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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
  • B22D11/003—Aluminium alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels

Definitions

• the present invention is directed to a process for the production of 5XXX series aluminum alloys, from continuously cast aluminum strip suitable for using in automotive and transportation applications, exhibiting superior or at least equivalent mechanical, microstructural, corrosion resistance and formability properties than those of similar alloys produced by the DC casting routes.
• Weight reduction is a primary goal in transportation industry including especially automotive and marine technologies not only to improve fuel economy, but also to improve performance, safety & durability and to reduce emissions.
• the use of light-weight materials is one of the most promising ways of achieving this goal and aluminum currently offers the greatest potential for cost-effective weight savings in automotive body structures.
• Aluminum has the advantage over competitive materials due to a very attractive combination of density, strength, formability and ease of recycling. Although there is extensive use of aluminum in die-cast parts, wrought aluminum has so far been confined to relatively few applications.
• Al-Mg 5XXX series
• Al-Mg alloys have been used to form auto body trim parts, doors, hood, truck vessels, fuel tanks, pressurized air vessels of trucks, truck tanks, ships and their infrastructure and superstructure, dump truck bodies, cryogenic vessels and LPG tanks.
• Present invention relates to an aluminum alloy with high mechanical properties and method for its manufacture. Therefore, the invention has industrial applicability in the field of processing metals.
• a wrought Al-Mg alloy sheet produced through Twin Roll Casting technique and accordingly processed to its final gauge aiming to provide superior or at least equivalent microstructural, mechanical, corrosion resistance and formability properties compared to their counter parts produced by DC casting and mill route is provided.
• the sheet product contains essentially between 0,5-6,5 %Mg, 0, 0-0,50 % Si, 0, 0- 0,60 % Fe, 0, 0-1,2 % Mn, 0, 0-0,50%Cr by weight.
• Figure 1 is the flowchart showing the casting process according to the present invention
• Figure 2-a is the flowchart showing cold rolling and annealing processes according to an embodiment of the invention where no homogenization treatment is applied.
• Figure 2-b is the flowchart showing cold rolling and annealing processes according to another embodiment of the invention where a homogenization treatment is applied immediately after casting.
• Figure 2-c is the flowchart showing cold rolling and annealing processes according to a further embodiment of the invention where a homogenization treatment is applied following a cold rolling process.
• FIG 3 shows photographs of very fine discrete particles near the surface of (a) Alloy A, (c) Alloy B and (e) Alloy C in as-cast materials where interdendritic network of primary phases in the interior of the same strips are shown for (b) Alloy A, (d) Alloy B and (f) Alloy C.
• Figure 4 shows photographs of the staining observed after 96 hrs exposure to salt spray, on following samples (a) DC-cast A, (b) DC-cast B (c) strip cast A w/homog, (d) strip cast A w/o homog., (e) strip cast B w/homog., (f) strip cast B w/o homog. and (g) strip cast C w/homog.
• the present invention is directed to a process for the preparation of 5XXX series aluminum alloys, from continuously cast aluminum strip suitable for using in automotive and other transportation applications, exhibiting superior or at least equivalent mechanical, microstructural, corrosion resistance and formability properties than those of similar alloys produced by the DC casting routes.
• Twin Roll Casting technology When compared to the DC casting and hot mill method, Twin Roll Casting technology has a relatively shorter process route (Fig. 1) with less working of the metal. As is claimed in number of publications, the processing route, that comprises DC casting and successive hot mill operations, is envisioned as a unique way for the production of 5XXX series aluminum alloys in different thickness.
• the microstructure of the as-cast strip is characterized by a dendritic structure of the aluminum solid solution with the primary phases marking the dendrite boundaries.
• the interdendritic network of the primary phases is well defined in the interior of the strip whereas it is deteriorated somewhat and is replaced by a very fine dispersion of discrete particles near the surface.
• the dendritic structure is quite uniform across the thickness of all strip samples.
• the microstructural features, i.e. dendrite arm spacing, primary particle size are relatively smaller at the surface and coarsened only slightly when approaching the center of the strip.
• variations across the thickness of the 5XXX as-cast strip are not as prominent as they are in some common foil and finstock alloys. The extent of supersaturation was largest in the alloys having high Mg content.
• Alloy B strip shows traces of surface segregation with eutectic rich bands, running in the casting direction, only along the edges of the cast strip. These bands, however, do not penetrate deep into the strip and were estimated to be less than 5 ⁇ m deep in the most severe cases. It should be noted that this edge region of any cast strip is removed by an edge trimming operation during cold rolling. There is hardly any evidence of surface segregation in Alloy A and Alloy C strip. Some intergranular and centerline segregation is also observed in all strip samples. The latter occasionally produced channels of solute-rich material and is most prominent in the Alloy B. Although centerline segregation is believed to have negative effects on mechanical properties -at least to some extent-, these effects may be minimized with appropriate casting parameters.
• Two different processing routes (Fig. 2a and 2b-2c)wherein existence of homogenization treatment determining this difference, can be applied to the as-cast strip.
• Homogenization treatment of the strip is performed at the temperature between 420° and 550 °C for a period of time, preferably not less than 4 hours and not more than 15 hours.
• Homogenization treatment is carried out in an inert gas atmosphere of the batch annealing furnaces.
• two different methods are employed depending on when it is applied: While homogenization treatment can be performed at the casting gauge (Fig. 2b), it can also be applied after a first cold rolling pass that must provide at least 25% reduction in the thickness of as-cast strip (Fig. 2c).
• the grain structure at the final gauge is improved in a profound way when cast strip is homogenized after a cold rolling pass .
• the homogenized strip material is subjected to cold rolling wherein no recrystallization anneal is applied until a critical gauge. Recrystallization anneal at this critical gauge and subsequently applied predetermined amount of cold working and application of back annealing procedure at the final gauge, as a final step in the production cycle, provides strain hardened and partially annealed, H2X tempers, final products including, H22, H24, H26.
• Recrystallization at the final gauge in practice of the present invention is in the range of 280° to about 375°C, preferably for about 2 to 8 hours.
• as-cast strip Prior to the recrystallization anneal applied to obtain 0 temper material at the final gauge, as-cast strip is cold rolled to the final gauge without applying any intermediate annealing in processing route as shown in Fig. 2a.
• the material that is subjected to the homogenization treatment, according to the processing routes shown in Fig. 2b and 2c is also cold rolled to the aimed gauge without application of intermediate annealing.
• Intermediate annealing applied at the predetermined stage of the processing route is also considered as recrystallization anneal and carried out by applying the same temperature and time combination.
• Back annealing temperatures to render H2X temper materials at the final gauge are in the range of 130°-250°C, preferably 2 to 8 hours.
• Aforementioned processing routes of the present invention that comprises a homogenization treatment, can be altered in the way of eliminating homogenization treatment by keeping the other down stream operations in effect (Fig. 2-a). Absence of homogenization step in the processing route does not create substantial changes in the mechanical properties, microscopic features, corrosion resistance and formability properties of the Twin Roll Cast 5XXX series alloys at different tempers (soft, strain hardened, or H2X/H3X) of final gauges. This radical alteration in the processing route provides significant contribution to the economical aspect of Twin Roll Cast 5XXX series alloys, as well.
• the melt was thoroughly mixed and then in-line refining was applied with chlorine and inert gas mixture to reduce the hydrogen content of the melt below 0,20ml/100 grams of metal and its inclusion content. Hydrogen gas level was reduced to 0,12ml/100 grams of metal.
• the metal was cast in the form of 1750 mm wide, 5,35 mm thick industrial size coils. Prior to cold rolling operation, one of the cast coil was homogenized in inert atmosphere. Coil was cold rolled in successive passes to its final gauge of 1mm without any intermediate recrystallization anneal. Soft temper of the material was achieved with final a recrystallization anneal. Another coil was processed through the same processing route, with the exception of homogenization treatment, to the final gauge of 1mm.
• An aluminum alloy in accordance with the present invention designated "B” consisted essentially of the elements stated in Table 3. This alloy was cast into 5,45 mm thick strip.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Metal Rolling (AREA)
• Continuous Casting (AREA)

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• 2001
  • 2001-09-25 EP EP01970501A patent/EP1440177A1/de not_active Withdrawn
  • 2001-09-25 WO PCT/TR2001/000046 patent/WO2003027345A1/en not_active Application Discontinuation
  • 2001-09-25 US US10/490,111 patent/US20040256079A1/en not_active Abandoned

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