【発明の詳細な説明】[Detailed description of the invention]
本発明はCu―Zn―Al系形状記憶合金を工業的
に製造する方法に関するものである。
従来Cu―Zn―Al系形状記憶合金は熱回復繰返
形状記憶を有することが知られており、実験室的
に鋳塊を熱間圧延や熱間鍛造した加工材より切出
して造られているが、工業的に安定して製造する
方法は知られていない。
本発明はこれに鑑み種々研究の結果、従来冷間
加工が困難とされていたCu―Zn―Al系形状記憶
合金の組成を特定の範囲に限定し、更に加工条件
を制限することにより冷間加工の可能な工業的製
造方法を開発したもので、Al0.5〜2.5wt％（以下
wt％を単％と略記）とZn26〜36％を含み、残部
Cuからなる合金を550〜850℃の温度で熱間加工
した後、450〜650℃の温度で0.5〜２時間の中間
焼鈍と、加工率80％以下の冷間加工とを繰返し行
なうことを特徴とするものである。
即ち本発明は、上記組成範囲の合金を溶解鋳造
し、得られた鋳塊を550〜850℃の温度、望ましく
は600〜750℃の温度に加熱して熱間圧延又は熱間
鍛造により、直径10〜13mmの棒又は厚さ10〜13mm
の板とする。この棒又は板を450〜650℃の温度で
0.5〜２時間、望ましくは530〜580℃の温度で１
時間、中間焼鈍を行なうことにより、冷間圧延又
は冷間伸線による加工を可能とし、中間焼鈍後に
加工率80％以下の冷間加工を行ない、この中間焼
鈍と冷間加工を繰返し行なつて所望の形状に仕上
げるものである。
しかして本発明において、合金組成を上記の如
く限定したのはAl含有量が0.5％未満でも、Zn含
有量が26％未満でも、加工は容易なるも形状記憶
効果が小さいか又は全く示さないようになり、ま
たAl含有量が2.5％を越えても、Zn含有量が36％
を越えても、記憶効果は有するも上記加工が困難
となるためである。
また鋳塊の熱間加工温度を550〜850℃と限定し
たのは、850℃を越える温度では材料が軟かく、
変形態が大きすぎて取扱しずらいためであり、
550℃未満の温度では材料が硬くなり、わずかの
加工でも材料の割れを生じるためである。
また熱間加工の中間焼鈍を450〜650℃の温度で
0.5〜２時間としたのは、450℃未満の温度で0.5
時間未満の焼鈍では軟化せず、650℃を越える温
度で２時間を越える焼鈍では軟化するも結晶粒成
長を越し、材料としての各種特性を劣化させるた
めである。
更に中間焼鈍後の冷間加工率を80％以下とした
のは、上記中間焼鈍により冷間圧延や冷間伸線に
よる加工が可能となるも、80％を越えて冷間加工
を行なうと、加工の途中で板割れや断線が発生す
る恐れがあり、これが発生すると以後の冷間加工
が不可能となり、所望の形状を得ることができな
いためである。特に板厚や線径の小さいものを得
るためには、第１回目の冷間加工率を75％（断面
減少率）程度に止めて、上記中間焼鈍を行なつた
後、再び冷間加工を行なう。このようにして冷間
加工と中間焼鈍を繰返すことにより、板厚0.2〜
10mm、線径0.2〜８mmの製品を安定して製造する
ことができる。
以下、本発明を実施例について詳細に説明す
る。黒鉛ルツボを用いてCuを溶解し、湯面を木
炭で被覆した後、ZnとAlを順次添加して鋳造し、
第１表に示す組成の巾150mm、長さ200mm、厚さ25
mmの板用鋳塊と、厚さ巾ともに25mm、長さ300mm
の線棒用鋳塊を得た。この鋳塊表面を一面あたり
2.5mm面削した後、700℃の温度に加熱して熱間圧
延し、板用鋳塊については厚さ13mmに、綿棒用鋳
塊については直径12mmに加工した。
次に厚さ13mmの板について、550℃の温度で１
時間の中間焼鈍を行なつた後、冷間圧延により厚
さを4.0mmとし、この加工において板厚4.0mm以下
まで圧延を試みたが板割れが発生しその後の加工
が困難となつたため、圧延は板厚4.0mmで止め、
再び中間焼鈍（550℃×１時間）を行なつた後、
冷間圧延により厚さ１mmの板に仕上げた。また直
径12mmの棒について、580℃の温度で0.5時間の中
間焼鈍を行なつた後、冷間の溝ロール型圧延機に
より直径6.0mmに加工し、再び中間焼鈍（580℃×
0.5時間）を行なつた後、伸線機により直径2.7mm
まで加工した。この加工において2.7mm以下まで
伸線を試みたが、加工性が劣化し、断線が多発し
たため2.7mmで加工を止め、中間焼鈍（580℃×
0.5時間）を行なつてから伸線加工により、直径
1.2mmの線に仕上げた。
以上の加工において加工性の判定を行ない、そ
の結果を第１表に併記した。尚、第１表中〇印は
加工性が良好で、割れや断線等のないもの、×印
は加工性が悪く、加工の途中で割れや断線を起し
たものを示す。また仕上げた板及び線材について
形状記憶効果の有無を確認するため、第１表中No.
１〜５及びNo.７では直径1.2mmの線材を、またNo.
６及びNo.８については厚さ13mmの熱間圧延板より
厚さ５mm、巾２mm、長さ15mmに切出して試料と
し、これ等を800℃の温度で30分間加熱溶体化処
理した後、直ちに20℃の水に焼入れを行なつた。
これについて温度に対する電気抵抗の変化からマ
ルテンサイト変態点の有無を調べ、その結果を第
１表に併記した。尚、第１表中〇印は形状記憶と
しての変態点のあるもの、×印は変態点のないも
のを示す。
The present invention relates to a method for industrially manufacturing a Cu--Zn--Al based shape memory alloy. Conventional Cu-Zn-Al shape memory alloys are known to have shape memory through repeated heat recovery, and are manufactured in the laboratory by cutting ingots from hot-rolled or hot-forged processed materials. However, no method for industrially stable production is known. In view of this, as a result of various studies, the present invention limits the composition of Cu-Zn-Al-based shape memory alloys, which were conventionally considered difficult to cold-work, to a specific range, and further restricts the processing conditions. We have developed an industrial manufacturing method that allows processing, and Al0.5-2.5wt% (hereinafter
wt% is abbreviated as simple %) and Zn26-36%, the remainder
It is characterized by hot working an alloy consisting of Cu at a temperature of 550 to 850°C, followed by repeated intermediate annealing at a temperature of 450 to 650°C for 0.5 to 2 hours, and cold working at a processing rate of 80% or less. That is. That is, the present invention melts and casts an alloy having the above-mentioned composition range, heats the obtained ingot to a temperature of 550 to 850°C, preferably 600 to 750°C, and hot-rolls or hot-forges it to a diameter 10-13mm rod or thickness 10-13mm
The board shall be This rod or plate is heated to a temperature of 450 to 650℃.
1 for 0.5 to 2 hours, preferably at a temperature of 530 to 580℃.
By performing intermediate annealing for a long time, processing by cold rolling or cold wire drawing is possible, and after intermediate annealing, cold working with a processing rate of 80% or less is performed, and this intermediate annealing and cold working are repeated. It is finished into the desired shape. However, in the present invention, the alloy composition is limited as described above because even if the Al content is less than 0.5% or the Zn content is less than 26%, although processing is easy, the shape memory effect is small or does not appear at all. , and even if the Al content exceeds 2.5%, the Zn content will be 36%.
This is because, even if it exceeds the above, the above-mentioned processing becomes difficult, although the memory effect still exists. In addition, the hot working temperature of the ingot was limited to 550 to 850℃ because the material becomes soft at temperatures exceeding 850℃.
This is because the deformation is too large and difficult to handle.
This is because the material becomes hard at temperatures below 550°C, and even slight processing can cause the material to crack. In addition, intermediate annealing during hot working is performed at a temperature of 450 to 650℃.
The period of 0.5 to 2 hours is 0.5 at a temperature below 450℃.
This is because annealing for less than 1 hour does not soften the material, and annealing at a temperature exceeding 650° C. for more than 2 hours does soften the material, but the crystal grains grow beyond that and deteriorate various properties as a material. Furthermore, the reason why the cold working rate after intermediate annealing was set to 80% or less is that although the above intermediate annealing enables processing by cold rolling and cold wire drawing, if cold working is performed at a rate exceeding 80%, This is because there is a risk that plate cracking or wire breakage may occur during processing, and if this occurs, subsequent cold working becomes impossible and the desired shape cannot be obtained. In particular, in order to obtain thin sheets and wires with small wire diameters, the first cold working rate is kept at about 75% (section reduction rate), and after the above intermediate annealing, cold working is performed again. Let's do it. By repeating cold working and intermediate annealing in this way, the plate thickness is 0.2~
It is possible to stably manufacture products with wire diameters of 10 mm and wire diameters of 0.2 to 8 mm. Hereinafter, the present invention will be described in detail with reference to examples. After melting Cu using a graphite crucible and coating the molten metal surface with charcoal, Zn and Al are sequentially added and cast.
Width 150mm, length 200mm, thickness 25mm with the composition shown in Table 1
mm plate ingot, thickness width 25mm, length 300mm
An ingot for wire rods was obtained. One side of this ingot surface
After face milling 2.5 mm, it was heated to a temperature of 700°C and hot rolled, and the ingot for plates was processed into a thickness of 13 mm, and the ingot for cotton swabs was processed into a diameter of 12 mm. Next, a plate with a thickness of 13 mm was heated at a temperature of 550°C.
After an intermediate annealing, the thickness was reduced to 4.0 mm by cold rolling. During this process, an attempt was made to roll the plate to a thickness of 4.0 mm or less, but cracks occurred and subsequent processing became difficult. is stopped at a plate thickness of 4.0 mm,
After performing intermediate annealing again (550℃ x 1 hour),
It was finished into a plate with a thickness of 1 mm by cold rolling. In addition, a bar with a diameter of 12 mm was intermediately annealed at a temperature of 580°C for 0.5 hours, then processed into a diameter of 6.0mm using a cold groove roll rolling mill, and then intermediately annealed again (580°C
After 0.5 hours), the diameter is 2.7mm using a wire drawing machine.
Processed to. In this process, we attempted to draw the wire to 2.7 mm or less, but the workability deteriorated and wire breakage occurred frequently, so we stopped the process at 2.7 mm and carried out intermediate annealing (580℃
0.5 hours) and then wire drawing to reduce the diameter.
Finished with a 1.2mm line. Workability was evaluated in the above processing, and the results are also listed in Table 1. Note that in Table 1, the mark ○ indicates that the workability was good and there were no cracks or wire breaks, and the mark x indicates that the workability was poor and cracks or wire breaks occurred during processing. In addition, in order to confirm the presence or absence of shape memory effect on the finished plates and wires, No. 1 in Table 1 was used.
Wire rods with a diameter of 1.2 mm were used for Nos. 1 to 5 and No. 7, and No.
For No. 6 and No. 8, samples were cut out from a 13 mm thick hot-rolled plate into 5 mm thick, 2 mm wide, and 15 mm long, and after heating and solution treatment at a temperature of 800°C for 30 minutes, immediately Quenching was performed in water at 20°C.
The presence or absence of a martensitic transformation point was investigated based on the change in electrical resistance with respect to temperature, and the results are also listed in Table 1. In Table 1, the mark ◯ indicates that there is a transformation point as a shape memory, and the mark x indicates that there is no transformation point.
【表】
第１表から明らかなように本発明合金は熱間加
圧後、中間焼鈍を行なうことにより、その後の冷
間加工が可能となり、形状記憶効果を有すること
が判る。
これに対し、Zn含有量の少ない比較方法No.５
とAl含有量の少ない比較合金No.７では冷間加工
が可能なるも形状記憶効果がなく、またZn含有
量の多い比較方法（No.６）とAl含有量の多い比
較方法（No.８）では形状記憶効果を有するも、冷
間加工が困難であることが判る。
特に比較方法No.６及びNo.８は冷間圧延の途中で
割れを起し、伸線の途中で断線を起し、その後の
冷間加工が非常に困難であつた。
このように本発明によれば、従来冷間加工が困
難とされていたCu―Zn―Al系形状記憶合金の冷
間加工が可能となり、該合金を工業的に安定して
製造することができるもので、工業上顕著な効果
を奏するものである。[Table] As is clear from Table 1, the alloy of the present invention can be subjected to subsequent cold working by performing intermediate annealing after hot pressing, and it can be seen that it has a shape memory effect. On the other hand, comparative method No. 5 with low Zn content
Comparative alloy No. 7 with low Al content can be cold worked but has no shape memory effect, and comparative alloy No. 7 with high Zn content (No. 6) and comparative alloy No. 8 with high Al content can be cold worked. ) has a shape memory effect, but it is found that cold working is difficult. In particular, comparative methods No. 6 and No. 8 caused cracks during cold rolling and wire breakage during wire drawing, making subsequent cold working very difficult. As described above, according to the present invention, it is now possible to cold-work Cu-Zn-Al-based shape memory alloys, which were conventionally considered difficult to cold-work, and the alloy can be industrially and stably manufactured. It has a remarkable industrial effect.