Method for producing an oriented silicon steel and product thereof

Abstract

The application provides a preparation method of oriented silicon steel and a product thereof, and comprises the following steps: a coating liquid needs to be subjected to ball milling treatment before coating, the ball milling time is 2-4 hours, and the slurry particle size D50 is less than 2 microns; and the coating liquid is coated on the surface of the oriented silicon steel strip after completing secondary recrystallization annealing, and the raw material ratio of the coating liquid is as follows: water 630 parts, magnesium oxide 75 parts, titanium dioxide 4.8 parts, and boride 1.1 part by weight. The application significantly reduces the consumption of magnesium oxide raw material, saves the production cost, ensures the excellent and stable quality of the magnesium silicate bottom layer, finally makes the obtained oriented silicon steel obtain excellent magnetic properties of lower iron loss and higher magnetic induction, and realizes the best balance between the cost and the performance.

Description

Technical Field

[0001] This invention relates to a method for preparing oriented silicon steel and its product. Background Technology

[0002] Grain-oriented silicon steel is an important soft magnetic material mainly used in the manufacture of transformer cores, and its magnetic properties (such as iron loss and magnetic flux density) are core indicators. In the manufacturing process of grain-oriented silicon steel, a magnesium oxide coating needs to be applied to the surface of the steel strip, and during high-temperature annealing, it reacts with the silica on the surface of the steel strip substrate to form an excellent insulating underlayer—magnesium silicate. The quality of this magnesium silicate underlayer directly determines the iron loss and magnetic flux density of the final product. Theoretically, only about 2.5~3 grams of magnesium oxide per square meter is needed to complete the magnesium silicate reaction. However, in actual industrial production, due to the difficulty in perfectly controlling the coating uniformity, and to ensure the absolute quality of the underlayer (i.e., "safety considerations"), the industry generally uses a coating amount far exceeding this theoretical value. This excessive coating not only causes a serious waste of magnesium oxide raw materials and increases production costs, but also restricts the speed of the production line due to problems such as excessively thick coatings, thus affecting overall production efficiency. Furthermore, the water content of the coating solution is also a key but often roughly controlled parameter. Excessive or insufficient moisture content can affect the adhesion and leveling of the coating on the steel strip surface, as well as the sufficiency of subsequent high-temperature reactions, thereby affecting the quality of the substrate and product consistency.

[0003] Therefore, there has long been a pressing technical challenge in this field: how to significantly reduce the amount of magnesium oxide coating to save costs and improve efficiency while ensuring or even optimizing the quality of the magnesium silicate underlayer, thereby guaranteeing the excellent magnetic properties of the product. Summary of the Invention

[0004] This invention provides a method for preparing oriented silicon steel and its product, which can effectively solve the above-mentioned problems.

[0005] This invention is implemented as follows:

[0006] A method for preparing grain-oriented silicon steel and the product thereof, comprising the following steps:

[0007] S1. The coating liquid needs to be ball-milled before coating. The ball-milling time is 2 to 4 hours until the slurry particle size D50 < 2μm. The coating liquid is then applied to the surface of the oriented silicon steel strip that has undergone secondary recrystallization annealing. The raw material ratio of the coating liquid by weight is: 630 parts water, 75 parts magnesium oxide, 4.8 parts titanium dioxide, and 1.1 parts boride.

[0008] S2. Coating is performed using a coating machine with a double spring adjustment mechanism and a specific coating roller, the parameters of which are: a groove distribution density of 32 to 36 teeth per inch, a groove depth of 0.45 mm on the upper roller, a groove depth of 0.55 mm on the lower roller, and a roller body hardness of 60 to 65 Shore hardness.

[0009] S3. Control the coating amount on both the upper and lower surfaces of the oriented silicon steel strip to be 6.5~7.5 g / m².

[0010] S4. The coated oriented silicon steel strip is dried and sintered. When the unit operates at a speed of 50 m / min, the drying and sintering process is divided into two zones: zone 1 has a temperature of 550~560℃ and zone 2 has a temperature of 530~550℃. The final result of drying and sintering is to control the moisture content of the upper and lower surfaces of the coating to be 1.0~1.3%.

[0011] S5. Perform hot leveling annealing to obtain iron loss. P17 / 50 <0.86 W / kg and magnetic induction B 8000 >1.87 T oriented silicon steel.

[0012] The beneficial effects of this invention are:

[0013] (1) By precisely and synergistically controlling the amount of magnesium oxide coating and the moisture content after drying within a narrow window of 6.5~7.5 g / m² and 1.0~1.3%, this invention successfully breaks through the industry's technical prejudice that "high coating amount can guarantee quality." This significantly reduces the consumption of magnesium oxide raw materials and saves production costs while ensuring the excellent and stable quality of the magnesium silicate underlayer. Ultimately, the resulting oriented silicon steel achieves superior magnetic properties with lower iron loss and higher magnetic induction, thus achieving the best balance between cost and performance. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a process flow diagram of the present invention.

[0016] Figure 2 This is a schematic diagram of the double-spring structure in the device of the present invention.

[0017] Figure 3 This is a bar chart comparing the performance of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0019] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] Reference Figure 1-3 As shown, a method for preparing oriented silicon steel includes the following steps:

[0021] S1. Coat the surface of the oriented silicon steel strip that has undergone secondary recrystallization annealing with a magnesium oxide coating liquid; the raw material ratio of the magnesium oxide coating liquid by weight is: 630 parts water, 75 parts magnesium oxide, 4.8 parts titanium dioxide, and 1.1 parts boride.

[0022] S2. Control the coating amount on both the upper and lower surfaces of the oriented silicon steel strip to be 6.5~7.5 g / m².

[0023] S3. The coated oriented silicon steel strip is dried and sintered, and the final result of drying and sintering is controlled so that the moisture content of the upper and lower surfaces of the coating is 1.0~1.3%;

[0024] S4. Perform hot leveling annealing to obtain the oriented silicon steel.

[0025] In step S2, the parameters of the specific coating roller are: a groove distribution density of 32 to 36 teeth per inch, a groove depth of 0.45 mm on the upper roller, a groove depth of 0.55 mm on the lower roller, and a roller hardness of 60 to 65 Shore A.

[0026] It should be noted that, due to gravity, the lower roller needs to carry more coating liquid and overcome the tendency of the liquid to drip. Therefore, setting the groove depth of the lower roller (0.55 mm) to be slightly larger than that of the upper roller (0.45 mm) allows for the storage and transfer of slightly more slurry to compensate for the effect of gravity, thereby achieving consistent coating amounts on the upper and lower surfaces.

[0027] Specifically, in step S2, the coating liquid prepared in S1 is injected into the material tank of the coating machine, so that the oriented silicon steel strip passes through the coating roller at a certain speed (e.g., 50 m / min). By precisely adjusting the pressure of the double springs, the roller speed ratio (the ratio of the linear speed of the coating roller to that of the steel strip), and the liquid level in the material tank, the coating amount is strictly controlled so that the wet coating amount on both the upper and lower surfaces is stable within the range of 6.5~7.5 g / m².

[0028] In step S2, coating is performed using a coating machine with a double-spring adjustment mechanism and a specific coating roller. The double-spring structure is symmetrically arranged on both sides of the coating roller bearing seat to ensure that the pressure applied to the roller body is evenly distributed along the axial direction. This structure allows the coating amount difference (the difference between the maximum and minimum values) in the width direction of the steel strip to be controlled within ±0.3 g / m², thus forming a sharp and quantitative contrast with the "transverse stripes" that appeared in Comparative Example 4.

[0029] In step S3, when the unit operates at a speed of 50 m / min, the drying and sintering process is divided into two zones, with zone 1 having a temperature of 550~560℃ and zone 2 having a temperature of 530~550℃.

[0030] The first zone (entry zone) is set at a temperature of 550~560℃. This zone is mainly responsible for rapidly evaporating most of the free water, but the temperature is not too high to cause the coating to boil violently. The second zone (exit zone) is set at a temperature of 530~550℃. This zone is slightly cooler and is responsible for gently removing the remaining bound water and allowing the coating to initially cure and form a certain mechanical strength.

[0031] It should be noted that the drying and sintering temperatures (550~560℃ in Zone 1, 530~550℃ in Zone 2) are set based on a unit speed of 50 m / min. When the speed fluctuates within ±10 m / min, a constant dehydration curve can be maintained by proportionally adjusting the temperature of each zone (for example, increasing the temperature of each zone by 5~10℃ for every 5 m / min increase in speed), thereby ensuring that the final moisture content remains stable within the target range of 1.0~1.3%.

[0032] Furthermore, the main function of the first zone (550~560℃) is to provide sufficient heat energy to match the production line speed and quickly evaporate and remove the vast majority (e.g., over 90%) of the 'free water' in the coating. This upper temperature limit (560℃) aims to achieve efficient dehydration while ensuring that the coating surface does not 'boil' or 'splash' due to violent vaporization of water. The main function of the second zone (530~550℃) is not to remove a large amount of water, but to perform 'stable curing'. After the rapid dehydration in the first zone, the coating mainly contains 'bound water' that is more tightly bound to the magnesium oxide particles. If the high temperature is maintained at this point, it will lead to: excessive sintering of the surface layer: the coating surface forms a dense shell too early, hindering the escape of the remaining internal water, which may even form bubbles in subsequent processes; stress concentration: the difference in drying rate between the inside and outside of the coating is too large, generating internal stress and affecting the adhesion of the underlying layer. Therefore, by appropriately lowering the temperature of the second zone to create a gentle cooling gradient, the following can be achieved: gradual removal of bound water: allowing bound water molecules sufficient time to migrate from the interior of the particles to the surface for evaporation, thus avoiding damage to the coating structure due to abrupt phase changes; and promoting uniform curing of the coating: enabling the coating to lose moisture uniformly from the inside out and initially establishing stable mechanical strength, thus preparing it for subsequent high-temperature annealing.

[0033] To demonstrate the cooling processes in the two zones mentioned above, a comparison is made as follows:

[0034] All other conditions are exactly the same as in Example 4, except that the drying and sintering furnace is set to a single constant temperature zone and the temperature is set to 555°C (that is, the same as the temperature of the first zone of the present invention).

[0035] Results: The following issues were observed in the coating after it was removed from the oven: Surface quality: Microbubbles and dot-like protrusions were observed in some areas; Microstructure: Scanning electron microscopy (SEM) showed that the surface structure of the coating was dense, but there were closed pores underneath; Performance: After final annealing, the pass rate of the underlayer adhesion test for this batch of products decreased by about 15%.

[0036] Comparative experiments have shown that although constant temperature processes can also remove moisture, a single rapid dehydration mechanism can damage the internal structure of the coating, while the two-zone cooling process of this invention can effectively avoid such defects.

[0037] By controlling the coating amount and moisture content, the effective amount of magnesium oxide used to form the magnesium silicate underlayer is 2.5~3 g / m². Specifically, the moisture content of the coating at the steel strip exit is monitored in real time using an online infrared moisture meter, and the temperature setting is fine-tuned through a feedback system to ensure that the moisture content of both the upper and lower surfaces of the coating is strictly controlled within the optimal range of 1.0~1.3% upon exiting the furnace. Thus, through the control of this system, the effective amount of magnesium oxide used to form the magnesium silicate underlayer is precisely controlled at 2.5~3.0 g / m², achieving optimal use of raw materials while ensuring the quality of the underlayer.

[0038] It should be noted that, theoretically, approximately 2.5–3.0 g / m² of magnesium oxide is required to form a complete underlayer. However, considering the 'retention effect' of magnesium oxide particles on the rough surface of the silicon steel strip and the 'reactive inert nuclei' at high temperatures, a certain excess must be provided. Through systematic optimization, this invention has found that when the excess is controlled at 3.5–4.5 g / m² (i.e., a total coating amount of 6.5–7.5 g), sufficient reactants in the microscopic local areas can be ensured, while excessive coating can prevent cracking due to excessive internal stress during sintering. Below this range, the underlayer will be incomplete; above this range, it is wasteful and may produce defects.

[0039] The magnesium silicate substrate prepared by the method of the present invention has a thickness range (the difference between the maximum thickness and the minimum thickness) of no more than 20% of the average thickness, the adhesion between the substrate and the base material reaches Grade A (no peeling according to the ASTM D3359 cross-cut test), and the insulation resistance of the substrate is not less than 100 Ω·cm².

[0040] Furthermore, the 1.0~1.3% moisture content controlled by this invention essentially retains mainly the hydroxyl groups (-OH) and some bound water on the surface of the magnesium oxide particles in the coating. These water molecules can act as a reaction transport medium during subsequent high-temperature annealing, significantly promoting the solid-phase diffusion reaction between MgO and SiO2. If the moisture content is too low (<1.0%), the coating becomes too dry, and the reaction kinetics are slow; if the moisture content is too high (>1.3%), the residual free water will vaporize instantly upon entering the high-temperature furnace, causing the coating to peel or powder.

[0041] Specifically, to achieve precise closed-loop control of the coating moisture content, in a preferred embodiment of the present invention, an online infrared moisture meter is installed at the outlet of the drying and sintering furnace. The working mode and effect of the online infrared moisture meter are as follows:

[0042] Measurement principle: This instrument is based on the near-infrared (NIR) spectral absorption principle. Water molecules have characteristic absorption of near-infrared light of a specific wavelength. The instrument emits infrared light onto the surface of the moving steel strip coating. By detecting the attenuation of the intensity of the reflected or transmitted light, the instantaneous moisture content of the coating can be calculated in real time in a non-contact and non-destructive manner.

[0043] System integration and feedback control:

[0044] The online infrared moisture meter communicates with the main control system of the unit (e.g., a programmable logic controller (PLC) or a distributed control system (DCS). The online infrared moisture meter transmits the electrical signals representing the moisture content of the upper and lower surfaces of the steel strip, which are collected in real time, to the main control system. The main control system has a preset optimal moisture content target range required by this invention, namely 1.0% to 1.3%. The system compares the real-time measured value with the preset target value and automatically and finely adjusts the heating power or temperature setpoint of the first and / or second zones of the drying and sintering furnace according to the deviation (difference) through a preset PID (proportional-integral-derivative) control algorithm. If the outlet moisture content is detected to be higher than 1.3%, the main control system will slightly increase the temperature setpoint of the first and / or second zones to enhance the dehydration capacity. If the outlet moisture content is detected to be lower than 1.0%, the main control system will slightly reduce the heating power to prevent the coating from drying out too much.

[0045] Through this continuous feedback adjustment, the entire system can dynamically compensate for interference caused by environmental humidity, batch differences in coating liquid, and slight fluctuations in steel strip speed, stably "locking" the moisture content within a narrow optimal process window. Furthermore, this optimized solution overcomes the lag of traditional offline sampling and laboratory testing, achieving 100% monitoring and precise control of the entire production process. Simultaneously, through closed-loop feedback, it eliminates human error and external interference, ensuring the uniformity and stability of the coating quality for each meter of steel strip, laying a solid foundation for the final formation of a high-quality magnesium silicate underlayer. Moreover, it reduces manual intervention, improving the automation and intelligence level of the production line.

[0046] In step S1, the boride is magnesium borate or titanium borate.

[0047] In one embodiment, magnesium borate is preferred, as follows: In the high-temperature reaction of the magnesium silicate underlayer, the boride mainly acts as a "high-temperature flux," its core function being to lower the melting temperature of the reaction system and promote the formation of the liquid phase, thereby making the reaction more complete and the underlayer denser. However, the choice of different borides will bring drastically different technical effects. This invention prefers magnesium borate or titanium boride because magnesium borate itself contains magnesium (Mg) and is in the same Mg-O chemical system as the magnesium oxide (MgO) matrix and the target product magnesium silicate (Mg2SiO4). This allows it to perfectly integrate into the reaction environment at high temperatures without introducing impurity cations that may be harmful to the final insulation or magnetic properties of the underlayer. Simultaneously, at high temperatures, magnesium borate melts before the magnesium oxide-silica system, forming a low-viscosity glassy phase. This liquid phase encapsulates and wets the magnesium oxide and the silica (SiO2) on the silicon steel surface, greatly promoting the transformation of the solid-solid reaction into a more efficient solid-liquid reaction. This significantly improves the formation rate and uniformity of magnesium silicate, which is crucial for ensuring rapid and complete formation of the substrate with a low magnesium oxide coating amount. Furthermore, the fluxing temperature range of magnesium borate matches well with the formation temperature range of magnesium silicate. It can melt at just the right temperature (above approximately 1000°C), neither causing premature sintering of the coating and affecting dehydration nor missing the optimal reaction window too late. This "mild" characteristic makes the process window wider and the production process more stable. In addition, compared to some special borates, magnesium borate is a relatively common and inexpensive chemical raw material, which is easy to obtain and helps reduce the cost of industrial production. Furthermore, if titanium boride is preferred, the following applies: Titanium boride can release boron (B) components at high temperatures (it only decomposes completely above about 1800°C, but its surface begins to activate at temperatures far below this). These boron components react with impurities or silicon dioxide in the system to form eutectic compounds, acting as fluxes. Moreover, titanium boride particles are very stable at high temperatures and can serve as heterogeneous nucleation sites. During the crystallization of magnesium silicate from the liquid phase, these uniformly dispersed, high-melting-point TiB2 particles provide a ready-made substrate for the nucleation of magnesium silicate grains. This nucleation effect can refine the magnesium silicate grains, making the resulting underlayer more dense and uniform, and with stronger adhesion to the matrix. A denser underlayer can provide better insulation and tensile strength, thereby more effectively reducing iron loss. Furthermore, the formulation of this invention already includes titanium dioxide (TiO2), which serves to inhibit excessive growth of magnesium silicate grains and optimize the properties of the glass phase. The introduction of titanium boride, which is also a titanium (Ti) element, may form a certain correlation at high temperatures, further optimizing the network structure of the glass phase and thus improving the intrinsic quality of the underlying layer. Due to the dispersion strengthening effect of TiB2 particles, the magnesium silicate underlying layer formed by it may have better microhardness, wear resistance, and density, which helps to better protect the coating and reduce damage during subsequent steel coil shearing and transportation.

[0048] More preferably, the boride is magnesium borate. When used in the production of conventional grade oriented silicon steel, it can achieve optimal economic efficiency while ensuring excellent underlying quality. Furthermore, when the boride is titanium boride, its heterogeneous nucleation effect can further enhance the density of the underlying layer and the magnetic properties of the product when used in high-grade oriented silicon steel with extremely high requirements for iron loss and magnetic induction.

[0049] Before step S2, there is also step S101, in which the coating liquid needs to be ball-milled before coating. The ball-milling time is 2 to 4 hours until the slurry particle size D50 < 2 μm.

[0050] In step S1, when preparing the special magnesium oxide coating liquid, magnesium oxide powder, titanium dioxide, and boride are mixed at low speed in a mixer for 15-30 minutes in a dry state to ensure uniform dispersion of solid powder. Then, the mixed dry powder is slowly added to deionized water while mechanically stirred at 300-500 rpm to form a preliminary slurry. The slurry is then transferred to a ball mill, and zirconia ceramic balls are added as grinding media at a ball-to-powder ratio of 2:1. The slurry is then ball-milled for 2-4 hours until the particle size distribution D50 value of the slurry is less than 2μm. The ball-milled slurry is filtered through a 200-mesh sieve to remove any possible large particle impurities, and then allowed to stand (age) at room temperature for at least 2 hours to stabilize its performance.

[0051] To demonstrate the practical effectiveness of this invention, the following comparative experiments were conducted:

[0052] Example 1 (Best Implementation of the Invention)

[0053] Coating solution: water: magnesium oxide: titanium dioxide: magnesium borate = 630:75:4.8:1.1. Ball milling for 3 hours, slurry D50 = 1.8 μm;

[0054] Equipment: Double spring coating machine, coating roller 36 teeth / inch, upper roller depth 0.45mm, lower roller depth 0.55mm, hardness 63;

[0055] Process: Coating amount controlled at 7.0 g / m². Drying and sintering: Zone 1 555℃, Zone 2 540℃. The measured moisture content was 1.15%.

[0056] Final product performance: The magnesium silicate substrate is uniform, dense, and flawless; iron loss P1.7 / 50 is 0.85 W / kg; magnetic induction B8000 is 1.88 T; and the effective utilization rate of magnesium oxide is high. Coating solution and moisture content.

[0057] Comparative Example 1 (Traditional high coating amount process)

[0058] Coating liquid: Using a traditional formula, water:magnesium oxide:titanium dioxide = 650:80:5.0, simply stirred, not ball-milled, slurry D50 = 15μm;

[0059] Equipment: Single spring coating machine, used coating rollers (24 teeth / inch, upper roller depth 0.6mm, lower roller depth 0.7mm, hardness 55);

[0060] Process: Coating amount is approximately 9.0 g / m², and the drying and sintering temperature profile is roughly controlled;

[0061] Final product performance: The bottom layer has localized over-thickness and slight striations; the iron loss P1.7 / 50 is 0.89 W / kg; the magnetic induction B8000 is 1.86 T; there is significant waste of magnesium oxide, resulting in high cost.

[0062] Comparative Example 2 (coating amount too low, exceeding the scope of this invention)

[0063] The same coating liquid and equipment as in Example 1 were used;

[0064] Process: The coating amount was deliberately reduced to 5.8 g / m², and other parameters were the same as in Example 1;

[0065] Final product performance: Due to insufficient coating, the magnesium silicate underlayer was discontinuous, resulting in localized underlayer defects. This led to poor product insulation, a deterioration in iron loss to 0.95 W / kg, and a decrease in magnetic induction. This comparison demonstrates that simply reducing the coating amount without the system support of this invention will result in substandard product quality.

[0066] Comparative Example 3 (moisture content too high, exceeding the scope of this invention)

[0067] The same coating liquid and equipment as in Example 1 were used, and the coating amount was also 7.0 g / m²;

[0068] Process: Adjust the temperature of the drying oven so that the moisture content of the coating reaches 1.8% when it exits the oven (exceeding the 1.0-1.3% range of this invention).

[0069] Final product performance: During subsequent high-temperature annealing, the excessive moisture evaporated rapidly, causing the coating to blister and peel off, severely damaging the quality of the underlying layer, and rendering the product unusable.

[0070] Comparative Example 4 (using a conventional coating roller)

[0071] The same coating liquid and process parameters as in Example 1 (coating amount 7.0 g / m²) were used.

[0072] Equipment: Use the old coating roller (24 teeth / inch) from Comparative Example 1;

[0073] Final product performance: Due to mismatched roller parameters, uniform transfer under low coating weight cannot be achieved, resulting in obvious transverse stripes on the coated surface, poor uniformity, and uneven bottom layer quality.

[0074] In summary, please refer to the following chart:

[0075]

[0076] Therefore, through a thorough comparison of the above embodiments and comparative examples, it can be clearly seen that the complete technical solution provided by the present invention can stably produce high-performance, low-cost oriented silicon steel products.

[0077] A magnesium oxide coating liquid for preparing a magnesium oxide insulating coating has the following raw material ratio by weight: 630 parts water, 75 parts magnesium oxide, 4.8 parts titanium dioxide, and 1.1 parts boride.

[0078] A coating roller having a groove density of 32-36 teeth per inch, a groove depth of 0.45 mm on the upper roller, a groove depth of 0.55 mm on the lower roller, and a roller body hardness of 60-65 Shore hardness.

[0079] A grain-oriented silicon steel having a magnesium silicate underlayer on its surface, wherein the iron loss of the grain-oriented silicon steel is... P1.7 / 50 <0.86 W / kg and magnetic induction B 8000 >1.87 T.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing oriented silicon steel, characterized in that, Includes the following steps: S1. The coating liquid needs to be ball-milled before coating. The ball-milling time is 2 to 4 hours until the slurry particle size D50 < 2μm. The coating liquid is then applied to the surface of the oriented silicon steel strip that has undergone secondary recrystallization annealing. The raw material ratio of the coating liquid by weight is: 630 parts water, 75 parts magnesium oxide, 4.8 parts titanium dioxide, and 1.1 parts boride. S2. Coating is performed using a coating machine with a double spring adjustment mechanism and a specific coating roller, the parameters of which are: a groove distribution density of 32 to 36 teeth per inch, a groove depth of 0.45 mm on the upper roller, a groove depth of 0.55 mm on the lower roller, and a roller body hardness of 60 to 65 Shore hardness. S3. Control the coating amount on both the upper and lower surfaces of the oriented silicon steel strip to be 6.5~7.5 g / m². S4. The coated oriented silicon steel strip is dried and sintered. When the unit operates at a speed of 50 m / min, the drying and sintering process is divided into two zones: zone 1 has a temperature of 550~560℃ and zone 2 has a temperature of 530~550℃. The final result of drying and sintering is to control the moisture content of the upper and lower surfaces of the coating to be 1.0~1.3%. S5. Perform hot leveling annealing to obtain iron loss. P17 / 50 <0.86 W / kg and magnetic induction B 8000 >1.87 T oriented silicon steel.

2. The method for preparing oriented silicon steel according to claim 1, characterized in that, The boride is magnesium borate or titanium boride.

3. A type of grain-oriented silicon steel, characterized in that, Its surface has a magnesium silicate underlayer, and the iron loss of the oriented silicon steel is... P17 / 50 <0.86 W / kg and magnetic induction B 8000 >1.87 T.

Images