JP6969473B2 - Non-oriented electrical steel sheet - Google Patents

Description

The present invention relates to non-oriented electrical steel sheets.

The non-oriented electrical steel sheet is used, for example, for the iron core of a motor, and the non-oriented electrical steel sheet is excellent in all directions parallel to the plate surface (hereinafter, may be referred to as "all directions in the plate surface"). Also required are magnetic properties such as low iron loss and high magnetic flux density. Non-oriented electrical steel sheets used in HEV turbocharger motors are required to have good performance at ultra-high speed rotations of nearly 100,000 rpm. At this rotation speed, there is a demand for a material that has strength to withstand centrifugal force, is excellent in high-frequency iron loss, and has a high magnetic flux density.

Japanese Unexamined Patent Publication No. 3-126845 Japanese Unexamined Patent Publication No. 2006-124809 Japanese Unexamined Patent Publication No. 61-231120 Japanese Unexamined Patent Publication No. 2004-197217 Japanese Unexamined Patent Publication No. 5-140648 Japanese Unexamined Patent Publication No. 2008-132534 Japanese Unexamined Patent Publication No. 2004-323972 Japanese Unexamined Patent Publication No. 62-240714 Japanese Unexamined Patent Publication No. 2011-157603 Japanese Unexamined Patent Publication No. 2008-1276559

An object of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties and excellent strength.

The present inventors have made diligent studies to solve the above problems. As a result, it became clear that it is important to make the chemical composition, thickness and average crystal grain size appropriate. In the production of such non-oriented electrical steel sheets, the columnar crystal ratio and average crystal grain size in casting or rapid solidification of molten steel are controlled when obtaining steel strips for cold rolling such as hot-rolled steel strips. It was also clarified that it is important to control the rolling reduction of cold rolling and to control the sheet tension and cooling rate during finish annealing.

As a result of further diligent studies based on such findings, the present inventors have come up with various aspects of the invention shown below.

(1)
By mass%,
C: 0.0030% or less,
Si: 2.00% to 4.00%,
Al: 0.01% to 3.00%,
Mn: 0.10% to 2.00%,
P: 0.005% to 0.200%,
S: 0.0030% or less,
One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd: 0.005% to 0.200% in total,
Parameter Q: 2. When the Si content (% by mass) is [Si], the Al content (% by mass) is [Al], and the Mn content (% by mass) is [Mn]. 00 or more,
When the total of one or more selected from the group consisting of [P], Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd as the P content (% by mass) is [X1]. Parameter R represented by Equation 2: 0.0001 or more,
Sn: 0.00% to 0.40%,
Cu: 0.0% to 1.0%,
Cr: 0.0% to 10.0%,
Ni: 0.0% to 1.0% and balance: Fe and impurities,
Has a chemical composition represented by
Five particles less than 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd ^{per 10 μm 2.} That's all,
{100} Crystal orientation strength is 2.4 or more,
The thickness is 0.15 mm to 0.30 mm, and the thickness is 0.15 mm to 0.30 mm.
A non-oriented electrical steel sheet characterized by having an average crystal grain size of 25 μm or less.
Q = [Si] + 2 [Al]-[Mn] (Equation 1)
R = [P] × [X1] (Equation 2)

(2)
In the chemical composition
Sn: 0.02% to 0.40%, or Cu: 0.1% to 1.0%,
Or the non-oriented electrical steel sheet according to (1), wherein both of these are satisfied.

(3)
In the chemical composition
Cr: 0.2% to 10.0%
The non-oriented electrical steel sheet according to (1) or (2), wherein is satisfied.

(4)
In the chemical composition
Ni: 0.1% to 1.0%
The non-oriented electrical steel sheet according to any one of (1) to (3), wherein the product is satisfied.

According to the present invention, since the chemical composition, the thickness and the average crystal grain size are appropriate, it is possible to provide a non-oriented electrical steel sheet having excellent magnetic properties and excellent strength.

Hereinafter, embodiments of the present invention will be described in detail.

First, the chemical composition of the non-oriented electrical steel sheet according to the embodiment of the present invention and the molten steel used for manufacturing the same will be described. Although details will be described later, the non-oriented electrical steel sheet according to the embodiment of the present invention is manufactured through casting and hot rolling of molten steel, rapid solidification of molten steel, cold rolling, finish annealing and the like. Therefore, the chemical composition of non-oriented electrical steel sheets and molten steel takes into consideration not only the characteristics of non-oriented electrical steel sheets but also their treatment. In the following description, "%", which is a unit of the content of each element contained in non-oriented electrical steel sheets or molten steel, means "mass%" unless otherwise specified. The non-directional electromagnetic steel plate according to this embodiment has C: 0.0030% or less, Si: 2.00% to 4.00%, Al: 0.10% to 3.00%, Mn: 0.10%. ~ 2.00%, P: 0.005% ~ 0.200%, S: 0.0030% or less, selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd. More than one type: 0.005% to 0.200% in total, Si content (% by mass) is [Si], Al content (% by mass) is [Al], Mn content (% by mass) is [ Mn], the parameter Q represented by the formula 1 is 2.00 or more, the P content (% by mass) is [P], Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and When the total of one or more selected from the group consisting of Cd is [X1], the parameters R: 0.0001 or more, Sn: 0.00% to 0.40%, Cu: 0. It has a chemical composition represented by 0% to 1.0%, Cr: 0.0% to 10.0%, Ni: 0.0% to 1.0%, and the balance: Fe and impurities. Examples of impurities include those contained in raw materials such as ore and scrap, and those contained in the manufacturing process.
Q = [Si] + 2 [Al]-[Mn] (Equation 1)
R = [P] × [X1] (Equation 2)

(C: 0.0030% 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 0.0030%. Therefore, the C content is set to 0.0030% or less. The reduction of the C content also contributes to the uniform improvement of the magnetic properties in all directions in the plate surface.

(Si: 2.00% to 4.00%)
Si increases the electrical resistance, reduces the eddy current loss, reduces the iron loss, increases the yield ratio, and improves the punching workability to the iron core. If the Si content is less than 2.00%, these effects cannot be sufficiently obtained. Therefore, the Si content is set to 2.00% or more. On the other hand, when 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.

(Al: 0.10% to 3.00%)
Al increases electrical resistance, reduces eddy current loss, and reduces iron loss. Al also contributes to the improvement of the relative magnitude of the magnetic flux density B50 with respect to the saturated magnetic flux density. Here, the magnetic flux density B50 is the magnetic flux density in a magnetic field of 5000 A / m. If the Al content is less than 0.10%, these effects cannot be sufficiently obtained. Therefore, the Al content is set to 0.10% or more. On the other hand, when the Al content exceeds 3.00%, the magnetic flux density is lowered, the yield ratio is lowered, and the punching workability is lowered. Therefore, the Al content is set to 3.00% or less.

(Mn: 0.10% to 2.00%)
Mn increases electrical resistance, reduces eddy current loss, and reduces iron loss. When Mn is contained, the texture obtained by primary recrystallization tends to be a developed crystal having a {100} plane parallel to the plate surface (hereinafter, may be referred to as “{100} crystal”). .. The {100} crystal is a crystal suitable for uniformly improving the magnetic properties in all directions in the plate surface. Further, the higher the Mn content, the higher the precipitation temperature of MnS, and the larger the MnS that precipitates. Therefore, the higher the Mn content, the less likely it is that fine MnS having a particle size of about 100 nm, which inhibits recrystallization and growth of crystal grains in finish annealing, is deposited. If the Mn content is less than 0.10%, these effects cannot be sufficiently obtained. Therefore, the Mn content is set to 0.10% or more. On the other hand, when the Mn content exceeds 2.00%, the crystal grains do not grow sufficiently in the finish annealing, and the iron loss increases. Therefore, the Mn content is set to 2.00% or less.

(P: 0.005% to 0.200%)
P is an element necessary for increasing the strength by reacting with a phosphide element described later and precipitating as a phosphide or an acid phosphide. If the P content is less than 0.005%, the phosphide or acid phosphide will be insufficient, and the effect of increasing the strength cannot be obtained. Further, if the P content exceeds 0.200%, the processability is lowered, so the P content is set to 0.005% to 0.200%.

(S: 0.0030% or less)
S is not an essential element and is contained as an impurity in, for example, steel. S inhibits recrystallization and grain growth in finish annealing due to the precipitation of fine MnS. Therefore, the lower the S content, the better. Such an increase in iron loss is remarkable when the S content exceeds 0.0030%. Therefore, the S content is set to 0.0030% or less.

(One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd: 0.005% to 0.200% in total)
Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd react with S in the molten steel during casting or rapid solidification of the molten steel to form sulfides, acid sulfides or both precipitates. Generate. However, when Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd and P are abundant, a phosphide or an acid sulfide is produced and then a phosphide or an acid phosphide is produced. Hereinafter, Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd may be collectively referred to as "phosphorus element". The particle size of the precipitate of the phosphorus-affinitive element is usually about 1 μm to 2 μm, but when the cooling rate at the time of solidification is increased, the phosphide or acid phosphide becomes a fine precipitate of 1 μm or less. Therefore, these fine precipitates dramatically increase the material strength. Moreover, since this precipitate is stable up to the temperature at which iron melts again, the thermal stability is very high. If the total content of the phosphorus-affinitive element is less than 0.005%, these effects cannot be stably obtained. Therefore, the total content of phosphorus-affinitive elements is 0.005% or more. On the other hand, when the total content of the phosphorus-affinitive element exceeds 0.200%, the strength is increased, but the material becomes brittle and unsuitable for a material rotating at high speed. Therefore, the total content of the phosphorus-affinitive element is 0.200% or less.

(Parameter Q: 2.00 or more)
If the parameter Q represented by Equation 1 is less than 2.00, ferrite-austenite transformation (α-γ transformation) may occur. Therefore, during casting or rapid solidification of molten steel, columnar crystals once formed are destroyed by α-γ transformation. Or the average crystal grain size becomes smaller. In addition, α-γ transformation may occur during finish annealing. Therefore, if the parameter Q is less than 2.00, the desired magnetic characteristics cannot be obtained. Therefore, the parameter Q is set to 2.00 or more. Further, if the parameter Q is 2.00 or more, the α-γ transformation does not occur, so the upper limit is not set.

(Parameter R: 0.0001 or more)
The phosphide element is mainly precipitated as a sulfide element, but if a large amount of the phosphide element is contained, a phosphide, an acid phosphide, or both can be precipitated in addition to the sulfide element. If the parameter R represented by the formula 2 is less than 0.0001, it is difficult to generate a phosphide or an acid phosphide of a phosphorus-affinitive element, and the strength is insufficient. Therefore, the parameter R represented by the equation 2 is 0.0001 or more. Further, if the parameter R is 0.0001 or more, a phosphide or an acid phosphide of a phosphorus affinity element can be produced, so an upper limit value is not set.

Sn, Cu, Ni, and Cr are not essential elements, but are optional elements that may be appropriately contained in the non-oriented electrical steel sheet up to a predetermined amount.

(Sn: 0.00% to 0.40%, Cu: 0.0% to 1.0%, Ni: 0.0% to 1.0%)
Sn, Cu, and Ni develop crystals suitable for improving magnetic properties by primary recrystallization. Therefore, when Sn, Cu, Ni, or two or more of these are contained, the texture in which {100} crystals suitable for uniformly improving the magnetic properties in all directions in the plate surface are developed is the primary recrystallization. Easy to obtain. Sn suppresses oxidation and nitriding of the surface of the steel sheet during finish annealing, and suppresses variation in crystal grain size. Therefore, Sn, Cu, Ni, or two or more of these may be contained. In order to sufficiently obtain these effects, Sn: 0.02% or more, Cu: 0.1% or more, Ni: 0.0% to 1.0%, or two or more of these are preferable. On the other hand, when Sn exceeds 0.40%, the above-mentioned action and effect are saturated and the cost is unnecessarily high, or the growth of crystal grains is suppressed in finish annealing. Therefore, the Sn content is set to 0.40% or less. If the Cu and Ni contents exceed 1.0%, the steel sheet becomes brittle, which makes hot rolling and cold rolling difficult, and makes it difficult to pass the annealed line for finish annealing. Therefore, the Cu and Ni contents are set to 1.0% or less.

(Cr: 0.0% to 10.0%)
Cr reduces high frequency iron loss. The reduction of high-frequency iron loss contributes to the high-speed rotation of the rotating machine, and the high-speed rotation contributes to the miniaturization and high efficiency of the rotating machine. Cr increases the electrical resistance, reduces the eddy current loss, and reduces the iron loss such as the high frequency iron loss. Cr lowers the stress sensitivity and contributes to the reduction of the magnetic properties due to the compressive stress introduced when forming the iron core and the deterioration of the magnetic properties due to the compressive stress acting at high speed rotation. Therefore, Cr may be contained. In order to sufficiently obtain these effects, Cr: 0.2% or more is preferable. On the other hand, when the Cr content exceeds 10.0%, the magnetic flux density decreases and the cost increases. Therefore, the Cr content is set to 10.0% or less.

Next, the texture of the non-oriented electrical steel sheet according to the embodiment of the present invention will be described. The non-oriented electrical steel sheet according to this embodiment has a {100} crystal orientation strength of 2.4 or more. If the crystal orientation strength is less than 2.4, the magnetic flux density decreases and the iron loss increases, or the magnetic characteristics vary between the directions parallel to the plate surface. The higher the {100} strength, the better, so the upper limit is not specified. The {100} crystal orientation intensity can be measured by X-ray diffraction or electron backscatter diffraction (EBSD) method. Since the angle of reflection of X-rays and electron beams from the sample differs depending on the crystal orientation, the crystal orientation intensity can be obtained from the reflection intensity or the like with reference to the random orientation sample.

Next, precipitates of phosphide and acid phosphide in the non-oriented electrical steel sheet according to the embodiment of the present invention will be described. In the non-oriented electrical steel sheet according to the present embodiment, among the precipitates of phosphide and / or acid phosphorification, 5 or more ^{particles having a diameter of less than 1 μm are present per 10 μm 2.} Particles of phosphide or acid phosphide less than 1 μm exist stably even at a temperature of about 1000 ° C., so that they are extremely excellent in thermal stability and can maintain high strength even at high speed rotation of 100,000 rpm. .. If the number of particles smaller than 1 μm of phosphide and / or acid phosphide is less than ^{5 per 10 μm 2} , sufficient strength cannot be obtained. Since the high strength contributes to the large amount, the upper limit is not particularly set, but it is desirable that the number is less than 150 because the effect is saturated. Further, when the phosphide, the acid phosphide, or both are 1 μm or more, it becomes technically difficult to precipitate a large number, and it becomes difficult to increase the strength. Therefore, it is necessary to make the particle size less than 1 μm.

The above precipitates can be observed, for example, by chemically polishing or electrolytically polishing the cross section of the steel plate with a scanning electron microscope (SEM). In the present invention, particles having a diameter of 100 to 3000 nm are observed, and components are identified by EDS.

Next, the average crystal grain size of the non-oriented electrical steel sheet according to the embodiment of the present invention will be described. The average crystal grain size of the non-oriented electrical steel sheet according to this embodiment is 25 μm or less. When the average crystal grain size exceeds 25 μm, the iron loss W3 / 10000 is high and sufficient strength cannot be obtained. Here, the iron loss W3 / 10000 is the iron loss at a magnetic flux density of 0.3 T and a frequency of 10000 Hz.

Next, the thickness of the non-oriented electrical steel sheet according to the embodiment of the present invention will be described. The thickness of the non-oriented electrical steel sheet according to this embodiment is, for example, 0.15 mm or more and 0.30 mm or less. If the thickness is more than 0.30 mm, excellent high frequency iron loss cannot be obtained. Therefore, the thickness is set to 0.30 mm or less. When the thickness is less than 0.15 mm, the magnetic properties on the surface of the non-oriented electrical steel sheet having low stability become dominant over the magnetic properties inside the high stability. Further, if the thickness is less than 0.15 mm, it becomes difficult to pass the annealing line for finish annealing, and the number of non-oriented electrical steel sheets required for a core of a certain size increases. As the number of man-hours increases, productivity decreases and manufacturing costs increase. Therefore, the thickness is set to 0.15 mm or more.

Next, the magnetic properties and mechanical properties of the non-oriented electrical steel sheet according to the embodiment of the present invention will be described. The non-oriented electrical steel sheet according to the present embodiment has, for example, a magnetic flux density B50: 1.61T or more in ring magnetic measurement and an iron loss W3 / 10000: non-oriented electrical steel sheet thickness of t (mm). When expressed, the magnetic characteristics expressed as 150 × [0.10 + 0.90 × {0.1 × (t / 0.20) + 0.9 × (t / 0.20) ^{2}] W / kg or less} Can be presented.

In the ring magnetic measurement, a ring-shaped sample collected from a non-oriented electrical steel sheet, for example, a ring-shaped sample having an outer diameter of 5 inches (12.70 cm) and an inner diameter of 4 inches (10.16 cm) is excited to generate magnetic flux. Flow around the entire circumference of the sample. The magnetic properties obtained by the ring magnetic measurement reflect the omnidirectional structure in the plate surface.

Further, the non-oriented electrical steel sheet according to the present embodiment can obtain mechanical properties having a top yield strength (YP) of 500 MPa or more.

Here, the mechanical properties can be tested by the method described in JIS. The test piece used is a JIS No. 5 test piece in which parallel portions of the test piece are aligned in the rolling direction of the steel sheet.

Next, the first manufacturing method of the non-oriented electrical steel sheet according to the embodiment will be described. In this first manufacturing method, molten steel casting, hot rolling, cold rolling, finish annealing and the like are performed.

In molten steel casting and hot rolling, molten steel having the above chemical composition is cast to produce ingots such as slabs, and this hot rolling is performed to form columnar crystals in the ingots such as slabs with the starting casting structure. A steel strip having a hot-rolled crystal structure of 80% or more in area fraction and an average crystal grain size of 0.1 mm or more is obtained.

Columnar crystals have a {100} <0vw> texture that is desirable for uniform improvement of magnetic properties of grain-oriented electrical steel sheets, particularly magnetic properties in all directions within the plate surface. The {100} <0vw> texture is a texture in which crystals with a plane parallel to the plate surface {100} plane and a rolling direction <0vw> are developed (v and w are arbitrary real numbers (v and w are arbitrary real numbers). (Except when both v and w are 0). If the proportion of columnar crystals is less than 80%, it is not possible to obtain a texture in which {100} crystals are developed by finish rolling. Therefore, the proportion of columnar crystals is 80%. The proportion of columnar crystals can be specified by microscopic observation. In the first production method, in order to make the proportion of columnar crystals 80% or more, for example, one surface of the slab at the time of solidification The temperature difference between the surface and the other surface is 40 ° C. or more. This temperature difference can be controlled by the cooling structure of the mold, the material, the mold taper, the mold flux, etc. The ratio of such columnar crystals is When molten steel is cast under the condition of 80% or more, a phosphor or acid phosphate having a phosphorus affinity element of 1 μm or less is produced, and the strength can be increased.

The smaller the average crystal grain size of the hot-rolled steel strip, the larger the number of crystal grains and the larger the area of grain boundaries. In the recrystallization of finish quenching, where crystals grow from within the crystal grains and from the crystal grain boundaries, the crystals that grow from within the crystal grains are {100} crystals that are desirable for magnetic properties, whereas the crystals that grow from the crystal grain boundaries. Is a crystal that is not desirable due to its magnetic properties, such as a {111} <112> crystal. Therefore, the larger the average crystal grain size of the hot-rolled steel strip, the more likely it is that {100} crystals desirable for magnetic properties will develop in finish annealing, especially when the average crystal grain size of the hot-rolled steel strip is 0.1 mm or more. , Excellent magnetic properties are easy to obtain. Therefore, the average crystal grain size of the hot-rolled steel strip is 0.1 mm or more. The average crystal grain size of the hot-rolled steel strip can be adjusted by adjusting the start temperature of hot rolling, the winding temperature, and the like. When the starting temperature is 900 ° C. or lower and the winding temperature is 650 ° C. or lower, the crystal grains contained in the hot-rolled steel strip are unrecrystallized and stretched in the rolling direction, so that the average crystal grain size is 0. A steel strip of 1 mm or more can be obtained.

The phosphorus-affinitive element can be put into the bottom of the last pot before casting in the steelmaking process, and molten steel containing elements other than the phosphorus-affinitive element can be injected into the pot to dissolve the phosphorus-affinitive element in the molten steel. preferable. This makes it difficult for the phosphorus-affinitive element to scatter from the molten steel, and also promotes the reaction between the phosphorus-affinitive element and P. The last pot before casting in the steelmaking process is, for example, the pot directly above the tundish of the continuous casting machine. Phosphide or acid phosphide of phosphorus affinity element can be produced finely and in large quantities by increasing the cooling rate at the time of solidification. For that purpose, for example, the temperature difference between the mold and the molten steel is increased, the casting speed is increased, the casting thickness is reduced, and the like.

When the reduction ratio of cold rolling is more than 90%, an texture that hinders the improvement of magnetic properties, for example, {111} <112> texture, tends to develop during finish annealing. Therefore, the rolling reduction of cold rolling is set to 90% or less. If the rolling reduction in cold rolling is less than 40%, it may be difficult to ensure the accuracy and flatness of the thickness of the non-oriented electrical steel sheet. Therefore, the rolling reduction ratio for cold rolling is preferably 40% or more.

Finish annealing causes primary recrystallization and grain growth, and the average crystal grain size is 25 μm or less. By this finish annealing, an aggregate structure in which {100} crystals suitable for uniformly improving the magnetic properties in all directions in the plate surface is obtained can be obtained. In the finish annealing, for example, the holding temperature is set to 800 ° C. or higher and 900 ° C. or lower, and the holding time is set to 10 seconds or longer and 60 seconds or lower.

When the sheet tension for finish annealing is more than 3 MPa, anisotropy elastic strain tends to remain in the non-oriented electrical steel sheet. Since the elastic strain having anisotropy deforms the texture, even if a texture in which {100} crystals are developed is obtained, this is deformed and the uniformity of the magnetic properties in the plate surface is lowered. Therefore, the plate tension for finish annealing is set to 3 MPa or less. Even when the cooling rate of finish annealing at 950 ° C. to 700 ° C. is more than 1 ° C./sec, elastic strain having anisotropy tends to remain in the non-oriented electrical steel sheet. Therefore, the cooling rate of finish annealing at 950 ° C to 700 ° C is preferably 1 ° C / sec or less.

In this way, the non-oriented electrical steel sheet according to the present embodiment can be manufactured. After finish annealing, an insulating film may be formed by coating and baking.

Next, a second manufacturing method of the non-oriented electrical steel sheet according to the embodiment will be described. In this second manufacturing method, rapid solidification of molten steel, cold rolling, finish annealing and the like are performed.

In the rapid solidification of molten steel, the molten steel having the above chemical composition is rapidly solidified on the surface of a cooling body that moves and renews, the ratio of columnar crystals is 80% or more in area fraction, and the average crystal grain size is 0.1 mm or more. Get a steel strip of.

In the second production method, in order to increase the proportion of columnar crystals to 80% or more, for example, the temperature of injection into the surface of the moving and renewing cooling body of molten steel is increased by 25 ° C. or more from the solidification temperature. In particular, when the temperature of the molten steel is higher than the solidification temperature by 40 ° C. or more, the ratio of columnar crystals can be made almost 100%. When the molten steel is solidified under the condition that the ratio of columnar crystals is 80% or more, a phosphide or an acid phosphide having a phosphide element of 1 μm or less is produced, and the strength can be increased.

Also in the second manufacturing method, the average crystal grain size of the steel strip is 0.1 mm or more. The average crystal grain size of the steel strip can be adjusted by the temperature of the molten steel when injected into the surface of the cooling body during rapid solidification, the cooling rate on the surface of the cooling body, and the like.

At the time of rapid solidification, the phosphorus affinity element is put into the bottom of the last pot before casting in the steelmaking process, molten steel containing elements other than the phosphorus affinity element is injected into the pot, and the phosphorus affinity element is added to the molten steel. It is preferable to dissolve it. This makes it difficult for the phosphorus-affinitive element to scatter from the molten steel, and also promotes the reaction between the phosphorus-affinitive element and P. The last pot before casting in the steelmaking process is, for example, the pot directly above the tundish of the casting machine that rapidly solidifies. Phosphide or acid phosphide of phosphorus affinity element can be produced finely and in large quantities by increasing the cooling rate at the time of solidification. For that purpose, for example, the temperature difference between the mold and the molten steel is increased, the casting speed is increased, the casting thickness is reduced, and the like.

Cold rolling and finish annealing may be performed under the same conditions as in the first manufacturing method.

In this way, the non-oriented electrical steel sheet according to the present embodiment can be manufactured. After finish annealing, an insulating film may be formed by coating and baking.

Such non-oriented electrical steel sheets according to the present embodiment exhibit excellent magnetic characteristics and mechanical characteristics, and are used for HEV turbocharger motors and the like. Further, the non-oriented electrical steel sheet according to the present embodiment can contribute to high efficiency and miniaturization of the rotating machine.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

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

(First test)
In the first test, molten steel having the chemical composition shown in Table 1 was cast to prepare a slab, and the slab was hot-rolled to have a columnar crystal ratio of 80% or more in terms of area fraction and average crystals. A steel strip having a particle size of 0.1 mm or more was obtained. The blanks in Table 1 indicate that the content of the element was below the detection limit, and the balance is Fe and impurities. Next, cold rolling and finish annealing of the steel strip were performed to produce various non-oriented electrical steel sheets having a thickness of 0.20 mm. Cold rolling is performed at a cold rolling temperature of 50 ° C. and a cold rolling reduction rate of 80%, and finish annealing is performed by heating the steel strip at a heating rate of 20 ° C./sec, and after reaching 900 ° C. and soaking for 15 seconds. It was air-cooled. Then, 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd of each non-directional electromagnetic steel plate. The number of particles less than 10 μm ² per 10 μm 2, the {100} crystal orientation strength I, and the average crystal grain size r were measured. The results are also shown in Table 1.

Then, the magnetic characteristics and mechanical characteristics of each non-oriented electrical steel sheet were measured. A ring test piece having an outer diameter of 5 inches and an inner diameter of 4 inches was used for this measurement. That is, the ring magnetic measurement was performed. The results are shown in Table 1. The iron loss W3 / 10000 is an excellent value if it is equal to or less than the evaluation standard W0 (W / kg) represented by the formula 3. That is, when the thickness was 0.20 mm, it was evaluated to be excellent at 150 (W / kg) or less. Further, the magnetic flux density B50 was evaluated to be excellent at 1.61T or more.
W0 = 150 × [0.1 + 0.9 × {0.1 × (t / 0.20) + 0.9 × (t / 0.20) ² }] (Equation 3)

Here, the mechanical properties were tested by the method described in JIS. The test piece used is a JIS No. 5 test piece in which parallel portions of the test piece are aligned in the rolling direction of the steel sheet. In order to withstand the rotation of the turbocharger, YP ≧ 500MPa was set as a good standard.

As shown in Table 1, the sample No. 1-No. 12, No. 14, No. 15, No. In No. 17, since the chemical composition was within the scope of the present invention and other conditions were within the scope of the present invention, good results were obtained in terms of magnetic properties and mechanical properties.

Sample No. In No. 13, since the phosphorus affinity element was hardly contained and the parameter R was too low, the top yield strength (YP) was insufficient, and the iron loss W3 / 10000 was high. Sample No. In No. 16, the content of the phosphorus affinity element was insufficient and the parameter R was too low, so that the upper yield strength (YP) was insufficient and the iron loss W3 / 10000 was high. Sample No. At 18, the parameter R was too low, so that the yield strength (YP) was insufficient, and the iron loss W3 / 10000 was high. Sample No. In No. 19, the content of the phosphorus affinity element was insufficient and the parameter R was too low, so that the upper yield strength (YP) was insufficient and the iron loss W3 / 10000 was high.

(Second test)
In the second test, molten steel (parameter R = 0.0006) having the chemical composition shown in Table 2 was cast to prepare a slab, and the slab was hot-rolled to divide the columnar crystals by area fraction. A steel strip having an average crystal grain size of 80% or more and an average crystal grain size of 0.1 mm or more was obtained. The balance is Fe and impurities. Next, cold rolling and finish annealing of the steel strip were performed to produce various non-oriented electrical steel sheets having a thickness of 0.20 mm. At this time, the production conditions were variously changed to produce a non-directional electromagnetic steel plate having a {100} crystal orientation strength I and a different number of particles of phosphide or acid phosphide less than 1 μm. Then, 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd of each non-directional electromagnetic steel plate. The number of particles less than 10 μm ² per 10 μm 2, the {100} crystal orientation strength I, and the average crystal grain size r were measured. The results are also shown in Table 2. The iron loss W3 / 10000, the magnetic flux density, and the top yield strength (YP) were also measured by the same procedure as in the first test, and are also shown in Table 2.

As shown in Table 2, the sample No. In No. 21, since the chemical composition is within the scope of the present invention and other conditions are within the scope of the present invention, good results were obtained in terms of magnetic properties and mechanical properties.

Sample No. At 22, per ^{10 μm 2} of particles less than 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd. Since the number of the above was too small, the yield strength (YP) was insufficient, and the iron loss of 3/10000 was high. Sample No. In No. 23, the magnetic flux density B50 was low because the {100} crystal orientation intensity I was too low.

(Third test)
In the third test, molten steel (parameter R = 0.0006) having the chemical composition shown in Table 3 was cast to prepare a slab, and the slab was hot-rolled to change the proportion of columnar crystals by area fraction. A steel strip having an average crystal grain size of 80% or more and an average crystal grain size of 0.1 mm or more was obtained. The blanks in Table 3 indicate that the content of the element was below the detection limit, and the balance is Fe and impurities. Next, cold rolling and finish annealing of the steel strip were performed to produce various non-oriented electrical steel sheets having a thickness of 0.20 mm. At this time, the cooling rate at the time of solidification was variously changed to produce non-directional electromagnetic steel plates having {100} crystal orientation strength I and different number of particles of less than 1 μm of phosphide and / or acid phosphide. Then, the number of particles of Mg phosphide and / or acid phosphide less than 1 μm ^{per 10 μm 2 of} each non-directional electromagnetic steel plate, {100} crystal orientation strength I, and average crystal grain size r were measured. .. The results are also shown in Table 3. Further, the iron loss W3 / 10000, the magnetic flux density B50, and the yield yield strength (YP) at 500 ° C. were also measured by the same procedure as in the first test, and are also shown in Table 3. Regarding the yield strength (YP) at 500 ° C., YP ≧ 330 MPa was used as a good criterion.

As shown in Table 3, the sample No. In 31 and 32, the average crystal grain size and the number of particles of phosphide and / or acid phosphide less than 1 μm are within the scope of the present invention, and other conditions are within the scope of the present invention. And good results were obtained in terms of mechanical properties.

Sample No. At 33, per ^{10 μm 2 of} one or more phosphide and / or acid phosphide less than 1 μm particles selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd. The top yield strength (YP) at 500 ° C. was insufficient because the number of the particles was too small. Sample No. In No. 34, the strength was increased by using niobium carbide as a substitute for the phosphide or acid phosphide, but the yield strength (YP) at 500 ° C. was insufficient. From this, it can be seen that the phosphide or acid phosphide of the phosphorus affinity element has excellent heat resistance.

(4th test)
In the fourth test, molten steel having the chemical composition shown in Table 4 was rapidly cooled and solidified to obtain a steel strip having a columnar crystal ratio of 80% or more in terms of area fraction and an average crystal grain size of 0.1 mm or more. .. The blanks in Table 3 indicate that the content of the element was below the detection limit, and the balance is Fe and impurities. Next, cold rolling and finish annealing of the steel strip were performed to produce various non-oriented electrical steel sheets having a thickness of 0.20 mm. Cold rolling is performed at a cold rolling temperature of 50 ° C. and a cold rolling reduction rate of 80%, and finish annealing is performed by heating the steel strip at a heating rate of 20 ° C./sec, and after reaching 900 ° C. and soaking for 15 seconds. It was air-cooled. Then, 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd of each non-directional electromagnetic steel plate. The number of particles less than 10 μm ² per 10 μm 2, the {100} crystal orientation strength I, and the average crystal grain size r were measured. The results are also shown in Table 4. The iron loss W3 / 10000, the magnetic flux density B50, and the top yield strength (YP) were also measured by the same procedure as in the first test, and are also shown in Table 4.

As shown in Table 4, the sample No. 101-No. 112, No. 114, No. 115, No. In 117, the chemical composition was within the scope of the present invention, and other conditions were within the scope of the present invention, so that good results were obtained in terms of magnetic properties and mechanical properties.

Sample No. In 113, since the phosphorus affinity element was hardly contained and the parameter R was too low, the upper yield strength (YP) was insufficient, and the iron loss W3 / 10000 was high. Sample No. At 116, the content of the phosphorus affinity element was insufficient and the parameter R was too low, so that the upper yield strength (YP) was insufficient and the iron loss of 3/10000 was high. Sample No. At 118, the parameter R was too low, so that the upper yield strength (YP) was insufficient, and the iron loss of 3/10000 was high. Sample No. In 119, the content of the phosphorus affinity element was insufficient and the parameter R was too low, so that the upper yield strength (YP) was insufficient and the iron loss of 3/10000 was high.

(Fifth test)
In the fifth test, molten steel having the chemical composition shown in Table 5 (parameter R = 0.0006) was rapidly cooled and solidified, the ratio of columnar crystals was 80% or more in terms of area fraction, and the average crystal grain size was 0. A steel strip of 1 mm or more was obtained. The balance is Fe and impurities. Next, cold rolling and finish annealing of the steel strip were performed to produce various non-oriented electrical steel sheets having a thickness of 0.20 mm. At this time, the cooling rate at the time of solidification was changed to produce a non-directional electromagnetic steel plate having a {100} crystal orientation strength I and a different number of particles of phosphide or acid phosphide less than 1 μm. Then, 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd of each non-directional electromagnetic steel plate. The number of particles less than 10 μm ² per 10 μm 2, the {100} crystal orientation strength I, and the average crystal grain size r were measured. The results are also shown in Table 5. The iron loss W3 / 10000, the magnetic flux density B50, and the top yield strength (YP) were also measured by the same procedure as in the first test, and are also shown in Table 5.

As shown in Table 5, the sample No. In 121, since the chemical composition is within the scope of the present invention and other conditions are within the scope of the present invention, good results were obtained in terms of magnetic properties and mechanical properties.

Sample No. At 122, per ^{10 μm 2 of} one or more phosphide and / or acid phosphide less than 1 μm selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd. Since the number of the above was too small, the yield strength (YP) was insufficient, and the iron loss of 3/10000 was high. Sample No. In 123, the magnetic flux density B50 was low because the {100} crystal orientation intensity I was too low.

(Sixth test)
In the sixth test, molten steel having the chemical composition shown in Table 6 (parameter R = 0.0006) was rapidly cooled and solidified, the ratio of columnar crystals was 80% or more in terms of area fraction, and the average crystal grain size was 0. A steel strip of 1 mm or more was obtained. The blanks in Table 6 indicate that the content of the element was below the detection limit, and the balance is Fe and impurities. Next, cold rolling and finish annealing of the steel strip were performed to produce various non-oriented electrical steel sheets having a thickness of 0.20 mm. At this time, the cooling rate at the time of solidification was changed to produce a non-directional electromagnetic steel plate having a different number of particles of {100} crystal orientation strength I and phosphide and / or acid phosphide less than 1 μm. Then, 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd of each non-directional electromagnetic steel plate. The number of particles less than 10 μm ² per 10 μm 2, the {100} crystal orientation strength I, and the average crystal grain size r were measured. The results are also shown in Table 6. Further, the iron loss W3 / 10000, the magnetic flux density B50, and the yield yield strength (YP) at 500 ° C. were also measured by the same procedure as in the first test, and are also shown in Table 6.

As shown in Table 6, the sample No. In 131 and 132, the average crystal grain size and the number of particles of phosphide and / or acid phosphide less than 1 μm are within the scope of the present invention, and other conditions are within the scope of the present invention. And good results were obtained in terms of mechanical properties.

Sample No. At 133, per ^{10 μm 2 of} one or more phosphide and / or acid phosphide less than 1 μm particles selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd. The top yield strength (YP) at 500 ° C. was insufficient because the number of the particles was too small. Sample No. In 134, the strength was increased by using niobium carbide as a substitute for the phosphide or acid phosphide, but the yield strength (YP) at 500 ° C. was insufficient. From this, it can be seen that the phosphide or acid phosphide of the phosphorus affinity element has excellent heat resistance.

Claims (4)

By mass%,
C: 0.0030% or less,
Si: 2.00% to 4.00%,
Al: 0.01% to 3.00%,
Mn: 0.10% to 2.00%,
P: 0.005% to 0.200%,
S: 0.0030% or less,
One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd: 0.005% to 0.200% in total,
Parameter Q: 2. When the Si content (% by mass) is [Si], the Al content (% by mass) is [Al], and the Mn content (% by mass) is [Mn]. 00 or more,
When the total of one or more selected from the group consisting of [P], Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd as the P content (% by mass) is [X1]. Parameter R represented by Equation 2: 0.0001 or more,
Sn: 0.00% to 0.40%,
Cu: 0.0% to 1.0%,
Cr: 0.0% to 10.0%,
Ni: 0.0% to 1.0% and balance: Fe and impurities,
Has a chemical composition represented by
Five particles less than 1 μm of one or more phosphide and / or acid phosphide selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd ^{per 10 μm 2.} That's all,
{100} Crystal orientation strength is 2.4 or more,
The thickness is 0.15 mm to 0.30 mm, and the thickness is 0.15 mm to 0.30 mm.
A non-oriented electrical steel sheet characterized by having an average crystal grain size of 25 μm or less.
Q = [Si] + 2 [Al]-[Mn] (Equation 1)
R = [P] × [X1] (Equation 2) In the chemical composition
Sn: 0.02% to 0.40%, or Cu: 0.1% to 1.0%,
The non-oriented electrical steel sheet according to claim 1, wherein both of these are satisfied. In the chemical composition
Cr: 0.2% to 10.0%
The non-oriented electrical steel sheet according to claim 1 or 2, wherein the product is satisfied. In the chemical composition
Ni: 0.1% to 1.0%
The non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the product is satisfied.