JP2013111604A - Casting method and casting die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting method and a casting die that can suppress formation of blowholes with simple and compact facility constitution without affecting the quality of a product.SOLUTION: There is provided a casting die 10 that has a cavity 10a filled with molten metal A for casting. In the casting die, a part forming the cavity 10a is formed of a thin plate part 21, while a deformation part 31 as a thin plate member having a larger coefficient of thermal expansion than the thin plate part 21 is provided on a surface of the thin plate part 21 on the opposite side from the side where the cavity 10a is formed, and a bimetal structure part 10b is formed from the thin plate part 21 and deformation part 31; further a heating means 41 for increasing the volume of the cavity 10a by expanding the deformation part 31 by heating the deformation part 31 before the cavity 10a is filled with the molten metal A is provided and also a cooling means 42 reducing the volume of the cavity 10a by contracting the deformation part 31 by cooling the deformation part 31 when the molten metal A is solidified is provided.

Description

  The present invention relates to a casting method and a casting mold, and specifically to a technique for improving casting quality.

  Conventionally, when a casting mold performs casting, the molten metal solidifies and shrinks, and a nest that is a hollow defect having a rough inner wall may be formed on the surface or inside of the product. The technique about the casting metal mold | die for suppressing generation | occurrence | production of such a nest is known, and the literature which discloses this also exists (for example, refer patent document 1 to patent document 3).

  In Patent Document 1, a pin is slidably disposed in a space communicating with a cavity inside a casting mold, and after the molten metal is filled in the cavity, the pin is projected to press the molten metal in the cavity. A technique for adding a hot water to perform the hot water action is described.

  Patent Document 2 describes a technique for increasing the density by changing the solidification form of the molten metal by adding an appropriate amount of elements such as zirconium and boron to the cast aluminum alloy that is the molten metal.

  Patent Document 3 describes a technique in which after a molten metal is filled in a cavity, a cooling pin is inserted into a casting mold to promote solidification of the molten metal.

Japanese Patent Laid-Open No. 10-146663 JP-A-8-134576 JP 2005-193246 A

  However, according to the configuration in which a device for controlling the pressure and heat in the casting mold is separately provided as in the techniques described in Patent Document 1 and Patent Document 3, the equipment configuration becomes complicated and large, and the cost increases. Connected.

  Further, as in the technique described in Patent Document 1, according to the configuration in which pressure is applied to a place away from the cavity, the effect on the product in the cavity is limited, and thus the generation of nests cannot be suppressed. There is. In addition, since pressure is applied to the molten metal located in a portion other than the cavity, there is a problem that the yield of the product deteriorates because the volume into which the molten metal flows increases.

  Moreover, according to the structure which changes the material component of a molten metal like the technique of the said patent document 2, while adding cost to an element, other characteristics (for example, tensile strength, thermal conductivity, etc.) are added. ) May be affected.

  In view of the above problems, the present invention proposes a casting method and a casting mold that can suppress the formation of nests without affecting the quality of products by a simple and compact equipment configuration. is there.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, in claim 1, a casting method is performed by filling a cavity formed in a casting mold with a molten metal, and at least a part of a portion forming the cavity in the casting mold is a thin plate portion. And a deforming portion that is a thin plate member having a coefficient of thermal expansion larger than that of the thin plate portion is provided on a surface of the thin plate portion opposite to the side on which the cavity is formed, and the thin plate portion and the deforming portion are provided. A bimetal structure is formed, and the deformed portion is expanded by heating the deformed portion to increase the volume of the cavity, and the molten metal is filled in the cavity after the heating step. A cooling step for reducing the volume of the cavity by shrinking the deformed portion by cooling the deformed portion when the molten metal solidifies after the filling step, and It is as it has.

  The solidification shrinkage according to claim 2, wherein in the heating step, the temperature at which the deformed portion is heated is determined by a volume reduction ratio of the cavity due to cooling of the deformed portion in the cooling step and a material characteristic of the molten metal. The rate is controlled to be the same.

  According to a third aspect of the present invention, the cooling of the deformed portion is started when the temperature of the cavity detected in the vicinity of the thin plate portion becomes lower than the solidification temperature of the molten metal.

  In Claim 4, the heat insulation process for delaying cooling of a molten metal is given beforehand to the surface at the side which forms the said cavity of the said thin-plate part.

  In claim 5, a casting mold in which a melt is filled in a cavity and casting is performed, and at least a part of a part forming the cavity in the casting mold is configured by a thin plate part, A deformed portion, which is a thin plate member having a coefficient of thermal expansion larger than that of the thin plate portion, is provided on the surface of the thin plate portion opposite to the side where the cavity is formed, and a bimetal structure is formed by the thin plate portion and the deformed portion. Heating means that expands the deformed portion by heating the deformed portion before the molten metal is filled into the cavity, thereby increasing the volume of the cavity; and the deformed portion when the melt is solidified. And a cooling means for reducing the volume of the cavity by contracting the deformable portion by cooling.

  7. The heating means according to claim 6, wherein the temperature at which the deformed portion is heated is determined by a volume reduction ratio of the cavity by cooling the deformable portion by the cooling means and a material characteristic of the molten metal. The shrinkage rate is controlled to be the same.

  In Claim 7, the temperature detection means exposed to the said cavity is arrange | positioned in the vicinity of the said thin-plate part, The temperature of the said cavity detected by the said temperature detection means became lower than the solidification temperature of the said molten metal. At this point, cooling of the deformed portion by the cooling means is started.

  According to an eighth aspect of the present invention, the surface of the thin plate portion on the side where the cavity is formed is preliminarily subjected to heat insulation processing for delaying the cooling of the molten metal.

  As effects of the present invention, the following effects can be obtained.

  According to the present invention, by forming the casting mold in the casting method with a simple and compact equipment configuration, it is possible to suppress the formation of nests without affecting the quality of the product.

Sectional drawing which showed the state before casting in the casting metal mold | die which concerns on one Embodiment of this invention. Sectional drawing which showed the state at the time of cavity formation similarly in a casting mold. Sectional drawing which similarly showed the state at the time of a heating process in a casting mold. Sectional drawing which similarly showed the state at the time of a filling process in a casting mold. Sectional drawing which similarly showed the state at the time of a cooling process in a casting mold.

  The casting mold and casting method according to the present invention will be described below. In this specification, for the sake of convenience, the right side in FIG. 1 will be described as the right side and the left side as the left side.

[Overall configuration of casting mold 10]
First, the overall configuration of the casting mold 10 will be described with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the casting mold 10 includes a fixed mold 11 and a movable mold 12 configured to be close to and away from the fixed mold 11. When the movable mold 12 approaches the fixed mold 11 in the direction of the arrow A shown in FIG. 1 and abuts as shown in FIG. 2, a cavity 10a is formed between the fixed mold 11 and the movable mold 12. Is done. For the fixed mold 11 and the movable mold 12 in this embodiment, SKD, which is steel for molds, is used as a material.

  As shown in FIGS. 1 and 2, a substantially cylindrical sleeve 17 is attached to the casting mold 10 so as to protrude rightward. Then, the short cylindrical plunger 18 is slid leftward in the sleeve 17 and the molten metal A supplied into the sleeve 17 is extruded from the hot water supply port 17a and filled into the cavity 10a for casting. (See FIGS. 3 and 4).

  The product cast by the casting mold 10 in the present embodiment includes, for example, an engine cylinder block, but the type of product is not limited. Moreover, ADC12 which is a general mass production die-cast material is used for the molten metal A in this embodiment. In the present embodiment, the casting mold 10 includes a decompression device for decompressing the inside of the cavity 10a, an extrusion device for extruding the cast product, and the like, and illustration and detailed description thereof are omitted. .

  The movable mold 12 in the casting mold 10 includes a thin plate portion 21 that is a thin plate-shaped portion at a portion forming the cavity 10a. Specifically, as shown in FIGS. 1 and 2, the end of the movable mold 12 on the fixed mold 11 side (the right end in FIGS. 1 and 2) and the portion forming the cavity 10 a is relative to the fixed mold 11. The thin plate portion 21 is formed with a small thickness in the approaching and separating direction of the movable mold 12.

  In the present embodiment, the cavity forming surface 21a that is the surface (the right side in FIGS. 1 and 2) on which the cavity 10a of the thin plate portion 21 is formed is preliminarily subjected to heat insulation processing for delaying the cooling of the molten metal A. ing. Specifically, a so-called carbon coating is performed in which the cavity forming surface 21a is covered with a nanocarbon carbon film. In addition, the said heat insulation process is not limited to carbon coating, For example, if it is a process which improves the heat insulation of the cavity formation surface 21a like ceramic spraying, it is possible to apply.

  In the present embodiment, the thin plate portion 21 is formed on the movable mold 12, but can also be formed on a portion of the fixed mold 11 where the cavity 10 a is formed. In the present embodiment, the entire portion of the movable mold 12 that forms the cavity 10a is configured as the thin plate portion 21, but only a part of the portion that forms the cavity 10a is configured as the thin plate portion 21. Is also possible.

  Further, a deformed portion 31 that is a thin plate member having a thermal expansion coefficient larger than that of the thin plate portion 21 is provided on the surface of the thin plate portion 21 opposite to the side on which the cavity 10a is formed (left side in FIGS. 1 and 2). Yes. In the present embodiment, duralumin having a higher thermal expansion coefficient than the SKD forming the movable mold 12 is used as the material for the deformable portion 31. Since the deforming portion 31 is heated by the heating means 41 in a heating step described later, an alloy having heat resistance is used as a material.

  As described above, the thin plate portion 21 and the deformed portion 31 having a larger coefficient of thermal expansion than the thin plate portion 21 are disposed adjacent to the left side of the cavity 10a, so that the left side of the cavity 10a is formed as a bimetal structure portion 10b. Will be formed. That is, when the temperature of the bimetal structure portion 10b formed by the thin plate portion 21 and the deformation portion 31 rises, the expansion amount of the deformation portion 31 becomes larger than the expansion amount of the thin plate portion 21, so that the bimetal structure as shown in FIG. The part 10b swells and deforms toward the deformation part 31 side. In other words, the deformable portion 31 is fixed to the movable mold 12 at opposite ends (upper and lower ends in this embodiment).

The casting mold 10 is provided with heating means 41 and cooling means 42.
The heating means 41 is composed of a heater or a burner, and is configured to be able to heat the deformable portion 31 before the molten metal A is filled in the cavity 10a. That is, the heating means 41 heats and expands the deformable portion 31 to expand and deform the bimetal structure portion 10b toward the deformable portion 31, thereby increasing the volume of the cavity 10a.

  The cooling means 42 is configured to discharge a cooling medium such as water, and is configured to be able to cool the deformable portion 31 when the molten metal A solidifies. That is, the cooling means 42 cools and contracts the deformable portion 31 and deforms the bimetal structure portion 10b swelled toward the deformable portion 31 to the original state, thereby reducing the cavity 10a to the original volume. .

  The heating means 41 and the cooling means 42 are respectively disposed in driving means (not shown), and their positions can be changed as appropriate. That is, when the deformation unit 31 is heated by the heating unit 41, the heating unit 41 moves to a position facing the deformation unit 31 as shown in FIG. 3, and when the deformation unit 31 is cooled by the cooling unit 42, As shown in FIG. 5, the cooling means 42 moves to a position facing the deforming portion 31.

  The heating unit 41 and the cooling unit 42 are electrically connected to the control device 40. The control device 40 includes an input function, a display function, a storage function, a communication function, various arithmetic functions, and the like, and is configured mainly with a microcomputer such as a CPU, a RAM, a ROM, and an interface. Then, based on a command from the control device 40, the heating means 41 and the cooling means 42 are driven and the deformation portion 31 is heated and cooled.

  Furthermore, in the casting mold 10 according to the present embodiment, a temperature sensor 23 that is a temperature detecting means that is exposed to the cavity 10 a is disposed in the vicinity of the thin plate portion 21. The temperature sensor 23 is configured to measure the temperature of the molten metal A filled in the cavity 10a as shown in FIG. The temperature sensor 23 is electrically connected to the control device 40, and is configured so that the control device 40 can receive molten metal temperature information measured by the temperature sensor 23.

[Casting method]
Next, a casting method using the casting mold 10 will be described with reference to FIGS.
After the movable mold 12 approaches and contacts the fixed mold 11 as shown by an arrow A in FIG. 1 and the cavity 10a is formed as shown in FIG. 2, the heating means 41 is deformed as shown in FIG. The deformable portion 31 is expanded by heating 31 to increase the volume of the cavity 10a (heating step). Further, during the heating step, as shown in FIG. 3, the molten metal A is supplied into the sleeve 17 from the hot water supply port 17a.

  In the heating step, the temperature of the bimetal structure portion 10 b is raised so that the expansion amount of the deformable portion 31 is larger than the expansion amount of the thin plate portion 21. Then, as shown in FIG. 3, the bimetal structure portion 10b is inflated toward the deformation portion 31 and deformed. At this time, the increased volume of the cavity 10a is set to the volume V1 (see FIG. 3) with respect to the volume V0 (see FIG. 2) of the original cavity 10a.

  In the present embodiment, the heating means 41 sets the temperature at which the deformed portion 31 is heated to the solidification shrinkage determined by the volume reduction rate of the cavity 10a due to the cooling of the deformed portion 31 in the cooling step described later and the material characteristics of the molten metal A. The rate is controlled to be the same.

  After that, the cavity 10a is decompressed by a decompression device (not shown), and then the short cylindrical plunger 18 is slid leftward in the sleeve 17 as shown in FIG. Then, the cavity 10a is filled (filling step). At this time, the molten metal A is filled in the cavity 10a which is increased from the original volume V0 by the volume V1.

  Further, as shown in FIG. 5, the cooling means 42 cools the deformable portion 31 to contract the deformable portion 31 and reduce the volume (V0 + V1) of the cavity 10a (cooling step). Specifically, the temperature of the bimetal structure portion 10 b is lowered, and the contraction amount of the deformable portion 31 is made larger than the contraction amount of the thin plate portion 21.

Then, as shown in FIG. 5, the bimetallic structure 10b swelled toward the deforming portion 31 is deformed to the original state, so that the cavity 10a is reduced to the original volume V0, and then the deforming portion 31 of the deforming portion 31 by the cooling means 42 is obtained. Cooling is stopped.
Thus, by reducing the cavity 10a and forcibly reducing its volume, the pressure applied to the melt A inside the cavity 10a is increased to prevent the formation of nests inside the product. .

  In the present embodiment, when the temperature of the cavity 10a detected by the temperature sensor 23 becomes lower than the solidification temperature of the molten metal A, cooling of the deformed portion 31 by the cooling means 42 is started.

  Here, as described above, the volume reduction rate of the cavity 10a due to the cooling of the deformable portion 31 and the solidification shrinkage rate determined by the material characteristics of the molten metal A are controlled to be the same. That is, the volume of the cavity 10a that is increased by the heating of the deformed portion 31 of the heating means 41 so that the reduction rate (V0 / (V0 + V1)) of the cavity 10a before and after cooling becomes the same as the solidification shrinkage rate of the molten metal A. Is set.

Specifically, the volume reduction rate of the cavity 10a according to the present embodiment is set to be 3%, which is about the same as the solidification shrinkage rate of the ADC 12 that is the molten metal A. When pure aluminum is used as the molten metal A, for example, the volume reduction rate of the cavity 10a is set to be 6.6%, which is the same as the solidification shrinkage rate of the pure aluminum that is the molten metal A.
In the liquid phase state of the molten metal A, it expands or contracts due to a temperature change, but it is very small compared with a volume change due to solidification contraction, and therefore it does not matter if it is not taken into consideration.

  Thereafter, after the movable mold 12 is separated from the fixed mold 11, the product is taken out from the casting mold 10 by extruding the product cast by an unillustrated extrusion device.

  According to the present embodiment, as described above, in the casting mold 10, the portion that forms the cavity 10 a is configured by the thin plate portion 21, and the thin plate portion 21 has a thin plate on the surface opposite to the side on which the cavity 10 a is formed. A deformed portion 31 which is a thin plate member having a larger coefficient of thermal expansion than the portion 21 is provided to form the bimetal structure portion 10b.

  In the casting method according to the present embodiment, the deforming portion 31 is expanded by heating the deforming portion 31, and the volume of the cavity 10a is increased. After the heating step, the molten metal A is filled in the cavity 10a. And a cooling step of reducing the volume of the cavity 10a by contracting the deformable portion 31 by cooling the deformable portion 31 when the melt A solidifies after the filling step.

  According to this embodiment, by configuring as described above, it is possible to simplify and downsize the equipment configuration as compared with a configuration in which a device for controlling pressure and heat in a casting mold is separately provided as in the prior art. Therefore, it is possible to reduce the cost for preventing the formation of nests in the product when casting.

  Moreover, since it is the structure which changes the volume of the cavity 10a directly, the influence on the product inside the cavity 10a can be enlarged, and generation | occurrence | production of a nest can be suppressed effectively. In addition, since the pressure is directly applied to the melt A located inside the cavity 10a, the volume into which the melt A flows is not increased more than necessary, so that the yield of the product can be prevented from deteriorating. it can.

Moreover, since the material component of the molten metal A is not changed, the cost increase due to the addition of elements and the influence on other characteristics of the product do not occur.
As described above, in the casting method using the casting mold 10 according to the present embodiment, it is possible to suppress the formation of nests without affecting the quality of the product with a simple and compact equipment configuration.

  Furthermore, in the present embodiment, in the heating step, the temperature at which the deformed portion 31 is heated is determined by the volume reduction rate of the cavity 10a due to the cooling of the deformed portion 31 and the solidification shrinkage rate determined by the material characteristics of the molten metal A. It is controlled to be the same.

  By configuring as described above, the rate at which the bimetal structure 10b swelled toward the deformed portion 31 is deformed to the original state and the cavity 10a is reduced to the original volume is the volume change rate due to the solidification shrinkage of the melt A. Match. Thereby, the pressure applied to the molten metal A inside the cavity 10a is adjusted to an appropriate value, and the formation of nests inside the product can be more effectively prevented.

In addition, in this embodiment, when the temperature of the cavity 10a detected in the vicinity of the thin plate portion 21 becomes lower than the solidification temperature of the molten metal A, cooling of the deformed portion 31 is started.
As a result, the timing at which the bimetal structure 10b swelled toward the deformed portion 31 is deformed to the original state and the cavity 10a is reduced to the original volume can be matched with the timing of solidification contraction of the molten metal A. That is, since the timing for applying pressure to the melt A inside the cavity 10a can be adjusted, the formation of nests inside the product can be more effectively prevented.

Moreover, in this embodiment, the carbon coating is previously given to the cavity formation surface 21a which is the surface by which the cavity 10a of the thin-plate part 21 is formed as a heat insulation process for delaying cooling of the molten metal A.
Thereby, since the wettability is lowered by covering the cavity forming surface 21a with the nanocarbon carbon film, solidification due to cooling of the molten metal A can be delayed. That is, since the cavity 10a can be reduced to the original volume before the molten metal A is completely solidified, the formation of nests inside the product can be more effectively prevented.

DESCRIPTION OF SYMBOLS 10 Casting die 10a Cavity 10b Bimetal structure part 11 Fixed type 12 Movable type 21 Thin plate part 31 Deformation part

Claims (8)

A casting method that is performed by filling a cavity formed in a casting mold with molten metal,
In the casting mold, at least a part of the portion forming the cavity is constituted by a thin plate portion, and the surface of the thin plate portion opposite to the side forming the cavity is heated more than the thin plate portion. A deformed portion which is a thin plate member having a large expansion coefficient is provided, and a bimetal structure is formed by the thin plate portion and the deformed portion,
Heating the deforming part to expand the deforming part to increase the volume of the cavity; and
A filling step in which the molten metal is filled into the cavity after the heating step; and
A cooling step of shrinking the deformation portion by cooling the deformation portion when the molten metal solidifies after the filling step, thereby reducing the volume of the cavity.
A casting method characterized by the above. In the heating step, the temperature at which the deformed portion is heated is the same as the volume reduction rate of the cavity due to the cooling of the deformed portion in the cooling step and the solidification shrinkage rate determined by the material characteristics of the molten metal. To be controlled,
The casting method according to claim 1, wherein: When the temperature of the cavity detected in the vicinity of the thin plate portion becomes lower than the solidification temperature of the molten metal, the cooling of the deformed portion is started.
The casting method according to claim 1, wherein the casting method is characterized. The surface of the thin plate portion on the side where the cavity is formed is preliminarily subjected to heat insulation processing for delaying the cooling of the molten metal,
The casting method according to any one of claims 1 to 3, wherein the casting method is characterized in that: A casting mold in which a cavity is filled with molten metal and casting is performed,
Of the portion forming the cavity in the casting mold, at least a part is constituted by a thin plate portion, and the surface of the thin plate portion opposite to the side forming the cavity is more thermally expanded than the thin plate portion. A deformed portion which is a thin plate member having a large rate is provided, and a bimetal structure is formed by the thin plate portion and the deformed portion,
Heating means for expanding the deformation portion by heating the deformation portion before the molten metal is filled in the cavity, thereby increasing the volume of the cavity;
Cooling means is provided for reducing the volume of the cavity by contracting the deformed portion by cooling the deformed portion when the molten metal solidifies.
A casting mold characterized by that. In the heating means, the temperature at which the deformed portion is heated is the same as the volume reduction rate of the cavity by cooling the deformed portion by the cooling means and the solidification shrinkage rate determined by the material characteristics of the molten metal. Control to be
The casting mold according to claim 5, wherein: In the vicinity of the thin plate portion, a temperature detecting means that is exposed to the cavity is disposed,
When the temperature of the cavity detected by the temperature detection unit becomes lower than the solidification temperature of the molten metal, the cooling unit starts cooling the deformed portion.
The casting mold according to claim 5 or 6, characterized by the above. The surface of the thin plate portion on the side forming the cavity is preliminarily subjected to a heat insulation process for delaying the cooling of the melt.
The casting mold according to any one of claims 5 to 7, characterized in that:

Images