【発明の詳細な説明】[Detailed description of the invention]
本発明は主として電力用トランス、カレントト
ランス、高周波トランス、リアクトルなどの電力
変換器の鉄心として用いられる鉄損が極めて低く
熱的安定性のよい非晶質合金に関するものであ
る。
鉄心用材料に要求される磁気特性としては、先
ず鉄損の低いこと、励磁特性の良いことが必要で
ある。特に鉄損は交流励磁される鉄心の中で熱と
して失われる電力で、全世界で日夜無駄に失われ
ている電力損失は莫大な額になると言われてい
る。また高周波トランスでは鉄損による熱は磁心
の温度を上昇させるため材料の選択、動作磁束密
度など設計上多くの制約をもたらしている。而し
て現在電力変換機器の磁心材料として、珪素鋼
板、薄物珪素鋼帯、フエライト、パーマロイ、鉄
粉などが具体的用途に応じて使用されているが、
広い応用分野にわたり特性と経済性とを満足させ
るような材料はなかつた。
ところが近年非晶質（アモルフアス）金属と呼
ばれる高温の溶融状態から超急冷することによつ
て液体と同じようなランダム（非同期）構造をも
つ合金薄帯を作る方法が開発された。この材料は
原理的に異方性がなく、電気抵抗が高く、薄いも
のが容易に得られるため広い周波数帯域で鉄損が
低く、励磁特性も良いので注目されている。しか
しながら電力トランス用途には飽和磁束密度BS
が珪素鋼板に比較してかなり低いこと、熱的安定
性が悪い等の欠点があり、実用化の問題点とされ
ていた。そのため飽和磁束密度を高めるため成分
組成の検討が種々なされ例えば特開昭54−61140
号公報、同55−158251号公報、同54−148122号公
報等の発明が提案されている。
しかしながらなお室温におけるBSの値17KGを
いくらか越える程度であり、珪素鋼の20KGには
及ばない。しかも公知のBSの高い組成をもつ合
金はいずれもトランス運転中の鉄心の温度（70〜
150℃）における低下率が大きく、使用される温
度における磁束密度は15〜16KG程度に低下して
珪素鋼との差は再び開いてしまう。さらに前記の
ような現在公知の合金系は熱的安定性が低い欠点
がある。従つて非晶質合金の特徴を生かすために
は原理的に低い鉄損をさらに下げ、かつ非晶質合
金共通の欠点である熱的不安定性を改良した合金
系を見出すことが実用上最も有利である。
本発明者らは多くの合金組成について、その磁
気特性および熱的安定性を調べた結果、鉄損の低
い組成と熱的安定性のすぐれた組成には対応関係
があることを見い出した。熱的安定性の高い組成
は熱処理によつて非晶質構造を安定化することが
でき、同時に鉄損も改善される。熱的に不安定な
組成に比べて高い熱処理温度を採用できるため、
鉄損改善の効果が大きいことを見出し、この具体
的組成を特願昭55−30253号および特願昭56−
32345号として出願した。これらはFeaSibBcCdな
る化学式で表示される実質的に非晶質である合金
で、ａ、ｂ、ｃ、ｄはそれぞれ原子数％で次の範
囲にあつた。
ａ＝74〜79
ｂ＝８〜19
ｃ＝６〜13
ｄ＝１〜3.5
ただし
ａ＋ｂ＋ｃ＋ｄ＝100
本発明者はこれらの組成範囲にある非晶質合金
の熱的安定性をさらに詳しく調査し、数十年にわ
たり安定な磁気特性を保証し得る合金組成を見出
した。
すなわち本発明はFeaSibBcCdなる化学式で表
示される実質的に非晶質である合金で、ａ、ｂ、
ｃ、ｄはそれぞれ原子数％で次の範囲にある。
ａ＝77〜79
ｂ＝８超〜12
ｃ＝９〜11
ｄ＝１〜３
ただし
ａ＋ｂ＋ｃ＋ｄ＝100
特に好ましくはFe78Si10B10C2の組成である。
これらの成分的要求を満たす非晶質合金は第１
表、第２表に示すように通常のトランス使用温度
よりもはるかに高い200℃においても磁気特性の
経時変化が本発明の組成範囲外のそれに比べて極
めて小さい。すなわち本発明の範囲の組成を有す
る非晶質合金は、同時に高い非晶質形成能（非晶
質になりやすさ）をもつため、厚いリボンを作る
ことが容易で、かつリボンの長手方向の特性変動
が小さいという実用上きわめて有利な特性を併せ
もつている。
本発明の非晶質合金を製造する方法は先にも触
れたように溶融状態の合金を回転するロールやド
ラムの外壁あるいは内壁に噴射、衝突させ片面か
ら冷却する方法（片ロール法および遠心急冷法）
あるいは１対のロールの間で両面から冷却する方
法（双ロール法）などによつて連続的に製造する
公知の方法いずれによつてもよい。
急冷された薄帯は一般にそのまま（as Cast）
の状態では充分な特性を示さないので、通常磁性
向上のために結晶化開始温度以下で熱処理され
る。熱処理をより効果的にするために、磁界中あ
るいは張力下で行なうのがよい。本発明の合金の
特徴は熱処理の効果にも表われる。すなわち、結
晶化開始温度が従来の高磁束密度合金に比べてき
わめて高いため、高い熱処理温度を採用できる。
高い熱処理温度は、冷却後に残留するひずみを充
分に除去することを可能とし、その結果鉄損の低
減率が大きい利点を有する。たとえば従来材では
特開昭55−158251号公報に開示される如く385℃
以下の温度で熱処理する必要があつたのに対し
て、本発明の合金では430℃までの高温での熱処
理を可能にした。
次に本発明の実施例を示す。
実施例 １
化学式Fe78Si10B10C2で表示される合金を、こ
の合金の液相温度より約100℃高い1100℃に加熱
し、冷却用の鋼製単ロールの表面で急冷した。得
られた薄帯は１チヤージ20mm巾で約300ｇであつ
た。得られた薄帯の磁場中焼鈍後の磁気特性およ
び200℃で2000時間経過後の磁気特性を第１表に
示した。但し焼鈍条件は磁界30Oe、390℃×30分
水素中であつた。また磁気特性は試料の大きさ20
mm巾×120mmとし、単板測定器により測定した。
第２表に示した比較例に比べて磁気特性の変化が
極めて小さいことが判る。
実施例 ２
第２表の各組成を有するように配合した原料を
溶解後、液相温度より50〜150℃高い温度から実
施例１と同じ方法により急冷し、非晶質合金薄帯
を得た。得られた薄帯の磁気特性および200℃で
2000時間経過後の磁気特性を比較例とともに示
す。この結果から明らかなように本発明の範囲の
組成を有する非晶質合金の鉄損および安定性は比
較例に比べて極めてすぐれている。特に鉄損の劣
化が小さい。
以上説明したように本発明は磁気特性の経時変
化が極めて小さく永年にわたり安定した特性を得
ることができる。
The present invention mainly relates to an amorphous alloy with extremely low iron loss and good thermal stability, which is used as the iron core of power converters such as power transformers, current transformers, high-frequency transformers, and reactors. The magnetic properties required of iron core materials include low core loss and good excitation properties. In particular, iron loss is the power lost as heat in an iron core that is excited by alternating current, and it is said that the power loss that is wasted day and night around the world is enormous. In addition, in high-frequency transformers, heat due to iron loss increases the temperature of the magnetic core, resulting in many design constraints such as material selection and operating magnetic flux density. Currently, silicon steel plates, thin silicon steel strips, ferrite, permalloy, iron powder, etc. are used as magnetic core materials for power conversion equipment, depending on the specific application.
There has been no material that satisfies properties and economy over a wide range of applications. However, in recent years, a method has been developed to create alloy ribbons with a random (asynchronous) structure similar to that of liquids by ultra-rapidly cooling metals from a high-temperature molten state called amorphous metals. This material has attracted attention because it has no anisotropy in principle, has high electrical resistance, can be easily made thin, has low iron loss over a wide frequency band, and has good excitation characteristics. However, for power transformer applications, the saturation magnetic flux density B S
It has disadvantages such as being considerably lower than that of silicon steel sheets and having poor thermal stability, which has been considered a problem for practical use. Therefore, in order to increase the saturation magnetic flux density, various studies have been made on the component composition, for example, in JP-A-54-61140.
Inventions such as Japanese Patent Publication No. 55-158251 and Japanese Patent No. 54-148122 have been proposed. However, it still slightly exceeds the B S value of 17KG at room temperature, which is lower than the 20KG of silicon steel. Moreover, all of the known alloys with high B S compositions have a temperature of the iron core during transformer operation (70~
(150℃), the magnetic flux density at the temperature used drops to about 15 to 16 kg, and the difference with silicon steel widens again. Furthermore, currently known alloy systems such as those mentioned above have the disadvantage of low thermal stability. Therefore, in order to take advantage of the characteristics of amorphous alloys, it is most advantageous in practice to find an alloy system that further lowers core loss, which is low in principle, and improves thermal instability, which is a common drawback of amorphous alloys. It is. The present inventors investigated the magnetic properties and thermal stability of many alloy compositions and found that there is a correspondence between compositions with low iron loss and compositions with excellent thermal stability. A composition with high thermal stability can stabilize the amorphous structure by heat treatment, and at the same time improve iron loss. Because higher heat treatment temperatures can be used compared to thermally unstable compositions,
It was discovered that the effect of iron loss improvement was large, and this specific composition was published in Japanese Patent Application Nos. 55-30253 and 1983-
The application was filed as No. 32345. These were substantially amorphous alloys represented by the chemical formula Fe a Si b B c C d , where a, b, c, and d were each in the following ranges in atomic percent. a=74~79 b=8~19 c=6~13 d=1~3.5 However, a+b+c+d=100 The present inventor investigated the thermal stability of amorphous alloys in these composition ranges in more detail, and found that several We have found an alloy composition that can guarantee stable magnetic properties for ten years. That is, the present invention is a substantially amorphous alloy represented by the chemical formula Fe a Si b B c C d , in which a, b,
c and d are each in the following range in atomic percentage. a=77-79 b=more than 8-12 c=9-11 d=1-3 However, a + b+c+d=100 Particularly preferred is the composition of Fe78Si10B10C2 . The first amorphous alloy that meets these chemical requirements is
As shown in Table 2, even at 200° C., which is much higher than the normal operating temperature of a transformer, the change in magnetic properties over time is extremely small compared to that outside the composition range of the present invention. In other words, an amorphous alloy having a composition within the range of the present invention also has a high ability to form an amorphous state (ease of becoming amorphous), so it is easy to make a thick ribbon, and the longitudinal direction of the ribbon is It also has the extremely advantageous property of having small characteristic fluctuations in practice. As mentioned above, the method for manufacturing the amorphous alloy of the present invention is to inject and collide the molten alloy against the outer or inner wall of a rotating roll or drum and cool it from one side (single roll method and centrifugal quenching method). law)
Alternatively, any known method may be used, such as continuous production by cooling from both sides between a pair of rolls (twin roll method). The rapidly cooled ribbon is generally cast as is.
Since it does not exhibit sufficient properties in this state, it is usually heat treated at a temperature below the crystallization initiation temperature to improve magnetism. In order to make the heat treatment more effective, it is preferable to perform it in a magnetic field or under tension. The characteristics of the alloy of the present invention also appear in the effects of heat treatment. That is, since the crystallization initiation temperature is much higher than that of conventional high magnetic flux density alloys, high heat treatment temperatures can be employed.
A high heat treatment temperature makes it possible to sufficiently remove the strain remaining after cooling, and as a result has the advantage of a large reduction rate in iron loss. For example, in the case of conventional materials, as disclosed in Japanese Patent Application Laid-Open No. 55-158251,
Whereas it was necessary to perform heat treatment at a temperature below 430°C, the alloy of the present invention allows heat treatment at a high temperature of up to 430°C. Next, examples of the present invention will be shown. Example 1 An alloy represented by the chemical formula Fe 78 Si 10 B 10 C 2 was heated to 1100° C., approximately 100° C. higher than the liquidus temperature of this alloy, and rapidly cooled on the surface of a single steel roll for cooling. One charge of the obtained ribbon had a width of 20 mm and a weight of about 300 g. Table 1 shows the magnetic properties of the obtained ribbon after annealing in a magnetic field and after 2000 hours at 200°C. However, the annealing conditions were a magnetic field of 30O e and 390°C for 30 minutes in hydrogen. In addition, the magnetic properties are determined by the sample size 20
mm width x 120 mm, and was measured using a single plate measuring device.
It can be seen that the change in magnetic properties is extremely small compared to the comparative example shown in Table 2. Example 2 After melting raw materials blended to have each composition in Table 2, they were rapidly cooled from a temperature 50 to 150°C higher than the liquidus temperature in the same manner as in Example 1 to obtain an amorphous alloy ribbon. . Magnetic properties of the obtained ribbon and at 200℃
Magnetic properties after 2000 hours are shown together with comparative examples. As is clear from these results, the core loss and stability of the amorphous alloys having compositions within the range of the present invention are extremely superior to those of the comparative examples. In particular, the deterioration of iron loss is small. As explained above, according to the present invention, the change in magnetic properties over time is extremely small and stable properties can be obtained over many years.
【表】【table】
【表】【table】