JPS6157108B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a silicon carbide fiber composite metal hollow body. Recently, metals, metals, etc. have been developed as a method for strengthening heat-resistant metal alloys that can withstand corrosion (erosion) caused by high-temperature gases and intense heat flow rates, especially in high-temperature combustion zones such as re-formation tubes, rockets, engine parts for gas turbines, and heat exchange equipment for nuclear reactors. Research and development is progressing on fiber-reinforced composite materials that combine oxide and other ceramic fibers within a base heat-resistant metal alloy to retain high high-temperature strength and the original toughness of the base metal, and some are being put into practical use. be. Known methods for compounding the fibers into a heat-resistant metal alloy include a powder metallurgy method in which the fibers are embedded in a layer of raw metal powder, and a casting method in which the fibers are brought into direct contact with a molten metal. However, the former method has a complicated manufacturing process and the fibers are easily damaged during the manufacturing process, while the latter method allows the fibers to be in close contact with the heat-resistant metal or alloy (base metal), but is likely to react with the molten metal. It often happens that the strength of the In particular, the method of directly using molten metal is suitable for mass production, but conventionally this method has been applied to metals with relatively low melting points such as aluminum and copper. For more than a few minutes,
The disadvantage is that the strength of the fibers deteriorates, and on the other hand, when a high-melting point metal such as steel is used as a matrix, the ceramic fibers deteriorate further and satisfactory results have not been obtained. The present invention provides a method for manufacturing a silicon carbide fiber composite metal hollow body, in which silicon carbide fibers are composited into a base metal, regardless of whether the metal is a low melting point metal or a high melting point metal, and the properties of the composite fiber are not deteriorated. After arranging a reinforcing cylindrical body made of silicon carbide fibers along the inner wall surface of a metal mold for centrifugal casting, molten metal is injected while rotating the mold, and then quenched. A method for manufacturing a silicon carbide fiber composite metal hollow body by solidifying, or after arranging a reinforcing cylindrical body made of silicon carbide fibers along the inner wall surface of a water-cooled mold, molten metal is injected into the mold, and the inner wall surface of the mold is According to the method for manufacturing a silicon carbide fiber composite metal hollow body, the molten metal is rapidly cooled and solidified to form a solidified layer of a predetermined thickness, and then the unsolidified metal in the mold is discharged outside the mold. Thus, the object of the present invention can be achieved. Next, the present invention will be explained in detail. Silicon carbide fibers that can be used in the present invention can be made by decomposing or reducing steam containing raw materials on the surface of a heated core wire and depositing SiC on the core wire, or by making carbon fibers by depositing SiC on the core wire.
It is possible to use SiC long fibers produced by causing a SiC reaction by applying SiCl ₄ gas. However, it can be made by the above two methods.
All SiC long fibers have a tensile strength of about 20 Kg/ ^mm2 , and of the two methods above, the former method not only depends on the material used as the core wire in low-temperature or high-temperature strength, but also in manufacturing cost. is also very expensive.
On the other hand, in SiC long fibers made by the latter method, the thickness of the core carbon fiber cannot be made uniform, so the thickness of the finished SiC long fibers is uneven, and the manufacturing cost is high. is high. It is also possible to use whiskers made of SiC, which have high density and tensile strength, but have a short diameter of about 1 to 10μ and a length of several centimeters or less, and become stronger as they grow larger. There are variations in the fibers and other properties, and it takes time and effort to braid them into woven fabrics or strings. The present inventors previously invented SiC long fibers and a method for producing the same,
No., Special Publication No. 57-53892, Japanese Patent Publication No. 51-149925,
JP-A-51-149926, JP-A-57-53893, JP-A-51-147624, JP-A-57-56566, JP-A-58
Although patent applications were filed under Japanese Patent Publication No. 38535 and Japanese Patent Publication No. 33682/1983, it was discovered that the SiC long fibers according to the above invention can be most suitably used in the present invention. The fibers produced by the method previously invented by the present inventors have high tensile strength, no variation in strength, high modulus of elasticity, long length, and can be mass-produced as described below. It is economical and can be used more advantageously than conventionally known SiC fibers. The silicon carbide fibers most preferably used in the method of the present invention are produced using organosilicon compounds classified into the following types (1) to (10) as starting materials. (1) Compounds containing only Si-C bonds (2) Compounds containing Si-H bonds in addition to Si-C bonds (3) Compounds containing Si-Hal bonds (4) Compounds containing Si-N bonds (5) ) Compounds with Si-OR (R-alkyl, aryl) bonds (6) Compounds with Si-OH bonds (7) Compounds with Si-Si bonds (8) Compounds with Si-O-Si bonds (9) Organosilicon compound esters (10) Organosilicon compound peroxide At least one or more organosilicon compounds belonging to the types (1) to (10) above are processed by at least one of irradiation, heating, and addition of a polycondensation catalyst. An organosilicon polymer compound having silicon and carbon as main skeleton components, for example, a compound having a molecular structure as shown below, is produced by a polycondensation reaction using a polycondensate. (stomach) (B) (c) (d) A substance containing the skeleton components described in (a) to (c) above as at least one of a chain structure and a tertiary structure, or a mixture of (a), (b), and (c). Examples of compounds having the above molecular structure include the following. (stomach) n=1: Poly(silmethylene siloxane) n=2: Poly(silethylene siloxane) n=6: Poly(silphenylene siloxane) (b) n=1: Poly(methylene oxy siloxane) n=2: Poly(ethylene oxy siloxane) n=6: Poly(phenyne oxy siloxane) n=12: Poly(diphenyne oxy siloxane) (c) n=1: polysilmethylene n=2: polysilethylene n=3: polysiltrimethylene n=6: polysiltriphenylene n=12: polysildiphenylene (d) as described in (a) to (c) above Those containing a skeleton component as at least one partial structure among chain, cyclic, and three-dimensional structures, or a mixture of (a), (b), and (c). After spinning the organosilicon polymer compound and heating the spun yarn at a low temperature in an oxidizing atmosphere,
Preheat in the temperature range of 1000 to 2000 °C in vacuum or in an atmosphere of one or more selected from inert gas, CO gas, hydrogen gas, and hydrocarbon gas. By firing at high temperatures, silicon carbide fibers with extremely high strength and high modulus of elasticity can be produced. The reason why the firing temperature is set in the temperature range of 1000 to 2000°C is as follows.
Firing at temperatures below 1000°C is not preferable because the silicon carbide crystals in the fibers are underdeveloped, resulting in low strength and elastic modulus of the fibers, and above 2000°C the decomposition reaction of silicon carbide becomes intense. The ratio of silicon and carbon contained in the organosilicon polymer compounds (a) to (d) above, which are the raw materials for the silicon carbide continuous fibers, is such that at least 5 atoms or more of carbon and 2 atoms of silicon are contained. Therefore, when this organosilicon polymer compound is spun and fired, many of the carbons bonded as side chains of the polymer will become hydrocarbons and volatilize, but at least
0.01% or more can remain in the silicon carbide fiber as free carbon. As shown in Table 1, the silicon carbide fibers produced as described above have much higher tensile strength and almost the same modulus of elasticity than conventional SiC fibers.

[Table] A feature of the present invention is that when SiC fibers come into contact with molten metal, they cause a chemical reaction, decompose, or are alloyed in the molten metal, resulting in fiber wear or deterioration of properties. By rapidly cooling and solidifying the molten metal by the method of the present invention, it is possible to suppress and prevent the above. In other words, in the case of metals or alloys with low melting points such as aluminum and copper, the molten metal temperature is lower than that of steel etc., and the casting temperature can also be lowered, so the molten metal is brought into contact with the SiC fiber for several minutes. Even though the damage caused by chemical reactions is relatively rare, deterioration of properties such as tensile strength could not be sufficiently prevented. However, according to the present invention, rapid cooling and solidification can be performed by centrifugal casting or casting using a water-cooled mold, and by casting a cylindrical hollow cast body, so not only the wear and tear of the fibers but also the deterioration of their properties can be minimized. can be suppressed and prevented. Furthermore, in the case of SiC fiber composite hollow bodies manufactured by contacting SiC fibers with molten metals with high melting points such as iron-based, nickel-based, cobalt-based, or chromium-based metals,
By centrifugal casting or water-cooled mold casting, and by forming a cylindrical hollow casting, the contact time between the molten metal and SiC fibers can be minimized, thereby preventing wear and property deterioration of the SiC fibers due to mutual contact. New knowledge that this can be prevented as much as possible,
The present invention has now been completed. In the present invention, as silicon carbide fibers produced by spinning an organosilicon polymer compound that can be advantageously used, silicon carbide fibers in which a relatively large amount of free carbon remains can also be used. The free carbon content can be adjusted to within a range of 30% or less by adjusting the atmosphere during preliminary calcination and/or high-temperature calcination during the manufacturing process from the organosilicon compound. When such free carbon is contained in the fiber, in addition to suppressing the decomposition of SiC by molten metal, when the matrix metal is a metal that combines with free carbon to form carbide, The effect is that the wettability between the fibers and the matrix metal increases, and various properties of the composite material are improved. In the present invention, in addition to the silicon carbide fibers containing free carbon that can be advantageously used, pre-fired fibers which are intermediate products thereof can be used. When this fiber is fired by heating with a molten metal at approximately 1200°C or higher, it changes to SiC. Therefore, in the hollow body manufactured by the present invention, the intermediate process product is mainly a silicon carbide fiber made of SiC. This will strengthen the hollow body. Even in such a pre-fired intermediate product, a predetermined amount of free carbon can remain within the range of 30% or less. That is, in the present invention, silicon carbide fibers containing SiC or SiC free carbon, or pre-sintered intermediate products of the fibers can be advantageously used. The manufacturing method of the present invention will be explained below with reference to the drawings. According to the first aspect of the present invention, for example, a reinforcing cylindrical body 4 made of braided or molded silicon carbide fibers is fixedly disposed along the inner wall surface 3a of a metal mold 3 for centrifugal casting shown in FIG. 3 is rotated at high speed around its long axis, the molten metal in the ladle 2 is injected into the mold 3, and the reinforcing cylindrical body 4 is cast into the inner wall surface 3a of the mold by centrifugal force, and the molten metal is rapidly solidified. In this way, the hollow body of the present invention can be obtained. In this case, as shown in FIG. 2, it is advantageous to forcefully cool the mold 3 by injecting cooling water from the nozzle 6, since it can further rapidly cool and solidify the mold. According to the second invention of the present invention, for example, an injection pipe 16 is attached to the upper part of the induction furnace 15 shown in FIG. A styrene synthetic resin pipe 12 supporting a reinforced cylindrical body 12a
was fixed with a riser body 13. Next, high pressure air is supplied to the induction furnace 1 from a pressurized air source (not shown) through an air pipe 17.
5 and rapidly pressurizes the surface of the molten metal in the furnace, the molten metal flows into the mold 11 through the injection pipe passage 16a, and the synthetic resin pipe 1
2 is melted and a silicon carbide fiber reinforced cylindrical body 12a is cast. When the feeder body 13 is filled with molten metal, the supply of high-pressure air is immediately stopped and the high-pressure air inside the induction furnace 15 is discharged to the outside through the exhaust pipe 18, thereby removing the molten metal from the center of the mold 11 into the induction furnace. 1
Return to within 5. As a result, a metal hollow body made of a composite of the silicon carbide fiber-reinforced cylindrical bodies can be manufactured. In the present invention, the following methods can be used to further prevent SiC fiber wear and property deterioration due to molten metal. (1) The surface of a cylindrical body made by braiding or molding composite SiC fibers into a cylindrical shape is coated with other types of ceramics to prevent direct contact with molten metal, thereby preventing wear and property deterioration due to molten metal. I can do it. The coating is performed, for example, by a radiation method such as plasma spraying. As for the various ceramics used here, oxides, nitrides, borides, or silicides, which are less reactive than SiC to molten metal, are advantageously used, especially Al ₂ O ₃ , TiO ₂ , ZrO _{2 ,} etc. can do. (2) By coating the surface of the SiC fibers to be composited with metal, it is possible to prevent SiC from being worn out and deteriorating its properties due to molten metal. The coating can be applied by electrodeposition, plasma spraying, vapor deposition, or the like. It is advantageous to use a metal that is of the same type as the molten metal or has a melting point similar to that of the molten metal, and has substantially the same properties as the hollow body according to the invention. (3) In addition to methods (1) and (2) above, using a metal powder molded body with embedded cylindrical braided SiC fibers as a reinforcing cylindrical body prevents the chemical reaction of the molten metal to the SiC fibers. This is advantageous in that it can be sufficiently prevented. In this case, it is advantageous that the reinforcing cylindrical body formed by molding the metal powder is sintered or once melted and then solidified as a result of casting, and that the cylindrical body is firmly welded to the molten metal after solidification. Therefore, the metal powder used here is
It is advantageous to use metal or alloy powders of a type that does not damage the SiC fibers and can be sintered or melted at the casting temperature of the molten metal, and, depending on the use of the hollow body, has corrosion resistance, It is further desirable to use a metal or alloy powder that has heat resistance, wear resistance, etc. (4) As a method of coating the surface of SiC fibers to be composited with various types of ceramics or metals, a reinforcing cylindrical body may be created by braiding or molding SiC fibers that have been previously coated with the above ceramic coating.
It is also possible to create a reinforcing cylindrical body by braiding or molding the SiC fibers without applying ceramic coating to the surface thereof, and then applying ceramic coating from the inside and outside. Next, the present invention will be explained with reference to examples. Example 1 As shown in Fig. 1, HK40 steel powder was applied to a reinforcing cylindrical body 4 made of braided silicon carbide fibers placed on the inner wall 3a of a centrifugal casting mold 3 (inner diameter: 160 mm, casting length: 3000 mm). is reinforced by plasma spraying and fixed to the mold 3. Next, molten metal equivalent to HK40 steel is produced in a separate induction furnace (not shown). Separately, a copper-iron alloy centrifugal casting mold 3 is rotated at about 260 rpm. At this time, the mold 3 is forcibly cooled by injecting cooling water from the nozzle 6 as shown in FIG. 2. Thereafter, by introducing the molten metal into the rotating mold 3 through the tundish 2, it was possible to cast the HK40 distant cast pipe 5 composited with silicon carbide fibers in a very short time. In this way, silicon carbide fiber is added to the volume percentage (target value) of 1%.
(a), 10% (b), 30% (c), and 55% (d) composite cast tubes were prototyped. In addition, as a comparative material, we prototyped a deep-cast pipe (E) without silicon carbide composite. The chemical composition of these cast tubes is shown in Table 2. In addition to this far-casting pipe, a cast iron mold and
Using 12Cr stainless steel mold, volume ratio 10%
(Target) A prototype cast pipe was manufactured in the manner described above. As a result of microscopic observation of specimens taken from this distant casting tube, it was found that in the case of the former cast iron mold, the silicon carbide fibers were partially dissolved, and in the latter case of the 12Cr stainless steel mold, most of the silicon carbide fibers were dissolved. I found out that it was.

[Table] Next, high-temperature tensile test pieces and creep test pieces were taken from the cast pipes of (a), (b), (c), (d), and (e), and each was heated to 1000 to 1500℃. The results of tests in the temperature range are shown in Figures 4 and 5. The high-temperature tensile strength is increased by the composite of silicon carbide fibers, but the low-temperature strength of (d) with a large volume fraction is somewhat low. This tendency was also observed in the case of creep rupture strength. Based on these test results,
It was confirmed that the effect of improving high-temperature strength properties by combining silicon carbide fibers is remarkable at high temperatures. Example 2 As shown in Figure 3, the chemical components shown in Table 3 were
An injection pipe 16 is attached to the upper part of the induction furnace 15 containing molten HK steel, and a silicon carbide fiber reinforced cylindrical body 12a knitted by an appropriate method is placed inside the water-cooled mold 11 provided at the upper part of the injection pipe 16. The supported styrene synthetic resin 12 was fixed with a feeder body 13.

[Table] Next, from the pressurized air source (not shown)
7, high pressure air is supplied into the induction furnace 15 to rapidly pressurize the molten metal M, so that the molten metal M flows into the mold 11 through the injection pipe passage 16a,
The synthetic resin pipe 12 is melted and the silicon carbide fiber reinforced cylindrical body 12a is cast in it. When the feeder body 13 is filled with molten metal M, the supply of high-pressure air is immediately stopped, and the high-pressure air in the induction furnace 15 is discharged to the outside through the exhaust pipe 18, thereby removing the molten metal in the center of the mold 11. is returned to the induction furnace 15. As a result, an HK14 steel pipe (f) composited with silicon carbide fiber-reinforced cylindrical body 12a was produced as a prototype. Also, do not use this equipment to composite silicon carbide fibers.
A prototype of HK14 steel pipe (G) was produced. Next, test pieces were cut from this steel pipe and subjected to high-temperature tensile tests and creep tests in the temperature range of 1000 to 1150°C. The results are shown in Figures 6 and 7. Composite metal hollow body using
It was confirmed that (F) is superior to steel pipe (G) that is not reinforced with fibers. In addition, mold 1 is a modified method of this pressure casting method.
1 and the injection pipe 16 are kept together in a vacuum or reduced pressure inert gas atmosphere, and by varying the pressure, the molten metal M is repeatedly raised and lowered into the mold 11 and the injection pipe 16, thereby producing the desired amount. It is also possible to maintain the wall thickness. Example 3 A fiber-reinforced composite metal hollow body was manufactured in the same manner as in Example 2 using a cylindrical braided body of alumina-coated silicon carbide fibers as a reinforcing cylindrical body. Its component composition is shown in Table 4. In the same table, (R) has the same components but uses fibers that are not coated with alumina.

[Table] A test piece was cut from this steel pipe and heated to 1000 to 1150℃.
Figures 8 and 9 show the results of high-temperature tensile tests and creep tests conducted in the temperature range of . According to the figure, it can be seen that both the tensile strength and creep rupture strength of the alumina-coated specimen are improved. As is clear from the above examples, from the viewpoint of wettability, it is preferable to use silicon carbide fibers produced by the above manufacturing method. Incidentally, as in Example 1, compounding silicon carbide fibers excessively does not necessarily lead to an improvement in the strength of the composite material, but rather makes it susceptible to damage during melting, which is undesirable, so the upper limit is about 50%. As described above, the present invention is particularly advantageous for manufacturing fiber-reinforced hollow bodies such as reformed machining tubes by rapidly solidifying molten metal in contact with silicon carbide fibers using a water-cooled mold with high thermal conductivity. . In addition to the above-mentioned cast steel, other molten metals can be used for the method of the present invention, and hollow body manufacturing methods include the centrifugal casting method shown in Fig. 1, the pressure casting method shown in Fig. 3, and the like. Casting methods that allow rapid solidification, such as over-casting methods that use water-cooled cores, are applicable. In addition, as a method of reinforcing the silicon carbide fiber reinforced cylindrical body, the plasma injection,
Although styrene resin is used, other waxes,
Any suitable reinforcing material such as pulp can be used.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of manufacturing silicon carbide fiber composite by centrifugal casting method, Figure 2 is an explanatory diagram illustrating the water cooling method of centrifugal casting type, and Figure 3 is an explanatory diagram of manufacturing silicon carbide fiber composite by pressure casting method. An explanatory diagram when manufacturing a hollow body. Figure 4 is a diagram showing the high temperature tensile strength of a silicon carbide fiber composite hollow body sample manufactured by centrifugal casting. Figure 5 is a diagram showing the high temperature tensile strength of a silicon carbide fiber composite hollow body sample manufactured by centrifugal casting. Diagram showing creep rupture strength of silicon carbide fiber composite hollow body sample,
Figure 6 shows the high temperature tensile strength of the silicon carbide fiber composite hollow body sample manufactured by the pressure casting method, and Figure 7 shows the high temperature tensile strength of the silicon carbide fiber composite hollow body sample manufactured by the pressure casting method. FIG. 8 is a diagram showing the high temperature tensile strength of the hollow body manufactured in Example 3, and FIG. 9 is a diagram showing the creep rupture strength of the same hollow body. 2... Tin, 3... Mold, 3a... Mold inner wall surface, 4... Silicon carbide fiber reinforced cylindrical body,
5...Hollow body, 6...Nozzle, 11...Water-cooled mold, 12...Styrene synthetic resin pipe, 12a...
Silicon carbide fiber reinforced cylindrical body, 13... riser body, 14... hollow body, 15... induction furnace, 16...
...Injection pipe, 17...Air supply pipe, 18...Exhaust pipe.

Claims (1)

[Claims] 1. Silicon carbide fibers braided into a cylindrical shape along the inner wall surface of a metal mold for centrifugal casting, or formed by coating this with metal or ceramic, or formed by braiding silicon carbide fibers along the inner wall surface of a metal mold for centrifugal casting. After arranging a silicon carbide fiber-reinforced cylindrical body made of either plastic or metal powder braided into a cylindrical shape, molten metal is injected while rotating the mold, and the mold is cooled with water from the outside. A method for manufacturing a silicon carbide fiber composite metal hollow body, characterized in that a composite metal hollow body reinforced with silicon carbide fibers is obtained by rapidly solidifying the molten metal while permeating the reinforcing cylindrical body by centrifugal force. 2. The method for manufacturing a silicon carbide fiber composite metal hollow body according to claim 1, wherein the reinforcing cylindrical body is a cylindrical body made of braided or molded silicon carbide fibers coated with metal or ceramic. 3. Braided silicon carbide fibers along the inner wall surface of a water-cooled mold, coated with metal or ceramic, or braided silicon carbide fibers into a cylindrical shape and molded with plastic or metal powder. After arranging the silicon carbide fiber reinforced cylindrical body made of either
The molten metal is injected into the mold and the mold is water-cooled from the outside to allow the molten metal to permeate into the silicon carbide reinforcing cylindrical body along the inner wall surface of the mold, while rapidly cooling and solidifying it to a predetermined thickness. After forming a solidified layer, the unsolidified metal in the mold is discharged outside the mold to obtain a composite metal hollow body reinforced with silicon carbide fibers. Method. 4. The method for manufacturing a silicon carbide fiber composite metal hollow body according to claim 3, wherein the reinforcing cylindrical body is a cylindrical body made of ceramic-coated silicon carbide fibers braided or molded.