JPH06142889A - Manufacture of composite aluminum member - Google Patents

Abstract

PURPOSE:To tightly join an aluminum-based material with an aluminum casting. CONSTITUTION:The oxide film on the surface is removed by dipping an annular aluminum alloy-made insert member 4 constituting the inner wall of a piston ring groove 3 in a piston 1, then dipped into molten alloy in which magnesium is added to the aluminum to form Al-Mg alloy layer on the surface. Thereafter, after removing the oxide film on the surface, the insert member 4 is cast-in with molten aluminum alloy forming the piston 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for integrally forming aluminum or an aluminum alloy on a substrate made of an aluminum material.

[0002]

2. Description of the Related Art Aluminum-based materials made of aluminum or aluminum alloys are widely used as various materials and parts as well as aircraft materials because of their lightness and strength. It may be desirable to have all or part of the material have a particular function. For example, you want to form an aluminum layer with excellent corrosion resistance on a high-strength aluminum alloy casting to obtain the desired corrosion resistance without compromising the weight advantage of a light metal material, or to roll it on the surface layer. In some cases, it may be desirable to arrange an aluminum plate or the like having excellent mechanical strength.

In this way, when all or part of the aluminum casting has a specific performance, or when it is necessary to form a certain part in a specific shape in advance, a base made of an aluminum-based material prepared in advance is used as the molten aluminum. A method of fixing by casting around at the time of pouring is considered, and such a method is often used in iron-based materials.

However, in the case of an aluminum material, since a dense oxide film is firmly formed on the surface layer, the contact interface with the molten metal cannot be sufficiently welded,
Therefore, the aluminum layer portion formed by the molten metal and the substrate are in an insufficiently bonded state. Further, when the degree of superheat of the molten metal is increased, or when the substrate is sufficiently preheated, welding phenomenon is observed, but the condition range is very narrow and uniform adhesion is difficult.

Therefore, when utilizing this cast-molding technique, it is sufficient to simply wrap and fix it, and there is a risk of repeated play of temperature differences and mechanical stress, which may cause backlash. Also, it cannot be used for those requiring sufficient mechanical strength and airtightness.

Therefore, for example, as in the manufacturing method described in JP-B-2-35627, a treatment solution containing an aluminum-based material and fluorine is brought into contact with each other to form potassium pentafluoroaluminate (K ₂ Al).
There is also provided one in which a chemical conversion treatment layer made of F ₃ ) is formed, and then the substrate on which the chemical conversion treatment layer is formed is brought into contact with a molten metal of aluminum or an aluminum alloy to be integrated.

Therefore, according to the conventional example described in this publication, when the chemical conversion treatment layer, which is the flux on the surface of the substrate, comes into contact with the molten metal and the temperature rises to start melting, the molten chemical conversion treatment layer becomes an aluminum-based material. Reacts on the surface of the material to remove the oxide film on the material. As a result, since a clean aluminum surface of the material appears, the wettability between the material and the molten metal is improved, the molten metal is spread to every corner of the substrate, and good adhesiveness is obtained.

[0008]

However, according to the conventional example described in the publication, as described above, the oxide film is removed by the chemical conversion treatment layer on the surface of the substrate, and the adhesive force is secured mainly by the wettability of the material and the molten metal. Therefore, a sufficient adhesive force cannot be obtained only by the main wettability, and there is a fear that the base material and the solidified aluminum material or the like are separated after the production.

[0009]

The present invention has been devised in view of the above-mentioned problems of the prior art. A substrate made of an aluminum-based material which is formed in a predetermined shape in advance is added to at least magnesium. And a step of forming the alloy layer on the surface of a substrate by immersing the substrate in the molten alloy, and thereafter bringing the substrate into contact with a molten aluminum or aluminum alloy.

In the present invention, the aluminum-based material means
It means a material made of aluminum or an aluminum alloy, and its composition is not particularly limited,
Silicon contained in ordinary aluminum alloys, Si, Cu,
One or more additive elements such as manganese Mn, zinc Zn, titanium Ti, chromium Cr, zirconium Zr, and magnesium Mg may be contained, and the content thereof is not particularly limited. In particular, a composite of SiC particles, Al ₂ O ₃ particles, Al ₂ O ₃ fibers, SiC fibers, Si particles, carbon fibers and the like as an aluminum material having wear resistance is industrially useful. The aluminum-based material may also be a composite material such as a clad material composed of different aluminum materials, for example, having a melting point of 1 or more than that of one of the aluminum materials in order to ensure welding with the molten metal.
An alloy having a temperature lower by 0 to 100 ° C., for example, an Al—Si eutectic alloy containing Si in an amount of 7 to 12% (weight, the same applies hereinafter) may be bonded or coated.

The substrate made of an aluminum material used in the present invention may be a cast product or a rolled / cast product, and its shape and size are not particularly limited.
It is selected and used according to the purpose.

The aluminum-magnesium alloy in which the aluminum-based material substrate is immersed in the present invention can be manufactured as follows.

Aluminum is put into an electric furnace using a graphite crucible and melted, and the temperature is maintained at 730.degree. Then 100
Magnesium dried at −200 ° C. is put into an aluminum melt using a phosphorizer and melted. In that case, it is advisable to flow a sulfur hexafluoride gas in order to prevent the oxidation of magnesium. If the amount of magnesium exceeds 30% by weight, the melting point will be 500 ° C or lower, and if it exceeds 40% by weight, the temperature will be 450 ° C. Thus, the melting point of aluminum decreases as magnesium is added to aluminum.

The amount of magnesium in the molten alloy of aluminum and magnesium is preferably 20 to 40% by weight in order to reduce the amount of the intermetallic compound of aluminum and magnesium having a brittle property formed in the alloy layer. The amount varies depending on the temperature and casting amount of the aluminum alloy melt to be brought into contact, which will be described later, the mold material, the plan, and the weight of the substrate, etc., to determine the optimum melting point of the melt.

Here, what is important is to add aluminum so that the melting point of the molten metal is at least not higher than the melting point of the aluminum-based material. To achieve that, aluminum, magnesium, silicon, nickel, copper, chromium, manganese, zinc, iron, other titanium,
You may add calcium, strontium, antimony, etc.

Thereafter, the aluminum-based material substrate is immersed in the molten alloy of aluminum magnesium described above.
The immersion time is not unconditionally determined depending on the amount of magnesium in the molten metal and the temperature of the molten metal, but, for example, when the amount of magnesium is 28% by weight and the temperature is kept at 520 ° C., it is 5 minutes to 20 minutes.
The range of minutes is good.

It was found that the surface of the substrate and magnesium in the molten metal react with each other by this immersion treatment, and an alloy layer of aluminum and magnesium is formed on the surface of the substrate.

Prior to this immersion, it is effective to remove the oxide film formed on the surface of the substrate. The method is, for example, dipping in sodium hydroxide, hydrogen fluoride or the like. Further, the surface of the substrate may be degreased with an organic solvent such as trichlorethylene before the step.

The substrate may be subjected to the above dipping treatment as it is as a raw material which is not machined. Further, it may be processed after being processed so as to have a predetermined shape, or after being assembled. The Al-M formed on the surface of the substrate in this way
In the g alloy layer, aluminum on the surface of the substrate, aluminum and magnesium in the molten magnesium are metallurgically bonded. Therefore, there is no clear interface between the substrate and the alloy layer, and they are bonded very strongly. Therefore, it does not peel off even if it is subjected to considerable strong working, so that it may be processed and then plastically worked into a predetermined shape.

Further, as described above, the base is immersed in a molten alloy of aluminum and magnesium to form A on the surface of the base.
Although an l-Mg alloy layer is formed, when the substrate is pulled up from the molten alloy, the surface of the Al-Mg alloy layer on the substrate surface is oxidized. Since this oxide layer hinders alloying due to subsequent contact with the molten aluminum, it is preferable to remove the substrate prior to preheating described later. As the method, shot blasting using glass beads or the like, or immersion treatment of the above-mentioned acid or alkali solution is also good.

Next, a step of bringing the molten aluminum into contact with the surface of the base body on which the Al-Mg alloy layer is formed by casting will be described.

First, as the aluminum melt used in the present invention, aluminum or aluminum alloy can be used, and it is needless to say that the same material as the aluminum-based material for the substrate can be used, and the temperature of the aluminum melt is Al--Mg. It suffices if it is higher than the melting point of the alloy layer, and almost all aluminum alloy materials can be used.

The step of contacting the molten aluminum with the substrate by casting is most preferably carried out in a non-oxidizing atmosphere, but it may be carried out in an atmosphere containing a small amount of oxygen or, in some cases, in the atmosphere.

In this contacting step, the Al-Mg alloy layer acts as follows. That is, when the Al-Mg alloy layer formed on the surface of the base comes into contact with the aluminum melt having a melting point higher than that of the alloy layer, the Al-Mg alloy layer reaches the melting point by the heat received from the aluminum melt and the Al-Mg alloy layer reaches the melting point. At the same time as the layer begins to melt, it fuses with the molten aluminum to alloy and solidify.

Al-by receiving heat from the molten aluminum
It facilitates the temperature rise of the Mg alloy layer, and the molten aluminum absorbs heat by contact with the substrate to lower the temperature and
The substrate may be preheated to prevent it from solidifying before alloying with the Mg alloy layer. The preheating temperature depends on the melting point of the Al-Mg alloy layer on the surface of the substrate, but is, for example, 150 to 4
50 ° C is good. What is important in the preheating is that the preheating does not form an oxide film on the surface of the substrate. Therefore, it is preferable to perform heating in a non-oxidizing atmosphere such as argon or nitrogen gas.

[0026]

EXAMPLES Examples of the present invention will be described below. As shown in FIG. 1, this embodiment is applied to an aluminum alloy piston 1 of an internal combustion engine, in which S is formed on the peripheral wall of a piston ring groove 3 formed on the outer periphery of a ring land portion 2.
An example is shown in which the insert member 4, which is a base body made of an aluminum alloy in which iC particles are dispersed, is cast.

That is, in this manufacturing method, as shown in FIG. 2, first, the insert member 4 is set in advance on the annular holder 6 fixed in the casting mold 5. An Al-Mg alloy layer is formed on the surface of the insert member 4 by the manufacturing process described above. Then, the molten aluminum is poured into the mold 5, and the insert member 4 is cast.

Table 1 below shows that the insert member 4 is made of Al-
The experimental results are shown for the case where the surface treatment of the Mg alloy layer is performed, the case where it is not treated, and the case where the chemical conversion treatment described in the above publication is performed.

[0029]

[Table 1]

As is clear from this experiment, in the case where the treatment as in this embodiment is not performed or the chemical conversion treatment is performed,
While the aluminum casting did not sufficiently bond to the insert member 4, the one subjected to the treatment of this example showed strong bonding.

The composite aluminum member obtained in this example did not easily peel even in the peel test, and good results were obtained.

Further, according to this embodiment, since the insert member 4 can be formed by an aluminum alloy material instead of cast iron without using the expensive molten metal forging method as in the prior art, the cost is wide. In addition to being able to reduce the weight and weight, good thermal conductivity can be ensured.

Needless to say, the present invention is not limited to the piston 1 of the above-mentioned embodiment, but can be applied to other aluminum alloy products.

[0034]

As is apparent from the above description, according to the manufacturing method of the present invention, a substrate of an aluminum-based material is immersed in a molten alloy of aluminum and magnesium so that the surface of the substrate is completely metallurgically bonded. By forming the Al-Mg alloy layer that forms the above, it is possible to easily join the aluminum-based material and the aluminum casting, which were conventionally considered to be impossible.

Therefore, it is possible to obtain a composite aluminum member in which one member has, for example, corrosion resistance and the other member has a high-strength function such as wear resistance, without impairing the advantage of aluminum that it is lightweight. it can.
In addition, it is possible to cast parts that have been finished in a specific shape in advance, and it is not necessary that there is only one part (base) that is cast into one casting, so that various complicated shapes can be made. .

Further, in the case of a cast product which has a conventional wall thickness and is liable to cause internal defects, a pre-prepared substrate is placed at that position to circulate the cast product, thereby producing a high quality cast product in which shrinkage defects are prevented. It has the advantage that it can be obtained.

Further, according to the present invention, since the surface can be coated with molten aluminum, the desired aluminum coating can be achieved without the drawbacks such as the change in thickness and the increase in hardness at the time of laminating like a conventional clad plate. It has many excellent effects such as obtaining a composite aluminum plate having layers.

[Brief description of drawings]

FIG. 1 is an enlarged view of an essential part showing a piston of an internal combustion engine applied in an embodiment of the present invention with a part thereof cut away.

FIG. 2 is a cross-sectional view showing a casting mold used in this example.

[Explanation of symbols]

 1 ... Aluminum alloy piston 2 ... Ring land part 3 ... Piston ring groove 4 ... Insert member (base) 5 ... Mold

Claims (1)

[Claims] 1. A substrate made of an aluminum-based material, which has been formed into a predetermined shape in advance, is immersed in an alloy melt made by adding at least magnesium to aluminum to form the alloy layer on the surface of the substrate. A method for producing a composite aluminum member, characterized in that the alloy is brought into contact with a molten metal of aluminum or an aluminum alloy.