Steel is an iron-carbon alloy with a carbon content of 0.0218% to 2.11%. In order to ensure its toughness and plasticity, the carbon content is generally not more than 1.7%. In addition to iron and carbon, the main elements of steel are silicon, manganese, sulfur and phosphorus. There are many ways to classify steel. Today we will take a look at the naming rules of steel.
01
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" represents the yield point value in MPa. For example, Q235 represents carbon structural steel with a yield point (σs) of 235 MPa.
③If necessary, the steel number can be marked with symbols indicating the quality grade and deoxidation method. The quality grade symbols are A, B, C, and D respectively.
Deoxidation method symbol: F for rimmed steel; b for semi-killed steel; Z for killed steel; TZ for special killed steel. Killed steel can be unmarked, that is, both Z and TZ can be unmarked. For example, Q235-AF represents Class A rimmed steel.
Carbon steel for special purposes: such as bridge steel, shipbuilding steel, etc., basically adopts the representation method of carbon structural steel, but adds letters indicating the purpose at the end of the steel number.
02
High-quality carbon structural steel
Representation method: number + (element symbol) + (deoxidation method symbol) + (symbol for special purpose).
① The first two digits of the steel number represent the carbon content of the steel, expressed in ten thousandths of the average carbon content. For example, the steel with an average carbon content of 0.45% has a steel number of "45". It is not a serial number, so it cannot be read as steel No. 45.
② For high-quality carbon structural steel with a high manganese content, the manganese element should be marked, 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.
03
Carbon tool steel
Method of representation: letter T + number + (element symbol) + (quality grade symbol).
① The steel number is prefixed with "T" to avoid confusion with other steel types.
② The number in the steel number indicates the carbon content, expressed in thousandths of the average carbon content. For example, "T8" means the average carbon content is 0.8%.
③ For those with higher manganese content, "Mn" is marked at the end of the steel number, 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 number to distinguish it, such as "T8MnA".
04
Free-cutting steel
Method of representation: letter Y + number + (element symbol).
① The steel number is prefixed 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 ten thousandths of the average carbon content. For example, the free-cutting steel with an average carbon content of 0.3% has a steel number of "Y30".
③ For those with a higher manganese content, "Mn" is also marked after the steel number, such as "Y40Mn".
05
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).
① The first two digits of the steel number indicate the carbon content of the steel, which is expressed in ten thousandths of the average carbon content, such as 40Cr.
② The main alloying elements in the steel, except for individual micro-alloying elements, are generally expressed in percentages. When the average alloy content is <1.5%, the steel number generally only indicates the element symbol without indicating the content. However, in special cases where confusion is likely to occur, the number "1" can also be marked after the element symbol, such as the steel numbers "12CrMoV" and "12Cr1MoV". The former has a chromium content of 0.4%~0.6%, and the latter has a chromium content of 0.9%~1.2%. The rest of the components are the same. When the average alloy element content is ≥1.5%, ≥2.5%, ≥3.5%, etc., the content should be indicated after the element symbol, which can be expressed as 2, 3, 4, etc. For example, 18Cr2Ni4WA.
③ Alloy elements such as vanadium V, titanium Ti, aluminum AL, boron B, and rare earth RE in steel are all micro-alloying 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%.
④ High-quality steel should add "A" at the end of the steel number to distinguish it from general high-quality steel.
⑤ For alloy structural steel for special purposes, the steel number is prefixed (or suffixed) with a symbol representing the purpose of the steel. For example, 30CrMnSi steel for rivets and screws is represented by ML30CrMnSi.
06
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).
① The representation method of steel number 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 number. For example, 16Mn steel, the special steel type used for bridges is "16Mnq", the special steel type for automobile beams is "16MnL", and the special steel type for pressure vessels is "16MnR".
07
Spring steel
Spring steel can be divided into two categories according to chemical composition: carbon spring steel and alloy spring steel. The steel grade representation method is basically the same as high-quality carbon structural steel, and the latter is basically the same as alloy structural steel.
08
Rolling bearing 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).
① The steel grade is prefixed with the letter "G" to indicate rolling bearing steel.
② The carbon content of high carbon chromium bearing steel is not marked, and the chromium content is expressed in thousandths, such as GCr15. The steel grade representation method of carburized bearing steel is basically the same as that of alloy structural steel.
09
Alloy tool steel and high-speed tool steel
① When the average carbon content of alloy tool steel is ≥1.0%, the carbon content is not marked; when the average carbon content is <1.0%, it is expressed in thousandths. For example, Cr12, CrWMn, 9SiCr, 3Cr2W8V.
② The method of expressing the content of alloy elements 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 to distinguish it from the method of expressing the general element content 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 expressed as "W18Cr4V". The steel grade with the letter "C" indicates that its carbon content is higher than the general steel grade without "C".
10
Stainless steel and heat-resistant steel
① The 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 prefixed with "00" and "0" respectively, such as 00Cr17Ni14Mo2, 0Cr18 Ni9, etc.
② The main alloying elements in the steel are expressed in percentages, while titanium, niobium, zirconium, nitrogen, etc. are marked according to the above-mentioned method of expressing micro-alloying elements in alloy structural steel.
11
Welding rod steel
Its steel number is prefixed with the letter "H" to distinguish it from other steel types. For example, stainless steel welding wire is "H2Cr13", which can be distinguished from stainless steel "2Cr13".
12
Silicon steel for electrical use
① The steel number consists of letters and numbers. The letter DR at the beginning of the steel number indicates hot-rolled silicon steel for electrical use, DW indicates cold-rolled non-oriented silicon steel for electrical use, and DQ indicates cold-rolled oriented silicon steel for electrical use.
②The number after the letter indicates 100 times the iron loss value (W/kg).
③The letter "G" at the end of the steel number indicates that it is tested at a high frequency; if "G" is not added, it indicates that it is tested at a frequency of 50 cycles.
For example, the steel number DW470 indicates that the maximum unit weight iron loss value of the cold-rolled non-oriented silicon steel product for electrical use at a frequency of 50 Hz is 4.7W/kg.
13
Pure iron for electrical use
①Its grade consists of the letters "DT" and numbers. "DT" means pure iron for electrical use, and the numbers indicate the sequence number of different grades, such as DT3. ②The letters added after the numbers indicate the electromagnetic properties: A-high grade, E-special grade, C-super, such as DT8A.
