The precise control of molten steel temperature in tundish is a key factor to ensure the quality of the cast billets, so it is important to develop permanent lining castables for tundish with low thermal conductivity and bulk density. In this work, the hydrophobic modification of pearlescent sand was carried out with hydrogen silicone oil, and 3% of modified pearlescent sand was added to mullitebauxite castable to realize its low thermal conductivity and light weight. It is found that modified pearlescent sand still has good hydrophobicity at 350 • C, the addition of modified pearlescent sand effectively increases the apparent porosity and reduces the bulk density of the castable. At 1500 • C, the bulk density of modified pearlescent sand-castable is 25.54% less than that of conventional castable.Compared with conventional castable, the mechanical properties and thermal shock resistance of modified pearlescent sand castable are worse, but they are sufficient to meet the use conditions of tundish permanent lining castable. At 600-1000 • C, the thermal conductivity of the modified pearlescent sand castable is about 30% lower than that of the conventional castable, which proves that the addition of modified pearlescent sand can significantly improve the thermal insulation performance of mullite-bauxite castable.
Bentonite is the most commonly used binder for iron ore pellets. However, due to its high alumina and silica content, the slag volume and energy consumption are increased. The aim of the present work is to identify the CSL (sodium ligninsulfonate added CaCO3) as an alternative binder in iron ore pelletization. FTIR and zeta potential tests verified that sodium ligninsulfonate (SL) reacted with magnetite mainly through ligand exchange, hydrogen bond and electrostatic interaction. Compared with SL, CSL has more active sites and stronger adsorbability. The strength of CSL preheated and roasted pellets was determined by TG and SEM. CaCO3 as a fluxing agent develops oxide bridging and bonding between the magnetite grains, forming more slag, reducing porosity and improving the compressive strength of roasted pellets. The experimental results show that it is feasible to add CaCO3 in SL as binder in pellet production.
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