JP2011131265A - Vacuum die casting apparatus and vacuum die casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum die casting method by which a casting product with a superior quality can be obtained by stabilizing a feed quantity of a molten metal to an injection sleeve in vacuum suction, and to provide a vacuum die casting apparatus by which the vacuum die casting method can be accomplished with a simple structure. <P>SOLUTION: An atmospheric release valve is installed which releases the air confined in a cavity into the atmosphere at the time of closing a fixed die and a movable die. With this installation, air inflow into a molten metal feeding tube and fluctuation of a molten metal surface in the feeding tube are suppressed, stabilizing the feeding amount of molten metal into the injection sleeve. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a vacuum die casting apparatus and a vacuum die casting method.

  The normal die casting method is a casting method in which a molten metal in a holding furnace is supplied into an injection sleeve with a ladle or the like, an injection plunger is operated to pass through a narrow gate, and injected into a mold cavity. The die casting method is widely applied to the production of aluminum alloy castings and the like because a casting with high dimensional accuracy is obtained and the cycle time is short. On the other hand, since the die casting method injects the molten metal at a high speed, it is easy to involve air and oxide. There is a vacuum die casting method as a method for reducing the entrainment of air and oxides. In recent years, the molten metal in the holding furnace is supplied into the injection sleeve through the hot water supply pipe by reducing the pressure in the cavity by vacuum suction. The vacuum die casting method that enables suction hot water supply under reduced pressure by extending the pressure reduction time and sufficiently reducing the pressure in the closed space from the cavity to the injection sleeve, further reducing the entrainment of air and oxides Has been developed and put to practical use.

  As a vacuum die casting apparatus that performs hot water supply by vacuum suction, for example, an apparatus disclosed in Patent Document 1 is known. FIG. 4 shows a vacuum die casting apparatus 100 of Patent Document 1. The apparatus 100 includes a cavity 145 formed by a fixed mold 142 and a movable mold 144, an injection sleeve 131 that communicates with the cavity 145, a holding furnace 111 that stores the molten metal M, one end connected to the injection sleeve 131, and the other. The end is provided with a hot water supply pipe 121 that is immersed in the molten metal M in the holding furnace 111. A vacuum valve 153 is provided between the cavity 145 and the vacuum device 150. Then, by the vacuum suction of the vacuum device 150 and the opening operation of the vacuum valve 153, the closed space from the cavity 145 to the injection sleeve 131 is decompressed, and the suction hot water supply for sucking the molten metal M into the injection sleeve 131 is performed. Further, in the vacuum die casting apparatus 100 of Patent Document 1, in order to accurately supply the molten metal M to the injection sleeve 131, the molten metal M in the holding furnace 111 is measured by the level sensor 112, the temperature sensor 113, and the weight meter 114. The measured value and the target value are compared by the computer 115, and the vacuum device 150 and / or the vacuum valve 153 are controlled, so that the hot water supply amount can be controlled with high accuracy. In FIG. 4, 121a is an orifice, 132 is an injection plunger, fixed platens 141 and 143 are movable platens, and 146 is a gate.

JP 2001-79654 A

  Normally, vacuum die casting equipment is provided with measures to ensure airtightness between the closed space defined by cavities, injection sleeves, and hot water supply pipes, and the outside, in order to improve the degree of pressure reduction during vacuum suction. Has been. For this reason, the vacuum die-casting device is higher in airtightness than a general die-casting device, and the air sandwiched between the cavity formed by the fixed mold and the movable mold during the mold clamping operation causes the cavity, the injection sleeve, and the hot water supply. It is difficult to dissipate from the closed space defined by the pipe, and flows into the hot water supply pipe via the injection sleeve and pushes the molten metal in the hot water supply pipe back to the holding furnace side. The temperature and volume of the air sandwiched between the cavities fluctuate as the temperature of the fixed mold or movable mold changes due to casting. For this reason, the amount of air flowing into the hot water supply pipe changes every casting shot, and the hot water surface position (hot water surface level) of the molten metal in the hot water supply pipe fluctuates vertically or the hot water surface fluctuates. As the amount of air flowing into the hot water supply pipe increases, the hot water surface position in the hot water supply pipe greatly decreases, and therefore the amount of hot water supplied to the injection sleeve in the reduced pressure suction after completion of mold clamping is reduced. The amount of hot water supplied to the injection sleeve is reduced by the air flowing into the hot water pipe being cooled and solidified by the molten metal adhering to the inner wall of the hot water pipe and the orifice, or by oxidizing the hot water pipe and orifice. Is further reduced.

  In the vacuum die casting method, when the molten metal supplied to the injection sleeve is advanced and the injection plunger fitted to the injection sleeve is advanced to fill the cavity, the fixed mold and / or the movable mold, the injection sleeve, and the injection are placed before the gate of the cavity. By forming a biscuit surrounded by the plunger and pressed by the injection plunger, and applying a high pressure to the cavity via this biscuit, it is possible to manufacture a high-quality cast product with few casting defects such as cast holes and non-rotation. . As the amount of hot water supplied to the injection sleeve decreases, the thickness of the formed biscuits becomes thinner, the biscuits solidify quickly and the pressure of the injection plunger is difficult to transmit to the cavity, and casting defects such as cast holes and non-rotations Is likely to occur.

  Further, when the amount of air flowing into the hot water supply pipe becomes extremely large, the air reaches not only the hot water supply pipe but also the inside of the holding furnace, and generates oxides, solidified pieces, and bubbles in the molten metal. The generated oxides, solidified pieces, and bubbles are caught in the molten metal at the time of hot water supply in a later casting shot, sucked together with the molten metal into the injection sleeve, and injected into the cavity. Causes defects.

  As a preventive measure for casting defects due to insufficient hot water supply to the injection sleeve, avoiding problems such as casting holes due to insufficient hot water supply by increasing the hot water supply in advance in anticipation of a decrease in hot water supply to the injection sleeve Is possible. However, the amount of air that is sandwiched between the cavities during mold clamping operation and flows into the hot water supply pipe changes every casting shot, so if the amount of air flowing in decreases and the hot water surface position in the hot water supply pipe rises unexpectedly, The amount of hot water supplied to the injection sleeve is excessive. When there is a large amount of hot water supplied to the injection sleeve, in the injection process including low to high speed by the injection plunger, excessive molten metal flows into the gate and cavity in advance at the low speed injection stage and solidification proceeds, and the subsequent high speed Without fusing with the molten metal that has flowed through the injection, casting defects such as hot water boundaries and non-circulation are likely to occur. In particular, if the gate is closed before the injection is completed, there arises a problem that a casting product cannot be obtained due to poor filling.

  The vacuum die casting apparatus shown in Patent Document 1 has been proposed with a focus on improving the accuracy of hot water supply at the stage where the molten metal is sucked into the injection sleeve while the cavity is decompressed after the clamping of the fixed mold and the movable mold is completed. Is. Further, in the conventional vacuum die casting apparatus, for example, removal of back pressure when supplying molten metal to the injection sleeve using an electromagnetic pump, formation of air flow for dispersion adhesion of the release agent in the cavity, and injection sleeve From the cavity to the injection sleeve after the clamping operation of the fixed mold and the movable mold is completed and before the cavity is depressurized by vacuum suction, for the purpose of preventing fluctuations in the hot water level in the hot water supply pipe when supplying lubricant There are some conventional techniques for pre-depressing the closed space and opening the atmosphere.

  However, as described above, in the vacuum die casting method, the air sandwiched between the cavities flows into the hot water supply pipe during the mold clamping operation before the mold clamping between the fixed mold and the movable mold is completed, and the amount of air flowing in is The molten metal in the hot water supply pipe fluctuates depending on the casting shot. In addition, due to fluctuations in the molten metal level in the hot water supply pipe, the amount of molten metal supplied to the injection sleeve in vacuum suction after completion of mold clamping varies, resulting in cast holes, molten metal boundaries, non-rotating, foreign matter There is no attempt to solve the problem that casting defects such as biting are likely to occur.

  The present invention has been made in view of the above situation, and by suppressing the inflow of air into the hot water supply pipe during mold clamping and the molten metal surface fluctuation of the molten metal in the hot water supply pipe, the mold after the mold clamping is completed. An object of the present invention is to provide a vacuum die casting method that can stabilize the amount of molten metal supplied to the injection sleeve by vacuum suction and obtain a casting of good quality. Another object of the present invention is to obtain a vacuum die casting apparatus that can achieve the above vacuum die casting method with a simple structure.

  In order to solve the above-mentioned problems, the present inventors have taken measures for dissipating air from a closed space defined by a cavity or the like so that the air sandwiched in the cavity does not flow into the hot water supply pipe during the mold clamping operation. Researched earnestly. As a result, the air sandwiched in the cavity is released to the atmosphere during the mold clamping operation, thereby suppressing the inflow of air into the hot water supply pipe and the fluctuation of the molten metal level in the hot water supply pipe, and the hot water supply of the molten metal to the injection sleeve. The inventors have obtained the knowledge that the amount can be stabilized and the above problems can be solved, and the present invention has been conceived.

  That is, the vacuum die casting apparatus of the present invention includes a cavity formed of a fixed mold and a movable mold, an injection sleeve communicating with the cavity, an injection plunger that can be fitted and moved forward and backward in the injection sleeve, and the injection sleeve A holding furnace in the lower part for containing the molten metal, a hot water supply pipe having one end communicating with the hot water inlet formed in the injection sleeve and the other end immersed in the molten metal in the holding furnace; A vacuum die casting apparatus having a pressure reducing means for supplying molten metal in a holding furnace to the injection sleeve through the hot water supply pipe, wherein the cavity and the injection sleeve are used during a clamping operation between the fixed mold and the movable mold. And an air release valve for releasing the pressure of the closed space defined by the hot water supply pipe to atmospheric pressure.

  In the vacuum die casting apparatus of the present invention, the atmosphere release valve is provided between a shutoff valve for preventing molten metal outflow installed in the fixed type or the movable type and a vacuum valve for opening and closing communication with the vacuum device. Preferably, the atmosphere release valve is provided in the injection sleeve, and the atmosphere release valve is a shutoff valve for preventing molten metal outflow that is installed in the fixed type or the movable type. It is also preferable to use both.

  In addition, the vacuum die casting method of the present invention includes an injection plunger for fitting a molten metal in a holding furnace to the injection sleeve via a hot water pipe by depressurizing the cavity formed by the fixed mold and the movable mold, and fitting the injection sleeve. In the vacuum die casting method of advancing and filling the cavity with the molten metal in the injection sleeve, the cavity, the injection sleeve, and the hot water supply during the clamping operation of the fixed mold and the movable mold before decompressing the cavity The pressure of the closed space defined by the pipe is released to atmospheric pressure by an atmospheric release valve.

  According to the vacuum die casting method of the present invention, air can be prevented from flowing into the hot water supply pipe during mold clamping. In addition to suppressing the decrease in the hole diameter of the hot water supply pipe and orifice, the amount of molten metal supplied to the injection sleeve by decompression suction after completion of mold clamping is stabilized, so Casting defects such as turning around can be reduced. Further, by suppressing the fluctuation of the molten metal surface in the hot water supply pipe, it is possible to reduce casting defects such as oxides and solidified pieces in the hot water supply pipe and the holding furnace, foreign matter biting and gas defects due to entrainment of bubbles. Therefore, according to the vacuum die casting method of the present invention, it is possible to reduce the tendency of occurrence of casting defects and obtain a cast product of good quality.

  In addition, according to the vacuum die casting apparatus of the present invention, the above-described vacuum die casting method has a simple structure and is economical because, for example, an existing apparatus is provided with a simple means of providing an air release valve. Can be achieved.

1 is a cross-sectional view of a vacuum die casting apparatus in Embodiment 1. FIG. FIG. 6 is a transverse cross-sectional view of a vacuum die casting apparatus in a second embodiment. FIG. 6 is a transverse cross-sectional view of a vacuum die casting apparatus in a third embodiment. It is a cross-sectional view of a conventional vacuum die casting apparatus disclosed in Patent Document 1.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of a vacuum die casting apparatus 1 in the first embodiment. In FIG. 1, the vacuum die casting apparatus 1 includes a fixed mold 42 attached to a fixed platen 41, a movable mold 44 attached to a movable platen 43, and a cavity for molding a cast product formed by the fixed mold 42 and the movable mold 44. 45. The injection sleeve 31 communicates with the cavity 45 through a gate 46. The injection sleeve 31 has an injection plunger 32 that can fit in the injection sleeve 31 and move forward and backward. By using the injection plunger 32 having a ring structure, the clearance generated between the injection plunger 32 and the injection sleeve can be reduced, which is advantageous in maintaining airtightness.

  Further, the vacuum die casting apparatus 1 includes a holding furnace 11 below the injection sleeve 31 for storing the molten metal M and holding it by heating with gas or the like. The molten metal surface position in the holding furnace 11 is preferably maintained at a fixed position by a molten metal surface position control device comprising a molten metal surface sensor, a computer, etc. (not shown).

  Further, the vacuum die casting apparatus 1 has a hot water supply pipe 21 that has one end communicating with a hot water supply port 31 a formed in the holding furnace 11 and the other end immersed in the molten metal M in the holding furnace 11. It is preferable that the hot water supply pipe 21 is detachably connected to the injection sleeve 31 via a hanger. Further, the hot water supply pipe 21 has an orifice 21a having a small diameter, and when the molten metal M is supplied to the injection sleeve 31 by vacuum suction, the hot water supply amount per unit time can be adjusted by changing the diameter of the orifice 21a. The hot water supply pipe 21 is preferably made of ceramic having both heat resistance and air tightness, and has a pipe structure in which the inner wall surface is coated with BN to prevent reaction with the molten metal, and the hot water supply pipe 21 is provided in the hot water supply pipe. It is preferable to keep the temperature heated to the same level as the molten metal temperature by a thermocouple for detecting the molten metal temperature, a heater and a heat insulating material surrounding the hot water supply pipe, and the like.

  The vacuum die casting apparatus 1 includes a vacuum device 50 including a vacuum pump 51 that is a decompression unit, a vacuum tank 52 that stores a vacuum pressure in the vacuum pump 51, a vacuum valve 53, an atmosphere from the vacuum tank 52. And a piping system connected to the cavity 45 via the release valve 54 and the shut-off valve 55. The vacuum valve 53 and the atmosphere release valve 54 can be used as long as they have a valve mechanism that can be opened and closed, such as a conventionally known electromagnetic valve. The shut-off valve 55 is a valve for preventing molten metal from flowing out of the cavity 45, and is preferably provided with a hydraulic or electric actuator in order to perform an opening / closing operation in a short time. In the first embodiment, the atmosphere release valve 54 is provided between the shut-off valve 55 and the vacuum valve 53, one end of the valve body communicates with the piping system of the vacuum device 50, and the other end opens to the atmosphere, and the vacuum Based on the operation signal of each part of the die casting apparatus 1, the opening / closing operation is performed by a control device (not shown).

  Next, the vacuum die casting method of the present invention will be described. First, the vacuum valve 53 is closed, the vacuum pump 51 of the vacuum device 50 is operated, and the vacuum pressure is stored in the vacuum tank 52. On the other hand, the air release valve 54 and the shutoff valve 55 provided in the piping system connected to the cavity 45 are both set to “open”.

  Clamping of the fixed mold 42 and the movable mold 44 is started by moving the movable mold 44 toward the fixed mold 42 from the mold open state where the fixed mold 42 and the movable mold 44 are separated from each other. At this time, the mold clamping is performed with the shut-off valve 55 and the air release valve 54 open, so that the air sandwiched between the cavities 45 formed by the fixed mold 42 and the movable mold 44 has the cavities 45, the injection sleeves 31 and Since the closed space defined by the hot water supply pipe 21 is exhausted to the atmosphere via the shut-off valve 55 and the atmosphere release valve 54, the pressure in the closed space is released to atmospheric pressure. Thereby, it is possible to prevent the air sandwiched between the cavities 45 from flowing into the hot water supply pipe 21 via the injection sleeve 31, and to suppress fluctuations in the molten metal level of the molten metal M in the hot water supply pipe 21.

  After the mold clamping is completed, the atmosphere release valve 54 is set to “closed” and the vacuum valve 53 is set to “open”, and the cavity 45 is connected to the vacuum device 50 that is a pressure reducing means, and pressure reduction by vacuum suction is started. Since the vacuum die casting apparatus 1 after mold clamping forms a closed space defined by the cavity 45, the injection sleeve 31, and the hot water supply pipe 21, the air in the closed space is exhausted (degassed) by the pressure reduction by the vacuum apparatus 50. At the same time, the molten metal M in the holding furnace 11 is supplied to the injection sleeve 31 via the hot water supply pipe 21.

  When the molten metal M in the injection sleeve 31 reaches a predetermined amount required for casting, the injection plunger 32 fitted to the injection sleeve 31 is advanced, and the molten metal M in the injection sleeve 31 is filled into the cavity 45 via the gate 46. Cast products are manufactured. The shut-off valve 55 and the vacuum valve 53 are set to “closed” at a timing when the molten metal M does not enter the piping system of the vacuum device 50 in the injection process.

  According to the vacuum die casting method of the first embodiment, the air sandwiched in the cavity can be prevented from flowing into the hot water supply pipe via the injection sleeve during the mold clamping operation, so that the molten metal in the hot water supply pipe can be prevented. It is possible to suppress variations in the molten metal surface level, such as variations in the molten metal surface level and undulations, and to prevent a decrease in the diameter of the hot water supply pipe and orifice. Therefore, since the fluctuation of the molten metal level in the hot water supply pipe can be suppressed, the amount of molten metal supplied to the injection sleeve is stabilized, and oxides, solidified pieces, and entrainment of bubbles in the hot water supply pipe and holding furnace are suppressed. Casting defects such as casting voids, hot water boundaries, non-rotation, foreign object biting, and gas defects are reduced.

  Normally, hot water pipes and orifices are regularly cleaned to remove solid deposits and oxide deposits from the molten metal adhering to the inner wall after leaving the injection sleeve for the purpose of maintaining the hole diameter. . As a secondary effect of the present invention, the frequency of cleaning hot water pipes and orifices can be reduced, and the useful life thereof can be extended.

(Embodiment 2)
FIG. 2 shows a cross-sectional view of the vacuum die casting apparatus 1 according to the second embodiment. In FIG. 2, the vacuum die casting apparatus 1 is different from the vacuum die casting apparatus 1 of the first embodiment described above only in the installation site of the atmosphere release valve 54, except that the atmosphere release valve 54 is provided on the injection sleeve 31. Same device configuration. In FIG. 2, the same parts as those in the vacuum die casting apparatus of FIG. In the atmosphere release valve 54 of the second embodiment, one end of the valve body communicates with the injection sleeve 31 and the other end is open to the atmosphere. In the vacuum die casting method of the second embodiment, a cast product is manufactured by the same method as the vacuum die casting method of the first embodiment.

(Embodiment 3)
FIG. 3 is a cross-sectional view of the vacuum die casting apparatus 1 according to the third embodiment. In FIG. 3, the vacuum die casting apparatus 1 is different from the vacuum die casting apparatus 1 of the first embodiment described above only in the location where the atmosphere release valve 54 is installed, and the atmosphere release valve 54 is replaced with a shutoff valve for preventing melt outflow. The apparatus has the same configuration except that it is also provided. In FIG. 3, the same parts as those of the vacuum die casting apparatus of FIG. The air release valve 54 of the third embodiment is installed in the fixed mold 42, one end of the valve body communicates with the cavity 45, and the other end is open to the atmosphere. In the vacuum die casting method of the third embodiment, a cast product is manufactured by the same method as the vacuum die casting method of the first embodiment.

  Also in the vacuum die casting methods of the second and third embodiments, as in the first embodiment, the mold is operated with the atmosphere release valve set to “open”, thereby defining the cavity, the injection sleeve, and the hot water supply pipe. By opening the closed space pressure to atmospheric pressure, the flow of air into the hot water supply pipe and the fluctuation of the molten metal level in the hot water supply pipe are suppressed, and the amount of hot water supplied to the injection sleeve is stable and good. A quality casting is obtained. Further, according to the vacuum die casting apparatus of the second and third embodiments, the above vacuum die casting method can be achieved economically with a simple structure.

  As mentioned above, although the typical example of this invention was demonstrated, this invention is not restricted to embodiment mentioned above, It can change in the range which does not deviate from the summary of invention. In particular, the atmosphere release valve is not limited to the above-described installation site and configuration, but in summary, it is an installation site or configuration that can release air sandwiched between cavities formed by a fixed mold and a movable mold during mold clamping operation. I need it.

DESCRIPTION OF SYMBOLS 1,100: Vacuum die casting apparatus 11, 111: Holding furnace 21, 121: Hot water supply pipe 21a, 121a: Orifice 31, 131: Injection sleeve 31a: Hot water supply port 32, 132: Injection plunger 41, 141: Fixed platen 42, 142: Fixed type 43, 143: Movable platen 44, 144: Movable type 45, 145: Cavity 46, 146: Gate 50, 150: Vacuum device 51: Vacuum pump 52: Vacuum tank 53, 153: Vacuum valve 54: Atmospheric release valve 55 : Shut-off valve 112: Level sensor 113: Temperature sensor 114: Weigh scale 115: Computer M: Molten metal

Claims (5)

  A cavity formed of a fixed mold and a movable mold, an injection sleeve communicating with the cavity, an injection plunger that can be fitted and moved forward and backward in the injection sleeve, and a holding furnace that is located below the injection sleeve and accommodates molten metal One end of which is in communication with a hot water outlet formed in the injection sleeve, and the other end is immersed in the molten metal in the holding furnace, and the cavity is decompressed to supply the molten metal in the holding furnace to the hot water pipe. A vacuum die-casting device having a pressure reducing means for supplying hot water to the injection sleeve via the closed mold defined by the cavity, the injection sleeve and the hot water supply pipe during the clamping operation of the fixed mold and the movable mold A vacuum die casting apparatus having an air release valve for releasing a space pressure to atmospheric pressure.   2. The atmosphere release valve is provided between a shutoff valve for preventing molten metal outflow installed in the fixed type or the movable type and a vacuum valve for opening and closing communication with a vacuum device. The vacuum die casting apparatus described in 1.   The vacuum die casting apparatus according to claim 1, wherein the atmosphere release valve is provided in the injection sleeve.   2. The vacuum die casting apparatus according to claim 1, wherein the atmosphere release valve is also used as a shutoff valve for preventing molten metal outflow that is installed in the fixed type or the movable type.   The cavity formed by the fixed mold and the movable mold is depressurized to supply the molten metal in the holding furnace to the injection sleeve through the hot water supply pipe, and the injection plunger fitted to the injection sleeve is advanced to move the molten metal in the injection sleeve. In the vacuum die casting method for filling the cavity, the pressure of the closed space defined by the cavity, the injection sleeve, and the hot water supply pipe during the clamping operation of the fixed mold and the movable mold before the cavity is decompressed A vacuum die-casting method characterized in that the pressure is released to atmospheric pressure by an air release valve.

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