JP5680244B1 - Alloy refinement method and precipitate refinement apparatus used therefor - Google Patents

Abstract

[PROBLEMS] To improve the performance of an alloy by increasing the expression of a nucleating element while maintaining a molten state and suppressing the growth of precipitates that grow around the nucleating element. Provided is a precipitate refinement method for an alloy and a precipitate refinement apparatus used therefor. An alloy precipitate refinement method is a method in which precipitates are refined in the course of cooling an Al or Mg hypereutectic alloy melt 11, which is higher than the liquidus temperature TL of the hypereutectic alloy. From the temperature T1 set high within the range of 2 to 10%, it is higher than the solidus temperature TS of the hypereutectic alloy and lower than the liquidus temperature TL within the range of 10% or less. The molten metal 11 is stirred until the set temperature T2. A precipitate refining apparatus 10 used in the alloy precipitate refining method has a stirring means 12 that is immersed in the molten metal 11 to stir the molten metal 11. [Selection] Figure 1

Description

The present invention relates to a manufacturing technique for an Al (aluminum ) hypereutectic alloy, and more specifically, an alloy precipitate refinement method for improving alloy performance and a precipitate refinement used therefor. Relates to the device.

It is known that an alloy can improve material properties such as strength and elongation by refining crystal grains. The refinement of the crystal grains is performed, for example, by a method of adding an additive other than the main element.
However, even if the above-described method is used, it has not been possible to meet the market demand for a higher performance alloy in recent years, and a search for new methods that do not rely only on the addition of additives continues.

  For example, there is a method of refining crystal grains (secondary precipitates) by applying pressure (extrusion, forging, rolling) or heat treatment to solidified state products (crystal grains that have been generated largely). . This is a technique that has been generally performed with the development of additive elements.

In addition, a method for rapidly cooling a liquefied molten metal to suppress the growth of crystal grains and miniaturizing the crystal grains has been known in recent years and has begun to be put into practical use.
The necessity of temperature control for improving the alloy performance as well as improving the yield rate of molded products has begun to be well known. In recent years, it has become possible to rapidly cool molten metal by controlling the temperature of the mold by not only heating the mold but also installing a cooling line in the mold. For example, there is a molding of an Al alloy containing high Si (silicon) aiming at improvement of strength which is a mechanical property.

In addition, in the cooling process from the temperature just above the liquidus line to the temperature just above the solidus line, an external action such as stirring is given to the molten metal in the liquefied state to produce a solid-liquid coexisting (semi-solidified) state metal slurry, In recent years, techniques for reducing the size of crystal grains have been well known.
For example, the molten metal is stirred in the above temperature range, the crystal grains of the main alloy compound are formed round and small, and the mechanical pressure applied until forming (solidification) is performed between the solid phase grains. This is a technology that improves the properties such as strength by allowing the liquid phase intervening to flow in a semi-solid state that plays a role of lubrication and deforming it by solidifying it in a state where the crystal grains are refined. is there.

  As mentioned above, as a method of improving the mechanical properties of the alloy, many studies of technology for reforming crystal grains have been conducted, except when reviewing the selection of the main element itself, Even when the method described above is used, there are the following problems.

  First, since the method of modifying the crystal grains of the solidified state is a modification from a state in which the number of crystals is determined, there is a limit to miniaturizing the crystal grains.

In addition, the method of rapidly cooling the liquefied molten metal from the liquefied state to solidifying is a technique for refining the crystal grains from the molten state, and is therefore effective for refining the crystal grains. Means.
However, when pouring molten metal into a mold having a product shape, it is necessary to spread the molten metal throughout the mold, and during this time cooling cannot be performed, and the generated primary crystals and eutectics grow. In addition, in the case of sand mold molding or the like, the cooling operation becomes more difficult, so there is a limit to the refinement of crystal grains (primary precipitates).

And in the semi-solidification method that gives external action such as stirring to the molten metal in the liquefied state and produces the metal slurry in the solid-liquid coexistence state, in order to mix the solid phase and the liquid phase, increase the number of solid phases. This is considered to be a sufficient method for suppressing the growth of crystal grains.
However, since the viscosity of the metal slurry increases as the solid phase ratio increases, the casting method that can be used is limited. Therefore, it is extremely difficult to manage the solid phase ratio and it is difficult to ensure stable quality.

When the crystal state of the Al alloy at the time when the refinement of crystal grains was not taken into consideration was confirmed with a microscope or the like, for example, as shown in FIG. 11, the crystal was enlarged and could not be said to be dense.
For this reason, in recent years, as shown in FIG. 12, the densification of the crystal is fixed to a certain degree by the combined use of the material technology using the additive element to which Ti (titanium) or B (boron) is added and the above-described processing process. It has become possible.

In particular, in the modification technology by the action of additive elements, additive elements have been devised and put into practical use for various purposes.
For example, an Al—Si—Cu (copper) -based alloy called ADC12 that is an Al alloy contains elements such as Cu, Si, Zn (zinc), and Fe (iron) in addition to Al as a main raw material. It is composed of that. This Al alloy is said to have good mechanical properties, machinability, and castability, and is widely used. Among them, Si plays an important role as an element that improves strength, which is a mechanical property. Yes.

The Al alloy described above contains about 12.7% by mass of Si.
In the process from the liquefied state to the solidification due to the temperature drop, as shown in FIG. 13, primary Al (Al) and eutectic Si are generated as primary precipitates in this Al alloy, and the eutectic Si fineness shown in FIG. As a result, the effect increases. In addition, by performing appropriate refinement, the tensile strength, which is a mechanical property, is increased by approximately 20% or more, and the elongation is increased by approximately 2 to 3 times as compared with a state in which refinement is not performed.

Traditionally, the technology that has been generally used to refine primary precipitates has the purpose of increasing the role of the elements that make up the alloy, although the additive elements themselves do not lead to improved mechanical properties. Techniques for further adding the elements described above are widely used.
In the case of the above-described Al alloy of ADC12, Si as a constituent element is an element for the purpose of improving the strength. According to the state diagram shown in FIG. 15, the amount of Si normally contained in ADC12 (≈12.7). % By mass), a eutectic (formation of needles) is produced by the eutectic reaction at the eutectic point (temperature 577 ° C.). If this eutectic Si grows long in the shape of needles, disadvantages such as easy cracking occur. Usually, the addition of Na (sodium) or Sr (strontium) suppresses the growth of eutectic Si and makes it fine. It is planned.
In this case, the nucleating element of Al is Ti or B, and the nucleating element of Si is P (phosphorus).

  In addition, a new technology that attempts to refine crystal grains by combining the above-described processing processes and additives, such as adding further fine Si particles, which are contained alloys, to semi-solidified materials. Etc. are also born (see, for example, Patent Document 1).

JP 2012-126959 A

As shown in FIG. 15, in a high-content Si alloy (hypereutectic alloy) in which the Si concentration (Si content or Si content) is increased to, for example, 13% by mass or more with the aim of further improving the strength as the alloy performance. Then, nuclei are formed from a higher temperature range, primary crystal Si (pointed granular material) is generated, and growth starts.
In particular, when the Si content is 20% by mass, the temperature at which nuclei are formed and the generation of primary crystal Si is about 650 ° C., and thereafter growth is started. Thereafter, as shown in FIG. Will be generated.

As a method for refining crystal grains in this case, for example, there is a method in which the addition of P is increased to increase nucleation (smaller each crystal) as shown in FIG. In this state, it cannot be added to the molten metal. Therefore, it performs the additive as a mixture with Cu, reaction with Na contained in the molten metal: by (P + 3Na Na 3 _P), the addition of certain level or higher from losing efficacy, there is a limit to the introduction of P .
That is, even if the above-described method is used, there is a limit to crystal miniaturization, and complete miniaturization cannot be achieved.

  The present invention has been made in view of such circumstances, and while maintaining a molten (liquefied) state, the expression of a nucleation element is increased, and the growth of precipitates that grow around the nucleation element is suppressed. Accordingly, an object of the present invention is to provide an alloy precipitate refinement method and a precipitate refinement apparatus used therefor capable of improving the alloy performance.

An alloy precipitate refinement method according to the first aspect of the present invention that meets the above-mentioned object is a method for refinement of precipitates in a cooling process of a molten alloy of an Al hypereutectic alloy having a Si concentration of 13% by mass or more. ,
The liquidus temperature of the hypereutectic alloy is TL (° C.),
From a temperature T1 (° C.) within a range of TL × 1.02 or more and TL × 1.10 or less,
Higher than the solidus temperature TS (° C.) of the hypereutectic alloy and up to a temperature T 2 (° C.) in the range of TL × 0.90 to TL × 0.98 ,
When the molten metal is stirred across the liquidus temperature TL (° C.) of the hypereutectic alloy ,
A stirring rod having a spiral projection on the outer peripheral surface is immersed in the molten metal, and the molten metal is stirred by vibrating the stirring rod in the axial direction .

In the alloy precipitate refinement method according to the first aspect of the invention, Fe and Si may be used as an alloy element on the condition that the hypereutectic alloy is an Al alloy.

In precipitates finer methods of the alloy according to the first invention, agitation of the molten metal can also be carried out using one or both either mechanical and electromagnetic.

The precipitate refiner according to the second invention that meets the above-mentioned object is a precipitate refiner used in the precipitate refinement method for an alloy according to the first invention, and comprises a stirring means provided with the stirring rod. Have.

In precipitates atomizer according to the second invention, the agitation means, but it may also have a rotatable stirring blade about the axis.
Here, the stirring means is further provided at a distance around the stirring blade, but it may also have a plurality of stirring rods that can vibrate in the axial direction.

  In the precipitate refinement apparatus according to the second invention, the area occupied by the stirring means on the surface of the molten metal is preferably 30% to 60% of the area of the surface of the molten metal.

An alloy precipitate refinement method and a precipitate refinement apparatus used therefor according to the present invention include a solution of a hypereutectic alloy in a cooling process of an Al hypereutectic alloy melt having a Si concentration of 13% by mass or more. Since the molten metal is stirred in the range from the temperature T1 (° C.) to the temperature T2 (° C.) straddling the phase line temperature, the expression of the nucleation element can be increased while the molten metal state is maintained. As a result, the growth of precipitates that grow centering on the nucleation element can be suppressed, so that the crystal grains can be refined, and as a result, the alloy performance can be improved.

  In particular, the precipitate refiner used in the alloy refinement method has an agitating means for agitating the melt by immersing it in the melt, so that the performance of the alloy can be improved with a simple configuration.

It is a perspective view of the precipitate refinement | miniaturization apparatus used for the precipitate refinement | miniaturization method of the alloy which concerns on one embodiment of this invention. It is explanatory drawing which shows the internal structure of the stirring rod of the stirring means of the deposit refinement | miniaturization apparatus. It is explanatory drawing which shows the flow of the molten metal at the time of use of the deposit refinement | miniaturization apparatus. It is a perspective view of the precipitate refinement | miniaturization apparatus used for the precipitate refinement | miniaturization method of the alloy which concerns on other embodiment of this invention. It is explanatory drawing which shows the flow of the molten metal at the time of use of the deposit refinement | miniaturization apparatus. 1 is a schematic view of a high Si content Al alloy (primary crystal Si) manufactured by applying the alloy precipitate refinement method according to Example 1. FIG. It is a schematic diagram of the high Si content Al alloy (primary crystal Si and eutectic Si) manufactured by applying the precipitate refinement method of the same alloy. (A) is a micrograph (× 500) of a die cast alloy cross section of a high Si content (Si: 14% by mass) Al alloy according to a conventional example, and (B) is a micrograph (× 200) of the die cast alloy cross section. . (A) is a micrograph (× 500) of a die-cast alloy cross section of a high Si content (Si: 14% by mass) Al alloy manufactured by applying the method for refinement of precipitates of an alloy according to Example 2, (B) is It is the microscope picture (x200) of the same die-cast alloy cross section. It is a graph which shows the influence which the casting method has on the tensile strength of an alloy. It is a schematic diagram of Al alloy (crystal). It is a schematic diagram of Al alloy (densified crystal). It is a schematic diagram of Al alloy (ADC12: Si concentration 12.7 mass%). It is a schematic diagram of Al alloy (ADC12: refined eutectic Si). It is explanatory drawing of the phase diagram of Si containing Al alloy. It is a schematic diagram of high Si content Al alloy (primary crystal Si and crystal Si). It is a schematic diagram of high Si content Al alloy (refined primary crystal Si and crystal Si).

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, a precipitate refiner (hereinafter also simply referred to as a refiner) 10 used in an alloy precipitate refiner method according to an embodiment of the present invention will be described with reference to FIGS.

The precipitate refiner 10 includes an agitation means 12 for agitating the molten metal 11 by immersing it in a molten metal 11 of an Al or Mg hypereutectic alloy (hereinafter also simply referred to as an alloy).
The stirring means 12 has a plurality of (three in this case) stirring rods 14 that are attached and fixed to the plate 13 so as to protrude downward and can vibrate in the axial direction.
Each stirring bar 14 includes a bottomed tube 16 provided with a spiral projection 15 on the outer peripheral surface. Note that a heater 17 and a thermocouple 18 for temperature management are inserted and arranged in a tube 16 of one stirring rod among the plurality of stirring rods 14.

The tube 16 is made of a material having a high melting point and high strength (for example, stainless steel or ceramics) in consideration of the reaction with the alloy that has become the molten metal 11 (suppressing and further preventing elution into the molten metal 11). It is preferable to select.
The tube 16 may be manufactured in a tubular shape in advance, or may be formed by machining or the like in a solid bar so that the heater 17 and the thermocouple 18 can be inserted. . In addition, a stirring rod can also be made into a bar, without making it tubular, In this case, a heater and a thermocouple are provided separately.

Further, it is preferable to use the same material as that of the tube 16 for the material of the spiral protrusion 15 provided on the outer peripheral surface of the tube 16.
The spiral protrusion 15 may be separately attached to the tube 16 or may be configured integrally with the tube 16.
Here, when the spiral protrusion is separately attached to the pipe, a wire or plate material of the same quality as the pipe is preferably attached and fixed to the outer peripheral surface of the pipe by welding or the like, and the spiral protrusion is configured integrally with the pipe. In this case, the outer periphery of the bar is preferably processed into a spiral shape or a hook shape.

A vibration motor 19 serving as a vibration generation source is installed on the side of the plate member 13.
As a result, by operating the vibration motor 19, kinetic energy (vibration motion) such as amplitude is transmitted to the stirring rod 14 via the plate member 13, so that the kinetic energy is melted by the vibration motion of the stirring rod 14. 11 can be directly applied to the molten metal 11 (see arrows in FIG. 3).

Note that the spiral projection 15 has a shape that protrudes widely from the peripheral surface of the tube 16 to the outside, so that the above-described motion effect can be transmitted to the molten metal 11 more efficiently.
However, the vibration motion in the molten metal of high-temperature and heavy specific gravity places a high load on the spiral projection and causes damage, so the projection of the spiral projection from the peripheral surface of the tube It is preferable to reduce the amount (for example, about 0.5 to 2 mm, preferably the lower limit is about 1 mm and the upper limit is about 1.5 mm).

As described above, the amount of protrusion of the spiral protrusion 15 provided on the peripheral surface of the pipe 16 is limited in strength, and therefore, the motion of the stirring rod 14 is performed throughout the molten metal 11 stored in the wide container 20. There is a possibility that sufficient energy cannot be given.
For this reason, according to the surface area of the molten metal 11, it is preferable to use a plurality of stirring rods 11 and stir the molten metal 11.

For example, the number of the stirring rods 14 is set so that the area occupied by the stirring means 12 at the surface 21 of the molten metal 11, that is, the total stirring rod 14, is 30% or more and 60% or less of the area of the molten metal 21 of the molten metal 11. It is preferable to adjust.
Here, when the occupied area of all the stirring rods is less than 30% of the surface area of the molten metal, the occupied area is too small, and as described above, the kinetic energy by the stirring rods cannot be sufficiently applied to the entire molten metal. There is a fear. On the other hand, when the occupied area of all the stirring rods exceeds 60%, the occupied area is too wide, and the amount of molten metal that can be stirred at one time is reduced, resulting in a decrease in work efficiency, and the number of stirring rods is increased. For this reason, the apparatus configuration is complicated, and costs are increased, which is uneconomical.
Therefore, the area occupied by all the stirring bars 14 on the molten metal surface 21 of the molten metal 11 is set to 30% to 60% of the area of the molten metal surface 21 of the molten metal 11, but the lower limit is 40%, further 45%, and the upper limit is 55. % Is preferable.

In addition, when there is much molten metal amount required for the casting performed at once, and the area of a molten metal surface becomes large, the deposit refinement | miniaturization apparatus 30 shown in FIG. 4, FIG. 5 can also be used.
Similarly to the precipitate refiner 10, the precipitate refiner 30 is also immersed in a molten Al or Mg hypereutectic alloy to stir the melt. Numbers are given and detailed explanations are omitted.

The precipitate refiner 30 includes a stirring means 31 that stirs the molten metal 11 by being immersed in the molten metal 11 of the hypereutectic alloy of Al or Mg.
The stirring means 31 is provided with a stirring blade 32 that can rotate around an axis, and a plurality of (here, two) stirring blades that are provided at intervals around the stirring blade 32 and can vibrate in the axial direction. It has a bar 14. Each stirring bar 14 is attached and fixed to the plate member 33 so as to protrude downward.
A hole 34 penetrating in the vertical direction is formed in the center of the plate member 33, and the stirring blade 32 is disposed in the hole 34 so as not to contact the plate member 33.

Thereby, since the stirring blade 32 can transmit only rotational motion to the molten metal 11 by the stirring motor 35 provided at the upper end portion thereof, the molten metal 11 stirred by the stirring blade 32 is placed outside the stirring blade 11. It forcibly contacts each arranged stirring rod 14 (see the white arrow in FIG. 5). Moreover, by vibrating each stirring rod 14 in the axial direction, the kinetic energy described above can be transmitted to the molten metal 11 in contact with each stirring rod 14, and the molten metal 11 can be stirred (see the arrow in FIG. 5).
Therefore, it is possible to cope with a case where the surface area of the molten metal surface 21 of the molten metal 11 is large. In addition, the number 36 in FIG. 4, FIG. 5 is a container (cup) in which the molten metal 11 is put.
Also for the precipitate refiner 30 described above, the total occupied area of the stirring means 31 at the molten metal surface 21 position of the molten metal 11, that is, the stirring blade 32 and the entire stirring rod 14, as with the precipitate refiner 10 described above, It is preferable to adjust the number of one or both of the stirring blade 32 and the stirring rod 14 so that the area of the molten metal 11 is 30% or more and 60% or less.
In addition, as a stirring means, you may use only one or several stirring blades which can rotate centering on an axial center.

As shown above, stirring of the molten metal can be performed mechanically, but can also be performed electromagnetically. The electromagnetic stirring may be performed alone or in combination with mechanical stirring.
For example, when the molten metal is pumped up with pressure from an alloy melting and holding furnace (hereinafter also simply referred to as a holding furnace) and hot water is supplied through piping or the like, high frequency and low Electromagnetic energy using frequency, microwave, motor coil, or the like can be applied to the molten metal to stir the molten metal.

Then, the precipitate refinement | miniaturization method of the alloy which concerns on one embodiment of this invention is demonstrated.
First, an example of an actual casting process will be described.
As a method for supplying molten alloy from the melting holding furnace to the casting machine, there are a method using a pump cup attached to the hot water supply machine, and a molten metal pumped out from the holding furnace using pressure or the like to the casting machine via a pipe or the like. There is a method of directly supplying hot water, etc., but in order to adjust the timing of hot water supply in accordance with the movement on the casting machine side, there is a step of temporarily storing (hereinafter also referred to as a storage step).

Most of the methods using the above-mentioned scooping cup do not manage the temperature of the molten metal in the storage process, and the fluidity of the molten metal is not significantly impaired by the time management during the hot water supply from the holding furnace to the casting machine. The operation is planned so that the storage process is completed while the temperature is kept to the extent that no phase develops).
The molten metal in this storage process drops in temperature due to heat dissipation and is in a stationary state, so that nucleation in the molten metal is slow, and primary crystals and eutectics are generated and grown, centering on few nuclei. Will be. That is, in the forming process of all alloys, there are nucleation, precipitation phase formation, and precipitation phase growth before stabilization from liquid to crystal grains depending on the temperature range.

  Therefore, the inventors have given the kinetic energy to the molten metal while performing the temperature control (heating) of the molten metal at a preselected temperature in the above-described storage process, and the molten metal (liquefied) state is maintained while maintaining fluidity. Thus, it was conceived that a high-quality alloy product can be produced by suppressing the growth of precipitates and promoting the expression of a substance (nucleation element) serving as a nucleus and using this molten metal for casting. That is, while maintaining the molten state, the nucleation element is expressed and increased, and by suppressing the growth of precipitates that grow around the nucleation element, the alloy performance is improved. It is characterized by the following configuration.

An alloy precipitate refining method according to an embodiment of the present invention is a method of refining precipitates in a cooling process of a molten Al or Mg hypereutectic alloy, and a liquidus line of a hypereutectic alloy. It is higher than the solidus temperature TS of the hypereutectic alloy and higher than the liquidus temperature TL from the temperature T1 set higher than the temperature TL within the range of 2% to 10% of the liquidus temperature TL. Is a method of stirring the molten metal using the precipitate refiner 10, the precipitate refiner 30, or the like up to a temperature T <b> 2 set low within a range of 10% or less of the liquidus temperature TL. Note that the temperature range of stirring described above is a temperature range selected based on a completely different standard from the temperature range intended for the conventional solid-liquid mixture state, and therefore, the conventional technology for the purpose of forming a solid phase is used. Is a completely different technology.
This will be described in detail below.

When stirring the molten alloy, the start of stirring of the molten metal was set at the temperature T1 described above because the nucleation element was expressed at a temperature equal to or lower than the liquidus temperature TL.
Therefore, the lower limit value of the temperature T1 at which the molten metal starts stirring is set to 2% (preferably 4%, more preferably 5%) higher than the liquidus temperature TL.
On the other hand, the upper limit value of the temperature T1 at which the molten metal starts stirring is set to a temperature 10% (preferably 7%) higher than the liquidus temperature TL than the liquidus temperature TL. Even if agitation is performed, the effect of agitation is small and the energy cost is high.

Further, the reason why the stirring of the molten metal is finished is set to the temperature T2 described above in order to continue to increase the number of nucleation elements expressed.
Therefore, although the upper limit value of the temperature T2 at the end of the stirring of the molten metal is set to a temperature lower than the liquidus temperature TL, the nucleation elements aggregate in the subsequent cooling process as the temperature approaches the liquidus temperature TL. Therefore, it is preferable to set the liquidus temperature TL to 2%, more preferably 5%.
On the other hand, the lower limit value of the temperature T2 at the end of the stirring of the molten metal needs to be higher than the solidus temperature TS as a matter of course. However, as the solidus temperature TS approaches, the remarkable increase in the number of nucleation elements cannot be expected, so the lower limit of the temperature T2 is set to 10% of the liquidus temperature TL rather than the liquidus temperature TL. The temperature was set low (preferably 7%).

By stirring the molten metal in the temperature range from the temperature T1 to the temperature T2 (until the hot water supply to the casting machine is started), it is possible to continue to increase the number of nucleating elements expressed.
As a result, the molten metal, which is in a state in which the enlargement of the crystal can be suppressed, is supplied to the casting machine and cast, thereby forming an alloy with improved alloy properties such as high strength by the refined crystal grains. It becomes possible.

In addition, as described above, when the molten metal is pumped up with pressure from the melting and holding furnace of the alloy and is supplied through a pipe or the like, casting is performed by the following method, for example.
First, in the melting furnace or the melting holding furnace, the melting operation is performed in a state where the temperature is higher than the temperature at which the contained elements begin to form nuclei and primary crystals are generated.
Next, expression of nucleation elements and refinement of precipitates are performed in the above-mentioned temperature range while giving kinetic energy to the molten metal itself filled in the melting and holding furnace by electromagnetic stirring or the like.
Then, while maintaining this state continuously, the necessary amount is pumped out and cast.

Here, an example of the target hypereutectic alloy is shown below.
As the hypereutectic alloy of Al, there is an Al—Si alloy using Si as an alloy element.
Thus, since the hypereutectic alloy of Al is used here, the Si concentration is more than 12.7% by mass (see FIG. 14), but in order to obtain the effects of the present invention, the Si concentration is 13 mass% or more is preferable, Furthermore, 18 mass% or more is preferable.
On the other hand, as the Si concentration increases, the effect of the present invention becomes remarkable, so the upper limit is not specified, but at present it is considered to be about 30% by mass.

As other Al hypereutectic alloys, Al-Fe-Si alloys using Fe and Si as alloy elements (Fe and Si are both contained in a larger amount than the ternary eutectic point with Al. Alloy).
This alloy is an alloy aiming at high strength among Al alloys. By controlling the temperature of the molten metal and stirring the molten metal with the precipitate refiner 10 or the like, crystals of the Al-Fe-Si compound can be obtained. As a result, it is possible to produce a higher strength alloy.

And as a hypereutectic alloy of Mg (magnesium), there is an Mg-Ca alloy using Ca (calcium) as an alloy element. The Ca concentration in the alloy is more than 16.2% by mass.
This alloy is an alloy that uses Ca as an additive in order to raise the burning point of Mg. However, the addition of Ca has a drawback that the alloy tends to become brittle. Therefore, since the temperature control of the molten metal and the stirring of the molten metal by the precipitate refining device 10 and the like can refine the crystals of the CaMg ₂ compound, the above-described drawbacks due to the addition of Ca are present. It is wiped off, and the mechanical properties can be maintained and further improved.

Here, the alloy having the above-described composition is exemplified as the hypereutectic alloy of Al or Mg.
However, as long as it is a hypereutectic alloy of Al or Mg, the alloy is not limited to the alloy having the above composition (for example, other additive elements may be included if necessary), and the temperature control of the above-described molten metal. As long as it is an alloy that can obtain the effect of stirring the molten metal by the precipitate refiner 10 or the like, it is included in the scope of the right of the present invention.

Next, examples carried out for confirming the effects of the present invention will be described.
First, a description will be given of test results obtained by casting a molten high Al content Al alloy (Si concentration: 20% by mass) with a die casting machine (Example 1).
According to the liquid phase line, the high Si-containing Al alloy described above has a temperature at which nucleation and crystallization starts at 650 ° C., so it is 680 ° C. in the molten metal holding furnace (about 5% higher than the temperature at which primary crystals are formed). % Of the molten metal kept at a high temperature) was pumped up in a pumping container attached to the tip of the hot water supply device, and waited in front of the casting machine.
Next, the stirring rod 14 of the precipitate refiner 10 described above is immersed in the molten metal in the standby container, and the temperature of the molten metal is kept at 630 ° C. or higher (a temperature about 3% lower than the liquidus). Thus, while controlling the temperature of the molten metal, kinetic energy such as vibration was applied to the molten metal.

  The temperature of the molten metal (680 ° C.) in the container gradually decreased while being given kinetic energy under the temperature control by the heater 17 (630 ° C.) and the thermocouple 18 disposed in the stirring rod 14. Then, when the temperature of the molten metal reaches 650 ° C., a nucleation compound (AlP) is formed using P as a nucleation element, and the formed nuclei form primary crystals from Si in the molten metal as shown in FIG. Si began to be generated. Because of the kinetic energy given during the expression of the nucleation element, a large amount of nucleation compound is generated, so that the growth of primary Si with a large amount of nuclei as the core is suppressed, and more nuclei are formed. Due to the development, primary Si was generated in a very small and large amount.

In this way, the molten metal in which a large amount of primary crystal Si is maintained in a fine and fine state is charged into a casting machine and filled into a casting mold, so that the molten metal temperature rapidly decreases.
As a result, Al forms a nucleation compound of TiB ₂ with Ti and B as nucleation elements, and the remaining Si becomes refined eutectic Si as shown in FIG. Molded as a high performance alloy product with crystal grains.

Next, a description will be given of test results obtained by casting a molten high Al content Al alloy (Si concentration: 14% by mass) with a die casting machine.
As shown in FIGS. 8 (A) and 8 (B), in the case of an Al alloy product manufactured using a normal die casting method (casting method) in which kinetic energy is not imparted to the molten metal, primary Si and eutectic Si are used. Both have grown greatly (conventional example).
On the other hand, under the above-described temperature control of the molten metal, the kinetic energy is imparted to the molten metal, and in the Al alloy product that is miniaturized, as shown in FIGS. 9A and 9B, the primary Si And eutectic Si were both miniaturized (Example 2).

  In addition, when the tensile strength was compared using these Al alloys, as shown in FIG. 10, the Al alloy whose crystal size was reduced was 20% or more as compared with the Al alloy produced by a normal casting method. It was confirmed to rise.

  The same tendency as described above was obtained for other Al hypereutectic alloys (for example, Al-Fe-Si alloys) and Mg hypereutectic alloys (Mg-Ca alloys).

  From the above, it has been confirmed that the alloy performance of the hypereutectic alloy of Al (or Mg) can be improved as compared with the prior art by the precipitate refinement method of the alloy of the present invention and the precipitate refiner used therefor. .

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, it is also within the scope of the present invention when a precipitate refinement method for an alloy of the present invention and a precipitate refinement apparatus used therefor are configured by combining some or all of the above-described embodiments and modifications. included.
Moreover, in the said embodiment, stirring of the molten metal was performed only in the temperature range from the temperature T1 straddling the liquidus temperature TL to the temperature T2. However, as long as the molten metal is stirred at least within this temperature range, the molten metal may be stirred from a temperature higher than the temperature T1, and the temperature lower than the temperature T2 (lower than the solidus temperature TS). The stirring of the molten metal can be finished at a high temperature).

10: precipitate refiner, 11: molten metal, 12: stirring means, 13: plate material, 14: stirring rod, 15: spiral protrusion, 16: pipe, 17: heater, 18: thermocouple, 19: motor for vibration 20: container, 21: hot water surface, 30: precipitate refiner, 31: stirring means, 32: stirring blade, 33: plate material, 34: hole, 35: motor for stirring, 36: container

Claims (3)

A method for refining precipitates in a cooling process of a molten Al hypereutectic alloy having a Si concentration of 13% by mass or more ,
The liquidus temperature of the hypereutectic alloy is TL (° C.),
From a temperature T1 (° C.) within a range of TL × 1.02 or more and TL × 1.10 or less,
Higher than the solidus temperature TS (° C.) of the hypereutectic alloy and up to a temperature T 2 (° C.) in the range of TL × 0.90 to TL × 0.98 ,
When the molten metal is stirred across the liquidus temperature TL (° C.) of the hypereutectic alloy ,
A method for refining a precipitate of an alloy, comprising: dipping a stirring rod provided with a spiral projection on an outer peripheral surface in the molten metal, and stirring the molten metal by vibrating the stirring rod in an axial direction . A precipitate refining apparatus for use in the method for refining precipitates of an alloy according to claim 1 , comprising a stirring means equipped with the stirring rod . 3. The precipitate refinement apparatus according to claim 2 , wherein an area occupied by the stirring means on the molten metal surface is not less than 30% and not more than 60% of an area of the molten metal surface. Device.