MECHANISM OF THE FORMATION OF LARGE-PORE IN THE ASSIMILATED PART IN THE SINTERING PROCESS OF PISOLITE ORE

Sintering experiments were carried out in order to clarify the mechanism of formation of large pore in the assimilated part in the sintering process of pisolite ore. Modeled briquette which consisted of disk-shaped pisolite ore as core and fine n-mixture of hematite ore and limestone as shell layer was used in the present experiments. The results obtained are summarized as follws: 1) When the shell layer was melted, large pore was formed in the assimilated part around the core ore. 2) The large pore in the assimilated part was formed by using not only unfired core ore but also that calcined at 800-degrees-C or 1300-degrees-C. It suggests that the water vapor generated by the dissociation of combined water in the ore was not only the cause of the large pore formation. 3) A mechanism of the formation of large pore in the assimilated part can be described by; (i) The combined water in core ore is dissociated by heating, and macro-pores and/or cracks were formed in core ore. ( ii ) Gas in macro-pores and cracks in core ore is liberated because of its volume expansion during heating and by assimilation of core ore to the melt. (iii) The gas is caught around the ore because the viscosity of melt is increased by assimilation of the ore to melts. (iv) After cooling, the large pore in the assimilated part is formed around the core ore.