1) Carbon structural steel

Representation method: Q+number+(quality grade symbol)+(deoxidation method symbol)+(special purpose symbol)

①The steel number is prefixed with "Q", which represents the yield point of the steel;

②The number after "Q" indicates the yield point value, and the unit is MPa. For example, Q235 represents a carbon structural steel with a yield point (σs) of 235 MPa;

③ If necessary, symbols indicating quality grade and deoxidation method can be marked after the steel number. The quality grade symbols are A, B, C, D, respectively.

Symbol of deoxidation method: F stands for boiling steel; b stands for semi-killed steel: Z stands for killed steel; TZ stands for special killed steel. For example Q235-AF means A-grade boiling steel.

Carbon steel for special purposes: such as bridge steel, marine steel, etc., basically use the representation method of carbon structural steel, but add a letter indicating the purpose at the end of the steel number.

 

2) High quality carbon structural steel

Representation method: number + (element symbol) + (deoxygenation method symbol) + (special purpose symbol)

①The two digits at the beginning of the steel number indicate the carbon content of the steel, which is expressed in ten thousandths 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 gauge steel.

②High-quality carbon structural steel with high manganese content should mark the manganese element, such as 50Mn.

③ Boiling steel, semi-killed steel and high-quality carbon structural steel for special purposes should be specially marked at the end of the steel grade. For example, semi-killed steel with an average carbon content of 0.1% has a steel grade of 10b.

 

3) Carbon tool steel

Representation method: letter T + number + (element symbol) + (quality grade symbol)

①The steel number is prefixed with "T" to avoid mixing with other steels.

②The number in the steel number indicates the carbon content, expressed in thousandths of the average carbon content. For example "T8" means an average carbon content of 0.8%.

③ For those with higher manganese content, mark "Mn" at the end of the steel grade, such as "T8Mn".

④The 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 number to show the difference, such as "T8MnA".

 

4) Free cutting steel

Representation method: letter Y + number + (element symbol)

①The steel number is crowned with "Y" to distinguish it from high-quality carbon structural steel.

②The number after the letter "Y" indicates the carbon content, expressed in ten thousandths of the average carbon content. For example, the free-cutting steel with an average carbon content of 0.3% has a steel grade of "Y30".

③ Those with higher manganese content are also marked with "Mn" after the steel number, such as "Y40Mn".

 

5) Alloy structural steel

Representation method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol)

①The two digits at the beginning of the steel number indicate the carbon content of the steel, expressed in ten thousandths of the average carbon content, such as 40Cr.

② The main alloying elements in steel, except for individual microalloying elements, are generally expressed in percent. When the average alloy content is less than 1.5%, only the element symbol is generally indicated in the steel grade, but the content is not indicated. However, in special cases, if it is easy to cause confusion, the number "1" can also be marked after the element symbol, such as the steel number. "12CrMoV" and "12Cr1MoV", the former has a chromium content of 0.4-0.6%, the latter is 0.9-1.2%, and the rest of the components are all the same. When the average content of alloying elements is ≥1.5%, ≥2.5%, ≥3.5%..., the content should be indicated after the element symbol, which can be expressed as 2, 3, 4...etc. For example 18Cr2Ni4WA.

③Alloying elements such as vanadium V, titanium Ti, aluminum AL, boron B, and rare earth RE in the steel are all microalloying elements, and 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%.

④For high-grade high-quality steel, "A" should be added at the end of the steel number to distinguish it from general high-quality steel.

⑤For special purpose alloy structural steel, the steel number is crowned (or suffixed) with a symbol representing the purpose of the steel. For example, the special 30CrMnSi steel for riveting screws, the steel number is expressed as ML30CrMnSi

 

6) Low alloy high strength steel

Representation method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol)

①The representation method of steel number is basically the same as that of alloy structural steel.

②For professional low-alloy high-strength steel, it should be indicated at the end of the steel number. For example, 16Mn steel, the special steel grade for bridges is "16Mnq", the special steel grade for automobile beams is "16MnL", and the special steel grade for pressure vessels is "16MnR".

 

7) Spring steel

Spring steel can be divided into two categories according to chemical composition: carbon spring steel and alloy spring steel. The steel number is expressed. 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

display method:

High carbon chromium bearing steel: letter G+Cr element symbols and numbers

Carburized bearing steel: letter G + number + main alloying element symbol and number + trace alloying element symbol + (quality grade symbol)

①The steel number is prefixed with the letter "G", which means rolling bearing steel.

② The carbon content of high carbon chromium bearing steel grades is not marked, and the chromium content is expressed in thousandths, such as GCr15. The steel number 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

①When the average carbon content of the 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 thousandths. For example Cr12, CrWMn, 9SiCr, 3Cr2W8V.

②The expression method of alloying 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 express it and the general element content in percent distinguish. For example Cr06.

③The steel grade of high-speed tool steel generally does not indicate the carbon content, but only indicates a few percent of the average content of various alloying elements. For example, the steel number of tungsten series high-speed steel is expressed as "W18Cr4V". The steel number with the letter "C" indicates that its carbon content is higher than the general steel number without "C".

 

10) Stainless steel and heat resistant steel

①The carbon content in the 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 number is preceded by "00" and "0" respectively, such as 00Cr17Ni14Mo2, 0Cr18 Ni9, etc. .

② The main alloying elements in the steel are expressed in percent, while titanium, niobium, zirconium, nitrogen, etc. are marked according to the above-mentioned expression method for microalloying elements in alloy structural steel.

 

11) Welding rod steel

Its steel number is preceded by the letter "H" to distinguish it from other steel types. For example, the stainless steel wire is "H2Cr13", which can be distinguished from the stainless steel "2Cr13".

 

12) Silicon steel for electrical use

①The steel number consists of letters and numbers. The letter DR in the head of the steel number means hot-rolled silicon steel for electrical use, DW means cold-rolled non-oriented silicon steel for electrical use, and DQ means cold-rolled oriented silicon steel for electrical use.

②The number after the letter represents 100 times the iron loss value (W/kg).

③ Those with the letter "G" at the end of the steel number indicate that they are inspected at a high frequency; those without "G" indicate that the frequency is 50 cycles. For example, the steel number DW470 indicates that the cold-rolled non-oriented silicon steel products for electrical use are at a frequency of 50 Hz. The maximum iron loss per unit weight is 4.7W/kg.

 

13) Pure iron for electrician

① Its grade consists of the letters "DT" and numbers, "DT" means pure iron for electricians, and the numbers represent the sequence numbers of different grades, such as DT3.

②The letters added after the numbers indicate the electromagnetic performance: A - advanced, E - special, C - super, such as DT8A.