Abstract A composite high-strength machine element such as a sleeve (FIG. 6) consists of a heavy load bearing or working portion composed of sintered powdered high-performance alloy and a supporting portion which undergoes less concentrated or intense loads is made of a base metal such as sintered powdered iron. Where the outer portion of the sleeve is the heavy load bearing portion (FIG. 1) and the inner sleeve is the lower-stressed portion (FIG. 2) the outer portion is provided with an internal taper while the inner portion is provided with a matching external taper. The two portions are separately formed from powdered metal by suitable dies in standard briquetting presses and are then sintered at temperatures from 2,100* to 2,150* F. (FIG. 5). After sintering, the two portions are maintained at or brought up to forging temperatures from 1,500* to 2,100* F. and forged by forcing them together in a hot-forging press (FIG. 3), thereby producing the composite high-strength machine element shown in FIG. 4, with the outer and inner portions firmly and inseparably forged into union with one another. The densities of the two powdered metal components are converted, from approximately 75 percent after briquetting, to 98 percent or more after being united by the hotforging operation. Photomicrographs of sections of such composite machine elements (FIG. 7), after subsequent carburizing and hardening heat treatment, show an excellent interlock resulting from a migration of the metals into one another at the tapered joint. Torsion tests (FIGS. 8 and 9) performed on test specimens cut longitudinally from these composite machine elements at the tapered joint between the two forged components show adequate strengths without failure along the junction surfaces. These strengths compare favorable with the strengths of similar single solid metal specimens. A modification (FIG. 6) differs from the foregoing form of the invention by employing slightly different converging tapers in the outer and inner components otherwise follows the same procedure set forth above, resulting in a similarly excellent interlock by migration of the metals at the interface, as also shown by photomicrographs (FIG. 10).
A method of making a composite high-strength sleeve, comprising forming an inner component briquette of powdered ferrous metal with a generally cylindrical inner surface therein and a generally frustoconical external surface thereon, froming an outer component briquette of powdered manganesemolybdenum powdered alloy with a generally-frustoconical internal surface therein and a generally cylindrical outer surface thereon, sintering said components individually, forgingly heating said components to a forging temperature, assembling said forgingly heated components into telescoped mating engagement with one another, and applying axial forging pressure to said forgingly heated components sufficient to unite said components in forged interlocking engagement with one another.
Claim 2
Independent Claim
101 words
A method of making a composite high-strength sleeve, comprising forming an inner component briquette of powdered ferrous metal with a generally cylindrical inner surface therein and a generally frustoconical external surface thereon, froming an outer component briquette of powdered manganesemolybdenum powdered alloy with a generally-frustoconical internal surface therein and a generally cylindrical outer surface thereon, sintering said components individually, forgingly heating said components to a forging temperature, assembling said forgingly heated components into telescoped mating engagement with one another, and applying axial forging pressure to said forgingly heated components sufficient to unite said components in forged interlocking engagement with one another.
Claim 3
Dependent Claim
70 words
A method of making a composite high-strength sleeve, according to claim 1, wherein the taper of said generally-frustoconical external surface is slightly less than the taper of said generally frustoconical internal surface, and wherein said application of said axial forging pressure to said forgingly heated components deforms said generally frustoconical external and internal surfaces of different tapers into mating interlocking engagement with one another at a common generally frustoconical interface.