PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 95 NR 7/2019 7 Marcos Flavio DE CAMPOS 1 Federal Fluminense University, Volta Redonda RJ - BRAZIL (1) doi:10.15199/48.2019.07.02 Methods for texture improvement in electrical steels Abstract. Aiming the development of high efficiency electric motors for electric vehicles, there is strong pressure for improvement of the magnetic properties of electrical steel sheets. One of the clearest possibilities is crystallographic texture enhancement. In this review, diverse methods for texture improvement are presented and discussed. All of them have the drawback of increasing the cost of material processing. Streszczenie. Materiały magnetyczne używane w pojazdach elektrycznych powinny mieć bardzo dobre właściwości. Jedną z metod ich poprawy jest polepszenie ich tekstury. W artykule przedtawiono metody poprawy tekstury oraz analizowano zalety iwady tych metod, włącznie z kosztami produkcji. Metody poprawy tekstury blach elektrotechnicznych Keywords: electrical steels, texture, rotating machines, electric car . Słowa kluczowe: blachy elektrotechniczne, tekstura, maszyny elektryczne. Introduction The autonomy of electrical cars can be increased by basically three ways: (i) batteries improvement, (ii) vehicle weight reduction (iii) increase of motor efficiency. As batteries improvement is very difficult and slow, due to need of long time tests [1], the increase of motor efficiency is the most clear alternative. Among the options for increasing motor efficiency is the texture enhancement. There are many ways for improving the texture in electrical steels. However, all of them may increase the cost of the steels. Other clear options to motor performance enhancement, from the material point-of-view, are increase of resistivity, thickness reduction [2] and materials with zero magnetostriction. This overview deals with improvement of the texture of commercial non-oriented electrical steels, and the needed materials for electric vehicles. The ideal texture for non- oriented electrical steels is {100} <0vw>. However, it should be noted that texture and the grain size [2] need to be optimized at the same time. Besides, the punching effect is very significant and can not be neglected [3,4]. The effect of plastic deformation is dominant [5,6] over the texture effect [7]. Punching can increase significantly the losses. Only with annealing and recrystallization, the plastic deformation is fully eliminated. The teeth are the region where high permeability is most necessary. Thus, the material should be free of plastic deformation, especially for applications where machine efficiency is really an issue. The recrystallization temperature of steels starts at ~500 o C [8]. This means that total elimination of plastic deformation requires annealing at such high temperatures and, besides, the coating of steel sheets should be resistant at more than 500 o C. These problems may explain why the electric motor industry avoids recrystallization annealing. However, for high efficiency motors applied in electric vehicles, the total elimination of deformation in the teeth region can be a real necessity. Another relevant issue is the anisotropy. Some steels have better properties at the rolling direction (usually due to Goss orientation {110} <001>, a recrystallization texture component). This can generate significant rotational losses [9]. The rotational losses depend strongly on sheet anisotropy [10]. The easy axis in bcc iron is <100>. This means that each bcc alpha-iron crystal has 3 easy axis: [100], [010] and [001]. The {100} planes have two easy axis direction parallel to the plane of the sheet. Goss grains have only one easy axis parallel to the plane of sheet. {111} direction does not have any easy direction parallel to the plane of the sheet. See Fig. 1 for illustration of the planes {110}, {110} and {111}. For better magnetic properties, the best plane is, thus {100}, which has 2 easy axis parallel to the sheet surface. The ideal texture {100} <0vw> indicates that the best situation is random distribution of these easy axis parallel to the sheet surface. Fig.1. Illustration showing the three main families of planes in a cubic crystal: {100}, {110}, and {111}. Note that the {100} planes are on the face of the cube Applications As can be seen in Table I, deep drawing steels for metal forming and GO (grain-oriented) electrical steels can have very optimized texture. This is possible because texture components as {111} <uvw> and Goss {110} <001> are