SK279465B6 - Method for production of a compact vehicle wheel made of light metal - Google Patents

Abstract

A vehicle wheel made of light metal and consisting of a hub and a rim surface is produced by a process comprising the steps of producing a substantially disc-shaped crude billet from an extruded bolt or a similar rounded solid metal body, heating of a crude billet to a hot rolling temperature and subsequently orbitally rolling the crude billet so as to obtain a rotationally symmetric preformed material, splitting off of the outer portion of the preformed material, and afterwards forming (by cold forging) a rim surface by spinning the outer, split-off rim portion.

Description

Technical field

For various reasons, there is an increasing interest in the use of wheels made of light metal, especially aluminum but also of magnesium.

BACKGROUND OF THE INVENTION

Therefore, the demand for aluminum wheels has increased considerably in the market in recent years. The areas of greatest interest are sports cars and luxury cars. This clearly confirms the advantageous properties of the light metal wheels. The most important advantages are reduced weight, especially of the unsprung part, for better safety, better dissipation of brake heat, more attractive design possibilities, improved finish and corrosion resistance and fit for re-use. In particular, the reduction in demand for less lorries can be attributed to higher costs than traditional steel wheels, as these costs are too high.

Along with the overall trend to improve performance and produce more reliable parts, there is an increasing interest in light metal wheels. At the same time, requirements for stronger brakes are increasing. However, this requires more space and larger wheel dimensions, making the need for light metal wheels increasingly current.

Today, the light metal wheel market is dominated by cast aluminum wheels. This production is based on a well known technology. But casting wheels is a complicated and time-consuming process.

Another known method is the formation of light metal wheels by plastic processing of the rim of the disc, where the rim is first forged and then cut and compressed during a rotational or twisting process. Such a process is illustrated in Norwegian patent specification no. 154,908 and Swedish Patent Nos. However, the manufacture of light metal wheels by plastic processing using a cane as a starting point is a costly process involving a large loss of material. In addition, this procedure gives few possibilities to design the shape of the wheels and has therefore not been implemented to a greater extent.

SUMMARY OF THE INVENTION

The above drawbacks are largely overcome by the light metal wheel manufacturing method of the invention, which comprises the steps of: forming a substantially disc-shaped blank of a cast billet or similar rounded solid metal body, the outer flange of the material is split, and then formed the outer surface of the rim by forging the outer halved portion while rotating, the principle being that before the outer skirt portion is split, the blank is heated to a rolling temperature and then orbitally rolled to a rotational symmetrical preformed material.

In a preferred embodiment of the invention, the preformed material may be extruded or cold forged after orbital rolling but prior to cleavage to obtain a specific hub design. Further, the raw material can be extruded a cylindrical extrusion of aluminum or magnesium alloy.

The wheels produced by the process of the invention have the following advantageous properties: higher mechanical strength, resulting in a weight reduction of about 15 to 30%, improved corrosion resistance, multiple surface treatment options, improved material utilization, automated production capacity with short process duration and high reproducibility.

The method of making the light metal wheels of the invention is substantially simpler and more efficient than the prior art processes. The process according to the invention leads to a considerably lower material loss.

The invention will be described in more detail by way of example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an outline of an expensive step of the process according to the invention with a raw blank as set forth in claim 1; FIG. 2 shows another possible process step and FIG. 3 and 4 show a third step or a fourth step of the process according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned, it is known in the art to produce light metal wheels by plastically shaping the disc flange such that the flange is first forged and then split and pressed during rotation. The desired thickness accuracy and rounding of this skirt are critical to the formation of wheels according to this known process.

By the method of the invention, the wheels can be manufactured without such a desired accuracy of the base casting. The first step of the method according to the invention is to form a substantially disc-shaped blank from a cast, billet or similar rounded solid metal body. This is a much more efficient solution than hitherto known, since the cast material can be used without prior processing. This results in not only lower material consumption, but also significantly lower material costs.

In a second step, the blank 1 is treated with a rotating anvil as shown in FIG. 1a, for a rotationally symmetrical object 2 with a specially determined cross-sectional geometry, as shown in FIG. lb. Rotation occurs between the operating rotating lower tool 3 and the freely movable upper tool 4, the so-called punch. The axes of rotation of the two tools together form a fixed angle, most often in the range of 1 to 10 degrees. The tools are shaped to give the product its characteristic shape. If desired, the lower tool 3 is provided with plungers 5 to facilitate handling of the preform, optionally with an ingot. In orbital rolling, the blank is heated to a rolling temperature depending on its material (e.g., 450 to 520 ° C). The heated blank 1 is placed on the lower tool 3 (FIG. 1a), which is then rotated. The upper tool moves downwards and starts to rotate when it meets the stock. When the stock stops rotating, the upper tool returns to its original position and the finished product can be removed.

In the case of wheels with a rotationally symmetrical embodiment of the wheel disc (hub), orbital rolling constitutes the entire plasticization treatment of the wheel disc into the finished product, namely the wheel.

However, aluminum alloys are very well suited for post-cold plasticization as the alloys are very easy to mold in a soft state. Thus, various processing methods, in particular cold forging, make it possible to use methods which lead to a better flexibility of the processing choice and more freedom in the choice of shape, while improving the structural and mechanical properties. Approach

SK 279465 Β6 can be carried out in one or several steps and allows very complex shaping, high geometric accuracy and smooth, and fine surface finish. Cold fittings open up design possibilities that go far beyond the rotational symmetry itself. In practice, the method according to the invention gives great possibilities and very little constraints on the freedom of the designer.

In FIG. 2a, 2b and 2c show examples of cold forging. After orbital rolling, the object 2 is pressed between the upper mold 6 and the lower mold 7 to give it the desired shape. As mentioned, this procedure is only one possibility and not an obligatory step according to the invention.

When the object 2 has been orbitally rolled or otherwise cold-forged or cold-pressed, its outer section will be split, which will form the surface of the wheel rim. This is the third step of the method of the invention and is illustrated in more detail in FIG. 3a and FIG. 3b. As shown, the object 2 is fastened in the rotating holder 8 and is split along its periphery by the splitting roller 9 into two rings 10 and 11.

The rim surface 13 is then forged in a rotary motion from the split ring 10 as shown in FIG. 3b and 4a. The object 2 is held in a rotating tool comprising an upper die 16 and a lower die 17.

The cylinder 12 rotates and extends the rings 10 and 11 of FIG. 3b and FIG. 4a outwards to rim flanges 14, 15 having different lengths (FIG. 4b). This fourth and final step of the process according to the invention facilitates an optimal distribution of the material, which in turn leads to low material consumption and advantageous economy in terms of weight. Due to the uniform supply of material, the rotatable forged surface has an advantageous structure and quality as compared to cast and machined surfaces.

Example 1

The workpiece is produced (cut) in the form of a disc from a cast or extruded billet of AlMgSi alloy (Fig. 1). The web is heated to a suitable hot forging temperature (520 ° C), and then orbital rolled (step 2) to bring it to a certain shape and size prior to further processing (the rolling depth determines the shape of the billet). The rolled blank can be further processed according to steps 3 and 4 of the process of the invention. However, since it is desirable to give the wheel a certain shape deviating from rotational symmetry, the rolled material is cold forged. After cold forging, the workpiece is fixed in the splitting device and cut along the periphery of the workpiece (step 3). Then the surface of the refinery is forged in a cold rotation (step 4), and then the wheel is in its final shape.

The wheel is then heat treated, machined and machined on the surface, but these steps are not part of the method of the invention.

Example 2

A disc stock is formed from the cast or extruded bucket bar of AZ31 alloy (step 1). The blank is heated to 480 ° C and orbital rolled (step 2). In connection with this heat treatment of the billet, recrystallization occurs. Thus, the preformed billet will have adequate toughness in cold forging when the material must be maintained at a temperature of at least 220 ° C. After cold forging, the blank is melted (step 3) and baked under load at 450 ° C. Rotation of the rim surface (step 4) finally occurs at a temperature above 220 ° C.

Claims (4)

PATENT CLAIMS A method of manufacturing a solid light alloy vehicle wheel comprising a hub and a rim portion, wherein in a first step a substantially disc blank is formed from a cast billet or similar rounded solid metal body, in a third step the outer portion of the material flange is split and in a fourth step, the outer surface of the rim of the outer halved portion is formed while rotating, characterized in that prior to the third step, a second step is introduced in which the blank is heated to a high rolling temperature and subsequently orbitally rolled to rotational symmetrical preformed material. A method according to claim 1, characterized in that the preformed material is cold pressed or forged after orbital rolling and before disassembly to obtain the desired specific wheel hub shape. Method according to claims 1 and 2, characterized in that the blank is formed from a cylindrical extrusion of an aluminum alloy. Method according to claims 1 and 2, characterized in that the blank is formed from a cylindrical extrusion of a magnesium alloy. 4 drawings