KR102177044B1 - Grain oriented electrical steel sheet and manufacturing method of the same - Google Patents

Abstract

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of heating the slab; Manufacturing a hot-rolled steel sheet by hot rolling the slab; Annealing the hot-rolled steel sheet; Hot-rolled sheet The step of first cold rolling the annealed hot-rolled steel sheet; Decarburization annealing the first cold-rolled steel sheet; Secondary cold rolling the steel sheet on which the decarburization annealing has been completed; It includes the step of continuously annealing the steel sheet on which the secondary cold rolling is completed, and the step of batch annealing the continuously annealed steel sheet.

Description

Grain-oriented electrical steel sheet and its manufacturing method {GRAIN ORIENTED ELECTRICAL STEEL SHEET AND MANUFACTURING METHOD OF THE SAME}

It relates to grain-oriented electrical steel sheet and its manufacturing method. Specifically, it relates to a grain-oriented electrical steel sheet in which magnetic properties are improved by including a plurality of cold rolling and decarburization annealing processes, and a manufacturing method thereof.

A grain-oriented electrical steel sheet is a soft magnetic material that has excellent magnetic properties in the rolling direction, which is composed of crystal grains having a so-called Goss orientation whose crystal orientation is {110}<001>.

The grain-oriented electrical steel sheet is produced by heating the slab and then rolling to the final thickness through hot rolling, hot-rolled sheet annealing, and cold rolling, and then subjected to primary recrystallization annealing and high-temperature annealing to form secondary recrystallization.

In general, the secondary recrystallization annealing process of grain-oriented electrical steel sheet requires a low temperature increase rate and long-term purifying annealing at a high temperature, which can be said to be a process that consumes a lot of energy. Since secondary recrystallization is formed through such an extreme process to manufacture a grain-oriented electrical steel sheet having excellent magnetic properties, the following difficulties arise in the process.

First, due to the heat treatment in the coil state, a temperature difference between the outer and inner windings of the coil occurs, and the same heat treatment pattern cannot be applied to each part, resulting in a magnetic deviation between the outer and inner windings. Second, since various surface defects occur in the process of coating the surface with MgO after decarburization annealing and forming the base coating during high temperature annealing, the error rate is lowered. Third, since the decarburized plate after decarburization annealing is wound in a coil shape and then subjected to planarization annealing again after high-temperature annealing to perform insulation coating, the production process is divided into three stages, resulting in a problem that the error rate decreases.

In order to overcome such process limitations, a technique using normal crystal growth has been proposed without using the secondary recrystallization phenomenon by adjusting the decarburization annealing and cold reduction rate. However, through continuous annealing, there is a limit to the grain growth of the final grain due to a short heat treatment time of several minutes, and there is a limit to improvement of iron loss due to the failure to grow into grains having an optimal grain size.

A grain-oriented electrical steel sheet and a manufacturing method thereof are provided. Specifically, by including a plurality of cold rolling and decarburization annealing processes, a grain-oriented electrical steel sheet having improved magnetic properties and a method of manufacturing the same are provided.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of heating the slab; Manufacturing a hot-rolled steel sheet by hot rolling the slab; Annealing the hot-rolled steel sheet; Hot-rolled sheet The step of first cold rolling the annealed hot-rolled steel sheet; Decarburization annealing the first cold-rolled steel sheet; Secondary cold rolling the steel sheet on which the decarburization annealing has been completed; It includes the step of continuously annealing the steel sheet on which the secondary cold rolling is completed, and the step of batch annealing the continuously annealed steel sheet.

The slab is in weight %, Si: 1.0% to 4.0%, C: 0.1% to 0.4%, and the balance may contain Fe and unavoidable impurities.

The slab may further include Mn: 0.1 wt% or less and S: 0.005 wt% or less.

In the step of annealing the hot-rolled sheet, a decarburization process may be included.

The step of annealing the hot-rolled sheet may be annealed at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C.

The step of decarburizing annealing the first cold-rolled steel sheet may be annealed at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C.

The step of decarburizing annealing the first cold-rolled steel sheet may be annealed in an austenite single phase region or a region in which a composite phase of ferrite and austenite exists.

After the step of decarburizing annealing the first cold-rolled steel sheet, the average diameter of the crystal grains may be 150 to 250㎛.

The step of decarburizing annealing the first cold-rolled steel sheet and the step of secondary cold rolling the steel sheet on which the decarburization annealing is completed may be repeated two or more times.

The step of continuous annealing may be annealed at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C.

The step of continuous annealing may be annealing for 1 to 5 minutes.

The batch annealing step may be annealing at a temperature of 1000° C. to 1200° C. and a dew point temperature of -20° C. or less.

The batch annealing step can be annealing for 1 to 8 hours.

After the batch annealing step, the volume fraction of the crystal grains forming an angle of 15 degrees or less from {110}<001> may be 40% or more.

After the batch annealing step, a grain area fraction having a diameter of 1000 μm to 5000 μm among the total grains may be 20 to 70%.

The grain-oriented electrical steel sheet according to an embodiment of the present invention may have a grain area fraction having a diameter of 1000 μm to 5000 μm among the total grains of 20 to 70%.

The electrical steel sheet is a weight %, Si: 1.0% to 4.0%, C: 0.005% or less (excluding 0%), and the balance may contain Fe and inevitable impurities.

The electrical steel sheet may further include Mn: 0.1 wt% or less and S: 0.005 wt% or less.

The volume fraction of crystal grains forming an angle of 15 degrees or less from {110}<001> may be 40% or more.

The Goth grains having a ratio (D2/D1) of the circumscribed circle diameter (D1) to the inscribed circle diameter (D2) of 0.5 or more may be 95 area% or more of the total Goth grains.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has excellent magnetic properties by stably forming Goth grains having a large diameter while using normal crystal growth.

In addition, since AlN and MnS are not used as grain growth inhibitors, there is no need to heat the slab at a high temperature of 1300°C or higher.

In addition, it is not necessary to remove the precipitates N and S, the purification annealing time can be relatively shortened, and productivity can be improved.

In addition, it is possible to provide a grain-oriented electrical steel sheet having magnetic properties cracked in the width direction.

1 is a photograph of an observation of the surface of a grain-oriented electrical steel sheet prepared in Inventive Material 2 with a scanning electron microscope.
2 is a photograph of the surface of the grain-oriented electrical steel sheet prepared in Comparative Material 2 observed with a scanning electron microscope.

Terms such as first, second and third are used to describe various parts, components, regions, layers, and/or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a 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 for referring only to specific embodiments and is not intended to limit the present invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” specifies a specific characteristic, region, integer, step, action, element and/or component, and the presence of another characteristic, region, integer, step, action, element and/or component It does not exclude additions.

When a part is referred to as being "on" or "on" another part, it may be directly on or on another part, or other parts may be involved in between. In contrast, when a part is referred to as being “directly above” another part, no other part is intervened.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in a commonly used dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal meaning unless defined.

In addition, unless otherwise specified,% means% by weight, and 1 ppm is 0.0001% by weight.

In an embodiment of the present invention, the meaning of further including an additional element means to include the remaining iron (Fe) by replacing the amount of the additional element.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of heating the slab; Manufacturing a hot-rolled steel sheet by hot rolling the slab; Annealing the hot-rolled steel sheet; Hot-rolled sheet The step of first cold rolling the annealed hot-rolled steel sheet; Decarburization annealing the first cold-rolled steel sheet; Secondary cold rolling the steel sheet on which the decarburization annealing has been completed; It includes the step of continuously annealing the steel sheet on which the secondary cold rolling is completed, and the step of batch annealing the continuously annealed steel sheet.

Hereinafter, each step will be described in detail.

First, the slab is heated.

The slab is in weight %, Si: 1.0% to 4.0%, C: 0.1% to 0.4%, and the balance may contain Fe and unavoidable impurities.

The reason for limiting the composition is as follows.

Silicon (Si) improves iron loss by lowering the magnetic anisotropy of the electrical steel sheet and increasing the specific resistance. When the Si content is less than 1.0% by weight, the iron loss is inferior, and when the Si content is more than 4.0% by weight, brittleness increases. Therefore, the content of Si in the grain-oriented electrical steel sheet after the slab and the final annealing step may be 1.0 to 4.0% by weight. More specifically, the content of Si may be 1.5 to 3.5% by weight.

The content of C in the slab may be 0.1 to 0.4% by weight, because carbon (C) requires a process in which the C in the center is released to the surface in order to diffuse the Goss grains in the center during intermediate decarburization annealing and final decarburization annealing. . More specifically, the content of C in the slab may be 0.15 to 0.3% by weight. In addition, the amount of carbon in the final grain-oriented electrical steel sheet after the final annealing step in which decarburization is completed may be 0.0050% by weight or less. More specifically, it may be 0.002% by weight or less.

The slab may further include Mn: 0.1 wt% or less and S: 0.005 wt% or less.

Mn and S form MnS precipitates and hinder the growth of Goss 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 inevitably mixed during the steel making process, Mn and S in the grain-oriented electrical steel sheet after the slab and the final annealing step can be controlled to Mn: 0.1% by weight or less and S: 0.005% by weight or less.

The balance contains Fe and unavoidable impurities. The inevitable impurities are impurities that are mixed in the steel making step and the manufacturing process of the grain-oriented electrical steel sheet, and since this is widely known in the field, a detailed description will be omitted. Specifically, components such as Al, N, Ti, Mg, and Ca react with oxygen in the steel to form oxides, and therefore, it is necessary to strongly suppress them, so that each component can be managed at 0.005% by weight or less. In one embodiment of the present invention, the addition of elements other than the above-described alloy components is not excluded, and may be variously included within the scope not impairing the technical spirit of the present invention. When additional elements are further included, the remainder of Fe is replaced and included.

More specifically, the slab may be composed of weight %, Si: 1.0% to 4.0%, C: 0.1% to 0.4%, and the balance of Fe and unavoidable impurities.

The slab heating temperature may be 1100° C. to 1350° C. higher than the usual heating temperature. When the temperature of the slab is high, there is a problem in that the hot-rolled structure becomes coarse and adversely affects the magnetism. However, in the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, the hot-rolled structure does not coarsen even when the slab reheating temperature is high because the carbon content of the slab is relatively high, and by reheating at a higher temperature than usual, during hot rolling More advantageous.

Next, the slab is hot-rolled to manufacture a hot-rolled steel sheet.

Hot-rolling can be manufactured into a hot-rolled sheet having a thickness of 1.5 to 4.0 mm by hot rolling so that it can be manufactured to a final product thickness by applying an appropriate rolling rate in the final cold rolling step.

The hot rolling temperature or cooling temperature is not particularly limited, but as an example of excellent magnetism, the hot rolling end temperature is set to 950°C or less, and the cooling can be rapidly cooled with water and wound at 600°C or less.

Next, the hot-rolled steel sheet is annealed. In this case, the annealing of the hot-rolled sheet may include a decarburization process. Specifically, the hot-rolled sheet annealing may be annealed at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C. After the annealing described above, an additional annealing may be performed at a temperature of 1000 to 1200° C. and a dew point temperature of 0° C. or less. It can be pickled after hot-rolled sheet annealing.

Next, primary cold rolling is performed to manufacture a cold-rolled steel sheet.

It is known that it is effective to perform cold rolling once at a high pressure drop rate close to 90% in the usual manufacturing process of grain-oriented electrical steel sheet. This is because only Goss grains among the primary recrystallized grains create a favorable environment for grain growth. However, the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention is to internally diffuse Goss grains generated by decarburization annealing and cold rolling without using abnormal grain growth of Goss grains. It is advantageous to form a plurality of distributions.

Therefore, when cold rolling is performed at a reduction ratio of 50% to 70% during cold rolling, a plurality of Goss textures may be formed in the surface layer. More specifically, it may be 55% to 65%.

Next, the cold-rolled steel sheet is decarburized and annealed. In this case, the decarburization annealing may be performed in an austenite single phase region or a region in which a composite phase of ferrite and austenite exists. Specifically, it may be annealed at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C. In addition, the atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. In addition, the amount of decarburization during decarburization annealing may range from 0.0300% by weight to 0.0600% by weight. After the annealing described above, an additional annealing may be performed at a temperature of 1000 to 1200° C. and a dew point temperature of 0° C. or less.

In this decarburization annealing process, the size of grains on the surface of the electrical steel sheet grows coarse, but the grains inside the electrical steel sheet remain in a fine structure. After the decarburization annealing, the average diameter of the crystal grains may be 150 μm to 250 μm. At this time, the crystal grains are surface ferrite grains. In addition, the diameter of a crystal grain assumes an imaginary circle having the same area as the crystal grain, and means the diameter of the circle.

Next, the steel sheet on which the decarburization annealing has been completed is subjected to secondary cold rolling. Since the secondary cold rolling is the same as the primary cold rolling, a detailed description will be omitted.

The step of decarburization annealing the above-described cold-rolled steel sheet and the step of secondary cold-rolling the steel sheet on which the decarburization annealing is completed may be repeated two or more times. By repeating two or more times, a large number of Goss textures can be formed in the surface layer.

Next, the steel sheet on which the secondary cold rolling has been completed is continuously annealed.

The step of continuous annealing is annealing at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C. In the cold-rolled sheet before continuous annealing, decarburization annealing proceeds, so that the amount of carbon remains 40% to 60% of the carbon weight of the slab. Therefore, in the step of continuous annealing, the crystal grains formed in the surface layer are diffused into the inside as carbon is removed. In the step of continuous annealing, decarburization can be performed so that the amount of carbon in the steel sheet is 0.005% by weight or less.

The step of continuous annealing may be annealing for 1 to 5 minutes. The purpose of the continuous annealing step is to grow crystal grains above a certain size after decarburization of carbon in steel. The reason is that the fraction of Goss grains continuously increases through the process of decarburization and grain growth immediately thereafter. This is because Goss grains grow while encroaching on surrounding Non-Goss grains. However, considering the productivity of continuous annealing, since the annealing time is limited within a few minutes, it can be said that crystal growth is limited. In an embodiment of the present invention, it is to be argued that crystal growth is induced through additional batch annealing, thereby reducing iron loss. At this time, the Goss fraction does not increase, but the iron loss decreases due to the effect of increasing the grain size.

After the step of continuous annealing, an annealing separator may be applied. Since the annealing separator is widely known in the art, a detailed description will be omitted. For example, an annealing separator containing MgO as a main component can be used.

Next, the continuous annealed steel sheet is batch-annealed. Batch annealing refers to annealing by winding a steel sheet in a coil shape.

In the batch annealing step, an aggregated structure with a Goth orientation spread in the continuous annealing step is grown. In the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, the Goth texture may have a diameter of 5 mm or less, unlike a case in which the grains are grown by abnormal grain growth in the related art. Specifically, the fraction of crystal grains having a diameter of 1000 um to 5000 um is increased. Accordingly, there are a large number of Goth grains having a smaller grain size than the conventional grain-oriented electrical steel sheet manufactured by abnormal grain growth, but the size of the grains can be adjusted to an appropriate size so as to reduce iron loss as much as possible. More specifically, a grain area fraction having a diameter of 1000 μm to 5000 μm among the total grains may be 20 to 70%. At this time, the grain area fraction was measured on a plane parallel to the rolled plane (ND plane) of the steel sheet. More specifically, a grain area fraction having a diameter of 1000 μm to 5000 μm among the total grains may be 20 to 60%. More specifically, a grain area fraction of the total grains having a diameter of 1000 μm to 5000 μm may be 20 to 50%.

The batch annealing step may be annealed at a temperature of 1000° C. to 1200° C. and a dew point temperature of -20° C. or less.

In addition, the batch annealing step may be annealing for 1 to 8 hours. More specifically, it can be annealed for 2 to 5 hours.

In addition, in the manufacturing method of the grain-oriented electrical steel sheet according to an embodiment of the present invention, the Goth fraction is high, and the magnetism is improved. Specifically, the volume fraction of crystal grains forming an angle of 15˚ or less from {110}<001> may be 40% or more. More specifically, it may be 40% to 75%. More specifically, it may be 45 to 60%.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has a grain area fraction of 20 to 70% with a diameter of 1000 μm to 5000 μm among the total grains.

The area distribution of the crystal grains has been described in detail with respect to the manufacturing method of the grain-oriented electrical steel sheet, and therefore, overlapping descriptions are omitted.

The electrical steel sheet is a weight %, Si: 1.0% to 4.0%, C: 0.005% or less (excluding 0%), and the balance may contain Fe and inevitable impurities.

The electrical steel sheet may further include Mn: 0.1 wt% or less and S: 0.005 wt% or less.

Except for C, since it is the same as the content of the slab component, redundant descriptions will be omitted.

The volume fraction of crystal grains forming an angle of 15 degrees or less from {110}<001> may be 40% or more.

The Goth grains having a ratio (D2/D1) of the circumscribed circle diameter (D1) to the inscribed circle diameter (D2) of 0.5 or more may be 95 area% or more of the total Goth grains. In an embodiment of the present invention, crystal grains of the above-described shape are formed due to a unique manufacturing process.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has a high Goth fraction, thereby improving magnetism. Specifically, the iron loss (W _17/50 ) may be 1.3 W/kg or less. More specifically, iron loss (W _17/50 ) may be 1 to 1.3 W/kg. More specifically, it may be 1.1 to 1.25W/kg. The iron loss W _17/50 is a size (W / kg) of the iron loss is derived from 1.7Tesla and 50Hz conditions.

Hereinafter, specific examples of the present invention will be described. However, the following examples are only specific examples of the present invention, and the present invention is not limited to the following examples.

Example 1

A slab containing 2.32% Si: 2.32% C: 0.195% by weight and containing the balance Fe and inevitable impurities was heated at a temperature of 1250°C, followed by hot rolling, followed by annealing temperature of 950°C and a dew point temperature of 60°C. Annealed. Thereafter, the steel sheet was cooled, pickled, and cold-rolled at a reduction ratio of 65% to produce a cold-rolled sheet having a thickness of 0.8 mm.

The cold-rolled sheet was subjected to decarburization annealing for 80 seconds in a humid mixed gas atmosphere of hydrogen and nitrogen at a temperature of 950°C (dew point temperature of 60°C), and then cold-rolled at a reduction rate of 65% to obtain a cold-rolled sheet with a thickness of 0.28 mm. Was produced.

After the final annealing, decarburization annealing was performed for 2 minutes in a wet mixed gas atmosphere of hydrogen and nitrogen at a temperature of 950° C. (dew point temperature of 60° C.), and then as summarized in Table 1, hydrogen and nitrogen at 1100° C. Heat treatment was performed in a mixed gas atmosphere of (dew point temperature of 60° C.), or heat treatment was performed for the time shown in Table 1 in a mixed gas atmosphere of hydrogen and nitrogen at 1200° C. in a coil state.

Table 1 is a table showing the Goss fraction of grains of grain-oriented electrical steel sheets after high-temperature annealing according to Examples, area fractions of grains of 1 mm or more and 5 mm or less, and iron loss. The Goss fraction was measured as the volume fraction of crystal grains forming an angle of 15 degrees or less from {110}<001>. After surface cleaning of the finally obtained steel sheet, iron loss was measured under conditions of 1.7 Tesla and 50 Hz using a single sheet measurement method.

1100℃ Continuous Annealing Time (Min.) Batch annealing time (Hr) 1 to 5mm grain area fraction (%) Goss fraction (%) Iron loss (W17/50)
(W/Kg) Remark - - 3 48 1.75 Comparative material 1 3 - 8 59 1.55 Comparative material 2 - 0.3 14 55 1.55 Comparative material 3 - 2 22 58 1.27 Invention 1 - 3 51 72 1.17 Invention 2 - 4 44 59 1.23 Invention 3 - 5 48 57 1.25 Invention 4 - 10 74 55 1.48 Comparative material 4

As shown in Table 1, it can be seen that Inventive Materials 1 to Inventive Materials 4 subjected to batch annealing for an appropriate time have a high area fraction of crystal grains having a diameter of 1 to 5 mm. Although the Goth fraction is relatively low compared to the comparative material, it can be confirmed that the iron loss is rather excellent.

1 and 2 show photographs of observing the surfaces of grain-oriented electrical steel sheets prepared from Inventive Material 2 and Comparative Material 2 with a scanning electron microscope.

As can be seen in FIGS. 1 and 2, it can be seen that the grains of the grain-oriented electrical steel sheet manufactured in Inventive Material 2 are formed relatively large.

The present invention is not limited to the above embodiments and/or embodiments, but may be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains change the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented in other specific forms without doing so. Therefore, it should be understood that the embodiments and/or embodiments described above are illustrative and non-limiting in all respects.

Claims (14)

In% by weight, Si: 1.0% to 4.0%, C: 0.005% or less (excluding 0%), Mn: 0.1% by weight or less (excluding 0%), S: 0.005% by weight or less (excluding 0% And the balance contains Fe and unavoidable impurities,
A grain-oriented electrical steel sheet having a grain area fraction of 20 to 70% with a diameter of 1000 μm to 5000 μm among the total grains. The method of claim 1,
A grain-oriented electrical steel sheet with a volume fraction of 40% or more of crystal grains forming an angle of 15 degrees or less from {110}<001>. The method of claim 1,
A grain-oriented electrical steel sheet in which the ratio of the diameter of the circumscribed circle (D1) to the diameter of the inscribed circle (D2) (D2/D1) is 0.5 or more and 95 area% or more of the total Goth grains. Heating the slab containing Fe and unavoidable impurities in weight %, Si: 1.0% to 4.0%, C: 0.1% to 0.4%, and the balance;
Manufacturing a hot-rolled steel sheet by hot rolling the slab;
Annealing the hot-rolled steel sheet;
First cold rolling the annealed hot-rolled steel sheet;
Decarburization annealing the first cold-rolled steel sheet;
Secondary cold rolling the steel sheet on which the decarburization annealing has been completed;
Continuous annealing the steel sheet on which the secondary cold rolling has been completed, and
Including the step of batch annealing the continuously annealed steel sheet,
The step of decarburizing annealing the first cold-rolled steel sheet is annealing at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C,
The continuous annealing step is annealing for 1 to 5 minutes,
The batch annealing step is a method of manufacturing a grain-oriented electrical steel sheet annealing for 1 to 8 hours. The method of claim 4,
A method of manufacturing a grain-oriented electrical steel sheet comprising a decarburization process in the step of annealing the hot-rolled sheet. The method of claim 4,
The step of annealing the hot-rolled sheet is a method of manufacturing a grain-oriented electrical steel sheet annealing at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C. delete The method of claim 4,
The step of decarburization annealing the first cold-rolled steel sheet is a method of manufacturing a grain-oriented electrical steel sheet in which annealing is performed in an austenite single phase region or a region in which a composite phase of ferrite and austenite exists. The method of claim 4,
After the step of decarburizing annealing the first cold-rolled steel sheet, the average diameter of the grains is 150 to 250㎛ method for producing a grain-oriented electrical steel sheet. The method of claim 4,
The step of decarburizing annealing the first cold-rolled steel sheet and the step of secondary cold-rolling the steel sheet on which the decarburization annealing has been completed are repeated two or more times. The method of claim 4,
The continuous annealing step is a method of manufacturing a grain-oriented electrical steel sheet annealing at a temperature of 850°C to 1000°C and a dew point temperature of 50°C to 70°C. delete The method of claim 4,
The batch annealing step is a method of manufacturing a grain-oriented electrical steel sheet annealing at a temperature of 1000° C. to 1200° C. and a dew point temperature of -20° C. or less. delete

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