The relationship between the strength and the microstructure of ferro-coke with hyper-coal (HPC) addition is investigated. In particular, we focused on the adhesiveness of coal particles. The strength of ferrocoke was evaluated by a tensile strength test and coke microstructure with increasing the amount of HPC addition was observed. In the observation of the microstructure, absolute maximum length and roundness of pores were measured. The result indicated that the strength of ferro-coke

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... es with an increase in the amount of HPC, because voids between coal particles decrease and adhesiveness of coal particles improve. A pore roundness of less than 0.2 intends coke strength, and the index decreases with HPC addition. We found that a pore roundness of less than 0.05 is included in voids between coal particles. It is suggested that mutual adhesiveness of coal particles is one of the factors affecting coke strength, and this factor can be evaluated by pores of roundness less than 0.05.