Stainless steel with austenitic structure at room temperature is nonmagnetic, with high toughness and plasticity, but its strength is low, which can only be strengthened by cold working and may lead to certain magnetism.
ferritic stainless steel
The matrix is ferritic stainless steel, which is magnetic and generally cannot be hardened by heat treatment, but cold working can improve its strength. Ferritic stainless steel has good corrosion resistance and oxidation resistance because of its high chromium content, but its mechanical properties and technological properties are poor
Martensite stainless steel
The matrix is martensitic stainless steel, which is magnetic, but its mechanical properties can be adjusted by heat treatment.
duplex stainless steel
(austenite-ferrite)
Stainless steel with both austenite and ferrite matrix is magnetic and can be strengthened by cold working. This kind of steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no brittleness at room temperature, and its intergranular corrosion resistance and weldability are significantly improved. At the same time, compared with austenitic stainless steel, it has high strength and obviously improved intergranular corrosion resistance and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel.
precipitation hardening stainless steel
stainless steel whose matrix is austenite or martensite and can be hardened by precipitation hardening treatment. Stainless steel with ultra-high strength is often used in nuclear power, aerospace and other industries.
Marking method of stainless steel
International chemical element symbols and domestic symbols are used to indicate chemical composition, and Arabic letters are used to indicate composition content. For example: 6Cr19Ni1 (China, Russia)
Use fixed digits to represent steel series or numbers.
For example, the American Iron and Steel Institute uses three digits to indicate various standard grades of malleable stainless steel. Among them:
Austenitic stainless steel is marked with numbers of 2 series and 3 series.
ferritic and martensitic stainless steels are represented by 4 series numbers.
heat-resistant chromium alloy steel, precipitation hardening stainless steel and high alloy with iron content less than 5% are named by patent names or trademarks, such as 5 series and 6 series.
the serial number is composed of Latin letters and sequences, which only indicates the purpose.
For example, China uses Chinese phonetic abbreviations to indicate its use, and the new brand standard of stainless steel of P- open hearth steel, F- boiling steel and T8- Te8
29 is interpreted
1) The previous old brand: the number before Cr indicates the content of several thousandths of carbon.
such as 21 (1Cr17Mn6Ni5N) and 44A (7Cr17), which respectively represent 1‰ and 7 ‰ of C content;
if C≤.8% is low carbon, the mark is "", such as 34 (cr18ni9);
if C≤.3% is ultra-low carbon, the mark is "", such as 316L (Cr17Ni14Mo2).
2) Now the new brand: the number before Cr indicates the content of C in several ten thousandths.
if 21 (12Cr17Mn6Ni5N), it means that the content of C is 12/1 (.12%);
if 34 (6Cr19Ni1), it means that the content of C is six ten thousandths (.6%);
if it is 316L (22Cr17Ni12Mo2), it means that the content of C is 2.2 ‰ (.22%).
description of special symbols (taking 34 as an example)
Japanese JIS standard: SUS 34
American ASME standard: SA24-34 or SA24TP34
American ASTM standard: A24-34 or A24TP34
* with "-"and "plus" in the middle.
h is suffix: it means high carbon content, and it is mainly used in high temperature occasions;
n is suffix: it means adding element N to improve the strength of steel, such as: 34N；;
ln is a suffix, which means that the carbon content is low and the element N is added, such as: 34LN；;
No.1 is suffix: indicating hot rolled surface;
2b is suffix: it means the steel plate with good surface after hot rolling and cold rolling, which meets the requirements of mirror surface;
2d is suffix: it means the steel plate with general surface after hot rolling and cold rolling;