Steel is an iron-carbon alloy with a carbon content of 0.0218% to 2.11%. In order to ensure its toughness and plasticity, carbon content generally does not exceed 1.7%. In addition to iron and carbon, main elements of steel include silicon, manganese, sulfur and phosphorus. There are various ways of classifying steel. Today, let's take a look at naming rules of steel.

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

 

①Steel number is prefixed with "Q", which represents yield point of steel; ②Number after "Q" represents yield point value, and unit is MPa. For example, Q235 means carbon structural steel with a yield point (σs) of 235 MPa; ③If necessary, symbol indicating quality grade and deoxidation method can be marked after steel number. 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 representation method of carbon structural steel, but add a letter indicating purpose at end of steel number.

Representation method: number + (element symbol) + (deoxygenation method symbol) + (special purpose symbol). ①Two digits at the beginning of steel number indicate carbon content of steel, which is expressed in ten thousandths of average carbon content. For example, for steel with an average carbon content of 0.45%, 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 manganese element, such as 50Mn. ③Boiled steel, semi-killed steel and high-quality carbon structural steel for special purposes should be specially marked at the end of steel grade. For example, semi-killed steel with an average carbon content of 0.1% has a steel grade of 10b.

Representation method: letter T + number + (element symbol) + (quality grade symbol). ①Steel number is prefixed with "T" to avoid mixing with other steels. ②Number in steel number indicates carbon content, expressed in thousandths of 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". ④Phosphorus and sulfur content of high-quality carbon tool steel is lower than that of general high-quality carbon tool steel. Letter "A" is added at the end of steel number to show difference, such as "T8MnA".

Representation method: letter Y + number + (element symbol). ①Steel number is crowned with "Y" to distinguish it from high-quality carbon structural steel. ②Number after letter "Y" indicates carbon content, expressed in ten thousandths of average carbon content. For example, 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 steel number, such as "Y40Mn".

Representation method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol). ①Two digits at beginning of steel number indicate carbon content of steel, expressed in ten thousandths of average carbon content, such as 40Cr. ② Main alloying elements in steel, except for individual microalloying elements, are generally expressed in percent. When average alloy content is less than 1.5%, only element symbol is generally indicated in steel grade, but content is not indicated. However, in special cases, if it is easy to cause confusion, number "1" can also be marked after element symbol, such as steel number. "12CrMoV" and "12Cr1MoV", the former has a chromium content of 0.4-0.6%, the latter is 0.9-1.2%, and rest of components are all same. When average content of alloying elements is ≥1.5%, ≥2.5%, ≥3.5%..., content should be indicated after 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 steel are all microalloying elements, and although content is very low, they should still be marked in 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 steel number to distinguish it from general high-quality steel. ⑤ For special purpose alloy structural steel, steel number is crowned (or suffixed) with a symbol representing purpose of steel. For example, special 30CrMnSi steel for riveting screws, steel number is expressed as ML30CrMnSi.

Representation method: (special purpose symbol) + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol) + (special purpose symbol). ①Representation method of steel number is basically same as that of alloy structural steel. ②For professional low-alloy high-strength steel, it should be indicated at the end of steel number. For example, 16Mn steel, special steel grade for bridges is "16Mnq", special steel grade for automobile beams is "16MnL", and special steel grade for pressure vessels is "16MnR".

 

Spring steel can be divided into two categories according to chemical composition: carbon spring steel and alloy spring steel. Steel number is expressed. The former is basically same as high-quality carbon structural steel, and the latter is basically same as alloy structural steel.

Representation method: high carbon chromium bearing steel: letter G + Cr element symbol and number; carburized bearing steel: letter G + number + main alloy element symbol and number + trace alloy element symbol + (quality grade symbol). ①Steel number is prefixed with letter "G", which means rolling bearing steel. ②Carbon content of high carbon chromium bearing steel grades is not marked, and chromium content is expressed in thousandths, such as GCr15. Steel number representation method of carburized bearing steel is basically same as that of alloy structural steel.

①When average carbon content of alloy tool steel grade is ≥1.0%, carbon content is not marked; when average carbon content is less than 1.0%, it is expressed in thousandths. For example Cr12, CrWMn, 9SiCr, 3Cr2W8V. ②Expression method of alloying element content in steel is basically same as that of alloy structural steel. However, for alloy tool steel grades with low chromium content, chromium content is expressed in thousandths, and "0" is added before number indicating content, so as to express it and general element content in percent distinguish. For example Cr06. ③Steel grade of high-speed tool steel generally does not indicate carbon content, but only indicates a few percent of average content of various alloying elements. For example, steel number of tungsten series high-speed steel is expressed as "W18Cr4V". Steel number with letter "C" indicates that its carbon content is higher than general steel number without "C".

①Carbon content in steel grade is expressed in thousandths. For example, average carbon content of "2Cr13" steel is 0.2%. If carbon content in steel is ≤0.03% or ≤0.08%, steel number is preceded by "00" and "0" respectively, such as 00Cr17Ni14Mo2, 0Cr18 Ni9, etc. . ② Main alloying elements in steel are expressed in percent, while titanium, niobium, zirconium, nitrogen, etc. are marked according to above-mentioned expression method for microalloying elements in alloy structural steel.

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

①Steel number consists of letters and numbers. Letter DR in the head of 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. ②Number after letter represents 100 times iron loss value (W/kg). ③ If letter "G" is added to the end of steel number, it means that it is inspected at high frequency; if "G" is not added, it means that it is inspected at a frequency of 50 cycles.
For example, steel grade DW470 indicates that maximum iron loss per unit weight of cold-rolled non-oriented silicon steel products for electrical use is 4.7W/kg at a frequency of 50 Hz.

① Its grade consists of letters "DT" and numbers, "DT" means pure iron for electricians, and numbers represent sequence numbers of different grades, such as DT3. ②Letters added after numbers indicate electromagnetic performance: A - advanced, E - special, C - super, such as DT8A.