JPH03219020A - Production of nonoriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To produce a nonoriented silicon steel sheet well balanced between magnetic flux density and iron loss by casting a thin slab from a molten steel with a specific composition, applying hot rolling and cold rolling to this thin cast slab under respectively specified conditions, and carrying out annealing. CONSTITUTION:A thin slab of about 7-50mm thickness is cast from a molten steel having a composition consisting of, by weight, <=0.01% C, 0.1-<1.7% Si, <1% Al, <1.7% (Si+1.7Al), <=0.003% N, <=0.005% S, and the balance Fe with inevitable impurities. Subsequently, while this thin cast slab is not cooled down to a temp. of the A3 point or below, hot rolling is exerted at <= about 20 deg.C/sec average cooling rate at >=20% rolling reduction so that the total rolling reduction is regulated to 80-95%, followed by coiling at about 600-750 deg.C. The resulting hot rolled plate is subjected, in the above state or after annealing, to cold rolling once or to cold rolling twice or more while being process-annealed between the cold rolling stages, and the resulting cold-rolled sheet is annealed at about 750-1000 deg.C for about 0.5-5min in a nonoxidizing atmosphere of <= about 0 deg.C dew point. By this method, the nonoriented silicon steel sheet most suitably balanced between magnetic flux density and iron loss can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a non-oriented 11 magnetic steel sheet, particularly a non-oriented electrical steel sheet having a good magnetic flux density-core loss balance.

[Conventional technology and issues to be solved]

Non-oriented electrical steel sheets have less anisotropy in magnetic properties than grain-oriented electrical steel sheets, and therefore are generally used for rotating machine cores. In addition, since it is cheaper than grain-oriented electrical steel sheets,
Some of them are also applied to static equipment such as transformers or ballasts. The characteristic values required of a non-oriented electrical steel sheet are mainly iron loss and magnetic flux density, and it is desirable to have a good magnetic flux density-iron loss balance with low iron loss and high magnetic flux density.

Conventionally, a number of manufacturing methods have been disclosed in order to manufacture non-oriented electrical steel sheets having such good magnetic properties. In particular, it is important to control the texture in order to improve the magnetic flux density, and (100) or (110)
) plane ratio and keep the (111) plane ratio low. To this end, we have developed a technology to improve the hot-rolled sheet structure by annealing the hot-rolled sheet, and by optimizing the cold rolling ratio. Techniques have been disclosed for controlling the recrystallized texture during annealing, and techniques for selecting a texture favorable for magnetic properties by performing cold pressing and annealing two or more times. These techniques are techniques for optimizing the conditions of processes after hot rolling. However, in order to optimize the texture after final annealing, texture control at the hot rolling stage is an important key, and in this sense, each of the above-mentioned techniques cannot sufficiently improve the texture. Can not.

In other words, these techniques use hot-rolled sheets obtained by hot-rolling approximately 200 m of slabs, and do not actively attempt to improve the texture during the hot-rolling stage.

On the other hand, strip casting, which has attracted attention in recent years from the viewpoint of energy saving and process saving, allows direct casting to a thickness similar to that of conventional hot rolled sheets.
It is possible to obtain a texture different from that of hot-rolled sheets produced by conventional methods. That is, according to strip casting,
Since the cooling rate of the molten metal is fast, a columnar structure is formed throughout the entire thickness of the plate. In addition, in steel containing 1.7% or more of SL, since α-γ transformation does not occur, the columnar structure is maintained even after the slab is cooled. Such a columnar structure is (100)
(uvw) orientation, and has the most favorable texture for magnetic properties.

Therefore, in the production of non-oriented electrical steel sheets, a thin slab with columnar crystals is cast as thinly as possible by strip casting, and then the next process of cold rolling and annealing is performed (100%
) (uvig) Techniques aimed at maintaining tissues have been disclosed (for example, Japanese Patent Laid-Open No. 62-240714, Japanese Patent Laid-open No. 62-240714)
3-60227).

However, less than 1.7% Si with α-γ transformation
In steels containing a large amount of (100) (
uvw) The structure becomes random, making it extremely difficult to maintain the cast structure.

In view of these problems, the present invention aims to improve the magnetic flux density-core loss balance in non-oriented electrical steel sheets undergoing α-γ transformation by controlling the texture of hot-rolled sheets using a thin slab-direct hot rolling process. This invention discloses a method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties.

That is, in the present invention, C≦0.01% by weight.

0.1≦Si<1.7%, 81<1%, (SL+1.7
At)<1.7%, N≦0.003%, S≦0.005
%, the balance Fe and unavoidable impurities is cast into a thin slab, and then hot rolling is started without cooling the slab below the A3 point, and in the hot rolling process, the material temperature reaches A1. In addition to rolling with a reduction amount of 20% or more until reaching the point, the total reduction amount during hot rolling is 80 to 95%, and the hot rolled sheet is rolled as it is or after annealing the hot rolled sheet, once or The feature is that cold rolling is performed two or more times with intermediate annealing in between, and then annealing is performed.

[For production]

In order to obtain an excellent balance between magnetic flux density and iron loss in a non-oriented electrical steel sheet with a structure having α-γ transformation, the present invention applies a thin cast slab direct hot rolling method to obtain α-γ during hot rolling. The aim is to control the structure of hot-rolled sheets by utilizing transformation, and to improve the magnetic properties after final annealing.

In order to clarify the effects of the present invention, the following experiments were conducted.

30+nn+ 1.63% Si steel with the composition shown in Table 1
After casting into a thin slab, γ
Area (1230~1000℃) -5X 10-'℃1
Sample cooled by sec and then furnace cooled to room temperature (FC material)
Photographs (A) and (B) in FIG. 1 show the cross-sectional structure of a slab of a sample (MC material) whose γ region was cooled to -5°C by EC and cooled to room temperature in a mold. According to this, photo (B)
Since the cooling rate of the slab is high in the MC material, the columnar structure immediately after casting is maintained. On the other hand, since the cooling rate of the FC material in photo (A) is low, it becomes fine equiaxed grains due to α → γ → α transformation. In addition, the MC material was reheated to 1050
Even when soaking at ℃X5+oin, the columnar structure is maintained as shown in photo (C), so after casting, hot rolling starts at 1050℃ without dropping below the AJ point (1000'C). In the case of the rolled material (IIDR material) as well, it is clear that the structure of the slab immediately before the start of hot rolling is a columnar structure similar to the MC material.

Hot-rolled sheets of the above-mentioned FC and MC materials and hot-rolled sheets obtained by soaking at 1050°C x 5+ uin without falling below A3 point after casting and then starting hot rolling (IIDR material)
were cold-pressed and annealed in the following steps.

Figure 2 shows the thermal history of each slab up to hot rolling.

In addition, in hot rolling, I-I DR material, CCR material (MC
40% by A3 point (+000°C) for both
% to obtain a hot rolled sheet (rolling ratio: 91.7%) with a thickness of 2.5 uwn.

Hot-rolled sheet ↓ Hot-rolled sheet annealing: 800°C x 5 min, air-cooled cold pressure (plate thickness 0, 5 nwn) ↓ Annealing: 750-920°C x 2 +++ in, air-cooled,
The X-ray integrated reflection intensity ratio of the steel plate thus obtained in 25%+1□+75% Ar is shown in FIG. 3 in relation to the final annealing temperature.

According to this, I(D R material is FC material whose slab is below A3 point before hot rolling at any annealing temperature, M
Compared to C material, (200) and (100) components are high, and (22
2.) It can be seen that the components are low. in general.

In order to improve the magnetic flux density of a non-oriented electrical steel sheet, it is desirable to accumulate as many (100) axes, which are easy magnetization directions, on the surface of the steel sheet as possible, and for this purpose, the effective crystal planes are (100) or ( 110) Then, (111
) crystal planes that do not include the axis of easy magnetization should be avoided as much as possible. Therefore, II D R material is more
It is clear that the magnetic flux density is higher than that of MC material and FC material. That is, even if the structure immediately before hot rolling is the same columnar structure, the above-mentioned difference in texture occurs depending on whether or not the slab falls below the A3 point from solidification to hot rolling.

As the thickness of the slab becomes thinner, the heat removal rate increases, the solidification rate increases, and a fine columnar structure is formed immediately after solidification. The columnar structure generated during solidification has a texture consisting of (100) (uν), which is a texture that is good for magnetic properties and contains the largest number of easy magnetization axes. The accompanying steel passes through point A4 and point A3 in the cooling stage after solidification.

At this time, it reaches room temperature through α→γ and γ→α transformations.

If the temperature of the slab is below the A1 point before hot rolling, α → γ and γ → α transformation occur during the cooling stage of the slab, and further α transformation occurs during reheating.
→ Since the γ transformation occurs, the slab undergoes three transformations after solidification until the start of hot rolling, and the texture of the slab becomes completely random.

On the other hand, if rolling is started without going below the A3 point after solidification, the α→γ transformation will occur only once at the A4 point when the slab is cooled, and the holding time in the γ region until hot rolling will also be shortened. Because of the short length, the transformation is not completed in the entire slab, and (100)(u
A structure close to νV> will be maintained.

Furthermore, it has become clear that when hot rolling is started before the A3 point is reached after solidification of the slab, the rolling reduction in the γ region greatly contributes to improving the magnetic flux density, as described below.

After casting the steel with the composition of Na 1 to 3 in Table 2 into a thin slab with a thickness of 40+nmt, it was cooled at 1.5°C/see, and at the cooling stage, the Na
Start hot rolling at 000 to 1150°C, change the rolling reduction until passing the A3 point, determine the magnetic flux density after cold rolling and annealing, and examine the effect of the above rolling reduction on the magnetic flux density. Study was carried out. In addition, Nα4 steel is a steel type that does not have an A3 point.

For comparison, this was also cast and cooled in the same manner, ]00
Similar measurements were carried out by changing the rolling reduction rate until passing 0'C. In addition, in the above hot rolling, the final plate thickness is 2.0~
It was set to 2.5 mmt (total reduction amount 93.75 to 95%) and cooled to room temperature by standing to cool. In order to simulate the cooling after coiling during hot rolling in an actual machine, hot rolled sheets of NLll, 2.3.4 each composition were heated at 660°C, 680°C, and 5°C, respectively.
After soaking in a furnace at 50° C. and 700° C. for 30 sins, cooling was performed in the furnace. Furthermore, the hot-rolled plate of Isao 3.4 is 870℃×1.
The hot rolled sheet was annealed with air cooling of 5 ml. Next, after carrying out pickling to remove scale, it was cold pressed to a thickness of 0.5 mm, and then in an atmosphere of 25% H and -75% N2, Na 1 was
00'CX 1.5 win, Na2 is 830℃
x 1.5 min, Na 3.4 at 880℃ x 2m
1n air-cooled annealing was performed.

FIG. 4 shows the measurement results of the above-mentioned magnetic flux density, and it is clear from the measurement results that the magnetic flux density increases rapidly by applying a rolling reduction of 20% or more at point A1 or higher. By rolling the (100) <uvw> structure remaining in the slab before passing the A1 point, not only can the texture of the hot rolled sheet with good magnetic properties be formed, but also the texture can be rolled by the time the slab passes the A3 point. This is because the processed structure can be recovered and recrystallized by the transformation energy when passing the A3 point.

On the other hand, regarding the formation of ferrite structure and texture during hot rolling, not only the reduction ratio above the A3 point described above but also the total reduction ratio during hot rolling have a large effect, and the formation of texture after cold rolling and annealing, Even the magnetic flux density is affected.

Steels with compositions Nα5 and &6 in Table 3 are used, with respective thicknesses of 8 and 10
After casting into a thin slab of 115.20.30.40.50.80, it is cooled to 4.2 to 1℃ and 8 ec.
Hot rolling was started at 0°C, and by the time the A□ point was passed during rolling, a reduction of 23 to 47% was performed to obtain a hot rolled sheet with a thickness of 1.4 to 2.5 m, and the sheet was left to cool to room temperature. Cooled. The magnetic flux density of these hot-rolled sheets after cold rolling and annealing was measured, and the influence of the total rolling amount during hot rolling on the magnetic flux density was investigated.

In addition, Nα7 steel is a steel type that does not have an A1 point, but when thin slabs of each thickness are cast and cooled in the same manner as above, 23 to 47% of the steel is The hot-rolled sheets were rolled to a thickness of 1.4 to 2.5+n++, cooled down to room temperature, and the magnetic flux densities of these hot-rolled sheets after cold pressing and annealing were measured. In addition, in order to simulate the cooling after coiling during hot rolling in an actual machine, the hot rolled sheets of each composition of Cooling was performed. Furthermore, Nα7
The hot-rolled sheet was subjected to air-cooled hot-rolled sheet annealing at 870° C. and 1.5 ml. 0.5m after pickling these hot rolled sheets
Nn5 was cold pressed to a thickness of t, and then Nn5 was heated at 800℃
6 is 850℃X2 lll1n, Na7 is 880℃X
Air-cooled annealing was performed for 2 ml. In addition, as a comparative material, a slab of 7# of the same composition and thickness was cast, and then air-cooled to room temperature.

It was reheated to 1250° C., processed and treated according to the same schedule, and subjected to the same 1llllll determination.

FIG. 5 shows the measurement results of the magnetic flux density, and it was found from the measurement results that the magnetic flux density can be maximized at a total rolling reduction of 80 to 95% during hot rolling. This is because when the (100) (IIVW) structure maintained until just before hot rolling is processed by hot rolling, the rotation of the crystal axis accompanying the shear deformation and shear deformation of the crystal causes the subsequent recovery of the structure and the recrystallization process. This is due to the matching with the new texture formation in . Furthermore, in the case of a rolling reduction of 95% or more, the strain introduced during hot rolling becomes too large, which inhibits the recovery of ferrite and the progress of recrystallization, thereby inhibiting the formation of ferrite structure during hot rolling. Further, when the slab rotates once around point A3 after solidification and before hot rolling, as shown in FIG. 5, conditions are not obtained in which the magnetic flux density changes significantly in the hot rolling reduction ratio.

Below, one component of the present invention will be specifically explained.

In the method of the present invention, as the material steel, C: 0.01% or less,
Si: 0.1% or more and less than 1.7%, l: less than 1%, (S
i+1.7All): less than 1.7%, N: 0.
Use steel that satisfies the composition conditions of 0.003% or less and s: 0.005% or less. The reason for this limitation will be explained below.

C: If it exceeds 0.01%, it is harmful to core loss, which is one of the magnetic properties, so the upper limit of C is 0.01%. In addition, in order to suppress the deterioration of iron loss due to magnetic aging, C:
A content of 0.005% or less is desirable. Also, C is o, oos
If magnetic properties are a problem in steel containing ~0.01%, C in the steel can be reduced to 0.00% or less by decarburization annealing at the hot-rolled plate annealing or the final annealing stage.

Si: Si must be added in an amount of 0.1% or more in order to increase the specific resistance of steel and reduce iron loss. but,
When 1.7% or more of Si is added, transformation disappears and the steel becomes α single-phase steel, making it impossible to improve the texture by utilizing transformation in the present invention. For the above reasons, Si is 0.1% or more1
．． Less than 7%.

A1: Like Si, Aρ is also an effective element for increasing the resistivity of steel and reducing iron loss, but if it is added in an amount of 1% or more, the transformation point disappears and it becomes α single phase steel. It becomes impossible to improve the texture by using metamorphosis. Therefore, Afi is set to less than 1%. Further, in order to sufficiently deoxidize Ml, it is desirable that An content be 0.001% or more.

(Si+1.71m): Both Si and AQ are effective elements for reducing iron loss, but at the same time
It is also a hemiforming element. When Si+1.7Ajl is 1.7% or more, it becomes a ferritic single phase steel, so in the present invention, (
Si+1.7A11. ): Must be less than 1.7%.

N: If added in excess of 0.003%, the iron loss will deteriorate in the solid solution state, and for this reason, the upper limit of N will be reduced to 0.
．． 003%. In addition, in steels to which AQ is added, the precipitation of AfiN particles impairs ferrite grain growth during annealing and deteriorates iron loss, so it is desirable to reduce AQ as much as possible.

S: Like N, it degrades iron loss in a solid solution state, so it is specified as 0.005% or less.

Note that other components are not particularly limited, but as described below, Mn=0.01 to 2.
It is preferable that P: 0% and P: 50.1%.

Mn: Mn is an austenite-forming element, and its addition can lower the A1 point.
In high-volume steel, this is effective to ensure a rolling reduction of 20% or more at the A1 point or higher. However, addition of more than 2.0% reduces ductility during cold rolling, so 2.0%
The following are desirable.

P: By adding P, it is possible to increase the specific resistance of the steel and reduce iron loss, but if it exceeds 0.1%, the cold rollability will deteriorate significantly, so it is preferably 0.1% or less.

In addition, if AIIN is finely precipitated and deteriorates ferrite grain growth during final annealing, B should be changed to B/N:
This can be improved by adding in a range of 0.5 to 2.0. This is because coarse N particles preferentially precipitate compared to ^12N particles. Furthermore, even in steel without addition of B, by adding B, solid solution N can be fixed as nN and iron loss can be improved.

Next, casting and rolling conditions will be explained.

The product thickness of a non-oriented electrical steel sheet is generally 0.50 mm or 0.350111 mm. In general, it is known that a good texture can be obtained by applying a reduction of 60 to 80% in cold pressing of a non-oriented fl magnetic steel sheet. Therefore, in order to make the hot rolled sheet the product thickness by one cold rolling, the hot rolled sheet thickness must be 1.0 to 2,5.
Must be In.

In the present invention, the total rolling reduction during hot rolling is defined as 85 to 95%, and therefore, when the molten steel is made into a thin slab, the thickness is preferably 7 to 50+n+++. Further, when cold pressing is performed two or more times, the plate thickness can be up to 100 mm.

Furthermore, in the present invention, it is important that the slab after the test does not pass through point A1 before hot rolling starts. therefore,
Regarding the cooling rate of the slab, there is no need to specifically limit it as long as the condition that the slab does not pass through point A3 before hot rolling starts is met.

However, when the cooling rate is high, there is a problem that not only uneven cooling occurs at the center and some corners of the vI piece, but also the temperature at some corners becomes below the A1 point. Therefore, although it is possible to hot-roll immediately after casting, A1
Due to the practical process constraints for starting heat retention when heat retention is performed above the point, the average cooling rate of the slab is 20℃.
It is preferred that it is less than or equal to 8e. In the present invention, even when the cooling rate is high, it is also an effective means to uniformly heat the product using a heat retaining cover or high-frequency induction heating immediately after VI manufacturing. Here, when soaking a thin slab before hot rolling, there is no particular limit on the soaking time, but if soaking for more than 30 minutes, oxidation of the slab surface will become a problem, so the soaking time should be is 3
Preferably within 0 minutes. By adopting such a process, compared to the conventional process of reheating a 200 mm thick slab and subjecting it to rough rolling and finish rolling, it is possible to omit the reheating and rough rolling processes, and the cost is significantly reduced. It is also possible to achieve significant cost reductions.

In the present invention, after hot-rolling a thin slab under conditions such as "double series", the hot-rolled sheet is usually wound into a coil and allowed to cool. Since this cooling after winding is gradual cooling, recrystallization and grain growth of the ferrite structure of the hot rolled sheet can be promoted during this cooling. For this reason, it is desirable to wind the film at a temperature of 600 to 750°C. Also,
In order to enhance this effect, it is also possible to cover the coil with a heat insulating cover immediately after winding the coil for the second time, and to cool it in a furnace in a non-oxidizing atmosphere such as Ar. On the other hand, when the hot-rolled sheet is further annealed after hot-rolling and winding, there is no particular restriction on the winding temperature during hot-rolling. In particular, hot-rolled sheet annealing promotes agglomeration and coarsening of fine precipitate particles, and even if the annealing temperature during final annealing is lowered, grain growth to Ferrite 1 is good, reducing iron loss. I can do it. Hot-rolled plate annealing is 750 to 950 in the case of continuous annealing.
In the case of oven batch annealing, the hot-rolled sheet is pickled and then heated to 700°C in a non-oxidizing atmosphere.

Furthermore, when hot-rolled sheet annealing is performed, by starting hot-rolled sheet annealing before the hot-rolled coil after winding has cooled down to room temperature, energy during heating can be saved, which is effective from the viewpoint of energy saving. Further, if the hot rolled sheet is directly passed through the hot rolled sheet annealing line after hot rolling finishing, there is no need to wind up the hot rolled sheet.

In addition, when cold rolling is performed two or more times, intermediate annealing is performed between cold rolling to recover the structure and perform recrystallization treatment. Intermediate annealing is 750 to 95 when continuous annealing is performed.
0'Cx0.5~5+nin, in case of open batch annealing, 700~850℃X1=lO in non-oxidizing atmosphere
It is desirable to set the condition to hr. The final annealing is performed to recrystallize and grow grains in the ferrite structure, and to control the ferrite grains to have an optimal balance between core loss and magnetic flux density.The conditions are as follows: 750~1000℃X0.5~ in non-oxidizing atmosphere
It is desirable to perform soaking for 5 minutes.

〔Example〕

Example 1 Using steel having the composition shown in Table 4 as a raw material, non-oriented electrical steel sheets were manufactured by the method of the present invention and the comparative method under the conditions described below, and their magnetic properties were investigated. The results are shown in Table 5.

After casting molten steel of composition I to a thickness of 251 mm, the average temperature is 2°C/
sec, hot rolling was started at 1100°C, and after rolling by 60% at point A3 or above, further rolling was carried out at 800°C for 1.
Finished as a hot-rolled sheet with a thickness of 6nnt (total rolling reduction rate of 93.6%)
). After pickling this hot-rolled sheet, it was cold-pressed to a thickness of 0.5 nwnt and 870' in a 25% 11□-75% N2 atmosphere.
CX 1.5mln, air-cooled annealing was performed.

After casting molten steel of Kikura Kunkamei composition I to a thickness of 25 net, the average was 56C/
After cooling for 10 minutes in a furnace at 1150℃,
Hot rolling was started at 1100°C, and after 60% reduction at the A3 point or higher, further rolling was carried out at 810°C to form a hot rolled sheet with a thickness of 1.6 ng++ (total reduction rate 93.6%). . The subsequent conditions are the same as in Method (1) of the present invention.

After casting molten steel with the Kimihadade brain composition ■ to a thickness of 25 mm, the average temperature was 5℃ 8e.
After cooling at 1150°C for 25 minutes in a furnace at 1150°C,
Hot rolling was started at 00°C, and after rolling by 60% at the A3 point or higher, further rolling was carried out at 800°C to finish a hot rolled sheet with a thickness of 1.6+n+++ (total rolling reduction rate of 93.6%). The subsequent conditions are the same as in method (1) of the present invention.

After casting the molten steel of the Kimi Asajuku group composition worker to a thickness of 10 + nn +, an average of 10
After cooling at ℃/see and holding in a furnace at 1150℃ for 30 minutes, hot rolling was started at 1100℃.A.

After 60% reduction, further rolling was performed at 800°C.
．． Finished into a 6-inch thick hot-rolled plate (total rolling reduction 93.6
%). The subsequent conditions are the same as in method (1) of the present invention.

After casting molten steel of composition I to a thickness of 25mm, the average temperature was 2℃8e.
After cooling at 840°C, hot rolling was started at 1100°C, and after 60% reduction at point A1 or above, further rolling was performed at 840°C to 4.0ne.
It was finished into a hot rolled sheet with a thickness of t (total rolling reduction rate of 84%). This hot-rolled sheet was subjected to air-cooled hot-rolled sheet annealing at 800°C x 1m1n in a 25% 11□-75% N2 atmosphere, and then 2.
It was cold-pressed to 6 nwnt, and intermediate annealing was performed at 830° C. for 1.5 min in an air-cooled atmosphere in a 25% H2-75% N2 atmosphere. Further cold pressure to 0.5nrnt, 870℃×1.5
min air cooling finish annealing 25%I+2-75%N2
I went in the atmosphere.

Molten steel with composition J was cast into a slab with a thickness of 220 mm, cooled at an average rate of 0.6°C/sec, and then roughly rolled for 3
5net thickness, and then finish rolling was started at about 1050°C and finished at 830°C, making a 1.6 field thick hot rolled sheet (total rolling reduction rate of 99%). After pickling this hot rolled sheet, 0.5
+lln was cold pressed to a thickness of 870℃Xi, 5m1n
, air-cooled annealing was performed.

Comparative method (2) After casting molten steel of composition J into a slab with a thickness of 220 mm, -
After being allowed to cool to room temperature, it was reheated to 1200°C, hot rolled, cold pressed, and annealed according to the same schedule as Comparative Method (1).

After casting molten steel of composition I to a thickness of 25 nwnt, it was first air-cooled to room temperature and then reheated to 1200°C.

Hot rolling was started at 1100° C., and after 60% rolling at the A1 point or higher, further rolling was carried out at 810° C. to produce a hot rolled sheet with a thickness of 1.6 umnt (total rolling reduction ratio 93.6%). After pickling this hot-rolled sheet, it was cold-pressed to a thickness of 0.5 mm+ and 25%
11□-870℃X 1,5 u in 75% N2 atmosphere
+in, air-cooled annealing was performed.

After casting molten steel with composition I to a thickness of 10+nmt, an average of 30℃
After cooling to 900°C at 8 ec, then heating to 1150°C, hot rolling was started at 1100°C, and 7
After 0% reduction, further rolling was performed at 800℃ to 1.6net
Finished into a thick hot-rolled plate (total rolling reduction 84%). The following conditions are listed in Table 5 of the present invention method. +3+: 800°C XI, 5mln, air cooling, 25
%lI2-75%N2, PlI□O/PH2=0.00
5G (21: 770℃×5hr, furnace cooling, 75%+1
2-25%N2, P)120/PH2=0.05 In addition, the atmosphere during final annealing is as follows:Gf3)
:2S%11□-75%N2, pH□0/1)H
2=0.15 Other than G(3): 25%112-75%N2, PH207
PH2=o, oog The C contents of G(2) and G(3) after final annealing were 0.0018% and 0.0043%, respectively.

The magnetic properties of the obtained steel plate were determined by its manufacturing conditions and Example 2. After casting the test steel shown in Table 6 into a 30+nmt thin slab,
Start hot rolling without dropping below A3 point, and after hot rolling, cold rolling (
The plate thickness was 0.5 mm, and annealing was performed. Hot rolling and annealing conditions are shown in Table 7.

However, for A(3) and G(2), the hot rolled sheets were annealed under the following conditions.

[Brief explanation of drawings]

FIGS. 1(A) to (C) are photographs showing the cross-sectional metal structure of each slab of FC material, MC material, and MC material reheated at 1050°C x 5 m1n, respectively. FIG. 2 is a graph showing the thermal history up to hot rolling when each of the slabs shown in FIG. 1 was hot rolled. FIG. 3 shows hot-rolled sheets made from the slabs shown in FIGS.
It is a graph showing the X-ray integrated reflection intensity ratio of a steel plate obtained by final annealing in relation to the final annealing temperature. Figure 4 shows a
It is a graph showing the influence of Ar of the slab and the intended hot rolling reduction rate on the magnetic flux density after final annealing. FIG. 5 is a graph showing the influence of the total rolling reduction during hot rolling of a thin slab on the magnetic flux density after final annealing. Diagram suburb? Great figure! t 5 big j 5 4 L self 1 (0C) Fig. 0 5 80 85 90 95 Roller during suspension (2 → NO, 14: +000'lJI, l-n*L roller (
'/-) Procedural official document (method) % formula % l, Indication of the case 1990 Patent Application No. 11720 2, Name of the invention Method for manufacturing non-oriented electrical steel sheet 3, Person making the amendment Related Patent Applicant (412) II Honkoukan Co., Ltd. Amendment 1, in the specification of the present application, page 35, lines 2 to 4, ``Figures 1 (A) to (C) are each...'' This is a photograph showing .
It is a photograph showing the cross-sectional metal structure of each slab of the X5m1n reheated material. 4. Date of amendment order: February 12, 1991 5. Agent: 1-114-5 Kyobashi, Chuo-ku, Tokyo, T'le G' [D 03-3535-1050 Subject of amendment

Claims (1)

[Claims] In weight%, C≦0.01%, 0.1≦Si<1.7%,
Al<1%, (Si+1.7Al)<1.7%, N≦0
．． After casting molten steel consisting of 0.003%, S≦0.005%, balance Fe and unavoidable impurities into a thin slab, hot rolling is started without cooling the slab to below the A_3 point. In the rolling process, rolling is performed to a reduction amount of 20% or more until the material temperature reaches point A_3, and the total reduction amount during hot rolling is set to 80 to 95%, and the hot rolled sheet is used as it is or as a hot rolled sheet. After annealing, one time or intermediate annealing two times
1. A method for producing a non-oriented electrical steel sheet, which comprises cold rolling more than once and then annealing.