JP2016078086A - Powder mold release agent, mold gravity casting method and casting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder mold release agent which, as the powder mold release agent applied on a cavity surface of a mold in mold gravity casting, has a fine casting structure, can manufacture a cast product excellent in mechanical characteristics and can improve productivity of the cast product.SOLUTION: A powder release agent 1A includes a porous center core material 2A and a plurality of spherical particles 3A with which the surface of the center core material 2A is covered. The center core material 2A and each spherical particle 3A are respectively made of inorganic compound. A diameter of each spherical particle 3A is smaller than a diameter of the center core material 2A. A median particle size of the powder release agent 1A applied on a cavity surface of the mold is 10 to 50 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a powder mold release agent applied to the cavity surface of a mold in mold gravity casting, a mold gravity casting method using the powder mold release agent, and a mold using the powder mold release agent. The present invention relates to a casting system for performing gravity casting.

  In the automobile industry, as a response to environmental problems and safety problems, it is required to reduce the weight of the vehicle body while maintaining the vehicle body function. Among them, attempts have been made to replace the constituent materials of the car body or to make the material itself thin, and replacing the steel plate that has been used conventionally with aluminum, or making the aluminum thin is the above weight reduction. It is effective.

  When manufacturing a vehicle body using a thin aluminum plate material, it is required to integrate complex shapes without joining the plate materials by welding. Methods that meet this requirement include casting such as die gravity casting, low pressure casting (for example, Patent Document 1), and die casting (for example, Patent Document 2).

  However, low-pressure casting as disclosed in Patent Document 1 requires a means for pressurizing the inside of the melting furnace and a mechanism for depressurizing the cavity, which increases costs. Further, in die casting as disclosed in Patent Document 2, a communication circuit and a vacuum device for decompressing the inside of the mold cavity are required, which increases costs. In contrast, mold gravity casting is simpler than other casting methods because it can fill the cavity with molten aluminum only by gravity, and is advantageous in reducing the cost of casting equipment and mold production. is there.

  In conventional mold gravity casting, a heat-insulating ceramic-based coating agent is applied to the surface of a mold cavity for the purpose of ensuring hot water performance and preventing the mold from damaging. Hereinafter, the surface of the cavity is appropriately abbreviated as the cavity surface. Patent Document 3 discloses a powder release agent used in die casting of aluminum alloy or the like. The powder release agent of Patent Document 3 is a mixture of a powdery or granular release agent base material made of an inorganic compound that is solid and used as a lubricant, and an organic compound that imparts adhesion to the release agent base material. It is a thing.

JP 2012-176424 A JP 7-47455 A Japanese Patent Laid-Open No. 5-92232

  By the way, in the conventional mold gravity casting, in order to improve the hot water resistance, the above-mentioned ceramic coating agent is applied thickly on the cavity surface. For this reason, there is a limit to the size and thickness of a cast product that can be manufactured, and the vertical and horizontal dimensions cannot be made larger than 0.5 m, and the thickness cannot be made thinner than 4 mm. For this reason, the conventional mold gravity casting has not been suitable for the production of large thin cast products. In order to improve the meltability of the molten metal, it is possible to make the mold temperature higher than 300 ° C. In this case, however, it takes a long time to solidify the molten metal, resulting in a coarse cast structure. High casting strength cannot be obtained.

  Moreover, the powder mold release agent of patent document 3 may generate | occur | produce gas by an organic compound thermally decomposing in contact with a molten metal. And when gas is generated in this way, a gas defect occurs in the cast product, and a high-quality cast product with excellent mechanical properties cannot be obtained.

  The present invention has been made in view of the above-mentioned matters, and its purpose is that the cast structure is fine, so that it is possible to produce a cast product having a large tensile strength and elongation rate and excellent mechanical properties. , Providing a powder mold release agent capable of improving the productivity of a cast product, a mold gravity casting method using the powder mold release agent, and a casting system for performing mold gravity casting using the powder mold release agent It is to be.

  A powder release agent according to a first aspect of the present invention is a powder release agent applied to a cavity surface of a mold in mold gravity casting, and includes a porous core material and the core Composed of a plurality of spherical particles covering the surface of the material, the core material and each spherical particle are each made of an inorganic compound, the diameter of each spherical particle is smaller than the diameter of the core material, The median particle diameter of the powder release agent applied to the cavity surface of the mold is 10 μm or more and 50 μm or less.

  A mold gravity casting method according to a second aspect of the present invention is a mold gravity casting method using the powder release agent, and the powder release agent is applied to a cavity surface of the mold. A coating process and a filling process for filling the mold cavity with molten metal while tilting the mold, and the temperature of the mold during execution of the coating process and the filling process is 300 ° C. or less. is there.

  Preferably, the temperature of the mold at the time of performing the coating step and the filling step is 160 ° C. or higher and 260 ° C. or lower.

  Preferably, in the coating step, the powder release agent charged negatively or positively is ejected to the cavity surface of the mold having a polarity opposite to that of the powder release agent. The powder release agent is applied to the cavity surface of the mold.

  Preferably, in the application step, ions released from the needle electrode by application of voltage adhere to the powder release agent, so that the powder release agent is charged negatively or positively, and the needle The voltage applied to the electrode is adjusted based on the relative humidity of the casting environment.

  A casting system according to a third aspect of the present invention is a casting system that uses the powder release agent, the casting part including a mold, and provided on both sides of the casting part. An inclined casting machine provided with a pair of support portions that are rotatably supported, a robot arm, a pipe arranged along the robot arm, and the powder fixed to the robot arm and supplied to the pipe A robot provided with a nozzle for ejecting a body release agent and a robot main body for controlling the operation of the robot arm, and connected to the pipe to supply the powder release agent to the pipe by an air flow. And a furnace for storing molten metal for filling the cavity of the mold, and one side and the other having a straight line as a boundary on which the pair of support portions are arranged Side That is, the robot and the powder supply device are arranged on one side, the furnace is arranged on the other side, and the separation distance between the powder supply device or the robot body and the inclined casting machine is the casting distance. It is larger than the turning radius of the part.

  The powder release agent of the present invention is applied to the cavity surface of the mold, thereby improving the hot water property of the molten metal filled in the cavity and the heat insulation between the molten metal and the mold. Therefore, by applying the powder mold release agent of the present invention to the cavity surface, even if the temperature of the mold is adjusted to a low temperature, the filling rate of the molten metal into the cavity is increased, and the cast product is formed into a desired shape. Can be molded. And since the temperature of a metal mold | die can be made low as mentioned above, the solidification time of a molten metal can be shortened. For this reason, since the cast structure of a cast product can be made small, it is possible to manufacture a cast product having a large tensile strength and elongation rate and excellent mechanical properties. And since the solidification time of a molten metal can be shortened as mentioned above, the productivity of a casting can be improved.

It is a partial cross section figure which shows the powder mold release agent which concerns on embodiment of this invention. It is a partial cross section figure which shows the powder mold release agent which concerns on embodiment of this invention. It is a photograph which shows the core material of the powder mold release agent shown in FIG. It is a photograph which expands and shows the surface of the core material shown in FIG. It is a top view which shows the casting system which concerns on embodiment of this invention. It is a top view which shows the casting system which concerns on embodiment of this invention. It is a side view which shows an inclination casting machine and a robot. It is a side view which shows an inclination casting machine and a robot. It is a front view of an inclination casting machine. It is a front view of an inclination casting machine. It is a side view which shows a metal mold | die, a lower mold | type installation plate, and an upper mold | type installation plate. It is a side view which shows a metal mold | die, a lower mold | type installation plate, and an upper mold | type installation plate. It is a side view which shows a metal mold | die, a lower mold | type installation plate, and an upper mold | type installation plate. It is sectional drawing of a metal mold | die. It is sectional drawing of a metal mold | die. It is a schematic sectional drawing which shows an electrostatic application nozzle. It is a flowchart which shows the process of the metal mold | die gravity casting method which concerns on embodiment of this invention. It is a graph which shows the example of the temperature transition of a metal mold | die when the process of FIG. 17 is repeated in multiple times in the condition where circulation of a heat carrier is performed. It is a graph which shows the example of the temperature transition of a metal mold | die when the process of FIG. 17 is repeated in multiple times in the condition where circulation of a heat carrier is not performed. It is a graph which shows the relationship between the charge amount of a powder mold release agent in case the voltage applied to a needle electrode is constant, and relative humidity. It is a graph which shows the relationship between the absolute value of the electrification amount of a powder mold release agent, and the adhesion amount of the powder mold release agent per unit area of a cavity surface. It is a photograph which shows the sample of the cast product of an Example. It is a photograph which shows the sample of the cast of a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 1 and 2 are partial cross-sectional views showing powder release agents 1A and 1B according to an embodiment of the present invention. FIG. 3 is a photograph showing the core material 2A of the powder release agent 1A shown in FIG. FIG. 4 is an enlarged photograph showing the surface of the core material 2A shown in FIG.

  The powder release agents 1A and 1B shown in FIGS. 1 and 2 are applied to the cavity surface of the mold in the mold gravity casting. A powder release agent 1A shown in FIG. 1 includes an intermediate core material 2A and a plurality of spherical particles 3A. The powder release agent 1B shown in FIG. 2 is composed of an intermediate core material 2B and a plurality of spherical particles 3B. Hereinafter, the powder release agents 1A and 1B are collectively referred to as powder release agent 1 as appropriate, the core materials 2A and 2B are collectively referred to as intermediate material 2, and the spherical particles 3A and 3B are collectively referred to. Will be referred to as spherical particles 3 as appropriate.

  In the powder release agent 1 shown in FIGS. 1 and 2, the core material 2 is porous, and the plurality of spherical particles 3 cover the surface of the core material 2. The diameter of each spherical particle 3 is smaller than the diameter of the core material 2. The core material 2 and each spherical particle 3 are each formed from an inorganic compound. The core material 2A of the powder release agent 1A shown in FIG. 1 contains diatomaceous earth, and the core material 2B of the powder release agent 1B shown in FIG. 2 contains zeolite. The spherical particles 3A and 3B shown in FIGS. 1 and 2 are made of, for example, amorphous silica.

  In the powder release agent 1A shown in FIG. 1, the center core material 2A has a hollow spherical shape (FIGS. 1 and 3), and the wall of the center core material 2A has an inner outer side of the center core material 2A. A large number of through-holes 4A to be communicated are formed (FIGS. 1 and 4). The diameter of each through-hole 4A is 200 nm or more and 500 nm or less.

  In the powder release agent 1B shown in FIG. 2, the core material 2B has a solid spherical shape (FIG. 2), and a large number of holes 4B penetrating the core material 2B are formed. The material 2B has a sponge shape.

  The median particle diameter of the powder release agents 1A and 1B applied to the cavity surface of the mold is 10 μm or more and 50 μm or less, and more preferably 20 μm or more and 30 μm or less. The median particle size of the powder release agents 1A and 1B is determined by adding 0.1 g of a sample of the powder release agents 1A and 1B to a beaker and adding 100 g of an aqueous solution containing 1 wt% dispersion to the beaker. This was measured with a laser diffraction particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.) after being subjected to a dispersion treatment with sound waves for 2 minutes. When the median particle diameter of the powder release agents 1A and 1B is less than 10 μm, the median particle diameter of the powder release agents 1A and 1B becomes a value close to the surface roughness of the cavity surface, and the irregularities on the cavity surface are powdered. The body release agents 1A and 1B are buried, and the range of the cavity surface exposed without being covered by the powder release agents 1A and 1B is increased. Then, when the exposed cavity surface and the molten metal come into contact with each other, sufficient fluidity of the molten metal cannot be obtained. When the median particle diameter of the powder release agents 1A and 1B is larger than 50 μm, after the molten metal is filled, transfer marks of the powder release agents 1A and 1B remain on the surface of the cast product taken out from the mold. As a result, the surface quality of the cast product deteriorates. For this reason, the post process which grind | polishes the surface of a casting is required, and a cost becomes high.

  The powder release agents 1A and 1B include, for example, diatomaceous earth (Radiolite 800 manufactured by Showa Chemical Industry Co., Ltd.) that becomes the core materials 2A and 2B, and amorphous silica (DSL Japan Co., Ltd.) that forms the spherical particles 3A and 3B. Carplex # 80) is premixed at a weight ratio of 96 wt%: 4 wt%, and then mixed at room temperature with a pot mill (processing frequency: 15 Hz, processing time: 2 hours). For the mixing process, a mixer including a Henschel mixer can be used. In addition, it is necessary to use the mixer which does not give an impact and a shear force to the core materials 2A and 2B for the mixing process.

  According to the powder release agent 1 of this embodiment, since the core material 2 and each spherical particle 3 are inorganic compounds, the powder release agent 1 is adhered to the cavity surface, so The molten metal can be filled into the cavity without generating pyrolysis gas due to heat. For this reason, gas defects do not occur on the surface or inside of the cast product, so that a high-quality cast product, that is, a cast product with excellent mechanical properties can be obtained.

  Further, since the core material 2 is porous, the powder release agent 1 has an air layer inside the core material 2. When filling the molten metal with the powder release agent attached to the cavity surface, the air layer inside the core material 2 functions as a heat insulating layer, so that the heat insulation between the molten metal and the mold is improved. Thus, the fluidity of the molten metal is improved and the molten metal is smoothly filled even in the range of the cavity that forms the thin portion of the cast product.

  Further, since the spherical particles 3 cover the surface of the core material 2, the rolling action is imparted to the surface of the core material 2, and the powder release agent 1 is easy to roll. Therefore, when the powder release agent 1 is applied to the cavity surface, the powder release agent 1 can be spread over the entire cavity surface. For this reason, it can prevent that an adhesion spot arises in a casting. In addition, since the aggregation of the core core materials 2 can be alleviated, a nozzle for ejecting the powder release agent from a tank (corresponding to powder supply devices 13A and 13B described later) for storing the powder release agent 1 ( It is possible to prevent the powder release agent 1 from aggregating on the wall surfaces of the pipes (corresponding to the later-described electrostatic nozzles 63, 64) (corresponding to the later-described piping 61, 62). For this reason, the powder release agent 1 can be stably applied to the cavity surface.

  Next, a casting system and a casting method for performing die gravity casting using the above-described powder release agent 1 (FIGS. 1 and 2) will be described.

  FIG.5 and FIG.6 is a top view which shows the casting system 10 which concerns on embodiment of this invention. The casting system 10 of this embodiment includes an inclined casting machine 11, a robot 12, powder supply devices 13A and 13B, a furnace 14, a voltage control device (not shown), and a humidity sensor (not shown). And a mold temperature sensor (not shown).

  7 and 8 are side views showing the tilt casting machine 11 and the robot 12. 9 and 10 are front views of the tilt casting machine 11. FIG.

  As shown in FIGS. 5 to 10, the inclined casting machine 11 is provided on the casting part 16 having the mold 15 (FIGS. 9 and 10) and on both sides of the casting part 16, and can rotate the casting part 16. And a pair of support portions 17A and 17B.

  As shown in FIGS. 9 and 10, in addition to the above-described mold 15, the casting part 16 includes a lower mold installation plate 20, an upper mold installation plate 21, a fixing plate 22, a tie bar 23, and a hydraulic cylinder 24. And a coupling 25 and a connecting rod 26. The upper mold installation plate 21 is disposed above the lower mold installation plate 20. The fixed plate 22 is disposed above the upper mold installation plate 21. The mold 15 includes an upper mold 30 and a lower mold 31 that are opposed to each other in the vertical direction. The upper mold 30 is fixed to the lower surface of the upper mold installation plate 21. The lower mold 31 is fixed to the upper surface of the lower mold installation plate 20. The tie bar 23 extends upward from the lower mold installation plate 20, penetrates the upper mold installation plate 21, and the upper end is fixed to the fixed plate 22. The hydraulic cylinder 24 is fixed to the upper surface of the fixed plate 22. The coupling 25 is fixed to the upper surface of the upper mold installation plate 21. The connecting rod 26 passes through the fixed plate 22 and connects the hydraulic cylinder 24 and the coupling 25, and transmits the driving force of the hydraulic cylinder 24 to the coupling 25.

  Each of the pair of support portions 17A and 17B includes a column body 40, a rotation shaft 41, and a suspended body 42. The column body 40 is erected on the floor surface at the side of the casting part 16, and a hole 43 is formed at the upper end of the column body 40. The hole 43 extends in the horizontal direction and opens to the casting part 16 side. The rotating shaft 41 is inserted into the hole 43 of the column body 40 and can be rotated by power such as a motor. A portion 41 a on the casting portion 16 side of the rotating shaft 41 extends from the opening of the hole 43. The suspended body 42 is joined to the portion 41 a of the extending rotation shaft 41. The suspended body 42 extends downward from the joining position, and the lower end portion of the suspended body 42 is joined to the end surface of the lower mold installation plate 20.

  11 to 13 are side views showing the mold 15, the lower mold installation plate 20, and the upper mold installation plate 21. 14 and 15 are cross-sectional views of the mold 15. FIG. 14A shows a cross section when the mold 15 is in the state shown in FIG. 11, and FIG. 14B shows a cross section when the mold 15 is in the state shown in FIG. FIG. 15 shows a cross section when the powder release agent 1 is applied to a cavity surface 32 a of the upper mold 30 and a cavity surface 33 a of the lower mold 31 which will be described later.

  In the casting portion 16 described above, the coupling rod 26 (FIGS. 9 and 10) transmits the driving force of the hydraulic cylinder 24 to the coupling 25, so that the coupling 25, the upper mold installation plate 21, and the upper mold 30 are vertically moved. It can be moved to. When the upper mold 30 is raised, the upper mold 30 and the lower mold 31 are separated from each other as shown in FIGS. 10, 13, and 14 (b). Then, when the upper mold 30 is lowered from the mold open state, as shown in FIGS. 9, 11, and 14 (a), the upper mold 30 and the lower mold 31 are brought into a closed state. Become. In this mold closed state, the cavity 32 and the gate Y of the mold 15 are configured by the recess 32 of the upper mold 30 and the recess 33 of the lower mold 31 (FIG. 14A). The gate Y is for guiding the molten metal to the cavity K, and opens on one side of the mold 15. A bucket 35 is fixed to a side surface of the lower die 31 at a position directly below the gate Y. The bucket 35 stores molten metal poured into the gate Y. Here, the surface of the recess 32 of the upper mold 30 indicated by reference numeral 32a and the surface of the recess 33 of the lower mold 31 indicated by reference numeral 33a correspond to the cavity surface of the mold 15 to which the powder release agent 1 is applied. . In the above-described mold opening state (the state shown in FIGS. 10, 13, and 14 (b)), the surface 32 a of the recess 32 of the upper mold 30 and the surface 33 a of the recess 33 of the lower mold 31 are exposed. Hereinafter, the surface 32 a of the recess 32 of the upper mold 30 is referred to as a cavity surface 32 a of the upper mold 30, and the surface 33 a of the recess 33 of the lower mold 31 is referred to as a cavity surface 33 a of the lower mold 31.

  Due to the rotation of the rotating shafts 41 of the support portions 17A and 17B, the suspended body 42 and the casting portion 16 are tilted (extend in the horizontal direction) shown in FIG. 6 from the non-tilt state (extend in the vertical direction) shown in FIG. Until the state). And since the casting part 16 can rotate in this way, the metal mold | die 15 can be tilted from the horizontal state shown in FIG.9, FIG11 and FIG.14 (a) to the upright state shown in FIG. (FIG. 9, FIG. 11 and FIG. 14 (a) show when the casting part 16 is in the state of FIG. 5, and FIG. 12 shows when the casting part 16 is in the state of FIG. 6). Due to the tilting of the mold 15, the molten metal stored in the bucket 35 is filled into the cavity K through the gate Y.

  As shown in FIG. 14, a heat medium flow path 50 is formed in the mold 15 (the upper mold 30 and the lower mold 31). The heat medium flow path 50 is formed to adjust the temperature of the mold 15 (the upper mold 30 and the lower mold 31). By adjusting the temperature of the heat medium to be circulated through the flow path 50, the mold 15 can be heated at the time of remaining heat, or the mold 15 can be cooled after casting. Further, a mold temperature sensor (not shown) measures the temperature of the gate vicinity portion 36 and the cavity vicinity portion 37 in the mold 15. Based on the measured value of the mold temperature sensor, the temperature of the heat medium that flows through the flow path 50 in the vicinity of the gate 36 or in the vicinity of the cavity 37 is controlled. By this temperature control, a low temperature heat medium is circulated in the flow path 50 in the vicinity of the gate 36 where the thickness is thick and tends to be high due to the heat of the molten metal, while in the cavity vicinity 37 where the thickness is thin and easy to become low, A high-temperature heat medium can be circulated through the flow path 50.

  As shown in FIGS. 5 to 8 and 15, the robot 12 includes a robot arm 60, a first pipe 61, a second pipe 62, an upper mold nozzle 63, and a lower mold nozzle 64 (FIG. 15). And a robot body 65.

  The robot arm 60 is formed by connecting a plurality of arm bodies via a joint mechanism. The joint mechanism transmits the rotation of the drive source to the arm body, so that the arm body swings up and down and left and right. , Rotate around the axis.

  The upper mold nozzle 63 and the lower mold nozzle 64 are provided for applying the powder release agent 1 to the cavity surface 32 a of the upper mold 30 and the cavity surface 33 a of the lower mold 31. As shown in FIG. 15, the upper mold nozzle 63 is fixed to the tip of the upper surface 60 a of the robot arm 60. The lower mold nozzle 64 is fixed to the tip of the lower surface 60 b of the robot arm 60.

  The first pipe 61 is provided to supply the powder release agent 1 to the upper mold nozzle 63. As shown in FIG. 15, the first pipe 61 is disposed along the upper surface 60 a of the robot arm 60, and the tip is connected to the upper mold nozzle 63. The second pipe 62 is provided to supply the powder release agent 1 to the lower mold nozzle 64. The second pipe 62 is disposed along the lower surface 60 b of the robot arm 60, and the tip is connected to the lower mold nozzle 64.

  The robot body 65 controls the operation of the robot arm 60. As shown in FIG. 15, by controlling the robot body 65, the tip of the robot arm 60 can be inserted between the upper mold 30 and the lower mold 31 when the mold 15 is in the mold open state, The tip of the robot arm 60 can be extracted from between the upper die 30 and the lower die 31 (FIG. 7 shows the operation when the tip of the robot arm 60 is inserted between the upper die 30 and the lower die 31. FIG. 8 shows the operation when the tip of the robot arm 60 is extracted from between the upper die 30 and the lower die 31). As shown in FIG. 15, when the tip of the robot arm 60 is inserted between the upper mold 30 and the lower mold 31, the upper mold nozzle 63 faces the cavity surface 32 a of the upper mold 30, and the lower mold The working nozzle 64 faces the cavity surface 33 a of the lower mold 31.

  As shown in FIGS. 5 and 6, the powder supply device 13 </ b> A is connected to the base end of the first pipe 61, and generates an air flow that pumps the powder release agent 1, The powder release agent 1 is supplied to the first pipe 61 and ejected from the upper mold nozzle 63. The powder supply device 13B is connected to the base end of the second pipe 62, and generates an air flow for pumping the powder release agent 1, thereby supplying the powder release agent 1 to the second pipe. It is supplied to 62 and ejected from the lower mold nozzle 64. As shown in FIG. 15, the powder supply apparatuses 13 </ b> A and 13 </ b> B generate the above-described air flow when the nozzles 63 and 64 face the cavity surfaces 32 a and 33 a of the upper mold 30 and the lower mold 31, thereby generating the nozzle 63. , 64, the powder release agent 1 is ejected. As a result, the powder release agent 1 ejected from the upper mold nozzle 63 is sprayed onto the cavity surface 32 a of the upper mold 30, and the powder release agent 1 ejected from the lower mold nozzle 64 becomes the lower mold 31. Is blown onto the cavity surface 33a. The flow rate of the air flow generated in the powder supply devices 13A and 13B can be controlled independently, so that the amount of the powder release agent 1 ejected from the nozzles 63 and 64 (in the pipes 61 and 62). The amount of the powder release agent 1 to be supplied) can be adjusted independently. Further, by introducing different types of powder release agents into the powder supply devices 13A and 13B, the powder release agent sprayed on the cavity surface 32a of the upper mold 30 and the powder sprayed on the cavity surface 32a of the lower mold 31 It can be changed from a release agent. For example, when the powder release agent 1A shown in FIG. 1 is put into the powder supply device 13A and the powder release agent 1B shown in FIG. The powder release agent 1A is sprayed on the surface 32a, and the powder release agent 1B is sprayed on the cavity surface 33a of the lower mold 31.

  In this embodiment, the ground wire 91 is attached to the mold 15 (upper mold 30 or lower mold 31) in order to ensure that the powder release agent 1 is adhered to the cavity surfaces 32a and 33a of the upper mold 30 and lower mold 31. (FIG. 16) is installed, and an electrostatic coating nozzle is used as the upper mold nozzle 63 and the lower mold nozzle 64. As shown in FIGS. 15 and 16, the upper mold nozzle 63 and the lower mold nozzle 64, which are electrostatic application nozzles, are provided in the cylindrical nozzle portion 80 and the opening of the nozzle portion 80, and corona discharge. Needle electrode 81 for generating The powder release agent 1 conveyed by the air flow generated by the powder supply devices 13A and 13B is introduced into the nozzle portion 80 of the nozzles 63 and 64 through the pipes 61 and 62, and It is ejected from the opening of the nozzle portion 80.

  As shown in FIG. 16, the needle electrode 81 (first needle electrode) of the upper mold nozzle 63 and the needle electrode 81 (second needle electrode) of the lower mold nozzle 64 are respectively connected to the HV power supply 90 via the electric wires 82. The voltage is applied to the needle electrodes 81 of the nozzles 63 and 64 from the HV power supply 90, and these needle electrodes 81 emit negative ions. And this negative ion adheres to the powder mold release agent 1 ejected from the opening (opening of the nozzle part 80) of the nozzle 63 for upper mold | types, and the nozzle 64 for lower mold | types, The said powder mold release agent 1 Is negatively charged. Then, the negatively charged powder release agent 1 approaches the upper mold 30 and the lower mold 31 so that negative charges in the upper mold 30 and the lower mold 31 are released to the ground through the ground wire 91. Positive charges are collected on the cavity surfaces 32 a and 33 a of the upper mold 30 and the lower mold 31. As a result, the cavity surfaces 32a and 33a of the upper mold 30 and the lower mold 31 have a positive polarity opposite to that of the powder release agent 1, so that the negatively charged powder release agent 1 is transformed into the upper mold 30 and It is attracted to the cavity surfaces 32 a and 33 a of the lower mold 31 and adheres to the cavity surfaces 32 a and 33 a of the upper mold 30 and the lower mold 31.

  A voltage control device and a humidity sensor (not shown) prevent the amount of the powder release agent 1 from adhering to the cavity surfaces 32a and 33a of the upper mold 30 and the lower mold 31 from fluctuating according to the relative humidity of the casting environment. Provided. The humidity sensor is installed in the vicinity of the mold 15 and measures the relative humidity of the installed casting environment. Relative humidity is the amount of water vapor contained in the air at a certain temperature divided by the amount of saturated water vapor at that temperature. The voltage control device includes a CPU, a memory, a communication interface, and the above-described HV power supply 90, and can communicate with a humidity sensor or a mold temperature sensor via a wire or wirelessly. In the memory of the voltage control device, voltage control indicating the relationship between the voltage applied from the HV power supply 90 to the needle electrodes 81 of the nozzles 63 and 64, the relative humidity of the casting environment, and the temperature of the upper mold 30 and the lower mold 31. Data is stored in advance. The voltage control device receives the relative humidity and the measured values of the upper mold 30 and the lower mold 31 from the humidity sensor and the mold temperature sensor, and based on the measured values of the humidity and temperature and the voltage control data, the nozzle The voltage applied to the 63 and 64 needle electrodes 81 is controlled. As a result, the amount of negative ions released from the needle electrode 81 is set to a value corresponding to the relative humidity of the casting environment and the temperature of the upper mold 30 and the lower mold 31, and negative charging according to the amount of negative ions is performed. The powder release agent 1 ejected from the nozzles 63 and 64 is charged by the amount. As a result, the charge amount of the powder release agent 1 ejected from the nozzles 63 and 64 becomes a value corresponding to the relative humidity of the casting environment and the temperature of the upper mold 30 and the lower mold 31. For this reason, it can prevent that the quantity of the powder mold release agent 1 adhering to the cavity surfaces 32a and 33a of the upper mold | type 30 or the lower mold | type 31 is fluctuate | varied with relative humidity or mold temperature. The voltages applied to the needle electrodes 81 of the upper mold nozzle 63 and the lower mold nozzle 64 can be controlled independently.

  The furnace 14 (FIGS. 5 and 6) stores a molten metal for filling the cavity K of the mold 15. For example, the furnace 14 is a smelting furnace capable of heating and melting a metal such as aluminum and storing the molten metal.

  When a metal such as aluminum is melted in the furnace 14, the furnace 14 generates a high heat of about 100 ° C. For the purpose of minimizing the influence of the heat of the furnace 14 on the powder release agent 1, the casting system 10 employs a layout in which the powder supply devices 13A and 13B and the robot 12 are kept away from the furnace 14. Yes. Specifically, as shown in FIG. 5 and FIG. 6, the powder supply devices 13 </ b> A and 13 </ b> B are provided on one side of the one side and the other side with the boundary on the straight line X where the support portions 17 </ b> A and 17 </ b> B are arranged A robot 12 is arranged, and a furnace 14 is arranged on the other side. The other side is an area where workers perform work for casting. In order to prevent the powder supply devices 13A, 13B and the robot 12 from interfering with the rotation of the casting portion 16, the distance between the powder supply devices 13A, 13B and the robot main body 65 with respect to the inclined casting machine 11 is set to be equal to the casting portion. 16 is set to be larger than the rotation radius R (FIGS. 6 to 9). The separation distance is a distance from the axis of the rotation shaft 41. H shown in FIGS. 7 and 8 indicates the rotation trajectory of the upper end of the casting part 16 (the upper end of the hydraulic cylinder 24), and the above-described rotation radius R (FIGS. 6 to 9) indicates the rotation in the mold closed state. This corresponds to a linear distance between the axis of the shaft 41 and the upper end of the casting part 16 (the upper end of the hydraulic cylinder 24).

  FIG. 17 is a flowchart showing the steps of the mold gravity casting method according to the embodiment of the present invention. Hereinafter, the die gravity casting method according to this embodiment will be described with reference to FIG. In the process of FIG. 17, the temperature of the mold 15 (the upper mold 30 and the lower mold 3) is 300 ° C. or lower, preferably 160 ° C. or higher and 260 ° C. by circulating the heat medium to the flow path 50 (FIG. 14). It is performed under the following conditions.

  First, an application | coating process is performed (step S1-S3). In this coating step, the powder release agent 1 is applied to the cavity surfaces 32a and 33a of the mold 15 (upper mold 30 and lower mold 31). Specifically, first, the mold 15 is set to a horizontal state and a mold open state (the states of FIGS. 10, 13, and 14B) (step S1). Then, by the operation of the robot arm 60 toward the inclined casting machine 11 (the operation shown in FIG. 7), the tip of the robot arm 60 is inserted between the upper die 30 and the lower die 31 as shown in FIG. The upper mold nozzle 63 and the lower mold nozzle 64 are made to face the cavity surfaces 32 and 33a of the upper mold 30 and the lower mold 31, respectively (step S2). Then, the negative mold-charged powder release agent 1 is ejected from the upper mold nozzle 63 and the lower mold nozzle 64, and the powder mold release agent 1 is positively charged to the upper mold 30 and the lower mold 30. It apply | coats to the cavity surfaces 32a and 33a of the type | mold 31 (step S3).

  When this step S3 is executed, a voltage control device (not shown) receives a measured value of relative humidity from a humidity sensor (not shown), and receives an upper mold from a mold temperature sensor (not shown). The measured value of the temperature of 30 or the lower mold 31 is received.

  The voltage control device controls the voltage applied to the needle electrode 81 of the upper die nozzle 63 based on the relative humidity, the temperature of the upper die 30 and the voltage control data. As a result, the amount of negative ions released from the needle electrode 81 of the upper die nozzle 63 is set to a value corresponding to the relative humidity and the temperature of the upper die 30, and the negative charge amount corresponding to the amount of negative ions is obtained. The powder release agent 1 ejected from the upper mold nozzle 63 is charged.

  Further, the voltage control device controls the voltage applied to the needle electrode 81 of the lower mold nozzle 64 based on the relative humidity, the temperature of the lower mold 31 and the voltage control data. As a result, the amount of negative ions emitted from the needle electrode 81 of the lower die nozzle 64 is set to a value corresponding to the relative humidity and the temperature of the lower die 31, and the negative charge amount corresponding to the amount of negative ions is obtained. The powder release agent 1 ejected from the lower mold nozzle 64 is charged.

  After the coating process, a filling process is executed (steps S4 to S6). In this filling step, the molten metal in the furnace 14 is filled into the cavity K of the mold 15.

  Specifically, first, the robot arm 60 moves toward the robot body 65 (the operation shown in FIG. 8), and the tip of the robot arm 60 is extracted from between the upper mold 30 and the lower mold 31 to obtain a mold. 15 is assumed to be a mold closed state (states of FIGS. 9, 11, and 14A) (step S4). When forming a cast product having a cavity, the tip of the robot arm 60 is extracted from between the upper die 30 and the lower die 31 and then the shell core (between the upper die 30 and the lower die 31). (Not shown) is set and the upper mold 30 is lowered to place the shell core in the cavity K. Next, using a heat-resistant container called a ladle, a molten metal such as aluminum in the furnace 14 is put into the bucket 35 (step S5). Next, the rotary shaft 41 is rotated to incline the mold 15 so that the molten metal charged into the bucket 35 is filled into the cavity K through the gate Y by the action of gravity (step S6). The rotation of the rotary shaft 41 in step S6 is performed until, for example, the mold 15 reaches an upright state (state shown in FIG. 12) in order to flow the molten metal into the cavity K.

  After the filling process, a coagulation process is performed (step S7). In this solidification step, the temperature of the heat medium circulated in the flow path 50 of the mold 15 is lowered and the mold 15 is cooled, so that the molten metal filled in the cavity K is solidified. As a result, a cast product is formed in the cavity K (when the molten aluminum is stored in the furnace 14 and the molten aluminum is filled in the cavity K, the cast aluminum product is formed in the cavity K. ).

  After the coagulation process, a demolding process is executed (step S8). In this mold removal step, the mold 15 is rotated from the upright state (the state shown in FIG. 12) to the horizontal state (the state shown in FIGS. 11 and 14A) by the rotation of the rotary shaft 41, and then the mold 15 is moved. The cast product is removed from the mold 15 in the mold open state (the state shown in FIGS. 13 and 14B).

  Thus, one casting is completed. In the case of continuously producing other castings, after the end of step S8, the process returns to step S1 and the steps S1 to S8 are repeated. In each step S1 to S8, the temperature of the mold 15 is 300 ° C. or less, preferably 160 ° C. by circulating a heat medium through the flow path 50 of the mold 15 (upper mold 30 or lower mold 31). The temperature is set to 260 ° C. or lower.

  FIG. 18 shows an example of the temperature transition of the mold 15 when the process of FIG. 17 is repeated a plurality of times in a state where the heat medium is circulated through the flow path 50. In the example shown in FIG. 18, the temperature of the mold 15 can be stably maintained in the range of 160 ° C. or more and 260 ° C. or less in each treatment by circulation of the heat medium to the flow path 50. As a result, a cast product as a product was produced in each treatment.

  In the present embodiment, casting can be performed even when the heat medium is not circulated through the flow path 50. FIG. 19 shows an example of the temperature transition of the mold 15 when the process of FIG. 17 is repeated a plurality of times in a state where the heat medium is not circulated through the flow path 50. When the heat medium is not circulated through the flow path 50, the temperature of the mold 15 depends on the temperature of the molten metal filled in the cavity K. In the example shown in FIG. 19, the temperature of the mold 15 in each process is maintained within a range of 300 ° C. or less, and a cast product as a product can be manufactured in each process.

  In the example of FIG. 18, since the heat medium is circulated through the flow path 50, the temperature distribution of the mold 15 in each process is uniform compared to the example in FIG. 19, and the mold in each process is performed. The temperature difference between the 15 high-temperature parts (near the gate) and the low-temperature parts (near the cavity and the baseboard) could be kept small. As a result, in the example of FIG. 18, the quality of the cast product obtained by each process is uniform compared to the example of FIG. 19, and the cast product obtained by each process is the machine between the parts. The difference in target characteristics was small.

  According to the present embodiment, the powder release agent 1 is applied to the cavity surfaces 32 a and 33 a of the mold 15, so that the meltability of the molten metal filled in the cavity K, the molten metal and the mold 15, The heat insulation of is improved. For this reason, even if the temperature of the mold 15 is adjusted to a low temperature of 260 ° C. or less, the filling rate of the molten metal into the cavity K can be increased and the cast product can be molded into a desired shape. And since the temperature of the metal mold | die 15 can be made low as mentioned above, the solidification time of a molten metal can be shortened. For this reason, the cast structure of the cast product can be reduced. Thereby, it is possible to manufacture a cast product having a high tensile strength and an excellent elongation and excellent mechanical properties. Moreover, since the solidification time of a molten metal can be shortened as mentioned above, the productivity of a cast product can be improved.

  Further, the powder release agent 1 does not need to be thickly applied to the cavity surfaces 32a and 33a, and can improve the hot water property of the molten metal filled in the cavity K. Therefore, the use of the powder release agent 1 makes it possible to produce a large thin cast product having a large vertical and horizontal dimension and a small thickness.

  Further, the powder release agent 1 charged to the negative polarity is ejected to the cavity surfaces 32a and 33a of the mold 15 having the positive polarity, so that the powder release agent 1 is surely provided to the cavity surfaces 32a and 33a. Can be attached to. Further, since the voltage applied to the needle electrode 81 of the upper mold nozzle 63 and the lower mold nozzle 64 is adjusted based on the relative humidity of the casting environment, it is ejected from the upper mold nozzle 63 and the lower mold nozzle 64. The charge amount of the powder release agent 1 is a value corresponding to the relative humidity of the casting environment. Thereby, it can prevent that the quantity of the powder mold release agent 1 adhering to the cavity surfaces 32a and 33a of the upper mold | type 30 or the lower mold | type 31 fluctuates with relative humidity. This effect will be described in detail with reference to FIG. 20 and FIG.

  FIG. 20 is a graph showing the relationship between the charge amount of the powder release agent 1 and the relative humidity when the voltage applied to the needle electrode 81 is constant. FIG. 21 is a graph showing the relationship between the absolute value of the charge amount of the powder release agent 1 and the adhesion amount of the powder release agent 1 per unit area of the cavity surfaces 32a and 33a.

  When the voltage applied to the needle electrode 81 is constant, as shown in FIG. 20, the charge amount is low when the relative humidity is high, and the charge amount is high when the relative humidity is low. As shown in FIG. 21, the adhesion amount of the powder release agent 1 is proportional to the charge amount, the adhesion amount is small when the charge amount is low, and the adhesion amount is large when the charge amount is high. Become. As is clear from the above, when the voltage applied to the needle electrode 81 is constant, the amount of adhesion decreases when the relative humidity is high, and the amount of adhesion increases when the relative humidity is low. On the other hand, according to the present embodiment, the voltage applied to the needle electrode 81 is adjusted according to the relative humidity. Therefore, even when the relative humidity is low or high, the charge amount of the powder release agent 1 is Can always be constant. And from this, since the adhesion amount of the powder release agent 1 can be made constant regardless of humidity, the dimensions and thickness of the cast product can always be made desired.

  Moreover, in the casting system 10 of this embodiment, as shown in FIG.5 and FIG.6, among one side and the other side which make a boundary on the straight line X by which support part 17A, 17B is arrange | positioned, it is powder on one side. Since the body supply device 13 and the robot 12 are arranged and the furnace 14 is arranged on the other side, the powder supply device 13 and the robot 12 can be moved away from the furnace 14. Therefore, the influence which the heat | fever of the furnace 14 has on the powder mold release agent 1 can be suppressed small. Further, since the powder supply device 13 and the robot 12 can be arranged on the same side, the powder supply device 13 and the robot 12 can be brought close to each other. Thereby, since the extension of the pipe line (pipe 61, 62) connecting the upper mold nozzle 63 or the lower mold nozzle 64 and the powder supply device 13 can be shortened, the powder release agent 1 stays in the pipe line. Can be prevented. Further, since the extension of the pipe line can be shortened as described above, it is not necessary to increase the pressure of the air flow generated by the powder supply device 13, and the powder release agent 1 is ejected from the nozzles 63 and 64. be able to.

  Further, according to the layouts of FIGS. 5 and 6 described above, the robot 12 does not exist on the side of the support portions 17A and 17B. It is possible to insert between the upper mold 30 and the lower mold 31. That is, when the robot 12 is present on the side of the support parts 17A and 17B, the support parts 17A and 17B are interposed between the robot 12 and the casting part 16, so that the tip of the robot arm 60 is raised. When inserting between the mold 30 and the lower mold 31, it is necessary to cause the robot arm 60 to perform an operation to avoid the support portions 17A and 17B and the tie bar 23. For this reason, the structure and operation of the robot arm 60 must be complicated. On the other hand, according to the layouts of FIGS. 5 and 6, the robot 12 does not exist on the side of the support parts 17 </ b> A and 17 </ b> B (because the robot 12 does not exist on the straight line X). The support portions 17A and 17B are not interposed between the two. Therefore, it is not necessary to cause the robot arm 60 to perform the operation of avoiding the support portions 17A, 17B and the like as described above, and the tip of the robot arm 60 is inserted between the upper mold 30 and the lower mold 31, The nozzles 63 and 64 can face the cavity surfaces 32 a and 33 a of the upper mold 30 and the lower mold 31. Therefore, it is easy to apply the powder release agent 1 to the cavity surfaces 32 a and 33 a of the upper mold 30 and the lower mold 31.

  Moreover, since the separation distance of the powder supply devices 13A and 13B and the robot main body 65 with respect to the inclined casting machine 11 is set to be larger than the rotation radius R of the casting portion 16, the powder supply device 13 and the robot 12 are cast. The rotation of the part 16 is not hindered. Thereby, gravity casting in the casting part 16 is performed smoothly.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made.

  For example, in the above-described embodiment, an example in which the powder release agent 1 charged to the negative polarity is ejected to the cavity surfaces 32a and 33a of the mold 15 having the positive polarity is shown. The powder release agent 1 charged to the positive polarity may be ejected to the cavity surfaces 32a and 33a of the mold 15 having the negative polarity. In this case, by controlling the voltage applied to the needle electrode 81 (FIG. 16), positive ions are released from the needle electrode 81, and the positive release causes the powder release agent 1 to be positive. Is charged. The positively charged powder release agent 1 approaches the cavity surfaces 32a and 33a of the mold 15 so that the cavity surfaces 32a and 33a of the mold 15 have a negative polarity. Even in this case, since the powder release agent 1 and the cavity surfaces 32a and 33a have opposite polarities, the powder release agent 1 can be reliably attached to the cavity surfaces 32a and 33a.

  In the above-described embodiment, an example in which the powder release agent 1 is charged by applying a voltage to the needle electrode 81 has been described. However, the method of charging the powder release agent 1 is not limited thereto. For example, a tribo method in which the powder release agent 1 is charged by friction when the powder release agent 1 hits the inner walls of the nozzles 63 and 64 may be employed.

  Further, the structure of the robot arm 60 is not limited to the structure shown in FIGS. The robot arm 60 may have any structure that allows the nozzles 63 and 64 to face the cavity surfaces 32 a and 33 a of the mold 15. In addition, the fixing position of the nozzles 63 and 64 in the robot arm 60 is not limited to the tip of the robot arm 60 but can be set to an arbitrary position of the robot arm 60.

  The inventors of the present invention are machines of a cast product formed by the gravity casting method of the present invention (hereinafter referred to as a cast product of the example) and a cast product formed by a conventional gravity casting method (hereinafter referred to as a cast product of a comparative example). A test comparing the mechanical properties was conducted. Hereinafter, this test will be described.

  The cast product of the comparative example is formed by applying a conventional ceramic type coating agent to the cavity surfaces 32 a and 33 a of the mold 15.

The cast product of the example is formed by the process of FIG. 17, and in the coating process (steps S <b> 1 to S <b> 3), the powder release that is negatively charged using a corona charge type electrostatic coating nozzle. The agent 1 was applied to the cavity surfaces 32a and 33a of the mold 15 having positive polarity. The core material 2 contained in the powder release agent 1 is a compound of diatomaceous earth and silica (weight% of diatomaceous earth is 96% and weight% of silica is 4%). The median particle diameter of the powder release agent 1 is 25 μm. The voltage applied to the needle electrode 81 of the electrostatic coating nozzle is 50 KV. The flow rate of the air flow that conveys the powder release agent 1 is 4.0 m ³ / h.

  In the filling step (steps S4 to S6), after pouring a molten aluminum alloy (AC4C) of 750 ° C. to 780 ° C. from the furnace 14 into the bucket 35, the molten metal in the bucket 35 is rotated by rotating the mold 15. Was filled into the cavity K. Then, after 140 seconds from the start of rotation of the mold 15, the mold was opened (step S8) to obtain the cast product of the example.

  And the structure | tissue observation of the casting product of the Example obtained by said method and a comparative example was performed. During this observation, the sample was cut out from the cast product with a microcutter, embedded in light and curable resin, and the embedded sample was coarsely polished with sandpaper and buffed with 1 μm diamond paste. A mirror finish was performed. Thereafter, the mirror-finished sample was etched with a Keller solution and observed with an optical microscope. 22 and 23 are photographs taken with an optical microscope, FIG. 22 shows the surface of the sample of the example, and FIG. 23 shows the surface of the sample of the comparative example. As is clear from comparison between FIGS. 22 and 23, the sample of the example had a finer cast structure than the sample of the comparative example.

  In this test, secondary dendrite arm spacing (SDAS), tensile strength, and elongation were measured for the castings of Examples and Comparative Examples.

  Secondary dendrite arm spacing (hereinafter referred to as SDAS) is obtained by randomly selecting a dendrite-like portion from the surface of a sample shown in a photograph of an optical microscope and calculating the length and the number of branches.

  When measuring the tensile strength and elongation rate, a sample was cut out from the cast product using a wire electric discharge machine (Brother Kogyo Co., Ltd .: HS300). Then, the electric discharge machining surface of the sample was polished with sandpaper, and the electric discharge machining affected part was removed. The other surfaces were left as cast. And the heat processing was performed with respect to the sample. In this heat treatment, the sample is subjected to a solution treatment at 525 ° C. for 8 hours, and then the sample is left overnight at room temperature, and then the sample is subjected to an aging treatment at 160 ° C. for 6 hours. . Then, the tensile strength / elongation rate of the sample before the heat treatment and the tensile strength / elongation rate of the sample after the heat treatment were measured with an Instron type tester. This measurement was performed at room temperature, and the tensile speed of the Instron type tester was 3 mm / min. The measurement results of SDAS / tensile strength / elongation are shown in Table 1 below.

  As shown in Table 1, in the comparative example, SDAS was 20 μm to 40 μm. In contrast, in the examples, SDAS was 8 μm to 15 μm, which was about 50% (1/2) of the comparative example. From this, it was confirmed that according to the gravity casting method of the present invention, the solidification structure of the cast product can be reduced.

  Moreover, about the tensile strength before heat processing, the measured value of the Example became 1.3 times (130%) of the measured value of a comparative example. About the tensile strength after heat processing, the measured value of the Example became 1.17 times (117%) of the measured value of the comparative example. Moreover, about the elongation rate before heat processing, the measured value of an Example becomes 2.33 times (233%) of the measured value of a comparative example, and the measured value of an Example about the elongation rate after heat processing is a comparative example. The measured value was 1.56 times (156%). From the above, according to the gravity casting method of the present invention, it was confirmed that a cast product having a large tensile strength and elongation rate and excellent mechanical properties can be formed.

  Moreover, in this test, the weight of the casting of the comparative example and the weight of the casting of the example were measured, and the weight ratio of the comparative example to the example (weight of the comparative example: weight of the example) It was confirmed that the ratio was 100: 54 (that is, the example was confirmed to be 46% lighter than the comparative example). The difference in weight between this example and the comparative example is that the powder mold release agent 1 of the present invention produces a hot water runnability higher than that of the conventional ceramic type coating agent, so that the minimum thickness of the example is 2 mm. This is because the thickness of the example can be made thinner than the thickness of the comparative example.

1A, 1B Powder release agent 2A, 2B Core material 3A, 3B Spherical particle 10 Casting system 11 Inclined casting machine 12 Robot 13 Powder supply device 14 Furnace 15 Mold 16 Casting part 17A, 17B Support part 30 Upper mold 31 Lower mold 32 Upper mold recess 33 Lower mold recess 32a Upper mold cavity surface 33a Lower mold cavity surface 60 Robot arm 61, 62 Pipe 63 Upper mold nozzle 64 Lower mold nozzle 65 Robot main body 70 Input unit 71, 72 Connecting tube 81 Needle electrode K Cavity

Claims (6)

A powder release agent applied to the cavity surface of the mold in mold gravity casting,
A porous core material,
Composed of a plurality of spherical particles covering the surface of the core material,
The core material and each spherical particle are each composed of an inorganic compound,
The diameter of each spherical particle is smaller than the diameter of the core material,
The powder release agent having a median particle diameter of 10 μm or more and 50 μm or less applied to the cavity surface of the mold. A mold gravity casting method using the powder release agent according to claim 1,
An application step of applying the powder release agent to the cavity surface of the mold;
Filling the mold cavity with molten metal while tilting the mold,
The mold gravity casting method, wherein the temperature of the mold during execution of the coating step and the filling step is 300 ° C. or less.   The mold gravity casting method according to claim 2, wherein a temperature of the mold during execution of the coating process and the filling process is 160 ° C or higher and 260 ° C or lower.   In the coating step, the powder mold release agent charged negatively or positively is ejected onto the cavity surface of the mold having the opposite polarity to the powder mold release agent. The mold gravity casting method according to claim 3, wherein the powder release agent is applied to a cavity surface of the mold. In the coating step, the ions released from the needle electrode by application of voltage adhere to the powder release agent, so that the powder release agent is charged negatively or positively,
The mold gravity casting method according to claim 4, wherein the voltage applied to the needle electrode is adjusted based on a relative humidity of a casting environment. A casting system using the powder release agent according to claim 1,
A tilt casting machine provided with a casting part provided with a mold, and a pair of support parts provided on both sides of the casting part and rotatably supporting the casting part;
A robot arm, a pipe arranged along the robot arm, a nozzle fixed to the robot arm and ejecting the powder release agent supplied to the pipe, and controlling the operation of the robot arm A robot provided with a robot body, and
A powder supply device connected to the pipe and supplying the powder release agent to the pipe by an air flow and ejecting the powder from the nozzle;
A furnace for storing molten metal for filling the cavity of the mold,
Of the one side and the other side with the straight line on which the pair of support parts are arranged as a boundary, the robot and the powder supply device are arranged on one side, and the furnace is arranged on the other side,
A casting system in which a separation distance between the powder supply device or the robot body and the inclined casting machine is larger than a turning radius of the casting part.