DE10253339B3 - Process for producing a hot strip, hot strip and non-grain-oriented electrical sheet made from it for processing into non-grain-oriented electrical steel - Google Patents

Abstract

The invention relates to a hot strip which is particularly suitable for the production of non-grain-oriented electrical steel with improved electromagnetic properties. This is achieved by the hot strip being made from a steel which (in mass%) C: 0.010%, Si: 1.0-1.5%, Al: <0.4%, with Si + 2 Al 1, 85%, Mn: 0.5%, Cu: <0.05%, Ti: <0.01%, P: 0.1%, Sn: <0.15%, Sb: <0.15%, optional S, O and N, the sum of the contents of these elements being 0.02%, and the remainder containing iron and unavoidable impurities, and that the hot strip has largely been eliminated in such a way that the excretions present on average have a particle size of at least 300 nm. Furthermore, the invention relates to a cold-rolled and finally annealed non-grain-oriented electrical steel strip produced from a hot strip according to the invention. In addition, the invention relates to a method for hot strip production of the electrical steel strip according to the invention.

Description

The invention relates to a method to make one for determine the processing into non-grain-oriented electrical steel Hot strip. About that In addition, the invention relates to a for the production of non-grain-oriented Electrical steel specific hot strip and a non-grain oriented produced from it Electrical steel.

Under the term "non-grain oriented Electrical sheet " here under DIN EN 10106 ("final annealed electrical sheet") and DIN EN 10165 ("not finally annealed electrical sheet") falling products Roger that. About that also become stronger anisotropic grades are included as long as they are not grain-oriented electrical sheets be valid. In this respect, the terms "steel strip for electromagnetic Purposes "and" sheet steel for electromagnetic Purposes "as well as" electrical steel "and" electrical sheet "are used synonymously.

"J ₂₅₀₀ " hereinafter denotes the magnetic polarization at a magnetic field strength of 2500 A / m and a frequency of 50 Hz. "P _1.5 " is the magnetic loss at a polarization of 1.5 T and a frequency of 50 Hz Roger that.

From the manufacturing industry the demand is made, not grain-oriented electrical sheets to disposal in which the magnetic polarization values compared to conventional Electric sheets are not only raised, but also with them improved loss values are realized. A decrease in values The magnetic loss is always advantageous when the total loss of electrical, based on electrical sheets of the in question Art electrical machines lowered and associated with it the efficiency of these machines is to be improved.

By increasing the magnetic polarization will the for the equivalent Magnetization required field requirements reduced. In all use cases, in which the structure of the magnetic field based on an electrical Excitation occurs in this way, in addition to iron losses especially lower the copper losses, so as a result as well improved efficiency is achieved.

• – Erschmelzen des Stahls,
• – Vergießen des Stahls zu Brammen oder Dünnbrammen,
• – soweit erforderlich, Wiedererwärmen der Brammen oder Dünnbrammen,
• – Einsetzen der Brammen oder Dünnbrammen in eine Warmwalzstraße,
• – Vorwalzen der Brammen oder Dünnbrammen,
• – Fertigwarmwalzen der Brammen oder Dünnbrammen zu einem Warmband, dessen Enddicke typischerweise zwischen 2 mm und 3 mm liegt,
• – soweit erforderlich Glühen und Beizen des Warmbands, wobei diese Warmbandbehandlungen als kombiniertes Glühbeizen ausgeführt werden können,
• – ein- oder mehrstufig mit zwischengeschalteter Glühung erfolgendes Kaltwalzen des Warmbands zu einem Kaltband, und
• – Schlussglühen solcher Kaltbänder, die mit einem > 65 betragenden Gesamtumformgrad kaltgewalzt worden sind, oder
• – Glühen und Nachwalzen solcher Kaltbänder, die mit einem höchstens 20% betragenden Gesamtumformgrad kalt nachgewalzt worden sind.

The production of non-grain-oriented electrical steel (NO electrical steel) usually comprises the following steps:

• Melting the steel,
• - casting the steel into slabs or thin slabs,
• - if necessary, reheating the slabs or thin slabs,
• - inserting the slabs or thin slabs into a hot rolling mill,
• - rolling the slabs or thin slabs,
• Finish hot rolling the slabs or thin slabs into a hot strip, the final thickness of which is typically between 2 mm and 3 mm,
• - if necessary, annealing and pickling of the hot strip, whereby these hot strip treatments can be carried out as combined annealing,
• - Single or multi-stage with intermediate annealing cold rolling of the hot strip into a cold strip, and
• - final annealing of cold strips that have been cold-rolled with a total forming degree of> 65, or
• - Annealing and re-rolling of such cold strips, which have been cold-rolled with a maximum degree of total deformation of 20%.

The large number of such conventional ones Procedure to be carried out Work steps leads to high expenditure on equipment and costs. Therefore, has been younger Time increased worked on shedding of the steel and the subsequent ones Coordinating rolling processes in hot strip production so that a continuous succession of the casting and rolling process under Saving reheating and pre-rolling with an optimal work result.

So-called "CSP plants" have been set up for this purpose. In these devices, which are also called "casting and rolling plants" the steel is cast into a continuously drawn strand, of the "in-line" thin slab be divided, which are then also hot rolled "in-line" to hot strip. The in the operation of casting and rolling systems Experience gained and the advantages of "in-line" casting-rolling are, for example in W. Bald et al. "Innovative Band Production Technology ", Stahl und Eisen 119 (1999) No. 3, pages 77-85, or C. Hendricks et al. "Commissioning and first results of the casting and rolling plant Thyssen Krupp Stahl AG ", Stahl und Eisen 120 (2000) No. 2, pages 61-68.

In addition to the prior art explained above, the DE 100 15 691 C1 a method for the cost-effective production of non-grain-oriented electrical sheet with good magnetic properties is known. In this process, a steel strip cast from the casting heat, which (in mass%) 0.0001 to 0.05% C, not more than 1.5% Si, not more than 0.5% Al, the sum of the Si content and twice the Al content not greater than 1.8, 0 , 1 to 1.2% Mn and the balance iron and unavoidable impurities, is rolled directly into a hot strip. The rolling conditions are chosen so that the ferrite transformation is not completed by the end of the rolling and at least the last rolling pass is carried out in the austenite / ferrite area. According to an embodiment variant of the known method, the hot strip obtained is coiled at a temperature of at least 700 ° C. in order to positively influence grain size, texture and precipitations.

The invention was based on the object to create a hot strip, which can be produced in a special way of high quality non grain oriented electrical steel. Furthermore should a non grain oriented electrical sheet be developed, the opposite superior to the electrical sheets known from the prior art has magnetic properties. Finally, there should be a procedure be specified, with which a preliminary product for a not grain-oriented electrical sheet or strip can be produced that across from the prior art further improved magnetic properties has.

With regard to the preliminary product this task through a hot strip for the production of non-grain oriented Electrical steel loosened, where the hot strip is made of steel with (in mass%) C: ≤ 0.010%, Si: 1.0-1.5 %, Al: <0.4%, with Si + 2Al ≤ 1.85 %, Mn: ≤ 0.5 %, Cu: <0.05%, Ti: <0.01%, P: <0.1%, Sn: <0.15%, Sb: <0.15%, optional S, O and N, where the sum of the contents of these elements is ≤ 0.02%, and the balance is iron and unavoidable impurities and extensive excretion takes place in the hot strip in this way is that the existing excretions have an average particle size of at least Own 300 nm. The size of the particles should preferably be distributed so that among the existing ones Excretions the proportion of excretions with particle sizes of 50 to 190 nm is reduced to small traces. To do this, the Particle size of the excretions for the most part Part more than 300 nm.

The invention is based on knowledge that significantly improved magnetic properties Set electrical sheets with silicon and aluminum contents of the order of magnitude selected according to the invention leave, if the formation of excretions is controlled in such a way that the number of fine excretions is reduced to a minimum. Surprised has been shown that the formation of as possible few and at the same time if possible huge Excretions with particle sizes of more than 300 nm directed procedure of the structural and Elimination state of the hot strip according to the invention designed so is that this is cheap Elimination characteristics of the hot strip over the for the production of the usually manufacture electrical steel further steps to complete the product inherited with the result that an end product with excellent magnetic Properties is obtained.

The structure of the finished not grain-oriented Electrical steel is due to the excretion state set according to the invention of the hot strip over the entire strip thickness is particularly homogeneous, since there are no minor excretions are more present, the emergence of such a homogeneous structure could interfere with the further processing of the hot strip according to the invention. Accordingly lie the good values of polarization and magnetic losses of electrical sheet according to the invention also particularly evenly distributed in front.

With regard to the non-grain-oriented electrical steel sheet, the above-mentioned object is achieved by a cold-rolled and finally annealed non-grain-oriented electrical steel sheet, which is produced from a hot strip obtained according to the invention and has a final thickness of up to 0.75 mm and polarization values J ₂₅₀₀ which are suitable for a Electrical steel 0.50 mm thick at 50 Hz and magnetic reversal losses P _1.5 of 4.4 W / kg to 5 W / kg at least 1.65 T and at 50 Hz and magnetic reversal losses P _1.5 of less 4.4 W / kg be at least 1.67 T.

This is caused by the excretion state inherited from the hot strip and the resulting grain size distribution of the structure. This leads to average grain diameters D _{K of} the finished electrical steel strip from 50 μm to 80 μm with a median value of 35 μm to 65 μm. At the same time, 90% of the structural grains, when considering their percentage total frequency distribution (SHV), fulfill the condition: 1.3 * D K - 30 μm <SHV <1.3 * D K + 15 μm.

Electrical sheet according to the invention with these microstructural properties points to conventional produced non-grain-oriented electrical sheet of the same composition significantly improved electromagnetic properties.

• – Erschmelzen einer Stahlschmelze, die (in Massen-%) C: ≤ 0,010 %, Si: 1,0–1,5 %, Al: < 0,4 %, mit Si + 2Al ≤ 1,85 %, Mn: ≤ 0,5 %, Cu: < 0,05 %, Ti: < 0,01 %, P: < 0,1 %, Sn: < 0,15 %, Sb: < 0,15 %, wahlweise S, O und N, wobei die Summe der Gehalte dieser Elemente ≤ 0,02 % ist, und als Rest Eisen und unvermeidbare Verunreinigungen enthält,
• – Vergießen der Schmelze zu einer Dünnbramme,
• – unmittelbar anschließend erfolgendes Ausgleichswärmebehandeln der Dünnbramme bei einer 1040 °C bis 1160 °C betragenden Ofentemperatur T_E, wobei sich die jeweils eingehaltene Behandlungsdauer t_H in Minuten wie folgt berechnet: tH[min] = –1/0,01873 * ln(((TE–870,934 °C) + ΔT)/528,83 °C),mit: –40 °C ≤ ΔT ≤ 40 °C,
• – unmittelbar auf die Ausgleichswärmebehandlung folgendes Warmwalzen und
• – Haspeln des Warmbandes.

With regard to the production process, this object is achieved according to the invention in that a hot strip is produced for the processing into electrical grain that is not grain-oriented, and in addition to this following steps:

• - Melting a steel melt, the (in mass%) C: ≤ 0.010%, Si: 1.0-1.5%, Al: <0.4%, with Si + 2Al ≤ 1.85%, Mn: ≤ 0.5%, Cu: <0.05%, Ti: <0.01%, P: <0.1%, Sn: <0.15%, Sb: <0.15%, optionally S, O and N, the sum of the contents of these elements being ≤ 0.02% and the remainder containing iron and unavoidable impurities,
• - pouring the melt into a thin slab,
• - Immediately afterwards, the heat treatment of the thin slab is carried out at an oven temperature T _{E of} 1040 ° C to 1160 ° C, the treatment time t _H in minutes being calculated as follows: t H [min] = -1 / 0.01873 * ln (((T e -870.934 ° C) + ΔT) / 528.83 ° C), with: –40 ° C ≤ ΔT ≤ 40 ° C,
• - Hot rolling immediately following the heat treatment and
• - reeling the hot strip.

• – Erschmelzen einer Stahlschmelze, die (in Massen-%) C: ≤ 0,010 %, Si: 1,0–1,5 %, Al: < 0,4 %, mit Si + 2Al ≤ 1,85 %, Mn: ≤ 0,5 %, Cu: < 0,05 %, Ti: < 0,01 %, P: < 0,1 %, Sn: < 0,15 %, Sb: < 0,15 %, wahlweise S, O und N, wobei die Summe der Gehalte dieser Elemente ≤ 0,02 % ist, und als Rest Eisen und unvermeidbare Verunreinigungen enthält,
• – Vergießen der Schmelze zu einer Dünnbramme,
• – unmittelbar anschließend erfolgendes Ausgleichswärmebehandeln der Dünnbramme bei einer 25 bis 70 Minuten betragenden Behandlungsdauer t_H, wobei sich die jeweils eingehaltene Ofentemperatur T_E in Grad Celsius der Ausgleichswärmebehandlung wie folgt berechnet: TE[°C] = 528,83 * exp((–0,01873 * tH) + 870,934) + ΔT,mit: –40 °C ≤ ΔT ≤ 40 °C,
• – unmittelbar auf die Ausgleichswärmebehandlung folgendes Warmwalzen und
• – Haspeln des Warmbandes.

In the same way, the above-mentioned object with regard to the production method is also achieved by a method for producing a hot strip intended for processing into non-grain-oriented electrical steel, in which the following steps are carried out:

• - Melting a steel melt, the (in mass%) C: ≤ 0.010%, Si: 1.0-1.5%, Al: <0.4%, with Si + 2Al ≤ 1.85%, Mn: ≤ 0.5%, Cu: <0.05%, Ti: <0.01%, P: <0.1%, Sn: <0.15%, Sb: <0.15%, optionally S, O and N, the sum of the contents of these elements being ≤ 0.02% and the remainder containing iron and unavoidable impurities,
• - pouring the melt into a thin slab,
• - Immediate heat treatment of the thin slab with a treatment time t _{H of} 25 to 70 minutes, the furnace temperature T _E in degrees Celsius of the heat treatment being calculated as follows: T e [° C] = 528.83 * exp ((- 0.01873 * t H ) + 870.934) + ΔT, with: –40 ° C ≤ ΔT ≤ 40 ° C,
• - Hot rolling immediately following the compensating heat treatment and
• - reeling the hot strip.

Both configurations of the method according to the invention correspond to one another. However, while in the first case the treatment time is determined as a function of the oven temperature, in the second case the relevant calculation formula has been changed so that the required oven temperature T _E can be determined based on a given treatment time. In this way, on the one hand, the practical procedure has been taken into account, in which an oven temperature is usually known, according to which the duration of the treatment depends. On the other hand, the second approach offers the possibility of optimizing the overall sequence of the method according to the invention by specifying a treatment duration that is suitable for the process flow and on the basis of which the furnace temperature must be based.

The thickness of the course of the implementation of the Process variant according to the invention produced thin slab is typically 35 to 100 mm.

One in compliance with the invention According to the invention, hot strip produced in predetermined working steps is characterized by this from that in the finished hot strip there is an extensive elimination is done in such a way that the excretions present in the finished hot strip an average particle size of at least Own 300 nm. The particle sizes should be distributed so that among the existing excretions the proportion of excretions with particle sizes from 50 to 190 nm to low Traces is reduced. For this, the particle size of the excretions should predominate Part more than 300 nm.

The invention is based on knowledge that significantly improved magnetic properties Set electrical sheets with silicon and aluminum contents of the order of magnitude selected according to the invention leave when these electrical sheets are produced on a casting and rolling machine A suitable compensation heat treatment is carried out during the processing. This heat treatment has a precisely specified temperature within narrow limits or timing to follow. In this way, the formation of excretions in the generated according to the invention Hot strip controlled so that the number of fine excretions on is reduced to a minimum.

Surprisingly, it has been shown that in the case of Ver, according to the invention, aimed at the formation of as few and as large as possible precipitates with particle sizes of more than 300 nm driving the structural and excretion state of the hot strip according to the invention is designed such that this favorable excretion characteristic of the hot strip is inherited via the further steps which are usually carried out for the production of the finished electrical sheet up to the completion of the product, with the result that an end product with excellent magnetic properties is obtained ,

The structure of the finished is not grain-oriented Electrical steel is due to the excretion state set according to the invention of the hot strip over the entire strip thickness is particularly homogeneous, since there are no minor excretions are more present, the emergence of such a homogeneous Structure at could interfere with the further processing of the hot strip according to the invention. Accordingly are the good values of polarization and magnetic losses of electrical sheet according to the invention also distributed particularly evenly in front.

The invention uses in this way the opportunities offered by the consistent use of a casting and rolling system one optimized in terms of labor and costs Procedure by starting with the casting of the thin slab the individual steps of hot strip production according to the invention "in-line" directly on top of each other carried out below become. The balance heat treatment of the thin slabs is essential, the given duration in a certain temperature window and at a given temperature in a defined time window. The corridor within which the effects used according to the invention occur is limited to a small temperature or time span, which is by those specified in the invention Formulas for determining the heat treatment temperature Express deviations ΔT in the furnace target temperature.

Only by complying with the Invention determined process parameters during the heat treatment of the thin slab is the target according to the invention Emergence as possible less and, if available, coarse excretions at the same time extensive suppression because of its negative influence on the magnetic properties particularly undesirable Excretions with particle sizes in the range safely reached from 50 nm to 190 nm.

The number, size and distribution of the hot strip according to the invention leaves existing excretions electron microscopy in a known manner or by means of others determine suitable detection and evaluation methods. So you can the excretion state, for example with a transmission electron microscope (TEM) about Kohlenstoffausziehabdrücke with a lower detection limit of 5 nm and with excretions from a diameter of 30 nm with a personal scanning electron Determine Microscope (PSEM) by image analysis using the mass contrast. For the Determination of the chemical composition of the excretions is available for example EDX analysis.

Is that generated according to the invention Hot strip processed into non-grain-oriented electrical sheet, so the hot strip can first hot strip cooling be subjected. This additional annealing of the hot strip improves the texture. she should always done this way be that there is none in terms of the intended improvement the magnetic properties undesirable changes in the excretions comes.

According to a particularly suitable one Embodiment of the invention, the hot strip after rolling in the finishing line at a reel temperature of less than 600 ° C, ideally in particular less than 530 ° C, coiled. Coiling at these temperatures leads to the alloys in question to a solidified hot strip condition, so that as a result improved magnetic properties can be achieved.

Alternatively, it can be convenient if the reel temperature is at least 720 ° C, ideally at least 750 ° C. at Maintaining such a high reel temperature can completely anneal hot strip or at least to a significant extent can be saved. The hot strip is already softened in the coil, whereby its properties determine Features such as grain size, texture and excretions, are positively influenced. This is how annealed hot strips can be used produce particularly good magnetic and technological properties.

Before or after the if necessary hot strip annealing the hot strip is usually pickled. Subsequently the hot strip is then applied to the pickling or hot strip annealing cold rolled, this cold rolling in two or two in a known manner be carried out in several stages with intermediate annealing can. Close to the cold rolling usually a final heat treatment at who performed so is that there is no austenite formation.

Tabelle I To demonstrate the improvements that occurred in the procedure according to the invention, two steel melts with the composition given in Table I were melted (content data in% by mass):

Table I

From the steel I three thin slab samples I-P1, I-P2 and I-P3 were then produced in a casting and rolling mill in a known manner, while the steel II was cast into thin slab samples II-P1 and II-P2. Subsequently, the thin slab samples I-P1, I-P2, I-P3, II-P1 and II-P2 ran "inline" with a temperature T _VO into a compensating furnace in which they heated to a furnace temperature T _E for a holding time t _H have been.

After completion of the equalization heat treatment carried out in this way, the thin slab samples I-P1, I-P2, I-P3, II-P1 and II-P2 in turn immediately afterwards entered a hot rolling mill, in which they started from a hot rolling start temperature W _AT and at a hot rolling temperature W _{ET have been} hot rolled to the final hot strip thickness.

The hot-rolled strips, which were hot-rolled from the thin slab samples I-P1, I-P2, I-P3, II-P1 and II-P2, were then split in the hot-rolled state. The first half of the hot strips obtained in this way has been aged at a temperature T _H in order to simulate reeling at higher temperatures T _H.

The second half of the hot strips was in contrast, cooled directly in air to room temperature to to simulate a reel variant in which with temperatures below 500 ° C coiled becomes. After the outsourcing, they are subjected to the outsourcing Hot strip halves pickled and in a conventional manner to an electrical steel EI-1, EI-2 and EI-3 as well as EII-1 and EII-2 with a thickness of 0.50 mm been cold rolled.

The cold-rolled electrical strips EI-1, Finally, EI-2 and EI-3 as well as EII-1 and EII-2 are in a continuous furnace have been subjected to shot-annealing in a manner which is also known.

Tabelle II Table II shows the processing of thin slab samples I-P1, I-P2, I-P3, II-P1 and II-P2 into electrical strips EI-1, EI-2 and EI-3 as well as EII-1 and EII- 2 operating parameters set.

Table II

Tabelle III The electromagnetic properties of the finished electrical strips EI-1, EI-2 and EI-3 as well as EII-1 and EII-2 in the longitudinal direction are listed in Table III. P _{1.0 is} the loss of magnetization with a polarization of 1.0 T, with P _1.5 the loss of magnetization with a polarization of 1.5 T and with P _1.7 the loss of magnetization with a polarization of 1.7 T. referred to a frequency of 50 Hz. Furthermore, in Table III with J ₈₀₀ the magnetic polarization with a magnetic field strength of 800 A / m, with J ₁₀₀₀ the magnetic polarization with a magnetic field strength of 1000 A / m, with J ₂₅₀₀ the magnetic polarization with a magnetic field strength of 2500 A / m, with J ₅₀₀₀ the magnetic polarization with a magnetic field strength of 5000 A / m and with J ₁₀₀₀₀ the magnetic polarization with a magnetic field strength of 10000 A / m.

Table III

In the attached diagram 1, the magnetic reversal loss P _{1.5 shows} the magnetic polarization values J _2500, the mixed value A _M and, determined in the longitudinal direction for the electrical strips EI-1, EI-2 and EI-3 as well as EII-1 and EII-2 compared to the longitudinal value A _{L of} the magnetic polarization J ₂₅₀₀ , which could be determined for non-grain-oriented sheets of comparable composition produced conventionally without hot strip annealing.

In the attached diagram 2 is EI-1 for the electrical steel strips and EI-3 the grain size distribution shown. By the straight lines G1, G2 that according to the invention narrowed down as the optimally defined range of median values.

Diagram 3 shows the corresponding cumulative frequency distribution SHV for electrical strips EI-1 and EI-3. The optimal range of the cumulative frequency distribution is flat if bounded by straight line G.

Diagram 4 shows the area within which the compensating heat treatment according to the invention is carried out. The upper horizontal line G _{o defines} the maximum permissible temperature of 1160 ° C and the lower horizontal line G _u the minimum required temperature of 1040 ° C. The two lines L, shown in dashed lines and running from the top left to the bottom right, limit the period of time within which the heat treatment according to the invention can be carried out at a given temperature. The optimal duration of treatment is illustrated by the solid line L _opt running in the middle between the lines L.

Finally, in diagram 5, which corresponds to diagram 4 in terms of the straight lines G _o , G _u and the lines L, L _opt , the optimum temperature L _opt that results from observing the regulations according to the invention and the limit temperatures T permissible within the tolerance for a given time period t1 _min and T _max specified. Likewise, in diagram 5, for a given temperature T1, the optimum duration L _opt that results when the regulations according to the invention are observed and the minimum permitted duration t _min within the tolerance and the maximum permitted duration t _{max are} entered.

In practice, in general the temperature of the oven predetermined and a certain interval of necessary duration of the heat treatment taking into account the respective cycle time of the casting and rolling system used.

Claims (11)

Hot strip for the production of non-grain oriented electrical steel, whereby the Hot strip from a steel which (in mass%) C: ≤ 0.010 Si : 1.0-1.5 % Al: <0.4 %, with Si + 2Al ≤ 1.85 % Mn: ≤ 0.5 % Cu: <0.05 % Ti: <0.01 % P: <0.1 % Sn: <0.15 % Sb: <0.15 % optionally S, O and N, the sum of the contents of these Elements ≤ 0.02 % and the balance contains iron and unavoidable impurities, generated is and with extensive excretion in the hot strip is done in such a way that the existing excretions on average a particle size of at least Own 300 nm. Hot strip according to claim 1, characterized in that among the existing excretions the proportion of excretions with particle sizes of 50 nm to 190 nm is reduced to traces. Hot strip according to one of the preceding claims, characterized characterized that the particle size for the most part more than Is 300 nm. Cold-rolled and finally annealed non-grain-oriented electrical steel sheet or sheet, produced from a hot strip procured according to one of claims 1 to 3, - with a final thickness ≤ 0.75 mm, - and with polarization values J ₂₅₀₀ , which is required for a 0.50 mm thick electrical steel strip 50 Hz and magnetization losses P _1.5 of 4.4 W / kg to 5 W / kg are at least 1.65 T and at 50 Hz and magnetization losses P _1.5 of less 4.4 W / kg are at least 1.67 T, - in that the mean grain diameter D _{K of} the finished electrical steel is 50 μm to 80 μm with a median value of 35 to 65 μm and - in the percentage total frequency distribution (SHV) 90% of the grains fulfill the following condition: 1.3 * D K - 30 μm <SHV <1.3 * D K + 15 μm. Method for producing a hot strip intended for processing into non-grain-oriented electrical steel, in which the following steps are carried out: melting a steel melt which (in mass%) C: ≤ 0.010%, Si: 1.0-1.5%, Al: <0.4%, with Si + 2Al ≤ 1.85%, Cu: <0.05%, Ti: <0.01%, P: <0, 1%, Sn: <0.15%, Sb: <0.15%, optionally S, O and N, where the sum of the contents of these elements is ≤ 0.02%, and the rest contains iron and unavoidable impurities, Pouring the melt into a thin slab, - immediately afterwards, the heat treatment of the thin slab is carried out at an oven temperature T _{E of} 1040 ° C to 1160 ° C, the treatment time t _H in minutes being calculated as follows: t H [min] = -1 / 0.01873 * ln (((T e -870.934 ° C) + ΔT) / 528.83 ° C), with: -40 ° C ≤ ΔT ≤ 40 ° C, - hot rolling immediately after the compensating heat treatment and - reeling of the hot strip. Method for producing a hot strip intended for processing into non-grain-oriented electrical steel, in which the following steps are carried out: melting a steel melt which (in mass%) C: ≤ 0, 010 Si: 1, 0 - 1, 5%, Al: <0.4%, with Si + 2Al ≤ 1.85%, Mn: ≤ 0.5%, Cu: <0.05%, Ti: <0.01%, P: <0.1%, Sn: <0.15%, Sb: <0.15%, optionally S, O and N, where the sum of the contents of these elements is ≤ 0.02%, and the rest contains iron and unavoidable impurities, - casting of the melt to a thin slab, - immediately afterwards the heat treatment of the thin slab with a treatment time t _{H of} 25 to 70 minutes, the furnace temperature T _{E of} the heat treatment in degrees Celsius being calculated as follows: T e [° C] = 528.82 * exp ((- 0.01873 * t H ) + 870.934) + ΔT, with: –40 ° C ≤ ΔT ≤ 40 ° C, - hot rolling immediately after the compensating heat treatment and - reeling of the hot strip. Method according to one of claims 5 or 6, characterized in that that the thickness of the thin slab Is 35 to 100 mm. Method according to one of claims 5 to 7, characterized in that that the reel temperature is less than 600 ° C. A method according to claim 8, characterized in that the reel temperature is less than 530 ° C. Method according to one of claims 5 to 9, characterized in that that the reel temperature is more than 720 ° C. A method according to claim 10, characterized in that the reel temperature is more than 750 ° C.