JPH05220506A - Manufacture of electric steel sheet for laminated iron core excellent in punching property and weldability - Google Patents

Abstract

PURPOSE:To obtain an electric steel sheet for laminated iron core not only having good punching property but combining both of good weldability and occupying volume rate. CONSTITUTION:At the time of manufacturing the electric steel sheet with an insulating film, at least the final pass in the final cold rolling stage is rolled by using a rolling roll having the surface properties that the arithmetic mean deviation of profile SRa of the roll surface is 0.20 to 0.80mum and the number of recessed part is >=50 per unit area of 1mm<2> that is cut by the center plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic steel sheet for laminated cores, and particularly to improve punchability and weldability.

[0002]

2. Description of the Related Art Electric iron plates used for motors, transformers, etc. are required not only to have excellent magnetic properties but also to have good punchability from the viewpoint of mass productivity. An insulating coating is applied. However, this coating has a problem in terms of weldability such as blowholes caused by a large amount of gas generated from the organic resin during welding. In order to eliminate this point, a method of applying an organic coating after applying a surface roughness of 20 Hr.msμinch or more to the steel sheet surface (Japanese Patent Publication No. 496744) or giving roughness to the organic coating itself. A method of preventing the formation of blowholes by dissipating the gas generated during welding (Japanese Patent Publication No. 49-19078) has been proposed. However, with these methods, the space factor is
It is not preferable because it decreases to 97-98%.

Therefore, in Japanese Patent Laid-Open No. 54-134043,
A method of depositing an organic coating having a coating thickness of 1 to 2.5 g / m ² on a steel sheet having a surface roughness of 0.35 to 0.6 μm in terms of centerline average roughness Ra has been proposed. However, even with this method, blowholes are found to occur depending on the welding location, and good weldability is not always obtained stably.Therefore, it is necessary to take measures such as increasing the film thickness to improve punchability. There was a problem that it could not be applied. As described above, conventionally, when the surface roughness Ra is increased in order to improve the weldability, the space factor is lowered, and there is a disadvantage that the film thickness cannot be made sufficiently thick.

[0004]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and is advantageous for a laminated electromagnetic steel sheet with an insulating coating, which is excellent not only in weldability and punchability but also in a high space factor. The purpose is to propose a new manufacturing method.

[0005]

Means for Solving the Problems Now, as a result of intensive studies to achieve the above-mentioned object, the inventors have simply adjusted the surface roughness of the steel plate surface when laminating end faces of electromagnetic steel plates. It is not enough to adjust the surface shape such as rolling pattern and rolling flaws. Specifically, the three-dimensional surface roughness of the steel plate is 0.15 to 0.50 μm in the center plane average roughness SRa and the cutting at the center plane By adjusting so that the surface area ratio is 80% or less and the number of convex parts cut by the central surface per unit area 1 mm ² is 50 or more, weldability and space that have been difficult to be compatible with conventional products It was newly found that both of the rates can be improved. Therefore, the inventors next proceeded with research on an advantageous method for producing an electromagnetic steel sheet having the above-described preferable surface shape. This invention discloses the development result.

That is, the present invention relates to a Si-containing hot rolled sheet containing 1
In the method for producing an electrical steel sheet with an insulating coating, which comprises a series of steps of performing a final finishing annealing after performing two or more cold rolling including intermediate or intermediate annealing, and further forming an insulating coating in the final cold rolling. A rolling roll having at least the final pass of the process in which the average roughness SRa of the roll surface is 0.20 to 0.80 μm, and the number of recesses per unit area 1 mm ² cut by the center line is 50 or more. It is a method for producing a magnetic steel sheet for laminated core, which has excellent punchability and weldability.

First, the process of clarifying the present invention will be described. The inventors used steel sheets with an organic resin-containing insulating coating having various surface roughnesses, and after laminating each of them, welded their cross sections and investigated their weldability.
As a result, in the evaluation of the two-dimensional surface roughness that has been conventionally used, it was found that the weldability varies even with the same surface roughness, and the two-dimensional surface roughness cannot always accurately evaluate the weldability. did. Therefore, a new evaluation based on the three-dimensional surface roughness was conceived, and the three-dimensional roughness was measured again and reexamined. The obtained result is the center surface average roughness SRa.
FIG. 1 shows the relationship between the cut surface area ratio and the center surface area.

As is clear from the figure, when the surface roughness exceeds 0.50 μm in the center surface average roughness SRa, the space factor deteriorates,
If SRa was less than 0.15 μm, welding failure occurred. The influence of such surface roughness was the same as before, but there was a difference in weldability even with the same roughness. That is, SRa is 0.15 ~
Even in the range of 0.50 μm, when the area ratio of the cut surface in the central plane exceeds 80%, the weldability was rapidly deteriorated.

The reason why the results shown in FIG. 1 are obtained has not been clarified yet, but it is presumed as follows. That is, when the area ratio of the cut surface exceeds 80%, it means that there are many recesses on the surface of the steel sheet. Then, when an insulating coating is applied to the surface of the steel sheet and baked, the concave portion is filled with the coating. When such a material is welded, the amount of generated gas locally increases, and the generated gas does not escape smoothly. However, SRa is 0.15-0.50 μm and the cut surface area ratio is 80%.
Even in the following cases, there were occasions where welding defects occurred.

Then, as a result of further studying various three-dimensional parameters, it was found that the number of projections per unit area cut by the center plane has a strong correlation with weldability. Fig. 2 shows a unit area 1 cut by the center plane.
The results of an examination of the relationship between the number of protrusions per mm ² and weldability are shown below. As is clear from the figure, good weldability cannot be obtained when the number of protrusions cut by the center plane per unit area 1 mm ² is less than 50.

The center plane average roughness SRa is the area S _M extracted from the roughness curved surface on the center plane, and the orthogonal coordinate axes, the X axis, and the Y axis are placed on the center plane of the extracted portion. The roughness surface is Z = f (X,
When expressed by Y),

[Equation 1] Is the value given by (unit: μm). The cut surface area ratio in the center plane is given by the area ratio S ′ / S _M × 100 (unit%) of the area S ′ cut in the center plane in the unit area S _M. Furthermore, the number of convex portions means the unit area S
It is the number of particles (the number of protrusion shapes) cut at the center plane of _M , and is obtained as N = S ′ / DOT when the data sampling area is DOT.

In order to obtain the above-mentioned surface texture, the inventors have made various studies, and based on the idea that adjusting the surface texture of the rolling roll is the simplest and most effective, further studies have been conducted. FIG. 3 shows the results of examining the surface shape of the electrical steel sheet when rolling was performed by using rolling rolls having different SRa and number of recesses on the roll surface in the final pass of the cold rolling. .. As is apparent from the figure, the preferable surface texture, that is, the three-dimensional roughness SRa of 0.15 to 0.50 μm in SRa and the steel plate surface shape in which the number of projections per unit area 1 mm ² is 50 or more are obtained. To achieve this, the center surface average roughness SRa of the roll surface should be 0.20 to 0.80 μm and the unit area 1
It was clarified that the number of recesses per mm ² should be 50 or more. And if rolled using a roll having the above-mentioned surface shape, the cut surface area ratio by the central plane ≦ 80
It has been confirmed that the 100% condition is almost 100% achieved. However, if the rolling speed is extremely slow or fast, or if a rolling oil having an extremely high viscosity is used, the cut surface area ratio may exceed 80%, so caution is required.

[0013]

Next, the reason for limitation will be described. By the way, the electrical steel sheet for laminated core usually has Si: 3.5 wt% (hereinafter simply indicated as%)
Manufactured by cold-rolling a hot-rolled sheet containing the following and optionally containing Al, Mn, etc. once or twice or more by cold rolling including intermediate annealing, and then subjecting to final finish annealing .. In the present invention, the final pass in the cold rolling, center surface average roughness SRa of the roll surface is 0.20 ~ 0.
80 μm and a unit area of 1 mm cut by the center line
It is rolled with a rolling roll having a surface texture in which the number of recesses per ² is adjusted to 50 or more.

When SRa is smaller than 0.20 μm, the SRa of the steel sheet obtained is smaller than 0.15 μm and the weldability is poor. On the other hand, when SRa exceeds 0.80 μm, the SR of the steel sheet obtained is
SRa is 0 because the space factor deteriorates when a exceeds 0.50 μm.
It was limited to 20 to 0.80 μm. If the number of recesses per unit area 1 mm ² is less than 50, weldability may deteriorate even if SRa: 0.20 to 0.80 μm is secured. This is because the small number of recesses means that the surface of the steel sheet after rolling has few protrusions and the recesses are deep, and does not contribute to the escape of gas generated during welding. Therefore, the number of recesses must be 50 or more. Note that as the number of recesses increases, the number of low projections increases, and the steel sheet surface after rolling has a uniform appearance. As the processing means for obtaining such roll surface properties, any of grindstone grinding, energy beam irradiation, etching, etc. is suitable.

By using such a rolling roll, the transfer rate on the surface of the rolling roll is almost the same even if the rolling reduction is changed.
Since it is about 70% or less, the surface of the electromagnetic steel sheet can have desired properties. Further, even if the rolling speed or the rolling oil used during rolling is changed, the desired surface texture can be obtained even if the condition of some oil pits changes. Regarding the amount of rolling by the same roll, it is preferable to carry out while checking the surface shapes of various electromagnetic steel sheets.

Next, as the insulating coating used in the present invention, a coating containing an organic material is suitable for the purpose of improving punchability. When the organic resin film is used alone as the insulating film, one or two selected from acrylic resin, alkyd resin, phenol resin, epoxy resin, melamine resin, silicone resin and amino resin or modified products thereof are used. More than one species are advantageously matched.

As the insulating coating, it is also possible to use a mixed coating of one or two chromate type and phosphate type and an organic resin. Here, the chromate type is one of divalent oxides, hydroxides and carbonates of calcium, magnesium and zinc dissolved in dichromate or chromic acid of calcium, magnesium and zinc. Or 2
A mixture of more than one species, or even titanium oxide,
One or more kinds of colloidal silica, colloidal alumina, boric acid and an organic reducing agent are added.
Phosphate-based refers to the dissolution of divalent or trivalent oxides, hydroxides, or carbonates of calcium, magnesium, aluminum, zinc, etc. in calcium, magnesium, aluminum, zinc phosphates or phosphoric acid. One or a mixture of two or more of the above, or a mixture of one or more of titanium oxide, colloidal silica, colloidal alumina and boric acid. As the organic resin to be further mixed, water-soluble or emulsion type acrylic resin and its copolymer, vinyl acetate resin and its copolymer, Veova resin, styrene resin copolymer,
Amino resin, alkyd resin, phenol resin, maleic anhydride copolymer, epoxy resin or modified product thereof, etc. 1
One or more species are advantageously matched.

Further, the insulating coating may be a two-layer coating. In this case, it is preferable to form one or two of the above-mentioned chromate-based and phosphate-based coatings, and then superimpose an organic resin coating thereon. The amount of the insulating coating deposited here is preferably 0.3 to 1.3 g / m ² (per surface). This is because sufficient punchability cannot be obtained if the amount of adhesion is less than 0.3 g / m ² , while weldability deteriorates if it exceeds 1.3 g / m ² . In the present invention, the composition of the electromagnetic steel sheet as a material is not particularly limited, and any conventionally known non-oriented electrical steel sheet is suitable.

[0019]

EXAMPLES Example 1 C: 0.025% and Si: 0.10% are contained, and the balance is substantially
A hot rolled sheet of electromagnetic steel with a composition of Fe was cold rolled to 0.
It was a cold-rolled sheet with a thickness of 50 mm. At that time, in the final rolling pass, the center surface average roughness SRa of the roll surface was 0.35 μm and the unit area was 1 mm.
Rolling was performed using a rolling roll having a surface texture with 64 recesses per ² pieces. After that, after the final finish annealing, the following treatment liquid 1 was applied to the surface of the steel sheet with a coating weight of 0.
After coating so that 8 g / m ² (per surface), 400
Baked at 1 ° C for 1 minute.

[0020]

[Table 1] [Treatment liquid 1] ・ 30% magnesium dichromate solution: 130 parts by weight CrO ₃ minutes: 32.5 parts by weight ・ Acrylic-vinyl acetate resin emulsion (resin solid content: 50%): 20 parts by weight ・ Ethylene glycol : 10 parts by weight Boric acid: 10 parts by weight The results of examining the space factor, punchability and weldability of the thus obtained electromagnetic steel sheet with an insulating coating are as follows.

[Table 2] Space factor: 99.7% Punchability: 1 million times Weldability: 100 cm / min is good. However, the punchability is the burr height when punching with a die diameter of 15 mmφ steel die. Evaluation was made by the number of punches until reaching 50 μm.

Example 2 C: 0.025% and Si: 0.10%, the balance being substantially
A hot rolled sheet of electromagnetic steel with a composition of Fe was cold rolled to 0.
It was a cold-rolled sheet with a thickness of 50 mm. At that time, in the final rolling pass, the center surface average roughness SRa of the roll surface was 0.75 μm and the unit area was 1 mm.
Rolling was performed using a rolling roll having a surface texture in which the number of recesses per ² was 82. After that, after the final finish annealing, the following treatment liquid 2 was applied to the surface of the steel sheet with a coating weight of 0.
400 g / m ² (per surface) after coating
Baked at 1 ° C for 1 minute.

[Treatment Liquid 2] Polyester resin / melamine resin: 75/25 The results of examining the space factor, punchability and weldability of the thus obtained electromagnetic steel sheet with an insulating coating are as follows.

[Table 3] Space factor: 99.4% Punchability: 1.1 million times Weldability: 120 cm / min, all good

Example 3 C: 0.003% and Si: 0.25%, Mn: 0.22% and Al: 0.25
%, And the balance being substantially Fe, a hot rolled sheet of electromagnetic steel was cold rolled into a cold rolled sheet of 0.50 mm thickness. At that time, the final pass of the cold rolling was performed using a rolling roll having a surface texture in which the center surface average roughness SRa of the roll surface was 0.55 μm and the number of recesses per unit area 1 mm ² was 108. Then, after performing final finish annealing, the following treatment liquid 3 was applied to the surface of the steel sheet so that the coating weight was 0.8 g / m ² (per surface), and then the coating was baked at 400 ° C. for 0.8 minutes. After that, the treatment liquid 4 was further added, and the coating weight was 0.4 g /
After coating so as to be m ² (per surface), it was baked at 400 ° C. for 1 minute.

[0024]

[Table 4] [Treatment liquid 3] ・ 30% magnesium dichromate solution: 130 parts by weight CrO ₃ minutes: 32.5 parts by weight ・ Ethylene glycol: 10 parts by weight

[Treatment Liquid 4] Alkyd Resin / Melamine Resin: 75/25 The results of examining the space factor, punching property and weldability of the thus obtained electromagnetic steel sheet with an insulating coating were as follows.

[Table 5] Space factor: 99.4% Punchability: 1.1 million times Weldability: 100 cm / min, all good

Example 4 C: 0.003% and Si: 0.34%, the balance being substantially
A hot rolled sheet of electromagnetic steel with a composition of Fe was cold rolled to 0.
It was a cold-rolled sheet with a thickness of 50 mm. At that time, the first pass of the final rolling pass was rolled by using a rolling roll having a surface texture in which the center surface average roughness SRa of the roll surface was 0.75 μm and the number of recesses per unit area 1 mm ² was 82, and then The final rolling pass,
Rolling was performed using a rolling roll having a surface texture in which the center surface average roughness SRa of the roll surface is 0.50 μm and the number of recesses per unit area of 1 mm ² is 65. After that, after performing final finish annealing, the above treatment liquid 1 was applied to the surface of the steel sheet so that the coating weight was 1.2 g / m ² (per surface),
It was baked at 400 ° C for 1 minute. The space factor, punchability and weldability of the thus obtained magnetic steel sheet with an insulating coating were examined and the results were as follows.

[Table 6] Space factor: 99.5% Punchability: 1.2 million times Weldability: 100 cm / min, all good

Comparative Example 1 C: 0.025% and Si: 0.10% are contained, and the balance is substantially
A hot rolled sheet of electromagnetic steel with a composition of Fe was cold rolled to 0.
It was a cold-rolled sheet with a thickness of 50 mm. On the final pass of the cold rolling, the center surface average roughness SRa of the roll surface is 0.18 μm and the unit area is 1 mm ²
Rolling was performed using a rolling roll having a surface texture of 35 concave portions per hit. After that, final finishing annealing is performed, and then the treatment liquid 1 is applied to the surface so that the coating weight is 0.8.
400 ℃ after applying so that g / m ² (per surface)
Baked for 1 minute. Thereafter, the treatment liquid 4 was further applied so that the coating weight was 0.4 g / m ² (per surface), and then baked at 400 ° C. for 1 minute. The space factor, punchability and weldability of the thus obtained magnetic steel sheet with an insulating coating were examined and the results were as follows.

[Table 7] Space factor: 99.6% Punchability: 900,000 times Weldability: Poor at 30 cm / min

Comparative Example 2 C: 0.003% and Si: 0.35% are contained, and the balance is substantially
A hot rolled sheet of electromagnetic steel with a composition of Fe was cold rolled to 0.
It was a cold-rolled sheet with a thickness of 50 mm. At that time, the center pass average roughness SRa of the roll surface was 0.85 μm and the unit area was 1 in the final pass of cold rolling.
Rolling was performed using a rolling roll having a surface texture with 82 recesses per mm ² . Then, after the final finish annealing, the treatment liquid 1 is applied to the surface so that the coating weight is 0.8.
400 ℃ after applying so that g / m ² (per surface)
Baked for 1 minute. The space factor, punchability and weldability of the thus obtained magnetic steel sheet with an insulating coating were examined and the results were as follows.

[Table 8] Space factor: 98.6% Punchability: 1.2 million times Weldability: 120 cm / min

[0029]

As described above, according to the present invention, it is possible to obtain a magnetic steel sheet for a laminated iron core which has not only excellent punchability but also has both weldability and space factor, which have hitherto been difficult to achieve compatibility.

[Brief description of drawings]

FIG. 1 is a graph showing the effects of SRa and cut surface area ratio on weldability.

FIG. 2 is a graph showing the influence of the number of convex portions per unit area and the cut surface area ratio on weldability.

FIG. 3 is a graph showing the effect of cold rolling roll surface texture on the surface shape of a steel sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takafumi Obara 1 Kawasaki-cho, Chiba-shi, Chiba Inside the Technical Research Division, Kawasaki Steel Corporation (72) Inventor Hiroki Tomita 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama ) Kawasaki Steel Co., Ltd. Mizushima Steel Works

Claims (1)

[Claims] 1. A series of steps in which a hot-rolled Si-containing steel sheet is cold-rolled once or twice or more including an intermediate anneal, followed by final finishing anneal, and then forming an insulating film. In the method for producing an electrical steel sheet with an insulating coating, the center surface average roughness SRa of the roll surface is 0.20 to 0.80 μm and the unit area 1 mm ² cut by the center surface is at least the final pass of the final cold rolling step. The method for producing a magnetic steel sheet for laminated core having excellent punchability and weldability, which comprises rolling with a rolling roll having a surface texture in which the number of recesses is 50 or more.