Preparation method of oriented silicon steel and product thereof

Abstract

The invention provides a preparation method of oriented silicon steel and a product thereof. The preparation method comprises the following steps: preparing magnesium oxide coating liquid and coating the surface of an oriented silicon steel strip with the magnesium oxide coating liquid; the coating weights of the upper surface and the lower surface of the oriented silicon steel strip are controlled to be 6.5-7.5 g / m < 2 >; and the coated oriented silicon steel strip is dried and sintered, and the final drying and sintering result is controlled that the water content of the upper surface and the water content of the lower surface of the coating are both 1.0-1.3%. The magnesium oxide raw material consumption is remarkably reduced, the production cost is saved, meanwhile, the excellent and stable quality of the magnesium silicate bottom layer is ensured, finally, the obtained oriented silicon steel has the excellent magnetic performance of lower iron loss and higher magnetic induction, and the optimal balance of the cost and the performance is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of oriented silicon steel and its product. BACKGROUND

[0002] Oriented silicon steel is an important soft magnetic material mainly used for manufacturing transformer cores, and its magnetic properties (such as iron loss and magnetic induction) are core indicators. In the manufacturing process of oriented silicon steel, a magnesium oxide coating is applied to the surface of the steel strip, and during high-temperature annealing, it reacts with the silicon dioxide on the surface of the steel strip substrate to form a good insulating bottom layer-magnesium silicate. The quality of this magnesium silicate bottom layer directly determines the iron loss and magnetic induction values of the final product. In theory, only about 2.5-3 grams per square meter of magnesium oxide is needed to complete the magnesium silicate reaction. However, in actual industrial production, due to the difficulty in perfectly controlling the uniformity of the coating, and to ensure the quality of the bottom layer (i.e. "safety considerations"), the industry generally uses a coating amount much higher than this theoretical value. This excessive coating not only causes a serious waste of magnesium oxide raw materials, increasing production costs, but also restricts the improvement of production line speed due to problems such as excessive coating thickness, thereby affecting overall production efficiency. In addition, the water content of the coating liquid is also a key but often roughly controlled parameter. Too high or too low water content can affect the adhesion, leveling of the coating on the surface of the steel strip, and the completeness of the subsequent high-temperature reaction, thereby affecting the quality of the bottom layer and product consistency.

[0003] Therefore, there has been a long-standing technical contradiction in the field that needs to be solved: how to significantly reduce the amount of magnesium oxide coating to save costs and improve efficiency while ensuring and even optimizing the quality of the magnesium silicate bottom layer, thereby ensuring the excellent magnetic properties of the product. SUMMARY

[0004] The present application provides a preparation method of oriented silicon steel and its product, which can effectively solve the above problems.

[0005] The present application is implemented as follows: A preparation method of oriented silicon steel and its product, comprising the following steps: S1, applying a magnesium oxide coating liquid to the surface of the oriented silicon steel strip after completing the secondary recrystallization annealing; S2, controlling the coating amount on the upper and lower surfaces of the oriented silicon steel strip to be 6.5-7.5 grams per square meter; S3, drying and sintering the coated oriented silicon steel strip, and controlling the final result of drying and sintering to be the water content of the upper and lower surfaces of the coating being 1.0-1.3%; S4, performing hot flattening annealing to obtain the oriented silicon steel.

[0006] The beneficial effects of the present application are: (1) The application successfully breaks through the industry technical prejudice of "high coating amount to ensure quality" by precisely and cooperatively controlling the coating amount of magnesium oxide coating and the water content after drying in a narrow window of 6.5-7.5 g / m2 and 1.0-1.3%, respectively, thereby significantly reducing the consumption of magnesium oxide raw material, saving production cost, ensuring the excellent and stable quality of the magnesium silicate bottom layer, and ultimately making the obtained oriented silicon steel have excellent magnetic properties of lower iron loss and higher magnetic induction, achieving the best balance between cost and performance. BRIEF DESCRIPTION OF DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0008] Fig. 1 is the process flow chart of the present application.

[0009] Fig. 2 is a schematic diagram of a double-spring structure in the equipment of the present application.

[0010] Fig. 3 is a performance comparison column chart of the present application. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only to represent selected embodiments of the present application.

[0012] In the description of the present application, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0013] Referring to Figs. 1-3 , a preparation method of oriented silicon steel includes the following steps: S1, coating magnesium oxide coating liquid on the surface of the oriented silicon steel strip after secondary recrystallization annealing; the raw material ratio of the magnesium oxide coating liquid is 630 parts by weight of water, 75 parts of magnesium oxide, 4.8 parts of titanium dioxide, and 1.1 parts of boride; S2, controlling the coating amount of the upper surface and the lower surface of the oriented silicon steel strip to be 6.5-7.5 g / m2; S3, drying and sintering the coated oriented silicon steel strip, and controlling the final result of drying and sintering to be that the water content of the upper surface and the lower surface of the coating is 1.0-1.3%; S4, hot leveling annealing to obtain the oriented silicon steel.

[0014] In the S2 step, the parameters of the special coating roller are: the groove distribution density is 32-36 teeth per inch, the upper roller groove depth is 0.45 mm, the lower roller groove depth is 0.55 mm, and the roller body hardness is 60-65 Shore.

[0015] It should be noted that due to the effect of gravity, the lower roller needs to bear more coating liquid and overcome the tendency of liquid dripping. Therefore, the lower roller groove depth (0.55 mm) is set to be slightly larger than that of the upper roller (0.45 mm), which can store and transfer slightly more slurry to compensate for the gravity effect, so as to realize the uniformity of the coating amount of the upper and lower surfaces.

[0016] Specifically, in the operation of the S2 step, the coating liquid prepared in S1 is injected into the trough of the coating machine, and the oriented silicon steel strip passes through the coating roller at a certain speed (such as 50 m / min). By precisely adjusting the pressure of the double spring, the roller speed ratio (the ratio of the linear speed of the coating roller to the steel strip), and the liquid level of the trough, the coating amount is strictly controlled, and the wet coating amount of the upper surface and the lower surface is stabilized in the range of 6.5-7.5 g / m2.

[0017] In the S2 step, the coating is carried out by the coating machine with a double spring adjusting mechanism and using a special 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 uniformly distributed along the axial direction. This structure makes the coating amount difference (the difference between the maximum value and the minimum value) in the width direction of the steel strip controllable within ±0.3 g / m2, thereby forming a clear and quantitative contrast with the "horizontal stripes" appearing in Comparative Example 4.

[0018] In the S3 step, when the unit running speed is 50 m / min, the drying and sintering process is divided into two zones, where the temperature of zone 1 is 550-560℃, and the temperature of zone 2 is 530-550℃.

[0019] The first zone (entry zone) is set at a temperature of 550-560°C, which 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°C, which is slightly lower in temperature and is responsible for gently removing residual bound water and preliminarily solidifying the coating to form a certain mechanical strength.

[0020] It should be noted that the drying and sintering temperature (1 zone 550-560°C, 2 zone 530-550°C) is set based on a machine speed of 50 meters / minute. When the speed fluctuates within ±10 meters / minute, the dehydration curve can be maintained constant by adjusting the temperature of each zone in proportion (for example, if the speed increases by 5 meters / minute, the temperature of each zone is increased by 5-10°C accordingly), thereby ensuring that the final moisture content is stably within the target range of 1.0-1.3%.

[0021] Further, the main role of the first zone (550-560°C) is to provide sufficient heat energy to match the production line speed and rapidly evaporate and remove most (for example, more than 90%) of the 'free water' in the coating. The upper limit of this temperature (560°C) aims to achieve efficient dehydration while ensuring that the coating surface does not 'boil' or'sputter' due to the violent vaporization of water. The main role of the second zone (530-550°C) is not to remove a large amount of water, but to'stably solidify'. After rapid dehydration in the first zone, the main residual in the coating is 'bound water' that is more tightly combined with magnesium oxide particles. If the temperature is continued to be kept high at this time, it will lead to: over-sintering of the surface layer: the surface of the coating forms a dense shell too early, hindering the escape of the remaining water inside, which may form bubbles in subsequent processes; stress concentration: the difference between the drying rates inside and outside the coating is too large, generating internal stress and affecting the adhesion of the bottom layer. Therefore, appropriately reducing the temperature of the second zone forms a gentle temperature gradient, which can achieve: gentle removal of bound water: allowing bound water molecules enough time to migrate from the inside of the particles to the surface for evaporation, avoiding the destruction of the coating structure due to rapid phase change; promote uniform solidification of the coating: allowing the coating to uniformly lose water from the inside to the outside and preliminarily establish stable mechanical strength, preparing for entering the subsequent high-temperature annealing furnace.

[0022] In order to prove the above two-zone temperature reduction process, the following comparison is made: The other conditions are exactly the same as in Example 4, the only difference being that the drying and sintering furnace is set as a single constant temperature zone with a temperature of 555°C (i.e., the same as the temperature of the first zone of the present application); Results: After the coating is discharged, the following problems occur: surface quality: small bubbles and point-like protrusions are observed in some areas; microstructure: scanning electron microscopy (SEM) shows that the surface layer structure of the coating is dense, but there are closed pores below; performance: the pass rate of the bottom layer adhesion test of this batch of products after final annealing decreases by about 15%.

[0023] The comparative experiment proves that although the constant temperature process can also remove water, a single rapid dehydration mechanism will cause the internal structure of the coating to be damaged, and the two-zone cooling process of the present application can effectively avoid such defects.

[0024] By controlling the coating amount and moisture content, the effective amount of magnesium oxide participating in the formation of the magnesium silicate bottom layer is 2.5-3 g / m2. Among them, the moisture content of the coating at the outlet of the steel belt is monitored in real time by an online infrared moisture meter, and the temperature setting is adjusted by a feedback system to ensure that the moisture content of the upper and lower surfaces of the coating when leaving the furnace is strictly controlled in the best range of 1.0-1.3%. Therefore, through the control of the above system, the effective amount of magnesium oxide participating in the formation of the magnesium silicate bottom layer is accurately controlled in the range of 2.5-3.0 g / m2, realizing the optimal use of raw materials under the premise of ensuring the quality of the bottom layer.

[0025] It should be noted that, in theory, about 2.5-3.0 g / m2 of magnesium oxide is needed to form a complete bottom layer. However, considering the 'trapping effect' of magnesium oxide particles on the rough surface of the silicon steel strip and the'reaction inert core' at high temperature, a certain excess amount must be provided. The present application finds that when the excess amount is controlled in the range of 3.5-4.5 g / m2 (i.e. the total coating amount is 6.5-7.5 g), both the reaction reagents in the micro-local area are sufficient and the excessive coating does not crack due to excessive internal stress during sintering. Below this range, the bottom layer is missing, and above this range, it is wasted and may produce defects.

[0026] Among them, the magnesium silicate bottom layer prepared by the method of the present application has a thickness range (the difference between the maximum thickness and the minimum thickness) not more than 20% of the average thickness, the adhesion between the bottom layer and the substrate reaches A level (tested according to ASTM D3359 grid method, no peeling), and the insulation resistance of the bottom layer is not less than 100 Ω·cm2.

[0027] Further, the moisture content of 1.0-1.3% controlled by the present application essentially mainly retains the hydroxyl groups (-OH) on the surface of the magnesium oxide particles and part of the combined water. This part of water molecules can act as a reaction transmission medium in the subsequent high-temperature annealing process, significantly promoting the solid-phase diffusion reaction between MgO and SiO2. If the moisture content is too low (<1.0%), the coating is too dry and the reaction kinetics is slow; if the moisture content is too high (>1.3%), the residual free water will instantaneously vaporize when entering the high-temperature furnace, causing the coating to produce a blister or powder.

[0028] Specifically, to realize the precise closed-loop control of the moisture content of the coating, in a preferred embodiment of the present application, an online infrared moisture meter is arranged at the outlet of the drying and sintering furnace, and the working mode and effect of the online infrared moisture meter are as follows: Measurement principle: The instrument is based on the principle of near-infrared (NIR) spectrum absorption. Water molecules have characteristic absorption of near-infrared light of specific wavelength. The instrument emits infrared light to the surface of the moving steel belt coating, and by detecting the light intensity attenuation of the reflected light or transmitted light, the instantaneous moisture content of the coating can be calculated in real time without contact and non-destructively. System integration and feedback control: The online infrared moisture meter communicates data with the main control system (such as programmable logic controller PLC or distributed control system DCS) of the unit. The online infrared moisture meter transmits the electrical signals representing the moisture content of the upper and lower surfaces of the steel belt collected in real time to the main control system. The main control system internally presets the optimal moisture content target range required by the present application, i.e. 1.0% ~ 1.3%, and compares the real-time measurement value with the preset target value. According to the deviation (difference), the system automatically adjusts the heating power or temperature set value of the first zone and / or second zone of the drying and sintering furnace through the pre-set PID (proportional-integral-derivative) control algorithm. If the detected outlet moisture content is higher than 1.3%, the main control system will slightly increase the temperature set value of the first zone and / or second zone to enhance the dehydration capacity. If the detected outlet moisture content is lower than 1.0%, the main control system will slightly reduce the heating power to prevent the coating from being too dry.

[0029] Through this continuous feedback adjustment, the whole system can dynamically compensate for the interference caused by environmental humidity, coating liquid batch differences, and slight fluctuations in steel belt speed, and stably "lock" the moisture content in a narrow optimal process window. The preferred scheme overcomes the hysteresis of traditional offline sampling and laboratory testing, realizes 100% monitoring and precise control of the entire production process, eliminates human operation errors and external disturbances through closed-loop feedback, ensures the uniformity and stability of the coating quality of each meter of steel belt, lays a solid foundation for the formation of high-quality magnesium silicate base layer, and further reduces manual intervention, improves the automation level and intelligent degree of the production line.

[0030] In the S1 step, the boride is magnesium borate or titanium boride.

[0031] In one embodiment, if the preferred magnesium borate, as follows; in the high-temperature reaction of the magnesium silicate bottom layer, the boride mainly plays the role of "high-temperature flux", its core function is to reduce the melting temperature of the reaction system, promote the formation of liquid phase, so that the reaction is more complete, the bottom layer is more dense. But the choice of different borides will bring completely different technical effects. And the invention prefers magnesium borate or titanium boride, because magnesium borate itself contains magnesium (Mg) element, which is in the same Mg-O chemical system with magnesium oxide (MgO) and magnesium silicate (Mg2SiO4) target product, which makes it perfectly melt into the reaction environment at high temperature, without introducing impurity cations that may be harmful to the final bottom layer insulation performance or magnetic performance, at the same time, at high temperature, magnesium borate will melt before the magnesium oxide-silicon dioxide system, forming a low viscosity glass phase, this layer of liquid phase wraps and wets the silicon dioxide (SiO2) on the surface of magnesium oxide and silicon steel, greatly promoting the solid-solid reaction to more efficient solid-liquid reaction, thereby significantly improving the generation rate and uniformity of magnesium silicate, which is crucial to ensure that the bottom layer is quickly and completely formed at a lower magnesium oxide coating amount. Furthermore, the fluxing temperature range of magnesium borate matches well with the generation temperature range of magnesium silicate, it can melt at just the right temperature (above about 1000℃), neither too early to cause premature sintering of the coating and affect dehydration, nor too late to miss the best reaction window. This "moderate" characteristic makes the process window wider, the production process more stable, and compared with some special borides, magnesium borate is a relatively common and inexpensive chemical raw material, easy to obtain, which helps to reduce the cost of industrial production. In addition, if titanium boride is preferred, as follows; titanium boride can release boron (B) component at high temperature (above about 1800℃ to completely decompose, but its surface has started to activate at much lower temperature), which reacts with impurities or silicon dioxide in the system to form a eutectic, acting as a flux, and titanium boride particles are very stable at high temperature, which can act as heterogeneous nucleation points. In the process of magnesium silicate crystallization 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 generated bottom layer more dense, uniform, and with stronger adhesion to the substrate. A more dense bottom layer can provide better insulation and tension, thereby more effectively reducing the iron loss. Further, the formula of the invention already contains titanium dioxide (TiO2), which functions to inhibit the excessive growth of magnesium silicate grains and optimize the performance of the glass phase. The introduction of titanium boride, which also contains titanium (Ti) element, may form some correlation at high temperature, further optimizing the network structure of the glass phase, thereby improving the internal quality of the bottom layer. Due to the dispersion strengthening effect of TiB2 particles, the magnesium silicate bottom layer formed with their participation may have better microhardness, wear resistance, and density, which helps to better protect the coating during subsequent steel coil cutting and transportation, reducing damage.

[0032] More preferably, the boride is magnesium borate. When it is used in the production of the conventional grade of grain-oriented silicon steel, the best economy can be obtained while ensuring excellent quality of the underlayer. Further, when the boride is titanium boride, it is used in the high-grade grain-oriented silicon steel with extremely high requirements for iron loss and magnetic induction, and the underlayer density and product magnetic properties can be further improved by virtue of its heterogeneous nucleation effect.

[0033] Before the step S2, a step S101 is further included, the coating liquid needs to be subjected to ball milling treatment before coating, the ball milling time is 2-4 hours, until the particle size D50 of the slurry is less than 2 μm.

[0034] In the step S1, when the special magnesium oxide coating liquid is configured, the magnesium oxide powder, titanium dioxide and boride are mixed in a dry state in a mixer at a low speed for 15-30 minutes, to ensure that the solid powder is uniformly dispersed, then the mixed dry powder is slowly added into deionized water, while mechanical stirring is performed at a speed of 300-500 rpm, to form a preliminary slurry, the slurry is transferred to a ball mill, zirconium oxide ceramic balls are added as grinding medium, the ball-to-material ratio is 2:1, and then ball milling treatment is further performed for 2-4 hours, until the particle size distribution D50 value of the slurry is less than 2 μm, the slurry after ball milling is filtered through a 200-mesh screen to remove possible large-particle impurities, and then is left to stand (ageing) at room temperature for at least 2 hours, so as to stabilize the performance.

[0035] In order to prove the actual effect of the present application, the following experiments are performed for comparison: Example 1 (best embodiment of the present application) Coating liquid: water: magnesium oxide: titanium dioxide: magnesium borate = 630:75:4.8:1.1. Ball milling for 3 hours, slurry D50 = 1.8 μm; Equipment: double-spring coating machine, coating roll 36 teeth / inch, upper roll depth 0.45 mm, lower roll depth 0.55 mm, hardness 63; Process: the coating amount is controlled to be 7.0 g / m². Drying and sintering: zone 1 555℃, zone 2 540℃. The measured water content is 1.15%; Final product performance: the magnesium silicate underlayer is uniform, dense and flawless, the iron loss P1.7 / 50 is 0.85 W / kg, the magnetic induction B8000 is 1.88 T, and the effective utilization rate of magnesium oxide is high.

[0036] Comparative Example 1 (traditional high-coating amount process) Coating liquid: traditional formula is used, water: magnesium oxide: titanium dioxide = 650:80:5.0, simple stirring, no ball milling, slurry D50 = 15 μm; Equipment: single-spring coating machine, old coating roll (24 teeth / inch, upper roll depth 0.6 mm, lower roll depth 0.7 mm, hardness 55); Process: coating amount is about 9.0 g / m2, sintering temperature curve is roughly controlled; Final product performance: local over-thickness and slight strip exist in the bottom layer, iron loss P1.7 / 50 is 0.89 W / kg, magnetic induction B8000 is 1.86 T, magnesium oxide is wasted seriously, and cost is high.

[0037] Comparative Example 2 (coating amount is too low, beyond the scope of the application) The same coating liquid and equipment as in Example 1 are used; Process: coating amount is deliberately reduced to 5.8 g / m2, and other parameters are the same as in Example 1; Final product performance: due to insufficient coating amount, the magnesium silicate bottom layer is discontinuous, local bottom leakage occurs, the product has poor insulation, the iron loss deteriorates to 0.95 W / kg, and the magnetic induction also decreases. This comparison proves that simply reducing the coating amount without the support of the system of the application will result in unqualified product quality.

[0038] Comparative Example 3 (water content is too high, beyond the scope of the application) The same coating liquid and equipment as in Example 1 are used, and the coating amount is also 7.0 g / m2; Process: the drying furnace temperature is adjusted so that the coating water content reaches 1.8% (beyond the range of 1.0-1.3% of the application) when it is discharged; Final product performance: due to the high water content, the coating layer foams and peels off during subsequent high-temperature annealing, the bottom layer is seriously damaged, and the product is scrapped.

[0039] Comparative Example 4 (using a traditional coating roller) The same coating liquid and process parameters (coating amount 7.0 g / m2) as in Example 1 are used; Equipment: the old coating roller (24 teeth / inch) in Comparative Example 1 is used; Final product performance: due to the mismatch of the roller parameters, uniform transfer under low coating amount cannot be achieved, and obvious horizontal stripes appear on the surface after coating, the uniformity is poor, and the quality of the bottom layer is uneven.

[0040] Based on the above, the following chart can be referred to:

[0041] Therefore, through the sufficient comparison of the above examples and comparative examples, it can be clearly seen that the complete technical solution provided by the application can stably produce high-performance and low-cost oriented silicon steel products.

[0042] A magnesium oxide coating liquid for realizing the preparation method of the magnesium oxide insulation coating, wherein the raw material ratio is as follows in terms of weight parts: water 630 parts, magnesium oxide 75 parts, titanium dioxide 4.8 parts, and boride 1.1 part.

[0043] A coating roll has a groove density of 32-36 teeth per inch, an upper roll groove depth of 0.45 mm, a lower roll groove depth of 0.55 mm, and a roll body hardness of 60-65 Shore D.

[0044] An oriented silicon steel has a magnesium silicate underlayer on its surface, the oriented silicon steel has an iron loss P1.7 / 50 <0.86 W / kg and a magnetic induction B 8000 >1.87 T.

[0045] The above descriptions are only the preferred embodiments of the present application and are not intended to limit the present application. Various modifications and changes can be made on the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing an oriented silicon steel, characterized by, The method comprises the following steps: S1, coating magnesium oxide coating liquid on the surface of the oriented silicon steel strip after secondary recrystallization annealing; S2, controlling the coating amount of the upper surface and the lower surface of the oriented silicon steel strip to be 6.5-7.5 g / m2; S3, drying and sintering the coated oriented silicon steel strip, and controlling the final result of drying and sintering to be that the water content of the upper surface and the lower surface of the coating is 1.0-1.3%; S4, performing hot leveling annealing to obtain the oriented silicon steel.

2. A method of producing an oriented silicon steel according to claim 1, characterized in that, The raw material ratio of the magnesium oxide coating liquid is 630 parts by weight of water, 75 parts by weight of magnesium oxide, 4.8 parts by weight of titanium dioxide and 1.1 parts by weight of boride.

3. The method of claim 1, wherein the oriented silicon steel is prepared by the steps of: The coating is performed by a coating machine with a double-spring adjusting mechanism and using a special coating roller.

4. A method of producing an oriented silicon steel according to claim 3, characterized in that, The parameters of the special coating roller are that the groove distribution density is 32-36 teeth per inch, the upper roller groove depth is 0.45 mm, the lower roller groove depth is 0.55 mm, and the roller body hardness is 60-65 Shore.

5. The method of claim 1, wherein the oriented silicon steel is prepared by the steps of: When the unit running speed is 50 m / min, the drying and sintering process is divided into two zones, wherein the temperature of zone 1 is 550-560℃, and the temperature of zone 2 is 530-550℃.

6. The method of claim 2, wherein the oriented silicon steel is prepared by the steps of: The boride is magnesium borate or titanium boride.

7. The method of claim 2, wherein the oriented silicon steel is prepared by the steps of: The coating liquid needs to be treated by ball milling before coating, the ball milling time is 2-4 hours, and the slurry particle size D50 is less than 2 μ.

8. A method for producing the oriented silicon steel according to any one of claims 1 to 7, characterized by, The raw material ratio of the magnesium oxide coating liquid is 630 parts by weight of water, 75 parts by weight of magnesium oxide, 4.8 parts by weight of titanium dioxide and 1.1 parts by weight of boride.

9. A coating roll for use in the process according to any one of claims 1 to 7, characterized in that The groove density of the coating roller is 32-36 teeth per inch, the upper roller groove depth is 0.45 mm, the lower roller groove depth is 0.55 mm, and the roller body hardness is 60-65 Shore.

10. An oriented silicon steel characterized by, The oriented silicon steel has a magnesium silicate underlayer on the surface, and the iron loss of the oriented silicon steel P17 / 50 <0.86 W / kg and magnetic induction B 8000 >1.87 T.

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