KR102120277B1 - Grain oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

The grain-oriented electrical steel sheet according to an embodiment of the present invention is weight %, Si: 2.0 to 4.5%, C: 0.005% or less (excluding 0%), Mn: 0.005 to 0.05%, S: 0.005% or less (0 %), Se: 0.0005 to 0.2% and the balance contains Fe and unavoidable impurities, and satisfies the following Equation 1.
[Equation 1]
3×[Mn] ≥ [Se] ≥ 1.5×[Mn]
(In formula 1, [Mn] and [Se] represent the content (% by weight) of Mn and Se, respectively.)

Description

GRAIN ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

It relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. Specifically, the present invention relates to a grain-oriented electrical steel sheet having improved magnetism and productivity by adding an appropriate amount of Mn and Se elements to a steel sheet without using AlN and MnS precipitates as a grain growth inhibitor, and a method for manufacturing the same.

In the grain-oriented electrical steel sheet, the orientation of all crystal grains on the steel sheet surface is {110} plane, and the crystal orientation in the rolling direction is parallel to the <001> axis, so-called Goss texture, and thus magnetic properties in the rolling direction of the steel sheet. This is an excellent soft magnetic material.

In general, magnetic properties can be expressed by magnetic flux density and iron loss, and high magnetic flux density can be obtained by accurately arranging the grain orientation in the {110}<001> orientation. The electric steel sheet having a high magnetic flux density can not only reduce the size of the iron core material of the electric machine, but also have a low hysteresis loss, which makes it possible to downsize the electric machine and increase efficiency.

Iron loss is a power loss consumed as thermal energy when an alternating magnetic field is applied to a steel sheet, and varies greatly depending on the magnetic flux density and thickness of the steel sheet, the amount of impurities in the steel sheet, the specific resistance, and the size of secondary recrystallized grains. The higher the specific resistance and the lower the plate thickness and the amount of impurities in the steel sheet, the lower the iron loss, which increases the efficiency of the electrical equipment.

In order to cope with global warming by reducing CO ₂ generation worldwide, it is a trend toward energy-saving and high-efficiency commercialization, and as the demand for the expansion and distribution of highly-efficient electric devices that use less electric energy increases, it becomes superior. There is an increasing social demand for the development of grain-oriented electrical steel sheets with low iron loss properties.

On the other hand, in the grain-oriented electrical steel sheet having excellent magnetic properties, the Goss texture in the direction of {110}<001> in the rolling direction of the steel sheet must be strongly developed, and in order to form such an aggregate, grains of the Goss orientation are 2 It is necessary to form abnormal grain growth called tea recrystallization. Unlike normal grain growth, this abnormal grain growth occurs when normal grain growth is inhibited from movement of grain boundaries normally growing by precipitates, inclusions, or elements that are solid or segregated at grain boundaries. As such, precipitates or inclusions that inhibit grain growth are specifically called grain growth inhibitors, and research on the manufacturing technology of grain-oriented electrical steel sheet by secondary recrystallization of {110}<001> Goss Defense is a powerful grain growth inhibitor. It has focused on securing excellent magnetic properties by forming secondary recrystallization with high integration for {110}<001> orientation using.

In the initially developed grain-oriented electrical steel sheet, MnS was used as a grain growth inhibitor, and was produced by two cold rolling methods. Thus, the secondary recrystallization was stably formed, but the magnetic flux density was not very high and the iron loss was high. Since then, a method of manufacturing a grain-oriented electrical steel sheet by using AlN and MnS precipitates in combination and cold rolling once with a cold rolling rate of 80% or more has been proposed.

In recent years, after cold rolling and decarburization once without using MnS, Goss using Al-based nitride that exerts a strong grain growth suppression effect by supplying nitrogen into the steel sheet through a separate nitriding process using ammonia gas A method of manufacturing a grain-oriented electrical steel sheet that causes secondary recrystallization of the grains has been proposed.

Until now, almost all manufacturers that produce grain-oriented electrical steel have mainly used production methods to secure secondary recrystallization and magnetic properties by using precipitates such as AlN and MnS[Se] as grain growth inhibitors. The method for manufacturing grain-oriented electrical steel sheet using AlN and MnS precipitates as a grain growth inhibitor has the advantage of stably causing secondary recrystallization, but in order to exhibit a strong grain growth inhibitory effect, the precipitates are very finely and uniformly distributed on the steel sheet. I have to. In order to distribute the fine precipitates uniformly, the slabs were heated to a high temperature for a long time before hot rolling to employ the coarse AlN and MnS precipitates present in the steel, and then hot rolling was performed within a very fast time to prevent precipitation. In the hot rolling must be finished. For this, a large-scale slab heating facility is required, and the hot rolling temperature and coiling process are strictly controlled to minimize precipitation during hot rolling, and precipitates employed in the hot rolled sheet annealing process after hot rolling are finely precipitated. There are restrictions that need to be managed. In addition, when the slab is heated to a high temperature, as the Fe ₂ SiO ₄ having a low melting point is formed, a slab washing phenomenon occurs and a hot rolling error rate is lowered.

In addition, a method of manufacturing a grain-oriented electrical steel sheet that forms secondary recrystallization by maximizing the difference in grain boundary mobility of grain boundaries according to crystal orientation by minimizing the content of impurities in the steel sheet without using precipitates has been proposed. In this technique, it was proposed to reduce the Al content and to control the contents of B, V, Nb, Se, S, P, and N in trace amounts, but only a small amount of Al formed a precipitate or inclusion to form a secondary recrystallization and magnetic It seems to be able to secure.

In addition, attempts have been made to utilize various precipitates such as TiN, VN, NbN, and BN as grain growth inhibitors, but failed to form a stable secondary recrystallization due to thermal instability and excessively high precipitate decomposition temperature.

One embodiment of the present invention is to provide a grain-oriented electrical steel sheet and its manufacturing method. Specifically, without using AlN, MnS precipitates as a grain growth inhibitor, by adding an appropriate amount of Mn, Se elements to the steel sheet, to provide a grain-oriented electrical steel sheet with improved magnetic properties and productivity and a method for manufacturing the same.

The grain-oriented electrical steel sheet according to an embodiment of the present invention is weight %, Si: 2.0 to 4.5%, C: 0.005% or less (excluding 0%), Mn: 0.005 to 0.05%, S: 0.005% or less (0 %), Se: 0.0005 to 0.2% and the balance contains Fe and unavoidable impurities, and satisfies the following Equation 1.

[Equation 1]

3×[Mn] ≥ [Se] ≥ 1.5×[Mn]

(In formula 1, [Mn] and [Se] represent the content (% by weight) of Mn and Se, respectively.)

The grain-oriented electrical steel sheet according to an embodiment of the present invention may satisfy Equation 2 below.

[Equation 2]

0.5×[Mn] ≥ [S]

(In Formula 2, [Mn] and [S] represent the content (% by weight) of Mn and S, respectively.)

The grain-oriented electrical steel sheet according to an embodiment of the present invention may further comprise 0.005 to 0.1% by weight of one or more of Sb and Sn, respectively or in combination.

The grain-oriented electrical steel sheet according to an embodiment of the present invention may further include Al in an amount of 0.01% by weight or less and N in an amount of 0.005% by weight or less.

The grain-oriented electrical steel sheet according to one embodiment of the invention can comprise inclusions containing Al, Mn, Si, Mg, Ca or Ti pieces / 200 mm ² or less.

Method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention in weight%, Si: 2.0 to 4.5%, C: 0.01 to 0.1%, Mn: 0.005 to 0.05%, S: 0.0005 to 0.02%, Se: 0.0005 To 0.2% and the balance comprising Fe and unavoidable impurities, and heating the slab satisfying the following Equation 1; Hot rolling a slab to produce a hot rolled sheet; Cold rolling the hot rolled sheet to produce a cold rolled sheet; First recrystallization annealing the cold rolled sheet; And secondary recrystallization annealing of the steel sheet subjected to primary recrystallization annealing.

[Equation 1]

3×[Mn] ≥ [Se] ≥ 1.5×[Mn]

(In formula 1, [Mn] and [Se] represent the content (% by weight) of Mn and Se, respectively.)

The slab can satisfy Equation 2 below.

[Equation 2]

0.5×[Mn] ≥ [S]

(In Formula 2, [Mn] and [S] represent the content (% by weight) of Mn and S, respectively.)

The slab may further contain 0.005 to 0.1% by weight of one or more of Sb and Sn, respectively or in combination.

The slab may further include 0.01% by weight or less of Al and 0.005% by weight or less of N.

After the step of manufacturing the hot rolled sheet, the edge crack of one side of the hot rolled sheet is 20 mm or less, and the distribution of the edge crack may be 10 pieces/m in the longitudinal direction of the steel sheet.

After the first recrystallization annealing of the cold rolled sheet, further comprising applying an annealing separator to the primary recrystallized annealing steel sheet, the annealing separator may include Mg oxide or Mg hydroxide, and metal sulfide or metal sulfide. Can be.

The annealing separator may include 100 parts by weight of Mg oxide or Mg hydroxide and 10 to 40 parts by weight of metal sulfur oxide or metal sulfide.

The second recrystallization annealing step includes a temperature raising step and a cracking step, and the temperature raising step may be performed in an atmosphere that satisfies Expression 3 below.

[Equation 3]

[N ₂ ] ≥ 3×[H ₂ ]

(In formula 3, [N ₂ ] and [H ₂ ] mean the volume% of N ₂ and H _{2 in} the atmosphere, respectively)

After the step of heating, the S content of the steel sheet may be more than twice the S content of the slab.

After the step of heating, the steel sheet may include a composite grain boundary segregation of S and Se or a composite precipitate of (Fe, Mn, Cu) (S, Se).

After the temperature rising step, a sulfur diffusion layer formed in the inner direction of the steel sheet is formed from the interface between the film and the steel sheet, and the sulfur diffusion layer may include 0.01 to 0.05% by weight of S.

The cracking step may be performed in an atmosphere containing at least 75% by volume of hydrogen.

The cracking step can be performed at 1000 to 1250°C.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has excellent magnetic properties by stably forming crystal grains of Goss orientation.

In addition, it is possible to minimize one-sided edge cracks of the hot-rolled sheet during the manufacturing process, thereby providing excellent productivity.

In addition, the cracking step in the secondary recrystallization annealing in the manufacturing process can be performed for a short time at a low temperature, and thus the productivity is excellent.

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 portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only to refer to a specific embodiment and is not intended to limit the invention. The singular forms used herein include plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” embodies a particular property, region, integer, step, action, element, and/or component, and the presence or presence of other properties, regions, integers, steps, action, element, and/or component. It does not exclude addition.

When referring to a part being "on" or "on" another part, it may be directly on or on the other part, or another part may be involved therebetween. In contrast, if one part is referred to as being “just above” another part, no other part is interposed therebetween.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are further interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted as ideal or very formal meanings unless defined.

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

In one embodiment of the present invention, the meaning of further including an additional element in the steel component means that the remaining amount of iron (Fe) is replaced by an additional amount of the additional element.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

In the existing grain-oriented electrical steel sheet technology, precipitates such as AlN, MnS, etc. are used as grain growth inhibitors, and all processes strictly control the distribution of precipitates and as conditions for removing precipitates remaining in the secondary recrystallized steel sheet. As a result, process conditions were extremely limited.

On the other hand, in one embodiment of the present invention, a precipitate such as AlN, MnS, etc. is not used as a grain growth inhibitor. By using the S, Se composite grain boundary segregation and the (Fe,Mn,Cu) (S, Se) composite precipitate as a grain growth inhibitor, it is possible to increase the Goss grain fraction and obtain an excellent magnetic steel sheet.

The grain-oriented electrical steel sheet according to an embodiment of the present invention is weight %, Si: 2.0 to 4.5%, C: 0.005% or less (excluding 0%), Mn: 0.005 to 0.05%, S: 0.005% or less (0 %), Se: 0.0005 to 0.2% and the balance contains Fe and unavoidable impurities.

First, the reason for limiting the components of the grain-oriented electrical steel sheet will be described.

Si: 2.0 to 4.5 wt%

Silicon (Si) is the basic composition of the electrical steel sheet, and increases the specific resistance of the steel sheet, thereby reducing the core loss of the transformer, that is, reducing the iron loss. If the Si content is too small, the resistivity decreases, the iron loss characteristics deteriorate, and the secondary recrystallization may become unstable due to the presence of a phase transformation section during the secondary annealing. When Si is excessively contained, the brittleness of steel becomes large, and cold rolling becomes extremely difficult. Therefore, Si may include 2.0 to 4.5% by weight. More specifically, Si may include 2.5 to 4.0% by weight.

C: 0.005% by weight or less

Carbon (C) is an austenite stabilizing element that causes phase transformation at a temperature of 900°C or higher, and suppresses the central segregation of S and Se slabs along with the effect of minimizing the coarse columnar structure generated in the performance process. It also promotes the work hardening of the steel sheet during cold rolling to promote the formation of secondary recrystallized nuclei in the {110}<001> orientation in the steel sheet. Therefore, there is no big restriction on the amount added, but if it is contained in the slab in an amount of less than 0.01% by weight, phase transformation and work hardening effects cannot be obtained. If it is added in excess of 0.1% by weight, there is a problem in operation due to hot-rolled edge-crack. In addition, a load of the decarburization process may occur during decarburization annealing after cold rolling. Therefore, the added amount in the slab can be 0.01 to 0.1% by weight. More specifically, the amount added in the slab may be 0.02 to 0.07% by weight.

In one embodiment of the present invention, decarburization annealing is performed in the first recrystallization annealing step during the manufacturing process, and the C content in the final electric steel sheet produced after decarburization annealing may be 0.005% by weight or less. More specifically, it may be 0.003% by weight or less.

S: 0.005% by weight or less

Sulfur (S) is an element having a grain growth inhibitory effect by reacting with Mn in steel to form MnS, but in one embodiment of the present invention, since MnS is not used as a grain growth inhibitor, the content of S is managed to a minimum. , Inhibits the formation of MnS. On the other hand, S is an important element for separating into a grain boundary like Se or forming a (Fe,Mn,Cu)(S,Se) complex precipitate to cause secondary recrystallization of the Goss orientation. Therefore, if the S in the slab is less than 0.0005%, the effect of suppressing crystal growth decreases, and on the contrary, when the content of S in the slab manufacturing step is high, it causes heat embrittlement and increases the occurrence of edge cracks during the performance and hot rolling, thereby decreasing the error rate. Therefore, the amount added in the slab can be 0.0005 to 0.02% by weight. Specifically, Equation 2 below may be satisfied.

[Equation 2]

0.5×[Mn] ≥ [S]

(In Formula 2, [Mn] and [S] represent the content (% by weight) of Mn and S, respectively.)

In an embodiment of the present invention, when the annealing separator is applied to the surface of the steel sheet subjected to primary recrystallization annealing, S is added during the heating process of the secondary recrystallization annealing by adding a metal sulfide or metal sulfur oxide to the annealing separator. By inducing diffusion into the river, it is possible to supplement the ability to inhibit crystal growth to cause secondary recrystallization of the Goss defense. However, S remaining in the final grain-oriented electrical steel sheet causes magnetic aging and deteriorates the magnetic properties. Therefore, S content in the final electrical steel sheet is 0.005% by weight or less by generating and removing H ₂ S gas after the second recrystallization growth of Goss grains Can be. More specifically, it may be 0.003% by weight or less.

Se: 0.0005 to 0.20 wt%

Selenium (Se) is treated as a key element in one embodiment of the invention. Se segregates into grain boundaries in complex with S, and at the same time forms (Fe,Mn,Cu)(S,Se) complex precipitates at grain boundaries, thereby strongly suppressing the movement of grain boundaries, resulting in {110}<001> Goss orientation grain 2 Promote secondary recrystallization.

Since the aforementioned Se has a higher atomic mass than S, when the same weight% is included, the number of actual atoms is less Se. Therefore, in order to obtain a sufficient crystal growth inhibitory effect, more Se than S must be added. In addition, Se has the same grain boundary segregation effect as S, but because it has a higher melting point or boiling point than S, it can exist relatively stably at high temperatures during grain boundary segregation, thereby weakening heat embrittlement, and thus edge cracking during hot rolling after playing and slab heating. The amount of occurrence is reduced.

However, the content of Se is preferably not more than 0.2% by weight. In the component system of the present invention added in combination with S, when it exceeds 0.2% by weight, the occurrence of edge cracks increases during performance and hot rolling due to excessive grain boundary segregation. Conversely, when added to less than 0.0005% by weight, segregation of Se and (Fe,Mn,Cu)(S,Se) precipitates are formed less and the grain growth inhibitory effect is deteriorated. Therefore, the amount of Se added in the slab and the final grain-oriented electrical steel sheet is limited to 0.0005 to 0.2% by weight. Specifically, the amount of Se added may be 0.01 to 0.1% by weight. More specifically, the amount of Se added may be 0.03 to 0.06% by weight.

Mn: 0.005 to 0.05% by weight

Manganese (Mn) has the effect of reducing the iron loss by increasing the specific resistance like Si. The main purpose of the addition in the prior art is to react with S in steel to form MnS precipitates to suppress grain growth. However, in an embodiment of the present invention, the MnS precipitate is not used as an inhibitor of grain growth, so it is necessary to limit it to within a certain content range.

The most ideal method is to not add Mn at all, but a certain amount of Mn content remains even after the use and blow-off of molten iron with a low Mn content during the steelmaking and steelmaking process. It is desirable to limit to. When a large amount of Mn is added, since MnS[Se] is precipitated, the grain boundary segregation of S and Se is small, so it is difficult to prevent crystal growth movement and it is also difficult to form a (Fe,Mn,Cu)(S,Se) complex precipitate. Moreover, MnS[Se] precipitates have a high solid solution temperature, so they exist as very large precipitates on the actual steel sheet and have poor crystal growth inhibition. In addition, in order to decompose MnS[Se] in the secondary recrystallization annealing purifying process, there is a disadvantage that annealing at a high temperature for a long time is required. For this reason, in one embodiment of the present invention, the maximum content of Mn is managed at 0.05% by weight or less. Although it is best not to add Mn, the lower limit of Mn can be limited to 0.005% by weight since the steelmaking process load increases to decrease the productivity to less than 0.005% by weight. In particular, it is necessary to limit the content of Se and Mn to the range of the following Equation 1 in order to reduce the hot-rolled edge crack and to obtain an appropriate crystal growth suppression effect during primary recrystallization annealing.

[Equation 1]

3×[Mn] ≥ [Se] ≥ 1.5×[Mn]

(In formula 1, [Mn] and [Se] represent the content (% by weight) of Mn and Se, respectively.)

0.005 to 0.1% by weight of one or more of Sb and Sn respectively or in combination

Tin (Sn) is a grain boundary segregation element, and has the effect of increasing the magnetic flux density by promoting the nucleation of the {110}<001> Goss bearing during hot rolling. Although adding Sn up to 0.1% by weight has the effect of increasing the Goss azimuth grains, when it is added in excess, the formation of non-uniform primary recrystallized microstructure by delaying the occurrence of cold rolled plate fracture and decarburization due to grain boundary oversegregation This can reduce magnetism.

Antimony (Sb) is a grain boundary segregation element similar to Sn, and has an effect of suppressing excessive growth of primary recrystallized grains. By adding Sb to suppress grain growth in the first recrystallization step, the nonuniformity of the primary recrystallized grain size along the thickness direction of the plate is removed, and at the same time, the secondary recrystallization is stably formed to make a more oriented electrical steel sheet with better magnetic properties. Can be. When the content of Sb is too large, decarburization may be prevented during the first recrystallization annealing, thereby deteriorating magnetic properties.

One or more of Sb and Sn may each contain 0.005 to 0.1% by weight, alone or in combination. When only Sb or Sn is included, each may contain 0.005 to 0.1% by weight alone. When Sb and Sn are included at the same time, 0.005 to 0.1% by weight may be included in the total amount. More specifically, it may include 0.005 to 0.05% by weight of Sb and 0.0005 to 0.05% by weight of Sn.

Al: 0.010% by weight or less

Aluminum (Al) is combined with nitrogen in the steel to form AlN precipitates, so in one embodiment of the present invention, the Al content is actively suppressed to avoid inclusions such as Al-based nitrides or oxides. If the content of Al is too high, the formation of AlN and Al ₂ O ₃ is promoted, and the purifying annealing time for removing it increases, and unremoved AlN precipitates and inclusions such as Al ₂ O ₃ remain in the final product to increase the coercive force. Since the iron loss may increase by increasing, the content of Al in the steelmaking step is actively suppressed to 0.010% by weight or less. More specifically, considering the load of the steelmaking process, the Al content can be controlled to 0.001 to 0.010% by weight.

N: 0.005% by weight or less

N is an element that reacts with Al and Si to form AlN and Si ₃ N ₄ precipitates. In an embodiment of the present invention, since AlN is not used as a grain growth inhibitor, Al is not added in the steelmaking step, and therefore N is not specifically added. For that reason, the upper limit of N is limited to a maximum of 0.005% by weight. In addition, N is not added or is preferably added at a minimum, but N is 0.0005 to 0.005% by weight in the steelmaking step because the denitrification load of the steelmaking process is significantly increased to manage N to less than 0.0005% by weight in the steelmaking step. It is limited. In one embodiment of the present invention, since the nitridation process can be omitted, the N content in the slab and the N content in the final grain-oriented electrical steel sheet may be substantially the same.

Other impurities

In addition to the above-described elements, impurities that are inevitably incorporated may be included. The remainder is iron (Fe), and when additional elements other than the above-described elements are added, the remainder includes iron (Fe) as a replacement.

In the grain-oriented electrical steel sheet according to an embodiment of the present invention, inclusions including Al, Mn, Si, Mg, Ca, or Ti may include 200/mm ² or less. By limiting the formation of inclusions in this way, deterioration of magnetic properties due to inclusions can be prevented.

In addition, as will be described later, as the annealing is performed in an atmosphere containing a large amount of N ₂ as shown in Equation 3 in the step of raising the temperature of the secondary recrystallization annealing, the sulfur compound S element added to the annealing separator diffuses into the steel and secondary to the Goss crystal grains. Recrystallization can stably form. If annealing is performed in an atmosphere that does not satisfy Equation 3, S does not diffuse into the steel and can be removed by forming H ₂ S gas.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has particularly excellent iron loss and magnetic flux density characteristics. And the grain-oriented electrical steel sheet according to one embodiment of the invention, the magnetic flux density (B ₈₎ is 1.895T or more, the iron loss (W _17/50) this can be not more than 1.01W / kg. At this time, the magnetic flux density B ₈ is the magnitude of the magnetic flux density (Tesla) induced under a magnetic field of 800 A/m, and the iron loss W 17/50 is the magnitude of the iron loss (W/kg) induced at 1.7 Tesla and ₅₀ Hz.

Method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention in weight%, Si: 2.0 to 4.5%, C: 0.01 to 0.1%, Mn: 0.005 to 0.05%, S: 0.0005 to 0.02%, Se: 0.0005 To 0.2% and the balance comprising Fe and unavoidable impurities, and heating the slab satisfying the following Equation 1; Hot rolling a slab to produce a hot rolled sheet; Cold rolling the hot rolled sheet to produce a cold rolled sheet; First recrystallization annealing the cold rolled sheet; And secondary recrystallization annealing of the steel sheet subjected to primary recrystallization annealing.

Hereinafter, a method of manufacturing a grain-oriented electrical steel sheet in each step will be described in detail.

First, the slab is heated. In the steelmaking step, main elements such as Si, C, Al, Mn, S, and Se can be controlled to an appropriate content, and an alloy element advantageous for forming a Goss aggregate can be added as needed. The molten steel whose components are adjusted in the steelmaking step is manufactured as slabs through continuous casting. A strip casting method in which hot rolled steel sheets are directly manufactured by injecting molten steel between twin rolls can be used.

Since the composition of the slab has been described in detail with respect to the composition of the electric steel sheet, redundant description is omitted.

The heating temperature of the slab is not limited, but when the slab is heated to a temperature of 1300° C. or less, it is possible to prevent the columnar crystal structure of the slab from growing coarsely and prevent cracking of the plate in the hot rolling process. Therefore, the heating temperature of the slab may be 1050 ℃ to 1300 ℃. In particular, in one embodiment of the present invention, since AlN and MnS are not used as the grain growth inhibitor, there is no need to heat the slab at a high temperature exceeding 1300°C.

Next, a hot rolled sheet is manufactured by hot rolling the slab. The hot rolling temperature is not limited, and in one embodiment, hot rolling may be terminated at 950°C or less. After cooling by water, it can be wound up to 600°C or less. It can be manufactured into a hot rolled sheet having a thickness of 1.5 to 4.0 mm by hot rolling. At this time, in one embodiment of the present invention, one-side edge cracks are reduced by appropriately limiting the contents of S, Se, and Mn. The one-side edge crack means a crack generated in the width direction of the steel sheet from the end of the steel sheet to the inside of the steel sheet. Specifically, in one embodiment of the present invention, the length of the edge crack on one side of the hot rolled sheet may be 20 mm or less. In addition, the distribution of edge cracks in the longitudinal direction of the hot rolled sheet may be 10/m. When the length of the one-side edge crack is long, the amount of cut is increased by that amount, and the real rate decrease is large. In addition, even in the case where the amount of edge crack formation is large, similarly, a decrease in the real rate is greatly caused. In one embodiment of the present invention, by reducing the edge cracks on one side of the hot-rolled sheet as much as possible, it is possible to prevent the fall of the error rate and improve productivity. More specifically, the length of one side edge crack of the hot rolled sheet may be 11 mm or less.

Next, the hot rolled sheet can be annealed as necessary. In the case of hot-rolled sheet annealing, in order to make the hot-rolled structure uniform, it can be heated to a temperature of 900°C or higher, cracked, and then cooled.

Next, a cold rolled sheet is manufactured by cold rolling the hot rolled sheet. For cold rolling, a cold rolled sheet having a thickness of 0.1 mm to 0.5 mm is manufactured by a cold rolling method including one cold rolling, multiple cold rolling, or intermediate annealing using a reverse rolling machine or tandem rolling machine. can do.

Further, during cold rolling, warm rolling can be performed to maintain the temperature of the steel sheet at 100°C or higher.

In addition, the final rolling reduction rate through cold rolling may be 50 to 95%.

Next, cold-rolled cold-rolled sheet is subjected to primary recrystallization annealing. In the first recrystallization annealing step, primary recrystallization occurs in which nuclei of goth grains are generated. In the first recrystallization annealing step, decarburization of the cold rolled sheet may be performed. For decarburization, annealing may be performed at a temperature of 800°C to 950°C and a dew point temperature of 50°C to 70°C. When heated above 950°C, the recrystallized grains grow coarsely, and the crystal growth driving force is lowered, so that stable secondary recrystallization is not formed. And the annealing time is not a big problem in exerting the effect of the present invention, but it is preferable to treat within 5 minutes in consideration of productivity.

Further, the atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. In addition, when decarburization is completed, the carbon content in the cold rolled sheet may be 0.005% by weight or less. More specifically, the carbon content may be 0.003% by weight or less. In addition, an appropriate amount of an oxide layer is formed on the surface of the steel sheet simultaneously with decarburization. The grain size of the recrystallized grain grown in the first recrystallization annealing process may be 5 µm or more. In one embodiment of the present invention, since the AlN grain growth inhibitor is not used, the nitridation process may be omitted.

Next, the second recrystallization annealing of the cold rolled sheet in which the first recrystallization annealing is completed. At this time, an annealing separator can be applied to the steel sheet on which the primary recrystallization annealing is completed.

The annealing separator may include Mg oxide or Mg hydroxide, and metal sulfide or metal sulfide.

In general, in the manufacture of grain-oriented electrical steel sheet, in the first recrystallization annealing step, silicon (Si), which is the component having the highest oxygen affinity in the steel sheet, reacts with oxygen to form SiO ₂ on the surface of the steel sheet. In addition, when oxygen gradually penetrates into the steel sheet during annealing, iron (Fe)-based oxides (Fe ₂ SiO _4, etc.) are further formed. That is, in the primary recrystallization annealing process, an oxide film containing the SiO ₂ and the iron (Fe)-based oxide is inevitably formed on the surface of the steel sheet.

After the primary recrystallization annealing process, an annealing separator mainly containing magnesium oxide or magnesium hydroxide is applied to the surface of the steel sheet, followed by a secondary recrystallization annealing process, wherein SiO ₂ in the oxide film is the magnesium oxide or magnesium hydroxide And reacts. This reaction may be represented by the following Chemical Reaction Scheme 1 or Chemical Reaction Scheme 2, which corresponds to a reaction for forming forsterite (Mg ₂ SiO ₄ ), that is, a coating layer (primary coating, base coating). The coating layer formed by the Mg oxide or Mg hydroxide may help to stably cause the secondary recrystallization in the secondary recrystallization annealing process.

[Chemical Reaction Formula 1] 2Mg(OH) ₂ + SiO ₂ → Mg ₂ SiO ₄ (Forsterite) + 2H ₂ O

[Chemical Reaction Formula 2] 2MgO + SiO ₂ → Mg ₂ SiO ₄ (Forsterite) + 2H ₂ O

On the surface of the grain-oriented electrical steel sheet, a coating layer mainly composed of forsterite is generally formed, except in special cases. The coating layer usually has an effect of preventing fusion between steel sheets wound with a coil, reducing tension loss and imparting insulation by imparting tension due to a difference in thermal expansion from the steel sheet.

In one embodiment of the present invention, in addition to this, by adding a metal sulfur oxide or metal sulfide, by diffusing the S in the steel sheet, it serves to reinforce the grain growth inhibitor.

The metal of the metal sulfide or metal sulfide is not particularly limited, and may be one or more selected from Sr, Mg, Ca, Ba, Ti, Sb and Sn. More specifically, it may be Mg.

Magnesium oxide in the annealing separator can also be hydrated with magnesium hydroxide by a solvent, and magnesium oxide and magnesium hydroxide are treated as one component. In addition, since the metal sulfur oxide or metal sulfide has the same role in supplying S, it is treated as one component.

The annealing separator may contain 10 to 40 parts by weight of metal sulfur oxide or metal sulfide, based on 100 parts by weight of magnesium oxide and magnesium hydroxide. When the amount of the metal sulfide or metal sulfide is too small, the crystal growth inhibitory power is insufficient, and the formation of secondary recrystallization of the Goss orientation may become unstable. If the metal sulfide or metal sulfide is too large, the balance of crystal growth driving force and suppression force for secondary recrystallization is broken, thereby deteriorating the magnetic properties, and the uniformity of the coating formed on the surface of the steel sheet is deteriorated. Therefore, it is necessary to control the content of the metal sulfide or metal sulfide within the above-described range. More specifically, the content of the metal sulfide or metal sulfide may be 15 to 30 parts by weight. When the metal sulfide or the metal sulfide is included alone, it is an amount alone, and when it is all included, it means the total amount.

The secondary recrystallization annealing step includes a temperature raising step and a cracking step. The heating step is a step of raising the cold-rolled sheet in which the first recrystallization annealing is completed to the temperature of the cracking step, and causes the second recrystallization of {110}<001> Goss defense.

In the heating step, the metal sulfur oxide or metal sulfide applied to the steel sheet is decomposed to diffuse S into the steel and form intergranular segregation and (Fe,Mn,Cu)(S,Se) complex precipitates, thereby secondary to the Goss orientation It can act as a crystal growth inhibitor to cause recrystallization.

In addition, after the temperature rising step, the S component in the film diffuses into the steel sheet, so that the S content of the steel sheet may be more than twice the S content of the slab.

After the temperature rising step, a sulfur diffusion layer formed in the inner direction of the steel sheet is formed from the interface between the film and the steel sheet, and the sulfur diffusion layer may include 0.01 to 0.05% by weight of S.

At this time, in order to suppress the release of H ₂ S gas by reacting with hydrogen used for controlling the atmosphere of the secondary annealing furnace before S is sufficiently diffused into the steel, the mixing ratio of hydrogen and nitrogen gas at the temperature raising step is as follows. (3) can be satisfied.

[Equation 3]

[N ₂ ] ≥ 3×[H ₂ ]

(In formula 3, [N ₂ ] and [H ₂ ] mean the volume% of N ₂ and H _{2 in} the atmosphere, respectively.)

The cracking step is a process of removing impurities present in the steel sheet, and the temperature of the cracking step is 1000°C to 1250°C, and may be performed for 20 hours or less. If the temperature is less than 1000°C, the Goth crystal grains may not grow sufficiently, resulting in a decrease in magnetism. When the temperature exceeds 1250°C, the grains may grow coarsely, and the characteristics of the electrical steel sheet may deteriorate. The heating step may be performed in a mixed gas atmosphere of hydrogen and nitrogen, and the cracking step may be performed in a hydrogen atmosphere, specifically, an atmosphere containing 75% by volume or more of hydrogen. At this time, the rest may be nitrogen gas. In an embodiment of the present invention, since grain growth inhibitors such as AlN and MnS are not used, it is not necessary to anneal for a long time at a high temperature to remove them, thereby improving productivity.

Thereafter, if necessary, an insulating film may be formed on the surface of the grain-oriented electrical steel sheet, or a magnetic domain refinement treatment may be performed. In one embodiment of the present invention, the alloy component of the grain-oriented electrical steel sheet means a steel sheet excluding a coating layer such as an insulating film.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for illustrating the present invention, and the present invention is not limited thereto.

Example 1

C:0.055%, Si:3.2%, Sb: 0.02%, Sn:0.04%, Al: 0.008%, N:0.002% by weight%, and the contents of Mn, S, and Se were changed as shown in Table 1 below. Slabs containing Fe and other inevitable impurities were prepared.

The slab was heated to a temperature of 1200°C and then hot rolled to a thickness of 2.6 mm. After measuring the depth of edge crack generation on one side of the hot rolled sheet, the hot rolled hot rolled sheet was heated to a temperature of 950°C and cracked for 120 seconds to anneal the hot rolled sheet.

Subsequently, the annealed hot rolled steel sheet was pickled, and then cold rolled to prepare a cold rolled sheet having a thickness of 0.30 mm. The cold rolled steel sheet was held at a temperature of 850°C for 180 seconds in a mixed gas atmosphere of hydrogen and nitrogen at a dew point temperature of 65°C for 180 seconds to perform decarburization and recrystallization heat treatment.

After the annealing separator containing 100 parts by weight of MgO and 20 parts by weight of MgSO ₄ was applied to the steel sheet, final secondary recrystallization annealing was performed in a coil shape. The secondary recrystallization annealing was heated to a mixed atmosphere of 75% by volume nitrogen and 25% by volume hydrogen up to 1050°C. After reaching 1050°C, the mixture was maintained in a 100% by volume hydrogen gas atmosphere for 20 hours and then annealed. After secondary recrystallization annealing the magnetic flux density of the steel sheet (B _8, 800A / m) and iron loss (W _17/50) a single sheet was measured by using a measurement method, measurement results with Mn, S, Se, and hot-rolled sheet according to the contents in Table 1 shows the amount of edge crack generation on one side.

division Mn
(wt%) S
(wt%) Se
(wt%) Whether Expression 1 is satisfied Equation 2
Satisfaction One side edge crack
(mm) Edge crack distribution
(Pcs/m) Magnetic flux density
(B8, Tesla) Iron loss
(W17/50, W/kg) Invention material 1 0.006 0.011 0.012 O X 13 9 1.898 1.01 Invention 2 0.011 0.005 0.032 O O 11 5 1.924 0.92 Invention 3 0.01 0.015 0.028 O X 14 10 1.901 0.99 Comparative material 1 0.028 0.011 0.095 X O 26 21 1.891 1.03 Invention 4 0.034 0.008 0.053 O O 3 6 1.911 0.94 Inventive material 5 0.03 0.004 0.046 O O 7 6 1.913 0.93 Comparative material 2 0.042 0.023 0.018 X X 21 12 1.857 1.11 Comparative material 3 0.038 0.006 0.055 X O 7 8 1.887 1.03 Invention 6 0.025 0.019 0.041 O X 12 8 1.9 0.99 Comparative material 4 0.046 0.013 0.065 X O 6 9 1.893 1.02 Comparative material 5 0.051 0.012 0.023 X O 4 7 1.868 1.07 Invention 7 0.033 0.01 0.055 O O 10 3 1.918 0.92 Invention 8 0.021 0.006 0.042 O O 9 5 1.919 0.93

As can be seen in Table 1, in the case of the invention material in which the S, Se and Mn contents were controlled within the scope of the present invention, both magnetic flux density and iron loss were excellent. In addition, the occurrence of edge cracks in the hot rolled sheet was less than 20 mm. On the other hand, it can be seen that among the invention materials, the occurrence of edge cracks on the one side is further reduced and the magnetism is more excellent than the case where the invention material that satisfies Expression 2 further does not satisfy Expression 2.

Example 2

C:0.061% by weight, Si:3.4%, Mn:0.025%, S:0.005%, Se:0.04%, Sb: 0.02%, Sn:0.06%, Al: 0.006%, N:0.0015% and balance Fe And other inevitably contained impurities.

The slab was heated to a temperature of 1250° C. and then hot rolled to a thickness of 2.3 mm, and then the hot rolled sheet was heated to a temperature of 1000° C. and cracked for 120 seconds to anneal the hot rolled sheet.

Subsequently, the annealed hot rolled steel sheet was pickled, and then cold rolled to produce a cold rolled sheet having a thickness of 0.23 mm. The cold rolled steel sheet was held at a temperature of 820°C for 150 seconds in a mixed gas atmosphere of humid hydrogen and nitrogen at a dew point temperature of 60°C for 150 seconds to perform decarburization and recrystallization heat treatment.

After applying an annealing separator to which MgSO ₄ was added to 100 parts by weight of MgO and MgSO ₄ as shown in Table 2, the final secondary recrystallization annealing was performed in the form of a coil. In addition, annealing was performed by changing the ratio of the mixed atmosphere of nitrogen and hydrogen in the process of raising the temperature of the secondary recrystallization annealing. After reaching 1100°C, the mixture was kept in a 100% by volume hydrogen gas atmosphere for 15 hours and then annealed. After the second recrystallization annealing, the magnetic flux density (B8,800A/m) and iron loss (W17/50) of the steel sheet were measured using a single sheet measurement method.

division Sulfur compounds
(Parts by weight) nitrogen
(volume%) Hydrogen
(volume%) Magnetic flux density
(B8, Tesla) Iron loss
(W17/50, W/kg) Invention 9 5 90 10 1.889 1.02 Invention 10 9 75 25 1.9 1.01 Invention 11 12 50 50 1.878 1.05 Invention 12 15 85 15 1.925 0.93 Invention material 13 21 85 15 1.931 0.92 Invention 14 26 75 25 1.922 0.95 Invention 15 28 80 20 1.923 0.93 Invention 16 36 75 25 1.919 0.94 Invention 17 32 25 75 1.883 1.05 Invention 18 39 10 90 1.874 1.05 Invention 19 43 75 25 1.901 One Invention material 20 42 90 10 1.899 One

As can be seen in Table 2, when the weight ratio of the sulfur compound in the annealing separator was controlled within the scope of the present invention, both magnetic flux density and iron loss were excellent. In addition, magnetic properties were excellent only when the volume% of nitrogen and hydrogen satisfies the range of Equation 3 during the high temperature annealing process. In addition, the occurrence of edge cracks on one side of the hot-rolled sheet was 10 mm or less, and the frequency of occurrence of edge cracks was reduced.

The present invention is not limited to the above embodiments, but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains have other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that can be carried out. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (17)

In weight %, Si: 2.0 to 4.5%, C: 0.005% or less (excluding 0%), Mn: 0.005 to 0.05%, S: 0.005% or less (excluding 0%), Se: 0.0005 to 0.2% And the balance includes Fe and unavoidable impurities,
Equation 1 below is satisfied,
Al, Mn, Si, Mg, Ca or the inclusions containing Ti 200 gae / mm ² or less grain-oriented electrical steel sheet comprising a.
[Equation 1]
3×[Mn] ≥ [Se] ≥ 1.5×[Mn]
(In formula 1, [Mn] and [Se] represent the content (% by weight) of Mn and Se, respectively.) According to claim 1,
A grain-oriented electrical steel sheet further comprising 0.005 to 0.1% by weight of one or more of Sb and Sn, respectively or in combination. According to claim 1,
A grain-oriented electrical steel sheet further comprising 0.01% by weight or less of Al and 0.005% by weight or less of N. delete In weight %, Si: 2.0 to 4.5%, C: 0.01 to 0.1%, Mn: 0.005 to 0.05%, S: 0.0005 to 0.02%, Se: 0.0005 to 0.2% and the balance contains Fe and unavoidable impurities and the following formula Heating a slab satisfying 1;
Hot rolling the slab to produce a hot rolled sheet;
Cold rolling the hot rolled sheet to produce a cold rolled sheet;
First recrystallization annealing the cold rolled sheet;
Applying an annealing separator to the primary recrystallized annealed steel sheet; And
And subjecting the steel sheet subjected to primary recrystallization annealing to secondary recrystallization annealing,
The annealing separator comprises 100 parts by weight of Mg oxide or Mg hydroxide and 10 to 40 parts by weight of metal sulfur oxide or metal sulfide,
The second recrystallization annealing step includes a temperature increase step and a crack step,
The heating step is a method of manufacturing a grain-oriented electrical steel sheet is performed in an atmosphere that satisfies the following equation (3).
[Equation 1]
3×[Mn] ≥ [Se] ≥ 1.5×[Mn]
(In formula 1, [Mn] and [Se] represent the content (% by weight) of Mn and Se, respectively.)
[Equation 3]
[N ₂ ] ≥ 3×[H ₂ ]
(In formula 3, [N ₂ ] and [H ₂ ] mean the volume% of N ₂ and H _{2 in} the atmosphere, respectively.) The method of claim 5,
The slab is a method of manufacturing a grain-oriented electrical steel sheet satisfying the following formula 2.
[Equation 2]
0.5×[Mn] ≥ [S]
(In Formula 2, [Mn] and [S] represent the content (% by weight) of Mn and S, respectively.) The method of claim 5,
The slab is a method of manufacturing a grain-oriented electrical steel sheet further comprising 0.005 to 0.1% by weight of one or more of Sb and Sn, respectively, individually or in combination. The method of claim 5,
The slab is a method of manufacturing a grain-oriented electrical steel sheet further comprising 0.01% by weight or less of Al and 0.004% by weight or less of N. The method of claim 5,
After the step of manufacturing the hot-rolled sheet, the method of manufacturing a grain-oriented electrical steel sheet having an edge crack of one side of the hot-rolled sheet of 20 mm or less and a distribution of the edge cracks of 10/m or less with respect to the lengthwise direction of the hot-rolled sheet. delete delete delete The method of claim 5,
After the heating step, the S content of the steel sheet is a method of manufacturing a grain-oriented electrical steel sheet that is at least twice the S content of the slab. The method of claim 5,
After the temperature rising step, the steel sheet is a method for manufacturing a grain-oriented electrical steel sheet comprising a composite grain boundary segregation of S and Se or a (Fe, Mn, Cu) (S, Se) composite precipitate. The method of claim 5,
After the temperature rising step, a sulfur diffusion layer formed in the inner direction of the steel sheet is formed from the interface between the film and the steel sheet, and the sulfur diffusion layer comprises S in an amount of 0.01 to 0.05% by weight. The method of claim 5,
The cracking step is a method of manufacturing a grain-oriented electrical steel sheet is performed in an atmosphere containing at least 75% by volume of hydrogen. The method of claim 5,
The cracking step is a method of manufacturing a grain-oriented electrical steel sheet is carried out at 1000 to 1250 ℃.