JPH0450367B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a non-oriented electrical steel sheet with low iron loss and high magnetic flux density. (Prior art) Conventional electrical steel sheets are generally used as a means of reducing iron loss from the viewpoint of reducing eddy current loss due to increased specific resistance.
A method of increasing the content of Si or Al has been used. In addition, as a method of obtaining excellent electromagnetic properties without adding these alloy components, there is a method in which a cold-rolled/annealed sheet is subjected to several percent skin pass rolling, punched by the user, and then subjected to strain relief annealing. (Japanese Unexamined Patent Publication No. 60-17014, etc.) In these conventional methods, the finish hot-rolling is generally 800°C or higher, and if the winding temperature is low and recrystallization has not progressed sufficiently, high-temperature hot-rolled sheet annealing is performed. After rolling, the product is cold-rolled to 75% or more and then annealed at high temperature for a short time. However, in the latter semi-process, as described above, several percent of skin pass rolling is performed on top of this. (Problems to be Solved by the Invention) The problems to be solved by the present invention are to reduce the amount of expensive alloying elements added to reduce iron loss, and to reduce the amount of expensive alloying elements that are required by semi-processed materials. Strain relief annealing is omitted. (Means for Solving the Problems) In order to solve the problems of the prior art, the present invention provides C: 0.05% or less, N: 0.010% or less, Si: 1% or less, Mn: 1% by weight. Below, P: 0.15%
Hereinafter, steel containing S: 0.010% or less, Al: 0.3% or less, and the balance consisting of Fe and unavoidable impurities, is subjected to at least Ar ₃ transformation point or less at the final stage of hot rolling, with or without lubrication at 500℃ or higher. Perform rolling of 30% or more,
After winding, the sheet is rolled as it is or hot-rolled, annealed, pickled, cold-rolled to 30% or more and 75% or less, and finally recrystallized.Features low iron loss and magnetic flux density. The present invention provides a method for manufacturing a non-oriented electrical steel sheet with high viscosity. The reasons for limiting the constituent elements of the present invention will be explained below. In addition, % in the following description is weight %. First, in the chemical composition of the steel of the present invention, a small amount of C is preferable in order to improve iron loss, and a preferable content is 0.005% or less in order to prevent magnetic deterioration due to aging. However, in the process of the present invention, the effect of improving iron loss was confirmed up to a C content of 0.05%, so the upper limit of the C content was set at 0.05%. Si is added for the purpose of improving iron loss, but as the amount of Si increases, the magnetic flux density decreases, and the advantage of the iron loss obtained by the manufacturing method of the present invention over the iron loss obtained by the conventional method becomes smaller. In addition, the upper limit of the amount of Si added is set to 1% in order to suppress the cost increase due to alloy addition, which is one of the main points of the present invention. N is also 0.010% in the steel of the present invention, which is better if it is less in order to improve iron loss.
was set as the upper limit. In particular, when suppressing the precipitation of AlN and lowering iron loss, it is preferable to add B to precipitate BN, but when the B/N ratio exceeds 1.5, excess B deteriorates magnetism, so the upper limit of the amount of B should be set. B/N
It was set at 1.5. In the steel of the present invention, P is added for the purpose of increasing strength to prevent the steel plate from becoming too soft and difficult to punch when the amount of Si is small. Adding P can improve iron loss, but if it exceeds 0.15%, hot workability deteriorates and there is a risk of hot rolling cracking, so the upper limit was set at 0.15%. Al is
Like Si, it may be added for the purpose of improving iron loss, but the upper limit is set to suppress the cost increase due to alloy addition.
It was set at 0.3%. Also, like P, Mn is added as necessary to increase strength, but if it exceeds 1%, the transformation point decreases, ferrite-austenite transformation is likely to occur during annealing, and magnetic deterioration is observed, so Mn is added. The upper limit of the amount was 1%. Furthermore, since S forms nonmetallic inclusions such as MnS that are harmful to improving magnetism, a stable effect of improving magnetism cannot be obtained unless the content is 0.010% or less. Next, we will discuss limitations on processing conditions. Ar ₃ transformation point [Ar ₃ (℃) = 916−509C−64Mn+
33Si + 50Al + 250P] The reason why at least 30% or more hot rolling must be performed is that rolling below the Ar ₃ transformation point reduces the (111) strength in the steel sheet and increases other strengths, especially (100) strength, which improves electromagnetic properties. gets better. This is because the rolling reduction ratio is 30% or more, at which the effect is fully manifested. Furthermore, this effect becomes more pronounced when the average coefficient of friction between the roll and the steel plate becomes 0.2 or less. The lower limit of this rolling temperature is set at 500° C. because at temperatures lower than this, the deformation resistance is high and the steel sheet becomes defective in shape, which is difficult to manufacture. Next, the reason why the cold rolling ratio was set to 30% or more and 75% or less will be explained. As shown in FIG. 1, the inventors of the present invention have discovered that iron loss can be significantly reduced by lowering the cold rolling rate. This effect is below Ar ₃ , 500
It is noticeable in materials that have been hot-rolled by 30% or more at temperatures above ℃. This seems to be because the (111) strength in the steel sheet can be kept low under these conditions. The lower limit of the cold rolling rate was set at 30% because if the cold rolling rate is less than this, the thickness of the hot-rolled sheet becomes too thin, which impedes productivity in the hot-rolling process. Figure 1 shows the contribution of low-reduction cold rolling to improving iron loss, which is one of the key points of the present invention, for steels with chemical compositions shown in Table 2. 500, the effect of which is within the scope of the present invention.
This is noticeable in materials that have been hot-rolled by 30% or more at temperatures above ℃ and below the Ar ₃ transformation point, and also indicates that hot-rolled plate annealing and lubricated rolling are more advantageous in improving iron loss. Hot-rolled plate annealing is performed at 730℃ for 1 hour, and final annealing is at 700℃.
I went there for an hour.

[Table] Even if the as-hot-rolled material is directly sent to the cold rolling process after hot rolling in the method of the present invention, the iron loss characteristics will be significantly improved compared to when a material with the same composition is manufactured using the conventional process. When this is subjected to hot-rolled plate annealing, the improvement in core loss characteristics becomes even more remarkable, and the magnetic flux density also improves. (Example) Table 1 shows the components, process conditions, and magnetic properties of the product sheets of the steel of the present invention and comparative steel. This material is produced by heating continuously cast pieces in the range of 1250℃ to 1000℃ and finishing them into hot-rolled sheets with a thickness of 1.0 to 3.0 mm by continuous hot rolling.
It was then cold rolled to a final thickness of 0.5mm.
Recrystallization treatment after cold rolling was performed by continuous annealing at 800 to 900°C for 2 minutes. Materials with hot rolled plate annealing: 800~
Continuous annealing was performed at 850°C for 2 minutes. The electromagnetic properties showed iron loss W _15/50 and magnetic flux density B ₅₀ in the L and C directions. In addition, the average friction coefficient of rolling at 500℃ is less than 0.2 from Ar ₃ when lubricated rolling is performed during hot rolling.
It showed approximately 0.28 in the non-lubricated state. This friction coefficient is a value calculated from the actually measured advance rate. Examples Nos. 1 to 8 in Table 1 are ultra-low carbon steels with a low Si content of 0.017. The iron loss value obtained using the method of the present invention for this steel type is approximately 6 W/Kg, which is significantly improved compared to the value of approximately 8.5 W/Kg obtained using the conventional method for comparative materials. It is recognized that hot-rolled sheet annealing and lubricated rolling contribute to improving iron loss. In addition, when sample No. 6 was annealed for a long time to grow grains, W15 _/50 improved to 5W/Kg. This means that the iron loss is further reduced by increasing the temperature and length of the final annealing. No.9 to No.11 are Si
The iron loss of the sample containing 0.8% of carbon steel is better than that of ultra-low carbon steel, but the improvement in iron loss by the method of the present invention is not as remarkable as that of ultra-low carbon steel. No. 2 to No. 15 are samples with P added, and No. 16 to No. 18 are samples with Mn added, and it can be seen that iron loss is improved in both steel types by the rolling process according to the method of the present invention. Also, from No.19 to No.
21, a similar effect appears in a material in which B is added so that the B/N ratio is approximately 1. No. 22 to No. 24 are low carbon steels with a C content of 0.04%, and although iron loss increases due to an increase in C content, it can be confirmed that iron loss is improved by passing through the process of the present invention.

【table】

[Table] (Effects of the invention) According to the method of the present invention, not only can the amount of alloying elements (particularly the amount of Si) be significantly reduced to obtain the same electromagnetic properties, but also it is possible to significantly reduce the amount of alloying elements (particularly the amount of Si). It is possible to obtain excellent electromagnetic properties that could only be obtained by performing post-skin pass rolling and final strain relief annealing by the user.
Further, according to the present invention, it is possible to economically produce a non-oriented electrical steel sheet with a high magnetic flux density and low iron loss with a composition similar to that of a normal cold-rolled steel sheet, which is of great industrial benefit.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the contribution of low pressure cold rolling to improving iron loss in the present invention.

Claims (1)

[Claims] 1% by weight: C: 0.05% or less, N: 0.010% or less,
Si: 1% or less, Mn: 1% or less, P: 0.15% or less,
Contains S: 0.010% or less, Al: 0.3% or less, and the balance is
At the final stage of the hot rolling process, steel consisting of Fe and unavoidable impurities is rolled by at least 30% in a temperature range below the Ar ₃ transformation point and above 500°C, and after being rolled, the steel is rolled as it is or annealed as a hot rolled sheet. 30% or more after pickling
A method for producing a non-oriented electrical steel sheet with excellent electromagnetic properties, characterized by cold rolling of 75% or less and finally recrystallization treatment. 2 C: 0.05% or less, N: 0.010% or less, in weight%
Si: 1% or less, Mn: 1% or less, P: 0.15% or less,
S: 0.010% or less, Al: 0.3% or less and B/
At the end of the hot rolling process, steel containing 1.5 or less N and the remainder Fe and unavoidable impurities is heated to a temperature below the Ar ₃ transformation point.
Rolling of at least 30% in a temperature range of 500℃ or higher, after rolling, as is or hot-rolled plate annealing, after pickling, cold rolling of 30% to 75%, and finally recrystallization treatment. A method for manufacturing a non-oriented electrical steel sheet with excellent electromagnetic properties. 3 Ar 30% of the temperature range below ₃ transformation point and above 500℃
The method according to claim 1 or 2, wherein the above rolling is performed with lubrication and with an average friction coefficient of 0.2 or less between the roll and the steel plate.