Method for preparing high performance ferrous materials

The present invention provides a method for making metal parts from metal powder compositions comprising an iron base metal powder and an amide lubricant. The method comprises the steps of compacting said composition, pre-sintering the compacted composition, compacting the compacted and pre-sintered composition, and sintering the recompacted composition. The metal parts have improved physical and mechanical properties.

If you were to search for Method for preparing high performance ferrous materials using relaxed search criteria, these patents would come up:

What is claimed is:

1. A method of making a sintered metal part from a metal powder composition comprising an iron-based metal powder and an amide lubricant, the metal powder compositioncontaining carbon in an amount from 0.3 to 0.8 weight percent, the method comprising the steps of:

(a) compacting the composition at a temperature within the range of from 212.degree. to 350.degree. F.;

(b) pre-sintering the compacted composition at a temperature within the range of from 1350.degree. to 1580.degree. F.;

(b) lubricating the pre-sintered part with a lubricant;

(c) recompacting the compacted and pre-sintered composition; and

(d) sintering the recompacted composition at a temperature of 2000.degree. to 2400.degree. F. in a N.sub.2 atmosphere incorporating up to about 75% hydrogen by volume.

2. The method according to claim 1, wherein the recompacted, sintered part produced in step (e) has an ultimate tensile strength greater than 150,000 psi.

3. The method according to claim 1, wherein the recompacted, sintered part produced in step (e) has an impact energy of greater than 20 ft-lbf.

4. The method according to claim 1, wherein the recompacted, sintered part produced in step (e) has a traverse rupture strength of greater than 250,000 psi.

5. The method according to claim 1, wherein said iron based metal powder comprises at least one alloying element selected from the group consisting of molybdenum, manganese, magnesium, chromium, silicon, copper, nickel, gold, chromium, vanadium,columbium, carbon, graphite, phosphorus, and aluminum.

6. The method according to claim 5, wherein the iron based powder comprises pre-alloyed iron.

7. The method according to claim 6, wherein the pre-alloyed iron based powder is an atomized powder of iron containing dissolved molybdenum in an amount of from about 0.5-2.5 weight percent as an alloying element.

8. The method according to claim 6, wherein the iron-based powder is an admixture of two powders of pre-alloyed iron, the first powder containing about 0.5 to about 3 weight percent molybdenum and the second powder containing at least 0.15weight percent carbon and at least about 25 weight percent of a transition element selected from the group consisting of chromium, manganese, vanadium, columbium, and combinations thereof.

9. The method according to claim 6, wherein the pre-alloyed iron-based powder comprises iron that has been pre-alloyed with about 0.5-0.6 weight percent molybdenum, from about 1.5-2.0 weight percent nickel, and from about 0.1-0.25 weight percentmanganese.

10. The method according to claim 1, wherein said amide is present in an amount up to about 15% by weight of said composition.

11. The method according to claim 1, wherein said amide is the reaction product of about 10-30 weight percent of a C.sub.6 -C.sub.12 linear dicarboxylic acid, about 10-30 weight percent of a C.sub.10 -C.sub.22 monocarboxylic acid, and about40-80 weight percent of a diamine having the formula (CH.sub.2).sub.x (NH.sub.2).sub.2 where x is from 2 to about 6.

12. The method according to claim 11, wherein the monocarboxylic acid is stearic acid.

13. The method according to claim 11, wherein the dicarboxylic acid is sebacic acid.

14. The method according to claim 11, wherein the diamine is ethylene diamine.

15. The method according to claim 11, wherein the monocarboxylic acid is stearic acid, the dicarboxylic acid is sebacic acid and the diamine is ethylene diamine; and wherein the amide lubricant has a melting point range that is greater than atleast about 300.degree. F.

16. The method according to claim 10, wherein the lubricant is present in an amount of from 0.1 to about 1 weight percent.

17. The method according to claim 10, wherein the amide lubricant comprises at least 65 percent by weight diamides.

18. The method according to claim 5, wherein the metal powder has 4% by weight of nickel.

19. The method according to claim 1, wherein the pre-sintering step in step (b) is conducted at a temperature from about 60% to about 75% of the final sintering temperature in step (e).

20. The method according to claim 1, wherein the sintering step in step (e) is conducted at a temperature of about 2200.degree. to about 2400.degree. F.

21. The method according to claim 1, wherein the sintering step in step (e) is conducted at a temperature of about 2200.degree. to about 2300.degree. F.

22. The method according to claim 1, wherein the compacting step in step (a) is conducted at a temperature of from about 285.degree. to about 350.degree. F.

23. The method according to claim 1, wherein the compacting step in step (a) is conducted at a pressure of from about 3 to about 100 tsi.

24. The method according to claim 1, wherein the compacting step in step (a) is conducted at a pressure of from about 35 to about 60 tsi.