Reference content on q345 and q355 steel standards

1.q345 steel standard:

q345 steel is a commonly used structural steel in China, and its standard is GB/T 1591-2008 “Technical Conditions for High Strength and low alloy Structural Steel”. According to the standard, the chemical composition requirements of q345 steel include: The carbon content shall not exceed 0.20%, the silicon content shall not exceed 0.55%, the manganese content shall not exceed 1.00-1.60%, the phosphorus content shall not exceed 0.045%, the sulfur content shall not exceed 0.045%, the niobium content shall not exceed 0.15%, the titanium content shall not exceed 0.20% and the aluminum content shall not exceed 0.015%. In addition, q345 steel also has some mechanical property requirements, such as tensile strength should not be less than 470MPa, yield strength should not be less than 345MPa, elongation should not be less than 21%.

2.q355 steel standard:

q355 steel is a new generation of high-strength and low-alloy structural steel, and its standard is GB/T 1591-2018 “Technical Conditions for High-strength and low-alloy Structural Steel”. According to the standard, the chemical composition requirements of q355 steel are similar to those of q345, but there are some minor differences. For example, q355 steel contains no more than 0.35% silicon, between 1.00-1.60% manganese, 0.030% phosphorus, 0.030% sulfur, 0.15% niobium, 0.20% titanium, and 0.015% aluminum. In terms of mechanical properties, the tensile strength of q355 steel shall not be less than 470MPa, the yield strength shall not be less than 355MPa, and the elongation shall not be less than 22%.

3.The difference between q345 and q355 steel:

Although both q345 and q355 steels are high-strength low-alloy structural steels, there are some differences in their chemical composition and mechanical properties. First of all, in terms of chemical composition, q355 steel has higher silicon content and lower phosphorus and sulfur content than q345 steel. These small differences may affect the heat treatment properties and corrosion resistance of steel.

In terms of mechanical properties, the yield strength of q355 steel has been improved compared with q345 steel, from 345MPa to 355MPa. This means that q355 steel has better bending strength and durability. In addition, the elongation of q355 steel is slightly higher than that of q345 steel, which indicates that it has better plasticity.

In summary, despite some minor differences between the q345 and q355 steel standards, both are high-strength low-alloy structural steels that are suitable for a variety of structural engineering and construction fields. According to the specific engineering requirements and conditions, it is very important to select the appropriate steel standard to ensure the quality and safety of the project.

The above content is for reference only, and the specific parameters shall be subject to the corresponding standard documents.