US2229330A - Porous metal product and method of making same - Google Patents

Description

1, 1941- A. J. LANGHAMMER ETAL 2,229,330

POROUS METAL PRODUCT AND METHOD OF MAKING SAME Filed March 8, 1937 INVENTOR ANTHONY d LANGHAMMER M0 WILLIAM G. GAL/(INS. 4L!

fcza a -F ATTORNEYS man M 1941 '2 z29 330 uNi'rEo STATES PATENT OFFICE.

Anthony J. Langhammer and William G. Calkins,

- Detroit, Mich., assignors to Chrysler Corporation, Highland Park, Mich., a. corporation of Delaware Application March 8, 1937, Serial No. 129,595

2 Claims. (01. 75-22) proved metal articles of this character which are powdered metal of higher melting point, used in 5 of a porous nature and particularly useful in frlcmanufacturing porous metal articles embodying tion and anti-friction elements, such as bearings. the invention and magnified approximately 172 One of the main objects of the invention is to times, the particular metal photograph being of improve the physical characteristics, such as powdered sponge iron. 1o ductility and strength of powdered metal prod- Fig. 5 is a perspective view of a bearing emucts of this kind, by increasing the adhesion of bodylng the invention. I the powdered metal particles to each other, and Powdered metal products of the type to :which particularly by increasing "the number of indlthis invention relates. may be put to numerous vidual bonds between adjacent particles of uses, but because of the porosity and lubricant powdered metal. I absorbing capacity of such products, they are Another object of the invention is the provision particularly suitable for hearing purposes. In of articles fabricated from a mixture of powdered general, products of this kind are manufactured metals having difierent melting points, in which by thoroughly mixing together two or more the quantity of powdered metal of higher m'eltpowdered metals in selected proportions. The ing point by far exceeds the quantity of powdered powdered metals usually have diflerent melting metal of lower melting point, but in which there points, and there is present a substantially are present substantially as many or more pargreater quantity of the powdered metal of higher ticles of the powdered metal of lower melting melting point than that of the lower melting point. j point. In addition to the powdered metals, which Further objects of the invention are to provide constitute the main constituents of the mixture, articles of this character in which there are there may be added relatively small quantities of present at least one particle of the powdered solid lubricants such as graphite, which it may metal oi lower melting point to bond each par-- be desired to retain in the final product. The ticle of powdered metal of higher melting point mixture may also contain volatile or other lubrito the next adjacent similar particle; to provide a cants which are mainly removed during the sinmixture of such powdered metals in which the tering operation, thesematerials being provided particles of lower melting point aresubs'tantially to lubricate the surfaces of the dies or molds in smaller than those of higher melting point; and which the powdered mixture is compressed. to provide a compressed and sintered powdered The powdered constituents of the mixture are metal structure which has substantially each parthoroughly incorporated together and distributed ticle of metal of higher melting point bonded to 7 throughout each other by a suitable mixing opereach adjacent particle of similar metal by a paration and they are then compressed under high ticle of the metal of lower melting point. unit pressure into briquettes of desired shape.

An illustrative embodiment and diagrammatic The briquettes are then removed from the die and 40 explanation of the invention is shown in the acsintered, preferably in a reducing or non-oxidizcompanying drawing, in which: ing atmosphere, at a temperature above the melt- Flg. 1 is.a diagrammatic illustration of the aping point of the powdered metal of lower melting proximate relationship and comparative size of temperature and below the melting temperature particles of powdered metal included in powdered of the metal of higher melting point. During metal mixtures used in manufacturing articles this sintering operation, the particles 01 metal of embodying the invention. highermelting point are bonded together by the Fig. 2 is a diagrammatic illustration of the apparticles of metal of lower melting point. proximate relationship and relative size of the -For the purpose of illustration, powdered iron articles of powdered metal conventionally used in and powdered copper particles are shown in the the manufacture of compressed and sintered drawing, although combinations of other metals bearing products. Y ,of different melting points may he used to equal Fig. 3 isa sketch of a micro-photograph of the advantage in the practice of the invention.

powdered metal of lower melting point, used in In Fig. 1 of the drawing, there is diagramm nllf ul Porous bearing articles embodymatically illustrated the relationship and relative a This invention relates to improvements in compressed and sintered powdered metal articles and ing the invention and magnified approximately 172 times, the particular metal photographed being copper.

Fig.4 is a sketch of a micro-photograph of the the illustration shown, there are nine large circles Ill, which represent particles of powdered iron, and ten small circles H, which represent particles of powdered copper. Each particle of powdered iron is shown to be approximately of the order of ten times as large as a corresponding particle of powdered copper Ii, this illustration being diagrammatically illustrative of the relative average sizes of a large number of particles. This figure approximately represents the relative size of the particles of iron and copper in a mixture comprising substantially ten percent copper and ninety percent iron, the size of the particles being illustrative of the quantity by weight thereof.

By thoroughly mixing the powdered metal, an arrangement thereof corresponding approximately to the diagrammatic illustration shown in Fig. l is obtainable. Each particle of iron Ill has between it and the next successive particle of iron a small particle of copper i I and by predetermining the sizes of the particles such that there is a greater number of particles of copper than particles of iron, an extra particle, or extra particles of copper may be provided in a central location with respect to the particles of iron. When the particles of a mixture of powdered iron and powdered copper are arranged in a manner approaching that illustrated in Fig. 1, and the mixture is then compressed and sintered, the particles of powdered copper between adjacent particles of powdered iron fuse and provide bonds between the iron particles. The centrally located particle of powdered copper also fuses to provide additional bonds between all of the particles of powdered iron with which it is associated. In this manner, each particle of powdered iron is rigidly bonded to an adjacent particle of powdered iron by several copper bonds.

When the particles of powdered copper are substantially the same size as the particles of powdered iron, as illustrated in Fig. 2, or larger than the iron particles, the number of bonds between the particles of powdered iron resulting from the sintering operation is materially less than the number of bonds provided by the invention.

From a consideration of the micro-photograph shown in Figs. 3 and 4, it is obvious that a mathematically accurate and precise relationship of sizes of powdered metals of different melting tem- 'peratures and arrangement thereof, such as that shown in Fig. 1, cannot be obtained, but by properly predetermining the size of the metals of different melting points and taking into account the quantity and density thereof, it is possible to approach or approximate the arrangement and relative sizes illustrated in this figure. In general, it is sufficient to obtain meritorious results from practice of the invention if the particles of metal of lower melting point are present in number of substantially the same order as the number of particles of metal of higher melting point. When this condition exists, the resulting bearing I4, shown in perspective in Fig. 5, has all of its powdered metal particles rigidly bonded together by a much larger number of bonds than have been heretofore provided and the porous structure is therefore less susceptible'to fracture and capable of withstanding greater loads. The increased number of bonds betweenv the metal particle resuits in an increase in both structural strength and ductility of the finished product.

The powdered metals should preferably have the following screen analysis:

Iron particles All through 150 mesh Approximately will be collected on screens of between 150 and 325 mesh Approximately-25% through 325 mesh.

Ninety percent of the powdered copper particles should be capable of passing through a 325 mesh screen.

This invention may be practiced in the formation of porous products manufactured from mixtures of powdered materials having the following compositions:

Regardless of the particular proportions and nature of the constituents of mixtures of powdered material from which porous metal products may be formed, predetermining of the size of the particles of higher melting point with respect to the particles of metal of lower melting point in accordance with this invention, will result in the attainment of superior structural properties in the final products formed from the mixture.

Although but several specific embodiments of the invention is herein shown and described, it will be understood that various changes in the size, shape and arrangement of parts may be made without departing from the spirit of our invention.

We claim:

1. A sintered porous bearing structure comprising substantially by weight of powdered iron and substantially 10% by weight of powdered copper particles, the particles of powdered copper being fused to adjacent particles of powdered iron for providing a substantially fused bond therebetween and being of such order of size that when unfused substantially 90% thereof will pass through a 325 mesh screen and said particles of powdered iron being of such order of size that substantially all thereof will pass through a mesh screen, substantially 75% thereof will be collected on screens of between 150 to 325 mesh and substantially 25% thereof will pass through a 325 mesh screen.

2. The method of making a porous metal bearing structure which comprises compressing into a briquette a mixture comprising substantially 10% by weight of powdered copper and 90% by weight of powdered iron, the particles of powdered iron being of an average size in volume approximately ten times that of the average size in volume of the particles of powdered copper, and sintering said briquette in a non-oxidizing atmosphere at a temperature between the melting temperature of said powdered iron and said powdered copper for forming fused bonds between portions of adjacent particles of said powdered iron.

ANTHONY J. LANGHAMMER. WILLIAM G. CALKINS.

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