Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • 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
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/14—Producing integrally coloured layers

Definitions

• the invention relates to aluminum alloy products in the form of extruded profiles or cold rolled sheets with a uniformly gray, lightfast surface and a light reflectivity of at most 50% obtained by anodic oxidation in an electrolyte.
• the invention also relates to a method for producing these products.
• the two-stage electrolytic dyeing processes represent a diverse group.
• an oxide layer of approximately 20 ⁇ m thick is produced in a sulfuric acid or sulfuric acid / oxalic acid bath by means of direct current with a density of 100 to 200 A / m 2 .
• direct current with a density of 10 to 150 A / m 2 is deposited from metal salt solutions of suitable composition to adhere metal compounds to the pore base of the oxide layer, thereby producing a permanent and lightfast color.
• Another group of processes for producing lightfast gray colorations consists in single-stage color anodization, in which oxide layers with a natural intrinsic color are produced in a special electrolyte by means of direct current of 70 to 800 A / m2 density.
• the electrolyte that determines the color tone consists of organic acids, optionally with additions of sulfuric acid.
• Aluminum alloys are mostly used as materials AlMn, AIMg and AlMgSi.
• decorative gray tones can also be produced with standard anodizing processes. These inexpensive and widespread anodizing processes work with direct current of 80 to 300 A / m 2 density and use a sulfuric acid electrolyte, often with small additions of carboxylic acids.
• a known aluminum alloy contains 4.5% silicon and 0.5% magnesium.
• An oxide layer with a thickness of approximately 18 ⁇ m is formed after 40 minutes, which has a medium-gray inherent color.
• the light reflectivity, as a measure of the gray tone is 20%. After an oxidation time of 60 minutes, the oxide layer measures 27 ⁇ m and has a dark gray intrinsic color with 13% light reflectivity. The reflectivity was determined using a LANGE UME 1-LFE 1 measuring device.
• the inventor has therefore set himself the task of creating aluminum alloy products of the type mentioned at the outset and a process for their production which, with the usual anodizing processes, without an additional coloring step, enables a uniform, structure-free, lightfast, gray surface of at most 50% light reflectivity It should be possible to produce a wide range of shades of gray with a constant alloy composition.
• the object is achieved according to the invention in that the alloy of 1.20 to 1.60% iron and 0.25 to 0.55% manganese with a weight ratio of iron to manganese between 2.8 and 5 to 0.20% silicon and 0.30% copper, up to 5% magnesium, up to 0.10% chromium, up to 2% zinc, up to 0.25% zirconium, up to 0.10% titanium, rest of aluminum and a total of up to 0.50% of other elements, whereby the light reflectivity with constant alloy composition with oxide layers from 5 to 30 ⁇ m between 8 and 45% is adjustable and is less than 30% for oxide layers of 10 ⁇ m.
• Within the scope of the invention is also a method for producing these aluminum alloy products with a uniformly gray, light-fast surface and a light reflectivity of at most 50% by anodic oxidation in an electrolyte, which is characterized in that when processing an alloy consisting of 1.20 to 1.60% iron and 0.25 to 0.55% manganese with a weight ratio of iron to manganese between 2.8 and 5 and up to 0.20% silicon, up to 0.30% copper, up to 5% magnesium, up to 0.10% chromium, up to 2% zinc, up to 0.25% zirconium , up to 0.10% titanium, the rest aluminum and altogether up to 0.50% other elements from the casting to the product, all treatment temperatures are kept below 560 ° C and the residence time in the temperature range between 540 and 560 ° C is a maximum of 4 hours.
• All treatment temperatures are preferably selected in the lowest possible range for processing and the residence time at temperatures above 300 ° C. is kept as short as possible.
• An advantageous embodiment consists in carrying out the anodic oxidation using direct current in a sulfuric acid electrolyte with 10 to 25% by weight sulfuric acid and up to 5% carboxylic acids.
• the surface of the aluminum workpieces can be pretreated by grinding, brushing, polishing, etching, glossing and the like.
• a rectangular strand of 320 x 1080 mm 2 cross section was cast from an alloy with 1.42% iron, 0.44% manganese, 0.06% silicon and the rest aluminum with 0.07% impurities.
• the conventionally cast ingot was milled 10 mm on both sides. This could be dispensed with when using hot top or magnetic field molds.
• the ingot was then heated to 520 ° C and fed to a hot rolling stand without holding time and rolled into a sheet 8 mm thick.
• the plate emerging at a temperature of 450 ° C. was passed through a water box and cold-rolled to a thickness of 1.0 mm. After a final annealing of 3 hours at 320 ° C, the sheet had a tensile strength R m of 142 MPa, a yield strength Rp Q. 2 of 104 MPa and an elongation A 5 of 40%.
• Sheets of 980 x 980 mm2 were anodized in an electrolyte.
• the bath contained 180 g sulfuric acid and 10 g oxalic acid per liter.
• the density of the direct current was 150 A / m 2 .
• the oxide layer of a sheet anodized for 20 minutes measures 10 ⁇ m.
• the sheet shows a uniform, medium gray color over the entire surface.
• the light reflectivity determined with the LANGE UME 1-LFE 1 measuring device is 21%.
• Sheets oxidized for 40 minutes have an oxide layer 20 ⁇ m thick.
• the light reflectivity of the even dark gray surface is 12%.
• a round bolt with a diameter of 200 mm was cast from an alloy with 1.45% iron, 0.43% manganese, 0.15% zirconium, 0.05% silicon and the rest aluminum with 0.04% impurities.
• the bolt was turned over 2 mm deep and quickly heated to 490 ° C for extrusion and pressed into 3 profiles, each with a cross-sectional area of 140 mm2, without holding time.
• the strands having press weld seams emerged from the die at a temperature of 540 ° C. and were cooled with moving air.
• Tensile tests showed a tensile strength R m of 160 MPa and a yield strength R p 0.2 of 85 MPa.
• a round bolt with a diameter of 160 mm was cast from an alloy with 1.48% iron, 0.40% manganese, 1.2% magnesium, 0.05% silicon and the rest aluminum with 0.04% impurities.
• the bolt was overturned 3 mm deep and quickly heated to 380 ° C for extrusion and pressed after a holding time of one hour to a rectangular profile with 4 x 30 mm 2 cross section at a speed of 16 m / minute.
• the strand emerged from the die at a temperature of 460 ° C. and was cooled in air.
• the tensile strength R m was 215 MPa, the yield strength Rpo. 2 106 MPa and the elongation at break A 5 21%. After stretching by 3%, an R m of 220 MPa, an R p 0.2 of 173 MPa and an A 5 of 19% were measured.
• Strand sections were anodized in a bath with 180 g sulfuric acid and 10 g oxalic acid per liter at a direct current with a density of 150 A / m 2 . After 25 minutes of treatment, the oxide layer measured 12 ⁇ m. The reflectivity is 18%.
• S Trang press profile from the example 2 were measured at 25 ° C in an aqueous bath with 75 g of sulfosalicylic acid, 50 g of tartaric acid and 5 g of sulfuric acid per liter at a direct current having a density of 150 A / m 2 anodically oxidized. After 25 minutes of treatment, the oxide layer thickness was 9 ⁇ m. The R eflekt Chemistry dark gray surface was 12%.
• Extruded profiles from Example 2 were anodized at 20 ° C. in a bath with 160 g sulfuric acid and 20 g glycerol per liter for 40 minutes at a direct current density of 150 A / m 2 .
• the thickness of the resulting oxide layer is 22 ⁇ m, the reflectivity 11%.
• Extruded profiles from Example 2 were anodized at 20 ° C. in a bath with 200 g sulfuric acid per liter for 20 minutes.
• the current density alternated with a frequency of 25 Hz between the two levels 150 and 200 A / m 2 , each with a dwell time of 20 ms.
• the resulting oxide layer measures 12 ⁇ m and has a reflectivity of 16%.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Extrusion Of Metal (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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• 1986
  • 1986-05-17 DE DE19863616725 patent/DE3616725A1/de not_active Withdrawn
• 1987
  • 1987-04-30 DE DE8787810276T patent/DE3767558D1/de not_active Expired - Fee Related
  • 1987-04-30 EP EP87810276A patent/EP0246186B1/fr not_active Expired - Lifetime
  • 1987-05-12 US US07/048,802 patent/US4806211A/en not_active Expired - Lifetime

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