Preparation method of high-magnetic-induction oriented silicon steel and high-magnetic-induction oriented silicon steel

Abstract

The invention discloses a preparation method of high-magnetic-induction oriented silicon steel and the high-magnetic-induction oriented silicon steel. The preparation method specifically comprises the following steps that cold-rolled strip steel is provided; after the cold-rolled strip steel is subjected to decarburization annealing operation, nitriding treatment is conducted, and nitrided cold-rolled strip steel is obtained; wherein the nitriding treatment comprises at least two nitriding stages, the temperatures of the multiple nitriding stages are increased step by step, and the total content of nitrogen elements permeated into the cold-rolled strip steel in the multiple nitriding stages is 100 ppm to 250 ppm; the surface of the nitrided cold-rolled strip steel is coated with an annealing isolation coating, coiling is conducted, and a steel coil is obtained; and the steel coil is sequentially subjected to high-temperature annealing treatment, tensile stress coating coating, stretching flattening annealing and surface nicking treatment, and the oriented silicon steel finished product is obtained. The invention relates to the technical field of oriented silicon steel, the nitriding layer depth in the nitriding process can be increased, the morphology and size of formed nitride can be improved, more fine and dispersed inhibitors can be finally formed, and the magnetic level of the prepared high-magnetic-induction oriented silicon steel can be improved.

Description

Technical Field

[0001] The invention belongs to the field of high magnetic induction oriented silicon steel, relates to oriented silicon steel technology, and specifically provides a preparation method of high magnetic induction oriented silicon steel and high magnetic induction oriented silicon steel. Background Art

[0002] Oriented silicon steel refers to steel with strong {110} <001> Texture (i.e. Goss texture) is a soft magnetic low-carbon silicon-iron alloy material containing about 3% silicon. <001> The direction is the easy magnetization direction, <111> The direction is the hard magnetization direction, so it has a single {110} <001> Textured oriented silicon steel has excellent magnetic properties along the rolling direction and is an ideal material for manufacturing transformer cores.

[0003] There are two main production technologies for high magnetic induction oriented silicon steel, namely, hot-rolled slab high-temperature heating high magnetic induction oriented silicon steel (referred to as high-temperature high magnetic induction oriented silicon steel) and hot-rolled slab low-temperature heating high magnetic induction oriented silicon steel (referred to as low-temperature high magnetic induction oriented silicon steel).

[0004] Among them, low-temperature high magnetic induction oriented silicon steel has become the mainstream product of high magnetic induction oriented silicon steel in China due to its low production cost and high yield rate. Its main characteristics are that the inhibitor has a very low inhibitory effect on the grains before decarburization annealing; after decarburization annealing, nitriding treatment is used to inhibit the continued growth of primary recrystallized grains after decarburization annealing; during high-temperature annealing, part of the infiltrated nitrogen element is converted into AlN, which plays a role in inhibiting the growth of secondary recrystallized grains. Therefore, the nitriding effect has a great influence on the magnetic level of the final product of low-temperature high magnetic induction oriented silicon steel.

[0005] The conventional production process of low temperature and high magnetic induction oriented silicon steel is as follows:

[0006] (1) Steelmaking in converter or electric furnace, after secondary refining and continuous casting, slabs with qualified composition are obtained;

[0007] (2) The continuous casting billet is subjected to low-temperature heating in a heating furnace, hot rolling, normalizing heat treatment, pickling, and cold rolling to obtain a oriented silicon steel cold-rolled sheet with a qualified thickness;

[0008] (3) The cold-rolled sheet is alkali washed, decarburized in a humidified H2 and N2 mixture, and then nitrided in a H2, N2, and NH3 mixture;

[0009] (4) applying an annealed isolation coating with MgO as the main component, and coiling the coating after drying;

[0010] (5) The steel coil is subjected to high temperature annealing treatment;

[0011] (6) Applying tensile stress coating, stretching and flattening annealing, and surface scoring treatment;

[0012] (7) The steel coils are finally graded, cut and packaged.

[0013] However, in the above preparation process, since the nitriding time of low-temperature high-magnetic induction oriented silicon steel is very short, usually shorter than 60s, and the thickness and structure of the oxide film formed on the surface of the steel plate during the decarburization annealing process will be different, the depth of the nitriding layer is unstable, and the Si3N4 formed by the N element infiltrated into the steel plate and Si is also large in size and has a large morphology difference. Therefore, in the subsequent high-temperature annealing process, the N element infiltrated into the steel plate is easy to escape from the steel plate, resulting in less effective AlN formed in the end. Correspondingly, the magnetic level of the high-magnetic induction oriented silicon steel is reduced, and there are certain defects.

[0014] Therefore, a preparation method of high magnetic induction oriented silicon steel and high magnetic induction oriented silicon steel are needed to solve the above problems. Summary of the invention

[0015] The present invention aims to solve at least one of the technical problems existing in the prior art; for this purpose, the present invention proposes a preparation method of high magnetic induction oriented silicon steel and high magnetic induction oriented silicon steel, so as to increase the depth of the nitriding layer during the nitriding process, correspondingly improve the morphology and size of the formed nitride, and finally form more fine dispersed effective inhibitors to improve the magnetic level of the prepared high magnetic induction oriented silicon steel. The present invention adopts a multi-stage nitriding operation, and the temperature of the nitriding stage is gradually increased. The two-stage nitriding is mutually conditional and has an interactive effect, which can effectively improve the surface quality of the prepared oriented silicon steel and make the nitrogen element diffuse more evenly inside the oriented silicon steel, that is, to achieve the purpose of improving the morphology and size of the formed nitride. Moreover, by limiting the total content of nitrogen infiltrated into the cold-rolled strip in multiple nitriding stages, the nitrogen can effectively form fine, dispersed and evenly distributed nitrides with other elements in silicon steel (such as silicon, aluminum, etc.). These nitrides can be converted into more effective inhibitors during subsequent processing and use, which is beneficial to the formation of a single Gaussian texture during the secondary recrystallization process, thereby achieving the purpose of improving the magnetic ability of silicon steel.

[0016] To achieve the above object, the first aspect of the present invention provides a method for preparing high magnetic induction oriented silicon steel, which specifically comprises the following steps:

[0017] Providing a cold-rolled steel strip that has been through smelting, hot rolling, normalizing pickling and cold rolling processes;

[0018] After the cold-rolled steel strip is subjected to decarburization annealing, it is subjected to nitriding treatment to obtain the nitrided cold-rolled steel strip; wherein the nitriding treatment includes at least two nitriding stages, and the temperature of the multiple nitriding stages is increased step by step, and the total nitrogen content of the cold-rolled steel strip in the multiple nitriding stages is 100ppm-250ppm;

[0019] Applying an annealing isolation coating on the surface of the cold-rolled steel strip after nitriding, and coiling the steel strip to obtain a steel coil;

[0020] The steel coil is sequentially subjected to high temperature annealing treatment, tensile stress coating coating, stretching flattening annealing and surface notching treatment to obtain a oriented silicon steel product.

[0021] Furthermore, the thickness of the cold-rolled steel strip is 0.18 mm-0.35 mm.

[0022] Further, the nitriding treatment includes a first carburizing stage and a second nitriding stage;

[0023] The temperature of the first nitriding stage is 750°C-860°C, and the nitriding time is 4s-30s;

[0024] The temperature of the second nitriding stage is 780° C.-930° C., and the nitriding time is 10s-60s.

[0025] Furthermore, the nitrogen content in the cold-rolled steel strip during the first nitriding stage is 50ppm-150ppm;

[0026] The nitrogen content infiltrated into the cold-rolled steel strip during the second nitriding stage is 50ppm-150ppm.

[0027] Furthermore, the method for detecting the nitrogen content of the cold-rolled steel strip is to use a nitrogen oxygen analyzer for detection.

[0028] Furthermore, the main component of the annealed isolation coating is magnesium oxide.

[0029] On the other hand, the present invention further proposes a high magnetic induction oriented silicon steel, which is prepared by using a preparation method of high magnetic induction oriented silicon steel and high magnetic induction oriented silicon steel as described in the above embodiments.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] By adopting a multi-stage nitriding operation and increasing the temperature of the nitriding stage step by step, the two-stage nitriding is mutually conditional and interactive, which can effectively improve the surface quality of the prepared oriented silicon steel and make the nitrogen element diffuse more evenly inside the oriented silicon steel, that is, to achieve the purpose of improving the morphology and size of the formed nitride. In addition, by limiting the total content of nitrogen elements infiltrated into the cold-rolled strip steel in multiple nitriding stages, the nitrogen element can effectively form fine, dispersed and evenly distributed nitrides with other elements in the silicon steel (such as silicon, aluminum, etc.), and these nitrides can be converted into more effective inhibitors in the subsequent processing and use process, which is conducive to the formation of a single Gaussian texture in the secondary recrystallization process, so as to achieve the purpose of improving the magnetic ability of the silicon steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 The present invention is a flowchart of a method for preparing high magnetic induction oriented silicon steel in one embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0035] Embodiment 1

[0036] See also Figure 1 The first aspect of the present invention provides a method for preparing high magnetic induction oriented silicon steel, which specifically comprises the following steps:

[0037] Providing a cold-rolled steel strip that has been through smelting, hot rolling, normalizing pickling and cold rolling processes;

[0038] After the cold-rolled steel strip is subjected to decarburization annealing, a nitriding treatment is performed to obtain a nitrided cold-rolled steel strip; wherein the nitriding treatment includes at least two nitriding stages, and the temperature of the multiple nitriding stages is increased step by step, and the total nitrogen content infiltrated into the cold-rolled steel strip in the multiple nitriding stages is 100ppm-250ppm;

[0039] By carrying out nitriding with gradually increasing temperature, the two-stage nitriding is mutually conditional and interactive, thereby effectively improving the surface quality of the prepared oriented silicon steel and making the nitrogen element diffuse more evenly inside the oriented silicon steel, thereby achieving the purpose of improving the morphology, size and distribution of the formed nitride.

[0040] Moreover, by limiting the total content of nitrogen infiltrated into the cold-rolled strip in multiple nitriding stages, the nitrogen can effectively form fine, dispersed and evenly distributed nitrides with other elements in silicon steel (such as silicon, aluminum, etc.). These nitrides can be converted into more effective inhibitors during subsequent processing and use, which is beneficial to the formation of a single Gaussian texture during the secondary recrystallization process, thereby achieving the purpose of improving the magnetic ability of silicon steel.

[0041] Applying an annealing isolation coating on the surface of the cold-rolled steel strip after nitriding, and coiling the steel strip to obtain a steel coil;

[0042] The steel coil is sequentially subjected to high temperature annealing treatment, tensile stress coating coating, stretching flattening annealing and surface notching treatment to obtain a oriented silicon steel product.

[0043] In this embodiment, the thickness of the cold-rolled steel strip is 0.18 mm-0.35 mm. Experimental measurements show that when the thickness of the cold-rolled steel strip is 0.18 mm-0.35 mm, the magnetic capacity of silicon steel is optimal.

[0044] In other embodiments, the nitriding treatment is further defined. Specifically, the nitriding treatment includes a first carburizing stage and a second nitriding stage.

[0045] The temperature of the first nitriding stage is 750°C-860°C, and the nitriding time is 4s-30s, and the temperature of the second nitriding stage is 780°C-930°C, and the nitriding time is 10s-60s.

[0046] It should be particularly noted that the nitrogen content infiltrated into the cold-rolled steel strip in the first nitriding stage is 50ppm-150ppm, and the nitrogen content infiltrated into the cold-rolled steel strip in the second nitriding stage is 50ppm-150ppm.

[0047] It should also be noted that the method for detecting the nitrogen content of the cold-rolled steel strip is to use a nitrogen oxygen analyzer for detection. The specific principle is the thermal conductivity detection method, that is, there is a thermistor in the thermal conductivity cell of the nitrogen oxygen analyzer. When the carrier gas carries nitrogen, oxygen and other gases released from the cold-rolled steel strip sample into the thermal conductivity cell, the thermal conductivity of different gases is different from that of the carrier gas, which will cause the temperature of the thermistor to change, and then cause the resistance to change, generate an electrical signal, and determine the nitrogen content by detecting the electrical signal.

[0048] In this embodiment, the main component of the annealed isolation coating is magnesium oxide.

[0049] Embodiment 2

[0050] On the other hand, the present invention further proposes a high magnetic induction oriented silicon steel, which is prepared by using a preparation method of high magnetic induction oriented silicon steel and high magnetic induction oriented silicon steel as described in the above embodiments.

[0051] In order to intuitively demonstrate the difference between the high magnetic induction oriented silicon steel proposed in this embodiment and the high magnetic induction oriented silicon steel prepared in a conventional manner, the following examples are listed here for illustration.

[0052] Example 1

[0053] A 0.18 mm cold-rolled strip was prepared using the method in Example 1, and the temperature of the first nitriding stage was 755° C., the nitriding time was 5 s, and the nitrogen content infiltrated into the steel plate was 55 ppm. The temperature of the second nitriding stage was 790° C., the nitriding time was 55 s, and the nitrogen content infiltrated into the steel plate was 55 ppm.

[0054] Comparative Example 1

[0055] A 0.18 mm cold-rolled steel strip was prepared by conventional methods. During the nitriding treatment, the nitriding temperature was 800° C., the nitriding time was 30 s, and the nitrogen content penetrated into the steel plate was 200 ppm.

[0056] Example 2

[0057] A 0.23 mm cold-rolled strip was used and prepared by the method in Example 1. The temperature of the first nitriding stage was 780° C., the nitriding time was 10 s, and the nitrogen content penetrated into the steel plate was 85 ppm. The temperature of the second nitriding stage was 840° C., the nitriding time was 30 s, and the nitrogen content penetrated into the steel plate was 80 ppm.

[0058] Comparative Example 2

[0059] A 0.23 mm cold-rolled steel strip was prepared by conventional methods. During the nitriding treatment, the nitriding temperature was 800° C., the nitriding time was 45 s, and the nitrogen content penetrated into the steel plate was 180 ppm.

[0060] Example 3

[0061] A 0.27 mm cold-rolled strip was prepared by the method in Example 1, and the temperature of the first nitriding stage was 810° C., the nitriding time was 15 s, and the nitrogen content penetrated into the steel plate was 110 ppm. The temperature of the second nitriding stage was 890° C., the nitriding time was 20 s, and the nitrogen content penetrated into the steel plate was 100 ppm.

[0062] Comparative Example 3

[0063] A 0.27 mm cold-rolled strip was used and prepared by a conventional method. During the nitriding treatment, the nitriding temperature was 800° C., the nitriding time was 50 s, and the nitrogen content penetrated into the steel plate was 160 ppm.

[0064] Example 4

[0065] A 0.30 mm cold-rolled strip was prepared by the method in Example 1, and the temperature of the first nitriding stage was 840° C., the nitriding time was 20 s, and the nitrogen content penetrated into the steel plate was 125 ppm. The temperature of the second nitriding stage was 930° C., the nitriding time was 12 s, and the nitrogen content penetrated into the steel plate was 60 ppm.

[0066] Comparative Example 4

[0067] A 0.30 mm cold-rolled steel strip was prepared by a conventional method. During the nitriding treatment, the nitriding temperature was 800° C., the nitriding time was 55 s, and the nitrogen content penetrated into the steel plate was 140 ppm.

[0068] Example 5

[0069] A 0.35 mm cold-rolled strip was prepared by the method in Example 1, and the temperature of the first nitriding stage was 855° C., the nitriding time was 28 s, and the nitrogen content penetrated into the steel plate was 148 ppm. The temperature of the second nitriding stage was 920° C., the nitriding time was 40 s, and the nitrogen content penetrated into the steel plate was 80 ppm.

[0070] Comparative Example 5

[0071] A 0.35 mm cold-rolled steel strip was prepared by conventional methods. During the nitriding treatment, the nitriding temperature was 800° C., the nitriding time was 50 s, and the nitrogen content penetrated into the steel plate was 130 ppm.

[0072] Example 6

[0073] A 0.23 mm cold-rolled strip was prepared by the method in Example 1, and the temperature of the first nitriding stage was 840° C., the nitriding time was 20 s, and the nitrogen content penetrated into the steel plate was 180 ppm. The temperature of the second nitriding stage was 890° C., the nitriding time was 30 s, and the nitrogen content penetrated into the steel plate was 100 ppm.

[0074] Comparative Example 6

[0075] A 0.23 mm cold-rolled steel strip was prepared by conventional methods. During the nitriding treatment, the nitriding temperature was 800° C., the nitriding time was 35 s, and the nitrogen content penetrated into the steel plate was 188 ppm.

[0076] The magnetic ability test results of the above examples and comparative examples are shown in the following table:

[0077]

[0078] According to the parameters in the above table, the high magnetic induction oriented silicon steel prepared by the method described in Example 1 (such as Examples 1 to 5) has a significantly lower average iron loss and a significantly higher average magnetic polarization intensity than the high magnetic induction oriented silicon steel prepared by the conventional method (such as Comparative Examples 1 to 5). That is, under the condition of equal finished product thickness specifications, the product obtained in this embodiment can obtain a higher magnetic polarization intensity and a lower iron loss, and achieve the purpose of not significantly increasing the production cost and not reducing the production efficiency.

[0079] In addition, in order to explore the influence of the nitrogen content infiltrated into the steel plate on the average iron loss and magnetization intensity of the prepared high magnetic induction oriented silicon steel, Example 6 and Comparative Example 6 are listed above. According to the parameters in the above table, when the sum of the nitrogen content infiltrated into the steel plate in the first nitriding stage and the second nitriding stage exceeds 250ppm, the high magnetic induction oriented silicon steel prepared by the method proposed in Example 1 has a higher average iron loss and a lower average magnetic polarization intensity than the high magnetic induction oriented silicon steel prepared in a conventional manner, that is, the surface of the high magnetic induction oriented silicon steel deteriorates and the magnetic properties are not significantly improved. For this reason, it is necessary to limit the sum of the nitrogen content infiltrated into the steel plate in the first nitriding stage and the second nitriding stage to between 100ppm-250ppm, so that the product obtained by the method proposed in Example 1 can obtain a higher magnetic polarization intensity and a lower iron loss to meet the actual application needs.

[0080] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A method for preparing high magnetic induction oriented silicon steel, characterized in that: The specific steps include: Providing a cold-rolled steel strip that has been through smelting, hot rolling, normalizing pickling and cold rolling processes; After the cold-rolled steel strip is subjected to decarburization annealing, it is subjected to nitriding treatment to obtain the nitrided cold-rolled steel strip; wherein the nitriding treatment includes at least two nitriding stages, and the temperature of the multiple nitriding stages is increased step by step, and the total content of nitrogen infiltrated into the cold-rolled steel strip in the multiple nitriding stages is 100ppm-250ppm; Applying an annealing isolation coating on the surface of the cold-rolled steel strip after nitriding, and coiling the steel strip to obtain a steel coil; The steel coil is sequentially subjected to high temperature annealing treatment, tensile stress coating coating, stretching flattening annealing and surface notching treatment to obtain a oriented silicon steel product.

2. The method for preparing high magnetic induction oriented silicon steel according to claim 1, characterized in that: The thickness of the cold-rolled steel strip is 0.18 mm to 0.35 mm.

3. The method for preparing high magnetic induction oriented silicon steel according to claim 1, characterized in that: The nitriding treatment includes a first carburizing stage and a second nitriding stage; The temperature of the first nitriding stage is 750°C-860°C, and the nitriding time is 4s-30s; The temperature of the second nitriding stage is 780° C.-930° C., and the nitriding time is 10s-60s.

4. The method for preparing high magnetic induction oriented silicon steel according to claim 3, characterized in that: The nitrogen content infiltrated into the cold-rolled steel strip during the first nitriding stage is 50ppm-150ppm; The nitrogen content penetrated into the cold-rolled steel strip in the second nitriding stage is 50ppm-150ppm.

5. A method for preparing high magnetic induction oriented silicon steel according to claim 1 or 4, characterized in that: The method for detecting the nitrogen content of the cold-rolled steel strip is to use a nitrogen oxygen analyzer for detection.

6. The method for preparing high magnetic induction oriented silicon steel according to claim 1, characterized in that: The main component of the annealed isolation coating is magnesium oxide.

7. A high magnetic induction oriented silicon steel, characterized in that: The high magnetic induction oriented silicon steel is prepared by the preparation method of any one of claims 1 to 6.

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