Metal fusion bonding – Process – Specific mode of heating or applying pressure
Reexamination Certificate
2001-06-07
2004-01-20
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Specific mode of heating or applying pressure
C228S157000, C228S190000, C228S193000, C228S203000, C228S235300, C228S262100, C228S262500, C228S262510, C148S415000, C148S417000
Reexamination Certificate
active
06679417
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and system for the fabrication of component parts. More specifically, the present invention relates to an overall method and system to create reliable and structurally sound component parts.
As is well known, strong, robust and reliable component parts are necessary for many applications. The tempering of component parts provides many benefits, such as the necessary material strength and desirable structural characteristics. One classical method of tempering involves placing component parts into a large heating furnace to elevate the component temperature to a high level. Subsequently, the parts are removed from the heating furnace and placed in a large cooling bath. This cooling bath is typically made up of a very large pool of water which allows the parts to be completely submerged. When placed in this cooling bath, the temperature of the component parts will quickly drop down to desired levels. This process achieves various temper levels including, O, F, T-4, and T-6 (and possibly others). Obviously, the strength and hardness of the raw material itself will greatly affect the performance of the resulting end product.
As would be expected, the heating furnace and the cooling bath typically used are both very large components which require large amounts of space in a manufacturing facility. This is especially true when manufacturing fairly large component parts.
In addition to the large amounts of manufacturing space, complex and complicated material handling mechanisms are often required. Each time parts are handled by various mechanisms, surface contamination becomes a concern. Specifically, it is important that the various surfaces of the material remain clean and free of contamination in order to accommodate further processing. For example, it is important to avoid the formation of oxides if roll bonding is anticipated. Naturally, there may be other contamination issues which may arise.
The incorporation of heat treating steps into the overall manufacturing process must also be carefully considered. As is well known, the quenching of formed components may have an adverse affect on component configuration. For example, if a component is stamped to have a desired cross-sectional configuration, and then quenched, the product configuration may change. Should this happen, the product must then be restriked or reformed, in order to achieve the most desired configuration once again. Obviously, the restriking or reforming of parts creates additional costs and complications to the manufacturing process. Thus, by carefully considering this potential problem during the manufacturing operations, this can easily be avoided.
Similarly, the proper incorporation of the heat treating steps and manufacturing may provide manufacturing advantages and capabilities not otherwise obtainable. Using a process known as retrogression heat treating, a material can be heated to achieve a lower temper in order to accommodate certain manufacturing operations. Examples of retrogression heat treating can be found in U.S. Pat. No. 5,911,844 entitled “Method for Forming a Metallic Material”, and, U.S. Pat. No. 6,033,499 entitled “Process for Stretch Forming Age Hardened Aluminum Alloy Sheets”. Both of these patents deal with the localized heating and forming of component parts, in order to accommodate product forming.
When manufacturing products using 6000 series aluminum sheets, raw material is often supplied at an “F temper.” However, in order to increase the strength of this material, the tempering process would preferably be used to create parts having a T-6 temper.
When manufacturing component parts, roll bonding is one efficient method available. In this process, two sheets of material are introduced to a roll bonding mill whereby they are compressed or sandwiched together to create a molecular bond between the two sheets. By selectively patterning a bond inhibitor (e.g. a graphite, titanium dioxide (TiO
2
), or like material) the bond can be created in selected areas while avoided in other areas. The two sheets of material can be selectively separated at a later time (as dictated by the bond pattern), to create several structural components. For example, manifolds that require fluid flow in a predetermined pattern or area can easily be fabricated utilizing this process. The process of roll bonding is further outlined in U.S. Pat. Nos. 3,340,589 and 2,957,230.
As appreciated by those familiar with this technology, roll bonding is best suited for relatively thin sheets of material. Using these thinner sheets allows for the easy handling by the rolling mill because only limited separation between work rolls is required. Consequently, roll bonding has traditionally been best suited for non-structural components such as manifolds, etc.
In automotive applications, there are needs for all types of manufactured components. One such category is structural components such as frames, load bearing members, bracketry, etc. Naturally, many of these have a fairly significant weight handling and strength requirements. Consequently, when trying to implement these structural components in aluminum, structural aluminum is typically best suited. This structural aluminum includes 5,000 and 6,000 series aluminum alloys which typically contain some portion of magnesium. 3,000 series alloys may also be used.
Due to the magnesium contained in typical structural aluminum, it traditionally has not been easily roll bonded. When heated prior to introduction into the roll bonding press, an oxide is often created on the surface. This oxide prohibits the aluminum from easily being bonded. The weight handling requirements, combined with the complications of roll bonding structural aluminum, have typically suggested that roll bonded structures could not be easily used for these automotive applications.
In addition to the weight handling capabilities that are required for automotive component applications, actual weight is a continuing consideration. Naturally, automakers are constantly looking for ways to reduce weight, thus increasing fuel economy, etc. This naturally suggests that aluminum would be an appropriate material for use in automotive components due to its weight characteristics. However, aluminum has inherent strength constraints. Consequently, steel has traditionally been used to achieve the required strength and other methods have been attempted to reduce weight.
As mentioned above, certain structural aluminum alloys certainly do display strength characteristics which would allow their use as structural components. Two primary complications exist with the use of aluminum components, however: (1) the aforementioned complications in roll bonding high strength aluminum alloys, and (2) additional raw material required to achieve the necessary strengths. To obtain these necessary strengths, heavier gauges of material is often required. This inherently requires the use of more raw materials—a raw material which is more expensive than steel to start with. Consequently, other methods (beyond simply using heavier gauge materials) are necessary in order to achieve the desired strength while staying within cost constraints.
Roll bonding itself provides further advantages by allowing the formation of complex structures due to the ability to create intricate patterns of bond inhibitor. More specifically, curves and/or bends can easily be created by appropriate patterning of the bond inhibiting material pattern. Similarly, diameter variations can also be easily accomplished.
In light of the above advantages, it would be beneficial to utilize the processes of roll bonding to create structural members. Further, the tempering of these parts is further beneficial.
Another technology which is becoming widely used in the fabrication of structural components, including aluminum components, is hydroforming. As is well known, hydroforming involves the placement of a preformed blank within the hydroforming die and injecting a fluid into a closed interior cavity of the blan
Dziadosz Lawrence M.
Fulton Clarence W.
Dunn Tom
Edmondson L.
Tower Automotive Technology Products, Inc.
Van Dyke Gardner, Linn & Burkhart, LLP
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