JP4200526B2 - Method for producing unidirectional silicon steel sheet - Google Patents

Description

【００１９】
同表から明らかなように、良好な二次再結晶組織ひいては磁気特性を得るためには、熱間圧延終了後、２秒から６秒までの間について
Ｔ(t) ≦ FDT−｛(FDT−700)／６｝×ｔ
満足する条件下で冷却させる必要があることが究明された。
【００２０】
熱間仕上げ圧延終了後の温度履歴が二次再結晶後の磁気特性に影響を及ぼす理由は、必ずしも明確ではないが、以下のとおりと考えられる。
すなわち、実験１の結果より、特性劣化の原因となる抑制力の弱いインヒビターが形成される析出ノーズが、図11に斜線で示すように存在することが推定される。
また、実験２の結果からは、熱延終了から２秒後までに
Ｔ₁ ＝２／３ＦＤＴ＋700 ／３（℃）以下に冷却することで特性が良好となることが、さらに実験３の結果からは、熱延終了から６秒後までに 700℃以下に冷却することで特性が良好となることが判った。
つまり、図11中斜線で示した析出ノーズの下部境界（太線部）が２秒でＴ₁ ℃、６秒で 700℃の点を通るライン、即ち
Ｔ(t) ＝ FDT−｛(FDT−700)／６｝×ｔ
で近似されると考えられる。
従って、実験４のパターン中、Ａ，Ｄ，Ｅ，Ｇ，Ｈは２〜６秒間の冷却履歴が部分的にＴ≧ FDT−｛(FDT−700)／６｝×ｔとなり、抑制力の弱いインヒビターの析出ノーズにかかるため、特性が劣化したものと考えられる。
【００２１】
次に、インヒビターとしてAlＮ以外にMnSeおよびMnＳを併せて含有する場合について検討した。
（実験５）
表２に示す組成になる鋼を、真空溶解により溶製し、鋳込み後、1200℃に再加熱し、厚み：40mmに圧延した。これより厚み40mm×幅300mm ×長さ400mm の試料を採取し、1300℃に加熱してインヒビター成分を溶体化した後、熱間圧延により板厚：2.3 mmの熱延板とした。この時、熱間圧延終了温度を1100℃〜900 ℃とし、熱間圧延終了から６秒までの冷却条件を図８から図10に示した冷却パターンの一部と同じになるようにした。ついで、500 ℃まで急冷し、同温度に１時間保持してから、室温まで空冷した。
その後、熱延板焼鈍を施したのち、一次冷間圧延、中間焼鈍、二次冷間圧延により0.23mm厚に仕上げた。ついで、湿水素雰囲気中にて 850℃、２分間の脱炭・一次再結晶焼鈍後、MgO を主成分とする焼鈍分離剤を塗布してから、乾水素雰囲気中で1200℃、10時間の最終仕上げ焼鈍を施した。
かくして得られた製品の磁気特性について調査した結果を、表３に示す。
なお、表３には、実験４の同一冷却パターンで得られた結果との差（ΔＢ₈ 、ΔＷ_17/50 ）についても併記した。
【００２２】
【表２】

【００２３】
【表３】

【００２４】
表３によれば、Seおよび／またはＳを添加することにより、実験４と同じ冷却パターンを採用した場合に磁気特性が向上していることが判る。この理由は、AlＮの他に、MnSeやMnＳがインヒビターとして機能するからである。
【００２５】
最後に、熱間圧延終了後、巻取りまでの後半の冷却速度の影響を調査した。
（実験６）
表４に示す組成になる鋼を、真空溶解により溶製し、鋳込み後、1200℃に再加熱し、厚み：40mmに圧延した。なお鋼７は実験４と同一成分である。これより、厚み40mm×幅300mm ×長さ400mm の試料を採取し、1300℃に加熱してインヒビター成分を溶体化した後、熱間圧延により板厚：2.3 mmの熱延板とした。この時、熱間圧延終了温度を1100℃〜900 ℃とし、熱間圧延終了から６秒までの冷却条件を図８から図10に示す冷却パターンの一部と同じになるようにした。
その後、500 ℃までを10〜35℃／ｓの冷却速度で冷却し、同温度に１時間保持してから、室温まで空冷した。
その後、熱延板焼鈍を施したのち、一次冷間圧延、中間焼鈍、二次冷間圧延により0.23mm厚に仕上げた。ついで、湿水素雰囲気中にて 850℃、２分間の脱炭・一次再結晶焼鈍後、MgO を主成分とする焼鈍分離剤を塗布してから、乾水素雰囲気中で1200℃、10時間の最終仕上げ焼鈍を施した。
かくして得られた製品の磁気特性について調査した結果を、図12〜15に整理して示す。
【００２６】
【表４】

【００２７】
図12〜14の結果によれば、Seおよび／またはＳを含有する組成のものは、熱間圧延終了６秒後から 500℃までを25℃／ｓ以下の速度で冷却することにより、磁束密度が向上していることが判る。
この点、図15の結果によれば、AlＮ単独添加では６秒後以降の冷却速度の効果は特に認められなかった。
【００２８】
このように、熱間圧延終了後、巻取りまでの後半の冷却速度を規制することにより、AlＮおよびSe，Ｓを複合含有する組成において特に磁気特性が向上する理由は、次のとおりと考えられる。
MnSeやMnＳは熱間仕上げ圧延前段で析出する。AlＮは仕上げ圧延終了後に、既に析出しているMnSeまたはMnＳ上に優先して析出し、複合析出物となる。この場合冷却速度が遅いと複合析出物が安定となって、より強力なインヒビターとなる。この点、AlＮ単独の場合にはこのような効果は認められない。
【００２９】
【作用】
次に、この発明において、素材の成分組成を前記の範囲に限定した理由について説明する。
Ｃ：0.01〜0.10wt％
Ｃは、熱間圧延、冷間圧延中の組成の均一微細化のみならず、ゴス方位の発達に有用な元素であり、少なくとも0.01wt％は含有させる必要がある。しかしながら、0.10wt％を超えて含有すると脱炭が困難となり、かえってゴス方位に乱れが生じるので上限は0.10wt％とする。なお、好ましい範囲は0.03〜0.08wt％である。
【００３０】
Si： 2.5〜4.5 wt％
Siは、鋼板の比抵抗を高め、鉄損の低減に寄与する。Si含有量が、2.5 wt％未満では鉄損低減効果が十分ではなくまた純化と２次再結晶のため行われる高温での仕上げ焼鈍において、α−γ変態による結晶方位のランダム化が生じ十分な磁気特性が得られない。一方、4.5 wt％を超えると冷間圧延性が損なわれ、製造が困難となる。従って、Si含有量は 2.5〜4.5 wt％とする。なお、好ましくは 3.0〜3.5 wt％の範囲とするのがよい。
【００３１】
Mn：0.02〜0.12wt％
Mnは、熱間脆性による熱間圧延時の割れ防止するのに有効な元素であり、その効果は0.02wt％未満では得られない。一方、0.12wt％を超えて添加すると磁気特性を劣化させる。従って、Mn含有量は0.02〜0.12wt％とする。なお、好ましくは0.05〜0.10wt％の範囲とするのがよい。
【００３２】
Al：0.005 〜0.10wt％
Alは、AlＮを形成してインヒビターとして作用する元素である。Al含有量が、0.005 wt％未満では抑制力の確保が十分ではなく、一方、0.10wt％を超えるとその効果が損なわれるので、 0.005〜0.10wt％とする。なお、好ましい範囲は0.01〜0.05wt％である。
【００３３】
Ｎ：0.004 〜0.015 wt％
Ｎは、AlＮを形成してインヒビターとして作用する元素である。Ｎ含有量が、0.004 wt％未満では抑制力の確保が十分ではなく、一方、0.15wt％を超えるとその効果が損なわれるので、 0.004〜0.15wt％とする。なお好ましい範囲は0.006 〜0.010 wt％である。
【００３４】
この発明では、インヒビターとして、上記したAlＮの他、MnSeやMnＳを複合添加することは有利であり、その好適含有量は次のとおりである。
Se：0.005 〜0.06wt％
Seは、MnSeを形成してインヒビターとして作用する有力な元素である。Se含有量が、0.005 wt％未満では抑制力の確保が十分ではなく、一方0.06wt％を超えるとその効果が損なわれる。従って、単独添加、複合添加いずれの場合とも0.005 〜0.06wt％とする。なお、好ましい範囲は 0.010〜0.030 wt％である。
【００３５】
Ｓ：0.005 〜0.06wt％
Ｓは、MnＳを形成してインヒビターとして作用する有力な元素である。Ｓ含有量が、0.005 wt％未満では抑制力の確保が十分ではなく、一方、0.06wt％を超えるとその効果が損なわれるので、単独添加、複合添加いずれの場合とも 0.005〜0.06wt％とする。なお、好ましい範囲は0.015 〜0.035 wt％である。
【００３６】
なお、この発明においては、インヒビター成分として上記したAl、Ｓ, Seの他に、Cu, Sn, Sb, Mo, TeおよびBi等も有利に作用するのでそれぞれ前記成分に併せて含有させることもできる。これらの成分の好適添加範囲はそれぞれ、Cu, Sn：0.01〜0.15wt％、Sb, Mo, Te, Bi：0.005 〜0.1 wt％である。また、これらの各インヒビター成分についても、単独使用および複合使用いずれもが可能である。
【００３７】
次に、製造条件について説明する。
上記の好適成分組成範囲に調整した溶鋼は、好ましくは連続鋳造により、スラブとしたのち、1280℃以上の温度に加熱してから、熱間圧延に供する。
ここに、スラブ加熱温度を1280℃以上としたのは、インヒビターとして使用されるAlＮやMnSe, MnＳを十分に解離固溶させるためである。好ましい温度範囲は1350〜1450℃である。
【００３８】
熱間圧延工程において、仕上げ圧延の終了温度を 900〜1100℃としたのは、終了温度が 900℃に満たないと仕上げ圧延スタンド内で望ましくないインヒビターの析出が起こり、一方1100℃を超えると通板と冷却の両立が極めて困難となるからである。特に好ましい仕上げ圧延の終了温度は 950〜1000℃である。
【００３９】
この発明では、上記の温度範囲にて仕上げ圧延を終了したのち、２〜６秒間については、次式
Ｔ(t) ≦ FDT−｛(FDT−700)／６｝×ｔ
を満足する条件下で制御冷却を行うことが肝要であり、かくしてはじめて不良発生がほとんどない良好な二次再結晶が進行し、ひいては優れた磁束密度および鉄損が得られるのである。
【００４０】
ついで、インヒビターとして、 Al Ｎと MnSe および／または Mn Ｓを複合含有する場合には、仕上げ圧延終了後６秒から巻取りまでについては、25℃／ｓ以下の速度で冷却することが好ましい。
ここに、巻取りまでの冷却速度を25℃／ｓ以下としたのは、25℃／ｓを超える速度では、好適なAlＮおよびMnSe，MnＳの複合析出物が得られず、ひいては優れた磁気特性が得られないからである。
また、巻取り温度 500〜600 ℃程度とするのが好ましい。
【００４１】
なお、この発明では、製造条件については、上述したスラブ加熱温度および熱間仕上げ圧延後の冷却条件以外は特に制限はなく、熱間圧延、熱延板焼鈍、酸洗、中間焼鈍、冷間圧延、脱炭焼鈍、焼鈍分離剤塗布および仕上げ焼鈍などの各工程における製造条件はそれぞれ公知の方法にしたがって行えばよい。
【００４２】
【実施例】
表５に示す組成になる溶鋼から、連続鋳造により、厚み：210 mm、幅：1000mmサイズのスラブを作製した。
このスラブを、通常のガス加熱炉にて1200℃に加熱したのち、誘導式電気炉にて1430℃まで加熱し、インヒビター成分を完全に溶体化したのち、熱間粗圧延ついで熱間仕上げ圧延を行い、2.3mm 厚の熱延板とした。
この時、冷却を制御し板温を調整した。その際の板温を放射温度計によりオンライン計測した結果を、同じく表５に示す。
その後、各熱延板について、熱延板焼鈍を施したのち、一次冷間圧延、中間焼鈍、二次冷間圧延により0.23mm厚に仕上げた。ついで、湿水素雰囲気中にて 850℃、２分間の脱炭・一次再結晶焼鈍後、MgO を主成分とする焼鈍分離剤を塗布してから、乾水素雰囲気中で1200℃、10時間の最終仕上げ焼鈍を施した。
かくして得られた製品の磁気特性および二次再結晶不良発生面積率について調査した結果を、表５に併記する。
【００４３】
【表５】

【００４４】
同表から明らかなように、この発明に従い得られた適合例は、二次再結晶不良の発生がほとんどなく、優れた磁束密度および鉄損特性を得ることができた。
これにより、この発明に従い仕上げ熱延後に制御冷却を行うことにより、二次再結晶不良率が低減し、高磁束密度でかつ低鉄損の一方向性電磁鋼板を製造できることが確認された。
【００４５】
【発明の効果】
かくして、この発明によれば、インヒビターとしてAlＮさらにはMnＳやMnSeを複合含有する場合において、製品の二次再結晶不良率を格段に低減でき、ひいては高磁束密度でかつ低鉄損の優れた磁気特性を有する一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】仕上げ圧延終了温度と仕上げ圧延後の保持時間が磁気特性に与える影響を示した図である。
【図２】実験２における、仕上げ圧延後の温度履歴を示す模式図である。
【図３】仕上げ圧延終了温度と仕上げ圧延終了２秒後の温度が磁気特性に与える影響を示した図である。
【図４】実験３における、仕上げ圧延後の温度履歴を示す模式図である。
【図５】仕上げ圧延終了温度：900 ℃、Ｔ₁ ：833 ℃の場合における、仕上げ圧延終了２秒後からの時間（ｔ）と温度（Ｔ₂ ）が磁気特性に与える影響を示した図である。
【図６】仕上げ圧延終了温度：1000℃、Ｔ₁ ：900 ℃の場合における、仕上げ圧延終了２秒後からの時間（ｔ）と温度（Ｔ₂ ）が磁気特性に与える影響を示した図である。
【図７】仕上げ圧延終了温度：1100℃、Ｔ₁ ：966 ℃の場合における、仕上げ圧延終了２秒後からの時間（ｔ）と温度（Ｔ₂ ）が磁気特性に与える影響を示した図である。
【図８】仕上げ熱延終了後の冷却条件を示す温度履歴曲線図である。
【図９】仕上げ熱延終了後の冷却条件を示す温度履歴曲線図である。
【図１０】仕上げ熱延終了後の冷却条件を示す温度履歴曲線図である。
【図１１】抑制力の弱いインヒビターの析出ノーズを示す模式図である。
【図１２】実験６における、仕上げ圧延終了後６秒以降の冷却速度と磁気特性との関係を示すグラフである。
【図１３】実験６における、仕上げ圧延終了後６秒以降の冷却速度と磁気特性との関係を示すグラフである。
【図１４】実験６における、仕上げ圧延終了後６秒以降の冷却速度と磁気特性との関係を示すグラフである。
【図１５】実験６における、仕上げ圧延終了後６秒以降の冷却速度と磁気特性との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a unidirectional silicon steel sheet having excellent magnetic properties, and in particular, intends to further improve the magnetic properties by adding a device to the cooling process up to winding after hot rolling. It is.
[0002]
[Prior art]
Unidirectional silicon steel sheets are mainly used as iron core materials for transformers and other electrical equipment, and as their characteristics, high magnetic flux density and low iron loss are required.
Such a unidirectional silicon steel sheet is usually heated to a temperature of 1250 ° C or higher after a silicon-containing steel slab having a thickness of about 100 to 300 mm, and then hot-rolled once or intermediately. After cold rolling at least twice, and finishing to the final sheet thickness, decarburization and primary recrystallization annealing are performed, and then an annealing separator is applied, followed by final recrystallization and purification. Manufactured by finishing annealing.
[0003]
That is, the slab is first heated to a high temperature to completely dissolve the inhibitor component, and then the primary recrystallization structure is controlled by hot rolling, cold rolling, followed by decarburization and primary recrystallization annealing. By subjecting the primary recrystallized structure to secondary recrystallization in the {110} <001> orientation by performing final finish annealing, desired magnetic properties are obtained.
[0004]
In order to effectively promote the secondary recrystallization described above, first, a precipitated phase called an inhibitor for suppressing the normal growth of primary recrystallized grains is dispersed uniformly and finely in the steel, and the primary recrystallization is also performed. It is important to distribute the crystal structure uniformly and appropriately in the thickness direction. Further, as the inhibitor, sulfides such as MnS, MnSe, AlN and VN, selenides, nitrides and the like are suitable, and substances having extremely low solubility in steel are used.
In any case, in order to obtain a good secondary recrystallization structure, it is important to control the inhibitor from precipitation of the inhibitor in hot rolling to the subsequent secondary recrystallization. It can be said that the importance of such inhibitors has been increasing in order to ensure the above.
[0005]
By the way, conventionally, from the viewpoint of inhibitor control, as a technique focusing on the temperature history from finish rolling to winding in the hot rolling process, for example, JP-A-59-50118, JP-A-64-73023 And JP-A-2-263924, JP-A-4-323, JP-A-2-274811 and JP-A-5-295442.
However, since the above-mentioned technique only defines the average cooling rate until the coiling temperature and the coiling after the hot rolling is completed, or at most only the holding temperature immediately after the hot rolling is completed, None of the techniques provided a sufficiently satisfactory inhibitor dispersion and thus no magnetic properties.
[0006]
In this respect, the inventors firstly, as a solution to the above-mentioned problem, cooling processing after the end of hot rolling, specifically, the steel plate temperature in 2 to 6 seconds within a predetermined range in relation to the elapsed time. A method for producing a unidirectional silicon steel plate comprising controlling was developed and disclosed in Japanese Patent Application No. 6-236667.
That is, after finishing rolling, cooling until winding is performed in the following formula 2 ≦ t ≦ 6: T (t) ≦ FDT − {(FDT−700) / 6} × t
Where t: elapsed time since finish rolling (s)
T (t): Steel plate temperature after t seconds (° C)
FDT: Finishing rolling finish temperature (° C)
Thus, the dispersion of the inhibitor was appropriately controlled, and the production of a unidirectional silicon steel sheet having excellent magnetic properties was successfully achieved.
[0007]
[Problems to be solved by the invention]
The present invention relates to the improvement of the above-described novel manufacturing technique, and realizes a further improvement in magnetic properties by regulating the cooling rate after the above cooling process until further winding.
[0008]
That is, the gist configuration of the present invention is as follows.
1. C: 0.01-0.10 wt%
Si: 2.5-4.5 wt%
Mn: 0.02 to 0.12 wt%,
Al: 0.005 to 0.10 wt% and N: 0.004 to 0.015 wt%
And the balance is Fe and an inevitable impurity composition of a silicon steel slab, heated to a temperature of 1280 ° C or higher, then hot rolled, and then cold once or two times with intermediate annealing After rolling and finishing to the final thickness, decarburization and primary recrystallization annealing are performed, after which the annealing separator is applied, and then the final finishing annealing is performed to produce a unidirectional silicon steel sheet. On the occasion
In the above hot rolling step, the finish rolling finish temperature is in the range of 900 to 1100 ° C., and for 2 to 6 seconds after the finish rolling is finished, the following formula T (t) ≦ FDT − {(FDT−700) / 6} × t
Where t: elapsed time since finish rolling (s)
T (t): Steel plate temperature after t seconds (° C)
FDT: Finishing rolling finish temperature (° C)
Manufacturing method of an oriented silicon steel sheet you wherein control cooling to Rukoto under conditions satisfying the.
[0009]
2. In the above 1, the steel slab is further
At least one selected from Se and S: 0.005 to 0.06 wt%
Ri Do the composition containing the method for producing a grain-oriented silicon steel sheet, which comprises cooling an additional finish rolling completion after 6 seconds until the winding below 25 ° C. / s rate.
3 . In the above 1 or 2 , the steel slab is further
Cu: 0.01 to 0.15 wt%,
Sn: 0.01-0.15wt%,
Sb: 0.005 to 0.1 wt%,
Mo: 0.005-0.1 wt%,
Te: 0.005-0.1 wt% and
Bi: 0.005-0.1 wt%
A method for producing a unidirectional silicon steel sheet, comprising a composition containing one or more selected from among the above.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The elucidation process of the present invention will be described below.
As a result of detailed review of various factors in the hot rolling process in order to achieve the above-mentioned object, the inventors have obtained the cooling history after finishing rolling in hot rolling as described below. By controlling, a good inhibitor distribution was obtained, and as a result, the secondary recrystallization failure rate of the product was reduced, and it was found that a product having a high magnetic flux density and a low iron loss can be obtained.
(Experiment 1)
First, an experiment was conducted to clarify the influence of steel sheet temperature history after finish rolling on inhibitor dispersion.
C: 0.07wt%, Si: 3.05wt %, Mn: 0.06wt%, Al: 0.020 wt% and N: look including the 0.0090Wt%, balance steel comprising the composition of Fe and unavoidable impurities, by vacuum melting After melting and casting, it was reheated to 1200 ° C. and rolled to a thickness of 40 mm. A sample having a thickness of 40 mm, a width of 300 mm, and a length of 400 mm was collected from the sample, heated to 1300 ° C. to form a solution of the inhibitor component, and then hot rolled into a hot rolled sheet having a sheet thickness of 2.3 mm. At this time, the hot rolling end temperature was variously changed in the range of 700 to 1200 ° C., and held at that temperature for 1 to 7 seconds, respectively. Then, it was rapidly cooled to 500 ° C., kept at the same temperature for 1 hour, and then air-cooled to room temperature.
Then, after hot-rolled sheet annealing, it was finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
[0011]
FIG. 1 shows the result of investigation on the magnetic properties of the product thus obtained.
In the figure, the horizontal axis is the holding time after finishing rolling, the vertical axis is the finishing rolling finishing temperature, and the magnetism of the product corresponding to each condition is represented by symbols ◯ and X. ○ indicates that magnetism of B ₈ : 1.88T or more and × indicates that B ₈ : less than 1.88T was obtained.
As is clear from the figure, in order to achieve fine inhibitor dispersion and obtain good magnetism, it is necessary to set the hot rolling end temperature to 900 ° C or higher in the steel sheet temperature history immediately after finishing rolling. There was found. It was also found that when the holding time exceeds 2 seconds, the magnetic properties deteriorate instead.
[0012]
Therefore, next, after finishing rolling, an experiment was conducted to clarify the steel sheet temperature history after 2 seconds.
(Experiment 2)
C: 0.08wt%, Si: 3.20wt %, Mn: 0.05wt%, Al: 0.025 wt% and N: look including the 0.0085Wt%, balance steel comprising the composition of Fe and unavoidable impurities, by vacuum melting After melting and casting, it was reheated to 1200 ° C. and rolled to a thickness of 40 mm. A sample having a thickness of 40 mm, a width of 300 mm, and a length of 400 mm was collected from the sample, heated to 1300 ° C. to form a solution of the inhibitor component, and then hot rolled into a hot rolled sheet having a sheet thickness of 2.3 mm. At this time, the hot rolling end temperature (FDT) is set to 900 ° C., 1000 ° C. and 1100 ° C., and after 2 seconds, it is cooled so as to reach each temperature (T ₁ ) of 800 ° C. or more below each hot rolling end temperature. After that, it was rapidly cooled to 500 ° C., kept at the same temperature for 1 hour, and then air-cooled to room temperature.
This temperature history is shown in FIG.
[0013]
Then, after hot-rolled sheet annealing, it was finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
FIG. 3 shows the results of investigation on the magnetic properties of the product thus obtained.
As is apparent from the figure, the maximum temperature (T _1C ) at which good magnetic properties are obtained varies depending on the hot rolling end temperature, and T _1C is expressed by the following equation as shown by the dotted line in the figure. Turned out to be.
T _1C = 2/3 × FDT + 700/3
[0014]
(Experiment 3)
C: 0.04wt%, Si: 3.00wt %, Mn: 0.06wt%, Al: 0.03wt% and N: 0.0090wt% only contains the balance being a steel comprising the composition of Fe and unavoidable impurities, by vacuum melting After melting and casting, it was reheated to 1200 ° C. and rolled to a thickness of 40 mm. A sample having a thickness of 40 mm, a width of 300 mm, and a length of 400 mm was collected from the sample, heated to 1300 ° C. to form a solution of the inhibitor component, and then hot rolled into a hot rolled sheet having a sheet thickness of 2.3 mm. At this time, the hot rolling end temperature (FDT) was set to 900 ° C., 1000 ° C. and 1100 ° C., and after 2 seconds, continuously cooled to T _1C corresponding to each hot rolling end temperature, and further, T ₂ ° C. for t seconds. Until cooled continuously. Then, it rapidly cooled to 500 degreeC, hold | maintained at the same temperature for 1 hour, and then air-cooled to room temperature.
This temperature history is shown in FIG.
[0015]
Then, after hot-rolled sheet annealing, it was finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
The results of investigating the magnetic properties of the product thus obtained are shown in FIGS.
As is clear from the figure, regardless of the FDT, it was found that good magnetic properties can be obtained when t ≦ 4 seconds (6 seconds after the end of hot rolling) and T ₂ ≦ 700 ° C.
From Experiments 2 and 3 above, in order to obtain good magnetic properties, it is necessary to make T _1C or less 2 seconds after the end of hot rolling and 700 ° C. or less 6 seconds after the end of hot rolling. I understand.
[0016]
Therefore, next, the influence of the cooling history between 2 seconds and 6 seconds after the end of hot rolling was investigated.
(Experiment 4)
C: 0.05wt%, Si: 2.95wt %, Mn: 0.061 wt%, Al: 0.023 wt% and N: look including the 0.0085Wt%, balance steel comprising the composition of Fe and unavoidable impurities, by vacuum melting After melting and casting, it was reheated to 1200 ° C. and rolled to a thickness of 40 mm. A sample having a thickness of 40 mm, a width of 300 mm, and a length of 400 mm was collected from the sample, heated to 1300 ° C. to form a solution of the inhibitor component, and then hot rolled into a hot rolled sheet having a sheet thickness of 2.3 mm. At this time, the hot rolling end temperature (FDT) was set to 1000 ° C., and cooling from the end of hot rolling to 6 seconds was performed along the temperature history curves of A to I shown in FIGS.
In the figure, the straight line connecting the hot rolling end point, the T _1C ° C point 2 seconds after the hot rolling end point and the 700 ° C point 6 seconds after the hot rolling end point is shown by bold lines. This curve is expressed by the following equation.
T (t) = FDT − {(FDT−700) / 6} × t
Where t: elapsed time since finish rolling (s)
T (t): Steel plate temperature after t seconds (° C)
[0017]
Then, it was rapidly cooled to 500 ° C., kept at the same temperature for 1 hour, and then air-cooled to room temperature.
Then, after hot-rolled sheet annealing, it was finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
Table 1 summarizes the results of investigations on the magnetic properties and the secondary recrystallization defect area ratio of the products thus obtained. The secondary recrystallization failure area ratio is an area ratio occupied by crystal grains having a diameter of 2 mm or less in the product plate after finish annealing.
[0018]
[Table 1]

[0019]
As is clear from the table, in order to obtain a good secondary recrystallization structure and thus magnetic characteristics, T (t) ≦ FDT − {(FDT− 700) / 6} × t
It has been determined that cooling is necessary under satisfactory conditions.
[0020]
The reason why the temperature history after the hot finish rolling has an influence on the magnetic properties after the secondary recrystallization is not necessarily clear, but is considered as follows.
That is, from the results of Experiment 1, it is estimated that there is a precipitation nose in which an inhibitor having a weak inhibitory force that causes characteristic deterioration is formed, as shown by hatching in FIG.
In addition, from the result of Experiment 2, it is found that the characteristics are improved by cooling to T ₁ = 2/3 FDT + 700/3 (° C.) or less by 2 seconds after the end of hot rolling. It was found that the characteristics were improved by cooling to 700 ° C. or less within 6 seconds after the end of hot rolling.
That is, the lower boundary (thick line portion) of the precipitation nose shown by hatching in FIG. 11 passes through the point of T ₁ ° C in 2 seconds and 700 ° C in 6 seconds, that is, T (t) = FDT − {(FDT−700 ) / 6} × t
It is thought that it is approximated by.
Therefore, in the pattern of Experiment 4, A, D, E, G, and H have a cooling history of 2 to 6 seconds partially T ≧ FDT − {(FDT−700) / 6} × t, and the suppression force is weak. It is thought that the characteristics deteriorated because of the precipitation nose of the inhibitor.
[0021]
Next, the case of containing MnSe and MnS in addition to AlN as an inhibitor was examined.
(Experiment 5)
Steel having the composition shown in Table 2 was melted by vacuum melting, cast, reheated to 1200 ° C., and rolled to a thickness of 40 mm. A sample having a thickness of 40 mm, a width of 300 mm, and a length of 400 mm was collected from the sample, heated to 1300 ° C. to form a solution of the inhibitor component, and then hot rolled into a hot rolled sheet having a sheet thickness of 2.3 mm. At this time, the hot rolling end temperature was set to 1100 ° C. to 900 ° C., and the cooling conditions from the end of hot rolling to 6 seconds were made to be the same as part of the cooling pattern shown in FIGS. Then, it was rapidly cooled to 500 ° C., kept at the same temperature for 1 hour, and then air-cooled to room temperature.
Then, after hot-rolled sheet annealing, it was finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
Table 3 shows the results of investigation on the magnetic properties of the products thus obtained.
In Table 3, the difference (ΔB ₈ , ΔW _17/50 ) from the result obtained with the same cooling pattern in Experiment 4 is also shown.
[0022]
[Table 2]

[0023]
[Table 3]

[0024]
According to Table 3, it can be seen that by adding Se and / or S, the magnetic characteristics are improved when the same cooling pattern as in Experiment 4 is employed. This is because, besides AlN, MnSe and MnS function as inhibitors.
[0025]
Finally, after the end of hot rolling, the influence of the cooling rate in the latter half until winding was investigated.
(Experiment 6)
Steel having the composition shown in Table 4 was melted by vacuum melting, cast, reheated to 1200 ° C., and rolled to a thickness of 40 mm. Steel 7 has the same components as in Experiment 4. From this, a sample having a thickness of 40 mm × width 300 mm × length 400 mm was taken, heated to 1300 ° C. to form a solution of the inhibitor component, and then hot rolled to obtain a hot rolled sheet having a thickness of 2.3 mm. At this time, the hot rolling end temperature was set to 1100 ° C. to 900 ° C., and the cooling conditions from the end of hot rolling to 6 seconds were made the same as part of the cooling pattern shown in FIGS.
Then, it cooled to 500 degreeC with the cooling rate of 10-35 degreeC / s, and hold | maintained at the same temperature for 1 hour, Then, it air-cooled to room temperature.
Then, after hot-rolled sheet annealing, it was finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
The results of the investigation on the magnetic properties of the product thus obtained are shown in FIGS.
[0026]
[Table 4]

[0027]
According to the results of FIGS. 12 to 14, the composition containing Se and / or S has a magnetic flux density by cooling from 500 seconds to 500 ° C. at a rate of 25 ° C./s or less after 6 seconds from the end of hot rolling. It can be seen that is improved.
In this regard, according to the results of FIG. 15, the effect of the cooling rate after 6 seconds was not particularly observed with the addition of AlN alone.
[0028]
As described above, the reason why the magnetic properties are particularly improved in the composition containing AlN, Se, and S by restricting the cooling rate in the latter half of the period after the hot rolling to the winding is considered as follows. .
MnSe and MnS are precipitated before the hot finish rolling. AlN is preferentially deposited on MnSe or MnS already deposited after finish rolling, and becomes a composite precipitate. In this case, when the cooling rate is low, the composite precipitate becomes stable and becomes a stronger inhibitor. In this regard, such an effect is not observed in the case of AlN alone.
[0029]
[Action]
Next, in the present invention, the reason why the component composition of the material is limited to the above range will be described.
C: 0.01 to 0.10 wt%
C is an element useful not only for uniform refinement of the composition during hot rolling and cold rolling but also for the development of Goss orientation, and it is necessary to contain at least 0.01 wt%. However, if it exceeds 0.10 wt%, decarburization becomes difficult, and the Goss orientation is disturbed. Therefore, the upper limit is made 0.10 wt%. In addition, a preferable range is 0.03-0.08 wt%.
[0030]
Si: 2.5-4.5 wt%
Si increases the specific resistance of the steel sheet and contributes to the reduction of iron loss. If the Si content is less than 2.5 wt%, the iron loss reduction effect is not sufficient, and in the final annealing at a high temperature performed for purification and secondary recrystallization, the crystal orientation is randomized due to α-γ transformation and is sufficient. Magnetic properties cannot be obtained. On the other hand, if it exceeds 4.5 wt%, the cold rolling property is impaired and the production becomes difficult. Therefore, the Si content is 2.5 to 4.5 wt%. In addition, Preferably it is good to set it as the range of 3.0-3.5 wt%.
[0031]
Mn: 0.02-0.12wt%
Mn is an element effective for preventing cracking during hot rolling due to hot brittleness, and the effect cannot be obtained at less than 0.02 wt%. On the other hand, adding over 0.12 wt% degrades the magnetic properties. Therefore, the Mn content is 0.02 to 0.12 wt%. In addition, Preferably it is good to set it as the range of 0.05-0.10 wt%.
[0032]
Al: 0.005 to 0.10 wt%
Al is an element that forms AlN and acts as an inhibitor. If the Al content is less than 0.005 wt%, the inhibitory power is not sufficiently secured. On the other hand, if the Al content exceeds 0.10 wt%, the effect is impaired, so 0.005 to 0.10 wt%. In addition, a preferable range is 0.01-0.05 wt%.
[0033]
N: 0.004 to 0.015 wt%
N is an element that forms AlN and acts as an inhibitor. If the N content is less than 0.004 wt%, the inhibitory power is not sufficiently secured. On the other hand, if it exceeds 0.15 wt%, the effect is impaired, so 0.004 to 0.15 wt%. A preferred range is 0.006 to 0.010 wt%.
[0034]
In the present invention, it is advantageous to add MnSe or MnS in addition to the above-mentioned AlN as an inhibitor, and the preferred content thereof is as follows.
Se: 0.005 to 0.06wt%
Se is a powerful element that acts as an inhibitor by forming MnSe. If the Se content is less than 0.005 wt%, the inhibitory power cannot be secured sufficiently, while if it exceeds 0.06 wt%, the effect is impaired. Therefore, 0.005 to 0.06 wt% is set for both single addition and composite addition. A preferred range is 0.010 to 0.030 wt%.
[0035]
S: 0.005 to 0.06 wt%
S is a powerful element that forms MnS and acts as an inhibitor. If the S content is less than 0.005 wt%, the inhibitory power is not sufficiently secured. On the other hand, if it exceeds 0.06 wt%, the effect is impaired, so 0.005 to 0.06 wt% for both single addition and combined addition . In addition, a preferable range is 0.015-0.035 wt%.
[0036]
In the present invention, Cu, Sn, Sb, Mo, Te, Bi and the like other than the above-described Al, S, Se as an inhibitor component also act advantageously, and can be contained in combination with the respective components. . The preferred addition ranges of these components are Cu, Sn: 0.01 to 0.15 wt% and Sb, Mo, Te, Bi: 0.005 to 0.1 wt%, respectively. Each of these inhibitor components can be used alone or in combination.
[0037]
Next, manufacturing conditions will be described.
The molten steel adjusted to the above preferred component composition range is made into a slab, preferably by continuous casting, and then heated to a temperature of 1280 ° C. or higher and then subjected to hot rolling.
The reason why the slab heating temperature is set to 1280 ° C. or more is to sufficiently dissociate and dissolve AlN, MnSe, and MnS used as inhibitors. A preferred temperature range is 1350-1450 ° C.
[0038]
In the hot rolling process, the finish rolling finish temperature is set to 900 to 1100 ° C. If the finish temperature is less than 900 ° C, undesirable inhibitor precipitation occurs in the finish rolling stand, while if the finish temperature exceeds 1100 ° C, This is because it is extremely difficult to satisfy both the plate and the cooling. A particularly preferable finish rolling end temperature is 950 to 1000 ° C.
[0039]
In the present invention, after finishing rolling in the above temperature range, for 2 to 6 seconds, the following formula T (t) ≦ FDT − {(FDT−700) / 6} × t
Therefore, it is important to perform controlled cooling under the conditions satisfying the above, and thus, good secondary recrystallization with almost no occurrence of defects proceeds, and as a result, excellent magnetic flux density and iron loss can be obtained.
[0040]
Next, when Al N and MnSe and / or Mn S are contained in combination as an inhibitor, it is preferable to cool at a rate of 25 ° C./s or less from 6 seconds after the finish rolling to the winding.
Here, the cooling rate until winding is 25 ° C./s or less. When the rate exceeds 25 ° C./s, suitable composite precipitates of AlN, MnSe, and MnS cannot be obtained, and as a result, excellent magnetic properties. It is because it cannot be obtained.
The winding temperature is preferably about 500 to 600 ° C.
[0041]
In addition, in this invention, there is no restriction | limiting in particular about manufacturing conditions other than the slab heating temperature mentioned above and the cooling conditions after hot finish rolling, Hot rolling, hot-rolled sheet annealing, pickling, intermediate annealing, cold rolling Manufacturing conditions in each step such as decarburization annealing, annealing separator coating, and finish annealing may be performed according to known methods.
[0042]
【Example】
From the molten steel having the composition shown in Table 5, a slab having a thickness of 210 mm and a width of 1000 mm was produced by continuous casting.
This slab is heated to 1200 ° C in a normal gas heating furnace, then heated to 1430 ° C in an induction electric furnace, and the inhibitor component is completely in solution, followed by hot rough rolling followed by hot finish rolling. The result was a 2.3 mm thick hot rolled sheet.
At this time, the cooling was controlled to adjust the plate temperature. Table 5 shows the results of online measurement of the plate temperature at that time using a radiation thermometer.
Thereafter, each hot-rolled sheet was subjected to hot-rolled sheet annealing, and then finished to a thickness of 0.23 mm by primary cold rolling, intermediate annealing, and secondary cold rolling. Next, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes in a wet hydrogen atmosphere, an annealing separator containing MgO as the main component is applied, followed by a final treatment at 1200 ° C for 10 hours in a dry hydrogen atmosphere. Finish annealing was performed.
Table 5 shows the results of investigations on the magnetic properties and secondary recrystallization failure area ratio of the products thus obtained.
[0043]
[Table 5]

[0044]
As is apparent from the table, the conforming example obtained according to the present invention hardly caused the occurrence of secondary recrystallization failure, and was able to obtain excellent magnetic flux density and iron loss characteristics.
Thus, it was confirmed that by performing controlled cooling after finish hot rolling according to the present invention, the secondary recrystallization failure rate is reduced, and a unidirectional electrical steel sheet with high magnetic flux density and low iron loss can be produced.
[0045]
【The invention's effect】
Thus, according to the present invention, when AlN, MnS, and MnSe are combined as an inhibitor, the secondary recrystallization failure rate of the product can be remarkably reduced, and as a result, excellent magnetic properties with high magnetic flux density and low iron loss. A unidirectional electrical steel sheet having characteristics can be obtained stably.
[Brief description of the drawings]
FIG. 1 is a diagram showing the influence of finishing rolling finishing temperature and holding time after finish rolling on magnetic properties.
2 is a schematic diagram showing a temperature history after finish rolling in Experiment 2. FIG.
FIG. 3 is a diagram showing the influence of the finish rolling end temperature and the temperature 2 seconds after the finish rolling end on the magnetic properties.
4 is a schematic diagram showing a temperature history after finish rolling in Experiment 3. FIG.
FIG. 5 is a graph showing the influence of time (t) and temperature (T ₂ ) from 2 seconds after completion of finish rolling on magnetic properties when finish rolling finish temperature is 900 ° C. and T _{1 is} 833 ° C. is there.
FIG. 6 is a diagram showing the influence of time (t) and temperature (T ₂ ) after finishing rolling for 2 seconds on the magnetic properties when finishing rolling finish temperature is 1000 ° C. and T _{1 is} 900 ° C. is there.
FIG. 7 is a graph showing the effect of time (t) and temperature (T ₂ ) after finishing rolling for 2 seconds on the magnetic properties when finishing rolling finish temperature is 1100 ° C. and T _{1 is} 966 ° C. is there.
FIG. 8 is a temperature history curve diagram showing cooling conditions after finishing hot rolling.
FIG. 9 is a temperature history curve diagram showing cooling conditions after finishing hot rolling.
FIG. 10 is a temperature history curve diagram showing cooling conditions after finishing hot rolling.
FIG. 11 is a schematic diagram showing a precipitation nose of an inhibitor having a weak inhibitory power.
FIG. 12 is a graph showing the relationship between the cooling rate and magnetic properties after 6 seconds after finishing finish rolling in Experiment 6.
FIG. 13 is a graph showing the relationship between the cooling rate and magnetic properties after 6 seconds after finishing finish rolling in Experiment 6.
FIG. 14 is a graph showing the relationship between the cooling rate and magnetic properties after 6 seconds after finishing finish rolling in Experiment 6.
15 is a graph showing the relationship between the cooling rate and magnetic properties after 6 seconds from the end of finish rolling in Experiment 6. FIG.

Claims (3)

C: 0.01-0.10 wt%
Si: 2.5-4.5 wt%
Mn: 0.02 to 0.12 wt%,
Al: 0.005 to 0.10 wt% and N: 0.004 to 0.015 wt%
And the balance is Fe and an inevitable impurity composition of a silicon steel slab, heated to a temperature of 1280 ° C or higher, then hot rolled, and then cold once or two times with intermediate annealing After rolling and finishing to the final thickness, decarburization and primary recrystallization annealing are performed, after which the annealing separator is applied, and then the final finishing annealing is performed to produce a unidirectional silicon steel sheet. On the occasion
In the above hot rolling step, the finish rolling finish temperature is in the range of 900 to 1100 ° C., and for 2 to 6 seconds after the finish rolling is finished, the following formula T (t) ≦ FDT − {(FDT−700) / 6} × t
Where t: elapsed time since finish rolling (s)
T (t): Steel plate temperature after t seconds (° C)
FDT: Finishing rolling finish temperature (° C)
A method for producing a unidirectional silicon steel sheet, characterized in that controlled cooling is performed under conditions satisfying The steel slab according to claim 1, further comprising:
At least one selected from Se and S: 0.005 to 0.06 wt%
Ri Do the composition containing the method for producing a grain-oriented silicon steel sheet, which comprises cooling an additional finish rolling completion after 6 seconds until the winding below 25 ° C. / s rate. The steel slab according to claim 1 or 2 , further comprising:
Cu: 0.01 to 0.15 wt%,
Sn: 0.01-0.15wt%,
Sb: 0.005 to 0.1 wt%,
Mo: 0.005-0.1 wt%,
Te: 0.005-0.1 wt% and
Bi: 0.005-0.1 wt%
A method for producing a unidirectional silicon steel sheet, comprising a composition containing one or more selected from among the above.

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