JP4670230B2 - Non-oriented electrical steel sheet - Google Patents

Description

【００２１】
表１より、従来の固溶強化、細粒強化および析出強化を利用した鋼種１〜３では、引張強さ700MPa以上の高い強度が得られているが、周波数１kHzでの鉄損Ｗ_5/1kは20Ｗ／kgを超えており、励磁実効電流も高い値となっている。
これに対して、Cuの析出強化を利用した材料では、鉄損、励磁実効電流および強度共に良好な値を示している。この理由は、時効処理を経て析出した数nm〜数10nm程度の非常に微細なCu析出物は、転位をピン止めすることにより高強度化に寄与するものの、磁壁の移動はほとんど妨げないため、良好な鉄損が得られたものと考えられる。
すなわち、Cu析出を利用した本発明では、従来の高強度電磁鋼板で達成することができなかったレベルの、強度−磁気特性バランスが得られることがわかる。
【００２２】
次に、高強度化に必要なCu添加量を調査するための実験を行った。すなわち、Ｃ：0.0020％、Si：3.0％、Mn：0.18％、Ｐ：0.01％およびAl：0.60％を含み、Cuを0.01〜５％の範囲で変化させた鋼スラブを、熱間圧延後900℃で30ｓの熱延板焼鈍を行い、0.20mm厚に冷間圧延し、900℃×30ｓの仕上げ焼鈍を施し、さらに550℃×１ｈの時効処理を施した。かくして得られた鋼板について、JIS Z2241に準拠した引張試験により引張強さを調査した。
【００２３】
その調査結果を、Cu添加量と引張強さとの関係として、図１に示す。図１から、強度を向上させるためにはＣｕ添加量を0.5％以上とする必要があることがわかる。すなわち、Cuが0.5％未満では、時効処理を行ったとしても十分なCu析出が得られないためである。一方、４％を超えてCuを添加すると、逆に強度は低下する。これは粗大な析出物が形成されるためである。従って、Cuの添加量は、0.5％以上４％以下とする。
【００２４】
ここで、本発明において、Cuはモータコアの状態で微細に析出していることが特徴であり、この点から従来の集合組織制御等の目的から、Cu添加を行った電磁鋼板とは全く異なるものである。
【００２５】
なお、Cuを析出させるための時効処理は、400℃〜650℃にて10min〜1000ｈとすることが推奨される。
【００２６】
製品板の板厚は0.05〜0.27mmとする。これは、板厚を0.27mm以下とすることにより高周波鉄損が低下し、Ｉ×Ｗ_5/1k≦5.5×10^４となりモータ効率が向上するためである。しかし、板厚が0.05mm未満では積層枚数が増大し、作業工数が増えるため下限を0.05mmとする。
【００２７】
また、高強度材における励磁実効電流および鉄損とモータ効率との関係を調査するため、８極のＩＰＭモータを試作した。モータは、ロータ外径110 mm、ステータ外径160 mmおよび固定子スロット数は24とし、永久磁石はNeFeB系の磁石を用いた。そして、コア材料として、種々の高強度材料(TS>550MPa)を適用してモータを試作し、この試作モータにおける効率を調査した。ここで、モータ効率は、トルクの要求される周波数50Hzではティース磁束密度1.7Ｔで測定し、トルクがそれほど要求されない周波数１kHzではティース磁束密度0.5Ｔでの効率を評価し、その平均値とした。
【００２８】
図２に、このモータ効率と鋼板における励磁実効電流および鉄損との関係を示す。図２から、励磁実効電流4500Ａ／ｍ以下および鉄損20Ｗ／kg以下で、かつＩ×Ｗ_5/1k≦5.5×10^４の場合に90％以上の効率が得られていることがわかる。すなわち、励磁実効電流Ｉが4500Ａ／ｍ超の材料では、高トルク域で駆動した場合に銅損の上昇が大きいために効率が低下し、一方、鉄損20Ｗ／kg超では高周波駆動時の鉄損が大きいために効率が低下したものと考えられる。さらに、Ｉ×Ｗ_5/1kが5.5×10^４超の領域では、鉄損および銅損の両者が増大したことにより、効率が低下したものと考えられる。
【００２９】
従って、電磁鋼板をモータに適用した際の効率を考慮すると、周波数１kHzでの鉄損Ｗ_5/1kは20Ｗ／kg以下、1.7Ｔおよび50Hzでの励磁実効電流Ｉは4500Ａ／ｍ以下とし、さらにＩ×Ｗ_5/1k≦5.5×10^４とする。
【００３０】
以下に、本発明について、その構成要件毎に詳述する。
（鋼板の成分組成）
まず、成分組成範囲およびその限定理由を説明する。
Ｃ：0.02％以下
Ｃは、磁気時効の問題があるため、0.02％以下とした。
Ｐ：0.2％以下、
Ｐは、鋼板の高強度化に有効な元素であるが、0.2％を超えて添加すると鋳造時の中央偏析が生じやすく、また鋼板が脆化し冷間圧延性が著しく低下するため、0.2％以下とした。
【００３１】
Si：4.5％以下、
Siは、鋼板の固有抵抗を上げるために有効な元素であるが、4.5％を超えると冷間圧延性および温間圧延性が著しく低下するため、上限を4.5％、望ましくは飽和磁化の観点から4.0％未満とする。
【００３２】
Mn：３％以下、
Mnは、熱間圧延時の赤熱脆性を防止するために有効な元素であり、好ましくは0.05％以上で含有させるが、３％を超えると磁束密度を低下させるため、上限を３％とした。
【００３３】
Al：３％以下
Alは、Siと同様、固有抵抗を上げるために有効な元素であり、好ましくは0.1％以上で含有させるが、３％を超えると飽和磁化が低下するとともに、鋳造性等も著しく低下するため上限を３％とした。
【００３４】
Cu：0.5〜４％
Cuは、磁気特性を損なうことなく強度を上昇するために添加する成分であり、その上、下限を設定した理由は、上述した通りである。
【００３５】
本発明に係わる無方向性電磁鋼板の基本組成は以上の通りであるが、上記成分に加えて、磁気特性の改善元素として知られるSb、Sn、Ｂ、Ni、Cr、CoおよびREMを単独または複合で添加することが出来る。しかし、その添加量は本発明の目的を害さない程度にすべきである。具体的には、
Sb：0.005〜0.05％、
Sn：0.005〜0.1％、
Ｂ：0.0002〜0.002％、
Ni：0.1〜５％、
Co：0.2〜３％および
REM：0.001〜0.01％
である。また、Crに関しては、飽和磁化を低下させるため、添加する場合には0.8％以下とすることが望ましい。
【００３６】
引張強さは550MPa以上とし、より望ましくは600MPa以上とする。これは、550MPa未満の強度では高速回転時にローターが変形するためである。
【００３７】
（製造方法）
本発明に係わる鉄損に優れた高強度無方向性電磁鋼板を製造するには、まず、転炉あるいは電気炉などにて、前記した所定成分に溶製された鋼を、連続鋳造あるいは造塊後の分塊圧延により鋼スラブとする。次いで、得られたスラブを熱間圧延し、必要に応じて熱延坂焼鈍を施し、一回あるいは中間焼鈍を挟む二回以上の冷間圧延あるいは温間圧延を施して製品板厚とし、仕上げ焼鈍を施し、その後時効処理を施す。さらに、仕上げ焼鈍後のいずれかの段階において、必要に応じて絶縁被膜の塗布および焼き付け処理を行う。
【００３８】
引き続き行われる時効処理は、400℃以上650℃以下の温度で行うことが好ましい。すなわち、400℃未満の場合には、微細Cuの析出が不十分となり、高強度が得られない、おそれがある。一方、650℃を超えると、Cu析出物が粗大化して鉄損が劣化し強度上昇量も減少するため、良好な強度−鉄損バランスを有する電磁鋼板が得られない、おそれがある。さらに、適切な時効時間としては、処理温度にも依存するが、10min〜1000ｈが好適である。
なお、この時効処理の実施時期は、絶縁被膜の塗布焼付け前、焼付け後、プレス打ち抜きなどの加工後、などのいずれのタイミングで実施してもよいが、薄手材の打ち抜き時のたわみを防止するためには、打ち抜き前の時効が好ましい。
【００３９】
【実施例】
実施例１
転炉で吹練した後に脱ガス処理を行うことにより、表２に示す成分組成に調整した溶鋼から鋼スラブを鋳造し、このスラブを1140℃で１ｈ加熱した後、板厚2.0mmまで熱間圧延を行った。熱延仕上げ温度は800℃とした。巻取り温度は600℃とし、900℃×30ｓの熱延板焼鈍を施した。その後、0.18mm厚まで冷間圧延を行い、950℃×30ｓの仕上焼鈍を行い、種々の条件で時効処理を行った。
【００４０】
かくして得られた鋼板から採取した、25cmエプスタイン試験片を用いて磁気測定を行うとともに、JIS 13号Ｂ試験片を用いて引張試験を行った。各鋼板の磁気特性および引張強さを、表２に併せて示す。
【００４１】
【表２】

【００４２】
表２から、成分および時効処理条件を適切な範囲内としたものは、鉄損および強度に優れていることがわかる。
これに対し、Cuを添加しない場合（鋼板１および２）では、時効処理により強度が上昇しないことがわかる。また、時効処理時間が短い場合（鋼板３）や、時効処理温度が低い場合（鋼板９）ではCuが十分に析出しておらず、必要な強度レベルが得られていない。さらに、析出時間が長すぎる場合（鋼板８）や、時効温度が高すぎる場合（鋼板12）にはCuの析出物サイズが粗大となっており、鉄損が増大するとともに、強度上昇も小さくなっている。
【００４３】
実施例２
転炉で吹練した後に脱ガス処理を行うことにより、表３に示す成分組成に調整後鋳造して得た鋼スラブを、1140℃で１ｈ加熱した後、板厚2.0mmまで熱間圧延を行った。熱延仕上げ温度は800℃とした。巻取り温度は600℃とし、900℃×30ｓの熱延板焼鈍を施した。その後、表３に示す種々の板厚まで冷間圧延もしくは温間圧延を行い、表３に示す仕上焼鈍条件で焼鈍を行い、550℃×１ｈの時効処理を行った。
【００４４】
かくして得られた鋼板から採取した、25cmエプスタイン試験片を用いて磁気測定を行うとともに、JIS 13号Ｂ試験片を用いて引張試験を行った。各鋼板の磁気特性および引張強さを、表３に併せて示す。
【００４５】
【表３】

【００４６】
表３より、本発明に従う成分組成および板厚とした場合に、高周波磁気特性並びに強度に優れた電磁鋼板が得られることがわかる。
これに対し、Cuを添加していない場合（鋼板13）では強度が低く、細粒化により高強度化を図った場合（鋼板14）では、強度は高いものの鉄損が高くなっている。また、固溶強化により高強度化を図った場合（鋼板15）では、励磁実効電流が高くなっている。Cuが本発明範囲以上である鋼板20では、Cuが粗大化したため、鉄損が増大し、強度が低下している。
【００４７】
一方、板厚が本発明範囲をはずれている鋼板24では、鉄損が高くなっている。さらに、Siが本発明範囲を外れた鋼板29では励磁実効電流が高く、Ｐが本発明範囲を外れた鋼板30では、圧延時に鋼板が破断し、製品を得ることができなかった。また、AlおよびMnが本発明を外れた鋼板32および33では、励磁実効電流が高くなった。
【００４８】
【発明の効果】
以上述べたように、本発明によれば鉄損、強度バランスに優れ、励磁実効電流の低い材料を得ることができる。従って、本発明の無方向性電磁鋼板は、EVやHEVモータ、高速発電機、大型発電機のロータ材として好適である。
【図面の簡単な説明】
【図１】 Ｃｕ添加量と引張強さとの関係を示す図である。
【図２】 鉄損および励磁実効電流とモータ効率との関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-oriented electrical steel sheet, particularly a non-oriented electrical steel sheet having a characteristic of high strength and low iron loss, which is suitable for a part subjected to a large stress, such as a rotor of a high-speed rotary motor. It relates to the manufacturing method.
[0002]
[Prior art]
There is a strong demand for miniaturization and high efficiency in drive motors for electric vehicles (EV) and hybrid electric vehicles (HEV). In order to meet these demands, it is directed to increase the rotational speed of the rotor from the current several thousand to several tens of thousands. Therefore, a large centrifugal force acts on the rotor used in this high rotation type motor.
[0003]
In particular, in permanent magnets (IPM) motors, in which permanent magnets, which have become the mainstream of high-efficiency motors in recent years, are embedded inside the rotor, the force of the magnets popping out in the radial direction during high-speed rotation works. When the strength of the core is low, the core is deformed in the radial direction, and in an extreme case, the rotor and the stator come into contact with each other and the magnets are scattered. In order to suppress the deformation of the rotor, a material having excellent strength is required for the core material.
[0004]
On the other hand, when the motor rotates at high speed, the excitation frequency of the core material becomes high. Therefore, a material with low high-frequency iron loss is strongly demanded for the core material from the viewpoint of preventing heat generation of the motor. Has been. Therefore, there is a demand for a high strength magnetic steel sheet having high-frequency magnetic properties and a high strength as a motor material.
[0005]
As a high-strength electrical steel sheet used for such a high-speed rotating machine, for example, in Patent Document 1, 0.1 to 6% Mn and 0.3 to 6% Ni are added to steel containing Si: 2 to 3.5%, A technique for setting the crystal grain size to 30 μm or less is disclosed. However, although this technique has high strength, it has a problem that the iron loss W _15/50 is as high as about 6 W / kg due to the refinement of crystal grains.
[0006]
Patent Document 2 discloses a technique for increasing strength by adding Ti and V to steel of Si: 0.05 to 3.2% and using Ti and V-based carbonitrides. Although this technique has a tensile strength of 590 MPa or more, it has a problem that the iron loss is high because carbonitride precipitates relatively coarsely.
[0007]
On the other hand, as a low iron loss material for high frequency applications, for example, Patent Document 3 discloses a technique of a thin electromagnetic steel sheet containing Si: 1 to 4% and having a plate thickness of 0.1 to 0.25 mm. In this technique, although high-frequency iron loss is low, strength is not taken into consideration, and the application of the core material of a high-speed rotating machine is limited in terms of strength.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 64-226 [Patent Document 2]
JP 10-18005 A [Patent Document 3]
Japanese Patent Laid-Open No. 8-60311
[Problems to be solved by the invention]
As described above, none of the conventional techniques is satisfactory from the viewpoint of achieving both high strength and low iron loss.
Accordingly, an object of the present invention is to propose a non-oriented electrical steel sheet that has both good magnetic properties, particularly high-frequency magnetic properties and high strength.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the inventors have conducted various studies focusing on the age hardening phenomenon of Cu-containing steel, and as a result, have found a means for achieving both good iron loss and high strength. It came to establish. In other words, the precipitates in steel contribute to high strength, and at the same time, increase the iron loss by suppressing the domain wall movement, contrary to the conventional knowledge, adding an appropriate amount of Cu to the steel and performing an aging treatment Thus, it was newly found that when Cu is deposited very finely, the iron loss (historical loss) hardly deteriorates although the increase in strength is large. Furthermore, after adding Cu to precipitate Cu-based fine precipitates, by reducing the plate thickness, it is found that high strength can be achieved without impairing magnetic properties, and the present invention is completed. I reached.
[0011]
The gist configuration of the present invention is as follows.
(1) In mass%,
C: 0.02% or less,
P: 0.2% or less,
Si: 4.5% or less,
Mn: 3% or less,
Al: 3% or less and
Cu: 0.5-4%
, Balance Fe and inevitable impurity composition, plate thickness in the range of 0.05 to 0.27 mm , tensile strength of 550 MPa or more, iron loss W _{5 / 1k} of 20 W / kg or less, and frequency Non-oriented electrical steel sheet characterized in that the excitation effective current I at 50 Hz and magnetic flux density 1.7T is 4500 A / m or less, and further, the iron loss W _{5 / 1k} and the excitation effective current I satisfy the relationship of the following formula: .
I × W _{5 / 1k} ≦ 5.5 × 10 ⁴
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, the experimental results that led to the present invention will be described in detail. In the present specification, “%” representing a steel composition means “% by mass” unless otherwise specified.
First, in order to investigate the relationship between the strength and magnetic properties of a high-strength electrical steel sheet, the following four types of steel sheets were prepared.
Steel type 1: As a solid solution strengthened type electrical steel sheet, steel containing C: 0.002%, Si: 4.5%, Mn: 1%, P: 0.01%, Al: 0.6% and Mo: 1.5% is melted and heated. It was hot-rolled and annealed at 900 ° C. for 30 s, then hot-rolled at 400 ° C. and finished to 0.20 mm thickness, and 950 ° C. × 30 s finish annealing was performed.
[0015]
Steel type 2: As a grain refinement type electromagnetic steel sheet, steel containing C: 0.005%, Si: 3.5%, Mn: 1% and P: 0.05% is melted and hot-rolled and heated at 850 ° C for 30 s. After performing hot-rolled sheet annealing, it was cold-rolled to 0.20 mm thickness, and then subjected to finish annealing at 800 ° C. for 30 s.
[0016]
Steel type 3: Precipitation strengthened electrical steel sheet: C: 0.031%, Si: 2.6%, Mn: 0.2%, P: 0.02%, Al: 0.65%, N: 0.003%, Nb: 0.018% and Zr: 0.022% The steel containing was melted, hot-rolled and cold-rolled to a thickness of 0.20 mm, and subjected to finish annealing at 750 ° C. × 30 s.
About the above steel types 1-3, the aging treatment was not performed.
[0017]
Steel type 4: As an electrical steel sheet using precipitation strengthening of Cu, steel containing C: 0.002%, Si: 3.2%, Mn: 0.18%, P: 0.01%, Al: 0.55% and Cu: 1.1% is melted. After hot rolling, hot-rolled sheet annealing was performed at 900 ° C. for 30 s, cold-rolled to 0.20 mm thickness, subjected to finish annealing at 900 ° C. × 30 s, and further subjected to 550 ° C. × 1 h aging treatment.
[0018]
Table 1 shows the results of investigation on the magnetic properties and mechanical properties of the materials thus obtained. The magnetic characteristics were evaluated by a 25 cm Epstein method for iron loss W _{5 / 1k} at a magnetic flux density of 0.5 T and a frequency of 1 kHz, and an excitation effective current I at 1.7 T and 50 Hz. Moreover, the tensile test was done using the JIS 13 B test piece.
[0019]
Here, the reason for evaluating W _{5 / 1k} and the excitation effective current of 1.7 T and 50 Hz is as follows.
That is, the above-described high-frequency motors such as EV and HEV are driven in a wide frequency range from a low frequency range of about 50 Hz to a high frequency range. In the low frequency range, the magnetic flux is used at a high magnetic flux density particularly from the viewpoint of high torque. On the other hand, in the high frequency range, it is driven in a relatively low magnetic field range in order to suppress the induced voltage. This is because a large excitation current is required in the high torque region, so that a material having a high excitation effective current has a large copper loss, while a material having a high W _{5 / 1k} has a large iron loss in a high frequency region. For this reason, as a material for high frequency motors, a material with a low both is preferable.
[0020]
[Table 1]

[0021]
From Table 1, steel types 1 to 3 using conventional solid solution strengthening, fine grain strengthening and precipitation strengthening have obtained a high strength of 700 MPa or more, but iron loss W _{5 / 1k} at a frequency of 1 kHz. Is over 20 W / kg, and the excitation effective current is also high.
On the other hand, materials using Cu precipitation strengthening show good values for iron loss, excitation effective current and strength. The reason for this is that very fine Cu precipitates of several nanometers to several tens of nanometers deposited through aging treatment contribute to high strength by pinning dislocations, but the movement of the domain wall is hardly hindered. It is considered that good iron loss was obtained.
That is, in the present invention using Cu precipitation, it can be seen that a strength-magnetic property balance at a level that could not be achieved with a conventional high-strength electrical steel sheet can be obtained.
[0022]
Next, an experiment was conducted to investigate the amount of Cu added to increase the strength. That is, a steel slab containing C: 0.0020%, Si: 3.0%, Mn: 0.18%, P: 0.01% and Al: 0.60% and changing Cu in the range of 0.01 to 5% is obtained after hot rolling to 900%. Hot-rolled sheet annealing was performed at 30 ° C. for 30 s, cold-rolled to a thickness of 0.20 mm, finish-annealed at 900 ° C. × 30 s, and further subjected to aging treatment at 550 ° C. × 1 h. The steel sheet thus obtained was examined for tensile strength by a tensile test based on JIS Z2241.
[0023]
The result of the investigation is shown in FIG. 1 as the relationship between the Cu addition amount and the tensile strength. From FIG. 1, it is understood that the Cu addition amount needs to be 0.5% or more in order to improve the strength. That is, if Cu is less than 0.5%, sufficient Cu precipitation cannot be obtained even if aging treatment is performed. On the other hand, when Cu is added exceeding 4%, the strength decreases. This is because coarse precipitates are formed. Therefore, the addition amount of Cu is 0.5% or more and 4% or less.
[0024]
Here, in the present invention, Cu is characterized in that it is finely precipitated in the state of the motor core, and from this point, it is completely different from the electromagnetic steel sheet to which Cu is added for the purpose of conventional texture control, etc. It is.
[0025]
The aging treatment for precipitating Cu is recommended to be 10 min to 1000 h at 400 ° C. to 650 ° C.
[0026]
The thickness of the product plate shall be 0.05-0.27 mm . This is because by setting the plate thickness to 0.27 mm or less, the high-frequency iron loss is reduced and I × W _{5 / 1k} ≦ 5.5 × 10 ^{4 and the} motor efficiency is improved. However, if the plate thickness is less than 0.05 mm, the number of laminated layers increases and the number of work steps increases, so the lower limit is made 0.05 mm.
[0027]
In addition, an 8-pole IPM motor was prototyped to investigate the relationship between excitation effective current and iron loss and motor efficiency in high-strength materials. The motor had a rotor outer diameter of 110 mm, a stator outer diameter of 160 mm and a stator slot number of 24, and a permanent magnet was a NeFeB magnet. Then, we prototyped motors using various high-strength materials (TS> 550MPa) as core materials, and investigated the efficiency of these prototype motors. Here, the motor efficiency was measured at a tooth magnetic flux density of 1.7 T at a frequency requiring a torque of 50 Hz, and the efficiency at a tooth magnetic flux density of 0.5 T was evaluated at a frequency of 1 kHz at which the torque is not so required, and the average value was obtained.
[0028]
FIG. 2 shows the relationship between the motor efficiency and the effective excitation current and iron loss in the steel sheet. FIG. 2 shows that an efficiency of 90% or more is obtained when the excitation effective current is 4500 A / m or less, the iron loss is 20 W / kg or less, and I × W _{5 / 1k} ≦ 5.5 × 10 ⁴ . In other words, when the excitation effective current I exceeds 4500 A / m, the efficiency decreases due to the large increase in copper loss when driven in a high torque range, while the iron loss during high frequency driving increases when the iron loss exceeds 20 W / kg. It is thought that the efficiency was lowered due to the large loss. Furthermore, in the region where I × W _{5 / 1k} exceeds 5.5 × 10 ⁴ , it is considered that the efficiency has decreased due to an increase in both iron loss and copper loss.
[0029]
Therefore, the consideration of the efficiency in the application of the electromagnetic steel plates in the motor, iron loss W _{5 / 1k} in the frequency 1kHz is 20W / kg or less, exciting effective current I at 1.7T and 50Hz is less 4500A / m, Further, I × W _{5 / 1k} ≦ 5.5 × 10 ⁴ is set.
[0030]
Below, this invention is explained in full detail for every constituent requirement.
(Component composition of steel sheet)
First, the component composition range and the reason for limitation will be described.
C: 0.02% or less C has a problem of magnetic aging, so it was made 0.02% or less.
P: 0.2% or less,
P is an element effective for increasing the strength of a steel sheet, but if added over 0.2%, central segregation is likely to occur during casting, and the steel sheet becomes brittle and cold rollability is significantly reduced. It was.
[0031]
Si: 4.5% or less,
Si is an effective element for increasing the specific resistance of the steel sheet. However, if it exceeds 4.5%, the cold rolling property and the warm rolling property are remarkably lowered, so the upper limit is 4.5%, preferably from the viewpoint of saturation magnetization. Less than 4.0%.
[0032]
Mn: 3% or less,
Mn is an effective element for preventing red hot brittleness during hot rolling, and is preferably contained at 0.05% or more. However, if it exceeds 3%, the magnetic flux density is lowered, so the upper limit was made 3%.
[0033]
Al: 3% or less
Al is an element effective for increasing the specific resistance like Si, and is preferably contained in an amount of 0.1% or more. However, if it exceeds 3%, the saturation magnetization is lowered and the castability is significantly lowered. Was 3%.
[0034]
Cu: 0.5-4%
Cu is a component added to increase the strength without impairing the magnetic properties, and the reason for setting the lower limit is as described above.
[0035]
The basic composition of the non-oriented electrical steel sheet according to the present invention is as described above. In addition to the above components, Sb, Sn, B, Ni, Cr, Co and REM, which are known as elements for improving magnetic properties, are used alone or Can be added in combination. However, the amount added should be such that the object of the present invention is not impaired. In particular,
Sb: 0.005 to 0.05%,
Sn: 0.005 to 0.1%,
B: 0.0002 to 0.002%,
Ni: 0.1-5%
Co: 0.2-3% and
REM: 0.001 to 0.01%
It is. In addition, regarding Cr, in order to lower the saturation magnetization, when added, it is desirable to be 0.8% or less.
[0036]
The tensile strength is 550 MPa or more, more preferably 600 MPa or more. This is because the rotor is deformed at high speed when the strength is less than 550 MPa.
[0037]
(Production method)
In order to produce a high-strength non-oriented electrical steel sheet excellent in iron loss according to the present invention, first, a steel melted in the above-mentioned predetermined components in a converter or an electric furnace is continuously cast or ingoted A steel slab is formed by subsequent rolling. Next, the obtained slab is hot-rolled, subjected to hot rolling hill annealing as necessary, and subjected to cold rolling or warm rolling twice or more sandwiching one or intermediate annealing to obtain a product sheet thickness and finishing. Annealing and then aging treatment. Furthermore, at any stage after finish annealing, an insulating coating is applied and baked as necessary.
[0038]
The subsequent aging treatment is preferably performed at a temperature of 400 ° C. or higher and 650 ° C. or lower. That is, when the temperature is lower than 400 ° C., the precipitation of fine Cu becomes insufficient, and high strength may not be obtained. On the other hand, when the temperature exceeds 650 ° C., Cu precipitates are coarsened, the iron loss is deteriorated, and the amount of increase in strength is also reduced. Furthermore, the appropriate aging time is preferably 10 min to 1000 h, although it depends on the processing temperature.
The aging treatment may be carried out at any time before the insulating film is applied and baked, after baking, after processing such as press punching, etc., but it prevents deflection when punching thin materials. For this purpose, aging before punching is preferred.
[0039]
【Example】
Example 1
A steel slab is cast from molten steel adjusted to the composition shown in Table 2 by degassing after blowing in the converter, and this slab is heated at 1140 ° C for 1 h, then hot to a thickness of 2.0 mm. Rolled. The hot rolling finishing temperature was 800 ° C. The coiling temperature was 600 ° C., and hot-rolled sheet annealing at 900 ° C. × 30 s was performed. Thereafter, it was cold-rolled to a thickness of 0.18 mm, subjected to finish annealing at 950 ° C. × 30 s, and an aging treatment was performed under various conditions.
[0040]
Magnetic measurements were performed using 25 cm Epstein test pieces collected from the steel plates thus obtained, and tensile tests were performed using JIS 13 B test pieces. Table 2 shows the magnetic properties and tensile strength of each steel sheet.
[0041]
[Table 2]

[0042]
From Table 2, it can be seen that the components and aging treatment conditions within the appropriate ranges are excellent in iron loss and strength.
On the other hand, when Cu is not added (steel plates 1 and 2), it turns out that an intensity | strength does not raise by an aging treatment. Further, when the aging treatment time is short (steel plate 3) or when the aging treatment temperature is low (steel plate 9), Cu is not sufficiently precipitated, and a necessary strength level is not obtained. Furthermore, when the precipitation time is too long (steel plate 8) or when the aging temperature is too high (steel plate 12), the precipitate size of Cu is coarse, and the iron loss increases and the strength increase also decreases. ing.
[0043]
Example 2
After degassing after blowing in the converter, the steel slab obtained by casting after adjusting to the composition shown in Table 3 is heated at 1140 ° C for 1 h, and then hot rolled to a thickness of 2.0 mm. went. The hot rolling finishing temperature was 800 ° C. The coiling temperature was 600 ° C., and hot-rolled sheet annealing at 900 ° C. × 30 s was performed. Thereafter, cold rolling or warm rolling to various plate thicknesses shown in Table 3 was performed, annealing was performed under the finish annealing conditions shown in Table 3, and an aging treatment at 550 ° C. × 1 h was performed.
[0044]
Magnetic measurements were performed using 25 cm Epstein test pieces collected from the steel plates thus obtained, and tensile tests were performed using JIS 13 B test pieces. Table 3 shows the magnetic properties and tensile strength of each steel sheet.
[0045]
[Table 3]

[0046]
From Table 3, it can be seen that an electromagnetic steel sheet excellent in high-frequency magnetic characteristics and strength can be obtained when the component composition and thickness are in accordance with the present invention.
On the other hand, when Cu is not added (steel plate 13), the strength is low, and when the strength is increased by refining (steel plate 14), the iron loss is high although the strength is high. Further, when the strength is increased by solid solution strengthening (steel plate 15), the excitation effective current is high. In the steel plate 20 in which the Cu is within the range of the present invention, since the Cu is coarsened, the iron loss increases and the strength decreases.
[0047]
On the other hand, in the steel plate 24 whose plate thickness is out of the scope of the present invention, the iron loss is high. Furthermore, the steel sheet 29 with Si out of the scope of the present invention had a high excitation effective current, and the steel sheet 30 with P out of the scope of the present invention was broken during rolling and a product could not be obtained. Further, in the steel plates 32 and 33 in which Al and Mn deviate from the present invention, the excitation effective current was high.
[0048]
【The invention's effect】
As described above, according to the present invention, a material having an excellent iron loss and strength balance and a low excitation effective current can be obtained. Therefore, the non-oriented electrical steel sheet of the present invention is suitable as a rotor material for EVs, HEV motors, high speed generators, and large generators.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between Cu addition amount and tensile strength.
FIG. 2 is a diagram showing a relationship among iron loss, excitation effective current, and motor efficiency.

Claims (1)

% By mass
C: 0.02% or less,
P: 0.2% or less,
Si: 4.5% or less,
Mn: 3% or less,
Al: 3% or less and
Cu: 0.5-4%
, Balance Fe and inevitable impurity composition, plate thickness in the range of 0.05 to 0.27 mm , tensile strength of 550 MPa or more, iron loss W _{5 / 1k} of 20 W / kg or less, and frequency Non-oriented electrical steel sheet characterized in that the excitation effective current I at 50 Hz and magnetic flux density 1.7T is 4500 A / m or less, and further, the iron loss W _{5 / 1k} and the excitation effective current I satisfy the relationship of the following formula: .
I × W _{5 / 1k} ≦ 5.5 × 10 ⁴

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