Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a method of producing a
fiber-reinforced composite material.
Applicant has prevlously proposed a composite material
produced by the steps of partially diffusing and bonding inor-
ganic fibers, such as s-tainless steel ~ibers, with one another by
the use of a c~pper type soldering material or by baking to form
a fiber shaped article, filling a light alloy, as a matrix, in
the fiber shaped article by high pressure solidification casting
so as to cast the composite material and at the same time, to
reinforce a predetermined portion of the composite material by
the fibers. The high pressure solidification casting method can
be said to be an effective means for producing fiber-reinforced
composite materials of this kind because it can sufficiently fill
the fiber-shaped article with the matrix to form the composite.
It has now been found that since the fiber is heated to
high temperature during brazing and sintering, the fiber itself
it annealed and its strength tends to decrease, adversely affect-
ing the strength o~ the composite material to be obtained.
According to the present invention there is provided amethod of producing a fiber-reinforced composi-te ma-terial,
wherein a longitudinal fiber-shaped article is arranged in a cav-
ity of a casting mold, and molten me-tal is filled into said cav-
.~ty under a high (primary) hydrostatic pressure, in which the
longitwdinal fiber~shaped article is compressed in the proximity
of at least one of its end portions additionally under a sec-
ondary pressure ranging from 1,000 to 2,500 kg/cm2 after the
molten metal has partly solidified under the primary pressure
which is lower than the secondary pressure. Suitably the primary
pressure ranges from 360 to 600 kg~cm2. Desirably the additional
secondary pressure is exerted 1 to 10 seconds after the primary
pressure. More desirably with simultaneously adding the sec-
ondary pressure the primary pressure is increas~d to 1,000 to1,200 kg/cm2.
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In one embodiment of the present invention the casting
mold is heated to between 250 and 350C before casting is
effected. Suitably the fiber-shaped article is heated to between
460 to 700C before casting is effected. Desirably the fiber-
shaped article consists of metal fibers. Preferably said moltenmetal which is filled into the cavity is an aluminum alloy.
In a particular embodiment of the present invention the~
method is used for the manufacture of a connecting rod for an
internal-combustion engine, whose rod-forming portion is rein-
forced by said fiber-shaped article.
The present invention thus provides a fiber-reinforced
composite material having improved strength, by the use of pre-
cipitation hardening type stainless steel fibers as the reinforc-
ing fibers and applying specific heat treatment to the fibers and
to the composite material itself. The composite material of the
present invention comprises a precipitation hardenable type
stainless steel fiber-shaped article which is sub;ected to a pre-
cipitation hardening treatment after solution heat treatment, andan aluminum alloy matrix which fills the fiber-shaped article by
high pressure solidification casting to form the composite mate-
rial which is subjected to artificial aging trea-tment after solu-
tion heat treatment~
Hereinafter, one embodiment of the present invention
for a connecting rod for an internal combustion engine will be
described by way of the accompanying drawings, in which:-
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Figure 1 is a front view in longitudinal section
of a connecting rod according to the invention;
Figure 2 is a sectional view taken along line II-II
in Figure l; and
Figure 3 is a graphical illustration showing the
change of the proportional limit of elasticity for different
materials under specified conditions.
Figures 1 and 2 illustrate a connecting rod adapted
for use in an internal combustion engine using an aluminum
alloy as a matrix. The connecting rod comprises a rod por-
tion 1. A ring-like small end portion 2 and a semicircular
large end portion 3 axe integrally formed at opposite ends
of the rod portion 1. The rod portion 1 is reinforced by
a shaped body F of precipitation hardened stainless steel
fibers disposed in the axial direction of the rod portion.
The connecting rod is produced by the following
method.
First, precipitation hardenable type stainless
steel fibers of JIS SUS 631Jl having an 80 ~ diameter (here-
inafter called "PH steel fibers") are inserted together with
a copper
soldering material into a heat-resistant glass tube and are
held at 1,120C for 15 minutes to use the soldering material and
to locally diffuse and bond the fibers with one another, thereby
obtaining a fiber shaped article F. The resulting fiber shaped
article F is cooled at a cooling speed of 10C/sec.
The temperature of 1,120C described above is the
melting point of the copper soldering material and is the
solution point of the PH steel fibers. Accordingly, when cooled
from this temperature at the ra~e described above, the fiber
shaped article F is subjected to solution heat treatment and is
haxdened. The fiber shaped article F has a bulk density of
2.65 g/cc and has good shape retainability.
Next, the fiber shaped article F is placed into the
cavity of a die for molding the rod portion in its axial direc-
tion and the connecting rod is cast using an aluminum alloy (JIS
AC8B) as the matrix. At the same time, the matrix M fills the
fiber shaped article F at the rod portion 1 of the connecting
rod to become united therewith and form an integrated, composite
member. The connecting rod is allo~ed to cool.
After heating at 500C for 5 hours, the connecting rod
is cooled in such a manner that the rod is immersed in hot water
s~ored in a tank at-a temperature ~f at least 60C. By this
heat treatment,-the aluminum alloy as the matrix M is subjected
to solution heat treatment w~hile the PH steel fibers forming the
fiber shaped article F are subjected to the precipitation harden-
ing treatment.
The temperature for the solution heat treatment and
the precipitation hardening treatment i5 suitably from 45~C to
510C. If the temperature is below 450C, the precipitation
hardening treatment of the P~ steel Iibers is not achieved and
if it is above 510C, the aluminum alloy and the P~ steel fibers
are likely to react with each other.
After the treatments described above, the connecting rod is -~
heated at 170C for 10 hours and is then cooled in air at ambient
temperature to provide an artificial aging -treatment to the aluminum
alloy and to improve its strength.
Figure 3 illustrates the proportional limit of
elasticity of the PH steel fiber (I) and stainless steel fiber
(II) expressed by JIS SUS 27. Symbol A represents the elastic
limit before the heat treatment of each fiber, B the limit after
the solution heat treatment and C the limit after the pr~cipi-
tation hardening treatment. As can be seen from Fig. 3, the
strength of the PH steel fiber (I) can be drastically improved
by the heat treatment in comparison with that of the stainless
steel fiber (II). The pxoportional limit of elasticity of the
rod portion 1 of the connecting rod using the PH steel fiber
becomes 7,500 kg/mm2 due to the improvement in strength of this
PH steel fiber and to the improvement in strength by the
solution heat treatment and artificial aging treatment of the
aluminum alloy, and this value is found to be a d~astic im~rove-
ment when compared with the value 5,500 kg/m~2 of the rod portion
using the stainless steel fiber (II).
As described above, the present invention can provide a
fiber-reinforce~ composite material which is light in weight
and has improved strength and can be suitably used for automobile
components, such as a connecting rod for an internal combus~ion
engine. The present invention also has the advantage in the
production process that the precipitation hardening treatment
of the fiber shaped article and the solution heat treatment of .~.
the matrix can be carried out by a single process step due to
the combination of the precipitation hardening type stainless
steel fiber shaped article ~ith the aluminum alloy matrix.
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