Method for manufacturing a cold-rolled strip or sheet of a substantially equiatomic FECO alloy, cold-rolled strip or sheet of a substantially equiatomic FECO alloy, and magnetic components cut out therefrom

Abstract

The present invention relates to a substantially equiatomic FeCo alloy cold rolled strip or sheet, and to magnetic components cut therefrom, as well as to a method for producing a FeCo alloy cold rolled strip or sheet having a thickness of 1.5-2.5 mm and the following composition: 47.0%≦Co≦51.0%;trace≦V+W≦3.0%;trace≦Ta+Zr≦0.5%;trace≦Nb≦0.5%;trace≦B≦0.05%;trace≦Si≦3.0%;trace≦Cr≦3.0%;trace≦Ni≦5.0%;trace≦Mn≦2.0%;trace≦O≦0.03%;trace≦N≦0.03%. %; traces≦S≦0.005%; traces≦P≦0.015; traces≦Mo≦0.3%; traces≦Cu≦0.5%; traces≦Al≦0.01%; traces≦Ti≦0.01%; traces≦Ca+Mg≦0.05%; traces≦Rare Earths≦500ppm; the balance being Iron and impurities. A fully recrystallized hot rolled sheet or strip is prepared having a reduction of 70-90% and is carried out to reduce the strip or sheet to a thickness of ≦1mm. An intermediate annealing is carried out during the run, resulting in partial recrystallization of the strip or sheet, running at a speed (V) and with a temperature in the effective zone of the furnace of effective length (Lu) being between Trc and 900°C, the strip or sheet remaining therein for 15 seconds to 5 minutes at a temperature (T) such that 26°C.min≦(T-Trc).Lu / V≦160°C.min. The strip or sheet is cooled at at least 600°C / hour. A second step of cold rolling the annealed strip or sheet is carried out with a reduction of 60-80% to bring the strip or sheet to a thickness of 0.05-0.25 mm. A final annealing (Rf) of the cold rolled strip or sheet is carried out to achieve complete recrystallization, followed by cooling at 100-500°C / hour. Magnetic parts, such as magnetic cores, obtained from the strip or sheet produced by this method.

Description

Technical Field

[0001] The present invention relates to the field of cold-rolled strips and sheets of magnetic materials, and parts cut from such strips and sheets, and more particularly to strips and sheets made of substantially equiatomic FeCo alloys.

Background Art

[0002] Magnetic cores made from substantially equiatomic (and thus containing Fe and Co of substantially equal mass and atomic weight) soft magnetic FeCo alloys have often had about 2% V added and it has long been known that high power-to-mass or power-to-volume ratios can be obtained during energy conversion in electrical engineering. When aiming to reduce as much as possible the magnetic losses that cause heat dissipation, it is known that it is necessary to reduce the thickness of the strip forming the core cut from a previous strip or sheet.

[0003] In industrial practice, it is common to produce cold-rolled strips and sheets of equiatomic FeCo with a thickness of about 0.1 mm. However, the magnetic losses associated with these materials are still considered not to be sufficiently reduced. Further reduction can be achieved by using new raw materials and performing one or more remelts when producing the metal in ingot form to produce strips and sheets of high purity in terms of residual elements and inclusions. In this way, for a maximum sinusoidal induction of 2T, a low magnetic loss of about 25 W / kg can be obtained at 400 Hz in a 0.1 mm thick strip. However, such a manufacturing method is costly because it requires at least one additional remelt compared to normal equiatomic FeCo alloys.

[0004] As an example, in samples of a reference metal having the following composition in mass percentages summarized in Table 1 (Table 1), the following results are observed. Elements not mentioned are present only as impurities (trace amounts) resulting from melting at most and have no metallurgical effect.

[0005]

Table 1

[0006] Unlike other castings, in the Ref1 casting, remelting was not carried out and only vacuum induction melting (VIM) was carried out. Therefore, the normal inclusion distribution of the Fe-Co alloy was maintained, and in particular, oxides such as vanadium, silicon, aluminum, magnesium, calcium, etc., as well as nitrides of niobium and aluminum and silicon carbide were also maintained. Table 1, which is limited to the composition of the sample, cannot explain the abundance of such inclusions using only some of the elements dissolved in the metal.

[0007] The remelting of the castings Ref2 to Ref5 was carried out by vacuum arc remelting (VAR) on the castings first produced by VIM without adding Nb. Its main effect was to remove or fragment a considerable part of the stable precipitates (oxides, carbides, nitrides) of the metal matrix derived from VIM, and further directly remove some of the non-precipitate impurities (S, N, O) in the matrix by applying a vacuum.

[0008] The reference casting was hot-rolled into a strip with a thickness of 2 mm by blooming and strip mill (hot rolling), then hyper-quenched, and made to a thickness of 0.1 mm by single cold rolling.

[0009] At such a final state thickness, depending on whether there is interest in any application of a "rotating machine" (washer) or a "transformer" (tape-wound toroidal core), a washer in the form of 36 (outer diameter) × 30.5 mm (inner diameter) or 36 (outer diameter) × 25 mm (inner diameter), or a tape-wound toroidal core in the form of 30 × 20 mm (outer diameter and inner diameter respectively) × 10 mm (toroidal core height, corresponding to the width of the strip) can be manufactured.

[0010] In all cases, the test materials were heat-treated under pure hydrogen for 3 hours at 850 °C for samples Ref1, Ref2, and Ref3, and at 880 °C for samples Ref4 and Ref5. Cooling after the heat treatment was carried out at a rate of 250 °C / h in all cases in order to optimize the magnetic performance. At this cooling rate, the first crystalline magnetic anisotropy constant K1 (which significantly affects the magnetic properties) is canceled out.

[0011] The tape-wound toroidal core represents single-phase or three-phase transformer core applications, and the washer more specifically represents high-speed rotating actuator applications.

[0012] The measurement results of the coercive force field Hc, the losses at 2 T and 400 Hz, and the increase in losses observed between the washer and the toroidal core are summarized in Table 2.

[0013]

Table 2

[0014] It was found that by using re-dissolution, the magnetic loss of the toroidal core decreased by about 30% (comparison between Ref1 and Ref2 or Ref3 of the wound tape toroidal core), which is very important for many applications.

[0015] It was also found that the magnetic loss is 5 - 10% higher for the toroidal core depending on whether the measurement is carried out on the toroidal core along the rolling direction DL or on the washer, and thus carried out using the entire direction of the sheet. The above indicates that there is a specific anisotropy in the performance on the rolling plane.

[0016] On the other hand, when the final annealing temperature is raised from 850 °C to 880 °C, the level of magnetic loss decreases significantly in both the toroidal core and the washer, as can be seen from the comparison between Ref2 and Ref4 on the one hand and Ref3 and Ref5 on the other hand.

Summary of the Invention

Problems to be Solved by the Invention

[0017] The object of the present invention is to provide a means for obtaining a very low magnetic loss of typically 26.5 W / kg or less under an induction of 2 T at 400 Hz without the need for costly manufacturing by selecting raw materials as in the case of continuous metallurgical operations, to manufacturers of strips or sheets of equiatomic FeCo alloys and products cut from such strips or sheets.

Means for Solving the Problems

[0018] For this purpose, the subject of the present invention is a method for manufacturing a cold-rolled strip or sheet of a substantially equiatomic FeCo alloy, - preparing a hot-rolled sheet or strip having a thickness (e HR ) included in the range of 1.5 to 2.5 mm, the composition of which, in mass percentage, is as follows: * 47.0% ≦ Co ≦ 51.0%, preferably 47.0% ≦ Co ≦ 49.5%; * trace amount ≦ V + W ≦ 3.0%; preferably 0.5% ≦ V + W ≦ 2.5%; * trace amount ≦ Ta + Zr ≦ 0.5%; * trace amount ≦ Nb ≦ 0.5%, preferably trace amount ≦ Nb ≦ 0.1%; * trace amount ≦ B ≦ 0.05%, preferably trace amount ≦ B ≦ 0.005%; * trace amount ≦ Si ≦ 3.0%; * trace amount ≦ Cr ≦ 3.0%; * trace amount ≦ Ni ≦ 5.0%, preferably trace amount ≦ Ni ≦ 0.1%; * trace amount ≦ Mn ≦ 2.0%, preferably trace amount ≦ Mn ≦ 0.1%; * trace amount ≦ C ≦ 0.02%, preferably trace amount ≦ C ≦ 0.01%; * trace amount ≦ O ≦ 0.03%, preferably trace amount ≦ O ≦ 0.01%; * trace amount ≦ N ≦ 0.03%, preferably trace amount ≦ N ≦ 0.01%; * trace amount ≦ S ≦ 0.005%, preferably trace amount ≦ S ≦ 0.002%; * Trace amount ≤ P ≤ 0.015; preferably, trace amount ≤ P ≤ 0.007%; * Trace amount ≤ Mo ≤ 0.3%; preferably, trace amount ≤ Mo ≤ 0.1%; * Trace amount ≤ Cu ≤ 0.5%; preferably, trace amount ≤ Cu ≤ 0.1%; * Trace amount ≤ Al ≤ 0.01%; preferably, trace amount ≤ Al ≤ 0.002%; * Trace amount ≤ Ti ≤ 0.01%; preferably, trace amount ≤ Ti ≤ 0.002%; * Trace amount ≤ Ca + Mg ≤ 0.05%; preferably, trace amount ≤ Ca + Mg ≤ 0.001%; * Trace amount ≤ rare earth elements ≤ 500 ppm; * Iron and the balance which are impurities generated by melting; * The strip or sheet having a recrystallization start temperature (Trc) and a fine structure recrystallized 100% to prepare a hot-rolled sheet or strip consisting of; - Next, a first cold rolling step (LAF1) of the strip or sheet is performed in one or a plurality of passes at a total reduction ratio (TR1) of 70 to 90%, preferably 65 to 75%, to make the thickness (e1) of the strip or sheet ≤ 1 mm, preferably ≤ 0.6 mm; - Next, perform intermediate annealing (R1) while passing the strip or sheet through an annealing furnace to bring about partial recrystallization of the strip or sheet, where the strip or sheet is passed through the annealing furnace at a speed (V), the degree of partial recrystallization is 10 to 50%, preferably 15 to 40%, more preferably 15 to 30%, and the temperature of the strip or sheet in the effective zone of the furnace having an effective length (Lu) is included in Trc to 900 °C, preferably 700 to 880 °C, and the strip or sheet stays at a temperature (T) such that 26 °C min ≤ (T - Trc)·Lu / V ≤ 160 °C min, preferably 50 °C min ≤ (T - Trc)·Lu / V ≤ 160 °C min for 15 seconds to 5 minutes, where T and Trc are in °C, Lu is in m, and V is in m / min, and the strip or sheet is cooled to a temperature of 200 °C or less at a speed of at least 600 °C / h, preferably at least 1000 °C / h, more preferably at least 2000 °C / h at the exit of the furnace, to bring about partial recrystallization of the strip or sheet, - Next, perform a second cold rolling process (LAF2) on the annealed strip or sheet in one or more passes with a total reduction ratio of 60 to 80%, preferably 65 to 75%, to make the thickness (e2) of the cold rolled strip or sheet 0.05 to 0.25 mm, - Next, subject the cold rolled strip or sheet, or a portion previously cut out from the strip, to a stationary final annealing (Rf) at a temperature of 750 to 900 °C, preferably 800 to 900 °C, more preferably 850 to 880 °C in a neutral or reducing atmosphere, or in a vacuum, for at least 30 minutes, preferably at least 1 hour, to obtain complete recrystallization of the strip or sheet or the cut out portion, and then cool at a speed of 100 to 500 °C / h, preferably 200 to 300 °C / h is a method, characterized by the above.

[0019] According to a modification of the present invention, (V + W) / 2 + (Ta + Zr) / 0.2 ≥ 0.8%, preferably (V + W) / 2 + (Ta + Zr) / 0.2 ≥ 1.0%.

[0020] According to a modified example of the present invention, trace amount ≦ Si ≦ 0.1%.

[0021] According to a modified example of the present invention, trace amount ≦ Cr ≦ 0.1%.

[0022] According to a modified example of the present invention, before the first cold rolling step (LAF1), at least one additional cold rolling cycle (LAFi) + intermediate annealing (Ri) is carried out, and the cold rolled strip or sheet is within the thickness between the thickness (e HR ) after hot rolling and the inlet thickness of the first cold rolling (LAF1). During each additional annealing (Ri), the passing time of the strip in the effective zone of the furnace located between Trc and 900 °C results in complete recrystallization of the strip or sheet. The intermediate annealing (Ri) has a passing time between 10 seconds and 10 minutes, preferably between 15 seconds and 5 minutes, more preferably between 30 seconds and 5 minutes, in the zone of the furnace length Lu where the temperature of the strip is between Trc and 900 °C. Then, at the outlet of the furnace, the strip or sheet is cooled to a temperature of 200 °C or less at a rate of at least 600 °C / hour, preferably at least 1000 °C / hour, more preferably at least 2000 °C / hour. The strip or sheet has a fine structure that is 100% recrystallized after the last of the said additional annealing (Ri).

[0023] After hot rolling and before the first cold rolling (LAF1), by cooling the hot rolled strip or sheet from a temperature included between 800 and 1000 °C to room temperature at a rate of at least 600 °C / second, preferably at least 1000 °C / second, more preferably at least 2000 °C / second, the hot rolled strip or sheet can be super rapidly cooled.

[0024] The super rapid cooling may be carried out directly after hot rolling without any intermediate reheating.

[0025] The atmosphere of the annealing furnace may be a reducing atmosphere, preferably pure hydrogen.

[0026] At least one additional intermediate annealing may be continuous annealing of a strip or sheet in an annealing furnace, the temperature of the strip or sheet in the effective zone of the furnace being between Trc and 900 °C, the strip remaining in the effective zone for 15 seconds to 5 minutes, and the strip or sheet at the outlet of the furnace being cooled to a temperature of 200 °C or less at a rate of at least 600 °C / h, preferably at least 1000 °C / h, more preferably at least 2000 °C / h. At least one additional cold rolling (LAFi) is carried out in one or more passes, with a total reduction ratio of at least 40%.

[0027] After the final stationary annealing (Rf), additional continuous annealing of the strip or sheet may be carried out for at least 10 seconds, at most 1 hour, preferably 10 seconds to 20 minutes, such that the metal reaches at least 700 °C and at most 900 °C, and may subsequently be cooled at a rate of at least 1000 °C / h.

[0028] The present invention further relates to a substantially equiatomic FeCo alloy, - the composition of which, in mass percentage, * 47.0% ≤ Co ≤ 51.0%, preferably 47.0% ≤ Co ≤ 49.5%; * trace amount ≤ V + W ≤ 3.0%; preferably 0.5% ≤ V + W ≤ 2.5%; * trace amount ≤ Ta + Zr ≤ 0.5%; * trace amount ≤ Nb ≤ 0.5%, preferably trace amount ≤ Nb ≤ 0.1%; * trace amount ≤ B ≤ 0.05%, preferably trace amount ≤ B ≤ 0.005%; * trace amount ≤ Si ≤ 3.0%; * trace amount ≤ Cr ≤ 3.0%; * trace amount ≤ Ni ≤ 5.0%; preferably trace amount ≤ Ni ≤ 0.1%; * trace amount ≤ Mn ≤ 2.0%, preferably trace amount ≤ Mn ≤ 0.1%; * trace amount ≤ C ≤ 0.02%; preferably trace amount ≤ C ≤ 0.01%; * trace amount ≤ O ≤ 0.03%; preferably trace amount ≤ O ≤ 0.01%; * trace amount ≤ N ≤ 0.03%; preferably trace amount ≤ N ≤ 0.01%; * Trace amount ≤ S ≤ 0.005%; preferably, trace amount ≤ S ≤ 0.002%; * Trace amount ≤ P ≤ 0.015%; preferably, trace amount ≤ P ≤ 0.007%; * Trace amount ≤ Mo ≤ 0.3%; preferably, trace amount ≤ Mo ≤ 0.1%; * Trace amount ≤ Cu ≤ 0.5%; preferably, trace amount ≤ Cu ≤ 0.1%; * Trace amount ≤ Al ≤ 0.01%; preferably, trace amount ≤ Al ≤ 0.002%; * Trace amount ≤ Ti ≤ 0.01%; preferably, trace amount ≤ Ti ≤ 0.002%; * Trace amount ≤ Ca + Mg ≤ 0.05%; preferably, trace amount ≤ Ca + Mg ≤ 0.001%; * Trace amount ≤ rare earth elements ≤ 500 ppm; * The balance consisting of iron and impurities generated by dissolution; Comprising from - The fine structure of the alloy being completely recrystallized, and - The texture of the alloy being as follows: * Based on the surface area or volume, 8 - 20%, preferably 9 - 20% of the component {001}<110> having a misorientation of up to 15°; * Based on the surface area or volume, 8 - 25%, preferably 9 - 20% of the component {111}<112>c having a misorientation of up to 15°; * Based on the surface area or volume, 5 - 15%, preferably 6 - 11% of the component {111}<110> having a misorientation of up to 15°; * The remainder of the material consisting of other texture components having a misorientation of up to 15°, each corresponding to a maximum of 15% based on the area or volume, and the overlap between the other texture components and any of the components {001}<110>, {111}<112> and {111}<110> not exceeding 10% based on the area or volume Relating to an FeCo alloy characterized by

[0029] According to a modification of the present invention, (V + W) / 2+(Ta + Zr) / 0.2 ≥ 0.8%, preferably (V + W) / 2+(Ta + Zr) / 0.2 ≥ 1.0%.

[0030] According to a modification of the present invention, trace amounts ≦ Si ≦ 0.1%.

[0031] According to a modification of the present invention, trace amounts ≦ Cr ≦ 0.1%.

[0032] A further subject of the present invention is a magnetic component cut out from a substantially equiatomic FeCo alloy, characterized in that it results from the cutting out of a strip or sheet made of an alloy of the above type.

[0033] A further subject of the present invention is a magnetic core made of a substantially equiatomic FeCo alloy, characterized in that it is made from a magnetic component of the type cut out above.

[0034] As will be understood, the present invention is based, inter alia, on obtaining a strip or sheet by means of a series of process steps including cold rolling in at least two steps, i.e. in at least two cold rolling passes or at least two groups of successive cold rolling passes, these two passes or groups of passes being designated as LAF1 and LAF2, but separated by a specific intermediate annealing R1 of partial recrystallization only which is carried out continuously between the two passes or two groups of passes. Immediately after the two passes / pass groups, a final stress relief annealing is finally carried out, which results in a fully recrystallized strip. Such a process is applied to an alloy of a clearly defined composition and, depending on the processing conditions, creates within the cold rolled and annealed strip or sheet a specific texturing according to three given texture components and a given ratio.

[0035] Also, the sequence of two cold rolling operations separated by annealing which results in only partial recrystallization must start from a 100% recrystallized strip after the hot rolling operation and, if there is any subsequent treatment, by that treatment.

[0036] All such characteristics result in a very low magnetic loss of the strip or sheet.

[0037] In the following part, when referring to the "cold rolling process" and its reduction ratio, it should be understood that the cold rolling process is carried out in a plurality of passes that are immediately consecutive, thus including the case where there is no intermediate annealing, and the reduction ratio of this "cold rolling process" is the overall ratio obtained at the end of all passes of the process when there are a plurality of passes.

[0038] When applying the present invention, surprisingly, in order to obtain the expected performance, it is not necessary to prepare a metal with high chemical purity and high inclusivity, yet it is still desirable to start with impurities and inclusions at as low a concentration as possible in order to obtain performance that is even better than that of equivalent existing products.

[0039] The above indicates that general raw materials can be used and it is not necessarily required to use new raw materials that contain almost no residual elements and various impurities, and multiple re - melts during the production of the ingot from which the strip or sheet is obtained can be omitted. Of course, if it is desired to obtain a strip or sheet with exceptionally low magnetic loss, such an operation is not excluded from the method according to the present invention. However, in order to obtain a magnetic loss considered "low" according to the conventional criteria defined above, such an operation is no longer necessary.

[0040] The use of a series of steps according to the present invention, applied to a substantially equiatomic FeCo alloy, in which a certain alloying element can also be added in a relatively limited amount, has been found to result in a specific texture in which the components {001}<110>, {111}<112>, and perhaps to a lesser extent {111}<110> exist with an exact maximum disorientation for each of the components within the accuracy limits.

[0041] Surprisingly, such a texture allows for a relatively high concentration of impurities in the alloy to obtain low magnetic losses, the impurities are at a low level, and if to the extent necessary for prior art methods used in the production of strips and sheets of equiatomic FeCo alloys to obtain only low magnetic losses, it results in even lower magnetic losses.

[0042] The present invention will be better understood through the following description with reference to the following attached drawings.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0044] The present invention discusses a substantially equiatomic FeCo alloy having the following composition. All percentages are by mass. When referring to the presence of "trace" amounts, it should be understood that the element may be absent altogether or present only as impurities resulting from simple dissolution of the raw materials and production of the liquid metal, and the concentration may be at the limit of detectability of the element by the measuring device used. The above includes cases where the measuring device indicates a slight presence of the element while the actual concentration is zero.

[0045] The concentration of Co is included in the range of 47.0 to 51.0%, preferably 47.0 to 49.5%.

[0046] Such a concentration is necessarily close to an equiatomic composition of about 49% Co and about 49% Fe in an FeCo alloy containing an additional about 2% V.

[0047] Binary equiatomic FeCo alloys are known to have both a very high saturation magnetization value JSAT (2.35 T) and a very low crystalline magnetic anisotropy constant K1, and can be offset or at least significantly reduced by a cooling rate of about 250 °C / h (most commonly 100 - 500 °C / h, preferably 200 - 300 °C / h) after final annealing. Even a low or zero crystalline magnetic anisotropy constant significantly affects the magnetic properties of the alloy in direct current or low-frequency alternating current.

[0048] The concentration of V + W is included in the range of trace amounts to 3.0%, preferably 0.5 - 2.5%.

[0049] The presence of V and / or W is intended to reduce the degree of softening below 700 °C, thereby very preferably enabling the implementation of super rapid cooling following hot forming and maintaining good ductility of the metal with cold rolling in view. 2% V also makes it possible to double the electrical resistivity compared to FeCo without V, resulting in a significant reduction in magnetic losses at low frequencies and especially at medium frequencies, and thus, in the entire range of electrical technical applications, typically in low-frequency ground wave applications at several tens of Hz, and typically in aviation applications (transmitters, transformers, smoothing inductances) at several hundreds to thousands of Hz, particularly obvious reduction in magnetic losses. When V is 2% or more, and depending on the final annealing temperature Rf, an α + γ two-phase region undesirable for the magnetic performance of the alloy occurs. When V exceeds 3.0%, regardless of the temperature of the final annealing Rf, non-magnetic austenite γ is formed, and thereafter, the magnetic performance becomes clearly mediocre in the normal applications of equiatomic FeCo alloys. Therefore, the addition of V and / or W having substantially the same effect is not recommended when the total of V + W exceeds the aforementioned 3.0% limit.

[0050] The total concentration of Ta and Zr is included in the range of trace amounts to 0.5%.

[0051] Ta and Zr, like V and W, slow down the ordering rate. In this regard, the addition of 0.2% Ta has the same effect as 2% V and W. However, Ta and Zr do not affect the electrical resistivity, and thus the addition of V and W is preferred for the intended normal use of the alloys related to the present invention.

[0052] In order to appropriately consider the respective effects of V and W on the one hand and Ta and Zr on the other hand on the ordering rate, the effects of these two groups of elements should preferably be weighted according to the formula: (V + W) / 2 + (Ta + Zr) / 0.2 ≧ 0.8%, preferably (V + W) / 2 + (Ta + Zr) / 0.2 ≧ 1.0% should be weighted.

[0053] However, it is also necessary to satisfy the upper limits of the concentrations of V + W and Ta + Zr described above.

[0054] The concentration of Nb is included in a trace amount to 0.5%, preferably a trace amount to 0.1%.

[0055] This possible addition of Nb can prevent the appearance of brittle phases during possible reheating prior to the super-quenching of hot-formed semi-finished products, and thus can be interesting for successful cold rolling operations. However, Nb is a strong inhibitor of grain growth, making grain growth during the final static annealing Rf more difficult. Therefore, if the concentration of Nb is too high, good magnetic properties cannot be obtained. Furthermore, Nb easily combines with C, N, and O to form carbides, nitrides, carbonitrides, or oxides, which contribute to slowing down the growth of grains and reducing magnetic properties directly (by capturing Bloch walls) or indirectly (by limiting the crystal grain size).

[0056] Accordingly, depending on the manufacturing method used, with or without remelting, heating for a variable length of time before ultra-rapid cooling, or ultra-rapid cooling being carried out immediately after hot forming, limited or non-limited manufacturing involving oxidation, nitridation, carburization of liquid metal, a few percent of Nb, typically 0.10%, for example 0.04% or 0.07% of Nb may be added. If it exceeds 0.5%, the grain growth inhibition effect becomes excessive in obtaining the desired magnetic properties.

[0057] The concentration of B is contained in trace amounts to 0.05%.

[0058] B has a role similar to that of Nb, but for that purpose it also has a embrittling effect, and its presence also needs to be appropriately restricted.

[0059] The concentration of Si is contained in trace amounts to 3.0%, and in certain cases in trace amounts to 0.1%.

[0060] The concentration of Cr is contained in trace amounts to 3.0%, and in certain cases in trace amounts to 0.1%.

[0061] Si and Cr are known for their ability to significantly increase the electrical resistivity of the material. However, in the case of certain equiatomic FeCo alloys, such a function may be provided by, or already provided by, V, W, Ta, Zr. Also, Cr and Si, unlike V, do not decrease the ordering rate, but such a decrease is highly desirable for the alloys used in the present invention.

[0062] Therefore, Cr and Si are each allowed a ratio of up to 3.0% when a very high electrical resistivity is desired. However, the addition of V is preferred mainly to obtain an increase in electrical resistivity since it is accompanied by other beneficial effects as described above. Adding more Cr or Si will lower the saturation magnetic induction due to the resulting decrease in the concentration of Fe and Co obtained, and thus reduce the ability of the material to have a high output mass ratio. However, it should also be remembered that the size of electrical machines such as transformers, actuators, generators, etc. is limited, especially in the aviation field, due to heating by the Joule effect and magnetic losses in the magnetic core. Nevertheless, the addition of Si and / or Cr tends to reduce magnetic losses and thus increase the operating frequency and magnetic induction. As a result, it is possible to increase the output mass ratio or reduce the adverse effects due to the decrease in saturation magnetic induction. Therefore, in certain applications where the reduction of magnetic losses is highly regarded, the addition of Si and / or Cr can be overall advantageous.

[0063] In applications where the reduction of magnetic losses is not particularly required, it is recommended to limit Cr and Si to 0.1% each, which in many cases corresponds to simply not intentionally adding said elements during manufacturing.

[0064] The concentration of Ni is contained in trace amounts to 5.0%, preferably in trace amounts to 0.1%.

[0065] Ni is a ferromagnetic element, but it attracts much less attention compared to Fe and Co with respect to the saturation magnetization Jsat, and has no advantage of reducing the magnetocrystalline anisotropy constant K1 and increasing the resistivity. On the other hand, Ni improves ductility and may be of interest for cold rolling. The addition of Ni up to 5.0% is allowed, but in many cases, there is no need to add Ni, and the preferred maximum content of 0.1% often simply corresponds to the Ni present in the raw materials. In addition, not adding Ni contributes to suppressing the cost of the alloy.

[0066] The concentration of Mn is contained in trace amounts to 2.0%, preferably in trace amounts to 0.1%.

[0067] Except for the decrease in Jsat, Mn has neither particularly advantageous nor disadvantageous characteristics, nor does it have an advantage to offset the effect of the Jsat decrease. The addition can be up to 2.0%, but preferentially, the concentration obtained from the simple dissolution of the raw materials is sufficient, so the preferred maximum value is 0.1%.

[0068] The concentration of C is contained in trace amounts to 0.02%, preferentially in trace amounts to 0.01%. Therefore, the purpose is to ensure that there is no precipitation of carbides, and in particular, to prevent the formation of clusters of C atoms that capture Bloch walls and deteriorate the magnetic properties during the use of the material.

[0069] The concentration of S must not exceed 50 ppm (0.005%). This is because S tends to form fine precipitates of sulfides such as MnS during hot transformation, increasing the coercive field Hc (and thus the loss due to hysteresis) and decreasing the permeability μ, and thus increasing the number of ampere-turns required to magnetize the magnetic yoke, making it very unfavorable for the magnetic properties of the material. This means that the heating of the winding due to the Joule effect increases and the efficiency of the machine deteriorates. There is no favorable effect on the addition of S.

[0070] Similar to sulfides, P tends to form phosphides (such as phosphides of V) which are precipitates that interact with (capture) Bloch walls, and thus, similar to S, deteriorate the magnetic properties. The concentration of P is limited to a maximum of 150 ppm (0.015%), and preferentially to a maximum of 70 ppm (0.007%).

[0071] Compared with V, Mo does not significantly reduce the ordering. Furthermore, Mo is relatively expensive and has no magnetic moment, so the addition of Mo decreases the saturation magnetization (Jsat) while increasing the price of the material. The presence of Mo in the alloy is typically limited to 0.3%, and preferentially to a maximum of 0.1%.

[0072] Like Mo, Cu is relatively expensive, has no magnetic moment, and furthermore tends to promote the formation of copper clusters in an iron-rich matrix, acting as precipitates on the Bloch walls and thus causing deterioration of the magnetic properties Hc and μ. The presence of Cu is typically limited to a maximum of 0.5% in the alloy and preferably a maximum of 0.1% due to the wise selection of raw materials and the lack of intentional addition.

[0073] Like S and P, N and O are chemical oxidants, so they tend to form non-magnetic precipitates and interact unfavorably with the Bloch walls, thus significantly deteriorating Hc (by increasing Hc) and significantly deteriorating μ (by decreasing μ). The more N and O there are in the matrix, the greater the risk that these elements will encounter oxidizable elements such as Fe, Co, Mn, V, W, Ta, Zr, Nb, Ti, Ca, Mg, Al, Si, La, etc. at high temperatures. These elements are present in very large amounts in the matrix (such as Fe, Co, etc.) or exist as inevitable residues (such as Ca, Mg, Ti, Al, etc.). Despite vacuum melting of raw materials (VIM), and further vacuum remelting (VAR) or slag remelting (ESR) of ingots or electrodes, it is impossible to completely prevent a small part of the metal from being combined with oxidants such as O and N, etc. at several tens of ppm. The presence of up to 300 ppm of O and 300 ppm of N, preferably the presence of up to 100 ppm of O and up to 100 ppm of N, is allowed.

[0074] Si, Mn, especially Al, Ti, Ca, Mg, or rare earth elements such as La have a high affinity for oxidants such as O, N, S, and furthermore C, and can then form various precipitates (oxides, nitrides, sulfides, carbides) that greatly damage the magnetic properties. The number and size of such precipitates can be significantly reduced by remelting operations (VAR, ESR), but the more oxidizable elements there are initially (for example, in an ingot obtained from VIM treatment), the more precipitates will remain after remelting and thus until the final stage in the manufacture of the material. Therefore, it is important to reduce the presence of precipitates as much as possible at the starting point.

[0075] Therefore, the targets are Al at a maximum of 100 ppm (0.01%), preferably at a maximum of 20 ppm Al (0.002%), Ti at a maximum of 100 ppm (0.01%), preferably at a maximum of 20 ppm Ti (0.002%), Ca + Mg at a maximum of 50 ppm, preferably at a maximum of 10 ppm Ca + Mg. When adding rare earth elements, it is at a maximum of 500 ppm, and most specifically the target is to obtain a liquid bath by VIM with a very low chemical oxygen activity before adding the rare earth elements.

[0076] The remainder of the alloy consists of Fe and impurities resulting from melting.

[0077] It should be understood that the concentrations considered favorable for a particular element are independent of the concentrations considered favorable for other elements. In other words, without departing from the present invention, while one or more elements are within their preferred ranges, other elements may have a range that is not within their preferred range.

[0078] The composition of the alloy gives a complete recrystallization temperature, which is generally about 700 °C, while the start of recrystallization begins at about 600 °C after a recovery phenomenon (occurring at about 500 - 600 °C). While the strip is traveling through the annealing furnace at speed V, it is necessary to know the time (referred to as the "effective time" and denoted as "t u ") that the material stays in the recrystallization zone of the annealing furnace (in other words, the zone where the furnace temperature is at least 600 °C). The effective time can be determined experimentally or by calculation using models known to those skilled in the art. Within the framework of the present invention, the critical recrystallization temperature Trc at which the material begins to recrystallize is considered to be Trc = 600 °C. The effective length Lu of the furnace for recrystallization is Lu = V.t u and is quite easily measured by those skilled in the art during temperature measurement of the traveling strip.

[0079] According to the present invention, the starting point is a semi-finished product that is manufactured (it is desired to maintain an economical manufacturing method, and when the final performance of the product is simply equivalent to that of a normal product and not particularly improved over the normal product, it is manufactured without remelting, or when the goal is to obtain significantly better final performance, it is manufactured with remelting), cast, hot formed, and preferably ultra-rapidly cooled, using completely conventional forging and / or hot rolling forming parameters by conventional means. Such a process aims to prepare a semi-finished product suitable for cold rolling to obtain a strip or sheet of an equiatomic FeCo alloy (therefore, these two elements that are next to each other in the periodic table have very similar atomic masses (55.8 and 58.9 g / mol respectively), and its composition has a composition equivalent to that of a known equiatomic FeCo alloy, containing approximately the same amount of Co as Fe in both mass percentage and atomic percentage). Thus, the hot formed semi-finished product is typically obtained in the form of a strip with a thickness e HR is included in the range of 1.5 to 2.5 mm, typically about 2 mm. When the thickness exceeds 2.5 mm, there is a risk that even ultra-rapid cooling cannot remove heat quickly enough to prevent ultra-rapid and embrittling ordering.

[0080] At the end of hot rolling, the obtained strip, although not necessarily required, is very preferably subjected to ultra-rapid cooling. Such treatment is used on a very large scale to prevent the order / disorder transformation of the material, and the material remains in a substantially disordered structural state, changing little compared to its structural state obtained by hot rolling at a temperature above Trc, and for this reason, it has sufficient ductility to be cold rolled.

[0081] Therefore, by ultra-rapid cooling, the hot strip can be reliably cold rolled without problems to the final thickness of the cold rolling sequence, regardless of its thickness as long as it is 2.5 mm or less, and regardless of its composition as long as its composition is within the range set in the present invention.

[0082] When the temperature of the strip at the end of rolling is high enough and the hot rolling equipment allows it, direct ultra-rapid cooling can be carried out at the exit of hot rolling, that is, without intermediate reheating of the strip. Otherwise, it can be carried out after reheating the strip to a temperature higher than the order / disorder transformation temperature.

[0083] In practice, since embrittlement ordering is established at 720 °C to ambient temperature, there are two possibilities for ultra-rapid cooling: - Cooling the still-hot metal immediately after hot rolling, at the exit of the hot rolling equipment, for example using water, from a temperature of 800 - 1000 °C to room temperature rapidly (typically at least 200 °C / second, preferably at least 1000 °C / second, more appropriately at least 2000 °C / second); - Or, hot rolling, then slowly cooling, and thus making the brittle metal, heating it to 800 - 1000 °C and then rapidly, that is, at least 200 °C / second, preferably at least 1000 °C / second, more preferably at least 2000 °C / second, cooling it to room temperature.

[0084] Such treatments are themselves known to those skilled in the art.

[0085] At the end of the said operation sequence, the metal must be in a 100% recrystallized state, except when complete recrystallization is obtained by an additional annealing or an additional annealing carried out before the sequence LAF1 - R1 - LAF2. The said sequence is, as seen so far, one of the main elements of the present invention.

[0086] Hot rolling of an equiatomic FeCo alloy in strip form is, in most cases, carried out at about 900 °C, and then, while the strip is in a coiled state and staying, 100% or nearly 100% recrystallization is obtained.

[0087] A sheet that is not intended to be wound up with a hot-rolled product, and when it is found in a preliminary test that 100% recrystallization cannot be obtained structurally after hot rolling, in order to surely obtain a 100% recrystallized state, the heating time before hot rolling is adjusted, or the cooling after hot rolling is slowed down, for example, by placing the sheet under a hood, and the conditions of hot rolling and its accompanying operations can be adjusted.

[0088] Starting with a hot-formed, and when appropriate, ultra-rapidly cooled product that is 100% or almost 100% recrystallized makes it possible to subsequently carry out at least two cold rolling steps and at least one intermediate annealing according to the present invention, starting from a standard microstructure, so that the effect of subsequent operations on the texturing of the material can be predicted and controlled based thereon.

[0089] After hot rolling and, when appropriate, ultra-rapid cooling, in order to prevent mill scale incrustation on the strip surface in subsequent rolling operations, the metal is preferably subjected to chemical pickling and / or mechanical scale removal of the hot-rolled strip in a conventional manner. Such operations are not elements of the present invention since they do not affect the microstructure of the strip.

[0090] Next, the first cold rolling LAF1 of the 100% recrystallized semi-finished product with an initial thickness e HR is carried out in one or more passes, whereby the first recrystallized microstructure is destroyed. Polishing can be carried out before the first pass or between two passes. In this way, the semi-finished product becomes a thickness e1 that is less than 1 mm, preferably less than 0.6 mm, generally included in the range of 0.5 mm to 0.2 mm, typically 0.35 mm, and the thickness e1 can reach up to 0.12 mm. This corresponds to a total reduction ratio TR1 in the first cold rolling LAF1 according to the present invention that is included in the range of 70% to 90%.

[0091] Next, intermediate continuous annealing R1 is carried out on this semi-finished product in a tunnel furnace. This intermediate annealing R1 according to the present invention is always carried out continuously so as to obtain a sufficiently high forced cooling rate, that is, at least 600 °C / h, preferably at least 1000 °C / h, and more preferably at least 2000 °C / h, at the exit of the annealing furnace. This rate is achieved only when the strip is rewound, and thus does not take the form of a coil like the strip in a stationary annealing furnace.

[0092] The intermediate annealing R1 is carried out at a temperature such that the alloy is in a disordered ferrite phase. The above means that the temperature is included between the order / disorder transformation temperature of the alloy and the ferrite / austenite transformation temperature of the alloy. In a substantially equiatomic Fe-Co alloy in which the Co concentration is included in the range of 47.0 to 51.0% by mass, for example, the alloy related to the present invention, the temperature of the furnace atmosphere in the effective length of the annealing furnace must actually be included in the range of Trc to 950 °C. Lu is the "effective length" of the furnace, that is, among the length of the path of the strip passing through the furnace, it is the length in which not only the furnace atmosphere but also the strip itself is effectively at a temperature exceeding Trc. This leads to ignoring the parts closest to the inlet and outlet of the furnace in the determination of the parameters of the intermediate annealing R1 according to the present invention, and in this part, it is not certain that the effective temperature is sufficient because the passage of the strip is metallurgically efficient. A person skilled in the art will know how to determine, by measurement and up-to-date experiments, the length Lu in which the temperature of the treated strip is actually higher than the temperature Trc in a freely available furnace knowing the composition of the strip.

[0093] The atmosphere of the annealing furnace is preferably a reducing atmosphere and thus consists of pure hydrogen or a neutral hydrogen-neutral gas mixture (argon or nitrogen). A neutral atmosphere (for example, Ar and / or nitrogen) is also assumed, but having a reducing atmosphere ensures that there is no risk of causing surface oxidation of the strip that may be harmful to the proper execution of subsequent cold rolling even in the presence of an unwanted air inlet or insufficient purity of the neutral gas.

[0094] As described above, the temperature of the strip at the effective length Lu of the annealing furnace should be within the range of the recrystallization start temperature Trc (which can be considered to correspond to 600 °C as an appropriate approximation considering the composition of the strip targeted by the present invention and within the scope of the present invention) to 900 °C, preferably 700 to 900 °C. This temperature is for obtaining partial recrystallization more reliably and is sufficient for all alloy compositions related to the present invention. The effective temperature of the furnace atmosphere should be appropriately selected considering that it takes a variable and long time for heating after the strip enters the furnace and that the nature of the atmosphere can affect the heating time. Pure hydrogen is the most preferred normal gas from this perspective, but the heat transfer in the furnace can be improved by establishing a forced convection system, and a gas atmosphere with inferior heat transfer compared to pure hydrogen but easier to handle from the perspective of furnace operation safety can be used. Helium has better heat conduction than hydrogen and fewer safety problems, but helium is much more expensive and has no reducing property.

[0095] The strip must remain within the above temperature range for a period of 15 seconds to 5 minutes. At least in the case of the shortest period and the highest annealing temperature R1, the above may lead to imposing a temperature slightly higher than 900 °C, for example 950 °C, on the furnace atmosphere. Those skilled in the art can experimentally determine which temperature in the furnace is suitable for the strip itself to reach the temperature according to the present invention and which is also suitable for the goal of obtaining only partial recrystallization of the strip for the period according to the present invention, depending on the product being processed, its running speed, and the exact characteristics of the furnace.

[0096] The ratio of only partial recrystallization obtained after this intermediate annealing R1 should be included in the range of 10 to 50%, preferably 15 to 40%, more preferably 10 to 30%. If the degree of recrystallization is too low, the intermediate annealing R1 becomes unnecessary, while if the degree of recrystallization is too high, the magnetic loss of the final product deteriorates.

[0097] The speed V at which the strip passes through the furnace can be adapted, considering the length of the furnace, such that the passing time in the homogeneous temperature zone of the furnace is included between 10 seconds and 10 minutes, preferably between 15 seconds and 5 minutes. In any case, the residence time at a temperature included between Trc and 900 °C must be more than 15 seconds, and more appropriately more than 30 seconds, especially when the heat transfer conditions are not optimal. For an industrial furnace with a length of about 1 meter, the speed must be more than 0.1 m / min. For another type of industrial furnace with a length of 30 m, the running speed must be more than 2 m / min, preferably between 7 and 40 m / min. In general, a person skilled in the art knows how to adapt the running speed according to the length of the furnace available to him.

[0098] An additional condition is that, in the annealing R1 prior to the second cold rolling LAF2 described below, the following relationship is satisfied, whereby the strip is given its final thickness e2.

[0099] 26 °C.min.m ≤ (T - CRT).Lu / V ≤ 160 °C.min (T and Trc are in °C, Lu is in m, the speed V is in m / min, and it has been found that Trc = 600 °C is a suitable approximation).

[0100] Preferably, 50 °C.min ≤ (T - Trc).Lu / V ≤ 160 °C.min (with Trc = 600 °C as above).

[0101] These two inequalities are also valid for an intermediate thickness e1 of the strip other than 0.35 mm at the time of the intermediate annealing R1, for example in the case of 0.3 mm or 0.5 mm.

[0102] Surprisingly, in order to obtain a low magnetic loss (about 26.5 W / kg maximum) with the alloy used in the present invention, it has been found that, apart from the fully recrystallized structure aimed for after the final annealing, it is only necessary to obtain a partial recrystallization of the strip at a recrystallization rate of the above (10 to 50%, preferably 15 to 40%, more suitably 15 to 30%) at the end of the intermediate annealing R1. Therefore, for this purpose, it is not necessary to inject an excessive amount of heat into the strip during the partial recrystallization intermediate annealing R1 according to the present invention. However, there are minimum conditions to be satisfied for the above. Otherwise, significant partial recrystallization of the strip cannot be obtained and the intermediate annealing R1 will be wasted. If partial recrystallization cannot be obtained, LAF1 and LAF2 will be directly consecutive to each other, and as a result, it will be equivalent to the conventional case where there is only one cold rolling carried out in a plurality of passes without the partial recrystallization intermediate annealing R1 which is an essential element of the present invention.

[0103] The inventors, for example, in the case of an alloy related to the present invention where the start of recrystallization (temperature Trc) occurs at about 600 °C for annealing for several minutes, after final annealing on a wound toroidal core at 880 °C, during the intermediate annealing R1, in a furnace having an effective length (Lu) of 1 m, at a speed V of 3 m / min, at a temperature of 800 °C, by running the strip with an intermediate thickness e1 = 0.35 mm, at a final thickness e2 of 0.1 mm, succeeded in obtaining a low magnetic loss of less than 26.5 W / kg at 2 T / 400 Hz. Such annealing corresponds to (T - Trc).Lu / V = 67 °C min (T and Trc are in °C units, Lu is in m units, V is in m / min units), and is therefore less than 160 °C min and more than 50 °C min, and thus corresponds to the preferred requirements of the present invention. The recrystallization fraction obtained at the end of the intermediate annealing R1, measured by the EBSD (electron backscatter diffraction) technique, was 40%.

[0104] In another example, for an alloy in which the start of recrystallization (temperature Trc) occurs at about 600 °C for annealing for several minutes, during the intermediate annealing R1 of partial recrystallization, in a furnace having an effective length (Lu) of 2.3 m, at a speed of 3.6 m / min, at a temperature of 840 °C, by running the strip with an intermediate thickness e1 = 0.35 mm, at a final thickness of 0.1 mm, a low magnetic loss of less than 26.5 W / kg at 2T / 400 Hz was successfully obtained. Such annealing corresponds to (T - Trc).Lu / V = 153 °C·min, and thus in this case is also less than 160 °C·min and more than 50 °C·min. The recrystallization fraction obtained at the end of the intermediate annealing R1, measured by the EBSD technique, was 47%.

[0105] On the other hand, in the same annealing R1 of the strip performed at a speed of 2 m / min, excessive recrystallization occurred, and in the final state, a value of (T - Trc).Lu / V = 276 °C·min, and thus more than 160 °C·min, and a magnetic loss exceeding 26.5 W / kg was observed. The recrystallization fraction obtained at the end of the intermediate annealing R1, measured by the EBSD technique, was 72%.

[0106] In yet another example, for an alloy in which the start of recrystallization occurs at about 600 °C (Trc) for annealing for several minutes, during the intermediate annealing R1 of partial recrystallization, in a furnace having an effective length (Lu) of 4 m, at a speed of 7 m / min, at a temperature of 860 °C, by running the strip with an intermediate thickness e2 = 0.5 mm, at a final thickness e2 = 0.1, a low magnetic loss of less than 26.5 W / kg at 2T / 400 Hz was successfully obtained. Such annealing corresponds to (T - Trc).Lu / V = 149 °C·min, and thus less than 160 °C·min and more than 50 °C·min. The recrystallization fraction obtained at the end of the intermediate annealing R1, measured by the EBSD technique, was 25%.

[0107] It should be noted that the continuous processing furnace used may be of any type. In particular, the furnace may be a conventional resistance furnace or radiant furnace, a Joule effect annealing furnace, a fluidized bed annealing facility, or any other type of furnace.

[0108] At the exit of the furnace, the strip must be cooled at a sufficiently high rate to prevent the total order-disorder transformation during cooling. However, the inventors have found that, in most cases, in contrast to hot-rolled strips about 2 mm thick that must be quenched in order to be able to perform cold rolling without problems thereafter, thin (0.12 - 0.6 mm) cold-rolled strips that are intended to be cold-rolled again later are only subject to slight partial ordering up to the point where the low degree of brittleness reached does not very preferentially require the above-mentioned quenching carried out after hot rolling.

[0109] The inventors have surprisingly found that, on the condition that the disorder / order transformation is not complete, after the above-mentioned continuous intermediate annealing, the ability of the strip to be cold-rolled and cut (especially by shearing) is very good. The above means that, unexpectedly, such strips can be cold-rolled again despite the partial ordering that causes a certain degree of brittleness.

[0110] To prevent the disorder / order transformation from being complete, the cooling rate above 200°C must be at least 600°C / hour, preferably at least 1000°C / hour, more preferably at least 2000°C / hour. Therefore, cooling by forced convection or spraying of a coolant is actually necessary to achieve the desired minimum rate. When the temperature of the strip drops to 200°C, the order / disorder transformation no longer changes significantly, and the cooling rate from 200°C to ambient temperature is no longer important from such a perspective.

[0111] The cooling rate can be as high as theoretically possible considering the thickness of the strip and the available cooling means. However, in practice, exceeding 50,000°C / hour is not useful. A rate of 2,000°C / hour to 10,000°C / hour is usually sufficient, and forced convection is usually sufficient to obtain such a rate.

[0112] Furthermore, the annealing carried out before the final cold rolling (i.e., intermediate annealing R1) must satisfy the following two inequalities according to the temperature T of the strip represented in °C, the effective length Lu of the furnace represented in m (the length of the plateau or the maximum temperature T of the furnace exceeding the recrystallization start temperature Trc of the strip for several minutes of annealing, and the temperature Trc is considered to be equal to 600°C, an appropriate approximation for all alloys related to the present invention), and the strip speed V represented in m / min (in the case of the first inequality), and can also satisfy (in the case of the second inequality): * 26 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min * And preferably, 50 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min.

[0113] The reason for this will be described later.

[0114] Next, after the continuous intermediate annealing R1, the second cold rolling sequence LAF2 is carried out in one or more passes, whereby a thickness e2 typically included in the range of 0.05 - 0.25 mm, preferably 0.07 - 0.20 mm, is imparted to the strip. e2 is generally the final thickness intended for the cold rolled strip. According to the present invention, the reduction rate TR2 of this second cold rolling LAF2 is included in the range of 60 - 80%, preferably 65 - 75%.

[0115] The sequence LAF1 - R1 - LAF2, with two cold rolling operations LAF1 and LAF2 and an intermediate annealing R1 following hot rolling and preceding the final stress relief annealing Rf, is a typical preferred case of the present invention. In addition to LAF1, R1, and LAF2 implemented as described above, a greater number of cold rolling and intermediate annealing operations may be provided. Such additional cold rolling and intermediate annealing operations may be represented by LAFi and Ri respectively, and are initiated and implemented from the hot rolled and cooled semi - product according to the present invention. Therefore, all of the above operations must precede the sequence LAF1 - R1 - LAF2 which is essential in the present invention, and the semi - product must be 100% recrystallized after the last annealing Ri. This is for the reasons indicated above regarding the case where cold rolling and annealing are not carried out before the above sequence so that the sequence LAF1 - R1 - LAF2 according to the present invention starts with a 100% recrystallized microstructure.

[0116] Compared with the most common case of the operating sequence of LAF1 - R1 - LAF2, there may be only one additional cycle LAF1 - R1. However, the present invention is understood to cover cases where, in addition to LAF1 - R1 - LAF2, there are multiple such additional cycles LAF1 - R1 - LAF2, all carried out before LAF1. In any case, the annealing R1 carried out before the last cold rolling LAF2 must be carried out at a strip speed V (in m / min) under the following conditions according to the maximum temperature T of the strip, the effective length Lu of the furnace (the length of the furnace plateau or where the maximum temperature T is higher than the temperature Trc, the recrystallization start temperature of the strip for annealing in minutes, here 600 °C): * 26 °C.min ≤ (T - Trc).Lu / V ≤ 160 °C.min * Preferably, 50 °C.min ≤ (T - Trc).Lu / V ≤ 160 °C.min.

[0117] An example of such a process includes two additional cycles LAFi - Ri. In this case too, the thickness e of the preceding example HRStarting from a hot-formed strip with a thickness of 2 mm, first, in order to obtain a strip thickness ei-no.1 of up to 1.2 mm, the first cold rolling LAFi-no.1 is carried out at a speed TR(i = 1) of at least 40%, and then, after the last intermediate annealing, and thus before LAF1, in order to make it more certain that the sheet or strip can be completely recrystallized as required by the present invention, in any case, the metal is preferentially 100% recrystallized, and the first intermediate annealing Ri-no.1 will be carried out, where the passing time of the strip at a temperature of Trc~900 °C in the effective zone of the furnace is 10 seconds to 10 minutes, preferentially 15 seconds to 5 minutes, and more appropriately 30 seconds to 5 minutes. After the intermediate annealing Ri-no.1, it is cooled at a speed exceeding 600 °C per hour, and preferentially at a speed exceeding 1000 °C per hour, or at a speed exceeding 2000 °C per hour. In practice, exceeding 10,000 °C / h is not useful, and generally a speed of 2000 °C / h to 3000 °C / h is sufficient. Generally, when cold rolling is carried out after continuous intermediate annealing (Ri or R1), for reasons related to the ability of the strip to be cold rolled again and the suitability of cutting if useful, such rapid cooling is necessary for the above reasons.

[0118] Next, the second cold rolling LAFi-no.2 is carried out at a ratio of at least 40% of TRi-no.2 to a maximum thickness of 0.96 mm ei-no.2, followed by the second intermediate annealing Ri-no.2, and then cooling is carried out at a speed exceeding 600 °C / h, preferentially exceeding 1000 °C / h, and further exceeding 2000 °C / h. In practice, exceeding 10,000 °C / h is not useful, and generally a speed of 2000 °C / h to 3000 °C / h is sufficient. The Ri-no.2 annealing is characterized by the fact that the passing time of the strip at a temperature of Trc~900 °C in the effective zone of the furnace must be included between 10 seconds and 10 minutes, preferentially 15 seconds to 5 minutes, and even more appropriately 30 seconds to 5 minutes, and further by the fact that the metal is 100% recrystallized after the annealing Ri-no.2.

[0119] At this stage, the following typical and obligatory steps of the invention follow: LAF1-R1-LAF2 and Rf.

[0120] The first cold rolling LAF1 is carried out to 70 - 90%, in this case 80% is selected, and as a result, the strip thickness e1 becomes at most 0.19 mm. Thus, the 100% recrystallized fine structure derived from Ri-no.2 is destroyed.

[0121] Next, partial recrystallization annealing R1 is carried out, followed by cooling at a rate exceeding 600 °C / h, and preferably exceeding 1000 °C / h, or even 2000 °C / h. In practice, exceeding 10,000 °C / h is not useful, and generally a rate of 2000 °C / h - 3000 °C / h is sufficient. Annealing R1 is characterized by the running of a strip with an intermediate thickness e1 = at most 0.19 mm at a temperature of 820 °C at a speed of 12 m / min in a furnace with an effective length 4 m (Lu) for annealing for several minutes at about 600 °C (i.e., Trc) for an alloy where recrystallization starts. Such annealing corresponds to (T - Trc).Lu / V = 73.3 °C.min, and thus is less than 160 °C.min and more than 50 °C.min. Thus, this annealing meets the aforementioned requirements for annealing R1 preceding the final cold rolling.

[0122] Next, cold rolling LAF2, which is the fourth cold rolling in the above example, is carried out. LAF2 needs to have a reduction rate of 60 - 80%, here 70% is selected, whereby a strip with a final thickness e2 of at most 0.06 mm is produced.

[0123] Finally, the final static annealing Rf for full recrystallization is carried out, typically at 850 - 890 °C for several hours in a reducing atmosphere, for example at 880 °C for 3 hours in pure hydrogen, followed by cooling at a rate of 100 - 500 °C / h, preferably 200 - 300 °C / h, and the magnetocrystalline anisotropy constant K1 is strongly reduced or eliminated.

[0124] Therefore, it is considered to be quite sufficient to perform only two cold rolling sequences, end the intermediate annealing R1 (partial recrystallization) with a rapid quench (at least at 600 °C / h as described above), and obtain the distribution of the reduction rate TR between the double cold rolling operations that leads to achieving the desired final thickness shown above, prior to the final soaking annealing of the complete recrystallization Rf described in detail below.

[0125] On the other hand, as has been described so far, it is also conceivable to perform more than two (four in the previous example) cold rolling sequences with associated intermediate annealing and rapid quenching before Rf, and in this case, it is also possible to appropriately distribute the reduction rate of each cold rolling. However, at least from an economic point of view, it is beneficial not to increase the cold rolling and annealing sequences more than necessary empirically, and it is also clear that the two very special cold rolling sequences LAF1 and LAF2 are also separated by the same special continuous intermediate annealing with partial recrystallization R1 followed by rapid cooling, and LAF1 is preferably performed on the hot rolled semi-finished product that is completely recrystallized and, if appropriate, ultra-rapidly cooled, due to the narrow ranges of reduction rates TR1 and TR2 respectively.

[0126] The following conditions: - 26 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min (Trc is equal to 600 °C); - Preferably 50 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min; should be understood to be the conditions to be satisfied by the continuous annealing R1 prior to the final cold rolling LAF2.

[0127] On the other hand, such a condition does not necessarily have to be fulfilled by additional intermediate anneals R1 (if any), since in this case it is merely a requirement that the recrystallization is completed after the last additional anneal R1. It is merely a preference that the recrystallization is completed after other additional anneals Ri (if any). When such anneals are carried out, the time of passage through the effective zone of the furnace, in which a temperature of Trc ∼ 900 °C is exerted on the strip, must preferentially be comprised between 10 s and 10 min, preferentially between 15 s and 5 min, and even better between 30 s and 5 min.

[0128] What is necessary is to have a 100% recrystallized state just before LAF1 (and therefore after the last additional anneal Ri).

[0129] By way of example, the following scheme can be given for a production process sequence that includes several intermediate annealings R1 and that may be according to the invention: EXAMPLES

[0130] With two intermediate annealings Ri: 2mm thickness HR - hot rolling to a thickness of 1 mm with a reduction of 50%; - Ri-no.1 to a thickness of 100% recrystallization; - LAFi-no.2 to a thickness of 0.5 mm with a reduction of 50%; - Ri-no.2 to a thickness of 100% recrystallization; - LAF1 to a thickness e1 of 0.15 mm with a reduction of 70%; - R1 to a degree of recrystallization of 10-40%; - LAF2 to a thickness e2 of 0.06 mm with a reduction of 66%; - Rf standing under hydrogen at 850 °C for 3 hours to achieve full recrystallization. EXAMPLES

[0131] With 3 intermediate annealings Ri: 2.5mm thickness HRHot rolling up to - LAFi-no.1 up to a thickness of 1.5 mm with a reduction rate of 40% - Ri-no.1 up to a recrystallization rate of about 100% - LAFi-no.2 up to a thickness of 0.9 mm with a reduction rate of 40% - Ri-no.2 up to a recrystallization rate of about 100% - LAFi-no.3 up to a thickness of 0.5 mm with a reduction rate of 44% - Ri-no.3 up to a recrystallization rate of about 100% - LAF1 up to a thickness of 0.15 mm e1 with a reduction rate of 70% - R1 with a recrystallization rate of about 10 - 40% - LAF2 up to a thickness of 0.06 mm e2 with a reduction rate of 66% - Total recrystallization is achieved by standing for 3 hours under hydrogen at 850°C, Rf.

Example

[0132] When accompanied by two intermediate annealings Ri: Hot rolling up to a thickness of 1.5 mm e HR up to - LAFi-no.1 up to a thickness of 0.9 mm with a reduction rate of 40% - Ri-no.1 up to a recrystallization rate of about 100% - LAFi-no.2 up to a thickness of 0.5 mm with a reduction rate of 44% - Ri-no.2 up to a recrystallization rate of about 100% - LAF1 up to a thickness of 0.15 mm e1 with a reduction rate of 70% - R1 with a recrystallization rate of about 10 - 40% - LAF2 up to a thickness of 0.06 mm e2 with a reduction rate of 66% - Total recrystallization is achieved by standing for 3 hours under hydrogen at 850°C, Rf.

Example

[0133] When accompanied by intermediate annealing Ri: Hot rolling up to a thickness of 1.59 mm e HR up to - LAFi-no.1 up to a thickness of 0.95 mm with a reduction rate of 40% - Ri-no.1 up to a recrystallization rate of about 100% - LAF1 up to a thickness of 0.29 mm e1 with a reduction rate of 70% - R1 with a recrystallization rate of about 10 - 40% - LAF2 up to a thickness of 0.1 mm e2 with a reduction rate of 65% - Total recrystallization is achieved by standing for 2 hours under hydrogen at 870°C, Rf.

[0134] In all cases (LAF cold rolling sequences of two or more times), the material that has reached the final thickness undergoes a final stress relief annealing Rf on a strip or pre-cut and formed parts (winding tapes toroidal cores, rotors, and actuator stators of transformers). At this time, the strip is completely recrystallized, and the growth of ferrite grains is sufficiently advanced without entering the austenite region. Such sufficient growth of ferrite grains leads to low magnetic losses, but sufficient growth of ferrite grains cannot be obtained by continuous annealing with too short a time for such purposes.

[0135] Therefore, the stress relief annealing Rf is carried out in a vacuum or a non-oxidizing protective atmosphere, thus in a neutral or reducing protective atmosphere, for example, under nitrogen, under a nitrogen-hydrogen or argon-hydrogen mixed gas, under an inert gas such as argon, preferably under pure hydrogen, at a temperature of 750 - 900 °C, preferably 800 - 900 °C, more appropriately 850 - 880 °C, and is typically applied for more than 30 minutes, preferably more than 1 hour.

[0136] The cooling following the final annealing Rf may be carried out at any rate, but preferably at 100 °C / hour - 500 °C / hour, more appropriately 200 °C / hour - 300 °C / hour.

[0137] The reason for such a limitation is that the purpose of cooling is to optimize the magnetocrystalline anisotropy constant K1, and - In the case of slow cooling, a positive value K1 corresponding to an ordered alloy can be obtained; - In the case of very rapid cooling, a negative value K1 corresponding to a disordered alloy can be obtained due to this.

[0138] Optimal magnetic properties are obtained when K1 is equal to 0, that is, in the case of an optimized cooling rate within the aforementioned range, and thus most typically about 250 °C / hour.

[0139] The following experiments were carried out to demonstrate the advantages of the present invention.

[0140] Table 3 shows the composition of the five alloys used in mass percentage. Alloys 1 and 4 were produced from new and thus expensive raw materials by only one remelting. The other alloys 2 (which was the alloy designated as "Ref1" in Table 1 and whose composition follows the composition that can be used in the present invention), 3 and 5 were produced from normal raw materials without remelting and thus at the lowest possible cost. As a result, the concentrations of Mn, S, Ni, Cu, and Nb in Alloy 1 were obtained from the melting of the raw materials and the manufacturing conditions of the liquid metal rather than from the addition of the said elements, and were lower than the concentrations of these same elements in the other alloys, indicating that very high-purity raw materials were used in the case of the said alloy. All of these alloys have compositions that comply with the requirements of the present invention. The elements not specified are present only in the form of impurities at most and have no metallurgical effect. Also, the recrystallization start temperature Trc, which is involved in determining the parameters of the intermediate annealing R1 prior to the final cold rolling LAF2, was shown. As described above, all the temperatures are very close to 600 °C, as in the case of alloys having the general composition used in the present invention.

[0141]

Table 3

[0142] The ingots (dimensions 200×500×2500 mm) made from these alloys were hot-rolled and then super-rapidly cooled. It has been empirically found that if super-rapid cooling is not carried out, there is a high risk of strip breakage during cold rolling when cold rolling is carried out on products having an initial thickness of more than 2 mm.

[0143] Therefore, the product was continuously heated at 800 - 1200 °C, bloomed in the form of bars having a cross-section of 100×350 mm and a length of several meters, then hot cut, and cooled very slowly. Thereafter, it was reheated very slowly (for 16 hours) up to 1200 °C, followed by hot rolling with a strip mill, changing the thickness of the product from 100 mm to 2 mm in 16 consecutive passes. The last pass ended at 950 °C, and ultra-rapid cooling was carried out at a speed of about 1000 °C / second under a water jet. Next, cold winding of the hot strip thus obtained was performed.

[0144] The fine structure of the strip is 100% recrystallized and is a mixture of primary ferrite and martensite rapidly cooled from the austenite phase (which was in equilibrium with the primary ferrite at 950 °C), and to this mixture, transformation product secondary ferrite formed from austenite is added.

[0145] Thereafter, the hot strip was subjected to either single cold rolling or double cold rolling LAF1 and LAF2 with intermediate annealing R1 to obtain a cold strip.

[0146] Finally, the cold strip was subjected to a final stress relief annealing Rf under pure hydrogen, followed by forced cooling at 250 °C / hour.

[0147] The parameters and results of the experiments conducted on Alloys 1 - 5 in Table 3, which demonstrate the benefits of the present invention, are summarized in Table 4. The intermediate annealing was carried out in a furnace with an effective heating length of 2.3 m.

[0148]

Table 4

[0149] The first two lines of the table for Alloy 5 clearly show the favorable contribution of the double cold rolling process compared to the single cold rolling process (here sufficient for washers but insufficient for toroidal cores for (T - Trc).LuZV of 42 °C.min). The third line of the table corresponds to values of (T - Trc).Lu / V in the preferred range of 50 - 160 °C.min, and being in this preferred range shows an additional benefit of further reducing magnetic losses (here an additional 4% reduction).

[0150] Tests regarding single rolling are considered as reference tests regardless of whether remelting was carried out. More specifically, the tests carried out on Alloy 1 on ingots that underwent single rolling and ESR are desired to have losses of 26.5 W / kg or less at 2T and 400 Hz, which is typical for transformer core materials obtained at the cost of expensive remelting in this case. The tests carried out on Alloy 2 that underwent single cold rolling without remelting are typical for materials for rotors of rotating machines. Since there is no intermediate annealing, the relationship of (T - Trc).Lu / V has no meaning in this case, so it is expressed as "not relevant" in the corresponding column of Table 4.

[0151] Also, regarding the tests carried out on Alloy 2, increasing the running speed in the annealing furnace from 3.4 m / min to 3.6 m / min reduces the losses at 2T / 400 Hz, and it is interesting that there is a change from a value of 27 W / kg, which is considered almost acceptable but still too high for washers, to a value of 25.8 W / kg, which is considered appropriate. The reason above is that such an acceleration of the running speed changes the value of (T - Trc).Lu / V to be below 160 °C.min, which is the maximum value required by the present invention. The above clearly shows that it is appropriate to consider the said parameters.

[0152] The indicated practice, which involves no remelting and does not require particularly careful selection of the raw materials, shows that, even for alloys with not particularly high purity, when the precise conditions of the present invention are met, by performing double cold rolling with intermediate annealing, it is possible to retain low magnetic losses after final annealing carried out under conventional conditions (850 °C, 3 hours, or more appropriately 880 °C, 3 hours or 860 °C, 2 hours). Thereby, in all kinds of electrical technology applications, both a high power-to-mass ratio (which can be achieved with equiatomic FeCo alloys) and low magnetic losses of about 26.5 W / kg at 2 T, 400 Hz, or even lower magnetic losses in the most demanding applications in this regard are required. However, it has been found that in the present invention, it is possible to obtain such results without necessarily requiring the costly operation of selecting high-purity raw materials and ESR or VAR ingots.

[0153] The explanation for such an actual situation can be as follows in light of the experiences described below.

[0154] Using non-melted ingots having the compositions of alloy 2, alloy 3 and alloy 5 in Table 3 (Table 3), the conventional hot transformation of the ingots by blooming at 1100 - 1200 °C was applied as usual, followed by hot rolling to a thickness of 2 mm at 1000 - 1200 °C with a strip mill. Next, after ultra-rapid cooling to over 900 °C at a cooling rate of 1000 °C / second at the hot rolling exit, cold rolling was carried out to a thickness of 0.1 mm by single cold rolling with a reduction ratio of 95%, or by double cold rolling to 0.35 mm thickness (reduction ratio 82.5%) and then to 0.1 mm thickness (reduction ratio 71.4%) (thus also with an overall reduction ratio of 95%). Intermediate annealing was carried out at 840 °C with strip speeds of 3.6 m / min for alloy 2, 4.4 m / min for alloy 3, and 4.2 m / min for alloy 5 in a furnace with a homogeneous effective heating length Lu of 2.3 m. These three cases are listed in Table 4 (Table 4), and all can be used to obtain magnetic losses of less than 26.5 W / kg at 2 T / 400 Hz.

[0155] If all other conditions are the same, double cold rolling (LAF1 and LAF2) and intermediate annealing R1 appear to give a significantly changed texture to the strain-hardened strip. This significant texture difference remains without any significant change even after the final annealing Rf of complete recrystallization carried out under the conditions defined in the present invention. Table 5 shows the texture components {hkl} calculated with a maximum dispersion of 15° over three Euler angles with respect to the ideal orientation when the cold-rolled strip is simply in a strain-hardened state or in a completely recrystallized state after a final annealing at 850 °C for 3 hours <uvw>Indicates the volume fraction (unit: %). In the case of intermediate annealing, the effective length Lu of the furnace is 2.3 m.

[0156]

Table 5

[0157] From such results, it is clear that in the strain-hardened state after single cold rolling, texture component A is significantly stronger than the other major texture components B and C of the texture, typically having twice the strength. On the other hand, after double cold rolling according to the present invention, the three components have amplitudes of approximately 8 - 14% that are close to each other. The above is observed in a series of three tests.

[0158] In the test where final annealing was performed after single cold rolling, component A is even more dominant than in the strain-hardened state (40% compared to 25%) and has approximately eight times the strength of components B and C. On the other hand, in the double cold rolling and intermediate annealing according to the present invention, the ratios of components A, B, and C are hardly affected compared to the ratios in the strain-hardened state, and the amplitudes of these components remain close to or very close to each other (approximately 7 - 16% respectively), and component A is no longer necessarily dominant.

[0159] Such results further show that the metallurgical process of the present invention (double cold rolling range with intermediate annealing resulting in partial recrystallization) can be clearly identified without ambiguity on the final product (after final annealing to complete recrystallization, typically carried out at 850 °C for 3 hours) by quantitative characterization of its main texture components.

[0160] In fact, the case of the present invention corresponds to the fact that after final annealing Rf, the texture of the fine structure of the material characterized by EBSD is as follows: - Based on surface area or volume, 8 - 20%, preferably 9 - 20% of the {001}<110> component has an orientation deviation of up to 15° (component A in Table 5). - Based on surface area or volume, 8 - 25%, preferably 9 - 20% of the {111}<112> component has an orientation deviation of up to 15° (Component B in Table 5). - Based on surface area or volume, 5 - 15%, preferably 6 - 11% of the {111}<110> component has an orientation deviation of up to 15° (Component C in Table 5). - The remainder of the material consists of other texture components having an orientation deviation of up to 15°, each being up to 15% based on surface area or volume, and the overlap between said other texture components and any one of the components {001}<110>, {111}<112>, and {111}<110> does not exceed 10% of the surface area or volume of any one of the three components.

[0161] Its crystallographic orientation {hkl} such as 15° <uvw>It should be noted that due to the misorientation of each texture component identified for [[ID=]], two different crystallographic components may partially overlap (see, for example, References [1] to [5] cited below). Therefore, if it is found that a given texture component X occupies a proportion close to (but lower than) 15% of the material, a part of that 15% may actually be derived from any one of the major components A, B, and C that share part of its crystal orientation.

[0162] If it is desired to clearly distinguish the orientation or texture components A, B, and C from the remaining crystal orientation or the minor texture component X, and thus clearly associate the proportions of components A, B, and C with the advantageous magnetic properties of the present invention, it is necessary to be able to separate these representative components A, B, or C from the other minor component X with a sufficiently high accuracy, and thus it is necessary to define a criterion for having little overlap between these two types of components.

[0163] Detailed crystallographic analysis known to those skilled in the art, such as the typically well-known EBSD technique (References [6] and [7] listed below), can be used to identify each of the texture components that are clearly different from a random distribution and to determine the degree of possible overlap between the components. In the present invention, it is defined that the crystal orientation overlap between one of components A, B, or C on the one hand and the minor texture component X of the texture on the other hand should not exceed 10% of the surface area or volume fraction.

[0164] For example, adjacent to component A-{100}<011> having a misorientation of 15° around the ideal component (100)

[0001] , there is component X-{hkl} having a very close misorientation <uvw>, for example, when trying to identify an X1-{210}<011> with a 15° misorientation around the ideal component (210)

[0001] that forms an angle of 26.56° with respect to (100)

[0001] (therefore, there is an overlap since 26.56° < 2x15°), the overlap of the crystal orientation surface or volume fraction of A and X1 shall not exceed 10% of the total surface or volume fraction. In this case of the examples of X1 and A, if there is an overlap exceeding 10%, a component X2 that is slightly away from A and meets the <10% criterion is selected, for example, an X2-{320}<011> with a 15° misorientation around the ideal component (320)

[0001] that forms an angle of 33.69 degrees with respect to (100)

[0001] .

[0165] References for a good understanding of the concepts and methods described above are, in particular, as follows: (References)

[0166] The three texture components under consideration are the most sensitive to the change from single cold rolling to double cold rolling and are typically the components with the highest proportion in the final product, so they are the most characteristic components of the present invention.

[0167] Using alloy 2 with the composition shown in Table 3 (Table 3), the tests were carried out using the same procedure as in the previous tests. The following treatments were applied to the alloy: - Casting without VAR of an ingot with a cross-sectional area of 200×800mm 2 ; - Obtaining a hot strip with a thickness e of 2.0mm that is 100% recrystallized, the ingot was hot rolled at a temperature of 950 - 1200°C and then cooled (ultra-rapid cooling) at a rate of about 1000°C / second; HR [to obtain] - To obtain a cold strip with a thickness e1 of 0.35mm, the hot rolled sheet was cold rolled LAF1 of the ultra-rapid cooled hot strip with a reduction ratio of 83%; - Continuously perform an intermediate annealing R1 of partial recrystallization at a temperature of 760 - 810°C under pure hydrogen in an oven with an effective length Lu of 2.3m. The strip passes through this oven at a variable speed V (2.3 to 6.5 m / min) according to the test, and the temperature T of the effective zone also changes according to the test. After the final annealing Rf, the influence of (T - Trc).Lu / V on the magnetic loss at 2T and 400 Hz can be evaluated, and the degree of recrystallization after R1 measured by the EBSD (electron backscatter diffraction) method can be evaluated; following annealing R1, cooling is carried out to room temperature at a rate of 2500 °C / h; To obtain a cold strip with a final thickness e2 of - 0.10 mm, cold rolling LAF2 is carried out at a reduction rate of 71%; - The final stationary annealing Rf is carried out at a temperature of 850 °C for 3 hours under pure hydrogen to achieve complete recrystallization, and then cooled to room temperature at a rate of 250 °C / h.

[0168] In the test, after knowing the values of the strip speed V and the recrystallization threshold Trc (around 600 °C), the value of (T - Trc).Lu / V was considered. In this case, Lu (experimentally determined in advance by installing a thermocouple in the furnace) is 2.3 m, and is an amount considered to be within the scope of the present invention.

[0169] The magnetic loss was measured with a 0.1 mm thick washer and an inner diameter / outer diameter of 25 / 36 mm or 29.5 / 36 mm.

[0170] Table 6 shows the following magnetic hysteresis characteristics measured in direct current: the maximum induction Bm of the cycle for a maximum magnetic field of 20 Oe, the residual magnetism Br of the same cycle at a maximum magnetic field of 20 Oe, the ratio Br / Bm between Br and the maximum induction, and the coercive force field Hc, according to the continuous annealing conditions (temperature T and strip speed V). The table also shows the magnetic loss observed at 2T, 400 Hz, and an index equal to (T - 600).tu. This index represents the amount of energy supplied during the intermediate annealing and is defined in relation to the recrystallization start temperature Trc (here 600 °C) of the material. Lu is the "effective length" of the furnace, that is, the length of the path of the strip passing through the furnace where the strip is at a temperature exceeding Trc, and the "effective time" t u (Unit: minute) is the length of time the strip remains within the effective length of the furnace. The table also shows the ratio of the surface area or volume of three texture components (corresponding thereto) characteristic of the present invention.

[0171]

Table 6

[0172] Figures 1 and 2 show, for the implementation of 100% recrystallization before LAF1, the magnetic losses at 2T and 400 Hz and the recrystallization rate of the sample as functions of the amounts (T - 600) / V and (T - 600).Lu / V (600 °C is the value of Trc), respectively, as defined above.

[0173] It can be seen that the magnetic losses after LAF2 and Rf are lower the lower the amount of (T - 600) / V (where V is the strip speed), provided that all other conditions are the same (Figure 1). In order to stay within the original goal of the present invention of maintaining losses of about 26 W / kg without the need for careful selection of raw materials related to the complex manufacture of the ingot from which the strip is made, if a maximum loss of 26.5 W / kg is desired, for the specific embodiment, if it is desired to obtain a magnetic loss of 26.5 W / kg or less, it is highly preferable not to exceed a value of 80 °C min / m for (T - 600) / V, preferably 60 °C min / m (corresponding to a loss < 26 W / kg). Such a relatively low maximum value of (T - 600) / V (relative to the energy injected into the metal during R1) is closely related to a relatively low recrystallization rate after R1 and can be estimated to be 50% or less, preferably 40% or less, more appropriately 30% or less. In the best example, the recrystallization rate is about 15 - 17%. For the intermediate annealing to be useful, a minimum ratio of 10%, more appropriately 15%, is required.

[0174] The first example in Table 6 has a recrystallization degree of 40% in R1, and the magnetic loss at 2T and 400 Hz after the final annealing is 26 W / kg, which is slightly below the maximum allowable value of 26.5 W / kg. The above indicates that the value of (T - 600) / V of 60 - 80 °C·min / m may be suitable in this case, but it is not optimal.

[0175] The maximum value of (T - 600) / V that can be considered acceptable is merely an indicator since it is valid for this series of examples in the reduced range of the intermediate annealing temperature of 760 - 810 °C. The limits of 80 °C·min / m, preferentially 60 °C·min / m, correspond to a continuous annealing furnace with an effective length of 2.6 m. However (Figure 2), the calculation of this tolerance limit can be generalized to any effective length Lu as follows: (T - CRT)·Lu / V ≤ 60·Lu = 160 °C·min (where Trc = 600 °C). Therefore, if the furnace under consideration is three times longer, the limit of 160 °C·min remains unchanged for a strip with a thickness of 0.35 mm, and it is necessary to lower the furnace temperature T or increase the strip speed V such that (T - Trc)·Lu / V ≤ 160 °C·min. Thus, there is no need to over-recrystallize the strip during annealing R1, and the magnetic loss at the final thickness of 0.1 mm will be 26.5 W / kg or less on a washer annealed at 850 °C for several hours, and it will be even better if it is carried out above 850 °C (but less than 900 °C).

[0176] Other examples involve a furnace with an effective length of 2.3 m and a continuous intermediate annealing that varies from 3.6 to 4.4 m / min, with a temperature in the homogeneous zone of the furnace of 840 °C (thus above the first temperature zone considered above) during the continuous intermediate annealing, and relate to three different castings that follow the same metallurgical range (same reduction rate of cold rolling, same hot transformation, and same thickness after hot rolling), as shown in Table 5. Therefore, for such examples, with respect to the previously cited example with Lu = 2.6 m, it can be seen that in order to maintain (T - 600).Lu / V < 160 °C / min, when all other conditions are equal, if Lu decreases, the continuous annealing temperature T must necessarily increase. Therefore, in the use of the present invention, the first inequality can be used to consider the effective length Lu of the furnace.

[0177] In other words, experimentally and unexpectedly, it is necessary to exceed the complete recrystallization temperature Trc during the intermediate annealing R1 prior to the last cold rolling. This is about 600 °C for the alloys related to the described examples. However, if this temperature is reached, it can be seen that it is not necessary to add an excessive total amount of heat to the metal so as not to obtain excessive recrystallization. Such requirements are met by combining the temperature and duration of the intermediate annealing R1, and the latter parameter is represented by the running speed in the furnace for a given furnace length. By considering the parameter (T - Trc).Lu / V under the above conditions, this parameter can be examined to quantify the heat applied to the strip, assume the kinetics of recrystallization, and ensure that the recrystallization rate given by R1 remains within a predetermined range even if the temperature Trc is exceeded during R1.

[0178] If the intermediate annealing R1 prior to the final cold rolling LAF2 is insufficient to initiate recrystallization when the strip is at an intermediate thickness between the hot rolling strip thickness and the final thickness of the cold rolling strip, the intermediate annealing R1 has no required metallurgical effect, and from the perspective of the problems to be solved by the present invention, it is as if there is no intermediate annealing, and all that follows those initial cold rollings occurs as if they are simply additional passes that together constitute a single cold rolling process.

[0179] If a cold rolling sequence exceeding three times is carried out, and thus at least two intermediate annealings Ri and R1 are carried out, the annealing carried out before the last cold rolling LAF2 before the last intermediate annealing R1, i.e., the final annealing Rf, must meet the conditions required by the present invention regarding the degree of recrystallization of the semi-finished product before Rf.

[0180] Attempting to associate the measured values of magnetic loss with some of the most classical fine structure characteristics, such as grain size, a part of the α or γ fiber texture, no obvious results can be obtained. However, it can be hypothesized that the increased isotropy of the texture obtained by double cold rolling (see Table 5) contributes to such improvement.

[0181] On the other hand, empirically, it has been found that the influence of the recrystallization fraction is observed after the intermediate annealing R1. The recrystallization fraction should not be too high. In other words, for a predetermined temperature T greater than Trc, the time the strip stays in the effective length Lu of the annealing furnace should not be too long as shown by the following relational expression: 26 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min, Preferably, 50 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min This is one of the conditions for complying with the present invention.

[0182] However, recrystallization may be at least a little, but it must not be zero.

[0183] Regarding LAF1, R1, LAF2, and Rf, tests were carried out on samples that were not completely recrystallized (recrystallization rate 35%) before LAF1 under the same operating conditions as in the previous examples according to the present invention in Table 6 (the last row of Table 6). From this example, it is observed that compared with the examples according to the present invention, the texture component {111}<112> is much more clearly dominant on the final product, probably due to the stronger anisotropy of the texturing, the magnetic loss increases, and the double cold rolling included in the present invention was not fully corrected.

[0184] As a comparison, tests were carried out on a sample of alloy 2 hot-rolled and cooled under the same conditions as in the previous example. The sample was subjected to a single cold-rolling sequence LAF, changing the sample from 2.0 mm to 1.0 mm, and subsequently final Rf annealing was carried out under the same conditions as in the previous example.

[0185] After the final stationary annealing Rf, the sample has a magnetic loss of about 27 W / kg, and thus this value is considered too high to meet the objectives of the present invention.

[0186] The above shows that the double rolling LAF1 + LAF2, with an intermediate annealing R1, causes very partial recrystallization and, when carried out under the conditions defined by the present invention, substantially improves the magnetic loss of the metal even when all other conditions are the same. Before the final stationary annealing Rf for recrystallization, the strip, which is mainly strain-hardened or remains recovered, does not have the low magnetic loss of the strip treated according to the present invention if all other conditions are the same.

[0187] By satisfying the condition of 26 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min, preferably 50 °C·min ≤ (T - Trc)·Lu / V ≤ 160 °C·min, a degree of recrystallization sufficient to lower the magnetic loss to a desirable level is ensured.

[0188] In the described examples, after the stationary annealing Rf which is the final annealing, other heat treatments or thermo-mechanical treatments may be carried out, for example to improve the compatibility of cutting the strip obtained after the stationary annealing, provided that such treatments do not degrade the above-expected properties.

[0189] In fact, as described above, the final stress relief annealing Rf can be carried out on parts cut from cold-rolled strips (for example, rotors, stators, transformer core elements, etc.). However, if it is found that the suitability of the cold-rolled stress relief strip for being cut is not sufficient for the intended application, the stress relief Rf can be carried out on the coiled cold-rolled strip, and then, depending on conditions such as the running speed, length, and furnace temperature to reach a temperature of 700 to 900 °C in 10 seconds to 1 hour, preferably 10 seconds to 20 minutes, a new annealing can be continuously carried out on the stress relief strip at this time under a reducing atmosphere (preferably pure hydrogen). Such a temperature corresponds to the disordered ferrite region and needs to be reached before a sufficiently rapid temperature drop begins at this temperature. The annealing ends with a relatively rapid cooling (at least 1000 °C / h). Such a new annealing and subsequent cooling improve the suitability of the strip material for being cut and are advantageous for certain applications where the final parts (or assemblies of such final parts) have to be cut with high precision or under difficult conditions. The above does not affect the texturing of the strip. When exceeding 900 °C, a phase transformation occurs and the properties deteriorate.

[0190] More specifically, when the final parts are electrical technology parts, there is a case where unit parts larger than the final parts are stacked, each is coated with an insulating varnish, and assembled by adhesion to form a multi-layer assembly. The multi-layer assembly is then cut to its exact final dimensions, which can be easily done only when the unit parts have excellent cutting suitability, and in certain cases, only the last continuous annealing and subsequent cooling can be achieved.< / uvw> < / uvw> < / uvw>

Claims

A method for manufacturing a cold-rolled strip or sheet of a substantially equiatomic FeCo alloy, which is a magnetic material, comprising: - preparing a hot-rolled sheet or strip having a thickness (e ＨＲ ) included in the range of 1.5 to 2.5 mm, wherein the composition of the hot-rolled sheet or strip is, by mass percentage, as follows: * 47.0% ≤ Co ≤ 51.0%; * trace amount ≤ V + W ≤ 3.0%; * trace amount ≤ Ta + Zr ≤ 0.5%; * trace amount ≤ Nb ≤ 0.5%; * trace amount ≤ B ≤ 0.05%; * trace amount ≤ Si ≤ 3.0%; * trace amount ≤ Cr ≤ 3.0%; * trace amount ≤ Ni ≤ 5.0%; * trace amount ≤ Mn ≤ 2.0%; * trace amount ≤ C ≤ 0.02%; * trace amount ≤ O ≤ 0.03%; * trace amount ≤ N ≤ 0.03%; * trace amount ≤ S ≤ 0.005%; * trace amount ≤ P ≤ 0.015; * Trace amount ≤ Mo ≤ 0.3%; * Trace amount ≤ Cu ≤ 0.5%; * Trace amount ≤ Al ≤ 0.01%; * Trace amount ≤ Ti ≤ 0.01%; * Trace amount ≤ Ca + Mg ≤ 0.05%; * Trace amount ≤ rare earth elements ≤ 500 ppm; * The balance is iron and impurities generated by dissolution; * The recrystallization start temperature (Trc) and the strip or sheet having a fine structure recrystallized 100% to prepare a hot-rolled sheet or strip; - Next, the first cold rolling step (LAF1) of the strip or sheet is carried out in one or more passes at a total reduction ratio (TR1) of 70 to 90% to reduce the thickness (e1) of the strip or sheet to 1 mm or less; - Next, intermediate annealing (R1) is carried out while passing the strip or sheet through an annealing furnace, resulting in partial recrystallization of the strip or sheet. The strip or sheet is passed through the annealing furnace at a speed V, the degree of partial recrystallization is 10 to 50%, and the temperature of the strip or sheet in the effective zone of the furnace having an effective length Lu is included in Trc to 900 °C. The strip or sheet stays at a temperature T such that 26 °C min ≤ (T - Trc) × Lu / V ≤ 160 °C min for 15 seconds to 5 minutes in the effective zone having an effective length Lu. T and Trc are in °C units, Lu is in m units, V is in m / min units, and the strip or sheet is cooled to a temperature of 200 °C or less at a speed of at least 600 °C / h at the outlet of the annealing furnace, resulting in partial recrystallization of the strip or sheet; - Next, the second cold rolling step (LAF2) of the annealed strip or sheet is carried out in one or more passes at a total reduction ratio of 60 to 80% to make the thickness (e2) of the cold-rolled strip or sheet 0.05 to 0.25 mm; - Next, the cold-rolled strip or sheet, or a portion previously cut from the strip, is subjected to a stationary final annealing (Rf) at a temperature of 750 to 900 °C for at least 30 minutes in a neutral or reducing atmosphere, or in a vacuum, to obtain complete recrystallization of the strip or sheet or the cut portion, and then cooled at a speed of 100 to 500 °C / h is characterized in that A method in which, after hot rolling and before the first cold rolling (LAF1), the hot-rolled strip or sheet is supercooled by cooling the hot-rolled strip or sheet from a temperature included in the range of 800 to 1000 °C to room temperature at a rate of at least 600 °C / second. Claim 2 The method according to claim 1, characterized in that (V + W) / 2 + (Ta + Zr) / 0.2 ≥ 0.8%.

3. The method according to claim 1 or 2, characterized in that trace amount ≤ Si ≤ 0.1%.

4. The method according to claim 1 or 2, characterized in that trace amount ≤ Cr ≤ 0.1%.

5. Before the first cold rolling step (LAF1), at least one additional cold rolling cycle (LAFi) and an intermediate annealing (Ri) are carried out, so that the cold rolled strip or sheet has a thickness between the thickness after hot rolling (e ＨＲ ) and the inlet thickness of the first cold rolling (LAF1), and during each additional annealing (Ri), the passing time of the strip or sheet in the effective zone of the furnace located between Trc and 900 °C results in the full recrystallization of the strip or sheet, and the intermediate annealing (Ri) has a passing time between 10 seconds and 10 minutes in the zone of the furnace length Lu where the temperature of the strip is between Trc and 900 °C, and then, at the outlet of the furnace, the strip or sheet is cooled to a temperature of 200 °C or less at a rate of at least 600 °C / hour, and the strip or sheet has a fine structure that is 100% recrystallized after the last of the additional annealings (Ri). The method according to claim 1 or 2, characterized in that.

6. The method according to claim 1, characterized in that the ultra-rapid cooling is carried out directly after hot rolling without intermediate reheating.

7. The method according to claim 1 or 2, characterized in that the atmosphere of the annealing furnace is a reducing atmosphere.

8. At least one additional intermediate annealing is a continuous annealing of a strip or sheet in an annealing furnace, the temperature of the strip or sheet in the effective zone of the furnace being between Trc and 900 °C, the strip remaining in the effective zone for 15 seconds to 5 minutes, and the strip or sheet at the outlet of the furnace being cooled to a temperature of 200 °C or less at a rate of at least 600 °C / hour, and at least one additional cold rolling (LAFi) being carried out in one or more passes with a total reduction ratio of at least 40%, the method according to claim 5.

9. After the final stationary annealing (Rf), an additional continuous annealing of the strip or sheet is carried out for at least 10 seconds and at most 1 hour so that the metal reaches at least 700 °C and at most 900 °C, followed by cooling at a rate of at least 1000 °C / hour, the method according to claim 1 or 2.

10. A substantially equiatomic FeCo alloy, - The composition of the alloy is, by mass percentage, * 47.0% ≤ Co ≤ 51.0%; * trace amount ≤ V + W ≤ 3.0%; * trace amount ≤ Ta + Zr ≤ 0.5%; * trace amount ≤ Nb ≤ 0.5%; * trace amount ≤ B ≤ 0.05%; * trace amount ≤ Si ≤ 3.0%; * trace amount ≤ Cr ≤ 3.0%; * trace amount ≤ Ni ≤ 5.0%; * trace amount ≤ Mn ≤ 2.0%; * trace amount ≤ C ≤ 0.02%; * trace amount ≤ O ≤ 0.03%; * trace amount ≤ N ≤ 0.03%; * trace amount ≤ S ≤ 0.005%; * trace amount ≤ P ≤ 0.015; * trace amount ≤ Mo ≤ 0.3%; * trace amount ≤ Cu ≤ 0.5%; * trace amount ≤ Al ≤ 0.01%; * trace amount ≤ Ti ≤ 0.01%; * Trace amount ≤ Ca + Mg ≤ 0.05%; * Trace amount ≤ rare earth elements ≤ 500 ppm; * The balance consists of iron and impurities generated by dissolution thereof, - The fine structure of the alloy is completely recrystallized, and - The texture of the alloy is as follows: * Based on surface area or volume, component {001}<110> is 8 - 20%, and the component {001}<110> has an orientation deviation of at most 15°; * Based on surface area or volume, component {111}<112> is 8 - 25%, and the component {111}<112> has an orientation deviation of at most 15°; * Based on surface area or volume, component {111}<110> is 5 - 15%, and the component {111}<110> has an orientation deviation of at most 15°; The remainder of the material consists of other texture components, the other texture components have an orientation deviation of at most 15°, each corresponds to at most 15% based on area or volume, and the overlap of each other texture component with any one of the components {001}<110>, {111}<112> and {111}<110> does not exceed 10% of the area or volume of any one of the three components {001}<110>, {111}<112> and {111}<110> An alloy characterized by the above.

11. The alloy according to claim 10, characterized in that (V + W) / 2 + (Ta + Zr) / 0.2 ≥ 0.8%.

12. The alloy according to claim 10 or 11, characterized in that trace amount ≤ Si ≤ 0.1%.

13. The alloy according to claim 10 or 11, characterized in that trace amount ≤ Cr ≤ 0.1%.

14. A magnetic component cut out from a substantially equiatomic FeCo alloy, characterized by being produced from the cutting out of a strip or sheet of the alloy according to claim 10 or 11.

15. A magnetic core made of a substantially equiatomic FeCo alloy, characterized by being made from the cut-out magnetic component according to claim 14.

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