Definition of stainless steel
Stainless steel is a kind of high alloy steel which can resist corrosion in air or chemical corrosion medium. Stainless steel has beautiful surface and good corrosion resistance. It does not need surface treatment such as color plating
Stainless steel inherent surface properties, used in a variety of steel, commonly known as stainless steel. The representative properties are 13 chromium steel, 18 chromium nickel steel and other high alloy steel.
From the metallographic point of view, because the stainless steel contains chromium, a very thin chromium film is formed on the surface, which is separated from the oxygen invading into the steel and plays a role of corrosion resistance.
In order to maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 12% chromium.
Stainless steel type:
Stainless steel can be classified by use, chemical composition and metallographic structure.
The austenitic system steel is composed of 18% cr-8% Ni, and the addition amount of each element is different.
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Classified by chemical composition:
① CR series: ferrite series, martensite series
② Cr-Ni series: austenite series, abnormal series, precipitation hardening series.
According to the classification of metallographic structure:
① Austenitic stainless steel
② Ferritic stainless steel
③ Martensitic stainless steel
④ Duplex stainless steel
Identification method of stainless steel
Number and indication of steel
① The chemical composition is represented by international chemical element symbols and national symbols, and the content is represented by Arabic letters
For example, China and Russia 12CrNi3A
② Steel series or numbers are represented by fixed digit numbers, such as the United States, Japan, 300 series, 400 series and 200 series;
③ The serial number is composed of Latin letters and sequence, which only indicates the purpose.
Numbering rules in China
① Using element symbols
② Application, Chinese Pinyin, open hearth steel: P, rimming steel: F, killed steel: B, class a steel: A, T8: special 8
Composite steel, spring steel, such as: 20CrMnTi 60simn, (expressed in tens of thousands of C content)
Stainless steel, alloy tool steel (expressed in thousandth of C content), such as: 1cr18ni9ppm (i.e
0.1% C), stainless C ≤ 0.08% such as 0Cr18Ni9, ultra-low carbon C ≤ 0.03% such as 0cr17ni13mo
International stainless steel marking method
AIS uses three digits to indicate various standard grades of malleable stainless steel. Among them:
① Austenitic stainless steel is marked with 200 and 300 series numbers,
② Ferritic and martensitic stainless steels are represented by 400 series numbers. For example, some of the more common austenitic stainless steelsThis paper is provided by mechanical knowledge network, please pay attention to the content provided by mechanical knowledge network
They are marked with 201, 304, 316 and 310,
③ Ferritic stainless steel is marked with 430 and 446, while martensitic stainless steel is marked with 410, 420 and 440C