Effect of additives on formation of calcium ferrites in magnesiariched sinters

Production of rich-containing MgO sinters has become one of the effective ways to solve the problems,such as high viscosity and low desulfurization ability of the slag which was brought by large use of high-alumina iron ores in blast furnace. However,rich-containing MgO raw materials decrease the quantity of binding phase during sintering process to make the strength of sinter worse. This study aims to increase the amount of calcium ferrite(SFCA) by adding additives with low melting point into iron ore fines to improve the quality of sinters. The B2O3,CaCl2 and Na2SiO3 were used as additives to add into high-alumina iron ore fines with rich-containing MgO. The effect of additives on sintering process was investigated according to the results of patterns and optical microstructure of sintered samples from XRD. The results showed that the three kinds of additives have a promotion to form SFCA,but the effects are different. When the mass percent of MgO is 4%,the appropriate amount(mass percent)of B2O3,CaCl2 or Na2Si O is 0.094%,0.470% and 0.470%respectively. It can promote SFCA formation with more amount,and little additive is good for acicular morphology. Another result indicates that increase of binding phase helps to generate more magnetite under the high content of MgO.