A method for producing a powder metallurgy Fe-6.5%Si high silicon steel sheet

Abstract

The application provides a preparation method of powder metallurgy Fe-6.5%Si high silicon steel sheet, and belongs to the field of powder metallurgy and metal plastic processing. The application takes Fe-6.5%Si pre-alloyed spherical powder as raw material, adopts powder canning hot isostatic pressing method to prepare Fe-6.5%Si high silicon steel ingot, and sequentially passes through small deformation amount hot extrusion with an extrusion ratio of 4-7, hot rolling, warm rolling and cold rolling to prepare high silicon steel sheet with a thickness of 0.1-0.4mm. The preparation process provided by the application can be completed on existing conventional equipment, and industrialized production can be realized.

Description

A method for preparing Fe-6.5%Si high-silicon steel thin plates by powder metallurgy Technical Field

[0001] This invention relates to a method for preparing Fe-6.5%Si high-silicon steel thin plates by powder metallurgy, belonging to the fields of powder metallurgy and metal plastic processing. Background Technology

[0002] Silicon steel is an important magnetic material used in the power, electronics, and telecommunications industries to manufacture generators, motors, transformers, relays, instrument transformers, and other electrical instruments. Studies show that the magnetic properties of silicon steel are positively correlated with its Si content; as the Si content increases, the resistivity of silicon steel significantly increases, eddy current losses decrease, and relative permeability increases. In particular, when the Si content increases to 6.5 wt.%, the AC iron loss of the material decreases dramatically, and the magnetostriction coefficient becomes nearly zero, achieving optimal soft magnetic properties. Therefore, high-silicon steel is an ideal magnetic material for manufacturing cores and rotors, and has significant value in power equipment components, electric vehicles, and high-frequency applications.

[0003] While 6.5wt% Si silicon steel possesses excellent magnetic properties and broad application prospects, its brittleness and poor machinability make it difficult to produce thin sheets using conventional rolling methods. Globally, only one company in Japan has achieved large-scale production of 6.5wt% Si silicon steel using chemical vapor deposition (CVD). However, this high-temperature silicon infiltration process requires the use of highly toxic SiCl4 gas and generates large amounts of FeCl2 waste gas, causing severe environmental pollution. Although numerous attempts have been made to develop high-silicon steel production technologies, none other than CVD have been able to achieve large-scale production.

[0004] For example, the cladding rolling method developed by a Japanese steel pipe company requires special pre-rolling treatment, and the quality of the rolled material is difficult to control, resulting in high costs and low yield. The three-rolling method proposed by Russian scholars, when obtaining 6.5wt% high-silicon steel, involves additional treatments that make the process extremely complex. Rapid solidification methods suffer from limited strip width and thickness, and difficulty in controlling shape accuracy. Powder rolling offers low cost and near-net-shape forming capabilities, utilizing the excellent plastic deformation capacity of iron powder to effectively avoid the intrinsic brittleness of 6.5wt% Si silicon steel during processing. When using this method to prepare thin plates, brittle silicon powder and ductile iron powder are first prepared into a composite powder with good plasticity. This composite powder is then rolled to obtain powder strips, which are then sintered in sections, with alloying controlled to achieve the desired effect. However, high-silicon steel strips produced using the powder rolling-sintering process generally have internal voids formed by sintering shrinkage.

[0005] The powder sintering-rolling method theoretically avoids the problems of segregation and insufficient plasticity caused by coarse grains in the casting-rolling method, and also avoids the voids present in the powder rolling-sintering method. Therefore, this invention aims to provide a powder sintering-rolling method to achieve the preparation of high-silicon steel thin sheets. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing Fe-6.5%Si high-silicon steel thin sheets using powder metallurgy. By combining the advantages of powder metallurgy and rolling forming, high-performance high-silicon steel thin sheets can be prepared.

[0007] To achieve the above objectives, the technology of the present invention includes the following steps:

[0008] This invention discloses a method for preparing Fe-6.5%Si high-silicon steel thin plates by powder metallurgy. Fe-6.5%Si pre-alloyed powder is loaded into a sleeve and then subjected to hot isostatic pressing to obtain an ingot. The ingot is then hot-extruded to obtain a plate-shaped billet, which is then subjected to hot rolling, warm rolling, annealing, and cold rolling in sequence to obtain the final product.

[0009] The preparation method of this invention first uses powder-coated hot isostatic pressing to prepare Fe-6.5%Si high-silicon steel ingots with a density greater than 90%, then further densifies them by hot extrusion, and obtains a plate-shaped billet with a density greater than 95% suitable for rolling. The plate-shaped billet is then subjected to hot rolling, warm rolling, annealing, and cold rolling in sequence to obtain powder metallurgy Fe-6.5%Si high-silicon steel thin plates. The method of this invention can obtain Fe-6.5%Si high-silicon steel thin plates with a thickness as low as 0.1 mm.

[0010] In a preferred embodiment, the Fe-6.5%Si pre-alloyed powder has a particle size of -100 mesh.

[0011] In a preferred embodiment, the Fe-6.5%Si pre-alloyed powder is prepared by a rotating electrode atomization method.

[0012] In a preferred embodiment, the Fe-6.5%Si pre-alloyed powder is spherical in shape; the mass percentage of Si is 6.4-6.6%, the mass percentage of Fe is ≥93.4%, and the oxygen content is <800ppm.

[0013] In a preferred embodiment of the present invention, the Fe-6.5%Si pre-alloyed powder is a powder prepared by rotating electrode atomization, which has low oxygen content, good sphericity, and high density of the billet after hot isostatic pressing, which is beneficial to subsequent plastic forming.

[0014] In a preferred embodiment, Fe-6.5%Si pre-alloyed powder is packed into a stainless steel sleeve, vibrated to compact, vacuumed, sealed, and then subjected to hot isostatic pressing.

[0015] In actual production, the stainless steel sheath is preferably cylindrical, with a diameter of 140–150 mm, a height of 220–320 mm, and a wall thickness of 2 mm. During the evacuation process, the vacuum level inside the sheath is ensured to reach 1×10⁻⁶. -4 Under these conditions, the diameter of the billet after hot isostatic pressing is 120-130 mm and the height is 200-300 mm. This size is beneficial for the next step of selecting the extruder and controlling the extrusion ratio.

[0016] In a preferred embodiment, the hot isostatic pressing (HIP) treatment temperature is 1200–1250°C, the HIP treatment time is 3–4 hours, and the HIP treatment pressure is 120–140 MPa. In this invention, by employing the above-mentioned HIP conditions, a billet with a density greater than 90% can be obtained.

[0017] In a preferred embodiment, the extrusion ratio of the hot extrusion is 4 to 7. In this invention, the billet is further densified by using hot extrusion with a small deformation, resulting in a plate-shaped billet with a density ≥95%.

[0018] In industrial production, hot extrusion is preferably carried out on an extrusion press with an inner diameter of 130 mm. The die size of the extrusion die is preferably (20-25) mm × (100-110) mm, which can produce an extruded slab with a thickness of 20-25 mm and a width of 100-110 mm.

[0019] In this invention, hot isostatic pressing can obtain billets with a density greater than 90%. However, billets with this density are still prone to cracking if directly rolled. By adding an extrusion process, the triaxial hydrostatic stress provided by extrusion deformation is fully utilized, and billet densification can be achieved with only minor deformation. Furthermore, cylindrical billets obtained by hot isostatic pressing are not suitable for direct rolling; they need to be machined into rectangular billets suitable for rolling, leading to reduced material utilization. This invention obtains billets suitable for rolling by setting the dimensions of the extrusion die. It is evident that the purpose of extrusion in this invention is to achieve densification and obtain a billet shape suitable for rolling. Therefore, it is not necessary to meet the requirement of an extrusion ratio greater than 9 as in conventional extrusion. Moreover, the material of this invention has poor plasticity; a large extrusion ratio not only increases costs but also makes the extrusion process highly susceptible to cracking.

[0020] In a preferred embodiment, the billet temperature during hot extrusion is 1050–1100°C, the extrusion cylinder temperature is 500–600°C, and the extrusion speed is 4–8 m / min; air cooling follows hot extrusion. The inventors have discovered that by controlling the billet temperature within the above range during hot extrusion, the billet can possess good plasticity, achieving extrusion densification, while also avoiding grain growth during extrusion and the problem of partial overburning of the second phase due to excessively high temperatures.

[0021] In a preferred embodiment, the hot rolling process involves preheating the plate-shaped billet at 1050–1100℃ for 1–2 hours, performing multiple hot rolling passes, controlling the final rolling temperature of each pass to ≥1000℃, the pass reduction rate to 5–10%, the roll linear speed to 2–5 m / min, and finally rolling the billet to a thickness of less than 3 mm.

[0022] In a further preferred embodiment, during hot rolling, when the total deformation of the billet is <20%, the roll linear speed is controlled at 2-3 m / min; when the total deformation of the billet is 20-65%, the roll linear speed is controlled at 3-4 m / min; when the total deformation of the billet is >65%, the roll linear speed is controlled at 4-5 m / min; when the total deformation of the billet is <30%, the pass reduction rate is controlled at 5-6%; when the total deformation of the billet is 30-60%, the pass reduction rate is controlled at 6-8%; and when the total deformation of the billet is >60%, the pass reduction rate is controlled at 8-10%.

[0023] In a preferred embodiment, the warm rolling process involves preheating the hot-rolled billet at 550–600°C for 1–1.5 hours, followed by multiple passes of warm rolling, controlling the pass reduction rate at 5–6%, the roll linear speed at 5–10 m / min, and finally rolling the billet to a thickness of less than 1 mm.

[0024] The inventors discovered that controlling the temperature during warm rolling within the aforementioned range ensures that the material has good plastic deformation capacity to complete the warm rolling process, while also preventing grain growth that could affect mechanical properties. If the temperature is too low, the plastic deformation capacity will be poor, and cracking may occur.

[0025] In a further preferred embodiment, during the warm rolling process, when the total deformation during warm rolling is ≤50%, the roll linear speed is controlled at 5-7 m / min, and when the total deformation during warm rolling is >50%, the roll linear speed is controlled at 7-10 m / min.

[0026] In a preferred embodiment, the annealing is performed under vacuum conditions at a temperature of 750–800°C for 3–5 hours. In actual operation, the furnace is cooled after annealing.

[0027] In this invention, the purpose of annealing is to eliminate the internal stress caused by warm rolling to the greatest extent and improve the plasticity of the material to meet the requirements of further cold rolling. However, the annealing temperature has a certain impact on the subsequent cold rolling. If the temperature is too low, the internal stress caused by warm rolling cannot be eliminated to the greatest extent, and the material is not sufficiently softened, which is not conducive to subsequent cold rolling. If the temperature is too high, it will lead to the growth of recrystallized grains, resulting in poor plasticity, which is also not conducive to subsequent cold rolling.

[0028] In a preferred embodiment, during the cold rolling process, the reduction rate per pass is controlled to be 5-10%, the roll linear speed is 10-15 m / min, and the thickness is 0.1-0.4 mm after multiple passes of cold rolling.

[0029] In a further preferred embodiment, during cold rolling, when the total cold rolling deformation is ≤40%, the pass reduction rate is controlled at 8-10%, and the roll linear speed is 13-15 m / min; when the total cold rolling deformation is >40%, the pass reduction rate is controlled at 5-8%, and the roll linear speed is 10-13 m / min.

[0030] Throughout the rolling process of this invention, different pass reduction rates and roll linear speeds are preferred under different total deformation conditions. These are set based on the material's plastic deformation capacity, temperature drop, billet length, and precision control. For hot rolling and warm rolling, as rolling progresses, the alloy's microstructure changes from equiaxed to deformable, increasing deformation capacity. Appropriately increasing the pass deformation and rolling speed can still ensure good billet formability. In addition, as deformation progresses, the billet length increases, and increasing the speed can prevent excessive billet temperature drop due to prolonged rolling time, avoiding rolling temperatures below the set temperature range. For cold rolling, when the total deformation is less than 40%, the billet has good plasticity due to the preceding annealing process, allowing for single-pass high-reduction high-speed rolling. When the total deformation exceeds 40%, the material's plasticity deteriorates due to work hardening, requiring low-speed, low-deformation rolling. By controlling the process parameters throughout the rolling process of this invention, Fe-6.5%Si high-silicon steel sheets with a thickness as low as 0.1 mm can be obtained at low cost and high efficiency.

[0031] In a preferred embodiment, a two-roll hot rolling mill with a roll diameter greater than 200mm is used for hot rolling, a two-roll hot rolling mill with a roll diameter greater than 150mm is used for warm rolling, and a four-roll cold rolling mill with a diameter less than 100mm is used for cold rolling.

[0032] In this invention, by employing the aforementioned hot rolling mill and cold rolling mill, and by optimizing the billet thickness, roll speed, and deformation per pass during the rolling process, it is possible to ensure that the entire rolling process is carried out under low strain rate conditions. Therefore, cracking will not occur due to the increase in rolling speed. At the same time, it also effectively avoids the inability to meet the temperature range required for stable plastic deformation (the temperature ranges specified for hot rolling and warm rolling, respectively) due to excessive temperature drop of the sheet.

[0033] Using the above method, Fe-6.5%Si high-silicon steel sheets with a thickness of 0.1–0.4 mm and a width of 100–110 mm can be produced.

[0034] Furthermore, the Fe-6.5%Si high-silicon steel sheet obtained by cold rolling according to this invention has a microstructure consisting of elongated deformed grains. Depending on the material performance requirements of the application conditions, subsequent heat treatments can be performed to obtain different equiaxed grain structures, enabling the sheet to meet specific application requirements.

[0035] Advantages or beneficial effects of the present invention:

[0036] (1) The present invention uses pre-alloyed powder with extremely low segregation as raw material, which avoids the problem of severe segregation in the billet obtained by conventional casting process. The extremely low segregation in the billet can significantly improve the plastic deformation ability of the material.

[0037] (2) After hot isostatic pressing, small deformation extrusion is carried out, which makes full use of the mechanical characteristics of the triaxial hydrostatic stress of extrusion deformation, so that the non-dense billet obtained by hot isostatic pressing is further densified, thereby ensuring that the material does not crack due to the presence of holes during the rolling process.

[0038] (3) During hot rolling and warm rolling, the rolling speed and deformation per pass are adjusted according to the total deformation. This ensures that the rolling process maintains a low strain rate deformation, preventing cracking due to increased rolling speed. It also effectively avoids excessive temperature drop in the sheet metal, which would prevent the temperature range required for stable plastic deformation from being exceeded. Although the rolling process is carried out on different types of rolling mills, they are all general-purpose equipment with low equipment requirements, enabling industrial production. Attached Figure Description

[0039] Figure 1 shows the Fe-6.5%Si high silicon steel sheet prepared in Example 1 of the present invention. As can be seen from the figure, the sheet is flat and free of cracks.

[0040] Figure 2 shows the metallographic microstructure of Fe-6.5%Si high silicon steel sheet prepared in Example 1 of the present invention. As can be seen from the figure, the thickness of the alloy sheet is 0.4 mm, and the grains are elongated deformed structures.

[0041] Figure 3 shows the morphology of the failed sample in Comparative Example 1. Detailed Implementation

[0042] The following are preferred embodiments of the present invention, but not all embodiments. Without departing from the innovative principles of this process, any equivalent process modifications made based on the content of this specification, or direct or indirect applications in other related technical fields, shall be considered within the scope of patent protection of this invention.

[0043] Example 1

[0044] Fe-6.5%Si spherical pre-alloyed powder with a particle size of -100 mesh, prepared by rotating electrode atomization, was selected as the raw material. First, the pre-alloyed powder was loaded into a stainless steel sleeve with a diameter of 140 mm, a height of 220 mm, and a wall thickness of 2 mm, vibrated to compaction, and then evacuated to a vacuum level of 1 × 10⁻⁶. -4 After sealing, the sealing package is subjected to hot isostatic pressing at a temperature of 1200℃, a pressure of 140MPa, and a time of 4 hours. After cooling in the furnace, an ingot with a diameter of 120mm and a height of 200mm is obtained.

[0045] Hot isostatic pressing billets are extruded on an extruder with an inner diameter of 130 mm and an extrusion die size of 20 mm × 110 mm. The billet temperature is controlled at 1050℃, the extrusion cylinder temperature at 500℃, and the extrusion speed at 5 m / min. After extrusion, the billets are air-cooled to obtain a billet with a thickness of 20 mm and a width of 110 mm. The extrusion ratio during the extrusion process is 6.

[0046] The extruded billet is heated to 1100℃ and held at that temperature for 1 hour before being subjected to multi-pass hot rolling on a two-roll hot rolling mill with a roll diameter of 280mm. When the billet thickness is >16mm, the roll speed is controlled at 3m / min; when the billet thickness is 7mm–16mm, the roll speed is controlled at 4m / min; when the billet thickness is <7mm, the roll speed is controlled at 5m / min. When the billet thickness is greater than 14mm, the pass reduction rate is controlled at 5%; when the billet thickness is 8mm–14mm, the pass reduction rate is controlled at 8%; when the billet thickness is <8mm, the pass reduction rate is controlled at 10%. Rolling is stopped when the billet thickness reaches 3mm, and the billet is allowed to cool naturally in air.

[0047] The hot-rolled sheet is heated to 550℃ and held for 1.5 hours. Then, it is subjected to multi-pass hot rolling with a deformation of 5% per pass on a two-roll hot rolling mill with a roll diameter of 180mm. When the billet thickness is >1.5mm, the roll linear speed is controlled at 5m / min. When the billet thickness is <1.5mm, the roll linear speed is controlled at 10m / min. When the thickness is 1mm, rolling is stopped and the sheet is allowed to cool naturally in the air.

[0048] The sheet obtained by warm rolling was vacuum annealed at 750℃ for 5 hours and then cooled in the furnace.

[0049] The vacuum-annealed sheet is subjected to multiple cold rolling passes on a four-roll cold rolling mill with a work roll diameter of 80mm. When the billet thickness is >0.6mm, the pass reduction rate is controlled at 10% and the roll linear speed is 13m / min. When the billet thickness is <0.6mm, the pass reduction rate is controlled at 5% and the roll linear speed is 13m / min.

[0050] When the billet thickness reaches 0.4 mm, rolling is stopped, resulting in a Fe-6.5%Si high-silicon steel sheet with a thickness of 0.4 mm and a width of 110 mm.

[0051] During mass production, the yield rate was 100% according to statistics.

[0052] The magnetic induction intensity (B) of the thin plate obtained in Example 1 was tested. 800 The iron loss (P) is 1.26T. 2 / 10k The strength is 75 W / kg, the maximum permeability is 21000, and the coercivity is 11.2 A / m.

[0053] Example 2

[0054] Fe-6.5%Si spherical pre-alloyed powder with a particle size of -100 mesh, prepared by rotating electrode atomization, was selected as the raw material. First, the pre-alloyed powder was loaded into a stainless steel sleeve with a diameter of 150 mm, a height of 320 mm, and a wall thickness of 2 mm, vibrated to compaction, and then evacuated to a vacuum level of 1 × 10⁻⁶. -4 After sealing, the sealing sleeve is subjected to hot isostatic pressing at a temperature of 1250℃, a pressure of 120MPa, and a time of 3 hours. After cooling in the furnace, an ingot with a diameter of 130mm and a height of 300mm is obtained.

[0055] Hot isostatic pressing billets are extruded on an extruder with an inner diameter of 130 mm and an extrusion die size of 25 mm × 100 mm. The billet temperature is controlled at 1100℃, the extrusion cylinder temperature at 600℃, and the extrusion speed at 5 m / min. After extrusion, the billets are air-cooled to obtain a billet with a thickness of 25 mm and a width of 100 mm. The extrusion ratio during the extrusion process is 5.3.

[0056] The extruded billet is heated to 1050℃ and held at that temperature for 1.5 hours before being hot-rolled in multiple passes on a two-roll hot rolling mill with a roll diameter of 280mm. When the billet thickness is >20mm, the roll speed is controlled at 2m / min; when the billet thickness is 8.75mm–20mm, the roll speed is controlled at 3m / min; when the billet thickness is <8.75mm, the roll speed is controlled at 4m / min. When the billet thickness is greater than 17.5mm, the pass reduction rate is controlled at 6%; when the billet thickness is 10mm–17.5mm, the pass reduction rate is controlled at 6%; when the billet thickness is <10mm, the pass reduction rate is controlled at 8%. Rolling is stopped when the billet thickness reaches 2.8mm, and the billet is allowed to cool naturally in air.

[0057] The hot-rolled sheet is heated to 600℃ and held for 1 hour. Then, it is subjected to multi-pass hot rolling with a deformation of 5% per pass on a two-roll hot rolling mill with a roll diameter of 180mm. When the billet thickness is >1.4mm, the roll linear speed is controlled at 7m / min. When the billet thickness is <1.4mm, the roll linear speed is controlled at 10m / min. When the thickness is 0.8mm, rolling is stopped and the sheet is allowed to cool naturally in the air.

[0058] The sheet obtained by warm rolling was vacuum annealed at 800℃ for 3 hours and then cooled in the furnace.

[0059] The vacuum-annealed sheet is subjected to multiple cold rolling passes on a four-roll cold rolling mill with a work roll diameter of 80mm. When the billet thickness is >0.48mm, the pass reduction rate is controlled at 8% and the roll line speed is 15m / min. When the billet thickness is <0.48mm, the pass reduction rate is controlled at 5% and the roll line speed is 10m / min.

[0060] When the billet thickness is 0.1 mm, rolling is stopped, resulting in a Fe-6.5%Si high silicon steel sheet with a thickness of 0.1 mm and a width of 100 mm.

[0061] During mass production, the yield rate was 100% according to statistics.

[0062] The magnetic induction intensity (B) of the thin plate obtained in Example 2 was tested. 800 The iron loss (P) is 1.28T. 2 / 10k The strength is 72 W / kg, the maximum permeability is 22000, and the coercivity is 10.8 A / m.

[0063] Example 3

[0064] Fe-6.5%Si spherical pre-alloyed powder with a particle size of -100 mesh, prepared by rotating electrode atomization, was selected as the raw material. First, the pre-alloyed powder was loaded into a stainless steel sleeve with a diameter of 140 mm, a height of 270 mm, and a wall thickness of 2 mm, vibrated to compaction, and then evacuated to a vacuum level of 1 × 10⁻⁶. -4 After sealing, the sealing sleeve is subjected to hot isostatic pressing at a temperature of 1230℃, a pressure of 130MPa, and a time of 3.5 hours. After cooling in the furnace, an ingot with a diameter of 120mm and a height of 250mm is obtained.

[0065] Hot isostatic pressing billets are extruded on an extruder with an inner diameter of 130 mm and an extrusion die size of 20 mm × 100 mm. The billet temperature is controlled at 1080℃, the extrusion cylinder temperature at 550℃, and the extrusion speed at 5 m / min. After extrusion, the billets are air-cooled to obtain a thickness of 20 mm and a width of 100 mm. The extrusion ratio during the extrusion process is 6.6.

[0066] The extruded billet is heated to 1080℃ and held at that temperature for 2 hours before being hot-rolled in multiple passes on a two-roll hot rolling mill with a roll diameter of 280mm. When the billet thickness is >16mm, the roll speed is controlled at 3m / min; when the billet thickness is 7mm–16mm, the roll speed is controlled at 4m / min; when the billet thickness is <7mm, the roll speed is controlled at 5m / min. When the billet thickness is greater than 14mm, the pass reduction rate is controlled at 5%; when the billet thickness is 8mm–14mm, the pass reduction rate is controlled at 6%; and when the billet thickness is <8mm, the pass reduction rate is controlled at 9%. Rolling is stopped when the billet thickness reaches 2.5mm, and the billet is allowed to cool naturally in air.

[0067] The hot-rolled sheet is heated to 580℃ and held at that temperature for 1 hour. Then, it is subjected to multi-pass hot rolling with a deformation of 5% per pass on a two-roll hot rolling mill with a roll diameter of 180mm. When the billet thickness is >1.25mm, the roll linear speed is controlled at 5m / min. When the billet thickness is <1.25mm, the roll linear speed is controlled at 7m / min. When the thickness is 0.8mm, rolling is stopped and the sheet is allowed to cool naturally in the air.

[0068] The sheet obtained by warm rolling was vacuum annealed at 780℃ for 4 hours and then cooled in the furnace.

[0069] The vacuum-annealed sheet is subjected to multiple cold rolling passes on a four-roll cold rolling mill with a work roll diameter of 80mm. When the billet thickness is >0.48mm, the pass reduction rate is controlled at 9% and the roll line speed is 14m / min. When the billet thickness is <0.48mm, the pass reduction rate is controlled at 7% and the roll line speed is 12m / min.

[0070] When the billet thickness reaches 0.2 mm, rolling is stopped, resulting in a Fe-6.5%Si high-silicon steel sheet with a thickness of 0.2 mm and a width of 100 mm.

[0071] During mass production, the yield rate was 100% according to statistics.

[0072] The magnetic induction intensity (B) of the thin plate obtained in Example 3 was tested. 800 The iron loss (P) is 1.29T. 2 / 10k The strength is 76 W / kg, the maximum permeability is 20000, and the coercivity is 10.6 A / m.

[0073] Example 4

[0074] Fe-6.5%Si spherical pre-alloyed powder with a particle size of -100 mesh, prepared by rotating electrode atomization, was selected as the raw material. First, the pre-alloyed powder was loaded into a stainless steel sleeve with a diameter of 150 mm, a height of 220 mm, and a wall thickness of 2 mm, vibrated to compaction, and then evacuated to a vacuum level of 1 × 10⁻⁶. -4 After sealing, the sealing sleeve is subjected to hot isostatic pressing at a temperature of 1240℃, a pressure of 140MPa, and a time of 3.5 hours. After cooling in the furnace, an ingot with a diameter of 130mm and a height of 200mm is obtained.

[0075] Hot isostatic pressing billets are extruded on an extruder with an inner diameter of 130 mm and an extrusion die size of 25 mm × 110 mm. The billet temperature is controlled at 1080℃, the extrusion cylinder temperature at 580℃, and the extrusion speed at 5 m / min. After extrusion, the billets are air-cooled and then extruded again using a die with a die size of 25 mm × 110 mm to obtain a thickness of 25 mm and a width of 110 mm. The extrusion ratio during the extrusion process is 4.8.

[0076] The extruded billet is heated to 1060℃ and held at that temperature for 2 hours before being hot-rolled in multiple passes on a two-roll hot rolling mill with a roll diameter of 280mm. When the billet thickness is >20mm, the roll speed is controlled at 2.5m / min; when the billet thickness is 8.75mm~20mm, the roll speed is controlled at 3.5m / min; when the billet thickness is <8.75mm, the roll speed is controlled at 4.5m / min. When the billet thickness is greater than 17.5mm, the pass reduction rate is controlled at 5.5%; when the billet thickness is 10mm~17.5mm, the pass reduction rate is controlled at 7%; and when the billet thickness is <10mm, the pass reduction rate is controlled at 9%. Rolling is stopped when the billet thickness reaches 3mm, and the billet is allowed to cool naturally in air.

[0077] The hot-rolled sheet is heated to 580℃ and held at that temperature for 1 hour. Then, it is subjected to multi-pass hot rolling with a deformation of 5% per pass on a two-roll hot rolling mill with a roll diameter of 180mm. When the billet thickness is >1.5mm, the roll linear speed is controlled at 6m / min. When the billet thickness is <1.5mm, the roll linear speed is controlled at 9m / min. When the thickness is 0.7mm, rolling is stopped and the sheet is allowed to cool naturally in the air.

[0078] The sheet obtained by warm rolling was vacuum annealed at 800℃ for 4 hours and then cooled in the furnace.

[0079] The vacuum-annealed sheet is subjected to multiple cold rolling passes on a four-roll cold rolling mill with a work roll diameter of 80mm. When the billet thickness is >0.42mm, the pass reduction rate is controlled at 10% and the roll linear speed is 15m / min. When the billet thickness is <0.42mm, the pass reduction rate is controlled at 6% and the roll linear speed is 11m / min.

[0080] When the billet thickness reaches 0.3 mm, rolling is stopped, resulting in a Fe-6.5%Si high-silicon steel sheet with a thickness of 0.3 mm and a width of 110 mm.

[0081] During mass production, the yield rate was 100% according to statistics.

[0082] The magnetic flux density (B) of the thin plate obtained in Example 4 was tested. 800 The iron loss (P) is 1.29T. 2 / 10k The strength is 72 W / kg, the maximum permeability is 19000, and the coercivity is 11.5 A / m.

[0083] Comparative Example 1

[0084] Other process parameters are the same as in Example 1, except that after hot isostatic pressing, no extrusion deformation is performed, and hot rolling is performed directly. Due to the low density of the billet and the presence of many pores inside, the plastic deformation ability is very poor. The surface cracks severely after only 3 hot rolling passes (as shown in Figure 3), and the rolling fails.

[0085] Comparative Example 2

[0086] Other process parameters are the same as in Example 1, except that the rolling speed and deformation per pass are not changed during hot rolling. The linear speed of the rolls is fixed at 8 m / min and the reduction per pass is 15%. A faster rolling speed can shorten the rolling time per pass and reduce the temperature drop during rolling. However, the rapid rolling with large deformation leads to an increase in the strain rate during rolling, which worsens the plastic deformation ability of the alloy. After only two rolling passes, the billet edge cracks and is not suitable for further rolling.

[0087] Comparative Example 3

[0088] Other process parameters are the same as in Example 1. The warm rolling process is the same as the hot rolling process. The linear speed of the rolls is fixed at 3m / min. Since the length of the billet increases after hot rolling, the warm rolling process uses a lower speed. When the rolling reaches the second pass, the first half of the billet is relatively intact. However, due to the temperature drop, the plastic deformation ability of the alloy in the second half deteriorates, resulting in edge cracking and rolling failure.

[0089] Comparative Example 4

[0090] Other process parameters are the same as in Example 1, except that the annealing temperature after warm rolling is set to 650°C. Due to the low annealing temperature, the alloy is not fully softened. During the subsequent cold rolling process, when the plate thickness is 0.65 mm, some small cracks appear on the edge. When the thickness reaches 0.55 mm, the edge cracks expand severely and are not suitable for further rolling, resulting in rolling failure.

[0091] Comparative Example 5

[0092] Other process parameters are the same as in Example 1. However, to improve production efficiency, the roll linear speed is set to 20m / min during cold rolling. In the second pass of cold rolling, the sheet material suffers severe edge cracking and the rolling process fails.

[0093] Comparative Example 6

[0094] Other process parameters are the same as in Example 1, except that the billet heating temperature is set to 950°C during extrusion. For other materials with good plasticity, the extrusion process is subject to triaxial compressive stress, which is conducive to the development of material plasticity. Therefore, it is normal for the extrusion temperature to be 100-200°C lower than the rolling temperature. However, in this invention, when the extrusion temperature is reduced to 950°C, the material itself has poor plasticity, and there are still about 8%-10% porosity in the billet after hot isostatic pressing. Reducing the extrusion temperature directly leads to cracking of the billet after extrusion, making it impossible to proceed with subsequent rolling.

Claims

1. A method for preparing Fe-6.5%Si high-silicon steel thin plates by powder metallurgy, characterized in that: Fe-6.5%Si pre-alloyed powder is loaded into a sleeve and then subjected to hot isostatic pressing to obtain an ingot. The ingot is then hot-extruded to obtain a plate-shaped billet. The plate-shaped billet is then subjected to hot rolling, warm rolling, annealing, and cold rolling in sequence to obtain the final product. The hot rolling process involves preheating the plate-shaped billet at 1050~1100℃ for 1~2 hours, followed by multiple hot rolling passes, controlling the final rolling temperature of each pass to ≥1000℃, and finally rolling the billet to a thickness of less than 3mm. During hot rolling, when the total deformation of the billet is <20... When the total deformation of the billet is 20-65%, the roll speed is controlled at 2-3 m / min; when the total deformation of the billet is 20-65%, the roll speed is controlled at 3-4 m / min; when the total deformation of the billet is >65%, the roll speed is controlled at 4-5 m / min. When the total deformation of the billet is <30%, the pass reduction rate is controlled at 5-6%; when the total deformation of the billet is 30-60%, the pass reduction rate is controlled at 6-8%; when the total deformation of the billet is >60%, the pass reduction rate is controlled at 8-10%.

2. The method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel thin plate according to claim 1, characterized in that: The Fe-6.5%Si pre-alloyed powder has a particle size of -100 mesh; the Fe-6.5%Si pre-alloyed powder is prepared by rotating electrode atomization; the Fe-6.5%Si pre-alloyed powder is spherical; the mass percentage of Si is 6.4~6.6%, the mass percentage of Fe is ≥93.4%, and the oxygen content is <800ppm.

3. The method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel thin plate according to claim 1, characterized in that: Fe-6.5%Si pre-alloyed powder is packed into a stainless steel sleeve, vibrated, vacuumed, and sealed, and then subjected to hot isostatic pressing (HIP). The HIP temperature is 1200~1250℃, the HIP time is 3~4h, and the HIP pressure is 120~140MPa.

4. The method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel thin plate according to claim 1, characterized in that: The extrusion ratio of the hot extrusion is 4 to 7.

5. A method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel sheet according to any one of claims 1-4, characterized in that: The billet temperature during hot extrusion is 1050~1100℃, the extrusion cylinder temperature is 500~600℃, and the extrusion speed is 4~8m / min; after hot extrusion, the billet is air-cooled.

6. A method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel sheet according to any one of claims 1-4, characterized in that: The warm rolling process involves preheating the hot-rolled billet at 550-600℃ for 1-1.5 hours, followed by multiple warm rolling passes. The reduction rate per pass is controlled at 5-6%, and the roll speed is 5-10 m / min, until the final thickness of the billet is less than 1 mm. The annealing is carried out under vacuum conditions at a temperature of 750-800℃ for 3-5 hours. During the cold rolling process, the reduction rate per pass is controlled at 5-10%, and the roll speed is 10-15 m / min. A thin plate with a thickness of 0.1-0.4 mm is obtained through multiple cold rolling passes.

7. The method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel thin plate according to claim 6, characterized in that: During warm rolling, when the total deformation is ≤50%, the roll speed is controlled at 5~7 m / min; when the total deformation is >50%, the roll speed is controlled at 7~10 m / min. During cold rolling, when the total deformation is ≤40%, the pass reduction rate is controlled at 8~10%, and the roll speed is controlled at 13~15 m / min; when the total deformation is >40%, the pass reduction rate is controlled at 5~8%, and the roll speed is controlled at 10~13 m / min.

8. A method for preparing a powder metallurgy Fe-6.5%Si high-silicon steel sheet according to any one of claims 1-4, characterized in that: The hot rolling process uses a two-roll hot rolling mill with a roll diameter greater than 200mm, the warm rolling process uses a two-roll hot rolling mill with a roll diameter greater than 150mm, and the cold rolling process uses a four-roll cold rolling mill with a diameter less than 100mm.

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