Low-Cost Non-Oriented Electrical Steel Plate With Extremely Low Aluminum Content and Manufacturing Method Therefor

Abstract

Disclosed is a low-cost non-oriented electrical steel plate with an extremely low aluminum content, which plate comprises the following chemical elements in percentage by mass: 0.003% or less of C, 0.1%-1.2% of Si, 0.1%-0.4% of Mn, 0.01%-0.2% of P, 0.003% or less of S, 0.001% or less of Al, 0.003%-0.01% of O, 0.003% or less of N, and 0.005%-0.05% of Sn, with the condition Si.sup.2/P: 0.89-26.04 being satisfied. In addition, further disclosed is a method for manufacturing the non-oriented electrical steel plate. The method comprises steps of: (1) smelting; (2) continuous casting; (3) hot rolling: wherein a hot rolled plate is subjected to soaking and heat preservation by means of residual heat of hot rolled steel coils, rather than being subjected to normalizing treatment or cover furnace annealing after coiling; (4) primary cold rolling; and (5) continuous annealing. In the non-oriented electrical steel plate of the present invention, reasonable chemical ingredients and process designs are used, and the non-oriented electrical steel plate not only has excellent economy, but also has the properties of high magnetic induction and low iron loss.

Claims

1. A low-cost non-oriented electrical steel plate with an extremely low aluminum content, characterized by comprising the following chemical elements in percentage by mass: 0.003% or less of C, 0.1%-1.2% of Si, 0.1%-0.4% of Mn, 0.01%-0.2% of P, 0.003% or less of S, 0.001% or less of Al, 0.003%-0.01% of O, 0.003% or less of N, and 0.005%-0.05% of Sn, with the condition Si.sup.2/P: 0.89-26.04 being satisfied.

2. The non-oriented electrical steel plate according to claim 1, characterized by comprising the following chemical elements in percentage by mass: 0.003% or less of C, 0.1%-1.2% of Si, 0.1%-0.4% of Mn, 0.01%-0.2% of P, 0.003% or less of S, 0.001% or less of Al, 0.003%-0.01% of O, 0.003% or less of N, 0.005%-0.05% of Sn, and the balance of Fe and other unavoidable impurities, with the condition Si.sup.2/P: 0.89-26.04 being satisfied.

3. The non-oriented electrical steel plate according to claim 1 or 2, characterized by comprising 0.0005% or less of Al.

4. The non-oriented electrical steel plate according to claim 1 or 2, characterized by comprising 0.045-0.007% of O.

5. The non-oriented electrical steel plate according to claim 1 or 2 characterized by comprising 0.005-0.02% of Sn.

6. The non-oriented electrical steel plate according to claim 1 or 2, characterized in that Si.sup.2/P is 0.89-16.67.

7. The non-oriented electrical steel plate according to claim 1 or 2, characterized in that compared with conventional products of a same grade, the iron loss P.sub.15/50 of the non-oriented electrical steel plate is reduced by 0.2-0.8 W/kg on average, and a magnetic induction B.sub.50 of the non-oriented electrical steel plate is increased by 0.01-0.04 T on average.

8. A method for manufacturing the non-oriented electrical steel plate according to claim 1, characterized by comprising the steps of: (1) smelting; (2) continuous casting; (3) hot rolling: wherein a hot rolled plate is subjected to soaking and heat preservation by means of residual heat of hot rolled steel coils, rather than being subjected to normalizing treatment or cover furnace annealing after coiling; (4) primary cold rolling; and (5) continuous annealing.

9. The manufacturing method according to claim 8, characterized in that in step (1), ferrophosphorus, ferrosilicon and ferromanganese are added in sequence during deoxidation and alloying of RH refining.

10. The manufacturing method according to claim 9, characterized in that Al≤0.1% and/or Ti≤0.03% in the ferrosilicon.

11. The manufacturing method according to claim 8, characterized in that in step (3), the initial rolling temperature is controlled to be 1050-1150° C., the finish rolling temperature is controlled to be 650-950° C., the coiling temperature is controlled to be 650-850° C., the soaking and heat preservation temperature is controlled to be 650-850° C., and the heat preservation time is controlled to be at least 10 s.

12. The manufacturing method according to claim 8 or 11, characterized in that in step (3), rough rolling and finish rolling are completed in 2 to 8 passes.

13. The manufacturing method according to claim 8, characterized in that in step (5), the annealing is performed at 650-950° C. under an annealing atmosphere of a mixed gas of H.sub.2 and N.sub.2, wherein a volume proportion of H.sub.2 is 20-60%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] FIG. 1 schematically shows the relationship between the oxygen content in a non-oriented electrical steel plate according to the present invention and the iron loss P.sub.15/50 of a finished steel plate.

[0054] FIG. 2 is a microstructure diagram of a hot rolled steel plate in Example 2.

[0055] FIG. 3 is a microstructure diagram of a hot rolled steel plate in Comparative example 2.

[0056] FIG. 4 is a microstructure diagram of a finished non-oriented electrical steel plate in Example 3.

[0057] FIG. 5 is a microstructure diagram of a finished steel plate in Comparative example 3.

DETAILED DESCRIPTION

[0058] The low-cost non-oriented electrical steel plate with the extremely low aluminum content and the manufacturing method therefor according to the present invention will be further explained and described below in connection with the specific examples and the drawings. However, the explanation and description do not constitute an improper limitation to the technical solution of the present invention.

Examples 1-6 and Comparative Examples 1-6

[0059] Table 1 lists the mass percentages of chemical elements in the non-oriented electrical steel plates in Examples 1-6. It should be noted that unavoidable impurities in steel grades mainly include: Nb, V, Ti, Ca, Mg and REM.

TABLE-US-00001 TABLE 1 (%, the balance Fe and other unavoidable impurities) Chemical element Steel grade C Si Mn P S Al O N Sn Si.sup.2/P Example 1 0.0009 0.28 0.37 0.08 0.0024 0.0001 0.0091 0.0013 0.05 0.98 Example 2 0.0023 0.94 0.16 0.12 0.0019 0.0003 0.0057 0.0008 0.005 7.36 Example 3 0.0019 1.13 0.23 0.09 0.0016 0.0002 0.0032 0.0011 0.04 14.19 Example 4 0.0011 0.29 0.37 0.05 0.0011 0.0008 0.0054 0.0028 0.015 1.68 Example 5 0.0022 0.65 0.28 0.18 0.0022 0.0005 0.0041 0.0017 0.045 2.35 Example 6 0.0028 1.01 0.21 0.04 0.0009 0.0007 0.0064 0.0020 0.02 25.50

[0060] The non-oriented electrical steel plates in Examples 1-6 according to the present invention are all manufactured by the following steps: [0061] (1) smelting: after molten iron from a blast furnace and an appropriate amount of scrap steel are smelted in a converter, decarburization, deoxidization and alloying are completed in sequence during RH refining, and then a qualified slab is cast. Ferrophosphorus, ferrosilicon and ferromanganese are added in sequence during deoxidation and alloying of RH refining, wherein Al≤0.10% and/or Ti≤0.03% in the ferrosilicon. [0062] (2) continuous casting; [0063] (3) hot rolling: wherein the initial rolling temperature is controlled to be 1050-1150° C., the finish rolling temperature is controlled to be 650-950° C., the coiling temperature is controlled to be 650-850° C., the soaking and heat preservation temperature is controlled to be 650-850° C., and the heat preservation time is controlled to be at least 10 s, rough rolling and finish rolling are completed in 2 to 8 passes, and a target thickness of hot rolling is 1.2-2.8 mm; a hot rolled plate is subjected to soaking and heat preservation by means of residual heat of hot rolled steel coils, rather than being subjected to normalizing treatment or cover furnace annealing after coiling; and after the hot rolling is completed, the hot rolled steel coils are pickled; [0064] (4) primary cold rolling: once rolling to a target thickness; and [0065] (5) continuous annealing: wherein the annealing is performed at 650-950° C. for 180 s or less under an annealing atmosphere of a mixed gas of H.sub.2 and N.sub.2, wherein a volume proportion of H.sub.2 is 20%-60%.

[0066] Tables 2-1 and 2-2 list the specific process parameters of the manufacturing method of the non-oriented electrical steel plates in Examples 1-6. Wherein rough rolling and finish rolling passes in Table 2-2 represent the rolling times of rough rolling and finish rolling, respectively, for example, in Example 1, 4+7 means that rough rolling is completed in 4 passes, and finish rolling is completed in 7 passes.

TABLE-US-00002 TABLE 2-1 Step (1) Number Ferrosilicon quality Example 1 Al ≤ 0.1%, Ti ≤ 0.03%, P ≤ 0.05% Example 2 Al ≤ 0.10%, Ti ≤ 0.03%, P ≤ 0.05% Example 3 Al ≤ 0.10%, Ti ≤ 0.03%, P ≤ 0.05% Example 4 Al ≤ 0.10%, Ti ≤ 0.03%, P ≤ 0.05% Example 5 Al ≤ 0.10%, Ti ≤ 0.03%, P ≤ 0.05% Example 6 Al ≤ 0.10%, Ti ≤ 0.03%, P ≤ 0.05%

TABLE-US-00003 TABLE 2-2 Step (5) Step (3) Volume Soaking Rough Target proportion Initial Finish and heat rolling thickness of H.sub.2 in rolling rolling Coiling preservation Heat and finish of hot Annealing Annealing annealing temperature temperature temperature temperature preservation rolling rolling temperature time atmosphere Number (° C.) (° C.) (° C.) (° C.) time passes (mm) (° C.) (s) (%) Example 1 1085 883 792 715 25 s 4 + 7 2.6 810 15 30 Example 2 1120 864 702 653 12 h 4 + 7 2.0 730 20 35 Example 3 1147 687 661 651 44 h 4 + 7 2.8 900 25 55 Example 4 1132 943 679 667 12 h 4 + 7 1.5 680 60 40 Example 5 1109 747 712 673 60 s 4 + 7 2.3 760 35 45 Example 6 1064 793 737 655  6 h 4 + 7 1.8 950 20 50

[0067] Table 3 lists the mass percentages of chemical elements in the non-oriented electrical steel plates in Comparative examples 1-6.

TABLE-US-00004 TABLE 3 (%, the balance Fe and other unavoidable impurities) Chemical element Steel grade C Si Mn P S Al O N Sn Si2/P Comparative 0.0022 0.41 0.62 0.06 0.0035 0.01 0.0038 0.0008 0 2.80 example 1 Comparative 0.0027 1.35 0.36 0.04 0.0022 0.0008 0.0053 0.0016 0.15 45.56 example 2 Comparative 0.0014 0.05 0.82 0.05 0.0051 0.0007 0.0007 0.0023 0.02 0.05 example 3 Comparative 0.0021 0.29 0.19 0.05 0.0011 0.40 0.0022 0.0028 0.07 1.68 example 4 Comparative 0.0018 0.92 0.22 0.04 0.0022 0.0022 0.0125 0.0017 0.045 21.16 example 5 Comparative 0.0008 0.15 0.35 0.04 0.0009 0.022 0.0019 0.0020 0.12 0.56 example 6

[0068] Table 4 lists the specific process parameters of the manufacturing method of the non-oriented electrical steel plates in Comparative examples 1-6.

TABLE-US-00005 TABLE 4 Step (5) Step (3) Volume Soaking Rough Target proportion Initial Finish and heat rolling thickness of H.sub.2 in rolling rolling Coiling preservation Heat and finish of hot Annealing Annealing annealing temperature temperature temperature temperature preservation rollin rolling temperature time atmosphere Number (° C.) (° C.) (° C.) (° C.) time passes (mm) (° C.) (s) (%) Comparative 995 631 683 547 25 s 2 + 7 2.4 970 25 65 example 1 Comparative 1027 857 904 872 12 h 4 + 7 2.6 620 5 20 example 2 Comparative 1000 620 582 349 60 h 2 + 7 2.0 1000 40 40 example 3 Comparative 1183 820 631 583 0 6 + 7 2.0 650 10 0 example 4 Comparative 1200 952 723 623 26 h 4 + 7 1.8 500 25 10 example 5 Comparative 1035 982 924 901 0 4 + 7 3.5 600 5 0 example 6

[0069] It should be noted that the steel plates in Comparative examples 1-6 are manufactured by using only conventional process conditions, rather than the manufacturing process according to the present invention, and the steel plates in Comparative examples 1-6 correspond to those in Examples 1-6, respectively. Wherein the non-oriented electrical steel plate in Example 1 corresponds to steel of a national grade B50A1300 in Comparative example 1, the non-oriented electrical steel plate in Example 2 corresponds to steel of a national grade B50A800 in Comparative example 2, the non-oriented electrical steel plate in Example 3 corresponds to steel of a national grade B50A470 in Comparative example 3, the non-oriented electrical steel plate in example 4 corresponds to steel of a national grade B50A1300 in Comparative example 4, the non-oriented electrical steel plate in Example 5 corresponds to steel of a national grade B50A800 in Comparative example 5, and the non-oriented electrical steel plate in Example 6 corresponds to steel of a national grade B50A470 in Comparative example 6.

[0070] The non-oriented electrical steel plates with a final target thickness of 0.5±0.1 mm obtained by cold rolling in Examples 1-6 and the steel plates in Comparative examples 1-6 are subjected to various performance tests, and the obtained test results are listed in Table 5.

[0071] Table 5 lists the performance test results of the non-oriented electrical steel plates in Examples 1-6 as well as the steel plates in Comparative examples 1-6. Wherein, iron loss performance test: an iron loss performance test is performed by using an Epstein square based on the national standard GB/T 3655-2008 at a constant temperature of 20° C., wherein a specimen size is 30 mm×300 mm, a target mass is 0.5 kg, and a test parameter is P.sub.15/50.

[0072] Magnetic induction performance test: a magnetic induction performance test is performed by using the Epstein square based on the national standard GB/T 3655-2008 at a constant temperature of 20° C., wherein a specimen size is 30 mm×300 mm, a target mass is 0.5 kg, and a test parameter is B.sub.50.

TABLE-US-00006 TABLE 5 Iron loss Magnetic P.sub.15/50 induction B.sub.50 Number Grade (W/kg) (T) Example 1 B50A1300 5.4 1.79 Example 2 B50A800 4.4 1.74 Example 3 B50A600 3.2 1.71 Example 4 B50A1300 5.2 1.78 Example 5 B50A800 4.5 1.75 Example 6 B50A600 3.1 1.72 Comparative B50A1300 5.8 1.75 example 1 Comparative B50A800 5.0 1.72 example 2 Comparative B50A600 4.0 1.70 example 3 Comparative B50A1300 6.0 1.74 example 4 Comparative B50A800 5.2 1.72 example 5 Comparative B50A600 3.9 1.68 example 6

[0073] As can be seen from Table 5, there are obvious differences in iron loss P.sub.15/50 and magnetic induction B.sub.50 between the steel plates manufactured by using conventional process conditions in Comparative examples 1-6 and the non-oriented electrical steel plates in Examples 1-6. When the electromagnetic performance test density is 7.85 g/cm.sup.3, the iron loss P.sub.15/50 in Example 1 is reduced by 0.4 W/kg, and the magnetic induction B.sub.50 in Example 1 is increased by 0.04 T compared with those in Comparative example 1, which is mainly because in Comparative example 1, the Al content is as high as 0.01%, which has exceeded the upper limit of 0.001% in the claims of the present invention, and hot rolled steel coils are subjected to soaking and heat preservation at only 547° C., which does not meet the control range of 650-850° C.; when the electromagnetic performance test density is 7.80 g/cm.sup.3, the iron loss P.sub.15/50 in Example 2 is reduced by 0.6 W/kg, and the magnetic induction B.sub.50 in Example 2 is increased by 0.02 T compared with those in Comparative example 2, which is mainly because in Comparative example 2, the design of the content of Si and P does not match, resulting in that Si.sup.2/P is as high as 45.56, which has exceeded the upper limit of 26.04, and hot rolled steel coils are subjected to soaking and heat preservation at a temperature that is as high as 872° C., which does not meet the control range of 650-850° C.; when the electromagnetic performance test density is 7.70 g/cm.sup.3, the iron loss P.sub.15/50 in Example 3 is reduced by 0.8 W/kg, and the magnetic induction B.sub.50 in Example 3 is increased by 0.01 T compared with those in Comparative example 3, which is mainly because in Comparative example 3, the Si content is too low, so that Si.sup.2/P is only 0.05, which cannot meet the lower control limit of 0.89, and hot rolled steel coils are subjected to soaking and heat preservation at only 349° C., which does not meet the control range of 650-850° C.; when the electromagnetic performance test density is 7.85 g/cm.sup.3, the iron loss P.sub.15/50 in Example 4 is reduced by 0.8 W/kg, and the magnetic induction B.sub.50 in Example 4 is increased by 0.04 T compared with those in Comparative example 4, which is mainly because in Comparative example 4, the composition design of Al-containing steel is used, and as high as 0.4% of Al is added to the steel, resulting in the O content being lower than the lower control limit of 0.003% in the present invention and only 0.0022%, and at the same time, hot rolled steel coils are subjected to soaking and heat preservation at 583° C., which does not meet the control range of 650-850° C., and the soaking and heat preservation time is 0, which is lower than the design requirement of 10 s in the present invention; when the electromagnetic performance test density is 7.80 g/cm.sup.3, the iron loss P.sub.15/o in Example 5 is reduced by 0.7 W/kg, and the magnetic induction B.sub.50 in Example 5 is increased by 0.03 T compared with those in Comparative example 5, which is mainly because in Comparative example 5, the Al content is 0.0022%, which exceeds the upper control limit of 0.001% in the present invention, and the O content is as high as 0.0125%, which exceeds the design upper limit of 0.01% in the present invention; and when the electromagnetic performance test density is 7.70 g/cm.sup.3, the iron loss P.sub.15/50 in Example 6 is reduced by 0.8 W/kg, and the magnetic induction B.sub.50 in Example 6 is increased by 0.04 T compared with those in Comparative example 6, which is mainly because in Comparative example 6, the O content is only 0.0019%, which is lower than the design lower limit of 0.003% in the present invention, and when hot-rolled steel coils are subjected to soaking and heat preservation, although soaking and heat preservation are performed at a temperature that is as high as 900° C., the soaking and heat preservation time is 0, which is lower than the lower limit of the design requirement of 10 s in the present invention.

[0074] Thus, it can be seen that the non-oriented electrical steel plates in the examples of the present invention have excellent properties through the reasonable chemical composition design and process design. Compared with conventional products of the same grade, the iron loss P.sub.15/50 of the non-oriented electrical steel plate is reduced by 0.2-0.8 W/kg on average, and the magnetic induction B.sub.50 of the non-oriented electrical steel plate is increased by 0.01-0.04 T on average, achieving the characteristics of high magnetic induction and low iron loss while having good economy.

[0075] FIG. 1 schematically shows the relationship between the oxygen content in a non-oriented electrical steel plate according to the present invention and the iron loss P.sub.15/o of a finished steel plate.

[0076] As shown in FIG. 1, FIG. 1 schematically shows the relationship between the oxygen content and the iron loss P.sub.15/50 of the finished steel plate, wherein the steel plate shown in FIG. 1 is manufactured with a steel grade of a national standard grade B50A1300 as a standard, and other ingredients of the steel plate in FIG. 1 are all within the defined scope of the ingredients of the present invention, and the manufacturing methods therefor are also within the scope of the present invention. That is, the steel plate in FIG. 1 includes the following chemical elements in percentageby mass: 0.003% or less of C, 0.1%-1.2% of Si, 0.1%-0.4% of Mn, 0.01%-0.2% of P, 0.003% or less of S, 0.001% or less of Al, 0.003% or less of N, 0.005%-0.05% of Sn, and the balance of Fe and other unavoidable impurities, with the condition Si.sup.2/P: 0.89-26.04 being satisfied. And the manufacturing method for the steel plate includes the steps of: (1) smelting; (2) continuous casting; (3) hot rolling: wherein a hot rolled plate is subjected to soaking and heat preservation by means of residual heat of hot rolled steel coils, rather than being subjected to normalizing treatment or cover furnace annealing after coiling; (4) primary cold rolling; and (5) continuous annealing.

[0077] As can be seen from FIG. 1, the iron loss of the finished steel plate is closely related to the oxygen content in the steel. When the oxygen content is lower than 30 ppm, the iron loss of the steel plate will exceed 6.0 W/kg, and the lower the oxygen content, the higher the iron loss of the steel plate; and when the oxygen content is 30-100 ppm, the iron loss of the steel plate is generally lower, and the control effect can be stabilized at 5.5 W/kg or below; after the oxygen content is higher than 100 ppm, with the continuous increase of the oxygen content, the iron loss of the steel plate increases monotonously and rapidly, and when the oxygen content reaches 130 ppm, the iron loss of the steel plate can even reach 8.5 W/kg, which is much higher than the iron loss of the steel plate corresponding to the low oxygen content.

[0078] FIG. 2 is a microstructure diagram of a hot rolled steel plate in Example 2.

[0079] FIG. 3 is a microstructure diagram of a hot rolled steel plate in Comparative example 2.

[0080] As shown in FIGS. 2 and 3, the hot rolled steel plate corresponding to Example 2 can achieve complete recrystallization, the grains are uniform in size and coarse, and the average grain size can reach 80 μm, while the corresponding hot rolled steel plate corresponding to Comparative example 2 does not achieve complete recrystallization, recrystallization is only achieved at a position close to about 5% of the upper and lower surface of the hot rolled steel plate, and the middle of the steel plate is a fibrous incompletely recrystallized structure. The size of grains that can be recrystallized is relatively small, with an average of less than 50 μm.

[0081] FIG. 4 is a microstructure diagram of a finished non-oriented electrical steel plate in Example 3.

[0082] FIG. 5 is a microstructure diagram of a finished steel plate in Comparative example 3.

[0083] It can be seen in connection with FIGS. 4 and 5 that for Example 3, the microstructure of the finished strip steel is dominated by coarse equiaxed grains, the size of the long and short axes between the grains is close, the shape is regular, and the average recrystallization size is 75 μm. In Comparative example 3 of the same grade, there is a phenomenon that the grains cannot grow up effectively, the fine grains show local clusters and segregation, and the rest of the equiaxed grains that can complete recrystallization normally show the phenomenon of small grain size and uneven distribution.

[0084] It should be noted that the above-mentioned examples are only specific examples of the present invention. Obviously, the present invention is not limited to the above examples, and similar variations or modifications made therewith can be directly derived or can be easily thought of by those skilled in the art from the contents disclosed in the present invention, and all belong to the protection scope of the present invention.

[0085] In addition, the combination of the technical features in the present invention is not limited to the combination described in the claims of the present invention or the combination described in the specific examples, and all the technical features described in the present invention can be freely combined or combined in any way unless conflict with each other.

[0086] It should also be noted that the above-mentioned examples are only specific examples of the present invention. Obviously, the present invention is not limited to the above examples, and similar variations or modifications made therewith can be directly derived or can be easily thought of by those skilled in the art from the contents disclosed in the present invention, and all belong to the protection scope of the present invention.