Facing the increasing demand of iron and steel in the modern society, and with the development of production equipment and the increase of blast furnace tapping temperature, the refractory plant will increase the tapping volume and prolong the tapping time. Therefore, the use conditions of the blast furnace iron ditch are very harsh. The traditional tapping refractory is replaced by corundum, silicon carbide, graphite and other materials. In order to meet the use of refractory bricks for blast furnace trough, our company Zhengzhou colt of Refractories Co., through analysis and comparison of trial production of high aluminum silicon carbide brick.
Iron ditch refractory brick before using the high alumina brick, but found that the erosion of molten iron and high alumina brick in C, on the basis of this analysis, the erosion process of high alumina brick, the influence of C content in molten iron of brick corrosion, and the experiment results show that the corrosion is high alumina brick can be roughly divided into 3 layers, the surface metal adhesion layer, inner layer is the original brick layer, between the two is about 2mm thick porous layer. The main phase of the metamorphic layer is less than 100 micron m, with a large number of pores larger than 100 mu in the microstructure, but Fe is not observed. It can be seen from the interface between the metamorphic layer and the original brick that the original brick is AL2O3 - SiO2, that is, mullite particles. The columnar particles with a length of 100 m in the metamorphic layer are composed of corundum and columnar particles, and are found to be AL2O3 - SiO2 - FeO glass phases. It can be judged that these components are formed by the reaction of mullite aggregate to the composition of the molten steel during the erosion process. The occurrence of this phenomenon is related to whether C is contained in molten iron. That is to say, if there is C, AL2O3 SiO2 FeO system in molten iron, the FeO phase is reduced to metal Fe when the SiO2 component is reduced, and the remaining AL2O3 is precipitated as corundum crystal. Analysis of corrosion test results of high aluminum brick and iron, we can draw the following conclusions: high alumina brick and 1650 DEG C molten iron contact 5h, brick surface metamorphic layer, the metamorphic layer consists of corundum particles and SiO2 particles filled in AL2O3 - FeO glass phase composition: high alumina brick in molten iron erosion process C, not containing molten iron, then mullite aggregate dissolved to generate SiO2 - AL2O3 - FeO glass phase containing C in molten iron case, the glass phase is C reduction, generation of corundum and metal Fe. Therefore, the impact of the C elements in the molten iron on the corrosion of the high alumina brick has shortened the service life of the high alumina brick.
Our production of high aluminum silicon carbide brick through the experiment again, choose a high grade bauxite, corundum ash and SiC content of 94% silicon carbide sand and silicon carbide as raw materials. The pulp waste liquid is used as the binder. In order to prevent the oxidation of silicon carbide, three different oxidants have been selected to achieve a certain effect.
According to the requirements of the iron ditch for the refractory, the high aluminum silicon carbide brick should have good thermal shock stability, anti iron water sanding and erosion resistance. More than 80% of the brick weight is more than 50Kg, so the ultimate size of the particles should be properly expanded. This is beneficial to the thermal stability of the brick, the resistance to sand and the erosion resistance. The maximum particle size of the ingredients is 4mm, and the particle composition of various raw materials is shown in the following table:
According to the ratio of all kinds of raw materials, the raw materials are put into the mixer in the mixer. In order to make the additives such as anti oxidizing agent can be evenly distributed in the matrix, the premixing process is adopted. The feeding sequence is as follows: first, add high aluminum clinker, Zong Gangyu, SiC sand and dry mixed 5min, then add pulp waste liquid, wet mix 2min, add mixed fine powder, mix 15min after discharging, mix up 22min. Then in the 1000 tons of mechanical press, pressing machine, high aluminum silicon carbide brick molding press density were 2.76g/cm and 2.75g/cm high fand fand, aluminum silicon carbide sintered in low temperature stage, in order to avoid the inner residual moisture removal caused by excessive cracking, slowly warming, heating speed is 15 to 20 DEG C /h. In the middle temperature stage, the temperature can be heated freely. The final sintering temperature is 1430 C, the heat preservation is 36 hours, the thickness of the oxidation layer, the lower surface of the surface of the product is greatly reduced, and the sintering is fully sintered.
Using a high grade bauxite clinker, Zong Gangyu, silicon carbide as raw material, plus a small amount of auxiliary materials, high aluminum silicon carbide production has achieved good results in the application of iron ditch, can continue to use.