Researches On Purification And Application Of Iron Oxide Powers From Regenerated Hydrochloric Acids In Cold Rolling

In recent years, soft magnetic ferrite materials have been devoleping in the field of their functional properties such as high-frequency, high permeability and low loss. Therefore, miniaturization and light-duty of the electric components is a significant developing trend. The mass percentage of iron oxides is about 70% in the soft magnetic ferrite materials, and the raw material of iron oxides must meet the corresponding performance requirements. In order to product high-grade soft magnetic ferrite materials, the purity of iron oxides in the raw materials is required higher and higher. At present, the raw materials of iron oxide needed for the production of high-grade soft ferrite materials are mainly from iron oxide powders by spray roasting of the regeneration hydrochloric acids in cold-rolled steel plants. During iron oxide powder production process, these elements such as aluminum, silicon, sulfur, manganese, magnesium, potassium, sodium, phosphorus, chromium, nickel, copper and phosphorus are imported. Simultaneously, boron, calcium, titanium, niobium, vanadium and other elements are also introduced in the product process of some steel products. This thesis will focus on these studies on the relative purification technology of iron oxide powders from regeneration acids, the quality test technology of the iron oxide powders and the Mossbauer analysis of iron oxide powders and MnZn ferrite materials contaning a trace of B.The influencing factors related to the removing silicon of acid washing waste liquors by the flocculation were investigated. These included the concentration of flocculant solutions, the loading of flocculant solutions, the reaction temperature, the stirring rate and the stirring time. Through these experiments, the feasible technical conditions of removing silicon were confirmed. The removal ratio of silicon was up to 83%, which ensured the high purity of iron oxide powders. In addition, the kinetics of removing silicon process was also investigated. The calculated apparent active energy indicated that the process was controlled by physical factors. The above investigations provided the conditions for the preparation of iron oxide powders with high purity by further water washing.The water washing technology of iron oxide powders from the regeneration acid liquors with the removal of silicon was studied. The investigations included the grinding mothed, the ratio of raw material and water, the stirring time, the selection of filtration equipments and the drying method. Through these investigations, the feasible technical conditions of water washing were confirmed. According to the standard GB/T 24244-2009 (iron oxide powders as the raw materials of ferrite materials), the product of iron oxide powders reached to the first level (the standard of YHT1). And the content of Fe2O3 in iron oxide powders was above 99.40%. MnZn ferrite samples were also prepared using iron oxide powders by water washing as the raw materials. The main magnetic properties of the sample showed that its quality was superior to that of the imported iron oxide powder.The testing and analysis methods on the contents of chlorine, aluminum, silicon, sulfur, calcium, manganese, boron, titanium, magnesium, potassium, sodium, phosphorus, chromium, nickel, copper and other trace elements in iron oxide were studed. Various influencing factors on the final results were discussed in detail. From the results of the above discussions, the reasonable test conditions were obtained. The ion chromatography and ICP-AES method could be separately used to determine the content of chloride and the contents of aluminum, silicon, sulfur, calcium, manganese, boron, titanium, magnesium, potassium, sodium, phosphorus, chromium, nickel and copper in iron oxide powders.The preparation routes of MnZn ferrite materials were confirmed by the analysis of their crystalline structures and metal distributions. According to the actural production experiences, the technical process of ordinary drying method was used to prepare MnZn ferrite materials. The effects of the addition of B on the maganetic properties and microstructures of MnZn ferrite materials were investigated in detail. Below 10μg/g, the maganetic properties (power loss, initial permeability and density) of the samples were excellent and the microstructures of the samples presented fine crystals. Above 15μg/g, the maganetic properties of the samples decreased and the microsturctures of the samples presented giant crystals. Thruogh the theoretic calculation, the resuts on the atomic covering-layer on the MnZn ferrite particles at different additions of B were obtained. At the same time, the effects of different atomic covering-layer on the microsturctures and crystal sizes of MnZn ferrite materials were analyzed.The properties of imported and domestic iron oxide powders were analyzed by the Mossbauer. The results showed that the two kinds of samples presented the similar Mossbauer spectra and parameters and the Mossbauer quadrupole splitting value of the two samples were relatively small, which suggested that the symmetry of the electric field around iron oxide powders was good. The Mossbauer spectra and parameters suggested that the coordination environment around magnetic phase of Fe in MnZn ferrite materials was different from that in original iron oxide powders, and a high-proportion of doublet spectra was observed with a decreasing concentration of Mn in MnZn ferrite materials. For MnZn ferrite A or MnZn ferrites B, after the heat-treatment, their double peak areas were all reduced, both presented more than two Sextet sub-spectrums, and their differences in super-fine field were relatively large. These indicated that the distributions of Mn and Zn in the microsturctures were inhomogeneous in MnZn ferrite samples.Based on the researches on purification and application of iron oxide powers from regenerated hydrochloric acids in cold rolling, the national standard GB/T 24244-2009 (iron oxide powders as the raw materials of ferrite materials) were established. Its technical indexed were advanced and reasonable. In addition, it was a precursor for a strong applicability, and could advantageously promote the development of the production technology of ferrite materials from iron oxides in our country.