.-\
`
`(EH-lO452B)OO—749—3
`
`SILVER BRAZE ALLOY
`
`CROSS—REFERENCE TO RELATED APPLICATION(S)
`
`[0001] This application is-a continuation application of U.S.
`
`Patent Application Serial No. 09/752,000, filed December 29,
`
`2000, entitled SILVER BRAZE ALLOY, by Wangen Lin et al.
`
`BACKGROUND OF THE INVENTION
`
`[0002] The present invention relates to a silver brazing alloy
`
`and to a method of brazing metal parts.
`
`[0003]
`
`It is known to torch braze,
`
`induction braze,
`
`furnace
`
`braze, or vacuum braze metal parts, such as steel parts, using
`
`non—ferrous brazing alloys, also known as filler metals.
`
`Typical filler metals include silver, gold, nickel, and copper
`
`brazing alloys. Silver brazing alloys are more costly and,
`
`in
`
`general, melt at lower temperatures than copper alloys.
`[0004] One silver brazing alloy which has been used in the
`
`prior art is an alloy containing 56 wt% silver, 42 wt% copper,
`
`and 2.0 wt% nickel. Despite the wide spread use of this
`
`silver brazing alloy,
`
`there remains a need for an alloy which
`
`has improved brazing characteristics, particularly
`
`wettability.
`
`SUMMARY OF THE INVENTION
`
`[0005] Accordingly, it is an object of the present invention
`
`to provide a silver braze alloy having improved wettability.
`
`[0006]
`
`It is a further object of the present
`
`invention to
`
`provide an improved brazing method which does not require
`
`nickel plating of a stainless steel substrate prior to
`
`brazing.
`
`[0007] The foregoing objects are attained by the silver braze
`
`alloy and the brazing method of the present invention.
`
`[0008]
`
`In accordance with the present
`
`invention, a silver
`
`braze alloy consists essentially of from about 52.25 wt% to
`
`about 57.0-Wt% silver,
`
`from about 38.95 wt% to about 43.0 wt%
`1
`
`
`
`v
`
`(EH—lO452B)OO-749-3
`
`copper,
`
`from about 0.5 wt% to about 5.5 wt%, preferably from
`
`about 1.0 wt% to about 5.5 wt%, manganese and up to about 2.5
`
`wt%, preferably from about 1.5 wt% to about 2.5 wt% nickel.
`
`[0009] A.method for brazing a part in accordance with the
`
`present invention broadly comprises providing an article
`
`formed from a ferrous material, applying a brazing material to
`
`the article formed from an alloy consisting essentially of
`
`from about 52.25 wt% to about 57.0 wt% silver,
`
`from about
`
`38.95 wt% to about 43.0 wt% copper,
`
`from about 0.5 wt% to
`
`about 5.5 wt% manganese, and up to about 2.5 wt% nickel, and
`
`heating the article and the brazing material at a temperature
`
`in the range of from about 900°C to about 1050°C for a time
`
`period sufficient to melt the brazing material.
`
`[0010] Other details of the silver braze alloy and the method
`
`of the present invention, as well as other objects and
`advantages attendant thereto, are set forth in the following
`
`detailed description and the accompanying drawing.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`[0011] The figure is a graph showing the wetting angle which
`
`can be obtained by the alloys in accordance with the present
`
`invention as a function of the manganese content of the alloy.
`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
`
`[0012] A.silver braze alloy in accordance with the present
`
`invention consists essentially of from about 52.25 wt% to
`
`from about 38.95 wt% to about 43.0 wt%
`about 57.0 wt% silver,
`copper,
`from about 0.5 wt% to about 5.5 wt%, preferably from
`about 1.0 wt% to about 5.5 wt%, manganese and up to about 2.5
`
`wt%, preferably from about 1.5 wt% to about 2.5 wt%, nickel.
`
`The alloys of the present invention may also contain up to
`
`about 0.15 wt% total of other trace elements such as iron,
`
`zinc, silicon, phosphorous, sulfur, platinum, palladium,
`
`lead,
`
`gold, aluminum, magnesium,
`
`tin, germanium, carbon, and oxygen.
`
`A manganese addition within the foregoing ranges has been
`2
`.
`
`
`
`(EH-10452B) 00—749-3
`
`found to improve the brazing characteristics of the alloy of
`
`the present invention, particularly the wetting
`
`characteristics, as compared to a silver—copper—nickel brazing
`
`alloy consisting of 56wt% silver, 42 wt% copper, and 2.0 wt%
`
`nickel.
`
`[0013] Particularly useful brazing alloys in accordance with
`
`the present invention include:
`
`(1) a silver brazing alloy
`
`consisting essentially of 56 wt% silver, 42 wt% copper and 2.0
`
`wt% manganese; and (2) a silver brazing alloy consisting
`
`essentially of 0.5 to 5.5 wt% manganese with the remaining
`
`composition proportional to the 56 wt% silver, 42 wt% copper,
`
`and 2.0 wt% nickel alloy.
`
`[0014] The silver braze alloys of the present invention may be
`
`formed in any suitable manner known in the art and may be cast
`
`using any suitable technique known in the art into any desired
`
`form.
`
`For example,
`
`the silver braze alloys of the present
`
`invention can be in strip form, wire form,
`
`rod form, sheet
`
`form, foil form, pig form, powder form, shot form, chip form,
`
`paste form.
`
`[0015] The silver braze alloys of the present invention may be
`
`brazed at a temperature in the range of from about 900°C to
`
`about 1050°C, preferably from about 950°C to about 1050°C,
`
`for
`
`a time sufficient to melt the brazing alloy onto a substrate'
`
`formed from a ferrous material such as steel and stainless
`
`steel. Using the alloys of the present
`
`invention, brazing can
`
`be done using a furnace,
`
`locally using a torch, using an
`
`induction heater, dipped in a braze or flux bath, resistance
`
`heated,
`
`laser heated, or infrared heated. Depending on the
`
`brazing technique being employed, brazing may be carried out
`
`in an inert gas atmosphere, such as an argon atmosphere, or
`
`some other type of protective atmosphere.
`
`The silver braze
`
`alloy of the present invention melts at the aforementioned
`
`brazing temperatures and readily wets the ferrous substrate
`
`material to be joined without melting the ferrous substrate
`
`material.
`
`
`
`(EH—lO452B)OO-749—3
`
`[0016] The silver braze alloys of the present invention may be
`
`used to braze steel surfaces, particularly stainless steel
`
`surfaces. One of the advantages of the silver braze alloys of
`
`the present invention is that in an inert gas atmosphere, such
`
`as an argon atmosphere, no flux needs to be used and no nickel
`
`plating of the ferrous substrate material is required.
`
`[0017]
`
`It has been found that the silver brazing alloys of the
`
`present invention have better wettability and flow
`
`characteristics than other brazing alloys such as an alloy
`
`consisting of 56 wt% silver, 42 wt% copper, and 2.0 wt%
`
`nickel.
`
`[0018]
`
`To demonstrate the improved properties of the alloys of
`
`the present invention, a controlled amount of braze alloy
`
`consistent with the alloys of the present
`
`invention were
`
`applied to a series of stainless steel pieces.
`
`The braze
`
`volume was kept small to prevent excessive spreading of the
`
`alloy during the test.
`
`Each sample was then heated to a braze
`
`temperature of 900°C or 1000°C in a brazing furnace under a
`
`protective argon atmosphere.
`
`The braze alloy under the
`
`aforementioned brazing conditions melted and formed a wetting
`
`angle with the stainless steel piece.
`
`The angle at the line
`
`of contact between the liquid or solidified braze alloy and
`
`the stainless steel piece was then measured. This was done
`
`either in situ or after the piece had been cooled to room
`
`temperature.
`
`The resulting angle is an indicator of
`
`wettability.
`
`The lower the contact or wetting angle,
`
`the
`
`better the wetting behavior between the silver braze alloy and
`
`the base material. As can be seen from Fig. 1,
`
`the braze
`
`alloys_of the present invention heated to a temperature of
`
`1000°C exhibited wetting angles in the range of from
`
`approximately 1 degree to about 19 degrees and braze alloys of
`
`the present invention heated to a temperature of 900°C
`
`exhibited wetting angles which ranged from approximately 1
`
`degree to about 37 degrees.
`
`
`
`(EH-lO452B) 00—749—3
`
`[0019] The typical wetting angle for a 56Ag—42Cu—2Ni alloy can
`
`range anywhere from 10 to 90 degrees depending on the surface
`
`conditions of the stainless steel and the brazing temperature.
`
`As can be seen from the foregoing discussion,
`
`the silver
`
`brazing alloys of the present
`
`invention significantly reduce
`
`this wide range of wetting variability, producing generally
`
`low wetting angles and improved braze flow.
`
`.The foregoing
`
`test shows that the higher the manganese content of the alloy,
`
`the lower the wetting angle.
`Fig.
`1 clearly shows that alloys
`in accordance with the present invention having a manganese
`
`content greater than about 1.0 wt% to about 5.0 wt% provide
`
`excellent wettability properties.
`
`[0020]
`
`It is apparent that there has been provided in
`
`accordance with the present
`
`invention a silver braze alloy
`
`which fully meets the foregoing objects, means and advantages.
`
`While the present invention has been described in the context
`
`of specific embodiments thereof, other alternatives,
`
`modifications, and variations will become apparent to those
`
`skilled in the art having read the foregoing description.
`
`Therefore, it is intended to embrace those alternatives,
`
`modifications, and variations as fall within the broad scope
`
`of the appended claims.
`
`
