JPS6225628B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a silicon carbide sintered body having excellent tensile strength in a specific direction. Silicon carbide sintered bodies have low thermal expansion, high mechanical strength and thermal conductivity, and good oxidation resistance, so they are used as heat-resistant structural materials for heating elements, engine parts, and other parts.
Although this material has recently found wide range of uses, it suffers from the disadvantage that it has poor toughness compared to metals, and in particular has weak bulging strength. The present invention improves this and relates to a method for manufacturing a SiC sintered body that has extremely strong bulging strength in a specific direction, in which W fibers are arranged substantially parallel to each other in one plane or in one straight line, and carbon is Manufacture of a fiber-reinforced SiC sintered body, which is characterized by adding a binder contained therein, molding it, thermally decomposing it in a non-oxidizing atmosphere, allowing molten metal silicon to seep through, and making the entire fiber-reinforced SiC. This is a type of reaction sintering method for SiC, but because the W (tungsten) fibers are arranged substantially parallel, it has extremely strong tensile strength in the fiber elongation direction. It has high toughness because a small amount of metallic silicon remains. Next, to form this, if the W fibers are arranged in an unspecified direction on one plane and bonded, a thin plate that is strong against bending and tensile stress can be obtained, and if they are arranged radially, radial tensile stress, that is, centrifugal force It is possible to obtain thin plates and impellers that are particularly strong against
By winding and bonding it to the side surface of a cylindrical or rectangular tube, it is possible to obtain a cylinder or rectangular tube that is extremely resistant to gas stress and thermal strain caused by combustion, even when a combustion reaction occurs inside. Also, if they are arranged parallel to a straight line and joined together, a linear body that is particularly strong in that direction can be obtained, and if this is processed into a circular or coiled shape, it becomes suitable for rings, heat-resistant coil springs, etc. SiC
It has significantly greater toughness than a sintered body. Next, the carbon-containing binder must be adhesive and contain carbon, and pitch, tar, fatty acids, and especially thermoplastic or thermosetting resins can be effectively used. These may be arranged while being kneaded with the W fibers, or after the W fibers are arranged, they may be permeated by applying vibration to the liquid binder. In either method, it is necessary to sufficiently fill the voids between the fibers. If this is insufficient, the sintering will also be insufficient, resulting in a decrease in strength. Next, in order to thermally decompose this and leave carbon behind, a non-oxidizing atmosphere, specifically, a vacuum, hydrogen, argon, nitrogen or the like atmosphere may be used. The decomposed residual carbon at this time fills the gaps in the W in the form of porous and highly active carbon, making it easier for molten metal silicon to permeate through capillary action, and reaction sintering occurs sufficiently at around 1500°C. As a result, a sintered body of W fibers bonded by reactive sintered SiC is obtained, and since a small amount of silicon remains, the body has a significantly large swelling resistance in the direction of the fibers and has high toughness. Silicon carbide also has great oxidation resistance,
It is a high-strength component that can be used in various combustion equipment. The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto. Example 1 Commercially available W fibers were immersed in a mixture of isobutyl methacrylate, nitrocellulose, and dioctyl phthalate to which a small amount of trichlorethylene was added, then piled up in parallel and pressed to a thickness of 2.
A test piece measuring mm x width 10 mm x length 100 mm was created, dried, and heated to 800°C for 5 hours in an N ₂ atmosphere to thermally decompose the organic binder and create an object in which W fibers were bonded with carbon. Next, a metal silicon powder was placed in an alumina pod, one end of the test piece was placed in the powder, and the temperature was raised to 1430°C in a vacuum to melt the metal silicon and permeate it into the sintered body. ,
Reaction sintering was completed. Let this be No.1. Next, No. 1 except using Pitch instead of polyurethane resin.
It was made in the same manner as No. 2. In addition, a test piece with the same shape as No. 1 was prepared using a conventional well-known reaction sintering method and designated as No. 3R. The characteristics of this are shown in Table 1. Table 1 shows that the SiC sintered body of the present invention had a longitudinal bulge strength that was 70% greater and a transverse rupture strength that was about 40% greater than conventional reaction sintered SiC. This can expand the scope of its use as a heat-resistant structural material.

[Table] Example 2 Commercially available W fibers were arranged in parallel on one plane to a thickness of 1 mm, and after impregnated with tar mixed with carbon powder,
The fibers were arranged perpendicularly to the above fibers to a thickness of 1 mm, impregnated with tar mixed with carbon powder, pressed to form a flat plate with a thickness of 2 mm, and cut into disks with a diameter of 60 mm. Reactive sintered SiC in the same manner as in .2.
It was set as No.4. Separately, a disk of the same shape was obtained by a conventional reaction sintering method, and this was designated as No. 5R, and these were placed on the upper surface of the piston as shown in the side view in FIG. 1 in the figure is an aluminum alloy piston,
2 is a SiC sintered body. When this was installed in an internal combustion engine with a cylinder capacity of 1200 c.c. and operated for 100 hours, it achieved No.
5R had 4 out of 5 pieces damaged, but No. 4 didn't have 1 out of 5 breakage. Example 3 Commercially available W fibers were immersed in a molten pitch, and the diameter was 100 mm.
It was wound around the side of a 3 mm cylinder to a thickness of 3 mm, and then cooled to form a cylinder with an inner diameter of 100 mm, an outer diameter of 106 mm, and a length of 300 mm. After this, reaction sintering was carried out under the same conditions as in Example 2.
It will be SiC and number 6. Next, a cylinder with the same shape was manufactured using the conventional well-known reaction sintering method and named No. 7R. City gas is combusted inside this to raise the internal temperature to 3.
In a test where the temperature was raised to 600℃, 700℃, 800℃, and 900℃ in minutes, No. 7R broke down at 600℃, while No. 6 did not break even when the temperature rose to 900℃. ,
It was found to be extremely resistant to sudden heat. Example 4 A commercially available W fiber was made into a string with a diameter of 2 mm, immersed in a molasses solution to make it semi-dry, and wound into a spiral shape with a pitch of 10 mm on the surface of a cylinder with a diameter of 50 mm.
A coil spring of 100 mm was used, and No. 8 was made of reactive sintered SiC in the same manner as in Example 2. In addition, we fabricated a SiC coil spring with the same shape using the conventional reaction sintering method, named No. 9R, and compressed it in the axial direction in a 1000°C furnace to examine the amount of elastic deformation until fracture.
While 9R can be deformed by 5 mm, No. 8 of the present invention can be deformed by 9 mm, greatly improving its utility as a spring. As described above, the W sintered body according to the present invention has high tensile strength in a specific direction, is strong against vibration shock, is strong against thermal shock, and has large warm deformation, and can provide a method for manufacturing heat-resistant parts that are strong and have great industrial utility value. It is.

[Brief explanation of the drawing]

FIG. 1 is a side view of a piston equipped with a fiber-reinforced SiC sintered body of sample No. 4 of Example 2 of the present invention.

Claims (1)

[Claims] 1 W fibers are molded with a carbon-containing binder, and the binder is thermally decomposed in a non-oxidizing atmosphere;
Penetrated through molten metal silicon and reinforced with fiber throughout
A method for producing a fiber-reinforced SiC sintered body, characterized in that it is made of SiC. 2. The method for producing a fiber-reinforced SiC sintered body according to claim 1, wherein the W fibers are arranged substantially parallel to one plane. 3. The method for producing a fiber-reinforced SiC sintered body according to claim 1, wherein the W fibers are arranged substantially parallel to each other in a straight line. 4. The method for producing a fiber-reinforced SiC sintered body according to claim 1, wherein the carbon-containing binder is an organic resin.