Research and engineering application of steel corrosion in prefabricated building steel structure

The prefabricated building steel structure has the characteristics of energy saving, environmental protection and resource recycling, which is in line with the future development direction of buildings. However, ordinary steel is susceptible to corrosion, and the corrosion protection of steel surface is the content that must be considered in the design of steel structure at present. Due to the high cost of anti-corrosion operations, and the dust generated by rust removal, the organic chemicals of coatings and coated metals pollute the atmosphere and soil, which is an important factor restricting the development of building steel structures. Therefore, the development of non-painting new steel, reduce processing costs, reduce environmental pollution, for the development of building steel structure is of great significance. Therefore, the alloy elements of Ni, Cr and Cu were added to the steel to meet the requirements of atmospheric corrosion resistance. Combined with the rolling process characteristics of the section steel, V microalloying was adopted, and the V (C, N) dispersion precipitation was strengthened during the cooling process after rolling. The corrosion resistance of Q390NHD was studied by cyclic immersion comparative test. The corrosion problem exposed in the atmosphere for a long time is analyzed, and the feasibility of weathering steel as steel structure material for prefabricated buildings is demonstrated. The main chemical composition range of Q390NHD steel: m (C) ≤0.12%, m (Si) ≤0.50%, m (Mn) ≤1.50%, 0.20%≤m (Ni) ≤0.65%, 0.30%≤m (Cr) ≤1.25%, 0.20%≤m (Cu) ≤0.55%, m (V) ≤0.12%; Mechanical properties: The lower yield strength ReL is above 400 MPa, the tensile strength Rm is between 560 and 600 MPa, the yield strength ratio is not more than 0.80, the elongation of the short-proportion sample after fracture is not less than 25%, and the charpy impact energy at -20℃ is not less than 34 J/cm2. Meet the material performance requirements of steel structure components with seismic performance design in GB 50017-2017 “Steel Structure Design Standard”. In the 72-h weekly immersion test, the corrosion rate of Q390NHD steel is 1.665 g/ (m2·h), which is 47.0% of the general carbon steel, and its corrosion resistance is more than 2 times that of ordinary steel, which is equivalent to 09CuPCrNiA. According to the standard analysis of ISO 11844-1:2006, the corrosion thickness of Q390NHD steel 70a is estimated according to the upper limit of corrosion rate given by the indoor corrosion level IC3, and the total corrosion amount does not exceed 0.031mm. When it reaches IC4 level, it shall not exceed 0.3mm; Even the most severe indoor corrosion (IC5 level) does not exceed 0.7mm. Therefore, as long as the corrosion margin is properly increased, the application of Q390NHD steel in ordinary civil office and residential steel structure buildings can be paint-free.