Effects Of Si On Oxide Scale Microstructure And Corrosion Resistance Of Carbon Steel

Hot rolling strip production processes were simulated by Thermal Gravimetric Analyzer(TGA) in situation of different temperatures, and furnace(SPJX-8-13)heating was used to simulate the changes of heating time. The oxide scales were formed on two kinds of steels, which one steel consisted of 0.3%Si and other was 0.6%Si. The way of dry-wet alternation to accelerate corrosion was used, and NaHSO3 was used to evaluation the corrosion resistance of the two iron scales that contain different amounts of Si element. The microstructure and properties of the samples were analyzed by optical microscope(OM. And X-ray diffraction(XRD) and Energy Dispersive Spectrometer(EDS). Scanning Electron Microscopy(SEM) was used to study the effects of scale’s microstructure and properties on corrosion resistance under different heating temperature,holding time and Si content.The weight gains on per unit area of 0.3% Si steel was higher than 0.6%Si in the simulating experiment by Thermal Gravimetric Analyzer(TGA). When the temperature between 400℃and 800℃, the oxidation weight gain rate was little, oxidation weight curve was almost linear. Under the condition of 900℃~1200℃, the oxidation rate increasd, oxidation weight curve was parabolic. The generated under 900℃~1200℃oxide iron sheet can reduce the oxidation of steel substrate, the thickness of oxide was certain oxidation resistance at this time.The oxide structure were consisted of inner layer FeO, interface layer Fe3O4, the outer layer Fe2O3 inn the experiment of furnace heating. Between oxide scale and substrate interface was enrichment of Si oxide layer(mainly of Fe2SiO4 phase). Both enrichment of Si diffused in oxide layer, of different level to the oxide iron internal, and diffusion depth increases with the extension of heating time. During the heating temperature was 1200℃, the heating time for 30 min, 0.6% Si of the sample oxide and Si enrichment substrate interface layer to internal penetration steel matrix, and the heating time for 60 min was obvious.The corrosion weight gain of 0.6% Si was less than 0.3% Si by the analysis ofdry-wet alternation accelerated corrosion test, which the heating temperature was1150℃,The corrosion resistance of iron oxide of 0.6Si formed at 1150℃ for 30 minutes was the best.