Experimental analysis of intumescence fireproofing coating on base material of substation frames

In order to improve the fire resistance of the substation frame, an intumescence fireproof coating for the base material (Q235 steel and stainless steel) of substation frame was developed in this paper. The experiments of pull-out test, fire resistance test and electron microscope scanning were carried out to observe the mechanical properties, fire resistance properties and microphysical and chemical properties of the fireproof coating or base material. The main conclusions are summarized as follows: The bond strength of the Q235 steel to the intumescence fireproof coating is 1.26 MPa, which is greater than that of stainless steel at 0.506 MPa. Moreover, the variations of backside temperature and internal temperature of specimens with fireproofing coating are apparently different from those for conditions without fireproofing coating. For conditions with fireproofing coating, the backside temperature and internal temperature of specimens increase in the initial stage, while after the fireproofing coating is expanded and the insulation layer is formed on the surface, the rise rate of the temperature decreases. The average thermal insulation efficiencies of Q235 carbon steel and stainless steel are 240.32 min and 223.22 min, while the average values of fire resistance limit are 250.8 min and 244.2 min, respectively. The expansion multiples of the fireproofing coating for the two materials after being heated are between 50 and 60. Furthermore, the pull-out test would cause certain damage to the fireproof coating on the surface of steel components, and the damage to the Q235 steel sample was greater than that to the stainless steel sample. At the same time, the fireproof coating would undergo chemical reactions leading to expansion when heated, resulting in a dense surface and porous structure inside, which could reduce heat transfer to a certain extent.