JP5446377B2 - Oriented electrical steel sheet and manufacturing method thereof - Google Patents

Oriented electrical steel sheet and manufacturing method thereof Download PDF

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JP5446377B2
JP5446377B2 JP2009080768A JP2009080768A JP5446377B2 JP 5446377 B2 JP5446377 B2 JP 5446377B2 JP 2009080768 A JP2009080768 A JP 2009080768A JP 2009080768 A JP2009080768 A JP 2009080768A JP 5446377 B2 JP5446377 B2 JP 5446377B2
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多津彦 平谷
峰男 村木
高島　　稔
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本発明は、トランスやリアクトルなどの鉄心用として好適である高周波特性に優れた方向性高珪素鋼板に関するものである。   The present invention relates to a directional high silicon steel sheet excellent in high frequency characteristics suitable for use in iron cores such as transformers and reactors.

近年、珪素鋼板が広く用いられているトランスやリアクトルにおいては、鉄心の小型化や高効率化を図るため、その駆動周波数が年々高周波化されてきている。しかし、珪素鋼板の鉄損は、励磁周波数が高くなると急激に上昇することが知られており、これに伴い、珪素鋼板の鉄損による鉄心の温度上昇や効率の低下が問題となるケースが増加し、珪素鋼板の高周波鉄損を低減するための対策が講じられてきた。   In recent years, in transformers and reactors in which silicon steel plates are widely used, the driving frequency has been increased year by year in order to reduce the size and increase the efficiency of the iron core. However, it is known that the iron loss of silicon steel plates increases rapidly when the excitation frequency increases, and along with this, the number of cases where the temperature rise of the iron core and the efficiency decrease due to the iron loss of silicon steel plates increase. Measures have been taken to reduce the high-frequency iron loss of silicon steel sheets.

珪素鋼板の高周波鉄損を低減する手法としては、従来、板厚を薄くすることにより渦電流損を低減する方法、Si含有量を高めて固有抵抗を高くすることで渦電流の発生量を抑える方法があり利用されている。   Conventional methods for reducing the high-frequency iron loss of silicon steel sheets include reducing the eddy current loss by reducing the plate thickness, and suppressing the generation of eddy currents by increasing the Si content and increasing the specific resistance. There are ways to use it.

ここで、板厚0.05〜0.1mmの無方向性電磁鋼板は、数百〜数kHzの周波数領域でモータコアやトランス、リアクトルの鉄心として用いられている。一方、板厚0.05〜0.1mmの方向性電磁鋼板は、磁束密度が高いため鉄心の小型化に有利な反面、薄手化しても磁区幅が広いために異常渦電流損が大きく、その高周波鉄損が無方向性電磁鋼板より劣る場合もある。
上記の高周波用極薄電磁鋼板のSi量を高めて材料の固有抵抗を増せば、高周波鉄損を更に低減することができるが、Si量の増加とともに鋼板は硬く脆くなり薄板の製造はきわめて困難となる。そのため、通常は4%を超えてSiを添加することはない。 Here, non-oriented electrical steel sheets having a thickness of 0.05 to 0.1 mm are used as iron cores for motor cores, transformers, and reactors in a frequency range of several hundred to several kHz. On the other hand, a grain-oriented electrical steel sheet with a thickness of 0.05 to 0.1 mm is advantageous for downsizing the core because of its high magnetic flux density, but has a large abnormal eddy current loss due to its wide magnetic domain width even if it is thinned, and its high frequency iron loss. May be inferior to the non-oriented electrical steel sheet.
High-frequency iron loss can be further reduced by increasing the Si content of the above-mentioned ultra-thin electrical steel sheet for high-frequency use and increasing the specific resistance of the material. However, as the Si content increases, the steel sheet becomes harder and more brittle and it is extremely difficult to manufacture thin sheets. It becomes. Therefore, normally, Si is not added exceeding 4%.

最近では10kHzあるいはそれ以上の周波数で使用可能なトランス、リアクトル用材料が望まれている。このような周波数領域は、従来、ソフトフェライト、金属圧粉体、アモルファスなどの材料が用いられてきた分野である。しかしながら、フェライトは磁束密度が低いため鉄心が大型化してしまう、アモルファスは低鉄損である反面、磁歪が大きく騒音が問題とされる、またビルディングファクターが珪素鋼板に比べて劣る、更にセンダスト合金粉は磁歪・鉄損とも低いが高価であり珪素鋼板に比べて飽和磁束密度も低いなど、それぞれ一長一短を有している。   Recently, materials for transformers and reactors that can be used at a frequency of 10 kHz or higher are desired. Such a frequency region is a field where materials such as soft ferrite, metal green compact, and amorphous have been used. However, since ferrite has a low magnetic flux density, the iron core becomes large. Amorphous has low iron loss. On the other hand, magnetostriction is a big problem with noise, and the building factor is inferior to silicon steel. Has both advantages and disadvantages, such as low magnetostriction and iron loss, but is expensive and has a lower saturation magnetic flux density than silicon steel sheets.

このような現状に対して、珪素鋼板の高周波鉄損を低減する手段として、いくつかの技術が開示されている。特許文献１では浸珪法による6.5%Si鋼板の製造が開示されている。特許文献１は、板厚0.05〜0.3mmの3%Si鋼板を高温で四塩化珪素ガスと反応させて鋼中Si濃度を高めるプロセスである。古くから知られているように6.5%Si鋼板は3%珪素鋼の約二倍の固有抵抗を有し渦電流損失を効果的に低減できるため、高周波用材料として有利である。また磁歪が実質的にゼロであるため、鉄心の低騒音化に優れた効果を発揮する。   In response to this situation, several techniques have been disclosed as means for reducing high-frequency iron loss of silicon steel sheets. Patent Document 1 discloses the production of a 6.5% Si steel sheet by a siliconization method. Patent Document 1 is a process in which a 3% Si steel plate having a thickness of 0.05 to 0.3 mm is reacted with silicon tetrachloride gas at a high temperature to increase the Si concentration in the steel. As has been known for a long time, 6.5% Si steel sheet has a specific resistance approximately twice that of 3% silicon steel and can effectively reduce eddy current loss, and is therefore advantageous as a high frequency material. In addition, since the magnetostriction is substantially zero, it exhibits an excellent effect in reducing the noise of the iron core.

特許文献２では、浸珪プロセスにおいて表層Si濃度が6.5%となった時点でSi均一化拡散を中断することにより、板厚方向にSi濃度勾配が存在する鋼板を得、Si濃度勾配が存在する鋼板は、Siを均一化した場合より高周波での鉄損が低減できることが示されている。   In Patent Document 2, a steel sheet having a Si concentration gradient in the thickness direction is obtained by interrupting Si homogenization diffusion when the surface Si concentration reaches 6.5% in the siliconization process, and the Si concentration gradient exists. It has been shown that the steel sheet can reduce the iron loss at a higher frequency than when Si is made uniform.

特許文献３では、板厚方向にSi濃度勾配を有する珪素鋼板に関して、高周波鉄損を低減するために板厚方向のSi濃度差（最大−最小）と表層Ｓｉ濃度および鋼板表裏面のSi濃度差について規定している。とりわけ表層Si濃度が6.5%の場合に最も低い鉄損が得られるとしている。   In Patent Document 3, with respect to a silicon steel sheet having a Si concentration gradient in the sheet thickness direction, the Si concentration difference in the sheet thickness direction (maximum-minimum), the surface Si concentration, and the Si concentration difference between the steel sheet front and back surfaces in order to reduce high-frequency iron loss. It stipulates. In particular, the lowest iron loss is obtained when the surface Si concentration is 6.5%.

特許文献４には、方向性珪素鋼板を素材としてその板厚方向にSi濃度勾配をつける際、高周波鉄損を低減するための条件として表層Si濃度、濃化層の厚さ、および板厚中心付近のSi濃度が規定されている。特に、Si濃度5〜8％の領域が表層から板厚の10%以上の深さに存在していることが重要とし、いくつかの板厚Si濃度プロファイルの例が示されている。   In Patent Document 4, when a directional silicon steel sheet is used as a raw material and a Si concentration gradient is provided in the thickness direction, the surface Si concentration, the thickness of the concentrated layer, and the thickness center are given as conditions for reducing high-frequency iron loss. Near Si concentration is specified. In particular, it is important that a region having a Si concentration of 5 to 8% exists at a depth of 10% or more of the plate thickness from the surface layer, and some examples of plate thickness Si concentration profiles are shown.

特公平６−４５８８公報Japanese Patent Publication No. 6-4588 特公平５−４９７４４号公報Japanese Patent Publication No. 5-49744 特開２００５−２４０１８５号公報JP-A-2005-240185 特開２０００−４５０５３号公報JP 2000-45053 A

しかしながら、上記従来技術には以下の問題点がある。
特許文献１に開示されている高珪素鋼板は、数百Hz〜数kHzの領域で現在使われており、10kHz以上の高周波域では、より鉄損の低いアモルファス、金属圧粉体が使われるケースが多い。ただし、これらの磁性材料は磁歪が極めて大きく、可聴域(400〜20kHz)で励磁する場合には鉄心に防音を施す等の騒音対策が必要となる。
特許文献２および３では、無方向性珪素鋼板の板厚方向にSi濃度勾配を付けることにより5〜10kHz以上の高周波領域において同板厚の6.5%珪素鋼板より低い鉄損が得られたとしている。しかしながらアモルファス等の競合材と比較して十分な低鉄損化が得られているとは言い難く、更なる低鉄損化が望まれている。
特許文献４に開示された板厚方向Si濃度分布を有する方向性高珪素鋼板は、10kHz以上の高周波域において6.5%Si鋼板や板厚Si濃度分布を有する無方向性高珪素鋼板より低い鉄損値が得られている。また素材として方向性珪素鋼板を用いているため、その磁束密度は他の高周波用材料と比べてきわめて高い値を有する。しかしながら、特許文献４の明細書に開示されている板厚方向Si濃度プロファイルを満たしていたとしても、その鉄損値に大きなばらつきが生じ、条件によってはSi濃度分布を均一化した材料より高い鉄損値を示すものもあった。すなわち、高周波鉄損を低減するためにはSi濃度プロファイルを適正化するだけでなく、Si濃度プロファイルに反映されない別の因子を規定する必要がある。
さらに、特許文献２〜４のように、Siの濃度勾配が付与された場合、高Si材でありながらも、磁歪は３％Si無方向性電磁鋼板と同程度のレベルまで増大してしまう。このため、板厚方向にSi濃度勾配を有する電磁鋼板は、鉄損では6.5％珪素鋼板より優れているとしても、可聴域で励磁する場合は、騒音を低減する観点から6.5％珪素鋼板を選択するケースが少なくない。 However, the above prior art has the following problems.
The high silicon steel sheet disclosed in Patent Document 1 is currently used in the region of several hundred Hz to several kHz, and amorphous and metal compacts with lower iron loss are used in the high frequency region above 10 kHz. There are many. However, these magnetic materials have a very large magnetostriction, and when exciting in the audible range (400 to 20 kHz), it is necessary to take noise countermeasures such as soundproofing the iron core.
In Patent Documents 2 and 3, it is said that an iron loss lower than that of a 6.5% silicon steel plate of the same thickness was obtained in a high frequency region of 5 to 10 kHz or more by applying a Si concentration gradient in the thickness direction of the non-oriented silicon steel plate. . However, it is difficult to say that a sufficiently low iron loss is obtained as compared with competing materials such as amorphous, and a further reduction in iron loss is desired.
The directional high silicon steel sheet having a sheet thickness direction Si concentration distribution disclosed in Patent Document 4 has a lower iron loss than a 6.5% Si steel sheet or a non-oriented high silicon steel sheet having a sheet thickness Si concentration distribution in a high frequency region of 10 kHz or higher. The value is obtained. In addition, since a grain-oriented silicon steel plate is used as a material, the magnetic flux density has a very high value compared to other high frequency materials. However, even if the sheet thickness direction Si concentration profile disclosed in the specification of Patent Document 4 is satisfied, the iron loss value varies greatly, and depending on conditions, the iron concentration is higher than that of a material having a uniform Si concentration distribution. Some showed loss values. That is, in order to reduce high-frequency iron loss, it is necessary not only to optimize the Si concentration profile but also to define another factor that is not reflected in the Si concentration profile.
Furthermore, as in Patent Documents 2 to 4, when a Si concentration gradient is applied, the magnetostriction increases to a level comparable to that of a 3% Si non-oriented electrical steel sheet although it is a high Si material. For this reason, even if an electromagnetic steel sheet having a Si concentration gradient in the thickness direction is superior to a 6.5% silicon steel sheet in terms of iron loss, a 6.5% silicon steel sheet is selected from the viewpoint of reducing noise when excited in the audible range. There are many cases to do.

本発明は、かかる事情に鑑みなされたもので、板厚方向にSi濃度分布を有する方向性珪素鋼板の低鉄損化や磁歪低減のメカニズムを明らかにし、トランス、リアクトルなどの鉄心用として好適である高周波鉄損が低く、さらには、圧延直角方向の磁歪が小さい方向性珪素鋼板およびその製造方法を提供することを目的とする。   The present invention has been made in view of such circumstances, clarifying the mechanism of lowering iron loss and magnetostriction of a directional silicon steel sheet having a Si concentration distribution in the thickness direction, and suitable for iron cores such as transformers and reactors. An object of the present invention is to provide a grain-oriented silicon steel sheet having a low high-frequency iron loss and a small magnetostriction in the direction perpendicular to rolling, and a method for producing the same.

発明者らは、上記課題を解決すべく鋭意研究を重ねた。その結果、方向性電磁鋼板においては板厚方向の内部応力分布を適切な範囲に規定することで、高周波鉄損が飛躍的に低減することを見出した。さらに検討を進めたところ、このような鋼板では、圧延直角方向の磁歪が極めて小さくなることもわかった。そして、方向性電磁鋼板の結晶配向性（圧延方向と圧延直角方向の磁束密度の比）を規定することでも、高周波鉄損さらには圧延直角方向の磁歪が飛躍的に低減することを見出した。
特に、板厚方向にSi濃度分布を付与した場合、Si均一材に比べて圧延直角方向で磁歪が減少する現象は、無方向性電磁鋼板や方向性電磁鋼板の圧延方向に対しては認められなかった特異な現象である。 The inventors have intensively studied to solve the above problems. As a result, it has been found that, in the grain-oriented electrical steel sheet, the high-frequency iron loss is drastically reduced by defining the internal stress distribution in the thickness direction within an appropriate range. As a result of further investigation, it was found that such a steel sheet has extremely small magnetostriction in the direction perpendicular to the rolling. Further, it has been found that the high-frequency iron loss and the magnetostriction in the direction perpendicular to the rolling can be drastically reduced by defining the crystal orientation of the grain-oriented electrical steel sheet (ratio of the magnetic flux density in the rolling direction and the direction perpendicular to the rolling).
In particular, when Si concentration distribution is given in the thickness direction, the phenomenon that magnetostriction decreases in the direction perpendicular to rolling compared to Si uniform material is not observed in the rolling direction of non-oriented electrical steel sheets and grain-oriented electrical steel sheets. It is a unique phenomenon that did not exist.

以上のように、本発明は、上記知見に基づきなされたもので、その要旨は以下のとおりである。
［１］質量％で、C：0.005％以下、Si：４〜７％、Mn：0.005〜2.5％、Sol.Al：0.0080%以下、S：0.003%以下、N：0.005%以下を含有し、残部Feおよび不可避的不純物からなる方向性電磁鋼板であって、Si濃度が板厚中心部より板表面において高くなるSi濃度勾配を有し、圧延方向と平行な方向に内部応力として、70〜160MPaの範囲で板厚中心部に圧縮応力、板表面に板厚中心部と同じ大きさの引張応力を有することを特徴とする方向性電磁鋼板。
ここで板厚中心部および板表面の応力とは、実質的に反りのない平坦な板を幅30mm以下、長さ100mm以上に切断し、表裏面のうち片面のみ板厚の1/2深さまで化学研磨した際に生じる長手方向の反りの曲率半径から求めた値である。
［２］質量％で、C：0.005％以下、Si：4〜７％、Mn：0.005〜2.5％、Sol.Al：0.0080%以下、S：0.003%以下、N：0.005%以下を含有し、残部Feおよび不可避的不純物からなる方向性電磁鋼板であって、Si濃度が板厚中心部より板表面において高くなるSi濃度勾配を有し、圧延方向と圧延直角方向の1000A／mにおける磁束密度の比：Ｂ10(L)／B10(C)が1.2以上であり、かつ、圧延直角方向を1Tで励磁したときの磁歪振幅が１×10−６未満であることを特徴とする方向性電磁鋼板。
ただし、Ｂ10(L)：圧延方向の磁束密度、B10(C)：圧延直角方向の磁束密度である。
［３］前記［１］または［２］において、さらに、質量％で、Sb:0.005〜0.1％、Sn:0.005〜0.5％、Bi:0.001〜0.05％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする方向性電磁鋼板。
［４］前記［１］〜［３］のいずれかにおいて、さらに、質量％で、Cr:0.01〜0.8％、Ni:0.01〜1.0％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする方向性電磁鋼板。
［５］前記［１］〜［４］のいずれかにおいて、前記方向性電磁鋼板の表裏面での引張応力の差が8MPa以下であることを特徴とする方向性電磁鋼板。
［６］前記［１］〜［５］のいずれかにおいて、前記板厚中心部と前記板表面とのSi濃度差が質量％で1.5〜4.0％であることを特徴とする方向性電磁鋼板。
［７］前記［１］〜［６］のいずれかにおいて、板厚が0.05〜0.25mmであることを特徴とする方向性電磁鋼板。
［８］質量％で、C：0.02％以下、Si：４〜７％、Mn：2.5％以下、Sol.Al： 0.0300%以下、S：0.006%以下、N：0.01%以下を含有し、残部Feおよび不可避的不純物からなる成分組成を有し、板厚0.05〜0.25mmであるフォルステライト被膜を有しない方向性電磁鋼板、または前記成分組成になる二次再結晶した方向性電磁鋼板を冷延し板厚0.05〜0.25mmとした鋼板のいずれかを、1000℃以上に加熱しSi系のガスと反応させることにより鋼板表面からSiを添加する浸珪処理を行うに際し、浸珪開始から600℃以下に冷却されるまでに鋼板が通過する炉内各ゾーンの温度をTk(K)、炉内各ゾーンでの鋼板の滞在時間をtk(秒)とした時、下記式（１）を満足することを特徴とする方向性電磁鋼板の製造方法。
1.3×10-4≦（Σ tk×exp（-25000／Tk））／（d2 ×［質量%Si］add ）≦ 2.2×10-4 ・・（１）
ただし、dは板厚(mm)、［質量%Si］addは浸珪によるSi添加量を示す。
［９］前記［８］において、さらに、成分組成として、質量％で、Sb:0.005〜0.1％、Sn:0.005〜0.5％、Bi:0.001〜0.05％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする方向性電磁鋼板の製造方法。
［１０］前記［８］または［９］において、さらに、成分組成として、質量％で、Cr:0.01〜0.8％、Ni:0.01〜1.0％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする方向性電磁鋼板の製造方法。
［１１］前記［８］〜［１０］のいずれかにおいて、浸珪処理後の方向性電磁鋼板表面に、乾燥・焼き付け炉温度：600℃未満で絶縁被膜を被覆することを特徴とする方向性電磁鋼板の製造方法。
［１２］前記［８］〜［１１］のいずれかに記載の浸珪処理後の方向性電磁鋼板を加工した後に鉄心に組み上げる鉄心組立工程において、600℃以上かつ下記式（２）を満足する温度および時間で歪取焼鈍を行うことを特徴とする鉄心の製造方法。
（Σ t'k×exp（-25000／T'k））／（d2 ×［質量%Si］add）≦ 0.2×10-4 ・・（２）
ただし、T'k(K)は歪取焼鈍の温度、t'k(秒)はその温度での保持時間を示す。
［１３］前記［８］〜［１１］のいずれかに記載の浸珪処理後の方向性電磁鋼板表面に、乾燥・焼き付け炉温度：600℃以上で絶縁被膜を被覆する被膜コーティングと、これを加工した後に鉄心に組み上げる鉄心組立工程で歪取焼鈍を行う鉄心の製造方法において、前記被膜コーティングでの熱処理と前記歪取焼鈍とを合わせて、下記式（２）を満足する温度および時間で行うことを特徴とする鉄心の製造方法。
（Σ t'k×exp（-25000／T'k））／（d2 ×［質量%Si］add）≦ 0.2×10-4 ・・（２）
ただし、T'k(K)は被膜コーティング及び歪取焼鈍の各工程で熱処理される温度、t'k(秒)はその温度での保持時間を示す。 As described above, the present invention has been made based on the above findings, and the gist thereof is as follows.
[1] In mass%, C: 0.005% or less, Si: 4-7%, Mn: 0.005-2.5%, Sol.Al: 0.0080% or less, S: 0.003% or less, N: 0.005% or less, It is a grain-oriented electrical steel sheet composed of the remaining Fe and unavoidable impurities, having a Si concentration gradient in which the Si concentration is higher on the plate surface than the center of the plate thickness, and 70 to 160 MPa as internal stress in the direction parallel to the rolling direction. A grain-oriented electrical steel sheet having a compressive stress at the center of the plate thickness and a tensile stress of the same size as the center of the plate thickness at the plate surface.
Here, the stress at the center of the plate thickness and the surface of the plate means that a flat plate with substantially no warpage is cut to a width of 30 mm or less and a length of 100 mm or more, and only one side of the front and back surfaces is up to 1/2 the plate thickness. It is a value obtained from the radius of curvature of the warp in the longitudinal direction generated when chemical polishing is performed.
[2] By mass%, C: 0.005% or less, Si: 4-7%, Mn: 0.005-2.5%, Sol.Al: 0.0080% or less, S: 0.003% or less, N: 0.005% or less, It is a grain-oriented electrical steel sheet composed of the remaining Fe and inevitable impurities, and has a Si concentration gradient in which the Si concentration is higher at the plate surface than at the center of the plate thickness, and the magnetic flux density at 1000 A / m in the direction perpendicular to the rolling direction Ratio: B10 (L) / B10 (C) is 1.2 or more, and a magnetostriction amplitude when the perpendicular direction of rolling is excited at 1T is less than 1 × 10 −6 .
However, B10 (L): Magnetic flux density in the rolling direction, B10 (C): Magnetic flux density in the direction perpendicular to the rolling direction.
[3] In the above [1] or [2], at least one element selected from Sb: 0.005 to 0.1%, Sn: 0.005 to 0.5%, and Bi: 0.001 to 0.05% by mass% A grain-oriented electrical steel sheet comprising:
[4] In any one of the above [1] to [3], it further contains at least one element selected from Cr: 0.01 to 0.8% and Ni: 0.01 to 1.0% by mass. A grain-oriented electrical steel sheet characterized by
[5] The grain-oriented electrical steel sheet according to any one of [1] to [4], wherein a difference in tensile stress between the front and back surfaces of the grain-oriented electrical steel sheet is 8 MPa or less.
[6] The grain-oriented electrical steel sheet according to any one of [1] to [5], wherein a Si concentration difference between the center portion of the plate thickness and the plate surface is 1.5 to 4.0% by mass.
[7] The grain-oriented electrical steel sheet according to any one of [1] to [6], wherein the plate thickness is 0.05 to 0.25 mm.
[8] In mass%, C: 0.02% or less, Si: 4-7%, Mn: 2.5% or less, Sol.Al: 0.0300% or less, S: 0.006% or less, N: 0.01% or less, the balance Cold-rolling a grain-oriented electrical steel sheet having a component composition composed of Fe and inevitable impurities and having a forsterite film thickness of 0.05 to 0.25 mm, or a secondary recrystallized grain-oriented electrical steel sheet having the above-mentioned component composition When performing siliconizing treatment to add Si from the steel plate surface by heating any steel plate with a thickness of 0.05-0.25mm to 1000 ° C or higher and reacting with Si-based gas, 600 ° C from the start of siliconizing When the temperature of each zone in the furnace through which the steel plate passes until cooled down below is T k (K), and the stay time of the steel plate in each zone in the furnace is t k (second), the following equation (1) is obtained. A method for producing a grain-oriented electrical steel sheet, characterized by being satisfied.
1.3 × 10 −4 ≦ (Σ t k × exp (−25000 / T k )) / (d 2 × [mass% Si] add ) ≦ 2.2 × 10 −4 (1)
However, d is the plate thickness (mm), and [mass% Si] add indicates the amount of Si added by siliconization.
[9] In the above [8], at least one element selected from Sb: 0.005 to 0.1%, Sn: 0.005 to 0.5%, Bi: 0.001 to 0.05% as a component composition in [8] A method for producing a grain-oriented electrical steel sheet, comprising:
[10] In the above [8] or [9], the composition further contains at least one element selected from Cr: 0.01 to 0.8% and Ni: 0.01 to 1.0% by mass as a component composition. A method for producing a grain-oriented electrical steel sheet, comprising:
[11] The directionality according to any one of [8] to [10], wherein the surface of the grain-oriented electrical steel sheet after the siliconization treatment is coated with an insulating coating at a drying / baking furnace temperature of less than 600 ° C. A method for producing electrical steel sheets.
[12] In an iron core assembling process in which the grain-oriented electrical steel sheet after the siliconization treatment according to any one of [8] to [11] is processed and then assembled to the iron core, 600 ° C. or higher and the following formula (2) is satisfied. A method of manufacturing an iron core, characterized by performing strain relief annealing at a temperature and time.
(Σ t ′ k × exp (−25000 / T ′ k )) / (d 2 × [mass% Si] add ) ≦ 0.2 × 10 −4 (2)
However, T ′ k (K) indicates the temperature for strain relief annealing, and t ′ k (seconds) indicates the holding time at that temperature.
[13] A film coating for coating an insulating film at a drying / baking furnace temperature: 600 ° C. or higher on the grain-oriented electrical steel sheet surface after the siliconization treatment according to any one of [8] to [11], and In a method of manufacturing an iron core in which stress relief annealing is performed in an iron core assembling process that is assembled to the iron core after processing, the heat treatment in the film coating and the stress relief annealing are performed at a temperature and time satisfying the following expression (2). A method of manufacturing an iron core characterized by the above.
(Σ t ′ k × exp (−25000 / T ′ k )) / (d 2 × [mass% Si] add ) ≦ 0.2 × 10 −4 (2)
However, T ′ k (K) is the temperature at which the heat treatment is performed in each step of coating coating and strain relief annealing, and t ′ k (second) is the holding time at that temperature.

なお、本明細書において、鋼の成分を示す%、ppmは、すべて質量%、質量ppmである。   In this specification, “%” and “ppm” indicating the components of steel are mass% and mass ppm, respectively.

本発明によれば、高周波鉄損が低く、さらには、圧延直角方向の磁歪が小さい方向性珪素鋼板が得られる。   According to the present invention, a directional silicon steel sheet having low high-frequency iron loss and low magnetostriction in the direction perpendicular to rolling can be obtained.

表裏Si濃度差による板変形を示す図である。It is a figure which shows the board deformation | transformation by front and back Si concentration difference. 表裏面のSi濃度が高く、板厚中心部のSi濃度が低い鋼板に働く内部応力を示す図である。It is a figure which shows the internal stress which acts on the steel plate with high Si density | concentration of front and back, and low Si density | concentration of board thickness center part. Si濃度分布と片面化学研磨前後の板形状を示す図である。It is a figure which shows Si concentration distribution and the board shape before and behind single-sided chemical polishing. 磁化挙動と渦電流損低減の模式図である。It is a schematic diagram of a magnetization behavior and eddy current loss reduction. 圧延直角方向に励磁した際の磁束密度に対する磁歪の変化を示す図である。It is a figure which shows the change of the magnetostriction with respect to the magnetic flux density at the time of exciting in a rolling orthogonal direction. 方向性電磁鋼板の磁区構造を模式的に示した図である。It is the figure which showed typically the magnetic domain structure of a grain-oriented electrical steel sheet. 磁束密度Ｂ10の配向性（結晶配向性）と圧延直角方向の磁歪との関係を示す図である。It is a figure which shows the relationship between the orientation (crystal orientation) of magnetic flux density B10, and the magnetostriction of a rolling orthogonal direction. 内部応力と圧延直角方向の磁歪との関係を示す図である。It is a figure which shows the relationship between an internal stress and the magnetostriction of a rolling right angle direction.

以下に本発明を完成するに至った経緯も含め、詳細に説明する。
浸珪処理した鋼板で表裏面のSi濃度が異なる場合、図１に示すようにSi濃度の高い側が凹み、Si濃度の低い側が凸となる反りが発生する。これはSi濃度の高い側が縮もうとし、逆にSi濃度の低い側が伸びようとする力が働くためである。（このような応力の発生原因は、高Si部と低Si部の熱膨張差、格子定数の差、または浸珪反応による表層Fe原子の減少（FeCl2としてガス化）などが考えられる。）
また、鋼板を浸珪処理し、Siが拡散して板厚方向に均一化する前に炉から取り出し表裏面のSi濃度が高く、板厚中心部のSi濃度が低い試料を作製した場合、この試料に働く内部応力は、図２に示すように表層で引張、板厚中央で圧縮となることが予想される。
そこで実際に生じている応力を確認するため、フォルステライト被膜を除去した板厚0.21mmの方向性電磁鋼板を浸珪処理し、板厚方向にSi濃度勾配の有する幅30mm長さ280mm（長手が圧延方向）の試料を作製した。この試料に対して、単板測定器を用いて磁気特性を測定した。なお、磁気特性はJIS C 2556 電磁鋼板単板磁気特性試験方法に準じて行った。次に浸珪試料の片面のみフッ酸で板厚中心部まで化学研磨した後、鋼板の反り量を曲率半径rとして測定した。以上により得られた結果を図３に示す。なお、化学研磨前の試料には反りは殆ど認められなかった。
さらに、図3の結果を基に、上記で得られた曲率半径ｒから表層、板厚中心部の歪み量を計算し、化学研磨前に鋼板内部で生じている応力を次式のように定義して算出した。
表面に働く引張応力 ＝ 板厚中心部に働く圧縮応力＝ E×d／(2r) [MPa]
ここでEは圧延方向のヤング率で、方向性電磁鋼板の場合、E100=140×103 [MPa]とした。dは板厚[mm]、rは片面化学研磨後の板の曲率半径[mm]である。厳密には表面と板厚中心部で必ずしも応力が一致するとは限らないが、ここでは板の反りから上述のように算出した値を内部応力と定義する。
以上により得られた高周波鉄損（W1/10k）と内部応力との関係を表１に示す。 The details will be described below, including the background to the completion of the present invention.
When the Si concentrations of the front and back surfaces of the steel plates subjected to the siliconization treatment are different, as shown in FIG. This is because the force that tends to shrink the side with high Si concentration and conversely with the side with low Si concentration works. (Stress may be caused by the difference in thermal expansion between the high Si and low Si parts, the difference in lattice constant, or the decrease of surface Fe atoms due to the silicon immersion reaction (gasification as FeCl 2 ).)
In addition, when the steel sheet is subjected to siliconization treatment, the sample is taken out of the furnace before Si diffuses and becomes uniform in the thickness direction, and the Si concentration on the front and back surfaces is high and the Si concentration at the center of the thickness is low. As shown in FIG. 2, the internal stress acting on the sample is expected to be tensile at the surface layer and compressed at the center of the plate thickness.
Therefore, in order to confirm the actual stress, the directional electrical steel sheet with a thickness of 0.21 mm from which the forsterite film was removed was subjected to a silicidation treatment, and a width of 30 mm and a length of 280 mm (longitudinal length) with a Si concentration gradient in the thickness direction. A sample in the rolling direction) was prepared. The magnetic characteristics of this sample were measured using a single plate measuring instrument. The magnetic properties were measured in accordance with the JIS C 2556 electrical steel sheet single sheet magnetic property test method. Next, after chemically polishing only one side of the siliconized sample with hydrofluoric acid to the center of the plate thickness, the amount of warpage of the steel plate was measured as the radius of curvature r. The results obtained as described above are shown in FIG. In addition, almost no warping was observed in the sample before chemical polishing.
Further, based on the results of FIG. 3, the amount of strain at the surface layer and the center of the plate thickness is calculated from the curvature radius r obtained above, and the stress generated in the steel plate before chemical polishing is defined as follows: And calculated.
Tensile stress acting on the surface = compressive stress acting on the center of the plate thickness = E × d / (2r) [MPa]
Here, E is the Young's modulus in the rolling direction, and in the case of a grain-oriented electrical steel sheet, E100 = 140 × 10 3 [MPa]. d is the plate thickness [mm], and r is the radius of curvature [mm] of the plate after single-sided chemical polishing. Strictly speaking, the stress does not always coincide between the surface and the center of the plate thickness, but here, the value calculated as described above from the warp of the plate is defined as the internal stress.
Table 1 shows the relationship between the high-frequency iron loss (W1 / 10k) and the internal stress obtained as described above.

表1より、内部応力を有する試料B〜Dの高周波鉄損W1/10kは、板厚方向にSiを均一化して内部応力を除去した比較材Gより低い値を示しているのがわかる。一方、表層（板厚中心部）の内部応力の大きさが160MPaを超える試料A、及び70MPa未満の試料E、Fでは、逆に比較材Gに比べて高い鉄損値を示している。
また、鉄損を履歴損と渦電流損に分離すると、内部応力の増加のともない履歴損は増加している。逆に渦電流損は、内部応力を付与すると低下する傾向を示し、とくに内部応力110MPa付近では、比較材の半分以下まで渦電流損が低下することがわかる。ただし内部応力が160MPaを超える試料Aでは履歴損が大きいため、全体の鉄損値も比較材より劣位となる。
以上の結果から、高周波鉄損を低減するには渦電流損を大幅に低減し、かつ履歴損の増大を適度に留めるような最適な内部応力とすることが必要と考えられる。
ここで、内部応力付与による高周波鉄損低減のメカニズムについて説明する。
方向性珪素鋼板は引張応力を加えると軟磁気特性が改善され鉄損が低下する傾向を示すが、逆に圧縮応力を加えた場合は軟磁気特性が著しく劣化し鉄損は大幅に増加する。従って、通常は、方向性珪素鋼板では内部応力とくに圧縮応力を残すことは極力回避される。
たとえば、方向性電磁鋼板の表面にセラミックス膜などの高張力被膜を形成すると鋼板には全体的に引張応力が働く。これにより方向性電磁鋼板の磁区を細分化して低鉄損化を図ると同時に、鉄心として組み上げた際に圧縮応力が加わった場合、予め付与した引張応力と相殺させることで顕著な鉄損増加を抑制する効果も期待されている。
これに対し、本発明は、通常の方向性珪素鋼板とは異なり、上記表１の結果を基に、方向性珪素鋼板の板厚中心部に積極的に大きな圧縮応力を付与して軟磁気特性を劣化させ、逆に表層部分には大きな引張応力を付与して軟磁気特性を改善することで、高周波での渦電流損を劇的に低減するものである。
図４に渦電流損低減の模式図を示す。本発明の材料を磁化した場合、板厚中心部は大きな圧縮応力がかかっているため殆ど磁化せず、引張応力のかかった表層部分が優先的に磁化する。その結果、磁束が表層部に集中する。そして、板厚全体で均一に同じ磁化量まで励磁した場合と比較すると、板厚中心部の磁束変化がほとんど無いため、板厚方向に均一に磁化される応力除去材に比べ本発明材の渦電流損は大幅に低下することになる。
このように、図４に示すように板厚中央部で磁束の変化がなく表層のみ磁化されるのが理想的であり、この場合、渦電流損（古典渦電流損）は板厚全体で均一に磁化される場合の半分となる。しかし、表１に示す渦電流損実測値には異常渦電流損も含まれているため、実際に古典渦電流損を半減するまでには至らないが、内部応力を付与した方向性電磁鋼板では磁区が細分化され異常渦電流損も低減する効果もあると考えられ、それも含めて表１の試料Ｃでは比較材Ｇに対して全体の渦電流損が半減したものと推察される。実際、内部応力70MPa以上の試料をビッター法により肉眼で磁区観察する限り、方向性電磁鋼板特有の180°磁区模様は全く認められなかった。
以上より、圧延方向と平行な方向に内部応力として、板厚中心部に圧縮応力、最表層に引張応力を有することとする。そして、本発明では、70〜160MPaの範囲で板厚中心部に圧縮応力、板表面に板厚中心部と同じ大きさの引張応力を有することとする。この内部応力が70MPa未満の場合、履歴損増大分を打ち消してトータルの鉄損を下げるほど十分な渦電流損の低減効果は得られず、また内部応力が160MPaを超えた場合も、履歴損増大に対して渦電流損の低減効果が低下するためトータル鉄損が増加してしまう。 From Table 1, it can be seen that the high-frequency iron loss W1 / 10k of the samples B to D having internal stress is lower than that of the comparative material G in which Si is made uniform in the thickness direction to remove the internal stress. On the other hand, Sample A in which the magnitude of the internal stress of the surface layer (plate thickness center portion) exceeds 160 MPa and Samples E and F less than 70 MPa show higher iron loss values than Comparative Material G.
Further, when the iron loss is separated into the hysteresis loss and the eddy current loss, the hysteresis loss increases as the internal stress increases. Conversely, eddy current loss tends to decrease when internal stress is applied, and it can be seen that the eddy current loss decreases to less than half that of the comparative material, particularly in the vicinity of the internal stress of 110 MPa. However, in Sample A where the internal stress exceeds 160 MPa, the hysteresis loss is large, so the overall iron loss value is inferior to that of the comparative material.
From the above results, in order to reduce the high-frequency iron loss, it is considered necessary to achieve an optimum internal stress that significantly reduces the eddy current loss and moderately increases the hysteresis loss.
Here, the mechanism of high-frequency iron loss reduction by applying internal stress will be described.
A grain oriented silicon steel sheet tends to improve soft magnetic properties and decrease iron loss when tensile stress is applied, but conversely, when compressive stress is applied, soft magnetic properties deteriorate significantly and iron loss increases greatly. Therefore, in general, it is avoided as much as possible to leave internal stress, particularly compressive stress, in the grain-oriented silicon steel sheet.
For example, if a high-tensile film such as a ceramic film is formed on the surface of a grain-oriented electrical steel sheet, tensile stress acts on the steel sheet as a whole. As a result, the magnetic domain of the grain-oriented electrical steel sheet is subdivided to reduce iron loss.At the same time, when compressive stress is applied when it is assembled as an iron core, a significant increase in iron loss can be achieved by offsetting the tensile stress applied in advance. The suppression effect is also expected.
On the other hand, the present invention is different from ordinary directional silicon steel plates, and based on the results shown in Table 1 above, a large compressive stress is positively applied to the center of the thickness of the directional silicon steel plates to provide soft magnetic properties. On the contrary, by applying a large tensile stress to the surface layer portion to improve the soft magnetic characteristics, eddy current loss at high frequencies is dramatically reduced.
FIG. 4 shows a schematic diagram of eddy current loss reduction. When the material of the present invention is magnetized, a large compressive stress is applied to the central portion of the plate thickness, so that it is hardly magnetized, and the surface layer portion subjected to tensile stress is preferentially magnetized. As a result, the magnetic flux is concentrated on the surface layer. Compared with the case where the same magnetization amount is uniformly excited throughout the plate thickness, there is almost no change in the magnetic flux at the center of the plate thickness, so that the vortex of the present invention material compared to the stress relief material magnetized uniformly in the plate thickness direction. The current loss will be greatly reduced.
Thus, as shown in FIG. 4, it is ideal that only the surface layer is magnetized without changing the magnetic flux at the central portion of the plate thickness. In this case, the eddy current loss (classical eddy current loss) is uniform throughout the plate thickness. It is half that when magnetized. However, the measured eddy current loss shown in Table 1 includes abnormal eddy current loss, so it does not actually halve the classical eddy current loss. It is considered that the magnetic domains are subdivided and there is an effect of reducing abnormal eddy current loss. Including this, it is presumed that the total eddy current loss is reduced by half with respect to the comparative material G in the sample C of Table 1. In fact, as long as a sample having an internal stress of 70 MPa or more was observed with the naked eye by the Bitter method, no 180 ° magnetic domain pattern peculiar to grain-oriented electrical steel sheets was observed.
From the above, it is assumed that as the internal stress in the direction parallel to the rolling direction, compressive stress is present at the center of the plate thickness, and tensile stress is present at the outermost layer. In the present invention, in the range of 70 to 160 MPa, a compressive stress is provided at the center portion of the plate thickness, and a tensile stress having the same magnitude as that of the center portion of the plate thickness is provided on the plate surface. If this internal stress is less than 70 MPa, the effect of reducing the eddy current loss is not sufficient to cancel the increase in hysteresis loss and lower the total iron loss. Also, if the internal stress exceeds 160 MPa, the hysteresis loss increases. However, since the effect of reducing eddy current loss is reduced, the total iron loss increases.

なお、鋼板に内部応力を付与する際には、表裏面の応力差を小さくすることが肝要である。表裏面の応力差が大きくなると内部応力の釣り合いを保つため鋼板が変形し反りが発生する。この場合においても、渦電流損低減効果が減少し履歴損が増加するため、高周波での鉄損は劣化することになる。表裏面の応力差が8MPa以下であれば鋼板の反りは僅かで鉄損上昇も僅かであるが、8MPaを超えると反りが顕在化し鉄損も大幅に増大する。よって、方向性電磁鋼板の表裏面での引張応力の差が8MPa以下であることが好ましい。
鋼板にこのような内部応力分布を形成させる手段としては様々な方法が考えられる。例えば、気相浸珪法で表層からSiを添加した後、均一化する前に低温まで冷却しSi濃度勾配を残して応力を発生させるのが一般的である。しかし、この方法に限定されず、Siを含む薬剤を鋼板表面に塗布した後、熱処理して鋼板内部へ浸透させる固相浸透プロセス、あるいは、Siを含む溶融塩に漬けて浸透させる液相浸透プロセスを用いることもできる。
ここで、気相浸珪法を利用する場合、発明者らは既に平均Si量が4〜7%でかつ表層と板厚中心部のSi濃度差を1.5〜4%となるような濃度分布を材料に形成することにより、高周波鉄損を効果的に低減できることを見出している。しかしながら、上述のようなSi濃度プロファイルを有する板厚0.2mmの方向性電磁鋼板であっても、剪断等の加工歪みを除去することを目的として800℃で1hrの歪取焼鈍を施しところ、濃度プロファイルは殆ど変化しないにもかかわらず、高周波鉄損は歪取焼鈍前よりも増加する傾向が認められた。このときの内部応力の変化を調査したところ、歪取焼鈍前に93MPaあった内部応力が歪取焼鈍後には55MＰaまで低下していた。一方、同じSi濃度プロファイルを有する無方向性電磁鋼板においては、この程度の歪取焼鈍温度と時間で明確な鉄損増加は認められなかった。以上の結果より、方向性電磁鋼板においては、従来の無方向性電磁鋼板の例と異なり、高周波鉄損を低減するためには板厚方向のSi濃度分布を規定するだけでは不十分で、内部応力を適正化する必要があることがわかった。 When applying internal stress to the steel sheet, it is important to reduce the stress difference between the front and back surfaces. When the stress difference between the front and back surfaces increases, the steel sheet deforms and warps to maintain the balance of internal stress. Even in this case, the effect of reducing the eddy current loss is reduced and the hysteresis loss is increased, so that the iron loss at high frequency is deteriorated. If the stress difference between the front and back surfaces is 8 MPa or less, the warpage of the steel sheet is slight and the iron loss rises slightly, but if it exceeds 8 MPa, the warp becomes obvious and the iron loss increases greatly. Therefore, the difference in tensile stress between the front and back surfaces of the grain-oriented electrical steel sheet is preferably 8 MPa or less.
Various methods are conceivable as means for forming such an internal stress distribution on the steel sheet. For example, after adding Si from the surface layer by vapor phase siliconization, it is generally cooled to a low temperature before being homogenized to generate a stress while leaving a Si concentration gradient. However, it is not limited to this method, and after applying a chemical containing Si to the surface of the steel sheet, it is heat-treated so as to penetrate into the steel sheet, or a liquid phase infiltration process in which it is immersed in a molten salt containing Si. Can also be used.
Here, when using the vapor phase siliconization method, the inventors already have a concentration distribution in which the average Si amount is 4 to 7% and the difference in Si concentration between the surface layer and the thickness center is 1.5 to 4%. It has been found that high-frequency iron loss can be effectively reduced by forming the material. However, even with a 0.2 mm-thick grain-oriented electrical steel sheet having the Si concentration profile as described above, strain relief annealing is performed at 800 ° C. for 1 hour for the purpose of removing processing strain such as shearing. Although the profile hardly changed, the high-frequency iron loss tended to increase more than that before the strain relief annealing. When the change of the internal stress at this time was investigated, the internal stress which was 93 MPa before the stress relief annealing was reduced to 55 MPa after the stress relief annealing. On the other hand, in non-oriented electrical steel sheets having the same Si concentration profile, no clear increase in iron loss was observed at this degree of strain relief annealing temperature and time. From the above results, in the grain-oriented electrical steel sheet, unlike the conventional non-oriented electrical steel sheet, it is not sufficient to specify the Si concentration distribution in the thickness direction in order to reduce high-frequency iron loss. It was found that the stress needs to be optimized.

このように歪取焼鈍時にSi濃度勾配を有する方向性電磁鋼板が無方向性電磁鋼板に比べて高周波鉄損が劣化しやすい原因については、以下のように推測される。
無方向性電磁鋼板の場合、板厚方向にSi濃度勾配をつくり表層を軟磁気特性に優れた6.5%Siに近い組成とすることによって、材料を磁化した際に透磁率の極めて高い表層へ磁束を集中させ渦電流損を低減することができる。本発明で述べているように内部応力の効果もあると考えられるが、たとえ歪取焼鈍によって内部応力が緩和されたとしても、表層高Si部分と板厚中心部の低Si部分で透磁率が3倍以上の差を有しているため、表層が優先的に磁化する。
一方、方向性電磁鋼板の場合、元来圧延方向の軟磁気特性が優れているため、表層を6.5%Siとしてもその部分の透磁率増分は無方向性電磁鋼板の場合ほど顕著ではなく、磁束が表層に集中しにくい。実際に板厚方向にSi濃度勾配を有する方向性電磁鋼板の高周波鉄損が飛躍的に低減するのは、板厚中心部に極めて大きな圧縮応力がかかって透磁率が著しく低下し、その結果、表層部分に磁束が集中するためと考えられる。
すなわち、方向性電磁鋼板の場合、高周波鉄損を低減させているのは内部応力の存在であって、たとえSi濃度プロファイルが適正範囲であったとしても、600℃以上で熱処理された場合、内部応力が緩和されるのに伴い表層での磁束集中も緩和されて、渦電流損低減効果が薄れ高周波鉄損が上昇すると考えられる。このようなメカニズムに基づき、方向性電磁鋼板の高周波鉄損を効果的に低減するためには、Si濃度勾配、すなわち、Si濃度プロファイルのみならず、まず、内部応力の規定が必要との結論に達した。 The reason why the directional electrical steel sheet having the Si concentration gradient during the strain relief annealing is likely to deteriorate the high-frequency iron loss as compared with the non-oriented electrical steel sheet is estimated as follows.
In the case of non-oriented electrical steel sheets, by creating a Si concentration gradient in the thickness direction and making the surface layer a composition close to 6.5% Si with excellent soft magnetic properties, magnetic flux is transferred to the surface layer with extremely high permeability when the material is magnetized. Eddy current loss can be reduced. Although it is considered that there is an effect of internal stress as described in the present invention, even if the internal stress is relaxed by strain relief annealing, the permeability is high in the high Si portion of the surface layer and in the low Si portion of the center of the plate thickness. Since the difference is 3 times or more, the surface layer is preferentially magnetized.
On the other hand, in the case of grain-oriented electrical steel sheets, the soft magnetic properties in the rolling direction are excellent, so even if the surface layer is 6.5% Si, the permeability increase in that part is not as significant as in the case of non-oriented electrical steel sheets. Is difficult to concentrate on the surface. The fact that the high-frequency iron loss of the grain-oriented electrical steel sheet that actually has a Si concentration gradient in the sheet thickness direction is drastically reduced is that the magnetic permeability is significantly reduced due to the extremely large compressive stress applied to the center part of the sheet thickness. This is probably because the magnetic flux concentrates on the surface layer.
That is, in the case of grain-oriented electrical steel sheets, it is the presence of internal stress that reduces high-frequency iron loss, and even if the Si concentration profile is in the proper range, It is considered that as the stress is relaxed, the magnetic flux concentration on the surface layer is also relaxed, the effect of reducing eddy current loss is reduced, and the high-frequency iron loss is increased. Based on this mechanism, in order to effectively reduce the high-frequency iron loss of grain-oriented electrical steel sheets, it is concluded that not only the Si concentration gradient, that is, the Si concentration profile, but also the internal stress must be specified first. Reached.

次に、方向性電磁鋼板およびそれを浸珪処理した試料を圧延直角方向に励磁した場合の磁歪を調査した。得られた結果を図５に示す。
従来から知られているように、方向性電磁鋼板（浸珪前）の圧延直角方向の磁歪は極めて大きな値を示す。これを浸珪して5.3％までSi量を高め均一拡散した場合、磁歪は浸珪前に比べて低下する。これはSi量増加により材料の磁歪定数λ100、λ111の大きさが減少したことによるもので、従来知見から想定される現象である。一方、5.3％までSi量を高めた後、均一拡散を途中で中止することにより板厚方向にSi濃度勾配を与えることによって内部応力を付与した試料では、驚くべきことに圧延直角方向の磁歪が極めて低い値となることがわかった。このような現象はこれまで見出されなかった特異な現象である。 Next, the magnetostriction was investigated when the grain-oriented electrical steel sheet and the sample subjected to the siliconization treatment were excited in the direction perpendicular to the rolling direction. The obtained results are shown in FIG.
As is conventionally known, the magnetostriction in the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet (before siliconization) shows a very large value. When this is siliconized to increase the Si content to 5.3% and diffuse uniformly, the magnetostriction is lower than before siliconization. This is because the magnetostriction constants λ100 and λ111 of the material have decreased due to an increase in the amount of Si, which is a phenomenon assumed from the conventional knowledge. On the other hand, after increasing the Si content to 5.3%, the sample with the internal stress applied by applying a Si concentration gradient in the plate thickness direction by stopping the uniform diffusion in the middle surprisingly shows magnetostriction in the direction perpendicular to the rolling direction. It was found that the value was extremely low. Such a phenomenon is a unique phenomenon that has not been found so far.

方向性電磁鋼板の板厚方向に内部応力を付与した場合に認められる圧延直角方向での磁歪低減現象は次のようなメカニズムによって生じるものと考えられる。   It is considered that the phenomenon of magnetostriction reduction in the direction perpendicular to the rolling observed when internal stress is applied in the thickness direction of the grain-oriented electrical steel sheet is caused by the following mechanism.

方向性電磁鋼板はゴス方位、すなわち結晶の(110)面が圧延方向に平行で、〈100〉方向が圧延方向を向いた結晶の集まりであって、消磁状態のとき、ほとんどの磁気モーメントは圧延方向の磁化容易軸〈100〉を向いている。ここで、方向性電磁鋼板の圧延方向に圧縮応力をかけた場合、磁歪定数λ100は正のため、結晶の磁化容易軸は圧縮方向とは異なる方向の〈100〉軸に向こうとする。この圧縮応力によって生じた誘導磁気異方性により、材料の磁化容易軸は圧延方向に垂直で板面に対し、45°傾いた〈100〉軸となる。図６に圧延方向に圧縮応力をかける前と後での方向性電磁鋼板の磁区構造の比較を示す。   A grain-oriented electrical steel sheet is a collection of crystals whose Goss orientation, that is, the (110) plane of the crystal is parallel to the rolling direction and the <100> direction is oriented in the rolling direction. It faces the direction of easy magnetization <100>. Here, when compressive stress is applied in the rolling direction of the grain-oriented electrical steel sheet, since the magnetostriction constant λ100 is positive, the easy magnetization axis of the crystal tends to be directed to the <100> axis which is different from the compression direction. Due to the induced magnetic anisotropy caused by this compressive stress, the easy magnetization axis of the material is a <100> axis that is perpendicular to the rolling direction and inclined by 45 ° with respect to the plate surface. FIG. 6 shows a comparison of magnetic domain structures of grain-oriented electrical steel sheets before and after applying compressive stress in the rolling direction.

板厚方向にSi濃度勾配を付与した場合は、表層部に引張り、板厚中心部に圧縮の内部応力が働く。そして、方向性電磁鋼板を浸珪処理して板厚方向に適当なSi濃度勾配を与えて内部応力を付与すると、板厚中心部では大きな圧縮応力がかかるため、図６(b)のような磁区構造となるものと考えられる。なお、実際には圧延直角方向にも圧縮応力がかかっているが、この方向に最も近い〈100〉軸は板面に対して約45°傾いており、圧延方向の〈100〉軸に比べて圧縮応力の影響を受けにくい。すなわち、結果的に圧延直角方向で圧延面に45°傾いた〈100〉軸が磁化容易軸となる。図６(b)の磁区構造を有する材料を圧延直角方向に磁化した場合、1.3T程度までは磁化容易軸に向いた磁区の180°反転で磁化が進行すると考えられ、磁歪はほとんど変化しない。すなわち、圧延直角方向の磁歪が極めて低くなる。   When a Si concentration gradient is applied in the thickness direction, tension is applied to the surface layer, and compression internal stress acts on the thickness center. Then, when the internal stress is applied by applying a suitable Si concentration gradient in the sheet thickness direction by dip-treating the grain-oriented electrical steel sheet, a large compressive stress is applied at the center of the sheet thickness, and as shown in FIG. A magnetic domain structure is assumed. Actually, the compressive stress is also applied in the direction perpendicular to the rolling direction, but the <100> axis closest to this direction is inclined by about 45 ° relative to the plate surface, compared to the <100> axis in the rolling direction. Less susceptible to compressive stress. That is, as a result, the <100> axis inclined at 45 ° to the rolling surface in the direction perpendicular to the rolling becomes the easy magnetization axis. When the material having the magnetic domain structure shown in FIG. 6B is magnetized in the direction perpendicular to the rolling direction, it is considered that the magnetization proceeds by 180 ° reversal of the magnetic domain directed to the easy magnetization axis up to about 1.3 T, and the magnetostriction hardly changes. That is, the magnetostriction in the direction perpendicular to the rolling becomes extremely low.

なお、板厚方向に内部応力を有する鋼板は、表層部において引張応力が働くが、この領域はSi濃度が板厚中心部に比べて高く、磁歪の絶対値が小さいため、板内部ほど大きな影響は受けないものと考えられる。   In addition, the steel sheet with internal stress in the plate thickness direction is subjected to tensile stress at the surface layer, but this region has a higher Si concentration than the plate thickness center, and the absolute value of magnetostriction is small. Is considered not to be received.

以上の検討の結果、方向性電磁鋼板において、内部応力を規定することで、高周波鉄損が効果的に低減するのみならず、圧延直角方向の磁歪も低減されることがわかった。   As a result of the above examination, it was found that, in the grain-oriented electrical steel sheet, by defining the internal stress, not only the high-frequency iron loss is effectively reduced, but also the magnetostriction in the direction perpendicular to the rolling is reduced.

さらに磁歪の低減を検討していく中で、材料の結晶配向性も重要な要件となることがわかった。
通常、無方向性電磁鋼板の板厚方向にSi濃度勾配を与えて内部応力を付与した場合、圧延方向も圧延直角方向もともに磁歪は大きな値を示す。たとえば表層Si量が6.7％、板厚中心部が4.2％の無方向性電磁鋼板を1Tまで励磁した場合、磁歪は3〜5×10−６と通常の3％Si電磁鋼板と同程度の値を示す。しかしながら、方向性電磁鋼板に対して同様の内部応力を付与すると圧延直角方向の磁歪は極めて小さな値となることが上述の検討結果から明らかとなった。これが図６で説明したメカニズムによるものと考えると、ある程度ゴス集積度が高くないと効果的な鉄損低減が望めないと考えられる。そこで、Si濃度勾配を有する材料の結晶配向性と圧延直角方向磁歪の関係を調査した。なお、結晶配向性は、磁化力1000A/mにおける磁束密度B10の、圧延方向と圧延直角方向との比：B10(L)／B10(C)（Ｂ10(L)：圧延方向の磁束密度、B10(C)：圧延直角方向の磁束密度）で表すこととする。得られた結果を図７に示す。図７に示すように、B10(L)／B10(C)の増加とともに圧延直角方向の磁歪が減少し、B10(L)／B10(C)≧1.2であれば、1Tで励磁したときの磁歪が1×10−６未満と、無方向性電磁鋼板に比べ、小さな値を示すことがわかった。特に、B10(L)／B10(C)が1.35とゴス集積度の高い材料においては、圧延直角方向の磁歪は0.3×10−６と極めて小さな値を示した。 Furthermore, it was found that the crystal orientation of the material is an important requirement in the study of reducing magnetostriction.
Normally, when an internal stress is applied by applying a Si concentration gradient in the thickness direction of a non-oriented electrical steel sheet, the magnetostriction shows a large value in both the rolling direction and the direction perpendicular to the rolling direction. For example, when a non-oriented electrical steel sheet with a surface Si content of 6.7% and a center thickness of 4.2% is excited up to 1T, the magnetostriction is 3-5 × 10 −6, which is about the same as a normal 3% Si electrical steel sheet. Indicates. However, when the same internal stress is applied to the grain-oriented electrical steel sheet, the magnetostriction in the direction perpendicular to the rolling becomes an extremely small value from the above examination results. If this is considered to be due to the mechanism described with reference to FIG. 6, it is considered that effective reduction of iron loss cannot be expected unless the Goss accumulation degree is high to some extent. Therefore, the relationship between the crystal orientation of the material with Si concentration gradient and the magnetostriction in the direction perpendicular to the rolling direction was investigated. The crystal orientation is the ratio of the magnetic flux density B10 at a magnetizing force of 1000 A / m to the ratio between the rolling direction and the perpendicular direction of rolling: B10 (L) / B10 (C) (B10 (L): magnetic flux density in the rolling direction, B10 (C): Magnetic flux density in the direction perpendicular to rolling). The obtained results are shown in FIG. As shown in FIG. 7, the magnetostriction in the direction perpendicular to rolling decreases with an increase in B10 (L) / B10 (C). If B10 (L) / B10 (C) ≧ 1.2, the magnetostriction when excited at 1T is used. Is less than 1 × 10 −6, which is smaller than that of the non-oriented electrical steel sheet. In particular, in a material having a high Goss accumulation degree of B10 (L) / B10 (C) of 1.35, the magnetostriction in the direction perpendicular to the rolling was as small as 0.3 × 10 −6 .

以上から、圧延直角方向の磁歪を1×10−６未満とするためには、B10(L)／B10(C)≧1.2とする必要がある。なお、このようなB10(L)／B10(C)≧1.2である方向性電磁鋼板とするためには、後述するように方向性電磁鋼板あるいは更にこの方向性電磁鋼板に1回以上の冷間圧延を施して得られた鋼板を出発素材として適正な浸珪処理を施すことが好ましい。
さらに、圧延直角方向の磁歪を低減する観点から適切な内部応力の範囲を調査するため、以下の実験を行なった。
まず、板厚0.23mmの方向性電磁鋼板の被膜を酸洗により除去して板厚0.21mmとした後、1100〜1200℃に加熱して四塩化珪素ガスを用いて浸珪処理を行い、Siが均一化する前に冷却して種々のSi濃度勾配を有する試料を作製した。次に圧延直角方向が長手方向となるように試料を切り出し、単板磁気試験機により圧延直角方向に磁化したときの磁歪および高周波鉄損を測定した。一方、同条件で作製した後、圧延方向を長手方向として切り出した各試料に対し、フッ酸溶液を用いて片面を板厚中心まで化学研磨し、その時の板の反り量から圧延方向にかかる内部応力を算出した。なお、浸珪処理後の材料の圧延方向と圧延直角方向の磁束密度の比B10(L)／B10(C)は1.31〜1.35であった。 From the above, in order to make the magnetostriction in the direction perpendicular to rolling less than 1 × 10 −6 , it is necessary to satisfy B10 (L) / B10 (C) ≧ 1.2. In order to obtain such a grain-oriented electrical steel sheet that satisfies B10 (L) / B10 (C) ≧ 1.2, as described later, the grain-oriented electrical steel sheet or, moreover, this grain-oriented electrical steel sheet is subjected to one or more cold cycles. It is preferable to perform an appropriate siliconization treatment using a steel plate obtained by rolling as a starting material.
Furthermore, the following experiment was conducted in order to investigate an appropriate range of internal stress from the viewpoint of reducing magnetostriction in the direction perpendicular to rolling.
First, after removing the film of the grain-oriented electrical steel sheet having a thickness of 0.23 mm by pickling to obtain a sheet thickness of 0.21 mm, it is heated to 1100 to 1200 ° C. and siliconized using silicon tetrachloride gas. Samples with various Si concentration gradients were prepared by cooling before homogenization. Next, the sample was cut out so that the perpendicular direction to the rolling direction was the longitudinal direction, and the magnetostriction and high-frequency iron loss were measured when magnetized in the perpendicular direction to the rolling direction using a single plate magnetic tester. On the other hand, for each sample cut out with the rolling direction as the longitudinal direction after being manufactured under the same conditions, one side of the sample was chemically polished to the center of the plate thickness using a hydrofluoric acid solution, and the inside of the plate in the rolling direction from the amount of warpage of the plate at that time Stress was calculated. The ratio B10 (L) / B10 (C) of the magnetic flux density in the rolling direction and the direction perpendicular to the rolling of the material after the siliconizing treatment was 1.31 to 1.35.

これらの試料の内部応力と磁歪および高周波鉄損の関係を図８に示す。図8より、内部応力が70MPa以上に増加すると圧延直角方向の磁歪は急激に低下するが、それ以上ではほとんど変化しない。
以上より、圧延直角方向の磁歪を低減する観点からも、内部応力は70MPa以上であるのが好ましい。 FIG. 8 shows the relationship between the internal stress, magnetostriction, and high-frequency iron loss of these samples. As shown in FIG. 8, when the internal stress increases to 70 MPa or more, the magnetostriction in the direction perpendicular to the rolling decreases sharply, but hardly changes beyond that.
From the above, the internal stress is preferably 70 MPa or more from the viewpoint of reducing magnetostriction in the direction perpendicular to the rolling.

次に、本発明の方向性電磁鋼板の成分組成について説明する。本発明の方向性電磁鋼板は、質量％で、C：0.005％以下、Si：４〜７％、Mn：0.005〜2.5％、Sol.Al： 0.0080%以下、S：0.003%以下、N：0.005%以下含有し、残部Feおよび不可避的不純物からなる。なお、以下、成分に関する「%」表示は、特に断らない限り質量%を意味するものとする。
C：0.005％以下
Cは磁気特性に対して有害な元素であり、とくに本発明のように内部応力が存在する材料においては、0.005%を超えると鉄損が著しく増大する。一方、Si含有量の高い電磁鋼板ではC量が0.005%未満となると粒界破壊しやすく製品加工性が低下する。したがってC量は0.005%以下とした。
Si：４〜７％
Siは、磁気特性を改善するのに有効な元素であるが、７％を超えると鉄心などに加工する際、割れや欠けが生じやすいため、平均濃度として４〜７％を含有させる。
Mn：0.005〜2.5%
Mnは熱間加工性を改善する元素であるが、0.005%未満では効果がなく、2.5％を超えると二次再結晶が困難となるため、0.005〜2.5%とする。なお、磁気特性改善の観点から0.01％以上とすることが好ましい。
Sol.Al：0.0080%以下
Sol.Alを上記の範囲に制御する方法は、特に限定しないが、製鋼段階でのAl添加量の制御および/または素材の方向性珪素鋼板を得るまでの途中工程における焼鈍での脱Al量制御が、工業生産性の観点から有利である。なお、浸珪処理前にSol.Alを0.0080%以下に制御することにより、続く冷間圧延、浸珪処理後の集合組織が著しく改善される。
S：0.003%以下
N：0.005%以下
S、Nは微細な析出物を形成したり粒界偏析して鉄損を増大させるため上記のように上限を定めた。 Next, the component composition of the grain-oriented electrical steel sheet according to the present invention will be described. The grain-oriented electrical steel sheet of the present invention is in mass%, C: 0.005% or less, Si: 4-7%, Mn: 0.005-2.5%, Sol.Al: 0.0080% or less, S: 0.003% or less, N: 0.005 % Or less, consisting of the remainder Fe and inevitable impurities. Hereinafter, “%” in relation to components means mass% unless otherwise specified.
C: 0.005% or less
C is an element harmful to magnetic properties, and particularly in a material having internal stress as in the present invention, if it exceeds 0.005%, the iron loss is remarkably increased. On the other hand, when the C content is less than 0.005% in the electrical steel sheet having a high Si content, grain boundary breakage is liable to occur, and the product processability decreases. Therefore, the C content is 0.005% or less.
Si: 4-7%
Si is an element effective for improving the magnetic properties, but if it exceeds 7%, cracks and chips are likely to occur when it is processed into an iron core or the like, so 4 to 7% is contained as an average concentration.
Mn: 0.005-2.5%
Mn is an element that improves hot workability, but if it is less than 0.005%, there is no effect, and if it exceeds 2.5%, secondary recrystallization becomes difficult, so 0.005 to 2.5%. In addition, it is preferable to set it as 0.01% or more from a viewpoint of a magnetic characteristic improvement.
Sol.Al: 0.0080% or less
The method for controlling Sol.Al to the above range is not particularly limited, but control of Al addition amount in the steelmaking stage and / or removal Al amount control in annealing in the middle process until obtaining the directional silicon steel sheet of the material However, this is advantageous from the viewpoint of industrial productivity. By controlling Sol.Al to 0.0080% or less before the siliconizing treatment, the texture after the subsequent cold rolling and siliconizing treatment is remarkably improved.
S: 0.003% or less
N: 0.005% or less
S and N have upper limits as described above in order to form fine precipitates or segregate at the grain boundaries to increase iron loss.

Sb:0.005〜0.1％、Sn:0.005〜0.5％、Bi:0.001〜0.05％のうちから選ばれた少なくとも1種の元素を含有（好適）
方向性電磁鋼板に、さらに、Sb:0.005〜0.1%、Sn:0.005〜0.5%、Bi:0.001〜0.05%のうちから選ばれた少なくとも1種の元素を含有させると、その後の浸珪処理時や需要家での歪取焼鈍時に起こる鋼板への窒化による磁気特性の劣化を抑制できる。この効果を得るためには、Sbが0.005%以上、Snが0.005%以上、Biが0.001以上のいずれか1種以上が必要である。ただし、Sbが0.1%を、Snが0.5%を、Biが0.05%を超えると鋼板が脆化し、冷間圧延が困難になる。 Contains at least one element selected from Sb: 0.005-0.1%, Sn: 0.005-0.5%, Bi: 0.001-0.05% (preferred)
When the grain-oriented electrical steel sheet further contains at least one element selected from Sb: 0.005 to 0.1%, Sn: 0.005 to 0.5%, Bi: 0.001 to 0.05%, during the subsequent siliconization treatment In addition, it is possible to suppress the deterioration of magnetic properties due to nitriding of steel sheets, which occurs during strain relief annealing at the customer. In order to obtain this effect, at least one of Sb of 0.005% or more, Sn of 0.005% or more, and Bi of 0.001 or more is required. However, if Sb exceeds 0.1%, Sn exceeds 0.5%, and Bi exceeds 0.05%, the steel sheet becomes brittle and cold rolling becomes difficult.

Cr:0.01〜0.8％、Ni:0.01〜1.0％のうちから選ばれた少なくとも1種の元素を含有（好適）
Cr:0.01〜0.8%、Ni:0.01〜1.0%のうちから選ばれた少なくとも1種の元素を含有させると、鋼板の比抵抗を高め、鉄損を低減する。この効果を得るためには、Crが0.01％以上、Niが0.010％以上のいずれか1種以上が必要である。ただし、Crが0.8%を超えると飽和磁束密度が低下し、Niが1.0%を超えると鋼板が硬化し、冷間圧延が困難になる。 Contains at least one element selected from Cr: 0.01-0.8% and Ni: 0.01-1.0% (preferred)
When at least one element selected from Cr: 0.01 to 0.8% and Ni: 0.01 to 1.0% is contained, the specific resistance of the steel sheet is increased and the iron loss is reduced. In order to obtain this effect, at least one of Cr of 0.01% or more and Ni of 0.010% or more is required. However, if Cr exceeds 0.8%, the saturation magnetic flux density decreases, and if Ni exceeds 1.0%, the steel sheet is hardened and cold rolling becomes difficult.

そして、本発明では、Si濃度が板厚中心部より板表面において高くなるSi濃度勾配を有する。なお、板厚中心部と板表面とのSi濃度差を1.5〜4.0％の範囲とすることが、必要となる内部応力を付与する観点から好ましい。   In the present invention, there is a Si concentration gradient in which the Si concentration is higher at the plate surface than at the center of the plate thickness. In addition, it is preferable from the viewpoint of giving the required internal stress that the Si concentration difference between the plate thickness center portion and the plate surface is in the range of 1.5 to 4.0%.

また、板厚を0.05〜0.25mmとすることが好ましい。
板厚が0.05mm未満は製造コストや鉄心加工費の増大を招くため現実的ではない。一方、板厚0.25mmを超えるものは、既存の高周波用材料（板厚0.1mmの無方向6.5%電磁鋼板、リロールした板厚0.1mmの方向性電磁鋼板等）に比べて高周波鉄損が劣る傾向となる。 The plate thickness is preferably 0.05 to 0.25 mm.
A plate thickness of less than 0.05 mm is not realistic because it increases manufacturing costs and iron core processing costs. On the other hand, those with a thickness of more than 0.25 mm have inferior high-frequency iron loss compared to existing high-frequency materials (non-oriented 6.5% electrical steel sheet with a thickness of 0.1 mm, reoriented steel sheet with a thickness of 0.1 mm, etc.). It becomes a trend.

ここで、浸珪に供するフォルステライト被膜を有しない方向性電磁鋼板や浸珪前の冷間圧延（リロール）に供する方向性電磁鋼板の製造方法については特に限定されないが、例えば以下に説明する方法で製造する。   Here, there is no particular limitation on the method of manufacturing the grain-oriented electrical steel sheet that does not have a forsterite film to be subjected to siliconization or the cold-oriented rolling (reroll) before siliconization, but for example, the method described below Manufactured by.

方向性電磁鋼板の出発成分となるスラブの成分組成は、例えば、質量％で、C：0.02〜0.07％、Si：2.5〜4％、Mn：0.05〜2.5%、S：0.003%以下、N：0.005%以下、残部Feおよび不可避的不純物からなる。なお、二次再結晶にインヒビターを利用する場合には、Al：0.0025〜0.030％、Se：0.001〜0.03％、S：0.001〜0.03％およびN：0.003〜0.013％から選ばれた少なくとも１種の元素を含有することができる。また、好適には、Sb:0.005〜0.1％、Sn:0.005〜0.5％、Bi:0.001〜0.05％のうちから選ばれた少なくとも1種の元素を含有することができる。さらに好適には、Cr:0.01〜0.8％、Ni:0.01〜1.0％のうちから選ばれた少なくとも1種の元素を含有することができる。
そして、上記の成分組成を有するスラブに熱間圧延を施し、その後必要に応じて熱延板焼鈍を施してから、1回若しくは中間焼鈍を挟む2回以上の冷間圧延を施し、次いで必要に応じて脱炭焼鈍そして焼鈍分離剤の塗布を行ってから二次再結晶焼鈍を施すことによって方向性電磁鋼板を得る。その際、焼鈍分離剤を用いないか、その組成を調整することによりフォルステライトの形成を抑制する、もしくはフォルステライト被膜を除去することにより、フォルステライト被膜を有さない方向性電磁鋼板とする。 The composition of the slab that is the starting component of the grain-oriented electrical steel sheet is, for example, mass%, C: 0.02 to 0.07%, Si: 2.5 to 4%, Mn: 0.05 to 2.5%, S: 0.003% or less, N: 0.005% or less, balance Fe and inevitable impurities. In the case of using an inhibitor for secondary recrystallization, at least one selected from Al: 0.0025 to 0.030%, Se: 0.001 to 0.03%, S: 0.001 to 0.03%, and N: 0.003 to 0.013%. It can contain elements. Moreover, it is preferable to contain at least one element selected from Sb: 0.005 to 0.1%, Sn: 0.005 to 0.5%, and Bi: 0.001 to 0.05%. More preferably, it may contain at least one element selected from Cr: 0.01 to 0.8% and Ni: 0.01 to 1.0%.
Then, hot-rolled the slab having the above component composition, then subjected to hot-rolled sheet annealing as necessary, and then subjected to cold rolling twice or more sandwiching one or intermediate annealing, then necessary A grain-oriented electrical steel sheet is obtained by performing secondary decrystallization annealing after performing decarburization annealing and application of an annealing separator accordingly. At that time, a grain-oriented electrical steel sheet having no forsterite film is formed by suppressing the formation of forsterite by not using an annealing separator or adjusting the composition thereof, or by removing the forsterite film.

本発明の方向性電磁鋼板は、上記の方向性電磁鋼板、あるいは更にこの方向性電磁鋼板に1回以上の冷間圧延を施して得られた鋼板を出発素材とし、これらに対し、1000℃以上に加熱しSi系のガスと反応させることにより鋼板表面からSiを添加する浸珪処理を行うことで製造することができる。この時、浸珪開始から600℃以下に冷却されるまでに鋼板が通過する炉内各ゾーンの温度をTk(K)、炉内各ゾーンでの鋼板の滞在時間をtk(秒)とした時、下記式（１）を満足することとする。
1.3×10-4≦（Σ tk×exp（-25000／Tk））／（d2 ×［質量%Si］add ）≦ 2.2×10-4 ・・（１）
ただし、dは板厚(mm)、［質量%Si］addは浸珪によるSi添加量を示す。
以下、詳細に説明する。 The grain-oriented electrical steel sheet of the present invention is the above-described grain-oriented electrical steel sheet, or a steel sheet obtained by subjecting this grain-oriented electrical steel sheet to cold rolling at least once. It can be manufactured by performing a siliconizing treatment in which Si is added from the surface of the steel sheet by heating and reacting with Si gas. At this time, T k (K) is the temperature of each zone in the furnace through which the steel plate passes from the start of siliconization until it is cooled to 600 ° C or less, and t k (second) is the residence time of the steel plate in each zone in the furnace. The following formula (1) is satisfied.
1.3 × 10 −4 ≦ (Σ t k × exp (−25000 / T k )) / (d 2 × [mass% Si] add ) ≦ 2.2 × 10 −4 (1)
However, d is the plate thickness (mm), and [mass% Si] add indicates the amount of Si added by siliconization.
Details will be described below.

浸珪処理
気相浸珪法によってSiを添加する場合、Si系の反応ガスが十分に供給されているものとし、浸珪開始から浸珪終了して冷却されるまでの温度履歴（炉内各ゾーンの温度と板の滞在時間）が定まれば、板厚とSi添加量（浸珪量）に対応して板厚方向のSi濃度プロファイルはほぼ一義的に決まる。Si量が2.5〜4%の方向性電磁鋼板を浸珪処理する場合、以下のような条件で実施したとき、方向性電磁鋼板の高周波鉄損を大幅に低減するSi濃度プロファイルが得られる。以下の式（１）は、気相浸珪法によって板表面から供給されたSiを所定の濃度分布となるよう内部まで拡散させるための処理温度と時間の関係を示すものである。ゆえに、式（１）によって示されるものは気相浸珪法で適切なSi濃度分布を形成するための熱処理パラメータとなり、この値を制御することで鋼板内に適切な内部応力を与えるようなSi濃度分布を形成し高周波鉄損を低減することができる。
1.3×10-4≦（Σ tk×exp（-25000／Tk））／（d2 ×［質量%Si］add ）≦ 2.2×10-4・・（１）
ここでTkは浸珪開始後に鋼板が通過する炉内各ゾーンの温度、tkは炉内各ゾーンでの鋼板の滞在時間を示す。また、dは板厚(mm)、［質量%Si］addは浸珪によるSi添加量（板厚方向Si平均濃度の増加量）を示す。
なお炉内温度が連続的に変化する場合は、Σ tk×exp（-25000／Tk）が同じとなるように一定温度、一定時間で熱処理したものとみなすものとする。例えば、1200℃から700℃まで5分間で冷却される場合、Σ（tk×exp（-25000／Tk））〜1.9×10-6であるから、これは1200℃で45秒間熱処理されたものとみなす。 When Si is added by the vapor-phase siliconization method, it is assumed that the Si-based reaction gas is sufficiently supplied, and the temperature history from the start of siliconization to the completion of siliconization and cooling (each in the furnace If the temperature of the zone and the residence time of the plate are determined, the Si concentration profile in the plate thickness direction is almost uniquely determined corresponding to the plate thickness and the amount of Si added (the amount of silicon immersion). When siliconizing a grain-oriented electrical steel sheet having a Si content of 2.5 to 4%, when carried out under the following conditions, a Si concentration profile that significantly reduces high-frequency iron loss of the grain-oriented electrical steel sheet can be obtained. The following formula (1) shows the relationship between the processing temperature and time for diffusing Si supplied from the plate surface by vapor phase siliconization to the inside so as to have a predetermined concentration distribution. Therefore, what is expressed by the equation (1) is a heat treatment parameter for forming an appropriate Si concentration distribution by vapor phase siliconization, and by controlling this value, Si that gives an appropriate internal stress in the steel sheet. Concentration distribution can be formed and high-frequency iron loss can be reduced.
1.3 × 10 −4 ≦ (Σ t k × exp (−25000 / T k )) / (d 2 × [mass% Si] add ) ≦ 2.2 × 10 −4 (1)
Here, T k represents the temperature of each zone in the furnace through which the steel sheet passes after the start of siliconization, and t k represents the residence time of the steel sheet in each zone in the furnace. Further, d represents the plate thickness (mm), and [mass% Si] add represents the amount of Si added by the silicon immersion (increase amount of Si average concentration in the plate thickness direction).
If the temperature in the furnace changes continuously, it is assumed that the heat treatment is performed at a constant temperature and for a certain time so that Σ t k × exp (−25000 / T k ) is the same. For example, when cooled from 1200 ° C. to 700 ° C. for 5 minutes, Σ (t k × exp (−25000 / T k )) ˜1.9 × 10 −6 , so this was heat treated at 1200 ° C. for 45 seconds Consider it a thing.

上記式（１）の値が1.3×10-4より小さい場合でも、歪取焼鈍などの後工程で比較的高い温度で焼鈍してSi濃度分布を適正化することが可能であるが、実際は表層のSi濃度が高くなりすぎると浸珪処理の際に板変形を生じたり、その後の加工の際、剪断部に割れや欠けが発生しやすくなるため、実質的な下限として上記の値を定めた。一方、上記式（１）の値が2.2×10-4より大きい場合はSiの拡散・均一化が進み、内部応力が低下して高周波鉄損低減効果が失われてしまう。 Even if the value of the above equation (1) is smaller than 1.3 × 10 −4, it is possible to anneal Si at a relatively high temperature in the subsequent process such as strain relief annealing, but to optimize the Si concentration distribution. If the Si concentration is too high, plate deformation will occur during the siliconization treatment, and cracks and chips will likely occur in the sheared part during subsequent processing, so the above value was set as the practical lower limit. . On the other hand, when the value of is greater than 2.2 × 10- 4 above formula (1) proceeds diffusion-uniformity of the Si, the internal stress is lost high-frequency iron loss reduction effect decreases.

また連続ラインで浸珪処理する場合は、700℃以下の温度域でSi濃度プロファイルは短時間では変化しないため、（１）式の計算は実質的に700℃までとしてもよい。   In addition, when siliconizing is performed on a continuous line, since the Si concentration profile does not change in a short time in a temperature range of 700 ° C. or lower, the calculation of equation (1) may be substantially up to 700 ° C.

なお、先に特許文献４として記載した特開２０００−４５０５３号にいくつかの板厚Si濃度プロファイルの例が示されている。しかしながら、特許文献４では、浸珪処理および拡散処理後に絶縁被膜の形成（塗布焼き付け）や歪取焼鈍が行われており、本発明ではこのような浸珪後の熱処理条件に留意する必要があるが、特許文献４における高周波鉄損は同じ板厚について、本発明で得られる鉄損を上回っていることから、いずれも本発明の上記式（１）や（２）を満足するものではなく、本発明で所期する内部応力分布は得られていないことを述べておく。   In addition, Japanese Patent Application Laid-Open No. 2000-45053 previously described as Patent Document 4 shows some examples of plate thickness Si concentration profiles. However, in Patent Document 4, an insulating film is formed (coating baking) and strain relief annealing is performed after the siliconization treatment and the diffusion treatment. In the present invention, it is necessary to pay attention to such heat treatment conditions after the siliconization. However, since the high-frequency iron loss in Patent Document 4 exceeds the iron loss obtained by the present invention for the same plate thickness, neither satisfies the above formulas (1) and (2) of the present invention, It should be noted that the desired internal stress distribution is not obtained in the present invention.

絶縁被膜を被覆
浸珪処理した方向性電磁鋼板は、絶縁被膜を塗布された後、乾燥・焼き付け工程を通る。この時、乾燥・焼き付け炉温度は600℃未満が好ましい。600℃未満であれば、応力緩和が起こらず高周波鉄損は上昇しない。
しかしながら、例えば、設計的事項等の条件により600℃以上で熱処理される場合がある。このような場合は、時間とともに内部応力が緩和していくため高周波鉄損は上昇する。そこで400〜800℃の範囲で最適Si濃度の試料を熱処理したところ、以下の条件を満たしていれば600℃以上で熱処理したとしても同板厚、同Si量の均一材より低鉄損化であることが分かった。これより、下記式（２）を満足する温度および時間で行うことで、同板厚、同Si量の均一材より低鉄損化の方向性電磁鋼板が得られることになる。
（Σ t'k×exp（-25000／T'k））／（d2 ×［質量%Si］add）≦ 0.2×10-4 ・・式（２）
ここでT'k(K)は鋼板が熱処理される温度、t'kはその温度での保持時間を示す。
なお連続的に温度が変化する場合は、Σ t'k×exp（-25000／T'k）が等しくなるように一定温度で一定時間保持するものとみなす。 The grain-oriented electrical steel sheet coated with an insulating coating is subjected to a drying and baking process after the insulating coating is applied. At this time, the drying / baking furnace temperature is preferably less than 600 ° C. If it is less than 600 ° C, stress relaxation does not occur and high-frequency iron loss does not increase.
However, for example, heat treatment may be performed at 600 ° C. or higher depending on conditions such as design matters. In such a case, the internal stress relaxes with time, so the high-frequency iron loss increases. Therefore, when a sample with an optimal Si concentration was heat treated in the range of 400 to 800 ° C, even if heat treatment was performed at 600 ° C or higher if the following conditions were satisfied, the iron loss was lower than that of a uniform material with the same plate thickness and Si content. I found out. From this, by carrying out at the temperature and time which satisfy | fill following formula (2), the grain-oriented electrical steel sheet of lower iron loss than the uniform material of the same board thickness and the same Si quantity will be obtained.
(Σ t ′ k × exp (−25000 / T ′ k )) / (d 2 × [mass% Si] add ) ≦ 0.2 × 10 −4 Formula (2)
Here, T ′ k (K) is the temperature at which the steel sheet is heat treated, and t ′ k is the holding time at that temperature.
In the case where continuous temperature changes shall be deemed to be held Σ t 'k × exp (-25000 / T' k) a predetermined time at a constant temperature so that equal.

歪取焼鈍
浸珪処理した方向性電磁鋼板は、スリット、剪断、プレス等の様々な加工工程を経て鉄心として組み立てられるが、その際に歪取焼鈍が施されることがある。この場合も600℃以上での焼鈍で内部応力が緩和するため、上述の式（２）を満たすように歪取焼鈍温度と時間を定める必要がある。
また絶縁被膜の乾燥・焼き付けを600℃以上で行い、加工後に歪取焼鈍を施す場合は、被膜の熱処理工程と歪取焼鈍工程を合わせて式（２）を満たすような温度、時間を設定する必要がある。 The grain-oriented electrical steel sheet treated with strain relief annealing is assembled as an iron core through various processing steps such as slitting, shearing, pressing, and the like, and sometimes stress relief annealing is performed. Also in this case, since the internal stress is relaxed by annealing at 600 ° C. or higher, it is necessary to determine the strain relief annealing temperature and time so as to satisfy the above-described formula (2).
In addition, when the insulating film is dried and baked at 600 ° C. or higher and is subjected to strain relief annealing after processing, the temperature and time are set so as to satisfy Equation (2) by combining the heat treatment process and the strain relief annealing process of the film. There is a need.

表2に示す成分組成からなる鋼スラブを1400℃に加熱後、熱間圧延し2.5mmの熱延コイルとした。次いで、1000℃で1分間の熱延板焼鈍を施し、その後、一回目の冷間圧延（1.5mm厚までの圧延）、1100℃で1分間の中間焼鈍、二回目の冷間圧延（0.21mm厚までの圧延）を施して、製品板厚とした。
その後、850℃の湿H2中で脱炭・一次再結晶焼鈍を行った後、鋼板表面に、MgOを主成分とし、塩化マグネシウム1wt%と塩化アンチモン1wt%を含有させた焼鈍分離剤をスラリー塗布し、最終仕上げ焼鈍を施した。最終仕上げ焼鈍は、850℃で15時間保持した後、1200℃に昇温して、乾H2中で純化処理を行う方法を採った。以上により、表面のフォルステライト被膜が剥落した被膜なし方向性電磁鋼板を作製した。この鋼板はGoss方位からなる２次再結晶組織を呈し、B8=1.78〜1.92Tであり、Al量は0.003〜0.006%であった。
得られた方向性電磁鋼板に対して、窒素雰囲気中、昇温速度15℃/secで1200℃まで加熱した後、同温度で四塩化珪素濃度18%を含む窒素ガスを供給して90秒浸珪処理し、続いて1200℃で160秒拡散処理を行った後、600℃以下まで2分間で冷却した。このときSi添加量は1.4質量%で、式（１）：（Σ tk×exp（-25000／Tk））／（d2 ×［質量%Si］add）は1.8×10-4となった。また試料断面のSi濃度分布をEPMAにて確認したところ、表層と板厚中央部のSi濃度差は2.6%であった。
さらに、上記方向性電磁鋼板から30×280mmの試験片をレーザー加工機にて切り出し、N2中で表3に示す条件で熱処理（歪取焼鈍）をした後、JIS C 2556の方法に準じて、高周波鉄損W1/10k、1T励磁した時の磁歪振幅等の磁気特性を測定した。また、試料の内部応力は、磁気測定終了後に試料の片面のみ板厚中心部まで化学研磨して反った板の曲率半径から算出した。得られた結果を成分組成と併せて表2に示す。 A steel slab having the composition shown in Table 2 was heated to 1400 ° C. and hot-rolled to obtain a 2.5 mm hot-rolled coil. Next, hot-rolled sheet annealing was performed at 1000 ° C for 1 minute, and then the first cold rolling (rolling to a thickness of 1.5 mm), intermediate annealing at 1100 ° C for 1 minute, and the second cold rolling (0.21 mm) Rolling to a thickness) to obtain a product thickness.
After decarburization and primary recrystallization annealing in wet H 2 at 850 ° C, a slurry of annealing separator containing MgO as the main component, magnesium chloride 1wt% and antimony chloride 1wt% on the steel sheet surface Application and final finish annealing. The final finish annealing was carried out by maintaining the temperature at 850 ° C. for 15 hours, then raising the temperature to 1200 ° C. and performing a purification treatment in dry H 2 . Thus, a non-coated grain-oriented electrical steel sheet with the surface forsterite film peeled off was produced. This steel sheet exhibited a secondary recrystallized structure composed of Goss orientation, B8 = 1.78 to 1.92 T, and the Al content was 0.003 to 0.006%.
The obtained grain-oriented electrical steel sheet was heated to 1200 ° C at a temperature increase rate of 15 ° C / sec in a nitrogen atmosphere, and then nitrogen gas containing a silicon tetrachloride concentration of 18% was supplied at the same temperature for 90 seconds. Silica treatment was performed, followed by diffusion treatment at 1200 ° C. for 160 seconds, and then cooled to 600 ° C. or lower for 2 minutes. At this time, the amount of Si added is 1.4% by mass, and the formula (1): (Σt k × exp (−25000 / T k )) / (d 2 × [mass% Si] add ) is 1.8 × 10 −4. It was. Further, when the Si concentration distribution of the sample cross section was confirmed by EPMA, the difference in Si concentration between the surface layer and the central portion of the plate thickness was 2.6%.
Furthermore, after cutting out a 30 x 280 mm test piece from the grain-oriented electrical steel sheet with a laser processing machine and performing heat treatment (strain relief annealing) under the conditions shown in Table 3 in N 2 , according to the method of JIS C 2556 Magnetic characteristics such as magnetostriction amplitude when 1T excitation was performed were measured. Further, the internal stress of the sample was calculated from the radius of curvature of the warped plate after chemical polishing up to the center of the plate thickness only on one side of the sample after completion of the magnetic measurement. The obtained results are shown in Table 2 together with the component composition.

表2より、本発明例では、きわめて低い高周波鉄損を示しているのがわかる。また、磁歪も小さくなっている。
一方、条件から外れた場合、Siを均一化して内部応力を除去した比較材と比べて高周波鉄損W10/1kが増加することがわかる。なお800℃×5hrの歪取焼鈍後の試料表層と板厚中央部のSi濃度差は2.5%であり、焼鈍前のSi濃度プロファイルと比べて大きな違いは認められなかった。 From Table 2, it can be seen that the example of the present invention shows extremely low high-frequency iron loss. Also, the magnetostriction is small.
On the other hand, when the condition is not satisfied, it can be seen that the high-frequency iron loss W10 / 1k increases as compared with the comparative material in which Si is made uniform and internal stress is removed. Note that the difference in Si concentration between the surface layer of the sample after 800 ° C x 5 hours of strain relief annealing and the central portion of the plate thickness was 2.5%, and no significant difference was observed compared to the Si concentration profile before annealing.

表２記載の鋼種Bを用い、実施例１に従って板厚0.21mmの方向性電磁鋼板を作製した後、これを冷間圧延して板厚0.10mm、0.05mmのリロール板を作製した。この試料を100%N2中で15℃/sで1100℃まで加熱し60秒保持したところ、Goss方位からなる100μm未満の再結晶組織が得られ、板厚0.10mmではB8＝1.74T、板厚0.075mmでは1.79Tを示した。このように二次再結晶後に冷間圧延して得られた方向性電磁鋼板（リロール板）を、窒素雰囲気中、昇温速度15℃/secで1100℃まで加熱した後、同温度で四塩化珪素濃度15%を含む窒素ガスを供給し、浸珪時間、拡散温度および時間を変化させて種々の浸珪試料を作製した。 A steel sheet B shown in Table 2 was used to produce a grain-oriented electrical steel sheet having a sheet thickness of 0.21 mm according to Example 1, and then cold-rolled to prepare a rerolled sheet having a sheet thickness of 0.10 mm and 0.05 mm. When this sample was heated to 1100 ° C at 15 ° C / s in 100% N 2 and held for 60 seconds, a recrystallized structure of less than 100 µm consisting of Goss orientation was obtained, B8 = 1.74 T, plate thickness of 0.10 mm A thickness of 0.075 mm showed 1.79 T. The grain-oriented electrical steel sheet (reroll sheet) obtained by cold rolling after secondary recrystallization in this way is heated to 1100 ° C at a temperature increase rate of 15 ° C / sec in a nitrogen atmosphere, and then tetrachlorided at the same temperature. Nitrogen gas containing a silicon concentration of 15% was supplied, and various types of siliconized samples were prepared by changing the siliconizing time, diffusion temperature and time.

以上により得られた試料をレーザー加工機にて長手が圧延方向となるように30×280mmの試験片に切り出し、歪取焼鈍相当の熱処理を施した後、磁気特性はJIS C 2556 電磁鋼板単板磁気特性試験方法に準じて行った。
試料の内部応力は、磁気測定終了後に試料の片面のみ板厚中心部まで化学研磨して反った板の曲率半径から算出した。
得られた結果を表４に示す。 The sample obtained above was cut with a laser processing machine into a 30 x 280 mm test piece so that the length was in the rolling direction, and after heat treatment equivalent to strain relief annealing, the magnetic properties were JIS C 2556 electrical steel sheet single plate The test was performed according to the magnetic property test method.
The internal stress of the sample was calculated from the radius of curvature of the warped plate after chemical polishing to the center of the plate thickness only on one side of the sample after completion of the magnetic measurement.
Table 4 shows the obtained results.

表4より、本発明例では極めて低い高周波鉄損を示す。これは、浸珪条件として式（１）（２）を満足することでより効果的に内部応力が形成されていることによるものであり、その結果として、極めて低い高周波鉄損を示したといえる。
一方、条件を外れたものは、同程度のSi量を含むSi均一材（内部応力除去材）と同等か、より高い鉄損を示した。 From Table 4, the example of the present invention shows extremely low high-frequency iron loss. This is because internal stress is more effectively formed by satisfying the equations (1) and (2) as the siliconizing conditions, and as a result, it can be said that extremely low-frequency iron loss was exhibited.
On the other hand, those out of the condition showed an iron loss equivalent to or higher than that of a uniform Si material (internal stress relief material) containing the same amount of Si.

C:0.07%、Si:3.2%、Mn:0.08%、Al:0.025%、N:0.008%、Se:0,02%、Sb:0.03%を含有し、残部はFeおよび不可避的不純物からなる鋼スラブを、1400℃に加熱後、熱間圧延し2.5mmの熱延コイルとした。次いで、1000℃で1分間の熱延板焼鈍を施し、その後、一回目の冷間圧延(1.5m厚までの圧延)、1100℃で1分間の中間焼鈍、二回目の冷間圧延(0.23mm厚までの圧延)を施して、製品板厚とした。   Steel containing C: 0.07%, Si: 3.2%, Mn: 0.08%, Al: 0.025%, N: 0.008%, Se: 0,02%, Sb: 0.03%, the balance being Fe and inevitable impurities The slab was heated to 1400 ° C. and hot-rolled to obtain a 2.5 mm hot rolled coil. Then, hot-rolled sheet annealing was performed at 1000 ° C. for 1 minute, and then the first cold rolling (rolling to a thickness of 1.5 m), intermediate annealing at 1100 ° C. for 1 minute, and the second cold rolling (0.23 mm) Rolling to a thickness) to obtain a product plate thickness.

その後、850℃の湿H2中で脱炭・一次再結晶焼鈍を行った後、鋼板表面に、MgOを主成分とし、塩化マグネシウム1wt%と塩化アンチモン1wt%を含有させた焼鈍分離剤をスラリー塗布し、最終仕上げ焼鈍を施した。最終仕上げ焼鈍は、850℃で15時間保持した後、1200℃に昇温して、乾H2中で純化処理を行う方法を採った。かくして表面のフォルステライト被膜が剥落した膜なし珪素鋼板を作製した。この鋼板はゴス方位からなる2次再結晶組織を呈し、B8=1.86Tであった。 After decarburization and primary recrystallization annealing in wet H 2 at 850 ° C, a slurry of annealing separator containing MgO as the main component, magnesium chloride 1wt% and antimony chloride 1wt% on the steel sheet surface Application and final finish annealing. The final finish annealing was carried out by maintaining the temperature at 850 ° C. for 15 hours, then raising the temperature to 1200 ° C. and performing a purification treatment in dry H 2 . Thus, a filmless silicon steel sheet with the surface forsterite film peeled off was produced. This steel sheet exhibited a secondary recrystallized structure consisting of Goth orientation and B8 = 1.86T.

以上により得られた試料を、窒素雰囲気中、昇温速度15℃/Secで1200℃まで加熱した後、1200℃で四塩化珪素濃度18%を含む窒素ガスを供給して浸珪・拡散処理し、種々のSi濃度分布を有する試料を得た。なお浸珪後の試料の平均Si濃度は浸珪前後の重量減少率から求め、表層および板厚中心部のSi濃度は断面EPMAから求め、圧延方向の内部応力は図3に示す方法により求めた。
次いで、磁気特性を測定した。磁気特性は圧延方向及び圧延直角方向が長手となるようにそれぞれ30×280mmの板を切り出して単板磁気試験機にて測定した。なお結晶配向性を示す圧延方向及び圧延直角方向の磁束密度の比B10(L)／B10(C)は、1.32〜1.37であった。圧延直角方向の高周波鉄損W1/10kおよび1T励磁した時の磁歪振幅とともに各試料の特性を表５示す。なお試料9、10は板厚0.2mmの無方向性6.5%Si鋼板および板厚0.2mmのSi濃度勾配を有する無方向性5.5%Si鋼板の特性であり、比較のために示したものである。 The sample obtained above was heated to 1200 ° C in a nitrogen atmosphere at a rate of temperature increase of 15 ° C / Sec, and then subjected to siliconization and diffusion treatment by supplying nitrogen gas containing 18% silicon tetrachloride at 1200 ° C. Samples having various Si concentration distributions were obtained. The average Si concentration of the sample after siliconization was determined from the weight loss rate before and after siliconization, the Si concentration at the surface layer and the center of the plate thickness was determined from the cross-section EPMA, and the internal stress in the rolling direction was determined by the method shown in FIG. .
Next, the magnetic properties were measured. The magnetic properties were measured with a single plate magnetic tester by cutting out 30 × 280 mm plates so that the rolling direction and the perpendicular direction of rolling were the longitudinal direction. The ratio B10 (L) / B10 (C) of the magnetic flux density in the rolling direction and the direction perpendicular to the rolling direction showing the crystal orientation was 1.32 to 1.37. Table 5 shows the characteristics of each sample together with the high-frequency iron loss W1 / 10k in the direction perpendicular to the rolling and the magnetostriction amplitude when 1T is excited. Samples 9 and 10 are the characteristics of a non-oriented 6.5% Si steel plate with a thickness of 0.2 mm and a non-oriented 5.5% Si steel plate with a Si concentration gradient of 0.2 mm, which are shown for comparison. .

表5より、内部応力が70MPa未満の比較例では、圧延直角方向の高周波鉄損は高く、磁歪も極めて高い。
一方、内部応力が70MPa以上の本発明例では、圧延直角方向に磁化した場合、低鉄損かつ低磁歪を示す。
内部応力が160MPaを超える場合は鉄損が増大し、比較材として挙げた板厚0.2mの6.5%Si鋼板より劣位となった。 From Table 5, in the comparative example where the internal stress is less than 70 MPa, the high-frequency iron loss in the direction perpendicular to the rolling is high, and the magnetostriction is also extremely high.
On the other hand, in the example of the present invention having an internal stress of 70 MPa or more, when magnetized in the direction perpendicular to the rolling, low iron loss and low magnetostriction are exhibited.
When the internal stress exceeded 160 MPa, the iron loss increased and was inferior to the 6.5% Si steel sheet with a thickness of 0.2 m mentioned as a comparative material.

実施例３にて得られた板厚0.23mmの一方向性電磁鋼板の表面を洗浄した後、冷間圧延して板厚0.075mmとした。次いで、この試料を1100℃以上の温度で種々の時間焼鈍し、圧延方向のB8として1.65〜1.85Tを示す材料が得られた。これらの試料を窒素雰囲気中、昇温速度15℃/Secで1100℃まで加熱し、1100℃で四塩化珪素濃度15%を含む窒素ガスを供給し、90秒浸珪処理し、160秒拡散処理して取り出した。浸珪処理後の試料を圧延方向、圧延直角方向が長手となるようにそれぞれ切り出し、結晶配向性を表すB10(L/C)を評価したところ、1.09〜1.33の値が得られた。   After cleaning the surface of the unidirectional electrical steel sheet having a thickness of 0.23 mm obtained in Example 3, the steel sheet was cold-rolled to a thickness of 0.075 mm. Subsequently, this sample was annealed at a temperature of 1100 ° C. or higher for various times, and a material showing 1.65 to 1.85 T as B8 in the rolling direction was obtained. These samples were heated to 1100 ° C in a nitrogen atmosphere at a heating rate of 15 ° C / Sec, supplied with nitrogen gas containing 15% silicon tetrachloride at 1100 ° C, subjected to siliconization for 90 seconds, and diffusion treatment for 160 seconds And took it out. When the sample after the siliconization treatment was cut out so that the rolling direction and the direction perpendicular to the rolling direction were longitudinal, and B10 (L / C) representing the crystal orientation was evaluated, values of 1.09 to 1.33 were obtained.

次に、これら結晶配向性の異なる試料の圧延直角方向について、高周波鉄損W1/10kおよび1T励磁での磁歪振幅を測定した。なお、各測定方法は、実施例３と同様である。得られた結果を表６に示す。   Next, the high-frequency iron loss W1 / 10k and the magnetostriction amplitude in 1T excitation were measured in the direction perpendicular to the rolling direction of samples having different crystal orientations. In addition, each measuring method is the same as that of Example 3. The results obtained are shown in Table 6.

表6より、B10(L)／B10(C)の値が1.2未満の比較例では高い磁歪を示すのに対し、内部応力が70〜160MPaであり、B10(L)／B10(C)の値が1.2以上の本発明例では磁歪振幅が1×10−6未満と極めて低い磁歪を示した。また高周波鉄損もB10(L)／B10(C)の値が1.2以上の場合、同板厚の6.5%Si鋼板より低い値を示した。 From Table 6, the comparative example with B10 (L) / B10 (C) values less than 1.2 shows high magnetostriction, while the internal stress is 70-160 MPa, and the values of B10 (L) / B10 (C) However, in the present invention example of 1.2 or more, the magnetostriction amplitude was very low, less than 1 × 10 −6 . Also, the high frequency iron loss was lower than the 6.5% Si steel plate of the same thickness when the value of B10 (L) / B10 (C) was 1.2 or more.

本発明の方向性電磁鋼板は、高周波特性に優れるため、変圧器、モータ、リアクトル等を中心に鉄心材料として多様な用途に用いることができる。   Since the grain-oriented electrical steel sheet of the present invention is excellent in high-frequency characteristics, it can be used for various applications as a core material mainly for transformers, motors, reactors and the like.

Claims (12)

質量％で、C：0.005％以下、Si：4〜7％、Mn：0.005〜2.5％、Sol.Al：0.0080%以下、S：0.003%以下、N：0.005%以下を含有し、残部Feおよび不可避的不純物からなる方向性電磁鋼板であって、Si濃度が板厚中心部より板表面において高くなるSi濃度勾配を有し、圧延方向と平行な方向に内部応力として、70〜160MPaの範囲で板厚中心部に圧縮応力、板表面に板厚中心部と同じ大きさの引張応力を有し、表裏面での引張応力の差が8MPa以下であることを特徴とする方向性電磁鋼板。
ここで板厚中心部および板表面の応力とは、実質的に反りのない平坦な板を幅30mm以下、長さ100mm以上に切断し、表裏面のうち片面のみ板厚の1/2深さまで化学研磨した際に生じる長手方向の反りの曲率半径から求めた値である。 In mass%, C: 0.005% or less, Si: 4-7%, Mn: 0.005-2.5%, Sol.Al: 0.0080% or less, S: 0.003% or less, N: 0.005% or less, the balance Fe and It is a grain-oriented electrical steel sheet made of inevitable impurities, and has a Si concentration gradient in which the Si concentration is higher on the plate surface than the center of the plate thickness, and as an internal stress in the direction parallel to the rolling direction, in the range of 70 to 160 MPa. compressive stress in the thickness center portion, have a same magnitude of the tensile stress and the thickness center portion in a plate surface, oriented electrical steel sheet, wherein the difference between the tensile stress of the front and back surfaces is not more than 8 MPa.
Here, the stress at the center of the plate thickness and the surface of the plate means that a flat plate with substantially no warpage is cut to a width of 30 mm or less and a length of 100 mm or more, and only one side of the front and back surfaces is up to 1/2 the plate thickness. It is a value obtained from the radius of curvature of the warp in the longitudinal direction generated when chemical polishing is performed. 圧延方向と圧延直角方向の1000A／mにおける磁束密度の比：Ｂ10(L)／B10(C)が1.2以上であり、かつ、圧延直角方向を1Tで励磁したときの磁歪振幅が1×10−６未満であることを特徴とする請求項１に記載の方向性電磁鋼板。
ただし、Ｂ10(L)：圧延方向の磁束密度、B10(C)：圧延直角方向の磁束密度である。 The ratio of the magnetic flux density at 1000A / m of rolling direction and the direction perpendicular to the rolling direction: B10 (L) / B10 ( C) is not less than 1.2, and the magnetostriction amplitude when the direction perpendicular to the rolling direction was excited by 1T is 1 × 10 The grain- oriented electrical steel sheet according to claim 1, wherein the grain- oriented electrical steel sheet is less than -6 .
However, B10 (L): Magnetic flux density in the rolling direction, B10 (C): Magnetic flux density in the direction perpendicular to the rolling direction. さらに、質量％で、Sb:0.005〜0.1％、Sn:0.005〜0.5％、Bi:0.001〜0.05％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする請求項１または２に記載の方向性電磁鋼板。   Furthermore, it contains at least one element selected from Sb: 0.005 to 0.1%, Sn: 0.005 to 0.5%, and Bi: 0.001 to 0.05% by mass%. The grain-oriented electrical steel sheet described in 1. さらに、質量％で、Cr:0.01〜0.8％、Ni:0.01〜1.0％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする請求項１〜３いずれかに記載の方向性電磁鋼板。   The directionality according to any one of claims 1 to 3, further comprising at least one element selected from Cr: 0.01 to 0.8% and Ni: 0.01 to 1.0% by mass%. Electrical steel sheet. 前記板厚中心部と前記板表面とのSi濃度差が質量％で1.5〜4.0％であることを特徴とする請求項１〜４のいずれかに記載の方向性電磁鋼板。 Oriented electrical steel sheet according to any one of claims 1 to 4, wherein the Si concentration difference between the plate thickness center and the plate surface is 1.5 to 4.0% in mass%. 板厚が0.05〜0.25mmであることを特徴とする請求項１〜５いずれかに記載の方向性電磁鋼板。 The grain-oriented electrical steel sheet according to any one of claims 1 to 5 , wherein a plate thickness is 0.05 to 0.25 mm. 質量％で、C：0.005％以下、Si：４〜７％、Mn：0.005〜2.5％、Sol.Al：0.0080%以下、S：0.003%以下、N：0.005%以下を含有し、残部Feおよび不可避的不純物からなる成分組成を有する方向性電磁鋼板の製造方法であって、板厚0.05〜0.25mmであるフォルステライト被膜を有しない方向性電磁鋼板、または二次再結晶した方向性電磁鋼板を冷延し板厚0.05〜0.25mmとした鋼板のいずれかを、1000℃以上に加熱しSi系のガスと反応させることにより鋼板表面からSiを添加する浸珪処理を行うに際し、浸珪開始から600℃以下に冷却されるまでに鋼板が通過する炉内各ゾーンの温度をTk(K)、炉内各ゾーンでの鋼板の滞在時間をtk(秒)とした時、下記式（１）を満足することを特徴とする方向性電磁鋼板の製造方法。
1.3×10-4≦（Σ tk×exp（-25000／Tk））／（d2 ×［質量%Si］add ）≦ 2.2×10-4 ・・（１）
ただし、dは板厚(mm)、［質量%Si］addは浸珪によるSi添加量を示す。 In mass%, C: 0.005 % or less, Si: 4-7%, Mn: 0.005-2.5% , Sol.Al: 0.0080 % or less, S: 0.003 % or less, N: 0.005 % or less, the balance Fe and a method of manufacturing a grain-oriented electrical steel sheet to have a component composition consisting of unavoidable impurities, grain-oriented electrical steel sheet having no forsterite film is a thickness 0.05 to 0.25 mm, or secondary recrystallized oriented electrical When carrying out the siliconization treatment in which Si is added from the steel sheet surface by heating any one of the steel sheets having a thickness of 0.05 to 0.25 mm by cold rolling to a temperature of 1000 ° C. or more and reacting with a Si-based gas, When the temperature of each zone in the furnace through which the steel plate passes from the start until it is cooled to 600 ° C or lower is T k (K), and the residence time of the steel plate in each zone in the furnace is t k (seconds), the following formula A method for producing a grain-oriented electrical steel sheet, characterized by satisfying (1).
1.3 × 10 −4 ≦ (Σ t k × exp (−25000 / T k )) / (d 2 × [mass% Si] add ) ≦ 2.2 × 10 −4 (1)
However, d is the plate thickness (mm), and [mass% Si] add indicates the amount of Si added by siliconization. さらに、成分組成として、質量％で、Sb:0.005〜0.1％、Sn:0.005〜0.5％、Bi:0.001〜0.05％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする請求項７に記載の方向性電磁鋼板の製造方法。 Furthermore, as a component composition, it contains at least one element selected from Sb: 0.005 to 0.1%, Sn: 0.005 to 0.5%, and Bi: 0.001 to 0.05% by mass%. Item 8. A method for producing a grain-oriented electrical steel sheet according to Item 7 . さらに、成分組成として、質量％で、Cr:0.01〜0.8％、Ni:0.01〜1.0％のうちから選ばれた少なくとも1種の元素を含有することを特徴とする請求項７または８に記載の方向性電磁鋼板の製造方法。 Further, as the chemical composition, in mass%, Cr: 0.01~0.8%, Ni : according to claim 7 or 8, characterized in that it contains at least one element selected from among 0.01% to 1.0% A method for producing grain-oriented electrical steel sheets. 浸珪処理後の方向性電磁鋼板表面に、乾燥・焼き付け炉温度：600℃未満で絶縁被膜を被覆することを特徴とする請求項７〜９のいずれかに記載の方向性電磁鋼板の製造方法。 The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 9 , wherein the surface of the grain-oriented electrical steel sheet after the siliconization treatment is coated with an insulating coating at a drying / baking furnace temperature of less than 600 ° C. . 請求項７〜１０のいずれかに記載の浸珪処理後の方向性電磁鋼板を加工した後に鉄心に組み上げる鉄心組立工程において、600℃以上かつ下記式（２）を満足する温度および時間で歪取焼鈍を行うことを特徴とする鉄心の製造方法。
（Σ t'k×exp（-25000／T'k））／（d2 ×［質量%Si］add）≦ 0.2×10-4 ・・（２）
ただし、T'k(K)は歪取焼鈍の温度、t'k(秒)はその温度での保持時間を示す。 In the iron core assembly process of assembling the iron core after processing the grain oriented electrical steel sheet according to any one of claims 7 to 10 , distortion is removed at a temperature and time satisfying the following formula (2) at 600 ° C or higher. An iron core manufacturing method characterized by annealing.
(Σ t ′ k × exp (−25000 / T ′ k )) / (d 2 × [mass% Si] add ) ≦ 0.2 × 10 −4 (2)
However, T ′ k (K) indicates the temperature for strain relief annealing, and t ′ k (seconds) indicates the holding time at that temperature. 請求項７〜１０のいずれかに記載の浸珪処理後の方向性電磁鋼板表面に、乾燥・焼き付け炉温度：600℃以上で絶縁被膜を被覆する被膜コーティングと、これを加工した後に鉄心に組み上げる鉄心組立工程で歪取焼鈍を行う鉄心の製造方法において、前記被膜コーティングでの熱処理と前記歪取焼鈍とを合わせて、下記式（２）を満足する温度および時間で行うことを特徴とする鉄心の製造方法。
（Σ t'k×exp（-25000／T'k））／（d2 ×［質量%Si］add）≦ 0.2×10-4 ・・（２）
ただし、T'k(K)は被膜コーティング及び歪取焼鈍の各工程で熱処理される温度、t'k(秒)はその温度での保持時間を示す。 A coating film for coating an insulating film at a drying / baking furnace temperature: 600 ° C or higher on the surface of the grain-oriented electrical steel sheet after the siliconization treatment according to any one of claims 7 to 10 , and after assembling this, the iron core is assembled. In the manufacturing method of an iron core that performs strain relief annealing in an iron core assembling process, the heat treatment in the coating film and the stress relief annealing are performed at a temperature and time satisfying the following formula (2): Manufacturing method.
(Σ t ′ k × exp (−25000 / T ′ k )) / (d 2 × [mass% Si] add ) ≦ 0.2 × 10 −4 (2)
However, T ′ k (K) is the temperature at which the heat treatment is performed in each step of coating coating and strain relief annealing, and t ′ k (second) is the holding time at that temperature.
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