JP4129352B2 - Casting method of low pressure casting equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionCasting method of low pressure casting equipmentAbout.
[0002]
[Prior art]
  For example, for casting aluminum alloy or the like, low-pressure casting is widely used because mass production is possible, the solidification process is rational, the dimensional accuracy is good, and the equipment cost is relatively low.
[0003]
  The outline of the low pressure casting method will be described with reference to the conceptual diagram of the low pressure casting apparatus 100 shown in FIG.
[0004]
  The low pressure casting apparatus 100 includes a molten metal holding crucible 102 held in a molten metal heat-retaining furnace 101, a crucible lid 103 for sealing the molten metal holding crucible 102, and a stalk having a lower end extending into the molten metal holding crucible 102 through the crucible lid 103. 104 and a mold 105 installed above the stalk 104, and the molten metal holding crucible 102 is provided with a molten metal replenishing port and a compressed air inlet pipe (not shown).
[0005]
  In casting, a predetermined amount of the molten metal 120 is poured into the molten metal holding crucible 102 sealed by the crucible lid 103 from the molten metal replenishing port, and the molten metal replenishing port is closed with a lid or the like.
[0006]
  Next, a gas body having a pressure relatively lower than that of the compressed air inlet pipe, for example, compressed air is supplied to pressurize the molten metal surface 120 a, and the molten metal 120 is pushed up through the stalk 104 by this applied pressure to enter the cavity 106 of the mold 105. Pour hot water. The molten metal 120 filled in the cavity 106 begins to solidify from the upper end of the cavity 106, gradually progresses, and the portion of the gate 106a finally solidifies. The applied pressure in the molten metal holding crucible 102 by the gas body is maintained until solidification is completed up to the pouring gate 106a, and the applied pressure is released when the solidification is completed up to the pouring gate 106a. Further, after the temperature of the casting is lowered to a temperature at which deformation or galling does not occur even if the mold 105 is opened and released after being solidified, the mold is released from the mold 105 and carried out as a cast product.
[0007]
  From the start of pouring into the cavity 106 due to the pressurization of the molten metal surface 120a, the time for the molten metal 120 to solidify to the pouring gate 106a and release the pressurization is the hot water supply time, and the solidified casting becomes the mold 105. The time until the temperature of the casting drops to a temperature at which no deformation or galling occurs when the mold is opened and released is called solidification time.
[0008]
  These pouring time and solidification time are set artificially based on the experience and feeling of the casting worker for each casting based on the time experimentally confirmed in advance.
[0009]
  On the other hand, the molten metal 120 stored in the molten metal holding crucible 102 decreases with each casting as shown in FIGS. 10A, 10B, and 10C, and the molten metal surface 120a sequentially decreases. Therefore, in order to push up and fill the molten metal 120 into the cavity 106 of the mold 105, control of the applied pressure for applying a pressure corresponding to the difference h of the lowered molten metal surface 120a every casting, that is, control of the filling pressure. Is done.
[0010]
  For example, as shown in FIG. 9, the pressurizing value for each casting is stored in advance in a personal computer 107 or the like as shown in FIG. 9, and the control device 108 controls the on-off valve 109 according to this data. There is a method of automatically adjusting and pressurizing the pressure gas supplied from the pressure supply source 110.
[0011]
  As another method of controlling the applied pressure, a method of adjusting the pressure reducing valve (regulator) according to the experience and feeling of the casting operator while visually monitoring the appearance of the cast product for each casting, There is a method of checking a pressurization value and mechanically applying a constant pressure for each casting based on the pressurization value.
[0012]
[Problems to be solved by the invention]
  According to the low-pressure casting apparatus 100, since the casting in the cavity 106 of the mold 105 is gradually performed, the molten metal 120 that has flowed in first is pushed by the molten metal 120 pushed up later and flows to the tip. By solidifying the tip first, the occurrence of shrinkage nests and blowholes is suppressed, and a dense casting with high density can be made.
[0013]
  However, as shown in FIGS. 10A, 10B, and 10C, each time the casting is performed, the molten metal 120 is decreased, and a pressing force corresponding to the difference h of the molten metal surface 120a that is sequentially decreased is applied for each casting. Therefore, according to the pressurization adjustment method in which the pressurization value for each casting is stored in the personal computer 107 in advance and the pressurization force is automatically adjusted based on this data, the amount of the melt 120 supplied into the melt holding crucible 102, If there is an error between the molten metal 120 and the amount of the molten metal 120a stored in the personal computer 107, it is not controlled by the desired applied pressure, and there is a concern about the occurrence of poor hot water or a problem of spreading. The
[0014]
  Also, in the method of controlling the pressure by adjusting the pressure reducing valve based on the experience and feeling of the casting worker, there are individual differences depending on the casting worker, and it is difficult to ensure an appropriate pressing force. Furthermore, even in the pressurization control that is mechanically performed based on the pressurization value obtained for each casting obtained in advance from experimental values, there is a concern that similar problems may occur depending on the amount of the molten metal in the molten metal holding crucible 102.
[0015]
  On the other hand, the distance from the molten metal surface 120a to the cavity 106 is increased by the amount that the molten metal surface 120a is successively lowered for each casting, and the moving distance of the molten metal 120 for filling is increased and changed. For this reason, the molten metal temperature changes for each casting, and there is a possibility that a difference may occur in the quality of the cast product for each casting. Further, the moving distance and time of the molten metal 120 up to the cavity 106 are increased by the amount that the molten metal surface 120a is sequentially lowered for each casting, and the oxidation of the molten metal 120 is promoted as the time of contact with the air on the molten metal surface increases. The oxide is wound on the surface of the molten metal in the stalk 104 and pushed up into the cavity 106 of the mold 105 to cause deterioration in the quality of the cast product, and more oxide is deposited on the inner peripheral surface of the stalk 104 and the molten metal passage cross-sectional area is increased. There is a concern that the effect of the hot water from the gate 106a is reduced.
[0016]
  Therefore, an object of the present invention made in view of such a point is to secure a hot water supply effect from the gate and obtain a stable high-quality cast product.Casting method of low pressure casting equipmentIs to provide.
[0017]
[Means for Solving the Problems]
  The invention of the casting method of the low-pressure casting apparatus according to claim 1, which achieves the above object, comprises a stalk extending in the vertical direction, and a mold having a cavity formed continuously through a gate at the upper end of the stalk. A molten metal holding crucible in which the molten metal is stored, a pressure pot in a sealed state in which a lower part is immersed in the molten metal stored in the molten metal holding crucible, a hot water supply pipe connecting the pressurized pot and the lower end of the stalk, A suction port side valve body that opens and closes a suction port formed in a lower portion of the pressurization pot, a discharge port side valve body that opens and closes a discharge port of the hot water supply pipe that opens in the pressurization pot, and the inside of the pressurization pot And a holding furnace equipped with a pressure pot pressure reducing and pressurizing means for pressure reducing and pressurizing, wherein the pressure pot is depressurized by closing the discharge port and opening the suction port. The pressure pot is depressurized and sucked The first step of sucking the molten metal in the crucible holding the molten metal from the mouth into the pressure pot, and then closing the suction port and pressurizing the pressure pot by the pressure pot pressure reducing and pressurizing means and opening the discharge port A second step of pumping the molten metal in the pressurization pot into the stalk through the hot water supply pipe and pushing the molten metal up to a constant molten metal surface position set in advance in the stalk; From the state of holding the molten metal surface,Every castingAnd a third step of sequentially pumping the molten metal and filling the cavity with the molten metal in the stalk.
[0018]
  According to the first aspect of the present invention, the molten metal supply device pumps the molten metal in the crucible holding the molten metal and pushes it up to the constant molten metal surface position in the stalk and prevents the back flow to hold the molten metal surface in the stalk at the constant molten metal surface position. In the state where the molten metal surface is held on the constant molten metal surface, the molten metal for one casting in the molten metal holding crucible is sequentially pumped and the molten metal in the stalk is filled into the cavity to repeat the casting. The distance from the molten metal surface held at the constant molten metal surface position to the cavity is constant, the molten metal supply device in each casting cycle pushes up the molten metal surface in the stalk to fill the cavity, and the casting pressure is constant. It is not necessary to increase the filling pressure every time, simplifying the operation control, eliminating the difference in quality due to changes in the filling pressure, and producing a stable quality casting. It is.
[0019]
  Moreover, the distance from the constant molten metal surface to the cavity is close, the distance of the molten metal during filling is short, the temperature drop of the molten metal accompanying filling is suppressed, and the molten metal fluidity at the time of filling the cavity is good and the molten metal is excellent.
[0020]
  Furthermore, the movement time of the molten metal at the time of filling is short, the time of exposure to the air in the stalk when the molten metal moves is shortened, and the generation of oxide is reduced, so that the oxide is caught in the molten metal. The deterioration of the casting quality due to is avoided. Similarly, deposition of oxide on the inner peripheral surface of the stalk is suppressed, the molten metal passage cross-sectional area is secured, and the effect of the hot water from the gate is secured.
[0021]
  The invention according to claim 2 is the invention according to claim 1.Casting method of low pressure casting equipmentThe fixed molten metal surface position is set in the upper end of the stalk or in the vicinity of the upper end.
[0022]
  According to the invention of claim 2, by setting the position of the constant molten metal surface from the upper end of the stalk to the vicinity of the upper end, the moving distance of the molten metal from the molten metal surface to the cavity at the time of filling becomes shorter, and the temperature of the molten metal at the time of filling The reduction is further suppressed, and the time of exposure to the air in the stalk when the molten metal moves is shortened, and the generation of oxide is further reduced.
[0023]
  The invention according to claim 3 is the invention according to claim 1.Casting method of low pressure casting equipmentThe fixed molten metal surface position is set in a mold gate instead of in the stalk.
[0024]
  According to the invention of claim 3, by setting the constant molten metal surface position in the gate of the mold, the movement distance of the molten metal from the molten metal surface to the cavity at the constant molten metal surface position during filling can be extremely shortened. The temperature drop of the molten metal during filling can be extremely reduced, and the fluidity of the molten metal during filling can be ensured in the cavity. Moreover, the deterioration of the quality of the cast product due to the oxide being caught in the molten metal is avoided.
[0025]
  The invention according to claim 4The casting method of the low-pressure casting apparatus according to any one of claims 1 to 3.LeaveFurther, in the second step, when the molten metal surface position is detected by the molten metal surface position sensor, pressurization by the pressure pot depressurizing and pressing means is stopped.It is characterized by that.
[0026]
  Claim4According to the invention, the molten metal surface position sensor detects the molten metal surface at the constant molten metal surface position.If so, pressurization by the pressurizing pot decompression pressurizing means is stopped.Thus, the operation control of the molten metal supply device can be performed efficiently and reliably.
[0027]
  Claim5The invention of claim4 casting method of low pressure casting equipmentLeaveThe molten metal surface position sensor is a thermoelectric thermometer provided on a core pin protruding into the mold cavity or the gate, and detects the surface of the molten metal by measuring the temperature near the tip of the core pin. It is characterized by doing.
[0028]
  Claim5According to this invention, the molten metal surface position sensor can be formed without incurring complication of the mold by providing the thermoelectric thermometer on the casting pin protruding into the cavity or the gate.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present inventionCasting method of low pressure casting equipmentThe embodiment will be described with reference to FIGS. 1 to 8 by taking the casting of an aluminum alloy as an example.
[0030]
  1 is a conceptual diagram of a low pressure casting apparatus 1 including a holding furnace 10 and a casting machine 30, FIG. 2 is a schematic view of a main part of the low pressure casting apparatus 1, and FIG. FIG. 4 is an enlarged view of part B of FIG.
[0031]
  The holding furnace 10 includes a molten metal holding crucible 12 that is supported by the molten metal heat insulating furnace 11 and holds the molten metal 60, and the molten metal supply device 15 is suspended and supported by a support frame 13 provided above the molten metal holding crucible 12. Yes.
[0032]
  As shown in FIGS. 2 and 3, the molten metal supply device 15 is made of an aluminum alloy metal whose upper end is supported in a sealed state by a base 16 suspended and supported by a support frame 13 and whose lower portion is stored in a molten metal holding crucible 12. A bottomed cylindrical pressure pot 17 immersed in the molten metal 60 is provided.
[0033]
  A suction port 17 a communicating with the inside of the molten metal holding crucible 12 is formed at the bottom of the pressure pot 17. A base end of a hot water supply pipe 19 having a tip communicating with the stalk 33 of the casting machine 30 through the base portion 16 is inserted into the side portion of the pressure pot 17, and a discharge port 19 a formed in the hot water supply pipe 19 is added. An opening is formed in the pressure pot 17. The suction port 17a and the discharge port 19a are opened and closed by a suction port side valve body 18 and a discharge port side valve body 20 provided in the pressurizing pot 17, respectively.
[0034]
  Further, the molten metal supply device 15 includes a vacuum pump 22 for depressurizing the inside of the pressurization pot 17 through the suction / air supply tube 21, a pressure gas body, a main body in the pressurization pot 17 through the suction / airfeed tube 21. In the embodiment, it is constituted by a pressurizing pump 23 or the like that pressurizes by sending compressed air, and has a pressurizing pot depressurizing / pressurizing means 24 that depressurizes and pressurizes the inside of the pressurizing pot 17.
[0035]
  Further, in the pressure pot 17, the solution in the pressure pot 17 is dissolved.Hot waterA level sensor (not shown) for detecting the molten metal level of 60 is provided. Each operation control of the suction port side valve body 18, the discharge port side valve body 20, the vacuum pump 22, the pressurizing pump 23, and the like is performed by a control unit (not shown).
[0036]
  On the other hand, the casting machine 30 has a cylindrical stalk 33 whose upper end is attached to a base 31 via a stalk plate 32 and extends in the vertical direction, and the lower end of the stalk 33 is guided from the holding furnace 10. The tip of the hot water supply pipe 19 is connected.
[0037]
  A mold 40 is installed above the stalk 33. As shown in FIGS. 4 and 5, the mold 40 in the present embodiment includes a lower mold 41 fastened to the stalk plate 32 with bolts and the like, and a mold operating mechanism 50 (see FIG. 1) such as a hydraulic cylinder. An upper mold 42 that moves up and down so as to be able to move toward and away from the lower mold 41; and a pair of horizontal molds 43 that are provided on the die base 34 of the base 31 and that are movable toward and away from each other by a mold operating mechanism 50; The cavity 45 is formed by the cavity sides 41a, 42a, 43a, 44a of the lower mold 41, the upper mold 42, and the horizontal molds 43, 44.
[0038]
  The lower mold 41 is formed with a gate 46 that extends in the vertical direction so as to communicate the stalk 33 side and the cavity 45 side, and that the opening area of the intermediate portion is relatively small and gradually increases upward and downward. ing.
[0039]
  On the other hand, the upper mold 42 is formed by an upper large-diameter portion 47b and a lower small-diameter portion 47c through a step portion 47a, as shown in an enlarged view of the main part of the mold 40 in FIG. A cast pin mounting hole 47 is formed.
[0040]
  The core pin 48 is fitted to a relatively large diameter base portion 48b and a small diameter portion 47c that are fitted to the large diameter portion 47b via a step portion 48a that can be locked to the step portion 47a of the core pin mounting hole 47. The rod portion 48c has a shaft portion 48c, and is inserted into the core pin mounting hole 47 from above, and the step portion 48a is brought into contact with the step portion 47a of the core pin insertion hole 47 so that the shaft portion 48c moves inside the cavity 45. The front end 48d has a length that reaches the upper part of the gate 46 of the lower mold 42, and is held in a predetermined mounting position by being fitted into the core pin mounting hole 47.
[0041]
  The core pin 48 is internally provided with temperature measuring means in which a temperature measurement point a is set corresponding to the vicinity of the tip of the core pin 48, for example, a thermoelectric thermometer 49 using a thermocouple, and the core pin 48 is connected to the core pin 48. By mounting in the mounting hole 47, the temperature of the upper position in the gate 46 can be measured. Moreover, the thermoelectric thermometer 49 can be arrange | positioned, without complicating the structure of the metal mold | die 40 by installing the thermoelectric thermometer 49 in the core pin 48. FIG.
[0042]
  The temperature of the temperature measurement point a rises as the molten metal surface 60a of the molten metal 60 in the stalk 33 rises and approaches the temperature measurement point a. Therefore, the temperature of the temperature measurement point a on the molten metal surface 60a at a predetermined position is determined. By obtaining in advance by experiments, it is possible to detect the position of the molten metal surface 60a in the stalk 33, for example, the position of the molten metal surface 60a that has risen to the constant molten metal surface position L described later. That is, the thermoelectric thermometer 49 functions as a molten metal surface position sensor, and is sent as a molten metal surface detection signal detected by the thermoelectric thermometer 49 to a control unit provided in the molten metal supply device 15.
[0043]
  Further, after the temperature at the temperature measurement point a reaches the maximum value due to the heat of the molten metal 60 poured into the cavity 45, the molten metal 60 starts to solidify from the upper end and gradually falls, and the temperature at the temperature measurement point a. Since the temperature drops, the temperature of the temperature measurement point a when solidification has progressed to the gate 46 is experimentally confirmed and set in advance, and when this temperature is reached, the pouring time from the thermoelectric thermometer 49 is reached. It is transmitted to the control unit as a release signal. Further, the temperature at which the temperature at the temperature measurement point a continues to drop as the solidification progresses, and the temperature at which the solidified casting becomes a temperature at which no deformation or galling occurs even when the mold 40 is released. Is experimentally confirmed and set in advance, and when this temperature is reached, an electric signal is issued from the thermoelectric thermometer 49 to the control unit as a solidification time release signal.
[0044]
  The hot water supply pipe 19 disposed between the base 16 of the holding furnace 10 and the stalk 33 of the casting machine 30 is heated and kept warm by covering the outer periphery with a hot water supply pipe heater 51, and the outer periphery of the stalk 33 is also heated by the stalk heater 52. It is coated and heated and kept warm. The hot water supply pipe heater 51 and the stalk heater 52 may be formed by an integral heater.
[0045]
  Next, casting by the low-pressure casting apparatus 1 configured in this wayDirectionThe hot water filling operation flowchart shown in FIG. 6, the filling operation and repeated filling operation flowchart shown in FIG. 7, and the casting cycle explanatory diagram shown in FIG. 8 will be described.
[0046]
  Prior to the pouring of the molten metal 60 into the cavity 45 of the mold 40, the molten metal surface is placed at a predetermined height position of the stalk 33 of the casting machine 30, for example, a constant molten metal surface position L set at the upper end of the stalk 33 or a position near the upper end. Fill with hot water until 60a is reached.
[0047]
  This hot water filling operation will be described with reference to the hot water filling operation flowchart shown in FIG.
[0048]
  A molten metal 60 in which an aluminum alloy is dissolved is poured into the molten metal holding crucible 12 of the holding furnace 10 in advance, and a predetermined amount is stored and prepared.
[0049]
  In response to an instruction from the controller, the discharge port 19 is closed by the discharge port side valve body 20 at the proximal end of the hot water supply pipe 19 (step S1). Subsequently, the suction port 17a at the bottom of the pressurization pot 17 that has been closed by the suction port side valve body 18 is opened, and the inside of the molten metal holding crucible 12 and the pressurization pot 17 are communicated (step S2).
[0050]
  Next, the inside of the pressure pot 17 is depressurized by the vacuum pump 22 through the suction / air supply pipe 21, and the molten metal 60 in the molten metal holding crucible 12 is sucked from the suction port 17a to the vicinity of the upper end of the pressure pot 17 (step 3). . When the level sensor detects that the molten metal 60 has been sucked up to the vicinity of the upper end of the pressurizing pot 17, the decompression in the pressurizing pot 17 by the vacuum pump 22 is stopped, and the suction port 17a is closed by the suction port side valve element 18. Is closed (step S4).
[0051]
  Next, compressed air was supplied into the pressurizing pot 17 from the suction / air supply pipe 21 by the pressurizing pump 23 to pressurize the molten metal surface in the pressurizing pot 17 and was closed by the discharge port side valve body 20. The discharge port 19a is opened (step S5), and the molten metal 60 in the pressure pot 17 is pushed up to the constant molten metal surface position L set at the upper end of the stalk 33 or near the upper end through the hot water supply pipe 19 (step S6). The pressure which pushes up the molten metal 60 to the constant molten metal surface position L at this time is defined as a constant molten metal surface pressure.
[0052]
  When the molten metal 60 is pushed up to the constant molten metal surface position L, the molten metal surface 60a in the stalk 33 gradually approaches the temperature measurement point a of the thermoelectric thermometer 49 provided on the core pin 48 as the molten metal 60 is pushed up. As shown in the explanatory diagram of No. 8 casting cycle, the temperature at the temperature measurement point a is increased, and this temperature has reached the temperature A at which the molten metal surface 60a is located at the constant molten metal surface position L obtained experimentally in advance. It is detected by sensing with a thermoelectric thermometer 49.
[0053]
  When the molten metal surface 60a pushed up to the constant molten metal surface position L is detected by the thermoelectric thermometer 49 (step S7), the molten metal surface detection signal is sent from the thermoelectric thermometer 49 to the control unit, The pressurization in the pressure pot 17 is stopped, and at the same time, the discharge port 19a is closed by the discharge port side valve body 20 to prevent the reverse flow of the molten metal 60 from the stalk 33 and maintain the constant molten metal surface pressure. 60a is held at the constant molten metal surface position L (step S8).
[0054]
  Subsequent to the hot water filling operation from step 1 to step 8, the filling operation for filling the molten metal 60 into the cavity 45 of the mold 40 is started.
[0055]
  Next, the filling operation will be described with reference to the flowchart of the filling operation and repeated filling operation shown in FIG. 7 and the explanatory diagram of the casting cycle shown in FIG.
[0056]
  The suction port 17a closed by the suction port side valve body 18 in a state where the discharge port 19a is closed by the discharge port side valve body 20 and the molten metal surface 60a from the stalk 33 is held at the constant molten metal surface position L (step S11). Is released to release the constant molten metal surface pressure in the pressure pot 17 (step S12).
[0057]
  Next, the inside of the pressure pot 17 is decompressed by the vacuum pump 22 through the suction / air supply pipe 21, and the molten metal 60 for one casting of the cavity 45 is sucked into the pressure pot 17 from the suction port 17a (step S13). . When the molten metal 60 for one casting is sucked into the pressurizing pot 17, the decompression by the vacuum pump 22 is stopped, and the suction port 17a is closed by the suction port side valve body 18 (step S14). The amount of molten metal for one casting sucked and supplied to the pressure pot 17 is experimentally determined in advance, and a certain amount is secured by detecting suction to a certain position by a level sensor provided in the pressure pot 17. To do.
[0058]
  Subsequently, the pressurized pump 23 supplies compressed air from the suction / air supply tube 21 into the pressure pot 17 to pressurize the molten metal surface, and opens the discharge port 19a closed by the discharge port side valve body 20 ( Step S15). The molten metal 60 is pumped into the stalk 33 from the opened discharge port 19a through the hot water supply pipe 19, and the molten metal surface 60a is pushed up to fill the cavity 45, and the pressure required for the filling, that is, the filling pressure is maintained ( Step S16). Due to the melt heat of the melt 60 filled in the cavity 45, the temperature rise at the temperature measurement point a set on the core pin 48 starts as shown in FIG. 8, and the temperature detected by the thermoelectric thermometer 49 rises.
[0059]
  After the temperature of the temperature measurement point a reaches the highest point, for example, 600 ° C. due to the heat of the molten metal, the molten metal 60 filled in the cavity 45 starts to solidify from the upper end, and as the solidification progresses, the temperature measurement point a The temperature begins to drop.
[0060]
  When the thermoelectric thermometer 49 detects a temperature, for example, 530 ° C., at which the solidification has proceeded up to the gate 46 and the solidification has progressed to a preset temperature measurement point a (step S17), the thermoelectric temperature is detected. An electric signal is sent from the total 49 as a pouring time release signal, pressurization in the pressurization pot 17 by the pressurization pump 23 is stopped to release the filling pressure, and at the same time, the discharge port 19a is discharged from the discharge port side valve body 20 The melt surface 60a is held at the constant melt surface position L by closing and preventing the backflow of the melt 60 from the stalk 33 and maintaining the constant melt surface pressure (step S18).
[0061]
  Further, the solidification in the cavity 45 progresses and the temperature at the temperature measurement point a continues to fall, and the solidified and cast product does not cause deformation or galling even when the mold 40 is released, for example, When the thermoelectric thermometer 49 detects 490 ° C., the thermoelectric thermometer 49 generates an electric signal to the control unit as a solidification time release signal, and the mold 40 is opened by the mold operating mechanism 50 or the like, so that the casting solidified in the cavity 45 is obtained. It takes out and one casting cycle is complete | finished (step S19). Thereafter, the mold 40 is closed to enter the next molten metal filling standby state.
[0062]
  In the subsequent repeated filling operation, the suction port 17a is opened by the suction port side valve body 18 in a state where the discharge port 19a is closed by the discharge port side valve body 20 and the molten metal surface 60a of the stalk 33 is held at the constant molten metal surface position L. From step S11 for releasing the constant molten metal surface pressure in the pressurizing pot 17, the mold 40 is opened, the mold 40 is closed through step S19 for taking out the solidified casting in the cavity 45, and the next molten metal filling standby state is entered. By repeating steps S11 to S19, casting is continuously performed.
[0063]
  the aboveCasting method of low pressure casting equipmentAccording to the above, in the state where the molten metal surface 60a in the stalk 33 is maintained at the constant molten metal surface position L just below the cavity 45 by preventing the backflow from the stalk 33, the molten metal 60 is pushed out from the molten metal supply device 15 to the inside of the stalk 33. Since the molten metal surface 60a is pushed up and filled in the cavity 45 and cast,MeltingSince the distance from the molten metal surface position L to the cavity 45 is constant, the filling pressure for filling the cavity 45 by pushing up the molten metal surface 60a in the stalk 33 by the molten metal supply device 15 in each casting cycle is constant. Unlike the low pressure casting, it is not necessary to increase the filling pressure for each casting, and the filling pressure control means is not required, and the operation control of the low pressure casting apparatus 1 can be simplified.
[0064]
  Due to the constant molten metal surface position L, the molten metal surface 60a is close to the cavity 45, the moving distance of the molten metal 60 from the constant molten metal surface position L to the cavity 45 by the push-up is short, and the temperature drop of the molten metal 60 during filling is suppressed, The temperature of the molten metal 60 poured into the cavity 45 is maintained, and the molten metal fluidity at the time of filling the cavity 45 is good and the molten metal is excellent.
[0065]
  In addition, since the constant molten metal surface position L and the cavity 45 are close to each other, the moving time of the molten metal 60 during filling is short. As a result, the exposure time to the air in the stalk 33 when the molten metal 60 moves is short, and the generation of oxide is extremely small, and the oxide is caught in the molten metal 60 and pushed up into the cavity 45 to improve the quality of the cast product. It is avoided that the deterioration is caused, and oxides deposited on the inner peripheral surface of the stalk 33 are suppressed to secure a cross-sectional area of the molten metal passage, and a hot metal effect from the pouring gate is ensured to improve the efficiency of the casting operation. .
[0066]
  Furthermore, conventionally, a molten metal holding crucible has been arranged directly under the casting machine, and the molten metal holding crucible has been pressurized to fill the cavity with the molten metal. During the molten metal filling pressurization, the molten metal is supplied to the molten metal holding crucible. However, the molten metal holding furnace 11 provided with the molten metal holding crucible 12 and the casting machine 30 provided with the mold 40 are arranged separately, and the molten metal holding crucible 12 is affected. Since the pressurizing pot 17 that pressurizes the molten metal 60 is provided separately and separately, the molten metal can be replenished to the crucible 12 holding the molten metal at any time regardless of the filling of the molten metal into the cavity 45. Therefore, it is not necessary to stop casting, and the efficiency of casting work can be improved.
[0067]
  Further, the temperature of the temperature measurement point a when the molten metal 60 filled in the cavity 45 starts to solidify from the upper end and proceeds to the gate 46 is experimentally confirmed and set in advance. However, when the pouring gate 46 reaches a solidified temperature, it is transmitted from the thermoelectric thermometer 49 as a pouring time release signal to the control unit to release the filling pressure, so when the pouring gate 46 portion is truly solidified. The pouring time can be canceled. As a result, an appropriate pouring time is set and an appropriate hot-water filling effect is obtained, and the formation of nests at the gate 46 can be avoided. Similarly, the temperature of the temperature measurement point a when the solidified product is solidified and becomes a cast product is lowered to a temperature at which no deformation or galling occurs even when the mold 40 is released, is experimentally determined in advance. When the set temperature is reached, an electric signal is sent from the thermoelectric thermometer 49 to the control unit as a coagulation time release signal, and the mold is opened. The temperature at the time of mold release is set appropriately for the time, so that the galling and deformation generated in the cast product can be avoided, and the mold release is facilitated to ensure the quality of the cast product.
[0068]
  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the constant molten metal surface position L is set to the upper end of the stalk 33 or a position near the upper end. However, by setting the fixed molten metal surface position L in the gate 46 of the mold 40, the constant molten metal surface position L is made closer to the cavity 45. In addition, the temperature drop of the molten metal 60 at the time of filling is extremely reduced by extremely shortening the moving distance of the molten metal from the molten metal surface 60a at the constant molten metal surface position L at the time of filling to the cavity 45, and the melt fluidity at the time of filling is reduced. It can be secured. Furthermore, the generation of oxides is suppressed, and the deterioration of the quality of the cast product is further avoided. Further, when the tip 48 d of the casting pin 48 does not reach the gate 46 due to the shape of the cast product, the temperature measurement point a of the thermoelectric thermometer 49 is set in the cavity 45. Further, the thermoelectric thermometer 49 can be disposed in the vicinity of the gate 46 of the lower mold 41 without being disposed on the core pin 48.
[0069]
  Further, it is possible to form a cooling water passage in the mold 40 according to the shape and thickness of the cast product, and to control the solidification rate in the cavity 45 by the cooling water. Furthermore, a metal net that removes oxides and impurities that are generated in the melting process of the molten metal and are mixed in the molten metal and that suppresses the rise of the molten metal can be attached to the gate 46 formed in the lower mold 41. . In addition to casting an aluminum alloy, casting of a high melting point alloy such as copper or iron is also possible.
[0070]
【The invention's effect】
  Of the present invention described above.Casting method of low pressure casting equipmentAccording to the above, the molten metal supply device pumps the molten metal in the molten metal holding crucible and pushes it up to the constant molten metal surface position in the stalk and prevents the back flow to hold the molten metal surface in the stalk at the fixed molten metal surface position. Since the molten metal for one casting in the crucible holding the molten metal is sequentially pumped while being held on the constant molten metal surface, the molten metal in the stalk is filled into the cavity and casting is repeated, so that it is held at the constant molten metal surface position in each casting cycle. The distance from the molten metal surface to the cavity is constant, and the filling pressure for pushing up the molten metal surface in the stalk by the molten metal supply device in each casting cycle to fill the cavity is constant, and the filling pressure is increased for each casting cycle. This eliminates the need for pressure and simplifies the operation control of constant pressure casting equipment, eliminates the difference in quality caused by changes in filling pressure, and ensures stable quality castings. It is.
[0071]
  In addition, the distance from the surface of the molten metal to the cavity is close, the movement distance of the molten metal from the molten metal surface to the cavity during filling is short, and the temperature drop of the molten metal due to filling is suppressed, and the molten metal fluidity during filling is good. Excellent turnability.
[0072]
  Furthermore, the distance that the molten metal moves during filling is short, the time during which the molten metal is exposed to the air in the stalk is shortened, the generation of oxides is reduced, and the oxide is cast into the molten metal. Product quality degradation is avoided. Similarly, oxide accumulation in the stalk is suppressed, the molten metal passage cross-sectional area is secured, the effect of the hot water from the gate is secured, and a high-quality cast product can be obtained.
[Brief description of the drawings]
FIG. 1 is according to the present invention.Used for casting methodIt is a conceptual diagram of a low pressure casting apparatus.
FIG. 2 is a schematic view of the main part of the low-pressure casting apparatus.
FIG. 3 is an enlarged view of a part A in FIG. 2 showing a main part of the molten metal holding furnace.
FIG. 4 is a cross-sectional view showing the main part of the casting machine.
FIG. 5 is a cross-sectional view showing the main part of the mold, similarly.
FIG. 6 is also a hot water stuffing operation flowchart.
FIG. 7 is also a flowchart of a filling operation and a repeated filling operation.
FIG. 8 is also an explanatory diagram of a casting cycle.
FIG. 9 is a conceptual diagram of a conventional low-pressure casting apparatus.
FIG. 10 is an explanatory view showing a decrease in the melt surface of a conventional low pressure casting apparatus.
[Explanation of symbols]
1 Low pressure casting equipment
10 Holding furnace
12 molten metal holding crucible
15 Molten metal supply device
17 Pressurized pot
17a Suction port
18 Suction side valve body
19 Hot water pipe
19a Discharge port
20 Discharge port side valve body
21 Suction and air pipe
22 Vacuum pump
23 Pressure pump
24 Pressurizing pot pressure reducing means
30 casting machine
33 Stoke
40 mold
45 Habibiti
46 Yuguchi
48 Cast Pin
49 Thermoelectric thermometer (molten surface position sensor)
60 molten metal
60a molten metal surface
a Temperature measurement point
L Position of molten metal surface

Claims (5)

A stalk extending in the vertical direction, a mold having a cavity formed at the upper end of the stalk through a pouring gate, a molten metal holding crucible for storing molten metal, and a molten metal stored in the molten metal holding crucible A sealed pressure pot in which the lower part is immersed, a hot water pipe connecting the pressure pot and the lower end of the stalk, a suction port side valve body for opening and closing a suction port formed in the lower part of the pressure pot, A discharge port side valve body that opens and closes the discharge port of the hot water supply pipe that opens into the pressurization pot, and a holding furnace that includes a pressurization pot decompression and pressurization unit that depressurizes and pressurizes the pressurization pot. A low pressure casting apparatus casting method,
A first step of closing the discharge port and opening the suction port, and depressurizing the pressure pot by the pressure pot depressurization and pressurizing means to suck the molten metal in the crucible holding the molten metal from the suction port into the pressure pot. When,
Next, the suction port is closed, the inside of the pressure pot is pressurized by the pressure pot pressure reduction means, the discharge port is opened, and the molten metal in the pressure pot is pumped into the stalk through the hot water supply pipe. A second step of pushing and holding at a constant molten metal surface position set in the stalk;
Then, from the state in which the molten metal surface is held at the constant molten metal surface position, a third step of sequentially pumping the molten metal for each casting and filling the molten metal in the stalk into the cavity is provided. A casting method for a low-pressure casting apparatus. 2. The casting method for a low-pressure casting apparatus according to claim 1, wherein the constant molten metal surface position is set in an upper end or a vicinity of the upper end in the stalk . The method for casting a low-pressure casting apparatus according to claim 1, wherein the position of the constant molten metal surface is set in a mold gate instead of in the stalk . Furthermore, the said 2nd process stops the pressurization by the said pressurization pot pressure reduction pressurization means, when the molten metal surface of a fixed molten metal surface position is detected by the molten metal surface position sensor. The casting method of the low pressure casting apparatus of any one of these. The molten metal surface position sensor is a thermoelectric thermometer provided on a core pin protruding into the mold cavity or the gate, and detects the surface of the molten metal by measuring the temperature near the tip of the core pin. The casting method of the low-pressure casting apparatus according to claim 4, wherein:

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