ordinary people, the so-called stainless steel refers to 300 series stainless steel (especially 304 stainless steel).
2. Matian loose stainless steel
The representative steel type of this type of stainless steel is 410, and its chemical composition contains 13% chromium, less than 0.15% carbon and a small amount of other element alloys. The raw materials are cheap, magnetic, and can be hardened by heat treatment to increase strength. However, because it does not contain nickel, its corrosion resistance is inferior to that of ordinary 304 stainless steel, so it can only be used in mildly corrosive environments. General uses include bearings, medical appliances and knives.
3. Fertilizer stainless steel
The representative steel type of this type of stainless steel is 430, its standard chemical composition is 16-18% chromium, and its carbon content is low. This kind of stainless steel has magnetism. If the stainless steel plates we see can be adsorbed by magnets, they may belong to this kind of stainless steel. The price is relatively low due to nickel free, and the typical uses include kitchen appliances, weaving nets and accessories.
4. Precipitation hardening stainless steel
AISI number is 600 series stainless steel. In addition to chromium and nickel, this type of stainless steel also contains precipitation hardening elements such as copper, aluminum and titanium, which harden the material and increase its strength. The typical uses of this type of stainless steel are: valves, motor shafts, petrochemical equipment, golf heads, etc.
5. Duplex stainless steel
Typical grades of this type of stainless steel are 2205, i.e. 22% chromium and 5% nickel. This type of steel is characterized by good strength (better than 304) and corrosion resistance, so it is commonly used in petrochemical pipelines, pressure vessels and mandrels. The chemical composition of 304 grade stainless steel is 0Cr18Ni9.