EP0401098B1 - Hot rolled magnetic steel sheet - Google Patents

Abstract

Magnetic metal sheet obtained from a hot-rolled steel strip containing especially iron, silicon and aluminium and forming part of a class of sheets with oriented grain, characterised in that its composition is the following: silicon lower than 3.3%, aluminium between 1.5 and 8%, in concentration by weight, and in that the steel strip is subjected to cold rolling in two stages with a final reduction ratio of between 50 and 80%, the magnetic sheet obtained having a general texture of cubic type, at least 40% of the grain not departing by more than 15 DEG from the ideal cubic orientation (100) [001] in Miller's notation.

Description

The subject of the present invention is a sheet metal containing in particular iron, silicon and aluminum, and forming part of a family of oriented grain sheets having a texture of cubic type, that is to say a sheet having two directions. of easy magnetization, one confused with the rolling direction, the other perpendicular to the rolling direction, in the plane of the sheet, called transverse direction.

It is known that so-called non-oriented magnetic sheets are more particularly intended for the construction of circuits supplied with alternating current, including in particular those of rotating machines of high power. For the construction of these machines, it is important to have very efficient magnetic circuits.

The stator is made up of assembled sheets and these have a degree of efficiency which is evaluated according to two parameters which are the level of induction on the one hand, and the volume losses on the other hand.

The induction is limited by the saturation magnetization of the material, and the losses include losses by hysteresis and by eddy currents. Also, it is necessary to find a compromise between materials with strong saturation magnetization and low losses.

Non-oriented silicon steel sheets currently give the best results, since the particularly strong magnetization of iron is only slightly reduced by the addition of alloying elements, going from 2.16 Tesla for pure iron to 2.0 Tesla for the 3.2% silicon alloy.

The increase in electrical resistivity due to silicon reduces losses.

• les dents, dans lesquelles l'induction est orientée suivant une direction radiale,
• le dos du stator, dans lequel l'induction est orientée suivant une direction tangentielle, et
• la région médiane, dans laquelle l'induction tourne dans le plan des tôles.

Besides the nature and composition of the material, another important study parameter is the texture. In fact, still in rotating machines, the assemblies of stator sheets are divided into sectors, the volume of which is broken down into three essential regions:

• the teeth, in which the induction is oriented in a radial direction,
• the back of the stator, in which the induction is oriented in a tangential direction, and
• the middle region, in which the induction rotates in the plane of the sheets.

The known GOSS (110) [001] or oriented grain or G.O. ill-suited to such use, since they have a marked anisotropy, and even if the GOSS texture results in a very significant improvement in the magnetic properties in the rolling direction, its advantage disappears very quickly as soon as the induction deviates from the rolling direction. By bad magnetic properties is meant not only the high specific magnetic losses, but also the fact that it is necessary to apply a large amplitude excitation field to approach the saturation magnetization in a direction different from the direction rolling, which can lead to heating of the windings by Joule effect, detrimental to the life of the machine.

This is why, except in exceptional cases, GOSS texture sheets are not used by manufacturers of rotating machines who prefer so-called non-oriented sheets, in principle without texture, or with little rolling texture. marked.

Non-oriented grain sheets, called N.O., have a low anisotropy in the rolling plane, because the grains are distributed substantially randomly, which results in a statistically isotropic behavior. But the ternary alloy constituted by Iron, Silicon and Aluminum for example, has an important magnetocrystalline anisotropy energy which tends to maintain, inside each grain, the atomic magnetic moments parallel to the quaternary axes of the crystal. This results in a distribution in domains oriented along the directions of easy magnetization of the type [100].

However, the easiest magnetization mechanisms involve the displacement of walls, called BLOCH walls, between neighboring domains. It is therefore advantageous in N.O. sheets to preferentially orient these areas in the direction of flow flow.

Non-oriented silicon steel sheets are generally classified according to their specific losses W _15/50 (losses for a _peak induction B̂ = 1.5 Tesla at 50 Hertz expressed in watts per kilogram) and their magnetic induction B₅₀₀₀, in Tesla (magnetic induction induced in an excitation field of 5000 A / m). The highest quality sheet steel listed in JIS (Japanese industry standard) C2552 (1986) is grade 35.A.230 (thickness 0.35 mm, W _15/50 ≦ 2.30 W / Kg and B₅₀₀₀ ≧ 1.60 T).

We know from French patent FR-A-2 316 338, a process for manufacturing silicon steel sheets, of the non-oriented grain type, with low losses and strong magnetic induction.

This process applies to hot-rolled silicon steel sheets containing at most 0.020% carbon, 2.5 to 3.5% silicon, 0.1 to 1.0% manganese and 0.3 to 1.5% Aluminum, the rest being iron and accidental impurities. After a cold rolling in at least two stages, with an intermediate annealing and a continuous final annealing to obtain the final thickness, the method provides that the sulfur and oxygen contents are limited respectively to at most 0.0025% and 0.005 % and that the final cold rolling has a reduction rate of between 40 and 70%. The percentages given are expressed in weight concentrations.

• pertes dans le fer W_15/50, c'est à dire en watts/kilogramme à 50Hz pour B̂ = 1,5 Tesla, sensiblement égales à 2,3 W/kg pour une épaisseur de 0,35mm.
• induction magnétique B₅₀₀₀, (c'est à dire l'induction magnétique dans un champ de 5000 A/m) de 1,70 Tesla pour une épaisseur de 0,35 mm.
• allongement relatif à la rupture mesurée en sens long : 26%.
• allongement relatif à la rupture mesurée en sens travers : 29%.

With such a composition the following results are obtained:

• losses in the iron W _15/50 , that is to say in watts / kilogram at 50Hz for B̂ = 1.5 Tesla, substantially equal to 2.3 W / kg for a thickness of 0.35mm.
• magnetic induction B₅₀₀₀, (ie magnetic induction in a field of 5000 A / m) of 1.70 Tesla for a thickness of 0.35 mm.
• elongation relative to the break measured in the long direction: 26%.
• elongation relative to the break measured in the cross direction: 29%.

These favorable characteristics are obtained after an intermediate annealing not exceeding 950 ° C. conducted in an atmosphere of dry hydrogen, followed decarburization at 825 ° C and final annealing at 1050 ° C in an atmosphere of dry hydrogen also.

A comparative test was carried out with a sample having the same composition, with identical decarburization and final annealing, but with an intermediate annealing temperature of 1050 ° C.

The losses in the iron W _15/50 and the magnetic induction B₅₀₀₀ obtained are substantially the same, but in this case, the elongation relative to the break measured in the direction of rolling is 3% and the elongation relative to the break measured in the cross direction is 10%.

These results show that with a steel sheet having the composition of FR-A-2,316,338 and with an intermediate annealing greater than 950 ° C., the sheet becomes too brittle and rolling to the final thickness becomes impossible.

It should be noted that all of the examples of FR-A-2,316,338 are described with a proportion of silicon of between 2.5% and 3.5% and a proportion of aluminum not exceeding 1.5%, the steel becoming too brittle if the percentage of aluminum exceeds this value.

It is therefore clear from this patent that the addition of aluminum, in increasing quantity, causes an increasingly marked embrittlement of the alloy.

FR-A-2 186 714 also discloses a process for manufacturing magnetic sheets with isotropic magnetic properties by hot and cold rolling of a steel. The process consists in giving a steel with 0.1% maximum of carbon, 0.15 to 0.35% of manganese, 0.3 to 2.4% of aluminum, 0.25% maximum of copper, 0 _, 05% maximum of sulfur and 0.02% maximum of phosphorus, by rolling at 820-1080 ° C, a structure of which at least 5% have an orientation (100) 〈hkl〉, to be cold rolled with a reduction in cross-section from 50 to 85% and subjecting it to recrystallization annealing at 820 to 950 ° C.

It should be noted that the steel according to FR-A-2 186 714 contains copper in a proportion at most equal to 0.25% and does not contain silicon.

The present invention therefore aims to avoid the drawbacks mentioned above while increasing the percentage of aluminum and decreasing the percentage of silicon, and to provide a magnetic sheet containing in particular iron, silicon and aluminum having a so-called cubic texture, that is to say having two directions of easy magnetization in the plane of the sheet, one confused with the direction of rolling, the other with the direction transverse, and whose magnetic properties are improved by compared to existing non-oriented iron-silicon sheets, in particular, the permeability in large amplitude excitation fields and the specific losses at industrial frequency for a peak value of the induction of 1.5 Tesla or more, all with mechanical properties comparable to those of non-oriented iron-silicon sheets in common use.

• Silicium inférieur à 3,3%
• Aluminium compris entre 1,5 et 8%
• Manganèse inférieur à 0,2%
• Somme des résidus métalliques (Nickel, Chrome, Molybdène, Titane, Cuivre) inférieur à 0,1%
• Carbone inférieur à 30.10^-4%, soufre inférieur à 20.10^-4%, azote inférieur à 20.10^-4%, phosphore inférieur à 50.10^-4%.
• le reste étant du fer,

issue du laminage à chaud, est soumise à un recuit intermédiaire effectué en continu à une température supérieure à 950°C pendant 1 à 5 minutes, le taux de réduction du laminage à froid final étant compris entre 50 et 80%, de préférence entre 60 et 75%, présente une texture de type cubique, 40% au moins des grains ne s'écartant pas de plus de 15° de l'orientation cubique idéale (100) [001] en notation de MILLER.According to the invention, the magnetic grain oriented sheet having a cubic texture (100) [001], in MILLER notation having two directions of easy magnetization, one confused with the rolling direction, the other perpendicular to said rolling direction. and obtained from a hot rolled steel strip, containing in particular iron, silicon and aluminum and subjected to two cold rolling, separated by an intermediate annealing and followed by a final annealing, is characterized in that the steel strip of the following composition by weight:

• Silicon less than 3.3%
• Aluminum between 1.5 and 8%
• Manganese less than 0.2%
• Sum of metallic residues (Nickel, Chromium, Molybdenum, Titanium, Copper) less than 0.1%
• Carbon less than 30.10 ^-4% , sulfur less than 20.10 ^-4% , nitrogen less than 20.10 ^-4% , phosphorus less than 50.10 ^-4% .
• the rest being iron,

after hot rolling, is subjected to an intermediate annealing carried out continuously at a temperature above 950 ° C for 1 to 5 minutes, the reduction rate of the final cold rolling being between 50 and 80%, preferably between 60 and 75%, has a cubic type texture, at least 40% of the grains not deviating by more than 15 ° from the ideal cubic orientation (100) [001] in MILLER notation.

• la somme des pourcentages de silicium et d'aluminium est inférieure à 9% en concentration pondérale,
• la teneur en aluminium est de préférence comprise entre 1,5 et 5% en concentration pondérale,
• le recuit final est effectué en continu à une température comprise entre 950° et 1100°C pendant 1 à 5 minutes,
• le recuit final est effectué en statique à une température comprise entre 1000° et 1100°C pendant 1 à 5 heures.

According to other characteristics,

• the sum of the percentages of silicon and aluminum is less than 9% by weight concentration,
• the aluminum content is preferably between 1.5 and 5% by weight concentration,
• the final annealing is carried out continuously at a temperature between 950 ° and 1100 ° C for 1 to 5 minutes,
• final annealing is carried out statically at a temperature between 1000 ° and 1100 ° C for 1 to 5 hours.

une valeur supérieure à 0,70.The magnetic sheet according to the invention containing in particular iron, silicon and aluminum is characterized in that the cubic texture has characteristics of magnetocrystalline anisotropy which, measured according to the method of torsional balance, have for large maximum (M₁) and the small maximum (m₂) of values greater than 8000 and 5600 J / m³ and for the anisotropy coefficient $\text{ρ = m₂ / M₁}$

a value greater than 0.70.

The magnetic sheet according to the invention is further characterized in that the directions of easy magnetization are the rolling direction and the direction perpendicular to the rolling in the plane of the sheet.

• la Fig. 1 représente l'évolution des maxima m₂, M₁ du couple d'anisotropie mesurés à l'épaisseur intermédiaire après un premier laminage à froid et un recuit, en fonction de l'épaisseur intermédiaire.
• la Fig. 2 représente l'évolution des pertes à 1T-50Hz en fonction de la température du recuit final pour l'épaisseur de 0,35mm.
• la Fig. 3 représente l'évolution des pertes à 1,5 T-50Hz en fonction de la température du recuit final pour l'épaisseur de 0,35 mm.
• la Fig. 4 représente l'évolution des inductions B₈₀₀ et B₂₅₀₀ pour les champs d'excitation de 800A/m et 2500 A/m en fonction de la température du traitement final.

The tests described below with regard to attached drawings determine the characteristics of the magnetic sheet according to the invention.

• Fig. 1 represents the evolution of the maxima m₂, M₁ of the anisotropy couple measured at the intermediate thickness after a first cold rolling and annealing, as a function of the intermediate thickness.
• Fig. 2 represents the evolution of the losses at 1T-50Hz as a function of the temperature of the final annealing for the thickness of 0.35mm.
• Fig. 3 represents the evolution of the losses at 1.5 T-50 Hz as a function of the temperature of the final annealing for the thickness of 0.35 mm.
• Fig. 4 represents the evolution of the inductions B₈₀₀ and B₂₅₀₀ for the excitation fields of 800A / m and 2500 A / m as a function of the temperature of the final treatment.

The various stages of the manufacturing cycle have more or less marked influences on the characteristics of the sheet obtained, in particular the texture, the losses, the induction, as will be described with the aid of several examples.

Tests were carried out to verify the influence of the initial solidification texture of the ingot of the base steel on the final texture of the sheet.

Two forms of ingot molds were used, one of rectangular shape, the other of cylindrical shape.

These shapes simulate the phenomena likely to occur during solidification, one in continuous casting and the other by ingot.

An analysis of textures by technique corrosion figures show that the two ingots do not have a particularly marked solidification texture. The sheets obtained from the two ingots of different shapes have very similar magnetic properties and also similar grain sizes, initial shape of the ingot has no significant consequence on the texture of the sheets which results after the heat treatment.

• Décapage,
• 1er laminage à froid à l'épaisseur de 1 mm,
• Recuit intermédiaire en continu à 1020°C durant 2mn,
• 2ème laminage à froid à l'épaisseur de 0,35 mm,
• Recuit final statique à 1050°C durant 3 heures.

The ingot of the base steel is subjected to hot rolling to obtain a steel sheet with a thickness of approximately 2.5 mm. The treatment cycle for the hot rolled steel strip according to the invention is as follows

• Stripping,
• 1st cold rolling to the thickness of 1 mm,
• Intermediate annealing continuously at 1020 ° C for 2 minutes,
• 2nd cold rolling to the thickness of 0.35 mm,
• Final static annealing at 1050 ° C for 3 hours.

• a - par analyse chimique,
• b - par mesure optique pour la détermination de la dimension des grains,
• c - par la mesure des pertes magnétiques,
• d - par la mesure du couple d'anisotropie.

The characteristics of the samples are measured:

• a - by chemical analysis,
• b - by optical measurement to determine the grain size,
• c - by measuring the magnetic losses,
• d - by measuring the anisotropy torque.

The anisotropy torque is measured by means of a torsion balance. The principle of measurement is as follows:
After identifying the rolling direction, a disc with a diameter of approximately 15 mm is punched out of the sheet. This disc is then placed on a horizontal support, mobile around a vertical axis, and an external magnetic field saturates the sample in a variable direction of the horizontal plane identified by the angle made by the magnetization with the direction of rolling. In the presence of a volumetric anisotropy energy, the sample disc is subjected to a torque, which tends to align the magnetization of the disc in one of the preferred directions known as easy magnetization.

The measurement consists in varying the angle made by the magnetization with the rolling direction and in recording the mechanical torque which must be exerted on the disc to keep it fixed.

qui tend vers 1 dans le cas d'une anisotropie idéale, alors que la qualité de la texture cubique est d'autant meilleure que M₁ et m₂ sont plus élevés.The module of the torque as a function of the angle made by the magnetization with the rolling direction has substantially a sinusoidal shape having two successive different maxima M₁ and m₂ where M₁ is the large maximum and m₂ the small maximum, the anisotropy being characterized by report

which tends towards 1 in the case of an ideal anisotropy, while the quality of the cubic texture is all the better as M₁ and m₂ are higher.

The treatment cycle of the hot rolled steel strip includes two cold rolls and the determination of the influence of the reduction rates during these rollings is important to characterize the evolution of the texture. The measurement of the anisotropy torque is a parameter that allows us to appreciate this evolution.

The hot rolled steel strip is reduced after a first cold rolling to an intermediate thickness varying from 0.7 mm to 2 mm.

The study of the magnetocrystalline anisotropy couple after the first intermediate annealing makes it possible to know the direction or directions of easy magnetization, and the modifications of the anisotropy torque curve make it possible to identify the modifications of texture.

Table 1 presents the results of the measurements of anisotropy couples obtained on the strip reduced to the indicated thickness, of a steel according to the invention of composition Si, 1.92%, Al 1.86%.

These results show that for a suitable first cold rolling rate, certain samples have a cubic texture with two well marked easy magnetization directions respectively parallel and perpendicular to the rolling direction.

The variations of m₂ and M₁, and the measured value of ρ as a function of the intermediate thickness, shown in Figure 1, show that the texture is not very sensitive to the variation of the intermediate thickness between 0.7 and 1.5 mm, but degrades outside these limits.

The final texture can be influenced by the intermediate annealing of the manufacturing cycle according to the invention in particular by the atmosphere during this heat treatment.

The intermediate annealing to a thickness of 1 mm is carried out in a dry atmosphere of purified hydrogen, then by varying the oxygen level.

Table II summarizes the results obtained at the intermediate stage 1 mm and at the final stage 0.35 mm, for small and large maxima, as well as the corresponding anisotropy coefficients, the composition of the steel being Si 1.92%, Al 1.86%.

The values of ρ being higher after heat treatments in a dry atmosphere, it is deduced therefrom that the use of a humid atmosphere is less favorable than a dry atmosphere for obtaining a cubic texture.

The role of the final annealing is important since the annealing must repair the defects introduced by the second cold rolling and, moreover, the sheet resulting from this final annealing is directly used. The characteristics after the final annealing are therefore the final characteristics.

Two series of tests made it possible to study the characteristics of the sheets obtained after static final annealing, depending on the one hand on the variation of the temperature used of the final annealing in static and on the other hand as a function of holding time temperature.

The anisotropy torque measurements are indicated in Table III for the thickness of 0.35 mm, depending on the temperature of the final annealing.

The heat treatment temperature has no significant influence on the anisotropy curves, on the other hand the study of the magnetic losses measured respectively at two induction values of 1 Tesla and 1.5 Tesla as shown in the figures 2 and 3 shows a harmful increase in said magnetic losses, above a final annealing temperature of 1050 ° C. and below 950 ° C.

Likewise, the magnetization values as a function of the final annealing temperatures (for an annealing duration equal to 1 hour) shown in FIG. 4 show a reduction in the magnetization when the temperature of the final annealing increases.

The study of magnetic losses and magnetization makes it possible to determine a favorable temperature range for the final annealing, between 1000 ° and 1100 ° C.

The anisotropy measurements as a function of the duration of the final annealing at 1000 ° C. are collated in Table IV below. TABLE IV Duration of final static annealing M₁ (J / m³) m₂ (J / m³) ρ 1 hr 8,500 6,400 0.75 2 hrs 8,000 6,700 0.83 4 hrs 8,600 6,400 0.74 8 a.m. 8,200 6,900 0.84 32 h 8,100 6,200 0.76

The duration of the final annealing does not affect the value of the anisotropy beyond a certain stage, since the grains reach a size such that they pass through the sheet and their growth stops. From this state, the texture no longer changes.

Intermediate annealing can be carried out continuously at a temperature above 950 ° C for 1 to 5 minutes, and final annealing at a temperature between 950 ° and 1100 ° C also for 1 to 5 minutes.

Among the impurities that are inevitably found in the alloys used for the manufacture of magnetic iron - silicon - aluminum sheets, the four elements sulfur, carbon, oxygen and nitrogen cause deterioration in the magnetic characteristics.

The following two examples show the influence of these elements on the anisotropy.

• silicium inférieur à 3,3% de préférence inférieur à 2,5%
• aluminium compris entre 1,5 et 8% de préférence compris entre 1,5 et 5% en concentration pondérale tel que la somme des pourcentages de silicium et d'aluminium ne dépasse pas 9% en concentration pondérale.

The treatment of steel sheets containing silicon and aluminum in the following proportions:

• silicon less than 3.3% preferably less than 2.5%
• aluminum between 1.5 and 8% preferably between 1.5 and 5% by weight concentration such that the sum of the percentages of silicon and aluminum does not exceed 9% by weight concentration.

• un laminage à chaud
• un décapage
• un premier laminage à froid
• un recuit intermédiaire
• un deuxième laminage à froid
• un recuit final

permet d'obtenir une tôle ayant une texture générale de type cubique, 40% au moins des grains ne s'écartant pas de plus de 15° de l'orientation cubique idéale (100) [001] en notation de MILLER.This treatment comprising the following stages:

• hot rolling
• pickling
• a first cold rolling
• an intermediate annealing
• a second cold rolling
• final annealing

makes it possible to obtain a sheet having a general cubic type texture, at least 40% of the grains not deviating by more than 15 ° from the ideal cubic orientation (100) [001] in MILLER notation.

In Example 1, the composition of the steel is given in Table V. TABLE V % in weight in ppm 10⁻⁴% Yes Al VS S O NOT Mn Cu Co Or 1.88 1.80 50 3 19 17 20 50 50 50

The samples are produced from a hot-rolled sheet reduced to an intermediate thickness of 1 mm, then annealed under H₂ for 2 min at a temperature of 1020 ° C.

   L'anisotropie de la tôle est peu marquée, mais présente déjà une structure cubique, le rapport des maxima étant ρ = 0,85.The characteristic values of the measurement of the anisotropy torque are then: $$\text{M₁ = 5000 J / m³ m₂ = 4300J / m³ ρ = 0.85}$$

The anisotropy of the sheet is not very marked, but already has a cubic structure, the ratio of the maxima being ρ = 0.85.

Cold rolling is then carried out to obtain samples 0.35 mm thick which are subjected to annealing under H₂ for 3 hours at 1050 ° C.

• pertes à 1 Tesla - 50 Hz = 0,80 w/kg
• pertes à 1,5 Tesla - 50 Hz = 2,00 w/kg
• induction pour un champ continu
     de 800 A/m : 1,50 T
     de 2500 A/m : 2,63 T
• M₁ = 9000 J/m³
• m₂ = 6800 J/m³
• ρ = 0,76

   Le matériau obtenu au stade final est fortement anisotrope. Il présente une texture marquée, également d'allure cubique ( ρ = 0,76). Il est à noter, dans ce cas, que la texture obtenue équivaut à un mélange comprenant 46% d'une texture (100) [001] pure, le reste du matériau étant parfaitement isotrope. Que ce soit au stade intermédiaire, ou au stade final, la direction de laminage et la direction perpendiculaire à la direction de laminage peuvent être considérées comme des directions de facile aimantation.The sheet obtained can be characterized by the following results:

• losses at 1 Tesla - 50 Hz = 0.80 w / kg
• losses at 1.5 Tesla - 50 Hz = 2.00 w / kg
• induction for a continuous field
  from 800 A / m: 1.50 T
  from 2500 A / m: 2.63 T
• M₁ = 9000 J / m³
• m₂ = 6800 J / m³
• ρ = 0.76

The material obtained in the final stage is strongly anisotropic. It has a marked texture, also cubic in appearance (ρ = 0.76). It should be noted, in this case, that the texture obtained is equivalent to a mixture comprising 46% of a pure texture (100) [001], the rest of the material being perfectly isotropic. Whether at the intermediate stage or at the final stage, the rolling direction and the direction perpendicular to the rolling direction can be considered as directions of easy magnetization.

In Example 2, the composition of the steel is given by the following Table VI: TABLE VI % in weight 10⁻⁴% Yes Al VS S O NOT Mn Cu Co Or Cr 1.86 1.81 40 2 11 1 50 50 60 30 20

The procedure for obtaining the samples remains identical to that described in Example 1.

   Dans ce deuxième exemple, nous avons obtenu un pourcentage de texture cubique plus important que dans l'exemple 1 et nous pouvons remarquer qu'aussi bien les caractéristiques de pertes et que celles de l'aimantation sont améliorées.The characteristic values of the anisotropy couple and the magnetic losses are in this case: $$\begin{array}{c}\begin{array}{c}\text{M₁ = 10200 J / m³ m₂ = 8300 J / m³ ρ = 0.81}\\ \text{losses at 1 Tesla-50Hz = 0.76 w / Kg}\\ \text{losses at 1.5 Tesla-50Hz = 1.74 w / Kg}\\ \text{B₈₀₀ = 1.52 T B₂₅₀₀ = 1.64 T}\end{array}\end{array}$$

In this second example, we have obtained a higher percentage of cubic texture than in Example 1 and we can notice that both the loss characteristics and those of the magnetization are improved.

The present invention provides an improvement in magnetic properties compared to existing non-oriented iron-silicon sheets, while having mechanical properties comparable to those of non-oriented iron-silicon sheets in common use.

Claims (6)

1. Lamination having oriented grains with a cubic texture (100) [001], in Miller notation, having two easy magnetization directions, one coinciding with the rolling direction and the other perpendicular to said rolling direction and obtained from a hot rolled steel strip, containing in particular iron, silicon and aluminium and subject to two cold rolling operations, separated by an intermediate annealing and followed by a final annealing, characterized in that the steel strip with the following composition by weight:-
      silicon below 3.3%,
      aluminum between 1.5% and 8%,
      manganese below 0.2%,
      sum of the metallic residues (nickel, chromium, molybdenum, titanium, copper) below 0.1%,
      carbon below 30.10⁻⁴%, sulphur below 20.10⁻⁴%, nitrogen below 20.10⁻⁴%,
      oxygen below 20.10⁻⁴%, phosphorus below 50.10⁻⁴%,
      the remainder being iron,
   obtained from the hot rolling process, undergoes an intermediate annealing performed continuously at a temperature above 950°C to 1 to 5 minutes, the final cold rolling reduction rate being between 50 and 80%, preferably between 60 and 75%, has a cubic texture, at least 40% of the grains not differing by more than 15° from the ideal cubic orientation (100) [001] in Miller notation.
2. Lamination according to Claim 1, characterized in that the sum of the silicon and aluminium percentages is below 9% in weight concentration.
3. Lamination according to Claims 1 and 2, characterized in that the aluminium content is preferably between 1.5 and 5% in weight concentration.
4. Lamination according to any one of the Claims 1 to 3, characterized in that the final annealing is performed continuously at a temperature between 950 and 1100°C for 1 to 5 minutes.
5. Lamination according to any one of the Claims 1 to 3, characterized in that the final annealing is performed under static conditions at a temperature between 1000 and 1100°C for 1 to 5 hours.
6. Lamination according to any one of the Claims 1 to 5, characterized in that the cubic texture has magnetocrystalline anisotropy characteristics which, measured according to the torsion balance method, have for the large maximum (M1) and the small maximum (m2) values exceeding 8000 and 5600 d/m³ and for the anisotropy concentration $\text{ρ= m2/M1}$

   

   a value exceeding 0.70.

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