JP2008018461A - Pressure casting apparatus and pressure casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve quality of casting products formed by pressure casting process. <P>SOLUTION: When a filling rate of molten metal for a die cavity reaches a predetermined filling rate selected from a range from 93% to 98% by high-speed injection of molten metal, a plunger is deceleratingly controlled to boost a pressurizing force of the molten metal gradually. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure casting technique for pressurizing a molten metal after filling the molten metal.

  In a casting method in which a molten metal is injected and filled into a mold cavity, a cast hole may occur in the cast product as the molten metal solidifies and shrinks in the cavity. In the pressure casting method, it is possible to prevent the formation of such a cast hole by pressurizing the molten metal in the cavity after filling the molten metal. In order to effectively prevent the formation of a cast hole, it is effective to make the pressure of the molten metal higher. However, when the pressure of the molten metal is increased, there is a problem that the molten metal enters the separation surface of the mold and the burr is increased in the cast product. In addition, there is a problem that the mold is easily damaged by being exposed to high pressure, and its life is shortened.

  Patent Document 1 discloses a pressure casting method in which the pressure of molten metal is increased stepwise. In this pressure casting method, the generation of burrs is reduced by lowering the applied pressure relatively in the initial stage of pressurizing the molten metal, and then the solidification of the molten metal is slowed by increasing the applied pressure. The meat part and the inside can be stably pressurized.

JP 2004-122146 A

  However, simply increasing the applied pressure stepwise causes the formation of a void due to gas entrainment in the vicinity of the mold cavity surface that is rapidly solidified or in the thin part of the cast product in a low pressure state, resulting in high-quality casting. You may not be able to get the product and there is room for improvement.

  Accordingly, an object of the present invention is to improve the quality of cast products.

  According to the present invention, in the pressure casting apparatus in which the molten metal in the injection sleeve is injected into the mold cavity at high speed by the plunger and then the molten metal filled in the mold cavity is pressurized by the plunger, the molten metal is A moving speed control means for performing a high speed injection control for controlling the moving speed of the plunger and a deceleration control for decelerating the moving speed of the plunger so as to be injected into the mold cavity at a high speed; A pressure control means for controlling the pressure applied by the plunger to the filled molten metal, and the moving speed control means has a filling rate of 93% to 98% of the molten metal in the mold cavity by the high-speed injection control. When the predetermined filling rate selected from the range of% is reached, the deceleration control is performed, and the pressure control means The pressure pressure casting apparatus characterized by pressure-increasing stepwise are provided.

  In this pressure casting apparatus, when the filling rate of the molten metal reaches a predetermined filling rate selected from a range of 93% to 98%, the deceleration control is performed, and the pressure of the molten metal is increased. Increase the pressure step by step. By performing the high-speed injection control until the filling rate of the molten metal is within a range of 93% to 98%, the molten metal in the high temperature state can easily reach the entire mold cavity, and the applied pressure of the molten metal is relatively low in the initial stage. Even at a low pressure, the pressure applied to the molten metal acts to prevent the formation of a cast hole in the vicinity of the mold cavity surface or in the thin wall portion of the cast product. Then, by making the pressure of the molten metal relatively low in the initial stage, it is possible to reduce the occurrence of burrs and damage to the mold. Then, by increasing the pressure of the molten metal, it is possible to stably pressurize the thick-walled part and the inside of the cast product, in which solidification of the molten metal is slow. Thus, the present invention can improve the quality of the cast product.

  In the present invention, the pressure control means can employ a configuration in which the pressure is increased in two stages from a relatively low pressure to a high pressure. According to this configuration, it is possible to improve the quality of the cast product while preventing complication of the apparatus.

  Further, in the present invention, there is provided detection means for detecting the movement amount of the plunger, and the movement speed control means is a movement amount in which the movement amount detected by the detection means corresponds to the predetermined filling rate. In this case, it is possible to employ a configuration in which the deceleration control is performed. According to this configuration, the filling rate of the molten metal can be detected by the amount of movement of the plunger, and simpler control can be performed.

  Moreover, in this invention, the structure provided with the setting means which receives a user's designation | designated of the said predetermined filling rate and the switching timing from the said low pressure force to the said high pressure force can be employ | adopted. According to this configuration, the predetermined filling rate and the switching timing can be optimized more easily.

  Further, according to the present invention, in the pressure casting method, after the molten metal in the injection sleeve is injected into the mold cavity by the plunger, the molten metal filled in the mold cavity is pressurized by the plunger. A high-speed injection control step for controlling the movement speed of the plunger so that the high-speed injection into the mold cavity, a deceleration control step for reducing the movement speed of the plunger after the high-speed injection control step, and the mold A pressurizing step of pressurizing the molten metal filled in the cavity with a relatively low pressurizing force by the plunger and then pressurizing with a relatively high pressurizing force, and in the pressurizing step, When switching timing from the low pressure force to the high pressure force is set according to the execution time of the high-speed injection control process, and the execution time is relatively long , Pressure casting method characterized by relatively slower the switching timing is provided.

  In this pressure casting method, the switching timing from the low pressure force to the high pressure force is set according to the execution time of the high-speed injection control step, and when the execution time is relatively long, the switching Relatively slow the timing. When the execution time is relatively long, the molten metal filling rate in the high-speed injection control process becomes high. When the filling rate of the molten metal is high, it becomes easy for the molten metal in a high temperature state to reach the entire inside of the mold cavity, and even if the applied pressure of the molten metal is relatively low at the initial stage, the applied pressure to the molten metal acts, Occurrence of a cast hole near the mold cavity surface or in a thin part of a cast product is prevented. Then, by making the pressure of the molten metal relatively low in the initial stage, it is possible to reduce the occurrence of burrs and damage to the mold. Here, when the molten metal is pressurized in a state where the filling rate of the molten metal is relatively high, the generation of burrs is relatively increased. Therefore, generation of burrs can be prevented by relatively increasing the melt pressurizing time by the low pressure. Then, by increasing the pressure of the molten metal, it is possible to stably pressurize the thick-walled part and the inside of the cast product, which is slow in solidification of the molten metal. Thus, in the present invention, the quality of the cast product can be improved.

  Further, according to the present invention, in the pressure casting method, after the molten metal in the injection sleeve is injected into the mold cavity by the plunger, the molten metal filled in the mold cavity is pressurized by the plunger. A high-speed injection control step for controlling the movement speed of the plunger so that the high-speed injection into the mold cavity, a deceleration control step for reducing the movement speed of the plunger after the high-speed injection control step, and the mold A pressurizing step of pressurizing the molten metal filled in the cavity with a relatively low pressurizing force with the plunger and then pressurizing with a relatively high pressurizing force, and the low pressurizing force is provided. The pressure casting is set according to the execution time of the high-speed injection control process, and when the execution time is relatively long, the low pressure force is relatively lowered. A method is provided.

  In this pressure casting method, the low pressure force is set according to the execution time of the high-speed injection control process, and when the execution time is relatively long, the low pressure force is relatively low. When the execution time is relatively long, the molten metal filling rate in the high-speed injection control process becomes high. When the filling rate of the molten metal is high, it becomes easy for the molten metal in a high temperature state to reach the entire inside of the mold cavity, and even if the applied pressure of the molten metal is relatively low at the initial stage, the applied pressure to the molten metal acts, Occurrence of a cast hole near the mold cavity surface or in a thin part of a cast product is prevented. Then, by making the pressure of the molten metal relatively low in the initial stage, it is possible to reduce the occurrence of burrs and damage to the mold. Here, when the molten metal is pressurized in a state where the filling rate of the molten metal is relatively high, the generation of burrs is relatively increased. Therefore, the generation of burrs can be prevented by relatively reducing the low pressure. Then, by increasing the pressure of the molten metal, it is possible to stably pressurize the thick-walled part and the inside of the cast product, which is slow in solidification of the molten metal. Thus, in the present invention, the quality of the cast product can be improved.

  In the present invention, it is possible to adopt a configuration in which the high pressure force is set according to the execution time, and when the execution time is relatively short, the high pressure force is relatively high. When the execution time is relatively short, the molten metal filling rate in the high-speed injection control process is low. When the filling rate of the molten metal is low, it becomes difficult for the molten metal in a high temperature state to reach the entire inside of the mold cavity, and a void is likely to occur near the surface of a cast product that is rapidly solidified or in a thin portion. Therefore, the occurrence of a cast hole can be prevented by relatively increasing the high pressure.

  As described above, according to the present invention, the quality of a cast product can be improved.

<Device configuration>
FIG. 1 is a block diagram of a pressure casting apparatus A according to an embodiment of the present invention. The mold 10 is composed of a fixed mold 11 and a movable mold 12, and a cavity 13 is formed therein. During filling of the cavity 13 with the molten metal, the fixed mold 11 and the movable mold 12 are clamped by a mold clamping device (not shown).

  A gas vent valve 14 is disposed at the end of the cavity 13, and air in the cavity 13 is exhausted from the gas vent valve 14 while the cavity 13 is filled with molten metal. An ejector pin 15 is inserted into the movable die 12. The ejector pin 15 is supported by an ejector plate 16 and is used to separate the cast product from the movable die 12 when the movable die 12 is moved and the cast product generated in the cavity 13 is taken out.

  A sensor unit 17 is disposed in the ejector plate 16. The sensor unit 17 detects the melt pressure and the melt temperature of the melt filled in the cavity 13 through the ejector pin 15.

  The fixed mold 11 is formed with a molten metal introducing portion 11a, to which an end of the injection sleeve 20 is attached. The injection sleeve 20 is formed with a molten metal hot water supply port 21, and the molten metal is supplied into the injection sleeve 20 from the hot water supply device (not shown) through the hot water supply port 21. A plunger tip 31 of a plunger 30 is inserted into the injection sleeve 20. The plunger rod 32 of the plunger 30 is inserted into the injection cylinder 40, and a piston 41 is connected to the rear end thereof.

  The accumulators 51 and 52 store hydraulic oil whose hydraulic pressure is maintained at a predetermined pressure via a pump, a regulator, and the like (not shown). The accumulator 51 stores a relatively low pressure hydraulic oil, and the accumulator 52 stores a relatively high pressure hydraulic oil. An electromagnetic directional valve 60 is connected to the accumulators 51 and 52 through a pipe. The electromagnetic directional valve 60 is connected to the electromagnetic directional valve 61 by switching one of the accumulator 51 and the accumulator 52.

  The electromagnetic directional valve 61 includes a port connected to the electromagnetic directional valve 60 via the pipe 61a, a port connected to the oil drain 53, a port connected to the rear chamber 42 of the injection cylinder 40 via the pipe 61b, And a port connected to the flow rate control valve 70 and the backflow prevention valve 71 via the pipe 61c. Thus, when the molten metal is injected, the accumulator 51 or 52 and the rear chamber 42 are connected, and the front chamber 43 and the drain 53 of the injection cylinder 40 are connected via the flow rate control valve 70. When returning the injection cylinder 40 to the initial state, the front chamber 43 is connected via the accumulator 51 and the backflow prevention valve 71, and the rear chamber 42 and the drain 53 are connected.

  The flow control valve 70 is connected to the front chamber 43 of the injection cylinder 40 and adjusts the flow rate of the hydraulic oil discharged from the front chamber 43. Thereby, the moving speed of the plunger 30 is adjusted. The backflow prevention valve is connected to the front chamber 43 in parallel with the flow control valve 70, and is opened so that hydraulic oil is supplied into the front chamber 43 when the piston 41 is returned to the initial position after the molten metal is injected.

  The control unit 80 includes a CPU 81 that controls the pressure casting apparatus A, a RAM 82 that stores variable data and programs, a ROM 83 that stores fixed data and programs, and an HDD (a program that is executed by the CPU 81 and the like). Hard disk drive) and I / F (interface) 85. The I / F 85 is connected to the sensor unit 17, the flow rate control valve 70, the electromagnetic directional valves 60 and 61, and the movement amount sensor 33 that detects the movement amount of the plunger 30. The CPU 81 acquires detection results of the sensor unit 17 and the movement amount sensor 33 via the I / F 85. The CPU 81 controls the opening degree of the flow control valve 70 and the switching of the electromagnetic directional valves 60 and 61 via the I / F 85.

  An input device 86 and a display 87 are also connected to the I / F 85. The input device 86 is used by the user to input settings such as casting conditions. The display 87 is used to display various information.

<Operation of the device>
Next, the operation of the pressure casting apparatus A having such a configuration will be described. In the pressure casting apparatus A, molten metal is supplied from the hot water supply port 21 into the injection sleeve 20. The hydraulic oil is supplied from the accumulator 51 to the rear chamber 42 of the injection cylinder 40, and the plunger 30 moves to the injection sleeve 20 side. As a result, the molten metal in the injection sleeve 20 is injected into the cavity 13 by the plunger tip 31 of the plunger 30.

  After filling the cavity 13 with the molten metal, the plunger tip 31 pressurizes the molten metal with the pressure of the hydraulic oil of the accumulator 51. Thereafter, the supply of hydraulic oil to the rear chamber 42 of the injection sleeve 20 is switched to the accumulator 52, and the plunger tip 31 pressurizes the molten metal with a higher pressure. After pressing for a predetermined time, one unit of casting is completed.

  FIG. 2 (a) is a diagram showing a casting example showing the change over time in the injection speed and casting pressure during casting by the pressure casting apparatus A. FIG. First, control of injection speed (movement speed control of the plunger 30) will be described. The movement speed control of the plunger 30 is broadly divided into initial control in which the movement speed of the plunger 30 is low speed, high speed high speed injection control, and low speed deceleration control. In the case of this embodiment, hydraulic oil having a constant pressure is supplied from the accumulator 51 to the rear chamber 42 of the injection cylinder 40. Therefore, the moving speed of the plunger 30 depends on the amount of hydraulic oil discharged from the front chamber 43 per unit time.

  The amount of hydraulic oil discharged from the front chamber 43 is adjusted by the opening degree of the flow control valve 70. In the case of the initial control and the deceleration control, the opening degree of the flow control valve 70 is relatively narrowed, and the hydraulic oil discharge amount is relatively reduced. Thereby, the pressure difference of the hydraulic fluid between the front chamber 43 and the rear chamber 42 becomes small, and the moving speed of the plunger 30 becomes low. On the other hand, in the case of the high-speed injection control, the opening degree of the flow control valve 70 is relatively opened, and the hydraulic oil discharge amount is relatively increased. Thereby, the pressure difference of the hydraulic oil between the front chamber 43 and the rear chamber 42 is increased, and the moving speed of the plunger 30 is increased.

  The opening degree of the flow control valve 70 is controlled by the CPU 81. Therefore, the CPU 81 and the flow rate control valve 70 perform a high-speed injection control for controlling the moving speed of the plunger 30 and a deceleration control for reducing the moving speed of the plunger 30 so that the molten metal is injected into the cavity 13 at a high speed. It functions as a control means.

  In the present embodiment, the switching timing from the high-speed injection control to the deceleration control is determined by the molten metal filling rate in the cavity 13. The molten metal filling rate is proportional to the amount of movement of the plunger 30 as shown in FIG. Therefore, the switching timing according to the molten metal filling rate can be set by referring to the movement amount of the plunger 30. By detecting the movement amount of the plunger 30 by the movement amount sensor 33 and detecting the molten metal filling rate, the molten metal filling rate can be detected without actually measuring, and simpler control can be performed.

  The molten metal filling rate can also be derived from the molten metal pressure and molten metal temperature detected by the sensor unit 17. Therefore, it is possible to set the switching timing from the high-speed injection control to the deceleration control with reference to the melt pressure and the melt temperature detected by the sensor unit 17.

  Next, pressurizing force switching control will be described. In the present embodiment, the pressure applied to the molten metal is switched by the electromagnetic directional valve 60, and the supply source for supplying hydraulic oil to the rear chamber 42 of the injection cylinder 40 is switched from the accumulator 51 to the accumulator 52, so The pressure is increased in steps. Switching of the electromagnetic directional valve 60 is controlled by the CPU 81. Therefore, the CPU 81 and the electromagnetic directional valve 60 function as a pressure control means for controlling the pressure applied by the plunger 30 to the molten metal filled in the cavity 13.

  In this embodiment, the pressure of the molten metal is increased in two stages from a relatively low pressure to a high pressure, but may be three or more. However, if there are three or more stages, an additional accumulator is required. Therefore, the two steps can prevent the apparatus from becoming complicated.

<Relationship between injection conditions and pressure increase>
Increasing the pressure of the molten metal stepwise is effective in preventing the occurrence of burrs in the cast product and reducing damage to the mold 10. That is, making the pressure of the molten metal relatively low in the initial stage is effective in preventing the generation of burrs and reducing damage to the mold 10. Further, by increasing the pressure of the molten metal, it is possible to stably pressurize the thick part and the inside of the cast product, in which solidification of the molten metal is slow.

  However, when the pressure is low at the initial stage of pressurizing the molten metal, a cast hole may occur near the surface of the cavity 13 that is rapidly solidified or in a thin portion of the cast product. Accordingly, the start timing of the deceleration control is delayed, and the higher the molten metal filling rate by the high speed injection control, the easier the molten metal reaches the entire cavity 13 and the molten metal pressure is relatively low in the initial stage. Even so, the applied pressure acts on the molten metal, and the formation of a cast hole in the vicinity of the mold cavity surface or in the thin wall portion of the cast product is prevented. When the filling rate of the molten metal reaches a filling rate selected from the range of 93% to 98% by the high-speed injection control, the deceleration control is started to reduce the occurrence of the cast hole as will be described later.

  In this way, the quality of the cast product is improved by reducing the occurrence of burrs and reducing the occurrence of voids by injection conditions (timing to switch from high-speed injection control to deceleration control) and stepwise pressure increase. In addition, damage to the mold 10 can be reduced, and pressure casting can be optimized.

  Further, when the molten metal pressure is switched in two stages as in this embodiment, it is desirable to set the switching timing and pressure according to the execution time of the high-speed injection control as follows. First, when the execution time of the high-speed injection control is relatively long, the molten metal filling rate by the high-speed injection control is relatively high. Therefore, the switching timing of the applied pressure is relatively delayed. As described above, when the filling rate of the molten metal is high, the molten metal in a high temperature state easily reaches the entire inside of the cavity 13, and the occurrence of a cast hole is prevented even when the applied pressure is low. On the other hand, when the molten metal is pressurized at a high pressure while the filling rate of the molten metal is relatively high, the generation of burrs is relatively increased. Therefore, considering the occurrence of burrs and damage to the mold 10, it can be said that it is desirable to delay the switching timing of the pressing force when the execution time of the high-speed injection control is relatively long.

  Further, when the execution time of the high-speed injection control is relatively long, the low pressure force at the first stage is relatively lowered. As described above, when the molten metal filling rate by the high-speed injection control is high, the generation of the cast hole is reduced. Therefore, the low pressure applied at the first stage is relatively low for the generation of burrs and the damage of the mold 10. It can be said that it is desirable.

  Further, when the execution time of the high-speed injection control is relatively short, the high pressure force at the second stage is relatively increased. When the execution time of the high-speed injection control is relatively short, the molten metal filling rate in the high-speed injection control is low. When the filling rate of the molten metal is low, it becomes difficult for the molten metal in a high temperature state to reach the entire cavity 13, and a cast hole is easily generated. Therefore, the occurrence of a cast hole can be prevented by relatively increasing the high pressure applied at the second stage.

<Processing of control unit 80>
Next, processing executed by the CPU 81 will be described. FIG. 3A shows a flowchart at the time of casting condition setting processing, and FIG. 3B shows a flowchart at the time of casting execution. These programs are stored in the HDD 84 and executed by the CPU 81.

  First, referring to FIG. 3A, in S1, a condition setting process is executed, and then one unit of process is completed. In the condition setting process, a setting process for receiving a user's specification of casting conditions such as a filling rate that is a switching timing from the high-speed injection control to the deceleration control and a switching timing of the pressurizing force is performed.

  When the user designates the filling rate, this is converted into the movement amount of the corresponding plunger 30 and stored in the RAM 82 or HDD 84. Further, when the user designates the switching timing of the pressing force with time (waiting time), this is stored in the RAM 82 or the HDD 84. In the case of the present embodiment, the waiting time that defines the switching timing of the pressing force is measured when the filling rate of the molten metal is a predetermined value (for example, 90%). When the waiting time elapses, the pressure is switched from low pressure to high pressure. Note that the molten metal filling rate at which measurement is started is converted into the amount of movement of the plunger 30 and managed.

  The user can set the filling rate, which is the switching timing from high-speed injection control to deceleration control, and the switching timing of the applied pressure independently, so that the cast product can be prototyped under various conditions at the prototype production stage, The evaluation can be optimized.

  Next, the processing of the CPU 81 at the time of casting will be described with reference to FIG. After the mold 10 is set up and the molten metal is ready to be supplied, an injection start process is performed in S11. Here, the electromagnetic directional valve 60 is set so that the accumulator 51 and the electromagnetic directional valve 61 are connected. Further, the opening degree of the flow control valve 70 is set for throttle initial control. When the filling of the molten metal into the injection sleeve 20 is completed, the electromagnetic directional valve 61 is controlled to supply the rear chamber 42 hydraulic fluid of the injection cylinder 40 from the accumulator 51. Thereby, the plunger 30 moves to the injection sleeve 20 side, and injection of the molten metal into the cavity 13 starts.

  In S12, the detection result of the movement amount sensor 33 is acquired, and it is determined whether or not the movement amount of the plunger 30 is the movement amount corresponding to the switching timing from the initial control to the high-speed injection control. The movement amount corresponding to the switching timing from the initial control to the high-speed injection control is set in advance. If applicable, the process proceeds to S13, and if not, the process of S12 is executed again.

  In S13, high-speed injection control is started. Here, the opening degree of the flow control valve 70 is opened to a predetermined opening degree. Thereby, the moving speed of the plunger 30 is accelerated. In S14, it is determined whether or not the movement amount of the plunger 30 is a movement amount corresponding to the measurement start timing of the waiting time. If applicable, the process proceeds to S15, and if not, the process proceeds to S16. In S15, waiting time measurement is started.

  In S16, it is determined whether or not the movement amount of the plunger 30 is a movement amount corresponding to the filling rate that is the switching timing from the high-speed injection control to the deceleration control. If yes, go to S17, otherwise go to S18. In S17, deceleration control is started. Here, the opening degree of the flow control valve 70 is reduced to a predetermined opening degree. Thereby, the moving speed of the plunger 30 is decelerated.

  In S18, it is determined whether or not the waiting time when the measurement is started in S15 has elapsed. If applicable, the process proceeds to S19, and if not, the process returns to S14. In S19, the pressure is switched. Here, the electromagnetic directional valve 61 is controlled to connect the accumulator 52 to the rear chamber 42 of the injection cylinder 40 instead of the accumulator 51. As a result, the molten metal pressure in the cavity 13 is switched from the low pressure applied by the hydraulic oil in the accumulator 51 to the high pressure applied by the hydraulic oil in the accumulator 52.

  In S20, it is determined whether or not a predetermined time has elapsed. This time is a molten metal pressurizing time with a high pressure applied by the hydraulic oil of the accumulator 52. If applicable, the process proceeds to S21, and if not applicable, the process waits for elapse of time. In S21, end processing is performed. Here, preparation processing for the next casting process, such as taking out a cast product and returning the plunger 30 to the initial position, is performed. Thus, one unit of processing is completed.

<Experimental example>
When the filling rate, which is the timing for switching from high-speed injection control to deceleration control, is changed, and when the pressurizing force after filling the molten metal is set to one level and when the pressure is increased in two levels, the amount of casting burr generated and The incidence was examined. The object of casting is an engine cylinder block, and the molten metal is an aluminum alloy. The applied pressure after filling the molten metal was about 70 MPa in the case of one stage, and when the pressure was increased in two stages, the first stage was about 30 MPa and the second stage was about 70 MPa. When increasing the pressurizing force after filling the melt in two stages, the switching timing of the pressurizing time was 0.45 seconds after the melt filling rate was measured from 92%.

  FIG. 4 is a diagram showing experimental results. FIG. 4 (a) shows the relationship between the amount of cast burr generated and the filling rate as the switching timing from high speed injection control to deceleration control, and FIG. 4 (b) shows the cast hole. The relationship between the generation amount and the filling rate as the switching timing from the high-speed injection control to the deceleration control is shown. The amount of cast burrs generated is the average amount of cast burrs generated in each cast product after trial production of a plurality of cast products for each filling rate. The rate of occurrence of the casting hole is the rate of occurrence of the casting hole in a specific part (machined surface) of the cylinder block. is there.

  Looking at the result of FIG. 4 (a), when the applied pressure after filling the molten metal is increased in two stages, the amount of casting burr generated is remarkably reduced regardless of the filling rate as the switching timing. . This is considered to be due to the fact that when the applied pressure after filling the molten metal is increased in two stages, the initial applied pressure is about 40 MPa lower than that in the first stage.

  On the other hand, when looking at the result of FIG. 4B, when the pressurizing force after filling the molten metal is increased in two stages, a large change is seen in the occurrence rate of the cast hole depending on the filling rate as the switching timing, and the filling rate is When it is less than 93%, it is greatly inferior to the case where the applied pressure after filling the molten metal is one stage. However, when the pressure is 93% or more, particularly 94% or more, when the pressurizing force after filling the molten metal is increased in two steps, the rate of occurrence of the cast hole is equal to or lower than the case where the pressurizing force is set in one step. It has become.

  This is because when the pressurizing force is increased in two stages, the first stage is low pressure, and a void is likely to occur. However, by increasing the filling rate of the melt at the time of high-speed injection, the pressurizing force (the first stage) is increased. It is thought that the occurrence of cast holes could be reduced by the action of low pressure. Therefore, it is desirable that the filling rate as the switching timing from the high-speed injection control to the deceleration control is 93% or more, particularly 94% or more. When the filling rate exceeds 98%, a large impact pressure is generated in the molten metal due to the response limit of the deceleration control of the injection cylinder 40, and the casting burr increases rapidly.

It is a block diagram of the pressure casting apparatus A which concerns on one Embodiment of this invention. (A) is a figure which shows the example of a casting which shows the time-dependent change of the injection speed at the time of casting by the pressure casting apparatus A, and a casting pressure, (b) is a figure which shows the relationship between plunger moving amount and a molten metal filling rate. is there. (A) And (b) is a flowchart which shows the process which CPU performs. (A) And (b) is a figure which shows an experimental result.

Explanation of symbols

A Pressure casting apparatus 10 Mold 13 Cavity 20 Injection sleeve 30 Plunger 40 Injection cylinder 51, 52 Accumulator 80 Control unit

Claims (7)

In a pressure casting apparatus in which the molten metal in the injection sleeve is injected into the mold cavity at a high speed by the plunger, and then the molten metal filled in the mold cavity is pressurized by the plunger.
A moving speed control means for performing high speed injection control for controlling the moving speed of the plunger and decelerating control for reducing the moving speed of the plunger so that the molten metal is injected into the mold cavity at high speed;
A pressure control means for controlling the pressure applied by the plunger to the molten metal filled in the mold cavity,
The moving speed control means includes
When the filling rate of the molten metal into the mold cavity reaches a predetermined filling rate selected from a range of 93% to 98% by the high-speed injection control, the deceleration control is performed.
The pressure control means is
A pressure casting apparatus, wherein the pressure is increased stepwise.   2. The pressure casting apparatus according to claim 1, wherein the pressure control means increases the pressure from a relatively low pressure to a high pressure in two stages. Detecting means for detecting the amount of movement of the plunger;
The moving speed control means includes
3. The pressure casting according to claim 1, wherein the deceleration control is performed when the movement amount detected by the detection unit reaches a movement amount corresponding to the predetermined filling rate. 4. apparatus.   The pressure casting according to claim 2, further comprising setting means for receiving a user's designation of the predetermined filling rate and the switching timing from the low pressure force to the high pressure force. apparatus. In the pressure casting method in which the molten metal in the injection sleeve is injected into the mold cavity by the plunger, and then the molten metal filled in the mold cavity is pressurized by the plunger.
A high-speed injection control step for controlling the moving speed of the plunger so that the molten metal is injected at high speed into the mold cavity;
A deceleration control step of decelerating the moving speed of the plunger after the high-speed injection control step;
A pressurizing step of pressurizing the molten metal filled in the mold cavity with a relatively low pressurizing force by the plunger and then pressurizing with a relatively high pressurizing force;
With
In the pressurizing step, the switching timing from the low pressure force to the high pressure force is set according to the execution time of the high-speed injection control step, and when the execution time is relatively long, the switching timing A pressure casting method characterized by relatively slowing down. In the pressure casting method in which the molten metal in the injection sleeve is injected into the mold cavity by the plunger, and then the molten metal filled in the mold cavity is pressurized by the plunger.
A high-speed injection control step of controlling the moving speed of the plunger so that the molten metal is injected at high speed into the mold cavity;
A deceleration control step of decelerating the moving speed of the plunger after the high-speed injection control step;
A pressurizing step of pressurizing the molten metal filled in the mold cavity with a relatively low pressure by the plunger and then pressurizing with a relatively high pressure;
With
The pressure casting, wherein the low pressure force is set according to the execution time of the high-speed injection control step, and the low pressure force is relatively lowered when the execution time is relatively long Method.   The pressurization according to claim 6, wherein the high pressure force is set according to the execution time, and the high pressure force is relatively increased when the execution time is relatively short. Casting method.

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