JP3419016B2 - Electromagnetic steel sheet for laminated iron core with excellent edge weldability - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic steel sheet for laminated cores, the surface roughness of which is adjusted by using a rolling roll having an accurate uneven pattern on the surface, and particularly, the end face weldability of the steel sheet is improved. Is.

[0002]

2. Description of the Related Art Magnetic steel sheets 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 still has a problem in terms of weldability, such as generation of blowholes due to a large amount of gas generated from the organic resin during welding. As a solution to this point, a method of applying a surface roughness of 20 Hr.ms μinch or more to the surface of a steel sheet and then forming an organic coating (Japanese Patent Publication No. 49-6744).
Alternatively, a method of preventing the formation of blowholes by giving roughness to the organic coating itself and dissipating gas generated during welding (Japanese Patent Publication No. Sho 49-19078) and the like have been proposed.

Further, in JP-A-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, in this method, blowholes are observed to occur depending on the welding location, and good weldability is not always obtained stably.Therefore, it is necessary to increase the film thickness to improve punchability. There was a problem that it could not be applied.

[0004]

As described above, it has been difficult to completely prevent the generation of blowholes, and improvement thereof has been desired. The present invention advantageously responds to the above-mentioned demands, and an object thereof is to propose a magnetic steel sheet for laminated iron core that effectively prevents the generation of blowholes without adversely affecting the coating properties.

[0005]

Means for Solving the Problems Now, as a result of various investigations and studies in order to solve the above-mentioned problems, the inventors have found that when laminating end faces of electromagnetic steel sheets, rolling is performed rather than surface roughness of the steel sheets. It was found that the influence of the pattern and the pattern of surface irregularities such as rolling flaws was stronger. This invention is based on the above knowledge, and by appropriately controlling the uneven pattern on the surface of the steel sheet, the improvement of the weldability of the laminated end surface of the electromagnetic steel sheet for lamination having the organic insulating coating, which has been conventionally difficult, is realized. It is a thing.

That is, the gist of the present invention is as follows. 1. A magnetic steel sheet having surface irregularities adjusted by rolling rolls, the three-dimensional surface roughness of the steel sheet surface is 0.5 μm or less in the center surface average roughness SRa and the maximum height SR _max is 0.1.
~ 2.0 μm, and for each recess, centering on the point with the largest depthwise drop in the load curve (the point where the differential coefficient of the load curve is the minimum except for the point where the cutting surface area ratio is 0% or 100%) A magnetic steel sheet for laminated cores having excellent end face weldability, characterized in that the difference in the height direction between two points where the cutting surface area ratios differ from each other by ± 10% satisfies 50% or more of SR _max .

2. The electromagnetic steel sheet for laminated iron cores according to the above 1, which is excellent in end face weldability and is provided with an insulating coating film having an adhesion amount of 0.2 to 2.5 g / m ^{2 on} the steel sheet surface.

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,
Y), the following formula

[Equation 1] Is the value given by (unit: μm).

The load curve means a curve as shown in FIG. Ie maximum height in unit area
With SR _max as the maximum point on the vertical axis, cut height z (μm
) Is the vertical axis. On the other hand, the horizontal axis is the 100-percentage ratio of the cut area at each cutting level to the unit area (cut surface area ratio). At these coordinates, the load curve shows the relationship between the cutting height and the cutting surface area ratio when the cutting height z is gradually reduced from the maximum height SR _max . Therefore,
For example, the height of the convex portion when the cut surface area ratio is 10% is a value indicated by x in the figure. In addition, the recessed portion may be a so-called hole or a groove.

The present invention will be described in detail below. The inventors previously used steel sheets with an organic resin-containing insulating coating having various surface roughnesses, laminated the steel sheets, welded the cross-sections, and investigated their weldability. As a result, in the evaluation based on the two-dimensional surface roughness that has been conventionally used, the weldability varies even if the surface roughness is the same.
It has been found that the weldability cannot always be accurately evaluated by the two-dimensional surface roughness. Therefore, when a new evaluation based on the three-dimensional surface roughness was conceived, the measurement was conducted again by the three-dimensional roughness measuring device, and the re-examination was conducted, and the following results were obtained.

The obtained results are shown in FIG. 2 as a relationship between the center surface average roughness SRa and the cut surface area ratio in the center surface. Here, the cut surface area ratio in the central plane is the area ratio S ′ / S _{M of} the area S ′ cut in the central plane in the unit area S _M.
It is given at 100 (%). As is clear from the figure, when the surface roughness exceeds 0.50 μm in the center surface average roughness SRa, the space factor decreases. The influence of such surface roughness was the same as before, but there were differences in weldability even with the same roughness. That is, even if SRa was within the proper range of 0.50 μm or less, when the cut surface area ratio in the central plane exceeded 80%, the weldability was rapidly deteriorated.

[0012] In view of the above facts, the present inventors have conducted a more detailed investigation on the relationship between the surface roughness of the steel sheet and the weldability of the laminated end faces, and as a result, the weldability has many recesses on the surface of the steel sheet. It has been found that it becomes good when there is a gas escape route when TIG welding is performed by stacking layers. That is, it was newly found that the weldability strongly depends not on the surface roughness of the steel sheet but on the shape of the recess formed on the steel sheet surface.

Then, as a result of examining the shape of the recess, as shown in FIG. 3, there are many recesses each having a flat bottom surface and a contact angle between the bottom surface and the shoulder of the recess is nearly a right angle. It was found that the weldability was significantly improved in the case of doing.

Then, as a result of further studying the specific preferable shape of the concave portion, the three-dimensional surface roughness of the center surface average roughness SRa is 0.5 μm or less, and the maximum height SR _max is 0.1 to.
The cutting surface area ratio is 2.0μm, and the cutting surface area ratio is centered around the point with the largest depth direction drop on the load curve (the point where the differential coefficient of the load curve excluding the point where the cutting surface area ratio is 0% or 100% is the minimum) The difference in the height direction between two points that differ by ± 10%
It was found that particularly good weldability was obtained when SR _max was 50% or more.

Here, the point on the load curve where the depthwise drop is the largest, that is, the point where the differential coefficient of the load curve is the smallest, is the point indicated by point P in FIG. If the difference in height between points Q and R, where the area ratios differ by ± 10%, is ΔH, the larger the ΔH, the closer the angle between the bottom of the recess and the shoulder of the recess will be, and conversely, the smaller ΔH is. It is an obtuse angle, indicating that it is gentle.
The reason why the points with cut surface area ratios of 0% and 100% were excluded when obtaining the point with the smallest differential coefficient is that even if there are any high peaks or deep valleys at these points, it is affected. This is because it is easy and the differential coefficient immediately becomes −∞.

In the present invention, the reason why the shape of the recess is limited as described above will be described. First, as shown in Fig. 2 above, SRa was set to 0.5 µm or less because if this value exceeds 0.5 µm, the space factor will decrease.
Next, if SR _max is less than 0.1 μm, the recess will be filled when the insulating coating is applied, and the gas escape path will not be sufficiently secured, resulting in a decrease in TIG weldability. 0.1-2.0 μ
Limited to m range. In addition, the difference in the height direction between the two points where the cutting surface area ratios differ by ± 10% around the point where the depth difference in the load curve is the largest, that is, the point where the differential coefficient of the load curve is the minimum, is SR was a _max of 50% or more, when this value is less than 50% of SR _max, is a gentle shape of the unevenness, the gas loopholes when TIG welding filled recesses when subjected to insulating coating treatment ensuring not,
This is because the TIG weldability deteriorates.

Next, a method for manufacturing the steel sheet of the present invention will be described. In order to transfer and form an appropriate concavo-convex pattern on the surface of the steel sheet, an appropriate concavo-convex pattern must be formed on the surface of the rolling roll.

Conventionally, as a method for dull-finishing the surface of a roll for skin-pass rolling, a method by shot blasting, a method by electric discharge machining, and further, JP-A-62-62
There is a method by laser processing as disclosed in JP-A-224405, a method combining screen printing and etching or a combination of screen printing and plating as disclosed in JP-A-2-99208. However, the rolling roll dull-finished by the shot blasting method or the electric discharge machining method has an irregular roughness pattern formed on the surface. The pattern is also irregular. Moreover, it is impossible to form an arbitrary uneven pattern.

On the other hand, in the case of laser processing, although a regular roughness pattern can be obtained, as shown in FIG. 5, a portion away from the laser center is raised in a concentric circle by laser irradiation, whereby a fine pattern is formed. It is not possible to obtain a pattern and it is not possible to arbitrarily select the shape of the recess. In addition, since the roll is directly drilled with a laser beam, a laser oscillator is required to efficiently process a workpiece with a large area such as a rolling roll.
It requested 1kW or more high power is an inevitably forced to not give become carbon dioxide gas laser, processing apparatus becomes large in size, a large burden in terms of cost and maintenance. Further, in the concavo-convex pattern formed by melting the metal by the laser beam, the texture of the concavo-convex portion becomes austenite, and thus such a roll has poor wear resistance. Moreover, the diameter of the concave portion of the concavo-convex pattern is determined by the diameter of the laser beam converged by the condenser lens, but this diameter is physically about 100 μm because the wavelength of carbon dioxide laser light is long (10.6 μm).
There is also a disadvantage that you cannot do the following:

On the other hand, the method using the screen printing method is
As disclosed in Japanese Patent Laid-Open No. 2-99207, a fine pattern is printed on the surface of a rolling roll by screen printing, and then etching or plating is performed to form a fine pattern on the roll surface. It is a method that consists of transferring a fine pattern to the roll surface.However, in this method, the waviness that occurs when dull weighting is performed by mechanically hitting the grid particles onto the roll surface like the shot blasting method is applied to the roll surface. Since it does not occur and high energy is not concentrated in the processing part like electrical discharge machining or laser processing method, the hardness of the roll surface does not deteriorate and it is uniform, and the fine pattern is transferred from the roll to the steel sheet. It is possible.

Further, Japanese Patent Publication No. 62-11922 discloses a method of covering the surface with an acid corrosion resistant substance, locally destroying it with a laser beam, and chemically corroding the uncovered portion. ing. Further, in Japanese Patent Laid-Open No. 2-175882,
Using the improved method and apparatus for performing this technique efficiently and precisely and easily, a method for processing a roll having aligned or arbitrarily arranged irregularities, which comprises the following steps, is disclosed. That is, (1) an acid-corrosion-resistant resin liquid mixed with a light-absorbing material is applied to the surface of the rolling roll to form an acid-corrosion-resistant resin film, and (2) this resin film is continuously output at an average of 5 to 10 W. Marking is performed by using a Q switch / YAG laser having the above, and the roll surface is exposed in a desired pattern. (3) After that, an etching process is performed to impart a desired pattern to the roll surface.

Among the above-mentioned various uneven pattern forming methods, the screen printing method or the method of combining the acid corrosion resistant resin film and the Q switch / YAG laser forms a regular fine uneven pattern as described above. Therefore, by using these methods, it is possible to obtain any recess shape satisfying the requirements of the present invention.

[0023]

Next, as the insulating coating used in the present invention, an organic resin coating, a chromate-based and / or a mixed coating of a phosphate and an organic resin, or a chromate-based and / or
Alternatively, a two-layer coating in which an organic resin coating is formed on a phosphate coating can be used.

If the coating is an organic resin coating alone, acrylic resin, alkyd resin, phenol resin,
One or more selected from an epoxy resin, an ethylene resin, a melamine resin, a silicone resin and an amino resin, or modified products thereof are advantageously suitable.

It is also possible to use a mixed coating of one or two chromate-based and phosphate-based and an organic resin. Here, the chromate system is one of dichromate of calcium, magnesium and zinc, or divalent oxide such as calcium, magnesium and zinc, hydroxide and carbonate dissolved in chromic anhydride, or It is a mixture of two or more kinds, or one or more kinds of titanium oxide, colloidal silica, colloidal alumina, boric acid, an organic reducing agent and the like added thereto. As the phosphate system, calcium, magnesium, aluminum and zinc phosphates or phosphates are used to dissolve divalent or trivalent oxides, hydroxides and carbonates of calcium, magnesium, aluminum and zinc. One or a mixture of two or more of the above, or one or more of titanium oxide, colloidal silica, colloidal alumina, boric acid and the like added thereto.

The organic resin to be further mixed is a 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. One or more of maleic anhydride copolymers, epoxy resins and modified products thereof are advantageously suitable.
Furthermore, the insulating coating may have a two-layer structure. In this case, one or two chromate-based and phosphate-based coatings described above may be formed, and then an organic resin coating may be formed thereon.

Here, the adhesion amount of the insulating coating is 0.2 to
It is preferably 2.5 g / m ² . Because the amount of adhesion is
If it is less than 0.2 g / m ² , sufficient punching performance cannot be obtained,
On the other hand, if it exceeds 2.5 g / m ² , the weldability will deteriorate.

In the present invention, the composition of the electromagnetic steel sheet as a raw material is not particularly limited, and any conventionally known one is suitable. As for the method of obtaining the surface roughness, as described above, a method in which the surface of the roll is preliminarily subjected to surface processing using the Q switch-YAG laser so that the surface pattern after rolling falls within the scope of the present invention, and ,
A method using a screen printing method is preferable, but the method is not particularly limited to these methods, and the following methods can also be used. That is, by a method of treating the steel plate surface by polishing or etching so as to have a predetermined surface pattern, or by a method of performing a predetermined surface pattern by changing the rolling speed or the rolling oil used during rolling. is there.

[0029]

【Example】

Example 1 An electrical steel sheet containing C: 0.02% and Si: 0.20% and the balance being substantially Fe composition was rolled by a rolling roll whose surface was processed by a Q switch-YAG laser to obtain a three-dimensional surface roughness. However, the center surface average roughness SRa is 0.3 μm and SR _max is 1.5 μm.
When the load curve has a difference in lateral cross-sectional area ratio of ± 10% centering on the point with the largest depth direction drop, a recess having a deviation ΔH in the height direction of 0.9 μm was formed in a groove shape. . Then, the following treatment liquid 1 was applied to the surface of this magnetic steel sheet so that the coating weight was 1.0 g / m ^2, and then baked at 350 ° C. for 1 minute.

[0030]

[Table 1] [Treatment liquid 1] 30% magnesium dichromate solution: 130 parts by weight (CrO ₃ minutes): 32.5 parts by weight Acrylic resin emulsion (resin solid content: 40%): 25 parts by weight Ethylene glycol: 10 parts by weight boric acid: 10 parts by weight

The punching and welding properties of the thus-obtained magnetic steel sheet with an insulating coating were examined and the results are as follows. The punchability was evaluated by the number of punches until the burr height reached 50 μm when punching with a die diameter of 15 mmφ steel die. Weldability is as follows: electrode: Th-w, pressure: 100 kg / cm ² , electrode-material distance: 1.5 mm, Ar gas amount: 6 l / min, current: 120 A at various speeds. It was evaluated based on whether or not blowholes were generated when the test was performed. -Punchability: 1 million times-Welding property: 100 cm / min, good

Comparative Example 1 A magnetic steel sheet containing C: 0.02% and Si: 0.20% and the balance being substantially Fe composition was rolled by a rolling roll having a surface processed by an electric discharge machining method to give a three-dimensional surface roughness. Sag center surface average roughness SR
When a is taken to be 0.40 μm, SR _max is 1.8 μm, and the cross-sectional area ratios on the left and right sides differ by ± 10% from the point of _maximum load drop in the load curve, the deviation in the height direction Δ
The following treatment liquid 2 was applied to the surface of an electromagnetic steel sheet having H-shaped grooves of 0.4 μm and groove-shaped recesses, and then coated at a coating weight of 1.0 g / m ² and then baked at 380 ° C. for 1 minute.

[0033]

[Table 2] [Treatment liquid 2] ・ 30% magnesium dichromate solution: 130 parts by weight (CrO ₃ minutes): 32.5 parts by weight ・ Vinyl acetate-veova resin emulsion (resin solid content: 40%): 25 parts by weight ・Ethylene glycol: 10 parts by weight Boric acid: 10 parts by weight

The punching and welding properties of the thus obtained magnetic steel sheet with an insulating coating were examined and the results were as follows.・ Punchability: 1.1 million times ・ Welding property: Poor at 40 cm / min

Example 2 Using a rolling roll whose surface roughness was adjusted by the roll processing method shown in Table 5, unevenness having the concave shape shown in Table 5 was formed on the surface of the steel sheet. Then, on the surface of the steel plate, the treatment liquids 1 to 4
Was applied in a predetermined amount and baked at 350 ° C. for 1 minute.
The compositions of the treatment liquids 3 and 4 are as shown in Tables 3 and 4, respectively. Table 5 also shows the results of an examination of punchability and weldability of the thus obtained insulating coated electromagnetic steel sheet.

[0036]

[Table 3] [Treatment liquid 3] 30% magnesium dichromate solution: 130 parts by weight (CrO ₃ minutes): 32.5 parts by weight-Acrylic vinyl acetate resin emulsion (resin solid content: 40%): 25 parts by weight-Ethylene Glycol: 10 parts by weight Boric acid: 10 parts by weight

[0037]

[Table 4] [Treatment liquid 4] ・ Polyester resin / melamine resin: 75/25

[0038]

[Table 5]

As is clear from Table 5, all the steel sheets obtained according to the present invention have excellent punchability and weldability.

[0040]

As described above, according to the present invention, it is possible to obtain a magnetic steel sheet for a laminated iron core having both weldability and punchability, which have hitherto been difficult to achieve compatibility.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a load curve.

FIG. 2 is a graph showing the relationship between SRa and the area ratio of cut surface that affect weldability.

FIG. 3 is a schematic diagram showing a preferred recess according to the present invention.

FIG. 4 is a graph showing the surface unevenness in terms of the relationship between the cut surface area ratio and the height of a convex portion.

FIG. 5 is a schematic view showing a recess according to a conventional method.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Obara 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Works Ltd. Technical Research Division (72) Tomoyuki Ichi 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama No.) Kawasaki Steel Co., Ltd. Inside Mizushima Works (56) Reference JP-A-5-44051 (JP, A) JP-A-1-289103 (JP, A) JP-A-2-217447 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) C22C 38/00 303 H01F 27/245 C21D 8/12 H01F 1/16

Claims (2)

(57) [Claims] 1. A magnetic steel sheet having surface irregularities adjusted by rolling rolls, wherein the three-dimensional surface roughness of the steel sheet has a center surface average roughness SRa of 0.5 μm or less and a maximum height SR _max of 0.1.
~ 2.0 μm, and for each recess, centering on the point with the largest depthwise drop in the load curve (the point where the differential coefficient of the load curve is the minimum except the point where the cutting surface area ratio is 0% or 100%) A magnetic steel sheet for laminated cores having excellent end face weldability, characterized in that the difference in the height direction between two points where the cutting surface area ratios differ from each other by ± 10% satisfies 50% or more of SR _max . ^2. The electromagnetic steel sheet for laminated core according to claim 1, wherein the steel sheet surface is provided with an insulating coating having an adhesion amount of 0.2 to 2.5 g / m ² and is excellent in end face weldability.