JP2005082865A - Non-heat treated aluminum alloy for die-casting, die-cast product obtained by using the alloy, and method for producing the product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-heat treated aluminum alloy for die-casting capable of obtaining stably high strength and high elongation without being subjected to a solution treatment after casting, and further having excellent castability particularly in the point that casting cracks are hard to occur. <P>SOLUTION: The non-heat treated aluminum alloy for die-casting has a composition in which the mass ratio between Mg and Si is 0.1 to 0.5, and comprising, by mass, 3.5 to 5.0% Si, 0.35 to 2.5% Mg, 0.3 to 1.5% Mn, ≤0.15% Fe and ≤0.20% Ti, and the balance aluminum with inevitable impurities. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy for die casting. More specifically, the present invention can obtain excellent mechanical properties without performing heat treatment such as solution treatment or artificial aging after die casting, and has excellent castability, particularly excellent properties that do not cause casting cracks. The present invention relates to a non-heat treated aluminum alloy for die casting. The present invention further relates to a die-cast product using such an aluminum alloy and a method for producing the die-cast product.

  The die-casting method can be cast into a thin-walled casting, and has excellent characteristics such as high dimensional accuracy and high productivity. In recent years, aluminum alloy die castings have been used in which mechanical properties represented by strength and elongation are improved by performing heat treatment after casting by vacuum die casting.

However, such an aluminum alloy material needs to be subjected to solution treatment and aging treatment after die casting in order to obtain excellent mechanical properties. Therefore, a correction process for correcting the distortion generated during the water cooling after the solution treatment is necessary, and the productivity is poor and the cost is high.
JP-A-7-109537 can be cited as a document disclosing an aluminum alloy cast material having high tensile strength and elongation on the premise of solution treatment.

JP-A-7-109537

  In order to solve the problems of low productivity and high cost as described above, as a document disclosing an aluminum alloy for die casting that does not need to be heat-treated after die casting, there is, for example, JP-A-5-9638.

JP-A-5-9638

  However, Al-Mg-Mn (-Zr) alloys described in Patent Document 2 and the like do not need to be heat-treated and have high tensile strength and proof stress, but cracks occur during casting. It has the problem of being easy.

  The present invention has been made paying attention to the above-mentioned problems of the aluminum alloy for die casting represented by the one disclosed in Patent Document 2 that does not require a solution treatment. An object of the present invention is to provide a non-heat-treated aluminum alloy for die casting that has a high strength and a large elongation stably without being subjected to heat treatment such as aging, and is excellent in castability particularly in that it is less prone to casting cracking. To do.

  The object of the present invention further includes providing a die-cast product manufactured using the above-mentioned non-heat-treatable aluminum alloy for die-casting, and a manufacturing method for manufacturing the die-cast product.

  In order to achieve the above object, the present invention has a mass ratio of Mg to Si (Mg mass% / Si mass%) of 0.1 or more and 0.5 or less, Si: 3.5 mass% to 5.0 mass%, Mg: 0.35% by mass to 2.5% by mass, Mn: 0.3% by mass to 1.5% by mass, Fe: 0.15% by mass or less, Ti: 0.20% by mass or less, and a non-heat-treatable aluminum alloy for die casting made of the balance aluminum and inevitable impurities provide.

  Furthermore, according to one of the preferable embodiments of the present invention, in the above non-heat treated aluminum alloy for die casting, the Ti content is in the range of 0.10 mass% to 0.20 mass%.

  In addition, when any one or both of B: 0.001% by mass to 0.10% by mass and Zr: 0.05% by mass to 0.30% by mass are added to the non-heat treated aluminum alloy for die casting, the content of Ti is The range is preferably 0.05% by mass to 0.20% by mass.

  The present invention also provides a high-vacuum die-casting method in which any one of the above-mentioned non-heat treated aluminum alloys for die-casting is used as a method for producing an aluminum die-cast product which exhibits high strength and high elongation and does not cause casting cracks A manufacturing method for casting is provided.

  The present invention also provides an aluminum die-cast product produced by the above-described method, exhibiting high strength and high elongation, and having no casting cracks.

  Finally, the present invention provides a suspension arm, a subframe or a suspension link part of an automobile, which is manufactured by the above-described method, exhibits high strength and high elongation, and has no casting crack.

  Below, the effect | action of each component of the alloy of this invention mentioned above and the reason of quantitative limitation are demonstrated. In the present specification, the description of the content means mass% unless otherwise specified. In addition, when a numerical range is shown, unless otherwise specified, the range includes both the minimum value and the maximum value.

  Si is effective in suppressing casting cracks during die casting, and improves mechanical strength, wear resistance, machinability, and vibration resistance. However, if the amount is less than 3.5% by mass, the effect is small, and if it exceeds 5.0% by mass, the Mg-Si-based intermetallic compound crystallizes in a large amount and the elongation decreases, so Si is in the range of 3.5% to 5.0% by mass. did.

  Mg is dissolved in the matrix of the aluminum alloy to improve the strength, and a part of the Mg is precipitated together with the coexisting Si by natural aging to improve the strength. However, if the amount is less than 0.35% by mass, the effect of improving the strength cannot be expected. If the amount is 2.5% by mass or more, the strength is increased, but at the same time the decrease in elongation is remarkable.

  Mn has the effect of suppressing seizure of the product to the mold during die casting, and granulates the needle-like Fe compound to suppress the decrease in elongation due to the Fe compound. However, if the amount is less than 0.3% by mass, a sufficient effect for suppressing seizure to the mold cannot be obtained.If the amount exceeds 1.5% by mass, a coarse Al-Mn intermetallic compound is crystallized, and elongation decreases. Is in the range of 0.3 mass% to 1.5 mass%. In consideration of the seizure to the mold, it is more preferable to contain 0.6% by mass or more.

  Fe is an impurity inevitably mixed in the aluminum alloy, but has an effect of preventing seizure of the die-casting mold. However, when the Fe content is increased, the amount of acicular Fe-based intermetallic compounds crystallized and the elongation and toughness are lowered. Therefore, the Fe content is set to 0.15% by mass or less.

Ti, B, and Zr each have the effect of improving the mechanical properties of the die casting by refinement of the primary α (Al) phase by themselves or by forming a compound. However, in the case of Ti alone, less than 0.10% by mass, and when Ti and B or Zr coexist, if Ti is less than 0.05% by mass and B is less than 0.001% by mass or Zr is less than 0.05% by mass, the effect is On the contrary, if Ti exceeds 0.20% by mass, or B exceeds 0.20% by mass and Zr exceeds 0.30% by mass, TiAl ₃ particles, TiB ₂ particles, or Al-Zr compounds become coarse and primary α (Al ) Since the effect of refining the phase is reduced, Ti is 0.20% by mass or less, or Ti: 0.05% by mass to 0.20% by mass and B: 0.001% by mass to 0.10% by mass.

  In the present alloy, elements other than the elements described above can be allowed as impurities because they do not adversely affect the present alloy if they are 0.5% by mass or less. However, although Cu has the effect of improving the strength, it significantly reduces the corrosion resistance, so it is necessary to suppress it to 0.2% by mass or less.

In the alloy according to the present invention, the mechanical properties and age hardening characteristics of the alloy vary depending on the ratio of the Mg content to the Si content. When there is more Si than the balance composition (Mg mass / Si mass = 1.73) that contains Mg and Si necessary to form Mg ₂ Si without excess or deficiency (Mg mass / Si mass is less than 1.73) ), The Si particles crystallized during solidification and the strength increased. Moreover, since the casting crack was suppressed by the increase in the Si content, the ratio of the Mg content to the Si content was set to 0.5 or less in order to ensure the strength and castability (control of the casting crack).

  In addition to the relationship between Mg content and Si content described above, if the Si content exceeds a certain amount, ductility decreases due to crystallization of Al-Si intermetallic compounds, so the ratio of Mg content to Si content. (Mg mass / Si mass) was 0.1 or more. This ratio is particularly preferably 0.15 or more.

  The aluminum alloy for die castings according to the present invention has the above-described composition, and provides sufficient strength by solid solution strengthening by adding Mg and Mn and precipitation strengthening by natural aging by adding Mg and Si, and at the same time against elongation. In addition to reducing harmful Fe within the specified limits and adding Mn to minimize the adverse effects of the Fe compound to ensure sufficient ductility, the reduction of Fe improves the seizure resistance to the mold. ing. Therefore, by using the aluminum alloy, an aluminum die cast product having high strength and elongation can be stably obtained without performing heat treatment such as solution treatment or artificial aging treatment after casting.

  Therefore, the non-heat treated aluminum alloy for die casting according to the present invention can be used to suitably cast a vehicle body part such as a suspension mounting portion such as a suspension arm of a car, a subframe or a link part of a suspension.

  Further, when casting these aluminum die-cast products using the non-heat treated aluminum alloy for die casting, it is desirable to use a high vacuum die casting method. That is, by applying the high vacuum die casting method, gas entrainment into the product is reduced, and an aluminum die cast product that makes the best use of the excellent mechanical properties, particularly elongation and toughness, of the alloy of the present invention can be obtained.

  The non-heat-treatable aluminum alloy for die casting according to the present invention contains Si, Mg, Mn, Fe, and Ti as alloy components in predetermined ranges, respectively, so that by solid solution strengthening by addition of Mg and natural aging after die casting is cast. Sufficient strength can be obtained, and at the same time, Fe, which is harmful to elongation, can be reduced as much as possible to ensure better ductility, and the addition of Ti refines the primary α (Al) phase. This provides an excellent effect that a die-cast product having high strength and elongation can be obtained.

  A more preferable non-heat treated aluminum alloy for die casting according to the present invention is the above-described non-heat treated aluminum alloy for die casting, wherein the Ti content is further limited to a range of 0.10 mass% to 0.20 mass%, and the primary crystal α (Al ) The phase can be further refined to obtain a die cast product having higher strength and elongation.

  Other non-heat-treatable aluminum alloys for die casting according to the present invention, the Ti content is limited to the range of 0.05 mass% to 0.20 mass%, and further contains 0.001 mass% to 0.10 mass% B in mass ratio, Still another non-heat-treatable aluminum alloy for die casting based on the present invention contains 0.05 mass% to 0.30 mass% of Zr in a mass ratio, thereby miniaturizing the primary α (Al) phase and providing high strength and elongation. You can get a product.

  The method for producing an aluminum die-cast product provided by the present invention can provide an aluminum die-cast product particularly excellent in elongation and toughness by using a high-vacuum die-casting method when casting the aluminum alloy.

  The aluminum die-cast product provided by the present invention is based on the above-described method for producing an aluminum die-cast product, and a die-cast product having excellent mechanical properties can be obtained without performing a solution treatment after die casting.

  The present invention will be specifically described below based on examples.

[Test 1]
An aluminum alloy having the composition shown in Table 1 was melted at 750 ° C., and then bubbling with argon gas was performed for the purpose of removing inclusions and degassing.

  Next, after the molten aluminum alloy material was naturally cooled to a temperature of 720 ° C., gravity casting was performed on an iron casting cracking evaluation mold having a shape as shown in FIG.

  Then, after gravity casting, these aluminums are cooled by cooling in the mold until the temperature of the obtained casting is about 100 ° C. or less, and by investigating the number of cracks generated at positions as shown in FIG. The performance (cast crack resistance) related to casting cracking of the alloy was evaluated. The result of arranging the number of cracks at this time with respect to the Si content in the alloy is shown in FIG.

  FIG. 3 shows that the number of cracks is suppressed and the cast crack resistance is improved as the amount of Si added is increased.

  According to FIG. 3, none of the embodiments of the present invention has any casting cracks. On the other hand, in Comparative Examples 1 and 2, a casting crack has occurred, indicating that there is a problem in castability. About Comparative Examples 3 and 4, since the casting crack has not generate | occur | produced, it can be said that it has favorable performance regarding castability. However, as will be described later, since Comparative Examples 3 and 4 are insufficiently stretched, it cannot be evaluated that the resulting cast material has desired characteristics.

[Test 2]
In the same manner as in the above-described examples, an aluminum alloy having the composition shown in Table 2 was melted at 750 ° C., and then an argon gas bubbling treatment was performed for the purpose of removing inclusions and degassing. The compositions of the examples shown in Table 2 are different from the compositions of the examples shown in Table 1, but the comparative examples 6 and 7 shown in Table 2 are the same as the comparative examples 3 and 3 shown in Table 1. Note that it is the same as 4.

  Next, using a high vacuum die casting machine with a clamping force of 320 tons and applying a powder release agent to the mold, casting pressure 60Mpa, high injection speed 3.5m, in-sleeve vacuum 0.96 atm, vacuum valve part Each aluminum alloy was die-cast under the conditions of a vacuum degree of 0.95 atm. The molten metal temperature during casting was 680 ° C., and the product shape of the mold used for casting was a flat plate of 50 mm × 130 mm × 2 mm.

  Thereafter, a JIS No. 13B tensile test piece was cut out from each of the above plate die-cast materials and subjected to a static tensile test.

The results of the above test are shown in Table 3.

  Table 3 shows that the aluminum die cast material using the alloy according to the present invention has excellent mechanical properties. This is due to solid solution strengthening due to the addition of Mg and Mn and strength improvement due to precipitation strengthening due to the addition of Mg and Si, while reducing Fe as much as possible and minimizing the adverse effects of Fe by adding Mn. This is thought to be due to an increase in elongation. Furthermore, the improvement of mechanical properties by adding Ti, Ti + B, or Zr was confirmed.

  Cast products made of aluminum alloys for die casting need to have a good balance between proof stress and elongation, especially considering the use of die casting products as automotive suspension arms, subframes or suspension link parts It is important that a yield strength of 120 MPa or more and an elongation of 10% or more are secured. Considering this point, all of the examples of the present invention shown in Table 3 have the necessary characteristics, and all of the comparative examples are excellent in yield strength but insufficient in elongation.

  FIG. 4 shows the results of the tensile test shown in Table 3 arranged in relation to the ratio between the amount of Mg contained and the amount of Si. As shown in FIG. 4, excellent strength and elongation were stably observed when the ratio of Mg amount to Si amount (Mg mass / Si mass) was in the range of 0.1 to 0.5. However, even within this range, it can be seen that the elongation is significantly reduced when the amount of Si exceeds 5% by mass.

  In FIG. 4, since the proof stress is 143 MPa and the elongation is 13.4%, the comparative example 5 seems to have the above-mentioned desired characteristics as far as these values are seen. However, Comparative Example 5 contains Si: 1.0 and Mg: 2.4, and the ratio of the amount of Mg and the amount of Si is 2.4. This value substantially corresponds to Comparative Example 1 in Table 1, and the result of the casting crack test shown in FIG. 3 shows that many casting cracks are generated in Comparative Example 5. Therefore, Comparative Example 5 also does not have desired characteristics.

It is a conceptual diagram which shows the casting_mold | template for casting crack evaluation. It is a conceptual diagram which shows the generation | occurrence | production state of a casting crack. It is a graph which shows the relationship between Si content in an alloy, and the number of casting cracks. It is a graph which shows the relationship between the ratio of the tensile test result and the amount of Mg contained and the amount of Si.

Explanation of symbols

10 Mold for casting crack evaluation 20 Cast crack

Claims (6)

  The mass ratio of Mg and Si contained is 0.1 or more and 0.5 or less, Si: 3.5 mass% to 5.0 mass%, Mg: 0.35 mass% to 2.5 mass%, Mn: 0.3 mass% to 1.5 mass%, Fe: 0.15 mass Non-heat-treatable aluminum alloy for die casting containing not more than%, Ti: 0.20% by mass or less, and remaining aluminum and inevitable impurities.    The non-heat-treatable aluminum alloy for die casting according to claim 1, wherein the Ti content is 0.10% by mass or more.    The mass ratio of Mg and Si contained is 0.1 or more and 0.5 or less, Si: 3.5 mass% to 5.0 mass%, Mg: 0.35 mass% to 2.5 mass%, Mn: 0.3 mass% to 1.5 mass%, Fe: 0.15 mass % Or less, Ti: 0.05% by mass to 0.20% by mass, and B: 0.001% by mass to 0.10% by mass or Zr: 0.05% by mass to 0.30% by mass, any one or two, and the balance aluminum and Non-heat treated aluminum alloy for die casting made of inevitable impurities.   The manufacturing method of the aluminum die-cast product which casts the non-heat-treatment aluminum alloy molten metal for die-casting as described in any one of Claim 1 thru | or 3 by a high vacuum die-casting method.   An aluminum die-cast product manufactured by the method according to claim 4.   6. The aluminum die-cast product according to claim 5, wherein the aluminum die-cast product is an automobile suspension arm, subframe or suspension link part.

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