Aluminum alloy for casting-forging, aluminum casting-forging product and processes for production thereof

Abstract

There is disclosed a cast-forged product of an aluminum alloy consisting essentially of: 0.6 to 1.8 wt % of silicon; 0.6 to 1.8 wt % of magnesium; 0.8 wt % or less of copper; 0.2 to 1.0 wt % of manganese; 0.25 wt % or less of chromium; 0.0 to 0.15 wt % of titanium; and unavoidably contained impurities. When the product is used as various parts for automobiles formed of aluminum, such as suspension parts, frames, and parts for engines, the product is more superior in mechanical properties such as a tensile strength, proof stress, and elongation, and can be manufactured with a low cost.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a cast aluminum alloy for forging and an aluminum cast-forged product that is used for a vehicular part or the like and is less costly, and a method of manufacturing an aluminum cast-forged product. More particularly, it relates to a cast aluminum alloy for forging that is used to manufacture vehicular suspension parts which are required to be light in weight to improve fuel consumption of an automobile and can use useless forging materials such as flash generated in a forging process, an aluminum cast-forged product that has high mechanical properties and contains particular amounts of silicon, magnesium, copper, and manganese, and a method of manufacturing an aluminum cast-forged product. [0003] 2. Description of the Related Art [0004] It is said that global warming, which is one of global environmental problems, is greatly affected by carbon dioxide produced by all human activitie...

AI Technical Summary

Benefits of technology

[0020] The present invention has been developed in view of the above-described conventional problems, and an object thereof is to solve the problems with the conventional art and, more particularly, to provide an aluminum cast-forged product capable of satisfying needs of the market as an aluminum thick-wall processed product and having high tensile strength, proof stress, and elongation; and a method of manufacturing an aluminum cast-forged product. That is, the object is to provide an aluminum alloy material which can be cast / processed like high-concentration products such as AC4CH containing 3 wt % or more of silicon and which can be processed in a final shape of a desired component like AC4CH without requiring low-speed casting, an aluminum cast-forged product cast / forged by the material, and a method of manufacturing an aluminum cast-forged product. Another object of the present invention is to provide various lightweight parts for vehicles brought about by the above-described aluminum cast-forged product and the method of manufacturing the product, and accordingly to save fuel consumption of automobiles and to reduce the amount of emitted carbon dioxide and to contribute to environmental measures such as the prevention of global warming.

[0021] As a result of various studies on raw materials and manufacturing method for the thick-wall aluminum product to solve the above problems, the present inventors have found that an aluminum cast-forged product having a sufficient strength capable of meeting needs of market can be obtained by making predetermined amounts of silicon, magnesium, copper, manganese, and chromium, and optionally titanium contain therein, with improving fluidity and castability. Thus, the present invention has been completed.

[0023] To use the material in manufacturing a desired final product, assuming that a shape of the final product is 100%, the aluminum alloy is used to cast a preformed product having a forging ratio of 18 to 60%, and subsequently the preformed product may be cast and formed in the shape of the final product. Accordingly, it is possible to manufacture the parts for vehicles with a lower cost and higher productivity as compared with low-speed casting using AC4CH.

Problems solved by technology

However, such a material for lightening the weight is generally expensive.

However, castings having large thickness and high strength cannot be produced.

There is a problem that the application of cast parts to suspensions as a part light in weight since a failure of such a part due to insufficient strength directly leads to the safety problem.

However, these materials still have an unsolved problem of high cost, so that the application thereof is extremely limited at present.

Reasons why so-called aluminum products formed only by forging, such as the conventional A6061 alloy forged product are high in cost lie in that the number of manufacturing processes is large and that the raw material for forging itself is expensive and that wastes such as flash are caused during the manufacturing process and that useless materials such as the flash cannot be recycled as the raw material for forging.

Also, for a squeeze casting, because of a large number of processes and a low injection speed, the productivity is low and the cost reduction cannot be attained.

Although the strength is increased, there arises a new problem that a low cost cannot be attained, and the corrosion resistance is deteriorated because a larger amount of copper is contained than the conventional raw material for forging (A6061 alloy), and also the fluidity decreases so that the castability is poor because much magnesium is contained.

In this proposal, although castability is improved, the low cost cannot be attained yet as compared with the conventional raw material for forging (A6061 alloy), also the corrosion resistance is deteriorated because much copper is contained, and there remains anxiety when this material is used for the suspension part.

Also, there arises a problem that the fluidity decreases because much magnesium is contained, and the above-described rigorous control is needed in the casting process, and the manufacturing cost rather increases.

In this proposal, although a shape close to that of the final product can be formed at the time of the casting, and the manufacturing cost can be reduced because the forging can be performed by omitting an extrusion process, there arises a problem in that the strength decreases because an excessive amount of manganese is contained.

If the content thereof is high, however, intermetallic compounds are liable to be formed, and the strength is rather decreased.

However, in respect of the mechanical strength, it cannot be said that the material can sufficiently satisfy needs of the market, depending on use conditions.

There has been a demand for a low-cost aluminum product which is more superior in mechanical properties such as the tensile strength, proof stress, and elongation and which can be applied as various components for automobiles such as the suspension components, frames, and engine parts and which involves the low cost, but it is the present situation that an appropriate aluminum product has not been proposed yet.

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