JP2009102739A - Method for producing non-oriented magnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a non-oriented magnetic steel sheet having high ä100} integrating degree, improving magnetic flux density and reducing core loss. <P>SOLUTION: In the method for producing the non-oriented magnetic steel sheet having ≥3 random ratio of ä100} integrating degree at the center part in the sheet thickness; the steel composed of ≤0.01% C, 0.05-1% Si, 0.01-1% Mn, ≤0.15% P, ≤0.003% Al, ≥10 Mn/S and further, 0.43 of constitutional weight ratio [MnO/SiO<SB>2</SB>] of MnO and SiO<SB>2</SB>in the oxide series inclusion in the steel, is finish-rolled in the α phase range of ≥700°C by making a coefficient of friction between the steel and the roll, to ≤0.2, and continuously annealed at the α zone of ≥800°C. Further, a cold-rolling at ≤50% and the continuous annealing can be applied. Then, it is desirable that after adding Mn into the molten steel in a vacuum treating vessel, the component adjustment is performed by applying the vacuum-treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties widely used as an iron core of electrical equipment.

  Non-oriented electrical steel sheets have less magnetic anisotropy in the plane than directional electrical steel sheets, and are widely used for motor cores, small transformer cores, and the like. In order to increase the efficiency of these devices, magnetic steel sheets are required to be improved in magnetic properties such as low iron loss and high magnetic flux density.

  Conventionally, improvement of the magnetic properties of non-oriented electrical steel sheets has been achieved by increasing the content of alloy elements such as Si to increase the specific resistance of the steel and reducing iron loss, and reducing the impurities in the steel to produce crystal grains. There has been a focus on ways to improve growth. However, increasing the Si content tends to lower the magnetic flux density, so that there is a limit to high alloying, and the method for improving the growth of crystal grains has almost reached its limit. As a remaining method for improving the magnetic characteristics, a method of improving the texture and improving the magnetic flux density is considered.

  The texture of the non-oriented electrical steel sheet is a texture in which {100}, which is the crystal plane having the most <100>, which is the easy axis of crystal, is accumulated in parallel to the steel sheet surface (hereinafter simply referred to as “{100 } Texture) is ideal, and some implementation methods have been disclosed so far.

  There is a method using a columnar crystal structure that develops when steel solidifies. In this method, steel is cut out from a steel ingot having columnar crystals manufactured by a special casting method so that {100} is parallel to the plate surface, and annealed at a temperature of 1000 ° C. or higher. Although this concept can be applied to a method such as strip casting that has recently been put into practical use, it is not mass-productive, has a high cost, and cannot achieve a high degree of integration of <100>.

  There is a method in which a silicon steel sheet having a thickness of 0.15 mm or less is annealed at 1000 ° C. or more in a weak oxidizing atmosphere, and the {100} texture is increased by utilizing the difference in surface energy depending on the crystal orientation. In this method, after the crystal grains are once grown to a size of about the plate thickness, the crystal grains having {100} parallel to the plate surface are preferentially grown using the difference in surface energy as a driving force. However, in order to utilize the difference in surface energy, the thickness of the steel sheet needs to be 0.2 mm or less, and the box annealing to be heated to a high temperature of 1000 ° C. or higher is indispensable, so the productivity is not good.

  Patent Document 1 (U.S. Pat. No. 3,163,564 (1964)) discloses that {100} by rolling a silicon steel to which a small amount of Al or the like is added in an orthogonal direction (cross rolling) and performing a final annealing at a high temperature for a long time. A method for secondary recrystallization of <001> oriented crystal grains is disclosed. However, this method is also inferior in productivity and inferior in economic efficiency, like the method using the surface energy described above.

In Patent Document 2 (Japanese Patent Laid-Open No. 53-31515), a steel sheet that does not essentially contain C is heated to a γ single-phase region, and then gradually cooled to the A ₁ transformation point. Discloses a method of accumulating {100} in parallel to the plate surface. However, in this method, the strength of the X-ray integrated intensity of the {100} texture (hereinafter simply referred to as “{100} integration degree”) is low.

  Patent Document 3 (Japanese Patent Laid-Open No. 1-319632) discloses that a cold rolled steel strip containing Si, C, and N is decarburized and denitrified and annealed in a specific temperature range to increase the {100} accumulation degree. A method for producing a silicon steel sheet is disclosed. In this method, the {100} integration degree is 15 times or more compared to the {100} integration degree of the material having no orientation (hereinafter, simply referred to as “random ratio”). Annealing is necessary, resulting in poor productivity and high price.

  In Patent Document 4 (Japanese Patent Laid-Open No. 9-194939), a raw material of a non-oriented electrical steel sheet is hot-rolled into a coil shape and then wound into a coil shape. A method of manufacturing a hot rolled electrical steel sheet having a thickness of 1 mm or less to be finish-rolled is disclosed. This method is a method that can be manufactured at low cost because there is no cold rolling process, but the effect of improving the magnetic properties is insufficient.

  Precipitates such as fine AlN in non-oriented electrical steel sheets and non-metallic inclusions finely crushed by cold rolling inhibit the growth of crystal grains when annealing cold-rolled steel sheets, and magnetic It is known to cause the improvement of characteristics.

  In Patent Document 5 (Japanese Patent Application Laid-Open No. 63-195217), in order to eliminate such adverse effects of non-metallic inclusions, among the oxides of various compositions constituting oxide inclusions in steel, MnO Discloses a non-oriented electrical steel sheet excellent in magnetic properties with a weight ratio of 15% or less. In the present invention, if the weight ratio of MnO exceeds the above range, the softening point of inclusions is lowered and extended during rolling, which hinders crystal grain growth during annealing. However, even these methods have insufficient magnetic properties, and there are points to be improved in economy.

  In the above invention, as a method of reducing the weight ratio of MnO, a larger amount of Fe—Mn alloy than before is added at the time of steel leaving the converter to strengthen deoxidation of the molten steel by Mn. However, at the time of steel leaving the converter, the oxygen content in the molten iron is high, and since slag and steel are in a state of being strongly stirred, Mn is easily oxidized and easily transferred to slag. For this reason, the yield of Mn is poor and the component adjustment cannot be performed sufficiently. This method requires adjustment of the Mn component again after deoxidation with Al, so that it is not economical, and MnO is newly generated by addition of Mn at the end of refining.

  As described above, the non-oriented electrical steel sheet having a {100} texture disclosed so far does not have a sufficient {100} integration degree, and its manufacturing method lacks efficiency and economy. It was a problem.

U.S. Pat. 3163564 (1964) JP-A-53-31515 JP-A-1-319632 JP-A-9-194939 JP 63-195217 A

  The problem to be solved by the present invention is to provide a non-oriented electrical steel sheet having a high {100} degree of integration and greatly improving not only the magnetic flux density but also its iron loss and its inexpensive manufacturing method.

  The gist of the present invention resides in the method for producing a non-oriented electrical steel sheet described in (1) to (3) below.

(1) Chemical composition is% by weight, C: 0.01% or less, Si: 0.05-1%, Mn: 0.01-1%, P: 0.15% or less, S: 0.035 % Or less, Al: 0.003% or less, B: 0 to 0.01%, one or two of Sb and Sn in total 0 to 0.3%, total oxygen: 0.02% or less, The balance is steel composed of Fe and unavoidable impurities, the ratio of the Mn and S content in the steel is Mn / S of 10 or more, the weight of MnO and SiO _{2 in} the oxide inclusions present in the steel Hot rolling finish rolling of steel having a ratio MnO / SiO ₂ of 0.43 or less is performed under the condition that the friction coefficient between the steel and the roll is 0.2 or less and the rolling end temperature is an α phase region of 700 ° C. or more. A hot rolled steel sheet having a thickness of 1.0 mm or less, which is pickled and continuously annealed in an α phase region of 800 ° C. or higher. Method for producing a non-oriented electrical steel sheet integration of {100} of the central portion is 3 or more at random ratio.

(2) Chemical composition is% by weight, C: 0.01% or less, Si: 0.05-1%, Mn: 0.01-1%, P: 0.15% or less, S: 0.035 % Or less, Al: 0.003% or less, B: 0 to 0.01%, one or two of Sb and Sn in total 0 to 0.3%, total oxygen: 0.02% or less, The balance is steel composed of Fe and unavoidable impurities, the ratio of the Mn and S content in the steel is Mn / S of 10 or more, the weight of MnO and SiO _{2 in} the oxide inclusions present in the steel Hot rolling finish rolling of steel having a ratio MnO / SiO ₂ of 0.43 or less is performed under the condition that the friction coefficient between the steel and the roll is 0.2 or less and the rolling end temperature is an α phase region of 700 ° C. or more. The hot-rolled steel sheet having a thickness of 1.0 mm or less is cold-rolled at a reduction rate of 50% or less and annealed in the α phase region of 800 ° C. or more. Method for producing a non-oriented electrical steel sheet integration of {100} of the thickness center portion is 3 or more in a random ratio, wherein Rukoto.

(3) Mn is added to the molten steel in the vacuum treatment tank, and then vacuum treatment is performed to adjust C in the molten steel to 0.0005 to 0.01 wt% and free oxygen to 0.01 to 0.04 wt%. The steel is manufactured from molten steel obtained by adding Al and Si to control the chemical composition and oxide inclusion composition of the steel, and hot rolling the steel as described in (1) or (2) above. Method for producing an electrical steel sheet.
The present inventors paid attention to the usefulness of the {100} texture generated during hot rolling, and conducted detailed research on a method for stabilizing and further strengthening it, and obtained the following new findings.

  In general, a {100} texture is formed as a rolling texture at the center of the thickness of a hot-rolled steel sheet. However, since the {110} texture is strongly formed in the steel sheet surface layer due to shear deformation by the rolling roll, the range in which the {100} orientation is formed is only about ½ of the total thickness. The {100} texture itself is also unstable. For this reason, in the conventional hot-rolled steel sheet, even if a {100} texture is formed at the center of the steel sheet, it has been difficult to utilize this for improving the magnetic properties of the entire steel sheet. When hot rolling is performed with sufficient lubrication between the steel sheet and the roll during hot rolling, the development of {110} texture in the steel sheet surface layer portion is suppressed and the {100} accumulation degree in the center portion of the plate thickness is increased. A region with a high {100} integration degree is expanded from the center of the plate thickness to the surface direction. Furthermore, in the steel in which the ratio of MnO is reduced in the constituent composition of oxide inclusions, the {100} texture generated by the above-described lubrication hot rolling is further strengthened and can be stably maintained.

  Further, normally, when recrystallization annealing is performed after rolling, {111} texture develops and {100} accumulation degree decreases, whereas the hot rolled steel sheet obtained by the above-described method of the present invention is appropriately annealed. When applied, the {100} texture becomes extremely stable, and even after annealing, the {100} texture is sufficiently maintained, and conversely, the {111} texture becomes weak.

  In addition, the composition of inclusions can be controlled economically and easily by performing vacuum processing of molten steel and deoxidizer addition method for steelmaking operations, particularly decarburization as the main purpose, under specific conditions. The present invention has been completed based on these findings.

  The non-oriented electrical steel sheet obtained by the production method of the present invention is an electrical steel sheet having a very good magnetic property with a high magnetic flux density in which a {100} texture is developed at the center of the thickness. This non-oriented electrical steel sheet is excellent in economic efficiency because it has good magnetic properties even if it is not cold-rolled. Even better if cold rolled. For this reason, it is extremely suitable as an iron core of a high-performance electric machine having excellent versatility. According to the production method of the present invention, the composition can be stably controlled. Furthermore, since it is the method of carrying out lubrication rolling and continuous hot rolling, the non-oriented electrical steel sheet which has an unprecedented high magnetic flux density can be manufactured efficiently and stably stably.

  Hereinafter, embodiments of the present invention will be described in detail. First, the composition of steel used in the method of the present invention will be described. In addition, the% display of the chemical composition described below means weight%.

(A) Chemical composition of steel C: Since the magnetic properties are deteriorated, the smaller the steel product, the better. The C content is limited to 0.01% or less as a limit at which no significant adverse effects appear on the magnetic properties.

  Si: In addition to the action of deoxidizing steel, it has the action of increasing the electrical resistance of steel and reducing eddy current loss. In this invention, in order to deoxidize steel and to reduce iron loss, 0.05% or more of Si is contained. However, since the magnetic flux density decreases as the Si content increases, the upper limit of the Si content is 1% in order to ensure a sufficient magnetic flux density even for the purpose of reducing iron loss.

  Mn: 0.05% or more of Mn mainly for the purpose of deterring cracks (hot brittleness) during hot rolling caused by FeS and detoxifying MnS coarsely and making it harmless to crystal grain growth, And it is made to contain so that Mn / S may become 10 or more. Since Mn has an action of increasing the electric resistance of steel and reducing iron loss, it may be contained for the purpose of reducing iron loss. However, since Mn is expensive and its effect on reducing iron loss is smaller than that of Si, the upper limit of its content is 1%.

  P: P is an inexpensive element and may be contained because it has the effect of increasing the electrical resistance of steel and reducing iron loss and the effect of hardening steel and improving punchability. However, if excessively contained, the steel becomes brittle and rolling becomes difficult, so even if it is included, the content is made 0.15% or less.

  S: In addition to causing hot brittleness of steel, sulfide inclusions are formed and the magnetic properties are impaired. On the other hand, S has the effect of improving the punchability and machinability of the steel sheet. For this reason, when importance is attached to the magnetic characteristics, the content is preferably 0.006% or less. When emphasizing punchability and machinability, the content is preferably 0.015% or more and 0.035% or less.

  Al: Since it has a deoxidizing action of molten steel, it may be used as a deoxidizing agent. Most of the deoxidized product resulting from deoxidation using Al floats up and is removed from the molten steel, but the remainder remains in the steel as oxide inclusions. It is easy to form fine precipitates such as AlN. As these oxides and nitrides increase, it becomes an obstacle to crystal grain growth and domain wall movement, so it is preferable that Al is less. For this reason, the content of Al is set to 0.003% or less.

  B: Although not an essential element, the formation of {111} texture is suppressed during recrystallization during hot rolling or annealing after cold rolling, and the formation of {100} texture is promoted Since it is effective, it may be contained. In that case, it is effective to contain 0.0002% or more. However, if excessively contained, grain growth after completion of recrystallization is suppressed and iron loss is worsened, so the upper limit is preferably made 0.01%.

  Sb and Sn: Although not essential elements, both elements have the effect of suppressing the formation of {111} oriented recrystallized nuclei from the grain boundaries during steel recrystallization. Moreover, it has the effect | action which accelerates | stimulates the production | generation of a deformation zone and increases the recrystallization nucleus of {411} direction at the time of cold rolling. Since {411} is an orientation close to the {100} orientation, it contributes to improvement of the in-plane average magnetic characteristics. For this reason, in order to further improve the magnetic characteristics, it is effective to contain one or two of Sb and Sn in a total amount of 0.005% or more. However, if it is excessively contained, the steel becomes brittle and rolling becomes difficult, so the upper limit in the case of inclusion is preferably 0.3%.

  Total oxygen: Total oxygen consists of free oxygen (oxygen dissolved in the steel) and oxygen present as inclusions, and is determined by chemical analysis. There is little free oxygen in the steel sheet, and most of it exists as oxygen in inclusions. For this reason, increasing the total oxygen content of the steel means increasing inclusions. In order to suppress the total amount of oxide inclusions, the upper limit of the total oxygen content in the steel sheet is set to 0.02%.

  The steel plate obtained by the production method of the present invention is composed of Fe and inevitable impurities except for the above. Note that the N content as an unavoidable impurity is desirably 0.005% or less because there is a possibility that Si-Mn-N-based fine precipitates are generated due to the presence of Si and Mn. More desirably, it is 0.003% or less.

(B) Oxide inclusions The inclusions observed in the electrical steel sheet having a low Al content are mainly oxide inclusions mainly composed of SiO ₂ and MnO. When the ratio of MnO in the inclusions increases, the softening temperature of the inclusions decreases and the inclusions are easily stretched during hot rolling. Increasing inclusions stretched in the rolling direction impairs the degree of {100} texture accumulation at the center of the plate thickness after hot rolling, as well as the grain growth that occurs during and after hot rolling. Inhibits and prevents improvement of magnetic properties such as iron loss. In order to eliminate such adverse effects due to the oxide inclusions, the weight composition ratio of MnO to SiO ₂ constituting the oxide inclusions (MnO / SiO ₂ , hereinafter simply referred to as “MnO ratio”) is set to 0. 43 or less. The lower the MnO ratio, the better. However, if the ratio to SiO ₂ is 0.43 or less by weight, the above-mentioned harmfulness is greatly reduced. The MnO ratio is obtained by analyzing inclusions by an extraction / separation quantitative method using an iodine-methanol method.

(C) {100} degree of integration The higher the {100} degree of integration of the steel sheet, the easier the steel sheet is magnetized and the better the magnetic properties. In the non-oriented electrical steel sheet obtained by the production method of the present invention, the {100} integration degree in the center part of the plate thickness is 3 or more in a random ratio in order to increase the magnetic flux density and improve the magnetic properties. Preferably it is 5 or more, More preferably, it is 7 or more.

For example, the texture of the steel plate thickness center portion is obtained by removing one side of the steel plate to the plate thickness center portion by a method such as chemical polishing to obtain a sample having the plate thickness center portion as a measurement surface, which is subjected to X-ray diffraction. Measured by a method such as The random ratio can be easily obtained by using the {100} X-ray integral intensity of this measured value and a material having no orientation.
The steel plate obtained by the production method of the present invention also has a better {100} integration degree in the surface layer portion of the steel plate than the conventional one. If the steel sheet has a plate thickness central portion with a random ratio of 3 or more, a good degree of integration of 1 or more can be expected in the surface layer portion, and if the plate thickness center portion has a random ratio of 7 or more, a good integration degree of 3 or more can be expected. The degree of integration of the steel plate surface layer portion is measured after removing the outermost surface by a method such as a chemical polishing method by a thickness of about 10 μm in order to remove the uneven deformation portion of the outermost surface of the steel plate that occurs during rolling.

  The steel sheet according to the production method of the present invention is produced by treating molten steel melted in a converter or an electric furnace, casting it by a continuous casting method, etc., and hot rolling.

(D) Treatment of molten steel The treatment method of molten steel is not particularly limited, and the molten steel is vacuum-treated by a known method that is usually performed, and deoxidized with Al, Si, Mn, etc., and the final target The chemical composition may be adjusted to For example, the RH method or the VOD method is suitable for the vacuum processing. Molten steel adjusted to a predetermined chemical composition is cast into a slab. Although the casting method and conditions are arbitrary, it is good to make a slab using a well-known continuous casting method. In addition, it is preferable to perform a molten steel process with the following method.

Mn addition:
The Mn source is usually added at the time of steel output from the converter or after vacuum processing in a vacuum processing tank. However, after the molten steel melted in the converter or electric furnace is transferred to the vacuum processing tank, the amount required to finally become the target component of the steel sheet is predicted and the required Mn source before vacuum processing Is preferably added. If added after moving the molten steel into the RH treatment tank, there is almost no stirring with the slag, so Mn is oxidized and transferred to slag compared to the conventional method of adding a Mn source at the time of steel leaving the converter. There is little and the yield of Mn is good.

  Since the Mn source is introduced before the vacuum treatment, the oxygen content of the molten steel is high, and a part of Mn becomes Mn oxide and moves into the slag. However, as will be described later, when Al and Si are added after the vacuum treatment, MnO in the slag is dissociated and returned to the molten steel as metal Mn. Thereby, Mn content is adjusted to a target ingredient. Since the Mn source is added with little stirring with the slag, the MnO is increased in the slag only in the portion where the slag is in contact with the molten steel. For this reason, Mn is easily reduced by subsequent deoxidation. This is one of the reasons why Mn can be easily adjusted by the above-described method.

  If the Mn content is adjusted by such a method, the Mn content is gradually increased from a low state, so that MnO is hardly generated in the inclusions. Further, it is not necessary to supply a Mn source for adjusting the Mn component after vacuum treatment and Al deoxidation, which is a cause of the increase in the MnO ratio in the inclusions, and a target inclusion composition can be realized.

Vacuum processing:
After adding Mn to the molten steel, the ultimate vacuum and treatment time are controlled under reduced pressure to adjust the C content and free oxygen (oxygen dissolved in the molten steel) content in the molten steel. The decarburization reaction proceeds based on the relationship that “the solubility product of C and O in molten steel is constant according to the degree of vacuum”. The C content in the molten steel is controlled in the range of 0.0005 to 0.01%, desirably 0.002 to 0.005%. When the C content in the molten steel exceeds 0.01%, the final C content of 0.01% or less cannot be realized. Moreover, when less than 0.0005%, the free oxygen in molten steel will exceed 0.04%.

  Free oxygen in the molten steel is adjusted to a range of 0.01 to 0.04%. If this amount exceeds 0.04%, a large amount of inclusions are produced during the subsequent addition of Al and Si, the cleanliness of the steel sheet deteriorates, and the control of the inclusion composition becomes difficult. In addition, manufacturing problems such as nozzle clogging also occur. When free oxygen is less than 0.01%, decarburization becomes insufficient, and the C content of the steel sheet cannot be reduced.

Al, Si addition:
After adjusting C and free oxygen as described above, Al and Si are added. In order to reduce the total oxygen content and to control the composition of inclusions, it is desirable to add Si after adding Al. The purpose of the Al addition is to reduce not only the free oxygen required for decarburization but also the total oxygen content. If the molten steel is appropriately stirred with RH or the like, the total oxygen content can be made 0.006 or less even if the final Al content of the molten steel is 0.003% or less.

  In such a state, Si is added in an amount necessary to realize the target component of the steel sheet. According to this method, the target composition can be easily obtained not only for Si but also for Mn. Furthermore, the composition of inclusions can be controlled to the target composition.

(E) Hot rolling conditions In order to ensure the finish rolling temperature, the slab having the above-described chemical composition can be charged into a heating furnace or locally heated before rolling by a known method. If the heating temperature is lowered, the sulfide inclusions are coarsened and the magnetic properties are improved, so the heating temperature is preferably lowered within a range in which the finish rolling temperature can be secured. The heating temperature is preferably 1200 ° C. or lower, and more preferably 1150 ° C. or lower. If the finish rolling temperature can be secured, heating before rolling may be omitted to reduce manufacturing costs.

  The above slab is subjected to rough rolling according to a conventional method and then finish rolling. For a thin slab (thin slab), rough rolling may be omitted and finish rolling may be performed. The steel slab or thin cast slab after the rough rolling is once wound in a coil shape before the finishing mill and kept warm, or by using a heat retaining device or a heating device provided in front of the finishing mill or between stands. You may perform processes, such as preventing an effect.

  In finish rolling, it is preferable to perform rolling with lubrication so that the friction coefficient between the steel and the rolling roll is 0.2 or less. When the friction coefficient between the steel and the roll is increased, the shearing region of the steel plate surface layer portion is expanded, and the {110} texture is formed much stronger in the surface layer portion than {100}. For this reason, the {100} texture formed in the central portion of the plate thickness becomes weak, and the effect of improving the magnetic properties of the entire steel plate is not great.

  When lubricated and rolled so that the friction coefficient is 0.2 or less, shear deformation at the surface layer portion of the steel sheet is suppressed, the {110} accumulation degree at the surface layer part is weakened, and the {100} accumulation degree at the steel sheet center part is reduced. As the height increases, the region indicating the {100} texture is enlarged in the surface direction. The friction coefficient can be obtained by a commonly used method, for example, a method of calculating backward from the advanced rate.

  The friction coefficient may be set to 0.2 or less by applying a known rolling lubricant such as a synthetic ester to a steel sheet surface or a roll surface during hot rolling by a known method such as spraying. Hot lubrication is preferably performed at all rolling stands during finish rolling, but the friction coefficient may exceed 0.2 for the first stand of the finishing mill and the stand where the rolling reduction is less than 10%. This is because in the first stand, since the plate thickness is thick, the adverse effect of shear deformation is small, and if it is lubricated too much, the biting into the rolling roll may become unstable. If the rolling reduction is less than 10%, the adverse effect is slight even if the lubrication is not sufficient.

  The slab having the above chemical composition is hot-rolled to a thickness of 1 mm or less by the above-described method. The iron loss of the electromagnetic steel sheet is affected by the plate thickness, and if the thickness exceeds 1 mm, the iron loss becomes worse, which is not preferable.

  The finish rolling finishing temperature (finishing temperature) of the hot rolling is preferably set to a temperature range that becomes an α phase region of 700 ° C. or higher. When the steel is transformed after finish rolling, the texture is destroyed. Moreover, in order to prevent the shape defect at the time of steel plate rolling, the final reduction of finish rolling is preferably performed in the α phase region.

  In the production method of the present invention, the {100} texture at the center of the thickness obtained by rolling is stabilized and strengthened by recrystallization simultaneously with rolling. When the finishing temperature is less than 700 ° C., recrystallization during rolling becomes insufficient, so that the strengthening of {100} accumulation degree obtained by hot rolling becomes insufficient. For this reason, the finishing temperature is preferably 700 ° C. or higher.

  Although the coiling temperature after completion | finish of rolling is not specifically limited, In order to obtain a favorable texture, it is preferable to set it as the range of 500-750 degreeC.

(F) Hot-rolled sheet annealing Grows {100} -oriented crystal grains formed in the center of the plate thickness, increases the degree of integration and improves the magnetic flux density, and reduces the iron loss by reducing the hysteresis loss. In order to improve, it is desirable to anneal the hot rolled steel sheet. This annealing needs to be performed in a temperature range that does not cause γ transformation. Moreover, the higher the annealing temperature, the more the growth of crystal grains is promoted. For these reasons, the hot-rolled sheet annealing is preferably performed in an α phase region of 800 ° C. or higher. The upper limit of the annealing temperature is not particularly limited, but the upper limit is preferably 1100 ° C., which can be satisfactorily annealed by the continuous annealing method described below.

  The annealing method is preferably a continuous annealing method because high-temperature annealing is easy and the flat shape of the steel sheet can be kept good. The annealing time may be 10 seconds or more. It is desirable to carry out pickling according to a conventional method before annealing. Further, before annealing, skin pass rolling or the like may be performed according to a conventional method in order to adjust the flatness and surface roughness of the steel sheet. Furthermore, it is desirable to apply an insulating coating according to a conventional method after annealing.

(G) Cold rolling and annealing The above-mentioned hot-rolled steel sheet can be used as a non-oriented electrical steel sheet in that state. However, since it is a hot-rolled product, plate thickness accuracy and flat shape may not be preferable. In such a case, it is preferable to cold-roll and anneal the hot-rolled sheet and use it as a cold-rolled non-oriented electrical steel sheet.

  If the hot-rolled steel sheet is annealed prior to cold rolling, the {100} texture can be stabilized and further improved magnetic properties can be maintained when cold rolling and annealing are performed thereafter. preferable. In this case, annealing of the hot-rolled sheet is sufficient if crystal grain growth occurs. Therefore, the annealing temperature is preferably set to an α phase region of 600 ° C. or higher. The upper limit of annealing temperature should just be 1100 degrees C or less. The annealing method may be either continuous annealing or box annealing.

  The rolling reduction during cold rolling is preferably 50% or less. If it exceeds 50%, the accumulation degree of {111} texture becomes strong after annealing, which is not preferable. Preferably it is 20% or less. The lower limit of the cold rolling reduction is not particularly limited, but is preferably 0.5% or more in order to improve the plate thickness accuracy and the flat shape. More preferably, it is 1% or more.

  After cold rolling, annealing is performed to grow {100} oriented crystal grains to increase the {100} integration degree and to improve the magnetic flux density and iron loss. The higher the annealing temperature is, the more the growth of crystal grains is promoted. Therefore, the higher the annealing temperature is better, but it is necessary to carry out in a range not causing the γ transformation. For this reason, annealing is preferably performed in an α phase region of 800 ° C. or higher. The upper limit of the annealing temperature is not particularly limited, but the upper limit is preferably 1100 ° C., which can be annealed satisfactorily by the continuous annealing method. The annealing method is preferably a continuous annealing method that facilitates high-temperature annealing and can keep the flat shape of steel good. After the annealing, it is desirable to apply an insulating coating according to a conventional method.

  Non-oriented electrical steel sheets are manufactured on the premise that the steel sheet manufacturer performs finish annealing, and the user side uses the full process material that is used without annealing, and the user performs annealing after punching. However, the non-oriented electrical steel sheet of the present invention is suitable in any of these cases.

(Example 1)
Thirteen types of steel shown in Table 1 were manufactured in a converter-RH-continuous casting process.

  These steels were melted in a converter, the molten steel was subjected to vacuum processing using an RH vacuum processing apparatus, and after adjusting the amount of C and free oxygen in the molten steel, Al and Si were added.

  Steels A to G, L, and M added an Fe—Mn alloy to the molten steel in the RH tank before the vacuum treatment. Steel H is divided into two times when steel is removed from the converter, Steel I is divided into two times after completion of the vacuum treatment in RH, and Steels J and K are divided into two times after removal from the converter and after completion of the vacuum treatment in RH. A required amount of Fe—Mn alloy was added to adjust the Mn content.

  The molten steel is continuously cast into a slab, charged into a heating furnace, heated to 1180 ° C., roughly rolled into a steel piece with a thickness of 30 mm, and then with a continuous hot finish rolling mill, the thickness is 0.52 mm. A hot-rolled steel sheet was obtained. At the time of finish rolling, the synthetic ester oil was sprayed on the work rolls of the respective stands by spraying and lubricated. The coefficient of friction between the steel plate and the roll was measured by a known method obtained by calculating back from the advanced rate, and the value was 0.14. The finishing temperatures were 800 to 810 ° C., and the winding temperature was 660 to 680 ° C. These steel plates were cooled, pickled, skin pass rolled, rolled to 0.50 mm, and subjected to continuous annealing held at 900 ° C. for 1 minute. Then, the surface insulation coating which consists of a composite composition containing the organic component and inorganic component similar to a normal non-oriented electrical steel sheet was given.

From these steel plates, an X-ray diffraction test piece having a length of 25 mm and a width of 25 mm and a ring sample for measuring magnetic properties having an outer diameter of 45 mm and an inner diameter of 33 mm are punched out, and both are equivalent to continuous annealing held at 900 ° C. for 1 minute. Heat treatment was applied. The X-ray diffraction test piece was removed by chemically polishing one side to the center of the plate thickness, and the center of the plate thickness was X-ray diffracted to measure the {100} plane reflection integral intensity. Using a ring sample for measuring the magnetic flux density, the magnetic flux density (B ₅₀ ) and the saturation magnetic flux density (B _S ) at a magnetizing force of 5000 A / m were measured. Since the saturation magnetic flux density varies depending on the chemical composition of the steel, B ₅₀ / B _S was obtained, and the easiness of magnetization of steels having different chemical compositions was comparatively evaluated. In addition, the oxide inclusion composition of the steel sheet was determined by analysis by an extraction separation quantification method using a bromine-methanol method. The MnO ratio of the steel sheet is shown in Table 1, and the {100} integration degree and magnetic property measurement results are shown in Table 2.

  As shown in Table 2, steels A to G having a chemical composition and MnO ratio within the range defined by the present invention and having a random ratio of 3 or more had low iron loss and good magnetic flux density. In contrast, steel H has a chemical composition within the scope of the present invention, but has a high MnO ratio, steel I has a high oxygen content and a high MnO ratio, and steel J has a chemical composition within the scope of the present invention. However, since the MnO ratio is high and the S content of steel K is also high, the random ratio is inferior and the iron loss and magnetic flux density are not good. Steel M was unfavorable in magnetic properties due to its high total oxygen content. Steel L was too high in P content, causing cracks during skin pass rolling, and abandoned the subsequent treatment.

(Example 2)
A steel piece having a thickness of 30 mm obtained by rough rolling a slab having the same chemical composition as that of steel C described in Example 1 is lubricated in the same manner as in Example 1 and hot finish-rolled. A hot rolled steel sheet having a thickness of 0.7 mm was obtained while being variously changed, and wound at 600 ° C. Some slabs were rolled to 0.7 mm without lubrication. It was pickled after hot rolling and cold rolled to a thickness of 0.6 mm according to a conventional method. From these cold-rolled steel plates, a 25 mm long and 25 mm wide X-ray diffraction specimen and a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm were punched out and subjected to a heat treatment equivalent to continuous annealing held at 950 ° C. for 1 minute. . Thereafter, the X-ray diffraction test piece was removed by chemical polishing of one side to the center of the plate thickness, and the central portion of the plate thickness was X-ray diffracted to measure the {100} plane reflection integral intensity as in Example 1. did. Moreover, the magnetic flux density ( _B50 ) was measured using the ring test piece. These results are shown in Table 3 together with hot rolling conditions.

As shown in Table 3, Run No. 1-4 was hot-rolled at preferred conditions ranges, {100} integrated intensity is as high as more than 6 times in the randomly ratio, the magnetic flux density B ₅₀ is significantly better is there. On the other hand, in No. 5 in which the finish rolling temperature exceeded the α phase region, the {100} accumulation degree was low because of the γ → α transformation after rolling, and B ₅₀ was not preferable. In trial No. 6, since {100} integral strength was low because it was not lubricated during finish rolling, B ₅₀ was not preferable. In trial No. 7, the finish rolling temperature was too low, so that recrystallization after hot rolling became insufficient, the {100} integral strength was low, and B ₅₀ was not preferable.

(Example 3)
A slab having the same chemical composition as that of Steel C described in Example 1 is roughly rolled, and rolled under the same lubricating conditions as described in Test No. 4 of Example 2 to obtain a finished thickness of 0.53 to 0.00. Changed between 92 mm and hot rolled. The obtained steel sheet was cold-rolled at a reduction rate of 5 to 83% to obtain a steel sheet having a thickness of 0.5 mm, subjected to continuous annealing held at 1000 ° C. for 1 minute, and the same as described in Example 2 In this method, the central portion of the plate thickness was X-ray diffracted to measure {100} plane reflection integral intensity, and B ₅₀ was measured. Table 4 shows the cold rolling reduction and the measurement results.

If less 50% cold rolling reduction, it had sufficient good {100} texture and B _50. In particular, it was good when the cold pressure ratio was 20% or less. In the trial numbers 4 and 5 where the cold pressure ratio exceeded 50%, the {100} integral strength was remarkably lowered, and the obtained B ₅₀ was also low, which was not preferable.

  According to the production method of the present invention, the composition can be stably controlled. Also, since the method of the present invention is a method of lubrication rolling and continuous hot rolling, a non-oriented electrical steel sheet having an unprecedented high magnetic flux density. Can be manufactured efficiently and economically stably. The non-oriented electrical steel sheet produced by the method of the present invention is an electrical steel sheet having excellent magnetic properties, and is excellent in economic efficiency because it has good magnetic properties without being subjected to cold rolling. In addition, if a cold rolling is given, a further characteristic will improve. Therefore, this steel plate is suitable as an iron core for a high-performance electric machine having excellent versatility.

Claims (3)

Chemical composition is weight%, C: 0.01% or less, Si: 0.05-1%, Mn: 0.01-1%, P: 0.15% or less, S: 0.035% or less, Al: 0.003% or less, B: 0 to 0.01%, one or two of Sb and Sn in total 0 to 0.3%, total oxygen: 0.02% or less, balance is Fe And a steel composed of inevitable impurities, wherein the ratio Mn / S of the Mn / S content in the steel is 10 or more, and the weight ratio of MnO to SiO _{2 in} the oxide inclusions present in the steel MnO / Thickness is obtained by finishing hot rolling of steel with SiO ₂ of 0.43 or less under the condition that the friction coefficient between the steel and the roll is 0.2 or less and the rolling end temperature is an α phase region of 700 ° C. or more. Is a hot-rolled steel sheet having a thickness of 1.0 mm or less, which is pickled and continuously annealed in an α-phase region of 800 ° C. or more. Method for producing a non-oriented electrical steel sheet integration degree of {100} is 3 or more at random ratio. Chemical composition is weight%, C: 0.01% or less, Si: 0.05-1%, Mn: 0.01-1%, P: 0.15% or less, S: 0.035% or less, Al: 0.003% or less, B: 0 to 0.01%, one or two of Sb and Sn in total 0 to 0.3%, total oxygen: 0.02% or less, balance is Fe And a steel composed of inevitable impurities, wherein the ratio Mn / S of the Mn / S content in the steel is 10 or more, and the weight ratio of MnO to SiO _{2 in} the oxide inclusions present in the steel MnO / It was obtained by performing hot rolling finish rolling of steel with SiO ₂ of 0.43 or less under the condition that the coefficient of friction between the steel and the roll was 0.2 or less and the rolling end temperature was an α phase region of 700 ° C. or more. A hot-rolled steel sheet with a thickness of 1.0 mm or less is cold-rolled at a reduction rate of 50% or less and annealed in an α phase region of 800 ° C. or more. Method for producing a non-oriented electrical steel sheet integration of {100} of the thickness center portion is 3 or more in a random ratio, wherein.   Mn is added to the molten steel in the vacuum treatment tank, and then vacuum treatment is performed to adjust C in the molten steel to 0.0005 to 0.01 wt% and free oxygen to 0.01 to 0.04 wt%. A method for producing a non-oriented electrical steel sheet according to claim 1 or 2, wherein hot rolling is performed on a steel produced from a molten steel obtained by adding Si and Si to control the chemical composition and oxide inclusion composition of the steel. .