PROCESS FOR MANUFACTURING HIGH DENSITY ARTICLES FROM STAINLESS STEEL POWDER

• US 20190321891A1
• Filed: 05/10/2018
• Published: 10/24/2019
• Est. Priority Date: 05/17/2017
• Status: Abandoned Application

• Current Assignee: Keystone Powdered Metal Co. (Sumitomo Corporation)
• Original Assignee: Keystone Powdered Metal Co. (Sumitomo Corporation)
• Inventors: Anderson, Gary L., D'Aurora, Zachary, Imbrogno, Peter G., Bauer, Kevin A.
• Application Number:
  US15/976,544
• Publication Number:
  US 20190321891A1
• Time in Patent Office: Days
• CPC Class Codes: B22F 2201/01 Reducing atmosphere
• CPC Class Codes: B22F 2201/10 Inert gases
• CPC Class Codes: B22F 2201/20 Use of vacuum
• CPC Class Codes: B22F 2301/35 Iron
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/02 Compacting only
• CPC Class Codes: B22F 3/10 Sintering only
• CPC Class Codes: B22F 3/1007 Atmosphere B22F3/1021 takes precedence
• CPC Class Codes: B22F 3/17 by forging
• CPC Class Codes: B22F 5/08 of toothed articles, e.g. gear wheels; of cam discs
• CPC Class Codes: B22F 5/106 Tube or ring forms
• CPC Class Codes: C22C 2202/02 Magnetic
• CPC Class Codes: C22C 33/02 by powder metallurgy working metallic powder B22F
• CPC Class Codes: F02D 41/0097 using means for generating speed signals
• CPC Class Codes: F02P 7/067 Electromagnetic pick-up devices , e.g. providing induced current in a coil
• CPC Class Codes: F02P 7/0675 with variable reluctance, e.g. depending on the shape of a tooth
• CPC Class Codes: G01P 3/481 of pulse signals
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors
• CPC Class Codes: H01F 1/22 pressed, sintered, or bound together
• CPC Class Codes: H01F 41/0246 : Manufacturing of magnetic circuits by moulding or by pressing powder magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36

Abstract

It has been found that high density articles having improved strength, corrosion resistance, better durability, and decent magnetic characteristics can be manufactured from a ferritic stainless steel powder using a novel method. This technique is especially beneficial in manufacturing parts, such as, reluctor rings, tone wheels, trigger wheels, pump impeller blades, and EGR valves, in large quantities. This method involves (1) compacting the ferritic stainless steel powder in a mold into a green article, (2) sintering the green article at an elevated temperature under vacuum or a reducing atmosphere to produce a sintered article, and (3) forging the sintered article under a reducing or an inert gas atmosphere to a density of greater than 7.5 g/cc in the presence of a graphite free lubricant to produce the high density article.

Claims

1. A method for making a high density article from ferritic stainless steel powder wherein said article has good corrosion resistance, higher strength, and decent magnetic properties, said method comprising (1) compacting the ferritic stainless steel powder in a mold into a green article, (2) sintering the green article at an elevated temperature under vacuum or a reducing atmosphere to produce a sintered article, and (3) forging the sintered article under a reducing or an inert gas atmosphere to a density of greater than 7.5 g/cc in the presence of a graphite free lubricant to produce the high density article.

2. The method of claim 1 wherein the lubricant is a glass based forging lubricant.

3. The method of claim 1 wherein the lubricant is boron nitride.

4. The method of claim 1 wherein the reducing gas is hydrogen.

5. The method of claim 1 wherein the inert gas is a Nobel gas selected from the group consisting of helium, neon, and argon.

6. The method of claim 3 wherein the boron nitride is in hexagonal form and a density of about 2.1 g/cm³.

7. The method of claim 1 wherein the sintering step is carried out under vacuum.

8. A reluctor ring having improved strength, good corrosion resistance, better durability, and decent magnetic characteristics which is comprised of a wheel having an inside and an outside diameter, wherein a multitude of straight sided teeth are on the outside diameter of the wheel and wherein the reluctor ring is comprised of powder forged ferritic stainless steel having a density of at least 7.5 g/cc.

9. The reluctor ring of claim 8 wherein the reluctor ring is adapted for use in a sensor system for an antilock brake system.

10. The reluctor ring of claim 8 wherein the reluctor ring is adapted for use in a distributor-less ignition system.

11. A tone wheel which is comprised of a body having a convex outer surface with a plurality of surface features arranged annularly thereon about a central axis and a concave inner surface, wherein the tone wheel is comprised of powder forged ferritic stainless steel having a density of at least 7.5 g/cc.

12. The tone wheel of claim 11 wherein the tone wheel includes a plurality of annular flanges which extend inwardly from the inner surface toward the central axis.

13. The tone wheel of claim 12 wherein each flange has a mating surface for contacting a carrier with the mating surface being axially offset from the inner surface of the body.

14. The tone wheel of claim 13 wherein the surface features are ribs.

15. The tone wheel of claim 13 wherein the surface features are ridges.

16. The tone wheel of claim 13 wherein the surface features are raised strips.

17. A powder forged ferritic stainless steel part which is comprised of powder forged ferritic stainless steel which includes a performance enhancing agent selected from the group consisting of solid internal lubricants and wear resistant particles.

18. The part as specified in claim 17 wherein the solid internal lubricant is molybdenum disulfide and wherein the wear resistant particles are glass particles or ceramic particles.

19. The powder forged ferritic stainless steel part of claim 17 wherein the part is trigger wheel.

20. The powder forged ferritic stainless steel part of claim 17 wherein the part is pump impeller blade.