A non-oriented electrical steel sheet with excellent magnetic properties and a method for manufacturing the same

Abstract

The invention discloses a non-oriented electrical steel sheet with excellent magnetic properties, which contains Fe and inevitable impurities, and further contains the following chemical elements in the following mass percentages: 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%. In addition, the present invention also discloses a method for manufacturing the above-mentioned non-oriented electrical steel sheet with excellent magnetic properties, which comprises the following steps: (1) smelting and casting; (2) hot rolling, the steel coil after hot rolling is directly subjected to the next step without normalizing annealing or bell furnace annealing; (3) pickling; (4) cold rolling; (5) finished product annealing: from room temperature, the cold-rolled steel sheet is rapidly heated to the target soaking temperature at a heating rate of 80 to 1000°C / s. The non-oriented electrical steel sheet of the present invention has excellent electromagnetic properties, low iron loss and high magnetic induction, can be effectively used to make iron cores, and has good promotion prospects and application value.

Description

Technical Field

[0001] The present invention relates to a steel plate and a method for manufacturing the same, and in particular to a non-oriented electrical steel plate and a method for manufacturing the same. Background Art

[0002] For a long time, the goal pursued by the market and users for the iron cores of various electrical appliances, power tools and other products has been energy saving and consumption reduction. That is, the raw material of the iron core, the non-oriented electrical steel sheet, is required to have corresponding high magnetic induction and low iron loss characteristics.

[0003] Studies have shown that in order to obtain non-oriented electrical steel sheets with good electromagnetic properties, it is necessary to properly control the chemical composition of the steel and improve the grain size and favorable texture of the finished steel sheets.

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

[0005] For example, a Chinese patent document entitled "Non-oriented electrical steel sheet with excellent magnetic properties" with a publication number of 2008-260980 and a publication date of October 30, 2008 discloses a non-oriented electromagnetic steel sheet. In the technical solution disclosed in the patent document, the grain size and crystal texture of the hot-rolled sheet are improved by increasing the temperature of the hot-rolled slab out of the furnace, generally about 1230-1320°C, so that the surface state of the finished steel sheet is good and the magnetic induction is very high. However, in order to avoid the fact that non-metallic inclusions such as S and N will be fully dissolved and dispersed during the heating and rolling of the slab after the temperature of the slab is increased, thereby deteriorating the iron loss of the finished steel sheet, the technology also adopts the method of adding 0.005-0.03% calcium-containing alloy or rare earth to purify the molten steel, and strictly requires that the content of S and N must be less than 0.0015%. This design scheme not only increases the difficulty of smelting control, but also increases the production cost, and requires special slab heating equipment, which is not suitable for popularization and application.

[0006] Another example: A Chinese patent document with publication number CN101343683A, publication date January 14, 2009, and titled "A method for manufacturing low iron loss and high magnetic induction non-oriented electrical steel" discloses a method for manufacturing low iron loss and high magnetic induction non-oriented electrical steel. In the technical solution disclosed in the patent document, the process steps are: controlling the heating temperature of the ingot to 900-1150°C, cold rolling the hot-rolled plate to 0.50mm after regular pickling, and finally performing stress relief annealing in a hydrogen-nitrogen mixed gas to obtain a low iron loss and high magnetic induction non-oriented electrical steel product. Its advantage is that the non-oriented electrical steel product has excellent final magnetic properties, P 15 / 50 =3.1~3.8W / kg, B 5000=1.69~1.81T, and the ingot contains 1.0~2.0% Si, 0~0.60% Al, and 1.5%≤Si+3Al≤3.2%, and does not contain alloy elements such as Sn, Sb, Bi, Cu, Cr, Ni, B, Ca, Ce, etc. The production cost is greatly reduced, and the finished non-oriented electrical steel with excellent magnetic properties is produced.

[0007] Another example: A Chinese patent document with publication number CN104073715A, publication date October 1, 2014, and titled "A high magnetic induction non-oriented electrical steel and its manufacturing method" discloses a high magnetic induction non-oriented electrical steel. In the technical solution disclosed in the patent document, by controlling the heating rate of the normalizing heating section, controlling the speed of the normalizing cooling section, and adopting a suitable shot blasting and pickling process system, a raw material with excellent plate surface quality is provided for the subsequent process, and the magnetic induction B can be increased without adding additional alloy elements or changing the finished product annealing process. 50 The magnetic properties of the product can be further improved by optimizing the annealing process, and the magnetic induction can be further improved. The high magnetic induction non-oriented electrical steel can meet the requirements of conventional motors, and can also meet the requirements of high magnetic induction of electrical steel for high-efficiency and variable frequency motor cores, improve motor efficiency, and reduce product energy consumption and noise.

[0008] However, different from the above-mentioned existing technical solutions, the inventors adopted a new design idea and hoped to obtain a new non-oriented electrical steel sheet with excellent magnetic properties. The chemical composition of the steel was optimized and a reasonable manufacturing process was defined, which can effectively improve the electromagnetic properties of the non-oriented electrical steel sheet, reduce iron loss and increase magnetic induction. Summary of the invention

[0009] One of the objects of the present invention is to provide a non-oriented electrical steel sheet with excellent magnetic properties. The non-oriented electrical steel sheet has excellent electromagnetic properties and its iron loss P 15 / 50 ≤3.2W / kg, magnetic induction B 50 ≥1.75T, can be effectively used to prepare iron cores, and used in various electrical appliances and power tools, it has very good promotion prospects and application value.

[0010] In order to achieve the above object, the present invention provides a non-oriented electrical steel sheet with excellent magnetic properties, which contains Fe and inevitable impurities, and further contains the following chemical elements in the following mass percentages:

[0011] 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%.

[0012] Furthermore, in the non-oriented electrical steel sheet of the present invention, the mass percentage of each chemical element is:

[0013] 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 balance is Fe and unavoidable impurities.

[0014] In the non-oriented electrical steel sheet of the present invention, the design principles of each chemical element are as follows:

[0015] C: In the non-oriented electrical steel sheet of the present invention, the C content in the steel should not be too high. When the C content in the steel is higher than 0.0025%, more C-containing inclusions will be formed, which will lead to a significant increase in the magnetic aging of the finished steel sheet. Based on this, in the non-oriented electrical steel sheet of the present invention, the mass percentage of the C element is controlled to be 0<C≤0.0025%.

[0016] Si: In the non-oriented electrical steel sheet of the present invention, the Si content is medium-low. For the present technical solution, when the Si content is higher than 1.6%, it will not only increase the manufacturing cost of the steel, but also significantly reduce the magnetic induction of the finished steel sheet; and when the Si content is lower than 0.2%, it will not effectively reduce the iron loss. Based on this, in the non-oriented electrical steel sheet of the present invention, the mass percentage of the Si element is controlled between 0.2% and 1.6%.

[0017] Mn: In the non-oriented electrical steel sheet of the present invention, when the added Mn element content is higher than 0.6%, the favorable texture of the finished non-oriented electrical steel sheet will be significantly deteriorated; and when the Mn element content in the steel is lower than 0.2%, the control effect of S-containing inclusions cannot be achieved. Based on this, considering the influence of the Mn element content on the properties of steel, in the non-oriented electrical steel sheet of the present invention, the mass percentage of the Mn element is controlled between 0.2% and 0.6%.

[0018] Al: In the non-oriented electrical steel sheet of the present invention, when the Al content is higher than 0.6%, the castability of the molten steel will be significantly reduced; and when the Al content in the steel is lower than 0.2%, the iron loss cannot be effectively reduced. Based on this, in order to ensure that the Al element can play its beneficial effect, in the non-oriented electrical steel sheet of the present invention, the mass percentage of the Al element is controlled between 0.2% and 0.6%.

[0019] V: In the prior art, the V element introduced into the steelmaking process of non-oriented electrical steel is strictly controlled as an impurity element, and it is hoped that its content is as low as possible. Different from this, the present invention takes the V element as a beneficial element during the steelmaking process and consciously adjusts the content of the V element; from the previous method of reducing the V content as much as possible to reduce the content of harmful inclusions as much as possible, it is adjusted to consciously adding a certain amount of V content, and combined with the production process adjustment, by controlling the type and quantity of N-containing inclusions, the harmless treatment of Nb, V, and Ti content is achieved to the maximum extent. In this way, the chemical composition matching and combination that is beneficial to obtaining excellent magnetic properties, as well as the prerequisite for reasonable inclusion type control, are achieved.

[0020] In the non-oriented electrical steel sheet of the present invention, when the V content in the steel is lower than 0.001%, the control effect of C and N type inclusions cannot be achieved. However, it should be noted that the addition amount of V in the steel should not be too much. When the V content in the steel is higher than 0.008%, the number of C and N type inclusions containing V will increase significantly, and their size will be small. Based on this, in the non-oriented electrical steel sheet of the present invention, the mass percentage of V is controlled between 0.001 and 0.008%.

[0021] N: In the non-oriented electrical steel sheet of the present invention, when the N content is lower than 0.002%, it is not possible to achieve a reasonable control effect of C and N inclusions. However, it should be noted that the N content in the steel should not be too high. When the N content in the steel exceeds 0.0045%, the number of N inclusions will increase significantly, inhibiting the growth of the grain size of the finished steel sheet and deteriorating the electromagnetic properties of the finished steel sheet. Based on this, in the non-oriented electrical steel sheet of the present invention, the mass percentage of the N element is controlled between 0.002 and 0.0045%.

[0022] Meanwhile, it should be noted that, in the present invention, considering the difficulty of obtaining a lower N content, and the fact that under the condition of 0.2-0.6% Al content, it is easy to generate a large number of small AlN inclusions, the inventors choose to add 0.002-0.0045% N element to the steel, and add 0.001-0.008% V element in combination. Here, the main reason for adding V as a beneficial element is that the C and N compounds of V element have a much lower deterioration effect on the electromagnetic properties of the finished steel plate than the C and N compounds of Al, Nb, Ti, etc.; in addition, the C and N compounds of V element are relatively stable.

[0023] Nb: In the present technical solution, when the Nb content is higher than 0.003%, the C and N inclusions in the steel will increase abnormally, which will lead to a significant increase in the iron loss of the finished steel plate. Therefore, in the present invention, the Nb content is controlled to satisfy: 0<Nb≤0.003%.

[0024] Ti: In the present technical solution, when the Ti content is higher than 0.003%, it will also cause an abnormal increase in C and N inclusions in the steel, thereby causing a significant increase in the iron loss of the finished steel plate. Therefore, in the present invention, the Ti content is controlled to satisfy: 0<Ti≤0.003%.

[0025] Furthermore, in the non-oriented electrical steel sheet of the present invention, the mass percentage content of V element is 0.0015-0.0045%.

[0026] Furthermore, in the non-oriented electrical steel sheet of the present invention, among the inevitable impurities, S≤0.002%.

[0027] Different from the common design ideas in the past, in addition to strictly controlling the C content to reduce the generation of C-containing inclusions, the present invention also needs to strictly control the S content. This is because the higher the S content in the steel, the more S-containing inclusions will be generated at the end of the solidification of the molten steel or the end of the hot rolling, and the size of the S-containing inclusions is small, and their deterioration effect on the electromagnetic properties of the steel is much greater than that of the N-containing inclusions. However, it should be noted that the control difficulty of the S element is much lower than that of the N element; in order to obtain a lower S content, there are many technical means that can be selected in the actual operation process, such as: limiting the S content of raw and auxiliary materials for ironmaking and steelmaking, and deep desulfurization by adding desulfurizers in the molten iron pretreatment, converter smelting, and RH refining.

[0028] In the above scheme, under the premise of technical conditions and production costs, the inevitable impurities in the steel should be controlled as little as possible. Among them, when the S content is higher than 0.002%, the number of S-containing inclusions increases significantly, inhibiting the growth of the grain size of the finished steel plate and deteriorating the electromagnetic properties of the finished steel plate.

[0029] Furthermore, in the non-oriented electrical steel sheet of the present invention, the inclusions are inclusions containing C and N, and the main bodies of the inclusions are AlN, VN, VC, and V(CN).

[0030] In the present invention, by adopting the chemical element design of the present invention and carrying out smelting under appropriate smelting conditions, inclusions containing C and N can be obtained. The C and N inclusions in the steel are large in size and small in number. The main inclusions are AlN, VN, VC, and V(CN), and the inclusions contain a small amount of TiC, TiN, Ti(CN) and NbC, NbN, and Nb(CN).

[0031] Furthermore, in the non-oriented electrical steel sheet of the present invention, the size of inclusions containing C and N is 200-500 nm.

[0032] Furthermore, in the non-oriented electrical steel sheet of the present invention, 1.5≤AlN content / (VN content+VC content+V(CN) content)≤4.0 is satisfied. Such control is beneficial to the grain growth and iron loss reduction of the steel sheet during annealing.

[0033] Furthermore, in the non-oriented electrical steel sheet of the present invention, the iron loss P 15 / 50 ≤3.2W / kg, magnetic induction B 50 ≥1.75T.

[0034] Accordingly, another object of the present invention is to provide a method for manufacturing the above non-oriented electrical steel sheet with excellent magnetic properties, which is simple and feasible, and can obtain a non-oriented electrical steel sheet with excellent magnetic properties, and its iron loss P 15 / 50 ≤3.2W / kg, magnetic induction B 50 ≥1.75T.

[0035] In order to achieve the above-mentioned object of the invention, the present invention provides a method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties, which comprises the following steps:

[0036] (1) Smelting and casting;

[0037] (2) Hot rolling: the steel coil after hot rolling is directly subjected to the next step without normalizing annealing or bell furnace annealing;

[0038] (3) Pickling;

[0039] (4) Cold rolling;

[0040] (5) Finished product annealing: The cold-rolled steel sheet is rapidly heated to the target soaking temperature at a heating rate of 80 to 1000°C / s.

[0041] In the present invention, the inventor optimizes the chemical composition design of the steel, specifically adds V element to the steel, and strictly limits the content of harmful elements C and N in the steel, so as to effectively control harmful inclusions containing C and N in the steel. At the same time, according to the control requirements of harmful inclusions in the steel, the inventor also defines a reasonable manufacturing process, wherein the qualified ingot obtained by smelting and casting is not subjected to normalizing annealing or bell furnace annealing after hot rolling, and can be directly pickled and cold rolled to the target thickness once, and can be continuously annealed in an electromagnetic induction device with a rapid heating function, so as to obtain the non-oriented electrical steel sheet with excellent magnetic properties that the design requirements of the present invention meet. Among them, in the present invention, there are no special restrictions on the hot rolling, pickling and cold rolling links, and the principle is to increase the manufacturing cost and production difficulty of the steel as much as possible.

[0042] In addition, it should be noted that, in the prior art, although there are some technical solutions that do not require normalizing annealing or bell furnace annealing, these steels are mostly high-silicon steels with a high Si content. Unlike the prior art, the Si content in the steel of the present application is only between 0.2% and 1.6%, which is a medium-low silicon steel. Based on the medium-low silicon steel, it does not require the above-mentioned normalizing annealing or bell furnace annealing.

[0043] In step (5) of the above-mentioned manufacturing method of the present invention, the electromagnetic induction device with rapid heating function can be longitudinal magnetic or transverse magnetic, but its heating capacity needs to be sufficient to rapidly heat the cold-rolled steel plate to the target soaking temperature at a heating rate of 80 to 1000°C / s.

[0044] Compared with conventional annealing methods using gas and electric heating (generally less than 30°C / s), the present invention uses an electromagnetic induction heating device with a rapid heating and temperature rise function to perform finished product annealing, so as to achieve rapid heating of the cold-rolled steel sheet to the target soaking temperature in a shorter time. The starting temperature of the heating can be any temperature below the soaking temperature, such as heating from room temperature. This annealing method can effectively inhibit the recovery of the cold-rolled steel sheet during the continuous annealing process, and significantly increase the residual deformation energy storage of the cold-rolled steel sheet before recrystallization, thereby leading to the accumulation and increase of the nucleation driving force, and promoting nucleation and large-angle grain boundary migration. At the same time, it also reduces the preferred orientation of the crystal nucleus, which can ultimately reduce <111> / / ND recrystallization texture component strength, thus achieving higher magnetic induction and lower iron loss.

[0045] It should be noted that when the cold-rolled steel sheet is rapidly heated and annealed, the heating rate of the cold-rolled steel sheet needs to be limited to 80-1000℃ / s. The purpose is to further increase the driving force for nucleation and growth, so as to improve and control the final recrystallization effect and ensure that after the finished product annealing, the grain structure is coarse and uniform, and the proportion of harmful grain orientation is small. When the rapid heating heating rate is too slow, the heating rate is lower than 80℃ / s, the energy storage of cold rolling deformation is released too quickly, which is not conducive to the control of subsequent favorable texture; when the rapid heating heating rate is too fast, the heating rate is higher than 1000℃ / s, the equipment capacity requirements are too high, the cost is expensive, and the cold-rolled strip will stay in the high temperature stage for too long, resulting in poor uniformity of grain structure.

[0046] Furthermore, in the manufacturing method of the present invention, in step (5), the target soaking temperature is 800-1000°C.

[0047] Furthermore, in the manufacturing method described in the present invention, during the casting process of step (1), the superheat of the molten steel is controlled to be 10-35°C, the change time between the solid and liquid phases is controlled to be 10s-120min, and as the casting of the molten steel proceeds, the cooling rate of the ingot is controlled to be ≤10°C / min within the range of 900-1150°C.

[0048] In the above technical solution of the present invention, in order to ensure a good precipitation effect of C and N compounds of the V element, during the casting process, the superheat of the molten steel can be preferably controlled within the range of 10 to 35°C, and the change time between the solid and liquid phases can be adjusted within the range of 10s to 120min.

[0049] In addition, from the perspective of production efficiency and inclusion size control effect, the change time between the solid and liquid phases can be further preferably controlled within the range of 20s to 50min. The premise is that during the casting and solidification process of the molten steel, the cooling rate of the ingot is controlled within the range of 900 to 1150°C and is ≤10°C / min.

[0050] Furthermore, in the manufacturing method described in the present invention, in step (2), the time of the cast billet in the furnace is controlled to be 120 to 360 minutes during hot rolling, the starting 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.

[0051] Furthermore, in the manufacturing method described in the present invention, in step (2), the target thickness of the hot-rolled steel plate is controlled to be 0.8 to 3.5 mm; and in step (4), the steel plate is cold-rolled to the target thickness of the finished product in one step.

[0052] Compared with the prior art, the non-oriented electrical steel sheet with excellent magnetic properties and the manufacturing method thereof described in the present invention have the following advantages and beneficial effects:

[0053] Different from the traditional way of thinking, the present invention regards V element as a beneficial element and consciously adjusts the content of V element during the steelmaking process.

[0054] In the non-oriented electrical steel sheet described in the present invention, the inventors have adopted an optimized design for the chemical element composition ratio. After the continuous casting billet obtained by smelting and casting is hot-rolled, it does not need to be subjected to normalizing annealing or bell furnace annealing. After being directly pickled and cold-rolled, it is rapidly heated to ensure that the cold-rolled steel sheet is rapidly heated to the target soaking temperature at a higher heating rate, thereby obtaining the electromagnetic properties required by the design of the present invention.

[0055] The chemical element design concept of the present invention is completely different from the prior art, and the manufacturing method is simple and feasible. The non-oriented electrical steel sheet produced has the characteristics of high magnetic induction and low iron loss. 15 / 50 ≤3.2W / kg, magnetic induction B 50 ≥1.75T, can be effectively used to prepare iron core, and has good promotion prospects and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a microstructure photograph of the finished non-oriented electrical steel sheet of Example 5.

[0057] Figure 2 This is a microstructure photograph of the comparative steel plate of Comparative Example 3.

[0058] Figure 3 The relationship between the average size of C and N compound inclusions and the iron loss of the finished non-oriented electrical steel sheet is schematically shown. DETAILED DESCRIPTION

[0059] The non-oriented electrical steel sheet with excellent magnetic properties and the method for manufacturing the same according to the present invention will be further explained and illustrated below in conjunction with the accompanying drawings and specific embodiments of the specification. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0060] Examples 1-10 and Comparative Examples 1-3

[0061] Table 1 lists the mass percentages of various chemical elements in the non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3.

[0062] Table 1. (wt%, the balance is Fe and inevitable impurities other than S)

[0063]

[0064] In the present invention, the non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3 are prepared by the following steps (1) to (5):

[0065] (1) Smelting and casting are carried out according to the chemical composition ratio shown in Table 1: During the casting process, the superheat of the molten steel is controlled to be 10-35°C, and the change time between the solid and liquid phases is controlled to be 10s-120min. As the molten steel is cast, the cooling rate of the ingot is controlled to be ≤10°C / min in the range of 900-1150°C.

[0066] (2) Hot rolling: During hot rolling, the ingot furnace time is controlled to be 120-360 min, the start rolling temperature is controlled to be 1050-1150°C, and the final rolling is carried out in 2-8 passes. The final rolling temperature is controlled to be 650-950°C, and the coiling temperature is controlled to be 500-900°C. After hot rolling, the steel coil is directly subjected to the next step without normalizing annealing or bell furnace annealing.

[0067] (3) Pickling.

[0068] (4) Cold rolling: One-time cold rolling to the target thickness of the finished product is 0.50 mm.

[0069] (5) Finished product annealing: The cold-rolled steel sheet is rapidly heated to a target soaking temperature of 800 to 1000°C at a heating rate of 80 to 1000°C / s.

[0070] It should be noted that, in the present invention, the chemical composition and related process parameters of the non-oriented electrical steel sheets of Examples 1-10 all meet the control requirements of the design specifications of the present invention. However, in Comparative Examples 1-3, the control arrangements have chemical composition and process parameters that fail to meet the design requirements of the present invention.

[0071] Table 2 lists the specific process parameters of the non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3.

[0072] Table 2

[0073]

[0074] The non-oriented electrical steel sheets of the finally obtained finished products of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3 were sampled respectively, and the steel sheet samples of Examples 1-6 and Comparative Examples 1-3 were observed and analyzed. It was found that the steels of each Example and Comparative Example contained inclusions containing C and N, and the main inclusions were AlN, VN, VC, V(CN), and also contained a small amount of TiC, TiN, Ti(CN) and NbC, NbN, Nb(CN) generated by Nb and Ti elements.

[0075] Through further analysis and testing, the sizes of inclusions containing C and N in the steel plates of each embodiment and comparative example, as well as the proportion of AlN content / (VN content+VC content+V(CN) content) in the inclusions can be obtained respectively. The relevant observation and analysis results are listed in the following Table 3.

[0076] Table 3.

[0077] serial number A* B* Example 1 266nm 3.0 Example 2 459nm 3.3 Example 3 393nm 1.8 Example 4 496nm 1.5 Example 5 401nm 3.9 Example 6 308nm 2.2 Example 7 202nm 3.4 Example 8 475nm 2.9 Example 9 381nm 1.8 Example 10 284nm 4.0 Comparative Example 1 <![CDATA[ 84nm ]]> <![CDATA[ 0.8 ]]> Comparative Example 2 <![CDATA[ 117nm ]]> <![CDATA[ 1.3 ]]> Comparative Example 3 <![CDATA[ 52nm ]]> <![CDATA[ 0.2 ]]>

[0078] Note: In the above Table 3, A* represents the average size of inclusions containing C and N; B* represents AlN content / (VN content + VC content + V(CN) content).

[0079] Accordingly, after the above-mentioned observation and analysis of inclusions are completed, the non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3 finally obtained can be sampled again, and the magnetic induction B 50 and iron loss P 15 / 50 The test results are listed in Table 4 below.

[0080] The relevant performance testing methods are as follows:

[0081] Magnetic induction B 50 Test: Based on the national standard GB / T 3655-2008, the Epstein square circle method was used to test the iron loss performance. The test temperature was 20°C constant temperature test, the sample size was 30mm×300mm, the target mass was 0.5kg, and the test parameters were the magnetic induction B of the steel plates of each embodiment and the comparative example. 50 .

[0082] Iron loss P 15 / 50 Test: Based on the national standard GB / T 3655-2008, the Epstein square circle method was used to test the iron loss performance. The test temperature was 20°C constant temperature test, the sample size was 30mm×300mm, the target mass was 0.5kg, and the test parameters were the iron loss P of the steel plates in each embodiment and the comparative example. 15 / 50 .

[0083] Table 4 lists the magnetic induction B of the non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3. 50 and iron loss P 15 / 50 Test results.

[0084] Table 4.

[0085]

[0086] As shown in Table 4, in the present invention, the magnetic induction B of the non-oriented electrical steel sheets of Examples 1 to 10 is 50Between 1.75-1.79T, iron loss P 15 / 50 The magnetic properties of the steel plates are between 2.72-3.18 W / kg, which are significantly better than those of the comparative steel plates of comparative examples 1-3. Since comparative examples 1-3 do not meet the conditions specified in the technical solution, their implementation effects are inferior to those of embodiments 1-6 of the present case.

[0087] It can be seen from Tables 1 to 4 that in Comparative Example 1, the V content is 0.0004%, which exceeds the lower limit of the design requirement of the present invention by 0.001%; ​​the S content is 0.0027%, which exceeds the upper limit of the design requirement of the present invention by 0.002%. Correspondingly, the average size of C and N inclusions in the steel is 84nm, which exceeds the lower limit of the design requirement of the present invention by 200nm; B* is 0.8, which exceeds the lower limit of the design requirement of the present invention by 1.5. In addition, Comparative Example 1 only uses a conventional heating rate of 15℃ / s for finished product annealing. Therefore, the electromagnetic properties of the finished product of Comparative Example 1 are not good compared with the steel plate, and its iron loss P 15 / 50 3.16W / kg, magnetic induction B 50 is 1.73T. Among them, the magnetic induction B 50 Lower than the design requirements of the present invention.

[0088] In contrast, in Comparative Example 2, the Al content is 0.0025%, which exceeds the lower limit of the design requirement of the present invention by 0.2%; the N content is 0.0067%, which exceeds the upper limit of the design requirement of the present invention by 0.0045%. Correspondingly, the average size of C and N-oxide inclusions in the steel is 117nm, which exceeds the lower limit of the design requirement of the present invention by 200nm; B* is 1.3, which exceeds the lower limit of the design requirement of the present invention by 1.5. At the same time, the superheat of the molten steel during casting is 40°C, which exceeds the upper limit of the design requirement of the present invention by 35°C; and the temperature of the ingot when limiting the cooling rate of the ingot is as high as 1350°C, which exceeds the upper limit of the design requirement of the present invention by 1150°C. In addition, Comparative Example 2 only uses a conventional heating rate of 15°C / s for finished product annealing. Therefore, the electromagnetic properties of the finished product of Comparative Example 2 are poor compared to the steel plate, and its iron loss P 15 / 50 3.41W / kg, magnetic induction B 50 is 1.71T. Among them, the iron loss P 15 / 50 , magnetic induction B 50 All are lower than the design requirements of the present invention.

[0089] In contrast, in Comparative Example 3, the Mn element content is 0.65%, which exceeds the upper limit of the design requirement of the present invention by 0.6%; the S element content is 0.0042%, which exceeds the upper limit of the design requirement of the present invention by 0.002%; the V element content is 0.0008%, which exceeds the lower limit of the design requirement of the present invention by 0.001%. Correspondingly, the average size of C and N compound inclusions in the steel is 52nm, which exceeds the lower limit of the design requirement of the present invention by 200nm; B* is 0.2, which exceeds the lower limit of the design requirement of the present invention by 1.5. In addition, in Comparative Example 3, the casting temperature when limiting the cooling rate of the casting is as high as 750°C, which exceeds the lower limit of the design requirement of the present invention by 900°C. Therefore, the electromagnetic properties of the finished product of Comparative Example 3 are not good compared with the steel plate, and its iron loss P is 0.1%. 15 / 50 4.54W / kg, magnetic induction B 50 is 1.70T. Among them, the iron loss P 15 / 50 , magnetic induction B 50 All are lower than the design requirements of the present invention.

[0090] Figure 1 This is a microstructure photograph of the finished non-oriented electrical steel sheet of Example 5.

[0091] like Figure 1 As shown, in the embodiment of Example 5, the microstructure of the non-oriented electrical steel sheet has achieved complete recrystallization, and the recrystallized grains are all relatively uniform equiaxed grains, and the grain size is coarse and developed.

[0092] Figure 2 This is a microstructure photograph of the comparative steel plate of Comparative Example 3.

[0093] like Figure 2 As shown, in the implementation of comparative example 3, the microstructure of the comparative steel has achieved complete recrystallization, but the proportion of equiaxed crystals of the recrystallized grains is low, the size is small, and the grain size is relatively dispersed; the grains with larger grain size are abnormally grown "island grains".

[0094] Figure 3 The relationship between the average size of C and N compound inclusions and the iron loss of the finished non-oriented electrical steel sheet is schematically shown.

[0095] like Figure 3 As shown in the figure, with the increase of the average size of C and N compound inclusions in the steel, the iron loss of the finished non-oriented electrical steel sheet gradually decreases, and the iron loss remains stable in the range of 200-500nm, and the iron loss meets the upper limit 3.2W / kg control requirement of the invention design; after exceeding 500nm, the iron loss of the finished non-oriented electrical steel sheet increases with the increase of the average size of C and N compound inclusions in the steel, and cannot meet the iron loss control requirement of the invention design.

[0096] It should be noted that the prior art in the protection scope of the present invention is not limited to the embodiments given in the present application documents. All prior art that does not contradict the scheme of the present invention, including but not limited to prior patent documents, prior public publications, prior public uses, etc., can be included in the protection scope of the present invention.

[0097] In addition, the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0098] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A non-oriented electrical steel sheet with excellent magnetic properties, characterized in that: The mass percentage of each chemical element is: 0<C≤0.0025%; Si: 0.2~1.6%; Mn: 0.2~0.6%; Al: 0.2~0.6%; V: 0.0019~0.008%; N: 0.002~0.0045%; 0<Nb≤0.003%;0<Ti≤0.003%; The balance is Fe and unavoidable impurities; The inclusions are those containing C and N, and the main inclusions are AlN, VN, VC, and V(CN). The size of the inclusions containing C and N is 200 to 500 nm, and the inclusions satisfy 1.5≤AlN content / (VN content+VC content+V(CN) content)≤4.

0.

2. The non-oriented electrical steel sheet according to claim 1, characterized in that: The mass percentage content of V element is 0.0019-0.0045%.

3. The non-oriented electrical steel sheet according to claim 1, characterized in that: Among the inevitable impurities, S≤0.002%.

4. The non-oriented electrical steel sheet according to claim 1, characterized in that: Its iron loss P 15 / 50 ≤3.2W / kg, magnetic induction B 50 ≥1.75T.

5. A method for producing a non-oriented electrical steel sheet with excellent magnetic properties as claimed in any one of claims 1 to 4, characterized in that: Includes steps: (1) Smelting and casting; (2) Hot rolling: the steel coil after hot rolling is directly subjected to the next step without normalizing annealing or bell furnace annealing; (3) Pickling; (4) Cold rolling; (5) Finished product annealing: The cold-rolled steel sheet is rapidly heated to the target soaking temperature at a heating rate of 80 to 1000°C / s.

6. The manufacturing method according to claim 5, characterized in that: In step (5), the target soaking temperature is 800-1000°C.

7. The manufacturing method according to claim 5, characterized in that: During the casting process of step (1), the superheat of the molten steel is controlled to be 10-35°C, the change time between the solid and liquid phases is controlled to be 10s-120min, and as the molten steel casting proceeds, the cooling rate of the ingot is controlled to be ≤10°C / min within the range of 900-1150°C.

8. The manufacturing method according to claim 5, characterized in that: In step (2), during hot rolling, the furnace time of the cast slab is controlled to be 120 to 360 minutes, the starting 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.

9. The manufacturing method according to claim 5, characterized in that: In step (2), the target thickness of the hot-rolled steel plate is controlled to be 0.8 to 3.5 mm; and in step (4), the steel plate is cold-rolled to the target thickness of the finished product in one step.

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