Metal working – Method of mechanical manufacture – Structural member making
Reexamination Certificate
1999-07-06
2001-06-05
Rosch, I Cuda (Department: 3722)
Metal working
Method of mechanical manufacture
Structural member making
C029S897200, C228S181000
Reexamination Certificate
active
06240640
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing honeycomb structures made of titanium, and in particular for manufacturing honeycomb structures consisting of a planar assembly of a number of hollow columnar cells with titanium or a titanium alloy used as base material.
2. Description of the Related Art
Honeycomb cores consisting of a planar assembly of a number of hollow columnar cells have a variety of excellent characteristics such as high ratios of strength to weight, and are widely used as various of construction materials. Although metals, plastics, papers, or the like are used as the base material for these honeycomb cores depending on their use, typical metals are aluminum (aluminum alloy) and stainless steel.
Conventionally, the honeycomb cores are manufactured in the corrugation or expansion process. And, bonding in a striped pattern between cell walls of the honeycomb cores are performed by {circle around (1)} spot welding, {circle around (2)} adhesion, {circle around (3)} brazing.
In the corrugation process, after very thin foil-like base material is formed (corrugation) into corrugated sheets, a number of the corrugated sheets such formed are piled together in such a manner that the crests of a corrugated sheet and the troughs of the next corrugated sheet meet together with a half pitch shift between them. Each joint between the crests and troughs are bonded by {circle around (1)} using a spot welding device, {circle around (2)} adhesion with heating under pressure, {circle around (3)} brazing a brazing material, or the like. Hereby, the honeycomb core having the cell walls made of the corrugated sheets piled, and consisting of the planar assembly of the number of hollow columnar cells that are separated by the cell walls, has been manufactured.
On the other hand, in the expansion process, after {circle around (2)} adhesive or {circle around (3)} brazing material is applied in the striped pattern on the surfaces of very thin foil-like base material, a number of the base material sheets are piled with a half pitch shifting between them. Thereafter, the base material is bonded in a striped pattern with heating and pressing for {circle around (2)} adhesion or {circle around (3)} brazing, and the base materials piled are elongated by tensile force in direction of the pile. Thus, the honeycomb cores having the elongated base material as cell wall, and consisting of the planar assembly of the number of hollow columnar cells that are separated by the cell wall, have been thus manufactured.
In the fields where honeycomb cores made of metal are used as structure materials, namely, honeycomb cores having base material of metal such as aluminum, aluminum alloy, stainless steel, or the like are used as structure materials, for example, in the fields for manufacturing structure materials and parts of aircraft, it is desired for honeycomb cores to become more and more light and stiff, and have higher heat resistance, corrosion resistance, and the like.
Then, in the field for manufacturing aircraft and the like, as materials having these high excellent characteristic, in stead of aluminum (aluminum alloy) and stainless steel, the use of titanium (a titanium alloy) has been progressed.
However, in spite of these backgrounds, regarding to the honeycomb structure having base materials of titanium or a titanium alloy (hereinafter abbreviated simply as “titanium honeycomb”), some problems described below are pointed out in the manufacturing process.
Concerning the method for manufacturing titanium honeycomb, some problems as follows have been pointed out, conventionally.
1. Although the titanium honeycomb has been conventionally manufactured by the corrugation process, in the corrugation process, complex process and high production cost have been pointed out, because piling and bonding were performed after the corrugated sheets have been formed in this process.
Further, large space has been required from first to end of the process after all, because formation of corrugated sheets requiring large space is performed in the first step before piling and bonding. Thus, it has been pointed out that large-sized titanium honeycomb or titanium honeycomb having many cells are manufactured with difficulty. That is to say, it has been difficult to manufacture a large block of titanium honeycomb or the honeycomb structure having small-sized cells by the use of the corrugation process.
In this way, concerning the conventional method for manufacturing titanium honeycomb, with employing the corrugation process, high production cost and difficulty of manufacturing the large-sized titanium honeycomb are pointed out. (These problems are generally pointed out not only in the manufacturing method of the titanium honeycomb, but also in a method for manufacturing honeycomb cores by the corrugation process.)
2. When titanium honeycomb is manufactured by the corrugation process, each joint between the corrugated sheets (the cell walls) piled are bonded by {circle around (1)} spot welding, {circle around (2)} adhesion, {circle around (3)} brazing or the like as mentioned above.
And, first of all, in case of {circle around (1)} spot welding, it has been pointed out that the production cost becomes high because a number of spots have to be welded.
Furthermore, in the case of {circle around (2)} adhesion, it has been pointed out that the characteristics of the titanium honeycomb manufactured, such as stiffness, heat resistance, corrosion resistance, or the like are determined by the characteristics of the adhesive used. In other words, the difficulty is that the essential excellent characteristics of titanium or titanium alloy used as base material, such as stiffness, heat resistance, corrosion resistance, or the like, are not utilized.
Furthermore, in case of {circle around (3)} brazing, occurrence of erosion, generation of intermetallic compounds, and inclusion of undesirable metals are pointed out as problems.
That is, the base materials of titanium or titanium alloy (corrugated sheets and cell walls) are corroded with brazing material by heat or pressure in brazing, and as a result, erosion which means formation of holes and exfoliation on the surfaces occurred easily. Further, it is easy to generate rigid and brittle intermetallic compounds between the base materials of titanium or titanium alloy (the corrugated sheets) and brazing material, as results of the reaction and fusion. In addition, difficulty occurs in corrosion resistance of the titanium honeycomb, with the resulting that the joints between the respective base materials of titanium or titanium alloy (the corrugated sheets and the cell walls) are bonded with the brazing material having the metals which are different from the metal of base material.
Therefore, in case of brazing, difficulties occur in the properties of the produced titanium honeycomb, such as stiffness, corrosion resistance, or the like. Therefore, the difficulty is that the excellent identities of titanium or a titanium alloy, for example, stiffness, corrosion resistance, or the like, are not utilized as base materials.
As described above, concerning the conventional methods for manufacturing titanium honeycomb, problems have been pointed out in production cost, stiffness, heat resistance, corrosion resistance, or the like, because the joint in respective base materials are performed by {circle around (1)} spot welding, {circle around (2)} bonding, and {circle around (3)} brazing.
3. Considering the first problem described above, the expansion process has been employed instead of the corrugation process. Further, considering the second problem described above, the methods for manufacturing titanium honeycomb in which the diffusion bonding is performed for joining between respective base materials without {circle around (1)} spot welding, {circle around (2)} bonding, or {circle around (3)} brazing, have been developed recently. Inventors and an applicant of the present invention have been invented such a method and
Matsuoka Katsunori
Nakajima Jun
Flynn ,Thiel, Boutell & Tanis, P.C.
Nguyen Trinh
Rosch I Cuda
Showa Aircraft Industry Co., Ltd.
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