Lump ore and sinter behaviour during softening and melting

The softening and melting test is widely used to assess the behaviour of ferrous materials in the cohesive zone of a blast furnace. It is generally agreed that the performance of lump ores is inferior to sinter in the test. To understand the factors determining material behaviour, tests were terminated by quenching samples at different temperatures. The samples were then studied under an optical microscope. The formation of a low temperature liquid fayalite caused beds of lump ores to rearrange and contract earlier. Beds of fluxed sinter remained essentially intact with reduction until higher temperatures. The study also showed that results obtained for a mixed burden of 80% sinter and 20% lump ore – a ratio used in many blast furnaces – are not different to results obtained from tests using only sinter. This difference increases as the lump ore level is increased. These findings indicate that there is significant interaction between the material types in the test and that results from single material tests should not be used in isolation assess material performance in a blast furnace. Any prejudice against lump ores as a blast furnace feed material based on softening and melting test results for single materials is clearly incorrect.