JP3068329B2 - Manufacturing method of electrical steel sheet for laminated iron core with excellent punchability and 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 method for manufacturing a magnetic steel sheet for a laminated iron core, and more particularly to an improvement in the punching property and weldability.

[0002]

2. Description of the Related Art Electric iron plates used for motors, transformers and the like are required to have not only excellent magnetic properties but also good punching properties from the viewpoint of mass productivity, and generally include an organic resin in order to satisfy this requirement. An insulating coating is applied. However, this coating 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. In order to solve this problem, a method of forming an organic coating after applying a surface roughness of 20 Hr.msμinch or more to the steel sheet surface (Japanese Patent Publication No. 49-6744) and giving the organic coating itself a roughness. There has been proposed a method of preventing generation of blow holes by dissipating gas generated during welding (Japanese Patent Publication No. 49-19078). However, these methods inevitably increase the space factor.
It is not preferable because it is reduced to 97 to 98%.

[0003] In Japanese Patent Application Laid-Open No. 54-133403,
A method of forming 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 with a center line average roughness Ra has been proposed. However, even with this method, the occurrence of blowholes is observed depending on the welding location, and it is not always possible to obtain good weldability stably. There was a problem that it could not be applied.

By the way, the present inventors have previously solved the above-mentioned problem by assuming that the three-dimensional surface roughness of the steel sheet is 0.15 to 0.50 μm in terms of center plane average roughness SRa and the cut surface area ratio in the center plane. Developed electrical steel sheets for laminated iron cores that have both weldability and space factor by adjusting the number of protrusions per unit area 1 mm ² cut by the center plane to 80% or less and 50 or more. And disclosed in Japanese Patent Application No. 3-226426.

Further, the inventors have studied on an advantageous method for producing an electromagnetic steel sheet having the above-mentioned preferable surface shape. As a result, at least the final pass of the final cold rolling step, the center surface average roughness SRa of the roll surface is 0.20 to 0.80
μm and a unit area of 1 mm ² cut by the center plane.
It has been found out that a desired surface shape can be obtained by rolling with a roll having a surface texture of 50 or more concave portions per hit and disclosed in Japanese Patent Application No. 4-28237.

[0006]

However, even with the above technology, when the magnetic steel sheet is a high-grade grade containing a large amount of Si, a desired surface shape and, consequently, a predetermined characteristic cannot be obtained. Was. The present invention advantageously solves the above problems, and even if the target steel type is a high-grade electrical steel sheet containing a large amount of Si, a desired surface shape can be obtained, and thus excellent weldability and excellent punchability. Needless to say, an object of the present invention is to propose an advantageous method for producing a laminated electromagnetic steel sheet provided with an insulating film that can provide a high space factor.

[0007]

That is, the present invention includes the following.
After performing cold rolling once or twice or more including intermediate annealing on a hot-rolled Si steel sheet, a final finishing annealing is applied, and furthermore, an insulating steel sheet with an insulating coating is formed. In the production method, the pass before the final pass in the final cold rolling step is performed by adjusting the center plane average roughness SRa of the roll surface to
Rolling with a roll that satisfies the range of 0.50 to 1.50 μm, and further passing the final pass of the final cold rolling step, the roll has a center plane average roughness SRa of 0.20 to 0.80 μm and is cut by the center plane. And a roll having a surface texture of 50 or more concave portions per unit area of 1 mm ^2, which is a method for producing an electromagnetic steel sheet for a laminated iron core having excellent punching properties and weldability.

Hereinafter, the basic technical contents of the present invention will be described. The inventors first used steel plates with an organic resin-containing insulating film having various surface roughnesses, laminated them, welded the end faces thereof, and investigated the weldability. As a result, in the conventional evaluation of the two-dimensional surface roughness, it has been found that even if the surface roughness is the same, the weldability varies, and it is not always possible to accurately evaluate the weldability with the two-dimensional surface roughness. did. Therefore, a new evaluation based on three-dimensional surface roughness was newly conceived, and three-dimensional roughness was measured again and re-examined. As a result, a result as shown in FIG. 1 was obtained.

As shown in FIG. 1, when the surface roughness exceeds a center plane average roughness SRa of more than 0.50 μm, the space factor is deteriorated.
If SRa was less than 0.15 μm, poor welding occurred. The effect 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 to 0.50
Even in the μm range, the cut surface area ratio at the center plane is 80
%, Rapid deterioration of weldability was observed.

Therefore, in order to obtain good weldability without reducing the space factor, it is considered that SRa should be 0.15 to 0.50 μm and the cut surface area ratio should be 80% or less. However, even when the surface shape was adjusted to satisfy such conditions, welding defects sometimes occurred.

Then, when further examining various three-dimensional parameters, as shown in FIG. 2, it was found that the number of protrusions per unit area cut by the center plane had a strong correlation with weldability. In other words, when the number of protrusions per unit area of 1 mm ² cut by the center plane was less than 50, good weldability was not obtained.

[0012] From the many studies described above, in order to combine not only punchability but also weldability and space factor, which have been difficult to achieve in the past, the surface roughness of the steel sheet must be determined by measuring the center plane average roughness SRa.
It is determined that it is sufficient to adjust so that it is 0.15 to 0.50 μm, the cut surface area ratio at the center plane is 80% or less, and the number of protrusions per unit area 1 mm ² cut by the center plane is 50 or more. It was done.

[0013] The center surface average roughness SRa here, sampling the area S _M to the center plane from a roughness curved surface, orthogonal coordinate axes on the center plane of the extracted portion, X-axis, placing the Y-axis, the center plane The roughness surface is defined as Z = f (X,
Y), the following equation

(Equation 1) (Unit: μm). The cut surface area ratio at the center plane is given by 'area ratio S of' / S _M × 100 unit area S area is cut at the center plane of the _M S (in%). Further, the number of convex portions means the unit area S
The number of particles cut off at the center plane in _M (the number of protrusion shapes) N, and assuming that the data collection area is DOT, N = S ′ / DOT.

Next, the inventors of the present invention have conducted various studies on a method for obtaining the above-mentioned preferable surface shape, and have found that it is the simplest and most effective to adjust the surface properties of the rolling roll. Based on the idea, further investigation was conducted. As a result, as shown in FIG. 3, the above-mentioned preferred surface shape, that is, the three-dimensional roughness is 0.15 to 0.50 μm in SRa, and the number of protrusions per unit area 1 mm ² cut by the center plane is 50 or more. In order to obtain a surface shape that is as follows, at least the final pass of the final cold rolling step is performed so that the center surface average roughness SRa of the roll surface is 0.20 to 0.80 μm and the unit area 1
It has been found that rolling may be carried out using a roll having a surface shape of 50 or more concave portions per mm ² . If rolling is performed using a roll having the above-mentioned surface shape, the condition of the area ratio of the cut surface by the center plane ≦ 80% can be almost 100%.
% Has been confirmed to be achieved.

However, when the electromagnetic steel sheet is a high-grade grade containing a large amount of Si, a desired surface shape may not be obtained even if the above-described rolling treatment is performed.

Therefore, the present inventors pursued the cause and found that the cause was caused by a difference in hardness of the steel sheet. That is, high-grade grades are in steel
Since the Si content is about 3 wt% (hereinafter simply referred to as%), which is larger than that of the lower grade material (Si: about 0.3%), a satisfactory steel sheet surface shape can be obtained under the same conditions as the lower grade material. There was no. Therefore, in order to solve this problem, further investigation was made.In addition to the rolls used in the final pass of the final cold rolling process, the roll surface used in the previous pass should be modified. As a result, the above problem can be advantageously solved.

FIG. 4 shows that the cold rolling was performed using rolls with various SRa on the roll surface as rolling rolls used in the final pass and the preceding pass in the final cold rolling step. The results of examining the weldability are summarized and shown. In each of the rolling rolls used in the final pass, the number of projections per unit area of 1 mm ² cut by the center plane was in the range of 60 to 80.

As is apparent from FIG. 1, even if the SRa of the roll surface of the rolling roll used in the final pass is 0.20 to 0.80 μm, the SRa of the rolling roll surface of the preceding pass of the final pass is not reduced.
If it is less than 0.50 μm, satisfactory weldability could not be obtained. On the other hand, when SRa exceeded 1.50 μm, linear flaws called scratches occurred on the steel sheet surface. Therefore, in the present invention, the SRa on the surface of the rolling roll used in the preceding pass of the final pass is limited to the range of 0.50 to 1.50 μm.

When the surface of the rolling roll used for the final pass has an SRa of less than 0.20 μm, the finally obtained steel sheet has an SRa of less than 0.15 μm, resulting in poor weldability, while having an SRa of 0.80 μm. If it exceeds, the SRa of the final steel sheet exceeds 0.50 μm and the space factor deteriorates.
Was limited to the range of 0.20 to 0.80 μm. Unit area 1mm
^If the number of recesses per ² is less than 50, SRa: 0.20-0.
Even if 80 μm is secured, the weldability may deteriorate. This is because the fact that the number of concave portions is small means that the surface of the steel sheet after rolling has few convex portions and deep concave portions, and does not contribute to the escape of gas generated during welding. Therefore, the number of concave portions needs to be 50 or more. In addition, as the number of concave portions increases, the number of low convex portions increases, and the surface of the steel sheet after rolling has a uniform appearance. Note that when the rolling speed is extremely slow or fast, or when extremely high-viscosity rolling oil is used, the cut surface area ratio may exceed 80%.

[0020]

[Effect] The electromagnetic steel sheet for laminated iron core is usually 3.5% Si.
A hot-rolled sheet containing the following, if necessary, containing Al, Mn, etc., is manufactured by cold-rolling a sheet by cold rolling once or twice or more including intermediate annealing, and then performing a final finish annealing . According to the present invention, in the final cold rolling step, the preceding pass of the final pass is replaced with the center plane average roughness of the roll surface.
Rolling is performed using a rolling roll having an SRa of 0.50 to 1.50 μm.
Rolling is carried out by a roll of 20 to 0.80 μm and having 50 or more concave portions per 1 mm ^{2 of} unit area cut by the center line.

As the processing means for obtaining the roll surface properties as described above, any of grinding wheel grinding, energy beam irradiation, etching and the like are suitable. By using such a rolling roll, the transfer rate of the surface of the rolling roll is about 70% or less even if the rolling reduction is changed, so that the surface of the electromagnetic steel sheet can be made to have desired properties. Even if the rolling speed or rolling oil used during rolling is changed, the desired surface properties can be obtained even if the degree of formation of the oil pits slightly changes. The amount of rolling by the same roll is preferably performed while checking the surface shape of various electromagnetic steel sheets.

Next, as the insulating film used in the present invention, a film containing an organic substance is preferable for the purpose of improving the punching property. When an 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, silicon resin, amino resin, and modified products thereof are used. More than species are advantageously suited.

Further, as the insulating film, a mixed film of one or two of a chromate type and a phosphate type and an organic resin can also be used. Here, the term “chromate” refers to one kind of a substance obtained by dissolving divalent oxides, hydroxides and carbonates such as calcium, magnesium and zinc in dichromate of calcium, magnesium and zinc or chromic anhydride. Or 2
A mixture of more than one species, or additionally titanium oxide,
One or more of colloidal silica, colloidal alumina, boric acid, and an organic reducing agent are added.
Phosphate refers to the dissolution of divalent or trivalent oxides, hydroxides and carbonates such as calcium, magnesium, aluminum and zinc in phosphates or phosphoric acids of calcium, magnesium, aluminum and zinc. One or a mixture of two or more of these, or one or more of titanium oxide, colloidal silica, colloidal alumina, boric acid and the like are further added thereto. Further, as the organic resin to be mixed, a water-soluble or emulsion-type acrylic resin and its copolymer, a vinyl acetate resin and its copolymer, a veoba resin, a styrene resin copolymer,
1 such as amino resin, alkyd resin, phenol resin, maleic anhydride copolymer, epoxy resin or modified product thereof
The species or two or more are advantageously suitable.

Further, the insulating coating may be a two-layer coating. In this case, it is preferable to form one or two kinds of the above-mentioned chromate-based and phosphate-based films and then form an organic resin film thereon. It is preferable that the amount of the applied insulating coating is 0.3 to 1.3 g / m ² (per one side). This is because if the amount of adhesion is less than 0.3 g / m ² , sufficient punching properties cannot be obtained, while if it exceeds 1.3 g / m ² , the weldability deteriorates. In the present invention, the composition of the magnetic steel sheet as a raw material is not particularly limited, and any conventionally known non-oriented magnetic steel sheet is suitable.

[0025]

EXAMPLES Example 1 C: 0.025% and Si: 3.06%, with the balance being substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. At that time, for the pass before the final pass of the cold rolling process, the center surface average roughness SRa of the roll surface
Is rolled using a 0.80 μm rolling roll, while the final pass has a center surface average roughness SRa of 0.35 μm.
The roll was rolled using a roll having a surface texture of 58 μm and 58 concave portions per unit area of 1 mm ² . Then, after performing the final finish annealing, the following treatment liquid 1
Was applied so that the coating weight per unit area was 0.75 g / m ² (per side), and baked at 400 ° C. for 1 minute.

[0026]

[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 obtained by examining the appearance, space factor, punching property and weldability of the thus obtained magnetic steel sheet with an insulating coating were as follows.

[Table 2] Appearance: Good Space factor: 99.5% Punching property: 1 million times Weldability: Good at 100 cm / min for both. However, the punching property is the burr when punching with a die diameter of 15 mmφ steel die. Evaluation was made by the number of punches until the height reached 50 μm.

Example 2 C: 0.025% and Si: 3.21%, with the balance being substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. At that time, for the pass before the final pass of the cold rolling process, the center surface average roughness SRa of the roll surface
Is rolled using a 1.50 μm rolling roll, while the final pass has a center surface average roughness SRa of 0.65 mm.
The roll was rolled using a roll having a surface texture of 82 μm and 82 concaves per unit area of 1 mm ² . Then, after performing the final finish annealing, the following treatment liquid 2 is applied to the steel sheet surface.
Was applied so that the coating weight per unit area was 1.2 g / m ² (per side), and baked at 400 ° C. for 1 minute.

[Treatment solution 2] Polyester resin / melamine resin: 75/25 The results of examination of the appearance, space factor, punching property, and weldability of the thus obtained magnetic steel sheet with an insulating coating are as follows. Was.

[Table 3] Appearance: Good Space factor: 99.7% Punching property: 1.1 million times Weldability: Good at 120 cm / min

Example 3 C: 0.003% and Si: 0.25%, Mn: 0.22% and Al: 0.25
%, And the balance was substantially Fe, and the hot-rolled sheet of the electromagnetic steel was cold-rolled into a cold-rolled sheet having a thickness of 0.50 mm. At that time, for the pass before the final pass of the cold rolling process, rolling was performed using a roll having a center surface average roughness SRa of 0.80 μm on the roll surface, while for the final pass, the center surface average roughness of the roll surface was rolled. The roll was rolled using a roll having a surface texture of SRa of 0.55 μm and 103 concave portions per unit area of 1 mm ² . After the final finish annealing,
The following treatment liquid 3 was applied to the steel sheet surface with a coating weight of 0.5 g / m ^2.
(Per side) and then at 400 ℃
Bake for 0.8 minutes. Thereafter, the treatment liquid 4 was further applied so that the coating weight per unit area was 0.4 g / m ² (per side), and baked at 400 ° C. for 1 minute.

[0030]

[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 obtained by examining the appearance, space factor, punchability and weldability of the thus obtained magnetic steel sheet with an insulating coating were as follows.

[Table 5] Appearance: Good Space factor: 99.5% Punching property: 1,000,000 times Weldability: Good at 100 cm / min

Example 4 contains 0.003% of C and 0.34% of Si, and the balance is substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. At that time, for the pass before the final pass of the cold rolling process, the center surface average roughness SRa of the roll surface
Was rolled using a roll of 1.50 μm, while the final pass had a center surface average roughness SRa of 0.75 μm.
The roll was rolled using a roll having a surface texture of 88 μm and 88 concave portions per unit area of 1 mm ² . Then, after performing the final finish annealing, the treatment liquid 1
Was applied so that the coating weight per unit area was 1.1 g / m ² (per side), and baked at 400 ° C. for 1 minute. The results obtained by examining the appearance, the space factor, the punching property, and the weldability of the magnetic steel sheet provided with the insulating coating thus obtained were as follows.

[Table 6] Appearance: Good Space factor: 99.7% Punching property: 1.2 million times Weldability: Good at 100 cm / min

Comparative Example 1 C: 0.025% and Si: 3.21%, with the balance being substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. During the cold rolling, the center surface average roughness SRa of the roll surface is 1.
Rolling is performed using a 70 μm rolling roll, while the final pass has a center surface average roughness SRa of 0.35 μm on the roll surface.
Then, rolling was performed using a rolling roll having a surface texture of 72 concave portions per unit area of 1 mm ² . Then, after performing the final finish annealing, the surface of the processing solution 1
Was applied so that the coating weight per unit area was 1.1 g / m ² (per side), and baked at 400 ° C. for 1 minute. The results obtained by examining the appearance, the space factor, the punching property, and the weldability of the magnetic steel sheet provided with the insulating coating thus obtained were as follows.

[Table 7] Appearance: Linear flaws Space factor: 99.6% Punching property: 1.2 million times Weldability: Good at 100 cm / min

Comparative Example 2 C: 0.025% and Si: 3.21%, with the balance being substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. At that time, for the pass before the final pass, the center surface average roughness SRa of the roll surface was 0.45 μm
On the other hand, for the final pass, a roll having a center surface average roughness SRa of the roll surface of 0.35 μm and a number of concave portions per unit area of 1 mm ² of 55 is used. Rolled. Then, after performing the final finish annealing, the above-mentioned treatment liquid 1 was applied to the surface so that the coating weight per unit area was 0.8 g / m ² (per side).
Bake at 400 ° C. for 1 minute. The results obtained by examining the appearance, the space factor, the punching property, and the weldability of the magnetic steel sheet provided with the insulating coating thus obtained were as follows.

[Table 8] Appearance: Good Space factor: 99.8% Punching property: 900,000 times Weldability: Poor at 30 cm / min

Comparative Example 3 C: 0.003% and Si: 0.35%, the balance being substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. At that time, for the pass before the final pass, the center surface average roughness SRa of the roll surface was 0.80 μm
On the other hand, for the final pass, a roll having a center surface average roughness SRa of the roll surface of 0.15 μm and a surface texture of 82 concave portions per unit area of 1 mm ² was used. Rolled. Then, after the final finishing annealing, the above-mentioned treatment liquid 1 was applied to this surface so that the coating weight per unit area was 0.8 g / m ² (per side), and then baked at 400 ° C. for 1 minute. The results obtained by examining the appearance, the space factor, the punching property, and the weldability of the magnetic steel sheet provided with the insulating coating thus obtained were as follows.

[Table 9] Appearance: Good Space factor: 99.8% Punching property: 1.2 million times Weldability: Poor at 30 cm / min

Comparative Example 4 C: 0.003% and Si: 0.35%, the balance being substantially
A hot rolled sheet of electromagnetic steel having a composition of Fe is cold-rolled to a thickness of 0.
A 50 mm-thick cold rolled sheet was used. At that time, for the pass before the final pass, the center surface average roughness SRa of the roll surface was 0.80 μm
On the other hand, for the final pass, a roll having a center surface average roughness SRa of the roll surface of 0.18 μm and a number of concave portions per unit area of 1 mm ² of 35 is used. Rolled. Then, after performing the final finish annealing, the above-mentioned treatment liquid 1 was applied on the surface so that the coating weight per unit area was 0.7 g / m ² (per side).
Bake at 400 ° C. for 1 minute. Thereafter, the processing solution 4
Was applied so that the coating weight per unit area was 0.4 g / m ² (per side), and baked at 400 ° C. for 1 minute. The results obtained by examining the appearance, the space factor, the punching property, and the weldability of the magnetic steel sheet provided with the insulating coating thus obtained were as follows.

[Table 10] Appearance: Good Space factor: 99.6% Punching property: 900,000 times Weldability: Poor at 30 cm / min

[0037]

According to the present invention, the target steel sheet is
Even with a high-grade grade material containing a large amount of Si, it is possible to obtain a magnetic steel sheet for laminated iron cores that not only has excellent punching properties but also has both weldability and space factor, which were conventionally difficult to achieve. .

[Brief description of the drawings]

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

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

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

FIG. 4 is a graph showing the effect of the SRa of the roll surface of the rolling roll used in the final pass and the preceding pass of the final cold rolling process on the weldability.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mitsuhiko Hagiwara 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. Kawasaki Steel Corporation Mizushima Works (56) JP, A 60-204832 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 3/02 B21B 1/22 C21D 8/12

Claims (1)

(57) [Claims] 1. A series of steps of subjecting a hot-rolled Si-containing steel sheet to cold rolling once or twice or more including intermediate annealing, followed by final finishing annealing, and further forming an insulating coating. In the method for producing an electrical steel sheet with an insulating coating, the preceding pass of the final pass in the final cold rolling step is rolled with a roll having a center surface average roughness SRa of the roll surface satisfying a range of 0.50 to 1.50 μm. The final pass of the final cold rolling process is performed by adjusting the center surface average roughness SRa of the roll surface.
Rolling with a roll having a surface texture of 0.20 to 0.80 μm and having a surface texture of 50 or more per 1 mm ^{2 of} unit area cut by the center plane, characterized by excellent punching and weldability. Of manufacturing electrical steel sheets for laminated iron cores.