Iron-based amorphous alloy strip and preparation method therefor

Abstract

The present application provides an iron-based amorphous alloy strip and a preparation method thereof. The iron-based amorphous alloy strip has a chemical composition of FeaSibBcCd, wherein a, b, c, and d represent atomic percentages of corresponding components respectively; 80.4% ≤ a ≤ 83.5%, 3.98% ≤ b ≤ 9.5%, 9.58% ≤ c ≤ 12.0%, 0.1% ≤ d ≤ 1.3%, and 99.9% ≤ a+b+c+d ≤ 100%, with the balance being inevitable impurities. The present application achieves uniform cooling even under high cooling intensity through the regulation of composition, thereby obtaining an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity. The iron-based amorphous alloy strip exhibits superior soft magnetic properties, and the quality is ensured when it is applied to downstream products such as transformers.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Chinese patent application No. 2022116353760, filed on December 19, 2022, entitled "Iron-based Amorphous Alloy Strip and Preparation Method Thereof", which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present application relates to the field of power electronics, and in particular to an iron-based amorphous alloy strip and a preparation method thereof.BACKGROUND ART

[0003] Iron-based amorphous alloys exhibit magnetic anisotropy due to their unique microstructure and are widely used in the fabrication of transformer cores. Typically, during the slow cooling of molten metal in liquid state, crystallization will occur when the temperature reaches below the liquidus line. In contrast, the amorphous alloys are formed by changing the cooling rate of the molten metal so that its internal atoms are solidified into solid state before they can fully diffuse and rearrange, thereby its internal atoms retaining the disordered liquid-like state. This endows amorphous alloys with a lower magnetic anisotropy parameter <K> and the advantage of low no-load loss, thus positions them as a promising candidate to completely replace silicon steel.

[0004] With the rapid development of the power electronics industry in recent years, new goals such as "smart 5G" and " high energy efficiency " drive amorphous transformers toward to develop in the directions of "miniaturization" and "low loss". Consequently, alloy systems with high saturation magnetic induction have been continuously developed, particularly various alloy systems with high Fe content have emerged. It is well known that Fe element functions as a magnetic element in the composition system. Although alloys with high Fe content exhibit relatively high saturation magnetic induction (Bs > 1.60 T), their poor glass-forming ability makes it necessary to rely on high cooling rates to prepare fully amorphous quenched alloy strips. This causes the internal stress of the strips to be frozen before it can be released, and a large amount of quenched stress is retained inside, resulting in problems with the strips, such as warping on both sides, increased losses, and the like. Notably, there is a liquid-solid equilibrium zone at the cooling interface between the molten steel and the crystallizer, in which the liquid phase portion that has not been cooled is called as "molten pool". Cooling capacity differs between both sides of the molten pool and the center thereof in that cooling intensity on both sides of the molten pool is higher than that at the center of the molten pool. This is because both sides of the molten pool are affected by the "laminar airflow", and the energy at the edge of the strip on the crystallizer is different from that at the center of the strip, resulting in that a temperature difference between the center and both sides of the strip is present when the strip is peeled off from the surface of the crystallizer. Moreover, this phenomenon becomes more prominent as the width of the prepared strip increases, which increases the difficulty of preparing amorphous wide strips, and causes problems such as breakage, performance instability, and the like. Microscopically, the difference in cooling intensity between both sides of the strip and the center thereof will also induce the generation of lateral tensile stress inside the strip, finally resulting in the deterioration of the strip performance. In addition, when the non-uniformly cooled material is fabricated as a transformer core by the back-end application, there is also a problem of poor thermal stability, especially when the stress is not completely removed, it will also lead to problems with the core such as high excitation power, high noise, and the like.

[0005] Many researchers have also studied the non-uniform cooling phenomenon in the crystallizer and the molten pool caused by the high cooling intensity for the above-mentioned alloy systems with high saturation magnetic induction. In U.S. Patent No. 5456770, Sn elements are added to obtain high ductility strips and increase the formability for manufacturing wide strips, but it is obvious that the addition of Sn elements greatly increases the cost and cannot meet the requirements of industrial production. Chinese patent CN113151750A discloses the problem of transverse camber of strips when preparing strips with high saturation magnetic induction alloy systems. The strips prepared by controlling the trace elements in molten steel and manipulating the process parameters still suffer from the phenomenon of transverse camber, and the problem is not solved from a fundamental perspective. Some other researchers have conducted a series of experiments on the crystallizer structure. For example, patent CN114381673A achieves the neutralization of the cooling intensity at the center and both sides of the crystallizer by adjusting the internal water channel of the crystallizer along the width direction of the strip. However, although this method has been adjusted from the perspective of heat transfer and can achieve uniform cooling at the center and both sides of the strip, it requires corresponding adjustments for strips of different widths. Not only is the cost high, but the process is also highly complex and difficult to apply in industrial production.SUMMARY OF INVENTION

[0006] The present application provides an iron-based amorphous alloy strip and a preparation method thereof, which are used to solve the defect of non-uniform cooling of amorphous alloy systems with high saturation magnetic induction in the prior art.

[0007] The present application provides an iron-based amorphous alloy strip having a chemical composition of Fe a Si b B c C d , wherein a, b, c, and d represent atomic percentages of corresponding components respectively; 80.4% ≤ a ≤ 83.5%, 3.98% ≤ b ≤ 9.5%, 9.58% ≤ c ≤ 12.0%, 0.1% ≤ d ≤ 1.3%, and 99.9% ≤ a+b+c+d ≤ 100%, with the balance being inevitable impurities.

[0008] The present application primarily focuses on some improved designs for the composition of FeSiBC system, which is the most common system in industry. Unlike other systems such as FeSiBCu or FeSiBPCu, where the formation of nanoscale crystalline grains is induced by annealing treatments to enhance saturation magnetic induction, the FeSiBC system relies solely on increased Fe content to achieve the enhancement of saturation magnetic induction. However, the alloy composition with high Fe element content exhibit significantly reduced glass-forming ability, thereby imposing increasingly stringent requirements on cooling capacity. High cooling intensity exacerbates the cooling disparity between both sides of the molten pool and the center thereof, resulting in the deterioration of the soft magnetic properties of the strip, the deterioration of the performance of the transformer core at the application end, and also the instability of the heat treatment temperature for the transformer core.

[0009] To address the above problems, the present application achieves uniform cooling even under high cooling intensity through the regulation of composition, thereby obtaining an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity.

[0010] According to the iron-based amorphous alloy strip provided in the present application, the iron-based amorphous alloy strip has a saturation magnetic induction of ≥ 1.6 T. The high saturation magnetic induction in the present application refers to a saturation magnetic induction of no less than 1.6 T.

[0011] According to the iron-based amorphous alloy strip provided in the present application, Fe is present in an atomic percentage of 81.3% ≤ a ≤ 83.5%.

[0012] According to the iron-based amorphous alloy strip provided in the present application, Si is present in an atomic percentage of 5.62% ≤ b ≤ 9.5%.

[0013] According to the iron-based amorphous alloy strip provided in the present application, Fe is present in an atomic percentage of 82.63%, Si is present in an atomic percentage of 5.62%, B is present in an atomic percentage of 10.37%, and C is present in an atomic percentage of 1.28%.

[0014] According to the iron-based amorphous alloy strip provided in the present application, the iron-based amorphous alloy strip has a specific heat capacity at 100°C of 0.40-0.47 J / (g·°C).

[0015] According to the iron-based amorphous alloy strip provided in the present application, the iron-based amorphous alloy strip is divided into n equal zones along the width direction, with the edge zone accounting for 10% of the strip width designated as Zone a, and the central zone accounting for 10% of the strip width designated as Zone b, samples taken within the ranges of Zones a and b respectively are detected using a differential scanning calorimeter for first crystallization peak area thereof to obtain heat release values Qa and Qb, and the iron-based amorphous alloy strip has a variation coefficient δQ = (Qa-Qb) / Qa*100% of no more than 4%. This performance index demonstrates that the iron-based amorphous alloy strip of the present application exhibits cooling uniformity.

[0016] The iron-based amorphous alloy strip provided in the present application has a thickness of about 25 ± 3 µm and a width of 30-300 mm, and can be used in power electronics fields such as transformers, automotive motors, and the like.

[0017] The present application also provides a method for preparing the above-mentioned iron-based amorphous alloy strip, comprising: formulating raw materials according to Fe a Si b B c C d , melting and single-roller rapid quenching the formulated raw materials to obtain the iron-based amorphous alloy strip.

[0018] In this method, the melting can be conducted using a medium-frequency induction furnace to melt the raw materials into molten steel in an atmospheric environment.

[0019] Furthermore, in the single-roller rapid quenching process, the molten steel is dripped onto the surface of a copper roller under high-speed rotating, wherein the casting temperature of the molten steel is 1400-1465°C, the linear velocity of the copper roller is 19-25 m / s, the copper roller is internally provided with a cooling water channel, through which cooling water is supplied at a flow rate of 100-300 m 3< / h.

[0020] According to the method for preparing the iron-based amorphous alloy strip provided in the present application, after heat treatment, the iron-based amorphous alloy strip has a core loss P ≤ 0.2 W / kg and an excitation power Pe ≤ 0.33VA / kg under conditions of 1.3 T and 60 Hz, wherein the core loss and the excitation power of the strip can be measured using a silicon steel tester (B-H tester).

[0021] The present application provides an iron-based amorphous alloy strip and a preparation method thereof, which achieves uniform cooling even under high cooling intensity through the regulation of composition, thereby obtaining an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity. The iron-based amorphous alloy strip exhibits superior soft magnetic properties, and the quality is ensured when it is applied to downstream products such as transformers.DETAILED DESCRIPTION

[0022] In order to clarify the purpose, technical solution and advantages of the present application, embodiments of the present application will be described clearly and completely below. Obviously, the embodiments are described in an exemplary way, rather than in an exhaustive way. Based on the embodiments of the present application, all other embodiments obtained by those ordinarily skilled in the art without inventive efforts are within the scope of protection of the present application.

[0023] An embodiment of the present application provides an iron-based amorphous alloy strip having a chemical composition of Fe a Si b B c C d , wherein a, b, c, and d represent atomic percentages of corresponding components respectively; 80.4% ≤ a ≤ 83.5%, 3.98% ≤ b ≤ 9.5%, 9.58% ≤ c ≤ 12.0%, 0.1% ≤ d ≤ 1.3%, and 99.9% ≤ a+b+c+d ≤ 100%, with the balance being inevitable impurities.

[0024] The present application obtains an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity through the regulation of composition. The iron-based amorphous alloy strip of the present application has a saturation magnetic induction of ≥ 1.6 T. The cooling uniformity is characterized by the variation coefficient of the iron-based amorphous alloy strip δQ = (Qa-Qb) / Qa*100%, and the specific analysis is as follows: In industrial preparation of an amorphous strip with a width ranging from 30 mm to 240 mm, as the width of the strip increases, the width of the molten pool expands, and the difference in cooling intensity between both ends of the molten pool and the innermost center thereof becomes more pronounced. This creates a cooling disparity along the width direction of the strip: both sides of the strip exhibit stronger cooling capacity, resulting in a lower temperature when solidified into solid state at the molten pool, while the innermost center of the strip, due to the cooling disparity, is subjected to a higher temperature when the strip is solidified. In severe cases, transverse tensile stress appears in the strip along the width direction, causing the strip to exhibit transverse warping. The applicant conducted sampling and testing on strips with the above situations respectively, and the test results of the differential scanning calorimeter showed that when the strips sampled at the above different positions were heated, crystallization peaks of different sizes appeared at the same temperature. The corresponding first crystallization peak area (i.e., heat release value Q) was measured using software. At this time, it was observed that the Q values of strip samples from the center of the molten pool were generally lower than those from both sides of the molten pool. This indicates that the strip located at both sides of the molten pool retains more frozen energy when it is cooled at the molten pool, while the strip located at the center of the molten pool retains less frozen energy when it is cooled. Therefore, upon the strip is solidified, the strip temperature at the center is higher than that at both sides.

[0025] Research has shown that energy exchange at the molten pool is achieved through heat exchange via contact between the copper roller surface and the molten steel. For strips of the same width and thickness, the size or shape of the molten pool remains consistent, and the total heat withdrawn from the molten pool can be expressed by the following expression formula. ρ • V • c • Δ T = Q total

[0026] In the above formula, ρ represents the density of the melt being cooled, with the unit of g / cm 3< ; V represents the volume of the molten steel in the molten pool, with the unit of cm 3< ; c represents the specific heat capacity of the melt being cooled at that temperature, with the unit of J / (g·°C); ΔT represents the temperature difference before and after cooling of the melt being cooled, with the unit of °C; Q total represents the total heat exchange during the entire cooling process, with the unit of J.

[0027] If the micro-element zone at the outermost edge of the molten pool width is set as Zone a, and the micro-element zone at the innermost center of the molten pool is set as Zone b, assuming that the initial temperature T initial of molten steel is uniform across the molten pool before it is cooled, then Ta initial = Tb initial at this time, and afterwards set Ta and Tb to respectively represent the temperatures of the strip when cooled to solid state, and DSC is used to detect the sizes of first crystallization peak area of strip samples from Zone a and Zone b, i.e., the values of Qa and Qb.

[0028] In a specific embodiment of the present application, the iron-based amorphous alloy strip is divided into n equal zones along the width direction, with the edge zone accounting for 10% of the strip width designated as Zone a, and the central zone accounting for 10% of the strip width designated as Zone b, samples taken within the ranges of Zones a and b respectively are detected using a differential scanning calorimeter for first crystallization peak area thereof to obtain heat release values Qa and Qb, and the iron-based amorphous alloy strip has a variation coefficient δQ = (Qa-Qb) / Qa*100%. When δQ ≤ 4%, it demonstrates that the iron-based amorphous alloy strip of the present application exhibits good cooling uniformity.

[0029] Specifically, Fe element functions as a magnetic element in the alloy composition system, and the level of Fe element content will directly affect the saturation magnetic induction of the alloy system. Generally speaking, the higher the Fe element content, the higher the saturation magnetic induction of the alloy. However, as the Fe element content increases, the content of other amorphous elements has to be reduced, which decreases the glass-forming ability of the alloy composition, resulting in an increase in the difficulty of preparation. In the present application, the atomic percentage of Fe element is 80.4-83.5%. Specifically and non-limitingly, the atomic percentage of Fe element may be 80.40%, 80.54%, 80.61%, 80.75%, 82.63%, 83.2% or 83.5%. When the atomic percentage of Fe element is higher than 83.5%, the glass-forming ability significantly decreases, accompanied by deterioration of soft magnetic properties; conversely, when the atomic percentage of Fe element is lower than 80.40%, although the preparation proceeds smoothly, the saturation magnetic induction of the alloy falls below 1.60 T, which does not meet the requirements for high saturation magnetic induction.

[0030] Si element, as an amorphous-forming element, mainly functions to enhance glass-forming ability in the alloy system. In addition, molten steel containing Si element is prone to oxidation during atmospheric melting, forming a dense oxide film that adheres to the surface of molten steel and functions to isolate oxygen. Moreover, since Si is the element with the highest binding force with O in the alloy composition system, it also functions to reduce the oxygen content in molten steel, which enables the molten steel to have better fluidity to reduce the difficulty of preparation. Si element can also function to reduce iron loss and optimize the soft magnetic properties of the strip. In the present application, the atomic percentage of Si element is 3.98-9.5%. Specifically and non-limitingly, the atomic percentage of Si element may be 3.98%, 4.89%, 5.62%, 6.87%, 7.21%, 8.25% or 9.45%. When the atomic percentage of Si element is lower than 3.98%, the process smoothness is significantly reduced when the amorphous strip is prepared by single-roller rapid quenching method, and the surface of molten steel is exposed to the atmosphere, resulting in secondary oxidation to form oxidized slag and low cleanliness of molten steel. When the atomic percentage of Si element is higher than 9.5%, excessive surface tension of the alloy drastically reduces the heat transfer coefficient, resulting in a high variation coefficient δQ.

[0031] B element, with a relatively low atomic mass, can provide more atoms at the same mass fraction and exhibit a larger negative mixing enthalpy with Fe element. Therefore, B element mainly functions to enhance the glass-forming ability of the alloy system. However, excessive B element content will lead to the deterioration of the soft magnetic properties of the alloy, which is mainly manifested as reduced saturation magnetic induction and increased loss. In addition, the applicant observed through burn-off calculations that when B element content is high, the burn-off rate of B element reaches as high as 10%. This is because at normal melting temperature, with the increase of B element content, while Si remains unchanged, the activity of B element exceeds that of Si element, which causes a large amount ofB to combine with oxygen to form B 2 O 3 . This oxide, with a melting point below 500°C and much lower viscosity than SiO 2 , tends to remain entrapped in the molten steel, making it not easy to separate from the molten steel. It often causes surface defects of the alloy strip when casting in a non-vacuum environment, such as scratches on the strip surface, and reduced density and stacking factor. Conversely, when the atomic percentage of B element is low, the glass-forming ability of the alloy with high Fe content is insufficient, making it difficult to obtain a fully amorphous quenched alloy strip. In the present application, the atomic percentage of B element is 9.58-12.0%. Specifically and non-limitingly, the atomic percentage of B element may be 9.58%, 10.12%, 10.57%, 10.66%, 11.53% or 11.77%.

[0032] C element most notably functions to lower the melting point of the alloy system. Based on current knowledge of plain and high-carbon steels, the melting point of the alloy composition decreases by over 100°C for every 0.1% increase in the mass percentage of C element. Therefore, the addition of C element significantly lowers the melting point of the overall alloy, reduces the eutectic line temperature in the Fe-Si phase diagram, and thereby enhances the glass-forming ability of the alloy. Additionally, after the melting point of the alloy is lowered, the molten steel has better fluidity, allowing for lower casting temperature accordingly, reduced cooling capacity requirements for the crystallizer, and also decreased thermal erosion of the copper roller, thus lowering costs. However, it is not the case that the more C element, the better. The applicant found that when the atomic percentage of C element is higher than 1.5%, the toughness of the alloy composition decreases. This is because as the C content increases, the limit of cleavage cracks generated by the alloy when subjected to external stress decreases, shifting the fracture mode from ductile to brittle and resulting in more fragments of the alloy strip during the subsequent forming process. In the present application, the atomic percentage of C element is 0.1-1.3%. Specifically and non-limitingly, the atomic percentage of C element may be 0.12%, 0.45%, 0.54%, 0.86%, 1.19%, 1.24% or 1.28%.

[0033] In a specific embodiment of the present application, in the iron-based amorphous alloy strip, Fe is present in an atomic percentage of 82.63%, Si is present in an atomic percentage of 5.87%, B is present in an atomic percentage of 10.12%, and C is present in an atomic percentage of 1.28%. In this case, the preparation of strip proceeds smoothly, the saturation magnetic induction meets the requirement of ≥ 1.60 T, and δQ is only 0.5%, indicating excellent cooling uniformity.

[0034] The iron-based amorphous alloy strip provided in the embodiment of the present application has a specific heat capacity at 100°C of 0.40-0.47 J / (g·°C).

[0035] The embodiment of the present application also provides a method for preparing the above-mentioned iron-based amorphous alloy strip, comprising: formulating raw materials according to Fe a Si b B c C d , melting and single-roller rapid quenching the formulated raw materials to obtain the iron-based amorphous alloy strip.

[0036] Furthermore, in the single-roller rapid quenching process, the molten steel is dripped onto the surface of a copper roller under high-speed rotating, wherein the casting temperature of the molten steel is 1400-1465°C, the linear velocity of the copper roller is 19-25 m / s, the copper roller is internally provided with a cooling water channel, through which cooling water is supplied at a flow rate of 100-300 m 3< / h.

[0037] The iron-based amorphous alloy strip obtained by using the above-mentioned preparation method, after heat treatment, has a core loss P ≤ 0.2 W / kg and an excitation power Pe ≤ 0.33 VA / kg under conditions of 1.3 T and 60 Hz.

[0038] The technical effects achieved by the present application are demonstrated through specific examples below. It should be understood that the examples are only used to help better understand the present application and are not intended to limit the present application.Experiment 1: Effects of different compositions on Bs (saturation magnetic induction), glass-forming ability and cooling uniformity

[0039] The raw materials of different compositions were weighed and proportioned according to the prescribed ratios, and melted in a medium-frequency induction furnace to obtain molten steel in molten state. Subsequently, strips were prepared via the single-roller rapid quenching method, in which the molten steel at a specified temperature was directed through a nozzle slit of defined geometry onto the surface of a crystallizer under high-speed rotating. The casting temperature of the molten steel was 1420°C. The crystallizer, fabricated from beryllium copper, was internally provided with cooling water at a flow rate of 180 m 3< / h. The linear velocity of the crystallizer was 20 m / s.

[0040] During the preparation process, the smoothness of strip preparation was evaluated (during the preparation process, if all of the molten steel was successfully prepared into fully amorphous quenched strips via the single-roller rapid quenching method without any abnormalities, the process was evaluated as smooth strip preparation). The obtained strips were then detected using a vibration attenuation magnetometer for their saturation magnetic induction.

[0041] Table 1 below shows the preparation results of different compositions. Table 1ExampleFeSiBCSmooth strip preparationBsExample 181.613.2613.611.42Yes1.62Example 280.524.5413.431.41Yes1.6Example 382.173.3413.860.53Yes1.63Example 481.845.4612.140.46Yes1.62Example 582.776.2410.450.44Yes1.63Example 681.306.5610.661.38Yes1.62Example 781.927.219.511.26Yes1.62Example 880.507.2210.841.34Yes1.6Example 982.018.549.230.12Yes1.62Example 1082.535.9710.540.86Yes1.63Example 1183.245.849.581.24Yes1.64Example 1280.849.19.780.18Yes1.61Example 1381.287.5110.870.24Yes1.61Example 1480.879.249.080.71Yes1.61Example 1580.548.2510.660.45Yes1.60Example 1680.617.2111.540.54Yes1.60Example 1780.759.459.580.12Yes1.61Example 1882.635.6210.371.28Yes1.63Example 1980.406.8711.770.86Yes1.60Example 2083.204.8910.571.24Yes1.63Example 2183.203.9811.531.19Yes1.63Comparative Example 186.815.766.490.84No / Comparative Example 279.5710.259.540.54Yes1.57Comparative Example 381.554.2112.541.6No1.62Comparative Example 480.353.115.31.15No1.6

[0042] Fully amorphous quenched strips were obtained from the alloy systems of Example 1-21 by preparation via the single-roller rapid quenching method. The amorphous degree of the strips prepared in Example 1-21 was analyzed by XRD. The results showed that the strips prepared in the above examples were all completely amorphous, with only one broad and diffuse "steamed bun" peak within the range of 0-90°. The saturation magnetic induction thereof was detected by a vibration attenuation magnetometer respectively, with all values above 1.60 T.

[0043] As can be seen from Table 1, Comparative Example 1, with an atomic percentage of Fe element in the composition as high as 86.81 at%, exhibited curling, flame spurting and other phenomena during preparation, which were not observed in other examples or comparative examples. The strip surface of Comparative Example 1 was accompanied by obvious oxidative discoloration phenomenon during preparation, finally making it difficult to obtain an intact strip. Samples were taken and their internal structure was detected using XRD. XRD analysis revealed a diffraction peak at a position of 45°, indicating a crystallization phenomenon present in this composition and failure to achieve a fully amorphous quenched strip.

[0044] Although Comparative Example 2 yielded a fully amorphous quenched strip, the saturation magnetic induction thereof was limited to only 1.57 T due to low Fe content, making it difficult to meet the current high-Bs requirements. Therefore, in order to achieve a saturation magnetic induction of no less than 1.60 T, the atomic percentage of the Fe element content in the alloy composition system should be not lower than 80.4%. Example 6, with Fe content of 81.3%, yielded a strip prepared therefrom having a Bs of 1.62 T, suggesting Fe content more preferably in the range of 81.3%-83.50%.

[0045] In the alloy of Comparative Example 1, the atomic percentage of B element was only 6.49%, resulting in insufficient glass-forming ability of the alloy composition and increased requirements for cooling intensity. The applicant found that, in order to prepare fully amorphous quenched strips, the content of B element in the alloy system composition should not be lower than 9.0%. With the increase of the content of B element in the alloy composition, for example, when the content of B element in Comparative Example 4 reached 15.3%, the smoothness of preparation was significantly reduced, and defects such as scratches and slag lines appeared on the surface of the strip during the preparation process, resulting in a decrease in the stacking factor of the strip, and often problems such as decreased fluidity of molten steel and difficulty in withdrawal. Therefore, the content of B element should not be higher than 14.0%.

[0046] The composition of Comparative Example 3 showed high brittleness of the strip and poor smoothness during the preparation process. Although the saturation magnetic induction met the requirement of ≥ 1.60 T, due to the high brittleness, it still could not meet the requirements of industrial mass production during the subsequent applications. Therefore, the content of C should be lower than 1.5%.

[0047] The alloy strips with high saturation magnetic induction and high glass-forming ability were prepared as described above, but some compositions still exhibited the non-uniform cooling phenomenon.

[0048] The disparity in cooling intensity with different extents across the molten pool leads to the difference in heat release of the first crystallization peak of the strip. The cooling disparity across the molten pool represents the difference in heat exchange. Theoretically, heat exchange is related to the molten steel's heat capacity, density, and heat transfer coefficient with the copper roller. Since the specific heat capacity of substances is temperature-dependent, the specific heat capacity of molten steel with different compositions can be replaced by the specific heat capacity of the strip at a certain temperature, i.e., calculated by measuring the heat absorbed or released per unit mass of the strip with different compositions per 1°C increase or decrease. Similarly, due to challenges in measuring density of the molten steel at the molten pool, the density of the prepared strip can be used instead.

[0049] In order to further explore the appropriate composition range, the applicant selected some of the example compositions from the examples above, obtained the corresponding strips via the single-roller rapid quenching method, and then measured the specific heat capacity c of the strips with different compositions at 100°C and the density of the strips with different compositions at room temperature. In addition, DSC test was conducted on the strip samples with the same mass and size taken from the zone with a width accounting for 10% of the strip width at the strip edge and the zone with a width accounting for 10% of the strip width at the exact center. The heat release of the strip sample within 10% of the strip edge was set as Qa, and the heat release of the strip sample within 10% of the center was set as Qb; it is set that δQ = (Qa-Qb) / Qa * 100%, and the difference in the variation coefficient of different compositions was compared. Table 2 below shows δQ of different compositions obtained in the experiment. Table 2ExampleFeSiBCC (100°C)ρQaQbδQ=(Qa -Qb) / Qa * 100%Example 1580.548.2510.660.450.517.2743.5142.652.02%Example 1680.617.2111.540.540.507.3142.9642.121.99%Example 1780.759.459.580.120.517.2643.3242.751.34%Example 1882.635.6210.371.280.467.4142.1941.980.50%Example 1980.406.8711.770.860.497.3143.1142.12.39%Example 2083.204.8910.571.240.457.4743.9042.523.25%Example 2183.203.9811.531.190.457.5042.8842.151.74%Comparative Example 581.473.5413.611.280.467.4648.4046.314.51%Comparative Example 682.614.2111.661.420.457.4744.4142.544.39%Comparative Example 782.436.989.241.250.477.3750.3347.545.87%Comparative Example 880.4910.29.080.130.537.2644.0241.216.81%Comparative Example 981.776.2410.451.440.477.3744.9641.259.00%

[0050] From the data in Table 2, it can be seen that strips with a variation coefficient δQ lower than 4% were prepared in all of Examples 15-21, which means that the strips exhibited good cooling uniformity in the width direction, and particularly, the variation coefficient of Example 18 was as low as 0.5%. The low variation coefficient characterizes the uniformity of cooling in the width direction of the strip during the preparation process, and such strips with good uniformity typically maintain good appearance and magnetic properties during subsequent processing and heat treatment.

[0051] As the content of Fe element in the alloy composition system increases, the density of the strip increases, but the specific heat capacity of the alloy system decreases accordingly. Additionally, in addition to affecting the specific heat capacity of the alloy system, Si element also affects the surface tension of the alloy, thereby affecting the heat transfer coefficient between the molten steel and the surface of the crystallizer. For example, in Comparative Example 8, when Si content was higher than 9.5%, excessive surface tension of the alloy led to a significant decrease in the heat transfer coefficient, resulting in a high variation coefficient δQ. Therefore, the atomic percentage of the Si element is optimized to 3.98%-9.5%, and more preferably 5.62%-9.5%. For example, Example 18 achieved an extremely low variation coefficient δQ for the final prepared strip.

[0052] By comparing Example 17 with Comparative Example 7, it can be seen that when the content of B element is lower than 9.58%, the variation coefficient δQ is higher than 4%, while by comparing Examples 19 and 21 with Comparative Example 5, it is found that when the atomic percentage of B element exceeds 12%, it is also impossible to obtain a strip with consistent cooling strength. Therefore, the atomic percentage of B element is optimized to 9.58%-12.0%.

[0053] By comparing Example 20 with Comparative Example 9, it can be seen that when the content of C element in the alloy system is higher than 1.30%, the heat release difference between the edge and center of the strip becomes significant. Therefore, the atomic percentage of C element is optimized to 0.1%-1.3%.Experiment 2: Effects of cooling process on strip performance

[0054] In Experiment 1, strips with saturation magnetic induction of greater than 1.60 T, strong glass-forming ability and uniform cooling intensity were prepared. However, during subsequent preparation of the transformer core, performance fluctuations of strips were observed under different cooling processes. Therefore, the applicant further investigated the cooling process during the single-roller rapid quenching method.

[0055] Example 18 was used as the alloy composition in the following examples. Raw materials were weighed, melted in a medium-frequency induction furnace to obtain molten steel, and then prepared into strips via the single-roller rapid quenching method. In the single-roller rapid quenching method, experiments with different casting temperatures, different linear velocity, circulating water flow rates, etc. were carried out, and the strips were wound into toroidal cores, and after heat treatment, detected for core loss and excitation power under conditions of 60 Hz and 1.3 T using a silicon steel tester.

[0056] Table 3 below shows the soft magnetic properties under different cooling processes. Table 3ExampleCasting temperature °CLinear velocity m / sWater flow rate m 3< / h(1.3 T, 60 Hz) W / kgPe (1.3 T, 60 Hz) VA / kgExample 221415231240.180.26Example 231424241520.110.22Example 241433201800.140.27Example 251454252060.130.24Example 261462252140.190.31Example 271426251320.20.33Example 281434192000.170.28Comparative Example 101470252800.290.42Comparative Example 111435182400.390.6Comparative Example 121435291200.150.48Comparative Example 13144025820.360.62Comparative Example 141432244500.280.82

[0057] From the above results, it can be seen that through adjustments to the cooling process, including casting temperature, crystallizer linear velocity, water flow rate, etc., amorphous strips with excellent soft magnetic properties were prepared. After heat treatment, the strips exhibited core loss P of less than or equal to 0.2 W / kg and excitation power Pe of less than or equal to 0.33 VA / kg under conditions of 1.3 T and 60 Hz. As shown in Examples 22-28, the amorphous strip prepared in Example 23 achieved the optimal performance after heat treatment. The casting temperature directly affects the heat exchange between the crystallizer surface and the molten steel at the molten pool. The casting temperature must be higher than the melting point and maintain a certain degree of superheat to ensure that the fluidity of molten steel meets casting conditions. When the casting temperature is too high, such as Comparative Example 10, with a casting temperature of the molten steel as high as 1470°C, both core loss and excitation power of the strip increase, even though the linear velocity and water flow rate are increased accordingly, indicating insufficient cooling capacity.

[0058] Similarly, the crystallizer linear velocity critically influences the cooling capacity of the crystallizer. When the crystallizer linear velocity is low, more molten steel is withdrawn per unit area of the crystallizer surface and the energy is sufficient, resulting in decreased cooling capacity of the crystallizer accordingly. The applicant found that in the preparation of amorphous alloys with a high Bs alloy system, the crystallizer linear velocity must be maintained above 19 m / s to prepare fully amorphous quenched strips. However, it is not the case that the higher the crystallizer cooling intensity, the better. For example, in Comparative Example 12, when the crystallizer linear velocity was as high as 29 m / s, although core loss of the strip met the requirements, the excitation power was high. This is because the excessive cooling intensity freezes a large amount of quenched stress during cooling. During heat treatment, sufficient insulation is required to remove the residual quenched stress inside, but long-term insulation is obviously not conducive to the core loss of strips. Therefore, the crystallizer linear velocity is preferably in a range of 19-25 m / s.

[0059] The water flow rate of the crystallizer exerts effects analogous to linear velocity on the cooling capacity of the crystallizer. It is not the case that the stronger the cooling capacity of the crystallizer, the better. Excessive water flow rate will also lead to residual quenched stress, resulting in higher excitation power of the strip during the back-end application. After being fabricated into a transformer core, the strip is prone to suffering from problems such as excessive noise, as shown in Comparative Example 14. Conversely, as shown in Comparative Example 13, when the water flow rate of the crystallizer was only 82 m 3< / h, both core loss and excitation power of the strip after heat treatment increased, indicating insufficient cooling capacity of the crystallizer. In summary, the water flow rate of the crystallizer is preferably in a range of 100-300 m 3< / h.

[0060] In summary, the present application prepares amorphous alloy strips with high saturation magnetic induction, high glass-forming ability, uniform cooling intensity and excellent performance, solves the problem of non-uniform cooling for the alloy system with high Bs (≥ 1.60 T), and achieves the technical effect described in the present application.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, those ordinarily skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements should not cause the substance of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present application.

Examples

experiment 1

Effects of different compositions on Bs (saturation magnetic induction), glass-forming ability and cooling uniformity

[0039]The raw materials of different compositions were weighed and proportioned according to the prescribed ratios, and melted in a medium-frequency induction furnace to obtain molten steel in molten state. Subsequently, strips were prepared via the single-roller rapid quenching method, in which the molten steel at a specified temperature was directed through a nozzle slit of defined geometry onto the surface of a crystallizer under high-speed rotating. The casting temperature of the molten steel was 1420°C. The crystallizer, fabricated from beryllium copper, was internally provided with cooling water at a flow rate of 180 m 3< / h. The linear velocity of the crystallizer was 20 m / s.

[0040]During the preparation process, the smoothness of strip preparation was evaluated (during the preparation process, if all of the molten steel was successfully prepared into fully amor...

experiment 2

Effects of cooling process on strip performance

[0054]In Experiment 1, strips with saturation magnetic induction of greater than 1.60 T, strong glass-forming ability and uniform cooling intensity were prepared. However, during subsequent preparation of the transformer core, performance fluctuations of strips were observed under different cooling processes. Therefore, the applicant further investigated the cooling process during the single-roller rapid quenching method.

[0055]Example 18 was used as the alloy composition in the following examples. Raw materials were weighed, melted in a medium-frequency induction furnace to obtain molten steel, and then prepared into strips via the single-roller rapid quenching method. In the single-roller rapid quenching method, experiments with different casting temperatures, different linear velocity, circulating water flow rates, etc. were carried out, and the strips were wound into toroidal cores, and after heat treatment, detected for core loss an...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Chinese patent application No. 2022116353760, filed on December 19, 2022, entitled "Iron-based Amorphous Alloy Strip and Preparation Method Thereof", which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present application relates to the field of power electronics, and in particular to an iron-based amorphous alloy strip and a preparation method thereof.BACKGROUND ART

[0003] Iron-based amorphous alloys exhibit magnetic anisotropy due to their unique microstructure and are widely used in the fabrication of transformer cores. Typically, during the slow cooling of molten metal in liquid state, crystallization will occur when the temperature reaches below the liquidus line. In contrast, the amorphous alloys are formed by changing the cooling rate of the molten metal so that its internal atoms are solidified into solid state before they can fully diffuse and rearrange, thereby its internal atoms retaining the disordered liquid-like state. This endows amorphous alloys with a lower magnetic anisotropy parameter <K> and the advantage of low no-load loss, thus positions them as a promising candidate to completely replace silicon steel.

[0004] With the rapid development of the power electronics industry in recent years, new goals such as "smart 5G" and " high energy efficiency " drive amorphous transformers toward to develop in the directions of "miniaturization" and "low loss". Consequently, alloy systems with high saturation magnetic induction have been continuously developed, particularly various alloy systems with high Fe content have emerged. It is well known that Fe element functions as a magnetic element in the composition system. Although alloys with high Fe content exhibit relatively high saturation magnetic induction (Bs > 1.60 T), their poor glass-forming ability makes it necessary to rely on high cooling rates to prepare fully amorphous quenched alloy strips. This causes the internal stress of the strips to be frozen before it can be released, and a large amount of quenched stress is retained inside, resulting in problems with the strips, such as warping on both sides, increased losses, and the like. Notably, there is a liquid-solid equilibrium zone at the cooling interface between the molten steel and the crystallizer, in which the liquid phase portion that has not been cooled is called as "molten pool". Cooling capacity differs between both sides of the molten pool and the center thereof in that cooling intensity on both sides of the molten pool is higher than that at the center of the molten pool. This is because both sides of the molten pool are affected by the "laminar airflow", and the energy at the edge of the strip on the crystallizer is different from that at the center of the strip, resulting in that a temperature difference between the center and both sides of the strip is present when the strip is peeled off from the surface of the crystallizer. Moreover, this phenomenon becomes more prominent as the width of the prepared strip increases, which increases the difficulty of preparing amorphous wide strips, and causes problems such as breakage, performance instability, and the like. Microscopically, the difference in cooling intensity between both sides of the strip and the center thereof will also induce the generation of lateral tensile stress inside the strip, finally resulting in the deterioration of the strip performance. In addition, when the non-uniformly cooled material is fabricated as a transformer core by the back-end application, there is also a problem of poor thermal stability, especially when the stress is not completely removed, it will also lead to problems with the core such as high excitation power, high noise, and the like.

[0005] Many researchers have also studied the non-uniform cooling phenomenon in the crystallizer and the molten pool caused by the high cooling intensity for the above-mentioned alloy systems with high saturation magnetic induction. In U.S. Patent No. 5456770, Sn elements are added to obtain high ductility strips and increase the formability for manufacturing wide strips, but it is obvious that the addition of Sn elements greatly increases the cost and cannot meet the requirements of industrial production. Chinese patent CN113151750A discloses the problem of transverse camber of strips when preparing strips with high saturation magnetic induction alloy systems. The strips prepared by controlling the trace elements in molten steel and manipulating the process parameters still suffer from the phenomenon of transverse camber, and the problem is not solved from a fundamental perspective. Some other researchers have conducted a series of experiments on the crystallizer structure. For example, patent CN114381673A achieves the neutralization of the cooling intensity at the center and both sides of the crystallizer by adjusting the internal water channel of the crystallizer along the width direction of the strip. However, although this method has been adjusted from the perspective of heat transfer and can achieve uniform cooling at the center and both sides of the strip, it requires corresponding adjustments for strips of different widths. Not only is the cost high, but the process is also highly complex and difficult to apply in industrial production.SUMMARY OF INVENTION

[0006] The present application provides an iron-based amorphous alloy strip and a preparation method thereof, which are used to solve the defect of non-uniform cooling of amorphous alloy systems with high saturation magnetic induction in the prior art.

[0007] The present application provides an iron-based amorphous alloy strip having a chemical composition of Fe a Si b B c C d , wherein a, b, c, and d represent atomic percentages of corresponding components respectively; 80.4% ≤ a ≤ 83.5%, 3.98% ≤ b ≤ 9.5%, 9.58% ≤ c ≤ 12.0%, 0.1% ≤ d ≤ 1.3%, and 99.9% ≤ a+b+c+d ≤ 100%, with the balance being inevitable impurities.

[0008] The present application primarily focuses on some improved designs for the composition of FeSiBC system, which is the most common system in industry. Unlike other systems such as FeSiBCu or FeSiBPCu, where the formation of nanoscale crystalline grains is induced by annealing treatments to enhance saturation magnetic induction, the FeSiBC system relies solely on increased Fe content to achieve the enhancement of saturation magnetic induction. However, the alloy composition with high Fe element content exhibit significantly reduced glass-forming ability, thereby imposing increasingly stringent requirements on cooling capacity. High cooling intensity exacerbates the cooling disparity between both sides of the molten pool and the center thereof, resulting in the deterioration of the soft magnetic properties of the strip, the deterioration of the performance of the transformer core at the application end, and also the instability of the heat treatment temperature for the transformer core.

[0009] To address the above problems, the present application achieves uniform cooling even under high cooling intensity through the regulation of composition, thereby obtaining an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity.

[0010] According to the iron-based amorphous alloy strip provided in the present application, the iron-based amorphous alloy strip has a saturation magnetic induction of ≥ 1.6 T. The high saturation magnetic induction in the present application refers to a saturation magnetic induction of no less than 1.6 T.

[0011] According to the iron-based amorphous alloy strip provided in the present application, Fe is present in an atomic percentage of 81.3% ≤ a ≤ 83.5%.

[0012] According to the iron-based amorphous alloy strip provided in the present application, Si is present in an atomic percentage of 5.62% ≤ b ≤ 9.5%.

[0013] According to the iron-based amorphous alloy strip provided in the present application, Fe is present in an atomic percentage of 82.63%, Si is present in an atomic percentage of 5.62%, B is present in an atomic percentage of 10.37%, and C is present in an atomic percentage of 1.28%.

[0014] According to the iron-based amorphous alloy strip provided in the present application, the iron-based amorphous alloy strip has a specific heat capacity at 100°C of 0.40-0.47 J / (g·°C).

[0015] According to the iron-based amorphous alloy strip provided in the present application, the iron-based amorphous alloy strip is divided into n equal zones along the width direction, with the edge zone accounting for 10% of the strip width designated as Zone a, and the central zone accounting for 10% of the strip width designated as Zone b, samples taken within the ranges of Zones a and b respectively are detected using a differential scanning calorimeter for first crystallization peak area thereof to obtain heat release values Qa and Qb, and the iron-based amorphous alloy strip has a variation coefficient δQ = (Qa-Qb) / Qa*100% of no more than 4%. This performance index demonstrates that the iron-based amorphous alloy strip of the present application exhibits cooling uniformity.

[0016] The iron-based amorphous alloy strip provided in the present application has a thickness of about 25 ± 3 µm and a width of 30-300 mm, and can be used in power electronics fields such as transformers, automotive motors, and the like.

[0017] The present application also provides a method for preparing the above-mentioned iron-based amorphous alloy strip, comprising: formulating raw materials according to Fe a Si b B c C d , melting and single-roller rapid quenching the formulated raw materials to obtain the iron-based amorphous alloy strip.

[0018] In this method, the melting can be conducted using a medium-frequency induction furnace to melt the raw materials into molten steel in an atmospheric environment.

[0019] Furthermore, in the single-roller rapid quenching process, the molten steel is dripped onto the surface of a copper roller under high-speed rotating, wherein the casting temperature of the molten steel is 1400-1465°C, the linear velocity of the copper roller is 19-25 m / s, the copper roller is internally provided with a cooling water channel, through which cooling water is supplied at a flow rate of 100-300 m 3< / h.

[0020] According to the method for preparing the iron-based amorphous alloy strip provided in the present application, after heat treatment, the iron-based amorphous alloy strip has a core loss P ≤ 0.2 W / kg and an excitation power Pe ≤ 0.33VA / kg under conditions of 1.3 T and 60 Hz, wherein the core loss and the excitation power of the strip can be measured using a silicon steel tester (B-H tester).

[0021] The present application provides an iron-based amorphous alloy strip and a preparation method thereof, which achieves uniform cooling even under high cooling intensity through the regulation of composition, thereby obtaining an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity. The iron-based amorphous alloy strip exhibits superior soft magnetic properties, and the quality is ensured when it is applied to downstream products such as transformers.DETAILED DESCRIPTION

[0022] In order to clarify the purpose, technical solution and advantages of the present application, embodiments of the present application will be described clearly and completely below. Obviously, the embodiments are described in an exemplary way, rather than in an exhaustive way. Based on the embodiments of the present application, all other embodiments obtained by those ordinarily skilled in the art without inventive efforts are within the scope of protection of the present application.

[0023] An embodiment of the present application provides an iron-based amorphous alloy strip having a chemical composition of Fe a Si b B c C d , wherein a, b, c, and d represent atomic percentages of corresponding components respectively; 80.4% ≤ a ≤ 83.5%, 3.98% ≤ b ≤ 9.5%, 9.58% ≤ c ≤ 12.0%, 0.1% ≤ d ≤ 1.3%, and 99.9% ≤ a+b+c+d ≤ 100%, with the balance being inevitable impurities.

[0024] The present application obtains an iron-based amorphous alloy strip with high saturation magnetic induction, high glass-forming ability and cooling uniformity through the regulation of composition. The iron-based amorphous alloy strip of the present application has a saturation magnetic induction of ≥ 1.6 T. The cooling uniformity is characterized by the variation coefficient of the iron-based amorphous alloy strip δQ = (Qa-Qb) / Qa*100%, and the specific analysis is as follows: In industrial preparation of an amorphous strip with a width ranging from 30 mm to 240 mm, as the width of the strip increases, the width of the molten pool expands, and the difference in cooling intensity between both ends of the molten pool and the innermost center thereof becomes more pronounced. This creates a cooling disparity along the width direction of the strip: both sides of the strip exhibit stronger cooling capacity, resulting in a lower temperature when solidified into solid state at the molten pool, while the innermost center of the strip, due to the cooling disparity, is subjected to a higher temperature when the strip is solidified. In severe cases, transverse tensile stress appears in the strip along the width direction, causing the strip to exhibit transverse warping. The applicant conducted sampling and testing on strips with the above situations respectively, and the test results of the differential scanning calorimeter showed that when the strips sampled at the above different positions were heated, crystallization peaks of different sizes appeared at the same temperature. The corresponding first crystallization peak area (i.e., heat release value Q) was measured using software. At this time, it was observed that the Q values of strip samples from the center of the molten pool were generally lower than those from both sides of the molten pool. This indicates that the strip located at both sides of the molten pool retains more frozen energy when it is cooled at the molten pool, while the strip located at the center of the molten pool retains less frozen energy when it is cooled. Therefore, upon the strip is solidified, the strip temperature at the center is higher than that at both sides.

[0025] Research has shown that energy exchange at the molten pool is achieved through heat exchange via contact between the copper roller surface and the molten steel. For strips of the same width and thickness, the size or shape of the molten pool remains consistent, and the total heat withdrawn from the molten pool can be expressed by the following expression formula. ρ • V • c • Δ T = Q total

[0026] In the above formula, ρ represents the density of the melt being cooled, with the unit of g / cm 3< ; V represents the volume of the molten steel in the molten pool, with the unit of cm 3< ; c represents the specific heat capacity of the melt being cooled at that temperature, with the unit of J / (g·°C); ΔT represents the temperature difference before and after cooling of the melt being cooled, with the unit of °C; Q total represents the total heat exchange during the entire cooling process, with the unit of J.

[0027] If the micro-element zone at the outermost edge of the molten pool width is set as Zone a, and the micro-element zone at the innermost center of the molten pool is set as Zone b, assuming that the initial temperature T initial of molten steel is uniform across the molten pool before it is cooled, then Ta initial = Tb initial at this time, and afterwards set Ta and Tb to respectively represent the temperatures of the strip when cooled to solid state, and DSC is used to detect the sizes of first crystallization peak area of strip samples from Zone a and Zone b, i.e., the values of Qa and Qb.

[0028] In a specific embodiment of the present application, the iron-based amorphous alloy strip is divided into n equal zones along the width direction, with the edge zone accounting for 10% of the strip width designated as Zone a, and the central zone accounting for 10% of the strip width designated as Zone b, samples taken within the ranges of Zones a and b respectively are detected using a differential scanning calorimeter for first crystallization peak area thereof to obtain heat release values Qa and Qb, and the iron-based amorphous alloy strip has a variation coefficient δQ = (Qa-Qb) / Qa*100%. When δQ ≤ 4%, it demonstrates that the iron-based amorphous alloy strip of the present application exhibits good cooling uniformity.

[0029] Specifically, Fe element functions as a magnetic element in the alloy composition system, and the level of Fe element content will directly affect the saturation magnetic induction of the alloy system. Generally speaking, the higher the Fe element content, the higher the saturation magnetic induction of the alloy. However, as the Fe element content increases, the content of other amorphous elements has to be reduced, which decreases the glass-forming ability of the alloy composition, resulting in an increase in the difficulty of preparation. In the present application, the atomic percentage of Fe element is 80.4-83.5%. Specifically and non-limitingly, the atomic percentage of Fe element may be 80.40%, 80.54%, 80.61%, 80.75%, 82.63%, 83.2% or 83.5%. When the atomic percentage of Fe element is higher than 83.5%, the glass-forming ability significantly decreases, accompanied by deterioration of soft magnetic properties; conversely, when the atomic percentage of Fe element is lower than 80.40%, although the preparation proceeds smoothly, the saturation magnetic induction of the alloy falls below 1.60 T, which does not meet the requirements for high saturation magnetic induction.

[0030] Si element, as an amorphous-forming element, mainly functions to enhance glass-forming ability in the alloy system. In addition, molten steel containing Si element is prone to oxidation during atmospheric melting, forming a dense oxide film that adheres to the surface of molten steel and functions to isolate oxygen. Moreover, since Si is the element with the highest binding force with O in the alloy composition system, it also functions to reduce the oxygen content in molten steel, which enables the molten steel to have better fluidity to reduce the difficulty of preparation. Si element can also function to reduce iron loss and optimize the soft magnetic properties of the strip. In the present application, the atomic percentage of Si element is 3.98-9.5%. Specifically and non-limitingly, the atomic percentage of Si element may be 3.98%, 4.89%, 5.62%, 6.87%, 7.21%, 8.25% or 9.45%. When the atomic percentage of Si element is lower than 3.98%, the process smoothness is significantly reduced when the amorphous strip is prepared by single-roller rapid quenching method, and the surface of molten steel is exposed to the atmosphere, resulting in secondary oxidation to form oxidized slag and low cleanliness of molten steel. When the atomic percentage of Si element is higher than 9.5%, excessive surface tension of the alloy drastically reduces the heat transfer coefficient, resulting in a high variation coefficient δQ.

[0031] B element, with a relatively low atomic mass, can provide more atoms at the same mass fraction and exhibit a larger negative mixing enthalpy with Fe element. Therefore, B element mainly functions to enhance the glass-forming ability of the alloy system. However, excessive B element content will lead to the deterioration of the soft magnetic properties of the alloy, which is mainly manifested as reduced saturation magnetic induction and increased loss. In addition, the applicant observed through burn-off calculations that when B element content is high, the burn-off rate of B element reaches as high as 10%. This is because at normal melting temperature, with the increase of B element content, while Si remains unchanged, the activity of B element exceeds that of Si element, which causes a large amount ofB to combine with oxygen to form B 2 O 3 . This oxide, with a melting point below 500°C and much lower viscosity than SiO 2 , tends to remain entrapped in the molten steel, making it not easy to separate from the molten steel. It often causes surface defects of the alloy strip when casting in a non-vacuum environment, such as scratches on the strip surface, and reduced density and stacking factor. Conversely, when the atomic percentage of B element is low, the glass-forming ability of the alloy with high Fe content is insufficient, making it difficult to obtain a fully amorphous quenched alloy strip. In the present application, the atomic percentage of B element is 9.58-12.0%. Specifically and non-limitingly, the atomic percentage of B element may be 9.58%, 10.12%, 10.57%, 10.66%, 11.53% or 11.77%.

[0032] C element most notably functions to lower the melting point of the alloy system. Based on current knowledge of plain and high-carbon steels, the melting point of the alloy composition decreases by over 100°C for every 0.1% increase in the mass percentage of C element. Therefore, the addition of C element significantly lowers the melting point of the overall alloy, reduces the eutectic line temperature in the Fe-Si phase diagram, and thereby enhances the glass-forming ability of the alloy. Additionally, after the melting point of the alloy is lowered, the molten steel has better fluidity, allowing for lower casting temperature accordingly, reduced cooling capacity requirements for the crystallizer, and also decreased thermal erosion of the copper roller, thus lowering costs. However, it is not the case that the more C element, the better. The applicant found that when the atomic percentage of C element is higher than 1.5%, the toughness of the alloy composition decreases. This is because as the C content increases, the limit of cleavage cracks generated by the alloy when subjected to external stress decreases, shifting the fracture mode from ductile to brittle and resulting in more fragments of the alloy strip during the subsequent forming process. In the present application, the atomic percentage of C element is 0.1-1.3%. Specifically and non-limitingly, the atomic percentage of C element may be 0.12%, 0.45%, 0.54%, 0.86%, 1.19%, 1.24% or 1.28%.

[0033] In a specific embodiment of the present application, in the iron-based amorphous alloy strip, Fe is present in an atomic percentage of 82.63%, Si is present in an atomic percentage of 5.87%, B is present in an atomic percentage of 10.12%, and C is present in an atomic percentage of 1.28%. In this case, the preparation of strip proceeds smoothly, the saturation magnetic induction meets the requirement of ≥ 1.60 T, and δQ is only 0.5%, indicating excellent cooling uniformity.

[0034] The iron-based amorphous alloy strip provided in the embodiment of the present application has a specific heat capacity at 100°C of 0.40-0.47 J / (g·°C).

[0035] The embodiment of the present application also provides a method for preparing the above-mentioned iron-based amorphous alloy strip, comprising: formulating raw materials according to Fe a Si b B c C d , melting and single-roller rapid quenching the formulated raw materials to obtain the iron-based amorphous alloy strip.

[0036] Furthermore, in the single-roller rapid quenching process, the molten steel is dripped onto the surface of a copper roller under high-speed rotating, wherein the casting temperature of the molten steel is 1400-1465°C, the linear velocity of the copper roller is 19-25 m / s, the copper roller is internally provided with a cooling water channel, through which cooling water is supplied at a flow rate of 100-300 m 3< / h.

[0037] The iron-based amorphous alloy strip obtained by using the above-mentioned preparation method, after heat treatment, has a core loss P ≤ 0.2 W / kg and an excitation power Pe ≤ 0.33 VA / kg under conditions of 1.3 T and 60 Hz.

[0038] The technical effects achieved by the present application are demonstrated through specific examples below. It should be understood that the examples are only used to help better understand the present application and are not intended to limit the present application.Experiment 1: Effects of different compositions on Bs (saturation magnetic induction), glass-forming ability and cooling uniformity

[0039] The raw materials of different compositions were weighed and proportioned according to the prescribed ratios, and melted in a medium-frequency induction furnace to obtain molten steel in molten state. Subsequently, strips were prepared via the single-roller rapid quenching method, in which the molten steel at a specified temperature was directed through a nozzle slit of defined geometry onto the surface of a crystallizer under high-speed rotating. The casting temperature of the molten steel was 1420°C. The crystallizer, fabricated from beryllium copper, was internally provided with cooling water at a flow rate of 180 m 3< / h. The linear velocity of the crystallizer was 20 m / s.

[0040] During the preparation process, the smoothness of strip preparation was evaluated (during the preparation process, if all of the molten steel was successfully prepared into fully amorphous quenched strips via the single-roller rapid quenching method without any abnormalities, the process was evaluated as smooth strip preparation). The obtained strips were then detected using a vibration attenuation magnetometer for their saturation magnetic induction.

[0041] Table 1 below shows the preparation results of different compositions. Table 1ExampleFeSiBCSmooth strip preparationBsExample 181.613.2613.611.42Yes1.62Example 280.524.5413.431.41Yes1.6Example 382.173.3413.860.53Yes1.63Example 481.845.4612.140.46Yes1.62Example 582.776.2410.450.44Yes1.63Example 681.306.5610.661.38Yes1.62Example 781.927.219.511.26Yes1.62Example 880.507.2210.841.34Yes1.6Example 982.018.549.230.12Yes1.62Example 1082.535.9710.540.86Yes1.63Example 1183.245.849.581.24Yes1.64Example 1280.849.19.780.18Yes1.61Example 1381.287.5110.870.24Yes1.61Example 1480.879.249.080.71Yes1.61Example 1580.548.2510.660.45Yes1.60Example 1680.617.2111.540.54Yes1.60Example 1780.759.459.580.12Yes1.61Example 1882.635.6210.371.28Yes1.63Example 1980.406.8711.770.86Yes1.60Example 2083.204.8910.571.24Yes1.63Example 2183.203.9811.531.19Yes1.63Comparative Example 186.815.766.490.84No / Comparative Example 279.5710.259.540.54Yes1.57Comparative Example 381.554.2112.541.6No1.62Comparative Example 480.353.115.31.15No1.6

[0042] Fully amorphous quenched strips were obtained from the alloy systems of Example 1-21 by preparation via the single-roller rapid quenching method. The amorphous degree of the strips prepared in Example 1-21 was analyzed by XRD. The results showed that the strips prepared in the above examples were all completely amorphous, with only one broad and diffuse "steamed bun" peak within the range of 0-90°. The saturation magnetic induction thereof was detected by a vibration attenuation magnetometer respectively, with all values above 1.60 T.

[0043] As can be seen from Table 1, Comparative Example 1, with an atomic percentage of Fe element in the composition as high as 86.81 at%, exhibited curling, flame spurting and other phenomena during preparation, which were not observed in other examples or comparative examples. The strip surface of Comparative Example 1 was accompanied by obvious oxidative discoloration phenomenon during preparation, finally making it difficult to obtain an intact strip. Samples were taken and their internal structure was detected using XRD. XRD analysis revealed a diffraction peak at a position of 45°, indicating a crystallization phenomenon present in this composition and failure to achieve a fully amorphous quenched strip.

[0044] Although Comparative Example 2 yielded a fully amorphous quenched strip, the saturation magnetic induction thereof was limited to only 1.57 T due to low Fe content, making it difficult to meet the current high-Bs requirements. Therefore, in order to achieve a saturation magnetic induction of no less than 1.60 T, the atomic percentage of the Fe element content in the alloy composition system should be not lower than 80.4%. Example 6, with Fe content of 81.3%, yielded a strip prepared therefrom having a Bs of 1.62 T, suggesting Fe content more preferably in the range of 81.3%-83.50%.

[0045] In the alloy of Comparative Example 1, the atomic percentage of B element was only 6.49%, resulting in insufficient glass-forming ability of the alloy composition and increased requirements for cooling intensity. The applicant found that, in order to prepare fully amorphous quenched strips, the content of B element in the alloy system composition should not be lower than 9.0%. With the increase of the content of B element in the alloy composition, for example, when the content of B element in Comparative Example 4 reached 15.3%, the smoothness of preparation was significantly reduced, and defects such as scratches and slag lines appeared on the surface of the strip during the preparation process, resulting in a decrease in the stacking factor of the strip, and often problems such as decreased fluidity of molten steel and difficulty in withdrawal. Therefore, the content of B element should not be higher than 14.0%.

[0046] The composition of Comparative Example 3 showed high brittleness of the strip and poor smoothness during the preparation process. Although the saturation magnetic induction met the requirement of ≥ 1.60 T, due to the high brittleness, it still could not meet the requirements of industrial mass production during the subsequent applications. Therefore, the content of C should be lower than 1.5%.

[0047] The alloy strips with high saturation magnetic induction and high glass-forming ability were prepared as described above, but some compositions still exhibited the non-uniform cooling phenomenon.

[0048] The disparity in cooling intensity with different extents across the molten pool leads to the difference in heat release of the first crystallization peak of the strip. The cooling disparity across the molten pool represents the difference in heat exchange. Theoretically, heat exchange is related to the molten steel's heat capacity, density, and heat transfer coefficient with the copper roller. Since the specific heat capacity of substances is temperature-dependent, the specific heat capacity of molten steel with different compositions can be replaced by the specific heat capacity of the strip at a certain temperature, i.e., calculated by measuring the heat absorbed or released per unit mass of the strip with different compositions per 1°C increase or decrease. Similarly, due to challenges in measuring density of the molten steel at the molten pool, the density of the prepared strip can be used instead.

[0049] In order to further explore the appropriate composition range, the applicant selected some of the example compositions from the examples above, obtained the corresponding strips via the single-roller rapid quenching method, and then measured the specific heat capacity c of the strips with different compositions at 100°C and the density of the strips with different compositions at room temperature. In addition, DSC test was conducted on the strip samples with the same mass and size taken from the zone with a width accounting for 10% of the strip width at the strip edge and the zone with a width accounting for 10% of the strip width at the exact center. The heat release of the strip sample within 10% of the strip edge was set as Qa, and the heat release of the strip sample within 10% of the center was set as Qb; it is set that δQ = (Qa-Qb) / Qa * 100%, and the difference in the variation coefficient of different compositions was compared. Table 2 below shows δQ of different compositions obtained in the experiment. Table 2ExampleFeSiBCC (100°C)ρQaQbδQ=(Qa -Qb) / Qa * 100%Example 1580.548.2510.660.450.517.2743.5142.652.02%Example 1680.617.2111.540.540.507.3142.9642.121.99%Example 1780.759.459.580.120.517.2643.3242.751.34%Example 1882.635.6210.371.280.467.4142.1941.980.50%Example 1980.406.8711.770.860.497.3143.1142.12.39%Example 2083.204.8910.571.240.457.4743.9042.523.25%Example 2183.203.9811.531.190.457.5042.8842.151.74%Comparative Example 581.473.5413.611.280.467.4648.4046.314.51%Comparative Example 682.614.2111.661.420.457.4744.4142.544.39%Comparative Example 782.436.989.241.250.477.3750.3347.545.87%Comparative Example 880.4910.29.080.130.537.2644.0241.216.81%Comparative Example 981.776.2410.451.440.477.3744.9641.259.00%

[0050] From the data in Table 2, it can be seen that strips with a variation coefficient δQ lower than 4% were prepared in all of Examples 15-21, which means that the strips exhibited good cooling uniformity in the width direction, and particularly, the variation coefficient of Example 18 was as low as 0.5%. The low variation coefficient characterizes the uniformity of cooling in the width direction of the strip during the preparation process, and such strips with good uniformity typically maintain good appearance and magnetic properties during subsequent processing and heat treatment.

[0051] As the content of Fe element in the alloy composition system increases, the density of the strip increases, but the specific heat capacity of the alloy system decreases accordingly. Additionally, in addition to affecting the specific heat capacity of the alloy system, Si element also affects the surface tension of the alloy, thereby affecting the heat transfer coefficient between the molten steel and the surface of the crystallizer. For example, in Comparative Example 8, when Si content was higher than 9.5%, excessive surface tension of the alloy led to a significant decrease in the heat transfer coefficient, resulting in a high variation coefficient δQ. Therefore, the atomic percentage of the Si element is optimized to 3.98%-9.5%, and more preferably 5.62%-9.5%. For example, Example 18 achieved an extremely low variation coefficient δQ for the final prepared strip.

[0052] By comparing Example 17 with Comparative Example 7, it can be seen that when the content of B element is lower than 9.58%, the variation coefficient δQ is higher than 4%, while by comparing Examples 19 and 21 with Comparative Example 5, it is found that when the atomic percentage of B element exceeds 12%, it is also impossible to obtain a strip with consistent cooling strength. Therefore, the atomic percentage of B element is optimized to 9.58%-12.0%.

[0053] By comparing Example 20 with Comparative Example 9, it can be seen that when the content of C element in the alloy system is higher than 1.30%, the heat release difference between the edge and center of the strip becomes significant. Therefore, the atomic percentage of C element is optimized to 0.1%-1.3%.Experiment 2: Effects of cooling process on strip performance

[0054] In Experiment 1, strips with saturation magnetic induction of greater than 1.60 T, strong glass-forming ability and uniform cooling intensity were prepared. However, during subsequent preparation of the transformer core, performance fluctuations of strips were observed under different cooling processes. Therefore, the applicant further investigated the cooling process during the single-roller rapid quenching method.

[0055] Example 18 was used as the alloy composition in the following examples. Raw materials were weighed, melted in a medium-frequency induction furnace to obtain molten steel, and then prepared into strips via the single-roller rapid quenching method. In the single-roller rapid quenching method, experiments with different casting temperatures, different linear velocity, circulating water flow rates, etc. were carried out, and the strips were wound into toroidal cores, and after heat treatment, detected for core loss and excitation power under conditions of 60 Hz and 1.3 T using a silicon steel tester.

[0056] Table 3 below shows the soft magnetic properties under different cooling processes. Table 3ExampleCasting temperature °CLinear velocity m / sWater flow rate m 3< / h(1.3 T, 60 Hz) W / kgPe (1.3 T, 60 Hz) VA / kgExample 221415231240.180.26Example 231424241520.110.22Example 241433201800.140.27Example 251454252060.130.24Example 261462252140.190.31Example 271426251320.20.33Example 281434192000.170.28Comparative Example 101470252800.290.42Comparative Example 111435182400.390.6Comparative Example 121435291200.150.48Comparative Example 13144025820.360.62Comparative Example 141432244500.280.82

[0057] From the above results, it can be seen that through adjustments to the cooling process, including casting temperature, crystallizer linear velocity, water flow rate, etc., amorphous strips with excellent soft magnetic properties were prepared. After heat treatment, the strips exhibited core loss P of less than or equal to 0.2 W / kg and excitation power Pe of less than or equal to 0.33 VA / kg under conditions of 1.3 T and 60 Hz. As shown in Examples 22-28, the amorphous strip prepared in Example 23 achieved the optimal performance after heat treatment. The casting temperature directly affects the heat exchange between the crystallizer surface and the molten steel at the molten pool. The casting temperature must be higher than the melting point and maintain a certain degree of superheat to ensure that the fluidity of molten steel meets casting conditions. When the casting temperature is too high, such as Comparative Example 10, with a casting temperature of the molten steel as high as 1470°C, both core loss and excitation power of the strip increase, even though the linear velocity and water flow rate are increased accordingly, indicating insufficient cooling capacity.

[0058] Similarly, the crystallizer linear velocity critically influences the cooling capacity of the crystallizer. When the crystallizer linear velocity is low, more molten steel is withdrawn per unit area of the crystallizer surface and the energy is sufficient, resulting in decreased cooling capacity of the crystallizer accordingly. The applicant found that in the preparation of amorphous alloys with a high Bs alloy system, the crystallizer linear velocity must be maintained above 19 m / s to prepare fully amorphous quenched strips. However, it is not the case that the higher the crystallizer cooling intensity, the better. For example, in Comparative Example 12, when the crystallizer linear velocity was as high as 29 m / s, although core loss of the strip met the requirements, the excitation power was high. This is because the excessive cooling intensity freezes a large amount of quenched stress during cooling. During heat treatment, sufficient insulation is required to remove the residual quenched stress inside, but long-term insulation is obviously not conducive to the core loss of strips. Therefore, the crystallizer linear velocity is preferably in a range of 19-25 m / s.

[0059] The water flow rate of the crystallizer exerts effects analogous to linear velocity on the cooling capacity of the crystallizer. It is not the case that the stronger the cooling capacity of the crystallizer, the better. Excessive water flow rate will also lead to residual quenched stress, resulting in higher excitation power of the strip during the back-end application. After being fabricated into a transformer core, the strip is prone to suffering from problems such as excessive noise, as shown in Comparative Example 14. Conversely, as shown in Comparative Example 13, when the water flow rate of the crystallizer was only 82 m 3< / h, both core loss and excitation power of the strip after heat treatment increased, indicating insufficient cooling capacity of the crystallizer. In summary, the water flow rate of the crystallizer is preferably in a range of 100-300 m 3< / h.

[0060] In summary, the present application prepares amorphous alloy strips with high saturation magnetic induction, high glass-forming ability, uniform cooling intensity and excellent performance, solves the problem of non-uniform cooling for the alloy system with high Bs (≥ 1.60 T), and achieves the technical effect described in the present application.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, those ordinarily skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements should not cause the substance of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present application.

Examples

experiment 1

Effects of different compositions on Bs (saturation magnetic induction), glass-forming ability and cooling uniformity

[0039]The raw materials of different compositions were weighed and proportioned according to the prescribed ratios, and melted in a medium-frequency induction furnace to obtain molten steel in molten state. Subsequently, strips were prepared via the single-roller rapid quenching method, in which the molten steel at a specified temperature was directed through a nozzle slit of defined geometry onto the surface of a crystallizer under high-speed rotating. The casting temperature of the molten steel was 1420°C. The crystallizer, fabricated from beryllium copper, was internally provided with cooling water at a flow rate of 180 m 3< / h. The linear velocity of the crystallizer was 20 m / s.

[0040]During the preparation process, the smoothness of strip preparation was evaluated (during the preparation process, if all of the molten steel was successfully prepared into fully amor...

experiment 2

Effects of cooling process on strip performance

[0054]In Experiment 1, strips with saturation magnetic induction of greater than 1.60 T, strong glass-forming ability and uniform cooling intensity were prepared. However, during subsequent preparation of the transformer core, performance fluctuations of strips were observed under different cooling processes. Therefore, the applicant further investigated the cooling process during the single-roller rapid quenching method.

[0055]Example 18 was used as the alloy composition in the following examples. Raw materials were weighed, melted in a medium-frequency induction furnace to obtain molten steel, and then prepared into strips via the single-roller rapid quenching method. In the single-roller rapid quenching method, experiments with different casting temperatures, different linear velocity, circulating water flow rates, etc. were carried out, and the strips were wound into toroidal cores, and after heat treatment, detected for core loss an...

Claims

1. An iron-based amorphous alloy strip having a chemical composition of FeaSibBcCd, wherein a, b, c, and d represent atomic percentages of corresponding components respectively; 80.4% ≤ a ≤ 83.5%, 3.98% ≤ b ≤ 9.5%, 9.58% ≤ c ≤ 12.0%, 0.1% ≤ d ≤ 1.3%, and 99.9% ≤ a+b+c+d ≤ 100%, with the balance being inevitable impurities.

2. The iron-based amorphous alloy strip according to claim 1, wherein the iron-based amorphous alloy strip has a saturation magnetic induction of ≥ 1.6 T.

3. The iron-based amorphous alloy strip according to claim 1, wherein Fe is present in an atomic percentage of 81.3% ≤ a ≤ 83.5%.

4. The iron-based amorphous alloy strip according to claim 1, wherein Si is present in an atomic percentage of 5.62% ≤ b ≤ 9.5%.

5. The iron-based amorphous alloy strip according to claim 1, wherein Fe is present in an atomic percentage of 82.63%, Si is present in an atomic percentage of 5.62%, B is present in an atomic percentage of 10.37%, and C is present in an atomic percentage of 1.28%.

6. The iron-based amorphous alloy strip according to any one of claims 1 to 5, wherein the iron-based amorphous alloy strip has a specific heat capacity at 100°C of 0.40-0.47 J / (g·°C).

7. The iron-based amorphous alloy strip according to any one of claims 1 to 5, wherein the iron-based amorphous alloy strip is divided into n equal zones along the width direction, with the edge zone accounting for 10% of the strip width designated as Zone a, and the central zone accounting for 10% of the strip width designated as Zone b, samples taken within the ranges of Zones a and b respectively are detected using a differential scanning calorimeter for first crystallization peak area thereof to obtain heat release values Qa and Qb, and the iron-based amorphous alloy strip has a variation coefficient δQ = (Qa-Qb) / Qa*100% of no more than 4%.

8. A method for preparing the iron-based amorphous alloy strip according to any one of claims 1 to 7, comprising: formulating raw materials according to FeaSibBcCd, melting and single-roller rapid quenching the formulated raw materials to obtain the iron-based amorphous alloy strip.

9. The method for preparing the iron-based amorphous alloy strip according to claim 8, wherein in the single-roller rapid quenching process, the casting temperature of molten steel is 1400-1465°C, the linear velocity of a copper roller is 19-25 m / s, the copper roller is internally provided with a cooling water channel, through which cooling water is supplied at a flow rate of 100-300 m3 / h.

10. The method for preparing the iron-based amorphous alloy strip according to claim 9, wherein after heat treatment, the iron-based amorphous alloy strip has a core loss P ≤ 0.2 W / kg and an excitation power Pe ≤ 0.33 VA / kg under conditions of 1.3 T and 60 Hz.

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