Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D30/00—Cooling castings, not restricted to casting processes covered by a single main group
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/02—Making non-ferrous alloys by melting
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/02—Making non-ferrous alloys by melting
  • C22C1/026—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/047—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with magnesium as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent

Definitions

• the invention relates to a method of casting a light alloy produced by adding an additional element to a light metal, and to a casting manufactured by the method.
• a casting product is manufactured through casting using a light alloy such as an aluminum alloy or the like as a coarse material
• a light alloy such as an aluminum alloy or the like
• an aging treatment is performed after subjecting the casting product to a hardening treatment, with a view to improving the mechanical strength (tensile strength, elongation or the like) of the casting product.
• the light alloy is produced mainly from a light metal as a base material and an additional element added to the light metal. Then, after a molten metal is poured into a casting mold (a pouring process), the coarse material is coagulated while gradually cooling the entire casting mold (a casting mold cooling process). The coarse material is then released from the casting mold (a releasing process).
• the coarse material is heated up again to a predetermined temperature and held at this temperature for a predetermined time.
• the coarse material is thereby subjected to an aging treatment (an aging process). As a result, the mechanical strength of the casting product is improved.
• the coarse material made of the supersaturated light alloy needs to be subjected to the aging treatment after the hardening treatment is completed while minimizing to the best possible extent the dispersion of the amount of solid solution of the additional element in the coarse material.
• the supersaturated light alloy has the properties of allowing the solid solution element to separate out when being held at a predetermined temperature for a predetermined time.
• the time needed for the separation of the supersaturated solid solution element from the light alloy slightly differs depending on the types or the like of the light metal and the additional element, but has the properties of changing in accordance with the temperature of the light alloy. Consequently, in the course of cooling the coarse material from the casting mold cooling process to the coarse material cooling process, a large amount of the solid solution element non-uniformly separates out from the light alloy when the coarse material is cooled for a certain time or when the temperature of the coarse material is distributed according to a certain pattern.
• the coarse material has a temperature range in which the solid solution element in the light alloy rapidly separates out, namely, a temperature range in which the "separation time" is relatively short (hereinafter referred to as a "separation temperature range"). Then, when the function of cooling the casting mold is reinforced, a vicinity of that region (a surface portion) of the coarse material which is in contact with the casting mold is cooled to a temperature equal to or lower than the "separation temperature range" in a short time, and a large amount of the solid solution element is held in a supersaturated state.
• each of Japanese Patent Application Publication No. 8-225903 JP-A-8-225903
• Japanese Patent Application Publication No. 2005-169498 JP-A-2005-169498
• Japanese Patent Application Publication No. 2008-13791 JP-A-2008-13791
• Japanese Patent Application Publication No. 8-225903 JP-A-8-225903
• the coagulated aluminum alloy (the coarse material) is removed from the mold (the casting mold), immediately soaked in water, and then subjected to hardening. An aging treatment is performed after the completion of this hardening.
• JP-A-2005-169498 there is disclosed an art about a method of manufacturing a light alloy casting.
• This method is characterized in the following respects. After the coagulation of an aluminum alloy (a coarse material) poured into a casting mold, whose cavity is constituted by a sand mold forming a dead head portion and a mold arranged apart from the dead head portion to form part of the cavity, is completed, only the mold is separated with the sand mold left.
• This coagulated aluminum alloy (the coarse material) and this sand mold are soaked as a whole in water stored in a tank and subjected to a hardening treatment. Subsequently, the aluminum alloy (the coarse material) is subjected to an aging treatment with the aid of the heat retained by the dead head portion in a heat retention container.
• JP-A-2008-13791 there is disclosed an art about an aluminum alloy (a coarse material) manufactured in the following manner. After solution heating is carried out to hold a cast metal at a treatment temperature between 450°C and 510°C for a time equal to or longer than 30 minutes, the cast metal is subjected to water hardening. After that, this cast metal is subjected to an aging treatment to be held at a treatment temperature between 170°C and 230°C for 1 to 24 hours.
• JP-A-2008-13791 the coarse material can be reliably held in a supersaturated state by carrying out solution heating and water hardening prior to the aging treatment.
• the hardening treatment can be completed while minimizing to the best possible extent the dispersion of the amount of solid solution of the additional element in the light alloy. As a result, it seems possible to ensure uniform mechanical strength for the casting product.
• the management of the temperature of the casting mold before releasing the coarse material from the casting mold is not considered to be an indispensable factor. That is, the coarse material may already have been cooled to a temperature equal to or lower than the "separation temperature range" before being released from the casting mold. In such a case, even when the coarse material is directly soaked in water immediately after being released from the casting mold and then subjected to the aging treatment, uniform mechanical strength cannot be ensured for the casting product as in the aforementioned case where the function of cooling the casting mold is reinforced. On the contrary, the mechanical strength decreases in some cases.
• the coarse material is soaked in water from a temperature between 480°C and 580°C, at which the temperature of the coarse material is higher than the "separation temperature range" of the additional element. Therefore, there is no need to bother to provide means for managing the temperature of the casting mold.
• the temperature of the casting mold significantly falls every time a single casting product is manufactured through casting. This art is therefore not suited to the continuous manufacture of a large quantity of such casting products through casting.
• the coagulated coarse material and the sand mold are soaked in water as a whole.
• the sand mold absorbs water, becomes hard, and significantly deteriorates in collapsibility, thereby causing a deterioration in operability.
• this art is not suited to the continuous manufacture of a large quantity of such casting products through casting.
• the invention provides a method of casting a light alloy which allows a casting product to be manufactured through casting using a light alloy as a coarse material and ensures mechanical strength for the casting product through an aging treatment.
• uniform mechanical strength can be ensured for the casting product by performing the aging treatment after a hardening treatment is completed while minimizing to the best possible extent the dispersion of an amount of solid solution element in the light alloy.
• the invention also provides a casting manufactured by the method.
• a first aspect of the invention relates to a method of casting a light alloy to manufacture a casting product through casting.
• This casting method includes heating and melting a light alloy composed of a light metal as a base material and an additional element, and coagulating the molten light alloy through cooling such that a solid solution element remains within a separation temperature range, namely, a temperature range corresponding to a shortest elapsed time needed for separation of the solid solution element, which is contained in the light alloy, from the light metal when the light alloy has the solid solution element therein before being heated and when the light alloy is held at a predetermined temperature.
• the coagulated light alloy may be removed from a casting mold into which the molten light alloy may be poured to be coagulated.
• the casting mold may have cooling means.
• the cooling means may cool the casting mold so that the light alloy is cooled to a temperature higher than the separation temperature range.
• the light alloy may be removed from the casting mold before the temperature of the light alloy reaches the separation temperature range.
• the light metal may be an aluminum-silicon-copper-magnesium alloy.
• the additional element may be magnesium.
• the separation temperature range may be a range between 300°C and 400C°.
• a second aspect of the invention relates to a casting manufactured by the casting method according to the foregoing first aspect of the invention.
• FIG. 1 is a diagrammatic view showing a relationship between a temperature of a coarse material (unit (°C)) and an elapsed time at a time when a supersaturated solid solution element begins to separate out from a light alloy;
• FIG. 2 is a schematic view showing the overall configuration of a casting device that realizes "a method of casting a light alloy" according to the embodiment of the invention
• FIG. 3 is a schematic view showing the overall configuration of a coarse material cooling device that realizes the "method of casting the light alloy" according to the embodiment of the invention
• FIG 4 is a process chart showing the overall flow of a method of casting a light alloy according to one example of the invention.
• FIG 5 is a diagrammatic view showing how the temperature of the coarse material changes with the elapsed time in respective processes
• FIG 6 is a diagrammatic view showing a contrast between a case where a mold is subjected to temperature control and a case where the mold is not subjected to temperature control, in respect of changes with time in the temperature of the coarse material from a pouring process to a coarse material cooling process;
• FIG. 7 is a graph showing a contrast between the case where the mold is subjected to temperature control and the case where the mold is not subjected to temperature control, in respect of the solid solubility and hardness of the coarse material after an aging treatment.
• the casting method in this example is a method of casting a coarse material made of a light alloy, and aims at ensuring uniform mechanical strength (tensile strength, elongation or the like) for a casting product manufactured through casting. That is, the light alloy (hereinafter referred to as the coarse material) is mainly produced from a light metal as a base material and a solid solution element in the light metal. It should be noted herein that the light metal may not necessarily be a pure metal, but may be an alloy obtained by mixing two or more elements such as light metals with one another in advance.
• an aluminum-silicon alloy is used as the base material
• an Al-Si-Cu-Mg-type aluminum alloy which is produced by solidly dissolving magnesium as an additional element into the aluminum-silicon alloy and contains magnesium as the additional element, is used as the coarse material.
• the coarse material in a molten state is then coagulated while regulating the temperature for cooling a later-described casting mold 2 (see FIG. 2).
• the coagulated coarse material is then cooled in a short time, subjected to a hardening process to be tumed into a supersaturated solid solution, and then subjected to an aging treatment. As a result, the mechanical strength of the casting product is improved.
• the aging treatment refers to a treatment for developing a curing phenomenon by holding a coarse material made of a supersaturated solid solution at a predetermined temperature.
• the coarse material is heated up again to a temperature (e.g.,
• a surplus of the solid solution element in the saturated manner has the properties of separating out to the outside.
• the elapsed time needed for the separation of the surplus of the solid solution element from the light metal changes in accordance with the temperature of the coarse material.
• an axis of ordinate represents the temperature (unit (°C)) of the coarse material
• an axis of abscissa represents an elapsed time (unit (sec)) in a state where the coarse material is held at the temperature.
• a relationship between the temperature of the coarse material and the elapsed time is expressed by a curve at a time point when the supersaturated solid solution element begins to separate out from the light alloy. This curve protrudes leftward.
• the "separation time” temporarily decreases with falls in the temperature of the coarse material from a high-temperature side, but increases with falls in the temperature of the coarse material in a temperature range lower than a predetermined temperature (hereinafter referred to as a "peak temperature (T)").
• the “peak temperature (T)” slightly differs depending on the types or the like of the light metal and the additional element, it is known that the “peak temperature (T)" of magnesium is approximately equal to 350°C in the Al-Si-Mg-type aluminum alloy used as the coarse material in this example.
• a separation temperature range as a temperature range in which the solid solution element begins to separate out from within the light metal by "a separation time” relatively shorter than in other temperature ranges in the course of cooling the molten coarse material, and to set this "separation temperature range” to a range of about 50°C around the "peak temperature (T)", namely, between 300°C and 400°C.
• This "separation temperature range” can be said to be a temperature range conesponding to the shortest elapsed time needed for the separation of the solid solution element, which is contained in the light alloy, from the light metal when the coarse material is held at a predetermined temperature.
• the casting device 1 is a device for manufacturing a casting product with a desired shape through casting by gradually cooling and coagulating a coarse material in a molten state.
• the casting device 1 is mainly composed of the casting mold 2, first cooling means 3, first temperature detecting means 4, a first control device 5, and the like.
• the casting mold 2 is composed of a plurality of regions.
• the casting mold 2 is composed of a stationary mold 2A, and a movable mold 2B provided above the stationary mold 2A.
• the stationary mold 2A is removably secured to an upper face portion of a stationary frame 11 installed in the casting device 1.
• the movable mold 2B is removably secured to a lower face portion of a movable frame 12 provided above the stationary frame 11.
• the drive means for the movable frame 12 is electrically connected to the first control device 5, which will be described later.
• the first control device 5 controls the "closing” and the "opening" of the casting mold 2.
• Recess portions 2a and 2b are formed in an upper face portion of the stationary mold 2A and a lower face portion of the movable mold 2B respectively. Then, when the casting mold 2 is "closed", these recess portions 2a and 2b are thereby fitted to each other to form a cavity 21.
• a runner channel portion 2c is formed inside the stationary mold 2A.
• the runner channel portion 2c is a through-hole through which the outside of the casting mold 2 communicates with the cavity 21.
• the coarse material in a molten state is caused to flow into (poured into) the cavity 21 via the runner channel portion 2c.
• the casting mold 2 By using the casting mold 2 thus constructed, the coarse material in the molten state is coagulated into the desired shape, and the casting product is manufactured through casting. That is, the cavity 21 is formed in a shape corresponding to that of the casting product. After the coarse material in the molten state is poured into the cavity 21, the casting mold 2 is cooled by the first cooling means 3, which will be described later. The coarse material is thereby coagulated, and the casting product is manufactured through casting.
• a core (not shown) is provided, for example, inside the casting mold 2.
• the first cooling means 3 is means for managing the temperature of the coarse material poured into the cavity 21 by cooling the casting mold 2.
• the first cooling means 3 is composed of a supply source 31 that supplies a cooling medium such as coolant, circulating oil or the like, a plurality of communication channels 32 disposed inside the casting mold 2 (more specifically, the stationary mold 2A and the movable mold 2B), a pipeline member 33 that joins this supply source 31 and these communication channels 32 together, and the like.
• a first electromagnetically controlled valve 34 that controls the flow rate of the cooling medium is disposed in a midway portion of the pipeline member 33 and in the vicinity of the supply source 31.
• the first electromagnetically controlled valve 34 is electrically connected to the first control device 5, which will be described later. Then, when the cooling medium supplied from the supply source 31 is introduced into the communication channels 32 through the pipeline member 33, the flow rate of the cooling medium is changed to an arbitrary amount by operating the first electromagnetically controlled valve 34 on the basis of an electric signal transmitted from the first control device 5.
• the casting mold 2 is thereby cooled to a predetermined temperature. Then, when the casting mold 2 is cooled to the predetermined temperature, the coarse material poured into the cavity 21 is thereby cooled. As a result, the temperature management of the coarse material is carried out.
• the first temperature detecting means 4 is means for detecting the temperature of the coarse material, which is in contact with the cavity 21 from inside, by detecting the temperature of the casting mold 2.
• the first temperature detecting means 4 is designed as a known contact-type temperature sensor, and is secured to each of the stationary mold 2A and the movable mold 2B, which constitute the casting mold 2.
• the first temperature detecting means 4 is electrically connected to the first control device 5, which will be described later.
• a measurement value (a temperature of the casting mold 2) measured by the first temperature detecting means 4 is then converted into an electric signal and transmitted to the first control device 5. That is, the temperature of the casting mold 2 is detected as the temperature of the coarse material, which is in contact with the cavity 21 from inside, by the first temperature detecting means 4, and is transmitted to the first control device 5.
• the first temperature detecting means 4 can also be constituted by a known non-contact-type temperature sensor.
• This non-contact-type temperature sensor may be provided through each of the stationary mold 2A and the movable mold 2B to directly detect the temperature of the coarse material, which is in contact with the cavity 21 from inside.
• the first control device 5 is a device equipped with a storage portion and a calculation portion to control the operation of the entire casting device 1.
• the first control device 5 is designed to have input thereto a detection signal from the first temperature detecting means 4, and to control the operations of the drive means for the movable frame 12, the first electromagnetically controlled valve 34, and the like, thereby controlling the operation of the entire casting device 1.
• the coarse material cooling device 50 is a device for cooling a coarse material 100 released from the casting mold 2 to subject the coarse material 100 to a hardening treatment.
• the coarse material cooling device 50 has a heat retention chamber 51 into which the coarse material 100 to be cooled is thrown.
• the heat retention chamber 51 is equipped with second cooling means 52, second temperature detecting means 53, a second control device 54, and the like.
• the second cooling means 52 is means for cooling the coarse material
• the second cooling means 52 has a supply source 55 that supplies the cooling medium, a plurality of nozzles for injecting the cooling medium toward the coarse material 100, a pipeline member 57 that joins this supply source 55 and these nozzles 56 together, and the like.
• a second electromagnetically controlled valve 58 that controls the flow rate of the cooling medium is disposed in a midway portion of the pipeline member 57 and in the vicinity of the supply source 55.
• the second electromagnetically controlled valve 58 is electrically connected to the second control device 54, which will be described later. Then, when the cooling medium supplied from the supply source 55 is introduced into the nozzles 56 through the pipeline member 57, the flow rate of the cooling medium is changed to an arbitrary value by operating the second electromagnetically controlled valve 58 on the basis of an electric signal transmitted from the second control device 54.
• the flow rate of the cooling medium introduced into the nozzles 56 is controlled by the second control device 54.
• the temperature of the coarse material 100 is thereby cooled to a predetermined temperature.
• the coarse material 100 is subjected to the hardening treatment.
• the cooling medium is not limited to any particular type, but may be any substance, for example, a liquid such as cooling water, lubricating oil or the like, or a gas such as cooling air or the like.
• the second temperature detecting means 53 is means for detecting the temperature of the coarse material 100 thrown into the heat retention chamber 51.
• the second temperature detecting means 53 is designed as a known non-contact-type temperature sensor, and is so disposed inside the heat retention chamber 51 as to protrude toward the coarse material 100.
• the second temperature detecting means 53 is electrically connected to the second control device 54, which will be described later. A measurement value measured by the second temperature detecting means 53 (a temperature of the coarse material 100) is then converted into an electric signal and transmitted to the second control device 54. It should be noted that the second temperature detecting means 53 can also be constituted by, for example, a known contact-type temperature sensor.
• the second control device 54 is a device that is equipped with a storage portion and a calculation portion to control the operation of the entire coarse material cooling device 50.
• the second control device 54 is designed to have input thereto a detection signal from the second temperature detecting means 53, and to control the operations of the second electromagnetically controlled valve 58 and the like, thereby controlling the operation of the entire coarse material cooling device 50.
• control devices namely, the first control device 5 and the second control device 54 are provided for the casting device 1 and the coarse material cooling device 50 respectively in this embodiment of the invention
• the invention is not limited to this configuration.
• a single control device common to the casting device 1 and the coarse material cooling device 50 may be provided to control the operations of this casting device 1 and this coarse material cooling device 50 in a concentrated manner.
• the method of casting the coarse material in this embodiment of the invention mainly has a pouring process (step S 101), a casting mold cooling process (step S102), a releasing process (step S103), a coarse material cooling process (step S104), a post-treatment process (step S105), and an aging treatment process (step S106).
• the pouring process is a process of pouring a coarse material in a molten state, which is obtained by heating and melting a light alloy in a preceding process, into the cavity 21 of the casting mold 2 (see FIG. 2). That is, in the casting device 1, the casting mold 2 is "closed", and the coarse material in the molten state is poured into the cavity 21 through the runner channel portion 2c. The cavity 21 is then filled with the coarse material in the molten state.
• the pouring process (step S101) thus ends.
• the casting mold cooling process is a process of cooling the temperature of the casting mold 2 to a predetermined "casting mold cooling temperature (Tl)" to coagulate the coarse material in the molten state.
• (Tl)" is set to a temperature higher than the aforementioned “separation temperature range” and lower than an eutectic temperature of the coarse material. That is, as shown in FIG 5, in this embodiment of the invention, it is known that the eutectic temperature of the Al-Si-type alloy used as the coarse material is about 575°C, which is a temperature higher than a temperature range prescribed as the "separation temperature range", namely, a temperature range between 300°C and 400C°.
• the "casting mold cooling temperature (Tl)" is set to an arbitrary temperature in a range between 400°C and 575°C, and the information on the “casting mold cooling temperature (Tl)" is stored in advance in the storage portion of the first control device 5 (see FIG. 2). Then, when the cavity 21 of the casting mold 2 is filled with the coarse material in the molten state, the first control device 5 controls the first electromagnetically controlled valve 34 on the basis of the measurement value measured by the first temperature detecting means 4 to regulate the flow rate of the cooling medium supplied to the communication channels 32 by the first electromagnetically controlled valve 34. Thus, the casting mold 2 is gradually cooled before reaching the "casting mold cooling temperature (Tl)".
• the first control device 5 determines that the temperature of the coarse material has also become approximately equal to the “casting mold cooling temperature (Tl)", and controls the first electromagnetically controlled valve 34 to stop the supply of the cooling medium to the communication channels 32.
• the casting mold cooling process (step S102) thus ends.
• a releasing process (step S103) starts.
• the releasing process is a process of removing the coagulated coarse material from the casting mold 2 to release the coarse material from the casting mold 2.
• step S102 when the casting mold cooling process (step S102) ends, the first control device 5 controls the drive means for the movable frame 12 (see FIG. 2) to raise the movable frame 12, thereby "opening" the casting mold 2. The coarse material is then removed from the "opened” casting mold 2.
• step S103 thus ends.
• the temperature of the released coarse material which is slightly cooled through contact with outside air, reaches a temperature (T2) within the "separation temperature range" in the releasing process (step S103) as shown in FIG. 5.
• a coarse material cooling process (step S104) starts.
• the coarse material cooling process is a process of rapidly cooling the released coarse material to a predetermined "hardening temperature (T3)" to subject the coarse material to the hardening treatment.
• the "hardening temperature (T3)” is usually set to a temperature equal to or lower than 100°C. That is, as shown in FIG. 5, the “hardening temperature (T3)” is set to a temperature much lower than the aforementioned “separation temperature range”. This "hardening temperature (T3)” is then set in the second control device 54 (see FIG. 3), and is stored in advance in the storage portion of the second control device 54.
• step S104 When the coarse material cooling process (step S104) is started, the released coarse material is conveyed to the coarse material cooling device 50 and thrown into the heat retention chamber 51.
• the second control device 54 controls the second electromagnetically controlled valve 58 on the basis of the measurement value measured by the second temperature detecting means 53 to regulate the flow rate of the cooling medium supplied to the nozzles 56 by the second electromagnetically controlled valve 58.
• the coarse material is then rapidly cooled before reaching the "quenching temperature (T3)".
• the released coarse material is rapidly cooled to the "quenching temperature (T3)", which is much lower than the "separation temperature range”.
• T3 quenching temperature
• a post-treatment process (step S105) starts.
• the post-treatment process is a process of removing, for example, the core or the like from the coarse material, which is subjected to the quenching treatment through the coarse material cooling process (step S104), cleaning a surface portion of the coarse material, and the like so as to prepare for a subsequent aging treatment process (step S106).
• the coarse material is more or less lowered (or raised) through contact with outside air in the post-treatment process (step S105), the coarse material is held substantially at a predetermined temperature due to a small difference between the "quenching temperature (T3)" and the temperature of outside air, as shown in FIG. 5.
• the aging treatment process is a process of subjecting the coarse material, which is subjected to the quenching treatment through the coarse material cooling process (step S104), to an aging treatment to ensure uniform mechanical strength for a casting product manufactured through casting.
• step S105 when the post-treatment process (step S105) ends, the coarse material is thrown into a heat treatment furnace (an aging furnace) (not shown). As shown in FIG. 5, the coarse material thrown into the heat treatment furnace (the aging furnace) is rapidly heated up to a predetermined "aging temperature (T4)". After that, the coarse material is held at the "aging temperature (T4)" for a "predetermined time”. Then, after the lapse of the "predetermined time", the coarse material is rapidly cooled again to the "quenching temperature (T3)" (i.e., the temperature of the coarse material before the aging treatment), and is thereby subjected to the aging treatment. The aging treatment process (step S106) thus ends.
• step S106 When the aging treatment process (step S106) ends, the coarse material is removed from the heat treatment furnace (the aging furnace). The casting of the coarse material in this example thus ends.
• FIG. 6 is a graph in which changes with time in the temperature of the coarse material are recorded from the pouring process (step S101) to the coarse material cooling process (step S104).
• an axis of ordinate represents the temperature (unit (°C)) of the coarse material
• an axis of abscissa represents an elapsed time (unit (°Q).
• the casting method in this example is designed, as described above, to set the "casting mold cooling temperature (Tl)", which is higher than the "separation temperature range", in the casting mold cooling process (step S102) and control the function of cooling the casting mold 2 (more specifically, the first cooling means 3) such that the coarse material is gradually cooled toward the "casting mold cooling temperature (Tl)".
• the casting method according to the related art is designed to reinforce the function of cooling the casting mold 2 and perform control such that the temperature of the coarse material becomes low (i.e., a temperature t shown in FIG. 6) in the shortest possible time in the casting mold cooling process (step S102).
• step S lOl time elapses from the start of the pouring process (step S lOl) until the temperature of the coarse material reaches a temperature close to the eutectic temperature in the casting mold cooling process (step S102)
• step S102 there is no difference observed in changes with time in the temperature of the coarse material between the casting method in this example and the casting method according to the related art.
• the first control device 5 controls the operation of the first cooling means 3, so that the temperature of the coarse material gently falls. Then, when the casting mold cooling process (step S102) ends, the temperature of the coarse material reaches the "casting mold cooling temperature (Tl)", which is higher than the "separation temperature range”.
• step S102 After the casting mold cooling process (step S102) ends, the coarse material comes into contact with outside air through the releasing process (step S103), so that the temperature of the coarse material gently falls to reach the "separation temperature range".
• the releasing process (step S103) is carried out before the temperature of the coarse material reaches the "separation temperature range”.
• the releasing process (step S103) is carried out, the temperature of the coarse material reaches the "separation temperature range”. Consequently, in the casting method of this example, it takes longer for the temperature of the coarse material to reach the "separation temperature range" than in the casting method according to the related art.
• step S104 the coarse material cooling process
• step S102 after the casting mold cooling process (step S102) ends, the temperature of the coarse material is already approximately equal to the temperature of the coarse material (the temperature within the "separation temperature range") immediately after the start of the coarse material cooling process (step S104) in the casting method of this example. In consequence, the temperature of the coarse material does not change very much in the releasing process (step S103). After the releasing process (step S 103) ends, the coarse material cooling process (step S104) is swiftly started. The temperature of the coarse material changes past the "separation temperature range" in a short time, and the coarse material is further cooled rapidly.
• the temperature of the coarse material remains within the "separation temperature range" from a certain moment during the performance of the releasing process (step S 103) to an initial stage of the coarse material cooling process (step S104) (a range indicated by an arrow XI shown in FIG. 6).
• the temperature of the coarse material remains within the "separation temperature range” from a certain moment during the performance of the casting mold cooling process (step S 102) to the initial stage of the coarse material cooling process (step S104) (a range indicated by an arrow X2 shown in FIG. 6). Consequently, as shown in FIG.
• FIG. 7 is a view showing measurement values obtained by measuring two selected items, namely, a solid solubility (an amount of the solid solution element in the light metal) and a Vickers' hardness of the casting product manufactured through casting by the casting method of this example and the casting product manufactured through casting by the casting method according to the related art, with a view to quantitatively grasping the mechanical strength of each of the casting products. That is, an axis of ordinate on the left side on the sheet of FIG.
• the casting method in this example is designed, as described above, to set the "casting mold cooling temperature (Tl)", which is higher than the “separation temperature range” and control the function of cooling the casting mold 2 (more specifically, the first cooling means 3) such that the coarse material is gradually cooled toward the "casting mold cooling temperature (Tl)” in the casting mold cooling process (step S102).
• the casting method according to the related art is designed to reinforce the function of cooling the casting mold 2 and perform control such that the temperature of the coarse material becomes low (e.g., the temperature t shown in FIG 6) in the shortest possible time in the casting mold cooling process (step S102).
• the solid solubility of the casting product manufactured through casting by the casting method according to the related art is al (mass g)
• the solid solubility of the casting product manufactured through casting by the casting method of this example is a2 (mass%Mg) (al ⁇ a2). It is apparent that the amount of the solid solution element into the light metal is reliably increased by manufacturing the casting product through casting by the casting method of this example.
• the Vickers' hardness of the casting product manufactured through casting by the casting method according to the related art is bl (Hv)
• the Vickers' hardness of the casting product manufactured through casting by the casting method of this example is b2 (Hv) (bl ⁇ b2).
• a larger amount of the additional element can be solidly dissolved into the light metal by manufacturing the casting product through casting by the casting method of this example. It is therefore apparent that the Vickers' hardness is enhanced as well.
• the method of casting the coarse material in this example is a method of casting a coarse material (a light alloy) to manufacture a casting product through casting by heating and melting the coarse material (the light alloy), which is composed of a light metal as a base material and an additional element, and coagulating the molten coarse material (the light alloy) through cooling.
• the coarse material (the light alloy) is cooled such that the time during which the coarse material remains within the separation temperature range, namely, the temperature range corresponding to the shortest elapsed time needed for the separation of the solid solution element, which is contained in the coarse material (the light alloy) from the coarse material (the light alloy) becomes short.
• the time during which the temperature of the coarse material remains within the "separation temperature range" is shortened in comparison with the casting method according to the related art in the course of cooling the coarse material from the casting mold cooling process (step S102) to the coarse material cooling process (step S 104) without separately adding a process leading to an increase in the cost of equipment, for example, a process of liquefaction heating or the like.
• the amount of the additional element separating out from the light metal decreases, and the quenching treatment can be completed while minimizing to the best possible extent the dispersion of the amount of solid solution element in the light metal.
• the casting product having uniform mechanical strength is manufactured through casting.
• the casting method is equipped with the casting mold cooling process (step S102) of coagulating the coarse material (the light alloy) in the molten state, which is poured into the casting mold 2, and the releasing process (step S103) of removing from the casting mold 2 the coarse material (the light alloy) coagulated through the casting mold cooling process (step S102).
• the casting mold 2 has the first cooling means 3.
• the casting mold cooling process (step S 102) the casting mold 2 is cooled by the first cooling means 3, so that the coarse material (the light alloy) is cooled to the casting mold cooling temperature (Tl), which is higher than the "separation temperature range”.
• the releasing process (step S103) is carried out before the temperature of the coarse material (the light alloy) reaches the "separation temperature range".
• the releasing process (step S103) is carried out before the temperature of the coarse material reaches the "separation temperature range", and the temperature of the coarse material reaches the "separation temperature range” in the course of the releasing process (step S103).
• the time taken until the temperature of the coarse material reaches the "separation temperature range" is longer than in the casting method according to the related art, and the time during which the temperature of the coarse material remains within the "separation temperature range” can be shortened in comparison with the casting method according to the related art. Accordingly, as described above, the amount of the additional element separating out from the solid solution element decreases, and the hardening treatment can be completed while minimizing to the best possible extent the dispersion of the amount of solid solution of the additional element in the light metal. The coarse material with the dispersion of the amount of solid solution element thus minimized to the best possible extent is then subjected to the aging treatment. The casting product having uniform mechanical strength is thereby manufactured through casting.
• the coarse material (the light alloy) is an alloy containing aluminum-silicon alloy as the light metal and magnesium as the additional element.
• the separation temperature range is prescribed as the range between 300°C and 400°C.
• the coarse material made of the light alloy in the supersaturated state has the properties of allowing the solid solution element to separate out when being held at the predetermined temperature for the predetermined time.
• the time (the separation time) needed for the separation of the solid solution element slightly differs depending on the types or the like of the light metal and the additional element, but has the properties of changing in accordance with the temperature of the coarse material. That is, in the temperature range of the coarse material, while the temperature (the peak temperature (T)) corresponding to the shortest "separation time" exists, it is known that the "peak temperature (T)" concerning the alloy containing the aluminum-silicon alloy as the light metal and magnesium as the additional element is approximately equal to 350°C.
• the range of about 50°C around the "peak temperature (T)”, namely, the range between 300°C and 400°C is set as the "separation temperature range", and the time during which the temperature of the coarse material remains within the “separation temperature range” is shortened.
• the dispersion of the amount of solid solution element in the coarse material made of the aluminum alloy can thereby be minimized to the best possible extent.

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