UNDERSTANDING AND OPTIMISATION OF MgO HYDRATION RESISTANCE AND SPINEL FORMATION MECHANISMS FOR INCREASING PERFORMANCES OF DVM USED IN CRUCIBLE INDUCTION FURNACES MELTING STEEL

摘要

Two main aspects of Spinel forming DVM used in steel foundry applications were investigated with the aim of a general increase of product performance: Resistance of MgO against hydration and Spinel formation mechanisms. The quality and distribution of the MgO used in the DVM was studied, and its influence on the two properties evaluated. It was shown, using a specific test procedure for this work, that a proper choice of the intrinsic MgO raw material properties can considerably increase the hydration resistance of the product. This improvement results in a longer shelf life, a more robust behaviour for installation conditions and a higher safety factor during the furnace lifetime. The influence of the selected MgO raw material properties was then evaluated on the Spinel formation mechanisms. The microstructure of two DVMs containing two different MgO sources and distribution was studied using quantitative analysis and PTS characterisation. It was shown that using an optimal quality and distribution of the MgO source for hydration resistance can result in different Spinel formation mechanisms. It was verified, using corrosion tests in both laboratory and industrial scaled crucible induction furnaces, that the speed of Spinel formation and its final distribution in the lining may allow an increase in corrosion resistance of 25 % in the lining life.