JPS6144147B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing aluminum wheels for vehicles. BACKGROUND ART In recent years, attention has been paid to aluminum processing methods and lightweight properties, and so-called aluminum wheels made of aluminum alloys have been used as wheels for vehicles, particularly motorcycles and automobiles, and the demand for them has increased rapidly. However, aluminum wheels have inferior material strength compared to conventional iron wheels, and the wheels are important safety parts, so strength considerations are important. In this respect, forging is desirable, but products of this type are generally produced by casting in view of design versatility and cost. When manufactured using the casting method, the wall thickness is often considered excessive due to strength considerations, and the original purpose of using aluminum wheels, which is weight reduction, is not achieved effectively. There is no such situation. The present invention was invented in view of the above circumstances, and its purpose is to provide an inexpensive manufacturing method for aluminum wheels that can more effectively achieve weight reduction and greatly improve productivity. It's about doing. More specifically, the present invention provides that certain aluminum alloys, such as aluminum alloys containing 7.0 to 10.0% by weight of Si, 0.3 to 0.8% by weight of Fe, 0.15 to 0.4% by weight of Mg, and 0.2 to 0.8% by weight of Mn, are cast. This was done based on the knowledge that the mechanical properties of the material can be improved by subjecting it to appropriate heat treatment and roll processing, and by making the most of this improvement in mechanical properties, it also increases productivity. Our main focus is to provide high quality manufacturing methods. In the manufacturing method according to the present invention, first, a semi-finished product is formed using a die casting method using a certain type of aluminum alloy, for example, an aluminum alloy having the composition described above, and after heat-treating the semi-finished product, at least a portion of which is desired to be improved in strength, for example, the most A method characterized in that the flange portions forming the circumferential portions at both ends of the wheel shaft, which are easily damaged, are rolled into a final shape, and then subjected to heat treatment to obtain a finished product with desired strength, By adopting a die-casting process, we aim to reduce costs and improve productivity, and also make heat treatment possible, and roll processing improves the mechanical properties of the part, effectively increasing strength and effectively reducing weight. The aim is to achieve this goal. Embodiments of the present invention will be described below with reference to the drawings. Figure 1 schematically shows the manufacturing method of the present invention, and to outline the entire process, a semi-finished product is formed by die-casting an aluminum alloy material, and after the semi-finished product is subjected to a first heat treatment, the strength is improved. At least a portion of the desired part is rolled to obtain the shape of the finished product, followed by a second heat treatment to form the finished product. Explaining the aluminum alloy material here, the characteristics of the present invention, which enable die casting, plastic working, and improved mechanical properties of the material, are not phenomena observed in all types of alloys. , found in certain aluminum alloys. Such aluminum alloys, such as Si7.0~10.0wt%, Fe0.3~0.8
Weight%, Mg0.15~0.4wt%, Mn0.2~0.8wt%
It has been found that an aluminum alloy having a composition containing: Furthermore, when the aluminum wheel produced by the method of the present invention is subjected to a predetermined heat treatment after being cast by a nonporous die casting method such as a vacuum die casting method, an atmosphere flow die casting method, or an oxygen displacement die casting method, the aluminum wheel does not swell due to the expansion of air vesicles. This makes it possible to perform more preferable heat treatment. The first heat treatment performed on the semi-finished product thus formed is also limited to some extent in order to improve the mechanical strength of the material during subsequent rolling. As such a first heat treatment, 0.5 to 450 to 540℃
A heat treatment comprising heating for 10 hours followed by slow cooling has been found to be preferred. Especially in this first heat treatment, cooling conditions are an important factor, and furnace cooling was found to be the most preferable. The subsequent rolling process is preferably carried out on a part of the wheel that is easy to roll, such as the flange part, where it is most desirable to increase the mechanical strength for reasons such as manufacturing costs. It has been found that even in this roll processing, it is possible to achieve a good improvement in mechanical strength by setting the reduction ratio to approximately 50% in practice. The finished product thus formed is finally subjected to a second heat treatment, and as is well known, the strength of the finished product is improved by heat treatment.
As this second heat treatment, for example, 0.1
It has been found that heating for ~10 hours followed by rapid cooling is preferred. Here, the first heat treatment is a treatment that particularly affects the strength improvement due to roll processing, which is a feature of the present invention, but it is not limited to the one-time treatment described above, and may be further heated, for example, at 250 to 400°C for 1 to 10 hours. It has been found that more favorable results can be obtained by cooling (preferably slow cooling, more preferably furnace cooling). On the other hand, the second heat treatment is a so-called quenching treatment, and as known to those skilled in the art, preferable mechanical properties can be obtained by further heating at 140 to 210° C. for 1 to 16 hours and then rapidly cooling. The effects of the present invention will be described below based on the results of experiments conducted regarding the manufacturing method of the present invention described above. Example: Si8.3% by weight as aluminum alloy material,
A wheel 10 having a cross-sectional shape as shown in FIG. 2 was formed by an oxygen substitution die casting method using a material containing 0.5% by weight of Fe, 0.3% by weight of Mg, 0.6% by weight of Mn, and other impurities. Wheels are 41/2-12
This type is for automobiles with a rim width of 114.3 mm (4 1/2 inches) and a diameter of 304.8 mm (12 inches). Such a wheel was directly subjected to a second heat treatment to form a finished product, and the mechanical strength of the flange portion was measured. Here, as a second heat treatment, the sample was heated at 250° C. for 2 hours and then rapidly cooled. On the other hand, for other wheels, as the first heat treatment
After heating at 520° C. for 2 hours and cooling in a furnace, the flange portion of the wheel 10 as shown in FIG. was processed into rolls. The rolling reduction rate at this time was approximately 35%. Thereafter, a second heat treatment was performed in the same manner as the former wheel, and the mechanical strength of the flange portion was measured. The results are shown in Table 1.

[Table] As can be seen from Table 1, a remarkable improvement in elongation was observed especially in the roll-processed products. It was thought that this improvement in the elongation of the flange part, which is most likely to be damaged in actual use, would be a measure to prevent damage. Therefore, the impact test (JASO C608- standard of the Society of Automotive Engineers of Japan
75) are shown in Table 2.

[Table] As can be seen from Table 2, the impact test showed that the roll-processed product showed a remarkable improvement over the non-roll-processed product. As described above, according to the present invention, it is possible to advantageously utilize the improvement in mechanical properties obtained by selecting an aluminum alloy material, selecting a heat treatment, and then performing roll processing. Aluminum wheels can be produced with high productivity. Moreover, further effective weight reduction can be achieved due to improved mechanical properties.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the steps of the manufacturing method of the present invention. FIG. 2 is a sectional view showing roll processing of the flange portion. FIG. 3 is a front view showing an embodiment of the roll processing machine shown in FIG. 2. FIG. 4 is a partially enlarged view showing the shape of the flange portion before and after rolling. 1... Reduction roll, 2... Lower guide roll,
3... Drive roll, 10... Wheel.

Claims (1)

[Claims] 1. Casting an aluminum alloy by a die casting method to form a semi-finished product, subjecting the semi-finished product to a first heat treatment, and applying the method to form the semi-finished product subjected to the first heat treatment into a final shape. A part of the semi-finished product is rolled, and the final shape of the aluminum wheel product is rolled.
A method for manufacturing an aluminum wheel for a vehicle, comprising various steps, wherein the aluminum alloy contains 7.0 to 10.0% by weight of Si,
Fe0.3~0.8wt%, Mg0.15~0.4wt%, Mn0.2
-0.8% by weight, and the first heat treatment includes a step of heating at 450-540°C for 0.5-10 hours and then slowly cooling. 2 The first heat treatment is further performed at 250 to 400°C.
A method for manufacturing an aluminum wheel for a vehicle according to claim 1, characterized in that the method includes the step of heating for 10 hours.