JPH0643614B2 - Manufacturing method of semi-processed electrical steel sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a semi-processed electromagnetic steel sheet having excellent iron loss and magnetic flux density.

[Conventional technology]

Recently, due to the tight energy situation, there is a strong demand for saving energy consumption worldwide, and the reduction of power consumption by improving the performance of electrical equipment has become a major issue. Against this background, there has recently been an increasing demand for high-performance magnetic steel sheets having low iron loss and high magnetic flux density.

By the way, an electromagnetic steel sheet, especially a non-oriented electrical steel sheet, is often used after being manufactured by punching it into a complicated shape such as an I shape or an E shape. In this case, strain relief annealing is performed after the punching. Is customary.

This strain relief annealing is generally carried out under the conditions of about 750 ° C. × 2 h, and since the crystal grains can be coarsened, it can be used for improving the iron loss characteristics. Further, the smaller the grain size, the better the punching property of the electromagnetic steel sheet. Therefore, it is preferable to suppress the growth of the grain size before the punching.

Therefore, conventionally, there has been manufactured a non-oriented electrical steel sheet on the premise of carrying out the strain relief annealing, that is, a non-oriented electrical steel sheet capable of obtaining a predetermined iron loss characteristic only by carrying out the strain relief annealing. This is called a semi-process electrical steel sheet and is distinguished from a full-process electrical steel sheet that does not require strain relief annealing.

[Problems to be solved by the invention]

By the way, in the conventional magnetic steel sheet, the addition of Si and Al, which has the effect of increasing the specific resistance and reducing the eddy current loss, has been adopted for the purpose of reducing the iron loss. However, such addition of Si and Al, on the other hand, causes a decrease in magnetic flux density, and therefore it was impossible to achieve both low iron loss and high magnetic flux density in this type of electrical steel sheet.

Under these circumstances, development of a semi-processed electromagnetic steel sheet having a low iron loss and a high magnetic flux density has recently been advanced, and an effective manufacturing method has already been proposed. One of them is the method described in Japanese Patent Publication No. 61-7446.

This manufacturing method uses M instead of the above measures using Si and Al.
By using n, the improvement of the iron loss is achieved without the adverse effect of lowering the magnetic flux density, that is, while maintaining the high magnetic flux density. That is, this manufacturing method is C0.005% or less, Si0.1-1.0
%, Mn 0.75 to 1.50%, S 0.005% or less is used. However, in this method, hot-rolled sheet annealing is indispensable in order to achieve a sufficient magnetic flux density. Further, if skin pass rolling is not performed, a sufficient reduction in iron loss cannot be realized, but if this is done, a reduction in magnetic flux density cannot be avoided, and a sufficiently high magnetic flux density cannot be obtained.
As described above, in the method disclosed in Japanese Patent Publication No. 61-7446, it is actually difficult to achieve both low iron loss and high magnetic flux density, and there are disadvantages in terms of man-hours and cost.

The present invention has been made in view of the above circumstances, punching on the user side, after strain relief annealing, it is possible to realize a sufficiently low iron loss value and high magnetic flux density, and further, the manufacturing process can be simplified. It is intended to provide a method for manufacturing a process electromagnetic steel sheet.

[Means for solving problems]

Based on the above-mentioned conventional technique, the present inventors have found a method that enables compatibility of two characteristics of iron loss and magnetic flux density.
Diligently conducted experiments and research.

As a result, in accordance with the technique of Japanese Examined Patent Publication No. 61-7446, M
When n is contained in an amount of 0.75 to 1.5%, a large amount of C is coexistent with respect to Mn, and annealing after cold rolling is performed under the coexistence of Mn and C. Loss and magnetic flux density are both improved, and a sufficiently low iron loss can be secured even if skin pass rolling for reducing iron loss is omitted.
Further, in this case, it was found that the reduction of the magnetic flux density can be avoided by omitting the skin pass rolling, and a remarkably high magnetic flux density is realized in combination with the effect of annealing in the presence of C and Mn.

The present invention is based on the above findings and has as its gist the following production method.

C0.006-0.03%, Si0.1-1.0%, M
n 0.75-1.5%, P ≦ 0.150%, S ≦ 0.0
05%, Sol. Al 0.1-0.3%
Or Sol. Al less than 0.1 and B / N 0.5-
A hot-rolled steel sheet containing B in an amount of 1.5 and the balance of Fe and unavoidable impurities is descaled, or annealed at 650 to 850 ° C. for 30 seconds or more before or after descaling (hot-rolled sheet). Annealing), cold rolling, and then annealing to make the C content 0.005% or less, a method for producing a semi-process non-oriented electrical steel sheet.

In general, it is recognized that for this type of electrical steel sheet, the smaller the amount of C, the better. C is the final product stage,
This is because it works to cause magnetic aging and increase iron loss. From this viewpoint, it has been customary to regulate C to 0.005% or less.

On the other hand, in the present invention, C is initially 0.006 to 0.03%.
And more than 0.75% of Mn.
The coexistence of this large amount of C is followed by annealing after cold rolling. By carrying out the annealing in the coexistence of C and Mn, extremely low iron loss and high level magnetic flux density are realized. As mentioned above, Mn has a function of lowering iron loss as its own action, but if annealing is performed under the above-mentioned conditions, in addition to the original effect of Mn, another magnetic characteristic ( Iron loss, magnetic flux density) are improved, and this is the added form. From this, it is possible to achieve both iron loss and magnetic flux density at a high level without skin pass rolling.

The mechanism by which the magnetic properties are improved by annealing in the coexistence of C and Mn has not yet been fully clarified and it cannot be said clearly, but it is considered as follows.

Since Mn and C are a combination of elements having a strong affinity,
If an appropriate amount of C and Mn is present during annealing after cold rolling, C and Mn
It is conceivable that a large number of pairs will be formed. Such a pair of C and Mn affects the recrystallization behavior in the annealing process in a single state (solid solution state) different from that of each element. It is considered that the coexistence of Mn and C makes it easy to form a texture having a high degree of integration of the (100) plane or the (110) plane, which is advantageous in magnetic properties.

Even when the above-described annealing is performed, if the increased C amount is brought to the final product stage, naturally the adverse effect of increasing iron loss due to magnetic aging will occur. In order to avoid such adverse effects and maintain the original excellent magnetic properties, decarburization is performed in the annealing after cold rolling, and the C content is 0.005% or less at which magnetic aging does not substantially occur. It will be necessary to reduce it to the level of.

Hereinafter, each constituent element of the present invention will be specifically described.

First, regarding the steel components of the hot-rolled steel sheet, the reasons for limiting each component are as follows.

C: It is the most important element in the present invention together with Mn. Coexistence with Mn is significant, and in such a coexistence state, it contributes to the improvement of magnetic properties through annealing after cold rolling.

FIG. 1 is a plot diagram showing the effect of C on the magnetic characteristics and investigating the magnetic characteristics by changing the initial C amount (hot rolled sheet C amount). The steel materials other than C satisfy the conditions of the present invention (0.7% Si-1.2% Mn-0.0).
10% P-0.003 to 0.004% S), which is 0.5 mm thick in the process (the hot-rolled sheet annealing condition of the hot-rolled sheet annealed material is 800 ° C. × 2 minutes) shown in the examples below. Cold-rolled sheet, then annealed at 750 ° C. and decarburized to a C content of 0.005% or less (an initial C content of 0.005% or less is not decarburized). The values of iron loss and magnetic flux density in the figure are values after strain relief annealing (750 ° C. × 2 h [non-decarburization]) measured by the method shown in the examples.

Based on the data in the figure (material for omitting annealing of hot rolled sheet), C was 0.
It can be seen that when the content is 006% or more, the magnetic flux density is improved and the iron loss value is also reduced. However, this C content is 0.0
When it exceeds 30%, the magnetic flux density gradually decreases, and the iron loss tends to slightly increase. It is considered that such a tendency of deterioration of the magnetic properties is due to the fact that the decarburization annealing time for obtaining the final C content of 0.005% or less becomes longer as the initial C content increases, and the thickness of the internal oxide layer increases.

Therefore, the C amount (initial C amount) is 0.006 to 0.030.
The range is%.

Si: Si is an element that increases the specific resistance and effectively contributes to the reduction of iron loss, but on the other hand, it causes the reduction of the magnetic flux density.
When it exceeds 1%, the magnetic flux density is remarkably lowered, and the high magnetic flux density, which is one of the objects of the present invention, cannot be achieved. If it is less than 0.1%, a sufficient effect cannot be expected in terms of iron loss. Therefore, Si is set to the range of 0.1 to 1.0%.

Mn: C is an element that forms the basis of the steel of the present invention together with C,
In the coexistence with, it greatly contributes to the improvement of magnetic properties through annealing after cold rolling.

FIG. 2 is a plot of the results of investigating the magnetic characteristics by changing the amount of Mn. The data is C 0.02%, 0.0
Steel composition other than C and Mn satisfying the conditions of the present invention (Si: 0.5%, P: 0.015%, S: 0.00
2 to 0.003%) was made into a cold-rolled sheet by the same process as in FIG. 1 (without hot-rolled sheet annealing), of which C0.02% material was 7%.
Annealing is performed at 20 ° C to decarburize to 0.005% or less, and C
The 0.003% material was subjected to non-decarburization annealing at 750 ° C. for 1 h, and the magnetic properties after strain relief annealing were investigated in the same manner as in FIG. 1 for the thus obtained material. is there.

According to the figure, the initial C amount is 0.02% (within the range of the present invention).
In the case of No. 1, the magnetic flux density and the iron loss tend to be remarkably improved in the region where Mn is 0.75% or more. When the C content is 0.003% (outside the range of the present invention) and is originally low, the iron loss and the magnetic flux density are both inferior even when Mn is 0.75% or more. That is, it can be seen that annealing in the presence of an appropriate amount of C with the amount of Mn being 0.75% or more is extremely effective in obtaining good magnetic properties.

However, if the amount of Mn exceeds 1.5%, cracking during cold rolling tends to occur, and the Ac ₃ transformation point decreases, so that a sufficient annealing temperature cannot be obtained.

From the above, Mn was limited to the range of 0.75 to 1.5%.

P: P is an element effective in increasing the strength of the steel sheet and improving the punching property, but if it exceeds 0.150%, the embrittlement of the steel sheet cannot be avoided, and therefore it is limited to 0.150% or less. The lower limit is not specified because even if the amount of P is an unavoidable impurity, no particular problem occurs.

S: S forms sulfides and reduces the grain growth during annealing,
It is a harmful element that increases iron loss.

FIG. 3 is a plot diagram of experimental data showing the relationship between the S content and the magnetic properties. Steel having a constant S content and a constant content within the scope of the present invention (0.01% C-0 .30% S
i-0.85% Mn-0.060% P) is used as a material, and the process is exactly the same as in the case of FIG. 1 (without hot-rolled sheet annealing) except that annealing after cold rolling is performed at 700 ° C. Based on the results of investigation of magnetic properties.

As is clear from the figure, when the S content is 0.005% or less, the iron loss becomes a very good value.

Therefore, S is limited to 0.005% or less.

In the range of 0.005% or less, S is more advantageous in terms of iron loss, and therefore, the lower limit of S is not specified.

Sol. Al: Al has the effect of increasing the specific resistance and lowering the iron loss like Si. However, if the amount exceeds 0.3%, the magnetic flux density decreases, which is not preferable.

Here, Sol. Although it is not necessary to add Al of 0.1% or more, if it is less than 0.1%, in order to obtain a low iron loss, it is necessary to eliminate the tendency of grain growth during annealing due to precipitation of fine AlN. Yes, this is B to B / N0.
This can be achieved by adding an amount in the range of 5 to 1.5.

Therefore, in the present invention, sol. Al
0.1-0.3%, or Sol. It was decided to adopt any of the conditions that B was contained in an amount of B / N of 0.5 to 1.5 when Al was less than 0.1%.

In addition, Sol. When the amount of Al is an impurity level of 0.003% or less, naturally, the addition of B is unnecessary.

○ Next, the manufacturing process will be described.

The method of the present invention basically uses a hot-rolled steel sheet that conforms to the above-described compositional conditions, cold-rolls it after descaling, and then performs annealing, and in some cases before descaling. Alternatively, hot-rolled sheet annealing is performed later.

Here, the above-mentioned steps are as follows: Hot-rolled sheet annealing This annealing is effective for both magnetic flux density and iron loss. This is clear from the comparison between the annealed material for hot-rolled sheet and the omitted material shown in FIG.

The annealing condition needs to be 650 to 850 ° C. × 30 seconds or more. That is, at a temperature of less than 650 ° C., the effect of improving the magnetic properties cannot be sufficiently obtained, and at a temperature of more than 850 ° C., the crystal grains are coarsened to cause deterioration of cold rolling property and remarkable rough skin. If the annealing time is less than 30 seconds, the effect of annealing cannot be expected.

The process for obtaining the hot rolled sheet itself is not particularly limited. It is a usual method to go through the process of converter melting-continuous casting hot rolling, but in the case of the present invention, the same process can be used.

・ Descaling and cold rolling can be performed as usual. As for descaling, pickling is generally performed, and cold rolling is performed once in principle.

-Annealing after cold rolling As described above, the present invention has the greatest feature in that annealing after cold rolling is performed in a state where appropriate amounts of C and Mn coexist to improve both characteristics of magnetic flux density and iron loss. is there. The annealing after cold rolling plays such an important role in the present invention.

Annealing after cold rolling is generally continuous annealing or box annealing for the purpose of recrystallization and hardness adjustment performed on the manufacturer side,
Strain relief annealing is performed on the user side for the purpose of removing punching strain and coarsening of crystal grain size.

In the present invention, C and Mn must coexist at the stage of recrystallization after cold rolling. However, C is 0.0 in the final product.
If the content exceeds 05%, magnetic aging occurs and iron loss increases. Therefore, it is necessary to perform decarburization in the recrystallization step after cold rolling or in the subsequent steps, and decarburize either continuous annealing or box annealing on the manufacturer side after cold rolling or strain relief annealing on the user side. It should be annealed and C should be 0.005% or less. The lower limit of the final C amount is more advantageous for magnetic aging as the amount of C is smaller, and is not particularly limited.

That is, in the annealing after cold rolling in the present invention, as shown in Group I in FIG. 4, decarburization annealing which also serves as coexisting annealing of C-Mn is basically performed after cold rolling on the manufacturer side. However, as shown as II group in the figure,
It is also possible to carry out only C-Mn co-annealing on the manufacturer side and decarburize it by strain relief annealing on the user side.

Further, the decarburization annealing in the group I may be either OCA decarburization annealing (IA, B) or continuous annealing accompanied by decarburization (IC), and C-Mn coexisting annealing in the group II. Alternatively, either box annealing (II-A, B) or continuous annealing (II-C) may be used.

When adopting OCA furnace decarburization annealing or box annealing,
After the annealing, continuous annealing for flattening (IA, II-
It is preferable to carry out A) or an alternative skin pass rolling (IB, II-B) with a rolling reduction of 2% or less.

Regarding the decarburization annealing in Group I, it is preferable that the decarburization is not performed until the recrystallization is completed and the furnace atmosphere is adjusted so that the decarburization reaction starts after the recrystallization is completed.

In addition, when manufacturing an electromagnetic steel sheet, a step of further applying an insulating coating usually comes in, but in the case of the present invention, it is possible to carry out this coating step as the final step of the production. The invention includes such a case.

[Example 1] Steel of each component composition shown in Table 1 was melted in a converter and formed into a slab (250 mm thickness x 1000 mm width) by continuous casting, followed by hot rolling to obtain a thickness. A 2.3 mm hot rolled plate was obtained. Next, pickling-cold rolling (2.3 mm →
0.5 mm) -Annealed after cold rolling (manufacturer side) (conditions in Table 1). At this time, No. 3, 4, 7, 12, 14,
For Nos. 21 and 22, hot-rolled sheet annealing was performed under the conditions shown in the same table after the pickling, and for Nos. 4 to 8 and 22, after the cold rolling, after the skin pass rolling under the conditions shown in the same table. Was carried out. The No. 4 skin pass is a skin pass for grain coarsening, and the other skin passes are for the purpose of flattening after the OCA furnace decarburization annealing.

For each of the test steel plates thus obtained, stress relief annealing was performed under the conditions shown in the table (non-decarburizing: dry N ₂ atmosphere, decarburizing: 20% H ₂ , 80%
The magnetic properties (iron loss, magnetic flux density) were investigated by conducting N ₂ and dew point + 30 ° C.). The characteristic investigation was performed by collecting eight Epstein test pieces each having a width of 30 mm and a length of 280 mm from the rolling direction and the direction perpendicular thereto.

The results are shown in the right column of Table 1.

The results of the table will be described.

・ No. 1 is the most basic example of this type of electrical steel sheet, Si
Is included in order to improve iron loss.
This is inferior in terms of magnetic flux density.

-Nos. 2 to 4 are those in which decarburization was not performed in advance with the C amount as the final C amount level (0.005% or less) in the present invention. No. 2 had particularly high iron loss, and No. 3 had better iron loss and magnetic flux density than No. 2 because it was subjected to hot-rolled sheet annealing, but it is still not sufficient. No. 4 was skin-pass rolled and had very good iron loss, but a decrease in magnetic flux density was observed.

-No. 5 is an example of the present invention in which the material steel component is substantially the same as Nos. 2 to 4 except for the amount of C. This is because hot-rolled sheet annealing has not been performed, and in that respect, it has considerably excellent iron loss and magnetic properties as compared to No. 2 under the same conditions, and skin-pass rolling No. Although it is a little higher in terms of iron loss than that of 4, the magnetic flux density is superior,
It is superior in terms of the balance of both characteristics.

-Nos. 6 and 7 are two examples of the present invention which differ only in the presence or absence of hot-rolled sheet annealing. From the comparison of the two, hot-rolled sheet annealing is effective for both iron loss and magnetic flux density. It

・ No. 8 has an initial C amount within the range of the present invention (0.006 to 0.0
3%) above the upper limit, which is C during annealing after cold rolling.
Although the amount was decarburized to 0.003% or less, iron loss, compared with Example No. 6 of the present invention, which had substantially no difference except for the initial C amount,
Both magnetic flux densities are inferior.

・ No. 9 and 10 are two examples that differ only in the amount of Mn.
Is an example of the present invention because of an Mn amount below the range of the present invention.
Both iron loss and magnetic flux density are inferior to No. 10.

・ No. 11 to 14 are all examples of the present invention, and No. 11 and 12,
Nos. 13 and 14 differ only in the presence or absence of hot-rolled sheet annealing, and Nos. 13 and 14 are examples in which Al is added to the raw steel. From the comparison of No. 11 and 12, No. 13 and 14,
The effect of hot rolled sheet annealing on magnetic properties is clear. In addition, Nos. 13 and 14 in which Al is added are particularly superior in terms of iron loss.

・ No. 15 and 16 are two cases with and without B addition.
15 is Sol. Al0.030% with no addition of B, S
ol. When Al is less than 0.1%, B is B / N 0.5-1.
5 does not satisfy the requirement of the present invention that the heavy content is 5, and the iron loss is significantly inferior in comparison with Inventive Example No. 16 (B / N 0.9) satisfying this condition.

・ No. 17 is the final C amount level of the present invention (≤
0.005%) and no decarburization was carried out, and iron loss and magnetic flux density were worse than those of No. 11 of the present invention which was under substantially the same conditions except this point.

． Nos. 18 to 20 are conditions in which conditions other than the S amount are fixed and the S amount is changed to see the effect. Nos. 18 and 19 are S amounts.
This is an example of the present invention satisfying the condition of ≤0.005%, and No. 20 is an example that does not meet the condition. No. 18 and 19
There is no big difference in the magnetic characteristics, and all have good values,
No. 20 has a large iron loss value.

Nos. 21 and 22 are examples of the present invention in which Al is added.
Contains 0.1% or more of Al, and No. 22 is Al0.
When less than 1%, B is contained in an amount of B / N of 0.5 to 1.5, all of which show excellent values in terms of iron loss and magnetic flux density.

[Example 2] Example 1 was prepared by smelting steel having each of the component compositions shown in Table 2 in a converter.
Up to cold rolling under the same conditions as above, after that, annealing after cold rolling shown in the same table or further skin pass rolling was carried out, and then stress relief annealing was carried out under the conditions shown in the same table to evaluate the magnetic properties.

Nos. 1, 3 and 4 are examples of the present invention in which the treatment after cold rolling was carried out in various steps, and good magnetic properties were obtained in all cases.
No. 2 is an example in which the initial C content was set as the final C content level of the present invention and decarburization was not performed. Except this point, the iron loss and magnetic flux density were inferior to those of No. 1 under substantially the same conditions. ing.

〔The invention's effect〕

As is clear from the above description, in the production of the semi-processed electromagnetic steel sheet, the present invention can realize a sufficiently low iron loss as a characteristic after stress relief annealing without performing skin pass rolling for reducing the magnetic flux density. And has the effect of making it possible to achieve both magnetic flux density and iron loss, which have a reciprocal tendency.
Moreover, since no skin pass rolling is performed and the use of expensive elements is not required, it is advantageous not only in reducing man-hours but also in cost, and its practical value is extremely high.

[Brief description of drawings]

FIG. 1 is a plot of experimental data showing the effect of C on the magnetic properties, FIG. 2 is a plot of experimental data showing the effect of Mn on the magnetic properties, and FIG. 3 is a diagram showing the effect of S on the magnetic properties. FIG. 4 is a block diagram explaining various variations of annealing after cold rolling in the present invention.

Claims (4)

[Claims] 1. C0.006-0.030%, Si0.1
~ 1.0%, Mn 0.75 to 1.5%, P ≤ 0.150
%, S ≦ 0.005%, the balance being Fe and unavoidable impurities, the hot-rolled steel sheet is descaled, cold-rolled, and then annealed to make the C content 0.005% or less. And a method for manufacturing a semi-processed electrical steel sheet. 2. C0.006-0.030%, Si0.1
~ 1.0%, Mn 0.75 to 1.5%, P ≤ 0.150
%, S ≦ 0.005%, Sol. Al0.1-0.3
%, The balance being Fe and unavoidable impurities, the hot-rolled steel sheet is descaled, cold-rolled, and then annealed to make the C content 0.005% or less. Steel plate manufacturing method. 3. C0.006 to 0.030%, Si0.1
~ 1.0%, Mn 0.75 to 1.5%, P ≤ 0.150
%, S ≦ 0.005%, Sol. Containing less than 0.1% Al and further containing B in an amount of B / N 0.5 to 1.5,
A method for producing a semi-processed electromagnetic steel sheet, comprising descaling a hot-rolled steel sheet, the balance of which is Fe and unavoidable impurities, followed by cold rolling, followed by annealing to a C content of 0.005% or less. 4. 650-850 before or after descaling.
The method for producing a semi-processed electromagnetic steel sheet according to any one of claims 1 to 3, wherein annealing is performed at 30 ° C for 30 seconds or more.