JP2016047966A - COLD ROLLING METHOD FOR HIGH Si-CONTAINING ORIENTED MAGNETIC STEEL SHEET - Google Patents
COLD ROLLING METHOD FOR HIGH Si-CONTAINING ORIENTED MAGNETIC STEEL SHEET Download PDFInfo
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Abstract
Description
本発明は、主に変圧器の鉄芯として使用される方向性電磁鋼板の冷間圧延性の向上に関するものである。 The present invention relates to improvement of cold rolling property of grain-oriented electrical steel sheets used mainly as iron cores of transformers.
電磁鋼板は、大きく、無方向性電磁鋼板と方向性電磁鋼板に分類される。前者は、主に、モータ、発電機等の回転機器の鉄芯材料として使用され、後者は、主に、変圧器等の静止機器の鉄芯材料として使用されている。 Electrical steel sheets are broadly classified into non-oriented electrical steel sheets and directional electrical steel sheets. The former is mainly used as an iron core material for rotating devices such as motors and generators, and the latter is mainly used as an iron core material for stationary devices such as transformers.
電磁鋼板の電磁気的特性は、機器のエネルギー損失を減じるためには“鉄損が低いこと”、機器の小型化のためには“磁束密度が高いこと”が求められる。近年の省エネルギーの要請に基づき、更なる低鉄損電磁鋼板が求められるようになっている。 As for the electromagnetic characteristics of electrical steel sheets, “low iron loss” is required to reduce energy loss of equipment, and “high magnetic flux density” is required to reduce equipment size. Based on the recent demand for energy saving, a further low iron loss electromagnetic steel sheet has been demanded.
電磁鋼板の鉄損は、非特許文献１に記載されているように、渦電流損と履歴損とからなる。方向性電磁鋼板において、渦電流損を低減するためには、板厚を減じること及び固有抵抗を増すこと（具体的方法の一つとして高合金化、特に高Ｓｉ化）が必要である。履歴損を低減するためには、Goss方位集積度の向上、不純物・内部歪の低減が有効である。
As described in
一般に、鉄鋼材料において、Ｓｉ含有量を増加して高合金化すれば、脆くなることが知られているが、金属材料（特に、鉄鋼材料）の工業生産において、延性（靭性）に影響する因子は、次のように分類することができる。 In general, steel materials are known to become brittle if the Si content is increased to form a high alloy, but factors affecting ductility (toughness) in industrial production of metal materials (especially steel materials) Can be classified as follows.
(A)環境（外的）因子：試験温度、形状（サイズ）、加工（歪）速度等。 (A) Environmental (external) factors: test temperature, shape (size), processing (strain) speed, etc.
(B)母相因子（純粋金属相の物性値、粒内強度）：成分、相、及び／又は、析出物を含む格子欠陥等。 (B) Matrix factor (physical property value of pure metal phase, intragranular strength): Lattice defects including components, phases, and / or precipitates.
(C)多結晶体としての組織因子（粒界強度）：結晶粒径、粒界強度、集合組織等。 (C) Structure factor (grain boundary strength) as a polycrystal: crystal grain size, grain boundary strength, texture, etc.
方向性電磁鋼板の製造では、所要の磁気特性を確保するために、製造条件に係る因子は固定（規定）され、鉄損特性の向上のために、それとはほぼ独立に、Ｓｉ含有量を増加することが行われている。したがって、高Ｓｉ材の冷間圧延性を高めて、工業生産を確実に行うためには、上記(A)〜(C)の因子単独の影響を考慮するではなく、(A)〜(C)の因子が相互に影響し合って得られる効果を見出す必要がある。 In the manufacture of grain-oriented electrical steel sheets, factors related to the manufacturing conditions are fixed (regulated) to ensure the required magnetic properties, and the Si content is increased almost independently to improve the iron loss properties. To be done. Therefore, in order to improve the cold-rollability of the high Si material and reliably perform industrial production, it is not necessary to consider the influence of the above factors (A) to (C) alone, (A) to (C) It is necessary to find out the effect that can be obtained by these factors affecting each other.
例えば、方向性電磁鋼板の製造においては、一次再結晶集合組織の観点から、脱炭焼鈍工程までは、Ｃを０．０２５〜０．０９％程度含有せしめ、冷却速度を確保するので、熱間圧延鋼帯を焼鈍した後の金属組織は、パーライト、ベイナイト、及び、にフェライト相が混在し、その粒径は１０〜５０μｍ程度であるので、結晶粒径の微細化による延性向上効果は望めない。 For example, in the production of grain-oriented electrical steel sheets, from the viewpoint of primary recrystallization texture, until the decarburization annealing step, about 0.025 to 0.09% C is contained and the cooling rate is ensured. The microstructure of the rolled steel strip after annealing is a mixture of pearlite, bainite, and ferrite phase, and the grain size is about 10 to 50 μm. Therefore, the effect of improving the ductility due to the refinement of the crystal grain size cannot be expected. .
さらに、磁気特性は、製品の二次再結晶集合組織・粒径に大きく依存し、それらの適正化には、二次再結晶の二大要素であるインヒビターと一次再結晶集合組織の適正化が重要である。 Furthermore, the magnetic properties greatly depend on the secondary recrystallized texture and grain size of the product. To optimize them, it is necessary to optimize the two major elements of secondary recrystallization, the inhibitor and the primary recrystallized texture. is important.
特に、一次再結晶集合組織は、成分組成等、色々な因子に依存するが、最近、例えば、一次再結晶焼鈍の加熱速度と冷延圧下率の相関関係が見出され、冷間圧延率を大きくすることが試みられている（特許文献１、参照）。それ故、熱間圧延鋼帯の厚みを厚くする傾向にあり、冷間圧延での破断頻度が、Ｓｉ含有量の増大に伴って急増しているのが現実である。 In particular, the primary recrystallization texture depends on various factors such as the component composition, but recently, for example, a correlation between the heating rate of the primary recrystallization annealing and the cold rolling reduction rate has been found, and the cold rolling rate is reduced. An attempt has been made to increase the size (see Patent Document 1). Therefore, there is a tendency to increase the thickness of the hot-rolled steel strip, and it is a reality that the breaking frequency in the cold rolling rapidly increases as the Si content increases.
このような背景の下に、方向性電磁鋼板の分野では、従前、質量で約３％のＳｉを添加していたが、さらに、固有抵抗増加のためにＳｉ含有量を増加する要請が増し、今や、３．２％を超えるようになっている。Ｓｉ含有量が３．２％を超えると、鋼板は著しく脆くなり、冷間圧延性が悪化する。 Against such a background, in the field of grain-oriented electrical steel sheets, about 3% by mass of Si was previously added, but further, the demand for increasing the Si content for increasing the specific resistance increased. Now it is over 3.2%. If the Si content exceeds 3.2%, the steel sheet becomes extremely brittle and the cold rollability deteriorates.
このため、工業生産においては、かなりの困難を省みず圧延を行っているのが現実である。それ故、この課題を解決するための技術開発が求められている。 For this reason, in industrial production, it is a reality that rolling is carried out without considerable difficulty. Therefore, there is a need for technical development to solve this problem.
ところで、３．２％以上のＳｉを含む方向性電磁鋼板の冷間圧延性・生産性を改善するために、従前から、(a)鋼板の表面・端面の品位を向上させる、及び／又は、(b)圧延直前の鋼板の温度を上げる、ことが行われている。 By the way, in order to improve the cold rolling property / productivity of the grain-oriented electrical steel sheet containing 3.2% or more of Si, (a) improving the quality of the surface / end face of the steel sheet, and / or (b) The temperature of the steel plate immediately before rolling is increased.
(a)については、トリミングの刃のメンテナンスを充分に行い、edgeクラック（耳割れ）を低減する方法、さらに、トリミングを高温度で、及び／又は、熱延鋼帯熱処理前に行う方法がある。また、スラブ段階での表面疵の手入れや、熱間圧延での飛込み疵対策で、表面欠陥を低減する方法がある。 As for (a), there is a method of sufficiently maintaining the trimming blade to reduce edge cracks (ear cracks), and a method of performing trimming at a high temperature and / or before heat treatment of a hot-rolled steel strip. . In addition, there are methods for reducing surface defects by taking care of surface defects at the slab stage and by taking measures against flying defects during hot rolling.
(b)については、例えば、冷間圧延前にコイルをホットバス（温水槽）に浸漬する方法等で温度を上げる方法、又は、熱処理後室温まで冷却せずに、比較的高い温度（望ましくは５０℃超）のままで、直ちに冷間圧延を開始する方法等がある。 For (b), for example, a method of increasing the temperature by a method of immersing the coil in a hot bath (hot water tank) before cold rolling, or a relatively high temperature (preferably without cooling to room temperature after heat treatment) There is a method of immediately starting cold rolling while maintaining (over 50 ° C.).
しかし、これらの方法を完璧に行っても、鋼板特有の性質に起因して、破断・割れがしばしば生じる。特に、Ｓｉが３．２％を超えた場合、二パス目の圧延開始時に、破断・割れが多く発生する。 However, even if these methods are carried out perfectly, breakage and cracking often occur due to the unique properties of the steel sheet. In particular, when Si exceeds 3.2%, many fractures and cracks occur at the start of the second pass rolling.
さらに、特許文献２に開示されているように、熱間圧延鋼帯の焼鈍と冷間圧延の間で、鋼帯を温間に保持することは、磁気特性の点から好ましくないので、高Ｓｉ含有の方向性電磁鋼板の製造において、冷間圧延性の向上策が待たれている。 Furthermore, as disclosed in Patent Document 2, it is not preferable from the viewpoint of magnetic properties to keep the steel strip warm between the annealing and cold rolling of the hot-rolled steel strip. In the production of the contained grain-oriented electrical steel sheet, a measure for improving the cold rolling property is awaited.
本発明の目的は、Ｓｉを３．２％以上、４．０％以下含有する方向性電磁鋼板の製造において、所要の磁気特性を確保するために、規定された成分組成、熱処理条件、冷延前厚みを前提に、冷間圧延性を改善することである。 It is an object of the present invention to provide prescribed component composition, heat treatment conditions, cold rolling in order to ensure the required magnetic properties in the production of grain-oriented electrical steel sheets containing Si of 3.2% to 4.0%. It is to improve the cold rolling property on the assumption of the previous thickness.
本発明者らは、冷間圧延での鋼板の破断状況を鋭意調査した。その結果、一パス目の冷間圧延率が大きい場合、二パス目の圧延の開始時において鋼板をリールに巻き付ける際、鋼板に割れが発生し、この割れが起点となって破断が発生することを見出した。 The inventors of the present invention have intensively investigated the breaking state of the steel sheet in cold rolling. As a result, when the cold rolling rate of the first pass is large, when the steel plate is wound around the reel at the start of rolling of the second pass, a crack occurs in the steel plate, and the fracture starts from this crack. I found.
本発明は、上記知見に基づいてなされたもので、その要旨は、次のとおりである。 This invention was made | formed based on the said knowledge, The summary is as follows.
質量％で、Ｃ：０．０２５〜０．０９％、Ｓｉ：３．２〜４．０％、Ｍｎ：０．０８〜０．１０３％、Ａｌ：０．０２２〜０．０３３％、Ｎ：０．００６〜０．００８７％、Ｓｅｑ＝Ｓ＋０，４０６×Ｓｅ：０．０１０〜０，０２７％、Ｓｎ＋Ｓｂ：０．０２〜０．３０％を含有し、残部がＦｅ及び不可避的不純物からなる鋼スラブを熱間圧延し、その後、熱処理を施し、続いて、デスケリーリングを施し、その後、一回以上の冷間圧延を施し、次いで、脱炭・一次再結晶焼鈍、焼鈍分離剤塗布、二次再結晶焼鈍、平坦化焼鈍を施す一連の工程を有する方向性電磁鋼板の製造における冷間圧延方法において、冷間圧延を可逆冷間圧延機で行い、かつ、一パス目の冷間圧延を、局部伸びが２．５％以上となる冷間圧延率で行うことを特徴とする方向性電磁鋼板の冷間圧延方法。 In mass%, C: 0.025 to 0.09%, Si: 3.2 to 4.0%, Mn: 0.08 to 0.103%, Al: 0.022 to 0.033%, N: Steel containing 0.006 to 0.0087%, Seq = S + 0,406 × Se: 0.010 to 0.027%, Sn + Sb: 0.02 to 0.30%, with the balance being Fe and inevitable impurities The slab is hot-rolled, then heat-treated, followed by deskelling, followed by one or more cold rollings, followed by decarburization / primary recrystallization annealing, application of an annealing separator, two In the cold rolling method in the production of grain-oriented electrical steel sheets having a series of steps for performing next recrystallization annealing and flattening annealing, cold rolling is performed with a reversible cold rolling mill, and cold rolling in the first pass is performed. And performing at a cold rolling rate at which the local elongation is 2.5% or more. Cold rolling method of oriented electrical steel sheet.
本発明によれば、Ｓｉ量が３．２％を超える方向性電磁鋼板を可逆冷間圧延機で圧延する際、一パス目の冷間圧延率を適正化するで、鋼板の冷間圧延性を著しく改善することができる。 According to the present invention, when a grain-oriented electrical steel sheet having an Si content exceeding 3.2% is rolled by a reversible cold rolling mill, the cold rolling rate of the steel sheet is optimized by optimizing the cold rolling rate in the first pass. Can be significantly improved.
前述したように、本発明者らは、冷間圧延での鋼板の破断状況を鋭意調査した。その結果、一パス目の冷間圧延率が大きい場合、二パス目の圧延の開始時において鋼板をリールに巻き付ける際、鋼板に割れが発生し、この割れが起点となって破断が発生することを見出した。以下、詳細に説明する。 As described above, the present inventors diligently investigated the breaking state of a steel sheet in cold rolling. As a result, when the cold rolling rate of the first pass is large, when the steel plate is wound around the reel at the start of rolling of the second pass, a crack occurs in the steel plate, and the fracture starts from this crack. I found. Details will be described below.
(X) 本発明者らは、冷間圧延で発生する破断・割れの形態を鋭意調査した。冷間圧延工程は、材料力学的には、(1)円筒形リールへの巻き付け・解き、(2)ロールによる圧下、及び、(3)リールによる張力付与の３要素の有機的な連携で、鋼板を、所定の厚みに減厚する。 (X) The present inventors diligently investigated the form of fracture / cracking that occurs in cold rolling. In terms of material dynamics, the cold rolling process is organically linked by three elements: (1) winding and unwinding on a cylindrical reel, (2) rolling with a roll, and (3) tensioning with a reel. The steel plate is reduced to a predetermined thickness.
まず、本発明の主題である“(1)円筒形リールへの巻き付け”に係る“曲げ加工”について説明する。 First, “bending” related to “(1) winding around a cylindrical reel” which is the subject of the present invention will be described.
一般に、厚みのある金属材料を曲げる場合、外表面では張力が働き、内表面では、圧縮力が働く。板厚をｔ、巻付けリールの直径をＤとすると、鋼帯最表層での歪量ξは、ξ＝ｔ／（Ｄ＋ｔ）である。これは、近似的には、ξ≒ｔ／Ｄ−（ｔ／Ｄ）2であるが、一般に、リール径は、Ｄ＝５０８ｍｍ（２０インチ）の場合が多く、板厚は、ｔ＝１．８〜４．０ｍｍであるので、ｔ≪Ｄとなり、ξ≒ｔ／Ｄとしてよい。 In general, when a thick metal material is bent, a tension acts on the outer surface and a compressive force acts on the inner surface. Assuming that the plate thickness is t and the winding reel diameter is D, the strain amount ξ at the outermost layer of the steel strip is ξ = t / (D + t). This is approximately ξ≈t / D− (t / D) 2 , but generally, the reel diameter is often D = 508 mm (20 inches), and the plate thickness is t = 1. Since it is 8 to 4.0 mm, t << D and ξ≈t / D may be satisfied.
即ち、鋼帯最表層での歪量ξは、板厚ｔに比例して大きくなる。このξの大きさが、材料の降伏歪以上であると、塑性変形が生じ、また、さらに伸び以上であると破断する。この現象は、内表面では、同様な力（歪）が対称的に圧縮として働く。 That is, the strain amount ξ at the outermost layer of the steel strip increases in proportion to the plate thickness t. If the size of this ξ is greater than or equal to the yield strain of the material, plastic deformation occurs, and if it is greater than or equal to elongation, the material breaks. In this phenomenon, on the inner surface, a similar force (strain) acts symmetrically as a compression.
ところで、可逆式冷間圧延機では、左右に夫々１つ以上の円筒形リールを配置し、そのリール間に、圧下スタンドを配置している。したがって、上述の如く、板厚を薄くするか、リール径を大きくすると、ξが小さくなり、破断の可能性が低下する。 By the way, in the reversible cold rolling mill, one or more cylindrical reels are arranged on the left and right, respectively, and a reduction stand is arranged between the reels. Therefore, as described above, when the plate thickness is reduced or the reel diameter is increased, ξ is reduced and the possibility of breakage is reduced.
(Y) 次に、材料そのものの性質につき、通常の鋼材においては、冷間加工度が大きくなると、加工硬化して伸び（靭性・延性）が低下する。この現象は、加工度と硬化度は、単調減少関係にあり、加工の蓄積を考慮すると、指数関数的な関係になる。 (Y) Next, regarding the properties of the material itself, in a normal steel material, when the degree of cold work increases, work hardening and elongation (toughness / ductility) decrease. This phenomenon has a monotonously decreasing relationship between the degree of processing and the degree of hardening, and takes an exponential relationship in consideration of accumulated processing.
このように、材料の圧延性に関して総合的に勘案すると、鋼帯厚みと加工度は、トレードオフ（二律背反）の関係になる。本発明者らが、鋭意検討したところ、冷間圧延工程では、曲げ（鋼帯の厚み因子）のみではなく、鋼材の機械試験値に大きく依存することが判明した。 Thus, when comprehensively considering the rollability of the material, the steel strip thickness and the workability are in a trade-off relationship. As a result of intensive studies by the inventors, it has been found that the cold rolling process greatly depends not only on the bending (steel strip thickness factor) but also on the mechanical test value of the steel material.
次に、本発明者らが見出した知見、即ち、“破断は、一パス目の圧下率が大きい場合において、二パス目の開始時の巻付け割れを起因にして多く発生する”について考察する。 Next, the knowledge found by the present inventors, that is, “fracture occurs frequently due to winding cracks at the start of the second pass when the rolling reduction of the first pass is large”. .
板厚が影響する曲げによる脆化は、板厚に比例し、一方、加工硬化による脆化は、加工度（圧下率）と指数関数的な関係に従う。本発明者らは、この二つの単調現象を最適化する最適点があることを見出した。 The embrittlement due to bending influenced by the plate thickness is proportional to the plate thickness, while the embrittlement due to work hardening follows an exponential relationship with the degree of work (rolling rate). The present inventors have found that there is an optimum point for optimizing these two monotonic phenomena.
図１に、鋼帯厚み及び冷間圧延率と、脆化の程度の関係を概念的に示す。実線は、伸びと冷間圧延率の関係を示し、破線は、鋼帯の厚みと表面の張力の関係を示す。伸びは、冷間圧延率が高いと小さく（脆化）、冷間圧延率が低いと大きい。 FIG. 1 conceptually shows the relationship between the steel strip thickness and the cold rolling rate and the degree of embrittlement. The solid line shows the relationship between elongation and the cold rolling rate, and the broken line shows the relationship between the thickness of the steel strip and the surface tension. The elongation is small (embrittlement) when the cold rolling rate is high, and is large when the cold rolling rate is low.
一方、鋼板表面の張力は、鋼帯の厚みに比例する。この二つの関係の合成で、二パス目の圧延性が規定される。本発明者らは、その合成関数は極小値を有し、その極小点を達成する条件が好ましい条件であることを見出した。 On the other hand, the tension on the steel plate surface is proportional to the thickness of the steel strip. By combining these two relationships, the rolling property of the second pass is defined. The present inventors have found that the composite function has a minimum value, and the condition for achieving the minimum point is a preferable condition.
そして、二パス目の圧延の開始時に割れが多いことに注目して検討した結果、二パス目の板厚がある程度厚いことが必要であることを見出した。そこで、Ｓｉ含有量が異なる方向性電磁鋼板の熱間圧延焼鈍鋼帯について、冷間圧延率と局部伸びの関係を調査した。その結果を図２に示す。図２から、局部伸びが、その指標として重要であることが解る。 As a result of studying that there are many cracks at the start of rolling of the second pass, it was found that the plate thickness of the second pass needs to be somewhat thick. Therefore, the relationship between the cold rolling rate and the local elongation was investigated for hot-rolled annealed steel strips of grain-oriented electrical steel sheets having different Si contents. The result is shown in FIG. It can be seen from FIG. 2 that local growth is important as an indicator.
ここで、Ｓｉの含有量について説明する。なお、以下、成分組成に係る％は、質量％を意味する。 Here, the content of Si will be described. Hereinafter, “%” relating to the component composition means “% by mass”.
Ｓｉ含有量は、質量で３．２％以上とする。３．２％未満では、本発明を適用しなくても、冷間圧延性に大きな問題は生じない。Ｓｉ含有量が４．０％を超えると、冷間圧延以外の工程でも、鋼帯の通板性に課題が生じ、工業生産に適さない。Ｓｉ含有量が３．６％以上、４．０％の場合、本発明を適用すれば、破断率は減少するが、工業生産では限界に近いので、Ｓｉ含有量は、望ましくは３．６％以下である。 Si content shall be 3.2% or more by mass. If it is less than 3.2%, even if the present invention is not applied, no major problem occurs in cold rolling properties. If the Si content exceeds 4.0%, a problem arises in the sheet-passability of the steel strip even in processes other than cold rolling, which is not suitable for industrial production. When the Si content is 3.6% or more and 4.0%, if the present invention is applied, the fracture rate is reduced, but since it is close to the limit in industrial production, the Si content is preferably 3.6%. It is as follows.
本発明は、二次再結晶現象を活用する方向性電磁鋼板の冷間圧延性全般に関するものであるので、インヒビター形成元素（粒成長抑制剤）の種類は規定しない。インヒビター形成元素の量は、公知の技術に依ればよい。 Since the present invention relates to the general cold rolling property of grain-oriented electrical steel sheets utilizing the secondary recrystallization phenomenon, the type of inhibitor forming element (grain growth inhibitor) is not specified. The amount of the inhibitor forming element may be determined by a known technique.
例えば、二次再結晶を良好ならしめるために、Ａｌ、Ｎ、Ｍｎ、Ｓ、Ｓｅ、Ｓｂ、Ｓｎ、Ｂｉ、Ｂ等を、０．００３〜０．０４０％程度、組み合せて添加する。さらに、インヒビターの造り込みは、完全固溶型、充分析出型のどちらでもよい。 For example, in order to improve the secondary recrystallization, Al, N, Mn, S, Se, Sb, Sn, Bi, B and the like are added in combination in an amount of about 0.003 to 0.040%. Furthermore, the inhibitor may be built in either a completely solid solution type or a sufficiently precipitated type.
また、脱炭・一次再結晶後の窒化の有無も問わない。即ち、例えば、特許文献３〜７のいずれかの製造方法にも限定しない。本発明は、方向性電磁鋼板の冷間圧延全般に関して適用できるものでる。
Moreover, the presence or absence of nitriding after decarburization and primary recrystallization does not matter. That is, for example, the manufacturing method is not limited to any one of
Ｓｉ以外の成分を含有する場合は、下記の含有量範囲とすることが好ましい。 When it contains components other than Si, it is preferable to set it as the following content range.
Ｃは、０．０２５％より少ないと一次再結晶集合組織が適切でなくなり、０．０９％を超えると脱炭が困難になり工業生産に適していない。 When C is less than 0.025%, the primary recrystallization texture becomes unsuitable, and when it exceeds 0.09%, decarburization becomes difficult and is not suitable for industrial production.
Ａｌを含有する場合は、酸可溶性ＡｌがＮと結合してＡｌＮを形成し、主に、一次・二次インヒビターとして機能する。酸可溶性ＡｌＮは、窒化前に形成されるものと、窒化後、高温焼鈍時に形成されるものがある。この両方のＡｌＮの量を確保するために、Ａｌは、０．０２２〜０．０３３％が好ましい。０．０３３％を超えると、二次再結晶不良が生じ易くなり、０．０２２％より少ないと、Goss方位集積度が著しく劣化する場合がある。 In the case of containing Al, acid-soluble Al combines with N to form AlN, and mainly functions as a primary / secondary inhibitor. Some acid-soluble AlNs are formed before nitriding, and some are formed during high-temperature annealing after nitriding. In order to ensure the amount of both AlN, Al is preferably 0.022 to 0.033%. If it exceeds 0.033%, secondary recrystallization failure tends to occur, and if it is less than 0.022%, the Goss orientation integration degree may be significantly deteriorated.
後工程での窒化を前提とする場合、インヒビターの造込み方で、Ｎ含有量は異なるが、完全固溶型では０．００６％以下が望ましく、充分析出型では０．００６％以上が望ましい。 When nitriding in the post-process is premised, the content of N varies depending on the method of incorporation of the inhibitor, but 0.006% or less is desirable for the complete solid solution type, and 0.006% or more is desirable for the sufficiently precipitated type.
Ｍｎが０．０３％より少ないと、熱延鋼帯で割れが発生し易く、歩留まりが低下し、二次再結晶が安定しない。完全固溶型の場合、Ｍｎが０．０９％を超えると、ＭｎＳ、ＭｎＳｅが多くなり、固溶の程度が場所により不均一となって、実工業生産における安定生産に問題が生じる。一方、充分析出型の場合は、Ｍｎが０．０８％以上でないと、二次再結晶が安定しない。 If Mn is less than 0.03%, cracks are likely to occur in the hot-rolled steel strip, yield decreases, and secondary recrystallization is not stable. In the case of the complete solid solution type, if Mn exceeds 0.09%, MnS and MnSe increase, and the degree of solid solution becomes uneven depending on the location, causing a problem in stable production in actual industrial production. On the other hand, in the case of a sufficiently precipitated type, secondary recrystallization is not stable unless Mn is 0.08% or more.
Ｓ及びＳｅは、Ｍｎと結合して、インヒビターとして作用し、また、ＡｌＮの析出核としても有用である。完全固溶型の場合、Ｓeq＝Ｓ＋０．４０６×Ｓｅで、０．０１０〜０．０２７％含有することが好ましい。充分析出型の場合、Ｓeqは、０．０１０％以下が好ましい。Ｓeqが規定の範囲外の場合は、二次再結晶が不良になる。 S and Se combine with Mn to act as an inhibitor, and are also useful as AlN precipitation nuclei. In the case of a completely solid solution type, it is preferable that Seq = S + 0.406 × Se, and 0.010 to 0.027% is contained. In the case of a sufficiently precipitated type, Seq is preferably 0.010% or less. When Seq is out of the specified range, secondary recrystallization becomes poor.
Ｓｎ及びＳｂは、一次再結晶集合組織の改善に有効である。また、Ｓｎ及びＳｂは、粒界偏析元素であり、二次再結晶を安定化ならしめ、二次再結晶粒径を小さくする効果がある。Ｓｎ及びＳｂが、合計で０．０２％未満であると、添加効果が極めて小さい。一方、Ｓｎ及びＳｂが、合計で０．３０％を超えると、脱炭焼鈍時に酸化され難くなり、脱炭を著しく阻害し、また、グラス皮膜形成が不十分となる。 Sn and Sb are effective in improving the primary recrystallization texture. Sn and Sb are grain boundary segregation elements, and have the effect of stabilizing secondary recrystallization and reducing the secondary recrystallization grain size. When the total amount of Sn and Sb is less than 0.02%, the effect of addition is extremely small. On the other hand, when Sn and Sb exceed 0.30% in total, it becomes difficult to be oxidized during decarburization annealing, remarkably hinders decarburization, and glass film formation becomes insufficient.
熱間圧延鋼帯の冷間圧延前の焼鈍は必須である。この焼鈍は、通常、９５０〜１１７０℃の間で３０〜２４０秒程度行う。この焼鈍は、所定の磁気特性を得るために必須の焼鈍であり、鋼帯の組織・インヒビターの適正化・均一化が目的である。熱間圧延鋼帯の焼鈍条件は、インヒビターの種類、造込み方法により異なる。具体的には下記の条件である。 Annealing of the hot rolled steel strip before cold rolling is essential. This annealing is usually performed at a temperature between 950 and 1170 ° C. for about 30 to 240 seconds. This annealing is indispensable for obtaining predetermined magnetic characteristics, and is aimed at optimizing and homogenizing the structure and inhibitors of the steel strip. The annealing conditions of the hot-rolled steel strip vary depending on the type of inhibitor and the forming method. Specifically, the conditions are as follows.
(1) 完全固溶型で、ＡｌＮを主なインヒビターとする場合は、後工程の窒化の有無（特許文献４、７等、参照）にかかわらず、下記条件のどちらかである。均熱温度は、インヒビター元素の含有量で規定される。 (1) In the case of a completely solid solution type and AlN as a main inhibitor, the following conditions are satisfied regardless of the presence or absence of nitridation in the subsequent step (see Patent Documents 4, 7, etc.). The soaking temperature is defined by the content of the inhibitor element.
(1a) 一段サイクル：１０５０〜１１７０℃で３０〜２４０秒均熱し、その後、１５℃／秒以上の冷却速度で冷却する。 (1a) One-stage cycle: soaking at 1050 to 1170 ° C. for 30 to 240 seconds, and then cooled at a cooling rate of 15 ° C./second or more.
(1b) 二段サイクル：一段目は、１０５０〜１１７０℃で１５〜８０秒均熱し、その後、８７０〜９７０℃で２０〜１８０秒保定し、その後、１５℃／秒以上の冷却速度で冷却する。 (1b) Two-stage cycle: The first stage is soaked at 1050 to 1170 ° C. for 15 to 80 seconds, then held at 870 to 970 ° C. for 20 to 180 seconds, and then cooled at a cooling rate of 15 ° C./second or more. .
(2) 完全固溶型で、ＡｌＮを主なインヒビターとしない場合（特許文献５等、参照）は、９５０〜１０５０℃で３０〜１８０秒均熱そ、その後、１０℃／秒以上の冷却速度で冷却する。
(2) Completely solid solution type, when AlN is not the main inhibitor (see
(3) ＡｌＮを主なインヒビターとする充分析出窒化型の場合（特許文献６等、参照）は、上記(1a)の条件を適用する。 (3) In the case of a sufficiently precipitated nitriding type using AlN as a main inhibitor (see Patent Document 6, etc.), the above condition (1a) is applied.
このように、インヒビターの種類、造込みに拘わらず、熱間圧延鋼帯の焼鈍は、９５０℃以上の温度で行うので、焼鈍後の金属組織は、特に、鋼板表層部の金属組織は、再結晶して、大きくなり脆化する。 As described above, regardless of the type of inhibitor and the incorporation, the hot-rolled steel strip is annealed at a temperature of 950 ° C. or higher. Crystallizes and becomes large and brittle.
本発明は、この組織の脆化を、インヒビターの種類に拘わらず、熱間圧延鋼帯の焼鈍を行って改善するものである。 The present invention improves this embrittlement by annealing a hot-rolled steel strip regardless of the type of inhibitor.
即ち、方向性電磁鋼板の熱間圧延においては、基本的に、低い巻取り温度で巻き取るので、熱間圧延鋼帯の組織は、圧延組織を残したままの金属組織（結晶組織）で、結晶粒径が小さい組織である。それ故、熱間圧延鋼帯を焼鈍せずに、そのまま、冷間圧延を施すことができる。この場合、Ｓｉ含有量が３．２％を超えていても、特に大きな表面欠陥等が発生しなければ問題はないので、本発明には含まれない。 That is, in the hot rolling of the grain-oriented electrical steel sheet, since the coiling is basically performed at a low coiling temperature, the structure of the hot-rolled steel strip is a metal structure (crystal structure) while leaving the rolled structure, It is a structure with a small crystal grain size. Therefore, cold rolling can be performed as it is without annealing the hot-rolled steel strip. In this case, even if the Si content exceeds 3.2%, there is no problem unless a particularly large surface defect or the like is generated, so it is not included in the present invention.
なお、所謂、二回冷延法なる方向性電磁鋼板の製造方法があるが、これは、熱間圧延鋼帯の焼鈍を省き、熱間圧延、デスケリーング、冷間圧延、中間焼鈍、中間冷間圧延、一次再結晶・脱炭焼鈍、仕上げ焼鈍の工程からなるものである。 In addition, there is a so-called two-time cold rolling method for producing grain-oriented electrical steel sheets, but this eliminates the annealing of hot-rolled steel strip, hot rolling, deskeling, cold rolling, intermediate annealing, intermediate cold It consists of the steps of rolling, primary recrystallization / decarburization annealing, and finish annealing.
この方法において、磁気特性の安定化のために、はじめの冷間圧延の前に熱間圧延鋼帯に焼鈍を施す場合があるが、この場合は、本発明に含まれ、熱間圧延鋼帯に焼鈍を施さない場合は、上述の理由で、本発明に含まれない。 In this method, in order to stabilize the magnetic properties, the hot-rolled steel strip may be annealed before the first cold rolling. In this case, the hot-rolled steel strip is included in the present invention. When annealing is not performed, it is not included in the present invention for the reasons described above.
方向性電磁鋼板の製造においては、磁気特性を確保するために、冷間圧延時に、１５０℃以上に鋼帯を保定する、所謂、“温間圧延によるエージング（パス間時効）”（特許文献８、参照）が適用されている。このため、冷間圧延機は、可逆式冷間圧延機に限られる。上記のような高合金材は、基本的には、可逆式冷間圧延機でないと工業的に生産することができない。 In the production of grain-oriented electrical steel sheets, so-called “aging by warm rolling (aging between passes)” in which steel strips are held at 150 ° C. or higher during cold rolling to ensure magnetic properties (Patent Document 8). , See) has been applied. For this reason, the cold rolling mill is limited to a reversible cold rolling mill. Basically, the high alloy material as described above cannot be industrially produced unless it is a reversible cold rolling mill.
可逆式冷間圧延機としては、旧来の４ｈｉ、６ｈｉ、１２ｈｉ、ゼンジミァ圧延機、ＣＶＣ（クラウン可変制御式）圧延機等を使用することができ、圧延設備の種類に依らない。この場合、スタンド数は、２基までとするが、望ましくは１基である。 As the reversible cold rolling mill, a conventional 4hi, 6hi, 12hi, Sendzimir rolling mill, CVC (variable crown control type) rolling mill or the like can be used, and it does not depend on the type of rolling equipment. In this case, the number of stands is up to two, but preferably one.
圧延機の基数が増えても、冷間圧延自体に問題はないが、パス間における時効効果が少なくなり、また、オフゲージが長くなり歩留が低下するので、方向性電磁鋼板の製造におけるデメリットが大きい。さらに、一回冷間圧延法の場合は、通常、５パス以上で行われ、後半のパスは温間圧延により鋼帯の温度が上昇するので、脆性による圧延性の劣化は起こらない。 Even if the number of rolling mills is increased, there is no problem with cold rolling itself, but the aging effect between passes is reduced, and the off-gauge becomes longer and the yield is lowered, so there are disadvantages in the production of grain-oriented electrical steel sheets. large. Further, in the case of the single cold rolling method, usually, 5 passes or more are performed, and the temperature of the steel strip is increased by warm rolling in the latter half of the pass, so that deterioration of rollability due to brittleness does not occur.
次に、局部伸びについて説明する。鋼板の引張り試験での“全伸び”は、“弾性伸び”と“破断伸び（永久伸び）”に分けられ、さらに、“破断伸び（永久伸び）”は、ほぼ、“一様伸び”と“局部伸び”に分けられる。このうち、延性の指標となるのは、“局部伸び”であり、局部伸びが大きいほど延性が良い。 Next, local elongation will be described. “Total elongation” in the tensile test of steel sheets is divided into “elastic elongation” and “breaking elongation (permanent elongation)”. Furthermore, “breaking elongation (permanent elongation)” is almost equal to “uniform elongation” and “ It is divided into “local growth”. Among these, the index of ductility is “local elongation”, and the greater the local elongation, the better the ductility.
既に説明したように、金属材料は、塑性加工を施すと加工硬化して全伸びが減少し、局部伸びも減少する。局部伸びが２．５％以上となる冷間圧延率を、一パス目の冷間圧延に適用すれば、二パス目の圧延における巻付け割れが著しく低減する。一パス目に適用する冷間圧延率は、主に、Ｓｉ含有量で異なり、Ｓｉ含有量が高いほど、一パス目の冷間圧延率を減少させる必要がある。 As already described, when a metal material is subjected to plastic working, it is work-hardened to reduce the total elongation and local elongation. If the cold rolling rate at which the local elongation is 2.5% or more is applied to the cold rolling of the first pass, winding cracks in the rolling of the second pass are remarkably reduced. The cold rolling rate applied in the first pass is mainly different depending on the Si content, and it is necessary to decrease the cold rolling rate in the first pass as the Si content is higher.
図２に示すように、高Ｓｉ材ほど局部伸びが低下するので、冷間圧延率を低減する。即ち、高Ｓｉ材になれば、一パス目の冷間圧延率をより低減して、一パス目に適用する“局部伸びが２．５％以上となる冷間圧延率”を決定する。 As shown in FIG. 2, since the local elongation decreases as the Si content increases, the cold rolling rate is reduced. That is, if the material is a high Si material, the cold rolling rate in the first pass is further reduced, and the “cold rolling rate at which the local elongation is 2.5% or more” applied in the first pass is determined.
＜実験例＞
本発明に係る実験例について説明する。
<Experimental example>
An experimental example according to the present invention will be described.
図３に、充分析出窒化型の方向性電磁鋼板につき、Ｓｉ含有量別に、局部伸びと、冷間圧延時の巻付け割れ破断率（１０００トン当たりの破断回数）の関係を示す。局部伸び２．５％が、破断率３回／１０００トンに対応する。この破断率は、実生産では、４０コイルに一回の破断になり、この値以下を良好とする。 FIG. 3 shows the relationship between the local elongation and the winding crack breaking rate during cold rolling (the number of breaks per 1000 tons) for each Si content for a sufficiently precipitation-nitrided grain-oriented electrical steel sheet. A local elongation of 2.5% corresponds to a breaking rate of 3 times / 1000 tons. In the actual production, this breakage rate is one break for every 40 coils, and this value or less is considered good.
充分析出窒化型の方向性電磁鋼板は、次のように製造したものである。 A sufficiently precipitation-nitrided grain-oriented electrical steel sheet is manufactured as follows.
Ｓｉ含有量を３．０〜３．７％の範囲で変更し、その他の元素は、Ｃ：０．０６５〜０．０７５％、Ａｌ：０．０２６〜０．０２８５％、Ｎ：０．００７５〜０．００８８％、Ｍｎ：０．０９７〜０．１０３％、Ｓ：０．００５８〜０．００７５％、Ｓｎ：０．０５４〜０．０６７％、残部Ｆｅ及び不可避的不純物からなる溶鋼を溶製し、方向性電磁鋼板スラブとした。 The Si content is changed in the range of 3.0 to 3.7%, and other elements are C: 0.065 to 0.075%, Al: 0.026 to 0.0285%, N: 0.0075. ~ 0.0088%, Mn: 0.097 to 0.103%, S: 0.0058 to 0.0075%, Sn: 0.054 to 0.067%, molten steel consisting of the remainder Fe and inevitable impurities is melted It was made into a grain-oriented electrical steel sheet slab.
上記スラブを１２００℃以下の温度で再加熱して熱間圧延し、２．６ｍｍの熱間圧延鋼帯とした。その後、熱間圧延鋼帯を１１２０℃で２０秒均熱し、その後、９００℃で１００秒保定して、次いで、３０℃／秒の冷却速度で室温までウオータスプレイで冷却した。 The slab was reheated at a temperature of 1200 ° C. or less and hot-rolled to obtain a 2.6 mm hot-rolled steel strip. Thereafter, the hot-rolled steel strip was soaked at 1120 ° C. for 20 seconds, then held at 900 ° C. for 100 seconds, and then cooled by water spray to room temperature at a cooling rate of 30 ° C./second.
焼鈍後の熱間圧延鋼帯の表面のスケールを除去した後、可逆式冷間圧延機で圧延した。冷間圧延に際し、一パス目の冷間圧延圧下率を１５〜４５％の範囲で変化させ、局部伸びを１．５〜７．０％に変化させて冷間圧延を行い、最終製品厚みが０．２２０ｍｍの方向性電磁鋼板とした。この場合、上記鋼帯に、冷間圧延前の予熱は施さなかった。 After removing the scale of the surface of the hot rolled steel strip after annealing, it was rolled with a reversible cold rolling mill. During cold rolling, the cold rolling reduction ratio of the first pass is changed in the range of 15 to 45%, the local elongation is changed to 1.5 to 7.0%, and cold rolling is performed. A 0.220 mm grain-oriented electrical steel sheet was used. In this case, the steel strip was not preheated before cold rolling.
図３から、Ｓｉ含有量が３．６％未満の材料では、局伸びが２．５％以上であると、１０００ｔ当たりの二パス目の圧延時の巻付け割れ破断率が３回以下となり、良好な冷間圧延性を示すことが解る。 From FIG. 3, in the material having an Si content of less than 3.6%, when the local elongation is 2.5% or more, the winding crack breaking rate during the second pass rolling per 1000 t is 3 times or less, It can be seen that good cold rollability is exhibited.
次に、本発明の実施例について説明するが、実施例での条件は、本発明の実施可能性及び効果を確認するために採用した一条件例であり、本発明は、この一条件例に限定されるものではない。本発明は、本発明の要旨を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件を採用し得るものである。 Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
（実施例）
実験例と同様に、充分析出窒化型の方向性電磁鋼板に係る実施例について説明する。
(Example)
As in the experimental example, an example relating to a sufficiently precipitation-nitrided grain-oriented electrical steel sheet will be described.
表１に示す成分組成の鋼スラブを１２００℃以下の温度で再加熱して熱間圧延し、２．６ｍｍの熱間圧延鋼帯とした。その後、熱間圧延鋼帯を１１２０℃で２０秒の均熱し、その後、９００℃で１００秒保定し、次いで、３０℃／秒の冷却速度で室温までウオータスプレイで冷却した。 A steel slab having the composition shown in Table 1 was reheated at a temperature of 1200 ° C. or less and hot-rolled to obtain a 2.6 mm hot-rolled steel strip. Thereafter, the hot-rolled steel strip was soaked at 1120 ° C. for 20 seconds, then maintained at 900 ° C. for 100 seconds, and then cooled by water spray to room temperature at a cooling rate of 30 ° C./second.
焼鈍後の熱間圧延鋼帯の表面のスケールを除去した後、可逆式冷間圧延機で圧延した。冷間圧延に際し、一パス目の冷間圧延圧下率を変化させ、局部伸びを変化させて冷間圧延を行い、最終製品厚みが０．２２０ｍｍの方向性電磁鋼板とした。冷間圧延の際、２パス目に生じる１０００トン当たりの破断頻度を評価した。その結果を表２に示す。 After removing the scale of the surface of the hot rolled steel strip after annealing, it was rolled with a reversible cold rolling mill. During cold rolling, the cold rolling reduction ratio of the first pass was changed and the local elongation was changed to perform cold rolling to obtain a directional electrical steel sheet having a final product thickness of 0.220 mm. During cold rolling, the breaking frequency per 1000 tons generated in the second pass was evaluated. The results are shown in Table 2.
冷間圧延１パス後の局部伸びが２．５％以上である発明例Ｙ１〜Ｙ５は、冷間圧延２パス目に生じる割れ破断頻度が１０００トン当たり３回以下であるが、冷間圧延１パス後の局部伸びが２．５％未満である比較例Ｚ１〜Ｚ４は、割れ・破断頻度が１０００トン当たり３回超である。 Inventive examples Y1 to Y5 having a local elongation of 2.5% or more after one pass of cold rolling have a crack breaking frequency of 3 times or less per 1000 tons in the second pass of cold rolling. In Comparative Examples Z1 to Z4 in which the local elongation after the pass is less than 2.5%, the cracking / breaking frequency is more than 3 times per 1000 tons.
前述したように、本発明によれば、Ｓｉ量が３．２％を超える方向性電磁鋼板を可逆冷間圧延機で圧延する際、一パス目の冷間圧延率を適正化するで、鋼板の冷間圧延性を著しく改善することができる。その結果、方向性電磁鋼板の製造において、冷間圧延での生産性を向上させることができるので、本発明は、電磁鋼板製造産業において利用可能性が高いものである。 As described above, according to the present invention, when a grain-oriented electrical steel sheet having an Si content exceeding 3.2% is rolled by a reversible cold rolling mill, the cold rolling rate of the first pass is optimized, and the steel sheet The cold rolling property of can be remarkably improved. As a result, in the production of grain-oriented electrical steel sheets, productivity in cold rolling can be improved, so that the present invention has high applicability in the electrical steel sheet manufacturing industry.
Claims (1)
Ｃ ：０．０２５〜０．０９％、
Ｓｉ：３．２〜４．０％、
Ｍｎ：０．０８〜０．１０３％、
Ａｌ：０．０２２〜０．０３３％、
Ｎ ：０．００６〜０．００８７％、
Ｓｅｑ＝Ｓ＋０，４０６×Ｓｅ：０．０１０〜０，０２７％、
Ｓｎ＋Ｓｂ：０．０２〜０．３０％
を含有し、残部がＦｅ及び不可避的不純物からなる鋼スラブを熱間圧延し、その後、熱処理を施し、続いて、デスケリーリングを施し、その後、一回以上の冷間圧延を施し、次いで、脱炭・一次再結晶焼鈍、焼鈍分離剤塗布、二次再結晶焼鈍、平坦化焼鈍を施す一連の工程を有する方向性電磁鋼板の製造における冷間圧延方法において、冷間圧延を可逆冷間圧延機で行ない、かつ、一パス目の冷間圧延を、局部伸びが２．５％以上となる冷間圧延率で行うことを特徴とする方向性電磁鋼板の冷間圧延方法。 % By mass
C: 0.025 to 0.09%,
Si: 3.2 to 4.0%,
Mn: 0.08 to 0.103%,
Al: 0.022 to 0.033%,
N: 0.006 to 0.0087%,
Seq = S + 0,406 × Se: 0.010-0,027%,
Sn + Sb: 0.02 to 0.30%
A steel slab comprising Fe and the balance of inevitable impurities, followed by heat treatment, followed by deskelling, followed by one or more cold rollings, and then Cold rolling is reversible cold rolling in the cold rolling method in the production of grain-oriented electrical steel sheets having a series of steps of decarburization / primary recrystallization annealing, annealing separator coating, secondary recrystallization annealing, and flattening annealing. A cold rolling method for grain-oriented electrical steel sheets, characterized in that the cold rolling in the first pass is performed at a cold rolling rate at which the local elongation is 2.5% or more.
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| JPS59123712A (en) * | 1982-12-29 | 1984-07-17 | Kawasaki Steel Corp | Cold rolling method of electromagnetic steel sheet and its installation |
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