JPH07316612A - Consummable electrode - Google Patents

Abstract

PURPOSE:To improve yield by improving the uniformity of grain diameter and reducing the unnecessary secondary grain, in the production of powder by a rotary electrode method. CONSTITUTION:In a consummable electrode 1 used in the powder production by the rotary electrode method, plural pieces of angular projections having crest parts and trough parts in the working direction 3 of centrifugal force are arranged at the peripheral part of the electrode 1, and desirably, the interval between the projections is made to 1-4mm and the depth of the trough is made to >=0.2mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shape of a consumable electrode rod used in a rotating electrode method which is one of the methods for producing metal powder.

[0002]

2. Description of the Related Art In the rotating electrode method, the particle size of the obtained powder depends on the rotating speed of the electrode, and more specifically, for a homogeneous electrode rod, it is obtained by the centrifugal force that relates the rotating angular velocity and the radius of the electrode. The powder particle size is determined. Therefore, industrially, a powder having a predetermined particle size is obtained by controlling the rotation speed determined according to the material type and the electrode diameter. Since the speed is high speed of several thousand times or more per minute, the consumable electrode has a round bar shape, a cylindrical shape, or a disk shape.
A rotating body having a stable shape is used.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The metal powder obtained by the rotating electrode method has a perfect spherical shape and is extremely excellent in particle size uniformity as compared with other powder manufacturing methods. However, on the other hand, there are some essential problems. One of the reasons is that the yield of powder obtained with respect to the consumable electrode rod is low, which is a factor of high cost. Needless to say, the powder yield depends on most of the manufacturing expenses, so even if the yield can be raised even a small amount, it will greatly contribute to the cost reduction. Further, the rotating electrode method is significant because it can be used for an active and expensive material that cannot be produced by other methods.

From this point of view, although the powder produced by the rotating electrode method has good particle size uniformity, some of the powder particles are accompanied by particle size loss, which is impossible in the prior art. . That is, as an essential problem of the rotating electrode method, the obtained powder particle size is composed of two particle size distributions called primary particles and secondary particles, and the primary particle is controlled by the rotating speed of the electrode. Secondary particles are an unplanned by-product. The present invention provides a consumable electrode rod that can reduce the production of secondary particles.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a consumable electrode rod used when powder is produced by the rotating electrode method, in the form of angular protrusions having peaks and valleys in the peripheral direction of the electrode rod in the direction of centrifugal force. The consumable electrode rod is characterized in that a plurality of electrodes are provided. More preferably, the spacing between the projections is set to 1 to 4 mm, and the angular projections having a valley depth of 0.2 mm or more are provided to reduce the generation of secondary particles and to reduce the size of the projected particles. The product yield can be improved.

[0006]

In the rotating electrode method, the consumable electrode is rotated in the axial direction at a high speed, and one end face of the consumable electrode is melted by using an arc or the like, and the generated melt becomes a liquid film by the action of centrifugal force. The liquid film flows and heads to the peripheral portion of the electrode, and then the liquid film once restrained here is divided into droplets, which are separated and fly to the outer periphery of the electrode. During flight, it becomes spherical due to surface tension, solidifies, and is collected as powder.

The position where the secondary particles are formed is shown in FIG.
As shown in (b), the liquid film separation is torn into droplets, and at the time of separation, the particles are pulled by the primary particles 2 of the powder, which is the main droplet, and the portion that is left behind is the electrode side or the main droplet. The secondary particles 4 are independent droplets that cannot return to the side and are powdered.
Is. A phenomenon similar to this is observed when a highly viscous liquid is torn off, or when the restraining force is relatively large with respect to the detaching force, such as a water drop that naturally falls from a flat ceiling.

In the rotating electrode method, since the circumference of the electrode solid is orthogonal to the direction of centrifugal force, a large binding force also causes the generation of secondary particles. In view of this, in the present invention, as shown in FIG. 1 (a), an angular projection having peaks and troughs in the direction of centrifugal force is provided on the peripheral edge of the electrode from which the droplet separates, thereby weakening the constraint force of the droplet. , Made it easier to leave. As a concrete means thereof, a plurality of protrusions are provided on the side surface of the electrode rod. How to make the protrusions is
It suffices that the melting cross section always has a protrusion. However,
It is essential to have peaks and troughs in the direction of centrifugal force, and it is not possible to expect weakening of the constraint force of the liquid droplets especially in those without troughs, for example, those processed into polygonal columns. Further, since the liquid droplets are detached from almost the entire periphery of the melting surface of the electrode and are scattered radially, for the purpose of the present invention, the angular projection is not located at one location but over the entire circumference. A plurality is provided.

In the shape of the protrusions, it is preferable that the distance between the protrusions is 1 to 4 mm and the depth of the valley is 0.2 mm or more. If the distance between the protrusions is less than 1 mm, the droplets may straddle the protrusions and the adjacent protrusions at low speed rotation that can be achieved by the normal rotating electrode method, and the droplets may be separated by the protrusions. It becomes insufficient and the effect of reducing secondary particles is weakened. Further, if this distance exceeds 4 mm, the droplets may sometimes separate from between the protrusions, and this tendency is particularly remarkable at high speed rotation. Even in such a case, the amount of the secondary particles tends to increase in the case where the present invention is not applied. It should be noted that such a phenomenon can be easily identified by observing the consumable electrode after stopping the rotation after stopping the melting heat source.

Further, the reason for setting the depth of the valley to be 0.2 mm or more is that, when the depth is less than this, the desorption force of the melt is not concentrated on the protrusions and the droplet restraining force is the same as when there is substantially no protrusion, This is because the effect of the invention cannot be expected. The upper limit of the depth is not specified as it does not hinder the separation of the droplet of the present invention. However, in practice,
It is impossible to take an extreme value due to the strength of the material that can withstand the rotation of the electrode rod, and the upper limit is extremely common sense.

[0011]

[Examples / Comparative Examples] A pure titanium rod was used as a consumable electrode, and a projection, of various sizes shown below, was formed on all sides in the longitudinal direction by using cutting, knurling, and grinding methods for an original size of 50 mm. Was formed. Therefore, in the sliced cross section, ridges and valleys of the same size are present at any position. Melting by the rotating electrode method was carried out by helium plasma in a helium gas atmosphere. The obtained titanium spherical powder was classified by an ASTM standard sieve, and its particle size distribution was examined. In addition, in order to know the characteristics of the particle size distribution chart, the effect was judged by comparing the consumable electrode with a conventional round bar electrode not processed according to the present invention. In each melting, the plasma transfer current was 200 A and the voltage was 70 V.

Example (1) A chevron-shaped working electrode bar having a projection interval of 4 mm and a depth of 3 mm by cutting was used at a rotation speed of 4,500 rpm. The particle size distribution of the powder obtained at this time is shown by the dotted line in FIG. 2 (a). Here, the solid line is based on the round bar electrode used for comparison. As is clear from this figure, the amount of secondary particles decreased considerably, and the unprocessed one was 12.3%, while the processed one was 12.3%.
It was 1.9%.

Comparative Example (1) A powder was prepared in the same manner as in Example (1) using an electrode having a protrusion interval of 4 mm and a depth of 0 mm, that is, a polygonal cross section by cutting, and as a result, the particle size distribution of the powder was obtained. Is shown by the dotted line in FIG. At the same time, the solid line shows the one with a round bar electrode.
The amount of secondary particles was 12.3% when not processed, but 8.3% when processed, and the effect of processing the electrode is small.

Example (2) Two kinds of chevron-shaped consumable electrodes having a protrusion interval of 1 mm, a depth of 0.5 mm and a protrusion interval of 2.5 mm, and a depth of 1 mm were knurled to produce powder at an electrode rotation speed of 6,000 rpm. went. A particle size distribution chart of the obtained powder is shown in FIG. 3 by a dotted line, and FIG.
Have a projection interval of 1 mm and a depth of 0.5 mm, and Fig. 3 (b) shows those with 2.5 mm and 1 mm. Also here, the round bar electrode is shown by a solid line for comparison.
In each case, the one with the protrusions was 2.0% in (a) and 2.2% in (b) for the electrode processed, compared to 9.2% of the amount of secondary particles of the powder by the round bar electrode. Occurrence was suppressed.

Example (3) The protrusion interval was 1 mm, the depth was 0.2 mm, and the protrusion interval was 0 by grinding.
Two conical consumable electrode rods having a diameter of 7 mm and a depth of 0.2 mm were powder-produced at an electrode rotation speed of 8,000 rpm.
The particle size distribution of the obtained powder is shown in Fig. 4 (a) and Fig. 4 (b), respectively.
Is indicated by a dotted line. In addition, for comparison, a solid bar shows a case where a round bar electrode is used under the same conditions. As shown in FIG. 4, in the case of the round bar which is not processed, the amount of secondary particles of the powder is 9.0%, whereas in the case where the electrode is processed, it is 1.2% in (a),
In (b), the secondary particles decreased in 7.6% in the case of the present invention, and the degree of decrease was small in the case of the interval of 0.7 mm.

[0016]

The secondary particles, which are unavoidably generated in the rotating electrode method, are by-products although the amount thereof is small, so that they are accumulated in industrial production as the production progresses. On the contrary, paying attention to the fact that the secondary particles are fine particles, even if an attempt is made to produce them, the quantity is too small to be an industrial product. Therefore, in the present invention, the generation of secondary particles was sought to be reduced as much as possible, and the effect brought about was significant.

[Brief description of drawings]

FIG. 1 is a schematic diagram of generation of powder particles as seen from the melting surface of an electrode, (a) is an example of a consumable electrode of the present invention, and (b) is a case of a round bar electrode shown for comparison. Show.

FIG. 2 shows the particle size distributions of the powders obtained in Example (1) and Comparative Example (1), the solid line shows a conventional method, and the dotted line shows an electrode whose side surface is square-shaped.

FIG. 3 shows the particle size distribution of the powder obtained in Example (2), the solid line shows that by the conventional method, and the dotted line shows that by the electrode whose side surface is angularly processed.

FIG. 4 shows the particle size distribution of the powder obtained in Example (3), the solid line shows the one obtained by the conventional method, and the dotted line shows the one obtained by the electrode whose side surface is square-shaped.

[Explanation of symbols]

 1 Consumable electrode 2 Primary particle of powder 3 Rotation direction of electrode 4 Secondary particle

Claims (2)

[Claims] 1. A consumable electrode rod used when powder is produced by a rotating electrode method, wherein a plurality of angular protrusions having peaks and valleys are provided on a peripheral portion of the electrode rod in a direction in which centrifugal force acts. And consumable electrode rod. 2. The consumable electrode rod according to claim 1, wherein the interval between the protrusions is 1 to 4 mm, and the depth of the valley is 0.2 mm or more.