WO2008111723A1

WO2008111723A1 - Ball joint integrated aluminum control arm for automobile and method of fabricating the same

Info

Publication number: WO2008111723A1
Application number: PCT/KR2007/006825
Authority: WO
Inventors: Shin-Woo Kang; Seong-Hwan Kim; Seong-Gon Lim; Jung-Hwan Lee; Seong-Hoon Kang
Original assignee: Central Corporation
Priority date: 2007-03-09
Filing date: 2007-12-26
Publication date: 2008-09-18
Also published as: KR100829457B1

Abstract

Provided are a novel ball joint integrated aluminum control arm and a method of fabricating the same, capable of remarkably reducing manufacturing costs and initial investment costs in comparison with a general forging or casting/forging method, and substantially satisfying an elongation of a caulking part of a ball joint socket required in the ball joint integrated aluminum control arm. The method of fabricating a ball joint integrated aluminum control arm for an automobile, in which a ball joint socket is integrally formed with a body, includes: fabricating an intermediate article in which the ball joint socket is integrally formed with the body through casting; heating the intermediate article to be forged; and partially forging the ball joint socket part of the intermediate article.

Description

BALL JOINT INTEGRATED ALUMINUM CONTROL ARM FOR AUTOMOBILE AND METHOD OF FABRICATING THE

SAME

Technical Field

[I] The present invention relates to a ball joint integrated aluminum control arm for an automobile and a method of fabricating the same, and more particularly, to a ball joint integrated aluminum control arm for an automobile which is used in a suspension apparatus for an automobile and a method of fabricating the same. Background Art

[2] As shown in FIG. 1, a suspension apparatus for an automobile requires control arms such as an upper control arm, a lower control arm, and so on. A ball joint is fastened to the control arms by nuts, and so on.

[3] That is, in a conventional art, after fabricating the control arms and the ball joint, the ball joint is fastened or attached to the control arms.

[4] However, in order to skip the process of fastening or attaching the control arm to the ball joint, a ball joint integrated aluminum control arm, in which a socket (or referred to as a housing) of the ball joint is integrally formed with the control arm, has come into the market.

[5] FIG. 2 is a photograph of a ball joint integrated aluminum control arm, in which a socket 200 of a ball joint is integrally formed with a body 100 of a control arm. Here, the ball joint integrated aluminum control arm is shown in a state that a ball joint is not yet completed (assembly of a ball and a ball seat is needed).

[6] Hereinafter, a conventional method of fabricating the ball joint integrated aluminum control arm will be described.

[7] (1) Fabrication through Casting

[8] An aluminum alloy is low-pressure cast to manufacture a ball joint integrated aluminum control arm.

[9] The low-pressure casting method has advantages of lowering manufacturing cost, increasing a material recollecting rate, and fabricating an end-product by a single molding process.

[10] However, since aluminum products fabricated through low-pressure casting generally have an elongation lower than 7%, defects may be generated due to the low elongation at a caulking part of the ball joint socket.

[I I] That is, as shown in FIG. 3, when the caulking part of the ball joint socket is formed to prevent separation of a ball or a ball seat in the ball joint socket, the surface of the material may be cracked.

[12] Therefore, while the casting method has economical advantages, quality problems make it difficult to commercially adapt the casting method to the method of fabricating the ball joint integrated aluminum control arm.

[13]

[14] (2) Forging and Casting/Forging

[15] In manufacturing the ball joint integrated aluminum control arm, the elongation of the caulking part of the ball joint socket is very important. In order to solve the quality problem, an aluminum hot-forging process is widely used.

[16] However, the general forging process includes too many processes to decrease a material recollecting rate, thereby increasing manufacturing costs.

[17] In order to improve the general hot-forging process, a casting and forging method, i.e., Cobapress technology has been developed.

[18] As shown in FIG. 4, the method fabricates a preform using an aluminum alloy material through forging. Then, the entire preform is reheated for one hour to perform the next forging process. Next, the entire preform is forged again by a large capacity press of 2000 tons or more, and then, unnecessary parts are removed by the next trimming process.

[19] While the method can increase a material recollecting rate in comparison with the conventional forging method, since the entire preform should be reheated and hot- forged, a large capacity press of about 2000 tons or more should be used to form a heavyweight material of 2kg or more such as a control arm for an automobile through the forging process. Therefore, the expensive large capacity equipment required in the method increases initial investment costs, thereby largely increasing the entire manufacturing costs in comparison with the general casting method. Disclosure of Invention Technical Problem

[20] In order to solve the foregoing and/or other problems, it is an object of the present invention to provide a novel ball joint integrated aluminum control arm and a method of fabricating the same, capable of remarkably reducing manufacturing costs and initial investment costs in comparison with a general forging or casting/forging method, and substantially satisfying an elongation of a caulking part of a ball joint socket required in the ball joint integrated aluminum control arm. Technical Solution

[21] One aspect of the present invention provides a method of fabricating a ball joint integrated aluminum control arm for an automobile, in which a ball joint socket is integrally formed with a body, including: fabricating an intermediate article in which the ball joint socket is integrally formed with the body through casting; heating the intermediate article to be forged; and partially forging the ball joint socket part of the intermediate article.

Advantageous Effects

[22] In accordance with the present invention, it is possible to provide a novel ball joint integrated aluminum control arm and a method of fabricating the same, capable of remarkably reducing manufacturing costs and initial investment costs in comparison with a general forging or casting/forging method, and substantially satisfying an elongation of a caulking part of a ball joint socket required in the ball joint integrated aluminum control arm.

[23] That is, it is possible to sufficiently use a net shape forming method with low manufacturing costs and a high material recollecting rate, which are advantages of the conventional low-pressure casting method. In addition, since there is no necessity of additional equipment to the conventional casting line, except a heater for reheating, it is possible to fabricate the ball joint integrated aluminum control arm having good quality without an increase in production cost. Brief Description of the Drawings

[24] These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of exemplary embodiments of the invention, taken in conjunction with the accompanying drawings of which:

[25] FIG. 1 is a view showing a use state of a control arm;

[26] FIG. 2 is a photograph of a ball joint integrated aluminum control arm, in which a socket part of a ball joint is integrally formed with a body of the control arm;

[27] FIG. 3 is a photograph of a ball joint, a material surface of which is cracked after caulking;

[28] FIG. 4 is a flowchart of a conventional casting/forging method;

[29] FIG. 5 is a flowchart of a method of fabricating a ball joint integrated aluminum control arm in accordance with an exemplary embodiment of the present invention; and

[30] FIGS. 6 and 7 are a graph showing property variations and photographs of fine structure variations of products depending on deformation rates generated by partial pressing of a socket part of a ball joint in accordance with an exemplary embodiment of the present invention.

[31]

Mode for the Invention

[32] An exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[33] FIG. 5 is a flowchart of a method of fabricating a ball joint integrated aluminum control arm in accordance with an exemplary embodiment of the present invention.

[34] (1) Fabrication of Intermediate Article through Casting

[35] A casting aluminum material is low-pressure cast using a general low-pressure casting apparatus to fabricate a low-pressure cast aluminum control arm (hereinafter, referred to as an intermediate article).

[36] At this time, in order to obtain properties of an end-product, a cooling line using air or air/water may be installed in a casting mold to guide directional solidification and rapid molten metal cooling.

[37] In addition, the socket part of the ball joint as the intermediate article may be configured such that a deformation rate of the caulking part is 20% or more (preferably 30% or more) in order to increase an elongation during the next partial forging.

[38] FIGS. 6 and 7 show property variations and fine structure variations of the products depending on the deformation rate.

[39] After cutting a sprue of the fabricated intermediate article, existence of internal defects is determined through X-ray non-destructive inspection.

[40] Hereinafter, a difference between the fabrication method of the intermediate article in accordance with the present invention and the conventional casting and forging method will be described.

[41] In the conventional casting and forging method, since the large-sized press apparatus is used for the forging after fabricating a preform having a volume about 10-50% larger than the end-product during fabrication of the preform through casting, flash may be generated to decrease a material recollecting rate.

[42] On the other hand, the ball joint socket part of the intermediate article in accordance with an exemplary embodiment of the present invention is slightly larger than the ball joint socket part of the end-product, and the body of the control arm, except the ball joint socket, is equal to the end-product. That is, the body of the control arm, except the ball joint socket, can obtain properties of the control arm by fabricating the intermediate article.

[43] Therefore, since there is no flash generated from the body of the control arm, occupying most of the control arm, during the next forging process (since the body is not forged), the material recollecting rate in accordance with the present invention is remarkably higher than that of the conventional casting and forging method.

[44]

[45] (2) Heating Process of Intermediate Article

[46] When the ball joint socket part of the intermediate article is forged, in order to decrease press-forming resistance and readily perform the forming process using a general trimming press, at least the ball joint socket part should be heated. Of course, partial heating of the ball joint socket part may cause a reduction in time and cost.

[47] Since the ball joint socket part occupies about 10% of the entire area of the control arm, partial heating of the ball joint socket part remarkably reduces the heating time in comparison with the entire heating of the conventional casting and forging method, thereby reducing energy consumption and improving productivity.

[48] That is, in the embodiment, the ball joint socket part is heated at 400-550C within one minute using a cylindrical high-frequency induction heating apparatus.

[49] On the other hand, reheating of the conventional casting and forging method requires about one hour of heating time.

[50] After the partial heating, the intermediate article is conveyed to a forging press to be partially forged.

[51] While the conventional casting/forging method or forging method requires a process of applying or coating an release agent functioning as lubricant for products or molds during each operation such that aluminum products are smoothly formed during forging, since a forming surface requiring forging is very small, there is no necessity of frequent application of the release agent. Therefore, it is possible to reduce application costs.

[52]

[53] (3) Partial Forging Process of Intermediate Article

[54] Conventionally, an overflow is installed at an outer part of the cast product to prevent occurrence of internal pores and oxides in the cast product, thereby guiding the internal pores to the overflow and removing the internal pores. Such an overflow is manually removed after fabrication of the cast product.

[55] In this embodiment, the overflow is removed using a trimming press, and at the same time, a mold for partially pressing the ball joint socket is installed in the trimming press to forge the ball joint socket part.

[56] Conventional mold forging may be adapted to partially forge the ball joint socket part. While either flash forging (an open-type mold) or non-flash forging (a closed- type mold) of mold forging may be adapted in this embodiment, since the flash forging requires the following flash removal operation, the non-flash forging may be adapted as far as possible.

[57] In the case of the conventional casting and forging method, the control arm for an automobile having a weight of 2kg or more requires a large-sized press of 2000 tons or more. However, in this embodiment, since the ball joint socket part has a size of 50mm or less, a press having a capacity of about 200 tons can substantially perform the forging process. Such a capacity of the press means that the conventional trimming press can perform the forging process. [58] As a result of experiment, load required in the partial pressing of the ball joint socket having a diameter of 55mm and a height of 50mm was 104 tons. [59] The partial press-forming of the ball joint socket part can increase an elongation of the caulking part of the ball joint socket about 110% or more in comparison with the elongation of the control arm body. [60] FIG. 6 shows property variation of a product depending on a deformation rate generated by partial press-forming of the ball joint socket part, and FIG. 7 shows fine structure variation depending on the deformation rate. [61] At this time, the respective properties were measured according to KS B0802 Metal

Material Tensile Test Method. [62] As shown in FIG. 6, a point of a compression deformation rate of 0% means properties of a body of the control arm and properties of the ball joint socket part before compression deformation. [63] In addition, it will be appreciated that an elongation of the caulking part of the ball joint socket is gradually increased when the compression deformation rate is increased to 10%, 20%, 40%, and 60% through the forging process. [64] Further, it will be appreciated that the elongation in the compression deformation rate of about 20% or more is about 110% or more in comparison with the elongation in the compression deformation rate of 0% (the elongation of the body). [65] That is, the elongation was about 6% when the compression deformation rate is 0%, and the elongation was about 8% when the compression deformation rate is 20%.

Therefore, it will be appreciated that the elongation in the compression deformation rate of 20% is increased about 133% (8/6X100) in comparison with the elongation in the compression deformation rate of 0%. [66] The conventionally required elongation of the caulking part of the ball joint socket of the ball joint integrated control arm is about 8%. While a higher elongation may be required to increase quality depending on necessity, as shown in FIG. 6, it is possible to satisfy a required elongation by increasing a compression deformation rate depending on quality requirements. [67] While an exemplary embodiment of the present invention has been shown and described, it will be appreciated by those skilled in the art that various changes may be made to these embodiments without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Industrial Applicability [68] As can be seen from the foregoing, a novel ball joint integrated aluminum control arm and a method of fabricating the same in accordance with the present invention can remarkably reduce manufacturing costs and initial investment costs in comparison with a conventional forging or casting/forging method, and sufficiently satisfy an elongation of a caulking part of a ball joint socket required by the ball joint integrated aluminum control arm. [69]

Claims

[1] A method of fabricating a ball joint integrated aluminum control arm for an automobile, in which a ball joint socket is integrally formed with a body, the method comprising: fabricating an intermediate article in which the ball joint socket is integrally formed with the body through casting; heating the intermediate article to be forged; and partially forging the ball joint socket part of the intermediate article. [2] The method according to claim 1, wherein heating the intermediate article is partially heating the ball joint socket part of the intermediate article. [3] The method according to claim 1, wherein partially forging the ball joint socket part performs a trimming process of the intermediate article simultaneously therewith. [4] A ball joint integrated aluminum control arm for an automobile, in which a ball joint socket is integrally formed with a body, wherein an elongation of a caulking part of the ball joint socket is 110% or more of an elongation of the body. [5] The ball joint integrated aluminum control arm according to claim 4, wherein the body is fabricated by casting and the ball joint socket is fabricating by forging after the casting.