HIGH-PRESSURE CASTING METHOD AND HIGH-PRESSURE CASTING DEVICE

Abstract

Provided is a high-pressure casting method and a high-pressure casting device which are capable of safe and high-quality casting of a high-fusion-point metal having a fusion point exceeding 1000 K. After melting a casting material (1) inside a melting container (2) of cartridge type, the melting container (2) is linearly moved to pass through a guide (14) attached to a casting port bush (13) to thereby be communicated with the casting port bush (13). The melting container (2) is brought into close contact with the guide (14) and is setting to a cooling state. After the elapse of prescribed time, a plunger (50) is brought into contact with a plunger tip (4), and is immediately transferred together with a molten metal to the casting port bush (13). The molten metal is pressurized inside the casting port bush (13), and is injection-filled into a cavity (10).

Claims

1. A high-pressure casting method for injection-filling of a molten metal pressurized with a plunger into a cavity, in which a melting container of cartridge type constitutes an injection sleeve detachably communicating with a casting port bush, and a plunger tip which is slidably fitted in the injection sleeve and is not fixed to the plunger, the method comprising; after loading the melting container with a casting material, disposing the melting container in an induction heating coil and melting the casting material, in a state where the melting container is separated from the casting port bush and the plunger; linearly moving the melting container so as to pass through an inside of a guide connected to the casting port bush to thereby be communicated therewith, and setting the melting container to a cooling state in close contact with the guide; and subsequently, bringing the plunger into contact with the plunger tip, immediately transferring the plunger into the casting port bush together with the molten metal, and then pressurizing the molten metal inside the casting port bush and injection-filling the molten metal into the cavity.

2. The high-pressure casting method according to claim 1, the method further comprising melting the casting material in a vacuum atmosphere or an inert atmosphere and injection-filling the molten metal into the cavity in a depressurized state.

3. The high-pressure casting method according to claim 1, the method further comprising removing the injection sleeve, the plunger tip, and the casting port bush from a main body of a device for each molding.

4. The high-pressure casting method according to claim 1, the method further comprising inclining the melting container to a vertical direction in melting of the casting material.

5. The high-pressure casting method according to claim 1, the method further comprising mechanically stirring the molten metal in the melting container in melting of the casting material.

6. A high-pressure casting device for injection-filling of a molten metal pressurized by a plunger into a cavity, comprising: a cylindrical guide attached in a through-hole of a fixed die plate; a casting port bush detachably connected to an upper portion of the guide; an injection sleeve detachably communicating with a lower end of the casting port bush; a plunger tip which is slidably fitted in the injection sleeve and is not fixed to the plunger; a moving rod which linearly movies the injection sleeve so as to be detachably supported to pass through the guide, and communicates the injection sleeve with the lower end of the casting port bush; an induction heating coil which is disposed in a movable range of the injection sleeve and which is for melting the casting material in the injection sleeve; and a holder capable of gripping the injection sleeve to be disposed in the induction heating coil, and capable of receiving and sending the injection sleeve from and to the moving rod, wherein the guide is set so as to be brought into a close contact state in a state where the injection sleeve communicates with the casting port bush.

7. The high-pressure casting device according to claim 6, further comprising a vacuum chamber which covers a space including the holder, communicates with the casting port bush on one side, and has, on the other side, the moving rod that is slidably inserted while shielding outside air.

8. The high-pressure casting device according to claim 6, wherein the moving rod operates so as to extrude and remove the casting port bush together with the injection sleeve.

9. The high-pressure casting device according to claim 6, further comprising an inclination mechanism for inclining the injection sleeve to a vertical direction.

10. The high-pressure casting device according to claim 6, further comprising a rotation mechanism for rotating the injection sleeve around its center axis.

11. The high-pressure casting device according to claim 6, further comprising a shielding mechanism for freely openably/closably covering a part of an upper opening portion of the injection sleeve.

12. The high-pressure casting device according to claim 6, further comprising a nozzle for jetting an inert gas toward an inside of the injection sleeve.

13. The high-pressure casting device according to claim 6, wherein the injection sleeve is made of graphite.

14. The high-pressure casting device according to claim 6, wherein the plunger tip is made of graphite.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0064] FIG. 1 is a front view showing a partial cross-section of a schematic configuration according to an embodiment of the present invention.

[0065] FIG. 2 is a side view showing a partial cross-section of the schematic configuration according to an embodiment of the present invention.

[0066] FIG. 3 is a perspective view showing a partial cross-section of an injection sleeve according to an embodiment of the present invention.

[0067] FIG. 4 is a perspective view showing a partial cross-section of a modification of the injection sleeve as shown in FIG. 3.

[0068] FIG. 5 is a perspective view showing a partial cross-section of a guide according to an embodiment of the present invention.

[0069] FIG. 6 is a cross-sectional view of the guide as shown in FIG. 5.

[0070] FIG. 7 is a perspective view showing a partial cross-section of a modification of the guide as shown in FIG. 5.

[0071] FIG. 8 is a perspective view showing a partial cross-section of another modification of the guide as shown in FIG. 5.

[0072] FIG. 9 is a perspective view showing a partial cross-section of a schematic configuration including an inclination mechanism, a rotation mechanism, and a shielding mechanism according to an embodiment of the present invention, in a state before operation.

[0073] FIG. 10 is a perspective view showing a partial cross-section of the schematic configuration including the inclination mechanism, the rotation mechanism, and the shielding mechanism as shown in FIG. 9, in a state after operation.

[0074] FIG. 11 is a perspective view showing a partial cross-section of a holder according to an embodiment of the present invention.

[0075] FIG. 12 is a perspective view showing a partial cross-section of a modification of the holder as shown in FIG. 11.

[0076] FIG. 13 is a front view showing a partial cross-section of a schematic configuration according to another embodiment of the present invention.

[0077] FIG. 14 is a flowchart of a high-pressure casting method according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0078] Hereinafter, the present invention will be described in detail on the basis of embodiments shown in the drawings. However, the respective components, shapes, relative arrangement, and the like described in the embodiments are not intended to restrict the scope of the present invention, but are merely examples for explanation unless otherwise specified herein.

[0079] FIGS. 1 and 2 are front and side views showing partial cross-sections of the schematic configuration of a high-pressure casting device according to an embodiment of the present invention. A melting container 2 for melting a casting material 1 is constituted by an injection sleeve 3, and a plunger tip 4 which is slidably fitted in the injection sleeve 3 and is not fixed to a plunger 50. Both the injection sleeve 3 and the plunger tip 4 are made of graphite, and as shown in FIG. 3, an upper end outer circumference and a lower end inner circumference of the injection sleeve 3 are subjected to chamfering 3a and 3b, respectively. A stepped portion 3c is provided in the inner circumference near the lower end, for the purpose of preventing the plunger tip 4 from falling out.

[0080] FIG. 4 is a perspective view showing a partial cross-section of a modification of the injection sleeve 3. In this case, a retaining ring 5 is used for preventing the plunger tip 4 from falling out, and the injection sleeve 3 is provided with a groove portion 3d for mounting the retaining ring 5 therein.

[0081] In FIG. 1, a fixed mold 11 and a movable mold 12 which constitute a cavity 10 are fixed to a fixed die plate 21 and a movable die plate 22, respectively. The fixed die plate 21 and the movable die plate 22 are provided with cooling holes 21a and 22a, respectively. A guide 14 for performing positioning in communicating the injection sleeve 3 with a casting port bush 13 is attached to the fixed die plate 21, and the casting port bush 13 penetrates through the fixed mold 11 and can be detachably fitted to both the fixed mold 11 and the guide 14.

[0082] As shown in FIG. 5, the guide 14 has substantially a cylindrical shape, is provided with at least one slit 14a. A fitting portion 14b has an internal diameter which allows the casting port bush 13 to be detachably fitted on the basis of fitting states without rattling. As shown in FIG. 6, an inside of a guide portion 14c has a tapered shape slightly closed to the side where the injection sleeve 3 is inserted, and has a maximum internal diameter substantially the same as an external diameter of the injection sleeve 3. Therefore, the guide portion 14c is elastically widened by insertion of the injection sleeve 3, and performs guiding without rattling while maintaining a contact state until the injection sleeve 3 communicates with the casting port bush 13. In this way, the utilization of an elastic recovery force of the guide portion 14c allows making the center axis of the casting port bush 13 accurately coincident with the center axis of the injection sleeve 3, and allows realizing a close contact state sufficiently required for rapid cooling of the injection sleeve 3. Note that the guide 14 can also be constituted by arranging a plurality of guide segments 14f concentrically as a modification shown in FIG. 7.

[0083] The guide 14 receives heat from the injection sleeve 3, and radiates heat to the fixed die plate 21, and a flange portion 14e of the guide 14 is only fixed to the fixed die plate 21. Therefore, in the case of low heat capacity and poor thermal conductivity of the guide 14, the heat radiation does not keep up with the heat reception, and thus the temperature at the inside of the guide portion 14c increases in a short time, thereby making it difficult to rapidly cool the injection sleeve 3. Accordingly, the guide 14 is required to have a heat capacity at least equal to or more than that of the injection sleeve 3, and required to be constituted of a material having a high thermal conductivity such as metal or graphite, and as in another modification shown in FIG. 8, cooling holes 14h may be provided in the guide portion 14c for forced cooling. However, in this case, a water channel for supply and drainage of water to and from a cooling groove 14g is required to be provided in both the fixed die plate 21 and the fixed mold 11.

[0084] In FIG. 1, a fixed housing 61 and a movable housing 62 which surround the mold are attached to the fixed die plate 21 and the movable die plate 22, and the space around the mold is isolated in interlocking with opening and closing of the mold. Note that the parts for attaching the fixed housing 61 and the movable housing 62, and the parts for fitting between those housings are vacuum-sealed.

[0085] A vacuum chamber 60 is attached between a base plate 23 and the fixed die plate 21, and the respective attachment portions are vacuum-sealed. The vacuum chamber 60 is provided with a hatch 60a, an exhaust port 60b, a view port 60c, and a back port 60d, to which a leak valve 71, a vacuum gauge 73, and a vacuum evacuation device 74 are attached. The door 63 is openably/closably attached to the hatch 60a, and the space between the door 63 and the hatch 60a is vacuum-sealed.

[0086] The view port 60c is provided so that the inside of the injection sleeve 3 is observed by inclining the injection sleeve 3. A radiation thermometer 75 capable of observing the target substance through the view finder is attached outside the view port 60c, and makes it possible to measure the temperature of the casting material 1 while confirming a melting state of the casting material 1.

[0087] A back plate 80 is rotatably fitted to the back port 60d in a vacuum-sealed state, and a support arm 90 is attached to the vacuum chamber 60 side of the back plate 80, and an induction heating coil 15 is also attached via an insulation member 17. Furthermore, a sector gear 81, a rotation motor 96, and a shielding motor 104 are attached to the outside of the back plate 80. A rotation shaft 94 and a shielding shaft 101 rotatably penetrate through the back plate in a vacuum-sealed state. Moreover, a rotation table 91 having a large bevel gear 92 is rotatably fitted to the support arm 90, on which a holder 16 for detachably gripping the injection sleeve 3 is attached.

[0088] FIGS. 9 and 10 are perspective views of schematic configurations including an inclination mechanism, a rotation mechanism, and a shielding mechanism. FIG. 9 shows a state before operation, and FIG. 10 shows a state after operation. The inclination mechanism for inclining the injection sleeve 3 is constituted by the back port 60d, the back plate 80, the sector gear 81, a pinion gear 82, an inclination motor 83, and an inclination motor mount 84. The injection sleeve 3 is inclined by rotating, with the inclination motor 83, the back plate 80 via the sector gear 81 and the pinion gear 82, and by integrally inclining the holder 16 connected to the back plate 8 and the induction heating coil 15.

[0089] The rotation mechanism for rotating the injection sleeve 3 is constituted by the support arm 90, the rotation table 91, the large bevel gear 92, a small bevel gear 93, the rotation shaft 94, a coupling 95, the rotation motor 96, and a rotation motor mount 97. The rotation table 91, the large bevel gear 92, and the support arm 90 have holes through which the moving rod 51 penetrates. Furthermore, the injection sleeve 3 is rotated by leading the rotation of the rotation motor 96 disposed outside the vacuum chamber 60 to the inside of the vacuum chamber 60 via the coupling 95 and the rotation shaft 94 and by rotating the holder 16 attached to the rotation table 91 through conversion of the rotating direction at 90 with the small bevel gear 93 and the large bevel gear 92.

[0090] The shielding mechanism freely openably/closably covers a part of the upper opening portion of the injection sleeve 3 is constituted by a shielding plate 100, a shielding shaft 101, a spur gear 102, a pinion 103, a shielding motor 104, and a shielding motor mount 105. The shielding plate 100 is provided with a hole 100a for temperature measurement and internal observation. The upper opening portion of the injection sleeve 3 is shielded by decelerating rotation of the shielding motor 104 by the pinion 103 and the spur gear 102 to thereby transfer the rotation to the shielding shaft 101 and by rotating the shielding plate 100 until the plate is brought into contact with or substantially contact with the upper surface of the injection sleeve 3. A nozzle 106 attached to the shielding plate 100 communicates with the shielding shaft 101 having a hollow structure, and the inert gas introduced from a gas introduction valve 72 is jetted into the injection sleeve 3.

[0091] The induction heating coil 15 is fixed to the back plate 80 via the insulation member 17 and is installed so that the moving rod 51 passes through the center in a state where the center axis is vertically directed. Note that each space between the induction heating coil 15 and the insulation member 17, and between the insulation member 17 and the back plate 80 is vacuum-sealed with a not shown sealing member.

[0092] The holder 16 attached to the rotation table 91 detachably grips the melting container 2 and is disposed in the induction heating coil 15. The holder 16 is made of ceramic having excellent heat insulating property, has substantially a cylindrical shape, and is provided with at least one slit 16a as shown in FIG. 11. The lower side of a portion for gripping the melting container 2 is provided with a stepped portion 16b for preventing the melting container 2 from falling out, and the internal diameter of the stepped portion is larger than the external diameter of the moving rod 51 which penetrates through the holder 16 from the lower side to thereby allow pulling out the melting container 2 upward. Note that, in the same way as in the modification as shown in FIG. 12, the holder 16 can also be constituted by arranging a plurality of holder segments 16c concentrically, and graphite can also be used as the constituent material.

[0093] In FIG. 1, the moving rod 51 has a shape of pipe through which the plunger 50 penetrates, and is slidably fitted to the base plate 23. The space between the base plate 23 and the plunger 50 is vacuum-sealed for maintaining airtightness. The lower end of the moving rod 51 is fixed to a moving plate 24, and is lifted up and down by moving cylinders 42 and 43. Note that the external diameter of the moving rod 51 is smaller than that of the injection sleeve 3.

[0094] Hereinafter, processes for executing the above configuration will be described referring to the drawings. FIG. 14 is a flowchart of the high-pressure casting method according to the embodiment of the present invention.

[0095] In step S1, the injection sleeve 3 and the plunger tip 4 constitute the melting container 2. Note that, as the injection sleeve 3 and the plunger tip 4 which constitute the melting counter 2, new ones or clean ones after completion of maintenance are used for each molding.

[0096] In step S2, the casting material 1 by the amount necessary for the single molding is loaded in the melting container 2, and in step S3, the melting container 2 is gripped by the holder 16 and is disposed in the induction heating coil 15.

[0097] In step S4, the casting port bush 13 is inserted from above the fixed mold 11 and is fitted to the fixed mold 11 and the guide 14, and in step S5, the movable die plate 22 is moved toward the fixed die plate 21 side by a mold closing cylinder 40 and closes the mold by bringing the movable mold 12 in contact with the fixed mold 11. At this time, the space around the mold is shielded from the outside air by the fixed housing 61 and the movable housing 62.

[0098] In step S6, the vacuum evacuation device 74 is used for evacuating an inside of the vacuum chamber 60 and the cavity 10 from the exhaust port 60b to thereby depressurize the inside of the vacuum chamber 60 to the predetermined pressure while measuring the pressure by using the vacuum gauge 73.

[0099] In step S7, the inclination motor 83 is driven for rotating the back plate 80 and is inclined so that the melting container is directed toward the radiation thermometer 75. The shielding motor 104 is used to rotate the shielding plate 100 until the plate is brought into contact with or substantially contact with the upper surface of the injection sleeve 3. Then, the inert gas is introduced from the gas introduction valve 72 and is jetted into the injection sleeve 3 from the nozzle 106.

[0100] In step S8, electric current is applied to the induction heating coil 15 to start heating the melting container 2 and the casting material 1, and at the time when the casting material 1 starts melting or at the time when the temperature of the casting material 1 measured by the radiation thermometer 75 reaches the fusion point, the rotation motor 96 is driven to rotate the melting container 2 around the center axis. The center axis of the melting container 2 is in a state of being inclined from the vertical direction in step S7, and thus the molten metal inside the container is stirred through forced convection only by rotating the melting container 2 in one direction at constant speed. However, reversing the rotating direction or change in the rotating speed may also be added. Furthermore, in a case where strong stirring is performed, the inclination operation by the inclination motor 83 is repeated while rotating the melting container 2 by the rotation motor 96, and thus the molten metal is oscillated through composite rotating operation.

[0101] Even after the temperature of the molten metal measured by the radiation thermometer 75 reaches a predetermined temperature, the molten metal is continuously stirred until the temperature of the molten metal becomes thermally uniformized as a whole. The melting state is confirmed from the view finder of the radiation thermometer 75, and in a case where the time required for ensuring a thermally uniformized state of the molten metal is known, the methods of stirring and heating the molten metal may be continued only for the period corresponding to the known heating time.

[0102] After the molten metal is thermally uniformized to a predetermined temperature, in step S9, the back plate 80 is reversely rotated to vertically stand the melting container 2, and then its rotation is stopped and heating by the induction heating coil 15 is completed. Immediately thereafter, the moving rod 51 is raised to pull out the melting container 2 upward from the holder 16 for replacement, and then the melting container 2 is communicated with the casting port bush 13, by guiding with the guide 14. At this time, the melting container 2 is brought into a close contact state with the guide 14 under its elastic recovery force.

[0103] The melting container 2 is rapidly cooled by holding the above-described state for a predetermined period of time, and thus the temperature boundary layer is formed near the molten metal in contact with the injection sleeve 3 inside the melting container 2. Accordingly, it becomes possible to suppress intrusion of the molten metal into the gap between the injection sleeve 3 and the plunger tip 4, or the casting port bush 13 and the plunger tip 4, and to thereby prevent reverse jetting. However, excessively long retention time may deteriorate fluidity of the molten metal, and may cause formation of the solidified layer, and thus it is necessary to set the retention time in accordance with the excessive heating temperature of the molten metal and the injection speed, by preliminary molding to be described later.

[0104] After retaining the molten metal in the melting container 2 only for the predetermined retention time, in step S10, the plunger 50 is brought into contact with the plunger tip 4 at a predetermined speed, and the molten metal in the melting container 2 is immediately transferred to the casting port bush 13 and is injection-filled into the cavity 10. Also after completion of filling, pressurization is performed by the plunger 50 for several seconds until the molten metal in the casting port bush 13 is completely solidified.

[0105] In step S11, the leak valve 71 is opened to return the vacuum chamber 60 to atmospheric pressure, and in step S12, the movable mold 12 is moved by the mold closing cylinder 40 to thereby open the mold.

[0106] In step S13, the molded product in the cavity 10 is taken out, and in step S14, the injection sleeve 3 and the casting port bush 13 in the guide 14 are extruded with the moving rod 51 upward of the fixed mold 11; and the injection sleeve 3, the casting port bush 13, and the plunger tip 4 are removed from the main body of the device.

[0107] In step S15, the injection sleeve 3, the casting port bush 13 and the plunger tip 4 which have been removed are transferred for maintenance work, and clean members after completion of the maintenance are used for the next molding.

[0108] The determination of the retention time by preliminary molding is carried out in the following way. The excessive heating temperature of the molten metal is set primarily, and the injection speed is gradually increased while setting the retention time to zero. The amount of the molten metal intruding into the gap between the casting port bush 13 and the plunger tip 4 is confirmed for each molding (confirmation is made in removing the casting port bush 13 and the plunger tip 4), and when the amount of the molten metal intruding into the gap increases, the retention time is gradually increased to thereby suppress an intrusion amount. When the intrusion amount is within the allowable range, the injection speed is gradually increased again within the retention time. This operation is repeated until the cavity 10 is completely filled, and repetitive adjustment is performed by the change of the excessive heating temperature of the molten metal as necessary, with the result that the retention time for ensuring prevention of the reverse jetting can be determined while maintaining fluidity of the molten metal as a whole.

[0109] It is possible to reliably prevent the reverse jetting without impairing the molten metal fluidity by performing preliminary molding like this, and thus it is possible to safely realize the thin-wall molding through high-speed injection even by using the active metal having a high fusion point such as titanium alloy and zirconium alloy.

[0110] Furthermore, FIG. 13 is a schematic front view partially showing a cross section of the high-pressure casting device according to another embodiment of the present invention. In this embodiment, an integrated mold 110 manufactured through lost-wax casting and three-dimensional laminating molding method is available as the mold. A casting plate 111 which allows detachable mounting of the casting port bush 13 is attached to the fixed die plate 21. The integrated mold 110 is placed on the casting plate 111 by communicating a casting port 110a with the casting port bush 13, and is fixed by being pressed at the predetermined pressure via the movable die plate 22. Any other configurations are the same as those in the embodiment as shown in FIG. 1.

REFERENCE SIGNS LIST

[0111] 1 casting material [0112] 2 melting container [0113] 3 injection sleeve [0114] 3a chamfering [0115] 3b chamfering [0116] 3c stepped portion [0117] 3d groove portion [0118] 4 plunger tip [0119] 5 retaining ring [0120] 10 cavity [0121] 11 fixed mold [0122] 12 movable mold [0123] 13 casting port bush [0124] 14 guide [0125] 14a slit [0126] 14b fitting portion [0127] 14c guide portion [0128] 14d tapered portion [0129] 14e flange portion [0130] 14f guide segment [0131] 14g cooling groove [0132] 14h cooling hole [0133] 14i O-ring [0134] 14j plug [0135] 15 induction heating coil [0136] 16 holder [0137] 16a slit [0138] 16b stepped portion [0139] 16c tapered portion [0140] 16d holder segment [0141] 17 insulation member [0142] 20 top plate [0143] 21 fixed die plate [0144] 21a cooling hole [0145] 22 movable die plate [0146] 22a cooling hole [0147] 23 base plate [0148] 23a cooling hole [0149] 24 moving plate [0150] 25 bottom plate [0151] 30 tie bar (tie rod) [0152] 31 tie bar [0153] 32 tie bar [0154] 40 mold closing cylinder [0155] 40a mold closing rod [0156] 41 injection cylinder [0157] 42 moving cylinder [0158] 43 moving cylinder [0159] 50 plunger [0160] 51 moving rod [0161] 60 vacuum chamber [0162] 60a hatch [0163] 60b exhaust port [0164] 60c view port [0165] 60d back port [0166] 61 fixed housing [0167] 62 movable housing [0168] 63 door [0169] 71 leak valve [0170] 72 gas introduction valve [0171] 73 vacuum gauge [0172] 74 vacuum evacuation device [0173] 75 radiation thermometer [0174] 75a radiation thermometer mount [0175] 80 back plate [0176] 81 sector gear [0177] 82 pinion gear [0178] 83 inclination motor [0179] 84 inclination motor mount [0180] 90 support arm [0181] 91 rotation table [0182] 92 large bevel gear [0183] 93 small bevel gear [0184] 94 rotation shaft [0185] 95 coupling [0186] 96 rotation motor [0187] 97 rotation motor mount [0188] 100 shielding plate [0189] 100a hole [0190] 101 shielding shaft [0191] 102 spur gear [0192] 103 pinion [0193] 104 shielding motor [0194] 105 shielding motor mount [0195] 106 nozzle [0196] 110 integrated mold [0197] 110a casting port [0198] 111 casting plate