Effect Of Rare Earth On Inhibitor Precipitation Behavior Of Oriented Silicon Steel During Hot Rolling

The core material for manufacturing power equipment such as extra high voltage AC/DC transformers,energy efficient distribution transformers,converter valves and saturated reactors is silicon steel.The need to obtain high magnetic susceptibility and low iron loss in oriented silicon steel requires a sharp Gaussian structure with appropriate grain size.To obtain a large amount of Gaussian weave requires precise control during the hot rolling,normalization and annealing processes.The precise control of the hot rolling strip inhibiting precipitation behavior during the hot rolling process has an important impact on the organization control of the subsequent processes of the preparation of oriented silicon steel such as normalization of hot rolled sheet.In this thesis,the metallurgical characteristics of residual rare earths in smelting silicon steel by using Baiyun Ebo polymetallic co-associated ore as part of the raw material for iron making are fully considered in the composition design,simulating the residual rare earth content in Baiyun Ebo ore for experimental steel smelting,by comparing the tissue changes of two experimental steels with and without the addition of rare earths at high temperature ferrite zone after hot rolling with different holding times,using L78 quenching thermal expansion meter,Gleeble1500D,SEM,TEM,ICP and other research means.Gleeble 1500D,SEM,TEM,ICP,etc.were used to study the effect of rare earths on the recrystallization and inhibitor phase type,distribution and integral number of precipitated objects of oriented silicon steel in the ferrite zone at 1200°C after hot rolling deformation of 30%,holding time of 0s,50s,100,150s,300s and 600s.The influence of rare earths on the precipitation of inhibitor after deformation in the ferrite zone of silicon steel was analyzed.The results show that The number of sulfide-type inclusions and alumina-type inclusions in the fetching to silicon steel is less for silicate-type inclusions and more for spherical oxide-type inclusions.Observe the 200mm²field of view of the experimental steel,the total level of sulfide coarse inclusions without rare earths is 4,the total level of alumina-like inclusions is 8,the fine silicate inclusions are 14.5,the coarse inclusions are10.5,the fine spherical oxide inclusions are 5 and the coarse inclusions are 4.The experimental steel residual 43ppm La+6ppm Ce rare earth than no rare earth for the above inclusions total grade increment 75%,87.5%,34.5%,71.4%,140%,-37.5%.Rare earth residue of 73ppm La+16ppm Ce increased the above inclusions by 140%,175%,55.2%,128.6%,110%,and 100%,respectively.The residual amount of rare earth nearly doubled the relative content of the above inclusions and the residual amount of La+Ce did not change the type of inclusions in the ingots of oriented silicon steel,but reduced the fine inclusions and increased the coarse inclusions.There is no significant increase in the number of precipitates when the silicon steel is thermally deformed in the high temperature ferrite zone without static recrystallization;with the increase of holding time after thermal deformation,static recrystallization occurs in the thermally deformed silicon steel,and the inhibitor starts to precipitate and grows,the higher the recrystallization rate,the faster the growth of the number of precipitates.After the addition of rare earth lanthanum and cerium,hot rolled oriented silicon steel will reduce the amount of inhibitor precipitation,the higher the degree of static recrystallization occurs,the more obvious the effect of residual rare earth in steel.The amount of Cu₂S and Mn S in the precipitates of oriented silicon steel at the end of deformation at 1200℃is not much different,with the increase of recrystallization occurrence,the type of inhibitor precipitation remains unchanged,the amount of precipitation begins to increase,the growth rate of Cu₂S is significantly faster than Mn S.The amount of surface and heart inhibitor precipitation is different,mainly for the amount of Cu₂S precipitation changes,the most amount of precipitation on the surface of hot-rolled specimens,the least amount of the heart.