Effect of lanthanum on inclusions in non-oriented electrical steel slabs

The effect of lanthanum on the characteristics of inclusions in the slab of non-oriented electrical steels was investigated through industrial trials and thermodynamic analysis.The number,size,and chemical composition of inclusions in the surface,one-quarter of thickness and the center of slabs with and without lanthanum addition were statistically analyzed using an automatic inclusion analysis system.In the lanthanum-free slab,inclusions were predominately MgO.Al_(2)O_(3),MgO,and AlN as well as a small number of Al_(2)O_(3)-MgO-CaO and MgS.The number densities of oxide inclusions and AlN decreased from the surface to the center of the slab,which was ascribed to the difference in cooling intensity during the continuous casting.In the steel with lanthanum addition,inclusions were modified into LaAlO_(3) and La_(2)O_(2)S and gradually transformed into dual-phase MgO-La_(2)S3 with an increasing distance from the slab surface due to the reaction between the lanthanum-containing inclusion and the steel matrix.The uneven distribution of oxide inclusions along the thickness of the slab was eliminated in the lanthanum-bearing slab because the dissolved oxygen was remarkably decreased by lanthanum.Lanthanum-bearing inclusions were more likely to agglomerate AlN by inducing the heterogeneous nucleation of AlN on their surface,while small-size MgO.Al_(2)O_(3) inclusions hardly showed a coarsening effect on the size of AlN.

Effect of aluminum on secondary recrystallization texture and magnetic properties of grain-oriented silicon steel

The slab low-temperature reheating grain-oriented silicon steel was prepared in the laboratory,and the high-temperature annealing interruption tests were carried out.The effects of aluminum(which meant acid-soluble aluminum)on the grain size texture,precipitate,magnetic properties and their correlations were studied.The results showed that with the increase in aluminum element,the grain size decreased,while the intensity of{114}<481>and{111}<112>textures increased in the primary recrystallization structure.Meanwhile,the pinning force during the secondary recrystallization and the onset secondary recrystallization temperature were increased.The precipitates were concluded to have a more important role on determining the onset secondary recrystallization temperature than the primary grain size.The higher onset temperature resulted in sharper Goss texture and the better magnetic properties,but when the aluminum content came up to a certain extent,a fine-grain structure was developed.The most suitable aluminum content for present study was 0.025 wt.%,while the onset secondary recrystallization temperature and the primary texture were considered to be conducive to the sharpness of Goss texture.