EP3541969A1

EP3541969A1 - Method for producing a strip from a cofe alloy, and semi-finished product containing said strip

Info

Publication number: EP3541969A1
Application number: EP17811215.7A
Authority: EP
Inventors: Niklas Volbers; Jan Frederik FOHR
Original assignee: Vacuumschmelze GmbH and Co KG
Current assignee: Vacuumschmelze GmbH and Co KG
Priority date: 2016-11-18
Filing date: 2017-11-17
Publication date: 2019-09-25
Anticipated expiration: 2037-11-17
Also published as: EP3541969B1; WO2018091694A1; DE102016222805A1; US20190360065A1

Abstract

The invention relates, in one embodiment, to a semi-finished product, which comprises at least one metal strip consisting substantially of 35 wt% ≤ Co ≤ 55 wt%, 0 wt% ≤ V ≤ 3 wt%, 0 wt% ≤ Ni ≤ 2 wt%, 0 wt% ≤ Nb ≤ 0.50 wt%, 0 wt% ≤ Zr + Ta ≤ 1.5 wt%, 0 wt% ≤ Cr ≤ 3 wt%, 0 wt% ≤ Si ≤ 3 wt%, 0 wt% ≤ Al ≤ 1 wt%, 0 wt% ≤ Mn ≤ 1 wt%, 0 wt% ≤ B ≤ 0.25 wt%, 0 wt% ≤ C ≤ 0.1 wt%, remainder Fe and up to 1 wt% of impurities, wherein the impurities can have one or more of the group O, N, S, P, Ce, Ti, Mg, Be, Cu, Mo and W. The strip has a thickness d, wherein 0.05 mm ≤ d ≤ 0.5 mm, a Vickers hardness of greater than 300, an elongation at break of less than 5% and, after a heat treatment of the strip at a temperature between 700 °C and 900 °C, a permanent growth dl/l0 of less than 0.08%, preferably 0.06%, in the longitudinal direction of the strip and/or of less than 0.08%, preferably 0.06%, in the transverse direction of the strip.

Description

description

The invention relates to a semifinished product, in particular a semifinished product with at least one ribbon of a CoFe alloy and to processes for producing a CoFe alloy. SUMMARY OF THE INVENTION

Soft magnetic cobalt-iron (CoFe) alloys with a Co content of 49% are used because of their high saturation polarization. A CoFe alloy grade has a composition of 49 wt% Fe, 49 wt% Co, and 2% V, which may further contain additions of Ni, Nb, Zr, Ta, or B. In such a composition, a saturation polarization of about 2.3 T is achieved while sufficiently high electrical resistance of 0.4μΩηπ.

Such alloys find application e.g. as high-saturating flux guides or also for applications in electrical machines. When used as a generator or motor, stators or rotors are typically fabricated in the form of laminated packages. The material is used in strip thicknesses ranging from 0.50 mm to very thin dimensions of 0.050 mm.

The material is subjected to a heat treatment to obtain the magnetic properties, which is also referred to as magnetic annealing. This heat treatment takes place above the recrystallization temperature and below the phase transition a / y, usually in the range from 700 ° C. to 900 ° C.

In contrast to iron sheets made of iron-silicon (FeSi), CoFe tape is typically not already offered in final annealing. Finely annealed strip is soft due to a recrystallized structure and at the same time brittle due to the order setting and therefore can only be punched insufficiently. Furthermore, cutting or punching processes lead to a significant deterioration of the magnetic properties. Therefore, found on CoFe sheet after molding a final annealing, either on metal sheets, on individual lamellae or on finished laminated cores.

Due to the magnetic annealing, however, there is also a change in the dimensions of the sheet. This growth in length is in the range of 0.03% to 0.20%.

With knowledge of the growth can be compensated by a Vorhaltemaß the punch an isotropic growth within certain limits and / or the sheets or laminated cores can be reworked, as disclosed for example in WO 2007/009442 A2. Such processes are associated with higher costs and are not always practical depending on the geometry.

The object is therefore to provide a CoFe alloy and methods for producing a CoFe alloy, which has a reduced growth after the magnetic annealing.

According to the invention, in one embodiment, a method is provided for producing a CoFe alloy comprising. First, a melt consisting essentially of 35 wt .-% <Co <55 wt .-%, 0 wt .-% <V <3 wt .-%, 0 wt .-% <Ni <2 wt .-%, 0% by weight <Nb <0.50% by weight, 0% by weight <Zr + Ta <1, 5% by weight, 0% by weight <Cr <3% by weight, 0% by weight % <Si <3%, 0% <AI <1%, 0% <Mn <1%, 0% <B <0, 25% by weight, 0% by weight <C <0.1% by weight, remainder Fe and up to 1% by weight of impurities, the impurities comprising one or more of the group O, N, S, P , Ce, Ti, Mg, Be, Cu, Mo and W. The melt is poured off under vacuum and then solidified to a cast block. The ingot is hot rolled to a slab and then to a hot strip with a thickness Di. Thereafter, the hot strip is quenched from a temperature above 700 ° C to a temperature below 200 ° C. The hot rolled strip is cold rolled to an intermediate strip of thickness D2, the intermediate strip annealed at a temperature of above 700 ° C and at a temperature of above 700 ° C to a temperature of less than 200 ° C in a gaseous Cooled medium. The heat-treated intermediate strip is cold-rolled to a strip having a thickness D3 with a metallic bright surface, wherein the

Cold deformation (D2-D3) / D2- £ 80%, preferably <60%. After the intermediate annealing of the cold-rolled intermediate strip in the course, no quenching and pickling is carried out, so that the heat-treated intermediate strip has a metallically bright surface. The heat-treated intermediate strip is further processed with this metallic bright surface by another cold rolling. Thus, the manufacturing process is simplified. Further, the degree of cold working of the last cold rolling step is limited, which allows the resulting strip to be subjected to a final magnetic annealing, i. after a heat treatment at a temperature between 700 ° C to 900 ° C, a

Growth dl / lo in the longitudinal direction of the tape less than 0.08%, preferably 0.06% and / or in the transverse direction of the tape less than 0.08%, preferably 0.06%. In this case, lo denotes the initial length before final annealing, dl the absolute change in length after final annealing and dl / lo the relative

Length change relative to the initial length.

The magnetic final annealing of this CoFe alloy takes place above the recrystallization temperature and below the phase transition aJy. The recrystallization temperature and the temperature at which the a / y phase transition occurs is dependent on the composition of the CoFe alloy. Mostly, the final magnetic annealing is performed in the range of 700 ° C to 900 ° C. During the subsequent cooling, an order adjustment takes place, ie a B2 superstructure forms. Magnetic annealing and the associated adjustment of the setting result in a permanent change in the dimensions of the sheet at room temperature or a permanent increase in length. A strip with a starting length lo at room temperature before the final annealing thus has a length of lo + dl after the final annealing and at the same room temperature. In some embodiments, dl is greater than zero. This permanent growth in length is reduced by the method according to the invention. According to the invention, the permanent growth dl / lo in the longitudinal direction of the band is less than 0.08%, preferably 0.06% and / or in the transverse direction of the band less than 0.08%, preferably 0.06%. This small permanent growth is not achieved with ribbons of CoFe alloy made with one of the cold working degree of the last cold rolling step of more than 80%.

It was found to be a major factor influencing the size of this

Growth The degree of cold deformation (KV) is: The higher the cold working of the material, the more pronounced the growth in length after the final annealing. By using an intermediate annealing, the degree of cold deformation can be reduced in the last step, so that after the magnetic annealing, the strip shows a reduced growth in length.

The thickness of the strip, which is achieved by the hot rolling and / or the cold rolling, as well as the thickness of the strip, in which the intermediate annealing is performed, can be defined in more detail. For example, after hot rolling, the strip may have a thickness Di of 1.0 mm <Di <2.5 mm, before intermediate annealing, a thickness D2 of 0.1 mm <D 2 ^ 1, 0 mm and / or after the second cold rolling Have thickness D3 of 0.05 mm <D3 ^ 0.5 mm.

In one embodiment, the thickness of the hot roll strip is reduced from Di to D2 by means of cold rolling and / or the thickness of the intermediate strip from D2 to D3 by means of cold rolling. No further intermediate anneals are thus carried out.

The conditions of the intermediate annealing in the pass are selected so that the strip can be cold rolled after the intermediate annealing. In one

Embodiment, after the intermediate annealing, the intermediate band on a structure in which a ferritic recrystallized portion has a mean grain size of less than 10 μηπ and / or a ferritic recrystallized share no grains with a size greater than 10 μηπ. This structure can, for example, by a

Temperature of 800 ° C to 900 ° C are generated.

In one embodiment, after the intermediate annealing in a bending cycle test, the intermediate strip has a bending number up to breakage of at least 20. The Biegewechselnest can be used to determine the cold workability of the tape.

The intermediate annealing in the run can be carried out at a speed of 1 m / min to 10 m / min and the residence time of the strip in the heating zone of the continuous furnace with the temperature of 700 ° C to 1 100 ° C, preferably 800 ° C to 1000 ° C between 30 seconds and 5 minutes. The intermediate annealing of the intermediate strip in the course can be carried out at a temperature of 800 ° C to 900 ° C or 1000 ° C to 1 100 ° C. Depending on the length of the heating zone of the continuous furnace, the parameters annealing temperature and belt speed can be adjusted to set the properties shown here.

After the intermediate annealing, the strip may have substantially a deformation texture or a mixed texture with fractions of a former γ-phase in a matrix of an α-phase. A deformation structure can be achieved, for example, at a temperature of 800 ° C to 900 ° C. A mixed structure with portions of a former γ-phase in a matrix of an α-phase can in a

Temperature of 1000 ° C to 1 100 ° C can be achieved. The intermediate annealing may be under an inert gas or a dry one

hydrogen-containing atmosphere having a dew point of less than -30 ° C are performed. After the intermediate annealing in the pass is the

Intermediate belt cooled to a temperature less than 200 ° C in a gaseous medium such as an inert gas or a dry hydrogen-containing atmosphere. However, the intermediate band is not quenched, for example in water.

In an alternative method, the degree of deformation of the hot rolling is set so that the degree of cold rolling is lower than one remains predetermined limit, so that the length growth remains low after the magnetic annealing. This method of producing a CoFe alloy includes the following. A melt consisting essentially of 35 wt .-% <Co <55 wt .-%, 0 wt .-% <V <3 wt .-%, 0 wt .-% <Ni <2 wt .-%, 0 wt % <Nb <0.50 wt%, 0 wt% <Zr + Ta <1.5 wt%, 0 wt% <Cr <3 wt%, 0 wt% % <Si <3 wt .-%, 0 wt .-% <Al <1 wt .-%, 0 wt .-% <Mn <1 wt .-%, 0 wt .-% <B <0.25 wt %, 0% by weight <C <0.1% by weight, remainder Fe and up to 1% by weight impurities are provided, the

Contaminants may have one or more of the group O, N, S, P, Ce, Ti, Mg, Be, Cu, Mo and W. The melt is poured off under vacuum and then solidified to a cast block. The ingot is hot rolled to a slab and then to a strip of thickness Di, where 1 mm <Di <2 mm. Thereafter, the strip is quenched from a temperature above 700 ° C to a temperature below 200 ° C. The strip is cold rolled and the thickness of Di is reduced to a thickness D2, the degree of cold working (Di-D2) / Di being <80%, preferably <60%.

In this method, the degree of deformation of the hot rolling, and thus the thickness Di of the strip after hot rolling and before cold rolling, is adjusted so that the desired final thickness D2 can be achieved with a degree of deformation of less than 80%, preferably less than 60%. Typically, as compared with a conventional commercial process, the degree of deformation of hot rolling is increased and the degree of cold rolling is correspondingly reduced.

In one embodiment, the final thickness D2 is 0.05 mm <D2 ^ 0.5 mm. The heat treatment of the tape can take place under a dry hydrogen-containing atmosphere. Both alternative methods may further include forming at least one sheet from the strip. The sheet can be punched out of the band. A plurality of sheets may be joined together to form a laminated core. The band or the sheet or the laminated core can also at a temperature between 700 ° C to 900 ° C are heat treated, ie a magnetic annealing can be performed. This heat treatment takes place above the

Recrystallization and below the temperature of the phase transition α / γ instead, usually in the range of 700 ° C to 900 ° C. Upon subsequent cooling, an order adjustment takes place, i. it forms a B2 superstructure, and the desired magnetic properties, such as a

Saturation polarization of about 2.3 T, and an electrical resistance of 0.4 μΩηπ are generated. After this heat treatment of the ribbon, growth is dl / lo in

Length of the tape less than 0.08% and / or in the transverse direction of the tape less than 0.08% and / or a difference between the growth in

Longitudinal direction and the growth in the transverse direction of the belt less than 0.06%, preferably less than 0.04%. Lo is the initial length before final annealing, dl is the absolute change in length after final annealing, and dl / lo is the relative change in length relative to the initial length.

This growth is a lasting growth, which is caused by the magnetic annealing and the associated order setting. A strip with a starting length lo at room temperature before the final annealing thus has a length of lo + dl after the final annealing and at the same room temperature.

According to the invention, in one exemplary embodiment, a semifinished product is provided which comprises at least one metallic strip consisting essentially of 35% by weight <Co <55% by weight, 0% by weight <V <3% by weight, 0% by weight. % <Ni <2 wt%, 0 wt% <Nb <0.50 wt%, 0 wt% <Zr + Ta <1.5 wt%, 0 wt% < Cr <3% by weight, 0% by weight <Si <3% by weight, 0% by weight <Al <1% by weight, 0% by weight <Mn <1% by weight, 0 wt .-% <B <0.25 wt .-%, 0 wt .-% <C <0.1 wt .-%, balance Fe and up to 1 wt .-% impurities, wherein the impurities one or may have more of the group O, N, S, P, Ce, Ti, Mg, Be, Cu, Mo and W. The tape has a thickness d, where 0.05 mm <d <0.5 mm, a Vickers hardness of greater than 300, an elongation at break of less than 5%. After a heat treatment of the Bandes at a temperature between 700 ° C to 900 ° C has the band

Growth dl / lo in the longitudinal direction of the tape less than 0.08%, preferably 0.06% and / or in the transverse direction of the tape less than 0.08%, preferably 0.06%, on.

This semi-finished product thus has mechanical properties that are in one

cold-rolled state, namely an elongation at break of less than 5% and a Vickers hardness of greater than 300. This semi-finished product can

be further processed, for example, to form sheets from the tape and to build the sheets into a laminated core, which is heat treated to the

to set magnetic properties. This heat treatment of the strip is called magnetic annealing, since it serves to make the

adjust magnetic properties, and can be carried out at a temperature between 700 ° C and 900 ° C.

This growth is a lasting growth, which is caused by the magnetic annealing and the associated order setting. A strip with a starting length lo at room temperature before the final annealing thus has a length of lo + dl after the final annealing and at the same room temperature. In some embodiments, dl is greater than zero.

The band according to the invention makes it possible to produce sheet metal sections, subject them to a final annealing to set an optimum magnetism, and then to obtain a sufficiently high dimensional accuracy, so that a further correction of the geometry can be dispensed with. The potential disadvantages of subsequent geometry correction, e.g. by grinding, a deterioration of the magnetic permeability at these locations, the risk of eddy currents, since grinding processes can cause smearing of the slats, as well as higher costs. Thereby, in the application e.g. be set as a stator or rotor small air gaps, resulting in an improved efficiency of the electric machine.

In one embodiment, the band may have a smaller thickness, for example one with 0.05 mm <d <0.356 mm. Furthermore, the semi-finished a

Have variety of sheets that form a laminated core.

In one embodiment, after the heat treatment of the strip at a temperature between 700 ° C to 900 ° C, a difference between the

lasting growth in the longitudinal direction and the lasting growth in

Transverse direction of the band less than 0.06%, preferably less than 0.04%.

The CoFe tape according to the invention with significantly reduced growth has the further advantage that a punching tool can be designed so that it can be used for other alloys such as SiFe as well as for CoFe. This leads to an economic advantage in the high cost of such a tool.

Various CoFe alloys can be used. In other

Embodiments, the CoFe alloy has one of the following

Compositions on:

35 to 55 wt.% Co, up to 2.5 wt.% V, remainder Fe and up to 1 wt.

Impurities, for example 49% by weight Co, 49% by weight Fe and 2% by weight V,

45 wt .-% <Co <52 wt .-%, 45 wt .-% <Fe <52 wt .-%, 0.5 wt .-% <V <2.5 wt .-% balance Fe and up to 1 wt. % Impurities,

35 wt .-% <Co <55 wt .-%, preferably 45 wt .-% <Co <52 wt .-%, 0 wt .-% <Ni <0.5 wt .-%, 0.5 wt .-% <V <2.5 wt .-%, and up to 1 wt .-%

impurities

35 wt% <Co <55 wt%, 0 wt% <V <2.5 wt%, 0 wt% <(Ta + 2Nb)

<1 wt.%, 0 wt.% <Zr <1 .5 wt.%, 0 wt.% <Ni <5 wt.%, 0 wt.% <C <0.5 wt. , 0% by weight <Cr <1% by weight, 0% by weight <Mn <1% by weight, 0% by weight

<Si <1 wt .-%, 0 wt .-% <Al <1 wt .-%, 0 wt .-% <B <0.01 wt .-%, balance Fe and up to 1 wt .-% impurities, 47 wt .-% <Co <50 wt .-%, 1 wt .-% <V <3 wt .-%, 0 wt .-% <Ni <0.25 wt .-%, 0 wt .-% <C < 0.007 wt .-%, 0 wt .-% <Mn <0.1 wt .-%, 0 wt .-% <Si <0.1 wt .-%, 0.07 wt .-% <Nb <0.125 wt .-%, 0 wt .-% <Zr <0.5 wt .-%, balance Fe and up to 1 wt .-% impurities, or

49% by weight <Co <51% by weight, 0.8% by weight <V <1 .8% by weight, 0% by weight <Ni <0.5% by weight, balance Fe and up to 1 Wt .-% impurities.

CoFe based alloys are under the trade name VACOFLUX 50,

VACOFLUX 48, VACODUR 49, VACODUR 50, VACODUR S Plus, Rotelloy, HIPERCO 50, Permendur, AFK and 1 J22 available.

The impurities may have one or more of O, N, S, P, Ce, Ti, Mg, Be, Cu, Mo and W.

Embodiments will now be described with reference to the drawings and the following

Examples explained in more detail. shows a graph of measured average growth dl / 10 after a final annealing of strips cold rolled to different thicknesses d.

Figure 2 shows a graph of yield strength R _P o, 2 and tensile strength Rm in

Dependence on the temperature of the continuous annealing.

FIG. 3 shows optical images of the microstructure of three samples after one

Intermediate annealing at different temperatures.

FIG. 4 shows magnetization curves B (H) according to various

Intermediate annealing and a final annealing.

FIG. 5 shows a graph of the measured change in length in the rolling direction compared to the degree of cold deformation for two different samples. It has been found that the growth in length of a CoFe alloy strip after a final annealing is limited by a

Cold deformation can be reduced.

Figure 1 shows a graph of measured average growth dl / IO after a final annealing in% longitudinally on the 50% CoFe materials VACOFLUX 50 (49Fe-49Co-2V) and as a comparative example HIPERCO 50 (49Fe-49Co-2V). The tested samples had a thickness after a hot rolling of 2 mm or larger, and are cold rolled to different final thicknesses and thus subjected to different degrees of cold deformation, lo denotes the

Initial length before final annealing, dl the absolute change in length after

Final annealing and dl / lo the relative change in length relative to the

Original length.

This change in length or growth is a permanent change in length or a permanent growth, which is caused by the magnetic closing annealing and the associated order adjustment. A sample with a starting length lo at room temperature before the final annealing thus has a length of lo + dl after the final annealing and at the same room temperature.

While on hot rolling material, i. with 0% cold working (KV), still a small amount of elongation over the initial length in the range of 0.03% to 0.05% is measured at room temperature, a band with a band thickness of 0.35 mm already shows a lasting growth of over 0.10%. For even higher cold work, e.g. at a strip thickness of 0.10 mm, a permanent growth of more than 0.20% already takes place. This lasting change in length growth is likely due to an increasingly pronounced texture. These results show that an important factor influencing the size of this growth is the degree of cold deformation: the higher the cold deformation of the

Materials, the more pronounced the growth in length after the final annealing. Consequently, these results show that, in principle, the permanent change in longitudinal growth can be reduced if the degree of cold working is reduced. In principle, the degree of cold working can be reduced by performing an intermediate annealing between two cold working steps, each with a smaller degree of cold working. Due to the

Order setting by an intermediate annealing, however, a CoFe alloy is then brittle and no longer processable. Consequently, the brittleness is traditionally canceled by a subsequent quenching process. However, this quenching process is complex and associated with technical disadvantages and high costs.

According to the invention, the reduction of the degree of cold working at a given final thickness is achieved by introducing an intermediate annealing or by reducing the hot rolling thickness. According to the invention, an intermediate annealing in the run is carried out so that the work hardening caused by the rolling is reduced and at the same time a rollable structure is formed despite the embrittlement of setting due to the avoidance of coarse-grained ferrite. Further, after intermediate annealing, the tape is not quenched, for example, in water or oil, and not pickled, so that the tape is cold rolled to a metallic bright surface. Consequently, the process is simpler and less expensive to perform.

After the intermediate annealing, it is thus possible to carry out a further cold deformation to final thickness. By means of such a method, it is possible in principle to limit the degree of cold deformation to a final thickness of 0.50 mm or thinner to the extent that at the same time the growth in length is significantly reduced. The cold working according to the invention should be at most 80%, preferably up to 60%, as set forth by the following examples and experimental results. Intermediate annealing at thickness

Final thickness no Zwgl. 1, 0 mm 0.5 mm 0.35 mm 0.20 mm 0.10 mm

0,35 mm 83% 65% ( ^* ) 30% ( ^* ) - - -

0,20 mm 90% 80% ( ^* ) 60% ( ^* ) 43% ( ^* ) - -

0.10 mm 95% 90% 80% ( ^* ) 71% ( ^* ) 50% ( ^* ) -

0.05 mm 98% 95% 90% 86% 75% ( ^* ) 50% ( ^* )

Table 1

Table 1 shows the degree of cold deformation as a function of final thickness and

Intermediate annealing. The hot rolling thickness was assumed to be 2 mm. The states marked with ( ^* ) represent states according to the invention.

The material used was a band of the alloy VACODUR 49 having a composition of 48.6% by weight of Co, 1.86% by weight of V, 0.09% by weight of Nb, C <0.0070% by weight. %, Balance Fe and impurities. The strip was hot rolled to a thickness of 2 mm and then quenched in an ice-salt bath at a temperature above 700 ° C. Subsequently, the strip could be cold rolled to 0.35 mm thickness.

The intermediate annealing in the run was tested in a continuous furnace with an annealing zone of 6 m length. The temperatures selected were 850 ° C., 900 ° C., 950 ° C., 1000 ° C. and 1050 ° C., at a speed of 6 m / min. The annealing was carried out under dry H2. The different temperatures of the intermediate annealing in the course are referred to below as variants 1 to 5.

Table 2 shows the measured mechanical properties of

Continuously annealed strips of variants 1 to 5. The tensile specimens were taken along the rolling direction. The bending changes were determined on strips

(longitudinal / transverse to rolling direction). A bending test 900 ° C 6m / min across was not available. Figure 2 shows a graph of yield strength R _P o, 2 and tensile strength Rm of the tensile specimens against the temperature T of the continuous annealing at 6 m / min .. The state Ref.

indicates the condition of a sample without continuous annealing and thus a

Comparison condition.

The mechanical properties of these 0.35 mm thick samples show that in all passivated annealing variants (1-5) a high elongation at fracture of the material results. In the variants 1, 3, 4 and 5, moreover, the difference R _m to Rpo, 2 is relatively large (> 400 MPa), indicating good plastic deformability.

Variant Hardness modulus Rp0.2 Rm Rm-Rp0.2 A #bending change

Intermediate annealing in the pass

HV10 GPa MPa MPa MPa% longitudinal / transverse sampling

Hard-rolling reference 342 214 1119 1194 75 1.6> 20 / 3-7

1 850 ° C,

337 243 868 1322 454 16.0> 20/15 6 m / min

2 900 ° C,

256 223 514 798 284 8.0 3 / n.v. 6 m / min

3 950 ° C,

233 219 459 865 406 10.6 2-7 / 2 6 m / min

4 1000 ° C,

247 197 492 1084 592 18.5> 20 /> 20 6 m / min

5 1050 ° C,

266 224 576 1005 429 11.9> 20 /> 20 6 m / min

Table 2

Another proof of the different ductility is achieved by the number of bending changes in the bending change test. The states marked as variants 1, 4 and 5 show in both directions a high number of possible bending changes.

A metallographic study shows that the different variants have very different microstructures, which can be subdivided into three groups.

In variant 1, an intermediate annealing at low temperatures leads only to incomplete recrystallization. By way of example, the present structure was achieved at a temperature of 850 ° C. In variants 2 and 3, an intermediate annealing at 900 ° C. or 950 ° C. results in a ferritically recrystallized, coarse-grained microstructure.

In variants 4 and 5, an intermediate annealing in the two-phase region / y leads to a mixed structure with fractions of the former γ phase in a cc matrix. By way of example, the present structure was achieved at a temperature of 1000 ° C.

FIG. 3 shows optical images of the microstructure of three samples after one

Intermediate annealing at different temperatures. Variation 1 was heat treated at 850 ° C 6m / min and shows good rollability, N> 20, a strain texture and incipient recrystallization. Variant 3 was 6 m / min at 950 ° C

heat treated and shows poor rolling, N = 2-7 and is ferritically recrystallized. Variation 4 was heat treated at 1000 ° C 6 m / min and shows good rolling, N> 20, a non-uniform ferrite, mixed structure with portions of the former γ-phase in an a-matrix.

Table 3 shows the effect of additional cold working on the mechanical properties of pass annealed VACODUR 49. All annealed ribbons were rolled on a commercial 20 roll mill. A strong Hardening of the material is already shown at the first stitch, indicating that the material is in an orderly condition.

Table 3

The strips, which were made according to variants 1, 4 and 5, could be rolled to a thickness of 0.10 mm. In contrast, variants 2 and 3 showed strong brittleness and were sensitive to tension. Therefore, the material of variant 2 could not be rolled and the material of variant 3 only to a limited extent.

Surprisingly, it turned out in the experiments that there is the possibility to roll a CoFe strip after a continuous annealing, if the formation of a coarse-grained structure is avoided.

The growth in length after another heat treatment for adjusting the magnetic properties at a temperature between 700 ° C and 900 ° C, ie after a final annealing is examined. Table 4 shows the length growth (measured in the longitudinal direction) after magnetic final annealing of VACODUR 49, hot rolling thickness 2 mm. Both variants, ie variants 1 and 4, thus have a significantly reduced growth at low strip thickness.

Table 4

The tape thus obtained was characterized at intermediate thickness of 0.25 mm and at various final thicknesses of 0.20 mm and 0.10 mm, respectively, in terms of elongation. The measurement was carried out in each case on individual strips of length 1 65 mm, whose length was measured exactly before and after the final annealing (6h 880 ° C under H2). From the difference of the measuring lengths, the change in length d1 can be determined. If one sets these in relation to the initial length lo, one obtains the relative increase in length dl / lo. The measurements listed in Table 4 were always performed in the longitudinal direction, i.e., in the longitudinal direction. the growth along the rolling direction was determined.

In the conventionally prepared reference material, i. without intermediate annealing, the 0.35 mm thickness growth is already at 0.129%. As the cold deformation increases, the growth increases to 0.195% with a thickness of 0.10 mm.

The variant 1 according to the invention, on the other hand, has an end thickness of 0.10 mm which is considerably reduced in length. So it was on the tape of the magnetic final annealing at 0.10 mm, an average growth dl / lo measured in the longitudinal direction of 0.054%.

Also the band of variant 4 showed a reduced growth. A mean growth dl / lo in the longitudinal direction of 0.000% was measured, the individual values being between +0.013% and -0.010%.

If the cold deformation becomes too high after intermediate annealing, the growth increases again significantly. In the embodiment variant 4 (intermediate annealing 1000 ° C 6 m / min at 0.35 mm) is obtained at final thickness 0.055 mm, i. at 84% cold deformation already a very pronounced longitudinal growth dl / lo of 0.159% in the longitudinal direction.

The anisotropy of growth, i. the difference between the longitudinal and longitudinal growth of the tape is examined.

Table 5 shows length growth of the samples from VACODUR 49 after additional final annealing of 6 h at 880 ° C., measured on tensile specimens or longitudinal strips 165 mm × 20 mm. The condition hard, 0.10 mm, was on a

comparable sample measured from VACOFLUX 48, also after final annealing of 6 h at 880 ° C.

Growth after additional

final annealing

(6h 880 ° C)

Variant Continuous annealing End thickness longitudinal transverse | longitudinal - transverse | none 0.35 mm 0.129% 0.106% 0.023%

reference

Intermediate annealing 0.10 mm 0.210% 0.1 10% 0.100%

0.35 mm 0.035% 0.051% 0.01 6%

1 850 ° C, 6 m / min

0.10 mm 0.054% 0.052% 0.002%

0.35 mm 0.032% 0.058% 0.026%

4 1000 ° C, 6 m / min

0.10 mm 0.000% 0.056% 0.056%

Table 5

Variation 1 of Table 5 shows the advantageous property that the growth in the longitudinal and transverse directions is almost identical. The difference in the growth between the longitudinal and transverse directions, | longitudinal | transverse |, is 0.10 mm at only 0.002%. Thus, it is possible to hold punches according symmetrically. Stamped round parts are still round after the final annealing.

Variant 4 of Table 5 still has a slight anisotropy, but also shows in terms of amount also a significantly low growth in length. The difference between longitudinal and transverse direction | longitudinal - transverse | At about 0.06% of the initial length, it is much less than the difference observed with conventionally produced tape, which is about 0.10%.

Magnetically, both end-thickness variants show properties which correspond to what is obtained on the starting material at a thickness of 0.35 mm without continuous annealing. The following figure shows the new curves after magnetic annealing at different strip thicknesses. 4 shows magnetization curves and the influence of further cold deformation on the new curve B (H) of continuously annealed strip (850 ° C., 1050 ° C., 6 m / min in each case). The measurements were carried out on punched rings after a final annealing of 6 hours at 880 ° C in a dry H2 atmosphere.

In the figure 4 designates:

(a) a sample having a ribbon thickness of 0.35 mm in which no continuous annealing is performed (Reference)

(b) a sample having a ribbon thickness of 0.35 mm, in which a continuous annealing is carried out at 850 ° C and 6 m / min, (Reference)

(C) a sample which is subjected to a continuous annealing at 850 ° C and 6 m / min at a strip thickness of 0.35 mm and then cold worked to a strip thickness of 0.20 mm (according to the invention).

(d) a sample having a band thickness of 0.35 mm in which no continuous annealing is performed (Reference)

(e) a sample having a ribbon thickness of 0.35 mm, in which a continuous annealing is carried out at 1050 ° C and 6 m / min, (Reference)

(f) a sample subjected to a continuous annealing at 1050 ° C and 6 m / min at a strip thickness of 0.35 mm and then cold worked to a strip thickness of 0.20 mm (according to the invention).

These results show that the method according to the invention has little influence on the magnetization curve, so that band with suitable magnetic

Properties can be provided.

The second approach according to the invention is to reduce the hot rolling thickness, so that at a final thickness of 0.50 mm or thinner, the cold deformation at final thickness is 80% at the maximum. The thickness of the hot rolling strip is typically 2 mm to 4 mm for CoFe alloys. By reducing it to 1 mm, with a final thickness of 0.35 mm, it is possible to reduce the degree of cold deformation and thus the length of growth. Hot rolled strips were produced in the thicknesses according to Table 6 (WW thickness) and cold rolled in each case to different final thickness.

Table 6

Table 6 shows the degree of cold deformation as a function of final thickness and

Hot rolling thickness (without intermediate annealing). The states marked with ( ^* ) represent bands according to the invention.

FIG. 5 shows a graph of length growth (dl / lo) of strips of different hot rolling thickness from VACOFLUX 50 along the rolling direction after final annealing against the degree of cold deformation (Di-D2) / Di. The change in length in the rolling direction compared to the degree of cold deformation is shown for two different samples A and B after magnetic annealing. At a constant cold rolling thickness D2 of 0.35 mm, the hot rolling thickness Di was varied between 1.0 mm and 3.5 mm. For each data point, the associated hot rolling thickness (WW thickness) is marked with an arrow.

From these results it can be seen that the step from the WW thickness Di 3.5 mm to 2.0 mm already leads to a significant reduction of the growth on a sample with a final thickness D2 of 0.35 mm. For a WW thickness of 1, 0 mm or thinner, it is possible to obtain a final growth of 0.85 mm after final annealing of <0.08% at a final thickness of 0.35 mm. In a further investigation, a WW band of thickness 1.5 mm made of VACOFLUX 50 was rolled to an end thickness of 0.50 mm by way of example and subjected to a magnetic final annealing (4 h 820 ° C., H2). The length growth in this experiment was only 0.045%. Overall, it can be seen that for a final thickness of 0.50 mm or thinner with a correspondingly low hot rolling thickness, a strong reduction in longitudinal growth can be achieved.

In a specific example, the band according to the invention is produced in the following way:

- Hot rolling in thickness 2.5 mm to 1, 0 mm

Quenching temperatures above 700 ° C

Rolls at intermediate thickness (1, 0 mm to 0.20 mm)

Annealing in the course at 700 ° C to 1 100 ° C, preferably such that no coarse-grained ferritic structure is formed, but an incompletely recrystallized or a fine-grained recrystallized ferritic microstructure

Rolling at final thickness with cold working of up to 80%, preferably with cold working of up to 60%

Alternatively, in the case of a hot strip thickness of less than 2 mm, annealing in the pass can also be dispensed with, as long as the cold deformation is up to 80%, preferably up to 60%.

The tape according to the invention has the following properties:

Composition such as conventional CoFe tapes with approximately equal proportions of iron and cobalt and about 2 wt .-% Vanadiumzusatz.

Final thickness of the band 0.50 mm or thinner, preferably 0.356 mm or thinner

Vickers hardness> 300 HV

Elongation at break <5%

- a permanent growth in the longitudinal direction after magnetic

Final annealing <0.08%, preferably <0.06%

permanent growth in the transverse direction after magnetic annealing <0.08%, preferably <0.06% Difference between the permanent growth in longitudinal direction and the remaining transversal growth <0.06%, preferably <0.04%

Claims

claims

1 . A method of producing a CoFe alloy comprising:

Providing a melt consisting essentially of 35 wt% <Co <55 wt%, 0 wt% <V <3 wt%, 0 wt% <Ni <2 wt%, 0 Wt% <Nb <0.50 wt%, 0 wt% <Zr + Ta <1.5 wt%, 0 wt% <Cr <3 wt%, 0 wt% -% <Si <3 wt .-%, 0 wt .-% <Al <1 wt .-%, 0 wt .-% <Mn <1 wt .-%, 0 wt .-% <B <0.25 Wt .-%, 0 wt .-% <C <0.1 wt .-%, balance Fe and up to 1 wt .-% impurities, wherein the

Impurities may have one or more of the group O, N, S, P, Ce, Ti, Mg, Be, Cu, Mo and W,

Pouring the melt under vacuum and then solidifying to a cast block,

Hot rolling the ingot to a slab and then to a hot strip having a thickness Di, followed by quenching the strip from a temperature above 700 ° C to a temperature below 200 ° C;

Cold rolling the hot strip to an intermediate strip having a thickness D ₂ ,

Intermediate annealing of the intermediate strip in the flow at a temperature of above 700 ° C, wherein the intermediate strip at a temperature of above 700 ° C to a temperature of less than 200 ° C in a

is cooled gaseous medium,

Cold rolling the heat treated intermediate strip having a metallic bright surface to a strip having a thickness D3, wherein the

Cold deformation (D2-D3) / D2-i 80%, preferably <60%.

2. The method of claim 1, wherein 1, 0 mm <Di <2.5 mm.

3. The method of claim 1 or 2, wherein 0.1 mm <D2 ^ 1, 0 mm.

4. The method according to any one of claims 1 to 3, wherein 0.05 mm <D3 ^ is 0.5 mm.

5. The method according to any one of claims 1 to 4, wherein the thickness of the

Hot rolling bands from Di to D2 is reduced by means of cold rolling.

Method according to one of claims 1 to 5, wherein the thickness of the

Intermediate bands is reduced from D2 to D3 by means of cold rolling

7. The method according to any one of claims 1 to 6, wherein after

Intermediate annealing the intermediate band has a structure in which a ferritically recrystallized fraction has an average particle size of less than 10 μηπ.

Method according to one of claims 1 to 7, wherein according to the

Intermediate annealing the intermediate band has a structure in which a ferritic recrystallized portion does not have grains with a size greater than 10 μηπ.

9. The method according to any one of claims 1 to 8, wherein after

Intermediate annealing, the intermediate band in a Biegewechselnest a bending number to break of at least 20 has.

10. The method according to any one of claims 1 to 9, wherein the intermediate annealing is carried out in a continuous at a speed of 1 m / min to 10 m / min. 1 1. Method according to one of claims 1 to 10, wherein the residence time of the

Bandes in the heating zone of the continuous furnace with the temperature of 700 ° C to 1 100 ° C, preferably 800 ° C to 1000 ° C between 30 seconds and 5

Minutes. 12. The method according to any one of claims 1 to 1 1, wherein the intermediate annealing of the intermediate strip in a continuous at a temperature of 800 ° C to 900 ° C or 1000 ° C to 1 100 ° C.

13. The method according to any one of claims 1 to 12, wherein after

Intermediate annealing, the strip has substantially a deformation structure or a mixed structure with portions of a former γ-phase in an α-matrix. 14. The method according to any one of claims 1 to 13, wherein after the

Intermediate annealing in the pass the intermediate strip is cooled to a temperature less than 200 ° C in air.

15. The method according to any one of claims 1 to 14, wherein the intermediate annealing is carried out under an inert gas or a dry hydrogen-containing atmosphere.

16. A method of producing a CoFe alloy comprising:

Providing a melt consisting essentially of 35% by weight

% <Co <55 wt .-%, 0 wt .-% <V <3 wt .-%, 0 wt .-% <Ni <2 wt .-%, 0 wt .-% <Nb <0.50 wt %, 0% by weight <Zr + Ta <1, 5% by weight, 0% by weight <Cr <3% by weight, 0% by weight <Si <3% by weight, 0 wt% <Al <1 wt%, 0 wt% <Mn <1 wt%, 0 wt% <B <0.25 wt%, 0 wt% < C <0.1 wt .-%, remainder Fe and up to 1 wt .-% impurities, wherein the

Pouring the melt under vacuum and then solidifying to a cast block,

Hot rolling the ingot into a slab and then into a strip having a thickness Di, where 1 mm <Di <2 mm, followed by quenching the strip from a temperature above 700 ° C to a temperature below 200 ° C,

Cold rolling the strip and reducing the thickness of Di to one

Thickness D2, where the degree of cold working (Di-D2) / Di <80%, preferably <

60%.

17. The method of claim 1 6, wherein 0.05 mm <D2 ^ is 0.5 mm.

18. The method according to any one of claims 1 to 17, further comprising:

Form at least one sheet from the tape.

19. The method of claim 18, wherein the sheet is stamped from the strip.

20. The method of claim 18 or claim 19, further comprising:

Merging a variety of sheets to form a laminated core.

A method according to any one of claims 1 to 20, further comprising:

Heat treating the strip at a temperature between 700 ° C to 900 ° C.

22. The method of claim 21, wherein after the heat treatment of the strip a permanent growth dl / lo in the longitudinal direction of the belt is less than 0.08% and / or in the transverse direction of the belt is less than 0.08%, wherein the lo

Initial length before heat treatment, dl denotes the absolute change in length after heat treatment and dl / lo the relative change in length relative to the initial length. A method according to claim 21, wherein after the heat treatment of the belt, a difference between the longitudinal permanent growth and the transversal growth of the belt is less than 0.06%, preferably less than 0.04%. 24. The method according to any one of claims 21 to 23, wherein the heat treatment of the strip takes place under a dry hydrogen-containing atmosphere.

25. Semifinished product, comprising:

at least one metallic band consisting essentially of 35% by weight <Co <55% by weight, 0% by weight <V <3% by weight, 0% by weight <Ni <2% by weight, 0

Wt% <Nb <0.50 wt%, 0 wt% <Zr + Ta <1.5 wt%, 0 wt% <Cr <3 wt%, 0 wt% -% <Si <3 wt .-%, 0 wt .-% <Al <1 wt .-%, 0 wt .-% <Mn <1 wt .-%, 0 wt .-% <B <0.25 Wt .-%, 0 wt .-% <C <0.1 Wt .-%, balance Fe and up to 1 wt .-% impurities, wherein the

Impurities may have one or more of the group O, N, S, P, Ce, Ti, Mg, Be, Cu, Mo and W, wherein the metallic band has a thickness d, where 0.05 mm <d <0.5 mm is, has a Vickers hardness of greater than 300 and an elongation at break of less than 5% and after a

Heat treatment of the strip at a temperature between 700 ° C to 900 ° C, a permanent growth dl / lo in the longitudinal direction of the strip less than 0.08%, preferably 0.06% and / or in the transverse direction of the strip less than 0.08%, preferably 0.06%, where lo the initial length before the heat treatment, dl the absolute change in length after the

Heat treatment and dl / lo denotes the relative change in length based on the initial length.

26. A semifinished product according to claim 25, wherein 0.05 mm <d <0.356 mm.

27. A semifinished product according to claim 25 or claim 26, wherein the semifinished product has a plurality of sheets which form a laminated core.

28. Semi-finished product according to one of claims 25 to 27, wherein according to the

Heat treatment of the strip at a temperature between 700 ° C to 900

° C, a difference between the longitudinal permanent growth and the transversal growth of the ribbon is less than 0.06%, preferably less than 0.04%.