JPH08104923A - Production of non-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE: To provide a method for producing a non-oriented silicon steel sheet low in core loss particularly in the use of high frequency and good in workability. CONSTITUTION: This is the method for producing a non-oriented silicon steel sheet low in core loss in which the slab of a steel having a compsn. contg. <=0.010% C, 2.75 to 3.5% Si, 0.6 to 2.5% Mn, <=0.02% P, <=0.006% S, <=0.006% N and 1.5 to 2.5% Al, furthermore satisfying Si(%)+0.5Al(%) >=4.0, and the balance Fe with inevitable impurities is subjected to hot rolling, and the hot rolled sheet is annealed according to necessary, which is subjected to cold rolling at 40 to 80% rolling ratio, is subjected to process annealing at 650 to 1000 deg.C, is moreover subjected to cold rolling at 40 to 80% rolling ratio and is thereafter subjected to finish annealing. Thus, the non-oriented silicon steel sheet excellent in cold workability and punching workability and low in core loss in a high frequency region can be produced.

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 low iron loss, which is widely used as an iron core for electric equipment, and is particularly suitable for an iron core for electric equipment used under high frequency conditions. The present invention relates to a method for manufacturing a non-oriented electrical steel sheet.

[0002]

2. Description of the Related Art As an environment surrounding electrical equipment, there is a general tendency toward efficiency, size reduction and weight reduction of equipment, and more efficient inverter control is also becoming popular. Higher frequencies improve efficiency and enable downsizing,
It is expected that even among electric devices currently used at commercial frequencies, those to which high frequencies are applied will increase in the future.

Therefore, an electric component having a low energy loss under high frequency conditions is required, and an electromagnetic steel sheet used for the iron core is also required to have a low iron loss in a high frequency region.

Iron loss of electromagnetic steel sheets increases as the frequency increases. This is because iron loss is the sum of hysteresis loss and eddy current loss, and both losses increase as the frequency used increases. In particular, since eddy current loss increases in proportion to the square of the frequency, most of iron loss in the high frequency range is eddy current loss. That is, if the eddy current loss is reduced, the high frequency iron loss can be reduced.

In order to reduce the eddy current loss, the electrical resistance of the steel sheets is increased and the thickness of the laminated core is reduced. Si is more effective in increasing the electric resistance than any other element is added, but if Si is added at 4% or more,
Not only the material becomes hard, but it becomes brittle. For this reason, cracking is likely to occur in the rolling of steel sheets in the ordinary industrial production process, particularly in cold rolling, and further, it becomes more difficult to manufacture if a thin sheet thickness is preferable. Thinning the plate thickness also increases the number of layers to be used by the user,
In addition, there is a limit because the space factor decreases.

It has been known for a long time that when the amount of Si added is increased, the magnetostriction becomes almost zero at about 6.5%, the magnetic permeability shows a maximum, and the hysteresis loss becomes extremely low.
In this case, since a large amount of Si is contained, the electric resistance is high and the material has the best magnetic characteristics in the Fe-Si alloy system. However, if Si is 6.5%, it is extremely brittle, and it is impossible to carry out rolling by the usual method for manufacturing a thin plate. As a method for manufacturing such a high Si-containing steel sheet, a molten metal ultra-quenching method and a siliconizing method have been studied, and some have already been put into practical use, but for that purpose, special manufacturing equipment is required.

Japanese Unexamined Patent Publication (Kokai) No. 62-103321 discloses a method for producing high Si steel having poor workability by rolling.
This is intended to suppress cracking in the subsequent cold rolling by applying a large reduction in a low temperature region to a steel containing 4 to 7% of Si in a low temperature region to make the crystal grains fine. However, in order to obtain good magnetic properties in the finished steel sheet, it is necessary to anneal sufficiently to increase the crystal grains. This makes them extremely brittle and requires special tools and equipment to process them.

In order to increase the electric resistance, a method of adding a large amount of Al, which has almost the same effect as adding Si, can be considered.
In the non-oriented electrical steel sheet, in order to increase the electric resistance and prevent the precipitation of fine AlN which hinders the movement of the domain wall and deteriorates the magnetization characteristics, the addition of Si up to 1% A
1 is added. Further, Japanese Patent Laid-Open No. 3-24251 discloses an example of proposing addition of a large amount of Al. Si for this
A non-oriented electrical steel sheet in which Al is added in an amount of 1.5 to 8% at a content of 3.3% or less has been proposed.
It is said that when the ratio of is higher, the workability is improved and the magnetic properties are improved, and a 100 <001> texture, which is particularly preferable for motors, is likely to develop. In this publication, as a prior reference, French patent application No. 2,316,338 has Si: 2.5 to 3.5% and Al:
The case where 0.3 to 1.5% is added is introduced, and it is pointed out that the alloy becomes extremely brittle when Al exceeds 1.5% in this Si amount.

Although it has been known that an increase in the amount of Si added in this way increases the electric resistance and obtains a performance particularly suitable for use in a high frequency region, there is a problem that the workability of the material is significantly deteriorated. To prevent this, the amount of Si added should be suppressed and Al
It is possible to add a large amount of. However, there is a limit to ensuring workability while sufficiently increasing the electric resistance.

[0010]

The present invention has been made for the purpose of solving such a problem, and can be manufactured within a range of conditions that can be realized by the current thin steel plate manufacturing equipment. It is intended to provide a method for producing a non-oriented electrical steel sheet which is easy to punch a product steel sheet and has excellent magnetic properties and which has a low iron loss particularly in a high frequency range.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention have developed a non-oriented electrical steel sheet which has excellent magnetic properties particularly in a high frequency range, and on which cold rolling property at the time of production and punching property of a steel plate product are good. As a result of various studies on the manufacturing method, the following new findings were obtained.

(A) To reduce the eddy current loss as much as possible for the purpose of reducing the iron loss at high frequencies, as a result of studying a composite addition of Al, which has an effect of increasing electric resistance, which is close to that of Si, a suitable amount of A
It has been found that the addition of 1 l gives good magnetic properties.

(B) Al was added to a place where the amount of Si was increased to a limit near the allowable workability deterioration, and the workability deterioration was investigated. As a result, if the electric resistance was the same, Al was added more than Si addition alone. It was found that the workability was better with the composite addition. However, since the workability deteriorates as the addition amount of Al increases, there is a limit to the addition amount.

(C) When Mn is added in addition to the composite addition of Si and Al, the crack resistance during cold rolling and punching is improved, and if the addition amount is increased, the workability is impaired. It was found that the magnetic characteristics at high frequencies were improved without any increase.

(D) As a method for producing a steel sheet using a material to which Si, Al, and Mn are added in combination, it is necessary to take steps of cold rolling → intermediate annealing → cold rolling → final annealing after hot rolling to obtain magnetic properties. It was optimal for obtaining the desired texture.

(E) Further, in addition to the above (d), the hot rolling is followed by cold rolling after the hot rolling, so that the hot rolling sheet annealing is performed. When ridging becomes a problem, it was found to be effective in suppressing it.

Based on the above findings, (1) in wt%, C: 0.010% or less, Si: 2.75 to 3.5%, M
n: 0.6 to 2.5%, P: 0.02% or less, S: 0.006% or less, N: 0.006% or less, Al: 1.5% or more and less than 2.5%, and Si (%) + 0.5Al (%) ≥ 4.0 The steel slab, which has Fe and unavoidable impurities in the balance, is hot-rolled, cold-rolled at a rolling rate of 40 to 80%, then annealed at 650 to 1000 ° C, and then rolled at a further rolling rate. After cold rolling at 40 to 80%, finish annealing is performed to produce a non-oriented electrical steel sheet with low iron loss, and (2) after hot rolling a slab of steel having the composition described in (1) above, The hot rolled steel sheet is annealed at 650 to 1000 ℃, cold rolled at a rolling rate of 40 to 80%, then annealed at 650 to 1000 ℃, and then cold rolled at a rolling rate of 40 to 80%. , A method of manufacturing a non-oriented electrical steel sheet having low iron loss, which is subjected to finish annealing.

[0018]

The operation and effect and the reason for limitation will be described below for each constituent element of the method of the present invention.

(1) Chemical composition of material slab or product steel sheet (1) C content C is greatly deteriorated in magnetic properties, so it is made as low as possible. For this reason, the content should be 0.010% or less, but if it can be reduced, the magnetic properties will be improved, so it is desirable.
It is 0.005% or less.

(2) Si content Si is an element which has a great effect on the increase of electric resistance, and as the content increases, the eddy current loss decreases and the iron loss of the steel sheet decreases. However, as the content increases, it becomes hard and brittle, and if it exceeds 3.5%, cracking occurs in cold rolling or reduction becomes difficult. Further, when a steel sheet product is punched into a motor core or the like, tool wear is likely to increase and a defective shape or crack is likely to occur. On the other hand, if the content is less than 2.75%, the reduction of iron loss is insufficient. Therefore, the Si content range is 2.75 to 3.5%.

(3) Mn amount If Mn is added in a large amount, it is possible to improve workability deterioration such as cracking at the time of cold rolling or punching of the product due to the increase of Si and Al contents. One of the reasons for this is that the solid solution of Mn can suppress the coarsening of the crystal grain size during hot rolling, optimize the crystal grains of the product, and suppress the embrittlement. . Moreover, if the amount of addition is increased, the electrical resistance also rises, and the magnetic characteristics are improved without impairing the workability. However, excessive addition makes the material too hard, so it is not preferable to exceed 2.5%.

For this reason, the addition range of Mn is set to 0.6.
~ 2.5%

(4) S content The S content is preferably as small as possible because it combines with Mn in steel to form MnS precipitates and deteriorates the magnetic properties. The acceptable limit for this is 0.006% or less, but preferably 0.003%
It is the following.

(5) Amount of Al Addition of Al increases the electric resistance to the same extent as Si. Then, rather than the case where the electrical resistance is increased only by adding Si, the workability is better when the Si and Al are added in combination so that the electrical resistance values are about the same. The limit amount of addition of Al is S
Depending on the i content, up to 3.5% Si content is 1.5
%, Sufficient magnetic properties cannot be obtained. Also,
Addition of a large amount tends to increase the magnetostriction, and especially when the content is 2.5% or more, it increases remarkably. Magnetostriction is said to be a cause of noise, and moreover, an increase in magnetostriction also causes an increase in hysteresis loss. For this reason, the range of addition of Al is 1.5% or more and less than 2.5%.

(6) N content N combines with Al to form fine AlN precipitates, which impairs magnetic properties. Therefore, the lower the better.
0.006% is the upper limit of tolerance.

(7) Combined effect of Si and Al When the amount of Mn is not large, it was difficult to increase the contents of Si and Al because of the limit of cold working due to cracking. Improves workability. Further, in order to exhibit sufficiently excellent magnetic properties within the above-mentioned limit of the added amount, it is necessary that the Si amount and the Al amount are Si (%) + 0.5Al (%) ≧ 4.0. Below this limit, Mn
The workability can be maintained even if the amount is small, but the magnetic properties are insufficient.

(9) Inevitable Impurity Elements Any unavoidable impurity elements other than the above-mentioned elements deteriorate the magnetic properties, so the smaller the smaller the better. In particular, it is necessary to pay sufficient attention to reduce elements having a great influence on magnetic properties and workability, such as O, Ti, Nb and V.

(2) Manufacturing conditions (a) Hot rolling The slab used for hot rolling may be either a continuously cast slab or a slab of slabs, and the slab obtained by continuous casting may be directly rolled. The slab once cooled may be reheated. The hot rolling conditions are not particularly limited, but it is desirable that the slab heating temperature is 1200 ° C. or less and the finishing temperature is 750 to 850 ° C. from the magnetic characteristics.

The winding temperature is not particularly limited, but the magnetic properties tend to improve as the temperature increases. However, when the coiling temperature is increased, the oxide layer on the surface increases and it becomes difficult to remove it. However, in the method of annealing a hot-rolled sheet according to claim 2, since the influence of the coiling temperature is small, coiling at a low temperature causes less development of an oxide layer, and is preferably 60%.
It is 0 ° C or lower.

(B) Cold rolling After cold rolling the hot rolled steel sheet, it is annealed to be sufficiently recrystallized,
Further, cold rolling is performed to finish the plate thickness of the final product, whereby excellent magnetic properties can be obtained. The first cold rolling is called primary cold rolling, and the cold rolling after the intermediate annealing is called secondary cold rolling.
The magnetic properties of the final product are improved by cold rolling twice with an intermediate anneal in between, because the textures favorable for magnetic properties such as 110 <001> orientation and 100 <001> orientation tend to develop. .

The reduction ratio of cold rolling is set to 40 to 80% for both the primary cold pressure and the secondary cold pressure. However, if the reduction ratio is out of this range, sufficient magnetic properties cannot be obtained.

The cold rolling may be carried out at room temperature, but may be carried out by heating the steel sheet to 350 ° C. or lower in order to ensure prevention of cracking. If the temperature exceeds 350 ° C, it becomes difficult to control the shape of the steel sheet during rolling, and it is necessary to use rolling oil with special properties.

(C) Intermediate Annealing For the purpose of rolling a hard material, there is also the purpose of facilitating rolling by annealing and softening in the middle, but this improves the magnetic properties.
This is because a magnetically favorable texture can be developed. The annealing method may be either box annealing or continuous annealing, and it is not necessary to specify the soaking time as long as the material reaches the annealing temperature.

If the annealing temperature is less than 650 ° C., recrystallization does not proceed sufficiently and the effect of annealing cannot be obtained. On the other hand, if the annealing temperature exceeds 1000 ° C., the crystal grains become too coarse and cracks are likely to occur during cold rolling. Therefore, the intermediate annealing temperature is 650 to 1000 ° C. 650 to 900 for box annealing
In the case of continuous annealing, 750 to 1000 ° C is desirable.

(D) Finish annealing After finishing to a desired plate thickness by secondary cold pressure, finish annealing is performed to obtain magnetic properties as a product. The conditions are not particularly limited as long as the recrystallization is sufficiently performed and the crystal grains are appropriately grown, but the preferable annealing temperature is
700 to 1250 ℃. Insulation, if necessary, on the surface
A thin film may be applied and baked for the purpose of preventing rust or improving punching workability.

(E) Annealing of hot-rolled sheet In the above manufacturing process, if the hot-rolled sheet is annealed before the cold rolling after the hot rolling, the magnetic properties are further improved. It is considered that this is because a magnetically favorable texture easily develops. Further, by performing the hot-rolled sheet annealing, it is possible to reduce the ridging of the uneven defects that are likely to occur on the surface. Not only is the ridging unfavorable in appearance as a steel sheet product, but it also lowers the space factor of the laminated core of the final product and deteriorates its magnetic properties.

The annealing temperature of the hot-rolled sheet for obtaining such effects is suitably 650 ° C to 1000 ° C.

The holding time is sufficient if the material reaches this temperature, and soaking holding is not always necessary. Annealing temperature 6
If it is less than 50 ° C, recrystallization is insufficient and the magnetic properties are not improved.
If the temperature exceeds 1000 ° C, the crystal grains become too coarse and the mechanical properties deteriorate, and the effect of suppressing cracking and ridging is lost. 700 to 900 to maximize these effects
℃ is desirable.

[0039]

【Example】

[Example 1] Steels having the compositions shown in Table 1 were melted in a high-frequency vacuum melting furnace, and those steel pieces were heated to 1200 ° C, and then hot rolled at a finishing temperature of 850 ° C to a thickness of 2.3 mm. It was a rolled sheet. This is used as primary cold rolling to reduce the thickness to 0.80 mm at a reduction of 65%, then perform intermediate annealing by soaking for 1 hour or more at 750 ° C, and to reduce the thickness to 0.35 mm at a secondary cold rolling of 56%. I chose The test piece in which cracking occurred in cold rolling was hot-rolled at 300 ° C to a predetermined plate thickness.

The rolled steel sheet was annealed at 1000 ° C. for 1 minute, and then subjected to Epstein magnetic property measurement test pieces having a width of 30 mm and a length of 280 mm with the rolling direction and the direction perpendicular to the rolling as longitudinal directions. It was produced by punching. As for the test piece in which cracking occurred during punching, a test piece was prepared by electrical discharge machining.

After using these test pieces for strain relief annealing at 800 ° C. for 2 hours, the magnetic properties were measured. In general, non-oriented electrical steel sheets are measured for iron loss at a commercial frequency of 50 to 60 hertz, but in order to know the performance at high frequencies, iron loss at 400 hertz was measured. The results of these series of tests are also shown in Table 1. It should be noted that the magnetic properties are better when the iron loss is low and the magnetic flux density is high.

[0042]

[Table 1]

Steel type A which satisfies all the conditions defined in the present invention
The steel sheets manufactured from ~ E exhibited good magnetic properties, and had no cracks during cold rolling or punching at room temperature, and had good workability.

In steel types H to J in which Si (%) + 0.5 Al (%) is less than 4.0, iron loss is high, magnetic flux density is low, and magnetic properties are inferior to those of A to E. Also, Si
Even if (%) + 0.5Al (%) is 4.0 or more, in steel types F and G in which the amount of Si or the amount of Al exceeds the regulated values, cracks are generated from the end during cold rolling, and At that time, a crack was generated from the corner.

[Embodiment 2] In order to see the effect of the amount of Mn added, steels having the same Si content and Al content and different Mn contents were used in the high-frequency heating vacuum melting furnace with the steel types A or E of Embodiment 1. After being melted and made into a thin plate by the same method as in Test 1, the magnetic characteristics were measured. Table 2 shows the results.

[0046]

[Table 2]

With the steel types A0 and E0 in which the amount of Mn was lower than the range regulated by the present invention, cold rolling could be carried out without problems.
When the punching process was performed, fine cracks were generated from the edge part.
Therefore, the magnetic properties of these test pieces were not measured.

Further, with steel types A3 and E3 in which the amount of Mn exceeds the amount regulated by the present invention, it was not possible to reduce the pressure to the target thickness by cold rolling.

[Example 3] In order to know the effect of the reduction ratio of cold rolling, the steel type A of Example 1 and the steel type A1 of Example 2 were heat-treated at a plate thickness of 2.3 mm in the same manner as in Test 1. After finishing the rolled sheet, primary cold rolling, intermediate annealing and secondary cold rolling as shown in Table 3 were performed to finish a steel sheet having a thickness of 0.35 mm. Both the primary and secondary cold rolling were performed at room temperature, and the intermediate annealing was performed at 850 ° C for 1 hour. After the secondary cold rolling, a test piece was prepared in the same manner as in Example 1 and its magnetic characteristics were measured.

[0050]

[Table 3]

In the primary or secondary cold rolling, the steel sheets produced with the rolling reduction outside the range of the present invention have large iron loss and low magnetic flux density as compared with those of the present invention. Further, under the condition 6 in which it was attempted to finish the target sheet thickness by one cold rolling without intermediate annealing, cracking occurred during cold rolling.

Example 4 Steel type A used in Example 1,
And a hot rolled sheet having a plate thickness of 2.3 mm was prepared by the same method as in Example 1 using the steel piece of the steel type A1 of Example 2, and the reduction ratio of the primary cold rolling was set to 65%, as shown in Table 4. Intermediate annealing was performed at different temperatures, and secondary cold rolling with a reduction rate of 56% was performed to finish the sheet thickness to 0.35 mm. The intermediate annealing was a continuous annealing for 1 minute soaking. When the intermediate annealing temperature was 1030 ℃, cracking occurred in the secondary cold rolling. This was probably because the annealing temperature was too high and the crystal grains became coarse and brittle. After the secondary cold rolling,
Annealing was performed for 1 minute at 1000 ° C., and the magnetic characteristics were investigated in the same manner as in Example 1.

The results are summarized in Table 4. As can be seen from the table, when the temperature of the intermediate annealing was too low, sufficient magnetic properties could not be obtained.

[0054]

[Table 4]

Example 5 Steel type A used in Example 1,
Then, a hot rolled sheet having a plate thickness of 2.3 mm was formed from the steel piece of the steel type A1 of Example 2 by the same method as in Example 1, and then hot rolled sheet annealing was performed under the conditions shown in Table 5. Then, after undergoing primary cold rolling, intermediate annealing, and secondary cold rolling in the same steps and conditions as in Example 1, a steel sheet product was manufactured by soaking annealing at 1000 ° C. for 1 minute. A test piece was prepared from this steel sheet in the same manner as in Example 1,
Magnetic measurements and space factor tests specified in JIS C2550 were performed.

[0056]

[Table 5]

Condition 10 shown in Table 5 is an example of the present invention in which hot-rolled sheet annealing is not performed, and is shown as a comparison. In condition 11, the temperature was insufficient even when hot-rolled sheet annealing was performed, and the effect was not exhibited. These two conditions do not correspond to claim 2 of the present invention, and the effect of hot-rolled sheet annealing is not obtained, but they are included in claim 1, and a sufficient value is obtained as magnetic characteristics. ing.

Under the condition 12 in which the hot-rolled sheet was annealed under the conditions corresponding to claim 2 of the present invention, not only the magnetic characteristics were improved but also
The space factor has also improved. However, the annealing temperature is too high 13
Became brittle and cracked during cold rolling.

[0059]

According to the method of the present invention, it is possible to improve the magnetic properties of the electromagnetic steel sheet, particularly to reduce the iron loss in the high frequency range without deteriorating the cold workability. Therefore, it becomes possible to manufacture a low-loss non-oriented electrical steel sheet without using special equipment and to process the product steel sheet into a required shape.

[0060]

Claims (2)

[Claims] 1. By weight%, C: 0.010% or less, Si: 2.75
~ 3.5%, Mn: 0.6 ~ 2.5%, P: 0.02% or less, S:
0.006% or less, N: 0.006% or less, Al: 1.5% or more
Contains less than 2.5%, and Si (%) + 0.5Al (%)
A steel slab satisfying ≧ 4.0 with the balance being Fe and inevitable impurities is hot-rolled, cold-rolled at a rolling rate of 40 to 80%, and then annealed at 650 to 1000 ° C.,
Furthermore, after cold rolling with a rolling rate of 40 to 80%, finish annealing is performed to produce a non-oriented electrical steel sheet with low iron loss. 2. By weight%, C: 0.010% or less, Si: 2.75
~ 3.5%, Mn: 0.6 ~ 2.5%, P: 0.02% or less, S:
0.006% or less, N: 0.006% or less, Al: 1.5% or more
Contains less than 2.5%, and Si (%) + 0.5Al (%)
Satisfying ≧ 4.0, the balance is Fe and unavoidable impurities. After hot rolling a steel slab, the hot rolled steel sheet is
Iron that is annealed at 00 ℃, cold-rolled at a rolling rate of 40-80%, then intermediate-annealed at 650-1000 ° C, then cold-rolled at a rolling rate of 40-80%, and then finish-annealed. Manufacturing method of non-oriented electrical steel sheet with low loss.