Soft magnetic alloy and method for producing a soft magnetic alloy

Abstract

A soft magnetic alloy consisting of 47 wt% ≤ Co ≤ 50 wt%, 1 wt% ≤ V ≤ 3 wt%, 0 wt% ≤ Ni ≤ 0.25 wt%, 0 wt% ≤ C ≤ 0.005 wt%, 0 wt% ≤ Mn ≤ 0.1 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one element of niobium and tantalum in amounts of x wt% of niobium, y wt% of tantalum, other impurity elements in a total amount not exceeding 0.5 wt%, the remainder being iron, wherein 0 wt% ≤ x < 0.15 wt%, 0 wt% ≤ y ≤ 0.3 wt% and 0.14 consisting of a weight percent ≤ (y + 2x) ≤ 0.3 weight percent, and which was annealed at a temperature in the range of 730 °C to 880 °C for a time of 1 to 6 hours, wherein the soft magnetic alloy has a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 A / cm to 1.5 A / cm, where y = 0 and 0,07 wt% ≤ x < 0.15 wt% are, wherein the soft magnetic alloy has a composition selected such that the yield strength of the soft magnetic alloy is adjustable over a range of at least 130 MPa after annealing at 750 °C or at 871 °C.

Description

[0001] A ferromagnetic material that can be magnetized but tends to remain unmagnetized is described as soft magnetic. When a soft magnetic material is magnetized in a magnetic field and then removed from the magnetic field, it largely loses the magnetism it exhibited in the field. A soft magnetic material preferably exhibits low hysteresis loss, high magnetic permeability, and high magnetic saturation induction. Soft magnetic material is used in various static and rotating electrical devices such as motors, generators, alternators, transformers, and magnetic bearings.

[0002] US 5,501,747 A discloses a high-strength, soft-magnetic iron-cobalt-vanadium-based alloy, which further comprises 0.15 wt. % to 0.5 wt. % niobium and 0.003 wt. % to 0.02 wt. % carbon. This alloy is disclosed as having a combination of yield strength, magnetic properties, and electrical properties that makes it suitable for use as a rotating part, such as a rotor, of a rotating electrical machine. When the alloy is annealed at a temperature of not more than 740 °C for not more than about 4 hours, it exhibits a yield strength of at least 620 MPa at room temperature.

[0003] DE 699 04 367 T2 discloses a soft magnetic alloy consisting essentially of 45% to 55% cobalt; 0.75% to less than 1.5% vanadium, 0.15% to 0.5% niobium or tantalum or mixtures thereof, 0% to 0.3% manganese, 0% to 0.2% silicon, 0% to 0.1% carbon and the remainder iron, all percentages being by weight and based on the total weight of the alloy.

[0004] US 4 933 026 A discloses a soft magnetic cobalt / iron alloy consisting of 0.15-0.5% tantalum or niobium or tantalum plus niobium, 33-55% cobalt, the remainder being iron, apart from very minor alloying constituents and incidental impurities.

[0005] DE 696 11 610 T2 discloses a soft magnetic article formed from an alloy consisting essentially of (in weight percent) about -C 0.003-0.02 -Mn 0.10 max. -Si 0.10 max. -P 0.01 max. -S 0.003 max. -Cr 0.1 max. -Ni 0.2 max. -Mo 0.1 max. -Co 48-50 -V 1.8-2.2 -Nb 0.15-0.5 -N 0.004 max. -O 0.006 max. -, the remainder consisting essentially of iron.

[0006] US 2002 / 0 069 944 A1 discloses nanostructured materials and methods for producing nanostructured materials.

[0007] US 3 634 072 A discloses a magnetic alloy containing by weight about 0.5 to 2.5 percent vanadium, 45 to 52 percent cobalt, at least one element selected from the group consisting of about 0.02 to 0.5 percent niobium and about 0.07 to 0.3 percent zirconium, and the balance iron, excluding incidental impurities.

[0008] However, other soft magnetic alloys that have a combination of high yield strength and suitable magnetic properties suitable for applications such as rotating electrical equipment are desirable.

[0009] A soft magnetic alloy is provided which consists of 47 wt% ≤ Co ≤ 50 wt%, 1 wt% ≤ V ≤ 3 wt%, 0 wt% ≤ Ni ≤ 0.25 wt%, 0 wt% ≤ C ≤ 0.005 wt%, 0 wt% ≤ Mn ≤ 0.01 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one of the elements of niobium and tantalum in amounts of x wt% of niobium, y wt% of tantalum, other impurity elements in a total amount of not more than 0.5 wt%, balance iron. The niobium and tantalum contents are in the ranges of 0 wt% ≤ x < 0.15 wt%, 0 wt% ≤ y ≤ 0.3 wt% and 0.14 wt% ≤ (y+2x) ≤ 0.3 wt%, where y = 0 and 0.07 wt% ≤ x < 0.15 wt%.The soft magnetic alloy has a composition selected such that the yield strength of the soft magnetic alloy is adjustable over a range of at least 130 MPa after being tempered at 750 °C or at 871 °C.

[0010] The soft magnetic alloy was annealed at a temperature in the range of 730 °C to 880 °C for a time of 1 to 6 hours and has a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 to 1.5 A / cm.

[0011] The alloy is based on a 49%Co-2%V-Fe-type alloy, which further contains niobium and / or tantalum in amounts within the range of 0 wt.% ≤ x < 0.15 wt.% and / or 0 wt.% ≤ y ≤ 0.3 wt.%. The total amount of niobium and tantalum is described as (y+2x), meaning the amount of tantalum in weight percent, y, plus twice the amount of niobium in weight percent, 2x, are within a range of 0.14 wt.% to 0.3 wt.%. The alloy further includes a maximum carbon content of 0.007 wt.% and optionally Ni up to 0.2 wt.%.

[0012] The elements manganese and silicon are also optional and can be added to reduce the oxygen content of the alloy. Oxygen is not intentionally added to the alloy, but may be present as an impurity in amounts up to 0.009 weight percent. Other impurity elements, such as one or more of the elements Cr, Cu, Mo, Al, S, Ti, Ce, Zr, B, N, Mg, Ca, or P, may be present in a total amount not exceeding 0.5 weight percent.

[0013] The soft magnetic alloy is also free of boron. In this context, free of boron includes a boron content of less than 0.0007 weight percent as well as zero boron content.

[0014] For alloys of the 49%Co-2%V-49%Fe type, it is generally observed that the annealing temperature has opposing effects on the mechanical and magnetic properties. In particular, the yield strength is observed to increase with decreasing annealing temperatures, while the magnetic properties are observed to improve upon annealing at higher temperatures.

[0015] A combination of a niobium content, x, and / or tantalum content, y, in a relationship y+2x within the range of 0.14 to 0.3 weight percent and a carbon content of less than 0.005 weight percent or less than 0.003 weight percent yields a soft magnetic alloy with a yield strength that can be adjusted as desired over a range of 200 MPa to 450 MPa with appropriate selection of the tempering conditions. At the same time, it can be observed that the soft magnetic properties are suitable for soft magnetic parts, such as a rotor or stator of a rotating electrical machine.

[0016] A coercivity of 1.5 A / cm can be achieved for an alloy annealed at an annealing temperature of 730 °C, while a coercivity of 9.3 A / cm can be achieved for an alloy annealed at 880 °C.

[0017] One explanation for this behavior is the reduction of the carbon content, which promotes the formation of Laves phases (Co / Fe, Nb) while reducing the formation of carbides, thus allowing a suitably high yield strength to be obtained without resulting in a deterioration of the magnetic properties to a degree where they are no longer suitable for use in electrical machines.

[0018] In a rotating electrical machine, the rotor typically requires a higher yield strength than the stator because the rotor rotates during operation and is subject to centrifugal forces. It can be advantageous if the yield strength of the rotor material is sufficiently high so that the rotor remains below its elastic limit despite the centrifugal forces. In contrast, the stator is static and not subject to centrifugal force, so the stator can have a lower yield strength than the rotor.

[0019] Advantageously, the yield strength and the magnetic properties of the soft magnetic alloy according to the invention can be adapted by tempering the parts for the rotor and for the stator at different tempering temperatures, so that the same composition can be used for both the rotor and the stator of an electrical machine.

[0020] In another embodiment, the total content of niobium and tantalum is limited to 0.25, so that 0.14 wt% ≤ (y+2x) ≤ 0.25 wt%.

[0021] Tantalum is omitted so that y = 0, the niobium content is 0.07 wt% ≤ x < 0.15 wt%.

[0022] In a further embodiment, the upper limit of the nickel content is limited to 0.2 wt%, so that 0 wt% ≤ Ni ≤ 0.20 wt%.

[0023] The maximum amount of carbon can be reduced to 0 wt% ≤ C ≤ 0.003 wt%. Reducing the carbon content can be beneficial in improving magnetic properties.

[0024] As discussed above, manganese and silicon are optional. In some embodiments, the soft magnetic alloy contains manganese and / or silicon within a range of 0 wt. % y Mn ≤ 0.07 wt. % and / or 0 wt. % < Si ≤ 0.07 wt. %. In further embodiments, 0.07 wt. % < Mn ≤ 0.1 wt. % and / or 0.07 wt. % < Si ≤ 0.1 wt. %.

[0025] In one embodiment, the soft magnetic alloy has a yield strength (0.2% elongation), Rp 0,2 , between 200 MPa and 450 MPa in the tempered state. The yield strength can be adjusted as desired by adjusting the tempering conditions, in particular by selecting a suitable tempering temperature.

[0026] The soft magnetic alloys have a composition within the ranges specified above and exhibit a linear dependence of yield strength with tempering temperature. This feature is not exhibited by commercially available alloys with approximately 0.05 wt.% Nb and 100 ppm C, such as HIPERCO 50. In the following, alloys with approximately 0.05 wt.% Nb and 100 ppm C are referred to as reference alloys.

[0027] In one embodiment, the soft magnetic alloy comprises a yield strength (0.2% elongation) that is a linear function of the annealing temperature over an annealing temperature range of 740°C to 865°C or 730°C to 900°C.

[0028] In one embodiment, the soft magnetic alloy has a yield strength (0.2% strain) in one temperature condition that is within ± 10% of a linear function of the yield strength (0.2% strain) with respect to an annealing temperature achieved for the alloy.

[0029] In one temperature condition, the soft magnetic alloy may comprise a resistance of at least 0.4 µΩm and / or an induction B(8 A / cm) of at least 2.12 T.

[0030] As discussed above, the soft magnetic alloy comprises a combination of mechanical strength and soft magnetic properties suitable for soft magnetic parts of a rotating electrical machine. In one embodiment, the soft magnetic alloy is tempered such that, in the tempered state, it has an induction B(8 A / cm) of at least 2.12 T and a yield strength of at least 370 MPa. This combination of properties is suitable for a rotor of an electrical machine.

[0031] In a particular embodiment, the soft magnetic alloy, after annealing at a temperature in the range of 720°C to 900°C, has a yield strength in the range of 200 MPa to 450 MPa and a power loss density at 2 T and 400 Hz of less than 90 W / ≤. In further embodiments, for an annealing temperature of 720°C, the power loss density at 2 T and 400 Hz is less than 90 W / ≤, and for an annealing temperature of 900°C, it is less than 65 W / ≤.

[0032] A stator for an electric motor and a rotor for an electric motor comprising a soft magnetic alloy according to any one of the previously described embodiments are also provided. An electric motor comprising a stator and a rotor, each comprising a soft magnetic alloy having a composition according to any one of the previously described embodiments, is also provided. The rotor and the stator may have the same composition but different mechanical properties and magnetic properties. This can be achieved by tempering the rotor or parts forming the rotor under different tempering conditions compared to the stator or the parts forming the stator.

[0033] The rotor and / or stator may comprise a plurality of plates or layers stacked together to form a laminate.

[0034] The electrical machine can be a motor, a generator, an alternator or a transformer.

[0035] A method for producing a soft magnetic alloy is provided, which comprises: providing a melt consisting of 47 wt% ≤ Co ≤ 50 wt%, 1 wt% ≤ V ≤ 3 wt%, 0 wt% ≤ Ni ≤ 0.25 wt%, 0 wt% ≤ C ≤ 0.005 wt%, 0 wt% ≤ Mn ≤ 0.01 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one of niobium and tantalum in amounts of x wt% of niobium or y wt% of tantalum, further impurity elements in a total amount of not more than 0.5 wt%, balance Fe, where 0 wt% ≤ x < 0.15 wt%, 0 wt% ≤ y ≤ 0.3% by weight and 0.14% by weight ≤ (y+2x) ≤ 0.3% by weight, where y = 0 and 0.07% by weight ≤ x < 0.15% by weight.The soft magnetic alloy has a composition selected such that the yield strength of the soft magnetic alloy is adjustable over a range of at least 130 MPa after being tempered at 750 °C or 871 °C. This melt is cooled and solidified to form an ingot. The ingot is hot rolled, quenched, and then cold rolled. Subsequently, at least a portion of the ingot is tempered at a temperature in the range of 730 °C to 880 °C, producing a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 A / cm to 1.5 A / cm.

[0036] After cold rolling, the blank can be in the form of a plate or strip. Portions of the blank can be removed, for example, by punching or cutting, and the piece(s) can be tempered at a suitably selected temperature to obtain the desired mechanical and magnetic properties.

[0037] In further embodiments, at least a portion of the blank is annealed at a temperature in the range of 740°C to 865°C, or in a range of 730°C to 790°C, or in a range of 800°C to 880°C. The higher temperature range of 800 to 880°C may be used when a stator is to be made from the soft magnetic alloy, and the lower temperature range of 730°C to 790°C may be used when a rotor is to be made from the soft magnetic alloy.

[0038] In another embodiment, a thickness reduction of approximately 90% of the blank is achieved by hot rolling the blank. This thickness reduction can be selected to determine the desired thickness reduction in the subsequent cold rolling step and to select the amount of deformation introduced into the soft magnetic alloy.

[0039] The blank can be hot rolled at a temperature in the range of 1100 °C to 1300 °C. After hot rolling, the blank is allowed to cool naturally. After hot rolling, the strip is quenched from a temperature above 730 °C to room temperature or below room temperature. This can be done while the strip is cooling from the hot rolling temperature. Alternatively, the strip can be cooled to room temperature and then reheated to a temperature above 730 °C and quenched to room temperature or below room temperature.

[0040] After hot rolling and before cold rolling, the blank can be cleaned, for example, by pickling and / or mechanically treated, for example, by sandblasting, to clean the surface. This improves the surface quality of the blank after cold rolling and can also contribute to improving the magnetic properties of the alloy after tempering.

[0041] In one embodiment, a 90% thickness reduction of the blank is achieved by cold rolling the blank. After cold rolling, the thickness of the blank can range from 0.3 mm to 9.4 mm. This thickness is suitable for the production of laminated articles, such as laminated rotors and laminated stators for electrical machines.

[0042] A method for producing a semi-finished product is also provided, which comprises performing the method according to any of the previously described embodiments and comprises separating a portion of the blank to produce a semi-finished product.

[0043] A laminated article may be formed by assembling a plurality of semi-finished parts comprising a soft magnetic alloy according to any of the embodiments described above.

[0044] A rotor for an electric motor can be provided by annealing the soft magnetic alloy or laminated article according to any of the previously described embodiments at a temperature of 730°C to 790°C.

[0045] A stator for an electric motor can be provided by annealing the soft magnetic alloy or laminated article according to any of the previously described embodiments at a temperature of 800°C to 880°C.

[0046] Specific examples and embodiments will now be described with reference to the accompanying drawings and tables. Fig. 1 shows a graph of a yield strength Rp 0,2 depending on (Ta + 2 x Nb) for a low carbon content. Fig. 2 shows a graph of a yield strength Rp 0,2 depending on carbon for a Nb and Ta content according to the invention. Fig. Figure 3 shows a graph of magnetic induction B (3 A / cm) versus (Ta + 2 x Nb) for a low carbon content. Fig. Figure 4 shows a graph of a magnetic induction B (3 A / cm) as a function of the carbon content for a Nb and Ta content according to the invention. Fig. Figure 5 shows a graph of coercive field strength Hc versus (Ta + 2 x Nb) for a low carbon content. Fig. Figure 6 shows a graph of coercive field strength Hc as a function of carbon content for Nb and Ta content according to the invention. Fig. Figure 7 shows a graph of a power loss density P (2T; 400Hz) as a function of (Ta + 2 x Nb) for a low carbon content. Fig. Figure 8 shows a graph of a power loss density P (2T; 400Hz) as a function of the carbon content for alloys having an Nb and Ta content according to the invention. Fig. Figure 9 shows a graph of magnetic induction B (8 A / cm) versus (Ta + 2 x Nb) for a low carbon content. Fig. Figure 10 shows a graph of magnetic induction B (8 A / cm) as a function of carbon content for alloys having Nb and Ta content according to the invention. Fig. Figure 11 shows a graph of magnetic induction B (80 A / cm) versus (Ta + 2 x Nb) for low carbon contents. Fig. Figure 12 shows a graph of magnetic induction B (80 A / cm) as a function of carbon content for Nb and Ta contents according to the invention. Fig. Figure 13 shows a graph of a power loss density P (2T; 50Hz) as a function of (Ta + 2 x Nb) for low carbon contents. Fig. Figure 14 shows a graph of a power loss density P (2T; 50Hz) as a function of carbon content for Nb and Ta contents according to the invention. Fig. Figure 15 shows a graph of a range of yield strength as a function of Ta and Nb content for C ≤ 0.0070%. Fig. Figure 16 shows a graph of a range of yield strength versus carbon content for 0.14 wt% <= Ta + 2 x Nb <= 0.30 wt%. Fig. 17 shows a graph of the power loss density P (2T; 400 Hz) as a function of the yield strength Rp 0,2 . Fig. 18 shows a graph of a coercive field strength Hc as a function of the yield strength Rp 0,2 . Fig. 19 shows a graph of a power loss density P (2T; 50 Hz) as a function of the yield strength Rp 0,2 . Fig. 20 shows a graph of a magnetic induction B (3 A / cm) as a function of the yield strength Rp 0,2 . Fig. 21 shows a graph of a magnetic induction B (8 A / cm) as a function of the yield strength Rp 0,2 .

[0047] Table 1 shows a summary of the compositions, mechanical properties and magnetic properties of alloys and comparison alloys.

[0048] A soft magnetic alloy is provided which consists essentially of 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 ≤ 0.01 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one of the elements of niobium and tantalum in amounts of x wt% of niobium, y wt% of tantalum, balance iron. The alloy has the following properties: 0 weight percent ≤ x < 0.15 weight percent, 0 weight percent ≤ y ≤ 0.3, and 0.14 weight percent ≤ (y+2x) ≤ 0.3 weight percent. The soft magnetic alloy was annealed at a temperature range of 730 °C to 880 °C for a time of 1 to 6 hours and has a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 to 1.5 A / cm.

[0049] The soft magnetic alloy can be produced by providing a melt consisting essentially of 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 ≤ 0.01 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one element of niobium and tantalum in amounts of x wt% of niobium or y wt% of tantalum, balance Fe, where 0 wt% ≤ x < 0.15 wt%, 0 wt% ≤ y ≤ 0.3 wt% and 0.14 wt% ≤ (y+2x) ≤ 0.3 weight percent. The melt is then cooled and solidified to form an ingot. The ingot is then hot rolled, for example, at 1200 °C, cooled or reheated to 730 °C, and then quenched to room temperature. The ingot is then cold rolled at room temperature to a final thickness of, for example, 0.35 mm.Subsequently, at least a portion of the blank is annealed at a temperature in the range of 730 °C to 880 °C to form a semi-finished product having a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 A / cm to 1.5 A / cm.

[0050] The temperature is chosen so that it lies between the recrystallization temperature of about 720 °C and the transition phase from the alpha, α, phase to the gamma, γ, phase at about 885 °C. The tempering temperature is chosen within this range so that the semi-finished product has the desired mechanical properties, in particular the desired yield strength (0.2% elongation), Rp 0,2 , in combination with the desired magnetic properties, in particular power loss density.

[0051] It is observed that a composition of a niobium and / or tantalum content described by (y + 2x), where y is the tantalum content in weight percent and x is the niobium content in weight percent within the range of 0.14 to 0.3 weight percent, and a carbon content of less than 0.007 weight percent, less than 0.005 weight percent, or less than 0.003 weight percent, provides a soft magnetic alloy with a yield strength that can be adjusted as desired over a range of 200 MPa to 450 MPa by appropriate selection of the annealing temperature. At the same time, soft magnetic properties suitable for soft magnetic parts of rotating electrical machines can be obtained.

[0052] An advantage is that the yield strength and magnetic properties can be adjusted so that the same composition can be used for both the rotor and stator of an electrical machine by tempering the rotor and stator parts at different tempering temperatures. For example, rotor parts can be tempered at 750 °C and exhibit a higher yield strength than stator parts tempered at 870 °C. In this example, the stator exhibits significantly better magnetic properties than the rotor.

[0053] The composition, tempering conditions and measured mechanical and magnetic properties of sample alloys according to the invention and comparative alloys are summarized in Table 1.

[0054] In a first set of embodiments, the effect of composition on mechanical and magnetic properties is investigated. For each sample alloy, annealing at 750 °C for 3 hours and annealing at 871 °C for 2 hours are shown, connected by dashed lines.

[0055] In the figures, the dependence of niobium and tantalum (y + 2x) is shown as Ta + 2 x Nb.

[0056] Fig. 1 shows a graph of a yield strength Rp 0,2 depending on (Ta + 2 x Nb) for alloys with a low carbon content, in particular a carbon content of less than or equal to 0.007 wt% and different (x + 2x) values.

[0057] The lowest achievable yield strength and the highest achievable yield strength for each sample alloy increase by a similar amount with Nb and Ta content (y + 2x). The range over which the yield strength can be adjusted remains relatively large. This is advantageous because a single composition can encompass a wider range of yield strength when selecting tempering conditions.

[0058] Fig. 2 shows a graph of a yield strength Rü 0,2 as a function of carbon for a single Nb and Ta content (y + 2x) according to the invention. The yield strength increases with increasing carbon content. The range over which the yield strength can be adjusted by selecting the tempering temperature is reduced for increasing carbon contents. The carbon content should be kept low in order to be able to adjust the yield strength over a wider range.

[0059] Fig. Figure 3 shows a graph of magnetic induction B (3 A / cm) versus (Ta + 2 x Nb) for sample alloys with a carbon content of less than or equal to 0.007 wt%.

[0060] The magnetic induction B (3 A / cm) decreases with increasing Nb and Ta content, especially above 0.5. However, for alloys having a Ta and Nb content (x + 2x) according to the invention, namely within the range of 0.14 to 0.3 wt. percent, the decrease is moderate after annealing at 871 °C for 2 hours.

[0061] Fig. Figure 4 shows a graph of magnetic induction B (3 A / cm) versus carbon content for Nb and Ta contents (y + 2x) according to the invention. No significant trend is observed.

[0062] Fig. 5 shows a graph of a coercive field strength H cas a function of (Ta + 2 x Nb) for a carbon content of less than or equal to 0.007 weight percent. The difference in H c is lower for smaller (Ta + 2Nb) contents. The deterioration effect for H c the decreasing tempering temperature is smaller for lower Nb and Ta contents.

[0063] Fig. Figure 6 shows a graph of coercive field strength Hc as a function of carbon content for Nb and Ta contents (y + 2x) of less than 0.3.

[0064] Fig. Figure 7 shows a graph of power loss density P (2T; 400 Hz) versus (Ta + 2 x Nb) for low carbon contents of less than or equal to 0.007 wt.%. The losses remain low after an annealing temperature of 871 °C for 2 hours for Ta and Nb contents (y + 2x) of less than 0.3.

[0065] Fig. Figure 8 shows a graph of power loss density P (2T; 400 Hz) as a function of carbon content for alloys containing Nb and Ta according to the invention. A carbon content of 100 ppm increases losses starting at an annealing temperature of 871 °C for 2 hours. The carbon content should be kept low to achieve low losses.

[0066] Fig. Figure 9 shows a graph of magnetic induction B (8 A / cm) versus (Ta + 2 x Nb) for a low carbon content of up to 0.007. The magnetic induction B (8 A / cm) decreases with increasing Nb and Ta content. However, for alloys with Ta and Nb (y+2x) of less than about 0.3, the decrease is moderate after an annealing temperature of 871 °C for 2 hours.

[0067] Fig. Figure 10 shows a graph of magnetic induction B (8 A / cm) versus carbon content for alloys containing Nb and Ta according to the invention. A higher carbon content results in a lower magnetic induction.

[0068] Fig. Figure 11 shows a graph of magnetic induction B (80 A / cm) versus (Ta + 2 x Nb) for sample alloys with a carbon content of less than or equal to 0.007 wt.%. The magnetic induction B (80 A / cm) decreases with increasing Nb and Ta content. However, for alloys with a Ta and Nb content (y + 2x) of less than about 0.3, the decrease is moderate after an annealing temperature of 871 °C for 2 hours.

[0069] Fig. Figure 12 shows a graph of magnetic induction B (80 A / cm) as a function of carbon content for Nb and Ta contents according to the invention. No significant effect is observed.

[0070] Fig. Figure 13 shows a graph of power loss density P (2T; 50 Hz) versus (Ta + 2 x Nb) for carbon contents less than or equal to 0.007 wt.%. A sharp increase in losses is observed for (y + 2x) greater than 0.3.

[0071] Fig. Figure 14 shows a graph of power loss density P (2T; 50 Hz) as a function of carbon content for Nb and Ta contents (y + 2x) according to the invention. It is observed that alloys exhibit increasing losses with increasing carbon content.

[0072] Fig. Figure 15 shows a graph of the yield strength range for an alloy annealed at 750 °C for 3 hours and at 871 °C for 2 hours as a function of Ta and Nb content (y + 2x) for c ≤ 0.007%: The yield strength remains largely unchanged with increasing Ta and Nb.

[0073] Fig. Figure 16 shows a graph of the range of yield strength achieved for an alloy annealed at 750 °C for 3 hours and at 871 °C for 2 hours as a function of carbon content for 0.14 wt.% <= Ta + 2 x Nb <= 0.30 wt.%. The range over which the yield strength can be adjusted with a temperature difference of 121 °C decreases with increasing carbon content. The widest range of yield strength values ​​is achievable with a carbon content of less than 0.005 wt.%.

[0074] In a second set of embodiments described in the Fig. 17 to 21, the magnetic properties are calculated as a function of the yield strength, Rp 0,2 , shown.

[0075] In Fig. 17 to 21, "A" denotes alloys according to the invention, namely 0.15 wt.% ≤ (Ta + 3 x Nb) ≤ 0.30 wt.%, C ≤ 0.007%, and "B" denotes a comparative composition of a reference alloy with (Ta + 2 x Nb) ≤ 0.12 wt.%, 0.0080 wt.% ≤ C ≤ 0.0120 wt.%. These reference alloys have compositions similar to those disclosed in US Pat. No. 3,634,072 and similar to the commercially available alloy HIPERCO 50.

[0076] Fig. 17 to 21 show that the highest and lowest values ​​of Rp 0,2 are comparable to alloy “A”, which shows that the yield strength is adjustable over a wider range than is achievable with the reference alloy “B”.

[0077] Fig. 17 shows a graph of the power loss density P (2T; 400 Hz) as a function of the yield strength Rp 0,2and with significantly lower losses for the “A” alloys.

[0078] A soft magnetic alloy with a low power loss density is provided by the soft magnetic alloy according to the invention. The alloy can be used as a stator of an electrical machine due to its low losses and good magnetic properties.

[0079] Fig. 18 shows a graph of a coercive field strength Hc as a function of the yield strength Rp 0,2 , Fig. 19 shows a graph of a power loss density P (2T; 50 Hz) as a function of the yield strength Rp 0,2 , Fig. 20 shows a graph of a magnetic induction B (3 A / cm) as a function of the yield strength Rp 0,2 and Fig. 21 shows a graph of a magnetic induction B (8 A / cm) as a function of the yield strength Rp 0,2In general, it is observed that the magnetic properties improve with increasing Rp 0,2 worsen.

[0080] Fig. 17 to 21 show that due to the low carbon content of ≤ 0.007 wt% and 0.14 wt% ≤ (y + 2x) ≤ 0.3 wt% of the alloy according to the invention shown with "A", an increased range of yield strength values ​​from about 200 MPa to about 450 MPa can be provided for a single composition compared to composition B which has a lower value of (Ta + 2 x Nb) ≤ 0.12 wt% and a higher carbon content of 0.008 wt% ≤ C ≤ 0.0120 wt%.

Claims

[1] A soft magnetic alloy consisting of 47 wt% ≤ Co ≤ 50 wt%, 1 wt% ≤ V ≤ 3 wt%, 0 wt% ≤ Ni ≤ 0.25 wt%, 0 wt% ≤ C ≤ 0.005 wt%, 0 wt% ≤ Mn ≤ 0.1 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one element of niobium and tantalum in amounts of x wt% of niobium, y wt% of tantalum, other impurity elements in a total amount of not more than 0.5 wt%, balance iron, where 0 wt% ≤ x < 0.15 wt%, 0 wt% ≤ y ≤ 0.3 wt% and 0.14 weight percent ≤ (y + 2x) ≤ 0.3 weight percent, and which has been tempered at a temperature in the range of 730 °C to 880 °C for a time of 1 to 6 hours, wherein the soft magnetic alloy has a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 A / cm to 1.5 A / cm,where y = 0 and 0.07 wt% ≤ x < 0.15 wt%, wherein the soft magnetic alloy has a composition selected such that the yield strength of the soft magnetic alloy is adjustable over a range of at least 130 MPa after being tempered at 750 °C or at 871 °C., [2] The soft magnetic alloy according to claim 1, wherein 0.14 wt% ≤ (y + 2x) ≤ 0.25 wt%. [3] A soft magnetic alloy according to claim 1 or 2, wherein 0 wt% ≤ Ni ≤ 0.20 wt%. [4] A soft magnetic alloy according to claim 1, wherein 0 wt% ≤ C < 0.003 wt%. [5] A soft magnetic alloy according to any one of the preceding claims, which has a nickel content of 0 wt% < Ni ≤ 0.2 wt%. [6] A soft magnetic alloy according to any one of the preceding claims, which has a manganese content of 0 wt% < Mn ≤ 0.07 wt%. [7] Soft magnetic alloy according to one of the preceding claims, which has a silicon content of 0 wt% < Si ≤ 0.05 wt%. [8] A soft magnetic alloy according to any one of the preceding claims, wherein the soft magnetic alloy has a resistance of at least 0.4 µΩm. [9] A soft magnetic alloy according to any one of the preceding claims, wherein the soft magnetic alloy has an induction B (8 A / cm) of at least 2.12 T. [10] A soft magnetic alloy according to any one of the preceding claims, wherein in an annealed state the soft magnetic alloy has a yield strength (0.2% elongation) that is within ± 10% of a linear function of the yield strength (0.2% elongation) with respect to an annealing temperature. [11] A soft magnetic alloy according to any one of the preceding claims, wherein the soft magnetic alloy has a yield strength (0.2% elongation) which is a linear function of an annealing temperature over an annealing temperature range of 740 °C to 865 °C. [12] A soft magnetic alloy according to claim 11, wherein the soft magnetic alloy has a yield strength (0.2% elongation) that is a linear function of the annealing temperature over an annealing temperature range of 730 °C to 900 °C. [13] A stator for an electric motor comprising the soft magnetic alloy according to any one of claims 1 to 12. [14] A rotor for an electric motor comprising the soft magnetic alloy according to any one of claims 1 to 12. [15] An electric motor comprising the stator of claim 13 and the rotor of claim 14. [16] A process for producing a soft magnetic alloy comprising: - Providing a melt consisting of 47 wt% ≤ Co ≤ 50 wt%, 1 wt% ≤ V ≤ 3 wt%, 0 wt% ≤ Ni ≤ 0.25 wt%, 0 wt% ≤ C ≤ 0.005 wt%, 0 wt% ≤ Mn ≤ 0.1 wt%, 0 wt% ≤ Si ≤ 0.1 wt%, at least one element of niobium and tantalum in amounts of x wt% of niobium or y wt% of tantalum, further impurity elements in a total amount of not more than 0.5 wt%, balance iron, where 0 wt% ≤ x < 0.15 wt%, 0 wt% ≤ y ≤ 0.3 wt% and 0.14% by weight ≤ (y + 2x) ≤ 0.3% by weight, where y = 0 and 0.07% by weight ≤ x < 0.15% by weight; - cooling and solidifying the melt to form a blank; - Hot rolling of the blank, followed by - Quenching the blank from a temperature above 730 °C, followed by - Cold rolling of the blank, and subsequently - annealing at least a portion of the blank at a temperature in the range of 730 °C to 880 °C and producing a yield strength in the range of 200 MPa to 450 MPa and a coercive field strength of 0.3 A / cm to 1.5 A / cm, wherein the soft magnetic alloy has a composition selected such that the yield strength of the soft magnetic alloy is adjustable over a range of at least 130 MPa after being annealed at 750 °C or at 871 °C. [17] The method of claim 16, wherein at least a portion of the blank is annealed at a temperature in the range of 740°C to 865°C. [18] The method of claim 16, wherein at least a portion of the blank is annealed at a temperature in the range of 730°C to 790°C or in the range of 800°C to 880°C. [19] A method according to any one of claims 16 to 18, wherein a thickness reduction of the blank of 90% is produced by hot rolling the blank. [20] A method according to any one of claims 16 to 19, wherein the blank is hot rolled at a temperature in the range of 1100 °C to 1300 °C. [21] A method according to any one of claims 16 to 20, wherein after hot rolling the blank is cooled and quenched from a temperature above 730°C to room temperature or is cooled and reheated to a temperature above 730°C and then quenched to room temperature. [22] A method according to any one of claims 16 to 21, further comprising pickling the blank prior to cold rolling. [23] A method according to any one of claims 16 to 22, wherein a thickness reduction of the blank of 90% is produced by cold rolling the blank. [24] A method according to any one of claims 16 to 23, wherein after cold rolling the thickness of the blank is in the range of 0.3 mm to 0.4 mm. [25] A method of manufacturing a semi-finished part comprising a method according to any one of claims 16 to 24 and comprising dividing a part of the blank to form a semi-finished product. [26] The method of claim 25, further comprising assembling a plurality of semi-finished parts produced by the method of claim 25 and forming a laminated soft magnetic article. [27] A method of manufacturing a rotor for an electric motor comprising providing the soft magnetic alloy according to any one of claims 1 to 12 and annealing at a temperature of 730 to 790 °C. [28] A method of manufacturing a stator for an electric motor comprising providing the soft magnetic alloy according to any one of claims 1 to 12 and annealing at a temperature of 800°C to 880°C.

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