Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1078—Alloys containing non-metals by internal oxidation of material in solid state
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
  • C22C5/06—Alloys based on silver
  • C22C5/10—Alloys based on silver with cadmium as the next major constituent
• • 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

Definitions

• This invention relates to electrical contact materials, in particular internally oxidized Ag-SnO system alloy electrical contact materials, and to methods of making the same.
• Ag alloys which contain 0.5 to 12 weight % of Sn and which have been internally oxidized, have become widely used as electrical contact materials in various electrical devices such as switches, contactors, relays and circuit breakers.
• These Ag alloys which have been melted, cast, and rolled or drawn, and are generally in the form of thin plates with or without backing of thin pure Ag plates joined to the side of the Ag alloy thin plates, are internally oxidized by subjecting them to an oxygen atmosphere under pressure.
• Such alloys are different from those sintered Ag-metal oxide alloys which are made by mixing matrix Ag powders with powders of the metal oxides and sintering them.
• the former viz. internally oxidized Ag-Sn system alloys, are far superior to the latter in respect of their structural density, while the latter have a more uniform dispersion of metal oxides than the former. The latter may be very readily consumed in too rapid and frequent switching operations.
• internally oxidized Ag-Cd system alloys have a more uniform dispersion of metal oxides. This is chiefly because the diffusion velocity of Cd in a silver matrix is inherently well balanced with the diffusion velocity of oxygen in the internal oxididation, while the respective diffusion velocities are not so well balanced in the case of internal oxidation of Ag-Sn system alloys. For this reason, electrical contact materials made of internally oxidized Ag-Cd system alloys and methods for preparing them are not relevant when considering the preparation of Ag-Sn system alloys and the internal oxidation thereof.
• 4,472,211 discloses materials wherein a high contact resistance, which is caused by high concentration or supersaturation of metal oxides including tin oxides about a contact surface, is avoided by having solute metals sublimated, reduced or extracted about the contact surface before the internal oxidation thereof.
• the present invention therefore aims to provide internally oxidized Ag-SnO system alloy electrical contact materials having contact surfaces of a moderate initial contact resistance and having no depletion layer, and a method of manufacturing such contact materials, not using methods such as disclosed in the above-mentioned U.S. Patents which are difficult to adequately control.
• the present invention in one aspect provides an internally oxidized Ag-SnO system alloy electrical contact material, obtained by the complete internal oxidation of an alloy comprising 0.5 - 12 weight % of Sn, and 0.5 - 15 weight % of In or 0.01 - less than 1.5 weight % of Bi, the said alloy optionally including one or more metallic elements selected from 0.1 - 5 weight % of Cd, 0.1 - 2 weight % of Zn, 0.1 - 2 weight % of Sb, 0.01 - 2 weight % of Pb, and 0.1 - less than 2 weight % of In, characterized by having a forwardmost area of the internal oxidation along its progressive direction made as a contact surface.
• the invention in another aspect provides an internally oxidized Ag-SnO system alloy electrical contact material, which comprises a contact portion of a desired thickness made from an Ag alloy comprising 0.5 - 12 weight % of Sn, and 0.5 - 15 weight % of In or 0.01 - less than 1.5 weight % of Bi, the said alloy optionally including one or more metallic elements selected from 0.1 - 5 weight % of Cd, 0.1 - 2 weight % of Zn, 0.1 - 2 weight % of Sb, 0.01 - 2 weight % of Pb, and 0.1 - less than 2 weight % of In, and which alloy is at least twice as thick as the said desired thickness and additionally has an expected thickness of a depletion layer to be produced in the alloy, has been completely internally oxidized by having it fixedly sandwiched between pure silver thin layers, and horizontally cut in two, simultaneously removing the depletion layer therefrom.
• the invention in a further aspect provides a method of making an internally oxidized Ag-SnO system alloy electrical contact material, which comprises preparing an Ag alloy comprising 0.5 - 12 weight % of Sn, and 0.5 - 15 weight % of In or 0.01 - less than 1.5 weight % of Bi, the said alloy optionally including one or more metallic elements selected from 0.1 - 5 weight % of Cd, 0.1 - 2 weight % of Zn, 0.1 - 2 weight % of Sb, 0.01 - 2 weight % of Pb, and 0.1 - less than 2 weight % of In; completely internally oxidizing the alloy; and characterized by cutting the alloy so that the forwardmost area of the internal oxidation along its progressive direction in the alloy is exposed as a contact surface thereof.
• the invention in a still further aspect provides a method of making an internally oxidized Ag-SnO system alloy electrical contact material, which comprises preparing an Ag alloy of a desired thickness comprising 0.5 - 12 weight % of Sn, and 0.5 - 15 weight % of In or 0.01 - less than 1.5 weight % of Bi, the said alloy optionally including one or more metallic elements selected from 0.1 - 5 weight % of Cd, 0.1 - 2 weight % of Zn, 0.1 - 2 weight % of Sb, 0.01 - 2 weight % of Pb, and 0.1 - less than 2 weight % of In, which alloy is at least twice as thick as the said desired thickness and having an expected thickness of a depletion layer to be produced in the alloy, and fixedly sandwiched between pure silver thin layers; completely internally oxidizing the alloy; and cutting the alloy horizontally in two, simultaneously removing by said cutting the depletion layer from the alloy.
• the forwardmost area which consists of Ag matrices and one grain (for example) of tin oxides of a certain weight % of the Ag matrices can afford to the Ag matrices larger contact surfaces, compared to the rearmost area which consists of ten grains (for example) of the same weight % in total and Ag matrices.
• the larger are the precipitates of tin oxides the lesser becomes the strain to be produced in the tin oxides with the internal oxidation, so that precipitates come to have a moderate hardness which can scarcely bring about cracks of contact surfaces.
• Such fine internally oxidized Ag-Sn alloy structures at the front or forwardmost area of internal oxidation appear, when the alloy is oxidized from both sides, centrally in the alloy with a depletion zone therebetween; and when the alloy is oxidized from a single side, at the bottom opposite to a surface from which oxygen penetrates into the alloy. Since the depletion zone or a zone where tin oxides are poor or mostly absent lies usually next to the forwardmost area of internal oxidation, such area which is employed in this invention as a contact surface should be free from the above zones.
• Typical constituents of Ag-Sn alloys employable in this invention are those comprising Ag matrices, 0.5 -12 weight % of Sn, and 0.5 - 15 weight % of In, and those comprising Ag matrices, 3 - 12 weight % of Sn, and 0.01 - less than 1.5 weight % of Bi.
• Such constituents may optionally contain one or more metallic elements selected from 0.1 - 5 weight % of Cd, 0.1 - 2 weight % of Zn, 0.1 - 2 weight % of Sb, and 0.01 - 2 weight % of Pb.
• 0.1 - less than 2 weight % of In may be contained. Further, they may contain less than 0.5 weight % of one or more elements of the iron family (iron, cobalt, nickel).
• said Ag alloy is prepared as a flat plate or disk having a height which is at least twice a desired final height and additionally comprises a height of a depletion layer which is expected to be produced when the Ag-alloy is completely internally oxidized.
• Said Ag-alloy is backed at both its surfaces by thin pure Ag layers.
• the thus prepared Ag-alloy is completely internally oxidized in an oxygen atmosphere under pressure and at an elevated temperature.
• the backing thin pure Ag layers work as follows.
• the partial pressure of oxygen, which has been dissolved into silver at the elevated temperature, is comparatively low, and since the amount of oxygen which diffuses through the silver is constant at a predetermined specific temperature, and under an oxygen atmosphere of a predetermined specific pressure, the amount of oxygen which will diffuse into a metal alloy via the silver for oxidizing the former, can readily and freely be controlled.
• the oxygen in this instance is diffused into the metal alloy through the silver, and consequently at a selected direction of paths of oxygen, crystalline metallic grains oxidized and precipitated in the metal alloy are not arranged at random but can be prismatically aligned in the paths of oxygen. Since these prismatically aligned metallic oxides are also in parallel with electric current paths passing through the internally oxidized Ag alloy contact material the electrical resistance of the material is reduced.
• the completely internally oxidized Ag alloy plate or disk having a depletion layer which lies centrally and transversely to the axis or height of the plate or disk, is cut along the depletion layer by a super hard and high speed cutting device such as a mill with a width greater than the width of the depletion layer.
• a super hard and high speed cutting device such as a mill with a width greater than the width of the depletion layer.
• Two parts thus cut off from the plate or disk have respectively a completely internally oxidized Ag alloy body having a fresh contact surface of a moderate hardness and initial resistance and a pure silver backing at its bottom surface, and having no depletion layer.
• the above alloys (1) to (4) were melted in a high frequency melting furnace at about 1,100 to 1,200°C and poured into molds for obtaining ingots of about 5 Kg each. Each ingot was stripped at its one surface. Then, each ingot was butted at its stripped surface to a nickel plate by means of a hydraulic press, and rolled to a plate about 2.2 mm thick with the nickel back about 1 mm thick.
• Each plate was subjected to an oxygen atmosphere for 200 hours and at 650°C so that the plate was completely internally oxidized. Since the nickel back is un-oxidizable, internal oxidation progressed from the stripped surface only. Segregation of tin oxides was observed around the stripped surface. The internally oxidized structures which had been produced in the plate at the forwardmost area along the progressive direction of internal oxidation, viz. in this instance about 2 mm deep from the stripped surface, were extremely fine and completely free from the segregation of metal oxides. A depletion zone or a zone where tin oxides are mostly absent was next to said forwardmost area with a depth of about 1 mm.
• Each of the internally oxidized plates were placed in a hydrogen gas atmosphere and heated at 750°C for ten minutes, so that metal oxides about the stripped surface were reduced or decomposed whereby the stripped surface could be brazed to a movable or stationary contact base.
• the nickel plate can be replaced by other metals which are not oxidizable, and the reduction or decomposition of metal oxides about the stripped surface may be effected by heating in a flux or immersing it into an acid solution.
• the plates were horizontally cut at a plane 0.2 mm from the bottom. Also, plates were slit to obtain square electrical contacts of 5 mm sides and a thickness of 1.9 mm, having the forwardmost areas of internal oxidation along the progressive direction as contact surfaces, and the reduced or decomposed stripped surfaces as backs.
• the plates after the internal oxidation may be cut or pressed out to desired configuration before the internal oxidation.
• contacts were made from alloys (5) to (8) respectively corresponding to the alloys (1) to (4), i.e.
• each ingot was butted at its stripped surface to a pure silver plate by means of a hydraulic press, the platen of which was heated at about 440°C, and rolled to a plate of about 2 mm thickness, while annealing at about 600°C, at every stage of rolling achieving a 30% reduction.
• Each plate was internally oxidized in an oxygen atmosphere for 200 hours and at 650°C. Then, internally oxidized plates were pressed by a punch of 6 mm diameter to obtain electrical contacts 2 mm in thickness which were backed with a thin silver layer.
• An alloy ingot of composition Ag-Sn 8%-In 4% was drawn to a wire of 5 mm diameter, from which there were prepared a number of pieces each having a body portion of 5 mm diameter and 3.3 mm length, which was integrally provided at both its sides with projections of 2 . 5 mm diameter and 1 mm height.
• Those pieces were completely internally oxidized, and then cut in two transversely to their axes by a mill with a kerf of 0.3 mm, to produce rivet-shaped contact materials each having a contact head of 5 mm diameter and 1.5 mm height with a shank of 2.5 mm diameter and 1 mm height, which were characterized by making the forwardmost areas of internal oxidation as contact surfaces.
• the pieces may be subjected to a hydrogen atmosphere before or after they were cut in two so that the shank is brazeable to a contact support metal as described in Example 1.
• the rivet-shaped contact materials thus obtained had excellent physical and electrical characteristics, compared to corresponding convPntional contact materials. It was observed that the hardness of the contact materials thus obtained was about 30% less than that of conventional contact materials, and their initial contact resistance was as much as 50% less.
• the above alloys (9) to (12) were melted in a high frequency melting furnace at about 1,100 to 1,200°C and poured into molds for obtaining ingots of about 5 Kg. Each ingot was stripped at both its surfaces. Then, each ingot was butted at both its stripped surfaces to pure silver plates by means of a hydraulic press, platens of which were heated at about 400°C, and rolled to a plate of 3.1 mm thickness, while annealing at about 500°C, at every stage of rolling achieving a 30% reduction.
• Each plate of one of the above alloys (9), (10), (11) and (12) had a 2.5 mm thickness and was joined at both its surfaces by a pure silver layer of 0.3 mm thickness.
• Each plate was completely internally oxidized in an oxygen atmosphere for 200 hours and at 650°C.
• the plate had centrally a depletion layer of about 0.1 - 0.2 mm thickness.
• the plates were horizontally cut in two by a mill with a kerf of 0.5 mm.
• the plates were slit to obtain square electrical contacts of 5 mm sides and of a thickness of 1 mm, which were backed at one of the surfaces with a thin silver layer of 0.3 mm.
• the plates after the internal oxidation may be cut or pressed out to desired configurations before the internal oxidation.
• Ag-Sn system alloys were prepared by a melting method and then subjected to internal oxidation, they can be prepared by a powder metallurgical method preferably with subsequent forging and then be subjected to internal oxidation. It is a matter of course that internal oxidation mechanisms in the case of the latter alloys work exactly the same as in the case of the former alloys.
• the present invention is thus concerned with alloys produced by a powder metallurgical method as well as with alloys produced by a melting method.

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• Organic Chemistry (AREA)
• Contacts (AREA)
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Citations (6)

• 1986
  • 1986-04-14 IN IN287/CAL/86A patent/IN165226B/en unknown
  • 1986-04-30 NO NO861703A patent/NO861703L/no unknown
  • 1986-05-02 EP EP86303361A patent/EP0219924A1/en not_active Ceased
  • 1986-05-06 PT PT8251686A patent/PT82516B/pt not_active IP Right Cessation
  • 1986-05-13 CN CN 86103279 patent/CN1014329B/zh not_active Expired
  • 1986-05-14 BR BR8602289A patent/BR8602289A/pt unknown
  • 1986-06-23 ES ES556445A patent/ES8708252A1/es not_active Expired
  • 1986-08-12 CA CA000515771A patent/CA1296883C/en not_active Expired - Lifetime
  • 1986-08-27 AU AU61888/86A patent/AU581338B2/en not_active Ceased
  • 1986-08-29 DK DK414686A patent/DK414686A/da not_active Application Discontinuation

Patent Citations (6)

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