JP6593097B2 - Non-oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties and high strength, and a method for producing the same. More specifically, the present invention relates to an iron core of an electrical device that is required to have high energy efficiency and small size and high output simultaneously, such as a drive motor mounted on a compressor motor of an air conditioner, a hybrid vehicle, an electric vehicle, and a fuel cell vehicle. The present invention relates to a non-oriented electrical steel sheet suitable for a material and a manufacturing method thereof.

  Due to the recent increase in global environmental problems, electrical equipment is required to be small, high power, and high energy efficiency, and non-oriented electrical steel sheets, which are core materials, are strongly required to have both low iron loss and high magnetic flux density. ing.

  In particular, in a drive motor such as a hybrid vehicle or an electric vehicle, a means for increasing the number of revolutions is taken in order to compensate for a decrease in torque associated with downsizing. And when the number of rotations is increased, the frequency of the magnetic field applied to the steel sheet increases and the iron loss increases. Therefore, the non-oriented electrical steel sheet as the iron core material has a high frequency iron loss (high frequency iron loss). There is a need to reduce it. Further, in order to increase the rotational speed, there is a demand for strength that does not cause deformation or fatigue failure even at high speed rotation. Furthermore, in order to increase the efficiency of a drive motor such as a hybrid vehicle or an electric vehicle, sufficient cooling of the drive motor is required.

  As means for reducing high-frequency iron loss, sheet thickness is reduced, specific resistance is increased by increasing the content of alloy elements such as Si and Al, texture control is achieved by adding Sb and Sn, and high purity of steel sheet Etc. have been adopted. However, when Sb or Sn is added to the base steel plate in order to reduce iron loss, the film adhesion of the base steel plate may be lowered after performing strain relief tempering for the purpose of removing strain due to punching or processing. . As a result, the insulating coating may be peeled off from the surface of the mother steel plate and mixed with the refrigerant used for cooling the drive motor, thereby deteriorating the cooling performance.

In contrast, in Patent Document 1, at 1.3 g / m ² or less in the oxygen basis weight subscale of the lower edge coating, and the basis weight of the insulation coating, the type of the insulating coating is an inorganic or organic-inorganic composite coating It is said that 0.1 to 4.0 g / m ² is effective in the case of 0.1 to 12 g / m ² in the case of the organic coating. Further, in Patent Document 2, by specifying the Sb and Sn concentrations on the surface of the mother steel plate, the insulating film formed on the surface of the mother steel plate has excellent film adhesion that is difficult to peel off, and has excellent magnetic properties. A grain-oriented electrical steel sheet is provided. Thereby, it is avoided that the insulating coating is peeled off from the surface of the mother steel plate and mixed into the refrigerant to deteriorate the cooling performance. Furthermore, in Patent Document 3, by specifying the concentrations of Sb, Sn, and Al on the surface of the mother steel plate, deterioration of corrosion resistance due to oxidation during strain-relief tempering can be suppressed, and corrosion resistance and magnetic properties after strain-relief refractory purity. The non-oriented electrical steel sheet excellent in both is provided. Thereby, although it is supposed that the generation | occurrence | production of rust in a mother steel plate will be avoided, an effect is not enough about the adhesiveness of a film.

  However, the non-oriented electrical steel sheets described in Patent Documents 1 and 2 are of a degree sufficient to avoid peeling of the insulating coating from the surface of the mother steel sheet during long-term operation of a drive motor such as a hybrid vehicle or an electric vehicle. However, the coating adhesion of the insulating coating formed on the surface of the mother steel plate was not excellent. For this reason, at the time of long-term operation of a drive motor such as a hybrid vehicle or an electric vehicle, there is still a possibility that a problem arises that the insulating coating is peeled off from the surface of the mother steel plate and mixed into the refrigerant to deteriorate the cooling performance.

JP 2001-279400 A JP-A-8-291375 JP 2003-293101 A

  The present invention has been made in view of the above problems, and when Sb or Sn is added to a base steel plate in order to reduce high-frequency iron loss, Sb and Sn are segregated on the base steel plate surface, and the base steel plate surface By detoxifying the action of lowering the adhesion of the insulating coating formed on the insulating coating, it is possible to avoid the peeling of the insulating coating from the surface of the mother steel plate during long-term operation of a drive motor such as a hybrid vehicle or an electric vehicle. It is an object of the present invention to provide a non-oriented electrical steel sheet and a method for producing the same, which have excellent coating adhesion of an insulating film formed on the surface of the mother steel sheet.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research on changes in film adhesion of the insulating coating formed on the surface of the mother steel plate when other elements are segregated on the surface of the mother steel plate together with Sb and Sn. went. As a result, if Cu and Ni are segregated on the surface of the base steel plate together with Sb and Sn, the effect of lowering the film adhesion of the insulating coating due to Sb and Sn segregated on the surface of the base steel plate is counteracted and formed on the surface of the base steel plate. It has been found that the film adhesion of the insulating film can be further improved.

  The present invention has been made based on these findings, and the gist thereof is mass%, C: 0.004% or less, Si: 2.0% or more and 4.0% or less, Al: 2.0%. Hereinafter, Mn: 0.05% to 4.0%, S: 0.005% or less, N: 0.004% or less, P: 0.20% or less, Sn: 0.005% or more, 0.2% Hereinafter, Sb: 0.005% to 0.2%, Cu: 0.02% to 2.0%, Ni: 0.02% to 1.0%, with the balance being Fe and inevitable It is a non-oriented electrical steel sheet characterized by having a mother steel plate having a chemical composition made of impurities.

  Another gist is the non-oriented electrical steel sheet described above, wherein the Al content is 0.010% or less by mass.

Another aspect is the non-oriented electrical steel sheet described above, wherein the concentrations of Cu, Ni, Sn, and Sb on the surface of the base steel sheet satisfy the following formula (1): It is an electrical steel sheet.
([Cu] + [Ni]) / ([Sn] + [Sb])> 1.0 (1)
(Here, [X] in the formula represents the concentration of element X on the surface of the base steel plate expressed in mass%.)

  Furthermore, another gist is a method for producing the above-mentioned non-oriented electrical steel sheet, wherein a slab having the above-described chemical composition is heated to 1000 ° C. or higher in a heating furnace in which the oxygen concentration in the heating furnace atmosphere is 2% by volume or more. A slab heating step for heating to a temperature of 1250 ° C or lower, a hot rolling step for subjecting the heated slab to hot rolling, water cooling after the final rolling pass, and winding it in a coil shape at a temperature of 650 ° C or lower, and the above The hot-rolled steel sheet obtained by the hot-rolling process is subjected to hot-rolled sheet annealing / pickling process, and the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing / pickling process is cooled. It is a manufacturing method of a non-oriented electrical steel sheet characterized by having a cold rolling process which performs hot rolling, and a finish annealing process which performs finish annealing to the cold-rolled steel plate obtained by the cold rolling process.

  According to the present invention, the insulating coating formed on the surface of the mother steel plate is sufficient to avoid the peeling of the insulating coating from the surface of the mother steel plate during long-term operation of a drive motor such as a hybrid vehicle or an electric vehicle. It is possible to provide a non-oriented electrical steel sheet having excellent film adhesion and a method for producing the same. The non-oriented electrical steel sheet obtained by the present invention is extremely effective for miniaturization, high output and high energy efficiency of electrical equipment, and its industrial value is extremely high.

  Hereinafter, the non-oriented electrical steel sheet and the manufacturing method thereof according to the present invention will be described in detail.

A. Non-oriented electrical steel sheet Hereinafter, each structure in the non-oriented electrical steel sheet of the present invention will be described.

1. Chemical Composition First, the reasons for limiting the chemical composition of the base steel sheet in the non-oriented electrical steel sheet of the present invention will be described. In the following, the content of each component is a value in mass%.

(1) C
C is contained as an impurity, and if the content exceeds 0.004%, fine carbides are precipitated and the iron loss is remarkably increased. Therefore, the C content is 0.004% or less. From this viewpoint, the C content is preferably 0.003% or less, more preferably 0.002% or less.

(2) Si
Since Si has an action of increasing the specific resistance, it is contained for reducing iron loss. It is also effective for improving the strength of the steel sheet. However, if Si is contained excessively, the saturation magnetic flux density is decreased, resulting in embrittlement of the steel and an increase in the finish annealing temperature, and further increases the cost. From these viewpoints, the Si content is set to 2.0% to 4.0%. From these viewpoints, the Si content is preferably 2.5% or more, more preferably 3.0% or more, and the Si content is preferably 3.5% or less.

(3) Al
Al has the effect of increasing the specific resistance similarly to Si, so Al is contained for reducing iron loss. However, if Al is contained excessively, the saturation magnetic flux density is reduced, which is disadvantageous in terms of magnetic flux density. From these viewpoints, the Al content is set to 2.0% or less. Moreover, the Al oxide film formed on the surface of the mother steel sheet reduces the film adhesion of the insulating film formed on the surface of the mother steel sheet. For this reason, in order to improve the film adhesion of the insulating coating formed on the surface of the mother steel plate, Al content is suppressed so that the formation of the Al oxide coating on the surface of the mother steel plate is suppressed and the Si oxide coating is easily formed. It is preferred to reduce the amount. In this respect, the Al content is preferably 0.010% or less.

(4) Mn
Since Mn has the effect of increasing the specific resistance similarly to Si and Al, it is contained for reducing iron loss. However, if Mn is contained excessively, the saturation magnetic flux density is reduced, which is disadvantageous in terms of magnetic flux density. From these viewpoints, the Mn content is 0.05% to 4.0%. From these viewpoints, the Mn content is preferably 3.0% or less, more preferably 2.0% or less.

(5) S
When the content of S exceeds 0.005%, a large number of sulfides such as MnS are precipitated and the iron loss is remarkably increased. Therefore, the S content is 0.005% or less. From these viewpoints, the S content is preferably 0.003% or less, more preferably 0.002% or less.

(6) N
When the content of N exceeds 0.004%, an increase in iron loss becomes significant due to an increase in nitride. Therefore, the N content is 0.004% or less.

(7) P
P is an element effective for improving the strength of the steel sheet in the same manner as Si. However, if excessively contained, the steel will become brittle. From this viewpoint, the P content is 0.20% or less. When P is segregated on the surface of the base steel plate, the segregation site competes with Sn and Sb. Therefore, by segregating P on the surface of the base steel plate, the segregation of Sn and Sb to the surface of the base steel plate is suppressed, and the surface of the base steel plate The effect which suppresses the fall of the film adhesiveness of the insulating film formed in this is acquired. For this reason, in order to improve the film adhesion of the insulating coating formed on the surface of the base steel plate, it is preferable to contain P so that P is segregated on the surface of the base steel plate. In this respect, the P content is preferably 0.05% or more and 0.20% or less. Furthermore, from this viewpoint, the P content is more preferably 0.10% or more and 0.20% or less.

(8) Sn
Sn is contained because it has the effect of improving the texture of the electrical steel sheet and reducing iron loss. In addition, when heated to a high temperature in a nitrogen atmosphere containing hydrogen, there is also an effect of reducing iron loss by preventing intrusion of nitrogen from the steel surface and suppressing the formation of AlN. In addition, when Sn is contained, it segregates and concentrates on the surface of the mother steel sheet, thereby reducing the film adhesion of the insulating film formed on the surface of the mother steel sheet. By the action of canceling out, the effect of suppressing the decrease in the film adhesion can be obtained. However, when Sn is excessively contained, a decrease in film adhesion cannot be avoided in spite of the effect of counteracting the decrease in film adhesion due to Cu and Ni described later. Further, when Sn is excessively contained, crystal grain growth is inhibited. From these viewpoints, the Sn content is set to 0.005% or more and 0.2% or less. From these viewpoints, the Sn content is preferably 0.03% or more, and the Sn content is preferably 0.10% or less.

(9) Sb
Sb is included because it has an effect of improving iron loss. This effect is thought to be due to preventing nitrogen from entering from the surface of the steel and inhibiting the formation of AlN when heated to a high temperature in a nitrogen atmosphere containing hydrogen. Further, when Sb is contained, the film adhesion of the insulating film formed on the surface of the mother steel sheet is lowered by segregating and concentrating on the surface of the mother steel sheet, but the film adhesion deterioration due to Cu and Ni described later is reduced. By the action of canceling out, the effect of suppressing the decrease in the film adhesion can be obtained. However, when Sb is contained excessively, the decrease in the film adhesion cannot be avoided despite the effect of counteracting the decrease in the film adhesion due to Cu and Ni described later. Moreover, when Sb is contained excessively, crystal grain growth will be inhibited. From these viewpoints, the Sb content is set to 0.005% or more and 0.2% or less. From these viewpoints, the Sb content is preferably 0.01% or more, and the Sb content is preferably 0.10% or less.

(10) Cu
Cu segregates and concentrates on the surface of the mother steel plate together with Sn and Sb, thereby counteracting the decrease in film adhesion due to Sn and Sb segregated on the surface. Cu also has the effect of improving the strength of the steel sheet. For this reason, Cu is contained. However, when Cu is excessively contained, wrinkles are generated on the surface of the base steel sheet after hot rolling, resulting in a decrease in product yield. From these viewpoints, the Cu content is set to 0.02% or more and 2.0% or less. From these viewpoints, the Cu content is preferably 0.05% or more and 1.0% or less.

(11) Ni
Ni segregates and concentrates on the surface of the mother steel plate together with Sn and Sb, thereby counteracting the decrease in film adhesion due to Sn and Sb segregated on the surface. It also has the effect of improving iron loss. For this reason, Ni is contained. However, even if Ni is contained excessively, these actions and effects are saturated and disadvantageous in terms of cost, and also causes embrittlement of the steel. From these viewpoints, the Ni content is set to 0.02% or more and 1.0% or less. From these viewpoints, the Ni content is preferably 0.05% or more, more preferably 0.1% or more, and the Ni content is preferably 0.5% or less.

(12) Ca, Mg, and REM
Ca, Mg, and REM are effective elements for controlling the morphology of inclusions, and effectively act to reduce iron loss through the action of promoting the growth of crystal grains. Therefore, Ca, Mg, and REM may be contained instead of part of Fe. However, even if the content of any element exceeds 0.01%, the effect of the above action is saturated and disadvantageous in cost. Therefore, it is preferable that the Ca content is 0.01% or less, the Mg content is 0.01% or less, and the REM content is 0.01% or less. More preferably, the Ca content is 0.005% or less, the Mg content is 0.005% or less, and the REM content is 0.005% or less. In order to more reliably obtain the effect of the above action, the content of any element is preferably set to 0.001% or more.

(13) Remainder The remainder is Fe and inevitable impurities.
Of unavoidable impurities, Ti, V, Nb, Zr, and Se, which adversely affect the grain growth, are desirably reduced as much as possible, and preferably 0.008% or less, respectively.

2. Next, the relationship between the concentrations of Cu, Ni, Sn, and Sb on the surface of the mother steel plate will be described.

As described above, Sn and Sb are easily segregated on the surface of the base steel plate, and segregate and concentrate on the surface of the base steel plate, thereby reducing the adhesion of the insulating coating formed on the surface of the base steel plate. However, as described above, Cu and Ni segregate and concentrate on the surface of the mother steel plate together with Sn and Sb, thereby counteracting the decrease in coating adhesion.
In order to exert the effect, it is preferable to increase the ratio of the total concentration of Cu and Ni to the total concentration of Sn and Sb on the surface of the base steel plate. Specifically, Cu, Ni, Sn, and The Sb concentration preferably satisfies the following formula (1), and more preferably satisfies the following formula (1-2).
([Cu] + [Ni]) / ([Sn] + [Sb])> 1.0 (1)
(Here, [X] in the formula represents the concentration of element X on the surface of the base steel plate expressed in mass%.)
([Cu] + [Ni]) / ([Sn] + [Sb])> 1.5 (1-2)
(Here, [X] in the formula represents the concentration of element X on the surface of the base steel plate expressed in mass%.)

Here, in the present invention, the concentration [X] of the element X (X = Cu, Ni, Sn, Sb) on the surface of the mother steel plate expressed by mass% is measured by performing glow discharge optical emission spectrometry (GDS). This means the concentration obtained using the emission intensity Sx and Bx of the element X to be obtained. Specifically, the emission intensities Sx and Bx are obtained from the emission intensity of the element X when the elemental X is quantitatively analyzed from the outermost surface of the mother steel sheet by the GDS in the plate thickness depth direction. The maximum emission intensity of the element X in the analysis from the outermost surface to the 1 μm depth position is meant, and the emission intensity Bx means the emission intensity of the element X at the depth position of 10 μm from the outermost surface of the mother steel plate. And the density | concentration [X] of the element X in the mother steel plate surface represented by the mass% is calculated | required by following formula (2) using Sx and Bx. However, when the emission intensity Sx is obtained by GDS, the emission intensity information obtained from the outermost surface of the steel sheet after the start of GDS analysis to the depth position of 0.1 μm is not considered because the quantitative analysis accuracy is low.
[X] = Sx / Bx × (content of element X in mother steel plate) (2)

3. The thickness of the base steel plate The present invention is based on the premise that essentially low frequency iron loss is achieved. Therefore, the thickness of the mother steel plate is set to 0.30 mm or less. On the other hand, since excessive thinning may lead to an extreme decrease in space factor due to deterioration in flatness and a decrease in productivity of the iron core, the thickness of the base steel plate is set to 0.10 mm or more.

4). Insulating coating The non-oriented electrical steel sheet of the present invention may further have an insulating coating formed on the surface of the base steel plate in order to insulate between the steel plate laminations in the iron core.
The insulating film formed on the surface of the mother steel sheet needs to secure a film thickness in order to achieve insulation between the steel sheet laminations in the iron core, but if it is too thick, the film adhesion is lowered and the film is easily peeled off. From these viewpoints, the thickness of the insulating coating is 0.1 μm or more and 0.5 μm or less. When the thickness of the insulating coating exceeds 0.5 μm, the adhesion of the coating decreases. When the thickness of the insulating coating exceeds 0.5 μm, the magnetic steel sheet is punched into the motor core and subjected to strain relief annealing. It is presumed that the oxygen contained in the insulating coating reacts with the surface of the mother steel plate to form a new oxide coating.

5). Manufacturing method It is suitable to manufacture the non-oriented electrical steel sheet of the present invention by a manufacturing method of the non-oriented electrical steel sheet described later.

B. Hereinafter, each process in the manufacturing method of the non-oriented electrical steel sheet of the present invention will be described. The process conditions necessary for specifying the present invention relate to the slab heating process and the hot rolling process. The following description of the process conditions other than these shows general conditions for reference, and even if the conditions are not satisfied, the effects of the present invention can be obtained.

1. Slab Heating Step In the slab heating step, the slab having the above chemical composition is heated to a temperature of 1000 ° C. or more and 1250 ° C. or less in a heating furnace in which the oxygen concentration in the heating furnace atmosphere is 2% by volume or more.
In this invention, the temperature prescribed | regulated here means the surface temperature of a slab, and the surface temperature of a slab means the temperature measured with the contact-type thermometer or the radiation thermometer.

  The heating furnace atmosphere contains nitrogen, oxygen, water vapor, carbon monoxide, and carbon dioxide. The oxygen concentration in the heating furnace atmosphere is set to 2% by volume or more, while simultaneously promoting the generation of oxide scale on the slab surface. Since the effect of increasing the concentration of Cu and Ni in the steel is obtained, it leads to an improvement in the concentration of Cu and Ni on the surface of the mother steel plate of the final product, and effectively acts to suppress the decrease in film adhesion due to Sn and Sb. It is. In addition, heating to a temperature of 1000 ° C. or more and 1250 ° C. or less results in insufficient scale generation on the surface of the slab if the temperature is less than 1000 ° C., which deteriorates the surface properties of the steel sheet and causes breakage in the cold rolling process. Further, when the temperature exceeds 1250 ° C., sulfides in the slab are solid-dissolved and finely precipitated during hot rolling to deteriorate iron loss. From these viewpoints, the heating temperature is preferably set to 1050 ° C. or more and 1200 ° C. or less.

2. Hot rolling step In the hot rolling step, the heated slab is hot-rolled, and after the final rolling pass, it is water-cooled and wound into a coil at a temperature of 650 ° C or lower.
In the present invention, the temperature specified here means the surface temperature of the steel sheet after hot rolling, and the surface temperature of the steel sheet after hot rolling means a temperature measured by a contact-type thermometer or a radiation thermometer. To do.

  Water cooling after the final rolling pass and winding in a coil shape at a temperature of 650 ° C. or less means that if the coil winding temperature exceeds 650 ° C., the scale layer on the surface of the mother steel plate becomes thick and the scale removal by pickling is possible. This is because when pickling is strengthened for scale removal, the concentrations of Cu and Ni on the surface of the mother steel sheet are lowered, and the film adhesion due to Sn and Sb tends to be reduced. Moreover, the conditions of a hot rolling process other than this are not specifically limited.

3. Hot-rolled sheet annealing / pickling process In the hot-rolled sheet annealing / pickling process, hot-rolled sheet annealing and pickling are performed on the hot-rolled steel sheet obtained by the hot rolling process. Pickling and hot-rolled sheet annealing are in no particular order, and hot-rolled sheet annealing may be performed after pickling, or pickling may be performed after hot-rolled sheet annealing.

  The conditions for hot-rolled sheet annealing are not particularly limited. When hot-rolled sheet annealing is performed, the hot-rolled steel sheet is held in a temperature range of 700 ° C. to 1100 ° C. for 1 minute to 24 hours. It is preferable. If the hot-rolled sheet annealing temperature is below the above range, the strain accumulated in the hot-rolled steel sheet is not released, and the possibility of breaking in the subsequent cold rolling increases, and the hot-rolled sheet annealing time is This is because if the ratio is below the above range, the possibility of breakage by cold rolling increases for the same reason. Moreover, when the said hot-rolled sheet annealing temperature exceeds the said range, the addition to an installation will become large, and when the said hot-rolled sheet annealing time exceeds the said range, it will cause productivity deterioration. Moreover, it is preferable that an annealing atmosphere contains hydrogen from a viewpoint of suppressing the scale growth in the mother steel plate surface, and it is more preferable that hydrogen concentration shall be 10 volume% or more. Further, the annealing atmosphere preferably contains nitrogen as a main gas from the viewpoint of cost. The hot-rolled sheet annealing method can be either a continuous annealing type or a batch annealing type, and the hot-rolled sheet annealing conditions are for controlling the crystal structure in the base steel sheet after annealing according to the required magnetic properties and production efficiency. It is preferable to adjust. For example, in order to improve the magnetic flux density, it is preferable to adjust the annealing temperature and the annealing time so that the crystal grain size in the base steel plate after annealing is 40 μm or more.

  On the other hand, the conditions for pickling are not particularly limited. For example, the main component of the pickling solution is hydrochloric acid, and the temperature is 80 ° C. or higher.

4). Cold rolling step In the cold rolling step, the hot rolled annealed plate obtained by the hot rolled plate annealing / pickling step is subjected to cold rolling.

  Cold rolling conditions such as cold rolling reduction are not particularly limited, and may be normal conditions. For example, the cold rolling reduction is 70% or more.

5). Finish annealing step In the finish annealing step, the cold rolled steel sheet obtained by the cold rolling step is subjected to finish annealing.

  The finish annealing conditions are not particularly limited, and may be normal conditions. For example, the temperature and soaking conditions may be determined from the viewpoint of appropriate crystal grain size control so as to reach the target iron loss. The in-furnace tension during annealing is preferably less than 5 MPa so that the steel sheet is not distorted. The annealing atmosphere preferably contains a nitrogen-hydrogen mixed gas as a main component and suppresses oxidation as much as possible.

6). Other Steps The method for producing a non-oriented electrical steel sheet according to the present invention comprises an insulating film that forms an insulating film by applying and baking a coating liquid on the steel sheet surface obtained by the finish annealing process after the finish annealing process. You may have a formation process. The insulating film forming conditions and the coating solution may be as usual.

  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 and comparative examples.

Example 1
First, sample No. shown in Table 1 below. Steel having a chemical composition of A01 to C11 was vacuum melted, cast into a 25 kg ingot, heated to 1150 ° C., and forged into a 40 mm thick steel piece. Next, the steel slab was heated to 1150 ° C. at a surface temperature in a heating furnace in which the oxygen concentration in the heating furnace atmosphere was 2% by volume or more. Next, it was finished to a plate thickness of 2.0 mm by hot rolling. The hot rolling was finished at the hot rolling end temperature of 850 ° C. as the surface temperature. Next, the steel sheet after hot rolling was cooled with water to a surface temperature, held at 650 ° C. for 1 hour, and then air-cooled. Next, the air-cooled steel sheet was subjected to hot-rolled sheet tempering that was held at 1000 ° C. for 30 seconds in a nitrogen atmosphere and soaked, and then allowed to cool in the air. Next, the hot-rolled sheet pure steel sheet was pickled and finished to a thickness of 0.20 mm by cold rolling. Next, after the cold-rolled steel sheet was degreased, it was subjected to finish tempering that was soaked at 1000 ° C. for 10 seconds in a nitrogen-hydrogen mixed atmosphere. Next, an organic-inorganic composite coating liquid was applied to the surface of the steel plate after finish tempering and baked to form an insulating film having a thickness of 0.3 μm.

  About the non-oriented electrical steel sheet thus obtained, the ratio of the total concentration of Cu and Ni to the total concentration of Sn and Sb on the surface of the base steel plate (([Cu] + [Ni]) / ([Sn] + [Sb ])) Was calculated from the concentration [X] [mass%] of the element X (X = Cu, Ni, Sn, Sb) on the surface of the mother steel plate by glow discharge optical emission spectrometry (GDS). The results are shown in Table 1 below.

Moreover, the 1st peeling test was done with respect to the insulating film formed in the mother steel plate surface in the non-oriented electrical steel plate obtained in this way. In the first peel test, the tape was bent 180 degrees so as to be wound around a stainless steel rod having a diameter of 10 mm, and after the cellotape (registered trademark) was peeled and peeled off on the surface of the bent steel plate (the inner surface when bent), the insulation coating was peeled off. The presence or absence was visually evaluated, and the ratio of the area where the insulating coating was peeled was measured as the peel rate [%]. Further, as a result of the first peeling test, the non-oriented electrical steel sheet having no peeling of the insulating film was subjected to a heat treatment held at 600 ° C. for 2 hours in a nitrogen atmosphere and then subjected to the second peeling test. It was. Also in the second peel test, the insulation film was peeled off and peeled after the cell tape was bent 180 degrees so as to be wound around a stainless steel rod having a diameter of 10 mm, and the cell surface was peeled back (the inner surface when bent). [%] Was evaluated visually. Thereby, the film adhesion of the insulating film formed on the mother steel plate surface was evaluated. The results are shown in Table 1 below. The evaluation criteria for the coating adhesion of the insulating coating formed on the surface of the mother steel plate are as follows.
1: No peel in the first peel test, no peel in the second peel test 0: No peel in the first peel test, no peel in the second peel test -1: Peel rate in the first peel test 10% or less -2: 10% to 20% peel rate in the first peel test
-3: Peeling rate 20% to 30% in the first peel test
-4: peeling rate 30% to 40% in the first peeling test
-5: Peel rate of 40% or more in the first peel test

Moreover, a JIS No. 5 tensile test piece was collected from the non-oriented electrical steel sheet thus obtained, and a tensile test was performed to evaluate the yield stress (YS) [MPa]. Further, a 55 mm square single plate test piece was punched from the non-oriented electrical steel sheet thus obtained, and the iron loss W _10/400 [W / kg] (maximum magnetic flux at 400 Hz) was measured using a single plate magnetometer. The average value of the iron loss in the rolling direction and the iron loss in the direction perpendicular to the rolling in the case of alternating excitation at a density of 1.0 T was measured. The results are shown in Table 1 below.

  As shown in Table 1 above, Sample No. In A01 to A06, since Cu and Ni were not substantially contained, the film adhesion was lowered when the Sn and Sb contents were within the range specified in the present invention. In contrast, sample no. In A07 to A11, when the Cu and Ni contents are within the range specified in the present invention, ([Cu] + [Ni]) / ([Sn] + [Sb]) becomes larger than 1.0. The decrease in film adhesion was suppressed. Sample No. In A12 to A16, when the total content of Sn and Sb is constant, when the total content of Cu and Ni increases, ([Cu] + [Ni]) / ([Sn] + [ Although the film adhesion was improved from “−2” to “0” when Sb]) was 1.0, the film adhesion was not improved in proportion to the total content of Cu and Ni.

  Sample No. In B01 to B06, although Al-less, sample no. Similar to A01 to A06, since Cu and Ni are not substantially contained, the film adhesion was lowered when the Sn and Sb contents were within the range specified in the present invention. In contrast, sample no. In B07 to B10, sample No. Similarly to A07 to A11, when the Cu and Ni contents are within the range specified in the present invention, ([Cu] + [Ni]) / ([Sn] + [Sb]) is from 1.0. It became large and the fall of film adhesiveness was suppressed. Sample No. In B07-B10, sample No. which is not Al-less is Al-less. Compared with A07 to A11, the effect of suppressing the decrease in the film adhesion became more remarkable. Furthermore, sample no. Comparison between B15 and B16 is an example in which only the Al content of the steel sheet is different, and it was found that B15, which is Al-less, has superior film adhesion. Sample No. In B11 to B15, although Al-less, sample no. Similarly to A12 to A16, when the total content of Sn and Sb is constant, when the total content of Cu and Ni increases, ([Cu] + [Ni]) / ([Sn] Although the film adhesion was improved from “−1” to “1” when + [Sb]) was 1.0, the film adhesion was not improved in proportion to the total content of Cu and Ni. It was.

  Furthermore, sample no. In C01-C11, sample No. Compared to A01 to A16, the P content was increased, but the point that the film adhesion was lowered by the Sn and Sb content being within the range specified in the present invention was not changed. Sample No. In C01 to C11, the sample No. Compared with A01 to A16, the effect of suppressing the decrease in film adhesion was more remarkable when the Cu and Ni contents were within the range specified in the present invention.

(Example 2)
First, sample No. having the chemical composition shown in Table 2 below. E01-F05 steel was melted in vacuum, cast into a 25 kg ingot, heated to 1150 ° C., and forged into a 40 mm thick steel piece.

  Next, the steel slab was heated under various slab heating conditions shown in Table 2 below (heating temperature at the surface temperature in the heating furnace and oxygen concentration in the heating furnace atmosphere). Next, it was finished to a plate thickness of 2.0 mm by hot rolling. The hot rolling was finished at the hot rolling end temperature of 850 ° C. as the surface temperature. Next, the steel sheet after hot rolling was cooled with water to a surface temperature, held at 650 ° C. for 1 hour, and then air-cooled.

  Next, the air-cooled steel sheet was subjected to hot-rolled sheet tempering that was held at 1000 ° C. for 30 seconds in a nitrogen atmosphere and soaked, and then allowed to cool in the air. Next, the hot-rolled sheet pure steel sheet was pickled and finished to a thickness of 0.20 mm by cold rolling. Next, after the cold-rolled steel sheet was degreased, it was subjected to finish tempering that was held at 1000 ° C. for 10 seconds in a nitrogen-hydrogen mixed atmosphere and soaked. Next, an organic-inorganic composite coating liquid was applied to the surface of the steel plate after finish tempering and baked to form an insulating film having a thickness of 0.3 μm.

  About the non-oriented electrical steel sheet thus obtained, the ratio of the total concentration of Cu and Ni to the total concentration of Sn and Sb on the surface of the base steel plate (([Cu] + [Ni]) / ([Sn] + [Sb ])) Was calculated from the concentration [X] [mass%] of the element X (X = Cu, Ni, Sn, Sb) on the surface of the mother steel plate by glow discharge optical emission spectrometry (GDS). The results are shown in Table 2 below.

  Moreover, the 1st peeling test was done with respect to the insulating film formed in the mother steel plate surface in the non-oriented electrical steel plate obtained in this way. In the first peel test, after bending 180 degrees so as to be wound around a stainless steel rod with a diameter of 10 mm, and then peeling the cellulosic tape on the surface of the bent steel sheet (the inner surface when bent), the presence or absence of peeling of the insulating coating was visually observed. The ratio of the area from which the insulating coating was peeled was measured as the peel rate [%]. Further, as a result of the first peeling test, the non-oriented electrical steel sheet having no peeling of the insulating film was subjected to a heat treatment held at 600 ° C. for 2 hours in a nitrogen atmosphere and then subjected to the second peeling test. It was. Also in the second peel test, the insulation film was peeled off and peeled after the cell tape was bent 180 degrees so as to be wound around a stainless steel rod having a diameter of 10 mm, and the cell surface was peeled back (the inner surface when bent). [%] Was evaluated visually. Thereby, the film adhesion of the insulating film formed on the mother steel plate surface was evaluated. The results are shown in Table 2 below. The evaluation criteria for the coating adhesion of the insulating coating formed on the surface of the mother steel plate are as described above.

Moreover, a JIS No. 5 tensile test piece was collected from the non-oriented electrical steel sheet thus obtained, and a tensile test was performed to evaluate the yield stress (YS) [MPa]. Further, a 55 mm square single plate test piece was punched from the non-oriented electrical steel sheet thus obtained, and the iron loss W _10/400 [W / kg] (maximum magnetic flux at 400 Hz) was measured using a single plate magnetometer. The average value of the iron loss in the rolling direction and the iron loss in the direction perpendicular to the rolling in the case of alternating excitation at a density of 1.0 T was measured. The results are shown in Table 2 below.

  As shown in Table 2 above, Sample No. In E01, E02, and F01, when the oxygen concentration in the slab heating condition is less than 2% by volume, ([Cu] + [Ni]) / ([Sn] + [Sb]) is lowered, and the film adhesion Decreased. This is presumably because the effect of increasing the concentration of Cu and Ni on the slab surface was not obtained due to the low oxygen concentration.

As shown in Table 2 above, Sample No. In E05 and F05, the iron loss W _10/400 increased when the heating temperature in the slab heating condition exceeded 1250 ° C. This is presumably because the heating temperature was high, so that the sulfide in the slab was dissolved and finely precipitated during hot rolling to deteriorate the iron loss.

Claims (3)

By mass%, C: 0.004% or less, Si: 2.0% or more and 4.0% or less, Al: 2.0% or less, Mn: 0.05% or more and 4.0% or less, S: 0.00. 005% or less, N: 0.004% or less, P: 0.20% or less, Sn: 0.005% or more and 0.2% or less, Sb: 0.005% or more and 0.2% or less, Cu: 0. 2.0% 02% inclusive, Ni: contained 0.02% or more and 1.0% or less, have a base steel having a chemical composition the balance being Fe and unavoidable impurities, Cu in the base steel surface A non-oriented electrical steel sheet, wherein the concentrations of Ni, Sn, and Sb satisfy the following formula (1):
([Cu] + [Ni]) / ([Sn] + [Sb])> 1.0 (1)
(Here, [X] in the formula represents the concentration of element X on the surface of the base steel plate expressed in mass%.)
A non-oriented electrical steel sheet characterized by that.   The non-oriented electrical steel sheet according to claim 1, wherein the Al content is 0.010% or less by mass. A method for producing a non-oriented electrical steel sheet for producing the non-oriented electrical steel sheet according to claim 1 or 2,
The slabs having the chemical composition, the slab heating step of heating to a temperature of 1000 ° C. or higher 1250 ° C. or less in a heating furnace the oxygen concentration to 2% by volume or more in the heating furnace atmosphere,
Hot-rolling the slab after heating, water-cooling after the final rolling pass, and winding in a coil shape at a temperature of 650 ° C. or less; and
Hot-rolled sheet annealing / pickling process for subjecting the hot-rolled steel sheet obtained by the hot rolling process to hot-rolled sheet annealing and pickling,
A cold rolling process for cold rolling the hot rolled annealed sheet obtained by the hot rolled sheet annealing / pickling process;
A finish annealing step of subjecting the cold-rolled steel sheet obtained by the cold rolling step to finish annealing;
A method for producing a non-oriented electrical steel sheet, comprising: