JPH0791607B2 - Method for producing reinforcing fiber molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Objectives of the Invention (1) Field of Industrial Application The present invention relates to a method for producing a reinforcing fiber molding used for fiber-reinforcing a metal member or the like.

(2) Conventional Technology Conventionally, in the case of producing this type of molded body, an intermediate body is molded using a molding material having a reinforcing fiber and an inorganic binder,
Then, a method is used in which the intermediate is fired at a temperature at which the binding force of the inorganic binder is exhibited.

(3) Problems to be Solved by the Invention However, since the binding force exerting temperature of the inorganic binder is generally a high temperature of about 1000 ° C., the expansion of the reinforcing fiber is delayed until the inorganic binder exerts the binding force. However, there is a problem that it is difficult to obtain a fiber molded body having a normal shape because the intermediate body loses its shape due to the above.

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 provides a reinforcing fiber, an inorganic binder, and a binding force that exerts a binding force at a temperature lower than the binding force exerting temperature of the inorganic binder. A primary intermediate is formed by using a molding material having an auxiliary inorganic binder that can be dissolved at the binding force exerting temperature of the inorganic binder and can be eluted by an acid, and an additive that promotes the dissolution of the auxiliary inorganic binder. A step of firing the primary intermediate to obtain a secondary intermediate at a binding force exerting temperature of the inorganic binder; and a step of eluting the auxiliary inorganic binder from the secondary intermediate. To do.

(2) Action As described above, when the auxiliary inorganic binder is used, the auxiliary inorganic binder exerts a binding force to bond the reinforcing fibers to each other during the temperature rising process in the firing step, so that the shape of the primary intermediate is lost. Can be prevented, and a fiber molded body having a normal shape can be obtained.

Further, the auxiliary inorganic binder is eluted from the secondary intermediate by the acid, so that it does not have any influence on the fiber volume ratio of the fiber molded body. Moreover, the fiber volume ratio of the fiber molded body depends on the compounding amount of the auxiliary inorganic binder. Can be adjusted over a wide range. In the elution treatment with the acid, since the reinforcing fibers are firmly bound by the inorganic binder,
Even if the auxiliary inorganic binder is eluted, the secondary intermediate does not deform and the elution treatment is accelerated by the additive, so that the treatment time is shortened and the productivity of the fiber molding is improved. You can

(3) Practical Examples The following are applicable as the reinforcing fiber, inorganic binder, auxiliary inorganic binder, and additives that compose the molding material.

As the reinforcing fiber, a carbon fiber, an alumina fiber, a silica / alumina fiber, a silicon nitride fiber, a silicon carbide fiber, a whisker of these, or the like which does not react with an acid used in the elution treatment is used.

As the inorganic binder, silicon nitride, zirconia (ZrO ₂ ), powder such as alumina, silicon carbide, whiskers such as silicon nitride, alumina sol, silica sol, etc. are used, and the binding force exerting temperature of this inorganic binder is 600 ° C. or more. is there. In this case, in order to improve the binding force of the inorganic binder, a binding aid powder is used if necessary, and as the seed powder, Al ₂ O ₃ , Y ₂ O ₃ , MgO, S having a diameter of 0.1 to 1 μm is used.
Single powders such as iO ₂ and mixed powders thereof are applicable.
The blending amount of the binder powder with respect to the inorganic binder is appropriately 1/7 to 1/10 the weight of the inorganic binder.

Further, the auxiliary inorganic binder is lower than the binding force exerting temperature of the inorganic binder, that is, exerting the binding force at about 100 to about 800 ° C., so that the binding force can be maintained even at the binding force exerting temperature of the inorganic binder, The following are used: Al ₂ O ₃ 20 wt% or less Na ₂ O 8 to 40 wt% B ₂ O _{3 30 to} 65 wt% SiO ₂ 40 wt% or less. At least one of CaO and MgO is added, and the glassy, Al ₂ O ₃ —Na ₂ O—B ₂ O ₃ —S having an average diameter of 1 to 5 μm obtained through the steps of melting and crushing is added.
iO ₂ -based powder and Al ₂ O ₃ 20 wt% or less B ₂ O _{3 30 to} 65 wt% SiO ₂ 40 wt% or less K ₂ O 40 wt% or less Each powder is mixed, and CaO and MgO are mixed with the mixed powder. Of Al ₂ O ₃ —B ₂ O having a glassy average diameter of 1 to 5 μm obtained by subjecting each step of melting and crushing as described above by adding at least one of
₃ is a -SiO ₂ -K ₂ O-based powder.

The reason for limiting the blending amount of each powder as described above is that if the blending amount is deviated, crystals are precipitated in the powder as the auxiliary inorganic binder to form a non-uniform structure, and elution with acid becomes impossible. .

At least one selected from a boron-based compound and a phosphoric acid-based compound is used as an additive that accelerates the elution treatment of the auxiliary inorganic binder with an acid. in this case,
Boron compounds include sodium borate, borate salts such as ammonium borate, boric anhydride (B ₂ O ₃ ) and the like,
In addition, the phosphoric acid compound is sodium hexametaphosphate,
Metaphosphates such as sodium acid metaphosphate, orthophosphoric acid, phosphoric anhydride (P ₂ O ₅ ) and the like are included.

This additive has almost no involvement in the firing process of the reinforcing fibers, and therefore it is present in the secondary intermediate and functions to accelerate the acid leaching of the auxiliary inorganic binder, and then to the secondary intermediate. It is eluted from the body with the auxiliary inorganic binder.

The molding material is prepared by dispersing the reinforcing fiber, the inorganic binder, the binding aid powder, the auxiliary inorganic binder, and the additive, if necessary, in water to prepare a liquid or mud form. in this case,
Although the blending amount of each component varies depending on the target fiber volume ratio of the fiber molded body, for example, the blending amount of the reinforcing fiber is 55 to
When set to 65% by weight, the blending amount of the inorganic binder is 1 to 40% by weight, the blending amount of the binding aid powder is 1 to 5% by weight, and the blending amount of the auxiliary inorganic binder is 31 to 34% by weight. In addition, the compounding amount of the additive is set to 2 to 40% by weight, respectively. As a result, a fiber molding having a fiber volume ratio of 40 to 50% is obtained.

Since the auxiliary inorganic binder is eluted and removed, the fiber volume ratio of the fiber molded body varies depending on the compounding amount of the auxiliary inorganic binder. Therefore, by changing the compounding amount, the fiber volume ratio is in a wide range, for example, in the range of 8 to 50%. It can be adjusted over. In particular, a fiber molded product having a low fiber volume ratio, which cannot be obtained by the conventional method, can be obtained.

Further, the additive, when the fiber molded body is compounded with an aluminum alloy, a magnesium alloy or the like, improves mutual diffusibility and reduces the contact angle of the aluminum alloy or the like with respect to the fiber molded body to significantly improve its wettability. Since this has the effect of improving the bonding strength between the two, and when aiming at this effect, an additive is added in a slight excess so that it remains in a thin film form on the fiber surface of the fiber molding after the elution treatment. . At this time, the amount of the additive compounded is suitably 10 to 40% by weight.

Among additives, metaphosphate is effective in preventing lamination during pressure molding, and exerts strong shape-retaining performance when the solvent is too small.For example, water evaporation, during or after evaporation of organic components. In addition, it also has an effect of preventing loosening and cracking between fibers.

As the molding method of the primary intermediate, various methods such as an injection molding method, a pressure molding method and a slip casting method are applied. The molding pressure depends on the shape of the primary intermediate, etc.,
50 to 150 MPa is suitable.

The firing treatment is a one-step firing method in which firing is completed by heating at 1500 to 1850 ° C for 0.5 to 5 hours, or 1000 to 1200
Primary calcination by heating at ℃ for 0.5-12 hours and 1500-180
A two-stage firing method is adopted in which firing is completed through a secondary firing treatment of heating at 0 ° C for 0.5 to 5 hours. When the one-step firing method is adopted, it is natural that the elution treatment is performed after the firing treatment, but when the two-step firing method is adopted, the elution is performed after the primary firing treatment or after the second firing treatment. Processing is performed.

As the acid used for eluting the auxiliary inorganic binder from the secondary intermediate, a single acid such as HCl, HNO ₃ , HF, or a mixed acid thereof is mainly used. In some cases, CH ₃ C is added to the acid.
A small amount of organic acids such as carboxylic acids such as OOH and HCOOH are added. The elution treatment is performed by immersing the secondary intermediate in an acid solution heated at room temperature or 30 to 60 ° C. for a predetermined time. At that time, while circulating the acid solution, 8-24MHz
When the ultrasonic vibration is applied, the acid solution spreads over the auxiliary inorganic binder, and also has the effect of promoting the elution processing of the additive, so that the elution processing of the auxiliary inorganic binder can be completed in a short time.

The drawing shows the relationship between the elution treatment time for the secondary intermediate and the removal rate of the auxiliary inorganic binder after the primary calcination treatment. Line a corresponds to the present invention using the additive, and line b corresponds to the addition. It corresponds to a comparative example in which no agent is used.

In the present invention and the comparative example, ultrasonic vibration is used together with the elution treatment, and the acid solution is in a circulating state. The composition of the secondary intermediate in the present invention is as follows: silicon carbide whisker (reinforcing fiber) 40% by weight, silicon nitride (inorganic binder) 19% by weight, Y ₂ O ₃ (bonding aid powder) 1% by weight, Al ₂ O _3- Na ₂ O-B ₂ O
20% by weight of _3- SiO ₂ system powder (auxiliary inorganic binder) and 20% by weight of ammonium borate (additive). In the case of the comparative example, the composition is almost the same as the above, but the additive is not included.

As is clear from the drawing, in order to remove approximately 100% of the auxiliary inorganic binder, it takes about 4 to 5 minutes in the case of the line a of the present invention, but it takes 7 to 8 minutes in the case of the comparative example of the line b. .

[Example I] Al ₂ O ₃ 13.2% by weight Na ₂ O 28.1% by weight B ₂ O ₃ 39.3% by weight SiO ₂ 17.1% by weight MgO 2.3% by weight was used as an auxiliary inorganic binder and was vitreous and had an average diameter of 1 to 1. 5 μm Al ₂ O ₃ —Na ₂
O-B ₂ O ₃ to obtain a -SiO ₂ system powder.

Reinforcing fiber Silicon nitride whisker crystalline α phase, crystallinity approximately 100%, diameter 0.1-0.4 μm, length 5-20 μm (aspect ratio 20-10
0), density 3.18 g / cm ³ 32% by weight Inorganic binder Silicon nitride powder Maximum diameter 1 μm or less, average diameter 0.4 μm 1
0% by weight Binding aid powder Al ₂ O ₃ and Y ₂ O ₃ 0.1% by weight 0.2% by weight Auxiliary inorganic binder 27.8% by weight of the above powder Addition of 30% by weight of ammonium boron boron to water and organic compounding agent (powder) Wax system 40 by body weight ratio
%, A dispersant system 4%, an antifriction system 2%, and other 4%, and 20% of the organic matter remains after the solvent is dispersed) and mixed well to obtain a mud-shaped molding material.

Using this mud-like molding material, a pressure molding method is applied to mold a cylindrical primary intermediate body having a diameter of 40 mm and a length of 10 mm at a molding pressure of 50 MPa, 80 MPa, 100 MPa, 120 MPa, 150 MPa, 250 MPa. In this case, the pressure holding time is 1 minute. During this pressure molding, the lubrication function of the organic compounding agent facilitates the molding of the primary intermediate.

The primary intermediate is subjected to a primary drying treatment at 80 ° C. for 4 hours, a secondary drying treatment at 110 ° C. for 8 hours, and a tertiary drying treatment at 150 ° C. for 12 hours. In this drying treatment, the shape of the primary intermediate is maintained by the binder function of the organic compounding agent. After that, the organic components are removed at 650 ° C.

The primary intermediate is subjected to a primary calcination treatment in an N ₂ atmosphere at 1200 ° C. for 2 hours to obtain a secondary intermediate. When the temperature in the furnace reaches about 100 ° C during the temperature raising process in the primary firing process, the auxiliary inorganic binder exerts its binding force, so that the reinforcing fibers are bonded to each other by the auxiliary inorganic binder, which results in the primary intermediate Even if the body expands, its shape is prevented.

When the temperature in the furnace reaches 1000 ° C., the inorganic binder exerts its binding force, so that the reinforcing fibers are bound to each other by the organic binder.

After checking the presence or absence of cracks and hair cracks and the storage rate of the secondary intermediate, the secondary intermediate was treated with 20% HNO ₃ and 0.1% H
It is immersed in an acid solution of F, and the acid solution is kept for 5 minutes while applying ultrasonic vibration of 16 MHz to elute the auxiliary inorganic binder to obtain a fiber molded body having a fiber volume ratio of about 30%.

After that, the fiber molded body was subjected to ₂ hours of 1700 ° C. for 1 hour under N ₂ atmosphere.
Next firing treatment is performed.

The properties of the secondary intermediate and the fiber molded body are as shown in Table I and later.

As is clear from Table I, the molding pressure of the primary intermediate is 120 MPa.
In the following, the fiber molded body has a very small shrinkage ratio and has no defects such as peeling at the edge portion and the like, and therefore has good dimensional accuracy and a normal shape.

In the secondary intermediate, each silicon nitride fiber is bridge-bonded by silicon nitride powder, and the diameter of the silicon nitride powder is 1 μm or less and is substantially uniform.

On the other hand, in the fiber compact, the silicon nitride powder has a diameter of
It has grown to a columnar crystal of 0.4 to 0.5 μm and a length of about 4 to 6 μm, and it seems that silicon nitride whiskers have also partially grown.

As described above, a normal fiber molding can be obtained even if the molding pressure of the primary intermediate is increased up to about 120 MPa in the pressure molding method using a normal die, and the molding pressure rises and By improving the strength of the inorganic binder by the subsequent firing treatment, it is possible to obtain a fiber molding having a bending strength of 15 to 30 kg / mm ² . Comparing that the bending strength of the conventional fiber molded body was ² to 3 kg / cm ² , it is clear that the strength was significantly improved.

Example II

Example I and N ₂ atmosphere in the secondary intermediates Similarly, 1700
Secondary firing treatment is performed at 1 ° C. for 1 hour.

After that, the secondary intermediate is dipped in an acid solution consisting of 20% HNO ₃ and 0.1% HF, and the acid solution is kept for 10 minutes while applying ultrasonic vibration of 16 MHz to elute the auxiliary inorganic binder and the fiber A fiber molding with a volume ratio of about 30% is obtained.

The storage ratio and the like of the fiber molded body are shown in Table II, and the properties of the cotton are almost the same as in Example I.

Example III Al ₂ O ₃ 4.2 wt% B ₂ O ₃ 36.4 wt% SiO ₂ 27.5 wt% K ₂ O 30.3 wt% CaO 1.6 wt% was used as an auxiliary inorganic binder, and it was vitreous and had an average diameter of 1 to 1. 5 μm Al ₂ O ₃ -B ₂ O
₃ obtain -SiO ₂ -K ₂ O-based powder.

Reinforcing fiber Carbon fiber (milled fiber), diameter 30 μm, length 20-200 μ
m 7 wt% silicon carbide whisker β-type, diameter 0.05 to 1.5 μm length 20 to 200 μm (aspect ratio 20 to 200), density 3.18 g / cm ³ 18 wt% inorganic binder Silicon carbide whisker 5 wt% auxiliary inorganic binder Powder 40% by weight Additives Sodium hexametaphosphate 3% by weight and ammonium borate 27% by weight 30% by weight, water and the same organic compounding agent as in Example I are added and mixed thoroughly to obtain a muddy molding material. .

Using this muddy molding material, a slip casting method is applied to mold a cylindrical primary intermediate body having an outer diameter of 90 mm, an inner diameter of 82 mm and a length of 130 mm.

The primary intermediate is subjected to a primary drying treatment at 110 ° C for 12 hours at 150 ° C.
A second drying process is performed for 48 hours, and at the same time, some of the organic components are decomposed and removed.

The primary intermediate is installed in a vacuum furnace and the flow rate of nitrogen gas is 40 ml / min.
The organic component is removed by raising the temperature under a condition of a vacuum degree of 0.4 Torr and holding at 650 ° C. for 1 hour, and then performing a primary baking treatment at 1200 ° C. for 2 hours to obtain a secondary intermediate.

The secondary intermediate is dipped in an acid solution consisting of 4N HNO ₃ and 0.2% HF, and the acid solution is kept for 15 minutes while applying ultrasonic vibration of 16MHz to elute the auxiliary inorganic binder. A fiber molding with a rate of about 20% is obtained.

In this fiber molded product, carbon fibers are bridge-bonded by silicon carbide whiskers, but their compressive strength is greater than that of the conventional one, and it is about to be destroyed when pressed by hand.

After that, the fiber molding was placed in a N ₂ atmosphere at 1800 ° C. for 1 hour for 2 hours.
Next firing treatment is performed.

This secondary firing treatment further promotes the cross-linking by the silicon carbide whiskers, and the powdery carbon in the carbon fiber,
Since the additives and a part of the auxiliary inorganic binder start to react during the primary firing treatment and progresses, the bending strength of the fiber molded body is improved to 4 kg / mm ² .

In addition, the fiber molded body has no shape defect, and the shrinkage rate is as small as 0.2%, so that the dimensional accuracy is good.

The fiber molding obtained by the present invention is used for reinforcing various mechanical structural members.

For example, when a rocker arm for an internal combustion engine is manufactured using an aluminum alloy such as JIS AC4C, a fiber molded body that conforms to the shape is obtained, and the preheating temperature of the fiber molded body is 100
~ 1000 ℃, melt temperature 720 ~ 780 ℃, melt filling pressure 50 ~ 15
Casting is performed under the condition of 00 kg / cm ² .

C. Effect of the Invention According to the present invention, by using an auxiliary inorganic binder having the above-mentioned physical properties and an additive for promoting the dissolution treatment thereof,
A reinforcing fiber molding having a normal shape can be efficiently manufactured. Further, the fiber volume ratio of the reinforcing fiber molding can be adjusted over a wide range by the blending amount of the auxiliary inorganic binder, and in particular, a reinforcing fiber molding having a low fiber volume ratio which cannot be obtained by the conventional method can be obtained. .

[Brief description of drawings]

The drawing is a graph showing the relationship between the elution treatment time and the removal rate of the auxiliary inorganic binder.

Claims (1)

[Claims] 1. A reinforcing fiber, an inorganic binder, which exerts a binding force at a temperature lower than a binding force exerting temperature of the inorganic binder to maintain the binding force even at a binding force exerting temperature of the inorganic binder, and an acid. Forming a primary intermediate by using a molding material having an auxiliary inorganic binder that can be eluted by means of an additive and an additive that promotes the dissolution of the auxiliary inorganic binder; demonstrating the binding force of the primary intermediate to the inorganic binder. A method for producing a reinforcing fiber molding, comprising: a step of firing at a temperature to obtain a secondary intermediate; and a step of eluting the auxiliary inorganic binder from the secondary intermediate.