Method for forming a titanium nitride coating on grain-oriented silicon steel and a grain-oriented silicon steel

Abstract

The application discloses a method for forming a titanium nitride coating on oriented silicon steel and an oriented silicon steel, and belongs to the field of oriented silicon steel processing. The method comprises the following steps: dissolving pyrazine-2,3-dicarboxylic acid in ethanol, adding tetrabutyl titanate to stir and react, adding oxalic acid, and then adding water to form a sol; after the sol is aged, drying is performed, and the sol is ground into a gel powder; the gel powder is covered on polished oriented silicon steel, then heat treatment is performed at 1000 DEG C to 1050 DEG C in a flowing nitrogen atmosphere, and finally cooling is performed to room temperature. The application can prepare a dense titanium nitride coating on the surface of the silicon steel without corroding the oriented silicon steel, and the titanium nitride coating has strong adhesion; the excess gel powder which does not participate in forming the coating can be reused; in the method, no expensive equipment in PVD and CVD processes is needed, the process is simple, raw materials are easy to obtain, the cost is low, and the method is easy to implement in industrialization, and the application has important industrial practical significance for improving the performance of the oriented silicon steel and reducing the loss of a transformer.

Description

Technical Field

[0001] This invention relates to a method for forming a titanium nitride coating on oriented silicon steel and an oriented silicon steel, belonging to the field of oriented silicon steel processing. Background Technology

[0002] Grain-oriented silicon steel is a key soft magnetic material for manufacturing power transformer cores, and its performance directly affects the transformer's energy efficiency and energy consumption. During transformer operation, the core generates heat due to hysteresis and eddy current losses, leading to energy waste and shortening equipment lifespan. To reduce losses, tension coatings are often prepared on the silicon steel surface. Among these, titanium nitride (TiN) coatings have attracted attention because they can apply greater tension, improve magnetic domain structure, and reduce iron losses by approximately 40%. Currently, the preparation of TiN coatings mainly relies on physical vapor deposition (PVD) and chemical vapor deposition (CVD) technologies. However, these methods generally suffer from high equipment investment, complex processes, harsh production conditions, and potential adverse effects on the environment or subsequent processing, which restricts their large-scale application and cost control in industrial production.

[0003] Recently, a sol-gel method has emerged that can form a titanium nitride coating on the surface of grain-oriented silicon steel without relying on expensive PVD or CVD equipment, resulting in lower costs. However, the sol-gel method involves acid in its reaction system, and the process requires brushing the solution onto the grain-oriented silicon steel surface. The acid can corrode the steel, affecting its future service life. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a method for forming a titanium nitride coating on oriented silicon steel without corroding the surface of the oriented silicon steel, and provides oriented silicon steel obtained by the method.

[0005] The technical solution adopted by this invention to solve its technical problem is: In a first aspect, this application provides a method for forming a titanium nitride coating on oriented silicon steel, comprising the steps of: dissolving pyrazine-2,3-dicarboxylic acid in ethanol, adding tetrabutyl titanate and stirring to react, adding oxalic acid, and then adding water to form a sol, aging the sol and drying it, and grinding it into a gel powder; covering the gel powder onto a polished oriented silicon steel, and then performing a heat treatment at 1000°C to 1050°C in a flowing nitrogen atmosphere, and finally cooling it to room temperature.

[0006] The method for forming a titanium nitride coating on oriented silicon steel provided in this application can prepare a dense titanium nitride coating on the silicon steel surface with strong adhesion. Most of the excess gel powder that did not participate in the coating formation is also converted into titanium nitride, which can be recycled and used as a functional filler in coatings and plastics.

[0007] Furthermore, the mass of the pyrazine-2,3-dicarboxylic acid is equivalent to 8.4% to 14% of the mass of the ethanol.

[0008] Furthermore, the amount of water used is equivalent to 2.3 to 3.5 times the mass of the pyrazine-2,3-dicarboxylic acid.

[0009] Furthermore, the mass ratio of the tetrabutyl titanate to the pyrazine-2,3-dicarboxylic acid is 1:0.41~0.43.

[0010] Furthermore, the mass ratio of tetrabutyl titanate to oxalic acid is 1:0.4~0.6. Oxalic acid is used to adjust the carbon content of the system and the uniformity of the reaction. If the amount of oxalic acid is too small, the hydrolysate of tetrabutyl titanate cannot be uniformly dispersed in the sol, and precipitation will occur.

[0011] Furthermore, the heat treatment time is 25 min to 30 min.

[0012] Furthermore, the drying temperature is 85℃~90℃.

[0013] Furthermore, in the step of coating the gel powder onto the polished oriented silicon steel, 0.3g to 0.5g of the gel powder is applied to each cubic centimeter of polished oriented silicon steel.

[0014] From a reaction equilibrium perspective, this dosage is actually excessive. Not all the gel powder will participate in the formation of the titanium nitride coating; some gel powder will remain, still appearing as titanium nitride particles after heat treatment. This dosage ensures adequate coverage of the gel powder, resulting in a denser titanium nitride coating with stronger adhesion. However, excessive gel powder coverage will negatively impact mass and heat transfer during the heat treatment process.

[0015] In a second aspect, this application provides an oriented silicon steel with a surface covered by a titanium nitride coating prepared by the method described in the first aspect for forming a titanium nitride coating on oriented silicon steel.

[0016] Furthermore, the thickness of the titanium nitride coating is 0.4 μm to 0.6 μm.

[0017] The beneficial effects of this invention are: it does not corrode grain-oriented silicon steel, can prepare a dense titanium nitride coating on the surface of silicon steel with strong adhesion, and most of the excess gel powder that does not participate in the formation of the coating is also converted into titanium nitride, which can be recycled for other fields. The method does not require expensive equipment in processes such as PVD and CVD, the process is simple, the raw materials are readily available, the cost is low and it is easy to implement in industrialization. It has important industrial significance for improving the performance of grain-oriented silicon steel and reducing transformer losses.

[0018] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0019] Figure 1 The images show the XRD patterns of the polished substrate, the heat-treated silicon steel, and the remaining powder after heat treatment in Example 1.

[0020] Figure 2 These are electron microscope images of the substrate surface after polishing and the silicon steel surface after heat treatment in Example 1.

[0021] Figure 3 This is an electron microscope analysis image of the cross-section of the silicon steel after heat treatment in Example 1.

[0022] Figure 4 This is an analysis graph showing the effect of temperature increase on gel powder. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this invention.

[0024] It should be understood that, without conflict, any and all embodiments of the present invention can be combined with technical features of any other embodiment or multiple other embodiments to obtain other embodiments. The present invention includes such combinations to obtain other embodiments.

[0025] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter pertains. Where multiple definitions exist for a term, the definition herein shall prevail.

[0026] This application provides a method for forming a titanium nitride coating on oriented silicon steel, comprising the following steps: dissolving pyrazine-2,3-dicarboxylic acid in ethanol, adding tetrabutyl titanate and stirring to react, adding oxalic acid, and then adding water to form a sol, aging the sol and drying it, and grinding it into a gel powder; covering the gel powder onto polished oriented silicon steel, then heat-treating it in a flowing nitrogen atmosphere, and finally cooling it to room temperature.

[0027] The mechanism of coating formation is roughly as follows: After the gel powder is coated on the polished oriented silicon steel surface, it is heated in N2 atmosphere. The amorphous carbon formed by the pyrolysis of the precursor powder reacts with Fe on the silicon steel surface at 800℃ to form Fe3C, reaction formula (1). 3Fe + C = Fe3C (1; Fe3C + 0.5TiO2+ 0.25N2= 3Fe + 0.5TiN + CO (2); As the heat treatment temperature increases, Fe3C reacts with the titanium oxide formed by pyrolysis, with N2 as one of the nitrogen sources, thereby generating a TiN coating on the silicon steel surface, reaction formula (2).

[0028] Preparation Example 1 Pyrazine-2,3-dicarboxylic acid was dissolved in ethanol, and then tetrabutyl titanate was added. The mixture was stirred at room temperature for 1 hour to allow for complete reaction. Oxalic acid was then added, followed by a small amount of deionized water (equivalent to 3.1 times the mass of pyrazine-2,3-dicarboxylic acid) to obtain a sol. The sol was aged at room temperature, dried at 90°C, and ground to obtain the gel powder of Preparation Example 1. The mass ratio of tetrabutyl titanate:pyrazine-2,3-dicarboxylic acid:oxalic acid was 1:0.42:0.5.

[0029] Preparation Example 2 Pyrazine-2,3-dicarboxylic acid was dissolved in ethanol, and then tetrabutyl titanate was added. The mixture was stirred at room temperature for 1 hour to allow for complete reaction. Oxalic acid was then added, followed by a small amount of deionized water (equivalent to 3.5 times the mass of pyrazine-2,3-dicarboxylic acid) to obtain a sol. The sol was aged at room temperature, dried at 90°C, and ground to obtain the gel powder of Preparation Example 2. The mass ratio of tetrabutyl titanate:pyrazine-2,3-dicarboxylic acid:oxalic acid was 1:0.42:0.8.

[0030] Example 1 The surface of the polished oriented silicon steel was covered with a dry gel, with 0.4 g of the gel powder from Preparation Example 1 covering each cubic centimeter of polished oriented silicon steel. The mixture was then heated at 1000°C for 30 min in a flowing N2 atmosphere and then cooled to room temperature to obtain the oriented silicon steel of Example 1.

[0031] Comparative Example 1 The surface of unpolished oriented silicon steel was covered with dry gel, and 0.4 g of gel powder from Preparation Example 1 was covered per cubic centimeter of polished oriented silicon steel. The mixture was then heated at 1000°C for 30 min in a flowing N2 atmosphere and then cooled to room temperature to obtain the oriented silicon steel of Comparative Example 1.

[0032] Example 2 The surface of the polished oriented silicon steel was covered with a dry gel, with 0.5 g of the gel powder from Preparation Example 2 covering each cubic centimeter of polished oriented silicon steel. The mixture was then heated at 1000°C for 30 min in a flowing N2 atmosphere and then cooled to room temperature to obtain the oriented silicon steel of Example 2.

[0033] Comparative Example 2 The surface of the polished oriented silicon steel was covered with a dry gel, with 0.4 g of the gel powder from Preparation Example 1 covering each cubic centimeter of polished oriented silicon steel. The mixture was then heated at 400°C for 30 min in a flowing N2 atmosphere and then cooled to room temperature to obtain the oriented silicon steel of Comparative Example 2.

[0034] Comparative Example 3 The surface of the polished oriented silicon steel was covered with a dry gel, with 0.4 g of the gel powder from Preparation Example 1 covering each cubic centimeter of polished oriented silicon steel. The mixture was then heated at 800°C for 30 min in a flowing N2 atmosphere and then cooled to room temperature to obtain the oriented silicon steel of Comparative Example 3.

[0035] XRD analysis was performed on the polished grain-oriented silicon steel (without powder coating) of Example 1, the grain-oriented silicon steel obtained after heat treatment of Example 1, and the remaining powder after heat treatment of Example 1. The results are as follows: Figure 1 As shown.

[0036] Figure 1 In section (a), corresponding to the grain-oriented silicon steel obtained after heat treatment in Example 1, it can be seen that in the XRD pattern, 2 θ Characteristic diffraction peaks of TiN (PDF87-0629) were detected at 36.5°, 42.6°, and 61.8°, indicating the formation of TiN on the silicon steel surface. Furthermore, characteristic diffraction peaks of Fe (PDF87-0722) were also detected in the XRD pattern, indicating that the TiN coating on the silicon steel surface is relatively thin. The cell parameters of TiN in the coating were calculated. a =4.236Å, slightly lower than pure cubic TiN ( a The cell parameters are 4.238 Å, and the coating contains TiO₂. x N y Solid solution.

[0037] Figure 1 The powder remaining after heat treatment in Example 1 is shown in section (b). It can be seen that after heat treatment at 1000°C, the dry gel powder on the surface of silicon steel is also converted into TiN. The purity of TiN obtained was calculated to be ~98.3% using formula (3).

[0038] (3); Where m0 is the mass of TiN obtained, and m1 is the mass of TiN powder converted into TiO2 by calcination in air. M TiN The molecular weight of TiN is... M TiO2 is the molecular weight of TiO2.

[0039] Figure 1 In section (c), corresponding to the polished grained silicon steel of Example 1, the results show that the substrate (grained silicon steel) has no Mg2SiO4 underlayer on the surface after polishing, and the bonding... Figure 1 Analysis at point (a) further indicates that TiN was formed on the substrate surface after heat treatment.

[0040] The surfaces of the polished grained silicon steel (without powder coating) from Example 1 and the grained silicon steel obtained after heat treatment in Example 1 were observed and analyzed under a SEM electron microscope. Figure 2 The coated cross-section of the grained silicon steel obtained after heat treatment in Example 1 was observed and analyzed under a SEM electron microscope. Figure 3 . Figure 2 In section (a), the surface of the polished grained silicon steel from Example 1 is shown. Figure 2 In sections (b) and (c), the grained silicon steel obtained after heat treatment in Example 1 is shown. Section (c) is a high-resolution magnification of the area within the red box in section (b), showing that a golden TiN coating was formed on the surface of the silicon steel after heat treatment at 1000°C (see color). Figure 2 (Top left corner of b) The coating is dense and crack-free, but exhibits slight unevenness. The map (elemental surface scan) shows that the Ti element distribution is uneven, indicating that the coating thickness is not uniform. Figure 2 At point (d); look again Figure 3 , Figure 3 The first image from left to right at point (g) is the original electron microscope image, the second is the Fe element location distribution map, and the third is the Ti element location distribution map. The SEM and map images of the coating cross-section also show that the TiN coating thickness on the silicon steel surface is uneven, which is due to scratches on the substrate surface after polishing. The adhesion between the coating and the substrate was tested using the cross-cut adhesion test, achieving an ASTM level of 5B, indicating good bonding between the substrate and the coating. The cross-sectional SEM image also shows a tight bond between the coating and the substrate. The line distribution map indicates that the average thickness of the TiN coating is approximately 0.5 μm.

[0041] Example 2 uses the gel powder from Example 2. However, the amount of oxalic acid used in Example 2 was too high. The molecular structure of oxalic acid was not destroyed in the gel system. As the temperature increases, it will pyrolyze and produce gas. Excessive gas will affect the contact between the pyrolysis products and the silicon steel, resulting in uneven local coating growth.

[0042] The surface of Comparative Example 1 could not form a coating because the surface of the finished grain-oriented silicon steel had a magnesium silicate underlayer (Mg2SiO4), which had to be removed before a coating could be produced.

[0043] Thermogravimetric and differential scanning calorimetric analyses were performed on the gel powder prepared in Example 1, and the results are as follows: Figure 4 As shown in section (a). XRD analysis was performed on the grain-oriented silicon steels of Comparative Example 2 and Comparative Example 3, and the results are as follows. Figure 4 As shown in section (b). Comparative Example 2 and Comparative Example 3 grain-oriented silicon steels were observed and analyzed under a SEM electron microscope. SEM images are shown below. Figure 4 The EDS (energy dispersive spectroscopy) plots (c) (Comparative Example 2) and (d) (Comparative Example 3) corresponding to the SEM plots are shown below. Figure 4 There are three pictures, one above (c) and one below (e) and one below (f).

[0044] The TG-DSC curve (RT-1200°C, N2, 10°C / min) indicates that from RT (room temperature) to 400°C, the main process is the pyrolysis of the dry gel powder. Figure 4 As shown in section (b), after heat treatment at 400°C, no crystalline phase was detected in the XRD pattern of the dry gel, indicating that at this temperature, the dry gel pyrolyzes to form amorphous carbon and amorphous titanium dioxide. No significant weight loss was observed in the TG curve between 400°C and 800°C. After calcination at 800°C, characteristic diffraction peaks of TiO2 were detected in the XRD pattern, indicating that the main process between 400°C and 800°C was the crystallization of amorphous titanium dioxide. Significant weight loss was observed in the TG curve between 800°C and 1000°C, which is due to the carbothermic reduction nitridation reaction between the pyrolyzed amorphous carbon and titanium dioxide.

[0045] and Figure 2 Compared to point (a), the substrate of Comparative Example 2 showed little morphological change after heat treatment at 400°C in dry gel powder, and the EDS of region A indicated that the surface composition of the silicon steel remained unchanged after heat treatment at 400°C. However, in the figure corresponding to Comparative Example 3, the surface of the silicon steel showed significant changes after heat treatment at 800°C, with a large number of white particles appearing on its surface. The Gibbs free energy curve of reaction formula (1) ( Figure 4 The middle (e) indicates that when T>542°C, ΔG<0. The EDS plots of the junction points A and B show that after heat treatment at 800°C, Fe on the substrate surface reacts with the amorphous carbon formed by the pyrolysis of the gel powder to form granular Fe3C. The Gibbs free energy curve of reaction formula (2) ( Figure 4 The middle (f) indicates that when T>958°C, ΔG<0, and the whole system is a flowing N2 atmosphere. The CO content in the system is extremely low, which will also promote the reaction (2). Therefore, as the heat treatment temperature increases, Fe3C and TiO2 on the surface of silicon steel react in N2 atmosphere to form TiN coating.

[0046] Applying this application to actual silicon steel production scenarios, after decarburization, instead of applying magnesium oxide coating liquid, the gel dry powder can be uniformly sprayed onto the surface of the decarburized plate, and then a TiN coating is formed during the high-temperature annealing stage. Specifically, an Fe3C layer is formed on the silicon steel surface at 800℃, and at 1000℃, TiO2 replaces the carbon in Fe3C, and titanium reacts with N2 to form TiN. The replaced Fe anchors the titanium nitride coating onto the silicon steel surface.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for forming a titanium nitride coating on grain-oriented silicon steel, characterized in that the steps include... include: Pyrazine-2,3-dicarboxylic acid was dissolved in ethanol, tetrabutyl titanate was added and stirred to react, oxalic acid was added, and water was added to form a sol. The sol was aged, dried, and ground into a gel powder. The gel powder was coated on polished oriented silicon steel and then heat-treated at 1000℃~1050℃ in a flowing nitrogen atmosphere, and finally cooled to room temperature.

2. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, The mass of the pyrazine-2,3-dicarboxylic acid is equivalent to 8.4% to 14% of the mass of the ethanol.

3. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, The amount of water used is equivalent to 2.3 to 3.5 times the mass of the pyrazine-2,3-dicarboxylic acid.

4. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, The mass ratio of the tetrabutyl titanate to the pyrazine-2,3-dicarboxylic acid is 1:0.41~0.

43.

5. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, The mass ratio of tetrabutyl titanate to oxalic acid is 1:0.4~0.

6.

6. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, The heat treatment time is 25 min to 30 min.

7. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, The drying temperature is 85℃~90℃.

8. The method for forming a titanium nitride coating on grain-oriented silicon steel according to claim 1, characterized in that, In the step of coating the gel powder onto the polished oriented silicon steel, 0.3g to 0.5g of the gel powder is applied to each cubic centimeter of polished oriented silicon steel.

9. A type of grain-oriented silicon steel, characterized in that, The surface is covered with a titanium nitride coating prepared by the method of forming a titanium nitride coating on oriented silicon steel according to any one of claims 1 to 8.

10. The grain-oriented silicon steel according to claim 9, characterized in that, The thickness of the titanium nitride coating is 0.4 μm to 0.6 μm.

Images