Oriented silicon steel with stable magnetic performance and manufacturing method thereof

Abstract

The invention discloses oriented silicon steel with stable magnetic performance, which contains Fe and other inevitable impurities, and further contains the following chemical elements in percentage by mass: less than or equal to 0.0025% of C; 3.0 to 4.0% of Si; mn: 0.05 to 0.2%; s < = 0.0025%; the content of Als is 0.015 to 0.035 percent; n < = 0.0009%; 0.1 to 0.3 percent of Cu; at least one of Sn, Sb and Bi, and the total mass percentage of the Sn, the Sb and the Bi is 0.1-0.2%. The invention further discloses a manufacturing method of the oriented silicon steel. The manufacturing method comprises the following steps: smelting and casting; hot rolling; under micro pressure; normalizing and annealing; cold rolling; decarburization annealing and nitriding treatment; performing high-temperature annealing; coating an insulating coating; and flattening and annealing.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of steel and its manufacturing method, especially to a kind of oriented silicon steel and its manufacturing method. BACKGROUND

[0002] Oriented silicon steel is a soft magnetic functional material for manufacturing transformer core, and the general production process is steelmaking, hot rolling, normalizing pickling, cold rolling, decarburization annealing nitriding, high temperature annealing, hot stretching and annealing.

[0003] In recent years, with the implementation of transformer energy efficiency standards, the performance requirements of oriented silicon steel are also increasingly high. Among them, thickness thinning is an effective method to improve the performance of oriented silicon steel. Based on this, 0.20mm and 0.18mm oriented silicon steel have been developed, especially 0.18mm oriented silicon steel product, which has low iron loss and high magnetic induction, so it can meet the increasingly high requirements of transformer industry.

[0004] However, after the thickness of oriented silicon steel is thinned, it is not easy to occur secondary recrystallization, and it also faces the technical problem of unstable magnetic properties.

[0005] Therefore, some existing technologies have provided some technical solutions:

[0006] For example: the Chinese patent document with publication number CN103540846A, publication date January 29, 2014, and name "a thin gauge, ultra-low iron loss, low noise, high magnetic induction oriented silicon steel sheet and its preparation method" discloses a thickness of 0.18mm oriented silicon steel. In this technical solution, the content of Si element is 4.1-9%. Because of high Si content, the strip is prone to break during rolling, and batch manufacturing is problematic.

[0007] For example: the Chinese patent document with publication number CN104018068A, publication date September 3, 2014, and name "a preparation method of high magnetic induction oriented silicon steel with a thickness of 0.18mm" discloses a preparation method of high magnetic induction oriented silicon steel with a thickness of 0.18mm, but it uses a two-step rolling method, which increases the manufacturing cost. SUMMARY

[0008] One of the purposes of the present application is to provide an oriented silicon steel with stable magnetic properties. By adjusting the segregation elements, the secondary recrystallization can be improved, and the oriented silicon steel has good magnetic properties, and can maintain stable magnetic properties while having high magnetic induction.

[0009] In order to achieve the above purpose, the present application provides an oriented silicon steel with stable magnetic properties, which contains Fe and other unavoidable impurities, and further contains chemical elements with mass percentage as follows:

[0010] C≤0.0025%; Si: 3.0-4.0%; Mn: 0.05-0.2%; S≤0.0025%; Al: 0.015-0.035%; N≤0.0009%; Cu: 0.1-0.3%; at least one of Sn, Sb, Bi, with a total mass percentage content of 0.1-0.2%.

[0011] Further, in the oriented silicon steel described in the present application, the mass percentage content of each chemical element is:

[0012] C≤0.0025%; Si: 3.0-4.0%; Mn: 0.05-0.2%; S≤0.0025%; Al: 0.015-0.035%; N≤0.0009%; Cu: 0.1-0.3%; at least one of Sn, Sb, Bi, with a total mass percentage content of 0.1-0.2%; the balance being Fe and other unavoidable impurities.

[0013] Further, in the oriented silicon steel described in the present application, it has uniform equiaxed grains, and the average grain size of the uniform equiaxed grains is 4-9mm.

[0014] Further, in the oriented silicon steel described in the present application, the thickness is 0.15-0.30mm.

[0015] Further, in the oriented silicon steel described in the present application, the abnormal structure occurrence rate is ≤10%.

[0016] In the present application, the stability of magnetic properties can be characterized by the abnormal structure occurrence rate, which is defined in the present application as the area ratio of <4mm grain size for a sample plate of 500mm length*plate width size.

[0017] Further, in the oriented silicon steel described in the present application, the iron loss P 17 / 50 ≤1.0W / kg, magnetic induction B8≥1.91T.

[0018] Another object of the present application is to provide a manufacturing method of oriented silicon steel, which can make the secondary recrystallization of the steel plate perfect by controlling the composition of the casting blank and cooperating with the micro-pressing process, so as to realize higher magnetic induction while maintaining the stability of magnetic properties.

[0019] In order to achieve the above object, the present application provides a manufacturing method of oriented silicon steel, comprising the steps of:

[0020] (1) smelting and casting, the composition of the obtained casting blank is: C: 0.04-0.08%; Si: 3.0-4.0%; Mn: 0.05-0.2%; S: 0.005-0.01%; Als: 0.015-0.035%; N: 0.001-0.01%; Cu: 0.1-0.3%; at least one of Sn, Sb and Bi, the total content of which is 0.1-0.2%; the balance is Fe and inevitable impurities;

[0021] (2) hot rolling;

[0022] (3) slight reduction: 0 < reduction ratio of slight reduction ≤ 0.5%;

[0023] (4) normalizing annealing;

[0024] (5) cold rolling;

[0025] (6) decarburization annealing and nitriding treatment;

[0026] (7) high-temperature annealing;

[0027] (8) coating with an insulating coating and flat annealing.

[0028] In step (1) of the manufacturing method described in the application, the design principles of each chemical element in the casting blank are as follows:

[0029] C: in the casting blank of the oriented silicon steel described in the application, the C element can form a γ phase during hot rolling. When the mass percentage content of C element in the steel is too low, effective γ phase cannot be formed; when the mass percentage content of C element in the steel is too high, decarburization will be difficult. Therefore, in the casting blank of the oriented silicon steel described in the application, the mass percentage content of C element is controlled to be between 0.04-0.08%.

[0030] Si: in the casting blank of the oriented silicon steel described in the application, Si element can effectively increase the resistivity of the material and reduce the iron loss of the steel. The higher the content of Si element in the steel, the worse the manufacturability. When the mass percentage content of Si element in the steel is too high, the cold rolling breakage rate will increase; when the mass percentage content of Si element in the steel is too low, it cannot effectively reduce the iron loss and improve the performance. Therefore, in the casting blank of the oriented silicon steel described in the application, the mass percentage content of Si element is controlled to be between 3.0-4.0%.

[0031] Mn: In the oriented silicon steel casting blank described in the present application, the role of Mn element is similar to that of Si element, and it can also play a role in improving the resistivity of the material and reducing the iron loss of the steel. In addition, Mn can combine with S to form MnS as an inhibitor. However, it should be noted that when the mass percentage content of Mn element in the steel is too low, the inhibitor effect cannot be achieved; when the mass percentage content of Mn element in the steel is too high, the hot rolling workability and magnetic properties will be reduced. Therefore, in the oriented silicon steel casting blank described in the present application, the mass percentage content of Mn element is controlled to be between 0.05-0.2%.

[0032] S: In the oriented silicon steel casting blank described in the present application, S element mainly combines with Mn and Cu elements to form MnS or CuS as an inhibitor. When the mass percentage content of S element in the steel is too low, the inhibitor effect cannot be achieved effectively; when the mass percentage content of S element in the steel is too high, it is difficult to purify and desulfurize. Therefore, in the oriented silicon steel casting blank described in the present application, the mass percentage content of S element is controlled to be between 0.005-0.01%.

[0033] Als: In the oriented silicon steel casting blank described in the present application, Als element mainly forms AlN inhibitor with N element. When the mass percentage content of Als element in the steel is too high, the quality of the bottom layer will be poor; when the mass percentage content of Als element in the steel is too low, the inhibition effect cannot be achieved. Therefore, in the oriented silicon steel casting blank described in the present application, the mass percentage content of Als element is controlled to be between 0.015-0.035%.

[0034] N: In the oriented silicon steel casting blank described in the present application, N element can form AlN inhibitor with Als. When the mass percentage content of N element in the steel is too low, the inhibition effect is insufficient; when the mass percentage content of N element in the steel is too high, the steelmaking and casting are prone to blow, and the product will have peeling and blistering defects. Therefore, in the oriented silicon steel casting blank described in the present application, the mass percentage content of N element is controlled to be between 0.001-0.010%.

[0035] Cu: In the oriented silicon steel casting blank described in the present application, Cu element can improve the quality of the bottom layer containing segregation elements. When the mass percentage content of Cu element in the steel is too low, this effect cannot be fully achieved; when the mass percentage content of Cu element in the steel is too high, the bottom layer control becomes difficult. Therefore, in the oriented silicon steel casting blank described in the present application, the mass percentage content of Cu element is controlled to be between 0.1-0.3%.

[0036] Sn, Sb, Bi: In the cast slab of the oriented silicon steel described in the application, Sn, Sb and Bi elements belong to grain boundary segregation elements, which can further increase the inhibition capacity. In the cast slab of the oriented silicon steel described in the application, they can be added alone or two or three together, and the total amount is controlled at 0.1-0.2%. When the total content of grain boundary segregation elements in the steel is too high, the bottom layer control becomes difficult; when the total content of grain boundary segregation elements in the steel is too low, the effect of segregation and inhibition cannot be achieved.

[0037] The inventor found through research that the microstructure of the oriented silicon steel hot-rolled plate is different in each layer in the thickness direction: the surface layer is recrystallized grains, the subsurface layer is elongated recrystallized grains, and the center layer is deformed grains. Among them, GOSS grains mainly exist in the subsurface layer, and through the method of micro-rolling, the surface layer grains can be further micro-deformed, the deformation of the subsurface GOSS grains is increased, and the nucleation and growth of Goss grains in the subsequent normalizing annealing process is promoted, laying a foundation for secondary recrystallization.

[0038] The application adopts the micro-rolling process and the amount of segregation elements, and cooperates with normalizing annealing to obtain a suitable match of GOSS texture and inhibition force, and further obtain an oriented silicon steel with stable magnetic properties.

[0039] In the application, the GOSS texture control after hot rolling is very important in the production process of oriented silicon steel, which is usually distributed in the surface layer structure. Micro-rolling can make the surface layer GOSS texture micro-deform, and this micro-rolling can be realized by a hot-rolling flattening unit. If the rolling rate of micro-rolling is >0.5%, additional rolling equipment is needed, which increases the manufacturing difficulty.

[0040] Further, in step (2) of the manufacturing method described in the application, the hot-rolling heating temperature is 1100-1150℃.

[0041] Further, in step (5) of the manufacturing method described in the application, the cold-rolling reduction rate is 88-92%.

[0042] Further, in step (6) of the manufacturing method described in the application, the nitriding amount is controlled at 200-300ppm.

[0043] Further, in step (4) of the manufacturing method described in the application, two-stage normalizing annealing is adopted, wherein the first stage temperature T=1150+55xA+996xB, the holding time is 60-120s, wherein A represents the total mass percentage content of at least one of Sn, Sb and Bi, and B represents the rolling rate of micro-rolling; the second stage temperature is 900-950℃, and the holding time is 60-120s.

[0044] The oriented silicon steel and the manufacturing method thereof have the following advantages and beneficial effects compared to the prior art:

[0045] The oriented silicon steel and the manufacturing method thereof can make the secondary recrystallization perfect and have good magnetic properties by adjusting the segregation elements and controlling the micro-reduction rate, so that the higher magnetic induction is obtained while the magnetic properties are stable.

[0046] In some embodiments, the oriented silicon steel has a power loss P 17 / 50 ≤1.0 W / kg, a magnetic induction B8≥1.91 T, and an abnormal structure occurrence rate ≤10%. DETAILED DESCRIPTION

[0047] The oriented silicon steel and the manufacturing method thereof will be further explained and described in combination with specific examples, but the explanation and description do not constitute undue limitations on the technical solutions of the present application.

[0048] Examples 1-8 and Comparative Examples 1-7

[0049] The oriented silicon steel of Examples 1-8 and the comparative steel of Comparative Examples 1-7 are prepared by the following method:

[0050] (1) Smelting and casting: smelting and casting are performed, and the chemical composition ratio of the prepared cast blank is shown in Table 1;

[0051] (2) Hot rolling: the hot rolling heating temperature can be controlled to be 1100-1150℃;

[0052] (3) Micro-reduction: the reduction rate of micro-reduction is controlled to be 0< reduction rate of micro-reduction≤0.5%;

[0053] (4) Normalization annealing: two-stage normalization annealing is adopted, wherein the first stage temperature T=1150+55×A+996×B, the holding time is 60-120s, wherein A represents the total mass content of at least one of Sn, Sb and Bi, and B represents the reduction rate of micro-reduction; the second stage temperature is 900-950℃, the holding time is 60-120s, and then water cooling is performed;

[0054] (5) Cold rolling: the cold rolling reduction rate can be controlled to be 88-92%;

[0055] (6) Decarburization annealing and nitriding treatment: the decarburization annealing temperature is controlled to be 800-900℃, the nitriding amount is controlled to be 200-300ppm, and MgO is used for coating;

[0056] (7) high temperature annealing: the high temperature annealing temperature can be controlled to be first raised to 600-700℃, and then the temperature is kept for ≥20h; when the temperature is continuously raised to 800-1050℃, the annealing atmosphere is dry N2+H2 mixed gas with a volume percentage of not less than 50%; when the temperature is continuously raised to 1050-1150℃, the annealing atmosphere is dry N2+H2 mixed gas with a volume percentage of less than 50%; when the temperature is continuously raised to 1150-1200℃, the annealing atmosphere is pure H2;

[0057] (8) coating of an insulation coating and flat annealing: the insulation coating can be a conventional insulation coating material for oriented silicon steel, for example, an insulation coating composed of phosphate, silicon dioxide and chromic anhydride; the annealing temperature is 800-900℃.

[0058] It should be noted that the chemical element composition and the related process design of the oriented silicon steel of Examples 1-8 all meet the design specification requirements of the present application. The chemical element composition of Comparative Examples 1-2 does not meet the design specification requirements of the present application, and the process design of Comparative Examples 3-7 does not meet the design specification requirements of the present application.

[0059] Table 1 lists the chemical composition ratios of the cast blanks of the oriented silicon steel of Examples 1-8 and the comparative steel of Comparative Examples 1-7 of the present application.

[0060] Table 1. (wt%, the balance being Fe and other unavoidable impurities)

[0061] No. C Si Mn S Als N Cu Sn Sb Bi Sn + Sb + Bi Example 1 0.05 3.3 0.12 0.064 0.025 0.07 0.2 0.1 0 0 0.1 Example 2 0.04 3.0 0.19 0.005 0.015 0.01 0.1 0 0.15 0.05 0.2 Example 3 0.08 3.9 0.05 0.1 0.03 0.001 0.3 0.06 0.06 0.06 0.18 Example 4 0.07 3.2 0.14 0.085 0.035 0.0067 0.13 0 0.15 0 0.15 Example 5 0.07 3.2 0.14 0.085 0.032 0.0069 0.12 0 0.15 0 0.15 Example 6 0.05 3.3 0.12 0.064 0.025 0.07 0.2 0.1 0 0 0.1 Example 7 0.04 3.1 0.2 0.005 0.015 0.01 0.1 0 0.15 0.05 0.2 Example 8 0.08 3.9 0.05 0.1 0.03 0.001 0.3 0.06 0.06 0.06 0.18 Comparative Example 1 0.06 3.4 0.062 0.055 0.027 0.081 0.15 0.06 0 0 0.06 Comparative Example 2 0.06 3.3 0.057 0.068 0.028 0.074 0.15 0.08 0.08 0.08 0.24 Comparative Example 3 0.07 3.2 0.14 0.085 0.032 0.0067 0.12 0 0.15 0 0.15 Comparative Example 4 0.07 3.2 0.14 0.085 0.032 0.0067 0.12 0 0.15 0 0.15 Comparative Example 5 0.05 3.3 0.12 0.064 0.025 0.07 0.2 0.1 0 0 0.1 Comparative Example 6 0.04 3.1 0.19 0.005 0.015 0.01 0.1 0 0.15 0.05 0.2 Comparative Example 7 0.08 3.9 0.05 0.1 0.03 0.001 0.3 0.06 0.06 0.06 0.18

[0062] Table 2 lists the specific process parameters of the oriented silicon steel of Examples 1-8 and the comparative steel of Comparative Examples 1-7 of the present application.

[0063] Table 2.

[0064]

[0065] It should be noted that the first-stage normalizing annealing temperature in Comparative Examples 5-7 does not meet the formula T = 1150 + 55xA + 996xB.

[0066] Table 3 lists the chemical composition ratios of the finished oriented silicon steel of Examples 1-8 and the finished comparative steel of Comparative Examples 1-7 of the present application.

[0067] Table 3. (wt%, the balance being Fe and other unavoidable impurities)

[0068]

[0069]

[0070] The obtained oriented silicon steel of examples 1-8 and comparative steel of comparative examples 1-7 were sampled respectively, using a sample plate with a size of 500mm length*plate width, and the average grain size of secondary recrystallization of each example and comparative example was measured by referring to the intercept method in GB / T 6394-2017 Metal Average Grain Size Determination Method, and was listed in Table 4 below.

[0071] Table 4 lists the average grain observation results of the oriented silicon steel of examples 1-8 and the comparative steel of comparative examples 1-7 of the present application.

[0072] Table 4.

[0073] No. Average grain size (mm) Example 1 9 Example 2 8 Example 3 5 Example 4 8 Example 5 6 Example 6 4 Example 7 5 Example 8 7 Comparative Example 1 13 Comparative Example 2 10 Comparative Example 3 15 Comparative Example 4 12 Comparative Example 5 11 Comparative Example 6 11 Comparative Example 7 13

[0074] As can be seen from Table 3 above, the average grain size of the uniform equiaxed grains of the oriented silicon steel of examples 1-8 is all in the range of 4-9mm.

[0075] In addition, the oriented silicon steel of examples 1-8 and the comparative steel of comparative examples 1-7 of the present application were resampled, and the relevant performance tests were performed on the finished steel of each example and comparative example, and the performance test results were listed in Table 5. Among them, the relevant performance test methods are as follows:

[0076] Iron loss P 17 / 50 and magnetic induction B8: the iron loss P 17 / 50 and magnetic induction B8 of each example and comparative example were determined by referring to GB / T 13789.

[0077] Magnetic property stability: the abnormal structure occurrence rate was used to represent the magnetic property stability, and the abnormal structure occurrence rate was defined in the present application as the area ratio of <4mm grain size for a sample plate with a size of 500mm length*plate width.

[0078] Table 5 lists the relevant performance test results of the oriented silicon steel of examples 1-8 and the comparative steel of comparative examples 1-7 of the present application.

[0079] Table 5.

[0080]

[0081] As can be seen from Table 5 above, the iron loss P 17 / 50 of the oriented silicon steel of examples 1-8 of the present application is all less than 1.0W / kg, the magnetic induction B8 is all greater than or equal to 1.91T, and the abnormal structure occurrence rate is all less than or equal to 10%. It can be seen that the oriented silicon steel prepared by the present application can obtain good magnetic properties, and the magnetic properties are stable.

[0082] It should be noted that the combination of the technical features in the case is not limited to the combination of the claims in the case or the combination of the embodiments in the case. All the technical features disclosed in the case can be freely combined or combined in any way, unless contradictory.

[0083] It should also be noted that the above-mentioned embodiments are only specific embodiments of the present application. Obviously, the present application is not limited to the above-mentioned embodiments, and similar changes or modifications made in accordance with the disclosure of the present application are directly derived or easily conceived by those skilled in the art, and should all fall within the scope of protection of the present application.

Claims

1. A magnetically stable grain-oriented silicon steel, containing Fe and other unavoidable impurities, characterized in that, It also contains the following chemical elements in the following percentages by mass: C ≤ 0.0025%; Si: 3.0–4.0%; Mn: 0.05–0.2%; S ≤ 0.0025%; Als 0.015–0.035%; N ≤ 0.0009%; Cu: 0.1–0.3%; at least one of Sn, Sb, and Bi, with a total mass percentage of 0.1–0.2%.

2. The grain-oriented silicon steel as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: C ≤ 0.0025%; Si: 3.0–4.0%; Mn: 0.05–0.2%; S ≤ 0.0025%; Als 0.015–0.035%; N ≤ 0.0009%; Cu: 0.1–0.3%; at least one of Sn, Sb, and Bi, with a total mass percentage of 0.1–0.2%; the balance being Fe and other unavoidable impurities.

3. The grain-oriented silicon steel as described in claim 1 or 2, characterized in that, It has uniform equiaxed grains, and the average grain size of the uniform equiaxed grains is 4-9 mm.

4. The grain-oriented silicon steel as described in claim 1 or 2, characterized in that, Its thickness is 0.15 to 0.30 mm.

5. The grain-oriented silicon steel as described in claim 1 or 2, characterized in that, The incidence of abnormal tissue is ≤10%.

6. The grain-oriented silicon steel as described in claim 1 or 2, characterized in that, Its iron loss P 17 / 50 ≤1.0W / kg, magnetic induction B8≥1.91T.

7. The method for manufacturing grain-oriented silicon steel according to any one of claims 1-6, characterized in that, Including the following steps: (1) Smelting and casting, the composition of the obtained billet is: C: 0.04~0.08%; Si: 3.0~4.0%; Mn: 0.05~0.2%; S：0.005～0.01％； Als: 0.015–0.035%; N: 0.0010–0.01%; Cu: 0.1–0.3%; at least one of Sn, Sb, and Bi, with a total content of 0.1–0.2%; the balance being Fe and unavoidable impurities; (2) Hot rolling; (3) Under micro-pressure: 0 < micro-pressure reduction rate ≤ 0.5%; (4) Normalizing annealing; (5) Cold rolling; (6) Decarburization annealing and nitriding treatment; (7) High-temperature annealing; (8) Apply an insulating coating and perform a smooth annealing.

8. The manufacturing method as described in claim 7, characterized in that, In step (2), the hot rolling heating temperature is 1100~1150℃.

9. The manufacturing method as described in claim 7, characterized in that, In step (5), the cold rolling reduction rate is 88-92%.

10. The manufacturing method as described in claim 7, characterized in that, In step (6), the nitriding amount is controlled to be 200-300 ppm.

11. The manufacturing method according to any one of claims 7-10, characterized in that, In step (4), a two-stage normalizing annealing is adopted, wherein the temperature of the first stage is T=1150+55×A+996×B, and the holding time is 60-120s, where A represents the total mass percentage of at least one of Sn, Sb and Bi, and B represents the reduction rate under micro pressure; the temperature of the second stage is 900-950℃, and the holding time is 60-120s.

Images