JPH05195169A - Plural layer high silicon soft magnetic steel sheet having excellent cold-rollability and magnetic characteristic and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a high silicon soft magnetic steel having excellent magnetic characteristic by casting the high silicon steels having different Si contents to a plural layer steel slab having the specific thickness ratio and executing hot-rolling, cold-rolling and finish-annealing. CONSTITUTION:By casting molten steel, the plural layer steel slab composed of a surface layer part of the extremely low carbon high silicon steel containing <=0.006wt.% C and 4.0-7.1% Si and an inner layer part of the steel containing the extremely low carbon and the comparatively high silicon quality, such as <=0.006% C and 0.8-3.5% Si, and 0.1-0.3 ratio of thickness of the surface layer part to the inner layer part is manufactured. This steel slab is hot-rolled to make the hot rolled sheet, and if necessary, after executing an intermediate annealing, the oxide scale on the surface is pickled and removed, and the cold- rolling is executed to make the last sheet thickness, and successively, the last finish annealing is executed. The plural layer type high silicon soft magnetic steel sheet having excellent low iron loss characteristic in a high frequency range is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-silicon soft magnetic steel sheet having excellent magnetic properties, which is used as a soft magnetic material for iron cores of electric appliances and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Addition of Si improves iron loss characteristics, and 6.
It is known that since the magnetostriction approaches zero near 5%, the magnetic permeability is further improved and excellent magnetic properties are exhibited.
However, when the amount of Si added was 4.5% or more, the cold rolling property was significantly deteriorated and it was not put into practical use.

As a means for improving the cold rolling property, a method of controlling the structure of a hot rolled sheet has been disclosed (Japanese Patent Laid-Open No. 61-61)
No. 166923, JP-A No. 62-103321). However, the restrictions on the hot rolling conditions presented not only hinder the productivity, but are not necessarily good measures in terms of controlling the texture of the product sheet.

As another method, a method of improving cold rolling property by setting the rolling temperature of cold rolling to 350 ° C. to 450 ° C. (Japanese Patent Laid-Open No. 1-200702), workability, There are many problems in terms of surface texture. Even if these measures are taken, if the amount of Si added is 4.5% or more, it is difficult to roll a thin material having high deformation resistance.

On the other hand, in terms of magnetic characteristics, it is known that the high Si material exhibits particularly excellent magnetic characteristics in a high frequency range.
In this case, the effect is not sufficiently exhibited unless the plate thickness is reduced. Further, it is known that in the high frequency range, the magnetic flux concentrates near the surface.

[0006]

SUMMARY OF THE INVENTION The present invention provides a steel sheet having a low iron loss characteristic in a high frequency region and a method for producing the same, while avoiding the problem of the cold rolling of the high silicon soft magnetic steel sheet.

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted research on improvement of cold rolling property, and have confirmed that cold rolling property can be remarkably improved by using a double-layer steel sheet having a sandwich structure as the refractory rolling material. As a result of studying the application of this technology to a high silicon soft magnetic steel sheet, a multi-layer condition excellent in both cold rollability and magnetic properties was found.

The gist of the matter is the weight ratio, C ≦
A material containing 0.006%, Si: 4.0 to 7.1%, and a balance of Fe and unavoidable impurities as a surface layer material, and C
≤ 0.006%, Si: 0.8-3.5%, a sandwich structure cast multi-layer steel sheet having a material comprising the balance Fe and unavoidable impurities as an inner layer material, and a surface layer material / inner layer material plate. It is a multi-layered high silicon soft magnetic steel sheet having a thickness ratio of 0.1 to 0.3 and excellent magnetic properties.

Further, the present invention produces a multi-layered steel slab having the above-mentioned composition by casting, performs intermediate annealing, cold rolling and final annealing, if necessary, for hot rolling. It is a manufacturing method of a magnetic steel sheet.

The present invention will be described in detail below. First, the reasons for limiting the components will be described. The reason why the C content of the surface layer and the inner layer material is limited to 0.006% or less is that the magnetic properties of the product are significantly deteriorated when C content higher than this is added.

The amount of Si in the surface layer is limited to the range of 4.0 to 7.1% because the amount of Si required to obtain the low iron loss characteristics in the high frequency region is at least 4.0% or more. Further, addition of an excessive amount of Si has little effect of improving the low iron loss property and the cold rolling property is remarkably deteriorated, so 7.1% was made the upper limit.

On the other hand, the reason for limiting the Si content of the inner layer to the range of 0.8 to 3.5% is that the Si content necessary for obtaining excellent magnetic properties is at least 0.8% or more, and the cold ductility From this point of view, if the amount of Si in the inner layer exceeds 3.5%, the deformation resistance becomes high and thin rolling becomes difficult.

As components other than the above, the addition of elements such as Al and Mn which increase the electric resistance and lower the iron loss, and solid solution C,
The addition of carbonitride forming elements such as Ti and Nb for reducing N does not impair the gist of the present invention.

Next, the reasons for limiting the multilayer structure will be described. The plate thickness ratio of the surface layer material / inner layer material is limited to the range of 0.1 to 0.3 because when the plate thickness ratio is less than 0.1, sufficient low iron loss characteristics cannot be obtained in the high frequency region. This is because the upper limit is set to 0.3 because if the ratio of the surface layer material is further increased, the cold rolling property is significantly deteriorated and it is difficult to make the product thinner. The plate thickness ratio here is a value obtained by adding the plate thicknesses of the surface layer materials on both sides and dividing the value by the plate thickness of the inner layer material.

Further, the reason why the manufacturing method of the multi-layer structure is limited to the casting method is that in other manufacturing methods such as the rolling compression bonding method and the explosive bonding method, fracture occurs at the boundary surface during cold rolling, and the surface layer material is peeled off. Is likely to occur. In the high frequency range, magnetic flux concentrates near the surface, so high Si only needs to be the surface layer material.
A reduction in alloy cost can be achieved by the present invention.

[0016]

EXAMPLES Table 1 shows the chemical components of the materials used for the surface layer material and the inner layer material. The test material was made into multiple layers by casting, and after solidification, it was directly hot-rolled and 170 mm ingot was finish-rolled at about 950 ° C.
Continuous annealing at 00 ° C for 2 minutes or box annealing at 800 ° C for 3 hours was performed. Further, a part of the material which was annealed at 900 ° C. for 2 minutes was also put into the test material.

Table 2 shows material combinations, plate thickness ratios, experimental conditions, cold ductility, magnetic properties and the like.

[Table 1]

[0018]

[Table 2]

Experiment numbers 1, 2, 3, 7, 10, 11, 1
Nos. 3, 15, 16 and 17 show excellent cold ductility and magnetic properties in the range of the steel of the present invention. Experiment number 4 is C in the inner layer
Since the amount is large, deterioration of magnetism is observed. Experiment number 5 has a large iron loss because the amount of Si in the inner layer is as low as 0.5%. In Experiment No. 6, since the amount of Si in the inner layer was as high as 4.0%, the deformation resistance during cold rolling was high, the workability was poor, and ear cracking occurred.

In Experiment No. 8, the surface layer material contained a large amount of Si and cracked during cold rolling. In Experiment No. 9, excellent magnetic properties could not be obtained because the C content of the surface layer material was high. In Experiment No. 12, excellent magnetic properties could not be obtained because the proportion of the surface layer material was low. In Experiment No. 14, the proportion of the surface layer material was too high, the deformation resistance during cold rolling was high, the workability was poor, and cracking occurred.

Experiment No. 18 is a result of a multi-layer steel sheet produced by electron beam welding of the surface layer material and the inner layer material in a vacuum and then pressure bonding by hot rolling, which caused cracks during cold rolling. When the magnetism of the portion without cracks was examined, it was found that the iron loss was uniformly higher than that of the multilayer material of Experiment No. 3 made by casting. The reason why the cast multi-layer material exhibits superior cold ductility and magnetic properties compared to the pressure-bonded material has not been fully clarified, but it is presumed that the diffusion phenomenon near the boundary layer has an effect.

Further, the steel of the present invention is characterized in that it has a higher magnetic flux density than the single layer material of high Si steel. For example, the material of the B ₅₀ in Experiment No. 3 is 1.61, B ₅₀ of Experiment No. 1 is a value significantly higher than the 1.50 of comparative material of a single layer material of 1.60 and 6.5% Si ..

[0023]

EFFECTS OF THE INVENTION According to the present invention, it is possible to supply a thin plate having an excellent iron loss value in a high frequency range and a high magnetic flux density at a low cost, which can be rolled by an ordinary cold rolling to a very thin plate thickness without damage. ..

Claims (2)

[Claims] 1. By weight%, C ≦ 0.006%, Si: 4.0-7.1%, a material consisting of balance Fe and unavoidable impurities as a surface layer material, C ≦ 0.006%, Si: 0.8-3.5%, a sandwich-type cast multi-layer steel sheet having a material of the balance Fe and unavoidable impurities as an inner layer material, and a plate thickness ratio of surface layer material / inner layer material of 0.1 to 0.3. Multi-layer high-silicon soft magnetic steel sheet with excellent cold ductility and magnetic properties. 2. A compound steel sheet having excellent cold ductility and magnetic properties according to claim 1, wherein a multi-layer steel slab is produced by casting, hot rolling, intermediate annealing if necessary, cold rolling and final annealing are performed. Method of producing high-layer soft silicon soft magnetic steel sheet.