The characterization of interfaces between textural components in metallurgical cokes

Six coals, representing the rank range normally encountered in commercial coking, were carbonized in a small oven to give dense cokes, of tensile strength comparable with that of good-quality blast-furnace coke. Interfaces between the different textural components in the cokes were studied by polarized-light microscopy. It proved possible to classify interfaces according to their perceived quality, to quantify their occurrence by point-counting and to calculate interface quality indices for the coke as a whole or for interfaces involving individual textural components. Interfaces between vitrinite-derived reactive coke components were superior to those involving inerts, but the inerts content of a coke did not have a marked influence on the coke interface quality index. The highest coke interface quality index was observed for the coke from the coal with the highest dilatation. No clear evidence of an influence of interface quality on coke tensile strength is apparent from the present data.