GB2295341A

GB2295341A - Method for spinning vehicle wheel

Info

Publication number: GB2295341A
Application number: GB9423875A
Authority: GB
Inventors: Takashi Kato; Kimio Ochiai; Masaru Kurebayashi
Original assignee: Asahi Tec Corp
Current assignee: Asahi Tec Corp
Priority date: 1994-11-25
Filing date: 1994-11-25
Publication date: 1996-05-29
Also published as: DE4442465A1; GB9423875D0

Description

1 1

TITLE OF THE INVENTION METHOD FOR SPINNING VEHICLE WHEEL

2295341 BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to a method for spinning a vehicle wheel.

2. Brief Description of the Prior Art

A typical conventional method for spinning a vehicle wheel comprises the steps of placing a wheel material on a mandrel, rotating the mandrel together with the wheel material, and drawing the wheel material along the mandrel while pressing the wheel material with a pressure spatula, so that the wheel material will be formed into a predetermined configuration.

However, since the above conventional method simply utilizes ductility of the wheel material, the wheel material is susceptible to crack by undue force when the wheel material is rapidly formed into a complicated configuration.

OBJECT AND SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide a method for spinning a vehicle wheel which is capable of obviating the above-mentioned problem.

According to one aspect of the present invention, there is essentially provided, in order to achieve the above object, a 1 1 2 method f or spinning a vehicle wheel in which a cast vehicle wheel material is subjected to spinning while heating, the method comprising the steps of:

composing the vehicle wheel material, as a chief component, from an aluminum, and, as secondary components, from Si of 3 wt. t to 6 wt. and Mg of 0. 2 wt. % to 0. 5 wt. %; and heating the cast vehicle wheel material to a temperature in a range of from 230 C to 400C.

Since the vehicle wheel material, which is enhanced in ductility, is subjected to spinning treatment, the vehicle wheel material can easily be drawn along the mandrel and therefore, undue force is not incurred to the vehicle wheel material even when the wheel material is rapidly formed into a complicated configuration. As a result, the vehicle wheel material is not susceptible to crack. Moreover, as shown in Figs. 2 and 3, since the wheel material has a favorable degree of "elongation", formability is enhanced.

It is preferable that a rim material of the wheel material is placed on a mandrel with a peripheral edge portion of the rim material allowed to project higher than a highest convex portion of a working surface of the mandrel. Owing to this arrangement, when the rim material is drawn along the working surface of the mandrel, the rim material is intimately contacted with the working surface. As a result, the rim material can easily be spun.

3 If a rim material of the wheel material is formed such that the wall thickness of its peripheral edge portion is larger than that of its web portion, the rim material can more easily be drawn along the convex working surface of the mandrel. As a result, a predetermined dimension of the wall thickness of the raised portion can easily be maintained.

A peripheral wall like twist is preferably formed on an outer wall surface of a generally connecting portion between a disk portion and the rim material of the wheel material. Owing to this arrangement, since the connecting portion between the disk portion and the rim material can be reduced in wall thickness, the connecting portion is not readily rotted when the material is subjected to casting. Therefore, a favorable level of physical strength of a vehicle wheel thus spun can be maintained.

The rim material of the wheel material is placed on the mandrel preferably with a space formed between the rim material and a working surface of the mandrel, the space being gradually enlarged toward a peripheral end of the rim material. Owing to this arrangement, when the rim material is drawn along the working surface of the mandrel, the rim material can be contacted intimately with the working surface. As a result, the rim material can easily be formed into a predetermined configuration.

An angle formed between the rim material and the working 4 surface of the mandrel is preferably in a range of 50 to 30" Owing to this arrangement, the number of times for drawing the rim material, which Is required for achieving the abovementioned object, can be reduced.

Also, It is preferable that the rim material of the wheel material is gradually dilated toward a peripheral end thereof and the dilating angle is stePpingly varied toward the peripheral end. Owing to this arrangement, when the rim material is drawn along the working surface of the mandrel, the rim material can be contacted intimately with the working surface of the mandrel which is steppingly gradually dilated. As a result, the rim material can easily be formed into a predetermined configuration which is steppingly dilated.

If the dilating angle Is steppingly enlarged toward the peripheral end of the rim material, the working efficiency is more enhanced. Also, if the dilating angle is formed larger than a dilating angle of a working surface of a mandrel, the working efficiency is more enhanced.

The present inventor has paid attention to the following f act. That Is, it is stipulated in the standard (E. T. R. T. 0.) that If a horizontal extension including terminals of contours for bead retention on drop center rims is served as a reference line, a hump H must have a predetermined curvature in a predetermined range below the reference line. For example, as shown in Fig. 10, if the reference line is represented by L, the hump H must have a curvature of BR at a location 0. 9 mm above the reference line L irrespective of the length dimension of the contours for bead retention on drop center rims. Based on this finding, the inventor has worked out a method for stopping the drawing end in a position where the drawing end is not allowed to contact the mandrel, so that the rim width can be changed, if necessary, by properly determining the stop position for the drawing end of the rim material. Therefore, if this spinning method is employed, one mandrel is good enough to manufacture a variety of wheel rims having different widths. In other words, a different mandrel is not required for each of rims which have different widths. As a result, manufacturing costs of the wheel rim and therefore, of the vehicle wheel can be reduced.

If a material locking peripheral groove is formed in the surface of the mandrel such that the width of the groove is adjustable, the width of the locking peripheral groove can be adjusted in accordance with the width of the material. Therefore, if this spinning apparatus is employed, a different mandrel is not required for each of the working materials which have different widths. As a result, working efficiency is enhanced and working costs can be prevented from becoming high.

If an arrangement is made such that the mandrel is divided at a drop center working portion of the mandrel into an outer portion and an inner portion in a vertical direction relative 6 to an axis thereof, that an auxiliary working member is removably sandwiched between the outer and inner portions and that a stepped portion is provided on a contact surface of the material in the auxiliary working member, the rim width of the vehicle wheel can easily be adjusted by properly selecting an auxiliary working member having a desired width. Accordingly, a different mandrel is not required for each of the vehicle wheels which have different rim widths. This means that one mandrel is good enough for forming a variety of vehicle wheels which have different rim widths. As a result, the manufacturing costs of the mandrel can be reduced and management of the mandrels becomes easier.

According to another aspect of the invention, there is also provided a method for spinning a vehicle wheel in which a vehicle wheel material is subjected to spinning while heating, the method comprising the steps of forming the wheel material; then liquefying the same; then cold-spinning the same; and then subjecting the same to aging treatment.

Since an internal stress generated by the hot-spinning is removed and thereafter the material can be subjected to the cold-spinning, any twist caused by the hot-spinning can eventually be removed by the cold-spinning. Therefore, if this spinning method is employed, a material, which is difficult to be drawn, can easily be formed by spinning without the need of the work for removing the twist. As a result, the 7 spinning process for forming a desired product is simplified and therefore, the working efficiency is readily enhanced.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. I is an explanatory view for explaining a method for spinning a rim material according to one embodiment of the present invention; Figs 2 and 3 are graphs showing formability of a wheel material; Fig. 4 is an explanatory view for explaining a method for spinning a rim material according to another embodiment of the present invention; Fig. 5 is an explanatory view for explaining a method for spinning a rim material according to a further embodiment of the present invention; Figs. 6 and 7 are explanatory views for explaining a method for spinning a rim material according to still further embodiments of the present invention; Fig. 8 is a cross-sectional view showing one preferred mode 8 for carrying out a method f or spinning a wheel rim according to the present invention; Fig. 9 is a sectional view showing one embodiment of an apparatus for spinning a wheel rim according to the present Invention; and Fig. 10 is an explanatory view showing the configuration of a vehicle wheel.

DETAILED DESCRIPTION OF THE EMBODIMENT

In Fig. 1, reference character S denotes a spinning apparatus, and reference numeral 2 denotes a rotary shaft of the spinning apparatus S. The rotary shaft 2 is rotatable about an axis thereof. Reference numeral 3 denotes a mandrel. This mandrel 3 is removably attached to the rotary shaft 2. A peripheral surface of the mandrel 3 is served as a rim working surface 31 for spinning a vehicle wheel W. Reference numeral 4 denotes a case vehicle wheel material. The components of the material 4 include Mg: 0.15 wt.% to 0.4 wt.%, Ti="iO.2 wt.-%, Fe:i-0.3 wt.%, and Al: the remainder, or Si=;O.2 wt.%, Mg: 2.5 wt.% to 5.5 wt.%, Ti;0.2 wt.%, Mn;0.6 wt.%, and Al: the remainder. The vehicle wheel material may also be cast from an AC4C material. The wheel material 4 is placed on one surface of the mandrel 3 and sandwiched between the mandrel 4 and a tail stock 5. Therefore, when the mandrel 3 is rotated, the wheel material 4 is also rotated in the same direction together with 9 the mandrel 3. The wheel material 4 is made by casting. The wheel material 4 comprises a disk portion 41 which is sandwiched between the mandrel 3 and the tail stock 5, and a rim material (see the imaginary line of Fig. 1). In operation, the rim material 42 placed on and rotating together with the mandrel 3 is drawn with the use of a pressure spatula 6 in a direction as indicated by an arrow. As a result, a rim 421 is formed. Reference numeral 7 denotes a burner. This burner 7 is adapted to heat the rim material 42. The burner 7 is mounted on the pressure spatula 6 and moved together with the pressure spatula 6. Owing to this arrangement, a working portion of the pressure spatula 6 can be heated locally. For spinning the rim 421, it is preferable that the rim material 42 is heated to a temperature in a range of from 230"C to 4000C. If the temperature is lower than 230C, formability becomes poor and the rim material 42 is susceptible to crack. On the contrary, if the temperature is higher than 4000C, the disk portion 41 becomes too soft and is readily deformed. If the temperature range is further limited to 290C to 3600C, formability is further enhanced and therefore, cracks are not easily occurred. In order to set the temperature of the rim material 42 into the range required, the temperature of the working portion of the rim material 42 is measured by an infrared thermometer and the heating power of the gas burner 7 is adjusted by a feedback method. The burner 7 is ignited at the same time the mandrel 3 begins to rotate and extinguished at the same time the mandrel 3 stops rotation.

If at least one of the wheel material and the mandrel is preheated, the working efficiency of spinning operation is enhanced. In this case, if the mandrel is heated at a temperature lower than the heating temperature of the wheel material, a proper spinning of the wheel material is ensured preventing the temperature increase of the mandrel. In this case, it is preferable that the mandrel is heated at a temperature in a range of from 230"C to 260C.

In the case where the wheel W is formed by the spinning apparatus S, the cast wheel material 4 is placed on the mandrel 3. After the material 4 is sandwiched between the mandrel 3 and the tail stock 5, the mandrel 3 is rotated at a speed of about 300 RPM. Simultaneously, the burner 7 is ignited to start heating the rim material 42. When the temperature of the rim material 42 reaches the predetermined level (2300C to 4000C), the rim material 42 is drawn in the direction as indicated by the arrow with the use of the pressure spatula 6. As a result, the wheel W is obtained. After forming the wheel W, the mandrel 3 is caused to stop rotation. Simultaneously, the gas burner 7 is extinguished. The mandrel 3 and/or the pressure spatula 6 may also be heated at the same time the wheel material 4 is heated.

The wheel material 4 may include Si: 3 wt. % to 6 wt. %, and Mg: 0. 2 wt. % to 0. 5 wt. %. The reason why Si content is limited to 3 wt. -W to 6 wt. -W is that if Si content is lower than 3 wt. %, f lowability of a hot melt is lowered when the material 4 is cast and a shrinkage cavity tends to occur, and that if Si content is more than 6 wt. %, "elongation" is decreased although the strength of the wheel W is increased as shown in Figs. 2 and 3. Likewise, the reason why Mg is limited to 0. 2 wt. % to 0. 5 wt. % is that if the Mg content is lower than 0.2 wt. %, the resistance to tensile force is decreased, and that if MG content is higher than 0.5 wt. -%, the "elongation" of the wheel is decreased, as shown in Fig. 3. The elongation test (see Figs. 2 and 3) was carried out in such a manner as to spin a cup-like (wall thickness of 10 mm) test piece formed from a wheel material which was obtained by casting a spinning low Si material (Cu: 0.004 wtA, Si: 4.6 wt. Mg: 0.36 wt. %, Fe: 0. 12 wt. %, Mn: 0. 004 wt. %, Ti: 0. 10 wt. Sb: 0. 078 wt. %, and Al: the remainder) by a spinning machine. A test piece of a comparative example was made using a wheel material which was cast f rom a spinning 4C material (Cu: 0. 006 wt. %, Si: 6. 9. wt. Mg: 0.33 wt. %, Fe: 0.12 wt. %, Mn: 0.006 wt. %, Ti: 0.115 wt. Sb: 0. 112 wt. %, and Al: the remainder).

In this way, if the wheel material 4 contains Si: 3 wt. % to 6 wt. % and Mg: 0.2 wt - % to 0.5 wt. -W, it exhibits an excellent "elongation" as shown in Figs. 2 and 3 and therefore, formability is good when the wheel material 4 is subjected to 12 spinning - Figs. 4 and 5 show embodiments of the present invention in which the wheel material 4 thus obtained is used.

In Fig. 4, reference numeral 422 denotes a reverse side rim material portion in the rim material 42. This reverse side rim material portion 422 is turned out to be a reverse side rim portion when the material 422 is subjected to spinning. The reverse side rim material portion 422, as well as a front side rim material portion, is integrally formed with the disk portion 41 by forging or casting. The reverse side rim material portion 422 is of a sleeve-like configuration. A wall thickness A of the peripheral edge portion of the reverse side rim material portion 422 is larger than a wall thickness B of a basal portion thereof. Reference numeral 426 denotes a twist. This twist 426 is formed on an outer wall surface in a connecting portion between the reverse side rim material portion 422 and the disk portion 41. The twist 426 is allowed to extend, like a groove, over the peripheral surface of the reverse side rim material portion 422.

The wheel material 4 thus constructed is placed on the mandrel 3. At that time, a space P is f ormed between the reverse side rim material portion 422 and the rim working surface 31 of the mandrel 3. An angle 0 formed between the reverse side rim material portion 422 and the rim working surface 31 is preferably about 8 degrees (see Fig. 5). A 13 foremost end of the reverse side rim material portion 422 is allowed to project radially of the disk portion 41 exceeding a rim flange working surface (corresponding to the "highest convex portion" of claim 3) 311 of the mandrel 3.

When the mandrel 3 is rotated about its axis and the reverse side rim material portion 422 is drawn in the direction as indicated by the arrow with the use of the pressure spatula 6, the material portion 422 is gradually deformed into the states as indicated by imaginary lines (from the right to the left). As a result, a reverse side rim 422 and therefore, the wheel W are formed.

As shown in Fig. 5, the wheel material 4 is placed on the mandrel 3 in such a manner as to form the space P, which is gradually dilated toward a foremost end of the reverse side rim material portion 422, between the reverse side rim material portion 422 and the rim working surface 31 of the mandrel 3. The angle 0 formed between the reverse side rim material portion 422 and the rim working surface 31 is preferably about 5 to 30 degrees. The reasons are as follows. If the angle 0 is smaller than 5 degrees, a bottom surface of the reverse side rim material portion 422, which bottom surface is located on the foremost end side of the material portion 422 from an abutment portion of the material portion 422 when the pressure spatula 6 is brought into abutment with the material portion 422, is contacted with the rim working surface 31 of the mandrel 14 3. As a result, the drawing operation must be repeated several times to the reverse side rim material portion 422 in order to achieve the intended purpose because a drawing operation is limited in working amount. On the contrary, if the angle 0 Is larger than 30 degrees, a contact area between the reverse side rim material portion 422 and the pressure spatula 6 becomes too large when the pressure spatula 6 is brought into abutment with the reverse side rim material portion 422. As a result, there is a fear that the reverse side rim material portion 422 is broken during the course of the drawing operation.

As shown in Fig. 5, the reverse side rim material portion 422 is gradually dilated toward the peripheral end, and the dilating angles a,, a2 and a3 are steppingly enlarged toward the peripheral end. When the wheel material 4 thus constructed is placed on the mandrel 3, the dilating angles 61, 02 and 83 of the rim working surface 31 in the mandrel 3 are smaller than the dilating angles a,, a 2 and a 3 of the reverse side rim material portion 422. Accordingly, the space P, which is gradually dilated toward the foremost end, is formed between the rim working surface 31 and the reverse side rim material portion 422.

Figs. 6 and 7 show further embodiments of the present invention.

In Fig. 6, reference numeral 81 denotes a first spinning mandrel (hereinafter simply referred to as the "first mandrel"). The f irst mandrel 81 is rotatable about its axis. Reference numeral 812 denotes a tail stock. This tail stock 812 is coaxial with the first mandrel 81. The first mandrel 81 and the tail stock 812 have a rough working surface 811. This rough working surf ace 811 is used when a material 813 as later described is ruptured and roughly worked to manufacture an intermediate material 814.

A method for manufacturing the vehicle wheel W using the f irst and second mandrels 81 and 82 thus constructed will now be described.

First, an Al alloy material 813 manufactured by casting or forging is sandwiched between the f irst mandrel 81 and the tail stock 812. In that condition, the first mandrel 81 and the tail stock 812 are rotated about the co-axis and a rim material portion 812R of the material 813 heated to about 300C is ruptured into a state as indicated by an imaginary line (onedot chain line) by a rupture roller 817. Thereafter, the rim material portion 812R is drawn along the rough working surface 811 of the f irst mandrel 81 and the tail stock 812 with the use of a pressure spatula 818, thereby to form the intermediate material 814. At that time, opposite end portions of the intermediate material 814 are fully milled.

Thereafter, the intermediate material 814 is subjected to liquefying treatment at a temperature in a range from 520 OC to 5400C for 30 minutes to 90 minutes, so that the material is 16 softened and so that its internal stress (work -hardening) Is removed. Thereafter, the intermediate material 814 is cooled in water of at temperature in a range from 45 C to 70C.

As shown in Fig. 5, the intermediate material 814 thus cooled is sandwiched between the second mandrel 82 and the tail stock 826. In that condition, the second mandrel 82 and the tail stock 826 are rotated about the co-axis in the atmosphere of a normal temperature, and the intermediate material 814 is drawn along a finish working surface 822 of the second mandrel 82 and the tail stock 826 with the use of a pressure roller 819, thereby to f orm the wheel W. This spinning is performed in order to enhance dimensional accuracy and to remove the twist caused by heating. After the spinning is made, an aging treatment is performed at a temperature in a range from 170 OC to 180 C f or f ive to seven hours. If the finish spinning is performed at the same temperature as the aging treatment, the time required for aging treatment can be reduced.

Thereafter, the wheel W, which has been subjected to finish spinning, allows the opposite end portions to be subjected to cutting to form rim flanges 824 and 824. By this, the intended final product is completed (see the imaginary line of Fig. 7).

The present invention is likewise applicable to a method for spinning a rim for a two-pieces wheel using a metal tube.

According to the spinning method of this embodiment, since the wheel material is subjected to liquefying treatment after 17 it is subjected to hot-spinning, internal stress generated, if any, by the hot-spinning is removed and thereafter the material can be subjected to cold-spinning. As a result, any twist caused by the hot-spinning can eventually be removed by the cold-spinning.

Fig. 8 shows a further embodiment of the present invention. In Fig. 8, reference numeral 5 denotes a first mandrel. This first mandrel 5 includes an outer rim portion working surface 51. Reference numeral 52 denotes a fit-in shaft. The first mandrel 5 is allowed to project from an axis of the fit-in shaft 52. The function of this fit-in shaft 52 will be described later.

Reference numeral 3 denotes a second mandrel. This second mandrel 3 includes an inner rim portion working surface 31. Reference 32 denotes a fit-in hole. The second mandrel 3 is formed around an axis of the fit-in hole 32. The fit-in shaft 32 of the first mandrel 5 is reciprocally movably fitted in the f it-in hole 32 such that the first and second mandrels 5 and 3 are fixedly contacted to each other.

Reference numeral 91 denotes a locking peripheral groove. The locking peripheral groove 91 is formed in a boundary surface area between the first mandrel 5 and the second mandrel 3. The locking peripheral groove 91 is adapted to allow a working material 9 to be fixedly fitted therein. The working material 9 is preferably made by cutting crosswise a continuous 18 cast sleeve-like member. The width of the locking peripheral groove 91 can be increased by moving the first mandrel 5 in a direction as indicated by A relative to the second mandrel 3, in accordance with the width of the working material 9.

In this way, the first mandrel 5 and the second mandrel 3 are rotated about their co-axis with the working material 9 fixedly sandwiched in the locking peripheral groove 91, and the working material 9, which is being rotated together the first and second mandrels 5 and 3, is ruptured into a Y-configuration (see the configuration indicated by a one-dot chain line) by a rupture roller 61. Thereafter, the working material 9 thus ruptured is drawn with the use of a pressure spatula 6 along the working surfaces 51 and 31 of the first and second mandrel 5 and 3 until the working material 9 is formed into a generally rimlike configuration. At that time, a drawing end portion 91 of the working material 9 is stopped in a position where the drawing end portion 91 is not allowed to contact the second mandrel 3. Thereafter, the working material 9 is machined into a configuration as indicated by an imaginary line (one-dot chain line) so that a rim R is formed. Accordingly, by properly determining the stop position for the drawing end portion 91, a rim R having any desired width can be obtained. Since the drawing end portion 91 of the working material 9 is formed naturally into the rim-like configuration, the need of a provision of a rim f lange working portion on the mandrel 3 as 19 in the prior can be eliminated. If the rim R thus obtained is connected to a disk which has been separately manufactured, a vehicle wheel is accomplished.

Fig. 9 shows a further embodiment of the present invention. In Fig. 9, reference numeral 311 denotes a drop center working portion of the abovementioned second mandrel 3. This mandrel 3 is divided at the drop center working portion 311 into an outer portion 321 and an inner portion 322 in a direction vertical to an axis thereof. Reference numeral 323 denotes an auxiliary working member. This auxiliary working member 323 is removably sandwiched between the outer portion 321 and the inner portion 322. A peripheral surface of the auxiliary working member 323 is flush with a surface of the drop center working portion 311 of the second mandrel 3. The peripheral surface of the auxiliary working member 323 acts as the drop center working portion when the working material 9 is subjected to spinning. Reference numeral 324 denotes a stepped portion. This stepped portion 324 is formed on a contact surface between the outer portion 321 and the inner portion 322. This stepped portion 324 is suitable to be used for positioning the auxiliary working member 323. Reference numeral 325 denotes a fixing bolt. This f ixing bolt 325 is adapted to f ix the auxiliary working member 323 to the outer and inner portions 321 and 322. With the mandrel of this embodiment, a vehicle wheel W, which is to be formed by spinning, can be adjusted in rim width by properly selecting an auxiliary working member 323 having a desired width. The invention of the embodiment of Fig. 9 can also be applied to the embodiment of Fig. B. Although the invention has been described in detail by way of some preferred embodiments, the invention should not be limited to these embodiments, and many changes and modifications can be made by those skilled in the art without departing from the scope of the appended claims.

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Claims

WHAT IS CLAIMED IS: 1. A method f or spinning a vehicle wheel in which a

cast vehicle wheel material is subjected to spinning while heating, said method being characterized by comprising the steps of: composing said vehicle wheel material, as a chief component, from an aluminum, and, as secondary components, from Si of 3 wt. %- to 6 wt. % and Mg of 0. 2 wt. % to 0. 5 wt. %-; and heating said cast vehicle wheel material to a temperature in a range of from 230 OC to 4000C.
2. A method for spinning a vehicle wheel as claimed in claim 1, wherein a rim material of said wheel material is placed on a mandrel with a peripheral edge portion of said rim material allowed to project higher than a highest convex portion of a working surf ace of said mandrel.
3. A method for spinning a vehicle wheel as claimed in claim 1, further comprising the step of forming a rim material of said wheel material such that the wall thickness of peripheral edge portion thereof is larger than that of a web portion thereof.
4. A method for spinning a vehicle wheel as claimed in claim 1, further comprising the step of a peripheral wall like twist on an outer wall surface of a generally connecting portion between a disk portion and the rim material of said wheel material.

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5. A method f or spinning a vehicle wheel as claimed In claim 1, wherein a rim material of said wheel material is placed on said mandrel with a space f ormed between said rim material and a working surf ace of said mandrel, said space being gradually enlarged toward a peripheral end of said rim material.
6. A method f or spinning a vehicle wheel as claimed in claim 1, wherein an angle formed between said a rim material and a working surface of said mandrel is in a range of 50 to 30".
7. A method for spinning a vehicle wheel as claimed in claim 1, wherein a rim material of said wheel material is gradually dilated toward a peripheral end thereof and the dilating angle is steppingly varied toward the peripheral end.
8. A method for spinning a vehicle wheel by spinning as claimed in claim 7, wherein said dilating angle is steppingly enlarged toward the peripheral end of said rim material.
9. A method for spinning a vehicle wheel as claimed in claim 7, wherein said dilating angle is larger than a dilating angle of a working surf ace of a mandrel.
10. A method for spinning a vehicle wheel as claimed in claim 8, wherein said dilating angle is larger than a working surface of a mandrel.

1..

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11. A method for spinning a vehicle wheel as claimed in claim 1, wherein a drawing end of said rim material is stopped in a position where said rim material is not allowed to contact said mandrel.
12. A method f or spinning a vehicle wheel as claimed in claim 1, wherein a material locking peripheral groove is formed in the surface of said mandrel, said material locking peripheral groove being adjustable in width.
13. A method f or spinning a vehicle wheel as claimed in claim 1, wherein said mandrel is divided at a drop center working portion thereof into an outer portion and an inner portion in a vertical direction relative to an axis thereof, an auxiliary working member being removably sandwiched between said outer and inner portions, a stepped portion being provided on a contact surface of said material in said auxiliary working member.
14. A method for spinning a vehicle wheel in which a vehicle wheel material is subjected to spinning while heating, said method being characterized by comprising the steps of forming said wheel material; then liquefying the same; then coldspinning the same; and then subjecting the same to aging treatment.

4- FIG. 2 MJ%t(mm) WALL THICKNESS t (mm) -9iH(MM) HEIGHT H (mm) 1M01 COMPARATIVE EXAMPLE .... EMBODIMENT .... TEST PIECE FIG. 3 W4%) ELONGATION Jttz lb COMPARATIVE EXAMPLE WAR EMBODIMENT