JPH06158250A - Manufacture of aluminum alloy cast product having excellent mechanical characteristic - Google Patents

Abstract

PURPOSE:To manufacture an Al alloy cast product for automobile parts having the same degree of mechanical characteristic as a forged product in a low cost by using the Al alloy cast product as a blank and applying the specific forging work after applying the specific homogenizing treatment to this blank. CONSTITUTION:The Al alloy cast product is used as a blank and the homogenizing treatment is applied to the blank at 400-550 deg.C for >=1hr. By this treatment, solid solution is executed to the crystallized material generated at the time of casting to eliminate the segregation. Successively, to this blank, after heating at desirably about 350 deg.C, the forging work having >=30% cross sectional reducing ratio is applied. By this forging work, the internal defect in the cast blank is eliminated and also, the mechanical characteristic of strength, elongation, toughness, etc., is improved. Thereafter, heat treatment of solid solution treatment, tempering, etc., according to the demanded performance of this finish product is applied to this product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automobile brake parts,
Regarding the manufacturing method of cast aluminum alloy products used for underbody parts, etc., more specifically, aluminum for automobile parts having excellent mechanical properties, especially elongation and toughness, compared to conventional cast aluminum alloy products and having performance equivalent to that of forged products. The present invention relates to a method for manufacturing an alloy casting product.

[0002]

2. Description of the Related Art In automotive parts,
Aluminum and aluminum alloys are being used for the purpose of weight reduction, and aluminum alloys are also widely used for underbody parts that used to use iron-based materials to reduce unsprung weight. . Conventionally, as a material satisfying the requirements, a 6000 series wrought alloy, particularly JIS 6061, 6N, which has relatively good corrosion resistance and excellent workability.
01 alloy is often used and is manufactured by forging in order to obtain high strength and high toughness necessary for important safety parts. However, as a material for these forged products, usually, an extruded material cut into an appropriate length is often used,
Since many steps such as preforming, rough punching, and finish punching are performed, there are drawbacks that the yield is low and the manufacturing cost is high.

On the other hand, aluminum alloy castings are used in a considerable proportion in automobile parts because they can be manufactured in complex shapes at low cost. Al as a casting alloy
-Cu- (Si) -based AC1B, AC2B, Al-Si
There are AC3A, etc. of the system, but from the viewpoint of high strength, high toughness, and corrosion resistance, a small amount of Mg is added to the Al-Si base having good castability to improve heat treatment effect and improve mechanical properties of Al-Si- Cast alloys such as Mg-based AC4C and AC4CH are often used. However, these casting alloys have many internal defects during casting, and their strength level is lower than that of forged products, making it difficult to obtain stable performance. At present, it is limited to members with low required strength. With the recent trend toward aluminum in automobiles, weight reduction efficiency and cost reduction are indispensable. Therefore, it is strongly desired to develop a casting material that has performance equivalent to that of a forged product and that can reduce cost.

In order to satisfy this requirement, a forging material is cast from an Al--Cu alloy, an Al--Cu--Si alloy, or an AC4H alloy having an increased amount of Cu and Mg.
Next, a method is known in which the mechanical properties are improved by forging this forging material, but compared to extruded rods and extruded shapes of 6000 series wrought alloys that are normally used as hot forging materials, forging cracks. In addition to the fact that the degree of processing cannot be increased because it is liable to occur, and the mechanical properties after forging are low, the degree of freedom in designing parts is small.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and an object of the present invention is to provide an automobile having mechanical characteristics equivalent to those of a forged product and lower in cost than the forged product. It is to provide a method for manufacturing an aluminum alloy casting product for parts.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventors have conducted various studies on a method for improving performance by forging a casting material in order to improve forgeability and performance after forging. , It has been found that segregation of additional elements due to crystallized substances generated during casting of casting material deteriorates forgeability. As a result of intensive studies on a method for eliminating this segregation, the present invention has been completed.

That is, the present invention uses an aluminum alloy casting product as a material, and the material is used at a temperature of 400 to 550 ° C.
This is a method for producing an aluminum alloy casting product having excellent mechanical properties, which comprises performing a homogenizing treatment for not less than time and then performing a forging process with a cross-sectional reduction rate of 30% or more.

[0008]

The homogenization treatment is carried out in order to dissolve the crystallized substances formed in the casting product during casting to eliminate segregation, and the conditions are limited to 400 to 550 ° C. for 1 hour or longer. The reason is that if the temperature is lower than 400 ° C, the crystallized substances generated during casting may not be solid-dissolved and the material may not be homogenized. If the temperature exceeds 550 ° C, the product may melt. is there. If the time is less than 1 hour, homogenization will not proceed sufficiently.

Further, the reason why the cross-section reduction rate during forging is limited to 30% or more is that if the cross-section reduction rate is less than 30%, not only the strength improving effect due to work hardening cannot be obtained, but also the above-mentioned internal defects of the casting It is not preferable because it cannot be erased and the effect of improving elongation value and toughness cannot be obtained.

The performance of the aluminum alloy cast product of the present invention does not change particularly depending on the forging temperature, and is not particularly limited. However, forging cracks can be prevented by preferably heating to 350 ° C. or higher and then forging. .

The aluminum alloy cast product of the present invention is heat-treated according to the required performance of the final product, but the heat-treatment conditions are not particularly limited. That is, according to the alloy applied to the aluminum alloy casting product according to the present invention, JIS
Strength, elongation and toughness can be considerably improved by applying solution treatment and tempering conditions specified in the standard.

As the alloy applicable to the aluminum alloy casting product of the present invention, Al--Cu type alloy, Al--Si--Cu
Examples of the alloys include Al alloys and Al-Si-Mg alloys.

[0013]

EXAMPLES The present invention will be described in detail below based on examples. An alloy in which Cu is added to an alloy having a composition equivalent to JIS AC4CH standard (Al-7% Si 0.15% Fe-0.35
% Mg-2.00% Cu-0.1% Ti) was melted, and then cast-forged test pieces were sampled in a model die of 30 mmφ × 100 mml. Next, this forging test piece is shown in Table 1.
The sample was homogenized for 1 hour at various homogenizing temperatures shown in Table 1, forged at the cross-section reduction rate shown in Table 1, and visually checked for forging cracks. Then, the tensile test piece and the Charpy test piece were collected from the test piece that could be forged, and the tensile strength,
The Charpy impact value, which is an index value of proof stress, elongation value, and toughness, was measured. The results are shown in Table 1.

[0014]

[Table 1]

As is apparent from Table 1, the invention examples Nos. 1 and 2 which have been subjected to the homogenizing treatment and the forging process according to the method of the present invention have a considerably improved mechanical property, particularly the elongation value and the toughness value. . On the other hand, it can be seen that Comparative Examples Nos. 3 and 4 in which the cross-section reduction rate during forging or the homogenization treatment temperature is out of the range of the present invention, the degree of improvement in elongation and toughness is small. In addition, Comparative Example No. which was homogenized at 600 ° C. No. 5 melted, could not be forged, and Comparative Example No. 6, which was not homogenized, had large cracks during forging, and its mechanical properties could not be measured.

[0016]

As described above, according to the present invention, a casting product having excellent mechanical properties such as elongation and toughness can be obtained as compared with the conventional aluminum alloy casting product. It can be used as an underbody component requiring high toughness and a brake component requiring pressure resistance, and has industrially remarkable effects such as a performance equivalent to a forged product and a reduction in manufacturing cost.

Claims (1)

[Claims] 1. An aluminum alloy casting product as a material,
Manufacture of an aluminum alloy casting product excellent in mechanical properties, characterized by subjecting the material to homogenization treatment at a temperature of 400 to 550 ° C. for 1 hour or more, and then forging with a cross-section reduction rate of 30% or more. Method.