【発明の詳細な説明】[Detailed description of the invention]
（産業上の利用分野）
本発明は、銀―酸化物系の電気接点材料の製造
方法に係るものである。
（従来技術とその問題点）
従来、内部酸化可能な銀基合金を全面から内部
酸化してなる第１図に示すような銀の地１中に酸
化物粒子２を分散した銀―酸化物系の電気接点材
料が、継電器やスイツチなどに広く使用されてき
たが、この電気接点材料は内部酸化処理の終期
に、銀の組成に近い酸化物の希薄層３が中央部に
形成されるために、酸化物の希薄層３が接点作用
面となる状態になるまで消耗が進んだときには、
銀―酸化物系接点材料としての性能、即ち耐溶着
性、耐消耗性が著しく低下するという欠点があつ
た。
かかる欠点を解消する為に、内部酸化可能な銀
基合金板の片面にニツケル又はクロムを被覆して
内部酸化する方法や内部酸化可能な銀基合金板を
互いに重ね合わせて周囲を溶接しその後内部酸化
する方法が採られていたが、前者は内部酸化後電
気抵抗の高いニツケル又はクロム被覆層を除去し
なければならず、後者は内部酸化中に周囲の溶接
部に割れが発生し、そこから酸素が入り結局内部
酸化可能な銀基合金板の両面から内部酸化が進行
し、略中央部に酸化物の希薄層ができることが多
く、また内部酸化後は周囲の溶接部分を切断し重
ねられている銀基合金板を分離して使用するた
め、周囲の溶接部分はスクラツプとなり歩留が低
く、更に打抜きにより接点形状に加工されたもの
には適用できず、両者共に工程が煩雑で生産性が
低いと云う欠点があつた。
本発明は、上記の製造上の欠点を解消せんが為
になされたもので、中央部に酸化物の希薄層のな
い銀―酸化物系電気接点材料の生産性の高い製造
方法を提供せんとするものである。
（問題点を解決するための手段）
本発明の製造方法は、第２図に示すように内部
酸化可能な銀基合金４に酸素の透過しない銀基合
金５を圧接して２層材にした後、内部酸化せしめ
ることを特徴とするものである。従つて内部酸化
可能な銀基合金４の下面以外の表面６からのみ内
部酸化が始まり、酸化物の希薄層は、中央部にで
きず、第３図のような内部組織の電気接点材料を
得ることができる。
本発明において、酸素を透過しない銀基合金５
の層を設けた理由は、内部酸化可能な銀基合金４
を全面から内部酸化させないで、任意の面からの
み内部酸化させて中央部に酸化物の希薄層の発生
するのを防止する為であり、又酸素を透過しない
合金に銀を主成分とした合金を用いた理由は、内
部酸化可能な銀基合金４と酸素を透過しない銀基
合金５との境界面まで酸素が浸入した時、接合の
大部分を担つている銀が酸化物にならない性質を
利用してその境界面からの剥がれを防止せんが為
である。
次に本発明における酸素の透過しない銀基合金
について述べる。
銀基合金の内部酸化時において、既酸化部分と
未酸化部分の境界面（内部酸化最前線）に拡散し
たフリーの酸素の数が、その境界面に存在する酸
化され得る元素を全部酸化するに必要な数よりも
常に多ければ、内部酸化が進行（酸化部分の厚さ
が厚くなり、その分未酸化部分の厚さが薄くな
る）しやがては未酸化部分の厚さがゼロとなつて
内部酸化が全部終わる。このような銀基合金は内
部酸化可能な銀基合金即ち酸素を透過する銀基合
金である。これに対し、既酸化部分と未酸化部分
の境界面に拡散したフリーの酸素の数が、その境
界面に存在する酸化され得る元素を全部酸化する
に必要な数よりも少なければ、内部酸化はそこで
停滞して進行しなくなる。このような銀基合金酸
素拡散速度の極めて遅い銀基合金は本発明でいう
酸素の透過しない銀基合金である。
斯かる銀基合金は、添加元素の種数、添加量、
厚さによつて酸素が透過しない限界温度や限界酸
素分圧が定まるものである。実際には内部酸化し
たい銀基合金の内部酸化条件に従つて酸素を透過
しない銀基合金の添加元素の種類、添加量、厚さ
を決める。
添加元素としてAl、Mgは、少量の添加量で酸
素の透過しない銀基合金が得られるので特に好ま
しい。
本発明の実施例を示せば次の通りである。
（実施例 １）
11wt％Cd―Ag合金から成る内部酸化可能な銀
基合金４と、0.8wt％Ａ―Ag合金から成る酸素を
透過しない銀基合金５とを圧接して２層となし、
これを第２図に示す如く圧延して11wt％Cd―Ag
合金層1.2mm厚、0.8wt％Al―Ag合金層を0.2mm厚
となし、次いで750℃、酸素分圧６気圧の酸素雰
囲気中で72時間内部酸化処理を施したところ、中
央部に酸化物の希薄層のない第３図に示す如く内
部組織の電気接点材料が得られた。
（実施例 ２）
5wt％Sn―1wt％In―Ag合金と、1wt％Mg―
Ag合金とを圧接して２層となし、これを圧延し
て5wt％Sn―1wt％In―Ag合金層を0.6mm厚、1wt
％Mg―Ag合金層を0.15mm厚となし、次いで600
℃酸素分圧３気圧の酸素ふん囲気中で120時間内
部酸化処理を施したところ、中央部に酸化物の希
薄層のない第３図に示す如く内部組織の電気接点
材料が得られた。
（従来例）
0.8wt％Al―Ag合金から成る酸素を透過しない
銀基合金を圧接しない以外は全て実施例１と同じ
条件で内部酸化処理を施したところ、中央部に酸
化物の希薄層のある第１図に示す如く内部組織の
電気接点材料が得られた。
以上実施例１、２及び従来例で得られた電気接
点材料の表面及び断面の硬さを測定して内部酸化
の様子を調べたところ、下記の表のような結果が
得られた。
(Industrial Application Field) The present invention relates to a method for producing a silver-oxide electrical contact material. (Prior art and its problems) Conventionally, a silver-oxide system in which oxide particles 2 are dispersed in a silver base 1 as shown in Fig. 1, which is made by internally oxidizing the entire surface of an internally oxidizable silver-based alloy, has been developed. This electrical contact material has been widely used in relays, switches, etc., but this electrical contact material is difficult to use because at the end of the internal oxidation process, a dilute layer 3 of an oxide with a composition similar to that of silver is formed in the center. , when the wear progresses to the point where the dilute oxide layer 3 becomes a contact working surface,
The drawback was that the performance as a silver-oxide contact material, that is, the welding resistance and abrasion resistance were significantly reduced. In order to eliminate this drawback, there are methods such as coating one side of internally oxidizable silver-based alloy plates with nickel or chromium and internally oxidizing them, or stacking internally oxidizable silver-based alloy plates on top of each other, welding the periphery, and then internally oxidizing the plates. The former method requires removal of the nickel or chromium coating layer with high electrical resistance after internal oxidation, while the latter method causes cracks to occur in the surrounding weld during internal oxidation, and Oxygen enters and eventually internal oxidation progresses from both sides of the silver-based alloy plate, which can be internally oxidized, and a thin layer of oxide is often formed approximately in the center, and after internal oxidation, the surrounding welded parts are cut and overlapped. Since the silver-based alloy plate is separated and used, the surrounding welded parts are scrapped, resulting in a low yield.Furthermore, it cannot be applied to contacts that have been processed into contact shapes by punching, and both processes are complicated and productivity is low. The drawback was that it was low. The present invention was made in order to eliminate the above-mentioned manufacturing defects, and aims to provide a highly productive method for manufacturing a silver-oxide electrical contact material without a thin layer of oxide in the center. It is something to do. (Means for Solving the Problems) As shown in FIG. 2, the manufacturing method of the present invention is such that a silver-based alloy 5 that is impermeable to oxygen is pressure-bonded to a silver-based alloy 4 that can be internally oxidized to form a two-layer material. After that, it is characterized by internal oxidation. Therefore, internal oxidation starts only from the surface 6 other than the lower surface of the internally oxidizable silver-based alloy 4, and a thin layer of oxide is not formed in the center, resulting in an electrical contact material with an internal structure as shown in FIG. be able to. In the present invention, silver-based alloy 5 that does not permeate oxygen
The reason for providing this layer is that silver-based alloy 4, which can be internally oxidized,
This is to prevent the formation of a thin layer of oxide in the center by internally oxidizing only from any surface without internally oxidizing the entire surface, and to prevent the formation of a thin layer of oxide in the center. The reason for using this is that when oxygen penetrates to the interface between the internally oxidizable silver-based alloy 4 and the oxygen-impermeable silver-based alloy 5, the silver that makes up most of the bond does not turn into an oxide. This is to prevent peeling from the interface. Next, the oxygen-impermeable silver-based alloy of the present invention will be described. During internal oxidation of a silver-based alloy, the number of free oxygen diffused to the interface between the oxidized and unoxidized parts (internal oxidation front line) is large enough to oxidize all the oxidizable elements present at the interface. If the number is always greater than the required number, internal oxidation will progress (the thickness of the oxidized part will become thicker and the thickness of the unoxidized part will become thinner), and eventually the thickness of the unoxidized part will become zero and the internal All oxidation is complete. Such a silver-based alloy is an internally oxidizable silver-based alloy, that is, a silver-based alloy that is permeable to oxygen. On the other hand, if the number of free oxygen diffused to the interface between the oxidized and unoxidized parts is less than the number required to oxidize all the oxidizable elements present at the interface, internal oxidation will not occur. There it becomes stagnant and no progress is made. Such a silver-based alloy having an extremely slow oxygen diffusion rate is a silver-based alloy that does not allow oxygen to pass through in the present invention. Such a silver-based alloy is determined by the number of types of added elements, the amount added,
The critical temperature and critical oxygen partial pressure at which oxygen does not permeate are determined by the thickness. In fact, the type, amount, and thickness of the added element of the silver-based alloy that does not transmit oxygen are determined according to the internal oxidation conditions of the silver-based alloy to be internally oxidized. Al and Mg are particularly preferable as additive elements since a silver-based alloy through which oxygen does not permeate can be obtained with a small amount of addition. Examples of the present invention are as follows. (Example 1) An internally oxidizable silver-based alloy 4 made of a 11 wt% Cd-Ag alloy and an oxygen-impermeable silver-based alloy 5 made of a 0.8 wt% A-Ag alloy are pressed together to form two layers,
This was rolled to yield 11wt%Cd-Ag as shown in Figure 2.
An alloy layer of 1.2 mm thickness and a 0.8 wt% Al-Ag alloy layer of 0.2 mm thickness were then subjected to internal oxidation treatment for 72 hours at 750°C in an oxygen atmosphere with an oxygen partial pressure of 6 atm. An electrical contact material with an internal structure as shown in FIG. 3 without a diluted layer was obtained. (Example 2) 5wt%Sn-1wt%In-Ag alloy and 1wt%Mg-
Ag alloy is pressure-welded to form two layers, which are then rolled to form a 5wt%Sn-1wt%In-Ag alloy layer with a thickness of 0.6mm and a weight of 1wt.
%Mg-Ag alloy layer with a thickness of 0.15mm, then 600mm
When internal oxidation treatment was carried out for 120 hours in an oxygen atmosphere with an oxygen partial pressure of 3 atm (°C), an electrical contact material with an internal structure as shown in FIG. 3 without a thin layer of oxide in the center was obtained. (Conventional example) When internal oxidation treatment was performed under the same conditions as in Example 1 except that the oxygen-impermeable silver-based alloy made of 0.8wt% Al-Ag alloy was not pressure-welded, a thin layer of oxide was formed in the center. An electrical contact material having an internal structure as shown in FIG. 1 was obtained. When the hardness of the surface and cross section of the electrical contact materials obtained in Examples 1 and 2 and the conventional example was measured to examine the state of internal oxidation, the results shown in the table below were obtained.
【表】
上記表から明らかなように内部酸化可能な銀基
合金については従来例では酸化前よりも酸化後の
硬さが下がり、実施例では酸化前よりも酸化後の
硬さが上がり、また酸素の透過しない銀基合金に
ついては酸化前よりも酸化後の方が硬さが僅かに
下がつていることが判る。このことは従来例にあ
つては、内部酸化可能な銀基合金の中央部にやわ
らかい部分が発生したことになり、実施例にあつ
ては硬い部分が発生したことになる。つまり従来
例では酸化物の希薄層ができ、実施例では酸化物
分散層ができたことになる。一方実施例の酸素の
透過しない銀基合金では硬さが酸化前よりも酸化
後の方が僅かに低く、焼なましが起きた程度であ
る。このことは0.35wt％Al―Ag及び0.25wt％Mg
―Ag合金を内部酸化すると硬さ（HV）が100以
上にもなることを考えると、内部酸化が起きてな
いことを意味するものである。
（発明の効果）
以上のことから判るように本発明の製造方法
は、内部酸化可能な銀基合金に酸素の透過しない
銀基合金を圧接するだけで素材を作ることがで
き、後は所望の形状にして内部酸化するだけで、
中央部に酸化物の希薄層のない電気接点材料が得
られるので、従来法に比べ極めて生産性の高いも
のである。[Table] As is clear from the above table, for internally oxidizable silver-based alloys, in the conventional example, the hardness after oxidation is lower than before oxidation, and in the example, the hardness after oxidation is higher than before oxidation, and It can be seen that for silver-based alloys that do not allow oxygen to pass through, the hardness is slightly lower after oxidation than before oxidation. This means that in the conventional example, a soft portion was generated in the center of the internally oxidizable silver-based alloy, and in the example, a hard portion was generated. In other words, in the conventional example, a dilute oxide layer was formed, and in the example, an oxide dispersed layer was formed. On the other hand, the hardness of the oxygen-impermeable silver-based alloy of the example is slightly lower after oxidation than before oxidation, and is at a level where annealing has occurred. This means that 0.35wt%Al-Ag and 0.25wt%Mg
- Considering that internal oxidation of Ag alloys increases the hardness (HV) to over 100, this means that no internal oxidation has occurred. (Effects of the Invention) As can be seen from the above, the manufacturing method of the present invention makes it possible to produce a material simply by pressure-welding a silver-based alloy that is impermeable to oxygen to a silver-based alloy that can be internally oxidized, and then the desired material can be produced. Just shape it and oxidize it internally.
Since an electrical contact material without a thin layer of oxide in the center can be obtained, productivity is extremely high compared to conventional methods.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は、従来の電気接点材料の断面図、第２
図は、本発明に係る内部酸化前の素材の断面図、
第３図は本発明による電気接点材料の断面図であ
る。
４…内部酸化可能な銀基合金、５…酸素を透過
しない銀基合金、６…内部酸化可能な銀基合金の
下面以外の表面。
Figure 1 is a sectional view of a conventional electrical contact material, Figure 2 is a cross-sectional view of a conventional electrical contact material;
The figure is a cross-sectional view of the material before internal oxidation according to the present invention,
FIG. 3 is a cross-sectional view of an electrical contact material according to the present invention. 4... Silver-based alloy that can be internally oxidized, 5... Silver-based alloy that does not permeate oxygen, 6... Surface other than the lower surface of silver-based alloy that can be internally oxidized.