JPH05171280A - Production of nonoriented silicon steel sheet having superior magnetic property and excellent in external surface appearance - Google Patents

Abstract

PURPOSE:To produce a nonoriented silicon steel sheet having high magnetic flux density and excellent in external surface appearance by subjecting a hot rolled strip of low carbon steel to light-degree cold rolling and to short-time annealing, on the premise that continuous annealing is done, and controlling crystalline grain size. CONSTITUTION:A slab which has a composition consisting of, by weight, <=0.02% C, <=4.0% Si or (Si+Al), <=1.0% Mn, <=0.2% P, and the balance essentially Fe and further containing, if necessary, <=0.10%, in total, of Sb and/or Sn is hot-rolled into a hot rolled steel strip, cold-rolled at 5-15% draft, and annealed so that crystalline grain size is regulated to 100-200mum. Subsequently, one is formed to the final sheet thickness by means of cold rolling and then subjected to final annealing, and the other is cold-rolled at >=50% draft, annealed so that <=20mum crystalline grain size is reached, further cold-rolled at 1-15% draft to the product sheet thickness, and then subjected to final annealing.

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 excellent magnetic properties, and more particularly to a method for producing a non-oriented electrical steel sheet having a high magnetic flux density and a good surface appearance. ..

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are used as iron core materials for rotating machines such as various motors and stationary machines such as transformers and ballasts. Therefore, it is necessary to improve the magnetic flux density and reduce the iron loss of the electrical steel sheet used. By the way, it is known that in order to improve the magnetism of the non-oriented electrical steel sheet, the crystal grains of the steel strip before cold rolling may be coarsened.

As a method of coarsening the crystal grains of a steel strip before cold rolling, the inventors have previously disclosed that when hot rolling an electromagnetic steel material in Japanese Patent Publication No. 57-35628, the end temperature of hot rolling is set to the steel. The temperature above the Ar ₃ transformation point temperature determined by the chemical composition of is not exceeded, and then this hot rolled steel strip is kept at a temperature below the A ₃ transformation point temperature for 30 seconds or more.
We proposed a method of annealing for less than 15 minutes. Further, in Japanese Patent Laid-Open No. 2-182831, the hot rolling finish temperature is set to an Ar ₃ transformation point temperature or higher, and then the hot rolling steel strip is kept at the A ₃ transformation point temperature or lower for 30 to 15 seconds, and then the cooling rate is set. A method of controlling is disclosed.

However, in these methods, there is a case where coarsening of crystal grains does not easily occur on the side where the hot-rolled steel strip annealing time is short, and as a result, there is a defect that the magnetic characteristics are varied.
Further, on the long time side, the crystal grains may become excessively large, and as a result, there is a problem that the product is creased and the surface appearance is impaired. On the other hand, in Japanese Patent Application Laid-Open No. 58-136718, hot rolling is terminated in the γ phase region within a range not exceeding 50 ° C. higher than the Ar ₃ transformation point temperature determined by the composition in the steel as described above, and the winding is performed. A method is disclosed in which the taking temperature is raised from the A ₃ transformation point or lower to 700 ° C. or higher and the ferrite grain size of the hot-rolled steel strip is set to coarse grains of No. 4 or less to improve the magnetism.

Further, in Japanese Patent Laid-Open No. 54-76422, the coiling temperature after hot rolling is set to 750 to 1000 ° C., and the magnetism is improved by recrystallizing to a grain size No. 5 to 6 by self-annealing by the heat retained by the coil. A method for achieving this has been proposed. However, these methods of improving the magnetism by increasing the coiling temperature after hot rolling to 700 ° C or more and increasing the grain size before cold rolling can omit hot-rolled steel strip annealing, but the coiling temperature is high. Since the outer coil and the edge of the coil cool faster than the center of the coil, the temperature difference inside the coil becomes large, and eventually the uniform magnetism cannot be obtained over the entire coil and the acidity of the hot-rolled steel strip. There are defects such as poor descaling property due to washing.

In Japanese Patent Publication No. 452212/1985, a hot rolled steel strip is cold-rolled with a rolling reduction of 0.5 to 15%, and then relatively long in a temperature range from the recrystallization temperature to the A ₃ transformation point. A method is disclosed in which iron loss is improved by annealing for a long time to coarsen the crystal grains of the steel strip before the subsequent cold rolling. However, although the annealing of the hot-rolled steel strip by this method after light cold rolling is relatively low temperature for a short time, 800-850 ° C, 30 minutes-20 hours (the annealing time in each example is 10 hours). Since it is a long-time annealing premised on so-called box annealing, not only is it disadvantageous in terms of manufacturing cost, but the crystal grains sometimes become excessively large with a grain size of No. 2.2, which is a defect that impairs the surface appearance.

Further, in JP-A-1-306523, hot-rolled steel strip is annealed at 850-
It discloses a method of producing a non-oriented electrical steel sheet having a high magnetic flux density by performing the treatment at a temperature of 1000 ° C. for 0.5 to 10 minutes. Although the hot-rolled sheet annealing of this method is performed in a continuous furnace, the annealing time in the example requires a relatively long time of about 2 minutes, and as a result, large equipment is required, which is economically problematic.

As described above, in any of these cases, it is intended to improve the magnetic characteristics by coarsening the crystal grain size before cold rolling, but there is a limit to the improvement of the magnetic characteristics in consideration of the surface appearance and the economical efficiency of the equipment. there were. Further, as a method of manufacturing a semi-processed electromagnetic steel sheet, for example, Japanese Patent Laid-Open No. 1-139721 and Japanese Patent Laid-Open No. 1-191741 disclose 3 to 15% in the final step.
The method of giving a skin pass of the above and making it a product is disclosed. However, the skin pass rolling in the semi-processed material is intended to adjust the hardness of the product, and the annealing after working guarantees the magnetic properties on the premise of long-term retention such as 750 ° C. × 2 hr. Therefore, even if such a semi-processed material was annealed for a short time on the assumption of continuous annealing, it was not possible to stably obtain high magnetic properties.

[0009]

SUMMARY OF THE INVENTION In view of the above problems, the present invention has devised an annealing condition for achieving an appropriate coarsening of crystal grains of a hot rolled steel strip after light cold rolling, It is an object of the present invention to propose a method for producing a non-oriented electrical steel sheet which has a high magnetic property, particularly a high magnetic flux density, and a good surface appearance by controlling the diameter.

[0010]

[Means for Solving the Problems] That is, the present invention contains C: 0.02% or less, Si or Si + Al: 4.0% or less, Mn: 1.0% or less, P: 0.2% or less by weight%, and further Depending on the sum of one or two of Sb and Sn,
A slab containing 0.10% or less of which the balance is substantially Fe is hot-rolled to form a hot-rolled steel strip, and further cold-rolled at a reduction rate of 5 to 15%, and then the grain size is 100 to 200 μm. Is a final sheet thickness by further cold rolling, and is a method for producing a non-oriented electrical steel sheet having excellent magnetic properties and good surface appearance, which is characterized by performing final annealing.
Furthermore, the present invention is, by weight%, C: 0.02% or less, Si or Si + Al: 4.0% or less, Mn: 1.0% or less, P: 0.2.
% Or less, and if necessary, either Sb or Sn 1
A slab containing 0.10% or less of the total of two kinds or less and the balance being substantially Fe is formed into a hot-rolled steel strip by hot rolling, and further subjected to cold rolling with a reduction rate of 5 to 15%, and then crystallized. Annealed to a grain size of 100 to 200 μm, further cold rolled, then annealed to a grain size of 20 μm or less, and then 1
This is a method for producing a non-oriented electrical steel sheet having excellent magnetic properties and a good surface appearance, which is characterized by performing cold rolling up to 15% to obtain a product sheet thickness and then performing final annealing.

In each of the above inventions, the annealing for obtaining a crystal grain size of 100 to 200 μm is performed by heating to a predetermined temperature at a heating rate of 3 ° C./sec or more and holding at the temperature for 5 to 30 seconds for a short time. It is desirable to employ annealing.

[0012]

[Operation] First, the background of the present invention will be described based on experimental results. % By weight, C: 0.010%, Si: 0.15%,
Mn: 0.25%, P: 0.08%, Sb: 0.045%, S: 0.004
%, Al: 0.0008%, and the balance made up of molten steel consisting essentially of Fe was heated to 1250 ° C and hot rolled into a 2.3 mm thick hot rolled strip by ordinary hot rolling. Subsequently, the hot-rolled steel strip was lightly cold-rolled with a rolling reduction of 0 to 20%,
Short-time hot-rolled steel strip annealing was performed at a temperature of 00 ° C for 10 seconds in a continuous furnace. The heating rate at this time was 5 ° C./sec. The A ₃ transformation point temperature of this material was 915 ° C. Then, after pickling and finishing to 0.50 mm thickness by ordinary cold rolling,
A product was manufactured by continuous annealing that combines decarburization and recrystallization in a humid atmosphere at 800 ° C for 75 seconds. FIG. 1 shows the relationship between the magnetic flux density of these products and the cold rolling ratio when the hot-rolled steel strip is subjected to light cold rolling. From this figure, light cold rolling of hot-rolled steel strip can be performed with a reduction ratio of 5
It is clear that the magnetic flux density B _{50 of the} product treated to 15% and subjected to hot-rolled steel strip annealing at 850 to 915 ° C. (A ₃ transformation temperature) is higher than those treated under other conditions. And
The conditions under which this high magnetic flux density B ₅₀ was obtained, that is, the crystals after hot-rolled steel strip annealing at 850 to 915 ° C. for 10 seconds at a rolling reduction of 5 to 15% of hot-rolled steel strip Grain size 100 to 2
It was in the range of 00 μm, and there was no crease on the surface of the product, and the surface appearance was good.

By the way, although the magnetic flux density B ₅₀ was not improved so much, the crystal grains after annealing the hot-rolled steel strip had a grain size of less than 100 μm. Subjected to 5-15% of the light cold-rolled to a hot rolled strip, as described above, subsequent 850 to 915 ° C. In the hot rolled strip annealing (A ₃ transformation temperature), relatively high temperatures and short time of 10 seconds The reason that the magnetic flux density is improved in the process (1) is that the crystal grains grow into coarse grains due to the hot-rolled steel strip annealing, and as a result, the texture of the product can be improved. Further, the reason why the crystal grains are coarsened by annealing the hot-rolled steel strip is that the strain necessary for coarsening (abnormal growth) is applied to the hot-rolled steel strip by light cold rolling.

Furthermore, another experimental result will be shown. weight%
, C: 0.010%, Si: 0.15%, Mn: 0.25%, P: 0.08
%, Sb: 0.045%, S: 0.004%, Al: 0.0008%, and the balance is a slab made of molten steel consisting essentially of Fe at 1250 ° C.
Then, the hot-rolled steel strip having a thickness of 2.3 mm was formed by ordinary hot rolling. Subsequently, after performing a light cold rolling with a reduction rate of 10%, a short-time annealing for 10 seconds at a temperature of 915 ° C. was performed in a continuous furnace. The heating rate at this time was changed in the range of 1 to 5 ° C./sec. Observe the crystal grains after annealing the hot-rolled steel strip and confirm that the grain size is 200μ.
FIG. 2 shows the relationship between the heating rate and the ratio (area ratio) of grains coarser than m. When the number of coarse particles is large, the product plate is likely to be wrinkled. The state of occurrence of folds and wrinkles in the product plate is also shown, but it is clear from the figure that increasing the heating rate to reduce the proportion of coarse particles is advantageous for improving the surface properties.

It has been confirmed that even if the heating temperature is 850 ° C. or less, if the crystal grains can be coarsened to 100 μm or more by prolonging the annealing time, the same effect can be obtained. Next, the conditions of cold rolling / annealing subsequent to annealing of the hot rolled steel sheet will be described. Using a hot-rolled steel sheet having the same composition as the hot-rolled steel sheet described above, after performing 10% light cold rolling, in the hot-rolled steel sheet annealing,
Hold at a temperature of 900 ° C for 10 seconds. The crystal grain size at this time is
It was 120 μm. The annealed plate is cold rolled to 0.50
~ 0.65mm thickness. Then, it is annealed at 600 to 750 ℃ to make the crystal grain size 10 to 30 μm, and light cold rolled to 0 to 20% to give 0.50.
The product was finished to a thickness of mm and then annealed in a humid atmosphere at 800 ° C for 60 seconds to combine decarburization.

FIG. 3 shows the relationship between the magnetic flux density of these products, the crystal grain size after cold rolling annealing, and the reduction ratio in light cold rolling. As can be seen, during cold rolling / annealing after hot-rolled steel sheet annealing, B ₅₀ of a product having a grain size of 20 μm or less after cold-rolling annealing and a reduction ratio of 1 to 15% in light cold rolling is another condition. It is clear that it is higher than that of The product surface with high magnetic flux density was good without unfolding.

As described above, the magnetic flux density is improved by controlling the crystal grain size after the cold rolling annealing subsequent to the annealing of the hot rolled steel sheet and the cold rolling reduction ratio after that, and the crystal rotation and the orientation during grain growth. This is the effect of improving the texture by selection. Next, the reason why the light cold rolling of the hot rolled steel sheet is limited to the rolling reduction of 5 to 15% in the present invention will be described. When the hot-rolled steel sheet annealing following the light cold-rolling of the hot-rolled steel sheet is carried out at a relatively high temperature for a short time holding treatment or at a low temperature for a long time treatment, distortion is insufficient if the rolling reduction is less than 5%, and the hot rolled steel sheet The grain size does not reach 100 μm and the magnetic flux density cannot be improved because the grain size is not sufficiently coarsened during annealing. When the rolling reduction exceeds 15%, the same as in ordinary cold rolling, and the grain size becomes 1 after annealing of hot-rolled steel sheet.
This is because it will not be 00 μm.

Further, in the present invention, it is preferable that the heating rate is 3 ° C./sec or more in hot strip annealing. This is because if the heating rate is less than 3 ° C./sec, some grain growth occurs during heating, and uniform and appropriate grain growth does not occur when held at a relatively high temperature for a short time, and mixed grains tend to form. A more preferable heating rate is 5 ° C./sec or more. Next, the reason for limiting the crystal grain size of the hot rolled steel strip to 100 to 200 μm after cold rolling under light reduction and annealing to the hot rolled steel strip will be explained.

If the particle size exceeds 200 μm, the surface appearance of the product sheet is impaired, so in this case the particle size of 200 μm was made the upper limit.
In order to improve the magnetic properties, the lower limit is 100 μm.
And need to. The annealing conditions in this case are 5 to 30 at a relatively high temperature of 850 ° C. or higher and A ₃ transformation point or less when using a continuous annealing furnace which is advantageous in terms of manufacturing cost and quality stability.
A short time treatment of seconds is preferred. In this case, if the temperature is lower than 850 ° C, the grain growth becomes insufficient and the magnetic flux density cannot be sufficiently improved.

Further, the hot-rolled steel strip annealing temperature is from 850 ° C to
In the case of the A ₃ transformation point, if it is less than 5 seconds, the coarsening of the crystal grains is insufficient and the grain size does not reach 100 μm, so that the magnetic flux density is not improved much. If the holding time exceeds 30 seconds, the crystal grains become too coarse and the grain size becomes larger than 200 μm. As a result, although the magnetic flux density is improved, creases are generated on the product surface and the surface appearance is impaired. There is a problem that this tatami wrinkle causes a decrease in space factor.

Further, as described above, the crystal grain size is 100 to 2
After annealing to 00 μm, it was further cold-rolled and then annealed to a grain size of 20 μm or less.
It is also an aspect of the present invention to carry out final annealing after cold rolling to 15% to give a product sheet thickness. When the crystal grain size is reduced to 20 μm or less by intermediate cold rolling and annealing, the crystal rolling occurs due to the subsequent cold rolling under light pressure, and the subsequent final annealing suppresses the growth of (111) oriented grains that are disadvantageous to the magnetic properties. On the other hand, the upper limit was set in this way as a result of a detailed experiment because the grains tend to be eaten by silkworms.

Further, the light reduction cold rolling performed after the annealing for adjusting the grain size requires a reduction rate of 1% or more in order to improve the texture described above. However, if it exceeds 15%, recrystallization often occurs as in the case of normal cold rolling, so texture improvement that leads to improvement of magnetic properties cannot be expected. Next, the reasons for limiting the material components in the present invention will be described.

When C exceeds 0.02%, not only is it harmful to magnetism, but also decarburization is unsatisfactory during final annealing, which is disadvantageous for non-aging. Therefore, C is set to 0.02% or less. Si or Si + Al has a high specific resistance, and if the amount is increased, the iron loss decreases and the saturation magnetic flux density decreases. Therefore, iron loss
This amount is adjusted according to the magnetic flux density requirement. But,
If the Si + Al content exceeds 4.0%, the cold rolling property is significantly impaired, so the upper limit is 4%.

Since the magnetic flux density of Sb and Sn is improved by the improvement of the texture, it is desirable to add Sb and Sn as needed in order to obtain a particularly high magnetic flux density. Then Sb and Sn
If the total of one or two of them exceeds 0.10%, the magnetic properties are rather deteriorated. Therefore, the content is limited to 0.10% or less even when either of them is used alone or in combination. Mn is added as a deoxidizer or to control hot embrittlement due to S, but if it exceeds 1.0%, the cost increases, so Mn is 1.
0% or less.

P may be added in order to increase hardness and punchability, but if it exceeds 0.20%, it becomes brittle, so it is necessary to make it 0.20% or less. Next, examples of the present invention will be described. Note that Examples 1 to 5 correspond to the invention of claim 1, and Examples 6 to 9 correspond to the invention of claim 2, respectively.

[0026]

【Example】

Example 1 Molten steel in a converter and vacuum degassed molten steel are continuously cast,
Made slabs 1-9. Their chemical composition is C:
0.006%, Si: 0.35%, Mn: 0.25%, P: 0.08%, Al:
The balance was 0.0009% and the balance was essentially Fe. The slabs were hot rolled into ordinary hot rolled steel strips with a thickness of 2.3 mm. The A ₃ transformation point of the hot rolled steel strip was 955 ° C.

Subsequently, the hot-rolled steel strip was lightly and cold rolled, and then hot-rolled steel strip was annealed. Table 1 shows the cold rolling rate and the annealing conditions. Then, it was finished by cold rolling once to a thickness of 0.50 mm, and subsequently subjected to decarburization / recrystallization annealing at 850 ° C. for 75 seconds to obtain a product. Table 2 shows the results of measuring the magnetism of these products and the stress after strain relief annealing at 750 ° C for 2 hours with Epstein test pieces.
From these, if the reduction ratio of the hot-rolled steel strip and the annealing conditions of the hot-rolled steel strip are set to appropriate ranges as in the conformity example of the present invention,
After the hot-rolled steel strip is annealed, the crystal grains are appropriately coarsened, and as a result,
It is clear that the texture of the product can be improved and that the magnetic flux density B ₅₀ is high and the surface appearance is good.

[0028]

[Table 1]

[0029]

[Table 2]

Example 2 As in Example 1, C: 0.007%, Si: 1.0%, Mn: 0.
30%, P: 0.018%, Al: 0.30%, the balance is substantially
I made a slab that is Fe from 10 to 15. Then, a hot rolled steel strip having a thickness of 2.0 mm was formed by ordinary hot rolling. The A ₃ transformation point of these hot-rolled steel strips was 1050 ° C.

Subsequently, the hot-rolled steel strip was lightly and cold-rolled, and then hot-rolled steel strip was annealed. Table 3 shows those conditions. Next, after performing one cold rolling to a thickness of 0.50 mm,
The product was decarburized and recrystallized at 75 ° C for 75 seconds. Table 4 shows the results of measuring the magnetic properties of these products and the stress after annealing for 2 hours at 750 ° C with an Epstein test piece. From these, it is apparent that the conforming example of the present invention has a particularly excellent magnetic flux density and a good surface appearance as compared with the comparative example.

[0032]

[Table 3]

[0033]

[Table 4]

Example 3 Molten steel melted in a converter and subjected to vacuum degassing was continuously cast,
Made 16 to 22 slabs. Their chemical composition is C: 0.0
05%, Si: 0.33%, Mn: 0.25%, P: 0.07%, Al: 0.00
The balance was 08%, Sb: 0.050%, and the balance was essentially Fe. The slabs were hot rolled into ordinary hot rolled steel strips with a thickness of 2.3 mm. The A ₃ transformation point temperature of the hot rolled steel strip was 950 ° C.

Subsequently, the hot rolled steel strip is lightly and cold rolled,
Hot-rolled steel strip annealing was performed in a continuous furnace. Table 5 shows the cold rolling ratio and the annealing conditions. Next, it was finished by cold rolling once to a thickness of 0.50 mm, and then subjected to decarburization and recrystallization annealing at 810 ° C for 60 seconds to obtain a product. Table 6 shows the results of measuring the magnetism of these products and the stress after annealing for 2 hours at 750 ° C with an Ebstein sample. From these, if the reduction ratio of the hot-rolled steel strip and the subsequent hot-rolled steel strip annealing conditions are set in an appropriate range as in the conformity example of the present invention, a magnetic steel sheet having a particularly high magnetic flux density and a good surface appearance can be obtained. It is clear.

[0036]

[Table 5]

[0037]

[Table 6]

Example 4 As in Example 3, C: 0.008%, Si: 1.1%, Mn: 0.
Slab of 23 to 28 from molten steel consisting of 28%, P: 0.018%, Al: 0.31%, Sn: 0.055% and the balance being essentially Fe, C: 0.007%, Si: 1.1%, Mn: 0.30% , P: 0.019
%, Al: 0.30%, Sb: 0.03%, Sn: 0.03%, the balance is made of molten steel consisting of substantially 29% to 31% slab, and hot-rolled steel strip with a thickness of 2.0 mm is produced by normal hot rolling. And The A ₃ transformation point of 23 to 28 hot rolled steel strips is 1045 ℃ and the A ₃ transformation temperature of 29 to 31 hot rolled steel strips is A ₃
The transformation point was 1055 ° C.

Subsequently, the hot-rolled steel strip was lightly and cold-rolled, and then hot-rolled steel strip was annealed in a continuous furnace. Table 7 shows these light cold rolling and hot strip annealing conditions. Next, in one cold rolling, 0.
After finishing to a thickness of 50 mm, it was decarburized and recrystallized at 830 ° C for 75 s to obtain a product. Those products and 750 ℃,
Table 8 shows the results of measuring the magnetism after strain relief annealing of 2 Hr with an Epstein test piece.

From these, it is apparent that the conforming example of the present invention has a particularly excellent magnetic flux density and a good surface appearance as compared with the comparative example.

[0041]

[Table 7]

[0042]

[Table 8]

Example 5 C: 0.002%, Si: 3.26%, Mn: 0.14%, P: 0.02%,
Al: A molten steel containing 0.61% and the balance consisting essentially of Fe 32 to 32
37 slabs, C: 0.003%, Si: 3.31%, Mn: 0.
A slab of 38-41 from molten steel consisting of 15%, P: 0.02%, Al: 0.59%, Sb: 0.06% and the balance consisting essentially of Fe, and C: 0.002%, Si: 3.33%, Mn: 0.16%. , P: 0.02%,
A slab of 42 to 45 was made from molten steel consisting of Al: 0.62%, Sb: 0.03%, Sn: 0.04% and the balance consisting essentially of Fe, and a hot rolled steel strip with a thickness of 2.0 mm was formed by normal hot rolling. .. These 32-45 hot-rolled steel strips were untransformed steels.

Subsequently, the hot-rolled steel strip was lightly and cold-rolled, and then hot-rolled steel strip was annealed in a continuous furnace. Table 9 shows these light cold rolling and hot strip annealing conditions. Next, in one cold rolling, 0.
After finishing to a thickness of 50 mm, recrystallization annealing was performed at 1000 ° C for 30 seconds to obtain a product. Table 10 shows the results of measuring the magnetism of these products and the stress after strain relief annealing at 750 ° C x 2 hr using Epstein test pieces. From these, it is apparent that the conforming example of the present invention has a lower iron loss and a better surface appearance as the magnetic flux density improves, as compared with the comparative example.

[0045]

[Table 9]

[0046]

[Table 10]

Example 6 Molten steel melted in a converter and vacuum degassed was continuously cast,
Slavic. This C: 0.007%, Si: 0.15%, Mn: 0.
25%, P: 0.03%, Al: 0.0008% including the balance
The slab of Fe was hot rolled into a hot rolled steel sheet of 2.0 mm. A ₃ transformation point of the steel plate was 920 ° C..

This hot-rolled sheet is treated under the cold-rolling annealing conditions shown in Table 11 to obtain a structure having a crystal grain size shown in Table 11. Furthermore, after cold-rolling this to a thickness of 0.50 to 0.60 mm under heavy rolling, 60
Annealed at 0-800 ° C. Table 11 also shows the crystal grain size at that time. Furthermore, at the cold rolling reduction rate as shown in Table 11, 0.50 mm
Finished to a thick product thickness and decarburized and annealed at 800 ℃ for 75s to obtain a product.

The results and surface properties of these products measured with Epstein test pieces are also shown in Table 11. In addition, as a comparative example, a case in which a product is obtained by annealing after the second cold rolling is also included. It is apparent that the examples of the present invention are superior to the comparative examples in terms of magnetic flux density and surface properties.

[0050]

[Table 11]

Example 7 Molten steel melted in a converter and subjected to vacuum degassing was continuously cast,
Slavic. This C: 0.006%, Si: 0.18%, Mn: 0.
A slab containing 25%, P: 0.003%, Al: 0.0011%, and Sb: 0.06%, and the balance being substantially Fe was formed into a 2.0 mm hot-rolled steel sheet by ordinary hot rolling. The A ₃ transformation point of this steel sheet is
It was 925 ° C.

This hot-rolled sheet is treated under the cold-rolling annealing conditions shown in Table 12 to obtain a structure having a crystal grain size shown in Table 12. Furthermore, after cold rolling this to a thickness of 0.50 to 0.60 mm, 600 to 8
Annealed at 00 ° C. Table 12 also shows the crystal grain size at that time. Further, at a cold rolling reduction rate as shown in Table 12, a product thickness of 0.50 mm was finished, and decarburization annealing was performed at 800 ° C for 75 s to obtain a product.

Table 12 shows the results and surface properties of these products measured with Epstein test pieces. In addition, as a comparative example, a case in which a product is obtained by annealing after the second cold rolling is also included. It is apparent that the examples of the present invention are superior to the comparative examples in terms of magnetic flux density and surface properties.

[0054]

[Table 12]

Example 8 Molten steel melted in a melting furnace and vacuum degassed is continuously cast,
Slavic. This C: 0.008%, Si: 0.35%, Mn: 0.
35%, P: 0.05%, Al: 0.0012%, Sb: 0.05%, Sn: 0.
A slab containing 03% and the balance being substantially Fe was made into a 2.0 mm hot rolled steel sheet by ordinary hot rolling. A ₃ transformation point of the steel plate was 940 ° C..

This hot-rolled sheet is treated under the cold-rolling annealing conditions shown in Table 13 to obtain a structure having a crystal grain size shown in Table 13. Furthermore, after cold rolling this to a thickness of 0.50 to 0.60 mm, 600 to 80
Annealed at 0 ° C. Table 13 also shows the crystal grain size at that time. Further, at a cold rolling reduction ratio as shown in Table 13, a product thickness of 0.50 mm was finished, and decarburization annealing was performed at 800 ° C for 75 s to obtain a product.

Table 13 also shows the results and surface properties of these products measured with Ebstein test pieces. In addition, as a comparative example, a case in which a product is obtained by annealing after the second cold rolling is also included. It is apparent that the examples of the present invention are superior to the comparative examples in terms of magnetic flux density and surface properties.

[0058]

[Table 13]

Example 9 Molten steel melted in a converter and vacuum degassed is continuously cast,
Slavic. Slabs 97 to 101 have C: 0.002%, S
i: 3.31%, Mn: 0.16%, P: 0.02%, Al: 0.64%, and the balance consists essentially of Fe. The slabs of 102-106 are
C: 0.003%, Si: 3.25%, Mn: 0.15%, P: 0.02%,
Al: 0.62%, Sb: 0.05% are included, and the balance is substantially Fe.

The slabs of 107 to 111 have C: 0.002% and Si:
3.28%, Mn: 0.17%, P: 0.02%, Al: 0.58%, Sb: 0.
03%, Sn: 0.04% included, and the balance consisting essentially of Fe. The above slab was subjected to normal hot rolling to obtain a 2.0 mm hot rolled steel sheet. These steel sheets have not been transformed. This hot-rolled sheet is treated under the cold-rolling annealing conditions shown in Table 14 to obtain a structure having a crystal grain size shown in Table 14. Furthermore, this is 0.50-0.60mm
After cold rolling, it was annealed at 600 to 800 ° C. Table 14 also shows the crystal grain size at that time. Further, the product was finished by cold rolling reduction as shown in Table 14 to a product thickness of 0.50 mm and subjected to recrystallization annealing at 1000 ° C. for 30 s to obtain a product. Table 14 also shows the results and surface properties of these products measured with Epstein test pieces.

[0061]

[Table 14]

[0062]

As described above, the light-rolled steel strip is appropriately lightly and cold-rolled, and the hot-rolled steel strip is annealed to obtain proper crystal grains, or further, annealing after cold-rolling and light reduction are combined. By doing so, a non-oriented electrical steel sheet having a particularly high magnetic flux density and a good surface appearance can be manufactured stably at low cost.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a magnetic flux density B ₅₀ and a cold rolling rate of a hot rolled steel strip.

FIG. 2 is a graph showing a relationship between a heating rate and a ratio of coarse particles after annealing a hot rolled sheet.

FIG. 3 is a graph showing the relationship between the cold rolling rate before final annealing, the crystal grain size before that, and the magnetic flux density of the product.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takashi Obara 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (72) Hideo Kobayashi 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. (72) Inventor Kazumi Morita 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (no house number) Inside the Mizushima Steel Works, Kawasaki Steel Co., Ltd. (72) In-house Yoshiaki Iida, 1-chome, Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture Shi) Inside Kawashima Steel Co., Ltd. Mizushima Steel Works

Claims (4)

[Claims] 1. By weight%, C: 0.02% or less, Si or
A slab containing Si + Al: 4.0% or less, Mn: 1.0% or less, P: 0.2% or less, and the balance being substantially Fe, is hot-rolled into a hot-rolled steel strip, which is cold-rolled at a reduction rate of 5 to 15%. After rolling, it is annealed so that the grain size becomes 100-200 μm, and then cold-rolled to the final plate thickness, followed by final annealing, which has excellent magnetic properties and good surface appearance. Manufacturing method of grain-oriented electrical steel sheet. 2. C: 0.02% or less by weight%, Si or
A slab containing Si + Al: 4.0% or less, Mn: 1.0% or less, P: 0.2% or less, and the balance being substantially Fe, is hot-rolled into a hot-rolled steel strip, which is cold-rolled at a reduction rate of 5 to 15%. After rolling, annealing is performed to obtain a crystal grain size of 100 to 200 μm, further cold rolling is performed, annealing is performed to reduce the grain size to 20 μm or less, and cold rolling of 1 to 15% is performed. A method for producing a non-oriented electrical steel sheet having excellent magnetic properties and good surface appearance, which is characterized by performing final annealing after making the sheet thickness. 3. Annealing with a crystal grain size of 100 to 200 μm is performed by heating to a predetermined temperature at a heating rate of 3 ° C./sec or more,
The method for producing a non-oriented electrical steel sheet having excellent magnetic properties and good surface appearance according to claim 1 or 2, characterized in that the annealing is performed for a short time at the temperature for 5 to 30 seconds. 4. The slab composition, in% by weight, C: 0.02% or less, Si or Si + Al: 4.0% or less, Mn: 1.0% or less,
P: 0.2% or less, the sum of one or two of Sb and Sn is 0.10% or less, and the balance consists essentially of Fe, The magnetic material according to claim 1, 2 or 3. A method for producing a non-oriented electrical steel sheet with excellent characteristics and good surface appearance.