A low-temperature ultra-high magnetic induction oriented silicon steel strip and its preparation method

Abstract

The present invention provides a low-temperature ultra-high magnetic induction oriented silicon steel strip and a preparation method thereof. The raw materials thereof include the following chemical elements by mass percentage: C: 0.04%-0.055%, Si: 1.0%-2.8%, Mn: 0.01%-0.08%, S: 0.005%-0.01%, Als: 0.02%-0.025%, N: 0.002%-0.005%, B: 0.005%-0.015%, and the remainder is Fe and unavoidable impurity elements. The present invention avoids the processing difficulties caused by the addition of Sn and Bi elements by adding B elements to replace traditional elements such as Sn and Bi, and improves the quality of the surface layer of the strip. In addition, B can form BN with N, and can also segregate along the grain boundaries, thereby improving the inhibitor ability, which is conducive to improving the secondary grain orientation degree, and thus improving the magnetic induction performance of the strip.

Description

Technical Field

[0001] The present invention relates to the technical field of oriented silicon steel strip rolling, and in particular to a low-temperature ultra-high magnetic induction oriented silicon steel strip and a preparation method thereof. Background Art

[0002] Grain-oriented silicon steel is a key core material for electrical equipment such as transformers and reactors. Its high magnetic induction and low loss make it an indispensable soft magnetic material. Due to its complex preparation process, strict composition requirements, and the many factors that influence its magnetic properties, oriented silicon steel is considered a work of art in the steel industry.

[0003] Grain-oriented silicon steel can be divided into high-temperature grain-oriented silicon steel and low-temperature grain-oriented silicon steel based on the slab heating temperature. Due to the drawbacks of high-temperature slab heating technology, such as high energy consumption, short furnace life, numerous surface defects, and high burnout, low-temperature grain-oriented silicon steel has become the current and future development direction of high-magnetic-induction grain-oriented silicon steel.

[0004] To achieve higher magnetic induction intensity, existing technologies produce high-magnetic-induction oriented silicon steel by adding trace alloying elements such as Bi, Sn, and Sb and optimizing process parameters. However, the addition of elements such as Bi and Sn can easily cause edge cracking during hot rolling. Furthermore, under high-temperature smelting conditions, Bi easily volatilizes, making its content difficult to control. Furthermore, during subsequent high-temperature annealing, Bi easily accumulates on the surface and volatilizes in a gaseous state, resulting in poor quality of the underlying strip and reduced magnetic induction performance of the silicon steel strip.

[0005] Therefore, it is necessary to provide a new ultra-high magnetic induction oriented silicon steel strip and a preparation method thereof. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical problem that the magnetic induction performance of existing silicon steel strips is relatively low.

[0007] The purpose of the present invention is to adopt the following technical solutions to achieve:

[0008] The present invention provides a low-temperature ultra-high magnetic induction oriented silicon steel strip. The raw materials of the low-temperature ultra-high magnetic induction oriented silicon steel strip include the following chemical elements, calculated by mass percentage: C: 0.04%-0.055%, Si: 1.0%-2.8%, Mn: 0.01%-0.08%, S: 0.005%-0.01%, Als: 0.02%-0.025%, N: 0.002%-0.005%, B: 0.005%-0.015%, and the balance is Fe and unavoidable impurity elements.

[0009] Preferably, the chemical elements include: C: 0.055%, Si: 2.8%, Mn: 0.010%, S: 0.010%, Als: 0.025%, N: 0.005%, B: 0.005%, and the remainder is Fe and unavoidable impurity elements.

[0010] Based on the same inventive concept, the present invention also provides a method for preparing the low-temperature ultra-high magnetic induction oriented silicon steel strip, comprising: a hot rolling process, a normalizing process, a cold rolling process, a decarburization annealing process, a nitriding process and a high-temperature annealing process.

[0011] Preferably, the starting rolling temperature in the hot rolling process is 1100°C-1150°C, and the finishing rolling temperature is 950°C-1000°C.

[0012] Preferably, the total rolling force in the hot rolling process is 10T-30T, and the thickness of the strip after hot rolling is 2.0mm-2.3mm.

[0013] Preferably, the normalizing temperature in the normalizing step is 1000° C.-1050° C., and the normalizing time is 2 min-5 min.

[0014] Preferably, the atmosphere in the normalizing process is N2, and the gas flow rate is 1 L / min-10 L / min.

[0015] Preferably, the rolling rate in the cold rolling process is 150m / min-250m / min, and the cold rolling reduction ratio is 83%-90%.

[0016] Preferably, the number of rolling passes in the cold rolling process is 1, the total rolling force is 15T-50T, and the thickness of the strip after cold rolling is 0.25mm-0.35mm.

[0017] Preferably, the annealing temperature in the decarburization annealing is 850° C.-880° C., and the annealing time is 3 min-5 min.

[0018] Preferably, the dew point temperature in the decarburization annealing is 20° C.-35° C., the annealing atmosphere is a wet nitrogen-hydrogen mixture gas, the ratio of the nitrogen-hydrogen mixture gas is 1:3-1:1, and the gas flow rate is 4 L / min-8 L / min.

[0019] Preferably, the ratio between the nitrogen content infiltrated in the nitriding process and the Als element content and the B element content is:

[0020] 0.875≤[N] / [Als+B]≤1.75;

[0021] Wherein, [N] represents the percentage of infiltrated nitrogen content, [Als] represents the percentage of Als element, and [B] represents the percentage of B element.

[0022] Preferably, in the nitriding process, the nitriding time is 30s-60s, the nitriding temperature is 700°C-850°C, and the nitriding atmosphere is a mixture of N2, H2, and NH3.

[0023] Preferably, in the high-temperature annealing process, the annealing holding temperature is 1100°C-1200°C, the annealing holding time is 10h-40h, the heating rate is 20°C / h-50°C / h, the annealing atmosphere is a nitrogen mixture, the nitrogen ratio is 75%-90%, and the gas flow rate is 2L / min-5L / min.

[0024] Preferably, the magnetic induction value B of the strip after the high temperature annealing process is 800 ≥1.96T.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a low-temperature, ultra-high magnetic induction oriented silicon steel strip. The raw materials comprise the following chemical elements, calculated by mass percentage: C: 0.04%-0.055%, Si: 1.0%-2.8%, Mn: 0.01%-0.08%, S: 0.005%-0.01%, Als: 0.02%-0.025%, N: 0.002%-0.005%, B: 0.005%-0.015%, with the remainder being Fe and unavoidable impurities. By adding B to replace traditional elements such as Sn and Bi, the present invention avoids the processing difficulties associated with the addition of Sn and Bi, thereby improving the quality of the strip's surface layer. Furthermore, B can form BN with N and can also segregate along grain boundaries, enhancing its inhibitory capacity and improving the degree of secondary grain orientation, thereby enhancing the strip's magnetic induction properties.

[0027] In the nitriding process of the silicon steel strip preparation method of the present invention, the amount of nitrogen infiltration is further controlled according to the proportional relationship of 0.875≤[N] / [Als+B]≤1.75, and the magnetic induction value B is obtained after preparation by combining the process parameters such as hot rolling, normalizing, cold rolling, and high temperature annealing. 800 The oriented silicon steel strip with a magnetic induction value of >1.96T is much higher than the magnetic induction value of existing oriented silicon steel, and the preparation method of the present invention is simple to operate and has high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an electron microscope magnified image of the secondary grain structure in the low-temperature ultra-high magnetic induction oriented silicon steel strip of the present invention;

[0029] Figure 2 To invent the {200} pole figure of secondary grain structure in low-temperature ultra-high magnetic induction oriented silicon steel strip. DETAILED DESCRIPTION

[0030] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0031] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the literature in the art.

[0032] The present invention provides a low-temperature ultra-high magnetic induction oriented silicon steel strip, the raw materials of which include the following chemical elements by mass percentage:

[0033] C: 0.04%-0.055%, Si: 1.0%-2.8%, Mn: 0.01%-0.08%, S: 0.005%-0.01%, Als: 0.02%-0.025%, N: 0.002%-0.005%, B: 0.005%-0.015%, the balance being Fe and unavoidable impurity elements. Als is acid-soluble aluminum.

[0034] The method for preparing the low-temperature ultra-high magnetic induction oriented silicon steel strip of the present invention includes: S1 hot rolling process, S2 normalizing process, S3 cold rolling process, S4 decarburization annealing process, S5 nitriding process and S6 high-temperature annealing process.

[0035] In the hot rolling process of step S1, the starting rolling temperature is 1100°C-1150°C, the finishing rolling temperature is 950°C-1000°C, the total rolling force is 10T-30T, and the thickness of the strip after hot rolling is 2.0mm-2.3mm.

[0036] In the normalizing process of step S2, the normalizing temperature is 1000°C-1050°C, the normalizing time is 2 min-5 min, the normalizing atmosphere is N2, and the gas flow rate is 1 L / min-10 L / min.

[0037] In the cold rolling process of step S3, the rolling rate is 150m / min-250m / min, the cold rolling reduction rate is 83%-90%, the rolling pass is 1 time, the total rolling force is 15T-50T, and the thickness of the strip after cold rolling is 0.25mm-0.35mm.

[0038] In the decarburization annealing process of step S4, the annealing temperature is 850-880°C, the annealing time is 3-5 minutes, the dew point temperature is 20-35°C, the annealing atmosphere is a wet nitrogen-hydrogen mixture gas, the ratio of nitrogen-hydrogen mixture gas is 1:3-1:1, and the gas flow rate is 4 L / min-8 L / min.

[0039] In step S5, the nitriding process is performed for 30-60 seconds at a temperature of 700°C-850°C in a mixture of N₂, H₂, and NH₃. The ratio of the infiltrated nitrogen content to the Al₂ and B content is: 0.875 ≤ [N] / [Al₂ + B] ≤ 1.75, where [N] represents the percentage of infiltrated nitrogen, [Al₂] represents the percentage of Al₂, and [B] represents the percentage of B.

[0040] In the high-temperature annealing process of step S6, the annealing holding temperature is 1100°C-1200°C, the annealing holding time is 10h-40h, the heating rate is 20°C / h-50°C / h, the annealing atmosphere is a nitrogen mixture, the nitrogen ratio is 75%-90%, and the gas flow rate is 2L / min-5L / min.

[0041] The following specific embodiments are obtained by selecting the chemical element ratios and preparation process parameters of the low-temperature ultra-high magnetic induction oriented silicon steel strips in the above different ranges.

[0042] Examples 1-4

[0043] Table 1 shows the chemical element ratios and preparation process parameters of the low-temperature ultra-high magnetic induction oriented silicon steel strips of Examples 1-4:

[0044] Table 1

[0045]

[0046] Continued on next page

[0047]

[0048] Comparative Example 1

[0049] The chemical element content of the silicon steel strip in Comparative Example 1 is different from that in Example 1 in that Si is 3.7%, Al is 0.010%, and no B element is added (B: 0%).

[0050] The process parameters of the preparation method of the silicon steel strip in this comparative example 1 are exactly the same as those in the preparation method in Example 1, so they are not described here in detail.

[0051] Comparative Example 2

[0052] The chemical element content of the silicon steel strip in Comparative Example 2 is different from that in Example 2 in that 0.002% < 0.005% of the B element is added in Comparative Example 2, and [N] / [Als+B]≈0.7.

[0053] The process parameters of the preparation method of the silicon steel strip in this comparative example 2 are exactly the same as those in the preparation method in Example 2, so they are not described here in detail.

[0054] Comparative Example 3

[0055] The chemical element contents of the silicon steel strip in Comparative Example 3 are exactly the same as those in Example 3, and therefore are not described herein in detail.

[0056] The process parameters of the preparation method of the silicon steel strip in this comparative example 3 are different from those in the preparation method in Example 4 in that, in the S1 hot rolling process, the starting rolling temperature is 1080°C and the finishing rolling temperature is 900°C; in the S6 high-temperature annealing process, the heating rate is 80°C / h and the temperature is kept at 1050°C for 2h.

[0057] Results Test

[0058] The ultra-high magnetic induction oriented silicon steel strip samples in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to magnetic induction B 800 The test results are shown in Table 2:

[0059] Table 2

[0060]

[0061] Table 2 shows the magnetic induction values ​​B of the ultra-high magnetic induction oriented silicon steel strips in Examples 1-4 and Comparative Examples 1-3. 800 Comparison table.

[0062] By comparison, it can be seen that the magnetic induction value B of the ultra-high magnetic induction oriented silicon steel strip prepared by the present invention is 800 All exceeded 1.96.

[0063] Among them, when the B element is not added in Comparative Example 1, the magnetic induction value of the oriented silicon steel in Comparative Example 1 is significantly reduced to 1.887.

[0064] Compared with Comparative Example 1, when 0.0021%<0.005% of B element is added in Comparative Example 2, [N] / [Als+B]≈0.7, and the magnetic induction value of the oriented silicon steel in Comparative Example 2 significantly reaches 1.921.

[0065] In Comparative Example 3, in the S1 hot rolling process, the starting rolling temperature is 1080°C and the finishing rolling temperature is 900°C; in the S6 high-temperature annealing process, the heating rate is 80°C / h and the temperature is kept at 1050°C for 2h, the magnetic induction value of the oriented silicon steel also drops significantly to 1.903.

[0066] like Figure 1 and Figure 2 As shown, the secondary grain structure of the silicon steel strip in Example 2 is uniform and the orientation deviation angle is small.

[0067] Among them, Figure 2 In the graph, RD (Rolling Direction) represents the rolling direction, which is the direction of the material's movement along the rollers during the rolling process. In the pole figure, the RD axis characterizes the orientation distribution of grains in the rolling direction. TD (Transverse Direction) represents the transverse direction, which is perpendicular to the rolling direction and parallel to the sample surface. In the pole figure, the TD axis characterizes the orientation distribution of grains in the transverse direction.

[0068] It should be noted that the nitrogen content converted according to the proportional formula [N] / [Als+B] is as follows: the nitriding amount in Example 1 is 0.05925%, and the total N value of the silicon steel strip after nitriding is approximately 0.06125%; the nitriding amount in Example 2 is 0.02125%, and the total N value of the silicon steel strip after nitriding is approximately 0.02625%; the nitriding amount in Example 3 is 0.0335%, and the total N value of the silicon steel strip after nitriding is approximately 0.0375%; the nitriding amount in Example 4 is 0.04258%, and the total N value is approximately 0.04608%.

[0069] By comparison, it can be seen that when the nitrogen content is controlled at a lower penetration amount by the proportional formula in Example 2, the magnetic induction value B of the silicon steel strip after nitriding in Example 2 can be 800 Reaching a maximum value of 1.973.

[0070] Among them, AlN, formed by the combination of N and AlS, is the main inhibitor in grain-oriented silicon steel. Since B is added as a secondary inhibitor, excessive inhibitors will make it difficult to mature during high-temperature annealing, resulting in slow secondary recrystallization of the grains. Therefore, the initial silicon steel material is infiltrated with N in a proportional manner to ensure that N is not excessive and to maintain an appropriate balance between N, AlS, and B. This avoids the generation of excessive inhibitors during the nitriding process, which would reduce the magnetic induction properties of the silicon steel strip.

[0071] In summary, the ultra-high magnetic induction oriented silicon steel strip of the present invention undergoes processes such as hot rolling, normalizing, cold rolling, decarburization annealing, nitriding, and high-temperature annealing. By controlling the nitriding of the silicon steel strip within a specific ratio range ([N] / [Als+B]) in combination with the hot rolling temperature, annealing, and other processes, the magnetic induction value of the oriented silicon steel can be significantly improved. This preparation method is simple to operate and has high production efficiency, meeting the needs of enterprises for high-efficiency production.

[0072] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip, characterized in that: The raw materials include the following chemical elements by mass percentage: C: 0.04%-0.055%, Si: 1.0%-2.8%, Mn: 0.01%-0.08%, S: 0.005%-0.01%, Als: 0.02%-0.025%, N: 0.002%-0.005%, B: 0.005%-0.015%, the balance is Fe and unavoidable impurity elements; The preparation method includes: a hot rolling process, a normalizing process, a cold rolling process, a decarburization annealing process, a nitriding process and a high-temperature annealing process; The starting rolling temperature in the hot rolling process is 1100°C-1150°C, and the finishing rolling temperature is 950°C-1000°C; The ratio between the nitrogen content in the nitriding process and the Als and B content is as follows: 0.875≤[N] / [Als+B]≤1.75; Wherein, [N] represents the percentage of infiltrated nitrogen content, [Als] represents the percentage of Als element, and [B] represents the percentage of B element; The magnetic induction value B of the strip after the high temperature annealing process 800 ≥1.96T.

2. The method for preparing a low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, wherein: The chemical elements include: C: 0.055%, Si: 2.8%, Mn: 0.010%, S: 0.010%, Als: 0.025%, N: 0.005%, B: 0.005%, and the balance is Fe and inevitable impurity elements.

3. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The total rolling force in the hot rolling process is 10T-30T, and the thickness of the strip after hot rolling is 2.0mm-2.3mm.

4. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The normalizing temperature in the normalizing process is 1000° C.-1050° C., and the normalizing time is 2 min-5 min.

5. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The atmosphere in the normalizing process is N2, and the gas flow rate is 1 L / min-10 L / min.

6. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The rolling rate in the cold rolling process is 150m / min-250m / min, and the cold rolling reduction ratio is 83%-90%.

7. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The number of rolling passes in the cold rolling process is 1, the total rolling force is 15T-50T, and the thickness of the strip after cold rolling is 0.25mm-0.35mm.

8. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The annealing temperature in the decarburization annealing is 850° C.-880° C., and the annealing time is 3 min-5 min.

9. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: The dew point temperature in the decarburization annealing is 20° C.-35° C., the annealing atmosphere is a wet nitrogen-hydrogen mixture gas, the ratio of the nitrogen-hydrogen mixture gas is 1:3-1:1, and the gas flow rate is 4 L / min-8 L / min.

10. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: In the nitriding process, the nitriding time is 30s-60s, the nitriding temperature is 700°C-850°C, and the nitriding atmosphere is a mixture of N2, H2, and NH3.

11. The method for preparing low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that: In the high-temperature annealing process, the annealing holding temperature is 1100°C-1200°C, the annealing holding time is 10h-40h, the heating rate is 20°C / h-50°C / h, the annealing atmosphere is a nitrogen mixed gas, the nitrogen ratio is 75%-90%, and the gas flow rate is 2L / min-5L / min.

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