JPH1143746A - Grain-oriented silicon steel sheet extremely low in core loss and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grain-oriented silicon steel sheet having a low core loss by specifying the grain size and the componental compsn. of a steel sheet. SOLUTION: As for the grain size of the steel sheet, the area ratio of the grains of >=8 mm grain size is regulated to >=75%, and the average grain size of all crystal grains is regulated to <=25 mm. It has a compsn. contg., by weight, 1.5 to 7.0% Si, furthermore contg., as inhibitor auxiliary components, Mn, Cu, Sn, Ge, Bi, V, Nb, Cr, Te and Mo by 0.005 to 2.5% independently or in the total of >= two kinds, contg. 0.01 to 1.5% Ni, 0.01 to 0.15% Sb and 0 to 0.0050% B, in which, as impurities, the content of C is reduced to <=0.003%, the total content of S and Se to <=0.003%, that of N to <=0.003%, that of Al to <=0.002%, that of Ti to <=0.003% and that of P to <=0.30%, and the balance iron with inevitable impurities. Furthermore, as for the Sb content X and the Ni content Y, X>0.01, Y>0.01 and 0.3-7.5×<Y<1-10X are regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet having extremely low iron loss, particularly among grain-oriented electrical steel sheets used for an iron core of a transformer or a generator.

[0002]

2. Description of the Related Art Si is contained and the crystal orientation is (110).
Oriented electrical steel sheets oriented in the [001] or (100) [001] direction are widely used as various iron core materials in the commercial frequency range because of their excellent soft magnetic properties. At this time, the characteristic required for the magnetic steel sheet is that the iron loss, which is _generally expressed as W _17/50 (W / kg), which is the loss when magnetized to 1.7 T at a frequency of 50 Hz, is low. is important. The reason is that iron loss in the core of generators and transformers can be significantly reduced by using materials with low values of _{W17 / 50} , and the development of materials with low iron loss has been strongly demanded year by year. That is why. In general, to reduce iron loss in materials, it is effective to reduce eddy current loss.In order to increase electrical resistance, a method of increasing the content of Si, a method of reducing the thickness of a steel sheet, and a reduction in crystal grain size In addition, there is known a method of increasing the degree of integration of the crystal orientation to improve the magnetic flux density. Among these iron loss reduction methods, a method of increasing the Si content, a method of reducing the thickness of the steel sheet and a method of reducing the crystal grain size were examined.However, the method of increasing the Si content excessively increased the Si content. If it is contained, it is not preferable because it deteriorates the rollability and workability, and there is a limit in reducing iron loss, and the method of reducing the thickness of the steel sheet also causes an extreme increase in manufacturing cost, so the reduction of iron loss is no longer the limit. Is reaching.

[0003] Methods for improving the remaining magnetic flux density have been well studied so far.
No. 6-23820 discloses that after Al is added to steel, fine AlN is precipitated by hot rolling annealed at a high temperature of 1000 to 1200 ° C. after hot rolling and quenching treatment accompanying the addition, and then 80 to 95% of the applied technology under high pressure ratio is disclosed, and thereby in the B ₁₀ to obtain the value of the very high magnetic flux density of 1.95 T. This method takes advantage of the fact that finely dispersed AlN has a strong effect as an inhibitor that suppresses the growth of primary recrystallized grains, and achieves excellent orientation by secondary recrystallizing only nuclei with excellent crystal orientation. This is to obtain the crystal structure of the product. However, in this method, the crystal grain size generally becomes coarse,
It was difficult to obtain a low iron loss value, and it was difficult to completely dissolve AlN in solid solution annealing in hot-rolled sheet annealing, so that it was difficult to obtain a product having a high magnetic flux density stably. Japanese Patent Application Laid-Open No. 2-115319 discloses a method in which Sb is further contained as a segregation-type inhibitor and a product having a high magnetic flux density is obtained by applying a special final finish annealing method. It is difficult to say the degree of azimuth accumulation,
Moreover, when the content of Sb was increased in order to obtain a product with a high degree of integration, secondary recrystallization itself became insufficient, resulting in significant deterioration of iron loss characteristics. The Apart Sho 58-43445 discloses to this, the magnetic flux density of 1.89T in B ₈ by using a steel containing 0.0006 to 0.0080% of B and 0.0100% or less of N, devising decarburization annealing Are disclosed. Although this method can be said to be an industrially preferable method since a product having relatively stable magnetic properties can be obtained, it has not been industrialized because the magnetic flux density is low and the iron loss is not so good. Furthermore, Japanese Patent Publication No. 54-32412 discloses S or S as an inhibitor.
A technique using a combination of the Se group and the As, Bi, P, Sn, Cu, and Ni groups is disclosed, and although a relatively high magnetic flux density is obtained relatively stably, the iron loss characteristics are low. Had the problem of being bad. Separately from these technologies,
Japanese Patent No. 30718 discloses a method in which grooves are formed on the surface of a steel sheet after cold rolling to reduce the iron loss by forming grooves on the surface of a product sheet. However, this method also reduces the magnetic flux density and reduces the hysteresis. Since an iron loss is inevitably deteriorated due to an increase in the loss, a significant effect of reducing the iron loss cannot be obtained. Japanese Patent Application Laid-Open No. 5-345921 discloses an AlN, MnS
A technique is disclosed in which a predetermined amount of Ni is contained as the Si / C content ratio increases in the production of a grain-oriented electrical steel sheet containing Cu and Sn, using as an inhibitor. Japanese Patent Laid-Open No. Hei 2
In -30740, Sn: 0.03 to 0.3 in combination of Sn and Ni.
It is stated that excellent magnetic properties can be obtained at 25% and Ni: 0.35 to 2.0%. However, each of these methods
The crystal orientation of the product was not sufficiently integrated, and the iron loss value was not satisfactory.

[0004]

As described above, in order to reduce the iron loss of the grain-oriented electrical steel sheet, it is necessary to stably increase the degree of integration of the crystal orientation. It can be obtained stably. In the conventional method related to this technology, when the degree of integration of crystal orientation is increased, the crystal grain size inevitably increases, leading to deterioration and instability of the iron loss value. Due to the trade-off state of reducing the degree of integration of the crystal orientation and reducing the magnetic flux density when achieving this, it was not possible to stably produce a material with an extremely high degree of integration of the crystal orientation and low iron loss. However, it is an object of the present invention to solve the problem drastically. That is, this invention has solved instability of coarsening of crystal grain size of the product to obtain a very high value in the values of B ₈ in the preparation of oriented electrical steel sheet with an inhibitor of AlN, and essentially inherent It is an object of the present invention to propose a grain-oriented electrical steel sheet having extremely low iron loss and a method of manufacturing the same.

[0005]

Means for Solving the Problems In order to eliminate the above trade-off situation, the inventors added Ni as a measure for improving the texture and crystal structure to obtain a low iron loss, and added the amount of Ni added. A method for changing the amount of Sb added within a predetermined range in accordance with the present invention was newly devised. This is in addition to the inhibitor AlN
By adding Ni and Sb, it is possible to obtain an extremely strong inhibitory effect on the growth of primary recrystallized grains.
By combining the contents of Ni and Sb, an unprecedented improvement in the primary recrystallized texture is recognized, the secondary recrystallized grains are refined, and the average in-plane in the rolling direction from the (110) [001] orientation is obtained. The present invention is based on a new finding that the deviation angle is extremely small, and has completed the present invention by effectively utilizing the effect of the new finding.

The present invention, which is based on the above-mentioned findings, provides a steel sheet having a crystal grain having an average in-plane deviation angle in the rolling direction from the (110) [001] orientation of the crystal orientation within 4 degrees and a direction perpendicular to the rolling direction. The average in-plane angle difference between adjacent grains having a crystal grain size of 8 mm or more is within 7 degrees, the area ratio of crystal grains having a grain size of 8 mm or more is 75% or more, and the average crystal grain size of all the crystal grains is 25 mm. The following is the composition of the steel sheet.
5 to 7.0 wt%, and M
n, Cu, Sn, Ge, Bi, V, Nb, Cr, Te and Mo are used alone or in a total of two or more of 0.005 to 2.5 wt%, and Ni is 0.01 to 1.
5 wt%, 0.01 to 0.15 wt% of Sb and 0 to 0.0050 wt% of B, 0.003 wt% or less of C as impurities, 0.003 wt% or less of S and Se in total, 0.003 wt% or less of N, Al 0.00
2 wt% or less, Ti is reduced to 0.003 wt% or less, P is reduced to 0.30 wt% or less, and the balance consists of iron and unavoidable impurities.
A grain-oriented electrical steel sheet with extremely low iron loss, characterized in that the content X (wt%) and the Ni content Y (wt%) satisfy the relationship of the following formula, 0.3-0.3 when X> 0.01 and Y> 0.01. 7.5 X <Y <1
-10X (first invention), C: 0.035 to 0.100 wt%,
Si: 1.5 to 7.0 wt%, Mn: 0.02 to 0.20 wt%, S or
Se: 0.005 to 0.04 wt%, Al: 0.010 to 0.04 wt%, N: 0.
0010-0.0150, Sb: 0.01-0.15wt%, Cu, S
n, Ge, Bi, V, Nb, Cr, Te, and Mo, alone or in combination of two or more, in a content of 0.005 to 2.5 wt%, and further, Ni
After heating a slab containing iron and unavoidable impurities to 1300 ° C. or more, hot rolling and annealing a hot-rolled sheet, the content is 1.5% by weight, B: 0 to 0.050% by weight. Cold-rolled steel sheets of the final product thickness are obtained by performing cold rolling two or more times with intermediate annealing, then decarburization and primary recrystallization annealing are performed, and an annealing separator containing MgO as a main component is applied to the steel sheet surface. And then
In a method for producing a grain-oriented silicon steel sheet comprising a series of steps of performing a secondary recrystallization annealing and a purification annealing, a Sb content X (wt%) and a Ni content Y (wt%) in a slab are expressed by the following formula. Manufacture of grain-oriented electrical steel sheets with extremely low iron loss, characterized by raising the temperature in the temperature range of 500 ° C to 900 ° C for secondary recrystallization annealing at an average rate of 25 ° C / h or less A method (second invention), wherein X> 0.01 and Y> 0.01 and 0.3-7.5 X <Y
<1-10X In the first invention, the steel sheet surface has a width of 50 to 1000 μm and a thickness of 10 to 10 μm.
A grain-oriented electrical steel sheet with extremely low iron loss characterized by having grooves in the direction intersecting the rolling direction at a depth of 50 μm (No. 3
Invention), wherein the surface of the steel sheet is subjected to a mirror surface treatment or a crystal orientation enhancement treatment, and the surface is coated with an overcoating indirectly or directly, and thus has an extremely low iron loss directionality. An electromagnetic steel sheet (a fourth invention);
Further, the present invention provides a method for producing a grain-oriented electrical steel sheet having extremely low iron loss, wherein a magnetic domain refining treatment for forming a groove on the steel sheet surface is performed after the final cold rolling.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an experiment which led to the present invention will be described. (Experiment 1) 3.2 wt% (hereinafter simply referred to as “%”)
0.06% Mn, 0.05% C, 0.015% Se, 0.021% Al, 0.0090
% N, 0.005 to 0.15% of Sb, 0.005 to 1.
230 mm thickness with various composition changes in the range of 5%
Each slab of the grain-oriented electrical steel was heated to 1410 ° C., hot-rolled into a hot-rolled coil having a thickness of 2.4 mm, hot-rolled at a temperature of 990 ° C., and wound up at 600 ° C. These hot-rolled coils were heated at a rate of 6 ° C./s to 1000 ° C., subjected to hot-rolled sheet annealing for 30 seconds, cooled to room temperature at 17 ° C./s, pickled, and cold-rolled to 1.8 mm. Rolled to a thickness, then 1050 in an atmosphere of dew point 60 ° C, 50% N ₂ and 50% H ₂
Intermediate annealing was performed at 70 ° C. for 70 seconds. These coils were pickled, cold rolled at a temperature of 170 ° C to a final thickness of 0.22 mm, degreased, and then rolled on the steel sheet surface with a 180 μm wide groove extending perpendicular to the rolling direction. 4.
After forming at 5mm intervals, dew point 60 ℃ for 2 minutes at 850 ℃,
Decarburization annealing was performed in an atmosphere of 50% N ₂ and 50% H ₂ . After that, MgO containing 4% TiO ₂ is applied to the steel sheet surface as an annealing separator and wound into a coil, and then as a final finish annealing up to 750 ° C. in a N ₂ atmosphere at a heating rate of 30 ° C./h. After raising the temperature, and subsequently performing a holding treatment at 750 ° C for 20 hours, N was further increased from 750 ° C to 800 ° C at a rate of 15 ° C / h.
₂ atmospheres, up to 800-1050 ° C, 25% N ₂ and 75% H
In a mixed atmosphere of _2, up to 1,050-1,150 ° C. is heated in an H ₂ atmosphere, further subjected to soaking 5 hours at 1150 ° C. in an atmosphere of H ₂ cooling performs forced cooling in H ₂ to 800 ° C., 800 ° C
A thermal cycle and atmosphere cooling the following in N ₂ was employed: After the final annealing, the unreacted annealing separator was removed, and a tension coat consisting of 50% colloidal silica and magnesium phosphate was applied to obtain a product. Cut out Epstein size test specimens from each product along the rolling direction 800
After performing the strain relief annealing at 3 ° C. for 3 hours, the iron loss value W _17/50 and the magnetic flux density B ₈ at a magnetic flux density of 1.7 T were measured. These results are shown in FIGS.

Further, the steel plate was subjected to macroetching to determine the distribution of the crystal grain size, the average deviation angle α of the crystal orientation from (110) [001], and the analysis values of the components in the steel. The crystal grain size is determined by the equivalent circle diameter, the distribution is expressed by the area ratio, and the in-plane deviation angle of the orientation is measured at 300 mm square at 2.5 mm pitch (excluding abnormal values at the grain boundary part). The average value α of the shift angles was determined. These results are shown in FIGS.
Shown in

[0009]

[Table 1]

As is clear from FIG. 1, the amounts of Sb and Ni are
The magnetic properties (W _17/50 ) were very good in a certain range. In order to investigate the cause, we investigated the segregation of Sb using a decarburized annealed plate and found that the segregation of Sb increased with the increase of Ni segregation. That is,
It was newly found that co-segregation of Ni and Sb provided the most favorable results in magnetic properties. It has been newly found that by using this, the amount of Sb added can be reduced.

However, when Sb segregated to a certain amount or more, a phenomenon was observed in which the magnetic properties deteriorated in reverse. Sb like this
In order to analyze the phenomenon that magnetic properties deteriorate when segregation exceeds a proper value, investigations on products and decarburized annealed sheets were further conducted. As a result, it became clear that the cause of the poor magnetic properties was due to carbon remaining in the product. That is, if Sb and Ni excessively segregate at the grain boundaries of the decarburized annealed sheet, the decarburization reaction of carbon is inhibited during the decarburization annealing, and harmful carbon remains in the product. If Ni and Sb are added beyond the range indicated in the present invention, C is removed by ordinary decarburization annealing.
It was also found that it was extremely difficult to reduce the content to 0.003 wt% or less. From FIG. 1 and FIG.
It became clear that there was a certain relationship between the amount of Sb and the amount of Sb added. That is, Sb content X (wt%) and Ni content Y
(Wt%), it was found that the magnetic properties became good when the relationship of the following equation was satisfied. 0 if X> 0.01 and Y> 0.01
3 -7.5 X <Y <1-10X

Further, as shown in FIGS. 3 and 4 and Table 1, it has been found that the secondary recrystallized grain size of the product plate having good magnetic properties has a special distribution. That is, as shown in FIG. 3, the average in-plane deviation angle in the rolling direction from the (110) [001] orientation of the crystal orientation needs to be within 4 °, and even if it is within 4 ° in FIG. Crystal grain size 8
In-plane angle difference between grains of not less than 7 mm
It was found that the core loss was extremely low when the area ratio of the crystal grains of not less than mm was 75% or more and the average crystal grain size of all the crystal grains was not more than 25 mm. And, it became clear that the inclusion of Ni and Sb enters these particle size distributions.

In addition, when Ni and Sb are contained, it is necessary to pay special attention to the temperature rising rate in the final finish annealing as described later. The reason is that when Ni and Sb are added in combination,
This is considered to be because secondary recrystallization starts after the change in the segregation amount of Sb, the growth of primary recrystallized grains, and the change in texture gradually occur during the final annealing. An experiment for finding appropriate conditions for this will be described below.

(Experiment 2) C: 0.08%, Si: 3.55%, Mn:
0.075%, P: 0.002%, S: 0.001%, Cu: 0.05%,
A directional magnetic steel slab (250 mm thick) represented by the composition of Se: 0.023%, Al: 0.024%, N: 0.0095% is heated to 1390 ° C, and after hot rolling at a temperature of 890 ° C, 500 ° C. To form a hot-rolled coil having a thickness of 2.3 mm. These hot-rolled coils were heated to 890 ° C. at a heating rate of 8 ° C./s, subjected to hot-rolled sheet annealing for 60 seconds, cooled at 15 ° C./s, pickled, and cold-rolled to 1.8 mm. Rolled to thickness, dew point 50 ℃, 50% N
Intermediate annealing was performed at 1070 ° C. for 50 seconds in an atmosphere of ₂ and 50% H ₂ . After pickling, these coils are cold-rolled at a temperature of 200 ° C to a final thickness of 0.22 mm, and then degreased to a width of 100 μm and a depth of 20 μm on the steel sheet surface in a direction perpendicular to the rolling direction. Were formed at intervals of 5 mm in the rolling direction, followed by decarburizing annealing at 850 ° C. for 2 minutes. Thereafter, an annealing separator containing MgO as a main component was applied and wound into a coil shape, and then each coil was subjected to a final finish annealing under the conditions shown in Table 2. In addition, from room temperature to 900 ° C, N _{2 is used} alone, and above 900 ° C, 50% N ₂ + 50% H ₂ is used up to 1200 ° C.
H ₂ for soaking at 00 ° C and cooling from 1200 ° C to 800 ° C
Atmosphere, and thereafter the atmosphere of N ₂ gas.

After the final annealing, the unreacted annealing separator was removed, and a tension coat consisting of 50% colloidal silica and magnesium phosphate was applied to obtain a product. A specimen of Epstein size was cut out from each product along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then measured for iron loss value W _17/50 and magnetic flux density B ₈ at a magnetic flux density of 1.7 T. did. Furthermore, the macro-etching of the steel sheet is performed,
The average deviation angle of the crystal orientation from (110) [001] and the analysis value of the components in the steel were determined. The crystal grain size is determined by the equivalent circle diameter, the distribution is expressed by the area ratio, and the in-plane deviation angle of the orientation is 2.5.
The crystal orientation of 300 mm square was measured at mm pitch (excluding abnormal values at the grain boundaries), and the average value α of the in-plane misalignment angle was determined. Table 2 shows these results together with the iron loss characteristics.

[0016]

[Table 2]

As shown in Table 2, by changing the heating rate, the magnetic flux density B ₈ does not change much, but the size of the secondary recrystallized grains changes, and the value of the _iron loss value W _17/50 also changes. doing. In addition, when the retention was performed during the heating, the residence time at 500 to 900 ° C. was set to 16 hours or more, and the average heating rate was set to 25 ° C./h or less, the characteristics were also extremely good. 90
In the sample in which the heating rate was changed at a temperature exceeding 0 ° C., the secondary particle size did not change so much. Samples with good properties are probably subjected to slow heat treatment at low temperatures (500-900 ° C), so that the growth of primary recrystallized grains was suppressed, resulting in a gradual selection of Goss orientation and a sharper This is considered to be because excellent Goss orientation grains remain in large quantities.
In order to confirm this inference, the sample B was extracted during the secondary recrystallization annealing, and the texture change and the primary grain growth behavior were observed. As a result, it was clarified that when the average rate of temperature rise from 500 ° C to 900 ° C was 25 ° C / h or less, primary grain growth occurred without decreasing Goss strength. It was also found that this phenomenon was very remarkable in a material to which Sb and Ni were added in combination. For this reason, it has been found that it is very important to reduce the average rate of temperature rise from 500 ° C. to 900 ° C. in a material to which Sb and Ni are added in combination.

As another influential method of reducing iron loss, a method of irradiating the surface of a steel sheet with a laser or a plasma jet to subdivide magnetic domains is known, and is effective and applicable to the present invention. Above all, the method of providing grooves on the surface of the steel sheet is a more effective method because it resists strain relief annealing. In this case, it is effective to reduce the iron loss by providing grooves in the direction intersecting the rolling direction at a width of 50 to 1000 μm and a depth of 10 to 50 μm on the surface of the steel sheet. Furthermore, as a conventionally known method,
Mirroring the steel sheet surface and applying a crystal orientation enhancement treatment to the steel sheet surface so as to expose a crystal plane more advantageous in terms of magnetic properties are also effective in reducing iron loss. In these cases, since there is no forsterite-based coating on the steel sheet surface, a top coat is applied via plating or the like. Moreover, each of these means does not preclude combination.

Further, as an excellent method for more reliably obtaining the grain-oriented electrical steel sheet of the present invention, a method of forming a surface desiliconized layer in a cold rolling step, and an annealing method before final cold rolling are used. It is effective to perform an atmosphere treatment for forming a decarburized layer on the surface layer of the steel sheet and a rapid cooling treatment for enriching solid solution C. The surface desiliconization layer formation process is effective for growing primary recrystallized grains on the surface layer of the steel sheet in the final finish annealing and suppressing the appearance of secondary recrystallization of grains having inferior orientation, in this case 0.5 μm or more. It is desirable that the surface desiliconized layer be formed. Further, in the annealing before the final cold rolling, the atmosphere treatment for forming a decarburized layer in the surface layer of the steel sheet promotes the nucleation of crystal grains having an excellent orientation of the surface layer of the steel sheet. It is desirable to form a decarburized layer with a thickness of about 20 to 1/5. Further, in the cooling before the final cold rolling, increasing the solid solution C concentration in the steel by performing a quenching treatment is effective in increasing the nucleation frequency of the above-mentioned favorable secondary recrystallization orientation. In this case, the method of quenching and holding at a low temperature to precipitate fine carbides brings more excellent effects.

Further, a manufacturing method in which a slab having a low nitrogen concentration in steel is subjected to a nitriding treatment in a cold rolling step can also be applied to the present invention.

Next, with regard to the grain-oriented electrical steel sheet of the present invention and the method for producing the same, the requirements necessary for obtaining the effects of the present invention, the range thereof, and the operation will be described in detail. First, the constituent requirements of the grain-oriented electrical steel sheet of the present invention will be described. The steel of the magnetic steel sheet of the present invention is composed of polycrystal after secondary recrystallization. In order to reduce the hysteresis loss, the average of the area in the in-plane direction from the (110) [001] orientation of the crystal orientation is reduced. It is necessary that the deviation angle α is extremely excellent, that is, the deviation angle is within 4 degrees. Here, when α exceeds 4 degrees, deterioration of iron loss is caused by an increase in hysteresis loss.

Further, regarding the grain size distribution of each crystal grain, it is necessary that the area ratio of crystal grains having a circle equivalent diameter of equivalent area of 8 mm or more is 75% or more and the average grain diameter of all crystal grains is 25 mm or less. is there. As a result, the crystal grain distribution is polarized into coarse grains and fine grains, so that good magnetic properties can be stably obtained. Here, the area ratio of crystal grains having a diameter of 8 mm or more is 75%.
If it is less than the above, the ratio of the secondary recrystallized grains having a good orientation decreases, leading to deterioration of iron loss. On the other hand, when the average particle size exceeds 25 mm, the number of fine crystal grains decreases, which causes deterioration of iron loss. On the other hand, if the average in-plane angle difference between adjacent crystal grain sizes of 8 mm or more exceeds 7 degrees, the flow of magnetic flux becomes non-uniform, and the characteristics of actual equipment in a transformer or the like deteriorate.

Next, regulations on steel components will be described. Si is a component necessary for increasing the electric resistance and reducing the eddy current loss of the steel sheet. For this purpose, the content of 1.5% or more is required. However, when the content exceeds 7.0%, roll rolling becomes difficult, so the content is set in the range of 1.5 to 7.0%.

[0024] In steel, as an inhibitor auxiliary component,
Mn, Cu, Sn, Ge, Bi, V, Nb, Cr, Te, and Mo can be used alone or in combination of two or more. Their content is 0.005 to 2.5 wt%, alone or in combination of two or more. If the content of these components is less than 0.005%, it does not substantially function as an inhibitor, and if it exceeds 2.5%, the inhibitor becomes too coarse and the rollability is extremely deteriorated, so that the above range is set.

Sb is one of the constituent components that characterize the present invention, and segregates at the grain boundaries when present in steel,
It has an inhibitory effect on normal grain growth. As a result, the crystal grains of the product are coarsened and the degree of orientation integration is improved. For this effect, it is necessary to contain Sb in an amount of 0.01% or more, but if it exceeds 0.15%, decarburization becomes extremely difficult, so the content is set in the range of 0.005 to 0.15%. Ni is one of the features of the present invention, which increases the segregation effect of Sb and provides a uniform crystal structure during hot rolling of steel.
A component for increasing the degree of accumulation of the orientation of the next recrystallized grains and for stabilizing iron loss characteristics by obtaining the polarization of coarse grains and fine grains at the same time. To obtain this effect, 0.01% or more in steel Must be contained in In addition, by containing 0.01% or more,
It also has the effect of promoting the uniformization, purification, and film formation of the steel structure. On the other hand, if the content exceeds 1.5%, the saturation magnetic flux density decreases.

In addition, depending on the Sb content (X%), Ni
Adjusting (Y%) is one of the important requirements of the present invention. That is, the relationship X> 0.01 and Y> 0.01 between the Sb content X (wt%) and the Ni content Y (wt%)
It is important to satisfy 0.3-7.5 X <Y <1-10X. If this relationship is not satisfied, that is, if it is below this range, the segregation effect of Sb is too low to sufficiently improve the magnetic properties, and if it exceeds this range, C in the final product sheet 0.0030% or more remains.

In this steel sheet, if necessary, B is added.
It is also possible to make it contained in the range of 0.0050 or less. Since B is a component that easily forms fine particles, it is possible to adjust the frequency of fine particles by appropriately adding B. For this purpose, it is more preferable to contain B in an amount of 0.0003 to 0.0050%.

The steel sheet can contain up to 0.30% of P. P increases electrical resistance and is a beneficial component, but 0.30%
When it exceeds, the hardness becomes too hard and the plate is easily broken. Next, impurities in steel, which are all present in steel, increase the hysteresis loss and degrade iron loss, and thus need to be reduced. That is, C
, Ti and S should be 0.003% or less, S and Se in total should be 0.003% or less, O and Al should be 0.002% or less, and N should be 0.003% or less.

Next, the surface of the steel sheet of the present invention may be covered with a usual forsterite coating and coated with a known overcoating tension coating thereon, or the steel sheet surface may be mirror-finished, It may be in a state where a tension coating is formed. In addition, the (110) [001] crystal orientation in which the crystal orientation is selectively retained by performing a grain orientation selection process by a steel sheet surface treatment such as NaCl electrolysis to emphasize the crystal orientation that is advantageous for the magnetic characteristics, Alternatively, a tension film may be formed indirectly by interposing plating or the like.
These are means for better exerting the tension effect provided by the coating on the steel sheet surface.

Further, the surface of the steel sheet may be provided with grooves for subdividing magnetic domains. For this purpose, a width of 50-1000 μm and 10-
It is suitable for the purpose that grooves are present in the direction crossing the rolling direction at a depth of 50 μm. If the condition is not satisfied, it is difficult to obtain the magnetic domain refining effect by the groove, and the effect of improving iron loss is small. In addition, since the magnetic domain refining effect, the mirror-finish effect, and the crystal orientation enhancing effect of the grooves are not equal, it is more preferable to use both or the three in combination to obtain a low iron loss.

It is also possible to locally cause a minute strain generated by a laser, a plasma jet, or the like, which is known as one means of magnetic domain segmentation, inside the steel sheet.

Next, a method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. First, the composition range of the steel slab as the starting material will be described. Si is an essential component to increase electric resistance and reduce iron loss, and therefore, 1.5%
It is necessary to contain the above, but if it exceeds 7.0%, the workability is deteriorated, and it becomes extremely difficult to manufacture and process the product. Therefore, the content is made 1.5 to 7.0%. C is a component useful not only for uniform micronization of the structure during hot rolling and cold rolling but also for the development of Goss-oriented grains, and it is desirable to contain C at least 0.035%. However, if the content exceeds 0.10%, the Goss direction will be disturbed, so the upper limit is
About 0.10% is desirable.

In addition to these components, the steel must contain an inhibitor component for inducing secondary recrystallization, and it is necessary to contain Al and N as the inhibitor components. Of these, Al must be contained at 0.010 to 0.040%. Here, when the Al content is less than 0.010%,
The amount of AlN precipitated during the heating process of hot-rolled sheet annealing is insufficient, and does not function as an inhibitor. 0.04
If it exceeds 0%, the precipitated composite inhibitor becomes coarse, resulting in deterioration of the suppressing power. Therefore, the content of Al is set to 0.010 to 0.040%.

Similarly, N is a component constituting AlN.
If 0.0010% or more is present in the slab stage, it can be added to the steel by nitriding even during the cold rolling process, so that 0.0010% or more is sufficient. But 0.
If the content exceeds 0150%, blisters occur during hot rolling and cause defects, so the content is made 0.0010 to 0.0150%.

The inclusion of Sb as an inhibitor forms one feature of the present invention. Sb segregates at the crystal grain boundaries to exhibit a function as an inhibitor. For this purpose, 0.01% or more of Sb must be contained. But 0.15%
If it exceeds, the decarburization in the decarburization annealing will be insufficient, so it is set to 0.15%.

In addition, as an auxiliary component of the inhibitor, M
It is necessary to contain 0.005 to 2.5 wt% of n, Cu, Sn, Ge, Bi, V, Nb, Cr, Te, and Mo alone or in combination of two or more. These components form precipitates or segregate at the grain boundary interface or the precipitate interface to perform an auxiliary function for enhancing the suppressing force. In addition, Mn and Cu have an effect of increasing the electric resistance by the inherent addition, and from this point also have an effect of reducing iron loss. In order to have such an effect, it is necessary to contain these components alone or in combination of two or more kinds in a total amount of 0.005% or more. However, if the content exceeds 2.5%, the steel sheet becomes brittle and has poor decarburization. So 0.005 ~ 2.5
%.

S or Se is MnS, Cu ₂ S, MnSe, C
It is necessary to precipitate u ₂ Se etc. with AlN in a fine composite. For this purpose, it is necessary to contain 0.005% or more alone or in combination, but if it exceeds 0.04%, the precipitates become coarse. Therefore, it is contained in the range of 0.005 to 0.04%.

Further, it is effective to add B if necessary to develop fine grains, and for that purpose, it is effective to add 0.0003% or more. However, when the content exceeds 0.0050%, the effect saturates.
%. Further, it is permissible to contain P in a range of 0.30% or less because it has an effect of increasing electric resistance and reducing iron loss. However, if it exceeds 0.30%, the hardness of the steel sheet is excessively increased and the sheet is easily broken in the cold rolling step, so the content is set to 0.30% or less.

In such components and component ranges, it is particularly preferable to adjust Ni (Y%) according to the Sb content (X%).
This is one of the important requirements of the present invention. That is, the relationship X> 0.01 and Y> 0.01 between the Sb content X (wt%) and the Ni content Y (wt%) satisfies the content of 0.3−7.5 X <Y <1−10X. If the range conforms and falls below this range, the segregation effect of Sb is too low to improve the magnetic properties sufficiently, and if it exceeds this range, 0.0030% or more of C remains in the final product sheet. Resulting in.

The steel slab formulated to such a composition is usually 13
After being heated to 00 ° C. or higher and hot-rolled, it is subjected to decarburizing annealing and subsequent final finishing annealing after being made to have a final thickness by one or two or more cold rollings sandwiching intermediate annealing. .

It is desirable to control the temperature at the end of hot rolling between 850 and 1100 ° C. If the end temperature of the hot rolling is less than 850, the number of surface defects increases during the hot rolling. However, when the temperature exceeds 1100 ° C., sulfides and selenides are coarsely precipitated during hot rolling, and the inhibitory power of inhibitors is reduced, leading to deterioration of iron loss. Therefore, the end temperature of the hot rolling is preferably controlled between 850 and 1100 ° C.

The hot-rolled coil is preferably cooled rapidly and wound at a temperature of less than 700 ° C. in order to suppress coarse precipitation of AlN during hot rolling. The hot-rolled sheet manufactured in this manner is made the final thickness in a cold rolling step involving one or more cold rolling operations. At this time, usually, hot-rolled sheet annealing for improving the hot-rolled structure is performed before cold rolling. However, the technique of the present invention can be naturally applied to a manufacturing method without hot-rolling annealing.

The hot-rolled sheet annealing and the intermediate annealing are performed at a high temperature of 900 ° C. or more, and recrystallization is performed by using the strain introduced by hot rolling and cold rolling. In the cooling after annealing, rapid cooling to increase the amount of solute C in the steel is preferable because it has the effect of increasing the frequency of nucleation of secondary recrystallization. The process of precipitating in steel further promotes this effect and is therefore more advantageously adapted.

For the cold rolling, known aging between passes and warm rolling can be advantageously applied. After cold rolling, decarburization annealing is performed, but before that, it is also possible to perform a process of forming grooves on the surface of the steel sheet in order to subdivide the magnetic domains of the product and reduce iron loss. Also, from after cold rolling to before secondary recrystallization,
Point-like local heat treatment or chemical treatment for generating fine crystal grains can also be artificially performed.

The steel sheet after the cold rolling is subjected to a degreasing treatment and a decarburizing annealing is performed. The steel sheet after the decarburization annealing is coated with an annealing separator and then wound into a coil to be subjected to final finish annealing. At this time,
Various known annealing separators can be selected depending on whether or not a coating is formed on the steel sheet surface. That is, in order to form a forsterite coating on the steel sheet surface, Mg
An annealing separator containing O 2 as a main component is used, and an Al ₂ O ₃ -based annealing separator is used in many cases when the steel sheet surface is desired to be mirror-finished. It goes without saying that other known annealing separators can be applied.

The final finish annealing step is performed by annealing in a H ₂ atmosphere at a high temperature. That is, the H ₂ gas has an effect of growing the crystal grains of the surface layer of the steel sheet at the time of raising the temperature of the final finish annealing.
The development of secondary recrystallized grains can be suppressed, the degree of orientation accumulation can be increased, and iron loss can be reduced. In addition, H ₂ gas contains S, S in steel.
It also has the function of removing impurities such as e, O and N.

It is particularly important to control the average rate of temperature increase in the secondary recrystallization annealing at 500 to 900 ° C. to an extremely low level of 25 ° C./h or less. Secondary grains having a large but inferior orientation are formed and iron loss is deteriorated. 500
It is most preferable to carry out a low-temperature holding treatment in the range from ℃ to 900 ℃. In this case, the rate of temperature rise is calculated using the time required to reach from 500 ℃ to 900 ℃.

After the final annealing, the unreacted annealing separating agent on the surface of the steel sheet is removed, and if necessary, an insulating coating is further applied and baked for flattening annealing to obtain a product. At this time, using a tension coating as the insulating coating is more suitable for a steel sheet having iron loss. The steel sheet after the final annealing is subjected to a known magnetic domain refinement treatment, that is, a treatment of applying a plasma jet or a laser irradiation to a linear region or providing a linear dent region by a projection roll to reduce iron loss. Can also. In addition, if the film is not to be formed during the final annealing, the steel sheet is further subjected to a mirror finish treatment, or a grain orientation selection treatment is performed with NaCl electrolysis, etc. The method is most effective in reducing iron loss of the product.

[0049]

【Example】

(Example 1) After heating steel slabs of the symbols A to T having the components shown in Table 3 to 1435 ° C, forming a 45 mm sheet bar at 1230 ° C, and finishing the finish rolling at a temperature of 890 ° C to a thickness of 2.2 mm, It was cooled by spraying cooling water and wound into a coil at 600 ° C. to obtain a hot-rolled steel sheet. This steel sheet was heated to 1100 ° C at a heating rate of 10 ° C / s, subjected to hot-rolled sheet annealing for a soaking time of 30 seconds, mist-cooled, pickled, and cold-rolled to a thickness of 1.5 mm. .
Thereafter, an intermediate annealing is performed at 1080 ° C. for 50 seconds in an H ₂ atmosphere with a dew point of 50 ° C. to reduce the C content by about 0.01%, and
A quench treatment of 30 ° C / s was performed by spraying water mist to increase the amount. Then, by hot rolling at a steel sheet temperature of 220 ° C
The final thickness was 0.22 mm. After that, it is degreased, and the depth is 20μm, width 150μm from the rolling direction
Grooves are provided in the direction of 85 degrees at intervals of 5 mm in the rolling direction.
For a minute. Further, an annealing separator in which 3% of TiO ₂ is added to MgO is applied to the steel sheet, and as a final finish annealing, the temperature is raised to 900 ° C. in N ₂ at a rate of 18 ° C./h (500 ° C. to 90 ° C.).
Average heating rate in the temperature range of 0 ° C: 20 ° C), from 900 ° C to 10
The temperature was raised to 50 ° C in a mixed atmosphere of 25% N ₂ and 75% H _{2 at} a rate of 26 ° C / h. Then, the temperature was raised to 1150 ° C at a rate of 25 ° C / h in H ₂ and then 6 hours at 1150 ° C. After holding, the temperature was lowered. At this time 600
The temperature was lowered in H ₂ to 600 ° C. to form an atmosphere of N ₂ from 600 ° C.
After the final annealing, after removing the unreacted annealing separator,
Magnesium phosphate containing 50% colloidal silica was applied as a tension coating and baked at 800 ° C. to obtain a product. Table 4 shows the components of these products, and Table 5 shows the magnetic properties and secondary particle distribution. As shown in Tables 4 and 5, the grain-oriented electrical steel sheet having the component range, average grain size, crystal grain distribution, orientation integration degree, and impurity content of the present invention has extremely excellent iron loss characteristics.

[0050]

[Table 3]

[0051]

[Table 4]

[0052]

[Table 5]

(Example 2) A steel slab composed of the components indicated by the slab symbols A to D in Table 3 was heated to 1380 ° C, and then hot-rolled into a hot-rolled coil having a thickness of 2.1 mm. After finishing the hot rolling at a finishing end temperature of 920 ° C., a large amount of coil cooling water was sprayed to cool at a rate of 50 ° C./s and wound up at 600 ° C. This hot rolled coil is then speed
After raising the temperature to 1000 ° C. at 12 ° C./s, the sheet is annealed by hot-rolling for 30 seconds, then pickled, cold rolled to a thickness of 1.9 mm, and then subjected to a dew point of 40 ° C. and 35% N ₂ . Intermediate annealing was performed in an atmosphere of 65% H ₂ at 1120 ° C. for 50 seconds. After pickling, these coils were cold-rolled at a temperature of 180 ° C to a final thickness of 0.19 mm, and then degreased to form grooves on the steel plate surface at a width of 200 μm and a depth of 26 μm in the direction perpendicular to the rolling direction. After forming at intervals of 7 mm in the rolling direction, decarburizing annealing was performed at 850 ° C. for 2 minutes. Then, 3% Sb ₂ O to suppress film formation
_A mixed powder consisting of ₃ and 32% CaO, 25% Al ₂ O ₃ and 40% MgO is applied to the steel sheet surface as an annealing separator and wound into a coil, and then 500 ° C to 900 ° C as final finish annealing
At heating rate of 15 ° C. / h in N ₂ atmosphere until, 900 to 1050 ° C.
Until at a heating temperature of 20 ° C. / h in a mixed atmosphere of 25% N ₂ and 75% H _2, with H ₂ atmosphere until soaking 5 hours at up to 1050 to 1200 ° C. and 1200 ° C., heating rate With a temperature rise of 20 ° C / h,
To force cooling in H ₂ to 800 ° C., a 800 ° C. or less N ₂
A thermal cycle and atmosphere cooling inside was adopted. After the final finishing annealing, the annealing separator was removed, and then the steel sheet surface was subjected to grain orientation selection processing by NaCl electrolysis, thereby performing a processing to emphasize the (110) plane orientation. Thereafter, a two-layer tension coat composed of aluminum phosphate as the lower layer and 50% colloidal silica and magnesium phosphate as the upper layer was applied to obtain a product.
A specimen of Epstein size was cut out from each product along the rolling direction and subjected to strain relief annealing at 800 ° C. for 3 hours.
Iron loss value W _17/50 and magnetic flux density at 1.7 T magnetic flux density
The B ₈ were measured. Further, the steel sheet was subjected to macroetching to obtain the distribution of crystal grain size, the average deviation angle α of the crystal orientation from (110) [001], and the analysis value of the components in the steel. The crystal grain size is determined by the equivalent circle diameter, the distribution is expressed by the area ratio, and the in-plane deviation angle of the orientation is measured at 300 mm square at 2.5 mm pitch (excluding abnormal values at the grain boundary part). Table 6 shows these results together with the iron loss characteristics.

[0054]

[Table 6]

(Example 3) 0.055% of C, 3.45% of Si,
0.07% of Mn, 0.025% of Al, 0.08% of P, 0.015% of S
%, Sb 0.068%, Ni 0.15%, B 0.0010% and N
Four steel slabs containing 0.0075%, the balance being Fe and unavoidable impurities, were heated to 1430 ° C, rough rolled with a sheet bar thickness of 35mm, the finishing hot rolling end temperature was 960 ° C, and the sheet thickness was 1.8mm. After that, jet water is sprayed and quenched at a rate of 65 ° C / s.
It was wound into a coil at 0 ° C to obtain a hot-rolled steel sheet. The hot-rolled sheet annealing was performed at 1100 ° C. for 30 seconds in an N ₂ atmosphere, then cooled at 30 ° C./s, and held at 350 ° C. for 30 seconds to perform a carbide precipitation treatment. After this, each steel sheet is 150 to 23 by Sendzimer mill.
It was subjected to a constant temperature warm rolling at 0 ° C. and rolled to a final thickness of 0.26 mm. Thereafter, degreasing is performed, decarburization annealing is performed at 850 ° C. for 2 minutes, and 7.5% MgO containing 0.08% B is added.
Of TiO ₂ and 3% of SnO ₂ were applied and wound into a coil. These coils were subjected to final finishing annealing at a heating rate and an annealing atmosphere shown in Table 7 up to 850 ° C. in an N ₂ atmosphere, and up to 1180 ° C. in a mixed atmosphere of 25% N ₂ and 75% H _2. During the soaking at 1180 ° C., the temperature was kept in H ₂ for 5 hours and then the temperature was lowered. After removing the unreacted annealing separator, the coils were coated and baked with a tension coating containing 50% colloidal silica, and then plasma-irradiated with a plasma jet at a pitch of 6 mm in the width direction of the sheet to obtain products. Table 7 shows the magnetic properties of these products. As shown in Table 7, extremely low iron loss values were obtained for products in which the heating rate during the finish annealing was controlled within the range of the present invention.

[0056]

[Table 7]

[0057]

As described in detail above, according to the grain-oriented electrical steel sheet of the present invention and the method for producing the same, a method for producing a high magnetic flux density grain-oriented electrical steel sheet having extremely excellent iron loss characteristics becomes possible.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the contents of Ni and Sb contained in a slab of the steel of the present invention and magnetic properties (W _17/50 ).

FIG. 2 is a diagram showing the relationship between the magnetic properties (B ₈ ) and the contents of Ni and Sb contained in the steel slab of the present invention.

FIG. 3 is a graph showing a relationship between an average deviation angle of a (110) [001] orientation of a secondary recrystallized grain from a rolling direction and magnetic properties (W _17/50 ).

FIG. 4 shows that the average deviation angle of the (110) [001] orientation of the secondary recrystallized grains from the rolling direction is within 4 degrees, and that the adjacent secondary recrystallized grains of 8 mm or more have (110) [001]. FIG. 9 is a diagram showing a relationship between an average in-plane angle difference of azimuth and magnetic properties (W _17/50 ).

Claims (5)

[Claims] 1. The steel sheet according to claim 1, wherein:
10) The average in-plane deviation angle in the rolling direction from the [001] orientation is within 4 degrees, and the average in-plane angle difference between grains having a crystal grain size of 8 mm or more adjacent in the direction perpendicular to the rolling direction is within 7 degrees. The area ratio of the crystal grains having a grain diameter of 8 mm or more is 75% or more, the average crystal grain diameter of all the crystal grains is 25 mm or less, and the composition of the steel sheet contains 1.5 to 7.0 wt% of Si. Mn, Cu, Sn, Ge, Bi,
V, Nb, Cr, Te and Mo alone or in combination of two or more
0.005 to 2.5 wt%, Ni 0.01 to 1.5 wt%, Sb 0.01 to 0.
15wt% and 0 ~ 0.0050wt% of B, C as impurity
0.003 wt% or less, S and Se in total 0.003 wt% or less, N 0.003 wt% or less, Al 0.002 wt% or less, and Ti in 0.
003 wt% or less, P is reduced to 0.30 wt% or less, the balance consists of iron and unavoidable impurities, and the Sb content X (wt%)
A grain-oriented electrical steel sheet having extremely low iron loss, wherein the Ni content Y (wt%) satisfies the following expression. 0.3-7.5 with X> 0.01 and Y> 0.01 X <Y <1-10X 2. C: 0.035 to 0.100 wt%, Si: 1.5 to 7.
0 wt%, Mn: 0.02 to 0.20 wt�, S or Se: 0.005 to
0.04 wt%, Al: 0.010 to 0.04 wt%, N: 0.0010 to 0.015
0, Sb: 0.01 to 0.15 wt%, Cu, Sn, Ge, Bi,
V, Nb, Cr, Te and Mo alone or in combination of two or more
0.005 to 2.5 wt%, Ni is 0.01 to 1.5 wt%,
B: 0 to 0.050 wt% is contained, the remainder is a slab composed of iron and unavoidable impurities, heated to 1300 ° C. or higher, hot-rolled, hot-rolled sheet annealing, and then one or intermediate annealing 2
After performing cold rolling at least twice to form a cold-rolled steel sheet of final product thickness, decarburizing and primary recrystallization annealing is performed, and an annealing separator containing MgO as a main component is applied to the steel sheet surface, In a method for producing a grain-oriented silicon steel sheet comprising a series of steps of performing recrystallization annealing and purification annealing, the relationship between the Sb content X (wt%) and the Ni content Y (wt%) in a slab is represented by the following equation. Satisfaction, and 500 of secondary recrystallization annealing
A method for producing a grain-oriented electrical steel sheet having extremely low iron loss, characterized in that the temperature is raised in a temperature range of 25 ° C. to 900 ° C. at an average heating rate of 25 ° C./h or less. 0.3-7.5 X <Y with X> 0.01 and Y> 0.01
<1-10X 3. A steel sheet having a width of 50 to 1000 μm and a width of 10 to 50 μm.
2. The grain-oriented electrical steel sheet according to claim 1, wherein grooves are present in a direction intersecting the rolling direction at a depth of m. 4. The steel sheet according to claim 1, wherein the surface of the steel sheet is subjected to a mirror surface treatment or a crystal orientation enhancement treatment, and the surface is coated with an overcoating indirectly or directly. Grain-oriented electrical steel sheet with extremely low iron loss. 5. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein a magnetic domain refining treatment for forming a groove on the surface of the steel sheet is performed after the final cold rolling.