Non-oriented electrical steel sheet with good magnetic properties and method for manufacturing the same

Abstract

In the present invention, a non-oriented electrical steel sheet having good magnetic properties is disclosed. The non-oriented electrical steel sheet contains Fe and inevitable impurities, and further contains the following chemical elements by mass percentage: 0 < C ≤ 0.0015%, Si: 0.2 - 1.8%, Mn: 0.2 - 0.4%, Al: 0.2 - 0.6%, V: 0.002 - 0.005%, and N < 0.002%. Further, in the present invention, a manufacturing method for the non-oriented electrical steel sheet having good magnetic properties is disclosed. The manufacturing method includes the following steps: (1) a step of smelting and casting; (2) a step of hot rolling, wherein the steel coil obtained after hot rolling is not subjected to full annealing or coated annealing and directly enters the next step; (3) a step of pickling; (4) a step of cold rolling; and (5) a step of continuous annealing, wherein the steel sheet is rapidly heated to a target soaking temperature at a heating rate of 50 - 5000 °C / s after cold rolling.

Description

[Technical Field]

[0001] Technical field The present invention relates to steel sheets and methods for manufacturing the same, and more particularly to non-oriented electrical steel sheets and methods for manufacturing the same. [Background technology]

[0002] background In the prior art, non-oriented electrical steel sheets are commonly used to manufacture stators and rotors for iron cores used in motors, generators, compressors, and high-speed motors, drive motors, and other products.

[0003] However, in recent years, as the demand for high efficiency, energy saving, and consumption reduction has increased in the user market, existing non-oriented electrical steel sheets have gradually become unable to meet market demands; therefore, in order to satisfy the new technological demands of the market for non-oriented electrical steel sheets, it is urgent to develop non-oriented electrical steel sheets with higher magnetic induction and lower iron loss.

[0004] To achieve the best possible electromagnetic performance for non-oriented electrical steel sheets, some researchers have conducted numerous studies and achieved certain research results, but the results for practical applications have not been very satisfactory.

[0005] For example, Chinese patent application publication CN103014503A, published on April 3, 2013, entitled "Acid-resistant, non-oriented silicon steel with high magnetic induction and low iron loss without normalizing, and method for manufacturing the same," points out that by adding 0.20%-0.45% Sn+Cu to steel, the microstructure of the final strip steel can be improved due to grain boundary segregation, resulting in good magnetic induction performance. However, since Sn and Cu are precious metals, this significantly increases the manufacturing cost of the steel, and Cu tends to cause associated quality defects on the surface of the strip steel. Therefore, in practical application processes, the technical solution of this patent application has strict requirements for the manufacturing process, and the resulting product has relatively low cost performance.

[0006] As another example, Japanese Patent Application Publication No. 10-183227 and Japanese Patent Application Publication No. 2004-169141 point out that by adding appropriate amounts of rare earth elements and calcium alloys to the steel, inclusions in the steel can be removed by strong deoxidation and desulfurization of the molten steel, and the cleanliness of the steel can be improved, as a result the electromagnetic performance of the final strip steel can be efficiently and favorably improved. Furthermore, the above Japanese patent documents also point out that by reducing harmful elements C, S, O, N, Nb, V, and Ti in the steel, and at the same time combining high tapping temperature, high final rolling temperature, and high coil winding temperature in the hot rolling process, a hot-rolled steel sheet with coarse particles can be obtained, which is beneficial for roughening inclusions and therefore plays a good role in promoting the improvement of the magnetic performance of the final strip steel. However, the disadvantages of such technical solutions are that the significant increase in preheating temperature and the shift in the phase transition point result in high energy consumption during hot rolling, poor stability in the finish rolling process, and the high coil winding temperature easily cause red scale defects.

[0007] In view of the above, the inventors designed and intended to obtain a novel non-oriented electrical steel sheet having good magnetic performance, with the aim of improving the electromagnetic performance of electrical steel, reducing iron loss, and improving magnetic induction.

Summary of the Invention

Means for Solving the Problems

[0008] Gist of the Invention One object of the present invention is to provide a non-oriented electromagnetic steel sheet having good magnetic properties, which aims to improve the electromagnetic properties of the non-oriented electromagnetic steel sheet, reduce iron loss, and improve magnetic induction.

[0009] To achieve the above object, the present invention provides a non-oriented electromagnetic steel sheet having good magnetic properties, which contains Fe and inevitable impurities, and the following chemical elements in mass percentage: 0 < C ≤ 0.0015%, Si: 0.2 - 1.8%, Mn: 0.2 - 0.4%, Al: 0.2 - 0.6%, V: 0.002 - 0.005%, and N < 0.002% further includes.

[0010] Preferably, the non-oriented electromagnetic steel sheet according to the present invention has the following chemical elements in mass percentage: 0 < C ≤ 0.0015%, Si: 0.2 - 1.8%, Mn: 0.2 - 0.4%, Al: 0.2 - 0.6%, V: 0.002 - 0.005%, and N < 0.002%; and the balance is Fe and inevitable impurities contains.

[0011] The chemical elements for the non-oriented electromagnetic steel sheet according to the present invention are designed based on the following principles.

[0012] C: In the non-oriented electromagnetic steel sheet according to the present invention, the content of C in the steel should not be too high. When the content of C in the steel of the steel sheet of the present invention is higher than 0.0015%, C preferentially combines with Nb and Ti to form inclusions having a fine size, which causes an increase in iron loss. In view of this, in order to fully exert the beneficial effects of C, in the non-oriented electromagnetic steel sheet according to the present invention, the mass percentage content of C is controlled to be 0 < C ≤ 0.0015%.

[0013] Si: In this invention, Si is added to the non-oriented electrical steel sheet in a moderate to low content. If the Si content is higher than 1.8%, it not only increases the manufacturing cost of the steel sheet but also significantly degrades the magnetic induction of the steel; if the Si content is lower than 0.2%, the effect of effectively reducing iron loss cannot be achieved. In view of this, in the non-oriented electrical steel sheet according to the present invention, the mass percentage content of Si is controlled to be between 0.2% and 1.8%.

[0014] Mn: In the non-oriented electrical steel sheet according to the present invention, an appropriate amount of Mn is added together with S to form MnS, which is beneficial for controlling the shape and number of inclusions and can effectively reduce harm to magnetic performance; therefore, it is necessary to add 0.2% or more of Mn; on the other hand, if the content of added Mn is higher than 0.4%, the recrystallized structure deteriorates and the magnetic induction of the steel sheet decreases. In view of the above, and taking into account the beneficial and unfavorable effects of Mn, the mass percentage content of Mn in the non-oriented electrical steel sheet according to the present invention is 0.2-0.4%.

[0015] Al: In the non-oriented electrical steel sheet according to the present invention, if the Al content added to the steel for the steel sheet according to the present invention is higher than 0.6%, the performance of the steel sheet deteriorates significantly; on the other hand, if the Al content added to the steel sheet is lower than 0.2%, the good effect of reducing iron loss cannot be achieved. In view of this, in the non-oriented electrical steel sheet according to the present invention, the mass percentage content of Al is controlled to be between 0.2% and 0.6%.

[0016] V: In the prior art, V is usually regarded as a harmful element in non-oriented electrical steel sheets, and the lower the content of V, the better. However, in the non-oriented electrical steel sheet according to the present invention, V is used as an important beneficial element. Different from reducing the content of V as much as possible and reducing the content of harmful inclusions as much as possible in the prior art, in the present invention, an appropriate amount of V is intentionally added, and in combination with the adjustment of the manufacturing process and the control of the type and number of N-containing inclusions, the harmless treatment of Nb, V and Ti is maximally realized. In this way, the compatibility and combination of a reasonable prerequisite for controlling the chemical composition beneficial to obtaining good magnetic performance and the type of inclusions are realized.

[0017] In the technical solution according to the present invention, when the content of V in the steel is lower than 0.002%, the good effect of fixing C and N cannot be achieved, and the inclusions of V are diverse in size and small; on the other hand, when the content of V in the steel is too high and exceeds 0.005%, the number of inclusions formed by V together with C and N greatly increases, which strongly hinders particle growth and deteriorates the magnetic performance of the steel. Therefore, in order to exert the beneficial effect of V, in the non-oriented electrical steel sheet according to the present invention, the mass percentage content of V is controlled to be between 0.002% and 0.005%.

[0018] N: In the non-oriented electrical steel sheet according to the present invention, as a harmful impurity element, the content of N should not be too high. When the content of N in the steel exceeds 0.002%, the number of inclusions formed by N together with Nb, V, Ti, Al and other elements greatly increases, which strongly hinders particle growth and deteriorates the magnetic performance of the steel. In view of this, in the non-oriented electrical steel sheet according to the present invention, the mass percentage content of N is controlled to satisfy N < 0.002%.

[0019] Preferably, in the non-oriented electrical steel sheet according to the present invention, among the inevitable impurities, Nb ≤ 0.002% and Ti ≤ 0.002%.

[0020] In the above technical solution of the present invention, both Nb and Ti are inevitable impurity elements in steel, and the content of impurity elements in steel should be controlled as low as possible if technical conditions permit.

[0021] Nb: In the non-oriented electrical steel sheet according to the present invention, when the content of Nb is higher than 0.002%, the NbN inclusions in the steel increase abnormally, thereby causing a sharp increase in the iron loss of the finished steel sheet. Therefore, in the present invention, the impurity element Nb needs to be strictly controlled to satisfy Nb≤0.002%.

[0022] Ti: In the non-oriented electrical steel sheet according to the present invention, when the content of Ti is higher than 0.002%, the TiN inclusions in the steel increase abnormally, thereby causing a sharp increase in the iron loss of the finished steel sheet. Therefore, in the present invention, the impurity element Ti needs to be strictly controlled to satisfy Ti≤0.002%.

[0023] Preferably, the non-oriented electrical steel sheet according to the present invention contains N-containing inclusions as the main inclusions, and the N-containing inclusions include individual VN and AlN and / or composite VN, AlN, NbN and TiN.

[0024] Compared with "composite", the term "individual" refers to a state where different inclusions are not doped with each other.

[0025] Preferably, in the non-oriented electrical steel sheet according to the present invention, the N-containing inclusions have a size of 200-500 nm.

[0026] Preferably, in the non-oriented electrical steel sheet according to the present invention, the volume fraction ratio of VN to the N-containing inclusions is ≥0.85.

[0027] In the present invention, the content of the beneficial element V is controlled to be between 0.002% and 0.005% in order to form VN inclusions having a relatively large size as much as possible instead of minute NbN and TiN inclusions. In order to avoid the formation of C-containing inclusions such as minute NbN, TiN, Nb, V, Ti, etc., in the present invention, the content of C is strictly limited to 0 < C ≤ 0.0015%, and in the actual production process, the content of C can be more preferably controlled to 0 < C ≤ 0.0010% from the viewpoint of manufacturing difficulty. Under the conditions of the above chemical elements and when the content of Al in the steel is 0.2 - 0.6%, N-containing inclusions become the main factor limiting the magnetic performance of the finished steel sheet.

[0028] Therefore, in the present invention, it is preferably limited such that the volume fraction ratio of VN to N-containing inclusions in the steel is ≥ 0.85, and it is necessary to reduce the generation of non-VN type inclusions. The main principle of the adjustment in this specification is to adjust the content of V in the steel, thereby adjusting the ratio of VN inclusions in all N-containing inclusions in the steel. Furthermore, due to the high content of Al in the steel, which is between 0.2% and 0.6%, a large number of AlN inclusions can be formed in the steel. After collision, combination and floating, AlN inclusions having a relatively small size can remain in the steel and can combine with VN inclusions, thus increasing the size of the composite inclusions and reducing the harm caused by them.

[0029] Therefore, when the number of VN inclusions formed in the steel is too small, the composite effect with AlN inclusions cannot be achieved. In this case, the AlN inclusions are small in size and cannot be removed by floating and remain in the steel; when the number of VN inclusions is too large, in addition to the composite with AlN inclusions, individual AlN remains in the steel, and the harm caused by VN inclusions increases with the increase in the number of VN inclusions.

[0030] Preferably, in the non-oriented electrical steel sheet according to the present invention, the iron loss P 15 / 50 is ≤ 4.2 W / kg, and the magnetic induction B 50 is ≥ 1.73 T.

[0031] Therefore, another object of the present invention is to provide a method for producing non-oriented electrical steel sheets having the above-mentioned good magnetic performance, which is simple and feasible. By this method, non-oriented electrical steel sheets having good magnetic performance can be obtained, where the steel sheet has an iron loss P of ≤4.2 W / kg. 15 / 50 and magnetic induction B ≥ 1.73T 50 It has.

[0032] To achieve the above objective, the present invention provides a method for manufacturing non-oriented electrical steel sheets having good magnetic performance, comprising the following steps: (1) The process of smelting and casting; (2) Hot rolling process, in which the steel coil obtained after hot rolling is introduced directly to the next process without being subjected to normalizing annealing or cover annealing; (3) The process of pickling to obtain pickled steel sheets; (4) A process of cold rolling to obtain a cold-rolled steel sheet; and (5) Continuous annealing process, in which the cold-rolled steel sheet is rapidly heated to the target immersion temperature at a heating rate of 50-5000°C / s.

[0033] In this invention, the inventors optimize the design of the chemical composition of the steel and define a rational manufacturing process. Continuously cast slabs obtained after smelting and casting do not require normalizing annealing or coating annealing after hot rolling; the slabs can be subjected directly to pickling and cold rolling, and then continuously annealed in an electromagnetic induction device with rapid heating capabilities, thereby obtaining the electromagnetic performance required by the design of this invention. In this invention, there are no special requirements for hot rolling, pickling, and cold rolling, provided that the manufacturing costs and technical difficulties of the steel are not increased.

[0034] While there are several technical solutions in the prior art that do not require normalizing annealing or coating annealing, the steels prepared by these solutions are mostly high-silicon steels, and these steels have a high Si content; however, unlike the prior art described above, the Si content in the steel of the present invention is only 0.2-1.8%, which is a medium-to-low silicon steel, and it should be noted that normalizing annealing or coating annealing is not required when medium-to-low silicon steel is used.

[0035] In the steelmaking process of the present invention, strict control is required when designing the chemical composition of the steel, and the content of V in the steel should be particularly controlled. After smelting and casting, a steel ingot can be obtained; after hot rolling, the steel ingot does not require normalizing annealing or coating annealing; and after pickling and rust removal treatment, the pickled steel sheet can be cold-rolled to a target cold-rolled thickness in one step, and can be continuously annealed in an electromagnetic induction device with a rapid heating function, and the annealing atmosphere can be controlled to be a mixed gas of H2 and N2.

[0036] In step (5) of the manufacturing method according to the present invention, the electromagnetic induction device having a rapid heating function is not limited to longitudinal or transverse magnetic fields, but its heating capacity must satisfy the requirement of rapidly heating the cold-rolled steel sheet to the target immersion temperature during continuous annealing. The target immersion temperature can typically be 500-1100°C, and the heating start temperature can be a temperature lower than the immersion temperature, such as room temperature. The heating rate of the cold-rolled steel sheet in the present invention is controlled to be 50-5000°C / s, which is about 1-30°C / s higher than the heating rate of conventional continuous annealing equipment. However, in some embodiments, the heating rate can be controlled to be 80-550°C / s according to the production and actual quality requirements of the finished steel sheet.

[0037] Compared to conventional annealing methods using gas and / or electric heating, and slow heating (usually lower than 30°C / s), the present invention employs an electromagnetic induction device with a rapid heating function for continuous annealing, thereby achieving rapid heating of cold-rolled steel sheets to a specified target immersion temperature in a short time. The purpose of using rapid heating is to effectively suppress the recovery of the cold-rolled steel sheet during continuous annealing, and as a result, the residual deformation energy storage of the cold-rolled steel sheet can increase significantly before recrystallization, which can lead to the accumulation and increase of propulsion for nucleation, and can promote nucleation and migration of large-angle grain boundaries. At the same time, the preferred orientation of crystal nuclei is also reduced, and ultimately <111> / / ND recrystallization structure component strength may decrease. Therefore, by the continuous annealing method, steel can be obtained with higher magnetic induction and lower iron loss.

[0038] It should be noted that during rapid heating and continuous annealing of cold-rolled steel sheets, it is also necessary to appropriately limit the heating rate of rapid heating annealing to between 50°C / s and 5000°C / s in order to further increase the driving force for nucleation and growth, to improve and control the final recrystallization effect, and to ensure a low percentage of coarse grain structure and undesirable grain orientation after continuous annealing. If the heating rate of rapid heating is too low, and the heating rate is lower than 50°C / s, the energy storage of the cold-rolling deformation is released too quickly, which does not contribute to the subsequent desirable microstructure control; if the rapid heating rate is too high, and the heating rate is higher than 5000°C / s, the demands on equipment capacity are too high and the cost is high, which causes the cold-rolled strip to remain on the high-temperature stage for too long and results in poor grain structure uniformity.

[0039] Preferably, in the manufacturing method according to the present invention, the target immersion temperature in step (5) is 500-1100°C.

[0040] Preferably, in the manufacturing method according to the present invention, in step (5), the cold-rolled steel sheet is rapidly heated to the target immersion temperature at a heating rate of 80-550°C / s.

[0041] Preferably, in the manufacturing method according to the present invention, in step (2), the time the cast slab remains in the furnace during hot rolling is controlled to 120-360 minutes, the initial rolling temperature is controlled to 1000-1250°C, the final rolling temperature is controlled to 650-1000°C, and the coil winding temperature is controlled to 550-950°C.

[0042] Preferably, in the manufacturing method according to the present invention, in step (2), the target thickness of the hot-rolled steel sheet is controlled to be 0.8-3.5 mm; and in step (4), the pickled steel sheet is cold-rolled to the target cold-rolled thickness in one step.

[0043] Compared to conventional technology, the non-oriented electrical steel sheet with superior magnetic performance and its manufacturing method according to the present invention have the following advantages and beneficial effects: Unlike conventional technologies, in the steelmaking process of the present invention, V is used as a beneficial element, and the V content is intentionally controlled.

[0044] In the non-oriented electrical steel sheet according to the present invention, the inventors have optimized the chemical element composition ratio so that the continuously cast slab obtained after smelting and casting does not require normalizing annealing or coating annealing, and can be rapidly heated after direct pickling and cold rolling, ensuring that the cold-rolled steel sheet is rapidly heated to the target immersion temperature at a relatively high heating rate, and as a result the electromagnetic performance requirements designed in the present invention can be obtained.

[0045] The chemical element design concept of the present invention is completely different from the prior art, and the manufacturing method is simple and feasible; and the non-oriented electrical steel sheet manufactured in this way has the characteristics of high magnetic induction and low iron loss, and iron loss P 15 / 50 It is ≤ 4.2 W / kg, and magnetic induction B 50 The value is ≥ 1.73T. [Brief explanation of the drawing]

[0046] [Figure 1]Figure 1 schematically shows the relationship between the volume fraction ratio of vanadium nitride (VN) to N-containing inclusions in the steel and the iron loss P15 / 50 of the finished steel sheet in the non-oriented electrical steel sheet according to the present invention. [Figure 2] Figure 2 schematically shows the relationship between the heating rate of rapid heating in the non-oriented electrical steel sheet according to the present invention and the magnetic induction B50 of the finished steel sheet. [Figure 3] Figure 3 is a photograph of the microstructure of the completed non-oriented electrical steel sheet of Example 3. [Figure 4] Figure 4 is a photograph of the microstructure of the comparative steel in Comparative Example 2. [Modes for carrying out the invention]

[0047] Detailed explanation The non-oriented electrical steel sheet having good magnetic performance according to the present invention and the method for manufacturing the same will be further described and illustrated with reference to the accompanying drawings and specific examples. However, the description and illustration should not be construed as constituting an undue limitation to the technical solutions of the present invention.

[0048] Examples 1-6 and Comparative Examples 1-3 Table 1 shows the mass percentages of chemical elements in the non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-3.

[0049] [Table 1]

[0050] The non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-3 were all prepared by the following process: (1) A process for smelting and casting steel materials having the chemical composition shown in Table 1, in which the steelmaking process prioritizes achieving the designed objective of decarburization, followed by deoxidation and alloying, and then adjusting the V content to the target range according to the C, N, Nb and Ti content in the steel to obtain molten steel that satisfies the chemical composition design requirements, and then casting the molten steel into steel ingots of a specified size.

[0051] (2) Hot rolling process: During the hot rolling, the time for the slab obtained by casting the ingot is controlled to 120-360 minutes, the initial rolling temperature is controlled to 1000-1250°C, the final rolling temperature is controlled to 650-1000°C, the coil winding temperature is controlled to 550-950°C, and the hot rolling is performed in 2-8 passes, and the target thickness of the hot-rolled steel sheet is controlled to 0.8-3.5 mm, and the steel coil obtained after hot rolling is not subjected to normalizing annealing or coating annealing, but is directly introduced to the next process.

[0052] (3) A process of pickling to obtain pickled steel sheets.

[0053] (4) Cold rolling of the pickled steel sheet: Here, the pickled steel sheet is subjected to cold rolling to a target cold rolling thickness of 0.50 mm in one step.

[0054] (5) Continuous annealing step, in which the cold-rolled steel sheet is rapidly heated from room temperature to a target immersion temperature of 500-1100°C at a heating rate of 50-5000°C / s using a continuous annealing apparatus having an electromagnetic induction rapid heating device, and then immersed for a certain period, for example, 10-120 s; the heating rate may be controlled to be more preferably between 80°C / s and 550°C / s; during annealing, the annealing atmosphere may be controlled to be a mixed gas of H2 and N2.

[0055] It should be noted that in the present invention, the chemical compositions and associated process parameters in Examples 1-6 all satisfy the control requirements of the design specifications of the present invention. However, in Comparative Examples 1-3, at least one chemical composition or process parameter does not satisfy the design requirements of the present invention.

[0056] Table 2 shows the specific process parameters for the non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-3 in the above manufacturing process.

[0057] [Table 2]

[0058] Samples of the finished products of the non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-3 were taken respectively, and observed and analyzed. It was found that inclusions existed in the steels of the examples and the comparative examples, and the main inclusions were N-containing inclusions. Through further analysis and testing, the average sizes and specific compositions of the N-containing inclusions in the steels of the examples and the comparative examples were obtained, and the related observation and analysis results are described in Table 3 below.

[0059]

Table 3

[0060] After the observation and analysis of the above inclusions were completed, samples of the non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-3 were taken again, and the magnetic induction B 50 and iron loss P 15 / 50 of the steel sheets were tested, and the test results are described in Table 4 below.

[0061] The related performance test procedures are as follows.

[0062] Magnetic induction B 50 Test: According to the national standard GB / T 3655-2008, the iron loss performance test was carried out by the Epstein frame method. The test temperature was a constant temperature of 20 °C, the sample size was 30 mm × 300 mm, and the target mass was 0.5 kg. The magnetic induction B 50 of the steel sheets of the examples and the comparative examples was obtained by this test.

[0063] Iron loss P 15 / 50Testing: Iron loss performance tests were conducted using the Epstein frame method in accordance with national standard GB / T 3655-2008. The test temperature was a constant 20°C, the sample size was 30 mm × 300 mm, and the target mass was 0.5 kg. Iron loss P of the examples and comparative examples. 15 / 50 This was obtained through this test.

[0064] Magnetic induction B of non-oriented electrical steel sheets in Examples 1-6 and comparative steel sheets in Comparative Examples 1-3 50 and iron loss P 15 / 50 The test results are shown in Table 4.

[0065] [Table 4]

[0066] As shown in Table 4 above, in the present invention, the non-oriented electrical steel sheets of Examples 1-6 have a magnetic induction B in the range of 1.74-1.80 T. 50 and iron loss P within the range of 3.2-4.2 W / kg 15 / 50 These properties are all clearly superior to those of the comparative steel plates in Comparative Examples 1-3. Comparative Examples 1-3 do not satisfy the conditions specified in the technical solution of the present invention, and therefore the resulting technical effects are inferior to those of the present invention.

[0067] Figure 1 shows the volume fraction ratio of VN to N-containing inclusions in the steel and the iron loss P of the finished steel sheet in the non-oriented electrical steel sheet according to the present invention. 15 / 50 The relationship between them is shown diagrammatically.

[0068] As shown in Figure 1, during both conventional heating and rapid heating, an increase in the volume fraction ratio of VN to N-containing inclusions in the steel leads to an increase in the iron loss P of the finished steel sheet. 15 / 50 However, the iron loss P of the rapidly heated finished steel plate decreases. 15 / 50 The iron loss P decreases remarkably quickly, and when the volume fraction ratio of VN to N-containing inclusions in the steel reaches 85% or more, the iron loss P of the rapidly heated finished steel plate decreases. 15 / 50This can be lower than 4.2 W / kg, satisfying the design requirements of the present invention.

[0069] Figure 2 shows the heating rate of rapid heating in the non-oriented electrical steel sheet according to the present invention and the magnetic induction B of the finished steel sheet. 50 The relationship between them is shown diagrammatically.

[0070] As shown in Figure 2, when the heating rate of rapid heating in non-oriented electrical steel sheets increases, the magnetic induction of the finished non-oriented electrical steel sheet gradually increases and remains stable within the range of 50-5000°C / s, satisfying the control requirement of the present invention, which has a designed lower limit of 1.73T. After exceeding 5000°C / s, the magnetic induction of the finished non-oriented electrical steel sheet rapidly deteriorates, falling below the control lower limit of 1.73T, and failing to satisfy the control requirement for magnetic induction designed in the present invention.

[0071] Figure 3 is a photograph of the microstructure of the completed non-oriented electrical steel sheet of Example 3.

[0072] As shown in Figure 3, in the embodiment of Example 3, the microstructure of the non-oriented electrical steel sheet is completely recrystallized, and all of the recrystallized particles are relatively uniform equiaxed particles with a coarse and well-developed particle size.

[0073] Figure 4 is a photograph of the microstructure of the comparative steel in Comparative Example 2.

[0074] As shown in Figure 4, in the embodiment of Comparative Example 2, the microstructure of the comparative steel is completely recrystallized, but the proportion of equiaxed particles in the recrystallized particles is low, the size is fine, and the particle size distribution is relatively dispersed. Particles with larger particle sizes are abnormally grown "island particles."

[0075] It should be noted that the various combinations of features of the present invention are not limited to those described in the claims or embodiments, and that all features of the present invention can be freely combined or combined in any way, as long as they do not contradict each other.

[0076] It should also be noted that the above embodiments are merely specific embodiments of the present invention. The present invention is not limited to the above embodiments, and it is clear that those skilled in the art can make similar modifications, changes, or substitutions based on the disclosure of the present invention, all of which are within the scope of the claims.

Claims

1. The following chemical elements in mass percent: 0 < C ≤ 0.0010%, Si: 0.2-1.8%, Mn: 0.2-0.4%, Al: 0.2-0.6%, V: 0.002-0.005%, and N < 0.002%; and the remainder being Fe and unavoidable impurities. It consists of, It contains N-containing inclusions having a size of 200-500 nm, A non-oriented electrical steel sheet having a volume fraction ratio of VN to N-containing inclusions of ≥0.

85.

2. The non-oriented electrical steel sheet according to claim 1, wherein the unavoidable impurities satisfy Nb < 0.002% and Ti < 0.002%.

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the sheet contains N-containing inclusions as the main inclusions, and the N-containing inclusions comprise individual VN, AlN and / or composite VN, AlN, NbN and TiN.

4. Iron loss P ≤ 4.2 W / kg 15 / 50 and magnetic induction B ≥ 1.73T 50 A non-oriented electrical steel sheet according to claim 1 or 2, having the following characteristics.

5. A method for manufacturing a non-oriented electrical steel sheet according to claim 1 or 2, comprising the following steps: (1) The process of smelting and casting; (2) Hot rolling process, in which the steel coil obtained after hot rolling is introduced directly to the next process without being subjected to normalizing annealing or coating annealing; (3) The process of pickling to obtain pickled steel sheets; (4) A process of cold rolling a pickled steel sheet to obtain a cold-rolled steel sheet; and (5) Continuous annealing process, in which the cold-rolled steel sheet is heated to the target immersion temperature at a heating rate of 50-5000°C / s. A manufacturing method that includes this.

6. The manufacturing method according to claim 5, wherein step (5) satisfies at least one of the following conditions: The target immersion temperature is 500-1100°C; The cold-rolled steel sheet is heated to the target immersion temperature at a heating rate of 80-550°C / s.

7. The manufacturing method according to claim 5, wherein step (2) satisfies at least one of the following conditions: During hot rolling, the time the cast slab remains in the furnace is controlled to 120-360 minutes, the initial rolling temperature is controlled to 1000-1250°C, the final rolling temperature is controlled to 650-1000°C, and the coil winding temperature is controlled to 550-950°C. The hot-rolled steel sheet is controlled to have a target thickness of 0.8-3.5 mm; and / or In step (4), the pickled steel sheet is cold-rolled to the target cold-rolled thickness in a single step.

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