The classification of China's steel number expression method description
1. Description of steel number of carbon structural steel
is composed of Q+ number + quality grade symbol + deoxidation method symbol. Its steel number is crowned with “Q”, representing the yield point of the steel, followed by a number indicating the value of the yield point in MPa For example, Q235 indicates a carbon structural steel with a yield point (σ s) of 235 MPa.
If necessary, the steel number can be marked after the symbol indicating the quality grade and deoxidation method. Quality grade symbols are A, B, C, D. Deoxidation method symbols: F boiling steel; b indicates semi-sedated steel: Z indicates sedated steel; TZ indicates special sedated steel, sedated steel may not be marked symbols, that is Both Z and TZ may be left unmarked. For example, Q235-AF indicates A grade boiling steel.
special purpose carbon steel, such as bridge steel, marine steel, etc., basically using the carbon structural steel, but in the end of the steel number additional letters to indicate the purpose.
2. High quality carbon structural steel
two numbers at the beginning of the steel grades indicates the carbon content of the steel, to the average carbon content of a few ten thousandths, for example, the average carbon content of 0.45% of the steel, steel grades ” 45 “, it is not a sequential number, so can not be read as 45 steel.
high quality carbon structural steel with high manganese content, the manganese element should be marked out, such as 50Mn.
boiling steel, semi-sedimentation steel and special-purpose high-quality carbon structural steel should be specially marked at the end of the steel number, for example, the average carbon content of 0.1% of the semi-sedimentation steel, the steel number 10b.
3. Carbon tool steel
Steel grades crowned with ” T ” to avoid confusion with other steel types.
The number in the steel grades indicates the carbon content, expressed as a few thousandths of the average carbon content. For example, “T 8” means the average carbon content of 0.8%.
manganese content is higher, in the steel gradesat the end of the label ” Mn “, such as ” T8Mn “.
senior quality carbon tool steel phosphorus, sulfur content, than the general quality carbon tool steel low, in the steel grades at the end of the letter ” A “, to show the difference, such as ” T8MnA “.
4. Free cutting steel
steel number crowned with ” Y “, to distinguish it from high-quality carbon structural steel.
letter “Y” after the number indicates the carbon content, to the average carbon content of a few ten thousandths, for example, the average carbon content of 0.3% of free cutting steel, the steel number for “Y 30”.
manganese content is higher, also marked in the steel number after the “Mn”, for example, “Y40Mn”.
5. Alloy structural steel
two numbers at the beginning of the steel number indicates the carbon content of steel, to the average carbon content of a few ten thousandths, such as 40Cr.
steel in the main alloying elements, in addition to individual micro-alloy elements, generally expressed as a few percent. When the average alloy content < 1.5%, the steel number is generally marked only the element symbols, and not marked content, but in special cases easily confused, in the element symbols can also be marked with the number ” 1 “, such as steel number ” 12CrMoV ” and “12Cr1MoV”, the former chromium content of 0.4-0.6%, the latter is 0.9-1.2%, the rest of the composition of all the same. When the average content of alloying elements ≥ 1.5%, ≥ 2.5%, ≥ 3.5% ……, the content should be marked after the element symbol, can be expressed accordingly as 2, 3, 4 …… and so on. For example, 18Cr2Ni4WA.
steel in the vanadium V, titanium Ti, aluminum AL, boron B, rare earth RE and other alloying elements, are micro-alloying elements, although the content is very low, but still should be marked in the steel number. For example, in 20MnVB steel. Vanadium is 0.07-0.12%, boron is 0.001-0.005%.
Advanced quality steel should be added at the end of the steel number ” A “, to distinguish it from the general quality steel.
special purpose of the alloy structural steel, steel number crowned (or suffix) on behalf of the use of the steel symbol. For example, 30CrMnSi steel for riveting screw, the steel number is expressed as ML30CrMnSi.
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