JPH1121658A - Nonoriented silicon steel sheet reduced in iron loss after magnetic annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonorinted silicon steel sheet sufficiently reduced in iron loss after magnetic annealing and produced at a low cost. SOLUTION: This production of a nonoriented silicon steel sheet is based on the knowledge that iron loss characteristic after magnetic annealing can be effectively improved by the addition of a proper amount of Cr in the specific range of the amount of V. This steel sheet has a composition consisting of, by weight, 0-0.005% C, 0-0.2% P, 0-0.005% N, 0-1.0% Si, 0.05-1.0% Mn, 0-0.004% sol. Al, 0.02% S, 0.0020-0.010% V, >0.040-<0.10% Cr, and the balance essentially Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art Non-oriented electrical steel sheets are classified into full-process materials and semi-process materials according to the manufacturing method. Of these, the full process material obtains predetermined magnetic characteristics by finish annealing on the steel manufacturer side, while the semi-process material obtains the predetermined magnetic characteristics by performing strain relief annealing after punching at the customer. What you get. In the semi-process material, since the crystal grains grow simultaneously with the removal of the processing strain during the strain relief annealing, the iron loss can be further reduced. For this reason, the strain relief annealing is also called “magnetic annealing”.

In order to improve grain growth during magnetic annealing, it is effective to reduce the amount of inclusions and precipitates in a steel sheet. For this reason, various attempts have been made to render inclusions and precipitates harmless. For example, Japanese Patent Application Laid-Open No. 3-249115 discloses a technique for making MnS agglomerate and coarsening by optimizing the amount of Mn in steel to make it harmless, and Japanese Patent Application Laid-Open No. 62-199720 discloses a slab heating method. By setting the temperature to 1150 ° C. or less,
A technique for preventing the re-solid solution of MnS and subsequent fine precipitation is disclosed, and Japanese Patent Publication No. 56-34351 discloses a technique for maintaining the slab at a specific temperature to coagulate and coarsen AlN.

[0003] With the recent energy saving of electrical equipment, there has been a demand for magnetic steel sheets having a lower iron loss after magnetic annealing than ever before. However, when manufacturing such an electromagnetic steel sheet having a low iron loss, Mn as in the related art is used.
In an electromagnetic steel sheet in which S and AlN are coarsened, grain growth cannot be sufficiently performed during magnetic annealing. For this reason, an electromagnetic steel sheet having more excellent grain growth properties has been required.

From such a viewpoint, Japanese Patent Application Laid-Open No. 3-2041
No. 3 includes V and N, which are impurity elements in non-oriented electrical steel sheets.
V: 0.01 wt% or less, N: 0.005 w
A technique for reducing iron loss by controlling precipitation of vanadium carbonitride, which is harmful to magnetic properties, by controlling the iron loss to less than t% is disclosed. It is by no means satisfactory, and if the amount of V is reduced to reduce iron loss, the production cost will increase. Therefore, an object of the present invention is to solve such a problem and to provide a non-oriented electrical steel sheet which has sufficiently low iron loss after magnetic annealing and can be manufactured at low cost.

[0005]

Means for Solving the Problems The present inventors have investigated in detail the effect of V on iron loss after magnetic annealing.
Instead of reducing the amount as much as possible, rather, by adding a certain amount of V and then adding an appropriate amount of Cr, the iron loss characteristics after magnetic annealing can be effectively improved, and the adverse effect of V can be appropriately reduced. Have found that they can be avoided.

[0006] The present invention has been made based on such findings, and in terms of% by weight, C: 0 to 0.005%, and P: 0 to 0%.
0.2%, N: 0 to 0.005%, Si: 0 to 1.0
%, Mn: 0.05 to 1.0%, Sol. Al: 0
0.004%, S: 0 to 0.02%, V: 0.0020
It is a non-oriented electrical steel sheet with low iron loss after magnetic annealing, characterized in that: -0.010%, Cr: more than 0.040% and less than 0.10%, and the balance substantially consisting of Fe.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below together with the reasons for limiting the same. The present inventors magnetically annealed a non-oriented electrical steel sheet containing V and having the composition shown in Table 1, and performed a detailed analysis on V precipitates. As a result, VN is mainly composed of V precipitates, but V
-It was found to be a composite nitride of Cr. Usually, Cr is contained in steel sheet as an unavoidable impurity in an amount of 0.01 to 0.04 wt.
%, Which is a component contained as an impurity.
It was found that r was involved in the formation of precipitates in the form of a composite nitride with V.

[0008]

[Table 1]

Based on the above findings, the present inventors considered that intentionally adding Cr to increase the size of the composite nitride and improve the grain growth after magnetic annealing, The following experiment was conducted based on such an idea. That is, as shown in Tables 2 to 4, steel having a V content of 6 levels and a Cr content of 0.035 to 0.110 wt% was melted at a laboratory level, hot rolled, and then pickled. Was performed. Subsequently, the hot-rolled sheet was cold-rolled to a sheet thickness of 0.5 mm, subjected to finish annealing at 720 ° C. × 1 minute, and further subjected to magnetic annealing at 750 ° C. × 2 hours.

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

FIG. 1 shows the relationship between the iron loss W15 / 50 after magnetic annealing of the steel sheet obtained in this way and the amounts of V and Cr. According to this, Cr is 0.045 wt%.
The contained steel sheet has a reduced iron loss as compared with a steel sheet having a Cr content of 0.035 wt% from the vicinity where the V content is 0.0020 wt% or more, and conversely if the V content exceeds 0.010 wt%. In addition, iron loss is worse than that of a steel sheet having a Cr content of 0.035 wt%. Such an effect of improving iron loss by Cr is recognized when the Cr content is more than 0.040 wt% and less than 0.10 wt%, and particularly when the Cr content is 0.045 to 0.080 wt%.
Is remarkable in the range. On the other hand, when the V amount is 0.
In the range of less than 0020 wt% or more than 0.010 wt% and the range of Cr content of 0.040 wt% or less and 0.10 wt% or more, the effect and the effect of the above-described Cr addition are hardly observed.

The reason why the iron loss is effectively reduced by adding an appropriate amount of Cr in a specific V amount range as described above is as follows.
This is presumably because V and Cr become complex nitrides and become coarser as compared with the case where Cr is at an unavoidable impurity level as described above, thereby promoting crystal grain growth. When the V content and the Cr content are increased to some extent, a composite nitride is formed, but the absolute content thereof is increased, thereby hindering the growth of crystal grains. It is considered that iron loss worsens.

Hereinafter, the reasons for limiting the component composition of the steel sheet of the present invention will be described. Si is an element effective for increasing the specific resistance of the steel sheet. However, if the content exceeds 1.0 wt%, the magnetic flux density decreases with a decrease in the saturation magnetic flux density. , Without addition). When Al is added in a small amount, it forms fine AlN and impairs magnetic properties. Al: 0
0.004 wt% (including the case of no addition). C is 0 to 0.00 in order to cause a problem of magnetic aging.
5 wt% (including the case of no addition).

Mn is required to be 0.05 wt% or more in order to prevent red hot brittleness during hot rolling, but if it exceeds 1.0 wt%, the magnetic flux density is reduced.
t%. If N is contained in a large amount, it forms a nitride and deteriorates magnetic properties. Therefore, the N content is set to 0 to 0.005 wt% (including the case where N is not added). P is an element effective for improving the punching property of the steel sheet.
Exceeds 0.2 to 0.2 wt% (however,
(Including the case of no addition). S is M between steel and Mn
Form nS. From such a viewpoint, it is preferable that the S content is as small as possible. However, if the S content is 0.02 wt% or less, there is no particular problem.
(However, the case without addition is included).

Although V is contained in steel as an unavoidable impurity, as described above, the effect of the present invention is obtained only when V is in the range of 0.0020 to 0.010 wt%. Therefore, the V content is 0.0020 to
0.010 wt%. In order to further reduce iron loss, the upper limit of the V content is set to 0.0055 wt.
% Is preferable. Cr is the most important component element in the present invention, and as described above, it is necessary to contain Cr in a range of more than 0.040 wt% and less than 0.10 wt% in order to avoid the adverse effect of V. For this reason, the amount of Cr is 0.
More than 040 wt% and less than 0.10 wt%, particularly preferably 0.045 to 0.080 wt%.

In the steel sheet according to the present invention, the balance is substantially composed of Fe.
It is no problem to further add b, Sn of 0.2 wt% or less, B of 0.005 wt% or less, and Zr of 0.05 wt% or less. Of these elements, Sb, Sn
B and Zr improve the magnetic properties by controlling the texture, and B and Zr fix a part of nitrogen.

In the non-oriented electrical steel sheet of the present invention, since the desired effects can be obtained if the component composition in the steel sheet is within the above range, there are no particular restrictions on the production conditions. It can be manufactured sufficiently under the following manufacturing conditions. That is, the molten steel blown in the converter is degassed to adjust to a predetermined component, and then casting and hot rolling are performed. Hot-rolled sheet annealing after hot rolling may be performed, but is not essential. Next, after a single sheet of cold rolling or two or more times of cold rolling with intermediate annealing being performed to obtain a predetermined sheet thickness, final annealing is performed.

[0020]

EXAMPLE The molten steel was blown in a converter and then degassed to adjust the composition as shown in Table 5. After casting, the steel was hot-rolled to a thickness of 2.0 mm. Next, after pickling this hot-rolled sheet, cold rolling was performed to a sheet thickness of 0.5 mm,
After performing the finish annealing at 00 ° C. for 2 minutes, 750 ° C. ×
Magnetic annealing was performed for 2 hours. The magnetic properties of the obtained steel sheet were measured using a 25 cm Epstein test piece. The results are shown in Table 5. According to Table 5, it can be seen that the non-oriented electrical steel sheet of the present invention example has significantly improved iron loss characteristics after magnetic annealing as compared with the steel sheet of the comparative example.

[0021]

[Table 5]

[0022]

As described above, the non-oriented electrical steel sheet of the present invention has excellent iron loss characteristics after magnetic annealing, and has a high V loss in the steel.
It can be manufactured at low cost without excessively reducing the amount.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amounts of V and Cr in a steel sheet and iron loss after magnetic annealing.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshihiko Oda 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd.

Claims (1)

[Claims] C. 0 to 0.005% by weight, P:
0 to 0.2%, N: 0 to 0.005%, Si: 0 to 1.
0%, Mn: 0.05-1.0%, Sol. Al: 0
0.004%, S: 0 to 0.02%, V: 0.0020
A non-oriented electrical steel sheet with low iron loss after magnetic annealing, characterized in that: -0.010%, Cr: more than 0.040% and less than 0.10%, and the balance substantially consists of Fe.