JP2001295000A - High-silicon electrical steel sheet excellent in assembly workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-silicon electrical steel sheet excellent in assembly workability, which is manufactured by a rolling method and causes no rupture in an inserting step. SOLUTION: The high-silicon electrical steel sheet is obtained by forming an insulating film on the surface of a high-silicon steel sheet of 4-7 mass % content manufactured by a rolling method, based on the following findings: the occurrence of rupture in steel sheet at the assembly of a core using a high- silicon electrical steel sheet manufactured by a rolling method is caused by the inferior sliding property of the high-silicon steel sheet; and it is effective for improving this sliding property, to control the surface roughness of the steel sheet and the thickness of an insulating film to values in specific ranges, respectively. In the steel sheet, surface roughness Ra is >=0.10 μm and the average thickness of the insulating film is <=2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high silicon magnetic steel sheet suitable for a core of a transformer, a reactor, a motor and the like.

[0002]

2. Description of the Related Art Conventionally, a silicon steel sheet having a Si content of less than 4 mass% has been used as an electromagnetic steel sheet used as a core of electric equipment. However, such a conventional electromagnetic steel sheet has a problem that when the operating frequency of an electric device is increased as in recent years, iron loss is significantly increased. To solve this problem, a high-silicon magnetic steel sheet containing 4 mass% or more of Si has been developed. For example, a method for manufacturing the high-silicon magnetic steel sheet is disclosed in Japanese Patent Publication No. Hei 7-13262. And the siliconizing method disclosed in Japanese Patent Publication No. 5-49745.

[0003] Among these production methods, the rolling method means that a cast high silicon steel slab (or a high silicon steel slab which has been bulk-rolled after casting) is subjected to hot rolling, warm or cold rolling, oxide film removal, and the like. This is a manufacturing method of forming a thin plate through processes such as annealing and application of an insulating film. The siliconizing method is used to convert a steel sheet having a relatively small amount of Si (usually, Si: less than 4 mass%) with a reaction gas such as silicon tetrachloride. This is a method of producing a high silicon steel sheet by infiltrating Si into the surface layer of the steel sheet by contact and reaction, and then diffusing the surface layer Si in the thickness direction.

[0004]

However, when the present inventors manufactured a high-silicon magnetic steel sheet as described above and conducted a test of assembling the same into a core such as a transformer or a reactor, it was found that the steel sheet was manufactured particularly by a rolling method. It has been found that the following specific problems occur in the high silicon magnetic steel sheet. That is, the core assembly of the transformer and the reactor includes a step of laminating the cut steel plates, but the lamination does not simply stack the steel plates, but requires inserting another steel plate between the steel plates. And when using the high silicon electrical steel sheet manufactured by the rolling method, it turned out that a crack (break) frequently occurs in the high silicon steel sheet in this insertion process.

[0005] When cracks occur in the high silicon steel sheet as described above, it is necessary to completely remove the cracks, including minute fragments, in order to ensure the reliability of the transformer and the like. For this reason, after removing the debris from the steel sheet, the lamination assembly must be restarted from the beginning, and the assembly workability becomes very complicated. For this reason, there is a strong demand for the development of a high-silicon magnetic steel sheet manufactured by the rolling method, which does not break during the insertion step and has excellent assembling workability. Therefore, an object of the present invention is to provide a high silicon magnetic steel sheet which is manufactured by a rolling method and which does not break during the insertion step and has excellent assembling workability.

[0006]

Means for Solving the Problems The present inventors have conducted experiments and studies to elucidate the cause of the breakage of the steel sheet generated when assembling the core using the high silicon electrical steel sheet manufactured by the rolling method. As a result, the fracture is caused by the poor slip property of the high silicon steel sheet, and in order to improve the slip property, the steel sheet surface roughness (surface roughness of the insulating film surface)
It was found that it was effective to regulate the thickness of the insulating film to a specific range. The present invention has been made based on such findings, and the features thereof are as follows.

[1] The content of Si produced by the rolling method is 4 to
A high silicon electromagnetic steel sheet having an insulating film formed on the surface of a 7 mass% high silicon steel sheet, wherein the surface roughness Ra is 0.10 μm or more, and the average thickness of the insulating film is 2 μm or less. High-silicon electromagnetic steel sheet with excellent assembly workability.

[2] In the high silicon electrical steel sheet of the above [1],
The chemical composition of the steel sheet is substantially C: 5 to 300 mass pp
m, Si: 4-7 mass%, Mn: 0.01-1 mass
%, P: 0.01 mass% or less, S: 0.01 mass% or less, sol. Al: 0.0005 to 0.1 mass%, N: 3
A high-silicon magnetic steel sheet excellent in assembling workability, characterized by containing less than 00 mass ppm and the balance being Fe.

Here, the high silicon steel sheet manufactured by the rolling method to which the present invention is applied means a high silicon steel slab such as a continuous cast slab, a bulk rolled slab, a thin slab cast slab, and the like. It refers to a high silicon steel sheet manufactured by thinning through hot or cold rolling.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention and the reasons for limitation will be described below. High-silicon magnetic steel sheets are hard and relatively brittle because they contain a large amount of Si. For this reason, breakage occurs when excessive stress is applied during the insertion step in assembling the core. However, even a high silicon magnetic steel sheet manufactured by the siliconizing method does not break. As a result of investigating the cause, the high-silicon electrical steel sheet manufactured by the rolling method has poor slip property at the time of insertion, which causes the above-described fracture, and the slip property is related to the surface roughness of the steel sheet. Turned out to be. In other words, the high silicon electrical steel sheet manufactured by the siliconizing method has a good surface slippery when inserted, while the high silicon electrical steel sheet manufactured by the rolling method has a small surface roughness. The slip property during loading is inferior. It is contrary to conventional wisdom that the rougher the surface roughness is, the better the slipperiness is. However, in the case of the roughness of a micron unit, it is presumed that the rougher the surface is, the better the slipperiness is.

FIG. 1 shows the result of investigation on the relationship between the surface roughness Ra of a high silicon electrical steel sheet (Si content: 6.5 mass%) manufactured by the rolling method and the presence or absence of breakage during core assembly. In this test, a high-silicon electrical steel sheet having a thickness of 0.3 mm (insulating film thickness: 0.5 to 2.5 μm) was used as shown in FIG.
A transformer core having the structure shown in Fig. 1 was assembled, and the slip property was evaluated based on the presence or absence of breakage of the steel sheet when the steel sheet constituting the upper yoke was inserted. From the results of FIG. 1, it was found that when the surface roughness Ra of the high silicon electrical steel sheet (insulating film surface) was 0.10 μm or more, good slip properties were obtained, and the steel sheet was hardly broken.

However, there is an exception in the relationship between the surface roughness Ra of such a high silicon magnetic steel sheet and the slip property. Even when the surface roughness Ra of the high silicon magnetic steel sheet is large, the slip property is poor and breakage occurs. It turns out that there are cases. this is,
It is shown that another factor is related to the slip property of the high silicon electrical steel sheet, and as a result of further experiments,
It was found that the thickness of the insulating film was involved. In other words, it was found that even if the surface roughness of the steel sheet was rough, the slip property deteriorated when the thickness of the insulating film was large. It is presumed that this is because, when the insulating film is thick, the film fills in the concaves and convexes of the steel sheet surface and makes the surface substantially flat.

Here, when evaluating the relationship between the average thickness of the insulating film and the slipperiness, it is necessary to define the average thickness of the insulating film. The thickness of the insulating film is generally calculated by X-ray fluorescence analysis of the amount of Cr contained in the insulating film. Specifically, the amount of Cr contained in the insulating film is measured by X-ray fluorescence analysis, and the thickness of the insulating film is determined from the amount of Cr using a calibration curve corresponding to the components of the insulating film. The thickness of the insulating film calculated by this method is considered to represent the average thickness of the film, and is considered to be originally suitable as a value representing the average thickness of the uneven insulating film. . Therefore, the average thickness of the insulating film in the present invention is the thickness of the insulating film calculated by X-ray fluorescence analysis of the amount of Cr in the insulating film.

Results of investigation of the relationship between the average thickness of the insulating film and the slipperiness using high silicon electrical steel sheets having various surface roughnesses Ra of 0.10 μm or more (high silicon electrical steel sheets manufactured by a rolling method). Is shown in FIG. The slip property was evaluated based on the presence or absence of breakage during the assembly of the transformer shown in FIG. According to FIG. 3, good slip properties were obtained when the average thickness of the insulating film was 2 μm or less.

From the above results, according to the present invention, the surface roughness Ra
(Roughness of the insulating film surface) is 0.10 μm or more, and the average thickness of the insulating film is 2 μm or less. The thickness of the high silicon steel sheet of the present invention is not particularly limited, but usually has a thickness of about 0.05 to 0.5 mm. Further, the insulating film formed on the steel sheet is usually of an inorganic-organic mixed type.

Hereinafter, the chemical composition of the high-silicon magnetic steel sheet of the present invention and the reasons for the limitation will be described. The high silicon magnetic steel sheet of the present invention has a Si content of 4 to reduce high-frequency iron loss.
mass% or more. On the other hand, if Si exceeds 7% by mass, the production by the rolling method becomes extremely difficult. Therefore, the Si content is set to 7% by mass or less. Other components are not particularly limited,
From the viewpoint of magnetic properties, C: 5 to 300 massppm, M
n: 0.01 to 1 mass%, P: 0.01 mass% or less,
S: 0.01 mass% or less, sol. Al: 0.0005 to
It is preferable that the content be 0.1 mass% and N: 300 mass ppm or less.

C is preferably not more than 300 mass ppm in order to deteriorate magnetic properties and rollability. But,
If the C content is too low, it causes grain boundary oxidation and deteriorates the processability of the product, so that the content is preferably 5 mass ppm or more. Mn is 0.0% in order to secure rollability during hot rolling.
The content is preferably at least 1 mass%, but if it exceeds 1 mass%, it becomes difficult to manufacture by a rolling method, so it is preferable to set the upper limit to 1 mass%.

P and S are each preferably set to 0.01 mass% or less in order to deteriorate the rolling property. In order to reduce the content of these elements to less than 0.001 mass%, the cost is high. Therefore, the lower limit is usually about 0.001 mass%. Al is an element for improving the magnetic properties, and is preferably contained at 0.0005 mass% or more as sol.Al. However, since Al impairs the rolling property, it is preferable that the upper limit of sol.Al be 0.1 mass%.

N is 300 mass to degrade the magnetic properties.
It is preferable that the content be not more than ppm. In addition, since it is generally difficult to make the N content less than 5 mass ppm, the lower limit is usually about 5 mass ppm. Others are substantially made of Fe, and therefore do not prevent other elements such as unavoidable impurity elements from being contained in trace amounts as long as the effects of the present invention are not impaired.

The high silicon electrical steel sheet of the present invention is obtained by thinning a high silicon steel slab such as a continuous cast slab, a bulk-rolled slab, a thin slab cast slab and the like through hot rolling, warm or cold rolling,
It is manufactured by applying an insulating film to this. Specifically, for example, after casting smelted molten steel and, if necessary, slab rolling, it is manufactured by each process of hot rolling, warm or cold rolling, oxide film removal, annealing, and insulating film coating. Is done.

The surface roughness of the steel sheet can be determined, for example, by changing the surface roughness of a hot or cold rolling roll or by pickling conditions (concentration and temperature of hydrochloric acid in a pickling solution, acid temperature) for removing an oxide film. The surface roughness Ra of the steel sheet after the formation of the insulating film can be adjusted to 0.10 μm or more by appropriately adjusting these conditions. Further, the thickness of the insulating film can be adjusted by changing the roll speed, the roll pressing pressure, and controlling the amount of application, for example, when applying a coating liquid for the insulating film using a three-roll coater. .

[0022]

EXAMPLE Steel having the composition shown in Table 1 was subjected to a rolling method (hot rolling-warm rolling) to obtain sheet thicknesses of 0.3 mm and 0.2 mm.
A 0.1 mm high silicon magnetic steel sheet was manufactured. At this time, by changing the roll roughness of the warm rolling, or by changing the grinding roll roughness of the coil grinder performed for oxide film removal, to produce high silicon electrical steel sheets having various surface roughness Ra, Insulating films of various thicknesses were applied to the high silicon magnetic steel sheet.

A transformer core having the structure shown in FIG. 2 was assembled using these high silicon magnetic steel sheets, and the presence or absence of breakage of the steel sheets at that time was examined. In addition, when the plate thickness is 0.1 mm,
The buckled steel sheet was also evaluated as broken. The results are shown in Table 2 together with the thickness of the high silicon electromagnetic steel sheet, the surface roughness Ra, and the average thickness of the insulating film. According to the table, the steel sheet of the comparative example was broken when the core was assembled, whereas the high silicon steel sheet of the present invention was not broken, and good assembly workability was obtained.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above, the high-silicon magnetic steel sheet of the present invention exhibits good assembly workability that does not cause breakage during core assembly, and therefore has a remarkably higher core productivity than the conventional high-silicon steel sheet. The effect of improving is obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the surface roughness Ra of a high silicon electrical steel sheet manufactured by a rolling method and the presence or absence of breakage of the steel sheet during core assembly.

FIG. 2 is an explanatory view showing the structure of a transformer core used for evaluating the assembly workability;

FIG. 3 is a graph showing the relationship between the average thickness of an insulating film formed on a high silicon electrical steel sheet manufactured by a rolling method and the presence or absence of breakage of the steel sheet during core assembly.

Claims (2)

[Claims] 1. The method according to claim 1, wherein the content of Si produced by the rolling method is 4-7.
A high silicon electrical steel sheet having an insulating film formed on the surface of a mass% high silicon steel sheet, wherein the surface roughness Ra is 0.10 μm or more, and the average thickness of the insulating film is 2 μm or less. High-silicon electromagnetic steel sheet with excellent assembly workability. 2. The chemical composition of a steel sheet is substantially C: 5 to 5.
300 mass ppm, Si: 4 to 7 mass%, Mn: 0.0
1-1 mass%, P: 0.01 mass% or less, S: 0.0
1 mass% or less, sol. Al: 0.0005 to 0.1 mass
%, N: 300 mass ppm or less, the balance being Fe, the high silicon magnetic steel sheet excellent in assembly workability according to claim 1.