JPH05132728A - Molded body of reinforcement for composite material and its production - Google Patents

Abstract

PURPOSE:To increase the reinforcing effect and to supply a large-sized composite material by practically preventing the adverse effect on the composite material and allowing a binder to thinly and uniformly adhere to the surface of a reinforcement. CONSTITUTION:Magnesium salt and aluminum salt are newly added, other than the conventional organic binder, as binder for an inorganic reinforcement, such as alumina short fiber and aluminum borate whisker, and also water is added and they are mixed. The resulting mixture is poured into the desired mold so as to be formed into a molded body. This molded body is dried and burnt. By this method, the molded reinforcement body for composite material can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing material compact for composite materials used for strengthening aluminum alloys, magnesium alloys and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Generally, in the production of aluminum alloy matrix composites reinforced with short fibers or whiskers by high pressure casting, alumina material is used to control the shape of composite material, volume ratio of fibers, and dispersion state. An inorganic reinforcing material such as short fibers or aluminum borate whiskers is previously fixed with an organic binder or SiO ₂ to form a reinforcing material molded body,
The composite material is strengthened by impregnating the reinforcing material compact with an aluminum alloy, a magnesium alloy, or the like.

As a first method for producing the above-mentioned molded body of reinforcing material, first, water and an organic binder are added to an inorganic reinforcing material such as alumina short fibers and aluminum borate whiskers and mixed, and this mixture is desired. It is a manufacturing method in which the molded body is formed by pouring it into the mold, and the molded body is dried and baked.

In the second method for producing the reinforcing material molded body, water and SiO ₂ sol or, if necessary, an organic binder are added to the inorganic reinforcing material and mixed, and the mixture is made into a desired mold. It is a manufacturing method in which a molded body is formed by pouring, and the molded body is dried and baked.

[0005]

However, the reinforcing material molded body obtained by the first manufacturing method has a high strength in a dried state, but when it is fired, the organic binder burns out and the organic binder is absent. − Loses its role as a binder. For this reason, the strength of the reinforcing material molded body is remarkably reduced, the reinforcing material molded body is easily damaged during transportation, and is also easily damaged when high pressure casting is carried out and set in a mold. Therefore, there have been many accidents in which the reinforcing material molded body is easily damaged when high pressure casting is performed to impregnate the molten metal with the composite to form a composite.

Further, in the reinforcing material molded body obtained by the second manufacturing method, the organic binder burns out during firing, but since SiO ₂ remains, the strength is not significantly reduced. However, when this reinforcing material compact is subjected to high pressure casting and impregnated with a molten metal such as an aluminum alloy or a magnesium alloy to form a composite, the SiO ₂ is easily reduced when contacting with the molten metal and Si is alloyed. Γ-Al ₂ O ₃ is formed on the surface of the reinforcing material while being dissolved therein. The generated Si becomes defects in the composite material as coarse particles in the solidified structure, and easily deprives Mg which is an important alloying element such as aluminum alloy and magnesium alloy. As a result, the binder, SiO ₂ , disappears, causing softening of the reinforcing material molded body, resulting in a drastic decrease in strength. The phenomenon of softening has a large influence particularly when manufacturing a composite material having a large size, and thus there is a problem that a composite material having a large size cannot be manufactured.

FIG. 4 is a diagram for explaining the state in which Mg is solid-dissolved in the molten metal and decreases. This is a conventional product sample cut out from the state of FIG. 1, showing the Mg distribution in the cross section of 100 mm in length and 100 mm in width. It is the figure shown. This Mg distribution state will be described in detail. Since the molten metal is injected from the upper side of the reinforcing material molded body to permeate the composite material, Mg decreases as it goes downward, and the molten metal from the surroundings also decreases. It has been found that the Mg content decreases toward the central part due to the penetration of Mg. As a result, it was found in another experiment that the strength of the composite material was reduced to less than half the desired strength, and the cause of this strength reduction was the binder.
It came to discover that it was in SiO ₂ .
Therefore, the present inventor has focused on the development of a new stable binder that can substitute for SiO ₂ .

According to the present invention, the strength of the reinforcing material molded body can be sufficiently maintained, and the thermal strength can be extremely stable against metal hot water such as aluminum alloy and magnesium alloy, and further, strengthening for large size composite materials is possible. It is an object of the present invention to provide a reinforcing material molded body for composite material and a method for producing the same.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, that is, a reinforcing material molded body for composite material is an inorganic reinforcing material such as alumina short fiber or aluminum borate whisker. In addition to the conventional organic binder, a magnesium salt and an aluminum salt are newly added as the binder of 1. The manufacturing method is
At least a magnesium salt and an aluminum salt are added to the above-mentioned inorganic reinforcement, water is added and mixed, the mixture is poured into a desired mold to form a molded body, and the molded body is dried and fired to obtain a reinforcing material. It is a manufacturing method of a compact.

[0010]

Next, the operation of the present invention will be described in detail through experiments. First aluminum borate whisker (9Al ₂ O ₃ · ₂
Book consists of a B ₂ O ₃ Shikoku ALBOREX G) 100 parts, and 3.5 parts of a magnesium salt _{(MgCl 2 · 6H 2 O)} , and aluminum salt (AlCl ₃ · 6H ₂ O) 5 parts The reinforcing material molding of the invention has a whisker volume ratio of 20.
%, A diameter of 100 mm, and a height of 100 mm are prepared in advance and prepared in a cylindrical shape. Also, 100 parts of aluminum borate whiskers (9Al ₂ O ₃ .2B ₂ O ₃ ) and SiO 2
_A conventional reinforcing material molded body composed of 2 parts of ₂ sol is preliminarily formed into a cylindrical shape under the above-mentioned conditions and fired.
Next, the reinforcing material molded bodies of the present invention product and the conventional product are sequentially set in a predetermined mold. At this time, the reinforcing material compact is 800
The mold is heated to 250 ° C., and the mold is also preheated to 250 ° C. After setting the reinforcing material compact, preheated metal water (Al-1 wt% Mg-0.6 wt% S
i) is poured into the mold, and a casting pressure of 1000 kg / cm ² is applied so that the molten metal can sufficiently penetrate into the reinforcing material compact, and casting is performed. Then, the composite material is formed into a cylindrical shape having a diameter of 100 mm and a height of 100 mm to manufacture a composite material.

Samples having the dimensions shown in FIG. 1 are cut out from the composite material of each of the product using the product of the present invention and the product using the conventional product. In other words, length 100mm, width 100mm,
A sample with a width of 10 mm is cut out, and it is further stepped from top to bottom with a width of 10 mm to make samples of No01 to No10 as shown in FIG. .. After the treatment, the tensile test piece of the present invention and the conventional tensile test piece are subjected to a tensile test at room temperature. As a result of the test, as shown in FIG. 3, the data of the present invention is shown by white circles and the conventional product is shown by black circles.

As can be seen from this data, the product of the present invention has a strength variation of about 10% as compared with the strength variation of the conventional product, which is about 10%, and the change due to the position of the composite material is small. Further, when the minimum strengths were compared, it was confirmed that the product of the present invention was improved by about 50% over the conventional product. An X-ray diffraction analysis of the bonded portion of the reinforcing material molded body revealed that a peak of MgAl ₂ O ₄ appeared in addition to aluminum borate.
It was found that Al ₂ O ₄ (spinel) was generated and fully served as a binder. In addition, in the joint portion of the whiskers in this reinforcing material molded body, spinel that does not react with the molten metal after firing is MgCl ₂ (magnesium salt) and Al.
It was confirmed that Cl ₃ (aluminum salt) caused the bond between whiskers. Further E
When the line analysis by PMA was performed and confirmed, no clear appearance of segregation of Mg was observed. Therefore, the binder is MgAl ₂ O ₄ (spinel), and this component hardly reacts with Mg or Al.

[0013]

EXAMPLES Next, examples of the present invention will be described. First, using aluminum borate whiskers _{(9Al 2 O 3 · 2B 2} O 3) as an inorganic reinforcing material, using a MgCl ₂ · 6H ₂ O as the magnesium salt, the aluminum salt Al
Cl ₃ .6H ₂ O is used. Polyvinyl alcohol is used as the organic binder. As the magnesium salt, in addition to MgCl ₂ , MgSO ₄ , Mg (N
O ₃ ) _{2 and the} like, and the aluminum salt is AlC
In addition to l ₃ , Al ₂ (SO ₄ ) ₃ , aluminum alum or the like may be used, and as the organic binder, carboxymethyl cellulose, starch or the like may be used other than polyvinyl alcohol.

Next, the manufacturing method of the present invention will be described. First, aluminum borate whiskers (9Al ₂ O ₃ .2) are used.
The B ₂ O ₃₎ to 100 parts of the MgCl ₂ · 6H ₂ O 3~3.
5 parts, 4.5 to 5 parts of AlCl ₃ .6H ₂ O and ₂ to 3 parts of polyvinyl alcohol are added, and 100 parts of water is added.
Add 0 parts and mix. Then, this mixture is poured into a desired mold to form a molded body. It should be noted that the size of this molded body is preset after firing so that it has a cylindrical shape with a diameter of 100 mm, a height of 100 mm, and a whisker volume ratio of 20%. Next, the molded body is taken out of the mold and naturally dried, or in a urgent case, dried at a temperature of about 100 ° C. After drying, the molded body is fired at a temperature of 800 to 1000 ° C. for about 2 hours to complete the reinforcing material molded body. The drying time and firing time vary depending on the size of the molded body. The addition amount of MgCl ₂ .6H ₂ O is set to a minimum value of 0.1 part to a maximum value of 7 parts, and the addition amount of AlCl ₃ .6H ₂ O is set to a minimum value of 0.5 parts to a maximum value of 7 parts. When the addition amount of magnesium salt or aluminum salt is less than this minimum value, the function of the binder cannot be performed, and when the addition amount is more than this maximum value, the wettability between the reinforcing material and the metal hot water becomes worse, It has a negative effect on the strengthening.

[0015]

As described above, by manufacturing a composite material using the reinforcing material molded body of the present invention, the conventional SiO ₂
The generation of Si particles and segregation due to the reaction of Mg, which occurred when the binder of No. 1 was used, is almost eliminated, and the problem of adverse effects on the composite material can be solved.

Further, since the magnesium salt and the aluminum salt are used as the binder, even if they are mixed, they are not gelled and are in a solution state, so that they adhere thinly and uniformly to the surface of the reinforcing material, and as a result, the effect of strengthening is large, The strength of the reinforcing material molded body and the strength of the composite material can also be improved.

By using the reinforcing material molded body of the present invention, the strength of the molded body itself is improved as compared with the conventional product, and it is possible to sufficiently withstand high pressure casting and to supply a large-sized composite material. Therefore, it can be used as a reinforcing material for extrusion billets, internal combustion engine blocks, and marine pistons.

[Brief description of drawings]

FIG. 1 is an explanatory view of cutting a sample from a composite material cast using a reinforcing material molded body of the present invention.

FIG. 2 is an explanatory view showing a state in which a tensile test piece obtained by finely cutting out FIG. 1 is produced.

3 is an explanatory view showing the data results of the tensile test piece of FIG. 2. FIG.

FIG. 4 is a Mg distribution diagram of the conventional sample of FIG.

Claims (2)

[Claims] 1. A reinforcing material molded body for a composite material, which comprises an inorganic reinforcing material such as alumina short fibers or aluminum borate whiskers, a magnesium salt, and an aluminum salt. 2. To the inorganic reinforcement, at least magnesium salt and aluminum salt are added, water is added and mixed, the mixture is poured into a desired mold to form a molded body, and the molded body is dried. A method for manufacturing a reinforcing material compact for a composite material, which is formed by firing.