Atomization units for atomizing metal melts, especially for powder metallurgy purposes

Abstract

The invention relates to an atomization unit (1) for atomizing a metal melt, in particular for powder metallurgical purposes, which comprises a melting crucible (2) with a bottom outlet (4), a melt nozzle (16) arranged below the bottom outlet (4) and a gas nozzle (9) arranged preferably concentrically with respect to the melt nozzle (16), the melt nozzle (16) being made in multiple parts and having a circumferential wall and a nozzle core (17), the nozzle core (17) passing through a conical seat in the circumferential wall.

Description

[Technical Field]

[0001] The present invention relates to an atomization unit for atomizing a metal melt, in particular for powder metallurgy purposes, which comprises a melting crucible with a bottom outlet, a melt nozzle arranged below the bottom outlet, and a gas nozzle arranged concentrically with respect to the melt nozzle.

[0002] An atomization unit of the aforementioned type is known, for example, from German Patent No. 10044364. The atomization unit known from this publication includes a melting crucible with a bottom outlet, a support crucible with a wall surrounding the crucible, and a coaxial bottom opening. The atomization unit further includes a melt nozzle for forming a melt jet, a nozzle body corresponding to the melt nozzle and including an annular slit nozzle arranged concentrically with the melt nozzle, and at least one gas channel for supplying atomizing gas to the annular slit nozzle. In the unit described in German Patent No. 10044364, the support crucible and the nozzle body are surrounded by thermal insulation. An induction coil for heating the melt, the melting crucible, the support crucible, and the nozzle body is arranged outside the thermal insulation. A gas channel is guided through the wall of the support crucible to preheat the atomizing gas, thereby preventing the melt from cooling.

[0003] Further prior art is disclosed in German Patent Application Publication No. 3311343, German Patent Application Publication No. 3533964, German Patent Application Publication No. 4011392, German Patent Application Publication No. 19738682, US Patent Application Publication No. 5366204. 、 JP 2019-059989 A , DE 10340606 A1, EP 0451552 A1 and US 4449902 A1. This prior art, in particular that described in DE 100 44 364 C1, has the disadvantage that the heating of the melting crucible and the melt located therein, and the preheating of the atomizing gas, are carried out by a single external induction coil, which heats the supporting crucible and the nozzle body via the insulation that surrounds them from the outside.

[0004] This arrangement is particularly constructionally complex, since the melting crucible is surrounded by a support crucible through which the gas passage for the annular slit nozzle is guided.

[0005] In contrast to this, the present invention aims to provide a spray unit of the type mentioned at the beginning that is more compact and simpler in design, and further aims to provide such a spray unit that requires relatively little insulation effort, yet still reliably prevents the melt from freezing.

[0006] Cooling of the melt below the solidus temperature threatens the process reliability of the powder atomization apparatus in which the atomization unit is normally operated. In the case of powder atomization apparatuses using atomization units of the above-mentioned type, continuous operation is economically viable and therefore worth pursuing. Therefore, the process reliability of such units is an important quality criterion. Furthermore, it is desirable for the atomization or spraying unit to be as simple in construction as possible, which allows for easy and rapid maintenance of the melt nozzle.

[0007] This problem is solved by a spray unit having the features of claim 1.

[0008] Advantageous configurations of the spray unit are set forth in the dependent claims.

[0009] One aspect of the present invention relates to an atomization unit for atomizing a metal melt, particularly for powder metallurgy purposes, comprising a melting crucible with a bottom outlet, a pouring nozzle arranged below the bottom outlet, and a gas nozzle arranged concentrically with the melt nozzle, the melt nozzle being formed in multiple parts and having a circumferential wall and a nozzle core, the nozzle core passing through a conical seat provided in the circumferential wall. The circumferential wall provides thermal insulation for the nozzle core, particularly by contacting and at least partially surrounding the nozzle core over a large portion of its periphery. The circumferential wall also provides mechanical stabilization for the nozzle core. The nozzle core is preferably replaceably inserted into the circumferential wall and held by the circumferential wall.

[0010] Preferably, the jacket is configured as a nozzle brick, which has a conical through-guide as a seat for the nozzle core. The nozzle core may be configured to protrude or project from the jacket in the region of the nozzle tip. In this region, the melt nozzle may extend into the gas nozzle body. The gas nozzle body may be configured in multiple parts and, together with the nozzle core, may form an annular slot nozzle for the atomizing gas.

[0011] In the present invention The peripheral wall is heatable and in this way the nozzle core can be indirectly heated, and the peripheral wall is preferably directly thermally connected to the nozzle core.

[0012] In one preferred variant of the atomization unit according to the invention, it is envisaged that the nozzle core is held between the peripheral wall and the bottom of the melting crucible.

[0013] The nozzle core may have, for example, an annular collar, by means of which it is held concentrically and positively in a conical seat in the jacket, which for this purpose may form, on its side facing the melting crucible, an annular cylindrical step into which the collar of the nozzle core is inserted.

[0014] The wall may have at least one resistive heating element embedded therein, for example. The resistive heating element may be formed as a helical conductor, and the conductor may be completely embedded in the material of the wall, so that the resistive heating element forms a conical surrounding of the hole through the wall. The present invention also contemplates that the melting crucible is heated by a resistive heating element surrounding the periphery of the melting crucible.

[0015] In the present invention The peripheral wall of the melt nozzle has at least one heating element, 、 It is assumed that the contact surface of the peripheral wall is in contact with the There are The heating body can be configured, for example, as a heat pad.

[0016] Preferably, the heating element is embedded in the circumferential wall between the circumferential wall and the gas nozzle body of the gas nozzle. For example, one or more heating elements may be integrated into the bottom of the circumferential wall of the melt nozzle.

[0017] Preferably, the heating element is configured as a ceramic heating element. The ceramic heating element may, for example, consist entirely of silicon nitride or aluminum nitride. In particular, the heating element may be configured as a hot-pressed silicon nitride ring, which is inserted, for example, into a complementary recess on the bottom side of the jacket. Preferably, the heating element is in heat-conducting contact with both the jacket and the gas nozzle body, thereby enabling heating of both the jacket and the gas nozzle body, and thus also of the atomizing gas flowing through the gas nozzle body.

[0018] The present invention envisages that the melt nozzle is directly heated by a heating coil provided in the nozzle brick, and the gas nozzle body is directly heated by a heating element or heat pad located between the nozzle brick and the upper part or top surface of the gas nozzle body.

[0019] In one preferred and reasonable variant of the spray unit according to the invention, it is envisaged that the outer contour of the nozzle core, together with the melting crucible and the peripheral wall, forms a separation joint formed as a labyrinth seal, so that the material penetrating into the separation joint from the bottom outlet solidifies by making multiple detours within the separation joint, thus forming a reliable seal.

[0020] The invention will now be described with reference to the illustrated embodiments. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view of a spray unit according to the present invention; [Figure 2] 1 is a perspective view of a heating body of a spray unit according to the present invention; FIG.

[0022] The atomization unit 1, shown in cross section in FIG. 1, comprises a melting crucible 2 made of a refractory material with a wall 3. The periphery of the melting crucible 2, and thus the wall 3, is surrounded by a crucible heater 13, which heats the melting crucible 2 and indirectly heats the molten metal present in the melting crucible 2. The crucible heater 13 can be a resistance heating means, but can also be configured as an induction heater which heats the melting crucible 2 via a graphite susceptor. The melting crucible 2 has a bottom outlet 4 to which a multi-part melt nozzle 16 is connected. The melt nozzle 16 has a nozzle brick 7 as a circumferential wall and a nozzle core 17 inserted into the circumferential wall or nozzle brick 7. The nozzle brick 7 forms a conical seat for a nozzle core 17, which is formed complementarily to the nozzle brick 7, and the nozzle core 17 is inserted into the conical seat of the nozzle brick 7 by means of an annular collar 18. The collar 18 is supported on a cylindrical step 19 of the nozzle brick 7. The nozzle core 17 is replaceably inserted into the nozzle brick 7. Furthermore, the nozzle core 17 has a cylindrical collar 21, which is inserted into a corresponding recess 22 formed in the bottom of the melting crucible 2. The nozzle brick 7 and the bottom of the melting crucible 2 pass through the nozzle brick 7 and thus form two-sided enclosures for the nozzle core 17, which is fixed in a positively locked manner.

[0023] The bottom outlet 4 of the melting crucible 2 and the nozzle core 17 form a melt passage 20, which forms a nozzle tip 5 at the guide end of the nozzle core 17. The guide end of the nozzle core 17 extends through a gas nozzle body 8, which is composed of an upper nozzle section 14 and a lower nozzle section 15 and forms an annular slit nozzle 9 at the casting nozzle. Atomizing gas is supplied through the annular slit nozzle 9 to the molten metal jet emerging from the nozzle tip 5, atomizing or spraying the melt to form metal powder. The nozzle tip 5 opens into a spray tower (not shown), where the metal powder is collected. The atomizing gas is supplied radially through the gas nozzle body via gas passages 10.

[0024] The nozzle brick 7, which provides thermal insulation and mechanical stabilization for the nozzle core 17, has a heating coil 11, which may consist of, for example, one or more resistance heating elements, embedded in the nozzle brick 7 near the nozzle core 17. Power is supplied to the heating coil 11, which causes direct heating of the nozzle brick 7 and indirect heating by heat conduction of the nozzle core 17, which is replaceably inserted in the nozzle brick 7.

[0025] The melt nozzle 16 further comprises a heating element 12, which is preferably made entirely of ceramic and is configured as an annular heating element, forming a kind of heat pad. The heating element is shown in a perspective view in FIG. 2. The heating element 12 is inserted into a corresponding annular recess 23 in the bottom of the nozzle brick 7 and is in heat-conducting contact with both the nozzle brick 7 and the upper nozzle part 14 of the gas nozzle body 8. The heating element 12 may consist of, for example, silicon nitride and, when energized via a voltage source, causes direct heating or warming of the gas nozzle body 8 and the nozzle brick 7, thereby causing indirect heating of the nozzle core 17 and the atomizing gas flowing through the gas nozzle body 8. [Explanation of symbols]

[0026] 1 spray unit 2 melting pots 3. Wall of the crucible 4 bottom outlet 5 Nozzle tip 7. Nozzle brick for melt nozzle 8 Gas nozzle body 9 Annular slit nozzle 10 Gas passage 11 Heating coil 12 Heating element 13 Crucible heater 14 Upper nozzle part of the gas nozzle 15 Lower nozzle part of the gas nozzle 16 melt nozzle 17 Nozzle core of melt nozzle 18 Nozzle core collar 19 Step of conical seal seat 20 Melt passage 21 Nozzle core color 22 Recessed portion provided at the bottom of the melting crucible 23 Recessed portion provided at the bottom of the nozzle brick

Claims

1. A spraying unit (1) for spraying a molten metal, comprising: a melting crucible (2) with a bottom outlet (4); a melt nozzle (16) arranged below the bottom outlet (4); and a gas nozzle (9) arranged concentrically with the melt nozzle (16), wherein the melt nozzle (16) is formed from multiple parts and has a peripheral wall body and a nozzle core (17), and the nozzle core (17) penetrates a conical seat within the peripheral wall body, The spray unit (1) further comprises at least one heating body (12) contacting a contact surface at the bottom of the peripheral wall, the peripheral wall forming a conical surrounding of a hole passing through the peripheral wall and having at least one resistance heating element embedded therein.

2. 2. The spray unit (1) according to claim 1, wherein the circumferential wall is formed as a nozzle brick (7).

3. 3. A spray unit (1) according to claim 1 or 2, wherein the nozzle core (17) is held between the peripheral wall and the bottom of the melting crucible (2).

4. 3. A spray unit (1) according to claim 1 or 2, characterized in that the nozzle core (17) is held concentrically and form-fittingly in the conical seat of the circumferential wall by means of an annular collar (18).

5. 3. The spray unit (1) according to claim 1 or 2, wherein the heating body (12) is configured as a heat pad and is embedded between the circumferential wall body and the gas nozzle body (8) of the gas nozzle.

6. 3. The spray unit (1) according to claim 1 or 2, wherein the heating body (12) is formed as a ceramic heating element.

7. 6. The spray unit (1) according to claim 5, wherein the heating element (12) is inserted into a recess on the bottom side of the circumferential wall and is in thermally conductive contact with both the circumferential wall and the gas nozzle element (8).

8. 3. The atomization unit (1) according to claim 1 or 2, wherein the outer contour of the nozzle core (17) together with the melting crucible (2) and the circumferential wall forms a separation joint formed as a labyrinth seal.

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