JPH1180834A - Production of nonoriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silicon steel sheet excellent in magnetic properties without strictly controlling cold rolling conditions and annealing conditions by applying sufficient strains to the steel sheet in a hot rolling stage and improving its texture. SOLUTION: At the time of holding steel slab having a compsn. contg., by weight, <=0.005% C, 0.1 to 3.5% Si, <=2.0% Al and <=2.0% Mn under heating, thereafter subjecting it to hot rough rolling, then subjected it to hot finish rolling of one pass or two passes, subjecting it to cold rolling or warm rolling for one time or ∞two times including processes annealing to regulate its sheet thickness into final one, moreover subjecting it to finish annealing and subsequently applying it with insulated coating to produce a nonoriented silicon steel sheet, the hot finish rolling is executed under the conditions in which the draft in the final one pass is regulated to >=30%, or the draft in the final one pass is regulated to >=10% and the total draft of the final three passes to >=50%.

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. It can be manufactured by performing the cold rolling step and the annealing step performed thereafter under ordinary conditions without performing under special conditions.

[0002]

2. Description of the Related Art Conventional non-oriented electrical steel sheets are obtained by subjecting a silicon-containing steel slab to hot rolling, annealing of a hot rolled sheet and descaling as necessary, and then performing one or two cold rollings. After rolling, it is generally manufactured by performing finish annealing and further providing an insulating film. To improve the magnetic properties, it is described in JP-A-4-346621.

[0003]

However, the method described in the above publication is performed by strictly controlling the cold rolling conditions and the annealing conditions, so that the manufacturing process is complicated and the manufacturing cost increases. There is a problem.

[0004] The present invention advantageously solves the above-mentioned problems, that is, by imparting a sufficient strain in the hot rolling step to improve the texture, thereby reducing the cold rolling conditions and annealing conditions. An object of the present invention is to propose an advantageous method for producing an electromagnetic steel sheet having excellent magnetic properties, particularly high magnetic flux density, without strict control.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and have obtained the following findings. That is, in the conventional method of manufacturing an electromagnetic steel sheet,
Hot rolling was performed merely to reduce the thickness of the sheet, and was hardly studied from the viewpoint of forming a texture suitable for electrical steel sheets. By controlling the rolling reduction in the subsequent stand in the finish rolling, if the latter stand is subjected to rolling under stronger rolling conditions than those employed in the conventional process, the cold rolling conditions and the annealing conditions are strictly controlled. Without having to
It has been found that a non-oriented electrical steel sheet having excellent magnetic properties can be obtained.

[0006] The present invention is based on the above findings, and the gist configuration thereof is as follows. That is, in the first invention, C: 0.005 wt% or less, Si: 0.1 to 3.5 wt%, Al:
A steel slab having a composition containing 2.0 wt% or less and Mn: 2.0 wt% or less is subjected to hot rough rolling after heating and holding, and then to hot finishing rolling in one pass or two or more passes, and then once or in the middle In producing non-oriented electrical steel sheets by performing cold rolling or warm rolling two or more times including annealing to obtain a final thickness, applying final annealing, and then applying an insulating film, hot finishing rolling is performed. In a non-oriented electrical steel sheet having excellent magnetic properties.

[0007] In the second invention, C: 0.005 wt% or less,
Si: 0.1 to 3.5 wt%, Al: 2.0 wt% or less, Mn: 2.0 wt%
The steel slab having the composition containing the following is subjected to hot rough rolling after heating and holding, and then subjected to hot finishing rolling in 3 passes or more.
After that, a non-oriented electrical steel sheet is manufactured by performing cold rolling or warm rolling one or more times, including intermediate annealing, to a final thickness, further performing a final annealing, and then applying an insulating film. In doing so, the hot finish rolling is performed under the conditions of a final one-pass reduction ratio of 10% or more and a final three-pass total reduction ratio of 50% or more. This is a method for manufacturing a steel sheet.

[0008] In addition, in the above-mentioned first invention or the second invention, in order to further improve the texture and further increase the magnetic flux density, in addition to the above steel composition, Sb: 0.1 wt% or less and / or Sn : 0.1 wt% or less.

Further, in any of the above inventions, when it is necessary to eliminate the hot-rolled unrecrystallized region, after the hot finish rolling, one or more than two times of cold rolling including one-time annealing or Before performing the warm rolling, it is preferable to perform hot-rolled sheet annealing as necessary.

According to the present invention, if hot rolling, particularly hot finishing rolling conditions, are controlled, sufficient strain is introduced into the steel sheet to effectively improve the rolling structure, and the subsequent cold rolling conditions and annealing conditions are controlled. The desired objective is advantageously achieved without strict control of.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, the reason why the composition of the steel slab is limited to the above range in the present invention will be described.

C: 0.005 wt% or less C is a harmful component from the viewpoint of magnetic properties. When the C content exceeds 0.005 wt%, magnetic properties tend to deteriorate due to magnetic aging. Therefore, the C content was limited to 0.005 wt% or less.

Si: 0.1-3.5 wt% Si is a useful component for reducing iron loss by increasing the specific resistance. To sufficiently exhibit this effect, the Si content must be at least 0.1 wt%. Is required, but 3.
If it exceeds 5 wt%, not only does the magnetic flux density significantly decrease, but also the workability deteriorates. Therefore, the Si content is 0.1-3.
Limited to the range of 5 wt%.

Al: 2.0 wt% or less, Mn: 2.0 wt% or less Both Al and Mn have the effect of increasing the specific resistance similarly to Si, and are essential components in the present invention.
If the content exceeds 2.0 wt%, the cost will increase. Therefore, the contents of Al and Mn were both limited to the range of 2.0 wt% or less.

Sb: 0.1 wt% or less, Sn: 0.1 wt% or less Sb and Sn are both useful components for improving texture and improving magnetic properties.
At least one of them can be appropriately added. In addition, Sb
In the case of adding Sn and Sn, if each content exceeds 0.1 wt%, the cost will increase. Therefore, it is preferable to add each content of Sb and Sn within the range of 0.1 wt% or less. .

In addition, it is desirable to reduce harmful impurity elements as much as possible, and it is particularly desirable to reduce impurity elements such as S, N and O to 0.005 wt% or less.

The molten steel adjusted to the above-mentioned appropriate component composition range is preferably made into a slab by continuous casting, and then subjected to a heat treatment prior to hot rolling. Next, hot rough rolling is performed after hot rough rolling.

The main feature of the present invention is to optimize the rolling reduction conditions in the subsequent stand in the hot finish rolling, and more specifically, to perform the strong rolling reduction in the latter stand. Sufficient strain is introduced and the rolling structure is effectively improved, so that even if the subsequent cold rolling step and annealing step are performed under normal conditions, excellent magnetic properties, especially high magnetic flux density electrical steel sheets Which enables the production of

The rolling reduction in the latter stand in the hot finish rolling is, specifically, 30% in the final pass.
%, Or the rolling reduction in the last one pass must be 10% or more and the total rolling reduction in the last three passes must be 50% or more.

In the present invention, it is important to impart a sufficient amount of strain energy to the steel sheet in the subsequent stage of hot finish rolling.
If the rolling reduction in the last one pass is less than 30% or less than 30%, the total rolling reduction in the last three passes is 50
%, Sufficient strain cannot be introduced into the steel sheet, and the rolled structure cannot be effectively improved. Therefore, in this rolled structure, cold rolling and annealing are performed under normal conditions. This is because no improvement in magnetic properties can be expected.

Therefore, according to the present invention, the rolling reduction in the final pass in the hot finish rolling is 30% or more, or
The total rolling reduction of the passes was limited to 50% or more (however, the rolling reduction in the last one pass was 10% or more).

When the rolling reduction in the final one pass and the total rolling reduction in the final three passes exceed 80% and 90%, respectively, there is a tendency that the sheet passing property and the manufacturing cost of the steel sheet are deteriorated. Therefore, the rolling reduction in the last one pass and the final three
The upper limit of the total rolling reduction in the pass is 80% and
Preferably it is 90%.

Further, when it is necessary to eliminate the hot-rolled unrecrystallized region, after hot finishing rolling, hot rolling is performed before cold rolling or warm rolling two or more times including one time or intermediate annealing. It is preferable to perform sheet annealing.

In the present invention, it is important to comply with the above-mentioned hot finish rolling conditions, and other manufacturing conditions such as annealing, pickling, cold rolling, and conditions for forming an insulating film are not particularly limited. Instead, it can be performed within the range normally performed.

As an example, after hot finish rolling,
The hot rolled sheet is annealed at 930 ° C. for 3 minutes, pickled, cold rolled at a reduction of 65%, and then subjected to an insulating coating.

The above is only an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0027]

【Example】

Example 1 A steel slab having the composition shown in Table 1 was heated to 1100 ° C., and after hot rough rolling, the final pass of hot finish rolling was set to a rolling reduction of 32%, and a hot plate having a thickness of 1.2 mm was heated. The rolled sheet was pickled, cold rolled to a thickness of 0.5 mm, and then subjected to finish annealing at 850 ° C. for 1 minute in a mixed atmosphere of hydrogen and nitrogen. Further, as a conventional example, a slab of the same composition is heated to 1100 ° C., hot rough-rolled, and then hot-finish rolling (the rolling reduction in the last single pass in hot-finish rolling is 5%).
%) To a hot-rolled sheet with a thickness of 2.0 mm, and then to a sheet thickness of 0.5 mm under cold-rolling conditions for producing ordinary non-oriented electrical steel sheets, and then annealing under the same conditions as above. gave.

The non-oriented electrical steel sheet thus obtained was subjected to magnetic measurement by the electrical steel sheet test method specified in JIS C 2550, and the maximum magnetic flux density was 1.5 Tesla (T).
The iron loss value W _15/50 per kg at a frequency of 50 Hz and the magnetic flux density B ₅₀ at a magnetization force of 5000 A / m were determined. Table 2 shows the results.

[0029]

[Table 1]

[0030]

[Table 2]

As is clear from Table 2, the applicable examples of the present invention have excellent magnetic properties for all steel types as compared with the conventional examples.

Example 2 Steel slab containing 1.24 wt% of Si (steel type: A), Si: 3.
Steel slab containing 46wt% (steel type: B) and Si: 3.80
steel slab containing 1 wt% (steel type: C)
C., and after hot rough rolling, hot finish rolling was performed under the conditions shown in Table 3 for the total rolling reduction in the final three passes and the rolling reduction in the final one pass. After hot-rolled sheet annealing at 900 ° C for 2 minutes, scale removal by pickling, cold rolling to a sheet thickness of 0.5 mm, hydrogen and nitrogen In a mixed atmosphere of 850 ° C. for 20 seconds. The steel types A to C all have the following contents of C, Al and Mn.
It is adjusted within the proper range of the present invention.

The non-oriented electrical steel sheet thus obtained was subjected to magnetic measurement in the same manner as in Example 1, and the iron loss value W was measured.
_15/50 and determined for magnetic flux density B _50. Table 3 shows the results.

[0034]

[Table 3]

From Table 3, it can be seen that, in the hot finish rolling, the reduction rate in the final one pass is 30% or more, the reduction rate in the final one pass is 10% or more, and the total reduction in the final three passes. Steels 3, 5, 7, and 9 whose percentages do not correspond to 50% or more have inferior magnetic properties when compared with the same steel type. Also,
Steels 10 and 11 have the above-mentioned rolling reduction within the proper range of the present invention, but have a low magnetic flux density because the Si content is larger than the proper range of the present invention.

On the other hand, the steel composition is in an appropriate range, and the reduction rate in the final one pass in hot finish rolling is 30% or more, or the reduction rate in the final one pass is 10% or more and the final three passes. Steels 1, 2, 4, 6, and 8 corresponding to at least one of the total rolling reductions of 50% or more in the above have excellent magnetic properties when compared with the same steel type.

[0037]

As described above, according to the present invention, by devising the hot rolling step, the subsequent cold rolling step and annealing step can be performed under ordinary conditions without performing special conditions. A non-oriented electrical steel sheet having excellent characteristics can be manufactured.

Claims (4)

[Claims] C: 0.005 wt% or less, Si: 0.1 to 3.5 wt%
%, Al: 2.0 wt% or less, and Mn: 2.0 wt% or less. A steel slab having a composition containing the same is heated and held, then hot rough-rolled, and then subjected to hot finishing rolling in one pass or two or more passes. In producing a non-oriented electrical steel sheet by performing cold rolling or warm rolling two or more times including one time or intermediate annealing to a final thickness, further applying a final annealing and then applying an insulating film, A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, wherein hot finish rolling is performed under a condition of a final one-pass rolling reduction of 30% or more. 2. C: 0.005 wt% or less, Si: 0.1 to 3.5 wt%
%, Al: 2.0 wt% or less, and Mn: 2.0 wt% or less. A steel slab having a composition containing not more than 2 wt% is subjected to hot rough rolling after heating and holding, and then to hot finish rolling in 3 passes or more, and thereafter, once or In order to produce a non-oriented electrical steel sheet by performing cold rolling or warm rolling twice or more including intermediate annealing to obtain a final sheet thickness, further performing final annealing, and then applying an insulating film, A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, wherein the finish rolling is performed under the conditions of a final one-pass reduction ratio of 10% or more and a final three-pass total reduction ratio of 50% or more. 3. The method according to claim 1, wherein in addition to the steel composition, Sb: 0.1 wt% or less and / or
n: A method for producing a non-oriented electrical steel sheet containing 0.1 wt% or less. 4. The method according to claim 1, wherein after the hot finish rolling, the hot rolled sheet is annealed, then the scale is removed, and the annealing is performed once or halfway.
A method for producing a non-oriented electrical steel sheet which is subjected to cold rolling or warm rolling at least twice.