Alloy structural steel
1. The two digits at the beginning of the steel number indicate the carbon content of the steel, expressed in ten-thousandths of the average carbon content, such as 40cr.
2. The main alloying elements in steel, except individual microalloying elements, are generally expressed in a few percent.
When the average alloy content is less than 1.5%, generally only the symbol of the element is marked in the steel number, but not the content, but it is easy to cause confusion under special circumstances. The number "1" can also be marked after the element symbol, such as steel grade "12crmov" and "12cr1mov", the chromium content of the former is 0.4-0.6%, the latter is 0.9-1.2%, and the rest of the ingredients are all the same.
When the average content of alloying elements is ≥1.5%, ≥2.5%, or ≥3.5%, the content should be indicated after the element symbol, which can be expressed as 2, 3, 4, etc. accordingly. For example 18cr2ni4wa.
3. Vanadium v, titanium ti, aluminum al, boron b, rare earth re and other alloying elements in steel are all microalloying elements. Although the content is very low, they should still be marked in the steel number. For example, in 20mnvb steel.
4. For high-grade high-quality steel, "a" should be added at the end of the steel number to distinguish it from general high-quality steel.
5. For special-purpose alloy structural steel, the steel number is preceded (or suffixed) with a symbol representing the purpose of the steel. For example, for 30crmnsi steel specially used for riveting screws, the steel number is expressed as ml30crmnsi.
low alloy high strength steel
1. 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, 16mn steel, the special steel grade used for bridges is "16mnq", the special steel grade for automobile beams is "16mnl", and the special steel grade for pressure vessels is "16mnr".
