Silicon steel sheet core pile bonding, insulating and high-temperature-corrosion-resistant protection treatment method

Abstract

The invention belongs to the technical field of surface engineering technology and high-temperature environment corrosion protection, and particularly relates to a silicon steel sheet core pile bonding, insulating and high-temperature-corrosion-resistant protection treatment method, which comprises the following steps of: pre-paving a PEEK coating or PEEK paint doped with a hard material between silicon steel sheets, and sintering at high temperature under static pressure to obtain a silicon steel sheet core pile; a hard material doped PEEK coating or a silicon steel sheet core pile protected by a PEEK coating is formed, the distance between silicon steel sheets is controlled within 5 micrometers, the resistance between the silicon steel sheets is larger than or equal to 1 M omega.cm < 2 >, and the electrical performance of the silicon steel sheet core pile is not affected; the coating can be used for a long time in a 200 DEG C steam environment, the rusting phenomenon is avoided, and cracks and spalling on the surface are avoided; after the silicon steel sheet is boiled in boiling water at 100 DEG C for 12 hours and placed in air for 12 hours for seven cycles, no crack or crack appears on the surface, and no corrosion appears on a silicon steel sheet core pile; reliable corrosion protection is provided for the silicon steel sheet core pile under high-temperature and water environment conditions, and the service life is prolonged.

Description

Technical fields:

[0001] This invention belongs to the fields of surface engineering technology and high-temperature environment corrosion protection technology. Specifically, it relates to a method for bonding, insulating, and protecting silicon steel sheet cores against high-temperature corrosion, in order to solve the problem that silicon steel sheet motors cannot be used in high-temperature, humid steam or seawater. Background technology:

[0002] Silicon steel sheets are soft magnetic alloys of silicon and iron with extremely low carbon content. The silicon content is 0.5-4.5% and the carbon content is less than 0.08%. They have characteristics such as high magnetic permeability, low coercivity, and high resistivity. They also have low hysteresis loss and eddy current loss. As a magnetic material in motors, transformers, electrical appliances and electrical instruments, they are widely used in power systems such as vehicles, ships and generators.

[0003] Because silicon steel sheets have relatively low corrosion resistance, they require surface corrosion protection treatment to extend their service life. The preparation of the protective coating is the final step in silicon steel production. The type, process, and quality of the surface coating all affect the insulation, adhesion, stamping properties, and corrosion and rust resistance of the electrical steel, thus affecting its specific total loss and other magnetic properties, and even the safe operation of the entire transformer. Typically, a very thin (0.5-5 μm) insulating coating is applied to the surface of silicon steel sheets to give them high interlayer resistivity, minimizing interlayer power loss and protecting them from various corrosive media during storage, transportation, and use, thereby extending their service life.

[0004] Chinese Patent 202011372065.0 discloses a corrosion-resistant, high-efficiency non-oriented silicon steel sheet for motors and its production method, applying for a corrosion-resistant non-oriented silicon steel sheet based on the material direction.

[0005] Chinese Patent 202310790268.9 discloses a single-component, high-temperature resistant, fast-curing adhesive for silicon steel sheet rotors and its preparation method, and applies for corrosion protection and insulation of silicon steel sheets for battery cells and its treatment method, enabling silicon steel sheets to be used for a long time at 150℃.

[0006] Chinese Patent 201510527689.8 discloses an insulating and corrosion-resistant rotor silicon steel sheet and its heating method. The patent application is for an insulating and corrosion-resistant silicon steel sheet for a transformer core, which can prevent misalignment, improve core quality, save materials and energy, has strong insulation and corrosion resistance, low cost, and simple manufacturing process.

[0007] The magnesium silicate underlayer formed after high-temperature annealing of silicon steel possesses certain insulation and corrosion resistance, while simultaneously generating tensile stress within the steel, resulting in an interlayer resistivity greater than 4 Ω·cm. 2 / pieces, which meet the needs of coiled core distribution transformers, but for medium and large transformers with laminated cores, their resistance is not high enough, so an insulating coating must be applied to the surface.

[0008] Existing insulating coatings for grain-oriented silicon steel mainly fall into three categories: organic coatings, semi-inorganic coatings, and inorganic coatings. Organic coatings primarily consist of organic resins such as acrylic resin, vinyl acetate resin, modified alkyd resin, and epoxy resin. They are commonly used to manufacture high-grade silicon steel for large motors, exhibiting good film-forming properties, insulation, impact resistance, and high shear strength and interlayer resistance. However, they suffer from low film hardness, large thermal shrinkage, poor heat resistance and weldability, and are prone to creep after heating. As the organic resin content in the coating increases, shear strength improves while weldability decreases. In certain special applications, heat treatment at 600℃ is required before use as an insulating coating. Currently, organic coatings are gradually being phased out because most of the resin degrades and volatilizes at 600℃, losing its insulating ability and releasing harmful gases, causing environmental pollution. Furthermore, they cannot undergo stress-relief annealing.

[0009] To mitigate the adverse effects of large secondary grains on iron loss, Nippon Steel proposed a stress coating using ultrafine colloidal SiO2 incorporating a phosphate solution. This stress coating generates isotropic tensile stress on the steel plate surface, reducing iron loss and magnetostriction while simultaneously counteracting the negative effects of external stress on silicon steel. Kawasaki employs a stress coating primarily composed of magnesium phosphate (Mg(H2PO4)2) with added colloidal SiO2 and CrO3, improving moisture resistance and appearance. However, the chromium compounds contain hexavalent Cr, causing environmental pollution and posing challenges for wastewater treatment. Nippon Steel further proposed a solid-solution composite metal hydroxide with average particle sizes less than 1μm or 2-3μm, incorporating borates, acetates, and silicates. This improved adhesion, corrosion resistance, and sintering resistance; however, moisture resistance and heat resistance remained unsatisfactory. Adding fine-particle colloidal oxides reacts with free phosphoric acid to form more stable phosphoric acid compounds, which can improve moisture resistance and heat resistance, and also improve lubricity. To prevent the agglomeration of the colloidal oxide particles, organic acid salts are added. However, the coating liquid is unstable. Therefore, inorganic compounds such as Fe(OH)2 with ultrafine particles of about 10 nm are added to adjust the structure of the colloidal oxides and improve stability.

[0010] Semi-inorganic coatings are insulating coatings formed by mixing inorganic solutions of phosphates and chromates with latex resin solutions. Organic resin powder with a particle size of 2-50 μm is added to the latex resin, mixed with the inorganic solution, and then coated onto the surface of silicon steel and baked. Traditional semi-inorganic coatings use chromates as the inorganic component, which has good corrosion resistance. The organic resin powder is usually one or more copolymers or mixtures of polyethylene, polypropylene, polyamide, benzodiaminotriethylene, polypropylene resin, or polystyrene, among which polystyrene copolymers exhibit the best viscous strength.

[0011] Nippon Steel's tension coating, proposed in 1973, consists primarily of ultrafine colloidal SiO2 (silica sol) mixed with a phosphate coating solution. The tensile stress generated by the coating refines magnetic domains, effectively reducing iron loss and magnetostriction. Studies have shown that by adjusting the coating formulation, drying, and sintering processes, iron loss P1.7 can be reduced by 0.1 W / kg.

[0012] Magnesium oxide coating has a significant impact on the magnetic properties and surface properties of grain-oriented silicon steel. A ceramic insulating film is formed by chemical vapor deposition (CVD). Iron loss can be reduced by using laser treatment and altering the type of inorganic acid in the insulating film coating solution. Results show that by improving the composition of the insulating film coating solution, increasing viscosity stability, and reducing film tension, grain-oriented silicon steel sheets with high magnetic induction and low iron loss can be obtained.

[0013] Hot-rolled silicon steel is coated with an insulating varnish, and cold-rolled silicon steel with a glass coating is also coated with an insulating varnish. Pure organic coatings are less commonly used due to their low hardness and poor heat resistance. Later, phosphate surface coatings with better insulation properties were developed. However, previous coatings, which added chromates to improve corrosion resistance and interlayer resistance, posed serious environmental problems. Water-based chromium-free silicon steel coatings, with water as the main solvent, are considered environmentally friendly, but their practical application is limited by various factors.

[0014] In the production process of grain-oriented silicon steel, to prevent the steel sheet from bubbling during annealing, magnesium oxide (MgO) is coated on the surface of the steel sheet before high-temperature annealing. MgO reacts with the oxide layer formed on the surface of the steel sheet substrate to form a magnesium silicate underlayer. A phosphate tension coating is then applied to the outer surface, forming a double-layer structure of magnesium silicate underlayer and phosphate coating. Due to the difference in thermal expansion coefficients, the phosphate tension coating exerts a tension effect on the substrate after high-temperature cooling. The thermal expansion coefficient of the magnesium silicate underlayer is between that of the steel sheet and the phosphate coating, which is beneficial to the adhesion of the phosphate coating and the exertion of its tension effect.

[0015] With the development of electromechanical products and the expansion of their application fields, more and more underwater weapons and equipment, such as motors and transformers, are using silicon steel sheet core reactors. However, based on current literature and patent information, the anti-corrosion measures for silicon steel sheet core reactors are mainly aimed at corrosion problems in the atmospheric environment, and the protective effect is relatively poor. The coating strength, insulation performance, and waterproof corrosion resistance cannot meet the corrosion protection requirements of silicon steel sheets in underwater environments. In particular, silicon steel sheet core reactors need to withstand high-temperature steam erosion of about 200°C during use. Ordinary coatings soften and peel off at 80°C, and the anti-corrosion effect of high-temperature coatings is extremely poor. They are prone to cracking and loss of protective effect when the temperature changes. Therefore, the research and development of a high-performance and reliable protective coating is of great significance for promoting the widespread application of silicon steel sheet core reactors in underwater environments. Summary of the Invention:

[0016] The purpose of this invention is to overcome the shortcomings of existing technologies and to develop a method for bonding, insulating, and protecting silicon steel sheet core stacks against high-temperature corrosion, thereby solving the problems of deformation, cracking, and corrosion of silicon steel sheet substrates, and enabling silicon steel sheet core stacks to be used for a long time at temperatures not exceeding 200°C.

[0017] To achieve the above objectives, the silicon steel sheet core stack bonding, insulation, and high-temperature corrosion protection method of the present invention involves isolating the silicon steel sheets with a PEEK coating or PEEK paint. Since the silicon steel sheets easily come into contact and become conductive during the sintering process of the PEEK coating or PEEK paint, hard materials such as alumina ceramics or PEEK are added to provide a supporting structure. There are two methods:

[0018] The first method involves setting a 3-5 μm thick polyether ether ketone (PEEK) coating doped with non-conductive materials, including alumina powder, between silicon steel sheets. This coating serves to bond, isolate, and fix the materials. The non-conductive materials also include zirconium oxide, titanium oxide, silicon nitride, and boron carbide, which have relatively good compressive strength.

[0019] A PEEK layer or plastic layer with an alumina powder doping thickness greater than 200 μm is set on the outside of the silicon steel sheet to prevent water from penetrating into the silicon steel sheet. The plastic has a curvature of less than 5 μm and includes polytetrafluoroethylene (PTFE), PVC, polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, polycarbonate (PC), and polyamide (PA).

[0020] The specific process is as follows:

[0021] First, PEEK powder or plastic powder doped with alumina powder is laid at the bottom of the mold, wherein the doping ratio of alumina powder is 30-80% and the particle size is 20-200μm.

[0022] Then, the first layer of silicon steel sheet is laid, and polyether ether ketone (PEEK) powder doped with non-conductive material powder is deposited on the surface of the silicon steel sheet by electrostatic adsorption, or a polyether ether ketone (PEEK) suspension doped with non-conductive material powder is brushed on. The doping ratio of non-conductive material powder is 30-80%, and the particle size is less than 5μm.

[0023] Then, silicon steel sheets are laid layer by layer, and polyetheretherketone (PEEK) powder or suspension doped with non-conductive material powder is deposited or brushed on until the last silicon steel sheet, on which PEEK powder or plastic powder doped with alumina powder is laid.

[0024] Finally, place the mold in a resistance furnace and raise the temperature to 380-420℃ (within this temperature range, the alumina will not melt when sintering the PEEK coating). Hold the temperature for 20-30 minutes and then let it cool naturally to room temperature.

[0025] The second method involves placing a polyetheretherketone (PEEK) coating with a thickness of less than 5 μm between silicon steel sheets. This coating, which is doped with PEEK powder or non-conductive material powder, serves to bond, isolate, and fix the materials. The non-conductive materials include zirconium oxide, titanium oxide, silicon nitride, and boron carbide, which have relatively good compressive strength.

[0026] A PEEK coating with a thickness greater than 200μm, doped with PEEK powder, is applied to the outside of the silicon steel sheet to prevent water from penetrating into the silicon steel sheet. The PEEK coating can also be an organic coating that is resistant to high temperatures above 220°C, such as polytetrafluoroethylene (PTFE).

[0027] The specific process is as follows:

[0028] First, a 0.5mm thick layer of PEEK coating doped with PEEK powder is laid on the bottom of the mold. The doping ratio of PEEK powder is 30-80%, and the particle size is 20-200μm.

[0029] Then, the first layer of silicon steel sheet is laid, and a PEEK coating with a thickness of less than 5μm is brushed onto the surface of the silicon steel sheet. The doping ratio of PEEK powder or non-conductive material powder is 30-80%.

[0030] Then, silicon steel sheets are laid layer by layer, and PEEK coating with PEEK powder is brushed on until the last layer of silicon steel sheet, on which a 0.5mm thick PEEK coating with PEEK powder or non-conductive material powder is brushed on.

[0031] Finally, place the mold in a resistance furnace and raise the temperature to 220-260℃ (the PEEK powder will not melt when sintering the PEEK coating within this temperature range). Hold the temperature for 20-30 minutes and then let it cool naturally to room temperature.

[0032] Before implementing the silicon steel sheet core stacking bonding, insulation, and high-temperature corrosion protection treatment method of the present invention, the silicon steel sheet is cleaned with solvents such as ethanol and then dried for use.

[0033] The mold is a heat-resistant concrete mold, which is 1.5% larger than the silicon steel sheet. During processing, the gap between the silicon steel sheet and the mold is filled with a PEEK coating or a PEEK paint mixed with PEEK powder. In addition, the upper and lower parts of the mold are tapered, with the upper part being 0.5-1° wider than the lower part, which facilitates the removal of the silicon steel sheet core stack.

[0034] The silicon steel sheets are positioned using a key shaft. After aligning the silicon steel sheets using the key shaft clamping, the key shaft is removed and replaced with a shaft slightly smaller than the key shaft, and then a coating is applied.

[0035] The interlayer PEEK material can also be laid using a PEEK film. A PEEK film with a thickness of 10-50μm is selected, and alumina particles with a thickness of ≤5μm are bonded to the surface of the PEEK film using ordinary adhesive. PEEK sheets are used for the bottom and sides, and alumina particles or PEEK powder are bonded to the surface.

[0036] Compared with existing technologies, this invention pre-lays a PEEK coating or PEEK paint doped with hard material between silicon steel sheets. Through high-temperature sintering under static pressure, a silicon steel core stack protected by the PEEK coating or PEEK paint doped with hard material is formed. The insulation resistance between the silicon steel sheets is ≥1MΩ. After seven cycles of alternating placement in boiling water at 100℃ and room temperature air, there is no damage or corrosion. The PEEK coating can be used at 260℃, and the PEEK paint can be used at 200℃. In humid steam and seawater environments below 200℃, the PEEK coating or PEEK paint will not deform, crack, or soften, ensuring long-term protective performance. By using insulation, bonding, and high-temperature corrosion protection, the hard material-doped PEEK coating or PEEK paint is prepared, solving the problem of corrosion protection for long-term reliable use of silicon steel core stacks in water environments. Attached image description:

[0037] Figure 1 This is a schematic diagram of the structure of the silicon steel sheet core stack obtained in Example 1.

[0038] Figure 2 This is a schematic diagram of the silicon steel sheet core stack obtained in Example 2.

[0039] Figure 3 The diagram shows a comparison of the appearance of the silicon steel sheet core stack before and after treatment, where a represents before treatment and b represents after treatment.

[0040] Figure 4 This is a topographic image of the silicon steel sheet core stack obtained in Example 1.

[0041] Figure 5 This is a schematic diagram showing the weight change of the PEEK coating on the silicon steel sheet core stack obtained in Example 1 after long-term immersion in seawater at room temperature.

[0042] Figure 6 This is a schematic diagram of the immersion state of the silicon steel sheet core stack processed in Example 2.

[0043] Figure 7 This is a schematic diagram comparing the insulation resistance of the coating on the silicon steel sheet core stack treated in Example 2 before and after immersion.

[0044] Figure 8 This is a schematic diagram of the corrosion morphology of the coating on the silicon steel sheet core stack treated in Example 2 after immersion. Detailed implementation method:

[0045] The invention will be further described below through implementation examples and in conjunction with the accompanying drawings.

[0046] Example 1:

[0047] The silicon steel sheet core stacking, bonding, insulation, and high-temperature corrosion protection method involved in this embodiment uses 100 silicon steel sheets with a thickness of 0.1 mm as the substrate material.

[0048] A PEEK coating containing PEEK powder was applied between and on the outside of the silicon steel sheets. The amount of PEEK powder added was 50%, the particle size was ≤5μm, the sintering temperature was 220℃, the holding time was 30min, the furnace was opened and cooled naturally, the PEEK coating was reapplied after demolding, the secondary sintering temperature was 220℃, the holding time was 30min, and the furnace was opened and cooled naturally.

[0049] The structure of the silicon steel wafer core stack obtained after processing is as follows: Figure 1 As shown, the morphology is as follows Figure 4 As shown, the thickness increment is ≤0.5mm, and the weight change of the coating after long-term immersion in seawater at room temperature is as follows. Figure 5 As shown, during the immersion process, the PEEK coating only gained about 0.13% in weight, and the appearance of the coating did not change significantly, nor did it change color.

[0050] The silicon steel sheet core stack obtained in this embodiment underwent repair treatment:

[0051] Observe the surface morphology of the silicon steel sheet, clean the concrete residue adhering to the surface, and repair any defects such as obvious pores on the surface.

[0052] The repair material uses PEEK coating. The PEEK coating is brushed onto the defective area to completely cover it. It is then baked in an oven at 220-260℃ for 20-40 minutes. After that, the oven door is opened and the area is allowed to cool naturally, thus forming a complete PEEK layer / PEEK coating protection system.

[0053] Example 2:

[0054] The silicon steel sheet core stacking, bonding, insulation, and high-temperature corrosion protection method involved in this embodiment uses 100 silicon steel sheets with a thickness of 0.1 mm as the substrate material.

[0055] A polyetheretherketone (PEEK) coating doped with alumina powder is applied between silicon steel sheets and on the outside of the silicon steel sheets. The amount of alumina powder added is 50%, the particle size is ≤5μm, the sintering temperature is 400℃, the holding time is 30min, the furnace is opened and cooled naturally, repair treatment is performed, after demolding, PEEK coating is reapplied, the secondary sintering temperature is 220℃, the holding time is 30min, and the furnace is opened and cooled naturally.

[0056] The structure of the silicon steel wafer core stack obtained after processing is as follows: Figure 2 As shown, the thickness increment is ≤0.5mm, as... Figure 6 As shown, the coating was immersed in high-temperature seawater for seven cycles, and the resistance values ​​before and after immersion were as follows. Figure 7 As shown, the change in resistance is very small, and the morphology after immersion corrosion is as follows. Figure 8 As shown, no corrosion occurred.

Claims

1. A method for bonding, insulating, and providing high-temperature corrosion protection for silicon steel sheet cores, characterized in that, A PEEK coating or PEEK paint is applied between silicon steel sheets.

2. The method for bonding, insulating, and providing high-temperature corrosion protection for silicon steel sheet cores according to claim 1, characterized in that, Hard materials, including alumina ceramics and PEEK, are added to PEEK coatings or paints.

3. The method for bonding, insulating, and providing high-temperature corrosion protection for silicon steel sheet cores according to claim 2, characterized in that, A polyetheretherketone coating with a thickness of 3-5 μm, doped with a non-conductive material including alumina powder, is applied between silicon steel sheets. A PEEK layer or plastic layer with a thickness greater than 200 μm, doped with alumina powder, is set on the outside of the silicon steel sheet.

4. The method for bonding, insulating, and providing high-temperature corrosion protection for silicon steel sheet cores according to claim 3, characterized in that, Plastics with a curvature of less than 5 μm include polytetrafluoroethylene, PVC, polyethylene, polypropylene, polystyrene, ABS, polycarbonate, and polyamide.

5. The method for bonding, insulating, and providing high-temperature corrosion protection for silicon steel sheet cores according to claim 2, characterized in that, A polyetheretherketone coating with a thickness of less than 5 μm, doped with PEEK powder or non-conductive material powder, is applied between silicon steel sheets. A PEEK coating with a thickness greater than 200 μm, containing doped PEEK powder, is applied to the outside of a silicon steel sheet.

6. The preparation method of the silicon steel sheet core stacking, bonding, insulation, and high-temperature corrosion protection treatment according to claim 5, characterized in that, The PEEK coating is replaced with an organic coating that includes polytetrafluoroethylene and is resistant to damage at temperatures above 220°C.

7. The preparation method of the silicon steel sheet core stacking, bonding, insulation, and high-temperature corrosion protection treatment according to claim 3 or 5, characterized in that, Non-conductive materials include zirconium oxide, titanium oxide, silicon nitride, and boron carbide.

8. The preparation method of the silicon steel sheet core stacking, bonding, insulation, and high-temperature corrosion protection treatment according to claim 3, characterized in that, First, PEEK powder or plastic powder doped with alumina powder is laid at the bottom of the mold, wherein the doping ratio of alumina powder is 30-80% and the particle size is 20-200μm. Then, the first layer of silicon steel sheet is laid, and polyether ether ketone powder doped with non-conductive material powder is deposited on the surface of the silicon steel sheet by electrostatic adsorption, or a polyether ether ketone suspension doped with non-conductive material powder is brushed on. The doping ratio of non-conductive material powder is 30-80%, and the particle size is less than 5μm. Then, silicon steel sheets are laid layer by layer, and polyetheretherketone powder or suspension doped with non-conductive material powder is deposited or brushed on until the last silicon steel sheet, on which PEEK powder or plastic powder doped with alumina powder is laid. Finally, place the mold in an electric resistance furnace, raise the temperature to 380-420℃, hold it at that temperature for 20-30 minutes, and then let it cool naturally to room temperature.

9. The preparation method of the silicon steel sheet core stacking, bonding, insulation, and high-temperature corrosion protection treatment according to claim 5, characterized in that, First, a 0.5mm thick layer of PEEK coating doped with PEEK powder is laid on the bottom of the mold. The doping ratio of PEEK powder is 30-80%, and the particle size is 20-200μm. Then, the first layer of silicon steel sheet is laid, and a PEEK coating with a thickness of less than 5μm is brushed onto the surface of the silicon steel sheet. The doping ratio of PEEK powder or non-conductive material powder is 30-80%. Then, silicon steel sheets are laid layer by layer, and PEEK coating with PEEK powder is brushed on until the last layer of silicon steel sheet, on which a 0.5mm thick PEEK coating with PEEK powder or non-conductive material powder is brushed on. Finally, place the mold in an electric resistance furnace, raise the temperature to 220-260℃, hold it at that temperature for 20-30 minutes, and then let it cool naturally to room temperature.

10. A method for bonding, insulating, and providing high-temperature corrosion protection for silicon steel sheet cores according to claim 8 or 9, characterized in that, Before processing, clean the silicon steel sheet with solvents such as ethanol and dry it for later use; The mold is a heat-resistant concrete mold with a tapered structure at the top and bottom. The width of the upper part is 0.5-1° larger than that of the lower part, and the size is 1.5% larger than that of the silicon steel sheet. During processing, the gap between the silicon steel sheet and the mold is filled with a PEEK coating or a PEEK paint mixed with PEEK powder. The silicon steel sheets are positioned using a key shaft. After aligning the silicon steel sheets using the key shaft clamping, the key shaft is removed and replaced with a shaft slightly smaller than the key shaft, and then a coating is applied. The interlayer PEEK material is laid using a PEEK film with a thickness of 10-50μm. Alumina particles with a thickness of ≤5μm are bonded to the surface of the PEEK film using ordinary adhesive. PEEK sheets are used for the bottom and sides, with alumina particles or PEEK powder bonded to the surface.

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