Low-noise cold-rolled oriented electrical steel strip for transformer, preparation method thereof and transformer

Abstract

The invention belongs to the technical field of cold-rolled oriented electrical steel strip manufacturing, and particularly relates to a low-noise cold-rolled oriented electrical steel strip for a transformer, a preparation method of the low-noise cold-rolled oriented electrical steel strip and the transformer. The method comprises the following steps: heating a sheet billet to obtain a heated sheet billet, carrying out hot continuous rolling on the heated sheet billet to obtain a hot-rolled sheet, and sequentially carrying out normalizing pickling, primary cold rolling, decarburization annealing, secondary cold rolling, MgO separant coating, cover type high-temperature annealing, stretching leveling and insulating coating on the hot-rolled sheet to prepare a finished oriented electrical steel strip with the thickness of 0.15-0.20 mm, the slab comprises the following chemical elements in percentage by mass: 0.02% < = C < = 0.08%, 2.50% < = Si < = 3.20%, 0.10% < = Mn < = 0.50%, 0.02% < = P, 0.05% < = Als < = 0.15%, 0.10% < = Cu < = 0.50%, 0.05% < = Sb < = 0.15%, 0.005% < = S < = 0.015%, 0.005% < = N < = 0.015%, 0.004% < = Ti and the balance of Fe and inevitable impurities. The iron loss P1.7 / 50 of the cold-rolled oriented electrical steel strip finished product prepared by the method is less than or equal to 1.00 W / kg, the iron loss B8 is greater than or equal to 1.94 T, and the test noise of a transformer manufactured by the steel strip at a position of 3m is less than 15dB.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing cold-rolled grain-oriented electrical steel strips, and particularly relates to a low-noise cold-rolled grain-oriented electrical steel strip for transformers, a preparation method thereof, and a transformer. Background Art

[0002] In recent years, the manufacturing of cold-rolled grain-oriented electrical steel strips has developed greatly in China. Grain-oriented electrical steel strips are currently mainly used in the manufacturing of transformer cores. Transformers generate a lot of noise during operation due to material characteristics, which has an adverse impact in densely populated areas. With the increasingly fierce market competition, transformers have put forward higher requirements for the magnetic properties of grain-oriented electrical steel strips, especially for low noise. Therefore, it is very necessary to produce low-noise cold-rolled grain-oriented electrical steel strips for downstream users to manufacture transformers.

[0003] The prior art "A grain-oriented silicon steel with low-noise characteristics and a manufacturing method thereof" proposes to reduce the low-order harmonics in the magnetostriction waveform by controlling the tension range of the insulating coating applied to the silicon steel substrate between 6 and 8 MPa, thereby reducing the vibration of the iron core and effectively reducing the noise level of the transformer. At the same time, by controlling the Cu element and S element in the silicon steel substrate within a suitable range, the magnetic properties of the finished product are improved, and the grain size can be effectively controlled, so as to reduce the magnetostriction vibration and lower the noise level of the transformer. Although this prior art can reduce the noise performance of the transformer assembled from the prepared grain-oriented silicon steel, the reduction effect is not significant. In addition, the parameters to be adjusted in this prior art are too complicated, and the tensile test method and bending test method used to control the tension of the insulating coating require special equipment and technology, and the operation is relatively complicated. The ultrasonic method is relatively simple to operate, but it requires calibration and experience, and the accuracy of the results is easily affected by the coating material.

[0004] The prior art "A high magnetic induction grain-oriented silicon steel with low-noise characteristics and a production method thereof" proposes to add Ni and Cr alloying elements and control Ni+Cr at 0.03-0.08% and Cr / Ni at 1-6; and control the rapid heating of decarburization annealing at 100-300 °C / s to reduce the noise to 48-52 dB and B8 at 1.925-1.935 T, which not only reduces noise pollution but also has excellent magnetic properties. Although this prior art can also reduce the noise performance of the transformer assembled from the prepared grain-oriented silicon steel, the reduction effect is not significant. At the same time, Ni is a precious metal, and using Ni to prepare grain-oriented silicon steel will increase the cost and is not suitable for industrial production. Summary of the Invention

[0005] The object of the present invention is to address the deficiencies of the prior art in the production of low-noise grain-oriented steel, where the production process is complex and costly, and it is not suitable for industrial production. Therefore, a low-noise cold-rolled grain-oriented electrical steel strip for transformers, its preparation method, and a transformer are proposed. The preparation method of the present invention controls the chemical composition in the steel and adopts the process of thin slab continuous casting and rolling to obtain a grain-oriented electrical steel strip product with excellent magnetic properties and low noise. The finished iron loss P of the cold-rolled grain-oriented electrical steel strip with a thickness of 0.15 - 0.20 mm 1.7 / 50 ≤ 1.00 W / kg, B8 ≥ 1.94 T, and the noise of the transformer made of the steel strip is tested to be lower than 15 dB at 3 m.

[0006] The first aspect of the present invention proposes a preparation method of a low-noise cold-rolled grain-oriented electrical steel strip for transformers, and the preparation method includes the following steps:

[0007] Step S1: Heat a slab with a thickness ≤ 65 mm to obtain a heated slab, and perform hot continuous rolling on the heated slab to obtain a hot-rolled sheet;

[0008] Step S2: Normalize the hot-rolled sheet to obtain a normalized product, pickle the normalized product to obtain a pickled product, perform first cold rolling on the pickled product to obtain a first cold-rolled sheet, perform decarburization annealing on the first cold-rolled sheet to obtain a decarburization annealing product, perform second cold rolling on the decarburization annealing product to obtain a second cold-rolled sheet, coat the second cold-rolled sheet with MgO to obtain a coated product, perform finish annealing on the coated product to obtain a finish annealing product, and sequentially perform stretching and insulation coating on the finish annealing product to obtain a grain-oriented electrical steel strip with a thickness of 0.15 - 0.20 mm;

[0009] The mass percentage ratio of each chemical element in the slab is: 0.020% ≤ C ≤ 0.080%, 0.10% ≤ Mn ≤ 0.50%, P ≤ 0.02%, 0.05% ≤ Als ≤ 0.15%, 0.10% ≤ Cu ≤ 0.50%, 0.05% ≤ Sb ≤ 0.15%, 0.005% ≤ S ≤ 0.015%, 0.005% ≤ N ≤ 0.015%, Ti ≤ 0.004%, and the rest is Fe and inevitable impurities.

[0010] Preferably, the mass percentage distribution of each chemical element in the slab is: 0.040% ≤ C ≤ 0.060%, 2.80% ≤ Si ≤ 3.00%, 0.25% ≤ Mn ≤ 0.34%, 0.008% ≤ P ≤ 0.010%, 0.09% ≤ Als ≤ 0.12%, 0.22% ≤ Cu ≤ 0.38%, 0.09% ≤ Sb ≤ 0.12%, 0.008% ≤ S ≤ 0.012%, 0.008% ≤ N ≤ 0.013%, 0.0012% ≤ Ti ≤ 0.0014%, and the rest is Fe and inevitable impurities.

[0011] More preferably, the mass percentage distribution of each chemical element in the slab is: C: 0.040%, Si: 2.80%, Mn: 0.25%, P: 0.010%, Als: 0.09%, Cu: 0.38%, Sb: 0.09%, S: 0.008%, N: 0.013%, Ti: 0.0014%, and the rest is Fe and inevitable impurities.

[0012] More preferably, the mass percentage distribution of each chemical element in the slab is: C: 0.060%, Si: 3.00%, Mn: 0.34%, P: 0.008%, Als: 0.12%, Cu: 0.22%, Sb: 0.12%, S: 0.012%, N: 0.008%, Ti: 0.0012%, and the rest is Fe and inevitable impurities.

[0013] Preferably, in step S1, the heating conditions include: the heating temperature is 1150 - 1250 °C, and the heating time is 2.5 - 4 h.

[0014] Preferably, in step S1, the hot continuous rolling conditions include: the final rolling temperature is 900 - 1000 °C, and the coiling temperature is 500 - 600 °C.

[0015] Preferably, in step S1, the thickness of the hot rolled sheet is 2.0 - 2.5 mm.

[0016] Preferably, in step S2, the normalizing temperature is 1000 - 1100 °C, and the pickling temperature is 70 - 90 °C.

[0017] Preferably, in step S2, the number of passes of the first cold rolling is 5 - 6 passes, and the thickness of the first cold rolled sheet is 0.8 - 1.0 mm.

[0018] Preferably, in step S2, the decarburizing annealing treatment is carried out in a continuous annealing furnace. The annealing temperature is 800 - 900 °C, and the holding time is 2 - 4 min. The decarburizing annealing treatment is protected by a nitrogen-hydrogen mixed gas, wherein the volume percentage of hydrogen is 20 - 30%. The dew point inside the continuous annealing furnace is controlled at 20 - 30 °C.

[0019] Preferably, in step S2, the number of passes of the secondary cold rolling is 3 - 4 passes, and the thickness of the secondary cold rolled sheet is 0.15 - 0.20 mm.

[0020] Preferably, in step S2, the drying temperature during the MgO coating process is 450 - 550 °C.

[0021] Preferably, in step S2, the finish annealing treatment is carried out in a bell-type annealing furnace. The annealing temperature is 1100 - 1250 °C, and the holding time is 24 - 36 h. The finish annealing treatment is protected by a nitrogen-hydrogen mixed gas, wherein the volume percentage of hydrogen is 20 - 100%. When the furnace temperature of the bell-type annealing furnace is higher than 750 °C, full hydrogen protection is adopted.

[0022] Preferably, in step S2, the conditions for the insulation coating treatment include: the curing temperature is 300 - 450 °C.

[0023] Preferably, in step S2, the thickness of the grain-oriented electrical steel strip is 0.17 - 0.20 mm.

[0024] In a second aspect of the present invention, there is provided a low-noise cold-rolled grain-oriented electrical steel strip for transformers obtained by the above-described preparation method. The P of the grain-oriented electrical steel strip 1.7 / 50 ≤1.00 W / kg, where P 1.7 / 50 represents the iron loss value at a magnetic induction intensity of 1.7 T and a frequency of 50 Hz, and B8 ≥ 1.94 T, where B8 represents the magnetic induction intensity at a magnetic field strength of 800 A / m.

[0025] In a third aspect of the present invention, there is provided a transformer prepared from the above-described low-noise cold-rolled grain-oriented electrical steel strip for transformers.

[0026] In the low-noise cold-rolled grain-oriented electrical steel strip for transformers, its preparation method, and the transformer according to the present invention, the following beneficial effects are achieved:

[0027] In the present invention, by controlling the chemical composition of the steel, especially by adding 0.05-0.15% of the alloying element antimony (Sb), the inclusions and precipitate morphologies in the base material can be controlled, the resistance to magnetic domain movement inside the grains and at the grain boundaries can be weakened, and the effects of reducing iron loss and reducing noise can be achieved; and by adopting the process of thin slab continuous casting and rolling, an oriented electrical steel strip product with excellent magnetic properties and low noise can be obtained. The finished iron loss P of the cold-rolled oriented electrical steel strip with a thickness of 0.15-0.20 mm 1.7 / 50 ≤1.00 W / kg, B8≥1.94 T. The noise measured at 3 m for the transformer made of the steel strip is lower than 15 dB, which can meet the requirements of higher-end users of oriented silicon steel. Specific embodiments

[0028] The following will detail the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention and are not used to limit the present invention.

[0029] The first aspect of the present invention proposes a preparation method for a low-noise cold-rolled oriented electrical steel strip for transformers, and the preparation method includes the following steps:

[0030] Step S1: Heat a slab with a thickness ≤65 mm to obtain a heated slab, and perform hot continuous rolling on the heated slab to obtain a hot-rolled sheet;

[0031] Step S2: Normalize the hot-rolled sheet to obtain a normalized product, pickle the normalized product to obtain a pickled product, perform first cold rolling on the pickled product to obtain a first cold-rolled sheet, perform decarburization annealing on the first cold-rolled sheet to obtain a decarburization annealing product, perform second cold rolling on the decarburization annealing product to obtain a second cold-rolled sheet, coat the second cold-rolled sheet with MgO to obtain a coated product, perform finish annealing on the coated product to obtain a finish annealing product, and sequentially perform stretching and insulation coating on the finish annealing product to obtain an oriented electrical steel strip with a thickness of 0.15-0.20 mm; the mass percentage ratios of the chemical elements in the slab are: 0.020%≤C≤0.080%, 2.50%≤Si≤3.20%, 0.10%≤Mn≤0.50%, P≤0.02%, 0.05%≤Als≤0.15%, 0.10%≤Cu≤0.50%, 0.05%≤Sb≤0.15%, 0.005%≤S≤0.015%, 0.005%≤N≤0.015%, Ti≤0.004%, and the rest are Fe and unavoidable impurities.

[0032] In the specific embodiment of the preparation method of the present invention, in step S1, the thickness of the slab can be 60 mm, 63 mm or 65 mm.

[0033] In a preferred embodiment of the preparation method of the present invention, the mass percentage ratios of various chemical elements in the slab are as follows: 0.040% ≤ C ≤ 0.060%, 2.80% ≤ Si ≤ 3.00%, 0.25% ≤ Mn ≤ 0.34%, 0.008% ≤ P ≤ 0.010%, 0.09% ≤ Als ≤ 0.12%, 0.22% ≤ Cu ≤ 0.38%, 0.09% ≤ Sb ≤ 0.12%, 0.008% ≤ S ≤ 0.012%, 0.008% ≤ N ≤ 0.013%, 0.0012% ≤ Ti ≤ 0.0014%, and the balance is Fe and inevitable impurities.

[0034] In a more preferred embodiment of the preparation method of the present invention, the mass percentage ratios of various chemical elements in the slab are as follows: C: 0.040%, Si: 2.80%, Mn: 0.25%, P: 0.010%, Als: 0.09%, Cu: 0.38%, Sb: 0.09%, S: 0.008%, N: 0.013%, Ti: 0.0014%, and the balance is Fe and inevitable impurities.

[0035] In a more preferred embodiment of the preparation method of the present invention, the mass percentage ratios of various chemical elements in the slab are as follows: C: 0.060%, Si: 3.00%, Mn: 0.34%, P: 0.008%, Als: 0.12%, Cu: 0.22%, Sb: 0.12%, S: 0.012%, N: 0.008%, Ti: 0.0012%, and the balance is Fe and inevitable impurities.

[0036] In a specific embodiment of the preparation method of the present invention, in step S1, the heating conditions include: the heating temperature is 1150 - 1250 °C, for example, it can be 1150 °C, 1180 °C, 1220 °C or 1250 °C; the heating time is 2.5 - 4 h, for example, it can be 2.5 h, 3.0 h, 3.5 h or 4.0 h.

[0037] In a specific embodiment of the preparation method of the present invention, in step S1, the hot continuous rolling is carried out in a seven-stand continuous rolling mill, and the conditions of the hot continuous rolling include: the finishing rolling temperature is 900 - 1000 °C, for example, it can be 900 °C, 950 °C, 970 °C or 1000 °C; the coiling temperature is 500 - 600 °C, for example, it can be 500 °C, 560 °C, 575 °C or 600 °C.

[0038] In a specific embodiment of the preparation method of the present invention, in step S1, the thickness of the hot-rolled sheet is 2.0 - 2.5 mm, for example, it can be 2.0 mm, 2.2 mm or 2.5 mm.

[0039] In the specific embodiments of the preparation method of the present invention, in step S2, the normalizing treatment and pickling are both carried out on a normalizing and pickling line. Among them, the temperature of the normalizing treatment is 1000-1100°C, for example, it can be 1000°C, 1050°C or 1100°C; the temperature of the pickling is 70-90°C, for example, it can be 70°C, 80°C or 90°C.

[0040] In the specific embodiments of the preparation method of the present invention, in step S2, the first cold rolling is carried out on a 6-high reversible rolling mill. The number of passes of the first cold rolling is 5-6 passes, and the thickness of the first cold rolled sheet is 0.8-1.0 mm, for example, it can be 0.8 mm, 0.9 mm or 1.0 mm.

[0041] In the specific embodiments of the preparation method of the present invention, in step S2, the decarburizing annealing treatment is carried out in a continuous annealing furnace. The annealing temperature is 800-900°C, for example, it can be 800°C, 850°C, 870°C or 900°C, and the holding time is 2-4 min, for example, it can be 2 min, 3 min or 4 min; the decarburizing annealing treatment is protected by a nitrogen-hydrogen mixed gas. Among them, the volume percentage of hydrogen is 20-30%, for example, it can be 20%, 25% or 30%; the dew point in the continuous annealing furnace is controlled at 20-30°C, for example, it can be 20°C, 25°C or 30°C.

[0042] In the specific embodiments of the preparation method of the present invention, in step S2, the number of passes of the second cold rolling is 3-4 passes, and the thickness of the second cold rolled sheet is 0.15-0.20 mm, for example, it can be 0.15 mm, 0.18 mm or 0.20 mm.

[0043] In the specific embodiments of the preparation method of the present invention, in step S2, the MgO coating is carried out on a continuous coating unit. The drying temperature during the MgO coating process is 450-550°C, for example, it can be 450°C, 520°C or 550°C.

[0044] In the specific embodiments of the preparation method of the present invention, in step S2, the final annealing treatment is carried out in a batch annealing furnace. The annealing temperature is 1100-1250°C, for example, it can be 1100°C, 1150°C, 1200°C or 1250°C; the holding time is 24-36 h, for example, it can be 24 h, 30 h or 36 h; the final annealing treatment is protected by a nitrogen-hydrogen mixed gas. Among them, the volume percentage of hydrogen is 20-100%, for example, it can be 20%, 50% or 100%. When the furnace temperature of the batch annealing furnace is higher than 750°C, full hydrogen protection is adopted.

[0045] In the specific embodiments of the preparation method of the present invention, in step S2, the stretching is carried out on a planishing mill.

[0046] In the specific embodiments of the preparation method of the present invention, in step S2, the insulating coating treatment is carried out on a coating line. The conditions of the insulating coating treatment include: the curing temperature is 300 - 450 °C, for example, it can be 300 °C, 400 °C or 450 °C.

[0047] In the specific embodiments of the preparation method of the present invention, in step S2, the thickness of the grain-oriented electrical steel strip is 0.17 - 0.20 mm, for example, it can be 0.17 mm, 0.18 mm, 0.19 mm or 0.20 mm.

[0048] In the second aspect of the present invention, a low-noise cold-rolled grain-oriented electrical steel strip for transformers obtained according to the above-mentioned preparation method is provided. The P of the grain-oriented electrical steel strip 1.7 / 50 ≤1.00 W / kg, and P 1.7 / 50 represents the iron loss value at a magnetic induction intensity of 1.7 T and a frequency of 50 Hz, and B8≥1.94 T, where B8 represents the magnetic induction intensity at a magnetic field strength of 800 A / m.

[0049] In the third aspect of the present invention, a transformer prepared from the above-mentioned low-noise cold-rolled grain-oriented electrical steel strip for transformers is provided.

[0050] Unless otherwise specified, the test methods or testing methods described in the following examples are all conventional methods; unless otherwise specified, the reagents and materials are all obtained from conventional commercial channels or prepared by conventional methods.

[0051] Example 1

[0052] A preparation method of a low-noise cold-rolled grain-oriented electrical steel strip for transformers, the preparation method comprising the following steps:

[0053] Step S1: Continuously cast molten steel into a slab with a thickness of 65 mm. The slab directly enters a heating furnace for heating and heat preservation. The temperature of the heating furnace is 1220 °C, and the heating time is 2.5 h; it is rolled into a hot-rolled sheet with a thickness of 2.2 mm through a seven-stand continuous rolling mill. Among them, the final rolling temperature of the hot rolling is 950 °C, and the coiling temperature is 560 °C;

[0054] Step S2: The hot-rolled sheet is processed on a normalizing and pickling line. The normalizing temperature is 1050°C, and the pickling temperature is 80°C to obtain a pickled strip. The pickled strip is cold-rolled once on a six-high reversing mill and cold-rolled to a thickness of 0.8 mm after 6 passes to obtain a first cold-rolled sheet. The first cold-rolled sheet is subjected to decarburization annealing treatment in a continuous annealing furnace. The decarburization annealing temperature is 850°C, and the holding time is 3 min. It is protected by a nitrogen-hydrogen mixed gas, with the hydrogen content by volume percentage being 25%. The dew point in the furnace is controlled at 25°C to obtain a product after decarburization annealing treatment. The product after decarburization annealing treatment is cold-rolled a second time on a six-high reversing mill and cold-rolled to a thickness of 0.20 mm after 3 passes to obtain a second cold-rolled sheet. The second cold-rolled sheet is coated with a MgO isolating agent on a continuous coating unit, and the drying temperature is 520°C to obtain a coated product. The coated product is subjected to finish annealing treatment in a bell-type annealing furnace. The annealing temperature is 1200°C, and the holding time is 30 h. It is protected by a nitrogen-hydrogen mixed gas, with the hydrogen content by volume percentage being 50%. When the furnace temperature is higher than 750°C, it is protected by pure hydrogen gas to obtain a product after finish annealing treatment. The product after finish annealing treatment is subjected to stretch leveling on a temper mill, and the product after stretch leveling is coated with an insulating coating on a coating unit. The coating curing temperature is 400°C;

[0055] Among them, the mass percentage distribution of each chemical element in the slab is: C: 0.040%, Si: 2.80%, Mn: 0.25%, P: 0.010%, Als: 0.09%, Cu: 0.38%, Sb: 0.09%, S: 0.008%, N: 0.013%, Ti: 0.0014%, and the rest are Fe and inevitable impurities, obtaining cold-rolled grain-oriented electrical steel strip A1.

[0056] Example 2

[0057] A preparation method of a low-noise cold-rolled grain-oriented electrical steel strip for transformers, the preparation method comprising the following steps:

[0058] Step S1: Molten steel is continuously cast into a slab with a thickness of 65 mm. The slab directly enters a heating furnace for heating and holding. The temperature of the heating furnace is 1180°C, and the heating time is 3.0 h. It is rolled into a hot-rolled sheet with a thickness of 2.2 mm through a seven-stand continuous rolling mill. Among them, the final rolling temperature of the hot rolling is 970°C, and the coiling temperature is 575°C;

[0059] Step S2: The hot-rolled sheet is processed on a normalizing and pickling line. The normalizing temperature is 1050 °C, and the pickling temperature is 80 °C to obtain a pickled strip. The pickled strip is cold-rolled once on a 6-high reversible mill and cold-rolled to a thickness of 0.9 mm in 5 passes to obtain a first cold-rolled sheet. The first cold-rolled sheet is subjected to decarburization annealing treatment in a continuous annealing furnace. The decarburization annealing temperature is 870 °C, and the holding time is 3 min. It is protected by a nitrogen-hydrogen mixed gas, the volume percentage of hydrogen content is 25%, and the furnace dew point is controlled at 25 °C to obtain a decarburization annealing treatment product; the decarburization annealing treatment product is cold-rolled twice on a 6-high reversible mill and cold-rolled to a thickness of 0.20 mm in 4 passes to obtain a second cold-rolled sheet. The second cold-rolled sheet is coated with MgO isolating agent on a continuous coating unit, and the drying temperature is 520 °C to obtain a coated product; the coated product is subjected to finish annealing treatment in a bell-type annealing furnace. The annealing temperature is 1200 °C, and the holding time is 30 h; it is protected by a nitrogen-hydrogen mixed gas, the volume percentage of hydrogen content is 50%, and when the furnace temperature is higher than 750 °C, it is protected by pure hydrogen gas to obtain a finish annealing treatment product; the finish annealing treatment product is stretch-leveled on a temper mill, and the stretch-leveled product is coated with an insulating coating on a coating unit, and the coating curing temperature is 400 °C;

[0060] Among them, the mass percentage distribution of each chemical element in the slab is: C: 0.060%, Si: 3.00%, Mn: 0.34%, P: 0.008%, Als: 0.12%, Cu: 0.22%, Sb: 0.12%, S: 0.012%, N: 0.008%, Ti: 0.0012%, and the rest are Fe and unavoidable impurities, obtaining cold-rolled grain-oriented electrical steel strip A2.

[0061] Comparative Example 1

[0062] Implemented in the manner of Example 1, the difference is that the thickness of the slab is 70 mm, obtaining cold-rolled grain-oriented electrical steel strip B1.

[0063] Comparative Example 2

[0064] Implemented in the manner of Example 1, the difference is that the thickness of the obtained cold-rolled grain-oriented electrical steel strip B2 is 0.10 mm.

[0065] Comparative Example 3

[0066] Implemented in the manner of Example 1, the difference is that the thickness of the obtained cold-rolled grain-oriented electrical steel strip B3 is 0.30 mm.

[0067] Comparative Example 4

[0068] Implemented in the manner of Example 1, the difference is that the slab does not contain Sb element, obtaining cold-rolled grain-oriented electrical steel strip B4.

[0069] Test example

[0070] The iron losses P of A1 and A2 prepared in Examples 1-2 and B1-B4 prepared in Comparative Examples 1-4 were respectively tested 1.7 / 50 and magnetic induction B8. The test methods for the iron loss P 1.7 / 50 and magnetic induction B8 are: GB / T3655-2008 "Measurement Method for Magnetic Properties of Epstein Square Ring Electrical Steel (Strip)".

[0071] The corresponding transformers were respectively prepared from A1 and A2 prepared in Examples 1-2 and B1-B4 prepared in Comparative Examples 1-4, and the noise values of the transformers prepared from A1-A2 and B1-B4 were tested at 3 m. The test methods are: GB3096-2008 "Ambient Quality Standard for Noise"; ISO1996 "Acoustics - Description, Measurement and Assessment of Environmental Noise".

[0072] Table 1 P of A1-A2 and B1-B4 1.7 / 50 and B8 and the noise values of the prepared transformers were tested at 3 m

[0073] <![CDATA[Iron loss P 1.7 / 50 > <![CDATA[Magnetic induction B8]]> Noise value A1 0.98W / kg 1.95T 14dB A2 0.95W / kg 1.96T 12dB B1 0.99W / kg 1.95T 23dB B2 1.03W / kg 1.93T 25dB B3 1.12W / kg 1.94T 27dB B4 1.08W / kg 1.92T 23dB

[0074] From the results in Table 1, it can be seen that the cold-rolled grain-oriented electrical steel obtained by the method of the present invention has excellent magnetic properties and low noise. The finished product iron loss P of the cold-rolled grain-oriented electrical steel strip with a thickness of 0.15-0.20 mm 1.7 / 50 ≤1.00 W / kg, B8≥1.94 T, and the noise of the transformer manufactured from the steel strip tested at 3 m is less than 15 dB

[0075] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention

Claims

1. A preparation method of a low-noise cold-rolled grain-oriented electrical steel strip for transformers, characterized in that, The preparation method includes the following steps: Step S1: Heat a slab with a thickness ≤ 65 mm to obtain a heated slab, and perform hot continuous rolling on the heated slab to obtain a hot-rolled sheet; Step S2: Normalize the hot-rolled sheet to obtain a normalized product, pickle the normalized product to obtain a pickled product, perform first cold rolling on the pickled product to obtain a first cold-rolled sheet, perform decarburizing annealing on the first cold-rolled sheet to obtain a decarburizing annealing product, perform second cold rolling on the decarburizing annealing product to obtain a second cold-rolled sheet, coat the second cold-rolled sheet with MgO to obtain a coated product, perform finish annealing on the coated product to obtain a finish annealing product, and sequentially perform stretching and insulating coating on the finish annealing product to obtain an oriented electrical steel strip with a thickness of 0.15 - 0.20 mm; The mass percentage ratios of various chemical elements in the slab are: 0.020% ≤ C ≤ 0.080%, 2.50% ≤ Si ≤ 3.20%, 0.10% ≤ Mn ≤ 0.50%, P ≤ 0.02%, 0.05% ≤ Als ≤ 0.15%, 0.10% ≤ Cu ≤ 0.50%, 0.05% ≤ Sb ≤ 0.15%, 0.005% ≤ S ≤ 0.015%, 0.005% ≤ N ≤ 0.015%, Ti ≤ 0.004%, and the rest is Fe and unavoidable impurities.

2. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 1, characterized in that, The mass percentage ratios of various chemical elements in the slab are: 0.040% ≤ C ≤ 0.060%, 2.80% ≤ Si ≤ 3.00%, 0.25% ≤ Mn ≤ 0.34%, 0.008% ≤ P ≤ 0.010%, 0.09% ≤ Als ≤ 0.12%, 0.22% ≤ Cu ≤ 0.38%, 0.09% ≤ Sb ≤ 0.12%, 0.008% ≤ S ≤ 0.012%, 0.008% ≤ N ≤ 0.013%, 0.0012% ≤ Ti ≤ 0.0014%, and the rest is Fe and unavoidable impurities.

3. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 2, characterized in that, The mass percentage ratios of various chemical elements in the slab are: C: 0.040%, Si: 2.80%, Mn: 0.25%, P: 0.010%, Als: 0.09%, Cu: 0.38%, Sb: 0.09%, S: 0.008%, N: 0.013%, Ti: 0.0014%, and the rest is Fe and unavoidable impurities.

4. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 2, characterized in that, The mass percentage ratios of various chemical elements in the slab are: C: 0.060%, Si: 3.00%, Mn: 0.34%, P: 0.008%, Als: 0.12%, Cu: 0.22%, Sb: 0.12%, S: 0.012%, N: 0.008%, Ti: 0.0012%, and the rest is Fe and unavoidable impurities.

5. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 1, characterized in that, In step S1, the heating conditions include: the heating temperature is 1150 - 1250 °C, and the heating time is 2.5 - 4 h; The conditions for the hot continuous rolling include: the final rolling temperature is 900 - 1000 °C, and the coiling temperature is 500 - 600 °C; The thickness of the hot-rolled sheet is 2.0 - 2.5 mm.

6. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 1, wherein In step S2, the temperature of the normalizing treatment is 1000 - 1100 °C, and the temperature of the pickling is 70 - 90 °C; The number of passes of the first cold rolling is 5 - 6 passes, and the thickness of the first cold-rolled sheet is 0.8 - 1.0 mm; The decarburizing annealing treatment is carried out in a continuous annealing furnace. The annealing temperature is 800 - 900 °C, and the holding time is 2 - 4 min. The decarburizing annealing treatment is protected by a nitrogen-hydrogen mixed gas, wherein the volume percentage of hydrogen is 20 - 30%. The dew point in the continuous annealing furnace is controlled at 20 - 30 °C.

7. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 1, characterized in that, In step S2, the number of passes of the second cold rolling is 3 - 4 passes, and the thickness of the second cold-rolled sheet is 0.15 - 0.20 mm; The drying temperature during the MgO coating process is 450 - 550 °C; The final annealing treatment is carried out in a bell-type annealing furnace. The annealing temperature is 1100 - 1250 °C, and the holding time is 24 - 36 h. The final annealing treatment is protected by a nitrogen-hydrogen mixed gas, wherein the volume percentage of hydrogen is 20 - 100%. When the furnace temperature of the bell-type annealing furnace is higher than 750 °C, full hydrogen protection is adopted.

8. The preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 1, characterized in that, In step S2, the conditions of the insulating coating treatment include: the curing temperature is 300 - 450 °C; The thickness of the grain-oriented electrical steel strip is 0.17 - 0.20 mm.

9. A low-noise cold-rolled grain-oriented electrical steel strip for transformers obtained by the preparation method of the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to any one of claims 1 to 8, characterized in that, The P of the grain-oriented electrical steel strip 1.7 / 50 ≤ 1.00 W / kg, where P 1.7 / 50 represents the iron loss value at a magnetic induction intensity of 1.7 T and a frequency of 50 Hz, and B8 ≥ 1.94 T, where B8 represents the magnetic induction intensity at a magnetic field strength of 800 A / m.

10. A transformer prepared from the low-noise cold-rolled grain-oriented electrical steel strip for transformers according to claim 9.