Class I steel: It belongs to carbon steel, mainly including Q235, 20#, 20g, 20R, L210, S205, HP265, etc. The carbon content of this type of steel is less than 1.35% (0.1%-1.2%). In addition to iron and carbon, it may also contain a small amount of impurities such as silicon, manganese, phosphorus, sulfur, etc., but no other alloying elements. The performance of carbon steel mainly depends on the carbon content. An increase in carbon content will increase the strength and hardness of the steel, but will reduce its plasticity and toughness.

‌Class II steel: It belongs to low alloy steel, mainly including 16MnR, 12Cr1MoV, 20MnMoD, S240, L245, HP295, etc. The total amount of alloying elements in low alloy steel is less than 5%. One or more alloying elements are added to carbon steel to improve its performance. The alloy content of low alloy steel is below 5%. When it exceeds 5%, it is called medium alloy steel, and when it exceeds 10%, it is called high alloy steel.

‌Three types of steel‌: belong to martensitic stainless steel, ferritic stainless steel and chromium-molybdenum steel, mainly including 1Cr5Mo, 0Cr13, 1Cr17, 1Cr9Mo, etc. The corrosion resistance of this type of steel mainly depends on the chromium content, which is usually between 11.5% and 18%. Ferritic stainless steel contains chromium between 15% and 30%, has the characteristics of high thermal conductivity and good oxidation resistance, and is often used to manufacture parts resistant to atmospheric, water vapor, water and oxidizing acid corrosion.

‌Composition and performance characteristics of carbon steel‌:

‌Composition‌: Carbon steel is mainly composed of iron and carbon, and may also contain small amounts of silicon, manganese, phosphorus, sulfur and other elements. The higher the carbon content, the greater the hardness of the steel, the higher the strength, but the lower the plasticity.

‌Performance‌: The performance of carbon steel mainly depen