JPH07116510B2 - Non-oriented electrical steel sheet manufacturing method - Google Patents

Description

The present invention relates to a non-oriented electrical steel sheet, and more particularly to a method for producing a non-oriented electrical steel sheet having a good magnetic flux density-iron loss balance.

[Conventional technology and problems to be solved]

The non-oriented electrical steel sheet has a smaller anisotropy in magnetic properties than the grain-oriented electrical steel sheet, and therefore is generally used for iron cores of rotating machines. Also, because it is cheaper than grain-oriented electrical steel,
Some are also applied to static devices such as transformers and ballasts. The characteristic values required for the non-oriented electrical steel sheet are mainly the iron loss and the magnetic flux density, and it is desirable that the iron loss is low, and the magnetic flux density is high and the iron loss balance is good.

Heretofore, various manufacturing methods have been disclosed in order to manufacture a non-oriented electrical steel sheet having such good magnetic properties. In particular, it is important to control the texture in order to improve the magnetic flux density, and it is necessary to increase the ratio of (100) or (110) faces and keep the (111) face ratio low.
Therefore, the technology for improving the hot-rolled sheet structure by performing hot-rolled sheet annealing, the technology for controlling the recrystallized texture during subsequent annealing by optimizing the cold pressure ratio, further cold pressure, annealing A technique for selecting a texture preferable for magnetic properties by performing the treatment twice or more is disclosed. These techniques are techniques for optimizing the conditions of the steps after hot rolling. However, in order to optimize the texture after the final annealing, texture control in the hot rolling stage holds an important key, and in this sense, each technology described above can sufficiently improve the texture. Can not. In other words, these technologies are about 200m
It uses a hot-rolled sheet obtained by hot-rolling m slabs, and is not a technology that actively attempts to improve the texture at the hot-rolling stage.

On the other hand, according to strip casting, which has been attracting attention from the viewpoint of energy saving and process saving in recent years, since it is possible to directly cast into a plate thickness of the conventional hot rolled plate thickness,
It is possible to obtain a texture different from that of the hot rolled sheet produced by the conventional method. That is, according to strip casting,
Since the molten metal has a high cooling rate, it has a columnar structure over the entire plate thickness. Further, in the steel containing 1.7% or more of Si, since the α-γ transformation does not occur, the columnar structure is retained even after cooling the cast slab. Such a columnar structure has a {100} <uvw> orientation, and is the most preferable texture for magnetic properties. Therefore, also in the production of non-oriented electrical steel sheets, thin cast pieces having columnar crystals are cast as thin as possible by strip casting, and {10
A technique for maintaining the 0} <uvw> structure has been disclosed (for example, JP-A-62-240714 and JP-A-63-60227).
issue).

However, in the steel containing 1.7% or less of Si having α-γ transformation, in the cooling stage after casting, α
Since the {100} <uvw> structure generated at the casting stage is randomized by the −γ transformation, it becomes extremely difficult to maintain the cast structure.

In view of such problems, the present invention aims to improve the magnetic flux density-iron loss balance in a non-oriented electrical steel sheet that undergoes α-γ transformation, and controls the texture of a hot rolled sheet using a thin slab-direct hot rolling process. The method for producing a non-oriented electrical steel sheet having excellent magnetic properties is disclosed.

That is, according to the present invention, in weight%, C ≦ 0.01%, 0.1 ≦ Si
<1.7%, Al <1%, (Si + 1.7Al) <1.7%, N ≦ 0.003
%, S ≦ 0.005%, the balance Fe and the unavoidable impurities are cast into a thin slab, and then the slab is hot-rolled without cooling to a point A ₃ or less, and the hot-rolling step is performed. So with the material temperature makes a rolling reduction of 20% or more to reach the _three points a, the total amount of reduction during hot rolling 80% to 95%
And after annealing the hot rolled sheet as it is or after hot rolled sheet annealing,
It is characterized in that cold rolling is performed twice or more, including intermediate or intermediate annealing, and then annealing is performed.

[Operation] In the non-oriented electrical steel sheet having a structure having an α-γ transformation, the present invention applies a thin cast slab-direct hot rolling method to obtain an excellent magnetic flux density-iron loss balance. By utilizing the α-γ transformation, the structure of the hot rolled sheet is controlled to improve the magnetic properties after the final annealing.

The following experiments were conducted to clarify the effects of the present invention.

After casting 1.63% Si steel having the composition shown in Table 1 into a thin ingot with a thickness of 30 mmt, in the cooling stage, the γ region (1230 to 10
Sample (FC material) cooled at room temperature to -5 × 10 ^-2 ° C / sec and cooled to room temperature (FC material), and sample cooled at room temperature in the mold to -5 ° C / sec. Photographs (A) and (B) of FIG. 1 show the cross-sectional structure of the slab of (MC material). According to this, since the MC material in the photograph (B) has a high cooling rate of the slab,
The columnar structure immediately after casting is maintained. On the other hand, since the FS material in photograph (A) has a low cooling rate, it becomes fine equiaxed grains due to the α → γ → α transformation. Also, when the MC material is reheated and soaked at 1050 ° C for 5 minutes, as shown in photograph (C), the columnar structure is maintained, so after casting, it should be below A ₃ point (1000 ° C). However, even in the case of a straight rolled material (HDR material) in which hot rolling is started at 1050 ° C, it is clear that the structure of the cast slab just before the start of hot rolling has a columnar structure like the MC material.

Said the FC material and MC materials hot rolled plate, after casting, after soaking 1050 ° C. × 5min without below _three points A, hot-rolled sheet obtained by starting the hot rolled (HDR material) And were cold-pressed and annealed in the following steps. Fig. 2 shows the heat history of each cast piece until hot rolling. Also, HDR material is hot-rolled, CCR material (MC member, FC material) together make 40% reduction up to A ₃ point (1000 ° C.), the plate thickness 2.5m
It was a hot-rolled sheet of m (reduction ratio 91.7%).

Hot rolled sheet ↓ Hot rolled sheet annealing: 800 ℃ × 5min, air cooling ↓ Cold pressure (sheet thickness 0.5mm) ↓ Annealing: 750〜920 ℃ × 2min, air cooling, in 25% H ₂ + 75% Ar The X-ray integrated reflection intensity ratio of the steel sheet is shown in FIG. 3 in relation to the final annealing temperature.

According to this, the HDR material, at any annealing temperature,
It can be seen that the {200} and {100} components are higher and the {222} component is lower than the FC material and MC material in which the slab is below A ₃ point before hot rolling. In general, in order to improve the magnetic flux density of a non-oriented electrical steel sheet, it is desirable to integrate as many <100> axes, which are easy magnetization directions, on the steel sheet surface as much as possible. For this reason, the effective crystal plane is (100). Alternatively, a crystal plane such as the (110) plane, which does not include the easy axis of magnetization, such as the (111) plane, should be avoided as much as possible. Therefore, it is clear that the HDR material has a higher magnetic flux density than the MC material and the FC material. That is, even if the microstructure just before hot rolling is the same columnar structure, the above-mentioned difference in texture occurs depending on whether the slab falls below the A ₃ point from solidification to hot rolling.

When the thickness of the slab becomes thin, the heat removal rate becomes large, the solidification rate becomes large, and the columnar structure becomes fine immediately after solidification. The columnar structure formed during such solidification has a texture composed of {100} <uvw>, and is a texture having the most magnetic easy axes and good magnetic properties. Here, the steel accompanied by transformation passes through points A ₄ and A _{3 in} the cooling stage after solidification, and reaches room temperature through α → γ and γ → α transformations. If the temperature of the slab is lower than A ₃ point before hot rolling, α → γ and γ → α transformation occurs in the cooling stage of the slab, and α → γ transformation occurs during reheating. Three transformations are required before the start of rolling, and the texture of the slab is completely randomized.
On the other hand, if the rolling is started below the A ₃ point after solidification, the α → γ transformation is performed only once at the A ₄ point when the slab is cooled, and is maintained in the γ region until hot rolling. Since the time is short, the transformation is not completed in the entire slab and the structure close to {100} <uvw> is maintained.

Further, when the hot rolling is started after the solidification of the slab and the temperature does not fall below the A ₃ point, it was revealed that the rolling reduction in the γ region greatly contributes to the improvement of the magnetic flux density as described below.

After casting a thin cast strip having a thickness of 40mmt the steel composition of No.1~3 in Table 2, and cooled at 1.5 ° C. / sec, without falling below the _3-point A in the composition in the cooling step, 1000 Hot rolling was started at 1150 ° C, the rolling reduction until passing the A ₃ point was changed, the magnetic flux density after cold pressing and annealing was measured, and the effect of the rolling reduction on the magnetic flux density was examined. It was In addition, No. 4 steel
Although it is a steel type that does not have A ₃ points, for comparison, this was also cast-cooled in the same manner, and the reduction ratio until passing 1000 ° C. was changed, and the same measurement was performed. In the hot rolling, the final plate thickness was set to 2.0 to 2.5 mmt (total reduction amount 93.75 to 95%), and it was cooled to room temperature by cooling. In order to simulate the cooling after winding at the time of actual hot rolling, in hot rolled sheets of No. 1, 2, 3, 4 composition, 660 ℃, 680 ℃, 550 ℃
After soaking in a furnace at ℃ and 700 ℃ for 30 minutes, the inside of the furnace was cooled. Further, the hot-rolled sheets of Nos. 3 and 4 were subjected to air-cooled hot-rolled sheet annealing at 870 ° C for 1.5 minutes. Next, after pickling and removing the scale,
0.5mmt cold pressed to a thickness, followed by 25% H ₂ -75% N ₂ atmosphere, No.1 is 800 ° C. × 1.5 min, No.2 is 830 ℃ × 1.5min, No.
No. 3 and 4 were annealed by air cooling at 880 ° C for 2 minutes.

FIG. 4 shows the measurement results of the above-mentioned magnetic flux density. From the measurement results, it was revealed that the magnetic flux density sharply increases when the rolling point is reduced by 20% or more at the point A ₃ or higher.
This is because not only the texture of the hot-rolled sheet with good magnetic properties can be formed by rolling the {100} <uvw> structure remaining in the slab before passing the A ₃ point, but also by passing the A ₃ point. This is because the rolled processed structure can be recovered and recrystallized by the transformation energy when passing through the A ₃ point.

On the other hand, regarding the ferrite structure formation and texture formation during hot rolling, not only the above-mentioned reduction ratio of A ₃ point or more,
The total rolling reduction during hot rolling also has a large effect, and affects the cold pressing and texture formation after annealing, that is, the magnetic flux density.

Steels with compositions No. 5 and No. 6 in Table 3 are available with thicknesses of 8, 10, 1
After casting into thin slabs of 5, 20, 30, 40, 50, 80 mm, 4.2 to 1 ℃
/ sec, start hot rolling at 1000 ~ 1200 ℃ without lowering A ₃ point in each composition at that cooling stage, and reduce rolling by 23 ~ 47% before passing A ₃ point during rolling. Go 1.4
A hot rolled sheet having a thickness of 2.5 mm was left to cool to room temperature. The magnetic flux density after cold pressing and annealing was measured for these hot-rolled sheets, and the effect of the total reduction amount during hot rolling on the magnetic flux density was examined. Further, No. 7 steel is a steel type that does not have A ₃ points, but it is cast-cooled in the same manner as above with a thin slab of each of the above thicknesses, and at the cooling stage, before passing through 1000 ° C, 23 ~ A 47% reduction was performed to obtain a thickness of 1.4 to 2.5 mm, the temperature was cooled to room temperature by cooling, and the cold rolling of these hot rolled sheets and the magnetic flux density after annealing were measured. In order to simulate the cooling after winding in the actual hot rolling, in hot rolled sheets of No. 5, 6, and 7 compositions, after soaking for 1 hr in furnaces at 680 ° C, 700 ° C, and 710 ° C, respectively, Cooling was performed in the furnace. Furthermore, regarding No. 7 hot rolled sheet
870 ℃ × 1.5min Air-cooled hot-rolled sheet annealing. These hot-rolled sheets were pickled, then cold pressed to a thickness of 0.5 mmt, and then 25% H ₂ −
In a 75% N ₂ atmosphere, No.5 is 800 ℃ × 1.5min, No.6 is 850 ℃
× 2min, No.7 was annealed by air cooling at 880 ℃ × 2min. Also, as a comparative material, cast a thin slab of the same composition and thickness,
Once air-cooled to room temperature, it was reheated to 1250 ° C., processed and treated on the same schedule, and the same measurement was performed.

FIG. 5 shows the measurement results of the magnetic flux density. From the measurement results, it was found that the magnetic flux density can be optimized when the total rolling reduction during hot rolling is 80 to 95%. This is because when the {100} <uvw> structure maintained until just before hot rolling is processed by hot rolling, the rotation of the crystal axis due to the slip deformation and shear deformation of the crystal causes the subsequent recovery of the structure and recrystallization process. This is due to the fact that they were matched against the formation of a new texture of. Further, when the rolling reduction is 95% or more, the strain introduced during hot rolling becomes too large, so that the recovery of ferrite and the progress of recrystallization are suppressed, and the formation of the ferrite structure during hot rolling is hindered. Further, when the slab is below the A ₃ point before solidification after hot rolling, as shown in FIG.
The condition that the magnetic flux density is significantly improved cannot be obtained.

The constituent features of the present invention will be specifically described below.

The method of the present invention, as a raw material steel, C: 0.01% or less, Si: 0.1%
Above 1.7%, Al: less than 1%, (Si + 1.7Al): less than 1.7%, N: 0.003% or less, S: 0.005% or less. The reason for the limitation will be described below.

C: If it exceeds 0.01%, it is harmful to the iron loss of the magnetic properties, and therefore C has 0.01% as its upper limit. Further, in order to suppress deterioration of iron loss due to magnetic aging, C: 0.005% or less is desirable. When magnetic properties become a problem in steel containing 0.005 to 0.01% C, decarburization annealing is performed in the hot-rolled sheet annealing or the final annealing stage to make C in the steel 0.005%.
It can be less than or equal to%.

Si: Si increases the specific resistance of steel and lowers iron loss.
% Or more must be added. However, if Si is added in an amount of 1.7% or more, the transformation disappears to become an α single phase steel, and the texture cannot be improved by utilizing the transformation in the present invention.
For the above reasons, the Si content is 0.1% or more and less than 1.7%.

Al: Al is also an element effective for increasing the specific resistance of steel and lowering iron loss like Si, but if 1% or more is added, the transformation point disappears to become an α single phase steel. The transformation cannot be used to improve the texture. Therefore, Al is 1
Less than%. In order to perform sufficient deoxidation of molten steel,
Al: 0.001% or more is desirable.

(Si + 1.7Al): Si and Al are both effective elements for reducing iron loss, but are also ferrite forming elements.
When Si + 1.7Al is 1.7% or more, a ferritic single phase steel is obtained. Therefore, in the present invention, it is necessary to make (Si + 1.7Al.): Less than 1.7%.

If N is added in excess of 0.003%, iron loss is deteriorated in a solid solution state. Therefore, N has an upper limit of 0.003%. In addition, in the steel containing Al, the precipitation of AlN particles deteriorates the ferrite grain growth during annealing and the iron loss deteriorates.

As with S: N, since iron loss is degraded in the solid solution state,
It is specified as 0.005% or less.

The other components are not particularly limited, but as described below, Mn: 0.01 to 2.0%, P: ≤
It is preferably 0.1%.

Mn: Mn is an austenite forming element, and its addition can lower the A ₃ point, and in steels with high Si and Al contents, in order to secure a reduction rate of 20% or more at the A ₃ point or higher. It becomes effective. However, addition of more than 2.0% reduces ductility at cold pressure, so 2.0% or less is desirable.

The addition of P: P can increase the specific resistance of the steel and reduce the iron loss, but if it exceeds 0.1%, the cold ductility deteriorates significantly, so 0.1% or less is desirable.

Further, when AlN is finely precipitated and deteriorates the ferrite grain growth property during the final annealing, it can be improved by adding B in the range of B / N: 0.5 to 2.0.
This is because coarser BN particles preferentially precipitate than AlN particles. In addition, even in the steel containing no Al, B
By adding, it is possible to fix the solid solution N as BN and improve the iron loss.

Next, casting and rolling conditions will be described.

Non-oriented electrical steel sheets are generally 0.50 mm or 0.35 mm thick.
Is the product thickness. It is generally known that, in the cold pressure of a non-oriented electrical steel sheet, a good texture can be obtained by applying a reduction of 60 to 80%. Therefore, in order to make a hot rolled sheet into a product sheet thickness by one cold rolling, the hot rolled sheet thickness must be 1.0 to 2.5 mm. In the present invention, the total rolling reduction during hot rolling is defined as 85 to 95%,
Therefore, when the molten steel is a thin cast piece, the thickness is preferably 7 to 50 mm. Further, when the cold pressing is performed twice or more, the plate thickness can be up to 100 mm.

Further, in the present invention, it is important that the slab after solidification does not pass point A ₃ before the start of hot rolling. Therefore, the cooling rate of the slab is not particularly limited as long as the condition of not passing the point A ₃ before the start of hot rolling is satisfied. However, when the cooling rate is high, there are problems that not only uneven cooling occurs in the central portion and the corner portion of the slab but also the temperature at the corner portion becomes A ₃ point or less. Therefore, it is possible to perform hot rolling immediately after casting, but from the substantial process constraint for starting heat retention when performing heat retention at A ₃ points or more described later, the average cooling rate of the slab is It is preferably 20 ° C./sec or less. In the present invention, even when the cooling rate is high, it is an effective means to use a heat-retaining cover or high-frequency induction heating to soak the heat immediately after casting. Here, when soaking a thin slab before hot rolling, the soaking time is not particularly limited, but if soaking for more than 30 minutes, oxidation of the surface of the slab becomes a problem, soaking time Within 30 minutes is desirable.
By adopting such a process, it is possible to omit the reheating and rough rolling processes as compared with the conventional process of reheating a 200 mm thick slab and performing rough rolling and finish rolling, resulting in a significant cost reduction. You can also plan.

In the present invention, after the thin cast piece is hot-rolled under the above-mentioned conditions, the hot-rolled sheet is usually wound around a coil and allowed to cool. Since the cooling after the winding is slow cooling, recrystallization and grain growth of the ferrite structure of the hot rolled sheet can be promoted during that period. Therefore, it is desirable to wind at 600 to 750 ° C. Further, in order to enhance the effect, it is possible to cover the coil with a heat insulating cover immediately after winding and cool the furnace in a non-oxidizing atmosphere such as Ar. On the other hand, when hot-rolled sheet annealing is further performed after hot-rolling, there is no particular limitation on the winding temperature during hot-rolling. Particularly, when hot-rolled sheet annealing is performed, aggregation coarsening of fine precipitate particles is promoted, and even if the annealing temperature at the final annealing is lowered, the ferrite grain growth property becomes good and iron loss can be reduced. . For hot-rolled sheet annealing, continuous annealing is 750-950 ° C x 0.5-5 min.
In the case of open batch annealing, it is desirable to carry out the pickling of the hot rolled sheet and then the conditions of 700 to 850 ° C. for 1 to 10 hours in a non-oxidizing atmosphere.

Further, when performing hot-rolled sheet annealing, by starting hot-rolled sheet annealing before the coiled hot-rolled coil is cooled to room temperature, energy during heating can be saved, which is effective from the viewpoint of energy saving. Further, if the hot-rolled sheet annealing line is directly passed through the hot-rolled finish, it is not necessary to wind the hot-rolled sheet.

When cold rolling is performed twice or more, intermediate annealing is performed between cold rolling to recover the structure and recrystallize. Intermediate annealing is 750 to 950 ° C when this is performed by continuous annealing.
In the case of open batch annealing for 0.5 to 5 minutes, 700 to 850 ° C. for 1 to 10 hours is preferable in a non-oxidizing atmosphere. The final annealing is performed to recrystallize and grow grains in the ferrite structure and to control the ferrite grains so that the iron loss and the magnetic flux density are in an optimum balance, and the conditions are dry with a dew point of 0 ° C or less. 750-1 in non-oxidizing atmosphere
It is desirable to perform soaking at 000 ° C for 0.5 to 5 minutes.

〔Example〕

Example 1. A non-oriented electrical steel sheet was produced by the method of the present invention and the comparative method using the steel having the components shown in Table 4 as a raw material and the magnetic properties thereof were examined. The results are shown in Table 5.

Inventive method (1) Molten steel of composition I is cast to a thickness of 25 mmt, then cooled at an average of 2 ° C / sec, hot rolling is started at 1100 ° C, 60% reduction at A ₃ point or more, and further rolling is performed 800 Finished to a hot rolled sheet with a thickness of 1.6 mmt at ℃ (total reduction rate 93.6%). After pickling this hot rolled sheet, 0.5mmt
Cool down to thickness and 870 ℃ × 1.5 in 25% H ₂ −75% N ₂ atmosphere
min, air-cooled annealing was performed.

Inventive method (2) Molten steel of composition I is cast to a thickness of 25 mmt, cooled at an average of 5 ° C / sec, held in a furnace at 1150 ° C for 10 minutes, and hot rolled at 1100 ° C to start A ₃ point. After rolling down 60% above, further rolling at 810 ℃
Finished to a hot rolled sheet with a thickness of 1.6 mmt (total reduction rate 93.6%). The subsequent conditions are the same as in the method (1) of the present invention.

Inventive method (3) After casting molten steel of composition I to a thickness of 25 mmt, cooling it at an average of 5 ° C / sec, holding it in a furnace at 1150 ° C for 25 minutes, and then starting hot rolling at 1100 ° C, A ₃ point After rolling down 60% above, further rolling at 800 ℃
Finished to a hot rolled sheet with a thickness of 1.6 mmt (total reduction rate 93.6%). The subsequent conditions are the same as in the method (1) of the present invention.

Inventive method (4) Molten steel of composition I is cast to a thickness of 10 mmt, then cooled at an average of 10 ° C / sec, held in a furnace at 1150 ° C for 30 minutes, and hot rolled at 1100 ° C to start A ₃ point. After rolling down 60% above, further rolling at 800 ℃
Finished to a hot rolled sheet with a thickness of 1.6 mmt (total reduction rate 93.6%). The subsequent conditions are the same as in the method (1) of the present invention.

Inventive method (5) After casting molten steel of composition I to a thickness of 25 mmt, it is cooled at an average of 2 ° C / sec, hot rolling is started at 1100 ° C, and after 60% reduction at A ₃ point or more,
Further, it was rolled to finish a hot rolled sheet with a thickness of 4.0 mmt at 840 ° C (total reduction of 84%). About this hot rolled sheet 800 ℃ × 1mi
n, Air-cooled hot-rolled sheet annealing is performed in a 25% H ₂ −75% N ₂ atmosphere, and then cooled to 2.6 mmt, in a 25% H ₂ −75% N ₂ atmosphere.
Air-cooled intermediate annealing was performed at 0 ° C for 1.5 minutes. 0.5mmt
Cold-press to 870 ℃ × 1.5min and air-cooling finish annealing 25% H ₂ −7
It was conducted in a 5% N ₂ atmosphere.

Comparative method (1) After casting molten steel of composition J into a 220 mmt thick slab, an average of 0.6
Cooling at ℃ / sec, then rough rolling to 35mmt thickness,
Then, finish rolling was started at about 1050 ° C and finished at 830 ° C to obtain a hot rolled sheet with a thickness of 1.6 mmt (total reduction of 99%). After pickling this hot-rolled sheet, it is cold pressed to a thickness of 0.5mmt, 870 ℃ × 1.5
min, air-cooled annealing was performed.

Comparative method (2) Molten steel of composition J was cast into a slab with a thickness of 220 mmt, allowed to cool to room temperature, then reheated to 1200 ° C, hot rolled on the same schedule as in comparative method (1), and then cold pressed. , Annealed.

After casting comparison method (3) of molten steel having the composition I to 25mmt thickness, after once cooled to room temperature, reheated to 1200 ° C., hot rolled starting at 1100 ° C., A ₃
After rolling down 60% above the point, further rolling is performed and 1.6 mmt at 810 ° C.
Finished hot-rolled sheet with a total thickness (total reduction of 93.6%). After pickling the hot rolled sheet, Hiyaoshi to 0.5mmt _{thickness, 25% H 2 -75% N} 2
Air-cooled annealing was performed at 870 ° C for 1.5 minutes in the atmosphere.

Comparative method (4) After casting molten steel of composition I to a thickness of 10 mmt, the average is 900 at 30 ° C / sec.
After cooling to ℃, then heating to 1150 ℃, start hot rolling at 1100 ℃, 70% reduction at A ₃ points or more, then further rolling 80
Finished hot rolled sheet with a thickness of 1.6 mmt at 0 ° C (total reduction of 84%).
The subsequent conditions are the same as in the method (1) of the present invention.

Example 2. After casting the test steel shown in Table 6 into a thin slab of ₃₀ mmt, hot rolling was started without falling below A3 point, and after hot rolling, cold rolling (plate thickness 0.5 m
mt) and annealed. Table 7 shows the hot rolling and annealing conditions. However, for A (3) and G (2), hot-rolled sheet annealing was performed under the following conditions.

A (3): 800 ℃ × 1.5min, air cooling, 25% H ₂ −75% N ₂ , PH ₂ O
/ PH ₂ = 0.005 G (2): 770 ℃ x 5hr, furnace cooling, 75% H ₂ -25% N ₂ , PH ₂ O / PH
₂ = 0.05 The atmosphere during final annealing is as follows.

G (3): 25% H 2 -75% N 2, PH 2 O / PH 2 = 0.15 G (3) _{except: 25% H 2 -75% N} 2, PH 2 O / PH 2 = 0.008 G (2 ) And G (3) after the final annealing had a C content of 0.0018% and 0.0043%, respectively.

The magnetic properties of the obtained steel sheet are described below together with the manufacturing conditions.
Shown in the table.

[Brief description of drawings]

FIG. 1 is a photograph showing the cross-sectional metallographic structure of each of the slabs of FC material, MC material, and MC material reheated at 1050 ° C. for 5 minutes. Figure 2 shows
It is a graph which shows the heat history until hot rolling when each slab shown in FIG. 1 is hot rolled. FIG. 3 shows FIG. 1 (A).
The hot-rolled sheet made of each of the slabs shown in (C) to (C) is subjected to hot-rolled sheet annealing-cold pressure-final annealing, and the X-ray integrated reflection intensity ratio of the steel sheet obtained is related to the final annealing temperature. It is a graph shown. FIG. 4 is a graph showing the effect of the hot rolling reduction rate at the Ar ₃ point or higher of the thin cast piece on the magnetic flux density after the final annealing. FIG. 5 is a graph showing the effect of the total rolling reduction during hot rolling of a thin cast piece on the magnetic flux density after final annealing.

Claims (1)

[Claims] 1. In weight%, C ≦ 0.01%, 0.1 ≦ Si <1.7%,
Al <1%, (Si + 1.7Al) <1.7%, N ≦ 0.003%, S ≦
After casting molten steel consisting of 0.005%, balance Fe and unavoidable impurities into thin slabs, hot rolling is started without cooling the slabs to A ₃ point or less, and in the hot rolling step, the material temperature is Is rolled with a reduction amount of 20% or more until reaching A ₃ point, and the total reduction amount during hot rolling is set to 80 to 95%, and the hot rolled sheet is annealed as it is or after hot rolled sheet annealing. A method for producing a non-oriented electrical steel sheet, which comprises performing cold rolling twice or more with intermediate or intermediate annealing, and then performing annealing.