JP4132814B2 - Casting method of low pressure casting equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention casts molten metal supplied from a holding furnace with a casting machine.Casting method of low pressure casting equipmentAbout.
[0002]
[Prior art]
  For example, for casting of aluminum alloy or the like, low pressure casting is widely used because it can be mass-produced, the solidification process is reasonable, the dimensional accuracy is good, and the equipment cost is relatively low.
[0003]
  An outline of the low pressure casting method will be described with reference to a conceptual diagram of a 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 holding 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 move into the cavity 106 of the mold 105. Pour hot water into. The molten metal 120 filled in the cavity 106 begins to solidify from the upper end side of the cavity 106, gradually descends, and the portion of the gate 106a finally solidifies.
[0007]
  The pressure in the molten metal holding crucible 102 by compressed air is held until the molten metal 120 is solidified to the pouring gate 106a, and the pressurization is released when the solidification is completed up to the pouring gate 106a. Further, 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, and then the mold is released from the mold 105 and carried out as a cast product.
[0008]
  The time from the start of pouring into the cavity 106 due to the pressurization of the molten metal surface 120a until the molten metal 120 solidifies to the pouring gate 106a to release the applied pressure is the pouring time, and further solidified into a casting. The time during which the temperature of the casting falls to a temperature at which deformation and galling do not occur when the mold 105 is opened and released is called solidification time.
[0009]
  The pouring time and solidification time are generally set artificially based on the experience and feeling of the casting worker for each casting based on the time experimentally confirmed in advance.
[0010]
  On the other hand, as shown in FIG. 9A, the molten metal 120 stored in the molten metal holding crucible 102 is prepared so that the molten metal surface 120a is at a full level La before the start of casting. After the first casting, the molten metal surface 120a of the molten metal 120 is lowered to the molten metal surface level Lb shown in (b) after the first casting, and after the second casting, the molten metal surface 120a is moved to the molten metal surface level shown in (c). Decreases to Lc. Similarly, every time casting is performed, the molten metal surface 120a sequentially decreases.
[0011]
  Since the molten metal surface 120a is sequentially lowered every time casting is performed in this way, the molten metal filling speed and filling pressure into the cavity 106 of the mold 105 are changed every casting. Since the change of the molten metal filling speed and the filling pressure occurs, as shown in FIG. 10, a pressurizing force for applying a pressure corresponding to the difference h of the molten metal surface 120a lowered for each filling time and casting, that is, for each casting, Pressure correction of the filling pressure is performed. In this filling pressure correction method, for example, as shown in FIG. 11, a pressurization value for each casting based on a calculated value is stored in advance in the personal computer 107 or the like, and the control device 108 controls the on-off valve 109 according to this data to There is a method of automatically adjusting and pressurizing the pressure gas supplied from the supply source 110.
[0012]
  In addition, as another filling pressure correction method, a method of adjusting a pressure reducing valve (regulator) according to the experience and feeling of a casting operator while visually monitoring the appearance of a cast product for each casting, There is a method in which a pressurization value is checked and a constant pressure is mechanically applied for each casting based on the pressurization value.
[0013]
[Problems to be solved by the invention]
  According to the low-pressure casting apparatus 100, since the casting of the mold 105 into the cavity 106 is gradually performed, the molten metal 120 that has flowed in first is pushed by the molten metal 120 that is pushed up later and flows to the tip. It is solidified first to make a dense cast product with high density.
[0014]
  However, the distance from the molten metal surface 120a to the cavity 106 increases for each casting by the amount of change in which the molten metal surface 120a is lowered every casting, and the moving distance of the molten metal 120 until the filling of the molten metal 120 into the cavity 106 is completed. Increase change. For this reason, the position of the molten metal surface 120a returning into the stalk 104 after filling increases and changes every casting. Due to the change in the molten metal surface 120a in the stalk 104, the moving time of the molten metal 120 reaching the cavity 106 from the molten metal surface 120a in the stalk 104 becomes longer, and the temperature of the molten metal 120 supplied into the cavity 106 decreases and the molten metal in the casting is lowered. It affects hot water performance such as poor rotation and occurrence of hot water. In particular, it has been impossible to continuously produce a thin casting having a thickness of 2 mm or less, for example, with stable quality.
[0015]
  On the other hand, if the filling speed is increased to a certain level or higher in the process of filling the molten metal into the cavity 106, the sand core used for casting is broken, sand bite, rough skin, etc. are induced, and the filling pressure is rapidly reduced. This low pressure casting is impossible because it causes hot water and hot water boundaries.
[0016]
  Further, as the number of castings increases, the distance and time for the molten metal 120 to move in the stalk 104 become longer, and the oxidation of the molten metal 120 is promoted as the time for the molten metal surface to contact air in the stalk 104 increases. Oxide is entrained on the surface of the molten metal in the stalk 104 and pushed up into the cavity 106 to cause deterioration in the quality of the cast product, and when the amount of oxide deposited on the inner peripheral surface of the stalk 104 increases, the cross-sectional area of the molten metal passage becomes smaller. There is a concern that the quality of cast articles may be deteriorated due to the formation of a sinkhole inside the casting due to lack of hot water.
[0017]
  Accordingly, an object of the present invention made in view of such a point is to prevent a decrease in the melt temperature when filling the mold with the melt and to improve the hot water supply property, and to obtain a stable high-quality cast product.Casting method of low pressure casting equipmentIs to provide.
[0018]
[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 in which a continuous cavity is formed at the upper end of the stalk through a gate. A molten metal holding crucible for storing molten metal, a sealed pressure pot 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 pressure 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. A holding furnace provided with a pressure pot pressure reducing and pressurizing means for depressurizing and pressurizing, and a casting method of a low pressure casting apparatus, wherein the discharge port is closed and the suction port is opened to reduce the pressure in the pressure pot The pressure pot is depressurized by means of suction. From the first step of sucking the molten metal in the crucible holding the molten metal 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 in which the molten metal in the pressure pot is pumped into the stalk through the hot water supply pipe, and is pushed up to a constant molten metal surface position set in advance in the stalk, and then the fixed molten metal surface position. A third step of filling the molten metal at a high filling speed by setting the pressure pot depressurizing / pressurizing means to high pressure from a state where the molten metal surface is held to a position of a high-speed filling molten metal surface set in the cavity in advance; Then, from the position of the high-speed filling hot water surface to the completion of filling, the pressure pot pressure reducing meansAfter the suction pressure is reduced to a value obtained by adding the correction pressure to the preset filling holding pressure,It is characterized by comprising a fourth step of applying a low pressure and filling the molten metal at a low filling speed.
[0019]
  According to the first aspect of the present invention, in the state in which the backflow from the stalk is prevented and the molten metal surface in the stalk is maintained at the constant molten metal surface position, the molten metal surface in the stalk is pushed up by the pumping of the molten metal from the molten metal supply device. Since the inside is filled, the distance from the melt surface to the cavity at the constant melt surface position is kept constant in each casting cycle. As a result, in each casting cycle, it is not necessary to adjust the filling pressure control for pushing up the molten metal surface in the stalk to fill the cavity, so that the operation control can be simplified. Moreover, the filling of the molten metal into the cavity is performed in a short time by filling the high pressure pressurizing pot pressure reducing means from the constant molten metal surface position to the high speed filling molten metal surface position in the cavity at high pressure. The temperature drop of the molten metal is suppressed and the molten metal fluidity is good at the time of filling into the cavity. Fill with molten metalFillAs a result, the turbulent flow of the molten metal can be effectively calmed down, and the molten molten metal having a small temperature drop is filled in the cavity, and high quality casting without any entanglement defects is possible.
[0020]
  In addition, when the molten metal moves, the time during which the molten metal is exposed to the air in the stalk and the cavity is short, the generation of oxide is suppressed to a very low level, and deterioration of the quality of the cast product is avoided, and the inner peripheral surface of the stalk The oxide deposited on the surface is suppressed, the molten metal passage sectional area is secured, the effect of the hot water from the gate is secured, and the efficiency of the casting operation is obtained.
[0021]
  The invention according to claim 2 is the invention according to claim 1.Casting method of low pressure casting equipmentIn the above, the surface position of the constant melt 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 at the time of filling becomes shorter, the temperature drop of the molten metal is further suppressed, and the molten metal moves. In this case, the time of exposure to the air in the stalk is shortened, and the generation of oxide is reduced.
[0023]
  The invention according to claim 3 is the invention according to claim 1 or 2.Casting method of low pressure casting equipmentThe molten metal supply from the constant molten metal surface position to the high speed filling molten metal surface position is set at a predetermined molten metal supply time.
[0024]
  According to the invention of claim 3, the molten metal supply from the constant molten metal surface position to the high speed filling molten metal surface position is set by the molten metal supply time confirmed in advance by experiments or the like, so that the operation can be controlled stably and stably. it can.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, according to 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.
[0028]
  FIG. 1 is a conceptual diagram of a low-pressure casting apparatus 1 including a holding furnace 10 and a casting machine 40, and FIG. 2 is an enlarged view of a part A in FIG.
[0029]
  The holding furnace 10 includes a molten metal holding crucible 11 that is supported by a molten metal heat retaining furnace and holds the molten metal 60, and a molten metal supply device 15 is suspended and supported by a crucible lid 12 that covers the upper part of the molten metal holding crucible 11.
[0030]
  The molten metal supply device 15 is supported by being suspended from the crucible lid 12, and is bottomed by being immersed in a molten metal 60 of an aluminum alloy whose upper end is hermetically sealed by the pressure pot lid 17 and whose lower portion is stored in the molten metal holding crucible 11. A cylindrical pressure pot 16 is provided.
[0031]
  A suction port 16 a that communicates with the inside of the molten metal holding crucible 11 is formed at the bottom of the pressure pot 16. In the vicinity of the lower end of the side portion of the pressurizing pot 16, a discharge port 18 a opened at the base end of the hot water supply pipe 18 whose tip communicates with the lower end of the stalk 42 of the casting machine 40 is opened. The suction port 16a and the discharge port 18a are opened and closed by a suction port side valve body 19a and a discharge port side valve body 20a which are driven by actuators 19 and 20 provided in the pressure pot lid 17, respectively.
[0032]
  Further, the molten metal supply device 15 is provided with a pressure pot depressurization means 22 for controlling the pressure in the pressure pot 16. The pressurizing pot depressurizing / pressurizing means 22 is a relatively high-pressure gas body, as shown in FIG. 3, which is a compressed air having a relatively high pressure P1 in this embodiment.Is highA high-pressure pressurizing means 23 that feeds from the pressurized gas supply source 24 into the pressurization pot 16 at a high filling speed via a supply line 25 with a high-pressure pressurization valve 26 interposed therebetween, and a relatively low pressure that becomes a filling holding pressure P2 described later. Low-pressure pressurizing means 27 for sending compressed air from the low-pressure gas supply source 28 into the pressurization pot 16 at a low filling speed through a supply line 29 with a low-pressure pressurization valve 30 interposed, and a discharge line with an exhaust valve 34 interposed A pressure reducing means 31 that communicates with the pressure pot 16 through 33 and depressurizes the inside of the pressure pot 16 with the pressure reducing tank 32; and detects a pressure in the pressure pot 16 and a low pressure pressurizing valve 30 based on the detected pressure. And a pressure sensor 35 that controls opening and closing of the exhaust valve 34.
[0033]
  Further, a level sensor 36 that detects a melt surface 60 a of the melt 60 in the pressurization pot 16 is disposed in the pressurization pot 16. Each operation control of the molten metal supply device 15 is performed by a control unit (not shown).
[0034]
  On the other hand, the casting machine 40 has a cylindrical stalk 42 that is attached to and supported by a base 41 and extends vertically, and the tip of the hot water supply pipe 18 led from the holding furnace 10 is connected to the lower end of the stalk 42. Yes.
[0035]
  A mold 45 is installed above the stalk 42. The mold 45 in this embodiment is connected to and separated from the lower mold 46 by a lower mold 46 coupled to the base 41 and fastened to the stalk 42, and a mold operating mechanism (not shown) such as a hydraulic cylinder. An upper die 47 that can be moved up and down, and horizontal dies 48 and 49 that can move in a horizontal direction that are moved toward and away from each other by a mold operating mechanism, and each cavity side 46a of the lower die 46, the upper die 47, and the horizontal dies 48 and 49, A cavity 50 is formed by 47a, 48a, 49a.
[0036]
  The lower mold 46 has a vertical direction.InExtendingly, the stalk 42 side and the cavity 50 side are communicated, and the opening area of the intermediate portion is relatively small, and the gate 51 gradually increases as it moves upward and downward.
[0037]
  The mold 45 is provided with temperature measuring means for detecting the temperature of the temperature measuring point a set in advance in the upper position in the gate 51. The temperature measuring means can be constituted by, for example, a thermoelectric thermometer built in a cast pin or the like disposed in the upper die 47.
[0038]
  Since the temperature of the temperature measurement point a rises as the molten metal surface 60a of the molten metal 60 in the stalk 42 rises and approaches the temperature measurement point a, the position of the temperature measurement point a on the molten metal surface 60a at a predetermined position, For example, it is possible to detect the position of the molten metal surface 60a that has risen to a constant molten metal surface position L described later. The position of the molten metal surface 60a detected by the temperature measuring means is sent to the control unit of the molten metal supply device 15 as a molten metal surface detection signal.
[0039]
  In addition, since the temperature of the temperature measurement point a reaches the maximum value due to the heat of the molten metal 60 poured into the cavity 50, the molten metal 60 starts to solidify from the upper end or the tip and gradually decreases. The temperature of the temperature measurement point a when solidification has progressed to the gate 51 is experimentally confirmed and set in advance, and when this temperature is reached, the temperature measurement means starts as a pouring time release signal to the control unit. . Further, the temperature at which the temperature at the temperature measurement point a continues to decrease as solidification progresses, and the temperature at which the solidified casting becomes a temperature at which no deformation or galling occurs even when the mold 45 is released. Is experimentally confirmed and set in advance, and when this temperature is reached, a coagulation time release signal is issued from the temperature measuring means to the control unit.
[0040]
  The outer periphery of the hot water supply pipe 18 disposed between the holding furnace 10 and the stalk 42 of the casting machine 40 is covered and heated by the hot water supply pipe heater 55, and the outer periphery of the stalk 42 is also covered by the stalk heater 56. Heated and kept warm. The hot water supply pipe heater 55 and the stalk heater 56 may be formed by an integral heater.
[0041]
  Next, a casting method by the low-pressure casting apparatus 1 configured as described above will be described with reference to a hot water pouring operation flowchart shown in FIG. 4, a filling operation flowchart shown in FIG. 5, and an filling pressure pattern explanatory diagram shown in FIG. .
[0042]
  Prior to pouring of the molten metal 60 into the cavity 50 of the mold 45, a predetermined height position of the stalk 42 of the casting machine 40, for example, a filling start molten metal surface position set at the upper end of the stalk 42 or a position near the upper end is set. Hot water filling is performed until the molten metal 60 reaches the molten metal surface position L.
[0043]
  This hot water filling operation will be described with reference to the hot water filling operation flowchart of FIG. A molten metal 60 in which an aluminum alloy is dissolved is poured into the molten metal holding crucible 11 of the holding furnace 10 in advance, and a predetermined amount is stored and prepared.
[0044]
  In response to an instruction from the control unit, the discharge port 18a opened at the proximal end of the hot water supply pipe 18 is closed by the discharge port side valve body 20a (step S1). Subsequently, the suction port 16a at the bottom of the pressure pot 16 that has been closed by the suction port side valve body 19a is opened, and the inside of the crucible 11 holding the molten metal and the pressure pot 16 are communicated (step S2).
[0045]
  Next, the exhaust valve 34 is opened and the pressure tank 16 is decompressed by the decompression tank 32 through the discharge pipe 33, and the molten metal 60 in the crucible 11 holding the molten metal from the suction port 16 a is near the upper end of the pressure pot 16. (Step S3). When the level sensor 36 detects that the molten metal 60 has been sucked up to the vicinity of the upper end of the pressure pot 16, the exhaust valve 34 is closed to stop the pressure reduction, and the suction port 16a is closed by the suction side valve element 19a (step). S4).
[0046]
  Next, the high-pressure pressurizing valve 26 is opened, compressed air is supplied from the high-pressure gas supply source 24 into the pressurizing pot 16 to pressurize the molten metal surface in the pressurizing pot 16, and is closed by the discharge port side valve body 20a. The discharged discharge port 18a is opened (step 5), and the molten metal 60 in the pressurizing pot 16 is pushed up to the constant molten metal surface position L set at the upper end of the stalk 42 or near the upper end through the hot water supply pipe 18 (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.
[0047]
  When the molten metal 60 is pushed up to the constant molten metal surface position L, when the molten metal 60 is pushed up to the constant molten metal surface position L, the molten metal surface 60a in the stalk 42 gradually approaches the temperature measurement point a as the molten metal 60 is pushed up. The temperature at the temperature measurement point a rises, and this temperature is detected by detecting by the temperature measuring means that the molten metal surface 60a has been reached at the constant molten metal surface position L obtained experimentally in advance.
[0048]
  When the molten metal surface 60a pushed up to the constant molten metal surface position L by the temperature measuring means is detected (step S7), the molten metal surface detection signal is sent from the temperature measuring means to the control unit, and the high pressure pressurizing valve 26 is closed and pressurized. The pressurization in the pot 16 is stopped, and at the same time, the discharge port 18a is closed by the discharge port side valve body 20a to prevent the reverse flow of the molten metal 60 from the stalk 42, thereby maintaining the constant molten metal surface pressure 60a. Is held at the constant molten metal surface position L (step S8).
[0049]
  Subsequent to the hot water filling operation from step S1 to step S8, the filling operation for filling the molten metal 60 into the cavity 50 of the mold 50 is started.
[0050]
  Next, the filling operation will be described with reference to a filling operation flowchart shown in FIG. 5 and a filling pressurization pattern explanatory diagram shown in FIG.
[0051]
  The discharge port 18a is closed by the discharge port side valve body 20a, and the molten metal surface 60a of the molten metal 60 in the stalk 42 is held at the constant molten metal surface position L (step S11), and is closed by the suction port side valve body 19a. The suction port 16a is opened, and the constant molten metal surface pressure holding in the pressure pot 16 is released (step S12).
[0052]
  Next, the exhaust valve 34 is opened and pressurized by the decompression tank 32 through the discharge pipe 33.potThe inside of 16 is depressurized, and the molten metal 60 for one casting by the cavity 50 is sucked into the pressure pot 16 from the suction port 16a (step S13). When the molten metal 60 for one casting is sucked into the pressurizing pot 16, the discharge valve 34 is closed to stop the decompression by the decompression tank 32, and the suction port 16a is closed by the suction side valve body 19a (step S14). The amount of molten metal for one casting sucked and supplied into the pressure pot 16 is experimentally obtained in advance, and a certain amount is obtained by detecting suction to a certain position by the level sensor 36 provided in the pressure pot 16. Secure.
[0053]
  Subsequently, as shown in FIG. 3, the high pressure pressurizing valve 26 is opened with the low pressure pressurizing valve 30 and the exhaust valve 34 closed, and high pressure compressed air is supplied from the high pressure gas supply source 24 through the supply conduit 25 to the pressurizing pot. 16, the molten metal surface is pressurized and the discharge port 18a closed by the discharge port side valve body 20a is opened (step S15). The molten metal 60 is pumped into the stalk 42 through the hot water supply pipe 18 from the opened discharge port 18a, and the molten metal surface 60a is pushed up from the constant molten metal surface position L into the cavity 50.High speed filling of molten metalStart.
[0054]
  The pressurization in the pressurization pot 16 by opening the high-pressure pressurization valve 26 is the high pressure supplied from the high-pressure gas supply source 24 as shown in the filling pressurization pattern explanatory diagram of FIG. The compressed air is rapidly increased, and the molten metal surface is pressurized with a large pressurizing pressure P1. As a result, the molten metal 60 is pumped at a high pressure into the stalk 42 through the hot water supply pipe 18, the molten metal surface 60 a is pushed up from the constant molten metal surface position L, and the high-speed filling speed to the high-speed filling molten metal surface position L 1 set in the cavity 50 in advance. (Step S16).
[0055]
  The molten metal up to this high-speed filling position L1At high speedFor the filling, the molten metal filling time 60a required to push the molten metal surface 60a of the molten metal 60 up to the high speed filling molten metal surface position L1 from the opening of the high-pressure pressurizing valve 26 is experimentally confirmed in advance and set. When the time has elapsed, the high-pressure pressurization valve 26 is closed and the exhaust valve 34 is opened (step S17) as shown in FIG.Fulfillment ofAs shown in FIG. 6, the filling pot 16 is abruptly depressurized by stopping the filling and forcibly sucking it by the decompression tank 32.
[0056]
  Pressurizationpot16 is depressurized and pressurizedpotWhen the pressure sensor 35 detects the pressure P2 + α obtained by adding the correction pressure α to the filling holding pressure P2 that is slightly larger than the filling holding pressure P2 set in advance (step S18), a signal from the control unit causes a change in FIG. The exhaust valve 34 is closed and the low pressure pressurizing valve 30 is opened (step S19), and low pressure compressed air is supplied from the low pressure gas supply source 28 into the pressurizing pot 16 at a low filling speed. The inside of the pot 16 is held at the filling holding pressure P2. The filling of the molten metal into the cavity 50 is achieved by reducing the filling speed because low-pressure compressed air is supplied.
[0057]
  While the pressure pot 16 is suddenly depressurized from the start of depressurization in the pressurization pot 16 in step S16 until the low pressure pressurization valve 30 in step S19 is opened, pressurization of the molten metal surface by the pressure in the pressurization pot 16 is performed. As a result, the molten metal 60 is pumped into the stalk 42 through the hot water supply pipe 18, and the molten metal surface 60a rises from the high-speed filling molten metal surface position L1 shown in FIG. 50 is filled with the molten metal 60.
[0058]
  Here, if the exhaust valve 34 is closed and the low pressure pressurizing valve 30 is opened when the pressure in the pressurizing pot 16 is reduced to the filling holding pressure P2 in step S18, the filling holding pressure P2 set in advance by inertia is opened. It will be lower. In order to avoid this, as described above, when the pressure sensor 35 detects the pressure P2 + α obtained by adding the correction pressure α to the pressure P2 in step S17, the pressure in the pressure pot 16 is reduced by closing the exhaust valve 34 in advance. The filling holding pressure P2 can be reduced. This correction pressure α is set by experimental confirmation in advance.
[0059]
  In step S18, the low pressure pressurizing valve 30 is opened, and the compressed air from the low pressure gas supply source 28 is put into the pressurizing pot 16.Supplied at low filling speedThe inside of the pressure pot 16 is held at the filling holding pressure P2. The temperature rise at the temperature measurement point a is started by the melt heat of the melt 60 filled in the cavity 50, and the temperature detected by the temperature measuring means rises.
[0060]
  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 50 starts to solidify from the upper end, and as the solidification progresses, the temperature measurement point a The temperature starts to fall.
[0061]
  When the solidification proceeds to the gate 51 and the temperature measurement means detects a temperature, for example, 530 ° C., which has decreased to the temperature at which solidification has progressed to a preset temperature measurement point a (step S20), the temperature detection means. Then, the pressure holding release signal is sent, the low pressure pressurizing valve 30 is closed (step S21), the pressurization of the pressurizing pot 16 is stopped to release the holding pressure, and at the same time the discharge port 18a is closed by the discharge port side valve element 20a. The molten metal surface 60a is maintained at the constant molten metal surface position L by preventing the reverse flow of the molten metal 60 from the stalk 42 and maintaining the constant molten metal surface pressure (step S22). The time from the closing of the filling completion holding pressure valve 29 in step 18 to the closing of the low pressure pressurizing valve 30 in step S20 is a filling completion holding time T2, and this filling completion holding time T2 is confirmed in advance by experiments or the like. It can also be managed by time.
[0062]
  Further, the solidification in the cavity 50 proceeds and the temperature at the temperature measurement point a continues to drop, and even when the solidified and cast product is released from the mold 45, the deformation or galling does not occur. When the temperature detection means detects 490 ° C.,Temperature detection meansThen, a signal is issued to the control unit as a solidification time release signal, the mold 45 is opened, the casting solidified in the cavity 50 is taken out, and one casting cycle is completed (step S23). Thereafter, the mold 45 is closed to enter the next molten metal filling standby state.
[0063]
  Subsequent filling operations are performed by closing the discharge port 18a by the discharge port side valve body 20a and holding the molten metal surface 60a in the stalk 42 at the constant molten metal surface position L, while the suction port side valve body 19a holds the suction port. From step 11 in which the pressure on the constant molten metal surface in the pressure pot 16 is released by opening 16a, the mold 45 is opened, and the mold 40 is closed through step 21 in which the cast solidified in the cavity 50 is taken out. By repeating Step 11 to Step 21 to enter the molten metal filling standby state, casting is continuously repeated.
[0064]
  the aboveCasting method of low pressure casting equipmentAccording to this, the backflow from the stalk 42 is prevented, and the molten metal surface 60a in the stalk 42 is maintained at the constant molten metal surface position L directly below the cavity 50, and the molten metal 60 is pushed out from the molten metal supply device 15 to push the molten metal 60a. Since the molten metal surface 60a is pushed up and filled in the cavity 50, the molten metal surface 60a at the constant molten metal surface position L is close to the cavity 50 in each casting cycle, and the molten metal 60 moves from the fixed molten metal surface position L by the upward movement. The distance is short and the fixed hot water surface position L to the high speed filling hot water surface position L2 in the cavity 50.At highBy fast filling, the molten metal is filled into the cavity 50 in a short time. As a result, the temperature drop of the molten metal 60 is suppressed, the temperature of the molten metal 60 poured into the cavity 50 is maintained, the molten metal fluidity when filling the cavity 50 is good, and the high-speed charged molten metal of the cavity 50 By rapidly switching the molten metal 60 filled to the surface position L2 to the filling holding pressure P2, the turbulent flow of the molten metal 60 can be effectively calmed down, and the melted molten metal 60 with a small temperature drop is filled in the cavity 50. Therefore, it is possible to perform high-quality casting with excellent hot water resistance and no entanglement defects inside.
[0065]
  Since this hot water performance is ensured, for example, it becomes possible to continuously and stably produce a thin casting with a thickness of 2 mm, which was impossible with conventional low pressure forging, and it becomes possible to cast a thin casting. Can be reduced in weight. In addition, according to the casting apparatus 1 according to the present embodiment, the conventional 9 kg cylinder head can be reduced in weight by 1.2 kg (13%).
[0066]
  Furthermore, the movement time of the molten metal 60 at the time of filling is extremely short, the time during which the molten metal 60 is exposed to the air in the stalk 42 and the cavity 50 is short, the generation of oxide is extremely small, and the oxide is molten 60. It is avoided that the quality of the cast product is deteriorated due to being caught in the steel, and the oxide deposited on the inner peripheral surface of the stalk 42 is suppressed to secure the cross-sectional area of the molten metal passage, and the effect of the hot water from the gate is ensured. This improves the efficiency of casting operations.
[0067]
  Further, high-speed filling time T1 required for high-speed filling from the constant molten metal surface position L to high-speed filling hot-water surface position L1, and filling required for low-speed filling from high-speed filling hot-water surface position L1 to filling completion liquid surface position L2. By confirming the completion holding time T2 by an experiment or the like in advance, the operations of the high pressure pressurizing valve 26, the low pressure pressurizing valve 30, and the exhaust valve 34 of the molten metal supply device 15 can be managed according to time.ofSimplification is possible, and the filling speed of the molten metal 60 can be controlled.
[0068]
  Further, since the molten metal 60 is filled at a high speed from the constant molten metal surface position L to the high-speed filling molten metal surface position L1 in the cavity 50, the pouring time T can be greatly shortened, and an improvement in casting work efficiency can be expected. .
[0069]
【The invention's effect】
  According to the low pressure casting method and the low pressure casting apparatus described above, the molten metal surface in the stalk in which the molten metal stored in the molten metal holding crucible is pumped into the stalk by the molten metal supply device provided in the holding furnace and the backflow is prevented. Is maintained at the constant molten metal surface position, the molten metal is filled into the cavity by pumping the molten metal from the molten metal supply device, so that the distance from the molten metal surface to the cavity at the constant molten metal surface position is constant in each casting cycle. In the casting cycle, it is not necessary to adjust the filling pressure control for pushing up the molten metal surface in the stalk to fill the cavity, so that the operation control can be simplified. Also, from the constant molten metal surface position to the high-speed filling molten metal surface position in the cavitySet the pressure pot pressure reduction means to high pressureBy filling at high speed, the molten metal is filled in the cavity in a short time and the temperature drop of the molten metal is suppressed, and the molten metal fluidity at the time of filling is good.Filling the molten metal at low speed by setting the pressure pot pressure reduction means to low pressure.By switching to, the turbulent flow of the molten metal can be effectively subsided, and high quality casting without any entanglement defects is possible.
[0070]
  Also, the stalk when the molten metal moves and the time of exposure to the air in the cavity are short, the generation of oxide is extremely small, and it is avoided that the quality of the cast product is deteriorated, and it is deposited on the inner peripheral surface of the stalk. Oxide is suppressed, the molten metal passage cross-sectional area is secured, the effect of the hot water from the gate is secured, and the efficiency of the casting operation is 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 an enlarged view of a portion A in FIG.
FIG. 3 is a pressurizing circuit diagram of the pressurizing and depressurizing means.
FIG. 4 is also a hot water stuffing operation flowchart.
FIG. 5 is a flowchart of a filling operation in the same manner.
FIG. 6 is also an explanatory diagram of a filling pressure pattern.
FIG. 7 is a pressurizing circuit diagram for explaining the operation of the pressurizing and depressurizing means.
FIG. 8 is a pressurizing circuit diagram for explaining the operation of the pressurizing and depressurizing means.
FIG. 9 is a conceptual diagram of a conventional low-pressure casting apparatus.
FIG. 10 is also an explanatory diagram of pressure correction of a conventional filling pressure.
FIG. 11 is also an explanatory diagram of pressure correction of a conventional filling pressure.
[Explanation of symbols]
1 Low pressure casting equipment
10 Holding furnace
11 molten metal holding crucible
15 Molten metal supply device
16 Pressurized pot
16a inlet
17 Pressurized pot lid
18 Hot water supply pipe
18a Discharge port
19a Suction side valve body
20a Discharge port side valve body
22Pressurizing pot pressure reducing means
23 High pressure means
24 High pressure gas supply source
25 Supply pipeline
26 High pressure pressurizing valve
27 Low pressure means
28 Low pressure gas supply source
29 Supply pipeline
30 Low pressure pressurizing valve
31 Pressure reducing means
32 Depressurized tank
34 Exhaust valve
35 Pressure sensor
40 casting machine
41 base
42 Stoke
45 mold
50 Hability
51
60 molten metal
a Temperature measurement point
L Position of molten metal surface
L1 High speed filling hot water surface position
L2 Filling hot water surface position

Claims (3)

Stoke extending in the vertical direction, mold having a cavity formed at the upper end of the stalk through a pouring gate, a molten metal holding crucible in which the molten metal is stored, and a lower part in the molten metal stored in the molten metal holding crucible A pressure pot in a sealed state in which the pressure pot is immersed, a hot water supply pipe connecting the pressure 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 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 inside of the pressurization pot. A casting method for a low pressure casting apparatus,
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 depressurizing and pressing 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 the fixed molten metal surface position set in the stalk;
Next, from the state where the molten metal surface is held at the constant molten metal surface position, the pressure pot depressurizing / pressurizing means is pressurized at a high pressure from the high-speed filled molten metal surface position preset in the cavity, and the molten metal is melted at a high-speed filling speed. A third step of filling
Next, from the position of the high-speed filling hot water surface to the completion of filling, the pressure pot depressurizing / pressurizing means sucks and depressurizes to a value obtained by adding a correction pressure to a preset filling holding pressure, and then lowers the pressure to low pressure filling. A casting method for a low-pressure casting apparatus, comprising a fourth step of filling molten metal at a speed .   2. The casting method for a low-pressure casting apparatus according to claim 1, wherein the constant molten metal surface position is set to an upper end or a vicinity of the upper end of the stalk.   3. The casting method for a low-pressure casting apparatus according to claim 1, wherein the molten metal supply from the constant molten metal surface position to the high-speed filling molten metal surface position is set for a predetermined molten metal supply time.

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