JP5854234B2 - Method for producing grain-oriented electrical steel sheet - Google Patents
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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、鉄損が低くかつ鉄損のばらつきが小さい方向性電磁鋼板の製造方法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 method for producing a grain-oriented electrical steel sheet having low iron loss and small variation in iron loss.
電磁鋼板は、変圧器やモータの鉄心等として広く用いられている軟磁性材料であり、中でも大型の変圧器の鉄心等に使用される方向性電磁鋼板は、結晶方位がＧｏｓｓ方位と呼ばれる｛１１０｝＜００１＞方位に高度に集積し、磁気特性に優れるという特徴をもつ。このような結晶組織は、製造工程の仕上焼鈍において、Ｇｏｓｓ方位粒を優先的に成長させる二次再結晶を起こさせることによって得ることができる。 Electrical steel sheets are soft magnetic materials that are widely used as iron cores for transformers and motors. In particular, grain oriented magnetic steel sheets used for iron cores of large transformers have a crystal orientation called Goss orientation {110 } Highly integrated in the <001> orientation and has excellent magnetic properties. Such a crystal structure can be obtained by causing secondary recrystallization that preferentially grows Goss oriented grains in the final annealing of the manufacturing process.
従来、このような方向性電磁鋼板は、４．５ｍａｓｓ％以下程度のＳｉと、ＭｎＳやＭｎＳｅ，ＡｌＮなどのインヒビターを形成する成分を含有するスラブを、１３００℃以上の温度に加熱し、インヒビター成分を一旦固溶させたのち、熱間圧延し、必要に応じて熱延板焼鈍を施した後、１回または中間焼鈍を挟む２回以上の冷間圧延によって最終板厚とし、次いで、湿潤水素雰囲気中で脱炭焼鈍する一次再結晶焼鈍を施した後、鋼板表面にマグネシア（ＭｇＯ）を主剤とする焼鈍分離剤を塗布してから、二次再結晶を起こさせた後、１２００℃×５ｈｒ程度の純化処理でインヒビター成分を除去する仕上焼鈍を施すことによって製造されてきた（例えば、特許文献１、特許文献２参照）。
Conventionally, such a grain-oriented electrical steel sheet is obtained by heating a slab containing components that form an inhibitor such as MnS, MnSe, and AlN to a temperature of 1300 ° C. or higher by adding Si of about 4.5 mass% or less to an inhibitor component. After the solid solution is once dissolved, it is hot-rolled and subjected to hot-rolled sheet annealing as necessary, and then the final sheet thickness is obtained by one or more cold rollings sandwiching intermediate annealing, and then wet hydrogen After subjecting to primary recrystallization annealing to decarburize annealing in atmosphere, after applying an annealing separator mainly composed of magnesia (MgO) to the steel sheet surface, secondary recrystallization is caused, and then 1200 ° C. × 5 hr It has been manufactured by performing finish annealing to remove the inhibitor component by a degree of purification treatment (see, for example,
上述したとおり、従来の方向性電磁鋼板の製造方法においては、ＭｎＳやＭｎＳｅ，ＡｌＮなどの析出物（インヒビター）を形成する成分をスラブ段階で含有させ、１３００℃を超える高温でスラブを再加熱して上記インヒビター成分を一旦固溶させた後、後工程で微細に析出させることで、二次再結晶を発現させるという工程が採用されてきた。 As described above, in the conventional method for producing grain-oriented electrical steel sheets, a component that forms precipitates (inhibitors) such as MnS, MnSe, and AlN is included in the slab stage, and the slab is reheated at a high temperature exceeding 1300 ° C. Thus, after the above-mentioned inhibitor component is once dissolved, the step of causing secondary recrystallization by finely precipitating in a subsequent step has been adopted.
しかし、上記のような従来の方向性電磁鋼板の製造方法では、１３００℃を超える高温でスラブを再加熱する必要があったため、その製造コストは高いものとならざるを得ず、近年の製造コスト低減の要求に応えることができないという問題を残していた。この問題を解決する技術としては、例えば、特許文献３には、酸可溶性Ａｌ（ｓｏｌ．Ａｌ）を０．０１０〜０．０６０ｍａｓｓ％含有させたスラブの再加熱温度を低温に抑えて熱間圧延し、脱炭焼鈍工程を窒化雰囲気として窒化処理を施すことにより鋼中Ｎを増量することによって、二次再結晶時に（Ａｌ，Ｓｉ）Ｎを析出させ、インヒビターとして用いる方法が提案されている。 However, in the conventional method for producing a grain-oriented electrical steel sheet as described above, since the slab has to be reheated at a high temperature exceeding 1300 ° C., the production cost is inevitably high. The problem of not being able to meet the demand for reduction was left. As a technique for solving this problem, for example, Patent Document 3 discloses hot rolling by suppressing the reheating temperature of a slab containing 0.010 to 0.060 mass% of acid-soluble Al (sol. Al) to a low temperature. In addition, a method has been proposed in which (Al, Si) N is precipitated during secondary recrystallization and used as an inhibitor by increasing the amount of N in the steel by performing a nitriding treatment in a decarburizing annealing step.
しかし、（Ａｌ，Ｓｉ）Ｎは、鋼中に微細分散し、有効なインヒビターとして機能するが、Ａｌの含有量によってインヒビター強度が決まるため、製鋼でのＡｌの的中精度が十分でない場合には、十分な粒成長抑制力（インヒビター効果）が得られないことがある。なお、製造の途中工程で窒化処理を行ない、（Ａｌ，Ｓｉ）ＮあるいはＡｌＮをインヒビターとして利用する方法は、その他にも数多く提案されており、最近では、スラブ再加熱温度が１３００℃を超える製造方法等も開示されている。 However, (Al, Si) N is finely dispersed in steel and functions as an effective inhibitor. However, since the inhibitor strength is determined by the Al content, the accuracy of Al in steelmaking is not sufficient. In some cases, sufficient grain growth inhibiting power (inhibitor effect) cannot be obtained. Many other methods have been proposed in which nitriding is performed during the manufacturing process and (Al, Si) N or AlN is used as an inhibitor. Recently, the slab reheating temperature exceeds 1300 ° C. A method and the like are also disclosed.
一方、スラブ中にインヒビター形成成分を含有させずに二次再結晶を発現させる技術について検討が進められており、例えば、特許文献４には、より高純度化した鋼を用い、インヒビター成分を含有させずに、テクスチャー（集合組織）の制御によって、二次再結晶を発現させる、いわゆる「インヒビターレス法」の技術が開示されている。このインヒビターレス法は、高温のスラブ再加熱が不要であり、低コストで方向性電磁鋼板を製造することができるが、インヒビターを有しないが故に、製造工程における温度等のばらつきなどの影響を受けて、製品板の磁気特性も大きく変動し、安定した製造が難しいという問題点がある。 On the other hand, a technique for developing secondary recrystallization without containing an inhibitor-forming component in a slab has been studied. For example, Patent Document 4 uses a steel with higher purity and contains an inhibitor component. In addition, a so-called “inhibitorless method” technique is disclosed in which secondary recrystallization is expressed by controlling the texture (texture). This inhibitorless method does not require high-temperature slab reheating and can produce grain-oriented electrical steel sheets at low cost. However, because it does not have an inhibitor, it is affected by variations in temperature in the manufacturing process. As a result, the magnetic properties of the product plate also fluctuate greatly, and there is a problem that stable production is difficult.
また、集合組織の制御は、このインヒビターレス法においては重要な要素であることから、集合組織を適正に制御するため、例えば、温間圧延などの技術が多く提案されている。しかし、集合組織制御が十分に行えない場合には、インヒビターを用いる技術に比べて、二次再結晶後のＧｏｓｓ方位（｛１１０｝＜００１＞）への集積度は低くなり、磁束密度も低くなる場合が多かった。 In addition, since control of the texture is an important factor in this inhibitorless method, many techniques such as warm rolling have been proposed in order to appropriately control the texture. However, when texture control cannot be performed sufficiently, the degree of integration in the Goss orientation ({110} <001>) after secondary recrystallization is lower and the magnetic flux density is lower than in the technique using an inhibitor. There were many cases.
集合組織を制御することで磁気特性を向上させる技術としては、例えば、特許文献５には、一次再結晶焼鈍の加熱過程を急速加熱する方法が提案されている。この技術は、室温から再結晶温度近傍までを通電加熱あるいは誘導加熱などを用いて短時間で昇温することによって、通常の加熱速度では優先的に形成されるγファイバー（｛１１１｝組織）の発達を抑制し、二次再結晶の核となる｛１１０｝＜００１＞組織の発生を促進するものである。この技術を適用することで、二次再結晶後の結晶粒が細粒化し、鉄損を改善することができる。
As a technique for improving magnetic properties by controlling the texture, for example,
なお、インヒビターレス法を用いた方向性電磁鋼板においても、急速加熱技術の適用が検討されている。しかし、急速加熱では、鋼板内、特に、板幅方向の温度のばらつきが大きくなるため、製造条件のばらつきの影響を受けやすいインヒビターレス法では磁気特性の変動も大きくなる。そこで、例えば、特許文献６には、急速加熱で一旦７００℃以上まで加熱した後、７００℃以下まで冷却し、その後、４０℃／ｓ以下の昇温速度で再び加熱することで、鋼板の温度のばらつきを解消する技術が開示されている。しかし、この方法では、高温まで昇温したのち、冷却・再加熱を行う必要があるため、通常の急速加熱に比べて余分なエネルギーが必要となる上、焼鈍ラインも長くならざるを得ない。また、磁気特性も、昨今の需要家からの厳しい要求に応えられるレベルのものではなかった。 The application of rapid heating technology is also being studied for grain-oriented electrical steel sheets using the inhibitorless method. However, in rapid heating, the variation in temperature in the steel sheet, particularly in the width direction of the plate, is large, and therefore, in the inhibitorless method which is easily affected by the variation in manufacturing conditions, the fluctuation of magnetic characteristics is also large. Therefore, for example, in Patent Document 6, after heating to 700 ° C. or higher once by rapid heating, cooling to 700 ° C. or lower, and then heating again at a temperature increase rate of 40 ° C./s or lower, the temperature of the steel sheet A technique for eliminating the variation in the above is disclosed. However, in this method, since it is necessary to cool and reheat after raising the temperature to a high temperature, extra energy is required compared to normal rapid heating, and the annealing line must be lengthened. Also, the magnetic properties were not at a level that could meet the strict demands of customers today.
上述したように、インヒビターレス法を用いた方向性電磁鋼板の製造方法に、一次再結晶焼鈍の加熱過程で急速加熱する技術を適用した場合には、優れた磁気特性を安定して得るのが難しいという問題があった。 As described above, when the technology of rapid heating in the heating process of primary recrystallization annealing is applied to the method of manufacturing grain-oriented electrical steel sheets using the inhibitorless method, excellent magnetic properties can be stably obtained. There was a problem that it was difficult.
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、従来よりも低鉄損かつ鉄損のばらつきが小さい優れた鉄損特性を有する方向性電磁鋼板を得ることができるインヒビターレス法を用いた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 problems of the prior art, and an object thereof is to obtain a grain-oriented electrical steel sheet having excellent iron loss characteristics with lower iron loss and less variation in iron loss than in the past. It is to propose an advantageous production method using an inhibitorless method.
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、インヒビターレス法を用いた方向性電磁鋼板の製造方法において、その途中工程でＮを鋼中に拡散させ、窒化珪素を粒界に析出させて正常粒成長の抑制力として機能させるとともに、一次再結晶焼鈍の加熱過程における急速加熱の途中で、適正な温度で適正時間保持する保定処理を施すことで、従来よりも低鉄損でなおかつばらつきの小さい、優れた鉄損特性を有する方向性電磁鋼板を安定して製造することができることを見出し、本発明を開発するに至った。 The inventors have intensively studied to solve the above problems. As a result, in the method of manufacturing a grain-oriented electrical steel sheet using the inhibitorless method, N is diffused in the steel in the middle of the process, and silicon nitride is precipitated at the grain boundary to function as a suppressive force for normal grain growth. Directionality with excellent iron loss characteristics with lower iron loss and less variation than conventional by applying a holding treatment to hold at an appropriate temperature for an appropriate time during the rapid heating in the heating process of primary recrystallization annealing The inventors have found that an electromagnetic steel sheet can be stably produced, and have developed the present invention.
すなわち、本発明は、Ｃ：０．０８ｍａｓｓ％以下、Ｓｉ：２．０〜４．５ｍａｓｓ％、Ｍｎ：０．５ｍａｓｓ％以下、ｓｏｌ．Ａｌ：０．０１００ｍａｓｓ％未満、Ｓ，ＳｅおよびＯ：それぞれ０．００５０ｍａｓｓ％未満含有し、さらに、Ｎ：０．５２×ｓｏｌ．Ａｌ（ｍａｓｓ％）〜０．００８０ｍａｓｓ％の範囲で含有し、残部がＦｅおよび不可避的不純物の成分組成からなる鋼スラブを、熱間圧延して熱延板とし、１回または中間焼鈍を挟む２回以上の冷間圧延して最終板厚の冷延板とし、一次再結晶焼鈍の途中あるいは一次再結晶焼鈍後に窒化処理を施した後、鋼板表面に焼鈍分離剤を塗布し、仕上焼鈍する方向性電磁鋼板の製造方法において、前記一次再結晶焼鈍の加熱過程における５５０〜７００℃間を平均昇温速度５０℃／ｓ以上で急速加熱するとともに、２５０〜５５０℃間のいずれかの温度で昇温速度１０℃／ｓ以下で１〜１０秒間保持する保定処理を施し、前記窒化処理を、導入したＮが鋼板表層の窒化物層として留まる条件、かつ、増Ｎ量が０．００５０〜０．１０００ｍａｓｓ％の範囲となる条件で行い、前記仕上焼鈍の加熱過程における３００〜８００℃間の滞留時間を２０〜１５０時間とすることを特徴とする方向性電磁鋼板の製造方法を提案する。 That is, the present invention relates to C: 0.08 mass% or less, Si: 2.0 to 4.5 mass%, Mn: 0.5 mass% or less, sol. Al: less than 0.0100 mass%, S, Se and O: each contained less than 0.0050 mass%, and further, N: 0.52 × sol. A steel slab containing Al (mass%) to 0.0080 mass%, the balance of which is composed of Fe and inevitable impurities, is hot-rolled into a hot-rolled sheet and sandwiches once or intermediate annealing 2 Cold rolling more than once to make a cold-rolled sheet with the final thickness, and after performing nitriding treatment during or after primary recrystallization annealing, apply an annealing separator to the steel sheet surface, and finish annealing In the manufacturing method of the heat-resistant electrical steel sheet, rapid heating is performed at an average temperature increase rate of 50 ° C./s or more between 550 and 700 ° C. in the heating process of the primary recrystallization annealing, and at any temperature between 250 and 550 ° C. A holding treatment for holding at a temperature rate of 10 ° C./s or less for 1 to 10 seconds is performed, and the nitriding treatment is performed under conditions where the introduced N stays as a nitride layer on the surface of the steel sheet, and the increase in N amount is 0.0050 to 0.00. 1000mass Conducted under the condition that the range is proposed a method for manufacturing a grain-oriented electrical steel sheet characterized by a residence time between 300 to 800 ° C. in the final annealing heating process and 20-150 hours.
本発明の方向性電磁鋼板の製造方法に用いる上記鋼スラブは、上記成分組成に加えてさらに、Ｎｉ：０．００５〜１．５０ｍａｓｓ％、Ｓｎ：０．０１〜０．５０ｍａｓｓ％、Ｓｂ：０．００５〜０．５０ｍａｓｓ％、Ｃｕ：０．０１〜０．５０ｍａｓｓ％、Ｃｒ：０．０１〜１．５０ｍａｓｓ％、Ｐ：０．０００５０〜０．５０ｍａｓｓ％、Ｍｏ：０．０１〜０．５０ｍａｓｓ％およびＮｂ：０．０００５〜０．０１０ｍａｓｓ％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。 In addition to the above component composition, the steel slab used in the method for producing a grain-oriented electrical steel sheet according to the present invention further includes Ni: 0.005 to 1.50 mass%, Sn: 0.01 to 0.50 mass%, and Sb: 0. 0.005 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, Cr: 0.01 to 1.50 mass%, P: 0.00050 to 0.50 mass%, Mo: 0.01 to 0.50 mass % And Nb: one or more selected from 0.0005 to 0.010 mass%.
本発明によれば、インヒビター成分を含まない鋼スラブを用いる方向性電磁鋼板の製造方法に、一次再結晶焼鈍の加熱過程で急速加熱する技術を適用して、そのヒートパターンを最適化するとともに、製造工程の途中でＮを鋼中に拡散させて窒化珪素として粒界に析出させ、これをインヒビターとして活用する技術と組み合わせることで、従来よりも優れた鉄損特性を有する方向性電磁鋼板を安価にかつ安定して提供することが可能となる。 According to the present invention, to a method for producing a grain-oriented electrical steel sheet using a steel slab that does not contain an inhibitor component, a technique of rapid heating in the heating process of primary recrystallization annealing is applied to optimize the heat pattern, In the middle of the manufacturing process, N is diffused into the steel and precipitated at the grain boundaries as silicon nitride, and in combination with a technology that uses this as an inhibitor, a grain-oriented electrical steel sheet having iron loss characteristics superior to conventional ones is inexpensive. And can be provided stably.
まず、本発明の基本的な技術思想について説明する。
発明者らは、製造条件、特に一次再結晶焼鈍で急速加熱するときの、鋼板内の温度不均一による磁気特性のばらつきを抑制することを目的として、製造工程の途中でＮを鋼中に拡散させて窒化珪素として析出させ、これを正常粒成長の抑制力として機能させることを検討した。
すなわち、方向性電磁鋼板に、通常、数ｍａｓｓ％含まれているＳｉを窒化珪素として析出させ、これをインヒビターとして利用することができれば、窒化物形成元素（Ａｌ，Ｔｉ，Ｃｒ，Ｖ等）の多寡に拘らず、窒化処理時の窒化量を制御するだけで、従来技術の（Ａｌ，Ｓｉ）ＮやＡｌＮ等のインヒビターと同等の粒成長抑制力が得られるのではないかと考えた。
First, the basic technical idea of the present invention will be described.
The inventors have diffused N into the steel during the manufacturing process with the aim of suppressing variations in magnetic properties due to temperature non-uniformity in the steel sheet during rapid heating by manufacturing conditions, particularly primary recrystallization annealing. Then, it was deposited as silicon nitride, and it was studied to make it function as a suppressive force for normal grain growth.
That is, if Si that normally contains several mass% is deposited as silicon nitride on the grain-oriented electrical steel sheet and can be used as an inhibitor, nitride-forming elements (Al, Ti, Cr, V, etc.) Regardless of the amount, it was thought that by controlling the amount of nitriding during the nitriding treatment, it would be possible to obtain the same grain growth inhibitory force as that of conventional inhibitors such as (Al, Si) N and AlN.
純粋な窒化珪素（Ｓｉ３Ｎ４）は、ＡｌＮ中にＳｉが固溶した（Ａｌ，Ｓｉ）Ｎとは異なり、ベースの鋼との格子の不整合が大きく、また、共有結合性の複雑な結晶構造を有するため、粒内に微細に析出させることは極めて困難である。したがって、従来法のように窒化処理後、粒内にインヒビターとして微細に析出させることは困難であると考えられる。しかし、これを逆に利用することによって、窒化珪素を選択的に粒界に析出させることができる可能性がある。そして、もし、これが可能であれば、析出物が粗大であっても十分な正常粒成長の抑制力が得られるのではないかと考えた。 Pure silicon nitride (Si 3 N 4 ) has a large lattice mismatch with the base steel, unlike (Al, Si) N in which Si is dissolved in AlN, and has a complicated covalent bond. Since it has a crystal structure, it is extremely difficult to make it precipitate finely in the grains. Therefore, it is considered difficult to precipitate finely as an inhibitor in the grains after nitriding as in the conventional method. However, by utilizing this in reverse, there is a possibility that silicon nitride can be selectively deposited at the grain boundaries. And if this was possible, even if the precipitate was coarse, it was thought that sufficient suppression of normal grain growth could be obtained.
また、発明者らは、一次再結晶焼鈍の加熱過程で急速加熱を行うときの問題点である鋼板内の温度不均一を抑制する方法について検討した結果、加熱過程で急速加熱する際、再結晶温度以下の温度で鋼板の昇温速度をほぼ０（ゼロ）とし、その後、急速加熱することを考えた。すなわち、再結晶温度以下の温度で一旦昇温を中断し、適当な時間保持することで鋼板内の温度分布を均一化することができれば、その後の急速加熱においても、鋼板内の温度を均一化できるのではないかと考えた。 In addition, the inventors have studied a method for suppressing temperature non-uniformity in the steel sheet, which is a problem when performing rapid heating in the heating process of primary recrystallization annealing. The temperature rise rate of the steel sheet was set to approximately 0 (zero) at a temperature below the temperature, and then rapid heating was considered. In other words, if the temperature distribution in the steel sheet can be made uniform by interrupting the temperature rise at a temperature below the recrystallization temperature and holding it for an appropriate time, the temperature in the steel sheet will be made uniform even in the subsequent rapid heating. I thought I could do it.
そして、前述した窒化珪素をインヒビターとして活用する技術と、上記の一次再結晶焼鈍における急速加熱を適正化し、鋼板内の温度不均一を低減する技術とを組み合わせることで、二次再結晶を安定して起こさせることができれば、従来よりも優れた鉄損特性を有しかつばらつきの小さい方向性電磁鋼板を安定して得られることができるのではないかと考えた。そこで、上記考えを確認するため、以下の実験を行った。 And, by combining the technology that uses silicon nitride as an inhibitor described above and the technology that optimizes rapid heating in the primary recrystallization annealing and reduces temperature non-uniformity in the steel sheet, secondary recrystallization is stabilized. Therefore, it was thought that a grain-oriented electrical steel sheet having iron loss characteristics superior to conventional ones and small variations could be stably obtained. In order to confirm the above idea, the following experiment was conducted.
＜実験１＞
Ｃ：０．０４ｍａｓｓ％、Ｓｉ：３．５ｍａｓｓ％、Ｍｎ：０．０５ｍａｓｓ％、ｓｏｌ．Ａｌ：０．００６０ｍａｓｓ％、Ｎ：０．００５０ｍａｓｓ％、Ｓ：０．００１０ｍａｓｓ％、Ｓｅ：０．０００８ｍａｓｓ％およびＯ：０．００１０ｍａｓｓ％を含有する鋼スラブを熱間圧延して板厚２．４ｍｍの熱延板とし、１０００℃×１分の熱延板焼鈍を施した後、冷間圧延して最終板厚０．２７ｍｍの冷延コイルとし、得られた冷延コイルの長手方向中央部から、幅１００ｍｍ×４００ｍｍサイズの試料を採取し、この試料に脱炭焼鈍を兼ねた一次再結晶焼鈍を施した。
<
C: 0.04 mass%, Si: 3.5 mass%, Mn: 0.05 mass%, sol. A steel slab containing Al: 0.0060 mass%, N: 0.0050 mass%, S: 0.0010 mass%, Se: 0.0008 mass% and O: 0.0010 mass% is hot-rolled to a thickness of 2.4 mm. After subjecting to 1000 ° C. × 1 minute hot-rolled sheet annealing, it was cold-rolled to form a cold-rolled coil having a final sheet thickness of 0.27 mm, from the center in the longitudinal direction of the obtained cold-rolled coil A sample having a width of 100 mm × 400 mm was collected, and the sample was subjected to primary recrystallization annealing that also served as decarburization annealing.
上記一次再結晶焼鈍では、５０ｖｏｌ％Ｈ２−５０ｖｏｌ％Ｎ２、露点６１℃の湿潤雰囲気下で、８４０℃×９０秒の脱炭を行った。また、室温から８４０℃までは、誘導加熱装置を用いて加熱し、５５０℃から７００℃までの平均昇温速度は１２０℃／ｓとなるよう制御した。また、上記加熱途中の４００℃の温度で４秒間保持する保定処理を施した。なお、上記保定処理時間および５５０〜７００℃間の加熱時間を除く時間における平均昇温速度は１５℃／ｓとした。 In the primary recrystallization annealing, decarburization was performed at 840 ° C. for 90 seconds in a wet atmosphere of 50 vol% H 2 -50 vol% N 2 and a dew point of 61 ° C. Moreover, it heated using the induction heating apparatus from room temperature to 840 degreeC, and controlled the average temperature increase rate from 550 degreeC to 700 degreeC to be 120 degreeC / s. Moreover, the retention process hold | maintained at the temperature of 400 degreeC in the said heating for 4 second was given. In addition, the average temperature increase rate in the time excluding the holding treatment time and the heating time between 550 to 700 ° C. was 15 ° C./s.
次いで、上記一次再結晶焼鈍を施した試料の一部に対して、塩浴方式の窒化処理（バッチ処理）を、異なる温度、時間で施して鋼中のＮ量を増加させた。なお、窒化処理前後の試料について、全厚の鋼中窒素量を化学分析し、増Ｎ量を求めた。 Next, a part of the sample subjected to the primary recrystallization annealing was subjected to salt bath nitriding (batch treatment) at different temperatures and times to increase the amount of N in the steel. In addition, about the sample before and behind nitriding treatment, the nitrogen amount in steel of full thickness was chemically analyzed, and the amount of increase N was calculated | required.
その後、上記試料の表面に、ＭｇＯを主成分とし、ＴｉＯ２を５ｍａｓｓ％含有する焼鈍分離剤を水スラリ状にして塗布し、乾燥した後、仕上焼鈍を施した。この際、加熱過程における３００〜８００℃間の滞留時間は２０時間となるように制御した。
次いで、上記仕上焼鈍後の試料表面に、リン酸塩系の絶縁張力コーティングを塗布し、焼き付けて製品試料とした。なお、上記製品試料は、各製造条件につき２０枚作製した。
Thereafter, an annealing separator containing MgO as a main component and containing 5 mass% of TiO 2 was applied in the form of a water slurry on the surface of the sample, dried, and then subjected to finish annealing. Under the present circumstances, it controlled so that the residence time between 300-800 degreeC in a heating process might be 20 hours.
Next, a phosphate-based insulating tension coating was applied to the sample surface after the finish annealing and baked to obtain a product sample. In addition, 20 pieces of the product samples were produced for each production condition.
斯くして得た各製品試料について、周波数５０Ｈｚ、磁束密度１．７Ｔにおける鉄損Ｗ１７／５０を測定し、２０枚の試料の平均値を求めた。
図１は、窒化処理により増加したＮ量（増Ｎ量）と、鉄損Ｗ１７／５０との関係を示したものである。この図から、良好な鉄損特性を得るためには、窒化処理による増Ｎ量を５０〜１０００ｍａｓｓｐｐｍ（０．００５０〜０．１０００ｍａｓｓ％）の範囲とすることが必要であることがわかる。
About each product sample obtained in this way, the iron loss W17 / 50 in frequency 50Hz and magnetic flux density 1.7T was measured, and the average value of 20 samples was calculated | required.
FIG. 1 shows the relationship between the N amount increased by the nitriding treatment (increased N amount) and the iron loss W 17/50 . From this figure, it can be seen that in order to obtain good iron loss characteristics, it is necessary to increase the amount of N increased by nitriding treatment in the range of 50 to 1000 massppm (0.0050 to 0.1000 mass%).
＜実験２＞
上記実験１で作製した０．２７ｍｍの冷延コイルの長手方向中央部から、１００ｍｍ×４００ｍｍサイズの試料を採取し、脱炭焼鈍を兼ねた一次再結晶焼鈍を施した。上記一次再結晶焼鈍では、５５ｖｏｌ％Ｈ２−４５ｖｏｌ％Ｎ２、露点６０℃の湿潤雰囲気下で、８５０℃×８０秒の脱炭を行った。なお、室温から８５０℃までは、誘導加熱装置を用いて加熱し、その加熱途中の１００℃、２００℃、２５０℃、４００℃、５３０℃および６００℃の各温度で０〜２０秒間保持する保定処理を施した後、５５０℃（保定温度が６００℃の場合は６００℃）から７００℃までの平均昇温速度を１２０℃／ｓに制御した。なお、上記保定処理時間および５５０〜７００℃間の加熱時間を除く時間における平均昇温速度は１６℃／ｓとした。
<Experiment 2>
A sample having a size of 100 mm × 400 mm was taken from the central portion in the longitudinal direction of the 0.27 mm cold-rolled coil produced in
次いで、上記一次再結晶焼鈍後の試料に、塩浴方式で５５０℃×３０秒の窒化処理（バッチ処理）を施し、鋼中Ｎ量を増加させた。なお、化学分析により試料全厚の鋼中窒素量を定量分析したところ、窒化処理していない試料は０．００２０ｍａｓｓ％で、窒化処理した試料は０．０１２０ｍａｓｓ％（増Ｎ量：０．０１００ｍａｓｓ％）であった。 Next, the sample after the primary recrystallization annealing was subjected to nitriding treatment (batch treatment) at 550 ° C. for 30 seconds by a salt bath method to increase the amount of N in the steel. In addition, when the amount of nitrogen in the steel of the total thickness of the sample was quantitatively analyzed by chemical analysis, the sample not nitrided was 0.0020 mass%, and the sample nitrided was 0.0120 mass% (increased N amount: 0.0100 mass%). )Met.
その後、上記試料の表面に、ＭｇＯを主成分とし、ＴｉＯ２を５ｍａｓｓ％含有する焼鈍分離剤を水スラリ状にして塗布・乾燥した後、仕上焼鈍を施した。この際、加熱過程における３００〜８００℃間の滞留時間は２０時間となるようにした。
次いで、上記仕上焼鈍後の試料表面に、リン酸塩系の絶縁張力コーティングを塗布し、焼き付けて製品試料とした。なお、上記製品試料は、各製造条件につき２０枚作製した。
Thereafter, an annealing separator containing MgO as a main component and containing 5 mass% of TiO 2 in the form of a water slurry was applied and dried on the surface of the sample, followed by finish annealing. At this time, the residence time between 300 and 800 ° C. in the heating process was set to 20 hours.
Next, a phosphate-based insulating tension coating was applied to the sample surface after the finish annealing and baked to obtain a product sample. In addition, 20 pieces of the product samples were produced for each production condition.
斯くして得た各製品試料について、周波数５０Ｈｚ、磁束密度１．７Ｔにおける鉄損Ｗ１７／５０を測定し、２０枚の平均値を求めた。
図２は、一次再結晶焼鈍の急速加熱途中における各保定温度での保定時間と、鉄損Ｗ１７／５０との関係を示したものである。この図から、保定温度を２５０〜５５０℃、保定時間を１〜１０秒の範囲として施すことで、鉄損を低減できることがわかる。
For each product sample thus obtained, the iron loss W 17/50 at a frequency of 50 Hz and a magnetic flux density of 1.7 T was measured, and an average value of 20 sheets was obtained.
FIG. 2 shows the relationship between the holding time at each holding temperature and the iron loss W 17/50 during the rapid heating of the primary recrystallization annealing. From this figure, it can be seen that iron loss can be reduced by applying the holding temperature in the range of 250 to 550 ° C. and the holding time in the range of 1 to 10 seconds.
ここで、一次再結晶焼鈍の加熱過程において、上記のように適正温度で適正時間保持する保定処理を施すことで鉄損が低減する理由については、鋼板の温度不均一が解消されることの他に、以下のような理由があると考えている。
まず、冷間圧延後の鋼板を、転位がポリゴン化し、歪エネルギーが減少して、圧延組織が回復を起こす温度域に短時間保持した場合を考える。一般に、｛１１１｝方位には、冷間圧延時に多くの歪が導入され、他の方位と比較して蓄積される歪エネルギーが高い状態にあるため、回復時には｛１１１｝方位から優先的に歪エネルギーが解放される。その結果、回復が起こる温度で保持した場合には、圧延組織による蓄積歪エネルギーの差異は失われ、再結晶時における｛１１１｝組織の優先成長性も低下する。
Here, in the heating process of the primary recrystallization annealing, the reason why the iron loss is reduced by performing the holding treatment for holding the appropriate time at the appropriate temperature as described above is that the uneven temperature of the steel sheet is eliminated. I think there are the following reasons.
First, consider a case where the steel sheet after cold rolling is held for a short time in a temperature range in which dislocations become polygonal, strain energy decreases, and the rolled structure recovers. In general, in the {111} orientation, a lot of strain is introduced during cold rolling, and the accumulated strain energy is higher than that in other orientations. Energy is released. As a result, when held at a temperature at which recovery occurs, the difference in accumulated strain energy due to the rolling structure is lost, and the preferential growth property of the {111} structure during recrystallization also decreases.
上記のような回復挙動の変化によって、一次再結晶集合組織中の｛１１１｝方位が減少し、Ｇｏｓｓ方位粒（｛１１０｝＜００１＞）等、他の方位の存在比率が高まるので、二次再結晶組織の微細化と、高磁束密度化を同時に達成することができる。ただし、｛１１１｝方位は、二次再結晶時に、Ｇｏｓｓ方位粒に蚕食される組織であり、減らし過ぎても、二次再結晶が不安定となってしまう。そのため、微妙な操業条件の変動等によって、二次再結晶が起こらなかったり、二次再結晶が起こっても、二次再結晶粒の集積度が低下したりするおそれがある。これに対し、本発明の窒化処理は、一次再結晶の途中以後でインヒビターを強化するので、上記した微妙な操業条件の変動等の影響を受けることなく、二次再結晶を安定して発現させることができる。 Due to the change in the recovery behavior as described above, the {111} orientation in the primary recrystallization texture is decreased, and the presence ratio of other orientations such as Goss orientation grains ({110} <001>) is increased. Refinement of the recrystallized structure and high magnetic flux density can be achieved simultaneously. However, the {111} orientation is a structure phagocytosed by Goss orientation grains at the time of secondary recrystallization, and even if it is reduced too much, secondary recrystallization becomes unstable. Therefore, there is a possibility that secondary recrystallization does not occur due to subtle fluctuations in operating conditions or the like, and even if secondary recrystallization occurs, the degree of accumulation of secondary recrystallized grains may decrease. On the other hand, since the nitriding treatment of the present invention strengthens the inhibitor after the middle of the primary recrystallization, the secondary recrystallization can be stably expressed without being affected by the above-mentioned fluctuations in the delicate operating conditions. be able to.
なお、上述した考えによれば、加熱途中の回復が起こる温度で短時間の保定処理を施すことによる磁気特性向上効果が得られるのは、従来のラジアントチューブ等を用いた昇温速度（１０〜２０℃／ｓ）よりも速い昇温速度、具体的には５０℃／ｓ以上の昇温速度の場合に限られると考えられる。そこで、本発明においては、一次再結晶焼鈍の２００〜７００℃の温度範囲における昇温速度を５０℃／ｓ以上と規定する。
本発明は、上記の技術思想および実験結果に基いてなされたものである。
In addition, according to the above-described idea, the effect of improving the magnetic characteristics by performing a short-term holding treatment at a temperature at which recovery during heating is obtained can be achieved by using a conventional temperature increase rate (10 to 10). It is considered that the temperature rise rate is higher than 20 ° C./s), specifically, a temperature rise rate of 50 ° C./s or more. Therefore, in the present invention, the rate of temperature rise in the temperature range of 200 to 700 ° C. for primary recrystallization annealing is defined as 50 ° C./s or more.
The present invention has been made based on the above technical idea and experimental results.
次に、本発明の方向性電磁鋼板の素材となる鋼素材（スラブ）の成分組成について説明する。
Ｃ：０．０８ｍａｓｓ％以下
Ｃは、一次再結晶集合組織を改善する上で有用な元素であるが、０．０８ｍａｓｓ％を超えて含有すると、却って一次再結晶集合組織の劣化を招くので、上限を０．０８ｍａｓｓ％とする。なお、磁気特性を向上する観点からは、０．０１〜０．０６ｍａｓｓ％の範囲が好ましい。一方、磁気特性よりも、一次再結晶焼鈍における脱炭を省略あるいは簡略化するためには、Ｃを０．０１ｍａｓｓ％以下とするのが好ましい。
Next, the component composition of the steel material (slab) used as the material of the grain-oriented electrical steel sheet of the present invention will be described.
C: 0.08 mass% or less C is an element useful for improving the primary recrystallized texture. However, if it exceeds 0.08 mass%, the primary recrystallized texture is deteriorated. Is 0.08 mass%. In addition, from the viewpoint of improving magnetic characteristics, a range of 0.01 to 0.06 mass% is preferable. On the other hand, in order to omit or simplify the decarburization in the primary recrystallization annealing rather than the magnetic characteristics, it is preferable to set C to 0.01 mass% or less.
Ｓｉ：２．０〜４．５ｍａｓｓ％
Ｓｉは、鋼の電気抵抗を高めることによって、鉄損を低減する効果のある有用元素である。また、Ｓｉは、窒化珪素を形成し、インヒビターとして機能する元素でもある。斯かる効果を有効に発現させるためには、２．０ｍａｓｓ％以上添加する必要がある。一方、４．５ｍａｓｓ％を超えると、冷間圧延性が大きく低下するので、上限は４．５ｍａｓｓ％とする。
Si: 2.0 to 4.5 mass%
Si is a useful element that has the effect of reducing iron loss by increasing the electrical resistance of steel. Si is also an element that forms silicon nitride and functions as an inhibitor. In order to effectively exhibit such an effect, it is necessary to add 2.0 mass% or more. On the other hand, if it exceeds 4.5 mass%, the cold rollability is greatly reduced, so the upper limit is set to 4.5 mass%.
Ｍｎ：０．５ｍａｓｓ％以下
Ｍｎは、熱間圧延性を向上する効果があるため、０．００５ｍａｓｓ％以上含有させるのが好ましい。一方、０．５ｍａｓｓ％を超えて添加すると、一次再結晶集合組織が悪化して磁気特性の劣化を招くので、上限は０．５ｍａｓｓ％とする。好ましくは０．００５〜０．１ｍａｓｓ％の範囲である。
Mn: 0.5 mass% or less Since Mn has an effect of improving the hot rolling property, it is preferable to contain 0.005 mass% or more. On the other hand, if added over 0.5 mass%, the primary recrystallization texture deteriorates and the magnetic properties are deteriorated, so the upper limit is made 0.5 mass%. Preferably it is the range of 0.005-0.1 mass%.
Ｓ，ＳｅおよびＯ：それぞれ０．００５０ｍａｓｓ％未満
Ｓ，Ｓｅは、Ｍｎと粗大なＭｎＳやＭｎＳｅを形成して、また、Ｏは粗大な酸化物を形成して、一次再結晶組織を不均一にし、二次再結晶を阻害する元素である。特に、それぞれの含有量が０．００５０ｍａｓｓ％以上になると、二次再結晶を起こし難くなる。よって、これらの元素が、それぞれ０．００５０ｍａｓｓ％未満に制限する。好ましくは、それぞれ０．００３０ｍａｓｓ％以下である。
S, Se and O: each less than 0.0050 mass% S and Se form Mn and coarse MnS and MnSe, and O forms coarse oxide and makes the primary recrystallized structure non-uniform. , An element that inhibits secondary recrystallization. In particular, when the respective contents are 0.0050 mass% or more, secondary recrystallization hardly occurs. Therefore, these elements are limited to less than 0.0050 mass%, respectively. Preferably, it is 0.0030 mass% or less, respectively.
ｓｏｌ．Ａｌ：０．０１０ｍａｓｓ％未満
Ａｌは、鋼板の表面に緻密な酸化膜を形成し、窒化処理における窒化量の制御を困難にしたり、脱炭処理における脱炭を阻害したりする。そのため、Ａｌは、ｓｏｌ．Ａｌで、０．０１０ｍａｓｓ％未満に制限する。ただし、酸素親和力の高いＡｌは、製鋼で微量添加することによって鋼中の溶存酸素量を低減し、特性劣化につながる酸化物系介在物を低減するのに有効である。よって、磁性の劣化を防止する観点からは、０．０１０ｍａｓｓ％未満の範囲である程度含有することが望ましく、例えば、０．００２０ｍａｓｓ％以上含有することが好ましい。
sol. Al: less than 0.010 mass% Al forms a dense oxide film on the surface of the steel sheet, making it difficult to control the amount of nitriding in the nitriding treatment or inhibiting decarburization in the decarburizing treatment. Therefore, Al is sol. Al and limited to less than 0.010 mass%. However, Al having a high oxygen affinity is effective in reducing the amount of dissolved oxygen in steel by adding a small amount in steel making and reducing oxide inclusions that lead to deterioration of properties. Therefore, from the viewpoint of preventing the deterioration of magnetism, it is desirable to contain it to some extent within a range of less than 0.010 mass%, for example, 0.0020 mass% or more is preferable.
Ｎ：０．５２×ｓｏｌ．Ａｌ（ｍａｓｓ％）〜０．００８０ｍａｓｓ％
本発明は、窒化処理することによって窒化珪素を粒界に析出させ、インヒビターとして機能させることが特徴である。したがって、含有するＡｌは、窒化処理前に窒化物ＡｌＮとして固定し、析出させておく必要があり、そのためには、ＡｌＮを形成するのに必要な量以上のＮを事前に含有させておくことが必要である。ＡｌＮは、ＡｌとＮの原子がそれぞれ１：１で結合している。そこで、本発明では、Ｎを、ｓｏｌ．Ａｌの含有量（ｍａｓｓ％）に対して（Ｎの原子量（１４．００）／Ａｌの原子量（２６．９８））＝０．５２以上含有させる。一方、Ｎを過剰に含有させると、スラブ加熱時にフクレなどの欠陥を引き起こす原因となるため、上限は０．００８０ｍａｓｓ％とする。好ましくは０．００６０ｍａｓｓ％以下である。
N: 0.52 × sol. Al (mass%) to 0.0080 mass%
The present invention is characterized in that silicon nitride is precipitated at grain boundaries by nitriding to function as an inhibitor. Therefore, the contained Al must be fixed and precipitated as nitride AlN before the nitriding treatment, and for that purpose, more than the amount of N necessary to form AlN is contained in advance. is necessary. In AlN, Al and N atoms are bonded at a ratio of 1: 1, respectively. Therefore, in the present invention, N is changed to sol. (N atomic weight (14.00) / Al atomic weight (26.98)) = 0.52 or more with respect to the Al content (mass%). On the other hand, when N is excessively contained, it causes a defect such as blistering at the time of slab heating, so the upper limit is set to 0.0080 mass%. Preferably it is 0.0060 mass% or less.
本発明の方向性電磁鋼板は、磁気特性を改善することを目的として、上記必須成分に加えてさらに、以下の元素を適宜添加することができる。
Ｎｉ：０．００５〜１．５０ｍａｓｓ％
Ｎｉは、熱延板の組織の均一性を高め、磁気特性を改善する効果がある。上記効果を得るためには０．００５ｍａｓｓ％以上含有させることが好ましい。一方、１．５０ｍａｓｓ％を超えて添加すると、二次再結晶が困難となり、磁気特性が劣化するようになる。よって、Ｎｉは０．００５〜１．５０ｍａｓｓ％の範囲で添加するのが好ましい。
In the grain-oriented electrical steel sheet of the present invention, the following elements can be appropriately added in addition to the essential components for the purpose of improving magnetic properties.
Ni: 0.005 to 1.50 mass%
Ni has the effect of increasing the uniformity of the structure of the hot-rolled sheet and improving the magnetic properties. In order to acquire the said effect, it is preferable to contain 0.005 mass% or more. On the other hand, if it is added in excess of 1.50 mass%, secondary recrystallization becomes difficult and the magnetic properties deteriorate. Therefore, Ni is preferably added in the range of 0.005 to 1.50 mass%.
Ｓｎ：０．０１〜０．５０ｍａｓｓ％、Ｓｂ：０．００５〜０．５０ｍａｓｓ％
ＳｎおよびＳｂは、二次再結晶焼鈍中の鋼板の窒化や酸化を抑制し、良好な結晶方位を有する結晶粒の二次再結晶を促進して、磁気特性を向上する元素である。上記効果を得るためにはＳｎは０．０１ｍａｓｓ％以上、Ｓｂは０．００５ｍａｓｓ％以上含有させることが好ましい。しかし、それぞれ０．５０ｍａｓｓ％を超えて添加すると、冷間圧延性が低下する。よって、Ｓｎは０．０１〜０．５０ｍａｓｓ％、Ｓｂは０．００５〜０．５０ｍａｓｓ％の範囲で添加するのが好ましい。
Sn: 0.01-0.50 mass%, Sb: 0.005-0.50 mass%
Sn and Sb are elements that suppress the nitriding and oxidation of the steel sheet during the secondary recrystallization annealing, promote the secondary recrystallization of crystal grains having a good crystal orientation, and improve the magnetic properties. In order to acquire the said effect, it is preferable to contain Sn 0.01 mass% or more and Sb 0.005 mass% or more. However, when adding each exceeding 0.50 mass%, cold-rolling property will fall. Therefore, it is preferable to add Sn in the range of 0.01 to 0.50 mass% and Sb in the range of 0.005 to 0.50 mass%.
Ｃｕ：０．０１〜０．５０ｍａｓｓ％
Ｃｕは、二次再結晶焼鈍中の鋼板の酸化を抑制し、良好な結晶方位を有する結晶粒の二次再結晶を促進して磁気特性を効果的に向上させる働きがある。上記効果を得るためには０．０１ｍａｓｓ％以上含有させることが好ましい。しかし、０．５０ｍａｓｓ％を超えて添加すると、熱間圧延性の低下を招く。よって、Ｃｕは０．０１〜０．５０ｍａｓｓ％の範囲で添加するのが好ましい。
Cu: 0.01 to 0.50 mass%
Cu functions to suppress the oxidation of the steel sheet during the secondary recrystallization annealing, promote the secondary recrystallization of crystal grains having a good crystal orientation, and effectively improve the magnetic properties. In order to acquire the said effect, it is preferable to make it contain 0.01 mass% or more. However, if added over 0.50 mass%, the hot rolling property is lowered. Therefore, it is preferable to add Cu in the range of 0.01 to 0.50 mass%.
Ｃｒ：０．０１〜１．５０ｍａｓｓ％
Ｃｒは、フォルステライト被膜の形成を安定化させる働きがある。上記効果を得るためには０．０１ｍａｓｓ％以上含有させることが好ましい。しかし、１．５０ｍａｓｓ％を超えて添加すると、二次再結晶が困難となり、磁気特性が劣化するようになる。よって、Ｃｒは０．０１〜１．５０ｍａｓｓ％の範囲で添加するのが好ましい。
Cr: 0.01-1.50 mass%
Cr functions to stabilize the formation of the forsterite film. In order to acquire the said effect, it is preferable to make it contain 0.01 mass% or more. However, if it is added in excess of 1.50 mass%, secondary recrystallization becomes difficult and the magnetic properties deteriorate. Therefore, it is preferable to add Cr in the range of 0.01 to 1.50 mass%.
Ｐ：０．００５０〜０．５０ｍａｓｓ％
Ｐは、フォルステライト被膜の形成を安定化させる働きがある。上記効果を得るためには０．００５０ｍａｓｓ％以上含有させることが好ましい。しかし、０．５０ｍａｓｓ％を超えると冷間圧延性が低下する。よって、Ｐは０．００５０〜０．５０ｍａｓｓ％の範囲で添加するのが好ましい。
P: 0.0050 to 0.50 mass%
P has a function of stabilizing the formation of the forsterite film. In order to acquire the said effect, it is preferable to make it contain 0.0050 mass% or more. However, when it exceeds 0.50 mass%, the cold rollability is lowered. Therefore, it is preferable to add P in the range of 0.0050 to 0.50 mass%.
Ｎｂ：０．０００５〜０．０１０ｍａｓｓ％、Ｍｏ：０．０１〜０．５０ｍａｓｓ％
ＮｂおよびＭｏは、スラブ加熱時の温度変化による割れの抑制等を介して、熱延板におけるヘゲ等の表面欠陥を防止する効果を有する。上記効果は、それぞれＮｂ：０．０００５ｍａｓｓ％以上、Ｍｏ：０．０１ｍａｓｓ％以上で得られる。しかし、Ｎｂ：０．０１０ｍａｓｓ％超え、Ｍｏ：０．５０ｍａｓｓ％超えでは、炭化物や窒化物を形成し、これが最終製品まで残留して、鉄損劣化を引き起こす。よって、それぞれ上記範囲で添加するのが好ましい。
Nb: 0.0005 to 0.010 mass%, Mo: 0.01 to 0.50 mass%
Nb and Mo have an effect of preventing surface defects such as shavings in the hot-rolled sheet through suppression of cracks due to temperature changes during slab heating. The above effects can be obtained with Nb: 0.0005 mass% or more and Mo: 0.01 mass% or more, respectively. However, if Nb exceeds 0.010 mass% and Mo exceeds 0.50 mass%, carbides and nitrides are formed, which remain until the final product, causing iron loss deterioration. Therefore, it is preferable to add within the above ranges.
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。
まず、本発明の方向性電磁鋼板は、上述した成分組成に調整した鋼を溶製し、常法の連続鋳造法や造塊−分塊圧延法等で鋼スラブとし、所定の温度に再加熱した後、あるいは、再加熱することなく、熱間圧延に供する。なお、スラブを再加熱する場合の再加熱温度は１０００〜１３００℃の範囲とするのが好ましい。１３００℃を超える加熱は、スラブ中にインヒビター成分を殆ど含有させていない本発明では、エネルギーコストの上昇を招くだけであり、一方、１０００℃未満では、熱間圧延における圧延負荷が大きくなって、圧延することが困難となるからである。
Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
First, the grain-oriented electrical steel sheet of the present invention is a steel slab produced by melting a steel adjusted to the above-described component composition, using a conventional continuous casting method, ingot-bundling rolling method, etc. Or after hot rolling without reheating. In addition, it is preferable to make the reheating temperature in the case of reheating a slab into the range of 1000-1300 degreeC. In the present invention in which the inhibitor component is hardly contained in the slab, heating exceeding 1300 ° C only increases the energy cost. On the other hand, below 1000 ° C, the rolling load in hot rolling increases, It is because it becomes difficult to roll.
上記熱間圧延後の鋼板（熱延板）は、その後、必要に応じて熱延板焼鈍を施した後、１回の冷間圧延あるいは中間焼鈍を挟む２回以上の冷間圧延により最終板厚の冷延板とする。この冷間圧延は、常温で行ってもよいし、常温より高い温度、たとえば２５０℃程度に鋼板温度を上げて圧延する温間圧延としてもよい。 The hot-rolled steel sheet (hot-rolled sheet) is then subjected to hot-rolled sheet annealing as necessary, and then subjected to one cold rolling or two or more cold rollings sandwiching the intermediate annealing to obtain the final sheet. Thick cold-rolled sheet. This cold rolling may be performed at normal temperature, or may be warm rolling in which the steel sheet temperature is raised to a temperature higher than normal temperature, for example, about 250 ° C.
次いで、上記最終板厚とした冷延板に一次再結晶焼鈍を施す。
この一次再結晶焼鈍の目的は、圧延組織を有する冷延板に一次再結晶を起こさせて、二次再結晶に最適な一次再結晶組織および粒径に調整することにある。そのためには、一次再結晶焼鈍の焼鈍温度は８００〜９５０℃の範囲とすることが好ましい。なお、この一次再結晶焼鈍において脱炭を行う場合には、焼鈍雰囲気は湿水素窒素あるいは湿水素アルゴン雰囲気の湿潤雰囲気とすることが好ましい。
Next, primary recrystallization annealing is performed on the cold-rolled sheet having the final thickness.
The purpose of this primary recrystallization annealing is to cause primary recrystallization to occur in a cold-rolled sheet having a rolled structure so as to adjust the primary recrystallization structure and grain size to be optimal for secondary recrystallization. For that purpose, the annealing temperature of the primary recrystallization annealing is preferably in the range of 800 to 950 ° C. When decarburization is performed in this primary recrystallization annealing, the annealing atmosphere is preferably a wet atmosphere of wet hydrogen nitrogen or wet hydrogen argon atmosphere.
ここで、本発明の製造方法において重要なことは、上記一次再結晶焼鈍の加熱過程における５５０〜７００℃間を平均昇温速度５０℃／ｓ以上で急速加熱するとともに、２５０〜５５０℃間のいずれかの温度で昇温速度１０℃／ｓ以下で１〜１０秒間保持する保定処理を施す必要があることである。 Here, in the production method of the present invention, what is important is that between 550 and 700 ° C. in the heating process of the primary recrystallization annealing is rapidly heated at an average temperature increase rate of 50 ° C./s or more and between 250 and 550 ° C. That is, it is necessary to perform a holding treatment for holding at a temperature rising rate of 10 ° C./s or less for 1 to 10 seconds at any temperature.
５５０〜７００℃間の平均昇温速度が５０℃／ｓ未満であると、一次再結晶集合組織中のＧｏｓｓ方位を十分に増やすことができず、急速加熱の効果が得られない。好ましくは７５℃／ｓ以上である。なお、上記一次再結晶焼鈍の急速加熱に用いる加熱手段は、トランスバース方式あるいはソレノイド方式の誘導加熱装置や、鋼板に電流を流し、ジュール熱によって加熱する通電加熱装置のいずれを用いてもよく、また、適切なヒートパターンに制御できれば他の装置を用いてもよい。 If the average temperature rising rate between 550 and 700 ° C. is less than 50 ° C./s, the Goss orientation in the primary recrystallization texture cannot be increased sufficiently, and the effect of rapid heating cannot be obtained. Preferably it is 75 degrees C / s or more. The heating means used for rapid heating of the primary recrystallization annealing may be any of a transverse type or solenoid type induction heating device, or an electric heating device that supplies current to a steel plate and heats it by Joule heat. Other devices may be used as long as they can be controlled to an appropriate heat pattern.
また、上記昇温速度を１０℃／ｓ以下とする保定処理の時間は、１秒未満であると鋼板内の温度不均一解消に効果が小さく、一方、１０秒を超えると、過剰に歪が開放されて、｛１１１｝組織の成長が抑制され過ぎ、二次再結晶が不安定となる。好ましくは２〜８秒の範囲である。また、このときの昇温速度は負の値となっても良く、−５〜＋５℃／ｓ範囲内であれば、一定温度の保持と見做すことができる。
Moreover, the time of the holding | maintenance process which makes the said
さらに、本発明において重要なことは、上記一次再結晶焼鈍中あるいは一次再結晶焼鈍後に窒化処理を施すことが必要なことである。
なお、Ｓａｉ等の技術文献（Ｓａｉ Ｒａｍｕｄｕ Ｍｅｋａ ｅｔ ａｌ．：Ｐｈｉｌｏｓ Ｍａｇ ｖｏｌ．９２，Ｎｏ．１１，１１ Ａｐｒｉｌ ２０１２，１４３５−１４５５）には、冷間圧延後、一次再結晶をさせる前に窒化処理を施し、粒内に窒化珪素を析出させる技術が開示されている。しかし、冷間圧延後に窒化処理を行うと、転位上を窒素が拡散するため、本発明の技術思想である窒化珪素を粒界に析出させることが難しくなる。したがって、少なくとも再結晶が終わった一次再結晶焼鈍中あるいは一次再結晶焼鈍後のいずれかのタイミングで、窒化処理を行なうことが必要である。
Furthermore, what is important in the present invention is that it is necessary to perform a nitriding treatment during the primary recrystallization annealing or after the primary recrystallization annealing.
In addition, in the technical literature such as Sai (Sai Ramudu Mega et al .: Philos Mag vol. 92, No. 11, 11 April 2012, 1435-1455), after the cold rolling, nitriding treatment is performed before primary recrystallization. And a technique for depositing silicon nitride in the grains is disclosed. However, when nitriding is performed after cold rolling, nitrogen diffuses on dislocations, so that it is difficult to precipitate silicon nitride, which is the technical idea of the present invention, at grain boundaries. Therefore, it is necessary to perform the nitriding treatment at least at any timing during the primary recrystallization annealing after the recrystallization or after the primary recrystallization annealing.
また、上記窒化処理における増Ｎ量は０．００５０〜０．１０００ｍａｓｓ％の範囲とすることが必要である。増Ｎ量が０．００５０ｍａｓｓ％未満では、窒化処理効果が十分に得られず、一方、０．１０００ｍａｓｓ％を超えると窒化珪素の析出量が過多となり、二次再結晶を起こし難くなるからである。好ましくは０．００８０〜０．０６００ｍａｓｓ％の範囲である。 Further, the amount of increased N in the nitriding treatment needs to be in the range of 0.0050 to 0.1000 mass%. If the increased N amount is less than 0.0050 mass%, the nitriding effect cannot be sufficiently obtained. On the other hand, if it exceeds 0.1000 mass%, the amount of precipitated silicon nitride becomes excessive and secondary recrystallization is difficult to occur. . Preferably it is the range of 0.0080-0.0600 mass%.
また、上記窒化処理の処理温度は、Ｎが鋼中に拡散を起こすような高温とせず、鋼板表層に窒化物層が形成する８００℃以下の温度とするのが好ましい。本発明においては、窒化処理によって導入されたＮは、最終的には窒化珪素として析出させ、インヒビターとして用いることを想定している。そのためには、析出した窒化珪素は、鋼板の板厚方向に均一に分布している必要がある。しかし、８００℃を超える高温で窒化処理を行うと、Ｎが粒界を介して鋼板内部に大量に拡散するとともに、Ｓｉの拡散も促進されているため、Ｎが鋼板の板厚中心に到達する前に窒化珪素として析出してしまう。そこで、窒化処理は８００℃以下で行い、Ｎを鋼板表層の窒化物層として留めておき、続く仕上焼鈍あるいは単独に行う長時間の焼鈍においてＮを鋼中に拡散させ、均一に窒化珪素を析出させることが好ましい。ただし、窒化処理の時間が３０秒程度の短時間であれば、８００℃超えの温度で処理してもよい。 Further, the nitriding treatment temperature is preferably not higher than the temperature at which N diffuses in the steel, but not more than 800 ° C. at which the nitride layer is formed on the steel sheet surface layer. In the present invention, it is assumed that N introduced by nitriding is finally deposited as silicon nitride and used as an inhibitor. For this purpose, the deposited silicon nitride needs to be uniformly distributed in the thickness direction of the steel sheet. However, when nitriding is performed at a high temperature exceeding 800 ° C., N diffuses in a large amount inside the steel sheet through the grain boundary and Si diffusion is also promoted, so that N reaches the center of the thickness of the steel sheet. Precipitates as silicon nitride. Therefore, nitriding is performed at 800 ° C. or lower, N is kept as a nitride layer on the surface of the steel sheet, and N is diffused in the steel in the subsequent finish annealing or long-time annealing performed alone, thereby uniformly depositing silicon nitride. It is preferable to make it. However, if the nitriding time is as short as about 30 seconds, the processing may be performed at a temperature exceeding 800 ° C.
なお、上記窒化処理の方法は、窒化量を制御できれば特に制限はなく、例えば、ＮＨ３雰囲気ガスを用いるガス窒化法や、より窒化能に優れる塩浴窒化法を用いてもよい。また、上記窒化処理は、コイル状態で行ってもよいし、コイルを巻き戻したストリップ（鋼帯）の状態で行ってもよい。 The nitriding method is not particularly limited as long as the amount of nitriding can be controlled. For example, a gas nitriding method using an NH 3 atmosphere gas or a salt bath nitriding method having better nitriding ability may be used. Further, the nitriding treatment may be performed in a coil state or a strip (steel strip) obtained by rewinding the coil.
上記窒化処理を施した鋼板は、その後、鋼板表面に焼鈍分離剤を塗布し、二次再結晶させる仕上焼鈍を施す。上記焼鈍分離剤は、仕上焼鈍後の鋼板表面にフォルステライト被膜を形成するためには、主剤をマグネシア（ＭｇＯ）とする必要があるが、フォルステライト被膜の形成を必要としない場合には、主剤として、アルミナ（Ａｌ２Ｏ３）やカルシア（ＣａＯ）等、仕上焼鈍温度より高い融点を有する適当な酸化物を用いることができる。 The steel sheet subjected to the nitriding treatment is then subjected to finish annealing in which an annealing separator is applied to the steel sheet surface and secondary recrystallization is performed. In order to form a forsterite film on the surface of the steel sheet after finish annealing, the above annealing separator needs to use magnesia (MgO) as the main agent, but when the formation of the forsterite film is not required, the main agent As such, an appropriate oxide having a melting point higher than the finish annealing temperature, such as alumina (Al 2 O 3 ) or calcia (CaO), can be used.
また、上記仕上焼鈍は、加熱過程における３００〜８００℃間の滞留時間を５〜１５０時間の範囲とする必要がある。この間に前述した窒化処理で形成した表層の窒化物が分解し、Ｎが鋼中へ拡散する。本発明の鋼素材の成分系では、ＡｌＮを形成することができるＡｌが残存していないため、粒界偏析元素であるＮは粒界を拡散経路として鋼中へ拡散（粒界拡散）する。しかし、窒化珪素は、鋼との不整合性が大きいため、析出速度は極めて遅い。そのため、窒化珪素をインヒビターに用いて正常粒成長の抑制を図るためには、正常粒成長が進行する８００℃の段階で、十分な量の窒化珪素が粒界上に選択的に析出している必要がある。 Moreover, the said finish annealing needs to make the residence time between 300-800 degreeC in the heating process into the range of 5-150 hours. During this time, the nitride of the surface layer formed by the nitriding process described above is decomposed and N diffuses into the steel. In the component system of the steel material of the present invention, since Al that can form AlN does not remain, N which is a grain boundary segregation element diffuses into the steel (grain boundary diffusion) using the grain boundary as a diffusion path. However, since silicon nitride has a large incompatibility with steel, the deposition rate is extremely slow. Therefore, in order to suppress normal grain growth using silicon nitride as an inhibitor, a sufficient amount of silicon nitride is selectively deposited on the grain boundaries at the stage of 800 ° C. when normal grain growth proceeds. There is a need.
そこで、本発明においては、上記温度に到達する前の温度領域における滞留時間を５時間以上とすることで、窒化珪素は粒内には析出できないものの、粒界拡散したＮを窒化珪素として粒界上に選択的に析出させる。なお、滞留時間の上限は、窒化珪素を析出させる観点からは必ずしも設ける必要はないが、１５０時間を超える滞留は効果が飽和し、焼鈍コストの上昇を招くだけであるため、１５０時間以下に制限する。なお、焼鈍雰囲気は、Ｎ２，Ａｒ，Ｈ２あるいはこれらの混合ガスのいずれを用いてもよい。 Therefore, in the present invention, by setting the residence time in the temperature region before reaching the above temperature to be 5 hours or more, silicon nitride cannot be precipitated in the grains, but the grain boundary diffused N is regarded as silicon nitride. Precipitate selectively. The upper limit of the residence time is not necessarily provided from the viewpoint of precipitating silicon nitride, but the residence exceeding 150 hours only saturates the effect and causes an increase in annealing cost, so it is limited to 150 hours or less. To do. Note that N 2 , Ar, H 2 or a mixed gas thereof may be used for the annealing atmosphere.
Ａｌの含有量が制限され、ＡｌＮの形成に必要な量以上の過剰なＮを含有し、かつ、他のＭｎＳやＭｎＳｅ等のインヒビター成分をほとんど含有しないスラブを素材に用いて、上述の工程を経て製造される本発明の方向性電磁鋼板では、仕上焼鈍の加熱過程の二次再結晶開始までの段階において、従来のインヒビターに比べて粗大な、１００ｎｍ以上のサイズの窒化珪素を粒界に選択的に析出させることができる。 The above-mentioned process is performed using a slab in which the content of Al is limited, excessive N is contained in an amount more than necessary for the formation of AlN, and hardly contains other inhibitor components such as MnS and MnSe. In the grain-oriented electrical steel sheet of the present invention manufactured through the process, silicon nitride having a size of 100 nm or more, which is coarser than conventional inhibitors, is selected as a grain boundary in the stage up to the start of secondary recrystallization in the heating process of finish annealing. Can be deposited.
図３は、一次再結晶焼鈍後の鋼板に、増Ｎ量が０．０１００ｍａｓｓ％および０．０５００ｍａｓｓ％の窒化処理を施した後、３００〜８００℃の温度域の滞留時間が８時間となる昇温速度で８００℃まで昇温し、直ちに水冷して、その鋼板組織を走査型電子顕微鏡ＳＥＭで観察した結果と、粒界析出物をＥＤＸで同定した結果を示したものである。この図から、本発明において用いる窒化珪素の析出物は、従来利用されてきた微細な析出物（＜１００ｎｍ）のインヒビターとは異なり、最小のものであっても１００ｎｍを超える粗大な窒化珪素が粒界上に析出している様子を確認することができる。 FIG. 3 shows that the steel sheet after the primary recrystallization annealing is subjected to nitriding with an N increase of 0.0100 mass% and 0.0500 mass%, and then the residence time in the temperature range of 300 to 800 ° C. is 8 hours. The figure shows the results of observing the steel sheet structure with a scanning electron microscope SEM and the results of identifying the grain boundary precipitates with EDX. From this figure, the silicon nitride precipitate used in the present invention is different from the conventionally used fine precipitate (<100 nm) inhibitor, and even if it is the smallest, coarse silicon nitride exceeding 100 nm is grain-sized. It can be seen that it is deposited on the boundary.
なお、窒化珪素を粒界に選択析出させる工程は、現在の方向性電磁鋼板の製造プロセスでは、仕上焼鈍工程を利用するのがエネルギー効率上、最も有効である。しかし、窒化珪素の粒界への析出は、上記条件のヒートサイクルを付与できれば可能であるので、他の設備を用いて行ってもよい。また、窒化珪素を粒界に析出させる熱処理と、仕上焼鈍とを別々に行ってもよい。 In the process of selectively depositing silicon nitride at grain boundaries, in the current manufacturing process for grain-oriented electrical steel sheets, it is most effective in terms of energy efficiency to use a finish annealing process. However, precipitation of silicon nitride at the grain boundaries is possible as long as the heat cycle under the above conditions can be applied, and therefore, other equipment may be used. Further, heat treatment for precipitating silicon nitride at grain boundaries and finish annealing may be performed separately.
上記仕上焼鈍後の鋼板は、その後、水洗やブラッシング、酸洗等で、鋼板表面に付着した未反応の焼鈍分離剤を除去した後、平坦化焼鈍を施して形状矯正することが、鉄損の低減には有効である。 After the finish annealing, the steel sheet is then washed with water, brushed, pickled, etc. to remove unreacted annealing separator adhering to the steel sheet surface, and then flattened to correct the shape. It is effective for reduction.
さらに、鋼板を積層して使用する場合には、上記平坦化焼鈍において、あるいは、その前後において、鋼板表面に絶縁被膜を被成することが有効である。絶縁被膜の種類については、特に制限はないが、特開昭５０−７９４４２号公報や特開昭４８−３９３３８号公報に記載されているリン酸塩−クロム酸塩−コロイダルシリカを含有する塗布液を鋼板に塗布し、８００℃程度で焼き付ける方法が好適である。 Furthermore, in the case where the steel plates are laminated and used, it is effective to form an insulating film on the steel plate surface in the above-described flattening annealing or before and after that. The type of insulating coating is not particularly limited, but is a coating solution containing phosphate-chromate-colloidal silica described in JP-A-50-79442 and JP-A-48-39338. Is preferably applied to a steel plate and baked at about 800 ° C.
特に、鉄損の低減を図るためには、絶縁被膜として、鋼板に張力を付与する張力付与被膜を適用するのが好ましい。張力付与被膜の形成には、バインダーを介して張力被膜を塗布する方法や、物理蒸着法や化学蒸着法により無機物を鋼板表層に蒸着させる方法を採用することが、被膜密着性に優れかつ著しく鉄損低減効果が大きい絶縁被膜を形成することができるので、より好ましい。 In particular, in order to reduce iron loss, it is preferable to apply a tension-imparting film that imparts tension to the steel sheet as the insulating film. For the formation of a tension-imparting coating, it is possible to apply a method of applying a tension coating via a binder or a method of depositing an inorganic substance on the surface of a steel sheet by physical vapor deposition or chemical vapor deposition. Since an insulating film having a large loss reducing effect can be formed, it is more preferable.
また、鉄損をより低減するためには、磁区細分化処理を施すことが好ましい。処理方法としては、一般的に実施されている、最終製品板に溝を形成したり、電子ビーム照射やレーザ照射、プラズマ照射等によって線状または点状に熱歪や衝撃歪を導入する方法、最終板厚に冷間圧延した鋼板や中間工程の鋼板表面にエッチング加工を施して溝を形成したりする方法等を用いることができる。 Moreover, in order to further reduce the iron loss, it is preferable to perform a magnetic domain fragmentation process. As a processing method, a method of generally forming a groove in the final product plate, introducing a thermal strain or an impact strain in a linear or dotted manner by electron beam irradiation, laser irradiation, plasma irradiation, or the like, For example, a method of forming a groove by etching a steel sheet that has been cold-rolled to a final thickness or a steel sheet surface in an intermediate process can be used.
Ｃ：０．０６０ｍａｓｓ％、Ｓｉ：３．２５ｍａｓｓ％、Ｍｎ：０．０６ｍａｓｓ％、Ｓ：０．００１０ｍａｓｓ％、Ｓｅ：０．００１２ｍａｓｓ％、Ｏ：０．００１０ｍａｓｓ％、ｓｏｌ．Ａｌ：０．００５０ｍａｓｓ％およびＮ：０．００３０ｍａｓｓ％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する鋼を溶製し、連続鋳造法で鋼スラブとし、熱間圧延して板厚２．４ｍｍの熱延板とし、１０００℃×１分の熱延板焼鈍を施した後、冷間圧延して最終板厚０．２７ｍｍの冷延コイルとした。 C: 0.060 mass%, Si: 3.25 mass%, Mn: 0.06 mass%, S: 0.0010 mass%, Se: 0.0012 mass%, O: 0.0010 mass%, sol. Steel containing Al: 0.0050 mass% and N: 0.0030 mass%, the balance of which is composed of Fe and inevitable impurities, is melted, made into a steel slab by a continuous casting method, and hot-rolled into a plate A hot-rolled sheet having a thickness of 2.4 mm was subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute, and then cold-rolled to form a cold-rolled coil having a final sheet thickness of 0.27 mm.
次いで、上記冷延コイルの長手方向中央部から、幅１００ｍｍ×長さ４００ｍｍサイズの試料を採取し、５０ｖｏｌ％Ｈ２−５０ｖｏｌ％Ｎ２、露点５９℃の湿潤雰囲気下で８４０℃×８０秒の脱炭焼鈍を伴う一次再結晶焼鈍を施した。この一次再結晶焼鈍では、室温から８４０℃までは通電加熱装置を用いて加熱し、その際、一部の試料を除いて、加熱途中で、表１に記載の条件で保定処理を施し、その後、５５０℃（保定終了温度が５５０℃超えの場合は、保定終了温度）から７００℃までを、同じく表１に記載の昇温速度で加熱した。なお、上記保定処理時間および５５０〜７００℃間の加熱時間を除く時間における平均昇温速度は１８℃／ｓとした。
Next, a sample having a size of
次いで、上記一次再結晶焼鈍を施した試料に、一部を除いて、同じく表１に示す条件で窒化処理（バッチ処理）を施し、鋼中Ｎ量を増加させた。なお、窒化処理前後の鋼中Ｎ量は、化学分析法で試料全厚について定量した。
その後、上記試料の表面に、ＭｇＯを主成分とし、ＴｉＯ２を５ｍａｓｓ％含有する焼鈍分離剤を水スラリ状にして塗布・乾燥した後、３００〜８００℃間の滞留時間を２０時間とする仕上焼鈍を施し、その後、リン酸塩系の絶縁張力被膜を塗布し、焼き付けて製品板試料とした。なお、上記製品板試料は、各条件につき２０枚作製した。
Next, the sample subjected to the primary recrystallization annealing was subjected to nitriding treatment (batch treatment) under the same conditions as shown in Table 1 except for a part, thereby increasing the amount of N in the steel. The amount of N in the steel before and after nitriding was quantified with respect to the total thickness of the sample by chemical analysis.
Thereafter, an annealing separator containing MgO as a main component and containing 5 mass% of TiO 2 is applied to the surface of the sample as a water slurry and dried, and then the residence time between 300 to 800 ° C. is set to 20 hours. After annealing, a phosphate insulating tension coating was applied and baked to obtain a product plate sample. In addition, 20 pieces of the product plate samples were produced for each condition.
斯くして得た製品板試料についてＪＩＳ Ｃ２５５６に記載の方法で、周波数５０Ｈｚ、磁束密度１．７Ｔにおける鉄損Ｗ１７／５０を測定し、その結果を表１に併記した。なお、表１の鉄損値は、２０枚の試料の平均値である。表１から、本発明に適合する発明例の製品板試料は、いずれも良好な鉄損特性を有していることがわかる。 For the product plate sample thus obtained, the iron loss W 17/50 at a frequency of 50 Hz and a magnetic flux density of 1.7 T was measured by the method described in JIS C2556, and the results are also shown in Table 1. In addition, the iron loss value of Table 1 is an average value of 20 samples. From Table 1, it can be seen that all the product plate samples of the invention examples suitable for the present invention have good iron loss characteristics.
表２に示した符号Ａ〜Ｎの成分組成を有し、残部がＦｅおよび不可避的不純物からなる鋼を溶製し、連続鋳造法で鋼スラブとした後、熱間圧延して板厚２．４ｍｍの熱延板とし、１０００℃×１分の熱延板焼鈍を施した後、冷間圧延して最終板厚０．２７ｍｍの冷延コイルとした。 Thickness is obtained by melting steel having the composition of symbols A to N shown in Table 2 with the balance being Fe and inevitable impurities to form a steel slab by a continuous casting method, followed by hot rolling. A hot-rolled sheet of 4 mm was subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute, and then cold-rolled to form a cold-rolled coil having a final sheet thickness of 0.27 mm.
次いで、上記冷延コイルの長手方向中央部から、１００ｍｍ×４００ｍｍサイズの試料を採取し、５０ｖｏｌ％Ｈ２−５０ｖｏｌ％Ｎ２、露点６１℃の湿潤雰囲気下で８４０℃×８０秒の脱炭焼鈍を伴う一次再結晶焼鈍を施した。この一次再結晶焼鈍では、室温から８４０℃までをソレノイド式の誘導加熱装置を用いて加熱し、その際、加熱途中の４００℃の温度で５秒間保持する保定処理を施した後、再び昇温を開始し、５５０〜７００℃間の平均昇温速度が１００℃／ｓとなるように制御した。なお、上記保定処理時間および５５０〜７００℃間の昇温時間を除く加熱時間における平均昇温速度は１６℃／ｓとした。 Next, a sample having a size of 100 mm × 400 mm was taken from the center in the longitudinal direction of the cold-rolled coil, and decarburization annealing was performed at 840 ° C. × 80 seconds in a humid atmosphere of 50 vol% H 2 -50 vol% N 2 and a dew point of 61 ° C. The primary recrystallization annealing accompanied with was performed. In this primary recrystallization annealing, heating is performed from room temperature to 840 ° C. using a solenoid-type induction heating device, and at that time, a holding treatment is held for 5 seconds at a temperature of 400 ° C. during heating, and then the temperature is raised again. And the average temperature increase rate between 550 and 700 ° C. was controlled to be 100 ° C./s. In addition, the average temperature increase rate in the heating time excluding the above-mentioned retention treatment time and the temperature increase time between 550 to 700 ° C. was 16 ° C./s.
上記一次再結晶焼鈍後の試料は、その後、連続ガス窒化装置を用いて、４５０℃×３２０秒の窒化処理を施し、鋼中窒素量を増加させた。なお、上記窒化処理による増Ｎ量は、試料全厚について化学分析法で分析した結果、０．０５５０ｍａｓｓ％であることを確認した。
次いで、上記窒化処理後の試料表面に、ＭｇＯを主成分とし、ＴｉＯ２を５ｍａｓｓ％含有する焼鈍分離剤を水スラリ状にして塗布・乾燥した後、３００〜８００℃間の滞留時間を、表２に記載の時間とする仕上焼鈍を施し、その後、リン酸塩系の絶縁張力被膜を塗布し、焼き付けて製品板試料とした。なお、上記製品板試料は、各条件につき２０枚作製した。
The sample after the primary recrystallization annealing was then subjected to nitriding treatment at 450 ° C. × 320 seconds using a continuous gas nitriding apparatus to increase the amount of nitrogen in the steel. In addition, as a result of analyzing the total thickness of the sample by the chemical analysis method, it was confirmed that the increased N amount by the nitriding treatment was 0.0550 mass%.
Next, after applying and drying an annealing separator containing MgO as a main component and containing 5 mass% of TiO 2 in a water slurry on the sample surface after the nitriding treatment, the residence time between 300 to 800 ° C. Finish annealing was performed for the time described in 2, and then a phosphate-based insulating tension coating was applied and baked to obtain a product plate sample. In addition, 20 pieces of the product plate samples were produced for each condition.
斯くして得た製品板試料について、周波数５０Ｈｚ、磁束密度１．７Ｔにおける鉄損Ｗ１７／５０をＪＩＳ Ｃ２５５６に記載の方法で測定し、その結果を表２に併記した。表２から、本発明に適合する発明例の製品板試料は、いずれも良好な鉄損特性を有していることがわかる。 For the product plate sample thus obtained, the iron loss W 17/50 at a frequency of 50 Hz and a magnetic flux density of 1.7 T was measured by the method described in JIS C2556, and the results are also shown in Table 2. From Table 2, it can be seen that all of the product plate samples of the inventive examples suitable for the present invention have good iron loss characteristics.
Claims (2)
前記一次再結晶焼鈍の加熱過程における５５０〜７００℃間を平均昇温速度５０℃／ｓ以上で急速加熱するとともに、２５０〜５５０℃間のいずれかの温度で昇温速度１０℃／ｓ以下で１〜１０秒間保持する保定処理を施し、
前記窒化処理を、導入したＮが鋼板表層の窒化物層として留まる条件、かつ、増Ｎ量が０．００５０〜０．１０００ｍａｓｓ％の範囲となる条件で行い、
前記仕上焼鈍の加熱過程における３００〜８００℃間の滞留時間を２０〜１５０時間とすることを特徴とする方向性電磁鋼板の製造方法。 C: 0.08 mass% or less, Si: 2.0 to 4.5 mass%, Mn: 0.5 mass% or less, sol. Al: less than 0.0100 mass%, S, Se and O: each contained less than 0.0050 mass%, and further, N: 0.52 × sol. A steel slab containing Al (mass%) to 0.0080 mass%, the balance of which is composed of Fe and inevitable impurities, is hot-rolled into a hot-rolled sheet and sandwiches once or intermediate annealing 2 Cold rolling more than once to make a cold-rolled sheet with the final thickness, and after performing nitriding treatment during or after primary recrystallization annealing, apply an annealing separator to the steel sheet surface, and finish annealing In the manufacturing method of the electrical steel sheet,
In the heating process of the primary recrystallization annealing, rapid heating is performed at an average temperature increase rate of 50 ° C./s or more between 550 and 700 ° C., and at a temperature increase rate of 10 ° C./s or less at any temperature between 250 and 550 ° C. Apply the retention process for 1-10 seconds,
The nitriding process, conditions introduced N remains as the nitride layer of the steel sheet surface layer and carried out under the conditions increasing N content is in the range of 0.0050～0.1000Mass%,
A method for producing a grain-oriented electrical steel sheet, wherein a residence time between 300 to 800 ° C. in the heating process of the finish annealing is set to 20 to 150 hours.
In addition to the above component composition, the steel slab further includes Ni: 0.005 to 1.50 mass%, Sn: 0.01 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Cu: 0.00. 01 to 0.50 mass%, Cr: 0.01 to 1.50 mass%, P: 0.00050 to 0.50 mass%, Mo: 0.01 to 0.50 mass%, and Nb: 0.0005 to 0.010 mass% The method for producing a grain-oriented electrical steel sheet according to claim 1, comprising one or more selected from among the above.
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