JP4259177B2 - Non-oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

【００３５】
スラブ加熱温度は、ＢＮが固溶する温度以下でなければならないことが明らかである。
さらに、電子顕微鏡等で観察を進めた結果、ＢＮはMnＳと複合析出していることが明らかになった。Ｓは通常、Mnと結合し、MnＳとして析出している。しかしながら、ＢＮが鋼中に存在すると、MnＳはＢＮと地鉄の界面に析出する。この理由は、界面エネルギーがより低くなるためと考えられる。このため、MnＳとＢＮは複合析出物として、熱的に安定して存在することが可能となる。
【００３６】
通常、この発明のようにＳ量が低くなると、スラブ加熱時にMnＳは一旦固溶し、引き続く熱間圧延で再析出する。このようにして析出したMnＳは非常に微細で、熱延板粒径を細かくし、ひいては圧延後の再結晶焼鈍後の集合組織を劣化させるだけでなく、製品粒径を必要以上に細かくしてしまう。このため製品磁性が劣化してしまったと考えられる。
これに対し、ＢとＮが存在すると、ＢＮとMnＳが複合析出するため、界面エネルギーが低下し、安定的な析出物となる。このため、MnＳが固溶する温度に達しても複合析出物となった（MnＳ＋ＢＮ）は固溶しない。従って、スラブ加熱時に一旦固溶し、熱間圧延で再析出するような現象が起こらないため、熱延板粒径は大きく、その後に再結晶焼鈍後の集合組織と粒径を適正化することで製品磁気特性を向上させることができたと考えられる。
【００３７】
なお、スラブ加熱温度が低すぎても磁気特性が低下する。この原因は、スラブ加熱温度の低下に伴い仕上熱延温度が低下することにより、熱延板粒径が微細化することに起因すると考えられる。熱延後の冷間圧延で導入される歪みは、主に粒界近傍に蓄積され、引き続く仕上焼鈍でその歪み蓄積部から再結晶する。このため、熱延板粒経が細かいほど、仕上焼鈍後の粒径が細かくなり、磁気特性が劣化する。
【００３８】
（実験３）
さらに、SbやSnを添加した際の影響を調査するために、表１に示す成分を含有し、残部Feおよび不可避的不純物の組成になる各鋼種について、実験２と同様の方法で製品板を製造し、歪取り焼鈍を行った。
【００３９】
【表１】

【００４０】
歪取り焼鈍前後の製品板の鉄損について調査した結果を、図３に示す。
同図に示したとおり、SbおよびSnの一種または二種を添加することにより、歪取り焼鈍後の磁気特性が大幅に向上することが明らかとなった。
この理由についても、明確に解明されたわけではないが、SbやSnの偏析がTi，Nb, Ｖ等の析出挙動に影響を与え、析出を抑制すると共に、析出物の粗大化を促進したものと考えられる。
【００４１】
また、この発明の無方向性電磁鋼板では、需要家での加工性を損なうことのないように、鋼板のビッカース硬さを100 Hv以上とすることが好ましい。すなわち、この発明の無方向性電磁鋼板は、Alを低減しているだけでなく、磁束密度を高めるために合金元素を減らしているため、硬度が通常の電磁鋼板よりも大幅に低下している。このため、打ち抜きにより、ダレやつぶれが発生して、金型からの離脱が阻害されたり、打ち抜き後のカエリ高さが大きくなって、鋼板の占積率などに悪影響を及ばす。しかしながら、鋼板の硬さが170 Hv以上になると、逆に加工性が劣化するだけでなく、金型の早期摩耗が発生し易くなる不利が生じる。
【００４２】
さらに、プレス加工時の打ち抜き性を高めるためには、降伏点（ＹＰ）と引張強さ（ＴＳ）のバランスが非常に重要であることが明らかになった。
すなわち、ＴＳが高くなりすぎると、プレス加工後のバリやカエリが大きくなる傾向が認められた。電磁鋼板は積層して使用されるため、バリやカエリが大きくなるとうまく積層することができなくなってしまう。
そこで、このＹＰとＴＳバランスについて調査したところ、これらの比ＹＰ／ＴＳを0.80以上とする必要があることが解明された。
【００４３】
上記した鋼板硬さやＹＰ／ＴＳ比の調整は、主に熱間圧延条件と最終焼鈍温度による結晶粒径の適正化やＰやNiを添加することによって達成されるものであるが、不純物元素が多量に存在したり、最終焼鈍において酸化や窒化が生じた場合などには、所望の硬さを安定して得るのが困難となる。
従って、この発明に従って不純物を低減することは勿論、製造工程において、過度に酸化や窒化が生じない雰囲気で焼鈍することが有効である。
なお、この発明では、酸化や窒化の核となる鋼中Al量を低減しているため、他の鋼種に比べると酸化や窒化は生じにくい利点がある。
【００４４】
ここに、酸化や窒化に対する抑制効果があるSbやSnを添加することも、鋼板の硬さを調整するのに有用である。また，Sb、Snの添加は、窒化物の微細析出を抑制し、かつこれらの粒成長阻害効果を抑制することにより、磁気特性上より有利な集合組織の形成を促進させる上でも有効である。
これらの効果を得るには、Sb：0.005 〜0.10mass％、Sn：0.005 〜0.2 mass％の範囲で添加することが好ましい。
【００４５】
以下、この発明の各構成要件の限定理由について説明する。
まず、本発明において鋼の成分組成を上記の範囲に限定した理由について説明する。なお、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。
Si：0.1 〜1.2 ％
Siは、電気抵抗を増大させて鉄損を低減する効果があり、この鉄損改善のためには0.1 ％以上の含有が必要であるが、Si量が 1.2％超になると磁束密度が低下するだけでなく、硬度が上昇し加工性が劣化することから、Si量は 0.1〜1.2 ％の範囲に限定した。
【００４６】
Mn：0.005 〜0.30％
Mnは、良好な熱間加工性を得るために有用な成分であり、そのためには 0.005％以上の含有が必要であるが、 0.3％を超えると飽和磁束密度が低下するため、Mn量は 0.005〜0.30％の範囲に限定した。
【００４７】
Ｂ：0.0001〜0.0020％
この発明では、ＢＮをMnＳと複合析出させ、MnＳの熱間圧延工程での再析出を阻止することによって、再結晶焼鈍後の集合組織と結晶粒径の適正化を図っている。このためには、少なくとも0.0001％のＢが必要であるが、0.0020％を超えて多量に含有されるとＢＮの過剰な析出により、歪取り焼鈍後の粒成長性低下の弊害を招く。従って、Ｂ量は0.0001〜0.0020％の範囲に限定した。
【００４８】
Ｃ：0.0050％以下
Ｃは、磁気時効劣化を抑制し、かつ極低Al化による集合組織の改善効果を十分に発揮させるために、0.0050％以下に低減させる必要がある。なお、Ｃの低減は、溶鋼の段階で0.0050％以下としてもよいし、溶鋼段階で0.0050％を超えていても、途中工程での脱炭処理等により0.0050％以下としてもよい。
【００４９】
Ｓ：0.0050％以下
Ｓは、MnやトランプエレメントのCuなどと結合してMnＳや Cu₂Ｓとなり、結晶粒成長を妨げるので少ない方が好ましく、0.0050％以下に制限した。
【００５０】
Ｏ：0.0100％以下
T.Ｏ量が0.0100％を超えると酸化物が増え、結晶粒の成長を妨げるので、T.Ｏは0.0100％以下とした。
【００５１】
sol.Al：0.0004％以下、Ｎ：0.0030％以下、
優れた粒成長性と磁気特性を得るためには、鋼板中のAl量を0.0004％以下、Ｎ量を0.0030％以下に低減することが肝要である。すなわち、Al量が0.0004％を超えると、製品板においてAlＮが析出し、歪取り焼鈍後の粒成長性が劣化すると共に集合組織が劣化して、製品板の磁束密度が低下するため、Al量はsol.Alで0.0004％以下に限定する。
また、Ｎ量が0.0030％を超えると、種々の窒化物が形成されて、再結晶焼純時の集合組織の発達と結晶粒の成長が抑制され、鉄損が大きく劣化するため、Ｎ量は0.0030％以下に低減する。
【００５２】
Ti，ＶおよびNbを合計で 0.010％以下
Ti，NbおよびＶはいずれも、微細な窒化物を形成し、集合組織の形成および結晶粒の成長を阻害する成分であるが、これらの総量を規制することにより、製品の磁気特性と歪取り焼鈍後の磁気特性とを高度に両立することができる。すなわち、Ti，ＶおよびNbの総量を合計で 0.010％以下に低減することにより、Ti，NbおよびＶの窒化物または炭化物の製品板での析出挙動と歪取り焼鈍時の析出が制御され、磁壁移動に影響を及ぼす析出物の影響が小さくなり、歪取り焼鈍前後における製品板の磁気特性が向上する。
【００５３】
以上、基本成分について説明したが、本発明ではその他にも、以下に述べる元素を適宜含有させることができる。
Sn：0.005 〜0.2 ％およびSb：0.005 〜0.10％のうちから選んだ一種または二種 Sb，Snはいずれも、窒化物の析出形態および粒界移動時の良好な集合組織形成のために、有用な成分である。すなわち、SbおよびSnは、窒化物の微細析出を抑制し、かつこれらの粒成長阻害効果を抑制することにより、磁気特性上より有利な集合組織形成を促進させる上で有効である。これらの効果を得るためには、いずれも 0.005％以上含有させる必要があるが、Sbでは0.10％を超えると、またSnでは0.2 ％を超えるとその添加効果は飽和に達し、むしろ粒成長性を阻害するおそれがあるため、それぞれ上記の範囲で含有させることが好ましい。
【００５４】
Ｐ：0.001 〜0.2 ％およびNi：0.001 〜0.2 ％のうちから選んだ一種または二種ＰおよびNiは、微量の添加で硬度を向上させる有用元素である。需要家によって最適な硬度が異なるため、必要に応じてＰやNiをそれぞれ 0.001〜0.2 ％の範囲で含有させることは有利である。
【００５５】
さらに、硫化物を粗大化して鉄損を向上するために、REM やCaを製鋼段階で添加することも有効である。このREM やCaは、ミッシュメタルやCaSi, CaAl, CaＯフラックス等にて添加することができる。すなわち、REM やCaを添加することによって、粗大な硫化物（酸素を含む場合もある）が形成され、鉄損を向上することができる。
【００５６】
次に、この発明に従う製造方法について説明する。
上記の好適成分組成に調整した鋼を、転炉などで溶製し、通常の造塊法や連続鋳造法でスラブを製造してもよいし、100mm 以下の厚さの薄鋳片を直接鋳造法で製造してもよい。
熱間圧延に先立つスラブ加熱は、次式(1) を満足する温度範囲で行う。

スラブ加熱温度を、上記の範囲に限定したのは、前掲図２に示したとおり、上記の温度範囲でスラブ加熱を行うことにより、適正量のＢＮを確保し、効果的にＢＮとMnＳを複合析出させて、MnＳの熱間圧延工程での再析出による弊害を解消することができるからである。
【００５７】
ついで、熱間圧延を行うが、この熱間圧延に際し、仕上圧延出側温度は 800℃以上とする必要がある。というのは、仕上圧延出側温度を 800℃以上とすることにより、熱延板の粒径を大きくすることができ、ひいては冷延後の再結晶焼鈍後の粒径および集合組織を適正に制御することができるからである。
【００５８】
ついで、必要に応じて熱延板焼鈍を施し、さらに必要に応じて中間焼鈍を挟む１回以上の冷間圧延を施したのち、仕上焼鈍を施す。さらに、必要に応じて積層した鋼板の鉄損を改善するために、絶縁コーティングを施すが、この目的のためには、２種類以上の被膜からなる多層膜としてもよいし、樹脂等を混合させたコーティングを施しても良い。
【００５９】
【実施例】
表２に示す成分組成からなる鋼スラブを、連続鋳造にて製造した。このスラブを種々の温度で30分間加熱後、熱間圧延にて 2.8mmの熱延板とした。この時の熱延条件を表２に併記する。ついで、熱延板を酸洗後、スケールを除去してから、冷間圧延を行って、0.50mmの最終板厚に仕上げた。ついで、50％水素と50％窒素からなる雰囲気中にて 790℃、15秒の再結晶焼鈍を施したのち、重クロム酸塩と樹脂からなる半有機コーティング液を塗布し、300 ℃で焼き付けて、製品板とした。
かくして得られた製品板から、圧延方向と平行および圧延方向と直角にそれぞれサンプルを切り出し、JIS C 2550に準拠して磁束密度および鉄損を測定した。また、製品板の圧延方向断面における結晶粒径を、0.5mm²の面積中に存存する結晶粒数から円相当径として求めた。さらに、引張り試験を行って、ＹＰおよびＴＳを測定した。
【００６０】
ついで、製品板に対し 750℃、２ｈの歪取り焼鈍をAr雰囲気中で行ったのち、圧延方向と平行および圧延方向と直角に、それぞれサンプルを切り出し、JIS C2650に準拠して磁束密度および鉄損を測定した。また、歪取り焼純板の圧延方向断面の結晶粒径を0.5mm²の面積中に存在する結晶粒の個数から円相当径として求めた。
これらの測定結果を表３に示す。
【００６１】
【表２】

【００６２】
【表３】

【００６３】
表３に示したとおり、この発明に従う適正な成分組成範囲に成分調整し、ＢとＮ量に応じた適正温度でスラブ加熱し、ついで仕上圧延出側温度が 800℃以上の条件で熱間圧延を行うことにより、高強度で、かつ加工性およびリサイクル性に優れ、さらには歪取り焼鈍後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た。
【００６４】
【発明の効果】
かくして、この発明によれば、高強度で、加工性およびリサイクル性に優れ、かつ磁束密度が高い無方向性電磁鋼板を安定して得ることができる。
【図面の簡単な説明】
【図１】 粒成長性に及ばす（Ti＋Nb＋Ｖ）量およびsol.Al量の影響を示した図である。
【図２】 歪取り焼鈍後の磁気特性に及ぼすスラブ加熱温度および[Bppm][Nppm]量の影響を示した図である。
【図３】 歪取り焼鈍前後の磁気特性に及ばすSbおよびSnの影響を示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-oriented electrical steel sheet mainly used as an iron core material for electrical equipment, and more particularly to a high magnetic flux density non-oriented electrical steel sheet having high strength and excellent workability and recyclability, and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, in the global trend of saving energy including electric power, it is strongly desired to increase the efficiency of electrical equipment. In addition, from the viewpoint of miniaturization of electrical equipment, there is a growing demand for miniaturization of iron cores. Furthermore, in consideration of the environment, there is an urgent need to respond to recycling of iron core materials in electrical equipment.
[0003]
In order to increase the efficiency of electrical equipment and downsize the iron core, it is effective to improve the magnetic properties of the electrical steel sheet that is the material of the iron core. Here, in the field of conventional non-oriented electrical steel sheets, Si, Al, Mn, etc. in order to reduce eddy current loss by increasing electric resistance as a means of reducing iron loss, among other magnetic properties. Techniques for increasing the content have generally been used.
However, this method has an essential problem that a decrease in magnetic flux density is inevitable.
[0004]
Further, not only simply increasing the content of Si, Al, etc., but also a method of reducing C and S, and a method of increasing alloy elements such as adding Ni (for example, see Patent Document 1) This is a generally known method.
However, although the iron loss is improved by the method of adding an alloy element as described above, the effect of improving the magnetic flux density is small and not satisfactory. Moreover, since the hardness of the steel sheet increases with the alloy addition and the workability deteriorates, such a non-oriented electrical steel sheet is poor in versatility when processed and applied to electrical equipment. It was very limited.
[0005]
On the other hand, several methods for improving the magnetic properties by changing the manufacturing process to improve the degree of integration of crystal orientation of the product plate, that is, the texture, have been proposed. For example, a method of developing a {100} <UVW> structure by hot rolling steel containing Si: 2.8 to 4.0 mass% and Al: 0.3 to 2.0 mass% in a temperature range of 200 to 500 ° C is proposed. (For example, refer to Patent Document 2).
However, it has been difficult to say that the effect of improving magnetic properties by such a method is satisfactory.
[0006]
In addition, there are many cases where stress relief annealing is performed by customers, and the fact that the magnetic properties do not deteriorate after this annealing is an important performance required for non-oriented electrical steel sheets. There was also a problem.
[0007]
Furthermore, problems remained in processability and recyclability.
That is, if a certain amount of Al is included in the steel, the hardness of the steel plate is first increased and the workability is hindered, and the iron core material is recycled or scrapped at the customer. The problem was that the electrodes of the electric furnace were damaged.
In addition, when casting motor shafts using recycled iron cores, if Al is included, the surface oxidation of the molten steel proceeds during casting and the viscosity increases, and the moldability of the molten steel deteriorates. Therefore, it has been a problem that sound casting is inhibited.
[0008]
Therefore, in order to improve workability, recyclability, and magnetic flux density, it is useful to reduce the Al content. However, on the other hand, the reduction of Al leads to an increase in magnetic characteristics, particularly iron loss. Moreover, there is a disadvantage that iron loss after strain relief annealing also deteriorates.
This is because Al is a strong deoxidizing element. That is, when Al is added, Al is combined with oxygen during molten steel, and oxides in the steel are reduced. For this reason, the grain growth property of a crystal grain improves and an iron loss is reduced effectively. Moreover, it combines with N to form coarse AlN and improve grain growth. However, when only a very small amount of Al is present, the amount of oxide formed is small, and fine AlN is formed, which hinders crystal grain growth. Accordingly, it has been considered difficult to reduce Al in the production of non-oriented electrical steel sheets.
[0009]
For this reason, in patent document 3 and patent document 4, precipitation of AlN is prevented by adding B while ensuring deoxidation by containing 0.0050 to 0.1 mass% of low concentration Al as sol.Al. Yes.
However, it is not preferable that Al remains even in a small amount, and further improvement has been demanded.
[0010]
Further, in recent years, the strength of the rotor has been required as the motor speed has increased. In order to increase the strength, it is necessary to add an alloying element or make the particle size finer. However, these measures have the adverse effect of lowering the magnetic flux density and iron loss. It was.
[0011]
[Patent Document 1]
JP-A-3-281758 [Patent Document 2]
Japanese Patent Laid-Open No. 58-181822 [Patent Document 3]
Japanese Patent Publication No.62-56225 [Patent Document 4]
Japanese Examined Patent Publication No. 4-19297 [0012]
[Problems to be solved by the invention]
The present invention has been developed in view of the above-described present situation, and is advantageous in that it is a non-oriented electrical steel sheet having high strength, excellent workability and recyclability, and excellent magnetic properties after strain relief annealing. It aims at proposing together with various manufacturing methods.
[0013]
[Means for Solving the Problems]
That is, the gist configuration of the present invention is as follows.
1. In mass%
Si: 0.1-1.2%,
Mn: 0.005 to 0.30% and B: 0.0001 to 0.0020 %
And C: 0.0050% or less,
S: 0.0050% or less,
O: 0.0100% or less,
N: 0.0030% or less,
sol.Al: 0.0004% or less and
Ti, was reduced to 0.010% or less of V and Nb in total, the balance being Fe and becomes the composition of the unavoidable impurities, free ratio YP / TS tensile strength and yield point characterized in that at least 0.80 Oriented electrical steel sheet.
[0014]
2. In the above 1, the steel plate is further in mass%.
Sn: 0.005-0.2% and
Sb: 0.005-0.10%
Non-oriented electrical steel sheet you characterized by comprising a composition containing one or two or chosen from among the.
[0015]
3. In the above 1 or 2, the steel sheet is further added by mass% P: 0.001 to 0.2% and
Ni: 0.001 to 0.2%
Non-oriented electrical steel sheet you characterized by comprising a composition containing one or two or chosen from among the.
[0016]
4). In mass%
Si: 0.1-1.2%,
Mn: 0.005 to 0.30% and B: 0.0001 to 0.0020 %
And C: 0.0050% or less,
S: 0.0050% or less,
O: 0.0100% or less,
N: 0.0030% or less,
sol.Al: 0.0004% or less and
Ti, V and Nb are controlled to 0.010% or less in total, and the balance is Fe and unavoidable impurities. Steel slab is hot-rolled after slab, and then one or more times with intermediate annealing. In the manufacturing method of the non-oriented electrical steel sheet consisting of finish annealing after performing cold rolling, prior to hot rolling, after performing slab heating in a temperature range satisfying the following formula (1), finish rolling delivery temperature: 800 method for producing a non-oriented electrical steel sheet you and performing hot finish rolling at ℃ above conditions.
-19560 / (log [Bppm] [Nppm] -18.10) -273
<T (° C) <-19560 / (log [Bppm] [Nppm] -15.75) -273 --- (1)
[0017]
5. In the above 4, the steel plate is further in mass%.
Sn: 0.005-0.2% and
Sb: 0.005 to 0.10%
I selected one or method for producing a non-oriented electrical steel sheet you characterized by comprising a composition containing two kinds from among the.
[0018]
6). In the above 4 or 5, the steel plate is further in mass% P: 0.001 to 0.2% and
Ni: 0.001 to 0.2%
I selected one or method for producing a non-oriented electrical steel sheet you characterized by comprising a composition containing two kinds from among the.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The elucidation process of the present invention will be described below.
In order to increase the efficiency of electric motors and transformers, it is important to reduce copper loss and iron loss. To reduce both copper loss and iron loss, the magnetic flux density of the material must be reduced. There is a need to increase and reduce iron loss. However, since a specific resistance increasing component such as Si, which is generally added to reduce the iron loss, decreases the magnetic flux density, it is very difficult to achieve both a low iron loss and a high magnetic flux density.
[0020]
In this regard, the technique by improving the texture is an excellent means that can achieve both low iron loss and high magnetic flux density, but this means has its own limitations.
In other words, since the saturation magnetic flux density is determined by the amount of iron, even if the texture is improved by changing the manufacturing process, if an element other than iron is added, the saturation magnetic flux density is reduced accordingly. Is inevitable.
Therefore, in the present invention, a component system in which the Si content is reduced as much as possible, that is, a material having a Si content of 1.2 mass% or less was examined.
[0021]
The motor uses a magnetic steel sheet for a part called a stator and a part called a rotor. Here, since the rotor is a rotating part, a certain strength is required. In recent years, in order to increase the efficiency of a motor, there have been many examples in which a rare earth magnet is embedded in a rotor and rotated at a high speed. For this reason, the demands for the saturation magnetic flux density and strength have become much higher than before. Note that the upper yield point represented by YP is important for the strength at this time.
On the other hand, with respect to the stator, iron loss is the most important, and strength is not particularly required because it does not rotate. Thus, even if it is the electromagnetic steel plate used for the same motor, the performance requested | required by them differs greatly with a rotor and a stator.
That is, the rotor requires high magnetic flux density and high strength, and the stator requires low iron loss.
However, the rotor and the stator are usually punched out from the same steel plate by a press. If this is not done, the yield of the steel plate will be significantly reduced.
[0022]
Therefore, the inventors have intensively studied to develop a non-oriented electrical steel sheet suitable for both parts having different required characteristics, and as a result, have come to the following conclusion.
That is, the crystal grain size when shipping the product is made as small as possible, and the strength (YP) of the steel plate is made high. And after punching a steel plate with a press processing machine, only the particle diameter of the non-oriented electrical steel plate used for a stator is enlarged by carrying out the distortion removal annealing only of a stator by a consumer. Note that the strain relief annealing condition at the customer is about 750 ° C. for about 2 hours, and the pure atmosphere is the most in Ar gas. Therefore, this condition was determined as the strain relief annealing condition in the present invention.
[0023]
Furthermore, it has become clear that the balance between YP and TS (tensile strength) is very important in order to improve punchability during press working.
That is, when TS became too high, the tendency for burrs and burrs after press working to increase was recognized. Since magnetic steel sheets are used by being laminated, if burrs and burrs become large, they cannot be laminated well.
In order to solve this problem, it has been found that the ratio of YP and TS needs to be 0.80 or more.
[0024]
Next, based on the above findings, further study on the component composition of non-oriented electrical steel sheet that is excellent in workability and recyclability, and also excellent in high strength and magnetic flux density, and also in iron loss after strain relief annealing. Repeated.
First, Al has been conventionally added as indispensable for improving magnetic properties. However, since it hinders workability and recyclability, the present invention basically does not contain Al.
[0025]
In other words, in the steel plate manufacturing process, Al is used by a customer to accelerate the oxidation of the steel sheet surface in order to prevent the rolling roll from being worn in the rolling process and to inhibit the rollability or to increase the hardness of the steel sheet. It is a disadvantageous component in terms of workability, such as expediting the deterioration of the mold and increasing the working time and cost in the gap for punching. In addition, when the iron core material is recycled or scrapped by a customer, the electrode of the electric furnace is damaged. In addition, when casting motor shafts using recycled iron cores, if 0.1 mass% or more of Al is included, the surface oxidation of the molten steel progresses during casting and the viscosity increases, resulting in a molten steel mold. Since the filling property deteriorates, a sound casting may not be obtained, and the scrap containing Al is poor in recyclability.
Therefore, in order to improve workability, recyclability, and magnetic flux density, it is useful to reduce the Al content.
[0026]
However, on the other hand, the reduction of Al leads to an increase in magnetic characteristics, particularly iron loss. Moreover, the iron loss after strain relief annealing also deteriorates. The cause is that Al is a strong deoxidizing element. That is, when Al is added, Al is combined with oxygen during molten steel, and oxides in the steel are reduced. For this reason, the grain growth property of the crystal grains is improved, and the iron loss is greatly reduced. It also binds with N to form coarse AlN to improve grain growth. However, when only a very small amount of Al is present, the amount of oxide formed is small and fine AlN is formed, which hinders the grain growth of crystal grains. Therefore, as described above, conventionally, it has been considered difficult to reduce Al in the production of non-oriented electrical steel sheets.
In addition, as described in Japanese Patent No. 3013961, it has been considered extremely difficult to achieve 5 ppm or less of Al with industrial steelmaking technology. For this reason, the optimum component system in such a low Al region has not been clarified.
[0027]
However, very recently, with rapid progress in steelmaking technology, it has become possible to achieve extremely low Al concentrations. Along with this, completely new knowledge has been revealed by the inventors.
That is, as a result of analyzing many experimental results, the inventors reduced Al as much as possible, lowered the contents of S, N, O, Ti, V and Nb, added B, and further before hot rolling. Non-oriented electrical steel sheet with extremely good magnetic properties, recyclability, and workability by performing slab heating at a temperature corresponding to the amount of B and N and by setting the hot finish rolling outlet temperature to 800 ° C or higher. It has been determined that can be obtained.
[0028]
The experiment that led to the invention will be described below.
(Experiment 1)
Si: 0.8 mass%, Mn: 0.4 mass%, C: 0.0015 mass%, S: 0.0025 mass%, O: 0.0080 mass% and N: 0.0025 mass%, and Al in the range of 0 to 15 ppm, Further, steel ingots were produced in which Ti, Nb and V were variously changed in the ranges of Ti: 0.0002 to 0.0050 mass%, Nb: 0.0002 to 0.0080 mass%, and V: 0.0001 to 0.0080 mass%, respectively. Next, these steel ingots were heated at 1080 ° C, then hot rolled to 2.3 mm thickness, then pickled and finished to a final sheet thickness of 0.35 mm by cold rolling, then 850 ° C, 15 Second recrystallization annealing was performed to obtain a product plate.
The cross section in the rolling direction of these product plates was observed with an optical microscope, and the particle size was measured. The grain size was determined as the equivalent circle diameter by measuring the number of crystal grains existing in an area of 0.5 mm ² .
Subsequently, the product plate was subjected to strain-relief tempering at 750 ° C. for 2 hours in an Ar atmosphere, and the crystal grain size was measured in the same manner.
Thus, the result of obtaining the particle size ratio before and after the strain relief annealing is shown in FIG.
[0029]
As is clear from FIG. 1, even when the Al amount is as low as 0.0004 mass% or less, the grain size is more than doubled after strain relief annealing by suppressing the total amount of (Ti + Nb + V) to 0.010 mass% or less. It was possible to obtain a magnetic steel sheet that grows rapidly.
[0030]
As a result, since it is contained in hot metal and Si raw material, by reducing the amount of Ti, Nb and V inevitably mixed in the molten steel, even in a component system in which Al is extremely reduced, electromagnetic growth with extremely good grain growth is achieved. It was newly found that a steel plate can be obtained.
[0031]
Here, the reason why the grain growth property is very well stabilized by reducing the amount of Ti, Nb and V in the product plate is not necessarily clear, but Ti, Nb, and V are both nitride-forming elements. Yes, because it causes the same harm as finely precipitated AlN, which adversely affects grain growth, it is thought that by reducing these, this kind of harm can be prevented, resulting in good grain growth. It is done. In addition, it is thought that these precipitations occur by recrystallization annealing after cold rolling.
[0032]
(Experiment 2)
However, even when the amount of sol.Al, Ti, Nb and V is limited to a predetermined range and the grain growth property is very good, there are some cases where the absolute value level of the magnetic properties is low.
Then, next, in order to clarify this cause, the amount of B in molten steel and hot rolling conditions were examined.
First, Si: 0.9 mass%, Al: 0.0002 mass% and Mn: 0.15 mass%, and the contents of Ti, Nb and V as trace impurity elements are 0.010 mass% or less in total, and B: 0.5-50 Slab steel ingots with components adjusted to ppm and N: 10 to 50 ppm were produced and subjected to experiments. Next, these slabs were heated in a gas heating furnace, hot rolled into 2.5 mm thick hot rolled sheets, pickled, and then cold rolled to a final thickness of 0.5 mm. The product was recrystallized and annealed at 840 ° C for 10 seconds. Thereafter, strain relief annealing was performed at 750 ° C. for 2 hours in an Ar atmosphere.
From the product plate after strain relief annealing obtained in this way, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured according to JIS C 2550, and the average values were obtained. It was.
[0033]
FIG. 2 shows the result of examining the iron loss W _15/50 (W / kg) after strain relief annealing in relation to the B × N amount and the slab heating temperature.
As shown in the figure, it was found that an extremely low iron loss can be obtained when the B × N amount is limited to a certain range and the slab heating temperature is within a certain range.
[0034]
The cause is considered to be the solid solution / precipitation of BN precipitates, which are compounds of B and N, and the solubility product was examined.
As in the present invention, when nitride forming elements such as Al, Nb, and V are extremely reduced, N enters a solid solution state. Here, when B is present, BN is formed, and its solid solution precipitation is determined by the following solubility product.
log [Bppm] [Nppm] = -19560 / T (K) +15.75
In consideration of this relationship, the relationship between the slab heating temperature, the B content and the N content of the components was reviewed and plotted in FIG. 2, and as a result, very good characteristics can be obtained within the range of the following equation (1). It became clear.

[0035]
It is clear that the slab heating temperature must be below the temperature at which BN dissolves.
Furthermore, as a result of observing with an electron microscope or the like, it became clear that BN was complex-deposited with MnS. S is usually bonded to Mn and precipitated as MnS. However, when BN is present in the steel, MnS precipitates at the interface between BN and the ground iron. The reason for this is considered to be that the interfacial energy becomes lower. For this reason, MnS and BN can exist thermally and stably as a composite precipitate.
[0036]
Normally, when the amount of S becomes low as in the present invention, MnS once dissolves during slab heating and re-deposits by subsequent hot rolling. The MnS deposited in this way is very fine, and the hot-rolled plate grain size is made finer. As a result, not only the texture after recrystallization annealing after rolling is degraded, but also the product grain size is made finer than necessary. End up. For this reason, it is considered that the product magnetism has deteriorated.
On the other hand, when B and N are present, BN and MnS are compositely precipitated, so that the interface energy is reduced and a stable precipitate is formed. For this reason, even if it reaches the temperature at which MnS is dissolved, the composite precipitate (MnS + BN) is not dissolved. Therefore, since the phenomenon of once solid solution during slab heating and reprecipitation by hot rolling does not occur, the hot-rolled plate grain size is large, and then the texture and grain size after recrystallization annealing should be optimized It is thought that the product magnetic properties could be improved.
[0037]
Even if the slab heating temperature is too low, the magnetic properties are deteriorated. This is considered to be due to the fact that the finish hot rolling temperature is lowered as the slab heating temperature is lowered, whereby the hot-rolled plate particle size is refined. The strain introduced in the cold rolling after hot rolling is accumulated mainly in the vicinity of the grain boundary, and recrystallized from the strain accumulation portion in the subsequent finish annealing. For this reason, the smaller the hot-rolled sheet grain diameter, the finer the grain size after finish annealing, and the magnetic properties deteriorate.
[0038]
(Experiment 3)
Furthermore, in order to investigate the effect of adding Sb or Sn, the product plate was prepared in the same manner as in Experiment 2 for each steel type containing the components shown in Table 1 and having the balance of Fe and inevitable impurities. Manufactured and subjected to strain relief annealing.
[0039]
[Table 1]

[0040]
The result of investigating the iron loss of the product plate before and after strain relief annealing is shown in FIG.
As shown in the figure, it has been clarified that the addition of one or two of Sb and Sn greatly improves the magnetic properties after the stress relief annealing.
The reason for this is not clearly understood, but segregation of Sb and Sn affects the precipitation behavior of Ti, Nb, V, etc., and suppresses the precipitation and promotes the coarsening of the precipitate. Conceivable.
[0041]
Further, in the non-oriented electrical steel sheet of the present invention, it is preferable that the steel sheet has a Vickers hardness of 100 Hv or more so as not to impair the workability at the consumer. That is, the non-oriented electrical steel sheet of the present invention not only reduces Al, but also reduces the alloy elements to increase the magnetic flux density, so the hardness is significantly lower than that of normal electrical steel sheets. . For this reason, sag or crushing occurs due to punching, and the separation from the mold is hindered, or the height of burrs after punching increases, which adversely affects the space factor of the steel sheet. However, when the steel sheet has a hardness of 170 Hv or more, not only the workability is deteriorated, but also there is a disadvantage that early wear of the mold is likely to occur.
[0042]
Furthermore, in order to improve the punchability at the time of press working, it became clear that the balance between the yield point (YP) and the tensile strength (TS) is very important.
That is, when TS became too high, the tendency for burrs and burrs after press working to increase was recognized. Since magnetic steel sheets are used by being laminated, if burrs and burrs become large, they cannot be laminated well.
Then, when this YP and TS balance was investigated, it was clarified that the ratio YP / TS needs to be 0.80 or more.
[0043]
The adjustment of the steel sheet hardness and the YP / TS ratio described above is achieved mainly by optimizing the crystal grain size according to the hot rolling conditions and the final annealing temperature and adding P or Ni. When a large amount exists or oxidation or nitridation occurs in the final annealing, it is difficult to stably obtain a desired hardness.
Therefore, it is effective not only to reduce impurities according to the present invention, but also to anneal in an atmosphere in which excessive oxidation or nitridation does not occur in the manufacturing process.
In addition, in this invention, since the amount of Al in steel which becomes the nucleus of oxidation and nitriding is reduced, there is an advantage that oxidation and nitridation are less likely to occur compared to other steel types.
[0044]
It is also useful for adjusting the hardness of the steel sheet to add Sb or Sn having an effect of suppressing oxidation and nitriding. The addition of Sb and Sn is also effective in promoting the formation of a texture that is more advantageous in terms of magnetic properties by suppressing the fine precipitation of nitrides and suppressing the effect of inhibiting the grain growth.
In order to obtain these effects, it is preferable to add in the range of Sb: 0.005 to 0.10 mass% and Sn: 0.005 to 0.2 mass%.
[0045]
Hereinafter, the reason for limitation of each structural requirement of this invention is demonstrated.
First, the reason why the composition of steel is limited to the above range in the present invention will be described. Unless otherwise specified, “%” in relation to ingredients means mass%.
Si: 0.1-1.2%
Si has the effect of increasing the electrical resistance and reducing the iron loss. To improve this iron loss, it must contain 0.1% or more, but when the Si content exceeds 1.2%, the magnetic flux density decreases. In addition, since the hardness increased and the workability deteriorated, the Si amount was limited to the range of 0.1 to 1.2%.
[0046]
Mn: 0.005 to 0.30%
Mn is a useful component for obtaining good hot workability. To that end, it is necessary to contain 0.005% or more. However, if it exceeds 0.3%, the saturation magnetic flux density decreases, so the amount of Mn is 0.005%. Limited to a range of ~ 0.30%.
[0047]
B: 0.0001 to 0.0020 %
In this invention, BN is complex-precipitated with MnS, and the re-precipitation in the hot rolling process of MnS is prevented to optimize the texture and crystal grain size after recrystallization annealing. For this purpose, at least 0.0001% B is required. However, if it is contained in a large amount exceeding 0.0020 %, excessive precipitation of BN causes a problem of deterioration of grain growth after strain relief annealing. Therefore, the amount of B is limited to the range of 0.0001 to 0.0020 %.
[0048]
C: 0.0050% or less C is required to be reduced to 0.0050% or less in order to suppress the magnetic aging deterioration and to fully exhibit the texture improving effect due to the extremely low Al content. The reduction of C may be 0.0050% or less at the molten steel stage, or may be 0.0050% or less by decarburization treatment or the like in the intermediate process even if it exceeds 0.0050% at the molten steel stage.
[0049]
S: 0.0050% or less S is preferably MnS or Cu ₂ S by combining with Mn, Cu of the playing element, etc., and hinders crystal grain growth.
[0050]
O: 0.0100% or less
When the amount of T.O exceeds 0.0100%, oxides increase and hinder growth of crystal grains. Therefore, T.O is set to 0.0100% or less.
[0051]
sol.Al: 0.0004% or less, N: 0.0030% or less,
In order to obtain excellent grain growth and magnetic properties, it is important to reduce the Al content in the steel sheet to 0.0004% or less and the N content to 0.0030% or less. That is, if the Al content exceeds 0.0004%, AlN precipitates on the product plate, the grain growth property after strain relief annealing deteriorates, the texture deteriorates, and the magnetic flux density of the product plate decreases. Is limited to 0.0004% or less in sol.Al.
Further, if the N content exceeds 0.0030%, various nitrides are formed, and the development of the texture and the growth of crystal grains at the time of recrystallization annealing are suppressed, and the iron loss is greatly deteriorated. Reduce to 0.0030% or less.
[0052]
Ti, V and Nb in total 0.010% or less
Ti, Nb, and V are all components that form fine nitrides and inhibit the formation of texture and the growth of crystal grains. By controlling the total amount of these, the magnetic properties and strain relief of the product can be reduced. Highly compatible with the magnetic properties after annealing. That is, by reducing the total amount of Ti, V and Nb to 0.010% or less in total, the precipitation behavior of Ti, Nb and V nitride or carbide products and the precipitation during strain relief annealing are controlled, and the domain wall The influence of precipitates that affect movement is reduced, and the magnetic properties of the product plate before and after strain relief annealing are improved.
[0053]
The basic components have been described above. However, in the present invention, other elements described below can be appropriately contained.
One or two types selected from Sn: 0.005 to 0.2% and Sb: 0.005 to 0.10% Sb and Sn are both useful for the formation of nitrides and good texture formation during grain boundary migration. Is an essential ingredient. That is, Sb and Sn are effective in promoting the formation of a texture that is more advantageous in terms of magnetic properties by suppressing the fine precipitation of nitrides and suppressing the effect of inhibiting the grain growth. In order to obtain these effects, it is necessary to contain 0.005% or more in all cases. However, when Sb exceeds 0.10% and Sn exceeds 0.2%, the addition effect reaches saturation, and rather the grain growth property is reduced. Since there exists a possibility of inhibiting, it is preferable to make it contain in said range, respectively.
[0054]
One or two kinds of P and Ni selected from P: 0.001 to 0.2% and Ni: 0.001 to 0.2% are useful elements that improve the hardness by adding a small amount. Since the optimum hardness varies depending on the customer, it is advantageous to contain P and Ni in a range of 0.001 to 0.2% as required.
[0055]
In addition, it is also effective to add REM and Ca at the steelmaking stage in order to coarsen the sulfide and improve iron loss. The REM and Ca can be added by misch metal, CaSi, CaAl, CaO flux or the like. That is, by adding REM and Ca, coarse sulfides (which may contain oxygen) are formed, and iron loss can be improved.
[0056]
Next, the manufacturing method according to the present invention will be described.
The steel adjusted to the above preferred component composition may be melted in a converter, etc., and slabs may be produced by the usual ingot-making method or continuous casting method, or thin cast pieces with a thickness of 100 mm or less are cast directly. You may manufacture by the method.
Slab heating prior to hot rolling is performed in a temperature range that satisfies the following equation (1).

The slab heating temperature is limited to the above range, as shown in FIG. 2 above, by carrying out slab heating in the above temperature range, an appropriate amount of BN is ensured and BN and MnS are effectively combined. This is because it is possible to eliminate the adverse effects caused by reprecipitation in the hot rolling process of MnS.
[0057]
Next, hot rolling is performed. At the time of this hot rolling, the finish rolling outlet temperature needs to be 800 ° C. or higher. This is because the grain diameter of the hot-rolled sheet can be increased by setting the finish rolling outlet temperature to 800 ° C or higher, and thus the grain size and texture after recrystallization annealing after cold rolling are appropriately controlled. Because it can be done.
[0058]
Subsequently, hot-rolled sheet annealing is performed as necessary, and further, one or more cold rollings sandwiching the intermediate annealing are performed as necessary, and then finish annealing is performed. Furthermore, in order to improve the iron loss of the laminated steel sheets as necessary, an insulating coating is applied. For this purpose, a multilayer film composed of two or more kinds of films may be used, or a resin or the like may be mixed. A coating may be applied.
[0059]
【Example】
Steel slabs having the composition shown in Table 2 were produced by continuous casting. The slab was heated at various temperatures for 30 minutes, and then hot-rolled into a 2.8 mm hot-rolled sheet. The hot rolling conditions at this time are also shown in Table 2. Next, after pickling the hot-rolled sheet, the scale was removed, and then cold rolling was performed to obtain a final sheet thickness of 0.50 mm. Next, after recrystallization annealing at 790 ° C for 15 seconds in an atmosphere consisting of 50% hydrogen and 50% nitrogen, a semi-organic coating solution consisting of dichromate and resin was applied and baked at 300 ° C. The product plate.
Samples were cut out from the product plates thus obtained in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C 2550. Further, the crystal grain size in the cross section in the rolling direction of the product plate was determined as the equivalent circle diameter from the number of crystal grains existing in the area of 0.5 mm ² . Further, a tensile test was performed to measure YP and TS.
[0060]
Next, the product plate was subjected to strain relief annealing at 750 ° C. for 2 hours in an Ar atmosphere, and then samples were cut out parallel to the rolling direction and perpendicular to the rolling direction, respectively, and the magnetic flux density and iron loss in accordance with JIS C2650. Was measured. Further, the crystal grain size of the cross section in the rolling direction of the strain relief baked pure plate was determined as the equivalent circle diameter from the number of crystal grains present in an area of 0.5 mm ² .
These measurement results are shown in Table 3.
[0061]
[Table 2]

[0062]
[Table 3]

[0063]
As shown in Table 3, the components are adjusted to an appropriate component composition range according to the present invention, slab heated at an appropriate temperature according to the amount of B and N, and then hot rolled under conditions where the finish rolling outlet temperature is 800 ° C or higher. By performing the above, it was possible to obtain a non-oriented electrical steel sheet having high strength, excellent workability and recyclability, and excellent magnetic properties after strain relief annealing.
[0064]
【The invention's effect】
Thus, according to the present invention, a non-oriented electrical steel sheet having high strength, excellent workability and recyclability, and high magnetic flux density can be stably obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the influence of the amount of (Ti + Nb + V) and the amount of sol.Al on grain growth properties.
FIG. 2 is a diagram showing the influence of the slab heating temperature and the amount of [Bppm] [Nppm] on the magnetic properties after strain relief annealing.
FIG. 3 is a diagram showing the influence of Sb and Sn on the magnetic properties before and after strain relief annealing.

Claims (6)

In mass%
Si: 0.1-1.2%,
Mn: 0.005 to 0.30% and B: 0.0001 to 0.0020 %
And C: 0.0050% or less,
S: 0.0050% or less,
O: 0.0100% or less,
N: 0.0030% or less,
sol.Al: 0.0004% or less and
Ti, was reduced to 0.010% or less of V and Nb in total, the balance being Fe and becomes the composition of the unavoidable impurities, free ratio YP / TS tensile strength and yield point characterized in that at least 0.80 Oriented electrical steel sheet. In Claim 1, a steel plate is further in mass%.
Sn: 0.005-0.2% and
Sb: 0.005-0.10%
Non-oriented electrical steel sheet you characterized by comprising a composition containing one or two or chosen from among the. The steel sheet according to claim 1 or 2, further comprising P: 0.001 to 0.2% by mass%.
Ni: 0.001 to 0.2%
Non-oriented electrical steel sheet you characterized by comprising a composition containing one or two or chosen from among the. In mass%
Si: 0.1-1.2%,
Mn: 0.005 to 0.30% and B: 0.0001 to 0.0020 %
And C: 0.0050% or less,
S: 0.0050% or less,
O: 0.0100% or less,
N: 0.0030% or less,
sol.Al: 0.0004% or less and
Ti, V and Nb are controlled to 0.010% or less in total, and the balance is Fe and unavoidable impurities. Steel slab is hot-rolled after slab, and then one or more times with intermediate annealing. In the manufacturing method of the non-oriented electrical steel sheet consisting of performing the finish annealing after performing the cold rolling of, prior to the hot rolling, after performing the slab heating in the temperature range satisfying the following formula (1), finish rolling delivery temperature: 800 method for producing a non-oriented electrical steel sheet you and performing hot finish rolling at ℃ above conditions.
-19560 / (log [Bppm] [Nppm] -18.10) -273
<T (° C) <-19560 / (log [Bppm] [Nppm] -15.75) -273 --- (1) In Claim 4, a steel plate is further in mass%.
Sn: 0.005-0.2% and
Sb: 0.005-0.10%
I selected one or method for producing a non-oriented electrical steel sheet you characterized by comprising a composition containing two kinds from among the. In Claim 4 or 5, a steel plate is further P: 0.001-0.2% by mass%, and
Ni: 0.001 to 0.2%
I selected one or method for producing a non-oriented electrical steel sheet you characterized by comprising a composition containing two kinds from among the.

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