EP4640864A1

EP4640864A1 - Non-oriented electrical steel sheet and method of manufacturing same

Info

Publication number: EP4640864A1
Application number: EP23907243.2A
Authority: EP
Inventors: Jae-Wan Hong; Kyu-Seok Han; June-soo PARK
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2022-12-21
Filing date: 2023-04-21
Publication date: 2025-10-29
Also published as: WO2024135950A1; JP2026500412A; MX2025005274A; CN120225712A; KR20240098914A

Abstract

The present invention relates to a non-oriented electrical steel sheet and a method of manufacturing same. One aspect of the present invention is to provide a non-oriented electrical steel sheet which has excellent iron loss and magnetic flux density characteristics, and a method of manufacturing same.

Description

Technical Field

The present disclosure relates to a non-oriented electrical steel sheet and a method of manufacturing the same.

Background Art

An electrical steel sheet may be a product used as a material for a transformer, a motor, and an electrical device. Differently from general carbon steel of which workability such as mechanical properties may be important, an electrical steel sheet may be a functional product of which electrical properties may be important. Required electrical properties may include low iron loss, high magnetic flux density, permeability, and space factor.
An electrical steel sheet may include an oriented electrical steel sheet and a non-oriented electrical steel sheet. An oriented electrical steel sheet may be an electrical steel sheet having excellent magnetic properties in the rolling direction by forming Goss texture ({110}<001> texture) throughout the steel sheet using abnormal grain growth referred to as secondary recrystallization. A non-oriented electrical steel sheet may have uniform magnetic properties in all directions on a rolled sheet.
As a process of producing a non-oriented electrical steel sheet, a method of hot-rolling, cold-rolling, and final annealing a slab and forming an insulating coating layer may be generally used.
As a process of producing an oriented electrical steel sheet, a method of hot-rolling, preliminary annealing, cold-rolling, decarburization annealing, and final annealing a slab and forming an insulating coating layer may be used.
Among these, a non-oriented electrical steel sheet may have uniform magnetic properties in all directions, such that a non-oriented electrical steel sheet may generally be used as a material for a motor core, an iron core of generator, an electric motor, and a small transformer. Representative magnetic properties of non-oriented electrical steel sheets may be iron loss and magnetic flux density. The lower iron loss, less iron loss may be lost during the process of magnetizing the iron core, which may improve efficiency. The higher the magnetic flux density, the greater the magnetic strength may be induced with the same energy, and since less current may be applied to obtain the same magnetic flux density, copper loss may be reduced, which may improve energy efficiency.
However, there may be a limitation in improvement of characteristics of a non-oriented electrical steel sheet based on general metallurgical techniques, and the degree of iron loss deterioration of a non-oriented electrical steel sheet not having undergone stress relief annealing after processing may not satisfy the strict iron loss-related energy efficiency regulations and the requirements of industries related to electric energy production, transmission, conversion, and utilization.
Recently, to meet demands of these industry demand, it may be necessary to develop a non-oriented electrical steel sheet having low iron loss and high magnetic flux density for manufacturing of a motor having higher efficiency.

Detailed description of present disclosure

Technical problems to solve

An aspect in the present disclosure is to provide a non-oriented electrical steel sheet having excellent iron loss and magnetic flux density properties, and a method of manufacturing the same.

Solution to Problem

According to an embodiment of the present disclosure, a non-oriented electrical steel sheet includes, by weight%, Si: 3.0 to 5.0%, Mn: 0.1 to 1.4%, Al: 0.3 to 1.3%, P: 0.001 to 0.01%, S: 0.003% or less (excluding 0%), C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), one or more of Sn: 0.001 to 0.08% and Sb: 0.001 to 0.08%, and a balance of Fe and inevitable impurities, wherein an average size of MnS precipitates is 0.5 µm or more, and wherein a fraction of precipitates having an average size of 3 µm or more is 5 area% or less of entire precipitates.
According to another embodiment of the present disclosure, a method of manufacturing a non-oriented electrical steel sheet includes heating a slab including, by weight%, Si: 3.0 to 5.0%, Mn: 0.1 to 1.4%, Al: 0.3 to 1.3%, P: 0.001 to 0.01%, S: 0.003% or less (excluding 0%), C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), one or more of Sn: 0.001 to 0.08% and Sb: 0.001 to 0.08%, and a balance of Fe and inevitable impurities; finishing hot-rolling the heated slab and obtaining a hot-rolled sheet; primary-cold-rolling the hot-rolled sheet at a cold reduction ratio of 40 to 79% and obtaining a first cold-rolled sheet; primary-annealing the first cold-rolled sheet; final cold-rolling the primary-annealed first cold-rolled sheet and obtaining a second cold-rolled sheet; and final annealing the second cold-rolled sheet, wherein, in the primary-cold-rolling, a finishing cold-rolling temperature is 50 to 160°C, and wherein, in the final annealing, the steel sheet is held for 50 to 120 seconds at 900 to 1100°C.

Advantageous Effects of Invention

According to an aspect of the present disclosure, a non-oriented electrical steel sheet having excellent iron loss and magnetic flux density properties and a method of manufacturing the same may be provided.

Best Mode for Invention

Hereinafter, a non-oriented electrical steel sheet according to an embodiment of the present invention may be described. First, an alloy composition may be described. The content of the alloy composition described below may be indicated in weight% unless otherwise indicated.

Si: 3.0 to 5.0%

Silicon (Si) may increase resistivity of a material and may reduce iron loss. When the content of Si is less than 3.0%, the effect of addressing iron loss may be insufficient. When the content of Si exceeds 5.0%, brittleness of the material may increase, and sheet breakage may occur during coiling and cold-rolling, such that rolling productivity may degrade rapidly. Accordingly, the content of Si may have a range of 3.0 to 5.0% preferably. An upper limit of the Si content may preferably be 4.5% more.

Mn: 0.1 to 1.4%

Manganese (Mn) may address iron loss by increasing resistivity of the material and may form sulfides. When the content of Mn is less than 0.1%, sulfides may be finely precipitated, which may degrade magnetism. When the content of Mn exceeds 1.4%, the formation of {111} texture may be promoted, which is unfavorable to magnetism, and magnetic flux density may decrease. Accordingly, the content of Mn may range from 0.1 to 1.4% preferably.

Al: 0.3 to 1.3%

Aluminum (Al) may reduce iron loss by increasing resistivity of the material, and may improve rolling properties or workability during cold-rolling. When the content of Al is less than 0.3%, reducing high-frequency iron loss may be ineffective, and the precipitation temperature of AlN may be lowered, and nitride may be finely formed, which may degrade magnetism. When the Al content exceeds 1.3%, nitrides may be excessively formed, which may deteriorate magnetism, and problems may occur in all processes such as steelmaking and continuous casting, such that productivity may significantly degrade. Accordingly, the Al content may range from 0.3 to 1.3% preferably.

P: 0.001 to 0.01%

Phosphorus (P) may segregate at grain boundaries and may improve texture, such that resistivity may increase and iron loss may be reduced. When the P content is less than 0.001%, the segregation amount may be relatively small such that the texture improvement effect may not be obtained. When the P content exceeds 0.01%, the formation of a texture unfavorable to magnetism may occur, such that there may be no effect of improving texture, and excessive segregation at grain boundaries may occur, and accordingly, rollability and workability may degrade, and production may become difficult. Accordingly, the P content may range from 0.001 to 0.01% preferably.

S: 0.003% or less (excluding 0%)

Sulfur (S) may suppress grain growth by forming fine sulfides in a base material and may weaken iron loss. When the S content exceeds 0.003%, S may combine with Mn, or the like, and may suppress grain growth or may excessively degrade magnetism after processing. Accordingly, the S content may range from 0.003% or less (excluding 0%) preferably.

C: 0.005% or less (excluding 0%)

Carbon (C) may suppress ferrite grain growth during annealing, may excessively deteriorate magnetism during processing, and may degrade magnetism by combining with Ti, or the like. When the C content exceeds 0.005%, magnetism may be excessively degraded. Accordingly, the C content may have a range of 0.005% or less (excluding 0%) preferably. The C content may more preferably be 0.004% or less, and even more preferably 0.003% or less.

N: 0.005% or less (excluding 0%)

Nitrogen (N) may worsen iron loss such that nitrogen (N) may form fine, long precipitates inside the base material by combining with Al, Ti, or the like, and may combine with other impurities and may form fine nitrides, thereby inhibiting grain growth. When the N content exceeds 0.005%, magnetism may be excessively degraded. Accordingly, the N content may have a range of 0.005% or less (excluding 0%) preferably. The content of N may more preferably be 0.004% or less, and even more preferably 0.003% or less.

Ti: 0.005% or less (excluding 0%)

Titanium (Ti) may have a strong tendency to form precipitates in steel, and may suppress grain growth by forming fine carbides or nitrides in a base material. When the content of Ti exceeds 0.005%, carbides and nitrides may be greatly formed, which may worsen iron loss and may deteriorate magnetism. Accordingly, the content of Ti may have a range of 0.005% or less (excluding 0%) preferably. The content of Ti may more preferably be 0.004% or less, and even more preferably 0.003% or less.

One or more of Sn: 0.001 to 0.08% and Sb: 0.001 to 0.08%

Sn: 0.001 to 0.08%

Tin (Sn) may segregate in the grain system and on the surface, may improve the texture of the steel sheet, and may improve magnetism by suppressing surface oxidation. When the Sn content is less than 0.001%, it may be difficult to sufficiently obtain the above-mentioned effect. When the Sn content exceeds 0.08%, the grain system segregation may become severe, the surface quality may deteriorate, hardness may increase, and cold-rolled sheet breakage may occur, which may degrade rollability. Accordingly, the Sn content may have a range of 0.001 to 0.08% preferably.

Sb: 0.001 to 0.08%

Antimony (Sb) may segregate in the grain system and on the surface, and may improve the texture of the steel sheet, and may improve magnetism by suppressing surface oxidation. When the content of the Sb is less than 0.001%, it may be difficult to sufficiently obtain the above-mentioned effect. When the content of Sb exceeds 0.08%, the grain system segregation may become severe, the surface quality may deteriorate, hardness may increase, and cold-rolled sheet breakage may occur, which may degrade rollability. Accordingly, the content of Sb may have a range of 0.001 to 0.08% preferably.
The total content of the Sn and Sb may be 0.1% or less. When the total content of Sn and Sb exceeds 0.1%, the degree of grain segregation may be large, crystal growth may be low, and magnetic properties may deteriorate.
A remainder of the present disclosure is iron (Fe). However, in a general manufacturing process, inevitable impurities may be inevitably added from raw materials or an ambient environment, and thus, impurities may not be excluded. A person skilled in the art of a general manufacturing process may be aware of the impurities, and thus, the descriptions of the impurities may not be provided in the present disclosure.
The non-oriented electrical steel sheet of the present invention may further include one or more of Nb: 0.005% or less and V: 0.005% or less.

Nb: 0.005% or less

Nb may form fine nitrides by combining with C, N, or the like, and may hinder domain movement, and thus, an upper limit thereof may be limited to 0.005%. More specifically, the content of Nb may be 0.0001 to 0.005%. More specifically, the content of Nb may be 0.0005 to 0.003%.

V: 0.005% or less

V may form fine nitrides by combining with C, N, or the like, and may hinder domain movement, and thus, an upper limit thereof may be limited to 0.005%. More specifically, the content of V may be 0.0001 to 0.005%. More specifically, the V content may be 0.0005 to 0.003%.
The non-oriented electrical steel sheet of the present invention may further include one or more of Cr: 0.01 to 0.5%, Ni: 0.05% or less, Cu: 0.005 to 0.2% and Zn: 0.01% or less.

Cr: 0.01 to 0.5%

Cr may improve iron loss by increasing resistivity. When the Cr content is less than 0.01%, the resistivity-increasing effect may not be sufficient. When the Cr content exceeds 0.5%, magnetic flux density may degrade. More specifically, the Cr content may be 0.02 to 0.3%.

Ni: 0.05% or less

Ni may react with impurity elements and may form fine sulfides, carbides, and nitrides, which have a detrimental effect on magnetism, and thus, an upper limit thereof may be limited to 0.05%. More specifically, the content of Ni may be 0.0001 to 0.050%. More specifically, the content of Ni may be 0.001 to 0.030%.

Cu: 0.005 to 0.2%

Cu may form sulfides with Mn. When the content of Cu is less than 0.005%, (Cu Mn)S may be finely precipitated, which may deteriorate magnetism. When the content of Cu exceeds 0.2%, high-temperature embrittlement may occur, which may form cracks during casting or hot-rolling. More specifically, the content of Cu may be 0.010 to 0.1%.

Zn: 0.01% or less

Zn may act as an impurity and may deteriorate magnetism, and thus, an upper limit thereof may be limited to 0.01%. More specifically, the content of Zn may be 0.0001 to 0.01%. More specifically, the content of Zn may be 0.001 to 0.008%.
The non-oriented electrical steel sheet of the present invention may further include one or more of Mo: 0.03% or less, B: 0.0050% or less, Ca: 0.005% or less and Mg: 0.005% or less.
The above elements may react with C, S, N, or the like, which may be inevitably included, and may form fine carbides, nitrides, or sulfides, which may adversely affect magnetic properties, and thus, an upper limit may be limited as mentioned above.
The non-oriented electrical steel sheet of the present invention may further include 0.20% or less (excluding 0%) of one or more of Bi, Pb, Ge and As individually or in combination.
When the aforementioned elements are additionally added, the elements may segregate in the grain system, may relieve stress concentration in the grain system during cold-rolling, and may inhibit recrystallization of <111>//ND orientation grains in the subsequent recrystallization annealing process, thereby improving magnetic flux density. When the elements are added appropriately, the aforementioned effect may be additionally obtained, but when the elements are included excessively, a large amount of segregation may occur, which may inhibit grain growth and may deteriorate magnetic flux density and iron loss. More specifically, 0.0001 to 0.20% of one or more of Bi, Pb, Ge and As may be included individually or in combination. More specifically, 0.001 to 0.10% of one or more of Bi, Pb, Ge and As may be included individually or in combination.
A non-oriented electrical steel sheet according to an embodiment of the present invention may preferably have an average size of MnS precipitates of 0.5 µm or more. When the average size of the MnS precipitates is less than 0.5 µm, magnetic properties may be deteriorated. The average size of MnS precipitates may more preferably be 0.7 µm or more. Since a larger average size of MnS precipitates may be referable, such that, in the present invention, an upper limit of the average size of MnS precipitates may not be specifically limited. However, an upper limit of the average size of the MnS precipitates may be 1.2 µm, as an example.
Also, in the non-oriented cold-rolled steel sheet of the present invention, a fraction of precipitates having an average size of 3 µm or more may preferably be 5 area% or less of the total precipitate. When the fraction of precipitates having an average size of 3 µm or more exceeds 5 area% relative to the total precipitates, grain growth may be excessively large during the final annealing process, such that it may be difficult to ensure the optimum grain diameter, and accordingly, iron loss may be deteriorated. In the present invention, a lower fraction of precipitates having an average size of 3 µm or more relative to the total precipitates may be advantageous, and thus, a lower limit thereof may not be limited. However, a lower limit of the fraction of precipitates having an average size of 3 µm or more relative to the total precipitates may be, for example, 0.5 area%.
As described above, the non-oriented electrical steel sheet of the present invention may have a thickness of 0.1 to 0.25 mm. Also, the magnetic flux density (B50) may be 1.74-0.028/t+0.00135/t² (t: thickness of the steel sheet) Tesla or higher, and iron loss (W10/400) may be 16.18-1.23/t+0.061/t² (t: thickness of the steel sheet)W/Kg or lower. In the present invention, higher magnetic flux density (B50) may be advantageous, and thus, there may be no particular limitation on an upper limit thereof. However, an upper limit of the magnetic flux density (B50) may be, for example, 1.73Tesla. Also, in the present invention, lower iron loss (W10/400) may be advantageous, there may be no particular limitation on a lower limit thereof. However, a lower limit of iron loss (W10/400) may be, for example, 7W/Kg.
Hereinafter, a method of manufacturing the non-oriented electrical steel sheet according to an embodiment of the present invention may be described.
First, a slab satisfying the aforementioned alloy composition may be heated. The slab heating temperature may be 1100 to 1180°C. When the slab heating temperature is lower than 1100°C, hot-rolling deformation resistance may be high, such that it may be difficult to perform hot-rolling. When the slab heating temperature exceeds 1180°C, fine precipitates may increase, which may worsen iron loss.
Thereafter, the heated slab may be finishing hot-rolled and a hot-rolled sheet may be obtained. The finishing hot-rolling temperature may be 870 to 950°C. When the finishing hot-rolling temperature is lower than 870°C, strength of the sheet increase, which may cause defects such as shape defects when coiling the coil. When the finishing hot-rolling temperature exceeds 950°C, the rolling speed may need to be increased, it may be difficult to perform hot-rolling.
In the present invention, considering the economic aspect, the hot-rolled sheet annealing process may not be performed on the hot-rolled sheet.
Thereafter, the hot-rolled sheet may be primary-cold-rolled with a cold reduction ratio of 40 to 79% and a first cold-rolled sheet may be obtained. When the cold reduction ratio is less than 40%, sufficient strain may not be applied in the primary-cold-rolling, such that magnetism may be deteriorated after the final annealing. When the cold reduction ratio exceeds 79%, the final cold reduction ratio may be low, such that magnetism may be deteriorated. Accordingly, the cold reduction ratio may have a range of 40 to 79%. A lower limit of the cold reduction ratio may more preferably be 50%. An upper limit of the cold reduction ratio may more preferably be 70%.
The finishing cold-rolling temperature during the primary-cold-rolling may be 50 to 160°C preferably. When the finishing cold-rolling temperature is less than 50°C during the primary-cold-rolling, deformation may be applied at a low temperature, and sites in which precipitates are formed may be excessively provided, such that fine precipitates may be formed and magnetism may be deteriorated. When the finishing cold-rolling temperature exceeds 160°C during the primary-cold-rolling, trace elements in steel may diffuse, such that fine precipitates may increase, and due to the oxide layer formed during the cold-rolling, magnetic properties may be deteriorated after the final annealing. Accordingly, the finishing cold-rolling temperature during the primary-cold-rolling may have a range of 50 to 120°C. An upper limit of the finishing cold-rolling temperature during the primary-cold-rolling may more preferably be 130°C.
Thereafter, the first cold-rolled sheet may be primary-annealed. The primary-annealing may be held for 60 to 350 seconds at 900 to 1140°C. When the holding temperature during the primary-annealing is lower than 900°C, recrystallization may not be sufficiently performed, which may deteriorate magnetism. When the holding temperature during the primary-annealing exceeds 1140°C, the grain size may become excessively large, it may be difficult to perform cold-rolling. A lower limit of the holding temperature during the primary-annealing may more preferably be 950°C. An upper limit of the holding temperature during the primary-annealing may more preferably be 1100°C. When the holding time during the primary-annealing is less than 60 seconds, it may be difficult to appropriately coarsen the precipitates, and distribution of fine precipitates may increase, which may deteriorate magnetism after the final annealing. When the holding time exceeds 360 seconds during the primary-annealing, the precipitates may be excessively coarse, which may deteriorate magnetic properties after the final annealing.
Thereafter, the primary-annealed first cold-rolled sheet may be final cold-rolled and a second cold-rolled sheet may be obtained. In the present invention, the cold reduction ratio may not be particularly limited during the final cold-rolling, and cold-rolling may be performed to satisfy the product thickness targeted in the present invention.
Thereafter, the second cold-rolled sheet may be final annealed. It may be preferable to hold the sheet for 50 to 120 seconds at 900 to 1100°C during the final annealing. When the holding temperature is less than 900°C during the final annealing, the optimum grain size may not be ensured, which may deteriorate magnetic properties. When the holding temperature exceeds 1100°C during the final annealing, the sheet may not withstand a weight thereof at high temperature such that it may be impossible to perform continuous annealing, or tension may greatly affect the sheet, such that magnetism may deteriorate. When the holding time is less than 50 seconds during the final annealing, the precipitates may not coarsen sufficiently, such that fine precipitates may be formed, which may worsen iron loss. When the holding time exceeds 120 seconds during the final annealing, the precipitates may coarsen excessively, such that the fraction of precipitates of 3 µm or more may increase, and accordingly, it may be difficult to control the grain size, which may deteriorate magnetism.

Mode for Invention

Hereinafter, the present disclosure may be described more specifically through embodiments. However, it should be noted that the embodiments below are merely intended to describe the present disclosure in greater detail based on embodiments, and are not intended to limit the scope of the rights of the present disclosure. This may be because the scope of rights of the present invention is determined by matters described in the claims and matters reasonably inferred therefrom.

(Embodiment)

A slab having the alloy composition of Table 1 as below was heated at 1130°C, and the heated slab was finishing hot-rolled at 930°C and a hot-rolled sheet was obtained. Thereafter, the hot-rolled sheet was primary-cold-rolled under the conditions listed in Table 2 as below and a first cold-rolled sheet may be obtained. Thereafter, the first cold-rolled sheet was primary-annealed for 120 seconds under the conditions listed in Table 2 as below. Thereafter, the primary-annealed first cold-rolled sheet was final cold-rolled under the conditions listed in Table 2 as below, and a second cold-rolled sheet was obtained, and thereafter, the second cold-rolled sheet was final annealed, thereby manufacturing a non-oriented electrical steel sheet.
The precipitates and electrical properties of the non-oriented cold-rolled steel sheet manufactured as above were measured, and the results are listed in Table 3 below.
The average size of the MnS precipitates and the fraction of precipitates having an average size of 3 µm or more as compared to the total precipitates were measured using SEM for a 2 mm × 2 mm area of the non-oriented cold-rolled steel sheet.

The magnetic flux density (B50) and iron loss (W10/400) were measured using the Epstein measurement method by adjusting the number of samples processed to a size of 305 mm × 30 mm in the rolling direction and the rolling vertical direction such that the weight of the sample was 400 to 450 g.

[Table 1]

Steel type	Alloy composition (weight%)
Steel type	Si	Mn	Al	Sn	Sb	Sn+Sb	P	S	C	N	Ti
A	3.23	0.72	0.84	0.03	0.02	0.05	0.008	0.001 5	0.001 7	0.001 3	0.001 3
B	3.41	0.52	0.72	-	0.05	0.05	0.007	0.001 8	0.002 3	0.001 2	0.001 7
C	3.75	0.43	0.38	0.07	-	0.07	0.009	0.001 4	0.001 8	0.001 0	0.001 5
D	3.31	1.27	0.72	0.02	0.04	0.06	0.006	0.001 7	0.002 4	0.000 9	0.001 4
E	3.38	0.37	1.15	0.05	-	0.05	0.008	0.001 5	0.001 5	0.001 3	0.001 8
F	3.82	0.54	0.91	0.03	0.03	0.06	0.009	0.001 3	0.002 1	0.001 9	0.001 6

[Table 2]

Classif ication	Ste el typ e	Hot-rolled sheet thickn ess (mm)	Cold reduction ratio in primary-cold-rolling (%)	Finishing cold-rolling temperature in primary-cold-rolling (°C)	Primar y-anneal ing temper ature (°C)	Final thic knes s (mm)	Final annealin g temperat ure (°C)	Final Annealin g time (sec)
Compara tive example 1	A	2.7	-	-	1080	0.25	960	80
Compara tive example 2	A	2.7	26	80	1080	0.25	960	80
Compara tive example 3	A	2.7	42	30	1080	0.25	960	80
Compara tive example 4	A	2.7	42	180	1080	0.25	960	80
Inventi ve example 1	A	2.7	48	100	1080	0.25	960	80
Inventi ve example 2	A	2.7	63	70	1080	0.25	960	80
Comparative example 5	A	2.7	81	120	1080	0.25	960	80
Inventi ve example 3	B	2.3	48	80	1040	0.25	960	80
Inventi ve example 4	B	2.3	57	80	1040	0.25	960	80
Inventi ve example 5	B	2.3	48	90	1040	0.20	960	80
Inventi ve example 6	B	2.3	57	70	1040	0.20	960	80
Inventi ve example 7	C	1.8	56	100	1060	0.25	960	100
Inventi ve example 8	C	1.8	56	90	1060	0.20	960	100
Inventi ve example 9	C	1.8	56	80	1060	0.15	960	100
Inventi ve example 10	C	2.0	56	90	1060	0.10	960	100
Inventi ve example 11	D	2.0	60	100	1020	0.15	960	90
Inventi ve example 12	D	2.0	60	110	1080	0.15	960	90
Inventi ve example 13	D	2.0	70	80	1020	0.10	960	90
Inventi ve example 14	D	1.8	70	70	1080	0.10	960	90
Inventi ve example 15	E	1.8	72	60	1050	0.10	950	70
Inventi ve example 16	E	1.8	72	80	1050	0.10	960	70
Inventi ve example 17	E	1.8	72	70	1050	0.10	970	70
Inventi ve example 18	E	1.8	72	100	1050	0.10	980	70
Compara tive example 6	F	2	62	80	1030	0.2	960	40
Inventi ve example 19	F	2	62	70	1030	0.2	960	70
Inventi ve example 20	F	2	62	90	1030	0.2	960	100
Compara tive example 7	F	2	62	80	1030	0.2	960	130

[Table 3]

Classifi cation	Average size of MnS precipitates (µm)	Fraction of precipitates having average size of 3 µm or more as compared to total precipitates (area%)	Magnetic flux density (B50) (Tesla)	Iron loss (W10/400) (W/Kg)
Comparat ive example 1	0.38	5.2	1.638	12.3
Comparat ive example 2	0.42	5.8	1.642	12.25
Comparat ive example 3	0.36	4.2	1.632	12.72
Comparat ive example 4	0.47	4.4	1.617	12.85
Inventiv e example 1	0.71	3.1	1.655	11.82
Inventiv e example 2	0.85	1.9	1.671	11.59
Comparat ive example 5	0.83	6.0	1.645	12.18
Inventiv e example 3	0.78	4	1.666	11.27
Inventiv e example 4	0.92	2.8	1.662	11.13
Inventiv e example 5	0.64	3.2	1.648	10.85
Inventiv e example 6	0.71	2.5	1.652	10.7
Inventiv e example 7	1.05	2.7	1.672	11.04
Inventiv e example 8	0.88	1.9	1.662	10.38
Inventiv e example 9	0.72	1.1	1.65	10.14
Inventiv e example 10	0.54	0.9	1.644	9.68
Inventiv e example 11	0.67	1.3	1.647	10.17
Inventiv e example 12	0.89	2.4	1.653	10.03
Inventiv e example 13	0.71	4.1	1.648	9.57
Inventiv e example 14	0.92	3.8	1.657	9.55
Inventiv e example 15	0.94	1.9	1.659	9.72
Inventiv e example 16	0.91	2.2	1.653	9.53
Inventiv e example 17	0.97	3.7	1.649	9.38
Inventiv e example 18	1.04	4.1	1.647	9.46
Comparat ive example 6	0.45	2.8	1.667	11.91
Inventiv e example 19	0.91	3.3	1.665	11.07
Inventiv e example 20	1.04	4.5	1.659	10.85
Comparat ive example 7	1.32	5.8	1.630	12.16

As indicated in Tables 1 to 3, in inventive examples 1 to 20, the alloy composition and manufacturing conditions proposed in the present invention were satisfied, such that the average size of the MnS precipitates and the fraction of precipitates having an average size of 3 µm or more as compared to the total precipitates, aimed to be obtained in the present invention, were ensured, and excellent magnetism was ensured.
In comparative examples 1 to 7, the manufacturing conditions of the present invention were not satisfied, such that the average size of the MnS precipitates or the fraction of precipitates having an average size of 3 µm or more as compared to the total precipitates, aimed to be obtained in the present invention, was ensured, such that magnetism was deteriorated.

Claims

A non-oriented electrical steel sheet, comprising:
by weight%, Si: 3.0 to 5.0%, Mn: 0.1 to 1.4%, Al: 0.3 to 1.3%, P: 0.001 to 0.01%, S: 0.003% or less (excluding 0%), C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), one or more of Sn: 0.001 to 0.08% and Sb: 0.001 to 0.08%, and a balance of Fe and inevitable impurities,

wherein an average size of MnS precipitates is 0.5 µm or more, and

wherein a fraction of precipitates having an average size of 3 µm or more is 5 area% or less of entire precipitates.
The non-oriented electrical steel sheet of claim 1, wherein Sn and Sb is 0.1% or less in total.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet further includes one or more of Nb: 0.005% or less and V: 0.005% or less.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet further includes one or more of Cr: 0.01 to 0.5%, Ni: 0.05% or less, Cu: 0.005 to 0.2% and Zn: 0.01% or less.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet includes one or more of Mo: 0.03% or less, B: 0.0050% or less, Ca: 0.005% or less and Mg: 0.005% or less.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet further includes 0.20% or less (excluding 0%) of one or more of Bi, Pb, Ge and As individually or in combination.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet has a thickness of 0.1 to 0.25 mm.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet has a magnetic flux density (B50) of 1.74-0.028/t+0.00135/t² (t: thickness of the steel sheet) Tesla or higher.
The non-oriented electrical steel sheet of claim 1, wherein the non-oriented electrical steel sheet has an iron loss (W10/400) of 16.18-1.23/t+0.061/t² (t: thickness of the steel sheet)W/Kg or lower.
A method of manufacturing a non-oriented electrical steel sheet, the method comprising:
heating a slab including, by weight%, Si: 3.0 to 5.0%, Mn: 0.1 to 1.4%, Al: 0.3 to 1.3%, P: 0.001 to 0.01%, S: 0.003% or less (excluding 0%), C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), one or more of Sn: 0.001 to 0.08% and Sb: 0.001 to 0.08%, and a balance of Fe and inevitable impurities;

finishing hot-rolling the heated slab and obtaining a hot-rolled sheet;

primary-cold-rolling the hot-rolled sheet at a cold reduction ratio of 40 to 79% and obtaining a first cold-rolled sheet;

primary-annealing the first cold-rolled sheet;

final cold-rolling the primary-annealed first cold-rolled sheet and obtaining a second cold-rolled sheet; and

final annealing the second cold-rolled sheet, wherein, in the primary-cold-rolling, a finishing cold-rolling temperature is 50 to 160°C, and

wherein, in the final annealing, the steel sheet is held for 50 to 120 seconds at 900 to 1100°C.
The method of claim 10, wherein Sn and Sb is 0.1% or less in total.
The method of claim 10, wherein the slab further includes one or more of Nb: 0.005% or less and V: 0.005% or less.
The method of claim 10, wherein the slab further includes one or more of Cr: 0.01 to 0.5%, Ni: 0.05% or less, Cu: 0.005 to 0.2% and Zn: 0.01% or less.
The method of claim 10, wherein the slab further includes one or more of Mo: 0.03% or less, B: 0.0050% or less, Ca: 0.005% or less and Mg: 0.005% or less.
The method of claim 10, wherein the slab further includes 0.20% or less (excluding 0%) of one or more of Bi, Pb, Ge and As individually or in combination.
The method of claim 10, wherein a temperature of heating the slab is 1100 to 1180°C.
The method of claim 10, wherein a temperature of the finishing hot-rolling is 870 to 950°C.
The method of claim 10, wherein, in the primary-annealing, the steel sheet is held for 60 to 360 seconds at 900 to 1140°C.