Non-oriented electrical steel sheet with good magnetic properties and its manufacturing method

Abstract

The present invention discloses a non-oriented electrical steel sheet with good magnetic properties. In addition to Fe and inevitable impurities, the non-oriented electrical steel sheet contains the following chemical elements by mass percentage: 0 < C ≤ 0.0025%, Si: 0.2 - 1.6%, Mn: 0.2 - 0.6%, Al: 0.2 - 0.6%, V: 0.001 - 0.008%, N: 0.002 - 0.0045%, 0 < Nb ≤ 0.003%, 0 < Ti ≤ 0.003%. Furthermore, the present invention discloses a method for manufacturing the above non-oriented electrical steel sheet with good magnetic properties. The manufacturing method includes: (1) a smelting and casting process; (2) a hot rolling process, in which normalizing or cover annealing is not performed on the steel coil after hot rolling, and it is directly fed into the next process; (3) a pickling process; (4) a cold rolling process, and (5) a process of annealing the finished product, which includes a step of rapidly heating the cold-rolled steel sheet from room temperature to the target soaking temperature at a heating rate of 80 - 1000 °C / second. The non-oriented electrical steel sheet of the present invention has good electromagnetic properties, low iron loss, and high magnetic flux density, can be effectively used to manufacture cores, has great potential for popularization, and high application value.

Description

[Technical field]

[0001] The present disclosure relates to a steel sheet and a manufacturing method thereof, and in particular to a non-oriented electrical steel sheet and a manufacturing method thereof. [Background technology]

[0002] For many years, the market and users have been demanding energy saving and low energy consumption in the iron cores of various electric devices, power tools, etc. In other words, non-oriented electrical steel sheets, which are the raw material for manufacturing such iron cores, are required to have the corresponding properties of high magnetic flux density and low core loss.

[0003] Research has shown that in order to obtain non-oriented electrical steel with good electromagnetic performance, it is necessary to properly control the chemical composition of the steel to improve the grain size and good texture of the finished steel sheet.

[0004] In the prior art, many researchers have conducted extensive research on the research topic of improving the electromagnetic performance of non-oriented electrical steel sheets and have achieved certain research results.

[0005] For example, JP 2008-260980 A (published on October 30, 2008, with the title "Method for Manufacturing High-grade Non-oriented Electrical Steel Sheet") discloses a non-oriented electrical steel sheet. In the technical solution disclosed in this application, the grain size and crystal texture of the hot-rolled sheet are improved by increasing the exit temperature of the hot-rolled slab (generally about 1230-1320°C). The finished steel sheet thus produced has a good surface condition and a high magnetic flux density. On the other hand, in order to prevent non-metallic inclusions such as S and N from being completely dissolved and dispersed during heating and rolling of the slab after increasing the exit temperature of the slab and thus worsening the iron loss of the finished steel sheet, this technology also employs a method of refining the molten steel by adding 0.005-0.03% of a calcium-containing alloy or rare earth element, and strictly requires that the contents of S and N be less than 0.0015%. This design not only makes the smelting difficult to control, but also increases manufacturing costs and requires special slab heating equipment, making it unsuitable for widespread use and application.

[0006] As another example, China Patent Application Publication No. 101343683A (published on January 14, 2009, with the title "Method for Producing Non-oriented Electrical Steel with Low Core Loss and High Magnetic Flux Density") discloses a method for producing non-oriented electrical steel with low core loss and high magnetic flux density. The technical solution disclosed in this application lists the following process steps: the heating temperature of the casting is controlled to 900-1150°C; the hot-rolled sheet is normalized and pickled, then cold-rolled once to a thickness of 0.50 mm; and finally, stress relief annealing is performed under a hydrogen-nitrogen mixed gas atmosphere to obtain a non-oriented electrical steel product with low core loss and high magnetic flux density. The advantage of this is that the final product of the non-oriented electrical steel has good magnetic performance (P 15 / 50 =3.1~3.8W / kg, B 5000=1.69~1.81T), the slab contains 1.0~2.0% Si and 0~0.60% Al, with 1.5%≦Si+3Al≦3.2%, and does not contain alloying elements such as Sn, Sb, Bi, Cu, Cr, Ni, B, Ca, and Ce, the manufacturing cost is significantly reduced, and a finished non-oriented electrical steel with good magnetic performance can be obtained.

[0007] As another example, China Patent Application Publication No. 104073715A (published on October 1, 2014, titled "High Flux Density Non-oriented Electrical Steel and Manufacturing Method Thereof") discloses a non-oriented electrical steel with high magnetic flux density. In the technical solution disclosed in this application, the heating rate of the normalizing heating section and the speed of the normalizing cooling section are controlled, and an appropriate shot blasting and pickling process system is adopted, so that raw material with excellent plate quality can be sent to the subsequent process, and magnetic flux density B can be increased without adding alloy elements or changing the continuous annealing process. 50 The magnetic flux density of the non-oriented electrical steel can be increased by 200-500 gauss and the actual physical quality level of iron loss can be improved by 3-5%. In addition, the magnetic performance of the product can be further improved by optimizing the annealing process, and the magnetic flux density can be further increased. The high magnetic flux density non-oriented electrical steel not only meets the requirements for traditional motors, but also meets the high magnetic flux density requirements for electrical steels for high-efficiency variable frequency motor cores, which can improve motor efficiency and reduce the energy consumption and noise of the product.

[0008] However, the present inventors hope to obtain a novel non-oriented electrical steel sheet with good magnetic properties by adopting a completely new design concept different from the above-mentioned existing technical solutions, which optimizes the chemical composition of the steel and defines a reasonable manufacturing process, thereby effectively improving the electromagnetic properties of the non-oriented electrical steel sheet, reducing the iron loss, and increasing the magnetic flux density. Summary of the Invention [Problem to be solved by the invention]

[0009] One of the objectives of the present disclosure is to provide a non-oriented electromagnetic steel sheet with good magnetic properties. The non-oriented electromagnetic steel sheet has good magnetic properties, with iron loss P 15 / 50 being 3.2 W / kg or less and magnetic flux density B 50 being 1.75 T or more. It can be effectively used to manufacture cores and can be used in various electrical appliances and power tools. It has a very high potential for popularization and a very high application value.

[0010] To achieve the above objective, the present disclosure provides a non-oriented electromagnetic steel sheet with good magnetic properties, which contains, in addition to Fe and inevitable impurities, the following chemical elements by mass percentage: 0 < C ≤ 0.0025%, Si: 0.2 - 1.6%, Mn: 0.2 - 0.6%, Al: 0.2 - 0.6%, V: 0.001 - 0.008%, N: 0.002 - 0.0045%, 0 < Nb ≤ 0.003%, 0 < Ti ≤ 0.003%.

[0011] The non-oriented electromagnetic steel sheet according to the present disclosure preferably contains, by mass percentage, the following chemical elements: 0 < C ≤ 0.0025%, Si: 0.2 - 1.6%, Mn: 0.2 - 0.6%, Al: 0.2 - 0.6%, V: 0.001 - 0.008%, N: 0.002 - 0.0045%, 0 < Nb ≤ 0.003%, 0 < Ti ≤ 0.003%, with the balance being Fe and inevitable impurities.

[0012] In the non-oriented electromagnetic steel sheet according to the present disclosure, the design principles of each chemical element are as follows.

[0013] C: In the non-oriented electromagnetic steel sheet according to the present disclosure, the C content in the steel should not be too high. When the C content in the steel exceeds 0.0025%, a large number of C-containing inclusions will be formed, and the magnetic aging of the finished steel sheet will increase significantly. Therefore, in the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage of C is controlled to be 0 < C ≤ 0.0025%.

[0014] Si: In the non-oriented electrical steel sheet according to the present disclosure, the Si content is medium to small. In the case of the present technical solution, if the Si content exceeds 1.6%, not only does the manufacturing cost of the steel increase, but the magnetic flux density of the finished steel sheet is significantly reduced. On the other hand, if the Si content is lower than 0.2%, the effect of effectively reducing iron loss cannot be obtained. Therefore, in the non-oriented electrical steel sheet according to the present disclosure, the mass percentage of Si is controlled to 0.2 to 1.6%.

[0015] Mn: In the non-oriented electrical steel sheet according to the present disclosure, if the content of added Mn exceeds 0.6%, the good texture of the finished non-oriented electrical steel sheet will be significantly deteriorated. On the other hand, if the Mn content in the steel is less than 0.2%, the effect of controlling S-containing inclusions cannot be obtained. Therefore, taking into consideration the effect of the Mn content on the properties of the steel, the mass percentage of Mn in the non-oriented electrical steel sheet according to the present disclosure is controlled to 0.2-0.6%.

[0016] Al: In the non-oriented electrical steel sheet according to the present disclosure, if the content of added Al exceeds 0.6%, the pourability of molten steel is obviously reduced. On the other hand, if the Al content in the steel is less than 0.2%, the effect of effectively reducing iron loss cannot be obtained. Therefore, in order to allow Al to exert its beneficial effect, the mass percentage of Al in the non-oriented electrical steel sheet according to the present disclosure is controlled to 0.2-0.6%.

[0017] V: In the case of the prior art, the V element in non-oriented electrical steel is an impurity element mixed in during the steelmaking process, and its content is strictly controlled. The lower the content, the better. In contrast, in the present disclosure, V is used as a beneficial element in the steelmaking process, and the V content is consciously adjusted. The present disclosure has changed from the conventional method of reducing the V content as much as possible to reduce the content of harmful inclusions as much as possible to a method of consciously adding a certain V content. By controlling the type and amount of N-containing inclusions and adjusting the manufacturing process at the same time, the present disclosure makes the contents of Nb, V, and Ti harmless to the maximum extent. In this way, a reasonable prerequisite for controlling the formulation and combination of beneficial chemical components and the type of inclusions to obtain good magnetic performance is realized.

[0018] In the non-oriented electrical steel sheet according to the present disclosure, if the V content in the steel is less than 0.001%, the effect of controlling C- and N-containing inclusions cannot be obtained. However, care should be taken not to add too much V element to the steel. If the V content in the steel exceeds 0.008%, the number of C- and N-containing inclusions containing V increases significantly and their size decreases. Therefore, in the non-oriented electrical steel sheet according to the present disclosure, the mass percentage of V is controlled to 0.001 to 0.008%.

[0019] N: In the non-oriented electrical steel sheet according to the present disclosure, if the N content is less than 0.002%, the effect of rationally controlling C and N-containing inclusions cannot be obtained. However, care should be taken not to make the N content in the steel too high. If the N content in the steel exceeds 0.0045%, the number of N-containing inclusions increases significantly, which inhibits grain growth in the finished steel sheet and deteriorates the electromagnetic performance of the finished steel sheet. Therefore, in the non-oriented electrical steel sheet according to the present disclosure, the mass percent of N is controlled to 0.002 to 0.0045%.

[0020] On the one hand, in the present disclosure, considering that it is difficult to reduce the content of N element and that a large amount of fine AlN inclusions are likely to occur when the Al content is 0.2 to 0.6%, it should be noted that the inventors selected to add 0.002 to 0.0045% of N to the steel together with 0.001 to 0.008% of V element. Here, the main reasons for adding V as a beneficial element are as follows. That is, the effect of carbides and nitrides of V on deteriorating the electromagnetic performance of the finished steel sheet is much smaller than that of carbides and nitrides such as Al, Nb, and Ti, and the carbides and nitrides of V are relatively stable.

[0021] Nb: In the technical solution of the present invention, when the Nb content exceeds 0.003%, the C and N-containing inclusions in the steel increase abnormally, and the iron loss of the finished steel sheet will increase rapidly. Therefore, in the present disclosure, the Nb content is controlled to satisfy 0 < Nb ≤ 0.003%.

[0022] Ti: In the technical solution of the present invention, even if the Ti content exceeds 0.003%, the C and N-containing inclusions in the steel increase abnormally, and the iron loss of the finished steel sheet will increase rapidly. Therefore, in the present disclosure, the Ti content is controlled to satisfy 0 < Ti ≤ 0.003%.

[0023] In the non-oriented electromagnetic steel sheet according to the present disclosure, the mass percentage of V is preferably 0.0015 to 0.0045%.

[0024] In the non-oriented electromagnetic steel sheet according to the present disclosure, the inevitable impurities preferably include S ≤ 0.002%.

[0025] Different from the general design concept in the past, in this disclosure, not only the C content is strictly controlled to reduce the formation of C-containing inclusions, but also the S content is strictly controlled. This is because the higher the S content in the steel, the more S-containing inclusions will be formed at the end of solidification of the molten steel or the end of hot rolling, and the smaller the size of the S-containing inclusions will be, which will make the electromagnetic performance of the steel much worse than that of the N-containing inclusions. However, it should be noted that it is much easier to control the content of S element than the content of N element. In order to keep the S content low, many technical measures can be selected in the actual operation process, such as limiting the S content in raw materials and auxiliary materials for iron and steelmaking, and adding desulfurization agents to carry out deep desulfurization in hot metal pretreatment, converter smelting, and RH refining.

[0026] In the above solutions, the less the inevitable impurities in the steel, the better, as far as technical conditions and production costs permit. If the S content exceeds 0.002%, the number of S-containing inclusions will increase significantly, which will hinder the grain growth of the finished steel sheet and deteriorate the electromagnetic performance of the finished steel sheet.

[0027] The non-oriented electrical steel sheet according to the present disclosure preferably contains C and / or N-containing inclusions, which are mainly composed of AlN, VN, VC, and V(CN).

[0028] In the present disclosure, the design of chemical elements according to the present disclosure is adopted, and smelting is performed under suitable smelting conditions, so that inclusions containing C and N can be obtained. The inclusions containing C and N in the steel are large in size and few in number, and the main inclusions are AlN, VN, VC, and V(CN), and also contain small amounts of TiC, TiN, Ti(CN), NbC, NbN, and Nb(CN).

[0029] In the non-oriented electrical steel sheet according to the present disclosure, the size of the C- and N-containing inclusions is preferably 200 to 500 nm.

[0030] In the non-oriented electrical steel sheet according to the present disclosure, the inclusions are preferably controlled to satisfy the following formula: 1.5≦AlN content / (VN content+VC content+V(CN) content)≦4.0. Such control is beneficial for grain growth of the steel sheet and reduction of iron loss during annealing.

[0031] In the non-oriented electrical steel sheet according to the present disclosure, the iron loss P 15 / 50 ≦3.2W / kg, magnetic flux density B 50 It is preferable that ≧1.75T.

[0032] Therefore, another object of the present disclosure is to provide a simple and feasible method for manufacturing the non-oriented electrical steel sheet having good magnetic properties. By adopting this manufacturing method, good magnetic properties (iron loss P 15 / 50 ≦3.2W / kg, magnetic flux density B 50 ≧1.75T) can be obtained.

[0033] In order to achieve the above object, the present disclosure provides a method for producing a non-oriented electrical steel sheet having good magnetic performance, comprising: (1) The process of smelting and casting molten steel to obtain slabs; (2) hot rolling the slab to obtain a steel coil, in which the hot-rolled steel coil is directly fed to the next process without being subjected to normalizing annealing or cover annealing; (3) pickling to obtain pickled steel sheet; (4) cold rolling the pickled steel sheet to obtain a cold-rolled steel sheet; and (5) A step of continuous annealing, in which the cold-rolled steel sheet is heated to a target soaking temperature at a heating rate of 80 to 1000° C. / sec. The present invention provides a method having the following structure:

[0034] In the present disclosure, the inventors have optimized the chemical composition of the steel, intentionally added V element to the steel, and strictly limited the content of harmful elements C and N in the steel, thereby effectively suppressing harmful C- and N-containing inclusions in the steel. At the same time, due to the need to suppress harmful inclusions in the steel, the inventors have also prescribed a reasonable manufacturing process. The qualified slab obtained by smelting and casting is pickled and cold rolled once to a target thickness without performing normalizing annealing or cover annealing after hot rolling, and then continuously annealed. Here, the continuous annealing can be performed in an electromagnetic induction device equipped with a rapid heating function. This makes it possible to obtain a non-oriented electrical steel sheet with good magnetic performance that meets the design requirements of the present disclosure. In the present disclosure, there are no special restrictions on hot rolling, pickling, and cold rolling, and the principle is that the manufacturing cost and production difficulty of the steel will not increase.

[0035] In addition, it should be noted that in the prior art, there are technical solutions that do not require normalizing annealing or cover annealing, but most of these steels are high silicon steels with a high Si content. Unlike the prior art, the steels of the present disclosure have a Si content of only 0.2-1.6%, making them medium to low Si steels. Although medium to low silicon steels are used in the present disclosure, the above-mentioned normalizing annealing and cover annealing processes are not required.

[0036] In step (5) of the manufacturing method according to the present disclosure, an electromagnetic induction device having a rapid heating function is used. This device is not limited to a vertical magnetic field or a horizontal magnetic field, but the heating capacity needs to meet the requirement of rapidly heating the cold-rolled steel sheet to a target soaking temperature at a heating rate of 80 to 1000°C / s.

[0037] Compared with conventional annealing methods using gas heating or electric heating (generally less than 30°C / sec), the present disclosure employs an electromagnetic induction heating device with a rapid heating function for continuous annealing, thereby enabling the cold-rolled steel sheet to be rapidly heated to a target soaking temperature in a short time. The temperature at which heating is started is not particularly limited as long as it is equal to or lower than the soaking temperature, and for example, heating may be started from room temperature. By adopting this annealing method, it is possible to effectively suppress the recovery of the cold-rolled steel sheet during continuous annealing, and to significantly increase the accumulated deformation energy remaining in the cold-rolled steel sheet before recrystallization, thereby accumulating and increasing the driving force for nucleation, and facilitating the nucleation and migration of high-angle grain boundaries. At the same time, it also reduces the preferred orientation of crystal nuclei, ultimately <111> / / The strength of the ND recrystallized texture components can be reduced, resulting in higher magnetic flux density and lower core loss.

[0038] In addition, during the rapid heating annealing of the cold-rolled steel sheet, the heating rate of the cold-rolled steel sheet must be limited to 80-1000°C / s, preferably 150-850°C / s, more preferably 250-750°C / s. This can further increase the driving force for generating and growing nuclei, improve and control the final recrystallization effect, make the grain structure after continuous annealing coarse and uniform, and reduce the proportion of harmful crystal orientation. If the heating rate of the rapid heating is too slow (heating rate is less than 80°C / s), the accumulated deformation energy of cold rolling is released too quickly and cannot be utilized for subsequent good texture control. If the rapid heating rate is too fast (heating rate is 1000°C / s or more), the requirements for equipment capacity are too high, resulting in high equipment costs, and the cold-rolled steel strip stays in the high temperature stage for too long, resulting in a decrease in the uniformity of the crystal grain structure.

[0039] In the production method of the present disclosure, the target soaking temperature in step (5) is preferably 800 to 1000°C.

[0040] In the manufacturing method of the present disclosure, in the casting step (1), it is preferable to control the superheat of the molten steel to 10 to 35° C. and the solid-liquid transition time to 10 seconds to 120 minutes. As the casting of the molten steel progresses, the temperature of the casting falls within the range of 900 to 1150° C., and the slab is cooled at a rate of 10° C. / min or less.

[0041] In the above technical solution of the present disclosure, in order to realize the effect of favorable precipitation of V carbides and nitrides during the casting process, it may be preferable to control the superheat of the molten steel within the range of 10 to 35°C and adjust the solid-liquid transition time within the range of 10 seconds to 120 minutes.

[0042] Furthermore, from the viewpoint of production efficiency and the effect of controlling the size of inclusions, the solid-liquid phase transition time is more preferably controlled within the range of 20 seconds to 50 minutes, even more preferably within the range of 2 minutes to 50 minutes, and even more preferably within the range of 10 minutes to 50 minutes. As a premise, during the casting and solidification of the molten steel, the temperature of the casting is within the range of 900 to 1150°C, and the slab is cooled at a rate of 10°C / min or less.

[0043] In the manufacturing method of the present disclosure, during the hot rolling in step (2), it is preferable to control the residence time of the slab in the furnace to 120 to 360 minutes, the initial rolling temperature to 1050 to 1150°C, the final rolling temperature to 650 to 950°C, and the coiling temperature to 500 to 900°C.

[0044] In the manufacturing method of the present disclosure, it is preferable to control the target thickness of the hot rolled steel sheet to 0.8 to 3.5 mm in step (2), and to obtain the target cold rolled thickness by a single cold rolling in step (4).

[0045] Compared with the prior art, the non-oriented electrical steel sheet with good magnetic performance and the manufacturing method thereof according to the present disclosure have the following advantages and beneficial effects:

[0046] Unlike conventional thinking, in the steelmaking process disclosed herein, V is considered to be a beneficial element, and the V content is consciously adjusted.

[0047] In the non-oriented electrical steel sheet according to the present disclosure, the inventors have adopted an optimized design for the ratio of chemical element components. The slab produced by smelting and casting does not need to be subjected to normalizing annealing or cover annealing after hot rolling, but can be pickled and cold rolled directly, followed by rapid heating, so that the cold rolled steel sheet can be rapidly heated to the target soaking temperature at a high heating rate, thereby obtaining the electromagnetic performance required by the design of the present disclosure.

[0048] The design concept of the chemical elements in the present disclosure is completely different from that of the prior art. In addition, the manufacturing method of the present disclosure is simple and feasible. The manufactured non-oriented electrical steel sheet has the characteristics of high magnetic flux density and low iron loss, and the iron loss P 15 / 50 is 3.2W / kg or less, magnetic flux density B 50 Since the non-oriented electrical steel sheet can be effectively used to manufacture iron cores, it is expected to be widely used and has high application value. [Brief description of the drawings]

[0049] [Figure 1] 1 is a photograph showing the microstructure of the finished non-oriented electrical steel sheet in Example 5. [Diagram 2] 1 is a photograph showing the microstructure of a comparative steel sheet in Comparative Example 3. [Diagram 3] FIG. 2 is a diagram showing a schematic diagram of the relationship between the average size of carbide inclusions and nitride inclusions and core loss in a finished non-oriented electrical steel sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The non-oriented electrical steel sheet having good magnetic properties and the manufacturing method thereof according to the present disclosure will be further described and illustrated with reference to the accompanying drawings and specific examples, however, these descriptions and illustrations are not intended to unduly limit the technical solutions of the present disclosure.

[0051] (Examples 1 to 10 and Comparative Examples 1 to 3) The mass percentages of the chemical elements in the non-oriented electrical steel sheets of Examples 1 to 10 and the comparative steel sheets of Comparative Examples 1 to 3 are listed in Table 1.

[0052] [Table 1]

[0053] In the present disclosure, the non-oriented electrical steel sheets of Examples 1 to 10 and the comparative steel sheets of Comparative Examples 1 to 3 were all produced through the following steps (1) to (5).

[0054] (1) Smelting and casting were performed according to the chemical composition ratios shown in Table 1. During casting, the superheat of the molten steel was controlled to 10 to 35°C, the solid-liquid phase transition time was controlled to 10 seconds to 120 minutes, and the cooling rate of the slab accompanying the progress of casting of the molten steel was controlled to 10°C / min or less within the range of 900 to 1150°C.

[0055] (2) Hot rolling: During hot rolling, the residence time of the slab in the furnace was controlled to 120-360 minutes, the initial rolling temperature was controlled to 1050-1150°C, the final rolling was performed in 2-8 passes, the final rolling temperature was controlled to 650-950°C, and the coiling temperature was controlled to 500-900°C. The steel coils after hot rolling were not subjected to normalizing annealing or cover annealing, and were directly fed to the next process.

[0056] (3) Pickling was performed to obtain pickled steel sheets.

[0057] (4) Cold rolling of pickled steel sheet: The pickled steel sheet was cold rolled once to a target cold rolled thickness of 0.50 mm.

[0058] (5) Continuous annealing: The cold-rolled steel sheet was rapidly heated to a target soaking temperature of 800 to 1000°C at a heating rate of 80 to 1000°C / s.

[0059] In the present disclosure, the chemical compositions and related process parameters of the non-oriented electrical steel sheets of Examples 1 to 10 all satisfy the control requirements of the design specifications of the present disclosure. On the other hand, in Comparative Examples 1 to 3, there are chemical compositions and process parameters that do not satisfy the design requirements of the present disclosure.

[0060] Table 2 lists specific process parameters for the non-oriented electrical steel sheets of Examples 1 to 10 and the comparative steel sheets of Comparative Examples 1 to 3.

[0061] [Table 2]

[0062] The finally produced finished non-oriented electrical steel sheets of Examples 1 to 10 and the comparative steel sheets of Comparative Examples 1 to 3 were sampled, and the steel sheet samples of Examples 1 to 10 and Comparative Examples 1 to 3 were observed and analyzed. It was found that both the steels of the Examples and the steels of the Comparative Examples contained C- and N-containing inclusions, which were mainly AlN, VN, VC, and V(CN) inclusions, and also contained small amounts of TiC, TiN, Ti(CN), NbC, NbN, and Nb(CN) produced from Nb and Ti.

[0063] Further analysis and testing were performed to obtain the size of C- and N-containing inclusions and the ratio of AlN content / (VN content+VC content+V(CN) content) for each of the example steel sheets and the comparative steel sheets. The relevant observations and analysis results are listed in Table 3 below.

[0064] [Table 3]

[0065] Therefore, after the observation and analysis of the above inclusions were completed, the finally produced non-oriented electrical steel sheets of Examples 1 to 10 and the comparative steel sheets of Comparative Examples 1 to 3 were sampled again, and the magnetic flux density B 50 and iron loss P 15 / 50 The test results obtained are listed in Table 4 below.

[0066] The relevant performance test methods are as follows:

[0067] Magnetic flux density B 50Test: The iron loss performance was tested by the Epstein frame method according to the Chinese national standard GB / T3655-2008. The test temperature was a constant temperature of 20°C, the sample size was 30 mm x 300 mm, and the target mass was 0.5 kg. The test parameters were the magnetic flux density B 50 It was decided.

[0068] Iron loss P 15 / 50 Test: The iron loss performance was tested by the Epstein frame method according to the Chinese national standard GB / T3655-2008. The test temperature was a constant temperature of 20°C, the sample size was 30mm x 300mm, and the target mass was 0.5kg. The test parameters were the iron loss P 15 / 50 It was decided.

[0069] The magnetic flux density B 50 and iron loss P 15 / 50 The results are listed in Table 4.

[0070] [Table 4]

[0071] As shown in Table 4 above, in the present disclosure, the non-oriented electrical steel sheets of Examples 1 to 10 have a magnetic flux density B 50 is in the range of 1.75 to 1.79 T, and the iron loss P 15 / 50 is in the range of 2.72 to 3.18 W / kg. The non-oriented electrical steel sheets of Examples 1 to 10 have significantly better magnetic performance than the comparative steel sheets of Comparative Examples 1 to 3. Comparative Examples 1 to 3 do not meet the conditions defined in the technical solution of the present disclosure, and therefore Comparative Examples 1 to 3 have inferior implementation effects to Examples 1 to 10.

[0072] Referring to Tables 1 to 4, in the case of Comparative Example 1, the V content is 0.0004%, which is lower than the design lower limit of 0.001% in the present disclosure, and the S content is 0.0027%, which is higher than the design upper limit of 0.002% in the present disclosure. Correspondingly, the average size of the carbide inclusions and nitride inclusions in the steel is 84 nm, which is smaller than the design lower limit of 200 nm in the present disclosure, and B * is 0.8, which is lower than the lower design limit of 1.5 in the present disclosure. Furthermore, since Comparative Example 1 simply adopts a conventional heating rate of 15° C. / sec for continuous annealing, the electromagnetic performance of the finished comparative steel sheet in Comparative Example 1 is not good, and the iron loss P 15 / 50 is 3.16W / kg, magnetic flux density B 50 is 1.73T. Magnetic flux density B 50 is below the design requirements of this disclosure.

[0073] On the other hand, in the case of Comparative Example 2, the Al content is 0.0025%, which is lower than the design lower limit of 0.2% in the present disclosure, and the N content is 0.0067%, which is higher than the design upper limit of 0.0045% in the present disclosure. Correspondingly, the average size of the carbide inclusions and nitride inclusions in the steel is 117 nm, which is smaller than the design lower limit of 200 nm in the present disclosure, and B * is 1.3, which is lower than the lower design limit of 1.5 in the present disclosure. Meanwhile, the degree of superheat of the molten steel during casting is 40°C, which exceeds the upper design limit of 35°C in the present disclosure. Also, the slab temperature when the cooling rate of the slab is limited is as high as 1350°C, which exceeds the upper design limit of 1150°C in the present disclosure. Furthermore, since Comparative Example 2 simply adopts a conventional heating rate of 15°C / sec for continuous annealing, the electromagnetic performance of the finished comparative steel sheet in Comparative Example 2 is not good, and the iron loss P 15 / 50 is 3.41W / kg, magnetic flux density B 50 is 1.71T. Iron loss P 15 / 50 and magnetic flux density B 50 Both are below the design requirements of this disclosure.

[0074] On the other hand, in the case of Comparative Example 3, the Mn content is 0.65%, which is higher than the design upper limit of 0.6% in the present disclosure, the S content is 0.0042%, which is higher than the design upper limit of 0.002% in the present disclosure, and the V content is 0.0008%, which is lower than the design lower limit of 0.001% in the present disclosure. Correspondingly, the average size of the carbide inclusions and nitride inclusions in the steel is 52 nm, which is lower than the design lower limit of 200 nm in the present disclosure, and B * is 0.2, which is lower than the lower design limit of 1.5 in the present disclosure. Furthermore, in Comparative Example 3, the slab temperature when the cooling rate of the slab is limited is 750°C, which is lower than the lower design limit of 900°C in the present disclosure. Therefore, the electromagnetic performance of the finished comparative steel sheet in Comparative Example 3 is not good, and the iron loss P 15 / 50 is 4.54W / kg, magnetic flux density B 50 is 1.70T. Iron loss P 15 / 50 and magnetic flux density B 50 Both are below the design requirements of this disclosure.

[0075] FIG. 1 is a photograph showing the microstructure of the finished non-oriented electrical steel sheet in Example 5.

[0076] As shown in FIG. 1, in the embodiment of Example 5, the microstructure of the non-oriented electrical steel sheet is completely recrystallized, and the recrystallized grains are all relatively symmetric equiaxed grains, and the grain size is large and developed.

[0077] FIG. 2 is a photograph showing the microstructure of the comparative steel sheet in Comparative Example 3.

[0078] As shown in Figure 2, in the embodiment of Comparative Example 3, the microstructure of the comparative steel is completely recrystallized, but the recrystallized grains have a small proportion of equiaxed grains, are small in size, and are relatively dispersed in grain size. Among them, the large grains are abnormally grown "island-like grains."

[0079] FIG. 3 is a diagram that illustrates the relationship between the average size of carbide inclusions and nitride inclusions and core loss in a finished non-oriented electrical steel sheet.

[0080] 3, as the average size of the carbide and nitride inclusions in the steel increases, the iron loss of the finished non-oriented electrical steel sheet gradually decreases and remains stable in the range of 200 nm to 500 nm, satisfying the control requirement of the upper design limit of 3.2 W / kg disclosed in the present disclosure. On the other hand, when the size exceeds 500 nm, as the average size of the carbide and nitride inclusions in the steel increases, the iron loss of the finished non-oriented electrical steel sheet increases, and the iron loss control requirement designed in the present invention cannot be satisfied.

[0081] It should be noted that the combinations of features of the present disclosure are not limited to the combinations set forth in the claims or in specific embodiments, but rather that any of the features of the present disclosure can be freely combined or combined in any manner as long as they are not mutually inconsistent.

[0082] It should also be noted that the above listed embodiments are merely specific examples of the present disclosure. It is obvious that the present disclosure is not limited to the above embodiments, and any similar variations or modifications that can be directly derived or easily substituted by those skilled in the art from the present disclosure are included in the scope of protection of the claims of the present invention.

Claims

1. In addition to Fe and unavoidable impurities, the following chemical elements, in mass percent: 0<C≦0.0025%, Si: 0.2-1.6%, Mn: 0.2-0.6%, Al: 0.2-0.6%, V: 0.001-0.008%, N: 0.002-0.0045%, 0<Nb≦0.003%, 0<Ti≦0.003% Non-oriented electrical steel sheets including.

2. The following chemical elements in mass percent: 0<C≦0.0025%, Si: 0.2-1.6%, Mn: 0.2-0.6%, Al: 0.2-0.6%, V: 0.001-0.008%, N: 0.002-0.0045%, 0<Nb≦0.003%, 0<Ti≦0.003% The non-oriented electrical steel sheet according to claim 1, comprising:

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the mass percentage of V is 0.0015 to 0.0045%.

4. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the unavoidable impurities include S≦0.002%.

5. 3. The non-oriented electrical steel sheet according to claim 1 or 2, comprising C- and / or N-containing inclusions, the C- and / or N-containing inclusions being mainly composed of AlN, VN, VC, and V(CN).

6. The non-oriented electrical steel sheet according to claim 5, wherein the size of the C and / or N-containing inclusions is 200 to 500 nm.

7. The inclusions have the following formula: 1.5≦AlN content / (VN content+VC content+V(CN) content)≦4.0 The non-oriented electrical steel sheet according to claim 5 , which satisfies the above.

8. Iron loss P １５／５０ is 3.2 W / kg or less, and the magnetic flux density B ５０ The non-oriented electrical steel sheet according to claim 1 or 2, wherein the strain is 1.75T or more.

9. A method for producing the non-oriented electrical steel sheet according to any one of claims 1 to 8, comprising the following steps: (1) smelting and casting molten steel to obtain slabs; (2) A process of hot rolling the slab to obtain a steel coil, in which the hot-rolled steel coil is directly fed to the next process without being subjected to normalizing annealing or cover annealing; (3) A step of obtaining a pickled steel sheet by pickling; (4) cold rolling the pickled steel sheet to obtain a cold-rolled steel sheet; and (5) A step of performing continuous annealing, in which the cold-rolled steel sheet is heated to a target soaking temperature at a heating rate of 80 to 1000 ° C. / sec.; The method according to claim 1,

10. The following conditions: In step (5), the target soaking temperature is 800 to 1000° C.; In the casting process of step (1), the molten steel has a superheat of 10-35°C, a solid-liquid transition time of 10 seconds to 120 minutes, a casting temperature in the range of 900-1150°C, and the slab is cooled at a rate of 10°C / min or less; In step (2), during the hot rolling, the slab is retained in the furnace for 120 to 360 minutes, the initial rolling temperature is 1050 to 1150°C, the final rolling temperature is 650 to 950°C, and the coiling temperature is 500 to 900°C; In step (2), the target thickness of the hot-rolled steel plate is 0.8 to 3.5 mm; and / or In step (4), the pickled steel sheet is cold-rolled to a target cold-rolling thickness in one go; The method according to claim 9 , wherein at least one of the following is satisfied:

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