JP2008231504A - Non-oriented electromagnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-oriented electromagnetic steel sheet which can stably realize an effect of reducing high-frequency iron loss due to the addition of Mn. <P>SOLUTION: The non-oriented electromagnetic steel sheet comprises, by mass%, 0.005% or less C, 1.5 to 4% Si, 1 to 5% Mn, 0.1% or less P, 0.005% or less S, 3% or less Al, 0.005% or less N; further 0.0010% or less Se; or 0.0020% or less Se, 0.0005 to 0.007% Ca; or 0.0020% or less Se, 0.0003 to 0.005% Mg; and the balance Fe with unavoidable impurities. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-oriented electrical steel sheet, and more particularly to a non-oriented electrical steel sheet having excellent high-frequency iron loss characteristics suitable for use in a hybrid electric vehicle or the like.

  The hybrid electric vehicle motor is designed to be driven in a high frequency range of 400 Hz to 2 kHz from the viewpoint of miniaturization and high efficiency. Therefore, it is desirable that the non-oriented electrical steel sheet used for the core material of such a motor has a low high-frequency iron loss. In order to reduce high-frequency iron loss, it is effective to reduce the plate thickness and increase the specific resistance.

  Of these, reducing the plate thickness not only causes a decrease in rigidity and makes it difficult to handle materials, but also increases the number of stamping steps and stacking steps in motor core manufacturing. On the other hand, in order to increase the specific resistance, addition of Si is effective and does not cause a reduction in the plate thickness, which is preferable in reducing the high-frequency iron loss. However, since Si is an element having a large solid solution strengthening ability, there is a problem that the material is hardened with the addition of Si and the rollability and workability are lowered.

As means for solving such problems, there is a technique of adding Mn instead of Si. Since Mn has a lower solid solution strengthening ability than Si, it is possible to improve high-frequency iron loss while suppressing deterioration in manufacturability. As a technique using such an effect of Mn, for example, in Patent Document 1, C: 0.005 mass% or less, Si: 0.5 to 2.5 mass%, Mn: 1.0 to 3.5 mass% A non-oriented electrical steel sheet containing Al: 1.0 to 3.0 mass% is disclosed. Patent Document 2 includes non-direction containing C: 0.01 mass% or less, Si: 3.0 mass% or less, Mn: 1.0 to 4.0 mass%, Al: 1.0 to 3.0 mass%. An electrical steel sheet is disclosed.
JP 2002-47542 A JP 2002-30397 A

  However, the techniques of Patent Documents 1 and 2 both increase the hysteresis loss as the amount of Mn added increases, and the expected loss of iron loss may not be obtained. There was a problem that the reduction effect could not be obtained stably.

  Then, the objective of this invention is providing the non-oriented electrical steel plate which can implement | achieve the high frequency iron loss reduction effect by Mn addition stably.

  In order to solve the problem of the conventional Mn-added non-oriented electrical steel sheet, that is, the problem that hysteresis loss increases due to the addition of Mn, the inventors have conducted intensive studies to find out the cause. As a result, Se inevitably mixed from ferromanganese used as a Mn raw material generates Mn and precipitates, and the presence of this Se precipitates hinders Mn's iron loss reduction effect. Therefore, in order to effectively exhibit the effect of reducing the iron loss of Mn, it has been found that the reduction of Se mixed as an inevitable impurity is effective, and the present invention has been completed.

  That is, the present invention is C: 0.005 mass% or less, Si: 1.5-4 mass%, Mn: 1-5 mass%, P: 0.1 mass% or less, S: 0.005 mass% or less, Al: 3 mass% Hereinafter, it is a non-oriented electrical steel sheet containing N: 0.005 mass% or less, further containing Se: 0.0010 mass% or less, and the balance being Fe and inevitable impurities.

  In the present invention, C: 0.005 mass% or less, Si: 1.5 to 4 mass%, Mn: 1 to 5 mass%, P: 0.1 mass% or less, S: 0.005 mass% or less, Al: 3 mass% In the following, N: 0.005 mass% or less, Se: 0.0020 mass% or less, Ca: 0.0005 to 0.007 mass%, the balance being Fe and unavoidable impurities It is a steel plate.

  In the present invention, C: 0.005 mass% or less, Si: 1.5 to 4 mass%, Mn: 1 to 5 mass%, P: 0.1 mass% or less, S: 0.005 mass% or less, Al: 3 mass% Hereinafter, N: 0.005 mass% or less, Se: 0.0020 mass% or less, Mg: 0.0003 to 0.005 mass%, the balance being Fe and unavoidable impurities It is a steel plate.

  Further, the non-oriented electrical steel sheet of the present invention may be one or two selected from Sb: 0.0005 to 0.05 mass% and Sn: 0.0005 to 0.05 mass% in addition to the above component composition. It contains seeds.

  The non-oriented electrical steel sheet of the present invention is characterized by being Ti: 0.002 mass% or less.

  According to the present invention, the high-frequency iron loss of the Mn-added non-oriented electrical steel sheet can be stably reduced, which contributes to the improvement of product quality and the yield. Furthermore, since the non-oriented electrical steel sheet of the present invention is excellent in high-frequency iron loss characteristics, it can be suitably used as a core material for motors for hybrid electric vehicles and machine tools.

An experiment that triggered the development of the present invention will be described.
In order to investigate the influence of Mn on the magnetic properties, the inventors investigated C: 0.0015 mass%, Si: 2.9 mass%, Al: 1.2 mass%, P: 0.01 mass%, S: 0.0007 mass. %, N: 0.0021 mass%, Mn was changed in the range of 0.1 to 3.5 mass%, melted in the laboratory, hot rolled into a hot-rolled sheet, and then 100 vol% Hot-rolled sheet annealing at 1000 ° C. for 30 seconds was performed in an N ₂ atmosphere. Next, the hot-rolled sheet was cold-rolled to form a cold-rolled sheet having a thickness of 0.30 mm, and then subjected to finish annealing at 950 ° C. for 30 seconds in an atmosphere of 20 vol% H ₂ -80 vol% N ₂ , and non-directional electromagnetic A steel plate was used.

Next, from the non-oriented electrical steel sheet obtained as described above, an Epstein test piece having a width of 30 mm and a length of 280 mm was cut out from the rolling direction and the direction perpendicular to the rolling direction, and in accordance with JIS C2550, a maximum magnetic flux density of 1.0 T, The iron loss W _10/400 at a frequency of 400 Hz was measured. The _{circles in} FIG. 1 show the results of the above measurement in _terms of the relationship between the Mn content and W _10/400 . From this result, when Mn is less than 1 mass%, the iron loss decreases with an increase in the Mn content. However, when it is 1 mass% or more, the decrease in iron loss is moderate, and in the high Mn region of 2% or more, the iron loss is rather low. It became clear that there was a tendency to increase.

  In order to investigate this cause, when the precipitate in steel was observed with TEM about 2 mass% Mn addition steel, it was recognized that the selenide of Mn has precipitated in the grain boundary. Moreover, when Se content in steel was quantitatively analyzed, it was found to be 11 to 15 mass ppm.

  Therefore, in order to clarify the influence of Se on the magnetic properties, C: 0.0016 mass%, Si: 2.8 mass%, Al: 1.3 mass%, P: 0.01 mass%, S: 0.0007 mass% , N: containing 0.0021 mass%, using a high-purity Mn raw material, steel in which the Mn content was changed in the range of 0.1 to 3.5 mass% was melted in the laboratory, and the above experiment was performed. It was set as the non-oriented electrical steel sheet on the same conditions. In addition, all Se content in the said steel was 5 massppm or less.

With respect to the non-oriented electrical steel sheet obtained as described above, the high-frequency iron loss W _10/400 was measured under the same conditions as in the above experiment, and the results are indicated by ◯ in FIG. From this result, when Se is reduced to 5 massppm or less, if Mn is less than 1 mass%, the effect of Mn on the iron loss reduction effect is small, but the iron loss decreases as the amount of Mn added increases, and Se reduction is reduced. It turns out that the effect appears. The cause of this is not clear at this time, but the amount of Mn selenide produced depends on the amount of Se. Therefore, the lower the Se, the smaller the amount of Mn selenide and the easier the grain growth. Furthermore, in high Mn steel, the driving force of grain growth is reduced due to the Mn solution drag, so even if there is a slight change (reduction) in the precipitate of Se, the grain growth property has a synergistic effect. It is considered that the effect of Se reduction appears as the Mn content increases. In addition, MnSe is considered as a selenium compound of Mn.

Next, in order to confirm the influence of Se on iron loss, C: 0.0020 mass%, Si: 3.10 mass%, Mn: 2.0 mass%, Al: 1.2 mass%, P: 0.01 mass%, S: 0.0004 mass%, N: 0.0018 mass%, and the content of Se is tr. Steel changed in a range of ˜50 mass ppm was melted in a laboratory, and a non-oriented electrical steel sheet was obtained under the same conditions as in the above experiment, and high-frequency iron loss W _10/400 was measured.

  The results are shown in FIG. 2 as the relationship between Se content and iron loss. From FIG. 2, it can be seen that the iron loss is greatly reduced when the Se content is 10 mass ppm or less. This is presumably because the selenide content of Mn decreased due to Se reduction, and the grain growth property improved. Therefore, in this invention, content of Se shall be 10 massppm or less. Preferably, it is 5 massppm or less.

Next, the reason for limiting the composition range of components other than Se will be described.
C: 0.005 mass% or less Since C is more than 0.005 mass%, Mn-based carbides are generated and the iron loss is increased, so the upper limit is made 0.005 mass%. Preferably it is 0.002 mass% or less.

Si: 1.5-4 mass%
Since Si is an element effective for increasing the specific resistance of the steel sheet, it is added in an amount of 1.5 mass% or more. However, if it exceeds 4 mass%, the iron loss is reduced, but the magnetic flux density is reduced as the saturation magnetic flux density is reduced. Therefore, Si is set to a range of 1.5 to 4 mass%.

Mn: 1 to 5 mass%
Since Mn is an element effective for increasing the specific resistance of the steel sheet, the lower limit is set to 1 mass%. On the other hand, if it exceeds 5 mass%, the magnetic flux density decreases, so the upper limit is set to 5 mass%. In order to further reduce the iron loss, it is more preferable that Mn is 1.5 mass% or more.

P: 0.1 mass% or less When P is added in excess of 0.1 mass%, the steel sheet becomes hard and rolling becomes difficult. Therefore, the upper limit is made 0.1 mass%.

S: 0.005 mass% or less If the content of S exceeds 0.005 mass%, iron loss increases due to precipitation of MnS, so the upper limit is made 0.005 mass%. Preferably, it is 0.001 mass% or less.

Al: 3 mass% or less Al, like Si, is an element effective for increasing the specific resistance. However, if it exceeds 3 mass%, the iron loss decreases, but the magnetic flux density decreases as the saturation magnetic flux density decreases, so the upper limit is set to 3 mass%.

N: 0.005 mass% or less When the content of N is large, it is combined with Al to increase the precipitation amount of AlN, which causes an increase in iron loss. Therefore, N is set to 0.005 mass% or less.

The non-oriented electrical steel sheet of the present invention can contain Ca and Mg in the following ranges in addition to the essential components.
Ca: 0.0005 to 0.007 mass%
Ca is combined with the precipitated selenide and coarsens the precipitate, and therefore has an effect of reducing iron loss. In order to acquire the said effect, adding 0.0005 mass% or more is preferable. On the other hand, if it exceeds 0.007 mass%, the precipitation amount of CaS and selenide increases excessively, and the iron loss increases on the contrary, so the upper limit is made 0.007 mass%. In addition, when adding Ca, since Se precipitates together with Ca, the content of Se can be allowed up to 20 massppm. However, even in this case, it is preferably 10 massppm or less, more preferably 5 massppm or less.

Mg: 0.0003 to 0.005 mass%
Mg forms an oxide in the steel, Se segregates in the oxide and coarsens, so it has the effect of reducing iron loss. In order to acquire the said effect, adding 0.0003 mass% or more is preferable, and addition of 0.0005 mass% or more is more preferable. On the other hand, it is difficult to add more than 0.005 mass%, and the cost is unnecessarily increased, so the upper limit is set to 0.005 mass%. In addition, when adding Mg, since Se precipitates together with Mg, the content of Se can be allowed up to 20 massppm. However, even in this case, it is preferably 10 massppm or less, more preferably 5 massppm or less.

Furthermore, in the non-oriented electrical steel sheet of the present invention, Sb and Sn can be added in the following ranges in addition to the essential components Ca and Mg.
Sb and Sn are preferably added in an amount of 0.0005 mass% or more because addition of 0.0005 mass% or more has the effect of improving the texture and improving the magnetic flux density. More preferably, it is 0.01 mass% or more. On the other hand, excessive addition tends to embrittle the steel sheet, so the upper limit is made 0.05 mass%.

Ti forms carbonitride with C and N in the steel. However, if the Ti content increases, the amount of carbonitride deposited increases and the iron loss increases, so it is limited to 0.002 mass% or less. It is preferable to do.
Other than the above components are Fe and inevitable impurities.

Next, the manufacturing method of the non-oriented electrical steel sheet of this invention is demonstrated.
The non-oriented electrical steel sheet of the present invention is not particularly limited with respect to the production method except that the component composition is within the range described above, and may be a generally known method. That is, the molten steel blown in the converter is degassed to adjust the component composition within the predetermined range, and continuously cast into a slab and hot rolled. The finish rolling finish temperature and the coiling temperature in hot rolling need not be particularly limited, and may be normal conditions. Moreover, although hot-rolled sheet annealing after hot rolling may be performed, it is not essential. Next, it is preferable to obtain a predetermined sheet thickness by two or more cold rollings with one cold rolling or intermediate annealing and finish annealing to obtain a product (non-oriented electrical steel sheet).

The molten steel blown in the converter is degassed, various steels having the component compositions shown in Tables 1-1 and 1-2 are melted, continuously cast into a slab, and the slab is 1100 ° C. × After heating for 1 hr, a hot rolled sheet having a plate thickness of 2.0 mm was formed by hot rolling at a finish rolling finishing temperature of 800 ° C. and wound at 610 ° C. Subsequently, this hot-rolled sheet was subjected to hot-rolled sheet annealing at 1000 ° C. for 30 seconds in a 100 vol% N ₂ atmosphere, and then cold-rolled to form a cold-rolled sheet having a thickness of 0.30 mm, and then 20 vol% in H ₂ -80vol% _{N 2} atmosphere, it was non-oriented electrical steel sheet subjected to annealing finishing under the conditions shown in Table 1.

From the non-oriented electrical steel sheet obtained as described above, an Epstein test piece having a width of 30 mm and a length of 280 mm is cut out from the rolling direction and the direction perpendicular to the rolling direction, and in accordance with JIS C2550, the maximum magnetic flux density is 1.0 T and the frequency is 400 Hz. The iron loss W _10/400 and the magnetic flux density B ₅₀ at a magnetic field strength of 5000 A / m were measured, and the results are shown in Tables 1-1 and 1-2.

From Tables 1-1 and 1-2, the non-oriented electrical steel sheet suitable for the composition of the present invention has an iron loss W _10/400 of 12.40 kg / kg or less and a magnetic flux density B ₅₀ of 1.64 T or more. It can be seen that the magnetic properties are excellent.

  The non-oriented electrical steel sheet of the present invention can be applied to fields such as an air compressor motor, a machine tool motor, and a high-speed generator in addition to the core material of an automobile motor.

It is a graph which shows the influence of Se content which has on the relationship between the iron loss of a non-oriented electrical steel sheet, and Mn content. It is a graph which shows the influence of Se content which has on the iron loss of a high Mn non-oriented electrical steel sheet.

Claims (6)

C: 0.005 mass% or less, Si: 1.5 to 4 mass%, Mn: 1 to 5 mass%, P: 0.1 mass% or less, S: 0.005 mass% or less, Al: 3 mass% or less, N: 0.00. A non-oriented electrical steel sheet containing 005 mass% or less, further containing Se: 0.0010 mass% or less, the balance being Fe and inevitable impurities. C: 0.005 mass% or less, Si: 1.5 to 4 mass%, Mn: 1 to 5 mass%, P: 0.1 mass% or less, S: 0.005 mass% or less, Al: 3 mass% or less, N: 0.00. A non-oriented electrical steel sheet containing 005 mass% or less, further containing Se: 0.0020 mass% or less, Ca: 0.0005-0.007 mass%, and the balance being Fe and inevitable impurities. C: 0.005 mass% or less, Si: 1.5 to 4 mass%, Mn: 1 to 5 mass%, P: 0.1 mass% or less, S: 0.005 mass% or less, Al: 3 mass% or less, N: 0.00. A non-oriented electrical steel sheet containing 005 mass% or less, further containing Se: 0.0020 mass% or less, Mg: 0.0003-0.005 mass%, and the balance being Fe and inevitable impurities. The non-oriented electrical steel sheet according to any one of claims 1 to 3, further comprising Sb: 0.0005 to 0.05 mass% in addition to the component composition. The non-oriented electrical steel sheet according to any one of claims 1 to 4, further comprising Sn: 0.0005 to 0.05 mass% in addition to the component composition. The non-oriented electrical steel sheet according to any one of claims 1 to 5, further containing Ti: 0.002 mass% or less in addition to the above component composition.

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