High-strength non-oriented electrical steel sheet having excellent electromagnetic properties and method for manufacturing the same

Abstract

Disclosed is a high-strength non-oriented electrical steel sheet with excellent electromagnetic properties, which contains Fe and inevitable impurities, and further contains the following chemical elements in the following mass percentages: 0 < C ≤ 0.004%; Si: 2.9-3.6%; Mn: 0.1-1.0%; Al: 0.4-1.4%; at least one of Sn and Sb, and the mass percentages of Sn and Sb satisfy: Sn: 0-0.20%, Sb: 0-0.10%; in the inevitable impurities, S ≤ 0.002%, N ≤ 0.002%, Ti ≤ 0.002%. The application also discloses a manufacturing method of the non-oriented electrical steel sheet, which comprises the following steps: smelting and casting; heating and hot rolling; normalizing or bell furnace annealing; the soaking temperature of the normalizing or bell furnace annealing is 820-950 ℃, and the soaking time is 60-180 s; cold rolling after pickling; continuous annealing; the soaking temperature of the continuous annealing is 700-950 ℃, the soaking time is 5-60 s, and the heating rate is 15-400 ℃ / s.

Description

Technical Field

[0001] This invention relates to a steel plate and a method for manufacturing the same, and more particularly to a non-oriented electrical steel plate and a method for manufacturing the same. Background Technology

[0002] As the thickness of non-oriented electrical steel sheets decreases, the iron loss, especially high-frequency iron loss, of the finished steel sheets is significantly reduced, and the magnetic induction intensity also decreases accordingly. On the other hand, with the need for miniaturization and high speed, higher requirements are placed on the strength of non-oriented electrical steel sheets.

[0003] In the prior art, existing patent literature covers the above-mentioned fields:

[0004] For example, Chinese patent document CN103498096A, published on January 8, 2014, entitled "Excellent Magnetic Performance Non-oriented Electrical Steel with Rm≥600MPa and its Production Method," discloses an excellent magnetic performance non-oriented electrical steel with Rm≥600MPa. Its composition, by weight percentage, is: Si: 2.5~3.5%, Mn: 0.1~1.0%, Ni+Al not exceeding 1.0%, N≤0.005%, S≤0.015%, C≤0.003%, P≤0.05%, with the remainder being iron and residual content. Furthermore, it must simultaneously satisfy 1.0≤Al / Ni≤2.0 and C+S+N≤0.007. The production steps are as follows: smelting in a converter and casting into billets; heating the continuously cast billets to a temperature not lower than 1050℃, with the hot-rolled billets in the furnace for not less than 120 minutes; during hot rolling, controlling the roughing rolling temperature to not lower than 900℃ and the plate thickness to not lower than 25mm, controlling the finishing rolling temperature to not lower than 750℃ and the plate thickness to not lower than 2.0mm, and the coiling temperature to not lower than 700℃; and during normalizing, controlling the normalizing homogenization temperature... The temperature should not be lower than 750℃, and the normalizing time should not be less than 1 minute. After pickling, the normalized steel coil is cold rolled. The pickling temperature is 60-100℃, and the pickling time is 2-5 minutes. Cold rolling is carried out in one pass, with 4-7 rolling passes. The total reduction rate of the first 3-6 passes should not be less than 80%, and the reduction rate of any single pass should not exceed 20%. Then, continuous annealing is carried out. The annealing temperature is not lower than 850℃, the soaking time is not less than 1 minute, and the atmosphere is conventional H. 2 +N 2 Mixture, N 2 / H 2 The concentration should not exceed 0.5, and the gas flow rate should not be less than 200 m³ / h. 3 The steel was cooled naturally to room temperature at a speed of [speed value missing]. This yielded a finished steel coil with a thickness of 0.35 mm. Its mechanical properties were Rm ≥ 600 MPa, ReL ≥ 500 MPa, and iron loss P [value missing]. 1.0 / 400 ≤17W / kg, magnetic induction B 5000≥1.66T.

[0005] For example, Chinese patent document CN101821418A, published on September 1, 2010, entitled "High-Frequency Non-directional Electromagnetic Steel Plate with Low Iron Loss and its Manufacturing Method," discloses a high-frequency non-directional electromagnetic steel plate with low iron loss and its manufacturing method. The steel plate, by mass percent, contains less than 0.005% C, 2.0%–4.0% Si, less than 1% Mn, and 0.1%–8.0%, with the remainder including Fe and unavoidable impurities. The Al concentration in the thickness direction is required to satisfy the following formula: 0.1 < (Xs - Xc) < 100. To improve the electromagnetic properties of the finished strip, one or more of the following should be added: less than 5% Cu, less than 1% Nb, less than 1% Ti, less than 5% Ni, less than 15% Cr, and one or more of the following: less than 0.5% Mo, W, Sn, Mg, Ce, etc. After hot rolling, an Al-containing coating is applied to the surface of the hot-rolled strip using vapor deposition or hot dipping, followed by cold rolling to 0.1–0.3 mm; finally, a final annealing is performed at 1000°C for 1 hour or more. Summary of the Invention

[0006] One of the objectives of this invention is to provide a high-strength non-oriented electrical steel sheet with excellent electromagnetic properties. This steel sheet, through optimized chemical composition design, has high yield strength before stress-relief annealing, while still exhibiting low iron loss and high magnetic induction after stress-relief annealing.

[0007] To achieve the above objectives, the present invention provides a high-strength non-oriented electrical steel sheet with excellent electromagnetic properties, which contains Fe and unavoidable impurities, and also contains the following chemical elements in the following mass percentages:

[0008] 0 < C ≤ 0.004%; Si: 2.9–3.6%; Mn: 0.1–1.0%; Al: 0.4–1.4%; at least one of Sn and Sb, and their mass percentage content satisfies: Sn: 0–0.20%, Sb: 0–0.10%; in unavoidable impurities, S ≤ 0.002%, N ≤ 0.002%, Ti ≤ 0.002%.

[0009] Furthermore, in the non-oriented electrical steel sheet described in this invention, the mass percentage content of each chemical element is as follows:

[0010] 0 < C ≤ 0.004%; Si: 2.9–3.6%; Mn: 0.1–1.0%; Al: 0.4–1.4%; at least one of Sn and Sb, and their mass percentage content satisfies: Sn: 0–0.20%, Sb: 0–0.10%; the balance being Fe and unavoidable impurities;

[0011] Among the unavoidable impurities, S ≤ 0.002%, N ≤ 0.002%, and Ti ≤ 0.002%.

[0012] The design principles of each chemical element in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention are as follows:

[0013] C: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of element C is higher than 0.004%, a large number of carbide inclusions will be generated, which will degrade the electromagnetic properties of the steel. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of element C is controlled to be 0 < C ≤ 0.004%.

[0014] Si: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of Si is less than 2.9%, the yield strength of the steel cannot be effectively improved; when the mass percentage of Si is greater than 3.6%, the cold rollability is significantly reduced. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Si is controlled between 2.9% and 3.6%.

[0015] Mn: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of Mn is less than 0.1%, surface defects of the cast billet are easily formed; when the mass percentage of Mn is greater than 1.0%, it significantly reduces the favorable grain texture and greatly deteriorates the magnetic induction of the steel. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Mn is controlled between 0.1% and 1.0%.

[0016] Al: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of Al element is less than 0.4%, the iron loss of the steel cannot be effectively reduced; when the mass percentage of Al element is greater than 1.4%, the favorable grain texture is significantly reduced, and the magnetic induction of the steel is greatly deteriorated. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Al element is controlled between 0.4% and 1.4%.

[0017] Sn and Sb: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, Sn and Sb elements can promote favorable texture growth, thereby effectively improving the magnetic induction of the steel. When Sn and Sb elements are added in excess, it will lead to grain size refinement and worsen the iron loss of the steel. At the same time, considering that the grain boundary segregation ability of Sb element is twice that of Sn element, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage content of Sn element is controlled between 0 and 0.20%, and the mass percentage content of Sb element is controlled between 0 and 0.10%.

[0018] In the above technical solution, S, N, and Ti are all impurity elements in steel. When technical conditions permit, to obtain steel with better performance and higher quality, the content of impurity elements in the steel should be reduced as much as possible. Specifically:

[0019] S: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of sulfur (S) exceeds 0.002%, it leads to an abnormal increase in sulfide inclusions in the steel, inhibiting grain growth and degrading iron loss. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of sulfur is controlled to S ≤ 0.002%.

[0020] N: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of nitrogen (N) exceeds 0.002%, it leads to an abnormal increase in nitride inclusions in the steel, inhibiting grain growth and degrading iron loss. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of nitrogen is controlled to N ≤ 0.002%.

[0021] Ti: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, when the mass percentage of Ti element exceeds 0.002%, it leads to an abnormal increase in nitride inclusions in the steel, inhibiting grain growth and degrading the steel's magnetism. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Ti element is controlled to Ti ≤ 0.002%.

[0022] Furthermore, in the non-oriented electrical steel sheet of the present invention, the mass percentage of Si+Al is 3.8-4.6%.

[0023] In this invention, considering both the manufacturing cost of non-oriented electrical steel sheets and the electromagnetic and mechanical properties, the mass percentage of Si+Al is controlled to be between 3.8% and 4.6%.

[0024] Furthermore, the non-oriented electrical steel sheet of the present invention also contains at least one of the following chemical elements:

[0025] 0 < Cu ≤ 0.5%;

[0026] 0 < Cr ≤ 0.5%;

[0027] 0 < Ni ≤ 0.5%;

[0028] Furthermore, the mass percentage of Cu+Cr+Ni is ≤1.2%.

[0029] The design principles of the above-mentioned chemical elements in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention are as follows:

[0030] Cu: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, Cu can improve the strength of the steel, promote the coarsening of sulfur compound inclusions, and thus reduce the iron loss of the steel. When the mass percentage of Cu exceeds 0.5%, the proportion of favorable crystal texture will be significantly reduced. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Cu is controlled between 0 < Cu ≤ 0.5%.

[0031] Cr: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, Cr can increase the resistivity of the steel, promote grain size increase, and thus reduce iron loss. When the mass percentage of Cr exceeds 0.5%, the proportion of favorable crystal texture will be significantly reduced. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Cr is controlled between 0 < Cr ≤ 0.5%.

[0032] Ni: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, Ni can improve the strength of the steel, promote favorable texture growth, and thus improve the magnetic induction of the steel. When the mass percentage of Ni exceeds 0.5%, it leads to a significant increase in manufacturing costs and production difficulty. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Ni is controlled between 0 < Ni ≤ 0.5%.

[0033] In this invention, considering the manufacturing cost of non-oriented electrical steel sheets as well as their electromagnetic and mechanical properties, the mass percentage of Cu+Cr+Ni is controlled to be 0 < Cu+Cr+Ni ≤ 1.2%.

[0034] Furthermore, the non-oriented electrical steel sheet of the present invention also contains at least one of the following chemical elements in mass percentage:

[0035] 0 < Mg ≤ 0.01%;

[0036] 0 < Ca ≤ 0.01%;

[0037] 0 < REM ≤ 0.01%.

[0038] The design principles of the above-mentioned chemical elements in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention are as follows:

[0039] Mg: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, Mg can effectively improve sulfide inclusions, enhance steel cleanliness, promote favorable texture formation, and increase grain size. When the mass percentage of Mg exceeds 0.01%, it inhibits microstructure recrystallization during continuous annealing. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Mg is controlled between 0 < Mg ≤ 0.01%.

[0040] Ca: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, Ca can effectively improve sulfide inclusions, enhance steel cleanliness, promote favorable texture formation, and increase grain size. When the mass percentage of Ca exceeds 0.01%, it inhibits microstructure recrystallization during continuous annealing. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of Ca is controlled between 0 < Ca ≤ 0.01%.

[0041] REM: In the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, REM element can effectively improve oxygen and sulfide inclusions, enhance steel cleanliness, promote favorable texture formation, and increase grain size. When the mass percentage of REM element exceeds 0.01%, it leads to a significant increase in the manufacturing cost of the steel. Therefore, in the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention, the mass percentage of REM element is controlled between 0 < REM ≤ 0.01%.

[0042] Furthermore, in the non-oriented electrical steel sheet described in this invention, the microstructure after stress-relief annealing is a fully recrystallized microstructure, and the ratio of the average grain size after stress-relief annealing to that before stress-relief annealing is 2 to 8.

[0043] Furthermore, in the non-oriented electrical steel sheet of the present invention, the relative concentration of nitrogen element [N] within 0.1 μm from the surface of the steel sheet to the thickness center direction after stress relief annealing is ≤6000ppm.

[0044] Furthermore, in the non-oriented electrical steel sheet described in this invention, its thickness is 0.15 to 0.30 mm.

[0045] Furthermore, in the non-oriented electrical steel sheet described in this invention, its yield strength Y before stress-relief annealing is... S ≥500MPa.

[0046] Furthermore, in the non-oriented electrical steel sheet described in this invention, the iron loss P after stress-relief annealing is... 1.0 / 400 ≤11.5W / kg, magnetic induction B 5000 ≥1.65T.

[0047] Another objective of this invention is to provide a method for manufacturing non-oriented electrical steel sheets. This method is simple, easy to control, low in cost, high in precision, and easy to implement, and can produce a non-oriented electrical steel sheet with excellent electromagnetic and mechanical properties.

[0048] To achieve the above objectives, the present invention provides a method for manufacturing non-oriented electrical steel sheets, comprising the following steps:

[0049] Smelting and casting;

[0050] Heating and hot rolling;

[0051] Normalizing or bell-type furnace annealing: The soaking temperature for normalizing or bell-type furnace annealing is 820-950℃, and the soaking time is 60-180s;

[0052] After pickling, cold rolling is performed;

[0053] Continuous annealing: The soaking temperature for continuous annealing is 700-950℃, the soaking time is 5-60s, and the heating rate is 15-400℃ / s.

[0054] Furthermore, in step (2) of the manufacturing method described in this invention, the furnace exit temperature of the billet heating is 1050-1200°C, the final rolling temperature is 800-950°C, and the coiling temperature is 550-780°C.

[0055] Furthermore, the manufacturing method of the present invention further includes step (6) stress-relief annealing: the soaking temperature for stress-relief annealing is T. 均热 =T 再结晶开始温度 +80~155℃.

[0056] The high-strength non-oriented electrical steel sheet with excellent electromagnetic properties and its manufacturing method described in this invention have the following advantages and beneficial effects:

[0057] The high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention achieves excellent electromagnetic and mechanical properties through a combination of chemical composition and corresponding production process design. It has high yield strength before stress-relief annealing and low iron loss and high magnetic induction after stress-relief annealing.

[0058] In some embodiments, the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention has a yield strength Y before stress-relief annealing. S ≥500MPa, iron loss P after stress-relief annealing 1.0 / 400 ≤11.5W / kg, magnetic induction B 5000 ≥1.65T.

[0059] The manufacturing method of high-strength non-oriented electrical steel sheet with excellent electromagnetic properties described in this invention improves the recrystallization effect, grain size and favorable texture ratio of the finished steel sheet by optimizing the continuous annealing and stress-relief annealing processes of the steel. This results in a non-oriented electrical steel sheet with high yield strength before stress-relief annealing and low iron loss and high magnetic induction after stress-relief annealing. Moreover, this manufacturing method is convenient, has a smooth process and high cost performance. Attached Figure Description

[0060] Figure 1 The surface microstructure of the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties before stress-relief annealing, as shown in Embodiment 2 of the present invention, is displayed.

[0061] Figure 2 The surface microstructure of the comparative steel plate in Comparative Example 2 before stress-relief annealing is shown.

[0062] Figure 3 The relationship between the continuous annealing heating rate of the comparative steel plate in Comparative Example 3 and the relative [N] content on the surface of the steel plate is shown.

[0063] Figure 4 The relationship between the continuous annealing heating rate and the relative [N] content on the surface of the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties in Embodiment 3 of the present invention is shown.

[0064] Figure 5 This invention demonstrates the ratio of the average grain size of the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties after stress-relief annealing to that before stress-relief annealing, and the yield strength Y of the finished steel sheet. S Iron loss P 1.0 / 400 The relationship. Detailed Implementation

[0065] The high-strength non-oriented electrical steel sheet with excellent electromagnetic properties and its manufacturing method described in this invention will be further explained and illustrated below with reference to specific embodiments and accompanying drawings. However, this explanation and illustration do not constitute an undue limitation on the technical solution of this invention.

[0066] Examples 1-10 and Comparative Examples 1-3

[0067] The high-strength non-oriented electrical steel sheets with excellent electromagnetic properties in Examples 1-10 of this invention and the comparative steel sheets in Comparative Examples 1-3 were all prepared using the following steps:

[0068] (1) Smelting and casting: The raw materials for steelmaking are blast furnace iron or high-quality scrap steel, or a combination of blast furnace iron and high-quality scrap steel in a certain proportion. The steelmaking technology is converter steelmaking and continuous casting, or electric furnace steelmaking and continuous casting.

[0069] In some specific implementations, magnesium and / or calcium and / or rare earth treatments may be performed.

[0070] (2) Heating and hot rolling: The furnace exit temperature of the billet can be controlled at 1050~1200℃, the final rolling temperature can be controlled at 800~950℃, and the coiling temperature can be controlled at 550~780℃; the thickness of the hot-rolled steel plate obtained is 1.6~2.8mm.

[0071] (3) Normalizing or bell-type furnace annealing: The soaking temperature of normalizing or bell-type furnace annealing is 820-950℃, and the soaking time is 60-180s.

[0072] (4) Cold rolling after pickling: After pickling, cold rolling is performed using a cold continuous rolling mill or a reciprocating rolling mill.

[0073] In some specific implementations, during cold rolling, the target thickness can be achieved in a single cold rolling operation, or by using a combination of cold rolling, intermediate annealing, and a second cold rolling operation to achieve the target thickness.

[0074] In some specific implementations, the target thickness of the cold-rolled non-oriented electrical steel sheet can be 0.15 to 0.30 mm.

[0075] (5) Continuous annealing: The continuous annealing temperature is 700-950℃, the heating time is 5-60s, and the heating rate is 15-400℃ / s.

[0076] In some embodiments, step (6) stress-relief annealing may also be included: the soaking temperature for stress-relief annealing is T. 均热 =T 再结晶开始温度 +80~155℃.

[0077] Tables 1-1 and 1-2 list the mass percentage of each chemical element in the non-oriented electrical steel sheets of Examples 1-10 and the comparative steel sheets of Comparative Examples 1-3 of the present invention.

[0078] Table 1-1. (wt%, balance Fe and other unavoidable impurities other than S, N, and Ti)

[0079]

[0080]

[0081] Table 1-2. (wt%, balance Fe and other unavoidable impurities besides S, N, and Ti)

[0082] serial number Si+Al Cu Cr Ni Cu+Cr+Ni Mg Ca REM Example 1 4.3 0 0 0 0 0 0 0 Example 2 4.2 0 0.1 0 0.1 0 0 0 Example 3 4.4 0.5 0 0 0.5 0 0.01 0 Example 4 3.8 0 0.5 0 0.5 0 0 0.01 Example 5 4.1 0 0 0.5 0.5 0.001 0 0 Example 6 4.6 0.1 0 0 0.1 0 0.001 0 Example 7 3.8 0.5 0.5 0.2 1.2 0 0 0.001 Example 8 4.1 0 0 0.1 0.1 0.002 0.002 0.002 Example 9 4.4 0.5 0.2 0.5 1.2 0.01 0.01 0 Example 10 4.2 0.2 0.5 0.5 1.2 0 0.01 0.01 Comparative Example 1 3.6 0.5 0.5 0.5 1.5 0 0 0 Comparative Example 2 3.8 0.5 0 0 0.5 0.01 0.01 0.01 Comparative Example 3 4.8 0 0 0 0 0.005 0.005 0

[0083] Tables 2-1 and 2-2 list the specific process parameters of the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties in Examples 1-10 of the present invention and the comparative steel sheets in Comparative Examples 1-3.

[0084] Table 2-1.

[0085]

[0086] Table 2-2.

[0087]

[0088] Samples of the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties from Examples 1-10 and the comparative steel sheets from Comparative Examples 1-3 were taken before and after stress-relief annealing. Microstructure observations were performed on each example and comparative example, and the results of microstructure observations before and after stress-relief annealing are listed in Table 3. Among them:

[0089] Microstructure: Using metallographic / optical microscopes and other observation equipment or devices, the cross-sectional microstructure perpendicular to the rolling direction of the steel plate was observed at magnifications of X50-X200.

[0090] Average grain size: Based on GB / T 6394-2017 Method for determining the average grain size of metals, the average grain size in the cross-section microstructure perpendicular to the rolling direction of the steel plate.

[0091] The concentration of nitrogen [N] in the 0.1 μm depth from the surface of the steel plate to the center of its thickness was measured using a LECO GDS glow discharge spectrometer.

[0092] Table 3 lists the microstructure observation results of the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties in Examples 1-10 of the present invention and the comparative steel sheets in Comparative Examples 1-3 before and after stress-relief annealing.

[0093] Table 3.

[0094]

[0095]

[0096] As can be seen from Table 3 above, the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties in Examples 1-10 of the present invention have a fully recrystallized structure after stress-relief annealing. Furthermore, the ratio of the average grain size after stress-relief annealing to that before stress-relief annealing is between 2 and 8. After stress-relief annealing, the relative concentration of N element [N] within 0.1 μm from the surface of the steel sheet to the thickness center is less than or equal to 6000 ppm.

[0097] Figure 1 The surface microstructure of the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties before stress-relief annealing, as shown in Embodiment 2 of the present invention, is displayed.

[0098] like Figure 1 As shown, the surface of the high-strength non-oriented electrical steel with excellent electromagnetic properties corresponding to Example 2 has relatively uniform equiaxed grains and an appropriate average grain size, which helps to improve the mechanical and electromagnetic properties of the steel.

[0099] Figure 2 The surface microstructure of the comparative steel plate in Comparative Example 2 before stress-relief annealing is shown.

[0100] like Figure 2 As shown, the surface equiaxed grain uniformity of the comparative steel plate corresponding to Comparative Example 2 is poor, with localized micrograin agglomeration and some large island-shaped grains, which will reduce the mechanical properties of the finished steel plate and lead to grain size growth and reduced black sheet iron loss in the stress-relieved annealing state.

[0101] Figure 3 The relationship between the continuous annealing heating rate of the comparative steel plate in Comparative Example 3 and the relative [N] content on the surface of the steel plate is shown.

[0102] like Figure 3 As shown in Comparative Example 3, the enrichment of nitrogen on the steel plate surface is very significant with increasing continuous annealing heating rate, especially within 0.1 μm from the surface to the center. When the heating rate exceeds 400 °C / s, the relative concentration of nitrogen exceeds the design limit of 6000 ppm.

[0103] Figure 4The relationship between the continuous annealing heating rate and the relative [N] content on the surface of the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties in Embodiment 3 of the present invention is shown.

[0104] like Figure 4 As shown, the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties corresponding to Example 3 does not show significant enrichment of N element on the steel sheet surface as the continuous annealing heating rate increases. When the heating rate reaches 800℃ / s, the relative concentration of N element within 0.1μm from the steel sheet surface to the center will not exceed the design upper limit of 6000ppm.

[0105] Samples of the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties from Examples 1-10 and the comparative steel sheets from Comparative Examples 1-3 were taken before and after stress-relief annealing. Mechanical property tests were performed on each example and comparative example, and the test results of various properties before and after stress-relief annealing are listed in Table 4. Among them:

[0106] Electromagnetic performance testing: Based on national standard GB / T 3655-2008, the Epstein square ring method was used to test iron loss and magnetic induction performance. The test temperature was a constant temperature of 20℃, the sample size was 30mm×300mm, the target mass was 0.5kg, and the test parameter was B. 5000 and P 1.0 / 400 .

[0107] Mechanical property testing: Based on national standard GB / T 228.1-2010, plate-shaped samples were used for mechanical property testing. The test temperature was a constant temperature of 20℃, the standard sample length was 50mm, and the test parameter was Y. S .

[0108] Table 4 lists the performance test results of the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties in Examples 1-10 of the present invention and the comparative steel sheets in Comparative Examples 1-3 before and after stress-relief annealing.

[0109] Table 4.

[0110]

[0111] As can be seen from Table 4 above, the thickness of the high-strength non-oriented electrical steel sheets with excellent electromagnetic properties in Examples 1-10 of the present invention is between 0.15 and 0.30 mm, and the yield strength Y before stress-relief annealing is... S All are greater than or equal to 500 MPa, and the iron loss P after stress-relief annealing 1.0 / 400 All are less than 11.5 W / kg, magnetic induction B 5000 Greater than or equal to 1.65T.

[0112] Figure 5This invention demonstrates the ratio of the average grain size of the high-strength non-oriented electrical steel sheet with excellent electromagnetic properties after stress-relief annealing to that before stress-relief annealing, and the yield strength Y of the finished steel sheet. S Iron loss P 1.0 / 400 The relationship.

[0113] like Figure 5 As shown, in this invention, the ratio of the average grain size after stress-relief annealing to that before stress-relief annealing has a suitable control range. A ratio that is too large or too small is detrimental to the iron loss P of the non-oriented electrical steel after stress-relief annealing as described in this invention. 1.0 / 400 The reduction in yield strength (Y) is also a concern. A small ratio of the average grain size after stress-relief annealing to that before stress-relief annealing is detrimental to the yield strength (Y) of non-oriented electrical steel before stress-relief annealing. S The improvement.

[0114] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0115] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A high-strength non-oriented electrical steel sheet with excellent electromagnetic properties, containing Fe and unavoidable impurities, characterized in that, It also contains the following chemical elements in the following percentages by mass: 0 < C ≤ 0.004%; Si: 2.9–3.6%; Mn: 0.1–1.0%; Al: 0.4–1.4%; at least one of Sn and Sb, and their mass percentage content satisfies: Sn: 0–0.20%, Sb: 0–0.10%; in unavoidable impurities, S ≤ 0.002%, N ≤ 0.002%, Ti ≤ 0.002%.

2. The non-oriented electrical steel sheet as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: 0 < C ≤ 0.004%; Si: 2.9–3.6%; Mn: 0.1–1.0%; Al: 0.4–1.4%; at least one of Sn and Sb, and its mass percentage content satisfies: Sn: 0–0.20%, Sb: 0–0.10%; balance is Fe and unavoidable impurities; Among the unavoidable impurities, S ≤ 0.002%, N ≤ 0.002%, and Ti ≤ 0.002%.

3. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, The mass percentage of Si+Al is 3.8%–4.6%.

4. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, It also contains at least one of the following chemical elements: 0 < Cu ≤ 0.5%; 0＜Cr≤0.5％； 0 < Ni ≤ 0.5%; Furthermore, the mass percentage of Cu+Cr+Ni is ≤1.2%.

5. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, It also contains at least one of the following chemical elements in the following mass percentages: 0 < Mg ≤ 0.01%; 0 < Ca ≤ 0.01%; 0 < REM ≤ 0.01%.

6. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, The microstructure after stress-relief annealing is a fully recrystallized microstructure, and the ratio of the average grain size after stress-relief annealing to that before stress-relief annealing is 2 to 8.

7. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, The relative concentration of nitrogen [N] in the steel plate after stress relief annealing is ≤6000ppm within a depth of 0.1μm from the surface to the center of the thickness.

8. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, Its thickness is 0.15 to 0.30 mm.

9. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, Its yield strength Y before stress relief annealing S ≥500MPa.

10. The non-oriented electrical steel sheet as described in claim 1 or 2, characterized in that, Its iron loss P after stress-relief annealing 1.0 / 400 ≤11.5W / kg, magnetic induction B 5000 ≥1.65T.

11. The method for manufacturing non-oriented electrical steel sheet according to any one of claims 1-10, characterized in that, Including the following steps: (1) Smelting and casting; (2) Heating and hot rolling; (3) Normalizing or bell-type furnace annealing: The soaking temperature of normalizing or bell-type furnace annealing is 820-950℃, and the soaking time is 60-180s. (4) Cold rolling is performed after pickling; (5) Continuous annealing: The continuous annealing temperature is 700-950℃, the heating time is 5-60s, and the heating rate is 15-400℃ / s.

12. The manufacturing method as described in claim 11, characterized in that, In step (2), the furnace exit temperature of the billet heating is 1050-1200℃, the final rolling temperature is 800-950℃, and the coiling temperature is 550-780℃.

13. The manufacturing method according to any one of claims 11-12, characterized in that, It also includes step (6) stress-relief annealing: the soaking temperature for stress-relief annealing is T. 均热 =T 再结晶开始温度 +80~155℃.

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