JP2016216779A - Grain oriented magnetic steel sheet and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain oriented magnetic steel sheet having uniform and good magnetic properties and film properties over all sheet width of a coil, and a production method for the grain oriented magnetic steel sheet.SOLUTION: The production method for the grain oriented magnetic steel sheet is provided in which a steel raw material containing, by mass%, C:0.002 to 0.10%, Si:2.0 to 8.0% and Mn:0.005 to 1.0% is hot-rolled, the resulting hot-rolled steel sheet is annealed if needed, then cold-rolled to obtain a cold-rolled steel sheet, the cold-rolled steel sheet is subjected to decarburization annealing under atmosphere in which P/Pis set to be 0.20 to 0.70, an annealing separating agent is applied to cold-rolled steel sheet, then the cold-rolled steel sheet is subjected to final annealing, and thus the grain oriented magnetic steel sheet with an underlayer coated film is produced. In the above production method, an element poor than Fe and noble than Si is electrodeposited on the surface of the cold-rolled steel sheet in an amount of 0.1 to 70 mg/mper a single side during time period between after the final annealing and before the decarburization annealing, and after the electrodeposition, the cold-rolled steel sheet is subjected to the decarburization annealing, so that grain oriented magnetic steel sheet is acquired in which a ratio of strength Ie in a sheet width-direction terminal portion, of the element poor than Fe and noble than Si to strength Ic in a sheet width-direction center portion is 0.7 to 1.3 when the surface of the cold-rolled steel sheet is analyzed by a fluorescent X-ray.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the grain-oriented electrical steel sheet. Specifically, the present invention relates to a grain-oriented electrical steel sheet having excellent magnetic properties and coating properties over the entire width of a product coil and a method for producing the grain-oriented electrical steel sheet.

  Electrical steel sheets are soft magnetic materials that are widely used as iron cores for transformers and motors. Among them, grain oriented electrical steel sheets are highly integrated in the {110} <001> orientation, in which the crystal orientation is called the Goss orientation, Because of its excellent magnetic properties, it is mainly used for iron cores of large transformers. In order to reduce the no-load loss (energy loss) in the transformer, it is necessary to have a low iron loss.

  Methods for reducing the iron loss of grain-oriented electrical steel sheets include increasing the Si content, reducing the plate thickness, improving the orientation of secondary recrystallized grains, refining the secondary recrystallized structure, and tensioning the steel sheet. Application and smoothing of the steel sheet surface are effective. Among the above methods, the method of controlling the secondary recrystallization to improve the orientation of the secondary crystal grains and the method of refining the secondary recrystallization structure include the type and amount of the inhibitor component, cold rolling. It is known that various factors such as rolling reduction, primary recrystallization annealing pattern, and surface state before secondary recrystallization influence.

By the way, as a method for improving the surface state before secondary recrystallization and obtaining good magnetic properties, for example, in Patent Document 1, Cu, Sn is applied to a steel plate surface finished to a final plate thickness by cold rolling. , Co, or Ni is electrodeposited with 0.1 or 70 mg / m ^{2 of} one or more metals or alloys, followed by decarburization annealing, so that there is no defect over the entire length of the coil. A technique for obtaining a grain-oriented silicon steel sheet having a uniform and excellent adhesion and excellent magnetic properties is disclosed.

Patent Document 2 uses a steel slab that does not contain an inhibitor component as a raw material, and is selected from Si, Cu, Sn, Co, and Ni on the steel plate surface prior to primary recrystallization annealing and application of an annealing separator. A technique for obtaining excellent magnetic properties and coating properties by electrodepositing one or two or more kinds of metal-containing materials in a range of 0.1 to 50 mg / m ² in total in terms of the metal element is disclosed.

Furthermore, in Patent Document 3, the steel sheet surface roughness after the final cold rolling is adjusted to an arithmetic average roughness Ra of 0.40 μm or less, and then Si is contained on the steel sheet surface by electrolytic degreasing prior to decarburization annealing. Disclosed is a technique for stably obtaining a high magnetic flux density product even in industrial production by performing a cleaning process to adhere 0.1 mg / m ² or more of electrodeposits to be deposited and then adjusting the atmosphere of decarburization annealing. ing.

JP 09-087744 A JP 2008-144231 A JP 09-031546 A

However, in the technique disclosed in Patent Document 1, secondary recrystallization may become unstable because Cu or Sn penetrates into the steel and forms precipitates during finish annealing. In particular, since secondary recrystallization annealing is batch-annealed in a state of being wound on a coil at a high temperature for a long time, the inner and outer winding portions of the coil, and the end portion and the central portion in the plate width direction, The temperature history is different, and the circulation of the atmospheric gas is also different. Therefore, there is a problem that it is difficult to develop uniform secondary recrystallized grains inside the coil.
Moreover, in the technique disclosed in Patent Document 2, as in Patent Document 1, Cu or Sn penetrates into the steel to form precipitates, and due to non-uniform annealing temperature inside the coil, There is a problem that variations in magnetic characteristics and film characteristics increase.
Furthermore, in the technique disclosed in Patent Document 3, a Si electrodeposit is formed before decarburization annealing, but the Si electrodeposit itself becomes a barrier during decarburization annealing and makes the internal oxidation of SiO ₂ nonuniform. There is. That is, if the cleaning before electrolysis is non-uniform due to a slight change in the electrolytic bath over time, the Si electrodeposit is not uniformly adhered to the plate surface, and the subscale protection becomes non-uniform. As a result, there is a problem that variation in magnetic characteristics in the product coil is increased or unevenness of the coating occurs.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide a grain-oriented electrical steel sheet having uniform and good magnetic properties and coating properties over the entire width of the coil, and its manufacture. Suggest a method.

  The inventors have intensively studied to solve the above problems. As a result, before applying decarburization annealing in an oxidizing atmosphere, a specific metal is electrodeposited on the surface of the steel sheet, and the internal oxide layer formed by the annealing is improved, so that the entire length of the product coil is uniform and The present invention was developed by finding that a grain-oriented electrical steel sheet having good magnetic properties and coating properties can be obtained.

  That is, the present invention is a grain-oriented electrical steel sheet having a forsterite undercoating, wherein the undercoating contains an element that is more base than Fe and noble than Si, and the surface of the undercoating is fluorescent X The directionality characterized in that the ratio (Ie / Ic) of the strength Ie at the end of the plate width to the strength Ic at the center of the plate width of the element when analyzed by a line is in the range of 0.7 to 1.3. It is a magnetic steel sheet.

Moreover, this invention contains C: 0.01-0.08mass%, Si: 2.0-4.5mass%, Mn: 0.02-0.20mass%, Furthermore, Al: 0.010- It contains 0.050 mass% and N: 0.003-0.020 mass%, or Al: 0.010-0.050 mass%, N: 0.003-0.020 mass%, S: 0.005-0 0.030 mass% and / or Se: 0.005 to 0.030 mass%, with the balance being Fe and unavoidable impurities hot-rolled into a hot-rolled sheet, without subjecting to hot-rolled sheet annealing or, after being subjected to hot rolled sheet annealing, once or a final thickness of the cold-rolled sheet by two or more cold rolling sandwiching the intermediate _annealing, and from 0.20 to 0.70 the _P H2O _/ P _H2 Decarburized in an atmosphere In the method for producing a grain-oriented electrical steel sheet consisting of a series of steps in which an annealing separator is applied to the steel sheet surface and finish-annealed, after the final cold rolling to decarburization annealing, than Fe. A method for producing a grain-oriented electrical steel sheet according to the above, characterized in that a base and noble element than Si is electrodeposited in an amount of 0.1 to 70 mg / m ² per side and thereafter decarburization annealing is performed.

Further, the present invention includes C: 0.01 to 0.08 mass%, Si: 2.0 to 4.5 mass%, Mn: 0.02 to 0.20 mass%, Al: less than 0.01 mass%, N: 0 0.005 mass%, S: less than 0.0050 mass%, and Se: less than 0.0050 mass%, with the balance being Fe and inevitable impurities, hot rolled into a hot-rolled sheet, hot-rolled sheet annealed Or after performing hot-rolled sheet annealing, a cold-rolled sheet having a final sheet thickness is formed by cold rolling at least once with intermediate or intermediate annealing, and P _H2O / P _H2 is 0.20 to 0.20. In a method for producing a grain-oriented electrical steel sheet comprising a series of steps in which an annealing separator is applied to the steel sheet surface after finishing decarburizing annealing in an atmosphere of 0.70 and finish annealing is performed after the final cold rolling. Until charcoal annealing, Fe Even nobler element is per side 0.1~70mg / m ² electrodeposited than Si in less noble, thereafter, a method of manufacturing the oriented electrical steel sheet and performing decarburization annealing.

  In addition to the above component composition, the steel material used in the method for producing a grain-oriented electrical steel sheet according to the present invention further includes Ni: 0.010 to 1.50 mass%, Cr: 0.01 to 0.50 mass%, and Cu: 0. 0.01 to 0.50 mass%, P: 0.005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Bi: 0.001 to 0.03 mass %, Mo: 0.005 to 0.100 mass%, B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Nb: 0.0010 to 0.0100 mass%, V: 0.00. 1 type or 2 types or more chosen from 001-0.010mass% and Ta: 0.001-0.010mass% are characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to manufacture stably and provide the grain-oriented electrical steel sheet which has a uniform and favorable magnetic characteristic and film characteristic over the whole board width of a product coil.

It is a graph which shows the influence which the amount of Zn electrodeposition has on a magnetic characteristic and film adhesiveness.

First, an experiment that triggered the development of the present invention will be described.
Steel containing C: 0.065 mass%, Si: 3.44 mass%, Mn: 0.08 mass%, Al: 0.03 mass% and N: 0.008 mass%, and a steel slab by a continuous casting method After that, it was reheated to 1410 ° C., hot-rolled to obtain a hot-rolled sheet having a thickness of 2.4 mm, subjected to hot-rolled sheet annealing at 1050 ° C. × 60 seconds, and then subjected to primary cold rolling to an intermediate sheet thickness. After being subjected to intermediate annealing at 1120 ° C. for 80 seconds, a cold rolled sheet having a final sheet thickness of 0.23 mm was obtained by warm rolling at 200 ° C.

Next, the cold-rolled sheet was degreased with an alkaline solution, pickled, and further subjected to electrolytic degreasing. In this case, 0.5% by mass of monoalkyl sulfate as a surfactant is dissolved in 3% by mass of NaOH, and 1.5% by mass of zinc gluconate (C ₁₂ H ₂₂ O ₁₄ Zn) is added. Two types were used: those prepared and those not added. In these liquids, electrolytic treatment was performed using a steel plate as a cathode, and Zn was electrodeposited while changing in a range of 0 to 100 mg / m ² per side. In addition, the electrodeposition amount of Zn was measured with fluorescent X-rays and obtained from a calibration curve prepared in advance.
Subsequently, decarburization annealing was performed in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 62.5 ° C., and maintained at a temperature of 840 ° C. for 100 seconds.

  Thereafter, an annealing separator containing 5% by mass of titanium oxide as an additive was added to the steel plate surface and dried, and then the steel plate was subjected to secondary recrystallization annealing and 1200 in a hydrogen atmosphere. After performing a final annealing consisting of a purification annealing that is maintained at a temperature of 7 ° C. for 7 hours, an unreacted annealing separator is removed, an insulating film is applied, and a flattening annealing that also serves as a baking of the film is performed at 800 ° C. × 30 It was applied in seconds to obtain a product coil.

The product coil obtained as described above was _{examined for} magnetic properties (iron loss W _17/50 , magnetic flux density B ₈ ) and film adhesion.
The magnetic properties were measured by the SST method (Single Sheet Tester).
Further, the film adhesion was evaluated by obtaining the minimum diameter at which the film did not peel off after the steel sheet was wound on a round bar having a different diameter after the product plate was subjected to 800 ° C. × 2 hours of strain relief annealing. .
The results of the measurement are shown in FIG. From this figure, both the magnetic properties and the film adhesion are improved as the Zn electrodeposition amount increases, but when it exceeds a certain amount, the tendency to deteriorate is recognized.

Although the mechanism by which such a phenomenon occurs is not sufficiently clear at present, the inventors consider as follows.
First, when Zn is not electrodeposited, SiO ₂ and Fe ₂ SiO ₄ particles are formed as internal oxides immediately under the surface of the steel sheet in the decarburization annealing. Further, when the dew point is high, that is, when the oxidizing property is high, in addition to the above, FeO is generated as an external oxide. This FeO decomposes during the subsequent finish annealing to release oxygen, decomposes the inhibitor and adversely affects the formation of the film, causing so-called "additional oxidation", degrading the magnetic properties and film properties. Let Even when FeO is not generated, the hydration water contained in the annealing separator into which MgO is slurried before finish annealing is released into the atmospheric gas as the finish annealing temperature increases, which oxidizes Fe on the steel sheet surface. Cause similar adverse effects.

On the other hand, when Zn is electrodeposited before decarburization annealing, during decarburization annealing, Zn is a lower element than Fe and noble than Si, that is, Zn is more easily oxidized than Fe. Since Si is less oxidized than Si, even if decarburization annealing is performed, Si forms SiO ₂ particles and forms an internal oxide (layer) regardless of the presence of Zn. However, Fe ₂ SiO ₄ becomes (Zn, Fe) ₂ SiO ₄ due to the presence of Zn, which is an element that is more easily oxidized than Fe. Further, FeO generated when the dew point (oxidation property) is high is also changed to (Zn, Fe) O due to the presence of Zn.

Since these Zn oxides have a stronger chemical bonding force than Fe, they react with the annealing separator MgO without being decomposed and releasing oxygen during finish annealing, and then the Mg ions and Zn ions are substituted. As a result, a forsterite (Mg ₂ SiO ₄ ) undercoat is formed. As a result, it is considered that additional oxidation is less likely to occur compared to the case where Zn is not electrodeposited, so that the magnetic properties and film properties are improved.

Furthermore, it should be noted that such metal electrodeposition has the effect of mitigating annealing non-uniformity during finish annealing.
Since the finish annealing is performed in a state of being wound around a coil, the conditions of the annealing atmosphere are greatly different between the center portion and the end portion in the plate width direction. That is, in the central portion of the plate width, the hydrated water of MgO and the oxygen released by the reduction of FeO stay for a long time and are adversely affected. Will quickly get out of the system. Therefore, the central portion of the plate width is more susceptible to additional oxidation than the end portion of the plate width, and the magnetic characteristics and the film characteristics are likely to deteriorate. However, when a metal such as Zn is electrodeposited, the occurrence of such additional oxidation is suppressed, so that a steel plate having uniform characteristics can be obtained even at the plate width end portion and the plate width central portion. The same effect also occurs in the inner and outer winding portions of the coil, and the uniformity of the longitudinal characteristics of the product coil is improved.
The present invention has been developed based on the above novel findings.

Next, the component composition of the steel material (slab) used for manufacture of the grain-oriented electrical steel sheet of the present invention will be described.
C: 0.01-0.08 mass%
If C is less than 0.01 mass%, the grain boundary strengthening effect is lost, and the slab is cracked, resulting in hindrance to production and surface defects. On the other hand, when it exceeds 0.08 mass%, it becomes difficult to decarburize and reduce to 0.005 mass% or less where magnetic aging does not occur in the decarburization annealing process performed in an oxidizing atmosphere. Therefore, C is preferably in the range of 0.01 to 0.08 mass%. More preferably, it is the range of 0.02-0.080 mass%.

Si: 2.0 to 4.5 mass%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. For this effect, a content of less than 2.0 mass% is not sufficient. On the other hand, if it exceeds 4.5 mass%, the workability deteriorates and it becomes difficult to roll and manufacture. Therefore, Si is preferably in the range of 2.0 to 4.5 mass%. More preferably, it is the range of 2.5-4.2 mass%.

Mn: 0.02 to 0.20 mass%
Mn is an element necessary for improving the hot workability of steel. If the effect is less than 0.02 mass%, it is not sufficient. On the other hand, if it exceeds 0.20 mass%, the magnetic flux density of the product plate decreases. Therefore, Mn is preferably in the range of 0.02 to 0.20 mass%. More preferably, it is the range of 0.03-0.15 mass%.

Components other than C, Si and Mn are different depending on whether or not an inhibitor is used in order to cause secondary recrystallization.
First, when an inhibitor is used to cause secondary recrystallization, for example, when an AlN-based inhibitor is used, Al and N are changed to Al: 0.010 to 0.050 mass%, N: 0.003, respectively. It is preferable to make it contain in the range of -0.020 mass%. When using an MnS / MnSe-based inhibitor, the amount of Mn described above and one or two of S: 0.005 to 0.030 mass% and Se: 0.005 to 0.030 mass% are contained. It is preferable to do so. If the amount of each additive is less than the above lower limit value, the inhibitor effect is not sufficiently obtained. On the other hand, if the amount exceeds the above upper limit value, the inhibitor component remains undissolved during slab heating, resulting in a decrease in magnetic properties. . AlN and MnS / MnSe inhibitors may be used in combination.

  On the other hand, when an inhibitor is not used to cause secondary recrystallization, the content of Al, N, S and Se, which are the above-described inhibitor forming components, is reduced as much as possible, Al: less than 0.01 mass%, N : It is preferable to use a steel material reduced to less than 0.0050 mass%, S: less than 0.0050 mass%, and Se: less than 0.0030 mass%.

  In the steel material used for manufacturing the grain-oriented electrical steel sheet of the present invention, the balance other than the above components is Fe and inevitable impurities. However, in order to improve the magnetic properties, in addition to the above components, Ni: 0.010 to 1.50 mass%, Cr: 0.01 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, P : 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Sn: 0.005-0.50 mass%, Bi: 0.001-0.03 mass%, Mo: 0.005-0 100 mass%, B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Nb: 0.0010 to 0.0100 mass%, V: 0.001 to 0.010 mass%, and Ta: One or more selected from 0.001 to 0.010 mass% may be added as appropriate. More preferably, Ni: 0.01-0.5 mass%, Cr: 0.01-0.3 mass%, Cu: 0.01-0.3 mass%, P: 0.005-0.2 mass%, Sb: 0.005-0.07 mass%, Sn: 0.005-0.2 mass%, Bi: 0.005-0.03 mass%, Mo: 0.005-0.05 mass%, B: 0.0002- It is in the range of 0.0020 mass%.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
A steel material (slab) may be manufactured by a conventionally known ingot-bundling rolling method or continuous casting method after melting the steel having the above-described component composition by a conventional refining process, or directly. A thin slab having a thickness of 100 mm or less may be manufactured by a casting method. The slab is subjected to a conventional method. For example, when it contains an inhibitor component, it is heated to about 1400 ° C. On the other hand, when it does not contain an inhibitor component, it is heated to a temperature of 1300 ° C. or lower and then subjected to hot rolling. . In addition, when not containing an inhibitor component, you may hot-roll immediately after casting, without heating. In the case of a thin slab, hot rolling may be performed, or hot rolling may be omitted and the subsequent process may be performed as it is.

  Thereafter, the hot-rolled sheet obtained by hot rolling is subjected to hot-rolled sheet annealing as necessary. The soaking temperature of this hot-rolled sheet annealing is preferably in the range of 800 to 1150 ° C. in order to obtain good magnetic properties. If it is less than 800 degreeC, the band structure formed by hot rolling will remain, it will become difficult to obtain the primary recrystallized structure of a sized grain, and the growth of a secondary recrystallized grain will be inhibited. On the other hand, when the temperature exceeds 1150 ° C., the grain size after hot-rolled sheet annealing becomes too coarse, and it becomes difficult to obtain a primary recrystallized structure of sized particles.

  Next, the hot-rolled sheet after hot-rolling or after hot-rolled sheet annealing is made into a cold-rolled sheet having a final sheet thickness by one or more cold rolling or two or more cold rollings sandwiching the intermediate annealing. The annealing temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. If it is less than 900 ° C., the recrystallized grains after the intermediate annealing become finer, and further, Goss nuclei in the primary recrystallized structure are reduced and the magnetic properties of the product plate are deteriorated. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become too coarse as in the case of hot-rolled sheet annealing, and it becomes difficult to obtain a primary recrystallized structure of grain size.

  In order to further improve the magnetic properties, the cold rolling with the final sheet thickness (final cold rolling) employs warm rolling in which the steel sheet temperature during rolling is increased to 100 to 300 ° C and rolled. It is effective to improve the primary recrystallization texture by performing aging treatment once or a plurality of times at a temperature of 100 to 300 ° C. during the cold rolling.

  In order to prevent additional oxidation in the above-described finish annealing, the cold-rolled sheet having the final thickness is electrodeposited with an element that is baser than Fe and nobler than Si on the surface of the steel sheet (electrodeposition). Analysis) is important. Here, the term “baser than Fe and noble than Si” means that it is easier to oxidize than Fe and harder to oxidize than Si at a high temperature when an internal oxide layer is formed by decarburization annealing. Examples of the metal element having such characteristics include Ti, Mn, Ta, Zn, and Cr.

The electrodeposition of metal (adhesion) amount is required to be a per side 0.1 mg / ^{m 2} or more 70 mg / ^{m 2} or less. In addition, although electrodeposition may be performed in multiple times instead of once, in that case, the amount of electrodeposition should be within the above range. The effect is insufficient in the electrodeposition of less than 0.1 mg / m ^2, whereas, when it is more than 70 mg / m ^2, by oxidation of the metal is electrodeposited before the decarburization annealing, decarburization annealing Since oxygen is prevented from diffusing from the surface of the steel sheet to the inside, the amount of oxygen is insufficient, and the film characteristics are deteriorated. A preferable electrodeposition amount is in the range of 0.1 mg / m ^{2 to} 50 mg / m ² .

  In addition, the method for electrodepositing the metal employs an electrolytic deposition method in order to ensure the adhesion of the electrodeposit and to easily control the amount of electrodeposition. The simplest method is normal electroplating. As the plating bath, it is desirable to use an alkaline bath in which sodium hydroxide, sodium silicate or the like is dissolved in order to prevent dissolution of the base iron. In this, a compound containing a desired metal ion is dissolved. As a metal compound that dissolves in an alkaline bath, it is preferable to use a metal chelate salt such as EDTA (ethylenediaminetetraacetic acid) or gluconic acid. Furthermore, it is preferable to add a surfactant to the alkaline bath in order to remove and emulsify the oil adhering to the steel plate. When electrolysis is performed in such a plating bath, it is possible to perform electrolytic degreasing together with metal electrodeposition.

The amount of metal electrodeposition can be controlled by adjusting the current density and time. Incidentally, if the amount of metal adhesion is about the present invention, the current density can be electrodeposited in about 0.1 to 100 A / dm ² , and the electrolysis time can be about 0.1 to 10 seconds.
The electrolytic treatment can be either constant current electrolysis or alternating current electrolysis. In the alternating current electrolysis, the total electrolysis time when the steel plate becomes a negative pole may be set within the above range.

  Then, the cold-rolled sheet subjected to the metal electrodeposition is subjected to decarburization annealing. It is preferable that the soaking temperature is 700 to 900 ° C., and the soaking time is 30 to 300 seconds. If the soaking temperature is less than 700 ° C or the soaking time is less than 30 seconds, decarburization is insufficient, the primary recrystallized grains are too small, and the magnetic properties of the product plate are deteriorated. If it exceeds 300 seconds or exceeds 300 seconds, the primary recrystallized grains become too large, and the magnetic properties of the product plate are deteriorated.

This decarburization annealing is a process of forming a subscale (SiO ₂ ) on the surface layer (directly below the surface) of the steel sheet. At this time, the metal electrodeposited in the previous process penetrates into the steel and simultaneously oxidizes on the steel sheet surface. Is done. The oxide on the surface of the steel sheet has a function of improving magnetic properties by suppressing additional oxidation in the subsequent finish annealing.

In order to form the subscale, the atmosphere in the decarburization annealing needs to be an oxidizing atmosphere (decarburization atmosphere) in the range of 0.20 to 0.70 at a steam-hydrogen partial pressure ratio P _H2O / P _H2. There is. Thereby, the quantity of the subscale formed in steel and the oxidation amount of an electrodeposited metal can be optimized. Preferred P _H2O / P _H2 is in the range of 0.30 to 0.60. In addition, when a steel material having a C concentration of 0.005 mass% or less is used, decarburization is not necessary from the viewpoint of preventing magnetic aging, but from the viewpoint of forming a subscale immediately below the surface. A decarburizing atmosphere is preferable.

  In the above decarburization annealing, the atmosphere does not have to be a constant condition. For example, the first half and the second half are divided into two stages, and the latter half is subjected to a reduction treatment with a low dew point (reducibility), or the atmosphere at the time of heating. And the soaking atmosphere may be made different. Furthermore, rapid heating that raises the temperature rising rate in the heating process to 50 ° C./s or more may be performed, or nitriding may be performed after decarburization annealing.

  Next, an annealing separator is applied to the surface of the steel plate subjected to the decarburization annealing. As the annealing separator, for forming a forsterite film, a material containing 50 mass% or more of MgO is used as a main agent. In MgO, Ti, Ca, Sr, Mn, Mo, Fe, One selected from oxides such as Cu, Zn, Ni, Sn, Al, K, Li, K, sulfates, chlorides, borates, silicates, nitrates, titanates, hydroxides, etc. Or what added 2 or more types may be used.

  The steel sheet coated with the annealing separator is then subjected to finish annealing in which it is subjected to a purification treatment after causing secondary recrystallization in a state of being wound around a coil. By this finish annealing, a secondary recrystallized structure highly accumulated in the Goss orientation can be developed and a forsterite film can be formed. The temperature of the finish annealing needs to be raised to 800 ° C. or higher for the purpose of secondary recrystallization, and is preferably raised to 1100 ° C. to complete the secondary recrystallization. In the subsequent purification annealing, it is preferable to raise the temperature to about 1200 ° C. in order to form a forsterite film. In addition, when using a steel material that does not contain an inhibitor-forming component, purification treatment is not necessary, but it is preferable to raise the temperature to about 1200 ° C. in order to form a forsterite film.

  The steel sheet that has undergone finish annealing is then washed with water, brushed, pickled, etc. to remove unreacted annealing separator adhering to the surface of the steel sheet, then coated with an insulating film, and then baked and shaped. It is preferable to carry out flattening annealing that also serves as correction to obtain a final product.

  The grain-oriented electrical steel sheet manufactured in this way has a plate width end with respect to the strength Ic at the center of the plate width when the concentration of the metal electrodeposited on the steel plate surface contained in the undercoat is measured by fluorescent X-rays. The ratio of the strength Ie (Ie / Ic) is in the range of 0.7 to 1.3 times. Here, the strength Ie of the plate width end portion is a sample having a width of 100 mm cut out from both width end portions after the end of 30 mm of the steel plate edges after removing the remaining annealing separator after finish annealing, It is the value of the electrodeposited metal when the surface is measured with fluorescent X-rays. In addition, when an insulating film is formed on the product plate, the film is removed by alkali cleaning or the like and then measured with fluorescent X-rays. A grain-oriented electrical steel sheet having an Ie / Ic value in the above range has good magnetic properties and coating properties, and is uniform in the plate width direction. However, when Ie / Ic is smaller than 0.7 or higher than 1.3, not only the magnetic properties and the film properties are inferior, but also non-uniform in the plate width direction.

  When it is desired to further reduce the iron loss, it is effective to perform the magnetic domain fragmentation process after the product plate is formed by the method of the present invention or in the intermediate process of forming the product plate by the method of the present invention. As a method for subdividing magnetic domains, a conventionally used method is to form a groove in the product plate, or a linear or dotted thermal strain or impact strain is introduced by irradiating the surface of the product plate with a laser or an electron beam. And a method of forming a groove by etching the steel sheet surface in an intermediate step after cold rolling to the final plate thickness. In particular, the product plate of the present invention is excellent in the adhesiveness of the coating, and the coating does not peel off even when irradiated with an electron beam. Therefore, the product plate is suitable for magnetic domain fragmentation treatment by electron beam irradiation.

A steel slab containing C: 0.070 mass%, Si: 3.43 mass%, Mn: 0.08 mass%, Al: 0.02 mass%, N: 0.008 mass% with the balance being Fe and inevitable impurities. After being manufactured by a continuous casting method and reheated to a temperature of 1350 ° C., it is hot-rolled to form a hot-rolled sheet having a thickness of 2.4 mm and subjected to hot-rolled sheet annealing at 1000 ° C. × 50 seconds, or Without applying hot-rolled sheet annealing, the intermediate sheet thickness is set to 1.8 mm by primary cold rolling, and after intermediate annealing at 1100 ° C. for 20 seconds, the second sheet is subjected to secondary cold rolling to obtain a final sheet thickness of 0.23 mm. Finished in cold rolled sheet. Thereafter, this cold-rolled sheet was degreased, and then an electrolytic solution obtained by adding various EDTA metal salts to sodium silicate 30 g / L and a surfactant 5 g / L, a bath temperature of 70 ° C., and a current density of 0.1 to 20 A. / Dm ² for 0-15 seconds to deposit various amounts of electrodeposited metal, then 840 ° C. in a humid atmosphere of 50 vol% H ₂ -50 vol% N ₂ , dew point 50-65 ° C. The decarburization annealing which hold | maintains for 100 second at the temperature of was performed.
Next, an annealing separator mainly composed of MgO was applied in the form of a slurry to the surface of the steel sheet, dried, and then subjected to secondary recrystallization, and then subjected to a finish annealing for carrying out a purification treatment at 1200 ° C. for 10 hours. The atmosphere of the finish annealing was H ₂ when maintaining at 1200 ° C. for the purification treatment, and N ₂ when raising and lowering the temperature. Thereafter, an insulating film mainly composed of magnesium phosphate-colloidal silica was applied and baked to obtain a product coil.

A sample is taken from the longitudinal center part of the product coil obtained in this way, and a test piece having a width of 100 mm is cut out from the center part of the plate width and both ends from which the edge is cut off by 30 mm, and each magnetic characteristic (magnetic flux) Density B ₈ , iron loss W _17/50 ) and bending adhesion (bending peel diameter) were measured. In addition, the magnetic value and bending adhesiveness of the plate width end portion were obtained by calculating the average value of both width end portions.
Similarly, after removing the insulating coating by alkali washing to expose the forsterite base coating, the electrodeposited metal concentration in the base coating was analyzed by fluorescent X-rays. The ratio (Ie / Ic) of the strength Ie at the edge portion of the plate width to the strength Ic at the width center portion was determined. The average value of both width ends was used as the strength Ie of both width ends.
The measurement results are shown in Table 1. From this table, the steel plates electrodeposited with metal under the conditions suitable for the present invention not only have good magnetic properties and film adhesion, but also have a small difference between the center and end of the plate width and are uniform. I know that there is.

Various steel slabs having the composition shown in Table 2 and the balance consisting of Fe and inevitable impurities are manufactured by a continuous casting method, reheated to a temperature of 1380 ° C., and then hot-rolled to obtain a thickness of 2 A hot-rolled sheet of 0.0 mm was subjected to hot-rolled sheet annealing at 1030 ° C. for 10 seconds, and then cold-rolled to finish a cold-rolled sheet having a final sheet thickness of 0.23 mm. Then, after degreasing this cold-rolled sheet, using an electrolytic solution in which various manganese gluconates were added to 30 g / L of sodium hydroxide and 5 g / L of a surfactant, the bath temperature was 70 ° C., the current density was 2 A / dm ^2. The electrode was subjected to electrolytic treatment for 1 second to electrodeposit metal. Thereafter, decarburization annealing was performed for 100 seconds at a temperature of 840 ° C. in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 50 to 65 ° C.
Next, an annealing separator mainly composed of MgO was applied in the form of a slurry to the surface of the steel sheet, dried, and then subjected to secondary recrystallization, and then subjected to a finish annealing for carrying out a purification treatment at 1200 ° C. for 10 hours. The atmosphere of the finish annealing was H ₂ when maintaining at 1200 ° C. for the purification treatment, and N ₂ when raising and lowering the temperature. Thereafter, an insulating film mainly composed of magnesium phosphate-colloidal silica was applied and baked to obtain a product coil.

The magnetic properties (iron loss W _17/50 ), bending adhesion (bending peel diameter) and (Ie / Ic) of the finish-annealed plate obtained as described above were measured in the same manner as in Example 1, and the result Are shown in Table 2. From this table, using steel materials having a composition suitable for the present invention, the steel sheets manufactured under the conditions suitable for the present invention not only have good magnetic properties and film adhesion, It can be seen that the difference between the central portion and the end portion is small and uniform.

Claims (4)

A grain-oriented electrical steel sheet having a forsterite undercoating, wherein the undercoating contains an element lower than Fe and noble than Si, and the surface of the undercoating is analyzed by fluorescent X-ray. A grain-oriented electrical steel sheet, wherein the ratio (Ie / Ic) of the strength Ie at the end portion of the plate width to the strength Ic at the center portion of the plate width of the element is in the range of 0.7 to 1.3. C: 0.01 to 0.08 mass%, Si: 2.0 to 4.5 mass%, Mn: 0.02 to 0.20 mass%,
Al: 0.010-0.050 mass% and N: 0.003-0.020 mass%, or
Al: 0.010-0.050 mass%, N: 0.003-0.020 mass%, S: 0.005-0.030 mass% and / or Se: 0.005-0.030 mass%, the remainder Hot rolled a steel material consisting of Fe and inevitable impurities to form a hot-rolled sheet, or without performing hot-rolled sheet annealing, or after hot-rolled sheet annealing, once or twice with intermediate annealing more to a final thickness of the cold-rolled sheet by cold _rolling, was subjected to decarburization annealing in an atmosphere to 0.20 to 0.70 of _P H2O _/ P _H2, the annealing separator was coated on the surface of the steel sheet, In the manufacturing method of grain-oriented electrical steel sheet consisting of a series of steps for finish annealing,
Between the last cold rolling and the decarburization annealing, 0.1 to 70 mg / m ² electrodeposition per side of the element that is lower than Fe and noble than Si is performed, and then decarburization annealing is performed. The method for producing a grain-oriented electrical steel sheet according to claim 1. C: 0.01 to 0.08 mass%, Si: 2.0 to 4.5 mass%, Mn: 0.02 to 0.20 mass%, Al: less than 0.01 mass%, N: less than 0.005 mass%, S : A steel material containing less than 0.0050 mass% and Se: less than 0.0050 mass%, the balance being Fe and unavoidable impurities is hot rolled into a hot-rolled sheet, without subjecting the hot-rolled sheet to annealing, or , it was subjected to hot rolled sheet annealing, the atmosphere to a final thickness of the cold-rolled sheet by between two or more cold rolling sandwiching once or intermediate _annealing, and from 0.20 to 0.70 the _P H2O _/ P _H2 In the manufacturing method of grain-oriented electrical steel sheet consisting of a series of steps of applying annealing separator to the steel sheet surface and finishing annealing after decarburizing annealing in
Between the last cold rolling and the decarburization annealing, 0.1 to 70 mg / m ² electrodeposition per side of the element that is lower than Fe and noble than Si is performed, and then decarburization annealing is performed. The method for producing a grain-oriented electrical steel sheet according to claim 1. In addition to the above component composition, the steel material further includes Ni: 0.010 to 1.50 mass%, Cr: 0.01 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, P: 0.00. 005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Bi: 0.001 to 0.03 mass%, Mo: 0.005 to 0.100 mass% , B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Nb: 0.0010 to 0.0100 mass%, V: 0.001 to 0.010 mass%, and Ta: 0.001. The method for producing a grain-oriented electrical steel sheet according to claim 2 or 3, comprising one or more selected from -0.010 mass%.

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