JP2017133080A - Oriented electromagnetic steel sheet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose an oriented electromagnetic steel sheet excellent not only in magnetic property, but also in film characteristics after stress relieving annealing, and a manufacturing method therefor.SOLUTION: In a manufacturing method of an oriented electromagnetic steel sheet consisting of a series of processes including hot rolling a steel raw material containing, by mass%, C:0.03 to 0.08%, Si:2.5 to 4.5% and Mn:0.03 to 0.30% to make a hot rolled sheet, cold rolling the same, conducting decarbonization annealing which serves a primary recrystallization annealing, then coating a surface of the steel sheet with an annealing separator and conducting finish annealing, the oriented electromagnetic steel sheet having average of standard deviation of O strength during mapping analysis of a forsterite under coated film surface with EPMA of 0.15 or less and flexure detachment diameter after conducting stress relieving annealing under DX gas atmosphere of 30 mmφ or less is obtained by precipitating 25/μmor more of metal particles with average particle diameter of 70 nm or less on a steel sheet surface between the cold rolling and the decarbonization annealing to make a final sheet thickness.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grain-oriented electrical steel sheet and a method for producing the grain-oriented electrical steel sheet, and more particularly to a grain-oriented electrical steel sheet having excellent magnetic properties and coating properties 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 the crystal orientation, imparting tension to the steel sheet, smoothing the steel sheet surface, and secondary recrystallization structure. It is known that grain refinement and the like are effective.

  In the above method, in order to improve the orientation of the crystal orientation by controlling the secondary recrystallization or to refine the secondary recrystallization structure, the type and amount of the inhibitor component, the cold rolling reduction rate It is necessary to optimize various factors such as the primary recrystallization annealing pattern and the surface state of the steel plate before the secondary recrystallization annealing.

By the way, as a method of improving the steel sheet surface state before the secondary recrystallization annealing and obtaining good magnetic properties, for example, in Patent Document 1, the steel sheet surface finished to the final sheet thickness by cold rolling, One or two or more metals or alloys selected from Cu, Sn, Co, and Ni are electrodeposited in an amount of 0.1 to 85 mg / m ² , and then decarburized and annealed, so that the total length and width of the coil are reduced. A method for producing a grain-oriented silicon steel sheet having a uniform and excellent adhesive film without defects and excellent magnetic properties is disclosed.

In Patent Document 2, a steel slab containing no inhibitor component is used as a raw material, and after primary recrystallization annealing, one or more metals selected from Si, Cu, Sn, Co, and Ni are selected on the steel sheet surface. The grain-oriented electrical steel sheet that obtains excellent magnetic properties and coating properties by electrodeposition of inclusions in a total amount in terms of the metal in the range of 0.1 to 50 mg / m ² and then applying an annealing separator. A manufacturing method is disclosed.

In Patent Document 3, the arithmetic average roughness of the steel sheet surface after the final cold rolling is adjusted to 0.40 μm or less, and Si is contained on the steel sheet surface by electrolytic degreasing prior to subsequent decarburization annealing. A directional electrical steel sheet having a high magnetic flux density is stably produced even in industrial production by performing a cleaning process for depositing electrodeposits of 0.1 mg / m ² or more and then performing decarburization annealing with an adjusted atmosphere. A method is disclosed.

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

However, according to the verification results of the inventors, the method disclosed in Patent Document 1 has a large variation in the effect of improving the magnetic characteristics and the film characteristics, and a stable effect cannot be obtained. Further, the method disclosed in Patent Document 2 is a technique mainly for improving the film characteristics, and the magnetic characteristics are also largely varied and may be deteriorated in some cases. Further, in the method disclosed in Patent Document 3, the Si electrodeposit is formed before decarburization annealing, but the Si electrodeposit itself becomes a barrier at the time of decarburization annealing, and the internal oxidation of SiO ₂ is made non-uniform. It happened frequently. That is, if there is a slight aging of the electrolytic bath or non-uniform cleaning before electrolysis, the Si electrodeposits do not adhere uniformly to the plate surface, so the subscale protection formed by decarburization annealing has a coil And unevenness in the magnetic properties increases, and unevenness in the coating properties increases.

  In addition, when a grain-oriented electrical steel sheet is used as a core of a transformer for a wound core, an EI core, etc., strain relief annealing is performed at a temperature of about 800 ° C. in order to remove strain introduced during processing. However, in this case, annealing is often performed in an atmosphere having high reactivity with the coating or the ground iron, such as air or DX gas. When annealing is performed in such an atmosphere, the coating film may be damaged and the coating adhesion may deteriorate. In particular, in the vicinity of the end face of the slit steel plate, the coating is easily peeled off, so that when the transformer is used, the steel plate conducts, and in some cases, the core may be melted down.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is not only excellent in magnetic properties, but also when performing strain relief annealing in a highly reactive atmosphere such as DX gas. An object is to provide a grain-oriented electrical steel sheet having excellent coating properties and to propose an advantageous manufacturing method thereof.

  The inventors have intensively studied to solve the above problems. As a result, not the type of metal electrodeposited on the steel sheet surface before decarburization annealing, but the deposition form of electrodeposited particles is important, and by optimizing this, internal oxidation formed during decarburization annealing It has been found that the layer is improved, and consequently the magnetic properties and film properties are improved, and the present invention has been developed.

  That is, the present invention is a grain-oriented electrical steel sheet having a forsterite undercoating, wherein the standard deviation of O intensity when mapping analysis of the surface of the undercoating with EPMA is 0.15 or less of the average value, A grain-oriented electrical steel sheet characterized by having a bending peel diameter of 30 mmφ or less after strain relief annealing in a gas atmosphere.

Further, the present invention contains C: 0.03 to 0.08 mass%, Si: 2.5 to 4.5 mass%, and Mn: 0.03 to 0.30 mass%, with the balance being Fe and inevitable impurities. After hot-rolling a steel material consisting of the above-mentioned steel into a hot-rolled sheet, or after subjecting to hot-rolled sheet annealing or without performing hot-rolled sheet annealing, it is cold-rolled twice or more sandwiched between intermediate annealing and final In the manufacturing method of grain-oriented electrical steel sheet consisting of a series of steps of applying a annealing separator to the steel sheet surface and finishing annealing after performing decarburization annealing that also serves as primary recrystallization annealing, as a cold-rolled sheet of plate thickness, The grain-oriented electrical steel sheet according to the above, characterized in that metal particles having an average particle size of 70 nm or less are deposited on the steel sheet surface by 25 particles / μm ² or more between the cold rolling and the decarburization annealing with the final sheet thickness. We propose a manufacturing method.

  The steel material used in the method for producing a grain-oriented electrical steel sheet of the present invention further contains Al: 0.01 to 0.03 mass% and N: 0.003 to 0.01 mass% in addition to the above component composition. Alternatively, Al: 0.01-0.03 mass%, N: 0.003-0.01 mass%, Se: 0.01-0.025 mass% and / or S: 0.01-0.025 mass% are contained. It is characterized by that.

  Moreover, in addition to the said component composition, the said steel raw material used for the manufacturing method of the grain-oriented electrical steel sheet of this invention is further Se: 0.01-0.025mass% and / or S: 0.01-0.025mass%. It is characterized by containing.

  Further, Al, N, S and Se in the inevitable impurities contained in the steel material used in the method for producing a grain-oriented electrical steel sheet according to the present invention are Al: less than 0.01 mass% and N: 0.0050 mass%, respectively. Less than, S: less than 0.0050 mass% and Se: less than 0.0030 mass%.

  Moreover, in addition to the said component composition, the said steel raw material used for the manufacturing method of the grain-oriented electrical steel sheet of this invention is further Ni: 0.01-0.4mass%, Cr: 0.01-0.25mass%, Cu : 0.01 to 0.30 mass%, P: 0.005 to 0.10 mass%, Sb: 0.005 to 0.10 mass%, Sn; 0.005 to 0.10 mass%, Bi: 0.005 to 0 .10 mass%, Mo: 0.005-0.10 mass%, B: 0.0002-0.0025 mass%, Te: 0.0005-0.01 mass%, Nb: 0.001-0.01 mass%, V: It contains one or more selected from 0.001 to 0.01 mass% and Ta: 0.001 to 0.01 mass%.

  ADVANTAGE OF THE INVENTION According to this invention, the grain-oriented electrical steel sheet which is excellent in both a magnetic characteristic and a film characteristic can be provided stably.

It is a graph which shows the influence which pickling conditions and the electrodeposition of Cu have on a magnetic characteristic and a film characteristic. It is a SEM image which shows the influence which the presence or absence of pickling has on the O distribution when the undercoat surface is subjected to mapping analysis by EPMA. It is a graph which shows the influence which pickling conditions and the presence or absence of electrodeposition of Cu have on the (standard deviation / average value) of O distribution when the undercoat surface is subjected to mapping analysis by EPMA. It is a figure which shows an example of the SEM image of the steel plate surface after metal electrodeposition. It is a SEM image which shows the influence which the presence or absence of pickling has on the precipitation state of the electrodeposited metal particle. It is a graph which shows the influence which hydrochloric acid pickling conditions have on the average particle diameter and precipitation density of electrodeposited metal particles.

When investigating the cause of the large variation, the inventors have greatly improved the magnetic properties when the electrodeposition of metal particles is performed on the steel plate surface before decarburization annealing, or not improved at all. The following experiment was conducted.
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 Then, 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 s, and then subjected to primary cold rolling to an intermediate thickness of 1 After being subjected to intermediate annealing of 1120 ° C. × 80 s, secondary cold rolling was performed at a temperature of 200 ° C. to obtain a cold-rolled sheet having a final thickness of 0.23 mm.

Next, the cold-rolled sheet was degreased with an alkaline solution, then washed with hydrochloric acid, and further subjected to electrolytic degreasing. At this time, the conditions of the hydrochloric acid pickling were divided into the following four levels.
Level 1) Without hydrochloric acid pickling Level 2) Immersion in 3 mass% hydrochloric acid aqueous solution with a liquid temperature of 50 ° C. Level 3) Immersion in 5 mass% hydrochloric acid aqueous solution with a liquid temperature of 60 ° C. Level 4) Liquid temperature is 70 ° C. Immerse in 10 mass% aqueous hydrochloric acid for 10 s

Further, above the electrolytic degreasing in an electrolytic bath, using an aqueous solution consisting of 3mass% NaOH + 0.5mass% surfactant + 1.5 mass% copper gluconate _{(C 12 H 22 O 14 Cu} ). In this bath, the steel plate was electrolyzed as a cathode, and Cu was electrodeposited at 50 mg / m ² per side in terms of metal. The amount of electrodeposition of Cu was quantified based on a calibration curve prepared in advance analyzed by fluorescent X-rays. For comparison, electrolytic degreasing was also performed in an electrolytic bath to which copper gluconate was not added.

Next, decarburization annealing was performed that also served as primary recrystallization annealing that was maintained at a temperature of 840 ° C. for 100 s in a humid atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 62 ° C.
After that, an annealing separator containing MgO as the main ingredient and titanium oxide added as 5 mass% in terms of Ti was applied to the steel sheet surface, dried, and then subjected to secondary recrystallization annealing and purification at 1200 ° C. × 7 hr in a hydrogen atmosphere. Finish annealing consisting of treatment was performed.
Thereafter, the unreacted annealing separator was removed, an insulating film was applied, and flattening annealing that combined baking and shape correction of the film was performed at 800 ° C. × 30 s to obtain a product plate.

The product plate thus obtained was examined for magnetic properties and film adhesion.
Here, the magnetic characteristics were measured by the method defined in JIS C2550, and the magnetic flux density B ₈ and the iron loss W _17/50 were measured.
Further, the adhesion of the film was subjected to strain relief annealing in a DX gas atmosphere (CO: 1 vol% + H ₂ : 1 vol% + CO ₂ : 12 vol% + balance: N ₂ , dew point: 10 ° C.) at 850 ° C. × 3 hr. The minimum diameter (bending peel diameter) at which the coating did not peel when the steel plate was wound around round bars having different diameters was measured.

  The results of the measurement are shown in FIG. From this figure, under the conditions where copper gluconate is not added, that is, when Cu electrodeposition is not performed, the magnetic properties and film adhesion show almost constant values regardless of the pickling conditions before electrodeposition. Under the conditions where Cu electrodeposition was performed, the magnetic properties and film properties were remarkably improved in the levels 2) and 3) which were pickled moderately. However, at the level 3) that was pickled excessively, the magnetic properties and the film properties were reduced to the same level as the conditions for non-electrodeposition. Further, in the level 1) where pickling is not performed, both the magnetic characteristics and the film characteristics are greatly deteriorated compared with the case where Cu is not electrodeposited.

  In order to investigate this cause, the surface of the steel sheet (with a base coat) after finish annealing was analyzed by EPMA. The analyzed region was 50 μm × 50 μm, and this region was subjected to oxygen (O) analysis at a 0.2 μm pitch and displayed as a mapping. As an example, the results of level 1) without pickling and the results of level 3) pickled with 5 mass% hydrochloric acid are shown in FIG. From this figure, the oxygen distribution is uneven in level 1) without pickling, whereas the oxygen distribution is uniform in level 3) pickled with 5 mass% hydrochloric acid, and the undercoat is uniform. It can be seen that it is formed.

  Next, with respect to the O intensity of the mapping data, the average value and standard deviation of all measured values were obtained, and the result of obtaining the ratio of the standard deviation to the average value for each level is shown in FIG. From this figure, it can be seen that levels 2 and 3 where pickling with 3 to 5 mass% hydrochloric acid and electrodeposition of Cu are the lowest, indicating that the uniformity of the undercoat is increased. Moreover, it turns out that this tendency is in good agreement with the tendency of magnetic characteristics and film adhesion.

Moreover, the SEM image after Cu electrodeposition of the level 1) not pickled and the level 3) pickled with 5 mass% hydrochloric acid is shown in FIG. In level 1) not pickled with hydrochloric acid, non-uniform Cu particles of different sizes are precipitated, whereas in level 3) pickled with 5 mass% hydrochloric acid, fine Cu particles are uniformly distributed. Precipitates. Furthermore, the average particle diameter and precipitation density of the electrodeposited Cu particles were determined by image analysis of the SEM image, and the results are shown in FIG. From this figure, at level 2) and level 3 where the magnetic properties and film adhesion were good, the average particle size of the electrodeposited Cu particles was 70 nm or less, and the precipitation density of the electrodeposited Cu particles was 25 particles / μm. ^It can be seen that Cu particles are most finely and uniformly deposited at level 3), which is ² or more, and shows the best characteristics.

As described above, the inventors consider as follows the cause of a large change in the precipitation form of Cu even when electrodepositing Cu with the same basis weight.
It has been known that the atmosphere during finish annealing greatly affects the magnetic properties. This is because moisture and nitrogen contained in the atmosphere enter into the steel during the finish annealing, and the inhibitor is decomposed or coarsened to reduce the grain growth inhibiting power. As a countermeasure, it is considered effective to make the internal oxide film formed by decarburization annealing uniform and dense. For this reason, many of the conventional techniques have focused on the cross-sectional structure of the internal oxide film and studied methods for obtaining an internal oxide film having a uniform and dense structure.

  However, as a result of the above-described experiment of the present invention, it has been clarified that the variation of the internal oxide film on the surface of the steel plate is large, which strongly influences the magnetic properties and coating properties of the product plate. In other words, even if the internal oxide film in the cross section is uniform and dense, if there is a rough part of the steel sheet surface that is rough and the shielding property of the atmosphere is weak, the components of the atmospheric gas enter from there and the magnetic properties And the film properties will be adversely affected. In order to prevent this, the uniformity of the internal oxide film within the steel sheet surface must be increased. Therefore, what is important is the deposited state of metal particles electrodeposited with metal. When decarburization annealing is performed in a state where metal particles are precipitated, internal oxidation proceeds with the precipitated particles as nuclei. Therefore, the internal oxidation can be caused uniformly by depositing the metal particles uniformly.

  Furthermore, in order to deposit metal particles uniformly, it is necessary to make the steel plate surface before electrolytic treatment uniform, and for that purpose, it is important to make the surface state uniform by prior pickling etc. It becomes. However, in the above experimental results, the metal particles did not precipitate uniformly when pickled too much. The cause of this is unknown, but it is thought that pits and rough skin were generated on the surface of the steel sheet due to excessive pickling and precipitation of coarse metal particles occurred from that point.

  In addition, if the steel plate surface is made uniform by pickling or the like, it is considered that uniform oxidation proceeds without depositing metal, but in the above experiment, such a result was not obtained. This is because even if we intend to make the surface state uniform, the way of oxidation during decarburization annealing differs due to the difference in crystal orientation, that is, the surface energy differs depending on the crystal orientation. This is probably because the amount of adsorbed oxygen molecules and water molecules is different. And it is thought that it is the metal particles deposited by electrolysis that alleviate this difference.

  As mentioned above, pickling and electrodeposition treatment of metal particles are performed to obtain a uniform internal oxide film not only in the cross-sectional direction but also in the surface direction of the steel sheet, so that the forsterite film (base film) after finish annealing is obtained. Uniformity is promoted. The degree of homogenization can be evaluated by the ratio of the standard deviation to the average value of O intensity on the surface of the undercoat obtained by mapping analysis with EPMA. And, when this ratio is small, that is, by forming a uniform undercoat, excellent magnetic properties and coating properties are achieved.

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: 0.03-0.08 mass%
If C is less than 0.03 mass%, the grain boundary strengthening effect is lost, and defects such as cracks in the slab are produced. On the other hand, if it exceeds 0.08 mass%, it becomes difficult to reduce to 0.005 mass% or less at which no magnetic aging occurs due to decarburization annealing. Therefore, C is in the range of 0.03 to 0.08 mass%. Preferably it is the range of 0.035-0.075 mass%.

Si: 2.5-4.5 mass%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. If this effect is less than 2.5 mass%, it 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 set to a range of 2.5 to 4.5 mass%. Preferably it is the range of 2.8-4.0 mass%.

Mn: 0.03-0.3 mass%
Mn is an element necessary for improving the hot workability of steel. If the effect is less than 0.03 mass%, it is not sufficient. On the other hand, if it exceeds 0.3 mass%, the magnetic flux density of the product plate decreases. Therefore, Mn is set to a range of 0.03 to 0.3 mass%. Preferably it is the range of 0.04-0.2 mass%.

About components other than said C, Si, and Mn, in order to produce secondary recrystallization, it differs with the case where an inhibitor is utilized and the case where it does not.
First, when an inhibitor is used to cause secondary recrystallization, for example, when an AlN inhibitor is used, Al and N are changed to Al: 0.01 to 0.03 mass%, N: 0.00, respectively. It is preferable to make it contain in the range of 003-0.01 mass%. When using MnS / MnSe inhibitors, one or two of S: 0.01 to 0.025 mass% and Se: 0.01 to 0.025 mass% in addition to the amount of Mn described above. It is preferable to contain. If the addition amount is less than the above lower limit value, the inhibitor effect cannot be sufficiently obtained. On the other hand, if the addition amount exceeds the upper limit value, the inhibitor component remains undissolved during slab heating, resulting in a decrease in magnetic properties. The above-described AlN-based and MnS / MnSe-based inhibitors may be used in combination.

  On the other hand, when an inhibitor is not used to cause secondary recrystallization, the contents of Al, N, S and Se as the inhibitor forming components described above are reduced as much as possible, and 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 addition to the above components, the steel material used for the grain-oriented electrical steel sheet of the present invention is Ni: 0.01-0.4 mass%, Cr: 0.01-0.25 mass%, Cu: 0.01-0.30 mass%, P: 0.005-0.10 mass%, Sb: 0.005-0.10 mass%, Sn; 0.005-0.10 mass%, Bi: 0.005-0. 10 mass%, Mo: 0.005-0.10 mass%, B: 0.0002-0.0025 mass%, Te: 0.0005-0.01 mass%, Nb: 0.001-0.01 mass%, V: 0 One or two or more selected from 0.001 to 0.01 mass% and Ta: 0.001 to 0.01 mass% may be appropriately contained.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
The steel material (slab) used for the production of the grain-oriented electrical steel sheet of the present invention is prepared by melting a steel having the above-described composition by a conventional refining process, and then performing a conventionally known ingot-bundling rolling method or continuous casting. It may be manufactured by a method, or may be a thin cast piece having a thickness of 100 mm or less by a direct casting method.

  According to a conventional method, the slab is reheated to a temperature of about 1400 ° C. when it contains an inhibitor component, and then reheated to a temperature of 1300 ° C. or less when it does not contain an inhibitor component. To serve. In addition, when an inhibitor component is not contained, you may perform hot rolling immediately after continuous casting, without reheating. 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.

  Next, 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 particle, and the development of secondary recrystallization 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.

  The hot-rolled sheet after hot-rolling or after hot-rolled sheet annealing is subjected to one or more cold rollings or two or more cold-rolling sandwiching the intermediate annealing to form a cold-rolled sheet having a final thickness. The soaking temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. If the temperature is lower than 900 ° C., the recrystallized grains after the intermediate annealing may become too fine, or the Gos nuclei in the primary recrystallized structure may decrease and the magnetic characteristics of the product plate may decrease. 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.

  Moreover, the cold rolling (final cold rolling) which makes the final sheet thickness is warm rolling in which the steel sheet temperature during rolling is raised to a temperature of 100 to 300 ° C., or 100 to 300 ° C. during the rolling. It is effective to improve the primary recrystallization texture and improve the magnetic properties by performing aging treatment once or a plurality of times at the above temperature.

Next, the cold-rolled sheet having the final sheet thickness is electrodeposited with metal particles on the surface of the steel sheet in a stage before decarburization annealing. Although it does not specifically limit as a metal element to electrodeposit, Si, Cu, Sn, Co, Ni, Ti, Mn, Ta, Zn, Cr etc. are suitable.
At this time, it is necessary that the average particle diameter of the metal particles to be electrodeposited is 70 nm or less and the precipitation density is 25 particles / μm ² or more. If the average particle size is too large or the precipitation density is too low, the internal oxidation during decarburization annealing cannot be made sufficiently uniform. Preferably, the average particle diameter of the metal particles is 50 nm or less, and the precipitation density is 45 particles / μm ² or more.

The amount of electrodeposition of the metal particles is preferably in the range of 0.1 to 70 mg / m ² per side. A plurality of metals may be electrodeposited, but even in that case, the range of 0.1 to 70 mg / m ² is preferable. If it is less than 0.1 mg / m ² , the electrodeposition effect is not sufficient. On the other hand, if it exceeds 70 mg / m ² , oxygen is diffused excessively on the steel sheet surface during decarburization annealing by the electrodeposited metal. This is because the amount of oxygen per unit area is hindered and the film properties are deteriorated. A more preferred range is from 0.1 to 50 mg / m ² .

  In the present invention, the metal is attached to the surface of the steel plate by electrodeposition. This is because the adhesion of the electrodeposit is ensured and the amount of electrodeposition is easily controlled. As the electrodeposition method, an ordinary electroplating method is suitable. The plating bath is adjusted by dissolving a compound containing a desired metal ion in an alkaline bath in which sodium hydroxide, sodium silicate, or the like is dissolved in order to prevent dissolution of the base iron. As the compound dissolved in the alkaline bath, it is preferable to use a metal chelate salt such as ethylenediaminetetraacetic acid EDTA or gluconic acid. When electrolysis is performed with such a liquid, it can be performed both as metal electrodeposition and electrolytic degreasing. Further, at this time, a surfactant for releasing and emulsifying oil adhering to the steel plate may be added.

In addition, as electrolysis conditions, in order to adhere a predetermined amount of metal, it is necessary to appropriately adjust the current density and electrolysis time. However, if the metal electrodeposition amount is about the present invention, the current density is 0.1 to 100 A. / Dm ² , and the electrolysis time is about 0.1 to 10 s. The electrolytic treatment can be either constant current electrolysis or alternating current electrolysis. However, in the alternating current electrolysis, it is preferable that the total electrolysis time when the steel plate becomes a negative pole falls within the above range. Further, in order to deposit metal particles uniformly and finely so as to have a deposition density specified by the present invention, for example, the steel plate before electrolysis is pickled or ground to increase cleanliness, or the alkaline concentration of the electrolytic bath It is effective to increase the value and decrease the concentration of the metal compound.

  The steel plate electrodeposited with the above metal particles is then subjected to decarburization annealing that also serves as primary recrystallization annealing. The soaking temperature in the decarburization treatment is preferably 700 to 900 ° C., and the soaking time is preferably in the range of 30 to 300 s. If the soaking temperature is less than 700 ° C. and the soaking time is less than 30 s, the decarburization may be insufficient or the primary recrystallized grains may become too small, and the magnetic characteristics may be deteriorated. On the other hand, when the soaking temperature exceeds 900 ° C. or the decarburization time exceeds 300 s, the primary recrystallized grains become too large, and the magnetic properties are deteriorated.

  In this decarburization annealing, a subscale (internal oxide layer) is formed inside the surface layer of the steel sheet, but the metal particles uniformly and finely electrodeposited in the previous step have a thickness of the internal oxide layer formed during the decarburization annealing. Uniform in the direction and surface direction. In addition, the electrodeposited metal particles themselves diffuse into the steel during decarburization annealing and are oxidized on the surface of the steel plate. This oxide has the effect of suppressing the additional oxidation in the subsequent finish annealing and improving the magnetic properties.

The atmosphere of decarburization annealing is preferably in the range of 0.3 to 0.6 in terms of water vapor-hydrogen partial pressure P _H2O / P _H2 (oxygen potential). Thereby, the amount of SiO ₂ formation on the surface layer of the steel sheet and the amount of oxidation of the electrodeposited metal can be optimized.

  The atmosphere during the decarburization annealing is not necessarily constant. For example, it is divided into two stages, the first half and the second half, and the reduction process is performed with the second half being a low dew point, or the atmosphere during heating is The atmosphere at the time of soaking may be made different. In addition, the heating rate during heating may be rapid heating, or nitriding may be performed after decarburization annealing.

  After the decarburization annealing, an annealing separator is applied to the steel sheet surface. This annealing separator contains at least 50 mass% MgO as a main agent, and includes oxides such as Ti, Ca, Sr, Mn, Mo, Fe, Cu, Zn, Ni, Sn, Al, K, and LiK, sulfuric acid. It is preferable to use a salt, chloride, borate, silicate, nitrate, titanate, hydroxide or the like to which one or more are added.

  The steel sheet coated with the annealing separator is then subjected to secondary recrystallization annealing and subsequent finishing annealing for purification treatment in a coiled state. As a result, a secondary recrystallized structure highly accumulated in the Goss orientation can be developed and a forsterite film can be formed. The finish annealing is preferably heated to 800 ° C. or higher in order to develop secondary recrystallization, and to about 1100 ° C. in order to sufficiently complete secondary recrystallization. Further, in the subsequent purification treatment, it is preferable to heat to a temperature of about 1200 ° C. in order to form a forsterite film. In addition, when using the raw material which does not contain an inhibitor formation component, you may abbreviate | omit a refinement | purification process.

  The forsterite coating (undercoating) of the grain-oriented electrical steel sheet thus manufactured has a uniform ratio of the standard deviation with respect to the average value of O intensity when the undercoating surface is subjected to mapping analysis by EPMA. It becomes. As a result, even with strain relief annealing in a highly reactive atmosphere such as DX gas, the base film does not deteriorate and a film having excellent adhesion can be obtained. In the EPMA mapping analysis, an area of 50 μm × 50 μm is measured at a pitch of 0.2 μm.

  The steel sheet after the above finish annealing is then washed with water, brushed, pickled, etc. to remove the unreacted annealing separator adhering to the steel sheet surface, and then coated with an insulating film, and this baking and shape correction are performed. It is preferable that the grain-oriented electrical steel sheet of the final product is obtained by performing planarization annealing that also serves as the end product.

  In order to further reduce the iron loss of the product plate, it is effective to perform a magnetic domain subdivision process. As a method of magnetic domain subdivision, a method of generally forming a groove in the final product plate or irradiating a laser or an electron beam to introduce linear or dotted thermal strain or impact strain, For example, a method of forming a groove by etching the steel sheet surface cold-rolled to the final thickness can be used. In the present invention, since a strong film that does not peel off even when irradiated with an electron beam can be formed, electron beam irradiation is preferable.

C: 0.070 mass%, Si: 3.4 mass%, Mn: 0.08 mass%, Al: 0.02 mass% and N: 0.008 mass%, the balance being Fe and inevitable impurities, a steel slab made of continuous casting After being reheated to a temperature of 1350 ° C. and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.4 mm, subjected to hot-rolled sheet annealing at 1000 ° C. × 50 s, and then subjected to primary cold rolling After an intermediate thickness of 1.8 mm and an intermediate annealing of 1100 ° C. × 20 s, secondary cold rolling was performed to finish a cold rolled sheet having a final thickness of 0.23 mm.
Next, after degreasing and pickling the cold-rolled sheet, using an electrolyte containing sodium silicate 30 g / L, surfactant 5 g / L, and various metal EDTA metal salts, a bath temperature of 70 ° C., At a current density of 0.1 to 20 A / dm ² , the electrolysis time was variously changed in the range of 0 to 15 s, and electrolytic treatment was performed to deposit metal particles on the steel sheet surface. At this time, the metal deposition state was changed by variously changing the metal salt concentration of the electrolytic solution and the pickling solution concentration before the electrolytic treatment.
Thereafter, the cold-rolled sheet is held in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 50 to 65 ° C. at a temperature of 840 ° C. for 100 s, and decarburization annealing that also serves as primary recrystallization annealing is performed. gave.
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 a finish annealing for a purification treatment of 1200 ° C. × 10 hr after the secondary recrystallization annealing. The atmosphere of the finish annealing was H _{2 at} 1200 ° C. holding for purification, and N ₂ at the time of temperature rise (including secondary recrystallization annealing) and at the time of temperature fall. Thereafter, an insulating film composed mainly of magnesium phosphate-colloidal silica was applied and baked by flattening annealing to obtain a product plate.

Samples were collected from the product plates obtained as described above, and evaluated for magnetic properties and bending adhesion after being subjected to strain relief annealing.
Here, as for the magnetic characteristics, the magnetic flux density B ₈ and the iron loss W _17/50 were measured by the method defined in JIS C2550.
Further, the adhesion of the film was subjected to strain relief annealing in a DX gas atmosphere (CO: 1 vol% + H ₂ : 1 vol% + CO ₂ : 12 vol% + balance: N ₂ , dew point: 10 ° C.) at 850 ° C. × 3 hr. The minimum diameter (bending peel diameter) at which the coating did not peel when the steel plate was wound around round bars with different diameters was measured.

In addition, the insulating film on the surface of the sample collected separately from the above measurement is removed by alkali washing, and a 50 μm × 50 μm area of the surface of the base film is analyzed by mapping analysis of O concentration at a 0.2 μm pitch with EPMA. The average value and standard deviation of all measured data of O intensity were determined, and the ratio of the standard deviation to the average value was obtained.
The measurement results are shown in Table 1. From this table, it can be seen that all the steel sheets suitable for the present invention are excellent in magnetic properties and coating properties.

A steel slab having various component compositions shown in Table 2 with the balance being Fe and inevitable impurities was manufactured by a continuous casting method, reheated to a temperature of 1380 ° C., and then hot-rolled to a thickness of 2.0 mm. The hot rolled sheet was subjected to hot rolled sheet annealing at 1030 ° C. × 10 s, and then cold rolled to finish a cold rolled sheet having a final sheet thickness of 0.23 mm.
Next, the cold-rolled sheet is degreased and pickled, and then an electrolytic solution to which sodium hydroxide 30 g / L, surfactant 5 g / L, and copper gluconate are added is used. The bath temperature is 70 ° C. and the current density is 2 A. Electrolytic treatment with an electrolytic time of 1 s at / dm ² was performed, and Cu was electrodeposited on the steel sheet surface. Under the present circumstances, the precipitation form of Cu particle | grains after electrolysis was variously changed by changing pickling conditions and the density | concentration of the copper gluconate of an electrolytic bath variously.
_{Then, 50vol% H 2 -50vol% N} 2, under a humid atmosphere with a dew point of 50-65 ° C., held between 100s at a temperature of 840 ° C., was subjected to decarburization annealing serving also as a primary recrystallization annealing, the MgO A main annealing separator was applied to the surface of the steel sheet in the form of a slurry, dried, and then subjected to a final recrystallization annealing followed by a finish annealing at a temperature of 1200 ° C. for 10 hours. The atmosphere of the finish annealing was H _{2 at} 1200 ° C. holding for purification, and N ₂ at the time of temperature rise (including secondary recrystallization annealing) and at the time of temperature fall. Thereafter, an insulating film composed mainly of magnesium phosphate-colloidal silica was applied and baked by flattening annealing to obtain a product plate.

  A sample was collected from the product plate obtained as described above, and the magnetic properties and film adhesion were evaluated in the same manner as in Example 1. It can be seen from the table that a grain-oriented electrical steel sheet having good magnetic properties and coating properties can be obtained by using a steel material having a composition suitable for the present invention.

Claims (6)

A grain-oriented electrical steel sheet having a forsterite base coating,
The standard deviation of O intensity when mapping analysis of the surface of the undercoat with EPMA is 0.15 or less of the average value,
A grain oriented electrical steel sheet having a bending peel diameter of 30 mmφ or less after strain relief annealing in a DX gas atmosphere. C: 0.03 to 0.08 mass%, Si: 2.5 to 4.5 mass%, and Mn: 0.03 to 0.30 mass%, and the remaining steel material consisting of Fe and inevitable impurities is hot. Rolled into a hot-rolled sheet, after having been subjected to hot-rolled sheet annealing or without being subjected to hot-rolled sheet annealing, cold-rolled at the final sheet thickness by cold rolling at least once with one or intermediate annealing in between In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of applying a annealing separating agent to the steel sheet surface after finishing decarburization annealing also serving as a primary recrystallization annealing, and finishing annealing,
2. The metal particles having an average particle diameter of 70 nm or less are deposited on the steel sheet surface at 25 particles / μm ² or more during the period from cold rolling to the final sheet thickness to decarburization annealing. A method for producing grain-oriented electrical steel sheets. The said steel raw material contains Se: 0.01-0.025mass% and / or S: 0.01-0.025mass% further in addition to the said component composition, The Claim 2 characterized by the above-mentioned. A method for producing grain-oriented electrical steel sheets. The steel material further contains Al: 0.01 to 0.03 mass% and N: 0.003 to 0.01 mass% in addition to the above component composition, or Al: 0.01 to 0.03 mass%. N: 0.003-0.01 mass%, Se: 0.01-0.025 mass% and / or S: 0.01-0.025 mass%, The direction according to claim 2 Method for producing an electrical steel sheet. Al, N, S and Se in the inevitable impurities contained in the steel material are Al: less than 0.01 mass%, N: less than 0.0050 mass%, S: less than 0.0050 mass%, and Se: 0.0030 mass. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein the grain-oriented electrical steel sheet is less than%. In addition to the above component composition, the steel material further includes Ni: 0.01 to 0.4 mass%, Cr: 0.01 to 0.25 mass%, Cu: 0.01 to 0.30 mass%, P: 0.00. 005 to 0.10 mass%, Sb: 0.005 to 0.10 mass%, Sn; 0.005 to 0.10 mass%, Bi: 0.005 to 0.10 mass%, Mo: 0.005 to 0.10 mass% , B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.01 mass%, Nb: 0.001 to 0.01 mass%, V: 0.001 to 0.01 mass%, and Ta: 0.001. The method for producing a grain-oriented electrical steel sheet according to any one of claims 2 to 5, comprising one or more selected from -0.01 mass%.

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