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US2851381A - Simultaneous infiltrating and obtaining a brazable surface - Google Patents

Simultaneous infiltrating and obtaining a brazable surface Download PDF

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Publication number
US2851381A
US2851381A US499517A US49951755A US2851381A US 2851381 A US2851381 A US 2851381A US 499517 A US499517 A US 499517A US 49951755 A US49951755 A US 49951755A US 2851381 A US2851381 A US 2851381A
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compact
silver
infiltrating
infiltrant
pressed
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US499517A
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Norman S Hoyer
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Gibson Electric Co
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Gibson Electric Co
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/021—Composite material
    • H01H1/023—Composite material having a noble metal as the basic material
    • H01H1/0233—Composite material having a noble metal as the basic material and containing carbides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/021—Composite material
    • H01H1/023—Composite material having a noble metal as the basic material
    • H01H1/0231—Composite material having a noble metal as the basic material provided with a solder layer
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/923—Physical dimension
    • Y10S428/924—Composite
    • Y10S428/925—Relative dimension specified
    • 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
    • Y10T428/12153—Interconnected void structure [e.g., permeable, etc.]

Definitions

  • My invention relates to improvements in infiltrated type powdered metals and more particularly to an improved method for manufacturing electrical contacts.
  • the improvement consists of preparing one surface of such a contact so that it is more easily and readily welded or silver soldered to its supporting arm.
  • the conventional steps in one method of manufacture of electrical contact materials comprising a refractory metal such as tungsten, molybdenum, or their carbides and a lower melting point conducting metal such as silver are as follows:
  • the refractory powders are either pressed alone or mixed with a comparatively small percentage of silver before pressing.
  • the pressed or green compact is then sintered in a furnace using a hydrogen or other reducing atmosphere.
  • the sintering temperature may be either above or below the melting point of the lower melting point constituent.
  • porosity is calculated and from this weight of silver or copper (whichever the case may be) that is to be infiltrated.
  • One of the more common methods of infiltrating a porous compact is to place the infiltrant on top of the compact, the compact being generally supported by a graphite boat.
  • the infiltrating temperature is somewhat above the melting point of the infiltrant.
  • an amount of infiltrant in excess of that which can be absorbed by the compact is used.
  • a small amount of excess infiltrant generally remains in the form of a lump or mound on the surface of the infiltrated compact.
  • Such residual infiltrant serves no useful purpose and, the usual procedure is to remove this lump and then solder-flush the surface of the contact which is to be welded or silversoldered to a contact carrying arm.
  • the excess infiltrant is spread over the surface of the compact, and the more uniform the percentage of is determined the coating of infiltrant which results provides a surface which is more readily welded or silver-soldered to the contact arm of the switch, circuit breaker or other electrical device to which the contact is to be secured.
  • my invention involves, in the infiltration of the compacted refractory, the application, to the infiltrat ing surface thereof, of a small amount of a powdered metal which in effect acts as a wetting agent for the surface of the compact and allows excess infiltrant to spread evenly over the surface.
  • Such a Wetting agent may alleviate or even eliminate the need for applying a solder-flush or other coating to the external surface of the infiltrated compact in order to make it readily weldable or more easily silver-soldered to another metallic surface. Even if a solder-flush is required, it may eliminate the necessity of removing excess silver before solder-flushing. In any event, it has a marked tendency to cause the infiltrant to spread evenly over the infiltrating surface without leaving unsilvered areas on the said surface. This is particularly important in the case of electrical contacts wherein it is necessary to obtain a secure joint between the contact and the contact carrying arm of the particular switch or circuit breaker to which the contact is attached.
  • the excess infiltrant is spread evenly over the surface of the refractory and in itself provides a surface which may be readily welded or silver-soldered when the contacts are attached to a metallic member.
  • the powder which I used in my invention is of approximately 200 mesh fineness but may vary generally between and 300 mesh. Although I prefer to use nickel, cobalt and iron may also be employed.
  • this finely divided powder prior to applying the infiltrant to the pressed and sintered compact may eliminate the necessity of using serrations or corrugations on the surface of the contact for the purpose of spreading the excess infiltrant. This is advantageous, particularly in those instances where serrated contacts are not acceptable. It should be noted, however, that my invention may also be used in connection with serrated contacts, if desired.
  • the electrical contacts to which I refer generally comprise tungsten, molybdenum, tungsten carbide, molybdenum carbide or mixtures thereof.
  • the infiltrating material is normally either copper or silver, generally present in amounts of twenty to sixty percent.
  • the nickel or other finely divided powder is spread over the surface of the compact to be infiltrated in any suitable fashion, such as by the use of a small artists type brush.
  • the nickel powder may be mixed with CCL; or other volatile vehicles so that the application is made more quickly and easily. This allows generally for a more uniform distribution of the nickel.
  • the vehicle volatizes quickly and does not interfere in any way with the subsequent infiltration.
  • a spraying technique may be used if desired.
  • the amount of powder used for any given compact generally is one percent of the weight of the infiltrant, but may vary generally between 0.2 and 2 percent.
  • the powder does not impede the infiltrant from permeating into the interconnected pores of the compact. It causes a wetting of the refractory surface which makes the infiltrant, silver or copper, spread more easily and cover that inch.
  • the pressed compacts are 'ducing atmosphere maintained Specific example A mixture of silver and tungsten powders containing about grams of tungsten and 5 grams of silver are intimately mixed.
  • the powders are then pressed in powder metal presses using a pressure of tons per square then sintered in a reat 2000 F. for about minutes.
  • the sintered compact is then infiltrated with silver, using about 6 grams of silver, at about 2000 F. This is suflicient to infiltrate the pores of the compact.
  • an electrical contact comprising a pressed and sintered refractory compact from the group consisting of tungsten, molybdenum and carbides thereof and infiltrated with from 20 to percent, by weight, of a lower melting point conductive metal from the group consisting of copper and silver, the improvement which comprises applying to only the infiltrating surface of the pressed and sintered refractory compact 0.2 to 2 percent by weight of a finely divided metallic wetting agent from the group consisting of iron, cobalt and nickel, and subsequently impregnating the said compact through the said coated infiltrating surface with the said lower.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Powder Metallurgy (AREA)
  • Contacts (AREA)

Description

improved and more economical nite States atent 2,851,381 Patented Sept. 9, 1958 SIIVIULTANEOUS INFILTRATING AND OBTAIN- ING A BRAZABLE SURFACE Norman S. Hoyer, Pittsburgh, Pa., assignor to Gibson Electnc Company, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application April 5, 1955 Serial No. 499,517
3 Claims. (Cl. 117-227) My invention relates to improvements in infiltrated type powdered metals and more particularly to an improved method for manufacturing electrical contacts. The improvement consists of preparing one surface of such a contact so that it is more easily and readily welded or silver soldered to its supporting arm.
The conventional steps in one method of manufacture of electrical contact materials comprising a refractory metal such as tungsten, molybdenum, or their carbides and a lower melting point conducting metal such as silver are as follows:
The refractory powders are either pressed alone or mixed with a comparatively small percentage of silver before pressing. The pressed or green compact is then sintered in a furnace using a hydrogen or other reducing atmosphere. The sintering temperature may be either above or below the melting point of the lower melting point constituent. After sintering, porosity is calculated and from this weight of silver or copper (whichever the case may be) that is to be infiltrated. One of the more common methods of infiltrating a porous compact is to place the infiltrant on top of the compact, the compact being generally supported by a graphite boat. The infiltrating temperature is somewhat above the melting point of the infiltrant. To be certain of complete infiltration an amount of infiltrant in excess of that which can be absorbed by the compact, is used. Thus, a small amount of excess infiltrant generally remains in the form of a lump or mound on the surface of the infiltrated compact. Such residual infiltrant serves no useful purpose and, the usual procedure is to remove this lump and then solder-flush the surface of the contact which is to be welded or silversoldered to a contact carrying arm. I have found that by applying a small amount of a fine powder from the group consisting of iron, cobalt or nickel to the infiltrating surface of the sintered compact prior to the infiltration step, the subsequent solder-flushing step may be eliminated. In any event, the excess infiltrant is spread over the surface of the compact, and the more uniform the percentage of is determined the coating of infiltrant which results provides a surface which is more readily welded or silver-soldered to the contact arm of the switch, circuit breaker or other electrical device to which the contact is to be secured.
Accordingly, it is an object of my invention to provide a method for producing a refractory-base material having a surface which is more readily welded or silversoldered.
' It is another object of my invention to provide an method of manufacturing electrical contacts which are readily welded or silver soldered to a contact carrying means and which comprises a pressed and sintered refractory metal and a lower melting point conducting metal.
'These and other objects of my invention will become more apparent from the following description.
Essentially my invention involves, in the infiltration of the compacted refractory, the application, to the infiltrat ing surface thereof, of a small amount of a powdered metal which in effect acts as a wetting agent for the surface of the compact and allows excess infiltrant to spread evenly over the surface.
Such a Wetting agent may alleviate or even eliminate the need for applying a solder-flush or other coating to the external surface of the infiltrated compact in order to make it readily weldable or more easily silver-soldered to another metallic surface. Even if a solder-flush is required, it may eliminate the necessity of removing excess silver before solder-flushing. In any event, it has a marked tendency to cause the infiltrant to spread evenly over the infiltrating surface without leaving unsilvered areas on the said surface. This is particularly important in the case of electrical contacts wherein it is necessary to obtain a secure joint between the contact and the contact carrying arm of the particular switch or circuit breaker to which the contact is attached.
By applying a finely divided powder of iron, cobalt, or nickel to the surface of the compact to which the infiltrant is to be applied prior to the infiltration step, the excess infiltrant is spread evenly over the surface of the refractory and in itself provides a surface which may be readily welded or silver-soldered when the contacts are attached to a metallic member.
The powder which I used in my invention is of approximately 200 mesh fineness but may vary generally between and 300 mesh. Although I prefer to use nickel, cobalt and iron may also be employed.
The use of this finely divided powder prior to applying the infiltrant to the pressed and sintered compact may eliminate the necessity of using serrations or corrugations on the surface of the contact for the purpose of spreading the excess infiltrant. This is advantageous, particularly in those instances where serrated contacts are not acceptable. It should be noted, however, that my invention may also be used in connection with serrated contacts, if desired.
The electrical contacts to which I refer, generally comprise tungsten, molybdenum, tungsten carbide, molybdenum carbide or mixtures thereof. The infiltrating material is normally either copper or silver, generally present in amounts of twenty to sixty percent.
As hereinbefore stated it has been found that copper or silver type electrical contacts braze or weld more efifectively to another metallic member (such as a contact carrying arm of a circuit breaker) either when the surface has been previously solder-flushed or a coat of silver is otherwise applied thereto. The necessity for such a coating operation is eliminated by virtue of the formation of the uniform layer of the excess infiltrant resulting from the use of my novel wetting agents. Moreover, my wetting agent also assures uniform overall thickness of the contact provided that the floor of the furnace is fiat at the time of infiltration.
The nickel or other finely divided powder is spread over the surface of the compact to be infiltrated in any suitable fashion, such as by the use of a small artists type brush. The nickel powder may be mixed with CCL; or other volatile vehicles so that the application is made more quickly and easily. This allows generally for a more uniform distribution of the nickel. The vehicle volatizes quickly and does not interfere in any way with the subsequent infiltration. A spraying technique may be used if desired.
The amount of powder used for any given compact generally is one percent of the weight of the infiltrant, but may vary generally between 0.2 and 2 percent. The powder does not impede the infiltrant from permeating into the interconnected pores of the compact. It causes a wetting of the refractory surface which makes the infiltrant, silver or copper, spread more easily and cover that inch. The pressed compacts are 'ducing atmosphere maintained Specific example A mixture of silver and tungsten powders containing about grams of tungsten and 5 grams of silver are intimately mixed. The powders are then pressed in powder metal presses using a pressure of tons per square then sintered in a reat 2000 F. for about minutes. The sintered compact is then infiltrated with silver, using about 6 grams of silver, at about 2000 F. This is suflicient to infiltrate the pores of the compact.
Prior to the infiltration, .06 gram of a 200 mesh nickel powder is brushed on the surface of the sintered compact. The temperature is then raised to 2200 F. for fifteen minutes and the silver infiltrates into the compact, the surface thereof having an even layer of excess silver.
The same procedure, when followed without the addition of the nickel powder to the infiltrated surface produces a surface having a localized lump of excess silver.
In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope described herein are obvious.
Accordingly, I prefer to be bound not by the specific 4 disclosure herein, but only by the appending claims.
I claim:
1. In the manufacture of an electrical contact comprising a pressed and sintered refractory compact from the group consisting of tungsten, molybdenum and carbides thereof and infiltrated with from 20 to percent, by weight, of a lower melting point conductive metal from the group consisting of copper and silver, the improvement which comprises applying to only the infiltrating surface of the pressed and sintered refractory compact 0.2 to 2 percent by weight of a finely divided metallic wetting agent from the group consisting of iron, cobalt and nickel, and subsequently impregnating the said compact through the said coated infiltrating surface with the said lower.
melting point conductive metal, thereby causing the excess infiltrant to spread evenly over-the said surface.
2. The method as set forth in claim 1 in which the metallic wetting agent is in the form of a powder of from to 300 mesh particle size.
3. The method of claim 2 in which the powder is nickel.
References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. IN THE MANUFACTURE OF AN ELECTRICAL CONTACT COMPRISING A PRESSED AND SINTERED REFACTORY COMPACT FROM THE GROUP CONSISTING OF TUNGEN, MOLYBDENUM AND CARBIDES THEREOF, AND INFILTRATED WITH FROM 20 TO 60 PERCENT, BY WEIGHT, OF A LOWER MELTING POINT CONDUCTIVE METAL FROM THE GROUP CONSISTING OF COPPER AND SILVER, THE IMPROVEMENT WHICH COMPRISES APPYING TO ONLY THE INFILTRATING SURFACE OF THE PRESSED AND SINTERED REFRACTORY COMPACT 0.2 TO 2 PERCENT BY WEIGHT OF A FINELY DIVIDED METALLIC WETTING AGENT FROM THE GROUP CONSISING OF IRON, COBALT AND NICKEL, AND SUBSEQUENTLY IMPREGNATING THE SAID COMPACT THROUGH THE SAID COATED INFILTRATING SURFACE WITH THE SAID LOWER MELTING POINT CONDUCTIVE METAL, THEREBY CAUSING THE EXCESS INFILTRANT TO SPREAD EVENLY OVER THE SAID SURFACE.
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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2927370A (en) * 1958-06-20 1960-03-08 Horizons Inc Seal material
US2928167A (en) * 1958-06-20 1960-03-15 Horizons Inc Seal material
US2974040A (en) * 1958-06-20 1961-03-07 Horizons Inc Process to produce void free refractory boride product
US2983996A (en) * 1958-07-30 1961-05-16 Mallory & Co Inc P R Copper-tungsten-molybdenum contact materials
US3128540A (en) * 1960-09-19 1964-04-14 Gibson Electric Company Electrical contact
US3145529A (en) * 1960-03-10 1964-08-25 Avco Corp Refractory composite rocket nozzle and method of making same
US3353933A (en) * 1966-03-11 1967-11-21 Mallory & Co Inc P R Tungsten powder bodies infiltrated with copper-titanium alloys
US3359623A (en) * 1965-05-13 1967-12-26 Talon Inc Method for making refractory metal contacts having integral welding surfaces thereon
US3366463A (en) * 1965-07-20 1968-01-30 Siemens Ag Sintered shaped structure formed of penetration-bonded metal, particularly for arcing electric contacts
US3382066A (en) * 1965-07-23 1968-05-07 Mallory & Co Inc P R Method of making tungsten-copper composites
US3407061A (en) * 1967-05-04 1968-10-22 Whittaker Corp Metal coating process
US3407048A (en) * 1968-01-22 1968-10-22 Mallory & Co Inc P R Molybdenum composite materials and method of making the same
US3409974A (en) * 1967-07-07 1968-11-12 Alloys Unltd Inc Process of making tungsten-based composite materials
US3957453A (en) * 1972-08-17 1976-05-18 Siemens Aktiengesellschaft Sintered metal powder electric contact material
FR2363178A1 (en) * 1976-08-27 1978-03-24 Siemens Ag VACUUM ELECTRIC SWITCH
FR2382758A1 (en) * 1977-03-03 1978-09-29 Siemens Ag FRITTED IMPREGNATED RAW MATERIAL FOR ELECTRICAL CONTACT PARTS AND ITS PREPARATION PROCESS
US6010659A (en) * 1995-10-10 2000-01-04 Abb Patent Gmbh Method and device for producing a contact element

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2313070A (en) * 1940-06-22 1943-03-09 Mallory & Co Inc P R Metal composition
US2358326A (en) * 1942-12-31 1944-09-19 Mallory & Co Inc P R Metal composition
US2370242A (en) * 1943-01-15 1945-02-27 Mallory & Co Inc P R Refractory metal composition
US2648747A (en) * 1950-08-24 1953-08-11 Gibson Electric Company Electrical contact
US2752666A (en) * 1954-07-12 1956-07-03 Sintercast Corp America Heat resistant titanium carbide containing body and method of making same

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2313070A (en) * 1940-06-22 1943-03-09 Mallory & Co Inc P R Metal composition
US2358326A (en) * 1942-12-31 1944-09-19 Mallory & Co Inc P R Metal composition
US2370242A (en) * 1943-01-15 1945-02-27 Mallory & Co Inc P R Refractory metal composition
US2648747A (en) * 1950-08-24 1953-08-11 Gibson Electric Company Electrical contact
US2752666A (en) * 1954-07-12 1956-07-03 Sintercast Corp America Heat resistant titanium carbide containing body and method of making same

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2928167A (en) * 1958-06-20 1960-03-15 Horizons Inc Seal material
US2974040A (en) * 1958-06-20 1961-03-07 Horizons Inc Process to produce void free refractory boride product
US2927370A (en) * 1958-06-20 1960-03-08 Horizons Inc Seal material
US2983996A (en) * 1958-07-30 1961-05-16 Mallory & Co Inc P R Copper-tungsten-molybdenum contact materials
US3145529A (en) * 1960-03-10 1964-08-25 Avco Corp Refractory composite rocket nozzle and method of making same
US3128540A (en) * 1960-09-19 1964-04-14 Gibson Electric Company Electrical contact
US3359623A (en) * 1965-05-13 1967-12-26 Talon Inc Method for making refractory metal contacts having integral welding surfaces thereon
US3366463A (en) * 1965-07-20 1968-01-30 Siemens Ag Sintered shaped structure formed of penetration-bonded metal, particularly for arcing electric contacts
US3382066A (en) * 1965-07-23 1968-05-07 Mallory & Co Inc P R Method of making tungsten-copper composites
US3353933A (en) * 1966-03-11 1967-11-21 Mallory & Co Inc P R Tungsten powder bodies infiltrated with copper-titanium alloys
US3407061A (en) * 1967-05-04 1968-10-22 Whittaker Corp Metal coating process
US3409974A (en) * 1967-07-07 1968-11-12 Alloys Unltd Inc Process of making tungsten-based composite materials
US3407048A (en) * 1968-01-22 1968-10-22 Mallory & Co Inc P R Molybdenum composite materials and method of making the same
US3957453A (en) * 1972-08-17 1976-05-18 Siemens Aktiengesellschaft Sintered metal powder electric contact material
FR2363178A1 (en) * 1976-08-27 1978-03-24 Siemens Ag VACUUM ELECTRIC SWITCH
FR2382758A1 (en) * 1977-03-03 1978-09-29 Siemens Ag FRITTED IMPREGNATED RAW MATERIAL FOR ELECTRICAL CONTACT PARTS AND ITS PREPARATION PROCESS
US6010659A (en) * 1995-10-10 2000-01-04 Abb Patent Gmbh Method and device for producing a contact element

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