JPH075985B2 - Manufacturing method of non-oriented electrical steel sheet having excellent iron loss characteristics and magnetic flux density in low magnetic field - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent iron loss characteristics and magnetic flux density in a low magnetic field.

[Conventional technology and problems to be solved]

In the manufacturing process of electromagnetic steel sheets, when strain is applied to the steel sheet, it is a general tendency that the final magnetic properties, especially the iron loss value, deteriorate due to the accumulation of internal stress due to lattice defects or strain of the lattice. Well known. This is because lattice defects or internal stress hinders domain wall movement in the magnetization process.

However, iron-based soft magnetic materials with a bcc structure (Si steel plates, etc.) have positive magnetostriction characteristics, so by applying tensile residual stress to the steel plate surface layer, the domain wall movement of the surface layer part Becomes easier and the iron loss decreases,
The presence of residual stress itself also improves the magnetic properties.

Such strain is generally given by coating an insulating coating having a lower thermal expansion coefficient than that of the base steel sheet and finally bake-annealing the iron loss in the grain-oriented Si steel sheet. Is a powerful tool for
Non-oriented Si steel sheets are disclosed in, for example, JP-A-56-55574 and JP-A-58-110679.

In contrast to such a technique, JP-A-55-85630 proposes a method of imparting tensile strain to a steel sheet in a recrystallization annealing process. The main point of this technique is to give the steel strip an elongation (tensile strain) in the following range defined by the annealing temperature in the annealing process.

0.0035T−3.8 ≦ logR ≦ −0.0035T−2.8 According to this proposal, the optimum elongation rate for improving iron loss increases as the high temperature annealing increases. However, according to the study by the present inventors, the optimum condition of the tensile strain to be applied in the annealing process in order to improve the magnetic properties is not related to the annealing temperature, and moreover, the amount of strain to be applied is excessive in the above proposal. It was found that the magnetic properties could not be sufficiently improved.

[Means for Solving the Problems]

In view of such a problem, the present invention is such that the optimum value of the tensile strain to be applied in the annealing process is always constant regardless of the annealing temperature, and that it exists in a region lower than the region defined in the above-mentioned conventional technique. Further, they have found that not only the improvement of iron loss characteristics but also the magnetic flux density in a low magnetic field can be effectively improved by imparting such a tensile strain in a low region, and the present invention has been completed.

That is, the features of the present invention are as follows.

(1) Upon final annealing of a steel sheet having a Si content of 1.0 to 4.0 wt% as the final plate thickness by cold rolling once or twice or more with intermediate annealing, a steel sheet is produced according to the Si content of the steel sheet. Is annealed at the following maximum heating temperature T (° C), and when 1.0 wt% ≤ Si <1.5 wt% 800 ≤ T ≤ 950 1.5 wt% ≤ Si <2.0 wt% 800 ≤ T ≤ 980 2.0 wt% ≤ When Si ≤ 4.0 wt% 870 ≤ T ≤ 1050 0.05-0.15% on steel plate by controlling unit tension during annealing
A method for manufacturing a non-oriented electrical steel sheet having excellent iron loss characteristics and excellent magnetic flux density in a low magnetic field, which is characterized by imparting elongation deformation.

(2) In the final annealing of a steel sheet having a Si content of 1.0 to 4.0 wt% as the final plate thickness by cold rolling once or twice or more with intermediate annealing, according to the Si content of the steel sheet, the steel sheet Is annealed at the following maximum heating temperature T (° C) and the unit tension σ (kg f / mm ² ) is controlled so as to satisfy the following conditions in relation to the maximum heating temperature T (° C).
A method for producing a non-oriented electrical steel sheet excellent in iron loss obtainability and magnetic flux density in a low magnetic field, which is characterized by imparting an elongation deformation of 05 to 0.15%.

 When 1.0 wt% ≤ Si <1.5 wt% 800 ≤ T ≤ 950 -0.0025T + 2.38 ≤ σ ≤ -0.0025T + 2.58 However, when σ ≥ 0.10 1.5 wt% ≤ Si <2.0 wt% 800 ≤ T ≤ 980 −0.0034T + 3.22 ≦ σ ≦ −0.0034T + 3.42 where σ ≧ 0.10 2.0wt% ≦ Si ≦ 4.0wt% 870 ≦ T ≦ 1050 −0.0017T + 1.80 ≦ σ ≦ −0.0017T + 2.00 where σ ≧ 0.10 Hereinafter, the details of the present invention will be described together with the reasons for limitation.

In the present invention, in the final annealing of a Si steel plate having a final thickness of Si: 1.0 to 4.0 wt% by cold rolling once or twice or more with intermediate annealing, iron loss gain and magnetic flux in a low magnetic field are obtained. In order to improve the density, the steel sheet is annealed at the following maximum heating temperature T (° C) according to the Si content of the steel sheet, and when 1.0 wt% ≤ Si <1.5 wt% 800 ≤ T ≤ 950 1.5 wt% ≤ When Si <2.0wt% 800 ≤ T ≤ 980 2.0wt% ≤ Si ≤ 4.0wt% 870 ≤ T ≤ 1050 0.05 ~ 0.15% on steel plate by controlling unit tension during annealing
Give elongation deformation.

Such a tension imparting effect is prominent mainly for improving the magnetic properties in the longitudinal direction of the steel sheet. This is bcc
It is because the adverse effect of magnetostriction in the iron-based magnetic material having a structure is reduced, and the iron loss gain and the magnetic flux density in a low magnetic field are improved by the subdivision of the magnetic domain accompanying the addition of a minute tension. It is considered that the effect is mainly exhibited in the process of transforming from paramagnetic to ferromagnetic via the Curie point during cooling. And, the present inventors, the improvement of the iron loss obtainability and magnetic flux density in a low magnetic field is recognized by this tension application, regardless of the annealing temperature, when elongation deformation of about 0.1 ± 0.05% is applied. I found that I was limited.

Fig. 1 shows the effect of the elongation deformation of the steel sheet in the final annealing on the iron loss characteristics and the magnetic flux density (B ₃ ) in a low magnetic field, as compared with the Si steel sheets with different Si contents (steel (2) in Table 1, ( 3), (5)
Demonstrating that, regardless of the Si content and the annealing temperature, a good effect of improving the magnetic properties is shown in the range of elongation deformation of 0.1 ± 0.05%.

Here, when the elongation deformation is less than 0.05%, the effect of imparting strain cannot be sufficiently expected, and in addition, the tension is too low, which causes a problem on the strip. On the other hand, if it exceeds 0.15%, the level itself of magnetic characteristics (iron loss characteristics and magnetic flux density in a low magnetic field) is deteriorated due to excessive introduction of internal stress and lattice defects. As described above, the present invention can effectively improve the iron loss characteristics and the magnetic flux density in a low magnetic field by imparting a relatively small elongation deformation to the steel sheet.

The reason for limiting the annealing heating temperature will be described later.

In the practice of the present invention, a horizontal type continuous annealing line capable of passing a low-strength steel sheet is mainly used, and it is at the maximum heating temperature that plastic deformation occurs due to application of tension in the line. Then, in order to obtain the elongation deformation of 0.1 ± 0.05%, it is necessary to apply tension under predetermined conditions according to the steel composition and heating temperature.

Figure 2 shows the relationship between the unit tension in the horizontal continuous annealing furnace, the iron loss characteristics of the steel sheet, and the magnetic flux density (B ₃ ) in a low magnetic field.
Si steel plates with different contents (steel (2), (3) in Table 1
(5)) was investigated, and the portion indicated by the arrow in the figure is the tensile deformation at which elongation deformation: approximately 0.1% is obtained.

FIG. 3 shows the range of appropriate tension and heating temperature in the above Si steel sheet. From the results of these experiments, it was found that the tension σ can be defined as a function of heating temperature depending on the Si content, and that the heating temperature also has an appropriate range depending on the Si content.

That is, the in-furnace unit tension σ (kg f / mm ² ) and the annealing heating temperature need to be adjusted as follows.

(1) 1.0 wt% ≤ Si <1.5 wt% 800 ≤ T ≤ 950 -0.0025T + 2.38 ≤ σ ≤ -0.0025T + 2.58 However, σ ≥ 0.10 (2) 1.5 wt% ≤ Si <2.0 wt% Case 800 ≦ T ≦ 980 −0.0034T + 3.22 ≦ σ ≦ −0.0034T + 3.42 However, σ ≧ 0.10 (3) When 2.0wt% ≦ Si ≦ 4.0wt% 870 ≦ T ≦ 1050 −0.0017T + 1.80 ≦ σ ≦ −0.0017T + 2.00 However, σ ≧ 0.10 The tension range is ± 0.1 kg f / mm ² with reference to the tension where the iron loss value is the lowest and the magnetic flux density in the low magnetic field is the highest based on Fig. 2 etc. In this range, elongation deformation: 0.05 to 0.15% can be secured. If the tension σ is less than 0.10 kg f / mm ² , the effect of imparting tension cannot be expected at all.

Regarding the annealing heating temperature, when the temperature is lower than the lower limit temperature of each Si level, sufficient ferrite grain growth does not occur and the magnetic property level itself becomes low. On the other hand, when the upper limit temperature of each Si level is exceeded, in addition to the problem of strip passing, the ferrite grains become excessively coarse and, conversely, iron loss increases.

The Si steel sheet targeted by the present invention contains 1.0 to 4.0 wt% of Si. If Si is less than 1.0 wt%, a sufficient low iron loss value cannot be obtained due to a decrease in resistivity. On the other hand, if it exceeds 4.0 wt%, the cold workability is significantly deteriorated.

〔Example〕

The cold-rolled steel sheet having the composition shown in Table 1 was finally annealed under the conditions shown in Table 2 to obtain a non-oriented electrical steel sheet. The magnetic properties of the obtained steel sheet are also shown in Table 2.

As can be seen from the table, the iron loss characteristics and the magnetic flux density in a low magnetic field are effectively improved by imparting a predetermined elongation deformation to the steel sheet being annealed by the method of the present invention.

[Brief description of drawings]

Figure 1 is intended to extend the amount of deformation of the steel sheet during final annealing showed the effect on the iron loss and magnetic flux density B _3. Figure 2 shows the relationship between the annealing furnace unit tension and iron loss and magnetic flux density B ₃ during final annealing. FIG. 3 shows an appropriate range of tension and heating temperature during final annealing.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshiaki Urabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) In-house Shoji Mitsukawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo (56) References JP 58-120733 (JP, A) JP 59-96227 (JP, A) JP 55-85630 (JP, A)

Claims (2)

[Claims] 1. A Si content of 1.0 to 4.0 wt% as a final plate thickness by cold rolling once or twice or more with intermediate annealing.
In the final annealing of the steel sheet of, according to the Si content of the steel sheet,
While annealing the steel sheet at the following maximum heating temperature T (° C),
During annealing, control the unit tension to 0.05 to 0.15% on the steel plate.
A method for manufacturing a non-oriented electrical steel sheet having excellent iron loss characteristics and excellent magnetic flux density in a low magnetic field, which is characterized by imparting elongation deformation. 1.0 wt% ≤ Si <1.5 wt% 800 ≤ T ≤ 950 1.5 wt% ≤ Si <2.0 wt% 800 ≤ T ≤ 980 2.0 wt% ≤ Si ≤ 4.0 wt% 870 ≤ T ≤ 1050 2. A Si content of 1.0 to 4.0 wt% as a final plate thickness by cold rolling once or twice or more with intermediate annealing.
In the final annealing of the steel sheet of, according to the Si content of the steel sheet,
While annealing the steel sheet at the following maximum heating temperature T (° C),
Iron characterized by imparting elongation deformation of 0.05 to 0.15% to steel sheet by controlling unit tension σ (kg f / mm ² ) so as to satisfy the following condition in relation to maximum heating temperature T (° C) A method for manufacturing a non-oriented electrical steel sheet having excellent loss characteristics and magnetic flux density in a low magnetic field. When 1.0 wt% ≤ Si <1.5 wt% 800 ≤ T ≤ 950 -0.0025T + 2.38 ≤ σ ≤ -0.0025T + 2.58 However, when σ ≥ 0.10 1.5 wt% ≤ Si <2.0 wt% 800 ≤ T ≤ 980 −0.0034T + 3.22 ≦ σ ≦ −0.0034T + 3.42 where σ ≧ 0.10 2.0wt% ≦ Si ≦ 4.0wt% 870 ≦ T ≦ 1050 −0.0017T + 1.80 ≦ σ ≦ −0.0017T + 2.00 where σ ≧ 0.10