JP2023091797A - casting method - Google Patents

Abstract

To provide a casting method which enables clamping force class down and cycle reduction without stopping the fluidization of a molten metal in a mold cavity.SOLUTION: A casting method using a vertical casting device in which a molten metal is injection-filled into a mold cavity formed by a mold closing operation in which a movable mold comes closer to a fixed mold, controls an injection step of filling-fluidizing the molten metal into the mold cavity based on the closing position of the movable mold during the mold closing operation, a pressure increase step of increasing the density of the molten metal in the mold cavity; a pressure holding step of compensating the solidification shrinkage of the molten metal, and a cooling step of cooling the molten metal to a prescribed temperature.SELECTED DRAWING: Figure 2

Description

The present invention relates to a casting method using a vertical casting apparatus, in which molten metal is injected and filled into a mold cavity formed by a mold closing operation in which a movable mold approaches a fixed mold.

Casting apparatuses used for casting and molding in which a molten metal such as an aluminum alloy is injected and filled into a mold cavity are classified into a horizontal casting apparatus and a vertical casting apparatus. In a horizontal casting apparatus, molten metal is horizontally injected from an injection device, the flow direction of the molten metal changes from the horizontal direction to the vertical direction, and the molten metal flows vertically in the mold cavity. Therefore, the flow of the molten metal is likely to be disturbed, and casting defects such as entrainment of air or gas, voids, blisters, wrinkles, weld boundaries, and burrs are likely to occur.

On the other hand, in the vertical casting apparatus, the molten metal is injected vertically from the injection device, the molten metal flows vertically in the mold cavity, and the flow direction of the molten metal does not change. Therefore, the flow of molten metal is stable, and casting defects are less likely to occur, making it suitable for casting parts that require airtightness and product strength. The object of the present invention is a casting method using this vertical casting apparatus.

Here, the vertical casting apparatus has a complicated structure and tends to be large because the injection apparatus and the mold clamping apparatus that supports the casting mold forming the mold cavity are arranged vertically up and down. In recent years, castings tend to be larger in size, and in order to improve productivity, there is an increasing tendency to simultaneously cast and mold a plurality of castings using a single casting mold. As a result, vertical casting apparatuses are becoming more complicated and larger. For that reason, a proposal that can realize a mold clamping force class down is desired. For example, casting molding using molten metal forging, in which a press operation (also referred to as compression operation) is performed to press the molten metal into a product shape after injection filling of the molten metal into the mold cavity, is considered suitable. Molten metal injection filling is performed toward a mold cavity that is larger than the product shape, so it is possible to fill with a low molten metal pressure (lower casting pressure), and the mold clamping force that acts as a reaction force to the molten metal pressure can be small. In addition, since the mold clamping force during the press operation acts on the entire surface of the molten metal, the press operation can be performed with a small mold clamping force (downsizing of the mold clamping device). Due to the effect of lowering the casting pressure and miniaturizing the mold clamping device, it is possible to reduce the size of the vertical casting device (mold clamping force class down). Many proposals have been made for casting using this molten metal forging.

For example, as shown in Patent Literature 1, casting is proposed using a vertical casting apparatus in which a shield block is arranged on the mold dividing surface around the mold cavity. First, the mold is closed to the position of the shield block by low-pressure mold clamping, and the molten metal is injected and filled into the mold cavity, which is larger than the volume of the final product. The shield block is equipped with a means for adjusting the amount of compression of the product during the compression operation. After the molten metal is injected and filled, it is switched to high-pressure mold clamping, and the compression operation is performed to the final compression position, thereby pressing the molten metal. Shape into product shape. It is said that this makes it possible to eliminate fluctuations in the compression rate of the product and obtain high-quality castings.

JP-A-11-147169

Here, in Patent Document 1, a molten metal is injected and filled into a mold cavity larger than the final product volume, and after injection filling, the mold cavity is compressed into the final product volume. In other words, the flow of the molten metal stops in the mold cavity when switching from the injection filling of the molten metal to the compression operation. Due to the stoppage of the flow of the molten metal, there is a high probability that product appearance defects such as wrinkles in the molten metal, boundaries between molten metals, and inclusion of foreign substances such as oxides will occur. In addition, the temperature of the molten metal is lowered, the fluidity of the molten metal is lowered due to the increased viscosity of the molten metal, and casting defects such as poor filling (product short circuit), voids, and blowholes caused by the flow of the molten metal are feared. Furthermore, a drop in the temperature of the molten metal causes a change in the metallographic structure during solidification, resulting in a decrease in the strength of the product and an abnormality in the strength of the cast product, such as a difference in strength depending on the part. As a result, in Patent Literature 1, although the effect of reducing the mold clamping force can be expected, the quality of the cast product remains uncertain.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a casting method capable of reducing the mold clamping force class and shortening the cycle without stopping the flow of the molten metal in the mold cavity.

The casting method of the present invention is a casting method using a vertical casting apparatus, in which molten metal is injected and filled into a mold cavity formed by a mold closing operation in which a movable mold approaches a fixed mold. Based on the mold closing position of the movable mold during operation, an injection step of filling and flowing the molten metal into the mold cavity, a pressure increasing step of increasing the density of the molten metal in the mold cavity, and solidification shrinkage of the molten metal. and a cooling process for cooling the molten metal to a predetermined temperature.

In the casting method of the present invention, the periphery of the mold cavity is formed by a sliding PL surface extending in the vertical direction and a contact PL surface extending in the horizontal direction, and within the range of the sliding PL surface, the mold The spatial volume of the cavity is variable, the spatial volume is the largest in the injection process, the spatial volume is gradually reduced from the injection process toward the pressure increasing process and the pressure holding process, and the cooling process It is preferable that the space volume is the smallest at , and that the contact PL surface comes into contact with the product volume.

Further, in the casting method of the present invention, the molten metal in the mold cavity exhibits a mold clamping flow in which it is pressed and flows due to the reduction of the space volume, and in the injection step, the injection flow of the molten metal from the injection device is accompanied by the injection flow of the mold. A clamping flow is added, and in the pressure increasing step, the clamping flow acts as a mold clamping pressure increase that increases the filling density of the molten metal, and in the holding pressure step, the clamping flow supplements the solidification shrinkage of the molten metal. It preferably acts as a holding pressure.

Furthermore, in the casting method of the present invention, it is preferable to provide means for exhausting gas within the mold cavity.

Moreover, in the casting method of the present invention, it is preferable to provide means for adjusting the amount of molten metal injected and filled into the mold cavity.

Furthermore, in the casting method of the present invention, it is preferable to provide means for preventing leakage of molten metal injected and filled in the mold cavity.

According to the present invention, it is possible to provide a casting method capable of reducing the mold clamping force class and shortening the cycle without stopping the flow of the molten metal in the mold cavity.

1 is a conceptual diagram showing a vertical casting apparatus according to an embodiment of the present invention; FIG. It is a figure which shows the casting method which concerns on embodiment of this invention. 1. It is a figure which shows the first half part of casting molding operation|movement using the vertical casting apparatus shown in FIG. 1. It is a figure which shows the latter half part of casting molding operation|movement using the vertical casting apparatus shown in FIG. It is a figure which shows the Example of the filling amount adjustment means of a molten metal. FIG. 5 is a diagram showing another embodiment of the molten metal filling amount adjusting means.

Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. In addition, the following embodiments do not limit the invention according to each claim. In addition, not all combinations of features described in the embodiments are essential for the solutions of the inventions according to the respective claims. In addition, in this embodiment, the scale and dimensions of each component may be exaggerated, and some components may be omitted.

(Vertical casting machine)
First, a vertical casting apparatus according to an embodiment of the present invention will be described with reference to FIG. A vertical casting apparatus 100 shown in FIG. 1 includes a casting mold 10 , an injection device 20 , a mold clamping device 30 and a control device 40 .

A casting mold 10 includes a fixed mold 11 and a movable mold 12 . The fixed mold 11 and the movable mold 12 are arranged vertically one above the other with the fixed mold 11 facing downward, and a mold cavity 13 is formed by a mold closing operation in which the movable mold 12 approaches the fixed mold 11. be. Further, the fixed mold 11 is provided with a gate 13G for filling the mold cavity 13 with molten metal. The stationary mold 11 and the movable mold 12 are heated and controlled to temperatures appropriate for the flow and cooling of the molten metal injected and filled into the mold cavity 13 by heating means (not shown). In addition, if necessary, a release agent is applied to the mold cavity 13 and the gate 13G before injection filling of the molten metal.

The injection device 20 is arranged vertically below the casting mold 10, and includes a molten metal holding furnace 22 that stores the molten metal M, a pressure chamber 21 that contains the molten metal holding furnace 22, and the molten metal M in the molten metal holding furnace 22. and a hot water supply pipe 23 that connects the gate 13G of the casting mold 10. The molten metal M is a metal material such as an aluminum alloy, which is appropriately selected and adjusted to a predetermined composition according to the use of the cast product, and is melted and held at a predetermined temperature. Therefore, the molten metal holding furnace 22 is provided with temperature control means (not shown). Alternatively, means for producing the molten metal M, such as a melting furnace, may be separately provided, and the molten metal M may be periodically replenished in the molten metal holding furnace 22 . The pressurizing chamber 21 is sealed, and for example, by supplying a pressurized gas into the pressurizing chamber 21 and pressurizing the inside of the pressurizing chamber 21, the molten metal M in the molten metal holding furnace 22 is pressed and the molten metal is supplied. The molten metal M rises in the pipe 23 and is injected and filled toward the mold cavity 13 via the gate 13G. It is preferable that the hot water supply pipe 23 is made of, for example, a ceramic material that has heat insulating properties and low wettability with the molten metal M. As shown in FIG. Furthermore, it is preferable to heat and maintain the hot water supply pipe 23 between the molten metal holding furnace 22 and the gate 13G at a predetermined temperature so that the molten metal M inside does not solidify.

The fixed mold 11 at the connecting portion between the hot water supply pipe 23 and the gate 13G is provided with opening/closing means 14 for opening/closing the gate 13G. When the mold cavity 13 is injected and filled with the molten metal M, the opening/closing means 14 is opened, and when the mold cavity 13 is not filled with injection, the opening/closing means 14 is closed. Foreign matter can be prevented from entering the molten metal M in the molten metal holding furnace 22 from the hot water supply pipe 23 during operation. Alternatively, it is possible to obtain the effect of shortening the casting cycle by simultaneously performing the cooling process, the process of removing the cast product, and the work of recovering the molten metal M remaining in the hot water supply pipe 23 . Further, for example, by filling the inside of the hot water supply pipe 23 with an inert gas such as nitrogen and keeping it in a sealed state, the oxidation prevention effect of the molten metal M can be obtained. Further, it is preferable to heat and hold the opening/closing means 14 together with the hot water supply pipe 23 at a predetermined temperature. An opening/closing means 14 such as a pin that advances and retreats toward the gate 13G may be provided at the position of the movable mold 12 facing the gate 13G.

The mold clamping device 30 includes a fixed platen 31 that supports the fixed mold 11 , a movable platen 32 that supports the movable mold 12 , and a mold clamping platen 33 that supports the mold clamping drive section 35 . The fixed platen 31 and the mold clamping platen 33 are connected by a plurality of tie bars 34 . A movable platen 32 arranged between a fixed platen 31 and a mold clamping platen 33 is penetrated by a plurality of tie bars 34, and the molds are opened and closed using the tie bars 34 as guides. Here, regarding the motion of the movable platen 32, the downward motion toward the fixed platen 31 is the mold closing motion, the upward motion away from the fixed platen 31 is the mold opening motion, the position where the mold closing motion is completed is the clamping limit, and the mold opening motion is completed. Define the position as the mold opening limit.

The mold clamping driving unit 35 performs mold opening/closing operations of the movable platen 32 and the movable mold 12 by hydraulic driving means such as a hydraulic cylinder. The mold clamping drive unit 35 is not limited to a hydraulic drive means such as a hydraulic cylinder, and may be an electric drive means combining a ball screw mechanism for converting rotary motion into linear motion and an electric motor. A combination of hydraulic drive means and electric drive means may be used. Alternatively, a toggle type mold clamping means combining a plurality of toggle link mechanisms may be used, or a hydraulic drive means or an electric drive means may be used for the mold opening/closing operation, and the pressure rising and lowering operations may be performed at the tips of the tie bars 34, for example. It may be a hybrid type mold clamping means in which a hydraulic cylinder or the like is arranged in the part. Mold clamping that can accurately control the mold opening/closing position and mold opening/closing speed of the movable mold 12 and the pressing force (called mold clamping force) between the fixed mold 11 and the movable mold 12 in the mold opening/closing operation, pressure increase operation, and pressure decrease operation. It is not limited as long as it is the device 30 .

The control device 40 includes an injection control unit 41 that operates the injection device 20 to control operations such as injection filling of the molten metal M, and a mold clamping control unit that operates the mold clamping drive unit 35 to control the operation of the mold clamping device 30. and a casting control unit 47 that transmits operation commands to the injection control unit 41 and the mold clamping control unit 46 based on a preset control pattern to perform casting.

Here, the injection control unit 41 includes a flow rate adjusting means 42 having a flow path switching function, a pressure adjusting means 43, a pressurized gas supply source 44, and a pressure measuring means for measuring the pressure of the pressurized gas in the pressurizing chamber 21. and measuring means 45 . The pressurized gas stored in the pressurized gas supply source 44 is adjusted to a predetermined pressure by the pressure adjusting means 43, adjusted to a predetermined flow rate by the flow rate adjusting means 42, and supplied into the pressurizing chamber 21 for injection control. The pressure in the pressurizing chamber 21 is controlled so that the target pressure set in the unit 41 and the pressure measured by the pressure measuring means 45 match. By controlling the pressure in the pressure chamber 21, the molten metal M in the molten metal holding furnace 22 is pressed, and the molten metal M is injected and filled into the mold cavity 13 via the feed pipe 23, the opening/closing means 14, and the gate 13G. is controlled. After injection filling, the flow rate adjusting means 42 is operated to discharge the pressurized gas in the pressurizing chamber 21, reduce the pressure in the pressurizing chamber 21, and remove the molten metal M remaining in the hot water supply pipe 23. A recovery operation of returning the molten metal to the molten metal holding furnace 22 is performed.

Inexpensive compressed air may be used as the pressurized gas, but from the viewpoint of stabilizing the quality of the molten metal M by preventing oxidation, it is preferable to use an inert gas such as argon or nitrogen. At this time, it is preferable to keep the pressure chamber 21 and the hot water supply pipe 23 filled with inert gas. As for nitrogen gas, a nitrogen gas generator that separates and collects only nitrogen gas from the air using a separation membrane, an adsorption membrane, or the like may be used as the pressurized gas supply source 44 .

Note that the injection device 20 and the control device 40 shown in FIG. Although the molten metal M is injected and filled into the cavity 13, the present invention is not limited to this. Alternatively, the molten metal M may be pressed by operating the piston and injection-filled through the hot water supply pipe 23 . Alternatively, an electromagnetic pump may be used to press the molten metal M from the molten metal holding furnace 22 and perform injection filling via the hot water supply pipe 23 . Further, for example, an injection device 20 having an injection sleeve (corresponding to a hot water supply pipe 23) and a plunger is arranged vertically below the mold clamping device 30, and the molten metal M is conveyed from the molten metal holding furnace 22 to the hot water supply pipe. The molten metal M may be supplied into 23, and injection filling may be performed by pressing the molten metal M in the hot water supply pipe 23 by the pressing operation of the plunger. In any case, the molten metal M in the molten metal holding furnace 22 is pressed, the molten metal M is injected and filled into the mold cavity 13 via the feed pipe 23, and the mold cavity 13 is vertically moved from the bottom to the top. A vertical casting apparatus 100 that fills and flows is used.

(Casting method)
Next, a casting method according to an embodiment of the present invention using the vertical casting apparatus 100 shown in FIG. 1 will be described with reference to FIG. FIG. 2(a) shows an operation waveform SH of the movable mold 12 in casting molding, with the horizontal axis representing the elapsed time and the vertical axis representing the closing position of the movable mold 12. FIG. Further, FIG. 2B shows the pressure waveform PH of the pressurized gas in the pressurizing chamber 21 in casting, where the horizontal axis is the elapsed time and the vertical axis is the pressure of the pressurized gas in the pressurizing chamber 21. .

First, as shown in FIG. 2A, when casting is started, the mold clamping control section 46 operates the mold clamping drive section 35 to perform a mold closing process. The movable mold 12 performs a mold closing operation toward the fixed mold 11 from the mold opening limit position. A mold closing position of the movable mold 12 is measured by a mold position sensor (not shown) or the like. When the mold closing position of the movable mold 12 reaches the injection start position S1, the mold clamping control section 46 transfers data to the injection control section 41 as switching time T1. At the same time, the mold clamping control unit 46 operates the mold clamping driving unit 35 based on a preset mold closing speed to control the speed of the mold closing process (mold closing operation of the movable mold 12). The mold cavity 13 is formed at the PL start position S0 before the injection start position S1. The spatial volume of the mold cavity 13 at the injection start position S1 is larger than the volume of the casting (referred to as product volume). Since the mold closing process by speed control is continued, the spatial volume of the mold cavity 13 gradually shrinks with the passage of time.

As shown in FIG. 2(b), the injection control unit 41 receives the data transfer for the switching time T1, operates the flow rate adjusting means 42, and starts supplying the pressurized gas into the pressurizing chamber 21. Pressure control of the pressurization chamber 21 is performed. According to the pressure control of the pressurization chamber 21 (increasing the gas pressure from PG2 to PG4), the molten metal M in the molten metal holding furnace 22 is pressed, and the metal mold is pushed through the hot water supply pipe 23, the opening/closing means 14, and the gate 13G. Injection filling of the molten metal M into the cavity 13 is performed (injection step). The gas pressure (PG2 to PG4) at this time is called injection casting pressure, and the flow of the molten metal M in the mold cavity 13 according to the injection casting pressure is called injection flow. Although the gas pressure (injection casting pressure) is linearly increased in FIG. 2(b), it may be increased stepwise, for example. Further, from the start of casting to the switching time T1, as a preliminary pressurization step, pressure control is performed to hold the height of the molten metal M in the hot water supply pipe 23 at a predetermined position and wait (gas pressure PG1). . As a result, the injection flow starts simultaneously with the start of the injection process, and timing adjustment between the injection process of the injection device 20 and the mold closing process of the mold clamping device 30 can be facilitated.

Here, in the injection process from the switching time T1 to the switching time T2, the flow of the molten metal M in the mold cavity 13 is due to injection flow by pressure control (gas pressures PG2 to PG3). At this time, since the space volume of the mold cavity 13 is larger than the product volume, even at a low gas pressure (PG2 to PG3) injection molding pressure, the molten metal M shows a stable filling flow and injection The effect of lowering the pressure of the process is obtained.

At the switching time T2, the molten metal M injected and flowed in the mold cavity 13 comes into contact with the movable mold 12 whose spatial volume is still being reduced. As a result, in the injection process after the switching time T2, the injection flow due to the pressure control (increasing the gas pressure from PG3 to PG4) is combined with the flow due to pressing of the molten metal M caused by the reduction of the spatial volume of the mold cavity 13 (mold clamping flow). flow) is added to cause the flow of the molten metal M in the mold cavity 13 (injection flow + mold clamping flow). The pressing force of the molten metal M required for this mold clamping flow is called mold clamping casting pressure, and the reduction of the spatial volume of the mold cavity 13 in which the mold clamping flow occurs is called mold clamping compression. The injection process due to the sum of the injection flow and the mold clamping flow shows a stable filling flow of the molten metal M even at a low gas pressure (PG3 to PG4) injection molding pressure, and the injection device 20 can reduce the pressure of the injection process. make sure. Furthermore, even at a low mold clamping casting pressure, a stable filling flow of the molten metal M is exhibited, and the effect of lowering the pressure of the injection process by the mold clamping device 30 is obtained (referred to as mold clamping force class reduction). In addition, the filling flow of the molten metal M before and after the switching time T2 does not stagnate, and the continuous and stable flow of the molten metal M in the mold cavity 13 is maintained throughout the entire range of the injection process (switching time T1 to T3). . The filling flow rate of the molten metal M is controlled by the gas pressure (PG2 to PG4) and the mold closing speed of the movable mold 12.

Next, as shown in FIG. 2A, when the mold closing position of the movable mold 12 reaches the pressure increase start position S2, the mold clamping control unit 46 transfers data to the injection control unit 41 as switching time T3. . At the same time, the mold clamping control unit 46 operates the mold clamping drive unit 35 to perform the pressure increasing process based on the preset mold closing speed and mold closing position. In the pressure increasing step, the mold clamping compression is used to increase the mold clamping casting pressure to increase the mold clamping flow, completely fill the mold cavity 13 with the molten metal M, increase the packing density of the molten metal M, This is intended to stabilize the quality of castings (referred to as mold clamping pressure increase). Therefore, the pressure increase start position S2 is set to the mold closing position of the movable mold 12 in anticipation of the amount of reduction in the spatial volume of the mold cavity 13 due to the mold clamping pressure increase. In other words, the amount of movement of the mold closing position of the movable mold 12 is used to control the pressure (mold clamping casting pressure) in the pressure increasing process. In addition, the mold closing speed of the movable mold 12 is used to control the pressure increasing speed of the mold clamping casting pressure in the pressure increasing process (referred to as mold clamping pressure increasing speed). The mold clamping flow of the mold clamping pressure increase directly and efficiently acts on the molten metal M in the mold cavity 13 . As a result, the mold clamping force can be lowered even in the pressure increasing process.

When the mold closing position of the movable mold 12 reaches the holding pressure start position S3, the mold clamping control section 46 transfers data to the injection control section 41 as switching time T4. At the same time, the mold clamping control unit 46 operates the mold clamping drive unit 35 to perform the pressure holding process based on the preset mold closing speed and mold closing position. In the holding pressure process, the mold clamping compression is used to adjust the mold clamping casting pressure, and the mold clamping flow is used to compensate for the solidification shrinkage of the molten metal M injected and filled in the mold cavity 13 (holding pressure flow) to improve the quality of castings (this is called mold clamping and holding pressure). Therefore, the holding pressure start position S3 is set to the mold closing position of the movable mold 12 in anticipation of the amount of reduction in the spatial volume of the mold cavity 13 due to the mold clamping and holding pressure. That is, the amount of movement of the mold closing position of the movable mold 12 is used to control the holding pressure flow in the holding pressure process. Further, the mold closing speed of the movable mold 12 is used to control the speed of solidification shrinkage of the molten metal M in the pressure holding process (referred to as mold clamping pressure holding speed). The holding pressure flow of the mold clamping and holding pressure directly and efficiently acts on the solidification shrinkage of the molten metal M in the mold cavity 13 . As a result, the mold clamping force can be lowered even in the holding pressure process.

When the mold closing position of the movable mold 12 reaches the mold clamping limit (switching time T5), the mold clamping control unit 46 operates the mold clamping drive unit 35 to hold the movable mold 12 at the mold clamping limit position. to cool the molten metal M in the mold cavity 13 to a temperature at which it can be taken out (cooling step). In the cooling step, the molten metal M is cooled at the mold clamping limit position where the spatial volume of the mold cavity 13 becomes the product volume, thereby obtaining a cast product with high dimensional accuracy. Also, the cooling process is set as a cooling time and time-managed. After completing the cooling process, the mold clamping control unit 46 operates the mold clamping drive unit 35 to open the movable mold 12 to the mold opening limit position (mold opening process), and using a take-out device (not shown) or the like, A casting is taken out from the mold cavity 13 .

Switching from the pressure increasing process to the holding pressure process and from the holding pressure process to the cooling process is performed by position management of the mold closing position of the movable mold 12 during the mold closing operation, but is not limited to this. For example, similarly to the cooling process, the pressure increasing time and the pressure holding time may be set and time management may be performed. Moreover, the pressure control may be such that the mold clamping casting pressure is set and the pressure increasing process and the pressure holding process are performed. In this case, the filling of the molten metal M in the mold cavity 13 and the filling density are adjusted (pressure increasing process) according to the mold clamping casting pressure, and the holding pressure flow of the solidification shrinkage of the molten metal M is adjusted (holding pressure). pressure step) is performed, and the mold closing operation of the movable mold 12 is stopped or the mold closing speed is reduced. It is assumed that each process is switched by detecting the stoppage of the mold closing operation or the deceleration of the mold closing speed.

In this way, by controlling all the casting and molding processes (injection process, pressure increasing process, holding pressure process, cooling process) based on the mold closing position of the mold closing operation of the movable mold 12, the mold cavity The stagnation and disturbance of the filling flow of the molten metal M in 13 can be eliminated. As a result, a stable flow of the molten metal M can be ensured, and casting defects, filling defects (product shorts), voids, casting failures, etc. due to disturbances in the molten metal flow such as wrinkles, molten metal boundaries, inclusion of foreign substances such as oxides, etc. It is possible to reliably prevent the occurrence of casting defects caused by the temperature drop of the molten metal M, such as porosity, solidified structure disturbance (segregation), and product strength fluctuations, and to enable the stable supply of high-quality castings.

The injection control unit 41 in the pressure increasing process and the pressure holding process performs control as shown in FIG. 2(b). First, in the pressure increasing process, since the mold clamping pressure increase by the mold clamping device 30 is already acting, the pressure increasing operation by the injection device 20 becomes unnecessary. Therefore, the injection control section 41 receives the data transfer of the switching time T3 and operates the flow rate adjusting means 42 to maintain the gas pressure PG4 in the pressurizing chamber 21 . This is to prevent the molten metal M in the mold cavity 13 from flowing backward from the gate 13G toward the hot water supply pipe 23 when the mold clamping pressure is increased. While the gas pressure is maintained at PG4, the opening/closing means 14 is operated to close the gate 13G. Also, the mold clamping pressure increase may be started at the same time as or after closing the gate 13G. Further, for example, when the injection flow from the injection device 20 reaches a predetermined filling amount within the switching time T2 to T3, the opening/closing means 14 may be operated to close the gate 13G at that point. Even in this case, since the mold clamping flow is continuing, the filling flow of the molten metal M in the mold cavity 13 does not stagnate. In this way, it is preferable to make an appropriate selection in consideration of the operating performance of the injection device 20 and the opening/closing means 14 .

Next, in the pressure holding process, since the mold clamping and holding pressure by the mold clamping device 30 is already acting, the pressure holding operation by the injection device 20 becomes unnecessary. Therefore, the injection control unit 41 receives the data transfer of the switching time T4, operates the flow rate adjusting means 42, discharges the pressurized gas from the pressurized chamber 21, and releases the pressurized gas in the pressurized chamber 21. is lowered to push down the molten metal M remaining in the hot water supply pipe 23 and return it to the molten metal holding furnace 22 (referred to as a molten metal recovery process). Similarly, the cooling process by the injection device 20 is also unnecessary. In FIG. 2(b), the recovery process of the molten metal M is started at the switching time T4 for ease of explanation, but from the viewpoint of shortening the casting cycle, it is preferable to start after the gate 13G is closed. For comparison, the dashed lines show the pressure waveforms FH in the pressure increasing process and the pressure holding process of the prior art.

In this manner, the molten metal recovery step for preparation for casting the next shot is performed simultaneously in the holding pressure step and the cooling step, thereby obtaining the effect of shortening the casting cycle. In addition, the injection filling amount of the molten metal M is controlled by the amount of movement of the movable mold 12 at the mold closing position (the spatial volume of the mold cavity 13). Therefore, the gas pressure (injection molding pressure) set in the injection device 20 may be within an appropriate range that ensures injection flow. For example, even if a high gas pressure is set, the injection filling amount of the molten metal M is restricted by the spatial volume of the mold cavity 13 . After the mold cavity 13 is filled with the molten metal M, even if the pressure control of the injection control unit 41 is continued, the molten metal M cannot be injected and filled beyond the spatial volume of the mold cavity 13 . As a result, when the mold cavity 13 becomes full, the injection flow from the injection device 20 naturally stops. This means that it is possible to solve the problem of the prior art that the injection flow slightly fluctuates and the injection filling amount fluctuates due to subtle changes in the temperature and composition of the molten metal M. As a result, it is possible to realize a stable supply of high-quality castings with little weight fluctuation.

(Casting molding operation)
Next, the casting operation of the casting method using the vertical casting apparatus 100 shown in FIG. 1 will be described with reference to FIGS. 3 and 4. FIG. 3 and 4 are enlarged views of the casting mold 10 shown in FIG. 1, and parts unnecessary for explanation are omitted.

Before starting casting, as shown in FIG. 3(a), the movable mold 12 is on standby at the mold opening limit position, and the molten metal M in the hot water supply pipe 23 is in a pre-pressurizing step at the surface position H1. , the opening/closing means 14 is closed. After the start of casting molding, the movable mold 12 performs a mold closing operation toward the fixed mold 11 (mold closing step). Since the fixed mold 11 and the movable mold 12 are arranged vertically above and below, the closing operation of the movable mold 12 suggests that the movable mold 12 moves downward vertically. At this stage, the sliding PL surface 15L of the fixed mold 11 and the sliding PL surface 15U of the movable mold 12 extending vertically upward from the periphery of the mold cavity 13 are separated.

When the mold closing position of the movable mold 12 is the PL start position S0, the two sliding PL surfaces (15L, 15U) are engaged to form the mold cavity 13. FIG. When the mold closing position of the movable mold 12 is the injection start position S1, the opening/closing means 14 is opened as shown in FIG. . At this stage, the molten metal M and the movable mold 12 are not in contact with each other. Further, the mold closing operation of the movable mold 12 after the injection start position S1 is speed-controlled based on the mold closing speed set in the mold clamping control section 46 .

As the mold closing operation of the movable mold 12 continues, the spatial volume of the mold cavity 13 is gradually reduced. Further, due to the continuation of the injection flow from the injection device 20, the injection filling amount of the molten metal M in the mold cavity 13 gradually increases. As a result, as shown in FIG. 3(c), the molten metal M and the movable mold 12 come into contact with each other at the switching time T2. After that, the mold clamping flow is added to the injection flow, and the filling flow of the molten metal M in the mold cavity 13 is performed. The addition of this injection flow and mold clamping flow has the effect of lowering the injection casting pressure and lowering the mold clamping force class of the mold clamping casting pressure. Furthermore, the filling flow of the molten metal M in the mold cavity 13 is accelerated, and injection filling can be completed in a short time. As a result, it is possible to obtain additional effects such as the effect of preventing the temperature of the molten metal from lowering, improving the fillability of the molten metal M into thin-walled portions, and improving the filling failure of large castings.

The inside of the mold cavity 13 is filled with the molten metal M due to the continuation of the filling flow that is the sum of the injection flow and the clamping flow. The mold closing position of the movable mold 12 is the pressure increase start position S2, and the inside of the mold cavity 13 is substantially filled with the molten metal M as shown in FIG. 4(d). At this stage, the two sliding PL surfaces (15L, 15U) are arranged continuously at the upper ends in the vertical direction, and the two PL surfaces (the contact PL surface 16L of the fixed mold 11 and the movable mold 12) extend in the horizontal direction. contact PL surface 16U) is separated while the amount of shrinkage of the spatial volume of the mold cavity 13 remains. When the pressure-increasing step and the pressure-holding step are performed in this state, the two contact PL surfaces (16L, 16U) gradually approach each other, and the spatial volume of the mold cavity 13 is reduced. Before or at the same time as the pressure increasing process is started, or when the filling amount from the injection device 20 reaches a predetermined amount, the opening/closing means 14 is closed to allow the molten metal to flow from the mold cavity 13 to the hot water supply pipe 23. Prevent backflow of M. After the opening/closing means 14 is closed, the molten metal M remaining in the hot water supply pipe 23 is recovered.

Due to the pressure increasing process and the pressure maintaining process, the spatial volume of the mold cavity 13 is reduced, and as shown in FIG. The space volume of the mold cavity 13 becomes the product volume, and the holding pressure process is completed. In the subsequent cooling process, the pressing force (referred to as mold clamping force) of the two contact PL surfaces (16L, 16U) is adjusted to maintain the contact state of the two contact PL surfaces (16L, 16U). After the cooling process is completed, the movable mold 12 is opened to the mold opening limit as shown in FIG. Take out the casting MC. After the cast product MC is removed, preparations for casting the next shot, such as cleaning the mold cavity 13 and applying a release agent, are performed.

Here, from the PL start position S0 of the mold closing position of the movable mold 12 to the mold clamping limit, the space volume of the mold cavity 13 is within the sliding range where the two sliding PL surfaces (15L, 15U) are fitted. can be varied. The spatial volume of the mold cavity 13 can be varied continuously from the injection process of casting to the holding pressure process within this sliding range. As a result, the filling flow of the molten metal M in the mold cavity 13 shows a continuous filling flow without stagnation. The spatial volume of the mold cavity 13 is the largest during the injection process, gradually shrinks toward the holding pressure process, becomes the smallest at the completion of the holding pressure process, and becomes the product volume at the mold clamping limit position.

Also, as shown in FIG. 15L, 15U). For example, the gap between the two sliding PL surfaces (15L, 15U) is adjusted to an appropriate range, and this gap is used as the exhaust means GR to exhaust gas. Also, fine slit grooves may be provided on the two sliding PL surfaces (15L, 15U), and these slit grooves may be used as the exhaust means GR. Alternatively, the two sliding PL surfaces (15L, 15U) may be partly or wholly formed of a porous metal or the like having countless fine holes through which only gas is permeable to serve as the exhaust means GR. Since the gas in the mold cavity 13 is lighter than the molten metal M, it is pushed by the filling and flowing molten metal M and flows toward the two slide PL surfaces (15L, 15U) positioned vertically above. Therefore, by providing the exhaust means GR on the two sliding PL surfaces (15L, 15U), the gas can be exhausted efficiently, and the residual gas failure can be reliably prevented.

Further, a double means for preventing leakage of the molten metal M injected and filled into the mold cavity 13 is provided. As shown in FIG. 3(a), the first leakage prevention means MS1 is provided on the two sliding PL surfaces (15L, 15U) together with the exhaust means GR. As a result, the effects of exhausting the gas and preventing the leakage of the molten metal M can be exhibited at the same time. For example, the gap between the two sliding PL surfaces (15L, 15U) is adjusted to about 0.05 mm. With such a gap, the molten metal M can be reliably prevented from leaking, and the gas can be discharged smoothly. The temperature of the casting mold 10 may rise due to the high temperature of the molten metal M, and the gap may change. Therefore, it is preferable to adjust the gap in anticipation of the temperature rise. Alternatively, for example, a mold material or the like whose thermal expansion coefficient is appropriately adjusted with respect to temperature rise may be used for the two sliding PL surfaces (15L, 15U). In addition, due to the long-term use of the casting mold 10, for example, the two sliding PL surfaces (15L, 15U) may be damaged by foreign matter such as solidified pieces of the molten metal M, and the gap may widen. There is concern that the molten metal M may leak through the gap. Therefore, the second leakage preventing means MS2 is provided on the two contact PL surfaces (16L, 16U) as shown in FIG. 3(b). At the mold clamping limit, a mold clamping force acts on the two abutting PL surfaces (16L, 16U) to firmly adhere to each other, thereby exhibiting the effect of preventing leakage.

(Molten metal filling amount adjusting means)
Up to this point, it is assumed that the molten metal filling amount from the injection device 20 to the mold cavity 13 is stable with high control accuracy, or that the amount of fluctuation is small enough not to affect the quality of the cast product MC. described as a condition. However, in actual casting molding, it is fully conceivable that the molten metal filling amount fluctuates greatly. For example, if the gas discharge in the mold cavity 13 is not sufficient and the remaining gas acts as a resistance to the filling flow, the melt viscosity changes due to changes in the temperature and composition of the molten metal M, resulting in a change in filling. For example, when the flow is disturbed, or when the accuracy of the pressure control of the pressurized gas is affected by fluctuations in the atmospheric pressure. Therefore, in the present invention, it is characterized in that a means for adjusting the filling amount of molten metal is provided in response to fluctuations in the filling amount of molten metal. Three examples of filling amount adjusting means will be described with reference to FIGS. 5 and 6. FIG.

In the first example, as shown in FIG. 5(a), the molten metal M is injected and filled into the mold cavity 13 with the injection casting pressure PS while the mold closing position of the movable mold 12 is fixed. The mold cavity 13 is gradually filled with the molten metal M, and the clamping casting pressure PM1, which indicates the pressure of the molten metal M in the mold cavity 13, gradually rises. When the injection casting pressure PS and the mold clamping casting pressure PM1 become equal (PS=PM1), the inside of the mold cavity 13 is filled with the molten metal M, and further injection filling of the molten metal M is impossible. Fill volume adjustment is performed. This principle is referred to as filling amount adjusting means MC1. Here, the mold closing position is the pressure increase start position S2 at which the reduction of the spatial volume of the mold cavity 13 in the pressure increase process and the pressure holding process is accurately controlled. That is, by accurately controlling the mold closing position of the movable mold 12, it is possible to easily eliminate fluctuations in the injection filling amount of the injection device 20. FIG.

In the second example, as shown in FIG. 5(b), the injection filling of the molten metal M continues toward the mold cavity 13 at the injection casting pressure PS in the switching time range from T2 to T3. The mold clamping flow is added to the injection flow, the mold cavity 13 is gradually filled with the molten metal M, and a mold clamping casting pressure PM2 is generated. As in FIG. 5A, the injection flow and the clamping flow are continued until the injection casting pressure PS and the clamping casting pressure PM2 become equal (PS=PM2). After that, the inside of the mold cavity 13 is filled with the molten metal M, and furthermore, due to the continuation of the injection flow and the mold clamping flow, a larger mold clamping casting pressure PM3 is generated (PM3>PM2 ), the balance with the injection casting pressure PS is lost (PM3>PS), and the molten metal M is returned to the injection device 20 through the hot water supply pipe 23 (referred to as backflow). Until the mold closing position of the movable mold 12 reaches the pressure increase start position S2, the excessive backflow of the molten metal M is continued, and the mold cavity 13 is filled with a filling amount of the molten metal M suitable for the space volume. is maintained. By closing the opening/closing means 14 at the pressure increase start position S2, the filling amount of the molten metal M corresponding to the spatial volume of the mold cavity 13 is ensured, and fluctuations in the injection filling amount of the injection device 20 can be easily eliminated. can. The adjustment of the molten metal filling amount by this backflow is defined as a filling amount adjusting means MC2. The backflowed molten metal M is mixed with the molten metal M in the molten metal holding furnace 22 and applied to casting the next shot.

In the third example, as shown in FIG. 6, the casting mold 10 is provided with a filling amount adjusting means MC3. As shown in FIG. 6(a), the configuration is such that a space is provided between two sliding PL surfaces (15L, 15U) and two contact PL surfaces (16L, 16U), and this space is filled with A quantity adjusting means MC3 is used. In FIG. 6(a), the filling amount adjusting means MC3 has a shape in which the space volume on the vertically upper side is widened, but is not limited to this. The spatial shape may be a combination of the direction and the horizontal direction. First, the mold closing position of the movable mold 12 starts the injection process at the injection start position S1. After that, the mold cavity 13 is filled with the molten metal M by combining the injection flow and the clamping flow. In the injection process, at least a part of the two sliding PL surfaces (15L, 15U) are not in a fitted state, and the mold cavity 13 and the filling amount adjusting space 17R are in a state of communication. If the filling amount of the molten metal M is excessive with respect to the spatial volume of the mold cavity 13, the molten metal M overflows from this communication state into the filling amount adjusting means MC3, and the space of the mold cavity 13 is filled. The full state is maintained with the filling amount of molten metal M suitable for the volume (this is called adjustment of the molten metal filling amount by overflow).

Next, as shown in FIG. 6(b), the state where the two sliding PL surfaces (15L, 15U) are completely fitted together is defined as pressure increase start position S2. That is, until the mold closing position of the movable mold 12 reaches the pressure increase start position S2, the adjustment of the molten metal filling amount is continued by overflow. A suitable filling amount of the molten metal M is ensured. After that, the opening/closing means 14 is closed, and the process proceeds to the pressure increasing step. The molten metal MF that has overflowed into the filling amount adjusting means MC3 is cooled in the range from the pressure increasing process to the cooling process, is removed from the casting mold 10, and is remelted in a melting furnace or the like in the process of removing the casting MC. Reuse.

(effect)
In this manner, the casting and molding operations of the injection process, the pressure increasing process, the pressure holding process, and the cooling process are controlled based on the mold closing position of the mold closing operation of the movable mold 12 . As a result, a stable flow can be ensured without stagnation or turbulence in the filling flow of the molten metal M in the mold cavity 13 . As a result, it is possible to reliably prevent casting defects such as wrinkles, hot water boundaries, inclusion of foreign matter such as oxides, unfilling, voids, blowholes, segregation, etc., and it is possible to provide a stable supply of high-quality cast products MC. . In addition, the addition of the injection flow from the injection device 20 and the mold clamping flow generated by mold clamping compression for reducing the spatial volume of the mold cavity 13 exerts the effect of lowering the pressure of the injection device 20 and the mold clamping device 30. To achieve a mold clamping force class-down so that a large casting MC can be cast with a small vertical casting apparatus 100.例文帳に追加Furthermore, since the preparatory process for casting the next shot such as the recovering process of the molten metal M can be carried out in parallel within the range from the pressure increasing process to the cooling process, shortening of the casting cycle can be expected. Furthermore, the quality of the casting MC is improved by the gas exhaust means GR in the mold cavity 13, the filling amount adjusting means (MC1 to MC3) for adjusting the injection flow of the molten metal M from the injection device 20, and the leakage preventing means MS of the molten metal M. It can provide stabilization and stable operation of casting.

Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the ranges described in the above-described embodiments. Various modifications or improvements can be added to the above embodiments.

REFERENCE SIGNS LIST 100 vertical casting device 10 casting mold 11 fixed mold 12 movable mold 13 mold cavity 13G gate 14 opening/closing means 20 injection device 21 pressure chamber 22 molten metal holding furnace 23 hot water supply pipe M, MF molten metal 30 mold clamping device 31 fixing Plate 32 Movable platen 33 Mold clamping plate 34 Tie bar 35 Mold clamping driving part 40 Control device 41 Injection control part 42 Flow rate adjusting means 43 Pressure adjusting means 44 Pressurized gas supply source 45 Pressure measuring means 46 Mold clamping control part 47 Casting control part SH Operating waveform PH, FH Pressure waveform S0 PL start position S1 Injection start position S2 Pressure increase start position S3 Holding pressure start position T1 to T5 Switching time PG1 to PG4 Gas pressure H1 Hot water surface position 15L, 15U Sliding PL surface 16L, 16U Contact PL surface MC Casting product PS Injection casting pressure PM1 to PM3 Mold clamping casting pressure GR Exhaust means MS1, MS2 Leakage prevention means MC1 to MC3 Filling amount adjustment means

Claims (6)

In a casting method using a vertical casting machine, in which molten metal is injected and filled into a mold cavity formed by a mold closing operation in which a movable mold approaches a fixed mold,
Based on the mold closing position of the movable mold during the mold closing operation, an injection step of filling and flowing the molten metal into the mold cavity, a pressure increasing step of increasing the density of the molten metal in the mold cavity, and A casting method characterized by controlling a holding pressure process for compensating for solidification shrinkage and a cooling process for cooling molten metal to a predetermined temperature. The periphery of the mold cavity is formed by a sliding PL surface extending in the vertical direction and a contact PL surface extending in the horizontal direction, and the spatial volume of the mold cavity is variable within the range of the sliding PL surface. The spatial volume is the largest in the injection step, gradually decreases from the injection step toward the pressure increasing step and the pressure holding step, and the spatial volume is the smallest in the cooling step. 2. The casting method according to claim 1, wherein said abutting PL surfaces abut to form a product volume. The molten metal in the mold cavity exhibits a mold clamping flow that is pressed and flows due to the reduction of the space volume, and in the injection step, the mold clamping flow is added to the injection flow of the molten metal from the injection device, and the pressure is increased. 2. In the step, the clamping flow acts as a mold clamping pressure increase that increases the packing density of the molten metal, and in the holding pressure step, the clamping flow acts as a clamping holding pressure that compensates for the solidification shrinkage of the molten metal. Or the casting method according to 2. 4. A casting method according to any one of claims 1 to 3, wherein means for evacuating gases within the mold cavity are provided. 4. The casting method according to any one of claims 1 to 3, further comprising means for adjusting the amount of molten metal injected and filled into said mold cavity. 6. The casting method according to any one of claims 1 to 5, wherein means for preventing leakage of molten metal injected and filled in said mold cavity is provided.

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