JP3399726B2 - Manufacturing method of non-oriented electrical steel sheet with high magnetic flux density and low iron loss - Google Patents

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 high magnetic flux density low iron loss non-oriented electrical steel sheet used as a core material for electric equipment.

[0002]

2. Description of the Related Art As an example of introducing a strain into a hot rolled sheet to heat-treat it to coarsen the grain size before cold rolling, JP-A-61-278818.
Japanese Patent Laid-Open No. 2-213418.
Japanese Patent Application Laid-Open No. 61-127818 discloses that a hot-rolled sheet is shot by using a peening machine or hard particles embedded on the outer periphery of a pinch roll of a hot-roll winder are used to give a working impression. , Aims to improve the magnetic properties.

Further, in Japanese Patent Laid-Open No. 2-213418, a slight reduction is applied before hot-rolled sheet annealing to improve grain growth during hot-rolled sheet annealing. However, this is done by using a special roll or peening machine, which not only increases the cost but also impairs the appearance of the product. Also,
In Japanese Patent Laid-Open No. 62-102506, the magnetic characteristics are improved by controlling the heating / cooling rate during annealing of the hot rolled sheet, but this method alone has little effect of improving the magnetic characteristics.

[0004]

As described above, the conventional technique of introducing working strain into the steel sheet at the time of hot rolling or regulating the heating rate / cooling rate during annealing of the hot rolled sheet has sufficient magnetic properties. However, it also leads to higher costs. Magnetic properties are sufficiently improved, and at low cost, in hot-rolled sheet annealing or self-annealing, strain is used as a driving force to grow crystal grains to coarsen the grain size before cold rolling, thereby proactively improving magnetic properties. A technique related to a method for manufacturing a non-oriented electrical steel sheet that is improved to the above has not yet been disclosed. In view of the above problems, the present invention provides a method for manufacturing a high magnetic flux density low iron loss non-oriented electrical steel sheet.

[0005]

According to the present invention, a working strain is introduced into a steel sheet at the time of winding after hot rolling, and the hot rolling condition is controlled as necessary so that the strain is caused during the subsequent hot rolled sheet annealing or self-annealing. Is used as a driving force to grow crystal grains, at which time the cooling rate is controlled to coarsen the grain size before cold rolling, thereby positively improving the magnetic properties.

The gist of the present invention is C ≦ 0.01 in% by weight.
0%, 0.1% ≦ Si ≦ 4.0%, Mn ≦ 1.5%, A
1 ≦ 1.5%, P ≦ 0.1%, S ≦ 0.01%, N ≦
Steel containing 0.01% and the balance Fe and unavoidable impurities is hot-rolled, then hot-rolled sheet is annealed, and cold rolled one or more times with intermediate annealing to obtain the final thickness. In the method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet, which is subjected to finish annealing, the temperature during winding after hot rolling is set to 8
Coil temperature is 00 ° C or less, coil outer diameter is 2700 mm or less, and plate thickness is 1.
2 mm or more, and the subsequent hot-rolled sheet annealing temperature is above the recrystallization temperature.
Within 5 minutes, the average crystal grain size should be 50 μm or more, and the heating rate
Is 10 ° C / sec or more and the cooling rate is 100 ° C / sec or less
The cold rolling ratio is 70 to 90%, and the method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet is provided.

When hot-rolled sheet annealing is carried out , preferably , when 1.7% <Si ≦ 4.0%, the hot-rolled sheet annealing temperature is set to the recrystallization temperature or more and 1200 ° C. or less, and 0.1% ≦ Si
When ≤1.7%, the annealing temperature is set to be not lower than the recrystallization temperature and not higher than Ac ₁ point. When performing self-annealing,
Annealing temperature is above recrystallization temperature within 5 hours, cooling rate is 1
It is to be set to 00 ° C / sec or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION First, the reasons for limiting the components of the present invention will be described. C is a harmful component that increases iron loss and causes magnetic aging, so is made 0.010% or less. S
As is well known, i is an element effective in reducing iron loss, and in order to obtain this effect, it is necessary to contain 0.1% or more. On the other hand, if the content thereof increases, the magnetic flux density decreases, rolling workability deteriorates, the finish annealing temperature rises, and the cost increases, so it is made 4% or less.

Like Mn, Mn is an element effective for reducing iron loss, but if it exceeds 1.5%, the magnetic flux density decreases, so it is made 1.5% or less. Further, in order to exert this effect, 0.2% or more is preferable. Al, like Si, has the effect of increasing the specific resistance and reducing the iron loss, so it may be contained, but in the present invention, the specific resistance may be increased by Si, so there is no particular lower limit. On the other hand, when the Al content is increased, the magnetic flux density is reduced like Si, so the content is made 1.5% or less.

If P exceeds 0.1%, iron loss is deteriorated, so P is made 0.1% or less. When S exceeds 0.01%, sulfides such as MnS are finely precipitated, which hinders grain growth during finish annealing and deteriorates iron loss, so S is made 0.01% or less. If N exceeds 0.01%, nitrides such as AlN are finely precipitated, which hinders grain growth during finish annealing and deteriorates iron loss, so N is set to 0.01% or less. B is effective for fixing N by fixing N. If it is less than 2 ppm, there is no addition effect, and if it exceeds 20 ppm, the effect saturates.

Conventionally used as elements for improving texture, Sn ≦ 0.2%, Sb ≦ 0.3%, Ni ≦
Addition of 3% does not impair the effects of the present invention. The same applies to the addition of Cr ≦ 3%, which improves rust resistance. Other than the above components, they are iron and inevitable impurity elements.

Next, the reasons for limiting the manufacturing conditions will be described. The action of annealing the hot-rolled sheet or self-annealing with the coil outer diameter of 2700 mm or less and the sheet thickness of 1.2 mm or more will be described below. First, set the outer diameter of the coil during hot rolling to 27
The reason why the thickness is set to 00 mm or less and the plate thickness is 1.2 mm or more is shown below.

C: 0.002%, Si: 3.10%, M
n: 0.20%, Al: 0.4%, P: 0.014%,
Steel with a composition of S: 0.0018% and N: 0.0014% is finished to a plate thickness of 2.0 mm at a hot rolling finishing temperature of 850 ° C.,
A hot-rolled sheet was produced under the condition of a coiling temperature of 680 ° C, and after cooling, the steel was bent on a cylinder having a changed outer diameter, annealed at 950 ° C, and cooled at 10 ° C / sec. did. Then 0.5
It was cold-rolled to a plate thickness of mm and finish-annealed at 800 ° C. The result is shown in FIG. It can be seen from FIG. 1 that the magnetic characteristics are improved by setting the outer diameter of the coil after winding the hot rolled plate to 2700 mm or less.

In addition, in FIG. 2, for steel manufactured in the same manner as in FIG. 1, the plate thickness after hot rolling was changed so that the coil outer diameter was 1000.
The change in B ₅₀ value when mm is shown. It can be seen that the magnetic characteristics are improved by setting the plate thickness of the coil after winding the hot rolled plate to 1.2 mm or more.

Although the details are not clear, it is considered that plastic strain is introduced into the hot rolled sheet when the outer diameter of the hot rolled sheet exceeds a certain value and the sheet thickness exceeds a certain value. In other words, the amount of strain introduced during winding is 2700 mm for the outer diameter of the coil.
Hereinafter , it is considered that the magnetic properties are improved by increasing the plate thickness to 1.2 mm or more, and the strain thereof becomes the driving force for grain growth in the heat treatment of the hot-rolled plate following the winding, and the crystal grain size becomes coarse. Thereby, good magnetic characteristics can be obtained over the entire length of the coil.

The temperature at the time of winding after hot rolling is set to 800 ° C. or lower,
The subsequent hot-rolled sheet annealing temperature is set to 5 minutes or more at the recrystallization temperature or higher so that the average crystal grain size is coarsened to 50 μm or more in the hot-rolled sheet annealing by using the strain introduced at the time of winding after hot rolling as a driving force. This is because the magnetic properties after finish annealing are significantly improved. When there is transformation, the hot-rolled sheet annealing temperature is preferably the recrystallization temperature or higher (0.1% ≦ Si ≦ 1.7%) and the Ac ₁ point or lower at which transformation does not occur. When there is no transformation (1.7% <Si ≦ 4.0%), the upper limit of 1200 ° C. is desirable in terms of cost.

It is desirable that the temperature at the time of winding after hot rolling is 1000 ° C. or less and the self-annealing temperature is at least the recrystallization temperature and within 5 hours, with the strain introduced at the time of winding after hot rolling as the driving force. , Average grain size of 50μm in hot-rolled sheet annealing
This is because the coarsening as described above significantly improves the magnetic characteristics after finish annealing.

By setting the heating rate at 10 ° C./sec or more and the cooling rate at 100 ° C./sec or less at the time of hot-rolled sheet annealing and the cooling rate at 100 ° C./sec or less at the time of self-annealing, cold rolling and finish annealing are performed. Magnetic properties are improved. The reason for this is not clear, but it is presumed that it is because an orientation preferred for magnetic properties is formed.

The reason why the hot-rolled sheet annealing time is within 5 minutes and the self-annealing time is within 5 hours is because the cost is increased if the time is longer than that. The hot rolling finishing temperature is set to Ar ₃ point or higher, the coiling temperature after hot rolling is set to Ar ₃ point or lower, and the coil outer diameter is 2
The effect of the present invention can be further enhanced by setting the thickness to 700 mm or less and the plate thickness to 1.2 mm or more, and the subsequent hot-rolled sheet annealing temperature to 800 ° C. or more and Ac ₁ point or less.

The effects of the present invention can be further enhanced by controlling the hot rolling conditions. Cold rolling rate is 7
A preferred orientation can be obtained at 0 to 90%. As described above, the feature of the present invention is to define the coil outer diameter at the time of hot rolling winding, the crystal grain size at the time of subsequent hot rolling processing, and the driving force of the plastic strain introduced at the time of hot rolling winding. As a result, the non-oriented electrical steel sheet having excellent magnetic properties is manufactured by coarsening.

[0021]

【Example】

(Example 1) A steel having the components as shown in Table 1 was subjected to a hot rolling coiling temperature of 740 ° C and a hot rolled sheet annealing temperature of 950 ° C x 2 minutes or 830 ° C x 2 minutes to obtain a hot rolled finished sheet. Thickness is 1.1 mm
Or 2mm, coil outer diameter 2500mm or 280
Table 1 shows the magnetic properties of the steel changed to 0 mm after finishing at a cold rolling rate of 75% and then finish annealing. It can be seen that all show excellent magnetic properties within the conditions of the present invention.

[0022]

[Table 1]

(Embodiment 2) Steels having the components shown in Table 2 were set to have a hot rolling coiling temperature of 740 ° C. and a hot rolled sheet annealing temperature of 9
When 50 ° C x 2 minutes or 830 ° C x 2 minutes, hot rolling finish sheet thickness is changed to 2 mm and coil outer diameter is changed to 1200 mm. Table 2 shows the magnetic characteristics of the. It can be seen that in both cases, both the heating rate and the cooling rate exhibit excellent magnetic properties within the conditions of the present invention.

[0024]

[Table 2]

Example 3 Steels having the components shown in Table 3 were heated to 740 ° C. at a hot rolling coil temperature and 9 at a hot rolled sheet annealing temperature.
Table 3 shows the magnetic properties when 50 ° C. × 2 minutes or self-annealing was performed at 830 ° C. for 60 minutes, and finish annealing was performed on steel having a hot rolled finish sheet thickness of 2 mm and a coil outer diameter of 1200 mm. It can be seen that in all cases, the cold rolling ratio exhibits excellent magnetic properties within the conditions of the present invention.

[0026]

[Table 3]

(Example 4) The magnetic properties of steels having the components shown in Table 4 when finish annealing was performed on steels having a hot rolled finished plate thickness of 2 mm and a coil outer diameter of 1200 mm were changed to Table 4 Shown in. It can be seen that in all cases, the crystal grain size was 50 μm or more, and the cold rolling ratio exhibited excellent magnetic properties within the conditions of the present invention.

[0028]

[Table 4]

[0029]

According to the present invention, an excellent high magnetic flux density, low iron loss non-oriented electrical steel sheet is obtained, and with the efficiency and miniaturization of electrical equipment, the non-oriented electrical steel sheet used as the iron core material thereof. Can fully meet the demand, and its industrial value is very large.

[Brief description of drawings]

FIG. 1 is a chart showing the relationship between magnetic flux density (B ₅₀ ) and iron loss value (W _15/50 ) when the coil outer diameter is changed.

FIG. 2 is a chart showing changes in B ₅₀ value when the plate thickness of a hot rolled plate is changed.

Front page continuation (72) Inventor Shinichi Kanao 1-1 Hibahata-cho, Tobata-ku, Kitakyushu City Nippon Steel Corporation Yawata Works (56) References JP-A-8-92643 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (4)

(57) [Claims] 1. By weight%, C ≦ 0.010%, 0.1% ≦ Si ≦ 4.0%, Mn ≦ 1.5%, Al ≦ 1.5%, P ≦ 0.1%, S ≦ 0.01%, N ≦ 0.01%, and the balance being Fe and unavoidable impurities, hot-rolled steel is subjected to hot-rolled sheet annealing once or twice with intermediate annealing. In the method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet, which is subjected to finish annealing after the final thickness is obtained by the cold rolling as described above, the temperature after hot rolling is 800 ° C or less and the coil outer diameter is 2700 mm or less, sheet thickness 1.2 mm or more, subsequent annealing temperature of hot rolled sheet is 5 minutes or more at recrystallization temperature or more, average grain size is 50 μm or more, and heating rate is 10
A method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet, characterized in that the cooling rate is 70 ° C / sec or more, the cooling rate is 100 ° C / sec or less, and the cold rolling rate is 70 to 90%. 2. The content of 1.7% <Si ≦ 4.0% by weight, and the annealing temperature of the hot rolled sheet is not less than the recrystallization temperature and is 1200 ° C.
The method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet according to claim 1, wherein: In wherein wt%, 0.1% ≦ Si ≦ 1.7 %, containing, according to claim 1, characterized in that the less recrystallization temperature or higher Ac ₁ point of the hot-rolled sheet annealing temperature Of manufacturing high magnetic flux density low iron loss non-oriented electrical steel sheet of. 4. In% by weight, C ≦ 0.010%, 0.1% ≦ Si ≦ 4.0%, Mn ≦ 1.5%, Al ≦ 1.5%, P ≦ 0.1%, S ≦ 0.01%, N ≦ 0.01%, and the balance being Fe and unavoidable impurities, steel is hot-rolled and then subjected to self-annealing once or twice or more with intermediate annealing. After making the final plate thickness by cold rolling,
In a method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet for which finish annealing is performed, the temperature after winding after hot rolling is 1000 ° C or less, the coil outer diameter is 2700 mm or less, and the plate thickness is 1.2 mm or more. The self-annealing temperature is above the recrystallization temperature within 5 hours, the average crystal grain size is above 50 μm, and the cooling rate is 10
A method for producing a high magnetic flux density low iron loss non-oriented electrical steel sheet, which is set to 0 ° C./sec or less and a cold rolling rate of 70 to 90%.