Short-process preparation method for high magnetic induction oriented silicon steel

Abstract

The present invention discloses a short-process preparation method for high magnetic induction oriented silicon steel, which belongs to the field of iron and steel metallurgy. The chemical composition of the oriented silicon steel is Si: 3.1~3.2 wt.%, Al: 0.025~0.030 wt.%, and the remainder is Fe and inevitable impurity elements in weight percentage; the method includes smelting and continuous casting → hot rolling process → cold rolling process → nitriding process → high temperature annealing process. The short-process process designed by the present invention can greatly reduce the input of alloy elements and make the initial components as pure as possible. In addition, the preparation process designed by the present invention can also greatly improve production efficiency while saving energy and reducing emissions.

Description

Technical Field

[0001] The invention belongs to the field of iron and steel metallurgy, and in particular relates to a short-process preparation method for producing high magnetic induction oriented silicon steel. Background Art

[0002] High magnetic induction oriented silicon steel is a very important electromagnetic material and is widely used in the production of transformer cores. High magnetic induction oriented silicon steel has very excellent electromagnetic properties in the rolling direction, such as high magnetic induction and low iron loss. These excellent electromagnetic properties are entirely dependent on the single and sharp Goss texture inside the finished plate. At present, the world economy is developing rapidly, and the upgrading of the power system is imminent. In the process of power transmission, the transformer is a very important link, so the efficient preparation of high magnetic induction oriented silicon steel with better performance is the most important goal at present. In the preparation process of high magnetic induction oriented silicon steel, it is necessary to go through many long and extremely complex process flows, such as smelting, RH refining, continuous casting, hot rolling, normalizing, cold rolling, MgO coating, decarburization, nitriding, high temperature annealing and flat stretching. If there is a problem in any process, the performance of the finished product will not meet the standard. In addition, due to the long process flow, its production efficiency is relatively low. The currently widely used oriented silicon steel manufacturing process requires the addition of a large amount of alloying elements, such as C, S, Mn, Cr, Sn and P, to the initial composition, which not only increases the manufacturing cost, but also reduces the purity of the molten steel. For oriented silicon steel with a narrow process window, the fewer alloy components, the purer the molten steel, and the higher the magnetic properties of the finished product. Therefore, it is of great significance to simplify the preparation process of high magnetic induction oriented silicon steel (including the initial composition system). Summary of the invention

[0003] The purpose of the present invention is to provide a short-process method for producing high magnetic induction oriented silicon steel. The method greatly reduces the initial component system, and the corresponding full-process preparation process is also very simple, which greatly reduces the input of raw materials and energy consumption and greatly improves the production efficiency.

[0004] A short-process method for producing high magnetic induction oriented silicon steel, wherein the chemical composition of the oriented silicon steel is Si: 3.1-3.2 wt.%, Al: 0.025-0.030 wt.%, and the balance is Fe and some inevitable impurity elements.

[0005] The method comprises smelting and continuous casting→hot rolling process→cold rolling process→nitriding process→high temperature annealing process.

[0006] Furthermore, the smelting and continuous casting are carried out according to the above-mentioned components.

[0007] Furthermore, the hot rolling process is:

[0008] (1) After the ingot is cast and before hot rolling, it is heat treated at 1150~1200℃ for 1.5~2 h, followed by hot rolling;

[0009] (2) The thickness of the slab before hot rolling is 22~23 mm, and the final rolling thickness is 2~2.2 mm; the hot rolling start temperature is 1150~1170℃, and the final rolling temperature is 1030~1050℃;

[0010] (3) Air cooling is performed after hot rolling. The purpose is to allow the hot-rolled grains to complete the static recrystallization process as much as possible during the slow cooling process.

[0011] Furthermore, in the hot rolling process, the reduction rate between each pass is 20-43%.

[0012] Further, the hot rolling schedule (thickness change) is 22~23 mm→15~16 mm→11~12 mm→8~9 mm→6~7 mm→4~5 mm→2.9~3.5 mm→2~2.2 mm, and the reduction rates between each pass are 27.3~34.8%, 20~31.3%, 18.2~33.3%, 12.5~33.3%, 16.7~42.9%, 12.5~40%, and 26.7~42.9%. Preferably, the hot rolling schedule (thickness change) is 22 mm→15.9 mm→11.5 mm→8.4 mm→6.1 mm→4.4 mm→3.1 mm→2.2 mm, and the reduction rates between each pass are 27.7%, 27.7%, 27%, 27.4%, 27.9%, 29.5%, and 29%, respectively.

[0013] Furthermore, the cold rolling process is:

[0014] (1) Before cold rolling, the hot-rolled plate is pickled to remove the oxide scale, and then cold rolled;

[0015] (2) The thickness before cold rolling is 2.2~2.3 mm, and the final rolling thickness is 0.26~0.27 mm.

[0016] Furthermore, during the cold rolling process, the reduction rate between each pass is about 21-25%.

[0017] Further, the cold rolling schedule (thickness change) is 2.2~2.3mm→1.75~1.80mm→1.36~1.45 mm→1.10~1.15 mm→0.85~0.90 mm→0.68~0.72 mm→0.49~0.55 mm→0.40~0.46 mm→0.30~0.39 mm→0.26~0.27 mm. Preferably, the cold rolling schedule is 2.3 mm→1.8 mm→1.43 mm→1.13 mm→0.89 mm→0.7 mm→0.55 mm→0.43 mm→0.34 mm→0.27 mm.

[0018] Furthermore, the nitriding process is: nitriding the cold rolled steel plate, the nitriding temperature is 800-820°C, the time is 55-60s, the atmosphere is a mixture of N2, H2 and NH3, wherein the volume fraction of N2 is 25%, the volume fraction of H2 is 60-65%, preferably 65%, and the volume fraction of NH3 is 10-15%, preferably 10%.

[0019] Furthermore, after the nitriding process is completed, the steel plate is subjected to high temperature annealing, wherein the high temperature annealing process is as follows: heating to 1180-1200°C at a rate of 15-20°C / h and keeping the temperature for 7-8h, and then cooling to room temperature at a rate of 60-70°C / h.

[0020] Among many processes, the present invention removes the normalizing and decarburizing processes for the following reasons: (1) No N element is added to the initial composition, but N element is obtained entirely by later nitriding. In this case, there is no initial intrinsic AlN, so there is no need for a normalizing process to control the precipitation behavior of intrinsic AlN; (2) Because normalizing is omitted, austenite is not required in the matrix, and carbon does not need to be added to the raw materials, so the decarburization annealing process is also eliminated. In addition, since hot rolling and cold rolling are completed in one go, the deformation energy storage and atomic dislocation degree inside the material are extremely high, and the grains can be refined during the initial recrystallization. At the same time, a large reduction rate can produce a large number of intragranular shear bands inside the matrix. During recrystallization annealing, Gossian grains will nucleate and grow inside these shear bands. Therefore, cold rolling immediately after hot rolling can increase the number of Gossian grains and ensure the smooth progress of secondary recrystallization in the later stage; (3) The large reduction rolling from hot rolling to cold rolling can produce extremely strong {111} <110> Texture, and {111} <110> The grains can be transformed into {111} during annealing <112> Recrystallized grains provide sufficient conditions for the growth of Gaussian grains. The above analysis confirms the feasibility of the simplified process from a mechanism perspective.

[0021] By adopting the short process designed by the present invention, a high magnetic induction oriented silicon steel with a thickness of 0.26-0.27 mm (iron loss P 17 / 50≤1.20 W / kg, magnetic induction J 800 ≥1.88 T). In addition, the core of the process of the present invention is that air cooling must be performed after hot rolling, so that the hot rolled deformed structure can fully exert the recrystallization process through slow temperature drop to achieve the purpose of homogenizing the structure.

[0022] Beneficial effects of the present invention:

[0023] The short process designed by the present invention can significantly reduce the input of alloy elements and make the initial components as pure as possible. In addition, the preparation process designed by the present invention can also greatly improve production efficiency while achieving energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the hot-rolled structure of the oriented silicon steel prepared in Example 1.

[0025] Figure 2 This is the cold-rolled structure of the oriented silicon steel prepared in Example 1.

[0026] Figure 3 This is the primary recrystallization structure of the oriented silicon steel prepared in Example 1 after nitriding. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] A short-process method for producing high magnetic induction oriented silicon steel, wherein the chemical composition of the oriented silicon steel includes Si: 3.1-3.2 wt.%, Al: 0.025-0.030 wt.%, and the balance is Fe and some inevitable impurity elements.

[0029] The method comprises smelting and continuous casting→hot rolling process→cold rolling process→nitriding process→high temperature annealing process.

[0030] Smelting and continuous casting: Smelting and continuous casting are carried out according to the above composition;

[0031] Hot rolling process: After the ingot is opened and before hot rolling, it is heat treated at 1150~1200℃ for 1.5~2 h, followed by hot rolling. The hot rolling procedure is 22~23 mm→15~16 mm→11~12 mm→8~9 mm→6~7 mm→4~5mm→2.9~3.5mm→2~2.2 mm. The reduction rates between each pass are 27.3~34.8%, 20~31.3%, 18.2~33.3%, 12.5~33.3%, 16.7~42.9%, 12.5~40%, 26.7~42.9%, respectively. The hot rolling start temperature is 1150~1170℃, and the final rolling temperature is 1030~1050℃. After the hot rolling, air cooling is carried out to enable the hot-rolled grains to complete the static recrystallization process as much as possible.

[0032] Cold rolling process: The cold rolling procedure is 2.2~2.3 mm→1.75~1.80 mm→1.36~1.45 mm→1.10~1.15 mm→0.85~0.90 mm→0.68~0.72 mm→0.49~0.55 mm→0.40~0.46 mm→0.30~0.39 mm→0.26~0.27 mm;

[0033] Nitriding process: The nitriding temperature is 800~820℃, the time is 55~60 s, and the atmosphere is a mixture of N2, H2 and NH3, in which the volume fraction of N2 is 25%, the volume fraction of H2 is 60%~65%, and the volume fraction of NH3 is 10~15%;

[0034] High temperature annealing process: heating to 1180~1200℃ at a rate of 15~20℃ / h and keeping warm for 7~8h, then cooling to room temperature at a rate of 60~70℃ / h, you can get 0.26~0.27 mm thick high magnetic induction oriented silicon steel with relatively ideal magnetic properties.

[0035] Example

[0036] 1. Select oriented silicon steel ingots with Si: 3.1-3.2 wt.%, Al: 0.025-0.030 wt.%, and the balance Fe and some inevitable impurity elements as raw materials, and perform hot rolling after blanking. The chemical composition and hot rolling process of the initial samples in the three embodiments are shown in Tables 1 and 2.

[0037] Table 1 Content of ingredients in Examples 1-3 (wt.%)

[0038]

[0039] Table 2 Hot rolling process of Examples 1-3

[0040]

[0041] 2. After hot rolling, the hot rolled plate is cooled by air cooling, so that the hot rolled deformed structure can complete the recrystallization process as much as possible and achieve the purpose of homogenization. Taking Example 1 as an example, after air cooling, the recrystallized structure is as follows: Figure 1 As shown. After a special hot rolling process, the hot rolled structure is a recrystallized structure and can be directly subjected to the subsequent cold rolling process.

[0042] 3. After the hot-rolled plate is pickled, it is cold-rolled at room temperature. The cold-rolling procedure is shown in Table 3. Using a smaller pass reduction rate during the cold rolling process can make the deformation more uniform, and the primary recrystallization grain structure will also be finer and more uniform. Taking Example 1 as an example, the cold-rolled structure is as follows Figure 2 As shown in Figure 2. After cold rolling, the structure is completely cold-deformed banded grains, and there are many intragranular shear bands.

[0043] Table 3 Cold rolling process of Examples 1-3

[0044]

[0045] 4. The cold rolled sheet is subjected to nitriding treatment, and the nitriding process is shown in Table 4. During nitriding, the cold rolled deformed structure will also undergo a static recrystallization process, thereby forming a primary recrystallization structure with a small size and a relatively uniform distribution. Taking Example 1 as an example, the cold rolled structure is as follows Figure 3 The primary recrystallization structure is uniform and relatively fine, which can meet the requirements of good abnormal growth of Goss grains during subsequent high-temperature annealing.

[0046] Table 4 Nitriding process of Example 1-3

[0047]

[0048] 5. After nitriding is completed, the nitrided plate is subjected to high temperature annealing treatment. The specific process is to heat up to 1200°C at a rate of 18°C / h and keep it at this temperature for 7 hours, and then cool it down to room temperature at a rate of 65°C / h. After high temperature annealing, the magnetic properties of the finished products of the three embodiments are shown in Table 5. Taking Embodiment 1 as an example, the magnetic properties of the finished product under the short process are relatively good, among which the iron loss P 17 / 50 is 1.15 W / kg, and the magnetic induction value is J 800 It is 1.891 T.

[0049] Table 5 Magnetic properties of finished products of Examples 1-3

[0050]

[0051] The present invention aims to optimize the existing process of high magnetic induction oriented silicon steel, and based on careful laboratory simulation research, develops a short-process preparation process for 0.26~0.27 mm thick high magnetic induction oriented silicon steel. The short-process process designed by the present invention can greatly simplify the complex long-process process, and the magnetic properties of the final product are relatively ideal, indicating that the process has certain feasibility. The process involved in the present invention can greatly simplify the preparation process of 0.26~0.27 mm thick high magnetic induction oriented silicon steel while greatly reducing production costs and improving production efficiency.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A short-process preparation method for high magnetic induction oriented silicon steel, characterized in that: The chemical composition of the oriented silicon steel is Si: 3.1-3.2 wt.%, Al: 0.025-0.030 wt.%, and the balance is Fe and unavoidable impurity elements. The method comprises smelting and continuous casting → hot rolling process → cold rolling process → nitriding process → high temperature annealing process; The hot rolling process is as follows: after the ingot is opened, a heat treatment is first performed at 1150-1200°C for 1.5-2 h, and then hot rolling is performed; the thickness of the slab before hot rolling is 22-23 mm, and the final rolling thickness is 2-2.2 mm; the hot rolling start temperature is 1150-1170°C, and the final rolling temperature is 1030-1050°C; air cooling is performed after the hot rolling is completed; The cold rolling process is as follows: the hot rolled plate is pickled before cold rolling, and then cold rolled; the final cold rolling thickness is 0.26-0.27 mm; The conditions of the nitriding process are as follows: the nitriding temperature is 800-820°C, the time is 55-60s, the atmosphere is a mixture of N2, H2 and NH3, wherein the volume fraction of N2 is 25%, the volume fraction of H2 is 60-65%, and the volume fraction of NH3 is 10-15%; The high temperature annealing process is: heating to 1180-1200° C. at a rate of 15-20° C. / h and keeping the temperature for 7-8 hours, and then cooling to room temperature at a rate of 60-70° C. / h.

2. The preparation method according to claim 1, characterized in that: In the hot rolling process, the reduction ratio between each pass is 20-43%.

3. The preparation method according to claim 2, characterized in that: In the hot rolling process, the reduction ratio between each pass is 27.3-34.8%, 20-31.3%, 27-33.3%, 27.4-33.3%, 27.9-42.9%, 29.5-40%, and 26.7-42.9%, respectively.

4. The preparation method according to claim 1, characterized in that: In the cold rolling process, the reduction rate between each pass is 21-25%.

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