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

A process is described for the preparation of an iron-base sintered alloy, well suited for use in valve mechanism members of parts of internal combustion engines, which has a porosity of from 5 to 15% and throughout the iron matrix of which is dispersed from 5 to 25% of an Fe-Mo intermetallic compound in the form of a phase harder than the matrix, which comprises admixing iron powder with an effective amount of each of phosphorus-containing alloy powder, carbon powder, Fe-Mo alloy powder, and at least one powder selected from the group consisting of copper powder, bronze (copper and tin alloy) powder and a combination of copper powder and tin powder; forming the resulting composition into a green compact having a density ratio of 70-90%, pre-sintering the green compact at a temperature of from 3000-9000 C., repressing the pre-sintered green compact until a density ratio of from 90-95% is reached, and finally sintering the repressed bodies at a temperature of from 10300-11300 C. in a reducing atmosphere