JPH09164465A - Method and device for vertical die cast - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast product of excellent quality by winding an electromagnetic coil around the outer circumference of a vertical cast-in sleeve, and performing the casting after a solidified layer to be formed in the vicinity of an inner wall of the sleeve is melted to prevent generation of the solidified layer formed on the inner wall of the sleeve. SOLUTION: When the molten metal 6 is poured in a sleeve 1, and the AC current of appropriate frequency is applied to an electromagnetic coil 8, the induction current is generated in the molten metal 6 in the sleeve 1 to heat the molten metal 6. Because the induction current flows in the molten metal 6 in the vicinity of the inner wall part of the sleeve 1, only the molten metal 6 in the vicinity of the inner wall part of the sleeve 1 is heated, and the temperature of only the molten metal 6 in the vicinity thereof rises. Because no chill layer is present in the sleeve, no chill layer is mixed in the cast, and an excellent cast product can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a vertical die casting method and apparatus which attaches importance to heat retention of a casting sleeve (hereinafter also simply referred to as a sleeve) of a vertical die casting machine. The purpose of semi-solid billet casting is to perform casting with a lean pouring force and to eliminate casting defects due to the inclusion of the chill layer on the outer periphery of the molten metal in the sleeve.

[0002]

2. Description of the Related Art Conventionally, a sleeve has a release agent attached thereto.
Cooling was performed from the outer periphery to optimize the gap between the plunger tip. Therefore, the outer periphery of the molten metal in the sleeve is cooled and a solidification layer is generated. When performing the casting operation, an extra casting force is required to crush the cylindrical solidification layer, and due to the inclusion of the solidification chill layer. There were defects, and the temperature of the molten metal was raised more than necessary to prevent the formation of a solidified layer, a large amount of heat was consumed, and the oxidation of the molten metal was severe, causing defects.

On the other hand, in order to reduce the crystal size of the cast product and to improve the physical properties, casting using a semi-solid billet has been carried out. Solidification progresses rapidly, making casting difficult.

Incidentally, the solidification start temperature of the molten alloy made of an aluminum alloy is approximately 620 ° C. and the solidification end temperature is around 570 ° C., although it varies depending on the composition of the alloy. Further, in the case of a semi-molten metal also called thixo, it is cast aiming at, for example, about 590 ° C. However, since the temperature of the sleeve is generally 300 ° C. or lower, the surface temperature of the molten metal immediately drops to 570 ° C. or lower, though it depends on the difference in heat capacity of the molten metal due to the difference in diameter of the sleeve.

On the other hand, a method is known in which a heater is attached to the outer peripheral surface of the sleeve to heat the molten metal in the sleeve so that the temperature of the molten metal in the sleeve does not drop too much.

[0006]

[Problems to be solved] As can be seen from the above,
In the case of squeeze casting and semi-solid billet casting, it is important to maintain the molten metal in the sleeve or the outer circumference of the semi-solid billet at a high temperature. Particularly, in the case of semi-solid billet casting, the temperature range of the billet that is good for casting is narrow, and heat retention is insufficient for the outer circumference, and rather heating is required. The same applies to magnesium casting.

However, if the temperature of the sleeve itself is made higher than that of the molten metal, the inner diameter of the sleeve becomes large due to thermal expansion, the gap between the sleeve and the plunger tip becomes large, and there is a high possibility that the molten metal will pour in or spout. Driving becomes difficult. Therefore, it is necessary to heat the outer circumference of the molten metal in the sleeve without raising the temperature of the sleeve itself.

On the other hand, in the conventionally known method in which the heater is heated from the outer circumference of the sleeve, not only the temperature of the sleeve itself is increased but also the entire molten metal in the sleeve is heated, and the molten metal temperature becomes too high accordingly. There are drawbacks.

[0009]

In the present invention, in order to solve such a problem, an electromagnetic coil is wound around the outer circumference of a sleeve, and an alternating current having an appropriate frequency is passed through the electromagnetic coil to flow molten metal or a semi-solid billet in the sleeve. Heat is generated by flowing an induction current to the outer peripheral portion of the, and the outer peripheral portion is prevented from cooling. Since the heat generation range differs depending on the sleeve diameter, molten metal or semi-solid billet conditions, select an AC current with a frequency that can be heated according to the target range.

Further, in order to make the electromagnetic induction effective, it is preferable to use ceramic as the material of the sleeve. If the sleeve is made of ceramic, it cannot be cooled by providing a water passage in it, and only heat is released. On the other hand, in consideration of the case where the sleeve needs to be cooled, the section of the electromagnetic coil spirally wound in the axial direction on the outer periphery of the vertical casting sleeve is made into a square tube shape, and the inside of the electromagnetic coil is The structure is such that cooling water can flow.

Further, in order to eliminate the harmful effects of heat conduction as much as possible and to make the heating action of the molten metal near the inner wall of the sleeve by electromagnetic induction more effective, the outer peripheral surface of the casting sleeve and the inside of the electromagnetic coil spirally wound. A heat resistant member is provided between the peripheral surface and
An interlayer insulating plate is provided between the upper and lower cross-sections of the electromagnetic coil, or a gap is created between the outer peripheral surface of the casting sleeve and the inner peripheral surface of the heat-resistant member provided on the outer peripheral surface of the casting sleeve depending on the heating state of the casting sleeve. The outer diameter of the casting sleeve and the inner diameter of the heat-resistant member were set so that the gaps could be generated and the gaps could be eliminated.

[0012]

When the molten metal is poured into the sleeve, since the inner surface of the sleeve is cold, the outer periphery of the molten metal in contact with the sleeve wall surface is cooled and solidification starts. Especially, the semi-solidified billet whose solidification in the outer circumference has already progressed, the magnesium whose solidification heat is about half that of aluminum, solidifies rapidly in the outer circumference and forms a solid cylindrical solidification layer, and when the plunger tip advances, It becomes a great resistance.

However, at this time, when an electric current is passed through the electromagnetic coil wound around the outer circumference of the sleeve, the induced current flows to the molten metal in the sleeve or the outer peripheral portion of the semi-solidified billet to generate heat and melt the solidified layer. ， Reduce the temperature difference between the metal inside and outside the sleeve. Therefore, when the plunger tip is advanced for casting, the resistance due to the solidified layer is reduced, the plunger pressure is effectively transmitted into the mold, and there is no chill layer generated on the inner wall of the sleeve. Casting defects due to the inclusion of a chill layer in the existing products can be eliminated, and good cast products can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an apparatus for carrying out the present invention, showing a sleeve portion of a vertical die casting machine. 1 is a vertical sleeve, 2 is a lower mold which is a fixed mold, 3 is an upper mold which is a movable mold, 13 is a mold cavity, 14 is a gate of the mold, 1
5 is a casting hole having the same diameter as the inner diameter of the sleeve 1, 4 is a plunger tip slidably provided in the sleeve 1, 5 is a plunger, 6 is molten metal, 16 is docking of the sleeve 1 and the lower mold 2. The surface. An induction current generator 7 for heating the molten metal is arranged on the outer circumference of the sleeve 1 over substantially the entire length thereof. The main part of the induced current generator 7 is, for example, an electromagnetic coil 8 formed by spirally winding a rectangular tube having a rectangular cross section.
It consisted of. Reference numeral 17 is a power source for generating an induced current.

When the molten metal 6 is poured into the sleeve 1 and an alternating current of an appropriate frequency is passed through the electromagnetic coil 8, the sleeve 1
An induced current is generated in the molten metal 6 inside and the molten metal 6 is heated. That is, when an alternating current having an appropriate frequency is applied to the electromagnetic coil 8, an induction current 18 as indicated by a two-dot chain line is generated around the electromagnetic coil 8 as schematically shown in FIG.
The molten metal 6 generates heat as shown by the heat generation state line 19. In this case, since the induced current 18 flows in the molten metal 6 near the inner wall of the sleeve 1, only the molten metal 6 near the inner wall of the sleeve 1 is heated, so that only the temperature of the molten metal 6 in the vicinity increases.

In this case, type of sleeve 1, sleeve 1
Since the thickness of the solidified layer generated around the outer periphery of the molten metal 6 differs depending on the state of the molten metal 6 poured into, the current power source having a frequency that meets the conditions is designed and installed. As a result, it is possible to prevent the formation of a hard solidified layer cylinder and facilitate casting. The current is passed through the electromagnetic coil 8
It is only necessary that the molten metal 6 is contained in the sleeve 1, and it is not necessary to heat it for the other time, and the temperature of the sleeve 1 does not rise.

In order to generate heat when an electric current is passed through the electromagnetic coil 8, the electromagnetic coil 8 is generally made of a rectangular tube, and cooling water is passed through a passage 9 inside the rectangular coil to cool it. Reference numeral 20 is a cooling water inlet, and 21 is a cooling water outlet. Reference numeral 10 is an interlayer insulating plate provided between the upper and lower cross-sections of the electromagnetic coil 8, 11 is a heat insulating cement, 12 is a heat-resistant plate, 17 is a power source for generating an induced current, and these form the induced current generator 7. . The heat insulating cement 11 and the heat resistant plate 12 constitute a heat resistant member provided between the outer peripheral surface of the sleeve 1 and the inner peripheral surface of the electromagnetic coil 8.

The sleeve 1 is heated by the molten metal 6 and its temperature rises. When the temperature rises, the sleeve 1 expands to have a slightly larger diameter and comes into contact with the heat-resistant plate 12 of the induced current generator 7. Therefore, the heat from the sleeve 1 is transmitted to the cooling water in the passage 9 through the heat resistant plate 12, the heat insulating cement 11 and the electromagnetic coil 8. Therefore, heat-insulating cement 1
The thickness of 1, the passage 9 in the electromagnetic coil 8, and the amount of cooling water are designed in consideration of this point as well. When strong cooling is required, a plurality of cooling water inlets and outlets may be provided in the middle of the electromagnetic coil 8 to allow a large amount of cooling water of low temperature to flow.

FIG. 3 shows the plunger tip 4 and the plunger 5.
Shows the state in which the molten metal 6 has been advanced to fill the mold cavity 13 and the casting has been completed. Generally, the casting pressure increases as the flow resistance in the mold increases immediately before the completion of filling. Therefore, if a cylindrical hole 15 having the same diameter as the sleeve diameter of an appropriate length is provided at the entrance of the gate 14 of the mold, the pressure rises only in this range during casting, and the melt 6 Is present, and when the molten metal passes through the docking surface 16 of the sleeve 1 and the lower mold 2, the pressure of the molten metal 6 is low, and it is not necessary to increase the circumferential strength of the sleeve 1 too much. Since the docking force of the sleeve 1 is small, it is not necessary to increase the axial strength of the sleeve 1 too much. Therefore, it is possible to use a ceramic having good insulating properties for the sleeve 1.

[0020]

In one embodiment of the present invention, the cooling rate of the surface of the molten metal differs depending on the size of the sleeve 1, the state of the molten metal 6, the temperature of the sleeve 1, etc. Therefore, according to these conditions, the inner wall of the sleeve 1 In order to heat the molten metal 6 near the portion, the frequency of the alternating current is set to 800 to 4000 hertz, preferably 1000 to 3000 hertz, and the electric power is set to 30 to
It was set to about 200 kW. In this way, the inside of the molten metal about 1 to 3 mm from the surface in contact with the inner wall of the sleeve 1 was used as the heat generating portion.

[0021]

As described above, according to the present invention, as set forth in the claims, a solidified solidified layer is not formed on the outer periphery of the molten metal in the casting sleeve, and the plunger for casting is formed. Is effectively used for filling the molten metal in the mold without reducing the force in the sleeve, and because there is no chill layer in the sleeve, there is no chill layer mixing in the cast product, so good casting is possible. You can get the goods.

That is, according to the present invention, a vertical casting sleeve device, in which an electromagnetic coil is spirally wound in the axial direction around the outer periphery of a vertical casting sleeve, is provided, and the electromagnetic coil is used for generating an induced current. When pouring the molten metal into the casting sleeve using a vertical die casting device with a power source connected, an alternating current with a frequency suitable for flowing an induced current to the molten metal near the inner wall of the casting sleeve is applied to the electromagnetic coil. Since it was made to flow, the molten metal near the inner wall of the casting sleeve, which is about to be solidified or semi-solidified by cooling from the wall of the casting sleeve, is reheated to reduce the melting or solidification ratio to reduce the casting resistance. The casting operation can be performed by reducing the size.

Then, the casting sleeve is made of a material, such as ceramic, which is hard to conduct electricity and heat, and only the outer peripheral surface of the molten metal is directly heated without heating the casting sleeve by an induced current to change the diameter of the casting sleeve. It is possible to increase the temperature of only the molten metal by reducing the amount of heat and preventing the gap between the casting sleeve and the plunger tip from increasing. Therefore, the outer peripheral portion of the molten metal in the casting sleeve is not too cold to form a solidified layer, and the temperature of the outer peripheral portion of the molten metal can be maintained at an appropriate temperature. The optimum temperature can be maintained.

Further, since the electromagnetic coil is used, it is sufficient to apply an electric current only while the molten metal is in the casting sleeve, there is no need to heat for the other time, and the temperature of the casting sleeve does not rise. Further, since the temperature of the casting sleeve does not rise and the gap between the casting sleeve and the plunger tip does not become large as described above, the molten metal may be inserted into the gap or the molten metal may be ejected from the gap. Good casting operation is carried out without any need.

Further, the electromagnetic coil spirally wound around the outer periphery of the casting sleeve has a rectangular cross section, a cooling water passage is provided inside the electromagnetic coil, and cooling water is provided at the upper end and the lower end of the electromagnetic coil. Since the entrance and exit of the electromagnetic coil are provided, if current is applied to the electromagnetic coil and heat is generated due to its own resistance and the temperature rises, cooling water is appropriately flowed through the passage in the rectangular cylindrical electromagnetic coil, The temperature rise of the electromagnetic coil can be suppressed.

Since a heat resistant member is provided between the outer peripheral surface of the casting sleeve and the inner peripheral surface of the spirally wound electromagnetic coil, and the interlayer insulating plates are provided between the upper and lower cross-sectional portions of the electromagnetic coil. , It is possible to suppress the unnecessary transfer of heat and current between each position, and this device can work well. Also,
Between the outer peripheral surface of the casting sleeve and the inner peripheral surface of the heat-resistant member provided on the outer peripheral surface of the casting sleeve, a gap may be created or eliminated depending on the heating state of the casting sleeve. Since the outer diameter and the inner diameter of the heat-resistant member are defined, it is okay if the diameter of the casting sleeve changes slightly due to heat. When the temperature of the casting sleeve is relatively low, since the outer peripheral surface of the casting sleeve is separated from the inner peripheral surface of the heat-resistant member on the outer periphery, it is not cooled from the outer periphery and the outer periphery of the casting sleeve is not cooled. If the surface becomes a little larger due to high heat and comes into contact with the inner peripheral surface of the heat-resistant member on the outer circumference, it will be slightly cooled from the outside, and the temperature of the casting sleeve can be maintained at an appropriate temperature accordingly.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a sleeve portion in a state of being docked with a lower mold, showing an embodiment of an apparatus for carrying out the present invention.

FIG. 2 is a diagram showing an example of a state in which an induction current is generated by an electromagnetic coil of the present invention.

FIG. 3 is a vertical cross-sectional view showing a state where the plunger of the embodiment of FIG. 1 has moved forward and molten metal has been filled in the mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sleeve (casting sleeve) 2 Lower mold 3 Upper mold 4 Plunger tip 5 Plunger 6 Molten metal 7 Induction current generator 8 Electromagnetic coil 9 Cooling water passage 10 Interlayer insulating plate 11 Heat insulating cement 12 Heat-resistant plate 13 Mold cavity 17 Power Supply for Generating Induced Current 18 Induced Current 19 Heat Generation State Line 20 Cooling Water Inlet 21 Cooling Water Outlet

Claims (8)

[Claims] 1. When a casting operation is performed using a vertical casting sleeve device in which an electromagnetic coil is spirally wound around the outer periphery of a vertical casting sleeve in the axial direction, molten metal is injected into the casting sleeve. When molten metal is poured into the casting sleeve, an alternating current with a frequency suitable for passing an induction current through the molten metal near the inner wall of the casting sleeve is passed through the electromagnetic coil, so that it is solidified or semi-solidified by cooling from the wall surface of the casting sleeve. A vertical die casting method in which the molten metal near the inner wall of the casting sleeve is reheated so that the melting or solidification ratio is small, and the casting resistance is reduced to perform the casting operation. 2. The frequency of the alternating current flowing through the electromagnetic coil is 8
The vertical die casting method according to claim 1, wherein the vertical die casting method is set to 0 to 4000 Hertz. 3. The vertical die casting method according to claim 1 or 2, wherein a casting sleeve made of a material such as ceramic that does not allow electricity and heat to pass easily is used as the casting sleeve. 4. A vertical casting sleeve device in which an electromagnetic coil is spirally wound around an outer circumference of a vertical casting sleeve in an axial direction, and a vertical casting sleeve device is connected to a power source for generating an induction current. Die casting equipment. 5. The vertical die casting apparatus according to claim 4, wherein the casting sleeve is a casting sleeve made of a material such as ceramics that does not easily conduct electricity and heat. 6. An electromagnetic coil spirally wound around the outer circumference of a casting sleeve has a rectangular cross section, cooling water passages are provided inside the electromagnetic coil, and cooling water is provided at the upper and lower ends of the electromagnetic coil. The vertical die-casting device according to claim 4 or 5, further comprising an entrance and exit. 7. A patent in which a heat-resistant member is provided between an outer peripheral surface of a casting sleeve and an inner peripheral surface of an electromagnetic coil wound in a spiral shape, and an interlayer insulating plate is provided between upper and lower cross-sections of the electromagnetic coil. The vertical die casting device according to claim 4. 8. A gap can be formed or eliminated between the outer peripheral surface of the casting sleeve and the inner peripheral surface of the heat-resistant member provided on the outer peripheral surface of the casting sleeve depending on the heating state of the casting sleeve. The vertical die casting device according to any one of claims 4 to 7, wherein the outer diameter of the casting sleeve and the inner diameter of the heat resistant member are determined.