Non-oriented electrical steel sheet and its manufacturing method

Abstract

The present invention discloses a non-oriented electrical steel sheet containing chemical elements with mass percentages of 0 < C ≤ 0.003%, Si: 1.6 - 3.4%, Mn: 0.1 - 1.2%, S ≤ 0.003%, Al: 0.1 - 3.0%, Sn: 0.005 - 0.2%, Ca: 0.0005 - 0.01%, O ≤ 0.003% and N ≤ 0.003%, with the balance being Fe and unavoidable impurities. In addition, the present invention further discloses a method for manufacturing the above non-oriented electrical steel sheet, which includes steps of smelting and casting, hot rolling, intermediate annealing, cold rolling, continuous annealing, and applying an insulation coating to obtain the finished non-oriented electrical steel sheet. The non-oriented electrical steel sheet has excellent magnetic properties.

Description

[Technical Field]

[0001] The present invention relates to a steel sheet and a manufacturing method thereof, and more particularly to a non-oriented electrical steel sheet and a manufacturing method thereof. [Background technology]

[0002] In recent years, with the gradual depletion of resources such as oil and coal, people's demand for clean energy, such as wind, tidal, and solar power, has become increasingly urgent. On the one hand, people are trying everything possible to convert these physical and thermal power sources into accessible electrical power resources and replace traditional oil and coal resources as much as possible; on the other hand, people are also paying more and more attention to improving efficiency and saving energy in aspects of daily power consumption. For example, with electric vehicles now increasingly being used, their drive motors are gradually developing toward miniaturization, precision, and high efficiency. Therefore, this requires that the corresponding non-oriented electrical steel sheet have the characteristics of high magnetic induction, low iron loss, and high strength, and more importantly, a thin gauge of generally 0.1 to 0.3 mm. This is because a thin gauge can significantly reduce the high-frequency iron loss of the finished strip steel. However, there are drawbacks to this, such as a decrease in magnetic induction and further reduction in mechanical strength, which will create new problems in the subsequent production, machining, and use of the steel sheet.

[0003] To alleviate the tradeoff between thickness reduction, high mechanical performance, and excellent electromagnetic properties, Patent Document 1, published on March 5, 1999, under the title "Non-oriented electrical steel sheet with low iron loss and small magnetic anisotropy and its manufacturing method," with publication number JP 11-61257, discloses an electrical steel sheet and its manufacturing method. The technical solution disclosed in the patent involves a low-temperature heat treatment of a continuously cast billet at a temperature in the range of 950-1150°C, followed by hot rolling of the intermediate billet and a post-rough rolling heat-retention treatment. The temperature drop before finish rolling must be controlled within 40°C, the finish rolling temperature must be limited to at least +20°C above the Ar1 phase transformation point, and the coiling temperature must be limited to 640-750°C. By controlling the conditions and method, a non-oriented electrical steel sheet with low magnetic anisotropy can be obtained.

[0004] Patent Document 2, entitled "Non-oriented electrical steel sheet with excellent machinability and low iron loss and its manufacturing method," published on December 12, 2001, and bearing publication number CN1326009A, discloses a non-oriented electrical steel sheet with excellent machinability and low iron loss. In the technical solution disclosed in the patent, the weight percentage of Si+Mn+Al in the steel is limited to about 5%, and 0.0005% or more of Mg treatment and / or Ca and / or REM treatment are adopted in the smelting process to remove non-metallic inclusions in the steel, provided that the total weight of the three components does not exceed 0.02%. To improve this type of control effect, the RH refining process requires the use of Al element to perform deep deoxidation of the molten steel, and the S content in the steel needs to be limited to within 0.01%. The target thickness of the hot-rolled strip steel is 2.3 mm. Cold rolling production can be carried out by using a first cold rolling or a second cold rolling in conjunction with intermediate annealing, and then the cold rolled strip is subjected to a final annealing at a temperature of 700-1100°C.

[0005] Patent Document 3, entitled "Non-oriented electrical steel sheet with low high-frequency core loss and manufacturing method thereof," with publication number CN101821418A and publication date September 1, 2010, discloses a non-oriented electrical steel sheet with low high-frequency core loss. The technical solution disclosed by the patent requires that the overall steel sheet contain the following mass percentages of elements: C: 0.005% or less, Si: 2.0% to 4.0%, Mn: 1% or less, and Al: 0.1% to 8.0%, with the remainder being Fe and unavoidable impurities. Furthermore, it requires that the Al content through the thickness of the sheet satisfy the following formula: 0.1<(Xs - Xc)<100. To improve the electromagnetic properties of the finished steel strip, the steel also needs at least one of 5% or less Cu, 1% or less Nb, 1% or less Ti, 5% or less Ni, and 15% or less Cr, as well as 0.5% or less Mo, W, Sn, Mg, Ce, etc. After hot rolling, evaporation or hot dipping is used to coat the surface of the hot-rolled steel strip with an Al-containing coating, which is then cold-rolled to a thickness of 0.1-0.3 mm; and finally, final annealing is performed at 1000°C or less for 1 hour or more. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 11-61257 A [Patent Document 2] Chinese Patent Application Publication No. 1326009 [Patent Document 3] Chinese Patent Application Publication No. 101821418 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a thin gauge non-oriented electrical steel sheet, which has excellent magnetic properties. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a thin-gauge non-oriented electrical steel sheet containing chemical elements in the following mass percentages: 0 < C ≤ 0.003%; Si: 1.6 - 3.4%; Mn: 0.1 - 1.2%; S ≤ 0.003%; Al: 0.1 - 3.0%; Sn: 0.005 - 0.2%; Ca: 0.0005 - 0.01%; O ≤ 0.003%; N ≤ 0.003%; the balance is Fe and other inevitable impurities.

[0009] In the thin-gauge non-oriented electrical steel sheet described in the present invention, the design principle of each chemical element is described below.

[0010] C: In the thin-gauge non-oriented electrical steel sheet according to the present invention, C will strongly hinder the grain growth of the finished steel sheet. And it tends to form fine precipitates in combination with Nb, V, Ti, or the like, thereby causing an increase in loss and generating magnetic aging. Therefore, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of C is controlled to be 0 < C ≤ 0.003%.

[0011] Si: In the thin-gauge non-oriented electrical steel sheet according to the present invention, Si will improve the resistivity of the material. And it can effectively reduce the iron loss of the steel. However, when the mass percentage of Si is higher than 3.4%, the magnetic induction of the steel will be considerably reduced. This will lead to a considerable reduction in the rolling property of cold rolling; when the mass percentage of Si is lower than 1.6%, the effect of reducing iron loss will not be achieved. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of Si is controlled to be 1.6 - 3.4%.

[0012] Mn: In the thin-gauge non-oriented electrical steel sheet according to the present invention, Mn combines with S to produce MnS, thereby reducing the deterioration of magnetic properties. However, when the mass percentage of Mn is lower than 0.1%, the sulfur retention effect will be poor. When the mass percentage of Mn is higher than 1.2%, the recrystallization effect of the steel will be suppressed. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of Mn is controlled to be 0.1 to 1.2%.

[0013] S: In the thin-gauge non-oriented electrical steel sheet according to the present invention, if the mass percentage of S exceeds 0.003%, the number of harmful inclusions such as MnS and CuS will increase significantly. This will strongly hinder grain growth and reduce the magnetic properties of the steel. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of S is controlled to be ≦0.003%.

[0014] Al: In the thin-gauge non-oriented electrical steel sheet according to the present invention, Al can improve the resistivity of the material and effectively reduce the iron loss of the steel. However, if the mass percentage of Al is higher than 3.0%, the magnetic induction of the steel will be significantly reduced. This will lead to a significant reduction in the rollability of the cold rolling; if the mass percentage of Al is lower than 0.1%, the effect of reducing iron loss will not be achieved. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of Al is controlled to be 0.1 to 3.0%.

[0015] Sn: In the thin-gauge non-oriented electrical steel sheet according to the present invention, if the mass percentage of Sn is lower than 0.005%, the effects of improving the steel structure and magnetic induction of the steel will not be achieved. If the mass percentage of Sn is higher than 0.2%, it will cause grain refinement and reduce the magnetic properties of the steel. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of Sn is controlled to be 0.005 to 0.2%.

[0016] Ca: In the thin-gauge non-oriented electrical steel sheet according to the present invention, if the mass percentage of Ca is lower than 0.0005%, the effect of removing oxide and sulfide inclusions will not be achieved. If the mass percentage of Ca is higher than 0.01%, grain refinement will easily occur, leading to a reduction in rollability in cold rolling. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of Ca is controlled to be 0.0005 to 0.01%.

[0017] O: In the thin-gauge non-oriented electrical steel sheet according to the present invention, if the mass percentage of O is higher than 0.003%, the number of oxide inclusions will increase significantly. This leads to grain refinement, which reduces the magnetic properties of the steel. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of O is controlled to be O≦0.003%.

[0018] N: In the thin-gauge non-oriented electrical steel sheet according to the present invention, if the mass percentage of N exceeds 0.003%, the precipitation of Nb, V, Ti, Al, etc. will increase significantly. This will strongly hinder grain growth and reduce the magnetic properties of the steel. Based on this, in the thin-gauge non-oriented electrical steel sheet according to the present invention, the mass percentage of N is controlled so that N≦0.003%.

[0019] Preferably, in the thin gauge non-oriented electrical steel sheet according to the present invention, the chemical elements further satisfy: 33×O / 16+S / 32≦12×Ca / 40.

[0020] In the above solution, it is believed that when the steel is cleaner, the grain growth of the finished steel plate is easier and the proportion of advantageous {100} surface texture will be higher. Therefore, by controlling the mass percentages of chemical elements to satisfy 33 × O / 16 + S / 32 ≦ 12 × Ca / 40, sufficient precipitation or early precipitation of harmful inclusions can be achieved, thereby reducing the harm caused by harmful inclusions. Furthermore, the large size of oxide and sulfide inclusions formed initially in steel, mostly belonging to deoxidation products, makes them easy to float upward. However, the size of oxide inclusions formed by secondary deoxidation is small and difficult to remove by flotation. Furthermore, these types of oxides have selectivity for the subsequent precipitation of sulfide inclusions due to their different sulfur contents. Typically, it is thought that aluminum oxides inhibit the precipitation of sulfide inclusions and delay their precipitation time, causing a reduction in the size and an increase in the number of sulfide inclusions. This would further degrade the electromagnetic properties of the finished steel sheet. To remedy this problem, calcium treatment can be employed to combine calcium oxide with aluminum oxide to form 12CaO 7Al2O3, which has a low melting point and relatively large size for easy flotation removal. This approach requires determining the relationship between calcium, oxygen, and sulfur. Additionally, without calcium treatment, sulfide inclusions are primarily MnS and Cu2S, and their size will gradually decrease while their quantity will gradually increase. This gradually leads to increased harm. In contrast, after calcium treatment, the affinity between calcium and sulfur is much greater than that between manganese and copper, resulting in a finite amount of CaS, which has a large size and a high melting point and can be easily flotted away by itself. Alternatively, the CaS may collide and aggregate with the large oxide inclusions mentioned above and ultimately be flotted away. To achieve this effect, it is necessary to ensure that the oxide and sulfide inclusions are sufficiently bonded to calcium. Therefore, preferably, each chemical element should be controlled to satisfy: 33×O / 16+S / 32≦12×Ca / 40.

[0021] Preferably, the thin gauge non-oriented electrical steel sheet according to the present invention further contains at least one of the elements Nb, V, or Ti, satisfying the following in mass percentage: Nb / 93+V / 51+Ti / 48≦C / 12+N / 14; and Nb+V+Ti≦0.01%.

[0022] In the above solution, it is considered that the harmful inclusions in non-oriented electrical steel sheets are mainly formed by C, S, O, and N elements, and C and N elements are mainly combined with Nb, V, and Ti elements, and the improved inclusions formed are mainly TiC, TiN, Ti(CN), NbC, NbN, Nb(CN), VC, VN, and V(CN). These types of inclusions have low melting points and low precipitation temperatures, and will easily repeat solidification and precipitation during continuous casting, hot rolling, and subsequent intermediate annealing and continuous annealing processes. Therefore, the inclusions will have small size and large number, easily form wedge-shaped domains, and have a strong pinning effect on crystal grains. This will greatly impair the magnetic induction and core loss of the finished steel sheet. Since Nb, V, and Ti are all trace residual elements with widespread sources and difficult removal, a promising approach is to consciously adjust their content ratios during the smelting process to ensure that the harmful inclusions they form are sufficiently precipitated and pre-precipitated. In this way, sufficient growth of inclusions can be facilitated, minimizing the damage caused by inclusions as much as possible. The saturated components required to reach the precipitation condition are required to be Nb / 93+V / 51+Ti / 48≦C / 12+N / 14 based on calculations of the thermodynamics of steady-state inclusion formation. Therefore, they should be controlled to be Nb / 93+V / 51+Ti / 48≦C / 12+N / 14 and Nb+V+Ti≦0.01%, thereby reducing the damage caused by inclusions to the finished steel sheet and improving the magnetic properties of the finished steel sheet.

[0023] Preferably, the thin gauge non-oriented electrical steel sheet according to the present invention has a thickness of 0.1 to 0.3 mm.

[0024] In the above solution, by adjusting the thickness of the hot-rolled steel sheet to, for example, 0.8-2.0 mm, and thereby obtaining a suitable cold-rolling reduction of, for example, 75%-90%, the crystal recovery can be effectively suppressed in the subsequent continuous annealing process. Moreover, the residual stored deformation energy before recrystallization will increase, which will result in an increase in the driving force for nucleation. This is <111> / / ND recrystallization reduces the strength of the structural components, thereby facilitating the improvement and enhancement of the electromagnetic properties, and finally obtaining a thin gauge non-oriented electrical steel sheet.

[0025] It should be noted that by reducing the thickness of the hot-rolled steel sheet, on the one hand, the overall temperature of the hot-rolled steel sheet in the hot-rolling process can be increased, and the temperature difference between the center and the upper and lower surfaces of the hot-rolled steel sheet can be reduced, promoting sufficient recrystallization and grain growth of the hot-rolled steel sheet, thereby increasing the proportion of favorable {100} surface texture and {110} surface texture; on the other hand, after reducing the cold-rolling reduction, the number of dislocations in the cold-rolled steel sheet can be reduced, which will not generate a large amount of lattice distortion and keep the stored energy low. Therefore, in the subsequent continuous annealing process, the crystal recovery can be effectively suppressed, which can increase the residual stored deformation energy before recrystallization. Therefore, the driving force for nucleation is increased, <111> / / ND recrystallization reduces the strength of the structural components, thereby facilitating the improvement and enhancement of electromagnetic properties. Here, the surface structure measurement method is based on the quantitative pole figure of metallic materials (YB / T5360-2006), and a Smart Lab X-ray diffractometer is used for the measurement.

[0026] Preferably, in the thin gauge non-oriented electrical steel sheet according to the present invention, the proportion of {100} surface texture is not lower than 15%.

[0027] Preferably, in the thin gauge non-oriented electrical steel sheet according to the present invention, the iron loss P 10 / 400 is less than 12W / kg, and magnetic induction B 50The measurement method for the electromagnetic properties is based on the Epstein square ring method (GB10129-1988) using a German Brockhaus magnetic measuring device, and the P 15 / 50 represents the iron loss measured under the conditions of 1.0T and 400Hz, and B 50 represents the magnetic induction measured under the condition of 5000 A / m.

[0028] Correspondingly, another object of the present invention is to provide a method for manufacturing a thin gauge non-oriented electrical steel sheet, which can provide a thin gauge non-oriented electrical steel sheet having excellent magnetic properties.

[0029] To achieve the above object, the present invention provides a method for manufacturing the above thin-gauge non-oriented electrical steel sheet: smelting and casting steps; Hot rolling step; Intermediate annealing step: The hot-rolled steel sheet is annealed at a first rate of 50 to 2000°C / s to a holding temperature of T holding Temp. Rapidly heat to the desired temperature, and keep it warm for 1 to 180 seconds. holding Temp. = T Curie temperature T Curie-Temp. +100k / v, where v is the first velocity and k is 100-450°C. 2 / s range is the recrystallization effect index of hot rolled steel sheet; Cold rolling step; Continuous annealing step: Rapidly heat the cold rolled steel sheet to the starting temperature T initial to the crystallization end temperature T crystallization-ending Heat at the second rate until T begins to heat. initial is the starting temperature of heating at the second rate, and then the cold rolled steel sheet is heated to a soaking temperature T soaking T soaking and the second rate is 100-5000°C / s; applying an insulating coating to obtain a finished non-oriented electrical steel sheet; Includes.

[0030] In order to achieve reduced equipment investment, improved production efficiency, and reduced energy consumption, the manufacturing method according to the present invention eliminates the normalizing treatment between hot rolling and cold rolling and instead utilizes an intermediate annealing process to rapidly and quickly heat and hold the hot-rolled steel sheet. The heating method can be, for example, ohmic heating or electromagnetic induction heating. When heating is performed at a first rate, a higher heating rate is more advantageous for suppressing the growth of harmful {111} surface texture, facilitating shape control of the equiaxed grain ratio, and improving the electromagnetic properties of the finished steel sheet. However, if the heating rate is too high, the equipment performance and investment requirements will also increase. Therefore, in some preferred embodiments, the first rate can be controlled to 50-400°C / s. Furthermore, in the technical solution according to the present invention, the warming time at the first rate can be controlled to 1-180 s, preferably 5-30 s. This is significantly reduced compared to the conventional normalizing soak time. At the same time, the heat retention temperature is: T heat retention temperature T holding Temp. = T Curie temperature T Curie-TempThe melting rate is controlled to +100 kJ / v, where v is the first rate and k is the recrystallization effect index of the hot-rolled steel sheet, and is determined by the design of the chemical components in the steel and the first rate. For example, Example A8 includes the following mass percentages of chemical elements in the steel sheet: 0.0022% C, 1.67% Si, 1.2% Mn, 0.0012% S, 1.52% Al, 0.2% Sn, 0.0008% O, 0.003% N, 0.0017% Nb, 0.0006% V, 0.0008% Ti, and 0.0063% Ca. and has a first rate of 400°C / s and a k-value of 450 s; Example A12 includes the following mass percentages of steel plate chemical elements: 0.0011% C, 2.98% Si, 0.55% Mn, 0.0008% S, 0.94% Al, 0.14% Sn, 0.001% O, 0.0015% N, 0.0015% Nb, 0.0021% V, 0.0014% Ti, and 0.0075% Ca, and has a first rate of 300°C / s and a k-value of 300 s. Typically, the higher the contents of the chemical elements Si, Mn, and Al, the higher the first rate and the larger the k-value, and the lower ... 2 It will take values ​​in the range / s.

[0031] In the subsequent continuous annealing process, ohmic heating or electromagnetic induction heating can be used. The heating is performed at a rapid heating start temperature T. initial to the crystallization end temperature T crystallization-ending The rapid heating process continues until the recrystallization of the cold rolled steel sheet is complete, because at this time, nucleation is already sufficient and no fibrous structure is present. Then, the cold rolled steel sheet is further heated at a conventional heating rate (e.g., 1-30°C / s) or a rapid heating rate (e.g., 100-5000°C / s) to a T soaking T. soakingThis method is used to heat the steel sheet to a high temperature for soaking and warming, resulting in sufficient grain growth and excellent magnetic properties. The decision to use rapid heating annealing is primarily based on production costs. While it contributes to production efficiency and electromagnetic properties, it is not a limiting factor. The second rate can be controlled to 100-5000°C / s, preferably 100-600°C / s. This is because: if the second rate is too slow, the stored deformation energy during cold rolling is released too quickly, which is detrimental to the subsequent control of the desired structure; or, if the second rate is too high, it imposes high requirements on equipment performance and costs, and further extends the warming time at the high temperature stage of the cold-rolled steel sheet, resulting in poor uniformity of the grain structure.

[0032] Preferably, in the manufacturing method according to the present invention, the first rate of the intermediate annealing step is 50 to 400° C. / s.

[0033] Preferably, in the manufacturing method according to the present invention, the second rate of the successive annealing steps is 100 to 600° C. / s.

[0034] Preferably, in the method of the present invention, in the continuous annealing step, the rapid heating start temperature T initial is the temperature between room temperature and the Curie temperature. initial If is higher than the Curie temperature, it is disadvantageous to obtain advantageous structures and reduce the occurrence of harmful structures.

[0035] Preferably, in the manufacturing method according to the present invention, in the continuous annealing step, the cold-rolled steel sheet is further annealed at a rate of 1 to 30°C / s to the soaking temperature T soaking T soaking is heated to

[0036] Preferably, in the manufacturing method according to the present invention, T soaking T soaking =T Crystallization end T crystallization-ending+(50~130)℃. If the soaking temperature is too low, the grain size after the completed crystallization will not grow sufficiently; if the soaking temperature is too high, it will be disadvantageous to obtain an advantageous structure, which will also increase the production cost.

[0037] Preferably, in the manufacturing method according to the present invention, the steel plate has a thickness of 0.8 to 2.0 mm after the hot rolling step.

[0038] Preferably, in the manufacturing method according to the present invention, in the cold rolling step, a primary cold rolling is adopted to roll the steel plate to a finished thickness, so as to reduce production burden and manufacturing cost.

[0039] Compared with the prior art, the thin gauge non-oriented electrical steel sheet and its manufacturing method according to the present invention have the following advantages and beneficial effects: The thin gauge non-oriented electrical steel sheet according to the present invention has the advantage of excellent magnetic properties and low iron loss P 10 / 400 is ≦12W / kg and magnetic induction B 50 is ≧1.68T.

[0040] In addition, the manufacturing method according to the present invention also has the above advantages and beneficial effects. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a schematic curve diagram of different annealing processes adopting the present technical solution and the prior art respectively. [Figure 2] FIG. 2 is a scanning electron microscope (SEM) image of the thin gauge non-oriented electrical steel sheet of Example A9. [Figure 3] FIG. 3 is a scanning electron microscope (SEM) image of the conventional steel sheet of Comparative Example A2. [Figure 4] Figure 4 shows the effect of different cold rolling reductions on magnetic induction. [Figure 5] Figure 5 shows a schematic representation of the effect of different mass percentages of Ca on core loss. [Figure 6] FIG. 6 is a structural diagram of the thin-gauge non-oriented electrical steel sheet of Example A15. [Figure 7] FIG. 7 is a structural diagram of the conventional steel sheet of Comparative Example A3. DETAILED DESCRIPTION OF THE INVENTION

[0042] The thin gauge non-oriented electrical steel sheet and its manufacturing method will be further described and illustrated below by referring to the specification and drawings of specific examples. However, the description and illustration do not constitute an undue limitation of the technical solution of the present invention. [Example]

[0043] [Examples A8 to A17 and Comparative Examples A1 to A7] The thin gauge non-oriented electrical steel sheets of Examples A8 to A17 and the conventional steel sheets of Comparative Examples A1 to A7 are manufactured by adopting the following steps.

[0044] (1) Mixing molten iron and scrap iron according to the chemical composition ratios shown in Table 1, then smelting in a converter, decarburizing, deoxidizing, and alloying in RH refining, and then subjecting the molten steel to continuous casting to obtain continuous cast billets.

[0045] (2) Hot rolling: The thickness of the steel sheet after hot rolling is controlled to be 0.8 to 2.0 mm.

[0046] (3) Intermediate annealing: The hot-rolled steel sheet is annealed at a first rate of 50 to 2000°C / s to a temperature of T holding Temp. Rapidly heat to the desired temperature, and keep it warm for 1 to 180 seconds. holding Temp = T Curie temperature T Curie-Temp +100k / v, where v is the first velocity and k is 100-450°C. 2 / s is the recrystallization effect index of hot-rolled steel sheets.

[0047] (4) Cold rolling: The steel plate is rolled through the first cold rolling process to a finished thickness of 0.1 to 0.3 mm.

[0048] (5) Continuous annealing: Cold-rolled steel sheet is rapidly heated to the starting temperature T initial to the crystallization end temperature T crystallization-ending and then rapidly heating the cold rolled steel sheet at a second rate to a soaking temperature T for further soaking and heat retention. soaking The second heating rate is 100 to 5000 °C / s, and the rapid heating start temperature T is T initial is the temperature between room temperature and the Curie temperature, and T is the soaking temperature. soaking =T Crystallization end T crystallization-ending +(50~130)℃.

[0049] (6) Applying an insulating coating to obtain the finished non-oriented electrical steel sheet.

[0050] Table 1 lists the mass percentage proportions of all chemical elements for the thin gauge non-oriented electrical steel sheets of Examples A8 to A18 and the conventional steel sheets of Comparative Examples 1 to A7.

[0051] [Table 1]

[0052] Note: In Table 1, A indicates whether Nb / 93+V / 51+Ti / 48≦C / 12+N / 14 is satisfied, B indicates whether 33×O / 16+S / 32≦12×Ca / 40 is satisfied, and C indicates whether Nb+V+Ti≦0.01% is satisfied.

[0053] Table 2 lists the specific technical parameters of the thin gauge non-oriented electrical steel sheets of Examples A8 to A18 and the conventional steel sheets of Comparative Examples A1 to A7.

[0054] [Table 2]

[0055] Table 3 lists all performance parameters of the thin gauge non-oriented electrical steel sheets of Examples A8 to A18 and the conventional steel sheets of Comparative Examples A1 to A7.

[0056] [Table 3]

[0057] According to Tables 1 and 3, the thin-gauge non-oriented electrical steel sheets of all the examples of the present invention have excellent magnetic properties, and an iron loss P of ≦12 W / kg. 10 / 400 and magnetic induction B ≥ 1.68T 50 It has.

[0058] FIG. 1 is a schematic process diagram showing the different annealing processes employed.

[0059] As shown in Figure 1, the manufacturing method adopted by the present invention employs rapid thermal annealing, which differs from conventional thermal annealing processes. To achieve reduced equipment investment, improved production efficiency, and reduced energy consumption, the present invention eliminates the normalizing treatment between hot rolling and cold rolling and instead utilizes an intermediate annealing process to rapidly and quickly heat and hold the hot-rolled steel sheet. The heating method can be, for example, ohmic heating or electromagnetic induction heating. When heating is performed at a first rate, a higher heating rate is more advantageous for suppressing the growth of harmful {111} surface texture, facilitating shape control of the equiaxed grain ratio, and improving the electromagnetic properties of the finished steel sheet. However, if the heating rate is too high, the requirements for equipment performance and investment will also increase. Therefore, in some preferred embodiments, the first rate can be controlled to be 50 to 400°C / s. Furthermore, the holding time at the first rate can be controlled to be 1 to 180 s. This is a significant reduction in the normalizing soaking time compared to the conventional thermal annealing process. holding Temp = T Curie temperature T Curie-TempIt is controlled at +100k / v, where v is the first speed and k is the recrystallization effect index of the hot-rolled steel sheet, and is determined by the design of the chemical components in the steel and the first speed. Typically, the higher the content of chemical components Si, Mn, and Al, the larger the first speed and the larger the k value, and the temperature range is 100-450°C. 2 It will take values ​​in the range / s.

[0060] In the subsequent continuous annealing process, ohmic heating or electromagnetic induction heating can be used. The heating is performed at a rapid heating start temperature T. initial to the crystallization end temperature T crystallization-ending The rapid heating process continues until the recrystallization of the cold rolled steel sheet is complete, because at this time, nucleation is already sufficient and no fibrous structure is present. Then, the cold rolled steel sheet is further heated at a conventional heating rate (e.g., 1-30°C / s) or a rapid heating rate (e.g., 100-5000°C / s) to a T soaking T. soaking This method involves heating the steel sheet to a temperature of 100°C / s for soaking and warming, resulting in sufficient grain growth and excellent magnetic properties. The decision to use rapid heating annealing is primarily based on production costs. While it contributes to production efficiency and electromagnetic properties, it is not a limiting factor. The secondary speed is 100-5000°C / s. This is because: if the secondary speed is too slow, the stored deformation energy during cold rolling is released too quickly, which is detrimental to subsequent structural control; or, if the secondary speed is too high, it imposes high requirements on equipment performance and costs, and further extends the warming time at the high temperature stage of the cold-rolled steel sheet, resulting in poor uniformity of the grain structure.

[0061] The thin-gauge non-oriented electrical steel sheet obtained by adopting the manufacturing method of the present invention has an iron loss P of ≦12 W / kg. 10 / 400 and magnetic induction B ≥ 1.68T 50 It has.

[0062] Figure 2 is a scanning electron microscope (SEM) image of the thin gauge non-oriented electrical steel sheet of Example A9. Figure 3 is a scanning electron microscope (SEM) image of the conventional steel sheet of Comparative Example A2.

[0063] It can be seen from Figure 2 that the S grains of the thin gauge non-oriented electrical steel sheet of Example A9 are regular in shape, uniform in size, and have a moderate distribution. In contrast, the conventional steel sheet of Comparative Example A2 in Figure 3 has fine grains, irregular in shape, large in size, and exhibits segregation.

[0064] Figure 4 shows the effect of different cold rolling reductions on magnetic induction.

[0065] As shown in Figure 4, when the cold rolling reduction is controlled to 75%-90%, the magnetic induction B ≥ 1.68T. 50 Thin gauge non-oriented electrical steel sheets with excellent magnetic properties can be obtained. This is because when the cold rolling reduction is controlled to be 75% to 90%, the crystal recovery can be effectively suppressed in the subsequent continuous annealing process, which can increase the residual stored deformation energy before recrystallization. Therefore, the driving force for nucleation is increased, <111> / / ND recrystallization reduces the strength of the structural components, thereby facilitating the improvement and enhancement of the electromagnetic properties, and finally obtaining a thin gauge non-oriented electrical steel sheet.

[0066] Figure 5 shows a schematic representation of the effect of different mass percentages of Ca on core loss.

[0067] As shown in Figure 5, when the mass percentage of Ca is lower than 0.0005%, the effect of removing oxide and sulfide inclusions cannot be achieved, and when the mass percentage of Ca is higher than 0.01%, grain refinement will easily occur, which will lead to a reduction in rollability in cold rolling. Based on this, an iron loss P≦12 W / kg 10 / 400In order to obtain a thin gauge non-oriented electrical steel sheet having the above properties, the mass percentage of Ca is controlled to be 0.0005-0.01%.

[0068] Fig. 6 is a structural diagram of the thin-gauge non-oriented electrical steel sheet of Example A15, and Fig. 7 is a structural diagram of the conventional steel sheet of Comparative Example A3.

[0069] According to Figures 6 and 7, it can be seen that compared with Comparative Example A3, the proportion of the {100} surface texture of the thin gauge non-oriented electrical steel sheet according to Example A15 is not lower than 15%.

[0070] In conclusion, from the above, it can be seen that the thin gauge non-oriented electrical steel sheet according to the present invention has the characteristics of excellent magnetic properties, and has an iron loss P≦12W / kg. 10 / 400 and magnetic induction B ≥ 1.68T 50 It can be seen that it has

[0071] In addition, the manufacturing method according to the present invention also has the above advantages and beneficial effects.

[0072] It should be noted that the part of the prior art within the protection scope of the present invention is not limited to the examples given in this specification. All prior art that is not inconsistent with the solution of the present invention, including but not limited to prior patent documents, prior publications, prior applications, etc., may all be included in the protection scope of the present invention.

[0073] In addition, the combinations of the technical features of the present disclosure are not limited to the combinations described in the claims or the combinations described in the specific examples. Unless there are contradictions between them, all technical features described in this specification can be freely combined in any way.

[0074] It should also be noted that the examples listed above are merely specific examples of the present invention. Obviously, the present invention should not be excessively limited to such specific examples. Any modifications or variations that can be directly or easily derived from the present disclosure by those skilled in the art are intended to fall within the scope of protection of the present invention.

Claims

1. containing chemical elements in mass percentages of 0<C≦0.003%, Si: 1.6-3.4%, Mn: 0.1-1.2%, S≦0.003%, Al: 0.1-3.0%, Sn: 0.005-0.2%, Ca: 0.0005-0.01%, O≦0.003% and N≦0.003%, and further containing at least one of Nb, V or Ti element, with the balance being Fe and unavoidable impurities; The mass percentages of O, S, and Ca elements are: 33×O / 16+S / 32≦12×Ca / 40 is satisfied, The mass percentage of Nb, V, or Ti element is Nb / 93+V / 51+Ti / 48≦C / 12+N / 14 and Nb+V+Ti≦0.01%, A non-oriented electrical steel sheet, characterized in that it satisfies the above.

2. 2. The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet has a thickness of 0.1 to 0.3 mm.

3. The non-oriented electrical steel sheet has an iron loss P of ≦12 W / kg １０／４００ and a magnetic induction B of ≥ 1.68 T ５０ The non-oriented electrical steel sheet according to claim 1, characterized in that it has

4. smelting and casting steps; a hot rolling step; The hot-rolled steel sheet is heated at a first rate of 50 to 400°C / s to a temperature T ｈｏｌｄｉｎｇ Ｔｅｍｐ Rapidly heat to T and keep warm for 1 to 180 seconds; T is the warming temperature T ｈｏｌｄｉｎｇ Ｔｅｍｐ = T Curie temperature T Ｃｕｒｉｅ－Ｔｅｍｐ +100k / v, where v is the first rate in °C / s and k is ２ 100 to 450°C in units of / s ２ an intermediate annealing step, wherein the recrystallization effect index of the hot-rolled steel sheet is in the range of / s; a cold rolling step; The cold rolled steel sheet is heated to the rapid heating start temperature T ｉｎｉｔｉａｌ to the crystallization end temperature T ｃｒｙｓｔａｌｌｉｚａｔｉｏｎ－ｅｎｄｉｎｇ and then further heating the cold rolled steel sheet to a soaking temperature T soaking T ｓｏａｋｉｎｇ and the second rate is between 100 and 5000°C / s. applying an insulating coating to obtain a finished non-oriented electrical steel sheet; The method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 3, comprising:

5. The method of claim 4, wherein in the continuous annealing step, the second rate is 100 to 600° C. / s.

6. In the continuous annealing step, the rapid heating start temperature T ｉｎｉｔｉａｌ The method according to claim 4, characterized in that the temperature is from room temperature to the Curie temperature.

7. In the continuous annealing step, the cold rolled steel sheet is further annealed at the soaking temperature T soaking T ｓｏａｋｉｎｇ 5. The method according to claim 4, wherein the heating is performed at a rate of 1 to 30° C. / s.

8. T-Soaking T ｓｏａｋｉｎｇ =T crystallization end T ｃｒｙｓｔａｌｌｉｚａｔｉｏｎ－ｅｎｄｉｎｇ The method according to claim 4, characterized in that the temperature is +(50 to 130)°C.

9. The method according to claim 4, wherein the steel plate after the hot rolling step has a thickness of 0.8 to 2.0 mm.

10. The manufacturing method according to claim 4, wherein in the cold rolling step, a primary cold rolling is adopted to roll the steel plate to a finished thickness.

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