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Aluminium-magnesium alloy plate or extrusion

a technology of alloy plate and magnesium alloy, applied in the field of aluminum-magnesium alloy plate or extrusion, can solve the problems of severe cracking, insufficient strength of mn level below 0.6%, and inability to provide the required weld strength

Inactive Publication Date: 2001-10-04
CORUS ALUMINUM WALZPRODUKTE GMBH (DE)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] By the invention we can provide alloy plate or extrusion having higher strength than AA5083, and particularly the welded joints of the present alloy can have higher strength than the standard AA5083 welds. Alloys of present invention have also been found with improved long term stress and exfoliation corrosion resistances at temperatures above 80.degree. C., which is the maximum temperature of use for the AA5083 alloy.
[0030] Ag: Ag may optionally be included in the alloy up to a maximum of 0.4%, preferably at least 0.05%, to improve further the stress corrosion resistance.

Problems solved by technology

Mg levels below 5.0% do not provide the required weld strength and when the addition exceeds 6.0%, severe cracking occurs during hot rolling.
Mn levels below 0.6% cannot provide sufficient strength to the welded joints of the alloy.
Above 1.2% the hot rolling becomes increasingly difficult.
At Zn levels above 1.5%, casting and subsequent hot rolling becomes difficult especially at industrial scale.
However, Ti in combination with Zr forms undesirable coarse primaries.
Fe: Fe forms Al-Fe-Mn compounds during casting, thereby limiting the beneficial effects due to Mn.
Therefore Si limits the beneficial effects of Mg.
However, Cr limits the solubility of Mn and Zr.
If the treatment is carried out below 400.degree. C., the resultant homogenisation effect is inadequate.
Furthermore, due to substantial increase in deformation resistance of the slab, industrial hot rolling is difficult for temperatures below 400.degree. C.
If the temperature is above 530.degree. C., eutectic melting might occur resulting in undesirable pore formation.
Cold rolling reductions in excess of 60% without any intermediate annealing treatment may cause cracking during rolling.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0038] Table 1 lists the chemical composition (in wt %) of the ingots used to produce soft and work-hardened temper materials. The ingots were preheated at a rate of 35.degree. C. / h to 510.degree. C. Upon reaching the preheat temperature, the ingots were soaked for a period of 12 h prior to hot rolling. A total hot reduction of 95% was applied. A reduction of 1-2% was used in the first three passes of hot rolling. Gradually the% reduction per pass was increased. The materials exiting the mill had a temperature in the range 300.+-.10.degree. C. A 40% cold reduction was applied to the hot-rolled materials. The final sheet thickness was 4 mm. Soft temper materials were produced by annealing the cold-rolled materials at 525.degree. C. for a period of 15 min. Work-hardened temper materials were produced by soaking the cold-rolled materials at 250.degree. C. for an hour. The heat-up period was 1 h. After the heat treatments, the materials were air-cooled. The tensile properties and corros...

example 2

[0045] DC cast ingots with composition listed in wt % in Table 3 (alloy D1) were homogenised using the conditions of 510.degree. C. / 12 h and hot rolled to plate of thickness 13 mm. The hot-rolled plates were further cold rolled to 8 mm thickness.

8TABLE 3 Element Mg Mn Zn Zr Cu Fe Si Ti Cr Al Alloy 5.2 0.8 0.8 0.13 <0.1 0.2 0.1 0.024 <0.01 Remainder D1

[0046] The plates were subsequently annealed at 250.degree. C. for a period of 1 h. The tensile properties and corrosion resistances of the plates were determined. ASTM G66 and ASTM G67 were used to assess susceptibilities to pitting and exfoliation and intergranular corrosion. The properties of the alloy D1 before welding are listed in Table 4 and compared with those of the standard AA5083 alloy. Each item of data listed in Table 4 is an average of ten tests carried out on samples produced from alloy D1. It is obvious from Table 4 that the alloy D1 has not only significantly higher proof and ultimate tensile strengths than the standard...

example 3

[0048] DC cast ingots with the same composition as alloy D1 of Example 2 were homogenised using conditions of 510.degree. C. / 12 h and hot rolled to plate of thickness 13 mm. The hot rolled plates were further cold rolled to 8 mm thick plates. The plates were subsequently annealed at 350.degree. C. for a period of 1 h. Thus produced `O` temper plates were subsequently heat treated by soaking samples at 100.degree. C. for various periods from 1 h to 30 days. For the reference purposes, samples from 8 mm, O temper AA5083 plates were also heat treated in parallel to these samples from alloy D1. The microstructures of the samples were characterized using a scanning Electron Microscope. Examination of the samples of AA5083 exposed to 100.degree. C. showed the precipitation of anodic intermetallics on the grain boundaries. It was also observed that as the exposure time at 100.degree. C. is increased, the boundary precipitation becomes more intensive. It becomes so intensive that eventually...

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Abstract

A high strength Al-Mg alloy in plate or extrusion form having significantly improved strength in both soft and work-hardened tempers as compared with AA5083 is provided. The materials have ductility, pitting, stress and exfoliation corrosion resistances equivalent to those of the AA5083. The materials have improved long term stress and exfoliation corrosion resistances at temperatures above 80° C. The composition is 5-6% Mg, >0.6-1.2% Mn, 0.4-1.5% Zn, 0.05-0.25% Zr, up to 0.3% Cr, up to 0.2% Ti, up to 0.5% each Fe and Si, up to 0.4% each Cu and Ag, remainder Al and inevitable impurities. Manufacture of plate of this alloy is by homogenizing an ingot, hot rolling the ingot into plate in the range 400-530° C., cold rolling the plate with or without inter-annealing, final and optionally inter-annealing of the cold rolled material at temperatures in the range 200-550° C.

Description

[0001] The present invention relates to an aluminium-magnesium alloy in the form of plates and extrusions, which is particularly suitable to be used in the construction of large welded structures such as storage containers and vessels for marine and land transportation. For example, the plates of this invention can be used in the construction of marine transportation vessels such as catamarans of monohull type, fast ferries, high speed light craft, and jet rings for the propulsion of such vessels. The alloy plates of the present invention can also be used in numerous other applications such as structural materials for LNG tanks, silos, tanker lorries and as tooling and moulding plates. Plates may have a thickness in the range of a few mm, e.g. 5 mm, up to 200 mm. Extrusions of the alloy of this invention can be used for example as stiffeners and in superstructures of marine vessels such as fast ferries.DESCRIPTION OF THE RELATED ART[0002] Al-Mg alloys with Mg levels >3% are exten...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C21/06C22C21/08B21C23/00C22C21/10
CPCC22C21/10C22C21/06
Inventor HASZLER, ALFRED JOHANN PETERSAMPATH, DESIKAN
Owner CORUS ALUMINUM WALZPRODUKTE GMBH (DE)
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