JP4265400B2 - Non-oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a non-oriented electrical steel sheet, particularly a non-oriented electrical steel sheet having high strength and excellent high-frequency iron loss, suitable for use in parts subjected to large stress, such as a rotor of a high-speed rotary motor, as a typical example. It is about the method.

  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, in recent years, the use of magnet-embedded DC inverter control motors with permanent magnets embedded in the rotor has been increasing from the viewpoint of improving motor efficiency. In addition, a large force is applied to the electromagnetic steel sheet used in the rotor. For this reason, high strength is required for electromagnetic steel sheets used in motors, particularly rotors.

  Since rotating devices such as motors and generators use electromagnetic phenomena, it is desirable that the material has magnetic properties, that is, low iron loss and high magnetic flux density. Normally, the rotor core is used by laminating non-oriented electrical steel sheets that have been stamped out of the stamp. 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 caster made of higher-strength cast steel. It is the present condition that we do not 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 electromagnetic steel sheets, which causes a reduction in motor efficiency. Therefore, there is a demand for a magnetic steel sheet having excellent magnetic properties and high strength 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 after increasing the Si content to 3.5 to 7.0 mass%. In Patent Document 2, the Si content is set to 2.0 to 3.5 mass%, the content of both Ni and Ni and Mn is increased, and the recrystallized grain size is controlled by manufacturing at a low temperature annealing of 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 mass% and fine carbides and nitrides of Nb, Zr, Ti, and V are precipitated. .

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 recrystallization grain growth by low-temperature annealing in order to increase mechanical strength, there is a problem in that magnetic characteristics, particularly iron loss at a relatively low frequency of 1 kHz or less is reduced. . Also, the amount of Si added was not over that of the conventional one, and the iron loss of 1 kHz or more was still insufficient.

  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.

  In addition, if a conventional non-oriented electrical steel sheet with a Si content of 3.5 mass% or less is used in a high-speed rotating motor used in the high frequency range of several hundreds of Hz to several tens of kHz, the iron loss increases and the motor efficiency decreases. It becomes. Therefore, the rotor core material of the high-speed rotary motor is required to have not only high strength but also excellent high-frequency iron loss characteristics.

  In order to improve the iron loss characteristics in this high frequency range, it is important to increase the electrical resistance of the steel, and generally a method of increasing the content of Si and Al has been adopted. However, if the amount of Si exceeds 3.5 mass%, the steel becomes extremely hard and brittle, and the workability deteriorates, so that it is difficult to manufacture and process by ordinary rolling. In particular, when the Si content exceeds 5.0 mass%, not only cold working but also warm working becomes impossible.

On the other hand, the applicant has found that by adding Cr to high-Si steel, the brittleness of high-Si steel can be improved and both high electrical resistance and workability can be achieved. A Fe-Cr-Si electrical steel sheet with excellent magnetic properties was proposed. This addition technology of Cr has made it possible to make a high alloy, so that not only excellent high-frequency iron loss characteristics but also solid solution strengthening resulted in a certain level of strength. The strength characteristics required for a rotary motor are still insufficient.
JP-A-60-238421 JP 62-256917 A JP-A-6-330255 Japanese Patent Laid-Open No. 11-343544

  As described above, none of the conventional methods is satisfactory from the viewpoint of achieving both high strength and low iron loss in a high frequency range in an electromagnetic steel sheet that can be stably industrially produced.

  The present invention proposes a non-oriented electrical steel sheet that has both good magnetic properties, particularly low iron loss and high strength in a high frequency range, and a manufacturing method that makes it possible to industrially produce this steel sheet. The purpose is to do.

  In order to solve the above-mentioned problems, the inventors have made various studies focusing on the age hardening phenomenon of steel containing Cu. That is, the steel having the components shown in Table 1 is hot rolled, then cold rolled to a thickness of 0.25 mm, and then subjected to finish annealing and aging treatment according to the conditions shown in Table 2, Strength and history loss were investigated. The results are also shown in Table 2.

Further, the diameter of the Cu-based precipitate in the steel sheet was also investigated, and the relationship between the diameter of the Cu-based precipitate and the hysteresis loss is shown in FIG. Here, the diameter of the Cu-based precipitate is the same as the diameter of the Cu-based precipitate existing in the range of 10 ⁸ nm ² when the steel sheet is observed (dark field image) using a scanning transmission electron microscope (STEM). It is obtained as an equivalent diameter, and the obtained values are averaged. Whether the observed precipitate was a Cu-based precipitate was identified by EDX analysis.

  The following findings were obtained from the results shown in Table 2 and FIG. In other words, despite the fact that precipitates in the steel sheet contribute to higher strength but deteriorate the hysteresis loss in order to suppress domain wall movement, contrary to the conventional knowledge, Cu deposited in an extremely fine size of 15 nm or less by aging treatment, The new knowledge that hysteresis loss hardly deteriorates while contributing to high strength was obtained.

  Based on this new knowledge, the combination of high electrical resistance technology by adding Cr and high strength technology by ultra-fine precipitation of Cu enables high-strength and good high-frequency magnetic properties that enable stable industrial production. This led to the development of a non-oriented electrical steel sheet.

The gist of the present invention is as follows.
(1) Si: 1.0 to 7.0 mass%, Cr: 1.0 to 8.0 mass%, Cu: 0.35 to 3.0 mass%, Mn: 3.0 mass% or less (including 0 mass%), Al: 3.0 mass% or less (0 mass% Containing), P: 1.0 mass% or less (including 0 mass%) and Ni: 5.0 mass% or less (including 0 mass%), the balance having a component composition of Fe and inevitable impurities, and Cu-based precipitation non-oriented electrical steel sheet you wherein the average particle size of the object is 15nm or less and the frequency of presence of Cu-based precipitates is 10 ⁶ / mm ² or more.

  The Cu-based precipitate in the present invention is substantially composed of simple Cu. However, when the precipitate is extremely fine, Cu may contain a solid solution of Fe, and such a case is also referred to as a Cu-based precipitate. Although coarse Cu-based precipitates may be observed on the grain boundaries depending on the production conditions, only the intragranular precipitates that substantially contribute to strengthening are targeted with respect to the precipitate diameter and existence frequency.

In (2) above (1), as the component composition further Sb: 0.002~0.5mass% and Sn: non-oriented electrical characterized in that it contains 0.002～0.5Mass% of either one or two steel sheet.

(3) Si: 1.0 to 7.0 mass%, Cr: 1.0 to 8.0 mass%, Cu: 0.35 to 3.0 mass%, Mn: 3.0 mass% or less (including 0 mass%), Al: 3.0 mass% or less (0 mass% P: 1.0 mass% or less (including 0 mass%) and Ni: 5.0 mass% or less (including 0 mass%), the remainder being hot-rolled into a slab having a component composition of Fe and inevitable impurities After annealing or annealing, cold rolling and / or warm rolling is performed to obtain the final thickness, and then final annealing is performed at a final temperature of 650 to 1150 ° C and a subsequent cooling process of 900 to 400 ° C. cooling rate applied under the conditions of more than 10 ° C. / s, then 400-650 manufacturing method of a non-oriented electrical steel sheet you characterized by applying aging treatment at a temperature of ° C..

(4) In the above (3), the component composition of the slab further contains any one or two of Sb: 0.002 to 0.5 mass% and Sn: 0.002 to 0.5 mass%. For producing high-strength non-oriented electrical steel sheets with excellent resistance.

  ADVANTAGE OF THE INVENTION According to this invention, the magnetic steel sheet which is excellent in a magnetic characteristic, especially a high frequency magnetic characteristic, and also has high intensity | strength can be provided stably.

Next, the present invention will be described in detail for each constituent requirement.
First, the component composition range and the reason for limitation will be described.
Si: 1.0-7.0mass%
Si is a main element that increases the electrical resistance of the steel sheet. In addition, it is a component effective for significantly increasing electrical resistance and improving magnetic properties particularly in the high frequency range due to a synergistic effect with Cr. However, if the Si content is less than 1.0 mass%, even if Si and Cr are used in combination, only the same electrical resistance as that of a conventional electromagnetic steel sheet can be obtained, so that good high-frequency magnetic characteristics cannot be obtained. On the other hand, when the Si content exceeds 7.0 mass%, even if Cr is used in combination, it is not possible to ensure the toughness at which normal rolling is possible. Therefore, the amount of Si is limited to the range of 1.0 to 7.0 mass%.

Cr: 1.0-8.0mass%
Cr is one of the most important components in the steel sheet of the present invention. In other words, Cr is a basic alloy component that greatly improves the specific resistance of steel by a synergistic effect with Si, and further improves the corrosion resistance. And even if it is Si + Al> 3.5 mass% or more, it is an extremely effective element for obtaining the toughness of the level which can be normally rolled, and it is preferable to make it contain at 2.0 mass% or more from that viewpoint. In addition, when the amount of Si or Al is less than the above case, workability can be secured even if the Cr amount is further reduced, but in order to realize the brittle improvement effect and high electrical resistance due to the Cr content. Requires 1.0 mass% or more of Cr. On the other hand, if the Cr content exceeds 8.0 mass%, the effect of improving toughness is saturated and the cost is increased, so the Cr content is limited to a range of 1.0 to 8.0 mass%.

Cu: 0.35-3.0 mass%
Cu is also the most important component in the steel sheet of the present invention. That is, by forming fine Cu-based precipitates by an aging treatment, a significant increase in strength can be achieved with almost no deterioration of iron loss (history loss). In order to obtain the effect, 0.35 mass% or more of Cu is necessary. On the other hand, if it exceeds 3.0 mass%, coarse precipitates are formed, so that the deterioration of iron loss increases and the strength increase margin also decreases. Therefore, the addition amount of Cu is regulated within the range of 0.35 to 3.0 mass%.

Mn: 3.0 mass% or less (including 0 mass%)
Mn is effective for further increasing the electric resistance, and further improvement in magnetic properties can be achieved without impairing the gist of the present invention. Therefore, it is preferably contained at 0.10 mass% or more. However, since the workability deteriorates when added in a large amount, the content is preferably limited to 3.0 mass% or less.

Al: 3.0 mass% or less (including 0 mass%)
Al is a nitride-forming element stronger than Cr, and is combined with nitrogen that penetrates from the steel sheet surface layer during annealing at the outermost layer, forming an AlN layer on the steel sheet outermost layer, and depositing AlN on the inner side. As a result, nitriding inside the steel sheet is prevented, and precipitation of Cr-based nitride is suppressed. In conventional electromagnetic steel sheets, AlN precipitation on the outermost layer deteriorates magnetic properties, so it has to be suppressed. However, in Fe—Cr—Si based electrical steel sheet, this AlN precipitation is very effective for improving magnetic properties. Further, Al forms coarse AlN together with the nitrogen contained from the time of steel melting, and has the effect of suppressing the precipitation of Cr-based nitrides by the nitrogen contained from the time of steel melting. In order to acquire such an effect, it is preferable to make it contain at 0.10 mass% or more. However, adding a large amount of Al also has the advantage of being able to increase electrical resistance, but if it exceeds 3.0 mass%, it will not be possible to ensure toughness that can be normally rolled even if Cr is contained, so When making it, it is preferable to regulate Al content to 3.0 mass% or less.

P: 1.0 mass% or less (including 0 mass%)
P is extremely effective for increasing the strength because a significant solid solution strengthening ability can be obtained even when added in a relatively small amount, and is preferably contained at 0.01 mass% or more. On the other hand, excessive inclusion causes embrittlement due to segregation, and causes intergranular cracking and lowering of rollability. Therefore, when contained, the content is preferably limited to 1.0 mass% or less.

Ni: 5.0 mass% or less (including 0 mass%)
Ni is an element effective for increasing the strength by solid solution strengthening, and is preferably contained at 0.50 mass% or more. However, if it exceeds 5.0 mass%, the effect is saturated and only increases the cost. Therefore, when it is contained, the upper limit is preferably 5.0 mass%.

Furthermore, any 1 type or 2 types of Sb: 0.002-0.5mass% and Sn: 0.002-0.5mass% can be contained.
Addition of Sb and / or Sn has an effect of suppressing nitriding. As a result, nitriding inside the steel plate is prevented, and as a result, precipitation of Cr-based nitrides can be suppressed. Since Cr-based nitride significantly deteriorates the magnetic properties, the addition of Sb and Sn to the Fe-Cr-Si-based electrical steel plate has a greater effect on improving the magnetic properties than in the case of conventional magnetic steel plates. When both Sb and Sn are 0.002 mass% or less, the nitriding suppression effect becomes insufficient. Further, Sb and Sn have an effect of improving the texture in addition to the effect of suppressing nitriding, and further contribute to the improvement of the magnetic properties of the steel sheet.
On the other hand, if it exceeds 0.50 mass%, the nitriding suppression effect is saturated and the cost is increased. Accordingly, the contents of Sb and Sn are in the ranges of Sb: 0.002 to 0.5 mass% and Sn: 0.002 to 0.5 mass%, respectively.

  Moreover, in this invention, about C, N, S, Ti, and Nb among unavoidable impurities, C: 0.010 mass% or less, N: 0.0050 mass% or less, S: 0.0050 mass% or less, Ti: 0.0050 mass% It is preferable to suppress below or below Nb: 0.0050 mass%.

C: 0.010 mass% or less Since C deteriorates the toughness of the Fe—Cr—Si based electromagnetic steel sheet, it is desirable to reduce it as much as possible. In the above component range, it is preferable to suppress the C content to 0.010 mass% or less. . Also, from the viewpoint of preventing hysteresis loss due to precipitates such as Cr-based carbides, the C content is preferably suppressed to 0.010 mass% or less.

N: 0.0050 mass% or less N is very easily combined with Cr and precipitates Cr-based nitride. Therefore, from the viewpoint of history loss deterioration, the N amount is preferably reduced to 0.0050 mass% or less. Moreover, since the toughness deterioration is caused when the N amount increases, it is preferably reduced as much as possible. From the viewpoint of toughness deterioration, the N amount is preferably suppressed to 0.0050 mass% or less.

S: 0.0050 mass% or less Since S produces precipitates such as MnS and CuS and deteriorates the hysteresis loss, the amount of S is preferably suppressed to 0.0050 mass% or less from the viewpoint of improving the hysteresis loss.

Ti: 0.0050 mass% or less and Nb: 0.0050 mass% or less
Ti and Nb are components for improving workability in ordinary Cr-containing steels, but are components that deteriorate magnetic properties. Since the improvement of workability in this invention is achieved by adding Cr and reducing C and N, the workability improvement action of Ti and Nb is not required. For this reason, it is desirable to reduce Ti and Nb as much as possible from the viewpoint of magnetic properties, and it is preferable that the allowable amount is 0.0050 mass% or less for both Ti and Nb.

  The amount of impurities other than C, N, S, Ti and Nb is not particularly limited, but in order to maintain good rupture characteristics and workability, it is necessary to limit to the same amount of impurities as conventional electromagnetic steel sheets. . In addition, it is more preferable to reduce all impurities including C, N, S, Ti, and Nb as much as possible from the viewpoints of both magnetic properties and workability.

Furthermore, in the electrical steel sheet of the present invention, it is necessary to finely precipitate Cu in the steel sheet. This is because even if Cu exists in a solid solution state (unprecipitated state), the strength is not increased.
And when precipitating Cu, it is necessary to make the average particle diameter of this Cu type precipitate into 15 nm or less. In other words, Cu-based precipitates whose diameter exceeds 15 nm not only deteriorates iron loss, but also does not contribute to high strength, so as fine precipitates of 15 nm or less that contribute to high strength without degrading iron loss. It is important to have Cu present.

Here, the diameter of the Cu-based precipitate is the same as the diameter of the Cu-based precipitate existing in the range of 10 ⁸ nm ² when the steel sheet is observed (dark field image) using a scanning transmission electron microscope (STEM). It is obtained as an equivalent diameter, and the obtained values are averaged.

It is also important that this Cu-based precipitate is present at 10 ⁶ pieces / mm ² or more in the steel sheet. That is, if the amount of the Cu-based precipitate is insufficient, the Cu-based precipitate hardly contributes to increasing the strength.

Next, the procedure for producing the steel plate of the present invention will be described in detail.
In order to produce a high-strength non-oriented electrical steel sheet having excellent iron loss according to the present invention, first, a steel melted in the above-mentioned predetermined components is continuously cast or manufactured in a converter or an electric furnace. A steel slab is formed by rolling after ingot. Next, the obtained slab is hot-rolled, subjected to hot-rolled sheet annealing as necessary, and subjected to cold rolling or warm rolling at least twice with one or intermediate annealing in between to obtain a product thickness. Annealing and then aging treatment. Furthermore, at any stage after finish annealing, an insulating coating is applied and baked as necessary.

The final finish annealing is performed for the purpose of obtaining an appropriate crystal grain size by recrystallization in order to remove the distortion caused by rolling and to obtain necessary iron loss characteristics. The suitable crystal grain size here is generally 20 to 200 μm, although it depends on the required iron loss level, and for that purpose, the final ultimate temperature in finish annealing needs to be 650 ° C. or higher. On the other hand, if annealing exceeding 1150 ° C. is performed, the grains become coarse and easily cause intergranular cracking, and the iron loss deterioration accompanying nitriding resistance on the steel sheet surface increases, so the upper limit is set to 1150 ° C.

  In this final finish annealing process, a reducing atmosphere of nitrogen + hydrogen is generally used in the production of non-oriented electrical steel sheets, and annealing in this atmosphere is advantageous in terms of cost. However, in the Fe—Cr—Si based electromagnetic steel sheet, Cr based nitride is formed by nitriding during the final finish annealing, which causes deterioration of magnetic properties. Therefore, it is necessary to suppress the precipitation of Cr-based nitrides. To that end, not only the addition of Sn, Sb, which is a nitriding inhibitor, and Al, which is a nitriding promoting element, but also the nitrogen partial pressure is reduced, It is also effective to control the nitrogen partial pressure in the annealing atmosphere, such as not using at all.

  Here, the inventors have newly 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. Considering such points, it was necessary to set the cooling rate of the finish annealing to 10 ° C / s or more in the temperature range of 900 ° C to 400 ° C in order to precipitate Cu-based precipitates finely. .

  Next, the 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-based precipitates are coarsened, the iron loss is deteriorated, and the amount of 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 time before the insulating film is applied and baked, after baking, or after processing such as press punching.

  In the present invention, the plate thickness of the steel plate is not particularly limited, but if the plate thickness is reduced, the effect of improving high-frequency magnetic properties is promoted. In order to obtain the effect remarkably, it is desirable that the plate thickness is 0.4 mm or less. However, if the plate thickness is made thinner than 0.01 mm, the manufacturing cost increases, so the plate thickness is preferably in the range of 0.01 to 0.4 mm.

  Steel having the components shown in Table 3 with the balance being Fe and an inevitable impurity composition was melted and hot rolled into a hot-rolled sheet having a thickness of 2.0 mm. This hot-rolled sheet was cold-rolled to obtain a cold-rolled sheet having a final thickness of 0.25 mm or 0.15 mm, and was subjected to final finish annealing under the annealing conditions shown in Table 4. At that time, the cooling process was set to 20 ° C./s in the temperature range from 900 ° C. to 400 ° C. Thereafter, the finish annealed plate was subjected to aging treatment at 500 ° C. and 10 hours. The product composition was the same as the steel composition shown in Table 3.

For the product plate thus obtained, the presence frequency and diameter of Cu-based precipitates were measured, and the high-frequency iron loss characteristics and yield strength were evaluated. In addition, the measurement of the presence frequency and the diameter of Cu-based precipitates was carried out in the range of about 10 ⁸ nm ² of the dark field image observed using STEM, and the precipitate diameter was the Cu-based precipitates existing in that range. Is the average value obtained as the equivalent circle diameter.

The iron loss W _{10 / 1k} (W / kg) was measured by the Epstein test method. The yield strength was determined by measuring the rolling direction of the product plate and the direction perpendicular thereto, and averaging the values.
These evaluation results are shown in Table 4.

As shown in Table 4, in all cases where the component composition was controlled within the range of the present invention, the average particle size of the Cu-based precipitates was 15 nm or less, and the presence frequency of the Cu-based precipitates was 10 ⁶ particles / mm ^2. As described above, it has high strength and excellent high-frequency iron loss.

  On the other hand, steel sheets made of steels A, H, Q, and Y with less Cu addition than the lower limit of the present invention show good high-frequency iron loss characteristics, but the presence frequency of Cu-based precipitates is outside the scope of the present invention. Therefore, the strength is insufficient. In steel sheets of steels F and W in which the Cu addition amount exceeds the upper limit of the range of the present invention, since the average grain size of the Cu-based precipitate exceeds 15 nm, both the high-frequency iron loss characteristics and strength are insufficient. For steels K, L, M, and N where the addition amount of Si and Cr is outside the range of the present invention, steel plates made of steel L and N to which Cu is added show high strength, but all the steel plates have low electrical resistance, Insufficient high-frequency iron loss characteristics.

Regarding the steels V, W, X, Y, and Z shown in Table 3, the final finish thickness was set to 0.15 mm in the same manner as in Example 1, and then final finish annealing was performed under the annealing conditions shown in Table 5. The cooling process in the final finish annealing was set to 20 ° C./s in the temperature range from 900 ° C. to 400 ° C. Thereafter, the finish annealed plate was subjected to aging treatment at 500 ° C. and 10 hours.
The steel sheet thus obtained was evaluated in the same manner as in Example 1, and the iron loss W _{0.5 / 20k} (W / kg) in a higher frequency range was investigated for the iron loss.

As shown in Table 5, the steel sheet made of steel Y with less Cu addition than the lower limit of the present invention shows good high-frequency iron loss characteristics, but the presence frequency of Cu-based precipitates is outside the scope of the present invention. Insufficient strength. In the steel sheet made of steel W in which the Cu addition amount exceeds the upper limit of the range of the present invention, the average grain size of the Cu-based precipitate exceeds 15 nm, and thus the high-frequency iron loss characteristics and strength are insufficient. In addition, the steel V, X, and Z steel plates whose compositions are controlled within the scope of the present invention have an average grain size of Cu-based precipitates of 15 nm or less and an existence frequency of Cu-based precipitates of 10 ⁶ pieces / mm ² or more. It has high strength and is excellent in high-frequency iron loss.

  Steel having the components shown in Table 6 with the balance being Fe and inevitable impurities was melted and hot rolled into a hot-rolled sheet having a thickness of 2.0 mm. This hot-rolled sheet is subjected to hot-rolled sheet annealing at a temperature of 900 ° C., and then a cold-rolled sheet having a final sheet thickness of 0.25 mm or 0.15 mm by a double cold-rolling method sandwiching intermediate annealing at 800 ° C. Final finish annealing was performed under annealing conditions. Thereafter, the finish annealed plate was subjected to an aging treatment under the conditions shown in Table 7. The product composition was the same as the steel composition shown in Table 6.

  The product plate thus obtained was evaluated in the same manner as in Example 1. As the evaluation results are also shown in Table 7, when the finish annealing condition and the aging treatment condition were controlled within the range of the present invention, excellent iron loss and high strength could be obtained in the product plate.

  On the other hand, when the cooling rate in the final annealing process was slow or the aging temperature was too high, the Cu-based precipitates became coarse, not only deteriorated the high-frequency iron loss characteristics, but also high strength could not be obtained. In addition, when the aging temperature is too low, the presence frequency of the Cu-based precipitate is outside the range of the present invention, and thus excellent high-frequency iron loss characteristics are shown, but high strength cannot be obtained.

It is a figure which shows the relationship between the diameter of Cu type precipitate, and a hysteresis loss.

Claims (4)

Si: 1.0-7.0mass%,
Cr: 1.0-8.0mass%,
Cu: 0.35-3.0 mass%,
Mn: 3.0 mass% or less (including 0 mass%),
Al: 3.0 mass% or less (including 0 mass%),
P: 1.0 mass% or less (including 0 mass%) and
Ni: 5.0 mass% or less (including 0 mass%)
And the balance has a component composition of Fe and inevitable impurities, the average particle size of the Cu-based precipitates is 15 nm or less, and the frequency of Cu-based precipitates is 10 ⁶ pieces / mm ² or more non-oriented electrical steel sheet characterized. In Claim 1, as a component composition, it is further
Sb: 0.002 to 0.5 mass% and
Sn: 0.002-0.5mass%
Non-oriented electrical steel sheet you characterized by containing one or two of. Si: 1.0-7.0mass%,
Cr: 1.0-8.0mass%,
Cu: 0.35-3.0 mass%,
Mn: 3.0 mass% or less (including 0 mass%),
Al: 3.0 mass% or less (including 0 mass%),
P: 1.0 mass% or less (including 0 mass%) and
Ni: 5.0 mass% or less (including 0 mass%)
Slab containing Fe and the inevitable impurities component composition, hot-rolled and left or annealed, and then cold-rolled and / or warm-rolled to the final thickness, then finished Annealing is performed under the condition that the final reached temperature is 650 to 1150 ° C. and the cooling rate at 900 to 400 ° C. in the subsequent cooling process is 10 ° C./s or more, and then an aging treatment is performed at a temperature of 400 to 650 ° C. method for producing a non-oriented electrical steel sheet shall be the features. In Claim 3, as a component composition of a slab,
Sb: 0.002 to 0.5 mass% and
Sn: 0.002-0.5mass%
Any one or the manufacturing method of the non-oriented electrical steel sheet you characterized by containing two.

Images