Dry powder metal compositions and methods of making and using the same

Abstract

The present invention provides powder metal compositions and methods of making and using the same. Powder metal compositions according to the invention are substantially dry and include a blend of base metal particles and a pressing aid. The pressing aid includes a micronized deformable solid material and a high melt point lubricating material, which have been pre-mixed or co-ground with each other. Powder metal compositions according to the present invention are particularly useful in applications where the pre-sintered density of the pressed metal part is less than or equal to about 6.9 g/cm 3 .

1 . A powder metal composition comprising:
 base metal particles; and   a pressing aid;   
     wherein the pressing aid comprises from a pre-mixed or co-ground blend of a micronized deformable solid material and a high melt point lubricating material, and 
     wherein the base metal particles, the pressing aid and any optional additives are physically mixed together to form a substantially homogeneous flowable dry powder. 
   
   
       2 . The powder metal composition according to  claim 1  wherein the pressing aid comprises from about 95% to about 60% of the micronized deformable solid material and from about 5% to about 40% of the high melt point lubricating material. 
   
   
       3 . The powder metal composition according to  claim 2  wherein the pressing aid is present in an amount of from about 0.5% to about 1.5% by weight of the powder metal composition. 
   
   
       4 . The powder metal composition according to  claim 1  wherein the micronized deformable solid material is a Fischer-Tropsch wax. 
   
   
       5 . The powder metal composition according to  claim 1  wherein the Fischer-Tropsch wax is highly oxidized polymethylene wax. 
   
   
       6 . The powder metal composition according to  claim 1  wherein the high melt point lubricating material is N,N′-ethylene bis-stearamide wax. 
   
   
       7 . The powder metal composition according to  claim 1  wherein the micronized deformable solid material and the high melt point lubricating material are co-ground together to a D 50  of less than about 40 μm. 
   
   
       8 . The powder metal composition according to  claim 1  wherein the powder metal composition does not include any zinc-containing lubricants. 
   
   
       9 . The powder metal composition according to  claim 1  wherein the base metal particles are selected from the group consisting of pure elemental metals, alloys of two or more metals and physical blends or mixtures of two or more thereof. 
   
   
       10 . The powder metal composition according to  claim 1  wherein the base metal particles are one or more selected from the group consisting of iron powders, steel powders, stainless steel powders, nickel powders, copper powders and brass powders. 
   
   
       11 . A method of forming a green compact comprising:
 providing a powder metal composition comprising base metal particles and a pressing aid, wherein the pressing aid comprises from a pre-mixed or co-ground blend of a micronized deformable solid material and a high melt point lubricating material, and wherein the base metal particles, the pressing aid and any optional additives are physically mixed together to form a substantially homogeneous flowable dry powder;   placing the powder metal composition into a mold cavity;   pressing the powder metal composition in the mold cavity to form a green compact; and   ejecting the green compact from the mold cavity.   
   
   
       12 . A method of forming a powder metal composition comprising:
 pre-mixing or co-grinding a micronized deformable solid material and a high melt point lubricating material together to form a pressing aid; and   physically mixing base metal particles with the pressing aid to form a substantially homogeneous flowable dry powder.   
   
   
       13 . The method according to  claim 12  further comprising:
 preselecting an amount of the pressing aid to be present in the powder metal composition within the range of 0.5% to about 1.5% by weight of the powder metal composition.   
   
   
       14 . The method according to  claim 13  wherein the preselected amount is determined in view of a desired lubricity and green strength of a metal part to be formed by pressing the powder metal composition to a density of less than or equal to about 6.9 g/cm 3 , wherein both the green strength and lubricity increase as the preselected amount increases.