JPH05179414A - Production of composite electrical contact material of ag-oxide series - Google Patents

Abstract

PURPOSE:To obtain a composite electrical contact material of Ag-CdO series excellent in spot weldability by heating a wire or bar of Ag-CdO material in a reducing atmosphere and reducing an oxide layer at the surface. CONSTITUTION:A mixture of Ag powder and CdO powder is compacted, sintered, and worked into a wire or bar by a hot extrusion method, or, a wire or bar of Ag-Cd alloy is subjected to internal oxidation and then to cold working at >=30% reduction of area and a wire or bar of Ag-CdO series where the crystalline grains at the time of internal oxidation are destroyed and working strain is allowed to remain in the inner part is produced. These materials are heated slowly up to >=600 deg.C at 40 to 100 deg.C/min heating rate in a reducing gaseous-mixture atmosphere where the volume ratio of N2 to H2 is regulated to 1:1 to 10:1, and the CdO as oxide at the surface of the wire or bar is reduced to Cd, by which the electrical contact material of Ag-CdO series in a state of wire or bar having a surface layer of Ag-Cd alloy can be produced. Because the surface is formed of an Ag-Cd layer increased in the proportion of Ag, the electrical contact material excellent in deposition characteristic at the time of welding can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a wire or strip of Ag-CdO composite electric contact material.

[0002]

2. Description of the Related Art Conventionally, Ag and Ag-N have been used as electrical contact materials.
i or Ag-CdO system is used. Among them, Ag-N
Since i has low contact resistance and little wear, i is widely used instead of Ag. In addition, Ag-Ni is easy to process and spot weld, so it is possible to automate the work of fixing it to the base material, etc., which has the great advantage that the assembly cost is low and the quality is stable. However, on the other hand, Ag
-Because it consumes more than Ag-oxide systems such as -CdO and has poor welding resistance, the range of use is limited to small capacity areas such as small switches.

Recently, the rationalization in each industrial field and the automation of mechanical devices have been remarkable, and the size and complexity of the devices have increased accordingly, and these control systems are rather downsized, the operation frequency is increased, and the capacity is increased. Is required. Therefore, the Ag-Ni system is reviewed, but from the above points, the welding resistance of Ag-Ni becomes a problem, and the development of alternative materials for it is desired.

Therefore, attempts are being made to improve the characteristics by adding various metal elements or metal oxides, nitrides, carbides, etc. to Ag-Ni. However, the stable contact resistance, workability and easiness of spot welding, which are the original features of Ag-Ni system, are hampered by the mixture of various additives, and no satisfactory results have been obtained. On the other hand, the Ag-CdO system is excellent in welding resistance and wear resistance and has a wide range of use, but it has problems in workability and weldability to base materials. This is because the oxide is present at the interface with the base material, so that the joint strength in spot welding or brazing is significantly smaller than that of a non-oxide material.

[0005]

[Problems to be Solved by the Invention] Therefore, these Ag-CdO
A composite material in which an oxide-free layer is formed on the base material for easy spot welding and brazing is considered. For example, a composite strip is obtained by joining an Ag-CdO-based strip and an Ag ribbon by the hot press bonding method, but when actually joining the base material and incorporating it into the switch and performing a test, the Ag-CdO It often separates from the boundary between Ag and Ag and does not reach a predetermined life.

[0006]

Means for Solving the Problems The present invention is a wire or strip of Ag-CdO, or a wire or strip of internally oxidized Ag-Cd wire or strip, or a mixture of Ag powder and CdO powder,
After molding and sintering this mixed powder, by hot extrusion etc.
Ag-CdO wire or strip, and after forming and sintering Ag-CdO powder or small pieces obtained by internal oxidation method or chemical treatment method, Ag-CdO wire or The material formed into a strip is gradually heated in a mixed atmosphere in which the volume ratio of N ₂ gas and H ₂ gas is in the range of 1: 1 to 10: 1. It is intended to solve the above-mentioned problem by heating the material to reduce the oxide layer on the surface and forming a reduction layer rich in Ag on the outer periphery of the wire or strip.

Generally, when an oxide of an Ag-CdO-based material is to be reduced, a rapid reaction occurs as soon as the reducing gas, for example, H ₂ and the oxide come into contact with each other, and the inside thereof is full of pores. Will have a sponge-like shape, resulting in an extremely fragile tissue as a material. Therefore, even if a reducing layer is obtained by contacting it with a reducing gas for the purpose of forming a reducing layer on the surface of a wire or strip by a normal method, the reducing layer is fragile, so brazing or welding to the base material. However, there is a risk of accidents such as contact loss, which is not practical.

Therefore, in the present invention, basically, a wire or strip having an appropriate working strain is used, and the volume ratio of N ₂ gas and H ₂ gas is 1: 1 to 10: 1 as the reducing gas. Range and
A desired reduction layer can be obtained by gradually increasing the reduction temperature. Here, the reason why the volume ratio of N ₂ gas and H ₂ gas is set in the range of 1: 1 to 10: 1 is that the desired uniform thickness is obtained when reducing the oxide layer on the surface of the wire or strip. In order to control the volume ratio of H ₂ gas to N ₂ gas is 1:
If it is 1.1 or more, it becomes difficult to control the reduction rate, and further, the amount of H ₂ gas increases, which affects safety. The volume ratio of the H ₂ gas for N ₂ gas is 10: is less than 1 is because the reducing power by the H ₂ gas is no longer possible to uniformly control the reduction layer without enough.

Further, the reason why cold working is performed on a wire or strip at a cross-section reduction rate of 30% or more is that the cold working of 30% or more causes, in a strict sense, an extremely fine grain in the vicinity of the oxide in the matrix. Cracks are generated, so that the infiltration of H _{2 and the} like into the matrix is not concentrated by the subsequent heating,
This is because voids are less likely to occur because they are dispersed appropriately. An ideal effect is produced by the synergistic action of such actions.

[0010]

EXAMPLES Examples of the present invention will be described below. First Example 4 mm diameter Ag produced by sintering, molding and extrusion
A wire of -15wt% CdO was drawn into a wire with a diameter of 2mm. The cold working ratio at this time was 75%.

This was set to 200 ° C., 350 ° C., 500 ° C., 600 ° C., 700 ° C. from the entrance side using a continuous furnace with five-point control, and N ₂ gas was supplied.
The volume ratio of H ₂ gas was adjusted to be 1: 1 and passed through at a speed of 100 mm / min to obtain a wire rod having a reducing layer on the outer periphery of the surface of the wire rod. The thickness of the reduction layer at this time is
It was about 0.12 mm. This is further drawn to a diameter of 1.
8 mm wire was used as sample A.

Second Embodiment 4 mm diameter Ag produced by sintering, molding and extruding
A wire of -10wt% CdO was drawn into a wire with a diameter of 2mm. The cold working ratio at this time was 55%. Using a continuous furnace with 5-point control, this is operated at 200 ℃, 350 ℃, 500 ℃, 6
Set at 50 ℃ and 800 ℃, the volume ratio of N ₂ gas and H ₂ gas is 2: 1.
The atmosphere was adjusted so as to obtain an atmosphere of, and the wire was passed at a speed of 95 mm / min to obtain a wire having a reducing layer on the outer periphery of the surface of the wire.

At this time, the thickness of the reducing layer was about 0.15 mm. This was further drawn into a wire rod having a diameter of 1.8 mm, which was designated as Sample B. Samples C to F shown in Table 1 were prepared in the same manner as in the first and second embodiments, and the wire rods of the samples A to F were cut to a length of 2 mm and then spot-welded. The material is stuck.

Next, a forming press was used to form a square having a thickness of 0.8 mm and a width and length of about 2.5 mm. Measure the shear strength of each contact and incorporate it into a commercially available contactor. Voltage 220V, current 78A, power factor 0.35
I did an implementation test. For comparison, the following two most standard conventional examples were prepared and comparative tests were conducted.

In the above embodiment, the method is not limited to the continuous furnace as long as it is a method capable of heating in stages, and the same applies to a batch type furnace. 1st conventional example 5 mm thick, 100 mm wide, 200 mm long Ag-13wt% Cd alloy plate and 0.5 mm thick, 100 mm wide, 200 mm long Ag plate are overlaid and joined by hot pressing. Thickness is 0 by cold rolling.
Processed to 8 mm.

Next, press punching into a size of 2.5 mm × 2.5 mm was performed, and the pellets were 750 ° C. in the atmosphere.
An internal oxidation treatment was performed in the electric furnace set to 1 to obtain an Ag-15wt% CdO 2 contact with an Ag layer formed on the back side. Second conventional example Ag-10w with Ag layer formed on the back side by the same method as the first conventional example
Got t% CdO contact.

[0017]

[Table 1]

[0018]

According to the present invention described in detail above, as shown in Table 1, the spot welding strength with the base material is excellent,
It has an extremely excellent effect in the contact opening / closing test by the actual machine.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

Means for Solving the Problems The present invention is a wire or strip of Ag-CdO, or a wire or strip of internally oxidized Ag-Cd wire or strip, or a mixture of Ag powder and CdO powder,
After molding and sintering this mixed powder, by hot extrusion etc.
Those without a Ag-CdO wire or strip material, was further molded and sintered powder or small pieces of Ag-CdO obtained from the internal oxidation or chemical treatment method, by hot extrusion, etc.
Formed Ag-CdO wire or strip into N ₂ gas and H ₂
In the mixed atmosphere in which the gas volume ratio is in the range of 1: 1 to 10: 1, the temperature is gradually raised and finally heated to 600 ° C or higher to reduce the oxide layer on the surface. In order to solve the above problem, a reducing layer rich in Ag is formed on the outer circumference of a wire or strip.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshitaka Kajiyama 2-9-12 Kajimachi, Chiyoda-ku, Tokyo Incorporated Tokuriki Head Office

Claims (5)

[Claims] 1. The temperature is gradually raised in a mixed atmosphere in which a wire or strip of Ag—CdO is mixed in a volume ratio of N ₂ gas and H ₂ gas in the range of 1: 1 to 10: 1. Finally, by heating it to 600 ° C or higher, the oxide layer on the surface is reduced, and an oxide reduction layer is formed on the outer circumference of the wire or strip. Production method. 2. The method according to claim 1, wherein the Ag-CdO-based wire or strip is used in a mixed gas atmosphere of N ₂ gas and H ₂ gas at a rate of 40 per minute.
A method for producing an Ag-oxide-based composite electrical contact material, which comprises reducing the oxide layer on the surface by raising the temperature at a rate of -100 ° C and finally heating it to 600 ° C or higher. 3. The Ag-Cd wire or strip according to claim 1, wherein the material is internally oxidized, and the material is subjected to cold working at a cross-sectional reduction rate of 30% or more to destroy crystal grains during internal oxidation. A method for producing an Ag-oxide composite electrical contact material, characterized in that a material having a working strain inside is used. 4. The Ag powder and the CdO powder according to claim 1, the Ag powder and the CdO powder are mixed, the mixed powder is molded and sintered, and then the Ag-CdO wire or strip is molded by hot extrusion or the like. A method for producing an Ag-oxide composite electrical contact material, which comprises using a material that has been subjected to cold working with a cross-sectional reduction rate of 30% or more and left a working strain inside the material. 5. The wire or strip of Ag-CdO according to claim 1, which is obtained by molding and sintering Ag-CdO powder or small pieces obtained by an internal oxidation method or a chemical treatment method, and then hot extruding or the like. Molded into a 30% cross-section reduction rate for this material
A method for producing an Ag-oxide-based composite electrical contact material, characterized by using a material that has been subjected to the above-mentioned cold working to leave a working strain inside the material.