KR101594601B1 - Oriented electrical steel sheets and method for manufacturing the same - Google Patents

Abstract

A directional electrical steel sheet and a method of manufacturing the same are provided. The grain-oriented electrical steel sheet according to the present invention contains 2.0 to 4.5% of Si, 0.001 to 0.10% of C, 0.010% or less of Al (not including 0%), 0.08% or less of Mn 0.001 to 0.10% of Sn, 0.001 to 0.10% of Sn and 0.001 to 0.10% of Bi, and the balance of 0.001 to 0.10% of Sn, 0.001 to 0.03% of S, 0.001 to 0.10% of Sb, Fe, and other inevitably impurities, wherein S, Sb, Sn and Bi satisfy the following relation: 0.005%? [S] + [Sb] + [Sn] + [Bi]? 0.15% [Sb], [Sn], and [Bi] are wt% of S, Sb, Sn, and Bi.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a directional electric steel sheet,

The present invention relates to a method for producing a directional electrical steel sheet, and more particularly, to a method for manufacturing a directional electrical steel sheet, in which a secondary recrystallization in a {110} < 001} orientation is stably formed, To provide a technique for efficiently producing a directional electric steel sheet having a very low iron loss at a low cost.

The oriented electrical steel sheet has a so-called Goss texture in which the orientation of all the grains on the steel sheet face is {110} plane and the crystal orientation in the rolling direction is parallel to the <001> axis, 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 precisely aligning the orientation of the crystal grains in the {110} < 001 > orientation.

Generally, a directional electric steel sheet having excellent magnetic properties is required to strongly develop a goss texture in a {110} < 001 > orientation in the rolling direction of a steel sheet. In order to form such a texture, It is necessary to form an abnormal crystal grain growth called recrystallization.

This abnormal crystal growth occurs when normal crystal growth inhibits the movement of grain boundaries normally grown by precipitates, inclusions, or elements segregated in the grain boundaries or solid solution, unlike ordinary grain growth.

As described above, precipitates and inclusions that inhibit grain growth are specifically referred to as crystal grain growth inhibitors. Studies on the production of grain oriented electrical steel sheets by secondary recrystallization in the {110} < 001 & Has been focused on securing good magnetic properties by forming secondary recrystallization with high degree of integration in the {110} < 001 > orientation.

Up to now, the grain oriented electrical steel sheet has been mainly manufactured by using a manufacturing method in which precipitates such as AlN and MnS [Se] are used as grain growth inhibitors to cause secondary recrystallization.

The directional electric steel sheet manufacturing method using such AlN and MnS precipitates as grain growth inhibitors has an advantage of stably inducing secondary recrystallization. However, in order to exhibit a strong grain growth inhibiting effect, the precipitates are distributed very finely and uniformly on the steel sheet .

In order to uniformly distribute the fine precipitates in this manner, the slab is heated at a high temperature of 1300 DEG C or higher for a long period of time before hot rolling to solidify coarse precipitates present in the steel, and then hot rolled in a very short time, The hot rolling should be finished.

To accomplish this, a large-scale slab heating apparatus is required. In order to suppress the precipitation as much as possible, it is necessary to control the hot rolling and the winding process very strictly, and to control the precipitates precipitated in the hot- .

In addition, when the slab is heated at a high temperature, the slab washing phenomenon occurs due to the formation of Fe ₂ SiO ₄ having a low melting point, thereby reducing the water content.

Along with the above-mentioned problems, a method of producing a directional electric steel sheet in which secondary recrystallization is caused by using AlN or MnS precipitates as a crystal grain growth inhibitor, requires a long period of 30 hours or more at a high temperature of 1200 ° C in order to remove precipitate components after completion of secondary recrystallization There is a problem that the complexity and the cost burden of the normal manufacturing worker must be annealed.

That is, if a precipitate such as AlN or MnS is used as a crystal grain growth inhibitor to cause secondary recrystallization, if such precipitates remain in the steel sheet, it may interfere with the movement of the billet, thereby increasing the history hands. To accomplish this, after completion of the second recrystallization, a long time refining annealing is performed at a high temperature of about 1200 ° C. using 100% hydrogen gas to remove precipitates such as AlN and MnS and other impurities.

By this refinement annealing, MnS precipitates are separated into Mn and S, Mn is dissolved in the steel, S diffuses to the surface and reacts with hydrogen gas in the atmosphere to form H ₂ S and is discharged.

In this refinement annealing process, AlN-based precipitates are decomposed into Al and N, and Al moves to the surface of the steel sheet and reacts with oxygen in the surface oxidation layer to form Al ₂ O ₃ oxides. The Al- AlN precipitates that have not been decomposed in the course of the process interfere with the movement of the magnetic domains in or near the surface of the steel sheet, thereby deteriorating iron loss.

AlN and MnS precipitates are not used as grain growth inhibitors but the surface energy is used as crystal growth driving force to grow the {110} < 001 > orientation first. However, the surface energy difference is effectively utilized There is a problem that the thickness of the steel sheet must be thin.

A directional electric steel sheet having excellent magnetic properties can be produced only under the condition that the steel sheet thickness is extremely thin (about 0.2 mm or less). However, the thickness of the directional electric steel sheet widely used at present in manufacturing the transformer is 0.23 mm or more, There is a technical difficulty in forming secondary recrystallization using surface energy in thickness. In addition, there is a problem in that the process using the surface energy greatly affects the process load in the cold rolling process when it is manufactured to a thickness of 0.20 mm or less.

In addition, in order to effectively utilize the surface energy, secondary recrystallization must be performed in a state in which oxide formation on the surface of the steel sheet is actively suppressed. Therefore, a high-temperature annealing atmosphere must be a vacuum or a mixed gas atmosphere of inert gas and hydrogen gas.

Since the oxide layer is not formed on the surface, formation of the forsterite film is impossible in the high temperature annealing process in which the final secondary recrystallization is formed, which makes it difficult to insulate and increase the iron loss.

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

The present invention is characterized in that at least one selected from S, Sb, Sn, Bi, or FeS segregated at grain boundaries alone serves as a grain growth inhibitor without using an AlN or MnS precipitate as a grain growth inhibitor, Direction oriented secondary recrystallization and minimizing the amounts of Al precipitates and oxides present in the secondary recrystallized steel sheet to provide a technique for efficiently and efficiently producing a grain-oriented electrical steel sheet having a low iron loss at low cost.

The grain-oriented electrical steel sheet according to the present invention contains 2.0 to 4.5% of Si, 0.001 to 0.10% of C, 0.010% or less of Al (not including 0%), 0.08% or less of Mn 0.001 to 0.10% of Sn, 0.001 to 0.10% of Bi, and 0.001 to 0.10% of Bi, and N: 0.005% or less (excluding 0%), S: 0.001 to 0.03% Part consists of Fe and other inevitably incorporated impurities.

[S], [Sb], [Sn], [Bi], and [Bi] Is the wt% of S, Sb, Sn, Bi).

The electrical steel sheet may be one in which at least one selected from S, Sb, Sn, Bi, or FeS precipitates segregated in grain boundaries acts as a grain growth inhibitor and is secondary recrystallized.

The density of the Al oxide in the thickness direction cross section of the grain-oriented electrical steel sheet may be 0.01 to 500 pieces / mm ² .

The directional electrical steel sheet may have a coercive force of 30 A / m or less under a condition of applying an alternating magnetic field of 50 Hz and 1.7 tesla.

A method for producing a grain-oriented electrical steel sheet according to the present invention comprises: 2.0 to 4.5% Si, 0.001 to 0.10% C, 0.010% or less Al (not including 0%) and 0.08% or less Mn 0.001 to 0.03% of S, 0.001 to 0.10% of Sb, 0.001 to 0.10% of Sn, 0.001 to 0.10% of Bi, and 0.001 to 0.10% of Bi, Providing a slab comprising the remainder Fe and other inevitably incorporated impurities; Preparing a hot-rolled steel sheet by reheating the slab and then hot-rolling the slab; Cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet; Decarburizing and annealing the cold-rolled steel sheet; Applying an annealing separator to the decarburization annealed steel sheet and performing secondary recrystallization annealing; .

[S], [Sb], [Sn], and [Bi] satisfy the relation of 0.005% ≤ [S] + [Sb] + [Sn] + [Bi] ≤ 0.15% S, Sb, Sn, and Bi).

Further comprising a step of annealing the hot-rolled steel sheet after the step of manufacturing the hot-rolled steel sheet, wherein the annealing of the hot-rolled steel sheet can be carried out at a temperature of 900 ° C or higher.

The step of producing the cold-rolled steel sheet may be performed by cold rolling twice or more including cold rolling or intermediate annealing once, and warm rolling may be carried out during cold rolling to maintain the temperature of the steel sheet at 100 캜 or higher.

Also, the decarburization annealing is carried out at a temperature of 750 ° C or more for 30 seconds or longer to reduce the carbon content of the steel sheet to 0.003% or less, and the size of the deformed cold rolled and recrystallized grain along with decarburization annealing may be 5 μm or more.

Also, the second recrystallization annealing step includes a temperature raising step and a refining annealing step. The annealing atmosphere is heat-treated using a mixed gas of hydrogen and nitrogen in the temperature raising step. In the refining annealing, At a temperature of 10 hours, preferably 1 hour or less.

The density of the Al oxide in the cross-section in the thickness direction of the directional electrical steel sheet after completion of the secondary recrystallization annealing may be 0.01 to 500 pieces / mm ² .

At least one selected from among S, Sb, Sn, Bi, and FeS may be secondary recrystallized by acting as a grain growth inhibitor.

INDUSTRIAL APPLICABILITY According to the present invention, the content of Al and N forming the Al-based oxide or the precipitate and the Mn forming the MnS precipitate are minimized in the steelmaking step, thereby reducing the manufacturing cost.

Further, as a crystal growth inhibitor required for secondary recrystallization formation, growth of the primary recrystallized grains is strongly suppressed by the grain boundary of Sn, Sb, Bi, and S precipitates and FeS precipitates, and secondary recrystallization is stably caused, It is possible to manufacture a grain-oriented electrical steel sheet having an extremely low iron loss property by minimizing the interference factor of the magnetic domain by reducing the amount of Al-based precipitates and oxides.

Further, when S, Sb, Sn, Bi, or FeS precipitates segregated in the grain boundaries are used, the frequency of occurrence of Al-containing precipitates and oxides in the secondary recrystallized electric steel sheet is higher than that of Al- And the occurrence frequency of oxides and inclusions is remarkably reduced, so that excellent iron loss characteristics are secured as compared with the case where AlN system precipitates are used as grain growth inhibitors.

In addition, since the purification annealing at a high temperature for removing precipitates such as AlN and MnS is unnecessary, the manufacturing cost is reduced.

In addition, FeS has a very low melting point of 1194 DEG C, so that the {110} < 001 > secondary recrystallization start temperature can be lowered to 1000 DEG C or lower, and decomposition of FeS and discharge of S .

In the case of Sn, Sb and Bi, diffusion at near the surface rather than segregation at grain boundaries at a high temperature of 1000 ° C or more stabilizes the surface oxide layer and prevents the oxide layer from falling into the steel sheet, Thereby alleviating the phenomenon of deterioration. Therefore, Sn, Sb and Bi are present on the surface of the steel sheet in the final product, and thus have excellent magnetic properties.

The grain-oriented electrical steel sheet according to the present invention comprises 2.0 to 4.5% of Si, 0.001 to 0.10% of C, 0.010% or less of Al (not including 0%), 0.08% or less of Mn 0.001 to 0.10% of Sn, 0.001 to 0.10% of Bi, and 0.001 to 0.10% of Bi, and N: 0.005% or less (excluding 0%), S: 0.001 to 0.03% And S, Sb, Sn, and Bi are each independently selected from the group consisting of Fe and other inevitably incorporated impurities,

[S], [Sb], [Sn], and [Bi] are the concentrations of Sb, Sb, Sn, and Bi in wt% %to be)

.

Further, at least one selected from S, Sb, Sn, Bi, or FeS segregated at grain boundaries acts as a grain growth inhibitor and is secondary recrystallized.

The density of the Al oxide in the thickness direction cross section of the grain-oriented electrical steel sheet may be 0.01 to 500 pieces / mm ² .

The directional electrical steel sheet may have a coercive force of 30 A / m or less under a condition of applying an alternating magnetic field of 50 Hz and 1.7 Tesla.

Hereinafter, reasons for limiting the components of the present invention will be described.

Si is a basic composition of an electric steel sheet, and plays a role of lowering the core loss, that is, the iron loss, by increasing the resistivity of the material. When the Si content is less than 2.0%, the resistivity decreases and the iron loss characteristic deteriorates. In the high temperature annealing, the second phase recrystallization becomes unstable due to the presence of the phase transformation section. When the Si content exceeds 4.5%, the brittleness of the steel becomes excessively large. The content of C for containing an austenite fraction of 40% or more is greatly increased, and the formation of secondary recrystallization becomes unstable. Therefore, Si is preferably limited to 2.0 to 4.5%.

Since Al forms bonds with nitrogen in the steel to form AlN precipitates, the Al content is positively suppressed in the present invention to avoid Al-based nitride and oxide formation. If the content of acid soluble Al exceeds 0.010%, the formation of AlN and Al ₂ O ₃ is promoted, and the annealing annealing time for removing the AlN and Al ₂ O ₃ is increased. The inclusions such as AlN precipitates and Al ₂ O ₃ , It is preferable that Al is not added in the present invention. However, the content of acid soluble Al is limited to 0.010% or less in consideration of the amount inevitably added in the steel making process.

When the Al content exceeds 0.01%, the number of Al-based inclusions and precipitates increases by 500 / mm ² or more, and the iron loss of the steel sheet also increases. Therefore, in order to reduce the number of Al-based inclusions and precipitates to 500 / mm ² or less, the Al content should be 0.01% or less.

The number of Al-based inclusions and precipitates is preferably as small as possible, and the number of Al-based inclusions and precipitates is preferably controlled to 0.01 to 500 / mm ² or less through possible process control.

Mn has an effect of increasing the specific resistance and decreasing the iron loss by the same as that of Si, and the purpose of adding Mn in the prior art was to react with S in the steel to form MnS precipitates to suppress grain growth.

However, in the present invention, since the MnS precipitate is not used as a grain growth inhibitor, the content of Mn is positively suppressed. Mn is preferably not added, but it is limited to 0.08% or less, more preferably 0.05% or less, in view of the amount that is inevitably added in the steelmaking process.

When Mn is added in an amount exceeding 0.08%, MnS is precipitated coarsely, so that the effect of S solely segregating in grain boundaries is deteriorated and precipitation of FeS is also difficult.

Further, it takes a long time to decompose MnS in the subsequent refining annealing step, and it may remain as a precipitate in the final product and cause iron loss to increase.

N reacts with Al to form AlN and Si ₃ N ₄ precipitates. As a result, the formation of AlN is positively suppressed by positively suppressing the content of acid soluble Al. However, if the content of N is large, it reacts with Al which is unavoidably present in the steel to form AlN, or it segregates in the grain boundary alone and affects grain boundary segregation of S, so that the content of N is controlled to 0.005% or less desirable.

C is an austenite stabilizing element that inhibits the slab center segregation of S as well as the effect of refining the coarse columnar structure occurring during the performance by causing a phase transformation at a temperature of 900 ° C or higher. It also promotes work hardening of the steel sheet during cold rolling, thereby promoting the formation of secondary recrystallization nuclei in the {110} < 001 > orientation in the steel sheet. Therefore, when the content is less than 0.001%, the effect of phase transformation and work hardening can not be obtained. When the content is more than 0.1%, occurrence of hot-edge-crack occurs, A load of the decarburization process is generated at the time of post decarburization annealing, and therefore the addition amount is preferably 0.001 to 0.10%.

S is an element that forms MnS, and is an important element for causing segregation in the grain boundaries alone or secondary sintering of the Goss orientation by forming FeS precipitates.

S is added alone in an amount of 0.001 to 0.03% as a content necessary for segregation at grain boundaries or formation of FeS.

If S is added in an amount less than 0.001%, the effect of suppressing grain growth due to grain boundary segregation or FeS precipitates of S alone is insufficient. If S is added in an amount exceeding 0.03%, the edge- -crack), which increases the possibility that the hot rolling operation becomes difficult.

Further, when Mn is mixed and contained inevitably in the steelmaking process, S reacts with Mn to form MnS. It is preferable to control so that the content of S alone does not react with Mn and is 0.001% or more. Also, it is preferable that S is added in an amount of 0.002% or more in the steelmaking process so that the amount of S present alone does not react with Mn and becomes 0.001% or more.

Sn is a typical intergranular element such as S, which is a typical component for inhibiting the growth of crystal grains in combination with S in the present invention. It is preferable to improve the texture of the primary recrystallization texture to improve the secondary recrystallization nuclei in the {110} < 001 & Making primary recrystallization microstructure that can grow. If the addition amount of Sn is less than 0.001%, the grain size is small and the effect of addition is not clear. If it is added in excess of 0.10%, segregation in the grain boundary occurs severely and the possibility of plate breakage in the cold rolling process is increased. 0.10%.

S is formed after the secondary recrystallization in the final annealing step, conventional and removed from the H ₂ gas atmosphere and the reaction plate to the H ₂ S gas to the long time annealing at 1200 ℃, is some amount of residue. The residual S is present in the grain boundary and does not adversely affect the magnetic properties of the electrical steel sheet. The S remaining on the steel sheet is preferably 0.0005% or more.

Sb is a component for inhibiting the growth of crystal grains along with S in the present invention as a grain boundary segregation element such as Sn and improves the texture of the primary recrystallization structure so that the secondary recrystallization nuclei in the {110} < 001 & Which makes the primary recrystallized microstructure. When the addition amount of Sb is less than 0.001%, the grain size is small and the effect of addition is not clear. If it is added in excess of 0.10%, segregation in the grain boundary occurs seriously and the possibility of plate breakage in the cold rolling process is increased. 0.10%.

Bi is a component which inhibits the growth of crystal grains together with S in the present invention as a grain boundary segregation element such as Sn and Sb described above and improves the texture of the primary recrystallization texture to improve the secondary recrystallization nuclei in the {110} < 001 & It makes primary recrystallized microstructure that can grow well. If the addition amount of Bi is less than 0.001%, the grain size is small and the effect of addition is not clear. If it is added in excess of 0.10%, segregation occurs at the grain boundaries seriously and the possibility of plate breakage in the cold rolling process is increased. 0.10%.

The total sum of the total content of the grain boundary elements of S, Sb, Sn and Bi described above is preferably 0.005 to 0.15%.

If the sum of the elements of the grain boundary segregation is less than 0.005%, the effect of inhibiting the grain growth is small. If the total grain segregation is more than 0.15%, the grain segregation is severe and the plate rupture may occur during cold rolling.

P is a segregation element such as Sn, Sb and Bi, and when it is added in a certain amount, it has an effect of refining the crystal grains, but is not as large as the inhibiting ability of Sn, Sb, Bi and S which are alloying elements of the present invention. However, when P is added in an amount of 0.001% or more, which can inevitably enter the P-alloy element rather than completely eliminated, the grain is uniformly refined. However, the addition of 0.1% or more may increase the brittleness of the steel sheet, which may cause sheet breakage during cold rolling, so that the appropriate addition amount is preferably 0.0010 to 0.1%.

Other alloying elements such as B, V, and Nb may be added as long as they do not interfere with the grain boundary segregation of S, Sn, Sb and Bi or the grain growth growth inhibiting effect of the FeS precipitates in addition to the above-described alloying elements. B, V, Nb and the like are each preferably 0.005% or less.

Hereinafter, a method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be described.

(Inclusive of 0%), Mn: 0.08% or less (inclusive of 0%), N: 0.005% or less, , 0.001 to 0.03% of S, 0.001 to 0.10% of Sb, 0.001 to 0.10% of Sn, and 0.001 to 0.10% of Bi, with the balance being Fe and other inevitably incorporated impurities S, Sb, Sn, Bi,

[S], [Sb], [Sn], and [Bi] are the concentrations of Sb, Sb, Sn, and Bi in wt% %to be)

Lt; / RTI &gt;

Other alloying elements such as B, V, and Nb may be added to the slab as long as it does not interfere with the intergranular segregation of S, Sn, Sb and Bi or the effect of inhibiting grain growth of FeS precipitates. , Nb and the like are each preferably 0.005% or less.

The slab is heated to a temperature of 1050 to 1280 캜 and hot rolled to produce a hot-rolled steel sheet. The hot rolled steel sheet can be manufactured from hot rolled steel sheet having a thickness of 1.0 to 4.0 mm by hot rolling so that the final cold rolled steel sheet can be manufactured at a final rolling thickness of 50 to 95%.

The hot-rolled hot-rolled sheet is subjected to hot-rolled sheet annealing as required or cold-rolled without hot-rolled sheet annealing. In the case of annealing the hot-rolled sheet, the hot-rolled sheet is heated to a temperature of 900 ° C or more to uniform the hot-rolled structure, and is then cooled for a predetermined time and cooled.

Thereafter, the cold rolling is carried out by using a reverse mill or a tandem mill to cold-roll two or more times including cold rolling or intermediate annealing to produce a cold-rolled sheet having a final product thickness. It is advantageous to perform warm rolling in which the temperature of the steel sheet is maintained at 100 DEG C or higher during cold rolling to improve the magnetic properties.

After the cold rolling is completed, decarburization and recrystallization annealing are performed. The decarburization and recrystallization annealing can be carried out at a temperature of 750 ° C or more for 30 seconds or more so that decarburization can occur to reduce the carbon content of the steel sheet to about 0.0030% or less. At the same time, an appropriate amount of oxide layer is formed on the surface of the steel sheet. In addition to the decarburization annealing, the deformed cold-rolled structure is recrystallized and crystallized to an appropriate size. At this time, the decarburization annealing temperature and the cracking time can be adjusted so that the size of the recrystallized grains can grow to 5 μm or more.

After the decarburization annealing, MgO as the annealing separator is applied and secondary recrystallization annealing is performed. Secondary recrystallization High-temperature annealing is performed by raising the temperature to a proper temperature elevation rate to cause secondary recrystallization in {110} < 001 > Goss orientation, followed by refining annealing, which is an impurity removal process. In the process, the annealing atmosphere gas is subjected to a heat treatment using a mixed gas of hydrogen and nitrogen in the heating process as in the usual case, and in the refining annealing, a method of removing impurities using 100% hydrogen gas can be applied.

Since the AlN and MnS precipitates are not used as the main grain growth inhibitors as in the present invention, it is sufficient to reduce the burden of the finishing annealing for decomposing and removing AlN and MnS, and to set the finishing annealing temperature to 1000 deg. The time required for the refining annealing depends on the refining annealing temperature, but it is possible to produce a grain-oriented electrical steel sheet having an extremely excellent magnetic property even at a temperature of 1000 to 1200 占 폚 within 10 hours, more preferably within 1 hour.

&Lt; Example 1 >

S, Sn, Sb, and Bi were added to the ingot in a different composition based on the contents of C: 0.05%, Si: 3.2%, Mn: 0.03%, Al: 0.003%, and N: 0.003% Lt; / RTI &gt;

Subsequently, the ingot was heated to a temperature of 1250 캜 and hot-rolled to a thickness of 2.3 mm. The hot-rolled hot-rolled sheet was heated to a temperature of 950 ° C, cracked for 180 seconds, and hot-rolled sheet annealed.

Hot-rolled sheet The annealed steel sheet was pickled and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.30 mm. The cold-rolled steel sheet was subjected to decarburization and recrystallization heat treatment at a temperature of 810 ° C for 180 seconds in a mixed gas atmosphere of wet hydrogen and nitrogen.

The steel sheet was coated with MgO as an annealing separator and finally annealed in a coiled state. The final annealing was carried out under a mixed atmosphere of 25% nitrogen and 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, it was maintained in 100% hydrogen gas atmosphere for 5 hours and then cooled.

The magnetic properties of the grain-oriented electrical steel sheet according to the changes of the contents of S, Sn, Sb and Bi, which are the main components of the present invention, are measured and shown in Table 1 below.

S (%) Sn (%) Sb (%) Bi (%) [S] + [Sb] + [Sn] + [Bi] (%) Magnetic flux density
(B ₁₀ , Tesla) Iron loss
(W _17/50 , W / kg) division 0.0008 0.0009 0.0005 0.0005 0.0027 1.725 1.68 Comparison 1 0.0050 0.0500 0.0010 0.0035 0.0595 1.931 0.95 Inventory 1 0.0100 0.0050 0.0045 0.0029 0.0224 1.923 0.93 Inventory 2 0.0200 0.0045 0.0050 0.0044 0.0339 1.935 0.94 Inventory 3 0.0300 0.0150 0.0052 0.0038 0.0540 1.922 0.92 Invention 4 0.0350 0.0410 0.0100 0.0380 0.1240 1.815 1.39 Comparative material 2 0.0150 0.1120 0.0380 0.0250 0.1900 1.746 1.72 Comparative material 3 0.0250 0.0450 0.1080 0.0033 0.1813 1.795 1.85 Comparison 4 0.0150 0.0400 0.0330 0.1010 0.1890 1.644 1.92 Comparative material 5 0.0250 0.0380 0.0580 0.0055 0.1265 1.937 0.91 Invention Article 5 0.0150 0.0736 0.0263 0.0172 0.1321 1.928 0.95 Inventions 6 0.0250 0.0077 0.0550 0.0060 0.0937 1.946 0.95 Invention 7 0.0150 0.0065 0.0081 0.0490 0.0786 1.955 0.91 Invention 8

As can be seen in Table 1, Inventive Material 1 to Inventive Material 8, in which the total content of S, Sn, Sb and Bi was controlled within the range of 0.005 to 0.15% of the present invention, are excellent in magnetic flux density and core loss.

The comparative material 1 was deficient in grain growth due to grain boundary segregation and FeS precipitates due to low S, Sn, Sb and Bi contents, and the magnetism was weakened. Comparisons 2, 3, 4 and 5 show that the content of each of S, Sn, Sb and Bi exceeded the standard, or that the total amount of added segregation elements exceeded 0.005 to 0.15%, making it difficult to control the primary recrystallization and rolling The formation of the secondary recrystallization was unstable and the magnetic flux density and iron loss were inferior.

&Lt; Example 2 >

, And as a base composition, 0.045% of C, 3.15% of Si, 0.020% of Mn, 0.020% of S, 0.05% of Sn, 0.03% of Sb and 0.015% And N were changed in vacuum to obtain ingots.

Subsequently, the ingot was heated to a temperature of 1200 DEG C and then hot-rolled to a thickness of 2.3 mm. The hot-rolled hot-rolled sheet was heated to a temperature of 1100 ° C and then cracked at 900 ° C for 120 seconds to anneal the hot-rolled sheet.

The hot-rolled steel sheet was then cooled, pickled, and cold-rolled to obtain a cold-rolled sheet having a thickness of 0.23 mm. The cold-rolled steel sheet was subjected to decarburization and recrystallization heat treatment at a temperature of 850 ° C for 180 seconds in a mixed gas atmosphere of wet hydrogen and nitrogen.

The thus prepared steel sheet was coated with MgO as an annealing separator and finally annealed in a coiled state. In the final annealing, a mixed atmosphere of 50% nitrogen + 50% hydrogen was set up to 1200 ° C. After reaching 1200 ° C., it was maintained in a 100% hydrogen gas atmosphere for 1 hour and then cooled.

Aluminum oxide densities, coercive force and magnetic properties were measured for the directional electrical steel sheets prepared respectively, and the results are shown in Table 2 below. The Al-based oxide density was calculated by observing the cross section in the thickness direction of the steel sheet and calculating the number of Al-based oxides per unit square meter.

The coercivity was obtained by measuring the applied magnetic field (A / m) at which the magnetic flux density of the steel sheet became 0 (zero) under an alternating magnetic field condition of 1.7 Tesla and 50 Hz.

Al (%) N (%) Al calculated cargo density
(1 / mm ² ) Coercivity
(A / m) Magnetic flux density
(B ₁₀ , Tesla) Iron loss
(W _17/50 , W / kg) division 0.0010 0.0015 0.05 8.4 1.954 0.89 Invention 9 0.0022 0.0025 1.5 12.5 1.939 0.90 Inventions 10 0.0045 0.0033 19 20.1 1.942 0.91 Invention invention 11 0.0052 0.0028 152 25.4 1.912 0.95 Invention 12 0.0037 0.0021 93 18.4 1.935 0.90 Invention invention 13 0.0028 0.0025 252 23.6 1.918 0.93 Invention Article 14 0.0110 0.0072 655 31.0 1.902 1.09 Comparative material 6 0.0170 0.0080 981 35.4 1.898 1.07 Comparison 7 0.0210 0.0075 1236 39.1 1.896 1.10 COMPARISON 8

As shown in Table 2, the inventive materials 9 to 14 in which the content of Al is suppressed to 0.01% or less and the content of N is suppressed to 0.005% or less are as low as 500 (number / mm ² ) or less of the density of the Al- Has a low value of 30 A / m or less and is excellent in magnetism.

On the other hand, the comparative materials 6 to 8 having an acid-soluble Al content exceeding 0.01% and an N content exceeding 0.005% had an Al-based oxide density of more than 500 (number / mm ² ) Respectively.

When the acid soluble Al content exceeds 0.01%, the Al-based oxides remain in the steel sheet in the final product after the secondary recrystallization annealing, thereby obstructing and fixing the movement of the magnetic wall under the AC magnetic field. In this case, A greater amount of force is applied to move the magnetic wall fixed by the oxides to overcome the obstruction of the oxides.

This force is expressed as coercive force, and the fact that coercivity is large means that there is more power to move the magnetic wall under the exchange magnetic field, which leads to an increase in core loss.

From the results shown in Table 2, the inventive materials 9 to 14 having a low Al-based oxide density have a low coercive force of 30 (A / m) or less, while the comparative materials 6 to 8 have an oxide density of 500 / mm ² , the coercive force becomes larger than 30 (A / m), and the iron loss is greatly increased.

While the present invention has been described in connection with certain exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (18)

(Not including 0%), Mn: not more than 0.08% (not including 0%), N: not more than 0.10% 0.001 to 0.10% of Sb, 0.001 to 0.10% of Sn, and 0.001 to 0.10% of Bi, and 0.001 to 0.005% (excluding 0%) of S; 0.0005 to 0.03% The remainder is a directional electric steel sheet made of Fe and other inevitably incorporated impurities,
The electrical steel sheet does not use AlN or MnS precipitates as a main grain growth inhibitor,
Wherein at least one selected from S, Sb, Sn, Bi, or FeS precipitates segregated in grain boundaries acts as a grain growth inhibitor and is segregated in grain boundaries. delete The method according to claim 1,
S, Sb, Sn, and Bi are
[S], [Sb], [Sn], and [Bi] are the concentrations of Sb, Sb, Sn, and Bi in wt% %to be)
Lt; / RTI &gt; The method according to claim 1 or 3,
Wherein the density of Al oxide in the cross section in the thickness direction of the grain-oriented electrical steel sheet is 0.01 to 500 pieces / mm ² . 5. The method of claim 4,
Wherein the directional electrical steel sheet has a coercive force of 30 A / m or less under the condition of applying an alternating magnetic field of 50 Hz and 1.7 Tesla. 6. The method of claim 5,
Wherein the directional electrical steel sheet further comprises B, V and Nb, and B, V and Nb are each 0.005% or less. (Not including 0%), Mn: not more than 0.08% (not including 0%), N: not more than 0.10% 0.001% or less (excluding 0%), S: 0.001 to 0.03%, Sb: 0.001 to 0.10%, Sn: 0.001 to 0.10% and Bi: 0.001 to 0.10%, the balance being Fe and other inevitably incorporated Providing a slab of impurities to the substrate;
Preparing a hot-rolled steel sheet by reheating the slab and then hot-rolling the slab;
Cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet;
Decarburizing and annealing the cold-rolled steel sheet; And
Applying an annealing separator to the decarburization annealed steel sheet and performing secondary recrystallization annealing; , &Lt; / RTI &
The secondary recrystallization annealing step includes a temperature increasing step and a refining annealing step,
Characterized in that the annealing atmosphere is subjected to heat treatment using a mixed gas of hydrogen and nitrogen in the temperature raising process, and in the refining annealing, cracking treatment is carried out at a temperature of 1000 to 1200 ° C within 10 hours by using hydrogen gas . 8. The method of claim 7,
S, Sb, Sn, and Bi are
0.005%? [S] + [Sb] + [Sn] + [Bi]? 0.15%
(Where S, Sb, Sn, and Bi are wt% of S, Sb, Sn, and Bi)
By weight based on the total weight of the steel sheet. 9. The method of claim 8,
Wherein the S is 0.002 to 0.03%. 9. The method of claim 8,
Further comprising the step of annealing the hot-rolled steel sheet after the step of manufacturing the hot-rolled steel sheet, wherein annealing the hot-rolled steel sheet is performed at a temperature of 900 ° C or higher. 10. The method of claim 9,
Wherein the cold rolled steel sheet is produced by cold rolling two or more times including cold rolling or intermediate annealing once and performing warm rolling in which the temperature of the steel sheet is maintained at 100 DEG C or higher during cold rolling, A method of manufacturing an electrical steel sheet. 11. The method of claim 10,
The decarburization annealing is carried out at a temperature of 750 ° C or more for 30 seconds or longer to reduce the carbon content of the steel sheet to 0.003% or less, and the size of the deformed cold rolled and recrystallized grain along with decarburization annealing is 5 μm or more. A method of manufacturing a steel sheet. delete 8. The method of claim 7,
And the cracking treatment is performed within 1 hour in the refining annealing. 8. The method of claim 7,
Wherein the slab further comprises B, V and Nb, and the B, V and Nb are each 0.005% or less. 15. A method according to any one of claims 7 to 12 or 14,
Wherein the density of the Al oxide in the cross-section in the thickness direction of the grain-oriented electrical steel sheet after completion of the secondary recrystallization annealing is 0.01 to 500 pieces / mm ² . 15. A method according to any one of claims 7 to 12 or 14,
Wherein the directional electrical steel sheet having undergone the secondary recrystallization annealing is at least one selected from among S, Sb, Sn, Bi, and FeS segregated in grain boundaries by acting as a grain growth inhibitor. (Inclusive of 0%), Mn: 0.08% or less (inclusive of 0%), N: 0.005% or less, 0.001 to 0.03% or less of S, 0.001 to 0.10% of Sb, 0.001 to 0.10% of Sn, and 0.001 to 0.10% of Bi, with the remainder being Fe and other inevitably incorporated The slab comprising the impurities is heated, the heated slab is hot-rolled, cold-rolled to produce a cold-rolled steel sheet, decarburization annealing is performed, secondary recrystallization annealing is performed, and H ₂ gas And S remaining after reacting with S is 0.0005 to 0.03%.