Apparatus For Making Metal Powder

Abstract

Apparatus for atomizing molten metal in which the upper portion of a ceramic nozzle distribution element coacts with the bottom of a source of molten metal such as a tundish to form a hollow stream of molten metal An array of fluid nozzles is located within the hollow stream, and the radially outwardly directed fluid jets atomize the falling curtain of molten metal into particulates which are driven outwardly and away from each other by the impinging fluid. The ceramic distribution element is preferably formed with channels which become progressively shallower downwardly toward the bottom of the ceramic element.

Description

BACKGROUND OF THE INVENTION

This invention relates to new and useful improvements in apparatus for atomizing a stream of molten metal into solidified particulates and, more particularly, to an improved nozzle structure for atomizing the stream of molten metal.

It is, of course, broadly old to atomize or break up a stream of molten metal into particulates through the impinging action of high pressure high velocity jets. Later refinements include the use of a ceramic nozzle to control the flow of metal from a supplying tundish to the atomizing zone, but even so, such problems as preventing the formation of satellite clusters, preventing backsplatter and metal buildup on the metal transmitting and fluid nozzles and obtaining more efficient conversion of a high percentage of the throughput into useful particulates remain.

SUMMARY OF THE INVENTION

It is, therefore, a principal object of this invention to provide an improved apparatus for atomizing a stream of molten metal to form metal powder which minimizes the backsplatter of metal and metal buildup on the nozzle itself as well as the formation of satellite or particle clusters caused by collisions between insufficiently solidified particles.

In carrying out the present invention, an atomizing structure is provided for use with a tundish or other container of a supply of molten metal which forms the molten metal into a hollow stream which surrounds an array of outwardly directed fluid nozzles. Jets from the fluid nozzles are directed radially outward from within the hollow metal stream and, on impingement with the stream, atomize it into particulates which fall radially outwardly away from each other and from the jet nozzles.

Preferably, the atomizing structure comprises a generally conical or frustro-conical ceramic element the upper portion of which is inserted into the bottom of a tundish to cause the flow of molten metal therefrom to progress downwardly in a progressively spreading manner to form a thin annular curtain or hollow stream falling from the bottom of the conical ceramic element.

A plurality of outwardly directed fluid nozzles are mounted to form an annular array within the curtain or hollow stream of falling molten metal to provide radially outwardly directed fluid jets which impinge against and atomize the metal into particulates. To facilitate formation of the desired thin walled curtain or hollow stream of molten metal the ceramic nozzle member has a plurality of channels formed on its surface which diverge from each other as they extend downwardly along the conically shaped member. For best results, the depth of each of the channels becomes progressively less as the circumference of the ceramic member increases for more uniform distribution of the molten flow.

In another embodiment, instead of discrete fluid nozzles, a substantially continuous slot is provided from which an essentially continuous, 360.degree. flow of fluid is emitted for atomizing the metal.

DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings in which

FIG. 1 is a somewhat schematic vertical section, partly in elevation, of an atomizing structure constructed in accordance with this invention;

FIG. 2 is a plan view of the structure in FIG. 1 and the adjacent portion of a tundish in which it is mounted; and

FIG. 3 is a detail vertical section taken along line 3--3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described in detail in connection with a preferred embodiment thereof as used with an inert gas as the atomizing fluid.

Referring to the drawings in detail, the invention, as illustrated, is embodied in an atomizing structure shown for illustrative purposes in association with a tundish generally indicated at 5. The structure comprises a ceramic, frusto-conical distributing element generally indicated at 6 and a nozzle assembly generally indicated at 7 for the atomizing fluid which in this instance is a gas.

The bottom of the tundish 5 is provided with an aperture 8, the side wall 9 of which is disposed at an angle conforming to the surface 10 of the ceramic distributing element 6 so that when the latter is seated in the aperture 8, the aperture is sealed except for channels 11 formed in the ceramic element 6.

The distributing element 6 is supported in operative relation to the tundish 5 on a feed pipe 17, yet to be described, and is preferably proportioned in such manner that its upper portion projects through and plugs the aperature 8.

The channels 11 formed in the outer surface of the distributing element 6 are preferably semicircular in cross section and form an annular array with the channels extending downwardly and diverging from one another. Each channel has a progressively smaller cross-section from top to bottom and preferably adjacent to the bottom of the distributing element 6 vanish and leave a bottom marginal portion which is free of channels. The channels 11 facilitate the formation of a substantially continuous annular curtain or hollow stream of molten metal which falls from the bottom periphery of the distribution element 11.

The bottom end of the distribution element 6 is recessed to receive and locate the nozzle assembly 7 on which the former is supported. The nozzle assembly 7 comprises a top stud or plug 12 and an intermediate generally tapered portion 13 which together mate with the complementarily formed recess in the distributing element 6. The intermediate portion 13 of the assembly 7 forms a plenum and is provided with an inclined outer wall 14 in which a plurality of fluid nozzles 15 are radially disposed. The inclination of wall 14 is such that the axes of fluid nozzles 15, which extend normal to the plane of the wall 14 extend in the desired direction for atomizing the molten metal. The angle of the nozzles is not critical but preferably they converge with the plane of the surface 10 of the distribution element 6. The lower portion of the assembly 7 is generally cylindrical and is threaded onto the gas feed pipe 17.

Thus, the fluid from the nozzles 15 is directed downwardly and outwardly beneath the outer edge of the bottom of the distributing element 6 for impingement against and atomization of the molten metal falling therefrom in a hollow stream thereby effecting an outward dispersion of the atomized particles which thus have more time to solidify before colliding with and thus preventing agglomeration with other particles.

While not essential, the walls of the tundish 5 can be heated to ensure desired fluidity in the molten metal. When required, the tundish 5 can be inductively heated by providing a susceptor or a separate radiant heating electrode can be provided just below the bottom of the tundish 5 and surrounding the atomizing nozzle assembly.

In operation, the pipe 17 is connected to a suitable supply of an atomizing fluid, preferably an inert gas such as argon under a pressure high enough to provide the desired atomization of the metal. To that end a pressure of at least about 300 psi is required. Molten metal is supplied to the tundish 5 and covers the upper portion of the distributing element 6 from which it passes through the channels 11 defined by the wall 9 of the tundish bottom aperture and the distributing element 6. The molten metal spreads out over the lower portion of element 6 and falls from it in a substantially continuous hollow stream which is broken up and atomized by the jets from nozzles 15.

In a further embodiment, most of the nozzles 15 can be merged to provide a substantially annular nozzle structure in the form of an annular slot which can be continuous except for about three narrow spiders.

While operation of the atomizing structure has been described in connection with the use of argon, the preferred atomizing fluid, other gases can be used and also a liquid such as water can also be used as the atomizing fluid.

It is, of course, to be understood that variations in arrangements and proportions of parts may be made within the scope of the appended claims. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

Claims

What is claimed is:

1. Apparatus for making metal powder by atomizing molten metal for use with a container for molten metal having a downwardly opening aperture, comprising a distributing element, means for supporting said distributing element in said aperture with the lower portion of said distributing element extending below said aperture and the upper portion of said distributing element forming an orifice with the wall of said aperture for the flow of molten metal therethrough, nozzle means below said distributing element and inwardly of the periphery of the latter for providing atomizing fluid jets outwardly directed with respect to the axis of said distributing element, whereby fluid exiting from the fluid nozzle means impinges molten metal falling from the periphery of said distributing element to atomize the same and drive the thus formed particulates outward.

2. The apparatus of claim 1 in which said distributing element has a plurality of downwardly extending channels formed in the surface thereof.

3. The apparatus of claim 2 in which said channels become progressively shallower from the upper to the lower ends thereof.

4. The apparatus of claim 3 in which the lower ends of said channels terminate adjacent to and spaced from the bottom peripheral edge of said distributing element.

5. The apparatus of claim 4 in which said distributing element is conically shaped, and said channels radiate downwardly.

6. The apparatus of claim 4 in which said distributing element is shaped as a frustum of a cone.

7. The apparatus of claim 1 in which said nozzle means includes a plenum, and said distributing element has a recess formed in the bottom thereof to receive said nozzle means.

8. Apparatus for making metal powder by atomizing molten metal, comprising a container for molten metal and having a downwardly opening aperture, a distributing element, means supporting said distributing element in said aperture with the lower portion of said distributing element extending below said aperture and the upper portion of said distributing element forming an orifice with the wall of said aperture for the flow of molten metal therethrough, means forming an array of fluid nozzles below said distributing element and inwardly of the periphery of the latter, said fluid nozzles being outwardly directed with respect to the axis of said distributing element, whereby fluid exiting from said fluid nozzles impinges molten metal falling from the periphery of said distributing element to atomize the same and drive the thus formed particulates outward.

9. The apparatus of claim 8 in which said distributing element has a plurality of downwardly extending channels formed in the surface thereof.

10. The apparatus of claim 9 in which said channels become progressively shallower from the upper to the lower ends thereof.

11. The apparatus of claim 10 in which said means forming said fluid nozzles includes a plenum communicating with said fluid nozzles, and said distributing element has a recess formed in the bottom thereof to receive said fluid nozzle- and plenum-forming means.