JP2002302730A - Aluminum cast-forged product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum cast-forged product having large tensile strength, 0.2% proof-stress and elongation, equal to or better than mechanical those of the conventional one, and excellent in corrosion resistance and for which the unused raw material for forging can be reused and which can be obtained with simpler producing process at a low cost. SOLUTION: An aluminum alloy for spreading is used as raw material and the weight ratio of contained copper is made small to suppress oxidizing deterioration and corrosion, and the low-cost aluminum product is cast-forged after performing a product in a shape similar to the finish product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aluminum casting and forging used for parts for vehicles and the like. More specifically, wrought aluminum alloy is used as a raw material, and it is made by forging after casting, and has excellent corrosion resistance and mechanical properties. Aluminum castings and forgings used for vehicle suspension parts.

[0002]

2. Description of the Related Art It is said that global warming, which is one of the global environmental problems, has a great influence on carbon dioxide in all human activities, and the reduction of carbon dioxide emitted from factories and power plants worldwide. Therefore, there is a strong demand for reducing the consumption of fossil fuels that generate carbon dioxide. At the Third Conference of the Framework Conventions on Climate Change held in Kyoto in 1997, the so-called Global Warming Prevention Conference COP3, Japan reported that greenhouse gas emissions mainly occupied by carbon dioxide were 2008-2012.
It promises to reduce the average year by 6% compared to 1990.

[0003] Based on the results of this meeting, target reference values for vehicle weight categories have been set for the fuel efficiency of automobiles, with the target year of 2010 for gasoline engines and 2005 for diesel engines. Also, tax measures have been taken to prefer low-emission vehicles and fuel-efficient vehicles. Therefore, in the future, as well as improving the understanding of environmental issues for car buyers and users, car manufacturers will promote the development of technologies for improving fuel efficiency and endeavor to develop vehicles with excellent fuel efficiency. It is thought that it is strongly required. In addition, competition among traders has intensified as automobile buyers' awareness has increased, and in order to overcome this, the development of fuel efficiency improvement technology has become more important.

[0004] Measures for improving fuel efficiency of automobiles include fuel cells,
Use of new power sources such as natural gas and electricity, or their hybrid use, or technical improvement of motor systems such as lean fuel engines and direct injection engines, and further improvement of loss in power transmission systems, Although there is a reduction in running resistance by improving the outer shape of the vehicle body, etc., the most effective is the reduction of the weight of the vehicle that can be used in combination with any other technology. If the vehicle itself is reduced in weight, the load on the power source is reduced, and the amount of fuel used can be reduced regardless of the power source.

In addition, since the weight reduction of the undercarriage of the automobile contributes to the improvement of the driving operability and the feeling of ride of the automobile, the undercarriage parts of the vehicle have a higher priority in the weight reduction. High target.

In general, when trying to reduce the weight of an automobile,
We face the challenge of improving costs. Lightweight technologies can be broadly divided into structural design technology and material technology.However, compared to the fundamental improvement of the body structure and structural components, which are structural design technologies, it is necessary to respond to the material technology, that is, change the materials used. It is said that it is easier to work on lighter.
However, these lightweight materials are generally expensive. Examples of the lightening material include resin materials such as FRP, thinning of iron by using high-tensile steel sheets, aluminum alloys, magnesium alloys, titanium alloys, ceramics, metal composite materials, and intermetallic compounds. Aluminum alloys have the lowest weaknesses such as corrosion resistance and are more expensive than iron, but among the lighter materials, aluminum alloys are easier to apply at lower cost.

[0007] Aluminum alloy has a density of about 1/3 that of iron, and cast products that are easier to manufacture are already used for engine cylinder heads, engine cylinder blocks, and the like. These castings are manufactured by high-speed injection molding, a so-called die-casting method, and have good production efficiency and can be manufactured at a relatively low cost. Inevitable,
It cannot have high mechanical strength. As described above, it is difficult to apply a cast product manufactured by a die-casting method to a suspension component that is required to be reduced in weight, because damage due to insufficient strength is directly linked to an important problem related to safety. There was a problem.

In the case of undercarriage parts, for example, a lower arm and an upper arm of a wishbone suspension, a knuckle arm that operates a tire in conjunction with a steering wheel, etc., even if the installation location is in a vehicle body, the vehicle is wet with rainwater that jumps off a road surface. There are many. In addition, during traffic jams, the vehicle is constantly in contact with exhaust gas discharged from surrounding vehicles, and is constantly exposed to a corrosive atmosphere during operation. Therefore, as a material condition of a vehicle's undercarriage parts, it is necessary to withstand a severe use environment and to have a low corrosiveness in order to maintain the safety of the vehicle for a long period of time. It is required to have sufficient properties of elongation and elongation, few defects, and lighter weight. Conventionally, A6
061 alloy forgings and AC4CH alloy squeeze castings (low-speed injection moldings) are already used in some cases, but these have not solved the problem of high cost.
At present, the application is extremely limited.

The reason why the so-called pure aluminum forged product such as the conventional A6061 alloy forged product is expensive is that the number of forging steps is large, the raw material for forging itself is expensive, and furthermore, during the forging process, And high cost forging raw materials are not efficiently formed into forged products due to waste such as burrs. Further, even with a squeeze cast product, the number of steps is large and the injection speed is low, so that productivity cannot be improved and cost reduction cannot be achieved.

As described above, in order to reduce the weight of a vehicle component, especially a suspension component, even if it is used in a corrosive atmosphere, it will not rust, deform or break for a long time. There has been a demand for lower cost aluminum products, but various improved aluminum alloys have been proposed as materials for manufacturing such aluminum products. According to JP-A-5-59477, coarsening of crystal grains is suppressed by adjusting components,
Forging aluminum alloys having excellent mechanical properties have been proposed. 1.0-1.5% by weight of silicon, 0.8-1.5% by weight of magnesium, 0.4-0.9% by weight of copper, 0.2-0.6% by weight of manganese, 0.3-% of chromium
It is said that the composition is adjusted to be a component containing 0.9% by weight and the like to improve the strength of the matrix and to suppress the coarsening of crystal grains, thereby realizing a tensile strength of 40 kgf / mm ² .

[0011] However, although the strength is improved in this proposal, the manufacturing method does not change and the cost is reduced only by changing the components of the conventional forging raw material.
Since it contains more copper than the conventional raw material for forging (A6061 alloy), its corrosion resistance is reduced, and there is a problem in applicability to vehicle suspension parts.

According to Japanese Patent Application Laid-Open No. 7-258784, an aluminum alloy material for forging having excellent castability and high strength has been proposed. 0.8-2.0 wt% silicon, 0.5-1.5 wt% magnesium, 0.5-1.0 wt% copper, 0.4-1.5 wt% manganese, 0.1-chromium
Using a melt of an aluminum alloy material adjusted to be a component containing 0.3% by weight and the like, a continuous casting is performed while controlling a cooling rate in a solidification process, then a soaking treatment is performed, and then a hot forging is performed. The aluminum alloy forged product obtained by solution treatment and further aging treatment, when casting into a shape close to the final product, has a casting crack that has occurred when using the conventional A6061 alloy as a raw material. It does not happen.

[0013] Also in this proposal, although the castability has been improved, the conventional forging raw material (A60
61 alloy), the manufacturing process is equivalent or rather complicated and does not lead to low cost. In addition, since it contains more copper, its corrosion resistance is reduced. Anxiety remained.

Furthermore, according to Japanese Patent Application Laid-Open No. 8-3675, a low-cost aluminum alloy for forging having excellent mechanical properties is proposed. 0.6-3.0% by weight of silicon;
0.2-2.0% by weight of magnesium, 0.3-1.0% of copper
Wt%, manganese 0.1-0.5 wt%, chromium 0.1
0.5% by weight, etc., and 1.5% of Mg ₂ Si
By forging an aluminum alloy whose composition has been adjusted to be not less than 10% by weight at an upsetting ratio of 10 to 50%,
No hot cracking occurs during casting, and strength can be improved after forging.

According to this proposal, at the time of casting, it can be formed into a shape close to the final product, and can be forged without the extrusion process.
Although the production cost is reduced, if the content of easily oxidizable copper is reduced to 0.3 to 0.5% by weight, the tensile strength and the 0.2% proof stress decrease, and after forging. Has a problem that the strength is lower than the standard value of A6061FD which is a conventional forged product.

[0016]

SUMMARY OF THE INVENTION As described above, as efforts to regulate and reduce carbon dioxide emissions have become active internationally, there has been an increasing demand for improving fuel efficiency of automobiles. Of aluminum alloys using relatively low-cost aluminum alloys among other materials, while maintaining high mechanical strength and excellent corrosion resistance, further reducing costs and applying it to various automotive suspension parts However, a suitable aluminum product has not been proposed.

The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to solve the problems of the conventional technology. More specifically, it has high tensile strength, 0.2% proof stress, and large elongation, has mechanical properties equal to or higher than conventional forged products, and has excellent corrosion resistance.
An object of the present invention is to provide an aluminum casting forged product which can reuse unnecessary forging raw materials and has a simpler manufacturing process and lower cost. The object of the invention is to apply the cast aluminum forged product to undercarriage parts of automobiles and the like to reduce fuel consumption, reduce carbon dioxide emissions, and contribute to environmental measures such as prevention of global warming.

The inventors of the present invention have conducted various studies on the raw materials and manufacturing methods of aluminum thick-walled products in order to solve the above-mentioned problems. The above-mentioned object can be achieved by providing a low-cost forged aluminum casting product through a preform molded product that is formed into a shape that is not too close to the final product shape by suppressing oxidative deterioration and corrosion. Was found.

[0019]

That is, according to the present invention, Al—Mg—Si is produced by casting and then forging.
A cast aluminum forged product containing a wrought aluminum alloy as a raw material, containing 0.1 to 0.4% by weight of copper, a tensile strength of 300 N / mm ² or more, and a 0.2% proof stress of 260 N / An aluminum casting and forging is provided, which has an elongation of 10% or more and a mm ² or more. This aluminum casting and forging can be suitably used as a vehicle suspension part.

Further, when the final shape of the aluminum cast and forged product is 100%, the working ratio is 18 to 60%.
Thus, there is provided a preform molded article which is cast as follows. Through this preform molded product, it is possible to suitably produce a vehicle suspension component as a final product.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of an aluminum cast and forged product of the present invention will be specifically described, but the present invention is not construed as being limited to these, and the scope of the present invention is not limited thereto. Various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the present invention.

The present invention is directed to a preform molded product in which an Al—Mg—Si-based aluminum alloy material for spreading is used as a raw material, and the raw material is melted and cast to have a working ratio of about 18 to 60% of the final product. And an aluminum cast forged product produced through a forging process.

The present invention is directed to an aluminum casting and forging product, wherein copper, which is easily oxidized among trace metals contained therein, is 0.1 to 0.1%.
0.4% by weight to improve corrosion resistance, tensile strength is 300N / mm ² or more, 0.2% proof stress is 260N
/ Mm ² or more and an elongation of 10% or more. The content of copper is preferably 0.1 to 0.2% by weight because corrosion resistance is further increased. The tensile strength is preferably 34.
0 N / mm ² or more, 0.2% proof stress is preferably 310 N
/ Mm ² or more, and the elongation is preferably 11% or more.
In addition, the tensile strength of the cast aluminum forged product of the present invention, 0.
The mechanical properties of 2% proof stress and elongation are based on Japanese Industrial Standard Z2.
It is determined according to the test method specified in 201. By suppressing the content of copper that contributes to strength but easily induces rust, such high strength has been realized, and undercarriage parts of automobiles used under corrosive atmosphere, for example,
It has become possible to use it suitably for parts of suspension systems and steering systems. Important parts around the foot, such as the lower arm and upper arm of the front wishbone suspension, the trailing arm of the rear swing arm suspension, the knuckle arm that operates the tire in conjunction with the steering, etc. By applying the costly aluminum cast and forged product of the present invention, the weight of the vehicle can be further reduced.

Hereinafter, the cast aluminum forged product of the present invention will be specifically described. The present invention uses an Al-Mg-Si-based wrought aluminum alloy, that is, an alloy of the 6000 series as a raw material, and keeps the copper content low. For example,
A6061 alloy suitably used for conventional forging can be used as a raw material. According to Japanese Industrial Standard H4040, the component standard of A6061 alloy is aluminum as a main component and other trace metals such as 0.4 to 0.8% by weight of silicon, 0.7% by weight or less of iron, and 0.8 to 0.8% of magnesium. 1.
2% by weight, copper 0.15 to 0.4% by weight, chromium 0.04
An alloy containing about 0.35% by weight. It can be said that it is an alloy material that has less copper that is easily oxidized and has sufficient corrosion resistance.

[0025] By containing copper,
It is an element that can improve strength. In a forged product containing copper, an Al-Cu or Al-Cu-Mg-based precipitate expressed by a so-called aging treatment, which is allowed to stand at room temperature after cooling and precipitate crystals over time, can be obtained. these by, in Al-Mg-Si alloy, the strength is improved by promoting the strength improving effect of Mg ₂ Si to precipitate. In the present invention, since it is necessary to have a strength higher than that of a conventional forged product, it is preferable to contain copper. However, for example, in consideration of application to products in which corrosion resistance is important, such as undercarriage parts of automobiles, copper which is easily oxidized is liable to be corroded when added too much, so that it may be contained in a small amount. It is important.

Copper is present in aluminum cast forgings in an amount of 0.1%.
It is preferable to contain 1 to 0.4% by weight. If the content of copper is less than 0.1% by weight, it does not contribute to the improvement of strength. If the content is more than 0.4% by weight, corrosion resistance is reduced and rust easily occurs, and strength is maintained for a long time under severe use conditions. It is not preferable because it becomes impossible.

In the present invention, since the wrought aluminum alloy is used as a raw material and then melted and cast, the raw material is, for example, a conventional raw material for forging, and a large amount of unnecessary raw material generated in a normal forging process. Burrs can be reused. Conventionally, burrs generated from the forging process are only recovered and reused as inexpensive ingots for castings, and have not been recycled as more expensive forging raw materials. In the present invention, unnecessary burrs generated from the forging process, which are approximately 30% of commonly used raw materials, are recycled as forging raw materials, thereby reducing raw material costs and reducing the cost of aluminum cast forged products. Has been realized.

Next, a method for manufacturing an aluminum cast forged product of the present invention will be described. As described above, it is possible to use unnecessary burrs that always occur during normal forging as a raw material, and it is preferable to use burrs as a raw material because it contributes to reduction in manufacturing cost. This raw material is a wrought aluminum alloy containing 0.1 to 0.4% by weight of copper.

This raw material is put into a melting furnace,
The mixture is heated to 780 ° C. to be melted, and then placed in a holding furnace and subjected to a degassing treatment and a deoxidizing treatment to obtain a molten metal. Then, a die is formed from the molten metal using a casting apparatus to obtain a forging material. At this time, the temperature of the mold is preferably adjusted to about 60 to 150 ° C.

Next, the forging material obtained by die molding using a casting apparatus is heated to a surface temperature of about 380 to 520 ° C., and is stamped by a forging press to obtain a rough forged product.

Then, after cooling the rough forged product, it is heated again to a surface temperature of about 380 to 520 ° C., and is subjected to finish stamping by a forging press to obtain a finished forged product. This finished forged product is trimmed and subjected to a heat treatment such as T6 treatment to be a forged product. The aluminum casting forging of the present invention is obtained by such a manufacturing process. The load of the forging press is, for example, approximately 2600-in rough forging in the case of a knuckle arm which is a vehicle suspension part.
It is 2800 tons and approximately 3200 to 3800 tons by finish forging.

In the present invention, burrs generated by the forging press and trimming during the manufacturing process of the present invention can also be collected by the deburring machine and reused again as a raw material of the aluminum casting and forging of the present invention. It is possible. Therefore, they are all recycled and do not become waste or inexpensive raw materials for casting.

In the method for manufacturing an aluminum cast forged product according to the present invention, in a casting performed after melting a raw material to obtain a molten metal, when a shape of a casting mold is set to 100% of a shape of a final forged product. In addition, it is preferable that the processing rate is approximately 18% to 60%. This is because the subsequent forging sufficiently improves the strength and can further simplify the forging process. That is, this processing rate is generally set to 18 to 60.
By setting the percentage, the balance between the strength improvement effect by forging and the cost reduction by simplifying the forging process is maintained. Here, the processing rate is a value representing the degree of processing, for example,
When the material A having the initial thickness D1 as shown in FIG. 3 is processed by the load F and becomes the thickness D2 after the processing, the processing rate R is represented by the following equation. R [%] = (D1−D2) / D1 × 100 (D1> D2) However, when the thickness D2 after processing is thicker, it is expressed by the following equation. R [%] = (D2−D1) / D1 × 100 (D2> D1) That is, in the present invention, when the final shape of the aluminum cast forged product is 100%, the working ratio is approximately 18 to 60%.
The preform molded product that is cast so that the final product is obtained by forging the preform molded product, and the thickness of each part of the preform molded product and the thickness of each corresponding portion in the final product Is to obtain a preform molded product having a shape such that the processing rate obtained by the above is approximately 18 to 60% in each part.

In the present invention, for example, undercarriage parts of automobiles and the like in which the use environment is not always good are used as final products, and it is of the highest priority that the mechanical strength and corrosion resistance are higher than those of conventional forged products. . For this reason, castability, that is, fluidity and shrinkage cavities are not superior to those of the original casting material. Therefore, in the process of obtaining a material for forging by casting, too much emphasis is placed on improving the efficiency of the manufacturing process, and when molding with a mold having a shape too close to the final product, defects such as cracks and pinholes are likely to occur. However, it is difficult to improve the strength by the subsequent forging effect, which is not preferable. Therefore, it is preferable to suppress the processing rate to the above.

In the method for manufacturing an aluminum cast forged product of the present invention, after the raw material is melted to obtain a molten metal, the working ratio of the casting mold when the shape of the final forged product is set to 100% is as follows: Since the shape is approximately 18 to 60% and the effect of improving strength by forging is obtained, the shape of the product is made closer to the shape of the product than the conventional raw material for forging, and it is easy to press. In addition, the manufacturing process is simplified as compared with processes such as extrusion, cutting, heating, rough forging, rough forging, finish forging, and trimming, thereby reducing the manufacturing cost.

[0036]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited to these examples. (Examples 1-4) Under the same conditions except that the content of copper was changed, four aluminum cast forgings were produced,
Each mechanical strength was measured. FIG. 1 is a diagram illustrating a knuckle arm which is a manufactured aluminum forged product. FIG. 1A is a top view of a knuckle arm preform molded product 21, and FIG. 1B is a top view of a knuckle arm product 22. By reducing the weight of such shaped parts at low cost and applying them to automobiles, fuel efficiency can be improved.

[0037] A scrap mainly composed of A6061 alloy burr was prepared and melted at a melt temperature of 730 ° C.
An Al-Cu master alloy was added into the furnace to reduce the copper content to 0.2.
A melt adjusted to 9% by weight was obtained. Based on this, a knuckle arm was manufactured as follows. In addition, the copper content was measured by an emission spectrometer. Thereafter, assuming that the shape of the final knuckle arm product 22 is 100%, a knuckle arm preform molded product 21 having a mold with a processing rate of 20 to 30% as compared with this is molded at a mold temperature of 100 ° C. . Next, the knuckle arm preform molded product 21 is subjected to a rough forging temperature of 400 ° C. (surface temperature).
A rough forging product was obtained by stamping by applying a rough forging load of 2800 tons by a forging press. Next, after cooling, the rough forged product was stamped again at a finish forging temperature of 460 ° C. (surface temperature) with a finish forging load of 3,200 tons by a forging press.
Finally, the shape was adjusted by trimming, heated at 520 ° C. for 3 hours (T4 treatment), cooled, and further heated at 180 ° C. for 6 hours (T6 treatment) to obtain a knuckle arm product 22 as a final product.

As the mechanical properties of the knuckle arm product 22 obtained, tensile strength, 0.2% proof stress, and elongation were measured. Test pieces were cut out from the manufactured knuckle arm products 22 at the test piece collection positions 41 to 43 shown in FIG. 2, and the mechanical properties of each were measured. Table 1 shows the results. In Examples 2 to 4, the content of copper was 0.29% by weight, which was the same as that of Example 1, and 0.15%, which was different from that of Example 1.
The knuckle arm product 22 was manufactured in the same manner as in Example 1 by adjusting the weight% and the weight to 0.40% by weight, and the same test was performed. Table 1 shows the results.

[0039]

[Table 1]

All the test pieces of the four products (Examples 1 to 4) had mechanical properties of tensile strength, 0.2% proof stress,
In the elongation, a value equal to or higher than the standard value of A6061FD-T6 according to Japanese Industrial Standard H4040 manufactured by the conventional forging process was secured. The range of mechanical properties obtained is generally as follows: tensile strength of 305 to 350 N / mm ² , 0.2% proof stress of 260 to 320 N / mm ² , elongation of 10 to 19%, and the aluminum casting of the present invention. It was confirmed that the forged product had higher mechanical strength than the conventional forged product.

[0041]

As described above, according to the present invention, tensile strength, 0.2% proof stress, and elongation are large, and have mechanical properties equal to or higher than those of conventional forged products, and corrosion resistance is improved. It is possible to provide a low-cost aluminum casting forging, which is excellent in that it can reuse unnecessary forging product raw materials, has a simpler manufacturing process, has good productivity, and has low productivity. And, as this aluminum cast forged product, for example, a lightweight vehicle suspension part is provided, so that the fuel consumption of the vehicle and the like is reduced, and the carbon dioxide emission is reduced, thereby contributing to the prevention of global warming. It works.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of an aluminum casting and forging product of the present invention. FIG. 1 (a) is a top view of a preform molded product, and FIG. 1 (b) is a top view of a final product. .

FIG. 2 is an explanatory view showing a test piece sampling position in a mechanical strength measurement of an aluminum casting and forging of the present invention.

FIG. 3 is a cross-sectional view of a forging material for explaining a working ratio.

[Explanation of symbols]

21: Knuckle arm preform molded product, 22: Knuckle arm product, 41, 42, 43 ... Test piece sampling position.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/047 C22F 1/047 // C22F 1/00 612 1/00 612 630 630A 630K 640 640A 683 683 694 694A F-term (reference) 3D001 AA17 AA18 DA04 3D034 BC26 4E087 AA10 BA04 BA24 HA81

Claims (4)

[Claims] Claims: 1. An aluminum alloy forged after being cast and then forged.
A cast aluminum forged product containing a g-Si based aluminum alloy for expansion as a raw material, containing 0.1 to 0.4% by weight of copper, a tensile strength of 300 N / mm ² or more, and a 0.2% proof stress. Is 26
An aluminum cast forged product characterized by having an elongation of at least 0 N / mm ^{2 and at} least 10%. 2. The forged aluminum casting according to claim 1, which is used as a vehicle suspension part. 3. When the final shape of the cast aluminum forged product according to claim 1 is 100%, the working ratio is 1%.
A preform molded product cast to 8 to 60%. 4. The preform molded product according to claim 3, wherein the product having the final shape is a vehicle suspension component.