JP5862873B2 - Method for producing grain-oriented electrical steel sheet - Google Patents
Method for producing grain-oriented electrical steel sheet Download PDFInfo
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- 229910001224 Grain-oriented electrical steel Inorganic materials 0.000 title claims description 23
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Description
本発明は、方向性電磁鋼板の製造方法に関し、具体的には、コイル全長にわたって磁気特性と被膜特性に優れる方向性電磁鋼板を製造することができる仕上焼鈍技術に関するものである。 The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet, and specifically relates to a finish annealing technique that can produce a grain-oriented electrical steel sheet that is excellent in magnetic characteristics and film characteristics over the entire length of a coil.
近年、地球温暖化を防止するため、省エネルギー化に対する要求が高まっている。それに伴い、変圧器や電動機等の鉄心材料として用いられる方向性電磁鋼板には、商用周波数における鉄損が低く、かつ、低磁場でも高い磁束密度を有する優れた磁気特性が強く求められるようになってきている。 In recent years, in order to prevent global warming, the demand for energy saving is increasing. As a result, grain-oriented electrical steel sheets used as core materials for transformers, electric motors, etc. are strongly required to have excellent magnetic properties with low core loss at commercial frequencies and high magnetic flux density even at low magnetic fields. It is coming.
上記方向性電磁鋼板は、鋼板の圧延方向に鉄の磁化容易軸である＜００１＞方位が高度に集積した結晶組織を有しているところに特徴があり、このような結晶組織は、製造過程の仕上焼鈍で、高温焼鈍して二次再結晶を起こさせ、｛１１０｝＜００１＞方位粒、いわゆる「ゴス粒」と称される結晶粒を優先的に巨大成長させることによって得られる。 The grain-oriented electrical steel sheet is characterized in that it has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly accumulated in the rolling direction of the steel sheet. In this final annealing, high temperature annealing is performed to cause secondary recrystallization, and crystal grains called {110} <001> orientation grains, so-called “goth grains”, are preferentially grown giant.
上記二次再結晶を発現させ、かつ、鋼板表面にフォルステライト（Ｍｇ２ＳｉＯ４）被膜を形成させるためには、高温長時間の熱処理が必要となる。そのため、仕上焼鈍は、一般にバッチ式の箱型焼鈍炉を用いて、コイルフォームで行われるのが普通である。ところが、コイルフォームで仕上焼鈍した鋼板は、コイルに巻かれた状態で二次再結晶するため、コイルセット（巻き癖）が発生する。しかし、二次再結晶粒の結晶方位は、一次再結晶集合組織に対応する結晶座標系により決定されるため、＜００１＞方位は、板面に平行には成長せず、図１（ａ）のように、板面に対する角度が鋼板の長さ方向で変化する。そのため、仕上焼鈍後、巻き癖を矯正して平坦化した製品板の結晶粒は、図１（ｂ）のように、同一結晶粒内でも＜００１＞方位の向きが長手方向で変化したものとなる。そして、この変化量は、コイルへの巻き取り径が小さいほど大きくなるため、製品板の方位集積度は、仕上焼鈍時のコイル外径側から内径側にいくに従い、順次、低下することとなる。 In order to develop the secondary recrystallization and to form a forsterite (Mg 2 SiO 4 ) film on the surface of the steel sheet, heat treatment at a high temperature for a long time is required. For this reason, the finish annealing is generally performed in coil form using a batch type box annealing furnace. However, since the steel sheet finish-annealed with coil foam is secondarily recrystallized in a state of being wound around a coil, a coil set (winding habit) is generated. However, since the crystal orientation of the secondary recrystallized grains is determined by the crystal coordinate system corresponding to the primary recrystallization texture, the <001> orientation does not grow parallel to the plate surface, and FIG. Thus, the angle with respect to the plate surface changes in the length direction of the steel plate. Therefore, the crystal grain of the product plate that has been flattened by correcting the curl after the finish annealing is such that the orientation of the <001> orientation has changed in the longitudinal direction even within the same crystal grain as shown in FIG. Become. And since this change amount becomes so large that the winding diameter to a coil is small, the orientation integration degree of a product board will fall sequentially as it goes to the inner diameter side from the coil outer diameter side at the time of finish annealing. .
さらに、最終冷延圧下率を８０％以上として製造する高磁束密度方向性電磁鋼板においては、二次再結晶粒の粒径は数１０ｍｍにも達するため、コイル曲率による方位集積度の低下は、最終冷延圧下率が６０％程度で二次再結晶粒径が５ｍｍ程度である汎用の方向性電磁鋼板と比較して遥かに大きくなる。図２は、単結晶を用いて、理想とするゴス方位からのずれ角のうち、板面からの傾き角（以下「β角」という。）が磁束密度Ｂ８に及ぼす影響を調査した結果を示したものである。この図から、β角が０〜２°の範囲では磁束密度の低下は小さいが、β角が２°を超えると、磁束密度が１°当り０．０３Ｔも低下することがわかる。 Furthermore, in the high magnetic flux density grain-oriented electrical steel sheet manufactured with a final cold rolling reduction of 80% or more, the secondary recrystallized grains have a grain size of several tens of millimeters. This is much larger than a general-purpose grain-oriented electrical steel sheet having a final cold rolling reduction of about 60% and a secondary recrystallization grain size of about 5 mm. FIG. 2 shows the result of investigating the influence of the tilt angle from the plate surface (hereinafter referred to as “β angle”) on the magnetic flux density B 8 out of the deviation angle from the ideal Goss direction using a single crystal. It is shown. From this figure, it can be seen that the decrease in the magnetic flux density is small when the β angle is in the range of 0 to 2 °, but when the β angle exceeds 2 °, the magnetic flux density is decreased by 0.03 T per 1 °.
このようなコイル曲率に起因するβ角の幾何学的増大を抑制する技術としては、特許文献１に、仕上焼鈍におけるコイル内径を６００ｍｍφ以上とする方法が提案されている。このコイル内径を大きくする方法は、原理的に正しいものであって、極めて有効な手段である。
As a technique for suppressing such a geometric increase in β angle due to the coil curvature,
ところで、鋼板をコイルフォームで仕上焼鈍する場合には、上記コイルセットの問題の他に、昇温時のコイル内温度の不均一に起因するコイル変形やコイル下部の座屈等の問題があることが知られている。さらに、コイル中巻部の磁気特性や被膜特性が劣化するという問題がある。この問題は、鋼板をコイルフォームで仕上焼鈍する場合、加熱過程においては、昇温速度が速いコイル外周面側と内周面側は、コイル中巻部より早く熱膨張しようとする。この場合、コイル外周面側は自由に熱膨張することができるが、コイル内周面側は、コイル中巻部によって熱膨張が阻害される。逆に言うと、コイル中巻部は、コイル内周面側によって圧縮され、コイルの巻き締まりが生じる。その結果、コイルに巻かれた鋼板間の焼鈍雰囲気が滞留して、二次再結晶の発現やフォルステライト被膜の形成が阻害されて、磁気特性の劣化や、被膜外観および被膜密着性といった被膜特性が劣化するというものである。 By the way, when finishing annealing a steel sheet with coil foam, there are problems such as coil deformation and buckling of the lower part of the coil due to non-uniform temperature in the coil at the time of temperature rise in addition to the problem of the above coil set. It has been known. Furthermore, there is a problem that the magnetic properties and film properties of the middle winding portion of the coil deteriorate. This problem is that when the steel sheet is finish-annealed with coil foam, in the heating process, the coil outer peripheral surface side and the inner peripheral surface side, which have a high temperature rising rate, try to thermally expand faster than the coil middle winding portion. In this case, the coil outer peripheral surface side can be freely thermally expanded, but the coil inner peripheral surface side is inhibited from thermal expansion by the coil middle winding portion. In other words, the coil middle winding portion is compressed by the coil inner peripheral surface side, and the coil is tightened. As a result, the annealing atmosphere between the steel sheets wound around the coil stays, and secondary recrystallization and forsterite film formation are inhibited, resulting in deterioration of magnetic properties and film characteristics such as film appearance and film adhesion. Will deteriorate.
この問題点は、特許文献１の技術のように、コイル内径を大きくしても改善されない。むしろ、コイル内径を大きくすると、仕上焼鈍加熱時におけるコイル内周面からの入熱量が大きくなり、コイル内周面側（内径部）と中巻部の温度差が拡大し、コイル内径部におけるコイル変形等や、コイル中巻部における磁気特性や被膜特性の劣化がより大きくなるという弊害が生じる。
This problem cannot be improved even if the coil inner diameter is increased as in the technique of
本発明は、従来技術が抱える上記問題点に鑑みてなされたものであり、その目的は、バッチ式箱型焼鈍炉を用いて素材鋼板をコイルフォームで仕上焼鈍して方向性電磁鋼板用を製造する際、コイル内温度分布によって起こるコイル中巻部における磁気特性および被膜特性の劣化を抑制することができる方向性電磁鋼板の有利な製造方法を提案することにある。 The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to produce a grain-oriented electrical steel sheet by finish annealing the steel sheet in coil form using a batch type box annealing furnace. It is an object of the present invention to propose an advantageous method for producing a grain-oriented electrical steel sheet capable of suppressing the deterioration of the magnetic characteristics and the film characteristics in the middle winding portion of the coil caused by the temperature distribution in the coil.
発明者らは、上記課題の解決に向けて鋭意検討を重ねた。その結果、コイル中巻部における磁気特性および被膜特性の劣化は、コイル内周面側の昇温がコイル中巻部より速いことに起因するコイル中巻部への圧縮応力に起因していることから、コイル内周面の昇温をコイル中巻部やコイル外周面に対して抑制してやればよいこと、そのためには、仕上焼鈍の加熱過程においてコイル内周面を積極的に冷却してやればよいことを想到し、本発明を開発した。 The inventors have intensively studied to solve the above problems. As a result, the deterioration of the magnetic properties and film properties of the coil middle winding part is caused by the compressive stress applied to the coil middle winding part due to the temperature rise on the inner peripheral surface side of the coil being faster than that of the coil middle winding part. Therefore, it is only necessary to suppress the temperature rise of the coil inner peripheral surface with respect to the coil middle winding part and the coil outer peripheral surface, and for that purpose, it is only necessary to actively cool the coil inner peripheral surface in the heating process of finish annealing. The present invention has been developed.
すなわち、本発明は、冷間圧延後、一次再結晶焼鈍し、焼鈍分離剤を塗布した鋼板をコイルに巻き取り、バッチ式箱型焼鈍炉で仕上焼鈍して方向性電磁鋼板を製造する方法において、上記コイルの内径を７００ｍｍφ以上、コイルの内径と外径の差を５００ｍｍ以上とし、かつ、上記仕上焼鈍では、コイル内周面の温度が、コイル外周面に対して２０℃以下となるように、コイル内周面を冷却しつつコイル全体を加熱することを特徴とする方向性電磁鋼板の製造方法である。
That is, the present invention is a method for producing a grain-oriented electrical steel sheet by cold rolling, followed by primary recrystallization annealing, winding a steel sheet coated with an annealing separator onto a coil, and finishing annealing in a batch type box annealing furnace. The inner diameter of the coil is 700 mmφ or more , the difference between the inner diameter and the outer diameter of the coil is 500 mm or more , and in the finish annealing, the temperature of the coil inner peripheral surface is 20 ° C. or lower with respect to the coil outer peripheral surface. A method for producing a grain-oriented electrical steel sheet, wherein the entire coil is heated while cooling the inner circumferential surface of the coil .
本発明の上記方向性電磁鋼板の製造方法は、加熱中のコイル内周面の温度が６００〜８００℃の範囲において、コイル内周面の温度が、コイル外周面に対して２０℃以下となるようにコイル全体を加熱することを特徴とする。
Method of producing the grain-oriented electrical steel sheet of the present invention, in the range temperature of 600 to 800 ° C. in coil inner circumferential surface of the addicting pressure, and the temperature in the coil peripheral surface, 20 ° C. or less with respect to the coil outer circumferential surface Thus, the entire coil is heated .
本発明によれば、方向性電磁鋼板の仕上焼鈍時に発生するコイル内温度分布を改善してコイル中巻部に掛かる圧縮応力を軽減し、磁気特性や被膜特性の劣化を防止することができるので、方向性電磁鋼板の品質向上や歩留まり向上、ひいては、変圧器や電動機等の省エネルギー化に大きく寄与する。 According to the present invention, it is possible to improve the temperature distribution in the coil generated during finish annealing of grain-oriented electrical steel sheets, reduce the compressive stress applied to the coil middle winding part, and prevent the deterioration of magnetic characteristics and film characteristics. This greatly contributes to improving the quality and yield of grain-oriented electrical steel sheets and, in turn, saving energy in transformers and electric motors.
発明者らは、上記課題を解決するべく、仕上焼鈍でコイルを加熱する際のコイル内温度分布と圧縮応力との関係について、次のような考察を行った。
仕上焼鈍におけるコイルの加熱は、コイルに被せられたインナーケースからの輻射熱によって行われるため、図３に示すように、コイルの外周面、内周面および上側面から加熱される。そのため、これらの部分は、コイル内部よりも早く高温となり、コイル内の半径方向の温度分布は、図４の線Ａで示したように、コイル外周面側、内周面側の順に高く、中巻部が最も低い温度分布になる。このような温度分布になると、コイル外周面側は、熱膨張してもその膨張を妨げられることはないが、内周面側の熱膨張は、低温の中巻部によって妨げられる。その結果、コイル中巻部には大きな圧縮応力が生じて磁気特性や被膜特性の劣化を引き起こす。
そこで、図４の線Ｂで示したように、コイル外周面に比べてコイル内周面の温度がより低下し、好ましくは、コイル外周面側から内周面側に漸次温度が低下する温度分布を実現できれば、加熱されるに従ってコイル外周面側から順次、熱膨張するので、コイル中巻部には大きな圧縮応力が発生せず、コイルが巻き締まりを起こすこともないと考えられる。
In order to solve the above-mentioned problems, the inventors made the following considerations on the relationship between the temperature distribution in the coil and the compressive stress when the coil was heated by finish annealing.
Since the heating of the coil in the finish annealing is performed by radiant heat from the inner case placed on the coil, the coil is heated from the outer peripheral surface, the inner peripheral surface and the upper side surface of the coil as shown in FIG. Therefore, these portions are heated faster than the inside of the coil, and the temperature distribution in the radial direction in the coil is higher in the order of the coil outer peripheral surface side and the inner peripheral surface side as shown by the line A in FIG. The winding has the lowest temperature distribution. With such a temperature distribution, the coil outer peripheral surface side is not hindered by thermal expansion, but the inner peripheral surface side thermal expansion is hindered by the low-temperature middle winding portion. As a result, a large compressive stress is generated in the middle winding portion of the coil, causing deterioration of magnetic characteristics and film characteristics.
Therefore, as shown by the line B in FIG. 4, the temperature distribution in which the temperature of the coil inner peripheral surface is lower than that of the coil outer peripheral surface, and preferably the temperature gradually decreases from the coil outer peripheral surface side to the inner peripheral surface side. If it can be realized, thermal expansion will occur sequentially from the outer peripheral surface side of the coil as it is heated. Therefore, it is considered that no large compressive stress is generated in the middle winding portion of the coil, and the coil is not tightened.
そこで、図４の線Ｂで示したような温度分布を実現するため、仕上焼鈍時にコイルに被せるインナーケースを改良し、コイル内周面を冷却することが可能な、図５に示したインナーケースを製作した。このインナーケース３は、アップエンドに載置した鋼板コイル１に被せるインナーケース３の上面中心部に、コイルの内周面１ａと対向する外管４ａと、その内側に内管４ｂを配設した２重管構造の円筒状凹部４を有するものであり、この２重管構造の円筒状凹部４の内管４ｂ内に、図５中に矢印で示したように、炉の上部から冷却ガス６を吹き込み、その後、その吹き込んだ冷却ガス６を内管４ｂと外管４ａとの間隙に流すようにすることで、冷却ガス６がスムーズに流れて外管４ａが効率よく冷却され、ひいては、コイル内周面１ａを効率よく冷却することができるようにしたものである。
Therefore, in order to realize the temperature distribution as shown by the line B in FIG. 4, the inner case shown in FIG. 5 can be improved by improving the inner case covered on the coil during finish annealing and cooling the inner peripheral surface of the coil. Was made. The
そこで、上記インナーケースを用いて、以下の実験を行った。
Ｃ：０．０７ｍａｓｓ％、Ｓｉ：３．３ｍａｓｓ％、Ｍｎ：０．０６ｍａｓｓ％、Ａｌ：０．０２ｍａｓｓ％、Ｎ：０．００８ｍａｓｓ％、Ｓｅ：０．０２ｍａｓｓ％およびＳｂ：０．０４ｍａｓｓ％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の鋼スラブを１４２０℃に加熱後、熱間圧延して板厚：２．３ｍｍの熱延板とし、１０００℃で３０秒の熱延板焼鈍を施した後、１回目の冷間圧延で中間板厚：１．８ｍｍの冷延板とし、１１２０℃で３０秒の中間焼鈍を施した後、加工発熱により鋼板温度を２２０℃まで昇温させる２回目の冷間圧延をして最終板厚：０．２３ｍｍの冷延板とした。
Therefore, the following experiment was performed using the inner case.
C: 0.07 mass%, Si: 3.3 mass%, Mn: 0.06 mass%, Al: 0.02 mass%, N: 0.008 mass%, Se: 0.02 mass% and Sb: 0.04 mass% Then, a steel slab having a composition composed of Fe and inevitable impurities as the balance is heated to 1420 ° C., and then hot-rolled to form a hot-rolled sheet having a thickness of 2.3 mm, and annealed at 1000 ° C. for 30 seconds. After the first cold rolling, a cold rolled sheet having an intermediate thickness of 1.8 mm is formed, and after intermediate annealing at 1120 ° C. for 30 seconds, the temperature of the steel sheet is raised to 220 ° C. by processing heat generation. A second cold rolling was performed to obtain a cold rolled sheet having a final sheet thickness of 0.23 mm.
次いで、露点６０℃の湿潤水素雰囲気下で８４０℃×１２０秒の脱炭を兼ねた一次再結晶焼鈍を施した後、ＭｇＯを主成分とする焼鈍分離剤を鋼板表面に塗布し、乾燥した後、内径：１０００ｍｍ、外径：２０００ｍｍのコイルＡ、および、内径：５００ｍｍ、外径２０００ｍｍのコイルＢの２種類のコイルに巻き取り、その後、上記２種類のコイルを、バッチ式箱型焼鈍炉を用いて、（Ｎ２＋Ｈ２）混合雰囲気下で１１７０℃まで昇温し、Ｈ２雰囲気下で５時間保持する仕上焼鈍を施した。 Next, after subjecting to primary recrystallization annealing also serving as decarburization at 840 ° C. for 120 seconds in a wet hydrogen atmosphere with a dew point of 60 ° C., an annealing separator mainly composed of MgO is applied to the steel sheet surface and dried. The inner diameter is 1000 mm, the outer diameter is 2000 mm, the coil A and the inner diameter is 500 mm, and the outer diameter is 2000 mm. The coil B is wound around two types of coils. The temperature was raised to 1170 ° C. in a (N 2 + H 2 ) mixed atmosphere, and finish annealing was performed for 5 hours in an H 2 atmosphere.
なお、上記仕上焼鈍では、図５に示した２重管構造の円筒状凹部を有するインナーケースを用い、仕上焼鈍の加熱過程の８００〜１１７０℃の間において、円筒状凹部の内管内に大気温度のＮ２ガスを５００Ｎｍ３／ｈｒ供給してコイル内周面を冷却した。また、上記加熱過程の温度は、コイル内径と外径の中間部、すなわち、コイルＡではコイル径が１２５０ｍｍの位置、コイルＢではコイル径が９００ｍｍの位置の板幅中央部に巻き込んだ熱電対で測定した温度とした。 In the finish annealing, an inner case having a cylindrical recess having a double-pipe structure shown in FIG. 5 is used, and the atmospheric temperature is set in the inner tube of the cylindrical recess between 800 and 1170 ° C. in the heating process of the finish annealing. The N 2 gas was supplied at 500 Nm 3 / hr to cool the inner peripheral surface of the coil. Further, the temperature of the heating process is an intermediate portion between the inner diameter and the outer diameter of the coil, that is, a coil coupled to a central portion of the plate width at a position where the coil diameter is 1250 mm in the coil A and a position where the coil diameter is 900 mm in the coil B. It was set as the measured temperature.
次いで、仕上焼鈍後のコイルは、未反応の焼鈍分離剤を鋼板表面から除去した後、５０ｍａｓｓ％のコロイダルシリカと燐酸マグネシウムからなるコーティング液を両面目付量が１０ｇ／ｍ２となるよう塗布し、９ＭＰａの張力を付与しつつ８４０℃の温度で平坦化焼鈍を施して絶縁被膜を被成し、製品コイルとした。 Next, after the finish annealing, after removing the unreacted annealing separator from the steel sheet surface, a coating liquid composed of 50 mass% colloidal silica and magnesium phosphate is applied so that the double-sided weight is 10 g / m 2 . A flattening annealing was performed at a temperature of 840 ° C. while applying a tension of 9 MPa to form an insulating film, thereby obtaining a product coil.
斯くして得られた製品コイルのコイル径５００ｍｍ（コイルＢの内径部）、７００ｍｍ、１０００ｍｍ（コイルＡの内径部）、１５００ｍｍおよび２０００ｍｍ（外径部）の各位置から試験片を採取し、圧延方向の磁束密度Ｂ８とフォルステライト被膜の密着性を評価した。なお、被膜密着性は、圧延方向：３０ｍｍ×圧延直角方向：３００ｍｍの試験片を種々の外径を有する丸棒に巻き付けて１８０度に折り曲げ、折り曲げ部分の被膜剥離が起こらない最小径で評価した。
Samples were collected from the positions of the
上記の実験結果について、コイル径と磁束密度Ｂ８との関係を図６に、コイル径と被膜密着性（最小曲げ剥離径）との関係をおよび図７に示した。これらの結果から、コイル内径を大きくしたコイルＡを、内周面側を冷却しつつ加熱して仕上焼鈍することにより、コイル全長にわたって磁束密度と被膜密着性が良好な方向性電磁鋼板が得られることがわかる。 The above experimental results, in Figure 6 the relationship between the coil diameter and the magnetic flux density B 8, shown in and Figure 7 the relationship between the coil diameter and the film adhesion (minimum bend Peeling diameter). From these results, a directional electrical steel sheet with good magnetic flux density and good film adhesion can be obtained over the entire length of the coil by heating and finishing annealing the coil A having a larger coil inner diameter while cooling the inner peripheral surface side. I understand that.
次に、本発明の方向性電磁鋼板の製造方法について説明する。
本発明の方向性電磁鋼板の素材に用いる鋼スラブは、連続鋳造法や造塊−分塊圧延法等、常法に準じて製造すればよく、特に制限はない。また、直接鋳造法で製造した厚さ：１００ｍｍ以下の薄鋳片を用いることもできる。
また、鋼スラブの成分組成についても、方向性電磁鋼板として従来公知のものであればよく、特に制限はないが、以下の成分組成を有するものであれば、好適に用いることができる。
Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
The steel slab used for the material of the grain-oriented electrical steel sheet of the present invention may be produced according to a conventional method such as a continuous casting method or an ingot-bundling rolling method, and is not particularly limited. Further, a thin cast piece having a thickness of 100 mm or less manufactured by a direct casting method can also be used.
Also, the component composition of the steel slab may be any conventionally known grain-oriented electrical steel sheet and is not particularly limited, but any component having the following component composition can be suitably used.
Ｃ：０．０１〜０．１０ｍａｓｓ％
Ｃは、相変態を利用して熱延板の結晶組織を改善するのに有用な元素であるだけでなく、ゴス方位粒を生成させるのに有用な元素であり、少なくとも０．０１ｍａｓｓ％含有させるのが好ましい。一方、０．１０ｍａｓｓ％を超えて含有すると、脱炭焼鈍で、磁気時効が起こらない０．００５ｍａｓｓ％以下まで脱炭することが難しくなる。よって、鋼スラブに含まれるＣは、０．０１〜０．１０ｍａｓｓ％の範囲とするのが好ましい。
C: 0.01-0.10 mass%
C is not only an element useful for improving the crystal structure of a hot-rolled sheet using phase transformation, but also an element useful for generating goth-oriented grains, and is contained at least 0.01 mass%. Is preferred. On the other hand, when it contains exceeding 0.10 mass%, it will become difficult to decarburize to 0.005 mass% or less by decarburization annealing and magnetic aging does not occur. Therefore, C contained in the steel slab is preferably in the range of 0.01 to 0.10 mass%.
Ｓｉ：２．０〜４．５ｍａｓｓ％
Ｓｉは、鋼の固有抵抗を高めて渦電流損を低減し、鉄損を低減するのに有用な元素であり、２．０ｍａｓｓ％以上含有させるのが好ましい。しかし、４．５ｍａｓｓ％を超えて添加すると、鋼が脆化し、冷間圧延して製造することは難しくなる。よって、Ｓｉは、２．０〜４．５ｍａｓｓ％の範囲とするのが好ましい。
Si: 2.0 to 4.5 mass%
Si is an element useful for increasing the specific resistance of steel, reducing eddy current loss, and reducing iron loss, and is preferably contained in an amount of 2.0 mass% or more. However, if added over 4.5 mass%, the steel becomes brittle and it is difficult to manufacture by cold rolling. Therefore, Si is preferably in the range of 2.0 to 4.5 mass%.
Ｍｎ：０．０１〜０．５ｍａｓｓ％
Ｍｎは、鋼の熱間加工性を向上させる効果があるので、０．０１ｍａｓｓ％以上添加するのが好ましい。しかし、０．５ｍａｓｓ％を超えて添加すると、一次再結晶集合組織が劣化し、ゴス方位に高度に集積した二次再結晶粒が得られ難く、磁気特性が低下するようになる。よって、Ｍｎは０．０１〜０．５ｍａｓｓ％の範囲とするのが好ましい。
Mn: 0.01 to 0.5 mass%
Since Mn has an effect of improving the hot workability of steel, it is preferable to add 0.01 mass% or more. However, if added over 0.5 mass%, the primary recrystallization texture deteriorates, secondary recrystallized grains highly accumulated in the Goth orientation are difficult to obtain, and the magnetic properties deteriorate. Therefore, Mn is preferably in the range of 0.01 to 0.5 mass%.
鋼スラブに含まれる上記Ｃ，ＳｉおよびＭｎ以外の重要な成分として、インヒビター成分がある。
このインヒビター成分は、二次再結晶を発現させるためにインヒビターを利用する場合には含有させることが必須であり、例えば、ＡｌＮをインヒビターに用いるときには、Ａｌ：０．０１０〜０．０３０ｍａｓｓ％、Ｎ：０．００３０〜０．０１００ｍａｓｓ％の範囲で、また、ＭｎＳおよび／またはＭｎＳｅをインヒビターに用いるときには、Ｓ，Ｓｅは単独あるいは合計で０．０１０〜０．０３０ｍａｓｓ％の範囲で含有させることが好ましい。なお、二次再結晶に利用する上記インヒビターは１種だけでもよいし、２種以上を用いてもよい。
As an important component other than the C, Si and Mn contained in the steel slab, there is an inhibitor component.
This inhibitor component must be contained when an inhibitor is used to develop secondary recrystallization. For example, when AlN is used as an inhibitor, Al: 0.010 to 0.030 mass%, N : In the range of 0.0030 to 0.0100 mass%, and when MnS and / or MnSe is used as an inhibitor, S and Se are preferably contained alone or in total in the range of 0.010 to 0.030 mass%. . In addition, the said inhibitor utilized for secondary recrystallization may be only 1 type, and may use 2 or more types.
一方、特開２０００−１２９３５６号公報に開示された技術のように、インヒビターを利用せず、固溶窒素の粒界移動抑制効果を利用して二次再結晶を発現させる場合には、Ａｌ，Ｎ，Ｓ，ＳｅおよびＢ等のインヒビター成分は極力低減することが望ましく、たとえば、Ａｌ：０．０１００ｍａｓｓ％以下、Ｎ：０．００５０ｍａｓｓ％以下、Ｓ：０．００５０ｍａｓｓ％以下およびＳｅ：０．００５０ｍａｓｓ％以下に低減することが好ましい。 On the other hand, as in the technique disclosed in Japanese Patent Application Laid-Open No. 2000-129356, when secondary recrystallization is expressed using the effect of suppressing the grain boundary migration of solute nitrogen without using an inhibitor, Al, Inhibitor components such as N, S, Se, and B are desirably reduced as much as possible. For example, Al: 0.0100 mass% or less, N: 0.0050 mass% or less, S: 0.0050 mass% or less, and Se: 0.0050 mass. It is preferable to reduce to less than%.
また、本発明の方向性電磁鋼板は、上記必須とする成分の他に、インヒビターの作用を補助し、鉄損や磁気特性をより改善するため、Ｃｒ：０．１ｍａｓｓ％以下、Ｎｉ：０．５ｍａｓｓ％以下、Ｍｏ：０．１ｍａｓｓ％以下、Ｃｕ：０．１０ｍａｓｓ％以下、Ｎｂ：０．０５ｍａｓｓ％以下、Ｓｂ：０．０１〜０．１０ｍａｓｓ％、Ｓｎ：０．０１〜０．２０ｍａｓｓ％およびＰ：０．０５ｍａｓｓ％以下のうちから選ばれる１種または２種以上を含有させることができる。ただし、これら元素の上記範囲を超える添加は、鋼を脆化し、熱間圧延や冷間圧延において割れや破断を引き起こし、製品歩留りの低下を招くので、添加する場合は、上記範囲とするのが好ましい。 Further, the grain-oriented electrical steel sheet of the present invention, in addition to the essential components described above, assists the action of an inhibitor and further improves iron loss and magnetic properties, so that Cr: 0.1 mass% or less, Ni: 0. 5 mass% or less, Mo: 0.1 mass% or less, Cu: 0.10 mass% or less, Nb: 0.05 mass% or less, Sb: 0.01 to 0.10 mass%, Sn: 0.01 to 0.20 mass%, and P: One or more selected from 0.05 mass% or less can be contained. However, addition of these elements beyond the above range causes embrittlement of the steel and causes cracking and fracture in hot rolling and cold rolling, resulting in a decrease in product yield. preferable.
次いで、上記鋼スラブは、所定の温度に再加熱した後、熱間圧延して熱延板とし、必要に応じて熱延板焼鈍を施した後、あるいは熱延板焼鈍を施すことなく、１回または中間焼鈍を挟む２回以上の冷間圧延により最終板厚の冷延板とする。なお、上記冷間圧延では、一次再結晶組織におけるゴス組織を発達させる観点から、加工発熱で鋼板温度を１００〜２５０℃に上昇させるか、あるいは、冷間圧延の途中で１００〜２５０℃の温度でパス間時効を１回または複数回施すことが好ましい。 Next, the steel slab is reheated to a predetermined temperature, and then hot-rolled to form a hot-rolled sheet, and after performing hot-rolled sheet annealing as necessary, or without performing hot-rolled sheet annealing, A cold-rolled sheet having a final thickness is obtained by cold rolling at least twice with intermediate or intermediate annealing. In the cold rolling, from the viewpoint of developing a goth structure in the primary recrystallized structure, the steel plate temperature is raised to 100 to 250 ° C. by processing heat generation, or a temperature of 100 to 250 ° C. during the cold rolling. It is preferable to apply aging between passes once or a plurality of times.
次いで、最終板厚とした冷延板は、一次再結晶焼鈍を施す。なお、この一次再結晶焼鈍は、鋼スラブ中のＣ量が高い場合には、湿潤水素雰囲気下で７５０〜９００℃の温度で脱炭焼鈍を兼ねて行い、Ｃ含有量を０．００５０ｍａｓｓ％以下、望ましくは０．００３０ｍａｓｓ％以下に低減するのが好ましい。 Next, the cold-rolled sheet having the final thickness is subjected to primary recrystallization annealing. In addition, this primary recrystallization annealing is also performed in the wet hydrogen atmosphere at a temperature of 750 to 900 ° C. in the case where the C content in the steel slab is high, and the C content is 0.0050 mass% or less. It is desirable to reduce it to 0.0030 mass% or less.
一次再結晶焼鈍後の鋼板は、その後、ＭｇＯを主体とする焼鈍分離剤を鋼板表面に塗布し、乾燥し、コイルに巻き取り、二次再結晶させると共に、フォルステライト被膜を形成させるため、バッチ式の箱型焼鈍炉を用いて１０００℃以上の温度で仕上焼鈍を施すのが好ましい。 The steel sheet after the primary recrystallization annealing is then batch coated with an annealing separator mainly composed of MgO on the steel sheet surface, dried, wound into a coil, subjected to secondary recrystallization, and a forsterite film is formed. It is preferable to perform finish annealing at a temperature of 1000 ° C. or higher using a box-type annealing furnace of the type.
この際、本発明においては、上記仕上焼鈍時のコイル内径を７００ｍｍφ以上とし、かつ、仕上焼鈍の加熱過程においてコイル内周面を冷却し、コイル内周面の温度をコイル内の最冷点の温度よりも低くしてやることが望ましい。
ここで、仕上焼鈍の加熱過程においてコイル内周面を冷却する理由は、図４のＢ線で示したように、コイル内の半径方向の温度分布をコイル外径側から内径側に向って温度が漸次低下するように、もしくは、それに近い温度分布となるように温度制御しつつ加熱することで、コイル内径部の熱膨張によって発生するコイル中巻部の圧縮応力を抑制し、全長にわたって磁気特性と被膜特性に優れる製品コイルを得るためである。
At this time, in the present invention, the inner diameter of the coil during the above-mentioned finish annealing is set to 700 mmφ or more, and the inner peripheral surface of the coil is cooled in the heating process of the final annealing, and the temperature of the inner peripheral surface of the coil is set to the coldest spot in the coil. It is desirable to make it lower than the temperature.
Here, the reason for cooling the inner peripheral surface of the coil in the heating process of the finish annealing is that the temperature distribution in the radial direction in the coil is changed from the outer diameter side to the inner diameter side as shown by the line B in FIG. By controlling the temperature so that the temperature gradually decreases or the temperature distribution is close to that, the compressive stress of the inner coil of the coil caused by the thermal expansion of the inner diameter of the coil is suppressed, and the magnetic properties are extended over the entire length. This is to obtain a product coil having excellent coating properties.
また、コイル内径を７００ｍｍφ以上とする理由は、７００ｍｍφ未満では、コイル内径部の湾曲（曲率）が大きく、平坦化焼鈍に伴なう方位劣化量が増大して磁気特性が低下する。また、コイル内径が７００ｍｍφ未満になるとコイル内周面の表面積が小さくなるため、コイル内周面の冷却が不足気味となり、図４のＢ線で示したようなコイル内温度分布を実現することが難しくなるからである。 The reason why the coil inner diameter is 700 mmφ or more is that when the coil inner diameter is less than 700 mmφ, the curvature (curvature) of the coil inner diameter portion is large, the amount of azimuth deterioration accompanying flattening annealing increases, and the magnetic characteristics deteriorate. Further, when the coil inner diameter is less than 700 mmφ, the surface area of the inner peripheral surface of the coil is reduced, so that the inner peripheral surface of the coil is not sufficiently cooled, and the temperature distribution in the coil as shown by line B in FIG. 4 can be realized. It will be difficult.
なお、仕上焼鈍の加熱過程におけるコイル内の温度分布は、図４のＢ線のように制御することが理想的である。しかし、現実的には、コイル内周面の温度を最冷点の温度より低くすることは難しいだけでなく、内周面の過剰な冷却は、コイル全体の昇温速度を遅くし、焼鈍時間の延長を来たすことになる。また、コイル中巻部が受ける圧縮応力が、磁気特性と被膜特性に悪影響を及ぼさない範囲内であれば、コイル内周面の温度が最冷点の温度より高くても許容できるはずである。そこで、本発明では、コイル内周面を冷却し、加熱中のコイル内周面の温度を、少なくとも当該温度が６００〜８００℃の範囲において、コイル外周面に対して２０℃以下に制御することが好ましい。すなわち、この温度域は、二次再結晶における粒界移動が開始する温度域であり、この温度域での応力が、二次再結晶に大きく影響するからである。 It is ideal to control the temperature distribution in the coil during the heating process of finish annealing as shown by line B in FIG. However, in reality, it is difficult not only to lower the temperature of the inner peripheral surface of the coil below the coldest temperature, but excessive cooling of the inner peripheral surface slows the temperature rise rate of the entire coil, and the annealing time. Will be extended. In addition, if the compressive stress received by the middle winding portion of the coil is within a range that does not adversely affect the magnetic characteristics and the film characteristics, it should be acceptable even if the temperature of the inner peripheral surface of the coil is higher than the coldest temperature. Therefore, in the present invention, the coil inner peripheral surface is cooled, and the temperature of the coil inner peripheral surface being heated is controlled to 20 ° C. or less with respect to the coil outer peripheral surface at least in the range of the temperature of 600 to 800 ° C. Is preferred. That is, this temperature range is a temperature range where grain boundary migration starts in the secondary recrystallization, and stress in this temperature range greatly affects the secondary recrystallization.
なお、コイル内周面を冷却する方法は、前述した、図５に示した２重管構造の円筒状凹部を上面中心部に設けたインナーケースを用いる方法に限定されるものではなく、その他の方法でもよく、特に制限はない。例えば、コイル内径部に冷却ガスを噴出する冷却塔を設置して冷却する方法等を用いてもよい。 The method for cooling the inner peripheral surface of the coil is not limited to the above-described method using the inner case in which the cylindrical concave portion of the double tube structure shown in FIG. There is no particular limitation on the method. For example, a method of cooling by installing a cooling tower for ejecting a cooling gas at the inner diameter of the coil may be used.
仕上焼鈍後の鋼板は、その後、未反応の焼鈍分離剤を鋼板表面から除去し、必要に応じて、絶縁被膜のコーティング液を塗布し、この焼付けと形状矯正を兼ねた平坦化焼鈍を施して製品板とする。なお、上記絶縁被膜は、鉄損をより低減するため、燐酸塩とコロイダルシリカを混合した張力付与被膜とするのが好ましい。 After finishing annealing, the steel sheet after finish annealing is used to remove the unreacted annealing separator from the surface of the steel sheet, and if necessary, apply a coating solution of an insulating coating, and perform flattening annealing that combines this baking and shape correction. Product plate. In addition, in order to further reduce iron loss, the insulating coating is preferably a tension applying coating in which phosphate and colloidal silica are mixed.
Ｃ：０．０７ｍａｓｓ％、Ｓｉ：３．３ｍａｓｓ％、Ｍｎ：０．０６ｍａｓｓ％、Ａｌ：０．０２ｍａｓｓ％、Ｎ：０．００８ｍａｓｓ％、Ｓｅ：０．０２ｍａｓｓ％およびＳｂ：０．０４ｍａｓｓ％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の鋼スラブを１４２０℃に加熱後、熱間圧延して板厚：２．３ｍｍの熱延板とし、１０００℃で３０秒の熱延板焼鈍を施した。次いで、上記熱延板を、１回目の冷間圧延で中間板厚：１．８ｍｍの冷延板とし、１１２０℃で３０秒の中間焼鈍を施した後、加工発熱で２２０℃まで鋼板温度を上昇させる２回目の冷間圧延をして最終板厚：０．２３ｍｍの冷延板とした。次いで、露点６０℃の湿潤水素雰囲気下で、８４０℃×１２０秒の脱炭を兼ねた一次再結晶焼鈍を施した後、ＭｇＯを主成分とする焼鈍分離剤を鋼板表面に塗布し、表１に示した、内径と外径寸法を有するコイルに巻き取った。 C: 0.07 mass%, Si: 3.3 mass%, Mn: 0.06 mass%, Al: 0.02 mass%, N: 0.008 mass%, Se: 0.02 mass% and Sb: 0.04 mass% Then, a steel slab having a composition composed of Fe and inevitable impurities as the balance is heated to 1420 ° C., and then hot-rolled to form a hot-rolled sheet having a thickness of 2.3 mm, and annealed at 1000 ° C. for 30 seconds. Was given. Next, the hot-rolled sheet is made into a cold-rolled sheet having an intermediate sheet thickness of 1.8 mm by the first cold rolling, subjected to intermediate annealing at 1120 ° C. for 30 seconds, and then the steel sheet temperature is increased to 220 ° C. by processing heat generation. The second cold rolling was performed to obtain a cold rolled sheet having a final sheet thickness of 0.23 mm. Next, after performing primary recrystallization annealing also serving as decarburization at 840 ° C. for 120 seconds in a wet hydrogen atmosphere with a dew point of 60 ° C., an annealing separator mainly composed of MgO was applied to the steel sheet surface, and Table 1 The coil having the inner diameter and outer diameter shown in FIG.
その後、上記コイルを、バッチ焼鈍炉にて、Ｎ２−Ｈ２混合雰囲気下で１１７０℃まで昇温し、Ｈ２雰囲気下で５時間保持する仕上焼鈍を施した。なお、上記仕上焼鈍では、図５に示した２重管構造の円筒状凹部を有するインナーケースを用い、加熱過程の炉温が４００〜１１７０℃の間では、上記円筒状凹部に大気温度のＮ２ガスを５００Ｎｍ３／ｈｒ供給してコイル内周面を冷却しつつ加熱した。また、上記加熱過程では、コイル内周面、外周面およびコイル中巻部（コイル内径と外径の中間部）の３点の板幅中央部に熱電対を巻き込み仕上焼鈍時におけるコイル内の温度変化を測定した。なお、上記冷却ガスは、コイル中巻部の温度で制御した。 Thereafter, the coil, in a batch annealing furnace, N 2 -H 2 mixed atmosphere at a temperature raised to 1170 ° C., subjected to finish annealing to 5 hours under an H 2 atmosphere. In the finish annealing, an inner case having a cylindrical recess having a double-pipe structure shown in FIG. 5 is used, and when the furnace temperature in the heating process is between 400 and 1170 ° C., the cylindrical recess has an atmospheric temperature of N. Two gases were supplied at 500 Nm 3 / hr to heat the coil inner peripheral surface while cooling. Further, in the heating process, the temperature in the coil at the time of finish annealing is obtained by winding a thermocouple in the central part of the three plate widths of the inner peripheral surface of the coil, the outer peripheral surface, and the middle winding part of the coil (intermediate part of the coil inner diameter and outer diameter) Changes were measured. In addition, the said cooling gas was controlled by the temperature of a coil inner volume part.
次いで、仕上焼鈍後のコイルは、未反応の焼鈍分離剤を除去した後、５０ｍａｓｓ％のコロイダルシリカと燐酸マグネシウムからなるコイティング液を両面目付量で１０ｇ／ｍ２となるよう塗布し、９ＭＰａの張力を付与しつつ、８４０℃の温度で平坦化焼鈍を施して絶縁被膜を被成し、製品コイルとした。 Next, the coil after the finish annealing is applied with a coating solution of 50 mass% colloidal silica and magnesium phosphate so that the weight per side is 10 g / m 2 after removing the unreacted annealing separator, While applying tension, planarization annealing was performed at a temperature of 840 ° C. to form an insulating film, thereby obtaining a product coil.
斯くして得た製品コイルの内径部、中央部および外径部の各位置から試験片を採取し、圧延方向の磁束密度Ｂ８とフォルステライト被膜の密着性を評価した。なお、被膜密着性は、圧延方向：３０ｍｍ×圧延直角方向：３００ｍｍの試験片を種々の外径を有する丸棒に巻き付けて１８０度に折り曲げ、折り曲げ部分の被膜剥離が起こらない最小径で評価した。 The inner diameter of the product coil obtained by thus, the central part and the test piece was taken from each position of the outer diameter was evaluated the adhesion of the rolling direction of the magnetic flux density B 8 and the forsterite film. The film adhesion was evaluated with the minimum diameter at which the test piece of rolling direction: 30 mm × rolling perpendicular direction: 300 mm was wound around a round bar having various outer diameters and bent at 180 degrees, and the film peeling of the bent portion did not occur. .
上記測定の結果を表１に示した。表１から、コイル内径を７００ｍｍφ以上とし、かつコイル内径部を冷却することによって、コイル全長にわたって磁気特性と被膜特性に優れる方向性電磁鋼板が得られること、中でも、コイル肉厚を薄くした発明例のＮｏ．４では最も効果が大きいことがわかる。
また、図８は、コイル半径方向３点の温度測定結果から、加熱過程でコイル外周面が８００℃に到達した時点におけるＮｏ．３，４および６の例のコイル内温度分布を推定した図である。コイル肉厚の厚い発明例のＮｏ．３は、同じ肉厚の比較例のＮｏ．６より温度分布は改善されているが、コイル内周面温度はコイル中巻部よりも若干高めとなっている。一方、コイル肉厚の薄い発明例のＮｏ．４は、理想に近い温度分布を示しており、これによって磁気特性や被膜特性が大幅に改善されたものと考えられる。
The measurement results are shown in Table 1. From Table 1, by directing the coil inner diameter to 700 mmφ or more and cooling the coil inner diameter portion, a grain-oriented electrical steel sheet having excellent magnetic properties and coating properties can be obtained over the entire length of the coil. No. It can be seen that 4 is the most effective.
Further, FIG. 8 shows that the No. 1 at the time when the outer peripheral surface of the coil reached 800 ° C. during the heating process based on the temperature measurement results at three points in the coil radial direction. It is the figure which estimated the temperature distribution in a coil of the example of 3, 4, and 6. FIG. No. of invention example with thick coil thickness. 3 is a comparative example No. 3 having the same wall thickness. 6, the temperature distribution is improved, but the inner circumferential surface temperature of the coil is slightly higher than that of the middle winding portion of the coil. On the other hand, No. of the invention example with thin coil thickness. No. 4 shows a temperature distribution close to ideal, which is considered to have greatly improved the magnetic characteristics and the film characteristics.
本発明の技術は、方向性電磁鋼板の仕上焼鈍に限定されるものではなく、例えば、冷延鋼板のバッチ焼鈍にも適用することができる。 The technology of the present invention is not limited to finish annealing of grain-oriented electrical steel sheets, and can be applied to batch annealing of cold-rolled steel sheets, for example.
１：鋼板コイル
１ａ：コイル内周面
１ｂ：コイル外周面
２：焼鈍炉の加熱炉
２ａ：バーナー
３：インナーケース（インナーカバー）
４：円筒状凹部
４ａ：円筒状凹部の外管
４ｂ：円筒状凹部の内管
５：冷却ノズル
６：冷却ガス
1:
4:
Claims (2)
上記コイルの内径を７００ｍｍφ以上、コイルの内径と外径の差を５００ｍｍ以上とし、かつ、上記仕上焼鈍では、コイル内周面の温度が、コイル外周面に対して２０℃以下となるように、コイル内周面を冷却しつつコイル全体を加熱することを特徴とする方向性電磁鋼板の製造方法。 In the method of producing a grain-oriented electrical steel sheet by cold rolling, primary recrystallization annealing, winding a steel sheet coated with an annealing separator on a coil, and finish annealing in a batch type box annealing furnace,
The inner diameter of the coil is 700 mmφ or more , the difference between the inner diameter and the outer diameter of the coil is 500 mm or more , and in the finish annealing, the temperature of the inner peripheral surface of the coil is 20 ° C. or lower with respect to the outer peripheral surface of the coil. A method for manufacturing a grain-oriented electrical steel sheet, wherein the entire coil is heated while cooling an inner circumferential surface of the coil .
Temperature of the coil inner circumferential surface of the pressurizing heat stroke is in the range of 600 to 800 ° C., the temperature of the coil circumference, characterized in that heating the entire coil such that 20 ° C. or less with respect to the coil outer circumferential surface The manufacturing method of the grain-oriented electrical steel sheet according to claim 1.
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