JPH02182380A - Nonconsumable electrode for oxygen plasma working - Google Patents

Abstract

PURPOSE:To reduce the manufacturing stages of the subject nonconsumable electrode and to extend the service life thereof by interposing an Al metallic spacer at a specified distance from the front end face of a holder and in the range within the specific % of the overall length of an operating insert in the contact surface between the holder and the operating insert. CONSTITUTION:The operating insert 2 made of Hf or a Hf alloy is penetrated and inserted from the front end face 1a of the holder 1 up to a through hole 1b on one face with the front end face 1a on a through hole 1d. The metallic spacer 3 made of Al or an Al alloy is arranged in the contact surface between the operating insert 2 inserted into the through hole 1d and the holder 1. The overall spacer 3 has >=3mm distance from the front end face 1a of the holder 1 and is arranged in the range within 80% of the overall length of the operating insert 2. By this method, the need to form the metallic spacer into a cup-shaped socket is eliminated and the manufacturing cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a non-consumable electrode used in an oxygen plasma arc torch.

<Prior Art> Today, when cutting or welding a workpiece such as a steel plate, an oxygen plasma arc is used.

As an electrode for generating the oxygen plasma arc,
A working insert made of hafnium or a hafnium alloy is fitted into a holder made of copper or a copper alloy, and a metal spacer made of aluminum or an aluminum alloy is placed on the entire contact surface between the holder and the working insert. This is known (Patent No. 877804).

This technique is advantageous because the metal spacer can serve as a heat shield to protect the holder from overheating and oxidation, thereby extending the life of the holder.

Further, when manufacturing an electrode using the above technique, first, a hole having a predetermined depth is bored from the end surface of the holder, and a cup-shaped aluminum socket is manufactured. After fitting and fixing a hafnium wire cut to a predetermined length into the aluminum socket, the aluminum socket is embedded and fixed in the hole of the holder.

<Problems to be Solved by the Invention> However, an electrode is manufactured using the above technique. This includes machining the holes for the holder and manufacturing the aluminum socket.

It takes a lot of time to embed an aluminum socket fitted with hafnium into a holder, which increases costs.

An object of the present invention is to provide a non-consumable electrode for oxidized plasma processing that maintains the advantages of an electrode in which a metal spacer is interposed at the contact surface between a holder and a working insert, and which can reduce costs. It is.

<Means for Solving the Problems> The non-consumable electrode for oxygen plasma processing of the present invention, which has solved the above problems, includes a holder made of copper or copper alloy and having a through hole formed therein for circulating a cooling fluid; a working insert made of hafnium or a hafnium alloy that is fitted through the holder from the front 41 side to the through hole;
A metal spacer made of aluminum or an aluminum alloy is disposed on the contact surface between the holder and the working insert within a range of 31 mm or more from the front end surface of the holder and within 80% of the total length of the working insert. It is composed of

According to the above-mentioned means, a through hole for circulating a cooling fluid is formed inside the holder made of hafnium or a copper alloy, and a hole made of hafnium or a hafnium alloy is formed by penetrating from the front end face of the holder to the through hole. Since the working insert is fitted, there is no need to make the hole formed in the holder a blind hole with a predetermined depth in order to fit the working insert.
It can be formed as a through hole from the front end surface of the holder to the through hole. This makes it easy to drill holes in the holder.

In addition, the contact surface between the holder and the working insert should be at least 3I from the front end surface of the holder, and 80mm of the total length of the working insert.
% or less, a commercially available aluminum pipe can be used as the metal spacer. Therefore, there is no need to manufacture an aluminum socket as in the past, and the number of manufacturing steps can therefore be reduced.

To fit hafnium as a working insert into the aluminum pipe as the metal spacer, grasp the end of a hafnium wire cut to a predetermined size, insert it into the aluminum pipe, and press from the outer periphery while rotating both. This allows the hafnium wire to be coated with aluminum. The hafnium wire coated with aluminum as described above is fitted into the through hole formed in the holder, and the holder is rotated and pressed from the outer periphery to form a contact surface between the holder and the hafnium wire. Aluminum spacers can be placed.

Furthermore, when oxygen plasma processing is performed using an electrode constructed by fitting a working insert made of hafnium or a hafnium alloy into the holder and placing an aluminum spacer as a metal spacer on the contact surface between the two, the electrode may break. The depth of hafnium consumed when
The range is 2.5 to 2.5. Therefore, it is necessary that the minimum length of the aluminum spacer is 31 or more. Furthermore, in the step of covering the hafnium wire with the aluminum spacer, a length of about 20% of the total length is required to grip the hafnium wire. Therefore, the maximum length of the 0;1 aluminum spacer needs to be within 80% of the hafnium wire.

<Example> Hereinafter, an example of a non-consumable electrode for oxygen plasma processing to which the above means is applied will be described with reference to the drawings.

FIG. 1 is a cross-sectional explanatory diagram of the electrode according to the present invention, FIG. FIG. 2 is a cross-sectional explanatory diagram of an electrode used for comparison with an electrode of the invention.

In FIGS. 1 and 2, a front end surface 1a is formed at the tip of a holder 1 made of copper or 1I-1 alloy, and a through hole is formed inside for flowing a cooling fluid such as water. 1b is formed. In addition, on the surface of the through hole 1b side facing the front end surface 1a, there is a protrusion 1 that is a part of the center of the holder l.
c is formed.

A through hole 1d is formed in the center of the holder 1 from the front end surface 1a to the through hole 1b.

A working insert 2 made of hafnium or a hafnium alloy is fitted into the through hole 1d so as to be flush with the front end surface 1a, penetrating from the front end surface 1a of the holder 1 to the through hole 1b.

A metal spacer 3 made of aluminum or an aluminum alloy is arranged on the contact surface between the working insert 2 fitted in the through hole 1d and the holder 1. The metal spacer 3 is disposed at least 3 mm from the front end surface 1a of the holder 1 and within 80% of the total length of the working insert 2.

Next, the case of manufacturing the electrode configured as described above will be described. First, a through hole 1b is formed inside the holder 1, and a protrusion IC is formed. Then, a through hole 1d is formed in the holder 1 from the front end surface 1a side of the holder 1.

In addition, the working insert 2 and the metal spacer 3 are each cut to a predetermined length, the working insert 2 is fitted into the metal spacer 3, and the ends of the working insert 2 are gripped and both are rotated, so that the outer periphery of the metal spacer 3 is cut. 1. Then, insert the working insert 2 covered with the metal spacer 3 into the through hole ld formed in the holder 1,
The working insert 2 and the metal spacer 3 are firmly held in the holder 1 by pressing the holder 1 from the outer periphery. Thereafter, the outer periphery of the holder I, including the front end surface 1a, is turned into a predetermined shape to form an electrode. At this time, the working insert 2.゛The metal spacer 3 and the front end surface 1a of the holder 1 can be configured to be on the same plane.

In the manner described above, it is possible to fit the working insert 2 into the holder l and to arrange the metal spacer 3 on the contact surface between the holder 1 and the working insert 2. Therefore,
Unlike the prior art, it is not necessary to form a metal spacer into a cup-shaped sogent, making it possible to reduce manufacturing costs.

The case where, for example, a steel plate is cut using the electrode constructed as described above will be explained with reference to FIG.

In the figure, a holder 1 is detachably attached to an electrode stand 4 by screwing or the like. Further, a cooling pipe 5 for conducting cooling water is provided in the through hole 1b of the holder 1. A nozzle cap 7 is removably attached to the tip of the plasma torch body 6.
The inside of the is cooled by cooling water. A nozzle 8 is formed by the nozzle camp 7.

Further, oxygen gas is supplied to the space formed by the holder 1 and the nozzle cap 7 from the M element through hole 9. When a plasma current is applied using the working insert 2 as a cathode and the steel plate A as an anode, a plasma arc 10 and oxygen gas are injected from the nozzle 8 toward the steel plate A.
The surface of the steel + FAA is melted and the steel + FAA is thermochemically cut. By moving the plasma torch and the steel plate 8 relative to each other in this state, the cutting of the steel 4yi, A progresses.

Next, the operating insert 2 during generation of a plasma arc will be explained.

The surface of the working insert 2 becomes hot due to the emission of thermoelectrons. In the case of an oxygen plasma torch, an oxidation reaction also occurs in the working insert 2, and the synergistic effect of the emission of thermionic electrons and the oxidation reaction brings the surface of the working insert 2 into a higher temperature state. At this time, the surface of the working insert 2 is melted and a part of it is vaporized, thereby being consumed. Therefore, in this embodiment, by fitting the working insert 2 through the holder 1 from the front end surface 1a to the through hole 1b, the working insert 2 can be directly cooled by the cooling water supplied to the through hole 1b. The cooling effect is enhanced.

Due to the oxidation reaction, oxidation products adhere to the surface of the working insert 2. Here, the relationship between the material of the working insert 2 and the oxidation products attached to the surface will be explained. In particular, by comparing the case where hafnium is used as the material of the working insert 2 and the case where zirconium is used as the material, it is found that in the present invention, hafnium is used for the working insert 2 and the contact between the working insert 2 and the holder 1 is The reason why the metal spacer 3 made of aluminum or aluminum alloy is used on the surface will be explained.

The oxidation product has a single crystal structure at room temperature, and changes from a tetragonal structure to a cubic structure as the temperature increases. That is, when the oxidation product, which was in a molten state when the plasma arc was generated, solidifies as the hot spot decreases and changes from a cubic crystal structure to a single crystal structure, about 7.4% of the zirconium oxide Volume increase has been measured.1. In addition, an increase in volume of about 3.4% was measured for hafnium oxide.

First, to explain the case where the metal spacer 3 is not arranged at the contact surface between the working insert 2 and the holder 1, due to the increase in the volume of the oxidation product, the boundary layer between the material and the oxidation product and the contact surface between the holder Stress is generated. That is, since the volume increase of the oxidation product is regulated by the holder, compressive stress is generated in the oxidation product and the oxidation product adheres to the holder. It is thought that the degree of occurrence of this stress is greater when zirconium is used as the material.

Then, when the next plasma arc is generated, the volume of the oxidized product decreases as the temperature rises, and the volume of the material increases due to thermal expansion. At this time, shear stress is generated at the boundary between the material and the oxidation product, causing the oxidation product to peel off from the back surface of the material.

It is considered that the shear stress generated at the interface between zirconium oxide and zirconium, which increases in volume, is greater than that generated at the boundary between hafnium oxide and hafnium. Further, tensile stress acts on the holder l due to a volume reduction of the oxidation product as the temperature rises. In this way, as the plasma arc is repeatedly generated and stopped, the material wears out faster, and when the plate reaches a certain limit, the oxidation products peel off from the material surface all at once, and at the same time, part of the holder At the same time as it peels off, the copper that is the material of the holder evaporates, leading to electrode breakdown.

Therefore, when comparing the case where zirconium is used as the material of the working insert 2 and the case where hafnium is used,
When hafnium is used, the amount of material wasted less with respect to the frequency of plasma arc generation, and therefore the life can be extended.

Next, a case will be described in which a metal spacer 3 is arranged on the contact surface between the working insert 2 and the holder l.

Due to the volume increase that occurs when the oxidation product changes from a high temperature state to a room temperature state, stress is generated at the contact surface between the holder 1 and the boundary layer between the material of the working insert 2 and the oxidation product. By forming a layer on the surface that can absorb the increase in volume of oxidation products, it is possible to suppress the generation of stress.

The layer needs to be formed in a range where the wear of the working insert 2 progresses and the electrode breaks down or exceeds this range, and even if a volume change occurs due to a change in the temperature of the working insert 2, The insert 2 is the holder 1
It is necessary to be able to hold the working insert 2 in such a way that it does not fall off, and it is necessary to be a good electrical and thermal conductor. Materials that meet these conditions include metals such as gold, silver, and aluminum, but the cost of the materials is limited.

Aluminum or an aluminum alloy is most suitable from the viewpoint of workability, availability, etc.

As explained above, in the electrode of the present invention, hafnium alloy is used as the working insert 2, and a metal spacer 3 made of aluminum or aluminum alloy is provided on the contact surface between the working insert 2 and the holder 1. are placed.

Next, an example of a comparative experiment will be explained between the electrode according to the present invention configured as described above and an electrode in which no metal spacer 3 is arranged on the contact surface between the holder 1 and the Iyakawa insert 2 made of hafnium as shown in FIG. do.

[Experimental example 1] Diameter of hafnium insert 1.5-m Length of hafnium insert 81M Diameter of copper holder Jg of 11 Tsuru aluminum spacer Length of 0.1 weight aluminum spacer 5sm Plasma arc current
250A oxygen gas flow rate 4ON j/s+in Arc time 1 sin Arc stop time 25sec Under the above conditions, the number of arc occurrences until the electrode is destroyed is 70 to 12
It was 0 times. Under the same conditions), the electrode shown in FIG. 4 was broken after 50 cycles (hereinafter, the number of breaks using the electrode shown in FIG. 4 is referred to as r standard durability number 1).

[Experimental Example 2] The working insert 2 and the metal spacer 3 were set to the following conditions,
When the other conditions were the same as in Experimental Example 1, the number of times it took to break was 120 to 220 times.

At this time, the standard durability was 90 times.

Diameter of hafnium insert 2 mm Length of hafnium insert 8 Sodium - Thickness of aluminum spacer Q, 2+U Length of aluminum spacer 6l - (Experimental example 3) Working insert 2 and metal spacer 3 were set to the following conditions,
When the other conditions were the same as in Experimental Example 1, the number of times it took to break was 120 to 180 times.

At this time, the standard durability was 90 times.

Diameter of hafnium insert 2mu Length of hafnium insert 81 ■Thickness of aluminum spacer 0.2 - Length of aluminum spacer 3 dragons [Experimental example 4] Working insert 2 and metal spacer 3 were set to the following conditions,
When other conditions were the same as in Experimental Example 1, the number of times it took to break was 130 to 170 times.

At this time, the standard durability was 90 times.

Diameter of hafnium insert 2 Length of hafnium insert 8 Thickness of I aluminum spacer Length of QJam aluminum spacer 4 - [Experimental example 5] Working insert 2 and metal spacer 3 were set to the following conditions,
When the other conditions were the same as in Experimental Example 1, the number of times it took to break was 120 to 190 times.

At this time, the standard durability was 90 times.

Diameter of hafnium insert 2Length of hafnium insert 8msThickness of aluminum spacer 0.21Length of aluminum spacer 51As mentioned above, the contact surface between the working insert 2 formed of hafnium and the holder 1 is formed of aluminum. When the metal spacers 3 were arranged in a range of 3 to 6 times, the life of the electrodes was approximately the same, and was improved by about 30 to 140% compared to the standard durability.

<Effects of the Invention> As explained in detail above, according to the non-consumable electrode for oxygen plasma processing of the present invention, through holes are formed for circulating cooling fluid inside the holder made of copper or copper alloy. At the same time, since the working insert made of hafnium or hafnium alloy is fitted through the holder from the front end face to the through hole, the hole formed in the holder for fitting the working insert is a blind hole having a predetermined depth. It is not necessary to do so, and it can be formed as a through hole from the front end surface of the holder to the through hole. This makes it easy to drill holes in the holder.

In addition, the contact surface between the holder and the working insert should be at least 3-1 from the front end surface of the holder and 8 of the total length of the working insert.
Since the metal spacer made of aluminum or aluminum alloy is interposed within the range of 0% or less, a commercially available aluminum pipe can be used as the metal spacer. Therefore, there is no need to manufacture aluminum spacers as in the past, and the number of manufacturing steps can therefore be reduced.

Therefore, production costs can be reduced.

Moreover, it has the feature that the life span can be extended by 30 to 140% compared to an electrode in which no metal spacer is disposed on the contact surface between the working insert and the holder.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory diagram of the electrode according to the present invention, Fig. 2 is a perspective explanatory diagram of main parts, Fig. 3 is a schematic explanatory diagram of oxygen plasma processing using the electrode of the present invention, and Fig. 4 is an explanatory diagram of the present invention. FIG. 1 is a holder, 1a is a front end surface, 1b is a through hole, IC is a protrusion, lft pole is a through hole, 2 is a working insert, and 3 is a gold spacer. Figure 1 Patent applicant: Koike Oxygen Industry Co., Ltd.

Claims (1)

[Claims] A holder made of copper or a copper alloy with a through hole formed therein for circulating a cooling fluid, and a working insert made of hafnium or a hafnium alloy fitted through the holder from the front end surface to the through hole. and a metal spacer made of aluminum or aluminum alloy is disposed on the contact surface between the holder and the working insert within a range of 3 mm or more from the front end surface of the holder and within 80% of the total length of the working insert. A non-consumable electrode for oxygen plasma processing.