JPH10158737A - Manufacture of hot final nonoriented silicon steel sheet with high magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacture of a hot final nonoriented silicon steel sheet having high magnetic flux density, used for an iron core material for electrical equipment. SOLUTION: This nonoriented silicon steel sheet is produced by hot-rolling a slab having a composition consisting of, by weight, >0.10-4.00% Si, 0.10-1.50% Mn, <=0.0050% C, <=0.0050% N, <=0.0050% S, and the balance Fe with inevitable impurities and then forming the resultant hot rolled plate, with or without application of an insulating film, into a final product. At this time, at the time of finish hot rolling, rolling is carried out at 5-50% draft per pass at one or more successive passes from the final pass side and at <=0.25 coefficient of friction between the steel plate and a rolling roll.

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 and 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, there has been a rapid increase in the efficiency of global energy conservation as a result of global energy 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]

SUMMARY OF THE INVENTION The present inventors have developed a so-called hot final product using a hot-rolled sheet as an end product in order to find a way to meet the demands of consumers for such non-oriented electrical steel sheets. Was 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, the inventors have found that a hot-final non-oriented electrical steel sheet having a high magnetic flux density can be stably manufactured by a method focusing on the following points, and have completed the invention. First, it is necessary to lower the coefficient of friction between the steel sheet and the rolling rolls in the final pass while ensuring a constant reduction rate per pass on the final pass side in the finishing hot rolling. The main feature is that the rolled sheet bar is joined to the preceding sheet bar before finish hot rolling, and the sheet bar is continuously subjected to finish hot rolling so that rolling with a low friction coefficient can be stably performed. Content.

The present invention has responded to such a strong demand for low-cost, high-flux-density non-oriented electrical steel sheets by customers, and has developed a method for producing high-flux-density non-oriented electrical steel sheets that can be reduced in size with high torque. To provide.

[0010]

The gist of the present invention is as follows.

(1) 0.10% <Si ≦ 4% by weight
00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.00
Using a slab containing 50%, N ≦ 0.0050%, S ≦ 0.0050%, and the balance being Fe and unavoidable impurities, hot-rolled to a hot-rolled sheet, and applying an insulating coating,
Alternatively, in the method for producing a non-oriented electrical steel sheet which is not subjected to final treatment, in the finish hot rolling, in one or more passes continuous from the final pass side, the rolling reduction of one pass is 5%.
% To 50% and a coefficient of friction between the steel sheet and the rolling roll of 0.25 or less is rolled.

(2) 0.10% <Si ≦ 4% by weight
00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.00
A slab containing 50%, N ≦ 0.0050%, S ≦ 0.0050%, further containing 0.10% ≦ Al ≦ 1.00%, and the balance being Fe and unavoidable impurities is used. (1) The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to (1).

(3) The oil according to (1) or (2), wherein a fat or oil having a volume ratio of 0.5 to 20% is mixed into the hot-rolled roll cooling water as a lubricant used in the finish hot rolling. A method for manufacturing non-oriented electrical steel sheets with high magnetic flux density.

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

(5) Finished hot-rolled steel sheet is pickled,
(1), (2), (3) or (4), the method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to (1), (2), (3) or (4).

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, regarding the components, 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, sufficient resistivity cannot be obtained, so it is necessary to add an amount exceeding 0.10%. On the other hand, the Si content is 4.00%
If the ratio exceeds, ear cracks at the time of rolling increase remarkably, and rolling becomes difficult and cost increases. Therefore, it is necessary to be 4.00% or less.

Al, like Si, has the effect of increasing the specific resistance of the steel sheet and reducing eddy current loss. For this reason, 0.10% or more is added as needed. On the other hand, Al
If the content exceeds 1.00%, the magnetic flux density decreases and the cost increases, so the content is set to 1.00% or less.

Mn, like Al and Si, has the effect of increasing the specific resistance of the 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 1.50%, 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 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.

The C content is set to 0.00% in order to prevent magnetic aging during use, reduce iron loss, and obtain more excellent properties.
It must be 50% or less.

S and N partially re-dissolve during the 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.

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 following experiment was conducted in order to investigate the influence of the average friction coefficient between the hot-rolled roll and the steel sheet during finishing hot-rolling on the magnetic properties of the product. Steel having the components shown in Table 1 was melted and subjected to finish hot rolling.

[0025]

[Table 1]

During the finishing hot rolling, the friction coefficient at the final stand was changed by changing the oil content of the roll cooling water. The coefficient of friction was calculated from the measured advanced rate. The finishing hot rolling end temperature was fixed at 860 ° C., the rolling reduction of the final stand was 25%, the thickness was 0.80 mm, and the Epstein sample was cut off by pickling to measure the magnetic properties.

FIG. 1 shows the relationship between the coefficient of friction and the product magnetic flux density at the final stand of the finish hot rolling. The coefficient of friction is 0.
It is understood that the magnetic flux density increases when the ratio is 25 or less. As can be seen from the above experiment, when the friction coefficient between the roll of finish hot rolling and the steel sheet exceeds 0.25, the effect of improving the magnetic flux density cannot be obtained.

Although the effect of improving the magnetic flux density can be seen in any of the stands during finishing hot rolling, the friction coefficient can be reduced.
According to the study results of the inventors, the effect of improving the magnetic flux density is greater when the friction coefficient is reduced near the final pass. Therefore, in the present invention, the low friction rolling is performed in one or more consecutive passes from the final pass side of the finish hot rolling. That is, low friction rolling may be performed only on the final pass, or may be performed on two or more consecutive passes including the final pass. Of course, the low friction rolling may be performed in all passes of the finish hot rolling. The lower limit of the friction coefficient is not particularly set, but if the value is excessively small, slippage occurs during rolling and the sheet cannot be passed stably.
It is preferably at least 05.

If the rolling reduction per pass of the low friction rolling is less than 5%, the effect of improving the magnetic flux density does not appear, and
%, A slip during rolling is likely to occur due to a lack of friction coefficient. Therefore, the rolling reduction per pass of low friction rolling is specified to be 5% or more and 50% or less.

In the case where the finishing hot rolling is performed at a low friction rate as in the present invention, when the sheet bar is bitten into the finishing hot rolling machine, a sheet bar biting failure occurs or the roll is not rolled during the finishing hot rolling. In some cases, slip occurs between the steel sheets, which significantly shortens the life of the rolling rolls and causes deep rolling flaws on the surface layer of the steel sheets. As a method of solving such a problem in the finish hot rolling with a low friction coefficient and performing a stable operation, the sheet bar after the rough rolling is joined to a preceding sheet bar before the finish hot rolling. It is particularly effective to continuously subject the sheet bar to finish hot rolling.

As a method of joining the preceding sheet bar and the succeeding sheet bar, a method of welding the trailing end of the preceding sheet bar to the leading end of the succeeding sheet bar and welding the butting portion, and pressing force on the butting portion , A method of laser welding the butt portion, a method of welding the butt portion by induction heating, or a combination thereof.

It is effective to mix fats and oils in the roll cooling water as a means for reducing the coefficient of friction between the steel sheet and the rolling roll during hot rolling. The amount of the fat is 0.5% or more and 20% or less by volume. A surfactant is added as necessary to prevent separation of the oil and fat from the cooling water. When the amount of fats and oils in the roll cooling water is less than 0.5%, the effect of improving the magnetic flux density cannot be obtained, and when it exceeds 20%, the effect is saturated and uneconomical, so the amount of fats and oils is 0.5% or more and 20% or less. And

As the oil or fat mixed in the roll cooling water, a known hot rolling oil for a finishing mill may be used. Examples of such hot rolling oils for finishing mills include, for example, Cudol 5149, Cudol 0B068,
Q-doll 4B313 (both trade names of Kyodo Yushi Co., Ltd.).

In the present invention, the hot rolling end temperature is not particularly specified, but from the viewpoint of improving workability, the finishing hot rolling end temperature is preferably 750 ° C. or higher.

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 then subjected to strain relief annealing to improve the 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.

[0037]

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 2 was heated by a usual method, finished to a coarse bar of 30 mm in thickness by a rough rolling mill, and then finished to a thickness of 30 mm by a finishing hot rolling mill. Finished to 8mm. The hot rolling end temperature was 860 ° C.
The friction coefficient was changed by adjusting the amount of oil and fat mixed in the roll cooling water during rolling, and the friction coefficient between the steel sheet and the roll in the final pass of the finishing hot rolling was obtained by actually measuring the advance rate of the final stand. The rolling reduction of the final pass was 25%.

[0038]

[Table 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 joined to the preceding sheet bar, Finish hot rolling was performed continuously. The joining of the sheet bars was performed by abutting and pressing the front end portion of the following sheet bar and the rear end portion of the preceding sheet bar, and laser welding the butted portion.

Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 3 shows the results of the magnetic measurement of the present invention and the comparative example. By controlling the final friction coefficient at the time of finishing hot rolling to 0.25 or less, a hot final non-oriented electrical steel sheet having a high magnetic flux density can be obtained.

[0041]

[Table 3]

Example 2 A slab for non-oriented electromagnetic steel having the components shown in Table 4 was heated by a conventional method, and finished into a 30 mm-thick coarse bar by a rough rolling mill. To 1.0 mm. Hot rolling end temperature is 86
0 ° C. The friction coefficient was changed by adjusting the amount of oil and fat mixed in the roll cooling water during rolling, and the friction coefficient between the steel sheet and the roll in the final pass of the finishing hot rolling was obtained by actually measuring the advance rate of the final stand. The rolling reduction of the last pass is 2
5%.

[0043]

[Table 4]

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, Finish hot rolling was performed continuously. The joining of the sheet bars was performed in the same manner as in Example 1.

Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 5 shows the magnetic measurement results of the present invention and the comparative example. By controlling the coefficient of friction of the final stand at the time of finishing hot rolling to 0.25 or less, a hot final non-oriented electrical steel sheet having a high magnetic flux density can be obtained.

[0046]

[Table 5]

Example 3 A slab for non-oriented electrical steel having the components shown in Table 6 was heated by a usual method, and finished with a rough rolling mill into a coarse bar having a thickness of 30 mm. To 0.8mm. Hot rolling end temperature is 87
0 ° C. The friction coefficient was changed by adjusting the amount of oil and fat mixed in the roll cooling water during rolling, and the friction coefficient between the steel sheet and the steel sheet in the final pass of the final hot rolling was determined by actually measuring the advanced ratio of the final stand. The rolling reduction of the final pass was 25%.

[0048]

[Table 6]

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, Finish hot rolling was performed continuously. The joining of the sheet bars was performed in the same manner as in Example 1.

Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 7 shows the results of the magnetic measurement of the present invention and the comparative example. By controlling the coefficient of friction of the final stand at the time of finishing hot rolling to 0.25 or less, a hot final non-oriented electrical steel sheet having a high magnetic flux density can be obtained.

[0051]

[Table 7]

[0052]

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

[Brief description of the drawings]

FIG. 1 shows the relationship between the coefficient of friction of the final stand and the magnetic flux density of a product during hot rolling.

Claims (5)

[Claims] 1. In% by weight, 0.10% <Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 A method for producing a non-oriented electrical steel sheet which is hot rolled by hot rolling a slab containing 0.0050%, with the balance being Fe and unavoidable impurities, and with or without an insulating coating, as a final product In the finishing hot rolling, the rolling reduction of one pass is 5% in one or more passes continuous from the last pass side.
A method for producing a non-oriented electrical steel sheet having a high magnetic flux density, characterized in that rolling is performed at a rate of at least 50% and a friction coefficient between the steel sheet and the rolling roll of 0.25 or less. 2. In% by weight, 0.10% <Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 2. A non-directional slab having a high magnetic flux density according to claim 1, wherein the slab contains 0.150% ≦ Al ≦ 1.00%, and the balance is Fe and unavoidable impurities. Manufacturing method of conductive electrical steel sheet. 3. A lubricant used in finish hot rolling,
The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to claim 1 or 2, wherein 0.5 to 20% by volume of a fat or oil is mixed into the hot-rolled roll cooling water. 4. 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.
A method for producing a non-oriented electrical steel sheet having a high magnetic flux density as described above. 5. The magnetic flux density according to claim 1, 2, 3 or 4, wherein the steel sheet after the finish hot rolling is subjected to pickling and skin pass rolling at a rolling rate of 2% or more and 20% or less. Highly non-oriented electrical steel sheet manufacturing method.