A method for manufacturing a low-magnetostriction oriented silicon steel sheet and an oriented silicon steel sheet

Abstract

The application discloses a manufacturing method of low-magnetostrictive oriented silicon steel, which comprises the following steps: (a) smelting and casting; (b) heating; (c) normalizing; (d) cold rolling; (e) decarburization annealing; (f) finished product annealing; (g) hot tensile annealing including insulating coating coating; characterized in that, wherein the step (g) comprises: (1) respectively coating the two surfaces of the silicon steel substrate with the insulating coating in equal coating amounts; (2) sintering and cooling; (3) performing single-sided laser marking on one surface of the silicon steel substrate coated with the insulating coating, wherein the side on which the single-sided laser marking is performed is defined as a first surface, and the other side opposite to the first surface is defined as a second surface; (4) detecting the deflection difference between the first surface and the second surface, and adjusting the coating amount difference of the insulating coating on the first surface and the second surface based on the deflection difference; wherein the coating amount of the insulating coating on the second surface is greater than that on the first surface.

Description

Technical Field

[0001] This invention relates to a steel plate and a method for manufacturing the same, and more particularly to an oriented silicon steel plate and a method for manufacturing the same. Background Technology

[0002] Currently, most existing transformer cores are made of grain-oriented silicon steel laminates or grain-oriented silicon steel windings. The main transformer performance indicators that transformer manufacturers and downstream users focus on are no-load loss characteristics and no-load excitation current characteristics, which correspond to the loss and excitation power characteristics of grain-oriented silicon steel, respectively.

[0003] The loss characteristics of grain-oriented silicon steel depend on hysteresis loss, which is influenced by the orientation degree and purity of the finished product, classical eddy current loss, which is influenced by thickness and resistivity, and anomalous eddy current loss, which is influenced by domain width. Therefore, current technologies generally reduce hysteresis loss by increasing the magnetic flux density through increasing the orientation degree of the Goss orientation; classical eddy current loss by increasing the Si content to increase resistivity or reducing the thickness of the steel plate; and anomalous eddy current loss by using scoring to reduce domain width.

[0004] With the continuous improvement of production processes and technologies for grain-oriented silicon steel, the grain orientation of industrially produced grain-oriented silicon steel has gradually approached its limit. Further reducing the thickness would significantly increase production costs and technical difficulties. Meanwhile, due to the coarse grains in high-magnetic-induction grain-oriented silicon steel, introducing localized residual stress on the steel plate surface through laser marking reduces the 180° main domain spacing along the rolling direction, thereby reducing abnormal eddy current losses. This is currently a convenient and economical method for reducing iron loss in high-magnetic-induction grain-oriented silicon steel.

[0005] In recent years, with the continuous increase in societal requirements regarding environmental noise, transformer manufacturers and downstream users have placed increasing emphasis on the noise performance of transformers. Transformer noise performance has become a key indicator of equal importance to no-load loss. With the continuous optimization of processing technology and transformer design by transformer manufacturers, the magnetostriction of grain-oriented silicon steel has become a major source of transformer noise.

[0006] During alternating current excitation, the dimensional changes in oriented silicon steel (OSS) finished sheets due to magnetization are called magnetostriction, which is one of the main sources of transformer noise. The magnetostriction mechanism in OSS is due to the change and rotation of the number of 90° magnetic domains perpendicular to the easily magnetized direction parallel to the rolling direction during magnetization. Ideally, OSS finished products have only 180° magnetic domains. However, due to orientation deviations, inclusions, grain boundaries, and other defects, small additional domains—willow-leaf domains (90° domains)—appear between the 180° magnetic domains to reduce static magnetic energy, leading to increased magnetostriction. Therefore, reducing the number of 90° domains (closed domains) can effectively reduce magnetostriction.

[0007] In the existing technology, the main methods used to reduce magnetostriction include: (1) increasing the orientation degree of the finished crystal to reduce magnetostriction; (2) reducing the thickness of the finished product to reduce magnetostriction; and (3) increasing the coating tension to reduce magnetostriction. All three of these technical solutions can reduce the magnetostriction of the oriented silicon steel finished plate, thereby reducing the transformer noise level.

[0008] Chinese patent document CN107210109A, published on September 27, 2017, entitled "Oriented Electromagnetic Steel Sheet and its Manufacturing Method and Method for Predicting Transformer Noise Characteristics," discloses an oriented electromagnetic steel sheet, its manufacturing method, and a method for predicting transformer noise characteristics. Regarding the magnetostrictive characteristics of the oriented electromagnetic steel sheet, this patent discloses a technical solution that controls the surface-back tension difference of the forsterite coating to be above 0.5 MPa while the total surface-back tension difference between the forsterite and the insulating coating is less than 0.5 MPa. It sets the acceleration or deceleration points under the magnetostrictive velocity level (dλdt) to four within one cycle of magnetostrictive vibration, and sets the velocity level change of adjacent velocity change points within the acceleration or deceleration region of the magnetostrictive vibration to 3.0 × 10⁻⁶. 4 The reduction of magnetostrictive properties is achieved within seconds. However, this technical solution, by adjusting the tension difference of MgO and the total tension difference of MgO + insulating coating, has limited improvement on the double-sided magnetostriction difference of single-sided laser-marked oriented silicon steel substrates, and is difficult to control. It is difficult to mass-produce oriented electromagnetic steel sheets with excellent noise characteristics and small deviation between the upper and lower surfaces of magnetostriction at a reasonable cost.

[0009] Chinese patent document CN106460111A, published on February 22, 2017, entitled "Low Iron Loss and Low Magnetostriction Directional Electromagnetic Steel Sheet," discloses a directional electromagnetic steel sheet with low iron loss and low magnetostriction. The directional electromagnetic steel sheet of this invention comprises a steel sheet substrate, a primary coating formed on the surface of the steel sheet substrate, and a tension insulating coating formed on the surface of the primary coating. The coating meets the following conditions: the ratio of the tension insulating coating thickness to the primary coating thickness is controlled to be ∈ (0.1, 3), the tension insulating coating thickness is controlled to be ∈ (0.5, 4.5) μm, and the total tension of the primary coating and the tension insulating coating is controlled to be ∈ (1, 10) MPa. Magnetic domain control is achieved by irradiating a laser onto the tension insulating coating. A strip sample with a length of 300 mm parallel to the rolling direction and a length of 60 mm parallel to the width direction is taken from the aforementioned directional electromagnetic steel sheet. At least one side of the sample is pickled to remove a portion from the surface of the tension insulating coating to a depth of 5 μm from the interface between the steel sheet substrate and the primary coating towards the steel sheet substrate. The warpage of the sample is then measured, and the warpage meets the specified conditions. However, this technical solution only considers the film thickness and tension of the primary coating and the tension insulating coating, resulting in limited improvement on the magnetostriction of the oriented silicon steel substrate and significant control difficulties. It is challenging to mass-produce oriented electromagnetic steel sheets with excellent noise characteristics and small magnetostrictive surface deviations at a reasonable cost.

[0010] Chinese patent document CN106029917A, published on October 12, 2016, entitled "Oriented Electromagnetic Steel Plate for Low-Noise Transformer and Manufacturing Method Thereof," discloses an oriented electromagnetic steel plate obtained by irradiating the surface of the steel plate with an electron beam having a diameter d of less than 0.40 m in a line region intersecting the rolling direction to perform magnetic domain refinement treatment. The plate forms a modulated irradiation line region in which repeating units are connected in the line region direction, and the period of the repeating unit in this modulated irradiation line region is set to 2. The modulated irradiation line region is set to repeat at intervals of 4.0 to 12.5 mm in the rolling direction, with a diameter of 3×d to 2.5×d mm. Furthermore, the electron beam intensity is set above the intensity required to form elongated, segmented magnetic domains along the modulated irradiation line region on the irradiated surface side, but below the intensity required to prevent coating damage and the formation of plastic strain regions on the irradiated surface side. This allows for magnetic domain refinement while simultaneously achieving low iron loss and low noise levels, conditions previously difficult to meet in transformers. It also enables the production of orientation-oriented electromagnetic steel sheets with low iron loss and low magnetostriction, a feature not previously observed. However, this technical solution only considers the influence of scoring conditions on magnetostriction, neglecting the matching issue between scoring and coating conditions. This makes it difficult to effectively mass-produce, stably, and cost-effective orientation-oriented electromagnetic steel sheets with excellent noise characteristics and minimal magnetostriction deviation between the upper and lower surfaces.

[0011] In summary, in view of the defects and deficiencies existing in the prior art, the present invention aims to provide a manufacturing method for low magnetostriction oriented silicon steel, which can solve the problem that uneven stress distribution introduced by single-sided laser marking causes the steel plate to bend towards the marked surface, resulting in excessive magnetostriction deviation between the marked and non-marked surfaces of the oriented silicon steel. Summary of the Invention

[0012] One of the objectives of this invention is to provide a method for manufacturing low magnetostriction oriented silicon steel. This method can solve the problem that existing laser-etching processes are used to obtain thin-gauge oriented silicon steel with low loss. However, due to the uneven stress distribution introduced by single-sided laser etching, the steel plate bends towards the etched surface, resulting in excessive magnetostriction deviation between the etched and non-etched surfaces of the oriented silicon steel.

[0013] To achieve the above objectives, the present invention provides a method for manufacturing low magnetostriction oriented silicon steel, comprising the steps of: (a) smelting and casting; (b) heating; (c) normalizing; (d) cold rolling; (e) decarburization annealing; (f) finished product annealing; and (g) hot stretching annealing including coating with an insulating coating; wherein step (g) includes:

[0014] (1) Apply an insulating coating of equal amount to both surfaces of the silicon steel substrate;

[0015] (2) Sintering and cooling;

[0016] (3) A single-sided laser marking is performed on one surface of a silicon steel substrate coated with an insulating coating, wherein the side with the single-sided laser marking is defined as the first surface and the other side opposite to the first surface is defined as the second surface.

[0017] (4) Detect the deflection difference between the first surface and the second surface, and adjust the difference in the amount of insulating coating on the first surface and the second surface based on the deflection difference; wherein the amount of insulating coating on the second surface is greater than the amount of insulating coating on the first surface.

[0018] In the technical solution described in this invention, the inventors have optimized the process flow of step (g) above. This requires first coating two surfaces of the silicon steel substrate with an equal amount of insulating coating, and then baking and sintering the insulating coating to form an insulating coating on both the first and second surfaces. The baking and sintering steps of the insulating coating can be performed according to existing technology, which enables the formation of an insulating coating of the same thickness on both surfaces of the silicon steel substrate.

[0019] Accordingly, for two silicon steel substrates with insulating coatings of the same thickness on both surfaces, the power of laser marking can be optimized based on the improvement rate of magnetic properties P17 / 50 and magnetostriction. By detecting the difference in deflection (representing the distance from the center of the bent end face of the steel plate to the original axis) of the first and second surfaces of the silicon steel substrate with the same amount of insulating coating after laser marking, the difference in the amount of insulating coating applied to the first and second surfaces before marking is adjusted according to the deflection difference.

[0020] Based on this, by adjusting the difference in the amount of insulating coating on the first and second surfaces to adjust the coating tension difference, the deflection difference between the first and second surfaces of the oriented silicon steel finished product caused by the uneven stress distribution introduced by single-sided laser marking can be effectively reduced, thus avoiding the reduction of magnetostriction deviation between the first and second surfaces.

[0021] In fact, single-sided laser etching on a silicon steel substrate with an insulating coating is a common practice in the prior art for refining magnetic domains in oriented silicon steel and reducing losses. Therefore, the manufacturing method designed in this invention has a very broad prospect for practical application.

[0022] Furthermore, in the manufacturing method of the present invention, in step (3), the coating amount difference of the insulating coating is determined based on the following formula:

[0023] Difference in insulation coating coverage = 3 × 10 -5 -0.407 × deflection difference, where the unit parameter for the difference in insulation coating coverage is g / m 2 The unit parameter for deflection difference is mm.

[0024] Furthermore, in the manufacturing method described in this invention, in step (2), the laser power X for single-sided laser marking is determined based on the following formula:

[0025] The set target value for magnetostriction is -0.0006 * X. 5 +0.012*X 4 -0.04*X 3 -0.18*X 2 +0.37*X+54.8; or

[0026] The set improvement rate of iron loss P17 / 50 before and after laser scoring is -0.177*X. 2 +3.2*X-2.4;

[0027] The unit parameter for the magnetostriction target value is db(A), and the unit parameter for the laser power is mJ / mm². 2 .

[0028] Furthermore, in the manufacturing method described in this invention, the components of the insulating coating are:

[0029] At least one of aluminum dihydrogen phosphate and magnesium dihydrogen phosphate: 2% to 25%;

[0030] Colloidal silica: 4%–16%;

[0031] Chromic anhydride: 0.15%–4.50%;

[0032] The remainder consists of water and other unavoidable impurities.

[0033] In the manufacturing method described above, the insulating coating can be used to improve the insulation of the silicon steel substrate surface. The insulating coating solution widely used in the prior art is an aqueous solution mainly composed of chromic anhydride, colloidal silica, and phosphates of Mg and Al. The designed insulating coating solution, after sintering, forms a transparent insulating coating on the surface of the silicon steel substrate, and the laser can directly reach the surface of the silicon steel substrate during subsequent laser marking.

[0034] Furthermore, in the manufacturing method described in this invention, in step (1), the initial coating amount on both surfaces is 4.0–4.5 g / m². 2 .

[0035] In this invention, the initial coating amount of the first and second surfaces can preferably be controlled at 4.0-4.5 g / m². 2 Between. Specifically, when the coating amount is less than 4.0 g / m². 2 When the insulating coating is too thin, the tensile strength imparted to the silicon steel substrate is low, resulting in insufficient magnetic optimization. However, when the coating thickness exceeds 4.5 g / m², the insulation coating becomes too thin. 2If the insulation coating is too thick, it will not only affect the stacking coefficient of the finished product, but also easily cause defects such as powdering and white edges during the shearing process.

[0036] Furthermore, in the manufacturing method described in this invention, in step (2): first, the temperature is heated to 800-900°C and held for 10-30 seconds, and then cooled to room temperature at a cooling rate of 5°C / s to 50°C / s.

[0037] Furthermore, in the manufacturing method described in this invention, in step (c), a two-stage normalization process is adopted: first, the temperature is heated to 1100-1200°C, and then cooled to 900-1000°C at a cooling rate of 1°C / s to 10°C / s; subsequently, the temperature is cooled to room temperature at a cooling rate of 10°C / s to 70°C / s.

[0038] Furthermore, in the manufacturing method described in this invention, in step (d), the cold rolling is performed by a single cold rolling or a two-stage cold rolling with an intermediate annealing step.

[0039] Furthermore, in the manufacturing method described in this invention, in step (e), a recrystallization annealing is performed at a temperature of 800–900°C, followed by coating with an annealing release agent.

[0040] In the above technical solution, in the existing process of preparing oriented silicon steel, an annealing release agent, such as magnesium oxide, needs to be applied to the surface of the silicon steel substrate before high-temperature annealing to prevent the steel plates from sticking together in a high-temperature environment.

[0041] Furthermore, in the manufacturing method described in this invention, in step (f), the annealing temperature is 1100-1200°C, and the holding time is 20-30 hours.

[0042] Accordingly, another object of the present invention is to provide a low magnetostriction oriented silicon steel sheet with very small magnetostriction deviation between the scored and unscored surfaces, and good average magnetostriction. The core made from this low magnetostriction oriented silicon steel sheet produces less vibration, thereby resulting in a low overall noise level for transformers with such cores.

[0043] To achieve the above objectives, the present invention proposes a low magnetostriction oriented silicon steel sheet, which is prepared by the above-described method for manufacturing low magnetostriction oriented silicon steel sheets.

[0044] Furthermore, in the manufacturing method described in this invention, the thickness is 0.18mm-0.23mm.

[0045] In this invention, the finished thickness of the low magnetostriction oriented silicon steel sheet is generally preferably controlled between 0.18 mm and 0.23 mm. When the finished thickness of the steel sheet is greater than 0.23 mm, the increased thickness leads to increased stiffness. After the formation of the insulating coating on the surface, the sheet becomes less sensitive to uneven stress distribution caused by laser marking, resulting in a smaller deflection difference caused by the uneven stress distribution due to marking.

[0046] Furthermore, in the manufacturing method described in this invention, the magnetostriction deviation between the first and second surfaces of the low magnetostriction oriented silicon steel is ≤2 dB(A), and the average magnetostriction of the low magnetostriction oriented silicon steel is ≤55 dB(A).

[0047] Compared with the prior art, the manufacturing method of the low magnetostriction oriented silicon steel sheet and the oriented silicon steel sheet of the present invention have the following advantages and beneficial effects:

[0048] The manufacturing method of low magnetostriction oriented silicon steel sheet described in this invention can solve the problem that uneven stress distribution introduced by single-sided laser marking in oriented silicon steel causes the steel sheet to bend towards the marked surface, resulting in excessive magnetostriction deviation between the marked and non-marked surfaces of the oriented silicon steel.

[0049] The manufacturing method of the present invention can be used to score a silicon steel substrate with the same amount of insulating coating on both sides, and obtain the difference in the tension of the insulating coating on the first surface and the second surface based on the deflection difference between the scored surface and the non-scored surface of the steel plate, so as to adjust the difference in the amount of insulating coating on the scored surface (first surface) and the non-scored surface (second surface), thereby reducing the magnetostriction deviation of the scored surface and the non-scored surface.

[0050] In this invention, the low magnetostriction oriented silicon steel sheet can achieve a magnetostriction deviation of ≤2dB(A) between the first and second surfaces, and an average magnetostriction of ≤55dB(A). The core made of this low magnetostriction oriented silicon steel produces low vibration, thereby making the transformer with such a core have a low overall noise level, which has excellent practical prospects. Attached Figure Description

[0051] Figure 1 The diagram schematically shows the curves of magnetostriction and magnetic improvement rate of the scored surface of the low magnetostriction oriented silicon steel sheet described in this invention as a function of laser scoring energy density.

[0052] Figure 2 The diagram schematically illustrates the curve showing the change in deflection difference between the first and second surfaces of a silicon steel substrate with the same amount of insulating coating on both sides as a function of laser marking energy density after single-sided laser marking.

[0053] Figure 3The illustration schematically shows the difference in the amount of insulating coating on the first and second surfaces required for the low magnetostriction oriented silicon steel of the present invention to remain straight under different deflection differences. Detailed Implementation

[0054] The manufacturing method of the low magnetostriction oriented silicon steel sheet and the oriented silicon steel sheet of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings. However, such explanation and description do not constitute an improper limitation on the technical solution of the present invention.

[0055] Examples 1-6 and Comparative Examples 1-4

[0056] The low magnetostriction grain-oriented silicon steel sheets of Examples 1-6 and the comparative grain-oriented silicon steel sheets of Comparative Examples 1-4 were all prepared using the following steps:

[0057] (a) Smelt according to the chemical composition shown in Table 1 and cast into slabs.

[0058] (b) Heating: Heat to 1200~1280℃, hold for 1~4h, and hot roll into strip steel.

[0059] (c) Normalization: A two-stage normalization process is adopted. First, the temperature is heated to 1100-1200℃, and then cooled to 900-1000℃ at a cooling rate of 1℃ / s to 10℃ / s. Subsequently, the temperature is cooled to room temperature at a cooling rate of 10℃ / s to 70℃ / s.

[0060] (d) Cold rolling: using a single cold rolling process or a two-stage cold rolling process with an intermediate annealing step.

[0061] (e) Decarburization annealing: Perform recrystallization annealing at a temperature of 800–900°C, and then coat with an annealing release agent.

[0062] (f) Finished product annealing: annealing temperature 1100~1200℃, holding temperature for 20-30h.

[0063] (g) Applying an insulating coating and hot stretching annealing to the annealed silicon steel substrate to prepare a low magnetostriction oriented silicon steel sheet with a thickness of 0.18 mm-0.23 mm:

[0064] First, an insulating coating of equal amount is applied to both surfaces of the silicon steel substrate. Then, baking and sintering are carried out, with the temperature controlled at 800-900℃ and held for 10-30 seconds. Then, the substrate is cooled to room temperature at a cooling rate of 5℃ / s-50℃ / s to obtain a silicon steel substrate containing an insulating coating.

[0065] One surface of a silicon steel substrate coated with an insulating coating is laser-etched on one side, wherein the side with the laser-etched surface is defined as the first surface and the other side opposite the first surface is defined as the second surface; the deflection difference between the first surface and the second surface is detected, and the difference in the amount of insulating coating on the first surface and the second surface is adjusted based on the deflection difference; wherein the amount of insulating coating on the second surface is greater than the amount of insulating coating on the first surface.

[0066] It should be noted that, in this invention, in step (g) above, the laser power X for single-sided laser marking can be determined by a set magnetostriction target value or a set improvement rate of iron loss P17 / 50 before and after laser marking. The set magnetostriction target value is -0.0006*X. 5 +0.012*X 4 -0.04*X 3 -0.18*X 2 +0.37*X+54.8; The set improvement rate of iron loss P17 / 50 before and after laser scoring = -0.177*X 2 +3.2*X-2.4; and the unit parameter for the magnetostriction target value is db(A), and the unit parameter for the laser power is mJ / mm². 2 .

[0067] Accordingly, the coating amount difference of the insulating coating can also be determined based on the following formula: Insulating coating amount difference = 3 × 10 -5 -0.407 × deflection difference, where the unit parameter for the difference in insulation coating coverage is g / m 2 The unit parameter for deflection difference is mm.

[0068] It should be noted that, in this invention, the relevant operations and specific manufacturing process parameters of the low magnetostriction oriented silicon steel sheets of Embodiments 1-6 all meet the design specifications of the preferred technical solution of this invention. However, the comparative oriented silicon steel sheets of Comparative Examples 1-4 do not control the difference in the amount of insulating coating applied based on the difference in deflection between the first and second surfaces caused by laser marking.

[0069] Table 1 lists the mass percentage of each chemical element in the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4.

[0070] Table 1. (wt%, balance is Fe and other unavoidable impurities)

[0071]

[0072]

[0073] In this invention, in order to obtain low magnetostriction oriented silicon steel with target performance, the operator needs to laser-scrib the first surface of a silicon steel substrate with the same amount of insulating coating on both sides; then detect the deflection difference between the first and second surfaces caused by the laser scribing, and determine the difference in the amount of insulating coating to be adjusted based on the deflection difference; then adjust the amount of insulating coating on the first and second surfaces before scribing to obtain low magnetostriction oriented silicon steel.

[0074] It should be noted that, in this embodiment, the specific components of the insulating coating applied to the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4 can be: at least one of aluminum dihydrogen phosphate and magnesium dihydrogen phosphate: 2% to 25%; colloidal silica: 4% to 16%; chromic anhydride: 0.15% to 4.50%; the remainder being water.

[0075] Table 2 lists the specific chemical composition of the insulating coatings applied to the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4.

[0076] Table 2. (wt%, balance is water and other unavoidable impurities)

[0077] serial number Aluminum dihydrogen phosphate Magnesium dihydrogen phosphate Colloidal silica Chromic anhydride Example 1 2％ 0 4％ 0.15％ Example 2 0 2％ 8％ 1％ Example 3 4％ 4％ 10％ 2％ Example 4 8％ 8％ 14％ 3％ Example 5 25％ 0 16％ 4％ Example 6 0 25％ 16％ 4.5％ Comparative Example 1 12％ 0 16％ 4.5％ Comparative Example 2 0 8％ 10％ 2％ Comparative Example 3 10％ 10％ 15％ 3％ Comparative Example 4 10％ 5％ 15％ 2％

[0078] Table 3-1 lists the specific process parameters for the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4.

[0079] Table 3-1.

[0080]

[0081] Table 3-2 lists the power of single-sided laser marking on the silicon-based steel plates of Examples 1-6 and the comparative steel plates of Comparative Examples 1-4, as well as the deflection difference, the amount of insulating coating on the surface, and the difference in the amount of insulating coating on the two surfaces of the resulting oriented silicon steel.

[0082] Table 3-2.

[0083]

[0084] As can be seen from Tables 3-1 and 3-2, the initial coating amount of the insulating coating on the first surface and the second surface is the same. The subsequent steps are to detect the deflection difference between the first surface and the second surface and adjust the coating amount difference of the insulating coating on the first surface and the second surface based on the deflection difference. The specific operation steps are to keep the coating amount of the insulating coating on the first surface unchanged, while adjusting the coating amount of the insulating coating on the second surface to be greater than that on the first surface.

[0085] Samples of the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4 were taken respectively, and the magnetostriction performance (magnetostriction velocity sound pressure level LvA) of the steel sheet samples of each example and comparative example was measured using a non-contact laser Doppler vibrometer TD9600 under the conditions of B=1.7T and f=-2MPa (in the actual working condition of the transformer, the oriented silicon steel is subjected to a compressive stress of 2-3MPa). The specific measurement method can be found in the IEC (International Electrotechnical Commission) technical report - IEC / TP 62581. The test results of the magnetostriction performance of each example and comparative example are listed in Table 4.

[0086] Table 4 lists the performance test results of the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4.

[0087] Table 4.

[0088]

[0089] Accordingly, 240KVA three-phase transformers were further fabricated using the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4, respectively. The noise of the three-phase transformers fabricated in each example and comparative example was tested under a magnetization condition of 50Hz and 1.7T (GB / T 1094.10-2003), and the test results are listed in Table 5.

[0090] Table 5 lists the noise test results of 240KVA three-phase transformers made from the low magnetostriction oriented silicon steel sheets of Examples 1-6 and the comparative oriented silicon steel sheets of Comparative Examples 1-4.

[0091] Table 5.

[0092]

[0093] As can be seen from Tables 4 and 5, the performance of each embodiment of the present invention is better than that of comparative examples 1-4. The magnetostriction deviation of the first and second surfaces of the low magnetostriction oriented silicon steel in each embodiment is significantly smaller than that of the comparative oriented silicon steel sheets of comparative examples 1-4.

[0094] As shown in Table 4, the magnetostriction deviation of the first and second surfaces of the low magnetostriction oriented silicon steel in Examples 1-6 is ≤2 dB(A), and their average magnetostriction is ≤55 dB(A). Correspondingly, as shown in Table 5, compared with Comparative Examples 1-4, the overall noise level of the 240 KVA three-phase transformer made from the low magnetostriction oriented silicon steel sheets of Examples 1-6 is significantly lower.

[0095] Figure 1 The diagram schematically shows the curves of magnetostriction and magnetic improvement rate of the scored surface of the low magnetostriction oriented silicon steel sheet described in this invention as a function of laser scoring energy density.

[0096] like Figure 1 As shown, with the increase of laser marking energy density, the magnetic properties of low magnetostriction oriented silicon steel sheets first increase and then tend to stabilize, while the magnetostriction performance first decreases and then increases.

[0097] Figure 2 The diagram schematically illustrates the curve showing the change in deflection difference between the first and second surfaces of a silicon steel substrate with the same amount of insulating coating on both sides as a function of laser marking energy density after single-sided laser marking.

[0098] from Figure 2 As can be seen, after single-sided laser marking is performed on a silicon steel substrate with the same amount of insulating coating on both sides as described in this invention, the deflection difference between the first and second surfaces of the silicon steel substrate will first increase and then tend to stabilize as the laser marking energy density increases.

[0099] Figure 3 The illustration schematically shows the difference in the amount of insulating coating on the first and second surfaces required for the low magnetostriction oriented silicon steel of the present invention to remain straight under different deflection differences.

[0100] like Figure 3 As shown, in order to maintain the flatness of the finished grain-oriented silicon steel and reduce the magnetostriction deviation on both sides, it is necessary to adjust the difference in the amount of insulating coating on the first and second surfaces according to the deflection difference caused by laser marking.

[0101] In summary, the manufacturing method of low magnetostriction oriented silicon steel in this invention can adjust the tension difference of the insulating coating on the etched and non-etched surfaces of a silicon steel substrate with consistent insulating coating on both sides by laser etching on one side, thereby reducing the magnetostriction deviation between the etched and non-etched surfaces of the oriented silicon steel.

[0102] The low magnetostriction oriented silicon steel produced by the above manufacturing method can ensure that the magnetostriction deviation of the oriented silicon steel with and without the etched surface is ≤2dB(A), and the average magnetostriction is ≤55dB(A). The core made of this low magnetostriction oriented silicon steel produces less vibration, thereby resulting in a low overall noise level for transformers with such cores.

[0103] It should be noted that the scope of protection of the prior art in this invention is not limited to the embodiments given in this application. All prior art that does not contradict the solution of this invention, including but not limited to prior patent documents, prior publications, prior public uses, etc., can be included in the scope of protection of this invention.

[0104] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0105] It should also be noted that the above examples are merely specific embodiments of the present invention, and the present invention is obviously not limited to the above embodiments, with many similar variations. All modifications that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should fall within the protection scope of this invention.

Claims

1. A method for manufacturing low magnetostriction oriented silicon steel, comprising the steps of: (a) smelting and casting; (b) heating; (c) normalizing; (d) cold rolling; (e) decarburization annealing; (f) finished product annealing; and (g) hot stretching annealing including coating with an insulating coating; characterized in that, Step (g) includes: An insulating coating of equal amount is applied to both surfaces of the silicon steel substrate. Sintering and cooling; (3) A single-sided laser marking is performed on one surface of a silicon steel substrate coated with an insulating coating, wherein the side with single-sided laser marking is defined as the first surface, and the other side opposite the first surface is defined as the second surface; wherein the laser power X for single-sided laser marking is determined based on the following formula: Set magnetostrictive target value = -0.0006*X 5 + 0.012*X 4 - 0.04*X 3 - 0.18*X 2 + 0.37*X + 54.8 or P of iron loss before and after the set laser scribe 17 / 50 Improvement rate = -0.177 * X 2 + 3.2 * X - 2.4; The unit parameter for the magnetostriction target value is db(A), and the unit parameter for the laser power is mJ / mm². 2 ; (4) Detect the deflection difference between the first surface and the second surface, and adjust the difference in the amount of insulating coating on the first surface and the second surface based on the deflection difference; wherein the amount of insulating coating on the second surface is greater than the amount of insulating coating on the first surface, and the difference in the amount of insulating coating is determined based on the following formula: Difference in the amount of insulating coating = 3 × 10 -5 -0.407 × deflection difference, where the unit parameter for the difference in insulation coating coverage is g / m 2 The unit parameter for deflection difference is mm.

2. The manufacturing method as described in claim 1, characterized in that, The components of the insulating coating are: At least one of aluminum dihydrogen phosphate and magnesium dihydrogen phosphate: 2%–25%; Colloidal silica: 4%–16%; Chromic anhydride: 0.15%–4.50%; The remainder consists of water and other unavoidable impurities.

3. The manufacturing method as described in claim 1, characterized in that, In step (1), the initial coating amount for both surfaces is 4.0~4.5 g / m². 2 .

4. The manufacturing method as described in claim 1, characterized in that, In step (2): First, heat to 800-900℃, hold for 10-30s, and then cool down to room temperature at a rate of 5℃ / s to 50℃ / s.

5. The manufacturing method as described in claim 1, characterized in that, In step (c), a two-stage normalization process is adopted: first, the temperature is heated to 1100-1200°C, and then cooled to 900-1000°C at a cooling rate of 1°C / s to 10°C / s; subsequently, the temperature is cooled to room temperature at a cooling rate of 10°C / s to 70°C / s.

6. The manufacturing method as described in claim 1, characterized in that, In step (d), the cold rolling is performed by a single cold rolling or a two-stage cold rolling with an intermediate annealing step.

7. The manufacturing method as described in claim 1, characterized in that, In step (e), a recrystallization annealing is performed at a temperature of 800–900 °C, followed by coating with an annealing release agent.

8. The manufacturing method as described in claim 1, characterized in that, In step (f), the annealing temperature is 1100-1200℃, and the holding time is 20-30h.

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