China's steel number representation method
I. overview of China's steel number representation method
the steel number for short is the name taken for each specific steel product, and it is a common language for people to understand steel. According to the national standard "steel product grade representation method" (GB), the steel grade representation method in China adopts a combination of Chinese phonetic alphabet, chemical element symbols and Arabic numerals. Namely:
① chemical elements in steel grades are represented by international chemical symbols, such as Si, Mn, Cr. Mixed rare earth elements are represented by "re" (or "XT")
② the product name, purpose, smelting and pouring methods are generally represented by the abbreviations of Chinese Pinyin, as shown in the table
③ the content (%) of main chemical elements in steel is expressed in Arabic numerals7.3 batch
II. Classification description of steel grade representation in China
1. Carbon structural steel
① consists of Q + number + quality grade symbol + deoxidation method symbol. Its steel grade is preceded by "Q", which represents the yield point of steel. The following numbers represent the yield point value, and the unit is MPa. For example, Q235 represents the yield point（ σ s) 235 MPa carbon structural steel
② if necessary, symbols indicating quality grade and deoxidation method can be marked after the steel number. The quality grade symbols are a, B, C and D respectively. Deoxidation method symbol: F refers to rimmed steel; B represents semi killed steel: Z represents killed steel; TZ refers to special killed steel, and killed steel can be unmarked, that is, both Z and TZ can be unmarked. For example, q235-af represents class a rimmed steel
③ carbon steel for special purposes, such as bridge steel, marine steel, etc., basically adopts the representation of carbon structural steel, but the letter indicating the purpose is added at the end of the steel number
2. High quality carbon structural steel
① the two digits at the beginning of the steel number represent the carbon content of the steel, which is expressed by a few tenths of the average carbon content. For example, for steel with an average carbon content of 0.45%, the steel number is "45", which is not a sequence number, so it cannot be read as 45 steel
② high quality carbon structural steel with high manganese content should be marked with manganese, such as 50Mn
③ rimming steel, semi killed steel and high-quality carbon structural steel for special purposes should be specially marked at the end of the steel grade, such as semi killed steel with an average carbon content of 0.1%, whose steel grade is 10B
3. carbon tool steel
① the steel grade is prefixed with "t" to avoid mixing with other steels
② the number in the steel grade indicates the carbon content, which is expressed as a few thousandths of the average carbon content. For example, "T8" means the average carbon content is 0.8%
③ for those with high manganese content, mark "Mn" at the end of the steel grade, such as "t8mn"
④ the phosphorus and sulfur content of high-quality carbon tool steel is lower than that of general high-quality carbon tool steel. The letter "a" is added at the end of the steel grade to show the difference, such as "t8mna"
4. Free cutting steel
① the steel grade is prefixed with "Y" to distinguish it from high-quality carbon structural steel
② after the letter "Y", it increased by 7.6% year-on-year; The figure of realizing tax revenue of 600million yuan indicates the carbon content, which is expressed by a few tenths of the average carbon content. For example, the steel grade of free cutting steel with an average carbon content of 0.3% is "Y30"
③ those with higher manganese content are also marked with "Mn" after the steel grade, such as "y40mn"
5. Alloy structural steel
① the two digits at the beginning of the steel grade indicate the carbon content of the steel, which is expressed as a few tenths of the average carbon content, such as 40Cr
② the main alloying elements in steel, except for some micro alloying elements, are generally expressed in percentage. When the average alloy content is less than 1.5%, generally only the element symbol is marked in the steel grade, but the content is not marked. However, in special cases, if it is easy to be confused, the number "1" can also be marked after the element symbol, such as the steel grades "12CrMoV" and "12Cr1MoV", the chromium content of the former is 0 6%, the latter is 0 2%, and the other components are all the same. When the average content of alloy elements is ≥ 1.5%, ≥ 2.5%, ≥ 3.5%... The content shall be marked after the element symbol, which can be expressed as 2, 3, 4. For example, 18Cr2Ni4WA
③ vanadium V, titanium Ti, aluminum Al, boron B, rare earth RE and other alloy elements in steel are all microalloyed elements. Although the content is very low, they should still be marked in the steel grade. For example, 20mnvb steel. Vanadium is 0 12%, boron 0 005%。
④ high quality steel should add "a" at the end of the steel grade to distinguish it from general high quality steel
⑤ for special purpose alloy structural steel, the steel grade is prefixed with (or suffix) a symbol representing the purpose of the steel. For example, the steel grade of 30CrMnSi steel for riveting is ml30crmnsi
6. The expression method of steel grade of low alloy high strength steel
① is basically the same as that of alloy structural steel
② for professional low-alloy high-strength steel, it should be indicated at the end of the steel grade. For example, 16Mn steel, the special steel for bridges is "16Mnq", the special steel for automobile girders is "16MnL", and the special steel for pressure vessels is "16MnR"
7. spring steel
spring steel can be divided into carbon spring steel and alloy spring steel according to chemical composition. The former is basically the same as high-quality carbon structural steel, and the latter is basically the same as alloy structural steel
8. rolling bearing steel
① the steel number is preceded by the letter "g", indicating the rolling bearing steel
② the carbon content of high carbon chromium bearing steel is not marked, and the chromium content is expressed in thousands, such as GCr15. The steel grade representation method of carburized bearing steel is basically the same as that of alloy structural steel
9. alloy tool steel and high-speed tool steel
① when the average carbon content of alloy tool steel grade is ≥ 1.0%, the carbon content is not marked; When the average carbon content is less than 1.0%, it is expressed in thousands. For example, Cr12, CrWMn, 9SiCr, 3Cr2W8V
② the expression method of alloy element content in steel is basically the same as that of alloy structural steel. However, for alloy tool steel grades with low chromium content, the chromium content is expressed in thousandths, and "0" is added before the number indicating the content, so as to distinguish it from the general element content expressed in percentages. For example, cr06
③ the steel grade of high-speed tool steel generally does not indicate the carbon content, but only the percentage of the average content of various alloy elements. For example, the steel grade of tungsten high-speed steel is "W18Cr4V". The steel grade with the letter "C" indicates that its carbon content is higher than that of the general steel grade without the letter "C"
10. stainless steel and heat-resistant steel
① the carbon content in the steel grade is expressed in thousands. For example, the average carbon content of "2Cr13" steel is 0.2%; If the carbon content in steel is ≤ 0.03% or ≤ 0.08%, the steel grade is prefixed with "00" and "0" respectively, such as 00Cr17Ni14Mo2, 0cr18 Ni9, etc
② the main alloy elements in the steel are expressed in percentage, while titanium, 5. Check whether the performance of the whole machine is normal. Niobium, zirconium, nitrogen... Etc. are marked according to the above expression method of alloy structural steel for microalloyed elements
11. Electrode steel
its steel grade is preceded by the letter "H" to distinguish it from other steels. For example, stainless steel welding wire is "H2Cr13", which can be different from stainless steel "2Cr13"
12. Silicon steel for electrical purposes
① the steel grade is composed of letters and numbers. The letter DR in the head of the steel grade indicates hot-rolled silicon steel for electrical purposes, DW indicates cold-rolled non oriented silicon steel for electrical purposes, and DQ indicates cold-rolled oriented silicon steel for electrical purposes
② the number after the letter represents 100 times the iron loss value (w/kg)
③ if the letter "g" is added at the end of the steel grade, it indicates that it is inspected at high frequency; If "g" is not added, it means that it is tested under the frequency of 50 cycles. For example, the steel grade dw470 indicates that the maximum iron loss per unit weight of cold-rolled non oriented silicon steel products for electrical purposes is 4.7w at the frequency of 50 Hz, which has the elegant visual effect of piano black/kg
13. pure iron for electrical purposes
① its brand is composed of letters "DT" and numbers, "DT" represents pure iron for electrical purposes, and numbers represent the sequence numbers of different brands, such as DT3
② the letter added after the number indicates electromagnetic performance: a - advanced, e - super, C - super, such as dt8a