JPH0342143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for pouring molten metal into a mold for casting molten metal into a cavity of a mold clamped in a die-casting machine.

[Prior art]

Die-casting machines have traditionally been widely used as a molding method for manufacturing precision products in large quantities.
This type of die casting machine casts the molten metal into the cavity at high speed and high pressure, so the gas in the cavity does not escape sufficiently, and this gas mixes with the molten metal and remains in the product, resulting in the formation of cavities. The drawback was that it reduced the quality of the product.

Therefore, various gas exhaust devices and molten metal casting methods that involve gas discharge have been proposed, such as those proposed by the present applicant in Japanese Patent Publication No. 58-46386 and Japanese Patent Publication No. 59-309. There is. However, even if molten metal is cast using such a gas exhaust device, if the cast product has a complicated shape, gas may be drawn into the deep parts and pinholes may be formed. It was not always possible to obtain a fully satisfactory effect. In addition, when a cast product consists of a thick wall part and a thin wall part, early cooling and solidification of the molten metal in the thin wall part prevents the molten metal from flowing to the subsequent parts, and even if the gas is discharged, there will be no shrinkage cavity. It was not possible to prevent the occurrence.

Therefore, the applicant company has recently considered using a copper-based mold to prevent the mold from cooling prematurely. However, copper-based molds have lower strength than iron-based molds, and with conventional casting pressures of 1000 to 1200 kg/cm, for example, the molds are easily damaged and cannot withstand long-term use. .

[Summary of the invention]

The present invention was made in view of the above points, and the surface layer of the copper base metal is made into an oxide layer in which Al ₂ O ₃ particles are dispersed and precipitated on the inner surface of the mold forming the cavity. The inserts for the thin-walled parts of the product and the inserts for the thick-walled parts of the product are provided with heat insulating materials interposed in the dividing surfaces between these inserts, and furthermore, the dividing surfaces between the inserts for the thin-walled parts of the product and the mold body. By providing a passage for a cooling medium and a heat medium that can perform both heating and cooling in the insert for the thin-walled part of the product, and a passage for a cooling medium that performs cooling in the insert for the thick-walled part of the product, Using a copper-based mold whose temperature can be partially controlled, the copper-based mold is clamped and a gas discharge passage communicating above the cavity formed inside the nest is used. Molten metal is poured into the cavity from below the mold while discharging gas to the outside of the mold via the mold gas exhaust device, and after the cavity is filled with the molten metal, the mold gas exhaust device is activated to open the gas exhaust passage. In addition to blocking the molten metal from flowing out of the mold, it is also necessary to prevent the molten metal from entering the mold for the thin-walled parts of the product. By sending a heat medium through the medium passage, the product is kept at a high temperature while being thermally isolated from the insert for the thick part of the product, which is cooled by the cooling medium sent through the cooling medium passage. When the molten metal in the thick part of the product has completely solidified, the insert for the thin part of the product is cooled by the cooling medium sent through the cooling medium passage, thereby eliminating pinholes and shrinkage. The present invention provides a method for pouring molten metal into a mold that makes it possible to obtain a healthy cast product without cavities. Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

FIG. 1 is a vertical cross-sectional view of a horizontal die-clamping, vertical casting die-casting machine shown to explain the method of pouring molten metal into a mold according to the present invention, and FIG.
3 is a longitudinal sectional view of the mold, and FIG. 4 is a front view from B in FIG. 3. In the figure, a die casting machine 1 is equipped with a horizontal mold clamping unit 2 and a vertical casting unit 3, and the horizontal mold clamping unit 2 includes a machine base 4 fixed to the floor,
A fixed platen 5 fixed to one end of the machine base 4 and a fixed platen (not shown) fixed to the other end of the machine base 4 so as to be movably adjustable are provided. Reference numeral 6 denotes a column that connects the four corners of both fixed plates and is fixed with a nut 7, and this column 6 has a movable plate 8 connected to the fixed plate 5.
It is instructed to freely move forward and backward in the near and far directions,
The movable platen 8 and a mold clamping cylinder (not shown) on the fixed platen side are connected by a toggle mechanism 9. 10 is a fixed mold mounted on the fixed platen 5 and whose movement in the vertical direction is regulated by a key 11; 12;
is a movable mold that is mounted on a movable platen 8 and whose movement in the vertical direction is regulated by a key 13, and these molds 10 and 12 are fitted so that they can be opened and closed horizontally with a dividing surface 14 as a boundary. are combined. Both molds 10 and 12 have a cavity 15 having the same shape as the cast product, a constriction 16 continuing below the cavity 15, and a large diameter vertical hole 17 opening downward following the constriction 16.
A shell contact surface 1, which is a plane orthogonal to the axis, is provided at the boundary between the constriction part 16 and the vertical hole part 17.
8 is formed. Further, a half-shaped fixing sleeve 19 is fitted into the vertical hole 17 . 20
is a product extrusion device that extrudes a cast product from inside the cavity 15. The molds 10 and 12 are provided with a gas exhaust device, a nest, and the like, the details of which will be explained after the overall outline is explained.

In such a horizontal mold clamping unit 2, by moving a piston rod of a mold clamping cylinder fixed to a fixed platen (not shown) back and forth, the movable platen 8 moves back and forth via a toggle mechanism 9 to clamp both molds 10 and 12. After the mold is opened and the mold is closed, molten metal is poured into the cavity 15 by the vertical casting unit 3.

The frame 21 of the vertical casting unit 3 is erected in a pit 22 provided below the mold clamp and supports the end of the machine base 4.
Inside the pit 1, a cast frame 24 connected to the lower column 6 by four support rods 23 is provided close to the bottom surface of the pit 22. A casting cylinder 25 is rotatably supported on the casting frame 24, and a plunger 27 is connected to the piston rod 26 via a coupling 28. The plunger 27 is moved by the hydraulic pressure of the casting cylinder 25. It is configured to go up and down. 29
is a block supported by fitting a pair of rams 30 implanted into the upper end surface of the casting cylinder 25 into ram holes, and the hole at the lower end is engaged with the piston rod 26, and this block The block 29 is moved up and down by pressure oil introduced into a cylinder 31 provided at the block 29 and by the lowering of the piston rod 26. A casting sleeve 32 formed in a cylindrical shape having the same center and the same diameter as the fixed sleeve 19 is fixed to the upper end of the block 29, and is fixed to the casting sleeve 32 by raising the block 29 with the hydraulic pressure of the cylinder. The sleeve 29 is pressed concentrically with the sleeve 29, and when the block 29 is lowered, the sleeves 32 and 19 are separated.

The plunger 27 is for lifting the molten metal injected into the casting sleeve 32 of the vertical casting unit 3, which is tilted by a tilting device to be described later, and casting it into the cavity 15. A plunger tip 33 is integrally formed at the upper end and has a cylindrical shape having the same diameter as the inner diameter of the casting sleeve 32 and slides within the casting sleeve 32 and the fixed sleeve 19.

Reference numeral 34 is a tilting cylinder pivotally supported on the frame 21 side, and the working end of its piston rod is pivotally connected to the casting cylinder 25, and when the block 29 is lowered, both sleeves 19,
By operating the tilting cylinder 34 with 32 spaced apart, the entire vertical casting unit 3 is configured to stand up and tilt between the casting position shown in the figure and the inclined pouring position. ing. Reference numeral 35 designates an adjustable stopper that abuts the injection cylinder 25 to limit its rotation toward the casting position.

Next, details of the fixed mold 10 and the movable mold 12 will be explained based on FIGS. 3 and 4. It should be noted that illustration of the product extrusion device 20 is omitted in FIGS. 3 and 4. In the figure, both molds 10, 12
is equipped with mold bodies 36 and 37 made of iron-based material, and these mold bodies 36 and 37 have a central nest 38 made of copper-based material with excellent thermal conductivity.
and the upper and lower nests 39 are joined at the dividing surface 14 and fitted into each other. The cavities 15 are formed on both sides of the dividing surface 14, which is the joint surface of the nests 38 and 39, and
The part corresponding to the upper and lower nests 39 is the thin part 15a of the product, and the part corresponding to the upper and lower nests 39 is the thick part 15b of the product. In this embodiment, the copper-based material forming the nests 38 and 39 is made of, for example, 0.01 to 5% by weight of Al and the balance is Cu.
Cu powder using Cu-Al solid solution alloy:
Embedded in a mixed powder consisting of Cu ₂ O powder: Al ₂ O ₃ powder = 1:0.8 to 1.2: 0.8 to 1.5, and heated at 800 to 1050°C in a vacuum of 10 ^-1 to 10 ^-20 Torr for 1 to 30 hours. By heating and holding, O ₂ naturally enters the Cu-Al solid solution alloy, and Al ₂ O ₃ particles are finely and uniformly dispersed, and the precipitated internal oxidation layer is transformed into an internal oxidation type copper base formed on the surface of the alloy. Alloy was used. This internally oxidized copper-based alloy has excellent thermal conductivity and has significantly higher high-temperature strength than pure copper, making it extremely suitable as a mold material for castings such as die casting. 40 and 41 are between the nests 38 and 39, the nest 38, and the mold body 3
The insulation material inserted between 6 and 37, 42 is the insert 3
8 is a cooling water passage for the product thin wall portion 15a formed within the insert 39; 43 is the product thick wall portion 1 formed within the insert 39;
5b, and 44 is a heat medium passage for the product thin wall portion 15a formed in the insert 38, which partially controls the temperature conditions in the inserts 38 and 39 made of copper-based material. It is configured so that it can be done.

Next, the gas exhaust device will be explained. An air cylinder 45 having an axis on the same plane as the dividing surface 14 is mounted on the upper end surface of the fixed mold 10.
A cylindrical spool 47 is integrally provided at the lower end of the piston rod 46 which moves up and down with air pressure, and the lower end of the spool 47 is fitted into the spool hole of the fixed mold 10. A valve 48 having a valve head 48a is supported within the spool 47 so as to be able to rise and fall while being biased in the upward direction by a tension spring 49. A locking mechanism 5 consisting of a ball
It is lightly regulated by the engagement between the ball 0 and the stepped portion of the valve 48. On the other hand, a gas exhaust passage 51 is opened at the upper end of the cavity 15 of the nests 38 and 39, and a valve head 48a of a valve 48 is seated at the upper open end. Further, a pair of bypasses 52 are branched from the middle of the gas discharge passage 51, and the upper end opening thereof is communicated with a gas passage 53 provided around the valve head 48a. When the valve 48 rises, the tapered surface of the valve head 48a seats on the valve seat of the spool 47, thereby being closed. Further, a vacuum generator 56 is connected to the open end of the gas passage 53 to the outside of the spool 47 via a conduit 55 equipped with a check valve 54.
It is configured to suck the gas inside and discharge it from the gas passage 53. Note that when the mold is opened, the spool 47 rises while holding the valve 48 as the piston rod 46 rises.

The casting operation of the die casting machine configured as above will be explained. When the fixed mold 10 and the movable mold are mounted on the fixed plate 5 and the movable plate 8, respectively, and the piston rod of the mold clamping cylinder (not shown) is advanced, the movable plate 8, which is in the mold opening position, is moved through the toggle mechanism 9. The mold is moved to the illustrated mold clamping position, and mold clamping is performed. During this mold clamping, the casting cylinder 2
Since the piston rod 26 of No. 5 has been lowered to the illustrated position, and the block 29 has been lowered further than the illustrated position, and both sleeves 19 and 32 are separated, when the piston rod of the tilting cylinder 34 is advanced, The entire vertical casting unit 3 tilts to the right in FIG. After injecting molten metal into the casting sleeve 32, the tilting cylinder 34 is operated again to vertically raise the vertical casting unit 3, and pressure oil is fed into the cylinder 31 of the block 29. , the block 29 is raised and the casting sleeve 32 is concentrically pressed against the lower surface of the fixed sleeve 19.

After this, pressure oil is introduced into the casting cylinder 25 to raise the piston rod 26, and the plunger 27 is raised via the coupling 28 to form the mold 1.
The mold 10,
The molten metal in the casting sleeve 32 is poured into the 12 cavities 15. In this example, the casting pressure and casting speed at this time were 300Kg/cm ² and 30Kg/cm 2 , respectively.
It is set to a low pressure of mm/sec and a low speed. In addition,
According to experiments, good quality cast products were obtained even when the casting pressure was as low as several tens of kg/cm ² , although there were differences depending on the type of cast product. According to the conventional die casting method, a casting pressure of 1000 to 1200 kg/cm ² and a high casting speed of 1 to 5 m/sec were required, but with the method of the present invention, copper-based Due to the synergistic effect of each component, such as the inserts 38 and 39 that can partially control the temperature inside the cavity 15 depending on the material, and the gas exhaust device from inside the cavity 15, the casting weight of several tens to 800 kg/cm ² is achieved. Insertion pressure and 10~
It has become possible to obtain cast products of sufficiently high quality even at a low casting speed of 80 mm/sec. Of course, it is possible to perform casting at high pressure and high speed as in the conventional method, but doing so not only wastes energy but also adversely affects the life of the mold and the allowable stress of various parts, which is not preferable.

Prior to such casting, a portion of the molten metal along the inner wall surface of the casting sleeve 32 begins to solidify, and a thin cylindrical solidified substance, a so-called shell, is generated. Plunger tip 3 maintains its cylindrical state as it rises.
3, the upper end of the shell is pushed up by the shell contact surface 1
8, the plunger tip 33 remains in the vertical hole 17 and does not enter the cavity 15 due to compression between the plunger tip 33 and the shell contact surface.

Prior to casting this molten metal, air is sent to the air cylinder 45 of the gas exhaust device, the piston rod 46 is lowered, and the valve 48 is opened to the gas exhaust passage 51.
The bypass 25 and the gas passage 53 are in communication with each other. Therefore, when the vacuum generator 56 is started at the same time as the molten metal is poured, the gas with a small mass in the cavity 15 is discharged from the cavity 15 through the bypass 52 and the gas passage 53 through the pipe 55 to the outside of the machine. In this case, this device transfers the molten metal to the molds 10 and 12.
It is a vertical casting mold for casting into the cavity 15 from directly below, and is linear from the casting sleeve 32 to the discharge port 55, and the casting direction and the flow direction of the molten metal in the cavity 15 are the same. Since it faces from the bottom to the top, the gas flow and
It is easy to discharge and the molten metal flows smoothly. In addition, for this reason, the casting pressure can also be small. In this way, gas continues to be discharged during pouring of the molten metal.

When the cavity 15 is filled with molten metal and the molten metal reaches the gas discharge path 51, the inertia or pressure caused by the casting of the molten metal overcomes the locking force of the locking mechanism 50, and the restriction is released. 48
rises and the tapered surface of the valve head 48a seats on the valve seat of the spool 47. Therefore, the bypass 52
The open end of is occluded and flows through bypass 52.

On the other hand, when injecting the molten metal into the cavity 15, a heating medium such as hot oil is flowed through the heating medium passage 44 until the solidification of the molten metal in the thick walled portion 15a of the cavity 15 is completed, and the temperature of the thin walled portion 15b is compared. At the same time as the solidification of the molten metal in the thick wall portion 15a is completed, the flow of the heat medium into the heat medium passage 44 is stopped, and instead, the cooling water passage 42 in the thin wall portion 15b is maintained at a high temperature.
The molten metal in the thin wall portion 15b is solidified by feeding cooling water into the thin wall portion 15b. In this device, by using a copper-based material with good thermal conductivity for the nests 38 and 39, heat conduction from the parts corresponding to the thick parts 15a of the nests 38 and 39 to the parts corresponding to the thin parts 15b is good. 15b can be maintained at a high temperature, the heat control effect by the heat medium and cooling water can be achieved, and the thin wall portion 15b will not solidify prematurely. This effect is further promoted by providing the heat insulating materials 40 and 41. In addition, due to vertical casting, the surface area in which the molten metal comes into contact with air within the casting sleeve 19 is extremely small compared to conventional horizontal injection, which allows the molten metal to rise smoothly during pouring, and at the same time improves the flow of gas. Not only is the entrainment extremely small and the drop in the temperature of the melt is small, but the thin solidified layer of molten metal that forms in the area in contact with the inner surface of the casting sleeve 19 does not enter the cavity 15. A large pressure corresponding to the feeder action is no longer required, and the casting speed is also not so necessary.The casting direction and the flow direction of the molten metal in the cavity 15 are in the same direction, which also makes it possible to cast at a low pressure and at a low speed. It is now possible to nest 3
Even if copper-based material is used for 8, 39, the nest 38, 3
9 will not be damaged by casting pressure.

After pouring the molten metal in this way, wait until the molten metal has solidified and cooled before pouring into the cylinder.
By removing the pressure oil in the casting cylinder 31 and lowering the block 29, the casting sleeve 32 is separated from the fixed sleeve 19, and at the same time, the pressure oil in the casting cylinder 35 is removed and the plunger 37 is lowered. Further, the piston rod 46 of the air cylinder 45 of the gas exhaust device is raised to raise the spool 47, and the valve 48 is lowered by means not shown against the tensile force of the tension spring 49.
The rise of the valve 48 is regulated. Then, by retracting the piston rod of the mold clamping cylinder, the movable platen 8 is moved away from the fixed platen 5 to open the mold, and one cycle is completed by extruding the cast product with the product extrusion device 20. do.

In addition, in this example, an example was shown in which the molten metal casting method according to the present invention is carried out using a die casting machine of horizontal mold clamping and vertical casting type, but the mold is clamped vertically and the molten metal is poured from below. It may be carried out using a die-casting machine with a vertical clamping type or a vertical casting type. Also,
The gas evacuation method is not limited to the method shown in the embodiments, and any type of method may be used, such as a degassing method using a reduced pressure method, for example.

〔Effect of the invention〕

As explained above, according to the method for pouring molten metal into a mold according to the present invention, Al ₂ O ₃ particles are dispersed in the surface phase of the copper-based alloy on the inner surface of the mold forming the cavity.
The precipitated oxide layer is used to insulate the inserts for the thin-walled parts of the product and the inserts for the thick-walled parts of the product, on the dividing surface between these inserts, and also on the dividing surface between the insert for the thin-walled parts of the product and the mold body. A cooling medium that performs both heating and cooling in the insert for the thin wall part of the product and a passage for the heat medium in the insert for the thick wall part of the product. By using a copper mold that can partially control the temperature by providing a passageway, the copper mold is clamped and the cavity formed in the nest is communicated with the upper part of the mold. Molten metal is poured into the cavity from the bottom of the mold while discharging gas to the outside of the mold via the mold gas exhaust device from the gas exhaust passageway, and after the cavity is filled with the molten metal, the mold gas exhaust device is used to block the gas exhaust passage and prevent the molten metal from flowing out of the mold.
From the time molten metal is poured into the cavity to the time when the molten metal solidifies in the thick part of the product, the insert for the thin wall part of the product is connected to the coolant passage by feeding the heat medium through the heat medium passage. It is thermally isolated from the insert for the thick part of the product, which is cooled by a cooling medium sent through the product, and maintained at a high temperature.When the molten metal in the thick part of the product has completed solidification, Since the insert for the thin part of the product is configured to be cooled by the cooling medium sent through the cooling medium passage, the insert that forms the cavity has excellent thermal conductivity on the inner surface of the copper mold. The mold temperature can be easily and partially controlled depending on the product shape, etc., and the oxidation layer on the surface of the insert makes it possible to forcibly obtain a satisfactory result. Because the gas has good fluidity, even products with complex shapes or differences in wall thickness can be processed by partially controlling the temperature of the insert in the desired state.
There are no pinholes caused by gas entrainment or shrinkage cavities caused by early solidification of the molten metal, which greatly improves the quality of the product, and the increased degassing makes it possible to inject the molten metal at low pressure and low speed.
It has various excellent effects such as not causing problems such as damage to the copper mold.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of a vertical injection type die casting machine with horizontal mold clamping shown to explain the method of pouring molten metal into a mold according to the present invention, and Fig. 2 is a longitudinal sectional view of a vertical injection die casting machine shown in Fig. 1.
3 is a longitudinal sectional view of the mold, and FIG. 4 is a front view from B in FIG. 3. 1...Die casting machine, 2...Horizontal clamping unit, 3...Vertical casting unit, 10...Fixed mold,
12...Movable mold, 15...Cavity, 15a
...Thick wall part, 15b... Thin wall part, 25... Casting cylinder, 32... Casting sleeve, 36, 37...
Mold body, 38, 39... nest, 45... air cylinder, 46... piston rod, 47... spool, 48... valve, 48a... valve head, 51...
Gas exhaust path, 52...bypass, 53...gas passage, 56...vacuum generator.

Claims (1)

[Claims] 1. On the inner surface of the mold forming the cavity, inserts for thin-walled parts of the product and for thick-walled parts of the product, in which the surface layer of the copper base metal is an oxidized layer in which Al ₂ O ₃ particles are dispersed and precipitated, are installed. A heat insulating material is inserted between the inserts and the dividing surface between the insert for the thin part of the product and the mold body, and a heating and cooling material is installed inside the insert for the thin part of the product. A copper-based copper-based product that can partially control the temperature by providing a cooling medium passage and a heat medium passage that performs both of these functions inside the insert for the thick wall part of the product. Using a mold, this copper mold is clamped, and gas is discharged to the outside of the mold through a mold gas exhaust device from a gas exhaust passage communicating above a cavity formed inside the insert. Molten metal is poured into the cavity from below the mold while being discharged, and after the cavity is filled with the molten metal, the mold gas discharge device is activated to block the gas discharge passage, and the insert for the thin part of the product is After the molten metal is poured into the cavity until the molten metal solidifies in the thick wall part of the product, the heat medium is fed through the heat medium passage, and the heat medium is fed through the cooling medium passage. The insert for the thick wall part of the product is thermally isolated from the insert for the thick wall part of the product, which is cooled by a cooling medium, and kept at a high temperature.When the molten metal in the thick wall part of the product has completed solidification, A method for casting molten metal into a mold, characterized in that the insert is cooled by a cooling medium sent through a cooling medium passage.