Non-oriented electromagnetic steel sheet and method for producing the same

Abstract

In the present invention, a non-oriented electrical steel sheet containing the following chemical elements in mass percent in addition to Fe and inevitable impurities is disclosed: C: 0.001 to 0.004%, Si: 2.0 to 3.8%, Mn: 0.05 to 1.0%, Al ≤ 1.51%, Ca: 0.0003 to 0.01%, Cr: 0.005 to 0.4%. Further, in the present invention, a method for manufacturing the non-oriented electromagnetic steel sheet is further disclosed. The manufacturing method includes the following steps: (1) a step of smelting and casting; (2) a step of heating and rolling, wherein a continuously cast slab is heated in a heating furnace, and when the temperature is raised to 1020°C or higher, the heating rate is controlled to be 0.8 to 2.0°C / min; the final rolling temperature is ≥ 880°C, and the residence time after the final rolling and before the laminar flow cooling is controlled to be 5 to 40 seconds; (3) a step of normalizing and annealing; (4) a step of pickling; (5) a step of cold rolling; (6) a step of continuous annealing; (7) a step of coating an insulating coating.

Description

Technical Field

[0001] Technical Field The present disclosure relates to a steel sheet and a method for manufacturing the same, and particularly to an isotropic electromagnetic steel sheet and a method for manufacturing the same.

Background Art

[0002] Background In recent years, with the rapid spread of the concept of environmental protection, in order to improve the natural environment, it has been desired to further save electric energy consumption by generally improving the power consumption efficiency. Therefore, currently, the requirements for isotropic electromagnetic steel sheets, such as being thin, having high magnetic induction, and having low iron loss, are becoming increasingly high.

[0003] The development of a new isotropic electromagnetic steel sheet that is thin, has high magnetic induction, low iron loss, and excellent mechanical properties, and can be used as steel for drive motors of new energy vehicles, steel for compressors of inverter air conditioners, and steel for high-speed rotating electric tools, has become an urgent task to meet the market demand.

[0004] In the current prior art, in the case of thin-specification steel sheets, the thickness of the finished products generally used in the industry is controlled to be 0.35 mm or less, or even 0.27 mm or less. However, due to the design requirements of miniaturization and weight reduction of the motor core, the magnetic circuit width or yoke width of the rotor core has become narrower, and the inertial centrifugal force of the rotor core during high-speed operation is very large. Therefore, problems such as deformation and fracture are likely to occur in thin steel sheets. Therefore, currently, when preparing isotropic electromagnetic steel sheets, the market and users have increasingly high requirements for the strength of the finished thin steel sheets.

[0005] Also, when the isotropic electromagnetic steel sheet is put into practical use as a stator core, the low iron loss P after stress relief annealing 1.0 / 400 and excellent magnetic induction B 5000It is expected to have. Therefore, developing non-oriented silicon steel with a thin specification, high strength, low iron loss, and high magnetic induction, as well as its manufacturing method, has great practical significance.

[0006] In response to this demand, some researchers have conducted extensive research and achieved certain research results, but the objective application effects of these patent technical documents are not very ideal:

[0007] For example, in the Chinese patent document with publication number CN107974620A, publication date May 1, 2018, and title "Non-oriented silicon steel with yield strength ≧ 600 Mpa for high-speed motor rotors and its manufacturing method", high-yield-strength non-oriented silicon steel and its manufacturing method are disclosed. The high-yield-strength non-oriented silicon steel has a chemical composition (wt%) of C: 0.001 - 0.003%, Si: 2.6 - 3.4%, Mn: 0.20 - 0.60%, P ≦ 0.005%, S ≦ 0.005%, Als: 0.75 - 0.95%, N: 0.002 - 0.006%, Nb: 0.053 - 0.20%. The manufacturing process adopted in this technical solution is: steelmaking in a converter and casting into slabs; heating of continuously cast slabs; conventional rough rolling and final rolling; annealing; cold rolling after pickling; continuous annealing. The finished steel plate with a thickness of 0.35 mm or less manufactured by this technical solution has a yield strength of ≧ 600 Mpa, a tensile strength of ≧ 700 Mpa, P 1.0 / 400 , and B of ≧ 1.60 T 5000 has. In this patent document, both the tensile strength and yield strength of the finished steel plate are very excellent, reaching above 700 MPa and above 600 MPa respectively, but the iron loss P 1.0 / 400 is as high as 35 W / kg, and the magnetic induction B 5000 is as low as 1.60 T, and its performance is still low.

[0008] As another example, Japanese Patent Document with Publication Number JP2012 - 136764, Publication Date July 19, 2012, and Title "Method for Manufacturing High - Strength Electromagnetic Steel Sheet" discloses a method for manufacturing a high - strength electromagnetic steel sheet having a chemical composition (wt%) of Si: 3.5 - 5.0%, S: 0.0005 - 0.0030%, Ca: 0.0015% or more, and Sn and / or Sb: 0.01 - 0.1%. By this technical solution including casting into a slab by an arc continuous casting machine, then hot rolling, annealing, one - time cold rolling, and continuous annealing in sequence, a high - strength electromagnetic steel sheet was obtained. Here, the surface center temperature of the continuous casting slab is 700°C or higher, the annealing temperature is 850 - 1000°C, the soaking time is 10s - 10min, and it is required that the hot - rolled steel sheet achieves 100% recrystallization with a grain size of 80 - 300μm after annealing: during continuous annealing, the annealing temperature is 670 - 800°C, the soaking time is 2s - 1min, and it is required to achieve 30 - 95% recrystallization, and the length of the recrystallized grain group is 2.5mm or less in the rolling direction. In addition, in the examples of this patent document, the tensile strength is nearly 700MPa and the iron loss P 10 / 400 is 20W / kg or more, but the yield strength of the finished steel sheet is not mentioned.

[0009] Based on this, the inventors, different from the above - mentioned existing technical solutions, designed and expect to obtain a new non - oriented electromagnetic steel sheet having thin thickness, high strength, low iron loss, and high magnetic induction and its manufacturing method to satisfy the requirements of the market and users.

Summary of the Invention

Means for Solving the Problems

[0010] Summary One of the objects of the present disclosure is to provide a non - oriented electromagnetic steel sheet. Through reasonable design of the chemical composition and optimization of the manufacturing process, the non - oriented electromagnetic steel sheet has excellent yield strength, tensile strength, and electromagnetic properties (yield strength ≥ 600Mpa, tensile strength ≥ 700Mpa, iron loss P 10 / 400 is ≤ 18.0W / kg, and magnetic induction B 5000can achieve (is ≧1.62 T), meet the requirements of low cost and low loss, and have characteristics such as low cost, wide application range, and good stability.

[0011] To achieve the above object, the present disclosure provides a non-oriented electromagnetic steel sheet. This non-oriented electromagnetic steel sheet contains the following chemical elements in mass percentage in addition to Fe and inevitable impurities: C: 0.001~0.004%, Si: 2.0~3.8%, Mn: 0.05~1.0%, Al≦1.51%, Ca: 0.0003~0.01%, Cr: 0.005~0.4%.

[0012] Preferably, in the non-oriented electromagnetic steel sheet of the present disclosure, the chemical elements in mass percentage are as follows: C: 0.001~0.004%, Si: 2.0~3.8%, Mn: 0.05~1.0%, Al≦1.51%, Ca: 0.0003~0.01%, Cr: 0.005~0.4%; the balance is Fe and inevitable impurities.

[0013] In the non-oriented electromagnetic steel sheet according to the present disclosure, the design principle of each chemical element is as follows: C: The C element can strongly inhibit the growth of particles in the finished strip steel. The C element is likely to combine with Nb, V, Ti, etc. to form fine precipitates, thereby causing an increase in loss and the occurrence of magnetic aging. Therefore, the C element content in the steel needs to be strictly controlled below 0.004%. However, it should be noted that the C element content in the steel should not be too low. When the C element content in the steel is less than 0.001%, it does not contribute to improving the mechanical strength of the finished steel sheet. Based on this, in order to fully exert the beneficial effects of the C element, the mass percentage content of the C element is controlled between 0.001~0.004% in the non-oriented electromagnetic steel sheet according to the present disclosure.

[0014] Si: When an appropriate amount of Si element is added to steel, it can not only increase the electrical resistivity of the steel, but also effectively reduce the iron loss of the steel. When the Si element content in the steel is higher than 3.8%, the magnetic induction of the steel significantly decreases, and the steel is prone to breakage during cold rolling; when the Si element content in the steel is less than 2.0%, the effect of reducing the iron loss of the steel is not significant. Based on this, in order to fully exert the beneficial effects of the Si element, the mass percentage content of the Si element is controlled between 2.0% and 3.8% in the non-oriented electrical steel sheet according to the present disclosure.

[0015] Mn: The Mn element can combine with the S element to form MnS, which can effectively reduce the risk to the magnetic properties of the steel. When the content of the Mn element in the steel is less than 0.05%, the S-fixing effect of the Mn element is poor; when the content of the Mn element in the steel exceeds 1.0%, the manufacturing cost of the steel significantly increases. Therefore, in order to fully exert the beneficial effects of the Mn element, the mass percentage content of the Mn element is controlled between 0.05% and 1.0% in the non-oriented electrical steel sheet according to the present disclosure.

[0016] Al: The Al element can have effects such as increasing the electrical resistivity of the material, thereby promoting the growth of the particle size, and reducing the iron loss of the material. If the content of the added Al is too high (exceeding 1.51%), casting becomes difficult during continuous casting, leading to a significant increase in manufacturing cost and significantly deteriorating the stability of cold rolling. Based on this, in the non-oriented electrical steel sheet according to the present disclosure, the mass percentage content of the Al element is controlled such that 0 < Al ≤ 1.51%.

[0017] Ca: Ca is a powerful deoxidizing and desulfurizing element. Ca can easily form large particle inclusions that are easily removed by floating, and can effectively reduce the risk to the magnetic properties of steel. Therefore, in order to fully exert the beneficial effects of the Ca element, it is necessary to add 0.0003% or more of Ca to the steel. However, it should be noted that the content of the Ca element in the steel should not be too high. When more than 0.01% of the Ca element is added to the steel, it will cause abnormal particle refinement and a decrease in the proportion of good crystal structures in the finished steel plate, thereby deteriorating the magnetic properties of the steel. Therefore, in order to exert the beneficial effects of the Ca element, the mass percentage content of the Ca element is controlled between 0.0003% and 0.01% in the non-oriented electromagnetic steel sheet according to the present disclosure.

[0018] Certainly, in some preferred embodiments, in order to achieve better implementation results, the mass percentage content of the Ca element can be more preferably controlled between 0.0005% and 0.004%.

[0019] Cr: The Cr element can combine with the N element to form Cr2N, which can effectively reduce the risk to the magnetic properties of the steel. When the content of the Cr element in the steel is less than 0.005%, the N-fixing effect of the Cr element is low, so it is necessary to add 0.005% or more of Cr to the steel. However, it should be noted that the content of the Cr element in the steel should not be too high. When more than 0.4% of Cr is added to the steel, it will cause abnormal particle refinement and a decrease in the proportion of good crystal structures in the finished steel plate, thereby deteriorating the magnetic properties of the steel. Based on this, considering the influence of the content of the Cr element on the performance of the steel, in the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage content of the Cr element is controlled between 0.005% and 0.4%.

[0020] Preferably, in the non-oriented electromagnetic steel sheet according to the present disclosure, among the inevitable impurities, P ≤ 0.02%, S ≤ 0.002%, N ≤ 0.004%, O ≤ 0.005%.

[0021] In the non-oriented electromagnetic steel sheet according to the present disclosure, P element, S element, N element and O element are all impurity elements of the non-oriented electromagnetic steel sheet, and these are impurity elements introduced into the steel from raw materials, auxiliary raw materials or the manufacturing process. If technical conditions permit, in order to obtain steel with better performance and better quality, the content of impurity elements in the steel should be reduced as much as possible.

[0022] P: When the mass percentage content of P element in the steel exceeds 0.02%, it will cause the occurrence of cold brittleness and easily reduce the manufacturability during the cold rolling process. Therefore, in the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage content of P element is controlled such that P ≤ 0.02%.

[0023] S: When the content of S element in the steel exceeds 0.002%, the amount of harmful inclusions such as MnS and Cu2S will increase significantly, thereby causing deterioration of the iron loss of the steel. Therefore, in the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage content of S element is controlled such that S ≤ 0.002%.

[0024] N: When the mass percentage content of N element in the steel exceeds 0.004%, the precipitates of N with Nb, V, Ti, Al, Cr, etc. will increase sharply in quantity and coarsen in size, which does not contribute to the improvement of the mechanical strength of the finished steel sheet and the reduction of the iron loss of the finished steel sheet. Therefore, in the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage content of N element is controlled such that N ≤ 0.004%.

[0025] O: When the mass percentage content of O element in the steel exceeds 0.005%, the amount of oxide inclusions will increase significantly, which does not contribute to the adjustment of the proportion of beneficial inclusions and deteriorates the magnetic properties of the steel. Therefore, in the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage content of O element is controlled such that O ≤ 0.005%.

[0026] Preferably, in the non-oriented electromagnetic steel sheet according to the present disclosure, the Ca element content is 0.0005 - 0.004%.

[0027] Preferably, in the non-oriented electromagnetic steel sheet of the present disclosure, the nitride inclusions in the steel include individual Cr2N, AlN or TiN, and composite inclusions formed by at least two of AlN, Cr2N and TiN.

[0028] Preferably, in the non-oriented electromagnetic steel sheet according to the present disclosure, the oxide inclusions [O] in the steel I , sulfide inclusions [S] I and nitride inclusions [N] I The volume ratio of nitride inclusions [N] in the steel to all of I is 0.42 ≦ [N] I / ([O] I + [S] I + [N] I ) ≦ 0.85.

[0029] Preferably, in the non-oriented electromagnetic steel sheet according to the present disclosure, the volume ratio of nitride inclusions with a size of 0.2 to 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 to 2.0 μm is 0.7 to 1.0.

[0030] Preferably, in the non-oriented electromagnetic steel sheet according to the present disclosure, the thickness of the non-oriented electromagnetic steel sheet is 0.15 to 0.35 mm.

[0031] Preferably, in the non-oriented electromagnetic steel sheet according to the present disclosure, the non-oriented electromagnetic steel sheet has a yield strength of ≧ 600 MPa, a tensile strength of ≧ 700 MPa, an iron loss P of ≦ 18.0 W / kg 10 / 400 , and a magnetic induction B of ≧ 1.62 T 5000 .

[0032] Correspondingly, another object of the present disclosure is to provide a method for manufacturing the above non-oriented electromagnetic steel sheet. This manufacturing method is simple and feasible. By this manufacturing method, a non-oriented electromagnetic steel sheet having excellent mechanical properties and electromagnetic properties can be obtained, and this non-oriented electromagnetic steel sheet has a yield strength of ≧ 600 MPa, a tensile strength of ≧ 700 MPa, an iron loss P of ≦ 18.0 W / kg 10 / 400and a magnetic induction B of ≧1.62 T 5000 having the same.

[0033] To achieve the above object of the present disclosure, the present disclosure provides a method for manufacturing a non-oriented electromagnetic steel sheet, including the following steps: (1) A step of smelting and casting to obtain a continuous casting slab; (2) A step of heating and rolling to obtain a steel sheet, comprising heating the continuous casting slab in a heating furnace, raising the temperature to 1020° C. or higher, controlling the heating rate to be 0.8 to 2.0° C. / min; controlling the final rolling temperature to be ≧880° C., and controlling the residence time after final rolling and before laminar flow cooling to be 5 to 40 s; (3) A step of annealing the steel sheet by normalizing; (4) A step of pickling; (5) A step of cold rolling; (6) A step of continuously annealing to obtain a finished steel sheet; (7) A step of coating an insulating coating on the surface of the finished steel sheet.

[0034] In the present disclosure, the inventors optimize the design of the chemical composition of the steel and limit a reasonable manufacturing process. After smelting and casting to obtain a continuous casting slab, the heating and temperature-raising process and the hot rolling process of the continuous casting slab are optimized, and then combined with subsequent normalizing annealing, pickling, cold rolling, continuous annealing and coating processes, so as to effectively manufacture a non-oriented electromagnetic steel sheet excellent in yield strength, tensile strength and electromagnetic properties. The manufactured non-oriented electromagnetic steel sheet can effectively meet the requirements of low cost and low loss, and has characteristics such as low cost, wide application range, and good stability.

[0035] In the smelting and casting process of step (1) of the present disclosure described above, the smelting and casting can specifically include four processes: molten iron pretreatment, converter smelting, RH refining, and continuous casting. In actual implementation, during the steelmaking process, the operator controls the molten steel from the blast furnace after molten iron pretreatment and feeds it into the converter together with an appropriate amount of high-quality scrap steel for rough refining, and then performs RH refining to decarburize, deoxidize, desulfurize, adjust the chemical composition of the steel, and perform calcium treatment. During this period, the operator adjusts the design of the chemical composition of the steel according to the design requirements of the present disclosure (especially to ensure that Ca, Cr, S, and N meet the design conditions), obtains molten steel that meets the design requirements of the chemical composition, and then can cast the molten steel into continuous casting slabs with a thickness of 120 - 250 mm and a width of 800 - 1400 mm by continuous casting according to a predetermined size.

[0036] The content of Ca element in the steel can be strictly controlled by the above smelting process and casting process, and the calcium content in the steel is restricted to be 0.0003 - 0.01%, preferably 0.0005 - 0.004%. In this way, after deoxidation, desulfurization, and calcium treatment of the molten steel, the amounts of oxides and sulfides in the steel are significantly reduced, the sizes of the residual oxides and sulfides in the steel are coarsened, and the harmfulness is significantly reduced. At the same time, in order to achieve a good control effect on nitrides, it is necessary to ensure that both the amount and size of nitrides are appropriate, and the mechanical strength of the finished steel plate should not be reduced, and the particles should not be refined to deteriorate the electromagnetic properties. Therefore, in the above heating and rolling process of step (2) according to the present disclosure, when the continuous casting slab is heated in a heating furnace and the temperature is raised to 1020 °C or higher, the heating rate of the continuous casting slab is controlled to be 0.8 - 2.0 °C / min.

[0037] Within this temperature range, if the heating rate of the continuous casting slab is lower than 0.8 ° C / min, the solid solution content of AlN inclusions, especially Cr2N inclusions, will increase significantly; correspondingly, during the subsequent final rolling and coiling process, as the temperature of the steel plate decreases, AlN and Cr2N inclusions will re-precipitate, at this time, the size of the precipitates is small, and the amount of precipitates increases significantly, so that the cleanliness of the steel will decrease significantly. At the same time, within this temperature range, the heating rate should not be too high. If the heating rate exceeds 2.0 ° C / min, the solid solution content of AlN inclusions, especially Cr2N inclusions, will decrease significantly. At this time, the fine AlN inclusions, especially Cr2N inclusions, precipitated at the end of the casting solidification of the molten steel cannot be completely dissolved, and still exist in a single form and small size, which has a negative effect on the recrystallization and the formation of good texture of the hot-rolled microstructure.

[0038] Furthermore, the inventors have considered the fact that during the cooling process from the high soaking temperature of the continuous cast slab to after rough rolling and after final rolling, as the end of rolling approaches, the temperature of the hot-rolled steel sheet decreases, the size of the precipitated nitrides becomes smaller, and the adverse effects become greater. In consideration of this, in designing, it is also necessary to control the final rolling temperature during the hot rolling process to ≧880°C in order to ensure that nitrides are sufficiently precipitated at the highest possible temperature stage; meanwhile, the residence time after final rolling and before laminar cooling should be controlled to be 5-40 seconds to promote the uniform growth and controlled size of the nitrides precipitated earlier.

[0039] Due to this heating and rolling process, the nitrides in the steel are mainly CrN, AlN, TiN, and there are small amounts of composite inclusions formed by at least two of AlN, CrN, and TiN. Here, the oxide inclusions [O] in the steel I , sulfide inclusions [S] I and nitride inclusions [N] I Nitride inclusions in steel for all of the above [N] I The volume ratio satisfies the following: 0.42≦[N] I / ([O] I +[S] I +[N]I ) ≤ 0.85.

[0040] On the one hand, the volume ratio of nitride inclusions with a size of 0.2 - 0.5 μm to oxide inclusions, sulfide inclusions, and nitride inclusions with a size of 0.2 - 2.0 μm can satisfy 0.7 - 1.0.

[0041] It should be noted that Ti in the above TiN inclusions is derived from inevitable Ti with an extremely low content in the steel. In the present disclosure, since Ti is an impurity element with an extremely low content, it is not specifically described or limited in part of the design of the elemental composition of the present disclosure.

[0042] In addition, in some embodiments of the manufacturing process of the present disclosure, the hot-rolled steel sheet obtained by step (2) can be rolled to a target thickness of 0.15 - 0.35 mm by one-pass cold rolling after normalizing annealing at 830 - 1000 °C for 10 - 300 s in a 100% nitrogen atmosphere, or can be rolled to a target thickness of 0.15 - 0.35 mm by the first-pass cold rolling + intermediate annealing + second-pass cold rolling. Finally, after further controlling the above cold-rolled steel sheet to be subjected to continuous annealing at 800 - 1000 °C × (10 - 120) s and subsequent insulation coating in a nitrogen-hydrogen mixed atmosphere with an H2 content of 30% or more, a desired non-oriented electrical steel sheet with a thin specification, high strength, low iron loss, and high magnetic induction can be obtained.

[0043] Compared with the prior art, the non-oriented electrical steel sheet and its manufacturing method according to the present disclosure have the following advantages and beneficial effects: In the non-oriented electrical steel sheet according to the present disclosure, the inventors optimized the chemical element composition ratio and the related manufacturing process. The non-oriented electrical steel sheet manufactured by the method of this specification has the characteristics of a thin specification, high strength, low iron loss, and high magnetic induction. The non-oriented electrical steel sheet after continuous annealing has excellent yield strength and tensile strength, and can be well applied to high-frequency and high-speed motors with a speed of 20,000 rpm or less.

[0044] In the present disclosure, the designed non-oriented electromagnetic steel sheet also has characteristics such as low cost, wide application range, and good stability. The non-oriented electromagnetic steel sheet has a yield strength of ≥600 MPa, a tensile strength of ≥700 MPa, an iron loss P of ≤18.0 W / kg 10 / 400 , a magnetic induction B of ≥1.62 T 5000 and has good promotion prospects and application value.

Brief Description of the Drawings

[0045]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0046] Detailed Description The non-oriented electromagnetic steel sheet and its manufacturing method according to the present disclosure will be further described and illustrated with reference to the attached explanatory drawings and specific examples. However, the description and examples do not constitute an excessive limitation on the technical solution of the present disclosure.

[0047] Examples 1 - 12 and Comparative Examples 1 - 5 Table 1 shows the mass percentages of chemical elements in the non-oriented electromagnetic steel sheets of Examples 1 - 12 and the comparative steel sheets of Comparative Examples 1 - 5.

[0048]

Table 1

[0049] The non-oriented electromagnetic steel sheets of Examples 1 to 12 and the comparative steel sheets of Comparative Examples 1 to 5 are manufactured by the following steps: (1) Step of smelting and casting according to the chemical composition ratios shown in Table 1: During the steelmaking process, hot metal pretreated blast furnace hot metal and an appropriate amount of high-quality scrap steel are charged into a converter for rough refining, and then RH refining is performed for decarburization, deoxidation, desulfurization, adjustment of the chemical composition of the steel, and calcium treatment. During this process, according to the design requirements of the present disclosure, the design of the chemical composition of the steel is adjusted (especially ensuring that Ca, Cr, S, and N meet the design conditions), and molten steel that meets the design requirements of the chemical composition is obtained. Then, according to a predetermined size, continuous casting slabs with a thickness of 120 to 250 mm and a width of 800 to 1400 mm are cast by continuous casting. (2) Step of heating and rolling: The obtained continuous casting slab is charged into a heating furnace for heating and temperature rise. The continuous casting slab is heated in the heating furnace, and when the temperature rises to 1020 °C or higher, the heating rate of the continuous casting slab is strictly controlled to be 0.8 to 2.0 °C / min. Also, the final rolling temperature should be controlled to be ≧880 °C, and the residence time after the final rolling and before the laminar flow cooling should be controlled to be 5 to 40 s. (3) Step of normalizing and annealing: Under a 100% nitrogen atmosphere, the normalizing and annealing temperature is controlled to be 830 to 1000 °C, and the normalizing and annealing time is controlled to be 60 to 300 s. (4) Step of pickling. (5) Step of cold rolling: It is rolled to a target thickness of 0.15 to 0.35 mm by a single cold rolling process, or is rolled to a target thickness of 0.15 to 0.35 mm by a double cold rolling process including the first cold rolling, intermediate annealing, and the second cold rolling. (6) Step of continuous annealing: Continuous annealing is performed in a nitrogen-hydrogen mixed atmosphere with an H2 content of 30% or more, the continuous annealing temperature is controlled to be 800 to 1000 °C, and the continuous annealing time is controlled to be 10 to 120 s. (7) Step of coating an insulating coating.

[0050] In the present disclosure, it should be noted that all of the chemical compositions and related process parameters of Examples 1 to 12 satisfy the management requirements of the design specifications according to the present disclosure; however, in Comparative Examples 1 to 5, although the comparative steels are also manufactured by the above-described process steps, there are parameters that do not conform to the design of the present disclosure in their chemical element compositions and / or related process parameters.

[0051] Table 2 shows the specific process parameters and final product thicknesses in the above manufacturing process of the non-oriented electrical steel sheets of Examples 1 to 12 and the comparative steel sheets of Comparative Examples 1 to 5.

[0052]

Table 2

[0053] Finally, the completed non-oriented electrical steel sheets of Examples 1 to 12 and the comparative steel sheets of Comparative Examples 1 to 5 obtained were sampled respectively. Then, the steel sheet samples of Examples 1 to 12 and Comparative Examples 1 to 5 were observed and analyzed. As a result, it was observed and found that the steel sheets of the examples and comparative examples all have inclusions such as oxide inclusions, sulfide inclusions and nitride inclusions.

[0054] By further analysis and testing, the volume ratio of nitride inclusions [N] to all of the oxide inclusions [O], sulfide inclusions [S] and nitride inclusions [N] in the steel sheets of each example and comparative example, and the volume ratio of nitride inclusions with a size of 0.2 to 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 to 2.0 μm can be obtained respectively. The related observation and analysis results are shown in Table 3 below. I sulfide inclusions [S] I and nitride inclusions [N] I for all of the oxide inclusions [O], sulfide inclusions [S] and nitride inclusions [N] I the volume ratio of nitride inclusions [N], and the volume ratio of nitride inclusions with a size of 0.2 to 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 to 2.0 μm can be obtained respectively. The related observation and analysis results are shown in Table 3 below.

[0055] The analysis and test methods of inclusions are carried out in accordance with the national standard GBT 10561.

[0056] Table 3 shows the observation and analysis results of inclusions in the steel plates of each example and comparative example.

[0057]

Table 3

[0058] Note: In Table 3 above, "A" represents [N] I / ([O] I + [S] I + [N] I ) and "B" represents the volume ratio of nitride inclusions with a size of 0.2 - 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 - 2.0 μm.

[0059] In the non - oriented electrical steel sheets manufactured in Examples 1 - 12, it was confirmed that the nitride inclusions were mainly single Cr2N, AlN, and TiN, and there was also a small amount of composite inclusions formed by at least two of AlN, Cr2N, and TiN.

[0060] After testing the inclusions in the sample steel plates of each example and comparative example, from Table 3 above, in Examples 1 - 12, the ratio of the volume percentage content of nitride inclusions [N] I , oxide inclusions [O] I , sulfide inclusions [S] I to the total volume percentage content of all nitride inclusions [N] I is specifically 0.42 - 0.85; furthermore, it is found that the ratio of nitride inclusions with a size of 0.2 - 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 - 2.0 μm in the steel is 0.71 - 0.99.

[0061] Correspondingly, after the above observations and analyses of the inclusions are completed, the finally manufactured non-oriented electromagnetic steel sheets of Examples 1 to 12 and the comparative steel sheets of Comparative Examples 1 to 5 can be sampled again, and the sample steel sheets of Examples 1 to 12 and Comparative Examples 1 to 5 are tested for mechanical properties, magnetic induction B 5000 and iron loss P 10 / 400 . The test results obtained are shown in Table 4 below.

[0062] The relevant performance test methods are as follows: Tensile test: According to the national standard GB / T 228.1-2010, Metallic materials - Tensile testing - Part 1: Method of test at room temperature, control the test temperature to be 20°C and the sample size to be 35 mm × 390 mm, and conduct a constant temperature test and a single plate test to measure the yield strength Y S and tensile strength T S of the steel sheets of the examples and comparative examples.

[0063] Magnetic induction performance test: Conduct the magnetic induction performance test using the Epstein square method according to the national standard GB / T 3655-2008. Control the test temperature to be 20°C for the constant temperature test, control the sample size to be 30 mm × 300 mm, and the target mass to be 0.5 kg. Based on this, measure the magnetic induction B 5000 of the steel sheets of the examples and comparative examples.

[0064] Iron loss performance test: Conduct the iron loss performance test using the Epstein square method according to the national standard GB / T 3655-2008. Control the test temperature to be 20°C for the constant temperature test, control the sample size to be 30 mm × 300 mm, and the target mass to be 0.5 kg. Based on this, measure the iron loss P 10 / 400 of the steel sheets of the examples and comparative examples.

[0065] The test results of the yield strength Y S , tensile strength T S , magnetic induction B 5000 and iron loss P 10 / 400 of the non-oriented electromagnetic steel sheets of Examples 1 to 12 and the comparative steel sheets of Comparative Examples 1 to 5 are shown in Table 4.

[0066]

Table 4

[0067] As shown in Table 4 above, in the present disclosure, the non-oriented electromagnetic steel sheets of Examples 1 to 12 have a yield strength of 611 to 656 MPa, a tensile strength of 706 to 785 MPa, a magnetic induction B of 1.63 to 1.66 T 5000 , and an iron loss P of 13.9 to 17.2 W / kg 10 / 400 . The comprehensive performance of the non-oriented electromagnetic steel sheets of Examples 1 to 12 is significantly better than that of the comparative steel sheets of Comparative Examples 1 to 5. Since Comparative Examples 1 to 5 do not meet the conditions defined by the present technical solution, the implementation effects of Comparative Examples 1 to 5 are also inferior to those of the present technical solution.

[0068] In combination with the data described in Table 1, Table 2, Table 3, and Table 4 above, further analysis and explanation can be provided for the five comparative examples manufactured in this specification.

[0069] In Comparative Example 1, the Mn element and S element added to the steel are 1.22% and 0.0025% respectively, both exceeding the upper limits of 1.0% and 0.002% of the design requirements of the present disclosure. Furthermore, the residence time of the continuous casting slab before hot rolling and final rolling and before laminar cooling is only 4 seconds, which is lower than the lower limit of 5 seconds of the design requirements of the present disclosure. Correspondingly, [N] in the steel I / ([O] I +[S] I +[N] I ) is only 0.37, which is lower than the lower limit of 0.42 of the design requirements of the present disclosure. Therefore, although the yield strength and tensile strength of the corresponding finished steel sheet manufactured by Comparative Example 1 are both qualified, the magnetic induction B 5000 is low and the iron loss P 10 / 400 is high, which are 1.59 T and 24.7 W / kg respectively, and do not meet the design requirements of the present disclosure.

[0070] In Comparative Example 2, the content of the Si element added to the steel is 3.90%, which exceeds the upper limit of 3.8% of the design requirements of the present disclosure. Further, during the hot rolling process of the continuous casting slab, the heating rate of the continuous casting slab in the temperature range of 1020 °C or higher is 2.5 °C / min, which is higher than the upper limit of 2.0 °C / min of the design requirements of the present disclosure. Correspondingly, the ratio of nitrides with a size of 0.2 - 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 - 2.0 μm in the steel is 0.64, which is lower than the lower limit of 0.70 of the design requirements of the present disclosure. Therefore, the yield strength, tensile strength and iron loss P of the corresponding finished steel plate manufactured according to Comparative Example 2 10 / 400 are all qualified, but the magnetic induction B 5000 is as low as 1.58 T, which does not meet the design requirements of the present disclosure.

[0071] In Comparative Example 3, the design of the chemical composition in the steel is qualified, but during hot rolling, the final rolling temperature of the continuous casting slab is only 820 °C, which is lower than the lower limit of 880 °C of the design requirements of the present disclosure. Further, the target thickness of the finished steel plate is 0.50 mm, which is higher than the upper limit of 0.35 mm of the design requirements of the present disclosure. Therefore, the yield strength Y S , tensile strength T S , magnetic induction B 5000 and iron loss P 10 / 400 of the corresponding finished steel plate manufactured according to Comparative Example 3 are unqualified, and they are 547 MPa, 679 MPa, 1.58 T and 18.9 W / kg respectively, and none of them meet the design requirements of the present disclosure.

[0072] In Comparative Example 4, the contents of the Cr element and N element added to the steel are 0.71% and 0.0051% respectively, which exceed the upper limits of 0.4% and 0.004% of the design requirements of the present disclosure. Also, in the manufacturing process, the heating rate of the continuous casting slab in the temperature range of 1020 °C or higher is 0.49 °C / min, which is lower than the lower limit of 0.8 °C / min of the design requirements of the present disclosure. Correspondingly, [N] in the steel I / ([O] I +[S]I +[N] I ) is as high as 0.92, which is higher than 0.85 that is the upper limit of the design requirements of the present disclosure. Therefore, the yield strength Y of the corresponding finished steel plate manufactured according to Comparative Example 4 S , magnetic induction B 5000 and iron loss P 10 / 400 are all unqualified, and they are 582 MPa, 1.60 T, and 22.1 W / kg respectively, and do not meet the design requirements of the present disclosure.

[0073] In Comparative Example 5, the contents of C element and Al element added to the steel are 0.0044% and 1.82% respectively, which exceed 0.004% that is the upper limit of C and 1.5% that is the upper limit of Al of the design requirements of the present disclosure. Further, in the manufacturing process, the residence time of the continuous casting slab after hot rolling and final rolling and before laminar flow cooling is 55 seconds, which is higher than 40 seconds that is the upper limit of the design requirements of the present disclosure. Correspondingly, the ratio of nitrides with a size of 0.2 - 0.5 μm to oxide inclusions, sulfide inclusions, and nitride inclusions with a size of 0.2 - 2.0 μm in the steel is 0.59, which is lower than 0.70 that is the lower limit of the design requirements of the present disclosure. Therefore, the yield strength Y of the corresponding finished steel plate manufactured according to Comparative Example 5 S , tensile strength T S and iron loss P 10 / 400 are all unqualified, and they are 559 MPa, 658 MPa, and 19.4 W / kg respectively, and do not meet the design requirements of the present disclosure.

[0074] Figure 1 schematically shows the relationship between [N] I / ([O] I +[S] I +[N] I ) and the yield strength of the finished steel plate.

[0075] As shown in Figure 1, as [N] I / ([O] I +[S] I +[N] I ) increases, the yield strength of the finished steel plate increases rapidly, and [N]I / ( [O] I + [S] I + [N] I ) reaches 0.42, it is observed and found that the yield strength of the finished steel plate can reach 600 MPa. Thereafter, [N] I / ( [O] I + [S] I + [N] I ) increases, the yield strength of the finished steel plate continues to increase at the same rate, and [N] I / ( [O] I + [S] I + [N] I ) reaches 0.85, the yield strength of the finished steel plate reaches its maximum. Thereafter, [N] I / ( [O] I + [S] I + [N] I ) further increases, the yield strength of the finished steel plate decreases rapidly, thereby not meeting the design requirements of the present disclosure.

[0076] Figure 2 schematically shows the relationship between nitride (0.2 - 0.5 μm) / oxide inclusions, sulfide inclusions and nitride inclusions (0.2 - 2.0 μm) and the magnetic induction B of the finished steel plate in the non - oriented electromagnetic steel plate according to the present disclosure. 5000 and.

[0077] As shown in Figure 2, for the volume percentage ratio of nitride inclusions with a size of 0.2 - 0.5 μm to all of the oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 - 2.0 μm, as the parameter value increases, the magnetic induction of the finished steel plate first increases rapidly, and it is observed and found that it reaches or exceeds 1.62 T or more, which is the design requirement according to the present disclosure, in the range of 0.7 - 1.0; thereafter, the magnetic induction begins to decrease rapidly, thereby not meeting the design requirements for controlling the magnetic induction of the finished steel plate according to the present disclosure.

[0078] Figure 3 schematically shows the relationship between the hot - rolling heating rate and the amount of inclusions in the non - oriented electromagnetic steel plate according to the present disclosure.

[0079] As shown in Fig. 3, during the hot rolling process, with the increase in the heating rate of the continuously cast slab, first, the number of inclusions in the steel decreases rapidly. When the heating rate is 0.8 °C / min, the amount of inclusions reaches 3.5×10 7 / mm 3 or less, and it remains basically stable before 2.0 °C / min. After that, the amount of inclusions begins to increase rapidly and gradually exceeds 3.5×10 7 / mm 3 which is observed and found.

[0080] Fig. 4 shows an image of the microstructure of the comparative steel in Comparative Example 1.

[0081] As shown in Fig. 4, through the observation of the microstructure of the comparative steel in Comparative Example 1, it is found that the inclusions in the steel of Comparative Example 1 have irregular shapes, small sizes, large numbers, and are clustered, which significantly inhibits the growth of the grain size during heat treatment annealing and deteriorates the good crystal structure of the finished steel plate, thereby deteriorating the electromagnetic properties.

[0082] Fig. 5 shows an image of the microstructure of the finished non-oriented electromagnetic steel sheet in Example 10.

[0083] As shown in Fig. 5, in this embodiment, in the finished non-oriented electromagnetic steel sheet of Example 10, the size of the inclusions is relatively large and uniform, has a regular shape as a whole, and the amount is small. This has little effect on the growth of the grain size during heat treatment annealing and contributes to improving the electromagnetic properties of the finished steel plate.

[0084] It should be noted that the prior art part within the protection scope of the present disclosure is not limited to one embodiment described in the application documents, and includes but is not limited to prior patent documents, prior publications, prior known uses, etc. All prior art that does not conflict with the solution of the present disclosure may be included in the protection scope of the present disclosure.

[0085] Furthermore, the combinations of the technical features of the present disclosure are not limited to the combinations described in the claims or in specific embodiments of the present disclosure, and all the technical features of the present disclosure can be freely combined in any way as long as they do not conflict with each other.

[0086] It should also be noted that the above-described embodiment is merely a specific example of the present disclosure. It is obvious that the present disclosure is not limited to the above-described embodiment, and similar variations or modifications are obvious to those skilled in the art or can be directly derived by those skilled in the art based on the present disclosure, and all of these are included within the protection scope of the present disclosure.

Claims

1. Anisotropic electromagnetic steel sheet containing the following chemical elements in mass percentage in addition to Fe and inevitable impurities: C: 0.001 - 0.004%, Si: 2.0 - 3.8%, Mn: 0.05 - 1.0%, 0 < Al ≤ 1.51%, Ca: 0.0003 - 0.01%, Cr: 0.005 - 0.4%.

2. The anisotropic electromagnetic steel sheet according to Claim 1, wherein the anisotropic electromagnetic steel sheet contains the following chemical elements in mass percentage: C: 0.001 - 0.004%, Si: 2.0 - 3.8%, Mn: 0.05 - 1.0%, Al ≤ 1.51%, Ca: 0.0003 - 0.01%, Cr: 0.005 - 0.4%, and the balance is Fe and inevitable impurities.

3. The anisotropic electromagnetic steel sheet according to Claim 1 or 2, wherein among the inevitable impurities, P ≤ 0.02%, S ≤ 0.002%, N ≤ 0.004%, O ≤ 0.005%.

4. The anisotropic electromagnetic steel sheet according to Claim 1 or 2, wherein the content of Ca element is 0.0005 - 0.004%.

5. The nitride inclusions in the steel are the individual Cr 2 N, AlN or TiN, and AlN, Cr 2 3. The non-oriented electrical steel sheet according to claim 1, comprising composite inclusions formed by at least two of N and TiN.

6. Oxide inclusions [O] in steel I , Sulfide inclusions [S] I and Nitride inclusions [N] I The nitride inclusions [N] in steel with respect to all of I The non-oriented electrical steel sheet according to claim 1 or 2, wherein the volume ratio satisfies the following: 0.42 ≦ [N] I / ([O] I + [S] I + [N] I ) ≦ 0.

85.

7. The anisotropic electromagnetic steel sheet according to Claim 1 or 2, wherein the volume ratio of nitride inclusions with a size of 0.2 μm - 0.5 μm to oxide inclusions, sulfide inclusions and nitride inclusions with a size of 0.2 μm - 2.0 μm is 0.7 - 1.

0.

8. The anisotropic electromagnetic steel sheet according to Claim 1 or 2, wherein the thickness of the anisotropic electromagnetic steel sheet is 0.15 - 0.35 mm.

9. An isotropic electromagnetic steel sheet having a yield strength of ≥600 MPa, a tensile strength of ≥700 MPa, and an iron loss P of ≤18.0 W / kg 10 / 400 , and a magnetic induction B of ≥1.62 T 5000 The isotropic electromagnetic steel sheet according to claim 1 or 2.

10. A method for manufacturing an anisotropic electromagnetic steel sheet according to any one of Claims 1 - 9, comprising the following steps: (1) A step of smelting and casting to obtain a continuous casting slab; (2) A step of heating and rolling to obtain a steel sheet, wherein the continuous casting slab is heated in a heating furnace, and when the temperature is raised to 1020 °C or higher, the heating rate is controlled to be 0.8 - 2.0 °C / min, the final rolling temperature is 880 °C or higher, and the residence time after the final rolling and before the laminar flow cooling is controlled to be 5 - 40 s; (3) A step of annealing the steel sheet by full annealing; (4) A step of pickling; (5) A step of cold rolling; (6) A step of continuous annealing to obtain a finished steel sheet; (7) A step of coating an insulating coating on the surface of the finished steel sheet.

11. The manufacturing method according to Claim 10, wherein in step (3), the temperature of the full annealing is controlled to be 830 - 1000 °C, and the time of the full annealing is 10 - 300 s.

12. The manufacturing method according to claim 10, wherein in step (6), the temperature of continuous annealing is controlled to be 800 to 1000 °C, and the time of continuous annealing is 10 to 120 s.

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