JP4696750B2 - Method for producing non-oriented electrical steel sheet for aging heat treatment - Google Patents

Description

  The present invention relates to a method for producing a non-oriented electrical steel sheet suitable as a material for a rotor core of a motor rotating at high speed. In particular, the present invention is suitable for an embedded magnet motor (IPM motor) or salient pole type surface magnet motor (saliency pole) that can withstand stress during rotation or stress fluctuation during acceleration / deceleration and requires excellent strength characteristics and magnetic characteristics. The present invention relates to a method for producing a non-oriented electrical steel sheet suitable as a material for a rotor core of a type SRM motor.

  In order to reduce greenhouse gases, new products that consume less energy are required in the fields of automobiles and home appliances. For example, in the automobile field, there is a hybrid drive vehicle (HEV) of a gasoline engine and a motor or an electric vehicle driven by a motor in order to reduce fuel consumption. In the home appliance field, there are high-efficiency air conditioners and refrigerators with low annual electricity consumption. These common technologies are motors, and high efficiency of the motors is an important technology. In the process of increasing motor efficiency, motor drive systems have become more sophisticated and various rotational drive controls have become possible. That is, the number of motors capable of variable speed operation and high speed operation at commercial frequency or higher has been increased by frequency control of the drive power source.

  In order to realize such a high-speed rotating machine, it is necessary to develop a rotor that can withstand high-speed rotation. In general, the centrifugal force acting on the rotor is proportional to the rotational radius and proportional to the square of the rotational speed. For this reason, when operating at high speed rotation, the force acting on the rotor may exceed 500 MPa, for example. Therefore, a material with high yield strength is required for the rotor. Furthermore, during rotor high-speed rotation operation, repeated stresses such as external vibration and frequent acceleration / deceleration may occur, so the rotor material must not only have high yield strength but also high fatigue strength. Is also needed. Since it is most effective to increase the tensile strength as a means for increasing the fatigue strength, it can be said that a high yield strength and a high tensile strength are necessary for the material of the rotor rotating at high speed.

  Usually, a laminated non-oriented electrical steel sheet is used for the motor rotor, but the motor that rotates at high speed as described above may not satisfy the required strength. In that case, high strength cast steel or the like is used as a rotor material. However, since the motor rotor uses magnetic properties at the time of rotation, the material is required to have excellent magnetic properties as well as mechanical properties as described above. In other words, an integral cast steel rotor has a problem that the eddy current loss becomes very large and the efficiency of the motor decreases. Further, in the case of an IPM motor, there arises a problem that magnet characteristics deteriorate due to heat generated by loss in the rotor.

  As described above, the rotor core material of the motor rotating at high speed as described above must have high mechanical strength and magnetically have high frequency and low iron loss. As means for increasing the strength of steel sheets, in the field of cold-rolled steel sheets, methods such as solid solution strengthening, precipitation strengthening, grain refinement strengthening, transformation strengthening are generally used, but excellent magnetic properties such as high strength and high frequency low iron loss are used. In general, there is a contradictory relationship, and it has been extremely difficult to satisfy these simultaneously.

  In order to solve such a problem, several proposals have recently been made regarding non-oriented electrical steel sheets having high tensile strength. For example, Patent Document 1 proposes a method in which the Si content is increased to 3.5 to 7.0%, an element having a large solid solution hardening is added thereto, and the tensile strength is increased. Further, in Patent Document 2, at least 2.0% or more and less than 4.0% Si is contained in a normal non-oriented electrical steel sheet, and at the same time, one or two of Nb and Zr, or one of Ti and V. Alternatively, a method for producing non-oriented electrical steel sheets with high yield strength and high mechanical strength and magnetic properties by utilizing two types of carbonitrides and controlling hot rolling conditions and finish annealing conditions is proposed. Has been. Furthermore, Patent Document 3 proposes a method of increasing the tensile strength by including a metal phase made of Cu having a diameter of 1.0 μm or less in the steel material.

JP 60-238421 A JP-A-6-330255 JP 2004-84053 A

However, since the steel sheet obtained by the invention described in Patent Document 1 is very brittle, there is a problem that it is easily broken during cold rolling and the yield is very low.
Moreover, in the invention described in Patent Document 2, since the finish annealing temperature is low, there is a problem that the crystal grain size of the steel sheet is very small and the iron loss is very inferior.
Furthermore, in the invention described in Patent Document 3, there is room for further improving the strength because the finish annealing conditions are not optimized. Further, since the hot rolled steel sheet is not annealed or annealed at a high temperature of 980 ° C., Cu is finely dispersed inside the hot rolled steel sheet, and the hot rolled steel sheet becomes very hard. Therefore, subsequent cold rolling becomes difficult and there is a problem inferior in productivity.

  This invention is made | formed in view of the said problem, and it aims at providing the manufacturing method of a non-oriented electrical steel sheet with high intensity | strength and low iron loss in a high frequency.

As a result of intensive research from the viewpoint of whether a steel sheet having excellent magnetic properties can be obtained by increasing the strength by precipitation strengthening by aging heat treatment, the present inventors have obtained Si, Al advantageous in both magnetic properties and strength properties. Based on the contained steel, Cu is used as a precipitation strengthening element, Ti, Nb, V, and Zr carbides are also used as required, and the final annealing conditions are optimized to improve strength and magnetic properties. The present inventors have found that a non-oriented electrical steel sheet having both of the above can be obtained and completed the present invention.
In the present invention, “carbide” includes carbonitride.

That is, the present invention is mass%, C: 0.02% or less, Si: 1.6% or more and 3% or less, Mn: 1% or less, P: 0.2% or less, S: 0.03% or less , Al: 0.1% or more and 3% or less, Ni: 2% or less, and Cu: more than 1%, 3% or less, and the balance is 2 MPa or more and 6 MPa or less in the cold-rolled steel sheet made of Fe and inevitable impurities The manufacturing method of the non-oriented electrical steel sheet for aging heat processing characterized by having the finish annealing process which performs finish annealing at the temperature of 900 degreeC or more and 1100 degrees C or less in the state which added tension | tensile_strength.

  According to the present invention, it is possible to produce a non-oriented electrical steel sheet for aging heat treatment with good magnetic properties by appropriately controlling the steel composition of the cold rolled steel sheet and the tension and temperature in the finish annealing process. it can. Moreover, the non-oriented electrical steel sheet with improved strength characteristics can be produced by subjecting the non-oriented electrical steel sheet for aging heat treatment obtained by the present invention to aging heat treatment. As described above, the present invention can provide a non-oriented electrical steel sheet suitable for a motor rotor that can be used stably without deformation or destruction during operation.

  Moreover, in this invention, it replaces with a part of said Fe, and it is preferable that the said cold-rolled steel plate contains B: 0.010% or less by the mass%. This is because by containing B, the toughness of the hot-rolled steel sheet, which is the material of the cold-rolled steel sheet, is improved, and breakage in the cold-rolling process can be suppressed.

  Furthermore, in the present invention, the cold-rolled steel sheet is replaced with a part of the Fe, and the total amount of at least one element selected from the group consisting of Ti, Nb, V, and Zr is 0. It is preferable to contain within the range of 01% or more and 0.1% or less. This is because the strength characteristics can be effectively improved by containing a predetermined amount of these elements.

  Moreover, in this invention, the hot-rolled sheet | seat which performs the hot-rolled sheet annealing which hold | maintains at the temperature of 600 degreeC or more and 900 degrees C or less for 2 hours or more to the hot-rolled steel sheet which is the raw material of the said cold-rolled steel sheet before the said finish annealing process. You may perform an annealing process and the cold rolling process which cold-rolls the said hot-rolled steel plate in which the hot-rolled sheet annealing was given. This is because by performing hot-rolled sheet annealing under predetermined conditions, the ductility of the steel sheet is improved, and breakage in the cold rolling process can be suppressed.

  According to the present invention, a non-oriented electrical steel sheet for aging heat treatment with low iron loss at high frequencies can be obtained, and when the aging heat treatment is applied to the non-oriented electrical steel sheet for aging heat treatment, the iron loss is low. In addition, it is possible to efficiently produce a non-oriented electrical steel sheet having high strength. If an iron core manufactured using such a non-oriented electrical steel sheet is incorporated into a motor rotor that rotates at high speed, the motor efficiency will not only increase, but it can be used stably for a long time without being deformed or broken during operation. It becomes. Such energy-saving effects can contribute to the creation of a future society with less impact on the global environment.

  In order to obtain a non-oriented electrical steel sheet having high strength and excellent magnetic properties, the present inventors have made a non-oriented electrical steel sheet high in strength by precipitation strengthening using an aging heat treatment. The effects of manufacturing conditions on the strength and magnetic properties of steel sheets were investigated. As a result, based on Si and Al-containing steels advantageous for both magnetic properties and strength properties, Cu is used as a precipitation strengthening element, and Ti, Nb, V, Zr carbides are also used as required. Furthermore, it has been found that a non-oriented electrical steel sheet having both strength characteristics and magnetic characteristics can be obtained by optimizing the finish annealing conditions. Hereinafter, the knowledge that has led to the present invention and the experimental results leading to it will be described.

In a vacuum melting furnace, the main components are mass%, C: 0.005%, Si: 2%, Mn: 0.2%, P: 0.09%, S: 0.002%, Al: 0.00. 7%, N: 0.002%, Cu: 2.0%, Nb: 0.03% After producing a slab that was heated at 1150 ° C, hot-rolled at a finishing temperature of 850 ° C, A hot-rolled steel sheet having a thickness of 2.5 mm was produced. This hot-rolled steel sheet was ground to a thickness of 2.0 mm, and further cold-rolled to a thickness of 0.35 mm. The cold-rolled steel sheet obtained by this cold rolling was subjected to finish annealing at 950 ° C. for 5 seconds while applying a tension of 0 to 8 MPa, then cooled to room temperature at an average cooling rate of 20 ° C./s, and a width of 55 mm. A single plate test piece having a length of 55 mm was prepared. And this aging test piece was subjected to aging heat treatment at 500 ° C. for 0.5 hour. The steel plate thus obtained was measured for yield strength, tensile strength, and iron loss W _10/400 .

Fig. 1 shows the relationship between tension during finish annealing and iron loss W _10/400 , Fig. 2 shows the relationship between tension during finish annealing and yield strength YP, and Fig. 3 shows the relationship between tension and tensile strength TS during finish annealing. Respectively. As is apparent from FIGS. 1 to 3, it has been clarified that it is effective to set the tension applied to the steel sheet during finish annealing to 2 to 6 MPa in order to achieve both high strength and high frequency and low iron loss.

Although the mechanism is not clear, the present inventors presume as follows.
That is, by applying tension during annealing at a high temperature, the steel sheet extends slightly and dislocations are introduced into the crystal grains. It is presumed that the strength of the steel sheet increases because fine Cu precipitates homogeneously by aging heat treatment using the dislocation as a precipitation site. Moreover, Nb in steel precipitates as Nb carbide by aging heat treatment. Since this Nb carbide also precipitates on the dislocations in the crystal grains and finely disperses, it is presumed that this Nb carbide contributed to further increase in strength.

Hereinafter, the manufacturing method of the non-oriented electrical steel sheet for aging heat treatment of this invention is demonstrated in detail.
The manufacturing method of the non-oriented electrical steel sheet for aging heat treatment of the present invention is, in mass%, C: 0.02% or less, Si: 1.6% or more and 3% or less, Mn: 1% or less, P: 0.2. %: S: 0.03% or less, Al: 0.1% or more and 3% or less, Ni: 2% or less and Cu: more than 1% and 3% or less, with the balance being Fe and inevitable impurities The present invention is characterized by having a finish annealing step in which a finish annealing is performed at a temperature of 900 ° C. to 1100 ° C. with a tension of 2 MPa or more and 6 MPa or less applied to the cold rolled steel sheet.

In the present invention, before the above-described finish annealing step, the steel ingot or steel slab having the above-described steel composition (hereinafter sometimes referred to as slab) is heated to a predetermined temperature and then hot-rolled. A rolling process and a cold rolling process in which cold rolling is performed on a hot rolled steel sheet obtained by the hot rolling process are performed. Moreover, you may perform the hot-rolled sheet annealing process which performs hot-rolled sheet annealing to a hot-rolled steel plate after the said hot rolling process.
Hereinafter, each process of the manufacturing method of the steel composition in this invention and the non-oriented electrical steel sheet for aging heat treatment of this invention is demonstrated.

1. Steel composition The slab or cold-rolled steel sheet used in the present invention is in mass%, C: 0.02% or less, Si: 1.6% or more and 3% or less, Mn: 1% or less, P: 0.2% S: 0.03% or less, Al: 0.1% or more and 3% or less, Ni: 2% or less, and Cu: more than 1% and 3% or less, with the balance being Fe and inevitable impurities It is.
“%” Indicating the content of each element means “mass%” unless otherwise specified .

(1) C
C is an element effective for increasing the strength of the steel sheet. However, if the C content exceeds 0.02%, carbides such as cementite and ε-carbide precipitate, and the magnetic property deterioration may become remarkable. Therefore, the C content is 0.02% or less. In order to further improve the magnetic properties, particularly to improve the iron loss, the upper limit of the C content is preferably 0.005%. On the other hand, when the carbide strengthening element such as Ti, Nb, V, Zr or the like is contained in an amount of 0.01% or more to enhance precipitation strengthening, the C content is preferably controlled to 0.005% to 0.02%. .

(2) Si
Si increases the specific resistance of steel and is effective in reducing iron loss. Si is also effective in increasing the strength of the steel sheet by solid solution strengthening. What is necessary is just to determine Si content according to a required iron loss characteristic and intensity | strength characteristic. However, if the Si content is less than 1.6%, the required strength and iron loss may not be obtained. On the other hand, if the Si content exceeds 3%, the dispersion state of Cu precipitates becomes non-uniform and the strength improvement effect tends to be saturated. Moreover, it may become easy to break in cold rolling, and the manufacturing cost may increase significantly. Therefore, the Si content is 1.6% or more and 3% or less. Furthermore, in order to suppress the yield reduction due to breakage during cold rolling, the Si content is preferably 1.6% or more and 2.5% or less.

(3) Mn
Mn is an unavoidable impurity and need not be added. However, Mn increases the specific resistance of steel and is effective in reducing iron loss. In order to acquire the effect, it is preferable to make it contain 0.1% or more. On the other hand, if the Mn content exceeds 1%, the raw material cost may increase. Therefore, the Mn content is limited to 1% or less.

(4) P
P is an unavoidable impurity and need not be added. However, P is an element effective for increasing the strength of the steel sheet by solid solution strengthening, and 0.05% or more is preferably contained in order to obtain the effect. On the other hand, if the P content exceeds 0.2%, the toughness of the steel deteriorates and there is a risk of fracture during cold rolling. Therefore, the P content is limited to 0.2% or less.

(5) S
S is an unavoidable impurity and does not need to be added. If the S content exceeds 0.03%, coarse Mn and Cu-containing sulfides are formed, the toughness of the steel deteriorates, and there is a risk of fracture during cold rolling. Therefore, the S content is limited to 0.03% or less. Moreover, in order to strengthen by the refinement | miniaturization by sulfide dispersion | distribution, it is preferable to contain S content 0.006% or more.

(6) Al
Al, like Si, increases the specific resistance of steel and is effective in reducing iron loss. Moreover, it is an element effective for deoxidation and can reduce nonmetallic inclusions. However, if the Al content exceeds 3%, the saturation magnetic flux density is remarkably lowered, and the core performance may be deteriorated. On the other hand, in order to efficiently deoxidize molten steel, it is necessary to contain 0.1% or more of Al. Therefore, the Al content is limited to 0.1% or more and 3% or less. In order to improve the magnetic flux density by improving the texture, the Al content is preferably 0.6% or more.

(7) Ni
Ni is an unavoidable impurity and need not be added. However, Ni is an element effective for increasing the strength of the steel sheet by solid solution strengthening, and 0.05% or more is preferably contained in order to obtain the effect. On the other hand, if the Ni content exceeds 2%, the raw material cost increases. Therefore, the Ni content is limited to 2% or less.

(8) Cu
Cu is an essential element in the present invention. As described above, when the Cu precipitate is very fine, there is an effect of improving the strength characteristics without substantially degrading the magnetic characteristics. However, when the Cu content is 1% or less, there is a possibility that a sufficient strength increase due to Cu precipitation cannot be obtained. On the other hand, the age hardening amount increases as the Cu content increases, but if it exceeds 3%, Cu precipitates are dispersed unevenly during finish annealing, resulting in a decrease in strength after aging heat treatment, and a decrease in the magnetic flux density of the steel sheet. There is a case. Therefore, the Cu content is limited to more than 1% and 3% or less. Moreover, it is preferable that Cu content is 1.5% or more and 2.5% or less from the point that precipitation strengthening becomes the most remarkable.

(9) B
B is an optional additive element and is not an essential element in the present invention. However, by containing 0.0003% or more of B, the toughness of the hot-rolled steel sheet is improved and it is difficult to break during cold rolling. On the other hand, if the B content exceeds 0.010%, a coarse B compound is produced, which may break during cold rolling. Therefore, the B content is preferably 0.010% or less. Further, from the viewpoint of steel plate manufacturability, the B content is more preferably 0.0003% or more and 0.0040% or less.

(10) Ti, Nb, V and Zr
Ti, Nb, V, and Zr form carbides and degrade the magnetic properties, so there is no need to add them. However, in order to improve the strength characteristics, it is effective to set the total content of Ti, Nb, V and Zr to 0.01% or more. On the other hand, if the total content of Ti, Nb, V and Zr exceeds 0.1%, carbides may be coarsely dispersed and the magnetic properties may be significantly deteriorated. Therefore, the total content of Ti, Nb, V and Zr is preferably 0.01% or more and 0.1% or less.

  In the present invention, the slab or cold-rolled steel plate preferably contains at least one element selected from the group consisting of Ti, Nb, V and Zr. At this time, as described above, Ti, Nb, The total content of V and Zr is preferably 0.01% or more and 0.1% or less. However, in order to ensure precipitation strengthening due to the formation of carbide, any one of Ti, Nb, V, and Zr is preferable. It is preferable that the content of one element is 0.01% or more.

(11) Other inevitable impurities Cr, Mo, and the like exist as components that may be mixed in steel by 0.01% or more in the steelmaking process. If the content of both Cr and Mo is reduced to 1% or less, the effects of the present invention will not be impaired. In addition, the impurity components other than the above components do not affect the effects of the present invention as long as the content is reduced to 0.05% or less.

2. Finish annealing step The finish annealing step in the present invention is a step in which finish annealing is performed at a temperature of 900 ° C. to 1100 ° C. with a tension of 2 MPa to 6 MPa applied to the cold-rolled steel sheet having the above-described steel composition. .

In the present invention, the control of the finish annealing condition is very important for improving the strength and magnetic properties after the aging heat treatment.
The final annealing temperature is 900 ° C. or higher and 1100 ° C. or lower. If the finish annealing temperature is less than the above range, recrystallization grain growth is insufficient and the magnetic properties may be significantly deteriorated. On the other hand, when the finish annealing temperature exceeds the above range, the particle size of the steel sheet becomes remarkably coarse, Cu precipitates after aging heat treatment are dispersed unevenly, and the strength may be lowered. In order to further reduce the iron loss, the higher the finish annealing temperature is, the better.
The tension applied to the steel plate during finish annealing is in the range of 2 MPa to 6 MPa. This is because, as can be seen from the above-described experimental results, it is effective to control the tension applied to the steel plate during finish annealing in order to increase the strength of the steel plate after the aging heat treatment.

3. Hot Rolling Step In the present invention, a hot rolling step of performing hot rolling may be performed after the slab having the steel composition described above is set to a predetermined temperature.
A general method can be used as hot rolling. Conditions such as the slab temperature, the finishing temperature in hot rolling, and the coiling temperature are appropriately selected depending on the steel composition of the slab, the thickness of the target steel sheet, and the like.
A hot-rolled steel sheet is usually subjected to cold rolling after removing scales generated on the surface of the steel sheet during hot rolling by pickling. When hot-rolled sheet annealing, which will be described later, is performed on a hot-rolled steel sheet, it may be pickled either before hot-rolled sheet annealing or after hot-rolled sheet annealing.

4). Hot-rolled sheet annealing step In the present invention, a hot-rolled sheet annealing step is performed in which the hot-rolled steel sheet obtained by the hot-rolling step is subjected to hot-rolled sheet annealing that is held at a temperature of 600 ° C or higher and 900 ° C or lower for 2 hours or longer. You may go. This hot-rolled steel sheet is a material for the cold-rolled steel sheet. Although the hot-rolled sheet annealing process is not necessarily an essential process, it is a useful process for increasing the efficiency of the subsequent cold rolling.

The annealing temperature in hot-rolled sheet annealing is preferably 600 ° C. or higher and 900 ° C. or lower. On the contrary, if the annealing temperature is less than the above range, the strength of the steel sheet becomes too high, and cold rolling may be difficult. On the other hand, even when the annealing temperature exceeds the above range, solid solution / reprecipitation of Cu occurs, the strength of the steel sheet increases, and cold rolling may become difficult. A more preferable annealing temperature is 650 ° C. or higher and 850 ° C. or lower.
The holding time at the annealing temperature is preferably 2 hours or more. When the holding time is less than 2 hours, Cu precipitates are refined, the strength of the steel sheet is increased, and cold rolling may be difficult. The holding time is more preferably 8 hours or longer. On the other hand, the upper limit of the holding time is not particularly limited, but is preferably 48 hours or less from the viewpoint of economy.

5. Cold rolling process In the present invention, cold rolling is applied to the hot rolled steel sheet obtained by the hot rolling process or the hot rolled steel sheet subjected to hot rolled sheet annealing in the hot rolled sheet annealing process. You may perform the cold rolling process to give.

Further, this step may be a step of subjecting the hot-rolled steel sheet to cold rolling twice or more with intermediate annealing. Although the intermediate annealing is not necessarily essential, the intermediate annealing has the advantage that the ductility of the steel sheet is improved and the breakage in cold rolling is reduced.
The conditions such as the annealing temperature in the intermediate annealing are preferably the same as those in the hot-rolled sheet annealing.

6). Others In the present invention, after the cold rolling step, according to a general method, a coating step of applying an insulating film made of only an organic component, only an inorganic component, or an organic-inorganic composite to the steel sheet surface may be performed. . Further, the coating process may be a process of applying an insulating coating that exhibits adhesive ability by heating and pressurizing. As a coating material exhibiting adhesive ability, an acrylic resin, a phenol resin, an epoxy resin, a melamine resin, or the like can be used.

Moreover, a non-oriented electrical steel sheet can be manufactured by performing an aging heat processing on the non-oriented electrical steel sheet for aging heat processing manufactured by this invention. Aging heat treatment is effective for increasing the strength of the non-oriented electrical steel sheet.
Conditions such as temperature, time, and atmosphere in the aging heat treatment are appropriately selected depending on the steel composition, target strength, and the like.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be described specifically by way of examples.
[Example 1]
The molten steel 230ton decarburized and desulfurized in the converter was taken out into the ladle, and the ladle was moved to the RH type vacuum degasser. After performing decarburization under reduced pressure with an RH type vacuum degassing apparatus and setting the C content in the steel to 0.015% or less, Si, Mn, P, S, Al, Cu, B, Ni, Ti, Nb, V And the content of Zr was adjusted and it was set as the slab with the continuous casting machine.
The slab was heated to 1150 ° C. in a heating furnace and hot-rolled at a finishing temperature of 800 to 850 ° C. and a winding temperature of 500 ° C. to obtain a hot-rolled steel sheet having a thickness of 2.0 mm. Next, it was pickled and descaled, annealed at 750 ° C. for 10 h, then cold-rolled to a thickness of 0.35 mm, finish annealed at 900-1050 ° C. with a tension of 2 MPa to 7 MPa, and an insulating film was applied to the steel sheet surface .
Table 1 below shows the component analysis values of the product, and Table 2 shows the finish annealing conditions.

A 28 cm Epstein test piece was collected from the steel sheet thus obtained and subjected to aging heat treatment at 500 ° C. for 0.5 h. About the steel plate after an aging heat processing, the iron loss _{W10 / 400} was measured by the method of JIS-C-2550 regulation. The magnetic flux density _B50 was also measured. Further, the steel sheet after the aging heat treatment was subjected to a tensile test specified in JIS-Z-2241 to measure the yield strength YP and the tensile strength TS. Table 2 below shows data of magnetic characteristics and strength characteristics.

A steel sheet having a steel composition within the range of the present invention had a yield strength YP of 600 MPa or more, a tensile strength TS of 750 MPa or more, and an iron loss W _10/400 of 25 W / kg or less, and required characteristics were obtained. . Also, the magnetic flux density _B50 was good. In particular, among the steel sheets having a steel composition within the scope of the present invention, the steel marks A5 to A13 having an Al content of 0.6% or more have a higher magnetic flux than the steel mark A4 having a relatively low Al content. Density _B50 was improved. On the other hand, the steel plate having a steel composition outside the range of the present invention had a yield strength YP of less than 600 MPa, which was clearly inferior to the examples of the present invention. Among them, steel sheet of the steel mark A3 is the magnetic flux density B ₅₀ was reduced to Cu content is large.

[Example 2]
Using the cold-rolled steel plates of steel marks A5 and A9 manufactured in Example 1, finish annealing was performed by changing the temperature from 850 ° C. to 1150 ° C. and the tension from 3 MPa to 7 MPa, and an insulating film was applied to the steel plate surface did. Table 3 below shows finish annealing conditions.

A 28 cm Epstein test piece was collected from the steel sheet thus obtained and subjected to aging heat treatment at 500 ° C. for 0.5 h. About the steel plate after an aging heat processing, the iron loss _{W10 / 400} was measured by the method of JIS-C-2550 regulation. The magnetic flux density _B50 was also measured. Further, the steel sheet after the aging heat treatment was subjected to a tensile test specified in JIS-Z-2241 to measure the yield strength YP and the tensile strength TS. Table 3 below shows data of magnetic characteristics and strength characteristics.

The steel sheet manufactured according to the finish annealing conditions specified in the present invention has a yield strength YP of 600 MPa or more, a tensile strength TS of 750 MPa, and an iron loss W _10/400 of 25 W / kg or less, and the required characteristics are obtained. It was. Also, the magnetic flux density _B50 was good. On the other hand, the steel sheet manufactured under conditions other than the provisions of the present invention had a yield strength YP of _less than 600 MPa or an iron loss W _10/400 of more than 25 W / kg, which was clearly inferior to the examples of the present invention. Among these, when the finish annealing temperature was less than 900 ° C., the magnetic flux density B ₅₀ was lowered.

[Example 3]
Using the hot-rolled steel sheet having a thickness of 2.0 mm with the steel mark A9 manufactured in Example 1, various hot-rolled sheet annealing was performed, and then the thickness was 0.35 mm with a lever-type cold rolling mill. The operability was evaluated according to the number of cold rolling passes. The results are shown in Table 4 below.

  When the annealing temperature in hot-rolled sheet annealing is 600 ° C. or more and 900 ° C. or less, it can be cold-rolled in 9 passes, whereas when the annealing temperature is less than 600 ° C. or more than 900 ° C., the annealed steel sheet is Since it was very hard, it could not be rolled to a thickness of 0.35 mm in 9 passes, and it was found that the operability was inferior.

It is a graph which shows the relationship between the tension _{| tensile_strength} at the time of finish annealing, and iron loss _{W10 / 400} . It is a graph which shows the relationship between the tension | tensile_strength at the time of finish annealing, and yield strength YP. It is a graph which shows the relationship between the tension | tensile_strength at the time of finish annealing, and tensile strength TS.

Claims (6)

  In mass%, C: 0.02% or less, Si: 1.6% or more and 3% or less, Mn: 1% or less, P: 0.2% or less, S: 0.03% or less, Al: 0.1 % To 3% or less, Ni: 2% or less, and Cu: more than 1%, 3% or less, with a balance of 2 MPa or more and 3 MPa or less applied to a cold-rolled steel plate made of Fe and unavoidable impurities. A method for producing a non-oriented electrical steel sheet for aging heat treatment, comprising a finish annealing step of performing finish annealing at a temperature of 900 ° C or higher and 1100 ° C or lower. 2. The non-oriented electrical steel sheet for aging heat treatment according to claim 1 , wherein the cold-rolled steel sheet contains B: 0.010% or less in mass% instead of a part of the Fe. Production method. In the cold-rolled steel sheet, at least one element selected from the group consisting of Ti, Nb, V, and Zr is 0.01% or more in total by 0.1% by mass instead of a part of the Fe. The method for producing a non-oriented electrical steel sheet for aging heat treatment according to claim 1 or 2 , wherein the non-oriented electrical steel sheet for aging heat treatment is contained. In mass%, C: 0.02% or less, Si: 1.6% or more and 3% or less, Mn: 1% or less, P: 0.2% or less, S: 0.03% or less, Al: 0.1 % To 3% or less, Ni: 2% or less and Cu: more than 1% and 3% or less, with a balance of 2 MPa to 6 MPa applied to a cold-rolled steel plate comprising Fe and inevitable impurities. A finish annealing step of performing finish annealing at a temperature of 900 ° C. or more and 1100 ° C. or less
Before the finish annealing step, a hot-rolled sheet annealing step for subjecting the hot-rolled steel sheet, which is a material of the cold-rolled steel sheet, to hot-rolled sheet annealing at a temperature of 600 ° C. or higher and 900 ° C. or lower for 2 hours or more, A method for producing a non-oriented electrical steel sheet for aging heat treatment, further comprising: a cold rolling process in which cold rolling is performed on the hot-rolled steel sheet subjected to sheet annealing. The non-oriented electrical steel sheet for aging heat treatment according to claim 4 , wherein the cold-rolled steel sheet contains B: 0.010% or less in mass% instead of a part of the Fe. Production method. In the cold-rolled steel sheet, at least one element selected from the group consisting of Ti, Nb, V, and Zr is 0.01% or more in total by 0.1% by mass instead of a part of the Fe. method for producing a non-oriented electrical steel sheet for aging of claim 4 or claim 5, wherein% by containing within the following range.

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