US3854519A

US3854519A - Apparatus for starting extrusion of filaments from metallic melts

Info

Publication number: US3854519A
Application number: US00429331A
Authority: US
Inventors: B Junker
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1973-12-28
Filing date: 1973-12-28
Publication date: 1974-12-17
Anticipated expiration: 1991-12-17

Abstract

An apparatus for extruding molten metals to form continuous filaments is provided with a mechanism for controlling the pressure level across the extrusion orifice which includes a means for introducing a pressurizing gas into the discharge cavity immediately below the orifice and a slide valve positioned downstream from the discharge cavity in the cooling column.

Description

United States Patent 11 1 Junker Dec. 17, 1974 APPARATUS FOR STARTING EXTRUSION 2,976,590 3/1961 Pond 164/283 5 x ()F FILAMENTS FROM METALLIC MELTS 3,216,076 11/1965 Alber et al 164/82 X [75] Inventor: Bernhard T. Junker, Raleigh, NC. [73] Assignee: Monsanto Company, St. Louis, Mo. Prlmary L'mmmer R' Spencer Annear [22] Filed: Dec. 28, 1973 [21] Appl. No.: 429,331 [57] ABSTRACT An apparatus for extruding molten metals to form [52] 164/274 164/82 264/176 F continuous filaments is provided with a mechanism for [51] lift. Cl. B22d 11/08 Controlling the pressure level across the extrusion [58] held of Search 164/66 283 fice which includes a means for introducing a pressur- 164/274; 264/176 F izing gas into the discharge cavity immediately below the orifice and a slide valve positioned downstream [56] References and from the discharge cavity in the cooling column.

UNITED STATES PATENTS 2,907.082 10/1959 Pond 164/66 1 Claim, 1 Drawing Figure I2 4 I II IO\ 1 I3 1' I I5 l l9 J -14 2O-HL 21 5 APPARATUS FOR STARTING EXTRUSION OF FILAMENTS FROM METALLIC MELTS This invention relates to a melt extrusion apparatus and more particularly to an improved apparatus for extruding low viscosity melts of the various metals and metal alloys to form continuous filamentary products.

Methods for forming metallic fibers and filaments by extruding a continuous stream of molten metal through a small orifice are known and have been described in US. Pat. Nos. 3,216,076 and 3,658,979. According to these methods, the melt of a metal or metal alloy is extruded at an appropriate velocity into a selective atmosphere. When the hot jet issuing from the extrusion orifice contacts this atmosphere a reaction occurs which results in the formation of a film about the jet surface. This film stabilizes the filamentary jet or stream against surface tension break-up until it is solidified by passage through a cooling column.

The apparatus employed in the practice of these methods is comprised essentially of a crucible for containing the melt with an orifice element in its base. The crucible is further provided with heating means to melt the charge and maintain it in the molten condition. In addition, means are provided for applying a positive head pressure to the molten charge contained within the crucible to force it through the orifice at an appropriate ejection velocity and into a discharge cavity where contact is made with the film forming atmosphere.

A troublesome problem commonly encountered when extruding metal filaments in accordance with these methods is the tendancy for molten metal charge to accumulate in the orifice capillary during the course of the pressurization cycle for imparting the necessary head pressure over the melt to effect proper streaming through the orifice. This causes great difficulty in attaining a proper streaming after the system becomes sufficiently pressurized and the production run often has to be aborted.

This problem has now been overcome by controlling the pressure across the orifice while the system is being adjusted to the desired operating conditions. This is accomplished by introducing a pressurizing gas into the discharge cavity immediately below the orifice. A slide valve positioned in the cooling column downstream from the discharge cavity prevents loss of pressure below the orifice when in closed position.

The afore-described procedure may be carried out in an apparatus having a design as illustrated in the accompanying drawing wherein the single FIGURE is a schematic sectional view of the presently preferred embodiment of the invention.

There is shown as generally represented by the numeral 10, a typical assembly for extruding a freestreaming molten jet from a metal melt. The assembly includes a crucible 11 for containing the melt enclosed within a pressure vessel 12. The crucible is provided with an orifice 13 through which is extruded a continuous stream or jet of molten metal generally denoted 14. The crucible rests upon a supporting insulating pedestal 15 of pyrolytic graphite construction which in turn rests upon pedestal l6 and 17 supported by the assembly base plate 18. Within pedestals l5 and 16 and immediately below orifice 13 is a discharge cavity 19. P0- sitioned beneath discharge cavity 19 is a vertically disposed elongated cooling column 20. A slide valve 21 is positioned in cooling column 20.

When proceeding to pressurize the system to impart the desired extrusion head pressure over the melt, a pressurized gas (source not shown) is introduced into discharge cavity 19 through port 22 in flange member 23 while slide valve 21 is in closed position to permit pressure control in the discharge cavity. When the desired operating conditions are attained for proper streaming of the melt, slide valve 21 is opened with a resulting rapid depressurization of discharge cavity 19 so that a fully developed molten metal stream through orifice 13 is established instantly. In the open position the slide valve plate is retracted completely and does not interfere with streaming in the cooling column.

As indicated, the pressure control is generally at a level which will prevent filling of the orifice capillary with molten metal; however, in some instances it may be desirable to control the pressure to a level which permits back bubbling of discharge cavity gas through the orifice. The latter control may be employed in those instances where gas refining of the metal charge may be desirable before commencing the extrusion operation.

It is to be understood that the embodiment disclosed herein is merely illustrative and that it can be modified or amended and that numerous other embodiments can be contemplated without departing from the spirit and scope of the invention.

1 claim:

1. In an apparatus for forming continuous filaments directly from the melt of a metal, wherein under a positive head pressure the melt is ejected through an orifice and into a discharge cavity as a molten metal stream from whence the stream descends in a downward vertical path through a cooling column positioned immediately beneath said discharge cavity, the improvement which comprises means for controlling the pressure level across the orifice, said means comprising: a slide valve positioned in said cooling column downstream from said discharge cavity and means for introducing a pressurizing gas into said discharge cavity.