GB491415A - Improvements in or relating to processes for improving the compressibility of metal powders - Google Patents

Abstract

The compressibility of quantities of powder which contain harder and softer metals is improved by using the soft metals in the form of a powder the volumetric weight of which is smaller than the volumetric weight of the harder metal powder used. Preferably a powder of softer metal is used of which the volumetric weight is roughly half or less than half of the volumetric weight of the harder metal. By "volumetric weight" is meant the weight of that amount of powder which, loosely poured out and shaken to a constant volume is present in unit volume. In examples, iron powder of which 3,3 gr. occupies 1 cc. may be mixed with copper powder, of which 2 gr. or preferably 1,4 gr. occupies 1 cc. The mixtures may contain 90 per cent iron, 10 per cent copper, of 80 per cent iron, 20 per cent copper. Components may also be added for hardening purposes. Antimony arsenic silicon phosphorus or sulphur may be employed for that purpose preferably in the form of pre-alloys such as phosphor-copper. These pre-alloys can be produced with both the softer and harder metals. When the softer metals are used as components of the pre-alloys only a portion of the softer metal of the mixture is used to form the pre-alloy. Oil-porous machine parts such as bearings and journals may be made by compressing and sintering suitable mixtures, such as, for example, a powder containing 20 per cent copper, 2 per cent antimony, 2 per cent graphite and the rest iron.