JPH0372379B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing aluminum casting.

[Prior art]

Generally, castings with undercuts or cavities are manufactured using a gravity casting machine, which is a relatively low-pressure casting machine, or a low-pressure casting machine, using a sand core made of molding sand hardened with phenolic resin, etc. ing.
However, low pressure casting machines have long cycles,
However, in recent years, castings using collapsible cores using high-pressure casting machines that can produce stable quality at high cycles have been introduced. production is awaited. There are two types of high-pressure casting machines: horizontal casting and vertical casting, depending on the casting direction.
A horizontal die casting machine is known as a horizontal die casting machine, and a vertical die casting machine is classified into vertical mold clamping and horizontal mold clamping depending on the difference in mold clamping.

In particular, vertical casting type high-pressure casting machines have a small contact area with the metal poured into the casting sleeve, so the temperature drop of the molten metal is small, and there is little entrainment of gas in the casting sleeve. This is a casting machine with many excellent features.

[Problem that the invention seeks to solve]

By the way, high-quality castings mean that there are no blowholes caused by gas entrainment inside the casting, or shrinkage cavities that occur during solidification and shrinkage, and that there are no collapses that form undercuts or hollow parts of the casting. No sand remains on the surface of the casting when the core is removed. Various attempts have been made to cast products using collapsible cores using high-pressure casting machines.
In particular, the method for producing castings using a collapsible core using a vertical casting machine invented by the applicant is as follows:
By reducing gas entrainment into the molten metal within the cavity, this casting method has been shown to be effective in reducing the number of cavities such as blowholes and linkages.

If the wall thickness of the casting is sufficiently thick and the hot water circulates even if the casting speed is slow, there will be less gas entrained in the casting sleeve of the vertical casting type, resulting in high-quality casting without cavities. However, if the wall thickness is so thin that the casting speed must be increased to allow the molten metal to circulate, gas will be drawn into the cavity, making it impossible to obtain a casting without cavities.

Furthermore, if gas does not escape completely and collects in a specific area within the cavity, it will be compressed adiabatically and the temperature of the surrounding area will rise.Especially when using a sand core, organic matter may be used as a binder for the sand. Due to high temperatures during use, it decomposes and the core collapses during molding of cast products. Even if it does not lead to collapse, it may cause the molten metal to be inserted into the sand core.

[Means and actions for solving problems]

As a result of repeated experiments, we found that for castings using collapsible cores that are thin to a certain extent, that is, those that have poor circulation unless cast at high speed, sufficient gas entrainment and discharge should be taken. It has been found that if this is done, there is no need to insert molten metal into the sand core, and it is possible to obtain a healthy, high-quality casting with no cavities.

〔Example〕

FIG. 1 is a longitudinal cross-sectional view of a horizontal clamping vertical casting die casting machine shown for explaining a pressure casting method using a collapsible core 2 according to the present invention. The die casting machine is equipped with a horizontal mold clamping unit 22 and a vertical casting unit 23, and the horizontal mold clamping unit 22 includes a machine base 24 fixed to the floor, a fixed platen 25 fixed to one end of the base 2
A stationary platen (not shown) fixed to the other end of 4 so as to be movably adjustable is provided.

There is a column 27 whose four corners of both fixed plates are restrained by nuts 26, and a movable plate 28 is supported on this column 27 so as to be able to move forward and backward in the direction of distance from the fixed plate 25. A toggle mechanism 29 connects the mold closing cylinder on the fixed plate side. A fixed mold 30 mounted on the fixed plate 25 and a movable mold 32 mounted on the movable plate 28 are joined to be horizontally openable and closable with a dividing surface 34 as a boundary. And both molds 30, 32
, a cavity 35 having the same shape as the cast product, a constriction 36 continuing below the cavity 35, and a large diameter vertical hole 37 continuing below and opening downward are divided by a dividing surface 34. Each is provided. or,
A product extrusion device 39 for extruding a cast product from the cavity 35 is installed on the movable mold 32 side. The mold is equipped with a gas exhaust device 100. Further, a collapsible core 2 is attached to the mold, which forms an undercut portion or a hollow portion of the cast product, is inserted into the mold each time the product is cast, and is removed together with the product from the mold.

In such a horizontal mold clamping unit 22, by moving the piston rod of the mold closing cylinder fixed to the stationary platen (not shown) back and forth, the movable platen 28 moves back and forth via the toggle mechanism 29, and both molds 30,
The mold is closed and opened at 32, and after the mold is closed, the molten metal is poured into the cavity 35 by the vertical casting unit 23.

On the other hand, the vertical casting unit 23 includes four tie rods 40 whose upper ends are screwed into screw holes provided in the horizontal member 25b of the stationary platen 25 and hang down. It passes through the gap 24a between the members and is inserted into a bit 41 provided below the floor surface. At the other end of the tie rod 40 is a frame 4 consisting of a pair of support members 42a and connecting members 42b and 42c connecting both ends of the support members 42a.
2 is engaged with the tie rod 40 by a pair of upper and lower nuts 43, 44, and the frame 42 is firmly supported in a horizontal state.

The injection device 45 is supported by the frame 42 so as to be freely tiltable. That is, the injection device 45 includes an injection cylinder 55 that is swingably supported by the frame 42. On both sides of the rod side block 46 of the injection cylinder 55,
A tilting shaft is provided, and by supporting this tilting shaft in the shaft hole of the frame 42, the injection device 4
5 is supported by a frame 42 in a freely tiltable manner. On both sides of the rod side block 46, there are a pair of upright docking rams 52, the main part of which is formed into a round bar shape, into which the cylinder hole of the sleeve frame 53 is slidably fitted. There is. The sleeve frame 53 is integrally formed with a coupling receiving part 53b at the lower end, a cylinder part 53c extending upward from both sides thereof, and a sleeve supporting part 53d connecting the cylinder parts 53c on both sides at the upper end. It is configured to be raised from the illustrated position by introducing hydraulic pressure into it.

The injection cylinder 55 is provided with a piston rod that moves up and down as pressure oil is introduced into the cylinder tube, and this piston rod passes through a rod hole in the frame 46. A cylindrical cast-in sleeve 58 is provided at the upper end of the sleeve frame 53.
A plunger tip, which is the tip of a plunger 59 , is supported and fixed in the casting sleeve 58 , and a plunger tip, which is the tip of a plunger 59 , is pivotally supported so as to be able to move up and down. It is concentrically connected to the piston rod. The outer peripheral surface of the lower end of the coupling ring 60 can come into contact with the inside of the upper surface of the coupling receiving part of the sleeve frame 53 or move away from it. As the sleeve frame 53 rises, the casting sleeve 58 fits into the vertical hole 37 shown in FIG. It is configured to rise along the inner holes of the insertion sleeve 58 and the fixed sleeve 38.

Next, a tilting device for tilting the entire injection device 45 in order to pour molten metal will be described. The rod side block 46 of the injection cylinder 55 and the head cover are vertically connected on one side by a pair of connecting plates 63, and a pair of brackets 64 are fixed to the connecting member 42b of the frame 42. It projects diagonally downward. Inclined cylinder 65
is rotatably supported by a bracket 64 via a bearing 66, and the working end of the piston rod 67 is connected to the connecting plate 63 by a pin 68, and injection is performed by moving the piston rod 67 forward and backward using pressure oil. The entire device 45 is configured to stand upright and tilt between the solid line position and the chain line position in FIG.

Next, the gas exhaust device 100 will be explained.
An air cylinder 145 having an axis on the same plane as the dividing surface 34 is attached to the upper end surface of the fixed mold 30, and a cylindrical spool 147 is integrated at the lower end of a piston rod 146 that moves up and down with the air pressure. The lower end of the fixed mold 30
is fitted into the spool hole. Spool 147
Inside, a valve 148 having a valve head 148a is supported so as to be able to rise and fall while being biased in the upward direction by a tension spring 149. The locking mechanism 150 is lightly regulated by the engagement between the ball of the locking mechanism 150 and the stepped portion of the valve. On the other hand, at the upper end of the cavity 35 of the nest, there is a gas discharge passage 15 provided on the dividing surface 34 of the mold.
1 is open, and a valve 14 is provided at the upper open end.
Eight valve heads 148a are seated. Further, a pair of bypasses 152 are branched from the middle of the gas discharge path 151, and the upper end opening thereof is connected to the valve head 148.
The valve head 148a is connected to a gas passage 153 provided around the spool 14, and this communication portion is connected to the spool 14 when the tapered surface of the valve head 148a rises due to the pressure of the molten metal.
It is configured to be closed by sitting on the valve seat No. 7. Also, a check valve 15 is provided at the open end of the gas passage 153 to the outside of the spool 147.
Vacuum generator 15 via line 155 with 4
6 is connected, and is configured to suck gas in the cavity 35 and discharge it from the gas passage 153. In addition, when the mold is opened, the spool 147 moves to the valve 14 due to the rise of the piston rod 146.
Rise while holding 8.

Next, the collapsible core 2 that constitutes the undercut or cavity of the casting will be described. A sand core was molded using shell molding sand consisting of 100 parts of JIS No. 7 silica sand as an aggregate, 2.0 parts of thermosetting phenolic resin as an organic binder, and 0.1 part of calcium stearate as a lubricant. The molding conditions were a mold temperature of 270°C and a firing time of 20 seconds.
Next, add 300 c.c. of colloidal silica (SiO ₂ 30%) as a binder, 10 g of sodium dodecylbenzenesulfonate as a lubricant, and 1 g of octyl alcohol as an antifoaming agent to the water in step 1, and mix well.
Next, 300 g of zircon flour ground to 300 mesh or less was added to this solution, and the mixture was thoroughly mixed and stirred to prepare a slurry solution. Then, after immersing the shell core in this slurry liquid for 1 minute to close the gaps on the surface of the sand core, immediately
The surface was cured by drying in a hot air dryer at ℃ for 30 minutes.

In addition, a 3% aqueous solution of water-soluble phenolic resin 1
500g of mica crushed to less than 300mesh inside, sodium dodecylbenzenesulfonate as lubricant
A slurry solution was prepared by adding 10 g of sand core and 1 g of octyl alcohol as an antifoaming agent and stirring well. This was again applied to the surface of the sand core with a brush and dried for 1 hour in a dryer at 120°C. In this manner, the coating agent made of the slurry solution described above is applied twice to the surface of the sand core, and the resulting core is set in the fixed mold 32.

The operation of the die casting machine configured as above will be explained.

Sleeve frame 53 and plunger 59
When the piston rod 67 is moved downward as shown in the figure and the injection device 45 is upright, pressure oil is introduced to the rod end side of the tilting cylinder 65 to move the piston rod 67 backward, and the entire injection device 45 moves along the tilting shaft. Center it and tilt it to the chain line position. Therefore, after pouring molten metal into the casting sleeve 58 using a ladle of a water heater (not shown), pressure oil is introduced into the head end side of the tilting cylinder 65 to rotate the injection device 45, so that the injection device 45 is in an upright position. Stop at.

Prior to this, on the one hand, the movable platen 28 is connected to the movable platen 28 via the toggle mechanism 29 by a mold-closing cylinder (not shown).
is moving forward, and the closing of both molds 30 and 32 is completed.

By simultaneously supplying oil to the cylinder hole in the sleeve frame 53 and the injection cylinder 55 in this state, the sleeve frame 53 leaves the dotting drum 52 in the molten metal holding state with the plunger 59 lowered within the casting sleeve 58. The casting sleeve 58 engages into the vertical hole 37 and is pressed against the lower end surface of the fixed sleeve 38. Then, when oil is further supplied to the injection cylinder 55, the plunger 59 rises, and the molten metal is injected into the cavity 35 through the sleeves 38, 58 and the runner gate 36. In this case, the casting pressure is several 100 kg/cm ²
The pressure was set to .

Prior to injection of this molten metal, the gas exhaust device 100
Air is being sent to the air cylinder 145, the piston rod 146 is lowered, and the valve 148 is seated at the open end of the gas discharge passage 151 to close it off, and the bypass 152 and the gas passage 1
53 are in communication. Therefore, when the vacuum generator 156 is started with the casting of the molten metal, the gas with a small mass in the cavity 35 is discharged from the cavity 35 through the bypass 152 and the gas passage 153 to the outside of the machine through the conduit 155. In this case, this device is a vertical casting mold for casting the molten metal into the cavity 35 from directly below the molds 30 and 32, and has a straight line from the casting sleeve 58 to the discharge passage 151, and has a straight line between the casting direction and the cavity. The flow direction of the molten metal in the 35 is the same, from bottom to top, so gas flow and discharge is easier compared to horizontal casting molds, and the molten metal flows smoothly. It will be done. For this reason, the casting pressure during the casting process can also be relatively small. In this way, gas continues to be discharged during pouring of the molten metal.

When the cavity 35 is filled with molten metal and the molten metal reaches the gas discharge part 151, the inertia or pressure caused by the casting of the molten metal is applied to the locking mechanism 150.
The valve 14 is released by overcoming the locking force caused by the valve 14.
8 rises, and the tapered surface of the valve head 148a seats on the valve seat of the spool 147. The open end of bypass 152 is thus closed and flow is allowed to flow through bypass 152. At this time, cavity 3
The molten metal in 5 and the collapsible core 2 contain several 100 kg/cm ²
high pressure is acting.

After the injection is completed and the molten metal is solidified and cooled, the pressure oil is removed from the cylinder hole in the sleeve frame 53 and is sent to the rod end side of the injection cylinder 55 to connect the sleeve frame 53 and the plunger 59.
are lowered together, and the casting sleeve 58 is separated from the fixed sleeve 38 at the lower part of the mold. Also,
The piston rod 146 of the air cylinder 145 of the gas exhaust device 100 is raised to release the spool 147.
is raised, and the valve is lowered by means not shown against the tension of the tension spring,
The locking mechanism 160 restricts the valve 148 from rising.

Then, a mold closing cylinder (not shown) is operated to open the mold, and the product is taken out from the mold using the product extrusion device 39, thereby completing one cycle.

In this experiment, aluminum alloy ADC1
2 was die-cast under the conditions of a molten metal holding temperature of 680°C and a metal pressure of 400 kg/cm ² .

After casting, when the sprue was cut and sand was removed from the sand core using sandplast, an insertion layer formed by the aluminum and sand particles mixed between the sand particles was generated, and a layer of sand was formed due to the high casting pressure. There was no damage to the core, it disintegrated easily, and the sand core could be completely removed. Furthermore, no shrinkage cavities were observed in the thick walled parts of the molded product, and no blowholes, which are defects caused by gas entrainment, were observed.

In this example, an example was shown in which the pressure casting method according to the present invention was carried out using a horizontal mold clamping, vertical casting type die casting machine, but the mold was closed vertically and the molten metal was poured from below. It may be carried out using a die-casting machine of a vertical mold clamping type or a vertical casting type.

〔Effect of the invention〕

As is clear from the above explanation, a collapsible core with a coating agent applied to the surface is used to create an undercut or hollow part of several 100 kg/cm ² .
When performing pressure casting at high pressures, a gas exhaust device exhausts the gas inside the mold through a gas exhaust passage that is provided on the dividing surface of the mold and directly communicates with the cavity of the mold. When pouring molten metal and sending molten metal into the cavity using a casting type pressure casting machine,
By casting in a manner that prevents gas from getting involved in the molten metal, it is possible to obtain molded products of very high quality without defects such as blowholes or shrinkage cavities.

In addition, when performing high-pressure casting of several 100 kg/cm ² using a core, the surface of the core must be It is necessary to apply a coating agent to the
Even in that case, in the present invention, the gas in the mold cavity is passed through the mold gas exhaust device from the gas exhaust passage that is provided on the dividing surface of the mold and directly communicates with the mold cavity. Since the molten metal is poured while being discharged directly to the outside, the gas in the mold cavity can be sufficiently discharged to the outside of the mold, and of course it is possible to cast without any gas inside the mold cavity. It is possible to easily obtain a high-quality cast product without cavities.

Furthermore, since the gas is sufficiently exhausted, no gas remains in the cavity. As a result, adiabatic compression does not occur and high-temperature areas are not generated, organic substances such as binders in the core decompose, and the core collapses during molding of cast products, or molten metal leaks into the core. There is no insertion, and a high-quality cast product in a desired shape can always be easily and reliably obtained.

[Brief explanation of drawings]

Fig. 1 is a partially sectional front view of the present invention;
The figure is a sectional view taken along the line -- in FIG. 1, and FIG. 3 is a partially enlarged view of the portion shown in FIG. 2...Collapsible core, 22...Horizontal clamping unit, 2
3... Vertical casting unit, 30... Fixed mold, 32... Movable mold, 35... Mold cavity, 38... Fixed sleeve, 45... Injection device, 55... Injection cylinder,
58...Casting sleeve, 65...Tilt cylinder, 1
00...Gas exhaust device, 145...Air cylinder,
147...Spool, 148...Valve, 151...Gas exhaust path, 152...Bypass, 156...Vacuum generator.

Claims (1)

[Claims] 1. When pressure casting castings with undercuts or cavities at high pressures of several 100 kg/cm ² using collapsible cores whose surfaces are coated with a coating agent,
Using a vertical casting type pressure casting machine, gas is supplied to the outside of the mold through a mold gas exhaust device from a gas exhaust passage that is provided on the dividing surface of the mold and communicates directly with the cavity of the mold. A collapsible method in which the molten metal is poured while being directly discharged, or the molten metal is poured while the gas is directly discharged while reducing the pressure to the outside of the mold, and the mold gas discharge passage is shut off after the cavity is filled with the molten metal. Pressure casting method using a core.