JPH06328194A - Casting mold - Google Patents

Abstract

PURPOSE:To obtain a product having a high strength and toughness practically without causing heat crack and segregation by providing a thin sheet metal-like vibration plate on the surface of the cavity side of a mold and vibrating it through the pressure fluctuation of a molten metal. CONSTITUTION:A thin sheet metal-like vibrating plate 22, which is vibrated through the fluctuation of a molten metal, is provided on a part of the surface on the cavity 2 side of a mold 1. The vibrating thin plate 22 is formed with the part to be vibrated of the mold 1 cut in two steps from the back side, and is constituted of a first thin plate part 23 in the center part and a somewhat thicker second thin plate part 24 in the periphery. A high pressure and a low pressure hydraulic oil in a hydraulic cylinder are pulsatively and alternately actuated, and a pressurizing force is pulsatively applied on a solidifying molten metal. When a pressure fluctuation is actuated at a high pressure level on the vibrating thin plate 22, the thin plate 22 is deviated. When the solidification progresses to be a low pressure level, the deviation of the thin plate 22 is reduced. By this pulsative pressurizing, nuclei are generated in the molten metal and the solidification progresses. A massy type solidified state generating a fine equi-axed system is developed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold used for pressure casting of a light metal alloy such as an aluminum alloy or a magnesium alloy.

[0002]

2. Description of the Related Art Conventionally, when casting a light metal alloy such as an aluminum alloy, in order to reduce shrinkage cavities,
A method has been adopted in which high pressure is continuously applied from the time the molten metal is cast into the mold until the solidification is completed. In particular, when high quality such as pressure resistance and high strength is required such as automobile parts, the above high pressure casting method is often used. As a casting die, a die having a predetermined thick thickness around the die cavity is used, and the cavity side surface of the die is not specially worked. .

[0003]

By the way, when the pressure is always kept at a constant high pressure as in the prior art, the cavity surface is cooled very rapidly, and the following problems occur. (1) Since solidification proceeds rapidly on the cavity surface of the mold, crystal nuclei are hardly released from the mold surface. Also,
Since the temperature gradient near the surface is large and the supercooled region is extremely narrow, the number of crystal nuclei generated in the supercooled region is also limited. As a result, the number of crystal nuclei decreases and the crystal grains become coarser, resulting in a decrease in strength. When high pressure is applied, shrinkage cavities disappear and the secondary DAS (dendritic arm spacing), which is the distance between dendrites, becomes finer, resulting in higher strength than gravity casting and low pressure casting. It is general, but only because the crystal grains become coarse,
The effects are offset. (2) Crystals rapidly solidified on the cavity surface grow in the heat flow direction to form columnar crystals. Hot cracking easily occurs between the grain boundaries or the dendrites that form each columnar crystal. (3) The solute element discharged between the dendrites is squeezed out to the non-solidified portion inside the product by the pressing force, causing a large segregation. This causes shrinkage cavities and a decrease in strength.

Therefore, in order to solve these problems, the present inventors made the invention described in Japanese Patent Application No. 4-342575 and applied for a patent. In that invention, by applying a pressing force to the molten metal in a pulsed manner, the crystal nuclei were grown and a fine equiaxed crystal structure was successfully obtained. However, in that case, as described above, the mold had no modification on the cavity-side surface of the mold, and therefore, in the case of a large casting or a complicated shape, it was partially There were places where pressure fluctuations did not propagate sufficiently. As a result, columnar crystals were partially generated.

[0005]

SUMMARY OF THE INVENTION In order to solve the above drawbacks, the present invention provides a method for filling a molten metal for casting into a cavity of a mold and applying a pressing force to the molten metal in a pulsed manner. A mechanism that amplifies the minute vibration of the molten metal by vibrating with a slight pressure fluctuation is incorporated in the mold. Then, the casting mold was provided with a thin plate-shaped vibrating plate portion that vibrates due to the pressure fluctuation of the molten metal on the cavity side surface of the casting mold.

[0006]

[Operation] When pressurizing casting in which a relatively large pressure and a small pressure are applied to the solidified molten metal in the mold cavity in a pulsed manner, the mold faced to the part where only a slight pressure fluctuation propagates. If the present invention is adopted, that portion vibrates, for example, from several μm to several 100 μm during casting. Then, in that part, the incident wave and the reflected wave, which are longitudinal waves propagating in the molten metal, are out of phase with each other, and minute vibrations start to occur. As a result, in the solidification form of the molten metal, not only the molten metal surface facing the cavity surface of the mold but also nuclei are generated in the molten metal and solidification proceeds. That is, it becomes a massy-type solidification morphology that produces a fine equiaxed crystal structure. In this way, in the massy type solidification morphology, hot cracking and segregation hardly occur, and a high-quality cast product having high strength and toughness can be obtained.

[0007]

1 to 3 are vertical sectional views showing a first embodiment of the present invention. FIG. 1 is an enlarged view of a portion A of FIGS. 2 and 3, and FIGS. There is. 1 to 3, 1 is a female mold having a relatively large cavity 2, 3 is a male mold, and the female mold 1 has a bottom portion 1a which can be attached to and detached from an upper main body 1c by a bolt 1b. Installed on. The male mold 3 has a hole 4 penetrating vertically, and the hole 4 is formed by a molten metal supply hole 5 and a relatively small cavity 6 in which a casting product is formed from above. The male mold 3 is fixed to the fixed plate 7. In this case, the stationary platen 7 is fixed in place by a member (not shown), and therefore the male die 3 is also stationary in place.

A pouring device 10 including a pouring sleeve 8 and a funnel 9 is provided on the fixed plate 7 so as to be vertically movable so that the sleeve 8 can be put into and taken out of the molten metal supply hole 5. . The pouring device 10 is also provided so as to be able to move laterally when the sleeve 8 is raised and the sleeve 8 has not entered the melt supply hole 5. Reference numeral 11 denotes a holding member for the female die 1 such as a movable plate, which is provided so as to be vertically movable by a driving device (not shown). 12 is a holding member 1
1 is an actuator connected below.

The actuator 12 includes the cavities 2, 6
A pressure can be applied to the solidified molten metal 13 in a pulsed manner, and as shown in FIG. 3, it has a hydraulic cylinder 12a, a piston rod 12b, and a pressure supply device 14.
The pressurizing force supply device 14 controls the pressure of the hydraulic oil supplied to the hydraulic cylinder 12a to, for example, 250 to 600 kg / cm.
² and a low pressure that is relatively lower than this high pressure, such as 0 to 300 kg / cm ² , and this high pressure and a relatively low low pressure are alternately pulsed (wavy 2) a supply pressure setting fluctuation device 15 including a servo valve and a relief valve that can act on the hydraulic cylinder 12a,
It has a pressurizing force fluctuation instructing device 16 having a built-in setter for the number of times (frequency) of pressurizing force fluctuation per unit time. 17 is a pump.

Above the male die 3, a molten metal supply hole 5 is provided.
Member 1 with push-out pin 18 attached to the bottom surface that can be taken in and out
9 is provided so as to be vertically movable and laterally movable. 20 is a fixed holding plate. Reference numeral 21 is a ceramic paper which is placed in contact with the inner surface of the cavity 2 during casting, and is a thin heat insulating material for casting in a state where the solid phase does not crystallize.

As shown in FIG. 1, a part of the surface of the mold 1 on the cavity 2 side, for example, the portion A in FIGS. 2 and 3, is a thin plate-like vibrating plate that vibrates due to the pressure fluctuation of the molten metal 13. The section 22 is provided. The structure of the die 1 of the diaphragm portion 22 is, for example, as shown in FIG. 1 and the following structure. The part of the mold 1 to be vibrated is formed by cutting in two steps from the back side, and the relatively thin circular first thin plate part 23 at the center and a circle slightly thicker than that around it. The second thin plate portion 24 having a shape is formed.

A portion cut into two stages of the mold 1, or
In consideration of the mounting of the block 25, the block 25 for pressing the diaphragm 22 is attached to the bolt 2 at the portion cut in three steps.
It was attached to the mold 1 by 6. On the surface of the block 25 on the diaphragm portion 22 side, a circular thin cutout portion 27 having a diameter larger than the inner diameter of the second thin plate portion 24 and smaller than the outer diameter thereof.
Is formed, and only the tip surface of the ring-shaped portion 28 on the outer periphery of the cutout portion 27 is pressed against the back surface of the second thin plate portion 24.

Next, this operation will be described. Figure 2
In the state shown in (1), the molten metal 13 is supplied into the cavity 2 through the pouring device 10 and poured. Molten metal 1 in cavity 2
After supplying 3, the pouring device 10 is moved to a position where it does not get in the way, and then the extrusion pin 18 is put into the molten metal supply hole 5. In this state, as shown in FIG. 3, the holding member 11, the female mold 1 and the like are raised, and are raised and pressed until the member 19 is pressed by the fixed holding plate 20.

At this time, as shown in FIG. 3, the male mold 3 is deeply inserted into the cavity 2 of the female mold 1,
The molten metal 13 enters the cavity 6 of the male die 3 and is pressed. At this time, the air in the cavity 6 escapes from a slight gap in the outer peripheral surface of the push pin 18. Cavity 6
The molten metal 13 therein is cooled and solidified to form a cast product. However,
Immediately after the molten metal 13 enters the cavity 6, or immediately before the filling is completed, the pressurizing force supply device 14 in the actuator 12 is actuated to, for example, a high pressure of 600 kg / cm ² and 60 kg in the hydraulic cylinder. / Cm ²
Such a relatively low pressure hydraulic oil is caused to act alternately in a pulsed manner at, for example, 10 Hz or 100 Hz, and a pressure is applied in a pulsed manner to the molten metal 13 which solidifies.

The high pressure may be appropriately set to, for example, 250 kg / cm ² or more, and the low pressure may be appropriately set to a pressure lower than the set high pressure. Of course, low pressure is 0kg
The pressure can be set to be / cm ^{2 or} a pressure relatively close to the set high pressure. When high pressure and low pressure are applied in pulses, the frequency is 0.5 to 1000.
It can also be set appropriately between Hz. If the frequency is too high, the installation and operation of the device may be hindered, so set the frequency to about 1000 Hz at most. It should be noted that normally, about 10 Hz or 100 Hz is sufficient.

FIG. 4 is a block diagram of the apparatus shown in FIGS.
C4CH aluminum alloy is poured into molds 1 and 3 with a mold temperature of 200 ° C. at a pouring temperature of 760 ° C. and a pressing force of 3
00 ± 40 kg / cm ² , that is, high pressure is 34
0 kg / cm ² , low pressure was set to 260 kg / cm ² , and 100 Hz pulse pressure was applied to the actuator 1
It is a time-pressurizing force curve when it is made to act on 2. In addition,
For reference, FIG. 4 also shows the moving stroke of the female die 1. The total time point shown in FIG. 4 was the time point at which the female die 1 was started to be raised after the hot water was supplied.

In this way, the solidification form of the molten metal is generally not only the molten metal surface facing the cavity surface of the mold, but also nuclei are generated in the molten metal and the solidification proceeds, resulting in equiaxed It becomes a so-called massy type solidification morphology in which crystals are formed. That is, since a high pressure and a low pressure that is relatively lower than this high pressure are alternately applied to the molten metal in a wavy manner, the heat transfer coefficient of the mold surface is temporarily reduced when low pressure is applied. The latent heat generated during solidification is not sufficiently removed from the mold surface, and the melt temperature partially rises. Such so-called recurrence causes crystal release and fusing release of dendrite branches. In addition, due to the pressure applied in a wavy manner, the molten metal flows, and this is also combined to promote crystal release and fusing release of dendrite branches.

Therefore, columnar crystals that are easily generated on the surface cannot be formed, and equiaxed crystals are generated on the entire inner surface of the cast product, and only equiaxed crystal zones are formed. In addition, segregation does not occur in the equiaxed zone. As a result, hot cracking does not occur, shrinkage cavities hardly occur, and high-quality cast products with high strength and toughness are obtained.

When the above operation is performed, in the present invention, the vibrating plate portion 22 incorporated in a part of the mold 1 acts as follows and vibrates, for example, from several μm to several hundred μm. . That is, at the high pressure level, the pressure fluctuation is
When it acts on the second thin plate portion 2
Since the inner peripheral portion of 4 contacts the portion of the block 25, the first thin plate portion 23 vibrates with this portion as a fulcrum. At this time, since the vibrating thin plate portion 23 has a small thickness but a small diameter, the vibrating thin plate portion 23 has greater rigidity than that when vibrating with the inner peripheral portion of the ring-shaped portion 28 as a fulcrum and is not destroyed. .

When solidification progresses to a low pressure level, the amount of bending of the diaphragm portion 22 decreases, and the diaphragm portion 22 begins to vibrate with the portion as a fulcrum. At this time, since the rigidity of the diaphragm portion 22 is reduced, a sufficient vibration amplitude can be secured even with a small pressure fluctuation.

Thus, although the pressure fluctuation is sufficiently propagated immediately after the molten metal is filled, the damping rate of the pressure fluctuation increases as the solidification progresses, and the sufficient pressure fluctuation does not propagate. In such a case, it has enough strength not to break even at high pressure, and vibrates so that the pulse pressurizing effect can be sufficiently amplified even when the pressure is attenuated.
The vibration plate 22 whose rigidity changes nonlinearly with the amount of bending is attached to the mold 1
Since it has been incorporated into, the effect of pulse pressurization is fully expressed even when coagulation progresses.

The effect of pulse pressurization is due to a phenomenon caused by a sudden change in the thermal resistance of the die surface due to pressure fluctuation, and a flow of the molten metal due to longitudinal waves propagating in the molten metal, that is, a minute vibration of the molten metal itself. It is manifested by the phenomenon. In the portion where only a slight pressure fluctuation propagates, the phenomenon caused by the sudden change of the thermal resistance of the die surface due to the pressure fluctuation cannot be expected. Therefore, it is necessary to amplify the minute vibrations of the molten metal itself due to the longitudinal waves propagating in the molten metal. If the mold surface does not vibrate at all, the mold surface becomes the fixed end. Therefore, due to the superposition of the longitudinal waves propagating in the molten metal and the reflected waves reflected from the mold surface, the molten metal itself does not generate microvibrations on the mold surface. However, when a part of the mold is vibrated as in the present invention, the phases of the incident wave and the reflected wave shift,
Minute vibrations start to occur. Especially the phase is 180-360
When the angle is shifted by °, the minute vibration is amplified by the superposition of the incident wave and the reflected wave. As a result, as described above, in the solidification form of the molten metal, not only the molten metal surface facing the cavity surface of the mold, but also nuclei are generated in the molten metal and solidification proceeds. That is, it becomes a massy-type solidification morphology that produces a fine equiaxed crystal structure. Moreover, hot cracking and segregation hardly occur, and high-quality cast products with high strength and toughness can be obtained. Casting by pulse pressurization is particularly useful when casting relatively thick or large cast products.

When the pressing force is applied in a pulsed manner for a predetermined time such as 20 seconds, it is stopped and the female die 1 is lowered to open the die. At that time, the extrusion pin 18 is lowered to move the inside of the cavity 6. Also lower casting products. When removing the cast product, the bolt 1b and the bottom 1a are removed.

FIG. 5 shows a second embodiment of the present invention and shows an example in which the present invention is applied to a horizontal die casting machine. In FIG. 5, 30 is a fixed plate, 31 is a movable plate, 32 is a fixed mold, 33 is a movable mold, 34 is a cavity, 35 is a casting sleeve, 36 is a casting plunger, 3
Reference numeral 7 denotes a pouring cylinder, and the pouring cylinder 37 has a pressurizing force supply device 14 including a supply pressure setting changing device 15 and a pressurizing force change instructing device 16, as in the first embodiment.
Also, the pump 17 is connected.

A thin plate-shaped vibrating plate portion 22 and a block 25 are provided on the surfaces of the fixed mold 32 and the movable mold 33 on the side of the cavity 34. Among those shown in FIG. 5, the movable mold 3
The structure on the 3 side was exactly the same as that shown in FIG. On the fixed mold 32 side, the vibration plate portions 22 having the structure shown in FIG. 1 were provided at two locations. However, the block 25 has a structure in which two pieces having the structure shown in FIG. 1 are horizontally connected. By doing so, the same effects as those described above can be obtained.

FIG. 6 shows a third embodiment of the present invention, which is a combination of the present invention having substantially the same structure as that shown in FIG. In FIG. 6, 1 is a die such as a female die, 22 is a vibrating plate portion composed of a first thin plate portion 23 and a second thin plate portion 24, and 25 is a thin plate portion 24 which is screwed to the back side of the die 1 and is pressed down. Block, 27 is a notch, and 28 is a ring-shaped portion. The function and effect of the mold shown in FIG. 6 are the same as those described with reference to FIG.

However, in FIG. 6, the first thin plate portion 2
The tip is in contact with the back side of the central part of 3 and the block 2
Deflection amount transmission rod 38 penetrating through the center of
And a thin circular flexure amount measuring plate 39 is pressed against the rear end surface of the flexure amount transmitting rod 38, and the pressing member 40 screwed to the block 25 supports the outer peripheral portion of the flexure amount measuring plate 39. Then, a strain gauge 41 was attached to the back surface of the flexure amount measuring plate 39, and the strain gauge 41 was connected to a strain amount measuring device main body (not shown) so that the pressure fluctuation in the mold could be measured by conversion. 42 is a bush.

The vibrating plate portion 22 bends due to the action of the pressure of the molten metal in the mold cavity, and accordingly the rear bending amount measuring plate 39 bends via the bending amount transmitting rod 38, and the bending amount is measured by a strain gauge. Measure at 41. Of course, when the pressure of the molten metal fluctuates, the fluctuation state is sequentially detected. in this case,
Since the flexure amount measuring plate 39 flexes in proportion to the magnitude of the pressure applied to the vibrating plate portion 22, the pressure can be measured even if only a small pressure fluctuation is applied.

[0029]

According to the present invention, a thin plate-shaped vibrating plate portion that vibrates due to pressure fluctuations of the molten metal is provided on the cavity side surface of the casting die. Therefore, when casting is performed using this die, a pulse is generated. When pressure is applied, the diaphragm vibrates, so
Microvibration can be amplified even in the portion where only a slight pressure fluctuation propagates, and as a result, the solidification morphology of the molten metal occurs not only on the surface of the molten metal facing the cavity surface of the mold, but also on the inside of the molten metal. Solidification progresses, resulting in a massy-type solidification morphology in which a fine equiaxed crystal structure is generated throughout, with almost no hot cracking or segregation, resulting in a high-quality cast product with high strength and toughness.

Although the pressure fluctuation is sufficiently propagated immediately after the molten metal is filled, the damping rate of the pressure fluctuation increases as the solidification progresses, and the sufficient pressure fluctuation does not propagate. Even if the pressure is high, the diaphragm has a strength that does not break and vibrates so that the pulse pressurizing effect can be sufficiently amplified even when the pressure is attenuated. If it is incorporated in the mold, the effect of pulse pressurization is fully expressed even when solidification progresses, and good casting results can be obtained reliably and easily.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment of the present invention, and
FIG. 4 is an enlarged cross-sectional view of a portion A of FIGS. 2 and 3.

FIG. 2 is a vertical sectional view showing a first embodiment of the present invention, showing a state during pouring.

FIG. 3 is a longitudinal sectional view showing a state of the apparatus shown in FIG. 2 at the time of pressurization and a first embodiment of a pressurizing force supply device section.

FIG. 4 is a time-hydraulic oil pressure and stroke diagram showing an embodiment in the case of applying a pressure force in a pulsed manner in the present invention.

FIG. 5 is a vertical cross-sectional view showing a second embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Female mold 2, 6 Cavity 3 Male mold 10 Pouring device 12 Actuator 13 Molten metal 14 Pressurization force supply device 15 Supply pressure setting fluctuation device 16 Pressurization pressure fluctuation instruction device 18 Extrusion pin 22 Vibration plate part 23, 24 Thin plate part 25 Block 27 Notch 28 Ring-shaped part 32 Fixed mold 33 Movable mold 34 Cavity 37 Casting cylinder 38 Bending amount transmitting rod 39 Bending amount measuring plate 40 Holding member 41 Strain gauge

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[Procedure amendment]

[Submission date] June 10, 1993

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Claims (1)

[Claims] 1. A casting mold in which a thin plate-shaped vibrating plate portion vibrating due to pressure fluctuations of the molten metal is provided on the surface of the casting mold on the side of the cavity.