JP6868030B2 - 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.

The grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction and composed of crystal grains having a crystal orientation of {110} <001>, also known as a Goss orientation.
Such a directional electromagnetic steel sheet is usually rolled to a final thickness of 0.15 to 0.35 mm by hot rolling, hot rolling sheet annealing, and cold rolling after slab heating, and then primary recrystallization annealing. And manufactured through high temperature annealing for secondary recrystallization.
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 secondary recrystallized Goth orientation 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 purified 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, the temperature deviation between the outer winding part and the inner winding part of the coil occurs due to the heat treatment in the coil state, the same heat treatment pattern cannot be applied to each part, and the magnetic deviation between the outer winding part and the inner winding part occurs. .. Second, after decarburization annealing, MgO is coated on the surface, and various surface defects occur in the process of forming Base coating during high-temperature annealing, which lowers the actual yield. Third, after the decarburized plate that has been decarburized and annealed is wound in a coil form, it is annealed at a high temperature and then flattened and annealed again to apply an insulating coating. Therefore, the actual yield is reduced by dividing the production process into three stages. Problems occur.

An object of the present invention is to provide a grain-oriented electrical steel sheet and a method for producing the same.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has Si: 1.0 to 4.0%, C: 0.002% or less (excluding 0%), and Bi: 0.001 to 10% by weight. It is characterized by containing 0.1% and the balance containing Fe and other unavoidable impurities.

Mn is 0.05% by weight or less (excluding 0% by weight), Al is 0.01% by weight or less (excluding 0% by weight), S is 0.001% by weight or less (excluding 0% by weight), and N. Can be further contained in an amount of 0.001% by weight or less (excluding 0% by weight).
P is 0.1% by weight or less (excluding 0% by weight), Mo is 0.05% by weight or less (excluding 0% by weight), Sn is 0.1% by weight or less (excluding 0% by weight), and Sb. May be further contained in an amount of 0.05% by weight or less (excluding 0% by weight).
It is preferable that the volume ratio of the crystal grains having a diameter of 20 to 500 μm is 80% or more.
The volume ratio of Goth crystal grains parallel to the plate surface of the steel sheet with an error range of 15 ° or less can be 80% or more.

The method for producing a directional electromagnetic steel sheet according to an embodiment of the present invention contains Si: 1.0 to 4.0% and C: 0.01 to 0.4% in% by weight, and the balance is Fe and others. The stage of heating a slab containing unavoidable impurities, the stage of hot-rolling a slab to produce a hot-rolled plate, the stage of hot-rolling a hot-rolled plate, and the stage of cold-rolling a hot-rolled plate that has been annealed. It includes a step of rolling to produce a cold-rolled sheet, a step of decarburizing the cold-rolled sheet, and a step of finally tanning an electromagnetic steel sheet that has been decarburized and annealed, and after a step of hot-rolling the hot-rolled sheet. The average grain size of the surface layer of the plate is 150 to 250 μm.

The slab may further contain 0.001 to 0.1% by weight of Bi.
The slab contains Mn of 0.05% by weight or less (excluding 0% by weight), Al of 0.01% by weight or less (excluding 0% by weight), and S of 0.001% by weight or less (excluding 0% by weight). , And N can be further contained in an amount of 0.001% by weight or less (excluding 0% by weight).
P is 0.1% by weight or less (excluding 0% by weight), Mo is 0.05% by weight or less (excluding 0% by weight), Sn is 0.1% by weight or less (excluding 0% by weight), and Sb. Is more preferably 0.05% by weight or less (excluding 0% by weight).

In the step of heating the slab, it is preferable to heat it to 1100 to 1350 ° C.
A decarburization process can be included in the stage of hot rolling plate annealing.
The stages of hot-rolled plate annealing are the first stage of hot-rolled plate annealing, which is annealed at a temperature of 850 ° C to 1000 ° C and a dew point temperature of 50 ° C to 70 ° C, a temperature of 1000 ° C to 1200 ° C, and a dew point of 0 ° C or less. It preferably includes a second stage of hot-rolled sheet annealing, which is annealed at temperature.
The first step of hot-rolled sheet annealing can be carried out for 10 to 300 seconds, and the second step of hot-rolled sheet annealing can be carried out for 10 to 180 seconds.

It is preferable that the steps from the step of manufacturing the cold-rolled sheet to the step of final annealing are continuously performed.
The step of manufacturing the cold-rolled plate and the step of decarburizing and annealing may be repeated two or more times and a plurality of times.
The decarburization annealing step can be annealed at a temperature of 850 ° C. to 1000 ° C. and a dew point temperature of 50 ° C. to 70 ° C.

The slab can further contain one or more of Ni and Cr, respectively, alone or in total amounts of 0.01% to 0.1% by weight.
The slab preferably further contains 0.005% by weight to 0.06% by weight of Sb.
The slab may further contain 0.001% to 0.015% by weight of Mo.
The slab preferably further contains one or more of Bi, Pb, Mg, As, Nb, and V in an amount of 0.0005% by weight to 0.005% by weight, respectively.
The slab can be heated to 1,050 ° C to 1,250 ° C.

The step of final annealing, the final implementing the final and first stage annealing, 1000 ° C. to 1200 temperature and _H 2 50 vol% or more of the atmosphere ° C. implementing annealed at 850 ° C. to 1000 ° C. and a dew point temperature of 70 ° C. or less It can include a second stage of annealing.
The first stage of final annealing can be carried out for 10 to 180 seconds and the second stage of final annealing can be carried out for 10 to 600 seconds.

According to the present invention, the method for producing a directional electromagnetic steel sheet of the present invention is a method for producing a directional electromagnetic steel sheet, which enables continuous annealing without performing batch annealing in a coil state at the time of final annealing. A manufacturing method can be provided.
Further, it is possible to produce a grain-oriented electrical steel sheet having excellent magnetism only by final annealing for a short time.
Moreover, the step of winding the cold-rolled steel sheet is not required.
Further, it is possible to provide a grain-oriented electrical steel sheet that does not use a crystal grain growth inhibitor.
It should be noted that immersion annealing can be omitted, and a grain-oriented electrical steel sheet having excellent magnetism can be stably produced.

This is the result of analyzing the crystal grain distribution after the hot-rolled plate containing 500 ppm of Bi in Example 2 was annealed by the hot-rolled plate. This is the result of analyzing the crystal grain distribution after the hot-rolled plate containing no Bi in Example 2 was annealed.

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 is referred to as the second part, component, region, layer or section within 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 text 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 above or with another part in between. In contrast, when one mentions that one part is "directly above" another, there is no other part in between.
Although not defined separately, all terms used herein, including technical and scientific terms, have the same meanings 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% by weight, and 1 ppm is 0.0001% by weight.
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.

In the existing directional electromagnetic steel sheet technology, precipitates such as AlN and MnS are used as crystal grain growth inhibitors, and the distribution of the precipitates is strictly controlled in all processes, and the secondary recrystallized steel sheet is used. The process conditions were very constrained by the conditions for removing the precipitates remaining inside.
On the other hand, in one embodiment of the present invention, precipitates such as AlN and MnS are not used as the crystal grain growth inhibitor, and secondary recrystallization is not used. In one embodiment of the present invention, by using Bi, the crystal grains in the surface layer portion are effectively grown at the stage of annealing the hot-rolled plate to increase the Goth crystal grain fraction, and an electromagnetic steel sheet having excellent magnetism is obtained. be able to.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has Si: 1.0 to 4.0%, C: 0.002% or less (excluding 0%), and Bi: 0.001 to 10% by weight. It contains 0.1% and the balance contains Fe and other unavoidable impurities.
Hereinafter, each component will be specifically described.

Silicon (Si) reduces the magnetic anisotropy of electrical steel sheets and increases specific resistance to improve iron loss. When the Si content is less than 1.0% by weight, the iron loss is inferior, and when it exceeds 4.0% by weight, the brittleness increases. Therefore, the Si content in the grain-oriented electrical steel sheet after the slab and the final annealing step may be 1.0% by weight to 4.0% by weight.
Carbon (C) requires a process in which C in the central portion escapes to the surface layer in order for Goth crystal grains in the surface layer to diffuse to the central portion during hot-rolled plate annealing, cold-rolled plate decarburization annealing, and final annealing. Therefore, the content of C in the slab may be 0.01 to 0.4% by weight. Further, the carbon content in the grain-oriented electrical steel sheet after the final annealing step in which decarburization is completed may be 0.0020% by weight or less.
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 weight, the effect may be negligible. On the contrary, when it is added in an amount of more than 0.1% by weight, non-uniformity of the size of the surface crystal grains is caused, so that it is preferable to add 0.001 to 0.1% by weight.

In one embodiment of the present invention, since precipitates such as AlN and MnS are not used as a crystal grain growth inhibitor, general directions such as manganese (Mn), aluminum (Al), nitrogen (N) and sulfur (S) are used. Elements used as essential in sex electromagnetic steel sheets are controlled within the range of impurities. That is, when Mn, Al, N, S and the like are inevitably further contained, Mn is 0.05% by weight or less, Al is 0.01% by weight or less, S is 0.001% by weight or less, and N is 0.001. It may be further contained in% by weight or less. More specifically, Al can be contained in an amount of 0.005% by weight or less.
Further, P is 0.1% by weight or less (excluding 0% by weight), Mo is 0.05% by weight or less (excluding 0% by weight), Sn is 0.1% by weight or less (excluding 0% by weight), And Sb may be further contained in an amount of 0.05% by weight or less (excluding 0% by weight).
Phosphorus (P) is a Goth crystal grain formation promoting element, and when excessively added, it may induce cracks and hinder crystal grain growth. Specifically, P can be contained in an amount of 0.001 to 0.1% by weight.

Molybdenum (Mo) is an element that promotes the formation of Goth crystal grains in hot-rolled plates. Although it does not prevent decarburization, an imbalance of crystal grains may occur when excessively added. Specifically, Mo can be contained in an amount of 0.001 to 0.05% by weight.
Tin (Sn) is a Goth crystal grain formation promoting element, and when excessively added, tin (Sn) may prevent decarburization by surface segregation and hinder crystal growth. Specifically, Sn can be contained in an amount of 0.001 to 0.1% by weight.
Antimony (Sb) is a Goth crystal grain formation promoting element, and when excessively added, it may prevent decarburization by surface segregation and hinder crystal growth. Specifically, Sb can be contained in an amount of 0.001 to 0.05% by weight.

In addition, as other unavoidable impurities, components such as Ti, Mg, and Ca react with oxygen in steel to form oxides, which hinder the movement of magnetic domains in the final product as inclusions and cause magnetic deterioration. Since it is possible, it is necessary to strongly suppress it. Therefore, when these are unavoidably contained, each component can be controlled to 0.005% by weight or less.
In the electrical steel sheet, the volume ratio of the crystal grains having a diameter of 20 to 500 μm may be 80% or more. When the volume ratio of the crystal grains having a diameter of 20 to 500 μm is less than 80%, the crystal grain growth may not be sufficient and the magnetism may decrease.

The volume ratio of Goth crystal grains parallel to the plate surface of the steel sheet with an error range of 15 ° or less may be 80% or more. If the volume ratio of Goth crystal grains is less than 80%, sufficient magnetism may not be ensured.
The method for producing a directional electromagnetic steel sheet according to an embodiment of the present invention contains Si: 1.0 to 4.0% and C: 0.01 to 0.4% in% by weight, and the balance is Fe and others. The stage of heating a slab containing unavoidable impurities, the stage of hot rolling the slab to produce a hot-rolled plate, the stage of annealing a hot-rolled plate, and the stage of cold-rolling a hot-rolled plate that has been annealed. It includes a step of rolling to produce a cold-rolled sheet, a step of decarburizing and annealing the cold-rolled sheet, and a step of final annealing of an electromagnetic steel sheet that has been decarburized and annealed.

Hereinafter, the method for manufacturing the grain-oriented electrical steel sheet will be specifically described for each step.
First, heat the slab.
Since the composition of the slab has been specifically described in relation to the composition of the electrical steel sheet, duplicate description will be omitted.
The slab heating temperature may be 1100 ° C. to 1350 ° C., which is higher than the normal heating temperature. When the temperature at the time of heating the slab is high, there is a problem that the hot-rolled structure becomes coarse and adversely affects the magnetism. However, in the method for producing a directional electromagnetic steel sheet according to an embodiment of the present invention, the carbon content in the slab is higher than before, and the hot-rolled structure does not become coarse even when the slab heating temperature is high, which is normal. In some cases, heating at a higher temperature is advantageous during hot rolling.

Next, the slab is hot-rolled to produce a hot-rolled plate. The hot rolling temperature is not limited, and as one embodiment, hot rolling can be completed at 950 ° C. or lower.
Next, the hot-rolled plate is annealed. At this time, the hot-rolled sheet annealing can include a decarburization process. Specifically, decarburization annealing can be carried out at a dew point temperature of 50 ° C. to 70 ° C. in an austenite single-phase region or a region in which a composite phase of ferrite and austenite is present. At this time, the temperature range may be 850 ° C to 1000 ° C. Further, the atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. Further, the amount of decarburized during decarburization annealing may be 0.0300% by weight to 0.0600% by weight. More specifically, in order to include a decarburization process, the steps of hot-rolled sheet annealing are the first step of hot-rolled sheet annealing, which is annealed at a temperature of 850 ° C. to 1000 ° C. and a dew point temperature of 50 ° C. to 70 ° C. , A second stage of hot rolled plate annealing, which is annealed at a temperature of 1000 ° C. to 1200 ° C. and a dew point temperature of 0 ° C. or lower. More specifically, the first step of hot-rolled sheet annealing can be carried out for 10 to 300 seconds, and the second step of hot-rolled sheet annealing can be carried out for 10 to 180 seconds.

In the decarburization annealing process, the size of the crystal grains on the surface of the hot-rolled sheet grows coarsely, but the crystal grains inside the electrical steel sheet remain as a fine structure. The size of the ferrite crystal grains on the surface portion after such decarburization annealing may be 150 μm to 250 μm. At this time, by adjusting the average grain grain size of the surface layer portion to the above-mentioned range, the goth crystal grain fraction of the grain-oriented electrical steel sheet finally produced can be increased, and the magnetism of the grain-oriented electrical steel sheet can be increased. Can be improved.
Next, the hot-rolled plate that has been annealed is cold-rolled to produce a cold-rolled plate. It is known that in a normal manufacturing process of a high magnetic flux density directional electromagnetic steel sheet, it is effective to carry out cold rolling once at a high pressure reduction rate close to 90%. This is because only Goth crystal grains among the primary recrystallized grains create an environment favorable for particle growth.
However, the method for producing a directional electromagnetic steel sheet according to an embodiment of the present invention does not utilize the abnormal grain growth of Goth-oriented crystal grains, and produces Goth crystal grains on 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 Goth-oriented crystal grains on the surface layer.
Therefore, when cold rolling is carried out at a rolling reduction of 50% to 70% during cold rolling, a large number of Goth textures are formed on the surface layer portion. Alternatively, it may be 55% to 65%.

Next, the cold rolled plate is decarburized and annealed. It can be annealed at a temperature of 850 ° C to 1000 ° C and a dew point temperature of 50 ° C to 70 ° C.
Further, when the cold rolling and decarburization annealing processes are carried out twice or more and a plurality of times, a large number of Goth textures are formed on the surface layer portion.
Next, the electromagnetic steel sheet that has been decarburized and annealed is finally annealed.
In the method for manufacturing grain-oriented electrical steel sheets according to an embodiment of the present invention, unlike the existing batch method, cold rolling can be followed by continuous final annealing. That is, the process from the stage of manufacturing the cold-rolled plate to the stage of final annealing is continuously performed. Therefore, it is not necessary to apply an annealing separator.

The final annealing steps are carried out in the first step of final annealing in which annealing is carried out at 850 ° C. to 1000 ° C. and a dew point temperature of 70 ° C. or lower, and in _{an atmosphere at a temperature of 1000 ° C. to 1200 ° C. and H 2} of 50% by volume or more. A second stage of final annealing and can be included. More specifically, the second stage of final annealing can be carried out in an atmosphere where _{H 2 is 90% by volume or more.}
As described above, in one embodiment of the present invention, Bi segregation can be used as the crystal grain growth inhibitor, and AlN precipitate is not used. Therefore, the burden of purification annealing for decomposing and removing AlN and MnS is reduced.

Hereinafter, the present invention will be described in more detail through examples. However, such examples are merely for exemplifying the present invention, and the present invention is not limited thereto.
Example 1
A slab containing Si: 3.23% and C: 0.25% by weight and consisting of the balance Fe and unavoidable impurities was heated at a temperature of 1250 ° C. and then hot-rolled to a thickness of 1.6 mm. .. Next, after annealing at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 120 seconds, the annealing temperature was 1100 ° C. in a mixed gas atmosphere of hydrogen and nitrogen having an annealing temperature of 0 ° C. or lower, and hot rolling was performed for the time summarized in Table 1 below. After plate annealing and cooling, pickling was carried out and cold rolling was carried out at a rolling reduction of 60%.
The cold-rolled cold-rolled sheet is again annealed at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 60 seconds, and then decarburized and annealed at an annealing temperature of 1100 ° C. and 50 seconds in a mixed gas atmosphere of hydrogen and nitrogen at a dew point temperature of 0 ° C. After carrying out and cooling, pickling was carried out and cold rolling was carried out at a reduction rate of 60%.

表１に示したとおり、熱延板焼鈍時、露点温度０℃以下、焼鈍温度１１００℃での焼鈍時間が長くなるほど表層部の結晶粒が成長して、ゴス分率および磁性に優れていることが分かる。しかし、焼鈍時間が適正値より長くなると、内部の結晶粒が成長して冷間圧延後の脱炭焼鈍時に組織が不均一になり、最終磁性が劣る原因となる。 Thereafter, at the time of final annealing, hydrogen at a temperature of 900 ° C., wet (dew point 60 ° C.) of nitrogen was carried out for 60 seconds decarburization annealing in a mixed gas atmosphere, heat treatment for 3 minutes at 100 vol% H ₂ atmosphere at 1050 ° C. Was carried out. The annealing time at 1100 ° C. during hot-rolled sheet annealing, the grain diameter of the surface layer after hot-rolled sheet annealing, the Goth crystal grain fraction of the final electrical steel sheet, and the magnetic properties of the final electrical steel sheet were measured and described below. It is shown in Table 1.

As shown in Table 1, the crystal grains on the surface layer grow as the annealing time at the dew point temperature of 0 ° C or lower and the annealing temperature of 1100 ° C becomes longer during hot rolling plate annealing, and the goth fraction and magnetism are excellent. I understand. However, if the annealing time is longer than the appropriate value, the crystal grains inside grow and the structure becomes non-uniform during decarburization annealing after cold rolling, which causes inferior final magnetism.

表２に示したとおり、Ｂｉを結晶粒成長抑制剤として用いて、熱延板焼鈍後の表層部の結晶粒粒径を適切に調節することができ、ゴス分率および磁性に優れていることが分かる。 Example 2
By weight%, Si: 3.22%, C: 0.245%, Bi is contained as shown in Table 2 below, and the slab consisting of the balance Fe and unavoidable impurities is heated at a temperature of 1250 ° C. and then 1.6 mm. Hot-rolled to the thickness of 1100 ° C, then annealed at an annealing temperature of 870 ° C and a dew point temperature of 60 ° C for 120 seconds, and then hot-rolled at an annealing temperature of 1100 ° C and 30 seconds in a mixed gas atmosphere of hydrogen and nitrogen with an annealing temperature of 0 ° C or less. After plate annealing and cooling, pickling was carried out and cold rolling was carried out at a rolling reduction of 60%.
The cold-rolled plate is again annealed by decarburization at an annealing temperature of 870 ° C. and an annealing temperature of 60 ° C. for 60 seconds, and then annealed at an annealing temperature of 1100 ° C. and 50 seconds in a mixed gas atmosphere of hydrogen and nitrogen at an annealing temperature of 0 ° C. After cooling, pickling was carried out and cold rolling was performed at a rolling reduction of 60%.
Thereafter, at the time of final annealing, hydrogen at a temperature of 900 ° C., wet (dew point 60 ° C.) of nitrogen was carried out for 60 seconds decarburization annealing in a mixed gas atmosphere, heat treatment for 3 minutes at 100 vol% H ₂ atmosphere at 1050 ° C. Was carried out. The Bi content during hot-rolled sheet annealing, the diameter of the crystal grains on the surface layer after hot-rolled sheet annealing, the Goth crystal grain fraction of the final electrical steel sheet, and the magnetic properties of the final electrical steel sheet were measured and shown in Table 2 below. Indicated.

As shown in Table 2, Bi can be used as a crystal grain growth inhibitor to appropriately adjust the grain size of the surface layer after annealing on a hot-rolled plate, and has excellent goth fraction and magnetism. I understand.

表３に示したとおり、熱延板焼鈍時、露点温度０℃以下、焼鈍温度１１００℃での焼鈍時間が長くなるほど表層部の結晶粒が成長して、ゴス分率および磁性に優れていることが分かる。しかし、焼鈍時間が適正値より長くなると、内部の結晶粒が成長して冷間圧延後の脱炭焼鈍時に組織が不均一になり、最終磁性が劣る原因となる。 Example 3
By weight%, a slab containing Si: 3.19%, C: 0.24%, Bi: 0.05% and composed of the balance Fe and unavoidable impurities was heated at a temperature of 1250 ° C. and then 1.6 mm. It is hot-rolled to a thickness, then annealed at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 120 seconds, and then annealed at a mixed gas atmosphere of hydrogen, a dew point temperature of 0 ° C. or lower, and nitrogen at a annealing temperature of 1100 ° C. and Table 3 below. The hot-rolled sheet was annealed for the time described in the above, cooled, pickled, and cold-rolled at a reduction rate of 60%.
The cold-rolled plate is again annealed by decarburization at an annealing temperature of 870 ° C. and an annealing temperature of 60 ° C. for 60 seconds, and then annealed at an annealing temperature of 1100 ° C. and 50 seconds in a mixed gas atmosphere of hydrogen and nitrogen at an annealing temperature of 0 ° C. After cooling, pickling was carried out and cold rolling was performed at a rolling reduction of 60%.
Thereafter, at the time of final annealing, hydrogen at a temperature of 900 ° C., wet (dew point 60 ° C.) of nitrogen was carried out for 60 seconds decarburization annealing in a mixed gas atmosphere, heat treatment for 3 minutes at 100 vol% H ₂ atmosphere at 1050 ° C. Was carried out. The annealing time at 1100 ° C. during hot-rolled sheet annealing, the grain diameter of the surface layer after hot-rolled sheet annealing, the Goth crystal grain fraction of the final electrical steel sheet, and the magnetic properties of the final electrical steel sheet were measured and described below. It is shown in Table 3.

As shown in Table 3, the crystal grains on the surface layer grow as the annealing time at the dew point temperature of 0 ° C or lower and the annealing temperature of 1100 ° C becomes longer during hot rolling plate annealing, and the goth fraction and magnetism are excellent. I understand. However, if the annealing time is longer than the appropriate value, the crystal grains inside grow and the structure becomes non-uniform during decarburization annealing after cold rolling, which causes inferior final magnetism.

表４、表５に示したとおり、Ｐ、Ｓｎ、Ｓｂ、Ｍｏなどの成分を適切な範囲で追加的に含む時、磁性を向上させる効果が得られることを確認できる。Ａｌ、Ｍｎの場合、酸化度が高くて多量含む場合、磁性に有害な方位の結晶粒を形成して、磁性に悪影響を及ぼすことを確認できる。 Example 4
By weight%, Si: 3.19%, C: 0.24%, Bi: 0.05%, P, Sn, Sb, Mo, Al, Mn are contained as shown in Table 4 below, and the balance Fe and A slab composed of unavoidable impurities is heated at a temperature of 1250 ° C. and then hot-rolled to a thickness of 1.6 mm. Then, after annealing at an annealing temperature of 870 ° C. and a dew point temperature of 60 ° C. for 120 seconds, hydrogen and a dew point temperature of 0. Annealing was carried out at a annealing temperature of 1100 ° C. for 120 seconds in a mixed gas atmosphere of hydrogen and nitrogen at ° C. or lower, and after cooling, pickling was carried out and 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 an annealing temperature of 60 ° C. for 60 seconds, and then annealed at an annealing temperature of 1100 ° C. and 50 seconds in a mixed gas atmosphere of hydrogen and nitrogen at an annealing temperature of 0 ° C. After cooling, pickling was carried out and cold rolling was performed at a rolling reduction of 60%. Thereafter, at the time of final annealing, hydrogen at a temperature of 900 ° C., wet (dew point 60 ° C.) of nitrogen was carried out for 60 seconds decarburization annealing in a mixed gas atmosphere, heat treatment for 3 minutes at 100 vol% H ₂ atmosphere at 1100 ° C. Was carried out. The size of the surface crystal grains of the hot-rolled annealed sheet, the Goth crystal grain fraction of the final electromagnetic steel sheet, and the magnetic characteristics of the final electromagnetic steel sheet were measured according to each component and are shown in Table 5 below.

As shown in Tables 4 and 5, it can be confirmed that the effect of improving magnetism can be obtained when components such as P, Sn, Sb, and Mo are additionally contained in an appropriate range. In the case of Al and Mn, when the degree of oxidation is high and a large amount is contained, it can be confirmed that crystal grains having an orientation harmful to magnetism are formed and adversely affect magnetism.

The present invention is not limited to the examples, and can be produced in various forms different from each other, and a person having ordinary knowledge in the technical field to which the present invention belongs is the technical idea and essential features of the present invention. You will understand that it can be implemented in other concrete forms without modification. Therefore, it should be understood that the above examples are exemplary in all respects and are not limiting.

Claims (10)

By weight%, Si: 1.0 to 4.0%, C: 0.01 to 0.4%, Bi: 0.001 to 0.1%, Mn: 0.05% or less (excluding 0% by weight) ), Al: 0.01% or less (excluding 0% by weight), S: 0.001% or less (excluding 0% by weight), N: 0.001% or less (excluding 0% by weight), P: 0 .1% or less (excluding 0% by weight), Mo: 0.05% or less (excluding 0% by weight), Sn: 0.1% or less (excluding 0% by weight), and Sb: 0.05% or less The stage of heating a slab, including (excluding 0% by weight) and the balance consisting of Fe and other unavoidable impurities,
The stage of hot-rolling the slab to produce a hot-rolled sheet,
The stage of annealing the hot-rolled plate,
The stage of cold-rolling a hot-rolled plate that has been annealed to produce a cold-rolled plate,
Including a step of decarburizing and annealing the cold-rolled sheet and a step of final annealing of the electromagnetic steel sheet for which decarburization and annealing has been completed.
In the final annealing step, the final annealing is carried out by continuous annealing, and the final annealing is carried out.
After the step of annealing the hot-rolled plate, the average crystal grain size of the surface layer of the hot-rolled plate is 150 to 250 μm.
After the final annealing step, the volume ratio of the crystal grains having a diameter of 20 to 500 μm is 80% or more.
A method for producing a directional electromagnetic steel sheet, characterized in that the volume ratio of Goth crystal grains parallel to the plate surface of the steel sheet in an error range of 15 ° or less is 80% or more. The method for producing a grain-oriented electrical steel sheet according to claim 1 , wherein the slab is heated to 1100 to 1350 ° C. at the stage of heating the slab. In the step of annealing the hot-rolled sheet, a manufacturing method of the grain-oriented electrical steel sheet according to claim 1 or 2 you comprising a decarburization process. The steps of hot-rolled sheet annealing are the first step of hot-rolled sheet annealing, which is annealed at a temperature of 850 ° C. to 1000 ° C. and a dew point temperature of 50 ° C. to 70 ° C., and a temperature of 1000 ° C. to 1200 ° C. and 0 ° C. or lower. The method for producing a directional electromagnetic steel sheet according to any one of claims 1 to 3 , further comprising a second step of hot-rolled sheet annealing, which is annealed at a dew point temperature. The production of the grain-oriented electrical steel sheet according to claim 4 , wherein the first step of the hot-rolled sheet annealing is carried out for 10 to 300 seconds, and the second step of the hot-rolled sheet annealing is carried out for 10 to 180 seconds. Method. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 5 , wherein the steps from the step of manufacturing the cold-rolled sheet to the step of final annealing are continuously performed. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 6 , wherein the step of manufacturing the cold-rolled sheet and the step of decarburizing and annealing are repeated two or more times. The grain-oriented electrical steel sheet according to any one of claims 1 to 7 , wherein the decarburization annealing step is annealed at a temperature of 850 ° C. to 1000 ° C. and a dew point temperature of 50 ° C. to 70 ° C. Production method. Wherein the step of final annealing, the first stage of the final annealing implementing annealing temperature and 70 ° C. below the dew point temperature of 850 ℃ ~1000 ℃, 1000 ℃ ~1200 temperature and _H 2 50 vol% or more of the atmosphere ° C. The method for producing a directional electromagnetic steel plate according to any one of claims 4 to 8 , further comprising a second step of final annealing carried out in 1. The method for manufacturing a grain-oriented electrical steel sheet according to claim 9 , wherein the first step of the final annealing is carried out for 10 to 180 seconds, and the second step of the final annealing is carried out for 10 to 600 seconds.

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