Ultrahigh magnetic induction oriented silicon steel and preparation method thereof

Abstract

The invention relates to ultrahigh magnetic induction oriented silicon steel and a preparation method thereof. The ultrahigh magnetic induction oriented silicon steel is prepared from the following components in percentage by weight: 1.5 percent to 2.2 percent of Si, 0.025 percent to 0.055 percent of C, 0.08 percent to 0.15 percent of Mn, 0.004 percent to 0.009 percent of S, 0.010 percent to 0.020 percent of Al, 0.002 percent to 0.005 percent of N and the balance of Fe and inevitable impurity elements. In the preparation process of the ultrahigh magnetic induction oriented silicon steel, the nitriding temperature is controlled to be higher than the phase transformation point temperature; and / or controlling the final annealing temperature to be below the phase transformation point temperature. And nitriding and final annealing processes are adjusted according to the phase transformation point temperature, nitriding is carried out above the phase transformation point temperature, and final annealing is carried out below the phase transformation point temperature. Compared with ferrite, austenite is more beneficial to nitriding amount, AlN inhibitor particles can be directly formed due to the fact that the nitriding temperature is high, and the process that Si3N4 is slowly converted into AlN in the final annealing process is omitted. And finally annealing is conducted below the phase transformation point temperature, it is guaranteed that the steel is always in a single ferrite state in the high-temperature annealing process, abnormal growth of Goss grains is promoted, and therefore the ultrahigh-magnetic-induction oriented silicon steel is prepared.

Description

Technical Field

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

[0002] Low-temperature slab heating technology for producing grain-oriented silicon steel offers advantages such as low energy consumption and a high yield rate, making it the most mainstream technology for producing high-magnetic-induction grain-oriented silicon steel. Due to insufficient inhibitors in the initial composition, low-temperature slab heating requires nitriding to replenish the inhibitors before final annealing. Nitriding is performed on the strip using a mixture of nitrogen, hydrogen, and ammonia in a certain proportion. The nitriding temperature is approximately 750°C, forming Si3N4 particles in the surface region. Subsequently, during the final annealing temperature rise, these Si3N4 particles gradually decompose to form the AlN inhibitor particles required for the secondary recrystallization of Goss grains.

[0003] High-induction oriented silicon steel typically contains approximately 3.0% to 3.3% silicon. During heating processes such as nitriding at 750°C and final annealing at 1200°C, it remains in a single ferrite phase and does not undergo a phase transformation to austenite. However, ultra-high-induction oriented silicon steel, with a silicon content below 3%, undergoes an austenite phase transformation above approximately 920°C. This makes it difficult for Goss-oriented grains to undergo secondary recrystallization during the final annealing step, resulting in poor magnetic properties in the finished strip after annealing.

[0004] Therefore, the existing final annealing process cannot meet the requirements of ultra-high magnetic induction oriented silicon steel, and it is urgent to adjust the temperature of the final annealing step to achieve secondary recrystallization of Goss grains. In addition, the final annealing temperature of high magnetic induction oriented silicon steel is high and the heating rate is slow. At 900-1000°C, Si3N4 particles gradually transform into AlN particles. Adjusting the final annealing process of ultra-high magnetic induction oriented silicon steel also requires adjustments to the nitriding process.

[0005] In summary, the problem of poor magnetic properties of existing ultra-high magnetic induction oriented silicon steel needs to be solved urgently. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of poor magnetic properties of existing ultra-high magnetic induction oriented silicon steel.

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

[0008] Disclosed is an ultra-high magnetic induction oriented silicon steel, comprising the following components, in weight percentage: Si: 1.5-2.2%, C: 0.025-0.055%, Mn: 0.08-0.15%, S: 0.004-0.009%, Al: 0.010-0.020%, N: 0.002-0.005%, and the remainder being Fe and unavoidable impurity elements.

[0009] Preferably, after nitriding treatment, the total N content of the ultra-high magnetic induction grain-oriented silicon steel is 0.010-0.016%.

[0010] Preferably, the magnetic induction value of the ultra-high magnetic induction grain-oriented silicon steel is above 2.0 T.

[0011] Based on the same inventive concept, the present invention also provides a preparation method of the ultra-high magnetic induction grain-oriented silicon steel, including smelting, hot rolling, normalizing, cold rolling, decarburizing annealing, nitriding and annealing to obtain the ultra-high magnetic induction grain-oriented silicon steel;

[0012] wherein, the nitriding temperature is controlled above the phase transformation point temperature; and / or

[0013] the final annealing temperature is controlled below the phase transformation point temperature.

[0014] Preferably, during the nitriding process, the temperature is controlled at 920-950 °C, and the nitriding atmosphere is a mixed gas containing NH3.

[0015] Preferably, the volume fraction of NH3 in the mixed gas is 20%-50%.

[0016] Preferably, during the nitriding process, the nitriding time is 15-30 seconds.

[0017] Preferably, in the final annealing treatment, the final annealing temperature is 890-920 °C, and the annealing time is 5-20 hours.

[0018] Preferably, in the final annealing treatment, the temperature is raised to 890-920 °C at a heating rate of 150-300 °C / h.

[0019] Preferably, in the final annealing treatment, the annealing atmosphere is pure H2.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The ultra-high magnetic induction grain-oriented silicon steel of the present invention, by weight percentage, includes the following components: Si: 1.5-2.2%, C: 0.025-0.055%, Mn: 0.08-0.15%, S: 0.004-0.009%, Al: 0.010-0.020%, N: 0.002-0.005%, and the rest is Fe and inevitable impurity elements; the finally obtained strip has a magnetic induction value B800≥2.0 T, far exceeding the existing high magnetic induction grain-oriented silicon steel value of 1.91-1.94 T.

[0022] The method for preparing ultra-high magnetic induction oriented silicon steel provided by the present invention controls the nitriding temperature above the phase transition point temperature; and / or controls the final annealing temperature below the phase transition point temperature. The nitriding and final annealing processes are adjusted according to the phase transition point temperature. Nitriding is carried out above the phase transition point temperature, and final annealing is carried out below the phase transition point temperature. Compared with ferrite, austenite is more conducive to the nitriding amount. In addition, due to the high nitriding temperature, AlN inhibitor particles can be directly formed, eliminating the process of the slow transformation of Si3N4 to AlN during the final annealing process. Final annealing below the phase transition point temperature ensures that it is always in a single ferrite state during the high-temperature annealing process, promoting the abnormal growth of Goss grains, thereby preparing ultra-high magnetic induction oriented silicon steel. Description of the Drawings

[0023] Figure 1 It is the metallographic diagram of the ultra-high magnetic induction oriented silicon steel of Example 1 of the present invention;

[0024] Figure 2 It is the metallographic diagram of the ultra-high magnetic induction oriented silicon steel of Example 2 of the present invention;

[0025] Figure 3 It is the metallographic diagram of the ultra-high magnetic induction oriented silicon steel of Example 3 of the present invention;

[0026] Figure 4 It is the metallographic diagram of the ultra-high magnetic induction oriented silicon steel of Example 4 of the present invention;

[0027] Figure 5 It is the {200} pole figure of the ultra-high magnetic induction oriented silicon steel of Example 1 of the present invention;

[0028] Figure 6 It is the {200} pole figure of the ultra-high magnetic induction oriented silicon steel of Example 1 of the present invention;

[0029] Figure 7 It is the {200} pole figure of the ultra-high magnetic induction oriented silicon steel of Example 1 of the present invention;

[0030] Figure 8 It is the {200} pole figure of the ultra-high magnetic induction oriented silicon steel of Example 1 of the present invention. Detailed Embodiments

[0031] The following embodiments are provided to better further understand the present invention, which is not limited to the described optimal implementation manner, and does not limit the content and protection scope of the present invention. Any product that is the same as 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.

[0032] For those embodiments in which specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed.

[0033] The production process flow of the ultra-high magnetic induction oriented silicon steel of this application is as follows:

[0034] Smelting: Steel is made in a converter or an electric furnace. After the molten steel undergoes secondary refining and continuous casting, a cast slab is obtained.

[0035] Hot rolling: The starting rolling temperature is 1000 - 1100 °C, the final rolling temperature is 900 - 950 °C, and the speed is 0.2 - 1.0 m / s.

[0036] Normalizing: The temperature is 950 - 1050 °C, and it is cooled in boiling water.

[0037] Cold rolling: The cold rolling reduction rate is 85 - 92%, and the cold rolling speed is 0.1 - 1.5 m / s.

[0038] Decarburizing annealing: The temperature is 800 - 900 °C, and the time is 2 - 4 min.

[0039] Nitriding: The steel plate rolled to the finished thickness is nitrided. The nitriding temperature is 920 - 950 °C, the NH3 concentration in the nitriding atmosphere is 20% - 50%, and the nitriding time is 15 - 30 s.

[0040] Final annealing: It is carried out according to the final annealing process. The heating rate is 150 - 300 °C / h, the final annealing temperature is 890 - 920 °C, the atmosphere is pure H2, and the time is 5 - 20 h.

[0041] Example 1

[0042] This example provides an ultra-high magnetic induction oriented silicon steel, which includes the following components by weight:

[0043]

[0044] The preparation method of the ultra-high magnetic induction oriented silicon steel in this example includes the following steps:

[0045] Smelting: Steel is made in a converter or an electric furnace. After the molten steel undergoes secondary refining and continuous casting, a cast slab is obtained.

[0046] Hot rolling: The starting rolling temperature is 1000 °C, the final rolling temperature is 900 °C, and the speed is 0.2 m / s.

[0047] Normalizing: The temperature is 1000 °C, and it is cooled in boiling water.

[0048] Cold rolling: The cold rolling reduction rate is 90%, and the cold rolling speed is 0.5 m / s.

[0049] Decarburizing annealing: The temperature is 850 °C, and the time is 3 min.

[0050] Nitriding: The steel plate rolled to the finished thickness is nitrided. The nitriding temperature is 920 °C, the NH3 concentration in the nitriding atmosphere is 50%, the nitriding time is 15 s, and the total nitrogen content is 0.010%.

[0051] Final annealing: It is carried out according to the annealing process. The heating rate is 300 °C / h, the final annealing temperature is 890 °C, the atmosphere is pure H2, and the time is 20 h.

[0052] Examples 2 - 4

[0053] The components of the ultra-high magnetic induction oriented silicon steel in Examples 2 to 4 are the same as those in Example 1, and the preparation methods are basically the same. The differences are shown in Table 1.

[0054] Table 1 Differences in process parameters

[0055]

[0056] Examples 5 - 7

[0057] The preparation method of the ultra-high magnetic induction oriented silicon steel in Examples 5 to 7 is the same as that in Example 1. The differences in components are shown in Table 2.

[0058] Table 2 Differences in chemical components

[0059]

[0060]

[0061] Comparative Example 1

[0062] The components of the oriented silicon steel in this comparative example are the same as those in Example 1. The difference in the preparation method is only that the nitriding temperature is 900 °C, the nitriding time is 5 s, and the total nitrogen content is 0.0065%.

[0063] Comparative Example 2

[0064] The components of the oriented silicon steel in this comparative example are the same as those in Example 2. The difference in the preparation method is only that the final annealing temperature is 950 °C, the atmosphere is pure H2, and the time is 8 h.

[0065] Comparative Example 3

[0066] The preparation method of the oriented silicon steel in this comparative example is the same as that in Example 3. The difference in components is only that the Si content is 2.4%.

[0067] Comparative Example 4

[0068] The preparation method of the oriented silicon steel in this comparative example is the same as that in Example 3. The difference in components is only that the Si content is 2.6%.

[0069] Experimental Example

[0070] The magnetic properties of the high magnetic induction oriented silicon steel obtained from Test Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 3 as follows.

[0071] Table 3 Magnetic Properties of Examples and Comparative Examples

[0072]

[0073]

[0074] From the above comparison, it can be seen that the magnetic induction of the oriented silicon steel in the examples is significantly higher than that in the comparative examples, belonging to ultra-high magnetic induction oriented silicon steel, and having more excellent and stable magnetic properties.

[0075] The ultra-high magnetic induction oriented silicon steel obtained from Examples 1 to 4 was observed under an electron microscope to obtain a metallographic diagram as shown in Figures 1 to 4 and the {200} pole figure was plotted as shown in Figures 5 to 8 where RD is the rolling direction and TD is the direction perpendicular to RD.

[0076] As shown in Figure 1 and Figure 5 , according to the metallographic diagram and {200} pole figure of Example 1, it can be known that under the implementation conditions adopted in Example 1, the strip underwent complete secondary recrystallization, the grain size was coarse, and the texture was a sharp Goss texture, with the Goss texture ratio reaching 94%.

[0077] As shown in Figure 2 and Figure 6 , according to the metallographic diagram and {200} pole figure of Example 2, it can be known that under the implementation conditions adopted in Example 2, the strip underwent complete secondary recrystallization, the grain size was coarse, and the texture was a sharp Goss texture, with the Goss texture ratio reaching 93%.

[0078] As shown in Figure 3 and Figure 7 , according to the metallographic diagram and {200} pole figure of Example 3, it can be known that under the implementation conditions adopted in Example 3, the strip underwent complete secondary recrystallization, the grain size was coarse, and the texture was a sharp Goss texture, with the Goss texture ratio reaching 95%.

[0079] As shown in Figure 4 and Figure 8 , according to the metallographic diagram and {200} pole figure of Example 4, it can be known that under the implementation conditions adopted in Example 4, the strip underwent complete secondary recrystallization, the grain size was coarse, and the texture was a sharp Goss texture, with the Goss texture ratio reaching 94%.

[0080] In summary, the method for preparing ultra-high magnetic induction oriented silicon steel provided by the present invention adopts low-temperature final annealing, and realizes secondary recrystallization of Goss grains at 890-920°C. It has a fast heating rate and a low temperature, avoiding the conventional 20-hour long final annealing at 1200°C. By using high-temperature nitriding, AlN inhibitor particles are directly formed after nitriding, which can increase the heating rate of the final annealing, shorten the final annealing time, and improve the efficiency. The magnetic induction value B800 of the finally obtained strip is ≥2.0T, far exceeding the existing high magnetic induction oriented silicon steel value of 1.91-1.94T.

[0081] The above are only examples of the present invention and are not intended 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. An ultra-high magnetic induction oriented silicon steel, characterized in that, Comprising the following components by weight percentage: Si: 1.5 - 2.2%, C: 0.025 - 0.055%, Mn: 0.08 - 0.15%, S: 0.004 - 0.009%, Al: 0.010 - 0.020%, N: 0.002 - 0.005%, and the balance being Fe and inevitable impurity elements.

2. The ultra-high magnetic induction oriented silicon steel according to claim 1, wherein, After nitriding treatment, the total N content of the ultra-high magnetic induction grain-oriented silicon steel is 0.010 - 0.016%.

3. The ultra-high magnetic induction oriented silicon steel according to claim 1, characterized in that, The magnetic induction value of the ultra-high magnetic induction grain-oriented silicon steel is above 2.0 T.

4. A method for preparing an ultra-high magnetic induction oriented silicon steel as described in any one of claims 1 to 3, characterized in that, Including smelting, hot rolling, normalizing, cold rolling, decarburizing annealing, nitriding, and final annealing to obtain ultra-high magnetic induction grain-oriented silicon steel; wherein, controlling the nitriding temperature above the austenite transformation point temperature; and / or controlling the final annealing temperature below the austenite transformation point temperature.

5. The preparation method according to claim 4, characterized in that, During the nitriding process, controlling the temperature at 920 - 950 °C, and the nitriding atmosphere is a mixed gas containing NH3.

6. The preparation method according to claim 5, characterized in that, The volume fraction of NH3 in the mixed gas is 20% - 50%.

7. The preparation method according to claim 4, characterized in that, During the nitriding process, the nitriding time is 15 - 30 seconds.

8. The preparation method according to claim 4, characterized in that, During the final annealing treatment, the final annealing temperature is 890 - 920 °C, and the annealing time is 5 - 20 hours.

9. The preparation method according to claim 8, characterized in that, During the final annealing treatment, heating up to 890 - 920 °C at a heating rate of 150 - 300 °C / h.

10. The preparation method according to claim 8, wherein During the final annealing treatment, the annealing atmosphere is pure H2.

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