CA1119436A - Alloy for use in brazed assemblies - Google Patents
Alloy for use in brazed assembliesInfo
- Publication number
- CA1119436A CA1119436A CA000321925A CA321925A CA1119436A CA 1119436 A CA1119436 A CA 1119436A CA 000321925 A CA000321925 A CA 000321925A CA 321925 A CA321925 A CA 321925A CA 1119436 A CA1119436 A CA 1119436A
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- Prior art keywords
- alloy
- aluminum
- weight
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-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
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- Conductive Materials (AREA)
- Coating With Molten Metal (AREA)
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- Superconductors And Manufacturing Methods Therefor (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved corrosion resistant aluminum alloy for use in the manufacture of brazed assemblies having improved sag resistant properties is disclosed. The alloy consists essentially of an aluminum base alloy containing from 0.05 to 0,4% chromium, from 0.02 to 0.9% manganese, up to 0.2%
iron, up to 0.1% silicon and the balance essentially aluminum.
An improved corrosion resistant aluminum alloy for use in the manufacture of brazed assemblies having improved sag resistant properties is disclosed. The alloy consists essentially of an aluminum base alloy containing from 0.05 to 0,4% chromium, from 0.02 to 0.9% manganese, up to 0.2%
iron, up to 0.1% silicon and the balance essentially aluminum.
Description
~ 3 .BAC~ROUND 0~ T~E INVENTION
Brazed aluminum eq~ipment i~s su~ect to the se~ere problem of intergran~lar corrosion in corrosi~e enviro~ments on ~oth clad and uncl~d s~r~aces. The corrosive en~ironments which can cause this pro~le~ i~ncl~de waker contai:ning dlssol~ed chlorider bicarbonate or s~l~ate ions, especially i~ the pH
of the water has a relati~ely low value. Such waters may condense as films on the fins of heat e~changer equipment used ~or automotive or ai~rcra~t air condit~onersl automoti~e radiators, gas lique~acti~on equipment or the li~e.
Intergranularcorrosion has also ~een encountered in : other applications, as on ~razed Fleaders inside a~tomoti~e radiators and heat e~changers generally In such cases, the coolant is us~all~ corrosi~e ~For example, if automot~Ye antifreeze solutions are used, poor maintenance can often ~ result in the sol~tion ~ecomi~ng corrosi~e for a ~ariety of ; reasons. Chief among these reasons are that the anti~reeze ~ay haYe ~een allowed to remain i~n the radi:ator ~or a number o~ years~with.o~t replacement w~ile replenishing the level wi~tFl.mi~tures o~ ~resh ant1~reèze sol~ti~n wl~tfi hard natural water~ Tfiese practices would deplete the corroslon inhi~itors and res~erYe al~alinity~co~ponents~ permi~ttin~ the coolant pH
t~ drop and allowing h.ea~y metal lons to accumulate from reaction o~ the acl~ds wltFI.copper allo~ and cast iron sur~ces ln tfie`coolant system~
~ 1 .~
CON-149~M
~ 3~
U.S. Patent~ 3,898,053 and 3~853,547 describe certain aluminum-sillcon brazing compositions for ~oining aluminum alloy components; however, these compositions do not solve the problem of lntergranular corrosion descri~ed herein~
above.
The problem of intergranular corroslon may occur whether flux brazing or vacuum brazing techniques are employed. There is evidence in the case of flux brazed aluminum Alloy 3003 (an aluminum ~ase alloy contain~ng from 0 05 to 0.20% copper, from 1 to 1.5% manganese, up to 0.6%
silicon and up to 0~7% iron) clad with aluminum Alloy 4343 ~an aluminum base alloy containing from 6.8 to 8.2~ silicon, up to o.8% iron~ up to 0~25% copper, up to 0-1% manganese, up to 0.2% zinc and the balance essentially aluminum) that the silicon rich eutectic formed when the Alloy 4343 brazing alloy is brazed can ml~rate into the grain boundaries o~ the Alloy 3003 component and can cause increased susceptlbility to intergranular corrosion. A similar silicon rich eutectic migration into the parent metal can occur in the case of vacuum brazed assemblies made from aluminum Alloy 3003 clad with the silicon rich aluminum vacuum brazing Alloy MD 150 (an aluminum base alloy containing about 9~5% silicon, 1.5% magnesium, up to 0.3% iron, up to 0.05% copper, up to 0.07% manganese~ up to 0~01% titanium and the balance essentlally aluminum~
or alumlnum vacuum brazin~ Alloy MD 177. The MD 177 alloy has substantially the same composition as MD 150 contalnlng in addition ~rom 0. o8 to 0.1% added bismuth~ In both MD 150 and MD 177 the magnesium addition is used to getter traces of oxygen in the vacuum brazin~ ~urnaces.
,, , .. .. , . . : , . ................ .
Brazed aluminum eq~ipment i~s su~ect to the se~ere problem of intergran~lar corrosion in corrosi~e enviro~ments on ~oth clad and uncl~d s~r~aces. The corrosive en~ironments which can cause this pro~le~ i~ncl~de waker contai:ning dlssol~ed chlorider bicarbonate or s~l~ate ions, especially i~ the pH
of the water has a relati~ely low value. Such waters may condense as films on the fins of heat e~changer equipment used ~or automotive or ai~rcra~t air condit~onersl automoti~e radiators, gas lique~acti~on equipment or the li~e.
Intergranularcorrosion has also ~een encountered in : other applications, as on ~razed Fleaders inside a~tomoti~e radiators and heat e~changers generally In such cases, the coolant is us~all~ corrosi~e ~For example, if automot~Ye antifreeze solutions are used, poor maintenance can often ~ result in the sol~tion ~ecomi~ng corrosi~e for a ~ariety of ; reasons. Chief among these reasons are that the anti~reeze ~ay haYe ~een allowed to remain i~n the radi:ator ~or a number o~ years~with.o~t replacement w~ile replenishing the level wi~tFl.mi~tures o~ ~resh ant1~reèze sol~ti~n wl~tfi hard natural water~ Tfiese practices would deplete the corroslon inhi~itors and res~erYe al~alinity~co~ponents~ permi~ttin~ the coolant pH
t~ drop and allowing h.ea~y metal lons to accumulate from reaction o~ the acl~ds wltFI.copper allo~ and cast iron sur~ces ln tfie`coolant system~
~ 1 .~
CON-149~M
~ 3~
U.S. Patent~ 3,898,053 and 3~853,547 describe certain aluminum-sillcon brazing compositions for ~oining aluminum alloy components; however, these compositions do not solve the problem of lntergranular corrosion descri~ed herein~
above.
The problem of intergranular corroslon may occur whether flux brazing or vacuum brazing techniques are employed. There is evidence in the case of flux brazed aluminum Alloy 3003 (an aluminum ~ase alloy contain~ng from 0 05 to 0.20% copper, from 1 to 1.5% manganese, up to 0.6%
silicon and up to 0~7% iron) clad with aluminum Alloy 4343 ~an aluminum base alloy containing from 6.8 to 8.2~ silicon, up to o.8% iron~ up to 0~25% copper, up to 0-1% manganese, up to 0.2% zinc and the balance essentially aluminum) that the silicon rich eutectic formed when the Alloy 4343 brazing alloy is brazed can ml~rate into the grain boundaries o~ the Alloy 3003 component and can cause increased susceptlbility to intergranular corrosion. A similar silicon rich eutectic migration into the parent metal can occur in the case of vacuum brazed assemblies made from aluminum Alloy 3003 clad with the silicon rich aluminum vacuum brazing Alloy MD 150 (an aluminum base alloy containing about 9~5% silicon, 1.5% magnesium, up to 0.3% iron, up to 0.05% copper, up to 0.07% manganese~ up to 0~01% titanium and the balance essentlally aluminum~
or alumlnum vacuum brazin~ Alloy MD 177. The MD 177 alloy has substantially the same composition as MD 150 contalnlng in addition ~rom 0. o8 to 0.1% added bismuth~ In both MD 150 and MD 177 the magnesium addition is used to getter traces of oxygen in the vacuum brazin~ ~urnaces.
,, , .. .. , . . : , . ................ .
- 2 -CON-14~-M
g~3~
Flux brazed assemblies made from No. 12 brazing sheet ~aluminum Allo~ 3003 clad on both sldes with aluminum Alloy 11343) and monolithic aluminum Alloy 3003 components are sensitized to corrosion by prolon~ed holding at elevated temperatures below the brazing temperatureO This practice is used to assure that the final relatively short tlme on both clad and unclad surfaces brazing step will liquify the brazing alloy everywhere in very large assem~lies.
The effect of this holding time, which may be up to 5 hours at 1000F for large gas llquefaction heat exchangers~
ls to coarsen cathodic iron rich second phase particles in the metal. This causes increased susceptibility to both intergranular corrosion and pitting corrosion o~ both clad and unclad surfaces.
In addition to the poor corrosion resistant properties of' typical alloys, such as 3003 used in the manufacture of brazed assemblies, it has been found that the sag resistant properties of those typical alloys leave much to be desired. Good sag resistant properties are most important in providing good dimensional stability in large brazed assemblies such as gas separation units.
Therefore, it would be hi~hly desirable to produce an alloy for use in the manufacture of brazed a semblies which exhibit improved and superior sag resistant properties as compared to those alloys previously known.
Accordlngly, it is the prlncipal ob~ect of the present invent~on to provide an improved alumlnum alloy for use in ... . . . . . ................................ . . .
the manufacture of brazed assemblies which is characterized by substantial resistance to lnter~ranular corrosion.
g~3~
Flux brazed assemblies made from No. 12 brazing sheet ~aluminum Allo~ 3003 clad on both sldes with aluminum Alloy 11343) and monolithic aluminum Alloy 3003 components are sensitized to corrosion by prolon~ed holding at elevated temperatures below the brazing temperatureO This practice is used to assure that the final relatively short tlme on both clad and unclad surfaces brazing step will liquify the brazing alloy everywhere in very large assem~lies.
The effect of this holding time, which may be up to 5 hours at 1000F for large gas llquefaction heat exchangers~
ls to coarsen cathodic iron rich second phase particles in the metal. This causes increased susceptibility to both intergranular corrosion and pitting corrosion o~ both clad and unclad surfaces.
In addition to the poor corrosion resistant properties of' typical alloys, such as 3003 used in the manufacture of brazed assemblies, it has been found that the sag resistant properties of those typical alloys leave much to be desired. Good sag resistant properties are most important in providing good dimensional stability in large brazed assemblies such as gas separation units.
Therefore, it would be hi~hly desirable to produce an alloy for use in the manufacture of brazed a semblies which exhibit improved and superior sag resistant properties as compared to those alloys previously known.
Accordlngly, it is the prlncipal ob~ect of the present invent~on to provide an improved alumlnum alloy for use in ... . . . . . ................................ . . .
the manufacture of brazed assemblies which is characterized by substantial resistance to lnter~ranular corrosion.
- 3 -3l~
It is still a further object of the present invention to provide an improved al~inum alloy for use in the manu-facture of brazed assemblies which is characterized by having substantial resistance to pitting corrosion.
It is still a further object of the present invention to provide an improved corrosion resistant aluminum alloy which is characterized by substantial resistance to sag.
Further objects and advantages will appear hereinbelow.
SUMMARY OF THE INVENTION
In accordance with the present invention it has now been found that the foregoing objects and advantages may be readily obkained. The aluminum alloy of the present invention is characterized by improved intergranular corrosion, pitting corrosion and sag resistant properties.
The alloy of the present invention is an aluminum base alloy consisting essentially of from 0.05 to 0.4 weight %
chromium, frorn 0.2 to 0.9 weight % manganese, up to 0.2 weight % iron, up to 0.1 weight % silicon and the balance essentially aluminum.
The present invention resides in an improved aluminum alloy for use in the manufacture of brazed assemblies. It is a particular and surprising feature of the present lnven-tion that the aluminum alloy of the present invention is characterized by greatly improved resistance to intergranular and pitting corrosion while obtaining superior sag resistant properties.
The present invention will be more readily understood from a consideration of the following illustrative drawings in which:
CON-14~--M
~ 36 Figures lA J lB and lC are photographs of clad and unclad sides of samples following exposure to a corrosive environment;
Figures 2As 2B, 2C and 2D are photomlcrographs at a magnification of 200X showing cross sections through composites after exposure to a corrosive envlronment;
Figures 3A, 3B, 3C and,3D are photomlcrographs at a magnification of 200X showing cross sections of composites after exposure to a corrosive environment; and Figure 4 is a graph depicting the improved sag resistank characteristics of the alloy of khe present invention as compared to alumlnum Alloy 3003, DET~ ED DESCRIPTION OF PRE ~
As described hereinabove, the alloy o~ the present inventlon is characterized by improved resistance to intergranular corrosion and pitting corrosion while exhibiting superior sa~ resistant properties as compared to alloys heretofore used ln the manu~acture of brazed assemblies. It is a ~inding of the present invention that the susceptibility of brazed assemblies to intergranular corrosion due to silicon mi~ration and coarsening of iron ,containing second phase particles may be drastically reduced by using a parent alloy containing significantly restricted concentrations of both lron and silicon to which specific amounts of manganese and chromium have been added as purposeful addit,ions.
'The effect of restricting the iron and silicon ' '' concentrations is to reduce the size and population density of second phase particles rich'in iron which are most ,~, ... . . ........ . . . . . . . . . . . . .
-~ 5 -; - `
COM~149-M
9~36 frequently alpha phase particles containing iron, silicon and manganese. Restricting the silicon concentration of the aluminum alloy of the present invention when it is used as the core alloy in a brazed composite allows the alloy to be a good solvent for the silicon rich eutectic which tends to migrate into the core from the cladding ~razing alloy~ The effect of this is to drastically reduce the dept~ to which such migration may occur into the parent metal and thereby greatly reduce intergranular corrosion.
Restricting the iron concentration of the alloy of the present invention while addlng purposeful additions of manganese and chromium prevents ~he formation of the hlghly cathodic FeA13 phase. This is true regardless of whether the alloy is used as the core of the composite or where the monolithic alloy is used in the manufacture of brazed assemblies. The effect of this restriction of iron and purposeful additions of manganese and chromium is to reduce the concentration of those highly cathodlc phases which result in severe intergranular and pitting corrosion.
In accordance wikh the present invention, the alumlnum alloy contains from about 0O05 to 0O4% chromium and preferably from 0.15 to 0.30% chromium. The manganese content is from 0.2 to 0.9% and preferably from 0.3 to 0.6 The iron content is up to 0.2%, preferably up to 0.1%
and optimally from 0.02 to o.o8%. The silicon content la up to 0 1% and pre~erably from 0~02 to 0. o8%.
The aluminum alloy of the present invention may be`
used either clad or unclad in the manufacture of ~razed ; 30 aluminum assemblie~. Any silicon containing aluminum CON-149~M
brazlng alloy may be employed as the cladding material ~hereln the sllicon content ranges from 4 to 14%, ~uch as, for example, the ~D 150 and MD 177 alloys and also alumlnum Alloy 4045 (an alum~num base alloy containing from 9 ko 11%
silicon).
- The deliberate manganese addition ln the core alloy as well as the restrictive concentration o~ iron performs a beneficlal role by preventing formation of t~e highly cathodic FeA13 phase which is present in commercial manganese free aluminum alloys> Concentrations of manganese beyond the desired range such as manganese concentrations o~ 1% or more which are present in commercial Alloy 3003 cause excessive precipitation o~ MnA16 particles. These particles have an electrode potential almost the same as an aluminum matrix in a substantially iron free system.
However) in coTmmercial purity aluminum base alloy matrices, there is sufficient iron present to cause the MnA16 particles to dissolve enough iron to become cathodic to the matrix aluminum and cause localized corroston. The chromium addition in the alloy o~ the present invention shifts the electrode potential of the metal in the noble direction. Thls, in a corrosive media, is enough to make the alloy o~ the present invention more noble than any cladding alloy used therewith in a compo~ite and thereby prevent anodtc dlssolutlon o~ the parent metal by a galvanic couple~ A second and perhaps more important role of the chromium is to act as a corrosion inhibitor at sttes o~ localtzed corrosion, such as pitsl grain boundaries or crevices which may occur on the unclad or monolithic , 30, alloy.' Where, suoh corros~:on occu~s, the corrosion product -~ 7,~ "
, .. , contains soluble chromate lons which may migrate to the anodic sltes where they act as anodic type corrosion inhibitors, In addi~ion to the above, the alloy o~ the pre~ent invention exhibits superior sag resistant properties to - those alloys prevlously used in brazed assem~lies or brazing composites such as aluminum Alloy 3003. This superior property can be attributable to the larger grains which are obtained in the allo~ of the present invention because of the restrictive additions of iron~ manganese, silicon and chromium. The larger grain size results in less graln boundary area in which slippage can occur thus resulting in sag. Thus~ the alloy of the present invention is particularly suited for use in the manufacturing o~
large brazed assemblies where dimensional integrity is of the essence.
The alloy of the present invention is particularly useful in the manufacture of brazed equipment by mass production methods involving either flux or vac~um brazing.
The alloy o~ the present invention has particular value ror equipment which is expected to encounter corroslve conditions whlch could cause intergranular corrosion o~ the alloy. Vacuum bra~ed alumlnum heater cores have been found to have severe intergranular corrosion problems when made using conventional brazing sheets wlth Alloy 3003 as the parent metal. These heater cores are used, ~or example, to provide warm air to warm the passenger .
compartment of passenger cars b~ abstracting e~cess heat from the automotive englne coolant~ The inter~ranular ~corr~slon results.~rom contact be~ween the corroslve: -8 ~
l~ig436 aqueous engine coolant and the lnternal surfaces o~ the plate channelsO When the alloy o~ the present invention is used as the core material in a brazing composite, it significantly reduces the intergranular corroslon which occurs in this type o~ application. Other automotive - applications exist for which a composite made with the alloy of the present invention is quite suita~le, lncludlng automotive radiators and oil coolers in the engine systems and also evaporators and condensers in automotive air conditioning systems. The alloy of the present invention is particularly suited to be used as a monolit~ic sheet in an assembly with the brazing alloy in the ~orm of another sheet or foil associated therewith. The alloy of the present invention is particularly suited for the use in the manufacture of brazed assemblies, particularly large brazed -~ assem~lies, where good dimensional stability is critical.
The present invention will be more readily understand-able from a consideration of the followlng illustrative examples .
EXAMPLE I
Two core ingots were cast having the compositlon set forth below, with Alloy A representing the material of the present invention and Alloy B being a comparative alloy.
Alloy A Alloy B
Silicon - 0.04% Chromium ~ 0.15%
Chromium - 0.3% Iron ~ 0~04%
Manganese - 0.4% Silicon - o.OII%
Iroh - 0.035% Aluminum - Balance Titanium - 0,01%
Aluminum - Balance ~ ~g - `- .
CON-149.-M
~9 ~3~
Direct chill castings of lngots of Alloys A and B were homogenized at 1125F for 8 hours using a maximum heat up ra~e from 600F of 50F per hour. The ingots were cooled from 1125F to 600F at 25F per hour and air cooled to room temperature~ The core materials of Alloys A and B
were scalped to 1.5" thicl{ness and were brushed on one side.
EXAMPLE II
-Durville ingots were cast to the compositions shown in Table I below, TABLE I
Al-loy Si Fe _ Mn Ti Mg Bi 4343 C 7.5 .35 .05 - .01 _ MD 150 D 9.7 .3 .05 .07 .01 1.5 MD 177 E 9.7 .3 .05 .07 .01 1.5 .l The ~oregoin~ Alloys C, D and E represent ilicon rich cladding alloys~ The Durville lngots of Alloys C, D and E
were scalped to 1.5" thickness. They were reheated to 800F
for l hour and hot rolled to 0.15" gage. The ~ot rolling scale was removed by caustic etching and rinsing.
EXAMPLE_III
Brazing sheets of Alloy C clad on Alloy A and Alloy C
clad on Alloy B were fabricated. In additiong for comparative purposes a brazing sheet of Alloy 4343 (Alloy C) clad on Alloy 3003 was prepared. All brazing sheets were one side clad only. The brazing sheets were fabricated by welding the appropriate brazing alloy to the wire brushed side of ~he pare~ alloy ~nd hot ~oli~ng t~e~andwich. ~An 800~F
-- 10 _ ., !
~ ~3~ CON-149 M
entry temperature was,used, Gne side was left unwelded to permit air to be expelled from the matlng surface. Hot rolling was continued until the sandwiches were 0.15 thick~ They were then cold rolled to 0,030" and annealed by heating to 660F at a rate of 25F per hour from 300F, held at 660F for 2 hours, cooled to 400F at 25F per hour, and air cooled from 400F to room temperature.
EXAMP'LE'IV
The brazing sheets were sub~ected to a simulated flux brazing cycle such as mighk be applied to a-bulky assembly.
The simulated flux bra~ing cycle included stacking 4" x 4"
sheets in a tray and placing the tray in a muffle furnace.
A thermocouple wàs present in a dummy load in the furnace ln order to determine metal temperature. Samples were heated to lOOO~F and held at this temperature for 5 hours to simulate the preheat step. They were then heated to 1115F for periods of 15 min~te ~ 30 minutes, 60 minutes and 300 minutes with some æamples unheated. The samples were then cut to 1" x l/2" specimens and a hole was punched near one of the l/2" edges to permi,t them to be supported on a nylon threaded rod support. All of the specimens ' were immersed for 140 hours at 40~F in a solution having composition set forth in ~able II below.
.. ~ .
. .
0.1 ~olar NaCl, 0,01 Molar NaN03 2.0 cc glacial acetic acid
It is still a further object of the present invention to provide an improved al~inum alloy for use in the manu-facture of brazed assemblies which is characterized by having substantial resistance to pitting corrosion.
It is still a further object of the present invention to provide an improved corrosion resistant aluminum alloy which is characterized by substantial resistance to sag.
Further objects and advantages will appear hereinbelow.
SUMMARY OF THE INVENTION
In accordance with the present invention it has now been found that the foregoing objects and advantages may be readily obkained. The aluminum alloy of the present invention is characterized by improved intergranular corrosion, pitting corrosion and sag resistant properties.
The alloy of the present invention is an aluminum base alloy consisting essentially of from 0.05 to 0.4 weight %
chromium, frorn 0.2 to 0.9 weight % manganese, up to 0.2 weight % iron, up to 0.1 weight % silicon and the balance essentially aluminum.
The present invention resides in an improved aluminum alloy for use in the manufacture of brazed assemblies. It is a particular and surprising feature of the present lnven-tion that the aluminum alloy of the present invention is characterized by greatly improved resistance to intergranular and pitting corrosion while obtaining superior sag resistant properties.
The present invention will be more readily understood from a consideration of the following illustrative drawings in which:
CON-14~--M
~ 36 Figures lA J lB and lC are photographs of clad and unclad sides of samples following exposure to a corrosive environment;
Figures 2As 2B, 2C and 2D are photomlcrographs at a magnification of 200X showing cross sections through composites after exposure to a corrosive envlronment;
Figures 3A, 3B, 3C and,3D are photomlcrographs at a magnification of 200X showing cross sections of composites after exposure to a corrosive environment; and Figure 4 is a graph depicting the improved sag resistank characteristics of the alloy of khe present invention as compared to alumlnum Alloy 3003, DET~ ED DESCRIPTION OF PRE ~
As described hereinabove, the alloy o~ the present inventlon is characterized by improved resistance to intergranular corrosion and pitting corrosion while exhibiting superior sa~ resistant properties as compared to alloys heretofore used ln the manu~acture of brazed assemblies. It is a ~inding of the present invention that the susceptibility of brazed assemblies to intergranular corrosion due to silicon mi~ration and coarsening of iron ,containing second phase particles may be drastically reduced by using a parent alloy containing significantly restricted concentrations of both lron and silicon to which specific amounts of manganese and chromium have been added as purposeful addit,ions.
'The effect of restricting the iron and silicon ' '' concentrations is to reduce the size and population density of second phase particles rich'in iron which are most ,~, ... . . ........ . . . . . . . . . . . . .
-~ 5 -; - `
COM~149-M
9~36 frequently alpha phase particles containing iron, silicon and manganese. Restricting the silicon concentration of the aluminum alloy of the present invention when it is used as the core alloy in a brazed composite allows the alloy to be a good solvent for the silicon rich eutectic which tends to migrate into the core from the cladding ~razing alloy~ The effect of this is to drastically reduce the dept~ to which such migration may occur into the parent metal and thereby greatly reduce intergranular corrosion.
Restricting the iron concentration of the alloy of the present invention while addlng purposeful additions of manganese and chromium prevents ~he formation of the hlghly cathodic FeA13 phase. This is true regardless of whether the alloy is used as the core of the composite or where the monolithic alloy is used in the manufacture of brazed assemblies. The effect of this restriction of iron and purposeful additions of manganese and chromium is to reduce the concentration of those highly cathodlc phases which result in severe intergranular and pitting corrosion.
In accordance wikh the present invention, the alumlnum alloy contains from about 0O05 to 0O4% chromium and preferably from 0.15 to 0.30% chromium. The manganese content is from 0.2 to 0.9% and preferably from 0.3 to 0.6 The iron content is up to 0.2%, preferably up to 0.1%
and optimally from 0.02 to o.o8%. The silicon content la up to 0 1% and pre~erably from 0~02 to 0. o8%.
The aluminum alloy of the present invention may be`
used either clad or unclad in the manufacture of ~razed ; 30 aluminum assemblie~. Any silicon containing aluminum CON-149~M
brazlng alloy may be employed as the cladding material ~hereln the sllicon content ranges from 4 to 14%, ~uch as, for example, the ~D 150 and MD 177 alloys and also alumlnum Alloy 4045 (an alum~num base alloy containing from 9 ko 11%
silicon).
- The deliberate manganese addition ln the core alloy as well as the restrictive concentration o~ iron performs a beneficlal role by preventing formation of t~e highly cathodic FeA13 phase which is present in commercial manganese free aluminum alloys> Concentrations of manganese beyond the desired range such as manganese concentrations o~ 1% or more which are present in commercial Alloy 3003 cause excessive precipitation o~ MnA16 particles. These particles have an electrode potential almost the same as an aluminum matrix in a substantially iron free system.
However) in coTmmercial purity aluminum base alloy matrices, there is sufficient iron present to cause the MnA16 particles to dissolve enough iron to become cathodic to the matrix aluminum and cause localized corroston. The chromium addition in the alloy o~ the present invention shifts the electrode potential of the metal in the noble direction. Thls, in a corrosive media, is enough to make the alloy o~ the present invention more noble than any cladding alloy used therewith in a compo~ite and thereby prevent anodtc dlssolutlon o~ the parent metal by a galvanic couple~ A second and perhaps more important role of the chromium is to act as a corrosion inhibitor at sttes o~ localtzed corrosion, such as pitsl grain boundaries or crevices which may occur on the unclad or monolithic , 30, alloy.' Where, suoh corros~:on occu~s, the corrosion product -~ 7,~ "
, .. , contains soluble chromate lons which may migrate to the anodic sltes where they act as anodic type corrosion inhibitors, In addi~ion to the above, the alloy o~ the pre~ent invention exhibits superior sag resistant properties to - those alloys prevlously used in brazed assem~lies or brazing composites such as aluminum Alloy 3003. This superior property can be attributable to the larger grains which are obtained in the allo~ of the present invention because of the restrictive additions of iron~ manganese, silicon and chromium. The larger grain size results in less graln boundary area in which slippage can occur thus resulting in sag. Thus~ the alloy of the present invention is particularly suited for use in the manufacturing o~
large brazed assemblies where dimensional integrity is of the essence.
The alloy of the present invention is particularly useful in the manufacture of brazed equipment by mass production methods involving either flux or vac~um brazing.
The alloy o~ the present invention has particular value ror equipment which is expected to encounter corroslve conditions whlch could cause intergranular corrosion o~ the alloy. Vacuum bra~ed alumlnum heater cores have been found to have severe intergranular corrosion problems when made using conventional brazing sheets wlth Alloy 3003 as the parent metal. These heater cores are used, ~or example, to provide warm air to warm the passenger .
compartment of passenger cars b~ abstracting e~cess heat from the automotive englne coolant~ The inter~ranular ~corr~slon results.~rom contact be~ween the corroslve: -8 ~
l~ig436 aqueous engine coolant and the lnternal surfaces o~ the plate channelsO When the alloy o~ the present invention is used as the core material in a brazing composite, it significantly reduces the intergranular corroslon which occurs in this type o~ application. Other automotive - applications exist for which a composite made with the alloy of the present invention is quite suita~le, lncludlng automotive radiators and oil coolers in the engine systems and also evaporators and condensers in automotive air conditioning systems. The alloy of the present invention is particularly suited to be used as a monolit~ic sheet in an assembly with the brazing alloy in the ~orm of another sheet or foil associated therewith. The alloy of the present invention is particularly suited for the use in the manufacture of brazed assemblies, particularly large brazed -~ assem~lies, where good dimensional stability is critical.
The present invention will be more readily understand-able from a consideration of the followlng illustrative examples .
EXAMPLE I
Two core ingots were cast having the compositlon set forth below, with Alloy A representing the material of the present invention and Alloy B being a comparative alloy.
Alloy A Alloy B
Silicon - 0.04% Chromium ~ 0.15%
Chromium - 0.3% Iron ~ 0~04%
Manganese - 0.4% Silicon - o.OII%
Iroh - 0.035% Aluminum - Balance Titanium - 0,01%
Aluminum - Balance ~ ~g - `- .
CON-149.-M
~9 ~3~
Direct chill castings of lngots of Alloys A and B were homogenized at 1125F for 8 hours using a maximum heat up ra~e from 600F of 50F per hour. The ingots were cooled from 1125F to 600F at 25F per hour and air cooled to room temperature~ The core materials of Alloys A and B
were scalped to 1.5" thicl{ness and were brushed on one side.
EXAMPLE II
-Durville ingots were cast to the compositions shown in Table I below, TABLE I
Al-loy Si Fe _ Mn Ti Mg Bi 4343 C 7.5 .35 .05 - .01 _ MD 150 D 9.7 .3 .05 .07 .01 1.5 MD 177 E 9.7 .3 .05 .07 .01 1.5 .l The ~oregoin~ Alloys C, D and E represent ilicon rich cladding alloys~ The Durville lngots of Alloys C, D and E
were scalped to 1.5" thickness. They were reheated to 800F
for l hour and hot rolled to 0.15" gage. The ~ot rolling scale was removed by caustic etching and rinsing.
EXAMPLE_III
Brazing sheets of Alloy C clad on Alloy A and Alloy C
clad on Alloy B were fabricated. In additiong for comparative purposes a brazing sheet of Alloy 4343 (Alloy C) clad on Alloy 3003 was prepared. All brazing sheets were one side clad only. The brazing sheets were fabricated by welding the appropriate brazing alloy to the wire brushed side of ~he pare~ alloy ~nd hot ~oli~ng t~e~andwich. ~An 800~F
-- 10 _ ., !
~ ~3~ CON-149 M
entry temperature was,used, Gne side was left unwelded to permit air to be expelled from the matlng surface. Hot rolling was continued until the sandwiches were 0.15 thick~ They were then cold rolled to 0,030" and annealed by heating to 660F at a rate of 25F per hour from 300F, held at 660F for 2 hours, cooled to 400F at 25F per hour, and air cooled from 400F to room temperature.
EXAMP'LE'IV
The brazing sheets were sub~ected to a simulated flux brazing cycle such as mighk be applied to a-bulky assembly.
The simulated flux bra~ing cycle included stacking 4" x 4"
sheets in a tray and placing the tray in a muffle furnace.
A thermocouple wàs present in a dummy load in the furnace ln order to determine metal temperature. Samples were heated to lOOO~F and held at this temperature for 5 hours to simulate the preheat step. They were then heated to 1115F for periods of 15 min~te ~ 30 minutes, 60 minutes and 300 minutes with some æamples unheated. The samples were then cut to 1" x l/2" specimens and a hole was punched near one of the l/2" edges to permi,t them to be supported on a nylon threaded rod support. All of the specimens ' were immersed for 140 hours at 40~F in a solution having composition set forth in ~able II below.
.. ~ .
. .
0.1 ~olar NaCl, 0,01 Molar NaN03 2.0 cc glacial acetic acid
4~0 cc 30% ~I22 all in l llter of distilled water 30 . , - , ,, ,~ ,~,- ,, ' ,,~ , - 11 .
~9436 CON-149-M
,~, , , j.,The,foregoln~,solution~,was d,esigned.to simulate,the, particularly corrosive service to whlch air liquidation heat exchangers are exposed. The photographs of Figure 1 show the appearance of the clad and unclad sides of the ; samples following this exposure. Figure lA represents Alloy C clad on Alloy A, Figure lB represents Alloy C
clad on Alloy B. Figure lC represents Alloy C clad on Alloy 3003 correspondlng to No. 11 brazing sheet. It is 1, apparent that the Alloy C clad on Alloy A sample of the present invention is complçtely free o~ visual evidence 1, of corrosion on both its clad and unclad surfaces. The Alloy C on Alloy B comparative materSal exhiblts some pits on the unclad side, but no attack on the clad side.
These pits were found to have the depths set forth in Table III below depending upon the time at 1115F.
TABLE III
Pitting into the unclad side of the C on B bra_in~_sheet 20 Time at 1115F Average pit depth in minutes in mlls __ , _ _ _ O. ' O
7.0 8.6 300 12.2 The No. 11 brazing sheet (Figure lC) is severely affected by the exposure on the unclad side where the brazing time is either zero or 300 minutes and is moderately affected for the 15, 30 and 60 minute brazing times. The form of attack was blister ~ormation, Examination of the clad side of the No. 11 brazing sheet'CFigure lC) shows severe attack only , ,ln the case of the samp,le which",had no~,b,een sub~ected to - - 12 - ~ -~ 4 3~ CON-149--M
- s~mulated brazin~:at lll5~F. -qhus~ it.can be seen that the.alloy o~- the ...
~ present lnvention wheth~r cl~d or unclad exhibits no corroslve attack on : either the clad or the unclad side~ In contrast, a sev~re pitting attack occurred on unclad aluminum Alloy 3003,' Flgures 2A, 2B, 2C and ZD represent phota~icrographs o~ cross sections through specimens of Alloy C clad on Allo~ A and No. 11 bra2ing sheet followlng exposure for 140 hours to the,corrosive solution of Table II at 25 F and 40F. The photcnicrographs are at a nagnification of 20ax. Flgure 2A represents Alloy C clad on Alloy A following exposure at 25F, Figure 2B represents Alloy C clad on Alloy A following exposure at 40F, Flgure 2C represents No. 11 ~razing sheet followins e~osure at 25F and Figure ZD represents No. 11 brazing sheet following exposure at 40F. The results shown in Figure 2 indicate that oNer a range Or flux brazing conditions the Alloy C clad on Alloy A brazing sheet o~ the present invention was much more resistant to inter-granular corrosion on the clad and unclad surfaces than the No. 11 brazing sheet. The results in Figure 1 show severe pitting on the core element on the comparative Alloy C clad ~20 on Alloy B brazing sheet. The Alloy A element o~ the Alloy C on Alloy A composite is the alloy containing 0.4% manganese and 0.3% chromium of our inventlon. The B component of the Alloy C on Alloy B brazing sheet is the 0.15% chromium, balance aluminum plu8 about 0.04% iron and 0.04% silicon.
The severe pitting Or this material shows that it is not sufficient to incorporate chromium ln a base with restricted iron and silicon contents. The deliberate manganese addition incorporated into Alloy A of the present invention is essentlal for adequate corrosion resistance~
. . . . .,. ,- . . ..... .. , . . ,. :, ..... .. .. . . . . . .... ...
3~ .
~, ~ 13 -~
943~i EXAM LE VI
Brazing sheets of Alloy D CMD 150) clad on Alloy 3003 and Alloy E CMD 1772 clad on Alloy 3003 plus brazing sheets o~ ~lloy D on Alloy A of the present lnvention and Alloy E
on Alloy A of the present invention were all sub~ected to ~imulated vacuum brazin~ treatment. ~he treatment consisted of holding the material for a total of 12 minutes in a vacuum furnace set at 1100F at a pressure of 2 x 10 4 Torr.
The specimens were then removed ~rom the furnace and air cooled. Samples were eYaluated for susceptibility to intergranular corrosion by immersing same ~or 24 hours in a boiling solution prepared by dissolving the materials set forth in Table IV below in 10 llters of distilled water;~
TABLE IV
1.48 grams Na2So4 1.65 grams NaCl 1.40 grams NaHC03 0.29 grams FeC13 0.39 grams CuS04 7H20 The specimens were allowed to remain in the solution for a ~urther 2~ hour period during which time the solution cooled to ambient temperature. The specimens were then removed from the solution and examlned for intergranular corros1on.
The specimen sur~aces were marked ln some places by whike corrosion product which corresponded to internal inter-granular corrosion. Metallographic cross sectioning of the specimens was carried out in the most extensive areas ; covered by the whlte corroslon product, Photomlcrographs at 200X magni~ication o~ the polished cross sections are ; 30 shown in Flgure 3. Figure 3A represents Alloy D clad on Alloy A, Figure 3B represents Alloy D clad on Alloy 3003, ~ ; Figùre 3C rapresents Alloy E`clad on Alloy A and Figure 3D
.~ , .
9~3~:i represents Alloy E c].ad on Alloy 3003~ The results clearly show that the c~mposite of the present invention is una~ected by the corrosi~e test ~edium using two types o~
vacuum brazing alloy. In contrast, co~posites using Alloy 30Q3 su~fered ~arying degres o~ intergranular corrosion depending upon whether the ~acuum braz~ng alloy is Alloy D
(.silicon plus magnesium~ or Alloy E (s~licon plus ~agnesium plus b~s~uthl.
EXA~PL~ VlI
___ Three core ingots were cast for each of the compositions set ~orth belo~ with Alloy X representlng the material of the present invention, Alloy Y being a comparati~e alloy and ; Alloy Z heing o~ the c~mposi.tion o~ aluminum Allo~ 3003~
\TAE~LE ~Y
Al~oy X ~ ~Alloy Y Allo~_Z~
.
S~licon up.to 0.1 Silicon - 0,21 Sllicon - 0,20 ~ron up to~.0~2 Iron - 0,34 Iron _ 0,52 Manganese ~ o~4a Copper - 0.20 Copper - 0.12 Chromi~m ~. 0,25 Manganese - 1,20 ~anganese - 1,16 20Titanium ~ O.010 Chromium - O.31 Titani~m - O,Dll Balance hlum~num Zinc - O.10 Balance Aluminum ~ Titanium ~ 0.010 ; Balance Aluminum One each of the direct chill castings o~ ingots of Alloys X, Y and Z were ho~ogenized at 1000F for 8 hours using a maxi~um heat up rate ~rom 600F of 50F per hour, Th.e ingots were then air cooled to room temperature. Th.e core materials of Alloys X, Y and Z were scalped to 1,511 thickness and were brushed on one side.
A second chill casting of ingots of each of the Alloys X, Y and Z were homogenized at 1060F ~or 8 hours again uslng a ma~imum heat up r2te fr~m 600F o~ 5QF per hour, The . 15 ~
43~
ingots, were cooled ~o~ 1050~ lQ25~ at 25oF pe~ hour and then were cooled to room temperature, The core materials of Alloys X~ Y and Z were scalped to 1.5" thickness and were brushed on one side.
The ~inal ingot of each Alloy X~ 'Y and 2 was homo-genized at 1125F for 8 hours using a maximum heat up rate from 600F of 50F per hour. The ingots were cooled from 1125F to 1025F at 25F per hour and were cooled to room temperature. The core materials of Alloys Xg Y and Z
were scalped to 1.5" thickness and were brushed on one side.
The nine ingots thus treated were processed in ~he following manner Por mechanical property evaluation, in particular, resistance to sag. The ingots were hot rolled at 800F and processed to final ~age without an inter-annealing~ A ~inal anneal was gi~en for each alloy at final gage at 660F for 2-1/2 hours. Resistance to sag was determined by measuring the deflection which occurred at the free end of an 8" long x 1" wide cantilevered sample (6" long pro~ect~ng length) after a simulated brazing cycle. Sag resistance of each of the giren alloycompositions was performed on samples having a gage of 0.030". The simulated vacuum brazing cycle consisted o~ heating the samples as rapidly as possible to 1100F, about 10 minutes for 0.030~ samples, followed by holding for 8 mlnutes at 1100F, then air cooled to room temperature. This simulated vacuum brazing cycle closely duplicates the commercial practice of heating from room temperature to 1070F in less than 1 minute, holding more than 1 minute at temperatures in excess of 1070F~ coollng ~rom lQ70~F
t,o 8Q0F`in,~ac~um ,and then ~an c,oollng to room temperature ' , - 16 - ~
~119436 CON~149-M
,The,,furnace temperature is 1100~ to 1110F and the total elapsed time ~s a~out 18 minutes from the start of the cycle to transfer ~or cooling fan.
Figure 4 graphically illustrates the comparative sag resistance o~ the alloy o~ the present invention ~ with that of comparative Alloy Y and Alloy Z, Alloy Z
being aluminum Alloy 3003, as a function o~ the homogeni-zation temperature. The typical homogenization temperature at which aluminum alloys are treated in the production of brazlng sheet ls in the order of 1100F to 1150F.
As can be seen from Figure 4, the alloy o~ the present invention exhibits superior sag resistant properties to that of either Alloy Y or Alloy Z (aluminum Alloy 3003), The alloy of the present invention exhibits ~rom about 1/5 to 1/25 of the sag deflection of aluminum Alloy 3003 when exposed to a slmulated brazing cycle, the di~ference in sag resistance being dependent upon prior homogenization treatment of the initial sheet in~ot. Thus, it can be een that the alloy of the present invention exhlbits superior sag resistance to those alloys normally used in the manufacture o~ brazed assemblies.
.30 , . '.
- 17 ~ .- .
~9436 CON-149-M
,~, , , j.,The,foregoln~,solution~,was d,esigned.to simulate,the, particularly corrosive service to whlch air liquidation heat exchangers are exposed. The photographs of Figure 1 show the appearance of the clad and unclad sides of the ; samples following this exposure. Figure lA represents Alloy C clad on Alloy A, Figure lB represents Alloy C
clad on Alloy B. Figure lC represents Alloy C clad on Alloy 3003 correspondlng to No. 11 brazing sheet. It is 1, apparent that the Alloy C clad on Alloy A sample of the present invention is complçtely free o~ visual evidence 1, of corrosion on both its clad and unclad surfaces. The Alloy C on Alloy B comparative materSal exhiblts some pits on the unclad side, but no attack on the clad side.
These pits were found to have the depths set forth in Table III below depending upon the time at 1115F.
TABLE III
Pitting into the unclad side of the C on B bra_in~_sheet 20 Time at 1115F Average pit depth in minutes in mlls __ , _ _ _ O. ' O
7.0 8.6 300 12.2 The No. 11 brazing sheet (Figure lC) is severely affected by the exposure on the unclad side where the brazing time is either zero or 300 minutes and is moderately affected for the 15, 30 and 60 minute brazing times. The form of attack was blister ~ormation, Examination of the clad side of the No. 11 brazing sheet'CFigure lC) shows severe attack only , ,ln the case of the samp,le which",had no~,b,een sub~ected to - - 12 - ~ -~ 4 3~ CON-149--M
- s~mulated brazin~:at lll5~F. -qhus~ it.can be seen that the.alloy o~- the ...
~ present lnvention wheth~r cl~d or unclad exhibits no corroslve attack on : either the clad or the unclad side~ In contrast, a sev~re pitting attack occurred on unclad aluminum Alloy 3003,' Flgures 2A, 2B, 2C and ZD represent phota~icrographs o~ cross sections through specimens of Alloy C clad on Allo~ A and No. 11 bra2ing sheet followlng exposure for 140 hours to the,corrosive solution of Table II at 25 F and 40F. The photcnicrographs are at a nagnification of 20ax. Flgure 2A represents Alloy C clad on Alloy A following exposure at 25F, Figure 2B represents Alloy C clad on Alloy A following exposure at 40F, Flgure 2C represents No. 11 ~razing sheet followins e~osure at 25F and Figure ZD represents No. 11 brazing sheet following exposure at 40F. The results shown in Figure 2 indicate that oNer a range Or flux brazing conditions the Alloy C clad on Alloy A brazing sheet o~ the present invention was much more resistant to inter-granular corrosion on the clad and unclad surfaces than the No. 11 brazing sheet. The results in Figure 1 show severe pitting on the core element on the comparative Alloy C clad ~20 on Alloy B brazing sheet. The Alloy A element o~ the Alloy C on Alloy A composite is the alloy containing 0.4% manganese and 0.3% chromium of our inventlon. The B component of the Alloy C on Alloy B brazing sheet is the 0.15% chromium, balance aluminum plu8 about 0.04% iron and 0.04% silicon.
The severe pitting Or this material shows that it is not sufficient to incorporate chromium ln a base with restricted iron and silicon contents. The deliberate manganese addition incorporated into Alloy A of the present invention is essentlal for adequate corrosion resistance~
. . . . .,. ,- . . ..... .. , . . ,. :, ..... .. .. . . . . . .... ...
3~ .
~, ~ 13 -~
943~i EXAM LE VI
Brazing sheets of Alloy D CMD 150) clad on Alloy 3003 and Alloy E CMD 1772 clad on Alloy 3003 plus brazing sheets o~ ~lloy D on Alloy A of the present lnvention and Alloy E
on Alloy A of the present invention were all sub~ected to ~imulated vacuum brazin~ treatment. ~he treatment consisted of holding the material for a total of 12 minutes in a vacuum furnace set at 1100F at a pressure of 2 x 10 4 Torr.
The specimens were then removed ~rom the furnace and air cooled. Samples were eYaluated for susceptibility to intergranular corrosion by immersing same ~or 24 hours in a boiling solution prepared by dissolving the materials set forth in Table IV below in 10 llters of distilled water;~
TABLE IV
1.48 grams Na2So4 1.65 grams NaCl 1.40 grams NaHC03 0.29 grams FeC13 0.39 grams CuS04 7H20 The specimens were allowed to remain in the solution for a ~urther 2~ hour period during which time the solution cooled to ambient temperature. The specimens were then removed from the solution and examlned for intergranular corros1on.
The specimen sur~aces were marked ln some places by whike corrosion product which corresponded to internal inter-granular corrosion. Metallographic cross sectioning of the specimens was carried out in the most extensive areas ; covered by the whlte corroslon product, Photomlcrographs at 200X magni~ication o~ the polished cross sections are ; 30 shown in Flgure 3. Figure 3A represents Alloy D clad on Alloy A, Figure 3B represents Alloy D clad on Alloy 3003, ~ ; Figùre 3C rapresents Alloy E`clad on Alloy A and Figure 3D
.~ , .
9~3~:i represents Alloy E c].ad on Alloy 3003~ The results clearly show that the c~mposite of the present invention is una~ected by the corrosi~e test ~edium using two types o~
vacuum brazing alloy. In contrast, co~posites using Alloy 30Q3 su~fered ~arying degres o~ intergranular corrosion depending upon whether the ~acuum braz~ng alloy is Alloy D
(.silicon plus magnesium~ or Alloy E (s~licon plus ~agnesium plus b~s~uthl.
EXA~PL~ VlI
___ Three core ingots were cast for each of the compositions set ~orth belo~ with Alloy X representlng the material of the present invention, Alloy Y being a comparati~e alloy and ; Alloy Z heing o~ the c~mposi.tion o~ aluminum Allo~ 3003~
\TAE~LE ~Y
Al~oy X ~ ~Alloy Y Allo~_Z~
.
S~licon up.to 0.1 Silicon - 0,21 Sllicon - 0,20 ~ron up to~.0~2 Iron - 0,34 Iron _ 0,52 Manganese ~ o~4a Copper - 0.20 Copper - 0.12 Chromi~m ~. 0,25 Manganese - 1,20 ~anganese - 1,16 20Titanium ~ O.010 Chromium - O.31 Titani~m - O,Dll Balance hlum~num Zinc - O.10 Balance Aluminum ~ Titanium ~ 0.010 ; Balance Aluminum One each of the direct chill castings o~ ingots of Alloys X, Y and Z were ho~ogenized at 1000F for 8 hours using a maxi~um heat up rate ~rom 600F of 50F per hour, Th.e ingots were then air cooled to room temperature. Th.e core materials of Alloys X, Y and Z were scalped to 1,511 thickness and were brushed on one side.
A second chill casting of ingots of each of the Alloys X, Y and Z were homogenized at 1060F ~or 8 hours again uslng a ma~imum heat up r2te fr~m 600F o~ 5QF per hour, The . 15 ~
43~
ingots, were cooled ~o~ 1050~ lQ25~ at 25oF pe~ hour and then were cooled to room temperature, The core materials of Alloys X~ Y and Z were scalped to 1.5" thickness and were brushed on one side.
The ~inal ingot of each Alloy X~ 'Y and 2 was homo-genized at 1125F for 8 hours using a maximum heat up rate from 600F of 50F per hour. The ingots were cooled from 1125F to 1025F at 25F per hour and were cooled to room temperature. The core materials of Alloys Xg Y and Z
were scalped to 1.5" thickness and were brushed on one side.
The nine ingots thus treated were processed in ~he following manner Por mechanical property evaluation, in particular, resistance to sag. The ingots were hot rolled at 800F and processed to final ~age without an inter-annealing~ A ~inal anneal was gi~en for each alloy at final gage at 660F for 2-1/2 hours. Resistance to sag was determined by measuring the deflection which occurred at the free end of an 8" long x 1" wide cantilevered sample (6" long pro~ect~ng length) after a simulated brazing cycle. Sag resistance of each of the giren alloycompositions was performed on samples having a gage of 0.030". The simulated vacuum brazing cycle consisted o~ heating the samples as rapidly as possible to 1100F, about 10 minutes for 0.030~ samples, followed by holding for 8 mlnutes at 1100F, then air cooled to room temperature. This simulated vacuum brazing cycle closely duplicates the commercial practice of heating from room temperature to 1070F in less than 1 minute, holding more than 1 minute at temperatures in excess of 1070F~ coollng ~rom lQ70~F
t,o 8Q0F`in,~ac~um ,and then ~an c,oollng to room temperature ' , - 16 - ~
~119436 CON~149-M
,The,,furnace temperature is 1100~ to 1110F and the total elapsed time ~s a~out 18 minutes from the start of the cycle to transfer ~or cooling fan.
Figure 4 graphically illustrates the comparative sag resistance o~ the alloy o~ the present invention ~ with that of comparative Alloy Y and Alloy Z, Alloy Z
being aluminum Alloy 3003, as a function o~ the homogeni-zation temperature. The typical homogenization temperature at which aluminum alloys are treated in the production of brazlng sheet ls in the order of 1100F to 1150F.
As can be seen from Figure 4, the alloy o~ the present invention exhibits superior sag resistant properties to that of either Alloy Y or Alloy Z (aluminum Alloy 3003), The alloy of the present invention exhibits ~rom about 1/5 to 1/25 of the sag deflection of aluminum Alloy 3003 when exposed to a slmulated brazing cycle, the di~ference in sag resistance being dependent upon prior homogenization treatment of the initial sheet in~ot. Thus, it can be een that the alloy of the present invention exhlbits superior sag resistance to those alloys normally used in the manufacture o~ brazed assemblies.
.30 , . '.
- 17 ~ .- .
Claims (5)
1. An improved corrosion resistant aluminum alloy exhibiting improved sag resistant properties when used in the manufacture of brazed assemblies, said alloy con-sisting essentially of from 0.05 to 0.4 weight % chromium, from 0.2 to 0.9 weight % manganese, up to 0.2 weight %
iron, up to 0.1 weight % silicon, balance essentially aluminum.
iron, up to 0.1 weight % silicon, balance essentially aluminum.
2. An aluminum alloy according to claim 1, wherein said alloy contains from 0.15 to 0.30 weight % chromium, from 0.3 to 0.6 weight % manganese, from 0.02 to 0.08 weight % iron, from 0.02 to 0.08 weight % silicon, balance essentially aluminum.
3. An aluminum alloy according to claim 1, wherein said alloy contains reduced size and population density of second phase iron containing particles, as compared to Aluminum Alloy 3003.
4. An aluminum alloy according to claim 1, wherein said alloy is substantially free from highly cathodic FeA13 phase.
5. An aluminum alloy according to claim 1, wherein said alloy contains up to 0.1 weight % iron.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US881,071 | 1978-02-24 | ||
| US05/881,071 US4167410A (en) | 1977-03-03 | 1978-02-24 | Alloy for use in brazed assemblies |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119436A true CA1119436A (en) | 1982-03-09 |
Family
ID=25377722
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000321925A Expired CA1119436A (en) | 1978-02-24 | 1979-02-20 | Alloy for use in brazed assemblies |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS54126616A (en) |
| AT (1) | AT367461B (en) |
| CA (1) | CA1119436A (en) |
| CH (1) | CH640273A5 (en) |
| DE (1) | DE2904219C2 (en) |
| FR (1) | FR2418275B1 (en) |
| IT (1) | IT1209445B (en) |
| NO (1) | NO790631L (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2489845B1 (en) * | 1980-09-11 | 1986-06-06 | Cegedur | BRAZABLE ALUMINUM ALLOY AND MANUFACTURING METHOD THEREOF |
| JPS6015709B2 (en) * | 1982-10-19 | 1985-04-20 | 古河アルミニウム工業株式会社 | Brazing sheet for aluminum heat exchanger |
| JPS60224736A (en) * | 1984-04-21 | 1985-11-09 | Kobe Steel Ltd | Aluminum alloy having superior pitting corrosion resistance |
| JP2707139B2 (en) * | 1989-07-05 | 1998-01-28 | 日本軽金属株式会社 | Pitting corrosion resistant aluminum alloy and method for producing the same |
| US5286316A (en) * | 1992-04-03 | 1994-02-15 | Reynolds Metals Company | High extrudability, high corrosion resistant aluminum-manganese-titanium type aluminum alloy and process for producing same |
| WO2021165264A1 (en) * | 2020-02-17 | 2021-08-26 | Hydro Extruded Solutions As | High corrosion and heat resistant aluminium alloy |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2207232C3 (en) * | 1971-02-24 | 1975-09-18 | Sumitomo Chemical Co., Ltd., Osaka (Japan) | Process for the production of inherently colored anodic oxide layers on aluminum alloys |
| US3923557A (en) * | 1973-11-12 | 1975-12-02 | Alusuisse | Corrosion resistant aluminum alloys |
-
1979
- 1979-01-26 CH CH79379A patent/CH640273A5/en not_active IP Right Cessation
- 1979-02-05 DE DE2904219A patent/DE2904219C2/en not_active Expired
- 1979-02-20 CA CA000321925A patent/CA1119436A/en not_active Expired
- 1979-02-23 IT IT7920496A patent/IT1209445B/en active
- 1979-02-23 AT AT0144079A patent/AT367461B/en not_active IP Right Cessation
- 1979-02-23 NO NO790631A patent/NO790631L/en unknown
- 1979-02-23 JP JP2060579A patent/JPS54126616A/en active Granted
- 1979-02-23 FR FR7904757A patent/FR2418275B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| IT7920496A0 (en) | 1979-02-23 |
| JPS6211062B2 (en) | 1987-03-10 |
| FR2418275A1 (en) | 1979-09-21 |
| NO790631L (en) | 1979-08-27 |
| JPS54126616A (en) | 1979-10-02 |
| IT1209445B (en) | 1989-08-30 |
| ATA144079A (en) | 1981-11-15 |
| DE2904219C2 (en) | 1983-04-14 |
| FR2418275B1 (en) | 1986-05-09 |
| CH640273A5 (en) | 1983-12-30 |
| AT367461B (en) | 1982-07-12 |
| DE2904219A1 (en) | 1979-08-30 |
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