What is the grade of steel?

1. Carbon structural steel

① consists of Q+ number + quality grade symbol + deoxidation method symbol. Its steel number is preceded by "Q", which represents the yield point of the steel, and the following number indicates the yield point value in MPa. For example, Q235 indicates a carbon structural steel with a yield point (σs) of 235 MPa.

② If necessary, the symbol indicating the quality grade and deoxidation method can be marked behind the steel number. The quality grade symbols are A, B, C and D respectively. Deoxidation method symbol: F stands for boiling steel; b for semi-killed steel: Z for killed steel; TZ indicates a special kill steel, and the kill steel may not mark the symbol, that is, Z and TZ are not marked. For example, Q235-AF indicates Class A boiling steel.

③ Carbon steel for special purposes, such as bridge steel, Marine steel, etc., basically uses the representation of carbon structural steel, but the letter indicating the use is added at the end of the steel number.

2. High quality carbon structural steel

The two digits at the beginning of the steel number indicate the carbon content of the steel, expressed in a few thousandths of the average carbon content, such as the average carbon content of 0.45% steel, steel number "45", it is not a serial number, so it can not be read as 45 steel.

② High-quality carbon structural steel with high manganese content should be marked with manganese, 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, such as semi-killed steel with an average carbon content of 0.1%, and its steel number is 10b.

3. Carbon tool steel

① The steel number is crowned with "T" so as not to be confused with other steels.

The number in the steel number indicates the carbon content, expressed in a few thousandths of the average carbon content. For example, "T8" indicates an average carbon content of 0.8%.

③ If the manganese content is higher, mark "Mn" at the end of the steel number, such as "T8Mn".

④ The phosphorus and sulfur content of high-grade carbon tool steel is lower than that of general high-quality carbon tool steel, and the letter "A" is added at the end of the steel number to show the difference, such as "T8MnA".

4. Free cutting steel

① The steel number is crowned with "Y" to distinguish it from high-quality carbon structural steel.

② The number after the letter "Y" indicates the carbon content, expressed in a few thousandths of the average carbon content, such as the average carbon content of 0.3% of free-cutting steel, its steel number is "Y30".

③ For those with higher manganese content, "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 a few thousandths of the average carbon content, such as 40Cr.

The main alloy elements in steel, in addition to individual microalloy elements, are generally expressed in a few percent. When the average alloy content

③ Alloy elements such as vanadium V, titanium Ti, aluminum Al, boron B, and rare earth RE in steel belong to microalloying elements, although the content is very low, it 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-grade high-quality steel should be added "A" at the end of the steel number to distinguish it from general high-quality steel.

⑤ Special purpose alloy structural steel, steel number prefix (or suffix) represents the use of the steel symbol. For example, the riveting screw special 30CrMnSi steel, steel number is expressed as ML30CrMnSi.

6. Low alloy high strength steel

The expression 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 marked at the end of the steel number. For example, the special steel grade of 16Mn steel used for Bridges is "16Mnq", the special steel grade of automobile girder is "16MnL", and the special steel grade of pressure vessels is "16MnR".

Seven. Spring steel

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

8. Rolling bearing steel

① Steel number with the letter "G", indicating the rolling bearing steel class.

② The carbon content of high-carbon chromium bearing steel is not marked, and the chromium content is expressed in a few thousandths. For example, GCr15. The steel number representation method 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 ≥1.0%, the carbon content is not marked; When the average carbon content Cr12, CrWMn, 9SiCr, 3Cr2W8V.

The expression method of alloy element content in steel is basically the same as that of alloy structural steel. However, for alloy tool steel numbers with low chromium content, the chromium content is expressed in a few thousandth, and "0" is added before the number indicating the content, in order to distinguish it from the general element content expressed by a few percent. For example, Cr06.

③ The steel number of high-speed tool steel generally does not mark the carbon content, only a few percent of the average content of various alloying elements. For example, the steel number of tungsten high-speed steel is expressed as "W18Cr4V". The steel number with the letter "C" indicates that its carbon content is higher than that of the common steel number without the "C".

10. Stainless steel and heat-resistant steel

① The carbon content in the steel number is expressed in a few 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 denoted by "00" and "0" respectively, such as 00Cr17Ni14Mo2, 0Cr18 Ni9 and so on.

② The main alloying elements in the steel are expressed in a few percent, while titanium, niobium, zirconium, nitrogen, etc., are marked according to the expression method of the microalloying elements in the above-mentioned alloy structural steel.

11. Welding rod steel

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

12. Silicon steel for electrical purposes

① The steel number consists of letters and numbers. The head letter of the steel number DR Stands for hot-rolled silicon steel for electrical purposes, DW stands for cold-rolled non-oriented silicon steel for electrical purposes, and DQ stands for cold-rolled oriented silicon steel for electrical purposes.

② The number after the letter indicates 100 times the iron loss (W/kg).

③ Adding the letter "G" to the end of the steel number means that it is tested at a high frequency; If "G" is not added, it means that it is tested at a frequency of 50 cycles. For example, the steel number DW470 indicates that the maximum iron loss per unit weight of cold-rolled non-oriented silicon steel products for electrical purposes at 50 Hz is 4.7W/kg.

13. Pure iron for electricians

① Its grade is composed of the letter "DT" and numbers, "DT" means pure iron used by electricians, and the numbers indicate the serial number of different grades, such as DT3.

② The letters added after the numbers indicate electromagnetic properties: A - advanced, E - super, C - super, such as DT8A.