A short process preparation method for ultra-thin high silicon steel strip

Abstract

The present invention discloses a short-process preparation method for an ultra-thin high-silicon steel strip. The steps include: smelting → twin-roller thin strip continuous casting → warm rolling → stress relief annealing → pickling → cold rolling → recrystallization annealing. The method of the present invention is green and environmentally friendly. Through continuous casting by a twin-roller thin strip continuous casting machine, the extremely fast cooling rate can effectively inhibit the transformation process of the ordered phase of high silicon steel during the solidification process, reduce the content of the ordered phase in the high silicon steel cast strip, and then reduce the order degree, thereby improving its processing performance. Secondly, the method can eliminate the large reduction hot rolling process in the traditional rolling process, and avoid the cracking of high silicon steel plates caused by excessive reduction during the rolling process. The method can prepare ultra-thin high silicon steel strips with good comprehensive magnetic properties without trimming.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material preparation, and in particular relates to a short-process preparation method of an ultra-thin high-silicon steel cold-rolled thin strip. Background Art

[0002] In the field of electricity and electronics, silicon steel is a kind of metal soft magnetic material with relatively excellent magnetic properties and the largest amount of use. It is often used to manufacture transformers, motors, generators and electrical components. With the increase of silicon content, the conductivity of silicon steel increases, the magnetic permeability increases, and the iron loss and magnetostriction coefficient decrease. With the silicon content in silicon steel increased to 6.5wt%, high silicon steel has lower iron loss at high frequency and has an extremely low magnetostriction coefficient, which can significantly reduce noise. It can be used to manufacture high-speed motors and high-frequency transformers, which is of great significance to energy saving, consumption reduction and noise reduction.

[0003] In the preparation method of high silicon steel, as the silicon content in silicon steel increases to 4.5wt%, a large number of iron-silicon covalent bonds and a large number of ordered phases will be generated inside the material matrix. At the same time, due to the solid solution strengthening effect of silicon elements, the material will be hard and brittle, and the preparation and processing is extremely difficult. Japanese patent JP5569223 successfully prepared high silicon steel strips by rapid solidification, which triggered a worldwide upsurge in the research of high silicon steel. However, due to the fast cooling rate when preparing high silicon steel strips by rapid solidification, a large number of dislocations and lattice distortions and other defects exist in the strip matrix, and there are also a large number of unreleased internal stresses. Due to the existence of these factors, the low-frequency magnetic properties of the strip are poor, and it needs to be heat treated before it can be used. At the same time, due to the limited width of the finished strip and the single product thickness specification, this technical bottleneck has not been solved, making it difficult for the technology to achieve industrial production, and industrialization has not yet been realized.

[0004] Japanese patent JP6326330 prepared high silicon steel strip by chemical vapor deposition (CVD). The principle is to perform siliconization treatment on the surface of ordinary silicon steel plate, and make the silicon content of the entire thin plate cross section reach 6.5% by homogenization diffusion heat treatment. However, the process is complicated. At the same time, the raw material SiCl4 used for siliconization is highly toxic and corrosive, which seriously pollutes the environment. The process has extremely high requirements on the sealing of the production line, and the daily maintenance is complicated. The exhaust gas emission pollutes the environment, and the production efficiency is low. The production cost is high and the cycle is long. The shortcomings cannot be widely used.

[0005] Japanese patents JP62103321, JP61166923, JP63227717A, and JP63069915A reported that the cold rolling formability of high silicon steel was effectively improved 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. Lin Junpin et al. reported in "6.5wt% Si High Silicon Steel Cold Rolled Sheet Preparation Process, Structure and Performance" that the alloy thin strip was prepared by the traditional hot rolling-cold rolling process. The prepared cold rolled thin strip has a good plate shape and a metallic luster on the surface. However, the high silicon steel thin strips prepared by these process methods still have certain edge cracks, and the process flow is long, the plate size is small, and edge cracks are easily generated during large reduction rolling. During the production process, continuous trimming is required to meet the subsequent rolling process, so the yield rate is low and the production cost is relatively high.

[0006] The advantages of twin-roller thin strip continuous casting technology such as short process, near-net shape and high efficiency are expected to realize large-scale mass production of high-silicon steel thin plates, and the process is environmentally friendly, so choosing twin-roller thin strip continuous casting process to prepare high-silicon steel is an excellent choice. At the same time, the extremely fast cooling rate can effectively inhibit the transformation process of the ordered phase of high-silicon steel during the solidification process, thereby reducing the content of the ordered phase in the high-silicon steel cast strip, and then reducing the degree of order. Secondly, the high-silicon steel cast strip prepared by this process is close to the thickness of the hot-rolled plate, so the large reduction hot rolling process in the traditional process can be omitted, avoiding the cracking of the high-silicon steel plate caused by excessive reduction during the rolling process.

[0007] Chinese patent ZL201010297551.0 discloses a non-oriented high-silicon electrical steel strip and a preparation method thereof, which directly prepares a 1.1 mm thick thin plate through a casting and rolling process, and prepares a 6.5 wt.% Si high-silicon steel thin plate with a width of 110 mm and a thickness of 0.35-0.50 mm through subsequent hot rolling and warm rolling processes. However, due to the high temperature of warm rolling and the presence of thermal convexity in the rollers during the rolling process, it is difficult to prepare thinner high-silicon steel. In addition, the warm-rolled plate has a poor shape and a rough surface, making it difficult to use. In addition, this method still requires high-temperature hot rolling, and the process flow is relatively long.

[0008] Chinese patent 201811279784.0 discloses a method for rolling a high silicon steel strip, using a high silicon steel cast strip with a thickness of 2 to 4 mm prepared by a double-roller thin strip casting process as a raw material, heating to 900 to 1100°C in a protective atmosphere, hot rolling to a thickness of 1 to 1.2 mm through at least one pass, and a total reduction rate of 50% to 60% for hot rolling, heating the high silicon steel hot-rolled strip to 320 to 500°C, and warm rolling to a thickness of 0.4 to 0.5 mm through at least one pass, and a total reduction rate of 50% to 70% for warm rolling, pickling to remove the oxide scale, and cold rolling to prepare a high silicon steel strip with good surface quality and plate shape, and excellent magnetic properties after annealing. However, the thickness of the cold-rolled plate prepared by this process is 0.2 to 0.3 mm, and the finished plate is relatively thick, and high-temperature hot rolling is still required, the process is relatively long, and the magnetic properties of the high silicon steel strip after annealing are relatively poor. Summary of the invention

[0009] In view of the above-mentioned problems and defects, the purpose of the present invention is to provide a short-process preparation method for ultra-thin high-silicon steel strips, so as to solve the problems of complex existing production process of high-silicon steel sheets, multiple manufacturing processes, high equipment requirements, high energy consumption, large environmental load and deterioration of product surface quality. This method is environmentally friendly and green, and the extremely fast cooling rate can effectively inhibit the transformation process of the ordered phase of high-silicon steel during the solidification process, reduce the content of the ordered phase in the high-silicon steel cast strip, and then reduce the order degree, and improve its processing performance. Secondly, this method can eliminate the large reduction hot rolling process in the traditional rolling process, and avoid the cracking of high-silicon steel plates caused by excessive reduction during the rolling process. This method can be used to prepare ultra-thin high-silicon steel strips with good comprehensive magnetic properties without trimming.

[0010] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0011] The present invention provides a short-process preparation method for an ultra-thin high-silicon steel strip, comprising the following steps:

[0012] (1) Smelting: Smelting in vacuum induction furnace;

[0013] (2) Twin-roller thin strip continuous casting: When the superheat of the molten steel reaches 10-80°C, the molten steel is continuously cast using a twin-roller thin strip continuous casting machine to obtain a cast strip, which is then air-cooled or water-cooled to room temperature;

[0014] (3) Warm rolling: The cast strip is warm rolled at 250-700°C, with 3-7 passes, and the steel is returned to the furnace for 0.5-2 min between passes. The reduction per pass is 5%-35%, and the total reduction is more than 60%, to obtain a warm rolled plate;

[0015] (4) Stress relief annealing: The warm rolled sheet is subjected to stress relief annealing at a temperature of 250 to 450° C. for 0.5 to 1.5 h to obtain a warm rolled annealed sheet;

[0016] (5) Pickling: Pickle the warm-rolled annealed sheet to remove the oxide scale, and then rinse and dry the warm-rolled sheet after pickling;

[0017] (6) Cold rolling: cold rolling the pickled warm-rolled sheet at room temperature, with 2 to 7 cold rolling passes, a pass reduction of 3% to 30%, and a total reduction of 40% to 88% to obtain a cold-rolled sheet;

[0018] (7) Recrystallization annealing: The cold rolled sheet is subjected to recrystallization annealing at a temperature of 800 to 1300° C. for a time of 0.5 to 2 h to obtain a finished high silicon steel strip.

[0019] In the above technical solution, further, the chemical composition of the molten steel is as follows by weight percentage: Si 4.5% to 7.5%, C 0.003% to 0.01%, N 0.001% to 0.003%, S 0.0005% to 0.002%, P 0.002% to 0.01%, and the remainder is iron and unavoidable impurities.

[0020] In the above technical solution, further, the roll width of the twin-roll thin strip continuous casting machine is 100-500 mm, the roll speed is 30-180 m / min, and the roll gap is 0.8-3 mm.

[0021] In the above technical solution, further, the thickness of the warm-rolled plate is 0.1 to 0.4 mm.

[0022] In the above technical solution, further, the thickness of the cold-rolled sheet is 0.05 to 0.1 mm.

[0023] In the above technical solution, further, the atmosphere of the recrystallization annealing is N2, H2 or a mixture of N2 and H2.

[0024] In the above technical solution, further, the pickling temperature is 30-80° C., the pickling solution is a hydrochloric acid aqueous solution with a mass concentration of 10%-30%, and the pickling time is 2-30 minutes.

[0025] In the above technical solution, further, the finished high silicon steel strip has a thickness of 0.05-0.1 mm and a width of 100-1500 mm; its magnetic properties are: magnetic induction intensity B8 is 1.28-1.36 T, B 50 1.66~1.75T, iron loss P 10 / 50 0.3~0.5W / kg, iron loss P 10 / 400 It is 3.5~4.8W / kg.

[0026] Beneficial technical effects of the present invention:

[0027] (1) The high silicon steel cold-rolled thin strip produced by the method provided by the present invention has a bright and smooth surface, thereby improving the quality of the product;

[0028] (2) In the method provided by the present invention, the large-reduction hot rolling process can be omitted, and the high-silicon steel strip can be directly prepared by warm rolling after twin-roll thin strip continuous casting, which shortens the process flow and greatly saves energy. The surface quality of the warm-rolled plate and the cold-rolled plate is good. While shortening the process flow, the processing performance and magnetic properties are not affected, and the short process and near-net-shape forming of the cold-rolled high-silicon steel strip are realized;

[0029] (3) The present invention avoids the cracking of high silicon steel plates caused by excessive reduction during rolling;

[0030] (4) The present invention uses a twin-roll thin strip continuous casting machine for continuous casting, and its rapid cooling effect can effectively reduce the order of the high silicon steel casting strip and improve the processing performance of the casting strip;

[0031] (5) The present invention successfully prepared high silicon steel cold-rolled thin strips with a thickness of 0.05 to 0.10 mm and a width of 100 to 1500 mm, realizing the preparation of large-size high silicon steel thin strips;

[0032] (6) The method of the present invention allows for more precise control of the properties and structure of high silicon steel strip to obtain a more consistent product, which will help improve the quality of the product.

[0033] In summary, the present invention makes the preparation of large-sized high-silicon steel strips more economical, reduces waste and energy consumption, has less impact on the environment, and helps to improve the sustainability of the production process. Due to the more efficient production method, high-silicon steel strips of different specifications and grades can be produced more flexibly to meet the needs of different customers and increase market share. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The short process flow chart of the preparation process of the ultra-thin high silicon steel strip of the present invention is as follows;

[0035] Figure 2 This is a photo of the medium temperature rolled plate of Example 1 of the present invention;

[0036] Figure 3 This is a diagram of the ordered phase morphology in the warm rolled plate annealing sample of Example 1 of the present invention;

[0037] Figure 4 These are photos of the finished high silicon steel cold-rolled thin strip in Example 1 of the present invention, a is before coiling, and b is after coiling. DETAILED DESCRIPTION

[0038] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0039] Example 1

[0040] The chemical composition of the high silicon steel of Example 1 is as follows by weight percentage: Si 6.45%, C 0.003%, N 0.002%, S 0.001%, P 0.005%, and the balance is iron and unavoidable impurities.

[0041] The process flow chart of the preparation of the high silicon steel strip is as follows: Figure 1 As shown, the following steps are included:

[0042] (1) Smelting: The molten steel is smelted in a vacuum induction furnace. The chemical composition of the molten steel is as follows by weight percentage: Si 6.45%, C 0.003%, N 0.002%, S 0.001%, P 0.005%, and the balance is iron and inevitable impurities;

[0043] (2) Twin-roller thin strip continuous casting: The liquid high silicon steel with a superheat of 30°C after smelting is cast into a twin-roller thin strip continuous casting machine with a roll width of 100 mm, a roll speed of 45 m / min, and a roll gap of 1.7 mm. The liquid high silicon steel forms a cast strip after exiting the roll gap, and the cast strip is water-cooled to room temperature;

[0044] (3) Warm rolling: The cast strip is warm rolled at 500°C to 0.15 mm, with 4 passes, and the rolling is returned to the furnace for 1 min between passes. The reduction per pass is 5% to 35%, and the total reduction is 91%. The warm rolled plate is obtained. The photo of the warm rolled plate is shown in Figure 2 As shown, it can be seen that the surface quality of the warm-rolled plate is good, the edges are flat and there are no cracks visible to the naked eye, showing good processing performance;

[0045] (4) Stress relief annealing: The warm rolled sheet is subjected to stress relief annealing at 350°C for 1 h. After stress relief annealing, the ordered phase in the sheet is Figure 3 As shown, it can be seen that the order degree in the warm rolled plate sample is very low, and no D03 ordered phase is found, so the warm rolled plate will show good room temperature processing performance;

[0046] (5) Pickling: The high silicon steel warm rolled annealed sheet is pickled to remove the oxide scale, the pickling temperature is 50°C, the pickling liquid is a hydrochloric acid aqueous solution with a mass concentration of 15%, and the pickling time is 5 min. After pickling, the warm rolled sheet is rinsed and dried;

[0047] (6) Cold rolling: The warm rolled sheet was cold rolled to 0.08 mm at room temperature. The number of cold rolling passes was 5, the reduction per pass was 3% to 30%, and the total reduction was 46.7%. The cold rolled sheet photo is shown in Figure 4 As shown, the surface quality of the cold-rolled sheet is good, there are no cracks visible to the naked eye, and it can be bent into a coil;

[0048] (7) Recrystallization annealing: The cold rolled sheet is recrystallized annealed in H2 atmosphere at a temperature of 1200°C for 1 h.

[0049] After testing, the magnetic induction intensity B8 of 0.08mm thick high silicon steel strip is 1.30T, B 50 is 1.69T, iron loss P 10 / 50 is 0.39W / kg, iron loss P 10 / 400 It is 4.0W / kg.

[0050] Example 2

[0051] The chemical composition of the high silicon steel of Example 2 is as follows by weight percentage: Si 6.25%, C 0.004%, N 0.0025%, S 0.002%, P 0.008%, and the balance is iron and unavoidable impurities;

[0052] The method for preparing the high silicon steel strip comprises the following steps:

[0053] (1) Smelting: High silicon steel is smelted in a vacuum induction furnace. The chemical composition of the high silicon steel is as follows by weight percentage: Si 6.25%, C 0.004%, N 0.0025%, S 0.002%, P 0.008%, and the balance is iron and unavoidable impurities;

[0054] (2) Twin-roller thin strip continuous casting: The liquid high silicon steel with a superheat of 50°C after smelting is cast into a twin-roller thin strip continuous casting machine with a roll width of 200 mm, a roll speed of 60 m / min, and a roll gap of 2 mm. The liquid high silicon steel forms a high silicon steel casting strip after exiting the roll gap, and the casting strip is water-cooled to room temperature;

[0055] (3) Warm rolling: The high silicon steel cast strip is warm rolled at 500℃ to 0.4mm, with 5 passes, and the furnace is returned to the furnace for 1min between passes. The reduction per pass is 5% to 35%, and the total reduction is 80%. The cold rolled sheet photo is as follows: Figure 2 As shown;

[0056] (4) Stress relief annealing: The warm rolled sheet is subjected to stress relief annealing at 400°C for 0.8h;

[0057] (5) Pickling: The high silicon steel warm rolled annealed sheet is pickled to remove the oxide scale. The pickling temperature is 60°C. The pickling liquid is a hydrochloric acid aqueous solution with a mass concentration of 13%. The pickling time is 4 minutes. After pickling, the warm rolled sheet is rinsed and dried.

[0058] (6) Cold rolling: The warm rolled sheet is cold rolled to 0.1 mm at room temperature, with 5 cold rolling passes, a pass reduction of 3% to 30%, and a total reduction of 75%. The surface quality of the cold rolled sheet is good, with no visible cracks and can be bent into coils;

[0059] (7) Recrystallization annealing: The cold rolled sheet was recrystallized in a H2 atmosphere at a temperature of 1100°C for 1.5 h.

[0060] After testing, the magnetic induction intensity B8 of 0.1mm thick high silicon steel strip is 1.33T, B 50 is 1.72T, iron loss P 10 / 50 is 0.46W / kg, iron loss P 10 / 400 It is 4.62W / kg.

[0061] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A short-process preparation method for ultra-thin high-silicon steel strip, characterized in that: The following steps are involved: (1) Smelting: Smelting is carried out in a vacuum induction furnace. The chemical composition of the molten steel is as follows by weight percentage: Si 4.5% to 7.5%, C 0.003% to 0.01%, N 0.001% to 0.003%, S 0.0005% to 0.002%, P 0.002% to 0.01%, and the balance is iron and unavoidable impurities; (2) Twin-roller thin strip continuous casting: When the superheat of the molten steel reaches 10-80°C, the molten steel is continuously cast using a twin-roller thin strip continuous casting machine to obtain a cast strip, which is then air-cooled or water-cooled to room temperature; (3) Warm rolling: The cast strip is warm rolled at 250-700°C, with 3-7 passes, and the steel is returned to the furnace for 0.5-2 min between passes. The reduction per pass is 5%-35%, and the total reduction is more than 60%, to obtain a warm rolled plate; (4) Stress relief annealing: The warm rolled sheet is subjected to stress relief annealing at a temperature of 250 to 450° C. for 0.5 to 1.5 h to obtain a warm rolled annealed sheet; (5) Pickling: Pickle the warm-rolled annealed sheet to remove the oxide scale, and then rinse and dry the warm-rolled sheet after pickling; (6) Cold rolling: cold rolling the pickled warm-rolled sheet at room temperature, with 2 to 7 cold rolling passes, a pass reduction of 3% to 30%, and a total reduction of 40% to 88% to obtain a cold-rolled sheet; (7) Recrystallization annealing: The cold rolled sheet is subjected to recrystallization annealing at a temperature of 800 to 1300° C. for a time of 0.5 to 2 h to obtain a finished high silicon steel strip.

2. The short-process preparation method of ultra-thin high-silicon steel strip according to claim 1, characterized in that: The roll width of the twin-roll thin strip continuous casting machine is 100-500 mm, the roll speed is 30-180 m / min, and the roll gap is 0.8-3 mm.

3. The short-process preparation method of ultra-thin high-silicon steel strip according to claim 1, characterized in that: The thickness of the warm rolled plate is 0.1 to 0.4 mm.

4. The short-process preparation method of ultra-thin high-silicon steel strip according to claim 1, characterized in that: The thickness of the cold rolled sheet is 0.05 to 0.1 mm.

5. The short-process preparation method of ultra-thin high-silicon steel strip according to claim 1, characterized in that: The atmosphere for recrystallization annealing is N2, H2 or a mixture of N2 and H2.

6. The short-process preparation method of ultra-thin high-silicon steel strip according to claim 1, characterized in that: The pickling temperature is 30-80° C., the pickling solution is a hydrochloric acid aqueous solution with a mass concentration of 10%-30%, and the pickling time is 2-30 minutes.

7. The short-process preparation method of ultra-thin high-silicon steel strip according to claim 1, characterized in that: The thickness of the finished high silicon steel strip is 0.05-0.1mm, and the width is 100-1500mm; its magnetic properties are: magnetic induction intensity B8 is 1.28-1.36T, B 50 1.66~1.75T, iron loss P 10 / 50 0.3~0.5W / kg, iron loss P 10 / 400 It is 3.5~4.8W / kg.

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