KR20000042518A - Method for producing oriented electric strip - Google Patents

Abstract

PURPOSE: A method is provided to produce an oriented electric strip having excellent magnetic property in a temperature of 1200 to 1280°C wherein melting scale is not generated and the strip is easily rolled. CONSTITUTION: A silicon steel slab is composed of 2.0 to 4.5wt% of Si, 0.010 to 0.095wt% of C, 0.010 to 0.040wt% of sol-Al, 0.002 to 0.020wt% of N, 0.05 to 0.45wt% of Mn, 0.002 to 0.20wt% of S, the remain of Fe and incidental impurities. The silicon steel slab is reheated in a low temperature and hot rolled and then annealed. Then, the slab is cold rolled in a final thickness, decarbonized, coated with an annealing separating agent and finally annealed to be an oriented electric strip.

Description

Manufacturing method of oriented electrical steel sheet

The present invention relates to a method for manufacturing low-temperature reheating oriented electrical steel sheet, and more particularly, to a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties while being reheated at a temperature of 1200-1280 ° C. that is easy to roll and does not generate a scale of melting. It relates to a method of manufacturing.

In manufacturing a grain-oriented electrical steel sheet, in order to manufacture a product having excellent magnetic properties, it is essential to have a so-called inhibitor whose primary recrystallized grains inhibit growth before the final high temperature annealing. As a method of securing the inhibitor, the reheating temperature is heated to a high temperature of about 1400 ° C. in the hot rolling process, and coarse AlN and MnS produced in the casting process employ precipitates to be finely dispersed and precipitated in the hot rolling and precipitation annealing processes. It's a common way. However, if the reheating temperature is increased, the error rate is lowered due to the so-called satellite phenomenon in which the surface of the slab is melted and melted during reheating, and the energy consumption to increase the temperature is not only high, but also the furnace must be repaired periodically. It is economical. In addition, due to the temperature deviation in the rolling length direction during hot rolling, the magnetism is a big problem, such as a deviation in the longitudinal direction occurs.

Therefore, efforts have been made to actively improve the problems in the hot rolling process, and various technologies have been proposed at present, and representative technologies are listed as follows.

First, Japanese Laid-Open Patent Publication No. 57-89433 discloses a technique for realizing a reheating temperature of 1100-1250 ° C by combining the columnar rate and cold rolling rate of slabs containing S, Se, Sb, Bi, Pb, Sn, and B. It is proposed. In addition, Japanese Patent Application Laid-Open No. 57-158332 proposes a method of lowering the reheating temperature by lowering Mn and lowering the Mn / S ratio to 2.5 or lower, and stabilizing the magnetism by adding Cu. Dong-A Publication 57-190324 discloses a method for lowering the reheating temperature below 1300 ° C by adding low C, S, Se, and B to the steel using MnS and AlN as an inhibitor and performing pulse annealing during the first recrystallization annealing. Is disclosed. In addition, Pub. No. 59-56522 has Mn of 0.08-0.45%, S of 0.007% or less, [Mn] [S] solubility of 1200 ° C or less, and P of 0.015-0.045% of P. It is revealed that low-temperature reheating is possible by increasing the temperature increase rate to 15 ° C / hr. The proposed prior arts have attempted reheating through adjustment of components, and these methods have a problem that is difficult to industrialize in terms of securing excellent magnetic properties.

On the other hand, Japanese Patent Application Laid-Open No. 62-40515 discloses that NH ₃ can be used to infiltrate nitrogen between the end of decarbonization and the second recrystallization start period to infiltrate the steel, thereby lowering the reheating temperature and securing excellent magnetic properties. This method is an advanced technology than the above-mentioned techniques, but includes an uneconomical factor such as installation of a nitriding furnace for nitriding treatment. Reflecting this aspect, a manufacturing method for settling without installing a nitriding furnace has been proposed in Dongbu Publication Nos. 2-294428 and 3-22324. However, this technology requires the slab heating temperature to be extremely low, below 1200 ° C, so a particularly powerful hot rolling machine is needed, and even if hot rolling is possible, the surface is damaged due to the high pressure between the steel sheet and the rolling roll. This happens. In addition, in the case of simultaneous processing of the general steel and the grain-oriented electrical steel sheet in an integrated steelworks, there are various problems in the hot rolling operation due to the different rolling temperatures of the plain steel and the grain-oriented electrical steel sheet.

Therefore, the present inventors have invented a method for securing excellent magnetic properties even after reheating (crude rolling) at 1000 ° C or more and 1250 ° C or less for the purpose of solving such a problem, and disclosed the technique in Korean Patent Laid-Open Publication No. 97-43184. have. However, the present inventors have continued to study this invention, but the rolling temperature is increased to 1250 ℃, but the lower the rolling temperature is excellent magnetic properties, the higher the rolling temperature is unstable magnetic properties excellent than 1200 ℃ It was discovered that there were defects that were difficult to obtain.

As described above, a problem in manufacturing excellent magnetic oriented electrical steel sheet is that when slab heating is performed at high temperature, the generation of melt scale increases, which hinders the operation of the heating furnace and the slab heating temperature is 1200. When the temperature is lower than or equal to 0 ° C, the deformation resistance of the steel sheet slab increases, so that the strength of the conventional hot rolling mill is weak, making it difficult to roll, and even when rolling, the probability of occurrence of defects called surface defects on the surface of the hot rolled sheet increases.

In order to overcome these drawbacks, the inventors continue to conduct research and experiments, find solutions, and propose the present invention.

SUMMARY OF THE INVENTION The present invention provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties while hot rolling at a conventional slab heating temperature at which the above-described defects do not occur, and an object thereof is provided.

The present invention for achieving the above object, Si: 2.0-4.5%, C: 0.010-0.095%, Sol-Al: 0.010-0.040%, N: 0.002-0.020%, Mn: 0.05-0.45%, Silicon steel slab composed of the remaining Fe and other unavoidable impurities is reheated at low temperature and hot rolled to form a hot rolled sheet, followed by precipitation annealing, cold rolling to a final thickness, and then decarbonization including sedimentation and annealing separator. In the method for producing a grain-oriented electrical steel sheet including a finish annealing step, the low temperature reheating is performed at 1200 to 1280 ° C;

The precipitation annealing is performed at 800 ± 50 ° C. to a cracking temperature of 980 ° C. or higher and 1250 ° C. or lower at a rate of 2 to 10 ° C./sec, and maintained at this cracking temperature for 1 to 120 seconds, followed by 900 ° C. to 980 ° C. The cooling to below temperature is completed within the range of 20 to 500 second, and then quenched to room temperature at a rate of 10 degrees C / sec or more.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention are seeking to develop a directional electrical steel sheet having excellent magnetic properties even at a reheating temperature that can be rolled by a conventional rolling mill without the occurrence of a melt scale, and in view of the optimization of the reheating temperature. Experiments show that deterioration problem can be solved if (1) control of primary recrystallization grain, (2) control of primary recrystallization texture structure, and (3) control of dispersion state of precipitate in inhibitor. Confirmed through, based on the experimental results it was possible to derive the precipitation annealing conditions of the present invention.

That is, the precipitation annealing of the present invention derived from the viewpoint of the above (1) (2) (3) is heated at a rate of 2 to 10 ° C / sec from 800 ° C to a cracking temperature of 980 ° C or more and 1250 ° C or less. It is maintained at the cracking temperature for 1 to 120 seconds and then completes the cooling from 900 ° C to more than 980 ° C in the range of 20 to 500 seconds, followed by quenching to room temperature at a rate of 10 ° C / sec or more. More specifically, the correlation between the factors to be controlled in the precipitation annealing process of the present invention and the conditions will be described below.

(1) control of primary recrystallized grains

In the present invention, in order to control the primary recrystallized grain, the cracking temperature in the precipitation annealing process is more preferably 980-1250 ° C. according to the following equation (1) according to the amount of Sol-Al (ppm) and the slab heating temperature (Ts). By controlling the crack temperature by this, the primary recrystallized grains can be made small to secure magnetic properties.

[Relationship 1]

1.04Ts-0.6Al-50≤Tk≤1.04Ts-0.6Al-10

Where Ts is slab heating temperature (℃) and Al is the content of Sol-Al (ppm).

In other words, the above equation (1) is derived based on the experimental results. The theoretical background is that the higher the slab heating temperature and the smaller the amount of Sol-Al, the smaller the primary recrystallized grain size. Therefore, it is due to the need to control the crack temperature Tk. The particle size after primary recrystallization annealing is influenced by the nitrogen content, S content, finish hot rolling start temperature, and primary recrystallization annealing conditions of the slab. The temperature at which the crack temperature is lower than the range of 980-1250 ° C. In addition, at high temperatures, the degree of integration of the secondary recrystallization direction is lowered and the magnetic flux density is lowered.

(2) control of the primary recrystallization group;

In the present invention, the control factor of the primary recrystallized texture structure is a temperature of 900 ~ 980 ° C that cracks at a temperature of 980 ~ 1250 ° C and then stops cooling at a constant rate. The higher the temperature (980 ° C), the higher the magnetic flux density after the secondary recrystallization, while the unstable expression of the secondary recrystallization becomes unstable, so the upper limit is less than 980 ° C. The lower limit is 900 ° C because secondary recrystallization occurs stably below this temperature, but secondary recrystallized grains with low magnetic flux density are more likely to grow.

Further, the primary recrystallized texture is controlled by quenching at a temperature of 10 ° C./sec or more from the temperature to room temperature. This is because the magnetic flux density is lowered when this rate is slower than 10 DEG C / sec, because the ideal goth orientation is reduced and the secondary recrystallized grains outside the ideal goth orientation are easily grown.

(3) Control of dispersed state of precipitate in inhibitor

The precipitate dispersion state of the inhibitor in the precipitation annealing process is controlled by the following three conditions. First, it is maintained for 1 to 120 seconds at the cracking temperature described in the above (1), because if it is out of this range, the dispersion state of the precipitate becomes worse and the dispersion of the orientation of the secondary recrystallization, which is expressed, becomes worse and the magnetic flux density decreases. . In addition, the temperature increase rate up to the cracking temperature in column (1) is limited to 2 ° C. or more and 10 ° C. or less. Since the dispersion of the inhibitor becomes worse when the temperature rises outside this temperature, the inhibitor is subjected to nitriding in a decarburization process. This is because the density of the secondary recrystallization direction is lowered even if it is strengthened, so that the magnetic flux density is low. In addition, the cooling time from the cracked temperature (980-1250 ° C.) to 900-980 ° C. is cooled between 20-500 seconds in the column (1), because the longer the time, the more favorable the precipitate for secondary recrystallization. This is because it develops in the preceding steps of the primary recrystallization annealing process and the secondary recrystallization annealing process, and therefore, at least 20 seconds or more is required. In addition, if the time is set to 500 seconds or less, the effect is not lost even if it is longer than that. However, the annealing time is unnecessarily long, so it is economically disadvantageous and limited to 500 seconds.

For this reason, the object of the present invention was achieved by precisely defining the precipitation treatment conditions of the hot rolled sheet, and the object of the present invention was achieved by the organic combination of the components of the silicon steel slab and the manufacturing process accordingly. It explains in full detail below.

[Components of Silicon Steel Slabs]

When C is less than 0.010%, secondary recrystallization occurs, but the magnetic flux density is low, and when it is added more than 0.095%, secondary recrystallization occurs and magnetic flux density is high, but it is economical because it takes a long time for decarburization in the primary recrystallization annealing process. As such, it is added at 0.010-0.095%.

The higher the Si content, the higher the resistivity, which reduces the eddy current loss of the product, so the more Si, the better. The reason for limiting Si to 2% or more is that the eddy current loss becomes large below this, which is not preferable. However, as the amount of Si added increases, plate breakage is more likely to occur in the cold rolling process, and the upper limit is 4.5% because it is beyond the object of the present invention to manufacture economically, since special consideration is required in cold rolling at 4.5% or more. Shall be.

Al forms (Al, Si) N after nitriding and acts as an inverter, but in this case, if it is not 0.010% or more as Sol-Al, it becomes difficult to grow crystal grains in the first recrystallization process, resulting in high magnetic flux density. Since it was hard to lose, the minimum was made into 0.010%. The upper limit is made 0.04% because if more than Al is present, the precipitate becomes too coarse, making it difficult to act effectively as an inhibitor.

N is added in an amount to disperse the inhibitor. That is, the inhibitor in the invention is mainly produced in the precipitation annealing process and the primary recrystallization annealing process. When N or more than 0.002% is not included before the hot rolling, the dispersion of the inhibitor becomes bad and high magnetic flux density is obtained. The lower limit was made 0.002% because it may not be obtained. In addition, when nitrogen is contained 0.02% or more, surface defects called blisters occur.

S is mainly related to (3) listed above in the present invention to precipitate MnS as precipitate nuclei of Al nitride and to precipitate AlN therein, so that the dispersion state of AlN is uniform, so that an ideal goth orientation occurs first. In addition, MnS acts directly as an inhibitor to help the ideal growth of the ideal goth defense, and has an effect on the primary recrystallized grain of (1). As S plays a role in controlling the primary recrystallized grain of (1), S has a function of reducing the particle size, so that S is better for increasing the primary recrystallized grain size. The upper limit of S addition is 0.2% because the upper limit of S addition is set because special measures are necessary to increase primary recrystallization and it is not economically advantageous if the amount of S added is increased. Next, in the role of an inhibitor, when S is 0.002% or less, since the number of precipitates is too small to act as the inhibitor itself, and also when it acts as precipitation nuclei of AlN, the lower limit is set to 0.002%. .

The reason for setting Mn from 0.05% to 0.45% is related to the above-described role of S as a precipitate forming element. Although MnS as a precipitate is formed even when Mn is 0.05% or less, in the case of Mn below this, the precipitate count is too small to serve as an inhibitor. This is because secondary recrystallization with high magnetic flux density does not occur because it does not play a role. The upper limit of Mn is 0.45% because the size of MnS as a precipitate is too large to act as an inhibitor.

[Manufacture process]

The slab formed as described above is reheated at a low temperature, wherein the reheating temperature is preferably set to 1200-1280 ° C. The reason for this is that when the reheating temperature is higher than 1280 ° C, the probability of the magnetic flux density of the product being 1.90T or less increases in the component of the present invention, which makes it difficult to employ it as an industrial manufacturing method. The lower magnetic flux density with the reheating temperature is due to the lower temperature of the primary recrystallization due to the high temperature heating, and as a result, the secondary recrystallization temperature is lowered, resulting in the secondary recrystallization with poor orientation. In addition, it is difficult to utilize MnS directly as an inhibitor when the reheating temperature is lower than 1200 ° C, and it requires a lot of energy required for rolling, and it is not economical because flaws are easily generated on the surface of the steel sheet during rolling. .

After reheating as above, hot rolling in a conventional manner, followed by precipitation annealing according to the present invention. Specifically, the precipitation precipitate is heated at a rate of 2 to 10 ° C./sec from 800 ± 50 ° C. to a crack temperature of more than 980 ° C. to 1250 ° C. and maintained at this crack temperature for 1 to 120 seconds, and then 900 ° C. The temperature is cooled to 20 ° C to 980 ° C or lower for 20 to 500 seconds, followed by rapid cooling to room temperature at a rate of 10 ° C / sec or more. The reason for the limitation of the precipitation annealing is as described above, and thus the overlapping explanation is avoided. Here, the temperature at which the temperature rise of the present invention starts up to the crack temperature is set to 800 ± 50 ° C in consideration of the fact that the section in which recrystallization takes place is approximately 800 ° C.

Precipitation annealing is followed by cold rolling. The rolling reduction rate at this time is preferably cold rolling at a reduction ratio of 81-95% in order to improve the orientation.

Then, decarbonization including sedimentation, in other words, nitriding is performed in the decarbonization annealing process. The annealing is preferably performed at a temperature of 850-1100 ° C., because the crystal grains are small at a temperature below 850 ° C. and the magnetic flux density is lowered. When the heating temperature is higher than 1100 ° C., the secondary recrystallization occurs at this temperature and a high magnetic flux density is obtained. Although it may be obtained, it is because it becomes uneconomical to become unstable and to heat at above this high temperature.

At this time, if the decarburization is a condition under which the decarburization and the settling mass are controlled, any one of the method of performing acupuncture after the decarburization is completed to an appropriate level and of the method of deburring from the initial stage of annealing simultaneously with decarburization can be applied. At this time, the atmosphere gas may be any mixed atmosphere that enables the decarburization of the appropriate level and the sedimentation of the present invention at the same time, but preferably a mixed gas of wet ammonia + hydrogen + nitrogen for industrial control of the sediment mass easily. It is good to use the atmosphere. In addition, the amount of nitrogen that enters the inside of the steel sheet at this time is influenced by the annealing temperature, the annealing time, the ammonia fraction in the atmosphere and is controlled to an appropriate amount of nitrogen according to the steel composition. The concentration of ammonia (NH ₃ ) which has the greatest influence among these variables is 0.05-5% in terms of obtaining a stable high magnetic flux density.

As described above, after the decarbonization annealing including the sedimentation and applying the annealing separator, and then finish annealing.

Finishing annealing may be carried out as usual. However, when the annealing is carried out at 50% or more in the high temperature annealing temperature rising process, stable and good magnetic properties are obtained. Therefore, heating in an atmosphere of 50% or more nitrogen in an area of 800 ° C or more during the temperature rising process of the finish annealing is preferable. In this case, the reason for limiting the temperature to 800 ° C. or higher is because the influence is less at this temperature. The amount of nitrogen may be 100%, but if it does not contain hydrogen at all, oxygen or the like may be oxidized in the atmosphere, and the steel sheet may be oxidized, and since it adversely affects the formation of the glass film, it is preferable to mix and process several percent hydrogen.

Hereinafter, the present invention will be described in more detail.

Example 1

C: 0.024%, Si: 3.20%, Mn: 0.2%, Al: 0.025%, S: 0.009%, N: 0.009% after heating the slab at a temperature of 1280 ° C for 2 hours, and rough rolling was started at 1270 ° C. After the finish rolling, a hot rolled sheet having a thickness of 2.3 mm was made. The hot rolled sheet was precipitated and annealed and cold rolled to a final thickness of 0.290 mm. Precipitation annealing changes the cracking temperature at 20 ℃ intervals between 1050 ℃ and 1210 ℃, and raises the temperature of each cracking temperature from 800 ℃ to the temperature of 5 ℃ / sec and maintains it at the cracking temperature for 60 seconds. The time from starting to reaching 950 degreeC was made into 120 second, and then quenched to room temperature at the speed of 30 degreeC / sec.

Subsequently, the cold rolled plate was subjected to primary recrystallization, nitriding and decarburization treatment continuously in a N ₂ -H ₂ -NH ₃ atmosphere containing 2.0% of NH ₃ at a temperature of 930 ° C for 2 minutes. Next, MgO was applied and heated to 1200 ° C. at a heating rate of 15 ° C./hr in an atmosphere of 50% N ₂ -H ₂ , followed by cooling after heating for 20 hours in an atmosphere of 100% H ₂ . Next, after the stress relief annealing, the magnetic properties were measured. The results are shown in Table 1.

Psalter Crack temperature at precipitation annealing (℃) Magnetic flux density (Tesla) One 1050 1.86 2 1070 1.88 3 1090 1.89 4 1110 1.90 5 1130 1.93 6 1150 1.95 7 1170 1.94 8 1190 1.90 9 1210 1.89 Optimum precipitation treatment cracking temperature: 1131.2-1171.2 (980-1250)

As shown in Table 1, it was found that the best magnetic flux density was obtained in specimens 5-7, and the crack temperature at this time was found to be almost identical to the temperature determined by the crack temperature equation presented in the present invention.

Example 2

A slab containing C: 0.024%, Si: 3.20%, Mn: 0.2%, Al: 0.025%, S: 0.009%, N: 0.009% was heated at a temperature of 1280 ° C for 2 hours, and then rough rolling was carried out at 1270 ° C. The hot rolled sheet having a thickness of 2.3 mm was made through finishing rolling. After the hot rolled sheet was subjected to precipitation treatment, it was cold rolled to a final thickness of 0.290 mm. In the precipitation treatment process, the temperature was raised from 800 ° C. to the crack temperature of 1150 ° C. as shown in Table 2 below, and maintained at this temperature for 60 seconds, and then started cooling to reach 950 ° C. in the same manner as in Example 1. Secondary recrystallization, nitriding and decarburization, MgO were applied and final high temperature annealing was performed. Next, after the stress relief annealing, the magnetic properties were measured. The results are shown in Table 2.

division Temperature increase rate during precipitation annealing (℃ / sec) Magnetic flux density (Tesla) Comparative material One 1.87 Invention 3 1.92 5 1.94 7 1.95 9 1.94 Comparative material 11 1.90 13 1.88

As shown in Table 2, it can be seen that it is possible to manufacture a grain-oriented electrical steel sheet having a very high magnetic flux density within the scope of the present invention.

Example 3

A slab containing C: 0.024%, Si: 3.20%, Mn: 0.2%, Al: 0.025%, S: 0.009%, N: 0.009% was heated at a temperature of 1280 ° C for 2 hours, and then rough rolling was carried out at 1270 ° C. The hot rolled sheet having a thickness of 2.3 mm was made by starting and finishing rolling. The hot rolled sheet was deposited and then cold rolled to a final thickness of 0.290 mm. In the precipitation treatment process, the temperature rises from 800 ° C. to 5 ° C. per second at a temperature rising rate to the crack temperature of 1150 ° C., and the holding time at the cracking temperature is changed as shown in Table 3 below, and then the cooling time until reaching 950 ° C. is 120. Seconds and then quenched to room temperature at 30 ° C / sec. The cold rolled plate was subjected to primary recrystallization, nitriding and decarburization, MgO, and final high temperature annealing in the same manner as in Example 1. Next, after removal of annealing, magnetic properties were measured. The results are shown in Table 3.

division Holding time (seconds) during precipitation annealing Magnetic flux density (Tesla) Comparative material 0 1.89 Invention 5 1.92 20 1.94 40 1.94 60 1.95 80 1.93 100 1.94 120 1.93 Comparative material 140 1.90

As shown in Table 3, it can be seen that it is possible to manufacture a grain-oriented electrical steel sheet having a very high magnetic flux density within the scope of the present invention.

Example 4

A slab containing C: 0.024%, Si: 3.20%, Mn: 0.2%, Al: 0.025%, S: 0.009%, N: 0.009% was prepared, heated at a temperature of 1280 ° C for 2 hours, and then crude at 1270 ° C. Rolling was started and hot rolled sheet having a thickness of 2.3 mm was made through finish rolling. The hot rolled sheet was precipitated and then cold rolled to a final thickness of 0.290 mm. In the precipitation treatment process, the temperature of the temperature rises from 800 ° C. to 5 ° C. per second, the crack temperature is increased to 1150 ° C., maintained at the crack temperature for 60 seconds, and then cooled to 950 ° C. in the time shown in Table 4 below. It was quenched at a rate of ° C / sec. The cold rolled plate was subjected to primary recrystallization, nitriding and decarburization, MgO, and final high temperature annealing in the same manner as in Example 1. Next, after the stress relief annealing, the magnetic properties were measured. The results are shown in Table 4.

division Cooling time during precipitation annealing (up to 900-980 ° C) (seconds) Magnetic flux density (Tesla) Comparative material 10 1.86 Invention 30 1.91 60 1.94 120 1.93 180 1.94 280 1.95 480 1.93 Comparative material 600 1.93

As shown in Table 4, it can be seen that it is possible to manufacture a grain-oriented electrical steel sheet having a very high magnetic flux density within the scope of the present invention.

Example 5

A slab containing C: 0.024%, Si: 3.20%, Mn: 0.2%, Al: 0.025%, S: 0.009%, N: 0.009% was prepared, heated at a temperature of 1280 ° C for 2 hours, and then at 1270 ° C. Rough rolling was started and finish rolling was performed to produce a hot rolled sheet having a thickness of 2.3 mm. The hot rolled sheet was precipitated and then cold rolled to a final thickness of 0.290 mm. In the precipitation treatment process, the temperature of the temperature rises from 800 ° C. to 5 ° C. per second to the crack temperature of 1150 ° C. and is maintained at the crack temperature for 60 seconds. Then, the cooling time until the temperature reaches 950 ° C. is 60 seconds. Was changed as shown in Table 5 below and cooled to room temperature. The cold rolled plate was subjected to primary recrystallization, decarburization, MgO, and final high temperature annealing in the same manner as in Example 1. Next, after the stress relief annealing, the magnetic properties were measured. The results are shown in Table 5.

division Cooling rate to room temperature during precipitation annealing (℃ / sec) Magnetic flux density (Tesla) Comparative material 5 1.86 Invention 10 1.93 20 1.95 30 1.94

As shown in Table 5, it can be seen that it is possible to produce a grain-oriented electrical steel sheet having a very high magnetic flux density at a cooling rate of 10 ° C or more per second, which is the scope of the present invention.

As described above, the present invention has a useful effect of providing a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties while being reheated at a temperature of 1200-1280 ° C. that is easy to roll and does not generate a scale of melting.

Claims (4)

By weight Si: 2.0-4.5%, C: 0.010-0.095%, Sol-Al: 0.010-0.040%, N: 0.002-0.020%, Mn: 0.05-0.45%, S: 0.002-0.20%, remaining Fe and The silicon steel slab made of other inevitable impurities is reheated at low temperature and hot rolled to make a hot rolled sheet, followed by precipitation annealing, cold rolling to a final thickness, decarbonization including sedimentation, and application of annealing separator. Next, in the method for producing a grain-oriented electrical steel sheet including a finish annealing step, the low temperature reheating is performed at 1200 to 1280 ° C; The precipitation annealing is performed at a temperature of 800 ± 50 ° C. to a crack temperature of 980 ° C. or more and 1250 ° C. or less at a rate of 2 to 10 ° C./sec, and maintained at this cracking temperature for 1 to 120 seconds, and then to 900 ° C. or more. Method for producing a grain-oriented electrical steel sheet characterized in that it comprises cooling to a temperature of less than 980 ℃ 20 to 500 seconds and then quenching at a rate of 10 ℃ / sec or more to room temperature The method according to claim 1, wherein the cold rolling is performed at a reduction ratio of 81 to 95%. The method of claim 1, wherein said decarburization annealing including chimjil is characterized in the works in a temperature zone of 850~1100 ℃ in deionized elastic atmosphere containing 0.05-5% and NH _3. The method according to claim 1, wherein the cracking temperature (Tk) of the precipitation annealing is obtained by the following equation. 1.04Ts-0.6Al-50≤Tk≤1.04Ts-0.6Al-10 Where Ts is slab heating temperature (℃) and Al is the content of Sol-Al (ppm).