【発明の詳細な説明】[Detailed description of the invention]
本発明は、銀−酸化錫系電気接点素材の製造方
法に係る。
耐溶着性、耐消耗性に優れ、安定した接点性能
を有する銀−酸化カドミウム系電気接点材料が、
従来より銀−酸化物系電気接点材料として広く使
用されてきたが、人体に有害なカドミウムを含む
為、最近ではその使用をひかえる傾向にある。
この為、銀−酸化カドミウム系電気接点材料と
同等以上の耐溶着性、耐消耗性を有し、かつ、安
定した接点性能を有する銀−酸化錫系電気接点材
料が知られている。ところが、銀−錫系合金は内
部酸化工程においてSnO2の化合物を作りやす
く、CdOに比し酸素の取り込み量が多い。その
ため、内部酸化すると体積膨張によつて酸化割れ
を起こしやすい。特に錫が高濃度の場合に著し
い。そのため、高濃度の酸化錫を含む銀系材料が
電気接点として優れた性質をもつと予想されてい
たにもかかわらず、各種粉末を混合する粉末冶金
法によつてしか製造せざるを得ず、内部酸化法を
利用した工業的に安価な製造方法は、知られてい
なかつた。
そこで本発明者は、上記要望を満さんが為に鋭
意攻究の結果、内部酸化法と粉末冶金法を組み合
わせて、工業的に安価な銀−酸化錫系電気接点素
材の製造方法を見い出したものである。
本発明の銀−酸化錫系電気接点素材の製造方法
は、酸化錫として13〜25重量％となる錫、酸化イ
ンジウムとして0.1〜７重量％となるインジウム
および残部銀より成る銀合金の粉粒体を内部酸化
した後焼結し、次いで押し出し加工することを特
徴とするものである。
まず、本発明における接点材料について説明す
る。
本発明の銀−酸化錫系電気接点材料において
は、接点の開閉時に発生するアークの熱によつ
て、銀中に分散した酸化錫の分散組織の変質が少
ない。即ち、酸化錫はアーク熱により分解し、金
属錫となつて固溶し、雰囲気中の酸素によつて再
び酸化して酸化錫となる。従つて、銀中における
酸化錫の占める割合の減少が少ない。また酸化イ
ンジウムも酸化錫と同様に接点開閉時のアーク熱
によつてその分散組織が変質することが少ない。
しかも、この酸化インジウムは、アーク熱で分解
して銀に固溶した錫の再酸化を、雰囲気中の酸素
によつて促進する。
即ち、アーク熱より分解した錫及びインジウム
は、銀に固溶して銀−錫−インジウムの微細な合
金を接点表面に作る。そして、錫及びインジウム
の再酸化過程において、インジウムは錫の酸化に
対してその析出態様を制御し、酸化錫−酸化イン
ジウムの微細な粒子の析出を可能にする。その結
果、接点表面での銀−酸化錫−酸化インジウムの
分散状態は、アーク熱によつて損なわれることが
少ないものとなる。従つて、接点材料の耐溶着
性、耐消耗性に優れ、接点の開閉回数にかかわら
ず、その接点性能は安定して維持できるものであ
る。
然して、本発明の銀−酸化錫系電気接点素材の
製造方法において、前述の如くその成分組成を限
定した理由について説明する。酸化錫が13重量％
未満では、大電流に対して安定した遮断能力がな
い。一方、25重量％を超えると電気伝導度が低く
なり、しかも接触抵抗が大きくなる。そのため、
特にノーヒユーズブレーカー用としては全く使用
し得なくなる。そこで、13〜25重量％の酸化錫が
好適である。また酸化インジウムが0.1重量％未
満では、銀中に固溶した分解錫の再酸化を促進さ
せることができず、安定した耐溶着性が得られな
い。一方、７重量％を超えると、13〜25重量％の
酸化錫がアーク熱のため分解して銀中に固溶した
錫を再酸化するには過剰となり、それ以上安定し
た耐溶着性が得られない。そこで、0.1〜７重量
％が好適である。
次に、本発明における銀合金の粉粒体を内部酸
化した後、焼結し、次いで押し出し加工すること
について説明する。
本発明の銀合金を内部酸化すると、高濃度の錫
のため、表面に酸化割れを生じ、粉粒体表面がも
ろくなり、内部は酸化バンドのため酸化物が大
い。そこで、このもろくなつた粉粒体を押し出し
加工しやすいように、焼結する。そして、この焼
結体を押し出すと、粉粒体がこわれ、内部の大き
い酸化物が露呈し、粉粒体外部の酸化層と混練さ
れ、最終的に均一な電気接点素材となる。従つ
て、各々の酸化物粉末と銀粉とを均一に混合した
と同一の結果が、簡単に得られる。しかも、粉末
冶金のように混合時のバラツキは全くない。
次に本発明による銀−酸化錫系電気接点素材の
製造方法の効果を明瞭ならしめる為に、その具体
的な実施例と従来例、そして粉末冶金法による比
較例との耐溶着及び耐消耗試験の結果などについ
て説明する。
下表の左欄に示す実施例１、２は、３mm以下の
粒、粉および針状の銀−錫−インジウム合金を、
溶解法によつて作り、これを500℃10気圧の酸素
雰囲気中で150時間内部酸化してから、圧縮成形
し、次いで焼結した後、押し出し加工によつて電
気接点素材となし、然る後、この電気接点素材を
頭部径５φmmのリベツト接点となし、これを台座
に固定して成るものである。また、比較例３、４
は、銀粉、酸化錫粉及び酸化インジウム粉の混合
したものを圧縮し、次いで焼結した後、押し出し
加工によつて電気接点素材となし、然る後、この
電気接点素材を頭部径５φmmのリベツト接点とな
し、これを台座に固定して成るものである。
然して、これら実施例１、２と比較例３、４、
及び従来例の銀＝15重量％酸化カドミウム電気接
点を、下記の試験条件にて耐溶着試験と耐消耗試
験を行つたところ、下表の右欄に示すような結果
を得た。
試験条件
開閉電圧：AC200V
開閉電流：3000A
接触力：300ｇ
開離力：500ｇ
開閉回数：50回
The present invention relates to a method for producing a silver-tin oxide electrical contact material. A silver-cadmium oxide electrical contact material with excellent welding resistance, wear resistance, and stable contact performance.
It has traditionally been widely used as a silver-oxide electrical contact material, but recently there has been a tendency to refrain from using it because it contains cadmium, which is harmful to the human body. For this reason, silver-tin oxide-based electrical contact materials are known that have welding resistance and abrasion resistance equivalent to or higher than silver-cadmium oxide-based electrical contact materials, and have stable contact performance. However, silver-tin alloys tend to form SnO 2 compounds during the internal oxidation process and take in more oxygen than CdO. Therefore, internal oxidation tends to cause oxidation cracking due to volumetric expansion. This is particularly noticeable when the concentration of tin is high. Therefore, although silver-based materials containing high concentrations of tin oxide were expected to have excellent properties as electrical contacts, they had no choice but to be manufactured using powder metallurgy, which involves mixing various powders. An industrially inexpensive manufacturing method using an internal oxidation method was not known. Therefore, as a result of intensive research to satisfy the above requirements, the inventors of the present invention have discovered an industrially inexpensive method for producing silver-tin oxide electrical contact materials by combining an internal oxidation method and a powder metallurgy method. It is something. The method for producing the silver-tin oxide electrical contact material of the present invention is to produce powder particles of a silver alloy consisting of 13 to 25% by weight of tin as tin oxide, indium of 0.1 to 7% by weight as indium oxide, and the balance silver. It is characterized by internally oxidizing, sintering, and then extruding. First, the contact material in the present invention will be explained. In the silver-tin oxide electrical contact material of the present invention, the structure of tin oxide dispersed in silver is hardly altered by the heat of the arc generated when the contact is opened and closed. That is, tin oxide is decomposed by arc heat, becomes metallic tin, forms a solid solution, and is oxidized again by oxygen in the atmosphere to become tin oxide. Therefore, the proportion of tin oxide in silver decreases little. Also, like tin oxide, indium oxide's dispersed structure is less likely to be altered by arc heat during contact opening and closing.
Moreover, this indium oxide promotes the reoxidation of tin, which is decomposed by arc heat and dissolved in silver, by oxygen in the atmosphere. That is, tin and indium decomposed by arc heat form a solid solution in silver to form a fine silver-tin-indium alloy on the contact surface. In the re-oxidation process of tin and indium, indium controls the precipitation mode of tin oxidation and enables the precipitation of fine particles of tin oxide-indium oxide. As a result, the dispersion state of silver-tin oxide-indium oxide on the contact surface is less likely to be damaged by arc heat. Therefore, the contact material has excellent welding resistance and wear resistance, and the contact performance can be stably maintained regardless of the number of times the contact is opened and closed. However, in the method for manufacturing the silver-tin oxide electrical contact material of the present invention, the reason why the component composition is limited as described above will be explained. 13% tin oxide by weight
If it is less than that, there is no stable breaking ability against large currents. On the other hand, if it exceeds 25% by weight, the electrical conductivity will be low and the contact resistance will be high. Therefore,
In particular, it cannot be used at all as a no-fuse breaker. Therefore, 13 to 25% by weight of tin oxide is preferred. Furthermore, if the indium oxide content is less than 0.1% by weight, reoxidation of decomposed tin dissolved in silver cannot be promoted, and stable welding resistance cannot be obtained. On the other hand, if it exceeds 7% by weight, 13 to 25% by weight of tin oxide decomposes due to arc heat and becomes too much to re-oxidize the tin solidly dissolved in silver, making it impossible to achieve stable welding resistance beyond this point. I can't. Therefore, 0.1 to 7% by weight is suitable. Next, the process of internally oxidizing the silver alloy powder, sintering, and then extruding the silver alloy powder according to the present invention will be described. When the silver alloy of the present invention is internally oxidized, oxidation cracks occur on the surface due to the high concentration of tin, the surface of the powder becomes brittle, and the interior is oxidized and contains a large amount of oxide. Therefore, this brittle powder is sintered to make it easier to extrude. Then, when this sintered body is extruded, the powder and granules are broken, and the large oxide inside is exposed, which is kneaded with the oxide layer outside the powder and granules, and finally becomes a uniform electrical contact material. Therefore, the same results as those obtained by uniformly mixing each oxide powder and silver powder can be easily obtained. Moreover, unlike powder metallurgy, there is no variation during mixing. Next, in order to clarify the effects of the method for producing a silver-tin oxide electrical contact material according to the present invention, welding resistance and abrasion resistance tests were conducted using specific examples, conventional examples, and comparative examples using powder metallurgy. We will explain the results etc. In Examples 1 and 2 shown in the left column of the table below, grains, powders, and needle-shaped silver-tin-indium alloys of 3 mm or less are
It is made by a melting method, internally oxidized at 500°C in an oxygen atmosphere of 10 atm for 150 hours, then compression molded, sintered, extruded into an electrical contact material, and then This electrical contact material is made into a rivet contact with a head diameter of 5φmm, which is fixed to a pedestal. Also, Comparative Examples 3 and 4
is made by compressing a mixture of silver powder, tin oxide powder and indium oxide powder, sintering it, and extruding it into an electrical contact material. This is a rivet contact that is fixed to a pedestal. However, these Examples 1 and 2 and Comparative Examples 3 and 4,
A welding resistance test and an abrasion resistance test were conducted on the conventional electrical contact made of 15% silver by weight and cadmium oxide under the following test conditions, and the results shown in the right column of the table below were obtained. Test conditions Switching voltage: AC200V Switching current: 3000A Contact force: 300g Breaking force: 500g Number of switching: 50 times
【表】
上記表の数値で明らかなように本発明による銀
−酸化錫系電気接点材料及び比較例の材料は、従
来の銀−酸化カドミウムの電気接点材料に比し、
著しく溶着発生回数が少なく、消耗量も少ないこ
とが判る。
次に、異常消耗の発生を次のようにして試験し
た。上記実施例１、２の素材と比較例３、４の素
材、そして従来例の素材、各々から製作した電気
接点のうち、各々任意に27個ずつ抜きとつた。そ
して、上記表の５種類の電気接点27個を９個ずつ
一まとめにして上記試験条件にて９台の耐消耗試
験機で３回行つた。その結果、実施例１、２及び
従来例の素材の電気接点各27個の消耗量は、いず
れもほぼ上記表に記載された数値どおりであつ
た。しかし、比較例３、４の素材の電気接点から
は異常に消耗するものがみられた。100mg以上消
耗したものが、比較例３のものから１個、比較例
４のものから２個あつた。このことから、粉末冶
金法で製造された電気接点には、異常消耗の生じ
やすいことが判る。
また、上記実施例１、２の素材を押し出し方向
に切断し、その断面組織を200倍の実体顕微鏡で
観察したところ、小さい繊維状組織の内部に酸化
物粒子の大きいものと小さいものが入り混つた組
織が見られた。これは、酸化割れを生じない銀−
酸化物系電気接点素材と比較すると、酸化割れの
部分から粉粒体が破壊されている結果、繊維状組
織が小さく、大小の酸化物粒子が混在している点
で相違し、比較例３、４の組織に近いものが得ら
れた。また、異常消耗した比較例３、４の素材の
電気接点の断面組織をＸ線マイクロアナライザー
で観察したところ、酸化錫と酸化インジウムの分
散は偏つていた。これは、酸化錫と酸化インジウ
ムの硬度が高く、両粉末同士が空隙を残したまま
不均一に混ざつてしまうからである。本発明によ
れば、均一に固溶した合金から酸化物を得るた
め、分散は均一であつた。このことから、従来の
ように均一に粉末を混合するという手段を経ない
でも、酸化割れを利用して、粉粒体の組織を安価
な方法で小さくすることができ、しかも、接点性
能がすぐれているという効果が得られた。
従つて、本発明の銀−酸化錫系電気接点素材の
製造方法は、酸化割れを利用した簡単安価な方法
であり、しかも、得られた電気接点は耐溶着性、
耐消耗性が銀−酸化カドミウム系電気接点よりも
優れ、安定した接点性能を有し、長寿命であり、
異常消耗もないので、従来の銀−カドミウム系電
気接点や、粉末冶金法による銀−酸化錫−酸化イ
ンジウム系電気接点にとつて代わることができ
る。以上のことから、本発明は画期的な電気接点
素材の製造方法と云える。[Table] As is clear from the values in the above table, the silver-tin oxide electrical contact material according to the present invention and the comparative example material have a lower
It can be seen that the number of occurrences of welding is significantly smaller and the amount of wear is also smaller. Next, the occurrence of abnormal wear was tested as follows. Of the electrical contacts made from the materials of Examples 1 and 2, the materials of Comparative Examples 3 and 4, and the conventional material, 27 contacts were arbitrarily extracted from each. Then, 27 electrical contacts of the 5 types shown in the above table were grouped into 9 pieces and tested three times using 9 wear resistance testers under the above test conditions. As a result, the amount of wear of each of the 27 electrical contacts made of the materials of Examples 1 and 2 and the conventional example was approximately as shown in the table above. However, some of the electrical contacts made of the materials of Comparative Examples 3 and 4 were found to be abnormally worn out. One sample from Comparative Example 3 and two samples from Comparative Example 4 consumed 100 mg or more. This indicates that electrical contacts manufactured by powder metallurgy are prone to abnormal wear. In addition, when the materials of Examples 1 and 2 were cut in the extrusion direction and the cross-sectional structure was observed with a stereomicroscope at 200x magnification, it was found that large and small oxide particles were mixed inside the small fibrous structure. Ivy tissue was visible. This is silver that does not cause oxidation cracking.
Compared with oxide-based electrical contact materials, the difference is that the fibrous structure is small and large and small oxide particles are mixed, as a result of the granular material being destroyed from the oxidation cracked part, Comparative Example 3, A tissue similar to that of No. 4 was obtained. Furthermore, when the cross-sectional structure of the abnormally worn electrical contacts of the materials of Comparative Examples 3 and 4 was observed using an X-ray microanalyzer, it was found that the distribution of tin oxide and indium oxide was uneven. This is because tin oxide and indium oxide have high hardness, and both powders are mixed non-uniformly with voids remaining. According to the present invention, the oxide was obtained from an alloy uniformly dissolved in solid solution, so that the dispersion was uniform. From this, it is possible to use oxidation cracking to reduce the structure of powder and granules in an inexpensive manner without going through the conventional means of uniformly mixing powder, and it also has excellent contact performance. The effect was obtained. Therefore, the method for producing the silver-tin oxide electrical contact material of the present invention is a simple and inexpensive method that utilizes oxidation cracking, and the obtained electrical contact has good adhesion resistance and
It has better wear resistance than silver-cadmium oxide electrical contacts, has stable contact performance, and has a long life.
Since there is no abnormal wear, it can replace conventional silver-cadmium electrical contacts or silver-tin oxide-indium oxide electrical contacts made by powder metallurgy. From the above, the present invention can be said to be an epoch-making method for manufacturing electrical contact materials.