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

Abstract

The invention relates to low-temperature high-magnetic-induction oriented silicon steel and a preparation method thereof.The preparation method comprises the following steps that a cold-rolled steel strip is obtained through smelting, continuous casting, casting blank heating, hot rolling, coiling, acid pickling and primary cold rolling; in the decarburization annealing process, a decarburization annealing section is divided into a front section, a middle section and a rear section according to the length ratio of 1: 1: 1, the partial pressure ratio # imgabs 0 # of the front section is controlled to be 0.17-0.35, the partial pressure ratio # imgabs 1 # of the middle section and the rear section is controlled to be 0.30-0.45, the volume ratio of hydrogen in the front section, the middle section and the rear section is 45-55 vol%, the annealing temperature is 820-860 DEG C, and the total time of decarburization annealing is 80-200 s; nitriding treatment; and the low-temperature high-magnetic-induction oriented silicon steel is obtained through separant coating, high-temperature annealing, stretching and flattening, insulating layer coating and finished product finishing and packaging. The method can prevent the phenomena of low oxygen content and thin oxide layer caused by insufficient oxidation degree of the middle and rear sections of the decarburization furnace due to excessive oxidation of the front section, and improves the oxygen content of the semi-finished product of the decarburization and nitridation unit.

Description

Technical Field

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

[0002] As the world pays more and more attention to sustainable development and energy efficiency, the rapid development of smart grids has brought new opportunities and challenges to the power industry. In this context, as the core component of transformers, the performance of oriented silicon steel directly affects the energy efficiency and environmental protection of power equipment. In recent years, with the improvement of new energy efficiency grade standards, low-temperature and high-magnetic induction oriented silicon steel has become the mainstream direction of the industry in terms of energy saving and consumption reduction and improving magnetic properties.

[0003] The successful manufacture of low-temperature, high-magnetic-induction oriented silicon steel depends especially on the decarburization and nitriding process. In this process, controlling the oxygen content is a key factor in ensuring the quality of the finished product. Too high an oxygen content will not only lead to a decrease in material performance, but also affect its surface insulation, which in turn affects the overall efficiency and reliability of the transformer. Therefore, how to effectively control the oxygen content in oriented silicon steel has become the focus of current research.

[0004] In the prior art, there are two main methods for controlling oxygen content:

[0005] ① By increasing the content of chromium (Cr) and tin (Sn) in the raw material components, the decarburization oxidation reaction can be promoted, thereby reducing the oxygen content of the final product. However, this method requires the raw material components to be re-proportioned, which in turn affects the process matching of the entire production process, resulting in increased production costs and poor economic efficiency.

[0006] ②Through the partial pressure ratio in the decarburization furnace The decarburization annealing is carried out by combining increasing and decreasing steps to increase the oxygen content. However, this method requires controlling the atmosphere partial pressure ratio Both are required to be controlled above 0.4. Too high atmosphere partial pressure ratio may lead to difficulty in oxidation of silicon steel strip, and defects such as blackening, yellowing, and floweriness may appear on the surface of the finished product, which reduces the qualified rate of the finished product and affects its insulation performance.

[0007] Therefore, in view of the shortcomings of the above-mentioned oxygen content control method, it is urgent to develop a new process or improve the existing process to achieve efficient and green production of low-temperature and high-magnetic induction oriented silicon steel. Summary of the invention

[0008] The purpose of the present invention is to provide a low-temperature high-magnetic induction oriented silicon steel and a preparation method thereof, which can improve the quality and performance of the product, reduce the production cost, realize the efficient and green production of low-temperature high-magnetic induction oriented silicon steel, and promote the sustainable development of the power industry.

[0009] To achieve the above object, the present invention provides a low-temperature high magnetic induction oriented silicon steel and a preparation method thereof, comprising the following steps:

[0010] Step S1, obtaining a cold-rolled steel strip through smelting-continuous casting-ingot heating-hot rolling-coiling-pickling-one cold rolling;

[0011] Step S2, decarburization annealing: During the decarburization annealing process, the decarburization annealing section is divided into three sections, namely, the front section, the middle section, and the rear section, which are divided into three sections with a length ratio of 1:1:1. The partial pressure ratio of the front section is controlled. 0.17~0.35, controlling the voltage ratio between the middle section and the rear end is 0.30-0.45, and the volume proportion of hydrogen in the front section, middle section and rear section is 45-55 vol%, the annealing temperature is 820-860 ° C, and the total time of decarburization annealing is 80-200 s;

[0012] Step S3, nitriding treatment;

[0013] Step S4, through coating of release agent - high temperature annealing - stretching and flattening - coating of insulating layer and finished product finishing and packaging, low temperature and high magnetic induction oriented silicon steel is obtained.

[0014] According to a technical solution of the present invention, in step S2, a dry nitrogen-hydrogen mixed gas accounting for 10-20% of the total gas volume of the whole section is introduced into the front section of the decarburization annealing, and a wet nitrogen-hydrogen mixed gas accounting for 40-45% is introduced into the middle section and / or the rear section;

[0015] Alternatively, a wet nitrogen-hydrogen mixture accounting for 10-20% of the total gas volume of the whole section is introduced into the front section of the decarburization annealing, and a wet nitrogen-hydrogen mixture accounting for 40-45% is introduced into the middle section and / or the rear section.

[0016] According to a technical solution of the present invention, in the step S1, a low-temperature and high-magnetic-induction oriented silicon steel ingot is formed by smelting and continuous casting; the composition of the ingot, in terms of mass percentage, comprises: Si: 3.0-3.5%, C: 0.04-0.07%, N: 0.008-0.011%, Als: 0.03-0.04%, Mn: 0.006-0.02%, S: ≤0.01%, Sn: 0.04-0.15%, Cr: 0.01-0.1%, and the remainder is Fe and unavoidable impurity elements.

[0017] According to a technical solution of the present invention, in step S1, the continuous casting billet is heated in a heating furnace, the billet heating temperature is 1100-1300° C., the heating time is 1-300 min, and the temperature equalization time is 1-60 min;

[0018] The thickness of the hot-rolled steel plate is 2.2±0.1mm; the thickness of the steel strip is 0.225±0.005mm;

[0019] The coiling temperature does not exceed 700°C, and the coiling is carried out quickly after rolling is completed.

[0020] According to a technical solution of the present invention, in step S3, during the nitriding treatment stage, NH 3 +N 2 +H 2 +H 2 O mixed gas, and the oxygen content of the oriented silicon steel after decarburization and nitriding is controlled to be 800-1100ppm, the nitriding amount is 180-250ppm, the nitriding temperature is 800-900℃, and the nitriding time is 20-30s.

[0021] According to a technical solution of the present invention, in step S3, N in the mixed gas 2 With H 2 The volume ratio is 1:(1~1.5), the partial pressure ratio is 0.07 to 0.15, and also contains 3 to 5 vol% NH 3 ; NH access 3 Flow rate: 5~8m 3 / h.

[0022] According to a technical solution of the present invention, in step S4, during the isolation agent coating stage, a high temperature annealing isolation agent containing MgO is coated on the steel plate after decarburization annealing.

[0023] According to one aspect of the present invention, a low-temperature high-magnetic induction oriented silicon steel is proposed, which is prepared by the preparation method of low-temperature high-magnetic induction oriented silicon steel as described in any one of the above technical solutions.

[0024] According to a technical solution of the present invention, the oxygen content of the low temperature high magnetic induction oriented silicon steel is 800-1100ppm, the nitriding amount is 180-250ppm, and the iron loss P 1.7 / 50 ≤0.95W / kg, magnetic induction B 800 It is 1.91~1.92T, and the average grain size is 20~25μm.

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

[0026] The invention discloses a low-temperature high magnetic induction oriented silicon steel and a preparation method thereof, by reducing the front-stage partial pressure ratio , which is conducive to the normal oxidation in the middle and back sections of the decarburization furnace, increases the oxygen content, and thickens the oxide layer. It can prevent the phenomenon of insufficient oxidation in the middle and back sections of the decarburization furnace due to excessive oxidation in the front section, resulting in low oxygen content and thin oxide layer, and increase the oxygen content of the semi-finished products of the decarburization and nitriding unit. The oxygen content of the oriented silicon steel after decarburization and nitriding is 800-1100ppm, and the nitriding amount is 180-250ppm, thereby increasing the oxygen content of the finished product, ensuring the quality of the bottom layer, and reducing the incidence of blackening, yellowing, and flower defects in the bottom layer of the finished product, and the iron loss P of the low-temperature high-magnetic induction oriented silicon steel 1.7 / 50 ≤0.95W / kg, magnetic induction B 800 It is 1.91~1.92T, and the average grain size is 20~25μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The surface quality diagram of the low-temperature high magnetic induction oriented silicon steel prepared by Example 1 of the present invention is schematically shown;

[0028] Figure 2 The surface quality diagram of the low-temperature high magnetic induction oriented silicon steel prepared by comparative example 1 of the present invention is schematically shown;

[0029] Figure 3 The surface quality diagram of the low-temperature high magnetic induction oriented silicon steel prepared by comparative example 2 of the present invention is schematically shown;

[0030] Figure 4 The surface quality diagram of the low-temperature and high-magnetic-induction oriented silicon steel prepared by Comparative Example 3 of the present invention is schematically shown. DETAILED DESCRIPTION

[0031] 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 are briefly introduced below.

[0032] A low-temperature high-magnetic-induction oriented silicon steel and a preparation method thereof of the present invention comprises the following steps:

[0033] Step S1, obtaining a cold-rolled steel strip through smelting-continuous casting-ingot heating-hot rolling-coiling-pickling-one cold rolling;

[0034] The low-temperature high-magnetic-induction oriented silicon steel ingot is smelted and continuously cast; the composition of the ingot, in percentage by mass, includes: Si: 3.0-3.5%, C: 0.04-0.07%, N: 0.008-0.011%, Als: 0.03-0.04%, Mn: 0.006-0.02%, S: ≤0.01%, Sn: 0.04-0.15%, Cr: 0.01-0.1%, and the balance is Fe and unavoidable impurity elements.

[0035] The continuous casting billet is heated in a heating furnace, the billet heating temperature is 1100-1300°C, the heating time is 1-300 minutes, and the temperature equalization time is 1-60 minutes;

[0036] The thickness of the hot-rolled steel plate is 2.2±0.1mm; the thickness of the steel strip is 0.225±0.005mm;

[0037] The coiling temperature does not exceed 700°C, and the coiling is carried out quickly after rolling is completed.

[0038] Step S2, decarburization annealing: During the decarburization annealing process, the decarburization annealing section is divided into three sections, namely, the front section, the middle section, and the rear section, which are divided into three sections with a length ratio of 1:1:1. The partial pressure ratio of the front section is controlled. 0.17~0.35, controlling the voltage ratio between the middle section and the rear end is 0.30-0.45, and the volume proportion of hydrogen in the front section, middle section and rear section is 45-55 vol%, the annealing temperature is 820-860°C, and the total time of decarburization annealing is 80-200s. It can be, for example, any one of 0.17, 0.18, 0.19, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35 or a range between any two thereof; the voltage divider ratio between the middle section and the rear end It can be, for example, any one of 0.30, 0.33, 0.35, 0.37, 0.40, 0.42, 0.45 or a range between any two of them; the volume proportion of hydrogen in the front section, middle section, and rear section can be, for example, any one of 45 vol%, 46 vol%, 47 vol%, 48 vol%, 49 vol%, 50 vol%, 51 vol%, 52 vol%, 53 vol%, 54 vol%, 55 vol% or a range between any two of them. the annealing temperature may be, for example, 820°C, 825°C, 830°C, 835°C, 840°C, 845°C, 850°C, 855°C, 860°C, or any range between two of them; the total time of the decarburization annealing may be, for example, 80s, 90s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, or any range between two of them.

[0039] By reducing the voltage divider ratio , which is conducive to the normal oxidation of the middle and rear sections of the decarburization furnace, increases the oxygen content, and thickens the oxide layer. It can prevent the phenomenon of insufficient oxidation in the middle and rear sections of the decarburization furnace due to excessive oxidation in the front section, resulting in low oxygen content and thin oxide layer. If the ratio exceeds 0.35, the steel strip will be difficult to oxidize and the oxygen content will be insufficient, which will lead to secondary uneven oxidation of the steel strip in the high-temperature annealing furnace (uneven furnace temperature and temperature difference), and the bottom layer of the finished product will become flowery and black. , which will cause the proportion of ferrous oxide in the oxide layer to increase, and gold will appear in the finished product.

[0040] During the decarburization annealing process, the following two methods can be used for ventilation to control the partial pressure ratio: .

[0041] Method 1: A dry nitrogen-hydrogen mixture accounting for 10-20% of the total gas volume of the whole section is introduced into the front section of the decarburization annealing, and a wet nitrogen-hydrogen mixture accounting for 40-45% is introduced into the middle section and / or the rear section.

[0042] Method 2: A wet nitrogen-hydrogen mixed gas accounting for 10-20% of the total gas volume of the whole section is introduced into the front section of the decarburization annealing, and a wet nitrogen-hydrogen mixed gas accounting for 40-45% is introduced into the middle section and / or the rear section.

[0043] In the same decarburization annealing section, the front The ventilation method is selected based on the relationship between the partial pressure ratio and the oxygen content of the steel plate after decarburization and nitriding. The specific method is as follows: After completing a decarburization and nitriding production, the steel plate is sampled and the oxygen content of the steel plate is measured. The voltage ratio was obtained after multiple tests. The relationship between the partial pressure ratio and the oxygen content of the steel plate after decarburization and nitriding is shown in the figure. Based on the expected oxygen content of the steel plate after decarburization and nitriding, the ventilation method is selected. For example, when the expected oxygen content of the steel plate after decarburization and nitriding corresponds to The voltage division ratio is 0.3, and the second method is easier to control the voltage division ratio.

[0044] Step S3, nitriding treatment;

[0045] During the nitriding treatment stage, 3 +N 2 +H 2 +H 2 O mixed gas, and the oxygen content of the oriented silicon steel after decarburization and nitriding is controlled to be 800-1100ppm, the nitriding amount is 180-250ppm, the nitriding temperature is 800-900℃, and the nitriding time is 20-30s.

[0046] N in the mixed gas 2 With H 2 The volume ratio is 1:(1~1.5), the partial pressure ratio is 0.07 to 0.15, and also contains 3 to 5 vol% NH 3 ; NH access 3 Flow rate: 5~8m3 / h.

[0047] Step S4, through coating of release agent - high temperature annealing - stretching and flattening - coating of insulating layer and finished product finishing and packaging, low temperature and high magnetic induction oriented silicon steel is obtained.

[0048] In the separator coating stage, a high temperature annealing separator containing MgO is coated on the steel sheet after decarburization annealing.

[0049] The technical solution of the method for preparing low-temperature and high-magnetic-induction oriented silicon steel of the present invention is further described below in conjunction with specific embodiments.

[0050] Example 1

[0051] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0052] Step S1, smelting in a conventional converter, vacuum treatment and continuous casting into a low-temperature high-magnetic induction oriented silicon steel ingot; the composition of the ingot, in terms of mass percentage, includes: Si: 3.3%, C: 0.05%, N: 0.006%, Als: 0.03%, Mn: 0.011%, S: 0.01%, Sn: 0.08%, Cr: 0.05%, Cu: 0.01%, and the balance is Fe and unavoidable impurity elements; the oriented silicon steel ingot is heated and then subjected to initial rolling, finishing rolling and coiling, and then pickled and then subjected to one-time cold rolling to obtain a cold-rolled steel strip; the heating temperature of the ingot is 1100°C; the thickness of the steel plate after finishing rolling is 2.2±0.1mm; the thickness of the steel strip is 0.225mm;

[0053] Step S2, decarburization annealing of the steel strip: the annealing temperature is controlled at 850°C, and the decarburization annealing section consists of a front section, a middle section, and a rear section with a length ratio of 1:1:1; the front section is a dry nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted 0.20; the middle and rear sections are wet nitrogen and hydrogen mixed gas, adjust the partial pressure ratio of this section is 0.32; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0054] Step S3: nitriding annealing of cold rolled sheet: 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.22, and the partial pressure ratio is 0.08, and also contains 4.8 vol% NH 3 ; NH access 3 Flow rate: 7.5m 3 / h;

[0055] Step S4, high temperature annealing, stretching and flattening, coating with insulating coating and finishing and packaging of finished products to obtain low temperature and high magnetic induction oriented silicon steel.

[0056] The oxygen content of the oriented silicon steel after decarburization and nitriding is 1057ppm, and the nitriding amount is 240ppm. The surface color of the finished product of the low-temperature high magnetic induction oriented silicon steel prepared in this embodiment is uniform, and the iron loss P 1.7 / 50 0.90W / kg, magnetic induction B 800 It is 1.917T and the average grain size is 22μm.

[0057] Example 2

[0058] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0059] The same step S1 as in Example 1;

[0060] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is dry nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. 0.25; the middle and rear sections are wet nitrogen and hydrogen mixed gas, adjust the partial pressure ratio of this section is 0.35; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0061] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.22, and the partial pressure ratio is 0.08, and also contains 3.8 vol% NH 3 ; NH access 3 Flow rate: 6m 3 / h;

[0062] The same step S4 as in Example 1.

[0063] The oxygen content of the oriented silicon steel after decarburization and nitriding is 953ppm, and the nitriding amount is 210ppm. The surface color of the finished product of the low-temperature high magnetic induction oriented silicon steel prepared in this embodiment is uniform, and the iron loss P 1.7 / 50 is 0.92W / kg, magnetic induction B 800 It is 1.913T and the average grain size is 24μm.

[0064] Example 3

[0065] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0066] The same step S1 as in Example 1;

[0067] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is dry nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. 0.25; the middle and rear sections are wet nitrogen and hydrogen mixed gas, adjust the partial pressure ratio of this section is 0.37; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0068] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.2, and the partial pressure ratio is 0.1, and also contains 4 vol% NH 3 ; NH access 3 Flow rate: 6.2m 3 / h;

[0069] The same step S4 as in Example 1.

[0070] The oxygen content of the oriented silicon steel after decarburization and nitriding is 1021ppm, and the nitriding amount is 230ppm. The surface color of the finished product of the low-temperature high-magnetic induction oriented silicon steel prepared in this embodiment is uniform, and the iron loss P 1.7 / 50 0.95W / kg, magnetic induction B 800 It is 1.912T and the average grain size is 22μm.

[0071] Example 4

[0072] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0073] The same step S1 as in Example 1;

[0074] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is wet nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. is 0.28; the middle and rear sections are wet nitrogen and hydrogen mixed gas, and the partial pressure ratio of this section is adjusted is 0.37; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0075] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.2, and the partial pressure ratio is 0.08, and also contains 5 vol% NH 3 ; NH access 3 Flow rate: 7.5m 3 / h;

[0076] The same step S4 as in Example 1.

[0077] The oxygen content of the oriented silicon steel after decarburization and nitriding is 900ppm, and the nitriding amount is 200ppm. The surface color of the finished product of the low-temperature high magnetic induction oriented silicon steel prepared in this embodiment is uniform, and the iron loss P 1.7 / 50 is 0.93W / kg, magnetic induction B 800 The T is 1.910 and the average grain size is 24 μm.

[0078] Example 5

[0079] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0080] The same step S1 as in Example 1;

[0081] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is wet nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. is 0.31; the middle and rear sections are wet nitrogen and hydrogen mixed gas, and the partial pressure ratio of this section is adjusted is 0.39; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0082] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.3, and the partial pressure ratio is 0.1, and also contains 5 vol% NH 3; NH access 3 Flow rate: 8m 3 / h;

[0083] The same step S4 as in Example 1.

[0084] The oxygen content of the oriented silicon steel after decarburization and nitriding is 850ppm, and the nitriding amount is 200ppm. The finished product of the low-temperature high-magnetic induction oriented silicon steel prepared in this embodiment has a uniform surface color and iron loss P 1.7 / 50 is 0.94W / kg, magnetic induction B 800 It is 1.911T and the average grain size is 24μm.

[0085] Comparative Example 1

[0086] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0087] The same step S1 as in Example 1;

[0088] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is wet nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. is 0.40; the middle and rear sections are wet nitrogen and hydrogen mixed gas, and the partial pressure ratio of this section is adjusted is 0.42; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0089] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.22, and the partial pressure ratio is 0.1, and contains 4.8 vol% NH 3 ; NH access 3 Flow rate: 8m 3 / h;

[0090] The same step S4 as in Example 1.

[0091] The oxygen content of the oriented silicon steel after decarburization and nitriding is 749ppm, and the nitriding amount is 185ppm. The surface of the finished product of the low-temperature high magnetic induction oriented silicon steel prepared in this embodiment is flowery, and the iron loss P 1.7 / 50 is 0.99W / kg, magnetic induction B 800 It is 1.891T and the average grain size is 28μm.

[0092] Comparative Example 2

[0093] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0094] The same step S1 as in Example 1;

[0095] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is wet nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. 0.45; the middle and rear sections are wet nitrogen and hydrogen mixed gas, adjust the partial pressure ratio of this section is 0.41; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0096] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.22, and the partial pressure ratio is 0.1, and contains 4.8 vol% NH 3 ; NH access 3 Flow rate: 7.5m 3 / h;

[0097] The same step S4 as in Example 1.

[0098] The oxygen content of the oriented silicon steel after decarburization and nitriding is 693ppm, and the nitriding amount is 180ppm. The surface of the finished product of the low-temperature high magnetic induction oriented silicon steel prepared in this embodiment is black, the color is uneven, and the iron loss P is 1.7 / 50 is 1.05W / kg, magnetic induction B 800 It is 1.892T and the average grain size is 29μm.

[0099] Comparative Example 3

[0100] A method for preparing low-temperature high-magnetic-induction oriented silicon steel comprises the following steps:

[0101] The same step S1 as in Example 1;

[0102] S2. Decarburization annealing of steel strip: annealing temperature is controlled at 850℃, and the decarburization annealing section consists of three sections: front section, middle section and back section with a length ratio of 1:1:1; the front section is wet nitrogen-hydrogen mixed gas, and the partial pressure ratio of this section is adjusted. is 0.42; the middle and rear sections are wet nitrogen and hydrogen mixed gas, and the partial pressure ratio of this section is adjusted is 0.46; the volume proportion of hydrogen in the three stages is 50 vol%, and the annealing time is 100 s;

[0103] S3, cold rolled sheet nitriding annealing: in NH 3 +N 2 +H 2 +H 2 O mixed gas, the nitriding temperature is 860℃, and the nitriding time is 20s; 2 With H 2 The volume ratio is 1:1.22, and the partial pressure ratio is 0.1, and contains 4.8 vol% NH 3 ; NH access 3 Flow rate: 7.5m 3 / h;

[0104] The same step S4 as in Example 1.

[0105] The oxygen content of the oriented silicon steel after decarburization and nitriding is 852ppm, and the nitriding amount is 200ppm. The finished product of the low-temperature high magnetic induction oriented silicon steel prepared in this embodiment has point-shaped gold exposure defects on the surface, uneven color, and iron loss P 1.7 / 50 is 0.96W / kg, magnetic induction B 800 The T is 1.900 and the average grain size is 26 μm.

[0106] Data statistics of the above Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0107] Table 1

[0108]

[0109] As shown in Table 1, combined Figures 1 to 4 The present invention reduces the front-end voltage ratio , which is conducive to the normal oxidation in the middle and back sections of the decarburization furnace, increases the oxygen content, and thickens the oxide layer. It can prevent the phenomenon of insufficient oxidation in the middle and back sections of the decarburization furnace due to excessive oxidation in the front section, resulting in low oxygen content and thin oxide layer, and increase the oxygen content of the semi-finished products of the decarburization and nitriding unit. The oxygen content of the oriented silicon steel after decarburization and nitriding is 800-1100ppm, and the nitriding amount is 180-250ppm, thereby increasing the oxygen content of the finished product, ensuring the quality of the bottom layer, and reducing the incidence of blackening, yellowing, and flowery defects in the bottom layer of the finished product.

[0110] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0111] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing low-temperature high magnetic induction oriented silicon steel, characterized in that: The following steps are involved: Step S1, obtaining a cold-rolled steel strip through smelting-continuous casting-ingot heating-hot rolling-coiling-pickling-one cold rolling; Step S2, decarburization annealing: During the decarburization annealing process, the decarburization annealing section is divided into three sections, namely, the front section, the middle section, and the rear section, which are divided into three sections with a length ratio of 1:1:

1. The partial pressure ratio of the front section is controlled. 0.17~0.35, controlling the voltage ratio between the middle section and the rear end is 0.30-0.45, and the volume proportion of hydrogen in the front section, middle section and rear section is 45-55 vol%, the annealing temperature is 820-860 ° C, and the total time of decarburization annealing is 80-200 s; Step S3, nitriding treatment; Step S4, through coating of release agent - high temperature annealing - stretching and flattening - coating of insulating layer and finished product finishing and packaging, low temperature and high magnetic induction oriented silicon steel is obtained.

2. The method for preparing low-temperature high magnetic induction oriented silicon steel according to claim 1, characterized in that: In step S2, a dry nitrogen-hydrogen mixed gas accounting for 10-20% of the total gas volume of the whole section is introduced into the front section of the decarburization annealing, and a wet nitrogen-hydrogen mixed gas accounting for 40-45% is introduced into the middle section and / or the rear section; Alternatively, a wet nitrogen-hydrogen mixture accounting for 10-20% of the total gas volume of the whole section is introduced into the front section of the decarburization annealing, and a wet nitrogen-hydrogen mixture accounting for 40-45% is introduced into the middle section and / or the rear section.

3. The method for preparing low-temperature high magnetic induction oriented silicon steel according to claim 1, characterized in that: In the step S1, the low temperature and high magnetic induction oriented silicon steel ingot is smelted and continuously cast; The composition of the ingot is calculated by mass percentage, including: Si: 3.0-3.5%, C: 0.04~0.07%, N: 0.008~0.011%, Als: 0.03~0.04%, Mn: 0.006~0.02%, S: ≤0.01%, Sn: 0.04~0.15%, Cr: 0.01~0.1%, the balance is Fe and unavoidable impurity elements.

4. The method for preparing low-temperature high magnetic induction oriented silicon steel according to claim 1, characterized in that: In the step S1, the continuous casting billet is heated in a heating furnace, the billet heating temperature is 1100-1300° C., the heating time is 1-300 min, and the temperature equalization time is 1-60 min; The thickness of the hot-rolled steel plate is 2.2±0.1mm; the thickness of the steel strip is 0.225±0.005mm; The coiling temperature does not exceed 700°C, and the coiling is carried out quickly after rolling is completed.

5. The method for preparing low-temperature high magnetic induction oriented silicon steel according to claim 1, characterized in that: In the step S3, the nitriding treatment stage is carried out under a mixed gas of NH3+N2+H2+H2O, and the oxygen content of the oriented silicon steel after decarburization and nitriding is controlled to be 800-1100ppm, the nitriding amount is 180-250ppm, the nitriding temperature is 800-900°C, and the nitriding time is 20-30s.

6. The method for preparing low-temperature high magnetic induction oriented silicon steel according to claim 1, characterized in that: In step S3, the volume ratio of N2 to H2 in the mixed gas is 1:(1-1.5), and the partial pressure ratio The NH3 content is 0.05-0.15, and it also contains 3-5 vol% NH3; the flow rate of NH3 introduced is 5-8m 3 / h.

7. The method for preparing low-temperature high magnetic induction oriented silicon steel according to claim 1, characterized in that: In the step S4, during the isolation agent coating stage, a high temperature annealing isolation agent containing MgO is coated on the steel sheet after decarburization annealing.

8. A low temperature and high magnetic induction oriented silicon steel, characterized in that: The low-temperature high-magnetic induction oriented silicon steel is prepared by the preparation method according to any one of claims 1 to 7.

9. The low temperature and high magnetic induction oriented silicon steel according to claim 8, characterized in that: The oxygen content of the low-temperature high magnetic induction oriented silicon steel is 800-1100 ppm, and the nitriding amount is 180-250 ppm.

10. The low temperature and high magnetic induction oriented silicon steel according to claim 8, characterized in that: The iron loss P of the low temperature high magnetic induction oriented silicon steel is 1.7 / 50 ≤0.95W / kg, magnetic induction B 800 It is 1.91~1.92T, and the average grain size is 20~25μm.

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