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
  • C22F1/047—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 of alloys with magnesium as the next major constituent
• • 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
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
• • 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
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon

Definitions

• the invention relates to an aluminum alloy, the use of an aluminum alloy strip or sheet, and a method for producing an aluminum alloy strip or sheet.
• Aluminum magnesium (AlMg) alloys of type 5xxx are used in the form of sheets or plates or strips for the construction of welded or joined structures, in shipbuilding, automotive and aircraft construction. They are characterized by a particularly high strength, with increasing the magnesium content, the strength of the AlMg alloys increase.
• Typical examples of the 5xxx aluminum alloys are, for example, aluminum alloys of the type AA 5049, AA 5454 or AA 5918.
• the alloys are AlMg 2 Mn (5049) AlMg 3 Mn (5454) or AlMg 3.5 Mn (5918) aluminum alloys ,
• the constant need for additional weight reduction requires aluminum alloys with higher strengths and thus with correspondingly higher magnesium (Mg-) held to provide the desired strengths.
• AlMgMn aluminum alloys with Mg contents of more than 2.4% by weight are increasingly prone to intergranular corrosion when exposed to elevated temperatures for longer times. It has been found that in AlMgMn aluminum alloys containing more than 2.4% by weight of magnesium at temperatures of 70 to 200 ° C., ⁇ -Al 5 Mg 3 phases precipitate along the grain boundaries. If the Grain boundaries are consistently occupied with ⁇ -particles, in the presence of a corrosive medium, the dissolution of these ⁇ -phases can lead to a selective corrosion attack along the grain boundaries.
• the aluminum alloy allows a content of up to 0.25 wt .-% zirconium, which is considered in terms of recycling of the aluminum alloy as critical. From the international patent application WO 99/42627 In addition, a zirconium-containing aluminum alloy is known, which indeed achieved very good results in the ASTM G67 test, but is problematic because of the necessarily present zirconium content in use.
• the present invention has the object to provide an aluminum alloy is available, which has only a low tendency to intergranular corrosion, ie in the ASTM G67 test a mass loss value ⁇ 15 mg / cm 2 , at the same time high strength and good formability provides and Contains standard alloy components, so that the recycling of the aluminum alloy is simplified.
• a use of the aluminum alloy and a method for the production of products of the aluminum alloy to be proposed.
• the above-described object for an aluminum alloy is achieved by comprising alloy components which have the following composition in% by weight: 2.91% ⁇ Mg ⁇ 4.5%, 0.5% ⁇ Mn ⁇ 0.8%, 0.05% ⁇ Cu ⁇ 0.30%, 0.05% ⁇ Cr ⁇ 0.30%, 0, 05% ⁇ Zn ⁇ 0.9%, Fe ⁇ 0.40%, Si ⁇ 0.25%, Ti ⁇ 0.20%,
• composition of the invention is based on the finding that the alloying components Zn, Cr, Cu and Mn at magnesium contents of at least 2.91 wt .-% suppresses the precipitation of ⁇ -Al 5 Mg 3 particles, by the presence of these alloying elements, the formation of ⁇ phases supported.
• the alloying component zinc can for example serve to compensate for 2.3 times the amount of magnesium above 2.91% by weight of Mg, so that the resulting aluminum alloy shows only a very slight tendency to intergranular corrosion.
• the efficiency of suppressing the intercrystalline corrosion or the excretion of ⁇ -phases decreases with the alloying components chromium, copper and manganese.
• aluminum alloys can be provided in any case, which have relatively high magnesium contents and thus show higher strengths without these tend to intercrystalline corrosion after exposure to temperature. Higher strengths with comparable corrosion resistance is achieved at a Mg content of at least 3.0 wt .-%.
• the aluminum alloy according to the invention In order to be able to produce the aluminum alloy according to the invention economically and, moreover, to have no negative effects with regard to formability and no or only slight changes in the physical properties of the aluminum alloy, for example during casting and rolling, it is advantageous according to a first embodiment of the aluminum alloy according to the invention, the following applies to the alloy components Zn, Cr, Cu and Mn: (2.3 *% Zn + 1.25 *% Cr + 0.65 *% Cu + 0.05 *% Mn) + 1.4 ⁇ % Mg.
• an upper limit of the addition of the alloy components Zn, Cr, Cu and Mn is given to one To achieve the most economical production of aluminum alloy. Additions beyond this upper limit show no additional positive effect on the resistance to intergranular corrosion. In addition, unwanted side effects due to high contents of the alloy components in this embodiment of the aluminum alloy according to the invention can be excluded.
• the alloying component Cu has the following content in% by weight: 0.05% ⁇ Cu ⁇ 0.20%, to make the aluminum alloy generally more corrosion resistant.
• the formability can be maximized by the alloying component Cr having the following content in% by weight: 0.05% ⁇ Cr ⁇ 0.20%.
• an aluminum alloy which is further optimized with respect to the addition of alloy components and which is resistant to intercrystalline corrosion is provided in that the alloy components Mg and Zn have the following contents in% by weight: 2.91% ⁇ Mg ⁇ 3.6% 0.05% ⁇ Zn ⁇ 0.75%.
• the reduction of the upper limit of the magnesium content allows a further reduction of the maximum zinc concentration, so that a cost-optimized aluminum alloy with very high resistance to intergranular corrosion can be provided.
• the Mg content of this embodiment is preferably 3.0% by weight to 3.6% by weight, in particular 3.4% by weight to 3.6% by weight.
• the aluminum alloy according to the invention can be further optimized with respect to its strength by virtue of the content of the alloying component Mg being at least 3.6% by weight and not more than 4.5% by weight.
• the increased magnesium contents cause a significant increase in the strength of the aluminum alloy with good formability. Due to the specific composition of the aluminum alloy according to the invention, this aluminum alloy shows only small mass losses ⁇ 15 mg / cm 2 despite the high Mg contents and is therefore free from intercrystalline corrosion according to ASTM G67.
• the Mg content is limited to a maximum of 4.0 wt .-% in order to improve the corrosion behavior.
• the aluminum alloys according to the invention are characterized in that, in addition to very good strength and formability, they also have a very good resistance to intergranular corrosion.
• Chassis and structural components of vehicles, automobiles or aircraft are frequently exposed to heat sources, for example the exhaust gases of the internal combustion engine or other heat sources, so that aluminum alloys, which tend to undergo intercrystalline corrosion after a heat treatment, can not normally be used here.
• heat sources for example the exhaust gases of the internal combustion engine or other heat sources
• aluminum alloys which tend to undergo intercrystalline corrosion after a heat treatment
• the use of an aluminum alloy strip or sheet according to the invention for the production of chassis and structural components also allows the use of higher-strength aluminum magnesium alloys with magnesium contents of at least 2.91 wt .-% in these applications due to the very good resistance to intergranular corrosion.
• the higher strength aluminum bands or sheets allow the reduction of wall thickness due to the increased strength. In this respect, they contribute to the further weight reduction of vehicles, ships or even aircraft.
• an aluminum alloy strip or sheet is used consisting of the aluminum alloy according to the invention for producing a chassis and structural part, which is arranged in the region of the engine, the exhaust system or other heat sources of a motor vehicle.
• a typical example of this is a spring or wishbone of a motor vehicle. Areas of this component, especially if they are located close to the engine, are permanently exposed to increased heat input.
• bands and sheets of erfindunmultien aluminum alloy new applications which are characterized by an increased heat input.
• an aluminum alloy strip or sheet consisting of the aluminum alloy according to the invention when the chassis or structural components have at least one weld.
• Welds are generally areas in which heat has entered the metal. This heat input can lead to intercrystalline corrosion, if the aluminum alloy tends to.
• the ⁇ -phase precipitate responsible for the intercrystalline corrosion is largely suppressed, so that the component can be readily welded and yet it does not tend to intergranular corrosion.
• an aluminum alloy strip or sheet of the aluminum alloy of the invention is particularly advantageous when the wall thickness of the aluminum alloy strip or sheet is 0.5 mm to 8 mm, optionally 1.5 to 5 mm. These wall thicknesses are very well suited to provide the necessary strength for a chassis or structural part.
• the aluminum alloy according to the invention does not require any specific heat treatment step, for example a solution annealing step at the end of the production process, but the aluminum alloy can be produced highly economically with conventional equipment, for example batch ovens. It is also conceivable to provide a direct casting of the strip in place of the casting of a rolling bar, which is then subsequently hot and / or cold rolled.
• Table 1 shows the chemical analyzes of the standard alloys ST 5049, ST 5454 and ST 5918 and the aluminum alloys V1, V2, V3 and V4 according to the invention.
• Mg Compensation the value of the amount of magnesium compensated by the alloy components, which is referred to as "Mg Compensation” and calculated by the following formula, is given. (2.3 *% Zn + 1.25 *% Cr + 0.65 *% Cu + 0.05 *% Mn) + 2.4.
• the minimum compensation is the value of the "compensated" Mg content, which is compensated at least by the alloy components Zn, Cr, Cu and Mn got to.
• the value given in Table 1 therefore corresponds to the Mg content of the respective aluminum alloys.
• the Mg compensation value is only relevant for aluminum alloys with magnesium contents of at least 2.91% by weight, this value is not recorded for the standard alloy ST 5049.
• the other standard alloys ST 5454 and ST 5918 have a Mg compensation value which is below the magnesium content of the alloy. As is known, these alloys tend to intergranular corrosion under certain conditions. The reason is considered that the Mg content of these aluminum alloys is not sufficiently compensated. The situation is different for the aluminum alloys V1, V2, V3 and V4 according to the invention, whose Mg compensation value is significantly higher than the Mg content of the respective aluminum alloy in% by weight.
• Rolling ingots were cast from all seven aluminum alloys and the ingots were cast at temperatures of 500 to Homogenized 550 ° C for at least two hours.
• the billets thus produced were hot rolled to hot strip at hot rolling temperatures of 280 ° C to 500 ° C and then cold rolled to final thickness, with intermediate annealing and final annealing of the cold strip at temperatures between 300 and 400 ° C in a batch oven.
• the strip thickness was 1.5 mm.
• Sheets were removed from the strips produced and their mechanical properties were determined in a tensile test according to DIN EN 10002-1 perpendicular to the rolling direction.
• the measured values are shown in Table 2. They show that the exemplary embodiment V1 according to the invention has, for example, a significantly higher tensile strength and yield strength than the standard alloy ST 5049.
• the elongation values Ag for the uniform elongation and A 50 mm of the alloy strips according to the invention and the standard alloys do not differ significantly, so that it can be assumed that the aluminum alloys according to the invention have an identical formability as the standard alloys.
• the alloy variant V2 also provides a higher tensile strength and a higher yield strength compared to the standard alloy ST 5454.
• the aluminum alloys according to the invention have very good mechanical characteristics and can be processed identically to the comparable standard alloys.
• test strips 50 mm long and 60 mm wide are cut from the sheet or strip and stored with or without thermal pretreatment in concentrated nitric acid at 30 ° C for 24 hours.
• Nitric acid preferentially dissolves ⁇ -phases from the grain boundaries and thus causes a significant mass loss during the subsequent weight measurement, provided that ⁇ -phases precipitated in the sample along the grain boundaries are present.
• the samples were subjected to a pre-treatment in the form of storage at elevated temperatures prior to a mass loss measurement according to ASTM G67.
• ASTM G67 a mass loss measurement according to ASTM G67.
• the samples were stored for 17, 100 and 500 hours at 130 ° C and then subjected to the mass loss test.
• a storage was carried out for 100 hours at 100 ° C in order to achieve the comparability of the aluminum alloys according to the invention with those known from the prior art aluminum alloys.
• Table 3 shows the respective experimental conditions of aging and the measured mass loss according to a test according to ASTM G67 in mg / cm 2 .
• ASTM G67 intergranular corrosion-resistant aluminum alloys achieve 1 to 15 mg / cm 2 mass loss, whereas unstable 25 to 75 mg / cm 2 mass loss.
• the standard alloy ST 5049 which has a relatively low magnesium content of 2.05% by weight, has the highest resistance to intergranular corrosion. Even with storage times of 500 hours at 130 ° C, this aluminum alloy does not change its corrosion behavior in the test. On the other hand, it also has the lowest mechanical strength values.
• the standard alloy ST 5454 and ST 5918 standard alloy behave The ST 5454 was rated at 500 hours presensitization at 130 ° C a mass loss of 16.2 mg / cm 2. The mass loss of the ST 5918 also shows a very marked increase in the storage of the samples for 100 hours or for 500 hours at 130 ° C Mass loss after storage in concentrated nitric acid to a maximum of 30.9 mg / cm 2 . If one compares the aluminum alloys according to the invention during storage for 500 hours at 130.degree. C., then these are significantly more stable to intercrystalline corrosion in spite of similarly high magnesium contents.
• the maximum mass loss of the aluminum alloy V4 according to the invention was 8.9 mg / cm 2 at 500 hours at 130 ° C. and thus lower by more than a factor of three than the standard alloy ST 5918. According to ASTM G67, it is considered stable to intercrystalline corrosion because of its Mass loss is less than 15 mg / cm 2 . Despite higher magnesium contents and higher strength values compared to the respective standard alloys ST5454 or ST5918, the aluminum alloy according to the invention is distinguished by excellent resistance to intergranular corrosion.

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• 2012
  • 2012-08-28 EP EP12182038.5A patent/EP2703508B1/de active Active
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• 2013
  • 2013-08-22 CN CN201380045479.4A patent/CN104797727B/zh not_active Expired - Fee Related
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• 2015
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