The Study On MgO-SiC Composites

With the rapid development of iron and steel industry, the demand for increasing the quality of products has been taken into consideration. "Clean steel" and "extra-clean steel" making is one of the important direction for iron and steel industry. However, it is inevitable that refractories contact with molten steel during iron and steel making, so the refractories has influence on the quality of molten steel. In order to reduce its pollution to molten steel, another function of refractory-purifying molten steel must be highlighted. The Base refractories has little effect on the total oxygen content of steel but has poor thermal shock property.The article is divided into four parts: the first part is effects of MgO-SiC composites on oxidation; the second part is the study on castable MgO-SiC; the third part is effects of different SiC content on thermal shock property of MgO-SiC composites; the forth part is the study of resistance of MgO-SiC composites to slag attack.In the first part, three facts, including temperature, tune and bonder on oxidation of MgO-SiC composites are discussed. The results were listed as following:1) From 1100 C mass change ratio of the MgO-SiC composites bonded by two kinds of bonders began to increase, which means that MgO-SiC composites began to oxidize. From 1200 C, mass change ratio of the MgO-SiC composites continued to increase. However, the speed ratio increased slowly.2) With the decrease of the apparent porosity of the samples, the mass gam increased slowly. The expansion and the sintering due to the formation of M2S decreased the apparent porosity, so the oxidization of the SiC weakened.3) During the oxidization of MgO-SiC composites, the oxidizing area and the mass gain increased as the oxidizing time increased. But with the prolongation of the oxidizing time, the oxidizing area and mass gain increased slowly.4) The oxidizing area and mass gain at 1500 C was less than that at 1350 C, which was attributed to the formation of M2S. The bonder had no obvious effect on the oxidization of the MgO-SiC composite.In the second part the author studied the effects of dispersant and water on the physical properties of MgO-SiC castable. The results show: In the MgO-SiC castable bonded by ultra-fine, the flowability of the castable was best when both C and G dispersant were used together. The optimum content of the water is 5% in the castable. The kinds of the dispersants had certain effects on the physical properties of the materials.In the third part the author studied the effect of the content of the SiC on the resistance of MgO-SiC composite to thermal shock. The results show that with the increase of the SiC, the property of the resistance of the MgO-SiC composites to thermal shock was increased, whichmeans that it had benefits to increase the thermal shock of the composites. When the content of the SiC reached 25%, the grains were hi the close packing and the physical properties of the composite were best.The fourth part was the study of the resistance of the composite to slag attack. The results show:In the multiple slag tests, as the increase of SiC, the content of M2S was increased and the content of CMS was decreased. Thus the property of the slag resistance of the composite was increased.Microsilica used as bonder, SiO2 in the fused slag and SiO2 conducted from the oxidization of SiC reacted with MgO to form M2S. The volume expansion clogged the pore of the composites, so the penetration of the slag was inhibited.When the content of microsilica was 5%, the physical properties were optimum. The suitable content of microsilica had benefits to the slag resistance of the composites.