SU900989A1 - Method of producing metallic powders - Google Patents

Description

one

The invention relates to powder metallurgy, in particular, to a method for producing powders from electrically conductive melts.

A known method for producing metal powders by spraying the melts with compressed gas or water 1.

A disadvantage of the known method is the possibility of oxidation of the powders.

- The closest to the technical essence and the achieved positive effect to the proposed is a method of obtaining metal powders with a spherical shape of particles by spraying a melt jet by electrodynamic forces arising from the flow of current through it, prn which the sputtering of the melt jet occurs in the arc gap the front of the jet and the fixed electrode 2.

The disadvantages of this method are the low yield of fine fractions of the powder, the change in the composition of the alloy during the spraying process, and the intense destruction of the electrodes.

The purpose of the invention is to increase the dispersion of powders, stabilize

composition and increase the service life of the electrodes.

This goal is achieved by the fact that in the method involving the spraying of a melt jet by passing an electric current through it, the electric current is supplied to the melt jet during the period of electric melt closure,

10 and during periods of melt jet disintegration into droplets, the supply of electric current is stopped.

The drawing shows the scheme of the proposed method.

15

The method is carried out as follows.

A jet of 1 metal, pouring out of container 2 with liquid metal 3 in contact with electrode 4, pa

20 gives to the second (lower) electrode 5 and closes an electrical circuit including a relatively powerful current source 6 and low-resistance wires 7 and 8. As it passes through the jet

25 electric currents in it arise electrodynamic forces, which, together with Joule heat, break it into droplets. The pause lasts until the moment that is intact.

Claims (2)

30 part of the strings, pada, again no lock no chain. Consistently with the jet include a controlled diode (thyristor 9 with control unit 10; power, thermal relay, specially selected resistance and zener diode. At the moment when the falling jet closes on the lower electrode, the thyristor is unlocked and the electric current through the jet increases very quickly circuit, and the Joule heat is intensely released in the jet. The boiling up is accompanied by vigorous vaporization and explosive destruction of the jet into tiny droplets. The presence of ionized particles and a small distance between the droplets leads to T to the occurrence of a pulsed discharge having a temperature of more than 5000 K. During this period, the resistance of the interelectrode gap increases, the current drops and conditions are created for ignition of the electric arc. from the jet, thus eliminating the ignition of the arc in the interelectrode gap. The control unit opens the thyristor at the moment of closing to the lower electrode of the new metal position. Then the whole cycle repeats, pp and me. A tin stream with a length of 5 mm, a diameter of 1.5 mm and an electric current passing through it with a density of about 500 A / mm and a voltage of 150 V was crushed into particles following 0 of its particle size distribution (the results were averaged over 5 experiments). are shown in the table. As follows from the example, the yield of finer fractions of the powder (-0.1 mm) in the proposed method increases by more than 3 times as compared with the known. In addition, due to the significant lowering of the thermal and electro-erosion effect of the electric arcs, the life of the graphite electrodes in the proposed method is increased 2.5 times compared with the known technology of their use. For electrodes prepared from zirconium dibide, the working life increases by more than 5 raE. The proposed method is expediently used to obtain powders from chemically active metals and from alloys that contain a component with high vapor pressure, for example, rare earth metal alloys and cobalt. So, for example, by spraying, according to a known method, the SmCOj alloy consisting of 66.2 and 33.0 wt.%, Respectively, of Co and Sm, powders are obtained that include 69.7% of Co and 29.5% of Sm, which indicates that p decreases the content of samarium in the powder, and its coercive force is 0.35 kOe. Crushing according to the proposed method makes it possible to stabilize the composition of the powder (66.1% Co and 32.8% Sm) and to increase its coercive force to 0.5 kOe. The method of obtaining metal powders, including spraying a melt jet by passing an electric current through it, characterized in that, in order to increase the dispersion of powders, stabilize the composition and increase the service life of the electrodes, an electric current is supplied to the melt jet electrical circuit, and during periods of disintegration of the jet of the melt into droplets the flow of electric current stops Sources of information taken into account in the examination 1. G. Meerson. Poroshkova metal lurgi. Production of meterelic powders. Lecture course. MISiS, 1974, p. 62-79. 2. Authors certificate of the USSR 305915, cl. In 22 F 9/00, 1970.