Steel number

1. Overview of my country’s steel grade representation method
Steel grades are referred to as steel grades, which are the names for each specific steel product and are a common language for people to understand steel. Our country’s steel grade representation method is based on national standards

The “Method of Representation of Steel Product Grades” (GB221-79) stipulates that the combination of Chinese pinyin letters, chemical element symbols and Arabic numerals shall be used for expression. which is:

① The chemical elements in steel grades are represented by international chemical symbols, such as Si, Mn, Cr… etc. Mixed rare earth elements are represented by “RE” (or “Xt”).

②Product name, use, smelting and pouring methods, etc., are generally expressed in Chinese pinyin abbreviations, see the table.

③The main chemical element content (%) in steel is expressed by Arabic numerals.

2. Classification description of the representation method of steel number in my country

1. Carbon structural steel

① Consists of Q+number+quality grade symbol+deoxidation method symbol. Its steel number is prefixed with “Q”, which represents the yield point of the steel, and the following number represents the value of the yield point, in units

For example, Q235 represents a carbon structural steel with a yield point (σs) of 235 MPa.

②If necessary, a symbol indicating the quality level and deoxidation method can be marked after the steel number. The quality grade symbols are A, B, C, D. Symbol of deoxidation method: F means boiling steel; b table

Shows semi-killed steel: Z stands for killed steel; TZ stands for special killed steel. Killed steel may not be marked with symbols, that is, both Z and TZ may not be marked. For example, Q235-AF represents Class A boiling steel.

③ Carbon steel for special purposes, such as bridge steel, ship steel, etc., basically uses the expression method 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 indicate the carbon content of the steel, 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”.

Serial number, so it cannot be read as 45 steel.

②High-quality carbon structural steel with high manganese content should be marked with manganese, 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 number. For example, the steel number of semi-killed steel with an average carbon content of 0.1% is 10b.

3. Carbon tool steel

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 that the average carbon content is 0.8%.

③For those with higher manganese content, mark “Mn” at the end of the steel number, such as “T8Mn”.

④The phosphorus and sulfur content of high-grade high-quality carbon tool steel is lower than that of general high-quality carbon tool steel. Add the letter “A” at the end of the steel number to show the difference, such as “T8MnA”.

4. Free cutting steel

①The steel number is prefixed 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, a 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

① The 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.

②The main alloying elements in steel, except for individual microalloying elements, are generally expressed in a few percent. When the average alloy content is less than 1.5%, generally only the element symbol is indicated in the steel number, and

The content is not indicated, but in special circumstances it is easy to cause confusion, the number “1” can also be marked after the element symbol, such as steel number “12CrMoV” and “12Cr1MoV”, the former contains chromium

The amount is 0.4-0.6%, the latter is 0.9-1.2%, and the rest of the ingredients are all the same. When the average content of alloying elements is ≥1.5%, ≥2.5%, ≥3.5%…, the element symbol should be

Indicate the content, which can be expressed as 2, 3, 4, etc. accordingly. For example, 18Cr2Ni4WA.

③ Alloying elements such as vanadium V, titanium Ti, aluminum AL, boron B, and rare earth RE in steel are all microalloying elements. Although the content is very low, they should still be marked in the steel number. For example, in 20MnVB steel.

Vanadium is 0.07-0.12%, and boron is 0.001-0.005%.

④High-grade high-quality steel should add “A” at the end of the steel number to distinguish it from general high-quality steel.

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

6. Low alloy high strength steel

① The representation method of steel grade 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”, and the special steel grade for automobile beams is “16MnL”

The special steel grade for pressure vessels is “16MnR”.

7. Spring steel

Spring steel can be divided into two types: carbon spring steel and alloy spring steel according to its chemical composition. The steel number expression method is basically the same as that of high-quality carbon structural steel.

The steel is the same.

8. Rolling bearing steel

①The steel number is prefixed with the letter “G”, which indicates the type of rolling bearing steel.

② The carbon content of high carbon chromium bearing steel grades is not marked, and the chromium content is expressed in parts per thousand, 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

① When the average carbon content of alloy tool steel grades is ≥1.0%, the carbon content is not marked; when the average carbon content is <1.0%, it is expressed in parts per thousand. For example Cr12, CrWMn, 9SiCr,

3Cr2W8V.

②The expression method of alloy element content in steel is basically the same as that of alloy structural steel. But for alloy tool steel grades with lower chromium content, the chromium content is expressed in parts per thousand, and is

Add “0” to the number indicating the content to distinguish it from the general element content expressed by a few percent. For example, Cr06.

③The steel grades of high-speed tool steels generally do not indicate the carbon content, only a few percent of the average content of various alloying elements. For example, the steel grade of tungsten high-speed steel is expressed as “W18Cr4V”.

Steel grades with the letter “C” indicate that their carbon content is higher than that of general steel grades without a “C”.

10. Stainless steel and heat-resistant steel

① The carbon content in steel grades is expressed in parts per thousand. For example, the average carbon content of “2Cr13″ steel is 0.2%; if the carbon content of the steel is ≤0.03% or ≤0.08%, the steel number is marked with ”

00″ and “0” mean it, such as 00Cr17Ni14Mo2, 0Cr18 Ni9, etc.

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

11. Electrode steel

Its steel number is prefixed with the letter “H” to distinguish it from other steels. For example, the stainless steel welding wire is “H2Cr13”, which can be distinguished from the stainless steel “2Cr13”.

12. Silicon steel for electrical engineering

①The steel number is composed of letters and numbers. The head letter DR of the steel number 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.

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

③If the letter “G” is added to the end of the steel number, it means the test is performed at high frequency; the one without “G” means the test is performed at a frequency of 50 cycles.

For example, steel number DW470 indicates that the maximum iron loss per unit weight of cold-rolled non-oriented silicon steel products for electrical purposes at a frequency of 50 Hz is 4.7W/kg.

13. Pure iron for electricians

① Its brand name is composed of letters “DT” and numbers. “DT” means pure iron for electricians, and the number means the serial number of different grades, such as DT3.

②The letter added after the number indicates the electromagnetic performance: A-high grade, E-super grade, C-super, such as DT8A.