JP2004332031A - Method for manufacturing non-oriented electromagnetic steel sheet superior in magnetic properties - Google Patents
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Abstract
Description
【0001】
【発明の属する技術分野】
本発明は、電気産業分野でのモータや小型トランスのコアに使用される磁気特性に優れた無方向性電磁鋼板の製造方法に関する。
【0002】
【従来の技術】
無方向性電磁鋼板は、主にモータコアに用いられるが、蛍光灯の安定器などの小型トランスにも使用される。これら電気機器にはエネルギー効率が求められるため、無方向性電磁鋼板には鉄損を少なくすることが要求されている。
鉄損を改善するために実施されてきた従来の主要な技術は、うず電流損を低減させるSiやAl以外の、いわゆる不純物とされる、例えばS,N,C,Oなどをいかに減少させてヒステリシス損を少なくするかであった。
【0003】
そして、析出物の形態としては、MnSやAlNなどが注目されてきたが、それ以外の析出物について詳細に調査されたことはあまりない。これは、実際に無方向性電磁鋼板を電子顕微鏡で詳細に観察してみると、MnSやAlN以外にも数多くの複合析出物、例えばZrCN,Mgのオキシサルファイド、Caのオキシサルファイド、NbCN、TiCS、CuSなどが多種多様に複合析出しており、極めて複雑な多次元成分析出物となっていたため解析が難しかったことにもよる。
【0004】
これら多種成分の析出量は製鋼での含有量に依存するが、ダイナミックな析出挙動は熱間圧延(以下、熱延と略す)や熱延板以降の熱処理条件によっても支配される。しかしながら、特に熱延工程での析出挙動について詳細に調べられたことは従来あまりない。
【0005】
熱延は通常、連続鋳造されたスラブをスラブ加熱され、加熱炉から抽出された赤熱スラブは数パスでのレバース圧延またはタンデム圧延によって、20〜70mm厚程度の粗バーと呼ばれる中間厚みに加工されてから、数台の仕上スタンドによって仕上圧延されて熱延板厚となり、次いで水冷されてから巻き取られる。粗圧延終了温度は粗圧延温度、仕上圧延終了温度は仕上温度と称される。
【0006】
従来の熱延での製造技術として、例えば特許文献1が知られている。この方法は、スラブを1150℃以下に加熱した後、60%以上の圧下率で粗圧延し、続いてこの粗バーを1000〜1150℃に加熱してから2〜10s保持する。その後仕上圧延して650℃以上で巻き取ることである。その目的はリジングの解消と鉄損改善である。しかしながら、この方法は粗バーを高周波加熱設備などで加熱する必要があり、このための設備投資や加熱によるコスト増の問題がある。
【0007】
また、特許文献2及び特許文献3は、いずれも粗圧延完了してから粗バーを粗圧延温度よりも20℃以上高く、かつスラブ加熱温度以下の温度に昇温させることで磁気特性を改善する技術である。この方法も粗バーを高周波加熱設備などで加熱する必要があり、このための設備投資や加熱によるコスト増の問題があって経済的でない。
【0008】
特許文献4は、Ti:0.002〜0.007%を含む珪素鋼を熱延で粗圧延してから900〜1100℃の温度範囲で10s以上滞留させることで、磁性焼鈍後の磁気特性が優れた無方向性電磁鋼板の製造方法である。しかしながら、Ti量が多いのでTi系の析出物が析出しやすく、磁気特性が不満であったし、熱延での粗バー段階での時間管理が面倒であった。
また、その他の磁性改善を目的とする熱延技術としては、例えば特許文献5〜9などがある。しかし、これらはいずれも仕上圧延の主に仕上温度に関するもので、特に熱延板の結晶粒径に着眼されているのみで、析出分散相を改善する技術ではなかった。
【0009】
【特許文献1】
特開平11−61256号公報
【特許文献2】
特開平11−61257号公報
【特許文献3】
特開平11−61258号公報
【特許文献4】
特開2002−161313号公報
【特許文献5】
特開平6−220537号公報
【特許文献6】
特開平4−180522号公報
【特許文献7】
特開平4−63228号公報
【特許文献8】
特開昭51−74923号公報
【特許文献9】
特表2002−543274号公報
【0010】
【発明が解決しようとする課題】
本発明は上記の点に鑑み、析出物の析出サイズを積極的に制御することにより、磁気特性の優れた無方向性電磁鋼板の製造方法を提供する。
【0011】
【課題を解決するための手段】
上記課題を解決するため、本発明は以下の構成を要旨とする。
(1)質量%で、
C ≦0.005%、 Si≦4%、
Al≦2%、 Mn≦1%、
P ≦0.1%、 S ≦0.005%、
0.01%≦Cu≦0.5%、
Ti<0.002%
であって、残部Feおよび不可避的成分を含有する連続鋳造スラブを1150℃以下で加熱し、粗圧延の圧下率を70%以上で粗圧延完了温度を870℃以上とすることを特徴とする磁気特性に優れた無方向性電磁鋼板の製造方法。
【0012】
本発明は、以下の三つのポイントとなる発見から構成される。
第一のポイントは、Cuを含む硫化物の析出形態は、高温での動的な加工変形に支配される。すなわち、温度×時間の析出速度論ではなく、動的に転位が導入されるときの析出が重要である。特にTiなどの不純物の少ない珪素鋼板では、高温での変形そのものによって硫化物サイズが決定されることを見出した。
【0013】
第二は、この高温域とは熱延での粗圧延過程に限定され、粗圧延による加工変形に伴なって硫化物析出形態が決まる。特に粗圧延温度が決定的である。粗圧延完了後の粗バーを加熱などしても、Cu2 Sなどの硫化物が微細に析出してくるので避けなければならない。
第三は、この粗圧延を制御することは工業的に十分可能なことである。なお、硫化物の構造は(Cu,Mn)1.8 S,MnS,Cu2 S,TiSやTi4 C2 S2 などである。
【0014】
【発明の実施の形態】
以下、本発明を詳細に説明する。まず、化学成分の限定理由について説明する。
C量は0.005%以下とする。この範囲に限定したのは、0.005%超のC量では磁気時効に問題があるためである。
【0015】
Si量は4%以下とする。Siは鋼板の固有抵抗を増加させ、鉄損改善に有効であるが、4%を超えると冷間圧延や打ち抜き加工での脆性破壊の問題があるので、4%以下とする。
【0016】
Al量は2%以下に制限する。Alも鋼板の固有抵抗を増加させ、鉄損改善に有効であることが知られているが、添加コストの面もあるので2%以下とする。
【0017】
Mn量は1%以下とする。Mnも鋼板の固有抵抗を増加させ、鉄損改善に有効であるが、添加コストの問題もあるので1%以下とする。またMnは硫化物を形成し、この硫化物が多量にそして微細に析出すれば、再結晶での結晶粒成長を阻害するし、磁壁移動の障害にもなって磁気特性を劣化させるので、特に熱延工程で析出挙動を制御する必要がある。
【0018】
P量は0.1%以下に制限する。Pはモータコアや小型トランスコア形状への打ち抜きに有効な元素で、特に打ち抜き鋼板のかえりを少なくする効果があるが、多すぎると添加コストの問題があるので0.1%以下とする。
【0019】
S量は0.005%以下とする。S量は多くなると硫化物の量も多くなるので鉄損が劣化する。この限界が0.005%である。
【0020】
Cu量は0.01%以上、0.5%以下に制限する。Cuは鋼板の固有抵抗を増加させて鉄損を低減する。上限量を0.5%としたのは、添加コストの面からである。また、CuはMnよりも硫化物を形成しやすく、Cu量が0.01%以上でCu系の硫化物を析出し、MnSよりも数十nm以下の微細なサイズに析出する傾向にある。
0.01%未満のCuではCu系の硫化物析出が少なく、本発明の熱延条件では磁気特性が不満となるので避ける。0.01%以上のCuで、このCu系硫化物が多量にそして微細に析出すれば、再結晶での結晶粒成長を阻害するし、磁壁移動の障害にもなって磁気特性を劣化させるので、後述する熱延工程で析出挙動を制御する必要がある。
【0021】
Ti量は0.002%未満に限定する。Tiは微量であっても微細なTi系硫化物、窒化物や炭化物を形成して、本発明の硫化物サイズ制御技術を活用しても鉄損が劣化する。この限界のTi量が0.002%である。Ti<0.002%の領域で、なおかつCu含有成分系で、後述の粗圧延温度の影響が初めて明確になってきたもので、従来の高Ti域では粗圧延温度の効果が不明確であった。
【0022】
その他の元素として、一次再結晶集合組織を改善する元素として知られているSn,Sb,Ni,Cr,Bなどを含有しても問題はないが、コスト面からそれぞれ0.1%以下が好ましい。また、NやOについては、従来通り少ないほうが好ましい。
【0023】
次に、本発明の製造方法について説明する。
熱延のスラブ加熱は、温度を1150℃以下に制限する。スラブ加熱が高いと硫化物、窒化物や炭化物が固溶して続く圧延段階で微細に析出するので避けなければならないが、その限界温度が1150℃である。また、固溶抑制のために低温加熱のほうが好ましいが、圧延機のミルパワーとの関連もあり、現在では900℃程度が能力限界と考えられる。加熱時間は通常の10分〜4時間である。
【0024】
加熱炉から抽出されたスラブは粗圧延される。粗圧延は数パスでレバースまたはタンデム圧延が採用可能である。粗圧延の始めまたは途中で竪ロールにより幅方向に圧下されることも問題ない。粗圧延の圧下率、粗圧延温度の二者が硫化物の析出形態を支配するので決定的に重要である。なお、従来技術の粗バーで加熱させたり所定時間を滞留させたりしても逆効果である。
【0025】
粗圧延の圧下率は70%以上とする。圧下率が70%未満では、微細な硫化物が析出しがたいので、本願発明の狙いとする析出制御が不要で対象外である。なお、この圧下率は通常の水平ロールによる圧下率の意味である。
【0026】
粗圧延温度は870℃以上とする。粗圧延温度は高温の方が鉄損改善されるが、870℃未満では鉄損が不満であるため避けなければならない。粗圧延温度が870℃未満となる低温では、粗圧延で硫化物が微細に析出する。
粗圧延温度は、粗バー(粗圧延後の鋼板の意味)の頭部、尾部で、例えば70℃程度の差で頭部が高温で尾部が低温となることもあるが、微細な硫化物を析出させないためには粗バーの全長で、すなわち尾部の低温部分でも870℃以上を確保しなければならない。このため、スラブ単重を少なくすることや、頭部から尾部にかけて加速圧延(ズーム圧延)することは効果的である。
【0027】
なお、スラブが加熱炉抽出されてから粗圧延完了までの時間については、長時間では硫化物が微細に析出する傾向であるため、500s以下の範囲がよい。更に好ましい範囲は400sであるが、工業的には100s以上は粗圧延完了に必要なので、100〜400sが望ましい。
【0028】
仕上圧延および巻き取りは従来の条件、例えば仕上温度が700〜1100℃、熱延板厚み1〜3mm、巻き取り温度400〜800℃が採用される。
【0029】
熱延板以降の工程については、従来の無方向性電磁鋼板製造工程を採用することができる。すなわち、熱延板焼鈍してもよいし省略も可能である。次いで冷延されてから再結晶焼鈍する。そのまま出荷することも可能であるし、数%のスキンパス圧延を実施してもよい。顧客で焼鈍されるいわゆるセミプロセス材としてもまた、焼鈍されないフルプロセス材としても使用が可能である。
以下、本発明の実施例について説明する。
【0030】
【実施例】
〔実施例−1〕
表1に示す各種成分を含有する連続鋳造スラブを鋳造し、加熱温度を1100℃として100分均熱してから抽出し、粗圧延を250mm厚から40mm厚までの84%圧下率で、7パスのレバース圧延として、粗圧延温度を930℃とした。加熱炉から粗圧延完了までの時間は300秒であった。次いで6スタンドでのタンデム仕上圧延を行い、2.5mm厚の熱延板を得た。
【0031】
仕上温度は870℃であった。巻き取り温度は600℃とした。0.3%Si材についてはこの熱延板を酸洗し、冷延して0.50mmとした。次いで連続焼鈍を800℃で5s均熱を水素中で実施した。また、3.1%Si材については熱延板を1000℃×30s均熱、窒素中で焼鈍し、酸洗後、0.35mmまで冷延してから、1050℃×5s均熱を水素中で実施した。磁気特性はエプスタイン試料で測定した。結果を表1に示す。
【0032】
【表1】
【0033】
実験 No.1〜4は、0.3%Si系でS量のみを変更したもので、本発明範囲内の0.005%以下のS量のものは優れた鉄損が得られた。
実験 No.5〜8は、3.1%Si系でTi量のみを変更したもので、本発明範囲外のTi量のものは鉄損特性が不満であった。実験 No.9〜12は、3.1%Si系でCu量のみを変更したもので、本発明範囲外のCu量のものは鉄損特性が不満であった。
【0034】
〔実施例−2〕
質量%で、0.003%C、0.5%Si、0.2%Al、0.1%Mn、0.04%P、0.002%S、0.05%Cu、0.001%Tiを含む連続鋳造スラブから切り出した鋼塊をラボ熱延した。この鋼塊に対して、加熱温度および粗圧延での圧下率を変更試験した。加熱での均熱時間は60分とした。
粗圧延は7パスのレバースとし、粗圧延後の厚さは25mmに固定して、粗圧延圧下率は粗圧延前の鋼塊厚さを調整して変更した。粗圧延温度は、900℃一定とした。
【0035】
加熱温度変更材の粗圧延温度を一定とするため、高温加熱材は粗圧延前で鋼塊を一時放冷させた。仕上圧延は3パスのタンデムとし、仕上温度は830℃一定で厚みは2.0mmとした。熱延板を酸洗後、0.50mm厚に冷延して、750℃×30秒の連続焼鈍を水素・窒素混合気流中で行った。55mm角の試料に打ち抜いてから、歪取焼鈍750℃×2h・N2 中で実施後、また鉄損と磁束密度をSST測定した。
【0036】
【表2】
【0037】
本発明の範囲内の加熱温度範囲(1150℃以下)および粗圧延圧下率範囲 (70%以上)のものは、優れた磁気特性が得られた。なお、本発明範囲では低磁場の100A/mでの磁束密度B1 も、従来の比較例に比べて優れていることが分かった。
【0038】
〔実施例−3〕
質量%で、0.002%C、3.0%Si、0.4%Al、0.2%Mn、0.006%P、0.0003%S、0.22%Cu、0.0002%Tiを含む連続鋳造スラブを鋳造した。なお、その他の元素も化学分析したがその結果は、0.0008%N、0.09%Ni、0.03%Cr、0.05%Sn、0.001%Nb、0.001%Sb、0.005%Mo、0.0007%Ca、0.0007%Mg、0.002%O、0.0003%B、0.0015%Zr、0.0005%Sbであったが、これら不可避的不純物は原料および耐火物やのろからの混入である。
スラブを1130℃で2h加熱してから、5パスのレバース粗圧延を行い、粗圧延温度を圧延までの時間、デスケ水量や圧下パターン(前段パス強圧下または後段パス強圧下)などの調整で表3に示すように変更した。
【0039】
粗圧延後の厚さは30mm(粗圧延圧下率88%)とした。なお、スラブ加熱炉抽出から粗圧延完了までの時間を測定し表3に示した。仕上圧延温度800℃、巻き取り温度700℃として、1.3mm厚の熱延板を得た。1100℃×60s均熱焼鈍してから、0.15mmまで冷延してから、1000℃×100s均熱の水素・窒素混合気流中で焼鈍した。磁気特性はエプスタイン試料で測定した。結果を表3に併せて示す。
【0040】
【表3】
【0041】
表3に示すように、本発明範囲である粗圧延温度が870℃以上のものは、優れた磁気特性が得られた。なお、同じ粗圧延温度(実験 No.5と6)では粗圧延完了までの時間が短い方が鉄損が少ない傾向であった。
【0042】
【発明の効果】
以上の如く本発明によれば、析出物の析出サイズを積極的に制御することにより、磁気特性の優れた無方向性電磁鋼板を製造することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties used for a core of a motor or a small transformer in the electric industry.
[0002]
[Prior art]
Non-oriented electrical steel sheets are mainly used for motor cores, but also for small transformers such as fluorescent light ballasts. Since energy efficiency is required for these electrical devices, non-oriented electrical steel sheets are required to reduce iron loss.
Conventional major techniques that have been implemented to improve iron loss are to reduce so-called impurities other than Si and Al, which reduce eddy current loss, such as S, N, C, and O, for example. It was to reduce the hysteresis loss.
[0003]
MnS, AlN, and the like have attracted attention as the form of the precipitate, but other precipitates have not been investigated in detail. This is because when a non-oriented electrical steel sheet is actually observed in detail by an electron microscope, there are many composite precipitates other than MnS and AlN, such as ZrCN, Mg oxysulfide, Ca oxysulfide, NbCN, TiCS , CuS and the like are complexly precipitated in a wide variety of forms, and are extremely complicated multi-dimensional component precipitates, which makes analysis difficult.
[0004]
The precipitation amount of these various components depends on the content in steelmaking, but the dynamic precipitation behavior is also governed by hot rolling (hereinafter abbreviated as hot rolling) and heat treatment conditions after the hot rolled sheet. However, the precipitation behavior in the hot rolling process has not been specifically investigated so far.
[0005]
Hot rolling is usually performed by slab heating a continuously cast slab, and the red hot slab extracted from the heating furnace is processed to an intermediate thickness called a coarse bar of about 20 to 70 mm thickness by reversing rolling or tandem rolling in several passes. Then, it is finish-rolled by several finishing stands to a hot-rolled sheet thickness, then cooled with water and wound up. The rough rolling end temperature is called a rough rolling temperature, and the finish rolling end temperature is called a finishing temperature.
[0006]
For example, Patent Document 1 is known as a conventional hot rolling production technique. In this method, after the slab is heated to 1150 ° C. or less, rough rolling is performed at a rolling reduction of 60% or more, and then the rough bar is heated to 1000 to 1150 ° C. and held for 2 to 10 s. Thereafter, finish rolling is carried out at 650 ° C. or higher. The purpose is to eliminate ridging and improve iron loss. However, in this method, it is necessary to heat the rough bar with a high-frequency heating equipment or the like, and there is a problem of equipment investment for this and an increase in cost due to heating.
[0007]
Further, Patent Documents 2 and 3 both improve the magnetic properties by raising the coarse bar to a temperature higher than the rough rolling temperature by 20 ° C. or more and lower than the slab heating temperature after the rough rolling is completed. Technology. This method also requires the coarse bar to be heated by a high-frequency heating facility or the like, and is not economical due to the capital investment and the cost increase due to heating.
[0008]
Patent Literature 4 discloses that, after roughly rolling a silicon steel containing Ti: 0.002 to 0.007% by hot rolling and retaining the steel for 10 s or more in a temperature range of 900 to 1100 ° C., the magnetic characteristics after magnetic annealing are improved. This is an excellent method for producing non-oriented electrical steel sheets. However, since the amount of Ti is large, Ti-based precipitates are likely to precipitate, and the magnetic properties are unsatisfactory, and time management in the rough bar stage in hot rolling is troublesome.
As other hot rolling techniques for improving magnetism, there are Patent Documents 5 to 9, for example. However, all of them relate mainly to the finishing temperature of the finish rolling, and particularly focus on the crystal grain size of the hot-rolled sheet, and are not techniques for improving the precipitated dispersed phase.
[0009]
[Patent Document 1]
JP-A-11-61256 [Patent Document 2]
JP-A-11-61257 [Patent Document 3]
JP-A-11-61258 [Patent Document 4]
JP 2002-161313 A [Patent Document 5]
Japanese Patent Application Laid-Open No. 6-220737 [Patent Document 6]
JP-A-4-180522 [Patent Document 7]
JP-A-4-63228 [Patent Document 8]
JP-A-51-74923 [Patent Document 9]
Japanese Unexamined Patent Publication No. 2002-543274
[Problems to be solved by the invention]
In view of the above, the present invention provides a method for producing a non-oriented electrical steel sheet having excellent magnetic properties by actively controlling the precipitate size of precipitates.
[0011]
[Means for Solving the Problems]
To achieve the above object, the present invention has the following features.
(1) In mass%,
C ≦ 0.005%, Si ≦ 4%,
Al ≦ 2%, Mn ≦ 1%,
P ≦ 0.1%, S ≦ 0.005%,
0.01% ≦ Cu ≦ 0.5%,
Ti <0.002%
Wherein the continuous casting slab containing the balance of Fe and unavoidable components is heated at 1150 ° C. or less, and the rough rolling reduction is 70% or more, and the rough rolling completion temperature is 870 ° C. or more. A method for producing non-oriented electrical steel sheets with excellent properties.
[0012]
The invention consists of the following three key findings:
The first point is that the precipitation form of sulfide containing Cu is governed by dynamic deformation at high temperature. In other words, it is not the temperature-time precipitation kinetics that is important, but the precipitation when the dislocations are introduced dynamically. In particular, it has been found that the sulfide size is determined by the deformation itself at a high temperature in a silicon steel sheet containing few impurities such as Ti.
[0013]
Second, the high temperature range is limited to the rough rolling process in hot rolling, and the sulfide precipitation form is determined by the working deformation due to the rough rolling. In particular, the rough rolling temperature is decisive. Even if the coarse bar after the completion of the rough rolling is heated, it must be avoided because sulfides such as Cu 2 S are finely precipitated.
Third, it is industrially sufficiently possible to control this rough rolling. The structure of the sulfide is (Cu, Mn) 1.8 S, MnS, Cu 2 S, TiS, Ti 4 C 2 S 2 and the like.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. First, the reasons for limiting the chemical components will be described.
The C content is 0.005% or less. The reason for limiting to this range is that if the amount of C exceeds 0.005%, there is a problem in magnetic aging.
[0015]
The amount of Si is set to 4% or less. Si increases the specific resistance of the steel sheet and is effective in improving iron loss. However, if it exceeds 4%, there is a problem of brittle fracture in cold rolling or punching, so Si is set to 4% or less.
[0016]
The amount of Al is limited to 2% or less. It is known that Al also increases the specific resistance of the steel sheet and is effective in improving iron loss. However, since there is also the cost of addition, the content is set to 2% or less.
[0017]
The Mn content is 1% or less. Mn also increases the specific resistance of the steel sheet and is effective in improving iron loss. However, there is a problem of addition cost, so Mn is set to 1% or less. In addition, Mn forms a sulfide, and if this sulfide is precipitated in a large amount and finely, it inhibits crystal grain growth in recrystallization and also hinders domain wall movement and deteriorates magnetic properties. It is necessary to control the precipitation behavior in the hot rolling process.
[0018]
The P content is limited to 0.1% or less. P is an element effective for punching into a motor core or a small transformer core shape. In particular, P has an effect of reducing burrs of a punched steel sheet, but if it is too large, there is a problem of addition cost, so P is set to 0.1% or less.
[0019]
The amount of S is set to 0.005% or less. As the amount of S increases, the amount of sulfide also increases, so that iron loss deteriorates. This limit is 0.005%.
[0020]
The Cu content is limited to 0.01% or more and 0.5% or less. Cu increases the specific resistance of the steel sheet and reduces iron loss. The upper limit is set to 0.5% from the viewpoint of addition cost. Further, Cu forms sulfides more easily than Mn, and when the amount of Cu is 0.01% or more, Cu-based sulfides tend to precipitate, and tend to precipitate to a fine size of several tens nm or less than MnS.
If the Cu content is less than 0.01%, Cu-based sulfide precipitates are small, and the magnetic properties are unsatisfactory under the hot rolling conditions of the present invention. If this Cu-based sulfide precipitates in a large amount and finely in 0.01% or more of Cu, the growth of crystal grains in recrystallization is hindered, and this also hinders domain wall movement and deteriorates magnetic properties. In addition, it is necessary to control the precipitation behavior in a hot rolling step described later.
[0021]
The amount of Ti is limited to less than 0.002%. Even though a small amount of Ti forms fine Ti-based sulfides, nitrides and carbides, iron loss is deteriorated even if the sulfide size control technology of the present invention is utilized. This limit of Ti content is 0.002%. In the region of Ti <0.002%, and in the Cu-containing component system, the effect of the rough rolling temperature, which will be described later, has become clear for the first time. In the conventional high Ti region, the effect of the rough rolling temperature is unclear. Was.
[0022]
As other elements, there is no problem if Sn, Sb, Ni, Cr, B, etc., which are known as elements for improving the primary recrystallization texture, are preferably 0.1% or less in terms of cost. . Further, as for N and O, it is preferable that the number is small as before.
[0023]
Next, the manufacturing method of the present invention will be described.
Slab heating of hot rolling limits the temperature to 1150 ° C or less. If the slab heating is high, sulfides, nitrides, and carbides must be avoided because they form a solid solution and precipitate finely in the subsequent rolling stage. However, the limit temperature is 1150 ° C. In addition, low-temperature heating is more preferable to suppress solid solution, but there is a relation with mill power of a rolling mill, and at present, about 900 ° C. is considered to be the capacity limit. The heating time is usually 10 minutes to 4 hours.
[0024]
The slab extracted from the heating furnace is roughly rolled. For rough rolling, reversals or tandem rolling can be adopted in several passes. There is no problem that the rolling is performed in the width direction by the vertical roll at the beginning or during the rough rolling. The rolling reduction of the rough rolling and the rough rolling temperature are crucial since they govern the sulfide precipitation form. It should be noted that heating with a conventional coarse bar or retaining for a predetermined time has an adverse effect.
[0025]
The rolling reduction of the rough rolling is 70% or more. If the rolling reduction is less than 70%, fine sulfides are difficult to precipitate, and the precipitation control aimed at by the present invention is unnecessary and is out of scope. The rolling reduction means a rolling reduction by a normal horizontal roll.
[0026]
The rough rolling temperature is 870 ° C. or higher. As for the rough rolling temperature, the higher the temperature, the better the iron loss. However, if the temperature is lower than 870 ° C., the iron loss is unsatisfactory and must be avoided. At a low temperature at which the rough rolling temperature is lower than 870 ° C., sulfides are finely precipitated by the rough rolling.
The rough rolling temperature is the head and tail of the coarse bar (meaning the steel sheet after rough rolling). For example, the head may be high and the tail may be low with a difference of about 70 ° C. In order to prevent precipitation, it is necessary to secure 870 ° C. or more over the entire length of the coarse bar, that is, even at the low temperature portion of the tail. For this reason, it is effective to reduce the single weight of the slab and to perform accelerated rolling (zoom rolling) from the head to the tail.
[0027]
The time from the extraction of the slab in the heating furnace to the completion of the rough rolling is preferably 500 s or less because sulfides tend to precipitate finely over a long time. A more preferable range is 400 s. However, 100 s or more is required for the completion of rough rolling industrially, so 100 to 400 s is desirable.
[0028]
For the finish rolling and winding, conventional conditions, for example, a finishing temperature of 700 to 1100 ° C, a hot-rolled sheet thickness of 1 to 3 mm, and a winding temperature of 400 to 800 ° C are employed.
[0029]
For the steps after the hot-rolled sheet, a conventional non-oriented electrical steel sheet manufacturing step can be adopted. That is, hot-rolled sheet annealing may be performed or may be omitted. Next, it is cold rolled and then recrystallized. It can be shipped as it is, or may be subjected to several percent skin pass rolling. It can be used as a so-called semi-processed material that is annealed by the customer or as a full-processed material that is not annealed.
Hereinafter, examples of the present invention will be described.
[0030]
【Example】
[Example-1]
A continuous cast slab containing the various components shown in Table 1 was cast, heated at a temperature of 1100 ° C., soaked for 100 minutes, and then extracted. Rough rolling was performed at 84% reduction from 250 mm to 40 mm thick in 7 passes. As the reversal rolling, the rough rolling temperature was 930 ° C. The time from the heating furnace to the completion of the rough rolling was 300 seconds. Next, tandem finish rolling was performed at six stands to obtain a hot-rolled sheet having a thickness of 2.5 mm.
[0031]
The finishing temperature was 870 ° C. The winding temperature was 600 ° C. For the 0.3% Si material, the hot rolled sheet was pickled and cold rolled to 0.50 mm. Subsequently, continuous annealing was carried out at 800 ° C. for 5 s in hydrogen. For the 3.1% Si material, the hot-rolled sheet was annealed in nitrogen at 1000 ° C. for 30 s, pickled, cold-rolled to 0.35 mm, and then soaked in hydrogen at 1050 ° C. for 5 s. It was carried out in. Magnetic properties were measured on Epstein samples. Table 1 shows the results.
[0032]
[Table 1]
[0033]
Experiment No. In Nos. 1-4, only the S content was changed in the 0.3% Si system, and those with S content of 0.005% or less within the range of the present invention obtained excellent iron loss.
Experiment No. Nos. 5 to 8 were 3.1% Si-based steels with only the Ti content changed, and those having a Ti content outside the range of the present invention were not satisfactory in iron loss characteristics. Experiment No. Nos. 9 to 12 are 3.1% Si-based alloys in which only the amount of Cu was changed, and those having a Cu amount outside the range of the present invention were not satisfactory in iron loss characteristics.
[0034]
[Example-2]
0.003% C, 0.5% Si, 0.2% Al, 0.1% Mn, 0.04% P, 0.002% S, 0.05% Cu, 0.001% by mass% A steel ingot cut from a continuous cast slab containing Ti was lab hot rolled. This steel ingot was tested by changing the heating temperature and the rolling reduction in the rough rolling. The soaking time for heating was 60 minutes.
The rough rolling was performed with 7 passes reversals, the thickness after the rough rolling was fixed at 25 mm, and the rough rolling reduction was changed by adjusting the thickness of the steel ingot before the rough rolling. The rough rolling temperature was constant at 900 ° C.
[0035]
In order to keep the rough rolling temperature of the heating temperature changed material constant, the steel ingot was temporarily cooled before the rough rolling of the high temperature heating material. Finish rolling was performed in three passes in tandem, the finishing temperature was 830 ° C., and the thickness was 2.0 mm. After pickling the hot-rolled sheet, the sheet was cold-rolled to a thickness of 0.50 mm and continuously annealed at 750 ° C. for 30 seconds in a mixed gas stream of hydrogen and nitrogen. After punching out a 55 mm square sample, the sample was subjected to strain relief annealing at 750 ° C. × 2 h · N 2 , and the iron loss and the magnetic flux density were measured by SST.
[0036]
[Table 2]
[0037]
In the case of the heating temperature range (1150 ° C. or less) and the rough rolling reduction rate range (70% or more) within the range of the present invention, excellent magnetic properties were obtained. In the present invention the range is also the magnetic flux density B 1 in a low magnetic field of 100A / m, it was found to be superior to conventional comparative example.
[0038]
[Example-3]
0.002% C, 3.0% Si, 0.4% Al, 0.2% Mn, 0.006% P, 0.0003% S, 0.22% Cu, 0.0002% by mass% A continuous cast slab containing Ti was cast. In addition, other elements were also chemically analyzed, but the results were as follows: 0.0008% N, 0.09% Ni, 0.03% Cr, 0.05% Sn, 0.001% Nb, 0.001% Sb, 0.005% Mo, 0.0007% Ca, 0.0007% Mg, 0.002% O, 0.0003% B, 0.0015% Zr and 0.0005% Sb. Is contamination from raw materials and refractories and sludge.
After heating the slab at 1130 ° C for 2 hours, perform 5-pass reversal rough rolling. 3 was changed as shown.
[0039]
The thickness after the rough rolling was 30 mm (rough rolling reduction 88%). In addition, the time from slab heating furnace extraction to completion of rough rolling was measured and shown in Table 3. A hot rolled sheet having a thickness of 1.3 mm was obtained at a finish rolling temperature of 800 ° C and a winding temperature of 700 ° C. After annealing at 1100 ° C. × 60 s, the steel sheet was cold-rolled to 0.15 mm, and then annealed in a hydrogen / nitrogen mixed gas stream at 1000 ° C. × 100 s. Magnetic properties were measured on Epstein samples. The results are shown in Table 3.
[0040]
[Table 3]
[0041]
As shown in Table 3, those having a rough rolling temperature of 870 ° C. or higher, which is the range of the present invention, exhibited excellent magnetic properties. At the same rough rolling temperature (Experiment Nos. 5 and 6), the shorter the time until the completion of the rough rolling, the smaller the iron loss tended to be.
[0042]
【The invention's effect】
As described above, according to the present invention, a non-oriented electrical steel sheet having excellent magnetic properties can be manufactured by actively controlling the precipitate size of precipitates.
Claims (1)
C ≦0.005%、
Si≦4%、
Al≦2%、
Mn≦1%、
P ≦0.1%、
S ≦0.005%、
0.01%≦Cu≦0.5%、
Ti<0.002%
であって、残部Feおよび不可避的成分を含有する連続鋳造スラブを1150℃以下で加熱し、粗圧延の圧下率を70%以上で粗圧延完了温度を870℃以上とすることを特徴とする磁気特性に優れた無方向性電磁鋼板の製造方法。In mass%,
C ≦ 0.005%,
Si ≦ 4%,
Al ≦ 2%,
Mn ≦ 1%,
P ≦ 0.1%,
S ≦ 0.005%,
0.01% ≦ Cu ≦ 0.5%,
Ti <0.002%
Wherein the continuous casting slab containing the balance of Fe and unavoidable components is heated at 1150 ° C. or less, and the rough rolling reduction is 70% or more and the rough rolling completion temperature is 870 ° C. or more. A method for producing non-oriented electrical steel sheets with excellent properties.
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