HIGH-MAGNETIC-INDUCTION ORIENTED SILICON STEEL AND MANUFACTURING METHOD THEREFOR

Abstract

Disclosed is a high-magnetic-induction oriented silicon steel, wherein the chemical elements thereof are, in mass percentage: Si: 2.0-4.0%; C: 0.03-0.07%; Al: 0.015-0.035%; N: 0.003-0.010%; Nb: 0.0010-0.0500%, the balance being Fe and inevitable impurities. The manufacturing method for the high-magnetic-induction oriented silicon steel includes the steps of: (1) smelting and casting; (2) heating a slab; (3) hot rolling; (4) cold rolling; (5) decarbonizing and annealing; (6) nitriding treatment; (7) applying an MgO coating; (8) high temperature annealing; and (9) applying an insulating coating; wherein a high-magnetic-induction oriented silicon steel is obtained by the manufacturing method, having an average primary grain size of 14-22 μm and a primary grain size variation coefficient of higher than 1.8; and wherein

[00001]$\mathrm{the}\mathrm{primary}\mathrm{grain}\mathrm{size}\mathrm{variation}\mathrm{coefficient}=\frac{\begin{array}{c}\mathrm{the}\mathrm{average}\mathrm{primary}\\ \mathrm{grain}\mathrm{size}\end{array}}{\begin{array}{c}\mathrm{standard}\mathrm{deviation}\mathrm{of}a\\ \mathrm{primary}\mathrm{grain}\mathrm{size}\end{array}}.$

Claims

1. A high-magnetic-induction oriented silicon steel, comprising the following chemical elements in mass percentage: Si: 2.0-4.0%; C: 0.03-0.07%; Al: 0.015-0.035%; N: 0.003-0.010%; Nb: 0.0010-0.0500%; and the balance being Fe and inevitable impurities.

2. The high-magnetic-induction oriented silicon steel as claimed in claim 1, characterized in that the high-magnetic-induction oriented silicon steel further comprises at least one of the following chemical elements: Mn: 0.05-0.20%, P: 0.01-0.08%, Cr: 0.05-0.40%, Sn: 0.03-0.30%, and Cu: 0.01-0.40%.

3. The high-magnetic-induction oriented silicon steel as claimed in claim 1, characterized in that S is lower than or equal to 0.0050%, V is lower than or equal to 0.0050%, and Ti is lower than or equal to 0.0050% among the inevitable impurities.

4. The high-magnetic-induction oriented silicon steel as claimed in claim 1, characterized in that the silicon steel has an iron loss P.sub.17/50 of lower than or equal to (0.28+2.5×t) W/kg, wherein t represents a sheet thickness in mm; and a magnetic induction B.sub.8 of more than or equal to 1.93 T.

5. A manufacturing method for the high-magnetic-induction oriented silicon steel as claimed in claim 1, comprising the steps of: (1) smelting and casting; (2) heating a slab; (3) hot rolling; (4) cold rolling; (5) decarbonizing and annealing; (6) nitriding treatment; (7) applying a MgO coating; (8) high temperature annealing; and (9) applying an insulating coating; wherein a high-magnetic-induction oriented silicon steel is obtained by the manufacturing method, having an average primary grain size of 14-22 μm and a primary grain size variation coefficient of higher than 1.8; and wherein $\mathrm{the}\mathrm{primary}\mathrm{grain}\mathrm{size}\mathrm{variation}\mathrm{coefficient}=\frac{\begin{array}{c}\mathrm{the}\mathrm{average}\mathrm{primary}\\ \mathrm{grain}\mathrm{size}\end{array}}{\begin{array}{c}\mathrm{standard}\mathrm{deviation}\mathrm{of}a\\ \mathrm{primary}\mathrm{grain}\mathrm{size}\end{array}}.$

6. The manufacturing method as claimed in claim 5, characterized in that in the step (2), a heating temperature and a heating time for the slab are 1050-1250° C. and less than 300 min, respectively.

7. The manufacturing method as claimed in claim 5, characterized in that in the step (4), the cold rolling has a reduction ratio of more than or equal to 85%.

8. The manufacturing method as claimed in claim 5, characterized in that in the step (5), a temperature and a time for the decarbonizing and annealing are 800-900° C. and 90-170 s, respectively.

9. The manufacturing method as claimed in claim 5, characterized in that in the step (6), infiltrated nitrogen content is 50-260 ppm.

10. The manufacturing method as claimed in claim 5, characterized in that in the step (8), a temperature and a time for the high temperature annealing are 1050-1250° C. and 15-40 h, respectively.

11. The manufacturing method as claimed in claim 5, characterized in that the manufacturing method also comprises a hot-rolled slab annealing step between the step (3) and the step (4), wherein a temperature and a time for the hot-rolled slab annealing are 850-1150° C. and 30-200 s, respectively.

12. The high-magnetic-induction oriented silicon steel as claimed in claim 2, characterized in that the silicon steel has an iron loss P.sub.17/50 of lower than or equal to (0.28+2.5×t) W/kg, wherein t represents a sheet thickness in mm; and a magnetic induction B.sub.8 of more than or equal to 1.93 T.

13. The high-magnetic-induction oriented silicon steel as claimed in claim 3, characterized in that the silicon steel has an iron loss P.sub.17/50 of lower than or equal to (0.28+2.5×t) W/kg, wherein t represents a sheet thickness in mm; and a magnetic induction B.sub.8 of more than or equal to 1.93 T.

14. The manufacturing method as claimed in claim 9, characterized in that the manufacturing method also comprises a hot-rolled slab annealing step between the step (3) and the step (4), wherein a temperature and a time for the hot-rolled slab annealing are 850-1150° C. and 30-200 s, respectively.

15. The manufacturing method as claimed in claim 10, characterized in that the manufacturing method also comprises a hot-rolled slab annealing step between the step (3) and the step (4), wherein a temperature and a time for the hot-rolled slab annealing are 850-1150° C. and 30-200 s, respectively.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] FIG. 1 shows the morphology of coarse MnS+AlN composite inclusions obtained with the prior art.

DETAILED DESCRIPTION

[0068] The high-magnetic-induction oriented silicon steel and its manufacturing method described herein will be further explained and described below with reference to the accompanying drawings and specific examples. However, the present disclosure is not limited to them.

[0069] FIG. 1 shows the morphology of coarse MnS+AlN composite inclusions obtained with the prior art.

[0070] As shown in FIG. 1, in the prior art, the size of the precipitated coarse MnS+composite inclusions was between 0.5-3.0 μm. According to the spectroscopic results, the elements at position 1 as indicated in the FIGURE are mainly elements Mn, S and Ti, and the elements at positions 2, 3, 4, 5, 6, 7, 8, 9 and 10 as indicated in the FIGURE are elements Al and N. Typically, the size of AlN precipitated separately is less than 400 nm. Thus, it is suggested that coarse MnS+AlN composite inclusions can significantly increase the difficulty of adjusting the morphology of inhibitors, which is not conducive to obtaining excellent magnetic properties.

[0071] Based on the above findings, the present inventors believe that the precipitation conditions of AlN can be improved by controlling the contents of elements such as Als, N, S, Ti, V and Nb, such that AlN is preferentially attached to Nb (C, N) instead of MnS precipitates. Therefore, the amount of coarse MnS+AlN composite inclusions precipitated is reduced, the finely dispersed precipitation of the primary inhibitor AlN is promoted, and the magnetic properties are improved. Thus, oriented silicon steels with a magnetic induction B.sub.8>1.93 T can be obtained. Due to the decrease of S content in the slab and the improvement of the primary inhibitor morphology, the manufacturing cost of inhibitor morphology adjustment and high temperature purification annealing process can be obviously reduced.

[0072] Test Methods

[0073] 1. Average Primary Grain Size and Standard Deviation of Primary Grain Size

[0074] The average primary grain size and the standard deviation of the average primary grain size were determined as follows: after obtaining the metallograph of primary grain size, the average primary grain size and the standard deviation of the average primary grain size were obtained through area method analysis.

[0075] 2. P.sub.17/50 and B.sub.8

[0076] P.sub.17/50 and B.sub.8 were obtained by using “Methods of measuring the magnetic properties of electrical steel sheet (strip) by means of an Epstein frame” in accordance with the National Standard GB/T 3655.

Examples A1-A11 and Comparative Examples B1-B7

[0077] High-magnetic-induction oriented silicon steels of Examples A1-A11 and comparative silicon steels of Comparative Examples B1-B7 were produced according to the following steps:

[0078] (1) smelting and casting: smelting with a converter or electric furnace and continuously casting into a slab according to the formulations as shown in Table 1;

[0079] (2) heating a slab: heating the slab at 1150° C. or below for 200 min;

[0080] (3) hot rolling: hot rolling the slab to a thickness of 2.3 mm;

[0081] (4) annealing: annealing the hot-rolled slab at a temperature of 1120° C. for 170 s, and then cooling;

[0082] (5) cold rolling: cold rolling to a finished product thickness of 0.29 mm with a cold rolling reduction ratio of 87.4%;

[0083] (6) decarbonizing and annealing: decreasing the [C] content in the steel slab to 30 ppm or below at a decarbonization temperature of 810-880° C. for a decarbonization time of 90-170 s;

[0084] (7) nitriding treatment: the infiltrated nitrogen content being set in the range of 131-210 ppm;

[0085] (8) applying a MgO coating: applying a MgO coating on the steel slab;

[0086] (9) high-temperature annealing: performing high-temperature purifying annealing under an atmosphere of 100% H.sub.2 at a temperature of 1200° C. for 25 hours; and

[0087] (10) applying an insulating coating, temper rolling and annealing: after uncoiling, applying insulating coating, performing hot stretching, temper rolling and annealing, and obtaining a high-magnetic-induction oriented silicon steel.

[0088] Table 1 lists mass percentages of chemical elements in high-magnetic-induction oriented silicon steels of Examples A1-A11 and comparative silicon steels of the Comparative Examples B1-B7.

TABLE-US-00001 TABLE 1 (wt%, balance being Fe and other impurities except S, V, and Ti) No. Si C Als N S V Ti Nb Mn P Cr Sn Cu A1  3.06 0.041 0.0310 0.0085 0.0046 0.0015 0.0044 0.0064 — 0.02 0.05 0.28 — A2  3.46 0.060 0.0296 0.0066 0.0036 0.0008 0.0033 0.0069 0.12 0.06 0.10 — 0.33 A3  3.17 0.055 0.0303 0.0092 0.0037 0.0037 0.0019 0.0029 0.16 0.05 0.38 0.03 — A4  3.17 0.048 0.0282 0.0064 0.0034 0.0010 0.0013 0.0084 0.11 0.03 0.26 0.12 0.19 A5  3.35 0.055 0.0271 0.0085 0.0028 0.0006 0.0028 0.0046 0.12 0.01 — 0.05 0.20 A6  3.16 0.053 0.0252 0.0054 0.0018 0.0014 0.0007 0.0053 0.06 — — 0.07 0.31 A7  3.67 0.069 0.0292 0.0075 0.0049 0.0004 0.0050 0.0145 0.05 0.04 — 0.09 0.23 A8  3.93 0.064 0.0262 0.0063 0.0039 0.0007 0.0018 0.0487 — 0.02 0.24 — — A9  3.17 0.050 0.0283 0.0064 0.0021 0.0016 0.0016 0.0012 — — 0.18 0.14 0.07 A10 3.26 0.051 0.0317 0.0096 0.0035 0.0009 0.0032 0.0201 0.19 — 0.24 0.27 0.03 A11 2.38 0.035 0.0162 0.0054 0.0026 0.0003 0.0014 0.0246 0.09 0.08 0.23 — — B1  3.18 0.046 0.0059 0.0036 0.0011 0.0012 0.0024 0.10 — 0.14 0.19 — B2  3.36 0.059 0.0303 0.0023 0.0021 0.0036 0.06 0.03 0.15 0.07 — B3  3.07 0.046 0.0293 0.0084 0.0043 — 0.10 0.04 — 0.15 0.15 B4  3.26 0.056 0.0252 0.0074 0.0023 0.0074 — 0.02 0.36 0.09 0.05 B5  3.19 0.051 0.0314 0.0026 0.0010 0.0008 — 0.17 0.07 0.08 0.08 0.35 B6  3.37 0.059 0.0305 0.0085 0.0028 0.0026 0.08 0.05 0.23 — 0.20 B7  3.57 0.068 0.0085 0.0019 0.0008 0.0043 0.0128 0.08 0.05 0.18 0.05 0.20

[0089] Table 2 lists average primary grain sizes, primary grain size variation coefficients and magnetic properties, P.sub.17/50 and B.sub.8, of finished products involved in Examples A1-A11 and Comparative Examples B1-B7.

TABLE-US-00002 TABLE 2 Average Primary grain Decarbonization Decarbonization Infiltrated P.sub.17/50 of fin- B8 of primary grain size variation temperature time nitrogen ished product finished No. size (μm) coefficient (° C.) (s) content (ppm) (W/Kg) product (T) A1  17.7 2.3 833 119 150 0.933 1.964 A2  16.8 2.2 833 121 163 0.930 1.946 A3  19.7 2.5 833 122 131 0.925 1.941 A4  22.2 1.9 838 117 170 0.960 1.947 A5  20.1 2.1 838 116 143 0.951 1.953 A6  18.5 1.9 838 114 180 0.939 1.958 A7  18.1 2.9 843 113 156 0.962 1.956 A8  14.7 2.3 843 115 138 0.941 1.957 A9  17.5 2.5 843 111 146 0.943 1.948 A10 16.6 2.4 848 112 150 0.953 1.954 A11 16.8 2.0 848 109 195 0.950 1.942 B1  2.1 838 115 162 1.356 1.729 B2  838 116 210 1.035 1.909 B3  18.9 838 118 153 0.973 1.907 B4  19.7 838 115 186 1.001 1.923 B5  18.7 843 110 135 1.103 1.872 B6  843 112 145 1.352 1.752 B7  18.7 1.9 843 115 183 1.069 1.897

[0090] As can be seen from Tables 1 and 2, the steel sheets of the present Examples A1-A11, particularly some preferred embodiments, exhibited generally better magnetic properties, such as higher magnetic induction B.sub.8 and lower iron loss P.sub.17/50, due to the slab composition of Als, N, S, V, Ti and Nb, as well as the qualified average primary grain sizes and primary grain size variation coefficients.

Examples A12-A14 and Comparative Examples B8-B13

[0091] The specific manufacturing steps for high-magnetic-induction oriented silicon steels of Examples A12-A14 and the comparative silicon steels of the Comparative Examples B8-B13 were as follows:

[0092] (1) smelting and casting: smelting with a converter or electric furnace and continuously casting into a slab according to the formulations as shown in Table 3;

[0093] (2) heating a slab: heating the slab at 1150° C. or below for 210 min;

[0094] (3) hot rolling: hot rolling the slab to a thickness of 2.6 mm;

[0095] (4) annealing: annealing the hot-rolled slab at a temperature of 1120° C. for 190 s, and then cooling;

[0096] (5) cold rolling: cold rolling to a finished product thickness of 0.27 mm with a cold rolling reduction ratio of 89.6%;

[0097] (6) decarbonizing and annealing: decreasing the [C] content in the steel slab to 30 ppm or below according to the decarbonization temperature and decarbonization time as shown in Table 3;

[0098] (7) nitriding treatment: the infiltrated nitrogen content being set in the range of 138-173 ppm;

[0099] (8) applying a MgO coating: applying a MgO coating on the steel slab;

[0100] (9) high-temperature annealing: performing high-temperature purifying annealing under an atmosphere of 100% H.sub.2 at a temperature of 1200° C. for 25 hours; and

[0101] (10) applying an insulating coating, temper rolling and annealing: after uncoiling, applying insulating coating, performing hot stretching, temper rolling and annealing, and obtaining a finished product of oriented silicon steel.

[0102] It should be noted that, for example, for the slab composition “Table 1-Al” of Example A12 in Table 3, it means that Example A12 performs smelting with the same chemical element composition with Example Al in Table 1. The slab compositions of other Examples and Comparative Examples can be deduced by analogy and will not be repeated here.

TABLE-US-00003 TABLE 3 Decarbonization Decarbonization Infiltrated Average Primary grain P.sub.17/50 of fin- B.sub.8 of Slab temperature time nitrogen primary grain size variation ished product finished No. composition (° C.) (s) content (ppm) size (μm) coefficient (W/Kg) product (T) A12 Table 1-A1 830 160 173 20.2 2.0 0.870 1.947 A13 Table 1-A2 840 155 169 16.5 2.4 0.861 1.953 A14 Table 1-A3 845 140 154 17.5 1.9 0.849 1.954 B8  Table 1-A1 790 150 149 1.9 0.923 1.894 B9  Table 1-A2 790 145 138 2.2 1.280 1.746 B10 Table 1-A3 790 130 153 2.5 1.083 1.841 B11 Table 1-A1 830 190 138 1.022 1.756 B12 Table 1-A2 840 185 173 0.923 1.927 B13 Table 1-A3 845 180 156 2.1 0.913 1.918

[0103] As can be seen from Table 3, by adjusting the decarbonization temperature and decarbonization time, the high-magnetic-induction oriented silicon steels, having the qualified average primary grain sizes and primary grain size variation coefficients, of Examples A12-A14, have achieved superior magnetic properties, such as higher magnetic induction B.sub.8 and lower iron loss P.sub.17/50.

Examples A15-A18 and Comparative Examples B14-B17

[0104] The specific manufacturing steps for high-magnetic-induction oriented silicon steels of Examples A15-A18 and comparative silicon steels of Comparative Examples B14-B17 were as follows:

[0105] (1) smelting and casting: smelting with a converter or electric furnace and continuously casting into a slab according to the formulations as shown in Table 4;

[0106] (2) heating a slab: heating the slab according to the parameters as shown in Table 4;

[0107] (3) hot rolling: hot rolling the slab to a thickness of 2.4 mm;

[0108] (4) annealing: annealing the hot-rolled slab at a temperature of 1100° C. for 150 s, and then cooling;

[0109] (5) cold rolling: cold rolling to a finished product thickness of 0.29 mm with a cold rolling reduction ratio of 87.9%;

[0110] (6) decarbonizing and annealing: decreasing the [C] content in the steel slab to 30 ppm or below at a decarbonization temperature of 840° C. for a decarbonization time of 150 s;

[0111] (7) nitriding treatment: the infiltrated nitrogen content being set in the range of 146-186 ppm;

[0112] (8) applying a MgO coating: applying a MgO coating on the steel slab;

[0113] (9) high-temperature annealing: performing high-temperature purifying annealing under an atmosphere of 100% H.sub.2 at a temperature of 1200° C. for 20 hours; and

[0114] (10) applying an insulating coating, temper rolling and annealing: after uncoiling, applying insulating coating, performing hot stretching, temper rolling and annealing, and obtaining a finished product of oriented silicon steel.

TABLE-US-00004 TABLE 4 Slab heating Slab heat- Average Primary grain Infiltrated P.sub.17/50 of fin- B.sub.8 of Slab temperature ing time primary grain size variation nitrogen ished product finished No. composition (° C.) (min) size (μm) coefficient content (ppm) (W/Kg) product (T) A15 Table 1-A4 1250 260 18.4 2.8 183 0.948 1.951 A16 1150 180 19.3 2.4 176 0.941 1.954 A17 1050 260 18.1 2.6 153 0.959 1.943 A18 1050 180 17.6 2.5 163 0.947 1.951 B14 Table 1-B3 1250 260 20.1 2.5 186 0.964 1.937 B15 1150 180 19.2 1.9 175 0.987 1.923 B16 1050 260 21.7 146 1.075 1.901 B17 1050 180 172 1.084 1.906

[0115] As can be seen from Table 4, the high-magnetic-induction oriented silicon steels of Examples A15-A18 exhibited excellent magnetic properties even with reduced slab heating temperature or reduced slab heating time. However, the magnetic properties of the comparative silicon steels of Comparative Examples B14-B17 deteriorated to varying degrees when slab temperature decreased or slab heating time shortened, because the chemical elements used were not within the scope limited by the present disclosure.

Examples A19-A22 and Comparative Examples B18-B21

[0116] The specific manufacturing steps for high-magnetic-induction oriented silicon steels of Examples A19-A22 and the comparative silicon steels of Comparative Examples B18-B21 were as follows:

[0117] (1) smelting and casting: smelting with a converter or electric furnace and continuously casting into a slab according to the formulations as shown in Table 5;

[0118] (2) heating a slab: heating the slab at 1120° C. or below for 210 min;

[0119] (3) hot rolling: hot rolling the slab to a thickness of 2.5 mm;

[0120] (4) annealing: annealing the hot-rolled slab according to the temperature and time as shown in Table 5, and then cooling;

[0121] (5) cold rolling: cold rolling to a finished product thickness of 0.23 mm with a cold rolling reduction ratio of 90.8%;

[0122] (6) decarbonizing and annealing: decreasing the [C] content in the steel slab to 30 ppm or below at a decarbonization temperature of 830° C. for a decarbonization time of 155 s;

[0123] (7) nitriding treatment: the infiltrated nitrogen content being set in the range of 133-182 ppm;

[0124] (8) applying a MgO coating: applying a MgO coating on the steel slab;

[0125] (9) high-temperature annealing: performing high-temperature purifying annealing under an atmosphere of 100% H.sub.2 at a temperature of 1210° C. for 20 hours; and

[0126] (10) applying an insulating coating, temper rolling and annealing: after uncoiling, applying insulating coating, performing hot stretching, temper rolling and annealing, and obtaining a finished product of oriented silicon steel.

TABLE-US-00005 TABLE 5 Hot-rolled slab Hot-rolled Average pri- Primary grain Infiltrated P17/50 B.sub.8 of Slab annealing slab annealing mary grain size variation nitrogen of finished finished No. composition temperature (° C.) time(s) size (μm) coefficient content (ppm) product (W/Kg) product (T) A19 Table 1-A5 1150 200 16.5 3.2 146 0.814 1.949 A20 1100 160 18.9 2.1 165 0.809 1.950 A21 1050 140 17.6 2.8 157 0.825 1.947 A22 1000 140 18.1 2.5 182 0.814 1.938 B18 Table 1-B4 1150 200 15.6 2.1 133 0.856 1.929 B19 1100 160 17.1 2.1 156 0.898 1.912 B20 1050 140 18.7 1.9 135 1.032 1.897 B21 1000 140 21.8 168 1.041 1.819

[0127] It can be seen from Table 5 that the high-magnetic-induction oriented silicon steels of Examples A19-A22 exhibited excellent magnetic properties even when hot-rolled slab heating temperature was reduced or hot-rolled slab heating time was shortened. However, magnetic properties of comparative silicon steels of Comparative Example B18-B21 deteriorated to varying degrees when hot-rolled slab heating temperature was reduced or hot-rolled slab heating time was shortened.

Examples A23-A30 and Comparative Examples B22-B33

[0128] The specific manufacturing steps for high-magnetic-induction oriented silicon steels of Examples A23-A30 and the comparative silicon steels of Comparative Examples B22-B33 were as follows:

[0129] (1) smelting and casting: smelting with a converter or electric furnace and continuously casting into a slab according to the formulations as shown in Table 6;

[0130] (2) heating a slab: heating the slab at 1120° C. or below for 210 min;

[0131] (3) hot rolling: hot rolling the slab to a thickness of 2.6 mm;

[0132] (4) annealing: annealing the hot-rolled slab at a temperature of 1100° C. for 160 s, and then cooling;

[0133] (5) cold rolling: cold rolling to a finished product thickness of 0.23 mm with a cold rolling reduction ratio of 91.2%;

[0134] (6) decarbonizing and annealing: decreasing the [C] content in the steel slab to 30 ppm or below at a decarbonization temperature of 835° C. for a decarbonization time of 155 s;

[0135] (7) nitriding treatment: the infiltrated nitrogen content being set in the range of 134-196 ppm;

[0136] (8) applying a MgO coating: applying a MgO coating on the steel slab;

[0137] (9) high-temperature annealing: performing high-temperature purifying annealing under an atmosphere of 100% H.sub.2 according to the temperature and time as shown in Table 6; and

[0138] (10) applying an insulating coating, temper rolling and annealing: after uncoiling, applying insulating coating, performing hot stretching, temper rolling and annealing, and obtaining a finished product of oriented silicon steel.

TABLE-US-00006 TABLE 6 High High Average Primary Infiltrated Finished P.sub.17/50 B.sub.8 of temperature temperature primary grain size nitrogen product of finished finished Slab annealing tem- annealing grain size variation content residual S product product No. composition perature (° C.) time (hr) (μm) coefficient (ppm) (ppm) (W/Kg) (T) A23 Table 1-A4 1250 15 15.3 2.6 182 <10 0.797 1.939 A24 1200 15 18.3 2.7 183 <10 0.798 1.937 A25 1150 20 18.6 1.9 183 <10 0.802 1.938 A26 1050 20 14.9 3.0 171 <10 0.809 1.937 A27 Table 1-A5 1250 15 18.8 2.5 155 <10 0.775 1.945 A28 1200 15 19.6 2.2 186 <10 0.790 1.948 A29 1150 20 20.4 2.9 179 <10 0.792 1.947 A30 1050 20 19.3 2.3 147 <10 0.794 1.947 B22 Table 1-B2 1250 15 17.8 2.3 145 <10 0.821 1.926 B23 1200 15 21.5 1.7 138 15 0.832 1.917 B24 1150 20 19.7 1.9 146 13 0.853 1.908 B25 1050 20 16.7 1.2 176 31 1.136 1.751 B26 Table 1-B3 1250 15 21.1 2.1 134 <10 0.817 1.919 B27 1200 15 16.6 1.3 194 15 0.816 1.920 B28 1150 20 17.6 1.4 190 14 0.873 1.876 B29 1050 20 14.9 1.9 196 21 1.256 1.651 B30 Table 1-B4 1250 15 20.6 1.3 191 <10 0.838 1.922 B31 1200 15 17.8 2.0 184 17 0.841 1.908 B32 1150 20 20.4 1.9 157 16 1.093 1.756 B33 1050 20 18.3 1.6 146 19 1.183 1.751

[0139] As can be seen from Table 6, for the high-magnetic-induction oriented silicon steels of Examples A23-A30, the residual S content in the finished product was lower than 10 ppm and there were no significant differences in magnetic properties even if the high temperature purifying annealing temperature was reduced or high temperature purifying annealing time was shortened. However, magnetic properties of comparative silicon steels of Comparative Examples B22-B33 deteriorated to varying degrees when the high temperature purifying annealing temperature was reduced or the purifying annealing time was shortened, and the residual S content in the finished product was relatively higher.

Examples A31-A33 and Comparative Examples B34-B37

[0140] The specific manufacturing steps for high-magnetic-induction oriented silicon steels of Examples A31-A33 and the comparative silicon steels of Comparative Examples B34-B37 were as follows:

[0141] (1) smelting and casting: smelting with a converter or electric furnace and continuously casting into a slab according to the formulations as shown in Table 7;

[0142] (2) heating a slab: heating the slab at 1100° C. or below for 180 min;

[0143] (3) hot rolling: hot rolling the slab to a thickness of 2.3 mm;

[0144] (4) cold rolling: cold rolling to a finished product thickness of 0.30 mm with a cold rolling reduction ratio of 87.0%;

[0145] (5) decarbonizing and annealing: performing decarbonizing and annealing according to the process parameters as shown in Table 7 to decrease the [C] content in the steel slab to 30 ppm or below;

[0146] (6) nitriding treatment: the infiltrated nitrogen content being set in the range of 131-192 ppm;

[0147] (7) applying a MgO coating: applying a MgO coating on the steel slab;

[0148] (8) high-temperature annealing: performing high-temperature purifying annealing under an atmosphere of 100% H.sub.2 at a temperature of 1200° C. for 20 hours; and

[0149] (9) applying an insulating coating, temper rolling and annealing: after uncoiling, applying insulating coating, performing hot stretching, temper rolling and annealing, and obtaining a finished product of oriented silicon steel.

TABLE-US-00007 TABLE 7 Decarbonization Decarbonization Average Primary grain Infiltrated P.sub.17/50 of B.sub.8 of Slab temperature time primary grain size variation nitrogen finished finished No. composition (° C.) (s) size (μm) coefficient content (ppm) product (W/Kg) product (T) A31 Table 1-A6 820 140 20.8 2.0 192 0.995 1.911 A32 825 140 20.7 2.4 176 0.963 1.925 A33 830 160 19.3 1.9 184 0.984 1.922 B34 Table 1-B5 820 140 131 1.182 1.722 B35 825 140 168 1.274 1.615 B36 830 160 176 1.286 1.618 B37 835 160 150 1.306 1.516

[0150] As can be seen from the Table 7, for Examples A31-A33, even if hot-rolled slab annealing was not performed, high-magnetic-induction oriented silicon steels were also obtained by adjusting the average primary grain size. In contrast, for comparative silicon steels of Comparative Examples B34-B37 without hot-rolled slab annealing, the primary grain size was not uniform and magnetic properties were poor due to weak inhibitory force of primary inhibitors.

[0151] It should be noted that in the above examples,

[00003]$\mathrm{primary}\mathrm{grain}\mathrm{size}\mathrm{variation}\mathrm{coefficient}=\frac{\begin{array}{c}\mathrm{average}\mathrm{primary}\\ \mathrm{grain}\mathrm{size}\end{array}}{\begin{array}{c}\mathrm{standard}\mathrm{deviation}\mathrm{of}\\ \mathrm{primary}\mathrm{grain}\mathrm{size}\end{array}}.$

[0152] As can be seen from the above, for high-magnetic-induction oriented silicon steels of the present disclosure, by designing the chemical composition of the silicon steel, the amount of the secondary inhibitors was ensured, the precipitate morphology of the primary inhibitors was finer and more dispersed, the primary grain size was more uniform, and then a high-level matching between the average primary grain size and the inhibitors during the secondary recrystallization was achieved. As a result, the finished products of the finally obtained high-magnetic-induction oriented silicon steels had sharp Goss texture and excellent magnetic properties, and the manufacturing cost could be further reduced.

[0153] In addition, the manufacturing method of the present disclosure also exhibited the advantages and beneficial effects as described above.

[0154] It should be noted that for the prior art part of protection scope of the present disclosure, it is not limited to the examples given in this application document. All the prior arts that do not contradict with the present disclosure, including but not limited to prior patent documents, prior publications, prior public use, etc., can be included in the protection scope of the present disclosure.

[0155] In addition, the combination of various technical features in the present disclosure is not limited to the combination described in the claims or the combination described in specific embodiments. All the technical features described in the present disclosure can be freely combined or combined in any way unless there is a contradiction between them.

[0156] It should also be noted that the above-listed Examples are only specific embodiments of the present disclosure. Apparently, the present disclosure is not limited to the above embodiments, and similar variations or modifications that are directly derived or easily conceived from the present disclosure by those skilled in the art should fall within the scope of the present disclosure.