JP4358550B2

JP4358550B2 - Method for producing non-oriented electrical steel sheet with excellent rolling direction and perpendicular magnetic properties in the plate surface

Info

Publication number: JP4358550B2
Application number: JP2003128909A
Authority: JP
Inventors: 猛久保田; 洋介黒崎; 岳顕脇坂
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2003-05-07
Filing date: 2003-05-07
Publication date: 2009-11-04
Anticipated expiration: 2023-05-07
Also published as: JP2004332042A

Description

【０００１】
【発明の属する技術分野】
本発明は、電気機器鉄心材料として使用される、磁気特性の優れた無方向性電磁鋼板の製造方法に関するものであり、特に分割鉄心型回転機や小型ＥＩ型変圧器鉄心材料として望ましい、鋼板の板面内圧延方向とその板面内垂直方向磁気特性に優れた無方向性電磁鋼板の製造方法を提供するものである。
【０００２】
【従来の技術】
近年、電気機器、特に無方向性電磁鋼板がその鉄心材料として使用される回転機、中小型変圧器、電装品等の分野においては、世界的な電力・エネルギー節減、地球環境保全の動きの中で、高効率化と小型化の要請はますます強まりつつある。このような社会環境下において、当然無方向性電磁鋼板に対しても、その性能向上は喫緊の課題として強く要請されている。
【０００３】
周知のように、無方向性電磁鋼板においては、その性能向上に対して数多の手段がとられてきた。鉄損低減についてみると、一般には電気抵抗増大による渦電流損低減の観点から、ＳｉあるいはＡｌ等の含有量を高める方法がとられてきた。しかし、この方法では反面、磁束密度の低下は避け得ないという問題点があった。
【０００４】
また、単にＳｉ、あるいはＡｌ等の含有量を高めるのみではなく、Ｃ，Ｓ，Ｎ等の高純度鋼化や、特許文献１に記載されているようなＣａ添加等の化学的処置による不純物の無害化等による鉄損低減もなされてきた。さらに、特許文献２に記載されているような仕上焼鈍条件の工夫等の製造プロセス上の処置もなされてきた。一方、高磁束密度化についても、特許文献３に記載されているような熱延板焼鈍条件と冷延条件の工夫等の製造プロセス上の処置や、特許文献４に記載されているようなＳｎ，Ｃｕ等の合金元素添加による一次再結晶集合組織改善による処置等がなされてきた。
【０００５】
しかし、上記のような処置により無方向性電磁鋼板の磁気特性の向上はなされても、最近の回転機における高効率化の急速な進展に伴い多用化されるようになった分割鉄心型回転機の、あるいは小型ＥＩ型変圧器の鉄心材料として使用される場合には、それらの要請に十分に応え得るものではなかった。
左記要請に応えるためには、無方向性電磁鋼板の｛１００｝集合組織、特に｛１００｝＜００１＞集合組織を発達させ、鋼板の板面内圧延方向とその板面内垂直方向磁気特性を向上させることが望ましい。
【０００６】
無方向性電磁鋼板において｛１００｝集合組織を発達させる手段としては、特許文献５に記載されているように、冷間圧延の圧下率を８５％以上、望ましくは９０％以上の強圧下とし、かつ仕上焼鈍を７００〜１２００℃で２分〜１時間の長時間とする方法があるが、この場合に得られる無方向性電磁鋼板の集合組織はむしろ｛１００｝＜０ｖｗ＞系であり、鋼板の板面内圧延方向とその板面内垂直方向磁気特性を向上させるのに望ましい｛１００｝＜００１＞系とは異なる。
また、上記のような長時間仕上焼鈍を施すことは、生産性の低下や製造コストの上昇、さらには設備制約上の問題が生じ、実用化には至っていない。
【０００７】
【特許文献１】
特開平３−１２６８４５号公報
【特許文献２】
特開昭６１−２３１１２０号公報
【特許文献３】
特開平３−２９４４２２号公報
【特許文献４】
特開平５−１４０６４８号公報
【特許文献５】
特公昭５１−９４２号公報
【０００８】
【発明が解決しようとする課題】
上記に鑑み本発明は、無方向性電磁鋼板において｛１００｝集合組織、特に｛１００｝＜００１＞系集合組織を発達させ、分割鉄心型回転機や小型ＥＩ型変圧器鉄心材料として望ましい、鋼板の板面内圧延方向とその板面内垂直方向磁気特性に優れた無方向性電磁鋼板を通常の製造工程によって得る方法を提供するものである。
【０００９】
【課題を解決するための手段】
本発明者らは、無方向性電磁鋼板の通常の製造工程において、冷間圧延前の結晶組織制御と冷間圧延圧下との組み合わせにより｛１００｝集合組織、特に｛１００｝＜００１＞集合組織を発達させ、分割鉄心型回転機や小型ＥＩ型変圧器鉄心材料として望ましい、鋼板の板面内圧延方向とその板面内垂直方向磁気特性に優れた無方向性電磁鋼板が得られないかとの観点から鋭意研究を積み重ねた。
その結果、冷間圧延前の結晶粒径をある値以上に粗大化させることにより、冷間圧延の圧下率を適切に選べば、短時間連続仕上焼鈍で、鋼板の板面内圧延方向とその板面内垂直方向磁気特性を顕著に向上させることが可能であることを究明した。
【００１０】
本発明は上記知見に基づきなされたものであり、その要旨は以下の通りである。
（１）質量％で、
Ｃ：０．００２％以下、Ｓｉ：０．１％以上０．８％未満、
Ａｌ：０．３％以上２．０％以下、Ｍｎ：０．１％以上１．５％以下
を含有し、かつ、Ｓｉ＋２Ａｌ−Ｍｎ：２％以上で、
Ｓ：０．００２％以下、Ｎ：０．００２％以下、
Ｔｉ：０．００２％以下、
残部Ｆｅおよび不可避不純物元素よりなる鋼を熱間圧延後、熱延板焼鈍を施し、一回の冷間圧延により最終板厚とした後、仕上焼鈍を施して分割鉄心型回転機または小型ＥＩ型変圧器鉄心用の無方向性電磁鋼板を製造する方法において、熱延板焼鈍後の平均結晶粒径を３００μｍ以上とし、冷間圧延を圧下率８５％以上９５％以下で施し、仕上焼鈍を７００℃以上９５０℃以下で１０秒以上１分以下施し、板面内圧延方向と板面内垂直方向に｛１００｝＜００１＞組織を発達させたことを特徴とする無方向性電磁鋼板の製造方法。
（２）質量％でさらに、
Ｖ：０．００３％以下、Ｚｒ：０．００３％以下、
Ｎｂ：０．００３％以下、Ａｓ：０．００３％以下
よりなる鋼を用いることを特徴とする前記（１）記載の無方向性電磁鋼板の製造方法。
【００１１】
【発明の実施の形態】
以下、本発明を詳細に説明する。
まず、本発明の鋼成分の限定理由について述べる。
Ｃは、鉄損を高める有害な成分であり、磁気時効の原因ともなるので、０．００２％以下とする。
【００１２】
Ｓｉは、前記のように、電気抵抗を増大させて渦電流損を減少させることにより鉄損を低減する作用のある成分であり、この作用を奏するためには０．１％以上含有させる必要がある。一方その含有量が増えると、前記のように磁束密度が低下し、かつ硬度の上昇を招いて打ち抜き加工性を劣化させ、また無方向性電磁鋼板の製造工程そのものにおいても冷延等の作業性の低下、コスト高ともなるので、０．８％未満とする。
【００１３】
Ａｌも、前記のように、Ｓｉと同様に電気抵抗を増大させて渦電流損を減少させることにより、鉄損を低減する作用のある成分である。また熱延板焼鈍時の結晶粒成長性を促進する作用を有し、特に上記のようにＳｉ含有量が０．８％未満の場合にこの作用は顕著である。これらの作用を奏するためには０．３％以上含有させる必要がある。一方、その含有量が増えると磁束密度が低下し、かつ降伏比の減少を招いて打ち抜き加工性を劣化させるので、２．０％以下とする。
【００１４】
Ｍｎも、電気抵抗を増大させて渦電流損を減少させることにより、鉄損を低減する作用を有する。この目的のためには０．１％以上含有させる必要がある。しかしその含有量が増えると、熱延板焼鈍時の結晶粒成長性そのものが低下するので、１．５％以下とする。
【００１５】
尚、上記合金元素成分のＳｉ，Ａｌ，Ｍｎ相互の間には、Ｓｉ＋２Ａｌ−Ｍｎ：２％以上の関係を満足する必要がある。これは、Ｓｉ＋２Ａｌ−Ｍｎが２％未満では、α−γ変態が存在する化学成分系となり、無方向性電磁鋼板の製造工程における焼鈍時、特に本発明の特徴とする熱延板焼鈍時に変態が生じ、熱延板焼鈍後の結晶粒径の粗大化を阻害し、続く冷間圧延の圧下率制御をもってしても、仕上焼鈍後の｛１００｝＜００１＞系集合組織の発達が抑制され、鋼板の板面内圧延方向とその板面内垂直方向磁気特性の向上が阻まれるためである。
【００１６】
Ｓは、ＭｎＳ等の硫化物の微細析出により、熱間圧延後の再結晶および結晶粒成長を阻害し、熱延板焼鈍後の結晶粒径の粗大化、及びこれに伴う熱延板集合組織の｛１００｝富化を阻むので、０．００２％以下とする。
【００１７】
Ｎは、ＡｌＮをはじめＴｉＮ等の窒化物の微細析出により、熱間圧延後の再結晶及び結晶粒成長を阻害し、熱延板焼鈍後の結晶粒径の粗大化、及びこれに伴う熱延板集合組織の｛１００｝富化を阻むので、０．００２％以下とする。
【００１８】
Ｔｉは、再結晶温度を上昇させ、無方向性電磁鋼板の製造工程における焼鈍時に再結晶およびそれに続く結晶粒成長を遅らせる。また、無方向性電磁鋼板の磁気特性にとって好ましくない｛１１１｝集合組織を発達させる。さらに、ＴｉＮやＴｉＣ等の微細析出とも相俟って、熱延板焼鈍後の結晶粒径の粗大化、およびこれに伴う熱延板集合組織の｛１００｝富化を阻害するので、０．００２％以下とする。
【００１９】
Ｖ，Ｚｒ，Ｎｂは、ＶＮ，ＶＣ等の炭化物や窒化物の微細析出により、熱間圧延後の再結晶および結晶粒成長を阻害し、熱延板焼鈍後の結晶粒径の粗大化、およびこれに伴う熱延板集合組織の｛１００｝富化を阻むので、それぞれ０．００３％以下とする。
【００２０】
Ａｓは、それ自身では、本発明の鋼成分範囲内では上述のような微細析出物を形成することはない。ただし、Ａｓが含有されるとＭｎＳ等の硫化物の微細析出を促進し、熱間圧延後の再結晶および結晶粒成長を阻害することとなり、熱延板焼鈍後の結晶粒径の粗大化、およびこれに伴う熱延板集合組織の｛１００｝富化を阻むので、０．００３％以下とする。
上述の成分以外は、Ｆｅおよび不可避不純物元素である。
【００２１】
次に、本発明の特徴とする、熱延板焼鈍後の結晶粒径と冷間圧延の圧下率との組み合わせが磁気特性に及ぼす効果について述べる。
表１に示した成分の鋼スラブを２．８ｍｍ厚に熱間圧延後、表２に示した焼鈍条件で熱延板焼鈍を施し、熱延板焼鈍後の結晶粒径を変化させ、また冷間圧延圧下率も変化させ、７５０℃で３０秒の仕上焼鈍を施した後、試料を採取し、磁気特性（磁束密度：Ｂ₅₀）を測定した。その測定結果も併せて表２に示す。
【００２２】
【表１】

【００２３】
【表２】

【００２４】
表２から、冷間圧延前、すなわち熱延板焼鈍後の平均結晶粒径と冷間圧延の圧下率との組合わせにより、７５０℃で３０秒の短時間連続仕上焼鈍で、鋼板の板面内圧延方向とその板面内垂直方向磁気特性を向上できることがわかる。特に、熱延板焼鈍後の平均結晶粒径を３００μｍ以上に粗大化させ、かつ冷間圧延の圧下率を８７．５％に制御したＮｏ．５では、著しくＬ方向（鋼板の板面内圧延方向）とＣ方向（その板面内垂直方向）のＢ₅₀が両方とも高く、鋼板の板面内圧延方向とその板面内垂直方向磁気特性の優れた無方向性電磁鋼板が得られる。
【００２５】
この場合、熱延板焼鈍後の平均結晶粒径を３００μｍ以上に粗大化させることにより、熱延板集合組織の｛１００｝富化も促進されており、熱延板焼鈍後、すなわち冷間圧延前の平均結晶粒径の粗大化と｛１００｝集合組織が、冷間圧延の圧下率制御との相乗効果により、仕上焼鈍後の｛１００｝＜００１＞系集合組織の発達を促進し、鋼板の板面内圧延方向とその板面内垂直方向磁気特性の顕著な向上に寄与しているものと推察される。
【００２６】
このように本発明の特徴は、熱延板焼鈍後の結晶粒径と冷間圧延の圧下率との組合わせにより、短時間連続仕上焼鈍で、鋼板の板面内圧延方向とその板面内垂直方向磁気特性の優れた無方向性電磁鋼板を製造可能にすることにある。
【００２７】
熱延板焼鈍後の平均結晶粒径は３００μｍ以上にする必要がある。熱延板平均結晶粒径が３００μｍ未満では、冷間圧延の圧下率を制御しても鋼板の板面内圧延方向とその板面内垂直方向磁気特性を向上させることはできない。尚、本発明に規定した鋼の不純物元素含有量であれば、熱延板焼鈍条件すなわち焼鈍温度と時間を、無方向性電磁鋼板の通常の製造工程範囲内で、特に２分未満の短時間焼鈍条件で適宜選定することにより、熱延板焼鈍後の平均結晶粒径を３００μｍ以上にすることができる。
【００２８】
冷間圧延の圧下率は８５％以上９５％以下とする。８５％未満では磁気異方性が大きくなり、特に鋼板の板面内圧延方向の板面内垂直方向磁気特性が向上しない。一方９５％超では、磁気異方性は減少するものの、無方向性電磁鋼板の磁気特性にとって好ましくない｛１１１｝集合組織が発達し、鋼板の板面内圧延方向とその板面内垂直方向とも磁束密度が低下する。
【００２９】
仕上焼鈍は７００℃以上９５０℃以下で１０秒以上１分以下とする。７００℃未満では冷間圧延後の一次再結晶が不完全となり、鋼板の板面内圧延方向とその板面内垂直方向とも磁気特性が向上しない。一方９５０℃超では、磁気異方性は減少するものの、無方向性電磁鋼板の磁気特性にとって好ましくない｛１１１｝集合組織が発達し、鋼板の板面内圧延方向とその板面内垂直方向とも磁束密度が低下する。また１０秒未満では、結晶粒の整粒性が悪く、鋼板の板面内圧延方向とその板面内垂直方向とも磁束密度の低下や鉄損の増加を招く。一方１分超ではその効果が飽和し、かつ生産性の低下や製造コストの上昇をも招く。
【００３０】
尚、本発明の特徴とする化学成分を有する鋼は、転炉あるいは電気炉等で溶製され、連続鋳造あるいは造塊後の分塊圧延によりスラブとされた後、上記の熱間圧延以降の処理が施される。
【００３１】
【実施例】
次に本発明の実施例を示す。
（実施例１）
表３に示した成分の鋼を１．２ｍｍ厚、２．０ｍｍ厚、３．２ｍｍ厚、５．７ｍｍ厚にそれぞれ熱間圧延後、１０００℃で１分間の熱延板焼鈍を施し、０．２５ｍｍ厚に冷間圧延した後、８５０℃で３０秒の仕上焼鈍を施し、その後、試料を採取し、磁気特性を測定した。その測定結果を表４に示す。尚、Ｌ方向は鋼板の板面内圧延方向を、Ｃ方向は鋼板の圧延方向に板面内垂直方向を示す。
本発明により、鋼板の板面内圧延方向とその板面内垂直方向磁気特性の優れた無方向性電磁鋼板の製造が可能であることがわかる。
【００３２】
【表３】

【００３３】
【表４】

【００３４】
（実施例２）
表５に示した成分の鋼を４．０ｍｍ厚に熱間圧延後、１０２５℃で４５秒間の熱延板焼鈍を施し、０．３５ｍｍ厚に冷間圧延（冷間圧延の圧下率：９１．３％）した後、９００℃で２０秒の仕上焼鈍を施し、その後、試料を採取し、磁気特性を測定した。その測定結果を表６に示す。尚、Ｌ方向は鋼板の板面内圧延方向を、Ｃ方向は鋼板の圧延方向に板面内垂直方向を示す。
本発明により、鋼板の板面内圧延方向とその板面内垂直方向磁気特性の優れた無方向性電磁鋼板が得られることがわかる。
【００３５】
【表５】

【００３６】
【表６】

【００３７】
【発明の効果】
以上のように、本発明法によれば、鋼板の板面内圧延方向とその板面内垂直方向鋼板の磁気特性に優れた無方向性電磁鋼板を得ることができ、電気機器、特に分割鉄心型回転機や小型ＥＩ型変圧器鉄心材料として無方向性電磁鋼板が用いられる場合における要請に十分に応えることができ、その工業的価値は極めて高い。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties, which is used as an electrical equipment iron core material, and is particularly desirable as a split iron core type rotary machine or a small EI type transformer core material. The present invention provides a method for producing a non-oriented electrical steel sheet excellent in the in-plane rolling direction and the perpendicular magnetic characteristics in the in-plane direction.
[0002]
[Prior art]
In recent years, in the fields of electrical machinery, especially rotating machines, medium- and small-sized transformers, electrical components, etc. in which non-oriented electrical steel sheets are used as iron core materials, there is a trend of global power and energy saving and global environmental conservation. Therefore, the demand for higher efficiency and smaller size is increasing. Under such a social environment, of course, improvement of the performance of non-oriented electrical steel sheets is strongly demanded as an urgent issue.
[0003]
As is well known, many measures have been taken to improve the performance of non-oriented electrical steel sheets. In terms of iron loss reduction, in general, from the viewpoint of reducing eddy current loss due to an increase in electrical resistance, a method of increasing the content of Si or Al has been taken. However, this method has a problem that a decrease in magnetic flux density is inevitable.
[0004]
In addition to simply increasing the content of Si, Al, or the like, impurities such as C, S, N, etc. made of high purity steel, or chemical treatment such as Ca addition as described in Patent Document 1 are also introduced. Iron loss has been reduced by detoxification and the like. Furthermore, measures in the manufacturing process such as a device for finishing annealing as described in Patent Document 2 have been taken. On the other hand, with regard to increasing the magnetic flux density, treatments in the manufacturing process such as hot strip annealing conditions and cold rolling conditions as described in Patent Document 3 and Sn as described in Patent Document 4 Treatments have been made by improving the primary recrystallization texture by adding alloying elements such as Cu and Cu.
[0005]
However, even though the magnetic properties of the non-oriented electrical steel sheet have been improved by the above-described measures, the split iron core type rotary machine has come to be used frequently with the rapid progress of high efficiency in recent rotary machines. When used as an iron core material for a small EI transformer, it has not been possible to fully meet these requirements.
In order to respond to the request on the left, the {100} texture of non-oriented electrical steel sheets, especially {100} <001> texture, is developed, and the in-plane rolling direction of the steel sheet and the perpendicular magnetic characteristics in the surface are determined. It is desirable to improve.
[0006]
As a means for developing the {100} texture in the non-oriented electrical steel sheet, as described in Patent Document 5, the rolling reduction ratio of cold rolling is 85% or more, preferably 90% or more, In addition, there is a method in which the finish annealing is performed at 700 to 1200 ° C. for 2 minutes to 1 hour, but the texture of the non-oriented electrical steel sheet obtained in this case is rather a {100} <0vw> system, This is different from the {100} <001> system, which is desirable for improving the in-plane rolling direction and the vertical magnetic characteristics in the in-plane direction.
In addition, the above-described long-time finish annealing causes a decrease in productivity, an increase in manufacturing cost, and a problem in equipment restriction, and has not been put into practical use.
[0007]
[Patent Document 1]
JP-A-3-126845 [Patent Document 2]
JP 61-231120 A [Patent Document 3]
JP-A-3-294422 [Patent Document 4]
Japanese Patent Laid-Open No. 5-14648 [Patent Document 5]
Japanese Patent Publication No. 51-942 [0008]
[Problems to be solved by the invention]
In view of the above, the present invention develops a {100} texture, particularly a {100} <001> texture, in a non-oriented electrical steel sheet, and is desirable as a split core type rotating machine or a small EI type transformer core material. The present invention provides a method for obtaining a non-oriented electrical steel sheet excellent in the in-plane rolling direction and the perpendicular magnetic characteristics in the in-plane direction by a normal manufacturing process.
[0009]
[Means for Solving the Problems]
In the normal manufacturing process of the non-oriented electrical steel sheet, the present inventors have obtained a {100} texture, particularly a {100} <001> texture by combining crystal structure control before cold rolling and cold rolling reduction. The non-oriented electrical steel sheet excellent in the in-plane rolling direction of the steel sheet and the perpendicular magnetic property in the surface of the steel sheet, which is desirable as a split core type rotating machine or small EI type transformer core material, can be obtained. We have earnestly researched from the viewpoint.
As a result, by coarsening the crystal grain size before cold rolling to a certain value or more, if the reduction rate of cold rolling is appropriately selected, it is possible to perform short-time continuous finish annealing, in-plane rolling direction of the steel sheet and its direction. It was clarified that the perpendicular magnetic properties in the plate plane can be remarkably improved.
[0010]
The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) In mass%,
C: 0.002% or less, Si: 0.1% or more and less than 0.8%,
Al: 0.3% or more and 2.0% or less, Mn: 0.1% or more and 1.5% or less, and Si + 2Al-Mn: 2% or more,
S: 0.002% or less, N: 0.002% or less,
Ti: 0.002% or less,
After the balance Fe and between the steel consisting of unavoidable impurity elements heat rolling, subjected to hot rolled sheet annealing, once after a final thickness by cold rolling, and facilities the finish annealing by segment core type rotating machine or small EI a method for producing a non-oriented electrical steel sheet for type transformer core, the average crystal grain size after hot-rolled sheet annealing and above 300 [mu] m, subjected to cold rolling to 95% reduction of 85% or more below the finish annealing Production of non-oriented electrical steel sheet, which is performed at 700 ° C. or more and 950 ° C. or less for 10 seconds or more and 1 minute or less to develop a {100} <001> structure in the in- plane rolling direction and in the in-plane vertical direction Method.
(2) Further in mass%,
V: 0.003% or less, Zr: 0.003% or less,
The method for producing a non-oriented electrical steel sheet according to the above (1), wherein steel comprising Nb: 0.003% or less and As: 0.003% or less is used.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
First, the reasons for limiting the steel components of the present invention will be described.
C is a harmful component that increases iron loss, and also causes magnetic aging, so it is 0.002% or less.
[0012]
As described above, Si is a component having an action of reducing iron loss by increasing eddy current loss by increasing electric resistance, and in order to achieve this action, it is necessary to contain 0.1% or more. is there. On the other hand, when the content is increased, the magnetic flux density is reduced as described above, and the hardness is increased to deteriorate the punching workability, and workability such as cold rolling is also used in the manufacturing process of the non-oriented electrical steel sheet itself. And the cost is high, so the content is less than 0.8%.
[0013]
As described above, Al is also a component having an action of reducing iron loss by increasing electric resistance and reducing eddy current loss in the same manner as Si. Moreover, it has the effect | action which accelerates | stimulates the crystal grain growth property at the time of hot-rolled sheet annealing, and especially this effect | action is remarkable when Si content is less than 0.8% as mentioned above. In order to exhibit these effects, it is necessary to contain 0.3% or more. On the other hand, if the content is increased, the magnetic flux density is lowered and the yield ratio is reduced to deteriorate the punching workability.
[0014]
Mn also has an effect of reducing iron loss by increasing electric resistance and reducing eddy current loss. For this purpose, it is necessary to contain 0.1% or more. However, if the content is increased, the crystal grain growth itself during the hot-rolled sheet annealing is lowered, so the content is made 1.5% or less.
[0015]
In addition, it is necessary to satisfy the relationship of Si + 2Al-Mn: 2% or more between Si, Al, and Mn of the alloy element components. If Si + 2Al-Mn is less than 2%, it becomes a chemical component system in which an α-γ transformation exists, and the transformation occurs during annealing in the manufacturing process of a non-oriented electrical steel sheet, particularly during hot-rolled sheet annealing, which is a feature of the present invention. Resulting in inhibiting the coarsening of the crystal grain size after hot-rolled sheet annealing, and even with the rolling reduction control of the subsequent cold rolling, the development of {100} <001> system texture after finish annealing is suppressed, This is because the improvement in the in-plane rolling direction of the steel sheet and the perpendicular magnetic characteristics in the in-plane direction are hindered.
[0016]
S inhibits recrystallization and grain growth after hot rolling due to fine precipitation of sulfides such as MnS, coarsening of crystal grain size after hot-rolled sheet annealing, and hot-rolled sheet texture accompanying this To prevent the {100} enrichment of 0.002% or less.
[0017]
N inhibits recrystallization and grain growth after hot rolling due to fine precipitation of nitrides such as TiN including AlN, coarsening of the crystal grain size after hot-rolled sheet annealing, and accompanying hot rolling. In order to prevent {100} enrichment of the plate texture, the content is set to 0.002% or less.
[0018]
Ti raises the recrystallization temperature and delays the recrystallization and the subsequent grain growth during annealing in the manufacturing process of the non-oriented electrical steel sheet. In addition, a {111} texture that is undesirable for the magnetic properties of the non-oriented electrical steel sheet is developed. Furthermore, in combination with fine precipitation of TiN, TiC, etc., it inhibits the coarsening of the crystal grain size after the hot-rolled sheet annealing and the {100} enrichment of the hot-rolled sheet texture associated therewith. 002% or less.
[0019]
V, Zr, Nb, due to fine precipitation of carbides and nitrides such as VN, VC, etc., inhibits recrystallization and grain growth after hot rolling, coarsening of crystal grain size after hot-rolled sheet annealing, and In order to prevent {100} enrichment of the hot-rolled sheet texture accompanying this, each content is set to 0.003% or less.
[0020]
As itself does not form fine precipitates as described above within the steel component range of the present invention. However, when As is contained, the fine precipitation of sulfides such as MnS is promoted, and recrystallization and crystal grain growth after hot rolling will be hindered. And the {100} enrichment of the hot-rolled sheet texture accompanying this is prevented, so the content is made 0.003% or less.
Other than the above-described components, Fe and unavoidable impurity elements.
[0021]
Next, the effect of the combination of the crystal grain size after hot-rolled sheet annealing and the cold rolling reduction ratio, which is a feature of the present invention, on the magnetic properties will be described.
A steel slab having the components shown in Table 1 is hot-rolled to a thickness of 2.8 mm, and then subjected to hot-rolled sheet annealing under the annealing conditions shown in Table 2, and the crystal grain size after hot-rolled sheet annealing is changed. The rolling reduction ratio was also changed, and after finishing annealing at 750 ° C. for 30 seconds, a sample was taken and the magnetic properties (magnetic flux density: B ₅₀ ) were measured. The measurement results are also shown in Table 2.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
From Table 2, the plate surface of the steel sheet was subjected to a short-time continuous finish annealing at 750 ° C. for 30 seconds before the cold rolling, that is, the combination of the average grain size after the hot-rolled sheet annealing and the rolling reduction of the cold rolling. It can be seen that the inner rolling direction and the perpendicular magnetic properties in the plate surface can be improved. In particular, No. 1 in which the average crystal grain size after hot-rolled sheet annealing was coarsened to 300 μm or more and the rolling reduction in cold rolling was controlled to 87.5%. 5, the B _{50 in the} L direction (the in-plate rolling direction of the steel plate) and the C direction (the vertical direction in the plate surface) are both significantly high, and the in-plane rolling direction of the steel plate and the in-plate vertical magnetic characteristics are both high. Excellent non-oriented electrical steel sheet.
[0025]
In this case, {100} enrichment of hot-rolled sheet texture is promoted by increasing the average grain size after hot-rolled sheet annealing to 300 μm or more, and after hot-rolled sheet annealing, that is, cold rolling. The coarsening of the previous average crystal grain size and the {100} texture promote the development of the {100} <001> texture after finish annealing due to a synergistic effect with the cold rolling reduction ratio control. It is inferred that this contributes to a significant improvement in the in-plane rolling direction and the perpendicular magnetic properties in the in-plane direction.
[0026]
As described above, the feature of the present invention is that the combination of the crystal grain size after hot-rolled sheet annealing and the cold rolling reduction ratio enables short-time continuous finish annealing, and the in-plane rolling direction of the steel sheet and the in-plane direction thereof. An object is to enable production of non-oriented electrical steel sheets having excellent perpendicular magnetic properties.
[0027]
The average crystal grain size after hot-rolled sheet annealing needs to be 300 μm or more. If the average crystal grain size of the hot-rolled sheet is less than 300 μm, it is impossible to improve the in-plane rolling direction of the steel sheet and the in-plane perpendicular magnetic characteristics even if the reduction ratio of cold rolling is controlled. In addition, if it is impurity element content of the steel prescribed | regulated to this invention, hot-rolled sheet annealing conditions, ie, annealing temperature, and time, within the normal manufacturing process range of a non-oriented electrical steel sheet, especially a short time of less than 2 minutes. By appropriately selecting the annealing conditions, the average crystal grain size after hot-rolled sheet annealing can be made 300 μm or more.
[0028]
The rolling reduction of cold rolling is 85% or more and 95% or less. If it is less than 85%, the magnetic anisotropy becomes large, and in particular, the in-plane perpendicular magnetic characteristics in the in-plane rolling direction of the steel sheet are not improved. On the other hand, if it exceeds 95%, the magnetic anisotropy decreases, but a {111} texture unfavorable for the magnetic properties of the non-oriented electrical steel sheet develops, and both the in-plane rolling direction of the steel sheet and its vertical direction Magnetic flux density decreases.
[0029]
The finish annealing is 700 ° C. or more and 950 ° C. or less and 10 seconds or more and 1 minute or less. If it is less than 700 degreeC, the primary recrystallization after cold rolling will become incomplete, and a magnetic characteristic will not improve in the plate surface rolling direction of the steel plate, and the vertical direction in the plate surface. On the other hand, when the temperature exceeds 950 ° C., the magnetic anisotropy decreases, but a {111} texture that is undesirable for the magnetic properties of the non-oriented electrical steel sheet develops, and both the in-plane rolling direction of the steel sheet and its vertical direction Magnetic flux density decreases. If it is less than 10 seconds, the grain size of the crystal grains is poor, and the magnetic flux density is reduced and the iron loss is increased in both the in-plane rolling direction of the steel plate and the vertical direction in the plate surface. On the other hand, if it exceeds 1 minute, the effect is saturated, and the productivity is lowered and the manufacturing cost is increased.
[0030]
In addition, the steel having the chemical component characterized by the present invention is melted in a converter or an electric furnace, and is made into a slab by continuous casting or ingot rolling after ingot forming, and then after the above hot rolling. Processing is performed.
[0031]
【Example】
Next, examples of the present invention will be described.
(Example 1)
The steels having the components shown in Table 3 were hot-rolled to 1.2 mm thickness, 2.0 mm thickness, 3.2 mm thickness, and 5.7 mm thickness, respectively, and then subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute. After cold rolling to a thickness of 25 mm, finish annealing was performed at 850 ° C. for 30 seconds, and then a sample was taken and measured for magnetic properties. The measurement results are shown in Table 4. The L direction represents the in-plane rolling direction of the steel sheet, and the C direction represents the in-plane vertical direction to the rolling direction of the steel sheet.
By this invention, it turns out that the manufacture of the non-oriented electrical steel sheet excellent in the in-plate rolling direction of the steel plate and the perpendicular magnetic property in the plate surface is possible.
[0032]
[Table 3]

[0033]
[Table 4]

[0034]
(Example 2)
The steel having the components shown in Table 5 was hot-rolled to a thickness of 4.0 mm, then subjected to hot-rolled sheet annealing at 1025 ° C. for 45 seconds, and cold-rolled to a thickness of 0.35 mm (cold rolling reduction ratio: 91. 3%), and then annealed at 900 ° C. for 20 seconds, after which a sample was taken and the magnetic properties were measured. The measurement results are shown in Table 6. The L direction represents the in-plane rolling direction of the steel sheet, and the C direction represents the in-plane vertical direction to the rolling direction of the steel sheet.
By this invention, it turns out that the non-oriented electrical steel plate excellent in the in-plate rolling direction of the steel plate and the perpendicular magnetic property in the plate surface is obtained.
[0035]
[Table 5]

[0036]
[Table 6]

[0037]
【The invention's effect】
As described above, according to the method of the present invention, it is possible to obtain a non-oriented electrical steel sheet that is excellent in the in-plane rolling direction of the steel sheet and the magnetic properties of the in-plane vertical steel sheet. The non-oriented electrical steel sheet can be satisfactorily met when a non-oriented electrical steel sheet is used as a core material of a rotary machine or a small EI transformer, and its industrial value is extremely high.

Claims

% By mass
C: 0.002% or less,
Si: 0.1% or more and less than 0.8%,
Al: 0.3% or more and 2.0% or less,
Mn: 0.1% or more and 1.5% or less, and Si + 2Al-Mn: 2% or more,
S: 0.002% or less,
N: 0.002% or less,
Ti: 0.002% or less,
After the balance Fe and between the steel consisting of unavoidable impurity elements heat rolling, subjected to hot rolled sheet annealing, once after a final thickness by cold rolling, and facilities the finish annealing by segment core type rotating machine or small EI a method for producing a non-oriented electrical steel sheet for type transformer core, the average crystal grain size after hot-rolled sheet annealing and above 300 [mu] m, subjected to cold rolling to 95% reduction of 85% or more below the finish annealing Production of non-oriented electrical steel sheet, which is performed at 700 ° C. or more and 950 ° C. or less for 10 seconds or more and 1 minute or less to develop a {100} <001> structure in the in- plane rolling direction and in the in-plane vertical direction Method.

In addition by mass%
V: 0.003% or less,
Zr: 0.003% or less,
Nb: 0.003% or less,
The method for producing a non-oriented electrical steel sheet according to claim 1, wherein the steel is made of As: 0.003% or less.