JP4598321B2

JP4598321B2 - Oriented electrical steel sheet with excellent magnetic properties

Info

Publication number: JP4598321B2
Application number: JP2001226408A
Authority: JP
Inventors: 辰彦坂井; 薫佐藤; 直也浜田; 聡新井; 英一難波
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2001-07-26
Filing date: 2001-07-26
Publication date: 2010-12-15
Anticipated expiration: 2021-07-26
Also published as: JP2003034822A

Description

【０００１】
【発明の属する技術分野】
本発明は、レーザビームを照射した鉄損と磁歪特性に優れる方向性電磁鋼板に関するものである。
【０００２】
【従来の技術】
従来、方向性電磁鋼板の製造方法において、鋼板表面にグラス皮膜を形成し、更に絶縁コーティングを施した後に板幅方向に線状で、且つ圧延方向に周期的な応力歪みを導入し、還流磁区を形成することで180 °磁壁間隔を細分化し、鉄損を減少させる方法が種々提案されてきた。中でも特開昭55-18566号公報に開示されるように、鋼板の表面にパルスYAG レーザビームを集光照射して、被照射部での皮膜の蒸発反力により歪みを導入する方法は、鉄損改善効果が大きく、且つ非接触加工であることから信頼性・制御性も高い優れた方向性電磁鋼板の製造法である。
【０００３】
ここでレーザ照射による鉄損改善の原理は次のように説明される。方向性電磁鋼板の鉄損は異常渦電流損とヒステリシス損に分離される。鋼板にレーザを照射すると皮膜の蒸発反力により表層に応力歪みが発生する。この歪みを源にして環流磁区が発生し、ここでの静磁エネルギーを最小化にするように180 ゜磁区が細分化される。その結果、180 ゜磁壁間隔に比例した渦電流損が減少し鉄損が低下する。
【０００４】
ところで方向性電磁鋼板の重要な磁気特性として磁歪がある。磁歪は外部磁界に対する鋼板伸縮のパラメータであり、電磁鋼板をトランスの鉄芯に使用する際の騒音発生の原因となる。近年のトランス低騒音化ニーズに応えるため磁歪低減の重要性は非常に高い。レーザ照射により発生する環流磁区は外部磁界を印加した場合、磁界方向に伸縮するため一般に磁歪を増大させる要因となり、特に外部磁界1.7〜1.9Ｔでの高磁場での磁歪の増大が大きい。従ってレーザ照射により環流磁区を形成することで鉄損の低減は図れるものの磁歪を増大させる可能性があった。
【０００５】
鉄損を十分を低下させ、且つ磁歪の増大を極力抑制するためには最適な環流磁区導入条件、すなわち最適レーザ照射条件が存在すると考えられる。しかし、従来の技術では鉄損を低減することのみに着眼し、その照射条件範囲も非常に広範囲である。例えば特開昭56-51528号公報、特公昭61-49366号公報に開示されるレーザ照射条件の範囲は照射ビーム径を0.01〜1mm、圧延方向照射間隔を2.5〜20mm、板幅方向間隔0.3〜1.0mmとなっている。このような広い照射条件範囲でもある程度の鉄損低減効果は得られると考えられる。しかしこれらの独立したパラメータの相関は不明確であり、鉄損改善効果を最大化させる具体的指標はなく、また磁歪性能を無視しているため低鉄損は得られてもトランスの騒音が大きくなるという問題があった。
【０００６】
【発明が解決しようとする課題】
本発明にて解決しようとする課題は、レーザ照射により磁気特性を改善した方向性電磁鋼板として、鉄損改善効果が最大化され、且つ磁歪増加を極力抑制した方向性電磁鋼板を提供することにある。
【０００７】
【課題を解決するための手段】
本発明は、上記課題を解決するもので、鋼板表面にグラス皮膜を形成し、更に絶縁コーティングを施した鋼板の一方の表面にパルスレーザを点列に集光照射して、板幅方向に線状で、且つ圧延方向に周期的な応力歪みを導入することにより、還流磁区を形成して鉄損を改善した方向性電磁鋼板であって、レーザ照射痕が円形あるいは楕円形であり、照射痕の圧延方向径をdl、板幅方向径をdc、照射痕の板幅方向間隔をPc、圧延方向間隔をPlとしたとき、以下の条件を全て満たすことを特徴とする方向性電磁鋼板である。
【０００８】
dl≦0.20mm
0.6≦（dc／Pc）≦1.0
0.040≦（dl／Pl）≦0.050
ただし、dl＝0.2ｍｍ、dc／Pc＝2／3、且つdl／Pl＝0.04のときを除く。
【０００９】
【発明の実施の形態】
本発明は、パルスレーザ照射によって形成される照射痕形状とその間隔を限定することで鉄損もさることながら、特に磁歪特性に優れた方向性電磁鋼板を提供するものである。以下にその限定の根拠と効果について実施例を用いて説明する。
【００１０】
【実施例】
図１はパルスレーザの点列照射痕の模式図である。圧延方向径ｄｌ、板幅方向径dcの照射痕の点列が圧延方向に間隔Pl、板幅方向に間隔Pcで形成される。照射痕径はレーザ集光ビーム径にほぼ一致する。レーザ照射による歪みを起点として環流磁区が形成され、その環流磁区幅は照射径にほぼ一致する。
【００１１】
まず、照射痕の板幅方向径ｄcと板幅方向間隔Pcの関係について説明する。効果的な鉄損改善効果を得るためには板幅方向に連続した環流磁区を形成することが好ましく、従って板幅方向に隣り合う環流磁区が接するかあるいは重なることが好ましい。そこで点列照射により形成される環流磁区を磁区観察用電子顕微鏡にて詳細に観察したところ、点列間隔が大きくなり、照射痕の板幅方向径ｄcと板幅方向照射間隔Pcが0の関係がｄc／Pc＜0.6の範囲では図２（ａ）に示すように隣り合う環流磁区が接しなくなるため、連続した環流磁区が形成されないことがわかった。また、図2（ｃ）に示す様に隣り合う照射痕が重なり合う場合、すなわちｄc／Pc＞1.0の範囲では一度歪みが付与された場所に更に不必要な歪みを与えることになり非効率的であるばかりでなく、過大な歪みによりヒステリシス損の大幅な増大につながる。従って、板幅方向に切れ目なく連続した環流磁区を効率的に形成するには図2（ｂ）に示す様な点列配置であり、ｄcとPcの関係は0.6≦（ｄc／Pc）≦1.0となることが最適である。
【００１２】
【表１】

【００１３】
次に、照射痕の圧延方向径ｄlの最適な範囲について説明する。表１はｄc／Pc＝0.67に固定し、ｄlとPlをパラメータにレーザ照射を行った際の鉄損改善率ηと磁歪λの測定結果である。ここでηは周波数50Hz、最大磁束密度1.7Tにおける鉄損Ｗ17/50の改善率であり、次式で定義される。尚、鉄損改善量は素材に大きく依存するため改善率の絶対値も素材によって変化する。しかし、同じ素材を用いる限りは改善効果は改善率の相対値で比較することが可能である。
η=（レーザ照射前鉄損−レーザ照射後鉄損）／（レーザ照射前鉄損）×100（％）
また、磁歪λは磁束密度1.9Ｔ、周波数50Hz、圧縮応力0.3kg/mm2での鋼板伸縮全幅の鋼板全長に対する比率で定義される。
【００１４】
この実施例ではＱスイッチYAGレーザを使用した。パルスエネルギーは4mJである。出力されるレーザビーム形状は僅かに楕円化しており、dc／dl＝1.1である。レーザビームを球面レンズで集光照射する場合、dcとdlの比率は常に一定である。よってdlを変化させる結果、同時にdcも変化する。そこで、本実施例ではｄc／Pc＝0.67に固定するためにdcの変化に合わせてPcも調整した。
【００１５】
この結果より、ｄl≦0.20mmの範囲では適当な圧延方向間隔Plを選ぶことで容易に鉄損改善率が10％を越えることがわかったが、dl＞0.20mmでは改善率はせいぜい10％以下であった。これはdlが大きくなると環流磁区幅の圧延方向幅も増加し、その結果ヒステリシス損失が増大するためであると考えられる。従って、dl＞0.20mmの範囲では鉄損改善効果が低くくなる問題があり、従ってdlの範囲はｄ≦0.20mmが最適である。
【００１６】
次に、Plとｄlの比率の最適範囲について述べる。表１よりdlが0.20mm以下においてｄl／Plと鉄損改善率ηの関係に注目するとdl／Pl＜0.04の範囲においてηは10％に達せず、鉄損改善効果は低い。磁区細分化効果は圧延方向に隣り合う環流磁区個々の細分化効果が繋がることにより効果が増大すると考えられる。従って、ある一定の環流磁区の圧延方向幅に対して間隔Plが広くなりすぎると、その繋がりの効果が減少し、鉄損改善率も減少するものと考えられる。ｄl／Pl≧0.04の範囲においては隣り合う環流磁区の細分化効果が繋がり、その結果、高い鉄損改善率が得られる。
【００１７】
一方、磁歪λはdl／Plの増加に伴いの増加することがわかった。環流磁区は圧延方向に加わる交番磁界に対してその方向に伸縮する性質を持つ。従って、環流磁区の量が増加すると伸縮量も増え、磁歪λが増大する。ｄl／Plが大きいということは鋼板に占める環流磁区体積の割合が大きいことを示すため、従って、ｄl／Plの増加に伴いλは増加するものである。表１の結果からｄl／Plに対してλの変化は非常に敏感であることがわかり、ｄl／Pl＞0.05にてその増加量が顕著であった。従って、磁歪の観点でのｄl／Pl≦0.05が最適な範囲である。このように、0.04≦ｄ／Pl≦0.05が鉄損と磁歪の両特性において同時に高い性能を得る範囲である。
【００１８】
尚、本実施例では楕円ビームを用いたが、レーザビーム形状が完全に円形であってもビームを高速スキャンして鋼板に照射する場合も照射痕はスキャン方向に長軸を持つ楕円となる。本発明は鋼板上に形成された照射痕の形状を限定することで磁気特性を大幅に改善した製品であり、特に照射するビームの形状を限定するものではない。また、照射痕がdc＝dlである円形であることも本発明の範囲に含まれることは明らかである。
【００１９】
【発明の効果】
以上説明したように、鋼板の一方の表面にパルスレーザを点列に集光照射するに際し、レーザ照射痕の圧延方向径、板幅方向径、照射痕の板幅方向間隔、圧延方向間隔を特定の条件下で制御することで高い鉄損改善効果とともに磁歪の増加を極力抑えた方向性電磁鋼板が得られるという利点を有する。
【図面の簡単な説明】
【図１】パルスレーザを点列照射して磁気特性を改善した方向性電磁鋼板の照射痕の説明図である。
【図２】レーザ照射後の方向性電磁鋼板の磁区構造の模式図で、照射痕の板幅方向間隔Pcと照射痕径dl、deおよび環流磁区構造の関係を示し、（ａ）はdc／Pc＜0.6の場合、（ｂ）は0.6≦（dc／Pc）≦1.0の場合、（ｃ）はdc／Pc＞1.0の場合の環流磁区構造を示す図である。
【符号の説明】
dl…パルスレーザ照射痕の圧延方向径
dc…パルスレーザ照射痕の板幅方向径
Pc…照射痕の板幅方向間隔
Pl…照射痕の圧延方向間隔
Pg…180゜磁区磁壁間隔
η…磁束密度1.7T、周波数50Hzにおける鉄損のレーザ照射による改善率
λ…磁束密度1.9Ｔ、周波数50Hz、圧縮応力0.3kg/mm2における磁歪
１…方向性電磁鋼板
２…レーザ照射痕
３…環流磁区
４…180°磁区[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grain-oriented electrical steel sheet excellent in iron loss and magnetostriction characteristics irradiated with a laser beam.
[0002]
[Prior art]
Conventionally, in a method for producing a grain-oriented electrical steel sheet, a glass film is formed on the steel sheet surface, and after applying an insulating coating, a linear stress is introduced in the sheet width direction and periodic stress strain is introduced in the rolling direction. Various methods have been proposed to reduce the iron loss by subdividing the 180 ° domain wall spacing by forming the. In particular, as disclosed in Japanese Patent Application Laid-Open No. 55-18566, a method of focusing and irradiating a surface of a steel sheet with a pulsed YAG laser beam and introducing strain by an evaporation reaction force of a film at an irradiated portion is an iron method. This is a method for producing an excellent grain-oriented electrical steel sheet that has a large loss improvement effect and high reliability and controllability because of non-contact processing.
[0003]
Here, the principle of iron loss improvement by laser irradiation is explained as follows. The iron loss of grain-oriented electrical steel sheet is separated into abnormal eddy current loss and hysteresis loss. When a steel sheet is irradiated with a laser, stress distortion occurs in the surface layer due to the evaporation reaction force of the film. This distortion is used as a source to generate a circulating magnetic domain, and the 180 ° magnetic domain is subdivided so as to minimize the magnetostatic energy. As a result, the eddy current loss proportional to the 180 ° domain wall spacing decreases and the iron loss decreases.
[0004]
Incidentally, magnetostriction is an important magnetic characteristic of grain-oriented electrical steel sheets. Magnetostriction is a parameter of steel sheet expansion / contraction with respect to an external magnetic field, and causes noise when the electromagnetic steel sheet is used as an iron core of a transformer. In order to meet the recent needs for transformer noise reduction, the importance of magnetostriction reduction is very high. The circulating magnetic domain generated by laser irradiation expands and contracts in the direction of the magnetic field when an external magnetic field is applied, and thus generally increases the magnetostriction. In particular, the increase in magnetostriction in a high magnetic field with an external magnetic field of 1.7 to 1.9 T is large. Therefore, although the iron loss can be reduced by forming the circulating magnetic domain by laser irradiation, the magnetostriction may be increased.
[0005]
In order to sufficiently reduce the iron loss and to suppress the increase in magnetostriction as much as possible, it is considered that there is an optimum circulating magnetic domain introduction condition, that is, an optimum laser irradiation condition. However, the conventional technique focuses only on reducing the iron loss, and the irradiation condition range is also very wide. For example, the ranges of the laser irradiation conditions disclosed in JP-A-56-51528 and JP-B-61-49366 are as follows: the irradiation beam diameter is 0.01 to 1 mm, the irradiation interval in the rolling direction is 2.5 to 20 mm, and the interval in the plate width direction is 0.3 to 1.0mm. It is considered that a certain degree of iron loss reduction effect can be obtained even in such a wide irradiation condition range. However, the correlation between these independent parameters is unclear, there is no specific index to maximize the iron loss improvement effect, and the magnetostriction performance is ignored, so even if low iron loss is obtained, the transformer noise is large. There was a problem of becoming.
[0006]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a grain-oriented electrical steel sheet that maximizes the iron loss improvement effect and suppresses an increase in magnetostriction as much as possible, as a grain-oriented electrical steel sheet with improved magnetic properties by laser irradiation. is there.
[0007]
[Means for Solving the Problems]
The present invention is intended to solve the above problems, forming a glass film on the steel sheet surface, and further condensed and irradiated with a pulsed laser to a point sequence on one surface of the steel sheet subjected to insulation coating, the line in the plate width direction And a directional electrical steel sheet in which a return magnetic domain is formed to improve iron loss by introducing periodic stress strain in the rolling direction, and the laser irradiation mark is circular or elliptical, rolling direction diameter dl, plate width direction diameter dc, the plate width direction distance irradiation signatures Pc, when the rolling direction spacing was Pl, oriented electrical steel sheet towards you and satisfies all of the following conditions It is.
[0008]
dl ≦ 0.20mm
0.6 ≦ (dc / Pc) ≦ 1.0
0.040 ≦ (dl / Pl) ≦ 0.050
However, except when dl = 0.2 mm, dc / Pc = 2/3, and dl / Pl = 0.04.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a grain-oriented electrical steel sheet that is particularly excellent in magnetostriction characteristics while limiting iron loss by limiting the shape and interval of irradiation marks formed by pulse laser irradiation. The basis and effect of the limitation will be described below with reference to examples.
[0010]
【Example】
FIG. 1 is a schematic diagram of a point laser irradiation mark of a pulse laser. A point sequence of irradiation traces having a rolling direction diameter dl and a sheet width direction diameter dc is formed at intervals Pl in the rolling direction and intervals Pc in the sheet width direction. The irradiation mark diameter substantially coincides with the laser focused beam diameter. A circulating magnetic domain is formed starting from distortion caused by laser irradiation, and the width of the circulating magnetic domain substantially matches the irradiation diameter.
[0011]
First, the relationship between the plate width direction diameter dc of the irradiation trace and the plate width direction interval Pc will be described. In order to obtain an effective iron loss improvement effect, it is preferable to form a continuous magnetic domain in the plate width direction, and it is preferable that adjacent adjacent magnetic domains in the plate width direction touch or overlap. Therefore, when the circulating magnetic domain formed by point sequence irradiation was observed in detail with a magnetic domain observation electron microscope, the interval between the point sequences increased, and the relation between the plate width direction diameter dc of the irradiation trace and the plate width direction irradiation interval Pc was 0. However, in the range of dc / Pc <0.6, the adjacent circulating magnetic domains are not in contact with each other as shown in FIG. Further, as shown in FIG. 2 (c), when adjacent irradiation marks overlap, that is, in the range of dc / Pc> 1.0, an unnecessary distortion is further applied to a place where the distortion is once applied, which is inefficient. Not only that, excessive distortion leads to a significant increase in hysteresis loss. Therefore, in order to efficiently form a continuous magnetic domain that is continuous in the plate width direction, a point sequence as shown in FIG. 2B is used, and the relationship between dc and Pc is 0.6 ≦ (dc / Pc) ≦ 1.0. Is optimal.
[0012]
[Table 1]

[0013]
Next, the optimum range of the rolling direction diameter dl of the irradiation mark will be described. Table 1 shows the measurement results of the iron loss improvement rate η and magnetostriction λ when dc / Pc = 0.67 and laser irradiation is performed using dl and Pl as parameters. Here, η is an improvement rate of iron loss W17 / 50 at a frequency of 50 Hz and a maximum magnetic flux density of 1.7 T, and is defined by the following equation. Since the iron loss improvement amount greatly depends on the material, the absolute value of the improvement rate also varies depending on the material. However, as long as the same material is used, the improvement effect can be compared with the relative value of the improvement rate.
η = (iron loss before laser irradiation−iron loss after laser irradiation) / (iron loss before laser irradiation) × 100 (%)
The magnetostriction λ is defined by the ratio of the total steel sheet expansion / contraction width to the total steel sheet length at a magnetic flux density of 1.9 T, a frequency of 50 Hz, and a compressive stress of 0.3 kg / mm 2.
[0014]
In this example, a Q-switched YAG laser was used. The pulse energy is 4mJ. The output laser beam shape is slightly elliptical and dc / dl = 1.1. When condensing and irradiating a laser beam with a spherical lens, the ratio between dc and dl is always constant. Therefore, as a result of changing dl, dc also changes. Therefore, in this embodiment, in order to fix dc / Pc = 0.67, Pc was also adjusted in accordance with the change of dc.
[0015]
From this result, it was found that the iron loss improvement rate easily exceeds 10% by selecting an appropriate rolling direction interval Pl in the range of dl ≦ 0.20 mm, but at dl> 0.20 mm, the improvement rate is at most 10% or less. Met. This is considered to be due to an increase in hysteresis loss as a result of an increase in dl, which also increases the width in the rolling direction of the reflux magnetic domain width. Therefore, in the range of dl> 0.20 mm, there is a problem that the effect of improving the iron loss is lowered. Therefore, the range of dl is optimally d ≦ 0.20 mm.
[0016]
Next, the optimum range of the ratio between Pl and dl will be described. From Table 1, when attention is paid to the relationship between dl / Pl and iron loss improvement rate η when dl is 0.20 mm or less, η does not reach 10% in the range of dl / Pl <0.04, and the iron loss improvement effect is low. It is considered that the magnetic domain refinement effect is enhanced by connecting the refinement effects of the individual reflux magnetic domains adjacent to each other in the rolling direction. Therefore, if the interval Pl becomes too large with respect to the rolling direction width of a certain circulating magnetic domain, it is considered that the effect of the connection is reduced and the iron loss improvement rate is also reduced. In the range of dl / Pl ≧ 0.04, the effect of subdividing adjacent circulating magnetic domains is connected, and as a result, a high iron loss improvement rate is obtained.
[0017]
On the other hand, it was found that the magnetostriction λ increases with an increase in dl / Pl. The circulating magnetic domain has the property of expanding and contracting in the direction with respect to the alternating magnetic field applied in the rolling direction. Therefore, when the amount of the reflux magnetic domain increases, the amount of expansion / contraction also increases and the magnetostriction λ increases. A large dl / Pl indicates that the ratio of the recirculating magnetic domain volume to the steel sheet is large, and therefore λ increases with an increase in dl / Pl. From the results of Table 1, it can be seen that the change of λ is very sensitive to dl / Pl, and the increase was remarkable when dl / Pl> 0.05. Therefore, dl / Pl ≦ 0.05 from the viewpoint of magnetostriction is the optimum range. Thus, 0.04 ≦ d / Pl ≦ 0.05 is a range in which high performance can be obtained simultaneously in both the iron loss and magnetostriction characteristics.
[0018]
In this embodiment, an elliptical beam is used. However, even when the laser beam shape is completely circular, the irradiation mark is an ellipse having a major axis in the scanning direction even when the beam is scanned at a high speed. The present invention is a product in which the magnetic characteristics are greatly improved by limiting the shape of the irradiation mark formed on the steel sheet, and does not specifically limit the shape of the beam to be irradiated. It is also clear that the irradiation mark is a circle with dc = dl, which is also included in the scope of the present invention.
[0019]
【The invention's effect】
As explained above, when condensing and irradiating one surface of a steel plate with a pulse laser in a point sequence, the rolling direction diameter of the laser irradiation trace, the plate width direction diameter, the plate width direction interval of the irradiation trace, and the rolling direction interval are specified. By controlling under these conditions, there is an advantage that a grain-oriented electrical steel sheet can be obtained in which an increase in magnetostriction is suppressed as much as possible together with a high iron loss improvement effect.
[Brief description of the drawings]
FIG. 1 is an explanatory view of an irradiation mark of a grain-oriented electrical steel sheet that has been improved in magnetic properties by irradiating a pulse laser with a point sequence.
FIG. 2 is a schematic diagram of the magnetic domain structure of a grain-oriented electrical steel sheet after laser irradiation, showing the relationship between the plate width direction interval Pc of irradiation marks, the irradiation mark diameters dl and de, and the reflux magnetic domain structure. In the case of Pc <0.6, (b) is a diagram showing a circulating magnetic domain structure in the case of 0.6 ≦ (dc / Pc) ≦ 1.0, and (c) in the case of dc / Pc> 1.0.
[Explanation of symbols]
dl… Rolling direction diameter of pulse laser irradiation trace
dc ... Diameter in the width direction of the pulse laser irradiation trace
Pc: Distance between irradiation marks in the plate width direction
Pl ... Rolling direction interval of irradiation marks
Pg ... 180 ° Domain wall spacing η ... Improvement rate of iron loss by laser irradiation at magnetic flux density 1.7T, frequency 50Hz λ ... Magnetic strain 1 at magnetic flux density 1.9T, frequency 50Hz, compressive stress 0.3kg / mm2 ... Laser irradiation mark 3 ... Frequency magnetic domain 4 ... 180 ° magnetic domain

Claims

A glass film is formed on the surface of the steel sheet, and one surface of the steel sheet that has been further coated with an insulating coating is focused and irradiated with a pulse laser beam in a sequence of dots , linear in the sheet width direction and periodic stress strain in the rolling direction. by introducing, a oriented electrical steel sheet having improved iron loss by forming the closure domains, the laser irradiation signatures is circular or elliptical, the rolling direction length of the laser irradiation signatures dl, the plate width direction the length dc, the plate width direction distance irradiation signatures Pc, when the rolling direction spacing was Pl, oriented electrical steel sheet towards you and satisfies all of the following conditions.
dl ≦ 0.20mm
0.6 ≦ (dc / Pc) ≦ 1.0
0.040 ≦ (dl / Pl) ≦ 0.050
However, except when dl = 0.2 mm, dc / Pc = 2/3, and dl / Pl = 0.04.