JPH1060531A - Production of nonoriented silicon steel sheet high in magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nonoriented silicon steel sheet high in magnetic flux density and used for the iron core material of electric apparatus. SOLUTION: This method for producing a nonoriented silicon steel sheet high in magnetic flux density is the one in which a steel having components contg., by weight, >0.10 to 2.00% Si, 0.1 to 1.0% Mn, 0.10 to 1.00% Al, <=0.0050% C, <=0.0050% N, <=0.0050% S, and the balance Fe with inevitable impurities is subjected to hot rolling to form into a hot rolled sheet, which is applied with insulated coating or is not applied with this to form into a final product. In this case, at the time of the finish hot rolling, it is executed in such a manner that the strain rate per at least one pass is regulated to >=150s<-1> and the tension between at least one set of stands is regulated to >=1.5kgf/mm<2> , and the finish hot rolling finishing temp. is regulated to 750 deg.C to (Ar3 +Ar1 )/2 or below. Furthermore, the sheet bars after rough rolling by the hot rolling are joined, which is subjected to the continuous finish hot rolling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a 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 field of electric machines, particularly rotating machines in which non-oriented electrical steel sheets are used, the trend toward high efficiency has been rapidly increasing in the context of global energy conservation and global environmental conservation. Is spreading. In response to such market demands, in non-oriented electrical steel sheets, attempts have been made to reduce energy loss during use by lowering iron loss, and low iron loss non-oriented electrical steel sheets centered on high Si component systems Has been developed.

[0003] On the other hand, some applications of non-oriented electrical steel sheets include:
Like motors in automobile power windows, the operating time is short, and iron loss does not require very good characteristics.
Rather, there is a demand for smaller size and lighter weight.
In such an application, it is possible to reduce the size of the rotating machine by increasing the torque at the time of startup and operation by increasing the magnetic flux density. Further, non-oriented electrical steel sheets used in such applications are characterized by low costs.

In the prior art, in order to increase the magnetic flux density of a non-oriented electrical steel sheet, a method of improving the magnetic flux density by coarsening the crystal grain size before cold rolling has been performed. For this purpose,
Generally, it has been practiced to perform hot-rolled sheet annealing by continuous annealing or box annealing to increase the crystal grain size before cold rolling and improve the recrystallization texture to improve the magnetic flux density. However, in this method, the cost increase is remarkable due to the addition of the hot-rolled sheet annealing step, and at present, it is unacceptable to consumers used for the above-mentioned purposes.

Therefore, as a technique for inexpensively coarsening the crystal structure of a non-oriented electrical steel sheet before cold rolling, a hot rolled sheet after finish hot rolling is wound at a high temperature of 700 ° C. to 1000 ° C. Japanese Patent Laid-Open No. 54-764 discloses a self-annealing method of annealing with heat.
No. 22 and Japanese Patent Publication No. 62-64444, the hot-rolling end temperature is set to a high temperature of 1000 ° C. or higher, and no water injection time is set. A method for achieving grain growth is disclosed.

However, even in these production methods, it is necessary to carry out a cold rolling step after the production of a hot rolled sheet, and thus the production cost is equivalent to the production cost of the conventional non-oriented electrical steel sheet production technology. The stringent demands for house cost reduction were not met.

[0007] In order to find a way to meet the demands of customers for such non-oriented electrical steel sheets, the present inventors have focused on the development of so-called hot final products using hot-rolled sheets as final products and studied. Among non-oriented electrical steel sheets, so-called cold-rolled electrical steel sheets have better magnetic properties than hot-final products, and the fact is that they have been switched to cold-rolled electrical steel sheets in the market. However, the inventors of the present invention have focused on the hot-rolling finishing technology for the purpose of improving the characteristics of a low-cost hot-final electrical steel sheet.

As a result, not only the iron loss is improved by merely reducing the thickness of the finished plate to reduce the eddy current loss, but the Si content exceeds 0.10% and is 2.00% or less.
0.10% or more and 1.00% or less, and Al containing 0.10% or more and 1.00% or less. At the time of finishing hot rolling, in at least one pass, increase the strain rate,
1. Increasing the tension between at least one set of stands increases the magnetic flux density of the product. 2. Control the finish hot rolling end temperature within a certain range to release rolling strain and improve magnetic properties. The sheet bar after the rough rolling is joined to the preceding sheet bar before the finish hot rolling, and the finish hot rolling under a high strain rate and high tension is stabilized by continuously subjecting the sheet bar to the finish hot rolling. And what can be done
The invention has been completed.

[0009]

SUMMARY OF THE INVENTION The present invention meets the strong demand for low-cost, high-flux-density non-oriented electrical steel sheets by such customers, and provides a high-flux-density non-directional steel sheet with high torque and miniaturization. An object of the present invention is to provide a method for manufacturing an electrical steel sheet.

[0010]

The gist of the present invention is as follows.

(1) 0.10% <Si ≦ 2.00% 0.10% ≦ Mn ≦ 1.00% C ≦ 0.0050% N ≦ 0.0050% S ≦ 0. Production method of non-oriented electrical steel sheet using a slab containing 0050% with the balance being Fe and unavoidable impurities, hot-rolled into a hot-rolled sheet, with or without an insulating coating, and as a final product In the finish hot rolling, at least 1
Finish hot rolling is performed on the pass at a strain rate of 150 s ^-1 or more and a tension between at least one set of stands of 1.5 kgf / mm ² or more, and a finish hot rolling end temperature of 750 ° C. or more (A _r3 + A _r1 ). / 2 or less, the method for producing a non-oriented electrical steel sheet having a high magnetic flux density.

(2) 0.10% ≦ by weight in steel
(1) wherein Al ≦ 1.00% is contained.
A method for producing a non-oriented electrical steel sheet having a high magnetic flux density as described in the above item.

(3) The method according to the above (1), wherein the sheet bar after the rough rolling is joined to a preceding sheet bar before the finish hot rolling, and the sheet bar is continuously subjected to the finish hot rolling.
(2) The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to the item (2).

(4) The steel sheet after the finish hot rolling is pickled,
%. The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to the above (1), (2) or (3), wherein a skin pass with a rolling ratio of not less than 20% and not more than 20% is applied.

Hereinafter, the present invention will be described in detail.

First, the components will be described. Si is added to increase the specific resistance of the steel sheet, reduce eddy current loss, and improve the iron loss value. If the Si content is 0.10% or less, the specific resistance required for the low iron loss non-oriented electrical steel sheet aimed at by the present invention cannot be sufficiently obtained, so it is necessary to add an amount exceeding 0.10%. is there. On the other hand, when the Si content is 2.
If it exceeds 00%, the edge cracks at the time of rolling increase remarkably, making the rolling difficult and increasing the cost.
It is necessary to:

Al, like Si, has the effect of increasing the specific resistance of the steel sheet and reducing eddy current loss. In order to obtain a low iron loss high magnetic flux density non-oriented electrical steel sheet aimed at by the present invention, it is necessary to add 0.10% or more. On the other hand, A
When the l content exceeds 1.00%, the magnetic flux density decreases,
Since the cost is high, the content is set to 1.00% or less.

Further, even if the Al content in the steel is less than 0.10%, 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 a steel sheet and reducing 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 1.00%, 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 1.00% 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 the value of Mn / S, which is the weight concentration ratio between Mn and S, is set to 2 in order to prevent hot embrittlement of the sheet bar joint due to the presence of the low-melting sulfide at the crystal grain boundaries.
This is because it is necessary to set it to 0 or more. In the component range defined in the present invention, the Mn content is 0.1% or more, and the S content is 0.0050% or less.
The value of S is kept at 20 or more, and there is no problem from this viewpoint.

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.

If the C content exceeds 0.0050%, the iron loss becomes worse due to magnetic aging during use and the energy loss during use increases. Therefore, it is necessary to control the content to 0.0050% or less.

S and N partially re-dissolve during slab heating in the hot rolling process, 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 hinders the growth of the crystal grains during the final annealing, the iron loss worsens.
% And N must be 0.0050% or less.

Next, the process conditions of the present invention will be described.

The steel slab comprising the above components is produced by melting in a converter and produced 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 following experiment was conducted in order to investigate the influence of the strain rate of the pass and the tension between stands on the magnetic properties of the finished product during hot rolling. Steel having the components shown in Table 1 was melted and subjected to finish hot rolling.

[0027]

[Table 1]

Strain speed of final pass during finishing hot rolling and final 2
The test was performed by changing the pass schedule to change the tension between the stands of the pass. Since the A _r3 point of this steel is 900 ° C and the A _r1 point is 869 ° C., the hot rolling finish temperature is (A _r3 + A _r1 ) / 2 or less and 750 ° C. or more.
The mixture was finished to a thickness of 0.8 mm, cooled with water, and wound at 550 ° C. An Epstein sample was cut from the obtained sample, and the magnetic properties were measured.

FIG. 1 shows the dependence of the product magnetic flux density on the strain rate of the final pass during hot rolling. At this time, the tension between the last two stands was 3.1 kgf / mm ² . FIG.
According to the figure, it is understood that the product magnetic flux density increases at a strain rate of 150 s ^-1 or more.

The calculation of the strain rate is performed by the following equation. Here, r is the rolling reduction% / 100, n is the number of rotations of the roll (rpm), R is the radius of the rolling roll (mm), and H0 is the plate thickness (mm) before rolling.

Strain rate = (2πn / (60r ^0.5 ))
(R / H ₀ ) ^0.5 ln (1 / (1-r)) Next, the same steel was used, the final stand strain rate of the hot-rolled finish was set to 325 s ⁻¹ , and the tension between the last two stands was changed. The experiment was performed under the same conditions. FIG. 2 shows the relationship between the tension between the last two stands and the magnetic flux density of the product during hot rolling. As shown in FIG. 2, it can be seen that the product magnetic flux density increases when the tension between the last two stands of the hot-rolled finish is 1.5 kgf / mm ² or more.

As can be seen from the above experiments, the strain rate in at least one pass is 150 s ^-1 or more and the tension between at least one set of stands is 1.5 kgf in the hot-rolled finish.
/ Mm ² or more. There is no particular upper limit on the strain rate. This is because the upper limit of the strain rate is naturally determined from the equipment capacity of the hot rolling mill and the shape controllability of the hot rolled sheet. That is, the strain rate is determined by the rolling speed, the diameter of the hot-rolled roll, and the amount of reduction. When the rolling speed and the amount of reduction are increased, the distortion speed increases, but it becomes difficult to control the shape of the hot-rolled steel sheet. Since non-oriented electrical steel sheets are used in layers,
Since strict control is required for the shape, there is naturally a limit in increasing the strain rate. From this viewpoint, the strain rate is limited to about 600 s ^-1 .

There is no upper limit on the tension between the stands. However, if the tension between the stands increases, deformation occurs at the time of passing, and the width of the plate becomes narrow. Therefore, it is necessary to increase the slab width to compensate for this. The limit of the tension from this viewpoint is about 10 kgf / mm ² .

Further, in order to stably perform the finishing hot rolling under a high strain rate and a high tension as in the present invention, the sheet bar after the rough rolling is joined to the preceding sheet bar, and the finish hot rolling is performed. It is particularly effective to perform rolling continuously.

When the hot-rolling end temperature is lower than 750 ° C., the rolling reaction force of the steel sheet increases to make rolling difficult, and the rate at which the strain introduced during hot rolling is recovered and released by recrystallization is drastically reduced. Since the magnetic properties are significantly deteriorated, the finish hot rolling end temperature is set to 750 ° C. or higher. Further, since the component system of the present invention has an αγ transformation, if the finish hot rolling end temperature is excessively increased, the crystal structure becomes fine at the time of cooling after the end of hot rolling, and the magnetic properties are significantly deteriorated. For this reason, the hot rolling end temperature is set to (A _r3 + A _r1 ) / 2 or less.

The hot-rolled sheet obtained by the above method may be used without being pickled. However, in order to improve the workability in a later step, the pickled sheet is subjected to pickling to remove oxides on the surface. It is more preferable to do so. Further, an insulating film may be provided on the surface.

Further, the hot-rolled sheet which has been pickled may be subjected to rolling of 2% or more and 20% or less and subjected to strain relief annealing to improve iron loss characteristics before use. At this time, if the rolling reduction is less than 2%, there is no effect of improving the magnetic properties, and if it exceeds 20%, the cost increases, so the rolling reduction is set to 2% or more and 20% or less. The strain relief annealing is preferably performed at a temperature of about 750 ° C. for the purpose of simplifying the annealing equipment.

[0038]

Next, an embodiment of the present invention will be described.

Example 1 A slab for non-oriented electromagnetic steel having the components shown in Table 2 was heated by a usual method, finished into a 50 mm-thick coarse bar by a rough rolling mill, and then finished by a finishing hot rolling mill. .8mm
Finished.

The strain rate in the final pass of the finishing hot rolling was controlled at 300 to 320 s ^-1 over the entire length of the coil. Further, in order to prevent a slip from occurring between the steel sheet and the work roll at the time of finishing hot rolling and forming a flaw on the surface of the steel sheet, the sheet bar after the rough rolling is welded to the preceding sheet bar, and the finishing hot rolling is performed. Rolling was performed continuously. The _Ar3 point of this steel is 900 ° C
Since the _{Ar 1} point is 870 ° C., the hot rolling finish temperature is (A _r3 + A _r1 ) / 2 or less and 750 ° C. or more.
° C.

Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 3 also shows the components of the present invention and comparative examples and the results of magnetic measurement.

As described above, the tension between the last two stands at the time of finishing hot rolling is increased to 1.5 kgf / mm ² or more, so that the magnetic flux density is high and the iron loss value is low. It is possible to obtain an electrical steel sheet.

[0043]

[Table 2]

[0044]

[Table 3]

Example 2 A slab for non-oriented electromagnetic steel having the components shown in Table 4 was heated by a usual method, finished to a rough bar having a thickness of 50 mm by a rough rolling machine, and then finished by a finishing hot rolling machine. 0.0mm
Finished. 2. Tension between the final two stands of hot-rolled finish
Rolling was performed while maintaining the pressure at 0 kgf / mm ² to 3.2 kgf / mm ² . Further, in order to prevent a slip from occurring between the steel sheet and the work roll at the time of finish hot rolling and forming a flaw on the surface of the steel sheet, the sheet bar after the rough rolling is welded to a preceding sheet bar, and the finish hot rolling is performed. Rolling was performed continuously. A of this steel
_{Since the r3} point is 901 ° C. and the A _r1 point is 868 ° C.,
The hot-rolling finishing temperature was set to 855 ° C. which was not more than (A _r3 + A _r1 ) / 2 and not less than 750 ° C. Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 5 also shows the components of the present invention and comparative examples and the results of magnetic measurement.

By increasing the strain rate of the final pass at the time of finishing hot rolling to 150 s ^-1 or more, it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss value and excellent magnetic properties. It is possible.

[0047]

[Table 4]

[0048]

[Table 5]

Example 3 A slab for non-oriented electromagnetic steel having the components shown in Table 6 was heated by a usual method, finished to a rough bar having a thickness of 50 mm by a rough rolling mill, and then finished by a finishing hot rolling mill. 0.0mm
Finished. 2. Tension between the final two stands of hot-rolled finish
It was rolled kept from 1 kgf / mm ² to 3.3 kgf / mm ^2. Further, in order to prevent a slip from occurring between the steel sheet and the work roll at the time of finishing hot rolling and forming a flaw on the surface of the steel sheet, the sheet bar after the rough rolling is welded to the preceding sheet bar, and the finishing hot rolling is performed. Rolling was performed continuously. Since the _{Ar 3} point of this steel is 891 ° C. and the _{Ar 1} point is 860 ° C., the hot-rolling finishing temperature is not more than (A _r3 + A _r1 ) / 2 and is 7 °.
The temperature was 850 ° C. which was 50 ° C. or higher.

Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 7 also shows the components of the present invention and comparative examples and the results of magnetic measurement.

By increasing the strain rate of the final pass at the time of finishing hot rolling to 150 s ^-1 or more, it is possible to obtain a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss value and excellent magnetic properties. It is possible.

[0052]

[Table 6]

[0053]

[Table 7]

[0054]

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 strain rate of the final pass during finish hot rolling and the product magnetic flux density.

FIG. 2 is a diagram showing the relationship between the tension between the last two stands during finishing hot rolling and the magnetic flux density of a product.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takehide Senuma 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division

Claims (4)

[Claims] 1.% by weight in steel 0.10% <Si ≦ 2.00% 0.10% ≦ Mn ≦ 1.00% C ≦ 0.0050% N ≦ 0.0050% S ≦ 0.0050 %, With the balance being Fe and unavoidable impurities, hot rolled into a hot rolled sheet, with or without an insulating coating, to produce a non-oriented electrical steel sheet as a final product. , At least 1
The pass is subjected to finish hot rolling at a strain rate of 150 s ^-1 or more and a tension between at least one set of stands of 1.5 kgf / mm ² or more, and a finish hot rolling end temperature of 750 ° C. or more (A
_r3 + _Ar1 ) / 2 or less. A method for producing a non-oriented electrical steel sheet having a high magnetic flux density. 2. The composition according to claim 1, wherein the weight percentage in steel is 0.10% ≦ Al
The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to claim 1, characterized by containing ≤ 1.00%. 3. The magnetic flux 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. A method for manufacturing non-oriented electrical steel sheets with high density. 4. The non-directional high-flux-density magnetic sheet according to claim 1, wherein the steel sheet after finish hot rolling is subjected to pickling and a skin pass with a rolling ratio of 2% or more and 20% or less is applied. Manufacturing method of conductive electrical steel sheet.