JPH0668143B2 - Method for manufacturing tubular fiber molding for reinforcement - Google Patents

Description

Detailed Description of the Invention A. OBJECT OF THE INVENTION (1) Field of Industrial Use The present invention relates to a reinforcing tubular fiber molding used for fiber-reinforcing a metal member or the like, particularly a fiber molding composed of at least carbon fiber and an inorganic binder Manufacturing method.

(2) Conventional technology Conventionally, this kind of fiber molded body seals both end openings of a breathable cylindrical molding die, and the molding die is immersed in an aqueous solution of a molding material containing at least carbon fiber and an inorganic binder. The step of dipping and adhering the molding material to the outer peripheral surface of the molding die by applying suction to the molding die to mold the molding material, pressing the molding material to the molding die to change the shape of the molding material. Preparation process, opening both ends of the molding die, drawing the molding die from the molding material, heating and drying the molding material, and calcining the molding material to partially carbon fiber with the inorganic binder. It is manufactured through a bonding process.

(3) Problems to be Solved by the Invention However, as described above, when the molding die is pulled out from the molded body material before heating and drying the molded body material, the molded body material contains a large amount of water and retains its shape. Since the property is poor, there is a problem that the material of the molded body is deformed and the dimensional accuracy of the fiber molded body is deteriorated.

It is an object of the present invention to provide the above manufacturing method capable of solving the above problems.

B. Structure of the Invention (1) Means for Solving the Problems The present invention has air permeability and seals the both end openings of a cylindrical molding die that uses shell sand as a constituent material, and forms the outer peripheral surface of the molding die. Covering with a thin film body having air permeability, the molding die is immersed in an aqueous solution of a molding material containing at least carbon fiber and an inorganic binder, and the molding material is formed into a thin film body by suctioning the molding material. A step of adhering to the outer peripheral surface of the molding die to form a molding material, a step of pressing the molding material against the molding die to adjust the shape of the molding material, and a heat drying of the molding material. By setting the molding die in a sintering furnace kept in an air atmosphere and setting the temperature in the furnace to 330 to 480 ° C. to completely burn out the thin film body and completely remove the molding die. A step of disintegrating; inerting the molded material And fired at the vinegar atmosphere,
And a step of partially binding the carbon fibers with the inorganic binder.

(2) Action When the molding die is completely collapsed after heating and drying the molding material as described above, it is possible to prevent deformation of the molding material and improve the dimensional accuracy of the fiber molding. It is possible to omit the drawing process.

The mold expands during heating and drying of the molded body material, and the expansion amount is absorbed by the buffering action of the thin film body, and the molding die expands before the mold die collapses. Since it is absorbed by the voids formed by the complete burnout, the molded material does not crack due to the expansion of the molding die.

Furthermore, since the molded body material is in contact with the molding die through the thin film body, the constituent material does not adhere to and remain on the molded body material after the molding die collapses, and thus the inner peripheral surface of the molded body material is smooth. Becomes

The temperature in the furnace at the time of the collapse treatment of the mold is set to 330 to 4
The reason for setting the temperature to 80 ° C. is as follows.

A mold made of shell sand will completely collapse when heated above 450 ° C. In this case, the decomposition temperature of the phenolic binder contained in shell sand is 320 to 360.
Since the decomposition is an exothermic reaction, the temperature of the mold is the temperature obtained by adding the heat generated by the decomposition of the phenolic binder (90 to 120 ° C) to the furnace temperature.

On the other hand, when the carbon fiber is heated in air to a temperature higher than 600 ° C., the oxidation reaction becomes active and the amount of carbon fiber is reduced.

Therefore, in order to prevent the weight loss due to the oxidation of the carbon fibers, the upper limit of the furnace temperature is set to 600 ° C.-120 ° C. = 480 ° C., and the lower limit of the furnace temperature is set as the minimum temperature required to collapse the mold. Set each to 450 ° C-120 ° C = 330 ° C.

When firing the molded body material in an inert gas atmosphere,
It is possible to prevent weight loss due to oxidation of carbon fibers.

(3) Example FIG. 1 shows a tubular fiber molding for reinforcement 1 obtained by the present invention.
The fiber molded body 1 is obtained by partially binding mixed short fibers of carbon fibers and alumina fibers as reinforcing fibers with silica sol, alumina sol as an inorganic binder, or a mixed sol thereof, and the matrix is infiltrated. It has a myriad of possible voids. In the fiber molded body 1, the fiber volume ratio (Vf) of the carbon fibers is, for example, 6 to 9%.
, And that of the alumina fiber, for example, is set to 12 to 19%, respectively.

This fiber molded body 1 is used for obtaining a fiber-reinforced composite cylinder sleeve by being compounded with an aluminum alloy matrix when casting an aluminum alloy cylinder block, for example. In this case, the carbon fiber improves the sliding characteristics of the inner peripheral surface of the cylinder sleeve mainly due to its lubricating ability,
Alumina fibers mainly contribute to the improvement of strength around the cylinder bore.

The mold is made of shell sand (grain size AFS35) and is formed into a cylindrical shape having air permeability. The outer diameter of this mold is 75m
m, wall thickness is about 5 mm, and radial crushing strength is 65 kg / cm ² .

FIG. 2 shows the relationship between furnace temperature and mold collapse rate. The disintegration rate of the molding die is'W ₁ / wherein w ₁ is the weight of sand generated by the disintegration of the molding die and w ₂ is the weight of the molding die.
It is represented by w ₂ ) × 100. Further, a is the case where the mold is held in the firing furnace for 60 minutes, while b is the case where the mold is held in the firing furnace for 30 minutes.

From FIG. 2, it is necessary to set the temperature in the furnace to 450 ° C. or higher in order to collapse the forming die 100%.

In this case, the decomposition temperature of the phenol-based binder contained in the shell sand is 320 to 360 ° C., and the decomposition is an exothermic reaction, so the temperature of the mold is generated at the furnace temperature due to the decomposition of the phenol-based binder. It becomes the temperature which added heat (90-120 degreeC).

FIG. 3 shows the heating temperature when the carbon fiber is heated in the air and the weight change due to the oxidation of the carbon fiber. It can be seen from FIG. 3 that when the carbon fiber is heated to a temperature higher than 600 ° C., the weight is rapidly reduced.

Therefore, in order to prevent the weight loss due to the oxidation of the carbon fibers, the upper limit of the furnace temperature is set to 600 ° C-120 ° C = 480 ° C, and the lower limit of the furnace temperature is set as the minimum temperature required to collapse the mold. Are set to 450 ° C.-120 ° C. = 330 ° C., respectively.

Next, a method of manufacturing the fiber molded body 1 will be described with reference to FIGS.

As shown in FIG. 4 (a), the entire outer peripheral surface of the molding die 2 is a thin film having air permeability and completely burned off at the collapse temperature of the molding die 2, for example, a thickness of 6-nylon. Cover with a stretchable thin cloth F of knitted knit with 0.10 mm.

As shown in FIG. 4 (b), holders 3 ₁ and 3 ₂ are attached to the openings of both ends of the molding die ₂ by adhesion, bolting or the like to seal the openings.

As shown in FIG. 4 (c), the mold 2 is immersed in an aqueous solution 4 of a molding material containing a mixed fiber of carbon fibers and alumina fibers and alumina sol, and suction is applied to the mold 2 by a pump 5 for pumping. Then, the molding material is attached to the outer peripheral surface of the molding die 2 with a predetermined thickness through the thin cloth F, and the molding material 6 is molded. The forming operation by the pumping pump 5 is performed for about 2 minutes.

As shown in FIG. 4 (d), the molding die 2 is installed in the pressure resistant container 7 of the rubber press, and pressurized air is supplied from the air pressure source 8 into the pressure resistant container 7 to form the molded material through the rubber 9. Mold 2 for 6
The outer peripheral surface is pressed with a pressure of 10 kg / cm ² , whereby the shape of the molded body material 6 is adjusted and, at the same time, the fiber volume ratio is determined.

In this case, the molding die 2 slightly contracts in diameter due to the pressing force, but since the thin cloth F follows the contracting action due to its contracting action, wrinkles do not occur in the thin cloth F, and therefore wrinkles do not occur. It is possible to prevent the inner peripheral surface of the molded body material 6 from being roughened by the transfer of. After the pressing force is released, the mold 2 is restored to its original state, but at this time, the thin cloth F stretches, so there is no problem.

As shown in FIG. 4 (e), both holders 3 ₁ ,
3 ₂ Remove the.

As shown by the line (I) in FIGS. 4 (f) and 5, the molding die 2 is installed in the drying furnace 10 kept in an air atmosphere, and the molded body material 6 is heated at a furnace temperature of 120 ° C. A drying process is performed for 60 minutes to remove water by evaporation. The thin cloth F starts to burn out during this heating and drying process. Further, the molding die 2 expands, but the expansion amount is absorbed by the voids generated by the partial burning of the thin cloth F and the cushioning action of the remaining thin cloth F, so that the molding material 6 expands the molding die 2 by expansion. Does not cause cracks.

As shown by the line (II) in FIGS. 2 (g) and 5,
The molding die 2 is installed in a firing furnace 11 kept in an air atmosphere, and the molding die 2 is subjected to a disintegration treatment at a furnace temperature of 450 ° C. for 30 minutes, and the thin cloth F is completely burned off in the temperature rising process. Let
By this disintegration treatment, the mold 2 is completely disintegrated.

Further, in FIG. 5, the chain line (III) shows the temperature change of the mold 2, and the temperature of the mold 2 rises above the temperature in the furnace due to the heat generated by the decomposition of the phenolic binder in the shell sand. Since the temperature is about 545 ° C. at the maximum, the carbon fiber is not reduced.

The mold 2 expands prior to the collapse of the mold 2,
The expansion amount is absorbed by the void g generated by the burning of the thin cloth F, and therefore, the crack does not occur in the molded body material 6 as described above.

Further, since the molded body material 6 is in contact with the molding die 2 through the thin cloth F, after the collapse of the molding die 2, the shell sand which is the constituent material thereof does not adhere to the molded body material 6 and remain there. The inner peripheral surface of the molded body material 6 becomes smooth.

As shown by the line (IV) in FIGS. 4 (h) and 5,
Next, only the green compact 6 was placed in the firing furnace 11 kept in an argon atmosphere, and the internal temperature of the green compact 6 was set to 800 ° C.
Is subjected to a baking treatment for 60 minutes. As a result, the mixed fibers are partially bonded by the alumina sol to obtain the fiber molded body 1 shown in FIG. In this case, since the firing treatment is performed in an argon atmosphere, the carbon fiber is prevented from being oxidized and its weight loss is prevented. Other inert gas may be used instead of argon.

The present invention is naturally applied to the production of a fiber molding having only carbon fibers as reinforcing fibers. Further, as the thin film body, it is also possible to use a breathable thin paper or the like in addition to a thin cloth.

C. EFFECTS OF THE INVENTION According to the present invention, since the molding die is completely collapsed after heating and drying the molded body material, it is possible to prevent deformation of the molded body material and improve the dimensional accuracy of the fiber molded body. It is possible to improve the production efficiency by omitting the mold drawing step.

Furthermore, by interposing a thin film body that can be completely burned during the collapse treatment of the molding die between the molding material and the molding die, cracks in the molding material due to thermal expansion of the molding die can be prevented and It is possible to prevent residue of the forming die constituent material from adhering to the forming material and obtain a fiber forming body of good quality.

Furthermore, since the mold disintegration treatment is performed in an air atmosphere, the cost associated with the treatment can be reduced, and the carbon temperature can be reduced by specifying the temperature in the furnace during the disintegration treatment and performing the firing treatment in an inert gas atmosphere. Fiber loss can be prevented.

[Brief description of drawings]

FIG. 1 is a perspective view of a fiber molding, FIG. 2 is a graph showing the relationship between furnace temperature and mold collapse rate, and FIG. 3 is a graph showing the relationship between heating temperature and carbon fiber weight. FIG. 4 is a manufacturing process drawing of the fiber molded body, and FIG. 5 is a graph showing the relationship between the time in the drying, disintegrating and firing and the temperature in the furnace. F ... Thin cloth as a thin film body, 1 ... Fiber molding, 2 ... Mold, 4 ... Aqueous solution of molding material,
5 ... Pumping pump, 6 ... Molded material, 8 ... Air pressure source, 10 ...
Drying furnace, 11 ... Baking furnace

Claims (1)

[Claims] 1. An air-permeable, cylindrical molding die made of shell sand as a constituent material is hermetically sealed at both end openings, and the outer peripheral surface of the molding die is covered with a breathable thin film body to form the molding die. A molded body which is immersed in an aqueous solution of a molding material containing at least carbon fiber and an inorganic binder, and is sucked into the molding die to adhere the molding material to the outer peripheral surface of the molding die through the thin film body. Molding the material; pressing the molding material against the molding die to adjust the shape of the molding material; heating and drying the molding material; keeping the molding die in an air atmosphere Installed in a sintering furnace and setting the furnace temperature to 330 to 480 ° C. to completely burn off the thin film body and completely collapse the molding die; Fired in an atmosphere to give the inorganic binder Method for producing a reinforced tubular fiber molding, which comprises using a; a step of coupling the carbon fibers partly by.