Investgation On The Damage Process And Its Influencing Factors Of Corundum-spinel Ladle Castables By Induction Furnace Rotary Dipping Method

With the continuous improvement of the quality of clean steel,the type of ladle lining refractories,the service performance and the impact on non-metallic inclusions in clean steel,which are in direct contact with molten steel or molten slag,have become increasingly important.At present,the use of corundum-spinel castables as the lining material for large ladle is common.In order to extend its service life,reduce the cost of clean steel smelting,and ensure the long-term safe operation of the ladle,the dynamic damage process of the corundum-spinel ladle castable is studied.And its influencing factors are all the more urgent.In this paper,corundum-spinel castables for clean steel refining ladle liners are the main research objects,and the static qualitative research of the traditional laboratory is turned into dynamic quantitative research.The dynamic damage rate and its law of change of corundum-spinel castables were studied by induction furnace rotary dipping.The influences of various factors such as time,temperature,rotating speed,number of thermal shocks,and different operating modes on the dynamic damage process of corundum-spinel castables were investigated.The effect of corundum-spinel castable specimen damage on inclusions in steel was studied.Orthogonal experimental design of major influencing factors,The effect of three factors and three levels on the damage rate of corundum-spinel castables was analyzed.The experimental results are as follows:?1?When the induction furnace rotary dipping experiment is performed,the fixed temperature is 1600°C.,the rotation speed is 60 r/min,and the number of times of thermal shock is 0,and the operation mode is uninterrupted.With the passage of time?0.5 to 9 hours?,the damage index of the corundum-spinel castable sample impregnation lower part gradually increased?25%to 70%?,and the damage index was positively correlated with time.The dynamic damage rate of the lower part of the sample is gradually reduced,and the initial damage rate is the largest,close to 50%,and eventually approaches zero.The damage rate of the sample at the three-phase interfacedecreasedfirstandthenincreased,andthendecreased?81%?6%?28%?8%?.The damage rate at the three-phase interface of the sample is greater than the destruction rate at the bottom of the sample impregnation.The dynamic damage index at the three-phase interface of the specimen is about 1.5 times the index of the lower part of the specimen impregnation.?2?When the fixed immersion time,rotating speed,number of thermal shocks,and operation mode are unchanged,Corrosion rate of corundum-spinel castable specimens in the lower part of the impregnation with the temperature decreased first and then increased?17%?13%?18%?.The lowest at 1700°C,the damage rate is about13%,the highest at 1800°C,and the damage rate is about 18%.When the fixed temperature,time,operation method,and thermal shock frequency are constant,The effect of different rotation speeds on the damage rate of the sample impregnation lower part is not significant.Regardless of whether it is intermittent operation or uninterrupted operation,the destruction rate of the lower part of the sample is gradually reduced.The maximum destruction rate of the lower part of the sample during the intermittent operation was 31%,Non-disruptive maximum damage rate is 16%.With the increase in the number of thermal shocks,the damage index of the sample under the immersion gradually increased?45%?100%?,However,the increase in the damage index?34%?12%?6%?3%?0%?has gradually decreased in proportion.The destruction rate of the lower part of the sample impregnation shows a trend of increasing first and then decreasing with the increase of the number of thermal shocks?11%?32%?15%?.?3?Through the three factors and three levels of orthogonal test analysis,The factor that most affected the damage of the corundum-spinel castables was the number of thermal shocks?B?,followed by the temperature factor?A?,and the influence of the operation method?C?was the smallest.The maximum factor combination for the damage of the sample was B3A1C2.?4?In the process of corundum-spinel castable specimens being damaged,the number of inclusions in the steel gradually increased with the extension of smelting time,and there was a tendency for aggregation to grow.Inclusions in steel gradually increase in size,and they will grow and gather in a certain period.The maximum diameter of the inclusions increases from 3?m to 55?m.After the sample is impregnated for 8h,the maximum diameter of inclusions in the steel increases to 52?m.The shape of the inclusions in the steel is irregularly spherical and the inclusions are Al₂O₃-SiO₂-FeO-CaO system.?5?The macroscopic observation,XRD and SEM analysis of the sample show that:The damage process of corundum-spinel castable specimens in the lower part of the impregnation is firstly the thermal stress of the specimens.The weakest area?corundum aggregate and matrix contact surface?generates micro-cracks,which extend from the micro-cracks to the main cracks,and the main cracks further increase,due to high temperature and thermal shock,in addition to steel slag infiltration,molten steel mechanical erosion and abrasion,resulting in Structural peeling.The damage of the lower part of the sample impregnation is divided into three broken belts,namely the metamorphic layer,the gradient layer and the original brick layer.Within the metamorphic layer there is an enrichment zone containing elements of Ca and Si.The typical thickness of the metamorphic layer is 109?m.There are cracks and holes inside the sample,and the molten steel and slag penetrate into it.The crack length is 3318?m.Molten steel and steel slag penetrate into the castable sample and chemically react with the corundum-spinel castable sample to produce Ca₃Mg?SiO₄?₂,Fe₁₆Mg₈O₃₂,and Ca₂Fe₂O₅ compounds.In this work,the dynamic damage rate of corundum-spinel castables was studied by induction furnace rotary dipping.The changing process of the dynamic damage of the sample and its influencing factors are discussed.The results of the study can reflect the actual operation of the lining refractory in a certain extent.It can provide practical guidance for reducing the consumption of refractory materials,increasing the service life of ladle and safe operation of ladle.