JP6763179B2 - Hot-rolled sheet for unidirectional electromagnetic steel sheet and its manufacturing method, and its unidirectional electromagnetic steel sheet manufacturing method - Google Patents

Description

The present invention relates to a hot-rolled sheet for grain-oriented electrical steel sheet with controlled deposits used for producing a unidirectional electrical steel sheet used for an iron core material of a transformer, a method for producing the same, and its unidirectionality. Regarding the manufacturing method of electrical steel sheets.

One-way electrical steel sheets are used as iron core materials for transformers. Since unidirectional electrical steel sheets are required to have a high magnetic flux density in the direction of magnetization, they are manufactured by selectively growing a crystal orientation called Goss, which has excellent magnetic properties, by utilizing secondary recrystallization. It is a functional material.

In recent years, in order to improve the energy efficiency of transformers, it has been required to further reduce the iron loss of grain-oriented electrical steel sheets. Since iron loss can be reduced by reducing the thickness of a unidirectional electromagnetic steel sheet, a thin unidirectional electromagnetic steel sheet is required.

In order to reduce the iron loss of grain-oriented electrical steel sheets, the precipitates that serve as inhibitors related to the expression mechanism of secondary recrystallization are appropriately controlled to obtain a secondary recrystallization structure with a high degree of magnetic flux integration. The magnetic flux density must be improved. As the precipitate used as an inhibitor, sulfide (MnS or the like) or nitride (AlN or the like) is generally known. Research on inhibitor control has been carried out conventionally, but the hot rolling process in which MnS is completely dissolved and then MnS is finely precipitated as an inhibitor stabilizes the secondary recrystallization structure and has a high magnetic flux density. This is an important process for realizing the production of directional electromagnetic steel sheets. Further, MnS precipitated on the hot-rolled sheet obtained by the hot-rolling step becomes a precipitation site of AlN in the subsequent hot-rolled sheet annealing, and by further performing decarburization annealing on the steel sheet after cold rolling together with AlN. The particle size of the obtained primary recrystallized grains is determined. Therefore, MnS precipitated on the hot-rolled plate directly or indirectly controls the behavior of secondary recrystallization.

In addition, secondary recrystallization starts from a decrease in inhibitor strength due to oxidation of AlN near the surface of the steel sheet, which is easily affected by the atmosphere during finish annealing, but when the plate thickness becomes thin, the effect of the atmosphere during finish annealing is affected. The proportion of the region in the thickness direction to be received increases. Therefore, the thinner the plate thickness, the more rapidly the inhibitor strength decreases due to the oxidation of the AlN inhibitor, and the preferential growth of Goss-oriented grains near the surface of the steel sheet becomes weaker. Therefore, normal grain growth and preferential growth of swinging Goss Is likely to occur, and secondary recrystallization becomes unstable. Further, another reason why the preferential growth property of the Goss-oriented grains in the vicinity of the surface of the steel sheet is weakened is that the primary crystal grains having random orientations other than Goss are larger than the Goss-oriented grains.

Therefore, in order to stabilize the secondary recrystallization structure and manufacture a unidirectional electromagnetic steel plate having a high magnetic flux density, the preferential growth potential of the Goss directional grains in the vicinity of the steel plate surface during the secondary recrystallization is further increased. In order to increase the concentration, it is necessary to control the primary recrystallization texture such as inhibitor control and crystal particle size control. Then, in order to control such a primary recrystallization texture, the conditions of the hot rolling process may be controlled.

As a technique for controlling the conditions of the hot rolling process, for example, the techniques disclosed in Patent Documents 1 to 4 are known. In the technique disclosed in Patent Document 1, temperature and time conditions are specified for the hot spreading step of the unidirectional electromagnetic steel sheet slab after the precipitate is completely dissolved, and the hot spreading is characterized by slow cooling. By the step, MnS used as an inhibitor is uniformly precipitated as fine particles at a high distribution density to improve the magnetic properties. However, this technique cannot eliminate the non-uniformity of secondary recrystallization that occurs especially in thin materials.

Further, in the technique disclosed in Patent Document 2, the slab is once cooled and then reheated, and the reheated slab is hot-rolled. However, although this technique has the effect of improving the surface texture of the steel sheet, it controls the primary recrystallization texture such as inhibitor control and crystal grain size control in order to stabilize the secondary recrystallization structure. is not.

Further, in the technique disclosed in Patent Document 3, in the hot rolling process in which the slab is heated, hot-rolled and then reheated, and the reheated steel sheet is hot-rolled again, the rolling temperature and the inter-pass time are set. It stipulates. However, this technique aims to prevent ear cracks from occurring in the hot rolling process when producing ultra-high silicon steel, and the secondary recrystallization structure of steel having a silicon concentration of about 3% by mass. The primary recrystallization texture is not controlled, such as inhibitor control or crystal grain size control, in order to stabilize the composition.

Further, in the technique disclosed in Patent Document 4, the crystal grain size is controlled by heating the slab, hot rolling it, and then reheating it, and then hot rolling the reheated steel sheet again. However, in this technique, since the precipitate is emulsified at the time of reheating after the first hot rolling, the effect of stabilizing the secondary recrystallization structure cannot be obtained.

JP-A-48-69720 Japanese Unexamined Patent Publication No. 5-179347 Japanese Unexamined Patent Publication No. 6-150162 Japanese Unexamined Patent Publication No. 48-53919

The present invention has been made in view of the above problems so that the secondary recrystallization structure can be stabilized in a thin unidirectional electrical steel sheet used as an iron core material for improving the efficiency of a transformer. It is an object of the present invention to provide a hot-rolled sheet for grain-oriented electrical steel sheet in which inhibitor control and crystal grain size control are performed in a hot rolling process, a method for producing the same, and a method for producing the grain-oriented electrical steel sheet. ..

In order to solve the above problems, the present inventors have investigated the cause of non-uniform secondary recrystallization in a thin unidirectional electromagnetic steel sheet. As a result, the preferential growth potential in the secondary recrystallization is increased in the directional grains having a large particle size when the primary recrystallization is completed. Therefore, in order to stabilize the secondary recrystallization structure in the thin unidirectional electromagnetic steel plate, At the time of completion of the primary recrystallization, the average grain size of the Goss azimuth grains in the region near the surface is made coarser than the average grain size of the crystal grains in the central region, and the inhibitor strength in the vicinity of the steel plate surface during the secondary recrystallization is increased. It was found that it is effective to maintain the preferential growth property of the Goss oriented grains in the vicinity of the surface of the steel plate even if the decrease occurs rapidly.

Then, at the time of completion of the primary recrystallization, the hot-rolled plate and hot rolling so that the average grain size of the Goss directional grains in the region near the surface can be coarser than the average grain size of the crystal grains in the central region. As a result of examining the above conditions, the hot-rolled sheet in which the average grain size of the Goss directional grains in the region near the surface is larger than the average grain size of the crystal grains in the central region, and the steel sheet containing segregation elements and then near the surface of the steel sheet. It was found that it is practically applicable to perform all or part of hot rolling under the condition that the temperature of the region is higher than the temperature of the central region.

The present invention is based on these findings, and the gist thereof is mass%, C: 0.1% or less, Si: 2.5 to 4.0%, Mn: 0.05 to 0. From the group consisting of 1%, S: 0.01-0.04%, Al: 0.01-0.05%, and N: 0.001-0.030%, and Bi, Pb, As, and Te. One type or two or more types to be selected: A hot-rolled plate for a unidirectional electromagnetic steel plate containing 0.0002% or more and 0.02% or less in total, and the balance is Fe and unavoidable impurities, and the plate thickness is 1. The ratio of the average grain size of the Goss directional grains in the region near the surface of the 1/10 to 1/5 layer to the average grain size of the crystal grains in the / 5 layer to the central region is 1.10 or more. It is a hot-rolled plate for unidirectional electromagnetic steel plate.

Another gist is the above-mentioned hot-rolled plate for unidirectional electromagnetic steel plate, which has a plate thickness of 1/5 layer to a plate thickness of 1/10 to 1/5 layer with respect to the average particle size of MnS in the central region of the center. The ratio of the average particle size of MnS in the region near the surface of the above surface is 1.10 or more, and the average particle size of MnS in the region near the surface is 300 nm or less. is there.

Another gist is the above-mentioned hot-rolled plate for unidirectional electromagnetic steel plate, which has a plate thickness of 1/5 layer to the center with respect to the distribution density of MnS in the region near the surface of the plate thickness of 1/10 to 1/5 layer. One direction, characterized in that the ratio of the distribution density of MnS in the central region of is 1.10 or more, and the distribution density of MnS having an average particle size of 1 μm or more in the region near the surface is 20 pieces / mm ² or less. It is a hot-rolled plate for sex electromagnetic steel plates.

Another gist is the above-mentioned hot-rolled sheet for unidirectional electromagnetic steel sheet, which is selected from the group consisting of Sb, Sn, and P in mass% instead of a part of Fe. Two or more types: Hot-rolled plates for unidirectional electrical steel sheets, which are characterized by containing 0.0004% or more and 0.5% or less in total.

In addition, other gist is by mass%, C: 0.1% or less, Si: 2.5 to 4.0%, Mn: 0.05 to 0.1%, S: 0.01 to 0.04. %, Al: 0.01-0.05%, and N: 0.001-0.030%, and one or more selected from the group consisting of Bi, Pb, As, and Te: 0 in total In the hot rolling step of hot rolling a slab containing 0002% or more and 0.02% or less and the balance being Fe and unavoidable impurities, the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc. : One direction, characterized in that the true strain of rolling applied to the steel sheet in a state where 1000 to 1100 ° C. satisfies the relationship of Ts−Tc ≧ 80 ° C. is 40% or more of the true strain of the entire hot rolling. This is a method for manufacturing a hot-rolled sheet for a sex electromagnetic steel sheet.

Another gist is the above-mentioned method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet, in which the ambient temperature of the slab cooled to 900 ° C. or lower as the surface temperature in the hot rolling step is increased. A hot-rolled sheet for a unidirectional electromagnetic steel sheet, which is charged into a heating furnace at 1200 ° C. or higher and hot-rolled on the slab extracted from the heating furnace within 1 hour after charging. It is a manufacturing method.

Another gist is the above-mentioned method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet. In the above-mentioned hot rolling step, the surface temperature of the rolled steel sheet is set to Ts from 1100 ° C. or higher to 600 to 750 ° C. After cooling at an average cooling rate of 2 ° C./s or higher to the following and holding for 0s to 300s in the temperature range of 600 to 750 ° C., the surface temperature of the rolled steel sheet is set to 1100 ° C. or higher and 1150 ° C. or lower. This is a method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet, which comprises heating and then further rolling.

Another gist is the above-mentioned method for manufacturing a hot-rolled sheet for unidirectional electromagnetic steel sheet. In the above-mentioned hot rolling step, after heating the slab to a surface temperature of 1.25 to 1400 ° C. This is a method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet, which comprises subjecting a slab after heating to the hot rolling.

Another gist is the above-mentioned method for manufacturing a hot-rolled sheet for grain-oriented electrical steel sheet, which is selected from the group consisting of Sb, Sn, and P in mass% instead of a part of Fe. One type or two or more types: A method for producing a hot-rolled sheet for a unidirectional electromagnetic steel sheet, which further contains 0.0004% or more and 0.5% or less in total.

In addition, other gist is the hot-rolled plate manufacturing process for manufacturing the hot-rolled plate for unidirectional electromagnetic steel sheet by performing the above-mentioned method for manufacturing the hot-rolled plate for unidirectional electromagnetic steel sheet, and the above-mentioned hot-rolled plate for unidirectional electromagnetic steel sheet. A hot-rolled plate annealing step of hot-rolling a hot-rolled plate, a cold rolling step of cold-rolling the steel sheet after the hot-rolled plate annealing, and a decarburization annealing of the steel plate after the cold-rolling. It is a method for producing a unidirectional electromagnetic steel sheet, which comprises a decarburization and anneal step and a finish anneal step of applying a finish anneal to the steel sheet after the decarburization and anneal.

Another gist is the above-mentioned method for manufacturing a unidirectional electromagnetic steel sheet, in which the above-mentioned hot-rolled sheet for unidirectional electromagnetic steel sheet is placed in a temperature range of 900 to 50 ° C. for 60 s or more in the above-mentioned annealing step. It is a method for manufacturing a unidirectional electromagnetic steel sheet, which is characterized in that it is subjected to hot-rolled sheet annealing to be held.

Further, another gist is the above-mentioned method for producing a unidirectional electromagnetic steel sheet, in which in the decarburization annealing step, the steel sheet after cold rolling is brought from a temperature of 350 ° C. or lower to 700 ° C. or higher and 850 ° C. or lower. A method for producing a unidirectional electromagnetic steel sheet, which comprises heating at a temperature rising rate of 100 ° C./s or more in a temperature raising process of raising the temperature to a temperature, and then subjecting the steel sheet after cold rolling to decarburization annealing. Is.

According to the present invention, heat for grain-oriented electrical steel sheets used for producing thin ultra-low iron-loss unidirectional steel sheets having excellent magnetic properties by expressing uniform secondary recrystallization. It is possible to provide a rolled plate and a method for producing the same, and a method for producing the unidirectional electromagnetic steel sheet thereof.

Hereinafter, the hot-rolled sheet for unidirectional electromagnetic steel sheet of the present invention, a method for producing the same, and a method for producing the unidirectional electromagnetic steel sheet will be described in detail.

A. Hot-rolled plate for unidirectional electromagnetic steel sheet The hot-rolled plate for unidirectional electromagnetic steel sheet of the present invention is a hot-rolled plate for unidirectional electromagnetic steel sheet having the following chemical components, and has a thickness of 1/5 layer to the center. It is characterized in that the ratio of the average particle size of the Goss oriented grains in the region near the surface of the 1/10 to 1/5 layer of the plate thickness to the average particle size of the crystal grains in the central region is 1.10 or more. Hereinafter, the hot-rolled sheet for unidirectional electromagnetic steel sheet of the present invention will be described in detail.

1. 1. Chemical components The reasons for limiting the chemical components in the present invention will be described in detail below. In the following, the content of each component is a value in mass%.

(1) C
When C is added, it is a useful element because the nucleation and growth of MnS during hot spreading can be controlled by the formed austenite phase, but if it is added in excess of 0.1%, decarburization or purification becomes difficult. .. If C remains on the product plate, it causes an aging phenomenon in which the magnetic characteristics deteriorate, so the upper limit of the content is set to 0.1%.

(2) Si
Since Si is an element useful for increasing the natural resistance and reducing the iron loss, 2.5 to 4.0% is added. If it is added in excess, hot rolling or cold rolling becomes difficult, so the upper limit of the content is set to 4.0%.

(3) Mn
Since Mn is an element necessary for finely precipitating MnS during hot rolling, 0.05 to 0.1% is added. If the content is less than this, a sufficient volume fraction of MnS cannot be obtained and the structure cannot be controlled. Therefore, the lower limit of the content is set to 0.05%. Further, even if Mn is added excessively, the effect of improving the structure control cannot be obtained, so the upper limit of the content is set to 0.1%.

(4) S
Since S is an essential element for precipitating MnS like Mn, 0.01 to 0.04% is added. If the content is less than this, a sufficient volume fraction of MnS cannot be obtained and the structure cannot be controlled. Therefore, the lower limit of the content is set to 0.01%. If it is added in an excessive amount, MnS tends to be coarsened and red-hot embrittlement makes it difficult to spread the heat. Therefore, the upper limit of the content is set to 0.04%.

(5) Al
Al is an element necessary for precipitating fine AlN on the interface between fine MnS and ground iron by annealing the hot-rolled plate after hot rolling that finely precipitates MnS, and is a unidirectional electromagnetic steel sheet. 0.01 to 0.05% is added for the purpose of improving the magnetic flux density of. If the content is less than this, the effective precipitation amount of AlN cannot be obtained, it cannot contribute to the structure control during finish annealing, and the magnetic flux density of the unidirectional electromagnetic steel sheet does not improve. Therefore, the lower limit of the content is set to 0. It is set to 01%. Further, when the content is larger than this, the growth of AlN becomes faster, and AlN is easily precipitated by itself in hot rolling, so that AlN is relatively coarsely precipitated, which is an effective pin for secondary recrystallization. The upper limit of the content is set to 0.05% because it does not exert a stopping force and adversely affects the preferential growth of Goss oriented grains and lowers the magnetic flux density.

(6) N
Like Al, N is an element necessary for annealing a hot-rolled plate to precipitate fine AlN, and 0.001 to 0.030% is added. If the content is less than this, the effective precipitation amount of fine AlN cannot be obtained, and the grain boundary pinning force required for structure control during finish annealing cannot be exerted. Therefore, the lower limit of the content is 0.001. %. Further, when the content is larger than this, AlN is likely to be precipitated alone in hot rolling, so that AlN is relatively coarsely precipitated and does not exert an effective pinning force in secondary recrystallization, and the Goss orientation. Since the preferential growth of grains is adversely affected and the magnetic flux density is lowered, the upper limit of the content is set to 0.030%.

(7) Bi, Pb, As, and Te
Bi, Pb, As, and Te are elements necessary to slow down the movement speed of grain boundaries by segregation, and one or more selected from the group consisting of Bi, Pb, As, and Te. Add 0.0002% or more and 0.02% or less in total.

In the hot rolling process described in "B. Manufacturing method of hot rolled sheet for unidirectional electromagnetic steel sheet 1. Hot rolling process" described later, the center temperature of the plate thickness of the slab becomes lower than the surface temperature. , The grain boundary mobility is smaller in the central region of the slab than in the region near the surface. In addition to this, the segregation of the above-mentioned elements slows down the movement speed of the grain boundaries. Therefore, the crystal grain size in the central region of the slab is significantly smaller than that in the region near the surface. As a result, in the hot-rolled plate for unidirectional electromagnetic steel plate, the average grain size of the Goss azimuth grains in the region near the surface of the plate thickness 1/10 to 1/5 layer is set to the plate thickness 1/5 layer to the central region of the center. It can be made significantly coarser than the average particle size of the crystal grains in all directions. Further, in the surface vicinity region, MnS can be remarkably coarse and low density as compared with the central region, and it is also possible to prevent MnS from becoming excessively coarse and low density in the surface vicinity region. .. As a result, even if the inhibitor strength near the surface of the steel sheet rapidly decreases during secondary recrystallization, the preferential growth of Goss azimuth grains near the surface of the steel sheet is remarkably maintained, and the thin unidirectional electromagnetic steel sheet is used. The secondary recrystallization structure can be remarkably stabilized.

Further, when the addition amount is less than 0.0002%, such an effect cannot be obtained, so the lower limit of the addition amount is set to 0.0002%. When the addition amount is more than 0.02%, the effect of stabilizing the secondary recrystallization is saturated and defects such as ear cracks are likely to occur during rolling, so the upper limit of the addition amount is set to 0.02%.
Bi, Pb, As, and Te are added in place of a part of Fe.

(8) Others It is preferable to add one or more selected from the group consisting of Sb, Sn, and P in a total of 0.0004% or more and 0.5% or less. Since the movement speed of the grain boundaries is further slowed down by segregation of these elements, the crystal grain size in the central region of the slab is significantly smaller than that in the region near the surface. As a result, in the hot-rolled plate for unidirectional electromagnetic steel plate, the average grain size of the Goss azimuth grains in the region near the surface of the plate thickness 1/10 to 1/5 layer is set to the plate thickness 1/5 layer to the central region of the center. It can be made coarser than the average particle size of the crystal grains in all directions. Further, in the region near the surface, MnS can be made coarser and lower in density than the central region more effectively. As a result, even if the inhibitor strength near the surface of the steel sheet rapidly decreases during secondary recrystallization, the preferential growth of Goss azimuth grains near the surface of the steel sheet is maintained more remarkably, and the thin unidirectional electromagnetic steel sheet is further maintained. This is because the secondary recrystallization structure in the above can be stabilized more remarkably.

Further, when the addition amount is less than 0.0004%, such an effect cannot be obtained, so that the lower limit of the addition amount is preferably 0.0004%. When the addition amount is more than 0.5%, the effect of stabilizing the secondary recrystallization is saturated and defects such as ear cracks are likely to occur during rolling. Therefore, the upper limit of the addition amount should be 0.5%. Is preferable.
In addition, Sb, Sn, and P are added in place of a part of Fe.

(9) Remaining Remaining is Fe and unavoidable impurities. Among the unavoidable impurities, Ti, V, Nb, and Zr, which adversely affect the grain growth property, are preferably reduced as much as possible, and each is preferably 0.008% or less.

2. 2. Average particle size of crystal grains In the hot-rolled plate for unidirectional electromagnetic steel plate of the present invention, the plate thickness is 1/5 layer to 1/10 to 1/5 layer of the average particle size of crystal grains in the central region of the center. The ratio of the average grain size of the Goss directional grains in the region near the surface is 1.10 or more. As a result, at the time of completion of the primary recrystallization, the average grain size of the Goss azimuth grains in the region near the surface can be significantly coarsened from the average grain size of the omnidirectional crystal grains in the central region. As a result, even if the inhibitor strength in the vicinity of the steel sheet surface rapidly decreases during secondary recrystallization, the preferential growth of Goss azimuth grains in the vicinity of the steel sheet surface is remarkably maintained, and the thin unidirectional electromagnetic steel sheet is used. The secondary recrystallization structure can be remarkably stabilized.
Here, in the present invention, the "average particle size of crystal grains" means the average value obtained by obtaining the diameters of circles having the same area with respect to the projected area of a plurality of observed crystal grains.

The ratio of the average grain size of the Goss azimuth grains in the region near the surface of the 1/5 to 1/5 layer thickness to the average grain size of the crystal grains in the central region of the 1/5 layer to the center is 1.20 or more. It is preferable to have. This is because the preferential growth property of the Goss oriented grains in the vicinity of the surface of the steel sheet can be maintained more remarkably.

3. 3. Precipitates The MnS precipitates will be described in detail below.

(1) Average Grain Size In the hot-rolled plate for unidirectional electromagnetic steel plate of the present invention, the surface of 1/5 layer to 1/5 to 1/5 layer thickness with respect to the average particle size of MnS in the central region of the center. The ratio of the average particle size of MnS in the vicinity region is 1.10 or more, and the average particle size of MnS in the vicinity of the surface region is preferably 300 nm or less. The reason why the ratio of the average particle size of MnS is 1.10 or more is that MnS becomes finer and denser in the central region than in the region near the surface, so that the primary recrystallization structure of the Goss orientation grain is set in the region near the surface. The structure is more remarkably advantageous for preferential growth, and the growth of primary recrystallized grains in the central region can be suppressed more remarkably during finish annealing, so that the preferential growth of Goss oriented grains in the vicinity of the steel plate surface is more remarkably maintained. This is because the secondary recrystallization structure of the thin unidirectional electromagnetic steel plate can be more significantly stabilized. On the other hand, the reason why the average particle size of MnS in the region near the surface is set to 300 nm or less is that if MnS becomes excessively coarse and low in density in the region near the surface, secondary recrystallization becomes unstable.

Here, in the present invention, the "average particle size of MnS" means the average value obtained by obtaining the diameters of circles having the same area with respect to the projected area for each of the observed multiple MnS. In the hot-rolled sheet for unidirectional electrical steel sheet, when the total amount of MnS deposited is the same, the smaller the average particle size of MnS, the higher the distribution density of MnS.

The ratio of the average particle size of MnS in the region near the surface of the 1/5 to 1/5 layer thickness to the average particle size of MnS in the central region of the plate thickness 1/5 layer to the center is 1.20 or more. Is preferable, and 1.30 or more is particularly preferable. Homogeneous and fine MnS suppresses crystal grain growth in the central region, and while suppressing crystal grain growth in the central region at high temperatures, MnS in the region near the surface grows ostwald to initiate secondary recrystallization, resulting in crystal grains. This is because secondary recrystallization that progresses by eating the food is remarkably likely to occur.

The average particle size of MnS in the region near the surface of the 1/10 to 1/5 layer thickness is preferably in the range of 80 nm to 300 nm, particularly in the range of 80 nm to 200 nm, particularly in the range of 80 nm to 160 nm. It is preferable to have. This is because when MnS has this average particle size, a sharp secondary recrystallization structure can be obtained. The average particle size of MnS in the 1/5 layer to the central region of the plate thickness is preferably in the range of 50 nm to 200 nm, particularly in the range of 50 nm to 180 nm, particularly in the range of 50 nm to 120 nm. Is preferable. This is because by dispersing fine MnS in the central region, grain growth in the central region during finish annealing is suppressed, and secondary recrystallization is remarkably stabilized.

(2) Distribution Density In the hot-rolled plate for unidirectional electromagnetic steel plate of the present invention, the plate thickness 1/5 layer to the central region of the MnS distribution density in the region near the surface of the plate thickness 1/10 to 1/5 layer. The ratio of the distribution density of MnS in the above surface is 1.10 or more, and the distribution density of MnS having an average particle size of 1 μm or more in the surface vicinity region is preferably 20 pieces / mm ² or less. The reason why the distribution density ratio of MnS is 1.10 or more is that MnS becomes finer and denser in the central region than in the region near the surface, so that the primary recrystallization structure is prioritized in the Goss orientation grain in the region near the surface. Since the structure is made more remarkably advantageous for growth and the growth of the primary recrystallized grains in the central region can be suppressed more remarkably during finish annealing, the preferential growth property of the Goss oriented grains in the vicinity of the steel plate surface is further remarkably maintained. This is because the secondary recrystallization structure of the thin unidirectional electromagnetic steel plate can be more significantly stabilized. On the other hand, the reason why the distribution density of MnS having an average particle size of 1 μm or more in the surface vicinity region is 20 pieces / mm ² or less is that when MnS becomes excessively coarse and low density in the surface vicinity region, secondary recrystallization occurs. This is because the crystals become unstable.

Here, in the present invention, the "MnS distribution density" means a value obtained by dividing the number of MnS counted by observing the mirror-polished cross section by the area of the observation field of view.

4. Plate Thickness The hot-rolled sheet for grain-oriented electrical steel sheet of the present invention is premised on being obtained by performing inhibitor control so as to develop uniform secondary recrystallization when producing a thin grain-oriented electrical steel sheet. .. Therefore, the thickness of the hot-rolled sheet should be within the range of 2.3 mm or less, preferably 2.1 mm or less, more preferably 2.0 mm or less, and 85% or more, 92 in the subsequent cold rolling process. It is preferable to perform cold rolling at a rolling reduction of% or less to obtain the final plate thickness. On the other hand, since the plate thickness after cold rolling becomes extremely thin and no improvement by the present invention is observed, the plate thickness of the hot-rolled plate is preferably in the range of 1.5 mm or more.

5. Manufacturing Method The hot-rolled sheet for unidirectional electromagnetic steel sheet of the present invention is prepared by the method for manufacturing a hot-rolled sheet for unidirectional electromagnetic steel sheet described in "B. Manufacturing method for hot-rolled sheet for unidirectional electromagnetic steel sheet" described later. It is preferable to manufacture.

B. Method for manufacturing hot-rolled sheet for unidirectional electromagnetic steel sheet The method for manufacturing a hot-rolled sheet for unidirectional electromagnetic steel sheet of the present invention includes a hot-rolling step of hot-rolling a slab having the above-mentioned chemical components. Hereinafter, a method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet of the present invention will be described.

1. 1. Hot rolling step In the hot rolling step, slabs having the above-mentioned chemical components are hot-rolled. Further, in the hot rolling step, the true rolling performed on the steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. The strain is set to 40% or more of the true strain of the entire hot rolling. As a result, in the hot-rolled plate for unidirectional electromagnetic steel plate, the average grain size of the Goss azimuth grains in the region near the surface of the plate thickness 1/10 to 1/5 layer is set to the plate thickness 1/5 layer to the central region of the center. It can be made coarser than the average particle size of the crystal grains in all directions. Further, in the region near the surface, MnS can be coarser and have a lower density than the central region.

Further, in the hot rolling step, the grain boundary mobility becomes smaller in the central region of the slab than in the region near the surface because the plate thickness center temperature of the slab is lower than the surface temperature. In addition to this, segregation of one or more elements selected from the group consisting of Bi, Pb, As, and Te contained in the slab slows down the movement speed of the grain boundaries. Therefore, the crystal grain size in the central region of the slab is significantly smaller than that in the region near the surface. As a result, in the hot-rolled plate for unidirectional electromagnetic steel plate, the average grain size of the Goss azimuth grains in the region near the surface of the plate thickness 1/10 to 1/5 layer is set to the plate thickness 1/5 layer to the central region of the center. It can be made significantly coarser than the average particle size of the crystal grains in all directions. Further, in the surface vicinity region, MnS can be remarkably coarse and low density as compared with the central region, and it is also possible to prevent MnS from becoming excessively coarse and low density in the surface vicinity region. ..

As a result, at the time of completion of the primary recrystallization, the average grain size of the Goss azimuth grains in the region near the surface can be significantly coarsened from the average grain size of the omnidirectional crystal grains in the central region. As a result, even if the inhibitor strength in the vicinity of the steel sheet surface rapidly decreases during secondary recrystallization, the preferential growth of Goss azimuth grains in the vicinity of the steel sheet surface is remarkably maintained, and the thin unidirectional electromagnetic steel sheet is used. The secondary recrystallization structure can be remarkably stabilized.
Here, the true strain of the whole hot rolling is preferably 50% or more. This promotes the precipitation of MnS, and the above effect is further remarkably enhanced.

Here, in the present invention, the "surface temperature Ts of the steel sheet" means the temperature measured by a contact type thermometer or a radiation thermometer. Further, in the present invention, the "plate thickness center temperature Tc of the steel sheet" means the temperature obtained by the heat conduction analysis by the commonly known difference method.

The slab having the above-mentioned chemical components can be obtained by, for example, melting steel in a converter or an electric furnace, vacuum degassing treatment if necessary, and then continuous casting or ingot rolling after ingot formation. Be done.

In the hot rolling step, the slab is roughly rolled and finish-rolled to finish a hot-rolled plate having a desired plate thickness. At this time, the hot rolling may be performed after heating the slab under the conditions described later. Further, the steel sheet which has been subjected to one or more rolling passes in the rough rolling may be cooled and held under the conditions described below, and then further heated to perform the finish rolling.

In the hot rolling step, the true strain of rolling applied to a steel plate in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. To make it 40% or more of the true strain of the whole hot rolling, one or two or more rolling passes arbitrarily selected from all the rolling passes of the rough rolling and the finish rolling are performed on the steel plate in a state satisfying the above relationship. It means that the true strain of one or more rolling passes performed on the steel plate in a state satisfying the above relationship is 40% or more of the true strain of all the rolling passes of the rough rolling and the finish rolling.

Further, in the hot rolling step, true strain of rolling is applied to a steel sheet in a state where a surface temperature Ts: 1100 to 1200 ° C. and a plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. There are mainly the following two preferable conditions for the operation management in which the true strain of the whole hot rolling is set to 40% or more.

Under the first condition, the slab cooled to a surface temperature of 900 ° C. or lower was charged into a heating furnace having an ambient temperature of 1200 ° C. or higher, and extracted from the heating furnace within 1 hour after the charging. The slab is hot-rolled as described above. As a result, the difference between the surface temperature of the slab and the center temperature of the plate thickness is secured, and in the subsequent hot rolling step, one or two or more rolling passes are performed with a surface temperature Ts: 1100 to 1200 ° C. and a center plate thickness. The temperature Tc: 1000 to 1100 ° C. is applied to the steel sheet in a state where the relationship of Ts−Tc ≧ 80 ° C. is satisfied. Then, the true strain of the 1 or 2 or more rolling passes performed on the steel sheet while satisfying the above relationship is set to 40% or more of the true strain of the entire hot rolling. As a result, in the hot-rolled sheet for grain-oriented electrical steel sheets, the average grain size of the Goss azimuth grains in the surface vicinity region is made significantly coarser than the average grain size of the omnidirectional crystal grains in the central region. Can be left. Further, in the region near the surface, MnS can be made coarser and lower in density than the central region more effectively.

Under the second condition, the rolled steel sheet is cooled to a surface temperature of Ts from 1100 ° C. or higher to 600 to 750 ° C. or lower at an average cooling rate of 2 ° C./s or higher, and is in a temperature range of 600 to 750 ° C. for 0s to 300s. After holding, the rolled steel sheet is heated to a surface temperature of 1100 ° C. or higher and 1150 ° C. or lower, and then further rolled. Specifically, for example, the surface temperature of the steel sheet after one or two or more rolling passes performed in the rough rolling or finish rolling is an average of 2 ° C./s or more from 1100 ° C. or higher to 600 to 750 ° C. or lower. After cooling at a cooling rate and holding the steel sheet in the temperature range of 600 to 750 ° C. for 0s to 300s, the steel sheet after the above 1 or 2 or more rolling passes is heated to a surface temperature Ts of 1100 ° C. or higher and 1150 ° C. or lower. Further, in finish rolling, one or two or more rolling passes are performed.

As a result, the difference between the surface temperature of the steel sheet and the center temperature of the sheet thickness after one or two or more rolling passes performed in the rough rolling or finish rolling is secured, and one or two or more rolling passes performed in the subsequent finish rolling. Is performed on the steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. Then, the true strain of the 1 or 2 or more rolling passes performed on the steel sheet while satisfying the above relationship is set to 40% or more of the true strain of the entire hot rolling. As a result, in the hot-rolled sheet for grain-oriented electrical steel sheets, the average grain size of the Goss azimuth grains in the surface vicinity region is made significantly coarser than the average grain size of the omnidirectional crystal grains in the central region. Can be left. Further, in the region near the surface, MnS can be made coarser and lower in density than the central region more effectively.

Further, in the hot rolling step, the true rolling performed on the steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. The strain is preferably 50% or more of the true strain of the entire hot rolling. In the hot-rolled plate for grain-oriented electrical steel sheets, the average grain size of the Goss-oriented grains in the region near the surface may be made coarser than the average grain size of the crystal grains in all directions in the central region. it can. Further, in the region near the surface, MnS can be made coarser and lower in density than the central region more effectively.

Further, in the hot rolling step, the above-mentioned rolling is performed on the steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. Of these, the true strain of rolling applied to the steel sheet at a surface temperature Ts: 1100 to 1150 ° C. is preferably 40% or more, and more preferably 50% or more of the true strain of the entire hot rolling. In the hot-rolled plate for unidirectional electromagnetic steel plate, the average grain size of the Goss azimuth grains in the region near the surface of the plate thickness 1/10 to 1/5 layer is set to the omnidirectional in the plate thickness 1/5 layer to the central region. It can be made coarser than the average particle size of the crystal grains. Further, in the region near the surface, MnS can be made coarser and lower in density than the central region more effectively. As a result, at the time of completion of the primary recrystallization, the average grain size of the Goss-oriented grains in the region near the surface can be significantly coarser than the average grain size of the crystal grains in all directions in the central region. The secondary recrystallization structure of the unidirectional electromagnetic steel plate can be more significantly stabilized.

Further, in the hot rolling step, it is preferable that the slab is heated to 1250 to 1400 ° C. at a surface temperature, and then the slab after heating is subjected to the hot rolling. Since the MnS that has already been precipitated can be completely dissolved before the hot rolling, the MnS is thickened in the 1/5 layer to the central region of the center by performing the hot rolling. It is possible to deposit finer and more densely than the region near the surface of the 1/10 to 1/5 layer. As a result, the growth of the crystal grains is remarkably suppressed in the central region, so that the primary recrystallized structure becomes a structure that is more remarkably advantageous for the preferential growth of the Goss-oriented grains, and the growth of the primary recrystallized grains is further remarkably made during finish annealing. Therefore, the preferential growth of Goss oriented grains in the vicinity of the surface of the steel sheet can be maintained more remarkably, and the secondary recrystallization structure of the thin unidirectional electromagnetic steel sheet can be more remarkably stabilized. Because.

Further, in the hot rolling step, the slab is one or more selected from the group consisting of Sb, Sn, and P in mass% instead of a part of Fe: 0 in total. It is preferable to further contain 0004% or more and 0.5% or less. Since the movement speed of the grain boundaries is further slowed down by segregation of these elements, the crystal grain size in the central region of the slab is significantly smaller than that in the region near the surface. As a result, in the hot-rolled plate for unidirectional electromagnetic steel plate, the average grain size of the Goss azimuth grains in the region near the surface of the plate thickness 1/10 to 1/5 layer is set to the plate thickness 1/5 layer to the central region of the center. It can be made coarser than the average particle size of the crystal grains in all directions. Further, in the region near the surface, MnS can be made coarser and lower in density than the central region more effectively. As a result, even if the inhibitor strength near the surface of the steel sheet rapidly decreases during secondary recrystallization, the preferential growth of Goss azimuth grains near the surface of the steel sheet is maintained more remarkably, and the thin unidirectional electromagnetic steel sheet is further maintained. This is because the secondary recrystallization structure in the above can be stabilized more remarkably.

2. 2. Hot-rolled sheet for unidirectional electromagnetic steel sheet The hot-rolled sheet for unidirectional electromagnetic steel sheet manufactured by the method for manufacturing the hot-rolled sheet for unidirectional electromagnetic steel sheet of the present invention is not particularly limited, but is described above. The hot-rolled sheet for unidirectional electromagnetic steel sheet described in "A. Hot-rolled sheet for unidirectional electromagnetic steel sheet" is preferable. This is because it can be used for producing a thin unidirectional electromagnetic steel sheet having more excellent magnetic properties by expressing more uniform secondary recrystallization.

C. Manufacturing method of unidirectional electromagnetic steel sheet The manufacturing method of the unidirectional electromagnetic steel sheet of the present invention is described in "B. Manufacturing method of hot-rolled sheet for unidirectional electromagnetic steel sheet" described above. A hot-rolled plate manufacturing process for manufacturing a hot-rolled plate for unidirectional electromagnetic steel sheets by performing a plate manufacturing method, and a hot-rolled plate annealing step for performing hot-rolled plate annealing on the above-mentioned hot-rolled plate for unidirectional electromagnetic steel sheets. A cold rolling step of cold rolling the steel sheet after hot rolling plate annealing, a decarburization annealing step of decarburizing the steel sheet after the cold rolling, and a finish annealing of the steel sheet after the decarburization annealing. It is characterized by having a finish annealing step of applying.
Hereinafter, each step in the method for manufacturing a unidirectional electromagnetic steel sheet of the present invention will be described.

1. 1. Hot-rolled plate manufacturing process In the above-mentioned hot-rolled plate manufacturing process, the method for manufacturing a hot-rolled plate for unidirectional electromagnetic steel sheets described in "B. Manufacturing method for hot-rolled plates for unidirectional electromagnetic steel sheets" is performed. Manufactures hot-rolled sheets for unidirectional electromagnetic steel sheets.

The hot-rolled sheet manufacturing conditions are as described in the above item "B. Manufacturing method of hot-rolled sheet for unidirectional electromagnetic steel sheet 1. Hot rolling process". The configuration of the hot-rolled sheet for unidirectional electromagnetic steel sheet is as described in the above item "A. Hot-rolled sheet for unidirectional electromagnetic steel sheet".

2. 2. Hot-rolled plate annealing step In the hot-rolled plate annealing step, the hot-rolled plate is annealed on the hot-rolled sheet for unidirectional electromagnetic steel sheet.

The conditions for annealing the hot-rolled sheet are not particularly limited, but in the hot-rolled sheet annealing step, the hot-rolled sheet for unidirectional electromagnetic steel sheet may be held in a temperature range of 900 to 1050 ° C. for 60 seconds or more. preferable. This is because when the hot-rolled plate is annealed under such conditions, AlN precipitates and acts as an inhibitor, and as a result, the degree of integration in the Goss orientation in the secondary recrystallization structure is further significantly improved.
In the hot-rolled plate annealing step, the steel sheet after the finish hot-rolling may be wound into a coil and kept in the above temperature range by the self-owned heat, or the hot-rolled plate after cooling is annealed. It may be kept in the above temperature range.

3. 3. Cold rolling step In the cold rolling step, cold rolling is performed on the steel sheet after annealing the hot-rolled sheet.

4. Decarburization annealing step In the decarburization annealing step, the steel sheet after cold rolling is subjected to decarburization annealing.

The decarburization annealing conditions are not particularly limited, but in the decarburization annealing step, the temperature of the steel sheet after cold rolling is raised from a temperature of 350 ° C. or lower to a temperature of 700 ° C. or higher and 850 ° C. or lower. It is preferable that the steel sheet after cold rolling is subjected to the decarburization annealing after heating at a temperature rise rate of 100 ° C./s or more in the warming process. This is because the Goss azimuth grain can be enlarged in the entire plate thickness direction when the primary recrystallization is completed by the action of rapid heating at the temperature rise during the primary recrystallization. As a result, a synergistic effect with the action of the structure of the hot-rolled sheet in the present invention is generated, and at the time of completion of the primary recrystallization, the average particle size of the Goss azimuth grains in the region near the surface becomes more remarkably large, and the secondary recrystallization Even if the inhibitor strength in the vicinity of the steel sheet surface rapidly decreases during crystallization, it can be expected that the preferential growth property of the Goss oriented grains in the vicinity of the steel sheet surface is maintained more remarkably. As a result, the secondary recrystallization structure of the thin unidirectional magnetic steel sheet can be more significantly stabilized.

5. Finish Annealing Step In the finish annealing process, the steel sheet after decarburization annealing is subjected to finish annealing. As a result, the steel sheet after decarburization annealing undergoes secondary recrystallization to obtain a unidirectional electromagnetic steel sheet.

6. In addition, the method for producing a unidirectional electromagnetic steel sheet of the present invention may further include a step generally performed in the method for producing a unidirectional electromagnetic steel sheet. Typical steps other than the above include melting, casting, hot winding, pickling, nitriding and annealing, annealing separator coating, purification annealing, and insulating film coating. In these steps, a plurality of steps may be performed by one passing plate in one manufacturing apparatus. Further, these steps may be performed by repeating a certain step a plurality of times or changing the order.

In the method for producing a unidirectional electromagnetic steel plate of the present invention, when a single AlN is precipitated by hot-rolling and hot-rolling sheet annealing and the precipitation density of AlN is insufficient, nitriding is performed after the decarburization annealing step and before the finish annealing step. It may have a nitriding annealing step of annealing. This makes it possible to avoid insufficient precipitation density of AlN.

In the nitriding annealing step, it is preferable to perform nitriding annealing in which the steel sheet after decarburization annealing is held in a temperature range of 700 ° C. or higher and 800 ° C. or lower for 30 s or more and 300 s or less.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same action and effect is the present invention. Is included in the technical scope of.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Example 1)
The slabs of steel numbers 1 to 15 and steel numbers 19 to 40 having the chemical components shown in Table 1 below are placed in a heating furnace having an ambient temperature of 1320 ° C. and held for 30 minutes to obtain the surface temperature in the table below. After heating to the slab heating temperature Ts0 shown in 2-1 the slabs extracted from the heating furnace were roughly rolled and finished rolled under the conditions shown in Table 2-1 below. Further, the slabs of steel numbers 16 to 18 having the chemical components shown in Table 1 below are cooled to 850 ° C. at a surface temperature, and then charged into a heating furnace having an ambient temperature of 1320 ° C. and held for 30 minutes. After heating to the slab heating temperature Ts0 shown in Table 2-1 below, the slabs extracted from the heating furnace were subjected to rough rolling and finish rolling under the conditions shown in Table 2-1 below.

In the above rough rolling, for the slabs of steel numbers 1 to 40, the surface temperature Ts1 [° C.] of the steel sheet on the inlet side, the plate thickness center temperature Tc1 [° C.], and the plate thickness t1 [mm] are shown in Table 2-1 below. The first rolling pass was made as shown in. Further, in the rough rolling and finish rolling, a plurality of sheets are continuously performed on a steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. The surface temperature Tss [° C.], the center temperature Tcs [° C.], Tss-Tcs [° C.], and the plate thickness ts [mm] of the steel sheet at the entrance side of the first rolling path in the rolling path of Surface temperature Tsf [° C.], plate thickness center temperature Tcf [° C.], Tsf-Tcf [° C.], and Tsf-Tcf [° C.] on the exit side of the final rolling pass in a plurality of rolling passes continuously performed on the steel sheet in a filled state. As shown in Table 2-1 below, the plate thickness tf [mm] was subjected to a plurality of rolling passes continuously performed on the steel sheet while satisfying the above relationship.
In hot rolling with steel numbers in which Tss, Tcs, and ts are Ts1, Tc1, and t1, the first rolling pass in the rough rolling is the above relationship in the rough rolling and finish rolling. Corresponds to the first rolling pass in a plurality of rolling passes continuously performed on a steel sheet in a state of satisfying the condition.

As described above, by performing the above-mentioned rough rolling and finish rolling, a hot-rolled plate having a finished plate thickness tff of 2.3 mm was obtained. Further, the true strain ep [−] of rolling performed in a plurality of rolling passes continuously performed on the steel sheet while satisfying the above relationship, and the true strain et [of the entire hot rolling consisting of the rough rolling and finish rolling. -] Are shown in Table 2-1 below. In addition, the ratio Ce (ep / et × 100) [%] of the true strain ep to the true strain et is shown in Table 2-1 below.

Further, the average particle size Dsg [μm] of the Goss directional grains, the average particle size ds [nm] of MnS, and the distribution density of MnS in the region near the surface of the obtained hot-rolled plate having a thickness of 1/10 to 1/5. ρs [μm ^-2], and the distribution density ρ1μm an average particle size of more than 1μm MnS [μm ^-2], and the total orientation of the crystal in the central region of the sheet thickness 1/5 layer to the center of the obtained hot-rolled sheet The average particle size Di [μm] of the grains, the average particle size di [nm] of MnS, and the distribution density ρi [μm- ² ] of MnS were investigated. Further, the ratio of the average particle size Dsg of the Goss directional grains Dsg in the region near the surface to the average particle size Di of the crystal grains in all directions in the central region Dsg / Di [−], and the region near the surface of MnS in the central region with respect to the average particle size di. The ratio ds / di [−] of the average particle size ds of MnS and the ratio ρi / ρs [−] of the distribution density ρi of MnS in the central region to the distribution density ρs of MnS in the region near the surface were calculated. The average particle size of the crystal grains is the value obtained by calculating and averaging the diameters of circles of the same area with respect to the projected area for each of the observed crystal grains, and the average particle size of MnS is the same for the observed multiple MnS with respect to the projected area. The average value of the diameters of the circles in the area, and the distribution density of MnS is the value obtained by dividing the number of MnS counted by observing the mirror-polished cross section by the area of the observation field. The obtained results are shown in Table 2-2 below.

Since the true strain ratio Ce of the hot-rolled plate of steel No. 19 was below the range of the present invention, the ratio Dsg / Di of the average particle size of the crystal grains was below the range of the present invention, and the average in the region near the surface was The distribution density ρ1 μm of MnS having a particle size of 1 μm or more exceeded the preferable range of the present invention, and the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density were below the preferable range of the present invention. Further, since the hot-rolled plate of steel number 20 has a low Ts1, the entire hot rolling is performed in a state where Ts: 1100 to 1200 ° C. and Tc: 1000 to 1100 ° C. do not satisfy the relationship of Ts−Tc ≧ 80 ° C. Therefore, the ratio Dsg / Di of the average particle size of the crystal grains is below the range of the present invention, and the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density of the present invention. It was below the preferred range. Further, in the hot-rolled plate of steel No. 21, since the plate thickness center temperature Tc increased during the rough rolling, the relationship between Ts: 1100 to 1200 ° C. and Tc: 1000 to 1100 ° C. was Ts-Tc ≥ 80 ° C. The true strain ep applied in a plurality of rolling passes continuously performed in the satisfying state becomes smaller, the ratio Dsg / Di of the average particle size of the crystal grains falls below the range of the present invention, and the true strain ratio Ce becomes Since it was below the range of the present invention, the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density were below the preferable range of the present invention.
Further, the hot-rolled plate of steel No. 22 has crystal grains because the total addition amount of one or more selected from the group consisting of Bi, Pb, As, and Te of the present invention was less than the range of the present invention. The ratio Dsg / Di of the average particle size was below the range of the present invention, and the distribution density ρ1 μm of MnS having an average particle size of 1 μm or more in the region near the surface was above the preferable range of the present invention.
Further, in the hot-rolled plates of steel numbers 23, 24, 25, 26 and 27, the total addition amount of one or more selected from the group consisting of Bi, Pb, As and Te of the present invention is the present invention. Because it exceeded the range of, it cracked during hot spreading.

Further, in the hot-rolled plate of steel No. 28, since the slab heating temperature Ts0 was below the preferable range of the present invention of 1.25 to 1400 ° C., the dispersion of MnS was insufficient, and the average particle size ds of MnS in the region near the surface was ds. Is above the preferred range of the present invention, the average particle size ratio ds / di of MnS and the distribution density ratio ρi / ρs are below the preferred range of the present invention, and the average particle size ratio Dsg / Di of the crystal grains is the present invention. It was below the range of.

Further, in the hot-rolled plate of steel No. 29, since the slab heating temperature Ts0 exceeded the preferable range of the present invention of 1.25 to 1400 ° C., the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density Was below the preferable range of the present invention, and the ratio Dsg / Di of the average particle size of the crystal grains was below the range of the present invention.

Further, in the hot-rolled plate of steel No. 30, not only the C content was above the range of the present invention, but also the true strain ratio Ce was below the range of the present invention, so that the ratio of the average particle size of the crystal grains was Dsg / Di fell below the scope of the invention. Further, in the hot-rolled plates of steel numbers 31 and 32, not only the Si content was outside the range of the present invention, but also the true strain ratio Ce was below the range of the present invention, so that the ratio Dsg of the average grain size of the crystal grains / Di fell below the scope of the present invention.

Further, since the Mn content of the hot-rolled plate of steel No. 33 is outside the range of the present invention, the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density are below the preferable range of the present invention. , The ratio of the average particle size of the crystal grains, Dsg / Di, was below the range of the present invention. Since the Mn content of the hot-rolled plate of steel No. 34 is outside the range of the present invention, the distribution density ρ1 μm of MnS having an average particle size of 1 μm or more in the region near the surface exceeds the preferable range of the present invention, and the average of MnS. The particle size ratio ds / di and the distribution density ratio ρi / ρs were below the preferable range of the present invention, and the average particle size ratio Dsg / Di of the crystal grains was below the range of the present invention. Further, since the S content of the hot-rolled plate of steel No. 35 is outside the range of the present invention, the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density are below the preferable range of the present invention. , The ratio of the average particle size of the crystal grains, Dsg / Di, was below the range of the present invention. Further, since the S content of the hot-rolled plate of steel No. 36 is outside the range of the present invention, the average particle size ds of MnS in the region near the surface and the distribution density ρ1 μm of MnS having an average particle size of 1 μm or more are the present invention. The ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density are below the preferable range of the present invention, and the ratio Dsg / Di of the average particle size of the crystal grains is the range of the present invention. It fell below.

Further, the hot-rolled plates of steel numbers 37 and 38 have an Al content outside the range of the present invention, and in Example 3 described later, secondary recrystallization does not occur due to finish annealing held at 1200 ° C., and the magnetic flux A unidirectional electrical steel sheet with extremely inferior density was obtained. Further, the hot-rolled plates of steel numbers 39 and 40 have an N content outside the range of the present invention, and in Example 3 described later, secondary recrystallization does not occur due to finish annealing held at 1200 ° C., and the magnetic flux A unidirectional electrical steel sheet with extremely inferior density was obtained.

On the other hand, the hot-rolled steel numbers 1 to 18 subjected to hot rolling under the conditions satisfying the requirements in the method for producing the hot-rolled plate for unidirectional electromagnetic steel plate of the present invention have an average grain size of crystal grains. The ratio of Dsg / Di is within the range of the present invention, the average particle size ds of MnS in the region near the surface, the distribution density ρ1 μm of MnS having an average particle size of 1 μm or more in the region near the surface, and the average particle size of MnS. The ratio ds / di and the distribution density ratio ρi / ρs were within the preferable range of the present invention.

(Example 2)
The slabs of steel numbers 41 to 58 having the chemical compositions shown in Table 3 below are placed in a heating furnace having an ambient temperature of 1320 ° C. and held for 30 minutes to obtain a surface temperature of the castings shown in Table 4-1 below. After heating to the one-side heating temperature Ts0, the slabs extracted from the heating furnace were roughly rolled and finish-rolled under the conditions shown in Table 4-1 below.

In the above rough rolling, the first rolling pass was performed so that the plate thickness t1 [mm] of the steel plate on the entry side was shown in Table 4-1 below. Further, a plurality of rolling passes continuously performed on the steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. The surface temperature Tss [° C.] of the steel sheet at the entry side of the first rolling pass in the rolling pass, the plate thickness center temperature Tcs [° C.], Tss-Tcs [° C.], and the plate thickness ts [mm], and the above-mentioned plurality of rolling. Table 4-1 below shows the surface temperature Tsf [° C.], center temperature Tcf [° C.], Tsf-Tcf [° C.], and plate thickness tf [mm] of the steel sheet on the exit side of the final rolling pass in the pass. It was done as shown. In the above rough rolling, the true strain epr [−] of rolling performed in a plurality of rolling passes continuously performed on the steel sheet while satisfying the above relationship is shown in Table 4-1 below. By performing the above rough rolling, a rough rolled plate having a plate thickness tff1 of 6.0 mm or 8.0 mm after rough rolling was obtained.

Then, as shown in the conditions shown in Table 4-1 below, the rough-rolled plate obtained by the rough rolling is subjected to a cooling start rate [° C.] of 1100 ° C. to a cooling arrival rate of 550 to 800 ° C. []. After cooling to [° C.] at an average cooling rate of 1.5 to 2.5 ° C./sec [° C./sec], the temperature is kept isothermal at the above cooling reaching rate for a holding time [sec] of 180 to 600 sec to set the surface temperature. After heating to the temperature at which the temperature was reached again [° C.], the above-mentioned finish rolling was performed under the conditions shown in Table 4-1 below.

Further, in the above-mentioned finish rolling, a plurality of rolling passes continuously performed on a steel sheet in a state where the surface temperature Ts: 1100 to 1200 ° C. and the plate thickness center temperature Tc: 1000 to 1100 ° C. satisfy the relationship of Ts−Tc ≧ 80 ° C. The surface temperature Tss [° C.] of the steel sheet at the entry side of the first rolling pass in the plurality of rolling passes, the plate thickness center temperature Tcs [° C.], Tss-Tcs [° C.], and the plate thickness ts [mm]. In addition, the surface temperature Tsf [° C.], the plate thickness center temperature Tcf [° C.], Tsf-Tcf [° C.], and the plate thickness tf [mm] of the steel sheet at the exit side of the final rolling pass in the above plurality of rolling passes are as follows. The procedure was as shown in Table 4-1. In the above finish rolling, the true strain epf [−] of rolling performed in a plurality of rolling passes continuously performed on the steel sheet while satisfying the above relationship is shown in Table 4-1 below. By performing the above-mentioned finish rolling, a hot-rolled plate having a finished plate thickness of 2.3 mm was obtained.

Further, the true strain et [−] of the entire hot rolling composed of the rough rolling and the finish rolling is shown in Table 4-1 below. The total true strain ep of the true strain epr applied to the steel sheet in the rough rolling state satisfying the above relationship and the true strain epf applied to the steel sheet in the state satisfying the above relationship in the finish rolling is shown in Table 4 below. It came to be shown in -1. Further, the ratio Ce (ep / et × 100) [%] of the true strain ep to the true strain et is shown in Table 4-1 below.

Further, the average particle size Dsg [μm] of the Goss directional grains, the average particle size ds [nm] of MnS, and the distribution density of MnS in the region near the surface of the obtained hot-rolled plate having a thickness of 1/10 to 1/5. ρs [μm ^-2], and the distribution density ρ1μm an average particle size of more than 1μm MnS [μm ^-2], and the total orientation of the crystal in the central region of the sheet thickness 1/5 layer to the center of the obtained hot-rolled sheet The average particle size Di [μm] of the grains, the average particle size di [nm] of MnS, and the distribution density ρi [μm- ² ] of MnS were investigated. Further, the ratio of the average particle size Dsg of the Goss directional grains Dsg in the region near the surface to the average particle size Di of the crystal grains in all directions in the central region Dsg / Di [−], and the region near the surface of MnS in the central region with respect to the average particle size di. The ratio ds / di [−] of the average particle size ds of MnS and the ratio ρi / ρs [−] of the distribution density ρi of MnS in the central region to the distribution density ρs of MnS in the region near the surface were calculated. The average particle size of the crystal grains is the value obtained by calculating and averaging the diameters of circles of the same area with respect to the projected area for each of the observed crystal grains, and the average particle size of MnS is the same for the observed multiple MnS with respect to the projected area. The average value of the diameters of the circles in the area, and the distribution density of MnS is the value obtained by dividing the number of MnS counted by observing the mirror-polished cross section by the area of the observation field. The obtained results are shown in Table 4-2 below.

In the hot-rolled plate of steel number 55, the total addition amount of one or more selected from the group consisting of Bi, Pb, As, and Te of the present invention was less than the range of the present invention, so that the average of the crystal grains was average. The particle size ratio Dsg / Di was below the range of the present invention, and the average particle size ds of MnS in the region near the surface was above the preferable range of the present invention.

In the hot-rolled plates of steel numbers 56 and 57, the true strain ratio Ce was below the range of the present invention, so that the ratio Dsg / Di of the average particle size of the crystal grains was below the range of the present invention, and the average grain of MnS. The diameter ratio ds / di and the distribution density ratio ρi / ρs were below the preferred range of the present invention.

On the other hand, the hot-rolled steel numbers 41 to 54 subjected to hot rolling under the conditions satisfying the requirements in the method for producing the hot-rolled sheet for unidirectional electromagnetic steel sheet of the present invention have the average grain size of the crystal grains. The ratio Dsg / Di was within the range of the present invention, and the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density were within the preferable range of the present invention.

Above all, the ratio of the average particle size of the crystal grains, Dsg / Di, is in a more preferable range for the hot-rolled plates of steel numbers 41 to 50 that satisfy the preferable cooling rate after rough rolling, the temperature reached for cooling, and the holding time of the present invention. Therefore, the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density became more preferable ranges. Among them, the hot-rolled plates of steel numbers 41, 44, 46, 47, and 49 having a true strain ratio Ce of 40 to 43% have the same chemical composition and a true strain ratio Ce of 40 to 43. The ratio Dsg / Di of the average particle size of the crystal grains was in the preferable range, and the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density were in the more preferable range than the steel number 1 which became%. .. Similarly, the hot-rolled plate of steel number 48 having a true strain ratio Ce of 50 to 52% has the same chemical composition and has a true strain ratio Ce of 50 to 52% from steel number 3. The ratio of the average particle size of the crystal grains, Dsg / Di, was in the preferable range, and the ratio of the average particle size of MnS, ds / di, and the ratio of the distribution density, ρi / ρs, were in the more preferable range.

(Example 3)
A part of the hot-rolled plates manufactured in Examples 1 and 2 was wound around a coil at the winding temperature CT [° C.] shown in Table 5 below, and then hot-rolled under the conditions shown in Table 5 below. It was annealed. Specifically, for the hot-rolled plates of steel numbers 1, 3, 16, 18, 41, 42, 44, 19, 22, 30, 32, 37, 38, 39, 40, 50, and 56, the temperature is 550 ° C. The coil wound by the winding temperature CT was heated to 1150 ° C., and then annealed with a hot-rolled plate kept at 900 ° C. for 80 seconds. Further, the hot-rolled plates of steel numbers 47, 48, and 50 were annealed by hot-rolling plates in which the coil wound at the winding temperature CT of 950 ° C. was held at the winding temperature CT for 80 seconds. After annealing these hot-rolled plates, as shown in Table 5 below, each hot-rolled annealed plate was cold-rolled to obtain a cold-rolled plate having a cold-rolled plate thickness tfff of 0.23 mm. .. After the cold rolling, the cold rolled sheet was decarburized and annealed under the conditions shown in Table 5 below. Specifically, hot-rolled plates other than steel number 44 are subjected to decarburization annealing held at 835 ° C for 120 seconds, and when the temperature is raised to 835 ° C for decarburization annealing, the temperature is raised from 300 ° C to 750 ° C. In the annealing process, the heating rate was set to 10 ° C./sec. Further, the hot-rolled plate of steel number 44 is subjected to decarburization annealing held at 835 ° C. for 120 seconds, and when the temperature is raised to 835 ° C. for decarburization annealing, the temperature rise process from 300 ° C. to 750 ° C. The temperature rising rate was set to 200 ° C./sec. After decarburization annealing, the temperature was raised to 1200 ° C. and finish annealing was performed in which the temperature was maintained at 1200 ° C. As a result, a unidirectional electromagnetic steel sheet was manufactured.

A magnetic measurement test piece having a size of 60 mm × 300 mm was sheared from the unidirectional electromagnetic steel sheet produced in this manner, strain-removed and annealed at 700 ° C., and then the magnetic flux density B8 [T] was measured. The results are shown in Table 5 below. In Table 5 below, the secondary recrystallization stability is indicated by a circle in the sample with B8 of 1.91 T or more, assuming that the secondary recrystallization is stabilized, and the secondary recrystallization is shown in the sample with B8 of 1.95 T or more. The secondary recrystallization stability is indicated by a ◎ mark as the crystal is further stabilized, and the secondary recrystallization stability is indicated by a △ mark as the secondary recrystallization is not stabilized in the sample with B8 less than 1.91T. In addition, the secondary recrystallization stability was indicated by x for those for which secondary recrystallization was not obtained.

As shown in Tables 1 and 3 above, the hot-rolled plates of steel numbers 22 and 55 do not contain an element selected from the group consisting of Bi, Pb, As, and Te, and therefore have an average grain size of crystal grains. As a result of the ratio Dsg / Di falling below the range of the present invention, both B8 fell below 1.91T and became inferior.

As shown in Table 2-1 above, the true strain ratio Ce of the hot-rolled plates of steel numbers 19 and 30 was below the range of the present invention, so that the ratio Dsg / Di of the average grain size of the crystal grains was the present invention. As a result of falling below the range of, B8 fell below 1.91T and was inferior.

On the other hand, in the hot-rolled plate of steel No. 1 having the same chemical composition as that of steel No. 19, since the true strain ratio Ce was within the range of the present invention, the ratio Dsg / Di of the average grain size of the crystal grains was high. As a result of being within the scope of the present invention, B8 was higher than 1.91T. Further, the hot-rolled plate of steel number 3 has the same chemical composition as steel number 1, but unlike steel number 1, the true strain ratio Ce is 50% or more of the preferable range of the present invention, and the crystal grains The result that the ratio Dsg / Di of the average particle size was 1.20 or more, which is the preferable range of the present invention, and the ratio ds / di of the average particle size of MnS and the ratio ρi / ρs of the distribution density were in the more preferable range of the present invention. , B8 was 1.947T, which was higher than steel number 1. Further, the hot-rolled plate of steel number 16 has the same chemical composition as steel number 1, and the true strain ratio Ce is about the same as that of steel number 1, but unlike steel number 1, the surface temperature of the slab is different. After cooling to 850 ° C., the steel was placed in a heating furnace having an ambient temperature of 1320 ° C. and held for 30 minutes to bring the surface temperature to the slab heating temperature Ts0 shown in Table 2-1 above. The rough rolling and finish rolling were performed, and as a result of the ratio Dsg / Di of the average particle size of the crystal grains being larger than that of steel number 1, B8 was 1.949 T, which was higher than that of steel number 1.

Further, unlike steel number 1, the hot-rolled plate of steel number 18 contains Sn in addition to Bi, and unlike steel number 1, the slab is cooled to a surface temperature of 850 ° C. and then has an atmosphere. By charging the steel into a heating furnace having a temperature of 1320 ° C. and holding it for 30 minutes, the surface temperature is set to the slab heating temperature Ts0 shown in Table 2-1 above, and then rough rolling and finish rolling are performed. The true strain ratio Ce is 50% or more of the preferable range of the present invention. As a result, in the unidirectional electromagnetic steel sheet of steel number 18, the ratio Dsg / Di of the average grain size of the crystal grains is larger than that of steel numbers 1 and 16, and B8 is 1.962T, which is significantly larger than that of steel numbers 1 and 16. It got higher.

Further, in the hot-rolled sheet of steel No. 30, not only the C content exceeds the range of the present invention, but also the true strain ratio Ce is below the range of the present invention, and the ratio Dsg of the average particle size of the crystal grains As a result of / Di falling below the scope of the present invention, in the unidirectional electromagnetic steel sheet of steel number 30, B8 was 1.844T, which was extremely inferior.

Further, in the hot-rolled sheet of steel number 32, not only the Si content is higher than the range of the present invention, but also the true strain ratio Ce is lower than the range of the present invention, and the ratio Dsg of the average particle size of the crystal grains is As a result of / Di falling below the range of the present invention, significant cracks occurred in the cold rolling, and a unidirectional electromagnetic steel sheet could not be manufactured.

Further, the hot-rolled plates of steel numbers 37 and 38 have a true strain ratio Ce within the range of the present invention and an average grain size ratio Dsg / Di of the crystal grains within the range of the present invention, but contain Al. The amount was out of the range of the present invention, the distribution density of AlN was not sufficient, and secondary recrystallization did not occur. Similarly, for the hot-rolled plates of steel numbers 39 and 40, the true strain ratio Ce is within the range of the present invention, and the average grain size ratio Dsg / Di of the crystal grains is within the range of the present invention. The content was outside the range of the present invention, the distribution density of AlN was not sufficient, and secondary recrystallization did not occur.

Further, in the hot-rolled plate of steel No. 56, the ratio Ce of true strain in the rough rolling and the finish rolling is less than the range of the present invention, and the ratio Dsg / Di of the average grain size of the crystal grains is the range of the present invention. As a result, B8 was inferior to 1.868T.

On the other hand, in the hot-rolled plates of steel numbers 41, 42, 44, 47, 48, 49 and 50, the ratio Ce of the true strain in the rough rolling and the finish rolling is within the range of the present invention, and the crystal grains As a result of the ratio Dsg / Di of the average particle size of the above being within the range of the present invention, B8 exceeded 1.950T, and good magnetic properties were obtained. Further, among these hot-rolled plates, the hot-rolled plate of steel number 42 has a ratio Ce of true strain between the rough rolling and the finish rolling of 50% or more of the preferable range of the present invention, and is an average grain of crystal grains. As a result of the diameter ratio Dsg / Di being larger than that of steel number 41, B8 was 1.959T, which was higher than that of steel number 41. Further, in the hot-rolled plate of steel number 44, the ratio Ce of true strain in the rough rolling and the finish rolling is about the same as that of steel number 41, and the ratio Dsg / Di of the average particle size of the crystal grains is steel number 41. It was about the same, but unlike steel number 41, when the temperature was raised to 835 ° C for decarburization annealing, the rate of temperature rise was set to 200 ° C / sec in the process of raising the temperature from 300 ° C to 750 ° C. As a result, B8 was 1.961T, which was higher than that of steel number 41. Further, the hot-rolled plate of steel number 47 has a true strain ratio Ce of the rough rolling and the finish rolling of the same as that of steel number 41, but unlike steel number 41, it has a winding temperature CT of 950 ° C. As a result of hot-rolled plate annealing in which the wound coil was held at the winding temperature CT for 80 seconds, B8 was 1.958T, which was higher than that of steel number 41.

Further, in the hot-rolled plates of steel numbers 48 and 50, the true strain ratio Ce in the rough rolling and the finish rolling is 50% or more of the preferable range of the present invention, and the ratio Dsg / Di of the average particle size of the crystal grains. Is larger than steel number 41, and unlike steel number 41, the coil wound at the winding temperature CT of 950 ° C. is subjected to hot-rolled plate annealing in which the coil is held at the winding temperature CT for 80 seconds. As a result, B8 Was 1.970 or more, and extremely good magnetic characteristics were obtained.

Claims (10)

By mass%, C: 0.1% or less, Si: 2.5~4.0%, Mn: 0.05~0.1 0%, S: 0.01 0 ~0.04 0%, Al: One or more selected from the group consisting of 0.01 0 to 0.05 0 % and N: 0.001 0 to 0.030 0 %, and Bi, Pb, As, and Te: 0 in total containing .0002% 0.02 100% or less, the balance being a hot rolled sheet for grain-oriented electrical steel sheet consisting of Fe and unavoidable impurities,
The ratio of the average grain size of the Goss azimuth grains in the region near the surface of the 1/5 to 1/5 layer thickness to the average grain size of the crystal grains in the central region of the 1/5 layer to the center is 1.10 or more. ,
The ratio of the average particle size of MnS in the region near the surface of the 1/5 to 1/5 layer thickness to the average particle size of MnS in the central region of the plate thickness 1/5 layer to the center is 1.10 or more, and the surface The average particle size of MnS in the vicinity region is 300 nm or less.
The ratio of the distribution density of MnS in the region near the surface of the 1/5 to 1/5 layer thickness to the distribution density of MnS in the central region of the 1/5 layer to the center is 1.10 or more, and the region near the surface A hot-rolled plate for a unidirectional electromagnetic steel plate, characterized in that the distribution density of MnS having an average particle size of 1 μm or more is 20 pieces / mm ² or less . One or more selected from the group consisting of Sb, Sn, and P in mass% instead of a part of the Fe: 0.0004% or more and 0.5% or less in total. oriented electrical steel sheet for hot-rolled sheet according to claim 1,. The method for manufacturing a hot-rolled sheet for unidirectional electrical steel sheet according to claim 1 or 2.
By mass%, C: 0.1% or less, Si: 2.5~4.0%, Mn: 0.05~0.1 0%, S: 0.01 0 ~0.04 0%, Al: 0.01 0 to 0.05 0%, and N: 0.001 0 ~0.030 00%, and Bi, Pb, as, and one or more selected from the group consisting of Te: 0 total containing .0002% 0.02 100% or less, in the hot rolling step the remainder subjected to hot rolling the cast slab consisting of Fe and unavoidable impurities, the surface temperature Ts: 1100 to 1200 ° C. and the thickness center temperature The true strain of rolling applied to a steel sheet in a state where Tc: 1000 to 1100 ° C. satisfies the relationship of Ts−Tc ≧ 80 ° C. is 40% or more of the true strain of the entire hot rolling. A method for manufacturing a hot-rolled sheet for directional electromagnetic steel sheets. In the hot rolling step, the slab cooled to a surface temperature of 900 ° C. or lower was charged into a heating furnace having an ambient temperature of 1200 ° C. or higher, and extracted from the heating furnace within 1 hour after charging. The method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet according to claim 3 , wherein the slab is hot-rolled. In the hot rolling step, the rolled steel sheet is cooled to a surface temperature of Ts from 1100 ° C. or higher to 600 to 750 ° C. or lower at an average cooling rate of 2 ° C./s or higher, and 0s to 0 s to a temperature range of 600 to 750 ° C. The unidirectionality according to claim 3 or 4 , wherein after holding for 300 s, the rolled steel sheet is heated to a temperature of 1100 ° C. or higher and 1150 ° C. or lower with a surface temperature of Ts, and then further rolled. A method for manufacturing a hot-rolled sheet for electromagnetic steel sheets. Claims 3 to 5 are characterized in that, in the hot rolling step, the slab is heated to a surface temperature of 1.25 to 1400 ° C., and then the slab after heating is subjected to the hot rolling. A method for manufacturing a hot-rolled sheet for a unidirectional electromagnetic steel sheet according to any one of the above. The slab is one or more selected from the group consisting of Sb, Sn, and P in mass% instead of a part of the Fe: 0.0004% or more and 0.5% or less in total. The method for producing a hot-rolled sheet for a unidirectional electromagnetic steel sheet according to any one of claims 3 to 6 , further comprising. A hot-rolled plate manufacturing process for manufacturing a hot-rolled plate for unidirectional electromagnetic steel sheets by performing the method for manufacturing a hot-rolled plate for unidirectional electrical steel sheets according to any one of claims 3 to 7 .
The hot-rolled sheet annealing step of annealing the hot-rolled sheet to the one-way electromagnetic steel sheet, and
A cold rolling step of cold rolling the steel sheet after hot rolling sheet annealing, and
The decarburization annealing step of performing decarburization annealing on the steel sheet after cold rolling, and
A method for producing a unidirectional electrical steel sheet, which comprises a finish annealing step of applying finish annealing to the steel sheet after decarburization annealing. The one according to claim 8 , wherein in the hot-rolled sheet annealing step, hot-rolled sheet annealing is performed in which the hot-rolled sheet for a unidirectional electromagnetic steel sheet is held in a temperature range of 900 to 1050 ° C. for 60 seconds or more. Manufacturing method of directional electromagnetic steel sheet. In the decarburization annealing step, the steel sheet after cold rolling was heated at a heating rate of 100 ° C./s or more in a heating process of raising the temperature from 350 ° C. or lower to 700 ° C. or higher and 850 ° C. or lower. The method for producing a unidirectional electromagnetic steel sheet according to claim 8 or 9 , wherein the steel sheet after cold rolling is later subjected to the decarburization annealing.