JP3379622B2 - Manufacturing method of hot final non-oriented electrical steel sheet with high magnetic flux density - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, in the field of electric machines, especially rotating machines in which non-oriented electrical steel sheets are used, there is a rapid movement toward higher efficiency among global movements for energy conservation and global environmental conservation. It 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 reducing iron loss, and low iron loss non-oriented electrical steel sheets centered on high Si component systems. Has been developed.

On the other hand, among the applications of the non-oriented electrical steel sheet,
Like a motor in a car power window, it has a short operating time and does not require good characteristics for iron loss.
On the contrary, there is a strong demand for smaller size and lighter weight.
In such applications, it is possible to downsize the rotating machine by increasing the magnetic flux density to increase the torque during startup and operation. Furthermore, the non-oriented electrical steel sheet used for such applications is strongly required to be low in cost.

In the prior art, in order to increase the magnetic flux density of the non-oriented electrical steel sheet, a method of coarsening the crystal grain size before cold rolling to improve the magnetic flux density has been used. For this purpose,
Generally, hot-rolled sheet annealing is performed by continuous annealing or box annealing to coarsen the grain size before cold rolling and improve the recrystallized texture to improve the magnetic flux density. However, in this method, the cost is remarkably increased due to the addition of the hot-rolled sheet annealing step, and it is the current situation that it cannot be accepted by the customers who are used for the above 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 to 1000 ° C. and held by a coil. A self-annealing method of annealing by heat is disclosed in JP-A-54-764.
No. 22 and Japanese Patent Publication No. 62-61644 set the hot rolling end temperature to a high temperature of 1000 ° C. or higher and set no water injection time to recrystallize the hot rolled structure before winding on a so-called run-out table. A method for grain growth is disclosed.

However, even in these manufacturing methods, since it is necessary to carry out a cold rolling step after the hot rolled sheet is manufactured, it is equivalent to the manufacturing cost of the conventional non-oriented electrical steel sheet manufacturing technology, and the recent demand. It was not possible to meet the strict demand for reducing the cost of the house.

[0007]

SUMMARY OF THE INVENTION The present inventors have developed a so-called hot final product, which uses a hot-rolled sheet as a final product, in order to find a measure to meet the demands of customers for such a non-oriented electrical steel sheet. I narrowed down and examined. Among non-oriented electrical steel sheets, so-called cold-rolled electrical steel sheets are superior in magnetic properties to hot final products, so that the market has been switched to cold-rolled electrical steel sheets. However, the present inventors have paid attention to the finish hot rolling technique and conducted an examination for the purpose of improving the properties of a low-cost hot final electrical steel sheet.

As a result, they have found that a hot final non-oriented electrical steel sheet having a high magnetic flux density can be stably manufactured by a method mainly focusing on the following points, and completed the invention. The first is to secure a constant rolling reduction per pass on the final pass side during finish hot rolling, while lowering the friction coefficient between the steel plate and the rolling roll in that pass. By joining the rolled sheet bar to the preceding sheet bar before finishing hot rolling and continuously subjecting the sheet bar to finishing hot rolling, it is possible to perform stable rolling with a low friction coefficient. It is the content.

The present invention, in response to such a strong demand for low cost high magnetic flux density non-oriented electrical steel sheet of the consumer, provides a method for producing a high magnetic flux density non-oriented electrical steel sheet which can be miniaturized with high torque. It is provided.

[0010]

The gist of the present invention is as follows.

(1) In% by weight, 0.10% <Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ containing 0.0050% and satisfies Mn / S ≧ 20, the slab and the balance being Fe and unavoidable impurities was hot rolled and hot-rolled sheet, the non-oriented electrical steel sheet to final product In the manufacturing method, when finishing hot rolling, the continuous 1
Only the final pass, or the final pass
The rolling reduction of 5% or more and 50% or less in each of continuous two or more passes including the steel sheet, and the rolling coefficient of the friction coefficient between the steel plate and the rolling roll being 0.25 or less are
A method for manufacturing a non-oriented electrical steel sheet having a high magnetic flux density of 1.0 mm or less .

(2) In% by weight, 0.10% <Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ A slab containing 0.0050% and satisfying Mn / S ≧ 20, 0.10% ≦ Al ≦ 1.00%, and the balance being Fe and inevitable impurities is used. (1) The method for producing a non-oriented electrical steel sheet having a high magnetic flux density as described in (1).

(3) As a lubricant used at the time of finish hot rolling, 0.5 to 20% by volume of fats and oils are mixed into cooling water for hot-rolled rolls, as described in (1) or (2). A method for manufacturing a non-oriented electrical steel sheet having a high magnetic flux density.

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

(5) 2% or more and 20% or more after pickling the steel sheet after hot rolling
The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to any one of (1) to (4) , characterized in that skin pass rolling having the following rolling rate is performed. (6) The hot-rolled sheet is provided with an insulating film (1)
Non-direction with high magnetic flux density according to any one of (1) to (5)
For manufacturing high-performance electrical steel sheet.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. First, the components will be described. 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, a sufficient specific resistance cannot be obtained, so it is necessary to add an amount exceeding 0.10%. On the other hand, Si content is 4.00%
If it exceeds 1.0%, the ear cracks during rolling increase remarkably, making rolling difficult and increasing the cost.

Al, like Si, also has the effect of increasing the specific resistance of the steel sheet and reducing eddy current loss. Therefore, 0.10% or more is added if necessary. On the other hand, Al
If the content exceeds 1.00%, the magnetic flux density decreases and the cost also increases, so the content is made 1.00% or less.

Similar to Al and Si, Mn 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, which deteriorates the magnetic properties. The amount should be 1.50% or less.

Further, the amount of Mn added is extremely important from the viewpoint of ensuring the strength of the high temperature sheet bar joint before finish hot rolling. This is because the value of Mn / S, which is the ratio of the weight concentration of Mn and S, is set to 2 in order to prevent hot embrittlement of the sheet bar joint due to the presence of sulfides having a low melting point at the grain boundaries.
This is because it is necessary to set it to 0 or more. In the component range specified in the present invention, the Mn content is 0.1% or more and the S content is 0.0050% or less, so that Mn /
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 of the product, magnetic properties, rust resistance, or other purposes, P,
Even if one or more of B, Ni, Cr, Sb, Sn, and Cu are contained in the steel, the effect of the present invention is not impaired.

The C content is 0.00% in order to prevent magnetic aging during use, reduce iron loss, and obtain better characteristics.
It should be 50% or less.

S and N partly re-dissolve during heating of the slab in the hot rolling process, and sulfides such as MnS and A during hot rolling.
Form a nitride such as 1N. The presence of these impedes grain growth of the hot-rolled structure and deteriorates iron loss, so S is 0.
0050% and N should be 0.0050% or less.

Next, the process conditions of the present invention will be described. The steel slab comprising the above components is melted in a converter and manufactured by continuous casting or ingot-slab rolling. The steel slab is heated by a known method. This slab is hot-rolled 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 finish hot-rolling on the product magnetic properties. Steel with the components shown in Table 1 was melted and finish hot rolling was performed.

[0025]

[Table 1]

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

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

The effect of improving the magnetic flux density can be seen even if the friction coefficient is reduced in any of the stands during finish hot rolling.
According to the results of studies by 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, low friction rolling is performed in one or more continuous passes from the final pass side of finish hot rolling. That is, low friction rolling may be performed only in the final pass or in two or more continuous passes including the final pass. Of course, low-friction rolling may be performed in all passes of finish hot rolling. Although the lower limit of the friction coefficient is not particularly set, if the value is excessively small, slippage occurs during rolling and stable striping cannot be performed.
It is preferably at least 05.

If the rolling reduction per pass of low friction rolling is less than 5%, the effect of improving the magnetic flux density does not appear, and
If the pressure is higher than%, slippage during rolling tends to occur due to insufficient friction coefficient. Therefore, the rolling reduction per pass of the low friction rolling is specified to be 5% or more and 50% or less.

When finishing hot rolling is carried out at a low coefficient of friction as in the present invention, when the sheet bar is caught in the finishing hot rolling machine, a defective biting of the sheet bar or a roll during finishing hot rolling is generated. In some cases, slips occur between the steel sheets, which significantly shortens the life of the rolling roll and causes deep rolling flaws on the surface layer of the steel sheet. To solve the problems in finishing hot rolling with such a low coefficient of friction, as a method of stably operating, the sheet bar after rough rolling is joined to the preceding sheet bar before finishing hot rolling, It is particularly effective to continuously subject the sheet bar to finish hot rolling.

As a method of joining the leading sheet bar and the trailing sheet bar, the trailing end portion of the leading sheet bar and the leading end portion of the trailing sheet bar are butted and the butted portion is welded, and the pressing force is applied to the butted portion. And a pressure welding method, a method of laser welding the butted portion, a method of welding the butted portion by induction heating, or a combination thereof.

Mixing oil and fat into the roll cooling water is effective as a means for reducing the coefficient of friction between the steel plate and the rolling roll during hot rolling for finishing. The amount of fats and oils is 0.5% or more and 20% or less by volume ratio. A surfactant is added as necessary to prevent the oil and fat from being separated from the cooling water. If the amount of oil or fat in the roll cooling water is less than 0.5%, the effect of improving the magnetic flux density cannot be obtained, and if it exceeds 20%, the effect is saturated and it is uneconomical. Therefore, the amount of oil or fat is 0.5% or more and 20% or less. And

As the oil and fat mixed in the roll cooling water, a known hot rolling oil for finish rolling mill may be used. Examples of such hot rolling oil for finish rolling mill include, for example, Cudor 5149, Cudor 0B068,
Cudor 4B313 (both are trade names of Kyodo Yushi Co., Ltd.).

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

The hot-rolled sheet obtained by the above method may be used without being pickled, but in order to improve the workability in the subsequent step, pickling is carried out to remove surface oxides. Is more preferable. Furthermore, an insulating film may be applied to the surface.

The hot-rolled sheet that has been pickled may be rolled by 2% or more and 20% or less and subjected to strain relief annealing to improve the core loss characteristics before use. At that time, if the rolling rate is less than 2%, there is no effect of improving the magnetic properties, and if it exceeds 20%, the cost increases, so the rolling rate 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]

EXAMPLES Next, examples 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 and finished to a rough bar having a thickness of 30 mm by a rough rolling mill, and then finished by a finishing hot rolling machine. Finished to 8 mm. 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 plate and the roll in the final hot rolling final pass was determined by measuring the advanced rate of the final stand. The rolling reduction in the final pass was 25%.

[0038]

[Table 2]

In order to prevent slippage between the steel sheet and the work roll during finish hot rolling and formation of flaws on the surface of the steel sheet, the sheet bar after rough rolling is joined to the preceding sheet bar, Finishing hot rolling was continuously performed. The joining of the sheet bars was performed by abutting the leading end portion of the trailing sheet bar and the trailing end portion of the preceding sheet bar by pressure welding, and by laser welding the abutting portion.

After that, it was cut into Epstein samples and the magnetic properties were measured. Table 3 shows the magnetic measurement results of the present invention and the comparative example. In this way, by controlling the final friction coefficient during finish hot rolling to be 0.25 or less, it is possible to obtain a hot final non-oriented electrical steel sheet having a high magnetic flux density value.

[0041]

[Table 3]

[Example 2] A slab for non-oriented electrical steel having the components shown in Table 4 was heated by a usual method and finished by a rough rolling machine into a coarse bar having a thickness of 30 mm, followed by a finishing hot rolling machine. Was finished to 1.0 mm. Hot rolling end temperature is 86
It was set to 0 ° C. The coefficient of friction was changed by adjusting the amount of oil and fat mixed in the roll cooling water during rolling, and the coefficient of friction between the steel sheet and the roll in the final hot rolling final pass was determined by measuring the advance rate of the final stand. The final pass reduction is 2
It was set to 5%.

[0043]

[Table 4]

In order to prevent slippage between the steel sheet and the work roll during finish hot rolling and formation of flaws on the surface of the steel sheet, the sheet bar after rough rolling is welded to the preceding sheet bar, Finishing hot rolling was continuously performed. The sheet bars were joined in the same manner as in Example 1.

Then, the sample was cut into Epstein samples and the magnetic characteristics were measured. Table 5 shows the magnetic measurement results of the present invention and the comparative example. In this way, by controlling the friction coefficient of the final stand during finishing hot rolling to be 0.25 or less, it is possible to obtain a hot final non-oriented electrical steel sheet having a high magnetic flux density value.

[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 by a rough rolling machine into a coarse bar having a thickness of 30 mm, followed by a finishing hot rolling machine. Finished with 0.8mm. Hot rolling end temperature is 87
It was set to 0 ° C. The coefficient of friction was changed by adjusting the amount of oil and fat mixed in the roll cooling water during rolling, and the coefficient of friction between the steel sheet in the final hot rolling final pass was determined by measuring the advanced rate of the final stand. The rolling reduction in the final pass was 25%.

[0048]

[Table 6]

Further, in order to prevent slippage between the steel sheet and the work roll during finish hot rolling and formation of flaws on the surface of the steel sheet, the sheet bar after rough rolling is welded to the preceding sheet bar, Finishing hot rolling was continuously performed. The sheet bars were joined in the same manner as in Example 1.

After that, it was cut into Epstein samples and the magnetic properties were measured. Table 7 shows the magnetic measurement results of the present invention and the comparative example. In this way, by controlling the friction coefficient of the final stand during finishing hot rolling to be 0.25 or less, it is possible to obtain a hot final non-oriented electrical steel sheet having a high magnetic flux density value.

[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 drawings]

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

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Claims (6)

(57) [Claims] 1. By weight%, 0.10% <Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 containing .0050%, and satisfies Mn / S ≧ 20, the slab and the balance being Fe and unavoidable impurities was hot rolled and hot-rolled sheet, the production of non-oriented electrical steel sheet to final product In the method, the continuous 1 from the final pass side during the finish hot rolling.
Only the final pass, or the final pass
Reduction ratio of the continuous two passes or more of each path, including a scan 5% to 50%, and the thickness of the friction coefficient is equal to or subjected to rolling than 0.25 between the steel sheet and the rolling rolls
A method for manufacturing a non-oriented electrical steel sheet having a high magnetic flux density of 1.0 mm or less . 2. In% by weight, 0.10% <Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 A slab containing 0.0050% and satisfying Mn / S ≧ 20, further containing 0.10% ≦ Al ≦ 1.00%, and the balance being Fe and inevitable impurities. Item 2. A method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to Item 1. 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 fats and oils is mixed into the hot-rolled roll cooling water. 4. The sheet bar after rough rolling is joined to the preceding sheet bar before finish hot rolling, and the sheet bar is continuously subjected to finish hot rolling.
A method for producing a non-oriented electrical steel sheet having a high magnetic flux density as described. 5. subjected to pickling steel sheet after final hot rolling, the magnetic flux density according to any one of claims 1 to 4, characterized by applying skin pass rolling of the rolling rate of 20% or less than 2% Highly non-oriented electrical steel sheet manufacturing method. 6. The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to claim 1, wherein an insulating film is applied to the hot rolled sheet.