Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2002-08-29
2003-08-12
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C148S518000, C148S528000, C148S535000, C228S101000, C228S214000, C228S262500, C228S262510, C428S648000, C428S654000, C428S658000, C428S668000, C428S674000, C428S675000, C428S680000, C428S935000, C428S936000
Reexamination Certificate
active
06605370
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method of manufacturing an aluminium or aluminium alloy joined product, such as a shaped and hollow member, comprising the sequential steps of: (a) providing two parts made of aluminium or aluminium alloy, each part having a peripheral flange, (b) positioning the two parts such that the peripheral flange of one part faces the peripheral flange of the other part, and joining the facing flanges of the two parts by heating. The invention further relates to a fluid or gas container manufactured by this method.
BACKGROUND OF THE INVENTION
The positioning of a fuel tank in a car has restrictions and requirements leading to a very complex shape which creates several difficulties in forming and manufacturing of such a fuel tank. Traditionally a major market share of such fuel tanks have been made from a high-density poly-ethylene polymer. However, due to changing legislative regulations, it appears questionable whether polymer-based fuel tanks can be used in cars in the future at reasonable costs. A potential change appears to be the use of steel or aluminium for such fuel tanks and for other complex shaped parts alike. However, steel and especially aluminium alloys have many restrictions on their formability and much of the research efforts are dedicated to improve the formability characteristics of these metals and to the methods of forming complex shaped parts thereof, for example by means of blow forming and hydroforming using a warm pressure medium. After forming complex shaped parts, the shaped parts are joined together to form a hollow member.
Such a method as set out in the preamble is known from German patent no. DE-195 31 035 C2. According to this known method at least parts of the edges or the flanges of aluminium or flat aluminium alloy sheets are placed on top of each other forming an assembly. The overlapping edges or flanges facing each other are joined together by means of a brazing operation. Multiple assemblies may be stacked together in one brazing furnace. Following the brazing operation the joined assembly is placed in a closable mould or die, after which the assembly is being expanded in a hydroforming process by means of the introduction of a heated oil having a temperature of more than 150° C. to form a shaped and hollow member or product, such as a fuel tank.
A disadvantage of the known method is that the flat aluminium alloy sheets in whole prior to hydroforming are being subjected to a brazing operation under a controlled atmosphere and using a NOCOLOK (trade name) brazing flux material. The brazing operation has the effect of a heat treatment, typically for several minutes at a temperature of about 590° C., on the aluminium alloy sheets and adversely affecting its formability characteristics for the subsequent hydroforming operation, and thereby restricting the choice for the aluminium alloy. Also, the temperature used for the brazing operation restricts the choice for the aluminium alloys to those aluminium alloys having no low melting phases of below 610° C. Furthermore, the use of a brazing flux material restricts the choice for the aluminium alloys further to those alloys having a very low Mg-content, and thereby excludes the use of AA5000-series aluminium alloys and most of the AA6000-series aluminium alloys. In addition, since a brazing flux material is used all the disadvantages of applying such a brazing flux material during assembling and the residual removal thereof after brazing are inherent to the brazing process used. And in addition, the assembling of inner parts like for example baffles in the hollow member is restricted.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of manufacturing an aluminium or aluminium alloy joined product, such as a shaped and hollow member, which method can be applied for a wide range of aluminium alloy parts.
It is another object of the invention to provide a method of manufacturing an aluminium or aluminium alloy joined product, such as a shaped and hollow member, which method can be applied under normal atmospheric conditions and on an industrial scale.
According to the invention there is provided a method of manufacturing an aluminium or aluminium alloy joined product, such as a shaped and hollow member, comprising the sequential steps of: (a) providing two parts made of aluminium or aluminium alloy, each part having a peripherical flange, (b) positioning the two parts such that the peripherical flange of one part faces the peripherical flange of the other part to form an assembly, and then joining the facing flanges of the two parts by heating. The method is characterised in that during step (b) the faces of the peripherical flanges of the two parts are coupled to each other via a separate aluminium joining product having a base substrate of an aluminium alloy comprising silicon in an amount in the range of 2 to 18% by weight, preferably 7 to 11%, and on the outer surface of the base a deposited layer comprising nickel and a further separately deposited layer on one side of the layer comprising nickel, and the separately deposited layer comprising a metal such that taken together the aluminium base substrate and all layers exterior thereto form a metal filler having a liquidus temperature in the range of 400 to 570° C., and preferably in the range of 500 to 540° C.
When using the separate aluminium joining product in the method according to the invention it has been found that a strong and reliable joint or bond between the two parts is obtained under normal atmospheric joining conditions, thus without the need for a vacuum atmosphere or the need for a protective gas atmosphere such as nitrogen or argon, or without the use of a brazing flux material such as mixtures of alkali and alkaline earth chlorides and fluorides commonly used in conventional brazing operations. The joint obtained is gas leak-tight, and the width of the joint can be arranged in dependence of the content of the final shaped and hollow member, e.g. certain fluids might require a longer diffusion barrier in order to meet legislative requirements on environment, safety or health. Since this method does not require special precautions with respect to the joining environment the method can be applied readily on an industrial scale.
Furthermore, in accordance with the invention it has been found that due to the use of the separate aluminium joining product and the possibility of local heating a wide variety of aluminium alloy parts can be joined to each other. It has been found that the manufacturing method can tolerate magnesium levels up to about 6% by weight in the aluminium alloy parts to be joined, while still resulting in a good bonding between the aluminium alloy parts. Also the aluminium base substrate of the separate aluminium joining product to be used in the method may tolerate high levels of magnesium. Aluminium alloy parts having a chemical composition within the Aluminium Association (“AA”)5000 series aluminium alloys and having Mg in a range of up to 6% by weight as one of the important alloying elements can be used, such as, but not limited thereto, AA5052, AA5754, AA5083, AA5383, AA5086, AA5182 and AA5059, and modifications thereof. Apart from the traditional AA3000-series aluminium alloys, also those aluminium alloys within the range of AA2000, AA6000 and AA7000 series aluminium alloys can be used now, enabling for the design of shaped and hollow members having a high strength. Although several of these high strength alloys may have relatively low melting eutectic phases or the like, due to the obtainable low melting point of the aluminium joining product, melting or partial melting of such phases does not occur during the formation of the joint in the method of this invention.
Preferably the aluminium alloy parts are made of sheet material, and can be in the form of a flat blank or in a pre-formed and shaped form, for example complex shapes formed by means of deep-drawing, blow forming or hydroforming.
Joining of the facing flanges of the
Smeyers Axel
Van Rijkom Jacobus
Wittebrood Adrianus Jacobus
Corus Aluminum Walzprodukte GmbH
Koehler Robert R.
Stevens Davis Miller & Mosher LLP
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