A method for preparing large-size high silicon steel thin strips by sectional plasticizing

Abstract

The application relates to a method for preparing large-size high-silicon steel thin strips through segmented plasticizing, wherein the high-silicon steel thin strips are composed of the following components: Si 4.5%-7.5%, B 0.005%-0.05%, Nb 0.005%-0.5%, C 0.001%-0.003%, N 0.001%-0.003%, S 0.0005%-0.002%, P 0.002%-0.01%, and the balance of iron and impurities; the preparation process comprises smelting, forging, hot rolling, segmented plasticizing treatment, stress relief annealing, cold rolling and recrystallization annealing; the rolling plasticity of the high-silicon steel is improved in a segmented mode without affecting the maximum cumulative rolling deformation, so that better toughening and plasticizing effects are obtained; the ordered structure recovery is avoided, the processing performance of the high-silicon steel is improved, the preparation of the high-silicon steel cold-rolled thin strips is completed without edge cutting, and the yield is improved; and finally, the large-size high-silicon steel thin strips with good plasticity and comprehensive magnetic properties are obtained.

Description

Technical Field

[0001] This invention relates to the field of silicon steel rolling technology, and in particular to a method for preparing large-size high-silicon steel strips using segmented plasticizing. Background Technology

[0002] In the fields of power, electronics, and military industries, silicon steel is a soft magnetic material with relatively excellent magnetic properties and the largest market share. It is commonly used to manufacture transformers, motors, generators, and electrical components, playing a vital role in economic development and construction. With increasing silicon content, the electrical conductivity and magnetic permeability of silicon steel increase, while iron loss and magnetostriction coefficient decrease. High-silicon steel, in particular, with a silicon content of 6.5 wt% or higher, exhibits even lower iron loss at high frequencies and has an extremely low magnetostriction coefficient, significantly reducing noise. It can be used to manufacture high-speed motors and high-frequency transformers, which is of great significance for energy conservation, emission reduction, and noise reduction.

[0003] As the silicon content in silicon steel increases to 6.5 wt%, a large number of iron-silicon covalent bonds and ordered phases will be generated inside the material matrix. At the same time, due to the solid solution strengthening effect of silicon, the material will be both hard and brittle, making preparation and processing extremely difficult.

[0004] For a long time, people have been committed to the development and research of high-silicon steel strips. Japanese patent JP5569223 successfully prepared high-silicon steel strips using a rapid solidification method, sparking a global surge in research on high-silicon steel. However, due to the rapid cooling rate during the preparation of high-silicon steel strips using this method, numerous dislocations and lattice distortions exist within the strip matrix, along with a large amount of unreleased internal stress. These factors result in poor low-frequency magnetic properties of the strip, requiring heat treatment before use. Furthermore, the strips prepared using this method have limited width and uniform thickness specifications, representing a persistent technical bottleneck that has hindered industrial production. To date, industrialization of this technology has not yet been achieved.

[0005] Japanese patent JP6326330 describes the preparation of high-silicon steel strips using chemical vapor deposition (CVD). The principle involves silicon infiltration on the surface of ordinary silicon steel sheets, followed by homogenization diffusion heat treatment to achieve a silicon content of 6.5% across the entire cross-section of the strip. However, this process is complex, and the raw material SiCl4 used for silicon infiltration is highly toxic and corrosive, causing severe environmental pollution. Furthermore, this process requires extremely high sealing of the production line, involves complex daily maintenance, pollutes the environment with exhaust emissions, has low production efficiency, and is costly and time-consuming. These drawbacks prevent its widespread application.

[0006] Compared with the methods mentioned above, the rolling process for producing strip has advantages such as simple process, low cost, and low energy consumption. Therefore, developing a rolling production process for high-silicon electrical steel strip remains a key research direction in this field. Japanese patents JP62103321, JP61166923, JP63227717A, and JP63069915A disclose methods to effectively improve the cold-rolling formability of high-silicon steel by limiting the grain size of the slab before hot rolling, the microstructure of the hot-rolled plate, the cold rolling process, and the rolling temperature. In their paper "Preparation Process, Structure, and Properties of Cold-Rolled Thin Sheets of 6.5wt% Si High-Silicon Steel," Lin Junpin et al. demonstrated that cold-rolled thin strips prepared using the traditional hot-rolling-cold-rolling process have good sheet shape and a metallic luster. However, the high-silicon steel thin strips prepared by the above methods still have certain edge cracks, and the size specifications of the high-silicon steel thin strips are relatively small (the width of the plates is no more than 100mm), indicating that there is still a gap to be bridged in achieving mass production of high-silicon steel thin strips.

[0007] Chinese invention patent application number 201310006692.6 discloses "a non-oriented high-silicon electrical steel strip and its preparation method," which directly produces a 1.1mm thick sheet through a casting and rolling process, and then produces a 6.5wt.%Si high-silicon steel sheet with a width of 110mm and a thickness of 0.35-0.50mm through subsequent hot rolling and warm rolling processes. However, due to the high temperature of warm rolling, thermal crowning occurs on the rolls during the rolling process, making it difficult to produce thinner high-silicon steel. In addition, the warm-rolled sheet has poor shape and a rough surface, making it difficult to meet the application requirements.

[0008] Chinese invention patent application number 201410489028.6 discloses a "short-process manufacturing method for cold-rolled non-oriented high-silicon steel sheets." The method involves obtaining a high-silicon steel strip through twin-roll casting, hot-rolling the high-silicon steel strip to obtain a hot-rolled sheet, cooling the hot-rolled sheet to 150–300°C for warm rolling to obtain a high-silicon steel warm-rolled sheet, pickling to remove surface iron oxide scale, and cold rolling at 50–100°C to obtain a high-silicon steel cold-rolled sheet with a thickness of 0.2–0.35 mm. The high-silicon steel cold-rolled sheet is then annealed in a hydrogen atmosphere to obtain a cold-rolled non-oriented 6.5 wt.% Si high-silicon steel sheet. The low warm rolling temperature used avoids the problem of poor sheet shape caused by thermal crown. In particular, cold rolling solves the problem of poor surface quality and makes it easy to produce thin, non-oriented high-silicon steel sheets with good shape and excellent surface quality. However, the process is very difficult to control, and the dimensions of the finished cold-rolled sheets are not specified. The overall magnetic properties of the products are relatively poor, making it difficult to achieve industrial production.

[0009] Chinese invention patent application number 201811279784.0 discloses a "rolling method for high-silicon steel strip". Using high-silicon steel cast strip with a thickness of 2-4 mm prepared by a twin-roll thin strip casting and rolling process as raw material, the strip is heated to 900-1100℃ under a protective atmosphere and hot-rolled at least once to a thickness of 1-1.2 mm with a total hot-rolling reduction of 50-60%. The hot-rolled high-silicon steel strip is then heated to 320-500℃ and warm-rolled at least once to a thickness of 0.4-0.5 mm with a total warm-rolling reduction of 50-70%. After pickling to remove oxide scale, the strip is cold-rolled to produce high-silicon steel strip with good surface quality and shape, exhibiting excellent magnetic properties after annealing. However, the cold-rolled sheet prepared using this method has a thickness of 0.2-0.3 mm, and the magnetic properties of the high-silicon steel strip after annealing are relatively poor.

[0010] Chinese invention patent application number 200710099130.5 discloses a "cold rolling preparation method for high-silicon steel thin plates," which prepares high-silicon steel thin strips with good shape and excellent magnetic properties through melting, forging, temperature-controlled hot rolling, heat treatment, temperature-controlled rolling, heat treatment, and repeated cold rolling. However, the high-silicon steel thin strips prepared by this method are relatively small in size, with a plate width of only 20-30 mm, which is difficult to meet user needs.

[0011] Chinese patent application No. 201310212112.9 discloses "A Chromium-Containing High-Silicon Steel Strip and Its Preparation Method," which uses industrial pure iron, commercial silicon, and pure chromium as raw materials. The raw materials are smelted in a medium-frequency vacuum induction furnace and cast into a billet at 1250–1650℃. The billet is then forged into a slab with a thickness of 10–20 mm at 800–1250℃. The slab is then hot-rolled into a strip with a thickness of 0.6–0.8 mm at 700–1250℃. Finally, the strip is warm-rolled to 0.2–0.3 mm at 150–750℃. This method features low cost, simple process, and the ability to utilize existing equipment. The prepared chromium-containing high-silicon steel strip exhibits significantly improved brittleness, enhanced plasticity, and good strip shape. Although this method can produce high-silicon steel strips with a thickness of 0.2–0.3 mm and improve the plasticity of high-silicon steel, the high-silicon steel strips have not undergone cold rolling, so their overall magnetic properties are relatively poor. Summary of the Invention

[0012] This invention provides a method for preparing large-size high-silicon steel strips through segmented plasticization. While not affecting the cumulative maximum rolling deformation, the method segmentally improves the rolling plasticity of high-silicon steel, achieving a better toughening and plasticizing effect. It avoids the restoration of the ordered structure while significantly improving the processing performance of high-silicon steel. The method ensures the smooth preparation of cold-rolled high-silicon steel strips without edge trimming and improves the yield, ultimately obtaining large-size high-silicon steel strips with good plasticity and comprehensive magnetic properties.

[0013] To achieve the above objectives, the present invention employs the following technical solution:

[0014] A method for preparing large-size high-silicon steel strips using segmented plasticizing, wherein the chemical composition of the high-silicon steel strips, by mass percentage, is: Si 4.5%–7.5%, B 0.005%–0.05%, Nb 0.005%–0.5%, C 0.001%–0.003%, N 0.001%–0.003%, S 0.0005%–0.002%, P 0.002%–0.01%, with the balance being iron and unavoidable impurities; the preparation of the high-silicon steel strips includes smelting, forging, hot rolling, segmented plasticizing treatment, stress-relieving annealing, cold rolling, and recrystallization annealing processes, specifically including the following steps:

[0015] 1) The high-silicon steel having the aforementioned chemical composition is smelted to obtain a high-silicon steel ingot;

[0016] 2) Forge the high-silicon steel ingot obtained in step 1) to obtain a high-silicon steel slab;

[0017] 3) The high-silicon steel slab obtained in step 2) is subjected to annealing heat treatment and then hot-rolled to obtain a high-silicon steel hot-rolled plate;

[0018] 4) The high-silicon steel hot-rolled plate obtained in step 3) is subjected to segmented plasticizing treatment to obtain high-silicon steel warm-rolled plate; the segmented plasticizing treatment includes multiple treatment stages, each of which involves warm rolling and post-rolling heat treatment of the plate; the medium-temperature plasticity and room-temperature plasticity of the plate are gradually improved through segmented plasticizing treatment.

[0019] 5) The high-silicon steel warm-rolled plate obtained in step 4) is subjected to stress-relief annealing treatment to obtain a high-silicon steel warm-rolled annealed plate;

[0020] 6) The high-silicon steel warm-rolled annealed sheet obtained in step 5) is cold-rolled to obtain a high-silicon steel cold-rolled sheet;

[0021] 7) The high-silicon steel cold-rolled sheet obtained in step 6) is subjected to recrystallization annealing to obtain the high-silicon steel strip finished product.

[0022] Furthermore, in step 1), the smelting process involves adding pure iron and pure silicon to a vacuum melting furnace. After the pure iron and pure silicon have completely melted, trace elements B and Nb are added before casting.

[0023] Furthermore, in step 2), the high-silicon steel ingot is heated to 1050-1250°C in the furnace and then forged into a high-silicon steel slab with a thickness of 10-20 mm.

[0024] Furthermore, in step 3), the annealing heat treatment temperature is 850–1200℃, the annealing time is 0.5–2h, the hot rolling temperature is 850–1200℃, and the thickness of the high-silicon steel hot-rolled plate is 1–5mm.

[0025] Furthermore, in step 4), the segmented plasticizing treatment includes 3 to 12 treatment stages, with a rolling temperature of 400 to 700°C for each treatment stage, and at least 2 rolling passes for each treatment stage; the rolling deformation per pass is 8% to 30%, and the total rolling deformation for each treatment stage is 40% to 80%.

[0026] Furthermore, in step 4), the post-rolling heat treatment is annealing, with an annealing temperature of 800–1050°C, a holding time of 0.5–2 hours, and a cooling method of air cooling, oil cooling, water cooling, or brine cooling.

[0027] Furthermore, in step 5), the stress-relief annealing temperature is 300–400°C, and the holding time is 0.5–1.5 h.

[0028] Furthermore, in step 6), the deformation amount of each cold rolling pass is 5% to 30%, and the total cold rolling reduction rate is 50% to 65%.

[0029] Furthermore, in step 7), the recrystallization annealing temperature is 750–1300℃, and the holding time is 0.5–1.5h.

[0030] Furthermore, the thickness of the high-silicon steel strip is 0.05–0.50 mm, and the width is 200–500 mm; the magnetic induction intensity B8 of the high-silicon steel strip is 1.32–1.38 T, and the iron loss P is… 10 / 50 The concentration is 0.40–0.65 W / kg, P 10 / 400 It ranges from 6.0 to 8.5 W / kg.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] (1) The surface of the high-silicon steel cold-rolled thin strip produced by the method of the present invention is bright and smooth;

[0033] (2) The present invention adopts a segmented plasticizing method, which can effectively reduce the order of high silicon steel, improve the room temperature plasticity and medium temperature plasticity of warm rolled plate, and thus effectively improve the processing performance of high silicon steel.

[0034] (3) After warm rolling, stress annealing is performed to reduce or eliminate residual stress in the strip, thereby reducing edge cracking during subsequent cold rolling and improving the yield of cold rolled products.

[0035] (4) The method described in this invention can successfully produce large-size high-silicon steel cold-rolled strips with a thickness of 0.05-0.50 mm, a width of 200-500 mm, and excellent comprehensive magnetic properties;

[0036] (5) The method described in this invention can more accurately control the performance and structure of high silicon steel strip, which helps to improve the quality, reliability and consistency of the product.

[0037] (6) The method described in this invention makes the preparation of large-size high-silicon steel strips more economical, reduces waste and energy consumption, has a smaller impact on the environment, and helps to improve the sustainability of the production process; it can produce high-silicon steel strips of different specifications and grades more efficiently and flexibly to meet the needs of different customers and increase market share. Attached Figure Description

[0038] Figure 1 This is a flow chart of the manufacturing process for large-size high-silicon steel strips described in this invention.

[0039] Figure 2 This is the tensile mechanical property curve of the high silicon steel warm-rolled plate (0.30 mm thick) at room temperature in Example 1 of the present invention.

[0040] Figure 3 The fracture morphology of a tensile specimen of a high-silicon steel warm-rolled plate (0.30 mm thick) at room temperature in Example 1 of this invention is shown. Figure 1 .

[0041] Figure 4 The fracture morphology of a tensile specimen of a high-silicon steel warm-rolled plate (0.30 mm thick) at room temperature in Example 1 of this invention is shown. Figure 2 . Detailed Implementation

[0042] This invention discloses a method for preparing large-size high-silicon steel strips using segmented plasticizing. The chemical composition of the high-silicon steel strips, by mass percentage, is: Si 4.5%–7.5%, B 0.005%–0.05%, Nb 0.005%–0.5%, C 0.001%–0.003%, N 0.001%–0.003%, S 0.0005%–0.002%, P 0.002%–0.01%, with the balance being iron and unavoidable impurities; such as Figure 1 As shown, the preparation of the high-silicon steel strip includes smelting, forging, hot rolling, segmented plasticizing treatment, stress-relieving annealing, cold rolling, and recrystallization annealing processes, specifically including the following steps:

[0043] 1) The high-silicon steel having the aforementioned chemical composition is smelted to obtain a high-silicon steel ingot;

[0044] 2) Forge the high-silicon steel ingot obtained in step 1) to obtain a high-silicon steel slab;

[0045] 3) The high-silicon steel slab obtained in step 2) is subjected to annealing heat treatment and then hot-rolled to obtain a high-silicon steel hot-rolled plate;

[0046] 4) The high-silicon steel hot-rolled plate obtained in step 3) is subjected to segmented plasticizing treatment to obtain high-silicon steel warm-rolled plate; the segmented plasticizing treatment includes multiple treatment stages, each of which involves warm rolling and post-rolling heat treatment of the plate; the medium-temperature plasticity and room-temperature plasticity of the plate are gradually improved through segmented plasticizing treatment.

[0047] 5) The high-silicon steel warm-rolled plate obtained in step 4) is subjected to stress-relief annealing treatment to obtain a high-silicon steel warm-rolled annealed plate;

[0048] 6) The high-silicon steel warm-rolled annealed sheet obtained in step 5) is cold-rolled to obtain a high-silicon steel cold-rolled sheet;

[0049] 7) The high-silicon steel cold-rolled sheet obtained in step 6) is subjected to recrystallization annealing to obtain the high-silicon steel strip finished product.

[0050] Furthermore, in step 1), the smelting process involves adding pure iron and pure silicon to a vacuum melting furnace. After the pure iron and pure silicon have completely melted, trace elements B and Nb are added before casting.

[0051] Furthermore, in step 2), the high-silicon steel ingot is heated to 1050-1250°C in the furnace and then forged into a high-silicon steel slab with a thickness of 10-20 mm.

[0052] Furthermore, in step 3), the annealing heat treatment temperature is 850–1200℃, the annealing time is 0.5–2h, the hot rolling temperature is 850–1200℃, and the thickness of the high-silicon steel hot-rolled plate is 1–5mm.

[0053] Furthermore, in step 4), the segmented plasticizing treatment includes 3 to 12 treatment stages, with a rolling temperature of 400 to 700°C for each treatment stage, and at least 2 rolling passes for each treatment stage; the rolling deformation per pass is 8% to 30%, and the total rolling deformation for each treatment stage is 40% to 80%.

[0054] Furthermore, in step 4), the post-rolling heat treatment is annealing, with an annealing temperature of 800–1050°C, a holding time of 0.5–2 hours, and a cooling method of air cooling, oil cooling, water cooling, or brine cooling.

[0055] Furthermore, in step 5), the stress-relief annealing temperature is 300–400°C, and the holding time is 0.5–1.5 h.

[0056] Furthermore, in step 6), the deformation amount of each cold rolling pass is 5% to 30%, and the total cold rolling reduction rate is 50% to 65%.

[0057] Furthermore, in step 7), the recrystallization annealing temperature is 750–1300℃, and the holding time is 0.5–1.5h.

[0058] Furthermore, the thickness of the high-silicon steel strip is 0.05–0.50 mm, and the width is 200–500 mm; the magnetic induction intensity B8 of the high-silicon steel strip is 1.32–1.38 T, and the iron loss P is… 10 / 50 The concentration is 0.40–0.65 W / kg, P 10 / 400 It ranges from 6.0 to 8.5 W / kg.

[0059] The rationale for the alloying element design of the high-silicon steel strip described in this invention is as follows:

[0060] Silicon (Si) is one of the most important elements in silicon steel. Its role is to increase the resistivity of iron, promote grain growth, and ultimately reduce coercivity, iron loss, and magnetic aging. With increasing Si content, resistivity ρ increases rapidly, while magnetic anisotropy K1, saturation magnetic induction Bs, and magnetostriction λs decrease significantly. Therefore, increasing Si content can substantially reduce iron loss and noise generated by equipment under high-frequency operating conditions. However, increasing Si content also generates a large number of Fe-Si covalent bonds and ordered phases within the matrix, thus reducing the machinability of silicon steel. Therefore, while increasing the silicon content, it is necessary to combine it with appropriate alloying elements and processing techniques to produce large-size, thin-gauge high-silicon steel strips.

[0061] In silicon steel, as the boron (B) / nitrogen (N) ratio increases, boron (B) can eliminate nitrogen (N) in the solid solution, thereby reducing strain-induced AlN precipitation. BN will co-precipitate with sulfides, further preventing the precipitation of fine MnS, CuS, FeS particles and reducing the damage to magnetic properties caused by these precipitates. Furthermore, while high-silicon steel generally has poor plasticity, this can be improved by refining the grain size. Boron's solubility in low-temperature ferrite is essentially zero; therefore, it exists as a precipitate, pinning grain boundary migration and effectively refining the grain size. It also increases grain boundary bonding and inhibits the formation of ordered phases. Grain refinement and microalloying can, to some extent, improve the plasticity of high-silicon steel.

[0062] Similar to boron (B), nitrogen (Nb) plays a similar role in improving the plasticity of silicon steel. Nb forms second-phase particles, hindering grain growth and enhancing its plasticity and processing properties. Nb is a strong carbonitride-forming element, readily combining with carbon and nitrogen to form fine compounds. During heating, these precipitates pin grain boundaries and inhibit grain growth. During rolling, they suppress recrystallization, preserving the deformed austenite and refining the post-phase transformation grain structure. Nb-containing precipitates dispersed in ferrite also improve both plasticity and strength, and inhibit grain coarsening in the heat-affected zone during welding. Studies have shown that Nb can also enhance the magnetic properties of silicon steel. Therefore, this invention improves the plasticity of high-silicon steel by comprehensively controlling the content of B and Nb, thereby enhancing its processing and magnetic properties.

[0063] The presence of carbon (C) and nitrogen (N) easily leads to the precipitation of carbides and nitrides in silicon steel, thereby reducing its magnetic properties. Excessive C content can also cause edge cracking in hot-rolled sheets, negatively impacting quality and production efficiency. Therefore, non-oriented electrical steels aim to reduce the C and N content in the finished product. At low temperatures, the solubility of C in ferrite is essentially zero. Below 300℃, C precipitates as Fe3C. High-temperature dissolved C also shows a clear tendency to precipitate, and under suitable conditions, it does so. However, the amount of Fe3C precipitated is small, and the interparticle spacing is large, making coarsening difficult; it often exists in a dispersed form, thus worsening the magnetic properties of silicon steel. Similarly, at low temperatures, the solubility of nitrogen (N) in ferrite is essentially zero. To achieve equilibrium, N exists as Fe4N. Excessive N content can damage the magnetic properties of silicon steel due to the precipitation of nitrides. Furthermore, C and N have high solid solubility at high temperatures. During rapid cooling from high temperatures, excess C and N cannot precipitate in time, forming a supersaturated solid solution. When the iron core operates for a long time, especially under conditions of 50–80°C, excess C and N atoms will precipitate as fine, dispersed carbides and nitrides, thereby increasing coercivity and iron loss, and causing magnetic aging. Therefore, in this invention, the C and N elements are controlled within 0.001%–0.003%.

[0064] Sulfur (S) is a harmful element. Sulfur and manganese readily form manganese sulfide inclusions, which hinder grain growth during annealing. Studies have shown that, at a given manganese content, iron loss increases with increasing sulfur content. At low temperatures, the solubility of S in ferrite is essentially zero; below 300°C, it precipitates as hexagonal FeS. Therefore, S dissolved at high temperatures has a significant tendency to precipitate, and under suitable conditions, sulfides will precipitate, further increasing iron loss. Therefore, the S content in this invention is controlled within the range of 0.0005% to 0.002%.

[0065] Phosphorus (P) can increase resistivity and reduce eddy current losses. P has a larger atomic radius than Fe and Si, which can improve hardness and stamping performance. However, P tends to segregate at dislocations and grain boundaries, increasing hysteresis losses. Simultaneously, P may enhance the {111} surface texture and {111}... <112> The texture is designed to reduce magnetic induction, so in order to balance iron loss and the stamping performance of the material, the P content is controlled at 0.002% to 0.01%.

[0066] The reasons for the selection of the preparation process and parameters for the high-silicon steel strip described in this invention are as follows:

[0067] As shown in the Fe-Si phase diagram, when the temperature is above 770℃, high-silicon electrical steel with a Si content of 6.5wt% exhibits an A2 disordered structure. Around 770℃, an order-disorder transition occurs between the A2 and B2 structures. At 600℃, a B2-DO3 transition occurs, resulting in a B2+DO3 two-phase structure at room temperature. It is generally believed that the transformation from the A2 disordered structure to the B2 ordered structure is a second-order phase transition, which is very rapid; the structural change is essentially a change in the occupancy probability of Fe and Si atoms in the crystal lattice. The transformation from the B2 ordered structure to the DO3 ordered structure is a first-order phase transition, which is relatively slow and can be effectively suppressed by rapid cooling. Warm rolling is the most critical step in preparing high-silicon steel strips. Therefore, this invention improves the warm rolling performance of high-silicon steel by heating the high-silicon steel above the order-disorder transition temperature to disorder the matrix, followed by rapid cooling to suppress the recovery of the ordered phase within the matrix. Furthermore, during the warm rolling process, the deformation-induced disorder in high-silicon steel reduces the degree of order within the matrix, thereby improving its processing performance. This repeated process progressively enhances the plasticity and processing properties of high-silicon steel, ultimately enabling large-size high-silicon steel to be warm rolled with large reductions, while ensuring that the sheet does not develop edge cracks during rolling, thus providing conditions for subsequent cold rolling deformation.

[0068] After high-silicon steel undergoes high-reduction warm rolling, significant residual stress accumulates within the warm-rolled sheet. Without treatment, this stress will cause widening deformation in the width direction during cold rolling, resulting in greater deformation in the middle section than at the edges, thus increasing edge tensile stress. If the warm-rolled sheet continues cold rolling, edge cracking or breakage will occur when the accumulated stress exceeds the material's yield strength. Stress-relief annealing effectively reduces residual stress, improves plasticity, and enhances processing performance in subsequent rolling processes, controlling edge cracking. This is a crucial step in improving the processing performance of high-silicon steel warm-rolled sheets. However, high-silicon steel with low orderliness will experience a further increase in matrix orderliness during high-temperature stress-relief annealing, reducing its room-temperature plasticity and cold-rolling processing performance. Conversely, if the stress-relief annealing temperature is low, the residual stress within the high-silicon steel may be difficult to reduce, resulting in persistently high residual stress in the warm-rolled sheet and severe edge cracking during subsequent cold rolling. To this end, the present invention reduces the residual tensile stress of high silicon steel warm-rolled plates by formulating a suitable stress-relief annealing process, while avoiding the reordering of the disordered structure after warm rolling deformation, thereby achieving smooth cold rolling of high silicon steel and finally obtaining high silicon steel cold-rolled thin plates with good surface quality and no edge cracks.

[0069] The segmented plasticizing technology described in this invention involves a multi-stage "warm rolling + post-rolling heat treatment" process for high-silicon steel hot-rolled plates. Through each treatment stage, the medium-temperature plasticity and room-temperature plasticity of the hot-rolled plates are progressively improved, ultimately achieving the goal of progressively improving the plasticity of high-silicon steel hot-rolled plates. The segmented plasticizing process may include 3 to 12 treatment stages.

[0070] The following embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0071]

Example

[0072] The chemical composition of the high-silicon steel strip in each embodiment is shown in Table 1. The forging, heat treatment and hot rolling process parameters in each embodiment are shown in Table 2. The segmented plasticizing process parameters in each embodiment are shown in Table 3. The stress-relief annealing and cold rolling process parameters in each embodiment are shown in Table 4. The dimensions and properties of the finished high-silicon steel strip in each embodiment are shown in Table 5.

[0073] Table 1. Chemical composition of high-silicon steel strip (mass percentage, %)

[0074] Example 1 6.45 0.02 0.015 0.0016 0.0012 0.002 0.005 Example 2 7.39 0.015 0.02 0.0023 0.0023 0.0018 0.003 Example 3 6.28 0.037 0.37 0.0014 0.0017 0.0017 0.004 Example 4 4.53 0.046 0.044 0.0025 0.0018 0.0013 0.006 Example 5 5.61 0.026 0.079 0.0030 0.0026 0.0009 0.008 Example 6 7.33 0.008 0.18 0.0021 0.0019 0.0014 0.009

[0075] Table 2 Forging, Heat Treatment and Hot Rolling Process Parameters

[0076]

[0077] Table 3. Segmented Plasticizing Process Parameters

[0078]

[0079] Table 4 Stress-relief annealing and cold rolling process parameters

[0080]

[0081] Table 5 Dimensions and properties of finished high-silicon steel strips

[0082]

[0083] like Figure 2 As shown, the tensile mechanical property curves of the 0.30mm thick high-silicon steel warm-rolled plate in Example 1 at room temperature are shown. It can be seen that the sample exhibits an obvious yield stage during the tensile process. Although the elongation is low at this point, it is still remarkable for high-silicon steel.

[0084] like Figure 3 , Figure 4 The image shown is a fracture morphology diagram of a room temperature tensile test specimen of a 0.30 mm thick high silicon steel warm-rolled plate in Example 1. It can be seen that the fracture surface is occupied by a large number of river patterns, but some dimple structures also appear, indicating that the high silicon steel specimen has a certain degree of plasticity.

[0085] The high-silicon steel cold-rolled strips prepared in Examples 1-6 have good surface quality, no visible cracks, and can be bent into rolls. After annealing, the cold-rolled strips have excellent comprehensive magnetic properties.

[0086] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing large-size high-silicon steel thin strips using segmented plasticizing, characterized in that, The chemical composition of the high-silicon steel strip, by mass percentage, is: Si 5.61%–7.5%, B 0.005%–0.008%, Nb 0.18%–0.5%, C 0.001%–0.0014%, N 0.001%–0.003%, S 0.0005%–0.002%, P 0.002%–0.01%, with the balance being iron and unavoidable impurities. The preparation of the high-silicon steel strip includes smelting, forging, hot rolling, segmented plasticizing treatment, stress-relieving annealing, cold rolling, and recrystallization annealing processes, specifically including the following steps: 1) The high silicon steel with the chemical composition is smelted to obtain a high silicon steel ingot; the smelting is carried out by adding pure iron and pure silicon in a vacuum melting furnace, and after the pure iron and pure silicon are completely melted, trace elements B and Nb are added before casting. 2) The high silicon steel ingot obtained in step 1) is forged to obtain a high silicon steel slab; after the high silicon steel ingot is heated in the furnace to 1080-1250℃, it is forged into a high silicon steel slab with a thickness of 10-20mm. 3) The high-silicon steel slab obtained in step 2) is subjected to annealing heat treatment and then hot-rolled to obtain a high-silicon steel hot-rolled plate; the annealing heat treatment temperature is 850~1200℃, the annealing time is 0.5~2h; the hot rolling start temperature is 1140~1200℃, and the thickness of the high-silicon steel hot-rolled plate is 1~5mm. 4) The high-silicon steel hot-rolled plate obtained in step 3) is subjected to segmented plasticizing treatment to obtain a high-silicon steel warm-rolled plate. The segmented plasticizing treatment includes multiple treatment stages, each of which involves warm rolling and post-rolling heat treatment of the plate. The segmented plasticizing treatment gradually improves the medium-temperature plasticity and room-temperature plasticity of the plate. Specifically, the segmented plasticizing treatment includes 3 to 12 treatment stages, with a warm rolling temperature of 400 to 700°C in each stage and at least 2 rolling passes in each stage. The rolling deformation per pass is 8% to 30%, and the total rolling deformation in each stage is 40% to 80%. The post-rolling heat treatment is annealing, with an annealing temperature of 800 to 1050°C, a holding time of 0.5 to 2 hours, and a cooling method of air cooling, oil cooling, water cooling, or brine cooling. 5) The high-silicon steel warm-rolled plate obtained in step 4) is subjected to stress-relief annealing to obtain a high-silicon steel warm-rolled annealed plate; the stress-relief annealing temperature is 300-400℃ and the holding time is 0.5-1.5h; 6) The high-silicon steel warm-rolled annealed sheet obtained in step 5) is cold-rolled to obtain a high-silicon steel cold-rolled sheet; the deformation per rolling pass is 5% to 30%, and the total reduction rate of cold rolling is 50% to 65%; 7) The high-silicon steel cold-rolled sheet obtained in step 6) is subjected to recrystallization annealing to obtain high-silicon steel strip finished product; the recrystallization annealing temperature is 750~1300℃, and the holding time is 0.5~1.5h; The high-silicon steel strip has a thickness of 0.05–0.50 mm and a width of 200–500 mm; the magnetic induction intensity B8 of the high-silicon steel strip is 1.32–1.38 T, and the iron loss P is… 10 / 50 The concentration is 0.40–0.65 W / kg, P 10 / 400 It ranges from 6.0 to 8.5 W / kg.

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