JP3057491B2 - Al alloy for die casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an Al alloy for da capitalize preparative, more particularly Al-Mg-Mn-Ni-based alloy.

[0002]

2. Description of the Related Art Heretofore, as this kind of Al alloy, an Al alloy capable of obtaining a die-cast casting having a relatively high strength in an as-cast state has been known (for example,
See JP-A-63-250438).

[0003]

At present, there has been an attempt to replace various steel parts with die castings made of Al alloys in order to reduce the weight of motorcycles. in this case,
Die castings must not only have high strength, but also have excellent impact resistance, that is, high toughness, due to the exposed parts.

[0004] In order to enhance the appearance and commercial value of a motorcycle, it is also necessary that the coating film is beautiful when anodized on a die-cast casting.

[0005] However, the conventional die cast casting made of an Al alloy can be used in an as-cast state, so that heat treatment is not required, so that productivity can be improved and production cost can be reduced. On the other hand, since the Ni content is set relatively high, such as 1% by weight ≦ Ni ≦ 5.5% by weight, the acicular intermetallic compound AlMnNi is likely to be coarsely formed, and as a result, the toughness is reduced. There is a problem that the film becomes relatively low and the degree of beauty of the film by the anodic oxidation treatment is low.

[0006]

The present invention SUMMARY OF THE INVENTION comprises providing the die casting Al alloy capable of obtaining a die cast capable of forming a beautiful anodized film has high toughness in cast state With the goal.

[0007] To achieve the above object, according to the present invention,
High toughness due to crystallization of fine intermetallic compound Al ₆ Mn
3.0% by weight ≦ Mg ≦ 5.5% by weight and 1.5% by weight ≦ Mn ≦ in order to produce a die cast casting capable of forming a beautiful anodic oxide film by adding no Si. 2.0% by weight and 0.5% by weight ≦ Ni ≦ 0.
9% by weight and the balance Al containing unavoidable impurities,
Disclosed is an Al alloy for die casting, wherein the flowability of the molten metal is good and the seizure to a mold is suppressed.

[0008] The die casting made of an Al alloy having the above-described structure has high toughness and a predetermined strength in an as-cast condition. In addition, it is possible to form a beautiful film by subjecting the die casting to anodizing treatment.

Further, the Al alloy has excellent castability such that the seizure of the Al alloy with the mold is suppressed and the fluidity thereof is good, and the occurrence of cracks in the die casting is small. Having.

The effects of each chemical component and the reasons for limiting its content are as follows.

Mg: Mg has the effect of improving the strength of the matrix by forming a solid solution in α-Al. However, when the Mg content is Mg <3.0% by weight, the strength of the matrix cannot be sufficiently improved. On the other hand, when the Mg content is more than 5.5% by weight, the tensile strength of the die-cast casting is improved. , Impact value, that is, toughness is reduced. In castability, a low Mg content, for example, 1.0 to 2.0% by weight significantly increases cracking susceptibility, while a high Mg content, for example,
At 6.0% by weight, the oxidation of the molten metal becomes severe and the fluidity deteriorates.

Mn: Mn forms an intermetallic compound AlMgMn in the early stage of solidification of a molten metal. Due to the large latent heat of solidification of the intermetallic compound, the liquid state allowing the flow of α-Al is maintained for a relatively long time, so that the fluidity of the molten metal is improved.
Mn also has the effect of suppressing seizure between the mold and the molten metal. Furthermore, under rapid cooling by die casting, Mn forms a solid solution in α-Al to increase the strength of the matrix, and the intermetallic compound Al ₆ Mn is finely dispersed and crystallized, so that the toughness and strength of the die casting are enhanced. Where M
When the n content is Mn <1.5% by weight, the effect of improving the fluidity of the molten metal and the effect of suppressing the seizure cannot be sufficiently obtained.
If Mn> 2.0% by weight, the intermetallic compound Al ₆ Mn is formed coarsely, and the toughness of the die casting decreases.

Ni: In the process of filling the molten metal into the mold,
During the crystallization of α-Al, Ni forms eutectic Al ₃ Ni,
Since the eutectic Al ₃ Ni exhibits a liquid phase state between both adjacent α-Als, the propagation of the injection pressure is easily performed, thereby reducing the cracks of the die casting due to the solidification shrinkage of the molten metal. . Ni has the effect of suppressing seizure between the mold and the molten metal, similarly to Mn. However, when the Ni content is Ni <0.5% by weight, the propagation of the injection pressure becomes insufficient. On the other hand, when Ni> 0.9% by weight, a large amount of the acicular intermetallic compound AlMnNi is likely to be generated coarsely. As a result, the elongation and impact value of the die casting decrease, and the beauty of the film formed by the anodic oxidation decreases.

Si, Fe: Si and Fe are inevitably mixed impurities during the production of the aluminum alloy and during the die casting process. Si promotes seizure between the mold and the molten metal, and segregates on the surface of the die casting to reduce the beauty of the film due to anodic oxidation. On the other hand, Fe promotes the formation of intermetallic compounds and causes the die casting. Since the mechanical strength of the casting is adversely affected, it is desirable that these Si and Fe be as small as possible.

According to the present invention, in addition to the chemical components, 0.1% by weight ≦ Ti ≦ 0.2% by weight and 0.00% by weight.
An Al alloy for high toughness die-casting containing at least one of 1% by weight ≦ Be ≦ 0.006% by weight is provided.

Ti forms an intermetallic compound Al ₃ Ti,
The Al ₃ Ti has α− in the thick part of the die casting.
It serves as a nucleus for producing Al and generates a fine structure, thereby suppressing cracking of the die casting. However, when the Ti content is less than 0.1% by weight, Al ₃ Ti is not sufficiently generated, while when the Ti content is more than 0.2% by weight, Al ₃ Ti is coarsely formed, which adversely affects the toughness of the die casting. Effect.

Be has the effect of preventing oxidation of the molten metal,
This suppresses the oxidative depletion of Mg and the generation of oxides in the molten metal. To ensure this effect, the Be content is set as described above.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [I] Strength and Toughness of Die Castings Table 1 shows the compositions of Examples 1 to 5 and Comparative Examples 1 to 6 of Al alloys for die casting .

[0019]

[Table 1]

Using an 800 ton die casting machine, each Al
A die casting 1 shown in FIG. 1 was cast from the alloy. The die casting 1 is a left rear frame component of a motorcycle body frame 2 of a motorcycle, and a right rear frame component 3 symmetrical to the left rear frame component 3 is provided on the body frame 2.

The casting conditions are as follows. Molten metal temperature: 730 ° C. in Examples 1 to 5 and Comparative Examples 1 to 4 and 680 ° C. in Comparative Example 5; Mold temperature: 200 to 250 ° C .; Two-stage injection method: Plunger speed 0.3 m / at low speed stage s,
In the high speed stage, the plunger speed is 1.3 m / s; casting pressure:
68.6 MPa; mold opening time: 8 seconds after filling. In each of the as-cast die-casting castings 1, a tensile test piece and a Charpy impact test piece were respectively manufactured from the upper front protrusion 4, and both tests were performed on these test pieces. The results shown in Table 2 were obtained. In Table 2, Examples 1 to 5 and Comparative Examples 1 to 6 of die castings were cast using Examples 1 to 5 and Comparative Examples 1 to 6 of Al alloy, respectively. This point is the same hereinafter.

[0022]

[Table 2]

As is evident from Table 2, Examples 1-5 have higher tensile strength, elongation and Charpy impact values than Comparative Examples 1-6. About 0.2% proof stress, Example 1
Is slightly lower than Comparative Examples 4 and 6,
To 5 have higher values than Comparative Examples 1 to 6. From these test results, it is clear that Examples 1 to 5 have excellent strength and toughness.

FIGS. 2 and 3 are micrographs showing Examples 1 and 3, respectively, and FIGS. 4 and 5 are micrographs showing metal structures (solidified structures) of Comparative Examples 2 and 4, respectively. Shooting position of these photos is approximately bisecting position of the wall thickness that only you to die cast.
Also, 0.5% hydrofluoric acid was used as a corrosive liquid.

In FIGS. 2 to 5, the matrix is α-Al in which Mg forms a solid solution, and eutectic Al ₆ Mn and eutectic Al ₃ Ni are crystallized in the gap between adjacent α-Al. .

In the first and third embodiments shown in FIGS.
The generation amount of the intermetallic compound AlMnNi is small and fine. On the other hand, in Comparative Example 2 shown in FIG. 4, since the Ni content was 1.05% by weight (> 0.9% by weight), the amount of the acicular intermetallic compound AlMnNi was large, and the amount was large. ing. Further, in Comparative Example 4 shown in FIG. 5, the Ni content was 2.23% by weight (> 0.9% by weight), which was larger than Comparative Example 2, and the Fe content was 0.46% by weight. Therefore, the acicular intermetallic compound Al
The amount of produced MnNi is larger than that of Comparative Example 2, and the size thereof is larger than that of Comparative Example 2. [II] Anodizing treatment on die castings Examples 1 and 3 and Comparative Examples 1 and 2 of the Al alloy in Table 1
4 and 5 were prepared. Then, similarly to the above [I], 80
Using a 0-ton die casting machine, a die casting 1 shown in FIG. 1 was cast from each Al alloy. The casting conditions are as described in [I] above.
Is the same as

Next, each die casting was subjected to anodic oxidation treatment to form a film on the surface. The anodic oxidation treatment was performed through the steps of degreasing, water washing, neutralization (10% nitric acid), water washing, electrolysis, water washing, sealing (acetic acid), and hot water washing. The electrolysis conditions are as follows. Electrolyte: 33% sulfuric acid; current density: 0.5 A / dm ² ; final voltage: 20 V (DC); electrolysis time: 15 minutes. Thereafter, the relationship between the thickness and the brightness of each film was measured, and the results shown in Table 3 were obtained.
The brightness was represented by a lightness index L according to the Hunter's color difference formula. Therefore, a larger L value indicates a brighter state,
A smaller value indicates a darker state.

[0028]

[Table 3]

FIG. 6 is a graph showing the relationship between the film thickness and the lightness index L for Examples 1 and 3 and Comparative Examples 1, 4 and 5 based on Table 3.

As is clear from Table 3 and FIG. 6, the films formed in Examples 1 and 3 have a higher brightness at each film thickness than the films formed in Comparative Examples 1, 4 and 5. It is large, and the decrease in brightness with an increase in the film thickness tends to be small.

The reason why the brightness of the coating in Comparative Examples 1 and 5 is low is that Comparative Examples 1 and 5 contain Si which is a chemical component for reducing the brightness. Since Si was segregated on the surface, the formation of the film was not uniform. In the case of Comparative Example 4, Ni
The brightness of the film is low due to the content of Ni> 0.9% by weight. [III] Castability of Al alloy (a) Seizure of molten Al alloy and mold In seizure of molten metal and Al alloy, part of Fe in the constituent material of the mold is dissolved in the molten Al alloy. It is caused by things.

Then, in Example 6 of the Al alloy shown in Table 4,
7 and Comparative Example 7 were prepared, and an experiment described below was performed on these.

[0033]

[Table 4]

First, Example 6 was melted, and the molten metal was dissolved in 8
The temperature was kept at 00 ° C., and then, in the melt, a diameter 20 mm and a length 1 made of JIS SKD61 which is a material for forming a mold were used.
Dip a 20mm round bar over a length of 100mm, then
Samples were taken from the molten metal every 5 minutes, 30 minutes, and 45 minutes, and the amount of Fe dissolved from the round bar was measured for each sample. The results shown in Table 5 were obtained.

[0035]

[Table 5]

FIG. 7 is a graph showing the relationship between the immersion time and the amount of Fe dissolved in Examples 6 and 7 and Comparative Example 7 based on Table 5. As is clear from FIG. 7, in Examples 6 and 7, the dissolution of Fe from the round bar is suppressed by Mn and Ni. Therefore, by using the melts of Examples 6 and 7, it is possible to greatly reduce seizure between the mold and the melt.

On the other hand, in Comparative Example 7, Mn (<1.5
%) And Ni (0% by weight) cannot be obtained, and the anti-seizure effect of the alloying element Fe is expected. In Comparative Example 7, however, the alloying element Si is used to form the intermetallic compound AlSiFe. In order to promote the dissolution of Fe from the round bar, the amount of Fe dissolved was larger than in Examples 6 and 7. Therefore, according to Comparative Example 7, it is not possible to improve the seizure property. (B) Insufficiency of filling / cracking etc. Examples 1 and 3 and Comparative Example 1 of the Al alloy in Table 1 were prepared. Then, using a 350ton die casting machine,
A die casting 5 shown in FIG. 8 was cast from each Al alloy. The casting conditions are the same as in [I] above. This die casting 5 is an engine cover of a motorcycle, and has a large thickness change. Next, each die casting 5
As a result of examining the properties, the results shown in Table 6 were obtained.

[0038]

[Table 6]

As is clear from Table 6, in Examples 1 and 3, the effect of improving the fluidity of the molten metal by Mn is obtained, so that there is no defective filling portion and the effect of suppressing the cracking of Ni or Ni and Ti. The number of locations where cracks are generated is significantly smaller than that in Comparative Example 1, and the sum of the lengths of the cracks, that is, the total length is also extremely short. Can be reduced.

From the above (a) and (b), it can be seen that Examples 1, 3, 6, and 7 of the Al alloy have better castability than Comparative Examples 1 and 7.

[0041]

According to the first aspect of the present invention, a die casting having a high toughness in an as-cast state and a required strength can be obtained . An Al alloy can be provided. Also, it is possible to obtain a beautiful film by subjecting the die casting to anodizing treatment. Further, the Al alloy has excellent castability.

According to the second aspect of the present invention, by configuring as described above, it is possible to provide an Al alloy further improved in castability in addition to the above-mentioned effects.

[Brief description of the drawings]

FIG. 1 is a perspective view of a motorcycle body frame provided with an example of a die casting.

FIG. 2 is a photomicrograph showing a metal structure of a die casting made of Example 1 of an Al alloy.

FIG. 3 is a micrograph showing a metal structure of a die-cast casting made of Example 3 of an Al alloy.

FIG. 4 is a photomicrograph showing the metal structure of a die casting made of Comparative Example 2 of an Al alloy.

FIG. 5 is a photomicrograph showing a metal structure of a die-cast casting made of Comparative Example 4 of an Al alloy.

FIG. 6 is a graph showing a relationship between a film thickness and a lightness index L.

FIG. 7 is a graph showing the relationship between the immersion time and the amount of Fe dissolved.

FIG. 8 is a front view of another example of the die casting.

[Explanation of symbols]

 1,5 Die casting

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiko Nakagawa 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda Technical Research Institute Co., Ltd. (56) References JP-A-1-247549 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 21/00-21/18

Claims (2)

(57) [Claims] 1. For the crystallization of a fine intermetallic compound Al ₆ Mn
Therefore , in order to produce a die-cast casting which is capable of achieving high toughness and capable of forming a beautiful anodic oxide film by adding no Si , 3.0% by weight ≦ Mg ≦ 5.5% by weight. 1.5% by weight ≦ Mn ≦ 2.0% by weight, 0.5% by weight ≦ Ni ≦ 0.9% by weight, and the balance of Al containing unavoidable impurities. An aluminum alloy for die casting, wherein seizure on a mold is suppressed. 2. The die-casting Al according to claim 1, which contains at least one of 0.1% by weight ≦ Ti ≦ 0.2% by weight and 0.001% by weight ≦ Be ≦ 0.006% by weight.
alloy.