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The invention relates to a preparation method of a new fireproof coating for steel structure. The experimental results showed that the ultra-thin fire retardant coating was prepared by using acrylic acid resin as the main film-forming material, melamine phosphate as the dehydration and carbonization agent, and proper amount of carbon forming agent and foaming agent, with the coating thickness of 2. Under the condition of 68mm, the fire resistance limit can be up to 96min, and the experiment shows that the content of each component of the fire retardant coating has a significant influence on the performance of the coating. Most of the major load-bearing components of modern large buildings rely on strong, lightweight steel. From the development trend of the steel structure will be the main form of future large buildings, however, fireproof property of the steel structure building is far worse than brick and reinforced concrete structure, due to steel mechanical strength is a function of temperature, generally speaking, the mechanical strength of steel will decrease along with the rise of temperature, when the temperature reaches a certain value, the steel will lose bearing capacity, the temperature is defined as the critical temperature of steel.

The critical temperature of commonly used building steel is about 540℃. In terms of building fire, the fire temperature is 800 ~ 1200 ℃, mostly in the fire within 10 min, the fire temperature can reach more than 700 ℃, the temperature field in the fire, to bare steel, in a few minutes can be up to 500 ℃ and reaches the critical value, the carrying capacity of the failure and lead to building collapse, in order to improve the refractory steel structure problem, since the 1970 s, began to fire retardant coating for steel structure of the study abroad and has obtained the remarkable result. Our country in the beginning of 80 time also began to steel structure fire retardant coating development, now also has obtained the very good result.