JP5960634B2 - Manufacturing method of casting made of Al-Si-Cu eutectic alloy - Google Patents

Description

  The present invention relates to a method for producing a casting made of an Al—Si—Cu eutectic alloy.

  Generally, there is a method in which a molten metal made of various metals is irradiated with ultrasonic waves to generate an acoustic flow or ultrasonic cavitation in the molten metal, and the molten metal is vibrated to refine the solidified structure.

  Patent Document 1 discloses a casting method for casting in which primary vibration α-Al is crystallized by applying ultrasonic vibration to the molten eutectic Al—Si alloy melt in the cooling process.

  By the way, it is known that a cast product made of an Al-Si-Cu eutectic alloy in which Cu is further alloyed with Al-Si has an improved tensile strength compared to a cast product made of an Al-Si alloy. It has been.

However, by including the Cu alloy, Al-Si-Cu-based eutectic alloy CuAl ₂ is produced in a casting made of (hypoeutectic alloy, is intended to include also hypereutectic alloy), coined by the CuAl ₂ The problem is that the ductility (or elongation) of the product decreases.

JP 2011-45909 A

  The present invention has been made in view of the above-described problems, and relates to a cast product made of an Al-Si-Cu eutectic alloy. In addition to having high tensile strength, Al-Si- that can improve ductility It aims at providing the manufacturing method of the castings which consist of Cu system eutectic alloy.

  In order to achieve the above object, a method for producing a cast product comprising an Al-Si-Cu eutectic alloy according to the present invention comprises a molten Al-Si-Cu eutectic alloy at a liquidus temperature or higher. The first step of irradiating the molten metal with ultrasonic waves until the temperature drops from the temperature equal to or higher than the liquidus temperature to the eutectic temperature, the ultrasonic irradiation to the molten metal is continued while maintaining the eutectic temperature. From the second step, the third step of producing the cast product precursor by casting the molten metal obtained in the second step, and the fourth step of producing the cast product by aging the cast product precursor. It will be.

  The casting method of the present invention not only irradiates the ultrasonic wave during the cooling process of the molten metal composed of the Al—Si—Cu eutectic alloy until the temperature falls from the temperature above the liquidus temperature to the eutectic temperature. The first feature is to continue the irradiation of ultrasonic waves to the molten metal while maintaining the eutectic temperature for a certain period of time, and after producing a cast product precursor from the obtained molten metal, The second feature is to produce a cast product by performing an aging treatment. Note that “until the eutectic temperature is lowered” means not only strictly the eutectic temperature but also around the eutectic temperature (for example, about 570 to 580 ° C. when 570 ° C. is the eutectic temperature). Including meaning.

  According to the first feature described above, first, the primary crystal Si can be finely granulated by performing ultrasonic irradiation from a temperature state in which the molten metal is higher than the liquidus temperature. By cavitation in the molten metal by this ultrasonic irradiation, or by increasing the pressure, the alloy can be non-equilibrium and the crystal precipitation form can be controlled.

  The melt is lowered to the eutectic temperature, and the ultrasonic irradiation is continued in the process of maintaining the eutectic temperature for a certain time, whereby non-equilibrium granular α-Al can be crystallized. If the ultrasonic irradiation is stopped after the eutectic temperature is reached, crystallization of nonequilibrium α-Al and primary Si is suppressed, and immediately after this stop, crystallization occurs as a eutectic. It is difficult to improve the wear resistance of the cast product due to the small amount of crystal Si crystallization.

  In addition, in the case of hypereutectic, if the ultrasonic irradiation is stopped at the eutectic temperature while the primary crystal Si has increased too much, the primary crystal is caused by the thermal insulation effect of the primary crystal that has crystallized at a high temperature due to non-equilibrium. Although there is a problem that the eutectic Si is coarsened as a result of the slow cooling of the eutectic between Si, this problem cannot occur in the second step of the present invention.

  An example of the “certain time” is about 1 minute.

  Here, solidification while applying vibration by applying ultrasonic waves to a molten metal in the cooling process can be referred to as “Sono solidification”.

  According to the verification by the present inventors, when the molten metal is rapidly cooled to the eutectic temperature and shifted to the casting process, although dendritic α-Al is confirmed, the non-equilibrium granular α It has been specified that -Al does not crystallize.

  In this way, the primary crystal Si is refined by sono-solidification, whereby the tensile strength of the cast product finally produced is improved.

  However, it has also been specified by the present inventors that the ductility (elongation rate, elongation at break) of the finally produced cast product is not improved in spite of the granular α-Al being crystallized by sono-solidification. ing.

This is because CuAl ₂ is generated because the alloy component contains Cu, and this is a cause of a decrease in ductility.

  Therefore, the cast product is manufactured by subjecting the cast product precursor to an aging treatment, which is the second feature described above.

Generally, mechanical properties of cast products, especially hardness, are increased by performing aging treatment, but according to the verification by the present inventors, eutectic is obtained by performing aging treatment on the cast product precursor. It has been specified that CuAl ₂ segregated in the structure can be eliminated, the ductility effect of granular α-Al can be obtained, and the ductility of the cast product can be improved.

  Here, examples of the aging treatment include a T6 treatment in which an artificial age hardening treatment is performed without performing cold working after the solution treatment.

  Thus, by performing the first step to the fourth step according to the present invention to produce a cast product made of an Al-Si-Cu eutectic alloy, Al having both high tensile strength and ductility. Cast products made of -Si-Cu eutectic alloy can be manufactured.

  As can be understood from the above description, according to the method for producing a cast product comprising an Al-Si-Cu eutectic alloy of the present invention, the liquid phase is cooled during the cooling process of the molten metal comprising the Al-Si-Cu eutectic alloy. While irradiating the ultrasonic wave from the temperature above the line temperature to the eutectic temperature, and continuing to irradiate the molten metal while maintaining the eutectic temperature for a certain period of time, casting from the resulting molten metal After the precursor is manufactured, the casting precursor is subjected to aging treatment to produce a cast product, thereby producing a cast product made of an Al-Si-Cu eutectic alloy with both high tensile strength and ductility. can do.

It is the figure which simulated the casting apparatus applied with the manufacturing method of this invention. It is the time-temperature graph of a molten metal, Comprising: It is the figure explaining the manufacturing method of this invention. It is the figure which showed the alloy composition used in Experiment 1 (in the case of normal solidification and the case of sono solidification), and a temperature-solid phase ratio graph. It is the figure which showed the time-temperature condition in Experiment 1, and the structure | tissue photograph figure. It is the figure which showed the time-temperature condition and structure | tissue photograph figure in Experiment 2 (fine primary-crystal Si crystallization conditions). It is the figure which showed the time-temperature condition and structure | tissue photograph figure in the experiment 3 (non-equilibrium (alpha) -Al crystallization conditions). It is the figure which showed the time-temperature condition and structure | tissue photograph figure in Experiment 4 (comparison of normal coagulation and sono coagulation). It is the figure which showed the measurement result of the tensile strength and breaking elongation of the cast in Experiment 4. It is a diagram showing a structure photograph view in Experiment 5 (Effect Study of the elongation at break by CuAl _2). It is the figure which showed the measurement result of the tensile strength and breaking elongation of the cast in Experiment 5. It is the figure which showed the structure | tissue photograph figure in Experiment 6 (change confirmation of eutectic Si by sono solidification). It is the figure which showed the measurement result of the structure | tissue photograph figure in Experiment 7 (change confirmation of the tensile characteristic by the form of eutectic Si), tensile strength, and elongation at break. It is the figure which showed the time-temperature condition and structure | tissue photograph figure in Experiment 8 (effect examination by the presence or absence of ultrasonic irradiation for a fixed time in eutectic temperature). It is the figure which showed the measurement result of the tensile strength and breaking elongation of the cast in Experiment 8. It is a structure photograph figure in experiment 9 (relationship specification of primary crystal Si amount and tensile properties). It is the figure which showed the measurement result of the tensile strength and breaking elongation of the cast in Experiment 9. It is the figure which showed the time-temperature condition and structure | tissue photograph figure in Experiment 10 (creation of the heterostructure using a low Si concentration alloy). It is the figure which showed the measurement result of the tensile strength and breaking elongation of the cast in Experiment 10.

  Hereinafter, an embodiment of a method for producing a casting made of an Al—Si—Cu eutectic alloy of the present invention will be described together with a production apparatus with reference to the drawings.

(About manufacturing equipment)
FIG. 1 is a diagram simulating a casting apparatus applied in the manufacturing method of the present invention. A casting apparatus 10 shown in the figure is an apparatus for irradiating a molten metal in a cooling process with ultrasonic waves and solidifying while ultrasonically oscillating, an ultrasonic generator 1, a processing vessel 2, a processing vessel fixing unit 3, The thermocouple 4, the upper and lower plates 5 and 6, and a melt temperature adjusting unit (not shown) are provided.

  The ultrasonic generator 1 is generally composed of an ultrasonic horn 7 that is an ultrasonic transmission unit and an ultrasonic vibrator 8 that is connected to the bottom of the ultrasonic horn 7. The ultrasonic horn 7 is made of a metal (Ti-6Al-4V (mass) that transmits vibration energy in a predetermined direction (in the present embodiment, the arrow direction shown in FIG. 1) generated by the ultrasonic vibrator 8 to the object to be transmitted. %) Alloy).

  The upper end surface of the ultrasonic horn 7 has a shape that can be placed in contact with the bottom of the processing container 2 that is a transmission object, and its outer peripheral surface has a fin shape to enhance the air cooling effect of the horn itself. Has been processed. Further, the ultrasonic transducer 8 is connected to a high frequency power source via an ultrasonic oscillator (not shown), and can generate ultrasonic vibration under a predetermined vibration condition. Here, the frequency band of the ultrasonic vibration is preferably in the range of 17 kH to 25 kH.

  The processing vessel 2 is a cup-shaped metal crucible (a SUS304 vessel having an upper inner diameter of 40 mm, a bottom inner diameter of 30 mm, and an effective depth of 33 mm). In this embodiment, the Al—Si—Cu alloy melt is stored.

  The processing container fixing unit 3 is an air cylinder having a rod 3a that can be expanded and contracted in the vertical direction. The rod 3a extends downward (processing container 2 side) at the tip of the rod 3a to hold the upper end of the processing container 2. The buffer material 3b for this is provided. The processing container fixing part 3 extends the rod 3a of the air cylinder downward, the lower surface of the cushioning material 3b is brought into contact with the upper end part of the processing container 2, and the upper end part of the processing container 2 is brought to a predetermined pressure toward the ultrasonic horn 7 side. It is possible to fix the processing container 2 so that it does not move.

  The thermocouple 4 is a means for measuring the molten metal temperature, and can be immersed in the molten metal stored in the processing container 2 to measure the molten metal temperature at a predetermined position in the molten metal. The thermocouple 4 is connected to a measurement recording unit (not shown), and the measurement recording unit is capable of recording while continuously monitoring the measured molten metal temperature. Moreover, it becomes possible to grasp | ascertain the crystal structure state formed in the cooling process of a molten metal with the molten metal temperature measured with the thermocouple 4, As a result, the raw material which has a desired crystal structure can be obtained.

  The upper plate 5 is a plate-like member for fixing and supporting the air cylinder that is the processing container fixing portion 3. The lower plate 6 is a plate-like member for fixing and supporting the ultrasonic horn 7 and the ultrasonic transducer 8. Further, the upper and lower plates 5 and 6 are arranged in a state where a predetermined interval is maintained, and the position of the lower plate 6 becomes the antinode of resonance of the ultrasonic transducer 8 when ultrasonic vibration is performed. Are arranged as follows.

  The molten metal temperature adjusting unit is means for adjusting the molten metal to a desired temperature by heating or cooling the molten metal. The molten metal temperature adjusting unit can adjust the temperature of the molten metal under predetermined conditions (temperature and time). For example, when the molten metal reaches the eutectic temperature in the cooling step, the molten metal is eutectic. It can be adjusted so that it can be kept at temperature.

  Next, a method for producing a cast product using the production apparatus will be described below.

(About manufacturing method)
FIG. 2 is a time-temperature graph of the molten metal and is a diagram illustrating the manufacturing method of the present invention.

  The manufacturing method shown in the figure is a manufacturing method of a cast product made of an Al—Si—Cu eutectic alloy. First, a molten eutectic alloy is produced with the Al-Si-Cu eutectic alloy at the liquidus temperature (660 ° C) or higher, until the temperature drops from the liquidus temperature (660 ° C) or higher to the eutectic temperature. The molten metal is irradiated with ultrasonic waves (first step).

  Next, ultrasonic irradiation to the molten metal is continued while maintaining the eutectic temperature (570 ° C.) (second step).

  Next, the molten metal is rapidly cooled and die-cast (cast) to produce a cast product precursor (third step).

  Finally, a casting product is manufactured by aging the casting product precursor (fourth step).

  By performing ultrasonic irradiation from a temperature state in which the molten metal is equal to or higher than the liquidus temperature in the first step, primary Si can be finely granulated.

  Then, the molten metal is lowered to the eutectic temperature, and the irradiation of ultrasonic waves is continued in the process of maintaining the eutectic temperature for a certain time in the second step, whereby the non-equilibrium granular α-Al is crystallized. Can be issued.

However, since the alloy component contains Cu, CuAl ₂ is generated, which causes a reduction in the ductility of the finally obtained cast product. Therefore, it is important to eliminate this CuAl ₂ .

Therefore, after the die casting is performed in the third step to manufacture the cast product precursor, the cast product is manufactured by performing the aging treatment such as the T6 process in the fourth step. Can eliminate CuAl ₂ segregated in the eutectic structure, thereby obtaining the ductility effect due to the granular α-Al, and improving the ductility of the cast product.

[Experiment 1]
The present inventors conducted an experiment to change the microstructure by sonocoagulation. Here, FIG. 3 is a diagram showing an alloy composition and a temperature-solid phase ratio graph used in Experiment 1 (in the case of normal solidification and sono solidification), and FIG. 4 is a time-temperature condition and structure in Experiment 1. It is the figure which showed the photograph figure.

  As shown in FIG. 4, refinement of primary Si and crystallization of nonequilibrium granular α-Al were confirmed by sono-solidification.

  In addition, when comparing the pattern that rapidly cools at 570 ° C and the pattern that rapidly cools at 565 ° C, the amount of α-Al crystallization may increase by performing sonosolidification to a temperature close to the eutectic temperature of 563 ° C. confirmed.

[Experiment 2]
The present inventors conducted an experiment to verify fine primary crystal Si crystallization conditions. Here, FIG. 5 is a diagram showing a time-temperature condition and a structure photograph in Experiment 2 (fine primary Si crystallization conditions).

  First, in the pattern of rapid cooling after ultrasonic irradiation between 700 ° C and 660 ° C, a large amount of fine primary crystal Si crystallizes despite the rapid cooling above the liquidus temperature (655 ° C). Yes. From this, it was confirmed that the primary crystal Si crystallization was promoted and the primary crystal Si was refined by irradiating the ultrasonic wave even at the liquidus temperature or higher.

  Moreover, it was confirmed that both the coarse primary crystal Si and the fine primary crystal Si were crystallized in the pattern of rapid cooling after ultrasonic irradiation between 600 ° C. and 570 ° C. It was confirmed that the coarsely crystallized primary crystal Si was not crushed even by ultrasonic irradiation.

[Experiment 3]
The present inventors conducted an experiment to verify the crystallization conditions of non-equilibrium α-Al. Here, FIG. 6 is a diagram showing a time-temperature condition and a structure photograph in Experiment 3 (non-equilibrium α-Al crystallization condition).

  First, dendritic α-Al that was confirmed during quenching was confirmed in the pattern of quenching after ultrasonic irradiation and holding at 600 ° C. for 1 minute. At 600 ° C., nonequilibrium granular α-Al does not crystallize.

  Further, in the pattern in which the sample was rapidly cooled after being irradiated with ultrasonic waves for 1 minute at 570 ° C., crystallization of α-Al was partially confirmed. From this, it was confirmed that ultrasonic irradiation for a certain period of time near the eutectic temperature is effective for non-equilibrium granular α-Al crystallization.

[Experiment 4]
The present inventors conducted experiments to verify the tensile strength and elongation at break of cast products by normal solidification and sonosolidification. Here, FIG. 7 is a diagram showing a time-temperature condition and a structure photograph in Experiment 4 (comparison between normal solidification and sono solidification), and FIG. 8 is a measurement result of tensile strength and breaking elongation of the cast product in Experiment 4. FIG.

  As shown in FIG. 8, the tensile strength is improved as a result of the refinement of primary crystal Si by sono-solidification.

  Moreover, although the granular α-Al crystallizes by sono-solidification, the elongation at break is not improved.

From this experimental result, it is considered that CuAl ₂ crystallized in the eutectic structure is influenced as the reason why the elongation at break is not improved.

[Experiment 5]
The present inventors conducted an experiment to verify the tensile strength and elongation at break of a casting made of an Al—Si based alloy and an Al—Si—Cu based alloy in order to confirm the effect of CuAl _{2 on the} elongation at break. Here, FIG. 9 is a diagram showing a structure photograph in Experiment 5 (examination of influence on breaking elongation by CuAl ₂ ), and FIG. 10 shows measurement results of tensile strength and breaking elongation of the cast product in Experiment 5. FIG.

  From FIG. 10, it was confirmed that even when granular α-Al crystallizes in a large amount, the elongation at break is significantly reduced due to the inclusion of Cu.

On the other hand, it was confirmed that the CuAl ₂ disappears and the elongation at break improves by performing the T6 treatment. This is considered to be a result of obtaining the ductility effect of α-Al by the disappearance of CuAl ₂ .

[Experiment 6]
The present inventors conducted experiments to confirm the change of eutectic Si due to sono-solidification. Here, FIG. 11 is a diagram showing a structure photograph in Experiment 6 (confirmation of eutectic Si change by sono-solidification).

  From FIG. 11, it was confirmed that by sono solidification, a large number of fine primary crystal Si was crystallized and eutectic Si crystallized coarsely.

[Experiment 7]
The present inventors conducted experiments to confirm changes in tensile properties due to the morphology of eutectic Si. Here, FIG. 12 is a diagram showing a structure photograph in Experiment 7 (confirmation of change in tensile properties depending on the form of eutectic Si) and measurement results of tensile strength and elongation at break.

  From FIG. 12, it was confirmed that the roughness of eutectic Si has an influence on tensile strength and elongation at break, and fine eutectic Si is preferable. Since eutectic Si is likely to become coarse due to sono-solidification, the tensile strength is reduced, so it is necessary to refine eutectic Si and reduce eutectic Si.

[Experiment 8]
The present inventors conducted an experiment to confirm the effect of the presence or absence of ultrasonic irradiation for a certain time at the eutectic temperature. Here, FIG. 13 is a diagram showing a time-temperature condition and a structure photograph in Experiment 8 (examination of the effect of the presence or absence of ultrasonic irradiation for a certain time at the eutectic temperature), and FIG. It is the figure which showed the measurement result of tensile strength and breaking elongation.

  From FIG. 14, α-Al was increased and elongation at break was improved by ultrasonic irradiation holding at 570 ° C. However, the tensile strength was slightly reduced as compared with the case where irradiation was not held. This is thought to be due to the increase in primary Si (13.2 area% at retention 0s, 18.2area% at retention 45s).

[Experiment 9]
The present inventors conducted experiments to identify the relationship between the amount of primary Si and tensile properties. Here, FIG. 15 is a structural photograph in Experiment 9 (identification of the relationship between the amount of primary Si and tensile properties), and FIG. 16 is a diagram showing the measurement results of the tensile strength and breaking elongation of the cast product in Experiment 9. .

  15 and 16, it was confirmed that both the tensile strength and the elongation at break decrease as the primary Si amount (area ratio) increases. Moreover, it is thought that the increase in the amount of primary Si due to sono-solidification decreases the tensile strength.

  From this experiment, it was determined that the use of a hypereutectic Al-Si-Cu alloy having a low Si concentration is preferable in order to reduce primary Si. Furthermore, it is necessary to examine the appropriate amount of Si by comparing it with the wear resistance that primary Si has a good effect.

[Experiment 10]
The present inventors tried to create a heterostructure using a low Si concentration alloy. Here, FIG. 17 is a diagram showing a time-temperature condition and a structure photograph in Experiment 10 (creation of a heterostructure using a low Si concentration alloy), and FIG. 18 is a diagram showing tensile strength and fracture of a cast product in Experiment 10. It is the figure which showed the measurement result of elongation.

  From FIG. 18, it was confirmed that primary Si can be suppressed by using a low Si alloy.

  Moreover, it was confirmed that the tensile strength was improved and the elongation at break was slightly improved by suppressing the primary crystal Si.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Ultrasonic generating part, 2 ... Processing container, 3 ... Processing container fixing | fixed part, 4 ... Thermocouple, 5 ... Upper plate, 6 ... Lower plate, 7 ... Ultrasonic horn, 8 ... Ultrasonic vibrator, 10 ... Casting apparatus

Claims (1)

A method for producing a casting made of an Al-Si-Cu eutectic alloy,
First, an Al-Si-Cu eutectic alloy is formed at a liquidus temperature or higher to form a molten metal of the eutectic alloy, and the molten metal is irradiated with ultrasonic waves until the temperature drops from the liquidus temperature to the eutectic temperature 1 step,
A second step of continuing the irradiation of ultrasonic waves to the molten metal while maintaining the eutectic temperature;
A third step of producing a cast product precursor by casting the molten metal obtained in the second step;
A method for producing a cast product comprising an Al-Si-Cu eutectic alloy comprising a fourth step of producing a cast product by aging the cast product precursor.