KR101177161B1 - High-strength electromagnetic steel sheet and process for producing the same - Google Patents

Abstract

An object of the present invention is to produce a high strength electromagnetic steel sheet having a high tensile strength of 500 MPa or more, and having magnetic properties excellent in wear resistance, magnetic flux density, and iron loss, and in mass%, C: 0.060% or less, Si: 0.2 to 6.5 %, Mn: 0.05 to 3.0%, P: 0.30% or less, S or Se: 0.040% or less, Al: 2.50% or less, N: 0.020% or less, or Cu: 0.001 to 30.0%, Nb: 0.03 to 8.0% In the manufacturing method of the high strength electromagnetic steel sheet which contains 1 or more types further and a process structure remains inside a steel plate, the average grain size D (micrometer) of the board | plate immediately before a process which finally forms the process structure which remains inside a steel plate By a method of producing a high strength electromagnetic steel sheet which is coarsened to D ≥ 20 µm and which is subjected to strain in the final processing step as a preferred manufacturing method and which does not undergo heat treatment in which the processed structure is lost. Obtained electromagnetic steel sheet.

High strength electromagnetic steel plate, tensile strength, iron loss, processing tissue, heat treatment

Description

High-strength electromagnetic steel sheet and its manufacturing method {HIGH-STRENGTH ELECTROMAGNETIC STEEL SHEET AND PROCESS FOR PRODUCING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high strength electromagnetic steel sheet, in particular a high strength non-oriented electromagnetic steel sheet. will be.

Background Art Conventionally, laminated electromagnetic steel sheets have been used for rotor (rotor) materials. However, in applications in which high speed rotation and larger rotor diameters are required, the centrifugal force applied to the rotors may exceed the strength of the electromagnetic steel sheets. In addition, many motors have a structure of assembling magnets to the rotor, and even though the rotational speed is not so high, the load on the rotor material itself during the rotation of the rotor is large, and the strength of the material is a problem in terms of fatigue strength. There is a lot of work.

In addition, the electromagnetic switch is required to wear a magnetic material excellent in wear resistance as well as electromagnetic characteristics because the contact surface wears with use.

In response to such a demand, in recent years, high strength non-oriented electromagnetic steel sheets have been examined and some proposals have been made. For example, in Japanese Patent Application Laid-Open No. Hei 1-627,4848 and Japanese Patent Application Laid-Open No. 61-84360, the Si content is increased and one kind of solid solution strengthening component such as Mn, Ni, Mo, Cr, or the like. Although it is proposed to use slab containing two or more kinds of materials, there is a possibility that plate breakage occurs frequently during rolling, and there is room for improvement such as lowering productivity and lowering yield. Since it contains a large amount of Mo and Cr, it becomes a very expensive material. Japanese Unexamined Patent Application Publication No. 2005-113185 and Japanese Unexamined Patent Application Publication No. 2006-070348 disclose a non-oriented electromagnetic steel sheet which obtains strength by remaining a processed structure, and also Japanese Patent Application Laid-Open No. 2006-009048, Japan In addition, Japanese Patent Application Laid-Open No. 2006-070296 discloses a non-oriented electromagnetic steel sheet in which recrystallization is suppressed by solid solution of Nb or the like. However, since they do not pay special attention to the grain size before forming a process structure, there exists a problem that a stable iron loss is not obtained.

Moreover, although the technique regarding the electromagnetic steel plate containing a large amount of Cu is disclosed by Unexamined-Japanese-Patent No. 2004-84053 and Unexamined-Japanese-Patent No. 2004-99926, it originates in the Cu phase which precipitated in steel, Reduction of eddy loss is not sufficient, and there is room for improvement in application to applications where high frequency characteristics are a problem.

As described above, many proposals have been made for high-strength electromagnetic steel sheets, but the situation is that they have not been reached until the industrially stable production using ordinary electromagnetic steel sheet manufacturing equipment while securing necessary magnetic properties. . The inventor first applied for a patent application in Japanese Patent Application No. 2003-347084 for a high strength electromagnetic steel sheet in which a processed structure remained in a steel sheet.

This technique does not deteriorate the magnetic properties even if the processed structure remains in the crystal structure. Considering the synergistic effect of the strength, this technique is not only a material strengthened with conventional solid solution elements or precipitates, but also has productivity and magnetic properties, particularly Considering the in-plane anisotropy of the magnetic flux density, it is made based on a very useful technique. However, for an electromagnetic steel sheet having a work structure, no clear metallurgy has been established on how to improve the balance between magnetic properties and mechanical properties, and no confirmation has been obtained that this technique is optimal in this respect.

In order to clarify this point, the inventors conducted detailed experiments, in particular, regarding the influence of the structure before rolling, and found that there is an area that is optimal for achieving both magnetic and mechanical properties in an electromagnetic steel sheet having a processed structure. In addition, in consideration of productivity, especially the mail order of the steel strip, it succeeded in setting an industrially optimal range.

The present invention has a high tensile strength (TS) of 500 MPa or more, for example, and has high wear resistance, and has excellent magnetic properties such as magnetic flux density (B50) and iron loss, especially when used under a high frequency magnetic field such as a motor rotating at high speed. It is an object to manufacture a high strength non-oriented electromagnetic steel sheet stably on-line, without changing it into a normal electromagnetic steel sheet, such as cold rolling property and annealing workability, for example. This invention is made | formed in order to solve the said subject, The summary is as follows.

(1) In mass%, C: 0.060% or less, Si: 0.2-6.5%, Mn: 0.05-3.0%, P: 0.30% or less, S or Se: 0.040% or less, Al: 2.50% or less, N: 0.040 In the manufacturing method of the high strength electromagnetic steel sheet which contains% or less and consists of remainder part Fe and an unavoidable impurity, and a process structure remains inside a steel plate, just before the process of finally forming the process structure remaining inside a steel plate. The average grain size d of the steel sheet in the steel sheet is 20 µm or more.

(2) In mass%, C: 0.060% or less, Si: 0.2-6.5%, Mn: 0.05-3.0%, P: 0.30% or less, S or Se: 0.040% or less, Al: 2.50% or less, N: 0.040 In the manufacturing method of the high strength electromagnetic steel sheet which contains% or less and consists of remainder part Fe and an unavoidable impurity, and a process structure remains inside a steel plate, just before the process of finally forming the process structure remaining inside a steel plate. Average grain size d (μm) of the steel sheet in

d ≥ (220-50 × Si%-50 × Al%)

The manufacturing method of the high strength electromagnetic steel plate characterized by the above-mentioned.

(3) The average crystal grain size d (mu m) of the steel sheet at the end of the step of finally forming the processed structure remaining inside the steel sheet,

d ≤ (400-50 × Si%), and

d ≤ (820-200 × Si%)

The manufacturing method of the high strength electromagnetic steel plate as described in (1) or (2) characterized by the above-mentioned.

(4) Production of the high strength electromagnetic steel sheet according to any one of (1) to (3), wherein the recrystallization rate of the steel sheet immediately before the step of finally forming the processed structure remaining inside the steel sheet is 50% or more. Way.

(5) The high-strength electromagnetic wave according to any one of (1) to (4), wherein the steel component contains at least one kind by mass% of Cu: 0.001 to 30.0% and Nb: 0.03 to 8.0%. Method of manufacturing steel sheet.

(6) One or more steel components in mass%, Ti: 1.0% or less, V: 1.0% or less, Zr: 1.0% or less, B: 0.010% or less, Ni: 15.0% or less, Cr: 15.0% or less, or It contains 2 or more types, The manufacturing method of the high strength electromagnetic steel plate in any one of (1)-(5).

(7) The steel component contains 0.5% or less in mass% of one or two or more of Bi, Mo, W, Sn, Sb, Mg, Ca, Ce, La, and Co in total ( The manufacturing method of the high strength electromagnetic steel plate in any one of 1)-(6).

(8) The method for producing a high strength electromagnetic steel sheet according to any one of (1) to (7), wherein the processed structure existing inside the steel sheet is 1% or more at an area ratio in cross-sectional observation.

(9) The method for producing a high strength electromagnetic steel sheet according to any one of (1) to (8), wherein the average dislocation density in the processed structure inside the steel sheet is 1 × 10 ¹³ / m 2 or more.

(10) It is a ferrite single phase or in mass% in the temperature range of 1150 degreeC from room temperature,

980-400 × C + 50 × Si-30 × Mn + 400 × P + 100 × Al-20 × Cu-15 × Ni-10 × Cr> 900

The high strength electromagnetic steel sheet as described in (1) characterized by the above-mentioned.

(11) A high strength electromagnetic steel sheet which is remarkably excellent in the magnetic properties according to the above (10), wherein the tensile strength is increased by 100 MPa or more by heat treatment at 450 ° C for 30 minutes.

(12) In the process of manufacturing the steel sheet according to the above (11), the final heat treatment after cold rolling is maintained in the temperature range of 800 ° C or higher for 5 seconds or more, and the austenite in the steel also at the highest achieved temperature in this heat treatment. A method for producing a high strength electromagnetic steel sheet, characterized by a heat treatment in which no knight phase is produced.

(13) In the process of manufacturing the steel sheet according to the above (10), the cooling step after holding for 5 seconds or more in a temperature range of 800 ° C or more is to be cooled to 300 ° C or less at a cooling rate of 40 ° C / sec or more. The manufacturing method of the high strength electromagnetic steel plate characterized by the above-mentioned.

(14) The method for producing a high strength electromagnetic steel sheet according to (10), wherein in the cooling step, the residence time of 700 to 400 ° C is 5 seconds or less.

1 is a diagram showing the strength-iron loss balance depending on the particle diameter before processing.

MEANS TO SOLVE THE PROBLEM The present inventors made various experiments and examined repeatedly in order to achieve the said objective. That is, the present invention is C: 0.060% or less, Si: 0.5-6.5%, Mn: 0.05-3.0%, P: 0.30% or less, S or Se: 0.040% or less, Al: 2.50% or less, N: 0.040% or less Steel sheet containing a steel sheet containing, if necessary, any one or more of Cu: 0.001% to 30.0%, or Nb: 0.05% to 8.0%. To increase the strength, (2) to coarsen the crystal structure immediately before forming the processed structure finally remaining in the steel sheet, and (3) to limit the above-described crystal structure from the viewpoint of the amount of Si to improve the flowability. In particular, in the steel sheet in which the processed structure remains and is produced in the electromagnetic steel sheet, it is possible to improve the balance between strength and magnetic properties with high productivity without causing troubles such as workability.

[Component Composition]

First, the component composition of the high strength electromagnetic steel sheet according to the present invention will be described.

C deteriorates the magnetic properties, so it is 0.060% or less. On the other hand, it is effective in improving the aggregate structure, and also has the effect of inhibiting the development of undesirable {111} orientation in magnetization and promoting the development of preferred orientation such as {110}, {100}, {114}, etc. . In addition, from the viewpoint of increasing the strength, in particular, increasing the yield stress, improving the warm strength, the creep strength, and improving the fatigue properties in the warmth, and in the case of Nb-containing steel, it also has the effect of delaying recrystallization by NbC. It is 0.0031 to 0.0301%, More preferably, it is 0.0051 to 0.0221%, More preferably, it is 0.0071 to 0.0181%, More preferably, it is 0.0081 to 0.0151%.

In the case where the effect as described above by C is not particularly important, or especially when the demand for magnetic aging is very strict, up to the stage of the slab, a higher C is contained in terms of deoxidation efficiency, and then the coil It is also possible to reduce C by decarburizing annealing. When the content is reduced to about 0.010% or less, it is advantageous to reduce the amount of C by the degassing equipment at the molten steel stage from the viewpoint of production cost. In particular, when the content is 0.0020% or less, the effect of reducing iron loss is remarkable, and in the steel of the present invention which does not require non-metallic precipitates such as carbides for high strength, it is possible to increase the strength even if it is 0.0015% or less, and even if it is 0.0010% or less, sufficient strength is increased. Is possible.

Si increases the specific resistance of the steel, reduces the eddy current, lowers the iron loss, and increases the tensile strength, but the effect is small when the added amount is less than 0.2%. Preferably it is 1.0% or more, More preferably, it is 1.5% or more, More preferably, it is 2.0% or more, More preferably, you may be 2.5% or more. In general, when used under a high frequency magnetic field, the loss caused by the eddy current increases. However, in the steel of the present invention containing the work structure, the loss of the eddy current is particularly suppressed. Therefore, it is effective to increase the Si content. However, if it exceeds 6.5%, the steel is significantly embrittled and the magnetic flux density of the product is lowered, so it is made 6.5% or less, preferably 4.0% or less. As described later, the optimum Si amount range is determined in consideration of the crystal structure immediately before forming the processed tissue finally remaining in the steel sheet, which is an important factor of the present invention. In addition to this crystal structure, in order to reduce the risk of embrittlement, 3.7% or less is preferable, and if it is 3.2% or less, there is a balance with other element amounts, but the embrittlement needs little consideration. Moreover, it is also possible to set it as less than 2.0%, less than 1.5%, and less than 1.0%.

In addition, when using solid solution Cu mentioned later, Si is effective in suppressing austenite phase formation at high temperature, making a ferrite phase stable at high temperature, and remarkably reducing the eddy loss loss by solid solution Cu. If it is less than 1.5%, the effect is small. In particular, in low Si steel, since the effect of reducing the eddy loss due to solid solution Cu tends to be weakened, the Si content is preferably 2.1% or more, and more preferably 2.6% or more.

Although Mn may be actively added in order to increase the strength of the steel, the steel of the present invention, which utilizes a processed structure as a main means of increasing strength, is not particularly required for this purpose. It is added for the purpose of reducing the iron loss by reducing the eddy current loss by increasing the resistivity or by coarsening the sulfide to promote grain growth, but excessive addition not only lowers the magnetic flux density but also generates the austenite phase at a high temperature. Since it promotes, it is made into 0.05 to 3.0%. Preferably it is 0.5%-2.5%, Preferably it is 0.5%-2.0%, More preferably, it is 0.8%-1.2%.

P is a remarkable element of the effect of increasing the tensile strength and contributes to stabilization of the ferrite phase at high temperature, but like Mn described above, it is not necessary to add it in the steel of the present invention. If it exceeds 0.3%, embrittlement is severe and processing such as hot rolling and cold rolling on an industrial scale becomes difficult, so the upper limit is made 0.30%. Preferably it is 0.20% or less, More preferably, it is 0.15% or less.

S is easy to bond with Cu added as needed in the steel of the present invention, and affects the formation behavior of the metal phase mainly composed of Cu, which is important for the purpose of Cu addition, and lowers the reinforcing efficiency. Therefore, care should be taken when containing a large amount. Further, depending on the heat treatment conditions, it is also possible to actively form fine Cu sulfide and to promote high strength. The sulfides formed may degrade magnetic properties, in particular iron loss. Especially when the management value of iron loss is strict, it is preferable that content of S is low, and is limited to 0.040% or less. Preferably it is 0.020% or less, More preferably, it is 0.010% or less. Se has almost the same effect as S.

Al is usually added as a deoxidizer, but it is also possible to suppress addition of Al and to deoxidize with Si. Since AlN is not produced | generated in Si deoxidation steel whose Al amount is about 0.005% or less, there is also an effect which reduces iron loss. On the contrary, it can be added actively to promote coarsening of AlN and reduce iron loss by increasing the resistivity, but if it exceeds 2.50%, embrittlement becomes a problem, so it is 2.50% or less, less than 2.0%, less than 1.8% Also makes it possible.

In addition, when using solid solution Cu as a reinforcing element, rather than these viewpoints of deoxidation and nitride formation, it is actively added as solid solution Al for ferrite phase stabilization at high temperature and suppression of eddy loss by electrical resistance increase. Moreover, it has the effect of promoting the remarkable reduction effect of eddy loss by solid solution Cu, and it is preferable to add actively like Si. Preferably it is 0.3% or more, More preferably, it is 0.6% or more, More preferably, it is 1.1% or more, More preferably, it is 1.6% or more, More preferably, you may be 2.1% or more. However, if it exceeds 2.50%, castability and embrittlement become problems, so it is made 2.50% or less.

N, like C, deteriorates the magnetic properties, so it is 0.040% or less. In Si deoxidized steel having Al of about 0.005% or less, high strength, in particular, increase in yield stress, increase in warm strength, creep strength, and fatigue properties in warm, and in the case of Nb-containing steel, recrystallization is delayed by NbN. In addition to having the effect of making it effective, it is an effective element from the viewpoint of improving the aggregate structure. From this viewpoint, Preferably it is 0.0031 to 0.0301%, More preferably, it is 0.0051 to 0.0221%, More preferably, it is 0.0061 to 0.0200%, More preferably, it is 0.0071 to 0.0181%, More preferably, it is 0.0081 to 0.0151%. When Al is about 0.010% or more, it is possible to increase the recrystallization delay effect by forming fine AlN by containing N in a large amount. However, since the efficiency of recrystallization delay is poor and the adverse effect on magnetic properties is relatively large, it is necessary to add it. There is no. In Al deoxidized steels, N should be 0.0040% or less, and when N is not expected to increase strength due to nitrides or recrystallization delay effect, N is preferably lower, and when it is 0.0027% or less, AlN in magnetic aging or Al-containing steels is used. The inhibitory effect of the deterioration of the characteristic is remarkable, More preferably, it is 0.0022%, More preferably, you may be 0.0015% or less.

Cu is contained in this invention as needed. Since Cu exists as solid solution Cu, there exists an effect which raises the recrystallization temperature of a steel plate and delays recrystallization of a steel plate. In the process reinforcement of the present invention, such an effect appears from about 0.001%, and depending on the amount of impurities, this effect can be obtained by Cu even without particularly actively adding Cu, but preferably Cu is 0.002% Or more, 0.003% or more, 0.005% or more, 0.007% or more, 0.01% or more, 0.02% or more, 0.03% or more, 0.04% or more, 0.05% or more, further 0.1% or more, 0.5% or more, 1.0% or more, 2.0% or more If it is contained, a further effect is obtained. When the Cu content is low, the recrystallization delay effect is reduced, and the heat treatment conditions for obtaining the recrystallization delay effect are limited to a narrow range, and the degree of freedom of management of production conditions and production adjustment may be reduced. On the other hand, when the content of Cu is excessively high, the influence on the magnetic properties is increased, and in particular, the increase in iron loss may be remarkable, so the upper limit from this point of view is preferably 8.0%, particularly preferably 5.5% or less. It is also possible to set it as less than 0.1% and less than 0.01 from a viewpoint of addition cost.

In the conventional steel, the effect of Cu is hardly seen in such a low Cu region, but in the steel of the present invention, even in such a small amount of Cu, a desirable effect is improved in the strength-iron loss balance improvement. This mechanism is not clear, but the following is considered. The high-density dislocations present in steel, such as the steel of the present invention, raise the iron loss in many cases, even if necessary for securing the strength. The increase in strength is related to the interaction between the potential remaining in the steel and the potential newly introduced when the steel sheet is deformed, or the ease of the action of the potential remaining in the steel. The harder the activity, the higher the strength. On the other hand, iron loss is related to the interaction with the magnetic wall moving when the potential remaining in the steel and the magnetic field are added, and the smaller the interaction, the higher the iron loss is suppressed. As a result, the interaction with dislocations is large (or the remaining dislocations themselves are difficult to work), and the interaction with the magnetic domains causes the load-iron loss balance to improve when many small dislocations remain. The magnitude of such interaction is basically considered to be related to the stress field (strain of crystal lattice) around the dislocation, and a small amount of Cu segregates around the remaining dislocation to improve the strength-iron loss balance. It is thought that the desired potential is selectively propagated in the process of forming the optimum stress field, or the remaining potential is formed, or the desired potential is selectively remained in the annealing process. It is not clear at what stage the effect of a small amount of Cu is exerted, but it can be explained by the change in the stress field caused by the difference in the atomic radius of Cu and Fe as one cause.

On the other hand, the present inventors have already applied for a technique of forming a metal phase mainly composed of Cu (hereinafter, referred to as "Cu metal phase" in the present specification) in the electromagnetic steel sheet to increase the strength, but with regard to the Cu metal phase Combination with this application does not impair the effects of the present invention at all. Although it does not specifically limit, The diameter of the Cu metal phase or Nb precipitate which exists in the steel of this invention is preferable about 0.20 micrometer or less. If it exceeds this, the efficiency of recrystallization delay will fall, a large amount of metal phases will be required, and the bad influence to a magnetic characteristic will become large easily. Also, like but not particularly limited, the number density of the Cu metal or Nb precipitate, Cu, Nb, or C content and there is a limit to the range that can be taken by the relationship between the size on precipitation, the degree of more than 20 / ㎛ ³ desirable. This effect is achieved in the above-mentioned Cu concentration range.

Moreover, when using solid solution Cu mentioned later as a reinforcing element, Cu can also be 2.0 to 30.0% as a range for expressing favorable high frequency characteristics. When the Cu content is low, the eddy loss reduction effect is reduced. On the other hand, when the Cu content is too high, it becomes difficult to suppress the formation of the metal phase mainly composed of Cu, and the effect of reducing eddy loss is reduced, and when a relatively coarse Cu metal phase is produced, the hysteresis loss is greatly increased. There is also a risk of cracking and damage to the steel sheet during hot rolling.

Therefore, content of Cu in this case becomes like this. Preferably it is 2.1% or more, More preferably, it is 2.6% or more, More preferably, it is 3.1% or more, More preferably, it is 3.6% or more, More preferably, it is 4.1% or more, More Preferably it is 4.6% or more. The upper limit is preferably 20.0%, more preferably considering the addition cost of Cu itself and the addition cost of Ni added for the purpose of suppressing surface damage [Cu scab] during hot rolling due to Cu. Preferably it is 15.0%, More preferably, it is 12.0%, More preferably, it is 10.0%. In addition, Cu added in high Si steel as in this case does not embrittle the steel and deteriorate the cold rolling property like Si or Al, as long as it is in solid solution, but also has a desirable effect of suppressing embrittlement by Si and the like. Moreover, like Cr mentioned later, magnetic flux density does not deteriorate drastically, and even if it contains relatively large quantity, it is small.

Nb is added as needed in this invention. Depending on the amount of C, N, and S contained, a large amount of fine precipitates such as carbides, nitrides, or sulfides are formed in the steel sheet, significantly deteriorating iron loss, and promoting the development of {111} texture after cold rolling and annealing. Since the magnetic flux density is lowered, it is not necessary to add it in the steel of the present invention. For this reason, Nb is 8% or less, Preferably it is 0.02% or less, More preferably, it is 0.0050% or less, More preferably, it is 0.0030% or less, and it becomes possible to obtain favorable iron loss.

However, mainly carbon / nitride (hereinafter, referred to as "Nb precipitate" in the present specification) of Nb has a function of delaying recrystallization of the steel sheet, and thus can be actively utilized in the present invention. In addition, the fine Nb precipitate also has the effect of increasing the strength in a range that does not adversely affect the magnetic properties. Moreover, it can also be utilized for strengthening as employment Nb. As this range, it is limited to 0.05 to 8.0%. Preferably it is 0.08 to 2.0%.

In addition, most elements that are used for high strength in the high strength electromagnetic steel sheet in the prior art not only need to be added, but also have an adverse effect on the magnetic properties. In the case of active addition, one or two or more of Ti, Zr, V, B, Ni, and Cr are added from the balance between the recrystallization delay effect, the high strength effect, the increase in cost and the deterioration of magnetic properties. Ti: 1.0% or less, Zr: 1.0% or less, V: 1.0% or less, B: 0.010% or less, Ni: 15.0% or less, Cr: 15.0% or less.

Ti, Zr and V form fine precipitates such as carbides, nitrides or sulfides in the steel sheet and are effective elements for increasing the strength, but the effect is relatively small compared to Nb, and the tendency to deteriorate iron loss is strong. In the case of using the partial recrystallized structure in the annealing step after cold rolling, the effect of promoting the integration into the {111} orientation, which is unfavorable for improving the magnetic flux density, is strong, so that the steel of the present invention can be a rather harmful element. For this reason, when strengthening by a precipitate is not intended, it is preferable to set it as 1.0% or less respectively. More preferably, it is 0.50% or less, More preferably, it is 0.30% or less, More preferably, it becomes possible to obtain favorable iron loss by setting it as 0.010% or less and 0.0050% or less.

Further, carbides, nitrides, and sulfide-forming elements such as Nb, Zr, Ti, and V may not be precipitated in the present invention unless they use their precipitation effects as described above, and Nb + Zr + Ti + V Is less than 0.1%, preferably less than 0.08%, more preferably 0.002 to 0.05%.

B segregates at grain boundaries and has an effect of suppressing embrittlement due to grain boundary segregation of P. However, in the steel of the present invention, embrittlement is not particularly a problem as in the high strength electromagnetic steel sheet of a conventional solid solution strengthening agent. The addition is not important. Rather, it is added at least 0.0002% for the purpose of delaying the recrystallization by the effect on the recrystallization temperature by the solid solution B. If it exceeds 0.010%, embrittlement becomes remarkable, so the upper limit is made 0.010%.

Ni also has an effect of raising the recrystallization temperature from about 0.001%, and even if contained in a concentration of 0.01% or less, there is an effect of fixing the potential to some extent, but preferably 0.05%, 0.1%, 0.5%, 1.0 If it is about%, 2.0%, and about 3.0%, the effect is exhibited more. Ni is also known to be effective for the prevention of surface roughness (Cu scave) during hot rolling by Cu, which is an element contained in the steel of the present invention as needed, and can also be added actively as this purpose. Moreover, since the adverse influence to a magnetic characteristic is comparatively small, it has the effect of improving a magnetic flux density, and the effect is recognized also in high strength, it is an element used in high strength electromagnetic steel sheets in many cases. When Ni is used for the purpose of prevention of Cu scab, it adds aiming at about 1/8 to 1/2 of Cu amount.

As described later, in the case of increasing the strength by utilizing solid solution Cu, by compounding Ni in combination, a significant eddy loss reduction effect that is not seen in the past is exhibited. Although the cause is not clear, the influence of the occupied position on the Fe crystal lattice of the solid solution Cu and the solid solution Ni, or the formation of a regular lattice related to any Ni and Cu is expected.

In addition, although Ni is effective also in improving corrosion resistance, it is preferable to make an upper limit into 15%, 10%, Preferably an upper limit into 5.0% in consideration of the bad effect to addition cost and a magnetic characteristic.

The upper limit of Cr is preferably 15.0% in consideration of an element added to improve the corrosion resistance and the improvement of the magnetic properties in the high frequency region, and also the adverse effects on the addition cost and the magnetic properties.

In particular, in the case where solid solution Cu is used as described later, these roles are sufficiently exhibited by Cu (or other elements such as Ni), and therefore it is not necessary to add them for this purpose. In the case of using solid solution Cu, Cr is added to control the stability of the ferrite phase at a high temperature, but the drop in magnetic flux density due to the addition is remarkable, and can be a harmful element. In addition, since the effect of reducing eddy loss due to solid solution Cu is remarkable in the low Cr steel, it is preferable not to add Cr unless there is any need. Although this reason is not clear, it is thought that the solid solution Cu effect is remarkable by the interaction phenomenon with the other element which contains Cr in addition to Si, Al, or Ni mentioned above. From this viewpoint, the addition cost is also considered, and the upper limit of Cr is 15%, preferably 8.0%, more preferably 4.9%, more preferably 2.9%, more preferably 1.9%, more preferably 0.9%, More preferably, it is preferable to set it as 0.4%.

In addition, about other trace elements, in addition to the quantity which is inevitable contained from an ore, scrap, etc., even if it adds for well-known various purposes, the effect of this invention is not impaired at all. In addition, the amount forms at least fine carbides, sulfides, nitrides, oxides, and the like, and some elements exhibit a retardation effect of recrystallization or a high strength. However, these fine precipitates have a large adverse effect on magnetic properties, and remain in the steel of the present invention. Since sufficient recrystallization delay effect is acquired by a process and recovery structure, it is not necessary to add these elements daringly.

The unavoidable content of these trace elements is usually about 0.005% or less for each element, but can also be added at about 0.01% or more for various purposes not described in this specification. Also in this case, one or two or more of Bi, Mo, W, Sn, Sb, Mg, Ca, Ce, and Co is made 0.5% or less in total from the balance of cost and magnetic properties.

The steel containing the said component is melted in a converter similarly to a normal electromagnetic steel plate, becomes a slab by continuous casting, and is manufactured in processes, such as a hot rolling, a hot rolled sheet annealing, cold rolling, and a finish annealing. In addition to these steps, the formation of an insulating film, a decarburization step, and the like do not impair the effects of the present invention at all. Moreover, it does not have a problem even if it manufactures by processes, such as thin slab which abbreviate | omits a hot rolled process by the quench-freezing solidification method, and a hot-rolling process, and continuous casting method.

[Processing Organization]

In this invention, it is necessary to form the special structure called "processed structure" in a steel plate in this invention. The term "processed structure" in the present invention is distinguished from "recrystallized structure" which occupies approximately the entire amount of the steel sheet in a normal electromagnetic steel sheet. Generally, it refers to a structure in which strain accumulated in the steel sheet by cold rolling is not sufficiently lost. More specifically, in the process of annealing a cold rolled steel sheet, the structure deformed by cold rolling and containing high-density dislocations is formed in a structure with low dislocation density ("recrystallized structure") generated by high temperature holding in the annealing process. Recrystallization proceeds by encroachment, but the area which is not encroached on this "recrystallization organization" is called "processing organization". Although the dislocation density is generally lowered by so-called recovery or the like during annealing, the processed structure is not as low as the recrystallized structure, and the distribution of strain is used in the "processed structure" and the "recrystallized structure". There is an uneven situation. The "processed structure" can also be obtained by further processing the recrystallized structure. In this case, a uniform strain remains in the tissue as a whole. In this invention, the target high strength is aimed at by utilizing this processed structure.

[Particle size before processing]

Next, the average grain size d of the steel sheet immediately before the process of forming the processed structure remaining in the steel sheet, which is characteristic of the present invention, will be described. Hereinafter, this particle diameter is described as "the particle size before processing." In the present invention, by coarsening the "particle size before processing" basically, the characteristics after processing, especially the strength-iron loss balance are significantly improved. "Particle size before processing" refers to the particle size at the time of hot-rolled sheet when cold-rolled a hot rolled sheet and restraining recrystallization at the time of subsequent annealing, and leaving a process structure to a final product. At this time, when hot-rolled sheet annealing which is generally performed in an electromagnetic steel sheet is performed, the particle size after hot-rolled sheet annealing becomes "particle size before processing." In addition, after cold rolling, the recrystallized steel sheet is re-rolled to leave the processed structure in the final product to have a particle size at the time of annealing plate. In addition, for example, when re-rolling is performed after cold rolling in the annealing process with the processed structure remaining, the effect of the processing in re-cold rolling may be large, but the processed structure formed from cold rolling is completely Is not lost, and is subjected to re-cold rolling and remains until after re-cold rolling. Therefore, the particle size before cold rolling, that is, the normal process, results in the particle size of the hot-rolled sheet being "pre-processing diameter".

In this invention, this "particle size before processing" d (micrometer) is prescribed | regulated to a specific range in relation of Si amount and Al amount. In other words, by satisfying the following formula 1 or formula 2, and formulas 3 and 4, the excellent strength-iron loss balance, which is a feature of the present invention, is achieved.

[Equation 1]

d ≥ 20 μm

[Formula 2]

d ≥ (220-50 × Si%-50 × Al%)

[Formula 3]

d ≤ (400-50 × Si%), and

[Formula 4]

d ≤ (820-200 × Si%)

Equation 1 simply indicates a case where "particle size before processing" is coarse than a specific size. Although the grain size of an ordinary steel sheet is controlled in the range of several micrometers to several 100 micrometers, it is necessary to set it as 20 micrometers or more in order to acquire the effect of this invention. Preferably it is 50 micrometers or more, More preferably, it is 100 micrometers or more, More preferably, it is 150 micrometers or more, More preferably, it is 200 micrometers or more, More preferably, it is 250 micrometers or more.

Equation 2 defines the "particle size before processing" in which the effect of the invention is obtained in terms of the Si amount and the Al amount. In general, a steel sheet having a high Si content and an Al content improves the strength-iron loss balance. It is because a high Si and high Al material tends to obtain a good strength-iron loss balance even if the "grain size before processing" is small. d ≥ (200-50 × Si%-50 × Al%), d ≥ (180-50 × Si%-50 × Al%), and d ≥ (150-50 × Si%-50 × Al%) . On the other hand, d≥ (220-50 * Si%) may be sufficient.

Equations 3 and 4 give the upper limit of the "particle size before processing". In general, the higher the Si material, the weaker the material is. However, if the "grain size before processing" is excessively coarse, it is also weak and difficult to process such as cold rolled steel. This upper limit depends on the steel component other than the amount of Si and the thermal history until processing, and also depends on the processing method of a steel plate, the target characteristic, etc.

Specific conditions for controlling the "particle size before processing" in the above-described range also depend on the steel component and the heat history up to the processing, and therefore, the specific conditions are not limited to a specific range. It is not difficult to determine suitable conditions by carrying out several heat treatment tests with respect to the steel plate which is a component and heat history corresponding to the above. All that is needed is to confirm the recrystallization and grain growth behavior of the steel plate, and to control the thermal history so as to become the target structure.

As the steel component, the higher the purity, the easier to granulate, and the reduction of C, N, and P is particularly effective. In addition, it becomes easy to achieve granulation of a hot rolled sheet by making it into a ferrite single phase steel componently, and suppressing the transformation in hot rolling.

Further, in order to achieve the granulation in the hot rolled sheet, hot rolled heating temperature rise, hot roll finish temperature rise, hot roll finish post-stage reduction ratio reduction, slow cooling after finish rolling, high temperature winding, high temperature long time hot rolled sheet annealing and the like are considered. In addition, when aiming at the granulation in the annealing plate, the annealing is easy at high temperature for a long time, but in the hot rolling, the precipitate is coarsened by the low temperature slab heating, the high temperature winding and the high temperature hot rolled sheet annealing conditions, and the grain growth at the time of annealing is improved. good. Specifically, for example, it is preferable to perform the annealing step immediately before forming the processed structure as in any of the followings.

(1) When two or more cold rollings sandwiching the intermediate annealing are carried out, the intermediate annealing immediately before the final cold rolling is carried out at a temperature above 850 ° C (preferably at least 860 ° C), or a time exceeding 30 seconds (preferably 35 seconds or more).

(2) For cold rolling, when hot-rolled sheet annealing is performed only once, the hot-rolled sheet annealing is performed at a temperature exceeding 1100 ° C. (preferably 1110 ° C. or more) or a time exceeding 30 seconds (preferably 35 seconds or more). Do it.

(3) In the case of neither (1) nor (2), the coiling temperature of hot rolled steel is performed at a temperature exceeding 700 ° C (preferably 710 ° C or more).

[Recrystallization Rate in Organizations before Processing]

In addition, depending on conditions, a process structure may remain in the steel plate just before the process of finally forming the process structure which remains in the inside of a steel plate. In such a case, in order to acquire the effect of this invention, it is preferable not to remain as much as possible the process structure immediately before the process which forms a process structure, and the recrystallization rate r just before the process which forms a process structure,

[Formula 5]

r ≥ 50%

It is preferable to set it as. More preferably, r is 90% or more, and immediately before the process of forming the processed structure is a completely recrystallized structure, and it is of course preferable to satisfy the above formulas 1 to 4. In addition, in the case where the unrecrystallized region remains partially in the structure immediately before the process of forming the processed structure, the effect of the invention can be obtained by satisfying Equation 5 above, but when the grain size of the recrystallized portion is coarse, the unrecrystallized portion Even if it exceeds 50%, the effect of this invention may appear. At this time, it is also possible to determine the effect of the invention in Formulas 1 and 2 by assuming that the unrecrystallized portion is a fine grain having a particle size of 5 µm, and this case is also included in the present invention.

[Measuring method of particle size before processing]

In addition, a grain size and a recrystallization rate are calculated | required by the structure observation of the plate cross section by etching normally performed by the structure observation of a steel material. The particle diameter is obtained from the area per crystal grain observed, the diameter when the cross-sectional area of the particle is assumed to be a circle, and the recrystallization rate is obtained from the area ratio of the unrecrystallized part in the observation area. Of course, the measurements need to be made over a sufficiently average area without bias.

[Effect of particle size before processing]

Although the mechanism for the effect of the "particle size before processing" is not clear, the influence of the change of the dislocation structure, the change of the aggregate structure, and the change of the potential structure after the process due to the difference of the aggregate structure before processing is considered. Although the details are not clear, finally, the dislocation structure in the processing structure acts as a strong obstacle to the potential to move by external stress, and a structure that is difficult to act as an obstacle to the magnetic wall to move by the external magnetic field. It is expected to change.

[The tensile strength]

The steel plate targeted by this invention shall have a tensile strength of 500 Mpa or more. If the steel sheet has a lower tensile strength than that of the steel sheet, it is possible to produce a steel sheet, which is mainly composed of solid solution elements such as Si and Mn, and is structurally completely occupied by recrystallized structure, without degrading productivity. This is because the material is remarkably superior in magnetic properties. The present invention is mainly limited to high-strength materials that cannot be manufactured without deteriorating productivity, mainly due to the usual solid solution strengthening. In order to make the advantages of the present invention more fragrance, it should preferably be applied to steel sheets of 600 MPa or more, more preferably of 700 MPa or more, more preferably 800 MPa or more, and is currently manufactured at all. A steel sheet of 900 MPa or more that is not available can also be manufactured, and a steel sheet of 1000 MPa or more that can not be conventionally imagined can be manufactured with high productivity.

In addition, when using as a rotor of a motor, since some deformation means the end of the lifetime as a component, it will have to evaluate by yield stress rather than tensile strength. Since the steel of the present invention retains the processed structure, the yield stress is high in the same strength as that of the solid solution strengthening steel and the precipitation strengthening steel, and exhibits more desirable characteristics in comparison with these conventional materials. In other words, the yield ratio is a relatively high value of about 0.7 to 1.0, and the material has a very strong correlation between the yield stress and the tensile strength. For this reason, even if it evaluates by yield stress, the superiority of the steel of this invention does not change completely, The effect of this invention is exhibited without a problem also in the use in which yield stress like a rotor becomes a problem.

[Processing tissue area rate]

This processed structure shall exist 1% or more by the area ratio in the cross-sectional structure observation of a steel plate. In the present invention, the cross-sectional structure observation is performed in a cross section in which one side of the cross section becomes the steel plate rolling direction and the other side becomes the steel plate sheet thickness direction. Although a method of exposing the structure by etching is used using a chemical such as a nitrile made from a common steel sheet, the method is not particularly limited to the observation method, and may be any method that can distinguish the recrystallized structure from the processed structure.

If the area ratio of the processed structure is 1% or less, the effect of increasing the strength becomes small. In the case where the processed structure is substantially 0%, it is a normal steel sheet itself, and controlling in the range of 0 to 1% is very practical because it is necessary to strictly control the temperature of annealing, etc., where the effect of increasing the strength is relatively small. . In practice, the area ratio of the processed structure is controlled to obtain the required strength level, but preferably 5% or more, more preferably 10% or more, more preferably 20% or more, more preferably 30% or more, More preferably, it is 50% or more, More preferably, it is 70% or more. There is no problem at all as 100% of the processed structure where substantially no recrystallized structure is observed. In this case, it is in the state of the so-called full hardening which does not anneal completely, or the situation of the recovery structure before annealing but before recrystallization starts.

Moreover, even if the processed structure is 95%, 90%, 85%, 80%, and less than 75%, the effect of the present invention can be obtained.

[Formation of processed tissue]

In the steel sheet of the present invention, the structure is adjusted according to the required strength and magnetic properties, but the adjustment can be performed by the steel component, the hot rolling history, the cold rolling rate, the annealing temperature, the annealing time, the heating rate, the cooling rate, or the like. In this case, the person skilled in the art can carry out without any problem by several trials. Alternatively, it is also possible to form a processed structure by applying an annealing to strain the steel sheet in which the recrystallized structure occupies the whole amount by re-cold rolling or the like. In this case, normally, strain is given uniformly macroscopically, so that the entire amount of the structure becomes the processed structure and corresponds to 100% of the processed structure. In this case, the strength and magnetic properties are controlled by the processing amount in consideration of the steel component, thermal history, characteristics, and the like before processing, but this can also be performed by a person skilled in the art without problems at all by several trials.

As a target, the temperature does not exceed 700 degreeC in the so-called normal low-grade electromagnetic steel sheet whose Si amount is about 1% or less, and the temperature which does not exceed 800 degreeC also in the so-called normal high-grade electromagnetic steel plate whose Si amount is about 3%, For example, by adding an appropriate amount of Cu, Nb, or the like, an inventive steel which is a complete recovery structure that does not recrystallize at all even at a temperature of about 900 ° C or more can be obtained. On the other hand, annealing at a temperature significantly different from that of an ordinary electromagnetic steel sheet requires a drastic change in the furnace temperature, which leads to a deterioration in workability and a problem in safety as described above due to the generation of unburned gas. There is a case. The lower limit of the annealing temperature for avoiding these problems due to cryogenic annealing is about 400 ° C or more.

The goal of the annealing time also depends on the temperature, but at least 5 seconds is required to effect the annealing. Since the annealing time depends on the component, the manufacturing history until heat treatment, etc., it cannot be specified uniquely, but the target is about 5 minutes at 850 ° C, 1 hour at 750 ° C, and 10 hours at 600 ° C. As described above, these temperature and time conditions are those skilled in the art, it is possible to find a condition that can enjoy the effect of the invention without any problem by a number of trials, and in other words, the recrystallization behavior of the target steel sheet To confirm.

In the case of newly forming the processed structure by re-cold rolling or the like, when the processing amount is low, it may be difficult to clearly indicate the presence of the processed structure in the above-described structure observation method. The size of the crystal grain in the plate | board thickness direction) / (the size of the crystal grain in a rolling direction) may be used, and this value shall be 0.9 or less. If it is 0.8 or less, the effect of high strength will be acquired clearly, Preferably it is 0.7 or less, More preferably, it is 0.6 or less, More preferably, it is 0.5 or less, More preferably, it is 0.3 or less. However, if this value is excessively low, deterioration of the magnetic properties will be remarkable, so care should be taken.

The above processing is usually carried out by cold rolling, but it is not necessary to be concerned with changes in strain or material within the provisions of the present invention. The method of tensile deformation by applying a stiffness, bending deformation by a leveler or the like, shot blasting or forging is irrelevant. On the contrary, since the dislocation structure can be changed to a desirable one in the present invention described later by the method of applying strain, further improvement of the characteristics is possible.

When this process is performed by cold rolling, although it can be easily estimated from the ratio of the size of the crystal grain mentioned above as a target of a reduction ratio, it is about 10 to 70%. When the material softened to the extent of the annealing process is further hardened by re-cold rolling, the material can be simply thinned, and the productivity of the ultra-thin electromagnetic steel sheet, which is a conventionally difficult material, is also improved. Such an ultra-thin electromagnetic steel sheet according to the present invention also has an advantage of being effective for reducing iron loss since the eddy current loss can be particularly suppressed when used under a high frequency magnetic field.

Also in the present situation, as in one method of the present invention, there are an electromagnetic steel sheet, so-called semi-process electromagnetic steel sheet, which is shipped as a product by performing skin pass rolling of about 1 to 20% on a steel sheet subjected to recrystallization annealing. This is achieved by obtaining a skin recrystallized structure by releasing the skin pass plate as a product, annealing under conditions where the motor is processed as a component at a motor manufacturer, and causing strain organic grain growth. Although it is sometimes called the skin pass method as a means of improving a characteristic, in this method, a process structure does not remain at the time of use as a member.

[Heat treatment after forming the processed structure]

This invention is essentially different from this steel plate and method, and after processing it as a component of an electric machine, heat processing is not fundamentally performed. Even when any heat treatment is performed by adhesion of the steel sheet, surface control, or the like, the processing structure defined in the present invention is not lost, and the present invention is limited to staying within the provisions of the present invention. This is because, in the case where the processed structure is lost or deviated from the prescribed range of the present invention, the strength of the steel sheet particularly required in the situation of actually using the motor is insufficient. The target of the temperature of this heat treatment is the same as the temperature condition in the steel plate annealing process mentioned above. The optimum conditions are that under the cooperation of those skilled in the art of manufacturing a steel sheet, or even without a cooperation, it is possible to find a condition that a manufacturer of an ordinary electric device can enjoy the effects of the invention without any problems by several trials.

[Potential density]

The effect of the "working structure" described above can also be evaluated by the dislocation density in the "working structure". The average dislocation density in the processed structure is 1 × 10 ¹³ / m 2 or more, more preferably 3 × 10 ¹³ / m 2 or more, more preferably 1 × 10 ¹⁴ / m 2 or more, more preferably 3 × 10 ¹⁴ / m 2 M 2 or more. This dislocation density is measured by a transmission electron microscope or the like. In an ordinary electromagnetic steel sheet in which the entire steel sheet is a recrystallized structure, the average dislocation density is about 1 × 10 ¹² / m 2 or less, so that it is 10 times or more as a sufficient difference for the classification of the processed structure.

In addition, in order to use it as a various member strictly also in a normal electromagnetic steel plate, processing, such as shearing and caulking, is performed by a manufacturer etc., and by this, the strain introduced in the steel plate remains few and influences a member characteristic. It is known to exert. Such a strain enters only the processed portion of the steel sheet, and unlike the strain that is consciously left on the entire surface of the steel sheet in the present invention, it hardly contributes to the increase in strength as the whole member.

[Why You Can Maintain Your Own Characters]

Although it is not clear to the cause which can maintain a favorable magnetic characteristic even if a process structure remains in a material like this invention, it thinks as follows. Conventionally, the processed structure significantly deteriorates the magnetic properties and is not considered as a means of increasing the strength of the material, and the high strength has been performed by grain refinement, solid solution strengthening, and precipitation strengthening. However, while the demand for high-strength materials is increased, the conventional high-strength means has to step up to a range of conditions that significantly deteriorate the magnetic properties, and in such a situation, when the high-strength means using the processing structure is seen again, it is a very unfavorable method. It is thought that it is one side that we cannot say.

In addition, what has been studied conventionally is that the influence of the processing structure is cold working on the material, and the strain is relatively small, and under such conditions, the dislocation structure in the material is relatively uniform, so-called cell structure and recovery. It is anticipated that they did not form a relatively stable dislocation arrangement such as tissue. At this level of processing, it was not attractive at all as a high-strengthening means. In this dislocation structure, dislocations are only obstacles to the movement of the magnetic walls, and deterioration of magnetic properties is remarkable, and it is considered that they have not been put to practical use.

On the other hand, in the case where cold working of a relatively high deformation amount is carried out as in the present invention, or in the processed structure recovered by annealing, dislocations form a relatively stable cell structure. The size of the cell is usually about 1 μm or less at a diameter of about 0.1 μm, the boundary of the cell is formed at a potential, and has a structure similar to that of ordinary crystal grains except that the crystal orientation difference with adjacent cells is small. It is possible to see it as an ultrafine grain, and it is thought that it is difficult to become an obstacle of the movement of the wall. In addition, such ultrafine grains have high strength, have ductility when processing is required, and are considered to be at a practically practical level in view of the balance between strength and magnetic properties.

In addition, in the steel of the present invention in which the work structure is present, addition of Si, Mn, Al, Cr, Ni, etc. is important for the use used under high frequency magnetic field in which the contribution of the eddy current loss is large in iron loss. Since it has a great influence on dislocation behavior such as recrystallization behavior, the development of dislocation reinforcing steel based on an electromagnetic steel sheet has a completely different meaning from that of so-called ordinary steel for processing used in automobiles and containers.

[Use of Employment Cu]

In addition, in the present invention, apart from conventionally known solid solution strengthening elements such as Si, an electromagnetic steel sheet containing solid solution Cu and having excellent high frequency magnetic characteristics without causing deterioration of magnetic properties or manufacturability associated with conventional alloying element addition. It is also possible to obtain (hereinafter referred to as solid solution Cu strengthening). in this case,

1) Conventionally, a large amount of Cu which cannot be seen is added.

2) It suppresses the formation of austenite phase in the high temperature region.

3) A large amount of Cu is dissolved by high temperature heat treatment in the ferrite region.

4) Cooling is controlled so that Cu which becomes supersaturated during cooling does not precipitate.

By the treatment, the added Cu exists as solid solution Cu in the final product, expresses an effect of suppressing eddy loss as unimaginable as before, and obtains a good high frequency iron loss, and also affects the magnetic flux density deterioration. Can be suppressed relatively small.

Solid solution Cu reinforcement is an effect independent of the above-mentioned process reinforcement, and can be implemented independently, even if it does not involve work reinforcement. In this case, for example, in mass%, C: 0.06% or less, Si: 1.5 to 6.5%, Mn: 0.05 to 3.0%, P: 0.30% or less, S or Se: 0.040% or less, Al: 2.50% or less , Cu: 2.0 to 30.0%, N: 0.0400% or less, an electromagnetic steel sheet containing a residual portion Fe and an unavoidable impurity and not containing a metal phase made of Cu in the steel material, and in some cases , Nb: 8% or less, Ti: 1.0% or less, B: 0.010% or less, Ni: 15.0% or less, Cr: 15.0% or less may further contain one or two or more kinds.

On the other hand, by using for work reinforcement, synergistic reinforcement effect is obtained in addition to the effect of raising the recrystallization temperature by solid solution Cu.

The effect of reducing the eddy loss and embrittlement effect when the amount of solid solution Cu is increased is not merely based on the amount of the solid solution element, and the interactive effect can be seen as described above. Set it. In the case of using the solid solution Cu reinforcement, it is preferable to finally perform a heat treatment for recrystallization and grain growth. Therefore, it is necessary to use the component considering the change in the amount of solid solution Cu due to the formation of precipitates containing Cu during the heat treatment. There is. In particular, in the transformation of the bristle phase during the heat treatment, not only the solubility of Cu changes greatly, but also the desirable texture in the magnetic flux density is lost. Therefore, when the solid solution Cu reinforcement is used, the transformation during the heat treatment should be basically avoided. It is. Specifically, it is a ferrite single phase or a mass% in the temperature range of 1150 degreeC from room temperature,

980-400 × C + 50 × Si-30 × Mn + 400 × P + 100 × Al-20 × Cu-15 × Ni-10 × Cr> 900

It is desirable to satisfy. Outside this range, undesirable transformation occurs during the heat treatment, and the possibility of significantly inhibiting the effect of solid solution Cu strengthening increases.

The characteristic of solid solution Cu reinforcement can be clearly shown also by a comparison with the characteristic with a general material. In comparison with a steel sheet having substantially the same steel component other than Cu and having a Cu: 0.1% and equal grain size, the steel sheet strengthened with _{solid solution} had an iron loss (W _10/400 ) of 0.8 times or less, 0.7 times or less, and 0.6 times. 0.5 times or less, 0.4 times or less, More preferably, 0.30 times or less are obtained.

Moreover, in the steel plate strengthened by solid solution Cu, tensile strength is 2.0 times or less compared with the comparative steel. In general, as the amount of solid solution increases, the strength increases due to solid solution strengthening, and in the case of a large amount of solid solution such as solid solution Cu strengthening, the strength increases depending on the element. Solid solution Cu in does not harden the material very much. More preferably, it is 1.7 times or less, More preferably, it is suppressed to 1.5 times or less. As the amount of solid solution Cu increases, the strength of the solid solution Cu reinforcement steel is high. Therefore, the smaller the strength increase, the less the increase in strength. It is characterized by being suppressed.

Moreover, when excess Cu in solid solution Cu reinforced steel is contained, remarkable precipitation of a metallic Cu phase may be observed. In addition, a significant increase in strength is observed with the precipitation of the metal Cu phase. In this case, moreover, it is accompanied by an increase in iron loss, especially eddy loss. Specifically, by heat treatment at 450 ° C. for 30 minutes, the water density of the metal phase mainly composed of Cu having a diameter of 0.02 μm or less in steel is increased to 20 / μm ³ or more, or the tensile strength is increased to 100 MPa or more. As described above, such heat treatment significantly increases eddy loss and deteriorates high-frequency magnetic properties for the purpose of strengthening solid solution Cu. Therefore, the heat treatment is not performed to control the material of the steel sheet. You can do it for

In order to contain a large amount of solid solution Cu which is characteristic in solid solution Cu reinforcement, it is effective to go through the following thermal history. It is maintained for 5 seconds or more in the temperature range of 800 degreeC or more in the final heat processing of the process of manufacturing a product board, usually recrystallization after cold rolling, and an austenite phase is produced | generated in steel also in the highest achieved temperature in this heat processing. It is not set. Preferably at least 900 ° C, more preferably at least 1000 ° C, more preferably at least 1050 ° C, and also preferably at least 10 seconds, more preferably at least 30 seconds, more preferably at least 60 seconds And temperature and time at which sufficient dissolution of Cu occurs in balance with the Cu content are sufficient to obtain the characteristic effects of the present invention. However, it is needless to say that it is necessary to control in addition to the viewpoint of controlling the grain size which greatly affects the magnetic properties.

It is well known that a grain size may deteriorate a magnetic characteristic even if it is too fine or too coarse, and an optimal particle size exists for use conditions. In addition, it is necessary to set the highest achieved temperature in a temperature range where no austenite phase is generated. If a small amount is produced, the adverse effect on the characteristics is small, but annealing is preferably performed on the complete ferrite. Since this temperature mainly depends on the steel component, it is not possible to describe the specific temperature. However, if the person skilled in the art has the above-mentioned Equation 1, and has knowledge of general metallurgy, By thermodynamic calculations with remarkable experiments or recent developments, it is possible to set an appropriate temperature range without any difficulty.

In addition, the cooling rate in the heat treatment step also becomes an important control factor. The reason for this is that Cu sufficiently dissolved in high temperature holding becomes supersaturated during cooling, and depending on the cooling rate, Cu may precipitate as a metal Cu phase, thereby reducing the effect of the present invention. In this invention, the cooling process after hold | maintaining preferable conditions in the temperature range of 800 degreeC or more for 5 second or more shall cool to 300 degrees C or less at the cooling rate of 40 degreeC / sec or more. In view of the purpose of the present invention, it is not exceeded that it is a high cooling rate, but if it is excessively quenched, it is necessary to pay attention because the characteristics may deteriorate due to thermal distortion. Preferably it is 60 degrees C / sec or more, More preferably, it is 80 degrees C / sec or more, More preferably, it is 100 degrees C / sec or more.

In particular, it should be noted that in the present invention, cooling in the temperature range where precipitation of the metal Cu phase takes place, and the residence time of 700 to 400 ° C becomes important. This is because precipitation is unlikely to occur because the supersaturation degree of Cu is low at 700 ° C or higher, and precipitation is less likely to occur because diffusion of Cu is suppressed at 400 ° C or lower. If the time is 5 seconds or less, preferably 3 seconds or less, and more preferably 2 seconds or less, precipitation of the metal Cu phase can be suppressed and the amount of solid solution Cu sufficient to obtain the effect of the invention can be ensured.

And after this heat treatment, it is preferable not to hold | maintain for 30 second or more in the temperature range exceeding 400 degreeC. This is because the deposition of the metal Cu phase is promoted by such a heat treatment to increase eddy loss.

By going through the above components and processes, the eddy loss reduction effect by the characteristic large amount of solid solution Cu can be expressed efficiently, and a high Cu electromagnetic steel sheet can be manufactured with little damage to castability and rolling property. On the other hand, when manufactured under the usual components and heat treatment conditions that are not aware of the maintenance of such a solid solution of Cu amount, not only a small portion of added Cu exists as a metal Cu phase or Cu sulfide having a small eddy loss reduction effect, but also embrittlement. Production of remarkably normal becomes difficult.

In addition, when using together with the process strengthening of this invention, said heat treatment may be annealed in 350-700 degreeC for 10 second-360 minutes so that a Cu metal phase may be precipitated finely in the state which recrystallization was suppressed. Of course, in long time annealing at high temperature, Cu metal phase will coarsen and a reinforcement capability will fall. At high temperatures, care must be taken so that the annealing time is not too long, and the lower the temperature, the longer the annealing becomes possible.

In the present invention, the metal Cu phase does not exist in the steel material, but this can be identified and confirmed by diffraction patterns such as an electron microscope, an attached X-ray analyzer, or the like. Of course, it can confirm also by methods other than this, such as a chemical analysis. In the present invention, a metal phase mainly composed of Cu is intended to be 0.010 µm or more in diameter. The reason for this is that if it is too fine at less than 0.005 µm, even if it is an analysis device with the highest precision in the current state, it becomes difficult to specify that it is a metal Cu phase to which the present invention is intended. In addition, even if any treatment is performed, in the steel of the present invention containing a large amount of Cu, since a precipitate containing any Cu is present locally, it is impossible to completely exclude the metal Cu phase. The present invention is limited to an electromagnetic steel sheet containing a considerable amount of Cu and also formed with a large amount of hardened or metallic Cu phase by the considerable heat treatment described in the present invention, and an essential feature of the present invention is that a large amount of solid solution Cu Of course.

[apply]

In addition, since the effect of this invention does not depend on the presence and the kind of the surface coating formed on the surface of an electromagnetic steel sheet normally, and also does not depend on a manufacturing process, it can be applied to a non-oriented or directional electromagnetic steel sheet. In particular, the steel of the present invention can give a feature that is significantly different from the steel sheet obtained by the conventional recrystallized structure in the in-plane anisotropy of properties. In terms of the magnetic flux density, in the cold hard state, the 45 ° direction (D direction) is higher than the rolling direction (L direction) or the coil width direction (C direction) from the rolling direction of the coil. . In the electromagnetic steel sheet having a normal recrystallized structure, in most cases, considering that the characteristics in the D direction are lower than those in the L or C direction, by appropriately adjusting the degree of recrystallization and recovery, the intermediate recrystallization step is controlled. It becomes easy to obtain the steel plate with little in-plane anisotropy. Almost no in-plane anisotropy is a steel plate which has the characteristics which can exhibit very desirable characteristics, such as a rotating machine.

The use is not particularly limited, and it is applied to all uses that require strength and magnetic properties in addition to the use of the rotor of motors used in home appliances or automobiles.

(First embodiment)

Slab heating temperature 1100 ° C, winding temperature 700 ° C from a 200 mm thick steel piece having a component of 0.002% C-3.0% Si -0.5% Mn -0.03% P -0.001% S -0.3% Al -0.002% N Was hot-rolled, the hot-rolled sheet annealing was changed to 800, 950 and 1050 ° C, and the particle diameters were changed to 10, 100 and 200 µm. After each hot rolled sheet was cold rolled, annealing was performed without annealing and 400 to 1000 ° C. for 30 seconds to prepare a product sheet having a plate thickness of 0.5 mm having different recrystallization rate and strength. About these, the mechanical property by _JIS5 test piece and the iron loss ( _{W10 / 400} ) by the SST test of the square whose side is 55 mm were evaluated. Both the mechanical properties and the magnetic properties were obtained from the following formulas for the rolling direction of the coil, the 45 ° direction and the right angle direction thereof.

X = (X ₀ + 2 × X ₄₅ + X ₉₀ ) / 4

Here, X <_0> , X <_45> , X <_90> is a characteristic of the rolling direction of a coil, 45 degree direction, and the right angle direction.

The results are shown in FIG. As is apparent from the results, a material having a coarse grain size of a hot rolled sheet, that is, a material produced under the conditions of the present invention has a good strength-iron loss balance.

(Second Embodiment)

From the 200-mm-thick steel piece which has the component of Table 1, the product board was manufactured on the manufacturing conditions shown in Table 2. Some materials were subjected to heat treatment (user annealing) assuming heat treatment at a motor manufacturer. For these, the characteristics were evaluated by mechanical properties, and a side 55 ㎜ the iron loss by the SST test, square (W _10/400) and the magnetic flux density (B ₂₅₎ according to JIS5 test specimen. Both the mechanical properties and the magnetic properties were obtained from the following formulas for the rolling direction of the coil, the 45 ° direction and the right angle direction thereof.

X = (X ₀ + 2 × X ₄₅ + X ₉₀ ) / 4

Here, X <_0> , X <_45> , X <_90> is a characteristic of the rolling direction of a coil, 45 degree direction, and the right direction.

The results are shown in Table 2. As is apparent from the results, the material produced under the conditions of the present invention is hard and excellent in magnetic properties. It is important to note that, in general, the characteristics of the Si amount vary greatly so that the electromagnetic steel sheet is sold classified by the amount of Si contained. In addition, the iron loss varies greatly depending on the plate thickness. Compared with low Si materials, high Si materials significantly reduce iron loss due to the difference in Si content, and even thinner plate thicknesses reduce iron loss. Therefore, when evaluating the effect of the present invention, the difference between Si amount and plate thickness is considered. It is necessary to compare the amount of Si and the sheet thickness with equivalent ones.

(Third Embodiment)

The steel plate which shows a component in Table 3 was made into the slab of 250 mm thickness, and the product board was manufactured on the conditions of Table 3 and Table 4. Magnetic flux density (B10) and iron loss ( _{W10 / 400} ) were measured by a square SST test having one side of 55 mm. The magnetic characteristic calculated | required the average value with respect to the rolling direction of a coil, 45 degree direction, and the right angle direction from the following formula | equation.

X = (X ₀ + 2 × X ₄₅ + X ₉₀ ) / 4

Here, X <_0> , X <_45> , X <_90> is a characteristic of the rolling direction of a coil, 45 degree direction, and the right angle direction.

As is apparent from the results shown in Table 4, the samples produced under the conditions of the present invention have good rollability in the cold rolling process and excellent magnetic properties. In addition, it has been confirmed that good iron loss in the steel of the present invention mainly depends on reduction of eddy loss.

According to the present invention, it is possible to stably manufacture a high strength electromagnetic steel sheet which is hard and has excellent magnetic properties. In other words, the present invention can obtain the desired strength even if the additive elements used for solid solution strengthening and precipitation strengthening are relatively low. Thus, the cold rolling property is improved, the productivity of the cold rolling process is improved, and within the usual operating range. Since the annealing can be performed, the workability of the annealing process is also improved. Moreover, by re-rolling after annealing, it becomes possible to simply produce the ultrathin material which was conventionally difficult to manufacture.

In addition, by using solid solution Cu, it is possible to stably produce an electromagnetic steel sheet having high high-frequency magnetic properties with low eddy loss without suppressing embrittlement and without causing cold rollability or the like.

As described above, since strength, fatigue strength, and wear resistance can be ensured, high-efficiency, miniaturization, ultra-long life, and the like of an ultra-high speed rotating motor or a motor incorporating a magnet in the rotor and an electromagnetic switch material are achieved.

Claims (15)

In mass%, C: more than 0.0%, 0.060% or less, Si: 0.2 to 6.5%, Mn: 0.05 to 3.0%, P: more than 0.0%, 0.30% or less, S or Se: more than 0.0%, 0.040% or less, In the manufacturing method of the high strength electromagnetic steel sheet which contains Al: more than 0.0%, 2.50% or less, N: more than 0.0%, 0.040% or less, remainder part Fe and an unavoidable impurity, and a process structure remain inside a steel plate After cold rolling after hot rolling, the average grain size d of the steel sheet at the time of the annealing plate at the time of annealing and re-rolling the recrystallized steel sheet to leave the processed structure in the final product is 150 µm or more, or after cold rolling after hot rolling. And an average grain size d of the steel sheet at the time of hot rolling when re-rolling in a state in which the processed structure remains in the annealing step is 150 µm or more. In mass%, C: greater than 0.0%, 0.060% or less, Si: 0.2 to 6.5%, Mn: 0.05 to 3.0%, P: greater than 0.0%, 0.30% or less, S or Se: greater than 0.0%, 0.040% or less, In the manufacturing method of the high strength electromagnetic steel sheet which contains Al: more than 0.0%, 2.50% or less, N: more than 0.0%, 0.040% or less, remainder part Fe and an unavoidable impurity, and a process structure remain inside a steel plate After the cold rolling after hot rolling, the average grain size d (µm) of the steel sheet at the time of the annealing plate at the time of annealing and re-rolling the recrystallized steel sheet to leave the processed structure in the final product is d? (220-50) X Si%-50 x Al%), or after the cold rolling after hot rolling, the average grain size d (µm) of the steel sheet at the time of hot-rolled sheet when re-rolling while remaining the processed structure in the annealing step, d ≥ (220-50 × Si%-50 × Al%) The method of the steel sheet. The method according to claim 1 or 2, wherein the average grain size d (㎛), d ≤ (820-200 × Si%) The manufacturing method of the high strength electromagnetic steel plate characterized by the above-mentioned. The method for producing a high strength electromagnetic steel sheet according to claim 1 or 2, wherein the recrystallization rate of the steel sheet at the time of the annealing plate or the hot rolled sheet is 50% or more. The method for producing a high strength electromagnetic steel sheet according to claim 1 or 2, wherein the steel component further contains at least one kind of Cu: 0.001 to 30.0% and Nb: 0.03 to 8.0%. The steel component according to claim 1 or 2, wherein the steel component is, by mass%, more than Ti: 0.0%, 1.0% or less, V: more than 0.0%, 1.0% or less, Zr: more than 0.0%, 1.0% or less, B: A method for producing a high strength electromagnetic steel sheet, further comprising one or more than 0.0%, 0.010% or less, Ni: more than 0.0%, 15.0% or less, Cr: more than 0.0%, 15.0% or less. The steel component according to claim 1 or 2, wherein the steel component is, in mass%, 0.5% or less in total of one or two or more of Bi, Mo, W, Sn, Sb, Mg, Ca, Ce, La, and Co. The manufacturing method of the high strength electromagnetic steel plate further containing. The said processed structure is 1% or more by the area ratio in sectional observation, The manufacturing method of the high strength electromagnetic steel sheet of Claim 1 or 2 characterized by the above-mentioned. The manufacturing method of the high strength electromagnetic steel sheet of Claim 1 or 2 whose average dislocation density in the said process structure is 1 * 10 <^13> / m <2> or more. The high-strength electromagnetic steel sheet according to claim 1 or 2, wherein the high-strength electromagnetic steel sheet is a ferrite single phase or a mass% in a temperature range of 1150 ° C from room temperature, 980-400 × C + 50 × Si-30 × Mn + 400 × P + 100 × Al-20 × Cu-15 × Ni-10 × Cr> 900 And the steel component contains, by mass%, Cu: 0.002 to 8.0%, Ni: more than 0.0%, 15.0% or less, and Cr: more than 0.0%, 15.0% or less. . The method of manufacturing a high strength electromagnetic steel sheet according to claim 1 or 2, wherein the high strength electromagnetic steel sheet is increased in tensile strength by 100 MPa or more by heat treatment at 450 ° C for 30 minutes. In the process of manufacturing the steel sheet according to claim 10, the final heat treatment after cold rolling is maintained for 5 seconds or more in a temperature range of 800 ° C. or higher, and an austenite phase is not generated in the steel even at the maximum achieved temperature in this heat treatment. A method for producing a high strength electromagnetic steel sheet, characterized in that the heat treatment is performed. In the process of manufacturing the steel sheet according to claim 10, the cooling step after holding for 5 seconds or more in a temperature range of 800 ° C or more is cooled to 300 ° C or less at a cooling rate of 40 ° C / sec or more. Method of preparation. The method for producing a high strength electromagnetic steel sheet according to claim 13, wherein in the cooling step, the residence time of 700 to 400 ° C is 5 seconds or less. The method according to claim 1 or 2, wherein the average grain size d (㎛), d ≤ (400-50 × Si%) The manufacturing method of the high strength electromagnetic steel plate characterized by the above-mentioned.

Images