JP6418226B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet suitable for a core material of a transformer.

  Oriented electrical steel sheet is a soft magnetic material used as a core material for transformers and generators, and has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned in the rolling direction of the steel sheet. . Such a texture preferentially grows grains of the {110} <001> orientation called the Goss orientation during secondary recrystallization annealing during the production process of grain-oriented electrical steel sheets. Formed through secondary recrystallization.

  For this grain-oriented electrical steel sheet, it is a common technique to use secondary precipitates called inhibitors to recrystallize grains having Goss orientation during finish annealing. For example, a method using AlN and MnS described in Patent Document 1 and a method using MnS and MnSe described in Patent Document 2 are disclosed and industrially put into practical use. Although the method using these inhibitors requires slab heating at a high temperature exceeding 1300 ° C., it is a very useful method for stably developing secondary recrystallized grains. Furthermore, in order to reinforce the action of these inhibitors, Patent Document 3 discloses a method using Pb, Sb, Nb and Te, and Patent Document 4 discloses Zr, Ti, B, Nb, Ta, V, Cr and Mo. A method of using is disclosed.

  Furthermore, Patent Document 5 contains 0.010 to 0.060% of acid-soluble Al (sol. Al), suppresses slab heating to a low temperature, and performs nitriding in an appropriate nitriding atmosphere in a decarburization annealing process, thereby performing secondary re-treatment. A method has been proposed in which (Al, Si) N is precipitated during crystallization and used as an inhibitor. (Al, Si) N functions as an effective inhibitor by being finely dispersed in the steel, but since the inhibitor strength is determined by the Al content, it is sufficient if the accuracy of Al content in steelmaking is not sufficient. In some cases, it was impossible to obtain a sufficient grain growth inhibitory force. Numerous methods have been proposed in which nitriding is performed during such an intermediate step and (Al, Si) N or AlN is used as an inhibitor.

  On the other hand, Patent Document 6 discloses a technique for developing Goss-oriented crystal grains by secondary recrystallization in a material that does not contain an inhibitor component. By eliminating impurities such as inhibitor components as much as possible, the grain boundary energy dependency of the grain boundary energy at the time of primary recrystallization becomes obvious, and the Goss orientation can be changed without using an inhibitor. This is a technique for secondarily recrystallizing grains, and this effect is called a texture inhibition effect. Since this method does not require fine dispersion of the inhibitor in steel, it does not require high-temperature slab heating, which has been essential so far.

Japanese Patent Publication No.40-15644 Japanese Patent Publication No.51-13469 Japanese Patent Publication No.38-8214 JP-A-52-24116 Japanese Patent No. 2782086 JP 2000-129356 JP

  However, with inhibitor-free materials, there is no inhibitor that suppresses grain growth during primary recrystallization annealing, and there is no inhibitor that has the function of aligning to a certain particle size. In many cases, the variation of the crystal grain size was large or the grain size distribution was uneven. For this reason, it has not always been easy to stably achieve good magnetic properties in the method of manufacturing grain-oriented electrical steel sheets using the inhibitorless method proposed so far.

  For example, at the time of slab heating, the slab is generally placed in a plurality of beams called skids in a furnace and annealed. In the slab, the position on the skid is lower in temperature than the position on the skid due to the effect of heat removal from the skid. That is, temperature fluctuations inevitably occur in the slab. In the inhibitor-less material, this variation is often directly linked to the above-described variation in the grain size after the primary recrystallization, resulting in variations in magnetic properties.

  An object of the present invention is to stabilize the magnetic properties of grain-oriented electrical steel sheets more than before and to effectively prevent deterioration of the magnetic properties.

Hereinafter, experimental results that led to the present invention will be described.
(Experiment 1)
Steel slab A containing C: 0.035%, Si: 3.33%, Mn: 0.08%, N: 25ppm, sol.Al: 55ppm, S: 12ppm by mass ratio, C: 0.036%, Si: 3.35%, Mn: Steel slab B containing 0.08%, N: 27ppm, sol.Al:52ppm, S: 77ppm, C: 0.035%, Si: 3.32%, Mn: 0.08%, N: 27ppm, sol.Al:51ppm, S: Steel slabs C each containing 75 ppm and Sb: 0.055% were produced by continuous casting, slab heating was performed at 1230 ° C. for 70 minutes, and finished to a thickness of 2.0 mm by hot rolling. At this time, the thickness of the sheet bar after the hot rolling rough rolling is 40 mm, the surface temperature at the center in the width direction immediately after the rough rolling is 1010 ° C, the lowest temperature in the longitudinal direction of one sheet bar, the highest temperature Was set to 1060 ° C., that is, the fluctuation margin was set to 50 ° C. Then, after hot-rolled sheet annealing in a dry nitrogen atmosphere at 1000 ° C. for 30 seconds, the sheet thickness was finished by cold rolling to 0.23 mm.

Further, primary recrystallization annealing was performed with decarburization in a humid atmosphere of 830 ° C. for 80 seconds, 50% H ₂ -50% N ₂ and dew point of 50 ° C. Further, an annealing separator mainly composed of MgO was applied, and secondary recrystallization annealing was performed at 1200 ° C. for 5 hours and maintained in a hydrogen atmosphere.

The magnetic flux density B ₈ (magnetic flux density when excited at 800 A / m) of the obtained sample was measured by the method described in JIS C2550. In this experiment, in order to evaluate the magnetic variation in the coil, the magnetic characteristics were evaluated at both the lowest and highest temperature positions of the sheet bar surface temperature immediately after rough rolling. The obtained results are shown in FIG. From this result, the steel slab A, which is an inhibitorless component system, has a large magnetic difference (difference in magnetic properties) between the lowest temperature portion and the highest temperature portion of the sheet bar surface temperature immediately after rough rolling, and the steel slab B with increased S The difference has been reduced, but the absolute value has decreased. On the other hand, in addition to the increase in S, the steel slab C added with Sb has a reduced magnetic difference and good magnetic properties.

First, the reason why the variation in magnetism due to the fluctuation of the sheet bar surface temperature immediately after the rough rolling of the hot rolling is suppressed by increasing the amount of the raw material S is not clear, but the inventors are as follows. I am thinking. As mentioned above, since inhibitor-less materials have few inhibitors (precipitates) that have the function of suppressing grain growth and aligning to a certain particle size during primary recrystallization annealing, the process conditions and material components have changed slightly. The fluctuation of the crystal grain size of the steel sheet after the primary recrystallization becomes large, or the grain size distribution becomes uneven. In the case of this experiment, by increasing the amount of material S, precipitates such as MnS or Cu ₂ S are formed, grain boundary segregation effect due to the solid solution S content is also exhibited, and the primary even if the sheet bar temperature fluctuates. It is thought that the effect of stabilizing the expression of secondary recrystallization by making the recrystallized grain size uniform in a narrow width is considered to have reduced the variation in final magnetism.

  However, when the amount of S in the material is increased, the magnetic difference is suppressed, but the problem that the magnetic characteristics themselves deteriorate is also clarified. As described above, in the inhibitorless material, since there are few elements that segregate and concentrate at the grain boundary, the grain boundary energy dependency of the grain boundary energy of the grain boundary at the time of primary recrystallization becomes obvious, The grain boundary orientation difference dependency causes a texture inhibition effect to secondary recrystallize grains having Gos orientation, but this effect is thought to be reduced by segregation and concentration of S. .

  Therefore, it is necessary to compensate for deteriorated magnetic properties by using grain boundary segregation elements such as Sb. Originally, the texture inhibition effect is weakened by increasing the amount of S, so there is no problem even if a new grain boundary segregation element is added. Rather, the primary recrystallization texture is changed and the Goss after the secondary recrystallization is changed. Since it has the effect of improving the azimuth sharpness, it can be said that it is essential for improving the magnetic properties.

  According to the above mechanism, Se having the same effect may be used instead of S, and Sn having the same effect may be used instead of Sb.

  In addition, it is considered that the main cause of the variation in the surface temperature of the central portion in the width direction immediately after the rough rolling described above is the skid that supports the slab used during slab heating before hot rolling. Specifically, the temperature of the position supported by the skid during slab heating is less likely to increase because the skid is in contact with the slab being heated, and the temperature is relatively low. Thus, it is considered that the surface temperature varies due to the structure in which the slab is supported by the skid during heating.

(Experiment 2)
The steel slab A and steel slab C used in Experiment 1 were slab heated at 1200 ° C. and then finished to a thickness of 2.2 mm by hot rolling. At this time, the thickness of the sheet bar after hot rolling rough rolling is 50 mm, and by changing the slab heating time and the time from the end of slab heating to the start of rough rolling, Regarding the surface temperature, the temperature fluctuation margin in one sheet bar was variously changed. Thereafter, hot-rolled sheet annealing in a dry nitrogen atmosphere was performed at 1075 ° C. for 60 seconds, and then finished to a sheet thickness of 0.27 mm by cold rolling. Further, primary recrystallization annealing was performed with decarburization in a humid atmosphere of 850 ° C. for 80 seconds, 60% H ₂ -40% N ₂ and a dew point of 60 ° C. Further, an annealing separator mainly composed of MgO was applied, and secondary recrystallization annealing was performed at 1200 ° C. for 10 hours under a hydrogen atmosphere.

The magnetic flux density B ₈ of samples obtained was measured by the method described in JIS C2550. In this experiment, in order to evaluate the magnetic variation in the coil, the magnetic characteristics were investigated at both the lowest temperature portion and the highest temperature portion of the surface temperature immediately after the rough rolling, and the magnetic variation in the coil was evaluated based on the difference.

  FIG. 2 shows the relationship between the obtained results and the fluctuation margin of the surface temperature after rough rolling. From this result, the steel slab A, which is an inhibitorless component system, has a large variation in magnetic flux density when the fluctuation margin exceeds 40 ° C, but the steel slab C to which S content is increased and Sb is added varies. It can be seen that the variation in magnetic flux density is small when the margin is 100 ° C. or less.

  As described above, it was confirmed that even if the amount of the material S was increased, the magnetic difference in the magnetic flux density was increased if the temperature variation after rough rolling was too large. In particular, in steel slabs with increased S content and addition of Sb, the temperature fluctuation after rough rolling in which this magnetic difference is large has increased dramatically compared to the inhibitorless material, and some fluctuation allowance is required. It can be said that increasing the material S content is extremely effective for obtaining stable magnetic characteristics with respect to industrial production conditions where inevitably occurs.

  From the above, other manufacturing conditions fluctuate by adding a small amount of S or Se to the inhibitorless component and regulating the fluctuation of the surface temperature in the center of the width direction of the sheet bar after hot rolling. However, it can be said that stable magnetic characteristics can be secured. In addition, the increase in S and / or Se can effectively prevent the texture inhibition effect from being weakened and the magnetic properties from being deteriorated by adding Sb and / or Sn.

The present invention has been completed based on the above experimental results, and the gist of the present invention is as follows.
1. % By mass
C: 0.100% or less,
Si: 2.00% to 8.00%,
Mn: 0.02% to 1.00%,
S and / or Se in total more than 0.0050% and less than 0.0100% and
A steel slab containing Sn and / or Sb in a total amount of 0.005% or more and 1.000% or less, suppressing N to less than 70 ppm and acid-soluble Al to less than 150 ppm, with the balance being 1300 steel slab having a composition composed of Fe and inevitable impurities Heating below ℃,
Hot-rolled steel sheet is subjected to hot rolling on the heated steel slab,
The hot-rolled steel sheet is subjected to cold rolling two or more times with one or more intermediate annealings to obtain a cold-rolled steel sheet having a final sheet thickness,
The cold rolled steel sheet is subjected to primary recrystallization annealing, and then subjected to secondary recrystallization annealing, a method for producing a grain-oriented electrical steel sheet,
A method for producing a grain-oriented electrical steel sheet, wherein the longitudinal variation of the sheet bar in the longitudinal direction of the sheet bar at the center in the width direction of the sheet bar immediately after the rough rolling of the hot rolling is within 100 ° C.

2. 2. The method for producing a grain-oriented electrical steel sheet according to 1 above, which contains 0.020% or more and 0.300% or less of Sn and / or Sb in total by mass%.

3. The component composition further includes:
% By mass
Ni: 0.005% to 1.5%,
Cu: 0.005% to 1.5%,
Cr: 0.005% to 0.1%,
P: 0.005% to 0.5%,
Mo: 0.005% to 0.5%,
Ti: 0.0005% to 0.1%,
Nb: 0.0005% or more and 0.1% or less,
V: 0.0005% to 0.1%,
B: 0.0002% to 0.0025%,
Bi: 0.005% to 0.1%,
Te: 0.0005% to 0.10% and
Ta: The method for producing a grain-oriented electrical steel sheet according to 1 or 2 above, containing one or more selected from 0.0005% to 0.01%.

4). The directional electromagnetic wave according to any one of 1 to 3 above, wherein the longitudinal variation of the sheet bar in the longitudinal direction of the sheet bar at the center in the width direction of the sheet bar immediately after the rough rolling of the hot rolling is within 70 ° C. A method of manufacturing a steel sheet.

5. The manufacturing method of the grain-oriented electrical steel sheet according to any one of the above 1 to 4, wherein the cold-rolled steel sheet is subjected to a magnetic domain refinement process.

6). 6. The method for producing a grain-oriented electrical steel sheet according to 5 above, wherein the magnetic domain refinement treatment is performed by electron beam irradiation on the cold-rolled steel sheet after the secondary recrystallization annealing.

7). 6. The method for producing a grain-oriented electrical steel sheet according to 5 above, wherein the magnetic domain refinement treatment is performed by laser irradiation of the cold-rolled steel sheet after the secondary recrystallization annealing.

  According to the present invention, it is possible to further stabilize the magnetic characteristics of the grain-oriented electrical steel sheet and to effectively prevent the deterioration of the magnetic characteristics as compared with the prior art.

The magnetic flux density B ₈ and the lowest temperature portion and the maximum temperature portion of the sheet bar surface after the rough rolling is a graph showing magnetic difference between the lowest temperature part and the highest temperature portion (B ₈ difference). The difference between the lowest temperature part and the highest temperature portion of the sheet bar surface after rough rolling (variation margin) is a graph showing magnetic difference between the lowest temperature part and the highest temperature portion (B ₈ difference).

  Hereinafter, the manufacturing method of the grain-oriented electrical steel sheet by one Embodiment of this invention is demonstrated. First, the reasons for limiting the component composition of steel will be described. In the present specification, “%” representing the content of each component element means “% by mass” unless otherwise specified.

C: 0.100% or less When C exceeds 0.100%, it is difficult to reduce to 0.005% or less where demagnetization annealing does not cause magnetic aging. Therefore, C is preferably in the range of 0.100% or less. More preferably, it is 0.020 to 0.080% of range.

Si: 2.00% to 8.00%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. If the effect is less than 2.00%, it is not sufficient. On the other hand, if it exceeds 8.00%, the workability is lowered and it becomes difficult to roll and manufacture. Therefore, Si is preferably in the range of 2.00 to 8.00%. More preferably, it is 2.50 to 4.50% of range.

Mn: 0.02% to 1.00%
Mn is an element necessary for improving the hot workability of steel. If the effect is less than 0.02%, it is not sufficient. On the other hand, if it exceeds 1.00%, the magnetic flux density of the product plate decreases. Therefore, Mn is preferably in the range of 0.02 to 1.00%. More preferably, it is 0.03 to 0.20% of range.

N: less than 70 ppm and sol.Al (acid-soluble Al): less than 150 ppm It is necessary to reduce N to less than 70 ppm and sol.Al to less than 150 ppm. That is, by reducing both components as much as possible, it is advantageous from the viewpoint of not reducing the effects of S and Se to suppress the formation of AlN-based precipitates. As described above, N and sol.Al are preferably reduced as much as possible. However, since the reduction requires a great deal of cost, N: less than 70 ppm and sol.Al: less than 150 ppm remain. Permissible. N is more preferably less than 50 ppm and sol.Al is preferably less than 100 ppm. Note that sol.Al may be contained in an amount of 30 ppm or more from the viewpoint that the deterioration of magnetic properties can be suppressed.

S and / or Se: more than 0.0050% in total and 0.0100% or less in total It is essential to further contain S and / or Se more than 0.0050% and 0.0100% or less in total. This is because, when S and / or Se is 0.0050% or less in total, as described above, the magnetic in-coil variation is caused. On the other hand, if S and / or Se exceeds 0.0100% in total, slab heating must be performed at a high temperature exceeding 1300 ° C in order to dissolve inclusions once in order to uniformly disperse S and Se in the steel. And a significant increase in cost becomes a problem. More preferably, it is 0.0055% or more and less than 0.0080%.

Sb and / or Sn: 0.005% or more and 1.000% or less in total
It is essential to contain Sb and / or Sn in a total amount of 0.005% to 1.000%. This is because if Sb and / or Sn is less than 0.005% in total, the magnetic flux density is lowered as described above. On the other hand, if Sb and / or Sn exceeds 1.000% in total, the primary recrystallization texture is greatly changed, which makes the secondary recrystallization unstable and causes magnetic deterioration. Preferably, it is 0.020% or more and 0.300% or less.

  The balance other than the above components in the grain-oriented electrical steel sheet of the present invention is Fe and inevitable impurities, but in addition, the following elements can be appropriately contained.

  Furthermore, for the purpose of improving magnetic flux density, Ni: 0.005-1.5%, Cu: 0.005-1.5%, Cr: 0.005-0.1%, P: 0.005-0.5%, Mo: 0.005-0.5%, Ti: 0.0005-0.1 %, Nb: 0.0005-0.1%, V: 0.0005-0.1%, B: 0.0002-0.0025%, Bi: 0.005-0.1%, Te: 0.0005-0.10% and Ta: 0.0005-0.01% One kind can be added alone or in combination. When the addition amount is less than the lower limit amount, the effect of improving the magnetic flux density is poor. When the addition amount exceeds the upper limit amount, secondary recrystallization failure is caused and the magnetic properties are deteriorated.

Next, the manufacturing method of the grain-oriented electrical steel sheet by one Embodiment of this invention is demonstrated.
[heating]
The slab is manufactured by the normal ingot casting method or the continuous casting method, and the components that are desirable to be added are added at the molten steel stage because it is difficult to add them in the middle of the process. . The slab is heated to 1300 ° C or lower, preferably soaked at 1270-1100 ° C. Since Al and N are reduced in this component system, high-temperature heating for dissolving them is not necessary. By reducing the temperature to 1300 ° C. or lower, the cost can be reduced.

[Hot rolling]
After the heating, hot rolling is performed. As for the hot rolling temperature, it is desirable that the starting temperature is 1000 ° C. or higher and the end temperature is 750 ° C. or higher for improving magnetic properties. However, the end temperature is desirably 1000 ° C. or lower in order to improve the shape.

  For the above-described reason, it is essential to suppress the variation in the surface temperature of the sheet bar within 100 ° C. at the surface temperature in the center portion in the width direction of the sheet bar immediately after the hot rolling. Further, from Experiment 2, it is preferable to suppress fluctuations in the surface temperature of the sheet bar to 70 ° C. or less. Here, the surface temperature of the sheet bar after rough rolling is measured by a contact-type thermometer equipped with a radiation thermometer and a thermocouple on the exit side of the rough rolling mill. The term “immediately after rough rolling” means within 5 seconds after the rough rolling is completed.

  In addition, since the temperature of the end portion of the sheet bar is excessively decreased, the central portion is measured in the width direction, and 3 m from the end portion is not considered in the longitudinal direction, and the longitudinal direction is continuously thereafter. The difference between the maximum value and the minimum value of the measured temperature is adopted as the temperature fluctuation allowance. In order to reduce this temperature fluctuation allowance, the soaking time in the slab heating is lengthened to promote the temperature rise in the slab position part on the skid, or after the slab heating, it takes a waiting time until rough rolling, etc. Thus, it can be achieved by measuring the temperature uniformity. However, when the waiting time is taken, since the rough rolling temperature itself is lowered, it is desirable to increase the soaking time in the slab heating.

[Hot rolled sheet annealing]
After hot rolling, hot-rolled sheet annealing can be performed as necessary. In that case, the hot-rolled sheet annealing temperature is desirably 800 ° C. or higher and 1100 ° C. or lower. If the hot-rolled sheet annealing temperature is less than 800 ° C., the band-like structure in the hot-rolled sheet cannot be recrystallized, and the magnetism may deteriorate. If it exceeds 1100 ° C., secondary recrystallization may become unstable. Desirably, the temperature is from 950 ° C to 1075 ° C. The annealing time is desirably in the range of 2 seconds to 120 seconds.

[Cold rolling]
After hot rolling or after hot-rolled sheet annealing, primary recrystallization annealing is performed after performing at least one cold rolling with intermediate annealing as necessary. The intermediate annealing temperature is preferably 900 ° C. or higher and 1200 ° C. or lower. When the intermediate annealing temperature is less than 900 ° C, the recrystallized grains become finer, the Goss nuclei in the primary recrystallized structure decrease, and the magnetism deteriorates. On the other hand, when the temperature exceeds 1200 ° C., the particle size becomes too coarse, which is extremely disadvantageous in realizing a primary recrystallized structure of sized particles. In the final cold rolling, the temperature of the cold rolling is increased to 100 ° C to 300 ° C, and the aging treatment in the range of 100 to 300 ° C is performed once or a plurality of times during the cold rolling, This is effective for improving the magnetic properties by changing the recrystallization texture.

[Primary recrystallization annealing]
In the next primary recrystallization annealing, the steel plate may be decarburized. An annealing temperature of 800 ° C. or higher and 900 ° C. or lower is effective from the viewpoint of decarburization. The annealing time is preferably 30 to 240 seconds. Further, from the viewpoint of decarburization, it is desirable that the atmosphere is a humid atmosphere. However, this does not apply when the content of C: 0.005% or less is not required. Further, it is desirable that the rate of temperature rise to the holding temperature is 50 ° C./s or more and 400 ° C./s or less because the final magnetic properties are good.

[Application of annealing separator]
An annealing separator is applied to the steel sheet after the primary recrystallization annealing as necessary. Here, when forming a forsterite film with an emphasis on iron loss, an annealing separation agent mainly composed of MgO is applied, and then secondary recrystallization annealing is performed by also performing purification annealing. The next recrystallized structure can be developed and a forsterite film can be formed. When the forsterite film is not required with emphasis on the punching processability, the annealing separator is not applied, or even when it is applied, MgO that forms the forsterite film is not used, but silica, alumina or the like is used. When these annealing separators are applied, it is effective to perform electrostatic application or the like that does not bring in moisture. A heat resistant inorganic material sheet (silica, alumina, mica) may be used.

[Secondary recrystallization annealing]
Next, by applying the secondary recrystallization annealing after applying the annealing separator mainly composed of MgO, it is possible to develop secondary grains having Goss orientation and to form a forsterite film. The secondary recrystallization annealing is desirably performed at 800 ° C. or higher for the secondary recrystallization. In order to complete the secondary recrystallization, it is desirable to hold at a temperature of 800 ° C. or higher for 20 hours or longer. In order to form a forsterite film, it is desirable to raise the temperature to about 1200 ° C.

[Flatening annealing]
After secondary recrystallization annealing, it is useful to perform water washing, brushing, and pickling to remove the attached annealing separator. Thereafter, it is effective to reduce the iron loss by further performing flattening annealing to correct the shape. The annealing temperature for planarization annealing is preferably 750 to 950 ° C., and the annealing time is preferably 5 seconds or more and 120 seconds or less.

[Insulating coating]
In the case where the steel plates are laminated and used, in order to improve iron loss, it is effective to apply an insulating coating to the steel plate surface before or after the flattening annealing. A coating capable of imparting tension to the steel sheet to reduce iron loss is desirable. It is desirable to employ a coating method by depositing an inorganic material on the surface layer of a steel sheet by a tension coating application method through a binder, physical vapor deposition method or chemical vapor deposition method, because it has excellent coating adhesion and a significant iron loss reduction effect.

[Magnetic domain subdivision processing]
In order to further reduce iron loss, it is desirable to perform magnetic domain fragmentation. As a processing method, a method of applying strain to an iron crystal lattice by an electron beam, a laser, or the like, which is generally performed, is desirable. Further, not only the final product plate, but also a method in which a groove is provided in advance in an intermediate product such as a cold-rolled plate that has reached the final finished thickness.
Other manufacturing conditions may follow the general manufacturing method of a grain-oriented electrical steel sheet.

  The present invention is a method that should also be referred to as Subtle Inhibition Control (SIC method). The SIC method is superior to the technique using the conventional inhibitor and the inhibitorless technique that can simultaneously achieve the low-temperature slab heating and the suppression of the iron loss fluctuation in the coil.

Example 1
Contains C: 0.062%, Si: 3.16%, Mn: 0.14%, sol.Al: 80ppm, N: 34ppm, S: 65ppm, Sn: 0.075% by weight, with the balance being composed of Fe and inevitable impurities A steel slab was manufactured by continuous casting, heated at 1230 ° C, then hot rolled to a thickness of 40 mm and finished to a thickness of 2.4 mm by finish rolling. At this time, by changing the soaking time at the time of slab heating as shown in Table 1, the temperature fluctuation in the sheet bar is changed at the surface temperature in the center in the width direction of the sheet bar immediately after the rough rolling of the hot rolling. It was. The difference between the minimum and maximum surface temperature of the sheet bar is also shown in Table 1 as the temperature fluctuation in the sheet bar. Here, the surface temperature of the sheet bar was measured using a radiation thermometer installed at the upper part on the exit side of the final rolling mill for rough rolling. This is a continuous measurement of the temperature at one central part in the width direction. Since the temperature at the end of the seat bar has dropped excessively, 3 m from the end is not taken into account in the longitudinal direction. After that, the longitudinal direction is continuously measured, and the maximum temperature is measured at the maximum temperature. The minimum part was defined as the lowest temperature part.

Then, these hot-rolled sheets were subjected to hot-rolled sheet annealing at 1050 ° C. for 15 seconds, then cold rolled to a thickness of 1.8 mm, subjected to intermediate annealing at 1000 ° C. for 100 seconds, and further cold-rolled. Finished to a thickness of 0.23 mm. Thereafter, primary recrystallization annealing was performed at 840 ° C. for 120 seconds in a humid atmosphere of 55% H ₂ -45% N ₂ and a dew point of 58 ° C. Thereafter, an annealing separator mainly composed of MgO was applied, and secondary recrystallization annealing was performed at 1230 ° C. for 2 hours in a hydrogen atmosphere.

Further, the magnetic domain was subdivided with an electron beam continuously at a pitch of 8 mm in the width direction. The magnetic flux density B ₈ of samples obtained was measured by the method described in JIS C2550. The measurement positions were the positions of the lowest temperature portion and the highest temperature portion immediately after rough rolling in the coil, and this magnetic difference was used as the fluctuation in the coil of the final magnetism. The obtained results are also shown in Table 1.

As is apparent from Table 1, it can be seen that a good magnetic flux density B ₈ can be obtained under the conditions within the scope of the present invention, and that the fluctuations are also small.

(Example 2)
A steel slab containing the various components listed in Table 2 and the balance being made of Fe and inevitable impurities was manufactured by continuous casting, heated at 1270 ° C, and then hot rough rolled to a thickness of 30 mm. Finished to a thickness of 2.7mm by finish rolling. At this time, the soaking time during slab heating was set to 70 minutes. At this time, the temperature fluctuation of the surface of the sheet bar was 60 ° C. at the surface temperature of the center portion in the width direction of the sheet bar immediately after the hot rolling.

Thereafter, hot-rolled sheet annealing was performed at 975 ° C. for 120 seconds, and then the sheet thickness was 1.7 mm by cold rolling. Then, after intermediate annealing at 1100 ° C. for 80 seconds, it was finished to a thickness of 0.20 mm by warm rolling at 120 ° C. Further, primary recrystallization annealing was performed in a humid atmosphere of 850 ° C. for 100 seconds and 60% H ₂ -40% N ₂ with a dew point of 60 ° C.

  Thereafter, an annealing separator mainly composed of MgO was applied, and secondary recrystallization annealing was performed at 1220 ° C. for 5 hours under a hydrogen atmosphere. Furthermore, the magnetic domain was subdivided at a 4 mm pitch continuously in the width direction with a laser. Thereafter, planarization annealing was performed at 820 ° C. for 30 seconds, which also served as a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

The magnetic flux density B ₈ of samples obtained was measured by the method described in JIS C2550. The measurement positions were the positions of the lowest temperature portion and the highest temperature portion immediately after rough rolling in the coil, and this magnetic difference was used as the fluctuation in the coil of the final magnetism. The obtained results are also shown in Table 2.

As is apparent from Table 2, it can be seen that a good magnetic flux density B ₈ is obtained under the conditions within the scope of the present invention, and that the fluctuation is also small.

(Example 3)
A steel slab containing the various components listed in Table 3 and the balance being made of Fe and inevitable impurities is manufactured by continuous casting, heated at 1180 ° C, and then hot hot rolled to a thickness of 45 mm. Finished to a thickness of 2.0 mm by finish rolling. At this time, the soaking time at the time of slab heating was 100 minutes, and the temperature variation in the sheet bar was 40 ° C. at the surface temperature in the center in the width direction of the sheet bar immediately after the hot rolling.

Thereafter, it was subjected to hot-rolled sheet annealing at 1070 ° C. for 10 seconds and then finished to a thickness of 0.23 mm by cold rolling. Further, primary recrystallization annealing was performed in a humid atmosphere of 865 ° C. for 100 seconds and 40% H ₂ -60% N ₂ with a dew point of 42 ° C. Thereafter, an annealing separation agent mainly composed of MgO was applied, and secondary recrystallization annealing was performed at 1200 ° C. for 3 hours and maintained in a 50% H ₂ + 50% N ₂ atmosphere.

Thereafter, flattening annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid. The magnetic flux density B ₈ of samples obtained was measured by the method described in JIS C2550. The measurement positions were the positions of the lowest temperature portion and the highest temperature portion immediately after rough rolling in the coil, and this magnetic difference was used as the fluctuation in the coil of the final magnetism. The results obtained are also shown in Table 3.

As is apparent from Table 3, it can be seen that a good magnetic flux density B ₈ can be obtained under the conditions within the scope of the present invention, and that the fluctuations are also small.

Claims (7)

% By mass
C: 0.100% or less,
Si: 2.00% to 8.00%,
Mn: 0.02% to 1.00%,
S and / or Se in total more than 0.0050% and less than 0.0100% and
A steel slab containing Sn and / or Sb in a total amount of 0.005% or more and 1.000% or less, suppressing N to less than 70 ppm and acid-soluble Al to less than 150 ppm, with the balance being 1300 steel slab having a composition composed of Fe and inevitable impurities Heating below ℃,
Hot-rolled steel sheet is subjected to hot rolling on the heated steel slab,
The hot-rolled steel sheet is subjected to cold rolling two or more times with one or more intermediate annealings to obtain a cold-rolled steel sheet having a final sheet thickness,
The cold rolled steel sheet is subjected to primary recrystallization annealing, and then subjected to secondary recrystallization annealing, a method for producing a grain-oriented electrical steel sheet,
A method for producing a grain-oriented electrical steel sheet, wherein the longitudinal variation of the sheet bar in the longitudinal direction of the sheet bar at the center in the width direction of the sheet bar immediately after the rough rolling of the hot rolling is within 100 ° C.   The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the content of Sn and / or Sb is 0.020% or more and 0.300% or less in terms of mass%. The component composition further includes:
% By mass
Ni: 0.005% to 1.5%,
Cu: 0.005% to 1.5%,
Cr: 0.005% to 0.1%,
P: 0.005% to 0.5%,
Mo: 0.005% to 0.5%,
Ti: 0.0005% to 0.1%,
Nb: 0.0005% or more and 0.1% or less,
V: 0.0005% to 0.1%,
B: 0.0002% to 0.0025%,
Bi: 0.005% to 0.1%,
Te: 0.0005% to 0.10% and
Ta: The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 or 2, comprising one or more selected from 0.0005% to 0.01%.   The directivity according to any one of claims 1 to 3, wherein the longitudinal variation of the sheet bar in the longitudinal direction of the sheet bar at the center in the width direction of the sheet bar immediately after the rough rolling of the hot rolling is within 70 ° C. A method for producing electrical steel sheets.   The manufacturing method of the grain-oriented electrical steel sheet according to any one of claims 1 to 4, wherein the cold-rolled steel sheet is subjected to a magnetic domain refinement process.   The method for producing a grain-oriented electrical steel sheet according to claim 5, wherein the magnetic domain subdividing treatment is performed by electron beam irradiation to the cold-rolled steel sheet after the secondary recrystallization annealing.   The method for producing a grain-oriented electrical steel sheet according to claim 5, wherein the magnetic domain refinement process is performed by laser irradiation of the cold-rolled steel sheet after the secondary recrystallization annealing.

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