KR101147648B1 - Magnesium alloy and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a magnesium-based alloy, a plurality of magnesium crystal grains constituting the magnesium alloy, and the intermetallic compound is formed 90% or more in the plurality of magnesium grain boundaries, less than 10% formed in the crystal grains It includes, The intermetallic compound is characterized in that at least any one selected from alkali metal oxides, alkali metal compounds, alkaline earth metal compounds are added to the molten metal of the magnesium alloy is generated by surface reaction with the molten metal.

Description

Magnesium alloy {MAGNESIUM ALLOY AND MANUFACTURING METHOD THEREOF}

The present invention relates to a magnesium-based alloy.

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. Representative protective gases include SF6, SO2, CO2, HFC-134a, Novec ™ 612, inert gases, and mixtures 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 SF6 gas has a global warming effect of 23,900 times that of CO2 gas, and thus, many studies have been under way to prevent the use of SF6 gas in developed countries.

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.

An object of the present invention is to overcome the above-mentioned conventional problems, to provide a magnesium-based alloy that can reduce or eliminate the protective gas.

Another object of the present invention is to provide a magnesium-based alloy for improving the cleanliness of the molten metal in the melting furnace, during the transfer of the molten metal or during the pouring of the molten metal.

Still another object of the present invention is to provide a magnesium-based alloy that can improve casting, forming, welding, and PM treatment ability without causing problems such as fluidity, hot cracking, and mold sintering.

Another object of the present invention is to reduce or eliminate the protective gas and at the same time reduce the manufacturing cost by using an inexpensive additive (at least one selected from alkali metal oxides, alkali metal compounds, alkaline earth metal oxides, alkaline earth metal compounds). It is to provide a magnesium-based alloy.

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

Another object of the present invention to provide a magnesium-based alloy that can improve the welding and joint performance.

It is still another object of the present invention to provide a magnesium-based alloy that is safe for various applications by increasing oxidation and fire resistance.

Another object of the present invention to provide a magnesium-based alloy that can improve the regeneration ability according to the flux type and temperature control.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular embodiments that are described. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, There will be.

Magnesium-based alloy of the present invention for achieving the above object, a plurality of magnesium crystal grains constituting the magnesium alloy; And at least 90% of the magnesium grain boundaries are formed, and less than 10% of the intermetallic compounds are present in the grains, wherein the intermetallic compounds are alkali metal oxides, alkali metal compounds, alkaline earth metal oxides. , At least one selected from alkaline earth metal compounds is added to the molten metal of the magnesium alloy to cause a surface reaction with the molten metal, and at least one selected from the alkali metal oxides, alkali metal compounds, alkaline earth metal oxides and alkaline earth metal compounds It is characterized in that the intermetallic compound is preferentially formed rather than dissociated in the molten metal and dissolved in the mother phase of the magnesium alloy.

Specifically, the intermetallic compound may include a compound of magnesium and alkali metal of the alloy, a compound of magnesium and alkaline earth metal of the alloy, an alloy component of the alloy and an alkali metal compound, and an alloy component of the alloy and alkaline earth metal. It is characterized by the presence of at least one form of the compound.

The magnesium crystal grains are characterized in that the pure magnesium crystal grains or magnesium alloy crystal grains.

The intermetallic compound is characterized in that 0.0001 to 30wt% is formed.

The magnesium alloy is characterized in that the ignition temperature is 500 to 1500 ° C.

More than 95% is formed in the plurality of magnesium grain boundaries, and less than 5% is formed in the grains, characterized in that it comprises an intermetallic compound present.

Magnesium-based alloy of the present invention for achieving the above object, a plurality of magnesium crystal grains constituting the magnesium alloy; And at least 90% of the magnesium grain boundaries are formed, and less than 10% of the intermetallic compounds are present in the grains. The intermetallic compounds may be alkali metal oxides, alkali metal compounds, or alkaline earth metal compounds. At least one selected from among the above is added to the molten metal of the magnesium alloy to cause a surface reaction with the molten metal, characterized in that at least a portion is generated by reaction.

As described above, 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 which suppresses the oxidation phenomenon.

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 be used at a low cost by purchasing an additive (at least one selected from alkali metal oxides, alkali metal compounds, alkaline earth metal oxides, alkaline earth metal compounds) added during the manufacturing process of magnesium alloy, the use of the protective gas In addition to the cost savings from reduction and elimination, the cost of additives is also reduced.

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 because the additive added during the manufacturing process of the magnesium alloy is present in the form of intermetallic 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, Have the ability to play. That is, it is not necessary to perform a separate additive addition process during the regeneration process of the magnesium alloy.

1 is a flowchart illustrating a method of manufacturing a magnesium-based alloy according to the present invention.
2 is a flowchart illustrating dissociation of an additive after adding alkaline earth metal oxide (CaO), which is one of the additives, to the molten magnesium.
3 is an exemplary diagram in which alkaline earth metal oxide (CaO), which is one of the additives in the present invention, is dissociated through stirring of the magnesium molten metal upper layer.
4 (a) to 4 (f) is a photograph of the EPMA experiment results of the magnesium-based alloy prepared in the present invention.
5 (a) to 5 (e) are photographs of the EPMA test results of the other magnesium-based alloy prepared in the present invention.
6 (a) to 6 (e) 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.
7 and 8 are graphs showing the results of the protective gas reduction experiment of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
9 is a graph showing the results of TGA experiment of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
10 and 11 are graphs showing the results of the AES experiment of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
12 is a graph showing the hardness at room temperature and high temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
13 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-based alloy according to the present invention.
14 is a graph showing the hardness at room temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
15 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 in the atmosphere and nitrogen atmosphere.
16 is a billet surface photograph of a magnesium alloy prepared by a method of manufacturing a magnesium-based alloy according to the present invention.
17 is a graph showing the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
18 is a graph showing the hardness of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
19 is a structure photograph of a magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
20 is hardness data of a magnesium alloy manufactured by the method of manufacturing a magnesium-based alloy according to the present invention.
21 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
22 is a structure photograph of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
23 is hardness data of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
24 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
25 is a graph of the ignition temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
26 is a graph showing the hardness test results of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
27 and 28 are graphs showing the results of ignition experiments of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
29 and 30 are graphs showing the results of the protective gas reduction experiment of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention.
31 and 32 are graphs showing the results of ignition experiments of magnesium alloys produced by the method for producing magnesium-based alloys according to the present invention.
33 to 35 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.
FIG. 36 shows the results of a DTA test in a dry air atmosphere to determine the effect of CaO addition on the ignition characteristics of the AZ91D magnesium alloy.
FIG. 37 shows the results of a DTA test in a dry air atmosphere to determine the effect of SrO addition on the ignition characteristics of the AZ31 magnesium alloy.
38 is a result of measuring the time to ignition by heating using a torch under the same conditions in order to compare the ignition characteristics of the CaO-added magnesium alloy in the present invention with conventional commercial high-temperature magnesium alloy.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. Like elements in the figures are denoted by the same reference numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

1 is a flowchart illustrating a method of manufacturing a magnesium alloy according to the present invention. As shown in the drawing, the method for producing a magnesium alloy according to the present invention includes a magnesium molten metal forming step (S1), an additive adding step (S2), a stirring step (S3), an exhausting step (S4) of an additive, an alkali metal or Alkaline earth metal exhaustion step (S5), casting step (S6), and solidification step (S6) 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. In the present invention, the temperature for dissolving the magnesium or magnesium alloy means the temperature at which the pure magnesium metal melts and the temperature at which the magnesium alloy melts. Depending on the type of alloy, the melting temperature may be different. For sufficient reaction, the additive is added while magnesium or magnesium alloy is completely dissolved. The dissolution temperature is sufficient as the temperature at which the solid phase is sufficiently melted and is present in the complete liquid phase. However, in view of the point that the temperature of the molten metal falls due to the addition of the additive in the present invention, it is necessary to maintain the molten metal in a sufficient temperature range.

Here, if the temperature is less than 400 ℃ magnesium alloy molten metal is difficult to form, if the temperature exceeds 800 ℃ there is a risk of ignition of magnesium molten metal. When the melting temperature is raised too high, sublimation of the liquid metal occurs, and due to the nature of magnesium, it may easily ignite to cause loss of the amount of molten metal and may adversely affect the final properties.

Protective gases used to suppress ignition of the molten metal when dissolving magnesium or alloys thereof include conventional SF6, SO2, CO2, HFC-134a, Novec ™ 612, inert gases and their equivalents, and also mixed gases thereof. .

Any magnesium alloy normally used in the industry can be used. 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 additive is preferably in a powder state to promote the reaction with the magnesium alloy. Preferably, the addition of a powdered state is desirable in order to increase the reaction surface area for an efficient reaction.

Here, the additive used in the additive addition step may be an alkali metal oxide, an alkali metal compound, 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.

As an additive, 0.0001 to 30 wt% may be added based on 100 wt% of the magnesium alloy. When the additive is less than 0.0001 wt%, the effect by the additive (increasing ignition temperature, decreasing oxidizing power, and decreasing protective gas) is small. In addition, when the additive exceeds 30wt%, the original magnesium or magnesium alloy does not appear. The input amount of the additive is determined according to the final target alloy composition of interest. In other words, the amount of CaO can be determined by inverse calculation according to the desired amount of Ca in the magnesium alloy.

In addition, the additive used in the additive addition step may have a size of 0.1 ~ 500㎛. If the size of the additive is too fine, less than 0.1㎛, it is difficult to be scattered by the sublimated magnesium or hot air to enter the furnace. Then, they coagulate with each other and become agglomerated without easily mixing with the molten metal in the liquid phase. In addition, when the size of the additive exceeds 500㎛, it is not preferable in view of increasing the surface area as mentioned when the additive is too thick. The particle size of the ideal powder is preferably 500 탆 or less. More preferably not more than 200 mu m.

In the stirring step (S3), the magnesium molten metal is stirred for 1 second to 60 minutes per 0.1 wt% of the additive.

If the stirring time is less than 1 second / 0.1 wt%, the additives are not sufficiently mixed in the molten magnesium, and if the stirring time exceeds 60 minutes / 0.1 wt%, the stirring time of the magnesium molten metal may be unnecessarily longer. In general, the time of stirring depends on the size of the molten metal and the amount of additives added.

The addition of the additive powder may be carried out by a method of adding a necessary amount at a time, but in terms of promoting the reaction and lowering the possibility of agglomeration of the powder, it is also preferable to add the powder sequentially by dividing it again or appropriately with a time difference after the first feeding.

Stirring Method and Conditions

Stirring is preferred for efficient reaction of the magnesium or magnesium alloy of the present invention with additives. The shape of the stirring is provided with a device capable of applying an electromagnetic field around the furnace containing the molten metal to generate an electromagnetic field field to induce the convection of the molten metal. It is also possible to perform artificial stirring (mechanical stirring) on the molten metal from the outside. In the case of mechanical stirring, the additive powder to be added may be appropriately stirred so as not to agglomerate. The ultimate goal of stirring is to properly induce the reaction of the molten metal with the incoming powder.

The time for stirring may vary depending on the temperature of the molten metal and the state of the powder to be charged (preheating state, etc.). Preferably, stirring is carried out until the powder is not visible on the surface of the molten metal. The reason is that the powder can be indirectly determined that the specific gravity is lower than that of the molten metal and flows on the molten metal in the steady state and when the powder is not visible on the molten metal, a sufficient reaction has occurred. Sufficient reaction herein means a state in which the additive is exhausted by substantially reacting with the molten metal.

Even if the powder is not found on the molten metal, the possibility of existence in the molten metal cannot be excluded. Therefore, the holding time after confirming the presence of the non-injured powder with the holding time after the stirring time and giving the time to finish the reaction of the unreacted powder This is necessary.

Time of agitation

It is effective to perform the timing of stirring simultaneously with the addition of powder. In addition, after the powder receives heat from the molten metal to reach a predetermined temperature or more, the reaction may be accelerated by starting stirring. Stirring is continued until no additive powder is detected on the surface of the melt. After the alkaline earth metal oxides have been exhausted by the reaction, the stirring is completed.

Surface reaction

When the additive is added to the molten metal, it is suspended on the surface of the molten metal without sinking into the molten metal due to the specific gravity difference.

In the case of alloying of a common metal, it is common to induce an active reaction by convection or stirring the molten metal and the alloying element metal. However, in the case of the present application, when an active reaction was induced, the additives introduced into the molten metal failed to react, remaining in the final material, thereby lowering physical properties or causing defects. That is, when the reaction in the molten metal is introduced rather than the surface of the molten metal, the additive is more likely to remain in the final molten metal than the reaction on the surface of the molten metal.

Therefore, in the present invention, it is important to create a reaction environment so that the oxide reacts on the surface of the molten metal rather than reacting in the molten metal. To do so, it is important not to force the oxide floating on the surface of the molten metal into the molten metal. It is important to simply spread the additive spread on the surface to spread evenly over the surface of the exposed melt.

It was better to do the reaction rather than to agitate, and it was better to stir on the outer surface (upper surface) than on the inside of the molten metal. That is, the outer surface (upper surface) was more responsive to the atmosphere and to the exposed powder. One side of CaO was better in contact with the atmosphere. The results were not good under vacuum or atmospheric gas. For sufficient reaction, it is necessary to stir the upper layer to induce the surface reaction.

Table 1 below shows the remaining amount of calcium oxide in the magnesium alloy according to the stirring method after adding 5, 10, 15 wt% calcium oxide having a particle size of 70 μm to the molten AM60B magnesium alloy in the present invention, respectively. Value. As the stirring method, the upper portion of the molten metal was stirred, the molten metal was stirred inside, and the other was not stirred. As the residual amount of calcium oxide was 5, 10, 15 wt%, the final residual amount was 0.001 and 0.002, respectively, as compared with the case of stirring only the upper part of the stirring and the case of not stirring, , And 0.005 wt%, respectively. That is, it can be seen that when CaO is stirred on the surface of Mg molten metal, most of CaO added is separated into Ca.

5 wt% CaO addition 10wt% CaO addition 15wt% CaO addition In alloy
CaO balance No agitation 4.5wt% CaO 8.7 wt% CaO 13.5 wt% CaO Stirring in the molten metal 1.2wt% CaO 3.1 wt% CaO 5.8 wt% CaO Molten metal upper layer
Stirring (present invention) 0.001wt% CaO 0.002wt% CaO 0.005wt% CaO

As illustrated in FIGS. 2 and 3, the oxygen component of the alkaline earth metal oxide as an additive is substantially removed over the molten surface through stirring of the molten upper layer. It is preferable that the agitation is performed at the upper layer portion of the depth of the molten metal from the surface of the molten metal to about 20% of the entire depth of the molten metal. At a depth of 20% or more, it is difficult to cause the surface reaction suggested by the present invention as a preferable example. More preferably, the stirring is performed at the upper layer part of about 10% of the total depth of the molten metal from the molten surface. This could minimize the disturbance of the molten metal by actually inducing the floating alkaline earth metal oxide in the 10% upper layer in the depth of the molten metal.

In the step of exhausting the additive (S4), through the reaction of the molten metal and the added additive, the additive is exhausted so as not to remain at least partially or substantially in the magnesium alloy. It is preferable that the additives added in the present invention are exhausted by sufficient reaction. However, it is also effective when the material remains unreacted and remains in the alloy and does not greatly affect the physical properties.

As an example, exhausting the alkaline earth metal oxide, which is one of the additives, removes the oxygen component from the alkaline earth metal oxide. The oxygen component may be removed in the form of oxygen (O ₂ ) gas, or may be removed in the form of dross or sludge through association with magnesium or its alloying elements in the molten metal. Then, the oxygen component is substantially removed over the surface of the molten metal through agitation of the molten upper layer. Figure 3 is an exemplary diagram representing the dissociation of the alkaline earth metal oxide as one of the additives through the stirring of the magnesium molten metal upper layer in the present invention.

In the alkali metal or alkaline earth metal reaction step (S5), the alkali metal or alkaline earth metal produced as a result of the exhaustion (dissociation) of the additive is reacted so as not to remain at least partially or substantially in the magnesium alloy. Here, the alkaline earth metal produced as a result of dissociation is compounded with at least one of magnesium, aluminum in the magnesium alloy, and other alloy elements (components) in the molten metal so as not to remain substantially. Herein, the compound refers to an intermetallic compound formed by combining a metal and a metal. Here, S4 and S5 are described by dividing them into steps to aid understanding as the reaction takes place simultaneously with stirring.

On the other hand, in the casting step (S6), the magnesium molten metal is cast in a mold at room temperature or preheated state. 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 can be gravity casting, continuous casting and the equivalent method.

As the temperature of the magnesium-based molten metal falls, at least one of magnesium, aluminum, and other alloying elements in the molten metal and the compound is formed in the magnesium-based alloy.

In the solidifying step S7, the mold is cooled to room temperature and a magnesium alloy (eg, magnesium alloy ingot) is taken out from the mold. The magnesium alloy prepared by the above method will be described below, but will have a form including at least one of magnesium, aluminum, and other alloy elements in the molten metal in the magnesium-based alloy.

Here is the formula of pure magnesium and alloy magnesium dissociated and reacted with calcium oxide (one of the additives).

In the case of pure magnesium molten metal, the magnesium component in the molten metal reacts with alkaline earth metal to form a magnesium (alkaline metal) compound. For example, when the alkaline earth metal oxide is CaO, Mg ₂ Ca is formed. Oxygen, which forms CaO, becomes O _{2 and} is discharged out of the molten metal or combined with Mg to form MgO and discharged in the form of dross (see Scheme 1 below).

Scheme 1

Pure Mg + CaO -> Mg (Matrix) + Mg ₂ Ca

... [O ₂ occurrence + MgO dross occurrence]

In the case of magnesium alloy molten metal, the magnesium component in the molten metal reacts with alkaline earth metal to form a magnesium (alkaline earth metal) compound or an aluminum (alkaline earth metal) compound. Also, magnesium and aluminum together with magnesium form compounds with alkaline earth metals. For example, when the alkaline earth metal oxide is CaO, Mg ₂ Ca, Al ₂ Ca, or (Mg, Al, other alloying elements) ₂ Ca is formed. Oxygen, which is composed of CaO, becomes O _{2 and} is discharged out of the molten metal as in the case of pure magnesium, or it is combined with Mg to be MgO and discharged in the form of dross (see Scheme 2 below).

Here, Ca provided in the additive showed a tendency to compound with other components than Mg in the alloy.

Scheme 2

Mg Alloy + CaO-> Mg Alloy (Matrix) +

(Mg ₂ Ca + Al ₂ Ca + (Mg, Al, other alloying elements) ₂ Ca}

... [O ₂ occurrence + MgO dross occurrence]

As described above, the present invention is a manufacturing method of magnesium alloy more economically than the conventional production method of magnesium alloy. Alkaline earth metals (eg Ca) are relatively expensive alloying elements compared to alkaline earth metal oxides (eg CaO), which acts as a factor to increase the price of magnesium alloy. In addition, it is relatively easy to alloy by adding alkaline earth metal oxide to magnesium or magnesium alloy in place of alkaline earth metal. On the other hand, the addition of chemically stable alkaline earth metal oxides (eg, CaO) without the addition of alkaline earth metals (eg, Ca) may result in the same or more alloying effects.

When the alkaline earth metal is directly added to magnesium or magnesium alloy, the solid solution of the alkaline earth metal occurs in the magnesium alloy, whereas in the case of using the technique of the present invention, the degree of solid solution is added when the alkaline earth metal oxide (CaO) is added. Compared with the direct addition of alkaline earth metals (Ca), there is no or very little solid solution. Therefore, when magnesium alloys are prepared by adding alkaline earth metal oxides, since the substantial amount of alkaline earth metals directly form intermetallic compounds of magnesium or Al (eg, Mg ₂ Ca or Al ₂ Ca), the physical properties of the alkali or earth metals are high. (E.g. Ca), it can be seen to be improved.

The intermetallic compound is mostly present at the interface that is outside of the magnesium grains, but may also be present inside the magnesium grains. Here, the magnesium crystal grains may be any one selected from pure magnesium grains, magnesium alloy grains, and equivalents thereof. The intermetallic compound may be at least any one of a compound of magnesium and alkali metal, a compound of magnesium and alkaline earth metal, a compound other than magnesium in the magnesium alloy and an alkali metal compound, and a compound other than magnesium and alkaline earth metal in the magnesium alloy. It may be one or a complex compound thereof.

In this way, the hardness (HRF) of the magnesium alloy (1) according to the present invention increases with the amount of the additive, but varies depending on the processing method and heat treatment, etc., the magnesium alloy (1) ) 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.

Figure 4 is an EPMA (Electron Probe Micro Analyzer) Mapping analysis of the constituents of the Mg alloy prepared by the present method by adding 0.45wt% CaO to the commercial magnesium alloy AM60B alloy. Figure 4 (b) is a photograph of magnesium, 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. Figure 4 (c) is a photograph of aluminum can be seen that a small amount present in the grain boundary. That is, the red part in the picture is aluminum. It can be seen that the presence region of Ca in Fig. 4 (d) is similar to the existence region of (c) Al. This is because Ca separated from CaO forms a phase with Al without being dissolved in Mg base (Al ₂ Ca phase formation). 4 (f) is a photograph of Mn, which shows that there is much less than aluminum at the grain boundary. Figure 4 (d) is a picture of calcium may be present in a small amount in the grain boundary. The red part in the picture is calcium. Looking at Figure 4 (e) it can be seen that almost no O in the alloy. This is because O is separated from CaO added to Mg alloy It is shown that it is removed in the molten state in the form of O2 gas or in the form of dross or sludge in the form of MgO. Here, Ca provided in the additive showed a tendency to compound with other components than Mg in the alloy. That is, when calcium oxide is added to the AM60B magnesium alloy, the calcium oxide is reduced and mainly exists in the form of an intermetallic compound of aluminum calcium (Al ₂ Ca) at the grain boundary.

FIG. 5 is a mapping picture of EPMA in which 0.52 wt% CaO is added to an AZ91D alloy which is a magnesium alloy different from FIG. As you can see in the picture, it shows the same result. As can be seen in Figures 4 and 5, it is shown that most of the intermetallic compound is formed at the grain boundary. However, it can be seen that there is a small amount of the intermetallic compound in the grains.

6 (a) to 6 (e) are photographs showing the results of a transmission electron microscope (TEM) experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention. Fig. 6 (a) is a photograph taken in the grains of magnesium alloy. As can be seen in Figure 6 (d) it can be seen that the position of the components of calcium overlap with the components of aluminum. This shows that aluminum and calcium form intermetallic compounds and exist mostly in grain boundaries but also in grains. The magnesium alloy of the present invention is polycrystalline. The proportions present in these grains depended on the type of alloy and the type and amount of additives added. In the intermetallic compound, 90% or less is formed at the grain boundaries of many magnesium crystals, and more than 10% exists in the grains. Since the intermetallic compound was present in less than 10% in the grains, physical properties expected in the present invention could be obtained. Preferably, less than 5% is more preferred for the desired physical properties of the present invention. The volume ratios of the intermetallic compounds formed here were analyzed using EPMA photographs and TEM photographs.

The intermetallic compound produced in the present invention is formed in grain boundaries or grains in proportion to the amount of the additive to be added.

The magnesium-based alloy prepared in the present invention is a casting alloy, a rough alloy (wrought alloy), a creep alloy (creep alloy), a damping alloy (damping alloy), degradable bio alloy (degradable bio alloy) and powder metal It can be used with at least one selected from powder metallurgy.

In one example, the casting alloy may be formed by mixing CaX in AZ91D, AM20, AM50, AM60. Here, CaX may be CaO, CaC2, CaCN2, and 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).

(Example 1)

In the magnesium alloy of the present invention, the AZ31 magnesium alloy, in which 1.5 to 12.5 wt% of calcium oxide having a particle size of 100 μm, is added, the hardness increases as the amount of calcium oxide (CaO) is increased. That is, the hardness of the AZ31 magnesium alloy without the addition of calcium oxide is approximately 40 at room temperature, and the AZ31 magnesium alloy with the addition of calcium oxide is continuously increasing in hardness than 40.

The hardness according to the wt% of such calcium oxide is shown in Table 2 below.

alloy Calcium oxide addition amount Hardness [Hv] Magnesium alloy
(AZ31) 1.5 wt% 52 3.7 wt% 55 7.4 wt% 58 12.5 wt% 60

Therefore, as shown in Table 2, it can be seen that the strength is continuously increased when 1.5 to 12.5 wt% of calcium oxide is added to the magnesium alloy, and at 12.5 wt%, the hardness is about 60, 50% of that of the conventional AZ31 magnesium alloy. It can be seen that the increase over.

(Example 2)

The mechanical properties of the magnesium-based alloy prepared by the present invention and the existing alloy (AM60) were compared. The magnesium-based alloy (AM60 + CaO) prepared by the present invention at room temperature showed better yield strength (YS), tensile strength (UTS) and elongation (EL) than the conventional AM60 alloy.

For example, the existing AM60 alloy has a yield strength of 115 [MPa], a tensile strength of 215 [MPa], and an elongation of about 6%.

However, magnesium alloy with 1.0wt% CaO added to AM60 alloy has yield strength of 152 [MPa], tensile strength of 250 [MPa] and elongation of 8%, which is superior to conventional AM60 alloy. Done

(Example 3)

The hardness at room temperature of the magnesium alloy prepared in the present invention was measured. It can be seen that the hardness of the AM50 magnesium alloy to which 1.2 to 5.6 wt% of strontium oxide having a particle size of 150 μm is added during the manufacturing process increases as the amount of addition of the strontium oxide increases. That is, the hardness of the AM50 magnesium alloy without the addition of strontium oxide is about 45 at room temperature, and the hardness of the AM50 magnesium alloy with the addition of a small amount of strontium oxide is about 50 or more.

The hardness according to the wt% of strontium oxide is shown in Table 3 below.

alloy Strontium Oxide Addition Hardness [Hv] Magnesium alloy
(AM50) 1.2 wt% 51 2.0 wt% 53 3.8 wt% 55 5.6 wt% 57

Therefore, as shown in Table 3, when the strontium oxide 1.2 to 5.6 wt% is added to the magnesium alloy, the strength is continuously increased, and at 5.6 wt%, the hardness is about 57% compared to the conventional AM50 magnesium alloy. It can be seen that the increase over.

(Example 4)

The mechanical properties of the magnesium alloy prepared by the present invention and the conventional alloy (AM50) were compared. The magnesium alloy (AM50 + SrO) prepared by the present invention at room temperature showed better yield strength (YS), tensile strength (UTS) and elongation (EL) than the conventional AM50 alloy.

For example, the existing AM50 alloy has a yield strength of 120 [MPa], a tensile strength of 170 [MPa], and an elongation of about 7%.

However, the magnesium alloy added 1.2 wt% SrO to the AM50 alloy has a yield strength of 152 [MPa], a tensile strength of 220 [MPa], and an elongation of about 11%. The mechanical properties are significantly better than those of the conventional AM60 alloy. It can be seen that.

(Example 5)

The hardness test result of the magnesium alloy prepared by another embodiment of the present invention was measured. To the AZ91 magnesium alloy was added 0.001 to 0.42 wt% of magnesium oxide (MgO) having a particle size of 150 µm. When magnesium oxide was added to the magnesium alloy, it was found that the hardness increased continuously compared to the case where no magnesium oxide was added.

That is, at room temperature, the hardness of the AZ91 magnesium alloy to which magnesium oxide is not added is about 51, and the hardness of the AZ91 magnesium alloy to which magnesium oxide is added is about 54 or more.

The hardness according to the wt% of magnesium oxide is shown in Table 4 below.

alloy Magnesium oxide addition amount Hardness [Hv] Magnesium alloy
(AZ91) 0.001 wt% 53 0.05 wt% 58 0.25 wt% 59 0.42 wt% 60

Therefore, as shown in Table 4, when the magnesium oxide 0.001 to 0.42 wt% is added to the magnesium alloy, the strength is continuously increased. At 0.42 wt%, the hardness is about 60% compared to the conventional AZ91 magnesium alloy. It can be seen that the increase over.

(Example 6)

The hardness at room temperature of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention was measured. It was found that the hardness of the AZ91D magnesium alloy containing 1-12 wt% of calcium oxide having a particle size of 100 μm was increased as the amount of added calcium oxide (CaO) increased. That is, the hardness of the AZ91D magnesium alloy without the addition of calcium oxide at room temperature is approximately 57, and the hardness of the AZ91D magnesium alloy with the addition of calcium oxide is continuously increasing than 57.

(Example 7)

The hardness of the magnesium alloy prepared by the method for producing a magnesium-based alloy according to the present invention was measured. Magnesium oxide (MgO) having a particle size of 150 mu m was added to the AM50 magnesium alloy in an amount of 3 to 12 wt%. When magnesium oxide was added, it was found that the hardness increased continuously as compared with the case without addition.

(Example 8)

After adding 5, 10 and 15 wt% of calcium oxide having a particle size of 70 μm to the molten metal of the AM60B magnesium alloy, the residual amount of calcium oxide in the magnesium alloy was measured according to the stirring method. In the stirring method, the upper layer stirring of the molten metal, the internal stirring of the molten metal, and the other one were not stirred. When only the upper portion of the agitation was stirred with different stirring conditions, the residual amount of calcium oxide was added as 5, 10, 15 wt% calcium oxide as compared with the case without stirring and the internal agitation. The final residual amount was 0.001, 0.002 , 0.005wt% was found to remain the smallest.

(Example 9)

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 wt%) 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 internally 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 5 below.

Powder size ～ 100㎛ ～ 200㎛ ～ 500㎛ Goal composition 1 wt% CaO 1 wt% CaO 1 wt% CaO ICP Component Analysis 0.45 wt% Ca 0.0078 wt% Ca 0.0042 wt% Ca 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 wt% of calcium oxide was added, 0.45 wt% of calcium was 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. Internal stirring reactions were less preferred than surface reactions.

7 and 8 are graphs showing the results of the protective gas reduction during dissolution of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

The results of FIG. 7 were obtained by experimenting at a die casting working melt temperature of 680 ° C., and the results of FIG. 8 were obtained by experimenting at 720 ° C. (overheated state).

In addition, in FIG. 7 and FIG. 8, "sealed" means a state in which outside air is not introduced as a conventional Mg melting furnace is used, and "unsealed" means an artificial state in which outside air is introduced.

First, as shown in FIG. 7, in an atmosphere of 680 ° C., when the air is inflowed (unsealed), SF 6 gas of 1,000 ppm in all of AZ91D, AZ91D-0.04wt% CaO, and AZ91D-0.13wt% CaO to suppress ignition. Was needed. However, in the absence of air (sealed), about 500 ppm of SF 6 gas was required for AZ91D and AZ91D-0.04 wt%, and 300 ppm of SF 6 gas was required for AZ91D-0.13 wt% CaO. . Therefore, in a typical die casting operation, when the air is not introduced, it can be seen that as the amount of the additive is added, the required amount of the protective gas for suppressing ignition decreases. It can be seen that it can be dissolved using a conventional protective gas such as nitrogen or argon.

Next, as shown in Figure 8, in the air inflow (unsealed) in the atmosphere of 720 ℃ (3,200ppm, 2,000ppm in AZ91D, AZ91D-0.04wt% CaO, AZ91D-0.13wt% CaO, respectively, to suppress ignition) , 1,000 ppm SF 6 gas was required. However, in the absence of air (sealed), approximately 500 ppm SF 6 gas was required for AZ91D and AZ91D-0.04 wt% CaO, and 300 ppm SF 6 gas was required for AZ91D-0.13 wt% CaO to prevent ignition. 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.

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

In FIG. 9, the X axis is time, and the Y axis is weight increase (%). 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-0.14wt% 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-0.14wt% CaO 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.

10 and 11 are graphs showing the results of the AES (Atomic Emission Spectrometer) experiment of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

In Fig. 10, 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-0.7wt% CaO, as shown in FIG. 11, oxygen is detected by about 26 minutes until the sputtering time is about 1 minute, and it can be seen that oxygen detection is reduced thereafter. That is, in the case of AZ91D-0.7wt% 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.

12 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. 12, it can be seen that the hardness of the AZ91D magnesium alloy added with 0.007 to 0.41 wt% CaO of calcium oxide increased as the amount of the calcium oxide increased. 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 (Mg17Al12) in the AZ91D magnesium alloy.

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

As shown in Figure 13 it can be seen that the ignition temperature of the magnesium alloy according to the addition amount of calcium oxide increases with the addition amount of the calcium oxide increases. 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 10)

14 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. 14, the hardness of the AZ91D magnesium alloy having 0.02 to 0.48 wt% of strontium oxide added during the manufacturing process increases 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.

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

As shown in FIG. 15, the AZ91D magnesium alloy to which strontium oxide was 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 11)

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

As shown in FIG. 16, the bead of the beryllium oxide, which is an alkaline earth metal oxide, and the AZ91D magnesium alloy for die casting, in which 0.0001 wt% and 0.5 wt% magnesium oxide were added, respectively, showed a billet even if a small amount of beryllium oxide was added. It can be seen that this shows a clean surface without oxidation or ignition. In addition, a clean billet which was not oxidized or ignited was obtained even by adding 0.5 wt% of magnesium oxide.

17 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. 17, as can be clearly seen from the ignition temperature of the AZ91D magnesium alloy for die casting in which beryllium oxide and magnesium oxide are added 0.0001wt% and 0.5wt%, respectively, the alkaline earth metal oxides of beryllium oxide and magnesium oxide It can be seen that the ignition temperature is improved according to the addition amount, thereby improving mechanical properties and oxidation characteristics.

18 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 can be clearly seen from the hardness of the AZ91D magnesium alloy for die casting in which beryllium oxide and magnesium oxide are added 0.0001% and 0.5%, respectively, as shown in FIG. 18, depending on the addition amount of beryllium oxide or magnesium oxide, which is an alkaline earth metal oxide It can be seen that the hardness is improved.

(Example 12)

19 is a structure photograph of a 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 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 as 0.007 wt% of calcium cyanamide (CaCN2) 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.

20 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. 20, the AZ91D magnesium alloy to which the calcium-based compound calcium cyanamide was added was measured to have a hardness of approximately 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.

21 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. 21, the AZ91D magnesium alloy to which the calcium-based compound calcium cyanamide is 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 13)

22 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. 22, 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 (CaC2), which is a calcium compound, and 0.03 wt% was added.

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

As shown in FIG. 23, 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.

24 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. 24, 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.

25 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. 25, the ignition temperature in the air atmosphere is a magnesium alloy (AZ91D-0.007wt% CaCN 2 / 0.03wt%) to which calcium-based compounds such as calcium cyanamide (CaCN2) and calcium carbide (CaC2) are added, respectively. Both CaC 2) exhibited 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 14)

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

As shown in FIG. 26, when calcium oxide was not added to the AM50 magnesium alloy, when about 0.05 wt% of calcium oxide was added, the hardness was about 50 when about 0.15 wt% 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.

27 and 28 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. 27, when calcium oxide was not added to the AM50 magnesium alloy, the ignition temperature was about 570 ° C. in an air atmosphere, but when about 0.05 wt% of calcium oxide was added, the ignition temperature increased to about 590 ° C. FIG. Moreover, when about 0.15 wt% of calcium oxide was added, the ignition temperature increased to about 610 ° C.

As shown in FIG. 28, 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 wt% of calcium oxide was added, the ignition temperature increased to about 570 ° C. FIG. Moreover, when about 0.15 wt% of calcium oxide was added, the ignition temperature increased to about 640 ° C.

(Example 15)

29 and 30 are graphs showing the results of protective gas reduction experiments during dissolution of the magnesium alloy prepared by the method for producing a magnesium alloy according to the present invention.

The results of FIG. 29 were obtained by experimenting at a die casting working melt temperature of 680 ° C., and the results of FIG. 30 were obtained by experimenting at 720 ° C. (overheated state).

As shown in FIG. 29, in an unsealed atmosphere with an atmosphere of 680 ° C, 500 ppm SF 6 gas is required at all of AZ31, AZ31-0.05wt% CaO, and AZ31-0.32wt% CaO to suppress ignition. It was. However, in the absence of air (sealed), approximately 100 ppm SF 6 gas is required for AZ31 and AZ31-0.05 wt% CaO, and 40 ppm SF 6 gas is required for AZ31-0.32 wt% CaO to suppress ignition. It was. Therefore, in a typical die casting operation, when the air is not introduced, it can be seen that as the amount of the additive is added, the required amount of the protective gas for suppressing ignition decreases, and when the amount of the additive is small according to the characteristics of the desired alloy, It can be seen that it can be dissolved using a protective gas such as nitrogen or argon.

Next, as shown in FIG. 30, in an unsealed state in which air is introduced at 720 ° C., 1,000 ppm SF6 gas is contained in AZ31, AZ31-0.05 wt% CaO, and AZ31-0.32 wt% CaO to suppress ignition. Needed. However, in the absence of air (sealed), about 200 ppm of SF6 gas was required for AZ31, and about 100 ppm of SF6 gas was required for AZ31-0.05 wt% CaO, and AZ31-0.32 wt% CaO to suppress ignition. In the case of 40 ppm SF6 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.

31 and 32 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. 31, when calcium oxide was not added to the AZ31 magnesium alloy, the ignition temperature was about 570 ° C. in the air atmosphere, but when about 0.3 wt% of calcium oxide was added, the ignition temperature increased to about 610 ° C. FIG.

As shown in FIG. 32, 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 wt% of calcium oxide was added, the ignition temperature increased to about 690 ° C. FIG.

33 to 35 are photographs showing the surface of the thin cast product of magnesium alloy prepared in the absence of the protective gas, in the presence of the protective gas and according to the method of the present invention.

As shown in FIG. 33, when the magnesium alloy is manufactured without the protective gas, the surface is blackened.

In addition, as shown in FIG. 34, 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, when the magnesium alloy is manufactured by adding calcium oxide as shown in FIG. 35, it can be seen that no ignition phenomenon or crack phenomenon is found.

Here, the magnesium alloys illustrated in FIGS. 33 to 35 all use AZ31 as an example.

36 shows the results of the DTA test in a dry air atmosphere to determine the effect of CaO addition on the ignition characteristics of the AZ91D magnesium alloy.

As can be seen in the experimental results of FIG. 36, it can be seen that the ignition temperature increases as the CaO content increases. When the amount of calcium oxide added is 15.7 wt%, it shows a high ignition temperature of about 1300 ° C, and it can be seen that the ignition temperature converges to some extent in the subsequent CaO addition.

Figure 37 shows the results of the DTA test in a dry air atmosphere to determine the effect of SrO addition amount on the ignition characteristics of the AZ31 magnesium alloy. As can be seen from the experimental results of FIG. 37, it can be seen that the ignition temperature increases as the content of strontium oxide increases. When 15.9 wt% of strontium oxide is added to the molten metal of magnesium-based metal, the ignition temperature is increased to 1400 ° C. After that, the ignition temperature is maintained to some extent until the addition of 25.8 wt% SrO.

38 is a result of measuring the time to ignition by heating using a torch under the same conditions in order to compare the ignition characteristics of the magnesium alloy added CaO as an additive to conventional commercial high-temperature magnesium alloy. As shown in the photograph, it can be seen that the magnesium alloy added with CaO is not fired for the longest time compared to other commercial magnesium alloys, and thus, the fire is suppressed. Among the alloys used in the experiment, Mg-3Al-1.13CaO alloy prepared by adding 1.13wt% of CaO showed the highest ignition resistance. In this case, fire occurred only after 200 seconds. In addition, when CaO is added to 1 wt% or more in all the alloys, regardless of the Al content, all alloys can be seen that the fire property is superior to the existing high-temperature magnesium alloy (AS21, AE44, MRI153, MRI230 in FIG. 38). In FIG. 38, Mg-3Al-1.13CaO alloy refers to an alloy prepared by the invention described above by adding 1.13wt% of CaO as an additive to a molten magnesium alloy of Mg-3Al. (The same applies to Mg-6Al-1CaO and Mg-9Al-1.02CaO.)

The present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be. The scope of the present invention is defined by the appended claims, and all differences within the scope of the claims are to be construed as being included in the present invention.

Claims (7)

A number of magnesium grains constituting the magnesium alloy; And,
90% or more is formed in the plurality of magnesium grain boundaries, and less than 10% is formed in the grains, and includes an intermetallic compound present,
In the intermetallic compound, at least one selected from among alkali metal oxides, alkali metal compounds, alkaline earth metal oxides and alkaline earth metal compounds is added to the molten metal of the magnesium alloy to cause a surface reaction with the molten metal.
At least one selected from the alkali metal oxides, alkali metal compounds, alkaline earth metal oxides and alkaline earth metal compounds is dissociated in the molten metal and preferentially forms the intermetallic compound rather than being dissolved in a matrix of magnesium alloy. Magnesium alloy.
The method of claim 1,
The intermetallic compound,
A compound of magnesium and alkali metal of the alloy,
A compound of magnesium and alkaline earth metal of the alloy,
An alloy component of the alloy and an alkali metal compound, and
Among the alloying component of the alloy and the compound of alkaline earth metal
Magnesium-based alloy, characterized in that present in at least one form.
The method of claim 1,
The magnesium crystal grains,
Magnesium-based alloy, characterized in that the pure magnesium crystal grains or magnesium alloy crystal grains.
The method of claim 1,
Magnesium-based alloy, characterized in that the intermetallic compound is formed from 0.0001 to 30wt%.
The method of claim 1,
The magnesium alloy is,
Magnesium-based alloy, characterized in that the ignition temperature is 500 to 1500 ℃.
The method of claim 1,
Magnesium-based alloy, characterized in that it comprises an intermetallic compound formed in the plurality of magnesium grain boundaries of 95% or more, less than 5% formed in the grains.
A number of magnesium grains constituting the magnesium alloy; And,
90% or more is formed in the plurality of magnesium grain boundaries, and less than 10% is formed in the grains, and includes an intermetallic compound present,
The intermetallic compound is characterized in that at least one selected from alkali metal oxide, alkali metal compound, alkaline earth metal compound is added to the molten metal of the magnesium alloy to cause a surface reaction with the molten metal, at least a part of the reaction occurs Magnesium alloy.

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