Non-oriented silicon steel and its manufacturing method

Abstract

This invention belongs to the field of non-oriented silicon steel, specifically, it relates to a non-oriented silicon steel and its manufacturing method. This invention discloses a non-oriented silicon steel comprising the following chemical composition by weight percentage: C≤0.0020%; S≤0.0020%; N≤0.0020%; Ti≤0.0020%; 0.20≤Si≤3.50%; 0.30≤Als≤1.00%; 0.10≤Mn≤0.70%; P≤0.1%; 0.01≤Sn≤0.12%; the balance being Fe and unavoidable impurities. The beneficial effect of this invention is that it provides a non-oriented silicon steel with a thickness of 0.25mm and P... 1.0 / 400 ≤12.0W / kg, P 1.0 / 1000 ≤45.0W / kg, B 5000 Non-oriented silicon steel with a weight of ≥1.65T and its manufacturing method.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented silicon steel, and more specifically, relates to a non-oriented silicon steel and its manufacturing method. Background Technology

[0002] For silicon steel used in new energy vehicles, while meeting the operating conditions of drive motors, greater emphasis is placed on iron loss at mid-to-high frequencies (200-3000Hz), with eddy current loss accounting for the largest proportion of total losses. Therefore, further reducing eddy current loss during material manufacturing and production becomes an effective means of controlling the total losses of silicon steel under mid-to-high frequency conditions. Lower P1.0 / 400 and higher magnetic induction B5000 are key indicators for silicon steel used in new energy vehicles. Under the same composition system, i.e., with the same raw materials for non-oriented silicon steel, optimizing total iron loss and optimizing magnetic polarization are mutually exclusive. The iron loss and magnetic polarization of non-oriented silicon steel are related to factors such as grain size, grain uniformity, surface condition, and the state of the surface oxide layer. How to reconcile the contradiction between iron loss and magnetic induction has become a key direction and a major challenge in the research and development of electrical steel for electric motors in new energy vehicles.

[0003] Among them, iron loss P 1.0 / 400 and P 1.0 / 1000 The total loss was measured at 1.0T under alternating magnetic fields with frequencies of 400Hz and 1000Hz, respectively; magnetic induction B. 5000 The magnetic polarization intensity is measured under a magnetic field strength of 5000 A / m; based on industry convention, the total loss can be represented by the letters P or W, and P will be used in the following text; B 5000 B can also be used 50 This means that B will be used throughout the following text. 5000 express.

[0004] Chinese patent document (I) CN103361544A discloses a non-oriented silicon steel for new energy drive motors and its manufacturing method. This method reduces iron loss by adding Sn content and controlling effective steelmaking and hot rolling processes. This solution addresses measures for the preceding processes; however, it does not yet explicitly address the control technology for the subsequent cold rolling and annealing processes.

[0005] Chinese Patent Document (II) CN107385335A discloses a non-oriented electrical steel sheet and its manufacturing method. This manufacturing method uses a suitable alloy composition system, effectively controls hot rolling, cold rolling, and annealing processes, and controls the P1.0 / 400 of the steel sheet within a defined range to produce high-performance silicon steel sheets. However, this process is difficult to control and is greatly affected by steelmaking. It lacks subsequent adjustment measures when there are deviations in composition control, and the produced steel sheets have a P1.0 / 400 ≤ 19W / kg, whose performance no longer meets the needs of current technological development.

[0006] Chinese Patent Document (III) CN115522127A discloses an ultra-thin non-oriented electrical steel and its manufacturing method. The manufacturing method includes the following process flow: molten iron pretreatment → converter smelting → alloy fine-tuning station → RH refining → continuous casting → hot rolling → normalizing and pickling → primary cold rolling → intermediate annealing → secondary cold rolling → continuous annealing → finishing → packaging. The non-oriented electrical steel obtained by this patent manufacturing method has P1.0 / 50 of 1.95-2.21 W / kg, B50 of 1.72-1.74 T, and W1.0 / 400 of 9.5-11.5 W / kg. The electrical steel in this patent exhibits low iron loss under medium and low frequency conditions, and B... 50 While the thickness of the non-oriented electrical steel prepared by this method is relatively high, it is only 0.120-0.140 mm, which is considered ultra-thin. However, under high-speed operation, the centrifugal force in a motor is significant, increasing the risk of breakage at weak points in the magnetic bridge of the iron core. Furthermore, the continuous reduction in the thickness of non-oriented electrical steel makes raw material production and processing difficult, increasing costs and impacting the overall economic viability of the motor. Therefore, considering both manufacturing and processing costs, a thickness of 0.2-0.25 mm is the optimal thickness for silicon steel used in new energy vehicle drive motors for the foreseeable future. However, improving the overall performance of 0.2-0.25 mm thick non-oriented silicon steel in existing technologies presents significant technological challenges. Summary of the Invention

[0007] 1. Technical problems to be solved

[0008] Existing technologies lack P-type silicon steel with a thickness of 0.25 mm. 1.0 / 400 Stably controlled at less than 12 W / kg, while simultaneously ensuring B 5000 Manufacturing method of non-oriented silicon steel with a weight of not less than 1.65T and corresponding products.

[0009] 2. Technical Solution

[0010] The summary section of this invention provides a brief overview of the concepts, which will be described in detail in the detailed description section that follows. This summary section is not intended to identify key or essential features of the claimed invention, nor is it intended to limit the scope of the claimed invention.

[0011] To address the technical problems mentioned in the background section, as a first aspect of the present invention, a specific embodiment of the present invention provides a non-oriented silicon steel comprising the following chemical composition by weight percentage:

[0012] C≤0.0020%;

[0013] S≤0.0020%;

[0014] N≤0.0020%;

[0015] Ti≤0.0020%;

[0016] 0.20% ≤ Si ≤ 3.50%;

[0017] 0.30% ≤ Als ≤ 1.00%;

[0018] 0.10% ≤ Mn ≤ 0.70%;

[0019] P≤0.1%;

[0020] 0.01% ≤ Sn ≤ 0.12%;

[0021] The balance consists of Fe and unavoidable impurities.

[0022] In the above-mentioned chemical composition of non-oriented silicon steel, C, S, N, and Ti are harmful elements. When the C content exceeds 0.0020%, magnetic aging will occur, which will worsen the iron loss of non-oriented silicon steel during use, leading to an increase in the coercivity and hysteresis loss of non-oriented silicon steel, while reducing its magnetic induction intensity. Based on this, the C content is controlled below 0.0020%.

[0023] When the S and N content is high, a large number of inclusions such as MnS, Cu2S and AlN will be generated, which will affect the performance of silicon steel. An important goal in processes such as slab heating and hot rolling is to control the precipitation of fine MnS particles and coarsen the existing MnS. Therefore, the weight percentage of S and N should be controlled to be less than or equal to 0.002%.

[0024] Non-oriented silicon steel has a polycrystalline structure, and its grain orientation and distribution ("texture") have a significant impact on its macroscopic properties. Increasing the Ti content leads to the formation of numerous small, stable Ti(CN) inclusions, hindering grain growth, increasing {111} grains and decreasing {100} grains in the finished product, negatively affecting the macroscopic properties of non-oriented silicon steel. Therefore, the Ti content is controlled below 0.002%.

[0025] Increasing the Si and Al content coarsens the grains of the finished non-oriented silicon steel, which helps reduce the number of domain walls, lower hysteresis loss, and thus reduce iron loss. However, excessively high Si and Al content can lead to poor cold deformation performance of non-oriented silicon steel during production. Therefore, the Si and Al content should be controlled at 0.20% ≤ Si ≤ 3.50% and 0.30% ≤ Al ≤ 1.00%.

[0026] In this invention, domain walls refer to the interfaces between individual grains. As the finished grains coarsen and the grain size increases, the number of domain walls increases, resulting in lower hysteresis loss, but a corresponding increase in eddy current loss. Therefore, the finished grain size of non-oriented silicon steel needs to be controlled within a reasonable range to balance the ratio between eddy current loss and hysteresis loss, thereby keeping the total loss within a reasonable range.

[0027] Mn has a relatively small effect on magnetic induction and is generally controlled below 0.15%. When the Mn content is >0.8%, the permeability decreases with increasing Mn content. Based on this, the content is controlled to be 0.10% ≤ Mn ≤ 0.70%.

[0028] Furthermore, the weight percentage of S is less than or equal to 0.001%; ​​the weight percentage of N is less than or equal to 0.0015%; and the weight percentage of Ti is less than or equal to 0.0015%.

[0029] As a second aspect of the present invention, a specific embodiment of the present invention provides a method for manufacturing the aforementioned non-oriented silicon steel, comprising the following steps:

[0030] S1. Continuous casting;

[0031] S2. Hot-rolled;

[0032] S3. Cold rolling in one step;

[0033] S4. Single annealing;

[0034] S5. Secondary cold rolling;

[0035] S6. Secondary annealing;

[0036] In particular, the heating process for step S6, the secondary annealing, adopts a segmented heating process, and the specific steps are as follows:

[0037] First stage: Raise the furnace temperature from room temperature to 400-600℃, with a heating rate of less than 20℃ / s;

[0038] Second stage: Raise the furnace temperature from 400-600℃ to the target temperature t1 at a rate of not less than 50℃ / s;

[0039] The third stage: raise the furnace temperature from t1 to the target temperature of 900-1020℃, and then hold it for 20-500 seconds.

[0040] The range of t1 is 870–920℃.

[0041] For example, t1 can be any value within the following range:

[0042] 870~880℃, 870~900℃, 870~920℃, 880℃~900℃, 880~920℃, 900~920℃.

[0043] It should be noted that due to energy loss during heat conduction, the temperature difference between the heating furnace and the steel is approximately 30°C. Therefore, in actual production, the actual temperature of the steel is approximately t1-30°C.

[0044] The first stage of heating, with a heating rate controlled below 20℃ / s, prevents surface oxidation caused by rapid heating. Furthermore, the target temperature of the first stage heating is lower than the crystal nucleation temperature. The lower heating rate in this stage ensures uniform heating of the steel. At the same time, a faster heating rate requires the use of an electric furnace, while a slower heating rate can be achieved using a gas furnace, which is more energy-efficient than an electric furnace. Therefore, controlling the heating rate below 20℃ / s in this stage can also save energy.

[0045] The second stage of heating, with a heating rate of no less than 50℃ / s, can optimize the texture. {111} grains, {110} grains, and {100} grains have different sensitivities to temperature. Under conventional techniques, more {111} grains are formed. However, under rapid heating, the proportion of {110} and {100} grains will increase, resulting in more favorable textures. At the same time, the composition of grains of various sizes is also more uniform, which is beneficial to improving the performance of the finished non-oriented silicon steel.

[0046] Further, in step S1, before continuous casting, the molten steel undergoes pretreatment, converter smelting, and vacuum treatment.

[0047] Furthermore, in step S1, the thickness of the slab obtained by continuous casting is 200-300 mm.

[0048] Furthermore, after step S1. continuous casting and before step S2. hot rolling, the steel is cooled to a temperature of not less than 550°C.

[0049] Furthermore, in step S2, during the hot rolling process, the steel is heated in a heating furnace at a temperature of 1100–1200℃ and the heating and holding time is ≥210 min; in step S2, the final rolling temperature of the hot rolling is 830–850℃.

[0050] Furthermore, in step S2, the thickness of the hot-rolled steel is 1.8–2.2 mm.

[0051] Furthermore, step S2. Hot rolling includes 3 passes of rough rolling and 7 passes of finish rolling.

[0052] Furthermore, three passes of rough rolling bring the steel to a thickness of 34 mm.

[0053] Furthermore, a 7-pass finishing rolling process reduces the steel thickness to 1.8–2.2 mm.

[0054] Furthermore, after hot rolling in step S2 and before cold rolling in step S3, the steel obtained from hot rolling in step S2 is pickled.

[0055] Furthermore, the pickling process uses one or more of the following: hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, sulfamic acid, citric acid, and EDTA.

[0056] Furthermore, hydrochloric acid is used for pickling.

[0057] Furthermore, the hydrochloric acid used for pickling has a mass concentration of 55% to 60%.

[0058] For example, the hydrochloric acid used for pickling has a mass concentration of 58%.

[0059] Furthermore, the pickling temperature is 60℃~100℃.

[0060] For example, the pickling temperature is 80℃.

[0061] Furthermore, after hot rolling in step S2 and before pickling the steel, it is air-cooled to 500-650°C and then coiled.

[0062] Furthermore, after hot rolling in step S2, and before air cooling and coiling of the steel, the steel is normalized at a normalization temperature of 850–950°C; for example, the normalization temperature can be 850°C, 900°C, or 950°C.

[0063] Furthermore, in step S3, the single cold rolling reduction rate is controlled at 80% to 90%.

[0064] Furthermore, the thickness of the steel obtained by one cold rolling is 0.28 to 0.32 mm.

[0065] The reduction rate is the percentage (%) of the reduction amount Δh to the height H of the workpiece before rolling or the height h after rolling, i.e., Δh / H×100% or Δh / h×100%. It is a deformation parameter that indicates the degree of relative compression deformation in the height direction during rolling.

[0066] In this invention, the reduction rate is the percentage (%) of the reduction amount Δh to the height H of the workpiece before rolling, i.e., Δh / H×100%.

[0067] Furthermore, in step S3, the number of rolling passes in a single cold rolling operation is 5 to 6.

[0068] Furthermore, in step S4, the first annealing adopts a rapid heating process with a heating rate of not less than 50℃ / s, and after heating to 820~950℃, it is held for 30~250s.

[0069] Step S4. The first annealing process uses a rapid heating process to ensure rapid grain growth. The faster heating rate enables the initial nucleation of favorable textures, which in turn increases the proportion of favorable textures.

[0070] Furthermore, in step S4, H2 and N2 are used as a protective atmosphere during the first annealing.

[0071] Furthermore, in the protective atmosphere, the H2 volume content is ≥45%, and the higher H2 volume content inhibits the formation of the inner oxide layer.

[0072] The aforementioned internal oxidation refers to the process by which oxygen diffuses into the interior of the alloy, selectively oxidizing it in the subsurface layer to form internal oxides.

[0073] Furthermore, in step S4, the dew point temperature is controlled to be -40 to -10°C during the first annealing process.

[0074] Furthermore, in step S5, the reduction rate is controlled to be 9-25% during the secondary cold rolling.

[0075] Furthermore, the thickness of the steel obtained by the second cold rolling is 0.25 mm.

[0076] The reduction rate affects the grain texture of steel. Different reduction rates will produce different texture evolutions. According to the performance requirements of non-oriented silicon steel products, the reduction rate needs to be reasonably controlled. An excessive reduction rate may increase the risk of strip breakage during cold rolling. In addition, it is necessary to coordinate with the parameter adjustment of the subsequent annealing process to obtain non-oriented silicon steel products with the required performance.

[0077] Furthermore, in step S5, the secondary cold rolling process consists of one rolling pass.

[0078] Furthermore, in step S5, the surface roughness Ra of the final roll in the secondary cold rolling process is ≤0.1μm.

[0079] Furthermore, step S6. Secondary annealing includes heating, holding, and cooling processes.

[0080] Furthermore, in step S6. Secondary annealing, the first and third heating stages use a protective atmosphere of H2 and N2 in a volume ratio of 4:6.

[0081] Furthermore, since the second stage of heating is a key step in crystal nucleation, in order to further reduce the possibility of oxide layer formation in the steel, in step S6. Secondary annealing, the H2 volume content during the second stage of heating is ≥45%.

[0082] Furthermore, after the holding process of the secondary annealing in step S6 is completed, the temperature is cooled to below 500°C at a cooling rate of less than or equal to 5°C / s.

[0083] Furthermore, the steel cooled after the second annealing in step S6 is coated with an insulating coating using a coating roller.

[0084] Furthermore, after applying the insulating coating, the coating is cured at a temperature of 500–600°C. For example, the insulating coating can be cured at temperatures of 500°C, 530°C, 550°C, 580°C, and 600°C.

[0085] Furthermore, the manufacturing method of non-oriented silicon steel includes the following steps in sequence:

[0086] Pretreatment; converter smelting; S1. continuous casting; S2. hot rolling; normalizing; coiling; pickling; S3. primary cold rolling; S4. primary annealing; S5. secondary cold rolling; S6. secondary annealing; applying insulating coating;

[0087] In particular, the heating process for step S6, the secondary annealing, adopts a segmented heating process, and the specific steps are as follows:

[0088] First stage: Raise the furnace temperature from room temperature to 400-600℃, with a heating rate of less than 20℃ / s;

[0089] Second stage: Raise the furnace temperature from 400-600℃ to the target temperature t1 at a rate of not less than 50℃ / s;

[0090] The third stage: raise the furnace temperature from t1 to the target temperature of 900-1020℃, and then hold it for 20-500 seconds.

[0091] Among them, t1 ranges from 870 to 920℃;

[0092] Step S3. Control the reduction rate to 80%–90% during the first cold rolling process;

[0093] Step S5. Control the reduction rate to 9-25% during the second cold rolling.

[0094] 3. Beneficial effects

[0095] The beneficial effects of this invention are as follows:

[0096] A thickness of 0.25mm, P is provided. 1.0 / 400 ≤12.0W / kg, P 1.0 / 1000 ≤45.0W / kg, B 5000 Non-oriented silicon steel with a weight of ≥1.65T and its manufacturing method.

[0097] More specifically:

[0098] This invention employs a double cold rolling and double continuous annealing process. While using an optimized continuous annealing process, the roll roughness of the final cold rolling pass is controlled to ensure the formation of the fiber texture. This results in a lower iron loss (P) in the non-oriented silicon steel compared to conventional processes. 1.0 / 400 Reduce by approximately 1.00 W / kg to achieve P 1.0 / 400 ≤12.0W / kg, and ensure B 5000 ≥1.65T. Furthermore, the non-oriented silicon steel of this invention exhibits lower iron loss (P) compared to conventional processes. 1.0 / 1000 Reduced by approximately 3.00 W / kg, P 1.0 / 1000 ≤45.0W / kg.

[0099] In this invention, controlling the annealing atmosphere and optimizing the annealing process effectively ensures that non-oriented silicon steel fully recrystallizes during annealing, thereby improving the favorable texture components and the oxide layer structure of the non-oriented silicon steel.

[0100] This invention optimizes the cold rolling process, including the reduction ratio distribution and intermediate annealing temperature, and improves the favorable texture composition to achieve the technical effect of reducing iron loss in medium and high frequencies. Detailed Implementation

[0101] Embodiments of the present invention will now be described in more detail. However, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0102] It should also be noted that, where there is no conflict, the features in the embodiments of this invention can be combined with each other. The invention will now be described in detail with reference to embodiments. Specific Implementation

[0104] Example 1

[0105] This embodiment provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by the method. The specific steps are as follows:

[0106] 1) RH refining: The molten iron that has undergone pretreatment and converter smelting is added to the RH furnace for refining and alloying under vacuum conditions, and each alloying element is added according to the composition design requirements.

[0107] 2) Continuous casting: The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 200 mm. The chemical composition of the slabs by weight percentage is C+S+N+Ti: 55 ppm, and the content of each element is ≤20 ppm; Si: 3.40%; Als: 0.65%; Mn: 0.60%; P: 0.01%; the remainder is Fe and unavoidable impurity elements.

[0108] 3) Hot rolling: The slab after continuous casting is heated in a heating furnace at 1180℃ and held for 210 minutes. Then it is rough rolled to a thickness of 34mm in 3 passes and finish rolled to a thickness of 2.0mm in 7 passes. After air cooling, the temperature is reduced to 580℃ and then coiled.

[0109] 4) Normalizing and pickling: The steel is normalized at 900℃ and then pickled with 58% hydrochloric acid at 80℃.

[0110] 5) Single cold rolling: cold rolling to the target thickness of 0.28 mm in 5 passes, with the total cold rolling reduction rate controlled at 86%;

[0111] 6) Single annealing: A rapid heating process is adopted, with a heating rate of 60℃ / s. The temperature is raised to 900℃ and held for 30s. H2 and N2 are used for protection during production, and the H2 volume content is 45%. The dew point in the furnace is controlled at -10℃.

[0112] 7) Secondary cold rolling: The 0.30mm steel is cold rolled again, and rolled in one pass to the target thickness of 0.25mm; the reduction rate is controlled at 10.7%, and then a second annealing is performed;

[0113] 8) Secondary annealing: includes heating, holding and cooling processes.

[0114] First, heating is performed using a segmented heating process, ultimately reaching the target temperature of 920℃. Then, the temperature is held for 30 seconds, followed by a cooling rate of 5℃ / s to below 500℃. The dew point inside the furnace is controlled at -10℃.

[0115] Specifically, the heating process during the secondary annealing is as follows:

[0116] First section: The furnace temperature is raised from room temperature to 400℃ at a rate of 20℃ / s, and the protective atmosphere is H2 and N2 in a volume ratio of 4:6.

[0117] The second section: The temperature of the heating furnace is raised from 400℃ to the target temperature t1, which is 870℃, at a heating rate of 50℃ / s, with H2 volume content of 45% and N2 volume content of 55%.

[0118] The third step: The furnace temperature is raised from t1 to the target temperature of 900℃, and then held for 30 seconds. The protective atmosphere is a mixture of H2 and N2 with a volume ratio of 4:6.

[0119] 9) Insulating coating application: The insulating coating is applied by a coating roller and cured at a temperature of 580℃.

[0120] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 11.82 W / kg, P 1.0 / 1000 It is 44.23 W / kg, magnetic induction B 5000 It is 1.659T.

[0121] Example 2

[0122] This embodiment provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by this method, which is basically the same as in Embodiment 1, except that the heating process in the secondary annealing process is as follows:

[0123] First section: The furnace temperature is raised from room temperature to 500℃ at a rate of 20℃ / s, and a protective atmosphere is prepared with H2 and N2 in a volume ratio of 4:6.

[0124] The second section: The furnace temperature is raised from 500℃ to the target temperature t1, which is 900℃, at a heating rate of 50℃ / s, with H2 volume content of 45% and N2 volume content of 55%.

[0125] The third step: The furnace temperature is raised from t1 to the target temperature of 1020℃, and then held for 30 seconds. The protective atmosphere is a mixture of H2 and N2 with a volume ratio of 4:6.

[0126] Everything else is the same as in Example 1.

[0127] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 11.72 W / kg, P 1.0 / 1000 It is 42.25W / kg, magnetic induction B 5000 It is 1.655T.

[0128] Example 3

[0129] This embodiment provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by this method, which is basically the same as in Embodiment 1, except that the heating process in the secondary annealing process is as follows:

[0130] First section: The furnace temperature is raised from room temperature to 600℃ at a rate of 20℃ / s, and a protective atmosphere is prepared with H2 and N2 in a volume ratio of 4:6.

[0131] The second stage: The furnace temperature is raised from 600℃ to the target temperature t1, which is 920℃, with the heating rate controlled at 50℃ / s, the H2 volume content is 45%, and the N2 volume content is 55%.

[0132] The third step: The furnace temperature is increased from t1 to the target temperature of 980℃, and then held for 30 seconds. The protective atmosphere is a mixture of H2 and N2 with a volume ratio of 4:6.

[0133] Everything else is the same as in Example 1.

[0134] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 11.92 W / kg, P 1.0 / 1000 It is 44.68W / kg, magnetic induction B 5000 It is 1.660T.

[0135] Comparative Example 1

[0136] This comparative example provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by this method. The specific steps are as follows:

[0137] 1) RH refining: The molten iron that has undergone pretreatment and converter smelting is added to the RH furnace for refining and alloying under vacuum conditions, and various alloying elements are added according to the composition design requirements.

[0138] 2) Continuous casting: The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 200 mm. The chemical composition of the slabs by weight percentage is Si: 3.40%; Als: 0.65%; Mn: 0.60%; P: 0.01%; C+S+N+Ti: 55 ppm, and the content of each element is ≤20 ppm, with the remainder being Fe and unavoidable impurity elements.

[0139] 3) Hot rolling: The slab after continuous casting is heated in a heating furnace at 1180℃ and held for 210 minutes. Then it is rough rolled to a thickness of 34mm in 3 passes and finish rolled to a thickness of 2.0mm in 7 passes. After air cooling, the temperature is reduced to 580℃ and then coiled.

[0140] 4) Normalizing and pickling: The steel is normalized at 900℃ and then pickled with 58% hydrochloric acid at 80℃.

[0141] 5) Cold rolling: The material is cold rolled in 6 passes to the target thickness of 0.25 mm, and the total cold rolling reduction rate is controlled at 87.5%.

[0142] 8. Annealing: The heating process adopts a rapid heating process with a heating rate of 60℃ / s, and finally heats to 920℃. The holding time is 30s. H2 and N2 are used as protective atmosphere in a volume ratio of 4:6.

[0143] 6) Insulating coating application: The insulating coating is applied by a coating roller and cured at a temperature of 580℃.

[0144] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 12.62 W / kg, P 1.0 / 1000 It is 49.63 W / kg, magnetic induction B 5000 It is 1.658T.

[0145] Comparative Example 2

[0146] This comparative example provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by the method, which is basically the same as Example 1, except that in the heating process of the secondary annealing, the temperature is directly raised to the target temperature of 920°C at a heating rate of 20°C / s, without segmented heating.

[0147] Everything else is the same as in Example 1.

[0148] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 12.73 W / kg, P 1.0 / 1000 It is 47.23 W / kg, magnetic induction B 5000 It is 1.661T.

[0149] Comparative Example 3

[0150] This comparative example provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by the method, which is basically the same as Example 1, except that the reduction rate of the first cold rolling and the second cold rolling are controlled at 50% and 75%, respectively.

[0151] Everything else is the same as in Example 1.

[0152] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 12.81 W / kg, P 1.0 / 1000 It is 49.25W / kg, magnetic induction B 5000 It is 1.658T.

[0153] Comparative Example 4

[0154] This comparative example provides a method for manufacturing non-oriented silicon steel and the non-oriented silicon steel obtained by the method, which is basically the same as Example 1, except that the chemical composition of the slab by weight percentage is Si: 3.40%; Als: 0.65%; Mn: 0.60%; P: 0.01%; C+S+N+Ti: 100ppm (greater than 55ppm), and the content of each element is 25ppm (greater than 20ppm), with the remainder being Fe and unavoidable impurity elements.

[0155] Everything else is the same as in Example 1.

[0156] The non-oriented silicon steel manufactured using the above process has excellent surface quality and high P content in the finished product. 1.0 / 400 It is 13.21 W / kg, P 1.0 / 1000 It is 521.23 W / kg, magnetic induction B 5000 It is 1.655T.

[0157] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or its application areas.

[0158] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

Claims

1. A method for manufacturing non-oriented silicon steel, characterized in that, Includes the following steps: S1. Continuous casting; S2. Hot-rolled; S3. Cold rolling in one step; S4. Single annealing; S5. Secondary cold rolling; S6. Secondary annealing; The heating process for the secondary annealing in step S6 adopts a segmented heating process, and the specific steps are as follows: First step: Raise the furnace temperature from room temperature to 400~600℃, with a heating rate of less than 20℃ / s; Second stage: Raise the furnace temperature from 400~600℃ to the target temperature t1 at a rate of not less than 50℃ / s; The third stage: raise the furnace temperature from t1 to the target temperature of 900~1020℃, and then keep it warm for 20~500s; Wherein, t1 is in the range of 870~920℃; The non-oriented silicon steel comprises the following chemical composition by weight percentage: C≤0.0020%； S≤0.0020%； N≤0.0020%； Ti≤0.0020%; 0.20≤Si≤3.50; 0.30≤Als≤1.00%; 0.10≤Mn≤0.70%; P≤0.1%； 0.01≤Sn≤0.12%; The balance consists of Fe and unavoidable impurities.

2. The method for manufacturing non-oriented silicon steel according to claim 1, characterized in that, in, In step S2, during hot rolling, the steel is heated in a heating furnace at a temperature of 1100~1200℃ and held for ≥210min; the final rolling temperature in step S2 is 830~850℃.

3. The method for manufacturing non-oriented silicon steel according to claim 1, characterized in that, After hot rolling in step S2 and before cold rolling in step S3, the steel obtained by hot rolling in step S2 is pickled.

4. The method for manufacturing non-oriented silicon steel according to claim 1, characterized in that, In step S3, the reduction rate is controlled to be 80%~90% during the first cold rolling.

5. The method for manufacturing non-oriented silicon steel according to claim 1, characterized in that, Step S4. The first annealing adopts a rapid heating process with a heating rate of not less than 50℃ / s, and is held at 820~950℃ for 30~250s.

6. The method for manufacturing non-oriented silicon steel according to claim 1, characterized in that, In step S5, the reduction rate is controlled to be 9-25% during the secondary cold rolling.

7. The method for manufacturing non-oriented silicon steel according to claim 1, characterized in that, In step S5, the roughness of the final roll of the secondary cold rolling process is Ra≤0.1μm.

8. The method for manufacturing non-oriented silicon steel according to claim 7, characterized in that, The steps are as follows: Pretreatment; converter smelting; S1. continuous casting; S2. hot rolling; normalizing; coiling; pickling; S3. primary cold rolling; S4. primary annealing; S5. secondary cold rolling; S6. secondary annealing; applying insulating coating; The heating process for the secondary annealing in step S6 adopts a segmented heating process, and the specific steps are as follows: First step: Raise the furnace temperature from room temperature to 400~600℃, with a heating rate of less than 20℃ / s; Second stage: Raise the furnace temperature from 400~600℃ to the target temperature t1 at a rate of not less than 50℃ / s; The third stage: raise the furnace temperature from t1 to the target temperature of 900~1020℃, and then keep it warm for 20~500s; Wherein, t1 is in the range of 870~920℃; In step S3, the reduction rate is controlled to be 80%~90% during the first cold rolling process; In step S5, the reduction rate is controlled to be 9-25% during the secondary cold rolling.

9. The method for manufacturing non-oriented silicon steel according to any one of claims 1 to 8, characterized in that, The weight percentage of S is less than or equal to 0.001%; ​​the weight percentage of N is less than or equal to 0.0015%; and the weight percentage of Ti is less than or equal to 0.0015%.