Refractory materials factory in the face of the increasing demand for steel in the present society, but also with the upsizing of production equipment, blast furnace iron temperature, iron output increase, iron output time. Therefore, the use conditions of blast furnace iron ditch are very harsh. The traditional iron ditch refractory has been replaced by corundum, silicon carbide, graphite and other materials. In order to meet the requirements of blast furnace iron ditch firebrick, our company Zhengzhou Juda Refractory Material Co., Ltd. made high alumina silicon carbide brick through analysis and comparison.
Tieshuigou firebrick used high-aluminum brick before, but it is found that the corrosion of high-aluminum brick is related to C in molten iron. On this basis, the corrosion process of high-aluminum brick is analyzed, and the influence of C content in molten iron on the corrosion of brick is analyzed. Through the experiment, it is found that the corroded high-aluminum brick can be roughly divided into three layers, the surface layer is the adhesion layer of molten iron, and the inner layer is the original brick layer. Between them is a porous metamorphic layer about 2mm thick. The main phase of the metamorphic layer is crystallites smaller than 100μm, and there are a large number of pores larger than 100μm in the microstructure, but no Fe was observed. It can be seen from the metamorphic layer/original brick interface that the original brick is Al2O3-sio2, namely mullite particles. The 100-μm columnar particles in the metamorphic layer are corundum, and the composition of columnar particles is Al2O3-SiO2-Feo glass phase. It can be concluded that these components are formed by the reaction of mullite aggregate with molten steel components during the erosion process. The occurrence of this phenomenon is related to whether there is C in the molten iron. That is to say, if there is C in the molten iron, the Al2O3-SiO2-Feo glass phase is reduced to metal Fe at the same time that the reduction of SiO2 component disappears, and the remaining AL2O3 is precipitated as corundum crystal. By analyzing the erosion test results of high-alumina brick and molten iron, the following conclusions can be drawn: After 5h contact between high-alumina brick and molten iron at 1650℃, metamorphic layer is formed on the surface of brick, which is composed of corundum particles and SiO2-Al2O3-Feo glass phase filled between particles: When the high alumina brick is corroded by molten iron, the molten iron does not contain C, so the mullite aggregate dissolves and generates SiO2-Al2O3-Feo glass phase. When the molten iron contains C, the glass phase is reduced by C to produce corundum and metal Fe. Therefore, the influence of C element in molten iron on the erosion of high alumina brick is to shorten the service life of high alumina brick.
We produced high alumina silicon carbide brick through the experiment again, the selection of first grade high alumina clinker, gray corundum and SiC content of 94% silicon carbide sand and silicon carbide powder as raw materials. The paper pulp waste liquid is used as binder. In order to prevent the oxidation of silicon carbide, three different oxidants were selected and some results were obtained.
According to the requirements of Tieditch for refractory materials, high alumina silicon carbide brick should have good thermal shock stability, resistance to hot metal sand and corrosion resistance. About 80% of bricks are more than 50Kg, so the limit size of particles should be properly expanded. This is beneficial for brick's thermal stability, sand resistance and erosion resistance. The limit particle size of ingredients is 4mm. The particle composition of various raw materials is shown in the table below:
According to the ratio of various raw materials, the raw materials into the sand mixer mixing. In order to make the admixtures such as anti-oxidants distributed evenly in the matrix, the premixing process was used. The feeding sequence is as follows: adding high aluminum clinker, brown corundum, SiC sand, dry mixing for 5min, adding pulp waste liquid, wet mixing for 2min, adding fine powder, mixing for 15min, discharging for a total of 22min. Then, in a 1000-ton mechanical press, the body densities of the high-aluminum silicon carbide bricks are 2.76g/cm³ and 2.75g/cm³ respectively. During the sintering of high-aluminum silicon carbide bricks at a low temperature, the temperature should be raised slowly at a rate of 15-20 ℃/h in order to avoid cracking caused by the rapid removal of residual water in the billet. The medium temperature stage can be heated freely. Z final firing temperature is 1430℃, hold for 36 hours, the product's oxide layer thickness, surface low melt greatly reduced, and fully sintered.
Using primary high alumina clinker, brown corundum, silicon carbide as raw materials, plus a small amount of auxiliary materials, the production of high alumina silicon carbide brick has achieved good results in the application of iron ditch, can be used continuously.