Metal fusion bonding – Process – Applying or distributing fused filler
Reexamination Certificate
2000-05-23
2003-07-01
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Applying or distributing fused filler
C164S076100
Reexamination Certificate
active
06585151
ABSTRACT:
BACKGROUND OF THE INVENTION
It has been recently noted that the potential for applying metal foams in lightweight construction is mainly based on the increased stiffness of two flat or curved sheets that are separated by a foam layer as compared to a single sheet of the same weight. Attempts have been made in the automotive industry to reduce weight by traditional measures, such as improving steel quality and reducing the thickness of steel sheets or sections, or by creating structures with variable wall thicknesses. Unfortunately, by decreasing wall thickness there is an increased potential for buckling of the structure. By using sandwiches with an aluminum-foam core, it is possible to obtain a higher stiffness and rigidity, maintaining stability against buckling and additionally making the use if the high energy dissipation capability of the foams. A recent highlight of lightweight construction is the use of aluminum-foam sandwiches (AFSs) in space-frame constructions. Karmann, a German car manufacturer, has demonstrated that an increasing structural rigidity for the entire car body can be achieved by using AFSs instead of conventional sheet panels. The use of such AFSs parts combines weight reductions with additional improvements of crash worthiness and also environmental advantages are realized because of the easy recyclability of the material.
Cellular metals can be effectively employed in many applications. Some applications may be for: lightweight structures as low cost replacement for honeycombs, etc.; energy absorbers for crash protection; heat exchanger materials; storage for fuels (e.g. hydrogen) and catalysts; sound dampening materials; thermal insulation, e.g., thermal protection systems: and prosthetic devices. Cell size, shape and geometry requirements vary for each application.
Several approaches are known for producing lightweight porous materials. Most of these approaches utilize foaming methods, i.e., via incorporating additives (or secondary materials) which cause gas evolution within the solid or liquid material. Other approaches rely on incorporating oxides (in the case of metal foams) to pin the boundaries of foam and make them stable so the cell walls do not collapse during processing. Introduction of foreign materials to metallic systems can cause detrimental effects and poor mechanical properties in certain reactive metals, e.g., titanium.
Open cell foams have certain advantages of closed cell foams. Due to open space between supports, fluid can be passed through such material to serve multifunctional needs, e.g. heat transfer applications, storage of fuel or catalyst, thermal protection prosthetic devices, etc.
It is thus necessary to develop methods for making open cell porous materials which do not rely upon the introduction of other contaminating elements. It is also of interests to fabricate porous solids whose unit cell size is approximately 1 mm or smaller (in the micron range) rather than several centimeters as for metal foams. Finer pore sizes leads to higher strength and stiffness in the final product. Moreover, materials containing large pore sizes are more difficult to machine without damaging the surface layers. Smaller pore sizes are superior as cutting often smears and closes surface pores.
Some patents with regard to the above approaches are as follows U.S. Pat. No. 5,112,697 to I. Jin, L. D. Kenny and H. Sang, teaches a method of foaming liquid aluminum to produce closed cell porous metals. U.S. Pat. No. 5,151,246 to J. Baumeister and H. Schrader teaches a powder metallurgy approach to cause foaming in the solid state to produce closed cell foams. U.S. Pat. No. 3,981,720 to S. E. Speed discusses foam structures. German patent DE40 18 360 to J. Baumeister discusses metal foams. U.S. Pat. No. 5,843,365 deals with directed fiber performing apparatus and method having fiber lay-up control. U.S. Pat. Nos. 4,999,240 and 5,128,174 teach metallized fiber/member structures and methods of producing same. U.S. Pat. No. 5,874,133 discusses process for making polyurethane composite. U.S. Pat. No. 5,097,887 shows process of making a pressure diecast fiber reinforced part. U.S. Pat. No. 3,989,548 teaches aluminum alloy products and methods of preparation. U.S. Pat. No. 5,983,973 discloses method for high throughput pressure casting. U.S. Pat. No. 5,981,083 teaches method of making composite castings using reinforcement insert cladding. U.S. Pat. No. 4,899,800 discusses metal matrix composite with coating reinforcing preform. U.S. Pat. No. 5,876,659 shows process for producing fiber reinforced composite. Metal foams are discussed in product information sheets from Cymat Corp. of Canada.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a method for producing microporous objects having a fiber, wire or foil core.
It is also an object of this invention to provide microporous objects having a fiber or foil core.
It is an object of this invention to create microporous objects by heating a material to its liquid state and pressurizing the material and extruding a stream of the liquid and partly solid material through an orifice into a cooler environment and controlling its deposition on to a substrate as a combination of the solid wire (or fiber) as well as liquid portions of the stream which help to weld the wire segments.
It is a further object of this invention to provide such microporous objects having a range of 100% solid to 95% porous in the same process and create either a fixed pore volume or a gradient porosity microstructure in the same part.
It is also a an object of this invention to provide articles by a rapid deposition process, rather than rely on slow and expensive investments casting process to produce intricate interior shapes.
It is a further object of this invention to provide such methods for making porous materials which do not rely upon the introduction of other contaminating elements, eliminate atmospheric contamination by performing the deposition operation in an inert environment.
It is a further object of this invention to fabricate porous solids whose unit cell size is approximately 1 mm or smaller (in the micron range) rather than several centimeters as for metal foams.
It is a further object of this invention to provide such materials having finer pore sizes that yields higher strength and stiffness in the final product.
It is a further object of this invention to provide such method for fabricating materials and the materials having smaller pore sizes to benefit the cutting of the materials.
It is a further object of this invention to create internal geometry of the microporous object by deformation, inserting various shaped inserts and using screening to create microchannels in the object.
The invention deals with the concurrent deposition of liquid undergoing solidification and in-situ welding by remelting of certain nodes of the immediately solidified wire by the newly arriving liquid wire which also solidifies instantaneously upon giving off its latent heat to partly melt the solid wire created in the prior instant. The invention is not about a method which has two separate steps: one of deposition and one of welding. The deposition and the welding are happening concurrently during the same action. An analogy using a building would be if you want to build a building you can first make steel beams and channels by melting, casting, and rolling steel. Then you place these steel joists and beams in proper positions and then you weld the joists together to create the skeletal structure of the building. However, if you could come up with a process by which in a single step the steel channels and beams are created and placed in certain geometric arrangement and are welded together to create the skeletal structure of the building, all occurring concurrently in the same process, that would be an extremely novel and non-obvious process.
The microporous objects are created by deposition of small dimensions of solid from liquid streams undergoing solidification with the simultaneous welding of the str
Burns Barbara M.
Dunn Tom
Pittman Zidia
The Regents of the University of Michigan
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