JPH0970602A - Manufacture of grain oriented electrical steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce an edge crack occurring at the time of the hot rolling of a grain oriented electrical steel sheet. SOLUTION: After heating a slab for a grain oriented electrical steel sheet, when attaining a hot rolled coil by performing hot rough rolling and then hot finish rolling, for a sheet bar after the hot rough rolling, with respect to the relationship of the thickness te (mm) of the side edge part of this sheet bar and the thickness tc (mm) of the center part in the width direction of the sheet bar, it must be a shape satisfying a following inequality, te-ec>=1(mm). Concretely, proper width drawing down is performed at the time of the rough rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet, and particularly to a method capable of reducing edge cracks during hot rolling of a grain-oriented electrical steel sheet slab. .

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as iron cores for transformers and other electrical equipment, and it is basically important that they have excellent magnetic characteristics such as magnetic flux density and iron loss value in order to meet such applications. . Therefore, what is important in the production of grain-oriented electrical steel sheets is that the orientation of the crystal grains that have undergone secondary recrystallization in the so-called finish annealing step is highly integrated in the {110} <001> orientation, the so-called Goss orientation. That is.

In order to effectively promote the accumulation of such secondary recrystallized grains, firstly, a dispersed phase called an inhibitor, which selectively suppresses the growth of primary recrystallized grains, is uniformly and appropriately added. It is important to form with a proper size. Examples of such inhibitors include sulfides, selenium compounds, and nitrides such as MnS, MnSe, AlN, and VN, which have extremely low solubility in steel. Therefore, conventionally, in the slab heating before hot rolling, high temperature heating is performed to completely dissolve the inhibitor, and the inhibitor is finely dispersed and precipitated in the process of secondary recrystallization after the hot rolling step. The method is taken. In addition, Sb, Sn, As,
Grain boundary segregation elements such as Pb, Ce, Cu and Mo are also used as inhibitors.

The second condition for effectively promoting the accumulation of the secondary recrystallized grains is to combine cold rolling at least once or twice and annealing at least once. It is important that the formed primary recrystallized grains have an appropriate size and uniform crystal grains throughout the plate thickness.

It is well known that it is important to satisfy the above-mentioned two conditions. Therefore, in the conventional general manufacturing process for manufacturing grain-oriented electrical steel sheet,
A slab having a thickness of 100 to 300 mm is heated at a temperature of 1250 ° C. or higher to completely dissolve the inhibitor component into a hot-rolled sheet, and then the hot-rolled sheet is subjected to one or two or more times including intermediate annealing. The final plate thickness is obtained by cold rolling, followed by decarburizing annealing, applying an annealing separator, and then performing final finishing annealing for the purpose of secondary recrystallization and purification.

In recent years, the demand for energy saving has further increased, and the needs for high magnetic flux density and low iron loss for grain-oriented electrical steel sheets have further increased. In order to meet these demands, in the production method of grain-oriented electrical steel sheet, reduction of product sheet thickness, high Si, and further laser beam, plasma jet irradiation, groove formation, etc. on the steel sheet after secondary recrystallization A method for directly subdividing the magnetic domain to achieve low iron loss has been adopted. In addition, adding two or more inhibitors in combination,
The grain growth suppressing force has also been increased, and further, so-called warm rolling has been performed in which the sheet temperature is increased in the cold rolling process. With these technologies and their advances,
It has become possible to obtain products with very good magnetic properties.

By the way, the grain-oriented electrical steel sheet is strongly desired not only for the above-mentioned magnetic properties but also for inexpensive supply, and it is an important issue for the manufacturer side to produce such a high-grade product with a high yield. ing. From the viewpoint of improving the yield, during hot rolling, it is an important issue how to prevent the occurrence of edge cracks at the edge portion of the hot rolled sheet as well as the surface texture.

[0008] There have already been many disclosures of a technique for preventing edge cracks in the hot rolling process during the production of grain-oriented electrical steel. For example, JP-A-55-62124, JP-A-61-96032, and JP-A-60-14520.
4, JP-A-61-71104, JP-A-60
-20916, JP-A-62-196328, JP-A-5-138207, and JP-A-3-133.
No. 501, JP-A-3-243244, JP-A-61-3837 and the like.

Among the publications listed above, JP-A-55-621
Japanese Patent Laid-Open No. 42-42 discloses a method of reducing the temperature drop during finish hot rolling to 220 ° C. or less. However, even if the temperature from the start to the end of finish rolling is regulated within this range as in this method, the effect of preventing edge cracks generated during rough rolling or in the preceding stage of finish rolling cannot be obtained. Further, the method described in the above-mentioned JP-A-61-96032 is also a method which substantially controls the reduction ratio after finish rolling, and similarly, prevents edge cracks occurring during rough rolling or in the preceding stage of finish rolling. No effect was obtained.

On the other hand, among the publications listed above, Japanese Patent Laid-Open No. 60-
145204, JP-A-61-71104,
JP-A-60-200916 and JP-A-62-196
The methods described in Japanese Unexamined Patent Application Publication No. 328, JP-A-5-138207 and the like are methods for preventing ear cracking by adjusting the shape of the side surface of the sheet bar during hot rolling. That is,
If the shape of the side surface is not good, a notch-shaped recess is created at the grain boundary part of the coarsely grown crystal, and this becomes the starting point of ear cracking.Thus, the shape of the side surface is adjusted to prevent ear cracking. , Some effect was seen. However, JP-A-60-145204 and JP-A-62-1
In these methods including Japanese Unexamined Patent Publication No. 96328, the effect of preventing edge cracking is small and the productivity of hot rolling is emphasized especially when the width reduction is performed on the exit side of the first pass of hot finish rolling. Today, I was not satisfied enough. In particular, little effect was observed on the edge cracks from the hot rough rolling to the finish rolling front stage.

Further, the above-mentioned JP-A-60-145204, JP-A-61-71104 and JP-A-62-19.
When performing width reduction on the inlet side of hot finish rolling as in the methods disclosed in Japanese Patent No. 6328 and JP-A-5-138207, width reduction is performed on the exit side of hot finish rolling as described above. Compared with the case, the effect of preventing ear cracking is greater. However, immediately before the first pass of hot finish rolling, it is unavoidable that the side surface of the steel material is deheated due to contact with the edging roll, so that the sheet bar has a local temperature difference in both the width direction and the longitudinal direction. As a result, uniformity was brought about, which promoted ear cracking, so that it was not possible to stably prevent ear cracking.

Further, as described in JP-A-54-31024, a method for controlling the final reduction ratio of hot rough rolling, and a slab as described in JP-A-3-133501. A method of applying width reduction and horizontal reduction after heating, a method of controlling a slab cast structure as described in JP-A-3-243244, and a slab as described in JP-A-61-3837. Although there are some effects on edge cracking in the method of making the cross-sectional shape into a special shape, such an effect is smaller than the method of width reduction during rough rolling, and it greatly depends on the width reduction method during rough rolling. Therefore, it was not an effective method.

On the other hand, some methods for preventing edge cracking have been proposed in which width reduction is performed during rough rolling. For example, in the above-mentioned Japanese Patent Laid-Open No. 60-200916, it is proposed to perform a width reduction of 5 to 40% during rough rolling.
With this method, the ear crack depth is 20 to 20 when hot rolling.
The big ear crack of 40mm is gone. However, even with this, a relatively large ear crack of 10 mm or more remained.

[0014]

DISCLOSURE OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and is a direction in which the edge cracks that occur during hot rolling of grain-oriented electrical steel sheets can be more effectively reduced. The purpose of the present invention is to propose a method for manufacturing a magnetic electrical steel sheet.

[0015]

Means for Solving the Problems In producing grain-oriented electrical steel sheets, the inventors have found a stand in which edge cracking occurs during hot rolling, a cross-sectional shape of the material during hot rolling and edge cracking in the hot rolled sheet. As a result of a detailed examination of the relationship between the frequency and the crack depth, it was revealed that the edge crack occurred before the finish rolling. It was also found that this edge crack has a close correlation with the cross-sectional shape of the sheet bar after rough rolling.
That is, when the thickness of the seat bar is thicker in the side edge portion (edge portion) than in the widthwise central portion, the occurrence of ear cracks is small and the ear crack depth is also small. The gist of the present invention based on the above findings is as follows.

C: 0.01 to 0.10 mass% and Si: 2.5 to 4.5
After heating the slab for grain-oriented electrical steel sheets containing mass%, hot rough rolling, then hot finish rolling, and then once or twice or more cold rolling with intermediate annealing sandwiched, the final sheet thickness In order to manufacture a grain-oriented electrical steel sheet by a series of steps of finishing, and then decarburizing and annealing, then applying an annealing separator to the surface of the steel sheet and then applying final finishing annealing, the sheet bar after the hot rough rolling Is the thickness t of the side edge of the seat bar.
Manufacture of grain-oriented electrical steel sheet characterized by having a shape satisfying the following equation te −tc ≧ 1 (mm) with respect to the relationship between e (mm) and the thickness tc (mm) of the widthwise central portion of the sheet bar. Method (first invention).

C: 0.01 to 0.10 mass% and Si: 2.5 to 4.5
After heating the slab for grain-oriented electrical steel sheets containing mass%, hot rough rolling, then hot finish rolling, and then once or twice or more cold rolling with intermediate annealing sandwiched, the final sheet thickness In order to manufacture a grain-oriented electrical steel sheet by a series of steps of applying an annealing separator to the surface of the steel sheet and then performing a final finish annealing after finishing and then decarburizing annealing, the final reduction of the hot rough rolling is applied. Side, the width reduction is performed with a reduction amount of 30 mm or more,
Further, a method for producing a grain-oriented electrical steel sheet (second invention), characterized by performing width reduction within a range of a reduction amount of 20 to 50 mm after the final reduction and before the start of finish rolling.

C: 0.01 to 0.10 mass% and Si: 2.5 to 4.5
After heating the slab for grain-oriented electrical steel sheets containing mass%, hot rough rolling, then hot finish rolling, and then once or twice or more cold rolling with intermediate annealing sandwiched, the final sheet thickness In order to manufacture a grain-oriented electrical steel sheet by a series of steps of applying a deannealing agent to the surface of the steel sheet and then performing a final finishing annealing after the decarburization annealing, The width reduction by the jar roll is performed for three or more passes, and the average value of the width reduction amounts of the final two passes of the width reduction passes is made larger than the average value of the width reduction amounts of the previous passes and the final two passes. The average value of the width reduction of the pass is 25 to 80
A method for manufacturing a grain-oriented electrical steel sheet (third invention), wherein the grain size is in the range of mm.

C: 0.01 to 0.10 mass% and Si: 2.5 to 4.5
After heating the slab for grain-oriented electrical steel sheets containing mass%, hot rough rolling, then hot finish rolling, and then once or twice or more cold rolling with intermediate annealing sandwiched, the final sheet thickness In order to manufacture a grain-oriented electrical steel sheet by a series of steps of applying a deannealing agent to the surface of the steel sheet and then performing a final finishing annealing after the decarburization annealing, A method for manufacturing a grain-oriented electrical steel sheet (4th invention), characterized in that the width reduction by the jar roll is performed under the condition that the following expression is satisfied in relation to the sheet thickness at the central portion of the steel sheet width direction at that time (fourth invention).

[Equation 2] Note 0.3 {(E ₁ / h ₁ ) + (E ₂ / h ₂ )} ≦ E / h E ₁ > 0, E ₂ > 0 where E and h are the final stand of the rough rolling mill, respectively. The width reduction amount (mm) between the first stand of the finish rolling mill, the plate thickness (mm) at the widthwise central portion, E ₁ and h ₁ are the width reduction amount (mm) between the last two stands of the rough rolling mill, respectively. The plate thickness (mm) in the width direction central part, and E ₂ and h ₂ are the width reduction amount (mm) between the 2nd stand and the 3rd stand from the last of the rough rolling mill, and the plate thickness (mm) in the width direction center part, respectively. .

In the first to fourth inventions, the temperature of the side surface of the sheet bar on the exit side of the final stand of the hot rough rolling is set to 1050 to 12
A method of manufacturing a grain-oriented electrical steel sheet, which comprises setting the temperature to 00 ° C. (Fifth invention)

In the first to fifth inventions, the method for producing a grain-oriented electrical steel sheet is characterized in that the temperature difference in the longitudinal direction of the side surface of the sheet bar on the exit side of the final stand of the hot rough rolling is set within 100 ° C. 6 invention).

In the first invention, the amount of C is 0.05 to 0.10 mass.
%, And the sheet bar temperature before finishing hot rolling (FE
When T) is 1100 ° C or higher, descaling using high-pressure water on the entry side of the finishing rolling mill is omitted to suppress the temperature drop of the sheet bar surface temperature, which is a method for producing a grain-oriented electrical steel sheet. (Seventh invention).

In the first invention or the seventh invention, the amount of C is 0.
If the sheet bar temperature (FET) before finishing hot rolling is 1100 ° C or higher in the range of 05 to 0.10 mass%, omit the strip coolant on the inlet side or inlet / outlet side of the first stand of the finishing mill. A method for manufacturing a grain-oriented electrical steel sheet, which suppresses a temperature drop of a sheet bar surface temperature (eighth invention).

C: 0.01 to 0.10 mass% and Si: 2.5 to 4.5
After heating the slab for grain-oriented electrical steel sheets containing mass%, hot rough rolling, then hot finish rolling, and then once or twice or more cold rolling with intermediate annealing sandwiched, the final sheet thickness In order to manufacture a grain-oriented electrical steel sheet by a series of steps of applying an annealing separation agent to the surface of the steel sheet and then applying final finishing annealing after finishing and then decarburizing annealing, during hot finish rolling, A method for producing a grain-oriented electrical steel sheet, characterized in that the tension is operated at 3 kgf / mm ² or less over the entire length of the sheet (ninth invention).

C: 0.01 to 0.10 mass% and Si: 2.5 to 4.5
When a slab for grain-oriented electrical steel sheets containing mass% is heated, then hot rough rolling is performed, and then hot finish rolling is performed to obtain a hot rolled coil, the sheet bar after the hot rough rolling is placed on the side of the sheet bar. Regarding the relationship between the edge thickness t e (mm) and the thickness tc (mm) of the widthwise central part of the sheet bar, a shape satisfying the following formula te −t c ≧ 1 (mm) is used, and at the time of hot finish rolling A method for producing a grain-oriented electrical steel sheet, characterized in that the tension between stands is operated at 3 kgf / mm ² or less over the entire length of the sheet (10th invention).

In the tenth aspect of the invention, the production of a grain-oriented electrical steel sheet characterized in that the flow rate of the cooling liquid to the work rolls of the hot finish rolling mill is changed in the roll axial direction to suppress the thermal crown of the work rolls. Method (11th invention).

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the experiments leading to the present invention and the results thereof will be specifically described. (Experiment 1) Two kinds of molten steel containing the composition shown in Table 1 were used.
It was melted using a 0 t converter and a vacuum degasser, and was continuously cast into a slab having a thickness of 220 mm and a width of 1100 mm. These slabs were heated in a gas heating furnace, pre-rolled to a thickness of 200 mm, further induction-heated to 1400 ° C. to perform solution treatment of the inhibitor component, and then hot rough rolling was performed to obtain a sheet bar having a thickness of 45 mm. At this time, the thickness of the central portion in the width direction and the side edge portion (end portion in the width direction) of the sheet bar were variously changed by controlling the horizontal roll shift and the width rolling by the vertical rolls, and these thicknesses were measured by an online measuring instrument. . Subsequently, hot finish rolling was performed to obtain a hot rolled sheet having a thickness of 2.4 mm. Over the entire length of these hot-rolled coils, the frequency of occurrence of ear cracks at the side edges (edge portions) and the depth of ear cracks (depth of ear cracks extending from the edge portion to the center in the width direction) were investigated. These results are shown in FIGS. 1a and 1b in relation to the widthwise central portion of the seat bar and the thickness of the side edge portions.

[0028]

[Table 1]

From FIGS. 1a and 1b, when the difference between the thickness tc of the central portion in the width direction of the seat bar and the thickness te of the side edge portion is 1 mm or more, that is, when te-tc ≥1 (mm), ear cracking occurs. The frequency is less than 30/100 m, and the depth of ear cracking is 10
It can be seen that good results are obtained with a small value of less than mm.

Next, the cross sectional shape of the sheet bar after rough rolling is
In order to satisfy the relationship of te-tc ≧ 1 mm as described above, from the idea that width reduction should be performed at the time of rough rolling, an experiment for finding a more suitable condition for such width reduction is given below. So went.

(Experiment 2) C: 0.060 mass%, Si: 2.95ma
ss%, Mn: 0.070 mass%, Se: 0.014 mass%, Al: 0.02
Steel containing 2 mass% and N: 0.0090 mass% was melted using a converter and a vacuum degassing device, and the thickness was 22 by continuous casting.
The slab was 0 mm wide and 1100 mm wide. After heating such a slab in a gas-fired furnace, it is pre-rolled to a thickness of 200 mm and
After induction heating to 00 ° C. for solution treatment of the inhibitor component, hot rough rolling was performed to obtain a sheet bar having a thickness of 45 mm. During this rough rolling, the roll gap of the width reduction roll was set to various values, width reduction was applied, and the width of the material to be rolled was measured online. Successively, finish hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.4 mm. The frequency of occurrence of edge cracks at the edge and the crack depth were observed over the entire length of these hot-rolled sheet coils.
Figures 2a and 2b show the relationship between the width reduction and the cracking condition before and after the rough rolling stand.

From FIGS. 2a and 2b, when the width reduction amount before the final horizontal reduction of the rough rolling is 30 mm or more and the width reduction amount after the final horizontal reduction of the rough rolling is 20 mm or more and 50 mm or less, the ear cracking frequency is particularly high. It can be seen that the number is 5 or less / 100 m and the depth of the edge crack is 5 mm or less, which is excellent.

Next, in Experiment 2 described above, the width reduction was performed twice. From the viewpoint that the width reduction can be performed three times or more, it is confirmed that the width reduction is performed three times or more. The following experiments were conducted in order to find the conditions that can reduce cracking.

(Experiment 3) C: 0.07 mass%, Si: 3.2 mass
%, Mn: 0.08 mass%, Se: 0.016 mass%, Al: 0.026 ma
ss%, N: 80wtppm, Sb: 0.025 mass% and Cu: 0.07ma
Molten steel containing ss% was melted using a 180 t converter and a vacuum degassing device, and continuously cast into a slab having a thickness of 220 mm and a width of 1100 mm. After heating such a slab in a gas heating furnace, preliminary rolling to a thickness of 200 mm, and induction heating to 1400 ° C to perform solution treatment of the inhibitor component, followed by hot rough rolling to 45
The sheet bar has a thickness of mm. During this rough rolling, width reduction was performed by an edger roll, and there were four types of width reduction of 3 to 6 passes, and the width reduction amount in each pass was variously changed. After rough rolling, finish rolling was performed to obtain a hot rolled sheet having a thickness of 2.4 mm.
The edge crack depth at the side edge was investigated over the entire length of these hot rolled coils. The result is shown in FIG.

From FIG. 3, the width reduction (edging) at the time of hot rough rolling is performed in three or more passes, and the average value of the width reduction by the edger rolls in the final two passes is set to 25 to 80 mm, and this final two passes. It can be seen that the ear crack depth can be stably suppressed within 10 mm by making the average value of the width reduction amount of the pass larger than the average value of the width reduction amount of the above passes.

Next, the following experiment was conducted from the viewpoint that there may be more preferable conditions when the width reduction is performed three times or more.

(Experiment 4) Two kinds of steel containing the components shown in Table 1 were melted using a 180 t converter and a vacuum degassing device, and a slab having a thickness of 220 mm and a width of 1100 mm was obtained by continuous casting. These slabs are heated in a gas-fired furnace and then pre-rolled to 200
mm thickness, and then induction heating to 1400 ° C to perform solution treatment of the inhibitor component, followed by hot rough rolling to a 40 mm sheet bar, at which time the pass schedule was variously changed and the bar was attached to the rough rolling facility. The thickness of the central portion of the plate and the plate width were measured online at any time, while the width reduction was variously changed by changing the opening degree of each edger roll. Then, finish rolling was performed to obtain a 2.4 mm hot rolled sheet.

The frequency of occurrence of edge cracks at the edges and the crack depth were observed over the entire length of these hot-rolled sheet coils. The results are shown in Table 2 together with the pass schedule and width reduction amount of the final 3 passes. The width reduction amount is the difference between the plate width before entering the edger roll and the plate width after passing through the edger roll.

[0039]

[Table 2]

The results of Table 2 are summarized and shown in FIGS. From these figures,

[Equation 3] 0.3 {(E ₁ / h ₁ ) + (E ₂ / h ₂ )} ≦ E / h E ₁ > 0, E ₂ > 0 where E and h are the final stand of the rough rolling mill and the finish, respectively. The width reduction amount (mm) between the first stand of the rolling mill, the plate thickness (mm) at the widthwise central portion, E ₁ and h ₁ are the width reduction amount (mm) and the width between the last two stands of the rough rolling mill, respectively. The plate thickness (mm) at the center in the direction, and E ₂ and h ₂ are the width reduction (mm) between the 2nd stand and the 3rd stand from the last of the rough rolling mill, and the plate thickness (mm) at the center in the width direction. It was found that ear cracks were less likely to occur in the region of.

Next, the thickness tc of the center portion in the width direction and the thickness te of the side edge portion of the seat bar obtained from the result of the above-described Experiment 1 are obtained.
With a difference of 1 mm or more, that is, te-t c ≧ 1 (mm), a comparatively high frequency of occurrence of ear cracking was analyzed. As a result, the C content was 0.05 mass% or more and before hot rolling was started. It was found that the frequency of occurrence of ear cracks slightly increased when the sheet bar temperature (FET) was 1100 ° C or higher.

Therefore, an experiment was conducted to find a condition capable of sufficiently reducing the ear crack even under such an unfavorable condition. As a result, it was found that it can be improved by suppressing the cooling before the finish hot rolling. The results will be specifically described below.

(Experiment 5) Steels having the compositions shown in Table 3 were melted,
Made into a slab by continuous casting, 1430 ℃ in an induction heating furnace
After heating for 30 minutes at 30 ° C., rough rolling was performed under the same conditions as in Experiment 1. At this time, the thickness difference between the widthwise center and the widthwise end of the seat bar is 1
It was set to mm or more. Then, in finishing hot rolling, after the sheet bar temperature before finishing hot rolling start to air cooling to a predetermined temperature, respectively, conditions for descaling using high pressure water, conditions for omitting descaling using this high pressure water, Furthermore, it was performed in combination with the condition that strip coolant was omitted on the inlet side or inlet / outlet side of the first stand of the finishing mill. Table 4 shows the results of observing the shape of the end portion in the width direction of the hot rolled coil thus obtained.

[0044]

[Table 3]

[0045]

[Table 4]

From Table 4, even when the amount of C is 0.05 mass% or more and the sheet bar temperature (FET) before the start of finishing hot rolling is 1100 ° C. or more, descaling using high-pressure water on the inlet side of the finishing hot rolling machine is performed. To suppress the temperature drop of the seat bar surface temperature and / or to omit the strip coolant on the entry side or the entry side of the finishing hot rolling machine No. 1 stand to reduce the frequency of ear cracking and reduce the depth. It turns out that can be small.

Further, such descaling and omission of the strip coolant do not need to keep the seat bar on the table for air cooling, unlike the prior art for preventing ear cracking, so that productivity is not hindered. It also improves efficiency. Furthermore, surface defects, which are thought to be caused by intergranular cracks as well as ear cracks, were reduced by avoiding rapid cooling at high temperature.

The reason why the occurrence of ear cracking is suppressed by the present invention as in the above experimental results is not necessarily clear, but it can be considered as follows.

First, according to the first aspect of the present invention, the thickness t e (mm) of the side edge portion of the seat bar and the thickness t of the center portion in the width direction of the seat bar are controlled by controlling the sectional shape perpendicular to the longitudinal direction of the seat bar.
Regarding the relationship with c (mm), the reason why the effect of suppressing ear cracking can be obtained by satisfying the following expression te −t c ≧ 1 (mm) is as follows. The ear cracks that occur are mainly generated before the hot finish rolling. It is considered that this is because when the grain-oriented electrical steel sheet is manufactured, the slab heating temperature is high and the rolling temperature is high, so that the grain boundary is weak in the finish rolling temperature range as compared with the ordinary steel. . Further, it is difficult for the ear cracks to occur in the hot rough rolling because the electromagnetic steel contains Si, so that the deformation resistance itself is low, and Si is an austenite (γ phase) because it is a ferrite (α phase) forming element. May not be generated, or even if it is generated in a small amount, and since the rolling temperature is higher, the deformation resistance may be less and the stress required for rolling deformation may be less, but in addition, it easily undergoes intragranular deformation. Therefore, it is considered that, as a result of the large tensile stress not acting on the grain boundary, grain boundary cracking, that is, ear cracking does not occur.

From this, it is considered that the tensile stress acting on the side edge portion of the sheet bar during the hot finish rolling, particularly when passing through the finish first stand, is involved in the occurrence of the edge crack. The sectional shape of the seat bar before passing through the finishing first stand is schematically shown in FIG. On the exit side of the finishing first stand, the thickness of the seat bar is the same in the width direction end portion and the width direction central portion, and on the finishing first stand entry side, the thickness of the seat bar width direction central portion is the width direction end portion. When it is larger than the thickness (Fig. 6c), the elongation in the rolling direction is large at the central portion in the width direction of the sheet bar and is small at the end portions in the width direction. For this reason, at the end portion in the width direction of the seat bar, a tensile stress stronger than that in the center portion in the width direction is exerted, and ear cracks are easily generated. On the contrary, the finishing first
When the center portion in the width direction of the sheet bar is thinner than the end portions in the width direction on the stand-in side (FIG. 6a), the elongation in the rolling direction is small in the center portion in the width direction of the sheet bar. Therefore, the tensile stress applied to the end portion in the width direction of the seat bar becomes small, and ear cracks are less likely to occur.

Further, the widthwise end portion of the sheet bar is more likely to lower the temperature than the widthwise central portion by radiating heat from the three surfaces, and therefore during the finish rolling, the deformation resistance is locally increased and a large tension is applied. It will cost you. In particular, when the thickness of the widthwise end portion is small, the temperature of the end portion is remarkably lowered, and this tendency is promoted. Therefore, it is considered that increasing the thickness of the end portion in the width direction of the seat bar, that is, the side edge portion also has the effect of suppressing ear cracking by reducing the temperature decrease of the side edge portion.

As described above, in the first aspect of the invention, the relation between the thickness t e (mm) of the side edge portion of the seat bar and the thickness t c (mm) of the center portion of the seat bar in the width direction is expressed by the following equation te −tc ≧ The reason why the shape satisfies 1 (mm) is to prevent ear cracking,
If the value of te-tc is less than 1 mm, the effect of preventing ear cracking is not sufficient. More preferably, the value of te-tc is set to 3 mm or more. On the other hand, the upper limit of the value of te-tc is not particularly limited, but if it is too large, there is a possibility that the shape may become defective and the rolling load may increase. desirable. Although there is no particular limitation on the specific means for shaping the sheet bar into the shape defined in the first aspect of the invention after hot rough rolling, the sheet bar may be placed on the inlet side or the outlet side of the rough rolling mill stand. It is effective to use an installed width reduction roll or width press device. In addition, a method of changing the shape of the horizontal roll, controlling roll shift, controlling tension between stands, and the like are also possible.

Therefore, in the second invention, the width reduction is performed so that the sheet bar has a shape as defined in the first invention. As a more preferred embodiment, the width of the sheet bar on the entry side of the final reduction of the hot rough rolling is set. The reduction is performed, and further the width reduction is performed after the final reduction and before the start of finish rolling. After the final reduction of this hot rough rolling, the width reduction until the start of finish rolling is to increase the thickness of the widthwise end portion of the sheet bar to form an edge-up shape before the finish rolling in which cracks occur. It is considered that this has a great effect on prevention of ear cracking.

Further, if there is a defective shape on the side surface of the seat bar, this defective shape becomes a starting point of ear cracking. Therefore, in order to prevent ear cracking, it is effective to adjust the shape of the side surface of the seat bar to eliminate the notch-shaped concave portion that becomes the starting point of cracking. This is an effect that can be expected in both width reduction before and after the final reduction of the hot rough rolling.

That is, according to the second aspect of the present invention, before and after the final rolling of the rough rolling for eliminating the notch-shaped recesses on the side surface of the sheet bar, the width reduction before and after the final rolling, and the roughening for making the sheet bar before the finishing rolling stand into the edge-up shape. It is considered that the excellent effect of preventing the ear crack was obtained due to the synergistic effect of both the width reduction after the final rolling of the rolling.

If the width reduction amount before the final reduction of the hot rough rolling is less than 30 mm, the effect of shaping the side of the sheet bar is not sufficient, and notched concave portions remain, so that more excellent prevention of ear cracking is achieved. No effect. Incidentally, the width reduction before the final reduction of such hot rough rolling is mainly to shape the side surface, excessive width reduction is not necessary, and if the width reduction amount is too large, the plate will buckle or buckle. Since the plate may bend in the width direction and may cause uneven rolling, the maximum width reduction amount is preferably about 70 mm.

Further, after the final reduction of the hot rough rolling, the plate thickness is thin, and therefore, as described in JP-A-61-71104, if the width reduction amount is 5 mm or more, the side surface is reduced. Although the shaping effect of is obtained, it is not enough to form an edge-up shape effective for preventing ear cracks,
A width reduction of 20 mm or more is required. And the width reduction amount
If it exceeds 50 mm, the widthwise end of the sheet bar becomes wavy in the lengthwise direction, and uneven stress is applied to this end during finish rolling, causing edge cracking.

Next, in the third aspect of the invention, the conditions that can reduce the edge cracks when the width reduction is performed three times or more are defined. In the hot rough rolling, an edger roll is used. The width reduction is performed for three or more passes, and the average value of the width reduction amounts of the final two passes of the width reduction passes is made larger than the average value of the width reduction amounts of the previous passes, and the width of the final two passes. The average amount of reduction is in the range of 25 to 80 mm. The reason why such a configuration is effective for preventing ear cracking is considered as follows.

In the width reduction after the final reduction whose main purpose is to increase the thickness of the widthwise end portion of the seat bar to form an edge-up shape, a large amount of reduction is required to prevent ear cracking. preferable. On the other hand, in the case where the width reduction is performed three times or more as in the third aspect of the invention, a plurality of width reductions having the main purpose of shaping the side surface of the sheet bar are applied before the final reduction of the hot rough rolling. Become. In such a plurality of width reductions before the final reduction, each width reduction amount is smaller than that in the case of performing the width reduction once before the final reduction as in the second invention. Therefore, from the viewpoint of preventing edge cracks mainly by thickening the edge part in the width direction of the seat bar to make it edge-up shape, the width reduction amount after the final reduction after the hot rough rolling is the width reduction amount before that. It is relatively large compared to the quantity.
As a result, the configuration of the third invention in which the average value of the width reduction amounts of the final two passes of the width reduction passes is made larger than the average value of the width reduction amounts of the previous passes is effective in preventing ear cracking. It is thought that it is.

Thus, in the third invention, if the average value of the width reduction of the edger roll in the final two passes is less than 25 mm, the recrystallization of the edge portion of the sheet bar becomes difficult to proceed, and coarse grains remain. In such a case, a large concave notch is likely to occur at the grain boundary portion, and as a result, the frequency of ear cracking increases. In addition, it is difficult to obtain a sufficient ear cracking effect because the shape correction effect of the edger roll is reduced. On the other hand, if the average value of the width reduction of the final two passes by the edger roll exceeds 80 mm, the shape becomes extremely bulged at the edge portion, resulting in defective shape.

Further, the average value of the width reduction amount by the edger roll before the final two passes does not have much influence on the occurrence of ear cracking, but the average value of the width reduction amount in the final two passes is not so much. It is important to be bigger than the previous one. This is because by making the average value of the width reduction amounts of the final two passes larger than the average value of the width reduction amounts before that, mainly the shape correction effect before finish rolling can be increased, and this is effective for preventing ear cracking. It is thought to contribute. If the number of passes for such width reduction is 3 or more,
There is no particular limitation. From the viewpoint of shape correction, it is more effective to perform only edging without rolling in the final two stands of rough rolling.

Next, in the fourth aspect of the invention, a more preferable condition for reducing the edge cracks when the width reduction is performed three times or more is defined. In the hot rough rolling, the edger is used. The width reduction by the roll is configured to be performed under the condition that the following formula is satisfied in relation to the plate thickness at the central portion in the width direction of the steel plate at that time.

[Equation 4] 0.3 {(E ₁ / h ₁ ) + (E ₂ / h ₂ )} ≦ E / h E ₁ > 0, E ₂ > 0 where E and h are the final stand of the rough rolling mill, respectively. The width reduction amount (mm) between the first stand of the finish rolling mill, the plate thickness (mm) at the widthwise central portion, E ₁ and h ₁ are the width reduction amount (mm) between the last two stands of the rough rolling mill, respectively. The plate thickness (mm) in the width direction central part, and E ₂ and h ₂ are the width reduction amount (mm) between the 2nd stand and the 3rd stand from the last of the rough rolling mill, and the plate thickness (mm) in the width direction center part, respectively. .

The reason why ear cracking is more effectively suppressed by the structure of the fourth invention is considered as follows.

0.3 {(E ₁ / h ₁ ) + (E ₂ /
The formula h ₂ )} ≦ E / h means that the width reduction between the final stand of rough rolling and the first stand of finish rolling is relatively larger than the width reduction before that. . When such width reduction is performed, the thickness of the widthwise end portion becomes larger than the thickness of the widthwise center portion in the sheet bar cross-sectional shape before finish rolling. Thus, ear cracking can be suppressed.

In this formula, the width reduction amount is expressed with respect to the thickness of the seat bar. This is because different plate thicknesses have different effects on the sectional shape of the sheet bar even with the same amount of reduction. In other words, if the plate thickness is large, it is difficult for the seat bar to have an edge-up shape even with a large reduction amount.

In such a formula, E ₁ and E ₂ take positive values. That is, it is essential to perform width reduction between the last two stands of the rough rolling mill and between the two stands and the three stands from the last of the rough rolling mill. This is because the shape of the side surface of the seat bar is adjusted as described above to eliminate the notch-shaped concave portion that is the starting point of the ear crack. More specifically, the rolled plate is normally expanded in width due to triaxial stress acting on both side edges thereof during rolling. At this time, when the shape of both side edges of the seat bar, that is, the shape of the ears is irregularly wavy, local stress concentration occurs, causing internal cracks and eventually causing ear cracks. Therefore, in order to correct the shape of the ears, width reduction is performed during rough rolling. Since it is desirable to correct such a shape at regular intervals while the deterioration of the cross-sectional shape is slight, E ₁ and E ₂ have positive values in the fourth invention.

Since the temperature is high during the rough rolling as described above, the deformation resistance is small and the tensile stress at the widthwise end is small. Therefore, during the rough rolling, ear cracks are less likely to occur, so that the values of E ₁ and E ₂ with respect to the thickness of the sheet bar may be small. Edge-up of the cross section of the sheet bar between the last two stands of the rough rolling mill or between the two stands and the third stand from the last of the rough rolling mill is effective from the viewpoint of preventing edge cracking, but continues if the edge-up amount is too large. During rolling, the stress state at the end portion in the width direction of the sheet bar becomes extremely uneven, so that cracks tend to occur. Therefore, the values of E ₁ and E _{2 with} respect to the thickness of the sheet bar are within a range that satisfies the relationship of 0.3 {(E ₁ / h ₁ ) + (E ₂ / h ₂ )} ≦ E / h.

However, in terms of the width reduction amount itself, E
_{Since the} plate thicknesses h ₁ and h ₂ are thicker than h, ₁ and E ₂ can take values larger than the width reduction amount E after the final horizontal reduction within the range satisfying the above formula. Therefore, it is possible to maximize the effect of adjusting the shape of the side surface of the seat bar to eliminate the notch-shaped recess that becomes the starting point of the ear crack. Therefore, ear cracking can be suppressed more effectively.

Next, in a fifth aspect of the invention, as a more preferable aspect of the first to fourth aspects of the invention, the temperature of the side of the sheet bar on the exit side of the final stand of hot rough rolling is set to 1050 to 1200 ° C. This is because the temperature on the side of the seat bar is 1050 ~
This is because in the range of 1200 ° C, the ear crack depth was within 5 mm, and better results were obtained. This FIG.
It shows the results of an experiment in which the temperature of the side of the sheet bar on the delivery side of the final stand of the hot rough rolling was variously changed in (Experiment 1) described above. The reason why the results shown in FIG. 7 were obtained is presumed to be that when the side temperature of the sheet bar was less than 1050 ° C., the inhibitor was coarsely precipitated at the grain boundaries, and cracks were generated from this as a starting point. On the other hand, when the side temperature of the sheet bar exceeds 1200 ° C., it is speculated that the crystal grains at the edge portion become coarse and cracks occur starting from the grain boundaries.

Next, in the sixth invention, as a more preferable embodiment of the first to fifth inventions, the temperature difference over the longitudinal direction of the side surface of the sheet bar on the final stand exit side of the hot rough rolling is set to 100 ° C.
Within. This is because, as shown in FIG. 8, if the temperature difference in the longitudinal direction of the side surface of the seat bar is within 100 ° C., the depth of the edge crack is within 3 mm, which is an extremely good level. The reason why the edge cracking increases when the temperature difference in the longitudinal direction on the side surface of the seat bar exceeds 100 ° C is that the high temperature part and the low temperature part are alternately arranged in the slab in such a case.
It is considered that during hot rough rolling, cracking has already occurred due to the difference in deformation resistance between the high temperature portion and the low temperature portion. The experimental results shown in FIG. 8 are the same as those in (Experiment 1) described above. After the induction heating of the slab at 1400 ° C., the edge heater is operated before the start of the hot rough rolling, and the output of the edge heater is By controlling the side temperature of the sheet bar after rough rolling. As a specific means for keeping the temperature difference in the longitudinal direction of the side surface of the seat bar within 100 ° C in this way, in addition to the method of using the edge heater described above, a sheet bar edge such as plasma heating of the edge portion or electron beam heating is used. Any method such as a method of controlled heating in the longitudinal direction or a method of enhancing uniformity during heating of the slab so that a temperature difference in the longitudinal direction of the sheet bar does not occur may be used.

Next, in the seventh and eighth inventions, the amount of C is
It is possible to sufficiently suppress the edge crack even in a condition where the edge crack is likely to occur in the range of 0.05 to 0.1 mass% and the sheet bar temperature (FET) before finishing hot rolling is 1100 ° C. or more. The reason why ear cracking is likely to occur under the condition that the C amount is in the range of 0.05 to 0.1 mass% and the sheet bar temperature (FET) before finish hot rolling is 1100 ° C. or higher is considered as follows.

As described above, it is considered that the α-γ transformation has hardly occurred just after the rough rolling of the hot rolling, but the sheet bar temperature (FET) before the finish hot rolling is
At 1100 ° C or higher, α-γ transformation is considered to be in progress. If the surface of the seat bar is rapidly water-cooled in such a state, the difference in the γ fraction based on the temperature difference between the surface of the seat bar and the inside becomes large and a difference in the deformation resistance between the surface and the inside occurs. Therefore, it is considered that ear cracking is promoted. This tendency becomes remarkable particularly in the vicinity of the side surface of the sheet bar where the temperature is likely to decrease or the higher the C content, the more the γ amount tends to increase.

Therefore, in the seventh and eighth inventions, water cooling of the surface of the sheet bar is avoided, and specifically, descaling using high-pressure water on the entry side of the finishing rolling mill is omitted, or the finishing rolling mill is omitted. By omitting strip coolant on the inlet side or inlet / outlet side of the first stand, the temperature drop of the seat bar surface temperature is suppressed, and ear cracking is sufficiently suppressed even under the above-mentioned disadvantageous conditions. Can be done.

Next, the ninth invention will be described. This ninth
The invention achieves the suppression of edge cracking that occurs during hot finish rolling by controlling the tension during this hot finish rolling.

That is, it is considered that the edge cracking at the time of hot rolling is caused by the material or when the tension acting on the widthwise side edge portion of the sheet bar becomes large and exceeds the deformability of the edge portion. It is conceivable that this edge crack causes a small edge crack in the front stand of the hot finish rolling mill, and in the latter stand, the plate thickness becomes thin so that the crack expands and becomes a large edge crack.

Here, when rolling the sheet bar by hot finish rolling, so-called plate thickness setup is carried out in which the opening of the reduction roll is set in advance on the basis of the deformation resistance of the sheet bar, the temperature, and the like. Therefore, in this hot finish rolling, if the deformation resistance and the temperature of the sheet bar are different from those predicted, the accuracy of the predicted rolling load deteriorates and the plate thickness error on the stand-out side increases. At this time, unbalance of mass flow may be caused and excessive tension may be generated between the stands. In particular, there is a problem at the leading end biting portion and the rear end portion of the sheet bar, and also during rolling of the steady portion, the tension may change due to a deformation resistance error due to a temperature error, which poses a problem. Such excessive tension is considered to be a factor in the occurrence of ear cracks.

In this respect, the conventional technique of Japanese Patent Laid-Open No. 61-9
Japanese Patent No. 6032 discloses a reduction in ductility 930-11
The method of limiting the rolling reduction in the temperature range of 50 ° C to 50% is not effective for preventing the above-mentioned ear cracking, but since the rolling reduction is suppressed, uniform organization after hot rolling is achieved. The magnetic properties may be deteriorated. In addition, Japanese Unexamined Patent Publication
In the method disclosed in Japanese Patent Application Laid-Open No. 2-196328, in which the width reduction is performed on the inlet side and the outlet side of the finishing rolling mill, the first finishing rolling mill row is used.
Although a slight effect was observed with respect to ear cracks generated in the stand, there was little effect with respect to the occurrence of ear cracks in and after the second stand, and ear cracks could not be prevented over the entire length of the coil.

Therefore, the ninth aspect of the present invention achieves the suppression of edge cracking that occurs during hot finish rolling by operating the tension between stands at 3 kgf / mm ² or less over the entire plate length during this hot finish rolling.

The results of experimentally obtaining the relationship between the ear crack and the tension between the stands will be described below. C: 0.05 mass%, Si: 3.
2 mass%, Mn: 0.06 mass%, Se: 0.01 mass%, Al: 0.02
Steel containing mass% and N: 0.007 mass% was melted using a 180 t converter and a vacuum degassing device, and continuously cast into a slab having a thickness of 220 mm and a plate width of 1100 mm. These slabs were heated in a gas combustion furnace, pre-rolled to a thickness of 200 mm, further induction-heated to 1400 ° C. to solution-inhibit, and then hot rough rolled to a sheet bar of a thickness of 45 mm.
Following this rough rolling, a finishing mill was used to finish the product to 2.4 mm. Here, the tension between the stands was intentionally increased at the central portion in the longitudinal direction of the coil. FIG. 9 shows the measured tension between the first stand and the second stand of the finish rolling equipment and the number of edge cracks in comparison during the finish rolling. Ear cracks were counted when the crack depth (distance from the edge) was 5 mm or more.
As is clear from FIG. 9, there is a good correlation between the inter-stand tension and the number of ears cracks generated over the entire length of the plate, and it is possible to prevent the ears crack from occurring by reducing the tension between the stands. Therefore, it is presumed that in the ninth invention, the tension acting on the edge portion can be reduced by reducing the tension between the stands, and the occurrence of ear cracks can be reduced.

FIG. 10 is a front view and a plan view schematically showing a front stand of a hot finish rolling mill train to which the ninth invention is applied. In FIG. 10, number 1
Is a sheet bar, 2 is a rolled sheet bar (referred to as a plate between stands), 3 is a work roll, 4 is a backup roll, 5 is a tension gauge between stands, 6 is a pinion stand, 7 is a motor, 8 is a motor. The control device 9 is a tension calculation device.

In the ninth invention, in order to prevent an excessive tension between the stands, the tension between the stands is detected by installing the tensiometer 5 between the stands as shown in FIG. 10,
The work roll peripheral speed is controlled so that the target tension is obtained. The structure is such that the plate pressed by the first stand bites into the second stand, and at the same time the inter-stand tension meter 5
The tension is detected by. When the detected tension is larger than the target tension, the motor speed control device 8 changes the speed of the motor so that the deviation becomes smaller. When the speed of the motor changes, a difference between the mass flow on the outlet side of the first stand and the mass flow on the inlet side of the second stand occurs, so that the tension between the stands can be reduced. Although such tension control is general, in the ninth aspect of the invention, the inter-stand tension is set to 3 kgf / mm ² or less over the entire width in order to prevent ear cracking. When the inter-stand tensiometer cannot be installed, the same effect can be obtained by the conventional looperless rolling method (calculating the inter-stand tension from the torque of the mill motor).

In the tenth aspect of the invention, the sheet bar after the hot rough rolling has a thickness t e (mm) at the side edge of the sheet bar and a thickness t c (mm) at the center in the width direction of the sheet bar. With regard to the relationship, the configuration is such that the following expression te-t c ≧ 1 (mm) is satisfied, and during hot finish rolling, the tension between stands is 3 kgf / mm ² or less over the entire plate length.

The ear crack preventing effect of the tenth invention will be described. FIG. 11 shows C: 0.05 mass%, Si: 3.2 mass%,
For steels containing Mn: 0.06 mass%, Se: 0.01 mass%, Al: 0.02 mass% and N: 0.007 mass%, an edger roll is arranged on the entry side of the finishing rolling mill row to perform various edger rolling conditions. The relationship between the edge-up amount (te-tc) and the edge crack at the widthwise end of the seat bar was investigated by. The number of ears cracks was checked at the tip of the coil. From this Fig. 11, the edger roll on the entry side of the finishing rolling facility was used to remove the sheet bar side end (25 mm from the side end
It can be seen that by setting the edge-up amount (te-tc) of the position) to 1 mm or more, the number of occurrence of ear cracks is significantly reduced. Further, the smaller the tension between the finishing first stand and the second stand, the less the ear cracking.

By increasing the plate thickness of the end portion on the side of the seat bar as described above, the edge cracking is reduced because the thickness of the end portion on the side of the sheet bar is increased to increase the rolling reduction of the end portion during rolling.
Inevitably, rolling distortion in the longitudinal direction becomes large with respect to the center of the plate width at the edges, so even if compressive stress or tension is applied to the side edges of the plate, a small force acts, causing ear cracking. Is expected to decrease.

FIG. 12 is a schematic view of the rough rolling mill outlet side and finishing in order to make the difference te −tc between the seat bar edge portion (te) and the central portion (tc) of 1 mm or more, which is suitable for the tenth invention. It is a schematic diagram of an edger roll installed on the inlet side of a rolling mill train and a front stand of a hot finish rolling mill.
An edger roll 10 is installed on the inlet side of the finishing rolling mill train, that is, on the outlet side of the rough rolling mill, and it is rolled down by a rolling-down position command device 13 so that the target edge-up amount is obtained based on the measurement result of the plate profile meter 11. Activate device 12 to activate edger roll
Controls the rolling position of 10. Here, as the sensor for measuring the sheet bar plate profile, a conventionally known profile meter such as X-ray, γ-ray or laser distance meter may be used.

The plate thickness at the side edge of the seat bar is preferably 1 mm or more thicker than the center thickness in a wide edge range, but it is preferably at least 1 mm at a position 25 mm from the side edge. In addition, the difference in plate thickness te −
If tc exceeds 10 mm, buckling in the plate width direction occurs, so
It is preferable to raise the edge portion up to about 10 mm at the maximum. In the tenth invention, the difference between the thickness of the edge portion and the thickness of the central portion is 1 mm or more as in the first invention, and the inter-stand tension is 3 kgf / mm ² or less by the inter-stand tension control as in the ninth invention. By doing so, ear cracking is prevented.

Next, in the eleventh invention, as a more preferable embodiment of the tenth invention, the flow rate of the cooling liquid to the work rolls of the hot finish rolling mill is changed in the roll axial direction to suppress the thermal crown of the work rolls. To do. The reason for changing the coolant flow rate in the roll axis direction is to prevent the thermal crown from growing as much as possible. That is, when the thermal crown becomes large, the same effect as when the work roll is provided with a convex crown is obtained, so that the rolling reduction at the plate end becomes small. Therefore, a large tension is generated at the end. As described above, since the edge cracks occur when the tension at the edge portion increases, the 11th aspect of the present invention aims to suppress the increase of the thermal crown by particularly cooling the axial center portion of the work roll during rolling. ing.
Since the thermal crown is a thermal expansion, its size can be easily obtained by measuring the surface temperature of the roll. Further, the relatively gentle cooling of the work roll in the region corresponding to the plate end portion also contributes to the prevention of the temperature decrease at the plate edge portion, which contributes to the prevention of the occurrence of edge cracks.

FIG. 13 shows the results of intensive cooling of the surface of the work roll corresponding to ½ of the plate width centering on the central portion in the roll axial direction. It can be seen from the figure that the occurrence of ear cracks can be effectively prevented by preventing the thermal crown from increasing.

FIG. 14 is a front view and a plan view schematically showing equipment suitable for application to the eleventh invention,
FIG. 15 shows a main part of this equipment, in which a coolant nozzle is provided in the barrel direction of the work roll 3 of the finishing rolling equipment.
20 are arranged. An electromagnetic valve 21 is arranged in each of the coolant nozzles, and the measurement result of a thermometer 24 for measuring the surface temperature of the work roll 3 is input from a temperature signal converter 25 to a control device 26, and this control device 26 causes the solenoid valve to operate. Pump 21 is controlled from coolant tank 22 by controlling turning on and off.
Changes the flow rate of the coolant introduced in the work roll axial direction. Thus, in addition to the structure of the tenth aspect of the invention, the eleventh aspect of the invention performs thermal crown control of the work roll.

The control method of the thermal crown is such that the difference in the surface temperature of the work rolls (the temperature difference between the part of the work roll rolling the central part of the plate width and the part rolling the plate edge part) is smaller than a predetermined temperature. The nozzles arranged in the barrel direction of the work roll are turned on and off. Although it is preferable to predict the thermal crown using a thermometer, the roll temperature may be calculated by the conventional work roll temperature calculation.

Next, typical compositional ranges of the grain-oriented electrical steel sheet to which the present invention is applied are as follows. C: 0.01 to 0.10 mass% C is a component useful not only for uniform dispersion of the composition during hot rolling and cold rolling but also for development of Goss-oriented crystal grains, and it is desirable to contain at least 0.01 mass%. . However, if the content exceeds 0.10 mass%, decarburization becomes difficult and the accumulation of Goss-oriented crystal grains is rather disturbed. Therefore, the upper limit is preferably 0.1 mass%.

Si: 2.5-4.5 mass% Si is an effective component for increasing the specific resistance of the steel sheet and reducing the iron loss, but if the content exceeds 4.5 mass%, the cold ductility is impaired, while If the content is less than mass%, not only the resistivity decreases, but also the crystal orientation becomes random due to α → γ transformation during the final finishing annealing performed for secondary recrystallization and purification. Since the iron loss reducing effect cannot be obtained, the Si content is preferably in the range of 2.5 to 4.5 mass%.

Mn: 0.02 to 0.12 mass% Mn is at least 0.02 mass% in order to prevent hot brittleness.
However, if the Mn content is too large, the magnetic properties are deteriorated, so the upper limit is preferably set to about 0.12 mass%.

As the inhibitor, MnS, MnSe type or
The AlN series can be used alone or in combination. Of the constituent components of MnS and MnSe as inhibitors, S,
At least one selected from Se: 0.005 to 0.06ma
Both ss% S and Se are effective as constituent components of the inhibitor that controls the secondary recrystallization of the grain-oriented electrical steel sheet. From the viewpoint of such suppressing power, at least about 0.005 mass% is required, but if the content exceeds 0.06 mass%, the effect is impaired. Therefore, the lower and upper limits are 0.00
It is preferably 5 mass% or 0.06 mass%.

Among the constituent components of AlN as an inhibitor, Al: 0.005 to 0.10 mass%, N: 0.004 to 0.015 mass
The ranges of% Al and N are also set to the above ranges for the same reason as in the case of MnS and MnSe described above.

As the inhibitor component, Cu, Sn, Sb, Mo, Ti, Bi and the like, besides the above-mentioned S, Se and Al, also act advantageously, so these components should be added in small amounts. You can also The preferred range of these components is Cu,
0.01 to 0.15 mass% Sn, 0.005 to 0.1 Sb, Mo, Ti and Bi
Mass%, and each of these inhibitor components can also be used alone or in combination of two or more.

A slab for such grain-oriented electrical steel sheets is used, for example, 13
After heating at 00 to 1420 ° C., hot rough rolling and then hot finish rolling are performed. During the hot rough rolling and finish rolling, the steps according to the present invention are performed. After that, one or two or more cold rollings with intermediate annealing are applied to finish to the final thickness, then decarburization annealing is applied, and then an annealing separator is applied to the surface of the steel sheet, followed by final finishing annealing. To obtain grain oriented electrical steel sheet.

[0098]

【Example】

(Embodiment 1) An embodiment of the first invention will be described. Steel having the components shown in Table 5 was melted by a converter and a vacuum degassing device, and continuously cast into a slab having a thickness of 220 mm and a width of 1200 mm. After heating these slabs in a gas-fired furnace, pre-rolling them to 200 mm
The thickness of the inhibitor was increased to 1420 ° C. in an induction heating furnace to solution-inhibit the inhibitor, and then rough rolling was performed to obtain a 50 mm sheet bar. The thickness of the sheet bar width center and the edge portion at this time were set to various values by the combination of horizontal roll shift control of the rough rolling rolls and width rolling by the vertical rolls, and the thicknesses were measured online. Subsequent hot rolling was performed to obtain a 2.4 mm hot rolled sheet. The frequency of occurrence of ear cracks and the crack depth were observed over the entire length of these hot-rolled sheets. FIG. 16 shows the relationship between the thickness of the sheet bar and the edge crack.

[0099]

[Table 5]

As can be seen from FIG. 16, the fitting example according to the first aspect of the invention is small in both the frequency of occurrence of cracks and the depth of cracks and good results are obtained. According to the invention, the cracks of edges generated in the edge portion of the hot rolled sheet are effective. It was shown that it can be prevented.

(Embodiment 2) An embodiment of the second invention will be described.
Steel having the components shown in Table 6 was melted by a converter and a vacuum degassing device, and continuously cast into a slab having a thickness of 220 mm and a width of 1150 mm. These slabs were heated in a gas combustion furnace, then heated to 1420 ° C. in an induction heating furnace to perform solution treatment of the inhibitor component, and then hot rough rolling was performed to obtain a sheet bar having a thickness of 40 mm. During this rough rolling, the width reduction roll was set to various values to perform the width reduction, and the width of the material to be rolled was measured online. Subsequent hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.6 mm. The frequency of occurrence of edge cracks at the ends and the crack depth were observed over the entire length of these hot-rolled sheet coils. Table 7 shows the relationship between the width reduction amount and the edge crack before and after the rough rolling final stand.
As can be seen from Table 7, in the conformity example according to the second invention, both the occurrence frequency of ear cracks and the crack depth were small, and good results were obtained.

[0102]

[Table 6]

[0103]

[Table 7]

(Embodiment 3) An embodiment of the third invention and the fifth and sixth inventions will be described. C: 0.065 mass%, Si: 3.2 mass%,
Mn: 0.07 mass%, Se: 0.018 mass%, Al: 0.026 mass
%, N: 86 wtppm, Sb: 0.028 mass% and Cu: 0.08 mass
% Molten steel was melted by a 180 t converter and a vacuum degassing device, and a plurality of slabs having a thickness of 210 mm and a width of 1400 mm were prepared by continuous casting. These slabs were heated in a gas-fired furnace, pre-rolled to a thickness of 200 mm, further induction-heated to 1400 ° C. for solution treatment of the inhibitor component, and hot-rolled into a sheet bar having a thickness of 45 mm. An induction heating type edge heater was arranged prior to this rough rolling, and the edge temperature of the slab was variously changed by controlling the heater output. Also,
At the time of this rough rolling, the width reduction was performed by the edger roll in four types of 3 to 6 passes, and the width reduction amount in each pass was variously changed.

After the hot rough rolling, finish rolling was continuously carried out to obtain a hot rolled sheet having a thickness of 2.4 mm. The edge crack depth of the edge portion (depth of the edge crack extending from the edge portion toward the center in the width direction) was investigated over the entire length of these hot-rolled coils. Table 8 shows the results. As is clear from Table 8, the conformity example according to the present invention can effectively reduce ear cracking more than ever before.

[0106]

[Table 8]

(Embodiment 4) An embodiment of the third invention and the fifth and sixth inventions will be described. C: 0.070 mass%, Si: 3.3 mass%,
Mn: 0.07 mass%, S: 0.019 mass%, Al: 0.024 mass
%, N: 84 wtppm, Cu: 0.12 mass% and Sn: 0.09 mass%
A molten steel containing slab was melted by a 180 t converter and a vacuum degassing device, and a plurality of slabs having a thickness of 210 mm and a width of 1400 mm were prepared by continuous casting. After heating these slabs in a gas combustion furnace,
After pre-rolling to a thickness of 200 mm and induction heating to 1400 ° C to solution-process the inhibitor component, hot rough rolling was performed to 45
The sheet bar has a thickness of mm. An induction heating type edge heater was arranged prior to this rough rolling, and the edge temperature of the slab was changed variously by controlling the current. In this rough rolling, the width reduction was performed by an edger roll in four types of 3 to 6 passes, and the width reduction amount in each pass was variously changed.

After the hot rough rolling, finish rolling was continuously carried out to obtain a hot rolled sheet having a thickness of 2.4 mm. The edge crack depth of the edge portion (depth of the edge crack extending from the edge portion toward the center in the width direction) was investigated over the entire length of these hot-rolled coils. The results are shown in Table 9. As is clear from Table 9, the conformity example according to the present invention can effectively reduce ear cracking more than ever before.

[0109]

[Table 9]

(Embodiment 5) An embodiment of the fourth invention will be described.
C: 0.055 mass%, Si: 3.25 mass%, Mn: 0.070 mass
%, S: 0.026 mass%, Al: 0.021 mass%, N: 0.0085
Steel containing mass% was melted by a 180 t converter and a vacuum degassing device and continuously cast into a slab with a thickness of 220 mm and a width of 1300 mm. After heating these slabs in a gas-fired furnace, they were heated to 1420 ° C in an induction heating furnace to solution-inhibit components, and then hot rough rolling was performed to a sheet bar with a thickness of 45 mm, followed by finish rolling. The hot rolled sheet had a thickness of 2.2 mm. At the time of this hot rough rolling, the opening degree of each edger roll is set to 3
The width reduction was performed by changing the street. Further, the thickness of the central portion in the width direction of the plate and the plate width were measured online at any time. The occurrence of edge cracking in these hot-rolled sheet coils was investigated and the results shown in Table 10 were obtained. As can be seen from the results, the conformity example according to the present invention has both the occurrence frequency of ear cracks and the crack depth,
Good results have been obtained.

[0111]

[Table 10]

(Embodiment 6) An embodiment of the fifth and sixth inventions will be described. C: 0.074 mass%, Si: 3.3 mass%, Mn: 0.07mass
%, Se: 0.017 mass%, Al: 0.023 mass%, N: 82 wtpp
18 steel containing m, Sb: 0.024 mass% and Cu: 0.07 mass%
A slab having a thickness of 220 mm and a width of 1400 mm was prepared by melting with a 0 t converter and a vacuum degassing device and continuous casting.
These slabs are heated in a gas combustion furnace and then pre-rolled to 200 mm
The thickness of the sheet was further increased by induction heating to 1400 ° C. to perform solution treatment of the inhibitor component, and then hot rough rolling was performed to obtain a sheet bar having a thickness of 45 mm. Prior to this rough rolling, an induction heating type edge heater was arranged and the temperature of the edge portion of the slab was changed variously by controlling the current. Further, in this rough rolling, the width reduction by the edger roll is intentionally changed by changing the reduction amount in various ways so as to intentionally change the thickness tc of the center portion in the width direction and the thickness te of the side edge portion of the sheet bar. . The tc and te were measured by an online measuring device.

After the completion of rough rolling, finish rolling was continuously performed to obtain a hot rolled sheet having a thickness of 2.4 mm. The frequency of occurrence of edge cracks at the edges and the depth of edge cracks (depth of edge cracks extending from the edge to the center in the width direction) were investigated over the entire length of these hot-rolled coils. Table 11 shows the results. As is clear from Table 11, the adaptation example according to the present invention can effectively reduce ear cracking more than ever before.

[0114]

[Table 11]

(Embodiment 7) An embodiment of the fifth and sixth inventions will be described. C: 0.070 mass%, Si: 3.2 mass%, Mn: 0.06 mass
%, S: 0.018 mass%, Al: 0.025 mass%, N: 88 wtpp
180 steel containing m, Cu: 0.10 mass% and Sn: 0.09 mass%
t A slab having a thickness of 220 mm and a width of 1400 mm was prepared by melting with a converter and a vacuum degassing device and continuous casting. These slabs were heated in a gas combustion furnace and then pre-rolled to a thickness of 200 mm, further induction-heated to 1400 ° C. to perform solution treatment of the inhibitor component, and then hot rough rolling was performed to obtain a sheet bar having a thickness of 45 mm. Prior to this rough rolling, an induction heating type edge heater was arranged and the temperature of the edge portion of the slab was changed variously by controlling the current. Further, in this rough rolling, the width reduction by the edger roll is intentionally changed by changing the reduction amount in various ways so as to intentionally change the thickness tc of the center portion in the width direction and the thickness te of the side edge portion of the sheet bar. . Also, this tc and t
e was measured by an online measuring instrument.

After the completion of rough rolling, finish rolling was carried out to obtain a hot rolled sheet having a thickness of 2.4 mm. The frequency of occurrence of edge cracks at the edges and the depth of edge cracks (depth of edge cracks extending from the edge to the center in the width direction) were investigated over the entire length of these hot-rolled coils. Table 12 shows the results. As is clear from Table 12, the adapted example according to the present invention can effectively reduce ear cracking more than ever before.

[0117]

[Table 12]

(Embodiment 8) An embodiment of the first, seventh and eighth inventions will be described. C: 0.072 mass%, Si: 3.28 mass%, Mn: 0.07
1 mass%, Se: 0.018 mass%, Al: 0.025 mass%, N:
0.0084 mass%, Sb: 0.023 mass% and Cu: 0.010 mass%
Steel containing steel is melted and made into a slab by continuous casting. 1420
After soaking at ℃ for 30 minutes, hot rough rolling was performed to obtain a sheet bar having a thickness of 40 mm. Before finish rolling, the width reduction by the edger was performed by changing the width reduction amount in various ways to change the value of te-tc, and also the cooling method of the sheet bar. Furthermore, after hot-rolling these materials to a thickness of 2.2 mm,
After annealing the hot-rolled sheet at 1000 ° C and performing the first cold rolling
Intermediate annealing was performed at 1100 ° C, and the second rolling was finished to 0.23 mm. Next, grooves having a depth of 20 μm and a width of 150 μm were introduced at a pitch of 5 mm in the width direction by the etching method for the purpose of subdividing the magnetic domains. After that, decarburization annealing was performed at 840 ° C., an annealing separating agent containing MgO as a main component was applied, and then final finishing annealing was performed in a N ₂ —H ₂ mixed atmosphere. Table 13 shows the frequency of occurrence of edge cracks in the hot rolled sheet and the magnetic characteristics of the product. It can be seen that the adaptation according to the invention effectively reduces ear cracking.

[0119]

[Table 13]

(Embodiment 9) An embodiment of the ninth, tenth and eleventh inventions will be described. C: 0.04 mass%, Si: 3.15 mass%, Mn: 0.07
A steel type containing mass%, Al: 0.026 mass% and N: 0.008 mass% was melted by a 180 t converter and a vacuum degassing device, and continuously cast into a slab having a thickness of 220 mm and a plate width of 1100 mm. After heating these slabs in a gas combustion furnace,
After pre-rolling to a thickness of 200 mm, induction heating was performed to a temperature of 1400 ° C to solution-inhibit the inhibitor component, and then hot rough rolling was performed to obtain a sheet bar having a thickness of 45 mm. Subsequent to this rough rolling, a finishing rolling facility was used to finish the plate to a thickness of 2.4 mm and a width of 1100 mm. An example of the finishing mill at this time is a continuous finishing mill having 7 stands as shown in FIGS. 17 (a) to (d), and the work roll diameter is 680 to 840 mm. Further, as shown in FIG. 17, a rolling mill of 6 stages is arranged in the 3 stands of the latter stage. The seat bar temperature on the side with the finishing stand is 1100
The temperature was ~ 1150 ° C. The target tension between stands is 1 kgf / mm ² between F1 and F4, and 1.5 kg between F4 and F7.
The setting value was f / mm ² . Under such conditions,
The following 5 examples were performed.

Adaptation example 1: Using the finishing rolling equipment train shown in FIG. 17 (a), the strip thickness deviation in the width direction is 0 (te-tc = 0).
By using a sheet bar of (about), the gain of the tension control is doubled to the normal value so that the inter-stand tension becomes the target tension in a short time. The reduction rate is
55% and the others did not exceed 50%.

Comparative Example 1: A sheet bar having a plate thickness deviation of 0 in the width direction was used by using the equipment row shown in FIG. 17 (a), but the tension control gain was set as usual. The reduction rate of each stand was set so as not to exceed 50%.

Comparative Example 2: Using the equipment row shown in FIG. 17 (d), a width press for shaping the end face on the entry side of the finish rolling mill was performed. The sheet bar used had a plate thickness deviation of 0 in the width direction, but the tension control gain was set as usual.
The reduction rate was set to 55% for the first and second stands, and did not exceed 50% for the other stands.

Adaptation example 2: Example of equipment shown in FIG. 17 (b),
That is, by using an equipment row in which an edger is installed on the entry side of the finishing stand, the plate thickness at a position 25 mm from the side edge of the sheet bar is made 1 mm or more thicker than the plate thickness in the central portion in the plate width direction. The measured value was in the range of 1.0 to 3.0 mm. With such a seat bar, tension between stands is 3 over the entire length of the plate.
Finish rolling was performed while controlling so that it was less than kgf / mm ² .

Adaptation example 3: the equipment sequence shown in FIG. 17 (c),
That is, using an equipment row in which an edger is installed on the entry side of the finishing stand and nozzles that can control the coolant flow rate in the roll axis direction are provided for the upper and lower work rolls of the finishing stand, the plate ends in the first to fourth stands are used. The temperature difference between the work roll temperature in the region where the strip is rolled and the work roll temperature in the region where the center of the plate width is rolled is set to be within 50 ° C. Further, in the 5th to 7th stands, it was set within 30 ° C. In this way, the plate thickness at the position 25 mm from the side edge of the seat bar is 1.5 to 3.5 mm larger than the plate thickness at the center in the plate width direction.
Finishing rolling was performed on the thickened sheet bar while controlling the tension between stands to be 3 kgf / mm ² or less over the entire length of the sheet.

First, the effect of the conforming example 1 will be clarified by comparing the conforming example 1 with the comparative examples 1 and 2. FIG. 18 shows the products (the 7th stand exit side) of 10 in the conformity example 1 and the comparative examples 1 and 2.
The number of ear cracks per 0 m was investigated on both sides. Also,
The first stand, which has a great influence on the occurrence of ear cracks-
The measurement results of the tension between the second stands are also shown together. In the conformity example 1, although the tension suddenly decreases to the target value after the second stand is bitten, and the tension stability between the first and second stands becomes small, it occurs at the tip of the seat bar. It can be seen that ear cracking is less than in Comparative Examples 1 and 2. In addition, Table 14 shows the results of investigating the number of ear cracks at the coil tip and the central portion in the longitudinal direction of the coil. The number of ear cracks was counted when the crack depth was 5 mm or more. It can be seen from Table 14 that the number of occurrence of ear cracks in the conforming example 1 is clearly smaller than that in the comparative examples 1 and 2.

[0127]

[Table 14]

Next, the effect of the conforming example 2 will be clarified by comparing the conforming example 2 with the comparative examples 1 and 2. Table 15 shows the results of examining the number of ear cracks at the coil tip 100 m and the coil longitudinal center 100 m. The number of ear cracks was counted when the crack depth was 5 mm or more. From Table 15, the difference between the plate thickness te at the edge part and the plate thickness tc at the center part in the plate width direction is set to 1 mm or more, and the tension between the stands is 3 kgf / mm ² over the entire plate length.
It will be understood that the following effect is more remarkable than Comparative Examples 1 and 2 when the following is performed.

[0129]

[Table 15]

Next, the effect of the conforming example 3 will be clarified by comparing the conforming example 3 with the comparative examples 1 and 2. Table 16 shows the results of investigating the number of ear cracks at the coil tip 100 m and the longitudinal center 100 m of the coil. The number of ear cracks was counted when the crack depth was 5 mm or more. From Table 16, conformance example 3
In Comparative Examples 1 and 2, the total coolant flow rate is
It can be seen that, in spite of the setting of 1500 liters / minute / stand, the conforming example 3 has a remarkable effect of suppressing ear cracking as compared with the comparative examples 1 and 2.

[0131]

[Table 16]

[0132]

As is apparent from the above description,
According to the present invention, when manufacturing the grain-oriented electrical steel sheet, it is possible to effectively reduce the edge cracks that particularly occur at the widthwise end portions of the hot-rolled sheet in the hot rolling step. As a result, the amount of cut-off edge due to ear cracking can be reduced, and the product yield can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the difference between the thickness of the center portion in the width direction of the seat bar and the thickness of the side edge portion on the occurrence frequency of edge cracks and the edge crack depth of the edge portion of the hot rolled coil.

FIG. 2 is a graph showing the relationship between the width reduction amount before and after the final horizontal rolling stand of rough rolling and the state of edge cracking.

FIG. 3 is a graph showing the relationship between the average value of the width reduction amounts of the final two passes by the edger roll, the average value of the width reduction amounts of the previous passes, and the ear crack generation status.

FIG. 4 is a graph showing the effect of width reduction after the final stand of rough rolling and width reduction before it on the edge cracking frequency of the hot rolled sheet.

FIG. 5 is a graph showing the influence of width reduction after the final stand of rough rolling and width reduction before it on the edge crack depth of the hot rolled sheet.

FIG. 6 is a schematic view of a cross sectional shape of the seat bar before passing through the finishing first stand for explaining the thickness tc and the edge thickness te of the center portion in the seat bar width direction.

FIG. 7 is a graph showing a preferable range of the slab side surface temperature on the delivery side of the final hot rough rolling stand for reducing the depth of edge cracking.

FIG. 8 is a graph showing a preferable range of the temperature difference in the longitudinal direction of the slab side surface temperature on the delivery side of the final stage of hot rough rolling for reducing the depth of edge cracking.

FIG. 9 is a graph showing the results of examining the relationship between the inter-stand tension and the number of occurrence of ear cracks over the entire length of the coil.

FIG. 10 is a schematic diagram showing an example of a hot rolling facility suitable for applying the ninth invention.

FIG. 11 is a graph showing the results of examining the relationship between the edge-up amount (te −t c) and the edge crack at the widthwise end portion of the seat bar by changing the tension between the stands.

FIG. 12 is a schematic view showing an example of hot rolling equipment suitable for application to the tenth invention.

FIG. 13 is a graph showing the results of examining the relationship between the edge-up amount (te −t c) and the edge crack at the widthwise end of the sheet bar by changing the work roll cooling.

FIG. 14 is a schematic diagram showing an example of hot rolling equipment suitable for application to the eleventh invention.

FIG. 15 is a diagram showing a main part of a hot rolling facility suitable for application to the eleventh invention.

FIG. 16 is a graph showing the relationship between the thickness of the sheet bar and the edge crack.

FIG. 17 is a diagram showing hot finish rolling equipment used in Example 9;

FIG. 18 is a graph showing the results of examining the number of occurrence of ear cracks and the tension over the entire length of the coil in the first fitting example and the first and second comparative examples.

[Explanation of symbols]

 1 sheet bar 2 plate (after rolling the sheet bar) 3 work roll 4 backup roll 5 tension gauge between stands 6 pinion stand 7 motor 8 motor speed controller 9 motor speed calculator 10 finishing stand entry side edger 11 seat bar profile meter 12 pressure reduction Device 13 Roll-down position command device 14 Intermediate roll 15 Width press device 20 Coolant nozzle 21 Coolant on / off solenoid valve 22 Coolant tank 23 Pump 24 Work roll thermometer 25 Temperature signal converter 26 Solenoid valve control device

Front page continuation (72) Kiyoshi Wakabayashi Kiyoshi Wakabayashi 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama (No address) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Tetsuo Toge 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama None) Mizushima Steel Works, Ltd., Kawasaki Steel Co., Ltd. (72) Inventor, Isamu Iwaki, Mizushima Kawasaki-dori, 1-chome, Kurashiki City, Okayama Prefecture (No street number) Mizushima Steel Works, Ltd., Kawasaki Steel Co., Ltd. (72) Mitsumasa Kurosawa Mizushima, Kurashiki City, Okayama Prefecture Kawasaki Dori 1-chome (no house number) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Hisashi Nakano 1-chome, Mizushima Kawasaki Dori Kawasaki City, Okayama Prefecture (no house number) Kawasaki Steel Co., Ltd. Mizushima Steel Co., Ltd. (72) Inventor Hikita Toshiki 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Inside Mizushima Steel Works (72) Inventor, Shoho Kitahama 1-chome, Mizushima-Kawasaki-dori, Kurashiki-city, Okayama Prefecture (not in number) Mizushima Steel Co., Ltd. (72) Inventor Hiroshi Yoshida Mizushima, Kurashiki City, Okayama Prefecture Kawasaki Dori 1-chome (without street number) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Masao Akita 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Kawasaki Steel Co., Ltd. Chiba Steel Works

Claims (11)

[Claims] 1. C: 0.01 to 0.10 mass% and Si: 2.5 to 4.
The slab for grain-oriented electrical steel sheets containing 5 mass% is heated, then rough hot-rolled, then hot-finished, and then cold rolled once or twice with intermediate annealing. In producing a grain-oriented electrical steel sheet by a series of steps of applying a finishing separation anneal after applying an annealing separator on the steel sheet surface after finishing to a thickness and then decarburizing annealing, the sheet after the hot rough rolling Regarding the relationship between the thickness te (mm) of the side edge portion of the sheet bar and the thickness tc (mm) of the center portion in the width direction of the sheet bar, the bar is formed into a shape satisfying the following formula te −tc ≧ 1 (mm). A method for manufacturing a grain-oriented electrical steel sheet. 2. C: 0.01 to 0.10 mass% and Si: 2.5 to 4.
The slab for grain-oriented electrical steel sheets containing 5 mass% is heated, then rough hot-rolled, then hot-finished, and then cold rolled once or twice with intermediate annealing. After manufacturing a grain-oriented electrical steel sheet by a series of steps of finishing after thickening, followed by decarburization annealing, applying an annealing separator on the steel sheet surface and then performing final finishing annealing, the final reduction of the hot rough rolling is performed. On the entry side, the width reduction is 30 mm.
A method for producing a grain-oriented electrical steel sheet, which is performed as described above, and is subjected to width reduction within a range of a reduction amount of 20 to 50 mm after the final reduction and before the start of finish rolling. 3. C: 0.01 to 0.10 mass% and Si: 2.5 to 4.
The slab for grain-oriented electrical steel sheets containing 5 mass% is heated, then rough hot-rolled, then hot-finished, and then cold rolled once or twice with intermediate annealing. In producing a grain-oriented electrical steel sheet by a series of steps of finishing after thickening and then applying decarburization annealing, then applying an annealing separator to the steel sheet surface and then performing final finishing annealing, during the hot rough rolling, The width reduction by the edger roll is performed for three or more passes, and the average value of the width reduction amounts of the final two passes of the width reduction passes is made larger than the average value of the width reduction amounts of the previous passes, and A method for manufacturing a grain-oriented electrical steel sheet, characterized in that the average value of the width reduction of two passes is in the range of 25 to 80 mm. 4. C: 0.01 to 0.10 mass% and Si: 2.5 to 4.
The slab for grain-oriented electrical steel sheets containing 5 mass% is heated, then rough hot-rolled, then hot-finished, and then cold rolled once or twice with intermediate annealing. In producing a grain-oriented electrical steel sheet by a series of steps of finishing after thickening and then applying decarburization annealing, then applying an annealing separator to the steel sheet surface and then performing final finishing annealing, during the hot rough rolling, A method for producing a grain-oriented electrical steel sheet, characterized in that the width reduction by an edger roll is performed under the condition that the following expression is satisfied in relation to the sheet thickness at the central portion of the steel sheet width direction at that time. [Equation 1] 0.3 {(E ₁ / h ₁ ) + (E ₂ / h ₂ )} ≦ E / h E ₁ > 0, E ₂ > 0 where E and h are the final stand of the rough rolling mill, respectively. The width reduction amount (mm) between the first stand of the finish rolling mill, the plate thickness (mm) at the widthwise central portion, E ₁ and h ₁ are the width reduction amount (mm) between the last two stands of the rough rolling mill, respectively. The plate thickness (mm) in the width direction central part, and E ₂ and h ₂ are the width reduction amount (mm) between the 2nd stand and the 3rd stand from the last of the rough rolling mill, and the plate thickness (mm) in the width direction center part, respectively. . 5. The grain-oriented electrical steel sheet according to claim 1, wherein the temperature of the side surface of the sheet bar on the exit side of the final stand of hot rough rolling is set to 1050 to 1200 ° C. Production method. 6. The direction according to claim 1, wherein the temperature difference in the longitudinal direction of the side surface of the sheet bar on the exit side of the final stand of the hot rough rolling is within 100 ° C. For manufacturing high-performance electrical steel sheet. 7. When the amount of C is in the range of 0.05 to 0.10 mass% and the sheet bar temperature (FET) before finish hot rolling is 1100 ° C. or higher, high pressure water on the inlet side of the finish rolling mill is used. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the scaling is omitted to suppress the temperature drop of the sheet bar surface temperature. 8. When the C content is in the range of 0.05 to 0.10 mass% and the sheet bar temperature (FET) before finish hot rolling is 1100 ° C. or higher, the first stand of the finish rolling mill or the inlet or outlet side. 8. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the strip coolant is omitted to suppress the temperature drop of the sheet bar surface temperature. 9. C: 0.01 to 0.10 mass% and Si: 2.5 to 4.
The slab for grain-oriented electrical steel sheets containing 5 mass% is heated, then rough hot-rolled, then hot-finished, and then cold rolled once or twice with intermediate annealing. In order to manufacture grain-oriented electrical steel sheet by a series of steps of applying thickening finish and then decarburizing annealing, then applying an annealing separator on the steel sheet surface and then applying final finishing annealing, at the time of hot finish rolling, stand A method for producing a grain-oriented electrical steel sheet, characterized in that the inter-tension is operated at 3 kgf / mm ² or less over the entire length of the sheet. 10. C: 0.01 to 0.10 mass% and Si: 2.5 to
After heating the slab for grain-oriented electrical steel sheet containing 4.5 mass%, hot rough rolling and then hot finish rolling to obtain a hot rolled coil, the sheet bar after the hot rough rolling is Regarding the relationship between the thickness te (mm) of the side edge portion and the thickness tc (mm) of the central portion in the width direction of the sheet bar, a shape satisfying the following formula te-tc ≥1 (mm) is used, and hot finishing rolling is performed. At this time, the method for producing a grain-oriented electrical steel sheet is characterized in that the tension between stands is operated at 3 kgf / mm ² or less over the entire length of the sheet. 11. The grain-oriented electrical steel sheet according to claim 10, wherein the flow rate of the cooling liquid to the work rolls of the hot finish rolling mill is changed in the roll axial direction to suppress the thermal crown of the work rolls. Manufacturing method.