Low cost bronze powder for high performance bearings
The present invention provides a new process for making a low cost powder for the manufacture of high performance bearings. Improved powders and sintered parts (e.g., bearings) are also provided. The powders of the present invention are formed by blending iron powder with fine cuprous oxide powder and elemental tin powder. The blended powders are then thermally treated under a reducing atmosphere to form a sintered cake, which is milled to a powder.
1 . A process for making a bronze powder comprising the following steps:
a. blending an iron powder with a cuprous oxide powder and a tin powder to form a blended powder,
b. thermally treating the blended powder in a reducing atmosphere at a temperature between about 600° F. and about 1700° F. to form a sintered cake, and
c. milling the sintered cake to form the bronze powder.
2 . The process of claim 1 which further comprises screening the bronze powder to a desired particle size fraction.
3 . The process of claim 1 , wherein the iron powder is sponge, atomized, or electrolytic iron powder.
4 . The process of claim 3 , wherein the iron powder is sponge iron powder.
5 . The process of claim 1 , wherein the iron powder has a particle size between about −325 mesh (<44 μm) and about −60 mesh (<250 μm).
6 . The process of claim 5 , wherein the iron powder has a particle size of approximately −150 mesh (<106 μm).
7 . The process of claim 1 , wherein the cuprous oxide powder has a median particle size (D 50 ) below about 50 μm.
8 . The process of claim 7 , wherein the cuprous oxide powder has a median particle size (D 50 ) of about 10-25 μm.
9 . The process of claim 1 , wherein the tin powder has a median particle size (D 50 ) below about 20 μm.
10 . The process of claim 9 , wherein the tin powder has a median particle size (D 50 ) of about 3-12 μm.
11 . The process of claim 1 , wherein the thermal treatment temperature is between about 800° F. to about 1600° F.
12 . The process of claim 11 , wherein the thermal treatment temperature is about 1300° F.
13 . The process of claim 1 , wherein the reducing atmosphere is pure hydrogen or a nitrogen/hydrogen mixture.
14 . A bronze powder made by the process of claim 1 .
15 . The powder of claim 14 , wherein the bronze powder has a particle size below about −20 mesh.
16 . The powder of claim 15 , wherein the bronze powder has a particle size of about −60 mesh.
17 . The powder of claim 14 , wherein the bronze powder has a copper content of about 10-70 wt. %.
18 . The powder of claim 17 , wherein the bronze powder has a copper content of about 20-50 wt. %.
19 . The powder of claim 14 , wherein the bronze powder has a tin content of about 1-7 wt. %.
20 . The powder of claim 19 , wherein the bronze powder has a tin content of about 2-5 wt. %.
21 . The powder of claim 14 , wherein the bronze powder is blended with 0.25 wt. % to 1.00 wt. % powdered lubricant.
22 . The powder of claim 21 , wherein the lubricant is a stearate or wax.
23 . A sintered part comprising a powder made by the process of claim 1 .
24 . The sintered part of claim 23 , wherein the part is a bearing.
25 . The sintered part of claim 24 , wherein the bearing is a oil impregnated self lubricating bearing.
26 . A composite powder made by mixing the powder of claim 1 with other alloying elements, plastics, solid lubricants, ceramics, or the like.
27 . An article made from the powder of claim 26 .
28 . A sintered part having 10 to 70 wt. % copper, 1 to 7 wt. % tin and 23 to 89 wt. % iron, wherein a substantial portion of pores present in the sintered part have dimensions less than 100 μm, and wherein the sintered part has a radial crush strength higher than 30,000 psi at a nominal sintered density of 6.3 g/cm 3 .