1. Overview of Steel Number Representation in China
The steel grade is abbreviated as steel grade. It is the name of each specific steel product. It is a common language for people to understand steel. According to the national standard "Steel Product Brand Representation Method" (GB221-79), the Chinese Pinyin alphabet, chemical element symbols and Arabic numerals are used to represent the steel number in our country. Namely: 1. Chemical elements in steel grades are represented by international chemical symbols, such as Si, Mn, Cr... And so on. Mixed rare earth elements are represented by "RE" (or "Xt"). (2) The product name, use, smelting and pouring methods are generally expressed by abbreviations of Chinese phonetic alphabet, as shown in the table. (3) The main chemical elements in steel (%) are expressed by Arabic numerals.
Classification and Explanation of the Representation Method of Steel Number in China
1. Carbon structural steel
It is composed of Q + digits + quality grade symbols + deoxidization method symbols. Its steel number is crowned with "Q", which represents the yield point of steel. The number behind it represents the yield point value. The unit is MPa, such as Q235, which represents the yield point (_s) of 235 MPa carbon structural steel.
(2) Signs indicating quality grade and deoxidization method can be marked after steel number if necessary. The quality grade symbols are A, B, C and D respectively. Deoxidization method symbol: F means boiling steel; B means semi-killed steel; Z means killed steel; TZ means special killed steel; killed steel can not be marked, that is, Z and TZ are not marked. For example, Q235-AF denotes grade A boiling steel.
(3) Special purpose carbon steels, such as bridge steels and marine steels, basically adopt the representation of carbon structural steels, but at the end of the steel number, a letter indicating the use is added.
2. High Quality Carbon Structural Steel
(1) The two digits at the beginning of the steel number indicate the carbon content of the steel, which is expressed in tens of thousands of parts of the average carbon content. For example, the steel with an average carbon content of 0.45% and the steel number of "45", which is not a sequence number, can not be read as steel 45.
(2) Manganese element should be marked in high-quality carbon structural steels with high manganese content, such as 50Mn.
(3) Boiling steel, semi-killed steel and high-quality carbon structural steel for special use should be marked at the end of steel grade, such as semi-killed steel with an average carbon content of 0.1% and steel grade of 10b.
3. Carbon tool steel
The steel number is crowned with "T" to avoid mixing with other steels.
(2) Numbers in steel grades represent carbon content, expressed as a few thousandths of the average carbon content. For example, "T8" means an average carbon content of 0.8%.
(3) For those with higher manganese content, the final mark of "Mn" in steel grade, such as "T8Mn".
(4) The phosphorus and sulfur content of high quality carbon tool steels is lower than that of general high quality carbon tool steels. The letter "A" is added at the end of the steel number to show the difference, such as "T8MnA".
4. Free-cutting steel
The steel grade is crowned with "Y" to distinguish it from high quality carbon structural steel.
(2) The number after the letter "Y" denotes the carbon content, expressed in tens of thousands of parts of the average carbon content, such as free-cutting steel with an average carbon content of 0.3%, whose steel number is "Y30".
(3) For those with higher manganese content, the "Mn" is also marked 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 tens of thousands of parts of the average carbon content, such as 40Cr.
(2) The main alloying elements in steel are generally expressed in percentages, except for individual microalloying elements. When the average alloy content is less than 1.5%, the steel number is usually marked only with element symbols, but not with content. But in special cases, the number "1" can be marked after element symbols, such as "12CrMoV" and "12Cr1MoV". The former contains 0.4-0.6% chromium and the latter 0.9-1.2% chromium. The other components are all the same. When the average content of alloying elements is more than 1.5%, > 2.5%, > 3.5%... When the content is marked after the element symbol, it can be expressed as 2, 3, 4... And so on. For example, 18Cr2Ni4WA.
(3) Vanadium, titanium, Ti, Al, B, RE and other alloying elements in steel belong to microalloying elements, although the content is very low, they should be marked in steel grade. For example, in 20MnVB steel. Vanadium is 0.07-0.12% and boron is 0.001-0.005%.
(4) High-grade and high-quality steel should be added "A" at the end of steel grade to distinguish it from general high-quality steel.
(5) Alloy structural steels for special purposes, with steel numbers crowned (or suffixed) as symbols for the purpose of the steel. For example, 30CrMnSi steel for riveting screw, the steel number is ML30CrMnSi.
6. Low Alloy High Strength Steel
(1) The representation of steel number is basically the same as that of alloy structural steel.
(2) For professional low alloy high strength steel, the steel grade should be marked at the end. For example, 16Mn steel for bridges is "16Mnq", "16MnL" for automobile girders and "16MnR" for pressure vessels.
7. Spring steel can be divided into carbon spring steel and alloy spring steel according to their chemical composition. The former is basically the same as high-quality carbon structural steel, and the latter is basically the same as alloy-bonded steel.
8. Rolling bearing steel
The letter "G" denotes the steel of rolling bearings.
(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 number representation 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 is more than 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.
(2) The expression method of alloy element content in steel is basically the same as that in alloy structural steel. However, for the alloy tool steel with lower chromium content, the chromium content is expressed in thousandths, and "0" is added before the number indicating the content, so as to distinguish it from the general element content expressed in percentages. For example, Cr06.
(3) The steel grades of high-speed tool steels generally do not indicate the carbon content, but only the average content of various alloying elements. For example, the steel number of tungsten high speed steel is denoted as "W18Cr4V". The carbon content of steel crown with the letter "C" is higher than that of general steel crown without the letter "C".
10. Stainless steel and heat resistant steel
The carbon content in steel grade is expressed in thousandths. For example, the average carbon content of "2Cr13" steel is 0.2%. If the carbon content in steel is less than 0.03% or less than 0.08%, the steel number is denoted by "00" and "0", respectively, such as 00Cr17Ni14Mo2 and 0Cr18Ni9.
(2) The main alloying elements in steel are expressed in percentages, while titanium, niobium, zirconium, nitrogen... The microalloying elements of the alloy structural steels mentioned above are indicated.
11. Welding rod steel is distinguished from other steels by the letter "H" on the front crown of its steel number. For example, stainless steel welding wire is "H2Cr13", which can be distinguished from stainless steel "2Cr13".
12. Silicon steel for electrical purposes
The steel number consists of letters and numbers. The header letter DR denotes hot-rolled silicon steel for electrical purposes, DW denotes cold-rolled non-oriented silicon steel for electrical purposes, and DQ denotes cold-rolled oriented silicon steel for electrical purposes.
(2) The number after the letter represents 100 times the iron loss value (W/kg).
(3) If the letter "G" is added at the end of the steel number, it means that it is tested at high frequencies; if no "G" is added, it means that it is tested at 50 cycles of frequencies. For example, steel number DW470 indicates that the maximum unit weight iron loss value of cold rolled non-oriented silicon steel products for electrical purposes is 4.7W/kg at 50 Hz frequency.
13. Electrical Pure Iron
Its brand number consists of the letters "DT" and numbers, "DT" denotes pure iron for electrical purposes, and numbers denote the order numbers of different brands, such as DT3.
(2) The letters added after the numbers indicate electromagnetic properties: A-advanced, E-super, C-super, such as DT8A.