Study On The Modification Of Steel Surface With Low Firing Enamel

With the advances in modern science and technology, We have higher requirements for the properties of the industrial materials. In the oil pipeline industry, because their poor working conditions, except the impact of fluid,they must also withstand the corrosion of the corrosive medium. So,It is required that the pipe wall material has not only good mechanical properties, but also corrosion resistance and wear resistance. It is difficult for pure metal to meet these requirements. The ceramic materials have high wear resistance and corrosion resistance, good high temperature stability, lowfriction coefficient, low thermal expansion coefficient, etc. Therefore, it is important to coat ceramic materials evenly on metal (or alloy) surface and obtain both the good mechanical properties of metal materials and excellent wear resistance and corrosion resistance of ceramic materials. The research has not only theoretical significance but also important useful value and has become another research focus.In this thesis, Our aim is to prepare enamel layer with low melting point on the surface of steel and iron in order to improve the wear and corrosion resistance of steel and iron surfaces. Excellent enamel was prepared by a dip method. The research contents are as follows:First, the steel and iron enamels were manufactured using various oxides as ceramic glaze components and iron and steel as the base. The effects of different sintering temperatures, sintering time, addition of nucleating agent TiO₂ on the production process, microstructure and properties of the surface enamel layers of the steel and iron were studied. The best sintering temperature, sintering time and the ceramic layer thickness were determined using orthogonal experiment after decarburization treatment.The results showed that after pre-decarbonization of the steel plate, the gas bubbles defects produced on the substrate surfaces during the firing were removed, and the effect of the gas holes on the latter properties was reduced. Under different sintering temperatures and sintering time, by macro-observation for the morphologies (smoothness, gloss, color, porosity, etc.), the optimum firing temperature and sintering time were obtained, and they were 780℃and 8min, respectively.Second, the phases in the enamel layer were analyzed using D/Max2500X Type X-ray diffractometer; the microhardness of the enamel layer was measured using FM-700 Type vickers hardness tester; the bonded interface and wear morphology of the enamel layer were observed using JSM-5600 Type scanning electron microscope (SEM).The results showed after adding nucleating agents, two new phases NaAlSi₂O₆ and AlK (P₂O₇) appeared in the enamel layer. Under the same sintering time, the addition of TiO₂ nucleating agent significantly increased the hardness of the enamel layer. Under the same firing temperature,the enamel hardness increased with increasing holding time. The adherence level between the enamel coating and the base metal was expressed using the ratioηof the interface length between enamel coating and base metal to the base metal length at unit length. The adhesion degree between enamel layer and the metal substrate increased with the increase of sintering temperature.Third, the wear resistance of ceramic layers was characterized using MG-2000 type tribometer, and the morphology of the worn surface was recorded using the JSM-5600 scanning electron microscope. The effects of the applied load and wearing time on the friction coefficient and mass loss of the enamel layer were discussed. The change of the wear resistance after adding nucleating agents TiO₂ was analyzed.The results showed that the friction coefficient reduced with increasing the load under different wear time. Under different loads, the friction coefficient increased with increasing the wearing time. The addition of nucleation agent TiO₂ significantly increased the friction coefficient of the enamel layer.Finally, the heat-resistant vibration of the enamel layer was determined according to national standard GB11419-89. The heat resistance was measured using the traditional method for measuring the softening point of ceramic, The acid and alkali resistances of the enamel layer were examined according to national standard GB4738.2-84.The results showed that the heat-resistant vibration temperature of the enamel layer is 420℃, the heat-resistant temperature is 690℃, and they are higher than those of the general industrial enamel required by the Ministry of Chemical Industry. Acid-resistant degree is 93.74%, and alkali-resistant degree is 95.45%.