JPH1088297A - Nonoriented silicon steel sheet reduced in iron loss after magnetic annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet capable of manufacture without increasing costs and sufficiently reduced in iron loss after magnetic annealing. SOLUTION: This nonoriented silicon steel sheet has a composition consisting of, by weight, <=0.005% C, <=0.2% P, <=1.5% Si, 0.2-0.8% Mn, <=0.004% (including 0%) Al, <=0.005% (including 0%) N, <=0.001% (including 0%) S, <=0.005% (including 0%) Ti, and the balance essentially Fe.

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 capable of obtaining a low iron loss after magnetic annealing.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are classified into full-process materials and semi-process materials according to their manufacturing methods. Among them, the full process material obtains predetermined magnetic characteristics by finish annealing on the steel maker side. On the other hand, the semi-process material obtains predetermined magnetic properties by performing strain relief annealing after punching in a customer. In the case of the semi-process material, the crystal grains grow simultaneously with the removal of the processing strain during the strain relief annealing, so that the iron loss can be further reduced. For this reason, the strain relief annealing is also called “magnetic annealing”.

Conventionally, inclusions and precipitates have been rendered harmless in order to improve the grain growth during magnetic annealing.

For example, JP-A-63-195217 discloses that Si = 0.1 to 1.0%, sol. Al = 0.0
In a steel sheet of 0.01 to 0.005%, SiO ₂ in steel,
M based on the total weight of the three types of inclusions, MnO and Al ₂ O ₃
A technique has been disclosed in which the morphology of inclusions is controlled by setting the weight ratio of nO to 15% or less to improve the grain growth during magnetic annealing.

Japanese Patent Laid-Open Publication No. Hei 8-3699 discloses S
When i = 1.0% or less and Al = 0.2 to 1.5%, R
A technique for improving grain growth during magnetic annealing by adding 2 to 80 ppm of EM is disclosed.

Further, Japanese Patent Application Laid-Open No. 5-234736 discloses that Si = 0.1 to 2.0% and Al = 0.1 to 1.0%.
%, S <0.003%, and Sn = 0.01 to 0.03% in steel sheets, SiO ₂ , MnO, and Al ₂ O ₃ .
10% by weight of MnO to the total weight of the inclusions
The form of the inclusions is controlled by the following, the hot rolling heating temperature is 900 to 1100 ° C., and the batch annealing after the hot rolling is performed at 70 ° C.
There is disclosed a technique for improving the grain growth by performing the process at 0 to 900 ° C.

[0007]

However, in the technology described in Japanese Patent Application Laid-Open No. 63-195217, the iron loss of the steel sheet after magnetic annealing is 4.44 to 4.75 W / Kg, which is satisfactory. is not. In the technique described in JP-A-8-3699, the cost increases because REM is used. In the technology described in JP-A-5-234736, Sn addition is essential,
Since batch annealing is required, an increase in cost cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and is a non-directional electromagnetic device which can be manufactured without increasing the cost and has sufficiently low iron loss after magnetic annealing. The purpose is to provide steel sheets.

[0009]

Means for Solving the Problems The above-mentioned problems are expressed in terms of% by weight,
C: 0.005% or less, P: 0.2% or less, Si: 1.
5% or less, Mn: 0.2 to 0.8%, Al: 0.
004% or less (including 0), N: 0.005% or less (0
), S: 0.001% or less (including 0), Ti:
The problem is solved by a non-oriented electrical steel sheet whose content is 0.005% or less (including 0) and the balance is substantially Fe. Here, "the balance is substantially Fe" means that unavoidable impurities and other trace amounts of additives not related to the technical idea of the present invention may be contained.

That is, the gist of the present invention is that the S content is 10 p
pm or less (including 0) and the Ti content is controlled to a very small amount of 50 ppm or less (including 0) to significantly reduce iron loss after magnetic annealing.

Hereinafter, the present invention will be described in detail based on experimental results. [Reason for limiting S content] First, in order to investigate the effect of S content on iron loss, C: 0.0026%, Si:
0.35%, Mn: 0.55%, P: 0.05%, t
r. Al%, Ti = 0.0020%, N = 0.0020
%, And steel with various S contents was melted in a laboratory and hot rolled.
Pickling was performed. Subsequently, the hot-rolled sheet was cold-rolled to a thickness of 0.5 mm, subjected to finish annealing at 750 ° C. × 1 min, and further subjected to magnetic annealing at 750 ° C. × 2 hours.

[0012] Figure 1 shows the iron loss W _{15/5 0} relationship after the S content and the magnetic annealing of samples obtained in this way. Here, the magnetic measurement was performed using a 25 cm Epstein test piece. FIG. 1 shows that when S ≦ 10 ppm, the iron loss W _15/50 is 4.0 W / kg or less, and the iron loss is significantly reduced.

From the above, the S content is set to 10 ppm or less, more preferably, 5 ppm or less.

[Reason for Limiting Ti Content] Next, in order to investigate the production stability of this steel type, C: 0.0030%, S
i: 0.35%, Mn: 0.50%, P: 0.100
%, Tr. Al, N = 0.0025%, S = 0.000
10 charge of 4% steel was melted, hot rolled, and then pickled. Subsequently, the hot-rolled sheet is cold-rolled to a sheet thickness of 0.5 mm, subjected to finish annealing at 750 ° C. × 1 min, and
Magnetic annealing was performed at 0 ° C for 2 hours. As a result, iron loss is 3.
It was found to vary greatly from 90 to 4.50 W / kg.

In order to investigate the cause, a thin film was prepared from a sample after magnetic annealing and observed by TEM. As a result, in the sample with low iron loss, fine precipitates were not observed, but in the sample with high iron loss, 50 nm
Some TiN was observed. From this, it became clear that the cause of the iron loss variation was due to the precipitation of fine TiN.

Therefore, in order to investigate the effect of Ti on grain growth, C: 0.0020%, Si: 0.35%,
Mn: 0.50%, P: 0.050%, tr. Al, N
= 0.0020%, S = 0.002%, and variously changed steel contents were melted in a laboratory, hot rolled, and then pickled.
Subsequently, the hot-rolled sheet was cold-rolled to a thickness of 0.5 mm,
Finish annealing at 50 ° C x 1 min.
Magnetic annealing was performed for 2 hours.

[0017] FIG. 2 shows the iron loss W _15/50 relationship after the Ti content and the magnetic annealing of samples obtained in this way. From FIG. 2, it can be seen that when Ti ≦ 50 ppm, the iron loss W _15/50 becomes 4.0 W / kg or less, and a low iron loss can be stably obtained.

From the above, Ti is set to 50 ppm or less, more preferably 20 ppm or less.

[Reasons for Limiting Other Components] Next, reasons for limiting other components will be described.

Although Si is an effective element for increasing the specific resistance of the steel sheet, if the content exceeds 1.5%, the magnetic flux density decreases with a decrease in the saturation magnetic flux density. Therefore, the upper limit is set to 1.5%.

Since Al forms AlN and lowers the grain growth, the content of Al is set to 0.004% or less.

C is 0.005% due to the problem of magnetic aging.
% Or less.

Mn is required to be at least 0.2% in order to prevent red hot brittleness during hot rolling, but when it exceeds 0.8%, the magnetic flux density is reduced. did.

P is an element necessary for improving the punching property of the steel sheet, but if added in excess of 0.2%, the steel sheet becomes brittle.

[0025] N is set to 0.005% or less because the precipitation amount of AlN increases when the N content is large, and the grain growth decreases and the iron loss increases even when the AlN becomes coarse.

[Manufacturing method] In the present invention, S, Ti
If the content is within a predetermined range, the production method may be an ordinary method. That is, the molten steel blown in the converter is degassed and adjusted to a predetermined component, and subsequently casting and hot rolling are performed. The finish annealing temperature and the winding temperature during hot rolling do not need to be particularly specified, and may be normal. In addition, hot-rolled sheet annealing after hot-rolling may be performed, but is not essential. Next, final cold-rolling or cold-rolling two or more times with intermediate annealing to obtain a predetermined sheet thickness is performed, followed by final annealing.

[0027]

EXAMPLES The steels shown in Table 1 were cast into a given component after being degassed after being blown in a converter,
After heating for 1 hour at a slab heating temperature of 1200 ° C., hot rolling was performed to a sheet thickness of 2.0 mm. Hot rolling finish temperature is 80
0 ° C. The winding temperature is 650 ° C for the steel sheets No. 1 to No. 13, No. 15 and No. 16, and 5 for the steel sheet No.
50 ° C. For No. 14 steel plate, 800
The hot rolled sheet was annealed at 3 ° C. for 3 hours. Next, this hot-rolled sheet was pickled, and then cold-rolled to a sheet thickness of 0.5 mm.
Annealing was performed under the finish annealing conditions shown in
hr magnetic annealing was performed.

The magnetic properties were measured using a 25 cm Epstein test piece. Table 1 also shows the magnetic properties of each steel sheet.

[0029]

[Table 1]

In Table 1, the steel sheets No. 1 to No. 11 are S
The content of i is at the level of 0.35%, and the finish annealing temperature is 750 ° C. Among them, those having No. 1 to No. 4 in which the S content and the Ti content are within the scope of the present invention are S or Ti.
W15 / ₅₀ is lower than those of Nos. 5 to 7 whose contents exceed the range of the present invention. No. 8 steel plate is Al
Since the content exceeds the range of the present invention, W _15/50 is high. No. 9 steel sheet is C, No. 10 steel sheet is Mn
However, the steel sheet No. 11 has a high W _15/50 because N exceeds the range of the present invention. Further, in the steel sheet No. 10 in which Mn exceeds the range of the present invention, the magnetic flux density _B50 is reduced.

The steel sheets No. 12 to No. 15 have a Si content of 0.7% and a finish annealing temperature of 800 ° C. Also in these, those of No. 12 to No. 14 in which the S content and the Ti content are within the range of the present invention are more W ₁₅ than those of No. 15 in which the Ti content exceeds the range of the present invention. _{/ 50} is low.

[0032] In steel sheet No.16, because the Si content exceeds the range of the present invention, W _15/50 is low but B ₅₀ also becomes lower.

The value of the iron loss W _15/50 is influenced by the Si content and the finish annealing temperature. When these values are the same, the steel sheet within the scope of the present invention has a low iron loss W _15/50 . It turns out that it has.

[0034]

As described above, in the present invention,
Since S is controlled to a very small amount of 10 ppm or less (including 0) and Ti is controlled to a very small amount of 50 ppm or less (including 0), a non-oriented electrical steel sheet having low iron loss after magnetic annealing can be manufactured at low cost. .

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the S content and iron loss after magnetic annealing.

FIG. 2 is a graph showing the relationship between the amount of Ti and iron loss after magnetic annealing.

Claims (1)

[Claims] (1) In weight%, C: 0.005% or less, P:
0.2% or less, Si: 1.5% or less, Mn: 0.2 to
0.8%, Al: 0.004% or less (including 0), N: 0.005% or less (including 0), S: 0.0
01% or less (including 0), Ti: 0.005% or less (0
And a balance substantially consisting of Fe, wherein the non-oriented electrical steel sheet has low iron loss after magnetic annealing.