JPH0570833A - Manufacture of silicon steel sheet by continuous annealing - Google Patents

Abstract

PURPOSE:To obtain a silicon steel sheet good in magnetic properties in the rolling direction as well as in its orthogonal direction by heating a steel slab having a specified compsn. at a specified temp., thereafter subjecting it to hot rolling, executing cold rolling including process annealing to regulate its sheet thickness into a final one, subjecting it to decarburizing annealing and thereafter executing continuous annealing under specified conditions. CONSTITUTION:A steel slab constituted of, by weight, 0.010 to 0.10% C, <=4.0% Si, 0.02 to 0.10% Mn, 0.005 to 0.030% Se and/or S and the balance Fe is heated at 1150 to 1250 deg.C and is thereafter subjected to hot rolling. This steel sheet is subjected to cold rolling for one or two times including process annealing to regulate its sheet thickness into a final one, and after that, it is subjected to decarburizing annealing and is subjected to short time finish annealing at 950 to 1200 deg.C for 10 to 600s by continuous annealing. Moreover, it is enable to execute 0.5 to 5.0% cold rolling as well after the decarburizing annealing. In this way, a silicon steel sheet having a suitable amt. of inhibitor components with moderate strength and proper secondary recrystals, stable in magnetic properties and suitable as the stock for generators and large size rotating machines can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an economical method for producing an electromagnetic steel sheet suitable as a material for a large rotating machine.

[0002]

2. Description of the Related Art A magnetic steel sheet used in a large-sized rotating machine is cold-rolled to a final product thickness, and then a so-called secondary crystal that preferentially grows crystal grains having a (110) 001 orientation during high temperature heating. It is manufactured by utilizing the crystallization phenomenon.

Currently, high-grade non-oriented electrical steel sheets or unidirectional electrical steel sheets are used for iron cores of generators, large motors, transformers and the like. However, the non-oriented electrical steel sheet has low magnetic flux density and iron loss in the rolling direction (L direction), and improvement in L direction characteristics is desired. Further, in the grain-oriented electrical steel sheet, since it is necessary to preferentially grow the crystal grains having the (110) 001 orientation, the final annealing requires heating for a long time, and therefore, the box annealing is usually used. )
Since it is highly integrated in the 001 direction, the characteristics in the L direction are excellent, but the characteristics in the direction perpendicular to the rolling direction (C direction) are significantly deteriorated. In addition, because of box annealing, the cost is high.

On the other hand, a method of manufacturing a unidirectional electrical steel sheet by employing continuous annealing for a short time instead of such expensive box annealing has been proposed. For example, in Japanese Examined Patent Publication No. 51-20373, a cold rolled sheet of unidirectional electrical steel is decarburized and annealed for secondary recrystallization, and then continuous annealing is performed.
A manufacturing method is disclosed in which the holding time at ° C is performed in a relatively short time of 5 to 10 minutes. In addition, JP-A-49
-95816 discloses that the cold rolled sheet with the final sheet thickness is 500-1000.
A method for producing a grain-oriented electrical steel sheet is described, in which rapid heating is performed at a heating rate of 0 ° C./min, and finish annealing is performed at a temperature of 950 ° C. or higher and 1200 ° C. or lower for 10 minutes or less. Furthermore, JP-A-55-58332
The publication discloses that C: 0.01 wt% (hereinafter simply referred to as%) material is used for finish annealing by rapid heating and short-time soaking without decarburizing annealing.

However, in Japanese Patent Publication No. 51-20373 and Japanese Patent Laid-Open No. 49-95816, AlN is used as the main inhibitor, but this AlN has a particularly strong inhibitory action and its secondary recrystallized grains are strong. Since it was integrated in the (110) 001 orientation, the C-direction characteristics were not improved, and there was a problem in that the characteristic difference between the L-direction and the C-direction was still large.

[0006]

As described above, according to the prior art, it is not possible to provide an inexpensive iron core material for generators and large motors, which has good characteristics in both the L and C directions. There wasn't. The present invention advantageously solves the above problems, and an object thereof is to propose a manufacturing method capable of inexpensively obtaining a magnetic steel sheet for a large-sized rotating machine having good magnetic properties in both the rolling direction and the direction perpendicular to the rolling direction. To do.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention are inexpensive, have better L-direction characteristics than non-oriented electrical steel sheets, and have C-direction characteristics better than unidirectional electrical steel sheets. Further, the inventors have earnestly studied about a method of manufacturing an electrical steel sheet which is excellent, and has a good balance of characteristics in the L and C directions.

As a result, although secondary recrystallization at the time of finish annealing is indispensable, in order to improve the C-direction characteristics, it is rather that the (110) 001 orientation is too strong to be integrated like the grain-oriented electrical steel sheet. It has been found to be disadvantageous, and it is desirable that the crystal orientations are appropriately dispersed. Then, for that purpose, it was found that it is extremely important to select an inhibitor component having an appropriate amount and strength, an appropriate secondary recrystallization annealing condition, and a cold rolling condition. This invention is
It is based on the above findings.

That is, the present invention provides C: 0.010 to 0.10.
%, Si: 4.0% or less, Mn: 0.02 to 0.10%, Se and / or S: 0.005 to 0.030%, and the balance substantially consisting of Fe, a steel slab having a temperature range of 1150 to 1250 ° C. After heating with a slab, hot rolling, and then cold rolling 1 to 2 times including intermediate annealing to obtain the final plate thickness, followed by decarburizing annealing,
This is a method for manufacturing an electrical steel sheet (first invention), which comprises performing a short-time finish annealing at 950 to 1200 ° C. for 10 to 600 s by continuous annealing.

The present invention also provides C: 0.010 to 0.10%, S
i: 4.0% or less, Mn: 0.02 to 0.10%, Se and / or S:
A steel slab containing 0.005 to 0.030% and the balance being substantially Fe is heated in a temperature range of 1150 to 1250 ° C, hot rolled, and then cooled once or twice including intermediate annealing. 0.5 ~ 5.0 after decarburization annealing after hot rolling
A method for manufacturing an electrical steel sheet, which comprises cold rolling at a reduction rate of 10% to obtain a final sheet thickness, and then performing continuous annealing for a short time annealing at 900 to 1200 ° C. for 3 to 600 s (second invention).
Is.

The present invention will be described in detail below. First, the experimental results which are the basis of the first invention will be described. The unidirectional silicon steel material having the composition shown in Table 1 below is
After heating to ℃, rolling reduction: 99%, finishing temperature: 860 ℃ hot rolling, then cold rolling: 75% cold rolling.
After the final plate thickness of 0.5 mm, decarburization annealing was performed at 800 ° C for 4 minutes, and then final annealing was performed at various heating temperatures and times. The relationship between the temperature and the heating time is shown in FIG.

[0012]

[Table 1]

As is clear from FIG. 1, when the material C% is too low as in the case of steel A, secondary recrystallization does not occur at all. The reason for this is that the band structure remains in the center of the plate thickness and inhibits secondary recrystallization.

Further, in FIG. 2, the slab heating temperatures of 1200 ° C. and 13
The relationship between the magnetic properties of C steel after secondary recrystallization at a temperature of 00 ° C and the heating temperature (holding for 60 s) is shown. As is clear from the figure, in the case of heating at high temperature for a short time, there is no significant difference in the magnetic properties in the L direction between the two steels as long as secondary recrystallization is performed. However, regarding the C-direction characteristics, the difference becomes remarkable depending on the slab heating temperature, and MnSe remains as a non-solid solution.
The difference in characteristics between the L and C directions is smaller when heated at 00 ° C. It can be seen that the finish annealing temperature must be 950 ° C or higher.

Next, the experimental results which are the basis of the second invention will be described. For B steel in Table 1, after decarburization annealing, 3
% Cold rolling, then finish annealing at various temperatures,
As a result of conducting the heating for a time, it was found that even if the heating temperature was 900 ° C., secondary recrystallization was carried out if a soaking treatment for 3 s or more was applied. FIG. 3 shows the relationship between the magnetic properties and the soaking temperature (holding for 10 s) in the case of performing cold rolling after decarburization annealing, in comparison with that in the case of not performing cold rolling. As is clear from the figure, good magnetic properties were obtained even at 900 ° C when cold rolling was performed. Of course, at each temperature of 950 ° C. or higher, a good improvement in characteristics was recognized. Thus, after decarburization annealing, by applying a minute strain under the presence of the inhibitor, the grain growth is promoted, and the advantageous improvement of the iron loss characteristics is achieved.

It is known that even in ordinary steel, grain growth is promoted by strain imparting-recrystallization, but the present invention is completely different from that, and in the presence of an inhibitor, very little strain is applied. Therefore, a remarkable effect can be obtained even with a finish annealing at a low temperature of 900 ° C. Moreover, by applying light reduction, the lower limit of the final annealing temperature can be expanded to 900 ° C. High-temperature annealing has a problem in that the plate is deformed and energy is saved, and low-temperature annealing has never been performed if desired properties can be obtained.

[0017]

Each constituent element of the present invention will be described in detail. First, the reason why the component composition of the material used is limited to the above range will be described. C: 0.010 to 0.10% C is an element necessary for destroying the cast structure during hot rolling and leaving no band structure, and 0.010% or more is necessary for sufficiently destroying this band structure. .. However, if it remains in the final product, it will deteriorate the magnetic properties,
The upper limit of the amount of raw material C was 0.10%, which can reduce the amount of product C by decarburization annealing before finish annealing so as not to adversely affect the magnetic properties.

Si: 4.0% or less Si is an element that has a dominant influence on the magnetic properties. Generally, as the amount of Si increases, the iron loss is improved, while the saturation magnetic flux density tends to decrease. .. The performance as a magnetic steel sheet is basically determined by the selection of this Si content. This invention aims to obtain good magnetic properties over a wide range of Si content so as to meet various requirements, but if it exceeds 4.0%, cold rolling becomes extremely difficult, so the upper limit is set to 4.0%. did. The lower limit is not particularly limited so that a sufficiently high magnetic flux density can be realized if necessary.

Mn: 0.02 to 0.10%, Se and / or S: 0.00
Regarding 5 to 0.030% Mn and the amount of S and / or Se, it is necessary that they exist so as to function as an inhibitor during the secondary recrystallization annealing, and the lower limit is determined from this point. However, since an excessively large amount of Mn, S, and Se rather deteriorates the magnetic characteristics, the upper limits are set in the above ranges from this point.

The slab containing the above components is subjected to slab heating prior to hot rolling. It is desirable that the treatment temperature in the slab heating is a temperature at which a desired amount of the inhibitor is solid-dissolved but not completely dissolved. The reason is that when the inhibitor is completely dissolved, the characteristics in the L direction are improved, but the characteristics in the C direction cannot be expected, as in the case of the ordinary grain-oriented electrical steel sheet. From this viewpoint, the slab heating temperature was limited to the range of 1150 to 1250 ° C.

Then, hot rolling is carried out, but the hot rolling conditions are not particularly different from the manufacturing conditions of the conventional unidirectional silicon steel sheet, and therefore the hot rolling conditions may be carried out under normal conditions. After hot rolling, depending on the amount of inhibitor and the thickness of the final product, cold rolling is performed once or twice including intermediate annealing at about 850 to 1000 ° C, and then at 750 to 900 ° C for 1 to 5 minutes. Decarburization annealing is performed in a moist hydrogen atmosphere.

After such decarburization annealing, the present invention further
Cold rolling of 0.5-5.0% can be added. The reason why the rolling reduction is limited to the above range is that if it is less than 0.5%, secondary recrystallization failure may occur, and secondary recrystallized grains cannot be stably obtained in the entire plate width direction. On the other hand, if it is more than 5.0%, extra rotation occurs in the crystal grains, and the texture after secondary recrystallization tends to accumulate in the orientation which is disadvantageous in terms of magnetic properties.
This is because the magnetic properties are deteriorated.

Then, the decarburized annealed plate or the cold rolled plate is annealed continuously, but the temperature rising conditions may be a normal temperature rising rate depending on the plate thickness and the equipment capacity (usually 5 to 150). C / s). Regarding the heating conditions, in the case of a decarburized annealed plate, it is necessary to secure a temperature of 950 ° C or higher for 10 seconds or more in order to promptly promote secondary recrystallization. At a temperature lower than this and a short time, secondary recrystallization is incomplete and stable magnetic characteristics cannot be obtained. On the other hand, decarburization
For cold-rolled sheets, it is necessary to secure at least 900 seconds at a temperature of at least 3 s. As a result, secondary recrystallization is still incomplete at a low temperature for a short time, and stable magnetic characteristics cannot be obtained.

However, if the heating temperature exceeds 1200 ° C., not only the restrictions on the equipment become large, but also the plate shape deteriorates, resulting in higher costs, and in the soaking time of more than 600 s, the secondary particles become even more granular. Not only does it grow and cause characteristic deterioration in the C direction, but the equipment becomes large and costly, which is contrary to the object of the present invention, which is an inexpensive method, so the upper limit was made 600 s.

After the annealing is finished, the product is subjected to a surface treatment such as an insulating film treatment as it is or according to a usual process, and then the product is obtained.

Since the electrical steel sheet obtained according to the present invention undergoes a continuous annealing process of rapid heating and short-time soaking, the magnetic properties in the L direction are slightly inferior to those of the unidirectional silicon steel sheet as compared with the box annealed material. However, the properties in the C direction are good, and the magnetic properties are much higher than those of the non-oriented electrical steel sheet. Therefore, when it is used as a magnetic steel sheet for generators, large motors, etc., significant advantages are obtained from both aspects of improving equipment performance and reducing costs.

[0027]

EXAMPLES Example 1 C: 0.036%, Si: 3.31%, Mn: 0.072% and Se: 0.022
% Of steel, the balance of which is substantially Fe, after heating the slab at various temperatures shown in Table 2 for 4 hours, then rolling reduction: 99%, finish rolling temperature: 860 ℃ Hot rolled sheet with a thickness of 2.7 mm by hot rolling, then pickled,
After primary cold rolling to a thickness of 0.65 mm, after intermediate annealing at 950 ° C for 3 minutes, secondary cold rolling was performed to a final product thickness of 0.35 mm. After that, decarburization annealing was performed at 800 ° C. for 4 minutes in a wet hydrogen atmosphere, and then secondary recrystallization annealing was performed in a continuous annealing line under various heating temperatures and heating time conditions shown in Table 2. The results of examining the magnetic properties of the products thus obtained are also shown in Table 2.

[0028]

[Table 2]

As is clear from the table, the magnetic material obtained according to the present invention has excellent magnetic characteristics in both the L and C directions. On the other hand, Comparative Example 1 in which the heating temperature is low
And Comparative Example 2 in which the heating time is short are both L direction and C
In Comparative Example 3 in which only the properties in the direction were low and the slab heating temperature was high and Comparative Example 4 in which the continuous annealing time was long, the properties in the C direction were inferior.

Example 2 C: 0.041%, Si: 2.95%, Mn: 0.068% and Se: 0.025
% Of steel, the balance of which is substantially Fe composition, after heating the slabs for 4 hours at various temperatures shown in Table 3, rolling reduction: 99%, finish rolling temperature: 870 ℃ Hot rolled to a thickness of 2.4 mm by hot rolling, then pickled,
After primary cold rolling to a thickness of 0.65 mm, after intermediate annealing at 950 ° C for 3 minutes, secondary cold rolling was performed to a final product thickness of 0.35 mm. After that, decarburization annealing was performed at 800 ° C. for 4 minutes in a wet hydrogen atmosphere, and then secondary recrystallization annealing was performed in a continuous annealing line under various heating temperatures and heating time conditions shown in Table 3. The results of examining the magnetic properties of the thus obtained products are also shown in Table 3.

[0031]

[Table 3]

As is clear from the table, the magnetic material obtained according to the present invention has good magnetic characteristics in both the L and C directions. On the other hand, in Comparative Example 1 in which both the heating temperature and the heating time are out of the proper ranges of the present invention, only poor magnetic properties are obtained in both the L direction and the C direction, and Comparative Example 2 in which the slab heating temperature is high and In Comparative Example 3 in which the annealing temperature is high, the characteristics in the L direction are excellent, but the characteristics in the C direction are inferior.

Example 3 C: 0.036%, Si: 3.31%, Mn: 0.072% and Se: 0.022
%, And the balance being substantially Fe composition, after the slab heating at the temperature shown in Table 4 for 4 hours,
After hot-rolling the hot-rolled sheet to a thickness of 2.7 mm, after pickling it to a thickness of 0.65 mm in the primary cold rolling, after intermediate annealing at 950 ° C for 3 minutes, 0.35 in the secondary cold rolling. Finished to a thickness of 0.37 mm. Then, after performing decarburization annealing at 800 ° C for 4 min in a wet hydrogen atmosphere, cold rolling was performed at various reduction ratios shown in Table 4,
After setting the final plate thickness to 0.35 mm, secondary recrystallization annealing was performed on the continuous annealing line at various soaking temperatures and times shown in Table 4 as well. The results of examining the magnetic properties of the product thus obtained are also shown in Table 4.

[0034]

[Table 4]

As is clear from the table, all the magnetic particles obtained according to the method of the present invention have excellent magnetic characteristics.

Example 4 C: 0.041%, Si: 2.95%, Mn: 0.068% and S: 0.025
%, And the balance being substantially Fe composition, after the slab heating at the temperature shown in Table 5 for 4 hours,
After hot-rolling the hot-rolled sheet to a thickness of 2.4 mm, after pickling it to a thickness of 0.65 mm in the first cold rolling, after intermediate annealing at 950 ° C for 3 minutes, 0.35 in the second cold rolling. Finished to a thickness of 0.37 mm. Then, after performing decarburization annealing at 800 ° C. for 4 minutes in a wet hydrogen atmosphere, cold rolling was performed at various rolling reductions shown in Table 5,
After setting the final plate thickness to 0.35 mm, finish annealing was performed on the continuous annealing line at various soaking temperatures and times as shown in Table 5. The results of examining the magnetic properties of the product thus obtained are also shown in Table 5.

[0037]

[Table 5]

As is clear from the table, all the magnetic particles obtained according to the method of the present invention had excellent magnetic characteristics.

Example 5 C: 0.037%, Si: 3.32%, Mn: 0.073% and Se: 0.021
% Of steel, the balance of which is substantially Fe, after heating the slab for 4 hours at various temperatures shown in Table 6, rolling reduction: 99%, finishing temperature: 855 ℃ hot Rolled to a hot rolled sheet with a thickness of 2.0 mm, then 1000 ℃, 30s
Was annealed, pickled, and then cold rolled to a thickness of 0.50 to 0.53 mm. Then, after decarburizing annealing at 800 ° C for 4 min in a wet hydrogen atmosphere, cold rolling was performed at various reduction ratios shown in Table 6 to obtain a final sheet thickness of 0.50 mm, and then a continuous annealing line. After that, finish annealing was performed at various soaking temperatures and times shown in Table 6. The results of examining the magnetic properties of the products thus obtained are also shown in Table 6.

[0040]

[Table 6]

[0041]

As described above, according to the first aspect of the present invention, the continuous annealing method which is usually carried out industrially has remarkably superior magnetic properties to non-oriented silicon steel sheets and is compared with unidirectional silicon steel sheets. Then, although the characteristics in the L direction are slightly inferior, it is possible to obtain an electromagnetic steel sheet having excellent C direction characteristics and good magnetic balance at low cost. Further, according to the second aspect of the invention, a lower temperature,
The above effects can be obtained by continuous annealing for a short time.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of finish annealing conditions on secondary recrystallization behavior.

FIG. 2 is a graph showing the effect of finish annealing conditions on L-direction and C-direction characteristics.

FIG. 3 is a graph showing the influence of finish annealing conditions on the properties in the L direction and the C direction when cold rolling is performed after decarburization annealing.

Claims (2)

[Claims] 1. C: 0.010 to 0.10 wt%, Si: 4.0 wt% or less, Mn: 0.02 to 0.10 wt%, Se and / or S: 0.005 to 0.030 wt%, the balance being substantially Fe. The steel slab that becomes the composition,
After slab heating in the temperature range of 1150 ~ 1250 ℃, hot rolling,
Then, after cold rolling 1 to 2 times including intermediate annealing to obtain the final plate thickness, decarburization annealing is performed and then continuous annealing is performed at 950 to
A method for manufacturing an electrical steel sheet, characterized by performing a short-time finish annealing at 1200 ° C for 10 to 600 s. 2. C: 0.010-0.10 wt%, Si: 4.0 wt% or less, Mn: 0.02-0.10 wt%, Se and / or S: 0.005-0.030 wt%, the balance being substantially Fe. The steel slab that becomes the composition,
After slab heating in the temperature range of 1150 ~ 1250 ℃, hot rolling,
Then, after cold rolling 1 to 2 times including intermediate annealing, decarburization annealing is performed, and then cold rolling at a reduction rate of 0.5 to 5.0% is performed to obtain a final plate thickness, and then continuous annealing is performed. A method for producing an electromagnetic steel sheet, which comprises performing a short-time annealing at 900 to 1200 ° C for 3 to 600 s.