JP2001032026A - Method for removing impurity in magnesium or magnesium alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove impurities and to easily and simply execute purification to a high degree by bringing a non-halogen system impurity removing agent contg. impurity removing elements such as boron, titanium, vanadium, niobium, hafnium and molybdenum into contact with the molten metal of magnesium or the like. SOLUTION: A non-halogen system impurity removing agent of a granular metal, compd., alloy or the like of about 1 μm to 5 mm contg. at least one or more kinds of impurity removing elements among boron, titanium, vanadium, niobium, hafnium and molybdenum and the molten metal of magnesium or a magnesium alloy of about 650 to 850 deg.C are mixed, stirred and brought into contact with. The impurity removing elements are hard to be dissolved and entered into solid solution in the magnesium molten metal, are moreover easily adsorbed, bonded and reacted with the impurities such as iron, copper and nickel contained therein to segregate them to the vicinities, swiftly precipitate and separate them away by the difference in specific gravity and moreover evade the intrusion of halogen elements to obtain magnesium or the like of high purity with high productivity without deteriorating the corrosion resistance thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for removing impurities from magnesium or a magnesium alloy.

[0002]

2. Description of the Related Art In recent years, there has been an increasing need for a lighter material, and magnesium or a magnesium alloy has attracted attention as a non-ferrous metal material which is lighter than aluminum.
Magnesium is the lightest among practical metal materials, and is therefore used not only as a material for aircraft but also as a material for automobiles. In particular, there is a strong demand for low fuel consumption due to the recent rise in environmental awareness, and it is necessary to further reduce the weight of automobiles. For this reason, in addition to engine head covers and wheels, structural parts such as engine blocks,
It is also being used for functional parts such as pistons.

As described above, as the use of magnesium or a magnesium alloy progresses, its durability and reliability have been strongly demanded. In particular, since magnesium or a magnesium alloy is an active metal, it is important to sufficiently increase its corrosion resistance in order to increase future demand.

[0004]

The corrosion resistance of magnesium or a magnesium alloy is strongly affected by impurities contained therein, for example, iron, copper, nickel and the like. Accordingly, there is a need for high-purity magnesium or magnesium alloy that does not contain such impurities.

However, as a crucible for refining magnesium or a magnesium alloy, a crucible made of iron (for example, made of stainless steel) is usually used, and mixing of iron or the like is inevitable. Iron crucibles are used for the following reasons.

[0006] Iron crucibles are inexpensive to manufacture and suitable for mass production. In addition, it has good workability and durability. Also,
Since iron crucibles have better thermal conductivity than ceramic crucibles and the like, magnesium and magnesium alloys can be easily dissolved. In addition, when using a crucible made of magnesium oxide or calcium oxide, silicon oxide used as a binder in the crucible melts into a molten metal such as magnesium, and the amount of impurities is reduced when an iron crucible is used. More than that. This is because magnesium is the active metal.

[0007] Further, since the raw material itself contains impurities such as iron, in any case, magnesium or a magnesium alloy contains impurities such as iron.
Magnesium is also an important resource and must be recycled efficiently. However, magnesium or magnesium alloy scrap often contains a large amount of iron or the like as compared with those new lump. for that reason,
It is important to efficiently remove the impurities contained therein and to recycle them into a magnesium alloy or the like having good corrosion resistance in order to effectively use resources.

Conventionally, as a method of removing such impurities, there has been a method of adding manganese or its compound or alloy. Manganese has little effect on the corrosion resistance of magnesium or a magnesium alloy, but manganese is dissolved or dissolved in magnesium or a magnesium alloy in a relatively large amount.

However, the manganese content may be limited depending on the purpose of use of the magnesium alloy or the like. In such a case, the method of removing impurities using manganese is not suitable. Manganese is dissolved or solidly dissolved in magnesium. Therefore, in order to separate and remove the compound of manganese and iron from the molten metal such as magnesium, it is necessary to add a relatively large amount of manganese, which is not preferable in terms of cost. Further, in order to separate and remove the compound of manganese and iron, sedation and holding for a long time are necessary, and productivity is poor. In addition to manganese, there is a method of removing impurities by passing titanium tetrachloride vapor or a halogenated derivative of boron through molten magnesium. For example, JP-B-31-504 and JP-A-58-968.
No. 30 discloses such a disclosure.

However, when a gas is passed through the molten magnesium as described above, the surface of the molten magnesium foams due to the blowing of the gas. Then, a large-scale device for preventing combustion and oxidation of magnesium due to the foaming is required separately. In addition, magnesium chloride is generated at the same time, which is not preferable. Further, it is necessary to separately collect unreacted halogen-based gas. In other words, in such a method, even if impurities such as iron can be removed, new inclusions are separately generated or production efficiency is deteriorated.

Accordingly, an object of the present invention is to efficiently remove impurities in magnesium or a magnesium alloy to easily obtain higher purity magnesium or the like.

[0012]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive research and various systematic experiments to solve such problems, the present invention has been achieved.In order to remove impurities in magnesium or magnesium alloy, magnesium or magnesium alloy melts A method for obtaining a higher purity magnesium or magnesium alloy by using a metal (simple substance), a compound or an alloy powder of an impurity removing element which is hardly dissolved in water and easily combined with impurities has been found.

That is, the method for removing impurities from magnesium or a magnesium alloy according to the present invention comprises the steps of: removing a halogen-free impurity removing agent containing at least one impurity removing element comprising boron, titanium, vanadium, niobium, hafnium and molybdenum; Alternatively, it is characterized in that impurities contained in the molten magnesium are removed by bringing the molten metal into contact with a molten magnesium alloy.

[0014] The impurity removing elements consisting of boron, titanium, vanadium, niobium, hafnium and molybdenum are hardly dissolved in molten magnesium or magnesium alloy, and the amount of solid solution in magnesium or magnesium alloy is extremely low. It is a small element. On the other hand, the impurity removing element is an element that is easily adsorbed, bonded or reacted with impurities contained in the magnesium or magnesium alloy melt.

The non-halogen impurity removing agent contains at least one of these impurity removing elements. Here, “non-halogen” is used for the following reason. For example, if impurities are removed using a halogen-based boron halide derivative or titanium tetrachloride, chlorides will be mixed as new inclusions. This is not preferable because it significantly deteriorates the corrosion resistance of magnesium or a magnesium alloy. The halogen-based impurity remover is passed through magnesium or a magnesium alloy as a gas. For this reason, the device becomes large, and in addition,
It is necessary to circulate or remove unreacted halogen-based gas, which makes it difficult to improve productivity.

Therefore, when a non-halogen impurity removing agent containing at least one of the above-mentioned impurity removing elements is brought into contact with a molten magnesium or magnesium alloy, the impurities contained in the molten metal are attracted to the impurity removing elements, and It can be segregated near the element to be removed. Then, a compound of the impurity removing element and the impurity sediments very quickly in the molten magnesium or magnesium alloy. Therefore, the molten magnesium or magnesium alloy and the compounds of the impurities are easily separated, and the impurities can be removed very efficiently. Then, there is no inconvenience as when a halogen-based impurity removing agent is used, the method is simple, and the productivity can be easily improved.

It is to be noted that the compound of the impurity-removing element and the impurity precipitates very quickly because its specific gravity is considerably larger than that of light metal magnesium or magnesium alloy, and it is dissolved in molten magnesium or magnesium alloy. Because it is difficult to form a solid solution.

Further, the impurity removing element itself hardly dissolves in the molten magnesium or magnesium alloy, and hardly forms a solid solution in magnesium or magnesium alloy. Therefore, only impurities can be removed, and the amount of the impurity removing element remaining in magnesium or magnesium alloy is very small. As a result, extremely high-purity magnesium or magnesium alloy can be obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various methods are conceivable for bringing a non-halogen-based impurity remover into contact with a molten magnesium or magnesium alloy. For example, the following methods are available.

As a first contact mode, a simple substance, a compound or an alloy of boron, titanium, vanadium, niobium, niobium, hafnium or molybdenum as an impurity removing element is added to a molten magnesium or magnesium alloy to bring them into contact. Yes, it is a preferred form. Particularly, the impurity removing element itself hardly dissolves in the magnesium or magnesium alloy melt. Therefore, even if a single element of the impurity removing element is added alone or in combination, a high-purity magnesium or magnesium alloy can be easily obtained. In addition, it becomes easy to mix alloy elements of the magnesium alloy.

Further, if the contact between the molten metal and the non-halogen-based impurity removing agent is promoted, the impurities can be removed efficiently. Therefore, it is preferable to appropriately stir the molten metal after adding the non-halogen-based impurity removing agent.

The higher the temperature of the molten metal after the addition of the non-halogen impurity removing agent, the more the diffusion proceeds, and the more the reaction proceeds. Therefore, it is preferable to set the temperature of the molten metal at 650 to 850 ° C. after the addition of the non-halogen impurity removing agent. If the temperature is lower than 650 ° C., the reaction and the like are not so promoted.
If the temperature exceeds 850 ° C., the amount of the impurity-removing element itself dissolved in magnesium or magnesium alloy gradually increases, and the combustion of magnesium easily occurs during stirring, which is not preferable.

Further, in order to promote the contact, it is preferable to increase the surface area of the non-halogen impurity removing agent. For example, the non-halogen-based impurity remover is preferably in the form of granules. In particular, it is preferable that the granule diameter be 1 μm to 5 mm.

The reason why the thickness is 5 mm or less is that more impurities can be removed while reducing the amount of the non-halogen impurity removing agent. The reason why the particle diameter is set to 1 μm or more is that if the particle size is too small and the particle size is too small, the sedimentation speed of the combined product of the impurity removing element and the impurity becomes slow, which is not preferable in terms of efficiency. In addition, if the particle size of the non-halogen-based impurity remover composed of a metal (simple), compound or alloy, etc. is too small, the metal, compound or alloy, etc. will condense and magnesium or magnesium alloy The apparent granule diameter becomes coarse. Therefore, the efficiency of impurity removal is eventually reduced.

Further, an adsorbed gas such as a metal, a compound, or an alloy is mixed into the molten metal at the same time, and it is not preferable because inclusions in the molten magnesium or magnesium alloy are increased.

As a second contact mode, a predetermined amount of a simple substance, compound or alloy of boron, titanium, vanadium, niobium, hafnium or molybdenum constituting the impurity removing element, and magnesium or magnesium alloy material are blended together. There is a form in which both are dissolved and brought into contact with each other, which is a preferable form.

In this way, the finely divided non-halogen impurity removing agent can be uniformly and easily dissolved in the molten magnesium or magnesium alloy, and the impurities can be removed during the melting step at the same time. In addition, it is efficient because the number of steps to be added later can be omitted.

In particular, when a compound or alloy of the above-mentioned impurity removing element and an element (alloy element) composed of magnesium, aluminum, zinc and manganese is used as a non-halogen-based impurity removing agent, the compound is dissolved in the molten magnesium or magnesium alloy. It is easy (has good wettability), the contact property is increased, and the removal of impurities is promoted. Also, it is often easier to obtain and cheaper than a simple substance.

As a third contact form, there is a form in which a molten metal of magnesium or a magnesium alloy is passed through a filter of a non-halogen-based impurity removing agent to bring them into contact with each other, which is a preferable form.

By appropriately selecting the contact area between the molten magnesium and the magnesium alloy through the filter of the non-halogen impurity removing agent, impurities can be efficiently and quickly removed. Further, since the impurity removing element hardly dissolves in the molten magnesium or magnesium alloy, the filter is less consumed, which is advantageous. The filter may be made of only a non-halogen impurity removing agent, but it is assumed that a base layer (for example, a wire mesh) made of iron, ceramic, or the like is coated (plated, vapor-deposited, etc.) with an impurity removing element. The filter layer may be formed by laying a granular non-halogen-based impurity removing agent in layers.

Further, if the shape or arrangement of the filter is devised, the impurities are segregated in the filter portion without waiting for the sedimentation of the combined substance of the impurity removing element and the impurity.
Since impurities can be removed from the molten magnesium or magnesium alloy, the productivity of magnesium or magnesium alloy is increased and the efficiency is extremely high.

As a fourth mode of contact, a container (such as a crucible) in which a non-halogen impurity removing agent is lined on its inner surface
Is used to melt magnesium or a magnesium alloy, which is a preferred form.

In particular, if the container is lined near the bottom of the container, the combined product of the impurity removing element and the impurity concentrates near the bottom, and the time required for sedimentation is extremely short.
This is convenient for improving productivity. In addition, when the crucible is made of iron, it is convenient that iron is not mixed in or suppressed from the crucible.

As described above, the non-halogen impurity removing agent may be a simple substance of the element for removing impurities, a compound containing one or more thereof, or an alloy. For example, compounds (including intermetallic compounds) include borides such as magnesium boride, aluminum boride, zinc boride, manganese boride, titanium boride, vanadium boride, niobium boride, hafnium boride, and boride. Molybdenum fluoride, boron oxide, borax, boron fluoride, boron carbide,
Boron nitride, silicon boride, and the like.

The alloys include magnesium-boron alloy, aluminum-boron alloy, zinc-boron alloy, manganese-boron alloy, titanium-boron alloy, vanadium-boron alloy, niobium-boron alloy, hafnium-boron alloy, molybdenum alloy -Boron alloy, zirconium-boron alloy, misch metal-boron alloy, titanium-magnesium alloy, titanium-aluminum alloy, titanium-aluminum-boron alloy, titanium-zinc alloy, titanium-manganese alloy, titanium-vanadium alloy, titanium-niobium Alloys, titanium-hafnium alloys, titanium-molybdenum alloys, and various compounds and alloys including vanadium, niobium, hafnium, and molybdenum.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples. (Manufacturing) (1) First Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) 1% by weight of a typical magnesium alloy (AZ9
1 alloy: Mg-9% Al-1% Zn) was used as the first embodiment of the present invention.

In preparing the molten magnesium alloy, the material used was pure magnesium (9
9.9%), pure aluminum (99.99%), and pure zinc (99.99%). Even if a high-purity raw material is used, iron may already contain 0.025% or more as an impurity. I understand.

These materials are made of stainless steel (SUS43)
0), and melted by heating in an electric furnace to prepare a molten magnesium alloy of about 1 kg. At this time,
In order to avoid mixing of iron from the crucible as much as possible, a crucible lined with magnesium oxide (MgO) on the inner surface was used. Next, when the molten metal was heated to reach 750 ° C., pellet-like particles having a length of 2 to 3 mm made of a simple substance of boron were added from above the molten metal. This addition amount aimed at 0.5% by weight of boron (B).

The pellet-like particles had a purity of boron alone of 99.5%, and contained 0.02% of iron as an impurity. Further, the melt was stirred for about 1 minute using a phosphorizer, and then sedated at 750 ° C. for 10 minutes.

After that, the crucible was taken out of the electric furnace, the molten metal of the magnesium alloy was slowly poured into the mold from the upper part of the crucible at a pouring temperature of 700 ° C. to produce a casting.
This was used as a test piece. The test piece is a bar having a length of 190 mm and an inverted trapezoidal cross section of lower base width 30 mm × upper base width 40 mm × height 40 mm. During this time, a small amount of sulfur is added to the surface of the magnesium alloy melt to prevent oxidative combustion.
Casting was performed with F ₆ gas (99.99%) sprayed.

After pouring, a precipitate covered with magnesium was observed at the bottom of the crucible. The precipitate was as large as the added boron pellets. (2) Second Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (Mg-9% Al-1% Zn-0.5M) containing 1% by weight-manganese (Mn) 0.5% by weight
n) is the second embodiment of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure aluminum (99.99%) and pure zinc (99.99%) shown in Table 1 were prepared.
%) And a magnesium-manganese alloy (Mg-3.5%)
Mn).

The following steps are the same as those in the first embodiment. In this embodiment, a precipitate covered with magnesium was observed at the bottom of the crucible. The precipitate was as large as the added boron pellets. (3) Third Example The target composition is the same as that of the second example, 9% by weight of aluminum (Al) -1% by weight of zinc (Zn) -0.5 of manganese (Mn).
Weight% magnesium alloy (Mg-9% Al-1%
Zn-0.5% Mn) was used as a third example of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure aluminum (99.99%) and pure zinc (99.99%) shown in Table 1 were prepared.
%) And magnesium-manganese alloy (Mg-3.5%
Mn).

The following steps are the same as in the second embodiment,
In this embodiment, the average particle size is 40 μm instead of boron alone.
m of titanium particles was added from above the melt. This addition amount aimed at 0.5% by weight of titanium (Ti). The purity of the titanium particles was 99.99%, and iron as an impurity was 0.0%.
It contained 01%.

In this example, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (4) Fourth Embodiment Same target composition as in the second embodiment: aluminum (Al) 9% by weight-zinc (Zn) 1% by weight-manganese (Mn) 0.5
Weight% magnesium alloy (Mg-9% Al-1%
Zn-0.5% Mn) was used as the fourth example of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure aluminum (99.99%) and pure zinc (99.99%) shown in Table 1 were prepared.
%) And a magnesium-manganese alloy (Mg-3.5%)
Mn).

The following steps are the same as in the second embodiment,
In the present example, instead of boron alone, flaky particles of vanadium (V) alone having a length of 2 to 5 mm were added from above the molten metal. The addition amount was targeted at 0.5% by weight of vanadium. The vanadium particles had a purity of 99.9% and contained iron as an impurity in an amount of 0.004%.

In this example, a small amount of flake-like precipitate covered with magnesium was observed at the bottom of the crucible. (5) Fifth Embodiment A magnesium alloy (Mg-9% Al-1) having the same target composition as in the second embodiment, 9% by weight of aluminum (Al), 1% by weight of zinc, and 0.5% by weight of manganese (Mn). % Zn-
0.5% Mn) was used as a fifth example of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure aluminum (99.99%) and pure zinc (99.99%) shown in Table 1 were prepared.
%) And a magnesium-manganese alloy (Mg-3.5%)
Mn).

The following steps are the same as in the second embodiment,
In this embodiment, niobium (Nb) is used instead of boron alone.
Pellet-shaped particles having a length of 1 to 3 mm made of a simple substance were added from above the molten metal. This addition amount is 0.5 wt% niobium.
Was targeted. The niobium particles had a purity of 99.9%.
In this case, the content of iron as an impurity was 0.001%.

In this example, a small amount of pellet-like precipitate covered with magnesium was observed at the bottom of the crucible. (6) Sixth Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (Mg-0.5%) containing 1% by weight, 0.5% by weight of manganese (Mn) and 0.38% by weight of boron (B).
9% Al-1% Zn-0.5% Mn-0.38% B) was used as the sixth example of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%), magnesium-manganese alloy (Mg-3.5% Mn) and boron shown in Table 1 were prepared. A first rod of an aluminum-boron alloy containing a compound of aluminum (Al-4% B: No. 1) was used. The first rod of this aluminum-boron alloy has a particle size of 5 to 5.
An alloy mainly containing a boron-aluminum compound having a size of about 10 μm. FIG. 1 shows a photograph of the structure of the Al-4% B alloy.

These materials are made of stainless steel (SUS43)
0), and melted by heating in an electric furnace to prepare a molten magnesium alloy of about 1 kg. At this time,
In order to avoid mixing of iron from the crucible as much as possible, a crucible lined with magnesium oxide (MgO) on the inner surface was used. In this example, since the elemental boron was already contained in the magnesium alloy material, the pellet-like particles of boron as in the first example were not added.

Next, the melt was stirred for about 1 minute using a phosphorizer, and then sedated at 750 ° C. for 10 minutes. After that, the crucible was taken out of the electric furnace and the pouring temperature was set to 7
At a temperature of 00 ° C., a molten magnesium alloy was slowly poured into the mold from the top of the crucible to produce a casting, which was used as a test piece. The shape of the test piece is the same as in the first embodiment.
During this time, a small amount of SF ₆ gas (99.99
%) Was sprayed.

In this example, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (7) Seventh Embodiment The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy containing 1% by weight-boron (B) 0.3% by weight (Mg-9% Al-1% Zn-0.3% B)
Was set as the seventh embodiment of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%) and pure aluminum (99.99%) shown in Table 1 were prepared.
%) And a first rod of an aluminum-boron alloy containing a boron-aluminum compound (Al-4% B: rod No. 1).

The following steps are the same as in the sixth embodiment. In this embodiment, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (8) Eighth Example The target composition is the same as that of the sixth example, 9% by weight of aluminum (Al) -1% by weight of zinc (Zn) -0.5 of manganese (Mn).
% By weight-magnesium alloy containing 0.38% by weight of boron (B) (Mg-9% Al-1% Zn-0.5% Mn-
0.38% B) was defined as an eighth embodiment of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%), magnesium-manganese alloy (Mg-3.5% Mn) and boron shown in Table 1 were prepared. -A second rod of an aluminum-boron alloy containing an aluminum compound (Al-4% B: rod No. 2) was used. The second rod of this aluminum-boron alloy is an alloy mainly containing a boron-aluminum compound having a particle size of about 2 to 5 μm, and is a finer boron-aluminum compound than the first rod.
It contains an aluminum compound. This Al-4%
FIG. 2 shows a structure photograph of the B alloy.

The following steps are the same as in the sixth embodiment.
Also in this example, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (9) Ninth Embodiment The same target composition as in the sixth embodiment, aluminum (Al) 9% by weight-zinc (Zn) 1% by weight-manganese (Mn) 0.5
% By weight-magnesium alloy containing 0.38% by weight of boron (B) (Mg-9% Al-1% Zn-0.5% Mn-
0.38% B) was defined as a ninth embodiment of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%), magnesium-manganese alloy (Mg-3.5% Mn) and boron shown in Table 1 were prepared. A first rod (Al-4% B: rod No. 1) of an aluminum-boron alloy containing a monoaluminum compound was used.

The following steps are the same as in the sixth embodiment,
Instead of stirring for about 1 minute using a phosphorizer, stirring was performed for 10 minutes at 450 rpm using a screw-shaped stirrer. Thereafter, the sedation was maintained at 750 ° C. for 10 minutes.
Also in this example, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (10) Tenth Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (Mg) containing 1% by weight, 0.5% by weight of manganese (Mn) and 0.45% by weight of titanium (Ti)
-9% Al-1% Zn-0.5% Mn-0.45% T
i) is the tenth embodiment of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%), magnesium-manganese alloy (Mg-3.5% Mn) and titanium -An aluminum-titanium alloy (Al-5% Ti) containing an aluminum compound (Al ₃ Ti) was used.

The following steps are the same as in the sixth embodiment. In this embodiment, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (11) Eleventh Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (Mg-9% Al-1% Zn-) containing 1% by weight, 0.5% by weight of manganese (Mn), 0.45% by weight of titanium (Ti), and 0.1% by weight of boron (B).
0.5% Mn-0.45% Ti-0.1% B) was used as an eleventh example of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%), magnesium-manganese alloy (Mg-3.5% Mn) and titanium shown in Table 1 were prepared. - aluminum compounds (Al ₃ Ti) and boron - titanium compound (TiB ₂₎
Aluminum-titanium-boron alloy (Al-
5% Ti-1% B) was used.

The following steps are the same as those in the sixth embodiment. In this embodiment, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (12) Twelfth Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (M) containing 1% by weight, 0.5% by weight of manganese (Mn), and 0.45% by weight of vanadium (V)
g-9% Al-1% Zn-0.5% Mn-0.45%
V) is the twelfth embodiment of the present invention.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure zinc (99.99%), magnesium-manganese alloy (Mg-3.5% Mn), aluminum and -An aluminum-vanadium alloy (Al-5% V) containing a vanadium compound (Al3V) was used.

The following steps are the same as in the sixth embodiment, and in this embodiment, a small amount of sludge-like precipitate was observed at the bottom of the crucible. (13) First Comparative Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (Mg-9% Al
-1% Zn) as a first comparative example.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure aluminum (99.99%) and pure zinc (99.99%) shown in Table 1 were prepared.
%).

These materials were made of stainless steel (SUS43)
0), and melted by heating in an electric furnace to prepare a molten magnesium alloy of about 1 kg. At this time,
The inner surface of the crucible was lined with magnesium oxide (MgO) in order to avoid mixing of iron from the crucible as much as possible. In the comparative example, no pellet-like particles of boron were added.

The melt was stirred for about 1 minute using a phosphorizer in the same manner as in the example, and then sedated at 750 ° C. for 10 minutes. Thereafter, the crucible was taken out of the electric furnace, the molten metal of the magnesium alloy was slowly poured into the mold from the top of the crucible at a pouring temperature of 700 ° C. to produce a casting, which was used as a test piece. The shape of the test piece is the same as in the first embodiment. During this time, in order to prevent oxidative combustion of the magnesium alloy melt, casting was performed in a state where a small amount of SF ₆ gas (99.99%) was sprayed on the surface of the melt.

In this comparative example, almost no precipitate was observed at the bottom of the crucible. (14) Second Comparative Example The target composition was 9% by weight of aluminum (Al) -zinc (Z
n) Magnesium alloy (Mg-9% Al-1% Zn-0.5M) containing 1% by weight-manganese (Mn) 0.5% by weight
n) was used as a second comparative example.

In preparing the molten magnesium alloy, pure magnesium (99.9%), pure aluminum (99.99%), and pure zinc (99.99%) shown in Table 1 were prepared.
%) And a magnesium-manganese alloy (Mg-3.5%)
Mn).

The subsequent steps were the same as in the first comparative example. In this comparative example, almost no precipitate was observed at the bottom of the crucible.

[0075]

[Table 1]

(Analysis and Evaluation of Test Specimens) Table 2 shows the analysis results of the chemical compositions of the first to twelfth examples and the first and second comparative examples.

Analytical Samples In both the examples and comparative examples, the obtained cast test pieces (upper bottom width 40 mm × lower bottom width 30 mm × height 40 mm × length 190 mm)
mm), a sample obtained by drilling from a substantially central portion was used as an analysis sample.

Analytical methods Analytical methods include inductively coupled plasma (ICP) emission analysis, absorption spectroscopy, gravimetry, and XRF (X-ray fluorescence analysis).
Was used. (1) About Examples 1 to 5 Examples in which boron, titanium, niobium and vanadium simple particles were added, as compared with Comparative Examples in which these were not added,
It turns out that the content of iron which is an impurity has decreased. In particular, the effect was great when titanium and vanadium were added.

At this time, the content of boron, titanium, niobium and vanadium in the test piece was 0.004% by weight or less. It can be seen that these impurity removing elements were very little dissolved in the magnesium alloy melt.
In particular, it can be seen that extremely high-purity magnesium or magnesium alloy can be obtained by using a non-halogen-based impurity removing agent containing boron, which is one of the impurity removing elements. (2) Sixth to Ninth Examples By adding a non-halogen-based impurity removing agent containing boron, which is one of the impurity removing elements, to the magnesium melt, iron as an impurity was removed in each case.

Here, the sixth and seventh embodiments in which a boron compound is added as an Al-B alloy into a molten magnesium alloy are more effective in removing iron than the first and second embodiments in which a simple substance of boron is added. Was effective. This is because the wettability between the boron-aluminum compound and the magnesium melt was superior to the wettability between the boron and the magnesium melt and the bond between the boron compound and the impurity iron was easy. it is conceivable that.

The iron concentration in the case where boron and manganese in the sixth embodiment were added simultaneously and the case where only boron in the seventh embodiment was added were almost the same. Similarly, the first and second
As can be seen from the examples and the first and second comparative examples, it was found that manganese forms a compound with iron, but the removal of precipitated iron is not as effective as the impurity removing element of the present invention.

This is because the manganese is easily dissolved and solid-dissolved in magnesium, and the dissolved manganese is very fine even when combined with iron, and is generally a Mn-Fe-Al compound which is said to be formed in molten magnesium. It is thought that this is because it easily penetrates into the molten magnesium.

Nevertheless, in order to coarsen the compound of manganese and iron and precipitate it in the molten magnesium, and to separate the compound from the molten magnesium, the amount of manganese added must be increased or the stirring must be carried out. It is necessary to prolong the sedation time afterwards. Therefore, it is considered that impurity removal using manganese is not as efficient as the impurity removal element of the present invention in terms of raw materials and time. Of course, even when manganese is contained, as shown in each example of the present invention,
If it also contains an impurity removing element such as boron,
The impurities are efficiently removed.

The sixth and eighth embodiments had the same target composition and the same amount of boron added, but the eighth embodiment significantly removed iron.

The precipitate in the molten magnesium in the sixth embodiment was observed by EPMA. According to this, it was clarified that iron was unevenly distributed around the boron-aluminum compound and bound to the surface of the boron-aluminum compound to precipitate. From this, it is considered that the larger the surface area of boron or the boron-aluminum compound as the impurity removing element, the easier it is to bond with the impurities contained in the molten magnesium and the impurities are effectively removed.

As described above, the Al used in the sixth embodiment
The boron-aluminum compound in the -4% B alloy had a particle size of about 5 to 10 μm, whereas the boron-aluminum compound in the Al-4% B alloy used in the eighth embodiment was And the particle size was about 2 to 5 μm.
From this, it is estimated that the surface area of the boron-aluminum compound in the eighth embodiment is several times the surface area of the boron-aluminum compound in the sixth embodiment. Eighth embodiment and sixth
It is considered that the amount of boron added was the same as in the example, and in the eighth example in which the surface area of the boron compound was large, the addition of the boron compound as an impurity removing element had more effect on the removal of iron.

As described above, if the surface area of the non-halogen impurity removing agent is increased by using the fine particles, it is understood that a sufficient impurity removing effect can be improved with a smaller amount of the impurity removing agent.

Although the sixth and ninth embodiments have the same target composition, the ninth embodiment has about ten times the stirring time of the molten metal as compared with the sixth embodiment. As a result, the concentration of iron as an impurity was drastically reduced to 1/5 or less. This is probably because the contact time between the boron compound and iron in the molten magnesium was increased.

Therefore, even if the amount of the impurity removing agent is reduced, it is understood that a sufficient impurity removing effect can be obtained by appropriately lengthening the stirring time of the molten metal. However, since the impurity removing element of the present invention has a strong bond with impurities, a sufficiently high purity magnesium or magnesium alloy can be obtained at a normal level even if the stirring time is shortened. (3) Sixth and Tenth to Twelfth Examples By adding a compound containing one or more of boron, titanium, and vanadium as impurity removing elements to a molten magnesium alloy, iron as an impurity is reduced. It is clear that the first and second comparative examples and the second to fourth comparative examples
It is understood from comparison with the embodiment.

Further, as can be understood from the eleventh embodiment, when both the boron and titanium are contained in the molten magnesium alloy, iron as an impurity is １ ／ or less of those of the comparative examples.
It can be seen that it is significantly reduced. Further, as can be seen from the twelfth embodiment, it is found that iron is significantly reduced when a vanadium compound is desired to be used.

In each of the sixth and tenth to twelfth embodiments, an impurity removing element (boron, titanium, vanadium) was used.
Since the content in the test piece was slight, it was understood that these elements were hardly dissolved in the molten magnesium alloy. In particular, as can be seen from the eleventh embodiment, when both titanium and boron are contained, the content of boron as an impurity removing element is very small, less than 0.001% by weight, and high purity magnesium or magnesium alloy is used. Is obtained. (4) Comparing the first, second, and sixth to ninth examples in which boron was added throughout, and the third to fifth, tenth, and twelfth examples in which boron was not added, and the second comparative example, the former was better. The amount of manganese contained in the test piece is remarkably small.

Although the content of manganese was originally small in the first example, the content in the test piece was less than 0.01%, so that the content of manganese was clearly lower than that in the first comparative example. It can be seen that it has been reduced.

Therefore, it can be understood that when boron is used as an impurity removing element, not only iron element as an impurity but also manganese can be removed. That is, manganese can be removed by using a non-halogen impurity removing agent containing boron as an impurity removing element. Therefore, since manganese can be removed in addition to the iron element and the like as impurities, it is understood that magnesium or a magnesium alloy with higher purity can be obtained.

Conversely, when it is desired to contain a desired amount of manganese, it is more preferable to include titanium, vanadium, niobium, etc. in the impurity removing element. This is very effective because it is possible to remove impurities such as iron element while maintaining a desired manganese content.

Instead of adding the impurity removing element later into the molten magnesium alloy as in the first to fifth embodiments, the impurity removing element is not added when the molten metal is adjusted as in the sixth to twelfth embodiments. When it is included, impurities can be simultaneously removed during the dissolving step, which is efficient.

Further, when a mother alloy which is an alloy element of a magnesium alloy contains an impurity removing element and is added to a molten magnesium alloy, the impurity removing element is finely and uniformly and easily mixed into the molten magnesium alloy. In addition, impurities are more efficiently removed.

As described above, in any of the first to twelfth embodiments, it can be understood that the use of the non-halogen-based impurity removing agent containing the impurity removing element of the present invention enabled efficient and sufficient removal of impurities.

In the present embodiment, boron and titanium, vanadium, and niobium have been described as examples of impurity removing elements. However, the present invention is not limited to these, and even when hafnium and molybdenum are used as impurity removing elements, impurities are removed in the same manner. it can. As can be inferred from the equilibrium diagram, these metals and compounds hardly dissolve in the molten magnesium.
Further, it is easy to form compounds with impurities.

In this embodiment, the content of the impurity removing element is set to about 0.4 to 0.5% by weight, but it is needless to say that the content is preferably adjusted according to the amount of the impurity. The effect of impurity removal increases as the amount of impurity removal elements increases. In practice, it is important to increase the contact area and contact time between the impurity removing element and the molten magnesium or magnesium alloy. Further, the amount of impurities to be removed is determined by the type, amount and surface area of the impurity-removing element, contact time, contact temperature, and the like.

However, any of the impurity removing elements of the present invention has a large impurity removing ability, so that even a small amount of the element is sufficiently effective.

[0101]

[Table 2]

(Analysis of Precipitate) In the first to fifth examples, the precipitate formed at the bottom of the crucible was subjected to EPMA (Electr
on Probe Xray Micro Analysis
zer). The analysis revealed the following.

When an aluminum-boron (Al-4% B) alloy is used as the non-halogen impurity removing agent, most of boron in the precipitate is AlB ₁₂ or Al
It was present as B ₂ compounds. In addition, the concentration of iron and manganese was high in and around these compounds in the precipitate. Therefore, it became clear that the aluminum-boron compound and iron (Fe) and manganese (Mn) were bonded.

[0104]

According to the method for removing impurities in magnesium or magnesium alloy of the present invention, impurities can be removed easily and efficiently. Further, since solid solution or mixing of the impurity removing element itself into magnesium or a magnesium alloy is extremely small, high-purity magnesium or a magnesium alloy having a desired composition can be easily obtained.

[0105]

[Brief description of the drawings]

FIG. 1 is a structural photograph of an aluminum-boron alloy (Al-4% B: No. 1) used in a sixth embodiment of the present invention.

FIG. 2 is a structural photograph of an aluminum-boron alloy (Al-4% B: No. 2) used in an eighth example of the present invention.

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[Procedure amendment]

[Submission date] July 28, 1999 (July 7, 1999
8)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Kawahara F-term in Toyota Central Research Laboratory Co., Ltd. 41-1, Oku-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi (reference) 4K001 AA38 BA23 EA04 GA13

Claims (1)

Claims Method for removing impurities from magnesium or magnesium alloy 1. A non-halogen impurity removing agent containing at least one or more impurity removing elements consisting of boron, titanium, vanadium, niobium, hafnium and molybdenum, and a molten metal of magnesium or a magnesium alloy. A method for removing impurities from magnesium or a magnesium alloy, comprising removing impurities contained therein.