Process for the preparation of sintered alloys for valve mechanism parts for internal combustion engines

摘要

A process for the preparation of an iron base sintered alloy well suited for use in valve mechanism members or parts of internal combustion engines, which has a porosity of 5 to 15% and throughout the iron matrix of which is dispersed an Fe-Mo intermetallic compound in the form of a phase harder than the said matrix, by using a powder mixture obtained by incorporating into finely divided iron powders having a particle size of not more than 30 microns the given amounts of copper powders, phosphorus-containing alloy powders, carbon powders and Fe-Mo alloy powders, or the given amounts of bronze powders and/or a mixture of copper powders and tin powders, phosphorus-containing alloy powders, carbon powders and Fe-Mo alloy powders. wherein the said iron powders are granulated alone or in combination with other powders to an apparent particle size of 30 to 200 microns, and the obtained powder mixture is formed into a green compact having a density ratio of 75 to 85%, which is in turn sintered at a temperature of 1030 DEG -1130 DEG C. in a reducing atmosphere.