JPH07185770A - Method for pressurize-casting aluminum alloy and pressurize-casting device - Google Patents

Abstract

PURPOSE:To obtain a sound cast product without segregation and plastic deforming structure by making a solid phase ratio at the surrounding part of a pressurizing pin a specific value or lower until the solid phase ratio at a shrinkage cavity developing part becomes the final solid phase ratio without heating the pressurizing pin. CONSTITUTION:A solid phase ratio adjusting means 5 adjusts the solid phase ratio so that the solid phase ratio of molten metal poured into a mold at the surrounding part of the pressurizing pin 4 is <=0.9 until the solid phase ratio at the shrinkage cavity developing part becomes the final solid phase ratio. A first heat conductivity adjusting means 51 uses a pressurizing pin tip 511 made of a low heat conductivity material for the pressurizing pin 4. A second heat conductivity adjusting means 52 is composed of an insert 521 set in the vicinity of a product cavity 23 in a first mold 21 and at a position faced to the pressurizing pin 4 and adjusts the heat conductivity by arranging the desired high heat conductivity material and properly changing the material. A cooling means 53 is composed of a cooling water introducing hole 531 arranged up to the neighborhood of back part of the insert 521 on the opposite side of the cavity 23 and a cooling water flow rate adjusting means to obtain a required temp. gradient at the thick part of the cavity 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure casting method and a pressure casting apparatus. More specifically, the present invention relates to a pressure casting method and a pressure casting method in which defects such as shrinkage cavity defects, plastic deformation structures and segregation structures are prevented. The present invention relates to a pressure casting device.

[0002]

2. Description of the Related Art In recent years, there has been an increasing need for weight reduction of parts, products, devices, etc., and various proposals have been made to manufacture these parts etc. from aluminum alloys. Among them,
Since the manufacturing cost is easy and the parts can be manufactured at low cost, various casting methods of aluminum alloys are being developed and put into practical use. However, the conventional casting method of an aluminum alloy has a problem that the strength of the casting is lowered because bubble nests due to entrainment of bubbles during filling of the molten metal and shrinkage nests due to solidification shrinkage occur in the casting.

Therefore, as a method for solving this problem of the prior art, after pressure pouring is performed while maintaining a depressurized state in the die hole of the die casting mold, the bearing which is the crankshaft holding portion before the molten metal solidifies. A "casting method of an Al alloy cylinder block" (Japanese Patent Laid-Open No. 63-16848) in which a secondary pressure is applied to a screw hole forming portion for attaching a cap by using a pressurizing body is proposed. ing. By this casting method, it is possible to suppress the amount of porosity generated, and for the bearing / cap mounting screw hole forming part,
By applying a secondary pressure, the crystal structure of the crankshaft bearing surface part including the bearing / cap mounting screw hole forming part is made uniform and fine, and the soundness is improved to improve the strength of the cylinder block. I am going to do it.

[0004]

However, in the casting method described in JP-A-63-16848, the pressure pin is located on the surface of the casting, and the heat of the casting is taken away through the pressure pin. Since solidification progresses from the pressure pin and the shrinkage cavity in the center of the casting is crushed, the solidified structure near the pressure pin must be plastically deformed, and the molten metal must be supplied to the shrinkage cavity from the site where solidification has progressed considerably. In addition, there is a problem that segregation occurs in which the residual liquid phase is squeezed out from the solidified layer near the pressure pin toward the shrinkage cavity.
In particular, these plastically deformed structures and segregation lower the casting strength, and thus there is a problem that it is difficult to obtain a product with design specifications.

Therefore, the inventors of the present invention have diligently studied to solve the above-mentioned problems of the prior art, and as a result of various systematic experiments, the present invention has been accomplished.

(Object of the Invention) An object of the present invention is to provide a pressure casting method and a pressure casting apparatus for producing a sound aluminum alloy casting which is free of segregation and / or plastic deformation structure.

The present inventors have focused on the following points with respect to the above-mentioned problems of the prior art. That is, if the liquid phase flows while engulfing the solid phase and the solid phase ratio that can effectively replenish the molten metal to the shrinkage cavity can be clarified, the plasticity can be improved by terminating the pressurization before reaching this solid phase ratio. We paid attention to the fact that it is possible to obtain a casting that is free from deformation and segregation.
Further, by clarifying the solid phase ratio of the shrinkage cavity generating portion which has become a casting defect and must be supplied with the molten metal, it was possible to prevent the shrinkage cavity by supplying the molten metal up to this solid phase rate. So, in order to realize these,
The present invention has been accomplished by focusing on the fact that the above-mentioned inconvenience can be solved by controlling the solid fraction of the pressure pin peripheral portion.

[0008]

[Means for Solving the Problems]

(Structure of the first invention) The pressure casting method for an aluminum alloy according to the present invention is a method for pressure casting an aluminum alloy in which a molten aluminum alloy is poured into a mold to form an aluminum alloy casting. The solid phase ratio of is set to 0.9 or less until the solid phase ratio of the shrinkage cavity generating portion reaches the final solid phase ratio without heating the pressing pin.

(Structure of the Second Invention) The aluminum alloy pressure casting apparatus of the present invention comprises a casting mold for casting aluminum alloy, a molten metal supply means for pouring the molten aluminum alloy into the casting mold, and a molten metal in the casting mold. In a pressure casting apparatus for an aluminum alloy, comprising: a molten metal pressurizing means for pressurizing, the apparatus heats the pressing pin by the solid fraction of the molten pin poured into the mold around the pressing pin. In addition, a solid phase ratio adjusting means for adjusting the solid phase ratio of the shrinkage cavity generation portion to 0.9 or less until the final solid phase ratio is provided, and the segregation structure and / or plastic deformation structure in the aluminum alloy casting are provided. It is characterized by preventing the occurrence of.

[0010]

The mechanism by which the aluminum alloy pressure casting method and the pressure casting apparatus of the present invention exhibit excellent effects is not clear yet, but it is considered as follows.

(Operation of the First Invention) In the aluminum alloy pressure casting method according to the first aspect of the present invention, the aluminum alloy pressure casting method comprises pouring a molten aluminum alloy into a mold to form an aluminum alloy casting. The solid fraction in the peripheral portion of the pressure pin is set to 0.9 or less until the solid fraction in the shrinkage cavity generating portion reaches the final solid fraction. As a result, the liquid phase in the molten metal of the pressurizing pin portion flows toward the shrinkage cavity generating portion while entraining the solid phase, so that the molten metal can be efficiently supplied to the shrinkage cavity portion. By doing so, the molten metal can be supplied to the shrinkage cavity portion without causing plastic deformation structure or segregation around the pressing pin portion. From this, it is considered that it is possible to manufacture a sound aluminum alloy casting without the occurrence of segregation and / or plastic deformation structure.

(Operation of the Second Invention) The aluminum alloy pressure casting apparatus of the present invention comprises an aluminum alloy casting mold, a molten metal supply means, a molten metal pressurizing means, and a solid fraction adjusting means. It becomes. When casting is performed using this apparatus, first, the molten aluminum alloy is poured into the molten metal supply means. Next, the molten metal is filled into the product cavity by the molten metal supply means. Next, the molten metal pressurizing means pressurizes the casting at a predetermined pressure and holds it in that state for a predetermined time, after which the mold is opened and the casting is taken out to complete the casting. At this time, the solid fraction in the peripheral portion of the pressure pin of the molten metal poured into the mold is set to 0.9 by the solid fraction adjusting means until the solid fraction in the shrinkage cavity generating portion reaches the final solid fraction. Adjusted as follows. As a result, the liquid phase in the molten metal of the pressurizing pin portion flows toward the shrinkage cavity generating portion while entraining the solid phase, so that the molten metal can be efficiently supplied to the shrinkage cavity portion. By doing so, the molten metal can be supplied to the shrinkage cavity portion without causing plastic deformation structure or segregation around the pressing pin portion. From this, it is considered that it is possible to manufacture a sound aluminum alloy casting without the occurrence of segregation and / or plastic deformation structure.

[0013]

【The invention's effect】

(Effect of the first invention) By the pressure casting method of the first invention,
It is possible to manufacture a sound aluminum alloy casting without segregation and / or generation of plastic deformation structure.

(Effect of the Second Invention) With the pressure casting apparatus of the second invention, it is possible to manufacture a sound aluminum alloy casting without segregation and / or generation of plastically deformed structure.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a more specific invention (other invention) of the aluminum alloy pressure casting method of the first invention and the aluminum alloy pressure casting apparatus of the second invention will be described.

(Description of Other Inventions) In the aluminum alloy pressure casting method and apparatus of the present invention, the target molten metal is an aluminum alloy molten metal, but the Si content of the aluminum alloy is 25 wt% or less. Is preferred. When the amount of Si is in this range, shrinkage cavities can be prevented by the method of the present invention, and a sound aluminum alloy casting that does not generate a plastic deformation structure can be manufactured.

In the pressure casting method and apparatus of the present invention, molten metal can be replenished to the shrinkage cavity generating portion by pressurization.
In order to prevent the occurrence of shrinkage cavities and obtain a cast product (cast product) free from both segregation and plastic deformation structure, the following conditions are suitable. A. The melt is a hypoeutectic aluminum alloy (the amount of primary crystal Al is 70
In the case of Al alloy of volume% or more) ... The solid fraction of the peripheral portion of the pressurizing pin is set within the range of 0.6 or less until the solid fraction of the shrinkage cavity generating portion reaches the final solid fraction. Pressure is applied in this state. B. The melt is a eutectic and hypereutectic aluminum alloy (primary crystal A
In the case where the amount of Al is 70% by weight, the solid fraction in the peripheral portion of the pressurizing pin is 0.8 or less until the solid fraction in the shrinkage cavity generating portion reaches the final solid fraction. Pressurization is performed in this state.

Further, in the pressure casting method and apparatus of the present invention, it is possible to supply molten metal to the shrinkage cavity generating portion by pressurization, to prevent shrinkage cavity generation and to obtain a casting (cast product) having no plastic deformation structure. The following conditions are suitable. A. When the molten metal is a hypoeutectic aluminum alloy ... The solid fraction in the peripheral portion of the pressure pin is set to be 0.7 or less until the solid fraction in the shrinkage cavity generating portion reaches the final solid fraction. Pressure is applied in this state. B. When the melt is a eutectic or hypereutectic aluminum alloy
-Pressing is performed in a state where the solid fraction around the pressurizing pin is within a range of 0.9 or less until the solid fraction of the shrinkage cavity generating portion reaches the final solid fraction.

In the pressure casting apparatus of the present invention, the solid fraction adjusting means determines the solid fraction of the molten metal poured into the mold in the peripheral portion of the pressure pin 4 and the solid fraction of the shrinkage cavity generating portion as the final solid fraction. It is a means for adjusting the solid phase rate so as to be within a predetermined range. Specifically, (1) thermal conductivity adjusting means ... By adjusting the thermal conductivity of a member in the peripheral portion of the product cavity, until the solid phase ratio of the shrinkage cavity generating portion reaches the final solid phase ratio, It is a means for adjusting the solid fraction of the molten metal poured into the mold in the peripheral portion of the pressurizing pin so as to fall within a predetermined range, and includes the following two means. First thermal conductivity adjusting means ... A thermal conductivity adjusting means composed of a low thermal conductivity member, which is provided in the peripheral portion of the thick portion of the product cavity on the side of the molten metal pressurizing means.
For example, a pressure pin or the like made of a low thermal conductivity member such as a ceramic material. Second thermal conductivity adjusting means ... A thermal conductivity adjusting means composed of a high thermal conductivity member provided in the peripheral portion of the thick portion of the product cavity facing the molten metal pressurizing means. For example, a nest may be provided in the peripheral portion, and various members made of a high thermal conductivity material such as copper may be prepared to adjust the thermal conductivity appropriately.

(2) Cooling means: By forcibly cooling the peripheral portion of the product cavity, the solid phase ratio of the shrinkage cavity generating part is adjusted to fall within a predetermined range until the solid phase ratio reaches the final solid phase ratio. It is a means. For example, it is a cooling means for adjusting the temperature gradient in the peripheral portion of the cavity on the side of the thick portion of the product cavity that faces the molten metal pressurizing means. For example, a cooling water flow rate control means is provided which is provided with a cooling water introduction hole capable of cooling the part and which controls / controls the flow rate of the cooling water introduced into the part by a computer.

As described above, the thermal conductivity adjusting means and /
Alternatively, a solid phase ratio adjusting means such as a cooling means adjusts the temperature state of the peripheral portion of the product cavity, and a suitable temperature gradient is formed in the peripheral portion, so that the periphery of the pressurizing pin 4 of the molten metal poured into the mold is adjusted. The solid fraction of the part can be adjusted to be within a predetermined range until the solid fraction of the shrinkage cavity generating portion reaches the final solid fraction.

Next, in the pressure casting method and apparatus of the present invention, the specific means, shape, structure, cooling capacity, and cooling of the cooling means, such as the thermal conductivity, material, shape and size of the thermal conductivity adjusting means. A preferable example of a method of determining a factor related to the solid fraction control such as a control method and a pressurization time will be described.

For example, a suitable example of determining the thermal conductivity of the pressure pin as the first thermal conductivity adjusting means is as follows. That is, k: thermal conductivity of the mold, k _p : thermal conductivity of the pressure pin, t _k : length of the mold, t _p : length of the pressure pin, t _m : length of the casting wall thickness , T _o : ambient temperature, T _m :
Pouring temperature, Q (1.0): Total latent heat of alloy used, Q
(X): The amount of latent heat released until reaching the solid fraction x shown in Table 1, (a) heat transfer amount from the mold q ₁ = −k (T _o −T _m ) / t _k・ ・ ・ (1) (b) Heat transfer amount from the pressurizing pin q ₂ = −k _p (T _o −T _m ) / t _p・ ・ ・ (2) (c) Required heat difference in the casting q _{m = 2 × (Q (1.0} ) -Q (x)) / t m ··· (3) Therefore, in order to satisfy the _{q m ≧ q 1 -q 2 ···} (4) is, k _p ≦ t _p × (k (T _m −T _o ) / t _k −2 × (Q (1.0) −Q (x)) / t _m ) / (T _m −T _o ) ... (5 ) A pressure pin having a thermal conductivity k _p that satisfies

[0024]

[Table 1]

That is, as a preferred example of the pressure casting method of the present invention, a casting apparatus having a pressure pin having a thermal conductivity satisfying the above expression (5) is used to obtain a predetermined solid phase rate. It is a casting method in which pressurization is completed at a certain time. Conventionally, since the range of solid fractions that can be pressurized is not known, pressure is applied even when the solidification of the periphery of the pressure pin progresses, so that a plastically deformed structure is generated in the periphery of the pressure pin. However, in the past, there was no problem because the required standard for the quality of the casting was not so high or the problematic part was removed to make the product. On the other hand, it is considered that the peripheral portion of the pressurizing pin needs to be in a complete liquid phase (solid phase ratio: 0.0) until the solidification of the central portion is completed. It has been considered practically impossible to provide such a temperature gradient. On the other hand, according to the present invention, the molten metal can be replenished to the shrinkage cavity generation portion by pressurization, for example, by the method and apparatus described above, it is possible to prevent shrinkage cavity generation and obtain a casting (cast product) having no plastic deformation structure. And That is,
When a conventional pressure pin made of a ferrous metal is used, a segregated and plastically deformed structure is exhibited, resulting in a decrease in mechanical strength. On the other hand, these problems could be solved by using the above-mentioned suitable pressure pin instead of the conventional iron-based metal for the pressure pin.

A preferable example of determining the cooling amount for leading to the thermal conductivity of the second thermal conductivity adjusting means and / or the cooling amount q _k of the cooling means is as follows. That is, k: thermal conductivity of the mold, k _p : thermal conductivity of the pressing pin,
t _k: the mold of length, t _p: the length of the pressure pin, t _m: casting thickness of the length, T _o: ambient temperature, T _m: pouring temperature, Q
(1.0): total latent heat quantity of the alloy used, Q (x): latent heat quantity released until the solid fraction x shown in Table 1 is obtained, and q _k ≧ 2 × (Q (1 .0) -Q (x)) / t m -k (T m -T o) / t k ··· (6) cooling means to achieve a cooling amount q _k which satisfies, and / or the second heat Adopt a conductivity adjusting means.

That is, as a preferred example of the pressure casting method of the present invention, a cooling apparatus and / or a second casting apparatus having a second thermal conductivity adjusting means are used, and a cooling method satisfying the above expression (6) is used. A pressure casting method or a pressure casting apparatus in which the amount is controlled.

By the pressure casting method and the pressure casting apparatus of the present invention, it is possible to manufacture a sound aluminum alloy casting free of segregation and / or plastic deformation structure.
Further, since the molten metal is replenished to the shrinkage cavity portion while the solid phase is involved, there is no problem such as different alloy components depending on the casting site. Further, there is an advantage that a hydraulic pressure as large as plastically deforming the solid phase is not required, and a pressure slightly higher than the injection pressure is sufficient.

The embodiments of the present invention will be described below.

(Explanation of the pressure casting apparatus of the first to third embodiments)

The aluminum alloy pressure casting apparatus used in the first to third embodiments will be described with reference to FIG. The casting apparatus 1 includes a mold 2, an injection plunger 3,
It comprises a pressure pin 4 and a solid fraction adjusting means 5.

The mold 2 comprises a first mold 21 and a second mold 22.
And can be hermetically sealed by an O-ring (not shown), and the product cavity 23 is formed by the mold. As the sealing means (method) for the first die 21 and the second die 22, in addition to the above-mentioned O-ring, a known method such as a sealing method using hydraulic pressure can be adopted.

The injection plunger 3 is a means for supplying and / or replenishing the molten metal, and comprises a plunger tip 31, a plunger rod 32, and an injection plunger driving means (not shown).

The pressure pin 4 is a means for pressurizing the molten metal, is provided in a portion corresponding to the thick portion of the product cavity 23, and has a pressure pin tip 41, a pressure pin rod 42, and a pressure pin driving means ( (Not shown). In this embodiment, the pressure pin is made of an iron material as in the conventional case.

The solid phase ratio adjusting means 5 sets the solid phase ratio of the molten metal poured into the mold in the peripheral portion of the pressurizing pin 4 until the solid phase ratio of the shrinkage cavity generating portion reaches the final solid phase ratio. It is a means for adjusting so as to fall within the range, and the first heat conductivity adjusting means 51 and the second heat conductivity adjusting means 51
The heat conductivity adjusting means 52 and the cooling means 53 are included.

The first thermal conductivity adjusting means 51 employs a pressure pin tip 511 made of a low thermal conductivity material instead of the conventional iron-based material for the pressure pin tip 41 of the pressure pin 4.

The second thermal conductivity adjusting means 52 is provided at a position close to the product cavity 23 of the first mold 21 and at a position facing the pressing pin 4 in the thick portion of the product cavity 23. And includes a nest 521. The nest 5
The material 21 has a material having a desired high thermal conductivity and can be appropriately replaced to adjust the thermal conductivity of the portion. In the initial stage, a member made of the same material as the mold is provided.

The cooling means 53 is a cooling water introducing hole 531 provided from this portion of the first mold 21 to the vicinity of the back portion of the insert 521 opposite to the cavity 23, and the cooling water introducing hole 53.
1. A cooling water flow rate control means (not shown) for adjusting / controlling the flow rate of the cooling water introduced into and out of the device 1 by a computer is formed, and the temperature gradient of the thick portion of the product cavity 23 is formed in a desired state (temperature gradient formation). means). In the initial stage, a member made of the same material as the mold is provided in the cooling water introduction hole 531 so as to bury the portion.

(First Example) In this example, only the first thermal conductivity adjusting means 51 was adopted as the solid-phase rate adjusting means 5. The means is composed of a pressure pin tip 511 made of zirconia and has a thermal conductivity of 6 × 10 ⁻³ cal / cm · sec.
At deg, this is the thermal conductivity satisfying x (adjusted solid fraction around the pressing pin) = 0.6 in the equation (5). The molten metal used in this example is an AC4C alloy (Al-6.86% S
i-0.58% Mg-0.06% Cu) hypoeutectic aluminum alloy.

First, the time required for the pressurizing pin portion 43 to have a predetermined solid fraction was obtained by solidification analysis. That is, solidification in the wall thickness of the present casting preferentially proceeds on the side opposite to the pressure pin.
Then, 5 seconds after the completion of the molten metal filling, the solid fraction of the peripheral portion of the pressure pin becomes 0.7. At this time, the solid phase ratio of the wall thickness central portion, which is the shrinkage cavity generating portion, was 0.99, indicating that the solidification was almost completed. Further, the tip of the pressure pin was changed to a material having a low thermal conductivity (thermal conductivity: 1.5 · 10 ⁻³ ), and the same solidification analysis was performed. As a result of the solidification analysis at this time, solidification around the pressure pin was further delayed, and the solid phase ratio around the pressure pin became 0.6 after 5.5 seconds. At this time, the solid phase ratio of the thickness center portion was 0.99, and the solidification was almost completed. Further, solidification analysis was performed by replacing the commonly used pressure pin material with carbon steel (thermal conductivity: 0.103). The solidification of the thick part progresses from the surface part, and the solid phase ratio around the pressurizing pin becomes 1.0 as quickly as 4.5 sec. At this time, the solid phase ratio of the central part of the thickness is 0.8. And was in a non-coagulated state. In addition, the time when the solidification of the central part of the wall thickness (the shrinkage cavity generating part) was almost completed was 5.5 seconds.

Next, casting was performed using the above casting apparatus. First, the molten aluminum alloy was poured into the iron sleeve 6. After that, the injection plunger 3 is driven,
The molten metal is cast into the product cavity 23 at a speed of 2.0 m / s.
Filled the department. Then, after the completion of the filling with the molten metal, the pressure pin 4 was operated to apply a pressure of 700 kg / cm ² , and after the lapse of 5 seconds in that state, the pressure was terminated, the mold was opened, and the casting was taken out.

Internal defects and plastic deformation of the obtained casting /
The generation of the segregated structure was investigated by observing the microstructure of the cross section of the casting. The results are shown in FIG. 2 as a partially enlarged explanatory view of the cross section of the casting. As is clear from FIG. 2, in the case of this example, a segregation structure was generated inside the casting, but no shrinkage cavity was observed. However, because of this, although there was some decrease in strength due to segregation, there was no problem in ensuring the airtightness of the product because no internal defects occurred, and a product with sufficient strength was obtained with sufficient strength. I understand that

(Second Embodiment) In the pressure casting apparatus of the first embodiment, the squeeze pin tip 511 of the pressure pin 4 is used.
A casting test was conducted in the same manner as above, except that the material was changed to magnesia, using the same apparatus as the pressure casting apparatus of the first embodiment, and using the same kind of molten metal, with a pressing time of 5.5 seconds. The magnesia squeeze pin tip 511 (41) has a thermal conductivity of 1.5 × 10 ⁻³ (cal · cm ⁻¹ · sec ⁻¹ · deg ⁻¹ ), which is expressed by the formula (5). X (adjusted solid phase ratio in the peripheral portion of the pressurizing pin) of 0.7 is a thermal conductivity that satisfies 0.7.

The internal defects and the like of the obtained casting were investigated in the same manner as in the first embodiment. The results are also shown in FIG. As is clear from FIG. 3, in the case of this example, no shrinkage cavity or plastically deformed structure was observed inside the casting. This is because the material of the squeeze pin tip 41 (511) portion of the pressure pin is the first in the present embodiment.
It is considered that the use of a member having a lower thermal conductivity than that of the example makes it possible to more appropriately adjust the solid fraction in the peripheral portion of the pressure pin. As a result, it was found that a casting product of sufficient quality was obtained in terms of strength and airtightness.

(Comparative Example 1) In the pressure casting apparatus used in the first embodiment, the tip of the pressure pin was changed to a carbon steel pressure pin tip which is a commonly used material. The same casting test was conducted with a pressing time of 5.5 sec using the same pressure casting apparatus and molten metal as in the first embodiment. The carbon steel pressure pin tip has a thermal conductivity of 0.103 (cal · cm ⁻¹ · sec ⁻¹ · deg ⁻¹ ).

The internal defects and the like of the obtained comparative casting were investigated in the same manner as in the first embodiment. The result is
Also shown in FIG. As is clear from FIG. 4, in the case of this comparative example, there were no internal defects such as shrinkage cavities, but plastic deformation and segregation structure were present. For this reason, the plastic deformation and the segregation cause a remarkable decrease in strength, and the product quality is not satisfactory.

(Comparative Example 2) In Comparative Example 1, since plastic deformation and segregation structure were present, casting was carried out earlier than in Comparative Example 1 for the purpose of eliminating defects in these structures. That is, the pressurization was performed so that the movement of the pressurizing pin was completed in the pressurizing time of 4 sec, and the casting was produced.

The internal defects and the like of the obtained comparative casting were examined in the same manner as in the first embodiment. The result is
Also shown in FIG. As is clear from FIG. 5, in the case of this comparative example, it was confirmed that there were two shrinkage cavities around the pressure pin. This is because the pressurizing pin 4 moves in the liquid phase by the hydraulic stroke, but has no pressurizing effect.

(Comparative Example 3) In Comparative Example 2, it was confirmed that shrinkage cavities were generated in the peripheral portion of the pressurizing pin because the pressurizing time was early. Therefore, in order to eliminate these problems, Comparative Example 2
Contrary to that of Comparative Example 1, casting was carried out with a delayed pressing time. That is, the pressurizing pin was operated by setting the pressurizing start time to 4.5 sec and the pressurizing end time to 5.5 sec. However, in this case, by delaying the pressurization time,
The pressure pin did not work.

The internal defects and the like of the obtained comparative casting were investigated in the same manner as in the first embodiment. The result is
It is also shown in FIG. As is clear from FIG. 6, in the case of this comparative example, since the pressure pin did not operate as described above, the solid phase around the pressure pin crystallized out, and a shrinkage cavity was formed around the pressure pin. Was confirmed to have occurred.

(Third Embodiment) In this embodiment, the second thermal conductivity adjusting means 52 and the cooling means 53 are adopted as the solid-phase rate adjusting means 5. As the second thermal conductivity adjusting means 52, the nesting 521 employs a material made of copper alloy as the high thermal conductivity member (thermal conductivity = 0.953 cal / cm · sec · deg.). Also, the cooling means 53. The cooling water is introduced into the cooling water introducing hole 531 and the cooling water flow rate control means (not shown) adjusts / controls the flow rate of the cooling water introduced into and out of the cooling water introducing hole 531 to add the cooling water. The solid fraction in the area around the compression pin is 0 until the solid fraction in the shrinkage cavity area reaches the final solidification rate.
It is controlled to be 8 or less. The molten metal used in this example is an ADC10 alloy (Al-10% Si-
It is a eutectic aluminum alloy of 2.5% Cu-0.15% Mg).

Next, casting was performed using the above pressure casting device. First, the molten aluminum alloy was poured into the iron sleeve 6. After that, the injection plunger 3 is driven, and the molten metal is poured into the product cavity 2 of the mold at a speed of 1.5 m / s.
Filled 3 parts. Next, after the completion of the filling of the molten metal, the pressure pin 4 was operated to apply a pressure of 600 kg / cm ² , and after the lapse of 5 seconds in that state, the pressure was terminated, the mold was opened, and the casting was taken out.

The internal defects and the like of the obtained casting were investigated in the same manner as in the first embodiment. The results are also shown in FIG. 7. As is clear from FIG. 7, in the case of this example, a segregation structure was generated inside the casting, but no shrinkage cavity was observed. In addition, since there is no plastically deformed structure and airtightness is maintained, it can be seen that sufficient product quality was obtained.

(Fourth Embodiment) The pressure casting apparatus of the third embodiment is the same as the pressure casting apparatus of the first embodiment except that the cooling capacity of the cooling means 53 is changed. A similar casting test was conducted using the same kind of molten metal with a pressurization time of 5.5 seconds. The cooling means 53 has a higher cooling capacity than that of the third embodiment, and the solid fraction in the peripheral portion of the pressurizing pin becomes 0 until the solid fraction in the shrinkage cavity generating portion reaches the final solidification percentage.
It is controlled to be 9 or less.

Investigation of internal defects and the like of the obtained casting was conducted in the same manner as in the first embodiment. The results are also shown in FIG. As is clear from FIG. 8, in the case of this example, no shrinkage cavity or plastically deformed structure was observed inside the casting. This is the cooling means 5 in this embodiment.
It is considered that by increasing the cooling capacity of No. 2, adjustment of the solid fraction in the peripheral portion of the pressurizing pin is more appropriate than in the case of the third embodiment.

(Comparative Example 4) In the pressure casting apparatus used in the first embodiment, the tip of the pressure pin is changed to a carbon steel pressure pin tip which is a commonly used material, and The same casting test was conducted at a pressing time of 5.7 seconds using the same pressure casting apparatus and the same molten metal as in the first embodiment, except that the heating heater was used for heating.
The carbon steel pressure pin tip has a thermal conductivity of 0.1.
03 (cal · cm ⁻¹ · sec ⁻¹ · deg ⁻¹ ). The heating was performed by the heater so that the pressure pin had a temperature of 500 ° C. FIG. 9 shows the solid fraction distribution immediately before pressurization. By heating the pressure pin, the temperature of the mold around the pressure pin increased, and the solidification around the pressure pin was delayed. The internal defects of this casting after pressurization were investigated. The result is shown in FIG. As is clear from the figure, the area around the pressurizing pin where coagulation was delayed became a hot spot, and shrinkage cavities were observed, which was not satisfactory in product quality.

(Comparative Example 5) In Comparative Example 4, since a satisfactory product could not be obtained by heating the pressure pin portion, the pressure pin was moved inward and the same conditions as in Comparative Example 4 were used. A casting test was conducted. By heating the pressurizing pin at the start of pressurization, the high temperature part became as shown in FIG. As the number of high temperature parts increased, shrinkage cavities were generated as shown in FIG. 12, and satisfactory product quality could not be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an aluminum alloy pressure casting apparatus used in first to third examples of the present invention.

FIG. 2 is a partially enlarged explanatory view showing a microstructure observation result of a casting cross section obtained in the first embodiment of the present invention.

FIG. 3 is a partially enlarged explanatory view showing a microstructure observation result of a casting cross section obtained in the second embodiment of the present invention.

FIG. 4 is a partially enlarged explanatory view showing a microstructure observation result of a comparative casting cross section obtained in Comparative Example 1.

5 is a partially enlarged explanatory view showing a microstructure observation result of a comparative casting cross section obtained in Comparative Example 2. FIG.

FIG. 6 is a partially enlarged explanatory view showing a microstructure observation result of a comparative casting cross section obtained in Comparative Example 3.

FIG. 7 is a partially enlarged explanatory view showing a microstructure observation result of a casting cross section obtained in the third embodiment of the present invention.

FIG. 8 is a partially enlarged explanatory view showing a microstructure observation result of a casting cross section obtained in a fourth example of the present invention.

FIG. 9 is a partially enlarged explanatory view illustrating a solid fraction distribution of a cross section of a comparative casting immediately before pressing in a casting test performed in Comparative Example 4.

10 is a partially enlarged explanatory view showing a microstructure observation result of a comparative casting cross section obtained in Comparative Example 4. FIG.

FIG. 11 is a partially enlarged explanatory diagram illustrating a temperature distribution of a cross section of a comparative casting immediately before pressing in a casting test performed in Comparative Example 5.

FIG. 12 is a partially enlarged explanatory view showing a microstructure observation result of a comparative casting cross section obtained in Comparative Example 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Aluminum alloy pressure casting apparatus 2 ... Mold 3 ... Injection plunger 4 ... Pressurizing pin 5 ... Solid-phase-ratio adjustment means 51 ... 1st thermal conductivity adjustment Means 52 ... Second thermal conductivity adjusting means 53 ... Cooling means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoji Awano 1st 41st Yokomichi, Nagakute-cho, Aichi-gun, Aichi-gun, Toyota Central Research Institute Co., Ltd. (72) Inventor Shinya Mizuno 1-Toyota-cho, Toyota-shi, Aichi Inside Toyota Motor Co., Ltd. (72) Inventor Yoshiro Kabahara 1 Toyota-cho, Toyota-shi, Aichi Inside Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. A method of pressure casting an aluminum alloy, comprising pouring a molten aluminum alloy into a mold to form an aluminum alloy casting, wherein the solid fraction of the peripheral portion of the pressure pin is set without heating the pressure pin. In addition, the aluminum alloy pressure casting method is characterized in that the solid fraction of the shrinkage cavity generation portion is set to 0.9 or less until it reaches the final solid fraction. 2. A mold for casting an aluminum alloy, and a molten metal supply means for pouring the molten aluminum alloy into the mold.
An aluminum alloy pressure casting apparatus comprising: a molten metal pressurizing means for pressurizing the molten metal in the mold, wherein the apparatus presses the solid phase ratio of the molten metal poured into the mold around the pressing pin. The solid phase ratio adjusting means for adjusting the solid phase ratio of the shrinkage cavity generation portion to 0.9 or less until the final solid phase ratio is reached without heating the pin is provided. And / or an aluminum alloy pressure casting apparatus which is characterized by preventing the generation of a plastically deformed structure.