JP6842550B2 - Directional electrical steel sheet and its manufacturing method - Google Patents

Description

The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same, and more specifically, a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet capable of continuous annealing without annealing in a batch form in a coil state at the time of final annealing. Regarding the manufacturing method.

The grain-oriented electrical steel sheet is a soft magnetic material having a crystal orientation of {110} <001>, which is also known as a grain having a Goss orientation and has excellent magnetic properties in the rolling direction.
Such a directional electromagnetic steel sheet is rolled to the final thickness by hot rolling, hot rolling, and cold rolling after slab heating, and then at a high temperature for primary recrystallization annealing and secondary recrystallization formation. Manufactured after annealing.
At this time, it is known that during high-temperature annealing, the slower the temperature rise rate, the higher the degree of integration of the Goss orientation to be recrystallized secondarily, and the better the magnetism. Normally, the rate of temperature rise during high-temperature annealing of grain-oriented electrical steel sheets is 15 ° C. or less per hour, and not only does it take 2 to 3 days just to raise the temperature, but also 40 hours or more of purification annealing is required. It can be said that this is a process that consumes a lot of energy. Further, in the current final high-temperature annealing process, since the annealing in the batch form is performed in the coil state, the following difficulties in the process occur. First, temperature deviations occur in the outer and inner winding parts of the coil due to heat treatment in the coil state, and the same heat treatment pattern cannot be applied to each part, causing magnetic variations in the outer and inner winding parts. To do. Second, after decarburization annealing, the surface is coated with MgO, and various surface defects occur in the process of forming Base coating during high-temperature annealing, which lowers the actual yield. Third, the decarburized plate that has been decarburized and annealed is wound into a coil, then annealed at a high temperature, then flattened and annealed again to apply an insulating coating. There is a problem that the value is reduced.

An object of the present invention is to provide a directional electromagnetic steel plate capable of continuous annealing without annealing in a batch form in a coil state at the time of final annealing, and a method for producing the same.

The method for producing a directional electromagnetic steel sheet according to the present invention contains Si: 1.0% to 4.0% and C: 0.1% to 0.4% in mass%, and the balance is Fe and other inevitable. A step of providing a slab composed of mixed impurities, a step of reheating the slab, a step of hot-rolling the slab to produce a hot-rolled steel sheet, and a step of hot-rolling the hot-rolled steel sheet. A step of primary cold rolling the hot-rolled steel sheet that has been annealed, and a step of decarburizing and annealing the primary cold-rolled steel sheet.
Wherein the steps of rolling decarburization annealed steel sheet secondary cooling, the steps of continuous final annealing the second cold-rolled steel sheet, comprising the steps of pickling the final annealed steel sheet, the acid look-containing forming a ceramic coating layer washed steel sheet, wherein the pickling stages, using 5 to 50 wt% of acid aqueous solution, 15 seconds to 100 seconds acid at a temperature of 50 to 100 ° C. It is characterized by washing.

The stage of annealing the hot-rolled plate is characterized by including a decarburization process.

The step of annealing the hot-rolled plate includes a step of annealing at a temperature of 850 ° C. to 950 ° C. and a dew point temperature of 50 ° C. or higher, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. It is a feature.

The steps of decarburizing and annealing the primary cold-rolled steel sheet are a step of annealing at a temperature of 850 ° C. to 950 ° C. and a dew point temperature of 50 ° C. or higher, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. It is characterized by including a stage of annealing.

The step of decarburizing and annealing the primary cold-rolled steel sheet and the step of secondary cold-rolling the decarburized and annealed steel sheet are repeated two or more times.

Wherein the step of final annealing, include the steps of annealing at 850 ° C. to 1000 ° C. of temperature and dew point temperature 70 ° C. or less, and a step of annealing at a temperature and _H 2 50 vol% or more of the atmosphere 1000 ° C. to 1200 ° C. It is characterized by.

The step of forming the ceramic coating layer is characterized in that the ceramic powder is supplied to a heat source in which the inert gas is turned into plasma to form the ceramic coating layer.

The ceramic powder is characterized by containing _{Al 2} O ₃ , SiO ₂ , TiO ₂ , or ZrO _2.

The steps from the primary cold rolling step to the step of forming the ceramic coating layer are performed continuously.

Further, the directional electromagnetic steel sheet according to the present invention contains Si: 1.0% to 4.0%, C: 0.002% or less (not including 0%) in mass%, and the balance is Fe and others. It contains a base material composed of impurities that are inevitably mixed and a ceramic coating layer formed on the surface of the base material, and the base material has a diameter of an circumscribed circle with respect to a surface perpendicular to the thickness direction of the steel plate. the ratio of (D1) and the inscribed circle diameter (D2) (D2 / D1) is 0.5 or more Goss grains, seen containing 95 area% or more in total Goss grains, the substrate, It contains an oxygen-deficient layer formed from the surface of the base material to the inside of the base material to a depth of 2 to 5 μm, and the oxygen-deficient layer contains 100 ppm or less of oxygen .

The oxygen-deficient layer is characterized by containing 100 ppm or less of Mg.

The thickness of the ceramic coating layer is 10 nm to 4 μm.

The ceramic coating layer is characterized by containing _{Al 2} O ₃ , SiO ₂ , TiO ₂ or ZrO _2.

The ceramic coating layer is characterized by forming a pattern having a width (w) of 10 to 100 mm and an interval (d) of 10 to 100 mm in the rolling direction.

The base material is characterized in that the ratio of crystal grains having a crystal grain size of 20 μm to 500 μm is 80% or more.

According to the present invention, it is possible to provide a method for producing a grain-oriented electrical steel sheet capable of performing continuous annealing without performing batch annealing in a coil state at the time of final annealing.
In addition, grain-oriented electrical steel sheets can be produced only by annealing for a short time.
Further, unlike the conventional method for manufacturing grain-oriented electrical steel sheet, the step of winding the cold-rolled steel sheet is not required.
Further, the method for producing a grain-oriented electrical steel sheet according to an embodiment of the present invention can provide a grain-oriented electrical steel sheet without using a crystal grain growth inhibitor.
Further, immersion annealing can be omitted.

A schematic cross section of a grain-oriented electrical steel sheet according to an embodiment of the present invention is shown. A schematic perspective view of a grain-oriented electrical steel sheet according to another embodiment of the present invention is shown. It is a photograph which shows the distribution of Goss crystal grains with respect to the plane perpendicular to the thickness direction of the base material by EBSD analysis in the production example. It is a photograph which shows the distribution of the crystal grain with respect to the plane perpendicular to the thickness direction of the base material in the comparative production example.

Terms such as first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and / or sections. These terms are used only to distinguish one part, component, area, layer or section from another part, component, area, layer or section. Therefore, the first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.
The terminology used herein is merely to refer to a particular embodiment and is not intended to limit the invention. The singular form used herein also includes multiple forms, unless the wording has a clear opposite meaning. As used herein, the meaning of "contains" embodies a particular property, region, integer, stage, behavior, element and / or component, and other characteristics, region, integer, stage, behavior, element and / or. It does not exclude the presence or addition of ingredients.

When referring to one part being "above" another part, this may be just above the other part, or with another part in between. In contrast, when one mentions that one part is "directly above" another, no other part intervenes between them.
Although not defined separately, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those with ordinary knowledge in the technical field to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and currently disclosed content, and are not interpreted in an ideal or very formal sense unless defined.
Further, unless otherwise specified,% means mass%, and 1 ppm is 0.0001 mass%. Further, the goth crystal grain means a crystal grain having a crystal orientation within 15 degrees from {110} <001>.
In one embodiment of the present invention, the meaning of further containing an additional element means that an additional amount of the additional element is substituted for the remaining iron (Fe).
Hereinafter, examples of the present invention will be described in detail so that a person having ordinary knowledge in the technical field to which the present invention belongs can easily carry out the examples. However, the present invention is feasible in a variety of different forms and is not limited to the examples described herein.

The method for producing grain-oriented electrical steel sheets of the present invention first contains, in mass%, Si: 1.0% to 4.0%, C: 0.1% to 0.4%, and the balance is Fe and others. Provided is a slab composed of impurities that are inevitably mixed. Further, the slab may further contain Mn: more than 0% and 0.1% or less, and S: more than 0% and 0.005% or less in mass%. Further, the slab may further contain Bi: 0.001% to 0.1% in mass%.

The reason for limiting the composition is as follows.
Silicon (Si) lowers the magnetic anisotropy of electrical steel sheets, increases specific resistance, and improves iron loss. When the Si content is less than 1.0%, the iron loss is inferior, and when it exceeds 4.0%, the brittleness increases. Therefore, after the slab and the final annealing step, the Si content in the grain-oriented electrical steel sheet may be 1.0% to 4.0%.
Carbon (C) is in the slab because the Goss crystal grains in the surface layer are diffused to the center during the intermediate decarburization annealing and the final decarburization annealing, so that the process in which C in the center escapes to the surface is required. The content of C in may be 0.1 to 0.4% by mass. Further, after the final annealing step in which decarburization is completed, the carbon content in the grain-oriented electrical steel sheet may be 0.0020% by mass or less.

Manganese (Mn) and sulfur (S) form MnS precipitates and prevent the growth of Goss crystal grains that diffuse to the center during the decarburization process. Therefore, it is preferable that Mn and S are not added. However, in consideration of the amount unavoidably mixed during the steelmaking process, Mn and S in the grain-oriented electrical steel sheet are controlled to Mn: 0.1% or less and S: 0.005% or less after the slab and the final annealing step. It is preferable to do so.
Bismuth (Bi) is a highly volatile segregation element, and when it is located on the surface layer, it has the characteristic of volatilizing on the surface and coarsening the crystal grains on the surface layer. The part has the effect of making the crystal grains finer. If it is contained in less than 0.001% by mass, the effect may be slight. On the contrary, when it is added in excess of 0.1% by mass, it causes non-uniformity in the size of surface crystal grains, so it is preferable to add 0.001 to 0.1% by mass.

A slab of such composition is reheated. The slab reheating temperature may be 1100 ° C to 1350 ° C, which is higher than the normal reheating temperature.
When the temperature at the time of heating the slab is high, there is a problem that the hot-rolled structure is coarsened and adversely affects the magnetism. However, in the method for producing grain-oriented electrical steel sheet of the present invention, the carbon content is higher than before, and the hot-rolled structure is not coarsened even if the slab reheating temperature is high, and reheating is performed at a higher temperature than usual. This is advantageous during hot rolling.
Next, the heated slab is hot-rolled to produce a hot-rolled steel sheet.
Next, the hot-rolled steel sheet is annealed. At this time, the hot-rolled plate annealing can include a decarburization process. Specifically, the hot-rolled plate annealing includes a step of annealing at a temperature of 850 ° C. to 950 ° C. and a dew point temperature of 50 ° C. or higher, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. be able to.
Next, after performing hot-rolled plate decarburization annealing, pickling is performed and primary cold rolling is performed to produce a cold-rolled steel sheet.

Next, the cold-rolled steel sheet is decarburized and annealed. At this time, the decarburization annealing step can be carried out in a region where an austenite single-phase region or a complex phase of ferrite and austenite is present. Specifically, it can include a step of annealing at a temperature of 850 ° C. to 950 ° C. and a dew point temperature of 50 ° C. or higher, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. The amount of decarburized during decarburization annealing may be 0.0300 wt% to 0.0600 wt%. Further, the atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. In such a decarburization annealing process, the size of the crystal grains on the surface of the electrical steel sheet grows coarsely, but the crystal grains inside the electrical steel sheet remain as a fine structure. After such decarburization annealing, the size of the surface ferrite crystal grains may be 150 μm to 250 μm.

Next, the decarburized and annealed steel sheet is secondarily cold-rolled. In a normal manufacturing process of a high magnetic flux density directional electromagnetic steel sheet, it is known that cold rolling is effectively performed once at a high pressure reduction rate close to 90%. This is because only the Goss crystal grains in the primary recrystallized grains create an advantageous environment for particle growth.
However, the method for producing a directional electromagnetic steel plate according to an embodiment of the present invention does not utilize the abnormal grain growth of the crystal grains in the Goss orientation, and produces the Goss crystal grains in the surface layer portion generated by decarburization annealing and cold rolling. Since it is internally diffused, it is advantageous to form a large number of Goss-oriented crystal grains on the surface layer.
Therefore, during cold rolling, when cold rolling is carried out at a rolling reduction of 50% to 70%, a large number of Goss textures are formed on the surface layer portion. Alternatively, it may be 55% to 65%.
The steps of decarburizing and annealing the cold-rolled steel sheet and the secondary cold rolling of the decarburized and annealed steel sheet can be repeated two or more times. By repeating the process twice or more, a large number of Goss textures are formed on the surface layer.

Next, the electromagnetic steel sheet that has been decarburized and annealed and secondarily cold-rolled is finally annealed.
In the method for producing grain-oriented electrical steel sheets of the present invention, unlike the existing batch method, cold rolling is followed by continuous final annealing.
The method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, final annealing comprises the steps of annealing at 850 ° C. to 1000 ° C. of temperature and dew point temperature 70 ° C. or less, 1000 ° C. to 1200 temperature ° C. and _H 2 50 It can include a step of annealing in an atmosphere of% by volume or more. The atmosphere for the second stage, may be H 2 ₉₀ vol% or more.
The cold-rolled plate before the final annealing is in a state where decarburization annealing has progressed and the carbon content of the raw steel remains 40% by mass to 60% by mass with respect to the carbon content of the minimum slab. Therefore, at the time of final annealing, in the first stage, the crystal grains formed on the surface layer are diffused inside while carbon is released. In the first stage, decarburization can be carried out so that the amount of carbon in the steel sheet is 0.01% by mass or less.
After this, in the second stage, the texture having the Goth orientation diffused in the first stage grows.

In the method for producing a directional electromagnetic steel plate of the present invention, the grain size of the goth texture may be 1 mm or less, unlike the case where the crystal grains are grown by the conventional abnormal particle growth. Therefore, it is possible to have an aggregate structure in which a large number of Goth crystal grains having a smaller crystal grain size than the conventional grain-oriented electrical steel sheet are present.
The steel plate manufactured in this way has a ratio (D2 / D1) of the diameter of the circumscribed circle (D1) to the diameter of the inscribed circle (D2) of 0.5 with respect to the plane perpendicular to the thickness direction of the steel plate. The Goth crystal grains as described above can contain 95 area% or more of the total Goth crystal grains. The crystal structure of the steel sheet will be specifically described in the grain-oriented electrical steel sheet described later.
On the other hand, in the conventional batch form, at the time of final annealing, an annealing separator containing MgO as a main component is applied, so that an MgO coating layer exists. However, the directional electromagnetic steel sheet according to one embodiment of the present invention is a batch. The MgO coating layer does not exist because the final annealing can be carried out in a continuous manner that is not in the form.
As a result, in the grain-oriented electrical steel sheet according to the embodiment of the present invention, the Mg content from the surface of the steel sheet to a depth of 2 μm to 5 μm may be 100 ppm or less.

Next, the final annealed steel sheet is pickled. The pickling step removes the oxide layer naturally formed on the surface of the steel sheet. After all, an oxygen-deficient layer containing oxygen at a depth of 500 ppm or less is formed at a depth of 2 μm to 5 μm from the surface portion of the steel sheet. On the other hand, in the final annealing step, a non-metal layer (base coating layer) is formed using an annealing separator such as MgO, and the non-metal layer is removed again. In the so-called glassless method, the non-metal layer is removed. However, some of the oxygen diffused from the non-metal layer remains on the surface layer of the steel plate, and the surface layer contains oxygen.
In the pickling step, a 5 to 50% by mass acid aqueous solution can be used. At this time, as the acid aqueous solution, an aqueous solution containing an inorganic acid such as hydrochloric acid, nitric acid, or sulfuric acid can be used. If the concentration of the aqueous acid solution is too low, proper pickling may not be performed. Further, if the concentration of the acid aqueous solution is too high, the roughness of the surface of the steel sheet may be excessively increased, which may adversely affect the magnetism.

The pickling step is performed at a temperature of 50-100 ° C. If the temperature is too low, problems with poor pickling can occur. If the temperature is too high, reoxidation problems can occur.
The pickling step can be pickled for 5 to 100 seconds. If the time is too short, the oxide layer may not be removed sufficiently. If the time is too long, the non-uniformity of the pickling ability between the inside of the crystal grains and the grain size can rather deteriorate the magnetism. More specifically, the pickling step can be pickled for 15 to 35 seconds.
As described above, the oxygen-deficient layer is formed inside the base material by the pickling step under appropriate conditions, the movement of magnetic domains is smoothed, the magnetic history loss is reduced, and the magnetism can be further improved.

Next, a ceramic coating layer is formed on the pickled steel sheet.
Plasma can be used in the step of forming the ceramic coating layer. Specifically, the ceramic coating layer can be formed by supplying ceramic powder to a heat source in which the inert gas is turned into plasma. As a method for forming the ceramic coating layer, in one embodiment of the present invention, a coating method using plasma can be used.
The ceramic powder can contain Al ₂ O ₃ , SiO ₂ , TiO ₂ , or ZrO ₂ . The inert gas can include argon gas.
As described above, in one embodiment of the present invention, the final annealing step operated in the conventional batch form can be operated in the continuous annealing step, and the stage of forming the ceramic coating layer from the stage of primary cold rolling. Is performed continuously.

FIG. 1 schematically shows a cross section of a grain-oriented electrical steel sheet according to an embodiment of the present invention. As shown in FIG. 1, the grain-oriented electrical steel sheet 100 according to the embodiment of the present invention includes a base material 10 and a ceramic coating layer 20 formed on the surface of the base material 10. Hereinafter, each configuration will be described in detail. In FIG. 1, the x direction means the width direction of the steel sheet, and the z direction means the thickness direction of the steel sheet. Although not shown in FIG. 1, the y direction means the rolling direction of the steel sheet.
The base material contains Si: 1.0% to 4.0%, C: more than 0% and 0.002% or less, and the balance consists of Fe and other unavoidably mixed impurities. Since the element content and the reason of the base material have been specifically described with respect to the above-mentioned method for manufacturing grain-oriented electrical steel sheets, duplicate description will be omitted. As described above, since the decarburization process is included in the manufacturing process, the carbon content in the substrate can be 0.002% by mass or less, unlike the carbon content in the slab. Further, the base material may further contain Mn: more than 0% and 0.1% or less, and S: more than 0% and 0.005% or less in mass%. Further, the base material may further contain Bi: 0.001% to 0.1% in mass%.

The base material is a goth crystal in which the ratio (D2 / D1) of the diameter of the circumscribed circle (D1) to the diameter of the inscribed circle (D2) is 0.5 or more with respect to the plane perpendicular to the thickness direction of the steel plate. The grains can contain 95 area% or more of the total Goth crystal grains. Here, the circumscribed circle means the smallest circle among the virtual circles surrounding the outside of the crystal grain, and the inscribed circle means the largest circle among the virtual circles contained inside the crystal grain. ..
In the structure of the base material of the present invention, Goth crystal grains on the surface grow inside the steel sheet, so that crystal grains in a round shape are generated. On the other hand, in the existing grain-oriented electrical steel sheet, crystal grains having an elliptical shape longer than the structure according to the present invention are generated.
As described above, further excellent magnetism can be obtained by the unique base material structure according to the embodiment of the present invention.
The size of the crystal grains of the base material according to one embodiment of the present invention may be 20 μm to 500 μm, which may be 80% or more of the total crystal grains.
The base material 10 can include an oxygen-deficient layer 11 formed inside the base material from the surface of the base material 10. More specifically, the oxygen-deficient layer 11 is formed at a depth of 2 μm to 5 μm from the surface of the base material 10 to the inside of the base material.

The oxygen-deficient layer 11 can contain oxygen in an amount of 500 ppm or less. The remaining composition is the same as the alloy composition of the base material described above. Unlike existing base coating-free steel sheets, the base coating is not removed after it is formed. Therefore, by removing the naturally formed oxide layer by pickling, an oxygen-deficient layer is formed on the surface of the steel sheet. Can be formed.
The formation of the oxygen-deficient layer 11 facilitates the movement of magnetic domains, reduces magnetic history loss, and further improves magnetism. More specifically, the oxygen-deficient layer 11 can contain oxygen in an amount of 100 ppm or less. Further, since the base coating layer containing forsterite is not formed, Mg is contained in the oxygen-deficient layer 11 in the impurity range. Specifically, Mg can be contained in an amount of 100 ppm or less.
A ceramic coating layer 20 is formed on the surface of the base material 10. When the oxygen-deficient layer 11 is contained in the base material 10, the ceramic coating layer 20 is formed on the oxygen-deficient layer 11. A strong tension can act on the steel sheet by the ceramic coating layer 20, and the effects of magnetic domain miniaturization and iron loss improvement are maximized.

The thickness of the ceramic coating layer 20 may be 10 nm to 4 μm. If the thickness is too thin, the tension effect is unlikely to occur. If the thickness is too thick, the effect of improving iron loss will not occur any more, but rather, the space factor when used for the iron core of the transformer after laminating the steel plate will decrease, and the no-load loss of the transformer will increase. Can be the cause.
The ceramic coating layer 20 can contain Al ₂ O ₃ , SiO ₂ , TiO ₂ , or ZrO ₂ .
The ceramic coating layer 20 is formed on the entire surface of the base material 10, but may be formed only on a part of the surface of the base material. When formed on a part of the surface of the substrate, it is also possible to form a pattern. Specifically, the ceramic coating layer 20 can form a pattern having a width (w) of 10 to 100 mm and an interval (d) of 10 to 100 mm in the rolling direction. FIG. 2 schematically shows an example in which the ceramic coating layer 20 forms a pattern. As described above, when the ceramic coating layer 20 forms a pattern, the magnetism can be further improved.

Hereinafter, a detailed description will be given through examples. However, the following examples merely exemplify the present invention, and the content of the present invention is not limited to the following examples.
Production example: After heating a slab containing Si: 3.23%, C: 0.25% and the balance consisting of Fe and unavoidable impurities at a temperature of 1250 ° C. in the production mass% of the directional electromagnetic steel plate base material. , Hot-rolled to a thickness of 1.6 mm, then annealed at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 120 seconds, then annealed at a dew point temperature of 0 ° C. or lower, an annealing temperature of 1100 ° C. in a mixed gas atmosphere of hydrogen and nitrogen. After hot rolling plate annealing for 200 seconds and cooling, pickling was carried out and primary cold rolling was carried out at a reduction rate of 60%.
The cold-rolled plate is again annealed at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 60 seconds, and then annealed at an annealing temperature of 1100 ° C. and decarburization for 50 seconds in a mixed gas atmosphere of hydrogen, dew point temperature of 0 ° C. or less, hydrogen and nitrogen. After cooling, pickling was carried out and secondary cold rolling was carried out at a reduction rate of 60%. The final thickness was 288 μm.
After that, at the time of final annealing, annealing was carried out for 60 seconds in a wet mixed gas atmosphere of hydrogen and nitrogen (dew point temperature 60 ° C.) at a temperature of 900 ° C., and then annealing was carried out in a 100% H ₂ atmosphere at 1050 ° C. for 3 minutes. .. The carbon content of the final steel sheet was 30 ppm.
A photograph showing the distribution of Goss crystal grains with respect to a plane perpendicular to the thickness direction by EBSD analysis is shown in FIG.
Table 1 is a table showing the relative sizes of the inscribed circle and the circumscribed circle of the Goss crystal grains in the production example shown in FIG. 3 and their ratios (D2 / D1).

As shown in Table 1, it can be confirmed that the ratio (D2 / D1) of all Goss crystal grains is 0.5 or more.

Comparative production example: After heating a slab containing Si: 3.23% and C: 0.25% in the production mass% of the directional electromagnetic steel plate base material and composed of the balance Fe and unavoidable impurities at a temperature of 1250 ° C. , Hot-rolled to a thickness of 1.6 mm, then annealed at a dew point temperature of 0 ° C. or lower, a mixed gas atmosphere of hydrogen and nitrogen, annealed at a baking temperature of 1100 ° C. for 200 seconds, cooled, and then pickled. Was cold-rolled to a thickness of 288 μm.
The cold-rolled plate is again annealed at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 60 seconds, and then annealed at an annealing temperature of 1100 ° C. and decarburization for 50 seconds in a mixed gas atmosphere of hydrogen, dew point temperature of 0 ° C. or less, hydrogen and nitrogen. performed, it was performed for 3 minutes final annealing at 100% _{H 2} atmosphere at 1050 ° C..
A photograph showing the distribution of Goss crystal grains with respect to a plane perpendicular to the thickness direction by EBSD analysis is shown in FIG.
Table 2 is a table showing the relative sizes of the inscribed circle and the circumscribed circle of the grain-oriented electrical steel sheet shown in FIG. 4 and their ratios (D2 / D1).

As shown in Table 2, since the base material produced in the comparative production example is an elliptical crystal grain having a long structure, the value of D2 / D1 is smaller than that of the base material according to one embodiment of the present invention. You can confirm that.

Example 1
The grain-oriented electrical steel sheet base material produced in the production example was pickled with an aqueous HCl solution having a concentration of 25% by mass at 80 ° C. _{After that, an Al 2} O ₃ coating was formed on the entire surface of the steel sheet to a thickness of 3 μm.
Table 3 shows the changes in the thickness of the base steel sheet and the changes in the magnetic properties due to the pickling time. In addition, the amount of oxygen in the oxygen-deficient layer from the surface to a depth of 3 μm was measured and shown in Table 3 below. Furthermore, the iron loss magnetic flux density is measured using the single sheet measurement method, and the iron loss (W _17/50 ) until it is magnetized to 1.7 Tesla at 50 Hz and the magnetic flux density induced under a magnetic field of 1000 A / m. (B ₁₀ ) was measured. The results are summarized in Table 3 below.

As shown in Table 3, it can be confirmed that the invention materials 1 to 7 that have undergone the pickling step are superior in magnetism to the comparative material 1 that has not undergone the pickling step at all. In particular, it can be confirmed that the invention materials 3 to 6 in which the pickling time is 15 to 30 seconds are more excellent in magnetism than the other invention materials.

Example 2
The grain-oriented electrical steel sheet base material produced in the production example was pickled with an aqueous HCl solution having a concentration of 25% by mass at 80 ° C. After that, the ceramic powder was supplied to a heat source in which argon (Ar) gas was turned into plasma at an output of 200 kW to form a ceramic coating layer. At this time, a pattern was formed with a coating width (w) of 30 mm and a coating interval (d) of 20 mm. The type of ceramic and the thickness of the ceramic coating layer were changed as shown in Table 4 below, and the changes in magnetic properties due to this were summarized in Table 4.

As shown in Table 4, the magnetism can be further improved by appropriately forming the ceramic coating layer.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, a person having ordinary knowledge in the technical field to which the present invention belongs may change the technical idea and essential features of the present invention. You will understand that it is feasible in other concrete forms.
Therefore, it should be understood that the examples described above are exemplary in all respects and are not limiting. The scope of the present invention is indicated by the scope of claims, which will be described later rather than the detailed description above, and the meaning and scope of the claims, and any modification or modified form derived from the concept of equality thereof, are the present invention. Must be interpreted as being included in the scope of.

100: Electrical steel sheet 10: Base material 11: Oxygen-deficient layer 20: Ceramic coating layer

Claims (15)

A step of providing a slab containing Si: 1.0% to 4.0% and C: 0.1% to 0.4% in mass%, with the balance consisting of Fe and other unavoidably mixed impurities.
The stage of reheating the slab and
At the stage of hot-rolling the slab to produce a hot-rolled steel sheet,
The stage of annealing the hot-rolled steel sheet and
The stage of primary cold rolling of the hot-rolled steel sheet that has been annealed, and
At the stage of decarburizing and annealing the primary cold-rolled steel sheet,
The method comprising rolling the secondary cold decarburization annealed steel sheet,
A step of continuous final annealing the rolled steel sheet between the secondary cooling,
A step of pickling the final annealed steel sheet,
Forming a ceramic coating layer on the pickled steel sheet, only including,
The pickling step is a method for producing a directional electromagnetic steel plate, which comprises pickling at a temperature of 50 to 100 ° C. for 15 to 100 seconds using an acid aqueous solution of 5 to 50% by mass. The method for manufacturing a grain-oriented electrical steel sheet according to claim 1, wherein the step of annealing the hot-rolled sheet includes a decarburization step. The step of annealing the hot-rolled plate includes a step of annealing at a temperature of 850 ° C. to 950 ° C. and a dew point temperature of 50 ° C. or higher, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. The method for manufacturing a directional electromagnetic steel plate according to claim 1 to 2, wherein The steps of decarburizing and annealing the primary cold-rolled steel sheet are a step of annealing at a temperature of 850 ° C. to 950 ° C. and a dew point temperature of 50 ° C. or higher, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. The method for producing a directional electromagnetic steel sheet according to any one of claims 1 to 3, wherein the method includes a step of annealing. Claims 1 to 4 are characterized in that the step of decarburizing and annealing the primary cold-rolled steel sheet and the step of secondary cold-rolling the decarburized and annealed steel sheet are repeated two or more times. The method for manufacturing a directional electromagnetic steel sheet according to any one of the above items. The final annealing step includes a step of annealing at a temperature of 850 ° C. to 1000 ° C. and a dew point temperature of 70 ° C. or lower, and a step of annealing at a temperature of 1000 ° C. to 1200 ° C. and an atmosphere of H250% by volume or more. The method for manufacturing a directional electromagnetic steel sheet according to any one of claims 1 to 5, which is characteristic. The step of forming the ceramic coating layer is according to any one of claims 1 to 6 , wherein the ceramic powder is supplied to a heat source obtained by converting an inert gas into plasma to form the ceramic coating layer. Directional electromagnetic steel plate manufacturing method. The method for producing a grain-oriented electrical steel sheet according to claim 7 , wherein the ceramic powder contains Al ₂ O ₃ , SiO ₂ , TiO ₂ , or ZrO _2. The production of the grain-oriented electrical steel sheet according to any one of claims 1 to 8 , wherein the step of forming the ceramic coating layer from the step of the primary cold rolling is continuously performed. Method. A base material containing Si: 1.0% to 4.0% and C: 0.002% or less (not including 0%) in mass%, and the balance consisting of Fe and other unavoidably mixed impurities.
Includes a ceramic coating layer formed on the surface of the substrate.
The base material has a ratio (D2 / D1) of 0.5 or more between the diameter of the circumscribed circle (D1) and the diameter of the inscribed circle (D2) with respect to the plane perpendicular to the thickness direction of the steel plate. grains, seen containing 95 area% or more in total Goss grains,
The base material contains an oxygen-deficient layer formed from the surface of the base material to the inside of the base material to a depth of 2 to 5 μm.
The oxygen-deficient layer is a grain- oriented electrical steel sheet containing 100 ppm or less of oxygen. The grain-oriented electrical steel sheet according to claim 10 , wherein the oxygen-deficient layer contains 100 ppm or less of Mg. The grain-oriented electrical steel sheet according to claim 10 or 11 , wherein the thickness of the ceramic coating layer is 10 nm to 4 μm. The grain-oriented electrical steel sheet according to any one of claims 10 to 12 , wherein the ceramic coating layer contains Al ₂ O ₃ , SiO ₂ , TiO ₂ , or ZrO _2. The ceramic coating layer according to any one of claims 10 to 13 , characterized in that the ceramic coating layer forms a pattern having a width (w) of 10 to 100 mm and an interval (d) of 10 to 100 mm in the rolling direction. The described grain-oriented electrical steel sheet. The grain-oriented electrical steel sheet according to any one of claims 10 to 14 , wherein the base material has a crystal grain size of 20 μm to 500 μm and a crystal grain ratio of 80% or more. ..