JPH0319290B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for uniformly mixing molten alloy and ceramic, which are difficult to mix with each other, to produce a homogeneous composite.

BACKGROUND OF THE INVENTION Recently, in order to obtain materials with properties suitable for various purposes, alloys have been mixed with various ceramic particles to form composites. For example, graphite particles are added to aluminum alloys and copper alloys to make them anti-friction materials, ultra-light vitreous microscopic hollow spheres such as glass balloons are mixed into aluminum alloys at high proportions to make lightweight composite materials, and aluminum alloys are made into lightweight composite materials. Adding short carbon fibers, fillers such as oxides and carbides to other alloys to improve their strength, adding shirasu to molten aluminum alloys,
It is known to add particles containing a foaming source such as mica and calcium carbonate to foam to form an ultra-lightweight foamed aluminum alloy.

However, the ceramics used in these composites generally have poor wettability with the molten alloy, and there is a difference in specific gravity between the two, so even if ceramic particles are added to the molten alloy and thoroughly stirred, the two will not be completely dispersed. It is difficult to separate the two during cooling and solidification. As a method to solve these difficulties, the surface of ceramic particles has been coated with metal in advance and this is added to the molten alloy, the temperature of the molten alloy, the alloy composition,
Methods such as mixing ceramic particles by strictly controlling the mixing conditions have been used, but the processing is complicated and the expected effects cannot be obtained, so this method is still not fully satisfactory as an industrial method. It cannot be called a thing.

In addition, as a method of increasing the viscosity of the molten alloy and making it possible to disperse ceramics, we use alloy components that have a wide temperature range between the solidus and liquidus lines. Stir vigorously,
A method of forming a highly viscous solid-liquid coexistence melt in which solid phase particles are uniformly dispersed, and adding ceramic particles such as silicon carbide, aluminum oxide, or silicon oxide to this, or adding air, oxygen, or dioxide into the molten alloy. Known methods include blowing in a gas such as carbon, stirring it, thickening it with fine oxide particles that are uniformly generated in the melt, and adding and mixing foamable ceramic to obtain an alloy foam. . However, these thickening methods have limitations on the molten alloys and ceramics to which they can be applied, as well as strict control of conditions, and cannot be said to be universally applicable.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of such conventional composite manufacturing methods and can be commonly applied to many alloys. The purpose of this invention is to provide a method for industrially manufacturing a homogeneous composite by uniformly mixing molten alloy and ceramic.

Means for Solving the Problems The present inventors have conducted various studies in order to develop an industrial manufacturing method for composites having such favorable characteristics. As a result, the present inventors have found that aluminum alloys, magnesium alloys, and It was discovered that when melts such as tin alloys, lead alloys, and zinc alloys are continuously stirred vigorously in the presence of oxygen, their viscosity increases significantly, and when ceramic particles are added, a sufficiently dispersed state can be obtained. Based on this knowledge, we have completed the present invention.

That is, the present invention provides an alloy-calcium mixture of one type of alloy selected from aluminum alloy, magnesium alloy, tin alloy, lead alloy, and zinc alloy and 0.05 to 5% calcium based on the weight. After melting, the molten mixture is continuously stirred vigorously in the presence of oxygen until it reaches a viscosity suitable for addition and mixing of ceramic particles to promote oxidation, and then ceramic is added and dispersed. A method of manufacturing a ceramic-alloy composite is provided.

The present invention will be explained in detail below.

It is generally observed that the addition of metallic calcium to a melt of the metal slightly increases the viscosity. This thickening phenomenon due to alloying is caused by, for example, titanium, iron, and molten aluminum.
This is a well-known phenomenon seen when copper is melted, and is an important phenomenon in casting. However, by increasing the viscosity due to the dissolution of calcium alone, it is not possible to obtain sufficient viscosity to allow the arbitrary addition and mixing of various ceramic particles. It's just a matter of getting caught.

On the other hand, the mechanism of thickening of a molten alloy containing calcium by stirring in the presence of oxygen can be considered as follows. In other words, since calcium is the element with the highest affinity for oxygen, after being added to the molten alloy and dissolved, the calcium component that comes into contact with air immediately oxidizes to become fine calcium oxide, which is dispersed in the molten alloy by stirring. do.
With continued stirring, the amount of calcium oxide in the molten alloy gradually increases, and at the same time the apparent viscosity increases significantly. A feature of the present invention is to utilize such preferential oxidation of calcium in the molten alloy.

As described above, the method of increasing the apparent viscosity by forcefully oxidizing the molten aluminum alloy by blowing air or the like into the molten aluminum alloy has been shown to be effective. It requires long air blowing and is dangerous for magnesium alloys, while air blowing has little thickening effect on tin alloys, lead alloys, and zinc alloys. Furthermore, the thickening method using the solid-liquid coexistence region of an alloy cannot be applied to eutectic alloys. Furthermore, the method of coating ceramic fine particles with a metal film in advance is economically disadvantageous.

In contrast, the method of the present invention preferentially oxidizes added calcium rather than oxidizing the molten alloy itself, so the oxidation rate is high, and therefore the thickening time is short, and it can be applied to any alloy system. It has excellent features such as being able to form a composite with any material or shape of ceramic particles.

Conventionally, there have been very few calcium additives for metals, and only a very small amount (0.01 to 0.02% or less) is known to be used as an antioxidant or deoxidizer. However, since calcium generally embrittles the alloy, it should be avoided to add a large amount.

As a result of thorough consideration of this point, the present invention has determined that the amount of calcium added to the melt of the alloy becomes noticeable from 0.05%, based on the weight of the melt, and increases when it exceeds 5%. Although the viscous effect increases, the alloy itself becomes significantly brittle and loses its properties, so the amount added is selected within the range of 0.05% to 5%. It is preferably in the range of 0.5% to 1%, but it varies depending on the type of molten alloy and the amount of ceramic particles added.

Effects of the Invention The method of the present invention can be commonly applied to many alloys, and can evenly mix molten alloy and ceramic, thereby easily obtaining a homogeneous composite. It has the remarkable effect of being able to

As already mentioned, the field of application of the present invention is the production of various ceramic-alloy composites that require the dispersion of ceramic particles in the alloy, and specifically, for example, graphite and alloy composites intended for anti-friction materials. Lightweight vitreous micro hollow spheres for the purpose of alloy composites and lightweight alloys.
Alloy composites, oxides and carbides for strengthening purposes,
It can also be applied to fine particles such as nitrides and carbon, short fiber/alloy composites, and foamed alloys using ceramics containing foaming sources such as shirasu, mica, carbonates, and hydrides for the purpose of ultra-light weight reduction. be.

Example Next, the present invention will be explained in detail by way of examples.

Example 1 5 g of calcium was added and mixed to 1 kg of Al-12% Si alloy kept in a molten state at 680°C in a #10 graphite crucible using an electric furnace, and after thickening treatment,
500 ml of shirasu balloons with an average particle diameter of 150 μm with residual structured water were added, kept in the furnace for about 5 minutes, and then cooled to obtain a homogeneous foamed aluminum alloy composite with a specific gravity of 0.52 due to the foaming phenomenon. In addition, when calcium was not added, many separation phenomena were observed during the mixing of the Shirasu balloon.

Example 2 Calcium was added 0.5% based on the weight of the Al-12%Si alloy kept in a molten state at 640°C in a #10 graphite lubricant in an electric furnace, and after thickening treatment, the length Approximately 5 mm of short carbon fibers (8 μm in diameter) were added. It was possible to mix 40 g of the short carbon fibers into about 400 g of Al-12%Si alloy. The structure after solidification showed a state in which carbon fibers were relatively well dispersed.

Example 3 10 g of calcium was added and mixed to 1 kg of Zu-4% Al alloy kept in a molten state at 500°C in a #10 graphite crucible using an electric furnace, and after thickening treatment,
100 g of alumina particles with a particle size of 80 μm were added. An alumina-Zn alloy composite was obtained by adding calcium. Note that if calcium is not added, a separation phenomenon occurs during the mixing of alumina and a composite cannot be obtained.

Claims (1)

[Claims] 1 After melting an alloy-calcium mixture of one type of alloy selected from aluminum alloy, magnesium alloy, tin alloy, lead alloy, and zinc alloy and 0.05 to 5% calcium based on its weight, A ceramic-alloy composite characterized in that the molten mixture is continuously stirred vigorously in the presence of oxygen to promote oxidation until a viscosity suitable for addition and mixing of ceramic particles is reached, and then ceramic is added and dispersed. manufacturing method.