Non-oriented electrical steel sheet with excellent magnetic properties and manufacturing method thereof

Abstract

Disclosed are a non-oriented electrical steel sheet with excellent magnetic properties and a manufacturing method thereof, wherein the mass percentage of the chemical components thereof are: C: 0-0.005%; Si: 2.1-3.2%, Mn: 0.2-1.0%, P: 0-0.2%, Al: 0.2-1.6%, N: 0-0.005%, Ti: 0-0.005%, Cu: 0-0.2%, and the balance of Fe and inevitable impurities; and at the same time, (the S content for forming MnS+the S content for forming CuxS)/the S content in the steel is required to be less than or equal to 0.2. The process for manufacturing the non-oriented electrical steel sheet of the present invention is simple and convenient, the chemical components of the steel are easy to control, the manufacturing process is stable, and the technical requirements are easy to realize.

Claims

1. A non-oriented electrical steel sheet with excellent magnetic properties, comprising the following chemical composition in percentage by mass: 0<C≤0.005%, Si: 2.1-3.2%, Mn: 0.2-1.0%, 0<P≤0.2%, Al: 0.2-1.6%, N: 0-0.005%, Ti: 0-0.005%, 0<Cu≤0.2%, with the balance being Fe and inevitable impurities; and the steel sheet meets the following Formula (1):
(the S content of the forming MnS+the S content of the forming Cu.sub.xS)/the S content in the steel≤0.2.

2. The non-oriented electrical steel sheet with excellent magnetic properties as claimed in claim 1, wherein the number of formed MnS having a size in the range of 0.2 μm to 0.5 μm is 5.0×10.sup.8 /mm.sup.3 or less, and in the case of the size of the formed MnS being in the range of 0.2 μm to 1.0 μm, the steel sheet meets the following Formula (2):
(the number of MnS inclusions having a size in the range of 0.5 μm to 1.0 μm)/(the number of MnS inclusions having a size in the range of 0.2 μm to 0.5 μm)≤0.2.

3. The non-oriented electrical steel sheet with excellent magnetic properties as claimed in claim 1, wherein iron loss (Pi.sub.15/50) of the non-oriented electrical steel sheet is not more than 2.4 W/kg.

4. A manufacturing method of the non-oriented electrical steel sheet with excellent magnetic properties as claimed in claim 1, comprising the following steps: 1) performing hot metal pretreatment of blast furnace hot metal for desulfurization, demanganization and removal of slag; 2) adding scrap steel and then conducting converter smelting; 3) conducting RH vacuum cycle degassing refining, which comprises: a) conducting deep decarburization to control the carbon content of liquid steel to 0.005% or less; b) conducting deoxidation and alloying treatment; c) optimizing the chemical composition of liquid steel, wherein the mass percentage of each element of the chemical composition in the liquid steel is as follows: 0<C≤0.005%, Si: 2.1-3.2%, Mn: 0.2-1.0%, 0<P≤0.2%, Al: 0.2-1.6%, N: 0-0.005%, Ti: 0-0.005%, 0<Cu≤0.2%, with the balance being Fe and inevitable impurities; d) refining and degassing; 4) casting the liquid steel to form a slab, wherein in the casting process, the cooling rate is controlled to be 2.5-25° C./min during a cooling process in which the surface temperature of the slab is lowered from 1100° C. to 700° C.; 5) hot rolling; 6) pickling; 7) cold rolling; 8) annealing; and 9) coating.

5. The manufacturing method of the non-oriented electrical steel sheet with excellent magnetic properties as claimed in claim 4, wherein in the casting process of step 4), the cooling rate is controlled to be 2.5-20° C./min during the cooling process in which the surface temperature of the slab is reduced from 1100° C. to 700° C.

6. The manufacturing method of the non-oriented electrical steel sheet with excellent magnetic properties as claimed in claim 4, wherein in the hot rolling of step 5), the rate of cooling a strip steel during a finishing rolling is not more than 20° C./s, the time from the end of the finishing rolling to the start of a water-cooling is not less than 5s, and coiling temperature is not lower than 600° C.

7. The manufacturing method of the non-oriented electrical steel sheet with excellent magnetic properties as claimed in claim 6, wherein in the hot rolling of step 5), the coiling temperature is not lower than 700° C.

Description

DETAILED DESCRIPTION

(1) The present invention will be further described with reference to the following Examples.

(2) Table 1 shows chemical compositions of electrical steel sheets of Examples and Comparative Examples of the present invention. Table 2 shows the process design and electromagnetic properties of Examples and Comparative Examples of the present invention.

(3) Hot metal and scrap steel were proportioned according to the chemical composition ratios in Table 1. After smelting in a 300-ton converter, decarburization, deoxidation and alloying were carried out in RH refining process. The Mn and Cu contents were dynamically adjusted according to the content of S in the steel, and the C, N, Ti and Al contents were controlled to meet the design requirements. The liquid steel was subjected to continuous casting to obtain a slab with a thickness of 170 mm-250 mm and a width of 800 mm-1400 mm, then the slab was sequentially subjected to hot rolling, pickling, cold rolling, annealing, and coating to obtain the final product. The process parameters and electromagnetic properties are shown in Table 2. During hot rolling, the slab was fully soaked at 1100° C. and heated to 1150° C. by short-term surface heating. During the process of hot rolling, the cooling rate and time of final rolling and coiling were strictly controlled to ensure the coiling temperature is not less than 700° C., so as to obtain suitable S content for forming Mn and Cu sulfides, and MnS contents in different ranges of size.

(4) TABLE-US-00001 TABLE 1 (unit: mass %) C Si Mn P Al Ti N Cu Comparative Example 1 0.0009 2.11 0.27 0.012 0.46 0.0014 0.0008 0.004 Comparative Example 2 0.0008 2.78 1.13 0.09 1.12 0.0022 0.0041 0.021 Comparative Example 3 0.0059 3.05 0.53 0.15 0.52 0.0013 0.0012 0.008 Comparative Example 4 0.0032 2.91 0.99 0.29 0.68 0.0004 0.0015 0.019 Comparative Example 5 0.0019 3.36 0.48 0.09 0.45 0.0029 0.0029 0.006 Comparative Example 6 0.0028 3.24 0.81 0.034 0.94 0.0008 0.0008 0.012 Example 1 0.0013 2.62 0.92 0.024 0.32 0.0006 0.0018 0.008 Example 2 0.0007 2.62 0.45 0.11 0.94 0.0013 0.0009 0.011 Example 3 0.0019 2.81 0.58 0.016 1.31 0.0006 0.0014 0.006 Example 4 0.0048 2.94 0.43 0.011 0.82 0.0015 0.0011 0.009 Example 5 0.0027 2.92 0.27 0.09 1.46 0.0004 0.0012 0.019 Example 6 0.0009 2.98 0.65 0.14 0.58 0.0009 0.0019 0.018 Example 7 0.0022 3.16 0.70 0.15 0.74 0.0008 0.0019 0.013 Example 8 0.0031 3.15 0.54 0.05 1.02 0.0002 0.0012 0.011 Example 9 0.0019 3.17 0.48 0.19 0.51 0.008 0.0008 0.012 Example 10 0.0041 3.09 0.51 0.07 0.69 0.0026 0.0007 0.017 Example 11 0.0032 3.16 0.36 0.15 0.49 0.0011 0.0016 0.007

(5) TABLE-US-00002 TABLE 2 the number the number air cooling S S of MnS of MnS cooling rate time from iron content content S (10.sup.8) (10.sup.7) of finishing final coiling loss (%) (%) content 0.2-0.5 0.5-1.0 rolling rolling to temperature P.sub.15/50 [MnS] [Cu.sub.xS] (%) μm μm E1 E2 (° C./min) coiling (s) ° C. (W/kg) Comparative 0.0004 0.0003 0.0041 3.1 2.9 0.17 0.09 4.1 8.4 563 3.42 Example 1 Comparative 0.0004 0.0005 0.0011 2.2 5.5 0.82 0.25 8.9 20.6 732 3.61 Example 2 Comparative 0.0002 0.0001 0.0018 8.6 6.5 0.17 0.08 20.5 4.1 655 3.24 Example 3 Comparative 0.0001 0.0001 0.0024 1.6 1.4 0.08 0.09 15.9 16.3 575 2.99 Example 4 Comparative 0.0004 0.0002 0.0032 2.9 6.5 0.19 0.22 26.2 7.4 721 2.52 Example 5 Comparative 0.0002 0.0003 0.0009 6.4 4.1 0.56 0.06 12.8 11.2 692 2.48 Example 6 Example 1 0.0005 0.0001 0.0038 1.7 2.1 0.16 0.12 7.2 5.3 651 2.28 Example 2 0.0002 0.0003 0.0029 4.8 4.1 0.17 0.09 11.6 6.8 752 2.22 Example 3 0.0001 0.0002 0.0017 2.9 5.2 0.17 0.18 18.2 11.4 711 2.04 Example 4 0.0002 0.0002 0.0022 2.2 1.6 0.18 0.07 3.7 10.5 683 2.12 Example 5 0.0001 0.0001 0.0014 4.1 8.1 0.14 0.20 6.5 9.1 702 2.03 Example 6 0.0001 0.0005 0.003 3.6 3.2 0.20 0.09 19.1 20.4 622 2.05 Example 7 0.0004 0.0001 0.0027 0.9 1.2 0.19 0.13 11.1 18.3 705 2.15 Example 8 0.0005 0.0003 0.0045 1.9 2.2 0.18 0.12 4.2 7.9 689 1.91 Example 9 0.0001 0.0001 0.0017 2.4 0.9 0.12 0.04 15.8 12.4 671 2.00 Example 10 0.0001 0.0001 0.0012 3.2 6.4 0.17 0.20 11.2 15.3 688 1.98 Example 11 0.0001 0.0002 0.0015 5.0 8.4 0.20 0.17 7.6 8.2 740 2.02 Notes: E1: (the S content for forming MnS + the S content for forming Cu.sub.xS); E2: the number of MnS in the range of 0.2 μm to 0.5 μm/ the number of MnS in the range of 0.5 μm to 1.0 μm.