JPS62284016A - Production of non-oriented electrical steel sheet having excellent electromagnetic characteristic - Google Patents

Abstract

PURPOSE:To economically produce a non-oriented electrical steel sheet having excellent electromagnetic characteristics by subjecting a steel having the specific compsn. consisting of C, N, Si, Mn, P, S, Al, B, and Fe to specific hot and cold rollings and recrystallization treatment. CONSTITUTION:The steel contg. <=0.05wt% C, <=0.010% N, <=1% Si, <=1% Mn, <=0.15% P, <=0.010% S, <=0.3% Al, and <=1.5% B in B/N ratio and consisting of the balance Fe and unavoidable impurities is subjected to at least >=30% rolling in the temp. region of the Ar3 transformation point -500 deg.C at the last phase of the hot rolling stage. The hot rolled sheet obtd. in such a manner is coiled and is subjected to pickling as it is or after the annealing of the hot rolled sheet. Such hot rolled sheet is subjected to 30-75% cold rolling and finally to the recrystallization treatment. The amts. of the costly alloy elements to be added are thereby reduced and the need for stress relief annealing is eliminated. The non-oriented electrical steel sheet having low iron loss and high magnetic flux density is thus obtd.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of manufacturing a non-oriented electrical steel sheet with low iron loss and high magnetic flux density.

(Prior Art) Conventional electromagnetic W4 plates generally have a method of increasing the content of Si, AJ, etc. from the viewpoint of reducing eddy current loss due to increased specific resistance as a means of reducing iron loss. Also,
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 that, it is cold-rolled by 75% or more and subjected to high-temperature short-time annealing to produce a product. However, in the latter semi-process, as mentioned above, several percent of skin bath rolling is performed thereon.

(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 aims to solve the problems of the prior art. Mr+: 1% or less, P: 0
．． 15% or less, S: 0.010% or less, hej! jO
, 3% or less and B/N of 1.5 or less, with the balance consisting of Fe and unavoidable impurities.
, below the transformation point, at least 30% rolling under lubrication or non-lubrication at 500°C or higher, after winding, as is or hot-rolled plate annealing and pickling, 30% or more 75%
The present invention provides a method for producing a non-oriented electrical steel sheet with low iron scrap and high magnetic flux density, which comprises performing the following cold rolling and finally recrystallizing.

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, the content of C is preferably as low as possible in order to improve core loss, and is preferably 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 0.05% C, so the upper limit of C content was set at 0.05%.
And so. Si is added for the purpose of improving iron loss, but as the amount of Si increases, the magnetic flux density decreases, and the difference in the iron loss obtained by the manufacturing method of the present invention over the iron loss obtained by the conventional method becomes smaller. Not only that, but also one of the main points of the present invention
The upper limit of the amount of St added is set at 1% in order to suppress the cost increase due to the addition of alloys. In order to improve iron loss, it is better to have less N, and in the steel of the present invention, the upper limit was set to 0.010%. In particular, when suppressing the precipitation of ^l and lowering iron loss, it is preferable to add B to precipitate BN, but when the B/N ratio exceeds 5, excess B deteriorates the magnetism.
The upper limit of the amount was set at R/N of 1.5. In the steel of the present invention, Si
P is added to increase strength to prevent the steel plate from becoming too soft and difficult to punch if the amount is small. Addition of 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%. As with St, ^l may be added for the purpose of improving iron loss, but the upper limit is set to 0.3% in order to suppress the cost increase due to alloy addition. Also, like P, Mn is added as necessary to increase strength, but if it exceeds 1%, the transformation point decreases, and ferrite-austenite transformation tends to occur during annealing, resulting in deterioration of magnetism. The upper limit of the amount added 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.

8r3 Metamorphosis point [8rs(”c)=916 5
09C64Mn+ 333i + 50AJ + 25
The reason why hot rolling must be done at least 30% below the Ar3 transformation point is that rolling below the Ar3 transformation point reduces the (111) strength in the steel sheet and increases other strengths, especially the (100) strength, which improves electromagnetic properties. gets better. This is because the rolling reduction ratio at which the effect is sufficiently exhibited is 30% or more. Moreover, this effect becomes more remarkable 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 a temperature lower than this, the deformation resistance is high and the steel plate may suffer from swelling and softening, which is difficult in manufacturing.

Next, the reason why the cold rolling ratio was set to 30% or more and 75% or less will be described. As shown in FIG. 1, the present inventors have discovered that iron loss can be significantly reduced by lowering the cold rolling rate. This effect is noticeable in materials hot-rolled by 30% or more at Ar3 or lower and 500° C. or higher. This seems to be because the (111) strength in the steel plate can be kept low under these conditions.

The reason why the lower limit of the cold rolling rate is set to 30% is that 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.

Furthermore, Figure 1 shows the contribution of low-pressure cold rolling to improving iron loss, which is the main point of the present invention, for the network of chemical components shown in Table 2. The effect is noticeable in materials that have been hot-rolled by 30% or more at 500°C or higher, which is the range of the present invention, and below the transformation point, and
This shows that hot-rolled sheet annealing and lubricated rolling are more advantageous in improving iron loss. Hot-rolled plate annealing was performed at 730°C for 1 hour, and final annealing was performed at 700°C for 1 hour.

Table 2 wt% 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 are significantly improved compared to when the material with the same components is manufactured by the conventional process. However, when hot-rolled sheets are annealed, 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 Eftft properties of the steel of the present invention and comparative steel. This material consists of 1 continuous cast piece.
It was heated in the range of 250°C to 1000°C, and was finished by continuous hot rolling into a hot-rolled plate having a thickness of 1.0 to 3.0 fi, and then cold rolled to a final plate thickness of 0.5 fi. Recrystallization treatment after cold rolling was performed by 800-b continuous annealing. Materials with hot rolled plate annealing: 800~
Continuous annealing was performed at 850°C for 2 minutes.

The electromagnetic characteristics are iron loss W1515o and magnetic flux density B in the L and C directions. showed that. In addition, the average friction coefficient of rolling at 500"C from Ar3 when lubricated during hot rolling was less than 0.2, and approximately 0.28 in the non-lubricated state. This friction coefficient was determined by the actually measured advanced rate. This is a calculated value.

Examples l1hl to 8 in Table 1 are ultra-low carbon steels with a low Si content of 0.017. The iron loss value obtained by the method of the present invention for this steel type is approximately 6.5 W/kg, which is significantly improved compared to the value of approximately 8.5 W/kg obtained by 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 the sample at No. 6 was annealed for a long time to cause grain growth, W, 5. , o improved to 5W/kg. This means that the iron loss is further reduced by increasing the temperature and length of the final annealing. 1lkL9 to 1kll contains 0.8% Si
In the sample with added carbon steel, the iron loss is superior to that of ultra-low carbon steel, but
The improvement in iron loss achieved by the method of the present invention is not so remarkable in ultra-low carbon steels. Floors 2 to 15 are P-added samples, floors 16 to 1
Ill118 is a sample to which Mn is added, and it can be seen that the iron loss of both steel types is improved by the rolling process according to the method of the present invention. Further, as seen in 11kL19 to Na21, a similar effect appears in materials in which B is added so that the B/N ratio is approximately 1. The amount of C from 22 to 24 is 0.0.
Although it is a 4% low carbon steel, the iron loss increases due to the increase in the amount of C, but it can be confirmed that the iron loss is improved by passing through the process of the present invention.

(Effects of the Invention) According to the method of the present invention, not only can alloying elements (particularly the amount of St) be significantly reduced to obtain equivalent electromagnetic properties, but also
Conventionally, with the same composition, it is possible to obtain excellent electromagnetic properties that could only be obtained through a semi-process (skin pass rolling is performed after the full process, and final strain relief annealing is performed by the user). In this case, non-oriented electrical steel sheets with high magnetic flux density and low iron loss can be economically produced with a composition similar to that of ordinary cold-rolled steel sheets, 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 (2)

[Claims] (1) C: 0.05% or less, N: 0.010% by weight
Below, 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/N of 1.5% or less, with the balance consisting of Fe and unavoidable impurities at the final stage of the hot rolling process. Rolling of at least 30% at a temperature below the transformation point and 500°C or higher, after winding, as is or hot-rolled plate annealing, after pickling, cold rolling of 30% to 75% and final. A method for producing a non-oriented electrical steel sheet with excellent electromagnetic properties, characterized by subjecting it to recrystallization treatment. (2) 3 in the temperature range below Ar_3 transformation point and above 500℃
2. The method according to claim 1, wherein the rolling is carried out with lubrication of 0% or more, and the average friction coefficient between the roll and the steel sheet is 0.2 or less.