ABSTRACT
Evaluation of the decrepitation is made using the assays defined by COISRMJ (Committee for Overseas Iron and Steelmaking of Japan Raw Materials) and ISO 8371. In both tests the sample is subjected to thermal shock by introducing them into a preheated oven at 700 °C. After 30 min the sample is removed for cooling in air and sieved, to measure the decrepitation index, which is the percentage of fines generated below 5 mm (COISRMJ) or 6.3 mm (ISO 8371). Lump ores considered good under thermal shock present decrepitation indexes not exceeding 5% when measured by the COISRMJ test or not exceeding 3% in the ISO 8371 test. However, due to increasing scarcity of lumpy iron ores, there is a widespread effort in the steel industry to enable the use of lump ores with higher decrepitation indexes.
