JP2002302729A - Aluminum cast and forged article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost aluminum cast and forged article which has excellent mechanical properties applicable to various automobile parts including suspension parts. SOLUTION: The aluminum cast and forged article is produced by undergoing forging after casting, and is used as parts for vehicles. The ratio in thickness between the thick part and the thin part is (3:1) to (10:1), and the thick part has no defects. The aluminum cast and forged part contains, by weight, 0.4 to 0.8% silicon, 0 to 0.7% iron, 0.8 to 1.2% magnesium, 0.15 to 0.4% copper and 0.04 to 0.35% chromium.

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, it relates to an aluminum cast forged product having excellent mechanical properties, which is used for vehicle undercarriage parts which are required to be reduced in weight in order to improve fuel efficiency of automobiles, and which is manufactured by forging after forging a raw material for forging. .

[0002]

2. Description of the Related Art It is said that global warming, which is one of the global environmental problems, has a great effect on carbon dioxide in all human activities. Therefore, reduction of carbon dioxide emitted from factories and power plants, There is a strong demand worldwide for reduction of fossil fuel consumption which causes odor. 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 this, the fuel efficiency of automobiles is calculated as follows:
With 2005 as the target year, target reference values for each vehicle weight category were determined. In addition, tax measures have been taken to favor low-emission vehicles, that is, fuel-efficient vehicles. In the future, with the improvement of car buyers and users' understanding of environmental issues,
There is a strong demand for automobile manufacturers to promote the development of technologies for improving fuel efficiency and to develop vehicles with excellent fuel efficiency. In addition, competition between dealers has become more intense as the awareness of car buyers has increased, and in order to overcome this,
Development of fuel efficiency improvement technology becomes 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 it is possible to reduce the amount of fuel used in any power source.

[0005] Furthermore, since the weight reduction of the undercarriage of the automobile contributes to the improvement of the driving operability and the feeling of riding of the automobile, the undercarriage parts have a higher priority in the weight reduction. Can be a high target.

When reducing the weight of an automobile, there is a problem to be improved, that is, an increase in cost. Lightweight technology is broadly divided into structural design technology and material technology. Compared with the fundamental improvement of the body structure and components, which are structural design technologies, responding to material technology, that is, changing the materials used is an easier approach to reducing weight, but these materials are generally expensive. is there. Lightening materials 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, intermetallic compounds, etc. Aluminum alloys are less expensive and more expensive than iron, but are more easily applied at lower cost among lightweight materials.

[0007] Aluminum alloys have a density of about 1/3 that of iron, and castings that are easier to manufacture are already widely 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. And cannot have high mechanical strength. As described above, it is difficult to apply a cast product manufactured by the die-casting method to the undercarriage parts for which weight reduction is demanded, 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, and a knuckle arm that operates a tire in conjunction with a steering, a shape required from a functional aspect is rich in unevenness, and a thick part and a thin part are required. There is a part, and the shape is not always preferable in obtaining strength. However, as described above, a reduction in weight is required in the future. Therefore, materials with low corrosiveness, sufficient strength and elongation characteristics, and few defects that can withstand harsh use environments and overcome the disadvantages in shape are suitable for materials such as undercarriage parts of vehicles. Becomes Conventionally, A6061 alloy forgings and AC4C
H alloy squeeze castings (low-speed injection molded products) and the like have already been partially used. However, these have not solved the problem of high cost, and their application is currently extremely limited.

The reason that a so-called pure aluminum forged product such as a conventional A6061 alloy forged product is expensive is that the number of forging steps is extremely large in order to produce a product in which a thick portion and a thin portion are mixed. And the cost of the forging raw material itself is high. 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 the shape is rich in irregularities and has a thick portion and a thin portion, the shape can be maintained for a long time. There is a need for lower cost aluminum products that do not deform, break, or corrode.

According to Japanese Patent Application Laid-Open No. 7-227639, a method for manufacturing a forged product is proposed in which a material having a non-approximate shape is formed by casting, and then a forged product is formed. . With the road wheel as the final product, the thickness ratio between the cast material and the forged final product is determined, and under these conditions, the effect of forging is fully exhibited, and improvement in strength and surface quality is realized. .

[0012] However, although the strength has been improved, the problem is mainly solved for the vehicle wheel.
There is no description about the shape and thickness of the product, and there is a lack of applicability to underbody parts such as the knuckle arm and upper arm which are more disadvantageous in obtaining strength.
Further, cost reduction has not been achieved.

[0013]

As described above, as efforts to regulate and reduce carbon dioxide emissions become active internationally, demands for improving fuel efficiency of automobiles have increased, and lightweight aluminum alloys have been used. It has been demanded that the used aluminum product can be applied to various vehicle suspension parts, but no suitable aluminum product has been proposed.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to solve the problems of the conventional technology. More specifically, it is an object of the present invention to provide a low-cost aluminum casting and forging product having mechanical properties applicable to a suspension component mainly to various automobile components, and at the same time. 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 processed products in order to solve the above-mentioned problems. The above object can be achieved by providing a low-cost aluminum casting forging having excellent corrosion resistance, high tensile strength, proof stress, high elongation, and having mechanical properties equal to or higher than conventional aluminum forgings. I found that.

[0016]

That is, according to the present invention, there is provided an aluminum cast forged product used as a vehicle component, which is manufactured by forging after casting, wherein the thickness of a thick portion and a thin portion is reduced. An aluminum casting forging having a ratio of 3: 1 to 10: 1 and having no defect in a thick portion is provided.

In the cast aluminum forged product of the present invention, silicon is 0.4 to 0.8% by weight, iron is 0 to 0.7% by weight, magnesium is 0.8 to 1.2% by weight, and copper is 0.15 to 0.15%.
Preferably, it contains 0.4% by weight and 0.04 to 0.35% by weight of chromium. Further, it is preferable to use an aluminum alloy for forging as a raw material.

Further, according to the present invention, there is also provided a preform molded product which is cast such that the working ratio is 18 to 60% when the final shape of the aluminum forged product as described above is 100%.

[0019]

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 uses an aluminum alloy material for forging as a raw material, melts the raw material, casts the raw material, obtains a preform molded product having a working ratio of about 18 to 60% of the final product, and performs a forging process. This is a cast aluminum forged product.

The present invention relates to an aluminum forged product, wherein a ratio of a thickness of a thick portion to a thickness of a thin portion is 3: 1 to 10: 1.
It is characterized by having no defect in the thick part. By realizing such a shape and quality, it has become possible to suitably use it for parts of a suspension system and a steering system which are around a vehicle. For example, the lower arms and upper arms of the front wishbone suspension, the trailing arms of the rear swing arm suspension, and knuckle arms that operate the tires in conjunction with the steering, etc., shapes that are not necessarily advantageous in maintaining strength. In this case, a lighter and lower cost aluminum casting and forging can be applied.

FIG. 1 is a view showing one embodiment of an aluminum cast forged product of the present invention. FIG. 1A is a top view of a knuckle arm preform molded product 21, and FIG.
(B) is a top view of the knuckle arm product 22. By reducing the weight of automobile parts having such a shape at low cost, it is possible to contribute to environmental improvement through improvement of fuel efficiency.
FIG. 6 is a view showing another embodiment of the cast aluminum forged product of the present invention, and is a plan view of a lower arm product 61. FIG. FIG. 7 is a side view of the lower arm product 61. The lower arm product 61 has a thick part 61 and a thin part 63, and the thickness ratio of the thick part thickness 72 and the thin part thickness 73 is:
It is approximately 3: 1.

Hereinafter, the cast aluminum forged product of the present invention will be specifically described. The present invention is an aluminum casting forged product which is made of an aluminum alloy for forging and has excellent corrosion resistance and mechanical strength. Examples of the raw material include an A6061 alloy suitably used in conventional forging, and an aluminum alloy for forging containing aluminum as a main component and a trace amount of metal. The kind and content of trace metals are silicon 0.4-0.8% by weight, iron 0.7% by weight
Hereinafter, 0.8 to 1.2% by weight of magnesium and 0.15% of copper
０．４0.4% by weight and chromium 0.04５0.35% by weight.

In the present invention, such an aluminum alloy for forging is used as a raw material and is melted and cast. Therefore, as a raw material for obtaining an aluminum cast forged product of this component, for example, a conventional raw material for forging is used. Accordingly, a large amount of unnecessary burrs generated in a normal forging process 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, unnecessary burrs generated during forging can be used as a raw material. This raw material contains 0.4 to 0.8% by weight of silicon, 0 to 0.7% by weight of iron, 0.8 to 1.2% by weight of magnesium, and 0.15% of copper.
It is preferably an aluminum alloy for forging containing about 0.4% by weight and 0.04% to 0.35% by weight of chromium,
It is important that impurities be contained as little as possible.

The raw material for forging is put into a melting furnace,
The mixture is heated to 80 to 780 ° C. to be melted, and then placed in a holding furnace and subjected to degassing treatment and 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 about 60 to 150.
It is preferable to adjust the temperature to ° 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 again heated 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 trimmed forged product is subjected to a heat treatment after trimming to obtain 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 about 2600 to 2800 tons for rough forging and about 3200 to 3800 tons for finish forging in the case of a delivery pipe as an automobile part.

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 producing an aluminum cast forged product of 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. 5 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 portion 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 ratio obtained by using the method is approximately 18 to 60% in each portion.

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 mechanical strength and corrosion resistance are equal to or 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 a raw material is melted to obtain a molten metal, a working ratio when a casting mold is set to a final forged product shape of 100% is: 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.

[0033]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited to these examples.

(Examples 1 and 2) Under the same conditions, two cast aluminum forgings having a thick portion and a thin portion were produced, and their mechanical strength, surface defects, and internal defects were confirmed by a test. FIG. 2 is a view showing a delivery pipe of an automobile part as an example of an aluminum cast and forged product. FIG. 2A is a perspective view of a delivery pipe preform molded product 31, and FIG. 2B is a perspective view of a delivery pipe product 32. Delivery pipe product 32
It has a thickness of 40 mm at the thickest part and 5 mm at the thinnest part.

An A6061 alloy scrap was prepared as a raw material, and a delivery pipe shown in FIG. 2 was manufactured based on the raw material according to the following process. A delivery pipe preform in which a raw material is melted at a temperature of 730 ° C. to obtain a molten metal, and then, when the shape of the final delivery pipe product 32 is set to 100%, a mold is formed into a shape having a processing rate of 18 to 25%. The molded article 31 was molded at a mold temperature of 100 ° C. Next, the delivery pipe preform molded product 31 was stamped at a rough forging temperature of 400 ° C. (surface temperature) with a rough forging load of 2,800 tons by a forging press to obtain a rough forged product. Next, at a forging temperature of 460 ° C (surface temperature),
Again, stamping was performed by a forging press at a finish forging load of 3,200 tons. Finally trim the shape by trimming, 520
After heating (T4 treatment) at 3 ° C. for 3 hours,
For 6 hours (T6 treatment) to obtain a delivery pipe product 32 as a final product.

The surface of the obtained delivery pipe product 32 was inspected for the presence or absence of a surface defect by fluorescence inspection. Further, the presence or absence of internal defects was examined by X-ray inspection.
Further, the delivery pipe product 32 is cut at a cutting location shown in FIG. 3A, and cut into twelve delivery pipe product cut pieces 1 to 12 shown in FIG. 3B, and each of them is subjected to polishing and color check. The presence or absence of internal defects was confirmed.

The mechanical properties were measured for tensile strength, proof stress, and elongation. From the produced delivery pipe product 32,
The test pieces were cut out at the test piece collection positions 41 to 43 shown in FIG. 4 and the mechanical properties were measured for each of them. Table 1 shows the results.

[0038]

[Table 1]

In both products (Examples 1 and 2), on the surface thereof, protrusions such as swelling and collapse, dents such as shrinkage nests, blown and pushed, or poor gloss and tears are observed. No surface defects were observed. In addition, X-ray inspection and inspection of cut pieces do not show any shrinkage cavities such as shrinkage cavities, pores such as pinholes and blowholes, foreign matter contamination, poor adhesion, etc., and also cause internal defects. I didn't.

[0040] The mechanical properties of all the test pieces of two products (Examples 1 and 2) in terms of tensile strength, proof stress and elongation were A606 manufactured by a conventional forging process.
The standard value of 1FD or more was secured. As described above, the aluminum cast forged product of the present invention has high quality without defects while being formed in a shape having a thick portion and a thin portion,
It was confirmed that it had more mechanical strength than conventional forged products.

[0041]

As described above, according to the present invention, the tensile strength, the proof stress, and the elongation can be improved even if the shape has a mixture of a thick portion and a thin portion applicable to various automobile parts. An aluminum cast forged product which is large, has mechanical properties equal to or higher than that of a conventional forged product, has excellent corrosion resistance, and is inexpensive, is provided. 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 a view showing another embodiment of the cast aluminum forged product of the present invention, FIG. 2 (a) is a perspective view of a preform molded product, and FIG. 2 (b) is a perspective view of a final product. It is.

FIG. 3 is a view showing an example of an internal inspection of an aluminum cast forged product of the present invention, wherein FIG. 3 (a) is an explanatory view showing a cut portion, and FIG. 3 (b) is an explanatory view showing a shape of a cut piece; FIG.

FIG. 4 is a diagram illustrating an example of the strength measurement of the cast aluminum forged product of the present invention, and is an explanatory diagram illustrating a test piece sampling position.

FIG. 5 is a cross-sectional view of a forging material for explaining a working ratio.

FIG. 6 is a view showing another embodiment of the cast aluminum forged product of the present invention, and is a plan view of a final product.

FIG. 7 is a view showing another embodiment of the cast aluminum forged product of the present invention, and is a side view of a final product.

[Explanation of symbols]

1-12: Delivery pipe product cut piece, 21: Knuckle arm preform molded product, 22: Knuckle arm product, 31: Delivery pipe preform molded product, 32
... Delivery pipe products, 41, 42, 43 ... Test piece sampling position, 61 ... Lower arm product, 62 ... Thick part, 63 ...
Thin portion, 72: Thick portion thickness, 73: Thin portion thickness.

Claims (4)

[Claims] 1. An aluminum cast forged product which is produced by forging after casting and used as a vehicle component, wherein the ratio of the thickness of the thick portion to the thin portion is 3: 1 to 10: 1. And an aluminum casting forged product having no defect in the thick portion. 2. 0.4 to 0.8% by weight of silicon, 0 to 0.1% of iron.
7% by weight, 0.8-1.2% by weight of magnesium, 0.1% of copper.
15-0.4% by weight, chromium 0.04-0.35% by weight
The cast aluminum forged product according to claim 1, further comprising: 3. The cast aluminum forged product according to claim 1, wherein a forged aluminum alloy is used as a raw material. 4. A preform molded product which is cast so that a working ratio thereof is 18 to 60% when a shape of a final product of the aluminum cast and forged product according to claim 1 is 100%.