Method of making sintered powder alloy compacts

A method for the manufacture of sintered alloy steel parts, characterized by compaction and sintering of an admixed powder having carbon in graphite powder form to obtain alloying, the admixture consisting of two powder types, one type being an iron based powder substantially devoid of alloying ingredients, and the other type being an alloying powder capable of sintering by formation of a low-melting point phase, said alloying powder consisting of at least three elements, two of said elements being selected from the group consisting of manganese, nickel, molybdenum, chromium, molybdenum when selected being no greater than 11% and the combination of molybdenum plus chromium when selected being no greater than 30%, the third element constituting iron in the range of 1-40% said alloyed powder constituting 0.25-6% of said admixed powder.

A method of producing a sintered metallic compact, comprising:

• (a) uniformly blending graphite powder, an iron based powder with an alloyed powder to form a mixture, said alloyed powder constituting 0.25-6% of said mixture and containing at least three elements selected from the group consisting of manganese, molybdenum, nickel and chromium, said manganese constituting at least 40% of said alloy powder and nickel constituting at least 5% of said alloy powder, said graphite being present in an amount effective to provide a predetermined carbon content in the resulting product,
• (b) compacting said mixture into a shape having a theoretical density of the order of 80%, and
• (c) heating such shape in the environment of a reducing atmosphere to a temperature in the range of 1800.degree.-2200.degree. F., for a period of time to liquify said alloy powder present in said mixture and thereby form a low melting liquid phase, and then allowing said shape to cool.

A method of establishing alloying between solid and liquid phases of a powder mixture, comprising:

• (a) uniformly blending a water atomized, iron based powder, devoid of alloying ingredients except for molybdenum which is prealloyed therewith in the range of 0.08-0.4% by weight, with a non-iron based additive powder consisting of alloying ingredients and having no greater than 14% copper and having at least two other elements but up to all elements selected from the group consisting of manganese, nickel, chromium, and iron, said two elements being selected and balanced to provide a span of melting temperatures for said admixture of no greater than 350.degree. F. and the admixture having a liquidus temperature of between 1900.degree.-2250.degree. F., said additive powder being present in an amount of 0.25-6% of said mixture,
• (b) compacting said mixture to a density of at least 70%, and
• (c) heating said compacted mixture to a temperature of about 2250.degree. F. for no greater than one hour, whereby the additive powder forms a liquid phase which readily diffuses along the particle boundaries and into the matrix of said iron powder thereby reducing the maximum diffusion distance to one particle radius or less.

A method for the manufacture of sintered alloy steel parts, characterized by the compaction and sintering of an admixed powder to obtain alloying, the admixture consisting of three powder types, one type being a low carbon iron based powder substantially devoid of alloying ingredients except for up to 1% of said alloying ingredients, another type being an alloy base powder capable of sintering by formation of a low-melting point liquid phase, said alloy base powder consisting of at least three elements, two of said elements being selected from the group consisting of manganese in the range of 40-60%, nickel, molybdenum, and chromium, and the third element constituting iron in the range of 1-40% and said third powder being graphite in an amount to directly constitute the desired carbon content of said sintered steel part.