Preparation method of base metal special for cold-rolled oriented silicon steel ultra-thin strip

Abstract

The invention discloses a preparation method of a base material special for a cold-rolled oriented silicon steel ultra-thin strip, and relates to the technical field of cold-rolled oriented silicon steel preparation. According to the preparation method of the base metal special for the cold-rolled oriented silicon steel ultra-thin strip, the problems that a traditional base metal is poor in surface quality and insufficient in grain uniformity are successfully solved through component optimization and process cooperative regulation and control; the surface of the prepared special base material is free of glass film bottom layers and oxide residues, high in smoothness and free of strong acid pickling, environmental pollution is avoided, and a clean substrate is provided for subsequent processing; the secondary recrystallization grain size uniformity is excellent, the orientation degree is high, the proportion of small grains is effectively reduced, and a solid foundation is laid for the stability of the magnetic performance of the ultra-thin strip. Meanwhile, the base metal is high in adaptability, the machining control is simple and the machining stability is good when the cold-rolled oriented silicon steel ultra-thin strip is subsequently prepared, and the fault risk in the production process is effectively reduced; and finally, the ultra-thin strip product is outstanding in magnetic performance advantage, lower in iron loss and higher in magnetic density.

Description

Technical Field

[0001] This application belongs to the field of cold-rolled grain-oriented silicon steel preparation technology, and particularly relates to a method for preparing a special base material for ultra-thin cold-rolled grain-oriented silicon steel strip. Background Technology

[0002] As a key material for core electronic components such as medium and high frequency transformers, cold-rolled grain-oriented silicon steel ultra-thin strip is produced industrially using conventional grain-oriented silicon steel as the base material and through processes such as coating removal, cold rolling, and annealing. The core lies in achieving performance control by relying on specific texture transformation rules.

[0003] However, traditional substrate preparation processes face three major technological bottlenecks: First, conventional substrate decarburization and annealing results in a firmly adhered magnesium silicate glass film substrate with "roots." Removing this substrate with strong acid washing leads to surface roughness, unstable iron loss in ultrathin strips, and environmental pollution. Some substrate-free technologies also suffer from oxide residues and excessive roughness. Second, secondary recrystallization results in uneven grain size and insufficient orientation. Some substrate-free technologies also exhibit an excessively high proportion of small grains, leading to poor magnetic property consistency in ultrathin strips. Third, existing technologies suffer from mismatched composition adjustments and process parameters, poor synergy, and reliance on specialized equipment, making industrialization difficult and costly.

[0004] These problems prevent traditional masterbatches from meeting quality standards, resulting in complex ultra-thin strip processing, large fluctuations in magnetic properties, and high production costs, making it difficult to meet the mass production demands of the electronics industry. Therefore, the industry urgently needs a dedicated masterbatch preparation method that balances surface quality, grain uniformity, and industrial feasibility. Summary of the Invention

[0005] To address some or all of the technical problems existing in the prior art, this application provides a method for preparing a special base material for cold-rolled grain-oriented silicon steel ultra-thin strip.

[0006] This application provides a method for preparing a special base material for cold-rolled grain-oriented silicon steel ultra-thin strip, comprising the following steps: Step S1: Composition adjustment, using Fe as the matrix, the basic components and composite elements are adjusted according to weight percentage; wherein, the basic components include Si, Al, N, Mn, S, Cu, the composite elements are one or more of Sn, Nb, Bi, and the remainder is Fe and unavoidable impurities; Step S2: Initial recrystallization annealing. The cold-rolled sheet prepared by smelting and rolling the composition in step S1 is annealed at a temperature of 820℃~880℃. In the heating zone of 400℃ to 750℃, a mixture of N2 and H2 is used as a protective gas. Step S3: Cold rolling treatment, with the cold rolling reduction rate controlled at 40%~60%, to achieve overall breakage and peeling of the oxide layer; Step S4: Applying the release agent, applying the release agent with [Cl] and [Na] ion additives, and controlling the hydration rate of the release agent after drying; Step S5: Secondary recrystallization annealing, using dry nitrogen-hydrogen mixture and pure hydrogen as annealing atmosphere for heating, holding at temperatures of 600℃~680℃ and 1150℃~1200℃ respectively, and then slowly cooling to 1000℃ to obtain the special base material.

[0007] Preferably, in step S1, the weight percentage content of each component is as follows: Si: 2.80%~3.25%, Al: 0.01%~0.03%, N: 0.007%~0.011%, Mn: 0.10%~0.30%, S: 0.005%~0.015%, Cu: 0.10%~0.70%, (Sn+Nb+Bi): 0.005%~0.085%.

[0008] Preferably, in step S2, the thickness of the cold-rolled sheet is 0.60mm~0.80mm, and the surface roughness is ≤0.2μm.

[0009] Preferably, in step S2, the dew point DP of the N2 and H2 mixture in the heating zone is ≥40℃, and the partial pressure ratio P(H2O) / P(H2) is ≥0.42.

[0010] Preferably, in step S4, the separating agent containing [Cl] and [Na] ion additives is MgO or Al2O3.

[0011] Preferably, in step S4, the hydration rate of the release agent after drying is ≤1.5.

[0012] Preferably, in step S5, the heating rate of the secondary recrystallization annealing is ≥15℃ / h.

[0013] Preferably, in step S5, the heat preservation time for the temperature range of 600℃~680℃ and the temperature range of 1150℃~1200℃ is 24h.

[0014] Preferably, in step S5, the cooling rate after heat preservation is ≤10℃ / h.

[0015] The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip of this application has the following advantages and positive effects: Through component optimization and synergistic process control, the problems of poor surface quality and insufficient grain uniformity of traditional base materials were successfully solved. The prepared special base material has no glass film underlayer or oxide residue on its surface, has high smoothness, and does not require strong acid pickling, thus avoiding environmental pollution and providing a clean substrate for subsequent processing. The secondary recrystallization exhibits excellent grain size uniformity and high orientation, effectively reducing the proportion of small grains and laying a solid foundation for the magnetic performance stability of ultra-thin strips. At the same time, the base material has strong adaptability, making subsequent processing control simple and ensuring good processing stability when preparing cold-rolled oriented silicon steel ultra-thin strips, effectively reducing the risk of failure during production. The final ultra-thin strip product has outstanding magnetic performance advantages, with lower iron loss and higher magnetic flux density, which can fully meet the stringent requirements of electronic components such as medium and high frequency transformers. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0017] The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip of this application includes the following steps: Step S1: Composition blending. Using Fe as the matrix, the basic components and composite elements are blended according to weight percentage. The basic components include Si, Al, N, Mn, S, and Cu; the composite elements are one or more of Sn, Nb, and Bi; the remainder is Fe and unavoidable impurities. The weight percentage content of each component is as follows: Si: 2.80%~3.25%; This range ensures the basic magnetic properties of silicon steel while avoiding excessive Si content that would increase material brittleness and processing difficulty, thus balancing magnetic properties and processing feasibility.

[0018] Al: 0.01%~0.03%; It precisely matches with N to form AlN inhibitors, which regulate the secondary recrystallization process by inhibiting abnormal grain growth; If the content is too low, it cannot form a sufficient amount of inhibitor, and if it is too high, it is easy to produce Al2O3 inclusions, which will affect the purity of the parent material.

[0019] N: 0.007%~0.011%; provides a sufficient source of elements for the formation of AlN inhibitors, ensuring the uniformity of the number and distribution of inhibitors, effectively controlling grain size, and avoiding internal defects such as pores caused by excessive N content.

[0020] Mn: 0.10%~0.30%; it combines with S to form MnS inhibitors, which in turn work with AlN inhibitors to regulate the secondary recrystallization rate, while improving the material's processing toughness and preventing cracks from forming during rolling.

[0021] S: 0.005%~0.015%; combines with Mn to form MnS inhibitor, which helps to refine the grains. The content needs to be strictly controlled. If it is too low, it cannot form an effective inhibitor, and if it is too high, it is easy to generate sulfide inclusions, which will affect the magnetic properties.

[0022] Cu: 0.10%~0.70%; promotes uniform grain growth and accelerates secondary recrystallization.

[0023] (Sn+Nb+Bi): 0.005%~0.085%; The addition of one or more of Sn, Nb, and Bi can specifically improve the extreme density of the base material {110}, significantly increasing the {110} density. <001> The quantity of secondary recrystallization nuclei (Gaussian nuclei) ensures uniformity in secondary recrystallization grain size and effectively increases the secondary recrystallization rate, thereby improving the annealing heating rate and reducing costs. Gaussian nuclei are crucial for ensuring the excellent magnetic properties of ultra-thin cold-rolled grain-oriented silicon steel strips. Sufficient and uniformly distributed Gaussian nuclei enhance the magnetic flux density and iron loss performance of the subsequent ultra-thin strips. 0.005% is the critical lower limit for the composite element to play its role; below this value, the number of Gaussian nuclei is insufficient, making it difficult to achieve texture optimization and grain homogenization. 0.085% is the upper limit to avoid negative impacts; above this value, elemental segregation is easily triggered, leading to localized structural defects and ultimately compromising grain uniformity and magnetic property stability.

[0024] Step S2: Initial recrystallization annealing. The cold-rolled sheet produced by smelting and rolling the composition prepared in step S1 is annealed. The thickness of the cold-rolled sheet is 0.60mm~0.80mm, which ensures that the initial recrystallization annealing is sufficient and uniform, leaving enough reduction space for subsequent cold rolling to remove the oxide layer, and avoiding damage to the substrate during processing due to excessive thickness. The surface roughness is ≤0.2μm, which reduces the unevenness of oxide layer adhesion and avoids the formation of localized stubborn oxide areas on the rough surface, laying the foundation for the complete removal of the oxide layer in subsequent cold rolling, and ensuring the final surface finish of the base material. The annealing temperature is 820℃~880℃, avoiding the brittle temperature range of the material, and promoting sufficient initial recrystallization. In the heating zone of 400℃ to 750℃, a mixture of N2 and H2 gas is used as a protective gas. The dew point DP of the N2 and H2 gas mixture in the heating zone is ≥40℃ to create a suitable oxidation atmosphere, ensuring the formation of a complete and loose oxide layer, avoiding insufficient oxidation due to excessively low dew point, or excessive oxidation due to excessively high dew point. The partial pressure ratio P(H2O) / P(H2) ≥0.42 controls the oxidation reaction intensity and ensures that the oxide layer only adheres to the surface and does not penetrate into the substrate.

[0025] Step S3: Cold rolling treatment. The cold rolling reduction rate is controlled at 40%~60%. The loose oxide layer is broken and completely peeled off by rolling stress. If the reduction rate is too low, the oxide layer cannot be completely peeled off. If it is too high, the matrix may be excessively deformed and scratches may be generated on the surface. At the same time, this reduction rate will not damage the matrix structure and ensure the stability of subsequent secondary recrystallization. In addition, the thickness specification of the base material is controlled according to the target thickness requirements of the cold-rolled grain-oriented silicon steel ultra-thin strip.

[0026] Step S4: Applying the release agent. Apply a release agent containing [Cl] and [Na] ion additives. After drying, control the hydration rate of the release agent to ≤1.5 to prevent the release agent from absorbing moisture and deteriorating, and ensure the stability of the release effect during the secondary recrystallization process. The release agent containing [Cl] and [Na] ion additives is MgO or Al2O3. MgO and Al2O3 are the base release agents to avoid the adhesion of the parent material during the secondary recrystallization process. The [Cl] and [Na] ion additives optimize the interface state between the release agent and the parent material, further inhibiting the formation of Mg2SiO4 glass film.

[0027] Step S5: Secondary recrystallization annealing. A dry nitrogen-hydrogen mixture and pure hydrogen are used as the annealing atmosphere for heating to avoid secondary oxidation caused by moisture in the atmosphere, ensuring the cleanliness of the base material surface and providing a stable thermodynamic environment for secondary recrystallization. The heating rate is ≥15℃ / h to improve production efficiency while ensuring uniform grain growth. Temperatures are held in the ranges of 600℃~680℃ and 1150℃~1200℃ respectively. The inhibitory effect is optimized in the 600℃~680℃ range to facilitate secondary recrystallization. Preparation: The secondary recrystallization is fully promoted in the range of 1150℃~1200℃ to ensure uniform grain growth and improved orientation. The holding time is 24h to ensure that the effect of each temperature range is fully utilized and to avoid incomplete secondary recrystallization and uneven grains due to insufficient holding. After holding, the temperature is slowly reduced to 1000℃ at a rate of ≤10℃ / h to obtain a special base material. Slow cooling avoids abnormal grain growth or internal stress, locks in a uniform and fine recrystallized structure and high orientation, and ensures the stability of the magnetic properties of the base material.

[0028] The present application will be further described below with reference to specific embodiments.

[0029] Table 1 shows the specific values ​​of chemical components and processes for each embodiment and comparative example of this application: ; Table 2 lists the performance test results of each embodiment and comparative example of this application: ; As can be confirmed from Tables 1 and 2, the preparation method of the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip provided in this application achieves the absence of glass film and oxide on the surface, while also ensuring the uniformity of the secondary recrystallized grain size, with the proportion of secondary recrystallized grains with a diameter of <5mm being <5%.

[0030] Using the invention examples and comparative examples as base materials, 0.08mm grain-oriented silicon steel ultrathin strip products were prepared by 50%~70% cold rolling followed by H2 protective annealing. The ultrathin strips prepared using comparative examples 1, 2, and 3 as base materials had different P values. 1.5 / 400 The values ​​were 13.8 W / kg, 18.4 W / kg, and 13.1 W / kg, respectively. 800 The values ​​are 1.76T, 1.68T, and 1.80T respectively, and the P of the ultrathin strips prepared using the invention as the base material is... 1.5 / 400 ≤11.5W / kg, B 800 With a thickness of ≥1.82T, it can be seen that the ultrathin strip prepared using the invention example has significant performance advantages.

[0031] This application successfully solves the problems of poor surface quality and insufficient grain uniformity of traditional base materials through composition optimization and synergistic process control. The prepared special base material has no glass film underlayer or oxide residue on its surface, has high smoothness, and does not require strong acid pickling, thus avoiding environmental pollution and providing a clean substrate for subsequent processing. The secondary recrystallization exhibits excellent grain size uniformity and high orientation, effectively reducing the proportion of small grains and laying a solid foundation for the magnetic performance stability of the ultra-thin strip. At the same time, the base material has strong adaptability, making the subsequent preparation of cold-rolled oriented silicon steel ultra-thin strips simple to control and with good processing stability, effectively reducing the risk of failure during production. The final ultra-thin strip product has outstanding magnetic performance advantages, with lower iron loss and higher magnetic flux density, which can fully meet the stringent requirements of electronic components such as medium and high frequency transformers.

[0032] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. At the same time, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a special base material for ultra-thin cold-rolled grain-oriented silicon steel strip, characterized in that, Includes the following steps: Step S1: Composition adjustment, using Fe as the matrix, the basic components and composite elements are adjusted according to weight percentage; wherein, the basic components include Si, Al, N, Mn, S, Cu, the composite elements are one or more of Sn, Nb, Bi, and the remainder is Fe and unavoidable impurities; Step S2: Initial recrystallization annealing. The cold-rolled sheet prepared by smelting and rolling the composition in step S1 is annealed at a temperature of 820℃~880℃. In the heating zone of 400℃ to 750℃, a mixture of N2 and H2 is used as a protective gas. Step S3: Cold rolling treatment, with the cold rolling reduction rate controlled at 40%~60%, to achieve overall breakage and peeling of the oxide layer; Step S4: Applying the release agent, applying the release agent with [Cl] and [Na] ion additives, and controlling the hydration rate of the release agent after drying; Step S5: Secondary recrystallization annealing, using dry nitrogen-hydrogen mixture and pure hydrogen as annealing atmosphere for heating, holding at temperatures of 600℃~680℃ and 1150℃~1200℃ respectively, and then slowly cooling to 1000℃ to obtain the special base material.

2. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 1, characterized in that, In step S1, the weight percentage content of each component is as follows: Si: 2.80%~3.25%, Al: 0.01%~0.03%, N: 0.007%~0.011%, Mn: 0.10%~0.30%, S: 0.005%~0.015%, Cu: 0.10%~0.70%, (Sn+Nb+Bi): 0.005%~0.085%.

3. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 2, characterized in that, In step S2, the thickness of the cold-rolled sheet is 0.60mm~0.80mm, and the surface roughness is ≤0.2μm.

4. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 3, characterized in that, In step S2, the dew point DP of the N2 and H2 mixture in the heating zone is ≥40℃, and the partial pressure ratio P(H2O) / P(H2) is ≥0.

42.

5. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 2, characterized in that, In step S4, the separating agent containing [Cl] and [Na] ion additives is MgO or Al2O3.

6. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 5, characterized in that, In step S4, the hydration rate of the release agent after drying is ≤1.

5.

7. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 2, characterized in that, In step S5, the heating rate of the secondary recrystallization annealing is ≥15℃ / h.

8. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 7, characterized in that, In step S5, the heat preservation time for the temperature range of 600℃~680℃ and the temperature range of 1150℃~1200℃ is 24h.

9. The method for preparing the special base material for cold-rolled grain-oriented silicon steel ultra-thin strip according to claim 8, characterized in that, In step S5, the cooling rate after heat preservation is ≤10℃ / h.