Q355C channel steel is a type of low-alloy high-strength structural steel that complies with the Chinese National Standard GB/T 1591-2018. This standard specifies the chemical composition and mechanical property requirements for Q355C. Q355C has a yield strength of 355 MPa, along with good weldability and machinability. In terms of chemical composition, the carbon content of Q355C does not exceed 0.20%, manganese content does not exceed 1.6%, silicon content does not exceed 0.55%, and both phosphorus and sulfur contents do not exceed 0.035%. These strict chemical composition requirements ensure the performance of Q355C channel steel in various engineering structures, such as bridges, buildings, and ships. The production and inspection of Q355C channel steel must adhere to national standards to guarantee its quality and performance.