JP2560090B2 - Non-oriented electrical steel sheet manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the production of non-oriented electrical steel sheets, and particularly to low iron loss, high magnetic flux density and high iron density suitable for iron core materials for rotating machines such as small motors. The present invention relates to a method for manufacturing a non-oriented electrical steel sheet having a small in-plane anisotropy of magnetic flux density with high productivity.

(Prior Art) In recent years, in the fields of various electric devices, from the viewpoint of energy saving and downsizing of the devices, magnetic steel sheets used as iron core materials thereof have high magnetic flux density and low iron loss. Is strongly demanded. In particular, in rotating machines such as small motors, since it is magnetized in all directions of the plate surface, a non-oriented electrical steel sheet with low iron loss and high magnetic flux density and small in-plane anisotropy of magnetic flux density is used for the iron core. Its use as a material is very advantageous.

Conventionally, as a method for producing a non-oriented electrical steel sheet with a small in-plane anisotropy, as described in JP-A-59-123715, the hot-rolled sheet structure by self-annealing is 85% or more as coarse grains. A method of performing strong cold rolling, in which a hot-rolled sheet having an unrecrystallized structure is cold-rolled at a rolling reduction of 75 to 85% by warm rolling as described in JP-A-60-125325 to substantially 85%. The method for carrying out the above-mentioned strong cold rolling, and further, as shown in JP-A-61-1838,
The recrystallization rate during intermediate annealing was set to 30 in the double cold rolling and double annealing method.
A method has been proposed in which the secondary cold rolling rate is controlled to 6% to 15% by controlling to 70%. In addition, JP-A-58-104155 discloses that low Si and high
A method of obtaining a non-oriented electrical steel sheet having a high magnetic flux density by cold rolling a material subjected to hot-rolled sheet annealing at a reduction rate of 30 to 85% and then performing finish annealing using Al steel is proposed. ing.

(Problems to be Solved by the Invention) However, any of the above methods has the following problems.

That is, in the method disclosed in JP-A-59-123715, the uniformity of magnetic properties in the coil (longitudinal direction and width direction) is poor due to the non-uniform temperature distribution during self-annealing. Further, since the film is wound at a high temperature, there is a problem that the scale layer develops quickly, the pickling property deteriorates, and the cost increases.

In the method according to Japanese Patent Laid-Open No. 60-125325, since it is warm rolling, the load on the rolling mill is large, and it may not be possible to roll it with a conventional rolling mill, which is a problem in practice.

The method according to Japanese Patent Laid-Open No. 61-3838 controls the recrystallization rate during intermediate annealing in the double cold rolling and double annealing method, but it is difficult to control the recrystallization rate and the cost increase due to the increase in the number of steps is avoided. I can't.

As described in JP-A-58-104155, when the amount of Si is excessively decreased, the specific resistance of the material decreases and the overcurrent loss increases, which is particularly important in motors. There is a problem that the iron loss in the high frequency region becomes large.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and has a low iron loss, a high magnetic flux density and a non-oriented electrical steel sheet having a small in-plane anisotropy of the magnetic flux density with high productivity. It is intended to provide a method that can be manufactured.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors have developed a non-directional electromagnetic having high productivity, low iron loss, high magnetic flux density, and small in-plane anisotropy of magnetic flux density. We have earnestly conducted research on measures to obtain steel sheets.

As a result, a steel slab with a characteristic composition in which the amount of Si is appropriately reduced is rolled in the γ region, and a hot rolled steel sheet is obtained by low-temperature winding, and hot rolled sheet annealing and cold rolling at a high pressure reduction rate are combined. The present invention has been made here by finding out that it is possible.

That is, the method for producing a non-oriented electrical steel sheet having low iron loss, high magnetic flux density and small in-plane anisotropy of magnetic flux density according to the present invention is C ≦ 0.01%, 0.3% <Si ≦ 1.0%, 0.1% ≦ Mn ≦ 0.7
%, P ≦ 0.1%, S ≦ 0.008% and Al ≦ 0.005% or 0.1%
A slab containing ≦ Al ≦ 0.5%, the balance of which is Fe and unavoidable impurities, is hot-rolled at a hot rolling finish temperature of Ar ₃ points or higher, and then rolled at 700 ° C. or less
Annealing is performed for 2 minutes or more in the temperature range of ℃ or more and Ac ₁ point or less, and in the subsequent cold rolling process, the final product thickness is obtained with a reduction rate of 75% or more and 90% or less, and then finish annealing is performed to reduce the iron loss. A magnetic steel sheet having a B ₅₀ representing a magnetic flux density of 1.76 T or more and a ΔB ₅₀ representing an in-plane anisotropy of the magnetic flux density of 0.04 or less is obtained.

 The present invention will be described in more detail below.

(Operation) First, the reasons for limiting the chemical components in the present invention will be described.

C: C is a harmful element in terms of magnetic properties, and the smaller the amount, the lower the iron loss, and also the deterioration of the iron loss due to aging can be prevented. Therefore, C ≦ 0.01%.

Si: Si reduces iron loss by increasing the specific resistance, but its effect is small at 0.3% or less, especially iron loss in the high frequency range deteriorates, and if it exceeds 1.0%, the magnetic flux density decreases. It is not preferable because it causes. Therefore, 0.3
% <Si ≦ 1.0%.

Mn: If Mn is less than 0.1%, hot brittleness increases, while if it exceeds 0.7%, the magnetic flux density decreases, which is not preferable. Therefore, 0.1% ≦ Mn ≦ 0.7%.

P: P is an element necessary for imparting appropriate hardness in consideration of punchability of the steel sheet, but if it is contained in excess of 0.1%, the steel sheet becomes brittle, which is not preferable. Therefore, P ≦ 0.
1%

S: If S is more than 0.008%, it precipitates as MnS, which is harmful to the magnetic properties, so it is an undesirable element. Therefore, S ≦
It is 0.008%.

Al: Al is 0.005% or less in order to prevent the precipitation of fine AlN harmful to the magnetic properties, or by adding a large amount of Al to precipitate as coarse AlN, in order to eliminate the adverse effect of AlN
0.1% or more. However, in the latter case, if the content exceeds 0.5%, the magnetic flux density decreases, which is not preferable. Therefore, Al ≦ 0.005% or 0.1 ≦ Al ≦ 0.5%.

 Next, the reasons for limiting the manufacturing conditions of the present invention will be described.

The steel slab having the above chemical composition is melted and cast by a usual method, and then subjected to hot rolling. The slab heating temperature is preferably as low as 1150 ° C. or lower in order to render the precipitates such as MnS harmless.

In hot rolling, the hot rolling finishing temperature is Ar ₃ points or more, since it is necessary to obtain uniform fine grains in order to make coarse grains during annealing of the hot rolled sheet, but the most desirable is Ar. ₃
The temperature just above the point. The winding temperature is 700
If the temperature is higher than ℃, the variation in temperature inside the coil during cooling of the coil becomes large, the structure becomes non-uniform, and the magnetic characteristics become non-uniform. Further, in the case of high temperature winding, the scale develops quickly, the treatment time in the pickling step before cold rolling becomes long, and the productivity deteriorates. From the above points, the winding temperature is 700
It should be below ° C.

The obtained hot-rolled steel sheet is subjected to hot-rolled sheet annealing in order to coarsen the crystal grains and improve the magnetic properties. In that case, if the annealing temperature is lower than 700 ° C., the crystal grains of the hot rolled sheet do not become sufficiently large. On the other hand, when the Ac ₁ point is exceeded, γ transformation is partially carried out and fine grains appear, which is not preferable. Therefore, the annealing temperature is 70
Limited to 0 ° C or higher and Ac ₁ point or lower. Further, if the annealing time is less than 2 minutes, the effect of annealing cannot be sufficiently obtained, so it is necessary to be 2 minutes or more.

Then, after pickling, cold rolling is performed, and it has been found through experiments and studies by the present inventors that the cold rolling rate needs to be 75% or more and 90% or less.

FIG. 1 shows the relationship between the cold rolling rate, the magnetic flux density B _50, and the in-plane anisotropy ΔB ₅₀ of the magnetic flux density. In the experiment, C: 0.0
After heating a steel slab containing 05%, Si: 0.39%, Mn: 0.25%, P: 0.08%, S: 0.002% and Al: 0.25% to 1100 ° C, finish by hot rolling at 920 ° C, 520 Rolled at ℃ to make hot-rolled sheets of various thicknesses, further heat-rolled sheet annealing at 750 ℃ × 3hr, after removing the scale in the pickling process, cold rolling 0.5mm
The magnetic flux density and the in-plane anisotropy of the magnetic flux density were examined for a product that was finished to a thickness and then subjected to finish annealing (850 ° C x 1 min). In the figure, L represents the rolling direction, C represents the direction perpendicular to the rolling direction, and ΔB ₅₀ = (B _{50 in} L direction) − (B _{50 in} C direction).

The magnetic flux density B ₅₀ obtained in the electrical steel sheet when the conventional method is applied to the above component system is 1.75 T at most. However, as shown in FIG. 1, a high magnetic flux density can be obtained by combining the hot-rolled sheet annealing and the cold rolling with a high pressure reduction ratio, and further, the difference in the magnetic flux density between the rolling direction and the direction perpendicular to the rolling direction. ΔB ₅₀ (in-plane anisotropy) also decreases. As is clear from the figure, B ₅₀ representing the magnetic flux density is a high magnetic flux density of 0.76 T or more, and ΔB ₅₀ representing the in-plane anisotropy of the magnetic flux density is 0.0
In order to manufacture a non-oriented electrical steel sheet as small as 4 or less,
The reduction ratio during cold rolling must be 75 to 90%, preferably 85 to 90%.

On the other hand, when the hot-rolled sheet annealing is not performed, as shown in FIG. 2 which shows the relationship between the cold rolling rate, the magnetic flux density and the in-plane anisotropy of the magnetic flux density, the cold rolling is performed at a high rolling reduction rate of 75 to 90%. It is clear that even if hot rolling is performed, high magnetic flux density cannot be obtained unless hot-rolled sheet annealing is performed.

Although finish annealing is performed after cold rolling, the conditions are not particularly limited, and 800 to 900 ° C is preferable.

 Next, examples of the present invention will be described.

(Example) A steel slab having the chemical composition shown in Table 1 was heated to 1150 ° C, hot-rolled in the γ range and wound at 520 ° C, and then under various conditions shown in the same table. The hot-rolled sheet was annealed, then pickled, and then cold-rolled at various reduction ratios to a sheet thickness of 0.5 mm, and finally annealed (850 ° C x 1 min) to produce a non-oriented electrical steel sheet.

 Table 2 also shows the magnetic properties of the obtained electromagnetic steel sheets.

In Table 2, test symbols A, B, E, and G show the case of manufacturing by the method according to the present invention, and all of them are materials having low iron loss, high magnetic flux density, and small in-plane anisotropy of magnetic flux density. Has been obtained.

On the other hand, the experimental symbols D and H are comparative examples in the case where the hot-rolled sheet annealing is not carried out, but the in-plane anisotropy of the magnetic flux density is about the same as that of the inventive example, but the magnetic flux density is the same. Value is small and iron loss is large.

In Comparative Example I having a large Si content, the in-plane anisotropy of the magnetic flux density is about the same, but the magnetic flux density is small. Further, in the case of Comparative Example J having a small Si content, the iron loss in the high frequency range is poor.

Further, Comparative Examples C and F having a low cold rolling rate have a low magnetic flux density,
The in-plane anisotropy of magnetic flux density is also large.

(Effects of the Invention) As described in detail above, according to the present invention, the heat produced by hot rolling in the γ region and low-temperature winding using the steel of the specific component composition in which the Si content is appropriately lowered. Since it is a process of applying hot rolling annealing and cold rolling at a high rolling rate to a rolled steel sheet, it is a non-directional electromagnetic having low iron loss, high magnetic flux density and small in-plane anisotropy of magnetic flux density. A steel plate is obtained. Moreover, the pickling process can be shortened, and the product can be manufactured with high productivity.

[Brief description of drawings]

Figure 1 shows the effect of cold rolling on the magnetic flux density B ₅₀ and the in-plane anisotropy (ΔB ₅₀ ) of the magnetic flux density of the material with large crystal grains by hot-rolled sheet annealing. it is a diagram showing the effect of cold rolling rate on plane anisotropy of the magnetic flux density B ₅₀ and the magnetic flux density in the material not performed plate annealing (ΔB _50).

Claims (2)

(57) [Claims] 1. In weight% (hereinafter the same), C ≦ 0.01%,
3% <Si ≦ 1.0%, 0.1% ≦ Mn <0.7%, P ≦ 0.1%, S ≦
A slab containing 0.008% and Al ≤ 0.005%, the balance of which is Fe and unavoidable impurities, was hot-rolled at a hot-rolling finishing temperature Ar of ₃ points or higher, and then rolled at 700 ° C or lower to produce a hot-rolled steel sheet. Annealed for 2 minutes or more in the temperature range of 700 ℃ or more and Ac ₁ point or less, and in the subsequent cold rolling process, 75% or more and 90% or more
The following reduction ratio in the final product thickness, then under the finish annealing, with a low iron loss, is B ₅₀ that represents a magnetic flux density more than 1.76T, ΔB ₅₀ to and representing in-plane anisotropy of the magnetic flux density of 0.04 or less A method for manufacturing a non-oriented electrical steel sheet, which comprises obtaining a certain electrical steel sheet. 2. The method according to claim 1, wherein the slab contains 0.1% ≦ Al ≦ 0.5%.