Patent ID: 6024915
Filing Date: 2000-02-15
Classification: B22F,C23C,Y10T

Abstract:
A process for producing a metal-base sinter comprising the steps of:(A) a dispersing step for dispersing a powder of metal core particles by a multiplicity of means for dispersion treatment of particles in a gaseous atmosphere to form a mixture of a gas and dispersed metal core particles, and charging into a coating space the powder of the metal core particles dispersed at a predetermined dispersity in accordance with an average diameter frequency distribution by volume,wherein said multiplicity of means for dispersion treatment of particles comprises at least one dispersing means for dispersing the metal core particles in the gaseous atmosphere and a final treating means, and wherein said final treating means is selected from between:(a) final dispersing means positioned most downstream among said multiplicity of means for dispersion treatment of particles and said at least one dispersing means; and(b) means for forming the mixture of the gas and the particles in the powder of dispersed particles at the predetermined dispersity which comprises;(b-1) means for selecting a mixture of the gas and the particles in the powder of dispersed particles at the predetermined dispersity that separates a portion of the powder that is composed of particles dispersed at a dispersity less than said predetermined dispersity from the mixture of the gas and the particles in the powder of core particles in which the particles in the powder of core particles are dispersed in the gaseous atmosphere, thereby selecting the mixture of the gas and the particles in the powder of dispersed core particles in which the particle in the powder of core particles are dispersed at a dispersity not less than said predetermined dispersity and present in the gaseous atmosphere mainly in a single-particle state; and(b-2) feedback means by which the portion of the powder that is composed of particles dispersed at the dispersity less than the predetermined dispersity and which has been separated by said means for selecting the mixture of the gas and the particles in the powder of dispersed particles at the predetermined dispersity is transported to the final dispersing means and/or treating means upstream of the final dispersing means; and(B) a coating step for allowing the particles in the powder of metal core particles that have been dispersed at the predetermined dispersity in the dispersing step (A) to contact and/or impinge against a precursor of a coat forming substance in a coating start region of the coating space as said particles are dispersed at the predetermined dispersity to satisfy preset conditions so that said particles are coated with the coat forming substance to produce coated metal particles, wherein said preset conditions are the following conditions:the dispersity .beta. should be at least 70% if those particles have an average diameter of no more than 10 .mu.m in the frequency distribution by volume;the dispersity .beta. should be at least 80% if those particles have an average diameter in excess of 10 .mu.m but no more than 20 .mu.m in the frequency distribution by volume;the dispersity p should be at least 90% if those particles have an average diameter in excess of 20 .mu.m but no more than 50 .mu.m in the frequency distribution by volume;the dispersity .beta. should be at least 95% if those particles have an average diameter in excess of 50 .mu.m but no more than 300 .mu.m in the frequency distribution by volume;the dispersity .beta. should be at least 97% if those particles have an average diameter in excess of 300 .mu.m but no more than 800 .mu.m in the frequency distribution by volume; andthe dispersity .beta. should be at least 99% if those particles have an average diameter in excess of 800 .mu.m in the frequency distribution by volume;(C) shaping step for shaping the coated particles produced in the coating step (B) or a mixture thereof into a shaped body of desired configuration; and(D) sintering the shaped body produced in the shaping step (C) at a predetermined pressure and temperature to produce the metal-base sinter.