Study On The Interaction Mechanism Between MgO-based Refractories For Filtration And Inclusions In Molten Steel

The inclusions in IF steel widely used in the production of automobile panels seriously deteriorates the stamping performance and surface quality,and it's of great significance to further improve the cleanliness of IF steel.In this research,microporous MgO was used to prepare multiple pore structure filter refractory,and the mechanism of that adsorption and removal of inclusions was explored to improve the cleanliness of IF steel compared with ordinary and magnesium carbon refractory.The interaction between three kinds of refractories and Al,Ti and Ce deoxidized IF molten steel.The change of cleanliness of molten steel,the formation mechanism of the interface layer between refractories and steel,and the behavior and mechanism of adsorption of inclusions in steel were discussed to prove the mechanism and feasibility of filtering,adsorbing and removing the inclusions in IF steel by microporous MgO refractory.The main conclusions obtained are as follows:?1?The micropores of refractory aggregate can effectively improve the thermal stability and thermal shock performance of refractories.Compared with ordinary MgO and magnesium carbon refractories,microporous MgO refractory has the best mechanical properties.Analysis of the inclusion characteristics in Al,Ti and Ce deoxidized steel shows that the typical inclusions in Al deoxidized steel are individual Al₂O₃ and Al-Mn-O composite inclusions;the inclusions in Ti deoxidized steel are mainly composed of Ti-Al-O composite inclusions wrapped or inlaid together with MnO;and the inclusions in Ce deoxidized steel are mainly blank and white Ce-O+Ce-Al-Mn-O composite inclusions with larger sizes.?2?With the extension of the time?0-35 min?in Al deoxidized steel,the oxygen content with different refractories of steel first increases and then decreases.Compared with ordinary magnesium refractory,microporous MgO and magnesium-carbon refractories have less oxygen to molten steel,while magnesium-carbon refractory has more serious carbon addition to molten steel and are not suitable for the control of composition of ultra-low carbon steel.As the reaction progressed,the inclusions in the three groups of steel are changed from the original Al₂O₃-MnO inclusions to Al-Mg-Si-Mn-O composite inclusions.?3?After being immersed in Al deoxidized steel for 35 minutes,the ordinary magnesium refractory is seriously eroded by the steel liquid,and a large number of cracks and holes are distributed on the surface.The surface of the microporous MgO refractory forms a continuous magnesium aluminum spinel layer,which is mainly the reaction product of the inclusion of MgO in the refractory and Al₂O₃ in steel,and a large number of uneven Al₂O₃ inclusion particles are adsorbed on the surface.And a smooth and dense MgO layer is formed on the surface of the magnesium-carbon refractory.The formation of the magnesium aluminum spinel and the MgO isolation layer reduces the erosion and corrosion of the refractory by the molten steel,and improves the cleanliness of the molten steel to a certain extent.?4?The mechanism of Al₂O₃ inclusions absorded by microporous MgO refractory is mainly the process of adsorption inclusions,stable adhesion,and formation of isolation layer.The adsorption of Al₂O₃ inclusions in steel mainly depends on the chemical reaction of Al₂O₃ and MgO at high temperature and the van der Waals force suffered by Al₂O₃ inclusions.And the existence of micro-nano pores improves the surface roughness of the refractory to provide conditions for the stable adhesion of inclusions.?5?Microporous MgO refractory can absorb TiO_x and rare earth oxides in steels,to a certain extent,improve the cleanliness of Ti and Ce deoxidized steels,but lower than that of Al deoxidized steel.The contact between the microporous MgO refractory and Ti and Ce deoxidized steel cannot form complete and continuous high melting point interface layers,but irregular transition layers,which cannot effectively hinder the corrosion of the molten steel to the refractory and the shedding of refractory particles.The main materials of the interface layer transition layer formed by Ti and Ce deoxidized steel and refractories are Fe TiO₃-MgAl₂O₄ and CeAlO₃-MgAl₂O₄two-phase materials,respectively.