How to distinguish steel grades

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In our country, the classification is based on the uses of steel: 1) Carbon structural steel: The notation format is Q+number+ (quality grade symbol) + (deoxidation method symbol) + (symbol for specific use). ① The steel grade is prefixed with “Q”, which indicates the yield strength of the steel； ②“The number following “Q” indicates the yield strength value, in MPa. For example, Q235 denotes a carbon structural steel with a yield strength (σs) of 235 MPa ； ③If necessary, symbols indicating the quality grade and deoxidation method can be indicated after the steel grade. The quality grade symbols are A, B, C, and D respectively. Deoxidation method symbol: F denotes boiling steel ； b denotes semi-killed steel: Z denotes killed steel ； TZ denotes special calm steel; calm steel does not require a symbol, meaning neither Z nor TZ needs to be indicated. For example, Q235-AF denotes grade A boiling steel. Special-purpose carbon steel: such as bridge steel and marine steel, basically uses the designation method for carbon structural steel, but letters indicating the purpose are added at the end of the steel grade. 2) High-quality carbon structural steel: Notation method: number + (element symbol) + (deoxidization method symbol) + (symbol for specific purpose). ① The first two digits of the steel grade indicate the carbon content of the steel, expressed as a fraction of ten thousand of the average carbon content. For example, steel with an average carbon content of 0.45% has the grade “45”; this is not a sequential number, so it should not be referred to as “steel grade 45”. ②For high-quality carbon structural steel with a high manganese content, the manganese element should be specified, such as 50Mn. ③Boiling steel, semi-killed steel, and high-quality carbon structural steels for special purposes should be specifically indicated at the end of their grade designation; for example, semi-killed steel with an average carbon content of 0.1% has a grade designation of 10b. 3) Carbon tool steel: Notation method: letter T + number + (element symbol) + (quality grade symbol). ① The steel grade is prefixed with “T” to prevent confusion with other types of steel. ② ②The number in the steel grade indicates the carbon content, expressed as a percentage of the average carbon content. For example, “T8” indicates an average carbon content of 0.8%. ③ ③For grades with a higher manganese content, “Mn” is indicated at the end of the steel grade, such as “T8Mn”. ④ ④The phosphorus and sulfur contents in high-grade high-quality carbon tool steels are lower than those in ordinary high-quality carbon tool steels; the letter “A” is added at the end of the steel grade to indicate this difference, such as “T8MnA”. ⑤ 4) Free-cutting steel ⑥ Notation: Letter Y + number + (element symbol) ⑦ ① The steel grade is prefixed with “Y” to distinguish it from high-quality carbon structural steel. ⑧ ②The number following the letter “Y” indicates the carbon content, expressed as a fraction of ten thousand of the average carbon content. For example, a free-cutting steel with an average carbon content of 0.3% has the designation “Y30”. ⑨ ③For those with a higher manganese content, “Mn” is also indicated after the steel grade, such as “Y40Mn”. ⑩ 5) Alloy structural steel: ⑪ Notation method: (special purpose symbol) + number + symbols and numbers of the main alloying elements + symbols of trace alloying elements + (quality grade symbol) + (special purpose symbol). ⑫① The first two digits of the steel grade indicate the carbon content of the steel, expressed as a fraction of ten thousand of the average carbon content; for example, 40Cr. ⑬②The main alloying elements in steel, with the exception of a few micro-alloying elements, are generally expressed as percentages. When the average alloy content is <1.5%, only the element symbols are usually indicated in the steel grade, without specifying the content; however, in cases where confusion might arise, the number \"1\" can also be added after the element symbol. For example, for the steel grades \"12CrMoV\" and \"12Cr1MoV\", the chromium content is 0.4–0.6% in the former and 0.9–1.2% in the latter, with all other components being identical. 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 represented as 2, 3, 4..., etc. accordingly. For example, 18Cr2Ni4WA. ⑭③Alloying elements in steel such as vanadium V, titanium Ti, aluminum AL, boron B, and rare earths RE all belong to micro-alloying elements; although their contents are low, they still need to be indicated in the steel grade. For example, in 20MnVB steel: vanadium is 0.07-0.12%, and boron is 0.001-0.005%. ⑮④High-grade quality steel should have “A” added at the end of its grade designation to distinguish it from ordinary quality steel. ⑯⑤Alloy structural steels for specific purposes have steel grades preceded by (or followed by) symbols indicating the purpose of that steel grade. For example, the 30CrMnSi steel used specifically for riveting screws is denoted by the steel grade ML30CrMnSi. ⑰ Low-alloy high-strength steel; ⑱ Notation method: (special-purpose symbol) + number + symbols and numbers of major alloying elements + symbols of trace alloying elements + (quality grade symbol) + (special-purpose symbol). ⑲① The notation method for steel grades is basically the same as that for alloy structural steels. ⑳②For low-alloy high-strength steels for professional use, it should be indicated at the end of the steel grade. For example, for 16Mn steel, the specific grade used for bridges is “16Mnq”, the one used for automobile frames is “16MnL”, and the one used for pressure vessels is “16MnR”. 217) Spring steel. Spring steel can be divided into two categories based on its chemical composition: carbon spring steel and alloy spring steel. The method of denoting their grades is basically the same as that for high-quality carbon structural steel for the former, and similar to that for alloy structural steel for the latter. 238) Designation method for rolling bearing steel: 25 High-carbon chromium bearing steel: letter G + symbol for Cr element plus a number. 26 Carburized bearing steel: letter G + a number + symbols and numbers for the main alloying elements + symbols for trace alloying elements + (quality grade symbol). 27 ① The steel grade is prefixed with the letter “G” to indicate that it belongs to the category of rolling bearing steel. 28② In high-carbon chromium bearing steel grades, the carbon content is not specified, while the chromium content is expressed as a percentage per thousand, for example in GCr15. The method of designating steel grades for carburized bearing steel is basically the same as that for alloy structural steel. 299) Alloy tool steels and high-speed tool steels 30① When the average carbon content of alloy tool steel grades is ≥1.0%, the carbon content is not indicated ； When the average carbon content is <1.0%, it is expressed as a per thousand. Such as Cr12, CrWMn, 9SiCr, 3Cr2W8V. 31② The method of expressing the content of alloying elements in steel is basically the same as that for alloy structural steel. However, for alloy tool steels with lower chromium contents, the chromium content is expressed as a few thousandths, and a “0” is placed before the digit indicating the amount, in order to distinguish it from the method of expressing the content of other elements as percentages. For example, Cr06. 32③ For high-speed tool steels, the carbon content is generally not indicated; instead, only the percentage average content of various alloying elements is specified. For example, the grade of tungsten-based high-speed steel is denoted as “W18Cr4V”. Steel grades marked with the letter “C” indicate that their carbon content is higher than that of standard steel grades that are not marked with “C”. 3310) Stainless steels and heat-resistant steels 34① The carbon content in the steel grade is expressed as a percentage per thousand. 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%, then “00” and “0” are prefixed to the steel grade respectively, such as 00Cr17Ni14Mo2, 0Cr18Ni9, etc. 35② The major alloying elements in steel are expressed as percentages, whereas titanium, niobium, zirconium, nitrogen, etc. are indicated using the same method used for micro-alloying elements in alloy structural steels. 3611) Welding rod steel 37: Its steel grade is preceded by the letter “H” to distinguish it from other types of steel. For example, the stainless steel welding wire is “H2Cr13”, which can be distinguished from the stainless steel “2Cr13”. 3812) Silicon steel for electrical use 39① The steel grade is composed of letters and numbers. The initial letters DR in the steel grade designation refer to hot-rolled silicon steel for electrical use, DW refers to cold-rolled non-oriented silicon steel for electrical use, and DQ refers to cold-rolled oriented silicon steel for electrical use. The number after letter 40② represents 100 times the iron loss value (W/kg). 41③ When the letter “G” is added at the end of the steel grade, it indicates that testing is carried out at high frequencies ； The absence of the “G” indicates that the test was conducted at a frequency of 50 Hz. 42 For example, the steel grade DW470 indicates that for cold-rolled non-oriented silicon steel products used in electrical applications, the maximum iron loss per unit weight at a frequency of 50 Hz is 4.7 W/kg. 4313) Pure iron for electrical use 44① Its grade is composed of the letters “DT” and numbers; “DT” denotes pure iron for electrical use, while the numbers indicate the sequence number of different grades, such as DT3. 45② The letter added after the number indicates the electromagnetic performance: A – advanced, E – top grade, C – superior; for example, DT8A.