US1286089A - Method of producing hollow objects of compressed metallic powder. - Google Patents

Description

. C. A. PFANSTIEHL. METHOD OF PRODUCING HOLLOW OBJECTS OF COMPRESSED METALLIC POWDER. APPLICATION FILED N 1 286,089. Patented Nov. 26, 1918.

k mm 257 r 17 6 /4 7 6 ED STATES PATENT OFFICE,

CARL A. PFANSTIEHL, OF HIGHLAND PARK,- ILLINOIS, ASSIGN OR TO PFANSTIEHL COM- PANY, INCL, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Nov. 26, 1918.

Application filed. November 4, 1916. Serial No. 129,602.

T all whom it may concern:

Be it known that I, CARL A. PFANs'rIEHL, a citizen of the United States, residing at Highland Park, in the county of Lake and nesium oxid, tantalum oxid and thorium oxid and many other substances are useful in their compressed form as dishes in which to perform certain chemical operations, as heating elements in' which to melt chemicals or metals. Some of these materials,

especially tungsten and tungsten oxid, but

many other materials to a less extent, resist flow during thecompressing operation, that is, unless means are provided for compressing the material in substantially straight lines the material will become more highly compressed at one point than another, and will therefore be weak or porous at the points of less compression.

It has been found that tungsten powder and other powders, the particles of which are very hard, can be pressed into solid homogeneous objects by so distributing the tungsten or other powder under the movable part of the press that in the final position of the press all parts of the powder have received the same amount of compression. This is more readily accomplished where the article to be formed is rectangue lar in shape, since when in that shape only one of the dimensions of the loosely packed powder needs to be changed by the compression. 1

The pressure under which tungsten and some other powders are converted into solid homogeneous articles is about one hundred thirty to one hundred sixty tons per square inch. At such a pressure as this copper will flow and can even be squirted in a manner similar to that in which lead pipe-and cable sheaths are made. By embedding a piece of copper in the powdered tungsten or other material to be compressed the copper by its propertyof flowing exerts :1 lat eral pressure upon the material being com pressed and thus overcomes the characteristic of the tungsten or other powder which prevents it from flowing under pressure.

It has been found that although copper at the pressure of one hundred thirty tons per square inch and over will readily flow to equalize pressures throughout the powdered material being compressed, nevertheless the tenacity of the copper is such as to prevent it. from being forced into the pores of the powdered material under compression.

The shape of the copper invariably changes during the compressing operation and the final shape to be secured must be determined by experimenting with different shaped copper inserts. Obviously, there are limitations to the shape which can be secured by means of the copper, but it has been found that almost any form of smoothly outlined interior can be produced by this process.

The materials whichI prefer to use in making chemical dishes and the like are not readily attacked by the ordinary acids, whereas copper is readily attacked. The copper may therefore be removed by the use of'nitric acid or if the powder be such as is attacked by nitric acid the copper may be removed by some other acid which does not attack the compressed powder.

One form of my invention and one method of carrying it out "are illustrated in the accompanying drawing, in which- Figure 1 represents a collapsible die and itsplunger filled with material for compression and also having the copper insert therein;

Fig.2 is a section of the materialafter compression; and

Fig. 3 is a perspective view of the material after the copper insert has been eaten out by the acid.

Similar characters of reference refer to similar parts throughout the several views.

The die illustrated herein forms no part of my present invention, this die being the subject matter of my co-pendin application, Serial No. 124,504., filed ctober 9, 1916, and entitled Means and method for compressing tungsten powder.

A die block 5 preferably of cast steel is provided with a plurality of removable members 6 having sloping faces which engage correspondingly sloping faces of the die block. The members 6 are made of the hardest tool steel of which are also made the base member 7 and plunger 8. The base 6 member 7 rests upon an insert 9 of steel which is somewhat harder than the cast steel block '5 but somewhat softer than the base member 7. Likewise the plunger 8 is carried in a supporting block 10 of steel [0 which is somewhat softer than the plunger 8, but which is somewhat harder than the press member 11 in which the member 10 is supported. Suitable end members not shown are provided, these end members be- '15 ing likewise formed with'sloping faces op posing 'the faces forming the walls of the die proper.

The rectangular chamber formed within the four walls and base of the die is filled to the top with powder 13 to be compressed. The copper insert 14 is then forced into the powder-until the upper and straight'face of the copper insert is flush with the top of .t'he die members 6. The plunger 8 is then operated preferably by means of an oil pump' and a pressure of substantially one hundred and fifty tons per square inch is exerted on the powder and copper. This pressure causes the copper to change its form and to thus exert a lateral pressure substantially equal to the downward pressure exerted by the plunger. After the compressing operation the pressure on the die members 6 is relieved by backing off the screws 16 and 17, thus permitting the cross bar 18 to rise slightly, at the same time the pressure upon the plunger 8 is relieved, andthe compressed material is allowed to expand. This expansion occurs 40 substantially equally in all directions, thus preventing the cracking of the compressed material.

The bar of material 19 with the copper 20 therein is placed in acid, the copper being thus -removed. The compressed material may then be Washed and dried and used in its compressed form, or maythereafter be sintered by passing through 'it an electric current sufficient to bring the metal to its welding temperature. Of course, if oxids are used they cannot be sintered in this manner, but if either metallic tungsten powder or metallic tantalum powder or in factany metallic powder is used, the articles may be sintered into solid metal. It is not always possible to perform this sintering 0peration by passing the electric current directly through the compressed material, becausethe material may by reason of its shape have greater cross section at some points than at others, by reason of Which the resistance would be greater at .some points than at others. The compressed object may, however, be supported upon a cradle of suitable material such as tungsten rods, whereon the compressed article may be brought to a temperature suflicient to cause the particles to become sintered together.

Although'but one form of compressed ob ect is herein illustrated, it may readily be seen that other forms can be made by merely changing the shape of the die and the shape of thecopper insert. It is possible also to use other metals than copper, though some of the softer metals such as lead cannot readily be used, because the lead will be forced Into the pores of the compressed material long beforethe necessary pressure has been reached to create a solid homogeneous article. WVhen the soft metal is later eaten out of the pores the compressed material is I left porous and therefore unfit for some purposes. If for any reason porous articles are desired, however, they may be constructed by the use of lead or other very soft metals.

Having thus described my invention, what I- claim as new and desire to secure by Letters Patent of the United States is:

1. The method of producing, hollow articles of compressed metallic powders which consistsin inserting a metal part having the property .to flow'under the pressure ofcompression, compressing the powder and metal part and thereafter removing the metal part by the action of acids.

2. The method of producing hollow articles of compressed tungsten, tantalum, magnesium oxid, thorium oxid or the oxids of tungsten and tantalum which consists in inserting a metal part within the unpacked powder to be compressed, compressing the powder about the metal part and thereafter

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