KR20100034773A - Magnesium alloy and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A magnesium alloy and a manufacturing method thereof are provided to reduce the cost by buying an additive added during the manufacturing process of the magnesium alloy in a lower price. CONSTITUTION: A magnesium alloy contains a magnesium crystal grain and an additive compound. The magnesium crystal grain includes a grain boundary. The additive compound is included in the grain boundary from the outside. The additive compound is selected from the group consisting of a compound of an alkali metal and magnesium, a compound of an alkaline earth metal and the magnesium and others.

Description

Magnesium alloy and manufacturing method

The present invention relates to a magnesium alloy and a method for producing the same.

In general, magnesium or magnesium alloy (hereinafter referred to collectively as magnesium alloy) is the lightest metal among practical metals, and is expected to be a lightweight structural material because of excellent specific strength and specific rigidity. It is also expected to be a substitute for resin-based materials. Magnesium alloy is manufactured by various manufacturing methods such as die casting and thixo casting, which is widely used as a case of an electronic device or a home appliance where strength is not a problem. In addition, even in automobiles, in order to reduce weight, practical use is made in the steering wheel, the cylinder head cover, and the like.

Magnesium alloy solution melted at high temperature, that is, molten metal is easily ignited. Therefore, various kinds of protective gases are used to prevent ignition of such magnesium alloy molten metal. Typical protective gases include SF ₆ , SO ₂ , CO ₂ , HFC-134a, Novec ™ 612, inert gas and mixed gas thereof.

However, most of the protective gases for suppressing the ignition of magnesium alloy molten metal are harmful to the human body and not only corrode iron equipment, but also are classified as greenhouse gases, and their use is strictly limited. For example, the SF ₆ Gas is CO ₂ It has a global warming effect of 23,900 times that of gas, so in developed countries SF ₆ Gas-free regulations have begun, and a lot of research is being done on gas replacement.

On the other hand, when calcium (Ca) is added to the magnesium alloy, it is known that ignition and oxidation at high temperatures are suppressed. However, the magnesium alloy added with calcium as described above has disadvantages such as fluidity, hot cracking and mold sintering. In addition, since the calcium is approximately $ 200 per kg, the manufacturing cost of magnesium alloy is increased. In addition, the calcium reduces the application range of the magnesium alloy by changing the original alloy specification of the magnesium alloy. Finally, the calcium dissipates during the treatment for recycling the magnesium alloy, thereby greatly reducing the recyclability of the magnesium alloy. In other words, in order to recycle the magnesium alloy, calcium must be added again, thus causing a cost increase.

SUMMARY OF THE INVENTION The present invention is to overcome the above-mentioned conventional problems, and an object of the present invention is to provide a magnesium alloy and a method for manufacturing the same, which can reduce or eliminate the protective gas.

Another object of the present invention is to provide a magnesium alloy for improving the cleanliness of the molten metal in the melting furnace, during the transfer of the molten metal, or during the injection of the molten metal, and a method of manufacturing the same.

Still another object of the present invention is to provide a magnesium alloy capable of improving casting, forming, welding and PM processing ability without causing problems such as fluidity, hot cracking and mold sintering, and a method of manufacturing the same.

It is still another object of the present invention to provide a magnesium alloy and a method of manufacturing the same, which can reduce or eliminate the protective gas and at the same time reduce the manufacturing cost by using an inexpensive additive.

It is still another object of the present invention to provide a magnesium alloy capable of maintaining the original use of an alloy and a method for producing the same by not adding an additive to change the original alloy composition ratio.

It is still another object of the present invention to provide a magnesium alloy capable of improving mechanical properties due to grain refinement and internal soundness and a manufacturing method thereof.

Still another object of the present invention is to provide a magnesium alloy and a method of manufacturing the same, which can improve welding and joint performance.

It is still another object of the present invention to provide a magnesium alloy which is safe for various applications by increasing oxidation and ignition resistance and a method of manufacturing the same.

It is still another object of the present invention to provide a magnesium alloy capable of improving the regeneration ability according to the flux type and temperature control and a method of manufacturing the same.

In order to achieve the above object, the magnesium alloy according to the present invention may include a plurality of magnesium crystal grains having a grain boundary, and an additive compound present in the grain boundary as an exterior instead of the interior of the magnesium grains.

The additive compound may be any one selected from compounds of magnesium and alkali metals, compounds of magnesium and alkaline earth metals, compounds other than magnesium in magnesium alloys and compounds of alkali metals, and compounds other than magnesium in magnesium alloys and compounds of alkaline earth metals. have.

The magnesium grains may be pure magnesium grains or magnesium alloy grains.

The additive compound may be one added 0.0001 to 30 parts by weight of magnesium alloy.

The additive compound may have a size of 0.1 ~ 500㎛.

The magnesium alloy may have a ignition temperature (° C) of 500 to 1500.

The magnesium alloy may be selected from cast alloys, wrought alloys, creep alloys, damping alloys, degradable bio alloys and powder metallurgy. At least one may be used.

In addition, the magnesium alloy manufacturing method according to the present invention in order to achieve the above object is a magnesium molten metal forming step of forming magnesium molten metal by melting in a crucible to a temperature of 600 ~ 800 ℃ in a protective gas atmosphere, and the magnesium An additive addition step of adding an additive to the molten metal, a stirring step of stirring the magnesium molten metal for 1 to 400 minutes, a casting step of casting the magnesium molten metal in a mold having a temperature of 100 to 300 ° C, and cooling the cast magnesium It may comprise a cooling step.

Magnesium used in the magnesium molten metal forming step may be pure magnesium or magnesium alloy.

The additive used in the additive addition step may be at least one selected from alkali metals, alkali metal oxides, alkali metal compounds, alkaline earth metals, alkaline earth metal oxides and alkaline earth metal compounds.

The alkali metal oxide may be at least one selected from sodium oxide or potassium oxide.

The alkaline earth metal oxide may be at least one selected from beryllium oxide, magnesium oxide, calcium oxide and strontium oxide.

The alkaline earth metal compound may be at least one selected from calcium carbide (CaC ₂ ), calcium cyanamide (CaCN ₂ ), calcium carbonate (CaCO ₃ ), and calcium sulfate hemihydrate (CaSO ₄ ).

The additive used in the additive addition step may be one added 0.0001 to 30 parts by weight based on 100 parts by weight of magnesium alloy.

The additive used in the additive addition step may have a size of 0.1 ~ 500㎛.

The additive used in the additive addition step may be to increase the ignition temperature and hardness of the prepared magnesium alloy, and to reduce the required amount of the protective gas.

The present invention can reduce or eliminate the amount of the protective gas classified as a greenhouse gas by increasing the ignition temperature during the manufacturing process of the magnesium alloy and adding an additive that suppresses oxidation.

In addition, the present invention may improve the cleanliness of the molten metal in the melting furnace, the transfer of the molten metal or the injection of the molten metal under the influence of the additive added during the manufacturing process of the magnesium alloy.

In addition, the present invention does not cause problems such as fluidity, hot cracking and mold sintering, it is also possible to improve the casting, forming, welding and PM processing ability. Moreover, the present invention can also improve the welding and joint performance for the same reason as above.

In addition, the present invention can purchase and use the additive added during the manufacturing process of the magnesium alloy at a low price, not only reduces the cost by using and reducing the use of the protective gas, but also reduces the cost by the additive.

In addition, the present invention can maintain the original use of the alloy as the additive added during the manufacturing process of the magnesium alloy does not change the original alloy composition ratio.

In addition, the present invention is excellent in crystal refining and internal integrity by the additives added during the manufacturing process of magnesium alloy, thereby improving mechanical properties.

In addition, the present invention increases the oxidation and ignition temperatures by the additives added during the manufacturing process of magnesium alloy, thereby improving safety in various applications.

In addition, the present invention is that the additive added during the manufacturing process of the magnesium alloy is present in the form of an additive compound at the grain boundary, not inside the grain, the additive does not react according to the flux and temperature effects supplied during the regeneration of the magnesium alloy, excellent regeneration Have the ability. That is, it is not necessary to perform a separate additive addition process during the regeneration process of the magnesium alloy.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

1 is a flowchart illustrating a method of manufacturing a magnesium alloy according to the present invention.

As shown in FIG. 1, the method for manufacturing a magnesium alloy according to the present invention includes a magnesium molten metal forming step (S1), an additive addition step (S2), a stirring step (S3), a casting step (S4), and a cooling step. (S5) is included.

In the magnesium molten metal forming step (S1), magnesium is put into a crucible and a temperature of 600 to 800 ° C. is provided in a protective gas atmosphere. The magnesium in the crucible is then dissolved to form a magnesium molten metal.

Here, when the temperature is less than 600 ° C, it is difficult to form magnesium molten metal, and when the temperature exceeds 800 ° C, there is a risk that the magnesium molten metal may ignite. In addition, the protective gas uses ordinary SF ₆ , SO ₂ , CO ₂ , HFC-134a, Novec ™ 612, an inert gas and its equivalents, and a mixed gas thereof to suppress ignition of the magnesium.

The magnesium used in the magnesium molten metal forming step may be any one selected from pure magnesium, a magnesium alloy, and an equivalent thereof. In addition, the magnesium alloy is AZ91D, AM20, AM30, AM50, AM60, AZ31, AS41, AS31, AS21X, AE42, AE44, AX51, AX52, AJ50X, AJ52X, AJ62X, MRI153, MRI230, AM-HP2, Mg-Al, Mg-Al-Re, Mg-Al-Sn, Mg-Zn-Sn, Mg-Si, Mg-Zn-Y and their equivalents may be any one selected from, but the magnesium alloy is not limited to the present invention.

In the additive addition step (S2), an additive in powder form is added to the magnesium molten metal.

Here, the additives used in the additive addition step may be an alkali metal, an alkali metal oxide, an alkali metal compound, an alkaline earth metal, an alkaline earth metal oxide, an alkaline earth metal compound and equivalents thereof, and a mixture thereof.

The alkali metal oxide may be at least one selected from sodium oxide, potassium oxide, and equivalents thereof. The alkaline earth metal oxide may be at least one selected from beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and equivalents thereof. The alkaline earth metal compound may be at least one selected from calcium carbide (CaC ₂ ), calcium cyanamide (CaCN ₂ ), calcium carbonate (CaCO ₃ ), calcium sulfate hemihydrate (CaSO ₄ ), and equivalents thereof. However, the additive is not limited to this kind. That is, the additive may be used as long as the ignition temperature of the magnesium alloy is high, the oxidizing power is reduced, and the required amount of the protective gas can be reduced.

The additive used in the additive addition step may be added 0.0001 to 30 parts by weight based on 100 parts by weight of magnesium alloy. When the additive is less than 0.0001 parts by weight, the effect by the additive (increasing ignition temperature, decreasing oxidizing power, and decreasing protective gas) is small. In addition, when the additive exceeds 30 parts by weight of the original magnesium or magnesium alloy does not appear.

In addition, the additive used in the additive addition step may have a size of 0.1 ~ 500㎛. The size of the additives less than 0.1 μm is difficult and expensive to make in reality. In addition, when the size of the additive exceeds 500㎛ the additive may not react with the magnesium molten metal.

In the stirring step (S3), the magnesium molten metal is stirred for 1 to 400 minutes.

If the stirring time is less than 1 minute, the additives are not sufficiently mixed in the molten magnesium, and if the stirring time exceeds 400 minutes, the stirring time of the magnesium molten metal may be unnecessarily longer.

In addition, in the stirring step as described above, the additive is not present inside the magnesium crystal grains or magnesium alloy crystal grains, but is present in the form of an intermetallic compound at the outside of the grains, that is, the grain boundary. That is, in this stirring step, the additive takes the form of an additive compound, more specifically, a compound of magnesium and an alkali metal, a compound of magnesium and an alkaline earth metal, a compound other than magnesium in the magnesium alloy and an alkali metal compound or magnesium in the magnesium alloy. It takes the form of a compound of a substance other than alkaline earth metals. Of course, the remaining elements of the additive (oxygen, carbon, nitrogen, etc.) all float on the surface of the magnesium molten metal, which is removed by manual or automatic equipment.

In the casting step (S4) to put the molten magnesium in a mold of 100 ~ 300 ℃ cast.

Herein, the mold may use any one selected from a mold, a ceramic mold, a graphite mold, and an equivalent thereof. In addition, the casting method may be gravity casting, continuous casting and the equivalent method. However, the type of the mold and the method of casting are not limited here.

In the cooling step S5, after cooling the mold to room temperature, a magnesium alloy (eg, magnesium alloy ingot) is taken out of the mold.

Here, the magnesium alloy prepared by the method as described above is composed of a plurality of magnesium crystal grains having a grain boundary, and an additive compound present in the grain boundary as an exterior instead of the interior of the magnesium crystal grains.

In addition, the material added during the manufacturing process of the magnesium alloy is simply defined as an additive, and the material added to the manufactured magnesium alloy is defined as an additive compound. That is, the material added to the prepared magnesium alloy is in the form of an intermetallic compound.

2 is a structure diagram of a magnesium alloy prepared according to the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 2, the magnesium alloy 1 produced according to the present invention comprises a plurality of magnesium grains 2 and an additive compound 3.

The plurality of magnesium grains (2) have a grain boundary, and the additive compound (3) is present in the grain boundary as the exterior, not the interior of the magnesium grains (2). That is, the additive compound (3) does not exist inside the magnesium grains (2), but exists in the grain boundary and forms an intermetallic compound.

Here, the magnesium grains 2 may be any one selected from pure magnesium grains, magnesium alloy grains, and equivalents thereof.

Further, the additive compound (3) is a compound of magnesium and alkali metals, a compound of magnesium and alkaline earth metals, a compound other than magnesium in the magnesium alloy and an alkali metal compound, and a compound of other than magnesium and alkaline earth metal in the magnesium alloy. It may be any one selected.

In addition, the additive compound (3) may be added 0.0001 to 30 parts by weight to 100 parts by weight of magnesium alloy. In addition, the additive compound (3) may have a size of 0.1 ~ 500㎛. The significance of this numerical range has already been described above.

As such, the magnesium alloy 1 according to the present invention may have a hardness (HRF) of 40 to 80. However, since these hardness values vary depending on the processing method and heat treatment, the hardness value of the magnesium alloy 1 according to the present invention is not limited. In addition, the magnesium alloy 1 has a ignition temperature (° C) of 500 to 1500 ° C, which improves the ignition resistance characteristics. In addition, as will be described below, the present invention significantly reduces the amount of protective gas used.

Meanwhile, the magnesium alloy may be formed of a casting alloy, a wrought alloy, a creep alloy, a damping alloy, a degradable bio alloy, and a powder metallurgy. Can be used as at least one selected from.

For example, the casting alloy may be formed by mixing CaX in AZ91D, AM20, AM50, and AM60. Here, CaX may be CaO, CaC ₂ , CaCN _2, or the like. However, the present invention is not limited to this kind.

The root alloy may be formed by mixing CaX with AZ31 and AM30.

The creep alloy may be formed by mixing CaX or SrO to Mg-Al, Mg-Al-Re. In addition, the creep alloy may be formed by mixing CaX in Mg-Al-Sn or Mg-Zn-Sn.

The damping alloy may be formed by mixing CaO with pure Mg, Mg-Si, SiCp / Mg.

The degradable bioalloy may be formed by mixing CaO with pure Mg.

The powder metallurgical may be formed by mixing CaX in Mg-Zn- (Y).

Hereinafter, examples and various experimental results of the present invention will be described.

(Example 1)

Three kgs of three AZ91D magnesium alloys were provided, each of which was heated to a temperature of 680 ° C. to form a melt. Subsequently, 30 g (1 weight part) of calcium oxide (CaO) of less than 100 micrometers, 100-200 micrometers, and 500 micrometers was put into each molten metal. Subsequently, each magnesium alloy molten metal was stirred for 10 minutes. Subsequently, each magnesium alloy molten metal was poured into a mold and gravity cast. Finally, after cooling the magnesium alloy, the components were analyzed through ICP (Inductively Coupled Plasma).

Powder size, target composition, component analysis and yield by ICP are shown in Table 1 below.

TABLE 1

Powder size ~ 100㎛ ~ 200㎛ ~ 500㎛ Goal composition 1 part by weight CaO 1 part by weight CaO 1 part by weight CaO ICP Component Analysis 0.45 parts CaO 0.0078 parts by weight CaO 0.0042 parts by weight CaO yield 45% 0.78% 0.42%

As described above, when the size of the calcium oxide is less than 100 μm, a yield of substantially 45% can be obtained. That is, when 1 weight part of calcium oxide was added, 0.45 weight part of calcium melt | dissolved in the molten magnesium. However, when the size of calcium oxide reaches 200 μm or 500 μm, the yield dropped to 0.78% and 0.42%, respectively.

3 to 8 are photographs showing the results of the Electron Probe Micro Analyzer (EPMA) experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

3 is a back scattering electron photograph of a magnesium alloy. As shown in FIG. 3, magnesium alloys generally form grains and grain boundaries. 4 is a photograph of magnesium, and the red region is magnesium. As shown in Figure 4 it can be seen that magnesium is composed of many grains and grain boundaries. In the picture, blue is the part without magnesium. 5 shows a small amount at the grain boundaries as a photograph of aluminum. In other words, the red part of the picture is aluminum. 6 is a photograph of zinc, indicating that there is much less than aluminum at grain boundaries. 7 is a photograph of calcium may be present in a small amount at the grain boundary. The red part of the picture is calcium. Figure 8 is a photograph of oxygen, it can be seen that almost does not exist.

In this way, the magnesium alloy may be composed of most magnesium, and aluminum, zinc and calcium may be present at grain boundaries. Practically, the aluminum, zinc and calcium are in the form of intermetallic compounds.

That is, when calcium oxide is added to the AZ91D magnesium alloy, the calcium oxide is reduced and exists in the form of an aluminum calcium (Al ₂ Ca) compound at the grain boundary. Although calcium oxide is thermodynamically more stable than magnesium, the phenomenon of reduction has not yet been clearly identified.

9 to 12 are photographs showing the results of a transmission electron microscope (TEM) experiment of the magnesium alloy prepared by the method of manufacturing a magnesium alloy according to the present invention.

9 is an enlarged image of a TEM, in which a black region is an aluminum calcium (Al ₂ Ca) compound. 10 is a magnesium image of portions other than the aluminum calcium compound. FIG. 11 is an aluminum image, and FIG. 12 is a calcium image. Therefore, it can be seen that aluminum and calcium exist in the form of an intermetallic compound in the magnesium grain boundary.

13 and 14 are graphs showing the results of the protective gas reduction experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

The results of FIG. 13 were obtained by experimenting at a die casting working melt temperature of 680 ° C., and the results of FIG. 14 were obtained by experimenting at 720 ° C. (overheated state).

In addition, in FIG. 13 and FIG. 14, "sealed" means a state in which outside air is not introduced, and "unsealed" means a state in which outside air is introduced.

First, as shown in FIG. 13, in an atmosphere of 680 ° C., when air is introduced (unsealed), SF ₆ gas of 1,000 ppm in all of AZ91D, AZ91D-0.04 parts by weight CaO and AZ91D-0.13 parts by weight CaO for ignition suppression Was needed. However, in the absence of air (sealed), approximately 500 ppm SF ₆ gas was required for AZ91D and AZ91D-0.04 parts by weight CaO, and 300 ppm SF ₆ gas was required for AZ91D-0.13 parts by weight CaO. It was. Therefore, it can be seen that in a condition where air is not introduced at a normal die casting operation temperature, as the amount of the additive is added, the required amount of the protective gas for suppressing ignition decreases.

Next, as shown in Figure 14, in the air inflow (unsealed) in the atmosphere of 720 ℃ (3,200ppm, 2,000ppm in AZ91D, AZ91D-0.04 parts by weight CaO, AZ91D-0.13 parts by weight CaO, respectively) , 1,000 ppm SF ₆ gas was required. However, air does not enter the state (sealed) in the substantially SF ₆ gas was 500ppm in the case of ignition for inhibiting AZ91D- AZ91D and 0.04 parts by weight of CaO necessary, AZ91D-0.13 parts by weight of SF ₆ gas of 300ppm is required in the case of CaO It was. Therefore, it can be seen that the amount of additives required for the protection gas for reducing the ignition decreases as the amount of the additive is increased in the condition that the air is not introduced even at the overheating temperature.

15 is a graph showing the results of TGA (Thermogravimetry Analyzer) experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

In FIG. 15, the X axis is time, and the Y axis is weight gain (%). In the case of the AZ91D, the weight may increase rapidly over time. That is, the oxidation phenomenon progressed rapidly. In the case of AZ91D-0.14 parts by weight CaO, the weight may gradually increase over time. That is, the oxidation phenomenon proceeded slowly. For example, after 400 minutes AZ91D increased to 113 and AZ91D-0.14 parts CaO increased to 101.

Therefore, it can be seen from the experimental results that the oxidation phenomenon of the magnesium alloy to which the additive is added is suppressed.

16 and 17 are graphs showing the results of the Atomic Emission Spectrometer (AES) experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

In Fig. 16, the X axis is the sputtering time and the Y axis is the detection amount. In the case of the AZ91D, about 40 minutes of oxygen is detected until the sputtering time of about 9 minutes, and since that time, oxygen detection decreases. That is, in the case of AZ91D, it means that the oxide film is formed relatively thick.

On the other hand, in the case of AZ91D-0.7 parts by weight CaO, as shown in FIG. That is, in the case of AZ91D-0.7 parts by weight CaO, it means that the oxide film is formed relatively thin.

Therefore, it can be seen from the experimental results that the oxidation phenomenon of the magnesium alloy to which the additive is added is suppressed.

18 is a graph showing the hardness at room temperature and high temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 18, the AZ91D magnesium alloy added with 0.007 to 0.41 parts by weight of calcium oxide in the manufacturing process may be seen to increase in hardness as the amount of calcium oxide added increases. That is, the hardness of the AZ91D magnesium alloy without the addition of calcium oxide at room temperature (25 ℃) is approximately 57, it can be seen that the hardness of the AZ91D magnesium alloy with a small amount of calcium oxide is increased to 68. When the temperature rises to 100 ° C and 150 ° C, it is slightly lower than the hardness value at room temperature because of the low thermal stability of the β phase (Mg ₁₇ Al ₁₂ ) in the AZ91D magnesium alloy.

19 is a graph showing the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 19, it can be seen that the firing temperature of the magnesium alloy according to the addition amount of calcium oxide increases together with the addition amount of the calcium oxide. That is, the ignition temperature of the AZ91D magnesium alloy in the atmospheric atmosphere is about 490 ° C, and the ignition temperature in the nitrogen atmosphere is about 510 ° C, whereas the ignition temperature of the magnesium alloy to which calcium oxide is added is about 100 ° C or more depending on the amount added. It can be seen that the ignition temperature has increased.

(Example 2)

20 is a graph showing the hardness at room temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 20, the AZ91D magnesium alloy to which 0.02 to 0.48 parts by weight of strontium oxide is added during the manufacturing process may increase in hardness as the amount of strontium oxide added increases. That is, at room temperature, the hardness of the AZ91D magnesium alloy without strontium oxide is about 57, and the AZ91D magnesium alloy with a small amount of strontium oxide is about 65.

21 is a graph showing the ignition temperature in the atmosphere and nitrogen atmosphere of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 21, the AZ91D magnesium alloy to which strontium oxide is not added has a ignition temperature of approximately 490 ° C. in an atmospheric atmosphere and approximately 510 ° C. in a nitrogen atmosphere. However, the ignition temperature of AZ91D magnesium to which strontium oxide was added increased approximately 100 ° C. or more depending on the amount added.

(Example 3)

22 is a photograph of the billet surface of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 22, a billet photograph of a beryllium oxide, which is an alkaline earth metal oxide, and an AZ91D magnesium alloy for die casting, in which 0.0001 parts by weight and 0.5 parts by weight of magnesium oxide were added, respectively, was added even if a small amount of 0.0001 parts by weight of beryllium oxide was added. It can be seen that this shows a clean surface without oxidation or ignition. In addition, even if 0.5 parts by weight of magnesium oxide was added, a clean billet which was not oxidized or ignited was obtained.

23 is a graph showing the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 23, the ignition temperature of the AZ91D magnesium alloy for die casting in which beryllium oxide and magnesium oxide were added 0.0001 parts by weight and 0.5 parts by weight, respectively, was clearly confirmed. It can be seen that the ignition temperature is improved according to the addition amount, thereby improving mechanical properties and oxidation characteristics.

24 is a graph showing the hardness of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 24, as can be clearly seen from the hardness of the die casting AZ91D magnesium alloy in which beryllium oxide and magnesium oxide are added in 0.0001 parts by weight and 0.5 parts by weight, respectively, the addition amount of beryllium oxide or magnesium oxide which is an alkaline earth metal oxide As can be seen that the hardness is improved.

(Example 4)

25 is a structure photograph of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 25, it can be seen that the grains of the AZ91D magnesium alloy to which the additive is added are not significantly different compared to the AZ91D magnesium alloy to which the additive is not added. Here, the additive was added by 0.007 parts by weight of calcium cyanamide (CaCN ₂ ) as a calcium compound. It can be seen that such a small amount of addition has no effect on the properties of the AZ91D magnesium alloy.

26 is hardness data of a magnesium alloy manufactured by the method of manufacturing a magnesium alloy according to the present invention.

As shown in FIG. 26, the hardness of the AZ91D magnesium alloy to which the calcium-based compound calcium cyanamide was added was measured to be about 66. That is, the hardness of the AZ91D magnesium alloy without any additives was about 62, whereas the hardness of the AZ91D magnesium alloy with calcium cyanamide was increased by about 4 degrees.

27 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 27, the AZ91D magnesium alloy to which the calcium-based compound calcium cyanamide was added has a ignition temperature of approximately 540 ° C. in the air. That is, since the ignition temperature of the AZ91D magnesium alloy to which the additive was not added was approximately 510 ° C in the air, the ignition temperature of approximately 30 ° C was increased by the addition of the additive.

(Example 5)

28 is a structure photograph of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 28, it can be seen that the grains of the AZ91D magnesium alloy to which the additive is added do not show a large difference compared to the AZ91D magnesium alloy to which the additive is not added. Here, the additive is calcium carbide (CaC ₂ ), which is a calcium compound, added 0.03 parts by weight.

29 is hardness data of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 29, the AZ91D magnesium alloy to which the calcium-based compound calcium carbide was added has a hardness of approximately 65.3. That is, since the hardness of the AZ91D magnesium alloy without any additives is about 62, the hardness increased by about three.

30 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 30, the AZ91D magnesium alloy to which the calcium-based compound calcium carbide is added has a ignition temperature of approximately 540 ° C. in nitrogen. That is, since the ignition temperature of the AZ91D magnesium alloy to which the additive was not added was approximately 510 ° C in nitrogen, the ignition temperature of approximately 30 ° C increased by the addition of the additive.

31 is the ignition temperature data of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 31, the ignition temperature in the air atmosphere is a magnesium alloy (AZ91D-0.007 parts by weight CaCN ₂ /0.03 to which calcium cyanide (CaCN ₂ ) or calcium carbide (CaC ₂ ), which are calcium compounds, is added, respectively. The parts by weight CaC ₂ both show a significantly improved ignition temperature of the heat resistant alloy compared to the pure magnesium alloy (AZ91D), which can be seen that the ignition temperature is greatly improved depending on the amount of calcium-based compound added.

(Example 6)

32 is a graph showing the hardness test results of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

As shown in FIG. 32, when calcium oxide was not added to the AM50 magnesium alloy, when about 0.05 parts by weight of calcium oxide was added, the hardness was about 50 when about 0.15 parts by weight of calcium oxide was added. Therefore, there was no effect on the microstructure and hardness values according to the addition of trace amounts of calcium oxide.

33 and 34 are graphs showing the results of ignition experiments of magnesium alloys produced by the method for producing magnesium alloys according to the present invention.

As shown in FIG. 33, when calcium oxide was not added to the AM50 magnesium alloy, the ignition temperature in the atmosphere was about 570 ° C., but when about 0.05 parts by weight of calcium oxide was added, the ignition temperature increased to about 590 ° C. Moreover, when approximately 0.15 parts by weight of calcium oxide was added, the ignition temperature increased to approximately 610 ° C.

As shown in FIG. 34, when calcium oxide was not added to the AM50 magnesium alloy, the ignition temperature was about 550 ° C. in a nitrogen atmosphere, but when about 0.05 parts by weight of calcium oxide was added, the ignition temperature increased to about 570 ° C. FIG. Moreover, when about 0.15 parts by weight of calcium oxide was added, the ignition temperature increased to about 640 ° C.

(Example 7)

35 and 36 are graphs showing the results of the protective gas reduction experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

The results in FIG. 35 were obtained by experimenting at a die casting working melt temperature of 680 ° C., and the results of FIG. 36 were obtained by experimenting at 720 ° C. (overheated state).

As shown in FIG. 35, in an unsealed state in which air is introduced at an atmosphere of 680 ° C., 500 ppm SF ₆ gas is required in all of AZ31, AZ31-0.05 parts by weight CaO and AZ31-0.32 parts by weight CaO to suppress ignition. It was. However, in the absence of air (sealed), approximately 100 ppm of SF ₆ gas is required for AZ31 and AZ31-0.05 parts by weight CaO, and 40 ppm of SF ₆ gas is required for AZ31-0.32 parts by weight CaO. It was. Therefore, it can be seen that in a condition where air is not introduced at a normal die casting working temperature, as the amount of the additive is added, the required amount of the protective gas for suppressing ignition decreases.

Next, as shown in FIG. 36, in a state in which air is introduced as an atmosphere of 720 ° C. (unsealed), SF ₆ gas of 1,000 ppm in AZ31, AZ31-0.05 parts by weight CaO and AZ31-0.32 parts by weight CaO for ignition suppression Was needed. However, in the absence of air (sealed), about 200 ppm SF ₆ gas was required for AZ31, and about 100 ppm SF ₆ gas was required for AZ31-0.05 parts by weight CaO, and AZ31-0.32 weight In the case of secondary CaO 40 ppm SF ₆ gas was required. Therefore, it can be seen that the amount of additives required for the protection gas for reducing the ignition decreases as the amount of the additive is increased in the condition that the air is not introduced even at the overheating temperature.

37 and 38 are graphs showing the results of ignition experiments of magnesium alloys produced by the method for producing magnesium alloys according to the present invention.

As shown in FIG. 37, when calcium oxide was not added to the AZ31 magnesium alloy, the ignition temperature was about 570 ° C. in an air atmosphere, but when about 0.3 parts by weight of calcium oxide was added, the ignition temperature increased to about 610 ° C. FIG.

As shown in FIG. 38, when calcium oxide was not added to the AZ31 magnesium alloy, the ignition temperature was about 640 ° C. in a nitrogen atmosphere, but when about 0.3 parts by weight of calcium oxide was added, the ignition temperature increased to about 690 ° C. FIG.

39 to 41 are photographs showing the surface of the thin cast product of magnesium alloy prepared in the absence of a protective gas, in the presence of a protective gas, and according to the method of the present invention.

As shown in FIG. 39, when the magnesium alloy is manufactured without the protective gas, the surface is blackened.

In addition, as shown in FIG. 40, even when a magnesium alloy is manufactured by spraying a protective gas, it can be seen that a crack phenomenon occurs due to the mixing of oxides.

However, as shown in FIG. 41, when magnesium alloy is manufactured by adding calcium oxide, no ignition phenomenon or crack phenomenon is found.

Here, all of the magnesium alloys illustrated in FIGS. 39 to 41 assume AZ31 as an example.

What has been described above is just one embodiment for carrying out the magnesium alloy according to the present invention and its manufacturing method, the present invention is not limited to the above-described embodiment, as claimed in the following claims Without departing from the gist of the present invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

1 is a flowchart illustrating a method of manufacturing a magnesium alloy according to the present invention.

2 is a structure diagram of a magnesium alloy prepared according to the method for producing a magnesium alloy according to the present invention.

3 to 8 are photographs showing the EPMA test results of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

9 to 12 are photographs showing the TEM test results of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

13 and 14 are graphs showing the results of the protective gas reduction experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

15 is a graph showing the TGA test results of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

16 and 17 are graphs showing the results of the AES experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

18 is a graph showing the hardness at room temperature and high temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

19 is a graph showing the ignition temperature in the atmosphere and nitrogen atmosphere of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

20 is a graph showing the hardness at room temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

21 is a graph showing the ignition temperature in the atmosphere and nitrogen atmosphere of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

22 is a photograph of the billet surface of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

23 is a graph showing the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

24 is a graph showing the hardness of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

25 is a structure photograph of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

26 is hardness data of a magnesium alloy manufactured by the method of manufacturing a magnesium alloy according to the present invention.

27 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

28 is a structure photograph of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

29 is hardness data of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

30 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

31 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

32 is a graph showing the hardness test results of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

33 and 34 are graphs showing the results of ignition experiments of magnesium alloys produced by the method for producing magnesium alloys according to the present invention.

35 and 36 are graphs showing the results of the protective gas reduction experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

37 and 38 are graphs showing the results of ignition experiments of magnesium alloys produced by the method for producing magnesium alloys according to the present invention.

39 to 41 are photographs showing the surface of the magnesium alloy prepared in the absence of the protective gas, the protective gas and according to the method of the present invention.

Claims (16)

A number of magnesium grains having grain boundaries; And, Magnesium alloy comprising an additive compound present in the grain boundary as the outside, not the inside of the magnesium grains. The method of claim 1, The additive compound is Compounds of magnesium and alkali metals, Compounds of magnesium and alkaline earth metals, A compound of a substance other than magnesium and an alkali metal in the magnesium alloy, and Magnesium alloy, characterized in that any one selected from compounds of magnesium and alkaline earth metal compound of the magnesium alloy. The method of claim 1, The magnesium grain is Magnesium alloy, characterized in that the pure magnesium grains or magnesium alloy grains. The method of claim 1, The additive compound is Magnesium alloy, characterized in that 0.0001 to 30 parts by weight added to 100 parts by weight of the magnesium alloy. The method of claim 1, The additive compound is Magnesium alloy, the size is 0.1 ~ 500㎛. The method of claim 1, The magnesium alloy is Magnesium alloy, the firing temperature (℃) is 500 to 1500. The method of claim 1, The magnesium alloy is Use at least one of casting alloys, wrought alloys, creep alloys, damping alloys, degradable bio alloys and powder metallurgy Magnesium alloy characterized by the above-mentioned. A magnesium molten metal forming step of melting magnesium into a crucible and dissolving it at a temperature of 600 to 800 ° C. in a protective gas atmosphere to form magnesium molten metal; An additive addition step of adding an additive to the magnesium molten metal; Stirring the molten magnesium for 1 to 400 minutes; A casting step of casting the molten magnesium into a mold at 100 ° C. to 300 ° C .; And, Method of producing a magnesium alloy, characterized in that it comprises a cooling step of cooling the cast magnesium. The method of claim 8, Magnesium used in the magnesium molten metal forming step A method for producing a magnesium alloy, characterized in that the pure magnesium or magnesium alloy. The method of claim 8, The additive used in the additive addition step is A method for producing a magnesium alloy, characterized in that at least one selected from alkali metals, alkali metal oxides, alkali metal compounds, alkaline earth metals, alkaline earth metal oxides and alkaline earth metal compounds. The method of claim 10, The alkali metal oxide is Method for producing a magnesium alloy, characterized in that at least one selected from sodium oxide or potassium oxide. The method of claim 10, The alkaline earth metal oxide is Method for producing a magnesium alloy, characterized in that at least one selected from beryllium oxide, magnesium oxide, calcium oxide, strontium oxide. The method of claim 10, The alkaline earth metal compound is Calcium carbide (CaC ₂ ), calcium cyanamide (CaCN ₂ ), calcium carbonate (CaCO ₃ ) and calcium sulfate hemihydrate (CaSO ₄ ) The method for producing a magnesium alloy, characterized in that at least one selected. The method of claim 8, The additive used in the additive addition step is Method for producing a magnesium alloy, characterized in that 0.0001 to 30 parts by weight based on 100 parts by weight of the magnesium alloy. The method of claim 8, The additive used in the additive addition step is A method for producing a magnesium alloy, characterized in that the size is 0.1 ~ 500㎛. The method of claim 8, The additive used in the additive addition step is A method for producing a magnesium alloy, characterized in that the ignition temperature and hardness of the manufactured magnesium alloy are increased, and the required amount of protective gas is reduced.

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