JP4337159B2 - Manufacturing method of silicon steel sheet and hot rolled steel strip material for silicon steel sheet - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、熱延鋼帯コイルの箱焼鈍後に冷間圧延を行う工程を含む、珪素鋼板の製造方法とこの製造方法に適合する熱延鋼帯素材に関する。
【０００２】
【従来の技術】
珪素鋼板は電磁材料として優れた特性を有しており、各種の電磁気製品に使用されている。
かかる珪素鋼板を製造するには、一般に、例えば、特開昭54-68717号公報に開示されているように、鋼片を加熱後、熱間圧延し、熱延鋼帯の焼鈍（母板焼鈍）を行ってから、冷間圧延と焼鈍とを施す工程が必要となる。
なかでも、無方向性珪素鋼板(JIS C 2552)の場合には、ユーザーにて打抜き加工され、積層して使用されるのが一般的であり、その多くは、打抜き加工後にユーザーにて歪み取り焼鈍を行う、いわゆるセミプロセス材として供給される。
【０００３】
このような珪素鋼板の製造工程において、通常は、熱間仕上圧延の温度をＡr3点以下にして、フェライト域圧延を行うことによって圧延歪みを付与し、コイル巻き取り後の自己焼鈍効果によって再結晶化を促進させる。その後、さらに熱延鋼帯焼鈍により、冷間圧延を行い、最終的に結晶粒を調整して、電磁特性の向上を図っている。
ところで、上記熱間圧延後に施される焼鈍は、多くが連続焼鈍により行われるものの、結晶粒を[100] 方向に揃えて電磁特性の向上を図るような場合には、一般に、結晶粒を粗大化かつ均一な大きさに調整するという目的から、箱焼鈍が採用されている。
【０００４】
【発明が解決しようとする課題】
かかる箱焼鈍、とりわけ鋼帯同士を密着状態にして焼鈍する、いわゆるタイト焼鈍により、熱延珪素鋼鋼帯を焼鈍するときには、板幅端部の部分は中央部の部分よりも焼鈍による熱の影響を受けやすくなる。このため、鋼帯の板幅端の部分の組織は中央部の部分よりも粗大化する。そしてこのような状態の熱延鋼帯を冷間圧延すると、鋼帯の板幅端部の部分では局部的な耳伸び（10〜15ｍｍ程度）を生じて形状不良を発生するという問題があった。
耳伸びが一旦発生すると、積層して使用することの多い珪素鋼板に必要な平坦度を損ない、品質の低下を招くのみでなく、歩留り・生産性の低下といった多くの障害がもたらされる。
【０００５】
しかし、珪素鋼板の冷間圧延時にみられる耳伸びを抑制するという見地からの研究は、これまでにさほど多くは行われていないのが実状である。わずかに、特開昭60-162751 号公報に、セミプロセス電磁鋼板の冷間圧延においてコイルエッジに不均一な伸びを示す領域が存在すること、この不均一な伸びは最終仕上げ焼鈍で600 〜800 ℃の温度で１〜２分間の短時間連続焼鈍を施せば解決できるとの記載があるにすぎない。
しかし、発明者らは、上記既知技術では、板幅端部の部分における耳伸びが大きくなった場合に、連続焼鈍によって修正しきれないことを確認した。
【０００６】
そこで、本発明の目的は、従来技術が抱えていたこのような問題を解決し、熱延鋼帯を箱焼鈍後に冷間圧延した際に、耳伸びを発生することのない、良好な形状をもつ珪素鋼板を得るための製造方法を提案することにある。
また、本発明の他の目的は、かかる製造方法に適用するための珪素鋼板用の熱延鋼帯を提供することにある。
なお、具体的には、冷間圧延し、連続焼鈍した後の耳伸びを２ｍｍ以下 (冷間圧延後にて５ｍｍ以下) の極めて少ない範囲に抑制するための珪素鋼板の製造方法と、この方法に適した熱延鋼帯素材を提案するものである。
【０００７】
【課題を解決するための手段】
発明者らは、上記の目的を達成すべく、局部的に大きな耳伸びを発生するコイルでは、変形抵抗に大きな違いがあるのではないかと考え、冷間圧延前の熱延鋼帯について板幅方向の硬度分布を調査した。その結果、耳伸びを生じるような従来の熱延鋼帯は、図１(b) に示すように、鋼帯の板幅端部の部分の硬度が中央部の部分よりも大きく低下していた。そこで、この幅方向の硬度差を解消することが耳伸びのない安定した冷間圧延を可能にすると考えた。
【０００８】
発明者らは、硬度差を低減するための有効な方法について鋭意実験を重ね、加熱してから熱間圧延終了までの冷却過程で、鋼帯の板幅端部分を中央部分よりも低温になるように、鋼帯の冷却を強めに行うことが極めて有効であることを知見した。このような熱間圧延後の冷却を行うことにより、コイル巻き取り後の自己焼鈍効果が幅端部では抑制され、その後の箱焼鈍で不均一な熱負荷を受けても、焼鈍後には、幅方向に一様な粒径分布となり、硬度ひいては冷間圧延性を均一にしうることがわかった。
【０００９】
本発明はこのような知見に基づいて完成されたものであり、その要旨とするところは次のとおりである。
（１）Ｃ：０.０２ｗｔ％以下、Ｓｉ：０.５〜３.５ｗｔ％を含有する珪素鋼スラブを加熱後、熱間圧延し、得られた熱延鋼帯をコイルに巻き取って箱焼鈍を施し、その後冷間圧延して珪素鋼板を製造するにあたり、スラブ加熱温度を１０９０〜１１５０℃、熱間圧延終了温度を８５０〜７５０℃にするとともに、該スラブ加熱から該熱間圧延終了までの温度低下量を２７０〜３５０℃に制御して、巻き取り後の熱延鋼帯における板幅端から１５ｍｍの位置のビッカース硬度を板幅端から１００ｍｍの位置より内側のビッカース硬度の平均値より３０以上高くし、箱焼鈍を８５０〜９００℃にて１〜１０時間施すことを特徴とする、珪素鋼板の製造方法。
【００１１】
（２）Ｃ：０.０２ｗｔ％以下、Ｓｉ：０.５〜３.５ｗｔ％を含有し、残部がＦｅおよび不可避的不純物からなる成分組成を有し、箱焼鈍後に冷間圧延を施すための珪素鋼板用の熱延鋼帯素材であって、該熱延鋼帯における板幅端から１５ｍｍの位置のビッカース硬度が、板幅端から１００ｍｍの位置より内側のビッカース硬度の平均値より３０以上高いことを特徴とする、珪素鋼板用の熱延鋼帯素材。
（３）上記成分組成に加えてさらに、Ａｌ：０．１〜１．０ｗｔ％、Ｍｎ：１．０ｗｔ％以下、Ｓ：０．００７ｗｔ％以下、Ｖ：０．５０ｗｔ％以下、Ｃｕ：０．５０ｗｔ％以下、Ｃｒ：０．５０ｗｔ％以下、Ｎｉ：０．５０ｗｔ％以下、Ｔｉ：０．５０ｗｔ％以下およびＳｂ：０．５０ｗｔ％以下のうちから選ばれる１種または２種以上を含有することを特徴とする上記の珪素鋼板用の熱延鋼帯素材。
【００１２】
【発明の実施の形態】
次に、上記要旨構成のとおりに限定した理由について説明する。
Ｃ：0.02wt％以下
Ｃは、電磁鋼板としての特性上有害な元素であることが知られており、最終的に少なくする必要がある。とくにＣ含有量が0.02wt％を超えると、熱延鋼帯焼鈍による脱炭量を考慮しても悪影響が残るので、0.02wt％以下とする。
【００１３】
Si：0.5 〜3.5 wt％
Siは、電磁特性を得るに必要な元素であり、少なくとも0.5 wt％の含有量は必要であるが、3.5 wt％を超えて含有すると冷間圧延性が極めて悪くなる。よって、Si量は0.5 〜3.5 wt％の範囲とする。
【００１４】
本発明における熱間圧延用の珪素鋼素材の成分には、上記Ｃ、Siのほか、必要に応じて、Al、Mn、Ｓ等を含むことができる。その好ましい含有範囲は以下のとおりである。
Alは、0.1 wt％より少ない場合にはAlＮが析出し、結晶粒の成長を抑制する作用があるため望ましくないが、1.0 wt％を超えて含有すると冷間圧延性が低下するので、1.0 wt％以下に止めるのが望ましい。
Ｓは、結晶粒の成長を阻害しない程度の含有量とするため、0.007 wt％以下の範囲とするのがよい。
またMnは、熱間脆性防止のために1.0 wt％以下添加され、鋼を強化する役目も有している。
そのほかに、Ｖ, Cu, Cr, Ni, Ti, Sb各0.50wt％以下を含むことができる。これら成分のほかは、電磁特性を維持するために、不純物を除き残部鉄とするのが望ましい。
【００１５】
スラブ加熱温度：1090〜1150℃
スラブ加熱温度が1090℃に満たないと熱間圧延そのものに支障をきたすほか、熱間圧延終了までの目標とする温度差が確保できなくなる。一方、1150℃を超えるとSiを含む強固なスケールが生成して、脱スケールが困難となり、鋼帯の表面性状に悪影響を及ぼす。よって、スラブ加熱は1090〜1150℃の温度範囲で行う。
【００１６】
熱間圧延終了温度：750 〜850 ℃
熱間圧延の終了温度は、必要な電磁特性を確保するために750 〜850 ℃とする。というのは、仕上げ圧延出側温度が850 ℃を超えると、α域圧延による歪みの付加が少なくなり、結晶粒成長の阻害要因となるとともに、スラブ抽出加熱温度との差が小さくなり、熱延鋼帯の板幅端部（すなわち、コイルエッジ部に相当）の軟化の要因となり好ましくない。また、750 ℃に満たないと、コイル巻き取り後の自己焼鈍効果を得、かつエッジ部の温度を低下させることが困難になる。
なお、上記熱間圧延終了温度は、鋼帯の板幅方向の中央部表面の位置で測定した値とする。
【００１７】
熱間仕上げ圧延時の冷却とコイル巻き取り前の硬度
スラブ加熱から熱間圧延終了までの温度低下量は、本発明の重要な要件である。この温度低下量が、270 〜350 ℃、好ましくは280 ℃〜320 ℃であれば、冷却に伴う板幅端部の過冷が適度に大きくなり、コイル巻き取り後における、板幅端部での自己焼鈍による再結晶は中央部と比較してほとんど行われない。このときに、板幅中央部のビッカース硬度は、板幅端部のビッカース硬度よりも３０以上、好ましくは３５以上高い値となる。しかるのち、この熱延鋼帯を焼鈍すると、板幅方向の粒径分布が一様となり、硬さも板幅方向に均一なものとなる。これにより、その後の冷間圧延において、耳伸びを生じることのない良好な冷間圧延性が得られるようになる。
なお、ここで板幅端部のビッカース硬度は、板幅端 (エッジ) から15mmの位置で測定した値を用いた。この位置は耳伸び発生領域の中央付近に位置し、またこの位置での硬度が耳伸び発生の有無ともっとも対応が良好であった。
また、板幅中央部のビッカース硬度は、文字どおり板幅中央部で測定してもよいが、板幅端から100 mmの位置より内側 (板幅中央側) であれば硬度は安定しているので、この領域内の平均値またはこの領域内の任意の点での測定値を採用してもよい。本明細書では平均値を採用した。
温度低下量が270 ℃に満たないと上記効果が十分には得られず、一方温度差の上限が350 ℃を超えると、コイルエッジ部の結晶成長が過度に抑制され、板幅端部と幅中央部との電磁特性に差が生じてしまう。なお、温度低下量はスラブ (またはシートバー) の板幅中央部での測定値とする。
【００１８】
図１は、従来の方法で製造した、箱焼鈍前 (図１(a))および箱焼鈍後 (すなわち冷間圧延前) (図(b))の板幅方向の硬度分布を示したものである。
図２は同様の、本発明法を採用して製造した、熱延鋼帯について箱焼鈍前 (図２(a))および箱焼鈍後 (図２(b))の板幅方向の硬度分布を示したものである。
なお、図１はスラブ加熱温度1070℃, 熱延終了温度 820℃ (温度低下量 250℃) の条件で、また図２はスラブ加熱温度1100℃、熱延終了温度 820℃ (温度低下量 280℃) の条件でそれぞれ熱延した後 700℃で巻取り, その後 860℃で８時間箱焼鈍を施したものである。
図１、２の比較より、本発明法を適用することにより、箱焼鈍前 (巻取り後) にて板幅端部のビッカース硬度を板幅中央部より30以上 (40) 高くすることができ、その結果、箱焼鈍後の硬度分布が板幅方向に均一になっていることがわかる。これに対して従来法においては、板幅端部のビッカース硬度が板幅中央部より26高いだけであり、箱焼鈍後に板幅端部付近の硬度が低下している。
ちなみに、図２の鋼帯を冷間圧延したところ耳伸びは２ｍｍ以下 (連続焼鈍後) で良好な冷間圧延性が得られたが、図１の鋼帯においては１２ｍｍの耳伸びが発生した。
なお、本発明で定めたような温度差の範囲に調整する手段としては、例えば、熱間圧延機において仕上圧延時の冷却水量を増やして全体を強冷却することにより中央部と板幅端部の温度差を拡大してもよいし、板幅端部のみ冷却を強化してもよい。また、通常は粗圧延機−仕上げ圧延機の間に設けている保熱設備を開放するといった処置を、単独または前記手段と併用して実施することも有効である。
【００１９】
巻き取り
熱間圧延後のコイル巻き取りの温度は、必要な電磁特性を確保するために 650〜 750℃とするのが望ましい。というのは、650 ℃に満たないと自己焼鈍効果による再結晶において十分な結晶粒の大きさを得ることが難しくなる。逆に、750 ℃を超えると仕上げ圧延後の冷却によるエッジの温度低下を期待することが困難となる。
【００２０】
箱焼鈍：850 〜900 ℃で１〜10時間
コイル巻き取り後の箱焼鈍の条件も、必要な電磁特性を確保するために重要であり、850 〜900 ℃にて１〜10時間行うものとする。この処理により、冷間圧延前に必要な電磁特性を得るための十分な結晶粒の大きさを実現できる。
【００２１】
【実施例】
表１に示す成分と残部が実質的にFeからなる成分組成のスラブを加熱し、粗圧延と仕上げ圧延からなる熱間圧延により板厚2.30mmとし、コイルに巻き取った。このとき、加熱温度Ｔ1 と熱間圧延終了温度Ｔ2 の温度差Ｔ1 −Ｔ2 を、各工程における冷却水の量により調整し、巻き取った。箱焼鈍後の鋼帯における、板幅中央部のビッカース硬度−板幅端部のビッカース硬度の値を種々の範囲に変化させた。これらの硬度の測定は短板を切り出した後、エッジから15mm、250 mm、500 mmの各位置において試験荷重５kgで行った。
コイルに巻き取った熱延鋼帯を、箱焼鈍（タイト焼鈍）したのち、板厚0.500 mmまで冷間圧延し連続焼鈍を施した。連続焼鈍後の耳伸びおよび電磁特性を測定した。なお、耳伸びは、長さ３ｍ程度に切断した鋼帯を張力を付与せずに平坦な定盤上に置き、耳部の定盤からの最高高さをテーパゲージで測定することにより求めた。
以上の工程における各製造条件と、得られた鋼帯について求めた諸特性を表２に併せて示す。
【００２２】
【表１】
【表２】
表１から、発明例はいずれも、熱延鋼帯焼鈍後の板幅方向の硬度が、中央部分と幅端部分と殆ど差がなく、冷間圧延し連続焼鈍を施した後の形状も耳伸びが２mm以下に抑制され極めて良好であった。本発明で、このような良好な特性がえられたのは、熱間圧延鋼帯をコイル巻き取りした段階では、鋼帯の幅端部分（コイルエッジ部分）の再結晶がほとんど行われず、箱焼鈍後に、板幅方向の組織がほぼ均一になったためであることを顕微鏡組織観察から確認できた。
また、発明例は、表１に示すように、透磁率、磁束密度および鉄損の各電磁特性は、それぞれμ≧3300、Ｂ50≧1.75（Ｔ）、Ｗ15／50≦4.80（ｗ／kg）の目標値を十分満足するレベルであることがわかった。
【００２５】
【発明の効果】
以上説明したように、本発明によれば、熱延鋼帯焼鈍後（冷間圧延前）の板幅方向の硬度を均一化させることができ、冷間圧延後の鋼帯形状の安定化を図ることができる。すなわち、従来は、連続焼鈍後においても耳伸びが10〜15ｍｍ程度発生していたが、本発明によれば耳伸びは２ｍｍ以下に抑制できる。
したがって、本発明によれば、冷延鋼帯の耳切りによる歩止り低下を抑制することができ、生産性、品質が大きく向上する。さらに、品質向上による工程数の減少などにより、コスト削減及び省エネルギーにも寄与する。
なお、本発明の技術は、タイト焼鈍を必要とする無方向性珪素鋼板のみでなく、オープン焼鈍を含めた箱焼鈍による無方向性珪素鋼板の製造に、また他の電磁鋼板にも適用できる。
【図面の簡単な説明】
【図１】箱焼鈍後の熱延鋼帯における板幅方向の硬度分布を示すグラフである（従来法）。
【図２】箱焼鈍後の熱延鋼帯における板幅方向の硬度分布を示すグラフである（本発明法）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a silicon steel sheet, including a step of cold rolling after box annealing of a hot-rolled steel strip coil, and a hot-rolled steel strip material suitable for this manufacturing method.
[0002]
[Prior art]
Silicon steel sheets have excellent characteristics as electromagnetic materials and are used in various electromagnetic products.
In order to manufacture such a silicon steel sheet, generally, as disclosed in, for example, JP-A-54-68717, a steel slab is heated and then hot-rolled to anneal a hot-rolled steel strip (base plate annealing). ), A process of cold rolling and annealing is required.
In particular, in the case of non-oriented silicon steel sheet (JIS C 2552), it is generally punched by the user and used in a stacked manner. Supplied as a so-called semi-process material for annealing.
[0003]
In the manufacturing process of such a silicon steel sheet, normally, the hot finish rolling temperature is set to Ar 3 point or less, and rolling distortion is imparted by performing ferritic zone rolling, which is repeated by the self-annealing effect after coil winding. Promotes crystallization. Thereafter, cold rolling is further performed by hot-rolled steel strip annealing, and finally crystal grains are adjusted to improve electromagnetic characteristics.
By the way, many of the annealing performed after the hot rolling is performed by continuous annealing. However, in order to improve the electromagnetic characteristics by aligning the crystal grains in the [100] direction, the crystal grains are generally coarse. Box annealing has been adopted for the purpose of achieving a uniform and uniform size.
[0004]
[Problems to be solved by the invention]
When annealing a hot-rolled silicon steel strip by so-called tight annealing, in particular, annealing the steel strips in close contact with each other, the plate width end portion is more affected by the heat than the center portion. It becomes easy to receive. For this reason, the structure of the plate width end portion of the steel strip becomes coarser than the central portion. And when cold-rolling a hot-rolled steel strip in such a state, there is a problem in that a shape defect occurs due to local ear elongation (about 10 to 15 mm) at the end portion of the strip width of the steel strip. .
Once the ear extension occurs, the flatness required for the silicon steel plates that are often used by being laminated is impaired, and not only the quality is degraded, but also many obstacles such as a decrease in yield and productivity are brought about.
[0005]
However, the reality is that not much research has been conducted so far to suppress the ear elongation observed during cold rolling of silicon steel sheets. Slightly, in Japanese Patent Application Laid-Open No. 60-162751, there is a region showing non-uniform elongation at the coil edge in cold rolling of a semi-processed electrical steel sheet, and this non-uniform elongation is 600 to 800 in the final finish annealing. There is only a statement that it can be solved by performing short-term continuous annealing for 1 to 2 minutes at a temperature of ° C.
However, the inventors have confirmed that with the above known technology, when the ear elongation at the end portion of the plate width increases, it cannot be corrected by continuous annealing.
[0006]
Therefore, the object of the present invention is to solve such a problem that the prior art has, and when the hot rolled steel strip is cold-rolled after box annealing, it has a good shape that does not cause ear elongation. It is to propose a manufacturing method for obtaining a silicon steel plate having the same.
Another object of the present invention is to provide a hot-rolled steel strip for a silicon steel sheet to be applied to the manufacturing method.
Specifically, a method of manufacturing a silicon steel sheet for suppressing the ear elongation after cold rolling and continuous annealing to an extremely small range of 2 mm or less (5 mm or less after cold rolling), and this method A suitable hot-rolled steel strip material is proposed.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the inventors consider that there is a large difference in deformation resistance in a coil that generates large ear elongation locally, and the plate width of the hot-rolled steel strip before cold rolling The hardness distribution in the direction was investigated. As a result, as shown in FIG. 1 (b), the conventional hot-rolled steel strip that causes ear elongation has had a lower hardness at the plate width end portion than at the central portion. . Therefore, it was considered that eliminating the hardness difference in the width direction would enable stable cold rolling without ear elongation.
[0008]
The inventors have conducted extensive experiments on effective methods for reducing the hardness difference, and in the cooling process from heating to the end of hot rolling, the sheet width end portion of the steel strip becomes lower than the center portion. Thus, it has been found that it is extremely effective to cool the steel strip strongly. By performing such cooling after hot rolling, the self-annealing effect after coil winding is suppressed at the width end, and even after receiving a non-uniform heat load by subsequent box annealing, It was found that the particle size distribution was uniform in the direction, and the hardness and thus the cold rolling property could be made uniform.
[0009]
The present invention has been completed based on such findings, and the gist thereof is as follows.
(1) A silicon steel slab containing C: 0.02 wt% or less and Si: 0.5-3.5 wt% is heated and then hot-rolled, and the resulting hot-rolled steel strip is wound around a coil to form a box In producing a silicon steel sheet by annealing and then cold rolling, the slab heating temperature is set to 1090 to 1150 ° C., the hot rolling end temperature is set to 850 to 750 ° C., and from the slab heating to the end of the hot rolling. The temperature drop amount is controlled to 270 to 350 ° C., and the Vickers hardness at a position 15 mm from the sheet width end in the hot-rolled steel strip after winding is calculated from the average value of the Vickers hardness on the inner side from the
[0011]
( 2 ) For containing C: 0.02 wt% or less, Si: 0.5-3.5 wt%, with the balance being composed of Fe and inevitable impurities, and performing cold rolling after box annealing It is a hot-rolled steel strip material for silicon steel sheets, and the Vickers hardness at a position 15 mm from the plate width end in the hot-rolled steel strip is 30 or more higher than the average value of the Vickers hardness on the inner side from the
(3) In addition to the above component composition, Al: 0.1 to 1.0 wt%, Mn: 1.0 wt% or less, S: 0.007 wt% or less, V: 0.50 wt% or less, Cu: 0. 50 wt% or less, Cr: 0.50 wt% or less, Ni: 0.50 wt% or less, Ti: 0.50 wt% or less, and Sb: 0.50 wt% or less A hot-rolled steel strip material for a silicon steel sheet as described above.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the reason for limitation as described in the above summary configuration will be described.
C: 0.02 wt% or less C is known to be a harmful element in terms of properties as a magnetic steel sheet, and it is necessary to finally reduce it. In particular, if the C content exceeds 0.02 wt%, adverse effects remain even when considering the amount of decarburization due to annealing of the hot-rolled steel strip.
[0013]
Si: 0.5 to 3.5 wt%
Si is an element necessary for obtaining electromagnetic characteristics, and a content of at least 0.5 wt% is necessary, but if it exceeds 3.5 wt%, the cold rolling property is extremely deteriorated. Therefore, the Si content is in the range of 0.5 to 3.5 wt%.
[0014]
In addition to the above C and Si, the components of the silicon steel material for hot rolling in the present invention can include Al, Mn, S and the like as necessary. The preferable content range is as follows.
If Al is less than 0.1 wt%, AlN precipitates and is undesirable because it has the effect of suppressing the growth of crystal grains. However, if it exceeds 1.0 wt%, cold rollability deteriorates, so 1.0 wt% It is desirable to keep it below%.
In order to make S content which does not inhibit the growth of crystal grains, it is preferable that S be in the range of 0.007 wt% or less.
Further, Mn is added in an amount of 1.0 wt% or less to prevent hot brittleness, and has a role of strengthening steel.
In addition, each of V, Cu, Cr, Ni, Ti, and Sb can be contained in an amount of 0.50 wt% or less. In addition to these components, in order to maintain electromagnetic characteristics, it is desirable to make the balance iron except impurities.
[0015]
Slab heating temperature: 1090-1150 ° C
If the slab heating temperature is less than 1090 ° C, hot rolling itself will be hindered, and the target temperature difference until the end of hot rolling cannot be secured. On the other hand, if the temperature exceeds 1150 ° C, a strong scale containing Si is generated, making descaling difficult, and adversely affecting the surface properties of the steel strip. Therefore, slab heating is performed in a temperature range of 1090 to 1150 ° C.
[0016]
Hot rolling finish temperature: 750-850 ° C
The end temperature of hot rolling is set to 750 to 850 ° C. in order to ensure necessary electromagnetic characteristics. This is because when the finish rolling exit temperature exceeds 850 ° C., the addition of strain due to α-region rolling decreases, which hinders crystal grain growth and reduces the difference from the slab extraction heating temperature. This is not preferable because it causes a softening of the plate width end portion (that is, the coil edge portion) of the steel strip. On the other hand, if the temperature is less than 750 ° C., it is difficult to obtain a self-annealing effect after coil winding and to reduce the temperature of the edge portion.
In addition, the said hot rolling completion temperature shall be the value measured in the position of the center part surface of the sheet width direction of a steel strip.
[0017]
Cooling during hot finish rolling and the amount of temperature decrease from the hardness slab heating before coil winding to the end of hot rolling are important requirements of the present invention. If this amount of temperature decrease is 270 to 350 ° C., preferably 280 ° C. to 320 ° C., the overcooling at the end of the plate width accompanying cooling becomes moderately large, and after winding the coil, at the end of the plate width. Recrystallization by self-annealing is hardly performed compared to the central part. At this time, the Vickers hardness at the center of the plate width is 30 or more, preferably 35 or more higher than the Vickers hardness at the end of the plate width. After that, when this hot-rolled steel strip is annealed, the particle size distribution in the plate width direction becomes uniform, and the hardness becomes uniform in the plate width direction. Thereby, in the subsequent cold rolling, good cold rolling properties that do not cause ear elongation can be obtained.
Here, the value measured at a position 15 mm from the plate width end (edge) was used as the Vickers hardness at the plate width end portion. This position is located near the center of the ear stretch generation region, and the hardness at this position is the best correspondence with the presence or absence of the occurrence of ear stretch.
In addition, the Vickers hardness at the center of the plate width may be measured literally at the center of the plate width, but the hardness is stable if it is on the inside (plate width center side) 100 mm from the end of the plate width. An average value in this region or a measured value at an arbitrary point in this region may be adopted. In this specification, an average value is adopted.
If the temperature drop is less than 270 ° C, the above effect cannot be obtained sufficiently.On the other hand, if the upper limit of the temperature difference exceeds 350 ° C, crystal growth at the coil edge is excessively suppressed, and the plate width end and width A difference will arise in the electromagnetic characteristic with a center part. The amount of temperature decrease is the value measured at the center of the plate width of the slab (or sheet bar).
[0018]
Fig. 1 shows the hardness distribution in the sheet width direction, manufactured by a conventional method, before box annealing (Fig. 1 (a)) and after box annealing (ie before cold rolling) (Fig. (B)). is there.
Fig. 2 shows the hardness distribution in the plate width direction before hot annealing (Fig. 2 (a)) and after box annealing (Fig. 2 (b)) of a hot-rolled steel strip manufactured using the same method of the present invention. It is shown.
Figure 1 shows the conditions of a slab heating temperature of 1070 ° C and a hot rolling end temperature of 820 ° C (temperature decrease of 250 ° C). Figure 2 shows a slab heating temperature of 1100 ° C and a hot rolling end temperature of 820 ° C (temperature decrease of 280 ° C). ) And then rolled at 700 ° C and then box annealed at 860 ° C for 8 hours.
From the comparison of Figs. 1 and 2, by applying the method of the present invention, the Vickers hardness at the end of the plate width can be increased by 30 or more (40) from the center of the plate width before box annealing (after winding). As a result, it can be seen that the hardness distribution after the box annealing is uniform in the plate width direction. On the other hand, in the conventional method, the Vickers hardness at the plate width end is only 26 higher than the plate width center, and the hardness near the plate width end is lowered after box annealing.
Incidentally, when the steel strip of FIG. 2 was cold-rolled, the ear elongation was 2 mm or less (after continuous annealing) and good cold-rollability was obtained, but the steel strip of FIG. .
As a means for adjusting the temperature difference range as defined in the present invention, for example, by increasing the amount of cooling water at the time of finish rolling in a hot rolling mill and strongly cooling the whole, the center portion and the plate width end portion The temperature difference may be enlarged, or cooling may be strengthened only at the end of the plate width. In addition, it is also effective to implement a measure such as opening a heat retention facility usually provided between the rough rolling mill and the finish rolling mill alone or in combination with the above means.
[0019]
The coil winding temperature after the coiling hot rolling is preferably 650 to 750 ° C. in order to ensure necessary electromagnetic characteristics. This is because if the temperature is less than 650 ° C., it is difficult to obtain a sufficient grain size in recrystallization by the self-annealing effect. Conversely, if it exceeds 750 ° C., it will be difficult to expect a decrease in the edge temperature due to cooling after finish rolling.
[0020]
Box annealing: 1 to 10 hours at 850 to 900 ° C. The conditions for box annealing after coiling are also important to ensure the necessary electromagnetic properties, and are performed at 850 to 900 ° C. for 1 to 10 hours. . By this treatment, it is possible to realize a sufficient crystal grain size for obtaining necessary electromagnetic characteristics before cold rolling.
[0021]
【Example】
The slab having the composition shown in Table 1 and the balance substantially consisting of Fe was heated, and the sheet thickness was adjusted to 2.30 mm by hot rolling consisting of rough rolling and finish rolling, and wound around a coil. At this time, the temperature difference T 1 -T 2 between the heating temperature T 1 and the hot rolling end temperature T 2 was adjusted by the amount of cooling water in each step and wound up. In the steel strip after box annealing, the value of the Vickers hardness at the center of the plate width-the Vickers hardness at the end of the plate width was changed in various ranges. The hardness was measured by cutting a short plate and then using a test load of 5 kg at positions 15 mm, 250 mm, and 500 mm from the edge.
The hot-rolled steel strip wound around the coil was subjected to box annealing (tight annealing), and then cold-rolled to a thickness of 0.500 mm and subjected to continuous annealing. The ear elongation and electromagnetic properties after continuous annealing were measured. The ear elongation was obtained by placing a steel strip cut to a length of about 3 m on a flat surface plate without applying tension, and measuring the maximum height of the ear portion from the surface plate with a taper gauge.
Table 2 shows the manufacturing conditions in the above steps and various properties obtained for the obtained steel strip.
[0022]
[Table 1]
[Table 2]
From Table 1, all of the inventive examples have almost no difference in the hardness in the sheet width direction after the hot-rolled steel strip annealing between the center portion and the width end portion, and the shape after cold rolling and continuous annealing is also heard. The elongation was suppressed to 2 mm or less and was very good. In the present invention, such good characteristics were obtained because at the stage where the hot-rolled steel strip was coiled, recrystallization of the width end portion (coil edge portion) of the steel strip was hardly performed, and the box It was confirmed from microscopic observation that the structure in the plate width direction was almost uniform after annealing.
In addition, as shown in Table 1, in the invention examples, the magnetic characteristics of magnetic permeability, magnetic flux density, and iron loss are μ ≧ 3300, B50 ≧ 1.75 (T), W15 / 50 ≦ 4.80 (w / kg), respectively. It was found that the target level was sufficiently satisfied.
[0025]
【The invention's effect】
As described above, according to the present invention, the hardness in the sheet width direction after hot-rolled steel strip annealing (before cold rolling) can be made uniform, and the steel strip shape after cold rolling can be stabilized. Can be planned. That is, conventionally, about 10 to 15 mm of ear elongation has occurred even after continuous annealing, but according to the present invention, the ear elongation can be suppressed to 2 mm or less.
Therefore, according to the present invention, it is possible to suppress a decrease in yield due to the cutting of the cold-rolled steel strip, and the productivity and quality are greatly improved. Furthermore, it contributes to cost reduction and energy saving by reducing the number of processes due to quality improvement.
The technique of the present invention can be applied not only to non-oriented silicon steel sheets that require tight annealing, but also to the manufacture of non-oriented silicon steel sheets by box annealing including open annealing, and to other electromagnetic steel sheets.
[Brief description of the drawings]
FIG. 1 is a graph showing the hardness distribution in the plate width direction in a hot-rolled steel strip after box annealing (conventional method).
FIG. 2 is a graph showing the hardness distribution in the plate width direction in a hot-rolled steel strip after box annealing (method of the present invention).
Claims (3)
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| JP02513599A JP4337159B2 (en) | 1999-02-02 | 1999-02-02 | Manufacturing method of silicon steel sheet and hot rolled steel strip material for silicon steel sheet |
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| JP02513599A JP4337159B2 (en) | 1999-02-02 | 1999-02-02 | Manufacturing method of silicon steel sheet and hot rolled steel strip material for silicon steel sheet |
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| TWI754548B (en) * | 2021-02-19 | 2022-02-01 | 日商日本製鐵股份有限公司 | Hot-rolled steel sheet for non-oriented electrical steel sheet and method for producing the same |
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| JP6620522B2 (en) * | 2015-11-05 | 2019-12-18 | 日本製鉄株式会社 | Hot rolled steel strip for non-oriented electrical steel sheet and method for producing non-oriented electrical steel sheet |
| CN108405628B (en) * | 2018-03-13 | 2020-04-07 | 武汉钢铁有限公司 | Optimal section profile control method for hot-rolled non-oriented silicon steel |
| CN109807192B (en) * | 2019-01-30 | 2020-08-04 | 武汉钢铁有限公司 | Method for controlling flanging of high-magnetic-induction oriented silicon steel coil |
| KR102683224B1 (en) * | 2019-03-20 | 2024-07-10 | 닛폰세이테츠 가부시키가이샤 | Non-oriented electrical steel sheet |
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| WO2022176154A1 (en) * | 2021-02-19 | 2022-08-25 | 日本製鉄株式会社 | Hot-rolled steel sheet for non-oriented electromagnetic steel sheet and method for manufacturing same |
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| TWI754548B (en) * | 2021-02-19 | 2022-02-01 | 日商日本製鐵股份有限公司 | Hot-rolled steel sheet for non-oriented electrical steel sheet and method for producing the same |
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