US3838982A - Impervious sintered iron-copper metal object - Google Patents

Impervious sintered iron-copper metal object Download PDF

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Publication number
US3838982A
US3838982A US00334242A US33424273A US3838982A US 3838982 A US3838982 A US 3838982A US 00334242 A US00334242 A US 00334242A US 33424273 A US33424273 A US 33424273A US 3838982 A US3838982 A US 3838982A
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metal
particles
impervious
percent
copper
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US00334242A
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H Sanderow
K Merz
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Northrop Grumman Space and Mission Systems Corp
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TRW Inc
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Priority to US00334242A priority Critical patent/US3838982A/en
Priority to US05/485,450 priority patent/US4050933A/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17—Metallic particles coated with metal
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12014—All metal or with adjacent metals having metal particles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12181—Composite powder [e.g., coated, etc.]

Definitions

  • the coating metal fills the voids between the particles so that the object is impervious to fluids.
  • the present invention relates to a metallic object formed by powder metallurgy, and more particularly to such a metallic object which is impervious to fluids and a method of making such metallic objects.
  • a method of making metallic objects generally includes the steps of compressing together and sintering under the application of heat, particles of the metal to bond the particles together as a rigid body.
  • the metal bodies made by this technique generally have a density of 80 percent to 90 percent of the theoretical density so as to include interconnected pores or voids. This pore network permits the passage of fluids through the body so that such bodies cannot be used to makeparts where imperviousness is required, such as parts for pumps, fluid transmission systems, etc.
  • Another technique which has been developed is a controlled oxidation of the compressed metal body, generally a steam oxidation process, to fill surface voids with oxides of the metal.
  • This technique has been found to be difficult to control as to the type of oxide formed, depth of the oxide layer, surface hardness and surface quality.
  • the overall cost of making the body is increased.
  • the bodies made by this technique are lower in density in order that a substantial oxide layer can be produced in the surface pores. This leads to a lower strength of the bodies as compared to standard bodies.
  • the bodies cannot be hardened by carburizing treatment, since carbon would react with the surface layer, reducing the oxide back to the metal and opening the surface pores.
  • Still another disadvantage of this technique is that the impervious layer is localized at the surface of the body. This precludes any surface finishing or metal working operations that would break the surface oxide layer.
  • a third technique which has been developed is to impregnate the pores of the body with a plastic or a liquid metal which is not soluble with the metal of the particles which form the body.
  • this technique also has the disadvantage of extra expense because of the additional processing required.
  • this technique has been found to be difficult to control and maintain long term part-to-part uniformity.
  • a plastic is used to impregnate the pores of the body, no additional strengthening is afforded by the plastic, leaving the final product with a lower tensile strength than can be achieved without impregnation.
  • a metal is used to impregnate the pores, relatively large contents of the metal are required to achieve imperviousness.
  • metal particles which are coated with a thin film of a metal having a melting temperature lower than that of the metal of the particles. After the coated particles are compressed to form the body, they are heated to the melting temperature of the coating metal. The melted coating metal flows to fill the voids between the particles. When the body is cooled, there is provided a body of the particles bonded together with the spaces between the particles being filled with the coating metal to provide an impervious body.
  • the drawing is an enlarged sectional view of a part of a metal body of the present invention.
  • the metal body of the present invention comprises particles 12 of a desired metal, such as iron.
  • a desired metal such as iron.
  • Each of the particles 12 is completely surrounded by a thin layer 14 of a metal, such as copper, having a melting temperature lower than the melting temperature of the metal of the particles 12.
  • the iron particles bond together by solid state diffusion while the layer 14 is molten and fills the voids between the particles 12.
  • the metal layer 14 filling most voids between the particles 12, renders the body 10 impervious to the flow of fluid through the body 10 by eliminating interconnected voids.
  • suitable metal bodies 10 can be obtained with the metal layer 14 being present in the amount of 12 to 16 percent by weight, up to 30 percent by weight of the metal layer 14 can also be used.
  • the individual metal particles 12 are first coated with the metal layer 14. This is preferably done by a chemical displacement process.
  • a 12 percent copper on iron particle can be made by starting with l00 mesh iron particles and an aqueous plating solution of CuSO .5l-I O. The amount of the copper sulfate solution is calculated to provide 12 percent copper in the bath. The solution is maintained at room temperature and a pH of 3 with H SO additions. The iron powder used is introduced into the solution, rapidly stirred for a period of 3 to 10 minutes, and removed from the solution. The coated powder is then washed in slightly acidified water and vacuum dried.
  • the coated particles are then mixed together with graphite (0.5 to 1.0 percent) and a lubricant such as zinc stearate (0.75 percent).
  • the graphite has been found to reduce the solubility of the copper in the iron. This leaves more of the copper to fill the pores or voids and make a more dense body.
  • the lubricant helps in the compacting of the body.
  • a charge of the coated particles is then compacted at a pressure of 35-50 tons per square inch and sintered for about 30 minutes at 2,050F in dissociated ammonia. The compacting presses the particles close together. The sintering causes the metal layer 14 to melt. The liquid metal flows and fills the voids between the particles. When the body cools, the metal solidifies and forms the impervious body 10.
  • the body Since the body is made entirely of metal and does not contain interconnecting voids extending therethrough, it can be surface hardened by carburization without destroying the imperviousness of the body. Also, the body can be surface ground, punched, reamed or otherwise machined without affecting the imperviousness of the body. By making the body of the coated metal particles, the impervious body can be made by a standard compression-sintering operation so as to maintain a low cost for making the body.
  • An impervious metal body comprising a plurality of iron powder particles bonded together, each of said particles being coated with a layer of copper, with the copper layer substantially filling the spaces between the particles so that the body is impervious, the body including from about 12% to about 30% by weight of copper.
  • a metal body in accordance with claim ll including carbon dispersed in the iron particles of the body.
  • a metal body in accordance with claim 3 including between 0.5 percent and 1.0 percent by weight of carbon dispersed in the iron particles of the body.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)

Abstract

A metallic object formed of metal particles compressed together to form a rigid object. Each of the metal particles is coated with a metal having a melting temperature lower than that of the metal of the particles. The coating metal fills the voids between the particles so that the object is impervious to fluids.

Description

States atet Sanderow et al.
[ Oct. 11,1974
TMPERVIOUS SINTERED IRON-COPPER METAL OBJECT Inventors: Howard I. Sander-ow, Cherry Hill,
N.J.; Kenneth M. Merz, Malvern, Pa.
Assignee: TRW Inc., Cleveland, Ohio Filed: Feb. 21, 1973 Appl. No.: 334,242
US. Cl 29/1825, 29/182, 75/212, 75/226 Int. Cl B221 l/00 Field of Search 75/212, 226; 29/1825, 29/182 References Cited UNITED STATES PATENTS 9/1952 Drapeau et a1. 75/212 3,142,894 8/1964 Ross et al. 75/212 3,520,680 7/1970 Orlemann 75/212 FOREIGN PATENTS OR APPLICATIONS 1,123,685 8/1968 Great Britain 75/212 779,969 7/1957 Great Britain 75/212 3,717,106 10/1962 Japan 75/212 Primary Examiner-Carl D. Quarforth Assistant Examiner-B. Hunt Attorney, Agent, or Firm-Jacob Trachtman 57 ABSTRACT A metallic object formed of metal particles compressed together to form a rigid object. Each of the e al par s s rqatedtw t h a metal ayingatn ia t.
temperature lower than that of the metal of the particles. The coating metal fills the voids between the particles so that the object is impervious to fluids.
4 Claims, 1 Drawing Figure PATENIED BET i 74 IMPERVIOUS SINTERED IRON-COPPER METAL OBJECT The present invention relates to a metallic object formed by powder metallurgy, and more particularly to such a metallic object which is impervious to fluids and a method of making such metallic objects.
A method of making metallic objects, known as powdered metallurgy, generally includes the steps of compressing together and sintering under the application of heat, particles of the metal to bond the particles together as a rigid body. The metal bodies made by this technique generally have a density of 80 percent to 90 percent of the theoretical density so as to include interconnected pores or voids. This pore network permits the passage of fluids through the body so that such bodies cannot be used to makeparts where imperviousness is required, such as parts for pumps, fluid transmission systems, etc.
Various techniques have been developed to form an impervious metallic body by powdered metallurgy. One technique is to raise the finished product density to achieve non-interconnected porosity. However, this technique requires large presses and high temperature sintering treatments. Also, it entails stringent process controls and numerous quality control and final part inspection operations. All of these requirements makes this technique very costly to carry out.
Another technique which has been developed is a controlled oxidation of the compressed metal body, generally a steam oxidation process, to fill surface voids with oxides of the metal. This technique has been found to be difficult to control as to the type of oxide formed, depth of the oxide layer, surface hardness and surface quality. Also, since it requires a secondary operation after the standard powdered metallurgy processing, the overall cost of making the body is increased. In addition, the bodies made by this technique are lower in density in order that a substantial oxide layer can be produced in the surface pores. This leads to a lower strength of the bodies as compared to standard bodies. Similarly, the bodies cannot be hardened by carburizing treatment, since carbon would react with the surface layer, reducing the oxide back to the metal and opening the surface pores. Still another disadvantage of this technique is that the impervious layer is localized at the surface of the body. This precludes any surface finishing or metal working operations that would break the surface oxide layer.
A third technique which has been developed is to impregnate the pores of the body with a plastic or a liquid metal which is not soluble with the metal of the particles which form the body. However, this technique also has the disadvantage of extra expense because of the additional processing required. Also, this technique has been found to be difficult to control and maintain long term part-to-part uniformity. When a plastic is used to impregnate the pores of the body, no additional strengthening is afforded by the plastic, leaving the final product with a lower tensile strength than can be achieved without impregnation. When a metal is used to impregnate the pores, relatively large contents of the metal are required to achieve imperviousness.
It is therefore an object of the present invention to provide a novel impervious metal body made by powdered metallurgy.
It is another object of the present invention to provide an impervious metal body made by powdered metallurgy which can be surface hardened without loosing imperviousness.
It is a further object of the present invention to provide a novel method of making an impervious metal body by powdered metallurgy.
It is still a further object of the present invention to provide a method of making a body by powdered metallurgy which provides imperviousness during the compression-sintering operation.
Other objects will appear hereinafter.
These objects are achieved by using metal particles which are coated with a thin film of a metal having a melting temperature lower than that of the metal of the particles. After the coated particles are compressed to form the body, they are heated to the melting temperature of the coating metal. The melted coating metal flows to fill the voids between the particles. When the body is cooled, there is provided a body of the particles bonded together with the spaces between the particles being filled with the coating metal to provide an impervious body.
The drawing is an enlarged sectional view of a part of a metal body of the present invention.
The metal body of the present invention, generally designated as 10, comprises particles 12 of a desired metal, such as iron. Each of the particles 12 is completely surrounded by a thin layer 14 of a metal, such as copper, having a melting temperature lower than the melting temperature of the metal of the particles 12. When the particles 12 are compressed together and sintered, the iron particles bond together by solid state diffusion while the layer 14 is molten and fills the voids between the particles 12. The metal layer 14 filling most voids between the particles 12, renders the body 10 impervious to the flow of fluid through the body 10 by eliminating interconnected voids. There must be at least 12 percent by weight of the metal layer 14. Although suitable metal bodies 10 can be obtained with the metal layer 14 being present in the amount of 12 to 16 percent by weight, up to 30 percent by weight of the metal layer 14 can also be used.
To make the metal body 10, the individual metal particles 12 are first coated with the metal layer 14. This is preferably done by a chemical displacement process. For example, a 12 percent copper on iron particle can be made by starting with l00 mesh iron particles and an aqueous plating solution of CuSO .5l-I O. The amount of the copper sulfate solution is calculated to provide 12 percent copper in the bath. The solution is maintained at room temperature and a pH of 3 with H SO additions. The iron powder used is introduced into the solution, rapidly stirred for a period of 3 to 10 minutes, and removed from the solution. The coated powder is then washed in slightly acidified water and vacuum dried.
The coated particles are then mixed together with graphite (0.5 to 1.0 percent) and a lubricant such as zinc stearate (0.75 percent). The graphite has been found to reduce the solubility of the copper in the iron. This leaves more of the copper to fill the pores or voids and make a more dense body. The lubricant helps in the compacting of the body. A charge of the coated particles is then compacted at a pressure of 35-50 tons per square inch and sintered for about 30 minutes at 2,050F in dissociated ammonia. The compacting presses the particles close together. The sintering causes the metal layer 14 to melt. The liquid metal flows and fills the voids between the particles. When the body cools, the metal solidifies and forms the impervious body 10.
Since the body is made entirely of metal and does not contain interconnecting voids extending therethrough, it can be surface hardened by carburization without destroying the imperviousness of the body. Also, the body can be surface ground, punched, reamed or otherwise machined without affecting the imperviousness of the body. By making the body of the coated metal particles, the impervious body can be made by a standard compression-sintering operation so as to maintain a low cost for making the body.
What is claimed is:
1. An impervious metal body comprising a plurality of iron powder particles bonded together, each of said particles being coated with a layer of copper, with the copper layer substantially filling the spaces between the particles so that the body is impervious, the body including from about 12% to about 30% by weight of copper.
2. A metal body in accordance with claim 1 in which the body includes between 12 percent and 16 percent by weight of copper.
3. A metal body in accordance with claim ll including carbon dispersed in the iron particles of the body.
4. A metal body in accordance with claim 3 including between 0.5 percent and 1.0 percent by weight of carbon dispersed in the iron particles of the body.

Claims (4)

1. AN IMPERVIOUS METAL BODY COMPRISING A PLURALITY OF IRON POWDER PARTICLES BONDED TOGETHER, EACH OS SAID PARTICLES BEING COATED WITH A LAYER OF COPPER, WITH THE COPPER LAYER SUBSTANTIALLY FILLING THE SPACES BETWEEN THE PARTICLES SO THAT THE BODY IS IMPERVIOUS, THE BODY INCLUDING FROM ABOUT 12% TO ABOUT 30% BY WEIGHT OF COPPER.
2. A metal body in accordance with claim 1 in which the body includes between 12 percent and 16 percent by weight of copper.
3. A metal body in accordance with claim 1 including carbon dispersed in the iron particles of the body.
4. A metal body in accordance with claim 3 including between 0.5 percent and 1.0 percent by weight of carbon dispersed in the iron particles of the body.
US00334242A 1973-02-21 1973-02-21 Impervious sintered iron-copper metal object Expired - Lifetime US3838982A (en)

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US05/485,450 US4050933A (en) 1973-02-21 1974-07-03 Impervious metal object and method of making the same

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5159708A (en) * 1974-11-22 1976-05-25 Dowa Mining Co
JPS51136508A (en) * 1975-05-21 1976-11-26 Akebono Brake Ind Co Ltd Pro cess for production of reinforced sintered friction material
US4011077A (en) * 1975-06-06 1977-03-08 Ford Motor Company Copper coated, iron-carbon eutectic alloy powders
US4050933A (en) * 1973-02-21 1977-09-27 Stanadyne, Inc. Impervious metal object and method of making the same
US4129443A (en) * 1975-06-06 1978-12-12 Ford Motor Company Method for improving the sinterability of iron powder derived from comminuted scrap metal
US4227928A (en) * 1978-05-01 1980-10-14 Kennecott Copper Corporation Copper-boron carbide composite particle and method for its production
US4323395A (en) * 1980-05-08 1982-04-06 Li Chou H Powder metallurgy process and product
US4648437A (en) * 1984-01-12 1987-03-10 Olin Corporation Method for producing a metal alloy strip
US4663242A (en) * 1983-05-27 1987-05-05 Olin Corporation Method for producing a metal alloy strip
US4833040A (en) * 1987-04-20 1989-05-23 Trw Inc. Oxidation resistant fine metal powder
US4939032A (en) * 1987-06-25 1990-07-03 Aluminum Company Of America Composite materials having improved fracture toughness
US4975333A (en) * 1989-03-15 1990-12-04 Hoeganaes Corporation Metal coatings on metal powders
GB2242912A (en) * 1989-08-29 1991-10-16 Hitachi Powdered Metals Sintered coated metal powder
US5240742A (en) * 1991-03-25 1993-08-31 Hoeganaes Corporation Method of producing metal coatings on metal powders
US20050003192A1 (en) * 1996-08-29 2005-01-06 Katsuto Nakatsuka Consolidated material of coated powders and process for producing the same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610118A (en) * 1948-06-17 1952-09-09 Glidden Co Sintered iron bodies and processes therefor
GB779969A (en) * 1955-03-04 1957-07-24 American Chem Paint Co Improvements in or relating to powder metallurgy
US3142894A (en) * 1962-08-31 1964-08-04 Chrysler Corp Sintered metal article and method of making same
GB1123685A (en) * 1965-03-17 1968-08-14 Birmingham Small Arms Co Ltd Improvements in or relating to metal powders and articles produced therefrom
US3520680A (en) * 1968-07-22 1970-07-14 Pfizer & Co C Process of producing steel

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610118A (en) * 1948-06-17 1952-09-09 Glidden Co Sintered iron bodies and processes therefor
GB779969A (en) * 1955-03-04 1957-07-24 American Chem Paint Co Improvements in or relating to powder metallurgy
US3142894A (en) * 1962-08-31 1964-08-04 Chrysler Corp Sintered metal article and method of making same
GB1123685A (en) * 1965-03-17 1968-08-14 Birmingham Small Arms Co Ltd Improvements in or relating to metal powders and articles produced therefrom
US3520680A (en) * 1968-07-22 1970-07-14 Pfizer & Co C Process of producing steel

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4050933A (en) * 1973-02-21 1977-09-27 Stanadyne, Inc. Impervious metal object and method of making the same
JPS5159708A (en) * 1974-11-22 1976-05-25 Dowa Mining Co
JPS5538019B2 (en) * 1974-11-22 1980-10-01
JPS51136508A (en) * 1975-05-21 1976-11-26 Akebono Brake Ind Co Ltd Pro cess for production of reinforced sintered friction material
JPS5521806B2 (en) * 1975-05-21 1980-06-12
US4011077A (en) * 1975-06-06 1977-03-08 Ford Motor Company Copper coated, iron-carbon eutectic alloy powders
US4129443A (en) * 1975-06-06 1978-12-12 Ford Motor Company Method for improving the sinterability of iron powder derived from comminuted scrap metal
US4227928A (en) * 1978-05-01 1980-10-14 Kennecott Copper Corporation Copper-boron carbide composite particle and method for its production
US4323395A (en) * 1980-05-08 1982-04-06 Li Chou H Powder metallurgy process and product
US4663242A (en) * 1983-05-27 1987-05-05 Olin Corporation Method for producing a metal alloy strip
US4648437A (en) * 1984-01-12 1987-03-10 Olin Corporation Method for producing a metal alloy strip
US4833040A (en) * 1987-04-20 1989-05-23 Trw Inc. Oxidation resistant fine metal powder
US4939032A (en) * 1987-06-25 1990-07-03 Aluminum Company Of America Composite materials having improved fracture toughness
US4975333A (en) * 1989-03-15 1990-12-04 Hoeganaes Corporation Metal coatings on metal powders
GB2242912A (en) * 1989-08-29 1991-10-16 Hitachi Powdered Metals Sintered coated metal powder
GB2242912B (en) * 1989-08-29 1993-10-27 Hitachi Powdered Metals Method for making sintered parts
US5240742A (en) * 1991-03-25 1993-08-31 Hoeganaes Corporation Method of producing metal coatings on metal powders
US20050003192A1 (en) * 1996-08-29 2005-01-06 Katsuto Nakatsuka Consolidated material of coated powders and process for producing the same
US6863979B2 (en) * 1996-08-29 2005-03-08 Nittetsu Mining Co., Ltd. Consolidated material of coated powders and process for producing same

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