JP2005126748A - High fatigue strength non-oriented magnetic steel sheet superior in magnetic properties, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-oriented magnetic steel sheet having adequate magnetic properties together with high strength and high fatigue strength. <P>SOLUTION: This non-oriented magnetic steel sheet has an elemental composition comprising 0.02% or less C, 4.5% or less Si, 3.0% or less Mn, less than 0.2% Al, 0.5% or less P, 0.2% to 4.0% Cu, 0.5% to 5.0% Ni, further one or two elements of Sb and Sn in an amount of 0.005-0.2% in total, and the balance Fe with unavoidable impurities; has a tensile strength TS of 500 MPa or higher; and a ratio FS/TS of 10<SP>7</SP>fatigue limit strength FS to the tensile strength TS of 0.85 or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a non-oriented electrical steel sheet, particularly a high-strength and low-iron suitable for use in parts subjected to large stress, such as rotors such as high-speed rotation motors, magnet-embedded motors and synchronous reluctance motors. The present invention relates to a non-oriented electrical steel sheet having a loss characteristic and a manufacturing method thereof.

  In recent years, with the development of motor drive systems, it is possible to control the frequency of the drive power supply, and the number of motors that perform variable speed operation and high-speed rotation above the commercial frequency is increasing. In such a motor that performs high-speed rotation, a rotor that can withstand high-speed rotation is required. That is, since the centrifugal force acting on the rotating body is proportional to the radius of rotation and increases in proportion to the square of the rotational speed, the stress acting on the rotor may exceed 600 MPa in medium and large high-speed motors. Therefore, in such a high-speed rotary motor, it is necessary that the strength of the rotor is high.

  In addition, the magnet-embedded DC inverter control motor, in which permanent magnets are embedded in the rotor, has been increased from the viewpoint of improving motor efficiency in recent years, because the magnet tends to jump out of the rotor by centrifugal force. Takes a great deal of power in suppressing this pop-up. In particular, in areas where the gap (width) between the magnet insertion holes (bridges) is narrowed in order to improve motor characteristics, further stress concentration occurs. High strength is needed.

  Furthermore, the synchronous reluctance motor, which has been developed to reduce the cost by omitting expensive magnets or reducing the amount of magnets used, has many slits in the rotor. Strength is important.

In addition, when these motors are used in applications such as drive motors for hybrid vehicles, they are accompanied by stress changes caused by changes in the number of rotations according to acceleration / deceleration operation, body vibrations, and vibrations of magnets in the magnet insertion holes. Therefore, it is not only high strength that can be applied to high-speed rotation and stress concentration part, but also fatigue characteristics under repeated stress below yield stress, that is, high fatigue strength. Is required.
Here, the fatigue strength can be expressed as a limit strength (fatigue limit strength) that does not break when a constant stress is repeatedly applied 10 ⁷ times.

  On the other hand, rotating devices such as motors and generators use an electromagnetic phenomenon, and therefore, it is desirable that the material has magnetic characteristics, that is, low iron loss and high magnetic flux density. Normally, the rotor core is used by laminating non-oriented electrical steel sheets that are stamped and punched. However, if the rotor material does not satisfy the above-mentioned mechanical strength in a high-speed rotary motor, it is necessary to use a higher strength cast steel material. It is the present condition that we cannot get. However, since the casting made of cast iron is an integral object, the eddy current loss due to the high-frequency magnetic flux called ripple loss acting on the rotor is larger than that of the rotor laminated with the electromagnetic steel sheets, which causes a reduction in motor efficiency. Therefore, a magnetic steel sheet having excellent magnetic properties and high strength is demanded as a rotor material.

In metallurgy, three methods of solid solution strengthening, precipitation strengthening, and crystal grain refinement are known as means for increasing strength, and examples applied to electrical steel sheets are also seen. For example, as a method utilizing solid solution strengthening, Patent Document 1 discloses a method of adding an element having a large solid solution strengthening capability while increasing the Si content to 3.5 to 7.0%. Further, in Patent Document 2, the recrystallized grain size is controlled by setting the Si content to 2.0 to 3.5%, increasing the content of Ni or both Ni and Mn, and manufacturing by low temperature annealing at 650 to 850 ° C. A method is disclosed. Furthermore, as a method of utilizing precipitation strengthening, Patent Document 3 discloses a method in which the Si content is set to 2.0 to 4.0% and fine carbides and nitrides of Nb, Zr, Ti, and V are precipitated.
JP-A-60-238421 JP 62-256917 A JP-A-6-330255

By these methods, an electrical steel sheet having a certain degree of strength can be obtained. However, the steel having a large amount of Si as described in Patent Document 1 has a disadvantage that the cold rolling property is remarkably lowered and stable industrial production becomes difficult. Furthermore, the steel plate obtained by this technique has a problem that the magnetic flux density B ₅₀ is significantly reduced to 1.56 to 1.60 T.

  In the method in Patent Document 2, since it is necessary to suppress recrystallized grain growth by low-temperature annealing in order to increase mechanical strength, there is a problem that iron loss at several hundred Hz from a commercial frequency having a relatively low frequency is lowered. was there. For this reason, it cannot be used for a stator member in which iron loss in these frequency ranges is important, and the yield during motor punching has been significantly reduced. That is, when punching out the stator and rotor, normally, the annular stator is first punched out from the same sheet of steel, while the rotor is punched out from the hollow portion to reduce waste. In this method, both of them need to be punched from separate steel plates, resulting in a decrease in yield.

  On the other hand, the method described in Patent Document 3 has a problem that iron loss is inferior because charcoal and nitride itself serve as a barrier for domain wall movement and charcoal and nitride hinder crystal grain growth of the electromagnetic steel sheet.

  As described above, none of the conventional methods is satisfactory from the viewpoint of achieving both high strength and low iron loss in an electromagnetic steel sheet that can be stably industrially produced. Further, in each of the conventional methods, no study has been made regarding fatigue characteristics, which are essentially important factors when considering the use state of the motor.

  An object of the present invention is to propose a non-oriented electrical steel sheet that has both good magnetic properties and high strength and high fatigue strength, and a manufacturing method that enables industrially stable production of this steel sheet. To do.

  In order to solve the above-mentioned problems, the inventors have made various studies focusing on the age hardening phenomenon of Cu-containing steel, and as a result, established means for achieving both good iron loss and high strength. I arrived. That is, the precipitate in steel contributes to high strength, and at the same time, suppresses domain wall movement and deteriorates, contrary to the conventional knowledge, by adding an appropriate amount of Cu to the steel and performing an aging treatment, 20 nm It is possible to precipitate Cu in the following ultrafine, and the ultrafine precipitate obtained in this way is very effective for increasing the strength, but iron loss (historical loss) is hardly deteriorated. Was newly discovered and shown in the specification of Japanese Patent Application No. 2002-353250.

  Furthermore, the inventors diligently studied a technique for improving fatigue characteristics in addition to the increase in strength by this Cu precipitation. That is, as a result of studying the influence of various alloy elements and ultrafine precipitation of Cu on fatigue characteristics, Cu and Ni or Cu and Mo were added together, and Al was further reduced, and then Sb and / or Sn It was found that very good high fatigue characteristics can be obtained by adding, and the present invention has been completed.

The gist configuration of the present invention is as follows.
(1) In mass%,
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Ni: Including 0.5% to 5.0%
One or two of Sb and Sn in total 0.005-0.2%
Contains, has a component composition of the balance Fe and unavoidable impurities, the tensile strength TS of not less than 500 MPa, and ¹⁰⁷ the ratio FS / TS of the fatigue limit strength FS and tensile strength TS is at least 0.85 A high fatigue strength non-oriented electrical steel sheet with excellent magnetic properties.

(2) In mass%,
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Mo: Including 1.0% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
Contains, has a component composition of the balance Fe and unavoidable impurities, the tensile strength TS of not less than 500 MPa, and ¹⁰⁷ the ratio FS / TS of the fatigue limit strength FS and tensile strength TS is at least 0.85 A high fatigue strength non-oriented electrical steel sheet with excellent magnetic properties.

(3) In mass%,
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0%,
Ni: 0.2% to 5.0% and
Mo: Including 0.2% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
Contains, has a component composition of the balance Fe and unavoidable impurities, the tensile strength TS of not less than 500 MPa, and ¹⁰⁷ the ratio FS / TS of the fatigue limit strength FS and tensile strength TS is at least 0.85 A high fatigue strength non-oriented electrical steel sheet with excellent magnetic properties.

(4) In mass%,
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Ni: Including 0.5% to 5.0%
One or two of Sb and Sn in total 0.005-0.2%
The steel slab containing slab is hot-rolled, then cold-rolled or warm-rolled to the final sheet thickness, and the final temperature reached 650-1100 ° C and 900-400 ° C. A high-fatigue strength non-directional electromagnetic with excellent magnetic properties, characterized in that the cooling rate is 1 ° C / s or higher, and after finishing annealing, aging treatment is performed at a temperature of 400 ° C to 650 ° C. Manufacturing method of steel sheet.

(5) In mass%,
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Mo: Including 1.0% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
The steel slab containing slab is hot-rolled, then cold-rolled or warm-rolled to the final sheet thickness, and the final temperature reached 650-1100 ° C and 900-400 ° C. A high-fatigue strength non-directional electromagnetic with excellent magnetic properties, characterized in that the cooling rate is 1 ° C / s or higher, and after finishing annealing, aging treatment is performed at a temperature of 400 ° C to 650 ° C. Manufacturing method of steel sheet.

(6) In mass%,
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0%,
Ni: 0.2% to 5.0% and
Mo: Including 0.2% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
The steel slab containing slab is hot-rolled, then cold-rolled or warm-rolled to the final sheet thickness, and the final temperature reached 650-1100 ° C and 900-400 ° C. A high-fatigue strength non-directional electromagnetic with excellent magnetic properties, characterized in that the cooling rate is 1 ° C / s or higher, and after finishing annealing, aging treatment is performed at a temperature of 400 ° C to 650 ° C. Manufacturing method of steel sheet.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide stably the magnetic steel plate which was excellent in a magnetic characteristic, has high intensity | strength, and was excellent in the fatigue characteristic.

Next, the present invention will be described in detail for each constituent requirement.
(Component composition of steel sheet)
First, the component composition range and the reason for limitation will be described. In the present specification, “%” representing a steel composition means “% by mass” unless otherwise specified.
C: 0.02% or less If the C content exceeds 0.02%, the iron loss deteriorates significantly due to magnetic aging, so it is limited to 0.02% or less.

Si: 4.5% or less
In addition to being useful as a deoxidizer, Si has a great effect of reducing the iron loss of the electrical steel sheet by increasing the electrical resistance. Furthermore, it contributes to strength improvement by solid solution strengthening. As a deoxidizer, the effect becomes remarkable when the content is 0.05% or more. Further, for reducing iron loss and strengthening solid solution, it is contained at 0.5% or more, more preferably 1.2% or more. However, if it exceeds 4.5%, the rollability of the steel sheet deteriorates severely, so its content is limited to 4.5% or less.

Mn: 3.0% or less
Mn is an element effective for improving hot brittleness in addition to being an element effective for improving strength by solid solution strengthening, and is preferably contained at 0.05% or more. However, excessive addition causes deterioration of iron loss, so its content is limited to 3.0% or less.

Al: Less than 0.2%
Al is an important element that needs to be particularly restricted in the present invention. Al is an element generally added to Si steel sheets together with Si because Al is effective as a deoxidizer and also has a large effect of reducing iron loss by increasing the electrical resistance of steel. However, it has been found that when 0.2% or more is contained, the fatigue strength decreases. This is presumably because, when 0.2% or more of Al is contained, the surface scale and the internal scale generated when the steel sheet is subjected to finish annealing become the starting point of fatigue failure. Therefore, the Al content is less than 0.2%, preferably 0.15% or less.

P: 0.5% or less P is an element that is extremely effective for increasing the strength because a substantial solid solution strengthening ability can be obtained even when added in a relatively small amount, and is preferably contained at 0.01% or more.
On the other hand, excessive content causes embrittlement due to segregation and causes intergranular cracking and deterioration of rolling properties, so the content is limited to 0.5% or less.

Next, the addition of Cu and Ni and / or Mo is the most important matter in the present invention.
Cu: 0.2% to 4.0%
By forming fine precipitates by aging treatment, Cu brings about a significant increase in strength with almost no deterioration of iron loss (history loss). In order to obtain the effect, 0.2% or more is necessary under the condition of containing Ni described later. On the other hand, if it exceeds 4.0%, coarse precipitates are formed, so that the deterioration of the iron loss increases and the strength increase margin also decreases. Therefore, the Cu content is in the range of 0.2% to 4.0%, preferably 0.3% to 2.0%.

Ni: 0.5% or more (or 0.2% or more) 5.0% or less
Ni itself is an element effective for increasing the strength by solid solution strengthening, but when added with Cu, it affects the solid solution precipitation state of Cu, and the effect of stably depositing extremely fine Cu precipitates by aging Have As a result, it is possible to greatly enhance the effect of increasing the strength due to Cu aging precipitation while reliably suppressing the deterioration of the magnetic properties accompanying this precipitation.

Ni also has the effect of significantly increasing the fatigue properties of the steel sheet. The reason for this is not necessarily clear, but it is presumed that Ni dissolved in the steel greatly enhances the stability of Cu precipitates in the presence of repeated stress. The addition amount for obtaining this effect varies depending on the presence or absence of Mo addition described later, and when not adding Mo, 0.5% or more of Ni is necessary. On the other hand, in the case where 0.2% or more Mo is added in combination, the effect is exhibited by adding Ni at 0.2% or more.
Furthermore, in steels to which a large amount of Cu is added, defects on the surface of the hot-rolled sheet called “hege” may become a problem, but Ni also has the effect of reducing the sag of the hot-rolled sheet and improving the yield of the steel sheet. In order to obtain these effects, addition of 0.5% or more is preferable. On the other hand, if it exceeds 5.0%, the effect will be saturated and only increase the cost, so the upper limit is set to 5.0%. More preferably, the range is 1.0% or more and 3.5% or less.

Mo: 1.0% or more (or 0.2% or more) 3.0% or less
When Mo is added together with Cu as well as Ni, it affects the solid solution precipitation state of Cu, and in addition to the effect of stable precipitation of extremely fine Cu precipitates by aging, Cu precipitates in the presence of repeated stresses Has the effect of increasing the stability of As a result, it is possible to greatly increase the strength by Cu aging precipitation, to suppress the deterioration of magnetic properties accompanying this precipitation, and to greatly improve the fatigue properties. The amount of Mo necessary for obtaining these effects varies depending on whether or not Ni is added. If Ni is not added, 1.0% or more is necessary. On the other hand, when adding together with 0.2% or more of Ni, the effect is exhibited by adding Mo at 0.2% or more. On the other hand, if it exceeds 3.0%, the effect is not only saturated, but also the grain growth in the finish annealing of the steel sheet is hindered, leading to deterioration of iron loss, so the upper limit is made 3.0%.

Sb and Sn: 1 type or 2 types in total 0.005-0.2%
In the present invention, Sb and Sn are effective elements for improving fatigue characteristics. This effect is exhibited when one or two of Sb and Sn are added in total to 0.005% or more, preferably 0.01% or more, to a steel whose Al content is limited to less than 0.2%. The reason for this is not clear, but Sb and Sn both segregate on the surface of the steel sheet to suppress oxynitridation during annealing, so the content of Al, which has the effect of promoting oxidation and nitridation, is limited, and Sb or Sn It is considered that the formation of the surface scale and the internal scale that becomes the starting point of fatigue fracture is suppressed by adding. On the other hand, if it exceeds 0.2%, grain growth is hindered and iron loss is deteriorated, so the upper limit is made 0.2%.

  In addition to the above elements, they are Fe (iron) and inevitable impurities. S and N as inevitable impurities are each preferably 0.01% or less from the viewpoint of iron loss.

The basic composition of the non-oriented electrical steel sheet according to the present invention is as described above. In addition to the above components, Zr, V, Ge, B, Ca, rare earth elements and Co, which are known as elements for improving magnetic properties, are used alone. Alternatively, they can be added in combination. However, the amount added should be such that the object of the present invention is not impaired. In particular,
For Zr and V, 0.1 to 3.0%
0.002-0.5% for Ge
0.001 to 0.01% for B, Ca, and rare earth elements
0.2 to 5.0% for Co
It is.

In the present invention, by the manufacturing conditions of the above composition range and below, can be stably optimizing the Cu precipitation after aging, resulting in tensile strength TS is 500MPa or more and 10 ⁷ fatigue limit The ratio FS / TS between strength FS and tensile strength TS is 0.85 or more.
Here, the tensile strength and fatigue strength of the non-oriented electrical steel sheet vary greatly depending on the alloy components such as Si, Al, and Mn, and also in the present invention, depending on the required strength and magnetic property level. Although the basic alloy composition can be selected, it is necessary to have a tensile strength of 500 MPa or more in order to use it as a high-speed rotating machine for the purpose of the present invention or a rotor material designed with a narrow slit interval. is there. The non-oriented electrical steel sheet of the present invention has not only a very high tensile strength but also a high fatigue limit even in a fatigue environment where repeated stress is applied, compared to conventional steels with the same amount of Si. There is a feature, the 10 ⁷ fatigue limit strength FS comes to have a 0.85 or a ratio FS / TS relative to the tensile strength TS.

  In other words, the ratio FS / TS in various conventional electrical steel sheets is usually kept at about 0.65 to 0.8, and the ratio FS / TS is 0.75 or less, particularly in a material having a high tensile strength. It was real. Even if the tensile strength is high and the steel plate has a low fatigue limit, when used as a rotor, even if it can withstand high-speed rotation for a short time, fatigue failure will occur in long-term operation at lower normal rotation. Therefore, the operation and design conditions such as the normal rotation speed and the gap between the magnet embedded slits must be greatly relaxed.

(Production method)
In order to produce a high fatigue strength non-oriented electrical steel sheet excellent in iron loss according to the present invention, first, a steel melted in the above-mentioned predetermined components in a converter or an electric furnace is continuously cast or A steel slab is formed by ingot rolling after ingot forming. Next, the obtained slab is hot-rolled, subjected to hot-rolled sheet annealing as necessary, and is subjected to cold rolling or warm rolling twice or more with intermediate or intermediate annealing to obtain a product sheet thickness, and finished. Apply annealing. Furthermore, if necessary, an insulating coating is applied and baked. The aging treatment for obtaining fine Cu precipitates may be performed after finish annealing or baking an insulating film, or may be performed after punching a motor core or the like.

  In the present invention, it is possible not to achieve high strength by significantly increasing the Si content of the material, but to achieve high strength by aging treatment in the subsequent process, and thus can be manufactured by ordinary cold rolling. . In addition, since warm rolling has the effect of improving the texture and improving iron loss and magnetic flux density, warm rolling can also be employed.

  The above-mentioned finish annealing is intended to remove distortion caused by rolling and to obtain an appropriate crystal grain size by recrystallization in order to obtain necessary iron loss characteristics. Although an appropriate crystal grain size depends on the required iron loss level, it is generally 20 to 200 μm, and for this purpose, the final ultimate temperature of finish annealing needs to be 700 ° C. or higher. On the other hand, if the annealing exceeds 1100 ° C, it becomes coarse grains and easily causes intergranular cracking, and the iron loss deterioration and fatigue strength reduction accompanying oxynitriding on the steel sheet surface increase, so the upper limit is 1100 ° C .

  The inventors have found that the cooling conditions for finish annealing are important when utilizing the fine precipitation of Cu. That is, in the cooling process of finish annealing, if the cooling rate from the solid solution temperature of Cu to 600 ° C is not fast enough, some Cu precipitates coarsely during cooling, which causes deterioration of iron loss. Subsequent aging annealing may increase the amount of coarse precipitates and may not provide sufficient strength. Here, in the case of containing only Cu and not containing Ni or Mo, the cooling rate was required to be 10 ° C./s or more in the temperature range of 900 ° C. to 400 ° C.

  However, when Ni and / or Mo within the scope of the present invention are contained together with Cu, if the cooling rate is 1 ° C./s or more, coarse precipitation during cooling can be suppressed, and the iron loss is greatly deteriorated by the subsequent aging treatment. A sufficient increase in strength can be obtained without accompanying. That is, when performing aging treatment by adding Cu and Ni or Mo in combination, stable characteristics can be obtained under more various finish annealing conditions than when Ni and Mo are not added. Therefore, when cooling after finish annealing, the temperature range from 900 ° C if the maximum temperature reached in annealing exceeds 900 ° C, and from the finish annealing temperature to 400 ° C if the maximum temperature reached in annealing is 900 ° C or less. The cooling rate is limited to 1 ° C / s or more.

  The subsequent aging treatment is performed at a temperature of 400 ° C. or higher and 650 ° C. or lower. That is, when the temperature is lower than 400 ° C., the precipitation of fine Cu becomes insufficient and high strength cannot be obtained. On the other hand, when the temperature exceeds 650 ° C., the Cu precipitates become coarse, so that the iron loss is deteriorated and the increase in strength is also reduced, so that an electrical steel sheet having a good strength-iron loss balance cannot be obtained. An appropriate aging time depends on the processing temperature, but is preferably 10 min to 1000 h. The aging treatment may be carried out at any timing before the insulating film is applied and baked, after baking, or after processing such as press punching.

  Based on steel A containing Si: 3%, Mn: 0.2% and Al: 0.5% shown in Table 1, solid solution strengthening (steel B), grain refinement strengthening (using steel A), carbide precipitation strengthening (Steel C) After hot rolling a steel slab obtained by melting a steel having a composition that incorporates various strengthening techniques of Cu aging precipitation strengthening (steel D to O), the conditions shown in Table 2 were used. After hot-rolled sheet annealing, the sheet thickness was finished to 0.35 mm by cold rolling or warm rolling (high Si steel), and then finish annealing was performed for a soaking time of 30 s. At that time, the cooling was performed at a cooling rate of 10 ° C./s in the temperature range of 900 ° C. to 400 ° C. For conditions 5 to 16 using the aging precipitation strengthening of Cu, a heat treatment was further performed at 500 ° C. for 2 hours. In addition, the component composition in the obtained steel plate was substantially the same as that in the slab stage.

Next, JIS No. 5 tensile test piece and the narrowest part width of 15mm R155mm fatigue test piece were cut out from the obtained steel plate in parallel with the rolling direction, respectively, and the tensile test and the tensile rate of 20Hz and stress ratio of 0.1 were cut. - performs a fatigue test of the tension type, was assessed 10 ⁷ times fatigue limit strength. Furthermore, magnetic measurements were performed using 25 cm Epstein specimens cut parallel and perpendicular to the rolling direction. The results are shown in Table 2, and the results arranged in relation to each characteristic are shown in FIGS.

As shown in Table 2, in Steel B (Condition 2), in which Si was strengthened by solid solution strengthening with respect to the standard condition 1, the increase in FS was small with respect to the increase in TS, and the ratio FS / TS Is as low as 0.78. In addition, the magnetic flux density is greatly reduced.
In addition, under the condition 3 in which the reference steel A is used and the annealing temperature is set to 800 ° C. to strengthen the grain refinement, the iron loss is remarkably deteriorated. In Steel C (Condition 4) in which carbide precipitation strengthening is performed, both the iron loss and the magnetic flux density are significantly deteriorated.
Steel D (Condition 5) with enhanced aging precipitation strengthening of Cu shows a significant increase in TS as compared with Condition 1 as a reference. On the other hand, the deterioration of the magnetic characteristics is slight. However, the improvement margin of the fatigue limit strength FS is small compared with the improvement margin of TS, and the ratio FS / TS is inferior at 0.75.

On the other hand, steels E, F, G, H, I, J (conditions 6, 7, 8, 9, 10, 11) to which one or two of Cu, Ni and Mo according to the present invention are added in combination are other Compared with the conditions 2 to 4 employing the strengthening mechanism, a high TS is shown while having a very good low iron loss and high magnetic flux density. Furthermore, the fatigue limit strength is improved corresponding to the improvement of TS, and the ratio FS / TS is also good at 0.91 to 0.88.
However, steels K and L whose Sb and Sn contents do not satisfy the scope of the present invention, and (Conditions 12 and 13) Steels M, N, and O that contain Sb and / or Sn but whose Al exceeds the scope of the present invention (Conditions) 14, 15, and 16) showed high TS but reduced fatigue limit strength.

  Steels Q, R, and S, steels U and V with varying amounts of Cu, Ni, and Mo added to steel P containing Si: 0.85% and steel T containing Si: 2.62% shown in Table 3 A steel plate having a thickness of 0.35 mm was manufactured under the conditions shown in Table 4. In addition, the component composition in the obtained steel plate was substantially the same as that in the slab stage. Next, after aging treatment at 500 ° C. for 5 hours, the tensile properties, fatigue properties, and magnetic properties were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4.

  Steel P to which Cu is not added (Condition 17), Steel Q to which Cu is added (Condition 18) shows a significant increase in strength, but the ratio FS / TS is small, and the effect of aging precipitation strengthening on the fatigue characteristics is That's not enough. On the other hand, steels R and S added with Ni or Mo satisfying the present invention together with Cu (conditions 19 and 20) sufficiently improve both tensile strength and fatigue strength while maintaining excellent magnetic properties. Further, in the condition 21 in which the cooling rate at the time of finish annealing for the steel S deviates from the range of the present invention, not only the strength increase due to aging is not sufficient, but also the iron loss is deteriorated. The same applies to 2.6% Si steel (steel T, U, V).

It is a figure which shows the relationship between tensile strength TS and ratio FS / TS. It is a figure which shows the relationship between fatigue limit strength and iron loss. It is a figure which shows the relationship between fatigue limit strength and magnetic flux density.

Claims (6)

% By mass
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Ni: Including 0.5% to 5.0%
One or two of Sb and Sn in total 0.005-0.2%
Contains, has a component composition of the balance Fe and unavoidable impurities, the tensile strength TS of not less than 500 MPa, and ¹⁰⁷ the ratio FS / TS of the fatigue limit strength FS and tensile strength TS is at least 0.85 A high fatigue strength non-oriented electrical steel sheet with excellent magnetic properties. % By mass
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Mo: Including 1.0% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
Contains, has a component composition of the balance Fe and unavoidable impurities, the tensile strength TS of not less than 500 MPa, and ¹⁰⁷ the ratio FS / TS of the fatigue limit strength FS and tensile strength TS is at least 0.85 A high fatigue strength non-oriented electrical steel sheet with excellent magnetic properties. % By mass
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0%,
Ni: 0.2% to 5.0% and
Mo: Including 0.2% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
Contains, has a component composition of the balance Fe and unavoidable impurities, the tensile strength TS of not less than 500 MPa, and ¹⁰⁷ the ratio FS / TS of the fatigue limit strength FS and tensile strength TS is at least 0.85 A high fatigue strength non-oriented electrical steel sheet with excellent magnetic properties. % By mass
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Ni: Including 0.5% to 5.0%
One or two of Sb and Sn in total 0.005-0.2%
The steel slab containing slab is hot-rolled, then cold-rolled or warm-rolled to the final sheet thickness, and the final temperature reached 650-1100 ° C and 900-400 ° C. A high-fatigue strength non-directional electromagnetic with excellent magnetic properties, characterized in that the cooling rate is 1 ° C / s or higher, and after finishing annealing, aging treatment is performed at a temperature of 400 ° C to 650 ° C. Manufacturing method of steel sheet. % By mass
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0% and
Mo: Including 1.0% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
The steel slab containing slab is hot-rolled, then cold-rolled or warm-rolled to the final sheet thickness, and the final temperature reached 650-1100 ° C and 900-400 ° C. A high-fatigue strength non-directional electromagnetic with excellent magnetic properties, characterized in that the cooling rate is 1 ° C / s or higher, and after finishing annealing, aging treatment is performed at a temperature of 400 ° C to 650 ° C. Manufacturing method of steel sheet. % By mass
C: 0.02% or less,
Si: 4.5% or less,
Mn: 3.0% or less,
Al: less than 0.2%,
P: 0.5% or less,
Cu: 0.2% to 4.0%,
Ni: 0.2% to 5.0% and
Mo: Including 0.2% to 3.0%
One or two of Sb and Sn in total 0.005-0.2%
The steel slab containing slab is hot-rolled, then cold-rolled or warm-rolled to the final sheet thickness, and the final temperature reached 650-1100 ° C and 900-400 ° C. A high-fatigue strength non-directional electromagnetic with excellent magnetic properties, characterized in that the cooling rate is 1 ° C / s or higher, and after finishing annealing, aging treatment is performed at a temperature of 400 ° C to 650 ° C. Manufacturing method of steel sheet.

Images