Source: http://www.google.com/patents/US7682704?dq=7,682,496
Timestamp: 2015-07-30 14:17:04
Document Index: 31958143

Matched Legal Cases: ['art.\n10', 'art.\n13', 'art.\n15', 'art 20', 'art 20', 'art 20', 'art 30', 'art 30', 'art 40', 'art 30']

Patent US7682704 - Microporous metal parts - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA metal injection-molding feedstock is heated and plasticized. Supercritical carbon dioxide is injected into the feedstock to form micropores when the pressure is reduced and a parts mold is filled. The micropores are retained when the green parts are debindered and sintered....http://www.google.com/patents/US7682704?utm_source=gb-gplus-sharePatent US7682704 - Microporous metal partsAdvanced Patent SearchPublication numberUS7682704 B2Publication typeGrantApplication numberUS 10/883,896Publication dateMar 23, 2010Filing dateJul 2, 2004Priority dateJul 20, 1999Fee statusPaidAlso published asDE10084853B3, DE10084853T0, DE10084853T1, US6759004, US20040250653, WO2001005542A1Publication number10883896, 883896, US 7682704 B2, US 7682704B2, US-B2-7682704, US7682704 B2, US7682704B2InventorsRatnesh K. DwivediOriginal AssigneeSouthco, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (77), Non-Patent Citations (18), Referenced by (2), Classifications (26), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetMicroporous metal parts
US 7682704 B2Abstract
1. A microporous metal part comprising:
a homogeneous interior core of sintered substantially uniformly sized metal powder particles and closed pores; and
a dense outer surface layer of said uniformly sized powder particles substantially without pores extending about said core;
wherein the closed pores are substantially uniformly sized and uniformly distributed throughout the core, and wherein said closed interior pores are substantially larger than said metal powder particles.
2. The part of claim 1, wherein said metal particles are substantially spherical.
3. The part of claim 1, wherein said closed pores are spherical.
4. The part of claim 1, wherein said closed pores are substantially uniformly sized within the range of 10-100 microns.
5. The part of claim 1, wherein said closed pores were formed with a gaseous medium.
6. The part of claim 5, wherein said part was formed using injection molding, wherein a feedstock containing said metal powder particles and said gaseous medium in a fluid state is injected into a mold held at a lower temperature and pressure, and wherein said dense surface resulted from said lower mold temperature.
7. The part of claim 1, wherein said part is a MIM product having had a green part state in which said metal powder particles and said closed pores are held in a binder matrix.
8. The part of claim 7, wherein said binder matrix includes a thermoplastic material.
9. The part of claim 1, wherein said closed pores comprise about 25-70 percent of the volume of said part.
10. The part of claim 1, wherein said closed pores are oval-shaped.
11. The part of claim 1, wherein said closed pores are 6-10 times the size of said metal powder particles.
12. A microporous metal part comprising sintered metal powder having gas formed closed interior pores and having a dense outer surface layer substantially absent of said gas formed closed interior pores, wherein the walls of said gas formed closed interior pores are formed of said sintered metal powder, and wherein said gas formed closed interior pores are substantially uniformly distributed and uniformly sized throughout the interior of said part.
13. A MIM part having a high proportion of closed interior pores and a good surface finish, comprising:
sintered metal powder substantially absent of interstitial voids;
a plurality of closed interior micropores being substantially uniform in size and distributed substantially uniformly throughout substantially the entirety of said sintered metal powder; and
a dense outer surface layer substantially absent of said closed interior micropores.
14. A microporous part comprising substantially uniformly sized sintered particles and uniformly sized closed pores, and a dense substantially uniformly thick outer surface layer of said sintered particles without said closed pores, said outer surface layer completely surrounding said sintered particles and uniformly sized closed pores, and wherein said closed pores comprise more than 25% of the volume of said part.
15. A microporous part comprising:
a homogeneous interior core of a mass of sintered powder particles and closed interior pores formed in said sintered powder particle mass; and
a dense outer surface layer of said sintered powder particle mass substantially without said closed interior pores;
wherein the closed interior pores are substantially uniformly distributed throughout the part inside the outer surface layer with the walls of said closed interior pores being of said sintered powder particle mass; and
wherein said closed interior pores are substantially larger than said powder particles. Description
This application is a Divisional of application Ser. No. 09/588,873 filed Jun. 6, 2000, now U.S. Pat. No. 6,759,004, and which claims benefit of provisional application 60/144,719 filed Jul. 20, 1999.
FIG. 7 is an SEM micrograph of the part of a comparative example in which the plasticized metal feedstock was not subjected to gas injection, shown at a high magnification, and evidencing the absence of micropores.
FIG. 8 is an SEM micrograph of the part of FIG. 3 after sintering, showing that the morphology of the microstructure remains unchanged from the green state. However, the parts do undergo approximately 18% linear shrinkage during debindering and sintering.
FIGS. 16 and 17 and are SEM micrographs of the part of FIG. 15 shown at higher magnifications.
The process of the present invention is illustrated schematically in FIG. 1, including FIGS. 1 a-d. FIG. 1 a depicts metal injection molding feedstock 10, which includes a binder phase 12, and a discrete metal powder phase 14. Physically, the feedstock 10 typically takes the form of small, uniformly sized granules that can be easily melted in the screw of an injection-molding machine.
As the MIM feedstock 10 moves along the barrel of the injection molding machine, pressure and temperature of the binder increases, and the binder melts to provide a molten slurry of metal particles dispersed in the hot, plasticized fluid binder. The hot, pressurized slurry is mixed with a pore-forming agent, preferably in the form of supercritical fluid, such as carbon dioxide or nitrogen. Gas bubbles are believed to be nucleated in the molten binder containing supercritical fluid as the pressure is decreased when the slurry is injected into a mold. As shown in FIG. 1 b, the bubbles form closed cells or pores 16 of relatively uniform size in the green part 20 shaped by the mold. The pores 16 in the green part 20 are defined by a matrix comprising the metal powder particles 14 and the now solidified binder 12.
The molded green part 20 is then released from the mold and is subjected to the debindering operation, as shown schematically by arrow B in FIG. 1. The debindering can be carried out by chemical leaching, by heating the part in a furnace to burn off the binder, or by a combination of chemical leaching and heating. As shown schematically in FIG. 1 c, the resulting debindered green part 30 retains the closed pores 16 formed in the injection molding process step, and the metal powder 14. However, the binder 12 has now been replaced by interstitial open pores 18.
As depicted schematically by step C of FIG. 1, once the binder has been leached away or burnt off, the debindered green part 30 is subjected to sintering in a furnace under appropriate conditions, to sinter together the metal powder particles 14. During the sintering process, the metal powder particles coalesce together to form a substantially continuous solid metal phase 22, and the interstitial porosity 18 is substantially eliminated. As shown schematically in FIG. 1 d, the resulting part 40 retains the closed pores 16 formed by the gas. The size of the pores has been reduced from those in the green part as a result of shrinkage. During the sintering process, the green part 30 undergoes about 15 to 25 percent shrinkage in all dimensions.
A modified injection molding machine, supplied by Arburg Inc., 125 Rockwell Rd., Newington, Conn. 06131, “Alrounder C500-250 Jubilee” had a capacity to exert a clamping force of 55 metric tonnes. The screw and barrel of the machine were modified in order to form microcellular plastics. A gas injection port was located in the middle section of the barrel through which carbon dioxide at a high pressure was injected into the plasticized metal feedstock as it traveled along the heated barrel. Average barrel temperature was maintained at approximately 190� C., while the average mold temperature was maintained at approximately 43� C. A ring mold (for producing Southco M 1-61-1 Mounting Bracket, Southco Inc. 210 N. Brinton Lake Rd., Concordville, Pa. 19331-0116, was used. In order to produce the green parts from the metal feedstock, the mold was closed and an adequate clamping force was maintained. The feedstock was fed into the front section of the barrel where it was rapidly heated to 190� C. and plasticized as it was transported to the front section of the barrel by movement of the screw. As the feedstock moved into the heated part of the barrel it melted (plasticized) and was compressed. The pressure in the molten feedstock reached approximately 21 MPa when carbon dioxide at 28 MPa was injected into the molten feedstock through fine orifices. The mass flow rate of the carbon dioxide fluid was 320 g/hr. The circumferential speed of screw rotation was maintained at 245 mm/sec. The special design of the screw aided in the dispersion and partial or full dissolution of the carbon dioxide fluid into the thermoplastic binder. Bubbles were nucleated into the feedstock as the binder underwent rapid decompression just as it was injected into the ring-mold at 110 MPa. The overall cycle time for this operation was measured at 33.5 seconds.
10.309% Ni
2.12% Mo
steel, gas-
1.35% C
4.28% Cr
4.66% Mo
Prealloyed M4
Feedstock Bulk
Side A, near nozzle
The photomicrograph in FIG. 11 shows the microstructure of the fracture surface of a tensile bar produced from Pre-alloyed 316L stainless steel feedstock after sintering, at a magnification of 50�. FIG. 11 also shows the dense skin on the surface of the tensile bar. As shown in the FIG. 11, the morphology of the pores in this sample is quite different from that in the sample produced from the Blended 4600 steel feedstock due to the difference in the rheological properties of the two feedstocks. Qualitatively, the 4600 steel appeared to contain higher volume fraction of porosity.
4-6% polyvinyl
6-8 Planet
alcohol, 1-1.5%
PIM316L-X
Aquamim PT.
difficult to inject
The Planet Polymer (9985 Businesspark Ave., Suite A, San Diego, Calif. 92131) feedstock, Aquamim PT-PIM316L-X, used a two component binder system. One of the components, polyvinyl alcohol, is water soluble while the other component polyethylene, is insoluble in water. During the solvent debindering operation, the water soluble component, polyvinyl alcohol, can be dissolved in water, leaving only polyethylene for subsequent removal by thermal debindering. It is believed that the feedstock contains between 6 to 8 weight percent binder. After the parts were injection molded under the conditions listed in Tables D1 and D2, the parts were debindered in flowing hot water between 80 to 100 degrees centigrade. During this treatment, most of the polyvinyl alcohol was removed, leaving polyethylene holding the part together. After debindering in water the parts are subjected to thermal debindering in a retort furnace in flowing hydrogen. The time-temperature schedule for this operation was: heat to 450� C. at 3� C./min, hold at 450� C. for 1 hour, heat to 950� C. at a rate of 3� C./min, hold at 950� C. for 1 hour, heat to 1360� C. at 10� C./min, hold at 1360� C. for 1 hour, and furnace cool. The debindering and sintering of the samples produced from the Planet Polymer feedstock was carried out by Taurus International.
As shown in the figures, the gas generated pores are between 25 and 70% volume of the sintered part. The smaller gas generated pores are approximately 6 to 10 times the diameter of the sintered metal powder particles.
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Why and where food and beverage processors use Mott Media. 4 pgs, Dec. 199815National Center for Excellence in Metalworking Technology-Porous Metallurgy Materials Engineering Knowledge Base-(including article from Office of Naval Research-New Class Material Based on Metal Foams Has Potential for Wide Range of Applications, Released Feb. 1, 1999).16National Center for Excellence in Metalworking Technology—Porous Metallurgy Materials Engineering Knowledge Base—(including article from Office of Naval Research—New Class Material Based on Metal Foams Has Potential for Wide Range of Applications, Released Feb. 1, 1999).17UltraMet-Ultramet Foams, Apr. 1998.18UltraMet—Ultramet Foams, Apr. 1998.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS9072811 *Sep 27, 2012Jul 7, 2015Chongqing Runze Pharmaceutical Company LimitedPreparation method for medical porous tantalum implant materialUS20140227428 *Sep 27, 2012Aug 14, 2014Chongqing Runze Pharmaceutical Company LimitedPreparation method for medical porous tantalum implant material* Cited by examinerClassifications U.S. Classification428/547, 428/613, 428/550International ClassificationB22F3/02, B22F3/11, B22F1/00, B32B5/14, B22F3/20, B22F3/22, B32B5/18Cooperative ClassificationB22F2998/00, Y10T428/12042, B22F2998/10, Y10T428/12479, B22F3/1125, B22F3/227, B22F2003/145, Y10T428/12021, B22F2003/1128, B22F2003/1106, B22F1/0059, B22F3/225European ClassificationB22F3/22D, B22F3/11D2, B22F1/00A4, B22F3/22ELegal EventsDateCodeEventDescriptionMay 25, 2010CCCertificate of correctionJul 30, 2013FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services