JP2851231B2 - Aluminum alloy casting for high pressure casting excellent in strength and toughness and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy casting used for automobile brake parts, suspension parts and the like.
More specifically, compared to conventional aluminum alloy castings,
The present invention relates to an aluminum alloy casting for high-pressure casting having improved elongation and toughness and having the same performance as a forged product, and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum and aluminum alloys have been used in automobile parts such as undercarriage parts, which conventionally used iron-based materials, for the purpose of weight reduction. Aluminum alloys are frequently used from the viewpoint of reducing unsprung weight. It has come to be. As the aluminum alloy, Al-Mg-Si based alloys having relatively good corrosion resistance and excellent workability, especially JIS6061 and 6N01 alloys, are often used. Forging is performed to obtain high strength and high toughness required as important security parts. It is manufactured by. However, these materials are often used by cutting extruded materials into appropriate lengths, and go through many steps such as preforming, roughing, finishing, etc., so that the yield is lowered and the manufacturing cost is increased. There is a disadvantage that.

On the other hand, aluminum castings are used in automobile parts at a considerable rate because complicated shapes can be manufactured at low cost. Al-Cu-
(Si) type AC1B, AC2B, Al-Si type AC
Although there is 3A or the like, Al-Si- alloys having improved mechanical properties by adding a small amount of Mg to Al-Si alloys having good castability from the viewpoints of high strength, high toughness, and corrosion resistance to give a heat treatment effect.
Cast alloys such as Mg-based AC4C and AC4CH are frequently used. However, these castings tend to have gas defects such as blisters and blisters after heat treatment due to the large number of internal defects during casting and the high amount of dissolved gas. In addition, since the strength level is low and stable performance is hard to be obtained as compared with a forged material, its use is currently limited to thin materials such as cases and covers, or members having relatively low required strength.

[0004] Since cost reduction is also essential, there is a strong demand for the development of a casting material having the same performance as a forged material and capable of reducing cost. In order to satisfy this demand, attempts have been made to overcome the casting problems by the high-pressure casting method, and some parts have been put to practical use using casting alloys (for example, JP-A-61-227142). JP-A-61-227146). However, high strength and high toughness sufficient to replace or reduce the thickness of important security components in which current forged products are used have not been obtained. Further, the dispersion of internal defects such as entrainment of the aluminum solidified film and oxide film during filling of the molten metal and the occurrence of shrinkage cavities due to insufficient casting pressure has not been suppressed stably.

[0005]

SUMMARY OF THE INVENTION The present invention increases the strength and toughness-improving elements and increases the toughness-inhibiting element S
It is an object of the present invention to provide an aluminum alloy casting for high-pressure casting which has the same mechanical performance as a forged material and is lower in cost than a forged material by reducing the i amount as much as possible, and a method for producing the same.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been intensively studied in view of the above circumstances, and as a result, an aluminum alloy casting for high pressure casting which has the same mechanical performance as a forged material and is lower in cost than the forged material, and a method for producing the same. Was developed.

That is, according to the first aspect of the present invention, it is preferable that, in terms of% by weight, 0.6 to 1.0% of Si , 0.6 to 1.0% of Cu ,
0.5-1.2%, Ti 0.002-0.20%, B
It is an aluminum alloy casting for high-pressure casting containing 0.0004 to 0.04%, with the balance being Al and unavoidable impurities.

Further, the invention according to claim 2 is characterized in that, by weight%, 0.6 to 1.0% of Si , 0.6 to 1.0% of Cu ,
0.5-1.2%, Ti 0.002-0.20%, B
After filling an aluminum alloy melt containing 0.0004 to 0.04% with the balance being Al and inevitable impurities at a melt temperature of 650 to 800 ° C.,
This is a method for producing an aluminum alloy casting for high-pressure casting, characterized in that the casting is directionally solidified from an initially solidified portion to a gate at a high pressure of kgf / cm ² or more.

[0009]

The reasons for adding the additional elements of the aluminum alloy casting according to the present invention and the reasons for limiting the amount of addition will be described.
In this specification,% alloy composition means% by weight.

Si and Mg: Si and Mg are effective elements for coexisting and precipitating Mg ₂ Si during heat treatment after casting to increase the strength.
%, Sufficient strength cannot be obtained, Si is 1.0%, M
If g exceeds 1.2%, the strength is sufficient, but the toughness and corrosion resistance are remarkably reduced, which is not preferable. Therefore, Si
Is 0.6 to 1.0%, and Mg is 0.5 to 1.2%.

[0011] Cu: Cu is effective for improving the strength after heat treatment together with Mg and Si. However, if the addition amount is less than 0.6%, sufficient strength cannot be obtained. It is not preferable because the corrosion resistance is deteriorated. Therefore Cu is 0.6-
1.0% .

Ti and B: Ti and B are effective in refining the casting structure, preventing casting cracks on the surface layer of the casting, and preventing macro segregation near the gate, which is the final solidified portion. Here, the addition amounts are 0.002% and 0.0%, respectively.
If the content is less than 004%, the above effects cannot be obtained. If the content is more than 0.20% and 0.04%, coarse inclusions are generated, and mechanical performance is deteriorated. Therefore, Ti 0.002-0.02%, B 0.0004-
0.04.

Next, a method for manufacturing an aluminum alloy casting according to the present invention will be described with reference to FIG. Aluminum alloy castings have good mechanical performance, especially internal defects that lower the elongation value, and obtain sound internal quality. Therefore, if the molten metal temperature at the gate (9) immediately before filling into the product part (2) is less than 650 ° C. This is not preferable because the solid phase ratio of the molten metal becomes high, and the casting pressure after filling in the product part (2) is difficult to propagate, and a local shrinkage cavity is generated. If the temperature exceeds 800 ° C., gas is easily absorbed in the molten metal and gas porosity is easily generated.
The temperature of the molten metal is 650 to 800 ° C. The temperature of the molten metal at the gate section (9) immediately before filling into the product section (2) is 650 to 80
The method of setting the temperature to 0 ° C is to raise the temperature of the molten metal when pouring the molten metal into the plunger sleeve with normal ladle water supply,
Alternatively, a method of coating a heat insulating material such as ceramic on the inner surface of the ladle to prevent the temperature of the molten metal from lowering can be considered. However, in this method, when pouring the molten metal from the ladle into the plunger, entrapment of the oxide film is unavoidable. Therefore, as a means for transferring the molten metal from the holding furnace to the plunger sleeve (4),
It is desirable to use a method such as an electromagnetic pump or a metal pump in which the molten metal is hardly turbulent and the pouring speed is high.

When the molten metal filled in the product part (2) is solidified, it is directionally solidified from the initial solidification part (2a) of the casting to the gate part (9) under a high pressure of 500 kgf / cm ² or more. If the casting pressure is less than 500 kgf / cm ² , shrinkage cavities and casting cracks occur frequently, and the mechanical performance, particularly the elongation value, is not preferred, which is not preferable. In addition, the solidification is the initial solidification part (2
When the final solidification part (2b) near the gate part (9) does not proceed sequentially from a) to the gate part (9), sufficient casting pressure does not propagate into the product part when the solidification part (2b) near the gate part (9) is solidified. It is not preferable because nests and casting cracks occur. When a normal die casting mold is used, an independent water-cooled pipe (6) from the initial solidification part (2a) to the final solidification part (2b) and the sprue part (9) of the mold is placed in the mold. This is easily achieved by reducing the amount of cooling water at the time of casting in the initial solidification part (2a) and gradually decreasing it in the center of the product, the final solidification part (2b) of the product, and the gate (9). That is, the cooling method of the mold is based on the initial solidification part (2a) of the product part.
From the temperature to the final solidification part (2b). In this specification, the directional solidification refers to the above-described solidification method. In addition, the initial solidification part of the cast product (2a)
Means the position of the product farthest from the gate (9).

The alloy casting of the present invention is subjected to heat treatment in accordance with the required performance of the final product, but the heat treatment conditions are not particularly limited. That is, according to the composition of the aluminum alloy casting according to the present invention, by performing the solution treatment and quenching specified in JIS standards, aging treatment conditions, strength,
Elongation and toughness can be adjusted.

[0016]

EXAMPLE The casting apparatus shown in FIG. 1 was used. This casting apparatus slides through a product part (2) formed in a mold (1), a molten metal supply path (3), a plunger sleeve (4) into which a fixed amount of molten metal is poured, and a plunger sleeve (4). A plunger tip (5) for moving and filling the molten metal into the product part (2) and pressurizing it. Here, the mold (1) is passed through the cold water pipe (6) at regular intervals along the product part (2), and the amount of cold water is changed from the initial solidification part (2a) to the final solidification part (2b) to reduce the temperature gradient. A structure that can be made.

An aluminum alloy having the composition shown in Table 1 was melted by a usual method, and degassing was performed by bubbling Ar gas at a melt temperature of 750 ° C. for about 20 minutes.
Pressure casting was performed using the casting apparatus shown in Table 2 under the casting conditions shown in Table 2 to produce a flat test piece having a thickness of 20 mm and a width of 100 mm. Here, the temperature of the molten metal was measured by a thermocouple (7) for measuring the temperature of the molten metal, which was installed at the gate (9). The temperature of the mold at the time of casting was controlled by changing the amount of water in the cold water pipe (6) at each location while performing casting. As for the casting pressure, the load applied to the plunger tip (5) at the time of casting was held as it was, and the load was divided by the cross-sectional area of the plunger tip (5), and the casting pressure was described in Table 2.

Cross sections of these aluminum alloy castings (flat test pieces) were polished, and internal defects such as shrinkage cavities and casting cracks were visually observed. Heat treatment (540 ° C)
, Then water-cooled and aged at 180 ° C. for 8 hours), and thereafter, tensile test pieces and Charpy test pieces are sampled to be index values of tensile strength, proof stress, elongation value, and toughness. The Charpy impact value was measured. The results are shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

As is apparent from Table 2, no internal defect was observed in the test piece in which the alloy of the present invention was cast under predetermined casting conditions.
AC4CH conventionally used for high-pressure casting
It can be seen that the strength and toughness are superior to the alloy casting.
On the other hand, when the alloy composition is not in the scope of the present application, sufficient strength and toughness cannot be obtained, and when the casting temperature or the casting pressure is low or the cooling temperature gradient of the mold does not exist even in the case where the alloy composition is within the scope of the invention, It can be seen that internal defects such as shrinkage cavities and casting cracks occur frequently in the product, and mechanical performance tends to deteriorate.

[0022]

As described above, according to the present invention, compared to the conventional aluminum alloy casting, the strength and toughness can be improved, and a casting free of internal defects such as shrinkage cavities and casting cracks can be obtained. It can be used for undercarriage parts where high strength and high toughness are required and brake parts where pressure resistance is required. Therefore, performance equivalent to that of conventional forged materials can be obtained, and manufacturing costs can be reduced. It has a significant effect.

[Brief description of the drawings]

FIG. 1 is a main cross-sectional view of a pressure casting apparatus according to an embodiment.

[Description of sign]

 1. Mold 2. Product part 2a. Initial solidification part 2b. Final solidification part 3. 3. Melt supply route Plunger sleeve 5. Plunger tip 6. 6. Cold water pipe 7. Thermocouple for measuring molten metal temperature Degassing section 9. Gate

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-227142 (JP, A) JP-A-63-103701 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 21/06 C22C 1/02 501 C22C 1/02 503

Claims (2)

(57) [Claims] 1. 0.6% to 1.0% by weight of Si, Cu
0.6-1.0% , Mg 0.5-1.2%, Ti0.0
An aluminum alloy casting for high-pressure casting, containing 02 to 0.20% and B of 0.0004 to 0.04%, with the balance being Al and unavoidable impurities. 2. 0.6% to 1.0% by weight of Si, Cu
0.6-1.0% , Mg 0.5-1.2%, Ti0.0
After filling an aluminum alloy melt containing 0.2 to 0.20% and B of 0.0004 to 0.04% with the balance being Al and inevitable impurities at a melt temperature of 650 to 800 ° C., the mold product section is filled with 500 kgf / cm. ^A method for producing a high-pressure cast aluminum alloy casting, comprising: directional solidification from an initially solidified portion of a casting product toward a gate under ^two or more high pressures.