JP6756565B2 - Manufacturing method of aluminum-based metal - Google Patents

Description

The present invention relates to a method for producing an aluminum-based metal containing B (boron).

Conventionally, a technique of adding B to aluminum is known. For example, Patent Document 1 discloses this kind of technology. In Patent Document 1, in a method for producing an Al-B alloy used as a conductivity improving material for an aluminum electric wire and a neutron absorber, KBF ₄ is added to an Al molten metal to make all boron into AlB ₂ crystals, and then K. ₂ A method of adjusting the viscosity of the molten Al-B by adding TiF ₆ is described.

Japanese Unexamined Patent Publication No. 4-333542

JIS standard A6063 aluminum alloys, etc. are extruded from aluminum alloys because they have the mechanical properties, corrosion resistance, and anodic oxidation treatment required for various building materials such as sashes, and are excellent in extrudability and hardenability. The highest production volume as a shape material. Further, the alloy containing a trace amount of B (boron) is excellent in the brilliance of the surface of the profile, and the effect is attracting attention from the viewpoint of design.

Generally, B is added using a commercially available Al—B mother alloy such as Al-4 wt% B. However, commercially available Al-B mother alloys such as Al-4 wt% B are expensive and cause an increase in manufacturing cost. In addition, B and transition metals (Ti, Cr, etc.) easily form compounds, and it is technically difficult to add B to a 6000 series aluminum alloy containing these transition metals, and improving the yield when B is added is a major issue. ing. _{B 2 O 3, H 2 BO} 3, NaB 4 O 7 and KBF ₄ but have studied additive mainly composed of, for showing the constant addition of B yield (about 5%) are the main component KBF ₄ It was the case. In this regard, Patent Document 1 describes an example in which KBF ₄ is used as an Al—B mother alloy.

FIG. 13 is a graph showing the yield of B addition by molten metal when KBF ₄ is added by a conventional method. However, as shown in FIG. 13, when KBF ₄ is used as the Al—B mother alloy, a certain yield can be secured with the pure aluminum molten metal, but a sufficient yield can be obtained with the 6000 series aluminum alloy molten metal such as JIS standard A6063. I couldn't get it. A method for improving the yield has been desired for both aluminum and aluminum alloys.

An object of the present invention is to provide a method capable of easily and efficiently improving the yield in the production of an aluminum-based metal in which B (boron) is added to aluminum or an aluminum alloy.

In the present invention, KBF ₄ and Al are mixed to prepare a mixed powder (for example, mixed powder 1 described later), and the molten aluminum or aluminum alloy (for example, molten metal 3 described later) is mixed in the mixing step. The present invention relates to a method for producing an aluminum-based metal, which comprises a molten metal step of adding a mixed powder of KBF ₄ and Al.

In the mixing step, it is preferable that the Al content in the mixed powder is adjusted to be 30% by mass or more and 70% by mass or less.

The molten metal temperature (addition temperature) in the molten metal step is preferably in the range of 650 ° C. or higher and 810 ° C. or lower.

In the molten metal step, it is preferable to add the mixed powder to the molten metal by immersing the mixed powder held in a holding member (for example, a phosphorizer 21 described later) in the molten metal.

Further, the method for producing an aluminum-based metal preferably further includes a step of pouring the molten metal into a mold, solidifying and extruding the molten metal after the molten metal step to produce an extruded profile.

According to the method for producing an aluminum-based metal of the present invention, the yield can be easily and efficiently improved.

It is a figure which shows typically the ball mill used in the mixing process which concerns on this embodiment. It is a figure which shows typically the state that the mixed powder of KBF ₄ and Al was added to the molten metal in the molten metal step which concerns on this embodiment. It is a graph which shows the effect by using the B additive of the Example on the B addition yield of a 6063 aluminum alloy. It is a graph which shows the difference of the B addition yield at the time of changing the Al content in 5w% increments in the range of 30 to 75 wt%. It is a graph which shows the relationship between temperature and BF ₃ dissociation pressure. 6 is an SEM image of the B additive (Al-50 wt% KBF ₄ ) of the example. It is a schematic diagram which shows the mixed state of Al and KBF ₄ in B additive. B additives _(KBF 4 _-50wt% Al) is a graph showing the relationship between the addition temperature and addition of B yields. It is a graph which shows the X-ray diffraction result of the B additive. A reflection electron image and EPMA surface analysis of B additive _(KBF 4 _-65wt% Al). A reflection electron image and EPMA surface analysis of B additive _(KBF 4 _-50wt% Al). It is a graph showing the addition of B yields comparison _KBF 4 _-65wt% Al and KBF ₄ in 6063 aluminum alloy melt. It is a graph which shows the B addition yield by molten metal when KBF ₄ is added by a conventional method.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the method for producing an aluminum-based metal according to an embodiment of the present invention, an Al-B alloy is produced using KBF ₄ as a mother alloy. The aluminum-based metal shall include both aluminum and an aluminum alloy.

Manufacturing method of Al-B alloy, and the melt adding a mixing step of mixing the KBF ₄ powder and Al powder, the pure Al molten or Al alloy melt the mixed powder 1 of KBF ₄ powder and Al powder to the melt, the melt Includes a molding step of extruding the aluminum from a mold to form an extruded profile.

First, the mixing process will be described. FIG. 1 is a diagram schematically showing a ball mill 10 used in powder mixing according to the present embodiment. The ball mill 10 shown in FIG. 1 is a crusher used to mix Al powder and KBF ₄ powder to obtain mixed powder 1.

The ball mill 10 is a planetary ball mill that crushes and agitates an object by the rotation motion of a container 11 containing a stirring ball 12 and the revolution motion of a stage (not shown) in which the container 11 is set. The ball mill 10 is operated at a predetermined rotation speed (for example, 200 rpm) and a predetermined time (for example, 20 minutes) with the Al powder, the KBF ₄ powder, and a plurality of balls 12 for stirring placed in the container 11 and covered with the lid 15. By allowing the mixture to be allowed to obtain a mixed powder 1 in which Al powder and KBF ₄ powder are mixed. In addition to the planetary ball mill, the mixing method in the mixing step may be a method and device for uniformly mixing such as a blender and a mixer, and can be appropriately changed depending on the circumstances.

Next, the molten metal process will be described. FIG. 2 is a diagram schematically showing a state in which the mixed powder 1 of KBF ₄ and Al is added to the molten metal 3 in the molten metal step according to the present embodiment. In FIG. 2, a mixed powder 1 of Al powder and KBF ₄ powder mixed by a ball mill 10 is wrapped in an aluminum foil 2 and set in a phosphorizer 21 and immersed in a molten aluminum or aluminum alloy 3 in a pit 20. Shown. In the molten metal step of the present embodiment, the mixed powder 1 is added and immersed at a temperature of 650 ° C to 810 ° C.

An aluminum foil 2 wrapped with a mixed powder 1 of Al powder and KBF ₄ powder in a state where a mold release agent (for example, Star Coat manufactured by Tokyo Morex Co., Ltd.) is applied to a titanium phosphorizer 21 is applied to the phosphorizer 21. Lock inward. As a method of locking the aluminum foil 2 in which the mixed powder 1 is wrapped in the phosphorizer 21, an appropriate method can be used. The phosphorizer 21 as the holding member may be any one that can set the aluminum foil 2 that wraps the mixed powder 1 and put it in the molten metal 3. The phosphorizer 21 of the present embodiment has a handle portion and a cup-shaped holding portion, and an aluminum foil 2 wrapping the mixed powder 1 is set inside the cup-shaped holding portion. Further, a cup-shaped holding portion having a through hole formed on the peripheral surface thereof can also be used.

In the present embodiment, the mixed powder 1 wrapped in the aluminum foil 2 is immersed in the molten metal 3 for a predetermined time (for example, 5 minutes), and then all the mixed powder 1 is scraped out from the phosphorizer 21 for a predetermined time (for example, 10 seconds to 10 seconds). After stirring for about 20 seconds, let stand for a predetermined time (for example, 30 minutes). Before moving to the next molding step, the mixture is stirred for a predetermined time (for example, 20 seconds), and the molten metal 3 is poured into a mold at room temperature.

In the molten metal step, a method may be adopted in which the molten metal 3 is stirred by a stirring device such as an impeller, and the aluminum foil 2 wrapping the mixed powder 1 of Al powder and KBF ₄ powder is added to the rotating vortex generated by the stirring. .. In this case, it is preferable to rotate the molten metal 3 at a rotation speed that does not scatter by stirring the impeller. Further, it is preferable to apply a release agent similar to that applied to the phosphorizer 21 to the impeller.

In the molding process, the molten aluminum 3 or the molten aluminum alloy 3 in which the mixed powder 1 is melted is poured into a mold at room temperature and extruded from the mold to extrude an aluminum metal (Al-B alloy) containing B. Manufactured as.

According to the present embodiment described above, the following effects are obtained.
The method for producing an aluminum-based metal of the present embodiment includes a mixing step of mixing KBF ₄ and Al to prepare a mixed powder 1, and mixing of KBF ₄ and Al mixed in a molten aluminum or aluminum alloy 3 in the mixing step. It includes a molten metal step of adding powder 1.
As a result, the yield of aluminum or an aluminum alloy can be effectively improved by adding a mixture of KBF ₄ powder and Al powder as a reaction aid to the molten metal as a B additive chemical.

Further, in the mixing step of the present embodiment, the Al content in the mixed powder 1 is adjusted to be 30% by mass or more and 70% by mass or less.
In this way, by increasing the Al content, the specific surface area of KBF ₄ can be increased and the reaction of Reaction Scheme 1 can be promoted, so that the molten metal step can be performed at a lower temperature and in a shorter time, and the yield is further improved. At the same time, the manufacturing process can be shortened.

Further, in the present embodiment, the molten metal temperature in the molten metal step is in the range of 650 ° C. or higher and 810 ° C. or lower.
As a result, since the target yield can be satisfactorily controlled, the temperature can be set according to the target yield, and the B-containing aluminum-based metal can be produced with the yield according to the manufacturing equipment and the production purpose. For example, a range of 760 ° C. or higher and 810 ° C. or lower is preferable from the viewpoint of improving the yield. Further, from the viewpoint of suppressing fuel costs during manufacturing, the range of 650 ° C. or higher and lower than 760 ° C. is preferable. In this way, by adjusting the temperature in the range of 650 ° C or higher and 810 ° C or lower according to the purpose, the yield can be controlled according to the restrictions of manufacturing equipment and production targets, and various production requirements can be flexibly met. Can be done. The temperature range shown as a preferable range (760 ° C. or higher and 810 ° C., 650 ° C. or higher and lower than 760 ° C., etc.) is relative and is an example. The use of the present invention is not limited to the illustrated range. For example, the yield improvement can be improved even in the range of 650 ° C. or higher and lower than 760 ° C.
Further, when KBF ₄ is used as an additive, Al and B react with each other, so that it depends on the reaction temperature. However, when AlB ₂ is used as the mother alloy of B, it is already AlB ₂ , so that it is as in the present embodiment. It is difficult to adjust the B-added yield depending on the temperature, and this also has an advantageous effect.

Further, in the molten metal step of the present embodiment, the mixed powder 1 is added to the molten metal 3 by immersing the mixed powder 1 held in the phosphorizer 21 as a holding member in the molten metal.
As a result, since it is held by the phosphorizer 21, the mixed powder 1 of KBF ₄ powder and Al powder is not dispersed in the molten metal, so that the reaction of reaction formula 1 can be efficiently caused and the yield is further improved. Can be made to. Further, as compared with the case of stirring using an impeller, oxygen and the like are less likely to be mixed, so that the reaction can proceed efficiently.

Further, the method for producing an aluminum-based metal of the present embodiment further includes a step of pouring the molten metal 3 into a mold, solidifying and extruding the molten metal 3 after the molten metal step to manufacture an extruded profile.
As a result, since the brilliance is improved by adding B, the extrusion speed is improved and a highly productive method for producing an extruded profile can be realized.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be appropriately modified.

Next, examples of the present invention will be described. In this example, as a comparative example, an Al-B alloy produced by using KBF ₄ which is not mixed with aluminum powder as a boron-added chemical, and as an example, a mixture of KBF ₄ powder and aluminum powder is used as a boron-added chemical. The B-added yield of the produced Al-B alloy was evaluated. The conditions of each process will be described.

The B-added yield in the present specification uses the value (theoretical value) when KBF ₄ is added and B is dissolved in 100% aluminum or an aluminum alloy as the denominator, and the value of B actually dissolved in the numerator (actual measurement). Value). The measured value was measured in a state where aluminum or an aluminum alloy was solidified.

In the mixing step, powder mixing was performed using a planetary ball mill P-6 manufactured by Fritsch. In this embodiment, the container 11 into which the object to be mixed is placed is made of 500 ml of aluminum, and the container 11 is covered with a lid 15 in a state where 20 balls 12 having a diameter (Φ) of 20 mm made of aluminum are placed in the container 11, and the rotation speed is 200 rpm. It was mixed for 20 minutes. The mixed powder 1 obtained by one mixing is 100 g.

In the molten metal step, the 6063 aluminum alloy was dissolved in the graphite crucible 20. The amount of dissolution per time is 900 g, and the B additive (Examples and Comparative Examples) is added to the molten metal 3 of the crucible 20 at a predetermined addition temperature by the addition method 1 under the following conditions with a target composition of 0.03% B. , B addition yield was evaluated. For comparison, pure aluminum was dissolved under the same conditions to evaluate the B-added yield.
Addition method 1:
The impeller was rotated at a rotation speed of 580 rpm (the maximum value at which the molten metal did not scatter), stirred for 5 minutes, and then poured into a columnar mold at room temperature for casting.

Table 1 is a table showing the difference in the B addition yield depending on the alloy type when KBF _{4 is} added in the comparative example. Although the yield of adding B reached 44% for pure Al, it was only 5% for the 6063 aluminum alloy, indicating that it is more difficult to add boron to the 6063 aluminum alloy than for pure Al by the conventional method.

Table 2 is a table showing the differences of B added yield due to alloying in _KBF 4 _-50wt% Al embodiment. In Table 2, commercially available aluminum powder KBF ₄ (≧ 99.7%, particle size 30 [mu] m) B added yield in _KBF 4 _-50wt% Al which confuse is shown. Note _that the KBF 4 -50wt% Al, a ratio of Al (mass%) in KBF ₄ powder and Al _powder, KBF 4 in -50wt% Al KBF ₄ is 50 mass%, Al powder 50% Indicates that. _Further, the KBF 4 -65wt% Al, indicating that KBF ₄ is 35 wt% Al powder is 65% by mass.

As shown in Table _2, B addition yield upon addition of KBF 4 -50wt% Al is improved pure Al even 58% and addition of B yield ratio, and 43% compared to the comparative example is 6063 aluminum alloy It was shown that the B-added yield was significantly improved.

Next, the addition method and the influence of the addition temperature (melt temperature) on the B addition yield when the 6063 aluminum alloy is used as the molten metal 3 will be described. The addition method 1 uses the above-mentioned impeller, and the addition method 2 uses the phosphorizer 21 performed under the following conditions. The other conditions are the same as the conditions of the mixing step and the molten metal step described above.
Addition method 2:
The B additive wrapped in the aluminum foil 2 is packed in the phosphorizer 21 and pushed into the molten metal 3 to react for 5 minutes, then the entire contents of the phosphorizer 21 are scraped off, stirred for 10 to 20 seconds, and then allowed to stand for 30 minutes. Then, the mixture was stirred again for about 20 seconds before pouring, and then cast into a columnar mold at room temperature.

Table 3 shows the effects of the addition method 1, the addition method 2, and the addition temperature on the B addition yield. In Table 3, the difference between the addition method 1 and the addition method 2 at the addition temperature of 760 ° C. in the molten metal step is shown in the B addition yield performed in Comparative Examples and Examples, and the B addition method 2 when the addition method 2 is selected at the addition temperature of 810 ° C. The added yield is shown.

In Table 3, the B addition yield in the 6063 aluminum alloy is superior to the addition method 2 using the phosphorizer 21 than the addition method 1 using the impeller, and that the temperature is 810 ° C rather than 760 ° C in the examples. However, it is shown that the yield of adding B is high.

FIG. 3 is a graph showing the effect of the use of the B additive in the examples on the B addition yield of the 6063 aluminum alloy, and summarizes the results of Tables 1 to 3. As shown in FIG. 3, when the reference B added yield due KBF ₄ alone of Comparative _Example, by using as an additive KBF 4 -50wt% Al, B addition yield is improved 900%. Further, in the melting step, the addition of the B-added chemical by the addition method 2 achieves a + 200% improvement in the B-added yield by raising the addition temperature to 810 ° C. That is, in the examples, by selecting the addition method 2 and setting the addition temperature to 810 ° C., the addition temperature is 760 ° C., and the B addition yield is improved by about 1500% as compared with the B addition yield of the comparative example performed in the addition method 1. It has been realized. As a result, it was clarified that a B-added yield comparable to that when Al-4 wt% was used as the B-added chemical at an addition temperature of 700 ° C. could be realized.

Next, the influence of the Al content in the B additive chemical will be described. FIG. 4 is a graph showing the difference in the B addition yield when the Al content is changed in 5 w% increments in the range of 30 to 75 wt%. The addition temperatures are 760 ° C. and 810 ° C., and in the melting step, the B additive chemical is added to the molten metal 3 by the addition method 2.

As shown in FIG. 4, at any of the addition temperatures, the B addition yield is improved as the Al content is increased. The maximum value of the B-added yield at the addition temperature of 760 ° C. is 67%, whereas the maximum value of the B-added yield at the addition temperature of 810 ° C. is remarkable, and the increase tendency of the B-added yield with the increase of the Al content is remarkable and exceeds 50 wt% Al. And, it exceeds the B addition yield level of Al-4 wt% B mother alloy and reaches about 90% at 50 wt% Al or more. By controlling the Al content in the B additive in this way, the B additive yield can be dramatically improved (1800% increase). The B-added yield of the aluminum alloy can be remarkably improved.

Next, the mechanism for improving the yield will be described. First, the relationship between the physical property value and temperature of KBF ₄ and the dissociation pressure of BF ₃ used in the following description will be described.

Although the physical and chemical properties of KBF ₄ are described in research papers and safety data sheets, there are various reports on the melting point and its decomposition. In the following explanation, the explanation will be based on the physical property values of the literature (Hideo Ohno, Kazuo Furukawa: JAERI-M 5053, (1972)) in which the physical property values of the inorganic melt are summarized by the Japan Atomic Energy Research Institute. According to this document, KBF ₄ undergoes a phase transition at a melting point of 570 ° C. and 283 ° C., and transforms from a low temperature phase (orthorhombic structure) to a high temperature phase (NaCl type face-centered cubic lattice).

FIG. 5 is a graph showing the relationship between temperature and BF ₃ dissociation pressure. KBF ₄ is decomposed into solid KF (s) and gaseous BF ₃ (g) by heating, and there is a relationship shown in FIG. 5 between the temperature and the BF ₃ dissociation pressure. In this way, it can be said that the decomposition temperature is determined by the BF ₃ dissociation pressure. The BF ₃ dissociation pressure gradually increases from around 600 ° C., and the decomposition reaction is particularly remarkable from around 750 ° C., and it is considered that KBF ₄ is completely decomposed in a short time. At each temperature, it decomposes until it reaches a fixed BF ₃ dissociation pressure, but since it is an experiment in an open system, it does not reach an equilibrium state, and the temperature at which the dissociation pressure reaches 1 atm is 930 ° C.

Next, the mechanism for improving the yield by mixing Al powder and KBF ₄ powder will be described.

Figure 6 is an SEM image of the embodiment of B additive _{(Al-50wt% KBF 4 =} KBF 4 -50wt% Al) KBF 4, be SEM image of low magnification compared to (a) is (b) , (B) is an enlarged SEM image of KBF ₄ .

As shown by the arrow in FIG. 6A, agglomerates of KBF ₄ are present between the rounded Al particles. Further, KBF ₄ fine particles are attached to the surface of the Al particles. When the B additive in such a state is heated, Al and KBF ₄ cause an intersolid reaction shown in Reaction Scheme 1.
(Reaction formula 1)
KBF ₄ (s) + 3Al (s) → 2AlB ₂ (s) + KAlF ₄ (s) [490 ° C]

In this embodiment, the B additive is wrapped in aluminum foil and then added to the molten metal 3. Therefore, it is considered that the B additive is dispersed in the molten metal 3 after causing the reaction of the reaction formula 1 immediately after the addition regardless of the addition method of the addition method 1 or the addition method 2.

When the addition method 1 and the addition method 2 are compared with each other, the method of filling the phosphorizer 21 of the addition method 2 with the B additive and adding it to the molten metal 3 can suppress the dispersion of the B additive in the molten metal 3. It can be said that it is advantageous in efficiently causing the reaction of Reaction Scheme 1. As a result, it is considered that the addition method 1 was able to achieve a higher addition yield at a lower temperature than the addition method 2.

As shown in the graph of FIG. 4, it is clear that the increase in Al content is a reaction promoter of Reaction Scheme 1.

Next, the relationship between the Al content and the yield will be described. FIG. 7 is a schematic view showing a mixed state of Al and KBF ₄ in the B additive. Specific gravity gamma _KBF4 of KBF ₄ at room temperature is 2.5, the specific gravity gamma _Al of Al is 2.7, can be regarded as γ _KBF4 ≒ γ _Al. Each particle (aggregate) considered cubes of the same size, it is they that the simulating KBF ₄ -50wt% Al when mixed randomly in FIG 7 (a). _Similarly, it simulates a mixed state of KBF 4 -65wt% Al is (b) in FIG.

By (a) (b) of FIG. _7, it can be seen that the direction of _KBF 4 _-65wt% Al as compared with KBF 4 -50wt% Al is discrete distribution form. _Thus, the specific surface area of KBF ₄ in KBF 4 -65wt% Al (surface area / volume) _is 1.36 times greater than KBF 4 -50wt% Al. As a _result, towards the KBF 4 -65wt% Al is considered to reaction rate of the reaction formula 1 is large. From this simulation result, it was found that the increase in Al content brings about an increase in the specific surface area of KBF ₄ and promotes the reaction of Reaction Scheme 1, so that B can be added at a lower temperature and in a shorter time.

Next, the relationship between the addition temperature and the yield will be described. Figure 8 is a graph showing the relationship between B additives _(KBF 4 _-50wt% Al) addition temperature and addition of B yields.

As shown in FIG. 8, the B addition yield increases as the molten metal temperature (addition temperature) rises. This suggests that there are reactions other than Reaction Scheme 1 that are more likely to occur at higher temperatures. For example, in Reaction Scheme 1, unreacted KBF ₄ reaches its melting point at 570 ° C.
KBF ₄ (s) → KBF ₄ (L) [570 ° C]

Then, when the temperature exceeds 570 ° C., the reaction formula 1 becomes the following reaction formula 2.
(Reaction formula 2)
2KBF ₄ (L) + 3Al (L) → 2AlB ₂ (s) + 2KAlF ₄ (s)

Since KAlF ₄ reaches its melting point at 590 ° C., the reaction between flux (KBF ₄ + KAlF ₄ ) and Al thereafter occurs. Here, it is considered that the flux tends to separate from the molten Al. Further, as shown in FIG. 5, when the temperature exceeds 750 ° C., the following decomposition reaction becomes remarkable.
(Reaction formula 3)
BF ₄ (L) ⇔ KF (s) + BF ₃ (g)

According to the reaction formula 3, it is considered that BF ₃ is also generated from KBF ₄ or dross sludge containing it. When BF ₃ comes into contact with the molten metal, the reaction formula 4) shown below may occur.
(Reaction formula 4)
BF ₃ (g) + Al (L) ⇔ B (s) + AlF ₃ (s)

Standard Gibbs free energy change .DELTA.G _T ^o of the reaction in Scheme 4, if always negative (e.g., 810 ° C. In ΔG ₈₁₀ ^o = -150J / mol) and from becoming the pressure _{P BF3} of BF ₃ is 1atm at or above room temperature If so, the reaction proceeds to the right. However, the pressure of BF ₃ reaches 1 atm at 930 ° C. as described above. Accordingly, 810 in ° C., the ΔGT the relationship of ^{_{ΔG T = ΔG T o + RTlnK}} p = -150 + 9004.5ln (1 / P BF3). _Thus, <in 0.98atm, ΔGT> P BF3 0, and therefore, the reaction will not proceed in the right direction. However, considering the temperature dependence of the B addition yield, the reaction formula 4 cannot be ignored. For example, assuming the generation of microscopic BF ₃ bubbles in the molten metal, there may be a case where P _BF3 > 1 atm. Since BF ₃ has a specific gravity about 2.3 times that of air, it tends to stay in the furnace, but considering the partial pressure, it is considered that the reaction does not occur through the surface of the molten metal.

Next, the mechanism of formation of AlB ₂ by KBF ₄ powder and Al powder in the B additive will be described.

FIG. 9 is a graph showing the X-ray diffraction results of the B additive. When B additives have been added to the 6063 aluminum melt, to clarify whether caused what phase change or reaction product by heating, compacting the KBF ₄ -50wt% Al in a hydraulic press, an electric furnace After heating at the set temperature of 100 ° C. to 1000 ° C. in 100 ° C. increments for 20 minutes, the presence or absence of reaction products was examined by qualitative analysis by X-ray diffraction and electron probe microanalyzer (EPMA).

For X-ray diffraction, the tube voltage was 45 kV and the tube current was 200 mA. The analysis conditions by EPMA are an accelerating voltage of 15 kV, a beam current of 100 nA, an analysis area of 120 × 90 μm, a measurement pitch of 0.3 μm, an image size of 400 × 300 pixcel, and an integration time of 10 ms / point. The spectroscopic crystal for B detection was LSA120. The reason for the compaction molding is that it is used for microstructure observation after heating.

(A) in FIG. 9 is an X-ray diffraction result after heating the B additive to 500 ° C. at every 100 ° C. while flowing argon in an electric furnace. Up to 300 ° C, only the peaks of the additive components (Al and KBF ₄ ) were confirmed, but above 400 ° C, the peak of KBF ₄ disappeared, and instead the peaks of AlB ₂ and KAlF ₄ were newly confirmed. No change in the position of the diffraction peak due to the phase transformation from the low temperature phase to the high temperature phase occurring at 283 ° C. was confirmed.

FIG. 9B in FIG. 9 shows the result of X-ray diffraction after heating from 600 ° C. to 1000 ° C. at every 100 ° C. as in (a). It was confirmed that the position of the diffraction peak hardly changed even at 600 ° C. or higher, and that there were three constituent phases, Al, AlB ₂ and KAlF ₄ . Note that the X-ray diffraction were similar results were obtained for the case of _KBF 4 _-50wt% Al.

From the result of (b) in FIG. 9, it can be seen that when the mixed powder 1 in which KBF ₄ and Al powder are mixed is preheated at 800 ° C., an Al−B compound is formed. The one in which such an Al-B compound was formed was added to the above-mentioned molten aluminum alloy, but B was not contained in the molten metal at all. It is presumed that this is because the by-products produced by preheating adhered to the Al-B compound and hindered the wettability with the molten metal. From this, it can be seen that it is preferable to add KBF ₄ and Al powder with a phosphorizer 21 after milling.

Figure 10 is a reflection electron image and EPMA surface analysis of B additive _(KBF 4 _-65wt% Al). In the analysis shown in FIG. _10, compacting the KBF 4 -65% Al, it was heated to 800 ° C. in an argon atmosphere. In the backscattered electron image, the black part represents the part having a lower average atomic number than the parent phase Al, and in the surface analysis result, it corresponds to the part having a large amount of B.

From the surface analysis results shown in FIG. 10, it can be seen that the elements B, F and K to be analyzed are all finely dispersed in the sample. The distribution positions of F and K overlap, but B exists independently of these elements. Further, when the portion having a high B concentration in FIG. 8 was quantitatively analyzed by EPMA, it was confirmed that the mol ratio of Al and B was approximately 1: 2. Taken together with the X-ray diffraction results, portion of high B concentration _{portion AlB} 2, F and K are overlapped can be said to be KAlF _4. From the above, it was histologically confirmed that in the process of adding the B additive, fine AlB ₂ particles were formed and spread in the molten metal to carry out the B addition. Further, it is considered that KBF ₄ is almost completely changed to AlB ₂ and KAlF ₄ by the solid phase reaction (reaction formula 1).

Figure 11 is a reflection electron image and EPMA surface analysis of B additive _(KBF 4 _-50wt% Al). The reflected electron image and the EPMA surface analysis result of the sample treated in the same manner as the analysis in FIG. 10 are shown.

As shown in FIG. 11, the main products are AlB ₂ and KAlF ₄ as in FIG. Further, KBF ₄ content in the B additive since more than _KBF 4 -65% Al, the amount produced of them also appear to have increased than that observed in (b) in FIG. In addition, as shown by the arrows in FIG. 11, many places in KAlF ₄ where only the F concentration was high were observed. Although not confirmed by X-ray diffraction, this suggests the formation of AlF ₃ , that is, the above-mentioned reaction equation 4 occurred, that is, the decomposition of KBF _{4 in} the flux (KBF ₄ + KAlF ₄ ). In FIG. _6, KBF 4 -50% Al is believed the reaction rate for a small specific surface area of KBF ₄ compared with KBF ₄ -65% Al is reduced. FIG. 10 shows the result after heating the B additive in a powder-molded state for 20 minutes, but in reality, the B additive is dispersed in the molten metal in a short time after the addition. The above _results, compared to the case of _{KBF 4 -65% Al, KBF 4} KBF 4 less consumed by -50% Al In Scheme 1, B is added is made based on Scheme 2 and Scheme 4 It shows that the ratio is high.

As a result of the above X-ray diffraction and EPMA analysis, it was clarified that the reaction of Reaction Scheme 1 easily occurs from a low temperature of around 400 ° C. and fine AlB ₂ is produced. Further, since the decrease in the Al content reduces the specific surface area of KBF ₄ and reduces the reaction rate of the reaction formula 1, the reaction amount of the reaction formula 1 in the B additive is reduced, and the reaction formula 2 in the addition of B is reduced. And it was found that the dependence of the reaction formula 4 becomes large.

It is considered that there are mainly two reactions related to the addition of B. One is the reaction formula 1 due to the solid phase reaction when the B additive is added, and the other is the reaction formula 4 due to the generation of BF ₃ at high temperature. By adjusting the production conditions so as to promote the reaction of both or any of these, it is possible to improve the yield of adding B. For _example, use as additives KBF 4 -50wt% Al, by setting the addition temperature to 810 ° C. In addition method 2, the conventional ratio 1500% of B added yield improvement have been made, Al-4 wt% B master alloy added Occasionally comparable B-added yields were obtained. Further, it was clarified that the B addition yield was dramatically improved (1800% increase) by adjusting the Al content, the addition method and the addition temperature in the B additive. For _example, KBF 4 _-50wt% higher B addition yield (90%) of Al is shown.

Figure 12 is a graph showing the addition of B yields comparison _KBF 4 _-65wt% Al and KBF ₄ in 6063 aluminum alloy melt. The conditions are the same as those described above. Conventionally, even if KBF ₄ is added to the 6063 aluminum alloy molten metal, a good yield cannot be obtained (see FIG. 13). However, as shown in FIG. 12, if Al powder is mixed with KBF ₄ by the method for producing an aluminum-based metal of the present embodiment, the yield of adding B can be significantly improved as compared with adding KBF ₄ alone to the molten metal. .. In Figure 12, 700 ℃, 750 ℃, in any case of 800 ° C., greater yield than those who _KBF 4 _-65wt% Al mixed with Al powder KBF ₄ was added to the melt at KBF ₄ alone It is improving. From this, it can be seen that the method for producing the aluminum-based metal of the present embodiment realizes a new B-adding technique that is inexpensive and highly reliable for improving the brilliance of the aluminum-based metal.

The present invention is not limited to the above-described embodiments, examples and measurement results, and its configuration and method can be appropriately changed depending on the circumstances.

1 Mixed powder of KBF ₄ and Al 2 Aluminum foil 3 Molten metal 21 Phosphorizer (holding member)

Claims (4)

A mixing step of mixing KBF ₄ and Al to make a mixed powder,
A molten metal step of adding a mixed powder of KBF ₄ and Al mixed in the mixing step to a molten aluminum or an aluminum alloy is included.
In the molten metal step, a method for producing an aluminum-based metal, in which the mixed powder held in a holding member while being wrapped in an aluminum foil is immersed in the molten metal to add the mixed powder to the molten metal. The method for producing an aluminum-based metal according to claim 1, wherein in the mixing step, the Al content in the mixed powder is adjusted to be 30% by mass or more and 70% by mass or less. The method for producing an aluminum-based metal according to claim 1 or 2, wherein the molten metal temperature in the molten metal step is in the range of 650 ° C. or higher and 810 ° C. or lower. The method for producing an aluminum-based metal according to any one of claims 1 to 3 , further comprising a step of pouring the molten metal into a mold, solidifying and extruding the molten metal after the molten metal step to produce an extruded profile.