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The modification mechanism of lanthanum on alumina inclusions in a nonoriented electrical steel at 1600 °C is investigated using laboratory experiments. Inclusions are analyzed using an automatic scanning electron microscope equipped with energy‐dispersive spectrum at 1, 5, 10, and 30 min after lanthanum treatment. The contents of total oxygen (TO), total sulfur (TS), and total lanthanum (TLa) in steel are analyzed. Results show that Al2O3 inclusions are modified by lanthanum in two ways. One is that the dissolved lanthanum directly reduces the aluminum in Al2O3 inclusions and forms LaAl11O18 or LaAlO3 ones. The other is that a new La2O2S or LaSx shell is preferentially generated at the outside of Al2O3 and forms multiphase inclusions. With time increasing, the La2O2S or LaSx shell gradually reacts with the Al2O3 core and generates stable lanthanum‐containing inclusions. At the initial stage of lanthanum treatment, many transient inclusions including LaSx, La2O2S, and La–P(–As) are formed due to the high concentration of lanthanum, while gradually redissolving with time increasing. With the increase in TLa content in steel, the formation sequence of stable inclusions is Al2O3 → LaAl11O18 → LaAlO3 → La2O2S → LaSx, which is consistent with thermodynamic analysis. [ABSTRACT FROM AUTHOR]

The dissolution behavior of lanthanum ferroalloy in a non-oriented electrical steel was investigated using a quartz sampler by controlling the contact time between the ferroalloy and molten steel. As the contact time increased, the network microstructure of the lanthanum was continuously destroyed and migrated towards the molten steel. The dissolved lanthanum reacted with the dissolved elements in the steel including Si, As, P and S. The formation sequence of inclusions was La-S → La-P-(As) → La-Si. [ABSTRACT FROM AUTHOR]

The effects of heating temperature (1100 °C, 1200 °C, 1300 °C, 1400 °C, 1500 °C) and heating time (15 minutes, 1, 3, 5 hours) on the transformation of LaAlO3 inclusions during the heating process in a solid non-oriented electrical steel were studied using laboratory experiments. The composition and morphology of inclusions in the steel before and after heating were analyzed using a scanning electron microscope (SEM) equipped with an energy dispersive spectrum (EDS). Steel samples with single-type LaAlO3 inclusions were prepared in molten steel at 1600 °C. When solid steel samples were heated at 1100 °C to 1400 °C for 3 hours, LaAlO3 inclusions were transformed into dual-phase Al2O3–La2S3 ones and the newly formed Al2O3 and La2S3 phases were increasingly separated with heating temperature increasing. The transformation degree reached the maximum at 1300 °C. When the sample was heated at 1500 °C, LaAl11O18 formed because dissolved oxygen reacted with dissolved aluminum and LaAlO3 inclusions. The transformation degree increased with heating time increasing at 1200 °C. Thermodynamic analysis was performed using FactSage and was consistent with observed results. A kinetic model was established to predict the composition of inclusions after the transformation of LaAlO3. [ABSTRACT FROM AUTHOR]

Industrial trials were performed to study the effect of calcium treatment on inclusions in non-oriented electrical steels. The evolution and characterization of inclusions in both molten steel and rolled steel were investigated, including a thermodynamic analysis using FactSage 7.1. In the Ca-treated steel, alumina inclusions were transformed into Al2O3-CaO-CaS, with a mass fraction of CaO that increased with increasing the Ca/S ratio. Inclusions of Al2O3-CaO-CaS were classified into wrapping and adhesion type according to their morphologies. Adhesion-type Al2O3-CaO-CaS inclusions were observed only in the steel with Ca/S > 0.84. The two types of Al2O3-CaO-CaS inclusions were transformed into Al2O3-CaS with distinctive morphologies. The mass fraction of Al2O3 and CaS in the inclusions was experimentally found to depend on the Ca/S ratio of the steel and confirmed by thermodynamic analysis. The two types of Al2O3-CaS inclusions could hardly be deformed during the hot-rolling process of the steel but showed different deformation behavior during the cold-rolling process of the steel. The component of CaS in the adhesion-type Al2O3-CaS inclusions was more easily separated from Al2O3 and formed a tail along the rolling direction of the steel, while only a little part of the CaS component broke off from the wrapping-type Al2O3-CaS inclusions. [ABSTRACT FROM AUTHOR]

The magnetic properties of electrical steels are improved with additions of silicon and aluminum; however, these elements also promote the formation of non-metallic inclusions. The presence of non-metallic inclusions in electrical steels severely affects its magnetic properties. In this work, the effect of cooling rate, superheat, and refractory composition on the formation of non-metallic inclusions has been investigated. The evolution in chemical composition has been reported using a new representation employing pseudo-quinary phase diagrams. It has been found that the concentration of MnO in the non-metallic inclusions plays a big role to control its population density. A critical value has been identified above which it is possible to achieve a large decrease in the total number of non-metallic inclusions in electrical steels, in addition to this, it was also possible to define the influence of cooling rate, superheat, and refractory chemical composition on the composition and population density of non-metallic inclusions. It was found that increasing cooling rate and a change of crucible from alumina-based to MgO-based, both increase the population density of NMI, on the contrary, superheat decreases the population density, depending on the concentration of MnO in the inclusions. [ABSTRACT FROM AUTHOR]

In this article the pinning effect of oxide particles on grain boundaries of a low aluminum non‐oriented electrical steel is studied. According to their locations and morphologies in annealed steel samples, oxide particles are classified into three types: globular ones at grain boundaries, globular ones in the interior of grains, and chain‐like ones pinning at grain boundaries. The chemical composition of oxide particles shows a significant influence on the probability pinning at grain boundaries. The elongation ratio of oxide particles becomes larger with the decrease in their viscosity that is determined by the chemical composition and temperature and is calculated using FactSage. Based on the thermodynamic analysis, small particles forming during solidification have more content of SiO2 due to the reaction between the dissolved oxygen and silicon in the steel. Particles of large size and large elongation ratio show larger pinning force on the grain growth. Removing large SiO2–Al2O3–MnO–CaO particles as far as possible, and controlling the composition of oxide particles to achieve larger viscosity than the steel matrix, will retard their elongation during the hot‐rolling process so that the magnetic properties of the steel are improved. [ABSTRACT FROM AUTHOR]

A plant experiment is conducted to study the effect of oxide inclusions on the magnetic properties of non‐oriented electrical steel. The morphology, size, and composition of oxide inclusions are investigated by an automated scanning electron microscope. In the liquid steel, the increase of the content of CaO in oxide inclusions promotes the inclusion size and decreases the width of the size distribution. Besides, the viscosity of oxide inclusions plays a key role on the deformation during the hot rolling process at 1000 °C. When the viscosity of inclusions is larger than that of the steel matrix, the oxide inclusions are nearly undeformed. While when the viscosity of inclusions is lower than that of the steel matrix, the inclusions are deformed into chain‐like shape and the elongation ratio increases with the decreasing of viscosity. Additionally, deformed oxide inclusions perform a greater pinning force on the moving of grain boundaries, which is verified by the measured results of the grain size. Thus, in terms of increasing the magnetic properties, the viscosity of oxide inclusions shall be controlled to larger than that of the steel matrix by adjusting the inclusion composition. This research focuses on the effect of oxide inclusions on the non‐oriented electrical steel deoxidized by silicon alloy. The increase of the CaO content in inclusions reduces the viscosity of inclusions. When the viscosity of inclusions is lower than that of the steel matrix, inclusions can be deformed and fractured during the hot rolling process, leading to a larger pinning effect on the grain growth and worse magnetic properties of final products. [ABSTRACT FROM AUTHOR]

• Both micro-sized inclusions and fine precipitates were statistically analyzed. • Proper La addition reduced inclusions, and enhanced grain size and texture factors. • The steel with 0.0006 wt% La possessed the best magnetic properties. • Excess rare earth sulfides deteriorated grain size and textures of steels. The effect of rare earth elements (REMs) on the magnetic properties of non-oriented electrical steels was studied using industrial trials. The variation of the magnetic properties was discussed in terms of the effect of inclusions, precipitates, grain size, and textures in the steel with and without REMs. Inclusions of MgO·Al 2 O 3 -CaS and (Mg, Mn, Ca)S in REMs-free steel were modified into composite ones of MgO·Al 2 O 3 -LaAlO 3 , La 2 O 2 S-MgO and (La, Ca)S in the steel with 0.0006% lanthanum, and to (La, Ce) 2 O 2 S-CaS-MgO, (Ce, La)S in the steel with 0.0007% lanthanum and 0.0015% cerium. The number density of fine MnS was remarkably decreased by the addition of REMs, leading to an increase in the average grain size. The steel containing 0.0006 wt% lanthanum possessed the best combination of core loss and magnetic induction due to the decrease of micro-sized inclusions and fine MnS, the increase of grain size, and the optimization of recrystallization textures. For the steel with excess REMs addition, the large number density of rare earth sulfides with the size of approximately 1 μm tended to deteriorate the grain size and textures. [ABSTRACT FROM AUTHOR]

• Calcium treatment inhibits (Mn,Cu)S precipitates and increases grain size. • Calcium treatment decreases the core loss of final products. • Inclusions of Al 2 O 3 -CaS-(CaO) deteriorates magnetic induction. The effect of calcium treatment on magnetic properties of non-oriented electrical steels was studied. Inclusions, precipitates, grain size and textures of final annealed sheets were analyzed and their effects on magnetic properties of the steel were discussed. Inclusions varied from Al 2 O 3 -MnS to Al 2 O 3 -CaS-(CaO) due to the reaction of calcium and sulfur after calcium treatment. The number density of (Mn,Cu)S precipitates decreased with the increasing Ca/S in the steel, which also favored to the grain growth of final products. Both of the texture factors of 100 / 111 and (100 + 110)/ 111 were increased from 0.22 and 0.34 to 0.37 and 0.50, respectively, due to the increase of the volume fraction of 100 from 8.34% to 15.80% with the increasing Ca/S from 0 to 1. The core loss decreased by 0.25 W/kg with Ca/S increasing from 0 to 1 in the steel, due to less (Mn,Cu)S precipitates and larger grain size. However, the increase in the number density of Al 2 O 3 -CaS-(CaO) inclusions caused by calcium treatment increased the volume fraction of 111 fiber textures, having a detrimental effect on the magnetic induction of the steel. Therefore, in order to improve the steel magnetic properties, inclusions of Al 2 O 3 -CaS-(CaO) formed after calcium treatment should be removed as much as possible. [ABSTRACT FROM AUTHOR]