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Naming rules of seven common steels
Steel is a general term for iron carbon alloy with carbon content between 0.02% and 2.11%. In actual production, steel often contains different alloy elements according to different uses, such as manganese, nickel, vanadium and so on. Nowadays, steel has become one of the most used materials in the world because of its low price and reliable performance. Do you know the naming rules of steel? Today, we will introduce that the classification of steel products in China is based on the classification of steel products
Carbon structural steel
Expression method: Q + number + (quality grade symbol) + (deoxidation method symbol) + (special purpose symbol)
① The steel grade with “Q” represents the yield point of steel;
② The number after “Q” represents the yield point value, in MPa. For example, Q235 is the yield point（ σ s) It is 235mpa carbon structural steel;
③ If necessary, the symbol indicating quality grade and deoxidation method can be marked after steel grade. The quality grade symbols are a, B, C and D respectively.
Deoxidation method symbol: F stands for rimmed steel; B for semi killed steel: Z for killed steel; TZ means special killed steel, and killed steel may not be marked, that is, both Z and TZ may not be marked. For example, q235-af stands for grade a rimmed steel.
Special purpose carbon steel: such as bridge steel, marine steel, etc., basically adopts the expression method of carbon structural steel, but the letter indicating the purpose is added at the end of the steel grade.
High quality carbon structural steel
Expression method: number + (element symbol) + (deoxidation method symbol) + (special purpose symbol)
① The two digits at the beginning of the steel grade indicate the carbon content of the steel, which is expressed in tens of thousands of the average carbon content. For example, if the average carbon content of the steel is 0.45%, the steel grade is “45”, which is not a sequence number, so it cannot be read as No. 45 steel.
② High quality carbon structural steel with high manganese content should be marked with manganese element, such as 50Mn.
③ Rimmed steel, semi killed steel and special purpose high quality carbon structural steel shall be specially marked at the end of the steel grade. For example, semi killed steel with an average carbon content of 0.1% shall have a steel grade of 10B.
Carbon tool steel
Expression method: letter T + number + (element symbol) + (quality grade symbol)
① The steel grade is marked with “t” to avoid mixing with other steels.
② The number in the steel grade represents the carbon content, expressed in thousandths of the average carbon content. For example, “T8” means that the average carbon content is 0.8%.
③ For those with higher manganese content, mark “Mn” at the end of steel grade, such as “t8mn”.
④ The phosphorus and sulfur content of high-quality carbon tool steel is lower than that of ordinary high-quality carbon tool steel. The letter “a” is added at the end of the steel grade to show the difference, such as “T8mna”.
Free cutting steel
Representation: letter Y + number + (element symbol)
① The steel grade is marked with “Y” to distinguish it from high-quality carbon structural steel.
② The number after the letter “Y” indicates the carbon content, which is expressed in tens of thousands of the average carbon content. For example, the steel grade of free cutting steel with the average carbon content of 0.3% is “Y30”.
③ For those with higher manganese content, “Mn” is also marked after the steel grade, such as “Y40mn”.
Alloy structural steel
Expression method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol)
① The two digits at the beginning of the steel grade indicate the carbon content of the steel, expressed in tens of thousands of the average carbon content, such as 40Cr.
② The major alloying elements in steel are generally expressed in percentage except for some microalloying elements. When the average alloy content is less than 1.5%, the steel grade is generally marked with element symbol instead of content. However, in special cases, the number “1” can be marked after the element symbol, such as steel grade “12CrMoV” and “12Cr1MoV”. The chromium content of the former is 0.4-0.6%, and that of the latter is 0.9-1.2%. Other components are all the same. When the average content of alloy elements is ≥ 1.5%, ≥ 2.5%, ≥ 3.5%… The content shall be indicated after the element symbol, which can be expressed as 2, 3, 4, etc. For example, 18Cr2Ni4WA.
③ Vanadium V, titanium Ti, aluminum Al, boron B, rare earth RE and other alloying elements in the steel are all microalloyed elements. Although the content is very low, they should still be marked in the steel grade. For example, in 20mnvb steel: vanadium is 0.07-0.12%, boron is 0.001-0.005%.
④ High quality steel should add “a” at the end of steel grade to distinguish it from general high quality steel.
⑤ Special purpose alloy structural steel, steel grade with (or suffix) to represent the use of the steel symbol. For example, the steel grade of 30CrMnSi for riveting is ml30crmnsi.
Low alloy high strength steel
Expression method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol)
① The expression method of steel grade is basically the same as that of alloy structural steel.
② Low alloy high strength steel for professional use should be marked at the end of steel grade. For example, 16Mn steel, the special steel used for bridge is “16Mnq”, the special steel used for automobile beam is “16MnL”, and the special steel used for pressure vessel is “16MnR”.
Stainless steel and heat resistant steel
① The carbon content of steel grade is expressed in thousandths. For example, the average carbon content of “2Cr13” steel is 0.2%. If the carbon content in the steel is ≤ 0.03% or ≤ 0.08%, the steel grade is preceded by “00” and “0”, such as 00Cr17Ni14Mo2, 0Cr18Ni9, etc.
② The main alloying elements in the steel are expressed in percentage, while Ti, Nb, Zr, N, etc. are marked according to the above-mentioned expression method of microalloying elements in the alloy structural steel.
Carbon structural steel
Expression method: Q + number + (quality grade symbol) + (deoxidation method symbol) + (special purpose symbol)
① The steel grade with “Q” represents the yield point of steel;
② The number after “Q” represents the yield point value, in MPa. For example, Q235 is the yield point（ σ s) It is 235mpa carbon structural steel;
③ If necessary, the symbol indicating quality grade and deoxidation method can be marked after steel grade. The quality grade symbols are a, B, C and D respectively.
Deoxidation method symbol: F stands for rimmed steel; B for semi killed steel: Z for killed steel; TZ means special killed steel, and killed steel may not be marked, that is, both Z and TZ may not be marked. For example, q235-af stands for grade a rimmed steel.
Special purpose carbon steel: such as bridge steel, marine steel, etc., basically adopts the expression method of carbon structural steel, but the letter indicating the purpose is added at the end of the steel grade.
High quality carbon structural steel
Expression method: number + (element symbol) + (deoxidation method symbol) + (special purpose symbol)
① The two digits at the beginning of the steel grade indicate the carbon content of the steel, which is expressed in tens of thousands of the average carbon content. For example, if the average carbon content of the steel is 0.45%, the steel grade is “45”, which is not a sequence number, so it cannot be read as No. 45 steel.
② High quality carbon structural steel with high manganese content should be marked with manganese element, such as 50Mn.
③ Rimmed steel, semi killed steel and special purpose high quality carbon structural steel shall be specially marked at the end of the steel grade. For example, semi killed steel with an average carbon content of 0.1% shall have a steel grade of 10B.
Carbon tool steel
Expression method: letter T + number + (element symbol) + (quality grade symbol)
① The steel grade is marked with “t” to avoid mixing with other steels.
② The number in the steel grade represents the carbon content, expressed in thousandths of the average carbon content. For example, “T8” means that the average carbon content is 0.8%.
③ For those with higher manganese content, mark “Mn” at the end of steel grade, such as “t8mn”.
④ The phosphorus and sulfur content of high-quality carbon tool steel is lower than that of ordinary high-quality carbon tool steel. The letter “a” is added at the end of the steel grade to show the difference, such as “T8mna”.
Free cutting steel
Representation: letter Y + number + (element symbol)
① The steel grade is marked with “Y” to distinguish it from high-quality carbon structural steel.
② The number after the letter “Y” indicates the carbon content, which is expressed in tens of thousands of the average carbon content. For example, the steel grade of free cutting steel with the average carbon content of 0.3% is “Y30”.
③ For those with higher manganese content, “Mn” is also marked after the steel grade, such as “Y40mn”.
Alloy structural steel
Expression method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol)
① The two digits at the beginning of the steel grade indicate the carbon content of the steel, expressed in tens of thousands of the average carbon content, such as 40Cr.
② The major alloying elements in steel are generally expressed in percentage except for some microalloying elements. When the average alloy content is less than 1.5%, the steel grade is generally marked with element symbol instead of content. However, in special cases, the number “1” can be marked after the element symbol, such as steel grade “12CrMoV” and “12Cr1MoV”. The chromium content of the former is 0.4-0.6%, and that of the latter is 0.9-1.2%. Other components are all the same. When the average content of alloy elements is ≥ 1.5%, ≥ 2.5%, ≥ 3.5%… The content shall be indicated after the element symbol, which can be expressed as 2, 3, 4, etc. For example, 18Cr2Ni4WA.
③ Vanadium V, titanium Ti, aluminum Al, boron B, rare earth RE and other alloying elements in the steel are all microalloyed elements. Although the content is very low, they should still be marked in the steel grade. For example, in 20mnvb steel: vanadium is 0.07-0.12%, boron is 0.001-0.005%.
④ High quality steel should add “a” at the end of steel grade to distinguish it from general high quality steel.
⑤ Special purpose alloy structural steel, steel grade with (or suffix) to represent the use of the steel symbol. For example, the steel grade of 30CrMnSi for riveting is ml30crmnsi.
Low alloy high strength steel
Expression method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol)
① The expression method of steel grade is basically the same as that of alloy structural steel.
② Low alloy high strength steel for professional use should be marked at the end of steel grade. For example, 16Mn steel, the special steel used for bridge is “16Mnq”, the special steel used for automobile beam is “16MnL”, and the special steel used for pressure vessel is “16MnR”.
Stainless steel and heat resistant steel
① The carbon content of steel grade is expressed in thousandths. For example, the average carbon content of “2Cr13” steel is 0.2%. If the carbon content in the steel is ≤ 0.03% or ≤ 0.08%, the steel grade is preceded by “00” and “0”, such as 00Cr17Ni14Mo2, 0Cr18Ni9, etc.
② The main alloying elements in the steel are expressed in percentage, while Ti, Nb, Zr, N, etc. are marked according to the above-mentioned expression method of microalloying elements in the alloy structural steel.
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