Classifications

• • 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

Definitions

• Aluminum sheet and other products have found wide acceptance in the architectural field where they form substantial portions or even all of the exterior of several high-rise or other type buildings. Especially useful are those aluminum products which, when anodized, achieve an integrally colored oxide coating.
• the integral color is preferable to a dyed or otherwise imparted color since it is more durable and has aesthetic advantages with respect to the depth of the color.
• aluminum alloy sheet products capable of economical and rapid color development in anodizing baths together with good forming characteristics and good corrosion resistance have been difficult to achieve. For instance, some products can achieve a desired color, for instance, a black color, but are not readily formed as by bending into the shapes desired for a given curtain wall design.
• an improved aluminum architectural sheet product which has high resistance to corrosion, is readily formed by bending or other working operations to produce desired shapes which when anodized are substantially free from any crackling or checking in areas where the sheet is bent.
• the sheet is capable of producing an integral black color within 30 minutes employing existing commercially accepted anodizing methods.
• the sheet is also capable of achieving gold or other colors by altering the anodizing conditions.
• the improved sheet is fashioned from an improved alloy consisting essentially of 0.4 to 0.6% copper, 0.1 to 0.25% chromium, 0.08 to 0.18% silicon, the balance being aluminum and not more than the following amounts of other elements and impurities: iron 0.3%, manganese 0.05%, zinc 0.05%, titanium 0.05%, magnesium 0.1%, all others being limited to 0.05% each and a total of 0.1%. Further the total amount of all impurities not including iron, should not exceed 0.2%. While magnesium has been described as an impurity, one preferred embodiment of the invention contemplates controlled additions of magnesium within the range of up to 0.1%, the preferred minium for magnesium being 0.005% and the preferred maximum being 0.05%. Within these limits magnesium confers an advantage on the improved sheet with respect to reducing any tendency for structural streaking.
• the improved method for producing the architectural sheet product contemplates providing a body of the alloy described above and homogenizing it at a sufficiently high temperature to dissolve the chromium and copper containing phases after which the metal is hot-warm rolled at controlled temperature levels to produce a sheet product.
• the sheet product so produced can, if desired, be further worked by cold rolling which can advantageously strengthen the sheet by strain hardening and the cold rolling can be preceded by an anneal. If ease of forming is important any cold rolling can be followed by an anmeal.
• the alloy is produced as an ingot by any of the means conventionally employed although continuous casting is preferred. Economical production requires starting with an ingot of substantial thickness, at least 8 inches and preferably 10 inches or more in thickness, for instance 12 inches or even greater. However, the hot rolling normally required in fabricating a rolled product from starting stock of this size seems to cause the bend appearance problem discussed above regardless of subsequent operations or treatments. However, as explained below certain special controls in accordance with the present improvement alleviates this condition thereby enabling economical production of an improved architectural sheet product.
• the ingot is homogenized by heating to a temperature of 1000 to 1 F., preferably 1050" to 1100 F., for a period typically ranging from about 4 to 20 hours or more. This assures solution of the copper and chromium containing phases and further spherodizes the constituent phases such as Al-Fe-Si and Al-iFe-Cr constituents.
• the ingot is then cooled to room temperature or cooled to about 800 F. for rolling. It is preferred that any cooling be fairly rapid as by cooling in open .air as opposed to furnace cooling and the improved method favors such rapid cooling rates as are commensurate with open air cooling.
• the homogenized ingot is scalped and rolled at controlled temperatures ranging from 300" to 800 F.
• the initial hot rolling passes impart certain characteristics to the grain structure of the rolling stock which are reflected in the final product regardless of the subsequent fabrication steps even if they include drastic cold reductions.
• the improved sheet alloy described above cannot sustain working operations above temperatures of about 850 F. without exhibiting appearance problems in bend areas. This effect seems connected with the fact that conventional hot working operations at temperatures of 850 to 950 F. can elongate the grains considerably without any significant amount of grain fragmentation occurring.
• the grain elongation effect is not of special significance it is especially important that the very first passes produce at least some significant amount of grain fragmentation across the long transverse direction or dimension as it is this which avoids the development of any banded grain structure.
• the long trans verse direction is that corresponding to the sheet width, that is normal to the sheet length and to the sheet thickness. -It has been found that the first hot rolling passes set the pattern for this effect which pattern exerts a strong influence on the final product regardless of subsequent fabricating operations, even drastic cold rolling and the drastic grain fragmentation associated therewith.
• the invention contemplates avoiding such operations at temperatures over 800 F. and instead contemplates hot rolling at rolling mill entrance temperatures of 600 to 800 F., preferably 700 to 800 -F. That is, the ingot or rolling stock is cooled to or reheated to provide a substantially uniform metal temperature of 600 or 700 to 800 F. as the metal enters the hot rolling mill.
• the metal can, however, be brought to a higher temperature, say 825 or 850 or even 900 -F. prior to rolling, so long as it is cooled to substantially not over 800 F. as it enters the rolling operations.
• the rolling stock is hot warm rolled at temperatures between the entrance temperature of not over 800 F. down to temperatures of 300 F. or higher. It is preferred that temperatures during the hot-warm rollingdo not fall below 375 F. and preferably not below 450 F.
• the extent of the rolling reductions at the controlled elevated temperatures should amount to at least 40% of the thickness of the starting stock and preferably at least 80%, and it is preferred that the reductions proceed without reheating the metal to compensate for heat lost in the rolling operation.
• These reductions at these controlled temperatures result in a grain structure which, while some- What elongated, is well fragmented in the transverse direction, the widest grain or grain fragment dimension being not over about 0.05 millimeter as measured in the transverse direction of the sheet at the conclusion of the controlled temperature rolling operations.
• the improved sheet product exhibits substantially complete freedom from structural streaking and, very significantly, greatly increased resistance to corrosion in polluted atmosphere thus providing for greatly improved and reduced maintenance costs on a completed building, especially a high-rise building which extends into the polluted atmospheres which seem to lurk above almost every site where large buildings are constructed.
• the sheet product exiting the controlled warm rolling operation can typically range in thickness from 0.075 to 0.25 inches and is useful in these and other thickness with or without further processing.
• the sheet can be annealed in order to soften it for further working or forming operations. For instance, it can be fully annealed at a temperature of around 600 to 700 F. and the sheet s0 treated exhibits less tensile strength but is easier to bend than in the condition as it exits the warm rolling operation.
• the sheet product can be further worked as by cold rolling with or Without tfirst annealing.
• the strain hardening effects of cold rolling would confer higher strength to the sheet which may be desired in some instances. Additionally some amount of cold rolling can sometimes reduce any structural streaking problems in the anodized sheet product.
• the desirability of annealing before cold rolling would depend to some extent on the degree of the cold reduction.
• One preferred embodiment of the invention contemplates providing the defined improved alloy as a cladding layer on an alloy core to provide a composite structure. This has the advantage of achieving a desired strength level from the core material while realizing the advantages of the invention in the cladding layer.
• a suitable core alloy is alloy 3003 which contains nominally 1.2% manganese and 0.12% copper, balance essentially aluminum.
• the invention contemplates the use of such clad composites featuring the improved alloy as a cladding on one or both faces of a sheet produced and a core composed of an aluminum alloy which aluminum alloy may typically contain up to 2%, for instance 0.3 to 2% of manganese.
• This type of core alloy is highly compatible with the improved alloy with respect to rolling and other fabricating characteristics thus enabling relatively economical production of a clad product.
• the cladding material in the improved alloy is fabricated into sheet according to the mehods here described. This sheet is placed on one or both sides of the core rolling stock and hot roll bonded thereto to provide a bonded composite which is reduced by rolling.
• the roll ing here does not need to proceed according to the improved controlled conditions since the cladding has already been previously broken down by the improved method.
• the sheet product can be anodized to develop integrally colored anodic coatings.
• the black color is characterized by apparent reflectance and yellowness levels of less than 4% as determined by Color-Eye measurement. Again the coating is about 0.71 mil in thickness.
• the electrolyte could contain one of the other sulfonic acids such as sulfosuccinic and sulfosalicyclic acids.
• anodic coating it is usually desirable to seal the anodic coating, for example, by immersing in hot (210 F.) water or other suitable solutions.
• the coloration and texture developed in the anodic treatment can be modified by treatment of sheet prior toanodic oxidation.
• the surface can be chemically brightened by washing with a solution of phosphoric and nitric acids or electrochemical procedures. Mechanical treatments such as buffing, polishing, sand blasting and the like can also be employed to alter the texture of the surface prior to anodizing.
• Example 1 A sheet product was fabricated from an alloy containing 0.47% Cu, 0.18% Fe, 0.07% Si, 0.17% Cr, 0.00% Mg, 0.02% Zn, 0.01% Ti, the balance aluminum.
• the alloy was continuously cast as an ingot which was homogenized at a temperature of 1100 F., cooled to room temperature in open air, scalped and then reheated to about 950 F.
• the scalped ingot was then introduced into a hot reversing mill at a conventional ingot metal temperature of 910 F. which reduced the thickness from about 12 inches to about 4 inches, a reduction of 67%.
• the 4-inch plate was then introduced to a second mill which reduced its thickness to about inch.
• This plate was then run through a continuous mill at an entry temperature of about 650 F. which reduced its thickness to about A; inch at an exit temperature of about 350 F.
• Sections of the sheet so produced were bent over a 4T radius (a radius of 4 times the sheet thickness) along a longitudinal direction and exhibited surface cracking folds, and objectional kinking and checking along the bend radius.
• the bent sheet sections were anodized in the sulfophthalic-sulfuric acid aqueous anodizing bath described above for 30 minutes to develop an integral black coating.
• Metallographic examinations made of transverse sections through the bend areas revealed objectionable thinning of the anodic coating in localized areas as a consequence of irregular formation of the coating over the roughened surface which considerably diminished the integrity of the coating.
• the anodized bend area also exhibited visual defects including kinking and surface cracking or checking which, regardless of coating integrity, themselves are highly objectionable for architectural application.
• Example 2 Improved sheet product was fabricated from an alloy containing 0.52% Cu, 0.22% Fe, 0.14% Si, 0.06% Mn, 0.007% Mg, 0.16% Cr, 0.025% Ti.
• the alloy was continuously cast as an ingot which was homogenized at a temperature of 1100 F., cooled .to room temperature in open air, scalped and then reheated to a temperature of 800 F.
• the scalped ingot was then introduced into a hot reversing mill at an ingot metal temperature of 760- 7-80 F. which reduced the thickness from about 14 inches to about 6 inches, a reduction of over 55%.
• the temperature exiting the mill was about 720 F.
• the 6-inch plate was then fed to a second mill which reduced its thickness to about 1 inch and the exit temperature of the second mill was about 650 F.
• the total hot reductions to this point amount to over 90% of the 14 inch thick starting stock.
• the l-inch plate was then run through a hot continuous mill where it sustained an 80% reduction to produce a sheet approximately /a inch in thickness at an exit temperature of about 350 F.
• Sections of this sheet were anodized in the sulfophthalic-sulfuric acid aqueous anodizing bath described above for 30 minutes and the integral coating exhibited a jet black color characterized by apparent reflectance and yellowness values both under 4% as determined with the Color-Eye instrument. Sections of this sheet also were bent over a IT radius along a longitudinal direction.
• a method of producing improved architectural sheet comprising the steps:
• a method of producing improved architectural sheet comprising the steps:
• a method of producing improved architectural sheet comprising the steps:
• An improved architectural sheet product composed of an alloy consisting essentially of 0.4 to 0.6% copper, 0.1 to 0.25% chromium, 0.08 to 0.18% silicon, the balance aluminum and not more than the following amounts of other elements and impurities: iron 0.3%, manganese 0.05%, magnesium 0.1%, zinc 0.05%, titanium 0.05%, all other impurities being limited to 0.05% each and a total of 0.1% the amount of all these elements and impurities other than aluminum, silicon, copper, chromium and iron not exceeding 0.2%, the sheet product exhibiting a substantial degree of grain fragmentation in the long transverse direction such that the largest grain or grain fragment size does not exceed about 0.05 millimeter in the long transverse direction as a result of controlled hot-warm rolling operations at temperatures of 300 or more but not to exceed 800 F., said sheet when bent to a radius of one time its thickness exhibiting substantial freedom from checks in the bend radius, said sheet further being characterized when anodized by the ability to develop an integral true black color said anodic coating having an improved level of
• the sheet product features at least one bend of a radius one time its thickness or more and features an integrally bonded anodic coating having an integral black color characterized by maxima of 4% for yellowness and apparent reflectance.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Metal Rolling (AREA)
• Panels For Use In Building Construction (AREA)
• Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
• Laminated Bodies (AREA)
• Cookers (AREA)

Priority Applications (11)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23116984

Family Applications (1)

Country Status (11)

Cited By (4)

• 1972
  • 1972-09-20 US US00290653A patent/US3827952A/en not_active Expired - Lifetime
• 1973
  • 1973-07-16 CA CA176,495A patent/CA996779A/en not_active Expired
  • 1973-08-01 AU AU58790/73A patent/AU467491B2/en not_active Expired
  • 1973-09-11 GB GB4269473A patent/GB1448146A/en not_active Expired
  • 1973-09-17 NL NL737312801A patent/NL152604B/xx not_active IP Right Cessation
  • 1973-09-18 NO NO3644/73A patent/NO135370C/no unknown
  • 1973-09-19 SE SE7312744A patent/SE396775B/xx unknown
  • 1973-09-20 DE DE2347882A patent/DE2347882C3/de not_active Expired
  • 1973-09-20 JP JP10643973A patent/JPS5442339B2/ja not_active Expired
  • 1973-09-20 FR FR7333842A patent/FR2200366B1/fr not_active Expired
  • 1973-09-20 IT IT52638/73A patent/IT996187B/it active

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