JP2008149358A - Casting method and casting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting method and a casting apparatus capable of performing the consistent casting while the casting quality is not affected even when the amount of a molten metal supplied into an injection sleeve is changed in a vacuum die casting method of differential pressure molten metal supply system. <P>SOLUTION: A pouring basin part 15 is provided on a part of a molten metal path 3 following a product cavity in a casting die 2. The pouring basin part 15 is provided with basin volume adjusting mechanisms (16, 17) for changing the filling volume of the molten metal in the casting die 2 by reducing the volume in the pouring basin part 15 according to the drop of the level of the molten metal surface in a molten metal holding furnace 9, so that the thickness of a biscuit 11 of the molten metal in the injection sleeve 4 is fixed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a casting method and a casting apparatus capable of stabilizing casting quality even if the amount of hot water supplied to a mold changes in a differential pressure hot water type vacuum die casting method.

  The die-casting method is known as a method for mass production of thin and precise casting products, but as an elemental technology for that purpose, it is possible to complete the filling of the molten metal in the mold cavity in a short time before solidification progresses. This is a casting technology that requires high-speed and high-pressure molten metal filling. For this reason, most of the air pre-existing in the cavity is trapped by the molten metal flowing into the cavity at a high speed, which may result in an unhealthy casting having many defects in the cavity.

  In order to cope with such drawbacks, a vacuum pump sucks a cavity functioning as a product shape part space of a casting mold and an injection sleeve that is connected to the cavity and is provided outside the gate. After a predetermined amount of molten metal is transferred from the molten metal holding furnace to the inside of the injection sleeve, the molten metal is pushed into the cavity from the injection sleeve by the stroke movement of the injection piston in the injection sleeve, and is charged. (See, for example, Patent Document 1 and Patent Document 2). In addition, the vacuum said here means decompressing to 100 hPa or less, and is called the vacuum as a general term of a casting technique.

  In the vacuum die casting method described above, a molten metal portion (so-called “biscuit”) that is sandwiched and pressed between a mold and an injection piston is present in front of the sprue in the injection sleeve, and the inside of the product cavity is inserted through this biscuit. Apply high pressure to the casting. For this reason, it is known that a high quality casting with few cast holes and oxides can be manufactured.

  However, in the differential pressure hot water type vacuum die casting method, generally, the amount of hot water to be supplied is determined by controlling the time of the hot water to be vacuumed from the molten metal holding furnace into the injection sleeve. Every time a casting shot in which the injection piston performs an injection operation, the molten metal surface in the molten metal holding furnace descends, and the amount of molten metal supplied into the injection sleeve decreases. Therefore, the thickness of the above-mentioned biscuits molded by the mold, injection sleeve, and injection piston fluctuates, resulting in variations in the casting pressure transmitted to the casting in the cavity, causing the casting quality to become unstable. There is. That is, when the thickness of the biscuits is thin, it tends to solidify immediately and the pressure is difficult to be transmitted, and the pressure is applied only to the biscuits. When the thickness of the biscuits is too thick, the pressure is not transmitted well to the casting in the cavity.

As a solution to this problem, at the stage where the molten metal level in the molten metal holding furnace does not decrease so much, the molten metal is supplied to the molten metal holding furnace, but in order to stabilize the amount of hot water supplied into the injection sleeve, It is necessary to replenish the molten metal to the molten metal holding furnace frequently, and a great replenishment man-hour is generated.
JP 57-152361 A Japanese Patent No. 2645488

  The present invention has been made in order to solve the above-described problems. In the vacuum die casting method of the differential pressure hot water supply method, even if the amount of hot water supplied into the injection sleeve changes, the casting quality is not affected. It is an object of the present invention to provide a casting method and a casting apparatus capable of performing the above.

  In order to achieve such an object, the casting method of the present invention comprises a melt path including a product cavity in a casting mold, and an injection sleeve provided outside the sprue connected to the melt path by a vacuum pump. And a vacuum state, a predetermined amount of molten metal is sucked and held in the inside of the injection sleeve from the molten metal holding furnace, and then the injection sleeve is moved by the stroke movement of the injection piston in the injection sleeve. In a casting method in which the product cavity is pressed and filled at a high pressure, and pressure is applied to the casting in the product cavity via a molten biscuits formed in front of the gate in the injection sleeve. A hot water pool portion is provided in a part of the molten metal path after the product cavity of the product cavity, and the volume in the hot water pool portion is set to the level of the molten metal in the molten metal holding furnace. By decreasing with a decrease, the changing the melt filled volume within the casting mold, characterized by a constant the thickness of the biscuit of the melt.

  Here, the “water reservoir” is not only the form of the literal water reservoir where the molten metal actually enters, as in the case of providing it in the overflow part or product cavity, but also in the case of providing it in the degassing runner part. It is a concept including a form that exists as a hollow portion into which molten metal does not enter.

  Further, the casting apparatus of the present invention includes a casting mold having a molten metal passage extending from the gate to the product cavity through the gate gate, and further to the degassing runner through the overflow portion, and the casting mold. An injection sleeve that is provided in communication with the gate and sucks and holds a predetermined amount of molten metal from the molten metal holding furnace through a suction pipe, and is inserted into the injection sleeve so as to move forward and backward. A casting apparatus comprising: an injection piston for filling molten metal in a sleeve into the product cavity and applying pressure to a casting in the product cavity via a molten metal biscuits formed before the gate in the injection sleeve In the casting mold, a hot water pool portion is provided in a part of the molten metal path after the product cavity in the casting mold, and the hot water pool portion is A hot water volume adjusting mechanism is provided that reduces the volume in the hot water reservoir in accordance with a decrease in the molten metal level in the molten metal holding furnace and changes the molten metal filling volume in the casting mold. .

  In the present invention, since the molten metal filling volume is reduced in accordance with the decrease in the molten metal level in the molten metal holding furnace (decreasing the amount of hot water supply), it is possible to always form a constant biscuit thickness and to produce a high quality product with no defect in the nest. Can be stably cast. Moreover, since the hot water pool is provided after the product cavity, the pressure propagation to the product portion can be made constant. Furthermore, since the thickness of the biscuits is constant even when the molten metal level of the molten metal holding furnace is lowered, it can be used up to the lower limit of the amount of molten metal in the molten metal holding furnace, thereby extending the hot water supply cycle. The hot water supply man-hour can be reduced.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view showing a casting apparatus according to the first embodiment of the present invention, and FIG. 2 is a front view showing a mold 2a on one side of the casting mold of FIG.

  The casting apparatus 1 has a casting mold 2 in which two molds 2 a and 2 b are joined via a seal packing 5 so that the mold can be divided at the time of product release after solidification of the molten metal. Inside the casting mold 2, a molten metal path 3 is formed from the gate 3 a to the product cavity 10 through the gate gate 12, and further to the degassing runner 13 through the four overflow portions 14. .

  The degassing runner portions 13 of the molten metal path 3 are gathered at one place, and a vacuum valve 18 is provided there, and is led to the outside of the casting mold 2 via the vacuum valve 18, and the casting mold 2 It is connected to a vacuum pump 19 provided outside.

  Moreover, this casting apparatus 1 has a molten metal holding furnace 9 for accommodating and holding the molten aluminum 8 before being poured into the casting mold 2 in a molten state.

  An injection sleeve 4 is provided outside the gate 3a of the casting mold 2 so as to communicate with the gate 3a. Further, one end of a suction pipe 7 is connected to the injection sleeve 4, and the other end of the suction pipe 7 is immersed in the molten aluminum 8 accommodated in the molten metal holding furnace 9.

  An injection piston 6 is inserted into the injection sleeve 4 so as to be movable back and forth, and the injection piston 6 is located farther from the casting mold 2 than the connecting portion between the injection sleeve 4 and the suction pipe 7 (retreat position). At some point, the injection sleeve 4 and the suction pipe 7 are in an open state in communication. When the vacuum valve 18 is opened in this open state, the inside of the injection sleeve 4 is sucked together with the product cavity 10 of the casting mold 2 by the vacuum pump 19. A predetermined amount of molten aluminum 8 is moved and held in the injection sleeve 4 from the molten metal holding furnace 9 through the suction pipe 7 based on the differential pressure by vacuum suction.

  The injection piston 6 is driven in the horizontal direction by a drive unit 20 composed of a cylinder, and performs a forward injection operation of moving to an injection position indicated by a broken line in FIG. By the forward injection operation of the injection piston 6, the molten aluminum 8 in the injection sleeve 4 is filled into the product cavity 10 and through the biscuits 11 of the molten aluminum 8 formed in front of the gate 3 a in the injection sleeve 4. Thus, high pressure is transmitted to the casting in the product cavity 10. Note that the suction pipe 7 is closed with respect to the injection sleeve 4 when the injection piston 6 moves before the connection portion between the injection sleeve 4 and the suction pipe 7.

By repeating the injection operation by the injection piston 6, the molten metal surface of the molten aluminum 8 in the molten metal holding furnace 9 is lowered from the upper limit level L1 in FIG. 3 (a) to the lower limit level L2 in FIG. 3 (b). A difference A in the amount of molten aluminum occurs. Along with this, the amount of molten aluminum in the injection sleeve 4 before hot water supply, that is, the thickness of the biscuits 11 of the molten aluminum 8 formed in front of the gate 3a is reduced, and the biscuits 11a having the thickness shown in FIG. What is present is changed to a biscuit 11b having a thickness shown in FIG.
For this reason, the pressure which crushes a defect to the molten metal in the product cavity 10 is not transmitted. That is, the casting pressure transmitted into the casting varies between the injection operations (shots) of the injection piston 6, which causes the quality to become unstable.

  Therefore, in order to eliminate this biscuit thickness difference B and always obtain a desired constant biscuit thickness, according to the present invention, a hot water reservoir is provided in a part of the molten metal path 3 after the product cavity in the casting mold 2. The hot water reservoir volume adjusting mechanism for changing the molten metal filling volume in the casting mold 2 by decreasing the volume in the hot water reservoir portion in accordance with the decrease in the molten metal level in the molten metal holding furnace 9. Provide.

  In the embodiment of FIG. 1, the overflow portion 14 of the casting mold 2 is used as the hot water reservoir portion 15, and the hot water reservoir portion 15 is provided with a hot water reservoir volume adjusting mechanism. FIG. 5 is an enlarged view of the hot water volume adjusting mechanism, where (a) is a front view and (b) is a cross-sectional view. As can be seen from FIG. 5, the hot water volume adjusting mechanism is inserted into the hot water pool portion 15, and is an insertion composed of a movable pin or a piece that changes the volume in the hot water pool portion 15 according to the amount of insertion. The member 16 and a drive unit 17 including a cylinder for driving the insertion member 16 are configured. As a means for changing the volume of the hot water puddle, the volume of the hot water puddle can be easily changed by providing the insertion member 16 composed of such a movable pin and a movable piece. The insertion member 16 is preferably provided with a cooling circuit, thereby preventing the molten aluminum 8 from being seized with heat.

  Further, the casting apparatus 1 is provided with a control means for controlling the hot water volume adjusting mechanism so that the thickness of the biscuits 11 of the molten aluminum 8 is constant. In order to construct this control means, as shown in FIG. 1, there is provided a molten metal level detecting means 21 for detecting the molten metal level in the molten metal holding furnace 9 linearly or stepwise, and is mainly composed of a computer. A control device 22 is provided. As the molten metal level detection means 21, for example, a sensor configured to linearly detect the molten metal level, such as a photoelectric sensor, or a sensor configured to detect in stages by a combination of a float and a plurality of proximity switches can be used. Further, the control device 22 has a function unit that drives the drive unit 17 of the hot water volume adjusting mechanism to adjust the insertion amount of the insertion member 16 so that the thickness of the biscuits 11 of the molten aluminum 8 is constant. Built by software.

  The control device 22 has the following general control functions. That is, when casting, under the condition that the vacuum pump is always operating, the vacuum valve 18 is opened to start vacuum suction of the molten aluminum 8 into the injection sleeve 4 (vacuum valve open). Processing for measuring a predetermined fixed suction time (molten metal hot water supply time) until the predetermined amount of molten aluminum 8 moves into the injection sleeve 4 after the opening of the molten metal (time processing for the molten metal hot water supply time), this molten metal hot water supply time After the elapse of time, the vacuum valve 18 is closed and the drive unit 20 is operated to start the forward injection operation of the injection piston 6 (injection operation process), and then the coagulation time has elapsed (pressure holding process). And a process of retracting the injection piston 6 after the mold is opened (retraction process of the injection piston 6).

  In addition to the above, the control device 22 performs the following control. That is, when the injection piston 6 repeats the injection operation, the molten metal level of the molten aluminum 8 in the molten metal holding furnace 9 decreases according to the number of injection operations (number of shots). The amount of decrease is detected linearly, for example. The control device 22 receives the detection signal from the hot water level detecting means 21 and increases the insertion amount of the insertion member 16 in the hot water volume adjusting mechanism in proportion to the detected decrease in the hot water level. Alternatively, one or more of the four insertion members 16 are selectively pushed into the molten metal filling volume in the casting mold 2 so that the thickness of the biscuits 11 of the molten aluminum 8 is constant. Change.

  By controlling in this way, the thickness of the biscuits becomes constant even if the molten metal level in the molten metal holding furnace 9 is lowered, so that it can be used up to the lower limit of the molten metal amount in the holding furnace, and the hot water supply cycle is extended. Can be reduced.

  However, in the control device 22, the control function unit for the hot water volume adjusting mechanism is actually configured as follows.

  First, as the molten metal level detecting means 21, a sensor that detects the molten metal level in the molten metal holding furnace 9 step by step is used. Here, a sensor configured by inserting a plurality of bar-shaped detectors having different lengths into the molten metal holding furnace 9 is used, and a detection signal is obtained each time the molten metal surface level is lowered by a certain height. The interval at which this detection signal is output is such that the detection signal is output once when the injection piston 6 performs a plurality of predetermined injection operations. When the injection piston 6 performs a plurality of predetermined injection operations, the control device 22 operates the drive unit 17 of the hot water volume adjusting mechanism, and the insertion member 16 of the hot water volume adjusting mechanism is operated. In the casting mold 2, the insertion amount is increased or one or more of the four insertion members 16 are selectively pushed in so that the thickness of the biscuits 11 of the molten aluminum 8 becomes constant. The molten metal filling volume is changed.

  In addition, since the molten metal level detecting means 21 detects the liquid level step by step, the amount of the molten metal level lowered does not coincide with the amount vacuumed into the injection sleeve 4. By feeding back the filling volume, etc., the hot water volume is optimized. When feedback control is performed to optimize the puddle volume, the puddle volume can be automatically changed during casting, and man-hours for changing conditions are not required.

  In the above embodiment, the molten metal holding furnace 9 is provided with a sensor that detects the actual molten metal level as the molten metal level detecting means 21 that detects the amount of decrease in the molten metal level in the molten metal holding furnace 9. From the product of the amount of decrease in the molten metal level (known amount) vacuumed by the injection operation of the injection piston 6 and the actual number of injection operations of the injection piston 6 (number of shots), the amount of decrease in the molten metal level Can be obtained by calculation, and the molten metal level detecting means 21 can be obtained by this calculation function.

  FIG. 6 shows an example in which the hot water reservoir 15a is provided in the degassing runner portion 13 of the casting mold 2 as a second embodiment of the present invention. The front view of the metal mold | die 2a which showed the T-shaped part (equivalent to G1 part of FIG. 2), (b) is sectional drawing which follows the BB line.

  In the case of the hot water reservoir 15a provided in the degassing runner portion 13 of the casting mold 2, the inside becomes a cavity, but the degassing runner portion 13 is closed on the vacuum valve 18 side, so that it is shown in FIG. Similarly to the case of the first embodiment, it is possible to construct a hot water volume adjusting mechanism that changes the molten metal filling volume (the volume after the product cavity) by changing the volume of the hot water reservoir 15a. The configuration of the hot water volume adjusting mechanism is the same as that of the first embodiment described with reference to FIG. 5 and is partially inserted into the hot water reservoir 15a. The insertion member 16 is composed of a movable pin or a piece whose volume is variable, and a drive unit 17 that drives the insertion member 16.

  FIG. 7 shows an example in which the hot water reservoir 15b is provided in the product cavity 10 of the casting mold 2 as a third embodiment of the present invention. The front view of the type | mold 2a, (b) is sectional drawing which follows the CC line.

  When the hot water reservoir 15b is provided in the product cavity 10 of the casting mold 2, the hot water reservoir 15b is provided in a portion of the product cavity 10 (corresponding to G2 in FIG. 2) that does not contribute to the product shape, that is, a portion to be cut off later. . In FIG. 7, the central circular portion into which the insertion member 16 is inserted is a portion that is later cut off. Even under this configuration, similarly to the case of the first embodiment shown in FIG. 1, a hot water volume adjusting mechanism for changing the molten metal filling volume is constructed by changing the volume of the hot water reservoir 15b. Can do. The configuration of the hot water volume adjusting mechanism is the same as that of the first embodiment described with reference to FIG. 5 and is partially inserted into the hot water reservoir 15b. The insertion member 16 is composed of a movable pin or a piece whose volume is variable, and a drive unit 17 that drives the insertion member 16.

  The present invention can be used in the field of casting.

It is a schematic diagram which shows the casting apparatus which concerns on the 1st Embodiment of this invention. It is the front view which showed the metal mold | die of the one side which comprises the metal mold | die for casting of FIG. It is the figure which showed a mode that the hot_water | molten_metal surface level in a molten metal holding furnace fell. It is the figure which showed a mode that the thickness of the biscuit in an injection sleeve decreased. 1 is an enlarged view of a hot water volume adjusting mechanism according to a first embodiment of the present invention, where (a) is a front view and (b) is a cross-sectional view. FIG. The hot water volume adjustment mechanism which concerns on the 2nd Embodiment of this invention is shown, (a) is a front view, (b) is sectional drawing. The hot water pool volume adjustment mechanism which concerns on the 3rd Embodiment of this invention is shown, (a) is a front view, (b) is sectional drawing.

Explanation of symbols

1 casting equipment,
2 Mold for casting,
3 Melt path,
3a
4 Injection sleeve,
5 Seal packing,
6 Injection piston,
7 Suction tube,
8 Molten aluminum,
9 Molten metal holding furnace,
10 product cavity,
11 Biscuits,
12 Yuguchi gate,
13 runners,
14 Overflow part,
15, 15a, 15b Hot water reservoir,
16 Insertion member,
17 drive unit,
18 vacuum valve,
19 vacuum pump,
20 drive unit,
21 hot water level detection means,
22 Control device.

Claims (8)

Injecting from the molten metal holding furnace by evacuating the molten metal path including the product cavity in the casting mold and the inside of the injection sleeve connected to the molten metal path and provided outside the gate by the vacuum suction means. After the molten metal is vacuumed and held inside the sleeve, the molten metal is pushed and filled from the injection sleeve into the product cavity by the stroke motion of the injection piston in the injection sleeve, and the gate in the injection sleeve is filled. In a casting method in which pressure is applied to a casting in the product cavity via a previously formed molten biscuits,
A hot water reservoir is provided in a part of the molten metal path after the product cavity in the casting mold,
The volume of the molten metal biscuits is controlled by changing the volume of the molten metal in the casting mold by reducing the volume in the molten metal reservoir in accordance with the decrease in the molten metal level in the molten metal holding furnace. A casting method characterized by:   The casting method according to claim 1, wherein the hot water pool portion is provided in any one of a degassing runner portion, an overflow portion, and a product cavity of the casting mold. A casting mold having a molten metal path that leads from the gate to the product cavity through the gate gate portion, and further to the degassing runner portion through the overflow portion,
An injection sleeve provided in communication with the pouring gate of the casting mold, and vacuum sucking and holding a predetermined amount of molten metal from the molten metal holding furnace through a suction pipe;
It is inserted into the injection sleeve so as to be able to move forward and backward, and the molten metal in the injection sleeve is filled into the product cavity by a forward injection operation, and through the molten metal biscuits formed in front of the gate in the injection sleeve. In a casting apparatus comprising an injection piston for applying pressure to a casting in the product cavity,
While providing a hot water reservoir in a part of the molten metal path after the product cavity in the casting mold,
A hot water volume adjusting mechanism for changing the molten metal filling volume in the casting mold by reducing the volume in the hot water pool according to a decrease in the level of the molten metal surface in the molten metal holding furnace. Provided,
A casting apparatus characterized by that.   The casting apparatus according to claim 3, wherein the hot water pool portion is provided in any one of a degassing runner portion, an overflow portion, and a product cavity of the casting mold.   The casting apparatus according to claim 3 or 4, further comprising a control means for controlling the hot water volume adjustment mechanism so that the thickness of the biscuits of the molten metal is constant. The hot water volume adjusting mechanism is composed of an insertion member that is partially inserted into the hot water reservoir, and the volume of the hot water reservoir is variable depending on the amount of insertion, and a drive unit that drives the insertion member. ,
The control means has a function of driving the drive unit of the hot water volume adjusting mechanism and adjusting the insertion amount of the insertion member so that the thickness of the biscuits of the molten metal is constant.
The casting apparatus according to claim 5.   The control means includes a molten metal level detecting means for detecting the molten metal level in the molten metal holding furnace linearly or stepwise, and the insertion of the insertion member is performed based on an output signal from the molten metal level detecting means. The casting apparatus according to claim 6, wherein the amount is controlled.   The casting apparatus according to claim 6, wherein the control unit operates a drive unit of the hot water volume adjusting mechanism when a plurality of predetermined injection operations are performed by the injection piston.

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