JP7352082B2 - Non-oriented electrical steel sheet - Google Patents

Description

The present invention relates to a non-oriented electrical steel sheet.

Non-oriented electrical steel sheets are used, for example, in the iron core of motors. ) requires excellent magnetic properties, such as low iron loss and high magnetic flux density. Although various techniques have been proposed so far, it is difficult to obtain sufficient magnetic properties in all directions within the plate surface. For example, even if sufficient magnetic properties are obtained in a certain direction within the plate surface, sufficient magnetic properties may not be obtained in other directions.

Patent No. 4029430 Patent No. 6319465

In view of the above problems, an object of the present invention is to provide a non-oriented electrical steel sheet that can obtain excellent magnetic properties averaged over the entire circumference (averaged in all directions).

The present inventors conducted extensive studies to solve the above problems. As a result, it became clear that it is important to make the chemical composition and the average grain size ratio of {100} crystal grains and {111} crystal grains appropriate. The production of such non-oriented electrical steel sheets is based on the assumption that the chemical composition is α-γ transformation system, the structure is refined by transformation from austenite to ferrite during hot rolling, and then cold rolling is carried out at a predetermined reduction rate. The intermediate annealing temperature is controlled within a predetermined range to cause overhang recrystallization (hereinafter referred to as bulging) to facilitate the development of {100} crystal grains, which are normally difficult to develop. By performing skin pass rolling and finish annealing, it has also become clear that it is important that the {100} crystal grains attack the {111} crystal grains.

As a result of further intensive studies based on such knowledge, the present inventors have come up with the following aspects of the invention.

(1)
In mass%,
C: 0.010% or less,
Si: 1.50% to 4.00%,
sol. Al: 0.0001% to 1.0%,
S: 0.010% or less,
N: 0.010% or less,
One or more types selected from the group consisting of Mn, Ni, Co, Pt, Pb, Cu, and Au: 2.50% to 5.00% in total,
Sn: 0.000% to 0.400%,
Sb: 0.000% to 0.400%,
P: 0.000% to 0.400%, and one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0 in total Contains .0100%,
Mn content (mass%) is [Mn], Ni content (mass%) is [Ni], Co content (mass%) is [Co], Pt content (mass%) is [Pt], Pb content amount (mass %) is [Pb], Cu content (mass %) is [Cu], Au content (mass %) is [Au], Si content (mass %) is [Si], sol. The Al content (mass%) was determined by [sol. Al], the following formula (1) is satisfied,
The remainder has a chemical composition consisting of Fe and impurities,
The plate thickness is 0.50 mm or less,
A non-directional electromagnetic device characterized in that d ₁₀₀ /d ₁₁₁ >1.1, where d ₁₀₀ is the average grain size of {100} crystal grains, and d ₁₁₁ is the average grain size of {111} crystal grains. steel plate.
([Mn]+[Ni]+[Co]+[Pt]+[Pb]+[Cu]+[Au])-([Si]+[sol.Al])>0%...(1)

(2)
In mass%,
Sn: 0.020% to 0.400%,
Sb: 0.020% to 0.400%, and P: 0.020% to 0.400%
The non-oriented electrical steel sheet according to (1) above, containing one or more selected from the group consisting of:

(3)
Contains one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0005% to 0.0100% in total in mass% The non-oriented electrical steel sheet according to (1) or (2) above.

According to the present invention, it is possible to provide a non-oriented electrical steel sheet that can obtain excellent magnetic properties throughout the circumference.

Embodiments of the present invention will be described in detail below.

First, the chemical composition of the steel material used in the non-oriented electrical steel sheet and the manufacturing method thereof according to the embodiment of the present invention will be explained. In the following description, "%", which is the unit of content of each element contained in a non-oriented electrical steel sheet or steel material, means "% by mass" unless otherwise specified. The non-oriented electrical steel sheet and steel material according to the present embodiment have a chemical composition in which ferrite-austenite transformation (hereinafter referred to as α-γ transformation) can occur, with C: 0.010% or less and Si: 1.50% or more. 4.00%, sol. Al: 0.0001% to 1.0%, S: 0.010% or less, N: 0.010% or less, one or more selected from the group consisting of Mn, Ni, Co, Pt, Pb, Cu, and Au. : 2.50% to 5.00% in total, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%, and One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: Contains 0.0000% to 0.0100% in total, and the remainder is Fe and impurities. It has a chemical composition consisting of: Furthermore, Mn, Ni, Co, Pt, Pb, Cu, Au, Si and sol. The content of Al satisfies a predetermined condition described below. Examples of impurities include those contained in raw materials such as ore and scrap, and those contained in manufacturing processes.

(C: 0.010% or less)
C increases iron loss and causes magnetic aging. Therefore, the lower the C content, the better. Such a phenomenon is remarkable when the C content exceeds 0.010%. Therefore, the C content is set to 0.010% or less. Reducing the C content also contributes to uniform improvement of magnetic properties in all directions within the plate surface. The lower limit of the C content is not particularly limited, but it is preferably 0.0005% or more, taking into account the cost of decarburization during refining.

(Si: 1.50% to 4.00%)
Si increases electrical resistance, reduces eddy current loss, reduces iron loss, increases yield ratio, and improves punching workability into an iron core. If the Si content is less than 1.50%, these effects cannot be sufficiently obtained. Therefore, the Si content is set to 1.50% or more. On the other hand, if the Si content exceeds 4.00%, the magnetic flux density decreases, the punching workability decreases due to an excessive increase in hardness, and cold rolling becomes difficult. Therefore, the Si content is set to 4.00% or less.

(sol.Al: 0.0001% to 1.0%)
sol. Al increases electrical resistance, reduces eddy current loss, and reduces iron loss. sol. Al also contributes to increasing the relative magnitude of the magnetic flux density B50 to the saturation magnetic flux density. Here, the magnetic flux density B50 is the magnetic flux density in a magnetic field of 5000 A/m. sol. If the Al content is less than 0.0001%, these effects cannot be sufficiently obtained. Furthermore, Al also has the effect of promoting desulfurization in steel manufacturing. Therefore, sol. Al content shall be 0.0001% or more. On the other hand, sol. If the Al content exceeds 1.0%, the magnetic flux density decreases, the yield ratio decreases, and the punching workability decreases. Therefore, sol. Al content shall be 1.0% or less.

(S: 0.010% or less)
S is not an essential element and is contained, for example, as an impurity in steel. S inhibits recrystallization and crystal grain growth during annealing due to fine MnS precipitation. Therefore, the lower the S content, the better. The increase in core loss and decrease in magnetic flux density due to inhibition of recrystallization and grain growth are significant when the S content exceeds 0.010%. Therefore, the S content is set to 0.010% or less. Note that the lower limit of the S content is not particularly limited, but it is preferably 0.0003% or more, taking into consideration the cost of desulfurization treatment during refining.

(N: 0.010% or less)
Like C, N deteriorates magnetic properties, so the lower the N content, the better. Therefore, the N content is set to 0.010% or less. Note that the lower limit of the N content is not particularly limited, but it is preferably 0.0010% or more in consideration of the cost of denitrification treatment during refining.

(One or more types selected from the group consisting of Mn, Ni, Co, Pt, Pb, Cu, and Au: 2.50% to 5.00% in total)
Since these elements are necessary for causing α-γ transformation, it is necessary to contain at least one of these elements in a total amount of 2.50% or more. On the other hand, if the total amount exceeds 5.00%, the cost may increase and the magnetic flux density may decrease. Therefore, the total content of at least one of these elements is 5.00% or less.

In addition, the following conditions are further assumed to be satisfied as conditions under which α-γ transformation can occur. In other words, Mn content (mass%) is [Mn], Ni content (mass%) is [Ni], Co content (mass%) is [Co], Pt content (mass%) is [Pt], Pb content (mass%) is [Pb], Cu content (mass%) is [Cu], Au content (mass%) is [Au], Si content (mass%) is [Si], sol. The Al content (mass%) was determined by [sol. Al], the following equation (1) shall be satisfied in mass %.
([Mn]+[Ni]+[Co]+[Pt]+[Pb]+[Cu]+[Au])-([Si]+[sol.Al])>0%...(1)

If the above-mentioned formula (1) is not satisfied, the α-γ transformation does not occur and the magnetic flux density becomes low.

(Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%)
Sn and Sb improve the texture after cold rolling and recrystallization, and improve the magnetic flux density. Therefore, although these elements may be contained as necessary, if they are contained in excess, the steel becomes brittle. Therefore, the Sn content and the Sb content are both 0.400% or less. Further, P may be included in order to ensure the hardness of the steel sheet after recrystallization, but if it is included in excess, it will cause embrittlement of the steel. Therefore, the P content is set to 0.400% or less. In order to impart further effects such as magnetic properties as described above, 0.020% to 0.400% Sn, 0.020% to 0.400% Sb, and 0.020% to 0.400% % of P is preferably contained.

(One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0.0100% in total)
Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd react with S in the molten steel during casting of the molten steel to generate precipitates of sulfides, oxysulfides, or both of these. Hereinafter, Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd may be collectively referred to as "coarse precipitate-forming elements." The particle size of the precipitates of coarse precipitate-forming elements is about 1 μm to 2 μm, which is much larger than the particle size (about 100 nm) of fine precipitates such as MnS, TiN, AlN, etc. Therefore, these fine precipitates adhere to the precipitates of coarse precipitate-forming elements, making it difficult to inhibit recrystallization and growth of crystal grains during annealing such as intermediate annealing. In order to fully obtain these effects, it is preferable that the total content of these elements is 0.0005% or more. However, when the total amount of these elements exceeds 0.0100%, the total amount of sulfides, oxysulfides, or both becomes excessive, and recrystallization and crystal grain growth during annealing such as intermediate annealing are inhibited. Therefore, the total content of coarse precipitate-forming elements is set to 0.0100% or less.

Next, the thickness of the non-oriented electrical steel sheet according to this embodiment will be explained. The thickness of the non-oriented electrical steel sheet according to this embodiment is 0.50 mm or less. If the thickness exceeds 0.50 mm, excellent high frequency iron loss cannot be obtained. Therefore, the thickness should be 0.50 mm or less.

Next, the metal structure of the non-oriented electrical steel sheet according to this embodiment will be explained. The non-oriented electrical steel sheet according to the present embodiment further has a strain distribution such that a high magnetic flux density can be obtained in all directions as a whole. The details of the manufacturing method will be described later, but the non-oriented electrical steel sheet according to this embodiment has a chemical composition in which α-γ transformation can occur, and when hot rolling is completed and then cooled, austenite transforms into ferrite. It undergoes metamorphosis and its structure becomes finer. Furthermore, in the non-oriented electrical steel sheet of this embodiment, by undergoing cold rolling, intermediate annealing, and skin pass rolling, the {100} crystal grains have relatively little strain, while the {111} crystal grains have relatively little strain. It has a structure. After that, by performing finish annealing, the {100} crystal grains eat away at the {111} crystal grains, the average grain size of the {100} crystal grains becomes larger than the average grain size of the {111} crystal grains, and the magnetic properties improve. improves. In the non-oriented electrical steel sheet according to the present embodiment, when the average grain size of {100} crystal grains is d ₁₀₀ and the average grain size of {111} crystal grains is d ₁₁₁ , d ₁₀₀ /d ₁₁₁ >1. It is 1. When (d ₁₀₀ /d ₁₁₁ ) is less than 1.1, the effect of improving magnetic properties becomes insufficient because the {100} crystal grains are insufficiently etched. Furthermore, although a large amount of strain remains after skin pass rolling, finishing annealing can release the strain and provide a non-oriented electrical steel sheet with excellent workability.

Note that the average grain size of {100} crystal grains and the average grain size of {111} crystal grains can be measured by electron backscatter diffraction (hereinafter referred to as EBSD). Based on the information obtained by EBSD, we extracted the grains within a margin of 20 degrees from [100], and calculated the average grain size using analysis software to obtain the circle equivalent average, which is the average grain size of {100} grains. shall be. On the other hand, those with a tolerance of 20 degrees or less are extracted from {111}, and the average grain size of the grains is calculated as a circle-equivalent average using analysis software, and the result is defined as the average grain size of {111} grains.

Next, the magnetic properties of the non-oriented electrical steel sheet according to this embodiment will be explained. When examining the magnetic properties, the non-oriented electrical steel sheet according to this embodiment is further annealed at 800° C. for 2 hours, and then the magnetic flux density is measured. Further, the magnetic flux density is measured after annealing at 800° C. for 2 hours. This non-oriented electrical steel sheet has the best magnetic properties in two directions where the smaller angle with the rolling direction is 45°. On the other hand, the magnetic properties are the poorest in two directions where the angle with the rolling direction is 0° and 90°. Here, the 45° is a theoretical value, and it may not be easy to match it to 45° in actual manufacturing. Therefore, theoretically, if the direction in which the magnetic properties are the best is two directions in which the smaller angle with the rolling direction is 45°, then in actual non-oriented electrical steel sheets, the 45° ° includes angles that do not (strictly) correspond to 45°. This is the same at 0° and 90°. Further, theoretically, the magnetic properties in the two directions where the magnetic properties are the best are the same, but in actual manufacturing, it may not be easy to make the magnetic properties in the two directions the same. Therefore, theoretically, if the magnetic properties in the two directions with the best magnetic properties are the same, the term "same" includes those that are not (strictly) the same. This is also true in the two directions where the magnetic properties are the worst. Note that the above angles are expressed assuming that both clockwise and counterclockwise angles have positive values. When the clockwise direction is a negative direction and the counterclockwise direction is a positive direction, the two directions in which the smaller angle is 45 degrees with the rolling direction mentioned above are the rolling directions mentioned above. There are two directions in which the angle with the smaller absolute value is 45° and -45°. Moreover, the two directions in which the smaller angle between the angles with the rolling direction mentioned above is 45° can also be written as two directions in which the angles with the rolling direction are 45° and 135°. When measuring the magnetic flux density in this embodiment, the magnetic flux density B50 in the 45° direction with respect to the rolling direction is 1.75T or more. Note that although the magnetic flux density is high in the 45° direction with respect to the rolling direction, a high magnetic flux density can be obtained even on an average around the entire circumference (average in all directions).

The magnetic flux density can be measured by cutting out a 55 mm square sample from a direction of 45°, 0°, etc. with respect to the rolling direction, and using a single plate magnetic measuring device.

Next, a method for manufacturing a non-oriented electrical steel sheet according to this embodiment will be described. In this embodiment, hot rolling, cold rolling, intermediate annealing, skin pass rolling, finish annealing, etc. are performed.

First, the above-mentioned steel material is heated and hot rolled. The steel material is, for example, a slab manufactured by normal continuous casting. Rough rolling and finish rolling of hot rolling are performed at a temperature in the γ range (Ar1 or higher). That is, it is preferable to perform hot rolling so that the temperature (finishing temperature) when passing through the final pass of finish rolling becomes Ar1 or higher. As a result, the structure becomes finer by transforming from austenite to ferrite through subsequent cooling. If cold rolling is then performed in the refined state, bulging tends to occur and {100} crystal grains, which are normally difficult to grow, can be made to grow easily.

Thereafter, the hot-rolled steel plate is wound up without being annealed, pickled, and then cold-rolled to the hot-rolled steel plate. In cold rolling, the reduction ratio is preferably 80% to 92%. Note that the higher the rolling reduction rate, the easier it is for {100} crystal grains to grow due to subsequent bulging, but it becomes more difficult to wind up the hot-rolled steel sheet, making the operation more difficult.

After the cold rolling is completed, intermediate annealing is subsequently performed. In this embodiment, intermediate annealing is performed at a temperature that does not transform into austenite. That is, it is preferable that the temperature of intermediate annealing be less than Ac1. By performing intermediate annealing in this manner, bulging occurs and {100} crystal grains tend to grow. Further, the time for intermediate annealing is preferably 5 to 60 seconds.

After the intermediate annealing is completed, a second cold rolling (skin pass rolling) is performed. If rolling is performed in a state where bulging has occurred as described above, {100} crystal grains will further grow starting from the portion where bulging has occurred. The rolling reduction ratio in skin pass rolling is preferably 5% to 25%, thereby creating a crystal structure in which {100} crystal grains have relatively little strain and {111} crystal grains tend to have strain.

After skin pass rolling, it is preferable to perform finish annealing to release strain and improve workability. It is preferable that the finish annealing is also performed at a temperature that does not transform into austenite, and the temperature of the finish annealing is less than Ac1. By performing finish annealing in this manner, the {100} crystal grains attack the {111} crystal grains, and the magnetic properties are improved. Further, the time for finish annealing is preferably 1200 seconds or less.

As described above, the non-oriented electrical steel sheet according to this embodiment can be manufactured.

Next, a non-oriented electrical steel sheet according to an embodiment of the present invention will be specifically described while showing examples. The examples shown below are merely examples of non-oriented electrical steel sheets according to embodiments of the present invention, and the non-oriented electrical steel sheets according to the present invention are not limited to the following examples.

(First example)
Ingots having the components shown in Table 1 below were produced by casting molten steel. Here, the left side of the equation represents the value on the left side of the above-mentioned equation (1). Thereafter, the produced ingot was heated to 1150° C. and hot rolled to a thickness of 2.5 mm. After completion of finish rolling, the hot rolled steel plate was cooled with water and wound up. The temperature at the final pass stage of finish rolling (finishing temperature) at this time was 800°C, which was higher than Ar1. Further, the winding temperature during winding was 500°C.

Next, scale was removed from the hot rolled steel plate by pickling, and cold rolling was performed until the plate thickness became 1.1 times the target thickness (0.110 to 0.550 mm). Then, intermediate annealing was performed by heating to 700° C., which is lower than Ac1, in a non-oxidizing atmosphere. Next, No. 110, No. 111 and no. For samples other than No. 115, a second cold rolling (skin pass rolling) was performed at a rolling reduction rate of 9% until the target thickness (0.10 to 0.50 mm) was achieved. In addition, No. 110 and no. No. 115 omitted the second cold rolling. Also, No. No. 111 was rolled to 0.40 mm in the first cold rolling, and rolled to 0.35 mm in the second cold rolling (skin pass rolling).

Then, after the second cold rolling (skin pass rolling), finish annealing was performed for 30 seconds at 800° C., which is lower than Ac1, and the mixed grain size was measured.

Next, in order to examine the magnetic properties, strain relief annealing was performed at 800° C. for 2 hours after finish annealing, and the magnetic flux density B50 was measured. The measurement samples were 55 mm square samples taken in two directions: 0° and 45° in the rolling direction. Then, these two types of samples were measured, and the value in the 45° direction with respect to the rolling direction was taken as the magnetic flux density B50 in the 45° direction, and the values at 0°, 45°, 90°, and 135° with respect to the rolling direction were The average value was taken as the all-circumference average of magnetic flux density B50. Table 1 shows the measurement results of mixed particle size and magnetic properties.

The underlines in Table 1 indicate conditions outside the scope of the present invention. Invention example No. 101~No. 107, No. 109, No. 111~No. No. 114 had a good magnetic flux density B50 in both the 45° direction and the average around the entire circumference. On the other hand, the comparative example No. In No. 108, the Si concentration was high, the value on the left side of the equation was 0 or less, and the composition did not undergo α-γ transformation, so the magnetic density B50 was low in all cases. Comparative example No. 110 and no. No. 115 had a low magnetic flux density because d ₁₀₀ /d ₁₁₁ was smaller than 1.1.

(Second example)
Ingots having the components shown in Table 2 below were produced by casting molten steel. Thereafter, the produced ingot was heated to 1150° C. and hot rolled to a thickness of 2.5 mm. After completion of finish rolling, the hot rolled steel plate was cooled with water and wound up. The finishing temperature at the stage of the final pass of finish rolling at this time was 830°C, which was all higher than Ar1. Further, the winding temperature during winding was 500°C.

Next, scale was removed from the hot rolled steel plate by pickling, and cold rolling was performed until the plate thickness became 0.385 mm. Then, intermediate annealing was performed by heating to 700° C., which is lower than Ac1, in a non-oxidizing atmosphere. Next, a second cold rolling (skin pass rolling) was performed until the plate thickness became 0.35 mm.

Furthermore, after the second cold rolling (skin pass rolling), finish annealing was performed for 30 seconds at 800° C., which is lower than Ac1, and the mixed grain size was measured.

Next, in order to investigate the magnetic properties, strain relief annealing was performed at 800° C. for 2 hours after finish annealing, and the magnetic flux density B50 and iron loss W10/400 were measured. The magnetic flux density B50 was measured using the same procedure as in the first example. On the other hand, iron loss W10/400 was measured as the average energy loss (W/kg) occurring around the entire circumference of the sample when an alternating current magnetic field of 400 Hz was applied so that the maximum magnetic flux density was 1.0 T. Table 3 shows the measurement results of mixed particle size and magnetic properties.

No. 201~No. No. 214 were all invention examples, and all had good magnetic properties. In particular, No. 202~No. 204 is No. 201, No. 205~No. The magnetic flux density B50 is higher than that of No. 214. 205~No. 214 is No. 201~No. Iron loss W10/400 was lower than 204.

Claims (3)

In mass%,
C: 0.010% or less,
Si: 1.50% to 4.00%,
sol. Al: 0.0001% to 1.0%,
S: 0.010% or less,
N: 0.010% or less,
One or more types selected from the group consisting of Mn, Ni, Co, Pt, Pb, Cu, and Au: 2.50% to 5.00% in total,
Sn: 0.000% to 0.400%,
Sb: 0.000% to 0.400%,
P: 0.000% to 0.400%, and one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0 in total Contains .0100%,
Mn content (mass%) is [Mn], Ni content (mass%) is [Ni], Co content (mass%) is [Co], Pt content (mass%) is [Pt], Pb content amount (mass %) is [Pb], Cu content (mass %) is [Cu], Au content (mass %) is [Au], Si content (mass %) is [Si], sol. The Al content (mass%) was determined by [sol. Al], the following formula (1) is satisfied,
The remainder has a chemical composition consisting of Fe and impurities,
The plate thickness is 0.50 mm or less,
A non-directional electromagnetic device characterized in that d ₁₀₀ /d ₁₁₁ >1.1, where d ₁₀₀ is the average grain size of {100} crystal grains, and d ₁₁₁ is the average grain size of {111} crystal grains. steel plate.
([Mn]+[Ni]+[Co]+[Pt]+[Pb]+[Cu]+[Au])-([Si]+[sol.Al])>0%...(1) In mass%,
Sn: 0.020% to 0.400%,
Sb: 0.020% to 0.400%, and P: 0.020% to 0.400%
The non-oriented electrical steel sheet according to claim 1, characterized in that it contains one or more selected from the group consisting of: Contains one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0005% to 0.0100% in total in mass% The non-oriented electrical steel sheet according to claim 1 or 2.