JPH10251751A - Production of nonoriented silicon steel sheet high in magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the magnetic flux density of a formed product by subjecting a steel slab having a specified compsn. contg. Si, Mn, C, N and S to finish hot rolling and thereafter coiling the coil while the tension between a final stand and a coiler is held to specific value. SOLUTION: A slab contg., by weight, >2.00 to 7.00% Si, 0.10 to 1.50% Mn, <=0.0050% C, <=0.0050% N, <=0.0050% S, and the balance Fe with inevitable impurities is subjected to hot rolling, is subjected to cold rolling for one time or >= two times including process annealing and is next subjected to finish annealing to produce a silicon steel sheet. At this time, after the completion of the finish hot rolling, the hot rolled sheet is coiled round a coil while the tension σ(kgf/mm<2> ) between a final stand and a coiler is held to satisfy the inequality in the relation with the finish rolling finishing temp. T( deg.C). The upper limit of the tension is not particularly set, but it is spontaneously decided from the shape controllability of the hot rolled sheet, and about 5kgf/mm<2> is the limit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet having a high magnetic flux density, which is used as a core material of electric equipment.

[0002]

2. Description of the Related Art In recent years, in the fields of electric machines, especially rotating machines and medium-sized and small-sized transformers in which non-oriented electrical steel sheets are used as iron core materials, worldwide electric power and energy savings, as well as chlorofluorocarbon gas regulations. Among the movements for global environmental conservation, such as the above, the movement for higher efficiency is rapidly spreading. For this reason, in order to improve the efficiency by reducing the iron loss, which is the energy loss during use, as much as possible, the demand for low iron loss electromagnetic steel sheets by customers is increasing.

On the other hand, in order to obtain the same output by reducing the size of the iron core in a rotating machine, it is necessary to increase the operating magnetic flux density.
For this purpose, a non-oriented electrical steel sheet having a high magnetic flux density is required. As described above, the reduction in the size of the rotating machine leads to a reduction in the weight of a moving body on which the rotating machine itself is mounted, such as an automobile or a train. Therefore, in recent years, there has been a strong demand from customers for non-oriented electrical steel sheets having low iron loss and high magnetic flux density.

[0004] Further, in the present age of entering the global competition era, there is a severe demand for customers to reduce the cost of non-oriented electrical steel sheets, and this is coupled with the aforementioned trend toward higher efficiency of electrical equipment. In fact, if the price is the same, the fact is that non-oriented electrical steel sheets with excellent magnetic properties are selected by consumers.

By the way, in non-oriented electrical steel sheets,
Conventionally, as a means of reducing iron loss, a method of increasing the content of Si, Al, or the like has been generally adopted from the viewpoint of reducing eddy current loss due to an increase in electric resistance. However, this method has a problem that the magnetic flux density cannot be reduced. In order to overcome such problems, a method of improving the magnetic flux density mainly by increasing the crystal grain size of the hot-rolled sheet has been performed.

Conventionally, in non-oriented electrical steel sheets having a high Si content, the growth of the crystal structure after finish hot rolling is insufficient, and in order to provide a material having a high magnetic flux density and a low iron loss, the finish heat After the completion of the rolling, it has been essential to perform annealing of the hot-rolled sheet by some method so as to make the crystal structure coarse. However, even if the magnetic properties of a product can be improved to some extent by performing hot-rolled sheet annealing, it has not been sufficient to meet the demands of customers for the above-mentioned high magnetic flux density and low iron loss material.

In view of the above problems, Japanese Patent Application Laid-Open No. Sho 5 (1993) discloses a means for improving the magnetic properties of a high Si non-oriented electrical steel sheet.
No. 9-74224 discloses that the Si content is 2.5% to 4.
In the case of 0% steel, in the single cold rolling method, in addition to restricting the impurities to S ≦ 15 ppm, O ≦ 20 ppm and N ≦ 25 ppm, the conditions for annealing the hot-rolled sheet are specified, and the cold rolling ratio is set to 65%. % Is disclosed in Japanese Unexamined Patent Publication No. 59-74225.
No. 2 discloses that S ≦ 15 ppm and O ≦ 20 in the double cold rolling method.
A technique is disclosed in which the intermediate annealing conditions are defined in addition to the setting of ppm and N ≦ 25 ppm, and the second cold rolling reduction is 70% or more.

However, as in these prior inventions,
Techniques centered on purifying steel have not been able to solve the problem unique to high-Si non-oriented electrical steel sheets, in which the magnetic flux density is not sufficiently improved even if the iron loss is improved.

Japanese Patent Application Laid-Open No. 54-76422 discloses a technique for inexpensively coarsening the crystal structure of a non-oriented electrical steel sheet before cold rolling to increase the magnetic flux density. The self-annealing method of winding at a high temperature of 1000 ° C. and annealing with the heat held by the coil is also disclosed in
No. 61644 discloses a method in which the hot-rolling end temperature is set to a high temperature of 1000 ° C. or higher and no water injection time is set, and the hot-rolled structure is recrystallized and grown on a so-called run-out table before winding. .

However, this technique has not solved the problem specific to high-Si non-oriented electrical steel sheets that the improvement of the magnetic flux density is still insufficient even if the crystal grain growth of the hot-rolled structure is attempted.

As a technique for improving the magnetic properties of a high-grade non-oriented electrical steel sheet having a high Si content and having a slow progress of recrystallization and grain growth by controlled hot rolling, Japanese Patent Laid-Open No.
No. 74222 discloses a technique in which the rolling reduction of a hot-rolled sheet is set to 700 ° C. or higher by setting the rolling reduction of the final hot-rolled final stand to 20% or more. In this prior invention, the aim is to increase the final stand draft and raise the winding temperature to promote recrystallization and grain growth of the hot-rolled structure after the end of hot-rolling, thereby improving magnetic properties. I have. However, when the Si content in the steel sheet is high, the subsequent grain growth is insufficient, and the problem specific to the high Si-based non-oriented electrical steel sheet that the improvement of the magnetic flux density is also insufficient is not solved.

On the other hand, Japanese Patent Laid-Open Publication No. Sho 56-38420 discloses that in order to improve the magnetic properties of a low-grade non-oriented electrical steel sheet having a transformation, finishing at a temperature lower than the intermediate temperature of the αγ2 phase region and higher than 750 ° C. A controlled hot rolling technology for terminating hot rolling is disclosed. However, at present, simply increasing the end temperature of hot rolling does not lead to supply of high magnetic flux density non-oriented electrical steel sheets required by customers.

As described above, in the prior art, both the low-grade low-grade electrical steel sheet having a low Si content and the high-grade non-oriented electrical steel sheet having a high Si content have a sufficiently high magnetic flux density and a low iron loss. It was not possible to manufacture grain-oriented electrical steel sheets, and it was not possible to meet the demands of the above-mentioned consumers for non-oriented electrical steel sheets.

[0014]

SUMMARY OF THE INVENTION The present invention is different from the concept of the control of the hot rolling end temperature and the pass schedule management from this point of view, as is the case with the control hot rolling performed in the prior art. In the finishing hot rolling of grain-oriented electrical steel sheets, it is possible to increase the magnetic flux density of the product by controlling the tension between the final stand and the coiler to a certain level or more, and to further reduce the sheet bar after rough rolling before finishing hot rolling. The tension is easily controlled from the final stand to the coiler by continuously applying the sheet bar to the finishing hot rolling, and the finishing hot rolling under high tension is performed stably. It is intended to provide a method for producing a non-oriented electrical steel sheet having a high magnetic flux density.

[0015]

The gist of the present invention is as follows. (1) 2.00% <Si ≦ 7.00% by weight in steel,
0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050
%, N ≦ 0.0050%, S ≦ 0.005
Using a slab containing 0%, the balance being Fe and unavoidable impurities, hot-rolled to a hot-rolled sheet, subjected to one or two or more cold-rolling steps including intermediate annealing, and then to finish annealing, In the method of manufacturing a non-oriented electrical steel sheet with or without an insulating coating, which is the final product, after finishing hot rolling, the tension σ (kgf / kgf) between the final stand and the coiler
mm ² ) in relation to the finish hot-rolling end temperature T (° C.), producing a non-oriented electrical steel sheet having a high magnetic flux density, wherein the hot-rolled sheet is wound around a coil while maintaining the following equation (1). Method. σ (kgf / mm ² ) ≧ 2-T ^0.3 + lnT ‥‥‥ (1) (2) As slab component, 0.10% or more by weight%
The preceding paragraph, characterized by containing 1.00% of Al.
(1) The method for producing a non-oriented electrical steel sheet according to (1).

(3) By weight%, 0.10% <Si ≦ 2.0
0%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.00
50%, N ≦ 0.0050%, S ≦ 0.0
A slab containing 050% with the balance being Fe and unavoidable impurities is hot-rolled into a hot-rolled sheet, and the hot-rolled sheet is cold-rolled once or twice or more with intermediate annealing. In a method for producing a non-oriented electrical steel sheet which is a final product including a step of forming a sheet and then performing a finish annealing and applying or not applying an insulating film, the finish hot rolling end temperature is 700 ° C. or more (Ar ₃ + Ar ₁ ) / 2 or less, and after finishing hot rolling, tension σ (kg
f / mm ² ) in relation to the finishing hot-rolling end temperature T (° C.), wherein the non-oriented electrical steel sheet having a high magnetic flux density is characterized in that the hot-rolled sheet is wound around a coil while maintaining the following equation (1). Manufacturing method. σ (kgf / mm ² ) ≧ 2-T ^0.3 + lnT ‥‥‥ (1) (4) As a slab component, 0.10% or more by weight%
1.00% Al and (Si + 2Al) ≦
The method for producing a non-oriented electrical steel sheet according to the above (3), wherein 2.5% is satisfied.

(5) After finishing hot rolling and before cold rolling, the steel sheet is subjected to continuous annealing at a temperature of 850 ° C. or more and 1150 ° C. or less for 20 seconds or more and less than 5 minutes. The magnetic flux density according to any one of (1) to (4) is high,
A method for manufacturing non-oriented electrical steel sheets with low iron loss. (6) After finishing hot rolling and before cold rolling, the steel sheet is subjected to box annealing at a temperature of 750 ° C. or more and 850 ° C. or less by box annealing for 5 minutes or more and less than 30 hours. ) To (4)
The method for producing a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss according to any one of the above.

(7) After finishing hot rolling, the temperature is 750 ° C. or more and 100
The magnetic flux density according to any one of the above (1) to (4), wherein the coil is wound around the coil at a temperature of 0 ° C. or less and self-annealed with the heat of the coil itself for 5 minutes to 5 hours. A method for manufacturing non-oriented electrical steel sheets with high iron loss. (8) Finish hot rolling end temperature T performed in the range of the following formula (2)
(1) through (7), wherein after the hot rolling is completed, the coil is wound around the coil without water injection for a time t defined by the following equation (3). The method for producing a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss according to any one of the preceding claims. 950 ≦ T (° C.) ≦ 1150 {(2) 9.6-8 × 10 ⁻³ T ≦ t (second) ≦ 15.6-8 × 10 ⁻³ T} (3)

(9) The sheet bars after the rough rolling are joined to the preceding sheet bar before the hot-rolling for finish, and the sheet bar is continuously subjected to the hot-rolling for the finish, wherein (1) to (8). )
The method for producing a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss according to any one of the above. (10) After the finish annealing, the reduction rate is 2% or more and 20% or more.
%. The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to any one of the above items (1) to (9), wherein a skin pass rolling step of at most% is performed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. [Reasons for specifying components] Si is added to increase the specific resistance of the steel sheet, reduce the eddy current loss, and improve the iron loss value. If the Si content is 0.10% or less, sufficient resistivity cannot be obtained, so it is necessary to add an amount exceeding 0.10%. On the other hand, if the Si content exceeds 7.00%, edge cracks at the time of rolling increase remarkably, making rolling difficult and increasing costs. Therefore, it is necessary to be 7.00% or less.

Al, like Si, has the effect of increasing the specific resistance of the steel sheet and reducing the eddy current loss. Therefore, it is necessary to add 0.10% or more. On the other hand, if the Al content exceeds 1.00%, the magnetic flux density decreases and the cost increases, so the content is set to 1.00% or less. Here, Al is added as needed, and the Al content is 0.1%.
Even if it is less than 0%, the effect of the present invention is not impaired at all.

Mn, like Al and Si, has the effect of increasing the specific resistance of the steel sheet and reducing the eddy current loss. For this purpose, the Mn content needs to be 0.10% or more. On the other hand, if the Mn content exceeds 1.50%, the deformation resistance during hot rolling increases and hot rolling becomes difficult, and the crystal structure after hot rolling tends to become finer and the magnetic properties deteriorate. The amount must be 1.50% or less.
Further, the amount of Mn addition is extremely important from the viewpoint of securing the strength of the high temperature sheet bar joint before the hot rolling. This is because Mn and S in order to prevent hot embrittlement of the sheet bar joint due to the presence of low-melting sulfide at the crystal grain boundaries.
This is because it is necessary to set the value of Mn / S, which is the ratio of the weight concentration to the above, to 20 or more. In the component range defined in the present invention, since the Mn content is 0.1% or more and the S content is 0.0050% or less, the value of Mn / S is maintained at 20 or more. there is no problem.

If the C content exceeds 0.0050%, the iron loss deteriorates due to magnetic aging during use and the energy loss during use increases, so that the C content is reduced to 0.0050% or less, preferably 0.0030% or less. It is necessary to control.

S and N partially re-dissolve during slab heating in the hot rolling step, and sulfides such as MnS and A
A nitride such as 1N is formed. Since the presence of these elements hinders the grain growth of the hot-rolled structure and deteriorates the iron loss, S is set to 0.1.
0050% and N must be 0.0050% or less.

In order to improve the mechanical properties, magnetic properties and rust resistance of the product or for other purposes, P,
Even if one or more of B, Ni, Cr, Sb, Sn, and Cu are contained in steel, the effect of the present invention is not impaired.

[Definition of Process Conditions] Next, the process conditions of the present invention will be described. The steel slab composed of the above components is produced by melting in a converter and being manufactured by continuous casting or ingot-bulking rolling. The steel slab is heated by a known method. This slab is subjected to hot rolling to a predetermined thickness.

The slab is rolled into a sheet bar by rough rolling, and is subjected to finish hot rolling. After the finish hot rolling, the product magnetic flux density can be improved by applying a tension σ defined by the equation (1) between the final stand and the coiler in relation to the finish hot rolling end temperature T (° C.). . σ (kgf / mm ² ) ≧ 2-T ^0.3 + lnT ‥‥‥ (1)

There is no particular upper limit on the tension. However, due to the shape controllability of the hot rolled sheet, the upper limit of the tension between the final stand and the coiler is naturally determined. That is, if the tension between the final stand and the coiler is increased, winding of the coil is facilitated, but the width of the steel sheet changes due to creep, and it is necessary to increase the slab width to compensate for this. Also,
This deformation causes a problem that the thickness deviation in the width direction of the steel sheet increases. Since non-oriented electrical steel sheets are laminated and used for use, strict control is required for thickness deviations in the sheet width direction and the longitudinal direction. Strict control is required for sheet thickness deviation. From these viewpoints, the tension between the final stand and the coiler is limited to about 5 kgf / mm ² .

Also, in the present invention, it has been found that the tension control between the final stand and the coiler plays an important role in improving the magnetic properties of the non-oriented electrical steel sheet. When roughly rolling into one sheet bar and rolling it one by one, the tension between the final stand and the coiler must be gradually reduced as the rolling of one sheet bar approaches the end. This is because, at the moment when the final end of the coil passes through the final stand of the finishing hot-rolling machine (so-called finishing finishing), a tensionless state is brought about, and not only the fluctuation of the tension applied to the steel sheet becomes extremely large, but also a high tension is applied. If the finish is lost in this state, the end portion of the steel sheet is wavy on the cooling zone, and the shape of the steel sheet at the time of winding is significantly deteriorated.

In order to solve these problems and continuously and stably carry out winding under high tension, the sheet bar after the rough rolling is joined to the preceding sheet bar, and the finish hot rolling is performed. Is particularly effective. In other words, the unfinished portion disappears due to the continuous hot rolling, and it is possible to suppress the fluctuation of the tension applied to the hot rolled sheet during the finish hot rolling. Furthermore, by installing multiple pinch rolls in front of the coiler and performing high-speed shearing between them, winding the coils in order, minimizes fluctuations in the tension applied to the hot rolled sheet during finishing hot rolling. It is possible to do. As a result, it is possible to minimize a change in magnetic flux density due to a change in tension in the longitudinal direction of the steel sheet.

The hot-rolled sheet obtained by the above method is subjected to one or two or more cold rollings including an intermediate annealing followed by a finish annealing, or to further improve the magnetic properties, Before the first cold rolling, apply hot-rolled sheet annealing by continuous annealing or box annealing, or wind the coil at high temperature and perform self-annealing with the retained heat, or finish hot rolling at high temperature A non-water injection time may be set, followed by cooling, winding and cold rolling.

The steel sheet after cold rolling is subjected to finish annealing and then coated with an insulating film, or is not subjected to a coating to obtain a final product. Further, the finish-annealed steel sheet may be subjected to a skin pass rolling step to obtain a product. When a skin pass rolling step is added, the effect cannot be obtained when the skin pass rolling ratio is less than 2%, and when the skin pass rolling ratio exceeds 20%, the magnetic properties are deteriorated.
% To less than 20%.

[Regarding Controlled Hot Rolling Process of Component System Having Transformation] 0.10% <Si ≦ 2.00% and (Si +
2Al) steel having a composition satisfying ≦ 2.5% or a composition having a high Mn content has α-γ transformation. In the case of such a non-oriented electrical steel sheet, the finish hot rolling end temperature is excessively increased, and if the γ phase ratio at the end of the finish hot rolling is excessively high, the γ phase is changed from the γ phase at the time of cooling after the end of the hot rolling. With the transformation to the phase, the crystal structure of the hot-rolled sheet becomes fine, and the magnetic properties after rolling and recrystallization are significantly deteriorated. Therefore, the hot rolling end temperature is (A
r ₃ + Ar ₁ ) / 2 or less. On the other hand, if the hot-rolling end temperature is lower than 700 ° C., the rolling reaction force of the steel sheet increases, making it difficult to perform rolling. Since the rate at which the introduced strain is sometimes recovered and released by recrystallization is drastically reduced, and the magnetic properties of the product are remarkably deteriorated, the finishing hot rolling end temperature is set to 700 ° C. or more.

In the case of a step of subjecting the obtained hot-rolled sheet to one final cold-rolling to a final thickness and subjecting it to finish annealing, or subjecting the first cold-rolling to finish annealing and skin pass rolling. On the other hand, the higher the hot rolling end temperature is (Ar ₃ + Ar ₁ ) / 2 as the upper limit, the coarser the crystal structure before cold rolling and the higher the product magnetic flux density. Conversely, when performing hot-rolled sheet annealing by continuous annealing or box annealing after finishing hot-rolling, grain growth during hot-rolled sheet annealing is promoted when the hot-rolling end temperature is lower,
The magnetic flux density of the product is higher. In the control hot rolling of the non-oriented electrical steel sheet having such a transformation, it is more preferable to control the hot rolling end temperature finely in a post-process.

[Regarding Process after Hot Rolling] The hot rolled sheet after pickling may be subjected to continuous annealing or box annealing. Further, the coil after hot rolling may be wound at a temperature of 750 ° C. or more and 1000 ° C. or less, and self-annealing may be performed with the heat held by the coil itself for 5 minutes or more and 5 hours or less. Alternatively, the coil may be wound up without performing water injection for a time specified by a specific formula after the end of hot rolling.

The hot-rolled sheet thus obtained is subjected to one cold rolling step and then to finish annealing, or to intermediate annealing and to two or more cold rolling steps, followed by finish annealing. May be applied. Rolling for finishing to the final sheet thickness may be performed by a known cold rolling technique.
In the case of the i-component system, the temperature of the steel sheet may be increased in accordance with the Si content to perform warm rolling in order to prevent breakage and edge cracks during rolling.

After the finish annealing, a skin pass rolling step may be further performed to obtain a product. When a skin pass rolling step is added, the effect cannot be obtained if the skin pass rolling ratio is less than 2%, and if it exceeds 20%, the magnetic properties deteriorate, so the content is set to 2% or more and less than 20%.

The reasons for defining each process defined by the present invention will be described below. First, how the tension between the final stand and the coiler at the time of finishing hot rolling in the hot strip annealing omitting process affects the magnetic properties will be described.

When the hot-rolled sheet annealing was omitted, the following experiment was conducted to investigate the effect of the tension between the final stand and the coiler on the product magnetic flux density after finishing hot rolling. Steel having the components shown in Table 1 was smelted to form a slab, and hot rolling was performed.

[0040]

[Table 1]

After finishing the hot rolling, a test was conducted by changing the tension between the final stand and the coiler, and the relationship between the hot rolling finishing temperature and the product magnetic flux density was examined in detail. Since the Ar ₃ point of the steel A is 904 ° C. and the Ar ₁ point is 870 ° C., the hot-rolling finishing temperature was changed to (Ar ₃ + Ar ₁ ) / 2 of 887 ° C. or less and 700 ° C. or more. In addition, steel B is 75
Change the hot rolling end temperature in the range of 0 ° C to 1050 ° C,
Both were finished to a thickness of 2.5 mm, cooled with water and wound at 550 ° C.

Thereafter, pickling and cold rolling were performed to a thickness of 0.50 mm.
After degreasing, the steel A was annealed at 750 ° C. for 30 seconds, and the Epstein sample was cut to measure magnetic properties. Steel B was pickled, cold rolled to a thickness of 0.50 mm, degreased, and then heated at 950 ° C.
After annealing for 30 seconds, the Epstein sample was cut and its magnetic properties were measured.

FIG. 1 shows the relationship between the hot-rolling end temperature during the finish hot rolling and the tension between the final stand and the coiler according to the experimental results of steel A, and FIG. The relationship between the end temperature and the tension between the final stand and the coiler is shown in FIG. According to FIGS. 1 and 2, it is understood that when the tension is equal to or higher than the boundary indicated by the equation (1), the product magnetic flux density of both the steel A and the steel B increases.

The tension between the last stand and the coiler is generally referred to as the tension between the last stand and the coiler. A pinch for stably performing winding immediately before the coiler. When a roll or the like is installed, the tension between the final stand and the pinch roll is indicated. Also,
In the case where the final end of the sheet bar has passed through the finishing hot-rolling machine and after finishing, no tension acts between the final stand and the pinch roll, so the tension between the pinch roll and the mandrel or the mandrel itself draws the hot-rolled sheet. Say the power.

As can be seen from the above experiments, if the relationship between the tension between the final stand and the coiler after finishing hot rolling and the temperature at the end of hot rolling in the finishing hot rolling satisfies the equation (1), It can be seen that the product magnetic flux density increases.

Next, a case of a process including hot-rolled sheet annealing by continuous annealing or box annealing will be described. The following experiment was conducted to investigate the effect of the tension between the final stand and the coiler on the magnetic properties of the product when hot-rolled sheet annealing was performed before cold rolling. Steels having the components shown in Table 2 were melted and subjected to finish hot rolling.

[0047]

[Table 2]

A test was conducted by changing the finishing hot rolling end temperature and the tension between the final stand and the coiler, and the relationship with the product magnetic flux density was investigated in detail. The hot rolled sheet was finished to a thickness of 2.5 mm, cooled with water, and wound at 550 ° C. This hot-rolled coil was annealed at 950 ° C. for 90 seconds in steel C in a continuous annealing furnace. This is pickled, cold rolled to a thickness of 0.35 mm, degreased,
After annealing at 0 ° C. for 30 seconds, an Epstein sample was cut out and its magnetic properties were measured.

FIG. 3 shows the relationship between the hot rolling end temperature during the finish hot rolling and the tension between the final stand and the coiler. According to FIG. 3, it can be seen that the product magnetic flux density of the steel C subjected to hot-rolled sheet annealing increases when the tension is equal to or greater than the boundary indicated by the equation (1).

As can be seen from the above experiments, in the finishing hot rolling, if the relationship between the tension between the final stand and the coiler after the finishing hot rolling and the hot rolling finishing temperature satisfies the equation (1). It is clear that the product magnetic flux density increases.

Next, in order to investigate the influence of the annealing time of the hot-rolled sheet and the annealing temperature of the hot-rolled sheet on the magnetic flux density by continuous annealing,
The following experiment was performed. Steel C having the components shown in Table 2 was melted and subjected to finish hot rolling. FIG. 4 shows the effect of the annealing time of the hot-rolled sheet on the product magnetic flux density by continuous annealing. As shown in FIG. 4, when the annealing time is 20 seconds or less, the effect of improving the magnetic flux density by hot-rolled sheet annealing is not obtained, and when the annealing time is 5 minutes or more, a deep scale is formed on the steel sheet surface, and pickling failure occurs,
Significant skin roughness occurred on the surface layer of the steel sheet. Therefore, in the present invention, the annealing time of the hot-rolled sheet by the continuous annealing is set to 20 seconds or more and 5 minutes or less. From the viewpoint of the effect of the annealing and the economical efficiency, the time of the hot-rolled sheet annealing by the preferable continuous annealing is 30 seconds or more and 3 minutes or less.

FIG. 5 shows the effect of the annealing temperature of the hot-rolled sheet on the product magnetic flux density due to continuous annealing. As shown in FIG. 5, when the annealing temperature is lower than 850 ° C., the effect of improving the magnetic flux density by hot-rolled sheet annealing in continuous annealing cannot be obtained, and the annealing temperature is 11 ° C.
Above 50 ° C., poor pickling occurred due to the formation of a deep scale, and marked surface roughness occurred on the surface layer of the steel sheet. Therefore, in the present invention, the hot-rolled sheet annealing temperature by continuous annealing is set to 850 ° C. or more and 1150 ° C. or less. The hot-rolled sheet annealing temperature by continuous annealing is preferably 850 ° C. or more and 1000 ° C. or less in view of the effect of annealing and economy such as pickling properties.

In the present invention, the hot-rolled sheet annealing may be performed by box annealing. At that time, if the hot-rolled sheet annealing temperature is lower than 750 ° C., the annealing time required for improving the product magnetic properties becomes extremely long, which is uneconomical. Further, if the annealing temperature is 850 ° C. or more, a large amount of investment is required for equipment investment in the furnace, and a phenomenon that the coil is seized during annealing occurs. When performing hot-rolled sheet annealing by box annealing for the above reasons, the lower limit of the annealing temperature is 750 ° C and the upper limit is 850 ° C. At this time, if the annealing time of the hot-rolled sheet in box annealing is 5 minutes or less, the annealing temperature necessary for improving the magnetic properties of the product becomes extremely high, and the equipment investment of the furnace itself becomes excessive, which is uneconomical. Is 5 minutes or more. If the hot-rolled sheet annealing time exceeds 30 hours, coil seizure occurs as in the case where the annealing temperature is excessively high. Therefore, the hot-rolled sheet annealing time in box annealing is set to 30 hours or less.

The hot-rolled sheet subjected to the hot-rolled sheet annealing in this manner may be subjected to a single cold rolling step and then to a finish annealing, or may be further subjected to a skin pass rolling step to obtain a product. The finish annealing is performed by continuous annealing. At that time, as disclosed in Japanese Patent Application Laid-Open No. 61-231120, the pre-stage is performed at a temperature range of 950 ° C. to 1100 ° C. for 5 seconds to 1 hour.
For a short time at 800 ° C to 950 ° C for 10 minutes.
Finish annealing may be performed by a method such as holding for 2 to 2 minutes.

Further, a case where a self-annealing process is adopted will be described. In the process of performing self-annealing by the retained heat of the hot-rolled coil, the following experiment was conducted to investigate the effect of the tension between the final stand and the coiler during the finish hot rolling on the magnetic properties of the product. Steels having the components shown in Table 3 were melted and subjected to finish hot rolling.

[0056]

[Table 3]

The hot rolling end temperature is 1000 ° C., water-cooled and wound at 860 ° C., immediately covered with a heat retaining cover, subjected to auxiliary heating by gas heating, and heated to 850 ° C. by the heat retained in the coil.
Self-annealing for 1 hour was performed. In this case, the tension of the tension between the final stand and the coiler defined by the equation (1) is
0.97 kgf / mm ² or more.

This was pickled, cold rolled to a thickness of 0.50 mm, degreased, and then annealed at 900 ° C. for steel D at 980 ° C. for 45 seconds and cut the Epstein sample to measure its magnetic properties. FIG. 6 shows the dependence of the product magnetic flux density on the tension between the final stand and the coiler during hot rolling. As shown in FIG. 6, when the tension between the final stand and the coiler is 0.97 kgf / mm ² or more, the product magnetic flux density increases, and when it is 0.97 kgf / mm ² or less, the product magnetic flux density decreases.

The coil winding temperature during self-annealing is 7
If the temperature is lower than 50 ° C., the magnetic properties are not sufficiently improved.
50 ° C. or higher. On the other hand, if the temperature is higher than 1000 ° C., the coil is likely to be displaced, and the surface layer of the steel sheet is oxidized too much. The time for self-annealing is 5
If the time is less than 10 minutes, the improvement of the magnetic properties is insufficient, so that the heat treatment is performed for 5 minutes or more. If the time exceeds 5 hours, oxidation of the steel sheet becomes severe, and poor pickling tends to occur.
The preferable self-annealing time is 30 minutes to 120 minutes in view of the effect of the annealing and the economy. In the present invention, in order to prevent oxidation of the coil during self-annealing, a reducing atmosphere containing hydrogen, or an inert gas atmosphere such as nitrogen or argon,
Alternatively, self-annealing may be performed under reduced pressure.

The hot-rolled sheet thus self-annealed may be subjected to one cold rolling step and then to finish annealing, or
Thereafter, a skin pass rolling step may be further performed to obtain a product. If the rolling rate of skin pass rolling is less than 2%, the effect cannot be obtained, and if it exceeds 20%, the magnetic properties deteriorate, so that the rolling rate is 2%.
To 20%.

The present invention can employ a process of providing no water injection for a certain period of time after the end of hot rolling. The following experiment was conducted to investigate the effect of the tension between the final stand and the coiler on the magnetic properties of the product in the process of providing no water injection for a certain time after finishing hot rolling. Steel F having the components shown in Table 4 was melted and hot-rolled for finishing.

[0062]

[Table 4]

The finishing hot rolling end temperature was kept constant at 1050 ° C. At this time, the tension of the tension between the final stand and the coiler defined by the expression (1) is 0.90 kgf / mm ² or more.
Also, from the equations (2) and (3), the no-water injection time is 3.
After 5 seconds, it was cooled and wound up at 680 ° C. This was pickled, cold rolled to a thickness of 0.50 mm, degreased,
The sample was annealed at 30 ° C. for 30 seconds, and the Epstein sample was cut to measure magnetic properties.

FIG. 7 shows the dependence of the product magnetic flux density on the tension between the final stand and the coiler during hot rolling. FIG.
It can be seen that the product magnetic flux density increases when the tension between the final stand and the coiler at the time of hot rolling is 0.90 kg / mm ² or more.

As can be seen from the above experiment, if the relationship between the tension between the final stand and the coiler after finishing hot rolling and the hot rolling finishing temperature in the finishing hot rolling satisfies the equation (1), It can be seen that the product magnetic flux density increases.
Although there is no regulation on the coil winding temperature, the coil must be wound at 750 ° C or lower to prevent the formation of an excessively oxidized layer on the surface of the steel sheet that has been hot-rolled at a high temperature and deteriorate the pickling properties. Is preferred.

The set time of no water injection after the end of hot rolling is determined as follows in relation to the hot rolling end temperature T ° C. In the present invention, the tension between the final stand and the coiler is investigated in relation to the hot-rolling end temperature, and the hot-rolling end temperature T
As a result of detailed studies by the inventors on the relationship between the magnetic properties and the time t (second) from the end of hot rolling to the start of water injection after completion of hot rolling, 950 ≦ T (° C.) ≦ 1150 (2) 9.6-8 × 10 ⁻³ T ≦ t (sec) ≦ 15.6-8 × 10 ⁻³ T ‥‥‥ (3) Within a range defined by (3), pickling property, sheet passing speed, and magnetic properties It has become possible to determine good conditions that satisfy Also, if the time from the end of hot rolling to the start of water injection exceeds the time defined by the formula (3), the time for cooling the steel sheet is insufficient, and the coil is wound at a high temperature or the rolling speed is reduced to sufficiently cool the steel sheet. Must be done, and productivity will deteriorate. Winding the coil at a high temperature is not preferable because it causes adverse effects such as occurrence of winding deviation and deterioration of pickling properties. Therefore, the no-water injection time is given by equation (3)
The time is not more than the upper limit time set in. If the non-water injection time is shorter than the time determined by the equation (3), the improvement of the magnetic properties is insufficient. Similarly, when the hot rolling end temperature T (° C.) is lower than 950 ° C., the improvement of the magnetic properties is insufficient. Also,
In order to raise the hot rolling end temperature to over 1150 ° C., it is necessary to significantly increase the heating temperature of the slab in the usual hot rolling process including rough rolling and finish rolling, and the precipitates that have re-dissolved during the slab heating become hot. The hot rolling end temperature is set to 1150 ° C. or less, since it is finely precipitated during rolling and significantly deteriorates magnetic properties.

In the present invention, one cold rolling step may be performed followed by finish annealing, or a skin pass rolling step may be further performed to obtain a product. When a skin pass rolling step is added, the effect cannot be obtained when the skin pass rolling ratio is less than 2%, and when the skin pass rolling ratio is more than 20%, the magnetic properties are deteriorated.
From the above, it is set to 20% or less.

[0068]

Next, an embodiment of the present invention will be described. Example 1 A slab for non-oriented electrical steel having the components shown in Table 5 was heated by a usual method, finished into a coarse bar having a thickness of 40 mm by a rough rolling mill, and then finished by a finishing hot rolling mill. Finished to 5mm. In the present invention, in order to stably control the tension between the final stand and the coiler, the sheet bar after the rough rolling is welded to the preceding sheet bar, and finish hot rolling is continuously performed.

[0069] Ar ₃ point of the steel G is 901 ° C., Ar ₁
Since the point is 872 ° C., the hot rolling finish temperature is (Ar ₃ +
Ar ₁ ) / 2 or less and 860 ° C. which is 700 ° C. or more,
It was cooled with water and wound up at 700 ° C. When the hot rolling end temperature is 860 ° C., the minimum value of the tension between the final stand and the coiler that can be calculated from the equation (1) is 1.17 kgf / mm ² .
As a comparative example, steels having the same composition were subjected to finish hot rolling under the same conditions except for the tension between the final stand and the coiler.

After pickling these steels, steel G was annealed at 750 ° C., steel H at 830 ° C., and steel I at 950 ° C. for 30 seconds, and an Epstein sample was cut out and the magnetic flux density was measured. For the sample, the tension in the longitudinal direction of the steel sheet during rolling was measured, so that the tension at the sampling position could be specified. Table 6 also shows the tensile and magnetic measurement results of the present invention and the comparative example.

As described above, by controlling the tension between the final stand and the coiler in accordance with the equation (1), it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties.

[0072]

[Table 5]

[0073]

[Table 6]

Example 2 A slab for non-oriented electromagnetic steel having the components shown in Table 7 was heated by a usual method, and finished into a coarse bar having a thickness of 40 mm by a rough rolling mill. To 2.0 mm. The finish hot rolling end temperature was 900 ° C., and immediately after the hot rolling was completed, the sheet was water-cooled and the hot rolled sheet was wound at 550 ° C. When the hot rolling end temperature is 900 ° C., the minimum value of the tension between the final stand and the coiler, which can be calculated from equation (1), is 1.11 kgf / mm ² .

The obtained hot rolled sheet was subjected to hot rolled sheet annealing in a continuous annealing furnace at 900 ° C. for steel J and 1000 ° C. for steel K for 2 minutes. After that, it is pickled and cold rolled to 0.50.
mm. This was heated in a continuous annealing furnace at 900 ° C.
The steel K was annealed at 980 ° C. for 30 seconds each. Thereafter, an Epstein sample was cut out and its magnetic properties were measured.

Further, the same conditions were applied to the steel K until the hot-rolled sheet annealing and pickling, and then the cold-rolled finished sheet thickness was set to 0.55 mm. This was annealed at 900 ° C. for 30 seconds in a continuous annealing furnace. Then, it was subjected to skin pass rolling to finish to 0.50 mm, cut into Epstein samples, subjected to strain relief annealing at 750 ° C. for 2 hours, and the magnetic properties were measured. Table 8 shows steel J and steel K.
The present invention and the comparative example are shown together with the results of tension and magnetic measurement.

As described above, by controlling the tension between the final stand and the coiler in accordance with the equation (1), it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties.

[0078]

[Table 7]

[0079]

[Table 8]

Example 3 A slab for non-oriented electromagnetic steel having the components shown in Table 9 was heated to 1200 ° C. by a usual method, finished to a rough bar of 30 mm thickness by a rough rolling mill, and then finished. Finished to 1.8 mm by hot rolling. The hot rolling end temperature is set to 1000 ° C., and after the end of the rolling, cooled to 650 ° C.
Rolled up. When the hot rolling end temperature is 1000 ° C., the minimum value of the tension between the final stand and the coiler, which can be calculated from the equation (1), is 0.96 kgf / mm ² .

Thereafter, the sheet temperature was set to 300 ° C. and 0.85 mm
This was subjected to intermediate annealing at 980 ° C. for 30 seconds, and then finished to 0.25 mm by warm rolling at 200 ° C., followed by pickling. This is heated at 850 ° C in a continuous annealing furnace for 3 hours.
Hold for 0 seconds, anneal, and 8% skin pass rolling.
Finished to 23mm. Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured after strain relief annealing at 800 ° C. for 2 hours. Table 10 also shows the tensile and magnetic measurement results of the present invention and the comparative example.

As shown in Table 10, by controlling the tension between the final stand and the coiler according to equation (1), it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties. It is.

[0083]

[Table 9]

[0084]

[Table 10]

Example 4 A slab for non-oriented electromagnetic steel having the components shown in Table 11 was heated by a usual method, and finished into a coarse bar having a thickness of 40 mm by a rough rolling mill. To 2.0 mm. The finishing hot rolling end temperature was 900 ° C., and after the rolling was completed, the roll was cooled and wound at 650 ° C. When the hot rolling end temperature is 900 ° C., the equation (1)
The minimum value of the tension between the final stand and the coiler which can be calculated from the above is 1.11 kgf / mm ² .

The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing in a box annealing furnace at 800 ° C. for 5 hours. Then, it was pickled and finished to 0.50 mm by cold rolling. The steel M was annealed at 900 ° C. for 30 seconds and the steel N at 980 ° C. for 30 seconds in a continuous annealing furnace. Thereafter, an Epstein sample was cut out and its magnetic properties were measured. Table 12 also shows the tensile and magnetic measurement results of the present invention and the comparative example.

As described above, by controlling the tension between the final stand and the coiler according to the equation (1), it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties.

[0088]

[Table 11]

[0089]

[Table 12]

Example 5 A slab for non-oriented electromagnetic steel having the components shown in Table 13 was heated by a usual method, and was finished into a rough bar having a thickness of 50 mm by a rough rolling machine. To 2.5 mm. The finish hot rolling end temperature was set to 1000 ° C., and after the rolling was completed, cooled and wound up at 875 ° C., and the coil was immediately charged into a heat retaining furnace and subjected to self-annealing at 850 ° C. for 1 hour. The hot rolling end temperature is 1000 ° C.
In the case of, the minimum value of the tension between the final stand and the coiler, which can be calculated from the equation (1), is 0.96 kgf / mm ² .

After that, pickling is performed, and cold rolling is performed to obtain 0.1%.
Finished to 50mm. The steel O was 950 in a continuous annealing furnace.
° C for 30 seconds, steel P at 975 ° C for 30 seconds, steel Q at 85
Annealed at 0 ° C. for 30 seconds. Thereafter, an Epstein sample was cut out and its magnetic properties were measured. Table 14 also shows the tensile and magnetic measurement results of the present invention and the comparative example.

As described above, by controlling the tension between the final stand and the coiler according to the equation (1), it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties.

[0093]

[Table 13]

[0094]

[Table 14]

Example 6 A slab for non-oriented electromagnetic steel having the components shown in Table 15 was heated by a usual method, and finished into a rough bar having a thickness of 50 mm by a rough rolling mill. To 2.5 mm. The finish hot rolling end temperature was set to 1020 ° C., the non-water injection time was set to 3.5 seconds, and 640
Wound at ℃. At this time, the tension between the final stand and the coiler determined from the equation (1) is 0.94 kgf / mm ² or more.

[0096] After that, pickling is carried out, and cold rolling is carried out.
Finished to 50mm. The steel R was 950 in a continuous annealing furnace.
C, the steel S was annealed at 980 C for 30 seconds each. Thereafter, an Epstein sample was cut out and its magnetic properties were measured. Table 16 also shows the tensile and magnetic measurement results of the present invention and the comparative example.

As described above, by controlling the tension between the final stand and the coiler according to the equation (1), it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties.

[0098]

[Table 15]

[0099]

[Table 16]

[Example 7] A slab for non-oriented electromagnetic steel having the components shown in Table 17 was heated by a usual method, and finished into a coarse bar having a thickness of 50 mm by a rough rolling mill. To 2.5 mm. Hot rolling end temperature is 1
050 ° C., changing the no-water injection time,
It was kept constant at 0 ° C. In this case, the tension between the final stand and the coiler defined by the equation (1) is 0.90 kgf / mm ² or more. Therefore, the tension between the final stand and the coiler is 1.
The hot rolled sheet was wound up while maintaining the pressure at 35 to 1.45 kgf / mm ² .
Further, in order to stabilize the tension between the final stand and the coiler, the succeeding sheet bar was welded to the rear end of the preceding sheet bar while being pressed, and hot rolling was continuously performed. Also,
The no-water injection time defined by the equations (2) and (3) is 1.
It is 2 seconds or more and 7.2 seconds or less.

Thereafter, pickling is carried out and cold rolling is carried out.
Finished to 50mm. This was heated at 900 ° C in a continuous annealing furnace for 3 hours.
Annealed for 0 seconds. Thereafter, an Epstein sample was cut out and its magnetic properties were measured. Table 18 shows the hot rolling conditions and the results of the magnetic measurement. As shown in Table 18, it is understood that good magnetic properties are obtained when the no-water injection time is 1.2 seconds or more.

As described above, by appropriately controlling the tension between the final stand and the coiler and appropriately controlling the cooling conditions after the end of hot rolling, the magnetic properties of a high magnetic flux density value and a low iron loss value can be obtained. It is possible to obtain an excellent non-oriented electrical steel sheet.

[0103]

[Table 17]

[0104]

[Table 18]

[0105]

As described above, according to the present invention, it is possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the hot-rolling end temperature, the tension between a final stand and a coiler, and the magnetic flux density of a product at the time of finishing hot-rolling in a one-time cold rolling method in which hot-rolled sheet annealing of 0.3% Si component is omitted.

FIG. 2 is a graph showing the relationship between the hot-rolling end temperature, the tension between the final stand and the coiler, and the magnetic flux density of the finished product in the finish hot-rolling in the one-time cold rolling method in which the hot-rolled sheet annealing of 2% Si component is omitted.

FIG. 3 is a diagram showing the relationship between the hot-rolling end temperature, the tension between the final stand and the coiler, and the magnetic flux density of the finished product during the finishing hot-rolling in the hot-rolled sheet annealing cold rolling method of a 2% Si-based component.

FIG. 4 is a view showing a relationship between a hot-rolled sheet annealing time and a product magnetic flux density in the hot-rolled sheet annealing single cold rolling method by continuous annealing of a 2% Si-based component.

FIG. 5 is a diagram showing the relationship between the hot-rolled sheet annealing temperature and the product magnetic flux density in the hot-rolled sheet annealing single cold rolling method by continuous annealing of 2% Si-based components.

FIG. 6 is a view showing the relationship between the tension between the final stand and the coiler and the magnetic flux density of the finished product at the time of finish hot rolling in the single cold rolling method after the self-annealing process after hot rolling of 2% Si and 3% Si components.

FIG. 7 is a diagram showing the relationship between the tension between the final stand and the coiler and the magnetic flux density of the final stand at the time of finish hot rolling in the single cold rolling method after the end of hot rolling of the 2.5% Si component system.

Claims (10)

[Claims] 1.% by weight: 2.00% <Si ≦ 7.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 A slab containing 0.0050%, with the balance being Fe and unavoidable impurities, is hot-rolled to give a hot-rolled sheet, and the hot-rolled sheet is subjected to one or two or more cold rolling steps including intermediate annealing. In a method of manufacturing a non-oriented electrical steel sheet which is a final product including a step of applying a cold rolled sheet and then performing a finish annealing and applying or not applying an insulating film, after finishing hot rolling, the final stand and the coiler Tension σ (kgf / m
m ² ) in relation to the finish hot rolling end temperature T (° C.), and manufacturing a non-oriented electrical steel sheet having a high magnetic flux density, wherein the hot rolled sheet is wound around a coil while maintaining the following equation (1). Method. σ (kgf / mm ² ) ≧ 2-T ^0.3 + lnT ‥‥‥ (1) 2. As a slab component, further in weight%:
The method for producing a non-oriented electrical steel sheet according to claim 1, wherein 0.10% to 1.00% of Al is contained. 3.% by weight: 0.10% <Si ≦ 2.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 A slab containing 0.0050%, the balance being Fe and unavoidable impurities, is hot-rolled into a hot-rolled sheet, and the hot-rolled sheet is subjected to one or two or more cold rolling steps including intermediate annealing. In a method for producing a non-oriented electrical steel sheet which is a final product including a step of forming a cold rolled sheet and then performing a finish annealing and applying or not applying an insulating film, the finish hot rolling end temperature is 700 ° C. or more (Ar ₃ + Ar ₁ ) / 2 or less, and after finishing hot rolling, the tension σ (kgf / mm ² ) between the final stand and the coiler is expressed by the following equation (1) in relation to the finishing hot rolling end temperature T (° C.). Non-directional electromagnetic with high magnetic flux density characterized by winding a hot rolled sheet into a coil while keeping the temperature Method of manufacturing the plate. σ (kgf / mm ² ) ≧ 2-T ^0.3 + lnT ‥‥‥ (1) 4. As a slab component, further by weight%
0.10% to 1.00% Al, and (Si
4. The method for producing a non-oriented electrical steel sheet according to claim 3, wherein (+ 2Al) ≦ 2.5% is satisfied. 5. After finishing hot rolling and before cold rolling, the steel sheet is subjected to continuous annealing at a temperature of 850 ° C. or more and 1150 ° C. or less for 20 seconds or more and less than 5 minutes. Item 5. The method for producing a non-oriented electrical steel sheet according to any one of Items 1 to 4, wherein the magnetic flux density is high and the iron loss is low. 6. After finishing hot rolling and before cold rolling, the steel sheet is subjected to box annealing at a temperature of 750 ° C. or more and 850 ° C. or less by box annealing for 5 minutes or more and less than 30 hours. Item 5. The method for producing a non-oriented electrical steel sheet according to any one of Items 1 to 4, wherein the magnetic flux density is high and the iron loss is low. 7. After finishing hot rolling, the temperature is 750 ° C. or more and 1000
The magnetic flux density is high according to any one of claims 1 to 4, wherein the coil is wound around the coil at a temperature of not more than 5 ° C and self-annealed by the heat held by the coil itself for 5 minutes to 5 hours. Method for producing non-oriented electrical steel sheet with low hardness. 8. In relation to the finishing hot rolling end temperature T (° C.) performed in the range of the following equation (2), water is not injected for a time t defined by the following equation (3) after the end of the hot rolling. The method for manufacturing a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss according to any one of claims 1 to 7, wherein the non-oriented electrical steel sheet is wound around a coil. 950 ≦ T (° C.) ≦ 1150 {(2) 9.6-8 × 10 ⁻³ T ≦ t (second) ≦ 15.6-8 × 10 ⁻³ T} (3) 9. The sheet bar according to claim 1, wherein the sheet bar after the rough rolling is joined to a preceding sheet bar before the hot rolling, and the sheet bar is continuously subjected to the hot rolling. 2. The method for producing a non-oriented electrical steel sheet according to claim 1 having a high magnetic flux density and a low iron loss. 10. The magnetic flux density according to claim 1, wherein after the finish annealing, a skin pass rolling step at a rolling reduction of 2% or more and 20% or less is further performed. Highly non-oriented electrical steel sheet manufacturing method.