JP2007016278A - Non-oriented electromagnetic steel sheet for rotor, and its manufacturing method - Google Patents
Non-oriented electromagnetic steel sheet for rotor, and its manufacturing method Download PDFInfo
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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 a method for manufacturing 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 problem in that the necessity for precision machining is required and the core manufacturing cost is significantly 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. .
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す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 provides a non-oriented electrical steel sheet having excellent mechanical characteristics and magnetic characteristics necessary as a rotor of a motor that rotates at high speed, and a method for manufacturing the same. The main purpose.
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、回復組織を得るためにはNb,Zr,TiおよびVの含有量を所定の範囲とすることが必要であることを見出し、これらの知見に基づいて、特願2004−183554、特願2004−252395にて高速回転するモータの回転子用として必要な優れた機械特性と磁気特性とを具備する無方向性電磁鋼板およびその製造方法を提案している。本発明者らは、回復組織を得るための条件についてさらに詳細に検討し、Nb,Zr,TiおよびVのなかでも特にNbを積極的に含有させることが最も効果的であることを見出し、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 can be achieved 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 it can be obtained. Furthermore, in order to obtain a recovery structure, it has been found that the contents of Nb, Zr, Ti and V need to be within a predetermined range, and based on these findings, Japanese Patent Application Nos. 2004-183554 and 2004 are disclosed. -252395 proposes a non-oriented electrical steel sheet having excellent mechanical and magnetic properties necessary for a rotor of a motor that rotates at high speed, and a method for manufacturing the same. The present inventors have examined the conditions for obtaining a recovered tissue in more detail, and found that it is most effective to contain Nb particularly among Nb, Zr, Ti and V, and this is the most effective. Completed the invention.
すなわち、本発明は、質量%で、C:0.06%以下、Si:3.5%以下、Mn:0.05%以上3.0%以下、Al:2.5%以下、P:0.30%以下、S:0.04%以下、N:0.02%以下、Nb:0.02%超を含有し、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90%未満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: 0.06% or less, Si: 3.5% or less, Mn: 0.05% or more and 3.0% or less, Al: 2.5% or less, P: 0 30% or less, S: 0.04% or less, N: 0.02% or less, Nb: more than 0.02%, and at least one selected from the group consisting of Nb, Ti, Zr and V Non-directional electromagnetic for rotor characterized in that element is contained within range satisfying formula (1) below, balance is substantially composed of Fe and impurities, and area ratio of recrystallized portion is less than 90% Provide steel sheet.
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。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をも満足するものとすることができるのである。 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. As a result, the magnetic characteristics and mechanical characteristics required for the rotor described above can also be satisfied.
また、本発明の回転子用無方向性電磁鋼板は、上記Feの一部に代えて、Cu、Ni、Cr、Mo、CoおよびWからなる群から選択される少なくとも1種の元素を下記の質量%で含有することが好ましい。
Cu:0.01%以上8.0%以下 Ni:0.01%以上2.0%以下
Cr:0.01%以上15.0%以下 Mo:0.005%以上4.0%以下
Co:0.01%以上4.0%以下 W:0.01%以上4.0%以下
上記元素の高強度化作用により、鋼板の強度をより高めることが可能となるからである。
Moreover, the non-oriented electrical steel sheet for rotors according to the present invention contains at least one element selected from the group consisting of Cu, Ni, Cr, Mo, Co and W instead of a part of the Fe described below. It is preferable to contain by mass%.
Cu: 0.01% to 8.0% Ni: 0.01% to 2.0% Cr: 0.01% to 15.0% Mo: 0.005% to 4.0% Co: 0.01% or more and 4.0% or less W: 0.01% or more and 4.0% or less The strength of the steel sheet can be further increased by the action of increasing the strength of the above elements.
さらに、本発明の回転子用無方向性電磁鋼板は、上記Feの一部に代えて、Sn、Sb、Se、Bi、Ge、TeおよびBからなる群から選択される少なくとも1種の元素を下記の質量%で含有することが好ましい。
Sn:0.5%以下 Sb:0.5%以下 Se:0.3%以下 Bi:0.2%以下
Ge:0.5%以下 Te:0.3%以下 B:0.01%以下
上記元素の粒界偏析により、効果的に再結晶を抑制することができるからである。
Furthermore, the non-oriented electrical steel sheet for a rotor of the present invention contains at least one element selected from the group consisting of Sn, Sb, Se, Bi, Ge, Te and B instead of a part of the Fe. It is preferable to contain by the following mass%.
Sn: 0.5% or less Sb: 0.5% or less Se: 0.3% or less Bi: 0.2% or less Ge: 0.5% or less Te: 0.3% or less B: 0.01% or less This is because recrystallization can be effectively suppressed by grain boundary segregation of elements.
またさらに、本発明の回転子用無方向性電磁鋼板は、上記Feの一部に代えて、Ca、MgおよびREMからなる群から選択される少なくとも1種の元素を下記の質量%で含有することが好ましい。
Ca:0.03%以下 Mg:0.02%以下 REM:0.1%以下
上記元素の硫化物形態制御作用により、磁気特性をさらに改善することができるからである。
Furthermore, the non-oriented electrical steel sheet for rotors of the present invention contains at least one element selected from the group consisting of Ca, Mg and REM in the following mass%, instead of a part of the Fe. It is preferable.
Ca: 0.03% or less Mg: 0.02% or less REM: 0.1% or less Magnetic properties can be further improved by the sulfide form controlling action of the above elements.
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820℃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 above-described steel composition, and a hot rolled steel sheet obtained by the hot rolling process is subjected to one time or intermediate annealing. For a rotor characterized by having a cold rolling step for performing cold rolling at least twice and a soaking step for soaking the cold rolled steel sheet obtained by the cold rolling step at 820 ° C. or less. A method for producing a non-oriented electrical steel sheet is provided.
本発明においては、均熱処理での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。また、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、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、機械特性だけでなく磁気特性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 temperature in soaking to a predetermined range, recrystallization is suppressed, and the recovered structure that has remained without annihilating dislocations introduced during processing to a predetermined plate thickness Therefore, the strength of the steel sheet can be increased. Moreover, since it does not accompany the high intensity | strength of the steel plate which uses for cold rolling, ie, the base material of cold rolling, the fracture | rupture at the time of cold rolling can be suppressed. 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 not only mechanical properties but also good 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 and breakage in the cold rolling process can be suppressed.
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, it is possible to stably manufacture a non-oriented electrical steel sheet having both excellent mechanical properties and magnetic properties necessary as a rotor of a motor that rotates at high speed without causing a significant increase in cost. is there. 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以上、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 the yield point and the 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 stress state described above, the tensile strength is 550 MPa or more, and considering the safety factor, 600 MPa or more, preferably 700 MPa or more is required.
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.
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り、特にNbの寄与が大きいためにNbを中心として適正量含有させる必要がある。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。
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. Further, in order to suppress recrystallization during soaking, it is necessary to contain Nb, Zr, Ti and V. In particular, since Nb contributes greatly, it is necessary to contain an appropriate amount centering on Nb. 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.
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%、P:0.01%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%と変化させた鋼と、主要成分が質量%で、Si:2.0%、Mn:0.2%、Al:0.3%、N:0.002%、P:0.01%であり、C,SおよびTiの含有量をそれぞれC:0.001〜0.04%、S:0.0002〜0.03%、Ti:0.001〜0.3%と変化させた鋼と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%, P: 0.01%, C, S and Nb Steel whose content was changed to C: 0.001 to 0.04%, S: 0.0002 to 0.03%, Nb: 0.001 to 0.6%, respectively, and the main component was mass%, Si: 2.0%, Mn: 0.2%, Al: 0.3%, N: 0.002%, P: 0.01%, and the contents of C, S and Ti are C: 0 0.001 to 0.04%, S: 0.0002 to 0.03%, Ti: 0.001 to 0.3%, and hot rolled to 2.3 mm, then 800 mm Hot-rolled sheet annealed at 10 ° C for 10 hours, further cold-rolled to 0.35 mm, soaked at 700 ° C for 20 seconds or at 750 ° C for 20 seconds It was subjected to physical. 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,N、およびTi,C,Nの含有量により規定される下記式(2)および(3)で示されるNb*およびTi*と、鋼板の引張強さとの関係を示す。
Nb*=Nb/93−C/12−N/14 (2)
Ti*=Ti/48−C/12−N/14 (3)
(ここで、式(2)および(3)中、Nb、Ti、CおよびNはそれぞれの元素の含有量(質量%)を示す。)
1 and 2, the following formula (2) defined by the contents of Nb, C, N, and Ti, C, N for each steel sheet subjected to soaking at 700 ° C. or 750 ° C. for 20 seconds. ) And (3) and the relationship between Nb * and Ti * and the tensile strength of the steel sheet.
Nb * = Nb / 93-C / 12-N / 14 (2)
Ti * = Ti / 48-C / 12-N / 14 (3)
(Here, in the formulas (2) and (3), Nb, Ti, C and N indicate the content (mass%) of each element.)
図1および図2より、Nb*>0、Ti*>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、Ti*>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*、Ti*は固溶Nb、固溶Ti含有量と対応しており、再結晶抑制には固溶Nb、固溶Ti含有量の確保が重要であると判明した。さらに、NbとTiを比較すれば、Nbの再結晶抑制効果の方がTiのそれよりも大きいため高強度化にはより有効であり、均熱処理での均熱温度が高温化した場合ほどその効果の差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 and Ti * > 0. Moreover, as a result of investigating the steel structure, recrystallization was suppressed only when Nb * > 0 and Ti * > 0, and the steel structure was a processed structure and a recovered structure. Nb * and Ti * correspond to the solute Nb and solute Ti contents, and it has been found that securing the solute Nb and solute Ti contents is important for suppressing recrystallization. Furthermore, if Nb and Ti are compared, the effect of suppressing recrystallization of Nb is greater than that of Ti, so it is more effective for increasing the strength. The higher the soaking temperature in soaking, the more It was also found that the difference in effect was large.
また、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Nbを積極的に含有させたうえで下記式(1)を満足させる必要があると判明し、本発明を完成したのである。
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。)
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。
In addition, Zr and V were also examined in the same manner as described above, and it was found that it was necessary to satisfy the following formula (1) after positively containing Nb in order to suppress recrystallization. Thus, the present invention has been completed.
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.)
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:0.06%以下、Si:3.5%以下、Mn:0.05%以上3.0%以下、Al:2.5%以下、P:0.30%以下、S:0.04%以下、N:0.02%以下、Nb:0.02%超を含有し、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種の元素を上記式(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90%未満であることを特徴とするものである。
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。また、本発明において、「残部が実質的にFeおよび不純物からなる」とは、本発明の効果を阻害しない範囲で他の元素を含有する場合を含むことを意味する。
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および再結晶部分の面積比率について説明する。
A. Non-oriented electrical steel sheet for rotors The non-oriented electrical steel sheet for rotors of the present invention is mass%, C: 0.06% or less, Si: 3.5% or less, Mn: 0.05% or more. 0% or less, Al: 2.5% or less, P: 0.30% or less, S: 0.04% or less, N: 0.02% or less, Nb: more than 0.02%, Nb, Ti And at least one element selected from the group consisting of Zr and V in a range satisfying the above formula (1), the balance being substantially composed of Fe and impurities, and the area ratio of the recrystallized portion being 90% It is characterized by being less than.
“%” Indicating the content of each element means “mass%” unless otherwise specified. Further, in the present invention, “the balance is substantially composed of Fe and impurities” means that it includes a case where other elements are contained within a range that does not impair the effects of the present invention.
Hereinafter, the steel composition and the area ratio of the recrystallized portion 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含有量は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含有量の上限値は0.06%とする。好ましくは0.04%以下、さらに好ましくは0.02%以下である。特に、C含有量が0.01%以下であれば、Nb/93+Zr/91+Ti/48+V/51−(C/12+N/14)>0なる条件を満たすのに必要なNb,Zr,TiおよびVの含有量が少なくてすむので製造コストの観点から望ましい。
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 secure the contents of solute 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 0.06%. Preferably it is 0.04% or less, More preferably, it is 0.02% or less. In particular, if the C content is 0.01% or less, Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14)> 0 necessary for satisfying the condition of Nb, Zr, Ti and V Since the content is small, it is desirable from the viewpoint of manufacturing cost.
(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。しかしながら、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。また、割れ抑制の観点からは3.0%以下が好ましい。さらに、Siを脱酸剤として使用する場合は0.01%以上含有させることが必要であるが、Alを脱酸剤として使用する場合もあるため、Si含有量の下限値は特に限定しない。固溶強化による鋼板の高強度化という観点からは、望ましい下限値は1.0%である。
(2) Si
Si is an element that has the effect of increasing electrical resistance and reducing eddy current loss. However, 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. Moreover, 3.0% or less is preferable from a viewpoint of crack suppression. Furthermore, when using Si as a deoxidizing agent, it is necessary to contain 0.01% or more, but since Al may be used as a deoxidizing agent, the lower limit of the Si content is not particularly limited. From the viewpoint of increasing the strength of the steel sheet by solid solution strengthening, the desirable lower limit is 1.0%.
(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3.0%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、0.05%とする。
(3) Mn
Mn has the effect of increasing electrical resistance and reducing eddy current loss, similar to Si. However, if Mn is contained in a large amount, the alloy cost increases, so the upper limit of the Mn content is 3.0%. On the other hand, the lower limit of the Mn content is determined from the viewpoint of fixing S, and is 0.05%.
(4)Al
Alは電気抵抗を高めるためSiと同様に渦電流損失を低減する。しかしながら、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。また、Alを脱酸剤として使用する場合は0.01%以上含有させることが必要であるが、Siを脱酸剤として使用する場合があるため、Al含有量の下限値は特に限定しない。固溶強化による鋼板の高強度化という観点からは、望ましい下限値は0.2%である。
(4) Al
Al increases eddy current loss in the same manner as Si because it increases electric resistance. However, when Al is contained in a large amount, the alloy cost increases and the leakage of magnetic flux occurs due to the decrease of the saturation magnetic flux density, so that the motor efficiency decreases. From these viewpoints, the upper limit of the Al content is 2.5%. Moreover, when using Al as a deoxidizer, it is necessary to contain 0.01% or more, but since Si may be used as a deoxidizer, the lower limit of the Al content is not particularly limited. From the viewpoint of increasing the strength of the steel sheet by solid solution strengthening, the desirable lower limit is 0.2%.
(5)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0.30%以下とする。
(5) 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 0.30% or less.
(6)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0.04%を上限とする。
(6) 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 0.04%.
(7)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によって再結晶を抑制するためには、N含有量は低減することが好ましい。しかしながら、N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の含有量は確保できる点を鑑み、N含有量の上限は0.02%とする。好ましくは0.01%以下、さらに好ましくは0.005%以下である。N含有量が0.005%以下であれば、Nb/93+Zr/91+Ti/48+V/51−(C/12+N/14)>0なる条件を満たすのに必要なNb,Zr,TiおよびVの含有量が少なくてすむので製造コストの観点から望ましい。
(7) 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, in order to suppress recrystallization by the solid solution Nb, Zr, Ti and V, it is preferable to reduce the N content. However, in view of the fact that the contents of solute Nb, Zr, Ti and V can be secured if the contents of Nb, Zr, Ti and V are increased accordingly even if the N content is large, The upper limit is 0.02%. Preferably it is 0.01% or less, More preferably, it is 0.005% or less. If the N content is 0.005% or less, the Nb, Zr, Ti and V contents necessary to satisfy the condition of Nb / 93 + Zr / 91 + Ti / 48 + V / 51− (C / 12 + N / 14)> 0 This is desirable from the viewpoint of manufacturing cost.
(8)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(4)を満足する範囲で含有させることが必要である。
Nb/93+Zr/91+Ti/48+V/51−(C/12+N/14)>0 (4)
(ここで、式(4)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。)
(8) 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 (4).
Nb / 93 + Zr / 91 + Ti / 48 + V / 51- (C / 12 + N / 14)> 0 (4)
(Here, in the formula (4), Nb, Zr, Ti, V, C and N indicate the content (mass%) of each element.)
上記式(4)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。
上述のとおり、これらの元素のなかでも固溶Nbの寄与が特に大きいため、本発明ではNbを積極的に含有させるものとし、Nb含有量は0.02%を超えるものとする。好ましくは0.04%以上である。Nbを積極的に含有させることは後述するように生産性向上にも大きく寄与する。一方、Nb含有量の上限は、後述する式(1)の上限を超えない範囲とする。
The left side of the above formula (4) 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 the carbide, nitride or carbonitride It corresponds to containing Nb, Zr, Ti or V in a solid solution state in which no precipitate is formed.
As described above, since the contribution of the solid solution Nb is particularly large among these elements, Nb is positively contained in the present invention, and the Nb content exceeds 0.02%. Preferably it is 0.04% or more. The positive inclusion of Nb greatly contributes to productivity improvement as will be described later. On the other hand, the upper limit of the Nb content is set so as not to exceed the upper limit of the formula (1) described later.
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。
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。また、冷間圧延時に割れが生じる場合もある。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。
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。)
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.
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. Moreover, a crack may arise at the time of cold rolling. 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)
(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再結晶抑制効果に及ぼす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。 Further, when considering sulfide, the contents of Nb, Zr, Ti and V in a solid solution state are also affected by the S content. However, since the influence of S on the recrystallization suppressing effect 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.
(9)Cu,Ni,Cr,Mo,CoおよびW
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より磁気特性と機械特性の両立を図っているため、この再結晶抑制効果を損なわない範囲でCu,Ni,Cr,Mo,CoおよびWからなる群から選択される少なくとも1種の元素を含有させることができる。これらの元素は鋼板を高強度化する作用を有するので、鋼板の強度をさらに高めるのに有効であり好ましい。
Cuは鋼板の固有抵抗を増加し、鉄損を低減する効果がある。しかしながら過度にCuを含有させると表面疵や冷間圧延時の割れの発生につながるため、Cu含有量は0.01%以上8.0%以下とすることが好ましい。
NiおよびMoは過度に含有させると冷間圧延時の割れの発生やコスト増加につながるため、Ni含有量は0.01%以上2.0%以下、Mo含有量は0.005%以上4.0%以下とすることが好ましい。
Crは鋼板の固有抵抗を増加し、鉄損を低減する効果がある。また耐食性を改善する効果も有する。しかしながら過度にCrを含有させるとコストが増加するため、Cr含有量は0.01%以上15.0%以下とすることが好ましい。
CoおよびWは、過度に含有させるとコストが増加するため、Co含有量は0.01%以上4.0%以下、W含有量は0.01%以上4.0%以下とすることが好ましい。
(9) Cu, Ni, Cr, Mo, Co and W
In the present invention, since the recrystallization itself is suppressed rather than the recrystallized grain size, the recrystallization itself is suppressed to achieve both magnetic properties and mechanical properties. Therefore, Cu, Ni, At least one element selected from the group consisting of Cr, Mo, Co and W can be contained. Since these elements have the effect of increasing the strength of the steel sheet, they are effective and preferable for further increasing the strength of the steel sheet.
Cu has the effect of increasing the specific resistance of the steel sheet and reducing iron loss. However, excessive inclusion of Cu leads to surface defects and cracking during cold rolling, so the Cu content is preferably 0.01% or more and 8.0% or less.
If Ni and Mo are excessively contained, cracks during cold rolling and an increase in cost are caused. Therefore, the Ni content is 0.01% or more and 2.0% or less, and the Mo content is 0.005% or more. It is preferable to make it 0% or less.
Cr has the effect of increasing the specific resistance of the steel sheet and reducing iron loss. It also has the effect of improving corrosion resistance. However, since the cost increases when Cr is excessively contained, the Cr content is preferably 0.01% or more and 15.0% or less.
When Co and W are excessively contained, the cost increases. Therefore, the Co content is preferably 0.01% or more and 4.0% or less, and the W content is preferably 0.01% or more and 4.0% or less. .
(10)Sn,Sb,Se,Bi,Ge,TeおよびB
本発明は再結晶を抑制することにより磁気特性と機械特性の両立を図っているため、粒界偏析により再結晶を抑制する効果を有するSn,Sb,Se,Bi,Ge,TeおよびBからなる群から選択される少なくとも1種の元素を含有させることが好ましい。これらの元素を含有させる場合には、熱間圧延工程での割れの発生およびコスト増加を抑制する観点から、各元素の含有量をSn:0.5%以下、Sb:0.5%以下、Se:0.3%以下、Bi:0.2%以下、Ge:0.5%以下、Te:0.3%以下、B:0.01%以下とすることが好ましい。これらの元素による再結晶抑制効果を確実に得るには、各元素の含有量をSn:0.001%以上、Sb:0.0005%以上、Se:0.0005%以上、Bi:0.0005%以上、Ge:0.001%以上、Te:0.0005%以上、B:0.0002%以上とすることが好ましい。
(10) Sn, Sb, Se, Bi, Ge, Te and B
Since the present invention attempts to achieve both magnetic properties and mechanical properties by suppressing recrystallization, it consists of Sn, Sb, Se, Bi, Ge, Te, and B, which have the effect of suppressing recrystallization by grain boundary segregation. It is preferable to contain at least one element selected from the group. When these elements are contained, the content of each element is Sn: 0.5% or less, Sb: 0.5% or less, from the viewpoint of suppressing the occurrence of cracks and cost increase in the hot rolling process. Preferably, Se is 0.3% or less, Bi is 0.2% or less, Ge is 0.5% or less, Te is 0.3% or less, and B is 0.01% or less. In order to reliably obtain the recrystallization suppressing effect by these elements, the content of each element is Sn: 0.001% or more, Sb: 0.0005% or more, Se: 0.0005% or more, Bi: 0.0005. % Or more, Ge: 0.001% or more, Te: 0.0005% or more, and B: 0.0002% or more are preferable.
(11)Ca,MgおよびREM
本発明で規定するS含有量の範囲内では再結晶抑制効果に及ぼすSの影響は認められなかったため、本発明においては硫化物の形態制御による磁気特性改善を目的としてCa,MgおよびREMからなる群から選択される少なくとも1種を含有させることができる。
ここでREMとは、原子番号57〜71の15元素、ならびに、ScおよびYの2元素の合計17元素をさす。
これらの元素を含有させる場合には、各元素の含有量はCa:0.03%以下、Mg:0.02%以下、REM:0.1%以下が好ましい。上記効果を確実に得るためには、各元素の含有量をCa:0.0001%以上、Mg:0.0001%以上、REM:0.0001%以上とすることが好ましい。
(11) Ca, Mg and REM
Since the influence of S on the recrystallization suppression effect was not recognized within the range of the S content defined in the present invention, in the present invention, it is composed of Ca, Mg and REM for the purpose of improving magnetic properties by controlling the form of sulfide. At least one selected from the group can be contained.
Here, REM refers to a total of 17 elements of 15 elements having atomic numbers 57 to 71 and 2 elements of Sc and Y.
When these elements are contained, the content of each element is preferably Ca: 0.03% or less, Mg: 0.02% or less, and REM: 0.1% or less. In order to reliably obtain the above effects, the content of each element is preferably set to Ca: 0.0001% or more, Mg: 0.0001% or more, and REM: 0.0001% or more.
(12)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。本発明は、再結晶組織を前提とした従来技術とは異なり、多く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強度を高めるものであるから、再結晶組織を前提とした従来技術において制限されていた元素の含有をより高いレベルまで許容することができる。例えば、Ta,Hf,As,Au,Be,Zn,Pb,Tc,Re,Ru,Os,Rh,Ir,Pd,Pt,Ag,Cd,HgおよびPoを総和で0.1%以下含有することができる。
(12) Others In the present invention, it is possible to contain elements other than the elements described above within a range not impairing the effects of the present invention. Unlike the prior art based on the premise of a recrystallized structure, the present invention increases strength by using a processed structure and a recovered structure in which many dislocations remain. Inclusion of limited elements can be tolerated to higher levels. For example, Ta, Hf, As, Au, Be, Zn, Pb, Tc, Re, Ru, Os, Rh, Ir, Pd, Pt, Ag, Cd, Hg, and Po are contained in a total amount of 0.1% or less. Can do.
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の限定理由について実験結果とともに説明する。
質量%で、C:0.002%、Si:2.8%、Mn:0.2%、Al:1.2%、S:0.006%、N:0.002%、P:0.01%、Nb:0.09%の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、680〜1050℃の種々の温度で10秒間保持する均熱処理を施した。このようにして得られた鋼板の引張強さを測定した。
図3に再結晶部分の面積比率と降伏点および引張強さとの関係を示す。再結晶の前段階である回復の進行とともに、再結晶部分の面積比率はゼロのまま降伏点および引張強さは低下する。再結晶開始後は,再結晶部分の面積比率の増加とともに降伏点および引張強さはさらに低下する。ここで、再結晶部分の面積比率は回転子用に必要な機械特性を確保する観点から定まるものである。安全率を考慮すれば、高速回転時の変形抑制の観点から、再結晶部分の面積比率は90%未満となる。好ましくは70%以下である。疲労破壊を抑制する観点からは40%以下が好ましく、さらに好ましくは25%未満である。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、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い。
2. Next, the reason for limiting the area ratio of the recrystallized portion in the present invention will be described together with the experimental results.
In mass%, C: 0.002%, Si: 2.8%, Mn: 0.2%, Al: 1.2%, S: 0.006%, N: 0.002%, P: 0.00. Hot rolled to 01%, Nb: 0.09% steel to 2.3 mm, hot-rolled sheet annealed at 800 ° C. for 10 hours, further cold rolled to 0.35 mm, 680-800 A soaking treatment was performed by holding at various temperatures of 1050 ° C. for 10 seconds. The tensile strength of the steel sheet thus obtained was measured.
FIG. 3 shows the relationship between the area ratio of the recrystallized portion, the yield point, and the tensile strength. With the progress of recovery, which is the pre-recrystallization stage, the yield point and tensile strength decrease while the area ratio of the recrystallized portion remains zero. After the start of recrystallization, the yield point and tensile strength further decrease as the area ratio of the recrystallized portion increases. Here, the area ratio of the recrystallized portion is determined from the viewpoint of securing the mechanical characteristics necessary for the rotor. Considering the safety factor, the area ratio of the recrystallized portion is less than 90% from the viewpoint of suppressing deformation during high-speed rotation. Preferably it is 70% or less. From the viewpoint of suppressing fatigue fracture, it is preferably 40% or less, more preferably less than 25%. From the viewpoint of mechanical properties, the area ratio of the recrystallized portion is preferably as low as possible, and it is preferable that the area ratio of the recrystallized portion is zero and the state is completely unrecrystallized (worked structure and recovery structure).
再結晶部分の面積比率制御には、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。本発明においては、再結晶抑制効果の大きいNbを積極的に含有させることを特徴としているため、このような再結晶部分の面積比率制御は、特願2004−183554および特願2004−252395で開示した技術よりも容易であり、生産性向上にもつながる。 To control the area ratio of the recrystallized portion, it is important to adjust the soaking temperature and soaking time during soaking. Since the present invention is characterized by positively containing Nb having a large effect of suppressing recrystallization, such area ratio control of the recrystallized portion is disclosed in Japanese Patent Application Nos. 2004-183554 and 2004-252395. It is easier than the developed technology and leads to improved productivity.
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縦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、この縦断面組織写真をもとに測定することができる。縦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 visual field in the longitudinal sectional structure photograph of the non-oriented electrical steel sheet for rotors of the present invention. It can be measured originally. As the longitudinal cross-sectional structure photograph, an optical microscope photograph can be used. For example, a photograph taken at a magnification of 100 times may be used.
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820℃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 method for producing a non-oriented electrical steel sheet for a rotor of the present invention includes a hot rolling process in which hot rolling is performed on a steel ingot or steel slab having the above-described steel composition, and a hot process obtained by the hot rolling process. A cold rolling process in which cold rolling is performed twice or more by sandwiching the rolled steel sheet once or by intermediate annealing, and a soaking process in which the cold rolled steel sheet obtained by the cold rolling process is soaked at 820 ° C. or less. It is characterized by having.
本発明によれば、均熱処理工程での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、これにより鋼板の高強度化が可能である。また、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。
以下、このような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。
According to the present invention, by setting the temperature in the soaking process to a predetermined range, recrystallization is suppressed, and disappearance of dislocations introduced during processing to a predetermined plate thickness is suppressed, and a large amount of The recovery structure in which dislocations are left can be the main component, which makes it possible to increase the strength of the steel sheet. In addition, since 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 cold rolling, it is possible to suppress breakage during cold rolling. . Furthermore, in the present invention, since a steel ingot or steel slab having a predetermined steel composition is used, and the temperature in the soaking process is set within a predetermined range as described above, the strength is increased. For example, a non-oriented electrical steel sheet for a rotor that satisfies the magnetic and mechanical characteristics required for a rotor of a drive motor can be stably manufactured without using expensive steel components or special processes. be able to.
Hereinafter, each process in the manufacturing method of such a non-oriented electrical steel sheet for rotors 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。
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。
(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.
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。
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。
また、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。
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.
The slab heating temperature is not particularly limited, but is preferably 1000 to 1300 ° C. from the viewpoint of cost and hot rolling properties. More preferably, it is 1050-1250 degreeC.
Moreover, various conditions of hot rolling are not specifically limited, For example, what is necessary is just to perform according to general conditions, such as finishing temperature 700-950 degreeC and coiling
(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。
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。
(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.
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.
本発明では冷間圧延により導入された転位の消滅を抑制して残存させることにより高強度化を達成しているため、導入された転位の量が少ない場合には十分な強度を確保できない。導入された転位の量は鋼板の強度で判別することができるため、本発明では均熱処理工程に供する前段階での引張強さを指標とし、圧延方向を長手方向とした測定値で850MPa以上とすることが好ましい。 In the present invention, the strength is increased by suppressing the disappearance of the dislocations introduced by cold rolling, so that sufficient strength cannot be ensured when the amount of dislocations introduced is small. Since the amount of dislocation introduced can be determined by the strength of the steel sheet, in the present invention, the tensile strength in the previous stage to be subjected to the soaking process is used as an index, and the measured value with the rolling direction as the longitudinal direction is 850 MPa or more. It is preferable to do.
この理由を実験結果に基づいて説明する。質量%で、C:0.003%、Si:2.9%、Mn:0.2%、Al:1.1%、S:0.001%、N:0.002%、P:0.01%、Nb:0.001%の組成を有する鋼(上述のNb*<0の鋼)と、C:0.002%、Si:2.8%、Mn:0.2%、Al:1.2%、S:0.006%、N:0.002%、P:0.01%、Nb:0.09%の組成を有する鋼(上述のNb*>0の鋼)とに熱間圧延を施して2.0mmとした後、750℃で10時間の熱延板焼鈍を行い、一回の冷間圧延にて0.35〜1.2mmの種々の板厚まで仕上げ、700℃で20秒間保持する均熱処理を施した。一部の熱延板については、熱延板焼鈍後に中間板厚を0.4〜1.8mm、中間焼鈍条件を750℃で10時間保持とした二回の冷間圧延にて0.35mmまで仕上げ、同様に700℃で20秒間保持する均熱処理を施した。これらの鋼板について均熱処理前後で圧延方向を長手方向として引張試験を実施した。 The reason for this will be described based on experimental results. In mass%, C: 0.003%, Si: 2.9%, Mn: 0.2%, Al: 1.1%, S: 0.001%, N: 0.002%, P: 0.00. Steel having a composition of 01%, Nb: 0.001% (steel of Nb * <0 described above), C: 0.002%, Si: 2.8%, Mn: 0.2%, Al: 1 .2%, S: 0.006%, N: 0.002%, P: 0.01%, Nb: 0.09% steel (having the above-mentioned Nb * > 0 steel) After rolling to 2.0 mm, hot-rolled sheet annealing is performed at 750 ° C. for 10 hours, and finished to various plate thicknesses of 0.35 to 1.2 mm by one cold rolling, at 700 ° C. A soaking treatment was performed for 20 seconds. For some hot-rolled plates, after hot-rolled sheet annealing, the intermediate sheet thickness is 0.4 to 1.8 mm, and the intermediate annealing conditions are maintained at 750 ° C. for 10 hours until cold rolling is performed to 0.35 mm Finishing was similarly performed soaking at 700 ° C. for 20 seconds. These steel sheets were subjected to a tensile test with the rolling direction as the longitudinal direction before and after soaking.
図4に均熱処理工程前後の引張強さを示す。Nb*>0の鋼に限り、一回冷延、二回冷延に関わらず均熱処理工程後の引張強さは均熱処理工程前の引張強さで整理できる。すなわち、固溶Nbを含有する鋼では、強度を確保するために必要な転位の量の目安として均熱処理工程前の引張強さを採用することができる。Ti,ZrおよびVについても同様の検討を実施し、本発明の鋼組成を備えていれば、強度を確保するために必要な転位の量の指標として均熱処理工程前の引張強さを採用することができるとの知見を得た。均熱処理工程後に十分な引張強さを確保するために必要な条件として、均熱処理工程の前段階で850MPa以上の引張強さを確保することが重要と判明したのである。
ここで、均熱処理工程の前段階における引張強さは、圧延方向を長手方向として採取した引張試験片にて測定することができる。
FIG. 4 shows the tensile strength before and after the soaking process. Only for steels with Nb * > 0, the tensile strength after the soaking process can be arranged by the tensile strength before the soaking process, regardless of cold rolling once or twice. That is, in steel containing solute Nb, the tensile strength before the soaking process can be adopted as a measure of the amount of dislocations necessary to ensure the strength. The same study is performed for Ti, Zr and V, and if the steel composition of the present invention is provided, the tensile strength before the soaking process is adopted as an index of the amount of dislocation necessary for ensuring the strength. The knowledge that it can be obtained. As a necessary condition for ensuring a sufficient tensile strength after the soaking process, it has been found important to secure a tensile strength of 850 MPa or more before the soaking process.
Here, the tensile strength in the previous stage of the soaking process can be measured with a tensile specimen taken with the rolling direction as the longitudinal direction.
十分に転位が導入されれば本発明の効果を得ることができるため、圧延時の鋼板温度、圧下率、圧延ロール径など、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。均熱処理工程に供する前に鋼板の平坦度を矯正する目的で軽加工を行う場合も、軽加工後で前述の引張強さを満足していれば本発明の効果を得ることができる。 Since the effects of the present invention can be obtained if sufficient dislocations are introduced, various conditions for cold rolling, such as the temperature of the steel sheet during rolling, the rolling reduction, and the diameter of the rolling roll, are not particularly limited. The material is appropriately selected depending on the steel composition of the material, the thickness of the target steel plate, and the like. Even when light processing is performed for the purpose of correcting the flatness of the steel sheet before being subjected to the soaking process, the effects of the present invention can be obtained as long as the above-described tensile strength is satisfied after the light processing.
(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820℃以下で均熱する工程である。
本発明は、均熱処理工程で進行する再結晶を抑制し、転位を残存させることを骨子としている。したがって、再結晶抑制効果が小さい場合には、均熱温度を通常の無方向性電磁鋼板の均熱温度よりも著しく低温化する必要がある。通常の無方向性電磁鋼板の連続焼鈍ラインでの均熱処理を前提とすれば、炉温が下がり、かつ安定化するまでは均熱処理に供することはできない。さらに、一旦炉温を下げた後は、通常の無方向性電磁鋼板の均熱温度まで炉温が上がり、かつ安定化するまでは、通常の無方向性電磁鋼板を均熱処理に供することもできない。これらのことから、再結晶抑制効果が小さい場合には、生産性を著しく低下させることが容易に想像できる。
本発明ではNb,Zr,TiおよびVのうち、Nbを積極的に含有させることを特徴としているため、再結晶を抑制する効果が大きい。したがって、均熱処理工程での均熱温度が高くとも加工組織および回復組織を得ることができ、特殊な均熱温度の機会を設ける必要がないため生産性を向上させることができる。具体的には、均熱処理工程の均熱温度が820℃以下であれば、所望の機械特性を得ることができる。機械特性の観点から好ましくは780℃以下、さらに好ましくは750℃以下である。この均熱温度は通常の無方向性電磁鋼板で実施する範囲内であり、生産性を阻害することはない。均熱温度が低ければ低いほど再結晶進行が抑制されるが、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、均熱処理により冷間圧延したままの状態よりも鉄損を改善する効果もあることから、均熱温度が低い場合には鉄損増加に繋がる。さらに、均熱温度が低い場合には、上述のとおり生産性が著しく低下する。そこで、平坦矯正および鉄損改善の観点から、好ましい均熱温度の下限値を500℃とする。さらに好ましくは600℃以上である。
(3) Soaking step The soaking step in the present invention is a step of soaking the cold-rolled steel sheet obtained by the cold rolling step described above at 820 ° C or lower.
The gist of the present invention is to suppress the recrystallization that proceeds in the soaking process and leave the dislocations. Therefore, when the recrystallization suppressing effect is small, it is necessary to make the soaking temperature significantly lower than the soaking temperature of a normal non-oriented electrical steel sheet. Assuming soaking in a continuous annealing line of a normal non-oriented electrical steel sheet, it cannot be subjected to soaking until the furnace temperature is lowered and stabilized. Furthermore, once the furnace temperature is lowered, the normal non-oriented electrical steel sheet cannot be subjected to soaking treatment until the furnace temperature rises to the soaking temperature of the normal non-oriented electrical steel sheet and stabilizes. . From these facts, it can be easily imagined that the productivity is remarkably lowered when the recrystallization suppressing effect is small.
Since the present invention is characterized by positively containing Nb among Nb, Zr, Ti and V, the effect of suppressing recrystallization is great. Therefore, even if the soaking temperature in the soaking process is high, a processed structure and a recovered structure can be obtained, and productivity can be improved because there is no need to provide a special soaking temperature opportunity. Specifically, if the soaking temperature in the soaking process is 820 ° C. or less, desired mechanical properties can be obtained. From the viewpoint of mechanical properties, it is preferably 780 ° C. or lower, more preferably 750 ° C. or lower. This soaking temperature is within the range to be implemented with a normal non-oriented electrical steel sheet, and does not hinder productivity. The lower the soaking temperature is, the more the recrystallization progress is suppressed. However, when the soaking temperature is low, the flatness of the steel sheet is not corrected, and the space factor when laminated on the rotor may decrease. Moreover, since it has the effect of improving the iron loss as compared with the state of cold rolling by soaking, it leads to an increase in iron loss when the soaking temperature is low. Furthermore, when the soaking temperature is low, the productivity is significantly reduced as described above. Therefore, from the viewpoint of flatness correction and iron loss improvement, a preferable lower limit value of the soaking temperature is set to 500 ° C. More preferably, it is 600 degreeC or more.
均熱処理は箱焼鈍で実施してもよいが、コイル状態で焼鈍に供されることに起因してコイルの巻きぐせ(コイルセットともいう)により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、均熱処理工程後に鋼板の平坦度や形状を矯正する矯正工程が必要な場合がある。したがって、生産性の観点からは連続焼鈍ラインにて実施することが望ましい。
なお、高温での均熱処理により再結晶が進行し、それに起因して機械特性が低下した場合には、工程増加はやむを得ないが均熱処理工程後に加工して強度を確保してもよい。
The soaking process may be carried out by box annealing, but the flatness of the steel sheet decreases or the shape deteriorates due to winding of the coil (also called coil set) due to the annealing in the coil state. In some cases, a straightening process for correcting the flatness and shape of the steel sheet after the soaking process may be necessary. Therefore, it is desirable to carry out in a continuous annealing line from the viewpoint of productivity.
If recrystallization proceeds by soaking at a high temperature and the mechanical properties are lowered due to this, the number of steps is unavoidable, but processing may be performed after the soaking step to ensure strength.
(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。
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。
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。
(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.
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.
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皮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 step, according to a general method, a coating step of applying an insulating film made of only an organic component, only an inorganic component, or an organic-inorganic composite to a steel sheet surface may be performed. preferable. 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。 Hereinafter, the present invention will be described specifically by way of examples and comparative examples.
[実施例1〜26]
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℃で熱間圧延を行い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11〜26では種々の温度で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では500℃で10時間保持する箱焼鈍による均熱処理を施した。このようにして、鋼板を作製した。
[Examples 1 to 26]
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 sheets, box annealing that is held for 10 hours in a hydrogen atmosphere or hot-rolled sheet annealing by continuous annealing that is held at 1000 ° C. for 60 seconds is performed for one cold rolling. And finished to a plate thickness of 0.35 mm. 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, in Examples 1 to 9 and 11 to 26, soaking was performed by continuous annealing that was held at various temperatures for 30 seconds. In Example 10, soaking was performed by box annealing held at 500 ° C. for 10 hours. In this way, a steel plate was produced.
[比較例1〜8]
上記表1に示す鋼組成を有する鋼を用いて、実施例1〜26と同様にして鋼板を作製した。
[Comparative Examples 1-8]
A steel plate was produced in the same manner as in Examples 1 to 26, using steel having the steel composition shown in Table 1 above.
[評価]
実施例1〜26および比較例1〜8の鋼板について、均熱処理の前段階における鋼板の機械特性、ならびに、均熱処理後の再結晶部分の面積比率、機械特性、磁気特性および疲労特性を評価した。
[Evaluation]
About the steel plates of Examples 1 to 26 and Comparative Examples 1 to 8, the mechanical properties of the steel plates in the stage before soaking, and the area ratio, mechanical properties, magnetic properties, and fatigue properties of the recrystallized portion after soaking were evaluated. .
再結晶部分の面積比率は、100倍の倍率で撮影した鋼板の縦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を行い評価した。均熱処理の前段階の鋼板については引張強さ:TSにて、均熱処理後の鋼板については降伏点:YPおよび引張強さ:TSにて評価した。
磁気特性については、55mm角の単板試験片にて、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。測定は圧延方向と圧延直角方向について実施し、それらの平均値を採用した。
疲労試験としては、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。
As the area ratio of the recrystallized portion, the ratio of the recrystallized grains in the visual field was calculated using an optical micrograph of the longitudinal section of the steel sheet taken at a magnification of 100 times.
The mechanical properties were evaluated by performing a tensile test using a JIS No. 5 test piece. The steel plate before the soaking was evaluated by tensile strength: TS, and the steel plate after the soaking was evaluated by yield point: YP and tensile strength: TS.
Regarding magnetic characteristics, a 55 mm square single plate test piece has a maximum magnetic flux density of 1.0 T, an excitation frequency of 400 Hz, an iron loss W 10/400, and a magnetic flux density B 50 of 5000 A / m. It was measured. The measurement was carried out in the rolling direction and the direction perpendicular to the rolling, and the average value thereof was adopted.
As the fatigue test, a test piece was collected 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”.
表2に、実施例1〜26および比較例1〜8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 26 and Comparative Examples 1 to 8, 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の鋼板は冷間圧延により導入される転位の量が十分でなかったため、降伏点および引張強さともに劣っていた。比較例7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8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冷間圧延時に破断した。
これに対して本発明で規定する要件を満足する実施例1〜26の鋼板では、熱延板焼鈍の方法、冷間圧延の回数に拘わらず、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。
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 sheet of Comparative Example 6 was inferior in yield point and tensile strength because the amount of dislocations introduced by cold rolling was not sufficient. The steel plate of Comparative Example 7 was inferior in yield point and tensile strength because the area ratio of the recrystallized portion was high. The steel plate of Comparative Example 8 broke during cold rolling because the Nb, Zr, Ti and V contents exceeded the upper limit of the range of the present invention.
On the other hand, in the steel plates of Examples 1 to 26 that satisfy the requirements specified in the present invention, regardless of the hot-rolled sheet annealing method and the number of cold rolling, the magnetic properties and mechanical properties showed excellent values. Thus, fatigue failure did not occur even under the stress conditions described above.
また、均熱温度が比較的高い条件であっても、再結晶抑制効果が大きいため優れた磁気特性、機械特性を有していることがわかった。さらに、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。 In addition, it was found that even under conditions where the soaking temperature is relatively high, the recrystallization suppression effect is large, and thus the magnetic properties and mechanical properties are excellent. Furthermore, by comparing Examples 13 and 14, it was found that the mechanical properties did not change even when the S content changed.
Claims (6)
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: 0.06% or less, Si: 3.5% or less, Mn: 0.05% or more and 3.0% or less, Al: 2.5% or less, P: 0.30% or less, S : 0.04% or less, N: 0.02% or less, Nb: more than 0.02%, and at least one element selected from the group consisting of Nb, Ti, Zr and V is represented by the following formula (1 ), The balance is substantially composed of Fe and impurities, and the area ratio of the recrystallized portion is less than 90%.
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.)
Cu:0.01%以上8.0%以下 Ni:0.01%以上2.0%以下
Cr:0.01%以上15.0%以下 Mo:0.005%以上4.0%以下
Co:0.01%以上4.0%以下 W:0.01%以上4.0%以下 The at least one element selected from the group consisting of Cu, Ni, Cr, Mo, Co, and W is contained in the following mass%, instead of a part of the Fe. Non-oriented electrical steel sheet for rotors.
Cu: 0.01% to 8.0% Ni: 0.01% to 2.0% Cr: 0.01% to 15.0% Mo: 0.005% to 4.0% Co: 0.01% or more and 4.0% or less W: 0.01% or more and 4.0% or less
Sn:0.5%以下 Sb:0.5%以下 Se:0.3%以下 Bi:0.2%以下
Ge:0.5%以下 Te:0.3%以下 B:0.01%以下 2. Instead of a part of the Fe, at least one element selected from the group consisting of Sn, Sb, Se, Bi, Ge, Te and B is contained in the following mass%. Or the non-oriented electrical steel sheet for rotors of Claim 2.
Sn: 0.5% or less Sb: 0.5% or less Se: 0.3% or less Bi: 0.2% or less Ge: 0.5% or less Te: 0.3% or less B: 0.01% or less
Ca:0.03%以下 Mg:0.02%以下 REM:0.1%以下 4. Instead of a part of Fe, at least one element selected from the group consisting of Ca, Mg, and REM is contained in the following mass%, and any one of claims 1 to 3 The non-oriented electrical steel sheet for rotors according to claim 1.
Ca: 0.03% or less Mg: 0.02% or less REM: 0.1% or less
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