JP4265508B2 - Non-oriented electrical steel sheet for rotor and manufacturing method thereof - Google Patents
Non-oriented electrical steel sheet for rotor and manufacturing method thereof Download PDFInfo
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- 229910000565 Non-oriented electrical steel Inorganic materials 0.000 title claims description 36
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 229910000831 Steel Inorganic materials 0.000 claims description 116
- 239000010959 steel Substances 0.000 claims description 116
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
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- Manufacturing Of Steel Electrode Plates (AREA)
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Description
本発明は、電気自動車、ハイブリッド自動車の駆動モータ、ロボット、工作機械などのサーボモータといった高効率モータの回転子に用いられる無方向性電磁鋼板およびその製造方法に関する。特に、高速回転する永久磁石埋め込み式モータの回転子として好適な優れた機械特性と磁気特性とを兼ね備え、さらにカシメ性と表面性状とに優れた無方向性電磁鋼板およびその製造方法に関する。 The present invention relates to a non-oriented electrical steel sheet used for a rotor of a high-efficiency motor such as a drive motor for an electric vehicle or a hybrid vehicle, a servo motor for a robot, a machine tool, and the like, and a method for manufacturing the same. In particular, the present invention relates to a non-oriented electrical steel sheet having excellent mechanical characteristics and magnetic characteristics suitable as a rotor of a permanent magnet embedded motor that rotates at high speed, and having excellent caulking properties and surface properties, and a method for producing the same.
近年の地球環境問題の高まりから、多くの分野において省エネルギー、環境対策技術が進展している。自動車分野も例外ではなく、排ガス低減、燃費向上技術が急速に進歩している。電気自動車およびハイブリッド自動車はこれらの技術の集大成といっても過言ではなく、自動車駆動モータ（以下、単に「駆動モータ」ともいう。）の性能が自動車性能を大きく左右する。 Due to the recent increase in global environmental problems, energy conservation and environmental countermeasure technologies have been developed in many fields. The automobile field is no exception, and technologies for reducing exhaust gas and improving fuel efficiency are advancing rapidly. It is no exaggeration to say that electric vehicles and hybrid vehicles are the culmination of these technologies, and the performance of automobile drive motors (hereinafter also simply referred to as “drive motors”) greatly affects the performance of automobiles.
駆動モータの多くは永久磁石を用いており、巻き線を施した固定子（ステータ）部分と永久磁石を配置した回転子（ロータ）部分とから構成される。最近では永久磁石を回転子内部に埋め込んだ形状（永久磁石埋め込み型モータ；ＩＰＭモータ）が主流となっている。また、パワーエレクトロニクス技術の進展により回転数は任意に制御可能であり、高速化傾向にある。したがって、鉄心素材は商用周波数（５０〜６０Ｈｚ）以上の高周波数域で励磁される割合が高まっており、商用周波数での磁気特性のみでなく、４００Ｈｚ〜数ｋＨｚでの磁気特性改善が要求されるようになってきた。また、回転子は高速回転時の遠心力のみならず回転数変動にともなう応力変動を常時うけることから、回転子の鉄心素材には機械特性も要求されている。特に、ＩＰＭモータの場合には複雑な回転子形状を有することから、回転子用の鉄心材料には応力集中を考慮して遠心力ならびに応力変動に耐えうるだけの機械特性が必要となる。また、ロボット、工作機械用のサーボモータ分野でも、駆動モータと同様に回転数の高速化が今後進行していくと予測される。 Many drive motors use permanent magnets, and are composed of a stator (stator) portion provided with windings and a rotor (rotor) portion provided with permanent magnets. Recently, a shape in which a permanent magnet is embedded in a rotor (permanent magnet embedded motor; IPM motor) has become mainstream. Further, with the advancement of power electronics technology, the rotational speed can be arbitrarily controlled, and there is a tendency to increase the speed. Therefore, the rate at which the iron core material is excited in a high frequency range higher than the commercial frequency (50 to 60 Hz) is increased, and not only the magnetic characteristic at the commercial frequency but also the improvement of the magnetic characteristic at 400 Hz to several kHz is required. It has become like this. In addition, since the rotor is constantly subjected not only to centrifugal force during high-speed rotation but also to stress fluctuations associated with fluctuations in the rotational speed, the rotor core material is also required to have mechanical characteristics. In particular, since the IPM motor has a complicated rotor shape, the core material for the rotor needs to have mechanical characteristics sufficient to withstand centrifugal force and stress fluctuation in consideration of stress concentration. Also, in the field of servo motors for robots and machine tools, it is predicted that the rotation speed will increase in the same way as drive motors.
従来、駆動モータの固定子は主に打ち抜き加工した無方向性電磁鋼板の積層により製造されていたが、回転子はロストワックス鋳造法あるいは焼結法などにより製造されることもあった。これは固定子には優れた磁気特性が、回転子には堅牢な機械特性が要求されることによる。しかしながら、モータ性能は回転子−固定子間のエアギャップに大きく影響されるため、上述の回転子では精密加工の必要性が生じ、鉄心製造コストが大幅に増加するという問題があった。コスト削減の観点からは、打ち抜き加工した電磁鋼板を使用すればよいが、回転子に必要な磁気特性と機械特性とを兼備した無方向性電磁鋼板は見出されていないのが現状であった。 Conventionally, the stator of the drive motor has been manufactured mainly by stacking non-oriented electrical steel sheets that have been stamped, but the rotor has also been manufactured by a lost wax casting method or a sintering method. This is because the stator requires excellent magnetic properties and the rotor requires robust mechanical properties. However, since the motor performance is greatly influenced by the air gap between the rotor and the stator, the above-described rotor has a need for precision machining, and there is a problem that the manufacturing cost of the iron core is greatly increased. From the viewpoint of cost reduction, it is only necessary to use a punched electrical steel sheet, but the current situation is that no non-oriented electrical steel sheet having both the magnetic and mechanical properties necessary for the rotor has been found. .
さらに、打ち抜き加工した電磁鋼板を積層する際の作業効率の観点からはカシメ性に優れていることが要求され、鉄心における鋼板の占積率を増加するためには電磁鋼板の表面性状が極めて重要となる。そこで、上述した磁気特性や機械特性に加えて、カシメ性および表面性状への要請も満足する電磁鋼板が強く求められている。 Furthermore, from the viewpoint of work efficiency when stacking punched electrical steel sheets, it is required to have excellent caulking properties, and the surface properties of the electrical steel sheets are extremely important for increasing the space factor of the steel sheets in the iron core. It becomes. Therefore, in addition to the magnetic characteristics and mechanical characteristics described above, there is a strong demand for electrical steel sheets that satisfy the requirements for caulking properties and surface properties.
優れた機械特性を有する電磁鋼板としては、例えば特許文献１に、３．５〜７％のＳｉに加えて、Ｔｉ，Ｗ，Ｍｏ，Ｍｎ，Ｎｉ，ＣｏおよびＡｌのうちの１種または２種以上を２０％を超えない範囲で含有する鋼板が提案されている。この方法では鋼の強化機構として固溶強化を利用している。しかしながら、固溶強化の場合には冷間圧延母材も同時に高強度化されるため冷間圧延が困難であり、またこの方法においては温間圧延という特殊工程が必須であることから、生産性向上や歩留まり向上など改善の余地がある。 As an electrical steel sheet having excellent mechanical properties, for example, in Patent Document 1, in addition to 3.5 to 7% Si, one or two of Ti, W, Mo, Mn, Ni, Co and Al are used. Steel sheets containing the above in a range not exceeding 20% have been proposed. In this method, solid solution strengthening is used as a steel strengthening mechanism. However, in the case of solid solution strengthening, the cold rolled base metal is also strengthened at the same time, so cold rolling is difficult, and in this method, a special process called warm rolling is indispensable. There is room for improvement such as improvement and yield improvement.
また、特許文献２には、２．０〜３．５％のＳｉ、０．１〜６．０％のＭｎに加えてＢおよび多量のＮｉを含有し、結晶粒径が３０μｍ以下である鋼板が提案されている。この方法では鋼の強化機構として固溶強化と結晶粒径微細化による強化とを利用している。しかしながら、結晶粒微細化による強化は比較的効果が小さいため、特許文献２の実施例に示されるようにＳｉを３．０％程度含有させた上に高価なＮｉを多量に含有させることが必須であり、冷間圧延時に割れが多発するという問題や、合金コスト増加という課題が残っている。 Patent Document 2 discloses a steel sheet containing B and a large amount of Ni in addition to 2.0 to 3.5% Si and 0.1 to 6.0% Mn, and having a crystal grain size of 30 μm or less. Has been proposed. In this method, solid solution strengthening and strengthening by refinement of crystal grain size are used as the strengthening mechanism of steel. However, strengthening by grain refinement is relatively ineffective, so it is essential to contain a large amount of expensive Ni in addition to about 3.0% Si as shown in the example of Patent Document 2. However, the problem of frequent cracking during cold rolling and the problem of increased alloy costs remain.
さらに、特許文献３および特許文献４には、２．０〜４．０％のＳｉに加えてＮｂ，Ｚｒ，Ｂ，ＴｉまたはＶなどを含有する鋼板が提案されている。これらの方法ではＳｉによる固溶強化に加えてＮｂ，Ｚｒ，ＴｉまたはＶの析出物による析出強化を利用している。しかしながら、このような析出物による強化は比較的効果が小さいため、特許文献３および特許文献４の実施例に示されるようにＳｉを３．０％程度させる必要があり、特に特許文献３の方法では高価なＮｉを多量に含有させることも必要となる。そのため冷間圧延時に割れが多発するという問題や、合金コスト増加という課題が残っている。 Furthermore, Patent Documents 3 and 4 propose steel sheets containing Nb, Zr, B, Ti, V, or the like in addition to 2.0 to 4.0% Si. In these methods, precipitation strengthening by precipitates of Nb, Zr, Ti or V is used in addition to solid solution strengthening by Si. However, since such strengthening by precipitates is relatively ineffective, it is necessary to make Si about 3.0% as shown in Examples of Patent Document 3 and Patent Document 4, and in particular, the method of Patent Document 3 Then, it is necessary to contain a large amount of expensive Ni. Therefore, the problem that cracks frequently occur during cold rolling and the problem of increased alloy costs remain.
また、特許文献５および特許文献６には、ＳｉおよびＡｌを０．０３〜０．５％と制限した上でＴｉ，ＮｂおよびＶ、あるいはＰおよびＮｉを含有する鋼板がそれぞれ提案されている。これらの方法では、Ｓｉによる固溶強化よりも炭化物の析出強化およびＰの固溶強化を利用している。しかしながら、これらの方法では、後述する駆動モータの回転子として必要な強度レベルを確保することができないという問題や、特許文献５および特許文献６の実施例に示されているように２．０％以上のＮｉ含有が必須であり、合金コストが高いという問題がある。 Patent Documents 5 and 6 propose steel sheets containing Ti, Nb and V, or P and Ni, respectively, after limiting Si and Al to 0.03 to 0.5%. In these methods, precipitation precipitation strengthening of carbide and solid solution strengthening of P are used rather than solid solution strengthening by Si. However, in these methods, there is a problem that a strength level necessary for a rotor of a drive motor, which will be described later, cannot be ensured, and as shown in Examples of Patent Documents 5 and 6, 2.0% There is a problem that the above Ni content is essential and the alloy cost is high.
さらに、特許文献７には、Ｓｉ：１．６〜２．８％であって、結晶粒径、内部酸化層厚み、および降伏点を限定した永久磁石埋め込み型モータ用無方向性電磁鋼板が提案されている。しかしながら、この方法による鋼板の降伏点では、高速回転する駆動モータの回転子としては強度不足である。 Further, Patent Document 7 proposes a non-oriented electrical steel sheet for embedded permanent magnet motors with Si: 1.6 to 2.8% and limited crystal grain size, internal oxide layer thickness, and yield point. Has been. However, at the yield point of the steel plate by this method, the strength is insufficient as a rotor of a drive motor that rotates at high speed.
また、ＪＩＳ Ｃ ２５５２に規定の無方向性電磁鋼板としては、いわゆる高グレード無方向性電磁鋼板（３５Ａ２１０，３５Ａ２３０など）が最も合金含有量が高く高強度であるが、機械特性レベルは上述の高張力電磁鋼板を下回っており高速回転する駆動モータの回転子としては強度不足である。 As non-oriented electrical steel sheets specified in JIS C 2552, so-called high grade non-oriented electrical steel sheets (35A210, 35A230, etc.) have the highest alloy content and high strength, but the mechanical property level is high as described above. The strength is insufficient as a rotor of a drive motor that is below the tension electromagnetic steel sheet and rotates at high speed.
上述したように、無方向性電磁鋼板の高強度化手法として従来から提案されている固溶強化および析出強化では冷間圧延の母材も強化されてしまうことから冷間圧延時に割れが多発し、結晶粒微細化による高強度化ではその強化量が不十分であるため回転子用途として実用に耐える強度を実現することができない。また、本発明者らは変態強化についても検討を行ったが、変態強化ではマルテンサイト等の変態組織が鉄損を著しく増大させることが判明し、回転子用途として実用に耐える磁気特性を実現することができない。 As mentioned above, the solid solution strengthening and precipitation strengthening conventionally proposed as methods for increasing the strength of non-oriented electrical steel sheets also strengthens the base material of cold rolling, so cracks frequently occur during cold rolling. In the case of increasing the strength by refining crystal grains, the amount of strengthening is insufficient, so that it is not possible to realize a strength that can be practically used as a rotor. In addition, the present inventors have also examined transformation strengthening, but it has been found that the transformation structure such as martensite significantly increases iron loss in transformation strengthening, and realizes magnetic characteristics that can be practically used as a rotor application. I can't.
本発明は、上記問題点に鑑みてなされたものであり、高速回転するモータの回転子として必要な優れた機械特性と磁気特性とを兼備し、さらにカシメ性および表面性状にも優れる無方向性電磁鋼板およびその製造方法を提供することを主目的とする。 The present invention has been made in view of the above problems, and has non-directionality that combines excellent mechanical properties and magnetic properties necessary for a rotor of a motor that rotates at a high speed, and also has excellent caulking properties and surface properties. The main object is to provide an electromagnetic steel sheet and a method for producing the same.
本発明者らは、回転子に適した磁気特性と機械特性とを兼ね備えた無方向性電磁鋼板の有するべき鋼組織について種々検討を行い、従来全く検討されていなかった加工硬化による高強度化に着目した。そして、加工時に導入される転位は鉄損に及ぼす影響が比較的小さいとの新知見を得て、従来の無方向性電磁鋼板の技術認識である完全な再結晶フェライト組織とは全く逆の技術思想に立脚して、鋼板の組織を多量の転位が残存した加工組織および回復状態の組織（以下、「回復組織」と称する。）とすることにより、回転子に要求される磁気特性および機械特性が得られることを見出した。さらには、均熱処理を行うことによりカシメ性が向上し、Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量を所定の範囲とすることにより良好な表面性状が得られることを見出し、本発明を完成させた。 The present inventors have made various studies on the steel structure that should be possessed by the non-oriented electrical steel sheet having both magnetic properties and mechanical properties suitable for rotors, and have achieved high strength by work hardening that has not been studied at all. Pay attention. The new knowledge that dislocations introduced during processing have a relatively small effect on iron loss has been obtained, and this technology is completely the opposite of the completely recrystallized ferrite structure that is the technical recognition of conventional non-oriented electrical steel sheets. Based on the idea, the magnetic structure and mechanical characteristics required for the rotor are obtained by making the structure of the steel sheet a processed structure in which a large amount of dislocations remain and a recovered structure (hereinafter referred to as “recovered structure”). It was found that can be obtained. Furthermore, it has been found that the caulking property is improved by performing a soaking treatment, and that a good surface property can be obtained by setting the contents of Nb, Zr, Ti and V within a predetermined range, and the present invention has been completed. .
すなわち、本発明は、質量％で、Ｃ：０．０４％以下、Ｓｉ：１．０％以上３．５％以下、Ｍｎ：０．１％以上２．５％以下、Ａｌ：０．２％以上２．５％以下、Ｓｉ＋Ａｌ：２．０％以上５．０％以下、Ｐ：０．２％以下、Ｓ：０．０３％以下、Ｎ：０．００５％以下を含有し、Ｎｂ、Ｔｉ、ＺｒおよびＶからなる群から選択される少なくとも１種の元素を、下記式（１）を満足する範囲で含有し、残部が実質的にＦｅおよび不純物からなり、再結晶部分の面積比率が２５％未満、伸びが２％以上であることを特徴とする回転子用無方向性電磁鋼板を提供する。
０＜Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−(Ｃ／１２＋Ｎ／１４)＜５×１０−３ （１）
（ここで、式（１）中、Ｎｂ、Ｚｒ、Ｔｉ、Ｖ、ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。）
That is, the present invention is, in mass%, C: 0.04% or less, Si: 1.0% to 3.5%, Mn: 0.1% to 2.5%, Al: 0.2% 2.5% or less, Si + Al: 2.0% to 5.0%, P: 0.2% or less, S: 0.03% or less, N: 0.005% or less, Nb, Ti And at least one element selected from the group consisting of Zr and V in a range satisfying the following formula (1), the balance being substantially composed of Fe and impurities, and the area ratio of the recrystallized portion being 25 The non-oriented electrical steel sheet for rotors is provided, characterized in that the elongation is less than 2% and the elongation is 2% or more.
0 <Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14) <5 × 10 −3 (1)
(Here, in the formula (1), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
本発明においては、再結晶部分の面積比率を適正に制御し、多くの転位が残存した鋼組織とすることにより強度を高めることができるので、機械特性および磁気特性が良好な回転子用無方向性電磁鋼板とすることができる。また、伸びを上記範囲とすることによりカシメ性を向上させることができる。さらに、上述した鋼組成とすることにより優れた表面性状を得ることができる。これにより、上述した回転子に要求される磁気特性および機械特性のみならず、カシメ性および表面性状をも満足するものとすることができる。 In the present invention, the area ratio of the recrystallized portion is appropriately controlled, and the strength can be increased by making the steel structure in which many dislocations remain. Steel sheet. Further, the caulking property can be improved by setting the elongation within the above range. Furthermore, excellent surface properties can be obtained by using the steel composition described above. As a result, not only the magnetic properties and mechanical properties required for the rotor described above, but also the caulking properties and the surface properties can be satisfied.
本発明は、また、上述した鋼組成を備える鋼塊または鋼片に熱間圧延を施す熱間圧延工程と、上記熱間圧延工程により得られた熱間圧延鋼板に一回または中間焼鈍をはさむ二回以上の冷間圧延を施す冷間圧延工程と、上記冷間圧延工程により得られた冷間圧延鋼板を５００℃以上７８０℃以下で均熱する均熱処理工程とを有することを特徴とする回転子用無方向性電磁鋼板の製造方法を提供する。 The present invention also includes a hot rolling process in which hot rolling is performed on a steel ingot or steel slab having the steel composition described above, and a hot rolled steel sheet obtained by the hot rolling process is subjected to one time or intermediate annealing. It has a cold rolling process for performing cold rolling twice or more and a soaking process for soaking the cold-rolled steel sheet obtained by the cold rolling process at 500 ° C. or more and 780 ° C. or less. A method for producing a non-oriented electrical steel sheet for a rotor is provided.
本発明においては、均熱処理での均熱温度を所定の範囲とすることにより、再結晶を抑制して、所定の板厚への加工の際に導入された転位を消滅させることなく残存させた回復組織を主体とすることができるので、鋼板の強度を高めることができる。さらに、均熱処理での均熱温度を所定の範囲とすることにより、伸びが適正範囲に制御されるためカシメ性も良好となる。また本発明によれば、冷間圧延に供する鋼板、すなわち冷間圧延の母材の高強度化を伴うことがないので、冷間圧延時の破断を抑制することができる。さらにまた、所定の鋼組成を備える鋼塊または鋼片を用いることにより、機械特性および磁気特性のみならず表面性状も良好な回転子用無方向性電磁鋼板を製造することができる。 In the present invention, by setting the soaking temperature in the soaking process within a predetermined range, recrystallization is suppressed and dislocations introduced during processing to a predetermined plate thickness are left without disappearing. Since the recovery structure can be the main component, the strength of the steel sheet can be increased. Furthermore, by setting the soaking temperature in the soaking process to a predetermined range, the elongation is controlled to an appropriate range, so that the caulking property is also improved. Further, according to the present invention, since there is no increase in strength of the steel sheet used for cold rolling, that is, the base material of cold rolling, it is possible to suppress breakage during cold rolling. Furthermore, by using a steel ingot or steel slab having a predetermined steel composition, it is possible to produce a non-oriented electrical steel sheet for a rotor that has good surface properties as well as mechanical and magnetic properties.
また、本発明の回転子用無方向性電磁鋼板の製造方法は、上記熱間圧延鋼板に熱延板焼鈍を施す熱延板焼鈍工程を有していてもよい。熱延板焼鈍を施すことにより、鋼板の延性が向上し冷間圧延工程での破断を抑制でき、さらには優れた表面性状を得ることができるからである。 Moreover, the manufacturing method of the non-oriented electrical steel sheet for rotors of this invention may have the hot-rolled sheet annealing process which performs hot-rolled sheet annealing to the said hot-rolled steel sheet. This is because by performing hot-rolled sheet annealing, the ductility of the steel sheet is improved, breakage in the cold rolling process can be suppressed, and excellent surface properties can be obtained.
本発明によれば、高速回転するモータの回転子として必要な優れた機械特性と磁気特性とを兼備し、さらにはカシメ性および表面性状にも優れた無方向性電磁鋼板を、多大なコスト増加を招くことなく安定に製造することが可能である。そのため、電気自動車やハイブリッド自動車の駆動モータ分野などにおける回転数の高速化に十分対応でき、その工業的価値は極めて高い。 According to the present invention, a non-oriented electrical steel sheet having excellent mechanical properties and magnetic properties necessary for a rotor of a motor that rotates at a high speed, and also having excellent caulking properties and surface properties is greatly increased in cost. It is possible to manufacture stably without incurring. Therefore, it can sufficiently cope with the increase in the rotational speed in the field of drive motors of electric vehicles and hybrid vehicles, and its industrial value is extremely high.
本発明で言及する回転子に用いる電磁鋼板として必要な特性とは、第一に機械特性であり、降伏点、および引張強さを指す。これは高速回転時の回転子の変形抑制のみならず、応力変動に起因する疲労破壊抑制を目的としている。近年の電気自動車、ハイブリッド自動車の駆動モータでは、回転子は２５０ＭＰａ程度の平均応力下で１５０ＭＰａ程度の応力振幅を受ける。したがって、変形抑制の観点から降伏点は４００ＭＰａ以上、安全率を考慮すると５００ＭＰａ以上を満たす必要がある。好ましくは５５０ＭＰａ以上である。また、上述の応力状態での疲労破壊を抑制する観点から引張強さは５５０ＭＰａ以上、安全率を考慮すると６００ＭＰａ、好ましくは７００ＭＰａ以上必要である。 The characteristics necessary for the electrical steel sheet used for the rotor referred to in the present invention are mechanical characteristics, which are yield point and tensile strength. This is intended to suppress not only the deformation of the rotor during high-speed rotation but also the fatigue failure caused by stress fluctuations. In drive motors of recent electric vehicles and hybrid vehicles, the rotor receives a stress amplitude of about 150 MPa under an average stress of about 250 MPa. Therefore, from the viewpoint of suppressing deformation, the yield point must be 400 MPa or more, and considering the safety factor, it is necessary to satisfy 500 MPa or more. Preferably it is 550 MPa or more. Further, from the viewpoint of suppressing fatigue failure in the above-described stress state, the tensile strength is 550 MPa or more, and 600 MPa, preferably 700 MPa or more is necessary in consideration of the safety factor.
また、回転子に用いる電磁鋼板として必要な第二の特性は磁束密度である。ＩＰＭモータのようにリラクタンストルクを活用するモータでは回転子に用いられる材質の磁束密度もトルクに影響を及ぼし、磁束密度が低いと所望のトルクを得られない。 The second characteristic necessary for the electromagnetic steel sheet used for the rotor is the magnetic flux density. In a motor that utilizes reluctance torque, such as an IPM motor, the magnetic flux density of the material used for the rotor also affects the torque. If the magnetic flux density is low, a desired torque cannot be obtained.
さらに、回転子に用いる電磁鋼板として必要な第三の特性は鉄損である。鉄損は不可逆な磁壁移動に起因するヒステリシス損失と、磁化変化に起因して発生する渦電流によるジュール熱（渦電流損失）とから構成され、電磁鋼板の鉄損はこれらの総和であるトータルの鉄損で評価される。回転子で発生する損失はモータ効率そのものを支配するものではないが、回転子の損失すなわち発熱により永久磁石が減磁するため、間接的にモータ性能を劣化させる。したがって、回転子に使用される材質の鉄損値の上限は永久磁石の耐熱温度の観点から決定され、固定子に使用される材質よりも鉄損値が高くとも許容されると想起される。 Furthermore, the third characteristic necessary for the electromagnetic steel sheet used for the rotor is iron loss. Iron loss consists of hysteresis loss due to irreversible domain wall motion and Joule heat (eddy current loss) due to eddy currents caused by magnetization changes. The iron loss of electrical steel sheets is the sum of these totals. It is evaluated by iron loss. Although the loss generated in the rotor does not dominate the motor efficiency itself, the permanent magnet is demagnetized due to the loss of the rotor, that is, heat generation, which indirectly deteriorates the motor performance. Accordingly, it is recalled that the upper limit of the iron loss value of the material used for the rotor is determined from the viewpoint of the heat resistance temperature of the permanent magnet, and is allowed even if the iron loss value is higher than the material used for the stator.
また、回転子に用いる電磁鋼板として必要な第四の特性は表面性状である。表面性状に劣る場合には、積層した場合の鋼板の占積率が低下するため、モータ効率が低下する。特にリラクタンストルクを活用するＩＰＭモータにおいて低下が顕著となる。 The fourth characteristic necessary for the electromagnetic steel sheet used for the rotor is the surface property. When the surface properties are inferior, the space factor of the steel plates when they are laminated decreases, so that the motor efficiency decreases. In particular, the decrease is significant in an IPM motor that utilizes reluctance torque.
さらに、回転子に用いる電磁鋼板として必要な第五の特性はカシメ性である。駆動モータの鉄心はカシメではなく溶接により固着されることもあるが、カシメにより一体化したものを溶接する場合が多く、カシメ性は鉄心の製造効率の観点から極めて重要な特性である。 Furthermore, the fifth characteristic necessary for the electrical steel sheet used for the rotor is caulking. The iron core of the drive motor may be fixed not by caulking but by welding, but the one integrated by caulking is often welded, and caulking is an extremely important characteristic from the viewpoint of iron core manufacturing efficiency.
本発明者らはこれらの特性を満足する無方向性電磁鋼板について鋭意検討を行った。まず、上述の着想をもとに回転子に適した磁気特性と機械特性とを兼ね備えた無方向性電磁鋼板の有するべき鋼組織について種々検討を行った。その結果、固溶強化および析出強化では冷間圧延母材も高強度化されるため冷間圧延時の破断が避けられないこと、結晶粒微細化のみでは要求レベルの機械特性を達成できないこと、および、マルテンサイト等の変態組織では鉄損が著しく増大することが判明した。さらに、強化機構として加工硬化について検討した結果、加工時に導入される転位は鉄損に及ぼす影響が比較的小さいことが判明した。これらの結果から、従来の無方向性電磁鋼板の技術認識である完全な再結晶フェライト組織とは全く逆に、多量の転位が残存した加工組織および回復組織とすることにより、回転子に要求される磁気特性と機械特性とが達成されるとの知見を得た。 The present inventors diligently studied non-oriented electrical steel sheets that satisfy these characteristics. First, based on the above-mentioned idea, various studies were made on the steel structure that the non-oriented electrical steel sheet having both magnetic characteristics and mechanical characteristics suitable for the rotor should have. As a result, the strength of the cold-rolled base metal is strengthened by solid solution strengthening and precipitation strengthening, so it is inevitable to break during cold rolling. And it turned out that iron loss increases remarkably in transformation structures, such as martensite. Furthermore, as a result of examining work hardening as a strengthening mechanism, it was found that dislocations introduced during processing have a relatively small effect on iron loss. From these results, it is required for the rotor to have a processed structure and a recovered structure in which a large amount of dislocations remain, contrary to the complete recrystallized ferrite structure that is the technical recognition of conventional non-oriented electrical steel sheets. It was found that the magnetic properties and mechanical properties can be achieved.
加工組織および回復組織は、所定の板厚への加工時に導入された転位を均熱処理時に消滅させることなく、あるいは消滅を抑制して残存させることにより得られる。そのため、固溶強化あるいは析出強化主体の従来技術とは異なり、冷間圧延母材の高強度化を伴うことなく高強度化が可能であり、冷間圧延時の破断を抑制できる。このような加工組織および回復組織を得るためには、通常冷間圧延後に行われる均熱処理での再結晶を抑制することが必要である。また、均熱処理時に再結晶を抑制するには、Ｎｂ，Ｚｒ，ＴｉおよびＶを含有させることが必要である。ただし、Ｎｂ，Ｚｒ，ＴｉおよびＶを過度に含有させると表面性状が劣化するため、Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量の適正化が重要となる。多量の転位を残存させることのみを目的とすれば、所定の板厚への加工後に均熱処理を施す必要はない。しかしながら、その場合には鋼板の変形能が著しく低いためカシメ性に劣る。本発明においては、良好なカシメ性を具備せしめるために均熱処理により変形能を改善する必要がある。
以下、本発明を完成させるに至った知見について説明する。
The processed structure and the recovered structure can be obtained by allowing dislocations introduced during processing to a predetermined plate thickness to remain without being eliminated during soaking or by suppressing the disappearance. Therefore, unlike the prior art mainly based on solid solution strengthening or precipitation strengthening, it is possible to increase the strength without increasing the strength of the cold-rolled base material, and to suppress breakage during cold rolling. In order to obtain such a processed structure and a recovered structure, it is necessary to suppress recrystallization in a soaking process that is usually performed after cold rolling. In order to suppress recrystallization during soaking, it is necessary to contain Nb, Zr, Ti and V. However, when Nb, Zr, Ti, and V are excessively contained, the surface properties deteriorate, so that it is important to optimize the contents of Nb, Zr, Ti, and V. If the purpose is to leave a large amount of dislocations, it is not necessary to perform soaking after processing to a predetermined plate thickness. However, in that case, the deformability of the steel sheet is extremely low, so that the caulking property is poor. In the present invention, it is necessary to improve deformability by soaking in order to provide good caulking properties.
Hereinafter, the knowledge that led to the completion of the present invention will be described.
主要成分が質量％で、Ｓｉ：２．０％、Ｍｎ：０．２％、Ａｌ：０．３％、Ｎ：０．００２％であり、Ｃ，ＳおよびＮｂの含有量をそれぞれＣ：０．００１〜０．０４％、Ｓ：０．０００２〜０．０３％、Ｎｂ：０．００１〜０．６％と変化させた鋼に熱間圧延を施して２．３ｍｍとした後、８００℃で１０時間の熱延板焼鈍を行い、さらに０．３５ｍｍまで冷間圧延し、７００℃で２０秒間保持あるいは７５０℃で２０秒間保持の２つの条件で均熱処理を施した。このようにして得られた鋼板の引張強さを測定した。 The main components are mass%, Si: 2.0%, Mn: 0.2%, Al: 0.3%, N: 0.002%, and the contents of C, S and Nb are respectively C: 0 0.001 to 0.04%, S: 0.0002 to 0.03%, Nb: 0.001 to 0.6% steel was hot rolled to 2.3 mm, and then 800 ° C Was subjected to hot rolling annealing for 10 hours, further cold-rolled to 0.35 mm, and subjected to soaking treatment under two conditions of holding at 700 ° C. for 20 seconds or holding at 750 ° C. for 20 seconds. The tensile strength of the steel sheet thus obtained was measured.
図１および図２に、７００℃または７５０℃で２０秒間保持の均熱処理を施したそれぞれの鋼板について、Ｎｂ，ＣおよびＮの含有量により規定される下記式（２）で示されるＮｂ＊と、鋼板の引張強さとの関係を示す。 1 and 2, Nb * represented by the following formula (2) defined by the contents of Nb, C and N for each steel plate subjected to soaking at 700 ° C. or 750 ° C. for 20 seconds The relationship with the tensile strength of a steel plate is shown.
Ｎｂ＊＝Ｎｂ／９３−Ｃ／１２−Ｎ／１４ （２）
（ここで、式（２）中、Ｎｂ，ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。）
Nb * = Nb / 93-C / 12-N / 14 (2)
(Here, in the formula (2), Nb, C and N indicate the content (mass%) of each element.)
図１および図２より、Ｎｂ＊＞０の場合にのみ優れた機械特性が得られることがわかった。また、鋼組織を調査した結果、Ｎｂ＊＞０の場合にのみ再結晶が抑制されており、鋼組織は加工組織および回復組織であった。Ｎｂ＊は固溶Ｎｂ含有量と対応しており、再結晶抑制には固溶Ｎｂ含有量の確保が重要であると判明した。さらに、均熱処理での均熱温度が高温化した場合にはＮｂ＊が高いほど再結晶抑制効果が大きくなることも判明した。 1 and 2, it was found that excellent mechanical properties can be obtained only when Nb * > 0. As a result of investigating the steel structure, recrystallization was suppressed only when Nb * > 0, and the steel structure was a processed structure and a recovered structure. Nb * corresponds to the solid solution Nb content, and it has been found that securing the solid solution Nb content is important for suppressing recrystallization. Furthermore, it has been found that when the soaking temperature in soaking is increased, the effect of suppressing recrystallization increases as Nb * increases.
また、Ｔｉ，ＺｒおよびＶについても上記と同様の検討を行い、それらの知見を合わせて再結晶抑制には下記式（３）を満足させる必要があると判明した。 Further, Ti, Zr, and V were also examined in the same manner as described above, and it was found that the following formula (3) needs to be satisfied in order to suppress recrystallization by combining these findings.
Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−（Ｃ／１２＋Ｎ／１４）＞０ （３）
（ここで、式（３）中、Ｎｂ，Ｚｒ，Ｔｉ，Ｖ，ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。）
Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14)> 0 (3)
(Here, in the formula (3), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
これらの鋼板の表面性状を調査したところ、Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−（Ｃ／１２＋Ｎ／１４）の数値が過度に高い場合にはリジングと呼ばれる表面欠陥が発生するとの知見を得た。これらの知見より、磁気特性と機械特性とを兼ね備えた上に、表面性状の劣化を抑制するには、Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−（Ｃ／１２＋Ｎ／１４）を適正範囲に制御する必要があると判明し、本発明を完成したのである。
以下、本発明の回転子用無方向性電磁鋼板およびその製造方法について詳細に説明する。
When the surface properties of these steel sheets were investigated, it was found that surface defects called ridging occur when the numerical value of Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14) is excessively high. . Based on these findings, Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14) is controlled within an appropriate range in order to suppress deterioration of surface properties while having both magnetic properties and mechanical properties. It was found that there was a need, and the present invention was completed.
Hereinafter, the non-oriented electrical steel sheet for rotors of the present invention and the manufacturing method thereof will be described in detail.
Ａ．回転子用無方向性電磁鋼板
本発明の回転子用無方向性電磁鋼板は、質量％で、Ｃ：０．０４％以下、Ｓｉ：１．０％以上３．５％以下、Ｍｎ：０．１％以上２．５％以下、Ａｌ：０．２％以上２．５％以下、Ｓｉ＋Ａｌ：２．０％以上５．０％以下、Ｐ：０．２％以下、Ｓ：０．０３％以下、Ｎ：０．００５％以下を含有し、Ｎｂ、Ｔｉ、ＺｒおよびＶからなる群から選択される少なくとも１種の元素を、下記式（１）を満足する範囲で含有し、残部が実質的にＦｅおよび不純物からなり、再結晶部分の面積比率が２５％未満、伸びが２％以上であることを特徴とするものである。
A. Non-oriented electrical steel sheet for rotors The non-oriented electrical steel sheet for rotors of the present invention is mass%, C: 0.04% or less, Si: 1.0% or more and 3.5% or less, Mn: 0.00%. 1% to 2.5%, Al: 0.2% to 2.5%, Si + Al: 2.0% to 5.0%, P: 0.2% or less, S: 0.03% or less , N: 0.005% or less, containing at least one element selected from the group consisting of Nb, Ti, Zr and V within a range satisfying the following formula (1), with the balance being substantially Further, it is composed of Fe and impurities, the area ratio of the recrystallized portion is less than 25%, and the elongation is 2% or more.
０＜Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−(Ｃ／１２＋Ｎ／１４)＜５×１０−３ （１）
（ここで、式（１）中、Ｎｂ、Ｚｒ、Ｔｉ、Ｖ、ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。）
0 <Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14) <5 × 10 −3 (1)
(Here, in the formula (1), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
なお、各元素の含有量を示す「％」は、特に断りのない限り「質量％」を意味するものである。
以下、本発明の回転子用無方向性電磁鋼板における鋼組成、再結晶部分の面積比率、および伸びについて説明する。
“%” Indicating the content of each element means “mass%” unless otherwise specified .
Hereinafter, the steel composition, the area ratio of the recrystallized portion, and the elongation in the non-oriented electrical steel sheet for rotor of the present invention will be described.
１．鋼組成
（１）Ｃ
ＣはＮｂ，Ｚｒ，ＴｉまたはＶと結びついて析出物を形成するため、固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量の減少に繋がる。したがって、固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量を確保するためには、Ｃ含有量を低減することが好ましい。しかしながら、過度のＣ含有量の低減は製鋼コストが増加する点や、Ｃ含有量が多くてもＮｂ，Ｚｒ，ＴｉおよびＶの含有量をそれに応じて増加させれば固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量は確保される点を鑑み、Ｃ含有量の上限は０．０４％とする。好ましくは０．０２％以下、さらに好ましくは０．０１％以下である。
1. Steel composition (1) C
Since C is combined with Nb, Zr, Ti or V to form a precipitate, it leads to a decrease in the content of solute Nb, Zr, Ti and V. Therefore, in order to ensure the content of the solid solution Nb, Zr, Ti and V, it is preferable to reduce the C content. However, excessive reduction of the C content increases the steelmaking cost, and even if the C content is large, if the contents of Nb, Zr, Ti and V are increased accordingly, solid solution Nb, Zr, Ti In view of securing the V and V contents, the upper limit of the C content is 0.04%. Preferably it is 0.02% or less, More preferably, it is 0.01% or less.
（２）Ｓｉ
Ｓｉは電気抵抗を高め、渦電流損失を低減する効果を有する元素である。また、固溶強化により鋼板の高強度化にも寄与する。そのためＳｉ含有量は１．０％以上とする。一方、多量のＳｉを含有させた場合には冷間圧延時の割れを誘発し、鋼板の歩留まり低下により製造コストが増加する。そのためＳｉ含有量は３．５％以下とする。割れ抑制の観点からは３．０％以下が好ましい。
(2) Si
Si is an element that has the effect of increasing electrical resistance and reducing eddy current loss. Moreover, it contributes to the strengthening of a steel plate by solid solution strengthening. Therefore, the Si content is 1.0% or more. On the other hand, when a large amount of Si is contained, cracks during cold rolling are induced, and the manufacturing cost increases due to a decrease in the yield of the steel sheet. Therefore, the Si content is 3.5% or less. From the viewpoint of suppressing cracking, 3.0% or less is preferable.
（３）Ｍｎ
ＭｎはＳｉと同様に電気抵抗を高め、渦電流損失を低減する効果がある。しかしながら、Ｍｎを多量に含有させると合金コストが増加するため、Ｍｎ含有量の上限は２．５％とする。一方、Ｍｎ含有量の下限はＳを固定する観点から定められるものであり、０．１％とする。
(3) Mn
Mn has the effect of increasing electrical resistance and reducing eddy current loss, similar to Si. However, since an alloy cost increases when Mn is contained in a large amount, the upper limit of the Mn content is set to 2.5%. On the other hand, the lower limit of the Mn content is determined from the viewpoint of fixing S, and is 0.1%.
（４）Ａｌ
ＡｌはＳｉと同様に電気抵抗を高め、Ｓｉより寄与は小さいものの固溶強化の効果も有する。そのためＡｌ含有量は０．２％以上とする。一方、多量にＡｌを含有させると合金コストが増加するとともに、飽和磁束密度低下により磁束の漏れが発生するためモータ効率が低下する。これらの観点からＡｌ含有量の上限は２．５％とする。
(4) Al
Al, like Si, increases the electrical resistance, and has a solid solution strengthening effect although it contributes less than Si. Therefore, the Al content is 0.2% or more. On the other hand, if Al is contained in a large amount, the alloy cost increases, and magnetic flux leakage occurs due to a decrease in saturation magnetic flux density, so that the motor efficiency decreases. From these viewpoints, the upper limit of the Al content is 2.5%.
（５）Ｓｉ＋Ａｌ
上述のとおりＳｉおよびＡｌは効果が類似しているため、磁気特性および機械特性の両立にはその合計量を規定する必要があり、ＳｉおよびＡｌの合計含有量を２．０％以上５．０％以下とする。ＳｉおよびＡｌの合計含有量が少なすぎると機械特性または磁気特性が劣ったものとなり、多すぎると冷間圧延時に破断するおそれがある。
(5) Si + Al
As described above, since Si and Al have similar effects, it is necessary to define the total amount in order to achieve both magnetic properties and mechanical properties. The total content of Si and Al must be 2.0% or more and 5.0%. % Or less. If the total content of Si and Al is too small, the mechanical properties or magnetic properties will be inferior, and if it is too large, there is a risk of breaking during cold rolling.
（６）Ｐ
Ｐは固溶強化により鋼板の強度を高める効果があるが、多量にＰを含有する場合には冷間圧延時の割れを誘発する。そのためＰ含有量は０．２％以下とする。
(6) P
P has the effect of increasing the strength of the steel sheet by solid solution strengthening, but when it contains a large amount of P, it induces cracks during cold rolling. Therefore, the P content is 0.2% or less.
（７）Ｓ
Ｓは鋼中に不可避的に混入する不純物であるが、製鋼段階で低減するにはコストが増加するためＳ含有量としては０．０３％を上限とする。
(7) S
S is an impurity inevitably mixed in the steel. However, since the cost increases to reduce it in the steelmaking stage, the upper limit of the S content is 0.03%.
（８）Ｎ
ＮはＮｂ，Ｚｒ，ＴｉまたはＶと結びついて析出物を形成するため、固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量の減少に繋がる。したがって、固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量を確保する観点からはＮ含有量を低減することが好ましい。そのためＮ含有量は０．００５％以下とする。
(8) N
Since N is combined with Nb, Zr, Ti, or V to form a precipitate, the content of solute Nb, Zr, Ti, and V is reduced. Therefore, it is preferable to reduce the N content from the viewpoint of securing the contents of the solute Nb, Zr, Ti and V. Therefore, the N content is 0.005% or less.
（９）Ｎｂ，Ｚｒ，ＴｉおよびＶ
均熱処理中の転位の消滅および再結晶を抑制し、加工組織および回復組織を得るためには析出物を形成していない固溶した状態のＮｂ，Ｚｒ，ＴｉまたはＶを含有させることが必要である。したがって、Ｎｂ，Ｚｒ，ＴｉおよびＶからなる群から選択される少なくとも１種の元素を、下記式（３）を満足する範囲で含有させることが必要である。
(9) Nb, Zr, Ti and V
In order to suppress dislocation annihilation and recrystallization during soaking, and to obtain a processed structure and a recovered structure, it is necessary to contain Nb, Zr, Ti, or V in a solid solution state in which precipitates are not formed. is there. Therefore, it is necessary to contain at least one element selected from the group consisting of Nb, Zr, Ti and V in a range satisfying the following formula (3).
Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−（Ｃ／１２＋Ｎ／１４）＞０ （３）
（ここで、式（３）中、Ｎｂ，Ｚｒ，Ｔｉ，Ｖ，ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。）
Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14)> 0 (3)
(Here, in the formula (3), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
上記式（３）の左辺は、Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量とＣおよびＮの含有量との差を表しており、この値が正であることは炭化物、窒化物または炭窒化物といった析出物を形成していない固溶した状態のＮｂ，Ｚｒ，ＴｉまたはＶを含有していることに対応する。 The left side of the above formula (3) represents the difference between the contents of Nb, Zr, Ti and V and the contents of C and N, and this value is positive that carbide, nitride or carbonitride It corresponds to containing Nb, Zr, Ti or V in a solid solution state in which no precipitate is formed.
図１および図２に示すように、均熱処理時の均熱温度が高温の場合、固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量が多ければ多いほど転位の消滅および再結晶を抑制する効果は大きくなり、加工組織または回復組織を得るには有効である。 As shown in FIGS. 1 and 2, when the soaking temperature during soaking is high, the more the content of solid solution Nb, Zr, Ti and V is, the more effective the effect of suppressing dislocation disappearance and recrystallization. It is effective for obtaining a processed structure or a recovered structure.
しかしながら、過度に固溶Ｎｂ，Ｚｒ，ＴｉおよびＶを含有する場合には熱間圧延時および熱延板焼鈍時にも転位の消滅および再結晶が抑制されるため、冷間圧延前の組織が未再結晶状態となる。その結果としてリジングと呼ばれる表面欠陥が生じ、鉄心に積層した場合の占積率が低下しモータ効率が低下するため好ましくない。固溶Ｎｂ，Ｚｒ，ＴｉおよびＶの含有量の上限値はこの観点から定められ、Ｎｂ，Ｚｒ，ＴｉおよびＶは下記式（１）で示される範囲で含有させる必要がある。 However, when excessively containing solute Nb, Zr, Ti, and V, dislocation disappearance and recrystallization are suppressed during hot rolling and hot-rolled sheet annealing, so that the structure before cold rolling is not yet obtained. Recrystallized state. As a result, surface defects called ridging are generated, which is not preferable because the space factor when laminated on an iron core is lowered and the motor efficiency is lowered. The upper limit of the content of the solute Nb, Zr, Ti and V is determined from this viewpoint, and Nb, Zr, Ti and V must be contained within the range represented by the following formula (1).
０＜Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−(Ｃ／１２＋Ｎ／１４)＜５×１０−３ （１）
（ここで、式（１）中、Ｎｂ、Ｚｒ、Ｔｉ、Ｖ、ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。）
0 <Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14) <5 × 10 −3 (1)
(Here, in the formula (1), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
また、硫化物を考慮すると固溶状態のＮｂ，Ｚｒ，ＴｉおよびＶの含有量はＳ含有量にも影響される。しかしながら、上述したＳ含有量の範囲内ではＳによる影響は認められなかったため、本発明においてはＳの項を省略した上記式（１）を採用した。Ｓの影響が認められなかった理由は明確でないが、凝固末期のＳが濃化した領域からＭｎＳとなって晶出するなどしてＭｎによりＳが固定されたためと考えられる。 In consideration of sulfide, the contents of Nb, Zr, Ti and V in the solid solution state are also affected by the S content. However, since the influence of S was not recognized within the range of the S content described above, the above formula (1) in which the S term was omitted was adopted in the present invention. The reason why the influence of S was not recognized is not clear, but it is considered that S was fixed by Mn by, for example, crystallization as MnS from a region where S at the end of solidification was concentrated.
（１０）その他
本発明においては、本発明の効果を損なわない範囲で上述した元素以外の元素を含有させることが可能である。本発明においては、再結晶粒径の細粒化ではなく再結晶そのものを抑制することにあるから、この再結晶抑制効果を損なわない範囲でＣｒ，Ｍｏ，Ｂ，Ｃｕ，Ｎｉ，ＣｏおよびＷなどを必要に応じて含有させてもよい。
(10) Others In the present invention, it is possible to contain an element other than the elements described above within a range not impairing the effects of the present invention. In the present invention, since recrystallization is not suppressed but the recrystallization itself is suppressed, Cr, Mo, B, Cu, Ni, Co, W and the like are within a range not impairing the recrystallization suppression effect. May be included as necessary.
Ｃｒ，ＭｏおよびＢを含有させる場合には、Ｃｒ，ＭｏおよびＢの含有量は、Ｃｒ：０．０１％以上、Ｍｏ：０．００５％以上、Ｂ：０．０００１％以上とすることが好ましい。一方、Ｃｒ，ＭｏおよびＢを多量に含有させても合金コストの観点から好ましくない。したがって、Ｃｒ，ＭｏおよびＢの含有量は、Ｃｒ：４．０％未満、Ｍｏ：４．０％未満、Ｂ：０．０１％未満とするのが好ましい。 When Cr, Mo and B are contained, the Cr, Mo and B contents are preferably Cr: 0.01% or more, Mo: 0.005% or more, and B: 0.0001% or more. . On the other hand, a large amount of Cr, Mo and B is not preferable from the viewpoint of alloy cost. Accordingly, the Cr, Mo and B contents are preferably Cr: less than 4.0%, Mo: less than 4.0%, and B: less than 0.01%.
また、ＣｕおよびＮｉも冷間圧延時に破断を引き起こすことの無い範囲で含有させることが可能である。ＣｕおよびＮｉの含有量は、それぞれ０．０１％以上２．０％以下の範囲で設定することができる。 Cu and Ni can also be contained in a range that does not cause breakage during cold rolling. The contents of Cu and Ni can be set in the range of 0.01% to 2.0%, respectively.
さらに、ＣｏおよびＷの含有量は合計で４．０％以下とするのが合金コストおよび冷間圧延性の観点から好ましい。 Furthermore, the total content of Co and W is preferably 4.0% or less from the viewpoint of alloy cost and cold rollability.
また、脱酸剤として、あるいはＳを無害化する元素としてＣａを０．０１％以下含有させても本発明の効果は損なわれない。 Further, the effect of the present invention is not impaired even if Ca is contained in an amount of 0.01% or less as a deoxidizer or as an element for detoxifying S.
２．再結晶部分の面積比率
次に、本発明における再結晶部分の面積比率について説明する。
本発明においては、鋼組成を上述した範囲となるように調整しても、再結晶部分の面積比率が２５％以上であると急激に強度が低下するため所望の機械特性が得られない場合がある。そのため、再結晶部分の面積比率は２５％未満とする。機械特性の観点からは再結晶部分の面積比率は低いほど好ましく、２０％以下であることが好ましい。また、再結晶部分の面積比率をゼロとし、完全に未再結晶状態（加工組織および回復組織）とすることが好ましく、そのためには均熱処理時の均熱温度や均熱時間などを調整することが重要である。
2. Next, the area ratio of the recrystallized portion in the present invention will be described.
In the present invention, even if the steel composition is adjusted so as to be in the above-described range, if the area ratio of the recrystallized portion is 25% or more, the strength is suddenly lowered, so that desired mechanical characteristics may not be obtained. is there. Therefore, the area ratio of the recrystallized portion is set to less than 25%. From the viewpoint of mechanical properties, the area ratio of the recrystallized portion is preferably as low as possible, and is preferably 20% or less. In addition, it is preferable that the area ratio of the recrystallized portion is zero, and it is preferable that the recrystallized portion is completely unrecrystallized (processed structure and recovered structure). is important.
ここで、再結晶部分の面積比率とは、本発明の回転子用無方向性電磁鋼板の圧延方向に平行な断面組織写真において視野中に占める再結晶粒の割合を示すものであり、この断面組織写真をもとに測定することができる。断面組織写真としては、光学顕微鏡写真を用いることができ、例えば１００倍の倍率で撮影した写真を用いればよい。 Here, the area ratio of the recrystallized portion indicates the ratio of the recrystallized grains in the field of view in the cross-sectional structure photograph parallel to the rolling direction of the non-oriented electrical steel sheet for rotors of the present invention. Measurements can be made based on tissue photographs. As the cross-sectional structure photograph, an optical micrograph can be used. For example, a photograph taken at a magnification of 100 times may be used.
３．伸び
次に、本発明における伸びについて説明する。
本発明においては、鋼組成および再結晶部分の面積比率を上述した範囲に制御しても、カシメ性が劣る場合がある。通常の無方向性電磁鋼板の場合には冷間圧延後に行われる均熱処理にて再結晶および結晶粒成長を進行させるため変形能は改善されるが、本発明においては再結晶を抑制しているため変形能の改善が十分でない場合がある。そこで、本発明においてはカシメ性に影響を及ぼす変形能の指標として鋼板の伸びを採用し、伸びを２％以上とする。望ましくは３％以上である。例えば冷間圧延後に均熱処理を施さない場合、鋼板の伸びは本発明範囲外となりカシメ性が劣る。
3. Elongation Next, the elongation in the present invention will be described.
In the present invention, the caulking property may be inferior even if the steel composition and the area ratio of the recrystallized portion are controlled within the above-described ranges. In the case of ordinary non-oriented electrical steel sheets, deformability is improved because recrystallization and grain growth are promoted by soaking performed after cold rolling, but recrystallization is suppressed in the present invention. For this reason, there is a case where the improvement of the deformability is not sufficient. Therefore, in the present invention, the elongation of the steel sheet is adopted as an index of deformability affecting the caulking property, and the elongation is set to 2% or more. Desirably, it is 3% or more. For example, when the soaking is not performed after cold rolling, the elongation of the steel sheet is outside the range of the present invention, and the caulking property is inferior.
ここで、伸びは、ＪＩＳ５号試験片を用いた引張試験を行うことにより測定した値とする。 Here, the elongation is a value measured by performing a tensile test using a JIS No. 5 test piece.
Ｂ．本発明の回転子用無方向性電磁鋼板の製造方法
次に、本発明の回転子用無方向性電磁鋼板の製造方法について説明する。
本発明の回転子用無方向性電磁鋼板の製造方法は、上述した「Ａ．回転子用無方向性電磁鋼板」の項に記載した鋼組成を備える鋼塊または鋼片に熱間圧延を施す熱間圧延工程と、上記熱間圧延工程により得られた熱間圧延鋼板に一回または中間焼鈍をはさむ二回以上の冷間圧延を施す冷間圧延工程と、上記冷間圧延工程により得られた冷間圧延鋼板を５００℃以上７８０℃以下で均熱する均熱処理工程とを有することを特徴とするものである。
B. Next, the manufacturing method of the non-oriented electrical steel sheet for rotors of the present invention will be described.
The manufacturing method of the non-oriented electrical steel sheet for rotors of this invention hot-rolls the steel ingot or steel slab provided with the steel composition as described in the term of the "A. non-oriented electrical steel sheet for rotors" mentioned above. Obtained by the hot rolling process, the cold rolling process in which the hot rolled steel sheet obtained by the hot rolling process is subjected to cold rolling twice or more with one or intermediate annealing, and the cold rolling process. And a soaking step of soaking the cold-rolled steel sheet at 500 ° C. or higher and 780 ° C. or lower.
本発明によれば、再結晶および結晶粒成長を目的として通常冷間圧延後に実施される均熱処理工程での均熱温度を所定の範囲とすることにより、再結晶を抑制し、所定の板厚への加工の際に導入された転位の消滅を抑制して、多量の転位を残存させた回復組織を主体とすることができる。これにより鋼板の高強度化が可能である。 According to the present invention, by setting the soaking temperature in the soaking process usually performed after cold rolling for the purpose of recrystallization and crystal grain growth within a predetermined range, recrystallization is suppressed and a predetermined plate thickness is achieved. The recovery structure in which a large amount of dislocations remain can be mainly formed by suppressing the disappearance of the dislocations introduced in the processing of the steel. Thereby, the strength of the steel sheet can be increased.
本発明においては、従来の固溶強化や析出強化のように冷間圧延に供する鋼板、すなわち冷間圧延の母材の高強度化を伴うことがないので、冷間圧延時の破断を抑制することができる。さらに本発明においては、所定の鋼組成を有する鋼塊または鋼片を用い、また上述したように均熱処理工程での均熱温度を所定の範囲とすることで高強度化を図ることから、従来のように高価な鋼成分を用いることも、特殊な工程を経ることもなく、例えば駆動モータの回転子として必要な磁気特性および機械特性を満足する回転子用無方向性電磁鋼板を安定して製造することができる。さらに、均熱処理工程を行うことにより変形能を改善し、伸びを適正範囲に制御できるためカシメ性も良好となる。またさらに、所定の鋼組成に制御することから鋼板の表面性状も良好となり、回転子を構成した際の占積率が向上しモータ効率を向上させることができる。
以下、本発明の回転子用無方向性電磁鋼板の製造方法における各工程について説明する。
In the present invention, there is no need to increase the strength of the steel sheet used for cold rolling as in the conventional solid solution strengthening and precipitation strengthening, that is, the base material of the cold rolling, so that the breakage during the cold rolling is suppressed. be able to. Furthermore, in the present invention, a steel ingot or steel slab having a predetermined steel composition is used, and, as described above, since the soaking temperature in the soaking process is within a predetermined range, the strength is increased. The non-oriented electrical steel sheet for rotors that satisfies the magnetic and mechanical properties required for a rotor of a drive motor, for example, can be stably used without using expensive steel components such as Can be manufactured. Furthermore, since the deformability is improved by performing the soaking process and the elongation can be controlled within an appropriate range, the caulking property is also improved. Furthermore, since the steel composition is controlled to a predetermined steel composition, the surface properties of the steel sheet are improved, and the space factor when the rotor is configured is improved, and the motor efficiency can be improved.
Hereinafter, each process in the manufacturing method of the non-oriented electrical steel sheet for rotors of this invention is demonstrated.
（１）熱間圧延工程
本発明における熱間圧延工程は、上述した鋼組成を備える鋼塊または鋼片（以下、「スラブ」ともいう。）に熱間圧延を施す工程である。
(1) Hot rolling process The hot rolling process in this invention is a process of hot-rolling the steel ingot or steel slab (henceforth "slab") provided with the steel composition mentioned above.
なお、鋼塊または鋼片の鋼組成については、上述した「Ａ．回転子用無方向性電磁鋼板」の項に記載したものと同様であるので、ここでの説明は省略する。 In addition, about the steel composition of a steel ingot or a steel piece, since it is the same as that of what was described in the term of the "A. non-oriented electrical steel sheet for rotors" mentioned above, description here is abbreviate | omitted.
本工程においては、上述した組成を有する鋼を、連続鋳造法あるいは鋼塊を分塊圧延する方法など一般的な方法によりスラブとし、加熱炉に装入して熱間圧延を施す。この際、スラブ温度が高い場合には加熱炉に装入しないで熱間圧延を行ってもよい。 In this step, the steel having the above-described composition is made into a slab by a general method such as a continuous casting method or a method of rolling a steel ingot, and is charged in a heating furnace and subjected to hot rolling. At this time, when the slab temperature is high, hot rolling may be performed without charging the heating furnace.
また、スラブ加熱温度は特に限定されるものではないが、コストおよび熱間圧延性の観点から１０００〜１３００℃とすることが好ましい。より好ましくは１０５０〜１２５０℃である。 Moreover, although the slab heating temperature is not specifically limited, it is preferable to set it as 1000-1300 degreeC from a viewpoint of cost and hot rolling property. More preferably, it is 1050-1250 degreeC.
熱間圧延の各種条件は特に限定されるものではなく、例えば仕上げ温度が７００〜９５０℃、巻き取り温度が７５０℃以下など、一般的な条件に従って行えばよい。 Various conditions of hot rolling are not particularly limited, and may be performed according to general conditions such as a finishing temperature of 700 to 950 ° C. and a winding temperature of 750 ° C. or less.
（２）冷間圧延工程
本発明における冷間圧延工程は、上記熱間圧延工程により得られた熱間圧延鋼板に一回または中間焼鈍をはさむ二回以上の冷間圧延を施す工程である。このような冷間圧延工程を行うことにより、鋼板を所定の板厚に仕上げる。
(2) Cold rolling process The cold rolling process in the present invention is a process in which the hot rolled steel sheet obtained by the hot rolling process is subjected to cold rolling twice or more with one or intermediate annealing. By performing such a cold rolling process, the steel sheet is finished to a predetermined thickness.
本工程においては、一回の冷間圧延で所定の板厚まで仕上げてもよいし、中間焼鈍を含む二回以上の冷間圧延によって仕上げてもよい。 In this step, the sheet thickness may be finished by one cold rolling or may be finished by two or more cold rollings including intermediate annealing.
また、冷間圧延の各種条件は特に限定されるものではなく、被圧延材の鋼組成、目的とする鋼板の板厚などにより適宜選択するものとする。 Various conditions for cold rolling are not particularly limited, and are appropriately selected depending on the steel composition of the material to be rolled, the thickness of the target steel sheet, and the like.
（３）均熱処理工程
本発明における均熱処理工程は、上述した冷間圧延工程により得られた冷間圧延鋼板を５００℃以上７８０℃以下で均熱する工程である。
(3) Soaking process The soaking process in the present invention is a process of soaking the cold-rolled steel sheet obtained by the above-described cold rolling process at 500 ° C. or more and 780 ° C. or less.
均熱処理は、箱焼鈍および連続焼鈍のいずれの方法で実施してもよい。この際、均熱温度が高温であると再結晶が進行するため十分な機械特性が得られない。そのため、均熱温度の上限は７８０℃とする。好ましくは７５０℃以下、さらに好ましくは７００℃以下である。均熱温度は低ければ低いほど再結晶進行が抑制されるが、連続焼鈍で均熱処理を実施する場合、均熱温度が低いと鋼板の平坦が矯正されずに回転子に積層した場合の占積率が低下する場合がある。また、均熱処理により変形能を改善し、カシメ性の指標である鋼板の伸びを所定の範囲に制御する必要があるため、均熱温度が低い場合にはこの目標を達成できない。そこで、平坦矯正およびカシメ性改善の観点から、均熱温度の下限値を５００℃とする。 The soaking may be performed by any method of box annealing and continuous annealing. At this time, if the soaking temperature is high, recrystallization proceeds and sufficient mechanical properties cannot be obtained. Therefore, the upper limit of the soaking temperature is 780 ° C. Preferably it is 750 degrees C or less, More preferably, it is 700 degrees C or less. The lower the soaking temperature, the lower the progress of recrystallization. However, when soaking is performed by continuous annealing, if the soaking temperature is low, the space when the steel sheet is laminated on the rotor without being flattened. The rate may decrease. Further, since it is necessary to improve the deformability by soaking and to control the elongation of the steel sheet, which is an index of caulking property, within a predetermined range, this target cannot be achieved when the soaking temperature is low. Therefore, the lower limit of the soaking temperature is set to 500 ° C. from the viewpoint of flatness correction and caulking improvement.
本発明において、均熱処理を箱焼鈍で実施する場合には、コイル状態で焼鈍に供されることに起因して鋼板の平坦度が低下したり、形状が劣化したりすることがあるため、均熱処理工程後に軽加工により鋼板の平坦度や形状を矯正する矯正工程を行ってもよい。 In the present invention, when the soaking is performed by box annealing, the flatness of the steel sheet may be lowered or the shape may be deteriorated due to being subjected to annealing in a coil state. You may perform the correction process which corrects the flatness and shape of a steel plate by light processing after a heat treatment process.
（４）熱延板焼鈍工程
本発明においては、上記熱間圧延工程により得られた熱間圧延鋼板に熱延板焼鈍を施す熱延板焼鈍工程を行ってもよい。この熱延板焼鈍工程は、熱間圧延工程と冷間圧延工程との間に行われる工程である。
(4) Hot-rolled sheet annealing process In this invention, you may perform the hot-rolled sheet annealing process which performs hot-rolled sheet annealing to the hot-rolled steel plate obtained by the said hot-rolling process. This hot-rolled sheet annealing process is a process performed between a hot rolling process and a cold rolling process.
熱延板焼鈍工程は必ずしも必須の工程ではないが、熱延板焼鈍工程を行うことにより、鋼板の延性が向上し冷間圧延工程での破断を抑制できる。また、鋼組成が特定範囲に制御されているため、熱延板焼鈍を実施することにより表面性状が良好となる。 The hot-rolled sheet annealing process is not necessarily an essential process, but by performing the hot-rolled sheet annealing process, the ductility of the steel sheet is improved, and breakage in the cold rolling process can be suppressed. Moreover, since steel composition is controlled by the specific range, surface property becomes favorable by implementing hot-rolled sheet annealing.
熱延板焼鈍は、箱焼鈍および連続焼鈍のいずれの方法で実施してもよい。また、熱延板焼鈍の各種条件は特に限定されるものではなく、熱間圧延鋼板の鋼組成などにより適宜選択するものとする。 Hot-rolled sheet annealing may be performed by any method of box annealing and continuous annealing. Moreover, the various conditions of hot-rolled sheet annealing are not specifically limited, It shall select suitably by the steel composition etc. of a hot-rolled steel plate.
（５）その他
本発明においては、上記均熱処理工程後（箱焼鈍による均熱処理工程後に軽加工により鋼板の平坦度や形状を矯正する矯正工程を行う場合には、その矯正工程後）に、一般的な方法に従って、有機成分のみ、無機成分のみ、あるいは有機無機複合物からなる絶縁被膜を鋼板表面に塗布するコーティング工程を行うことが好ましい。また、コーティング工程は、加熱・加圧することにより接着能を発揮する絶縁コーティングを施す工程であってもよい。接着能を発揮するコーティング材料としては、アクリル樹脂、フェノール樹脂、エポキシ樹脂またはメラミン樹脂などを用いることができる。
(5) Others In the present invention, after the soaking process (after the soaking process in the case of performing a straightening process to correct the flatness and shape of the steel sheet by light processing after the soaking process by box annealing), According to a typical method, it is preferable to carry out a coating process in which an insulating coating composed of only an organic component, only an inorganic component, or an organic-inorganic composite is applied to the surface of the steel sheet. Further, the coating process may be a process of applying an insulating coating that exhibits adhesive ability by heating and pressurizing. As a coating material exhibiting adhesive ability, an acrylic resin, a phenol resin, an epoxy resin, a melamine resin, or the like can be used.
なお、本発明により製造される回転子用無方向性電磁鋼板については、上述した「Ａ．回転子用無方向性電磁鋼板」の項に記載したものと同様であるので、ここでの説明は省略する。 Note that the non-oriented electrical steel sheet for rotors manufactured according to the present invention is the same as that described in the above-mentioned section “A. Non-oriented electrical steel sheet for rotors”, so the description here is as follows. Omitted.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.
以下、実施例および比較例を例示して、本発明を具体的に説明する。
［実施例１〜１６］
下記の表１に示す鋼組成を有する鋼を真空溶製し、これらの鋼を１１５０℃に加熱し、仕上げ温度８２０℃で熱間圧延を行って５８０℃で巻き取り、厚さが２．０ｍｍの熱間圧延鋼板を得た。これらの熱間圧延鋼板のうち一部を除いて水素雰囲気中にて７５０℃または８００℃で１０時間保持する箱焼鈍、あるいは１０００℃で６０秒間保持する連続焼鈍による熱延板焼鈍を施し、一回の冷間圧延にて板厚０．３５ｍｍまで仕上げた。また、一部の熱間圧延鋼板については、上記の熱延板焼鈍後、中間板厚まで冷間圧延した後、水素雰囲気中にて７５０℃または８００℃で１０時間保持する箱焼鈍、あるいは１０００℃で６０秒間保持する連続焼鈍による中間焼鈍を実施し、二回目の冷間圧延で０．３５ｍｍに仕上げた。さらに、一部の熱間圧延鋼板については熱延板焼鈍を施すことなく、一回あるいは中間焼鈍を含む二回の冷間圧延にて０．３５ｍｍに仕上げた。その後、実施例１〜９および１１〜１６には種々の均熱温度で３０秒間保持する連続焼鈍による均熱処理を施した。実施例１０には５００℃で１０時間保持する箱焼鈍による均熱処理を施した。
Hereinafter, the present invention will be described specifically by way of examples and comparative examples.
[Examples 1 to 16]
Steels having the steel compositions shown in Table 1 below are vacuum-melted, these steels are heated to 1150 ° C, hot-rolled at a finishing temperature of 820 ° C, wound up at 580 ° C, and a thickness of 2.0 mm. A hot rolled steel sheet was obtained. Except for some of these hot-rolled steel plates, hot-rolled sheet annealing is performed by box annealing that is held at 750 ° C. or 800 ° C. for 10 hours in a hydrogen atmosphere, or by continuous annealing that is held at 1000 ° C. for 60 seconds. The sheet thickness was finished to 0.35 mm by cold rolling. For some hot-rolled steel sheets, after the above-described hot-rolled sheet annealing, after cold rolling to an intermediate sheet thickness, box annealing that is held at 750 ° C. or 800 ° C. for 10 hours in a hydrogen atmosphere, or 1000 Intermediate annealing was performed by continuous annealing held at 60 ° C. for 60 seconds, and finished to 0.35 mm by the second cold rolling. Furthermore, some hot-rolled steel sheets were finished to 0.35 mm by performing cold rolling once or twice including intermediate annealing without performing hot-rolled sheet annealing. Thereafter, Examples 1 to 9 and 11 to 16 were subjected to soaking treatment by continuous annealing that was held at various soaking temperatures for 30 seconds. Example 10 was subjected to soaking treatment by box annealing held at 500 ° C. for 10 hours.
［比較例１〜１１］
上記の表１に示す鋼組成を有する鋼を用いて、実施例１〜１６と同様にして鋼板を作製した。
[Comparative Examples 1 to 11]
A steel plate having the steel composition shown in Table 1 was used to produce steel plates in the same manner as in Examples 1-16.
［評価］
実施例１〜１６および比較例１〜１１の鋼板について、再結晶部分の面積比率、機械特性、磁気特性、疲労特性および表面性状を評価した。
[Evaluation]
About the steel plates of Examples 1 to 16 and Comparative Examples 1 to 11, the area ratio, mechanical properties, magnetic properties, fatigue properties, and surface properties of the recrystallized portion were evaluated.
再結晶部分の面積比率は、１００倍の倍率で撮影した圧延方向に平行な断面の光学顕微鏡写真を用い、視野中に占める再結晶粒の割合を算出した。
機械特性は、ＪＩＳ５号試験片を用いた引張試験にて、降伏点：ＹＰ、引張強さ：ＴＳ、伸び：ＥＬにて評価した。
磁気特性は、ＪＩＳ Ｃ ２５５０に規定されるエプスタイン試験にて、最大磁束密度：１．０Ｔ、励磁周波数：４００Ｈｚでの鉄損Ｗ１０／４００と磁化力５０００Ａ／ｍでの磁束密度Ｂ５０とを測定した。
疲労試験は、打ち抜き加工により試験片を採取し、端面に研削加工を施すことなく打ち抜きのままで振動数６０Ｈｚの片振り電磁共振試験に供した。この疲労試験では、駆動モータの応力状態に対して安全率を考慮し、平均応力：３００ＭＰａ、応力振幅：１８０ＭＰａの条件で疲労破壊しなかったものを良好と判断した。また、繰り返し数は１０７まで実施し、この繰り返し数での破壊の有無で判断した。表２において疲労破壊のないものを「○」印、疲労破壊のあるものを「×」印で示した。
表面性状は、表面粗さ計で測定した山高さを指標とし、山高さ＜３μｍを良好、山高さ≧３μｍを不良とした。表２において良好なものを「○」印、不良のものを「×」印で示した。
As the area ratio of the recrystallized portion, the ratio of the recrystallized grains in the field of view was calculated using an optical micrograph of a cross section parallel to the rolling direction taken at a magnification of 100 times.
Mechanical properties were evaluated by a yield test: YP, tensile strength: TS, and elongation: EL in a tensile test using a JIS No. 5 test piece.
The magnetic characteristics are as follows. In the Epstein test specified in JIS C 2550, the maximum magnetic flux density is 1.0 T, the excitation frequency is 400 Hz, the iron loss W 10/400, and the magnetic flux density B 50 at a magnetizing force of 5000 A / m. It was measured.
In the fatigue test, a test piece was sampled by punching, and subjected to a single swing electromagnetic resonance test at a frequency of 60 Hz while being punched without grinding the end face. In this fatigue test, the safety factor was taken into consideration with respect to the stress state of the drive motor, and those that did not undergo fatigue failure under the conditions of average stress: 300 MPa and stress amplitude: 180 MPa were judged to be good. The number of repetitions was up to 10 7 , and the determination was made based on the presence or absence of destruction at this number of repetitions. In Table 2, those with no fatigue failure are indicated with “◯”, and those with fatigue failure are indicated with “x”.
The surface quality was determined by using the peak height measured with a surface roughness meter as an index, with peak height <3 μm being good and peak height ≧ 3 μm being poor. In Table 2, good ones are indicated by “◯”, and bad ones are indicated by “×”.
表２に、実施例１〜１６および比較例１〜１１の鋼板についての熱延板焼鈍条件、冷間圧延条件、均熱処理条件および評価結果をそれぞれ示す。 Table 2 shows hot-rolled sheet annealing conditions, cold rolling conditions, soaking conditions, and evaluation results for the steel sheets of Examples 1 to 16 and Comparative Examples 1 to 11, respectively.
比較例１の鋼板はＳｉ含有量が高いために冷間圧延時に破断した。また、比較例２の鋼板はＡｌ含有量が高いために磁束密度が低かった。比較例３の鋼板はＰ含有量が高いために冷間圧延時に破断した。さらに、比較例４の鋼板はＣおよびＭｎの含有量が高く、鋼組織がマルテンサイト組織であるために鉄損が著しく増大し、磁束密度も低かった。比較例５の鋼板はＮｂ，Ｚｒ，ＴｉおよびＶの含有量が本発明範囲外であるために再結晶が抑制されず、再結晶部分の面積比率が高くなり降伏点および引張強さともに劣っていた。比較例６，７の鋼板は均熱処理を施さないあるいは均熱温度が低いことに起因して伸びが低く、カシメ性に劣っていた。また、比較例８，９の鋼板は再結晶部分の面積比率が高いために降伏点および引張強さともに劣っていた。比較例１０の鋼板はＮｂ，Ｚｒ，ＴｉおよびＶの含有量が本発明範囲の上限を超えているためにリジングが発生し、表面性状の劣化により鉄心に積層した場合の占積率が低下するおそれがあった。比較例１１の鋼板はＳｉ＋Ａｌが本発明範囲外であるために降伏点および引張強さともに劣っていた。 The steel plate of Comparative Example 1 broke during cold rolling because of the high Si content. Moreover, since the steel plate of Comparative Example 2 had a high Al content, the magnetic flux density was low. Since the steel plate of Comparative Example 3 had a high P content, it broke during cold rolling. Further, the steel sheet of Comparative Example 4 had a high C and Mn content, and the steel structure was a martensite structure, so that the iron loss was remarkably increased and the magnetic flux density was low. In the steel sheet of Comparative Example 5, since the contents of Nb, Zr, Ti and V are outside the scope of the present invention, recrystallization is not suppressed, the area ratio of the recrystallized portion is increased, and the yield point and tensile strength are inferior. It was. The steel plates of Comparative Examples 6 and 7 had low elongation due to not being subjected to soaking heat treatment or low soaking temperature, and were inferior in caulking properties. Further, the steel sheets of Comparative Examples 8 and 9 were inferior in yield point and tensile strength because the area ratio of the recrystallized portion was high. In the steel sheet of Comparative Example 10, the content of Nb, Zr, Ti, and V exceeds the upper limit of the range of the present invention, so that ridging occurs and the space factor when laminated on the iron core decreases due to the deterioration of the surface properties. There was a fear. The steel plate of Comparative Example 11 was inferior in yield point and tensile strength because Si + Al was outside the scope of the present invention.
これに対して本発明で規定する要件を満足する実施例１〜１６の鋼板では磁気特性、機械特性とも優れた値を示しており、上述の応力条件でも疲労破壊を生じることはなかった。また、実施例１３および１４を比較することにより、Ｓ含有量が変化しても機械特性は変化しないことがわかった。 On the other hand, in the steel plates of Examples 1 to 16 that satisfy the requirements defined in the present invention, both the magnetic properties and the mechanical properties showed excellent values, and fatigue failure did not occur even under the stress conditions described above. Further, by comparing Examples 13 and 14, it was found that the mechanical properties did not change even when the S content was changed.
Claims (3)
０＜Ｎｂ／９３＋Ｚｒ／９１＋Ｔｉ／４８＋Ｖ／５１−(Ｃ／１２＋Ｎ／１４)＜５×１０−３ （１）
（ここで、式（１）中、Ｎｂ、Ｚｒ、Ｔｉ、Ｖ、ＣおよびＮはそれぞれの元素の含有量（質量％）を示す。） In mass%, C: 0.04% or less, Si: 1.0% to 3.5%, Mn: 0.1% to 2.5%, Al: 0.2% to 2.5% Si + Al: 2.0% to 5.0%, P: 0.2% or less, S: 0.03% or less, N: 0.005% or less , Cr: less than 4.0%, Mo: 4. Less than 0%, B: less than 0.01%, Cu: 2.0% or less, Ni: 2.0% or less, Co: 4.0% or less, W: 4.0% or less, Ca: 0.01% It contained the following, Nb, Ti, at least one element selected from the group consisting of Zr and V, containing a range satisfying the following formula (1), and the balance of F e and unavoidable impurities, A non-oriented electrical steel sheet for a rotor, wherein the area ratio of the recrystallized portion is less than 25% and the elongation is 2% or more.
0 <Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14) <5 × 10 −3 (1)
(Here, in the formula (1), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
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| KR101177161B1 (en) | 2006-06-16 | 2012-08-24 | 신닛뽄세이테쯔 카부시키카이샤 | High-strength electromagnetic steel sheet and process for producing the same |
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