KR101272733B1 - Al-Mg alloy and method of fabricating the same - Google Patents

Abstract

The present invention provides a method for producing an aluminum-magnesium alloy having a high magnesium composition but having excellent mechanical properties and high processability. According to one aspect of the invention, the step of adding magnesium to the first aluminum molten metal, casting the first aluminum molten metal added with magnesium to produce an aluminum-magnesium master alloy having a first magnesium composition, the second aluminum molten metal Adding the aluminum-magnesium mother alloy to and casting the second molten aluminum to cast an aluminum-magnesium alloy having a smaller second magnesium composition than the first magnesium composition. A method is provided.

Description

Al-Mg alloy and method of fabricating the same

TECHNICAL FIELD The present invention relates to a technique for producing an aluminum alloy, in particular, a method for producing by casting an aluminum-magnesium alloy containing magnesium as an alloying element, and an aluminum-magnesium alloy produced by such a method, furthermore, such an aluminum-magnesium alloy It is about the processed material manufactured by processing.

In the current aluminum (Al) alloy, magnesium (Mg) is one of the major alloying elements. When magnesium is added to aluminum, it may cause an increase in strength due to solid solution strengthening and corrosion resistance along with a smooth surface is improved. As can be seen from the aluminum-magnesium state diagram shown in FIG. 1, magnesium can be dissolved in aluminum at temperatures up to about 450 ° C. up to about 17.4% by weight (wt%).

However, during the alloying process of magnesium in the aluminum molten metal, oxides or inclusions may be mixed into the aluminum molten metal by the chemically high oxidizing magnesium, thereby causing a problem of lowering the cleanliness of the molten metal. As the amount of magnesium added to the molten aluminum increases, the problem of oxidation of magnesium becomes more serious. Such a decrease in the cleanliness of the molten metal may greatly affect the properties of the alloy cast.

For example, when casting molten aluminum whose cleanliness is degraded due to the addition of high magnesium, casting cracking may occur during casting. In addition, the cast aluminum-magnesium alloy is significantly reduced workability. For example, if the composition of magnesium in the aluminum-magnesium alloy is more than 8.5wt%, the processing in the industrial sense is practically impossible.

Therefore, when manufacturing an aluminum-magnesium alloy, it is common to design the composition of magnesium not more than 5wt% in consideration of castability and processability. Consider the method for applying the molten metal surface such as SF ₆ gas upon addition of magnesium as a protective gas in order to suppress the oxides and inclusions incorporated in accordance with this magnesium addition. However, this SF ₆ gas is equivalent to high increase the manufacturing cost As a gas that causes environmental problems, it is increasingly regulated worldwide. Therefore, there is an urgent need for the production of aluminum-magnesium alloys having as high a magnesium composition as possible while minimizing the use of such SF ₆ gas.

The present invention provides a method for producing an aluminum-magnesium alloy in the production of an aluminum-magnesium alloy having a high magnesium composition, while having excellent mechanical properties and high processability while minimizing the use of a protective gas. The foregoing problem has been presented by way of example, and the scope of the present invention is not limited by this problem.

An aluminum-magnesium alloy of one embodiment of the present invention is provided. Magnesium is added to the first aluminum melt. The magnesium-containing first molten aluminum is cast to prepare an aluminum-magnesium master alloy having a first magnesium composition. The aluminum-magnesium master alloy is added to the second molten aluminum. The second aluminum melt is cast to cast an aluminum-magnesium alloy having a smaller second magnesium composition than the first magnesium composition.

In one aspect of the manufacturing method, the holding time for melting the aluminum-magnesium master alloy in the step of adding the aluminum-magnesium master alloy is the time to hold for melting the magnesium in the step of adding magnesium Can be shorter.

In another aspect of the manufacturing method, the amount of the protective gas for preventing the ignition of magnesium in the step of adding magnesium may be greater than the amount of the protective gas used in the step of adding the aluminum-magnesium mother alloy. .

In another aspect of the manufacturing method, in the step of adding magnesium, a protective gas may be used to prevent ignition of magnesium, and in the step of adding the aluminum-magnesium master alloy, a protective gas may not be used.

According to another aspect of the present invention, there is provided a method of manufacturing an aluminum-magnesium alloy, comprising: providing an aluminum-magnesium master alloy having a first magnesium composition; Adding the aluminum-magnesium mother alloy to the molten aluminum; And casting the molten aluminum to cast an aluminum-magnesium alloy having a smaller second magnesium composition than the first magnesium composition.

The aluminum-magnesium alloy of one embodiment of the present invention is produced and provided by the above-described manufacturing method.

In one aspect of the aluminum-magnesium alloy, the aluminum-magnesium alloy may have a higher tensile strength and an equivalent elongation than commercially available aluminum-magnesium alloys having a lower magnesium content.

According to the present invention, after preparing the aluminum-magnesium master alloy having a high magnesium composition, it is diluted to prepare an aluminum-magnesium alloy, thus preparing an aluminum-magnesium alloy having excellent castability without using a protective gas. can do.

 The effects of the present invention are not limited to those mentioned above, and other effects, which are not mentioned above, will be clearly understood by those skilled in the art from the following description.

1 shows an aluminum-magnesium state diagram.
2 is a flowchart showing step by step a method for producing an aluminum-magnesium alloy according to the present invention.
3A and 3B show the results of observing the surface of residual water when SF ₆ gas is not used as a protective gas and when it is used.
Figures 4a and 4b is a result of comparing the state after extrusion of the aluminum-magnesium alloy prepared according to the present invention and the conventional aluminum-magnesium alloy.
5a and 5b show the microstructure and tensile test results of the aluminum-magnesium alloy cast in accordance with the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. In the drawings, the components may be exaggerated or reduced in size for convenience of description.

It can be understood that the range for weight% (wt%) does not include the boundary value when it is above or below, but includes the boundary value when it is simply designated as a range or above or below.

2 is a flowchart showing step by step a method for producing an aluminum-magnesium alloy according to the present invention.

First, to prepare an aluminum-magnesium master alloy is provided aluminum molten metal (S1). In this case, the aluminum molten metal may be referred to as a first aluminum molten metal provided to form an aluminum-magnesium mother alloy. Meanwhile, the aluminum molten metal provided to add the aluminum-magnesium mother alloy to be described later may be referred to as a second aluminum molten metal to distinguish it from the first aluminum molten metal.

In this case, the parent alloy refers to an alloy made to be added to the molten metal to be provided in a subsequent step, and the resultant product produced by adding the parent alloy separately is referred to as an alloy. Therefore, the alloy prepared by adding the aluminum-magnesium mother alloy prepared in the present invention to the molten aluminum is referred to as an aluminum-magnesium alloy.

Next, after the magnesium is added to the first aluminum molten metal, the magnesium is dissolved (S2). In this case, the composition of magnesium to be added may be set higher than that of a conventional aluminum-magnesium alloy in consideration of the ratio of dilution in the second aluminum molten metal.

In the manufacturing of the aluminum-magnesium mother alloy, the upper portion of the first aluminum molten metal to which magnesium is added may be protected by a protective gas. The protective gas may be SF6, SO2, CO2, HFC-134a, Novec ™ 612, inert gas and its equivalents, or a mixture thereof. When the protective gas is added with magnesium of high composition in the aluminum molten metal, oxides and other impurities may be prevented from intercalating due to a phenomenon in which magnesium in the molten metal reacts with oxygen in the atmosphere to ignite.

3A and 3B show the appearance of residual water when ₆ w% of magnesium is added to the molten aluminum, when SF ₆ gas is used as a protective gas and when it is not used. Referring to FIG. 3A, it can be seen that when the SF ₆ gas is not used, the residue is changed to black due to the oxidation of magnesium. On the other hand, referring to FIG. 3B, it can be seen that oxidation of the residual water hardly occurred when SF ₆ gas was used.

The first aluminum molten metal added with magnesium can be stirred by any suitable means. For example, it may be mechanically stirred using the stirring means installed in the lower part of the furnace or may be stirred using the electromagnetic stirring means installed outside the furnace.

After magnesium is sufficiently dissolved, the first aluminum molten metal is cast into a mold to prepare an aluminum-magnesium mother alloy (S3). In this case, the mold may use any one selected from a mold, a sand mold, a ceramic mold, a graphite mold, and an equivalent thereof. In addition, casting methods include sand casting, die casting, gravity casting, continuous casting, low pressure casting, squeeze casting, lost wax casting, thixo casting, and the like. However, the present invention does not limit the type of mold and the manner of casting.

The aluminum-magnesium mother alloy thus produced is added again as a source of magnesium to the second aluminum melt.

Specifically, a second molten aluminum is prepared (S4), and the prepared aluminum-magnesium mother alloy is added (S5). At this time, the aluminum-magnesium mother alloy has a reduced melting point compared to pure magnesium as in the aluminum-magnesium state diagram of FIG. 1.

For example, when the composition of magnesium in the aluminum-magnesium master alloy reaches about 38 wt%, the melting point is reduced by about 200 ° C compared to the melting point (651 ° C) of pure magnesium. The melting point of the aluminum-magnesium master alloy is determined by the composition of magnesium, and may be about 100 to 200 ° C. lower than the melting point of pure magnesium in view of the melting time. However, the composition of magnesium in the master alloy can be appropriately adjusted, and thus the aforementioned melting point reduction range can be appropriately selected.

Therefore, the aluminum-magnesium mother alloy added to the second aluminum melt may be dissolved at a relatively lower temperature than the magnesium added to the first aluminum melt. Due to this drop in melting point, substantially dissolution of magnesium in the second aluminum melt can be easily accomplished in a faster time. As described above, when the melting point of the master alloy is significantly lowered, the holding time for melting the master alloy may be shorter than the holding time for melting magnesium in the first aluminum molten metal. By shortening melting time of a master alloy, working time can be shortened.

In addition, when the aluminum-magnesium mother alloy is added to the second aluminum molten metal, magnesium is already alloyed in the aluminum, and thus the use amount of the protective gas is significantly larger than that of magnesium added to the first aluminum molten metal. Can be reduced. Even when the aluminum-magnesium mother alloy is added, the problem due to the ignition of magnesium generated in the molten aluminum is significantly reduced even when a protective gas such as SF ₆ is not used. Therefore, the aluminum molten metal containing magnesium can be kept clean even without using an expensive protective gas causing environmental problems such as SF ₆ gas. As such, since magnesium is added in the form of an aluminum-magnesium mother alloy in the molten aluminum, it is possible to stably add magnesium to a high composition without causing a problem of adding magnesium directly to the aluminum molten metal.

Stirring may be performed for sufficient dissolution of the aluminum-magnesium mother alloy added in the second aluminum melt. Since the stirring has already been described above, a detailed description thereof will be omitted.

The aluminum-magnesium mother alloy is sufficiently dissolved in the second molten aluminum and then cast to prepare an aluminum-magnesium alloy (S6). Since the casting method has already been described above, a detailed description thereof will be omitted.

According to the present invention, the composition of magnesium added in the second aluminum melt can be calculated using the aluminum amount of the second aluminum melt before the aluminum-magnesium master alloy is not added and the composition of aluminum and magnesium in the aluminum-magnesium master alloy. .

That is, dilution of magnesium in the aluminum-magnesium mother alloy occurs by adding the aluminum-magnesium mother alloy to the second molten aluminum, and the composition of the diluted magnesium may be expressed by Equation 1 below.

Where W _Mg and W _Al1 are the weights of magnesium and aluminum in the aluminum-magnesium master alloy, respectively, and W _Al2 is the weight of aluminum used to form the second aluminum melt.

By using this equation, the composition of magnesium in the target second aluminum molten metal can be designed.

In the present invention, the composition of magnesium in the aluminum-magnesium mother alloy has a relatively higher value than that of the aluminum-magnesium alloy, and the aluminum-magnesium alloy has a relatively low magnesium composition as diluted according to the above equation.

For example, the magnesium composition in the aluminum-magnesium master alloy may range from 5 to 40 wt%, from which the magnesium composition in the diluted aluminum-magnesium alloy ranges from 1 to 15 wt%, strictly 2 to 12 wt%, more stringent. Preferably it may have a range of 5 to 10wt%.

According to the present invention, once the aluminum-magnesium mother alloy having a high magnesium composition is prepared, an aluminum-magnesium alloy can be prepared as much as the inverse ratio of the dilution ratio in the dilution process. For example, in the case of preparing 100 g of the master alloy of 40 wt% magnesium, when the dilution rate is 0.25, it is possible to prepare a total of 400 g of the aluminum-magnesium alloy having the magnesium composition of 10 wt%.

In this case, the protective gas is used only in the manufacturing step of the aluminum-magnesium master alloy, and once the master alloy is manufactured, the protective gas is not used in the step of producing the aluminum-magnesium alloy through subsequent dilution. Therefore, it is possible to easily produce an aluminum-magnesium alloy having a high magnesium composition while minimizing the use of expensive and environmentally friendly protective gases such as SF ₆ gas.

Hereinafter, embodiments are provided to assist in understanding the present invention. It should be understood, however, that the following examples are for the purpose of promoting understanding of the present invention, but the present invention is not limited by the following examples.

4A and 4B show an aluminum-magnesium alloy prepared by diluting a magnesium-aluminum master alloy according to the present invention (Example 1) and an aluminum-magnesium alloy prepared by directly adding magnesium to an aluminum molten metal (Comparative Example 1 below). The result of having observed the extrusion state at the time of extrusion is shown.

In this case, the magnesium compositions of Example 1 and Comparative Example 1 were all 10 wt%, and the magnesium composition of the aluminum-magnesium master alloy used in the preparation of Example 1 was 38 wt%. In addition, Example 1 and Comparative Example 1 were both produced by extrusion after continuous casting in the form of a rod having a diameter of 180mm cross section.

 4A and 4B, while Example 1 shows a very good shape of the extrudates in which no cracks or abnormal defects occur in the extrudate after extrusion, in the case of Comparative Example 1, severe breakage is caused by a plurality of casting cracks during the extrusion process. You can see this happening.

From this, it can be seen that in the case of the aluminum-magnesium alloy prepared by the present invention, in comparison with the aluminum-magnesium alloy prepared by the conventional method, despite the high magnesium content of up to 10wt%, the workability is very excellent.

Therefore, according to the present invention, an aluminum alloy containing a high magnesium, for example, an aluminum-magnesium alloy having a composition of 5 wt% or more of magnesium, which is not substantially commercialized due to the conventional poor workability, is manufactured as an alloy having excellent workability. It is possible to.

In the manufacturing process of Example 1, magnesium was added to the aluminum molten metal in the form of an aluminum-magnesium master alloy, and thus the aluminum molten metal was able to maintain a very good molten state even without using a protective gas such as SF ₆ gas. Cast Example 1 is believed to have exhibited a very good condition after casting.

5A shows the results of observing the internal structure of the aluminum-magnesium alloy (Example 2) prepared in the same manner as in Example 1 except that the mold casting was performed with an optical microscope. Referring to FIG. 5A, the inside of Example 2 shows a very good structure in which no impurities such as oxides or other inclusions generated by oxidation of magnesium in the molten metal were found.

On the other hand, Example 2 exhibited excellent mechanical properties compared to commercial casting aluminum-magnesium alloy. Figure 5b shows the tensile characteristics of Example 2, Table 1 shows the mechanical properties on the KS D 6008 specification of Example 2 and AC7A-F alloy of commercial aluminum-magnesium main alloy.

Mg composition Tensile Strength (MPa) Elongation (%) Example 2 10wt% 233 12 AC7A-F 3.5-5.5wt% 210 12

It can be seen from FIG. 5B and Table 1 that the aluminum-magnesium alloy of Example 2 has an elongation equivalent to that of the AC7A-F alloy even though it has a better tensile strength than the AC7A-F.

In the case of the aluminum-magnesium alloy prepared by the conventional method, when the magnesium is increased to a high content, a casting crack is generated, and thus, an elongation is inferior. On the other hand, in Example 2, the composition of magnesium was 10wt%, and although the magnesium content was more than two times higher than that of the AC7A alloy, it has a superior elongation comparable to that of AC7A while having better tensile strength than the AC7A alloy. .

Considering the fact that Example 2 was prepared to have a high magnesium composition amounting to 10wt% without using a protective gas such as SF ₆ gas, it can be seen that the manufacturing method of the aluminum-magnesium alloy according to the present invention is very economical and effective. have.

By applying the present invention, even if the aluminum-magnesium alloy having the same composition as the conventional commercial metal can be made to exhibit better characteristics. For example, in the preparation of aluminum-magnesium-based main alloys or alloys for aluminum-magnesium processing materials of the 5000 series, 6000 series, and 6000 series, instead of the direct addition of magnesium in the form of an aluminum-magnesium master alloy, By preventing the oxidation problem of magnesium, it is possible to obtain better castability or mechanical properties.

The foregoing description of specific embodiments of the invention has been presented for purposes of illustration and description. Therefore, the present invention is not limited to the above embodiments, and various modifications and changes can be made by those skilled in the art within the technical spirit of the present invention in combination with the above embodiments. Do.

Claims (11)

Adding magnesium to the first aluminum melt;
Casting the first molten aluminum to which magnesium is added to produce an aluminum-magnesium master alloy having a first magnesium composition;
Adding the aluminum-magnesium mother alloy to a second molten aluminum; And
Casting the second molten aluminum to cast an aluminum-magnesium alloy having a smaller second magnesium composition than the first magnesium composition;
Lt; / RTI >
In the step of adding magnesium to use a protective gas to prevent the ignition of magnesium,
In the step of adding the aluminum-magnesium mother alloy, the protective gas is not used, aluminum-magnesium alloy manufacturing method. The method of claim 1, wherein the holding time for melting the aluminum-magnesium master alloy in the adding of the aluminum-magnesium master alloy is shorter than the holding time for melting of the magnesium in the adding of magnesium. Method for producing aluminum-magnesium alloy. The method of claim 1, wherein the melting temperature of the aluminum-magnesium mother alloy is lower by 100 to 200 ° C. than the melting temperature of the magnesium. The method of claim 1, wherein the second magnesium composition is 2 to 12 wt%. The method of claim 1, wherein the first magnesium composition is 5 to 40wt%. delete delete The method of claim 1, wherein adding the aluminum-magnesium mother alloy does not use SF ₆ gas as a protective gas. Providing an aluminum-magnesium master alloy having a first magnesium composition;
Adding the aluminum-magnesium mother alloy to the molten aluminum; And
Casting the molten aluminum to cast an aluminum-magnesium alloy having a smaller second magnesium composition than the first magnesium composition;
Lt; / RTI >
In the providing of the aluminum-magnesium master alloy, a protective gas is used to prevent ignition of magnesium,
In the step of adding the aluminum-magnesium mother alloy, the protective gas is not used, aluminum-magnesium alloy manufacturing method. delete delete

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