JPS59178184A - Production of rotary electrode - Google Patents

Abstract

PURPOSE:To improve joint quality and an electrode life by penetrating a low melting copper alloy on the inside of a thin-walled ring consisting of a sintered alloy of a metal having high m.p. in an inert gaseous atmosphere to form a composite disc thereby joining both without any shrinkage crack owing to a difference in the coefft. of thermal expansion. CONSTITUTION:Joining of an outside circumferential ring 1 and an inside base material 2 is accomplished by penetrating a low melting copper alloy on the inside of the sintered alloy ring 1. The generation of a tensile stress in the ring 1 owing to a difference in the coefft. of thermal expansion as in brazing is thus obviated and the wall thickness of the sintered alloy ring can be decreased. Since the low melting copper alloy is penetrated in an inert or reducing gaseous atmosphere, such an adverse influence which melts the sintered alloy or changes the compsn. thereof is eliminated and the defective joining between the ring 1 and the alloy 2 owing to the surface oxidation of said ring is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Due to its performance, rotary electrodes used in welding machines and the like use a sintered alloy containing a high-melting point metal such as snake alloy or copper-tungsten on the outer periphery of the electrode. There is something. These sintered alloys are generally used for iron or @-based base materials, but because their coefficient of thermal expansion is nearly twice as low as iron or copper-based base materials, the sintered alloys on the outer periphery are If the ring is too thick, there is a risk of cracks occurring within this sintered alloy.
Also, it is necessary to have a wide brazing gap, and the brazing properties are not good, such as the occurrence of brazing gaps. In order to eliminate these defects, as shown in FIGS. 1 and 2, a method has been adopted in which the sintered alloy on the outer periphery is suitably divided and brazed. However, according to this method, a brazed joint is present in the sintered metal part of the outer periphery, which is most necessary for welding characteristics, and this causes a reduction in service life due to local wear. Furthermore, in applications that require grooves to be machined on the outer periphery as shown in FIG. 2, the pitch of the grooves is fixed, which has the disadvantage that the degree of freedom in design is significantly restricted.

The present invention has been made to eliminate such drawbacks of rotary electrodes, and includes a method for manufacturing a rotary electrode whose outer peripheral portion is made of a sintered alloy containing a high-melting point metal. An integrated composite disk is created by melting a low melting point copper alloy such as brass or gun metal inside in an inert or reducing gas atmosphere, and then machined into an electrode shape. The present invention relates to a method of manufacturing a rotor'J-ME pole characterized by the following. In other words, the sintered alloy ring on the outer periphery and the low melting point copper-gold alloy base material are joined by melting the low melting point copper alloy inside the sintered alloy ring, so thermal expansion does not occur as in the case of brazing joining. Ui tensile stress on the outer periphery sintered alloy ring due to the difference in rate does not occur.

This is because the molten copper alloy begins to cool and solidify from the outer periphery in contact with the sintered alloy ring and progresses toward the center.
Stress due to shrinkage does not directly act on the sintered alloy ring. Therefore, the thickness of the sintered metal ring on the outer periphery can be made much thinner than that obtained by brazing.

In addition, by using a low melting point copper alloy such as brass or gunmetal as a base material, which has a lower melting point than the sintered alloy containing the high melting point metal on the outer periphery, it is possible to use a low melting point copper alloy such as brass or gunmetal as a base material. There is no adverse effect such as melting the sintered alloy on the outer periphery or changing its composition.

Moreover, these copper alloy base materials are generally used for electrical purposes, and are of course more effective than iron-based base materials.
It also has excellent oxidation resistance and is considered to be preferable in terms of rotary electrode performance.

In addition, using an inert or reducing gas atmosphere when melting and heating the low melting point copper alloy and dissolving it into the sintered alloy ring is because the outer sintered alloy ring contains high melting point metals such as tungsten and molybdenum that are easily oxidized. This is to prevent poor bonding with the copper alloy base material due to surface oxidation of the ring.

In addition to the aforementioned heavy alloy and copper tungsten, examples of sintered alloys containing high melting point metals include copper tungsten carbide, copper tungsten carbide,
Examples include copper molybdenum, copper titanium carbide, copper tantalum carbide, and copper chromium carbide.

Exception diameter: 166mmφ, inner diameter: 150tanφ, thickness: 3.3
Copper tungsten ring made of 20% copper, 80% tungsten and 6% copper, 2, 3% tungsten, 9 mm
A heavy alloy ring consisting of 4% alloy was produced by powder metallurgy. These rings were placed on a carbon plate, a 700# cut piece of a brass plate was placed inside the ring, and heated at 900° C. for 20 minutes in a reducing gas furnace. After cooling these integrally bonded products, they were processed into a disk shape with an outer diameter of 160 tnmψ and a thickness of 3 am, and the enlarged part was observed using a stereomicroscope.
It was confirmed that there were no nests or pinholes, and the zygote was in good condition. Furthermore, when these disks were cut appropriately and the shear strength of the joint was examined using a shear test method, both were found to be 15 to 9/9.
A bonding strength of 2 m2 or higher was obtained. In general, the bonding strength with the amount of brazing is 10 mm2 or more, and it was found that the bonding strength of the product of the present invention is sufficiently high. Furthermore, when these disks were processed into rotary electrodes and used for welding resistor lead wires using a welding machine, the life of the electrodes was improved by about 50% compared to conventional brazing amounts.

As described above, in a method for manufacturing a rotary electrode whose outer periphery is made of a sintered alloy containing a high-melting point metal, a material having a lower melting point, such as brass or gunmetal, is placed inside the thin ring made of the sintered alloy. Create an integrated composite disk by dissolving copper alloy in an inert or reducing gas atmosphere,
According to the present invention, which relates to a method for manufacturing a rotary electrode, which is characterized in that the rotary electrode is then machined into the shape of the electrode, the outer ring and the inner base material can be joined without worrying about cracking during brazing due to the coefficient of thermal expansion. It was found that the bonding quality and electrode life were improved. Furthermore, compared to rotary electrodes made using the conventional brazing method, the sintered metal on the outer periphery can be made into a thinner ring, which not only has an economical effect, but also makes it possible to use it with grooves on the outer periphery. In some cases, the degree of freedom in design increases, and it is considered to be a great contribution to industry.

[Brief explanation of the drawing]

1 and 2 show a rotor 1 non-electrode disk formed by a conventional brazing method, and FIG. 6 shows a rotary electrode disk according to the present invention. Patent applicant Nippon Tungsten Co., Ltd.

Claims (1)

[Claims] / In manufacturing a rotary electrode whose outer cylinder part is made of a sintered alloy containing a high melting point metal, a low melting point copper alloy such as brass or gunmetal, which has a lower melting point than the thin ring made of the sintered alloy, is inert or heated inside the thin ring made of the sintered alloy. A method for manufacturing a rotary electrode, characterized in that an integrated composite disk is created by melting in a reducing gas atmosphere, and then machined into an electrode shape.