JP2001073097A - Nonoriented silicon steel sheet excellent in magnetic characteristic and workability, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent magnetic characteristics and superior workability by providing a composition containing specific amounts of Si and also containing C, S, N, O and B in amounts made to specific values or below, respectively, specifying average crystal grain size, and regulating the area ratio of such crystal grains that have crystal face orientation within specific angle with respect to the <111> axis at the surface of a steel sheet to a specific percentage or below. SOLUTION: The nonoreinted silicon steel sheet has a composition containing, by weight, 2.0-4.0% Si and containing C, S, N, O and B in amounts made to <=50 ppm respectively and also has 50-500 μm average grain size, and further, the area ratio of grains having crystal face orientation within 15 deg. with respect to the <111> axis at the steel-sheet surface is regulated to <=20%. This steel sheet can be manufactured by forming a molten steel of this composition into slab, hot rolling the slab, carrying out hot rolled plate annealing if necessary, cold rolling the resultant place once or cold rolling it two or more times while performing process annealing between cold rolling steps to finish it to final sheet thickness, and then applying recrystallization annealing to the resultant sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet mainly used as a core material of electric equipment,
In particular, it is intended to improve not only magnetic properties such as iron loss and magnetic flux density but also workability.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for higher efficiency of electric equipment in the context of worldwide power and energy saving. Further, from the aspect of miniaturization of electric equipment, there is an increasing demand for miniaturization of iron core materials.

Conventionally, as a means for reducing iron loss of a non-oriented electrical steel sheet, a method of increasing the content of Si, Al, Mn, or the like has been used in order to reduce eddy current loss by increasing electric resistance. Was. However, this method has an essential problem that the magnetic flux density cannot be reduced.

[0004] Further, since non-oriented electrical steel sheets are mainly laminated to form an iron core after punching, not only magnetic properties but also good workability are required. However, when the content of Si, Al, Mn, etc. is increased in order to obtain a good iron loss, the hardness is increased and workability is deteriorated.
There was a very big problem. Therefore, when emphasis is placed on workability, it is necessary to use low-grade products having a low Si content even at the expense of iron loss.

[0005] Further, a method of not only increasing the content of Si and Al but also reducing C and S is disclosed in JP-A-58-1514.
Methods for increasing the alloy component, such as a method for adding B as described in JP-A No. 3 and a method for adding Ni as described in JP-A-3-281758, are generally known. I have. However, in the method of adding these alloy components, although the iron loss is improved, the effect of improving the magnetic flux density is small, and since the hardness increases with the addition of the alloy, there is a disadvantage that the workability is deteriorated. .

[0006] Further, several methods have been proposed for improving magnetic properties by changing the manufacturing process and improving the texture. For example, Japanese Patent Publication No. 58-181822 discloses that a steel containing 2.8 to 4.0% of Si and 0.3 to 2.0% of Al is warm-rolled in a temperature range of 200 to 500 ° C.
0｝ <UVW> The method of developing tissue is also
Japanese Patent No. 294422 discloses that Si: 1.5 to 4.0%, Al: 0.1 to 2.0%.
% Hot-rolled steel, then hot-rolled sheet annealing at a temperature of 1000 ° C or more and 1200 ° C or less and cold rolling at a reduction ratio of 80-90% to develop {100} structure Has been proposed.

However, the improvement of the magnetic characteristics by these methods is small. For example, in Example 2 of Japanese Patent Publication No. 58-191922, a component-based product (thickness: 0.35 mm) containing Si: 3.40% and Al: 0.60% has a magnetic flux density B ₅₀ : 1.70 T, iron loss W _15/50 : About 2.1 W / kg, and in Japanese Patent Publication No. 3-294422, it is a component-based product (sheet thickness: 0.50 mm) containing 3.0% Si, 0.30% Al, and 0.20% Mn. density B _50: 1.71
T, iron loss W _15/50 : _Only about 2.5 W / kg.

[0008] In addition, although measures have been taken in the production process, it is not enough to reduce the iron loss, and it cannot be said that the magnetic flux density is sufficient. As described above, a material with low iron loss and good workability has not been developed so far.

[0009]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and proposes a non-oriented electrical steel sheet having excellent magnetic properties and good workability, together with an advantageous method for producing the same. The purpose is to:

[0010]

Conventionally, the magnetic properties of non-oriented electrical steel sheets having a high Si content can be determined by, for example, performing hot-rolled sheet annealing at a high temperature or performing skin-pass rolling before hot-rolled sheet annealing. It has been known that the effect can be improved by increasing the crystal grain size before cold rolling, but its magnetic property improving effect is saturated when the increase in crystal grain size before cold rolling reaches a certain level. It was also known that some of them deteriorated. For example, as shown in FIGS. 1 to 4 in JP-A-59-74224, the magnetic properties show the best when the hot-rolled sheet (base plate) annealing temperature is about 1000 ° C. As described above, the technology for increasing the grain size before cold rolling, which is a conventional technology for a steel sheet having a high Si content, is a technology that has reached saturation as a technology for improving magnetic properties.

The present inventors have conducted intensive studies to overcome the limitations of the prior art for improving the magnetic properties of conventional high Si non-oriented electrical steel sheets, and as a result, have found that C, S, N, O and B The use of high-purity materials whose content has been reduced to 50 ppm or less, and more preferably, the inclusion of a fixed amount of Al, if the orientation of the crystals making up the steel sheet is properly controlled, would significantly improve the magnetic properties. New findings were obtained. In order to realize this, it was also found that it is particularly advantageous to appropriately control the rolling temperature in accordance with the crystal grain size before cold rolling. The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows. 1. Si: contains 2.0 to 4.0 wt%, and has a component composition in which the contents of C, S, N, O and B are each 50 ppm or less, the average crystal grain size is 50 to 500 μm, and the crystal plane orientation is < A non-oriented electrical steel sheet having excellent magnetic properties and workability, wherein the area ratio of crystal grains within 15 ° from the 111> axis to the steel sheet surface is 20% or less.

2. In the above item 1, the steel composition further comprises A
l: A non-oriented electrical steel sheet excellent in magnetic properties and workability, characterized by having a composition containing 0.0010 to 0.10 wt%.

3. In the above 1 or 2, the steel composition is
Ni: 0.01 to 1.50 wt%, Sn: 0.01 to 0.50 wt%, Sb:
0.005 to 0.50 wt%, Cu: 0.01 to 0.50 wt%, P: 0.005
A non-oriented electrical steel sheet having excellent magnetic properties and workability, characterized by having a composition containing at least one selected from 0.50 wt% and Cr: 0.01 to 1.50 wt%.

4. Si: 2.0 to 4.0 wt%, Mn: 0.005 to 1.
50 wt% and Al: 0.0010 to 0.10 wt%, and S,
The molten steel having a composition in which the contents of N, O and B are reduced to 50 ppm or less, respectively, is used as a slab, and after hot rolling,
An average crystal grain size consisting of subjecting a hot-rolled sheet to annealing as necessary, performing cold rolling once or twice or more with intermediate annealing to finish to a final sheet thickness, and then performing recrystallization annealing. Is 50 to 500 µm, and the area ratio of the crystal grains whose crystal plane orientation is within 15 ° from the <111> axis is on the steel sheet surface.
A method for manufacturing non-oriented electrical steel sheets that satisfy 20% or less and have excellent magnetic properties and workability.

5. 4. In the above item 4, wherein the average crystal grain size before final cold rolling is set to 100 μm or more, and at least one pass of final cold rolling is performed at a rolling temperature of 150 to 350 ° C. Method for manufacturing non-oriented electrical steel sheet with excellent properties.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, the effect of Al which appears remarkably in the present invention will be described based on experimental results. Si: 2.5 wt%, M
n: A steel ingot containing 0.12 wt% and containing at least 20 ppm or less of each of C, S, N, O and B, and containing Al in various ranges in the base steel. Then, these ingots were heated to 1100 ° C, hot-rolled into 2.4mm-thick hot-rolled sheets, annealed at 1175 ° C for 2 minutes, pickled, and heated to 250 ° C. Was finished into a cold-rolled sheet having a final thickness of 0.35 mm, and then subjected to recrystallization annealing at 1100 ° C. for 5 minutes to obtain a product sheet. 30 × 280 mm in the rolling (L) direction and the rolling right angle (C) direction from these product plates
An equal amount of Epstein test piece of each size was sampled, and the average values of the magnetic flux density and iron loss of each product plate in the L and C directions were measured.

FIGS. 1A and 1B show the relationship between the Al content of the material and the core loss and magnetic flux density of the product plate. As shown in the figure, the magnetic characteristics vary greatly depending on the amount of Al in the material,
0.001wt% (10 ppm) or more, 0.10wt% (1000 ppm) B 50 in the following ranges and W _15/50 or more 1.72T is 2.2 W / kg are substantially obtained following favorable values, in particular the amount of Al Is 0.005-0.020w
t% (50~200 pp) range B ₅₀ or more 1.75T of, W _15/50
However, excellent magnetic properties of 1.8 W / kg or less have been obtained.

Next, in order to find out the reason why excellent magnetic properties can be obtained, the crystal grain size of each product plate was examined. Normally, in non-oriented electrical steel sheets, iron loss improves when the crystal grain size of the product sheet is coarsened, but in this experiment, the effect of the amount of material Al on the crystal grain size of the product sheet is small,
The grain sizes were all about 200-300 μm, and the magnetic properties were almost independent of the grain growth behavior during recrystallization annealing.

Therefore, it is considered that the improvement of the magnetic properties when the Al content is in the range of 0.0010 to 0.10 wt% is attributed to the improvement of the crystal orientation.
This was performed by BackScattering Pattern (EBSP).
The measurement was performed in a 10 mm × 10 mm square area on the steel plate surface.
Performed on 2000 crystal grains. When the minimum angle difference between each crystal plane direction and the <111> axis was analyzed with respect to the obtained measurement results, the area ratio of crystal grains having a crystal plane direction within 15 ° from the <111> axis (hereinafter referred to as P ｛) 111 °) and magnetic properties. For comparison, the {111} plane intensity (hereinafter, referred to as I {111}) and the magnetic characteristics were determined by using an X-ray diffraction method that has been generally performed when evaluating a texture. A survey of the relationships was also conducted. In addition, the crystal plane orientation is <
111> The area ratio of crystal grains within 5 ° from the axis (hereinafter, referred to as
Q {111}) was also measured by the same method as that for P {111} described above.

FIG. 2 shows the relationship between the iron loss value of the product plate and P {111}. As shown in FIG.
There is a strong correlation between {111} and P {111}
Good iron loss (W _15/50 ≦ 2.
20W / kg). FIG. 3 shows the relationship between the product sheet iron loss value and I {111}, and FIG.
The relationship between the product sheet iron loss value and Q {111} is shown, but no clear relationship was observed in any case.

Thus, the iron loss of the product plate is P ｛11
It is not clear why the experimental results obtained that the correlation with 1 {} is very strong, but the correlation with I {111} and Q {111} are weak, but I {111} and Q
For {111}, only the strength of crystal grains near {111} was evaluated, whereas for P {111}, the allowable range was 15 °.
The contribution to the magnetic properties of crystal grains in many orientations other than {111}, for example, {544}, {554}, {221}, and {332}, is also evaluated. It is presumed that.

Further, the following experiment was conducted in order to clarify the influence of the texture on the magnetic characteristics. Si: 2.6
wt%, Mn: 0.13wt%, Al: 0.009wt%, C, S,
Steel ingots in which N, O and B were each reduced to 20 ppm or less were produced. Then, the ingot was heated to 1050 ° C, hot-rolled into a hot-rolled sheet having a thickness of 2.6 mm, then annealed at 1150 ° C for 3 minutes, then pickled, and then pickled from normal temperature to 400 ° C. Cold-rolled at various temperatures in the range of: Final thickness: 0.35mm
After refining, a recrystallization annealing was performed at 1050 ° C. for 10 minutes to obtain a product plate.

From the obtained product plate, 30 × 280 mm size Epstein test pieces were sampled in equal amounts in the rolling (L) direction and the rolling right angle (C) direction, and the magnetic flux density and iron loss of each steel sheet were determined as L and C. The average value in the direction was measured. The crystal grain orientation of the product sheet was measured by EBSP at 10 mm × 10 mm on the steel sheet surface.
Performed on about 2000 crystal grains in the area of mm square, P
{111} was determined.

FIGS. 5 (a) and 5 (b) show the relationship between the rolling temperature, the iron loss characteristics and P {111}. As shown in FIG. It can be seen that a low value is obtained by controlling the temperature in the range of 150 to 350 ° C., whereby an excellent iron loss value is obtained.

Next, an experiment was conducted in which a similar treatment was carried out using the steel ingot having the above components and changing the annealing temperature of the hot-rolled sheet in various ways. Equal amounts of 30 × 280 mm Epstein test pieces were sampled from the obtained product sheet in the rolling (L) direction and the rolling right angle (C) direction, and the average of the magnetic flux density and iron loss of each steel sheet in the L and C directions was obtained. The value was measured. The crystal grain orientation of the product sheet was measured by EBSP at 10 mm × 10 mm on the steel sheet surface.
Performed on about 2000 crystal grains in the area of mm square, P
{111} was determined.

FIGS. 6 (a) and 6 (b) show the results of a study on the relationship between the average grain size D after hot-rolled sheet annealing, the iron loss characteristics of the product sheet, and P {111}. As shown in the figure, the average grain size after hot-rolled sheet annealing, that is, the average grain size before final cold rolling was 100%.
It has been clarified that when the thickness is at least μm, P {111} is greatly reduced and the iron loss characteristics are further improved.

Next, the results of a study on the relationship between the Al content and the impurity content which have obtained the excellent effects of the present invention will be described. Si: 2.5 wt% and Mn: 0.12 wt%, and C,
A steel ingot group A (within the range of components of the present invention) in which S, N, O and B were each reduced to 20 ppm or less as a base, and the base steel contained various ranges of Al; %
And Mn: 0.12 wt%, and each of C, S, N, O and B is 50 ppm or more, and the total amount is 350 p
A steel ingot group B (outside the component range of the present invention) was manufactured based on a steel of not less than pm and containing various ranges of Al in the base steel. Then, these ingots were heated to 1100 ° C, and then hot-rolled into hot-rolled sheets of 2.4 mm thickness.
After hot-rolled sheet annealing, pickling, cold-rolling at a temperature of 250 ° C, final sheet thickness: 0.35mm, then 1050
The product plate was subjected to recrystallization annealing at ℃ for 10 minutes. With respect to the obtained product sheet, the crystal grain orientation was measured by EBSP for about 2000 crystal grains in a 10 mm × 10 mm square area on the steel sheet surface, and P {111} was obtained.

FIG. 7 shows the Al content and P in each steel ingot group.
This shows the relationship with {ll}. As shown in the figure, in the steel ingot group A in which the impurity elements C, S, N, O and B are reduced, P {ll} is 20 when the Al content is in the range of 0.001 to 0.10 wt%.
% Or less, but in the steel ingot group B containing a large amount of the impurity elements C, S, N, O and B, the P {ll}
Could not get.

As a result of further intensive studies based on this experiment, in order to obtain a product plate crystal structure in which P {ll}, which is advantageous for magnetic properties, is 20% or less, the impurity elements C,
It has been determined that it is important to reduce each of S, N, O and B to 50 ppm or less, and more preferably to control the Al content in the range of 0.0010 to 0.10 wt%.

As described above, in a high-grade non-oriented electrical steel sheet having a high Si content, a method of increasing the specific electric resistance has been adopted to improve iron loss. This method also has the effect of agglomerating and coarsening AlN, which is a precipitate in steel, which suppresses the growth of crystal grains, thereby promoting the growth of crystal grains. In order to obtain these effects, the higher the Al content, the better,
Conventionally, the Al content is at least 0.1 wt%, and usually about 0.5 to 1.0 wt% Al has been contained. However, according to experiments by the inventors, it is found that the texture is most preferably developed at an Al content much lower than that of the prior art, particularly at an Al content of 0.005 to 0.020 wt%, and P {ll} is not more than 20%. It was determined that both the magnetic flux density and the iron loss exhibited the best values.

As described above, the impurity elements C, S, N, O, and B in the raw material components are reduced to 50 ppm or less, respectively, and the amount of Al is controlled within a predetermined range.
Although the reason why a good texture with a low {ll} is developed has not always been clearly elucidated, the present inventors consider the following in connection with the effect of suppressing grain boundary migration of impurities. . That is, the effect of suppressing the movement of the grain boundary is also called a drag effect, and the strength differs depending on the difference in the grain boundary structure. The present inventors have studied the effect of the grain boundary character during the secondary recrystallization of grain-oriented electrical steel sheets. Discover that it will recrystallize next,
Acta Material, vol. 45 (1997), p. 85. Here, the azimuth difference angle is a minimum angle difference required for two crystal grains to make one crystal grain coincide with the other crystal grain by rotating the crystal orientation.

The grain boundary having a misorientation angle of 20 to 45 ° is obtained from experimental data by CGDunn et al. (AIME Transaction 188 (1949) 368).
According to page), it is a high energy grain boundary. The high energy grain boundary has a large free space in the grain boundary and has a random structure. Impurity elements C, S, N, O, present in steel
B and the like are likely to segregate at grain boundaries, particularly at high energy boundaries with disordered structures. On the other hand, Al is considered to have a smaller tendency to segregate at the grain boundary than these elements, but when added in a large amount of 0.1 wt% or more, the effect of suppressing segregation at the grain boundary is brought about. Therefore, when the impurity element or Al is present in a large amount, it is considered that there is no difference in the moving speed between the high energy grain boundary and another grain boundary. In this case, it is estimated that the grain growth becomes isotropic and the change in texture during the grain growth becomes small. On the other hand, by purifying the material, the effects of impurity elements, particularly C, S, N, O, and B, which have a strong tendency to segregate at grain boundaries, are eliminated as much as possible.
, A difference in the intrinsic moving speed depending on the structure of the high energy grain boundary becomes apparent, and only the high energy grain boundary moves preferentially during the grain growth process accompanying the recrystallization, and P
It is considered that the texture changes in the direction in which {ll} decreases, and as a result, the magnetic properties are improved.

When the Al content was less than 10 ppm, the magnetic properties tended to deteriorate, but in this case, it was observed that coarse silicon nitride was formed in the steel. As a result, it is estimated that the deformation behavior during cold rolling changes, P {ll} in the structure after recrystallization annealing increases, and the magnetic properties deteriorate. In contrast, the amount of Al
When it is contained at 10 ppm or more, the formation of such coarse silicon nitride is suppressed, and as a result, an increase in P {ll} due to a change in deformation behavior during cold rolling as described above was avoided. It is considered something.

As described above, P in the structure after recrystallization
The action of reducing {ll} is due to impurity elements C, S, N,
This is realized by reducing each of O and B to 50 ppm or less, but is more advantageously realized by controlling the Al content within a predetermined range as described above.

As in the present invention, the method of improving the texture and improving the magnetic properties without adding a large amount of Al is as follows:
In addition to the advantage that the saturation magnetic flux density is high due to the small amount of the alloying element added, there is also an advantage in ensuring the workability of the product that does not cause an increase in hardness. For example, in the present invention, Si
Even when the content of Si is 4.0 wt%, which is the upper limit of the content, the hardness of the steel sheet is about 240 in Vickers hardness, and good workability can be ensured.

As for the crystal grain size of the product sheet, the larger the grain size, the better the iron loss characteristics. However, the present invention can be used by adding this technique. In this case, an appropriate average crystal grain size is 50 to 500 μm.

The present inventors have further studied the elements to be added to the material, and found that the addition of Ni improves the magnetic flux density of the product. Although it is not clear for this reason, it is presumed that the fact that Ni is a ferromagnetic element contributes to the improvement of the magnetic flux density for some reason. In addition, it was observed that the addition of Sn, Sb, Cu, P, Cr and the like tended to improve iron loss. It is presumed that the reason is that the iron loss was reduced by increasing the electric resistance.

Next, the reasons for limiting the constituent elements of the present invention will be described. As a component of the magnetic steel sheet of the present invention, it is necessary to increase the electric resistance and reduce the iron loss by adding Si, but at least 2.0 wt% is required for improving the iron loss. However, when the content exceeds 4.0 wt%, not only the magnetic flux density decreases, but also the secondary workability of the product deteriorates significantly. Therefore, the Si content is limited to the range of 2.0 to 4.0 wt%.

Further, in order to realize the crystal orientation of the present invention, it is essential to reduce the trace components of the steel sheet.
It is necessary to reduce the contents of C, S, N, O and B to 50 ppm or less, preferably 20 ppm or less, respectively. This is because if the content is more than this, P {ll} in the crystal orientation of the product sheet increases, and the iron loss is greatly deteriorated.

Further, the average crystal grain size of the product plate is 50 to 500.
μm. This is because the average grain size is 50
If the thickness is less than μm, the hysteresis loss increases, so that the application of the present invention cannot avoid the loss of iron loss.Moreover, the hardness of the product plate increases, thereby deteriorating the workability. This is because the increase is extremely large and the iron loss is deteriorated even by applying the technology of the present invention.

In the present invention, control of the crystal orientation as described below is most important. That is, in order to obtain good magnetic properties, it is necessary to set the area ratio P {ll} of the crystal grains whose crystal plane orientation is within 15 ° from the <111> axis on the steel sheet surface to 20% or less. is there. This is because when P {ll} exceeds 20%, both the magnetic flux density and iron loss of the product are greatly deteriorated. In order to ensure good punching properties, Vickers hardness must be 2
Preferably it is 40 or less. As a method for achieving this, although various methods are conceivable, a method mainly by adjusting the amounts of components such as Si, Al, and Mn is advantageous.

Next, the reason for limiting the molten steel component in producing the magnetic steel sheet of the present invention will be described. Mn is an element necessary for improving hot workability. However, if it is less than 0.005 wt%, the effect of its addition is poor. If it exceeds 1.50 wt%, the saturation magnetic flux density decreases. ~ 1.50wt%
Range.

The most important requirements are S, N,
It is important to regulate the upper limit of the impurity elements of O and B to 50 ppm or less, preferably 20 ppm or less, respectively. In this regard, regarding C, 50ppm at the stage of molten steel component
Of course, it can be set as follows, but even if it exceeds 50 ppm in the molten steel stage, it can be reduced to 50 ppm or less by decarburization treatment in the middle step, in short, it is sufficient if it is 50 ppm or less during recrystallization annealing, preferably 20 ppm or less . When the content of these impurities exceeds 50 ppm, the selective movement of special crystal grain boundaries is hindered, P {ll} increases during recrystallization annealing, and magnetic properties deteriorate.

Further, control of the Al content is an advantageous technique for obtaining the non-oriented electrical steel sheet of the present invention.
It is necessary to limit Al to the range of 0.0010 to 0.10 wt%. This is because if Al exceeds 0.10 wt%, the movement of special crystal grain boundaries does not easily occur, P {ll} in the product plate increases, and iron loss is deteriorated, while Al is less than 0.0010 wt%. This is because silicon nitride precipitates, and similarly, the movement of special crystal grain boundaries does not easily occur, P {ll} increases, and iron loss deteriorates.

Further, Ni can be added to improve the magnetic flux density. However, the addition amount is 0.01wt
%, The effect of improving magnetic properties is poor, while 1.50 wt%
If the Nb content exceeds 1, the texture is insufficiently developed and the magnetic properties are degraded. Therefore, the Ni content is set in the range of 0.01 to 1.50 wt%. Further, in order to improve iron loss, Sn: 0.01 to 0.50
wt%, Sb: 0.005 to 0.50wt%, Cu: 0.01 to 0.50wt%,
It is also effective to add P: 0.005 to 0.50 wt% and Cr: 0.01 to 1.50 wt%. In any case, when the addition amount is less than the above range, the iron loss improving effect is poor, while when the addition amount is large, the saturation magnetic flux density is lowered.

Next, a manufacturing method according to the present invention will be described. The molten steel adjusted to the above preferable component composition is made into a slab by a usual ingot-making method or a continuous casting method. Further, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method. The slab is usually heated and subjected to hot rolling, but may be immediately subjected to hot rolling without heating after casting. In the case of a thin slab, hot rolling may be performed, or hot rolling may be omitted and the process may proceed directly to the subsequent steps. Next, if necessary, hot-rolled sheet annealing is performed, and further, if necessary, one or more times of cold rolling sandwiching intermediate annealing is performed, then continuous annealing is performed, and then, if necessary, insulating coating is performed. The insulating coating may be a multilayer film composed of two or more kinds of films, or may be a coating film in which a resin or the like is mixed.

In the present invention, the average grain size before cold rolling before final cold rolling is set to 100 μm or more, and the rolling temperature of at least one pass in the final cold rolling step is set to 150 to 350 ° C. or more. This is particularly effective in reducing {ll} and obtaining good magnetic properties. Average grain size before cold rolling
Means for increasing the thickness to 100 μm or more include performing hot-rolled sheet annealing or intermediate annealing at a high temperature of 1000 ° C. or more, and performing cold rolling of 3 to 7% prior to hot-rolled sheet annealing.

[0049]

Example 1 A slab having the composition shown in Table 1 was produced by continuous casting. Each slab was heated at 1150 ° C. for 20 minutes and then hot-rolled to a 2.8 mm thickness. Then, hot rolled sheet annealing is performed at 1150 ° C.
For 60 seconds, and then cold-rolled at a temperature of 270 ° C. to finish to a final thickness of 0.35 mm. Then, after performing recrystallization annealing at 1050 ° C. for 2 minutes in a hydrogen atmosphere, a semi-organic coating solution was applied and baked at 300 ° C. to obtain a product plate.

The magnetic properties (average of the rolling (L) direction and the direction perpendicular to the rolling (C) direction) of the product sheet thus obtained were measured. The orientation of crystal grains in a 10 mm × 10 mm square area of the surface was measured by EBSP, and the crystal plane orientation was <111.
> The area ratio P {ll} of the crystal grains on the steel sheet surface within 15 ° from the axis was measured. Further, the hardness and workability of the product plate were investigated. The workability was evaluated by laminating product plates to a height of about 10 mm, punching a hole having a diameter of 30 mm by an extrusion-type punching machine at 100 points, and evaluating the cracking rate at that time. Further, the average particle size after annealing of the hot-rolled sheet and in the product sheet was also measured. The results obtained are also shown in Table 1.

[0051]

[Table 1]

As is clear from the table, when the composition range of the present invention is satisfied, a product having not only good magnetic properties but also good workability is obtained.

Example 2 C: 38 ppm, Si: 3.74 wt%, Mn: 0.35 wt%, Al: 0.013
A slab containing wt%, S: 11 ppm, O: 7 ppm and N: 9 ppm, and the balance being substantially Fe, was produced by continuous casting. Next, after heating at 1100 ° C. for 20 minutes, the sheet was finished to a thickness of 3.2 mm by hot rolling, and then annealed with a hot rolled sheet at a temperature shown in Table 2 for 60 seconds. Then, after finishing to a final thickness of 0.50 mm by cold rolling at the temperature shown in Table 2, it was also subjected to recrystallization annealing for 120 seconds at the temperature also shown in Table 2, and an inorganic coating solution was applied at 300 ° C. The product plate was baked. The magnetic properties of the product plate thus obtained, P ｛ll
Table 2 also shows the results of measurements of l｝, hardness, workability, average particle size after annealing of the hot-rolled sheet and in the product sheet.

[0054]

[Table 2]

As shown in Table 2, it is found that by increasing the grain size before cold rolling and further increasing the rolling temperature, a product plate having particularly good magnetic properties and good workability can be obtained. .

Example 3 A thin slab (sheet thickness: 4.5 mm) having the composition shown in Table 3 was produced by a direct casting method. This thin slab was subjected to hot-rolled sheet annealing at 1150 ° C for 60 seconds, then cold-rolled at room temperature to an intermediate thickness of 1.2 mm, and after intermediate annealing at 1000 ° C for 60 seconds, cold-rolled at room temperature. Rolled to a final thickness of 0.35 mm. Subsequently, recrystallization annealing was performed in an Ar atmosphere at 1025 ° C. for 5 minutes to obtain a product plate. The magnetic properties of the product plate thus obtained, P ｛ll
Table 4 shows the results measured for l, hardness, workability, and average particle size.

[0057]

[Table 3]

[0058]

[Table 4]

As shown in Table 4, by using the component system satisfying the present invention, a product having good magnetic properties and workability was obtained.

[0060]

As described above, according to the present invention, it is possible to obtain an electromagnetic steel sheet having both good magnetic properties and workability.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of Al in steel, iron loss (W _15/50 ), and magnetic flux density (B ₅₀ ).

FIG. 2 is a graph showing the relationship between P {ll} and iron loss.

FIG. 3 is a graph showing a relationship between I {ll} and iron loss.

FIG. 4 is a graph showing a relationship between Q {ll} and iron loss.

FIG. 5: Rolling temperature, iron loss and P in cold rolling
It is the graph which showed the relationship with {ll}.

FIG. 6: Average grain size, iron loss and P ｛l after annealing of hot-rolled sheet
11 is a graph showing a relationship with｝.

FIG. 7 shows the amount of Al in steel and P ｛ll in steel ingot groups A and B.
It is a graph showing the relationship with l｝.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/16 H01F 1/16 A (72) Inventor Masaki Kono 1-chome Mizushima Kawasaki-dori (Kurashiki City, Okayama Prefecture) None) Inside the Mizushima Works of Kawasaki Steel Co., Ltd. (72) Inventor Michio Komatsubara 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Pref. CA07 CA09 FA12 HA01 HA03 HA05 5E041 AA02 AA19 CA02 HB05 HB07 HB11 NN01 NN06 NN18

Claims (5)

[Claims] (1) Si: contains 2.0 to 4.0 wt%, and contains C,
A steel sheet of a crystal grain in which the contents of S, N, O and B are each 50 ppm or less, the average crystal grain size is 50 to 500 μm, and the crystal plane orientation is within 15 ° from the <111> axis. Non-oriented electrical steel sheet excellent in magnetic properties and workability, characterized in that the area ratio on the surface is 20% or less. 2. The steel according to claim 1, wherein the steel composition further comprises A
l: A non-oriented electrical steel sheet excellent in magnetic properties and workability, characterized by having a composition containing 0.0010 to 0.10 wt%. 3. The steel composition according to claim 1, wherein the steel composition is
Ni: 0.01 to 1.50 wt%, Sn: 0.01 to 0.50 wt%, Sb:
0.005 to 0.50 wt%, Cu: 0.01 to 0.50 wt%, P: 0.005
A non-oriented electrical steel sheet having excellent magnetic properties and workability, characterized by having a composition containing at least one selected from 0.50 wt% and Cr: 0.01 to 1.50 wt%. 4. Si: 2.0 to 4.0 wt%, Mn: 0.005 to 1.50
wt% and Al: 0.0010 to 0.10 wt%, and S, N,
Molten steel having a composition in which the contents of O and B are reduced to 50 ppm or less, respectively, is used as a slab. Then, after hot rolling, hot-rolled sheet annealing is performed as necessary, and then once or twice with intermediate annealing Applying the above cold rolling to finish the final sheet thickness, and then performing recrystallization annealing, the average crystal grain size is 50
~ 500 μm, and the crystal plane orientation is 15 from the <111> axis.
A method for producing a non-oriented electrical steel sheet excellent in magnetic properties and workability, in which the area ratio of crystal grains within the range of less than 20% on the steel sheet surface is not more than 20%. 5. The method according to claim 4, wherein the average grain size before the final cold rolling is set to 100 μm or more, and at least one pass of the final cold rolling is performed at a rolling temperature of 150 to 350 ° C. For producing non-oriented electrical steel sheets having excellent magnetic properties and workability.