JPH05247604A - Soft magnetic iron plate having excellent magnetic properties and method for manufacturing the same - Google Patents

Abstract

(57) [Summary] [Structure] [Table 1] C: 0.003% or less, Si: 0.05
% Or less, Mn: 0.05 to 0.3%, Al: 0.05
% Or less, P + S: 0.03% or less, O:
It contains 0.015% or less and N: 0.005% or less, and the balance is substantially Fe composition, and the grain size of ferrite grains is 2 or less and -7 or more in terms of grain size number. [Effect] Even under mass production, a soft magnetic iron plate having a remarkably low coercive force and a high magnetic permeability can be stably obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic iron plate having excellent magnetic properties, which is suitable for use as a magnetic shield material, a yoke material for magnetic equipment and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, in the field of medical equipment, the practical use of a magnetic resonance tomography apparatus (MRI) utilizing a nuclear magnetic resonance phenomenon, a linear motor as a high-speed railway, etc. has been vigorously promoted, and accordingly, the There is a demand for a magnetic shield material having excellent magnetic characteristics as a leakage magnetic shielding material.
In addition, with the construction of giant accelerators such as SSC (Superconducting-Super-Collider) and elementary particle detectors, there is a demand for a large amount of soft magnetic iron plate having excellent soft magnetism as a yoke material for those magnetic devices. ing.

Various proposals have hitherto been made for a steel sheet having a high magnetic permeability and a high magnetic permeability. For example, JP-A-60-96749 discloses a steel sheet mainly composed of components of a thick plate. However, the magnetic permeability level is low. Further, Japanese Patent Laid-Open No. 3-94046 discloses a steel sheet for magnetic shield which is excellent in maximum magnetic permeability μ _max and magnetic flux density B ₁ .

[0004]

However, the coercive force is not taken into consideration in the conventional soft magnetic iron plate, and the coercive force obtained in mass production is at most about 1.9 Oersted (Oe), and μ _max. Was only a few thousand. The present invention advantageously solves the above problems, and has an object of proposing a soft magnetic iron plate having a remarkably low coercive force and a high magnetic permeability even under mass production, together with its advantageous manufacturing method. To do.

[0005]

Although it is considered that there are various factors such as strain and composition as factors generally governing the coercive force, the inventors' researches on this point indicate that the residual impurity composition Keeps contamination low, especially carbon
After suppressing to below ppm, after recrystallization annealing according to the usual method,
It was found that a soft magnetic steel sheet having a remarkably low coercive force and a high magnetic permeability can be obtained by performing the rolling treatment and the annealing treatment under special conditions. The present invention is based on the above findings.

That is, the present invention is

[Table 3] C: 0.003 wt% (hereinafter simply referred to as%), Si: 0.05% or less, Mn: 0.05 to 0.3%, Al: 0.05% or less, P + S: 0.03% or less, O: 0.015% or less, N : 0.005% or less, the balance being substantially Fe composition, and the crystal grain size of the ferrite grains is 2 or less and -7 or more in terms of grain size number. Is.

The present invention also provides

[Table 4] C: 0.003% or less, Si: 0.05% or less, Mn: 0.05 to 0.3%, Al: 0.05% or less, P + S: 0.03% or less, O: 0.015% or less, N: 0.005% or less, The rest is a slab having a substantially Fe composition, hot-rolled, then cold-rolled to a predetermined thickness, re-crystallized and annealed, and then secondary cold-rolled at a rolling reduction of 0.5 to 30%. After that, the final annealing is performed in the temperature range of 800 to 900 ° C, which is a method for producing a soft magnetic iron plate having excellent magnetic properties.

The present invention will be described in detail below. Si: 0.04%, Mn: 0.1%, Al: 0.03, (P + S): 0.01
%, O: 0.008% and N: 0.001% as basic components, and slabs containing various amounts of C were hot-rolled and then cold-rolled, and then recrystallized and annealed. After the secondary cold rolling, the final annealing treatment was applied to the remanent magnetization of iron plates with various grain sizes.
The results of examining Hc are shown in FIG. 1 in relation to the C content and the grain size. As is clear from the figure, Hc has a strong correlation with the C content, and by reducing the C content to 30 ppm or less, a low residual magnetization can be obtained. However, even if C ≦ 30 ppm, if the grain size exceeds 2 in terms of grain size, Hc will increase.

Next, FIG. 2 shows the results of examining the effect of P and S on the residual magnetization in relation to the C content. As is clear from the figure, by setting the C content to 30 ppm or less and reducing the (P + S) content to 0.03% or less, excellent residual magnetization of Hc ≦ 1.5 Oe is obtained.

[0010]

The reason why the component composition range of the soft magnetic iron plate is limited to the above range in the present invention will be described below. C: 0.003% or less As shown in Fig. 1 above, when the C content exceeds 0.003% (30 ppm), the residual magnetization increases and it becomes difficult to obtain a residual magnetization of 1.5 Oe or less, so the C content is 0.003% or less. To suppress.

Si: 0.05% or less Si is an element that causes deterioration of saturation magnetic flux density (B _S ) and magnetic permeability, and if it is contained in a large amount over 0.05%, good residual magnetization cannot be obtained. , 0.05% or less.

Mn: 0.05-0.3% Mn effectively contributes to the improvement of the surface properties, but the content is 0.
If less than 05%, the addition effect is poor, while if over 0.3%, the magnetic properties are adversely affected, so 0.05-0.3%.
It was made to contain in the range of.

Al: 0.05% or less When the Al content exceeds 0.05%, not only the crystal grain size in a predetermined range described later cannot be obtained, but also fine precipitates are formed by combining with nitrogen and oxygen, resulting in magnetic properties. Therefore, the content is set to 0.05% or less.

P + S: 0.03% or less P and S are both segregated at grain boundaries, and particularly S is a harmful element that forms a sulfide with Mn and inhibits the movement of the domain wall, and it is desirable to reduce it as much as possible. .. In particular, as shown in FIG. 2 above, since the residual magnetization increases when the (P + S) amount exceeds 0.03%, the total amount of P and S is limited to 0.03% or less.

O: 0.015% or less, N: 0.005% or less Both O and N are harmful elements that form inclusions and deteriorate the magnetic properties, but O: 0.015% or less, respectively.
N: Permissible within the range of 0.005% or less.

The component composition range has been described above.
In the present invention, it is not enough that the composition of components satisfies the above range, and it is important to limit the size of ferrite crystal grains to a predetermined range. That is, as shown in FIG. 1 above, when the ferrite grain size exceeds 2 in terms of grain size, Hc increases and Hc ≦ 1.5 Oe, which is the target of the present invention.
No excellent residual magnetization can be obtained. However, if the crystal grain size becomes coarser as the grain size number falls below -7, a problem occurs in terms of strength. Therefore, the size of ferrite crystal grains is limited to a range of 2 or less and -7 or more in terms of grain size number.

Next, the manufacturing method according to the present invention will be described. There is no particular limitation on the melting of the material, and any conventionally known melting method can be used. However, refining treatment such as vacuum degassing can reduce the mixing amount of impurity elements and the amount of non-metallic inclusions. It is advantageous in reducing the amount. Further, the hot rolling, cold rolling and recrystallization annealing treatments are not particularly limited and may be carried out according to the usual method.

In the method of the present invention, after each of the above treatments,
800-900 after the secondary cold rolling at the reduction rate of 0.5-30%
By performing the final annealing in the temperature range of ° C, the crystal grains are made to have a desired size, and thus the magnetic characteristics are improved. 3 (a) and 3 (b), recrystallization annealed sheets with a C content of 12 ppm were subjected to secondary cold rolling with various reduction rates, and then subjected to 750 ° C, 800 ° C, 880 ° C. The results of examining the values of Hc and μ _max after the final annealing for 30 seconds at each temperature are shown below. As is clear from the figure, the rolling reduction is 0.5
In the range of up to 30%, good magnetic properties are obtained at the subsequent final annealing temperature of 800 ° C or higher. Therefore, in this invention, the reduction ratio in the secondary cold rolling is 0.5 to 30%.
It was limited to the range of. The plate thickness after the secondary cold rolling is preferably about 1 to 6 mm. The reason is that if the plate thickness is less than 1 mm, practically there will be problems in strength, etc.
On the other hand, if it exceeds 6 mm, it becomes difficult to control the grain size under the annealing condition or the like.

Next, as shown in FIGS. 4 (a) and 4 (b), when a recrystallized annealed plate having a C content of 12 ppm was subjected to an annealing treatment by variously changing the annealing temperature after the secondary cold rolling. Hc and μ
_The results of examining the value of _max are shown using the cold rolling reduction rate as a parameter. As is clear from the figure, excellent magnetic properties were obtained by cold rolling at a predetermined rolling reduction and then performing final annealing in the temperature range of 800 to 900 ° C.
Therefore, in the present invention, the annealing temperature in the final annealing is limited to the range of 800 to 900 ° C. The annealing time is preferably 20 seconds or more in consideration of the moving speed of grain boundaries, recovery of strain introduced during cold rolling, and the like.

Further, in FIG. 5, the rolling reduction according to the method of the present invention:
The results of an examination of the remanent magnetization Hc after the final cold rolling at 880 ° C after the secondary cold rolling at 5% are shown. The Hc is remarkably reduced compared to the case without no reduction.

[0021]

【Example】

Example 1 C: 0.0018%, Si: 0.04%, Mn: 0.17%, P: 0.010
%, S: 0.007%, Al: 0.008%, O: 0.01% and N:
A slab containing 0.0019% and the balance being substantially Fe was hot-rolled and then cold-rolled, followed by recrystallization annealing at 880 ° C. Next, secondary cold rolling was performed under the conditions shown in Table 1 to finish the plate thicknesses of 1.2 mm, 1.6 mm, 3,0 mm and 6.0 mm, respectively, and then final annealing was also performed under the conditions shown in Table 5. Table 5 shows the results of examining the crystal grain size, the residual magnetization, and the maximum magnetic permeability of each iron plate thus obtained. For comparison, Table 5 shows the case where the same treatment was applied to a slab containing a large amount of C as 0.0043% (comparative material A) and a slab containing a large amount of Al as 0.08% (comparative material B). The results of the survey will also be shown.

[0022]

[Table 5]

As is clear from Table 5, the invention material is subjected to secondary cold rolling at a reduction ratio in an appropriate range, and then subjected to final annealing at an appropriate temperature, whereby grain sizes of -7 to 2 are obtained. An iron plate having crystal grains and good magnetic flux density is obtained. On the other hand, when the reduction ratio of the secondary cold rolling and / or the subsequent annealing temperature deviates from the proper range, the crystal grain size deviates from the proper range, and thus sufficient soft magnetic properties are not obtained.
Even if the comparative material A was subjected to secondary cold rolling and final annealing in an appropriate range, good soft magnetic properties were not obtained. This is because it contains a large amount of C. Also for the comparative material B, sufficient soft magnetic properties are not obtained for the same reason.

Example 2 A slab having the same composition as in Example 1 was subjected to recrystallization annealing in the same manner as in Example 1, and then subjected to secondary cold rolling and final annealing under the conditions shown in Table 6. did. Table 6 shows the results of investigating the crystal grain size, the residual magnetization and the maximum magnetic permeability of each iron plate thus obtained. In addition, in Table 6, for comparison, a slab containing a large amount of C of 0.0043%, and Al
The results of the survey when the same treatment is applied to a slab containing a large amount of 0.08% are also shown.

[0025]

[Table 6]

As is clear from Table 6, in the inventive material, good soft magnetic properties were obtained when the grain size number was in the proper range of -7 to 2, but when it was out of the proper range, the soft magnetism was found. The characteristics are favorable. On the other hand, for Comparative materials A and C, even if the crystal grain size numbers are within the proper range,
Good soft magnetic properties have not been obtained because it contains a large amount of Al and Al. As described above, when the component composition deviated from the proper range, good soft magnetic characteristics could not be obtained even if the crystal grain size was suitable.

[0027]

As described above, according to the present invention, a soft magnetic iron plate having a remarkably low coercive force and a high magnetic permeability can be stably obtained even under mass production on a factory scale.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the C content and the grain size that affect the remanent magnetization Hc of an iron plate.

FIG. 2 is a graph showing the influence of (P + S) on the remanent magnetization Hc of an iron plate in relation to the C content.

FIG. 3 is a graph showing the influence of the rolling reduction in the secondary cold rolling on the remanent magnetization Hc and the maximum magnetic permeability μ _max of the iron plate in relation to the final annealing temperature.

FIG. 4 is a graph showing the influence of the annealing temperature in the final annealing on the remanent magnetization Hc and the maximum magnetic permeability μ _max of the iron plate, in relation to the rolling reduction in the secondary cold rolling that precedes it.

FIG. 5 is a graph showing the value of remanent magnetization of an iron plate obtained by performing secondary cold rolling and final annealing under appropriate conditions according to the present invention in relation to the C content.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyohiko Nohara 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Headquarters (72) Inventor Kazuhiro Suzuki 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. Research headquarters

Claims (2)

[Claims] 1. C: 0.003 wt% or less, Si: 0.05 wt% or less, Mn: 0.05 to 0.3 wt%, Al: 0.05 wt% or less, P + S: 0.03 wt% or less, O: 0.015 wt% Below, N: 0.005 wt% or less is contained, the balance is substantially Fe composition, and the crystal grain size of the ferrite grains is 2 or less and -7 or more in terms of grain size number, which is excellent in magnetic properties. Soft magnetic iron plate. 2. C: 0.003 wt% or less, Si: 0.05 wt% or less, Mn: 0.05 to 0.3 wt%, Al: 0.05 wt% or less, P + S: 0.03 wt% or less, O: 0.015 wt% Hereinafter, a slab containing N: 0.005 wt% or less and the balance being substantially Fe composition is hot-rolled, and then cold-rolled to a predetermined thickness, followed by recrystallization annealing, and then 0.5 to A method for producing a soft magnetic iron sheet having excellent magnetic properties, which comprises performing secondary cold rolling at a reduction rate of 30% and then performing final annealing in a temperature range of 800 to 900 ° C.