NON-ORIENTED ELECTRICAL STEEL SHEET AND MANUFACTURING METHOD THEREFOR

Abstract

Disclosed is a non-oriented electrical steel sheet with low magnetic anisotropy, which comprises the following chemical elements in mass percentage: 0<C≤0.005%; Si: 2.0-3.5%; Mn: 0.1-2.0%; at least one of Sn and Sb: 0.003-0.2%; Al: 0.2-1.8%; the balance being Fe and inevitable impurities. Further disclosed is a manufacturing method for the above non-oriented electrical steel sheet with low magnetic anisotropy, which includes the following steps: (1) smelting and casting; (2) hot rolling; (3) normalizing; (4) cold rolling; (5) continuous annealing: rapidly heating a cold-rolled steel sheet from an initial temperature of 350° C.-750° C. to a soaking temperature at a heating rate of 50-800° C./s, and performing soaking and heat preservation; and (6) applying an insulating coating to obtain a finished non-oriented electrical steel sheet. The non-oriented electrical steel sheet is characterized by low iron loss and low magnetic anisotropy at high frequency.

Claims

1. A non-oriented electrical steel sheet, comprising the following chemical elements in mass percentage: 0<C≤0.005%; Si: 2.0-3.5%; Mn: 0.1-2.0%; at least one of Sn and Sb: 0.003-0.2%; Al: 0.2-1.8%; the balance being Fe and inevitable impurities.

2. The non-oriented electrical steel sheet as claimed in claim 1, characterized in that the electrical steel sheet has an average grain size of 90-140 μm.

3. The non-oriented electrical steel sheet as claimed in claim 1, characterized in that the inevitable impurities include: P≤0.2%, S≤0.003%, N≤0.02%, O≤0.002%, and Ti≤0.015%.

4. The non-oriented electrical steel sheet as claimed in claim 1, characterized in that the electrical steel sheet contains inclusions MnS and Cu.sub.2S, and the inclusions have a size of 150-500 nm.

5. The non-oriented electrical steel sheet as claimed in claim 4, characterized in that the inclusions have a shape of a sphere or a spheroid, and the inclusions have a plane projection of a circle or an ellipse.

6. The non-oriented electrical steel sheet as claimed in claim 5, characterized in that the inclusions have a plane projection of an ellipse, and the ellipse has a ratio of a long axis diameter to a short axis diameter of

7. The non-oriented electrical steel sheet as claimed in claim 1, characterized in that the electrical steel sheet has an iron loss P.sub.10/400 of ≤11.0 W/kg, a magnetic induction B.sub.50 of ≥1.66 T, and a magnetic anisotropy, which is a ratio of a difference between an iron loss P.sub.10/400 parallel to a rolling direction and an iron loss P.sub.10/400 perpendicular to the rolling direction to a sum of the iron loss P.sub.10/400 parallel to the rolling direction and the iron loss P101400 perpendicular to the rolling direction, of ≤10%.

8. A manufacturing method for the non-oriented electrical steel sheet as claimed in claim 1, comprising the following steps: (1) smelting and casting; (2) hot rolling; (3) normalizing; (4) cold rolling; (5) continuous annealing: rapidly heating a cold-rolled steel sheet from an initial temperature of 350° C.-750° C. to a soaking temperature at a heating rate of 50-800° C./s, and performing soaking and heat preservation; and (6) applying an insulating coating to obtain a finished non-oriented electrical steel sheet.

9. The manufacturing method as claimed in claim 8, characterized in that step (1) includes a converter tapping process, ladle slag is subjected to modification treatment in the converter tapping process to satisfy: (CaO)/(Al.sub.2O.sub.3)0.85, and T.sub.Fe≥13%, wherein (CaO) and (Al.sub.2O.sub.3) represent contents of CaO and Al.sub.2O.sub.3 in mass percentage, respectively.

10. The manufacturing method as claimed in claim 8, characterized in that in step (4), the steel sheet is directly rolled to a finished product thickness of 0.10-0.30 mm by using a single cold rolling process.

11. The manufacturing method as claimed in claim 8, characterized in that in step (5), the heating rate is 100-600° C./s.

12. The non-oriented electrical steel sheet as claimed in claim 3, characterized in that the electrical steel sheet has an iron loss P.sub.10/400 of 11.0 W/kg, a magnetic induction B.sub.50 of ≥1.66 T, and a magnetic anisotropy, which is a ratio of a difference between an iron loss P.sub.10/400 parallel to a rolling direction and an iron loss P.sub.10/400 perpendicular to the rolling direction to a sum of the iron loss P.sub.10/400 parallel to the rolling direction and the iron loss P.sub.10/400 perpendicular to the rolling direction, of ≤10%.

13. The non-oriented electrical steel sheet as claimed in claim 4, characterized in that the electrical steel sheet has an iron loss P.sub.10/400 of ≤11.0 W/kg, a magnetic induction B.sub.50 of ≥1.66 T, and a magnetic anisotropy, which is a ratio of a difference between an iron loss P.sub.10/400 parallel to a rolling direction and an iron loss P.sub.10/400 perpendicular to the rolling direction to a sum of the iron loss P.sub.10/400 parallel to the rolling direction and the iron loss P.sub.10/400 perpendicular to the rolling direction, of ≤10%.

14. The non-oriented electrical steel sheet as claimed in claim 6, characterized in that the electrical steel sheet has an iron loss P.sub.10/400 of ≤11.0 W/kg, a magnetic induction B.sub.50 of ≥1.66 T, and a magnetic anisotropy, which is a ratio of a difference between an iron loss P.sub.10/400 parallel to a rolling direction and an iron loss P.sub.10/400 perpendicular to the rolling direction to a sum of the iron loss P.sub.10/400 parallel to the rolling direction and the iron loss P10/400 perpendicular to the rolling direction, of ≤10%.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0041] FIG. 1 shows the distribution of harmful inclusions in the conventional steel sheet of Comparative Example A4.

[0042] FIG. 2 shows the type and size distribution of harmful inclusions in the non-oriented electrical steel sheet with low magnetic anisotropy of Inventive Example A16.

[0043] FIG. 3 schematically shows the relationship between different (CaO)/(Al.sub.2O.sub.3) and T.sub.Fe.

[0044] FIG. 4 schematically shows the relationship between different (CaO)/(Al.sub.2O.sub.3) and (CaO)/(SiO.sub.2).

[0045] FIG. 5 schematically shows the relationship between different grain sizes and magnetic induction B.sub.50.

[0046] FIG. 6 schematically shows the relationship between different grain sizes and iron loss P.sub.10/400.

DETAILED DESCRIPTION

[0047] The non-oriented electrical steel sheet with low magnetic anisotropy and manufacturing method therefor according to the present invention are further explained and illustrated below with reference to the drawings of the specification and the specific embodiments, however, the technical solution of the present invention is not limited to the explanation and illustration.

INVENTIVE EXAMPLES A9-A21 AND COMPARATIVE EXAMPLES A1-A8

[0048] The non-oriented electrical steel sheets of Inventive Examples A9-A21 and the conventional steel sheets of Comparative Examples A1-A8 were manufactured by the following steps:

[0049] (1) The molten iron and steel scrap were prepared according to the composition as shown in table 1. After converter smelting, the ladle slag was modified, and subjected to decarburization and alloying in RH refining. The molten steel was continuously cast to obtain a continuous casting slab with a thickness of 120-250 mm and a width of 800-1400 mm.

[0050] (2) Hot rolling: The continuous casting slab was sequentially subjected to rough rolling and finish rolling to obtain a hot-rolled steel sheet. The hot-rolled steel sheet had a thickness of 1.5-2.8 mm.

[0051] (3) Normalizing The hot-rolled steel sheet was normalized, wherein the soaking temperature was 800-1000° C. and the soaking time was 1-180 s during the normalization process.

[0052] (4) Cold rolling: The steel sheet was directly rolled to a thickness of 0.10-0.30 mm by using the single cold rolling process.

[0053] (5) Continuous annealing: The cold-rolled steel sheet was rapidly heated from an initial temperature of 350° C.-750° C. to a soaking temperature at a heating rate of 50-800° C./s, and soaking and heat preservation were conducted.

[0054] (6) An insulating coating was applied to obtain a finished non-oriented electrical steel sheet with a thickness of 0.10-0.30 mm.

[0055] It should be noted that in some preferable embodiments, the heating rate is 100-600° C./s.

[0056] In addition, in some preferable embodiments, the ladle slag was subjected to modification treatment in a converter tapping process to satisfy: (CaO)/(Al.sub.2O.sub.3)≥0.85 and T.sub.Fe≥13%, wherein (CaO) and (Al.sub.2O.sub.3) represent contents of CaO and Al.sub.2O.sub.3 in mass percentage, respectively.

[0057] Table 1 lists the mass percentages of chemical elements of the non-oriented electrical steel sheets according to Inventive Examples A9-A21 and the conventional steel sheets according to Comparative Examples A1-A8.

[0058] Table 2 lists the specific process parameters of the non-oriented electrical steel sheets according to Inventive Examples A9-A21 and the conventional steel sheets according to Comparative Examples A1-A8.

TABLE-US-00001 TABLE 1 (wt %, the balance being Fe and other inevitable impurities other than P, S, N, O and Ti) No. C Si Mn P S Al O N Sn Sb Ti Note A1 0.0011 1.22 1.85 0.11 0.0021 0.83 0.0006 0.0011 / / 0.0011 Comparative example A2 0.0021 1.85 2.52 0.06 0.0012 0.19 0.0011 0.0015 0 0.008 0.0017 Comparative example A3 0.0035 2.14 0.89 0.04 0.0009 1.16 0.0008 0.0029 0.11 0.04 0.0015 Comparative example A4 0.0028 2.29 0.25 0.18 0.0011 0.002 0.0019 0.0008 0.03 0.02 0.0008 Comparative example A5 0.0008 2.85 1.47 0.02 0.0005 1.89 0.0008 0.0017 0.001 0 0.0011 Comparative example A6 0.0044 3.15 0.58 0.13 0.0030 0.78 0.0017 0.0010 0.02 0.07 0.0014 Comparative example A7 0.0031 3.27 0.71 0.07 0.0008 2.25 0.0013 0.0012 0.04 0 0.0005 Comparative example A8 0.0016 3.62 0.16 0.03 0.0005 0.14 0.0008 0.0009 0 0.08 0.0025 Comparative example A9 0.0018 2.00 2.00 0.20 0.0030 0.20 0.0011 0.0014 0.008 0.003 0.0002 Inventive Example A10 0.0041 2.11 0.55 0.16 0.0021 1.80 0.0013 0.0007 0 0.005 0.0011 Inventive Example A11 0.0028 2.38 1.32 0.02 0.0026 0.93 0.0020 0.0006 0.008 0 0.0008 Inventive Example A12 0.0019 2.54 0.96 0.04 0.0022 0.92 0.0011 0.0008 0.002 0.011 0.0007 Inventive Example A13 0.0043 2.61 0.75 0.03 0.0011 0.55 0.0013 0.0016 0.005 0.005 0.0015 Inventive Example A14 0.0035 2.05 0.10 0.05 0.0015 1.27 0.0008 0.0020 0.15 0.05 0.0013 Inventive Example A15 0.0031 2.92 0.50 0.02 0.0008 0.82 0.0005 0.0008 0.02 0.09 0.0010 Inventive Example A16 0.0012 3.01 0.31 0.03 0.0008 0.42 0.0007 0.0005 0.04 0.02 0.0012 Inventive Example A17 0.0020 3.24 1.62 0.05 0.0016 0.81 0.0003 0.0013 0.05 0.12 0.0013 Inventive Example A18 0.0033 3.18 0.22 0.11 0.0002 0.60 0.0007 0.0007 0.07 0.01 0.0005 Inventive Example A19 0.0021 3.35 1.17 0.02 0.0008 0.22 0.0009 0.0011 0.05 0 0.0011 Inventive Example A20 0.0015 3.42 0.45 0.04 0.0011 0.45 0.0012 0.0014 0.03 0.08 0.0009 Inventive Example A21 0.0050 3.50 0.17 0.03 0.0015 1.00 0.0011 0.0006 0 0.003 0.0005 Inventive Example

TABLE-US-00002 TABLE 2 Size Ratio of Initial of long axis temp. MnS diameter/ for Average Iron Iron Iron Magnetic and short axis rapid Heating grain loss loss loss induction Magnetic (CaO)/ T.sub.Fe Cu.sub.2S diameter heating rate size P.sub.10/400 P.sub.10/400 L P.sub.10/400 C B.sub.50 anisotropy No. (Al.sub.2O.sub.3) [%] [nm] of ellipse [° C.] [° C./s] [μm] [W/kg] [W/kg] [W/kg] [T] [%] Note A1 0.21 13.8 95 2.5 20 600 78 12.7 5.64 7.06 1.64 11.2 Comparative example A2 0.89 15.9 83 3.7 650 400 82 11.4 4.97 6.43 1.62 12.8 Comparative example A3 1.27 3.1 154 2.9 450 300 82 11.8 5.26 6.54 1.63 10.8 Comparative example A4 2.23 16.8 231 4.8 800 900 69 12.5 5.51 6.99 1.63 11.8 Comparative example A5 1.88 5.2 317 2.8 20 15 72 12.2 5.46 6.74 1.65 10.5 Comparative example A6 0.43 18.4 65 5.2 500 100 53 13.0 5.80 7.20 1.65 10.7 Comparative example A7 0.21 20.5 38 1.7 350 400 71 12.2 5.23 6.97 1.63 14.3 Comparative example A8 1.57 17.1 417 1.3 200 200 82 11.7 5.25 6.45 1.64 10.2 Comparative example A9 0.87 16.5 163 3.5 350 200 118 11.0 5.05 5.95 1.68 8.2 Inventive Example A10 1.15 15.2 211 1.4 500 400 98 10.8 5.11 5.69 1.66 5.3 Inventive Example A11 1.32 16.8 418 3.2 700 800 121 10.6 4.81 5.79 1.70 9.2 Inventive Example A12 1.67 13.0 357 3.0 600 800 95 11.0 5.14 5.86 1.72 6.5 Inventive Example A13 1.85 13.8 259 1.8 450 50 127 10.5 4.82 5.68 1.70 8.1 Inventive Example A14 1.93 14.5 183 0.7 750 200 137 10.3 4.97 5.33 1.69 3.5 Inventive Example A15 0.97 18.2 326 2.8 600 200 122 10.7 5.07 5.63 1.71 5.2 Inventive Example A16 1.41 19.1 453 1.2 650 300 130 10.4 4.83 5.57 1.71 7.1 Inventive Example A17 0.87 18.4 194 1.5 700 450 118 10.6 5.04 5.56 1.72 4.9 Inventive Example A18 1.04 16.5 288 2.0 350 550 125 10.5 5.05 5.45 1.70 3.8 Inventive Example A19 1.38 17.3 391 3.2 550 250 107 10.7 5.02 5.68 1.69 6.2 Inventive Example A20 1.57 14.0 357 2.4 400 100 101 10.3 4.92 5.38 1.68 4.4 Inventive Example A21 1.79 15.1 254 1.1 500 700 123 10.5 5.06 5.44 1.72 3.6 Inventive Example

[0059] As can be seen from Tables 1 and 2, the non-oriented electrical steel sheets according to the Inventive Examples contained inclusions mainly composed of MnS and Cu.sub.2S, and the inclusions had a size of 150-500 nm. Furthermore, the inclusions had a shape of a sphere or a spheroid, and the inclusions had a plane projection of a circle or an ellipse. Furthermore, when the inclusions had a plane projection of an ellipse, the ellipse had a ratio of a long axis diameter to a short axis diameter of ≤4.0.

[0060] In addition, the non-oriented electrical steel sheets according to the Inventive Examples had an iron loss P.sub.10/400 of ≤11.0 W/kg, a magnetic induction B.sub.50 of ≥1.66 T, and a magnetic anisotropy (i.e., a ratio of a difference between an iron loss P.sub.10/400 L parallel to a rolling direction and an iron loss P.sub.10/400 C perpendicular to the rolling direction to a sum of the iron loss P.sub.10/400 L parallel to the rolling direction and the iron loss P.sub.10/400 C perpendicular to the rolling direction) of ≤10%.

[0061] In contrast, the conventional steel sheets according to the Comparative Examples did not achieve the technical effects brought by the Inventive Examples. That is, the conventional steel sheets according to the Comparative Examples exhibited poor control effect on magnetic induction and iron loss, and exhibited a large magnetic anisotropy. For example, for the conventional steel sheet in Comparative Example 1, the finished steel sheet had a high iron loss (12.7 W/kg), a low magnetic induction (1.64 T), and a magnetic anisotropy reaching 11.2%, owing to the facts that: the content of Si did not fall within the scope limited by the present invention, Sn and/or Sb were not added, and (CaO)/(Al.sub.2O.sub.3) was only 0.21, which resulted in the size of corresponding inclusions MnS and Cu.sub.2S being only 95 nm; in addition, a continuous annealing process according to the present invention was not used.

[0062] FIG. 1 shows the distribution of harmful inclusions of the convention steel sheet of Comparative Example A4. FIG. 2 shows the type and size distribution situation of harmful inclusions of the non-oriented electrical steel sheet with low magnetic anisotropy of Inventive Example A16.

[0063] As can be seen from FIGS. 1 and 2, the size of MnS (position “I” as shown in FIG. 2) of the non-oriented electrical steel sheet of Inventive Example A16 was obviously greater than that of MnS of the conventional steel sheet of Comparative Example A4.

[0064] The average size of peripheral Cu.sub.2S composite inclusions (position “II” as shown in FIG. 2) precipitated with MnS as the core was 300 nm. Compared with Comparative Example A4, the size of inclusions of Inventive Example A16 was 2-3 times larger, and therefore, the damage was greatly reduced.

[0065] When the ladle slag was subjected to modification treatment, a better control effect can be achieved by controlling (CaO)/(Al.sub.2O.sub.3)≥0.85 and T.sub.Fe≥13%. FIGS. 3 and 4 respectively indicate the control effect on the ladle slag, wherein FIG. 3 schematically shows the relationship between different (CaO)/(Al.sub.2O.sub.3) ratios and T.sub.Fe, and FIG. 4 schematically shows the relationship between different (CaO)/(Al.sub.2O.sub.3) ratios and (CaO)/(SiO.sub.2).

[0066] As can be seen from FIGS. 3 and 4, by increasing the content of T .sub.Fe in the slag, the reduction reaction of harmful element Ti in the slag and the steel can be effectively avoided; and by increasing the (CaO)/(Al.sub.2O.sub.3), it is conducive to absorb harmful inclusions such as CaO and Al.sub.2O.sub.3 in the steel, thereby promoting the desulphurization reaction and inhibiting the precipitation of sulfide inclusions in continuous casting and hot rolling processes.

[0067] FIG. 5 schematically shows the relationship between different grain sizes and magnetic induction B.sub.50. FIG. 6 schematically shows the relationship between different grain sizes and iron loss P.sub.10/400.

[0068] As can be seen from FIGS. 5 and 6, when the average grain size is in the range of 90-140 μm, the non-oriented electrical steel sheets of the present invention exhibited better magnetic properties, which had an iron loss P.sub.10/400 of ≤11.0 W/kg and a magnetic induction B.sub.50 of ≥1.66 T, this is because: when the average grain size is lower than 90 μm, due to inclusions pinning the grain boundary and insufficient driving force for grain growth, magnetic hysteresis loss of the steel sheet is dominated and relatively high, resulting in high iron loss; meanwhile, due to the poor stability of grain orientation control, the magnetic anisotropy (L, C) of the steel sheet will exceed the desired level, that is, a ratio of a difference between an iron loss P.sub.10/400 L parallel to a rolling direction and an iron loss P.sub.10/400 C perpendicular to the rolling direction to a sum of the iron loss P.sub.10/400 L parallel to the rolling direction and the iron loss P.sub.10/400 C perpendicular to the rolling direction is large. In addition, when the average grain size is higher than 130 μm, a harmful {111} plane texture will rapidly grow to swallow the proportion of a favorable {100} plane texture, thereby causing the magnetic induction to deteriorate.

[0069] In conclusion, it can be seen that the non-oriented electrical steel sheet with low magnetic anisotropy according to the present invention is characterized by low iron loss and low magnetic anisotropy at high frequency, through effective design of each component in the steel sheet.

[0070] In addition, the manufacturing method according to the present invention also has the above advantages and beneficial effects.

[0071] 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.

[0072] 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.

[0073] 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.