JP2000079801A - Manufacture of light-metal alloy wheel for automobible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a lightened light metal wheel with a low cost by casting a preform of a wheel, then forging a disc part of the preform at the next step, and spinning a rim part. SOLUTION: A disc part 1a is pressed and held by a pair of dies 5, 6 in a rocking forging process of the disc part 1a, one of dies 5 is rocked relative to the other die 6, and a rocking surface is rotated about an axle shaft center. In this rocking forging process, the disc part 1a is partially pressed in the peripheral direction, so that the pressure force can be reduced in comparison with the ordinary forging where the disc part 1a is pressed over entire area of its peripheral direction. To reduce the pressure force, the forging preform is heated to a hot area. In a spinning process of the rim part 1b, the preform is heated to the hot area. The final shape of the rim part 1b is formed by the spinning process. Whereby the lightened wheel free from the excess thickness can be manufactured with the low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lightweight, low-cost automobile wheel made of a light metal alloy.

[0002]

2. Description of the Related Art There are the following methods for producing a lightweight, light metal alloy automobile wheel. (1) Forged integrated wheel of wrought material (2) Welded assembling wheel of wrought material (3) Welded assembling wheel of press forged disc and cast rim of cast material In the above method (1), FIG. As described above, the material is cut in the step 11, heated in the step 12, forged in a step 13 by, for example, a 3000-ton hydraulic press, molded in the step 14 with a hot shrinker, subjected to solution treatment 15, quenching 16, aging. After each step of processing 17 and cutting 18, a wheel is formed. In the method (2), as shown in FIG. 10, the plate is bent in step 21 and flash butt welded in step 22,
In step 23, a rim is produced by roll forming,
In step 24, a disk is prepared by press plastic working, and in step 25, the rim and the disk are welded and joined to form a wheel. In the above method (3), as shown in FIG. 11, the material cast in step 31 and melted in step 32 is forged in step 33 to produce a disk with a single flange, and in step 34 the rim is cast by casting. It is manufactured, and in step 35, the rim and the disk are welded and joined to form a wheel.

[0003]

Generally, when a wheel is manufactured only by casting, there are the following problems. The thick part of the disk has a low cooling rate and a coarse metal structure, and thus has low strength and toughness. Since the rim thin portion has a high cooling rate, casting defects are apt to occur, and air leakage defects are likely to occur. Further, the methods for manufacturing the lightweight wheels (1), (2), and (3) described in the prior art have a problem that all of them are costly and have the following problems individually.
(1) Forged integrated wheel For normal die forging, the required pressure is 5000 ton or more even for small wheels for passenger cars, and the equipment cost is extremely high. In addition, a complex disk shape cannot be formed by one heat, and requires two or more heats. Further, since the shape of the rim cannot be completely formed by forging from the side, it takes a long time to perform cutting in a subsequent process. (2) Expandable assembly Since the disc is press-formed from a plate, it can be used only for designs with low designability. Since the rim is roll-formed, it is not possible to flexibly cope with a difference in rim width or the like, and a roll cost is required. Since the welded portion has a solidified structure after melting, the strength is weakened, and it is necessary to add extra meat to the structure. In addition, welding thermal deformation is likely to occur. (3) Casting forging + casting assembly For normal die forging, as in (1), equipment with high pressing force is required. Further, since the rim portion is a cast material, air leakage failure is likely to occur as in (2). Since the assembled portion is welded, the strength is low and has the same disadvantages as the welded portion (2). SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a lightweight metal alloy automobile wheel at low cost.

[0004]

(1) A step of casting a preform of a light metal alloy automobile wheel, a step of forging a disk portion of the preform, and a step of spinning a rim portion of the preform. A method for manufacturing a light metal alloy automobile wheel, comprising: (2) In the step of casting the preform, a plurality of lightening portions that open to the back side of the wheel are formed in the circumferential direction at the boundary between the rim and the disc of the preform in the circumferential direction. Manufacturing method for automotive wheels. (3) a step of casting a billet-shaped wheel material having a circular outer periphery made of a light metal alloy and having a certain thickness; a step of forging the billet-shaped wheel material to form a disk portion; and the disk portion is formed. Forming a rim by sping processing of the wheel material obtained. (4) a thick disk portion made of a light metal alloy at the center, a thin disk portion connected radially outward of the thick disk portion,
Casting a dish-shaped wheel material consisting of a rim-shaped part that is continuous with the thin-walled disc portion and rises in the axial direction over the entire circumference; and forging the thick disc portion and the thin disc portion of the disc-shaped wheel material to form a disc portion. And a step of forming a rim portion by spying the disc-shaped wheel material on which the disk portion is formed, to produce a light metal alloy automobile wheel. (5) In the step of casting the dish-shaped wheel material, a plurality of meat steal portions that open on the back side of the wheel are formed in the circumferential direction at the boundary between the rim and the disc of the dish-shaped wheel material in the circumferential direction. Of manufacturing a light metal alloy automobile wheel. (6) The disk portion before forging is cast to have a thickness of 30% or more of the thickness of the finished product plate (1) or (2), (4) or (5). Of manufacturing a light metal alloy automobile wheel. (7) The forging is swing forging (1) or (2).
Or (3) or (4) or (5), a method for producing a light metal alloy automobile wheel according to (1).

In the method of the present invention (1), the disk part is forged and the rim part is formed by spinning using a preform of a cast product, so that welding assembly is not required and the rim part is formed. A lightweight, low-cost wheel without air leakage can be manufactured. In the method of the present invention (2), the advantage of weight reduction can be added to the method of (1) by stealing meat at the time of casting. The present invention (3)
According to the method, since the shape of the wheel material of the casting is simple, the structure of the casting mold can be simplified, and the cost for manufacturing the mold can be greatly reduced. Further, since the wheel material is very simple, it is possible to obtain a wheel material free from casting defects such as poor running. In the method of the present invention (4),
Since the shape of the wheel material of the casting is simple according to the method of (3), the structure of the casting mold can also be simplified. Therefore, it is possible to greatly reduce the die manufacturing cost, and further, since the wheel material is very simple, a wheel material free from casting defects such as poor running of the melt can be obtained. In addition, it is easy to form the rim in the next forging step and spinning step, which is efficient. In the method of the present invention (5), the advantage of weight reduction can be added to the method of (4) by stealing the meat during casting. According to the method of the present invention (6), since the thickness of the disk portion before forging is cast to be 30% or more thicker than the thickness of the finished product plate, the material of the disk portion is forged. A rolling reduction of 30% that can contribute to improvement can be made possible. In the method of the present invention (7), since the forging is the swing forging, the pressing force is small and the equipment can have a relatively small capacity.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a light metal alloy automobile wheel according to a first embodiment of the present invention will be described below with reference to FIGS. The light metal alloy automobile wheel according to the first embodiment of the present invention comprises a step of casting a preform of the light metal alloy wheel shown in FIG. 1, a step of forging a disk portion of the preform shown in FIG. A step of spinning the rim portion of the shown preform.

More specifically, the automotive wheel made of a light metal alloy according to the first embodiment of the present invention is prepared by melting a light metal alloy → casting a preform (either gravity casting or low pressure casting as shown in FIG. 1) → Deburring (burring) → heating (however, if casting heat can be used, there is no need to provide a special heating step) → disk forging (preferably rocking forging for forging) → trimming (omitting the trimming step) → Heating (If the heat of the casting or forging process can be used, there is no need to provide a special heating process) → Spinning (flow forming) processing of the rim → Heat treatment → Painting (even if the painting process is omitted) Good) → cutting → painting.

In the casting step of the preform 1, as shown in FIG. 1, molten metal is injected into the product cavity 3 of the mold 2 in the case of gravity casting, and the upper space of the molten alloy reservoir 4 in the case of low pressure casting. The molten alloy is pushed up to the product cavity 3 by applying gas pressure to the preform 1 and solidified and opened to form the preform 1.
The disk portion 1a of the preform has a disk shape close to a full design in consideration of swing forging in the next step (mainly a disk shape crushed in the height direction). in this case,
It is desirable to use a casting mold invented by the applicant earlier (Japanese Patent Application Laid-Open No. 9-248666). Also, at the boundary between the rim of the preform and the disk where the rib of the disk is provided, a plurality of meat stealing portions 1c opened on the back side of the wheel in the circumferential direction (usually the number corresponding to the number of ribs). It is desirable to form. By forming this meat stealing portion 1c, it is possible to further reduce the weight while maintaining the rigidity.

The forging of the disk portion 1a is performed, for example, by using the method shown in FIG.
(However, the present invention is not limited to the swing forging, but may be a normal die forging). In the swing forging, a pair of dies 5 and 6 press the disk portion 1a, swing one mold 5 with respect to the other mold 6, and rotate the swing surface about the wheel axis. In the swing forging, since the disk portion 1a is locally pressurized in the circumferential direction, the pressing force may be smaller than that in a normal forging pressurized in the entire circumferential direction. In this case, only the disk section 1a is
Pressing is performed at a sheet thickness reduction rate of ５０50%. In order to reduce the pressing force, the forged preform 1 is heated to a hot region (200 to 550 ° C. for an aluminum alloy). However,
In the case of forging immediately after casting, when the preform 1 is at 200 to 550 ° C. due to residual heat of casting, special heating can be omitted.

In the spinning (flow forming) of the rim portion 1b of the preform 1, the preform 1 is heated to a hot region (200 to 550 ° C. for an aluminum alloy). However, if the temperature in the hot region is maintained immediately after the swing forging, heating can be omitted. The final shape of the rim 1b is produced by spinning. The product is molded so that the processing cost is as small as possible. A cutting allowance of 0 is also possible inside the rim. It is also possible to form a reinforcing rib on the inside by processing as a strength countermeasure shape.

Further, as a method of the second embodiment of the present invention,
As shown in FIG. 2, instead of casting the preform 1 shown in the first embodiment, instead of casting the preform 1, first, the outer periphery made of a light metal alloy has a circular shape (diameter D1). A step of casting a billet-shaped wheel material 7 having a constant thickness H1, a step of forming a disk portion by forging the billet-shaped wheel material 7, and a sping process of the wheel material on which the disk portion is formed, A method of manufacturing a light metal alloy automobile wheel, comprising the step of forming a rim portion, is also desirable. In this method, since the shape of the wheel material 7 of the cast product is simple, the structure of the casting mold is also simple, so that it is possible to greatly reduce the mold manufacturing cost. Because of its simplicity, a wheel material free from casting defects such as poor run-off is obtained. In addition, the shape of the wheel material of the cast product allows the wheel material to be supplied by continuous casting, so in some cases a continuous online process from the material can be realized, contributing to reducing the number of heats in the forging process. it can.

Further, according to the method of the third embodiment of the present invention, the wheel blank 8 to be cast is made of the wheel blank of the second embodiment of the present invention as shown in FIG.
a, a thin disk portion 8b extending radially outward of the thick disk portion 8a, and a rim element portion 8 connected to the thin disk portion 8b and rising in the axial direction over the entire circumference;
c is a dish-shaped wheel shape. Since the thick disk portion 8a corresponds to the hub mounting portion of the disk when the product is completed, the thickness is formed to be thicker in the same direction as the rim element 8c than the thin disk portion 8b.
Preferably, a disk-side rim element 8d extending in the axial direction on the opposite side to the rim element is formed in advance to form a disk forging step (including swing forging).
When the rim is formed in a later spinning step, it is easy to form. In this method, as compared with the first embodiment of the present invention, the shape of the cast wheel material 8 is also simple, and the structure of the casting mold is also simple. Since the wheel material 8 can be reduced and the wheel material 8 is very simple, it is possible to obtain a wheel material free from casting defects such as poor running. In the first and third embodiments of the present invention, the thickness of the portion corresponding to the disk when the casting is completed before the forging step is 30% or more of the thickness when the wheel is completed. Thickness plus cutting allowance is added to form a thicker plate, and in the forging process 30
It is desirable to forge at a draft of at least%. This allows
Even if there is a defect such as a blowhole, the defect can be crushed, and a disk part excellent in quality and strength can be formed. Also, the first
By using the casting mold (JP-A-9-248666) previously invented by the applicant described in the embodiment, the wheel is provided at the boundary between the rim of the preform and the disk where the disk rib is provided. It is desirable to form a plurality of (thus, usually, the number corresponding to the number of ribs) circumferentially multiple meat stealing portions 1c that are opened on the back side. By forming the meat steal portion 12a, further weight reduction can be realized.

A comparison between a light metal alloy automobile wheel manufactured by the above method and a wheel manufactured by another method (conventional method) is as follows. The comparison with the cast product is as follows. By forging (for example, rocking forging) the thick portion of the disk, the material is improved as shown in FIGS. The greater the sheet thickness reduction rate, the greater the material improvement. From the viewpoint of fatigue strength, it is considered that a life of equal to or more than 10% is obtained. Processing rate 10-50%
, Especially about 30%. The material of the rim rises by spinning as in the case of forging. However, since the rim has a high original strength, there is no remarkable improvement in the material as compared with the disk. However, since the defect leading to the air leakage is crushed, the air leakage defect rate is reduced from about 2% to about 0.

The comparison with the conventional forged integrated wheel is as follows. The pressing force of the disk portion is about 1/5 to 1/10 in the case of swing forging as compared with the case of normal die forging, and in a passenger car, a pressing force of 800 to 1000 tons is sufficient. In addition, since a complicated shape is almost formed at the casting stage, it can be sufficiently formed by one heat processing. Further, even when a circular cast billet wheel material is used, it is possible to form a required shape although the number of heats is slightly increased. Also, for the rim, the cutting allowance is 1m.
m or less. It was found that by selecting the processing speed and the processing roll, it is possible to form even a zero cutting allowance.

The comparison with the conventional wrench-mounted wheel is as follows. As for the disk portion, a disk shape substantially similar to that of the die forging can be formed by swing forging, and it is possible to cope with a much more complicated shape than press forming. As for the rim portion, the same preform could be formed from 12 inches to 18 inches by spinning. Because of the overall heating, the deformation is similar to a normal die forged wheel.

A comparison with the conventional cast forging + casting assembling wheel is as follows. With respect to the disc portion, the same operation as described in comparison with the forged integrated wheel can be obtained.
In addition, the same effect as described in comparison with the conventional wrench-mounted wheel can be obtained for the rim portion.

[0017]

According to the method of the first aspect, the preform is manufactured by casting, the disc is forged, and the rim is formed by spinning. A wheel with no defect and high shape accuracy (light weight without extra meat) can be manufactured at low cost (the shape is formed with a preform, so less forging and less pressing force). . According to the method of claim 2, in addition to the effect of claim 1, further weight reduction of the wheel can be realized. According to the method of claim 3, since the shape of the wheel material of the casting is simple and the structure of the casting mold is simple, it is possible to greatly reduce the mold manufacturing cost. Since the material is very simple, it is possible to obtain a wheel material free from casting defects such as poor running. According to the method of claim 4, since the shape of the wheel material of the casting is simple according to the method of claim 2, the structure of the casting mold can be simplified, and the production cost of the mold can be greatly reduced. In addition, since the wheel material is very simple, it is possible to obtain a wheel material free from casting defects such as poor running. In addition, it is easy to form the rim in the next forging step and spinning step, which is efficient. According to the method of claim 5, the effect of reducing the weight of the wheel can be added to the effect of claim 4. According to the method of claim 6, since the thickness of the disk portion before forging is cast to be 30% or more thicker than the thickness of the finished product, the rolling reduction is required when the disk portion is forged. It is possible to provide a wheel having a disc portion which is excellent in quality and strength. According to the method of claim 7, since the forging is the swing forging, the forging pressure can be reduced, and the equipment cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a preform casting step in a method for manufacturing a light metal alloy automobile wheel according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a shape of a wheel element formed by casting before being supplied to a forging process in a method for manufacturing a light metal alloy automobile wheel according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing the shape of another wheel element formed by casting before being supplied to a forging process in the method for manufacturing a light metal alloy automobile wheel according to the third embodiment of the present invention.

FIG. 4 is a cross-sectional view of a forging (oscillating forging) step in the method of manufacturing a light metal alloy automobile wheel according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view of a rim spinning (flow forming) step in the method for manufacturing a light metal alloy automobile wheel according to the embodiment of the present invention.

FIG. 6 is a graph showing tensile strength vs. reduction in thickness of a foil manufactured by the method of the present invention.

FIG. 7 is a graph showing the Charpy impact value versus the rate of reduction in sheet thickness of a wheel manufactured by the method of the present invention.

FIG. 8 is a graph of stress amplitude versus number of repetitions for a foil manufactured by the method of the present invention.

FIG. 9 is a manufacturing process diagram of a conventional wrought integrated forged wheel.

FIG. 10 is a manufacturing process diagram of a conventional wrought material welded assembling wheel.

FIG. 11 is a manufacturing process diagram of a conventional casting forging + casting assembly wheel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preform 1a Disk part 1b Rim part 1c Meat steal part 5, 6 Swing forging die 7, 8 Wheel material 8a Thick disc part 8b Thin disc part 8c Rim element shape part 12a Meat steal part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60B 3/06 B60B 3/06 (72) Inventor Masafumi Ohno 5-9, Yonbancho, Chiyoda-ku, Tokyo Topy Corporation (72) Inventor Masayuki Naka 9-5, Yonbancho, Chiyoda-ku, Tokyo Topy Industries F-term (reference) 4E087 AA10 CA07 CA41 EA37 HA12

Claims (7)

[Claims] 1. A light metal alloy made of a light metal alloy, comprising: a step of casting a preform of a light metal alloy automobile wheel; a step of forging a disk part of the preform; and a step of spinning a rim part of the preform. Manufacturing method for automotive wheels. 2. In the step of casting the preform, at a boundary between a rim and a disk of the preform,
2. The method for manufacturing a light metal alloy automobile wheel according to claim 1, wherein a plurality of carved portions that are opened on the back side of the wheel are formed in the circumferential direction. 3. a step of casting a billet-shaped wheel material having a circular outer periphery made of a light metal alloy and having a constant thickness; a step of forging the billet-shaped wheel material to form a disk portion; Forming a rim portion by sping processing the formed wheel material. A method for manufacturing a light metal alloy automobile wheel, comprising: 4. A thick disk portion made of a light metal alloy at the center,
A step of casting a dish-shaped wheel material comprising a thin disc portion connected radially outward of the thick disc portion, and a rim element-shaped portion connected to the thin disc portion and rising in the axial direction over the entire circumference; and Forming a disk portion by forging a thick disk portion and a thin disk portion, and forming a rim portion by spying a dish-shaped wheel material on which the disk portion is formed. A method for manufacturing a light metal alloy automobile wheel. 5. In the step of casting the dish-shaped wheel material, a plurality of meat steal portions that open to the back side of the wheel are formed in a circumferential direction at a boundary between a rim and a disc of the dish-shaped wheel material. 5. The method for producing a light metal alloy automobile wheel according to item 4. 6. The disk portion before forging is cast to have a thickness of 30% or more of the thickness of the finished product plate. 5. The method for producing a light metal alloy automobile wheel according to item 5. 7. The method for manufacturing a light metal alloy automobile wheel according to claim 1, wherein said forging is swing forging.