Metal working – Method of mechanical manufacture – Shaping by direct application of fluent pressure
Reexamination Certificate
2001-07-03
2003-06-03
Echols, P. W. (Department: 3726)
Metal working
Method of mechanical manufacture
Shaping by direct application of fluent pressure
C029S897200, C072S060000, C072S061000
Reexamination Certificate
active
06571450
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the monolithic molding of superplastic material by techniques such as superplastic molding and if necessary diffusion bonding using products having three or more layer-structure made up of metal plates such as titanium alloy, to produce the products used for parts that require particular a heat-resistance is required (e.g., body structure of airplane).
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Metals and alloys such as titanium and most of its alloys and nickel alloys have superplasticity characteristics. For instance, it is known that titanium alloys having appropriate compositions provide elongation of 300%. The superplastic materials can be rather easily molded using a superplastic molding process to provide products having even extremely complicated shape.
A process for monolithic molding of the above superplastic material using techniques of superplastic molding and diffusion bonding, is concretely explained with reference to
FIGS. 14
to
17
.
As shown in
FIG. 14
, three metal plates having superplasticity (e.g., titanium sheets)
1
,
2
and
3
are provided. In case the sheets
1
,
2
and
3
are superposed as indicated in
FIG. 15
, non-bonding regions
4
a
and
4
b
are provided on one side (i.e., surface of the sheet
1
intermediately located between the sheets
2
and
3
) and a non-bonding region
5
a
is provided on the other side such that a part of the non-bonding region
5
a
is overlapped with parts of the non-bonding regions
4
a
and
4
b
as seen on a plane surface. On portions that the non-bonding regions
4
a
and
4
b
are overlapped with the non-bonding region
5
a
as seen on the plane surface, gas holes
6
are provided beforehand respectively, and further a groove for introducing molding gas
7
is formed in contact with one end of the non-bonding region
4
a.
A core-sheet
1
, which is the above intermediate metal plate, is put between face sheets
2
,
3
, which are the above top and bottom metal plates. A hole for feeding molding gas
8
is provided in the face sheet
2
. The hole for feeding molding gas
8
is connected to one end of a passage for introducing molding gas, which is formed by the groove for introducing molding gas
7
and the face sheet
2
by superposing the face sheet
2
on the core sheet
1
.
An anti-bonding agent
9
(e.g., Yttria) is coated on the non-bonding regions
4
a
,
4
b
and
5
a
of the core sheet
1
, and the face sheets
2
and
3
are superposed on both sides of the core sheet
1
to form superposed sheets (laminate)
10
as shown in FIG.
15
.
Subsequently, the superposed sheets
10
are set in a molding die
30
consisting of a first molding die
31
and a second molding die
32
, and air of a first molding die interior
31
A and a second molding die interior
32
A is replaced with an inert gas while boundaries
11
and
12
between the core sheet
1
and each of the face sheets
2
and
3
are evacuated. Then the superposed sheets
10
and the molding die
30
are wholly heated to a desired temperature, and an inert gas is introduced into the first molding die interior
31
A and the second molding die interior
32
A to a desired pressure to diffusively bond the core sheet
1
to bonding regions
13
a
,
13
b
,
13
c
,
14
a
and
14
b
of each of the face sheets
2
and
3
. Thereafter, the inert gas within the interiors
31
A and
32
A is discharged.
Then, an inert gas is introduced into the non-bonding region
4
a
between the core sheet
1
and face sheet
2
. The inert gas is fed from a hole for providing molding gas
31
a
opened on the first molding die
31
through the hole for feeding molding gas
8
and the groove for introducing molding gas
7
. The inert gas introduced into the non-bonding region
4
a
having the anti-bonding agent
9
brings about superplastic deformation of the core sheet
1
and the face sheets
2
and
3
in the region corresponding to the non-bonding region
4
a
. Thereby the portions corresponding to the region
4
a
of these sheets are expanded to form a first enlarged room
15
a
. On the other hand, an inert gas is introduced into the non-bonding region
5
a
having the anti-bonding agent
9
through the gas hole
6
, and consequently the core sheet
1
and the face sheets
2
and
3
are superplastically deformed in the region corresponding to the non-bonding region
5
a
to form a second enlarged room
15
b.
Subsequently, the inert gas introduced into the second enlarged room
15
b
is further introduced into the non-bonding region
4
b
having the anti-bonding agent
9
through the gas hole
6
, and consequently the core sheet
1
and the face sheets
2
and
3
in the region corresponding to the non-bonding region
4
b
are superplastically deformed to form a third enlarged room
15
c
. Thus, as shown in
FIG. 17
, the inert gas is introduced until the face sheet
2
is pressed to be contacted with a molding surface
31
b
of the first molding die
31
and the face sheet
3
is also pressed to be contacted with a molding surface
32
b
of the second molding die
32
, and hence a product having a shape whose periphery reflects the molding surface
31
b
of the first molding die
31
and the molding surface
32
b
of the second molding die
32
is obtained.
The above-mentioned process for the monolithic molding of molding material using techniques such as superplastic molding and diffusion bonding, the technique comprising superposing plural titanium alloy sheets on which an anti-bonding agent is coated and introducing an inert gas into a molding die interior, is described in for example JP-A11-169977.
SUMMARY OF THE INVENTION
According to the prior art described above, constituent materials are superplastically molded and diffusively bonded to each other to be monolithically molded. Hence, even a product having a complicated shape can be rather easily molded, which results in simplification of process procedures and reduction of production cost as well as high strength of product.
In the above superplastic molding, though a core sheet
1
is mainly superplastically deformed to provide a desired molded product, face sheets
2
and
3
putting the core sheet therebetween are also deformed during superplastic deformation of the core sheet due to their superpasticity. In the deformation, the face sheets are influenced especially by pressure introduced in non-bonding regions
4
a
and
4
b
, and hence, as shown in
FIG. 18
, portions corresponding to enlarged rooms
15
a
,
15
b
and
15
c
of the face sheets
2
and
3
are forced to expand whereby local expansions are generated in the portions corresponding to the enlarged rooms
15
a
,
15
b
and
15
c
of the face sheets
2
and
3
. The local expansions occasionally cause wrinkles on the molded product.
The local expansions of the face sheets
2
and
3
can be avoided by an increase of thickness of the face sheets. However, the multi-layer hollow products obtained in the above techniques are desired to be light, and therefore the increased the thickness requires additional processing for reducing thickness of the face sheets
2
and
3
after the molding process. Further the yield of the products may reduce to increase the production cost.
In view of the above-mentioned problems, an object of the invention is to provide a process for the monolithic molding of superplastic material wherein generation of wrinkles on the molded product can be prevented by avoiding local expansion generated in the no-bonding regions of both sides (top and bottom sides) of three or more metal sheets (metal plates) when the metal plates are monolithically molded by means of superplastic molding.
The present invention to attain the object is provided by a process for the monolithic molding of superplastic material comprising the steps of:
providing at least three metal plates capable of superplastic molding and diffusion bonding,
applying an anti-bonding agent onto regions of the plates
Echols P. W.
Fuji Jukogyo Kabushiki Kaisha
Smith , Gambrell & Russell, LLP
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