WO2013100427A1

WO2013100427A1 - Magnesium deactivating agent and method for preparing a magnesium-alloy using the magnesium deactivating agent

Info

Publication number: WO2013100427A1
Application number: PCT/KR2012/010547
Authority: WO
Inventors: 김영민; 김하식; 유봉선; 임창동
Original assignee: 한국기계연구원
Priority date: 2011-12-29
Filing date: 2012-12-06
Publication date: 2013-07-04
Also published as: KR101223045B1

Abstract

The present invention provides a magnesium deactivating agent to be added for improving the flame retardancy and corrosion resistance of magnesium and a magnesium alloy, and more particularly, a magnesium deactivating agent which forms a stable protective film on the surface of magnesium by simply being added into most types of molten magnesium alloy, thus enabling melting and casting in air or a general inert atmosphere, thereby preventing the spontaneous ignition of a chip by significantly improving ignition resistance, and also improving the corrosion resistance and mechanical properties of an alloy. The magnesium deactivating agent according to the present invention is characterized by comprising 60 wt% to 41.6 wt% of Ca, 6 wt% to 45 wt% of Y, and Mg as the remainder, along with other inevitable impurities, wherein the contents of Ca and Y in the magnesium deactivating agent follow the mathematical equation: Y ≤ 64.3 - 1.4 Ca (wt %).

Description

[Specifications

[Name of invention]

Method of manufacturing magnesium alloy using magnesium deactivator and magnesium deactivator

[Technical Field]

The present invention relates to a magnesium deactivator, and more particularly, to a magnesium deactivator input to suppress activation reaction of magnesium when preparing a magnesium alloy, and a method of preparing magnesium using the magnesium deactivator. Background Art

Magnesium alloy is the lightest alloy with high specific strength and can be applied to various casting and processing processes. It is applicable to almost all fields requiring the weight reduction of automotive parts or electromagnetic parts and has a wide range of applications. Magnesium alloys, however, are electrochemically low-potential, highly active metals, and exhibit strong activity when contacted with oxygen or water. In commercial alloys, the ignition temperature does not exceed 550 ^° C. There are still limitations in terms of stability and reliability. Because of this, the scope of use is still limited compared to its potential, and cannot be used especially for applications requiring safety.

Due to this active reaction of the magnesium alloy, it is necessary to use an inert mixed gas of flux or CO ₂ + SF ₆ to produce an inert atmosphere during dissolution. The melt force used for melting and refining is chlorinated. There was a problem that residual chlorine remained inside the material and greatly degraded the corrosion resistance. Instead of using fluxes to solve these shortcomings, a method of melting and casting SF ₆ , CO 2 and Air in a mixed atmosphere is effective. However, SF ₆ is classified as a global greenhouse-induced substance with a global greenhouse effect of 23,900 times C0 ₂ , and is expected to be regulated in the future.

In order to solve this problem more fundamentally, researches to improve the oxidation resistance of magnesium alloy itself have been conducted to improve the firing temperature of magnesium alloy, especially by adding Ca, Be and rare earth metals. Conventionally, Ca is mainly used among the alloying elements added to the magnesium oxide alloy, because the price of the Ca element is lower than that of the rare earth metal, it is not toxic, and the ignition temperature is increased with respect to the amount added. However, in order to dissolve Ca by dissolving Ca in the molten alloy, the temperature of the molten metal must be maintained at a high temperature of 800 ^° C. or higher. At this time, magnesium having a low melting point may cause activation reaction such as ignition. In addition, it is very expensive to keep the temperature of the melt at a high temperature, so it is very difficult to manufacture magnesium alloys for small scale manufacturers that cannot greatly increase the silver content of the molten metal. This will cause the economy to fall.

[Detailed Description of the Invention]

[Technical Challenges]

Therefore, the present invention solves the above-mentioned problems, and when activating an alloy containing magnesium as an active metal as a main component, the activation reaction of magnesium can be suppressed as much as possible. The purpose is to provide a method.

In addition, an object of the present invention is to provide a method for producing a magnesium alloy that enables an environmentally friendly manufacturing process that does not use a protective gas that is an environmental pollutant such as SF ₆ .

In addition, an object of the present invention is to provide a method for producing a magnesium alloy that can provide economical and safety by lowering the temperature of the molten metal as much as possible when producing an alloy containing magnesium as an active metal.

Technical Solution

In order to achieve the above object, the present invention provides a configuration in which a magnesium deactivator is added to suppress activation reaction of magnesium in the manufacturing step of magnesium alloy.

The magnesium deactivator according to the present invention is added to suppress the activation reaction of magnesium in the manufacturing step of the magnesium alloy, 6% to 41.6% by weight of Ca, 6% to 45% by weight of Y, balance Including Mg and other unavoidable impurities, the content of Ca and Y is characterized by the following equation.

Equation: Y ≤ 64.3-1.4Ca (% by weight)

In addition, the magnesium deactivator contains 6% by weight to 33.8% by weight of Ca, 6% by weight to 42.2% by weight of Y, the balance of Mg and other unavoidable impurities, the content of Ca and Y is It is preferable to follow.

Equation: Y <50.0-1.3Ca (wt%) In addition, the present invention is a method for producing a magnesium alloy using a magnesium, deactivator:

Forming a magnesium deactivator soluble at 750 ^° C. or lower;

Forming a magnesium alloy melt containing at least magnesium;

Injecting a magnesium inactivator soluble in the magnesium alloy melt at 750 ^° C or less;

Manufacturing a molten magnesium alloy casting material by using a predetermined casting method for the molten metal including the magnesium deactivator,

The magnesium deactivator comprises 6% by weight to 41.6% by weight of Ca, 6% by weight to 45% by weight of Y, the balance of Mg and other unavoidable impurities, the content of Ca and Y according to the following equation It is characterized by.

Equation: Y <64.3― 1.4Ca (wt%)

Equation: Y <50.0-1.3Ca (increase%)

The reason for limiting the content of each component in the magnesium alloy according to the present invention is as follows.

Calp (Ca)

When the content of Ca is small, it is added to obtain a magnesium alloy of the desired composition. Since the amount of magnesium deactivator increases and the alloy to be added is calcified, Ca is preferably contained at least 6% by weight. In addition, when the content of Ca is too high, the melting temperature of the magnesium deactivator becomes high, which makes it difficult to achieve the purpose of lowering the silver content of the molten metal in the manufacture of the magnesium alloy. Therefore, Ca of the magnesium deactivator is preferably contained in 41.6% by weight, preferably 33.8% by weight or less.

Yttrium (Y)

When the content of γ is small, the amount of magnesium deactivator added to obtain a magnesium alloy of a desired composition is increased, and the alloy to be added is calcified, so that Y is preferably contained by 6 wt% or more. In addition, when the Y content is too high, the melting temperature of the magnesium deactivator becomes high, which makes it difficult to achieve the purpose of lowering the temperature of the molten metal in the manufacture of the magnesium alloy. Therefore, the Y of the magnesium deactivator is preferably contained in 45% by weight, preferably 42.2% by weight or less.

Total content of Ca-Y

When calcium and yttrium are added in combination, flame retardancy and corrosion resistance are significantly improved compared to alloys in which calcium and yttrium are separately added. This is because calcium oxide and yttrium oxide effectively form a dense protective film on the surface of the solid and liquid magnesium alloy to effectively suppress reaction with external oxygen. In addition, when a small amount of calcium and yttrium is added in combination with an alloy added with calcium alone, corrosion resistance may also be improved. Meanwhile, the melting points of calcium and yttrium in FIGS. 1 and 2 are 840 ^° C and 1522 ^° C, respectively, which are relatively high compared to magnesium, and are about 840 ^° C to add calcium and yttrium to the magnesium alloy. Should be raised to the above silver. In the case of general melting and casting companies, heating large amounts of molten metal to 84 0 ^° C or higher means a large increase in manufacturing costs, so the method of directly injecting calcium and yttrium into the molten metal is undesirable. Therefore, the present invention prepared magnesium deactivation to effectively alloy calcium and yttrium in the magnesium alloy melt while maintaining the existing equipment and process conditions in the general melting and casting site. In addition, as can be seen in Figure 3, at 700 ^° C Mg-Al-Ca state diagram (Fig. 3) to add a magnesium and yttrium in the grayed out area to prepare a magnesium deactivator, and the magnesium deactivator magnesium When added to the alloy, it can be easily alloyed even ^at about 700 ^° C. In FIG. 3, the equation obtained from the straight line 1 is as follows. The addition amount of the yttrium is preferably controlled within the range in which the equation 1 is satisfied according to the calcium addition amount. For example, when 30% by weight of calcium is added, the yttrium should be controlled to within 22% by weight.

Equation 1

Y (wt.%) <64.3-1.4 Ca (wt.%)

More preferably, it is preferable to control the content of calcium and yttrium according to equation (2) obtained from straight line 2 corresponding to the liquid single phase region.

Equation 2

Y (wt.) <50.0-1.3 Ca (wt.%)

On the other hand, when the aluminum element is added to the magnesium deactivator having the composition of Mg-Ca— Y, coarse A1 ₂ Y (melting point: 1490 ^° C) may be formed in a large amount, thus inactivating magnesium. It is preferable not to add aluminum to a topic.

Other unavoidable impurities

The magnesium deactivator according to the present invention may include impurities that are inevitably incorporated in the raw material or manufacturing process of the alloy, and especially iron (Fe), silicon ( Si) and nickel (Ni) are components that play a role in deteriorating the corrosion resistance of the final magnesium alloy product. Therefore, the Fe content is 0.004% by weight or less, Si content is 0.04% by weight, Ni content is preferably maintained to 0.001% by weight or less.

Advantageous Effects

The magnesium deactivator according to the present invention forms a dense complex oxide layer acting as a protective film on the surface of the molten metal by simply adding it to all kinds of magnesium alloy molten metal, thereby greatly improving the flame retardancy of the magnesium alloy, thereby increasing the flame resistance of the magnesium alloy in the atmosphere or general inert atmosphere (Ar, N ₂ ) can be melted, cast and processed, and can suppress spontaneous ignition of chips accumulated in the machining process.

In addition, the magnesium deactivator according to the present invention does not need to use the SF ₆ floating gas when added to the existing commercial magnesium alloy, it is suitable for reducing the manufacturing cost, worker health protection, environmental pollution prevention.

In addition, the magnesium deactivator according to the present invention can greatly improve the corrosion resistance of the magnesium alloy when added to the magnesium alloy.

In addition, the magnesium deactivator according to the present invention additional equipment or process conditions It is possible to improve flame retardancy and corrosion resistance at the same time just by adding it to the molten metal without changing.

In addition, the magnesium alloy containing the magnesium deactivator according to the present invention is extruded, plate, forging material, casting material that can be practically applied to the next-generation automobile, high-speed railway, urban railway, etc. requiring safety with excellent flame resistance and corrosion resistance Can be prepared.

[Brief Description of Drawings]

1 is a view showing a state diagram of the Mg—Ca binary alloy.

2 is a view showing a state diagram of an Mg—Y binary alloy.

Figure 3 is a diagram showing the Mg-Ca—Y state diagram at 700 ° C.

Figure 4 is a photograph showing the actual appearance of the Mg-30Ca-15Y (% by weight) deactivator prepared according to a preferred embodiment of the present invention.

5 is a diagram showing the results of EPMA analysis of the molten metal oxide surface layer after Mg-6Zn—ICa-Y (wt%) alloy prepared in accordance with a preferred embodiment of the present invention for 10 minutes at 670 ^° C.

Figure 6 is a photograph showing the surface change after the immersion test for 8 hours in the AZ31 alloy, AZ31-0.7Ca alloy and AZ31—0.5Ca-0.25Y alloy prepared in accordance with a preferred embodiment of the present invention in a 3.5% NaCl solution.

[The best form to carry out invention]

A method of preparing a magnesium alloy using a magnesium deactivator and a magnesium deactivator according to a preferred embodiment of the present invention will be described in detail below. Thread The examples are illustrative only and do not limit the invention.

The inventors of the present invention have prepared a magnesium deactivator having a variety of compositions to solve the problems of the prior art described above and to achieve the object of the present invention, the method of manufacturing a magnesium deactivator according to a preferred embodiment of the present invention is as follows. First, Comparative Examples 1 to 3 of Table 1 are commercially available magnesium mother alloys, and the chemical compositions shown in Table 1 are used in this experiment as they are. In Examples 1 to 3 of Table 1, after preparing a raw material of Mg (99.9%), Ca (99.5 or more), and Y (99.5 or more), the raw materials were dissolved and the strength casting method was performed. A magnesium deactivator having the composition described in Examples 1 to 3 was prepared. In particular, in order to alloy Ca and Y with a relatively high melting point in a magnesium molten alloy, they are completely dissolved by melting the silver of the molten metal from 850 ° C to 900 ° C in an induction furnace, and then gradually cooled to the casting temperature. After casting, a magnesium deactivator was prepared.

Table 1

Magnesium deactivator according to a preferred embodiment of the present invention having the composition Because it contains a large amount of Ca and Y, it is brittle enough to be broken even with a small lamination. In general, the smaller the size of the additive, the better the dissolution and the shorter the time for alloying. As shown in FIG. 4, the small amount of the magnesium deactivator crushed into the small size can be rapidly alloyed when the magnesium alloy is added to the molten metal to be added. have.

Table 1 Comparative Example 1 to Comparative Example 3, the composition and having magnesium added to the parent CaO powder of the alloy of Comparative Example 4 and Examples 1 to ^'inactive magnesium having performed the composition of Example 3. The net magnesium or magnesium alloy having different composition of the After the magnesium alloy was prepared, the effects of addition were compared, and the composition of the final product after addition was shown in Table 2. In addition, the addition temperature of the CaO powder, magnesium master alloy and magnesium deactivator according to Examples and Comparative Examples is 700 ^° C., and maintained for 5 to 20 minutes for alloying after addition to the magnesium molten metal. Until the alloying was finished, SF ₆ and CO ₂ mixed gas was applied to the upper part of the molten metal to prevent oxidation of the molten metal to prevent contact between the molten metal and the atmosphere. In addition, after the melting is completed, the die was cast without using a protective gas using a steel mold (steel mould), a cylindrical billet having a diameter of 55mm, length 100mm for the ignition experiment of the alloy casting material was prepared.

Table 2

In Table 2, Sample 6 Mg-2Sr alloy was prepared by adding 6.7% by weight of Mg-30Sr master alloy of Comparative Example 2 to pure magnesium, and Sample 9 Mg-3Al-0.8Zn-0.22Mn-0.7Ca alloy silver AZ31 alloy. It is manufactured by adding 2.4 weight% of Mg '30Ca master alloy of the comparative example 3 to (Sample 3). Similarly, the sample 10 Mg-6Al-0.7Ca alloy was obtained by adding 2.4 wt% of the Mg-30Ca master alloy of Comparative Example 3 to the Mg ᅳ 6A1 alloy (Sample 2), and the sample 11 Mg-6Al-0.7Ca alloy contained the Mg- It is prepared by adding 1.0% by weight of CaO powder of Comparative Example 4 to 6A1 alloy. In addition, sample 11 is distinguished from sample 10 in that some of the added CaO powder is contained in the casting material without being dissolved.

On the other hand, Sample 14 Mg-lCa-YY alloy is prepared by adding 5% by weight of XW-B deactivator of Example 2 to pure magnesium, Sample 15 Mg-6Al-lCa-LY alloy is carried out in the Mg-6A1 alloy It was prepared by adding 5% by weight of the XW-B deactivator of Example 2. Similarly, the sample 18, Mg— 8Sn-lAKLZn-0.3Ca-l.0Y alloy, is an Mg-8Sn-lAKLZn alloy (sample ) Was prepared by adding 3.4% by weight of the XW-C deactivator of Example 3.

Ignition temperature measurement of magnesium alloy

In order to measure the ignition temperature of the magnesium alloy, a chip of a predetermined size was obtained by chip-processing the outer shell of the cylindrical billet manufactured at a constant speed of 0.5 mm depth, pitch 0.1 mm, and 350 rpm. The chip o.ig obtained by the above method was put into a heating furnace maintained at loarc and heated up at a constant speed. In the temperature rising process, the silver started to rise rapidly due to the ignition of the sample was measured by the ignition temperature, and the results are shown in Table 3.

Table 3

In Table 3, the ignition temperature of Sample 13 to which the Mg-30Zr mother alloy of Comparative Example 1 was added was 577 ^° C, and the ignition temperature increased by only 31 ^° C compared to Sample 4 to which Comparative Example 1 was not added. I stopped. Therefore, it can be seen that the Mg-30Zr mother alloy of Comparative Example 1 is not effective in improving the ignition resistance of the magnesium alloy. On the other hand, when 2 wt% of Mg— 30Sr and Mg_30Ca master alloy of Comparative Example 2 and Comparative Example 3 containing Ca and Sr mainly added to the high temperature heat-resistant magnesium alloy were added to magnesium, Sample 6 and Sample in Table 3 As can be seen from the ignition temperature of 7, there was an increase in the ignition temperature of 146 ^° C and 266 ^° C, respectively, compared with 1 pure magnesium without the master alloy. From this, it can be judged that Ca is more effective than Sr in improving the fire resistance of magnesium for the same amount of addition. In addition, comparing the ignition temperatures of sample 11 in which 0.7% by weight of Ca was added to Mg-6A1 alloy and sample 12 in which CaO powder of Comparative Example 4 having a similar effect to Ca were added to Mg-6A1 alloy, are compared in Table 3. , Even though it contains the same amount of Ca in 0.7% by weight, it can be confirmed that adding the Mg-30Ca master alloy of Comparative Example 3 is more effective in improving the fire resistance than adding the CaO powder of Comparative Example 4.

In addition, in Table 3, when comparing the ignition temperatures of Samples 6 to 13 and the ignition temperatures of Samples 14 to 18, the case where the inactivating agent of Examples 1 to 3 was added to pure magnesium or magnesium alloy was Comparative Examples 1 to 4. It can be seen that the degree of ignition silver is further increased as compared with the case of adding the substance. In Table 3, the ignition temperature of sample No. 17 with 5.0 wt% of Example 2 added to the same alloy was about 120 ^° C higher than that of Sample 13 with 1.8 wt% of Comparative Example 1 added to the Mg-6Zn alloy. It can be confirmed that the ignition temperature of Sample 16, in which Example 1 was added to the same alloy, was higher than n ^° C, compared to Sample 9, in which 2.4 wt% of Comparative Example 3 was added. In addition, compared with sample 6 in which 6.7% by weight of Comparative Example 2 was added to pure magnesium, It can be confirmed that the pyrophoric silver of Sample 14, in which 5.0 wt% of Example 2 was added to nedium, was 42 ^° C higher.

Particularly, in the case of Mg-8Sn-lAl-lZn alloy 5 in Table 3, the ignition temperature was very low ^at 373 ^° C. By adding the deactivator of Example 3, the ignition temperature was increased to 583 ^° C. The reason for this result is that homogenization treatment should be performed at the temperature of about 500 ^° C for extrusion or rolling of Mg-8Sn-lAl—ΙΖη alloy, which is a processing alloy. There was a big problem that the risk of ignition during the heat treatment process significantly higher. Therefore, by adding Example 3 to the Mg-8Sn ᅳ ΙΑΙ-ΙΖη alloy to increase the ignition temperature to 583 ^° C it is possible to eliminate the risk of ignition during the heat treatment process.

On the other hand, the reason for the increase in the ignition temperature of the magnesium alloy through the addition of a magnesium deactivator is as shown in the Electron-Probe Micro- Analyzer (EPMA) results for the surface oxide layer of Mg-6Zn—ICa-lY alloy in Fig. This is because a dense oxide layer composed of CaO and Y ₂ O ₃ is formed on the surface of Y in contact with the molten metal, and this oxide layer effectively suppresses the continuous reaction of oxygen infiltrating into the molten metal.

Evaluation of Corrosion Characteristics of Magnesium Alloys

FIG. 6 shows the surface condition after AZ31 alloy, AZ31-0.7Ca alloy and AZ31—0.5Ca-0.25Y alloy were immersed in 3.5% NaCl solution for 8 hours. It can be seen that the corrosion resistance of the AZ31-0.7Ca alloy to which Comparative Example 3 is added is improved compared to the AZ31 alloy having a high corrosion degree on the surface. Generally corrosion is added when 1% or less of calcium is added It is known that the resistance is improved, and the same result can be obtained in this immersion test. On the other hand, in the case of the AZ31-0.5Ca—0.25Y alloy to which the XW-C deactivator of Example 3 was added, it was confirmed that almost no corrosion occurred on the surface. Compared to the AZ31-0.7Ca alloy containing an increase in%, as shown in Example 3, the addition of the deactivator means that the corrosion resistance of the magnesium alloy can be further improved.

Meanwhile, the magnesium inactivator should be selected differently according to the magnesium alloy composition, and in particular, the optimal inactivator should be selected in consideration of the reactivity between the major elements and Ca and Y in the magnesium alloy. In the case of Mg-Al-based alloys, it is preferable to limit the content of 때문에 because the AI ₂ Y phase is generated in the molten metal by the reaction of A1 and Y as the content of Y increases, in which case Ca / Y is large. Alternatively, it is preferable to select the deactivator as in Example 2. On the other hand, in the case of the Mg-Sn-based alloy, since Ca ₂ Sn phase is generated in the molten metal by the reaction of Sn and Ca, it is necessary to limit the amount of Ca added, so selecting an inactive agent as in Example 3 having a small Ca / Y is required. desirable.

According to the results of evaluating the ignition temperature and corrosion characteristics, when using the deactivator according to Examples 1 to 3, compared to Comparative Examples 1 to 4, by adding to the magnesium or magnesium alloy can further improve the fire resistance of the magnesium alloy ， At the same time, there is an advantage that can greatly improve the corrosion resistance. Therefore, it is confirmed that only a small amount of the magnesium deactivator according to the present invention to the existing magnesium or magnesium alloy is very effective in greatly improving the safety and reliability of the magnesium alloy. Can be. This makes it possible to operate in the air without using expensive SF ₆ gas, which causes environmental problems, thereby establishing an eco-friendly process and at the same time reducing manufacturing and environmental costs. Furthermore, magnesium alloys can be applied in a wider range of applications where safety is required by greatly improving the reliability of magnesium alloy products.

The magnesium alloy manufacturing method using the magnesium deactivator and the magnesium deactivator according to the preferred embodiment of the present invention has been described in detail with reference to the accompanying drawings. However, one of ordinary skill in the art will appreciate that the embodiments are merely illustrative of one example of the present invention and that various other modifications and variations are possible. Accordingly, the scope of the invention is limited only by the claims set forth below.

Claims

[Patent Claims]

[Claim 1]

As a magnesium deactivator added to suppress the activation reaction of magnesium in the manufacturing step of magnesium alloy,

6% to 41.6% by weight of Ca, 6% to 45% by weight of Y, the balance of Mg and other unavoidable impurities, Ca and Y content is characterized by the following equation Magnesium deactivator.

Y <64.

3―1.4 Ca (% by weight)

[Claim 4]

The method of claim 1, wherein the magnesium deactivator comprises 6% by weight to 33.8% by weight of Ca, 6% by weight to 42.2% by weight of Y, the balance Mg and other unavoidable impurities, the content of Ca and Y is Magnesium deactivator, characterized in that following the equation.

Y <50.0 ᅳ 1.3 Ca (% by weight)

[Claim 5]

The magnesium deactivator according to claim 1 or 4, wherein the magnesium alloy is an Mg—Al—Zn alloy.

[Claim 6]

Forming a magnesium deactivator soluble at 750 ° C. or lower;

Forming a molten magnesium alloy containing at least Mg; Injecting a magnesium inactivator soluble in the magnesium alloy melt at 750 ^° C or less;

Manufacturing a magnesium alloy cast material using the molten metal including the magnesium deactivator using a predetermined casting method,

The magnesium deactivator comprises 6% by weight to 41.6% by weight of Ca, 6% by weight to 45% by weight of Y, the balance of Mg and other unavoidable impurities, the content of Ca and Y according to the following equation Method for producing a magnesium alloy using a magnesium deactivator, characterized in that.

Y <64.3 — 1.4 Ca (% by weight)

[Claim 9]

The method of claim 6, wherein the magnesium deactivator comprises 6% to 33.8% by weight of Ca, 6% to 42.2% by weight of Y, the balance Mg and other unavoidable impurities, the content of Ca and Y is Method of producing a magnesium alloy using a magnesium deactivator, characterized in that following the equation.

Y <50.0-1.3 Ca (% by weight)

[Claim 10]

The method for producing a magnesium alloy using a magnesium deactivator according to claim 6 or 9, wherein the magnesium alloy molten metal containing at least magnesium is Mg ᅳ Al—Zn alloy molten metal.