JP3235356B2 - Non-oriented electrical steel sheet with excellent magnetic properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties.

[0002]

2. Description of the Related Art In general, non-oriented electrical steel sheets are prepared by degassing molten steel blown in a converter, adjusting to predetermined components, casting, and then hot rolling, pickling, and subsequent cold rolling. It is manufactured by a series of processes in which the final thickness is set and finally the final annealing is performed. During this final annealing, if the dew point is high, Si, Al, etc. contained in the steel are oxidized and SiO
_2. Internal oxides such as Al ₂ O ₃ are generated, and the magnetic properties are deteriorated. If the atmosphere contains a large amount of nitrogen, it reacts with Al in the steel to generate AlN, which also causes deterioration of magnetic properties.

As a technique for preventing such nitriding and internal oxidation, a technique disclosed in Japanese Patent Publication No. 58-30368 is known. This technique prevents the generation of AlN, SiO ₂ , and Al ₂ O ₃ by setting the hydrogen in the atmosphere to 45% or more and the dew point to 0 ° C. or less.

However, in a thin electrical steel sheet, the ratio of the surface layer of the steel sheet to the thickness of the steel sheet is large, so that the magnetic properties are significantly deteriorated even when a very small amount of nitride and oxide is formed on the surface layer of the steel sheet. there is a possibility. For example, in a 100% H ₂ atmosphere (dew point −30 ° C.) where it is said that no internal oxide is generated in the above publication,
When the present inventors performed annealing of the electromagnetic steel sheet to which Al was added, it was confirmed that Al ₂ O ₃ was generated in the surface layer portion of the steel sheet, and the iron loss was significantly increased as compared with vacuum annealing.

[0005] From the above, it can be said that in order to further reduce the iron loss of the magnetic steel sheet, the control of the annealing atmosphere alone in the above publication is insufficient. Such magnetic steel sheets are also required to have a high magnetic flux density. The present invention has been made in view of such circumstances, and has as its object to provide a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density.

[0006]

In order to solve the above-mentioned problems, the present inventors conducted various experiments. As a result, the composition of the portion of the surface layer portion of the magnetic steel sheet of 10 μm or more was so small that Al could be substantially ignored. (Hereinafter, tr.Al), it was found that internal oxides can be completely prevented even at a dew point of about -20 ° C. In addition, by using Al-added steel as the component of the inner layer of the steel sheet, the magnetic flux density
It has also been found that an electromagnetic steel sheet having an excellent iron loss balance can be obtained.

The present invention has been made on the basis of such findings, and a surface layer portion of Al: 0.004% or less and an inner layer portion of Al: more than 0.1% and 1% or less by mass%. And wherein the surface layer portion comprises Si:
0.1-3.2%, Al: 0.004% or less, C: 0.
005% or less, N: 0.005% or less, the balance of unavoidable impurities and the composition of Fe.
% Or less, and the thickness thereof is not more per side 10μm or more, the inner layer portion, in mass%, Si: from 0.1 to 3.2
%, Al: more than 0.1% and 1% or less , C: 0.005%
Hereinafter, there is provided a non-oriented electrical steel sheet having excellent magnetic properties, comprising N: 0.005% or less, a balance of unavoidable impurities and Fe.

Hereinafter, the present invention will be described in detail based on experimental results. (1) Surface Layer First, the steel sheet component is C = 0.030 wt%, Si = 3.
0 wt%, Mn = 0.12 wt%, P = 0.11 wt
%, S = 0.004 wt%, N = 0.0045 wt%, and a cold rolled sheet with various amounts of Al was placed in a 100% H ₂ atmosphere (dew points of −20 ° C. and −30 ° C.) in which no nitride was formed.
C.) and 900 ° C. in vacuum in a final anneal. FIG. 1 shows the values of iron loss at this time.

FIG. 1 shows that t of which Al is 0.004 wt% or less.
r. In the Al region, no increase in iron loss is observed even at a dew point of −20 ° C., but if the Al content exceeds 0.004 wt%, the iron loss increases even if final annealing is performed at a low dew point of −30 ° C. I understand.

When the surface layer of the steel sheet having an increased iron loss and containing more than 0.004% of Al was observed by SEM, 0.2 to 0.5 μm of Al ₂ O ₃ was observed from the surface layer of the steel sheet to about 10 μm. On the other hand, no internal oxides were observed in the steel sheet having an Al content of 0.004% or less where the iron loss did not increase.

Further, as shown in FIG. 1, when annealing is performed in a vacuum in which internal oxides are not generated, iron loss does not deteriorate. It can be seen that Al ₂ O ₃ was generated in the part.

When the annealing atmosphere is a vacuum atmosphere, naturally, neither nitride nor internal oxide is generated.
Although it is possible to obtain a steel sheet with low iron loss, it is practically impossible to perform vacuum annealing on an actual machine. Therefore, a method for obtaining a material with low iron loss in a 100% H ₂ atmosphere in which no nitride is generated. After that, the study was advanced.

FIG. 1 shows that, in order to further reduce the iron loss of the magnetic steel sheet by preventing the formation of Al ₂ O _{3 in} the 100% H ₂ atmosphere annealing, the Al content is set to 0.00.
It is understood that the content needs to be 4 wt% or less. However,
As can be seen from the results of SEM observation, Al ₂ O ₃ because it has generated only the steel sheet surface layer portion, considered may be a Al ≦ 0.004 wt% only steel sheet surface layer portion which is Al ₂ O ₃ to produce.

By the way, in an electromagnetic steel sheet, it is considered that SiO ₂ is generated in addition to Al ₂ O ₃ by internal oxidation, and the presence thereof increases iron loss. However, since Si is harder to oxidize than Al, the dew point of the final annealing is -2.
When the temperature is regulated to 0 ° C. or lower, generation of SiO ₂ can be prevented.

Next, the depth from the surface layer of the steel sheet in the region of Al ≦ 0.004 wt% was examined. FIG. 2 shows Table 1.
No. 5 (tr. Al steel) as the surface layer of the steel sheet (hereinafter referred to as tr.
Al layer), steel type 10 (0.4% Al steel) as an inner layer of steel sheet, an annealing temperature of 900 ° C. (annealing atmosphere: 10
0% H ₂ atmosphere, dew point −20 ° C.). It shows the relationship between the magnetic properties and the depth of the Al layer from the surface of the steel sheet.

FIG. 2 shows that tr. It can be seen that the iron loss is high when the Al layer is less than 10 μm, but decreases when the Al layer is 10 μm or more. This is because, as described above, Al ₂ O ₃ is generated from the surface of the steel sheet to a depth of about 10 μm. For this reason, in the case of Al ≦ 0.004 wt% of tr. The depth of the Al layer is 10 μm or more per one side of the steel plate.

Next, the tr. The ratio of the Al layer to the total thickness of the steel sheet will be described. FIG. 3 shows that the surface layer of the steel sheet is steel type 5 (tr. Al steel) of Table 1 and the inner layer of the steel sheet is steel type 10
(0.4% Al steel), annealing temperature 900 ° C
(Annealing atmosphere: 100% H ₂ atmosphere, dew point −20 ° C.), the tr. The relationship between the ratio of the Al layer to the total thickness of the steel sheet and the magnetic flux density is shown.

FIG. 3 shows that the tr. When the ratio of the Al layer is 40% or less, the magnetic flux density does not decrease. A
It can be seen that when the ratio of the l layer exceeds 40%, the magnetic flux density is significantly reduced. This is because tr. In the Al layer, A
Since the texture has not been improved by the addition of l,
This is because there are relatively many {111} planes that are disadvantageous to the magnetic characteristics. As the proportion of the Al layer increases, the magnetic flux density decreases. From this, t of the steel sheet surface layer
r. The ratio of the Al layer to the total thickness of the steel sheet needs to be 40% or less. This ratio was the same even when the thickness of the steel sheet was changed.

Based on the above, the tr. The Al layer was made to be 10 μm or more per one side and 40% or less in total on both sides of the steel sheet with respect to the total thickness of the steel sheet. (2) Inner Layer Next, the appropriate amount of Al in the inner layer of the steel sheet will be described. FIG.
Then, the steel sheet surface layer is made of steel type 5 (tr. Al steel) in Table 1,
C = 0.0031wt%, Si = 2.6w
t%, Mn = 0.12 wt%, P = 0.08 wt%, S
= 0.006 wt%, N = 0.046 wt%, A
The relationship between the amount of Al in the inner layer of the steel sheet and the magnetic flux density when the steel sheet having various amounts of l was annealed at an annealing temperature of 900 ° C. (annealing atmosphere: 100% H ₂ atmosphere, dew point −20 ° C.) Show. Here, the ratio of the inner layer of the steel sheet to the total thickness of the steel sheet is 6
5% and 80%.

FIG. 4 shows that A irrespective of the ratio of the inner layer portion of the steel sheet.
It can be seen that the magnetic flux density is improved when the amount of l is 0.1 to 1 wt%. This is because when the Al content is 0.1 to 1 wt%, the texture improving effect is large, but when the Al content is less than 0.1 wt%, the texture improving effect is small.
%, The magnetic flux density decreases as the saturation magnetic flux density decreases.

Since the dew point was set to -20 ° C., no SiO ₂ was observed as described above. (2) Components The reasons for limiting the components of the present invention will be described.

Si: Si is an element effective for increasing the specific resistance of the steel sheet, and it is necessary to contain 0.1 wt% or more in order to sufficiently exhibit this effect. On the other hand, the saturation magnetic flux density decreases with the addition of Si,
If it exceeds wt%, the value becomes too low. Therefore, S
The i amount was in the range of 0.1 to 3.2 wt%.

Al: The amount of Al needs to be different between the surface layer portion and the inside of the steel sheet as described above. First, when Al is added to the surface layer portion of the steel sheet, Al ₂ O ₃ is generated, so the Al amount is set to 0.004 wt% or less. On the other hand, in the inner layer portion, the amount of Al was set to 0.1 to 1 wt% in order to improve the magnetic flux density.

C: Since C has a problem of magnetic aging, the content is set to 0.005 wt% or less where such a problem does not occur. N: If N exceeds 0.005 wt%, the magnetic properties deteriorate, so N is set to 0.005 wt% or less.

In addition, it is preferable to add or regulate the following elements in the following ranges. Mn: Mn is required to be 0.1 wt% or more in order to prevent red hot brittleness during hot rolling, but when it is 1 wt% or more, magnetic properties are degraded. Therefore, the amount of Mn is 0.1 to
1 wt%.

S: Since S forms MnS or the like which deteriorates magnetic properties, S is less likely to form MnS or the like.
It is preferable to regulate the content to not more than 02 wt%. P: P is an element necessary for improving the punching property of the steel sheet. However, if added in excess of 0.2 wt%, the magnetic flux density will be reduced, so that it is preferably 0.2 wt% or less.

It should be noted that addition of Sb, Sn, B, Cu, and Zr for improving the magnetic properties may not be any.
In addition, unavoidable impurity elements other than these elements are allowed in an amount that is contained in ordinary steel.

(3) Manufacturing Method The method for manufacturing the steel sheet of the present invention is not particularly limited as long as it is a clad steel sheet comprising the above-described surface layer and inner layer before the final annealing. . For example, at the stage of slab, tr. Al steel and Al
After welding the added steel, it is integrated by hot rolling, The inside of the Al steel slab is hollowed out and the Al
Any means can be used, such as a cast-in method for casting the added steel, a method of pressing during cold rolling, and the like. Regardless of the stage at which the clad is formed, the steel sheet may be formed into an electromagnetic steel sheet through a normal process. That is, after performing normal hot rolling,
After pickling and, if necessary, hot-rolled sheet annealing, a predetermined sheet thickness is obtained by one cold rolling or two cold rolling steps with intermediate annealing, and finally final annealing is performed. Regarding the final annealing conditions, as described above, the dew point is set to −20 ° C. or less in order to prevent internal oxidation of Si. The final annealing temperature is not particularly limited, and is usually 700 to 9
It may be about 50 ° C.

[0029]

EXAMPLES Slabs of steel types 1 to 13 shown in Table 1 were welded in combinations and ratios as shown in Table 2, and hot rolled to obtain clad materials. However, the numbers 1, 2, 7, 9, 21, and 24 were not clad materials but single plates. The hot rolled sheet was pickled and cold rolled to 0.5 to 0.2 mm. Then, these cold press plates were annealed under the final annealing conditions shown in Table 2. In addition, numbers 1 to
As for Nos. 6 and 9 to 25, after hot rolling, hot rolled sheet annealing was performed.

The magnetic properties were measured by processing Epstein test pieces from each steel sheet and measuring the magnetic properties of these test pieces at a frequency of 50 Hz. Table 3 shows the magnetic properties (magnetic flux density and iron loss) of each steel sheet.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3] This confirms that the steel sheet in which the surface layer portion and the inner layer portion are defined according to the present invention has a better magnetic flux density-iron loss balance than the comparative example.

[0034]

As described above, according to the present invention, a non-oriented electrical steel sheet having low iron loss and high magnetic flux density can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of Al and iron loss.

FIG. The figure which shows the relationship between the depth from the steel sheet surface layer of an Al layer, and iron loss.

FIG. The figure which shows the relationship between the ratio of the Al layer to the total thickness of the steel sheet and the magnetic flux density.

FIG. 4 is a diagram showing the relationship between the amount of Al in a steel sheet inner layer and the magnetic flux density.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-10019 (JP, A) JP-A-2-221326 (JP, A) JP-A-53-109815 (JP, A) JP-A-3-109815 140442 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00-38/60

Claims (1)

(57) [Claims] 1. A magnetic steel sheet comprising, in mass%, a surface layer portion of Al: 0.004% or less and an inner layer portion of Al: more than 0.1% and 1% or less , wherein the surface layer portion is formed. Is Si:
0.1-3.2%, Al: 0.004% or less, C: 0.
005% or less, N: 0.005% or less, the balance of unavoidable impurities and the composition of Fe.
% Or less, and the thickness thereof is 10 μm or more per one side, and the inner layer portion is expressed by mass% and Si: 0.1 to 3.2.
%, Al: more than 0.1% and 1% or less , C: 0.005%
Hereinafter, a non-oriented electrical steel sheet having excellent magnetic properties, comprising N: 0.005% or less, and the balance of unavoidable impurities and Fe.