JPH06228644A - Production of silicon steel sheet for compact stationary device - Google Patents

Abstract

PURPOSE:To provide the method for producing a silicon steel sheet for a compact stationary device excellent in low magnetic field properties. CONSTITUTION:Steel stock contg. <=0.005% C, <=0.005% N, <=1.0% Mn, <=0.006% S and >=0.1% sol.Al and satisfying (Si+sol.Al) <2.0% is subjected to hot rolling at 700 to 850 deg.C and is thereafter coiled at <=600 deg.C. Before or after descaling, it is annealed at 700 deg.C to the A3 transformation point and is furthermore subjected to single cold rolling at <=80% draft. After that, its temp. is raised at >=100 deg.C/sec heating rate, and annealing is executed at 750 deg.C to the A3 transformation point. The compsn. of the same steel may be constituted of <=0.005% C, <=0.005% N, <=1.0% Mn, <=0.006% S and <=0.003% sol.Al, and (Si+sol.Al)<2.0 may be regulated as well. The nonoriented silicon steel sheet excellent in low magnetic field properties in the rolling direction and suitable as an iron core material for a compact stationary device can be obtd. without executing a complicated stage such as two time cold rolling.

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 an electromagnetic steel sheet which is used as an iron core material for a small static device and which has excellent low magnetic field characteristics in the rolling direction.

[0002]

2. Description of the Related Art Magnetic steel sheets are strongly required to have improved magnetic characteristics such as low iron loss and high magnetic flux density in order to reduce power loss and downsize equipment. Further, in order to reduce the exciting copper loss, there is also a strong demand for an electromagnetic steel sheet having excellent low magnetic field characteristics that can obtain a large magnetic flux density even with a small exciting current.

Further, with respect to magnetic steel sheets for stationary devices such as transformers and ballasts, since the magnetization direction is limited,
In terms of device performance, it is rather advantageous that the magnetic properties have anisotropy (direction). That is, a grain-oriented electrical steel sheet having excellent magnetic properties in only one direction is desirable.

However, the disadvantage of grain-oriented electrical steel sheets is that
High cost due to its manufacturing method including complicated steps such as high temperature annealing for a long time can be mentioned. Therefore, for a small static device that does not require as low iron loss as a large static device, a less expensive non-oriented electrical steel sheet is used, but for applications where the magnetization direction is limited, such as a static device, It goes without saying that an electromagnetic steel sheet having directivity in one direction as much as possible is preferable. From this point of view, the development of non-oriented electrical steel sheets having excellent magnetic properties in the rolling direction has been promoted.

For example, Japanese Patent Publication No. 56-43294 discloses S
i: 0.1 to 1.0%, and the total Al was adjusted to 0.007% or less. A hot-rolled steel sheet was cold-rolled twice with intermediate annealing so that the second rolling reduction was 2 to 15%, and A method for producing a non-oriented electrical steel sheet having a high magnetic permeability, which has a surface roughness of 15 μ-in, rms or less, has a magnetic permeability μ _15/50 in the rolling direction of 4500 or more is _disclosed .

In Japanese Patent Laid-Open No. 61-119618, C: 0.020%
The steel slab containing Si: 1.0% or less, Mn: 0.1 to 1.0%, and Al: 0.40% or less is hot-rolled and then cold-rolled twice with intermediate annealing without hot-rolled sheet annealing. A method for producing a magnetic steel sheet for iron core material of a small static device, in which the second rolling reduction is 3 to 7%, is shown.

In JP-A-2-305920, C: 0.015%
Below, Si: 0.1-1.5%, Mn: 0.1-1.5%, P: 0.15
% Or less, S: 0.008% or less, sol.Al: 0.01 to 1.0%, total N: 0.0050% or less and total O (oxygen): 0.02
% Or less, (sol.Al/Si): 0.02 or more, Al ₂ O ₃ / (
SiO ₂ + MnO + Al ₂ O ₃ ) × 100: After hot rolling a steel slab satisfying 40% or more, two cold rolling steps with intermediate annealing are performed.
The second rolling reduction is 3-10%, and the surface roughness of the steel sheet is
A method for producing a semi-process non-oriented electrical steel sheet with excellent magnetic properties and weldability of 15 μ-in, rms or less is shown.

However, in each of the methods disclosed in these publications, cold rolling is performed twice with intermediate annealing, so that the manufacturing process is complicated and economically disadvantageous. .

By the way, generally, as one of the methods for improving the magnetic properties of non-oriented electrical steel sheets, it is known to increase the heating rate before annealing after cold rolling. For example, in Japanese Unexamined Patent Publication No. 2-54720, the heating rate after cold rolling before annealing is 200 ° C./min or more, annealing is performed at an Ac ₃ transformation point or more, and cooling is performed at a rate of 10 ° C./sec or more. , A method of manufacturing a non-oriented electrical steel sheet having excellent magnetic properties in the circumferential direction is shown.

However, this method improves the average magnetic properties in each direction in the plate surface, but cannot obtain a non-oriented electrical steel sheet having particularly excellent magnetic properties in the rolling direction.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a magnetic steel sheet for a small static machine, which is capable of solving the above-mentioned problems and which is excellent in a low magnetic field characteristic in the rolling direction. .

[0012]

Means for Solving the Problems The gist of the present invention is as follows (1)
And the manufacturing method of (2).

(1) C: 0.005% or less, N: 0.005% by weight
% Or less, Mn: 1.0% or less, S: 0.006% or less and sol.A
l: Containing 0.1% or more, and (Si + sol.Al) <2.0%
The steel material consisting of Fe and unavoidable impurities in the balance is hot-rolled at a finishing temperature of 700 ° C to 850 ° C, and wound at a temperature of 600 ° C or less, and then before descaling or perform annealing at 700 ° C. or higher a ₃ transformation point temperature after further after one cold rolling with the following reduction ratio of 80%, the temperature was raised in the above heating rate of 100 ° C. / sec, 750 ° C. A method for manufacturing a magnetic steel sheet for a small stationary device excellent in low magnetic field characteristics, which comprises performing annealing at a temperature not higher than the A ₃ transformation point.

(2) C: 0.005% or less, N: 0.005% by weight
% Or less, Mn: 1.0% or less, S: 0.006% or less and sol.A
l: 0.003% or less, and (Si + sol.Al) <2.0
%, With the balance being Fe and unavoidable impurities, hot-rolled at a finishing temperature of 700 ° C to 850 ° C, then wound at a temperature of 600 ° C or less, and then before descaling. Alternatively, after annealing at a temperature of 700 ° C. or higher and A ₃ transformation point or lower, and further cold rolling once at a rolling reduction of 80% or lower, the temperature is raised at a heating rate of 100 ° C./sec or higher to 750 ° C. ℃
A method for manufacturing a magnetic steel sheet for a small stationary device excellent in low magnetic field characteristics, which comprises performing annealing at a temperature not higher than the A ₃ transformation point.

The inventors of the present invention have studied the method for producing the above electromagnetic steel sheet by the single cold rolling method, which has a simple process, and have obtained the following new findings.

(Si + sol.Al) in the steel material is less than 2.0% to keep the reduction ratio of cold rolling low, and to raise the temperature before finish annealing after cold rolling at a heating rate of 100 ° C / sec or more. By doing so, it is possible to obtain a non-oriented electrical steel sheet having excellent low magnetic field characteristics in the rolling direction by a simple process. This heating rate of 100 ° C./sec or more is not possible with ordinary continuous annealing, but the direct current heating method developed by the present applicant, that is, by contacting the steel sheet with two or more pairs of pinch rolls that also serve as electrodes A method of heating by directly energizing a steel plate (for example, Japanese Patent Application No. 3-14
(See No. 291) can be easily achieved.

[0017]

The knowledge on which the present invention is based will be described with reference to FIG.

FIG. 1 shows C: 0.002 as a base component.
%, Si: 0.7%, Mn: 0.21%, P: 0.03%, S: 0.0021
% And sol.Al:0.22%, the cold rolling reduction ratio is in the range of 67 to 83%, the heating rate for finish annealing is in the range of 10 to 180 ° C./sec, Magnetic flux density (B ₃ ) in a low magnetic field of 300 A / m when changed respectively
It is a figure which shows the change of.

Here, for these steel materials, the finishing temperature of hot rolling was 770 ° C., the coiling temperature was 500 ° C., and the sheet thickness was 3.
Hot rolled to 0 mm. After descaling these hot-rolled sheets by pickling, they are annealed at 800 ° C for 30 seconds, and the surface thickness is adjusted to 1.5 to 3 to change the reduction ratio of cold rolling.
The thickness was changed in the range of 0 mm, and then the final thickness was 0.5 mm by cold rolling. The reduction ratios of the cold rolling at this time are 67, 75, and 83% shown in the figure. After that, it was electrically heated to 880 ° C at a heating rate of 10 to 180 ° C / sec, and then continuously annealed at 880 ° C for 30 seconds. A strip-shaped sample in the rolling direction was taken from the obtained steel sheet and specified in JIS C 2550. Method was used to investigate the magnetic properties.

Incidentally, in the non-oriented electrical steel sheet, the above-mentioned magnetic properties are usually obtained by taking strip-shaped samples not only in the rolling direction but also in the direction orthogonal to the rolling direction, as specified in JIS C 2550. In the case of static machines, only the magnetic properties in the rolling direction are important.

As shown in the figure, the cold rolling reduction rate is 80%.
If it exceeds, the magnetic flux density (B ₃ ) will decrease. This tendency of decreasing the magnetic flux density becomes particularly remarkable when the heating rate is lower than 100 ° C / sec.

This is considered to be due to the following reason. That is, if the reduction ratio of the cold rolling is too high, as shown in Japanese Examined Patent Publication No. 64-55338, it approaches the magnetic properties averaged in the in-plane direction. It is understood that it has deteriorated. Further, when the heating rate becomes slower, the magnetic flux density tends to decrease, which is considered to be due to the development of texture which is disadvantageous to the magnetic properties. The reason for this is not clear, but as the heating rate increases, the magnetic properties favored during recrystallization (1
00) It is thought that this is because the texture easily develops.

Next, the reason why the composition of the steel material which is the object of the method of the present invention is limited as described above will be explained.

From the viewpoint of magnetic aging, the C: C content is preferably low. If the C content exceeds 0.005%, the low magnetic field characteristics deteriorate due to magnetic aging, so 0.005% was made the upper limit. 0.003% or less is desirable. There is no particular restriction on the lower limit.

N: If the N content exceeds 0.005%, nitrides such as AlN are generated, and the low magnetic field characteristics are deteriorated by suppressing grain growth during annealing, so 0.005% was made the upper limit. 0.003% or less is desirable. The lower limit is the same as that of C, and there is no restriction.

Mn: If the content exceeds 1.0%, the magnetic flux density decreases, so the Mn content was made 1.0% or less.

S: Mn and MnS are formed, and the S content is 0.006.
%, MnS hinders grain growth during annealing, deteriorates low magnetic field characteristics, and causes hot brittleness. Therefore, the S content is set to 0.006% or less. 0.003% or less is desirable. Note that the lower limit is not required in view of the low magnetic field characteristics.

Sol.Al: sol.Al content exceeds 0.003% and
In the range of less than 1%, AlN is finely precipitated and inhibits the growth of crystal grains after recrystallization, which adversely affects the magnetic properties. Therefore, sol. The range of Al content is 0.003 or less,
Or 0.1% or more.

Si + sol.Al: Both Si and sol.Al are elements that enhance the magnetic permeability and effectively contribute to the improvement of the low magnetic field characteristics. However, if Si + sol.Al is contained in excess of 2.0%, the magnetic flux density Since it causes a decrease, it was set to less than 2.0%.

P may be contained in order to adjust the hardness of the steel sheet, but if the P content exceeds 0.2%, the steel sheet becomes brittle and fracture easily occurs in cold rolling. Therefore, it should be 0.2% or less. desirable.

Next, the reason why the manufacturing process and manufacturing conditions are limited as described above will be explained.

The steel material having the above composition is melted in a converter or the like according to a conventional method, and is continuously cast or ingot-slab-rolled into a slab. Then, this slab is hot rolled,
After that, winding is performed, annealing is performed before or after descaling, and one cold rolling is performed to perform annealing. Each step after hot rolling will be described in detail below.

Hot rolling, winding In this step, the rolling finishing temperature is 700 ° C. or higher and 850 ° C. or lower,
The condition is that the coiling temperature is 600 ℃ or less.

As described above, the method of the present invention has an important point in improving the magnetic characteristics by promoting recrystallization and grain growth in the step of annealing the hot rolled sheet.

In order to sufficiently promote recrystallization and grain growth during annealing of the hot rolled sheet, sufficient strain is accumulated at the end of hot rolling, and the strain energy is not released until after winding. Must remain. Hot rolling
From this point of view, the rolling finishing temperature is preferably 850 ° C. or lower, and the winding is preferably performed at a low temperature at which strain energy is not released as much as possible.

In this case, the rolling finishing temperature is limited to the upper limit of 850 ° C. or less from the meaning of recrystallization and grain growth during annealing of the hot rolled sheet, but in reality, the rolling finishing temperature is If the temperature falls below 700 ° C, the rolling load will be too large, and it will be difficult to operate with ordinary rolling mills. From the above, the rolling finishing temperature was set to 700 ° C to 850 ° C.

Regarding the coiling temperature, when the temperature exceeds 600 ° C., the strain energy in the steel sheet is released and this energy is not accumulated, and recrystallization also begins to occur. The crystal grain growth becomes poor. Therefore, the upper limit of the coiling temperature was set to 600 ° C. The lower limit need not be set from the viewpoint of suppressing the release of strain energy.

Descaling Descaling is often carried out by pickling, but various mechanical descaling methods such as shot blasting and roll bender combination may be used. Descaling is performed before or after annealing the hot rolled sheet.

Annealing of hot-rolled sheet This step is for recrystallizing and grain-growing the hot-rolled sheet which has been hot-rolled and wound.

As the annealing method, either box annealing or continuous annealing can be adopted. In order to stably complete the recrystallization and the growth of crystal grains, it is necessary to raise the temperature to 700 ° C or higher for box annealing and 750 ° C or higher for continuous annealing. Annealing temperature
It is based on this that the temperature above 700 ° C is set. The upper limit, because the magnetic characteristics are deteriorated when transitioning to the austenite, or less A ₃ transformation point.

Cold rolling The reduction ratio of cold rolling is one of the important conditions of the present invention.
It should be below 80%. By performing cold rolling at such a reduction rate, the magnetic properties in the rolling direction of the product are improved. The lower limit is determined solely by operational constraints and is not limited. For example, in the case of the most common product with a plate thickness of 0.5 mm, the hot-rolled plate thickness is 1 mm if 50% reduction is to be achieved.
Therefore, it is practically impossible to carry out cold rolling at a rolling reduction of 50% or less.

Annealing after cold rolling Annealing after cold rolling is one of the important conditions of the present invention.
This annealing is intended to generate recrystallized grains advantageous for magnetic properties and to sufficiently grow the recrystallized grains in the process of recrystallizing the work structure after the cold rolling. Since the heating rate before annealing is increased in the method of the present invention, it is preferable to combine the heating by the direct current method and the continuous annealing method.

The heating rate for finish annealing after cold rolling is
At less than 100 ° C / sec, the magnetic flux density decreases (Fig. 1 above).
reference). Therefore, it is necessary to set the heating rate to 100 ° C / sec or more by heating with electricity.

The annealing temperature is not lower than 750 ° C. and not higher than the A ₃ transformation point. Will it not recrystallize at temperatures below 750 ° C?
Alternatively, grain growth does not occur sufficiently even when recrystallized. on the other hand,
If it exceeds the A ₃ transformation point, the magnetic properties deteriorate.

When manufacturing an electromagnetic steel sheet, usually, a step of applying an insulating coating after the above annealing is performed. Also in the method of the present invention, it is possible to add this coating step as the final step of manufacturing. In addition, the non-oriented electrical steel sheet is a full-process product that is shipped with the specified magnetic characteristics, and after the shipment, it is subjected to strain relief annealing (750 ° C x 2 hours) after punching and other processing, and then the specified There are semi-processed products that retain magnetic properties. In the former case as well, the user side is naturally subjected to strain relief annealing. Therefore, in this case, it is required that the prescribed magnetic characteristics are exhibited not only at the time of shipment but also after the user side is strain relief annealed. The method of the present invention can be applied to any of the above products.

[0046]

[Examples] Steel of each chemical composition shown in Table 1 (1) was melted in a converter and formed into a slab by continuous casting, followed by hot rolling, hot-rolled sheet continuous annealing, cold rolling and Finishing continuous annealing was performed. The manufacturing process and its conditions are shown in Table 1 (2). However,
When the heating rate before finishing continuous annealing was more than 100 ° C./sec, the direct current heating was also used under the following conditions. The line speed was 50 m / min, the final plate thickness was 0.5 mm, and the plate width was 1000 mm.

Direct energization heating was performed by arranging two pairs of pinch rolls having a roll diameter of 500 mm at the front and rear with a distance of 5 m from the traveling direction of the plate and supplying power consumption of 1300 kW between the front and rear pinch rolls. .

From each of the obtained steel plates, the magnetic flux density B ₃ was measured by the method specified in JIS C 2550. The strip samples at this time were also limited to the rolling direction for the same reason as in the case of FIG. The results are shown in the right column of Table 1 (2).

[0049]

[Table 1 (1)]

[0050]

[Table 1 (2)]

No. 1 and No. 2 show the influence of the (Si + sol.Al) content. In No. 2 in which this content exceeds the range specified in the present invention, the magnetic flux density is low.

No. 3 to No. 5 show the influence of the sol.Al content. sol.Al content is out of the range specified in the present invention
In No. 5, AlN is finely precipitated and the grain growth property during finish annealing after hot-rolled sheet annealing and cold rolling is deteriorated, so that the magnetic flux density is low.

No. 6 and No. 7 show the influence of the C content. In No. 7 in which the C content exceeds the upper limit defined by the present invention, the precipitated carbides deteriorate the grain growth property during finish annealing after hot-rolled sheet annealing and cold rolling, so that the magnetic flux density is low.

No. 8 and No. 9 show the influence of the N content. In No. 9 in which the N content exceeds the range specified in the present invention, the precipitated nitride deteriorates the grain growth property during finish annealing after hot-rolled sheet annealing and cold rolling, so that the magnetic flux density is low.

No. 10 and No. 11 are S contents, No. 12 and N
o.13 shows the effect of Mn content.
In No. 11 in which the S content exceeds the range specified in the present invention, the precipitated sulfide MnS deteriorates the grain growth property during finish annealing after hot-rolled sheet annealing and cold rolling, resulting in a low magnetic flux density. In No. 13 in which the Mn content exceeds the range specified in the present invention, the magnetic flux density is lowered.

Nos. 14 to 21 are the effects of manufacturing conditions on the component systems within the range defined by the present invention. Among these, in No. 15 to No. 21 in which one of the manufacturing conditions is out of the range defined by the present invention, the magnetic flux density is lower than that of No. 14 satisfying the condition of the present invention. In No. 15, the finishing temperature of hot rolling was too high, strain energy did not accumulate in the hot rolled sheet, and recrystallization and grain growth were not sufficiently performed during hot rolled sheet annealing, so the magnetic flux density became low. There is. No.16
However, since the coiling temperature of hot rolling is too high, the magnetic flux density is still low for the same reason as No.15. In No. 17, since the annealing temperature of the hot-rolled sheet was too low, grain growth did not occur sufficiently and the magnetic flux density was low. In No. 18, the reduction ratio of the cold rolling is too high, and the state is close to the state where the magnetic properties are averaged in the in-plane non-direction, so the magnetic flux density in the rolling direction is low. In No. 19, the heating rate before finish annealing was slow, and in No. 20, the temperature of finish continuous annealing was too low, so that sufficient grain growth did not occur and the magnetic flux density was low. In No. 21, since the temperature of the finish continuous annealing is too high, exceeding the A ₃ transformation point, the magnetic flux density is low.

[0057]

According to the method of the present invention, a non-oriented electrical steel sheet having a high magnetic field density and a high magnetic field density in a low magnetic field in the rolling direction, which is suitable as an iron core material for a small static machine, is manufactured. can do. Moreover, there is no need to go through complicated processes such as double cold rolling as in the prior art.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a reduction rate of cold rolling, a heating rate before finish annealing, and a magnetic flux density B ₃ in a low magnetic field of 300 A / m 2.

Claims (2)

[Claims] 1. By weight%, C: 0.005% or less, N: 0.005% or less, Mn: 1.0% or less, S: 0.006% or less and sol.Al: 0.
A steel material containing 1% or more and (Si + sol.Al) <2.0% with the balance being Fe and unavoidable impurities is hot-rolled at a finishing temperature of 700 ℃ to 850 ℃, and then 600 After coiling at a temperature of ℃ or less, then annealing before or after descaling at a temperature of 700 ℃ or more and A ₃ transformation point or less, and further cold rolling once at a rolling reduction of 80% or less. A method for manufacturing a magnetic steel sheet for a small static device excellent in low magnetic field characteristics, which comprises heating at a heating rate of 100 ° C./sec or more and annealing at a temperature of 750 ° C. or more and A ₃ transformation point or less. 2. C. 0.005% or less, N: 0.005% or less, Mn: 1.0% or less, S: 0.006% or less and sol.Al: 0.
A steel material containing less than 003% and satisfying (Si + sol.Al) <2.0% with the balance being Fe and inevitable impurities was hot-rolled at a finishing temperature of 700 ℃ to 850 ℃, and then 600 After coiling at a temperature of ℃ or less, then annealing before or after descaling at a temperature of 700 ℃ or more and A ₃ transformation point or less, and further cold rolling once at a rolling reduction of 80% or less. A method of manufacturing a magnetic steel sheet for a small static device having excellent low magnetic field characteristics, which comprises heating at a heating rate of 100 ° C./sec or more and annealing at a temperature of 750 ° C. or more and A ₃ transformation point or less.