Patent ID: 7347968
Filing Date: 2008-03-25
Classification: B21C,B22F,H01F

Abstract:
1. A process for manufacturing a compound sintered article having a cavity, comprising the sequential steps of: (a) providing a group of mixtures of powdered materials, each member of said group having, after sintering, one, and only one, functional property that is different from any functional property possessed, after sintering, by any other member of the group, a functional property being defined as a physical property selected from the group consisting of magnetic, corrosion resistant, controlled porosity, high thermal conductivity, high density high strength, low thermal expansion, wear resistant, high elastic modulus, high damping capacity, good machinability, highly fatigue resistant, high hardness, high toughness, high melting point, oxidation resistant, and easy joinability, and low internal stress; (b) adding lubricants and binders to all members of said mixtures group, thereby forming a first group of feedstocks, all of whose members shrink, after sintering, by amounts that differ from one another by less than about 1%; (c) forming a second group of feedstocks that will shrink, after sintering, by an amount that exceeds the amount that any member of said first feedstock group shrinks, after sintering, by at least 10%; (d) in a mold, compression molding a feedstock from either feedstock group, to form a green part; (e) transferring said green part to a different mold and then injecting into said different mold a quantity of a different feedstock, taken from either feedstock group; (f) repeating steps (d) and (e), each time using a different mold and a different feedstock, until all members of both feedstock groups have been molded, thereby forming a final compound green part; (g) removing all lubricants and binders from the final compound green part to form a powder skeleton; (h) sintering the powder skeleton; and (i) removing all loose parts, thereby forming the compound sintered article.