JPH0711045B2 - Method for producing SiC dispersed casting composite material - Google Patents

Description

The present invention relates to a method for producing a SiC dispersion cast composite material.

(Prior Art) Metal materials are widely used as raw materials, but depending on the application, the properties that the metal material originally possesses are not sufficient, and strength, wear resistance, workability, and dimensional accuracy may be further required. is there. Therefore, it has been conventionally known that other metal particles or ceramic particles are dispersed in a metal base material and used as a composite material in order to compensate for the insufficient physical properties of the metal material while keeping the excellent physical properties.

As a method for producing this kind of metal-based composite material, conventionally,
Mechanical alloying method, high pressure solidification method in which molten metal is pressed into a preform material, injection dispersion method, etc. are known, but the mechanical alloying method is costly and has a limited product size. Will be limited to. In addition, the molding of the preform material by the high-pressure solidification method is not only high in product cost but also has a problem in dimensional accuracy, and its practical application is delayed except for the fields of weapons and aircraft.

Compared to these methods, the jet dispersion method has the possibility of producing composite materials at the lowest cost and is the object of the present invention.
It is also used in the manufacture of SiC dispersion cast composite materials.

In the case of producing a metal-based composite material, there is a problem of wettability between the molten metal and the particles when adding the particles to the molten metal-based solution in any of the above methods, and it is difficult to create a condition in which the wettability is easy. Therefore, as a conventional method for improving this wettability, metal particles are pre-plated on the ceramic particles to be added, or surface active elements are added to the molten metal, and further, the ceramic particles are added to the molten metal in a vacuum or in the air for a long time. Although methods such as stirring have been proposed, the former method has a problem in terms of cost, and the latter method has a problem with the reaction between the molten metal and particles, which is less expensive than the SiC dispersion cast composite material that is the subject of the present invention. It is not suitable for various composite materials.

Further, among the above-mentioned conventional manufacturing methods, other than the mechanical alloying method, there is a problem in the dimensional accuracy of the product, and a large amount of cost is required for the final processing, which is one of the causes that prevent the practical use of the metal matrix composite material. Is one. In such a metal-based composite material, since the strength and the wear resistance are important, the workability is significantly deteriorated, and the improvement of the dimensional accuracy is strongly desired. Therefore, if the composite material is not limited to the composite material but limited to the composite material only, the processing and other problems can be reduced, and therefore a method is also considered.

In summary, it is desired to develop a method for manufacturing a metal matrix composite material which is inexpensive, has excellent dimensional accuracy, and can be applied to large materials.

Now, the development of metal-based composite materials is also being promoted in the field of cast iron, and SiC, which is relatively inexpensive and has a large hardness, has attracted attention as dispersed particles that enhance the strength and wear resistance of cast iron, and SiC particles are dispersed in cast iron. SiC dispersed casting composite materials have been developed as raw materials.

As is well known, the composition of cast iron is Fe, C, Si, S, P, and Mn. However, when the SiC particles are dispersed in the molten cast iron in an attempt to produce a SiC-dispersed cast composite material, if the amount is small, it will dissolve. If it is large, the material of cast iron deteriorates, and it is difficult to disperse a desired amount of SiC particles. Therefore, there is a problem that it is difficult to obtain a cast composite material having the desired and desired strength and wear resistance.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and an object thereof is to inexpensively and easily manufacture a cast composite material in which a desired amount of SiC particles are dispersed, and to achieve this object. In order to produce SiC dispersed casting composite material,
It is prepared by mixing with an alloy melt having an alloy composition that can stably coexist with SiC particles, and adding this SiC particle-mixed alloy melt to the alloy melt to be cast in the molten state or after solidifying once.

(Examples) The present invention will be described below with reference to examples of cast iron and aluminum alloy, but prior to that, the basic concept of the present invention will be described.

The inventors of the present invention have empirically known that if the dispersion of SiC is directly added to the molten metal of the casting alloy, the SiC particles float or separate in the molten metal or are melted, so that the addition is impossible.
Therefore, we considered making an alloy melt with a composition in which SiC can exist stably, and first adding SiC to this melt. This molten alloy is Fe-25% Si-0.2% C, Ni-25% Si-0.1
% C, Al-25% Si, etc. are considered. SiC particles are Fe-based, Ni
Although it is possible to mix it with the molten alloys in the atmosphere,
It was found that a vacuum of about 10 ^-4 torr or an inert gas atmosphere equivalent to this is required.

A SiC dispersion cast composite material having a desired composition can be manufactured by adding the SiC dispersion alloy melt thus produced as it is, or by solidifying it once and then refining it and adding it to the melt of the casting alloy.

(1) Experimental example of cast iron In a graphite crucible, 40% by volume of SiC particles is added and mixed in a molten Fe-25% Si alloy which is heated to 1500 ° C. When the mixture of the SiC particles and the Fe-Si alloy produced in this way is cooled and solidified, a mixture as shown in the photograph of Fig. 1 is obtained.

Meanwhile, 5% by volume of the SiC dispersion alloy melt prepared above and the solid SiC mixture shown in FIG. 1 were separately added to the cast iron melt melted at 1450 ° C. in a separately prepared graphite crucible, Was poured into the mold. When the presence of SiC was examined by cutting the upper part of the resulting cast iron composite material, the results shown in Table 1 below were obtained.

From the above experimental results, with C and Si having a (C + 1 / 3Si)% of 4/2% or less, SiC is extremely likely to be dissolved in the cast iron molten metal, and it is difficult to stably exist in the cast iron casting. It was also confirmed that the material of the obtained cast iron composite material deteriorates when (C + 1 / 3Si)% exceeds 4.8%.

Similar experiments were carried out using 0.05%, 0.01%, 0.15% and 0.25% S cast iron melts. S in molten metal is known as a surface active element, and as a result of experiments, it was found that 0.05% or more of S was contained.
Has the effect of slowing the rate at which SiC dissolves in cast iron melt,
It was confirmed to be extremely effective. On the other hand, if the amount of S is too large, the material deterioration of cast iron becomes remarkable, and the limit is 0.2%.

It is considered that SiC is more likely to be dissolved in the molten metal when it is solidified once and then added as particles, because it is destroyed by thermal shock and added to the molten metal.

(2) Experimental example of aluminum alloy In a graphite crucible, 40% by volume of SiC particles with a particle diameter of 0.5 mm is added and mixed in a molten aluminum / silicon (Al-25% Si) alloy. The mixture of the SiC particles and the Al-Si alloy thus produced is cooled and solidified.

4% by volume of the above solid SiC mixture was added to a molten aluminum melted at 750 ° C in a separately prepared graphite crucible, and the mixture was poured into a predetermined mold to make a composite of four types of aluminum alloy with a diameter of 10 mm to 40 mm. Manufactured sticks. When a part of them was taken and the existence of SiC was examined, the results shown in the following table were obtained.

In the case of aluminum alloys, the silicon in the alloy acts in the same way as C and Si in the case of cast iron, and as can be seen from the above experimental results, when Si is less than 2%, the dissolution of SiC into the aluminum melt is fast, Although not shown in 2, the properties of the aluminum alloy are extremely deteriorated at 20% or more. A composite material having a small Si content of 2% or less can be produced, but during use, Al ₄ C ₃ generated during solidification of the composite material may react with moisture in the air and be separated from the composite material.

Although two examples of cast iron and aluminum alloy have been exemplified above, it goes without saying that the production method of the present invention can be similarly applied to the production of an unexpected metal-based composite material.

(Effects of the Invention) As described above, in the present invention, when producing a SiC particle dispersion casting composite material, the SiC particles are mixed with a molten alloy having an alloy composition that can stably coexist with the SiC particles, and the SiC particles are mixed. Since the mixed alloy molten metal is added to the molten alloy in the molten state or once solidified and cast, the amount of SiC mixed with the metal base can be accurately controlled, and the SiC particle-dispersed cast composite material can be manufactured at low cost. In particular, when the present manufacturing method is applied to the production of a cast iron composite material, the composition of cast iron should be 4.2.
% ≤ C% + 1 / 3Si% ≤ 4.8%, the properties of cast iron are not deteriorated, and the material with improved strength and wear resistance due to SiC can be obtained, which is applicable to the production of composite material of aluminum alloy containing silicon. If the content of Si is 2.0% ≦ S
By selecting i% ≤ 20%, a material with a large composite effect can be obtained.

[Brief description of drawings]

FIG. 1 is a photograph showing the grain structure of a SiC grain mixed alloy used in the manufacturing method according to the present invention.

Claims (7)

[Claims] 1. SiC particles are mixed with a melt of a master alloy having an alloy composition of Fe-25% Si-0.2% C, and this SiC particle-mixed alloy is added to cast iron after being solidified or once solidified. A method for producing a SiC dispersion cast composite material, which comprises: 2. The alloy composition of the mother alloy is Ni-25% Si-0.1
% C. The method for producing a SiC dispersed casting composite material according to claim 1. 3. The composition of the cast iron is 4.2% ≦ C% + 1 / 3Si% ≦
It is 4.8%, The manufacturing method of the SiC dispersion casting composite material of Claim 1 or 2. 4. SiC particles are mixed with a mother alloy melt having an alloy composition capable of stably coexisting with the SiC particles, and the SiC particle mixed alloy is melted or once solidified, and then the S content is A method for producing a SiC dispersion cast composite material, which comprises adding to cast iron with 0.05% ≤ S ≤ 0.2%. 5. The S content of the cast iron is 0.05% ≦ S ≦ 0.2.
%, The method for producing a SiC dispersion cast composite material according to claim 1 or 2. 6. A silicon-containing aluminum alloy to be cast after mixing SiC particles into a molten alloy of a master alloy having an alloy composition of Al-25% Si, and after solidifying the SiC particle mixed alloy or once solidifying the molten alloy. A method for producing a SiC dispersion cast composite material, characterized by being added to. 7. The SiC according to claim 6, wherein the Si content of the silicon-containing aluminum alloy is 2.0% ≦ Si% ≦ 20%.
Manufacturing method of dispersion cast composite material.