JPS6022459B2 - Backing material that adheres the contact material to the base material - Google Patents

Description

[Detailed description of the invention] The present invention relates to a backing village for securing contact material to a backing.

For example, silver-cadmium oxide (hereinafter referred to as Ag-Cd○)
So-called silver-metal oxide (hereinafter referred to as Ag-Me0) contact materials, such as these, are very widely used because they have excellent anti-sagging properties and wear resistance, which are important for contacts in load circuits where many arcs occur. It is being BACKGROUND OF THE INVENTION Nowadays, electronic and electrical devices are becoming smaller and have longer lifespans, and contacts are being used under increasingly severe circuit conditions, and contact materials are being actively improved. Therefore, Ag-Cd
○ Since it is difficult to braze the contact material to the base material as it is, it is usually
I stretched the backing material 2 of g and attached the contact material 3.

However, the arc heat and Joule heat that accompany the opening and closing of the contact melt the contact surface, and the temperature of the contact continues to rise until it reaches a certain steady state. Volume expansion occurs in each part depending on the temperature.

i.e. operating equipment. Repeated pauses lead to heating and cooling of the contacts, and the volume increases and decreases between the contact material 3 and the lining material 2 according to their coefficient of thermal expansion. will repeat more rapid expansion and contraction.This frequent expansion (Fig. 2A) and contraction (Fig. 2B)
) results in the accumulation of stress mainly near the boundary between the contact material 3 and the backing material 2, resulting in the generation of minute cracks. When an external force such as an impact during opening/closing or a tensile force during opening is applied to this minute crack, the crack spreads in a wave-like manner along the stress-concentrated area, eventually causing the contact material 3 to break off and become abnormal. This will lead to wear and tear. Furthermore, recently Ag-C
Ag-Cd○ with added Z oxide and Sn oxide developed to improve welding resistance and wear resistance in d○ system.
There are alloys based on the alloys, but these have a coefficient of thermal expansion of 4.0% higher than that of simple Ag-Cd. .

The present invention aims to solve the above-mentioned drawbacks by using a material having a coefficient of expansion similar to that of the contact material for the backing material, thereby increasing the expansion of both. It is characterized by improving durability by keeping shrinkage almost the same. The present invention will be explained below. In the present invention, a backing material having a coefficient of thermal expansion close to that of Ag-Me◯ is obtained by making a material containing 2% or less of metal oxide through internal oxidation of Ag.

Elements that can be internally oxidized in Ag alloys include Li, A,
Mg, Zr, Fj, Cd, Mn, Si, Bi and ln
and so on.

However, if a large amount of these elements is added and internal oxidation is caused, the brazing properties will decrease and the coefficient of linear expansion will decrease.

For this reason, the amount of alloying elements to be added was experimentally investigated while taking into account the relationship among brazability, strength, and coefficient of linear expansion, and the result was the above-mentioned value of 2% or less. Examples of the present invention will be described below.

All alloys used as backing materials were melted, rolled or drawn into the desired shape, and then internally oxidized in an atmosphere of 80,000 ml.

After this, various characteristics were measured. The strength of the brazed part is 4◇
The tensile strength of the Ag-based internally oxidized alloy and yellow steel (alloy %, Cu-Z) butt-brazed (BAg-1) was evaluated. Table 1 shows a comparison of the green expansion coefficient and the tensile strength of the brazed part.

The linear expansion coefficient of the alloy made by adding the elements in Table 1 and internally oxidizing it is almost the same as that of the most common contact material Ag-Cd0,
Ag is large.

Also, the brazeability of the alloy is slightly lower than that of Ag, but
The tensile strength is increased compared to Ag, and in particular, the Ag-A alloy is significantly improved. The above alloy was adhered to an Ag-12% Cd alloy and internally oxidized.

The thus obtained Ag-Cd○ contact was brazed to an alloy, incorporated into an electromagnetic switch, and subjected to a switching test of 30,000 times under the following electrical load conditions. The occurrence of cracks was investigated by observation using an optical microscope.

Voltage: 440V/AC Current: 480A Power factor: 0.35 Opening/closing frequency: 300 (Sw/h) All of the silver brazing layers made of Ag show cracking, and some even peel off before 30,000 cycles. Admitted.

The occurrence of this crack is thought to be caused by thermal stress caused by repeated opening and closing. In the case of the present invention, in which an internally oxidized Ag-based alloy was used for the brazing silver layer, no peeling was observed, and it became clear that it could sufficiently withstand thermal stress. As described above, by using an alloy containing 2% or less metal oxide in Ag as the backing material for the Ag-Me○ type contact material, it has an expansion coefficient similar to that of the Ag-Me○ type contact material. It can be used as a lining material, and because the lining material expands and contracts in the same way as the contact material due to operation and rest of the contact material, it prevents the occurrence of cracks near the joint between the contact material and the lining material. As a result, accidents such as loss of contact material can be eliminated.

In each of the examples, a metal oxide was used as the metal contained in Ag, but the same effect can be obtained by using a metal nitride, a metal columnaride, or a metal carbide.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the state in which the contact material is brazed to the base material, Figures 2 A and B are cross-sectional views showing the heating and cooling states, and Figure 3 is a cross-sectional view showing the state of heating and cooling.
The figure is a cross-sectional view showing a state in which the contact material has peeled off. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a backing material for attaching a silver-metal oxide contact material to a base material, the silver-metal oxide contact material contains 2% or less of a metal compound in silver. A lining material for fixing a contact material to a base material, characterized by being made of a material having a coefficient of thermal expansion approximately equal to . 2. A backing material for fixing the contact material according to claim 1 to a base material, which is made of a material containing metal oxide in silver. 3. A backing material for fixing the contact material according to claim 1 to a base material, which is made of a material containing metal nitride in silver. 4. A backing material for fixing the contact material according to claim 1 to a base material, which is made of a material containing metal boride in silver. 5. A backing material for fixing the contact material according to claim 1 to a base material, which is made of a material containing metal carbide in silver.