RU2606674C2 - Ejection nozzle for spraying melts - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: ejection nozzle for spraying melts has housing with annular slot for hot compressed gas supply, union with protective cover and central channel to feed melt. Outlet edge of protective cover has semi-circular cutouts with radius r=(0.5÷1.0) mm, located at equal distances from each other. Minimum number of cutouts n_min= 2, and maximum n_max=πR/2r, where R is radius of outlet edge of protective cover, mm. Higher fine fraction in the sprayer is ensured.

EFFECT: invention can be used for production of metal powders.

1 cl, 2 dwg, 3 tbl, 1 ex

Description

The invention relates to the field of powder metallurgy, in particular to devices for producing powders by spraying metal melts by a gas stream.

Known nozzle for spraying molten metals, including a housing with an annular slot for supplying compressed gas, a nipple with a central channel for supplying melt, equipped with a protective cover, while the output of the channel for feeding melt is made in the form of a cone with an angle at the apex equal to (10 60) degrees [1].

Ejection nozzles are known in which, to increase the dispersion of the obtained powder (spray), channels are made for additional input of compressed gas into the melt spraying zone [2] or into the metal wire [3].

The closest in technical essence is the nozzle for receiving powders of molten metals [4], containing a housing with an annular slot for supplying hot compressed gas, a nipple for supplying melt and a protective cover. The nipple and the protective cover are equipped with interconnecting divider-destabilizers in the form of radial or tangential slit-like grooves, the rear walls of which are made in the form of bevels with an angle of inclination (30 ÷ 45) degrees to the nozzle axis.

The disadvantages of this nozzle are the increased consumption of atomizing gas through slit-like grooves, as well as low productivity and possible blockage of the metal supply channel, associated with a decrease in the ejection effect when gas is injected into the melt through the grooves in the nipple.

The technical result of the invention is to increase the mass fraction of the finely dispersed fraction in the spray formed during the spraying of the molten metal, while maintaining the flow rate of the atomizing gas and nozzle performance.

The technical result is achieved by the fact that an ejection nozzle is developed comprising a housing with an annular slot for supplying hot compressed gas, a nipple with an associated protective cover and a central channel for supplying the melt. Cutouts of a semicircular shape with a radius in the range r = (0.5 ÷ 1.0) mm, located at equal distances from each other, are made on the output edge of the protective cover. The minimum number of cuts n _min = -2, and the maximum is determined by the ratio n _max = πR / 2r, where R is the radius of the output edge of the protective cover.

The resulting positive effect of the invention is associated with the following factors.

1. When gas flows from the nozzle, the cutouts in the protective cover create disturbances in the annular gas stream in the immediate vicinity of the dispersion zone (the region of gas – melt interaction), which increases the dispersion of the obtained powder without loss of productivity and increase gas consumption.

2. The value of the cutout radius r, varying from 0.5 to 1.0 mm, is determined by the fact that the cutouts are located on the sharp output edge of the cone of the protective cover. For cutouts with a radius of less than 0.5 mm, the disturbing effect on the gas flow will be negligible. The increase in the radius of the cuts more than 1.0 mm does not give a positive effect, since the cross-sectional area for the gas passage increases rapidly with distance from the output edge of the protective cover (Fig. 1). In this case, the gas velocity in the annular channel between the inner conical surface of the cover 4 and the inner conical surface of the protective cover 3 decreases and, therefore, the disturbing effect of the cuts on the gas flow is reduced.

3. The uniform arrangement of cuts around the circumference of the output edge of the protective cover (at the same distance from each other) ensures the symmetry of the perturbations of the gas stream during its interaction with the melt film. This allows to increase the degree of dispersion of the melt.

4. The minimum number of cut-outs n _min = 2 is determined by the condition of ensuring the symmetry of the perturbations of the gas flow (for n = 1, the symmetry is broken and the perturbations of the gas flow affect only a small part of the melt film).

5. The maximum number of cuts is limited to n _max = πR / 2r, which corresponds to the condition that the distance between the cuts is equal to their diameter. With a larger number of cutouts, the perturbations introduced by them into the gas jet close together, which leads to a decrease in the ejection action of the jet and a decrease in the nozzle productivity.

An example implementation of the invention

In FIG. 1 shows an example of an ejection nozzle for atomizing an aluminum melt. The nozzle consists of a housing 1, a nipple for supplying a molten aluminum 2, a protective steel cover 3, a cap 4, nozzles for supplying a melt 5 and hot compressed gas 6 (nitrogen). A cavity 7 for compressed hot gas is made in the housing 1, the output of which is an annular nozzle formed by the outlet of the cover 4 and the nose of the nipple 2. On the outlet edge of the steel protective cover 3, 2 (Fig. 2a) or 4 (Fig. 2b) are symmetrical located cutout 8 of a semicircular shape with a radius of r = 0.6 mm. These cutouts do not change the width of the gap of the annular nozzle for compressed gas, which is determined by the distance between the cover 4 and the nose of the nipple 2 protruding from the protective steel cover 3.

The ejection nozzle operates as follows. Through the pipe 6 into the cavity 7 of the nozzle body 1 serves hot compressed gas (nitrogen with a controlled oxygen content) under excess pressure up to several tens of atmospheres. When gas flows from the annular nozzle, a rarefaction is created in the region of the outlet cone of the nipple 2, which, due to the ejection effect, ensures the flow of molten metal through the nozzle 5 into the central channel of the nipple 2. A thin melt film is formed under the action of the radial pressure drop in the output conical part of the nipple channel. to the outlet section of the nozzle. When a metal melt film interacts with an annular supersonic gas flow, the film is destroyed with the formation of droplets of spray. The cutouts 8 in the steel protective cover 3 create additional perturbations in the gas stream, which increase the dispersion efficiency of the melt.

The effectiveness of the claimed ejection nozzle is confirmed by the results of comparative tests of the basic version of the nozzle (without cutouts in the protective cover) and the nozzle with two cutouts of radius r = 0.6 mm. The tests were carried out on the industrial site of the company LLC “SUAL-PM” (Shelekhov, Irkutsk region).

The operational efficiency of the basic and declared versions of the ejection nozzle was estimated by the results of dispersed analysis of spray samples obtained by spraying aluminum melt in the ASD mode under the following identical conditions: aluminum melt temperature of 980 ° C, nitrogen temperature of 600 ° C, nitrogen flow rate of 660 m ³ / h, nitrogen pressure in front of the nozzle 6.0 MPa.

The basic and claimed ejection nozzles had the same assembly parameters: the diameter of the hole in the narrowing part in the nipple is 3.6 mm; annular gap between the nipple and the cover 0.65 mm; the size of the protruding part of the nipple nose over the cap is 1.2 mm.

Evaluation of the dispersed composition of the samples was carried out on a device "Analysette 22" company FRITSCH (Germany). The results of the dispersed analysis of powders obtained by atomizing aluminum with the base and claimed nozzles are given in the Test Data Sheets (tables 1, 2).

Tables 1, 2 show the particle diameters of aluminum, for which the mass fraction of particles of smaller diameter is 10% (d10), 50% (d50) and 90% (d90) of the mass of the processed metal, the mass fraction of particles with a diameter of less than 10 μm ( 0 ÷ 10) and the mean specific surface area of particles (S _beats ). The indicated parameters are given for the precipitation chamber (pulverizate), coarse (No. 1) and fine (No. 2) cyclones, and a bag filter (R / F). The total yield of the powder fraction with a particle diameter of less than 10 μm (as a percentage of the mass of the processed metal) is also given.

Table 3 compares the main characteristics that determine the efficiency of the spray:

- d50 is the median diameter, for which half the mass of the produced powder are particles with a diameter of d≤d50;

- (0 ÷ 10) microns - the yield of the powder fraction with a particle diameter of less than 10 microns as a percentage of the mass of the processed metal.

Analysis of the dispersion characteristics of aluminum powders shown in table 3 showed that the claimed ejection nozzle provides a decrease in the median particle diameter of the spray of 31.4% (from 24.2 to 16.6 μm) and an increase in the yield of the fine fraction of aluminum powder (with a particle diameter of less than 10 μm) by 8.5% for pulverizate and 5.5% for a total powder yield.

Thus, the proposed ejection nozzle for spraying melts provides an increase in the mass fraction of the finely dispersed fraction in the produced aluminum powder by introducing additional perturbations into the stream of atomizing gas by cutouts on the outlet edge of the nipple protective cover.

LITERATURE

1. A.S. USSR 550235, IPC B22D 23/08. Nozzle for molten metals / M.M. Chernyshov, B.P. Nazarov, V.G. Gopienko, I.D. Busalaev, V.K. Shcherbakov, I.V. Volkov, V.I. Grinko. - declared. 07/25/1975; publ. 03/15/1977.

2. Pat. RF 2296648, IPC B22F 9/08. Nozzle for spraying molten metals / A.V. Kuksa, A.V. Molkov, A.V. Gubanov. - declared. 10/19/2005; publ. 04/10/2007.

3. Pat. RF 2283728, IPC B22F 9/08. Nozzle for spraying molten metals / A.V. Kuksa, A.V. Molkov, M.P. Kononov, A.V. Gubanov, S.V. Linkov. - declared. 03/02/2005; publ. 09/20/2006.

4. Pat. RF 2321475, IPC B22F 9/08. Nozzle for spraying molten metals / A.V. Kuksa, A.V. Molkov, A.V. Gubanov, S.V. Linkov. - declared 02.05.2006; publ. 04/10/2008.

Claims (1)

An ejection nozzle for producing powder by melt spraying, comprising a housing with an annular slot for supplying hot compressed gas, a nipple with an associated protective cover and a central channel for supplying melt, characterized in that semicircular cutouts of radius r = (0, 5 ÷ 1.0) mm, located at equal distances from each other, the minimum number of which is n _min = 2, and the maximum is determined by the ratio n _max = πR / 2r, where R is the radius of the output edge of the protective cover, mm

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