RAPIDLY SOLIDIFIED HIGH SILICON STEEL WITH MINOR BORON ADDITION THAT IMPROVES MAGNETIC PROPERTIES

Abstract

Fe-6.5% Si electrical steel is alloyed with boron to reduce its melting temperature and interfacial energy to improve processability for melt-spinning applications. Boron additions from 0.01 wt % to 2.24 wt % into Fe-6.5% Si and its effect on ribbon thickness, grain size, magnetic, and mechanical properties are disclosed. Minor boron alloying significantly changed the melt pool stability and wetting on a melt-spinning quench wheel and in turn increased the quench rate with minimum impact on the magnetic saturation and ductility. Boron addition of less than 0.06 wt % was also found beneficial to the magnetic property of the alloy by lowering both its hysteresis and eddy current losses.

Claims

1. A method of preparing a ribbon of electrical steel comprising 6.5 wt % Si, the method comprising: directing a stream of the electrical steel in a molten form onto an outer surface of a rotating wheel; cooling the stream of electrical steel on the outer surface of the rotating wheel to form the ribbon; and spinning the ribbon off of the outer surface of the rotating wheel; wherein the ribbon comprises a thickness as measured perpendicular to the outer surface, the thickness being 0.1 mm or less; and wherein the electrical steel comprises from 100 ppm to 2100 ppm of B.

2. The method of claim 1, wherein the ribbon of electrical steel comprises a saturation magnetization of at least 17.6 kG (1400 kA/m).

3. The method of claim 1, wherein the ribbon of electrical steel comprises a Vickers hardness (HV) in a range from 300 to 500.

4. The method of claim 1, wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, a maximum permeability (p.sub.max) of the ribbon of electrical steel is greater than 1000.

5. The method of claim 1, wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, coercivity (H.sub.c) of the ribbon of electrical steel is less than 0.7 Oe (55 A/m).

6. The method of claim 1, wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in an alternating current mode at a frequency of 400 Hz, an iron loss of the ribbon of electrical steel is 12 W/kg or less.

7. The method of claim 1, wherein the ribbon of electric steel comprises about 14 wt % or less of FeSiB eutectic phase.

8. The method of claim 1, wherein the ribbon of electrical still comprises from 500 ppm to 1500 ppm of B.

9. The method of claim 1, wherein the ribbon comprises a length of at least 10 m.

10. The method of claim 1, wherein the ribbon comprises a width in a range from 1 mm to 300 mm.

11. An electrical steel structure, comprising: a ribbon having a length, a width, and a thickness, the length being perpendicular to the width and the thickness being perpendicular to both the length and the width; wherein the ribbon comprises Fe-6.5% Si and 100 ppm to 2100 ppm of B; and wherein the thickness of the ribbon is 0.1 mm or less.

12. The electrical steel structure of claim 11, wherein the ribbon comprises a magnetic saturation of at least 17.6 kG (1400 kA/m).

13. The electrical steel structure of claim 11, wherein the ribbon comprises a Vickers hardness (HV) in a range from 300 to 500.

14. The electrical steel structure of claim 11, wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, a maximum permeability (.sub.max) of the ribbon is greater than 2000.

15. The electrical steel structure of claim 11, wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, coercivity (H.sub.c) of the ribbon is less than 0.7 Oe (55 A/m).

16. The electrical steel structure of claim 11, wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in an alternating current mode at a frequency of 400 Hz, an iron loss of the ribbon is 12 W/kg or less.

17. The electrical steel structure of claim 11, wherein the ribbon comprises about 14 wt % or less of FeSiB eutectic composition.

18. An electrical component comprising a plurality of layers of the electrical steel structure according to claim 11 arranged in a stack.

19. The electrical component of claim 18, wherein the electrical component comprises at least a part of a stator or a rotor of an electric motor or at least a part of a core of a transformer.

20. The electrical component of claim 18, further comprising a plurality of layers of insulation in the stack, wherein a layer of insulation is provided between every one to ten layers of the electrical steel structure.

21. The electrical component of claim 20, wherein the electrical component comprises at least part of a stator or rotor of an electric motor or at least part of a core of a transformer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0031] FIG. 1 is a schematic depiction of a melt-spinning apparatus for producing a ribbon of Fe-6.5% Si electrical steel, according to an exemplary embodiment;

[0032] FIG. 2 depicts DSC curves showing the melting points of Fe6.5% Si alloys with various levels of boron additions (wt %), according to exemplary embodiments;

[0033] FIG. 3 is a graph of the melting onset of the liquidus phase and the intermetallic phase of Fe-6.5% Si electrical steel as a function of boron content, according to exemplary embodiments;

[0034] FIG. 4 is a graph of the ratio of heat of fusion between the solid solution phase and the eutectic phase, according to exemplary embodiments;

[0035] FIGS. 5A and 5B depict XRD patterns for Fe-6.5% Si alloys with various levels of boron additions labeled by weight percent for cast and spun samples, respectively, according to exemplary embodiments;

[0036] FIGS. 6-8 are SEM images of the Fe-6.5% Si samples with 0.04 wt %, 0.10 wt %, and 0.21 wt % of boron additions, respectively, according to exemplary embodiments;

[0037] FIG. 9 is a graph of magnetic saturation of drop cast Fe-6.5% Si alloys with varying levels of boron additions, according to exemplary embodiments;

[0038] FIG. 10 is a graph of hardness of drop cast Fe-6.5% Si alloys with varying levels of boron additions, according to exemplary embodiments;

[0039] FIGS. 11 and 12 are high-speed camera snapshots of the melt spinning process of Fe-6.5% Si with no boron and with 0.21 wt % of boron addition, respectively, depicting the melt, the ribbon, the detach point;

[0040] FIG. 13 is a graph of maximum permeability () and coercivity (Hc) of annealed Fe-6.5% Si ribbons with varying levels of boron additions under a maximum magnetic flux density of 1 Tesla in DC;

[0041] FIG. 14 is a graph of iron losses and thickness of annealed Fe-6.5% ribbons with varying levels of boron additions under 10 kG (1 T) magnetic flux density with excitation source in alternating current mode at a frequency of 400 Hz; and

[0042] FIG. 15 depict various electrical components that can be fabricated from ribbons of Fe-6.5% Si steel, according to embodiments of the present disclosure.

[0043] While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Embodiments of the present disclosure relate to a method of melt-spinning Fe-6.5% Si electrical steel alloyed with boron and to a ribbon produced by the method. As will be discussed more fully below, the addition of boron to Fe-6.5% Si electrical steel improves the cooling of the melt when contacting a spinning wheel during the melt-spinning process. Specifically, the boron lowers the melting temperature of the electrical steel and improves the wettability of the electrical steel on the surface of the spinning wheel. The improved wettability increases the contact time between the surface of the spinning wheel and the electrical steel, allowing for increased heat dissipation from the resulting ribbon.

[0045] Additionally, the boron does not substantially affect the ductility of the electrical steel such that long continuous ribbons of uniform width and thickness can be produced. Notwithstanding, the ribbon retains sufficient hardness to provide good deformation when processed into laminated structures for electric motor or transformer parts through conventional methods, such as stamping.

[0046] Further, the addition of a small amount of boron surprisingly enhances magnetic properties of the electrical steel ribbon, including doubling permeability and decreasing coercivity. The effect of boron on the properties of the Fe-6.5% Si electrical steel is far greater than would be expected from the small amounts of boron added (e.g., in a range of 100 ppm to 2100 ppm). These and other aspects and advantages of the disclosed method of melt-spinning an Fe-6.5% Si electrical steel having alloying additions of boron and ribbon produced by same will be described more fully below and in relation to the figures provided herewith. These embodiments are provided by way of illustration and not limitation.

[0047] Fe-6.5% Si is too brittle for typical cold rolling and stamping to make electric motor and transformer components. Melt-spinning offers a way to rapidly solidify the electrical steel to retain some ductility, but the melting temperature of Fe-6.5% Si is too high (by at least 300 C.) for melt-spinning using existing apparatuses. By adding boron to the Fe-6.5% Si electrical steel composition, the enhanced wettability allows the melt to stay on the wheel for an extra of time, which will allow more heat to be dissipated through the wheel. Moreover, the addition of boron lowers the melting temperature, which reduces the overall amount of the heat to be dissipated. Together, these two effects allow for the melt-spinning of Fe-6.5% Si, and the ribbons formed therefrom have advantageous mechanical and magnetic properties.

[0048] FIG. 1 depicts an apparatus 100 for melt-spinning of a ribbon of Fe-6.5% Si alloyed with boron. As shown in FIG. 1, the apparatus 100 includes a crucible 110 containing metal feedstock 120. The metal feedstock 120 is Fe-6.5% Si alloyed with boron. In one or more embodiments, the Fe-6.5% Si comprises 100 ppm to 2100 ppm of boron, in particular 500 ppm to 1500 ppm of boron. This level of boron addition is more than mere impurity levels, which would be less than 100 ppm (e.g., 10 to 50 ppm), and reflects an intentional addition of boron to the electrical steel composition to achieve the desired properties as discussed below. Advantageously, the addition of boron helps to decrease the melting temperature, lowering the temperature needed to perform the melt-spinning process. In one or more embodiments, the ribbon of electric steel comprises up to 14 wt % of FeSiB eutectic composition.

[0049] Disposed around the crucible 110 is a heating element 130. In one or more embodiments, the heating element 130 is, for example, an inductive heating element, among other possibilities. The heating element 130 is configured to melt the metal feedstock 120, and the molten metal feedstock 120 is forced through a nozzle 140 of the crucible 110 as a stream 150 of molten metal. In one or more embodiments, the metal feedstock 120 is forced through the nozzle 140 using pressurized gas, such as an inert gas (e.g., argon).

[0050] The stream 150 is directed onto a spinning wheel 160. As shown in FIG. 1, the wheel 160 is depicted as rotating, which allows the stream 150 to contact an uncovered surface of the wheel 160. In this way, the surface of the wheel 160 immediately cools the stream 150 of molten metal to produce a solidified ribbon 170. To facilitate cooling, in one or more embodiments, the wheel 160 is cooled with a fluid, such as water. In one or more embodiments, the wheel 160 is rotating at a speed of at least 3 m/s (tangential speed), in particular a speed of at least 7 m/s (tangential speed). The degree of cooling is dependent, at least in part, on the length of time that the stream/ribbon 150/170 is in contact with the outer surface of the wheel 160. According to embodiments of the present disclosure, contact between the stream/ribbon 150/170 is enhanced based on the boron additions to the Fe-6.5% Si, which improves the wettability of the molten electrical steel on the wheel 160. Further, in one or more embodiments, the ribbon of electric steel is in contact with the outer surface of the rotating wheel 160 over an arcuate distance (D) of at least 25 mm. In one or more embodiments, the rotating wheel has a diameter of 250 mm or more. In one or more embodiments, the ribbon of electric steel is in contact with the rotating wheel 160 for at least 5 of rotation (as denoted by rotation angle in FIG. 1).

[0051] The rapid solidification of the molten metal to form the ribbon 170 allows the Fe-6.5% Si metal to bypass or partially bypass the ordered phases (specifically, B2 and D0.sub.3) that result in brittleness. As will be discussed more fully below, the ribbon 170 exhibits sufficient ductility for melt-spin processing while retaining sufficient hardness for stamping procedures. Electrical steel ribbons 170 according to the present disclosure may be used in electrical components 200 as shown in FIG. 15, such as stators 210 or rotors 220 of electric motors or in transformer cores 230. The structures may be formed using a stack of ribbons 170 that may be stamped to near net-shape and laminated together. In one or more embodiments, at least some of the ribbons 170 within the stack are coated with an insulating material (e.g., varnish) or separated by a sheet of insulating material (e.g., paper). For example, a layer of insulation (e.g., varnish or paper) is provided between every layer or up to every ten layers of ribbons 170. In one or more embodiments, the laminated ribbons 170 are joined together using one or more pins extending through the stack, using welds, or using adhesives, amongst other possibilities.

[0052] While the ductility allows for continuous ribbons of uniform width and thickness to be produced and handled, the ribbons 170 should be sufficiently hard to allow for stamping into stator 210, rotor 230, or transformer core 230 shapes to be used in laminations. The ductility of the electrical steel ribbons is described below in relation percentage of samples that withstand parallel plate bending tests. In one or more embodiments, the ribbon of electrical steel comprises a Vickers hardness (HV) in a range from 300 to 500, in particular in a range from 370 to 430.

[0053] In one or more embodiments, the ribbons 170 produced via melt-spinning have a thickness (dimension of ribbon 170 perpendicular to the outer surface of the wheel 160) of 0.1 mm or less, in particular in a range from 0.05 mm to 0.1 mm and most particularly about 0.03 mm. The thickness of the ribbon 170 can be controlled, e.g., based on the speed of the spinning wheel 160 and the rate of flow of the stream 150 of molten metal. In one or more embodiments, the ribbons 170 have a width in a range from 1 mm to 300 mm. Commercially, melt-spun ribbons 170 are typically produced having widths of about 50 mm or about 250 mm. Further, in one or more embodiments, the ribbons 170 may be melt-spun to lengths up to 1000 m. While not particularly limited, the ribbons 170 typically have a length of at least 10 m when produced via melt-spinning.

[0054] Advantageously, the ribbon 170 of Fe-6.5% Si electrical steel comprising boron additions according to the present disclosure exhibits desirable magnetic properties for use as components in electric motors or transformers. In one or more embodiments, the ribbon of electrical steel comprises a saturation magnetization of at least 17.6 kG (1400 kA/m). In one or more embodiments, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, a maximum permeability (.sub.max) of the ribbon of electrical steel is at least 4000. In one or more embodiments, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, coercivity (H.sub.c) of the ribbon of electrical steel is less than 0.7 Oe (55 A/m). In one or more embodiments, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in an alternating current mode at a frequency of 400 Hz, an iron loss of the ribbon of electrical steel is 12 W/kg or less.

EXPERIMENTAL EXAMPLES

[0055] Fe-6.5% Si electrical steel was first pre-alloyed by arc melting of high-purity iron and silicon chunks (>99.9%) in an arc furnace under an argon atmosphere. High-purity boron chunks were then added to the iron-silicon melt. In particular, the boron chunks were submerged in the iron-silicon melt to minimize the mass loss (<0.1% mass loss after melting). In the samples prepared, boron was added in an amount in a range from 0.01 wt % to 2.24 wt %. The samples were flipped at least three times to ensure homogeneity during each arc melting. The arc melted buttons were then drop cast into 10 mm diameter rods.

[0056] The Fe-6.5% Si rods were melted and heated to 1650 C. inside a quartz crucible using induction heating. The meltstock was injected onto a rotating copper wheel spinning at 20 m/s tangential speed with an overhead pressure of 120 Torr. The nozzle orifice was 0.81 mm in diameter, and the melt spinning chamber was filled with of He after 3 vacuum flushes. To probe the melt spinning process, a 12-bit complementary metal-oxide semiconductor (CMOS) high-speed camera was set up and focused on the side profile of the ribbon as the ribbon was being produced.

[0057] The melting behavior of the alloys was measured by differential scanning calorimetry (NETZSCH, DSC 404). The heating rate was 10 C./min. The cross-sectional micrographs of the samples were taken using a scanning electron microscope (SEM) (Teneo, FEI Inc) equipped with an energy-dispersive X-ray spectroscopy (EDS) detector. The X-ray diffraction (XRD) patterns were collected via Bruker DaVinci D8 system equipped with a Cu target. Microhardness tests were conducted on polished cross-sections using a microhardness tester (LECO LM 247AT). The magnetic properties of the alloys were measured using Vibrating Sample Magnetometer (VSM) (Versalab, Quantum Design, Inc.) up to 30 kOe (237 kA/m) magnetic field. The closed-loop magnetic measurement was done using a computer-automated soft magnetic test station (model SMT-700, KJS Associates/Magnetic Instrumentation) with a single-strip test fixture. The melt-spun ribbons were annealed in a sealed quartz tube filled with Ar at 1100 C. for 2 hours and then were assembled into a plate 18 mm wide by 65 mm long for the magnetic measurement. A magnesium oxide (MgO) coating was applied to the ribbons to prevent inter-ribbon adhesion during annealing and was removed after the annealing. The densities of the alloys needed for the flux density calculation were measured on drop-casted samples using Archimedes' method.

[0058] The DSC curves in FIG. 2 show the melting behavior of the alloys. The melting onset of the liquidus is depressed, accompanied by the formation of a eutectic phase with boron alloying. The eutectic temperature (1145-1160 C.) in FIG. 2 (first dip in each of the B-alloyed curves) correlates well with the eutectic temperature in FeB or FeSiB phase diagram. The onsets of the liquidus and the eutectic are plotted in FIG. 3 as a function of boron content. The liquidus onset for the Fe-6.5% Si was 1415 C., and it was lowered by 15 C. with 0.21 wt % of boron, which was further lowered to 1350 C. with 1.10 wt % of boron. When boron is added to 2.24 wt % (close to the eutectic composition), the melting point of Fe-6.5% Si is fully depressed to the eutectic temperature of 1145 C., which is 270 C. lower than its original melting point. The 2.24 wt % (10 at %) of boron addition will bring the alloy into the amorphous region. The formation of an amorphous structure is confirmed on melt-spun ribbon with 2.24 wt % boron alloying through XRD studies (not shown). By estimating the heat of fusion or change in enthalpy in melting (area under the curve), FIG. 4 shows the relative fractions of the solid solution and eutectic phases. The amount of eutectic phase increases rapidly with increasing boron additions. The amount of eutectic is 14.2% with 0.21 wt % of boron addition, where it increases to 54.1% and 100% with 1.10 wt % and 2.24 wt % of boron additions, respectively.

[0059] The Fe-rich side of the FeB phase diagram consists of Fe.sub.2B and Fe solid solution with a maximum solubility of 0.02 at % with a eutectic temperature of 1175 C. According to the 10 at. % Si vertical section of FeSiB pseudo-binary phase diagram, a ternary eutectic is present between Fe, Fe.sub.2B, and Fe.sub.2.7Si.sub.0.3B. The eutectic temperature is 1112 C. The eutectic temperature is in good agreement with the lower temperature peak by the DSC (1150 C.), considering a higher Si % (12.14 at %) in Fe-6.5% Si alloy.

[0060] The formation of intermetallics and its eutectics (especially in FIG. 8) in the as-cast samples (having 0 wt %, 0.2 wt %, 0.5 wt %, and 1 wt % B) can be identified in the XRD patterns of FIG. 5A and the SEM microstructure in FIGS. 6-8, having 0.2 wt %, 0.5 wt %, and 1 wt % B, respectively. The shift in the XRD for the 0.02 wt % B is reversed compared to rest suggests that the composition of the matrix is not taking up all the solutes. The micrographs show that the fraction of intermetallic phase increases with increasing boron addition. The XRD patterns and the phase diagram analysis suggest that the intermetallic could be Fe.sub.2.7Si.sub.0.3B.sub.2. The intermetallic effectively pins the gain growth of the Fe-6.5% Si solid solution phase, which may lead to lower eddy current losses at high frequencies. The cooling rate (10.sup.6 C./s) for the as-spun sample seems fast enough to prevent intermetallic precipitation where only BCC solid solution phase is present in the XRD patterns (FIG. 5B).

[0061] To study the physical properties of the alloy with boron alloying, the saturation magnetization Ms and the microhardness were measured. As shown in FIG. 9, overall, the Ms drops almost linearly with boron alloying. Boron, being a paramagnetic element, dilutes the ferromagnetic moment of iron. The drop in Ms is minor, being only 0.5 kG/at % B. Interestingly, saturation magnetization Ms increased with 0.04 wt % boron alloying, which has previously been reported in boron additions to electrical steel. Below a critical concentration, boron segregation in the grain boundary was believed to result in increased grain coarsen, leading to higher flux density (permeability) and lower core losses. As shown in FIG. 10, the microhardness of the samples does not follow a monotonic relationship with boron content. Rather, the hardness drops initially, then rise with increasing boron content. It is well known that hardness is closely related to grain size (Hall-Petch relationship) and intermetallic formation. The formation of the intermetallic phase and refined grains (FIGS. 6-8) with boron alloying (>0.10 wt %) are responsible for the increase in hardness observed. The hardness of Fe-6.5% Si is also closely related to its ordering degree. A lower ordering degree resulting from faster cooling can significantly reduce the hardness of Fe-6.5% Si. Boron alloying forms a low melting eutectic that aids the cooling of Fe-6.5% Si. The lower ordering degree due to faster cooling is responsible for the initial (B0.10 wt %) hardness reduction. Such an initial drop in hardness is consistent with the reported increased ductility with minor amounts of boron additions.

[0062] High-quality ribbon/tape production (i.e., uniform thickness and width) of Fe-6.5% Si depends heavily on the flow characteristics of the alloy during the melt spinning or planar flow casting process. An essential parameter for the flow characteristics is the melt-wheel contact distance. For Fe-6.5% Si, a longer wheel contact distance resulted from a more stable melt pool is desirable as it improves the cooling of the ribbon. Longer wheel contact distance also has significant practical importance. It helps heat management during manufacturing (by removing heat from the ribbon to the wheel and avoiding ribbons leaving the wheel red hot) and aids in controlling detached angles when a ribbon detachment mechanism is used. The ribbon(melt)-wheel contact distance was evaluated via a high-speed camera by imaging the side profile of the ribbon as it is being formed. The white triangle symbols in FIGS. 11 and 12 mark where the ribbon is detached from the wheel for Fe-6.5% Si containing 0 wt % B and for Fe-6.5% Si containing 0.21 wt % B, respectively. It quantitatively shows an improved wheel contact with boron alloying. This is direct evidence of better flow characteristics from added boron owing to improved wetting and reduced viscosity. Boron alloyed ribbons also are longer and more continuous, with improved surface quality.

[0063] A parallel plate bending test was also performed to characterize the ductility of the as-spun ribbon. This test quantifies the bending strain of the sample when bending the ribbon between two plates until the ribbon breaks. The distance of the two parallel plates is noted, and together with the thickness of the ribbon were used to calculate the bending strain. Due to the high ductility of the ribbon, the number of ribbons that broke when the two plates completely close, i.e., the spacing of the parallel plates becomes zero, were counted. The likelihood of fracture (out of 10 tests for each composition) are 0%, 10%, 10%, and 50% for the 0%, 0.046%, 0.1%, and 0.207% boron alloyed samples, respectively. It suggests that minor boron alloying (0.10 wt %) has a minimum impact on the ductility of the samples. However, there is a noticeable ductility decrease when 0.21 wt % boron is added due to excess intermetallic formation.

TABLE-US-00001 TABLE 1 Fracture performance for Fe-6.5% Si alloy ribbons alloyed with boron Ribbon's Boron Content Likelihood of Fracture (wt %) (%) 0 0 0.05 10 0.10 10 0.21 50

[0064] The as-spun Fe-6.5% Si ribbons are known to have high hysteresis losses due to their refined grain size. Therefore, the melt-spun ribbons were fully annealed for a more representative magnetic property and iron loss measurement. FIG. 13 shows that the permeability (.sub.max) of the alloy under direct current (DC) condition increases to a maximum at 0.01 wt % boron addition, then it drops with higher levels of boron additions. The coercivity (H.sub.c) of the alloy was also the lowest at 0.01 wt % boron addition, and then it increased when more boron was added.

[0065] For the alternating current (AC) 400 HZ condition (FIG. 14), the iron loss decreased significantly initially (31.7% coreless reduction in the case of 0.01 wt % boron addition) then it started to increase. For the range (up to 0.06 wt %) of boron addition shown in FIG. 14, the boron addition significantly lowers the DC hysteresis losses by increasing permeability and lower coercivity. Ribbon thickness measurement (FIG. 14) also reveals that the boron-added samples are thinner, which leads to lower classical eddy current loss. Therefore, the minor boron-added Fe-6.5% Si annealed ribbons showed a lower total iron loss, which is a sum of hysteresis loss, classical eddy current loss, and anomalous loss. The reduction of ribbon thickness with boron addition directly resulted from the improved wetting and lower viscosity of the melt, as described above.

[0066] Typically, the hysteresis loss tends to be higher on thinner ribbons because of the more refined boundary condition for grain growth when annealed. Here, it is apparent that the boron additions in Fe-6.5% Si facilitated the grain growth during the annealing though the ribbon thickness is thinner. In this way, the boron facilitated coarsening behavior during annealing. Conventionally, there has been a dilemma for iron loss minimization for melt-spun ribbons: if the ribbon is thin, it may have higher hysteresis loss due to limited grain growth; if the ribbon is thick, it may have high eddy current loss. Boron addition mitigates the dilemma, which is the key to lower iron losses.

[0067] Based on the experimental examples, the effect of boron addition on the processing, magnetic, and mechanical properties of Fe-6.5% Si has been demonstrated. Boron addition resulted in eutectic formation, which is beneficial for the viscosity reduction of the Fe-6.5% Si alloy. Further, boron addition improved the processability of the alloy resulting in improved melt/ribbon wheel contact with enhanced cooling. Because of this, the resulting ribbons are able to be more continuous and longer, with improved surface quality. A critical amount of boron addition to the Fe-6.5% Si was found to be around 0.06 wt %. Below this critical amount, improved DC and AC magnetic properties were observed, which can relate to the boron-segregated grain boundary that facilitated grain growth and improved wetting. The hardness of the alloy with less than 0.06 wt % of boron is also lower, owing to the improved solidification characteristics. Above 0.06 wt %, or in some cases, 0.10 wt % of boron addition, the formation of intermetallic negatively impacts the alloy's physical properties, resulting in lower saturation, higher hardness, and decreased ductility. Overall, minor boron addition was found to be an effective processing additive to Fe-6.5% Si production by melt spinning, which can improve the quality of the ribbon/tape. It is also a valid addition to improve the magnetic properties of the alloy with both lowered hysteresis and eddy current losses.

[0068] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0069] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0070] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.