Low-temperature ultrahigh-magnetic-induction oriented silicon steel strip and preparation method thereof

Abstract

The invention provides a low-temperature ultrahigh-magnetic-induction oriented silicon steel strip and a preparation method thereof, and the low-temperature ultrahigh-magnetic-induction oriented silicon steel strip comprises the following chemical elements in percentage by mass: 0.04%-0.055% of C, 1.0%-2.8% of Si, 0.01%-0.08% of Mn, 0.005%-0.01% of S, 0.02%-0.025% of Als, 0.002%-0.005% of N, 0.005%-0.015% of B and the balance of Fe and inevitable impurity elements. The B element is added to replace traditional Sn, Bi and other elements, the machining problem caused by addition of the Sn and Bi elements is solved, and the quality of the surface layer of the strip is improved. In addition, B and N can form BN and can also be segregated along the grain boundary, the inhibiting agent capacity is improved, the secondary grain orientation degree can be improved, and then the magnetic induction performance of the strip is improved.

Description

Technical Field

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

[0002] Grain-oriented silicon steel is the core key material for electrical equipment such as transformers and reactors. It has the advantages of high magnetic induction and low loss, and is an indispensable important soft magnetic material. Due to the complex preparation process of grain-oriented silicon steel, strict composition requirements, and many factors affecting magnetic properties, it is also regarded as a handicraft 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 according to the slab heating temperature. Due to the disadvantages of high energy consumption cost, short furnace life, many surface defects of products, and high burning loss in the high-temperature slab heating technology, at present, low-temperature grain-oriented silicon steel has become the main development direction of current and future high magnetic induction grain-oriented silicon steel.

[0004] In order to obtain a higher magnetic induction intensity, in the prior art, high magnetic induction grain-oriented silicon steel is produced by adding trace alloying elements such as Bi, Sn, Sb, and optimizing process parameters. However, adding elements such as Bi and Sn easily causes edge cracking during hot rolling, and Bi element is easy to volatilize under high-temperature smelting conditions, and the content of Bi element is difficult to control. At the same time, Bi element is easy to enrich on the surface and become gaseous volatilization during subsequent high-temperature annealing, resulting in poor quality of the bottom layer of the strip and reducing the magnetic induction performance of the silicon steel strip.

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

[0006] The object of the present invention is to solve the technical problem of low magnetic induction performance of the existing silicon steel strip.

[0007] The object of the present invention is achieved by adopting the following technical solutions: The present invention provides a low-temperature ultra-high magnetic induction grain-oriented silicon steel strip. By mass percentage, its raw materials include the following chemical elements: 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.

[0008] 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 balance is Fe and unavoidable impurity elements.

[0009] 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, including: a hot rolling process, a normalizing process, a cold rolling process, a decarburizing annealing process, a nitriding process, and a high-temperature annealing process.

[0010] Preferably, the starting rolling temperature in the hot rolling process is 1100°C - 1150°C, and the final rolling temperature is 950°C - 1000°C.

[0011] 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.

[0012] Preferably, the normalizing temperature in the normalizing process is 1000°C - 1050°C, and the normalizing time is 2min - 5min.

[0013] Preferably, the atmosphere in the normalizing process is N2, and the gas flow rate is 1L / min - 10L / min.

[0014] Preferably, the rolling rate in the cold rolling process is 150m / min - 250m / min, and the cold rolling reduction rate is 83% - 90%.

[0015] Preferably, the number of rolling passes in the cold rolling process is 1 pass, the total rolling force is 15T - 50T, and the thickness of the strip after cold rolling is 0.25mm - 0.35mm.

[0016] Preferably, the annealing temperature in the decarburizing annealing is 850°C - 880°C, and the annealing time is 3min - 5min.

[0017] Preferably, the dew point temperature in the decarburizing annealing is 20°C - 35°C, the annealing atmosphere is a wet nitrogen-hydrogen mixed gas, the ratio in the nitrogen-hydrogen mixed gas is 1:3 - 1:1, and the gas flow rate is 4L / min - 8L / min.

[0018] Preferably, the proportional relationship between the nitrogen content infiltrated in the nitriding process and the Als element content and the B element content is: 0.875 ≤ [N] / [Als + B] ≤ 1.75; wherein, [N] represents the percentage content of the infiltrated nitrogen content, [Als] represents the percentage content of the Als element, and [B] represents the percentage content of the B element.

[0019] Preferably, the nitriding time in the nitriding process is 30s - 60s, the nitriding temperature is 700°C - 850°C, and the nitriding atmosphere is a mixed gas of N2, H2, and NH3.

[0020] 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.

[0021] Preferably, the magnetic induction value B of the strip after the high-temperature annealing process 800 ≥1.96T.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a low-temperature ultra-high magnetic induction grain-oriented silicon steel strip. By mass percentage, its raw materials include the following chemical elements: 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 inevitable impurity elements. By adding element B to replace traditional elements such as Sn and Bi, the present invention avoids the processing difficulties brought by the addition of Sn and Bi elements and improves the quality of the strip surface. In addition, B can form BN with N and can also segregate along the grain boundaries, improving the inhibitor ability, which is beneficial to increasing the secondary grain orientation degree and further enhancing the magnetic induction performance of the strip.

[0023] In the nitriding process of the preparation method of the silicon steel strip of the present invention, the infiltration amount of nitrogen element is further controlled according to the proportional relationship 0.875 ≤ [N] / [Als + B] ≤ 1.75. Combining process parameters such as hot rolling, normalizing, cold rolling, and high-temperature annealing, an oriented silicon steel strip with a magnetic induction value B 800 > 1.96T is obtained, which is much higher than the magnetic induction value of the existing oriented silicon steel. Moreover, the preparation method of the present invention is simple to operate and has high production efficiency. Description of the Drawings

[0024] Figure 1 is an electron microscope magnification diagram of the secondary grain structure in the low-temperature ultra-high magnetic induction grain-oriented silicon steel strip of the present invention; Figure 2 is the {200} pole figure of the secondary grain structure in the low-temperature ultra-high magnetic induction grain-oriented silicon steel strip of the invention. Detailed Embodiments

[0025] The following embodiments are provided to better understand the present invention further. They are not limited to the best implementation mode, and do not constitute a limitation to the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0026] For those embodiments where specific experimental procedures or conditions are not specified, the operations or conditions of the conventional experimental procedures described in the literature in this field can be followed.

[0027] The present invention provides a low-temperature ultra-high magnetic induction oriented silicon steel strip. By mass percentage, its raw materials include the following chemical elements: 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 inevitable impurity elements. Among them, Als is acid-soluble aluminum.

[0028] Among them, the preparation method of 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 decarburizing annealing process, S5 nitriding process, and S6 high-temperature annealing process.

[0029] In the step S1 hot rolling process, the starting rolling temperature is 1100°C - 1150°C, the final 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.

[0030] In the step S2 normalizing process, the normalizing temperature is 1000°C - 1050°C, the normalizing time is 2min - 5min, the normalizing atmosphere is N2, and the gas flow rate is 1L / min - 10L / min.

[0031] In the step S3 cold rolling process, the rolling rate is 150m / min - 250m / min, the cold rolling reduction ratio is 83% - 90%, the number of rolling passes is 1, the total rolling force is 15T - 50T, and the thickness of the strip after cold rolling is 0.25mm - 0.35mm.

[0032] In the step S4 decarburizing annealing process, the annealing temperature is 850°C - 880°C, the annealing time is 3min - 5min, the dew point temperature is 20°C - 35°C, the annealing atmosphere is a wet nitrogen-hydrogen mixture, the ratio in the nitrogen-hydrogen mixture is 1:3 - 1:1, and the gas flow rate is 4L / min - 8L / min.

[0033] In the nitriding process of step S5, the nitriding time is 30 s - 60 s, the nitriding temperature is 700°C - 850°C, and the nitriding atmosphere is a mixed gas of N2, H2, and NH3. Among them, the proportional relationship between the infiltrated nitrogen content and the Als element content and the B element content is: 0.875 ≤ [N] / [Als + B] ≤ 1.75; [N] represents the percentage content of the infiltrated nitrogen content, [Als] represents the percentage content of the Als element, and [B] represents the percentage content of the B element.

[0034] In the high-temperature annealing process of step S6, the annealing holding temperature is 1100°C - 1200°C, the annealing holding time is 10 h - 40 h, 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 2 L / min - 5 L / min.

[0035] The chemical element ratios and preparation process parameters of the low-temperature ultra-high magnetic induction oriented silicon steel strips within the above different ranges are selected to obtain the following specific examples.

[0036] Examples 1 - 4 Table 1 shows the comparison of the chemical element ratios and preparation process parameters of the low-temperature ultra-high magnetic induction oriented silicon steel strips in Examples 1 - 4 as follows: Table 1

[0037] See the following table on the next page

[0038] Comparative Example 1 The difference in the chemical element content of the silicon steel strip in this Comparative Example 1 from that in Example 1 is that in this Comparative Example 1, Si: 3.7%, Al: 0.010%, and the B element is not added (B: 0%).

[0039] The preparation method of the silicon steel strip in this Comparative Example 1 is exactly the same as the process parameters of the preparation method in Example 1, so it will not be elaborated here.

[0040] Comparative Example 2 The difference in the chemical element content of the silicon steel strip in this Comparative Example 2 from that in Example 2 is that in this Comparative Example 2, the B element is added at 0.002% < 0.005%, and [N] / [Als + B] ≈ 0.7.

[0041] The preparation method of the silicon steel strip in this Comparative Example 2 is exactly the same as the process parameters of the preparation method in Example 2, so it will not be elaborated here.

[0042] Comparative Example 3 The chemical element content of the silicon steel strip in Comparative Example 3 is exactly the same as that in Example 3, so it will not be elaborated here.

[0043] The difference in the process parameters of the preparation method of the silicon steel strip in Comparative Example 3 and the preparation method in Example 4 is that in the S1 hot rolling process, the starting rolling temperature is 1080 °C and the final rolling temperature is 900 °C; in the S6 high-temperature annealing process, the heating rate is 80 °C / h and it is held at 1050 °C for 2 h.

[0044] Result Test The magnetic induction B of the ultra-high magnetic induction grain-oriented silicon steel strip samples in Examples 1-4 and Comparative Examples 1-3 was respectively 800 The test results are shown in Table 2: Table 2

[0045] Table 2 is a comparison table of the magnetic induction values B of the ultra-high magnetic induction grain-oriented silicon steel strips in Examples 1-4 and Comparative Examples 1-3. 800 Comparison table.

[0046] By comparison, it can be seen that the magnetic induction value B of the ultra-high magnetic induction grain-oriented silicon steel strip prepared by the present invention 800 all exceed 1.96.

[0047] Among them, when the B element was not added in Comparative Example 1, the magnetic induction value of the grain-oriented silicon steel in Comparative Example 1 decreased significantly to 1.887.

[0048] Compared with Comparative Example 1, when 0.0021% < 0.005% of the B element was added in Comparative Example 2 and [N] / [Als + B] ≈ 0.7, the magnetic induction value of the grain-oriented silicon steel in Comparative Example 2 reached 1.921 significantly.

[0049] When in the S1 hot rolling process of Comparative Example 3, the starting rolling temperature is 1080 °C and the final rolling temperature is 900 °C; in the S6 high-temperature annealing process, the heating rate is 80 °C / h and it is held at 1050 °C for 2 h, the magnetic induction value of the grain-oriented silicon steel also decreased significantly to 1.903.

[0050] As Figure 1 and Figure 2 shown, the secondary grain structure of the silicon steel strip in Example 2 is uniform and the orientation deviation angle is small.

[0051] Among them, in Figure 2Among them, RD (Rolling Direction) represents the rolling direction, that is, the direction in which the material moves along the rolling mill during the rolling process. In the pole figure, the RD axis is used to characterize the orientation distribution characteristics of grains in the rolling direction. TD (Transverse Direction) represents the transverse direction, that is, the direction perpendicular to the rolling direction and parallel to the sample surface. In the pole figure, the TD axis is used to characterize the orientation distribution characteristics of grains in the transverse direction.

[0052] It should be noted that the nitrogen content infiltrated is calculated according to the proportional formula [N] / [Als+B] as follows: the nitriding amount in Example 1 is 0.05925%, and the total N value of the silicon steel strip after nitriding is about 0.06125%; the nitriding amount in Example 2 is 0.02125%, and the total N value of the silicon steel strip after nitriding is about 0.02625%; the nitriding amount in Example 3 is 0.0335%, and the total N value of the silicon steel strip after nitriding is about 0.0375%; the nitriding amount in Example 4 is 0.04258%, and the total N value is about 0.04608%.

[0053] By comparison, it can be seen that when the nitrogen content in Example 2 is controlled at a lower infiltration amount through the proportional formula, the magnetic induction value B of the silicon steel strip after nitriding in Example 2 800 can reach the maximum value of 1.973.

[0054] Among them, AlN formed by the combination of N and Als is the main inhibitor of grain-oriented silicon steel. Since B is added as an auxiliary inhibitor, too many inhibitors will make it difficult to ripen during the high-temperature annealing process, resulting in a slow secondary recrystallization process of grains. Therefore, the initial silicon steel material infiltrates N elements according to the proportional relationship to ensure that N is not excessive and maintain an appropriate balance among N, Als, and B, avoiding the generation of too many inhibitors during the nitriding process and reducing the magnetic induction performance of the silicon steel strip.

[0055] In summary, the ultra-high magnetic induction grain-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 proportional range ([N] / [Als+B]) and coordinating with processes such as hot rolling temperature and annealing, the magnetic induction value of the grain-oriented silicon steel can be significantly improved. The preparation method is simple in operation, high in production efficiency, and meets the requirements of high-efficiency production of enterprises.

[0056] The above are only examples of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention pending approval.

Claims

1. A low-temperature ultra-high magnetic induction oriented silicon steel strip, characterized in that, By mass percentage, its raw materials include the following chemical elements: 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.

2. The low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 1, characterized in that, 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 unavoidable impurity elements.

3. A method for preparing a low-temperature ultra-high magnetic induction oriented silicon steel strip as described in any one of claims 1-2, characterized in that, Include: Hot rolling process, normalizing process, cold rolling process, decarburizing annealing process, nitriding process, and high-temperature annealing process.

4. The preparation method of the low-temperature and ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, In the hot rolling process, the starting rolling temperature is 1100°C - 1150°C, and the final rolling temperature is 950°C - 1000°C.

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

6. The method for preparing a low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, In the normalizing process, the normalizing temperature is 1000°C - 1050°C, and the normalizing time is 2min - 5min.

7. The preparation method of the low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, In the normalizing process, the atmosphere is N2, and the gas flow rate is 1L / min - 10L / min.

8. The method for preparing a low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, In the cold rolling process, the rolling rate is 150m / min - 250m / min, and the cold rolling reduction rate is 83% - 90%.

9. The preparation method of the low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, In the cold rolling process, the number of rolling passes is 1, the total rolling force is 15T - 50T, and the thickness of the cold-rolled strip is 0.25mm - 0.35mm.

10. The preparation method of the low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, In the decarburizing annealing, the annealing temperature is 850°C - 880°C, and the annealing time is 3min - 5min.

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

12. The preparation method of the low-temperature and ultra-high magnetic induction oriented silicon steel strip according to claim 3, wherein, In the nitriding process, the proportional relationship between the nitrogen content infiltrated and the contents of Als element and B element is: 0.875 ≤ [N] / [Als + B] ≤ 1.75; Among them, [N] represents the percentage content of the infiltrated nitrogen content, [Als] represents the percentage content of the Als element, and [B] represents the percentage content of the B element.

13. The method for preparing a low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 12, wherein 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.

14. The method for preparing a low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, 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 mixture, the nitrogen ratio is 75% - 90%, and the gas flow rate is 2L / min - 5L / min.

15. The preparation method of the low-temperature ultra-high magnetic induction oriented silicon steel strip according to claim 3, characterized in that, The magnetic induction value B of the strip after the high-temperature annealing process 800 ≥ 1.96 T.

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